Applied Catalysis B, Environmental (v.140-141, #C)

Co3O4/CNTs were prepared as catalysts for the catalytic combustion of toluene. The defects of CNTs facilitated the catalytic combustion conversion of toluene, and the ―COOH on CNTs could promote the selectivity to CO2. Thus, Co3O4/CNT catalysts demonstrated high catalytic performance, indicating a potential application for the catalytic combustion of VOCs.The catalytic performance of the supported Co3O4 on CNTs (Co3O4/CNTs) in the catalytic combustion of toluene was improved by tuning the surface structures of CNTs. The study results showed that the surface defect structures of CNTs could not only enhance the ability of Co3O4 to develop reduction/oxidation cycles, but also increase the proportion of the adsorbed oxygen species to the surface lattice oxygen ones. Thus, the defects of CNTs could improve the catalytic activity of Co3O4/CNTs and lower the complete conversion temperature of toluene. Moreover, the CO2 selectivity increased along with increasing the ―COOH amount of the CNTs. Therefore, by tuning the defect density and ―COOH amount, the conversion of toluene was completed at 257 °C and the selectivity to CO2 achieved to ∼100% on Co3O4/CNTs-120 catalyst, which is much better than Co3O4/Beta, Co3O4/ZSM-5 or Co3O4/SBA-15. Furthermore, compared with Pd/Beta and Pd/SBA-15 catalysts, Co3O4/CNTs showed a similar or even better catalytic performance, indicating the great potential application of Co3O4/CNT catalysts for the catalytic combustion of toluene.
Keywords: Catalytic combustion; VOCs; Co3O4/CNTs; Defects; ―COOH groups;

Low-temperature synthesis and characterization of rutile nanoparticles with amorphous surface layer for photocatalytic degradation of caffeine by Matic Krivec; Ricardo A. Segundo; Joaquim L. Faria; Adrián M.T. Silva; Goran Dražić (9-15).
Rutile (TiO2) nanoparticles were prepared by a low-temperature hydrothermal process from titanium(IV) isopropoxide as a precursor and without any additional calcination step. The particles were characterized with several techniques (XRD, BET, UV–vis spectrometry, TEM/HRTEM/SAED, FT-IR) and their photocatalytic efficiency was evaluated on the degradation of caffeine. The as-prepared rutile particles exhibited a rod-like morphology with a prism body and pyramidal ends. The low-temperature hydrothermal synthesis introduced an amorphous layer that was around 1-nm thick and uniformly covered the surfaces of the particles. The enhanced photocatalytic properties of the particles confirmed the positive impact of the amorphous surface layer in comparison to the fully crystallized surface of commercial rutile particles and to particles that were synthesized using a conventional high-temperature calcination route. The amorphous surface layer seems to enhance the adsorption of both oxygen and caffeine on the surface of the particles and, therefore, improves the photocatalytic activity of the rutile particles. Being the case, the electron transfer to the adsorbed oxygen is more efficient, increasing the life-time of the photogenerated holes, which contributes to the degradation of caffeine via the formation of reactive radicals and/or by direct oxidation.
Keywords: Rutile nanoparticles; Low-temperature hydrothermal synthesis; Amorphous surface layer; Photocatalysis;

Hybrid Cu–ZnO–ZrO2/H-ZSM5 system for the direct synthesis of DME by CO2 hydrogenation by G. Bonura; M. Cordaro; L. Spadaro; C. Cannilla; F. Arena; F. Frusteri (16-24).
One-step CO2 hydrogenation reaction to dimethyl ether (DME) was studied on a hybrid system characterized by different reactor bed configurations (physical mixing, dual-bed and mono-bed). Homemade Cu–ZnO–ZrO2 methanol catalytic system and a commercial H-ZSM5 zeolite were used to realize the hybrid system. The influence of preparation method on activity, selectivity and yield in the temperature range of 453–513 K at 3.0 MPa and CO2/H2/N2 feed concentration of 3/9/1 has been evaluated. The results obtained under kinetic conditions show a superior specific productivity of ca. 430  g total MeOH k g cat − 1  h − 1 at 513 K using the hybrid catalyst prepared by physical mixing. A combined effect of sites located at metal/oxide(s)-acid interface to drive DME synthesis through a consecutive mechanism was claimed as the main factor affecting the CO2 conversion and DME productivity.
Keywords: CO2 hydrogenation; DME synthesis; Cu–ZnO–ZrO2 catalysts; Hybrid systems;

Electrical and catalytic properties of cerium–tin mixed oxides in CO depollution reaction by Anca Vasile; Veronica Bratan; Cristian Hornoiu; Monica Caldararu; Niculae I. Ionescu; Tatiana Yuzhakova; Ákos Rédey (25-31).
AC electrical conductivity of CeO2 catalyst samples containing 5, 10 and 20 wt% SnO2 prepared by co-precipitation and of SnO2 and CeO2 pure oxides (prepared under the same conditions) was measured in operando conditions. The measurements were carried out at a frequency of 1592 Hz in the temperature range from room temperature up to 400 °C, using successively programmed heating–cooling cycles under various atmospheres. The catalyst samples were tested in the catalytic oxidation of CO in presence and in absence of oxygen in the same temperature range (30–400 °C). An improved deep oxidation of carbon monoxide has been found with these co-precipitated mixed oxides compared to pure components, leading to a better catalytic activity at lower temperature. The band gap energies were estimated based on the UV–Vis spectra and correlated with XRD results and AC electrical conductivity data. These results show the influence of the tin oxide on the electrical properties and oxygen mobility of the catalytic systems studied and on the surface behaviour of ceria.
Keywords: Tin–cerium mixed oxides catalysts; Electrical conductivity; Surface dynamics; CO oxidation;

Electrochemical photocatalytic degradation of dye solution with a TiO2-coated stainless steel electrode prepared by electrophoretic deposition by Wei-Chieh Lin; Chien-Hung Chen; Han-Yu Tang; Yu-Cheng Hsiao; Jill Ruhsing Pan; Chi-Chang Hu; Chihpin Huang (32-41).
This study demonstrates a new model for the treatment of azo dye wastewater by means of a heterogeneous photocatalytic degradation coupled with the homogeneous electrochemical Fenton reaction, and is called electrochemical photocatalytic (ECPC) degradation. Titanium dioxide-coated stainless steel (P25-TiO2/SS) mesh was employed as a photo-anode, covered with a uniform layer of P25-TiO2 using electrophoretic deposition (EPD) in a 2-propanol suspension with 10−4  M Zn(NO3)2, at a deposition time of 1 min. After annealing in air at 350 °C for 1 h, a crack-free, porous P25-TiO2 layer of ca. 2.14 μm was obtained. Potential bias was used to enhance the photocatalytic degradation of P25-TiO2/SS towards the target pollutant, azo dye orange G, in an undivided cell under ultraviolet light irradiation. Heterogeneous photocatalytic degradation and a homogeneous electro-Fenton reaction occurred in the system simultaneously when H2O2 and Fe2+ were electrochemically generated on the graphite cathode and photo-anode, respectively, under a suitable potential bias, enhancing the de-colorization and removal of total organic carbon.
Keywords: Photocatalytic degradation; Electrochemical Fenton reaction; Dye; Electrophoretic deposition; Titanium dioxide;

Room-temperature catalytic removal of low-concentration NO over mesoporous Fe–Mn binary oxide synthesized using a template-free approach by Zhu Shu; Yu Chen; Weimin Huang; Xiangzhi Cui; Lingxia Zhang; Hangrong Chen; Guobin Zhang; Xiangqian Fan; Yongxia Wang; Guiju Tao; Dannong He; Jianlin Shi (42-50).
A novel template-free approach, the controlled thermal decomposition of single-phase Fe–Mn binary oxalate, was proposed and used to synthesize mesoporous Fe–Mn binary oxide, which possessed homogeneous worm-like mesopores (4–5 nm) and high surface areas above 200 m2/g. The catalyst was efficient in the catalytic removal of low-concentration NO at room temperature: 100% removal of 10 ppm NO in the first 4 h at a high space velocity of 40,000 h−1 on a Fe–Mn binary oxide with a Fe/Mn ratio of 1/4 calcined at 300 °C. Catalysts with other Fe/Mn ratios or calcined at higher temperatures showed lower NO removal performances. A synergetic effect between Mn n+ and Fe n+ was proposed and believed to be responsible for the catalytic conversion of NO and O2 into NO2, which was subsequently adsorbed and/or absorbed as nitrates on the binary oxide.
Keywords: Mesoporous Fe–Mn binary oxide; Low-concentration NO; Catalytic oxidation; Adsorption; Room temperature;

Effect of Sn surface states on the photocatalytic activity of anatase TiO2 by Freddy E. Oropeza; Bastian Mei; Ilia Sinev; Ahmet E. Becerikli; Martin Muhler; Jennifer Strunk (51-59).
The influence of surface Sn-doping on the photocatalytic properties of anatase TiO2 has been investigated in samples prepared by a grafting route using Sn(IV) tert-butoxide as Sn precursor. The grafting procedure leads to the formation of isolated Sn(IV) sites on the surface of anatase TiO2 powders as gauged by structural characterisation based on XRD, Raman spectroscopy and XAS. Studies of the surface reduction based on TPR experiments and XPS provide the conditions for a selective reduction of surface Sn(IV) to the divalent oxidation state. Electronic structure characterisation based on valence band XPS and DRS shows that there is a slight widening of the band gap upon Sn(IV)-grafting, but Sn(II) related states emerge at the top of the main valence band upon reduction at temperatures up to 350 °C, and this induces visible light absorption. Grafting of TiO2 with Sn(IV) increases the formation rate of •OH radicals on the surface of the material. Reduction of the Sn(IV)-grafted TiO2 to form surface Sn(II) brings about substantial increase of the photocatalytic efficiency for the methylene blue degradation under irradiation with λ  ≥ 320 nm compared with Sn(IV)-grafted and pure anatase TiO2. This observation is explained based on a surface hole trapping by the Sn(II)-related surface states which lie above the top of the main valence band and can therefore act as trapping sites for holes produced under photoexcitation.
Keywords: Photocatalysis; TiO2; SnO2; Dye degradation; Grafting; Surface doping; Temperature-programmed reduction; X-ray absorption spectroscopy; X-ray photoelectron spectroscopy; Surface charge trapping;

Alkaline metals modified Pt–H4SiW12O40/ZrO2 catalysts for the selective hydrogenolysis of glycerol to 1,3-propanediol by Shanhui Zhu; Xiaoqing Gao; Yulei Zhu; Yifeng Zhu; Xiaomin Xiang; Caixia Hu; Yongwang Li (60-67).
Catalytic hydrogenolysis of glycerol to value-added 1,3-propanediol (1,3-PDO) holds the potential to utilize the large surplus of crude glycerol from biodiesel industry. A series of alkaline metals (Li, K, Rb and Cs) modified Pt–H4SiW12O40/ZrO2 catalysts were prepared, characterized and evaluated for this reaction. The bulk and surface features of these catalysts were characterized by several techniques, including BET, CO-chemisorption, XRD, Raman, SEM-EDX, NH3-TPD and FTIR of adsorbed pyridine. Among them, Li exchanged H4SiW12O40 (HSiW) exhibited superior activity and maximum 1,3-PDO selectivity due to the enhanced Brønsted acid sites. This catalyst achieved 120 h long-term stability owing to the strong interaction of active components with ZrO2, remaining of unique Keggin structure as well as the enhanced water-tolerance. There is a linear relationship between 1,3-PDO yield and concentration of Brønsted acid sites, providing direct evidence that Brønsted acid sites are responsible for the selective formation of 1,3-PDO from glycerol hydrogenolysis.
Keywords: Glycerol; Hydrogenolysis; 1,3-Propanediol; Alkaline metals; Silicotungstic acid;

Optimization of electrospun TiO2/CuO composite nanofibers shows that TiO2/CuO composite nanofibers with 6 mol.% Cu, calcined at 450 °C for 45 min, exhibited the highest H2 generation from 10% (v/v) methanol aqueous solution. The significance of balance and synergy among the essential physicochemical properties such as morphology, porosity, specific surface area, degree of crystallinity, crystal size, as well as elemental states on the photocatalytic H2 generation of electrospun TiO2/CuO composite nanofibers was further revealed by means of varying the synthesis calcinations temperatures. Calcinations at temperature above and below 450 °C showed negative effect on the H2 generation. This was ascribed to the temperature effect on transformation of crystalline phase, crystal growth, mesoporosity formation, and Cu valence state which has thus adversely affected the synergy among the physicochemical properties governing the photocatalytic activity of TiO2/CuO composite nanofibers. Good stability with negligible Cu leaching and reusability were also attained with the composite nanofibers. This study serves as a significant advancement platform to designing and fabricating high efficient and stable TiO2/CuO composite nanofibers via facile electrospinning thus promoting its application potential as an economical photocatalyst for production of clean energy.
Keywords: Electrospinning; Hydrogen generation; Nanofibers; TiO2/CuO;

Ozonation of bezafibrate promoted by carbon materials by Alexandra Gonçalves; José J.M. Órfão; Manuel Fernando R. Pereira (82-91).
Two carbon materials (multi-walled carbon nanotubes, MWCNT, and activated carbon, AC) were investigated as ozonation catalysts for the mineralization of bezafibrate (BZF) in water. For comparative purposes, kinetic results obtained in the absence of catalyst (single ozonation) and adsorption experiments were also presented. Removal of BZF in the presence of MWCNT is mainly due to a catalytic process, contrarily to what occurs in the presence of activated carbon, which acts mainly as adsorbent. 3-[(4-chlorophenyl)formamido]propanoic acid (BBR), 4-chorobenzoic acid (pCBA) and 4-chloro-N-[2-(4-hydroxyphenyl)ethyl]benzamide (BBV) were detected as primary products of single and catalytic ozonation of BZF, whereas oxalic, pyruvic and oxamic acids were identified as refractory final oxidation products. The original chlorine of BZF is completely converted to chloride ion and part of nitrogen is converted to NH4 +, NO3 and NO2 . The presence of the radical scavenger tert-butanol during catalytic and single ozonation evidenced the participation of HO radicals in the oxidation process, especially in the mineralization of several intermediates. Microtox tests revealed that simultaneous use of ozone and AC originated lower acute toxicity, which may be due to the contribution of adsorption for the removal from the solution of BZF and its oxidation compounds. The time course of all detected compounds is studied and, as a result, the transformation pathway for the complete mineralization of BZF by single and catalytic ozonation in the presence of the selected carbon materials is also elucidated. Successive experimental runs of BZF degradation carried out with MWCNT show that the catalyst suffers some deactivation as a result of the introduction of oxygenated surface groups on the surface.
Keywords: Catalytic ozonation; Carbon materials; Bezafibrate; Reaction pathways; Toxicity;

This paper presents the removal of the antibiotic tetracycline (TeC) from water using electrochemical advanced oxidation processes (EAOPs); namely electrochemical oxidation (EO) and electro-Fenton (EF). The effect of different cathode materials (carbon-felt and stainless steel) on the direct/indirect electro-oxidation of tetracycline, and that of different anode materials (Ti/RuO2–IrO2, Pt and BDD) on both processes was systematically investigated for the first time. The EO process was found to be more efficient in using the carbon-felt cathode than the stainless steel cathode. The EO and the EF processes using BDD anode demonstrated superior oxidation/mineralization power. Almost total mineralization (TOC removal up to 98%) of 100 mg L−1 TeC solutions was achieved after 6 h treatment either by EO and/or EF treatment with BDD anode. The oxidative degradation of TeC followed pseudo-first-order-reaction kinetics in using all tested electrodes and anode/cathode configurations. Apparent rate constants of different anode/cathode configurations increased in the following sequence: Ti/RuO2–IrO2/stainless steel < Ti/RuO2–IrO2/carbon-felt < BDD/carbon-felt (EO) < BDD/carbon-felt (EF). The electrical energy consumed per gram of TOC removal was calculated for different electrode configurations to assess the cost effectiveness of the EO and the EF processes to mineralize TeC in water.
Keywords: Tetracycline; Electro-oxidation; Degradation kinetics; Rate constants; Mineralization;

The initial reaction rates on a per site basis for aqueous-phase hydrogenation (APH) of different oxygenated compounds: including acetaldehyde, propanal, acetone, xylose, furfural, and furfuryl alcohol and aqueous-phase hydrogenolysis of tetrahydrofurfuryl alcohol (THFA) and xylitol were measured over various alumina-supported monometallic catalysts (Pd, Pt, Ru, Rh, Ni, and Co) in a high-throughput reactor. These oxygenated compounds have the same functionality that is found in aqueous solutions derived from biomass including pyrolysis oils and aqueous hydrolysis solutions. The initial rate of APH of the different carbonyls groups was dependent on the functionality of the feed molecule and catalyst used. Ru was the most active metal for APH of acetaldehyde, propanal, acetone, and xylose. Pd was the most active metal for APH of furfural and furfuryl alcohol. Only Pt and Ni catalysts were able to produce 1,2-pentanediol and 1,5-pentanediol from aqueous-phase hydrogenolysis of THFA. Ru was active for conversion of THFA but only made coke. The initial activity for aqueous-phase hydrogenolysis of xylitol decreased in the order of Ru > Co > Pt > Ni ≥ Pd. The initial rates of APH of carbonyl groups (C=O bond) measured in this study decreased in the order: hydrogenation of acetone > hydrogenation of acetaldehyde and propanal > hydrogenation of xylose > hydrogenation of furfural. The initial rates of aqueous-phase hydrogenolysis of THFA and xylitol were much lower than the initial rate for APH of C=O and C=C bonds.
Keywords: Aqueous-phase hydrogenation; Aqueous-phase hydrogenolysis; Binding energy; Biomass conversion; Heterogeneous catalysts; High-throughput;

Three different methods of modification (impregnation, photodeposition and mechanical alloying) were used to obtain a series of novel Cu/TiO2 photocatalysts. Two Cu(II) salts: (Cu(NO3)2 and Cu(CH3COO)2) as well as metallic copper were applied as modifying agents. The influence of the modification procedure and copper precursor on the physico-chemical properties and photoactivity of the photocatalysts towards formation of useful hydrocarbons from acetic acid were especially investigated. Various gaseous products were identified during the photocatalytic process: CH4, CO2, C2H6, C3H8 and H2. The amounts of those compounds were strongly dependent on the photocatalyst type. Crucial features affecting the photoactivity of the obtained materials were the amount of Cu and phase composition of the samples. Nonetheless, most of the Cu/TiO2 photocatalysts revealed significantly improved activity in the photocatalytic generation of useful aliphatic hydrocarbons and hydrogen compared to the crude TiO2 or commercial TiO2 P25.
Keywords: Photocatalysis; Hydrocarbons; Hydrogen; Acetic acid; Cu/TiO2;

This study focuses on the evaluation of the catalyst activity and reutilization in the catalyzed hydrolysis of sodium borohydride (NaBH4). To date, few studies on reutilization are available in literature. In the present study, a facile method was used to obtain a highly efficient catalyst, Ru nanoparticles deposited on external surface of montmorillonite (Ru/MMT). Catalytic activity and reutilization were evaluated by analyzing the H2 generation rate from an alkaline NaBH4 solution. The catalytic activity of the as-prepared Ru/MMT was determined as a function of the catalyst amount, NaBH4 concentration, and temperature. By using the as-prepared Ru/MMT catalyst with a concentration of 1 wt% NaBH4, an average hydrogen generation rate as high as 28,500 ± 500 mL min−1  g(Ru)−1 is achieved at 25 °C. The kinetic study demonstrates that the hydrolysis reaction is first-order in terms of the catalyst concentration and zero-order in terms of the substrate concentration. The apparent activation energy of NaBH4 hydrolysis is 54.7 ± 1 kJ/mol, which is lower than most Ru-based catalysts reported in literatures. However, the catalytic activity of the reused catalyst dramatically decreased, with only 49% of the initial H2 generation rate remaining after 10 runs. The degradation mechanism of the Ru/MMT catalyst during cycling was investigated and discussed in detail. Before and after 10 reutilizations, the textural properties of the catalysts were characterized based on the nitrogen adsorption–desorption isotherms (obtained using Brunauer–Emmett–Teller analysis), the surface morphology (obtained using field-emission scanning electron microscopy, and transmission electron microscopy), and on the surface composition (obtained using energy-dispersive X-ray spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy). The deterioration of the reused catalyst seemed to be caused by the aggregation and partial fall-off of the Ru nanoparticles deposited on the MMT external surface.
Keywords: Hydrogen generation; Ruthenium nanoparticles; Montmorillonite; Sodium borohydride;

Three kinds of mesoporous silica (MCM-41, FSM-16 and SBA-15) of different pore size and texture were synthesized by templating method. Co-B nanoparticle catalysts were supported over these mesoporous silica by impregnation–reduction method in order to study the effect of support pore structure on the catalytic properties in H2 production by hydrolysis of Ammonia Borane (AB). TEM and N2 adsorption–desorption isotherm results clearly revealed that size, dispersion degree, and location of Co-B particle is affected by the pore texturing of the support. It also showed that the catalyst particle acquires directly the size of the support pores only for SBA-15 whereas there is no correlation of the particle size and pore size for MCM-41 and FSM-16. Co-B supported over SBA-15 silica was found to be the most active catalyst as inferred from the observed hydrogen generation rates in the hydrolysis reaction compared to that produced by MCM-41 and FSM-16 supported catalyst. Higher activity for SBA-15 support is mainly attributed to the geometrical confinement of Co-B particles within the pores which creates smaller Co-B particles (6 nm) with uniform size distribution and higher degree of dispersion as compared to MCM-41 and FSM-16 support where the Co-B particles lie on the external surface with broad size distribution. Open and interconnected pores of SBA-15 can also provide easy passage for reactant and product during the course of reaction. The Co-B particles supported in the interconnected pores of SBA-15 produce lower effective activation energy barrier related to the hydrolysis process of AB than that established with MCM-41 and FSM-16 supported catalyst. Most importantly, the thicker pore walls of SBA-15 assist in avoiding the agglomeration of Co-B particles and even provide high stability at elevated temperatures (873 K) at which unsupported Co-B catalyst gets completely destroyed.
Keywords: Cobalt Boride; Mesoporous silica; Ammonia Borane; Hydrogen generation; Nanoparticles;

TiO2–RuO2 electrocatalyst supports exhibit exceptional electrochemical stability by Chih-Ping Lo; Guanxiong Wang; Amod Kumar; Vijay Ramani (133-140).
Titanium dioxide–ruthenium dioxide (TiO2–RuO2; TRO) powders were prepared in both the hydrous and anhydrous form using a wet chemical synthesis procedure. These materials were characterized by XRD, TEM, and BET. Their electrical conductivity and electrochemical properties such as stability under potential cycling, electrochemical surface area (ECSA), electrocatalytic activity, and fuel cell performance were measured. Anhydrous TiO2–RuO2 (TRO-a) demonstrated exceptional electrochemical stability compared to baseline Vulcan XC-72R carbon when tested using an aggressive accelerated stability test (AST) protocol. The various TRO powders were catalyzed by depositing platinum nanoparticles by an impregnation–reduction method to yield Pt/TRO electrocatalysts. The Pt/TRO-a electrocatalysts had a mass activity of 54 mA m g Pt − 1 and a specific activity of 284 μ A c m Pt − 2 for the oxygen reduction reaction. Fuel cell polarization data was obtained on membrane electrode assemblies (MEAs) prepared with Pt/TRO and baseline Pt/C electrocatalysts showed that the Pt-TRO-based MEAs exhibited very good performance. The performance obtained was below the Pt/C benchmark, however, further improvements in performance are expected with greater optimization of the Pt particle size and electrode structure.
Keywords: Electrocatalyst support; Polymer electrolyte fuel cell; Carbon corrosion; Mixed metal oxides;

Upconverter Er3+ doped β-Bi2O3 nanosheets with selectively exposed reactive {0 0 1} facets as the main external surfaces were fabricated by a novel and simple approach for the first time. The products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The introduction of 0.8 wt% Er3+ significantly improved the photocatalytic activities of the β-Bi2O3. The enhanced photocatalytic activity of β-Bi2O3 nanosheets can be attributed to the exposed reactive {0 0 1} facets and the dopant Er3+ which can transform visible light into ultraviolet light. Both the acetic acid and alcohol contributed to the formation of nanosheets. This synthetic approach exhibited good versatility in fabricating other porous materials.
Keywords: Upconversion; β-Bi2O3; Nanosheets; Facets; Photocatalysis;

This study is dedicated to the development of thermally stable LaCo1−x Fe x O3 perovskite based catalysts for the decomposition of N2O at medium and high temperature, in representative compositions of exhaust gas from ammonia burner in nitric acid plants. In these specific conditions, N2O coexists with a large amount of NO x . Up to now, lab-scale investigations were usually restricted to low amount of NO x and water while both can originate drastic changes in the catalytic performances related to activation/deactivation phenomena. The impact of NO concentration in terms of activity and stability has been discussed at moderate temperature and correlated to extensive bulk and surface characterization from different techniques (X-ray diffraction, Raman spectroscopy, XPS, Mössbauer spectroscopy, Tof-SIMS). It was found that the catalytic performances in terms of activity and stability depend on the relative concentration of Co with the best performances recorded on LaCo0.2Fe0.8O3.
Keywords: N2O decomposition; LaCo1−x Fe x O3; Nitric acid plants; XPS; Tof-SIMS;

Red phosphor/g-C3N4 heterojunction with enhanced photocatalytic activities for solar fuels production by Yu-Peng Yuan; Shao-Wen Cao; Yu-Sen Liao; Li-Sha Yin; Can Xue (164-168).
We report a composite photocatalyst by coupling red phosphor (r-P) and graphitic carbon nitride (g-C3N4). The introduction of g-C3N4 onto r-P surface led to considerable improvement on the photocatalytic activity for H2 production and CO2 conversion into valuable hydrocarbon fuel (CH4) in the presence of water vapor. The enhancement could be attributed to the effective separation of photogenerated electrons and holes across the r-P/g-C3N4 heterojunction. Owing to the advantages of non-toxicity, low cost and abundance in nature, this active heterostructural r-P/g-C3N4 photocatalyst would have great potential for efficient solar fuels production.
Keywords: Photocatalysis; H2 production; CO2 conversion; Heterostructure; Carbon nitride;

Photocatalysis on yeast cells: Toward targets and mechanisms by Sana Thabet; Michele Weiss-Gayet; Frederic Dappozze; Pascale Cotton; Chantal Guillard (169-178).
We have investigated the antimicrobial effects of photocatalysis on yeast (Saccharomyces cerevisiae), an essential eukaryotic unicellular model of living cells. As compared to UV-A irradiation, photocatalytic inactivation kinetics revealed a faster microbial cell cultivability inactivation. Optimal experimental conditions required a semiconductor concentration of 0.1 g/l with 3.8 mW/cm2 UV-A radiance intensity. Cell viability was monitored by plasma membrane permeability and loss of enzymatic activity using double fluorescent dye staining and flow cytometry. Plasma membrane permeability and enzymatic activity were almost simultaneously targeted. Esterase enzymatic activity decreased progressively, suggesting that the intracellular protein pool was sequentially damaged by the treatment. In yeast cells, the presence of a thick cell wall did not prevent the plasma membrane from being a prime photocatalytic target. Monitoring of chemical byproducts confirmed the loss of membrane integrity. A massive loss of potassium, major cation in yeast, that was released first and in large amounts, remained constant beyond 5 h of treatment and was correlated to the number of damaged membrane-cells. On the contrary, ammonium ions concentration gradually increased, suggesting their generation through the photocatalytic process, probably via amino acid and protein degradation. Oxamic and oxalic acid that could also arise from damages to amino acids were detected. Amino acid analysis revealed a main component, increasing over time, corresponding to glycine. Glycine could be produced via the transformation of other amino acids, released from cell wall, membrane and intracellular proteins.
Keywords: Photocatalysis; Yeast; Viability; Cytometry; Byproducts;

A BiOCl film synthesis from Bi2O3 film and its UV and visible light photocatalytic activity by Kan Li; Yanping Tang; Yunlan Xu; Yalin Wang; Yuning Huo; Hexing Li; Jinping Jia (179-188).
Display OmittedA facile method was proposed to prepare BiOCl film on a Ti substrate using Bi2O3 film reacting with Cl in acidic condition. The as-prepared BiOCl film was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectra (UV–vis DRS). The BiOCl film owned a hierarchical nanostructure and a nucleation–dissolution–recrystallization growth mechanism was observed according to the FESEM at different reaction time. The photocatalytic activity of the BiOCl film was investigated by degradation of 50 mL 5 mg L−1 Rhodamine B (RB) solution under UV and visible light, strong adsorption capacity (more than 10% RB adsorbed on the surface before light on) and excellent photocatalytic performance were observed. 100% and more than 90% color removal efficiencies were achieved under UV and visible light in 120 min and 180 min, better than that obtained by TiO2 film, especially under visible light. Meanwhile more than 90% and 70% TOC could also be removed under UV and visible light in the same condition. The analysis of RB photocatalytic degradation mechanisms suggested that the prepared BiOCl film exhibited high activity for direct semiconductor photoexcitation RB degradation under UV light, while it also possessed superior activity for indirect RB photosensitization degradation under visible light. The prepared BiOCl film also exhibited excellent photocatalytic activity for other dye solutions and possessed the potential application in wastewater treatment.
Keywords: BiOCl film; Bi2O3 film; Photocatalysis; Rhodamine B; Dye sensitization;

Fabrication of wire mesh-supported ZnO photocatalysts protected against photocorrosion by Tan T. Vu; Laura del Río; Teresa Valdés-Solís; Gregorio Marbán (189-198).
In this work a catalyst consisting of high surface area ZnO nanoflowers supported on a stainless steel wire mesh was synthesized by hydrothermal growth, and tested for the catalytic photodegradation of methylene blue under UV irradiation. The stability of the photocatalyst was evaluated by assessing the evolution over several reaction stages of catalytic activity and ZnO loss. The initial high activity of this catalyst was followed by a significant decrease after successive reaction cycles due to the dissolution of the ZnO as a consequence of photocorrosion. Impregnation of the catalyst with small amounts of silver enhanced its initial catalytic activity, but failed to produce the photostabilisation of the catalyst that has been reported in the literature. Dip-coating the photocatalyst (either undoped or silver doped) with a diluted polysiloxane solution produced a transparent polysiloxane coating that completely prevented photocorrosion and allowed a stable catalytic activity to be maintained over 8 reaction stages at values higher than those obtained with uncoated catalysts after just 2–3 reactions stages with negligible loss of ZnO.
Keywords: Methylene blue; Photocatalysis; Photocorrosion; ZnO; Stainless steel wire mesh;

Enhanced performance in catalytic combustion of toluene over mesoporous Beta zeolite-supported platinum catalyst by Chunyu Chen; Jie Zhu; Fang Chen; Xiangju Meng; Xiaoming Zheng; Xionghou Gao; Feng-Shou Xiao (199-205).
Mesoporous Beta zeolite-supported Pt catalyst (Pt–R/Beta-H) exhibits much higher catalytic activities and longer catalyst life as well as lower apparent activation energy in combustion of toluene than conventional Beta zeolite-supported Pt catalyst (Pt–R/Beta). This phenomenon could be strongly related to the presence of mesoporosity in Beta-H zeolite, which is favorable for mass transfer and dispersion of Pt particles.Removal of volatile organic compounds (VOCs) has recently been attracted much attention, and catalytic combustion is one of good methods for solving this problem. In this research, we show a successful preparation of mesoporous Beta zeolite-supported Pt catalyst (Pt–R/Beta-H) and its superior performance in the catalytic combustion of toluene. N2 sorption isotherms show that the mesopore volume of Pt–R/Beta-H reaches 0.18 cm3/g, and TEM images exhibit that the Pt particles exist in both micropores and mesopores of the sample. Interestingly, the Pt particles on Pt–R/Beta-H have higher dispersion than the Pt particles on conventional Beta zeolite (Pt–R/Beta). XPS spectra also reveal that Pt–R/Beta-H has higher Pt0/Pt2+ ratio than Pt–R/Beta. Very importantly, Pt–R/Beta-H exhibits much higher catalytic activities and longer catalyst life as well as lower apparent activation energy in the catalytic combustion of toluene than Pt–R/Beta. The extraordinary performance in the catalytic combustion of toluene over Pt–R/Beta-H catalyst is of great importance for obtaining clean environment and enhancing human health.
Keywords: Mesoporous Beta zeolite; Supported platinum catalyst; Catalytic combustion; Volatile organic compounds (VOCs); Toluene;

Novel Pt catalyst on ruthenium doped TiO2 support for oxygen reduction reaction by N.R. Elezović; B.M. Babić; V.R. Radmilovic; Lj.M. Vračar; N.V. Krstajić (206-212).
Ruthenium doped titanium oxide support was synthesized. The support was characterized by BET (Brunauer, Emmett, Teller) and X-ray diffraction techniques (XRD). Determined specific surface area was 41 m2  g−1. XRD revealed presence mainly TiO2 anatase phase and some peaks belonging to rutile phase. No Ru compounds have been detected.Platinum based catalyst on this support was prepared by borohydride reduction method. The catalyst was characterized by scanning transmission electron microscopy (STEM, HAADF) and electron energy loss spectroscopy (EELS). Homogenous Pt particle distribution over the support, with average Pt nanoparticle diameter of 3 nm was found. This novel catalyst was tested for oxygen reduction in acid solution. It exhibited remarkable higher catalytic activity in comparison with Pt/C, as well as with Pt nanocatalysts at titanium oxide based supports, reported in literature.
Keywords: Titanium oxide based support; Pt/RuTiO2 catalyst; Oxygen reduction reaction; Acid solution;

Microwave-assisted synthesis of (S)Fe/TiO2 systems: Effects of synthesis conditions and dopant concentration on photoactivity by K. Esquivel; R. Nava; A. Zamudio-Méndez; M. Vega González; O.E. Jaime-Acuña; L. Escobar-Alarcón; J.M. Peralta-Hernández; B. Pawelec; J.L.G. Fierro (213-224).
TiO2 and Fe(S)-doped TiO2 photocatalysts have been synthetized by a microwave-assisted method and deeply characterized by means of several techniques (N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), TEM, high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), temperature-programmed desorption of NH3 (TPD-NH3) and UV–vis diffuse reflectance, Raman and XPS spectroscopic techniques). The synthetized samples were tested in the photodegradation of methyl red dye under UV irradiation at room temperature. Depending on the temperature and duration of the microwave synthesis, some changes in the textural and crystalline structure of the titanium dioxide were observed which influenced on the photocatalytic activity. The best photocatalyst found in this study was the one doped with S (0.1 wt.%) prepared by microwave-assisted synthesis at 215 °C for 60 min and calcined at 550 °C. The enhancement of color removal over this sample (49% of color removal) was associated to the formation of anatase phase and the enhancement of the sample acidity with respect to undoped TiO2 sample. A volcano-shaped curve was obtained for methyl red degradation against TiO2 crystal size. Catalyst calcination at 700 °C led to a drastic drop in activity due to formation of large TiO2 crystals of rutile phase, as confirmed by XRD.
Keywords: Microwave photocatalysis; Fe/TiO2; S/TiO2; X-ray diffraction; Photodegradation; Methyl red;

Comparative studies of photocatalytic and photoelectrocatalytic inactivation of E. coli in presence of halides by Guiying Li; Xiaolu Liu; Haimin Zhang; Po-Keung Wong; Taicheng An; Huijun Zhao (225-232).
Display OmittedThe bactericidal performances of photocatalytic and photoelectrocatalytic systems in absence and presence of low concentrations of X (X = Br, Cl) were quantitatively studied and meaningfully compared under identical experimental conditions. The photoelectrocatalytic system in presence of low concentration of Br was found to be the most effective bactericidal system amongst all systems investigated, capable of inactivating 100% of 9.0 x 106  CFU/mL Escherichia coli within 1.57 s. The photocatalytically generated active oxygen species are important attributes to the bactericidal performance of all cases investigated except the case of photoelectrocatalytic inactivation in presence of Br for which the bactericidal performance is dominated by the photoelectrocatalytically generated Br• /Br2. The results revealed that in a photocatalysis or photoelectrocatalysis bactericidal process, X acts as an electron mediator that does not change its chemical form before and after bactericidal process, and a high bactericidal performance photoelectrocatalytic system can be established with Br concentration as low as 50 μM. The findings of this work confirm that new forms of effective bactericides such as X• /X2 can be generated in situ via a photocatalysis or photoelectrocatalysis process for high performance bactericidal system.Keywords: Biohazards; Disinfection; Br• /Br2; Photocatalysis; Photoelectrocatalysis

Lithium ion-inserted TiO2 nanotube array photoelectrocatalysts by Unseock Kang; Hyunwoong Park (233-240).
A quick electrochemical Li ion insertion into TiO2 nanotube arrays (TNTs) markedly enhances the photoelectrochemical and photoelectrocatalytic performance. Potential pulses (−1.0 ∼ −1.7 VSCE for 1–11 s in 1 M LiClO4) to pre-annealed TNTs effectively insert Li ions (pre-annealed Li-TNTs) into the mouth/wall and bottom TiO2 depending on the insertion condition. Pre-annealed Li-TNTs prepared under an optimal Li ion insertion condition (−1.4 VSCE for 3 s) exhibit ∼70%-enhanced photocurrent generation, ∼2.5 fold-higher incident photon-to-current efficiency, and an improved photoelectrocatalytic activity for the degradation of phenolic compounds in 1 M KOH electrolyte. A change in photoluminescence (PL) emission spectra and decrease in charge transfer resistance by Li ion insertion suggest that the inserted Li ions play a role in inhibiting charge recombination by compensating for the photogenerated Ti3+ charges (Li+-Ti3+-OH). However, as KOH concentration is diluted such enhanced Li+ effects gradually vanish primarily due to liberation of reversibly inserted Li ions. To insert Li ions irreversibly, the potential pulses were applied to non-annealed TNTs followed by annealing (post-annealed Li-TNTs). Comparison between pre-annealed and post-annealed Li-TNTs in circum-neutral pH (0.1 M Na2SO4 at pH ∼6) indicates that the former exhibits a similar performance to bare TNTs (absence of Li ion effect), whereas the latter shows a superior performance with ca. 2.5-fold higher photoelectrochemical and photoelectrocatalytic activities. Detailed surface analyses (XPS, XRD, PL, SEM, ICP-MS, etc.) and Li+-induced reaction mechanism were discussed.
Keywords: Photoelectrochemical; Photoelectrocatalytic; Charge separation; IPCE; Solar fuels;

This work aims at revealing the role of pristine layered double hydroxide (LDH) materials in the elimination of organic pollutants from solution. Typical LDH samples, ZnCr- and MgAl-LDHs (with Zn2+/Cr3+ or Mg2+/Al3+ molar ratio 2), are prepared and used for the removal of methylene blue (MB), methyl orange (MO), and formaldehyde. The systematic investigations of structural characterization and periodic density functional theory (DFT) calculation of the LDH samples demonstrate that: (1) no electron–hole pairs could be generated for MgAl-LDHs under the irradiation of visible light due to the large calculated gap energy above 5.0 eV. (2) ZnCr-LDHs are sensitive to the irradiation of visible light with the calculated gap energy between 2.0 and 3.0 eV, but the rapid charge recombination and low efficiency in electron/hole separation would suggest that photocatalytic activity of ZnCr-LDHs would be greatly limited. In the experimental work, ZnCr- and MgAl-LDHs show no photocatalytic activity for the removal of formaldehyde under the visible light. The disposal of the organic dyes molecules in the solution would be caused by the photoassisted degradation and surface adsorption effect rather than the photocatalysis impact for both LDH samples. This is confirmed by the elimination tests that carry out in the dark condition with the similar procedure under visible light irradiation. Moreover, the two types of LDH samples exhibit the different adsorption capability for the MB and MO molecules due to the different colloidal properties of the LDH samples, which is revealed by Zeta potential measurement. The above finding that elimination of organic dyes from solution by the pristine LDH samples through photoassisted degradation and adsorption processes would be important for the rational design and use of clay-like materials for the treatment of sewage containing toxic compounds.
Keywords: Layered double hydroxides; Organic pollutants; Photoassisted; Density functional theory;

An interesting NiO@Au ensemble was identified, and such ensemble induces a high surface concentration of Ni2O3–Au+ active sites, which govern the high low-temperature activity. The Ni2O3 specimens not only promote the formation of Au+ and stabilize them, but also provide active O species to Au+, where alcohols are oxidized.Microfirous-structured Au/Ni-fiber catalysts prepared by Au galvanic deposition method are active and selective for the gas-phase oxidation of alcohols. The nature of their excellent low-temperature activity is explored especially by means of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES). An interesting NiO@Au ensemble nanostructure (i.e., partial coverage of Au particles with NiO segments) was clearly identified, which is governing the high low-temperature activity. XPS and XANES studies indicate that the NiO@Au ensembles provide a unique synergistic effect, inducing a high surface concentration of Ni2O3–Au+ hybrid active sites. The Ni2O3 specimens not only promote the formation of Au+ cations and stabilize them but also serve as active O species reservoir. It is also proposed that O2 is activated on the oxygen vacancy of Ni2O3 and then the adsorbed O atoms spill over onto Au+ cations to react with alcohols.
Keywords: Gold catalyst; Alcohol oxidation; Nanostructure; Active site; Galvanic reaction;

Study of Ru―Ni/TiO2 catalysts for selective CO methanation by Shohei Tada; Ryuji Kikuchi; Atsushi Takagaki; Takashi Sugawara; S.Ted Oyama; Kohei Urasaki; Shigeo Satokawa (258-264).
The removal of CO from reformate streams by selective CO methanation was investigated over TiO2 supported Ru―Ni bimetallic and monometallic catalysts. The combination of Ru and Ni enhanced CO methanation at low temperatures. The introduction of Ni into Ru/TiO2 decreased the CO2 conversion rate at 260 °C from 10 to 7.3 μmol min−1  gcat −1. The use of Ru and Ni, thus, expands the temperature range of selective CO methanation. Transmission electron microscopy and temperature programmed reduction by H2 confirmed that Ru species were in close proximity to Ni species on Ru―Ni/TiO2, indicating a decrease in direct contact between Ru and TiO2. Fourier transform infrared spectroscopy techniques revealed that the decomposition of the formate species, formed during CO2 methanation, is slow over Ru―Ni/TiO2, in contrast to Ru/TiO2.
Keywords: Ruthenium; Nickel; Titania; Selective CO methanation; CO removal process;

Isocyanate formation and reactivity on a Ba-based LNT catalyst studied by DRIFTS by Yaying Ji; Todd. J. Toops; Mark Crocker (265-275).
Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS), coupled with the use of isotopically-labeled reactants (15N18O and 13CO), were employed to study the formation of isocyanate species during NOx reduction with CO, as well as isocyanate reactivity toward typical exhaust gas components. DRIFTS demonstrated that both Ba–NCO and Al–NCO were simultaneously formed during NOx reduction by CO under dry lean-rich cycling conditions. The Ba–NCO band was more intense than that of Al–NCO, and became comparatively stronger at high temperatures. During rich purging at 300 and 400 °C, a near linear relationship was found between the increase in Ba–NCO band intensity and the decrease in Ba–NO3 band intensity, suggesting that Ba–NCO is directly derived from the reaction of Ba nitrate with CO. Both temperature-programmed surface reaction (TPSR) and isothermal reaction modes (ISR) were utilized to study the reactivity of isocyanate species under lean conditions. Simultaneous DRIFTS and mass spectrometric measurements during TPSR indicated that isocyanate reaction with H2O, O2, NO and NO/O2 took place almost immediately the temperature was raised above 100 °C, and that all NCO species were removed below 300 °C. The evolution of the NCO IR bands during ISR at 350 °C demonstrated that the kinetics of NCO hydrolysis are fast, although a delay in N2 formation indicated that N2 is not the initial product of the reaction. In contrast, immediate N2 evolution was observed during NCO reaction with O2 and with NO + O2. Overall, it can be inferred that under dry cycling conditions with CO as the sole reductant, N2 is mainly generated via NCO reaction with NO/O2 after the switch to lean conditions, rather than being evolved during the rich phase. However, in the presence of water, isocyanate undergoes rapid hydrolysis in the rich phase, N2 generation proceeding via NH3.
Keywords: NOx reduction; Isocyanate; Ba nitrate; Carbon monoxide; Hydrolysis; Isotopic labeling;

A series of novel catalyst complexes for the selective catalytic reduction of NO x to NH3 were prepared by doping CeO2–WO3/TiO2 with different loadings of SiO2. The complexes were synthesized by impregnating P25 with colloidal silica to form a complex support. The NO x conversion values and the calculated reactive rate constants confirm that the presence of SiO2 increased the reaction activity at low temperatures. This increase in activity may be directly correlated to the increase in the presence of unstable Brønsted acid sites as well as active nitrite, monodentate nitrates and adsorbed NO2, as opposed to an increase in the BET surface area and a change in the redox properties. Furthermore, the surface bridging and bidentate nitrate species that originated from the adsorption of NO x were quite stable and inactive below 300 °C. Finally, both Ti(1)Si(0) and Ti(3)Si(1) catalysts were employed to study the reaction mechanism by in situ IR spectroscopy at 200 °C. The two catalysts exhibited similar reaction mechanisms, wherein the Lewis and Brønsted acid sites reacted with active nitrite, monodentate nitrates and adsorbed NO2 species.
Keywords: DeNO x ; Selective catalytic reduction; SiO2; CeO2; WO3;

This study demonstrates a facile approach based on microwave irradiation for the preparation of rutile/titania-nanotube composites that exhibit highly efficiency in visible light induced photocatalysis. The obtained nanocomposites were characterized using XRD, Raman, FESEM, TEM, N2 physisorption isotherms at 77 K and UV–vis DRS techniques. The results show that the nanocomposites exhibit multilayer-wall morphologies with open-ended cylindrical structures. The presence of the rutile phase in the titania nanotubes enhanced the light-harvesting efficiency in photocatalytic reactions. By H2-thermal treatment, the optical absorption of the nanocomposite extends to the visible light region up to 600 nm. It is believed that thermal-treatment gives rise to create active surface oxygen vacancies, which are responsible for visible light absorption and the promotion of electrons from the localized states to the conduction band. The catalytic results revealed that the nanocomposites exhibited higher photocatalytic activities toward the decomposition of nitric oxide and the degradation of methylene blue compared with commercial P25 TiO2.
Keywords: Rutile/titania-nanotube; Microwave synthesis; Photocatalysis; NO decomposition; In situ EPR;

A series of V/CeO2, V/TiO2, V/Al2O3, V/ZrO2, V/CeO2–ZrO2, V/TiO2–Al2O3, and V/CeO2–Al2O3 metal oxide nanoparticles were synthesized by a one-step rapid FSP (flame spray pyrolysis) synthesis technique. Benefiting from the short residence time and high quenching rate during the single-step flame spray process, V4+, V3+ ions are successfully incorporated into the crystal lattice of various metal oxide supports. Our XRD, BET studies reveal that the V doping into Al2O3, Al2O3–TiO2, and CeO2–Al2O3 favors the formation of highly dispersed surface vanadia nanoparticles (5.8–9.4 nm), whereas, the V doping into ZrO2, CeO2–ZrO2 and CeO2 led to the primary particle size (19–45.5 nm, formation of bulk particles) growth and thus inhibition in the catalytic activity. It is remarkable to note that the average particle size (nm) of vanadia in our flame-made catalysts has direct relation with the SCR activity. As can be envisaged from XPS spectra, as-synthesized V/ZrO2 sample primarily consists of V5+ species due to the formation of ZrV2O7 solid solution as a result of zirconia migration into the V2O5 crystallites. Our XPS results imply that the formation of surface V2O3 species is improved enormously by the addition of Al2O3 (V3+/V n+  = 0.36, 0.38, and 0.41 for V/TiO2–Al2O3, V/Al2O3, V/CeO2–Al2O3, respectively), whereas, the addition of TiO2 led to the formation of surface VO2 species (V4+/V5+  = 0.88, 1.57 for V/TiO2, V/TiO2–AlO3, respectively). Among all the catalysts, high surface (V3+  + V4+)/V n+, and V4+/V n+ concentrations were observed for the V/TiO2–Al2O3, V/Al2O3, V/CeO2–Al2O3, respectively. It is highly remarkable to note that the SCR performance of all the as-prepared catalysts is indeed correlated with the surface (V3+  + V4+)/V n+, and V4+/V5+ concentrations. The reduction (H2-TPR) profiles reveal that the vanadium oxide reduction peak has shifted to much lower temperatures in Al-modified catalysts, indicating high reduction potential of the high-coverage VO x species. This is primarily due to the penetration of the active component into the pores of the support during the flame spray pyrolysis step itself, which in turn, results in a high dispersion of the active component on the support. Clearly, the close proximity of the support to these sites will mean that the support exerts some influence on the behavior of the oxygen species attached to the vanadium. The catalytic performance of various V/M′ (M′ = Ce, Al, Ti, Zr, Ce–Zr, Ti–Al, and Ce–Al) flame-made catalysts (with consistent V content V/M′ = 0.17) was studied for the low-temperature SCR reaction at a range of temperatures (140–360 °C) at gas hourly space velocity (GHSV) = 24,000 h−1. The intrinsic activity of V/Ti–Al, V/Al, V/Ce–Al catalysts with V/M′ = 0.17 atomic ratio measured under differential reaction conditions, was found to be highly active, selective toward nitrogen and broadening the temperature window for optimal operation of this reaction.
Keywords: Low-temperature NH3-SCR; Vanadia (VO x ); Nitric oxide (NO); Flame spray pyrolysis;

Erbium doped TiO2–Bi2WO6 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Rhodamine B. From the structural and morphological characterization it has been stated that the presence of Er3+ induces a progressive russelite cell contraction due to its incorporation in the Bi2WO6 lattice in substitutional sites. The best photocatalytic performance was attained for the samples with 1 at% of Er. From the study of the photocatalytic activity under different irradiation conditions it can be inferred that Er3+ presence induces a significant improvement of the photoactivity in the UV range. The evolution of band-gap values seems to be similarly related with the reaction rate progression. Thus, the higher band-gap values in lower Er doped systems would be the cause of a better electron hole separation under UV irradiation.
Keywords: Erbium; TiO2; Bi2WO6; Photocatalysis; Solar-like;

Sesame-biscuit-like Bi2O2CO3/Bi2MoO6 nanoplatelets with adjustable content of Bi2O2CO3 were successfully prepared by a facile anion exchange method under hydrothermal treatment. The heterojuncted Bi2O2CO3/Bi2MoO6 nanoplatelets exhibited a 64-fold faster rate than the single Bi2MoO6 nanoparticles toward photocatalytic degradation of RhB.Heterostructured sesame-biscuit-like Bi2O2CO3/Bi2MoO6 nanocomposites were successfully prepared via a facile anion exchange approach under hydrothermal process with the graphitic carbon nitride (g-C3N4) as the precursor of carbonate anion. The Bi2O2CO3/Bi2MoO6 nanocomposites are based on ca. 30–45 nm thick single-crystal Bi2MoO6 nanoplatelets embedded with homogeneously dispersed Bi2O2CO3 nanoparticles (less than 10 nm). The intimate interfacial contact between the Bi2O2CO3 nanoparticles and the Bi2MoO6 nanoplatelets endows the nanocomposite catalysts with high visible light photocatalytic activity for the degradation of rhodamine B. The photocatalyst prepared with 11 wt% g-C3N4 as the precursor shows the highest activity, which can degrade 99% rhodamine B in 30 min. The degradation rate of the Bi2O2CO3/Bi2MoO6 photocatalyst is more than 64 times faster than that of using bare Bi2MoO6 under visible light irradiation. The dramatically enhanced photocatalytic activity of the Bi2O2CO3/Bi2MoO6 photocatalysts can be attributed to the large heterojunction interface, intrinsically layered structure, two-dimensional morphology and effective separation of the photoinduced carriers at the interfaces and in the semiconductors. In addition, the Bi2O2CO3/Bi2MoO6 catalyst is highly stable during the reaction and can be used repeatedly. These features suggest the current heterostructured photocatalysts can be applied in environmental remediation and waste water treatment. This method may usher a new phase for the synthesis of novel and highly efficient Bi2O2CO3-based heterostructures for light-harvesting and energy conversion applications.
Keywords: Heterostructure; Bi2O2CO3; Bi2MoO6; Hydrothermal synthesis; Anion exchange; Photocatalysis;

PMMA-templating generation and high catalytic performance of chain-like ordered macroporous LaMnO3 supported gold nanocatalysts for the oxidation of carbon monoxide and toluene by Yuxi Liu; Hongxing Dai; Jiguang Deng; Lei Zhang; Baozu Gao; Yuan Wang; Xinwei Li; Shaohua Xie; Guangsheng Guo (317-326).
Rhombohedrally crystallized chain-like LaMnO3 and its supported gold (xAu/LaMnO3; x  = 1.4, 3.1, and 4.9 wt%) catalysts have been prepared using the poly(ethylene glycol)-assisted polymethyl methacrylate-templating and gas bubble-assisted polyvinyl alcohol-protected reduction methods, respectively. It is shown that there were good correlations of surface adsorbed oxygen species concentration and low-temperature reducibility with catalytic activity of the samples for the oxidation of CO and toluene. Among the LaMnO3 and xAu/LaMnO3 samples, 4.9Au/LaMnO3 performed the best, giving the T 50% and T 90% of 61 and 91 °C for CO oxidation, and of 201 and 226 °C for toluene combustion, respectively. The apparent activation energies (29–50 and 47–62 kJ/mol) of the chain-like LaMnO3 and xAu/LaMnO3 samples were much smaller than those (63 and 97 kJ/mol) of the bulk LaMnO3 sample for the oxidation of CO and toluene, respectively. We believe that the higher surface area and oxygen adspecies concentration and better low-temperature reducibility as well as the strong interaction between Au nanoparticles and chain-like LaMnO3 support might account for the high catalytic performance of 4.9Au/LaMnO3.
Keywords: Polymethyl methacrylate-templating strategy; Chain-like perovskite-type oxide; Lanthanum manganite supported Au catalyst; CO oxidation; Toluene combustion;

The properties of a series of negatively-charged phosphorus (P)-doped titanium(IV) oxide (TiO2) particles were investigated for their dependence on P concentration. XRD peak broadening demonstrated that the crystallite sizes of the P-doped TiO2 particles decreased with increasing P concentration, suggesting that P atom dopants inhibit crystalline growth. The P-doped TiO2 nanoparticles exhibited a pale yellow color. The UV–vis diffuse reflection spectra of the P-doped TiO2 nanoparticles demonstrated a continuous and tailing absorption in the visible region. The broad absorption band in the range of 500–600 nm increased with increasing P content, presumably due to an increase in the density of oxygen vacancies. However, the increase in the density of the oxygen vacancies did not correspond to the change of phenol degradation rate under visible-light irradiation. The results suggest that the oxygen vacancies in P-doped TiO2 are inactive to visible light.
Keywords: Titania; Phosphorus; Photocatalysis; Phosphorus-doped titania; Phosphide;

Low-temperature water-gas shift on Pt/Ce1−x La x O2−δ : Effect of Ce/La ratio by Klito C. Petallidou; Angelos M. Efstathiou (333-347).
Display OmittedPt nanoparticles (1.0–1.4 nm size) supported on Ce1−x La x O2−δ (x  = 0.0, 0.2, 05, 0.8 and 1.0) carriers, the latter prepared by the citrate sol–gel method, were tested toward the water-gas shift (WGS) reaction in the 200–400 °C range. A deep insight into the effect of Ce/La atom ratio of support chemical composition on the catalytic performance (CO conversion vs. temperature and stability) and kinetic rates of Pt-loaded catalysts was realized after employing HAADF/STEM, in situ Raman and DRIFT spectroscopies under different gas atmospheres, temperature-programmed surface reaction (TPSR) in He and O2/He gas atmospheres following WGS reaction, CO-TPD, in situ UV–vis/DRS, oxygen storage capacity measurements, and transient 18O-isotopic exchange studies followed by WGS reaction. It was found that doping of ceria with 20 at.% La3+ has increased significantly the catalytic activity of 0.5 wt% Pt/Ce0.8La0.2O2−δ solid in the 250–350 °C range, whereas addition of 50–80 at.% La3+ in ceria caused a negative effect on the CO conversion with respect to pure ceria. It was found that the Ce/La atom ratio in Ce1−x La x O2−δ influences the catalytic site reactivity (k) along the Pt-support interface. The optimum La3+-dopant concentration of 20 at.% (Ce/La = 4/1) used in Pt/Ce0.8La0.2O2 compared to the worst one of 80 at.% (Pt/Ce0.2La0.8O2−δ , Ce/La = 1/4) correlates with (i) the higher specific kinetic rate per length of Pt-support interface (μmol CO cm−1  s−1), (ii) the higher concentration of oxygen vacant sites, (iii) the lower amount (μmol/g−1) of “carbon” accumulated during WGS and best stability with time on stream, (iv) the lower apparent activation energy (kcal mol−1) of WGS reaction, (v) the lower degree toward Pt oxidation (largest Pt2+/Pt4+ ratio), (vi) the lower Ce1−x La x O2−δ support energy band gap, and (vii) the lower mobility of surface lattice oxygen.
Keywords: Water-gas shift reaction; Ce1−x La x O2; UV–vis/DRS; OSC; 18O transient isotopic exchange;

A simple, cheap and reproducible method to produce a C-doped TiO2 photocatalyst is presented, which can harvest visible light. This doped catalyst is able to degrade a stable organic dye molecule, Remazol Brilliant Blue® (RBB), under sunlight and visible light alone and its activity is compared to P25. XPS analysis clearly showed that carbon was introduced into the TiO2 lattice but at much lower doping levels than initially added during the synthesis. BET and diffuse reflectance spectroscopy indicated that the doped catalysts had larger surface area and improved light absorption in the visible region than P25. However, under full sunlight this did not translate into improved photocatalytic activity when compared to P25. Even though the UV cut-off sunlight spectrum permitted P25 to discolor RBB, no actual dye mineralization was observed by total organic carbon (TOC) analysis. In contrast, the doped catalyst did not only achieve discoloration of RBB but also removed 70% of organic carbon. This gives the doped catalyst a clear advantage to operate with visible light alone, which can be produced in a much more economical way, and may therefore reduce treatment costs of wastewater from textile and other industries using dyes. Among several reactive dyes, RBB was particularly found to be the most recalcitrant to discoloration with TiO2 and this study opens a way to address this issue. The photocatalytic mechanism is discussed.
Keywords: Carbon-doped TiO2; Sol–gel method; Photocatalytic oxidation; Remazol Brilliant Blue®; Full and cut-off sunlight;

Removal of 2-nitrophenol by catalytic wet peroxide oxidation using carbon materials with different morphological and chemical properties by Rui S. Ribeiro; Adrián M.T. Silva; José L. Figueiredo; Joaquim L. Faria; Helder T. Gomes (356-362).
Carbon materials with distinct morphological and chemical characteristics, namely activated carbons, carbon nanotubes, glycerol-based carbon materials and carbon xerogels, were tested for the removal of 2-nitrophenol (2-NP) in aqueous solutions, either by pure adsorption or by catalytic wet peroxide oxidation (CWPO).The results obtained in adsorption experiments carried out at pH 3, T  = 323 K, adsorbent load of 0.1 g L−1 and 2-NP concentration of 100 mg L−1, show that, in general, the activated carbons have superior adsorption performances compared to the other carbon materials tested, exhibiting removals of 2-NP up to 316 mg g−1 after 150 min of adsorption.In the CWPO experiments, whilst the activated carbons and carbon xerogels were not able to improve the removal of 2-nitrophenol, in comparison with the removals observed in pure adsorption experiments performed at the same conditions, the use of carbon nanotubes (CNT) and a glycerol-based carbon material (GBCM) resulted in increments in the removal of 2-NP as high as 83% and 56%, respectively. Removals of about 80% after only 30 min and higher than 90% after 150 min of reaction (equivalent to 929 mg g−1) are reached when using CNT as catalysts. The leaching of Fe (present as impurity in the CNT) at the end of the CWPO experiment was found to be negligible. The opposite was observed for classical iron supported on activated carbons, with catalytic activities resulting from the homogeneous contribution of Fe that is leached to the liquid phase. The superior performances found for CNT, makes this catalyst a promising system for CWPO.
Keywords: Carbon nanotubes; Glycerol-based carbon materials; Iron leaching; Catalytic wet peroxide oxidation (CWPO); 2-Nitrophenol;

Au–Cu bimetallic catalysts supported on TiO2 were prepared by sequential deposition–precipitation with urea method. Au0 is in interaction with CuO supported of titania after calcination and Au–Cu bimetallic particles are formed after reduction in hydrogen. The activation in air produced more active catalysts than the activation in hydrogen.Au–Cu bimetallic catalysts supported on TiO2 were prepared for the first time by sequential deposition–precipitation with the urea method, copper first then gold. Au–Cu catalysts with four different Au:Cu atomic ratios were synthesized (1:0.4 to 1:1.2). This method allowed quantitative deposition of both copper and gold and the formation of small metal particles. Characterization by TPR and by DRIFTS coupled with CO adsorption showed that when the samples were activated in air at 300 °C gold was present in metallic form, copper in the form of an oxide, and Au and Cu were in interaction, probably forming a Au/CuO/TiO2 system. When the catalysts were activated in hydrogen at 300 °C, the metal particles were smaller (2 nm) and bimetallic. The activation of Au–Cu catalysts in air at 300 °C produced more active catalysts than the activation under hydrogen at the same temperature. However, whatever the activation procedure, the highest catalytic activity in CO oxidation was obtained for the catalyst with an Au:Cu ratio of 1:0.9. This calcined catalyst also presented a TOF almost 3 times higher and a better temporal stability than monometallic gold catalysts in the reaction of CO oxidation at 20 °C. Compared to monometallic catalysts, the better catalytic results obtained with calcined Au–Cu/TiO2 indicate a promoting effect between gold and copper oxide in the reaction of CO oxidation.
Keywords: CO oxidation; Gold; Copper; Bimetallic catalysts;

Tailoring properties of platinum supported catalysts by irreversible adsorbed adatoms toward ethanol oxidation for direct ethanol fuel cells by Marta C. Figueiredo; Annukka Santasalo-Aarnio; Francisco J. Vidal-Iglesias; José Solla-Gullón; Juan M. Feliu; Kyosti Kontturi; Tanja Kallio (378-385).
In this work ethanol oxidation on carbon supported Pt catalysts modified with irreversibly adsorbed adatoms is reported. This study concerns understanding of the effect of a second metal on real catalysts in conditions as close as possible to those applied in fuel cells systems. The results were acquired using cyclic voltammetry, chronoamperometry and in situ infra-red techniques always taking into account the future application of the electrocatalyst materials in fuel cells. Foreign adatoms, both Bi and Sb, irreversibly adsorbed on a Pt electrode were studied, and revealed to enhance catalytic activity toward a more efficient ethanol oxidation. The catalytic enhancement continuously increased with the coverage of the adatom on the surface up to coverages close to saturation. With these high coverages a decrease of the activity was observed suggesting that free platinum atoms are required to oxidize ethanol. The results suggest that the adatoms play a third body role avoiding the poisoning of the Pt sites that will then be free for oxidizing ethanol. However, electronic effects on Pt/C–Bi and bifunctional mechanism at Pt/C–Sb are also suggested. The oxidation products were identified by in situ FTIR and are mainly acetaldehyde and acetic acid for the three catalysts. CO2 was also observed for the unmodified Pt/C and interestingly for the Pt/C–Sb electrodes.
Keywords: Platinum; Electrocatalysis; Ethanol oxidation; Adatoms; Direct ethanol fuel cells (DEFCs);

Activity and deactivation of catalysts based on zirconium oxide modified with metal chlorides in the MPV reduction of crotonaldehyde by Juan F. Miñambres; Alberto Marinas; José M. Marinas; Francisco J. Urbano (386-395).
The Meerwein–Ponndorf–Verley (MPV) reduction of crotonaldehyde to but-2-enol was conducted in the presence of ZrO2 based catalysts modified by impregnation with gold, cobalt, nickel or zinc chloride. The resulting solids were characterized in depth and used as catalysts in the previous reaction, where they provided high but-2-enol yields at the expense of a considerable loss of activity with time on stream. The catalysts were found to contain both Brønsted and Lewis acid sites active in the reaction. Based on the results, however, the Lewis sites are much more active but undergo much stronger deactivation than the Brønsted sites. Judging by the reactivity and characterization of the spent catalysts, the Brønsted sites are seemingly more selective despite their lower activity. Modifying ZrO2 with metal chlorides enhanced the surface Lewis acidity although these sites were found to be responsible for the surface deposition of carbonaceous species leading to catalyst deactivation. The presence in the Au/ZrO2 catalyst of a type of Lewis acid sites that scarcely deactivates in the process might be related to the presence of metallic Au particles interacting with chlorinated species.
Keywords: Metal chloride modified zirconia catalysts; Meerwein–Ponndorf–Verley reduction; Chemoselective crotonaldehyde reduction; Surface acidity; Catalyst deactivation;

Regeneration of coked zeolite from PMMA cracking process by ozonation by Supaporn Khangkham; Carine Julcour-Lebigue; Somsak Damronglerd; Chawalit Ngamcharussrivichai; Marie-Hélène Manero; Henri Delmas (396-405).
Regeneration of coked ZSM-5 zeolite was performed by oxidation with ozone at low temperature range (<150 °C) so that to restore catalytic activity. Physicochemical properties of the samples were characterized by several techniques: thermogravimetry (nature of coke deposit), elemental analysis (carbon content), porosimetry (surface area and pore size), ammonia temperature-programmed desorption and pyridine adsorption followed by infrared spectroscopy (acidity). Reactions were carried out at various temperatures, gas hourly space velocities and inlet concentrations of ozone. They showed that partially coked samples (containing 3 wt.% of C) can be successfully regenerated by ozone with carbon removal up to 80%.Carbon removal is improved by increasing the inlet ozone concentration in the range 16–50 g/m3, with almost linear trend, and by increasing time on stream until it plateaus after 2 h. Coke oxidation with O3 starts at low temperature and exhibits an optimum at about 100 °C. At higher temperatures, the rate of ozone decomposition becomes much faster than its pore diffusion rate, so that radical species are no longer available for the coke deposit within the particles and the overall oxidation yield decreases. Indeed, catalytic decomposition of ozone is found to occur significantly above 100 °C: O3 decomposition reaches 90% with fresh ZSM-5 catalyst. Thus regeneration of coked zeolite particles involves both complex chemical reactions (coke oxidation and O3 decomposition to active but unstable species) and transport processes (pore diffusion to the internal coked surface).Ozonation can restore both textural and acidic properties, allowing the catalyst to almost recover its initial activity in poly(methyl metacrylate) cracking. The activity results are well correlated with the carbon removal efficiency.
Keywords: Coke; Ozone; ZSM-5; Acid sites; Plastic wastes;

Influence of co-existing alcohol on charge transfer of H2 evolution under visible light with dye-sensitized nanocrystalline TiO2 by Masato M. Maitani; Conghong Zhan; Dai Mochizuki; Eiichi Suzuki; Yuji Wada (406-411).
The dye-sensitized nanocrystalline TiO2 colloidal suspension in aqueous systems has been applied for H2 evolution in the photocatalytic water splitting under visible irradiation. We have reported that the conversion efficiency is strongly influenced by the combination of dye-sensitizers and co-existing species in the suspension system. We herein analyze the fluorescence quenching of the dye-sensitized TiO2 nanoparticles in the suspensions and photoelectrochemical properties of dye-sensitized nanoporous TiO2 films. The combination of dye-sensitizers and co-existing species dominates the charge recombination resulting in significant differences in the efficiencies of the proton reduction into H2.
Keywords: Dye-sensitization; TiO2; Water splitting; Photocatalysts; Electron transport;

Emerging pollutants, such as drugs, are considered a potential hazard to the environment, and therefore advanced oxidation processes are being considered candidate tools for their elimination. Here, different oxidation processes have been investigated for the degradation of the non-steroidal antiinflammatories diclofenac and meclofenamic acid, derived from the model compound 2,6-dichlorodiphenylamine. They include oxidation under photo-Fenton conditions and treatment with organic photocatalysts such as rose Bengal (RB) and triphenylpyrylium (TPP+) salts. The role of the transient species involved in these processes (hydroxyl radical, singlet oxygen and radical cations, respectively) has been investigated by means of photophysical experiments. Based on the obtained results, participation of hydroxyl radical in photo-Fenton degradation appears feasible whereas singlet oxygen has been demonstrated to be unreactive for the degradation of the selected drugs. Finally the photocatalytic activity of triphenylpyrilium salts has been ascribed to electron transfer from the drugs to the triplet excited state of TPP+; ground state complexes have also been observed in this case, although their contribution to the photodegradation process is only marginal.
Keywords: Emerging pollutants; Laser flash photolysis; Triplet; Quenching;

An effective Pd-promoted gold catalyst supported on mesoporous silica particles for the oxidation of benzyl alcohol by Xu Yang; Chao Huang; Zhiyong Fu; Huiyu Song; Shijun Liao; Yunlan Su; Li Du; Xinjun Li (419-425).
A bimetallic Pd-promoted gold catalyst with mesoporous silica nanoparticles (MSNs) as support, PdAu/MSN, was prepared by an impregnation–hydrogen reduction method, and its catalysis for the base-free oxidation of benzyl alcohol was investigated. It was found that adding a small amount of Pd, with a Pd/Au atomic ratio as low as 0.05/1, can significantly decrease the size of the gold particles and at the optimal Pd/Au atomic ratio of 0.2/1, the catalyst Pd0.2Au/MSN showed 8 times and 3 times higher activity than the monometallic catalysts Au/MSN and Pd/MSN, respectively.A bimetallic Pd-promoted gold catalyst with mesoporous silica nanoparticles (MSNs) as support, PdAu/MSN, was prepared by an impregnation–hydrogen reduction method, and its catalysis for the base-free oxidation of benzyl alcohol was investigated. It was found that adding a small amount of Pd, with a Pd/Au atomic ratio as low as 0.05/1, can significantly decrease the size of the gold particles and thereby remarkably enhance the catalyst's activity for aerobatic oxidation. At the optimal Pd/Au atomic ratio of 0.2/1, the catalyst Pd0.2Au/MSN showed 8 times and 3 times higher activity than the monometallic catalysts Au/MSN and Pd/MSN, respectively. The prepared catalysts were comprehensively characterized by XRD, DRUV-vis, TEM, XPS, and H2-TPR to correlate the enhanced activity with the promotional effect induced by adding Pd.
Keywords: Alcohol oxidation; Gold; Mesoporous silica; Palladium; Synergy effect;

Lanthanum-based perovskites as catalysts for the ozonation of selected organic compounds by C.A. Orge; J.J.M. Órfão; M.F.R. Pereira; B.P. Barbero; L.E. Cadús (426-432).
The ozonation of two model compounds (oxalic acid and dye C. I. Reactive Blue 5) was carried out in the presence of La containing perovskites prepared by the citrate method. With the exception of LaFe0.9Cu0.1O3, all samples are active in the catalytic ozonation of oxalic acid, some of them allowing fast degradation of the compound. The presence of lattice vacancies on the perovskites surface and tuning of oxidation ability by the B cation play a key role in oxalic acid removal. Sample LaCoO3 was considered the best catalyst in oxalic acid degradation; in addition to its high activity, no metal leaching was observed. Regarding colour removal from the dye solution, single ozonation was slightly more efficient than catalytic ozonation in the presence of LaCoO3. On the other hand, ozonation catalyzed by LaCoO3 improved the TOC removal, allowing almost complete mineralization of the solution after 3 h of reaction under the conditions tested.
Keywords: Perovskites; Catalytic ozonation; Oxalic acid; Textile dye;

Facile large-scale synthesis of β-Bi2O3 nanospheres as a highly efficient photocatalyst for the degradation of acetaminophen under visible light irradiation by Xin Xiao; Ruiping Hu; Chao Liu; Chunlan Xing; Cheng Qian; Xiaoxi Zuo; Junmin Nan; Lishi Wang (433-443).
A facile solvothermal–calcining route for the large-scale synthesis of uniform β-Bi2O3 nanospheres has been demonstrated. The morphology, structure, and photoabsorption of β-Bi2O3 were characterized, and the effects of the preparation conditions on the structural properties of products were analyzed. The results show that monodisperse bismuth nanospheres are formed through the solvothermal reaction where the d-fructose acting as the dominant reductant, and subsequently converted to β-Bi2O3 nanospheres after the calcination in air. It is shown that the composition and structure of the products are greatly affected by the amount of d-fructose, the solvothermal and calcination temperature. The formation mechanism of β-Bi2O3 nanospheres is assumed to undergo the “in situ reduction” of Bi(III)–ethylene glycol complex spheres which serve as self-sacrificing templates, followed by the “in situ oxidation” of bismuth nanospheres by oxygen during the calcination in air. The visible light-induced photocatalysis of the synthetic photocatalysts applied to the degradation of acetaminophen (APAP, a widely occurring human-derived pharmaceutical found in the environment) has been studied systematically. The photocatalytic reaction of APAP over the β-Bi2O3 nanospheres follows pseudo first-order kinetics according to the Langmuir–Hinshelwood model, and exhibits a higher reaction rate constant, which is 2.5, 7, 8.1, and 79 times higher than that of commercial Bi2O3, synthetic α-Bi2O3, nitrogen doped TiO2 (N-TiO2), and Degussa P25, respectively. The superior photocatalytic activity is attributed to the narrower band gap energy (approximately 2.36 eV), nanostructure, good dispersion and high oxidation power of the β-Bi2O3 nanospheres. Only one intermediate at m/z 110 can be detected by liquid chromatography/mass spectrometry (LC/MS) in the photodegradation process, while several low-molecular-weight organic acids were identified by ion chromatography (IC) analysis. By combining with the experimental determination of reactive oxygen species in the photocatalytic process and the theoretical calculation of frontier electron density of APAP, a simple, hole-predominated photodegradation pathway is proposed. In addition, the high mineralization efficiency indicates that the as-synthesized β-Bi2O3 nanospheres photocatalyst can avoid secondary pollution during photocatalysis, which is important in practical applications.
Keywords: β-Bi2O3 nanospheres; Photocatalysis; Visible light; Acetaminophen; Photodegradation mechanism;

Perchloroethylene gas-phase degradation over titania-coated transparent monoliths by Filipe V.S. Lopes; Sandra M. Miranda; Ricardo A.R. Monteiro; Susana D.S. Martins; Adrián M.T. Silva; Joaquim L. Faria; Rui A.R. Boaventura; Vítor J.P. Vilar (444-456).
Perchloroethylene (PCE) has been detected as one of the major pollutants in indoor air of wastewater treatment plants (WWTPs) with closed facilities. Its hazardousness requires the complete PCE removal from air. For this reason, gas-phase photooxidation of PCE was studied in a continuous-flow tubular photoreactor under simulated solar radiation. Since negligible degradation of PCE was observed by photolysis, photocatalytic oxidation (PCO) experiments were carried out employing a catalytic bed of cellulose acetate monoliths (CAM) coated with TiO2 (TiO2-CAM). The three TiO2-CAM samples tested (3, 6, and 9 TiO2 dip-coating layers), showed that the catalytic activity increases considerably with the number of layers (∼92% for the 9-layered TiO2-CAM). Different conditions of feed flow rate, pollutant concentration, feed relative humidity, and incident irradiance were tested for the 9-layered TiO2-CAM photocatalyst in order to assess the most relevant operating parameters. Taking into consideration the small path of the photoreactor employed (0.16 m length), PCO of PCE showed interesting results, achieving degradation efficiencies between 90 and ∼98%, depending on the operating conditions used. The mathematical modelling of PCE kinetics through PCO suggested that there is no competition between PCE and H2O molecules to the surface active sites, even considering them as independent molecules that target distinct surface active sites (Langmuir–Hinshelwood bimolecular competitive two types of sites rate model). The validation of the PCO mathematical model at lab-scale allowed predictive simulations for PCO of PCE that can be used for possible scale-up a unit aiming at completely mineralization of PCE under solar irradiation. Finally, identification of PCE by-products allowed the complete formulation of a feasible reaction mechanism.
Keywords: Photocatalysis; Air decontamination; Perchloroethylene; TiO2 thin-films; Acetate cellulose monoliths; Artificial sunlight;

The wide occurrence of sunscreen agent micropollutants in natural environment received extensive attention in recent years due to their potential endocrine disrupting effect. The present study focuses on the kinetics and mechanism of photocatalytic degradation of sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in illuminated TiO2 suspensions. Photocatalysis of PBSA was systematically investigated under different process conditions and water matrices. Experimental results demonstrated that PBSA photocatalytic reactions followed pseudo-first-order kinetics. Radical scavenging experiments indicated that hydroxyl radical (HO•) is the predominant reactive species responsible for an appreciable degradation of PBSA. Second-order rate constant of PBSA-HO• reaction was determined to be 5.8 x 109  M−1  s−1 by competition kinetics method. Major intermediates included hydroxylated products, benzamide, hydroxylated benzamidine, hydroxylated 2-pheny-1H-benzimidazole as well as phenylimidazolecarboxylic derivatives which were elucidated by means of high performance liquid chromatograph–mass spectrometry (HPLC–MS) technique. Four carboxylic acids, oxalic, malonic, acetic and maleic acids, were detected during PBSA photocatalysis by HPLC–UV analysis. Ion chromatography (IC) results revealed that the sulfonic group of PBSA was primarily converted to sulfate ion while nitrogen atoms were released predominantly as ammonium and to a lesser extent as nitrate. The reduction of TOC processed much more slowly compared to PBSA degradation, however, approximately 80% TOC was removed after 720 min irradiation. A comparison of photocatalytic degradation of PBSA and structurally related compounds revealed that the 5-sulfonic moiety in PBSA had negligible effect on the photocatalysis of 2-pheny-1H-benzimidazole while 2-phenyl substituent stabilized the benzimidazole ring system to photocatalytic degradation.
Keywords: Photocatalysis; 2-Phenylbenzimidazole-5-sulfonic acid; Hydroxyl radical; Photoproducts; Degradation pathways;

Degrading perchloroethene at ambient conditions using Pd and Pd-on-Au reduction catalysts by Zhun Zhao; Yu-Lun Fang; Pedro J.J. Alvarez; Michael S. Wong (468-477).
Perchloroethene (PCE) is a common groundwater contaminant, due to its common use as a dry-cleaning solvent. Current treatment methods are limited in their ability to remove PCE from contaminated sites in an efficient and cost effective manner. Palladium-on-gold nanoparticles (Pd-on-Au NPs) have been shown to be highly catalytically active in the hydrodechlorination (HDC) of trichloroethene (TCE) and other chlorinated compounds. However, the catalytic chemistry of such nanoparticles for PCE HDC in water has not been systematically addressed in the literature. In this paper, we assess the catalytic properties of ∼4 nm Pd-on-Au NPs, ∼4 nm Pd NPs, and Pd/Al2O3 for water-phase PCE HDC under ambient conditions. The Pd-on-Au NPs exhibited volcano-shape activity as a function of Pd surface coverage (sc). Maximum activity was at 80 ± 0.8 sc% (pseudo-first order rate constant of ∼5000 L/gPd/min), which was ∼20x and ∼80x higher than that for Pd NPs and Pd/Al2O3 at room temperature and pH 7. A complete mechanistic model of PCE HDC that coupled gas–liquid mass transfer with the surface reactions was developed and found to be consistent with the observed concentration-time profiles for the 3 catalyst types. The formation and subsequent reaction of daughter products (TCE, dichloroethene isomers, vinyl chloride, and ethene) followed the stepwise dechlorination of the PCE chlorine groups. The final reaction products were ethane and minor amounts of n-butane/butenes. This study establishes the enhanced degradation chemistry of PCE using model Pd-on-Au catalysts and suggests the volcano-shape structure-activity dependence can be generalized from PCE and TCE to other organohalides.
Keywords: Tetrachloroethene; Perchloroethene; Palladium; Gold; Hydrodechlorination; Nanoparticles;

The electro-reduction of CO2 was investigated on a polypyrrole-coated copper catalyst, for the first time. The experiments were carried out at different pressure conditions (1, 10, 20, 40 and 60 bars), varying film thicknesses (0.5, 0.9, 1.4, 2.1 and 5.4 μm) and at different potential values (−0.8, −1.0, −1.5, −2.0, −2.5, −3.0 V Pb(Hg) x /PbSO4/SO4 −2) in CH3OH/0.1 M LiClO4/H+ electrolyte system. At −0.8 V and −1.0 V, it was obtained only HCOOH and CH3COOH. At more negative values, gaseous products such as CH4, C2H4, C2H6 and CO were detected, additionally. The coating of copper electro-catalyst with a conducting polymer causes a shifting of the product distribution to hydrocarbons, especially to methane.
Keywords: CO2 reduction; Copper; Polypyrrole electrode; High pressure; Methane;

A series of CeO2–WO3 (W x Ce) catalysts were prepared for the SCR of NO x with NH3. Among the three representative samples, the W1Ce catalyst exhibited great activity during SCR reaction and a large amount of N2 from NH3 oxidation, whereas the W0.05Ce catalyst yielded more NO from NH3 oxidation than the W3Ce at high temperature. Three types of metal oxide species (isopolytungsten species, Ce2(WO4)3 compounds and crystalline WO3) were observed on the catalyst surfaces with increased WO3 loading. CeO2, rather than WO3 or Ce2(WO4)3, presented favorable reducibility behavior. Furthermore, CeO2 with intrinsic oxygen vacancies and unsaturated W n+ cations of crystalline WO3 provided Lewis acid sites; meanwhile, the W―O―W or W=O modes of Ce2(WO4)3 provided Brønsted acid sites. Based on the Raman spectra, the W―O species of the [WO4] or [WO6] units could be the active sites. The results suggest a reaction mechanism consisting of two independent cycles, denoted as a redox cycle due to the excellent oxygen storage capability and reducibility of cubic fluorite CeO2 (for NH3 activation) and an acid site cycle, resulting from Brønsted acid sites formed on the W―O―W species of Ce2(WO4)3 (for NH3 adsorption). Surface nitrate species cannot be involved directly in SCR reaction with gaseous NH3; additionally, the adsorbed NO2 demonstrated activity over the W1Ce catalyst at 200 °C.
Keywords: DeNO x ; NH3-SCR; CeO2; Ce2(WO4)3; In situ IR; Raman;

In situ poly(methyl methacrylate)-templating generation and excellent catalytic performance of MnO x /3DOM LaMnO3 for the combustion of toluene and methanol by Yuxi Liu; Hongxing Dai; Jiguang Deng; Yucheng Du; Xinwei Li; Zhenxuan Zhao; Yuan Wang; Baozu Gao; Huanggen Yang; Guangsheng Guo (493-505).
5, 8, 12, and 16 wt% MnO x /3DOM LaMnO3 are prepared using the in-situ PMMA-templating strategy. The high oxygen adspecies concentration, good low-temperature reducibility, and strong interaction between MnO x and LaMnO3 are responsible for the excellent catalytic performance of 12 wt% MnO x /3DOM LaMnO3 for toluene and methanol combustion.Rhombohedrally crystallized three-dimensionally ordered macroporous (3DOM) LaMnO3 supported MnO x (5, 8, 12, 16 wt% MnO x /3DOM LaMnO3) catalysts were prepared using the in situ tryptophan-assisted poly(methyl methacrylate)-templating strategy. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the combustion of toluene and methanol. It is shown that the MnO x /3DOM LaMnO3 samples displayed a 3DOM architecture and a high surface area of 19–31 m2/g. The 12 wt% MnO x /3DOM LaMnO3 sample showed the highest oxygen adspecies concentration and the best low-temperature reducibility as well as the highly dispersed MnO x particles on the LaMnO3 surface, giving the highest TOF values of 7.9 x 10−6  s−1 for toluene combustion at 160 °C and 7.3 x 10−6  s−1 for methanol combustion at 80 °C. The apparent activation energies of the MnO x /3DOM LaMnO3 catalysts were 61–62 and 48–54 kJ/mol for toluene and methanol combustion, respectively. It is concluded that the excellent catalytic performance of 12 wt% MnO x /3DOM LaMnO3 was associated with its highest oxygen adspecies concentration, best low-temperature reducibility, and strong interaction between MnO x and 3DOM LaMnO3.
Keywords: Three-dimensionally ordered macroporous perovskite; Supported manganese oxide catalyst; Metal oxide–support interaction; Toluene combustion; Methanol combustion;

Cu-containing MFI zeolites as catalysts for wet peroxide oxidation of formic acid as model organic contaminant by Oxana P. Taran; Svetlana A. Yashnik; Artemiy B. Ayusheev; Anna S. Piskun; Roman V. Prihod’ko; Zinfer R. Ismagilov; Vladislav V. Goncharuk; Valentin N. Parmon (506-515).
The catalytic behavior of different Cu(Fe)/zeolite catalysts with the MFI morphology in wet peroxide oxidation of formic acid as a model organic substrate was thoroughly examined. The influence of the method for Cu2+ ions introduction into the zeolite matrix, Cu loading and the electron state of Cu on catalytic properties of zeolites, including their stability to leaching of Cu was studied. Cu-substituted ZSM-5 zeolites with the atomic ratio Si/Al = 30 and Cu content of 0.5–1.5, which were prepared by ion exchange, were shown most promising for wet peroxide oxidation. The impact of temperature, initial pH and concentrations of reagents on the catalytic performance of the catalyst with the optimal composition also was studied. The characterization of fresh and spent catalysts using UV–vis DR and ESR spectroscopic techniques led to suppose that the high efficiency of Cu-ZSM-5 to redox reactions in aqueous media is provided by nanostructured square-planar copper oxide clusters localized in the zeolite channels.
Keywords: Cu-exchanged zeolites; Cu-ZSM-5; Catalytic wet peroxide oxidation; Formic acid;

Vapour phase H2O2 decomposition on Mn based monolithic catalysts synthesized by innovative procedures by L. Micoli; G. Bagnasco; M. Turco; M. Trifuoggi; A. Russo Sorge; E. Fanelli; P. Pernice; A. Aronne (516-522).
Manganese oxide catalysts supported on monolithic yttria stabilized zirconia honeycombs were studied for H2O2 decomposition in view of space propulsion applications. The materials were prepared by impregnation (IM), precipitation (PR) and sol–gel (SG) methods and characterized by N2 adsorption, SEM and H2 temperature programmed reduction (TPR). The catalytic activity for H2O2 decomposition was studied under vapour phase conditions. The tests were carried out in a flow apparatus at T  = 200 °C, gas hourly space velocity (GHSV) = 2.00 and 2.67 s−1, H2O2 concentrations of 11.3 mol%. The redox properties of the catalysts were markedly influenced by the preparation method. In the SG catalyst, a large fraction of Mn was not reducible in the TPR tests differently from the PR and IM materials. Despite this effect, the SG catalyst showed an activity comparable or higher than that of PR and IM, due to a more effective dispersion of Mn species. A too strong effect of space velocity on H2O2 conversion was attributed to an autocatalytic effect. A radical mechanism was hypothesized: it was assumed that a reaction between O2 and Mn species produced radicals that promoted the overall reaction.
Keywords: Sol–gel; MnO x /ZrO2 catalyst; H2O2 vapour decomposition; Space propulsion;

Quantum yield with platinum modified TiO2 photocatalyst for hydrogen production by Salvador Escobedo Salas; Benito Serrano Rosales; Hugo de Lasa (523-536).
The present study reports quantum yields for hydrogen production using a Pt modified titanium dioxide (DP25) photocatalyst in a slurry medium, under near-UV irradiation. The photocatalyst was prepared using the incipient wetness impregnation method. The modified photocatalyst exhibited a reduced energy band of 2.73 eV upon Pt addition. Experiments were performed in a Photo CREC Water II Reactor. This unit allows the establishment of macroscopic radiation balances. These irradiation balances showed a maximum LVREA (local volumetric rate of energy absorption) of 0.15 g/L. Regarding hydrogen formation via H• radicals, the addition of a 2 vol.% ethanol scavenger allowed achieving significant amounts of hydrogen free of oxygen. It was noticed that the rate of hydrogen formation in the presence of ethanol is a function of the pH of the water solution. It was also observed that the calculated 7.8% quantum efficiency showed good degree of photon utilization and confirmed the value of the Pt modified TiO2 photocatalyst and Photo CREC Water II Unit set up for hydrogen production, via water splitting.
Keywords: Near UV-light; Titanium dioxide; Platinum; Photo CREC reactor; Hydrogen; Quantum Yield;

Transition metal ions (M–TiO2, where M = Cu(II), Ni(II), Co(II) and Fe(III)) loaded TiO2 catalyst were successfully prepared by solid-state dispersion method. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET). Photocatalytic activities of bare and CuO, NiO, Co3O4, Fe2O3 loaded TiO2 catalysts were compared and the rate constant values were determined from the kinetic studies of the degradation of phenol. The extent of degradation of phenol and its mineralization were confirmed further by HPLC and TOC analyses. The 0.1CuO wt% TiO2 showed the highest percentage of phenol degradation (100%) and highest reaction rate (0.99 mg l−1  min−1) in 90 min. It was also found that the catalytic activity of 0.1CuO–TiO2 was found to be higher than nano TiO2 and P-25 photocatalyst. The profound effect of transition metal oxide catalyst for phenol degradation is generally considered due to the high surface area, small particle size, and high dispersion of CuO, and the presence of more surface OH groups than that of the pure TiO2 photocatalyst.
Keywords: Photocatalytic degradation; Phenol; Transition metal oxide; TiO2; UV irradiation; Characterization;

Photocatalytically enhanced Cr(VI) removal by mixed oxides derived from MeAl (Me:Mg and/or Zn) layered double hydroxides by Claudia Alanis; Reyna Natividad; Carlos Barrera-Diaz; Verónica Martínez-Miranda; Julia Prince; Jaime S. Valente (546-551).
This work aims to present a study of the adsorption and photocatalytic reduction of Cr(VI) by ZnAl, MgZnAl and MgAl mixed oxides derived from layered double hydroxides (LDHs). The effect of variables like Zn content and pH (3 and 6.5) on Cr(VI) removal efficiency is presented. The catalysts were characterized by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The reaction progress was verified by UV/vis spectrophotometry with a colorimetric method. A maximum of 99.5% Cr(VI) was photocatalytically removed and this process was approximately two times faster than adsorption. In addition, it was found that the use of these materials does not imply the addition of further chemicals to regulate pH since the free basic pH of the catalyst-contaminant suspension positively affects both adsorption and photo-reduction kinetics.
Keywords: Adsorption; Photoreduction; Chromium (VI) reduction; Hydrotalcites; Photocatalysis;

A facile approach is used to synthesize a multiwalled carbon nanotubes (MWCNTs) supported platinum nanochains (Pt-NCs) catalyst through the electrostatic self-assembly between phosphonate functionalized Pt-NCs and polyallylamine (PAH) functionalized MWCNTs. It is observed that Pt-NCs are highly dispersed and effectively anchored on the surface of PAH functionalized MWCNTs.We design and synthesize a multiwalled carbon nanotubes (MWCNTs) supported platinum nanochains (Pt-NCs) catalyst (Pt-NCs/MWCNTs) through the electrostatic self-assembly between phosphonate functionalized Pt-NCs and polyallylamine (PAH) functionalized MWCNTs. The grown mechanism, morphology, structure, and composition of the Pt-NCs are investigated by ultraviolet–visible (UV–vis), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential analysis. XPS and elemental maps measurements confirm the successful immobilization of PAH on the MWCNTs surface. The resultant Pt-NCs/MWCNTs catalyst exhibits better electrocatalytic activity for the oxygen reduction reaction (ORR) than the commercial Pt/C catalyst due to the unique structure and low hydroxyl surface coverage.
Keywords: Self-sssembly; Platinum nanochains; Carbon nanotubes; Oxygen reduction reaction; Electrocatalytic activity;

A comprehensive research focused on fundamental aspects in non metal ion doped titania based photocatalysis is discussed.The multifunctional and advanced semiconductor titania with superior physicochemical and opto-electronic properties is extensively investigated in wastewater purification mainly due to its non-toxicity, favorable band edge positions, water insolubility, multifaceted electronic properties, surface acid–base properties, super hydrophilicity and so on. However, large band gap and massive photogenerated charge carrier recombination hinders its wide application under natural solar light. Thus, altering the surface-bulk structure of titania is a major goal in the area of both materials and environmental chemistry for its better applications. The substitution of p block elements (B, C, N, F, S, P, and I) either at Ti4+ and O2− sites is a promising approach to overcome the aforementioned drawbacks. This review focuses on the photocatalytic activity of non metal doped titania for a wide variety of pollutants degradation under UV/visible light, with special emphasis on nitrogen doped TiO2. Further improvement in photoactivity of N–TiO2 is achieved via depositing with noble metals, co-doping with foreign ions, sensitization, surface modifications and heterostructuring with other semiconductors. The mechanism governing the photocatalytic reactions is discussed in the light of charge carrier generation–separation–transfer–recombination dynamics together with pollutant adsorption and their reactions with reactive oxygenated species in liquid or gaseous regime. We are positive that this review article will further stimulate our research interest on this intriguing hot topic.
Keywords: Titania; Non metal doping; Noble metal deposition; Codoping; Sensitization; Coupling with semiconductors; Reactive oxygen species; Interfacial charge transfer dynamics;

Preparation, characterization and application of K-PtCo/Al2O3 catalyst coatings for preferential CO oxidation by Xinhai Yu; Wei Yu; Hongliang Li; Shan-Tung Tu; Yi-Fan Han (588-597).
K-PtCo/Al2O3 catalyst coatings were studied concerning preferential oxidation of carbon monoxide (PROX) in hydrogen-rich gas streams. It has been found that the addition of potassium can enhance the catalytic activities at temperatures below 413 K, thus can widen the window of operation in terms of reaction temperatures. The most active catalyst coating of 1.5K-Pt2Co (Pt 1 wt.%, Co 2 wt.%, and K/Co molar ratio of 1.5) can reduce carbon monoxide concentrations from initial 1% to less than 10 ppm at a high GHSV of 120,000 ml g−1  h−1 in a temperature range 393–433 K. The structure of catalyst coatings has been thoroughly characterized using multi-techniques, such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR), in situ laser Raman spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The addition of K has evidenced to promote the formation of Pt3Co and increase the particle size as identified by TEM and XPS. Pt3Co plays an important role in PROX. For PtCo/Al2O3 catalyst coatings, a redox equilibrium for Co during PROX was found. In contrast, with the addition of K, this redox equilibrium disappeared, probably because of the increased amount of Pt3Co phase in the catalyst surface region.
Keywords: Preferential CO oxidation; Catalyst coating; Bimetallic PtCo catalysts; Micro-reactor; Hydrogen purification;

RGO/ZnO composites with different size of ZnO particles have been fabricated via a one-step facile solvothermal method. The photocatalytic activities of these composites have been investigated toward dye degradation and Cr (IV) reduction in an aqueous phase. It is found that ZnO-S1, with relatively small particles size distribution, is able to hybridize with RGO sheet more efficiently than that for the hybridization of ZnO-S2, with large particles size distribution, with RGO sheet. Such a particle size effect leads the more efficient interfacial interaction between ZnO-S1 and RGO, which leads to both the enhanced photoactivity and the significantly decreased photocorrosion. In addition, we have also used the radicals scavengers technique to study the role of photoactive species involved in the photocatalytic degradation of dye and reduction of Cr (VI).The composites of reduced graphene oxide/ZnO (RGO/ZnO) with different particles size of ZnO have been prepared via a facile solvothermal reaction of graphene oxide (GO) and ZnO in an ethanol-water solvent. It is found that the RGO/ZnO-S1 composite with ZnO particle size of 20–100 nm exhibits the enhanced photoactivity toward degradation of organic dyes and reduction of heavy metal ions Cr(VI) in water as compared to the bare ZnO-S1 sample under UV light irradiation. However, the RGO/ZnO-S2 composite with ZnO particle size of 50–500 nm shows decreased photoactivity as compared to bare ZnO-S2. The recycled photoactivity testing shows that, for RGO/ZnO-S1, the photocorrosion of ZnO-S1 is efficiently inhibited by the hybridization with RGO whereas the case is not for RGO/ZnO-S2. A collection of characterization techniques disclose that the smaller particles size for RGO/ZnO-S1 than that for RGO/ZnO-S2 leads to a more interfacial contact and a chemical bonding between RGO and ZnO-S1, thereby resulting in enhanced photoactivity and efficient anti-photocorrosion as observed for RGO/ZnO-S1. Furthermore, the possible reaction mechanism for degradation of dyes and reduction of Cr(VI) over RGO/ZnO-S1 has also been studied. Our results suggest that the semiconductor particles size has an important effect on the photocatalytic performance of RGO/semiconductor composites photocatalysts. The hybridization of RGO with ZnO in an appropriate manner is able to significantly inhibit the well-known photocorrosion of semiconductor ZnO. It is anticipated that this work would enrich the applications of RGO/semiconductor photocatalysts in environment purification.
Keywords: Reduced graphene oxide; ZnO; Photostability; Size and synergetic effect; Interfacial contact;

One-pot solvothermal syntheses of ternary heterostructured TiO2–Bi2MoO6/Bi3.64Mo0.36O6.55 controllable in terms of composition, morphology and structure: Materials of high visible-light driven photocatalytic activity by Jian-Ping Zou; Sheng-Lian Luo; Long-Zhu Zhang; Jun Ma; Si-Liang Lei; Long-Shuai Zhang; Xu-Biao Luo; Yan Luo; Gui-Sheng Zeng; Chak-Tong Au (608-618).
Novel trinary heterostructured TiO2–Bi2MoO6/Bi3.64Mo0.36O6.55 are synthesized by one-pot template-free solvothermal method. The compositions, morphologies and structures of the photocatalysts can be well controlled by adjusting the pH values, the ratio of alcohol/water and the content of TiO2 loading. And reasonable formation mechanisms and photocatalytic mechanism for the heterostructured photocatalysts are put forward, which provide a new photocatalytic reaction mode.Novel ternary heterostructured TiO2–Bi2MoO6/Bi3.64Mo0.36O6.55 were synthesized by a one-pot template-free solvothermal method. For comparison studies, Bi2MoO6, Bi3.64Mo0.36O6.55, Bi2MoO6/Bi3.64Mo0.36O6.55, TiO2–Bi2MoO6, and TiO2–Bi3.64Mo0.36O6.55 were also synthesized likewise. The photocatalysts were characterized by powder X-ray diffraction, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The experimental results showed that the composition, morphology and structure of the photocatalysts can be well controlled by adjusting the pH value, alcohol/water ratio, and TiO2 content. Based on the findings, we put forward a mechanism for the formation of the materials. Furthermore, the results of photocatalytic degradation of Rhodamine B (RhB) and o-nitrophenol over the as-prepared materials indicate that photocatalytic efficiency can be closely related to the composition, morphology and structure of the materials. The ternary heterostructured 5%TiO2–Bi2MoO6/Bi3.64Mo0.36O6.55 exhibits good visible-light driven photocatalytic activity in the degradation of RhB and o-nitrophenol, much higher than those of TiO2, Bi2MoO6, Bi3.64Mo0.36O6.55, and any combination of the three. Finally, a new mechanism for the photocatalytic action of the heterostructured materials was put forward. Overall, the investigation provides a new reaction mode to explain the effective interfacial charge transfer and the significant improvement in photocatalytic efficiency of the ternary heterostructured composites.
Keywords: Bismuth molybdate; Composite materials; Controllable syntheses; Heterostructured; Photocatalysis;

Photocatalytic oxidation of nitrogen oxides on N-F-doped titania thin films by Antigoni V. Katsanaki; Athanassios G. Kontos; Thomas Maggos; Miguel Pelaez; Vlassis Likodimos; Evangelia A. Pavlatou; Dionysios D. Dionysiou; Polycarpos Falaras (619-625).
Display OmittedVisible light activated nanostructured TiO2 with nitrogen and fluorine co-dopants were prepared by the surfactant assisted sol–gel method and immobilized on glass substrates by dip coating. The films were inserted inside a continuous flow photoreactor and examined for the photocatalytic oxidation of NO air pollutant with initial concentration of 200–800 ppbv. The modified catalysts exhibited significant photocatalytic activity under daylight illumination, with maximum percentage of NO removal equal to 24.2% and photooxidation rate up to 0.66 μg m−2  s−1. The reaction rates increased proportionally to the incident light intensity whereas for the strongly absorbed UV light a deviation from linearity was observed. Mass balance during photooxidation was confirmed by determining the amount of N O 3 − product residues onto the photocatalyst surface.
Keywords: Air treatment; Continuous flow reactor; Nitrogen-Fluorine doped TiO2; Daylight photocatalysis;

Sunlight-driven toluene photo-elimination using CeO2-TiO2 composite systems: A kinetic study by Mario J. Muñoz-Batista; Anna Kubacka; María Natividad Gómez-Cerezo; David Tudela; Marcos Fernández-García (626-635).
A kinetic study of the behavior observed in the photocatalytic degradation of toluene under sunlight-type excitation and using composite CeO2-TiO2 catalysts is presented. The study focuses on analyzing kinetic differences within a series of composite catalysts with varying CeO2:TiO2 molar ratios. To this end, intrinsic expressions to represent the kinetics of toluene photo-degradation were derived from a proposed reaction scheme. These expressions explicitly included the effect of photon absorption on the reaction rate and lead to a mathematical expression of the reaction rate including two adjustable parameters. The modeling of the radiation field in the reactor was accomplished by numerically solving the radiative transfer equation. The radiation field and kinetic schemes were jointly used into a partial differential equation corresponding to the mass balance of toluene. The mathematical model was solved with an algorithmic based in the method of lines to deal with the partial differential equation, coupled with a nonlinear least-squares fitting algorithm to obtain kinetic parameter value estimations. Experimental runs for single oxide and composite CeO2-TiO2 catalysts were used for the fitting process. Good agreement was obtained between model predictions and experimental data, with a root mean square error below 0.65%. The kinetic behavior of composite samples with respect to the titania reference seems intimately related with the hole handling steps of the mechanism.
Keywords: Toluene; Photocatalysis; Solar light; Photon absorption; Kinetics;

Four N–I co-doped TiO2 catalysts having Ti:N/I molar ratios of 1:1, 1:3, 1:5 and 1:10 were prepared via a sol–gel method using NH4I as N–I dopant precursor. A pure TiO2 (undoped) sample was also prepared by the same method for comparison. The catalysts were evaluated for the simultaneous photocatalytic reduction of Cr(VI) and oxidation of benzoic acid (BA). TiO2 anatase phase was formed for all N–I co-doped catalysts as shown by XRD. UV–vis diffuse reflectance spectra showed that N–I co-doping resulted in increased absorption at visible wavelengths and a decrease of the band gap energy (E g). The smallest E g value of 2.34 eV was observed for the 1:5 Ti:N/I molar ratio. The structure and photodynamics of the TiO2 catalysts was investigated in detail by Electron Paramagnetic Resonance (EPR) spectroscopy. The EPR data showed: [i] formation of non-photoactive NO centers and photoinduced Nb • paramagnetic species as a result of N doping, [ii] photoinduced Ti3+ surface ions, and [iii] formation of surfacial oxygen O2 radical ions and trapped holes TiO4+–O• . The Nb • species act upon the narrowing of the band gap and the production of photogenerated electrons, i.e. Ti3+ surface ions. These Ti3+ surface ions have a key role, capturing gas O2 and supporting both reduction and oxidation process. Cr(VI) reduction by the N–I co-doped catalysts followed the trend: TNI5 > TNI10 > TNI1 > TNI3 > TiO2[undoped] which correlates with the concentration of Nb • species formed and the narrowing of E g values. Oxidation of benzoic acid (BA) followed a more complex trend as follows: TNI1 > TNI3 > TNI10 > TNI5 which is the reverse of the trend for trapped holes TiO4+–O• . Finally progressive microwave EPR saturation experiments show that Nb • species are located deeper in the TiO2 lattice in particles with narrower E g values.
Keywords: N–I co-doped TiO2; Cr(VI) reduction; Benzoic acid oxidation; EPR; Nb • species;

This article reports on the preparation and characterization (SEM, SEM-EDX, XRD, diffuse reflectance spectroscopy, and BET surface area) of TiO2 particles supported on activated carbon (AC) particulates using a titanium oxysulphate precursor and subjecting the aqueous dispersion to microwave (MW) heating and to a more traditional heating method with an oil bath. The TiO2/AC composites were subsequently tested for their photoactivity through an examination of the transformation of a volatile organic pollutant (VOC) in air: iso-propanol. Under MW irradiation at 70 °C the synthesis resulted in the formation of a thin coating about the AC support, while TiO2 particles formed at higher temperatures; the average particle size of TiO2 tended to decrease with increase in reaction temperature from 426 nm at 80 °C to 243 nm at 180 °C. The accelerated heating of the AC-dispersed solution above 80 °C was confirmed by determining the dielectric loss (ε”) of the dispersion at various temperatures at the microwave frequency of 2.45 GHz. Subjecting the dispersion to oil-bath heating only led to formation of a thin film about the AC particulates. In the absence of the AC support TiO2 particle sizes averaged ca. 460 nm for the MW method, while they averaged around 682 nm with the oil-bath method. The BET specific surface area of the TiO2/AC composites was significantly greater for the MW heating method (ca. 990 m2  g−1 versus 848 m2  g−1 for the oil-bath method). Both UV–vis spectroscopy (estimated band-gap energy of TiO2/AC composites was 3.3 eV) and XRD spectra confirmed the anatase nature of the TiO2 specimens. The MW-produced TiO2/AC particulates proved to be nearly six-fold more photoactive in the photoinduced degradation of the VOC pollutant than those produced by the oil-bath method. A possible growth mechanism of the TiO2/AC composites is proposed.
Keywords: Titanium dioxide; Activated carbon; TiO2/AC composite; Microwave hydrothermal synthesis; Iso-propanol;

High catalytic activity of Co-Fe/α-Al2O3 in the steam reforming of toluene in the presence of hydrogen by Mitsuru Koike; Yuji Hisada; Lei Wang; Dalin Li; Hideo Watanabe; Yoshinao Nakagawa; Keiichi Tomishige (652-662).
The addition of hydrogen to the reactant gas for the toluene steam reforming enhanced the stability and activity of Co-Fe/α-Al2O3 (Fe/Co = 0.25), which is due to the suppression of the oxidation of the bcc Co-Fe alloy phase as the catalytically active species. It is characteristic that the adsorption of hydrogen on Co-Fe/α-Al2O3 was much stronger than that on Co/α-Al2O3, suggesting that the coverage of adsorbed hydrogen species can be rather high under the reaction conditions. The kinetics analysis gave almost first reaction order with respect to toluene and higher reactivity of toluene than benzene indicate that the activated adsorption of toluene can proceed via its methyl group and it can be assisted by adsorbed hydrogen species at the bcc Co-Fe alloy surface.
Keywords: Cobalt; Iron; Alloy; Steam reforming; Toluene;

Highly efficient application of activated carbon as catalyst for wet peroxide oxidation by C.M. Domínguez; P. Ocón; A. Quintanilla; J.A. Casas; J.J. Rodriguez (663-670).
This paper addresses the improved performance of activated carbons in catalytic wet peroxide oxidation (CWPO) of phenol as target compound. Initial cyclic voltammetry experiments show that hydrogen peroxide and phenol compete for the same active sites on the carbon surface. Then, a significant coverage of the carbon surface by phenol molecules is the approach attempted to increase the efficiency of hydrogen peroxide and the performance of the oxidation process.In this work, two commercial activated carbons, with different physical and electrochemical properties have been tested. The results demonstrate that working at high phenol concentration (5 g/L) and phenol/carbon mass ratio (2), unprecedented hydrogen peroxide efficiencies of around 100% are achieved, allowing high oxidation and mineralization degrees, i.e. 97% phenol and 70% TOC conversions at 80 °C with the stoichiometric dose of hydrogen peroxide required for complete mineralization of phenol. The oxidation route of phenol in the presence of activated carbon is also studied and a reaction pathway proposed. Resorcinol was a new by-product detected whose formation occurs upon reaction on the carbon surface. Condensation by-products, typically formed in Fenton oxidation of phenol, were not found in the effluents but adsorbed on the carbon surface causing a progressive deactivation upon use. The activity can be easily recovered by oxidative thermal regeneration (350 °C, 24 h).
Keywords: Activated carbon; Hydrogen peroxide; Cyclic voltammetry; Catalytic wet peroxide oxidation; Regeneration;

Green preparation of transition metal oxide catalysts using supercritical CO2 anti-solvent precipitation for the total oxidation of propane by Raimon P. Marin; Simon A. Kondrat; Rebecca K. Pinnell; Thomas E. Davies; Stan Golunski; Jonathan K. Bartley; Graham J. Hutchings; Stuart H. Taylor (671-679).
A series of metal oxide catalysts, including Fe3O4, NiO, CuO and Co3O4, have been prepared by supercritical anti-solvent precipitation and evaluated for the total oxidation of propane. Co3O4 was found to be the most active catalyst and our studies have focussed on this oxide. The addition of water as co-solvent in the supercritical anti-solvent preparation was investigated. Powder X-ray diffraction and infrared spectroscopy indicated that the addition of water promoted the formation of carbonate species in the catalyst precursors. The formation of the catalysts from the precursor were optimised by investigating the thermal treatment conditions, by studying variables including time, temperature and atmosphere. The optimal conditions for catalyst preparation required precursor precipitation containing 10 vol% water co-solvent followed by a 2 h calcination at 250 °C. These conditions produced Co3O4 with high surface areas (>100 m2  g−1), which were very active catalysts producing 50% propane conversion at 175 °C.
Keywords: Propane; Total oxidation; Supercritical anti-solvent precipitation; Metal oxides; Cobalt oxide;

UV and visible light optimization of anatase TiO2 antimicrobial properties: Surface deposition of metal and oxide (Cu, Zn, Ag) species by Anna Kubacka; Mario J. Muñoz-Batista; Manuel Ferrer; Marcos Fernández-García (680-690).
Presence of metallic Ag or oxidic Ag, Cu and Zn species on an anatase surface is shown to allow drastic modification of the disinfection capability of TiO2-based materials against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and upon both ultraviolet and visible light excitations. While Cu shows non-positive influence in the photo-elimination of the microorganisms, Zn and Ag always displays an improved performance with respect to the bare titania reference. In particular, Zn has a positive effect with decreasing importance with increasing wavelength whereas Ag always display an optimum performance, irrespective of the initial oxidation state, excitation wavelength and microorganism nature. The physico-chemical analysis of the samples together with a spectro-kinetic combination based in a Langmuir-Hinshelwood-like kinetic model and the use of electron paramagnetic resonance were utilized to analyze the roots of the mentioned Cu, Zn, Ag dependent disinfection behavior. The approach allows the critical analysis of the effects that the metal-containing phases exert in anatase and provides evidence that two physical phenomena are of importance to justify the disinfection capability modification of the anatase phase. Both adhesion to bacteria and hole-radical derived attack to the microorganism appear critical to interpret disinfection although their relative contribution vary with the excitation light wavelength as well as the nature of the metal-containing phase present at the anatase surface.
Keywords: Titania; Anatase; Silver, copper, zinc, oxides, biocide; Germicide; Disinfection;

Remarkable activity of Ag/Al2O3/cordierite catalysts in SCR of NO with ethanol and butanol by Pavlo Kyriienko; Nataliia Popovych; Sergiy Soloviev; Svitlana Orlyk; Stanislaw Dzwigaj (691-699).
Structured silver–alumina catalysts were prepared by the one-step deposition of Al2O3 directly on the surface of cordierite block matrices with subsequent incipient wetness impregnation of Al2O3/cordierite with an AgNO3 aqueous solution. The catalysts were characterized by BET, XRD, XPS and FTIR spectroscopy with CO and pyridine as molecule probe, diffuse reflectance UV–vis, TEM and SEM. The Ag/Al2O3/cordierite catalysts are highly active in SCR of NO with ethanol and butanol and very selective toward N2. The conversion of NO over 0.6%Ag/45%Al2O3/cordierite catalyst reaches the high values of 95–99% already at 250 °C and remains at this high level up to 430 °C. The optimal silver loading in the silver–alumina catalysts is differing for C2 and C4 alcohols. It is shown that the role of silver in the Ag/Al2O3/cordierite catalyst consists in the modification of both redox and acid–base properties of the catalyst surface. Isolated cations (Ag+) and/or silver nanoclusters (Ag n δ+) contain adsorbed oxygen in quantities sufficient only for the partial oxidation of alcohols toward oxygenated compounds, which then reduce NO.
Keywords: Silver–alumina; Cordierite; SCR of NO; Ethanol, Butanol;

The Heck coupling of iodobenzene with ethyl acrylate or styrene was used to assess the catalytic properties of biogenic nanoparticles of palladium supported upon the surface of bacterial biomass (bioPd), this approach combining advantages of both homogeneous and heterogeneous catalysts. The biomaterial was comparably active or superior to colloidal Pd in the Heck reaction, giving a final conversion of 85% halide and initial rate of 0.17 mmol/min for the coupling of styrene and iodobenzene compared to a final conversion of 70% and initial rate of 0.15 mmol/min for a colloidal Pd catalyst under the same reaction conditions at 0.5 mol.% catalyst loading. It was easily separated from the products under gravity or by filtration for reuse with low loss or agglomeration. When compared to two alternative palladium catalysts, commercial 5% Pd/C and tetraalkylammonium-stabilised palladium clusters, the bioPd was successfully reused in six sequential alkylations with only slight decreases in the rate of reaction as compared to virgin catalyst (initial rate normalised for g Pd decreased by 5% by the 6th run with bioPd catalyst cf. a decrease of 95% for Pd/C). A re-usable Pd-catalyst made cheaply from bacteria left over from other processes would impact on both conservation of primary sources via reduced metal losses in industrial application and the large environmental demand of primary processing from ores.
Keywords: BioPd; Biogenic nanoparticles; Desulfovibrio desulfuricans; Heck coupling; Palladium catalyst;

Effect of V2O5 loading of V2O5/TiO2 catalysts prepared via CVC and impregnation methods on NO x removal by Woojoon Cha; Sungmin Chin; Eunseuk Park; Seong-Taek Yun; Jongsoo Jurng (708-715).
In this study, V2O5/CVC-TiO2 materials with different concentrations of V2O5 were prepared via chemical vapor condensation (CVC) and impregnation. The catalytic activities of these materials were tested and the physicochemical characteristics were analyzed using XRD, BET, FT-IR spectroscopy, XPS, HR-TEM, EDX mapping, H2-TPR, and NH3-TPD. The NO x removal efficiency of the V2O5/CVC-TiO2 catalysts was higher than that of the V2O5/P25-TiO2 catalysts and increased with increasing V2O5 concentration. At 200 °C, the highest NO x conversion was observed using 7 and 10 wt.% V2O5/CVC-TiO2 catalysts. The NO x conversion curve reached a plateau corresponding to the maximum conversion when the V2O5 content was greater than 7 wt.%. The V2O5/CVC-TiO2 catalyst comprised mainly anatase-phase TiO2 and well-dispersed V2O5. A greater concentration of V (well-balanced V4+/V5+) species existed on the V2O5/CVC-TiO2 catalyst surface. H2-TPR and NH3-TPD testing confirmed that the V2O5/CVC-TiO2 catalyst is highly reducible and has many acidic sites.
Keywords: V2O5/TiO2; Chemical vapor condensation (CVC); SCR; NO x ;