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Applied Catalysis B, Environmental (v.138-139, #)

Editorial Board (pp. co2).

Outside Back Cover (pp. co4).

Editorial Board (pp. i).

Uniform hamburger-like mesoporous carbon-incorporated ZnO nanoarchitectures: One-pot solvothermal synthesis, high adsorption and visible-light photocatalytic decolorization of dyes by Mojiao Zhou; Xuehui Gao; Yong Hu; Jiafu Chen; Xiao Hu (pp. 1-8).

Display Omitted► Uniform hamburger-like mesoporous carbon-incorporated ZnO nanoarchitectures were synthesized by a facile one-pot solvothermal route. ► The as-obtained samples possessed a high surface area of 103.7m²g⁻¹ and narrow pore size distribution around 7.2nm. ► The products exhibited high adsorption capability for Congo red. ► They also demonstrated enhanced photocatalytic activity for the decolorization of dyes under visible-light illumination.Uniform hamburger-like mesoporous carbon-incorporated ZnO (MC-ZnO) nanoarchitectures were facilely prepared by a simple, economical and environmentally benign solvothermal method using ethylene glycol (EG) as solvent in the presence of glucose. The as-obtained samples possessed a high surface area of 104m²g⁻¹ and narrow pore size distribution around 7.2nm. The adsorption behavior of Congo red (CR) onto the products fitted well the Langmuir isotherm and the adsorption process followed the pseudo-second-order kinetic model. The maximum adsorption capacity of CR as 162mgg⁻¹ was achieved by Langmuir equation, while only 18.8mgg⁻¹ was found for by commercial ZnO nanoparticles. Furthermore, the as-prepared nanoarchitectures exhibited enhanced photocatalytic activity for the decolorization of photosensitized dyes (CR and rhodamine-B) under visible-light illumination. Therefore, the MC-ZnO nanoarchitectures developed in this work may be a promising potential material for wastewater treatment.

Keywords: Mesoporous; Carbon-incorporated ZnO; Solvothermal synthesis; Adsorption; Photodecolorization

A facile and low-cost synthesis of granulated blast furnace slag-based cementitious material coupled with Fe₂O₃ catalyst for treatment of dye wastewater by Yao Jun Zhang; Li Cai Liu; Lu Lu Ni; Bing Li Wang (pp. 9-16).

Display Omitted► A catalyst of slag-based cementitious material loaded Fe₂O₃ is firstly synthesized. ► The Fe₂O₃/ASCM catalyst is firstly used for the photocatalytic degradation of CR. ► The photocatalytic degradation of CR obeys second order reaction kinetics. ► A possible reaction mechanism was proposed.A facile and low-cost route was used to synthesize a novel catalyst of alkali-activated granulated blast furnace slag-based cementitious material (ASCM) coupled with Fe₂O₃ by a three-step reaction of polymerization, ion exchange and impregnation. The FESEM and XRD results revealed that a high compressive strength ASCM with mean particle size about 50nm was synthesized and Fe₂O₃ covered on ASCM surface in the form of clusters. The photoluminescence peak sharply decreases with increase of Fe₂O₃ content due to the recombination probabilities of photogenerated electron–hole pairs to be inhibited. The photocatalytic activities for degradation of Congo red (CR) dye were evaluated and the sample of ASCM loaded about 5wt% Fe₂O₃ showed the highest degradation efficiency under UV irradiation. The photocatalytic degradation of CR in solution obeys second order reaction kinetics and a possible reaction mechanism is proposed.

Keywords: Slag-based cementitious material; Fe; ₂; O; ₃; Photocatalysis; Reaction kinetics; Degradation efficiency

Multifunctional graphene oxide–TiO₂ microsphere hierarchical membrane for clean water production by Peng Gao; Zhaoyang Liu; Minghang Tai; Darren Delai Sun; Wunjern Ng (pp. 17-25).

Display Omitted► GO–TiO₂ microsphere hierarchical membrane was fabricated through assembling GO–TiO₂ composite on the surface of a polymer membrane. ► Large specific surface area with porous structure. ► Enhanced charge separation efficiency. ► Sustainably high water flux (ca. 60L/(m²h) within 15h). ► Enhanced strength and flexibility.The severe scarcity of clean water is arousing concern worldwide. The development of clean water production heavily relies on membrane technology, although the performance of current membranes is significantly restricted by membrane fouling. In this work, a novel graphene oxide (GO)–TiO₂ microsphere hierarchical membrane was fabricated through assembling GO–TiO₂ microsphere composite on the surface of a polymer filtration membrane. This kind of membrane possesses the multifunction of concurrent water filtration and degradation of pollutants. GO sheets play double roles in GO–TiO₂ membrane, including (1) cross linker for individual TiO₂ microspheres; and (2) electron acceptor to enhance photocatalytic activity. Hence, this novel membrane shows sustainably high permeate flux due to the hierarchical membrane structure, high photodegradation activity and no membrane fouling. The excellent performance of this GO–TiO₂ hierarchical membrane indicates its promising potential in clean water production field.

Keywords: Hierarchical membrane; Multifunction; Anti-fouling; Water production

Production of visible activity and UV performance enhancement of ZnO photocatalyst via vacuum deoxidation by Yanhui Lv; Chengsi Pan; Xinguo Ma; Ruilong Zong; Xiaojuan Bai; Yongfa Zhu (pp. 26-32).

Display Omitted► ZnO with visible activity and high UV activity was fabricated via vacuum deoxidation. ► The performance is regarded due to the introduction of surface oxygen vacancies. ► The concentration of surface oxygen vacancies could be controlled by tuning the temperature and time in vacuum. ► The enhancement in performance is due to the broadening of the valance band. ► The production of visible activity results from the narrow of energy band gap.ZnO photocatalyst with surface oxygen vacancies was obtained via vacuum deoxidation method. The concentration of surface oxygen vacancies could be controlled by tuning the temperature and time in vacuum, which governs the production of visible activity and the enhanced level of photocatalytic activity. The optimum UV photocatalytic activity and photocurrent of vacuum ZnO are almost 1.7 and 2.4 times as high as that of pure ZnO, respectively. Interestingly, the dramatic visible photocatalytic activity and distinct photocurrent both are generated due to the introducing of oxygen vacancies on ZnO surface. The enhancement in performance is attributed to the high separation efficiency of photogeneration electron–hole pairs due to the broadening of the valance band (VB) induced by surface oxygen-vacancies states. The production of visible photoactivity is demonstrated to be the narrow of energy band gap resulting from the rising of VB.

Keywords: Photocatalysis; Vacuum Deoxidation; ZnO; Surface oxygen vacancy

Oxidation of dichloromethane over Pt, Pd, Rh, and V₂O₅ catalysts supported on Al₂O₃, Al₂O₃–TiO₂ and Al₂O₃–CeO₂ by Satu Pitkäaho; Tuomas Nevanperä; Lenka Matejova; Satu Ojala; Riitta L. Keiski (pp. 33-42).

Display Omitted► All tested catalysts showed high activity in DCM oxidation. ► DCM oxidation was affected the most by GHSV, then with DCM and water concentration. ► Acidity and reducibility were key features when activity and selectivity are considered. ► After 40.3h in DCM oxidation the Pt/Al₂O₃ catalyst proved to be stable. ► DCM decomposed by detaching the chlorine prior to breakage of hydrogen.Pt, Pd, Rh and V₂O₅ metallic monolith catalysts supported on Al₂O₃, Al₂O₃–TiO₂ and Al₂O₃–CeO₂ were examined in the oxidation of dichloromethane (DCM). To improve the selectivity towards HCl and to prevent catalysts’ deactivation, the water amount in the feed gas mixture was adjusted to 1.5wt.%. All tested catalysts showed high activity in DCM oxidation and high selectivity towards HCl formation. Over Pt/Al₂O₃ and Rh/Al₂O₃, the 100% DCM conversions were reached at 420°C and 440°C and the maximum HCl yields detected were 92% and 93%, respectively. Addition of CeO₂ to the Al₂O₃ support affected the activity only a little, while somewhat more visible enhancement was seen with the addition of Pt, Pd, Rh and V₂O₅. However, more positive effect on the HCl and/or CO₂ yield was observed. Results showed that high acidity together with increased reducibility leads to an active catalyst for DCM oxidation. After the 40.3h stability test no obvious change in the Pt/Al₂O₃ catalysts’ performance was seen. Characterization showed no carbonaceous species on the catalyst's surface, but instead, some chlorine was detected on the surface that at this point did not affect the catalyst's activity or selectivity. The DCM decomposition seems to proceed on the catalyst surface via detaching the chlorine atoms before the breakage of the hydrogen bonds, hence following the order of the lowest bond energy in each step.

Keywords: Catalytic oxidation; Emission abatement; Chlorinated volatile organic compounds (CVOC); Dichloromethane (DCM); Methylene chloride; Reducibility; Acidity

RuO₂–SiO₂ mixed oxides as corrosion-resistant catalyst supports for polymer electrolyte fuel cells by Amod Kumar; Vijay K. Ramani (pp. 43-50).

Display Omitted► RuO₂–SiO₂ is a viable alternative to Vulcan XC-72R carbon. ► In-depth analysis of the fuel cell performance of Pt/RuO₂–SiO₂ electrocatalyst. ► RuO₂–SiO₂ electrocatalyst supports exhibit exceptional electrochemical stability.The objective of this study was to evaluate the suitability of mixed oxides of silica (SiO₂) and ruthenia (RuO₂) for use as electrocatalyst supports in polymer electrolyte fuel cells (PEFCs). The RuO₂:SiO₂ oxides were synthesized in three different molar ratios (0.1:0.9, 0.3:0.7 and 0.5:0.5). Of these formulations, RuO₂–SiO₂ (0.5:0.5) displayed high BET surface area (∼290m²g⁻¹), high electronic conductivity (>5Scm⁻¹), and outstanding electrochemical stability (change in double layer capacitance of <10% compared to 360% for Vulcan XC72 carbon upon rigorous accelerated potential cycling tests that mimic automotive drive cycles). The RuO₂–SiO₂ (0.5:0.5) support material was subsequently catalyzed by deposition of 24wt% of platinum nanoparticles. The resultant electrocatalyst yielded a mass activity of 50mAmg_Pt⁻¹ and an area specific activity of 156.3μAcm⁻² at 0.9V vs. RHE when tested in a fuel cell operating at 80°C and 75% relative humidity.

Keywords: Electrocatalyst support; Polymer electrolyte fuel cell; Carbon corrosion; Mixed metal oxides

Synthesis of nanosized Ce_0.85M_0.1Ru_0.05O2−_δ (M=Si, Fe) solid solution exhibiting high CO oxidation and water gas shift activity by Vijay M. Shinde; Giridhar Madras (pp. 51-61).

Display Omitted► Ru and Fe/Si modified CeO₂ were synthesized and characterized. ► Excellent catalytic activity for CO oxidation and water gas shift was observed. ► Cyclic redox behavior and high OSC were observed with the catalyst. ► Relation between activity and reducibility of the catalyst was discussed.Nanosized Ce_0.85M_0.1Ru_0.05O2−_δ (M=Si, Fe) has been synthesized using a low temperature sonication method and characterized using XRD, TEM, XPS and H₂-TPR. The potential application of both the solid solutions has been explored as exhaust catalysts by performing CO oxidation. The addition of Si- and Fe- in Ce_0.95Ru_0.05O2−_δ greatly enhanced the reducibility of Ce_0.85M_0.1Ru_0.05O2−_δ (M=Si, Fe), as indicated by the H₂-TPR study. The oxygen storage capacity has been used to correlate surface oxygen reactivity to the CO oxidation activity. Both the compounds reversibly release lattice oxygen and exhibit excellent CO oxidation activity with 99% conversion below 200°C. A bifunctional reaction mechanism involving CO oxidation by the extraction of lattice oxygen and rejuvenation of oxide vacancy with gas feed O₂ has been used to correlate experimental data. The performance of both the solid solutions has also been investigated for energy application by performing the water gas shift reaction. The present catalysts are highly active and selective towards the hydrogen production and a lack of methanation activity is an important finding of present study.

Keywords: Solid solution; Ceria supported catalyst; Oxygen storage capacity; CO oxidation; Redox mechanism; Water gas shift

A photo-catalysis and rotating nano-CaCO₃ dynamic membrane system with Fe-ZnIn₂S₄ efficiently removes halogenated compounds in water by Bo Gao; Lifen Liu; Jiadong Liu; Fenglin Yang (pp. 62-69).

Display Omitted► A continuous photocatalysis and CaCO₃ dynamic membrane reaction system is studied. ► CaCO₃ significantly enhanced dehalogenation under UV irrdiation. ► The hybrid system is steady during long-term operation. ► The hybrid system indicates great application prospect in wastewater treatment.A photo-catalysis and dynamic membrane reactor system (PMR), with coated nanoCaCO₃ layer on polypropylene non-woven fabric material, was studied for continuous photocatalysis and retention of catalysts in a single device, in removing halogenated compounds (2,4,6-Tribromophenol and 2,4-Dichlorophenol) in water. Both the batch and the continuous photocatalytic experiments were carried out to investigate the efficiency in COD removal, in removing halogenated compounds and in dehalogenation. A comparison of the separation performance of photocatalysts between bare (uncoated) and pre-coated nanoCaCO₃ dynamic membranes was conducted. The pre-coated dynamic membrane can significantly enhance the filtration performance and improve the retention of photocatalysts. Particularly, nanoCaCO₃ was found able to assist and improve debromination efficiency during UV irradiated photolysis. Tentative debromination pathway and dehalogenation mechanism were proposed. Due to the assisted additional reaction by the nanoCaCO₃ dynamic membrane, the PMR system with nanoCaCO₃-coating and Fe-ZnIn₂S₄ completely removed halogenated compounds, achieved highest COD removal (72% for 2,4,6-Tribromophenol and 75% for 2,4-Dichlorophenol), 85–90% debromination and 99% dechlorination efficiencies. The long-term continuous photocatalytic debromination experiments demonstrated that the dynamic membrane hybrid system was very steady in the long-term operation and the debromination maintained at about 85% during the 40h photocatalytic debromination reaction. The combination of dynamic membrane and photocatalysis provides a new alternative for practical application of photocatalysis.

Keywords: Abbreviations; PMR; photocatalytic membrane reactor; 2,4,6-TBP; 2,4,6-Tribromophenol; 2,4-DCP; 2,4-DichlorophenolPhotocatalytic membrane reactor; Dynamic membrane; 2,4,6-Tribromophenol; 2,4-Dichlorophenol

The effect of Ca²⁺ and Al³⁺ additions on the stability of potassium disilicate glass as a soot oxidation catalyst by Changsheng Su; Paul J. McGinn (pp. 70-78).

Display Omitted► Simple alkali disilicate glasses can provide the basis for effective soot catalysts. ► Catalytic activity and stability can be tailored through Al and Ca substitutions for K in K₂O·2Si₂O₂ glass. ► Substituting K₂O with CaO or Al₂O₃ gives a glass with improved chemical stability, but too much degrades the catalytic activity. ► Stable glass catalysts with soot combustion temperatures below 400°C have been achieved.Potassium disilicate (K₂Si₂O₅) glasses substituted with additions of Ca²⁺ and Al³⁺ have been prepared, characterized and tested as diesel soot oxidation catalysts. Ca and Al modify the silicate glass network, resulting in improved stability for catalyzing oxidation of diesel soot. TGA and water immersion studies showed that substituting K₂O with CaO can improve the chemical stability with a small loss of catalytic activity. (K₂O)_0.5(CaO)_0.5(SiO₂)₂ had a soot ignition temperature ( T_ig) around 410°C and also excellent catalytic stability with repeated soot oxidation cycling. Similarly, substituting with Al³⁺ gave improved stability, with (K₂O)_0.7(Al₂O₃)_0.3(SiO₂)₂ exhibiting a T_ig around 370°C and better stability than K₂O·2Si₂O₂. The activity results are interpreted with insights gained from FTIR characterization.

Keywords: Glass catalyst; Soot oxidation; Potassium silicate; Diesel particulate filter; Mixed ion effect

Aerobic oxidative desulfurization of model diesel using a B-type Anderson catalyst [(C₁₈H₃₇)₂N(CH₃)₂]₃Co(OH)₆Mo₆O₁₈·3H₂O by Hongying Lü; Wanzhong Ren; Weiping Liao; Wei Chen; Yang Li; Zhanghuai Suo (pp. 79-83).

Display Omitted► An Anderson-type catalyst [(C₁₈H₃₇)₂N(CH₃)₂]₃Co(OH)₆Mo^(V,VI)₆O₁₈ has been developed. ► The catalyst shows high activity in aerobic ODS and the TON can reach about 4200. ► The activity of catalyst may be related to the mixed-valence of molybdenum ions.A B-type Anderson polyoxomolybdates with mixed-valence molybdenum ions, [(C₁₈H₃₇)₂N(CH₃)₂]₃Co(OH)₆Mo^(V,VI)₆O₁₈, was prepared and characterized by Fourier transform infrared spectroscopy(FT-IR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), differential thermal analysis (DTA) and X-ray photoelectron spectrum (XPS). The polyoxometalate shows high catalytic activity in aerobic oxidative desulfurization of model diesel and the turnover number (TON) can reach about 4200 in absence of any sacrificial agent under mild conditions. The quaternary ammonium cations in the catalysts play a vital role in the aerobic oxidative desulfurization system. The catalytic activity for the oxidation of sulfur-containing compounds decreases in the order of 4,6-DMDBT>DBT>BT.

Keywords: Oxidative desulfurization; Diesel; Dioxygen; Anderson-type polyoxomolybdates

Fabrication, characterization and photocatalytic activity of TiO₂ layers prepared by inkjet printing of stabilized nanocrystalline suspensions by Marcela Černá; Michal Veselý; Petr Dzik; Chantal Guillard; Eric Puzenat; Martina Lepičová (pp. 84-94).

Display Omitted► Titanium dioxide was synthesized hydrothermally under different conditions. ► Photocatalytically active pure rutile was the dominant phase. ► Low viscosity stable jettable formulations were developed. ► Thin titania layers were prepared by inkjet printing. ► Morphology and roughness of the layers depends on synthesis conditions.Titanium dioxide (TiO₂) colloidal dispersions were synthesized by hydrothermal synthesis in acidic pH under various process conditions. Phase structure of prepared TiO₂ was identified as pure rutile by X-ray diffraction analysis and crystallite sizes determined by the Scherrer equation were in the range of 10–25nm. These values correlated with particle sizes observed by transmission electron microscopy (TEM). Afterwards, the prepared TiO₂ dispersions were used for the formulation of stable inkjet printable “inks”. Thin layers of nanocrystalline TiO₂ were deposited by inkjet printing onto soda-lime glass substrates. After sintering at 500°C, thin patterned films were obtained. Their basic physicochemical properties were characterized by standard methods. Optical microscopy and SEM imaging revealed highly structured topography of samples surface. Layer hardness was equivalent to the B pencil as determined by the “Pencil Hardness Test”. The topology and roughness were examined by atomic force microscopy and RMS roughness was in the range of 40–100nm. Band gap energy of TiO₂ determined by UV–vis reflection spectroscopy was consistent with known rutile values. The photocatalytic activity of printed layers was evaluated on the basis of 2,6-dichloroindophenoldiscoloration rate monitored by UV–vis spectroscopy and did not exceed the performanceof Aeroxide P-25. Despite average photocatalytic performace of this particular TiO₂ type, inkjet printing proved to be an efficient method for the fabrication of patterned titania films originating from nanocrystalline precursor.

Keywords: Photocatalytic activity; Hydrothermal synthesis; Inkjet printing; Colloidal dispersion

Synthesis, characterization and photocatalytic activity of visible-light plasmonic photocatalyst AgBr-SmVO₄ by Tingting Li; Yiming He; Hongjun Lin; Jun Cai; Lvzhuo Dong; Xiaoxing Wang; Mengfei Luo; Leihong Zhao; Xiaodong Yi; Weizheng Weng (pp. 95-103).

Display Omitted► Novel AgBr-SmVO₄ composite is prepared by deposition method. ► The AgBr-SmVO₄ composite degraded RhB 3.8× faster than AgBr under visible light. ► A charge transfer mechanism in the AgBr-SmVO₄ composite is suggested. ► The synergy of SmVO₄, AgBr and Ag is the origin of the high activity.A novel composite photocatalyst AgBr-SmVO₄ was synthesized by deposition method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectroscopy (DRS). The XRD, TEM, and XPS results indicated the prepared sample was actual a three-phase composite: SmVO₄, AgBr, and Ag during the photocatalytic reaction. Due to the plasmon effect of Ag nanoparticles, the composite exhibited excellent photoabsorption ability for visible light. The photoelectrochemical measurement verified that the suitable band potential of AgBr and SmVO₄ and the existence of metal Ag resulted in the high efficiency in charge separation of the composite. Photocatalytic degradation of rhodamine B (RhB) was carried out to evaluate the photocatalytic activity of AgBr/SmVO₄ under visible-light irradiation. The composite presented excellent photocatalytic activity due to the synergetic effect of SmVO₄, AgBr, and Ag nanoparticles. The photocatalytic activities of AgBr-SmVO₄ were differently affected by the AgBr content in the catalyst, AgBr-SmVO₄ amount, initial RhB concentration, and light sources. The highest degradation rate of 0.150min⁻¹ was obtained on the 50wt% AgBr-SmVO₄ sample, which was respectively 3.8 times and 25 times higher than that of AgBr and SmVO₄ photocatalyst. It was found thatO₂⁻ and Br⁰ acted as the main reactive species for the degradation of RhB under visible-light irradiation.

Keywords: AgBr/SmVO; ₄; Visible light irradiation; Composite; Plasmon

Stability improvement of Au/Fe–La–Al₂O₃ catalyst via incorporating with a Fe_xO_y layer in CO oxidation process by Caixia Qi; Shudong Zhu; Huijuan Su; Hui Lin; Rengui Guan (pp. 104-112).

Display Omitted► α-Fe₂O₃ was incorporated into Au/Fe–La–Al₂O₃ catalyst by post-adding iron nitrate with water, ethanol and acetone as solvents. ► On-line stability was enhanced with acceptable activity for the CO oxidation reaction. ► In situ thermal treatment can totally recover the spent Fe-modified catalysts but not the parent one. ► The corresponding catalysts exhibited the best catalytic performance when water was used as a solvent.Various amounts of α-Fe₂O₃ were incorporated into the parent Au/Fe–La–Al₂O₃ catalyst using post-adding iron nitrate precursor via the wetness impregnation method with water, ethanol, and acetone as solvents, respectively. Though post-addition of iron oxides makes gold particles aggregation with less catalyst activity than the parent one in the CO oxidation reaction, the most striking thing is that the Fe-modified catalysts present better online stability. At the same time, in situ thermal treatment can totally recover the activity of the spent Fe-modified catalysts but not the parent one. Water as a solvent performed better than ethanol and acetone; the corresponding catalysts exhibited the best catalytic performance with the most serious Au particle aggregation after post-addition of iron species.

Keywords: Au catalyst; Stability; Iron oxides; Solvent effect; CO oxidation; Au/Fe–La–Al; ₂; O; ₃

ZrNO–Ag co-sputtered surfaces leading to E. coli inactivation under actinic light: Evidence for the oligodynamic effect by S. Rtimi; M. Pascu; R. Sanjines; C. Pulgarin; M. Ben-Simon; A. Houas; J.-C. Lavanchy; J. Kiwi (pp. 113-121).

Display Omitted► Mechanism of the visible light photoinduced electron injection of Ag- and Zr-species. ► Co-sputtered Ag/Zr is effective in redox processes leading to Escherichia coli inactivation. ► The high resolution microscopy/EDAX is provided.This study reports visible light sensitive ZrNO and ZrNO–Ag polyester samples prepared by sputtering in an Ar/N₂/O₂ atmosphere leading to Escherichia coli bacterial inactivation. The bacterial inactivation by ZrNO avoids the increasing environmental concern involving the fate of Ag-leaching of many disinfectants. The simultaneous co-sputtering of ZrNO and Ag₂O enhanced the E. coli bacterial inactivation kinetics compared to the sequential sputtering of ZrNO and Ag. A reaction mechanism is suggested triggered by photoinduced interfacial charge transfer (IFCT) suggesting electron injection form the Ag₂O_cb to the ZrO_2cb. The sizes of the ZrO₂ and Ag nanoparticles in the co-sputtered ZrNO–Ag were 80–130nm and 8–15nm respectively as determined by high angular annular dark field (HAADF) microscopy. Evidence is presented by X-ray photoelectron spectroscopy (XPS) for the self-cleaning of the photocatalysts after bacterial inactivation. This enabled a stable catalyst reuse. The XPS experimental spectra of ZrNO and ZrNO–Ag were deconvoluted into their ZrN, ZrNO and ZrO₂ components. The amounts of Ag-ions released during bacterial inactivation were<5ppb/cm² and well below the Ag cytotoxic levels. Since no cytotoxicity was introduced during the bacterial inactivation process, the ZrNO–Ag disinfection proceeds through an oligodynamic effect.

Keywords: ZrNO sputtering; ZrNO–Ag co-sputtering; E. coli; Oligodynamic effect

The role of surface defect sites of titania nanoparticles in the photocatalysis: Aging and modification by Marija B. Radoičić; Ivana A. Janković; Vesna N. Despotović; Daniela V. Šojić; Tatjana D. Savić; Zoran V. Šaponjić; Biljana F. Abramović; Mirjana I. Čomor (pp. 122-127).

Display Omitted► Aging of TiO₂ NPs increases their crystallinity and photocatalytic activity. ► Dopamine modification of TiO₂ NPs reduced their photocatalytic activity. ► Aging of TiO₂/DAM NPs didn’t induce increase of photocatalytic activity.A study of photocatalytic activity of bare as prepared, bare aged and dopamine surface modified colloidal TiO₂ nanoparticles was obtained following degradation reaction of herbicide RS-2-(4-chloro-o-tolyloxy)propionic acid under UV light irradiation. Results showed that the most active photocatalyst is bare aged TiO₂ and the least active are dopamine modified nanoparticles. Results are discussed in the light of surface structure of TiO₂ nanoparticles. The study of surface modification of TiO₂ nanoparticles (4.5nm, TiO₂ NPs) with dopamine was also performed. The formation of inner-sphere charge-transfer complexes results in red shift of semiconductor absorption threshold (600nm), compared to bare TiO₂ NPs (380nm). Effective band gap energy of 3.2eV for bare TiO₂ NPs is reduced to 2.1eV for TiO₂/dopamine charge transfer complexes. The binding structure was investigated by UV-vis and FTIR spectroscopy. The obtained optimal geometry for binding of dopamine to surface Ti atoms was binuclear bidentate-bridging. From the Benesi–Hildebrand plot, stability constant of the order 10³M⁻¹ has been determined.

Keywords: Colloidal nanoparticles; Surface modification; Titanium dioxide; Photocatalysis

Solar light-activated photocatalytic degradation of gas phase diethylsulfide on WO₃-modified TiO₂ nanotubes by Mathieu Grandcolas; Thomas Cottineau; Alain Louvet; Nicolas Keller; Valérie Keller (pp. 128-140).

Display Omitted► We synthetized solar light responsive high surface area WO₃-modified TiO₂ nanotubes. ► We prepared TiO₂ nanotubes using hydrothermal synthesis in concentrated NaOH. ► WO₃/TiO₂ nanotubes exhibited high activity for degradation of diethylsulfide.► Correlation between surface species and the on-stream activity and deactivation. ► We proposed possible reaction mechanism pathways.Artificial solar light responsive high surface area WO₃-modified TiO₂ nanotubes have been efficiently used for performing the gas phase photocatalytic degradation of diethylsulfide, taken as simulant for the live yperite Chemical Warfare blister Agent, known as mustard gas. They were prepared by impregnating hydrothermally-synthesized titanate nanotubes with tungstate salt prior to the final calcination step. The influence of the WO₃ content, the inlet diethylsulfide concentration and the relative humidity on the photocatalytic activity as a function of time on stream has been investigated in terms of DES removal efficiency and of deactivation behavior. Modification of TiO₂ nanotubes with 4wt.% of WO₃ enhanced the photocatalytic activity in terms of DES removal efficiency and of resistance to sulfate deactivation. Correlation between the surface species and the on-stream activity and behavior of the photocatalysts was proposed, as well as possible reaction mechanism pathways.

Keywords: Photocatalysis; TiO; ₂; nanotubes; Hydrothermal synthesis; WO; ₃; modification; Diethylsulfide elimination

Activated carbon supported metal catalysts for reduction of nitrate in water with high selectivity towards N₂ by M. Al Bahri; L. Calvo; M.A. Gilarranz; J.J. Rodriguez; F. Epron (pp. 141-148).

Display Omitted► Grape seeds based Pd–Cu catalyst showed a very high nitrate removal activity. ► Absence of nitrite among the reaction products was detected. ► Chemical composition of the support can be responsible of that behavior. ► 2.5% Cu–<5% Pd (wt.) catalysts satisfied European Standards for drinking water.The catalytic removal of nitrate in water with hydrogen was investigated by using different activated carbon-supported metal catalysts. A commercial activated carbon (CAC) and one prepared by chemical activation of grape seeds with phosphoric acid (GS) were evaluated for the preparation of bimetallic catalysts (Pd–Cu, Pd–Sn and Pd–In). The support plays an important role in the catalytic performances for nitrate removal, affecting both activity and selectivity. Pd–Cu catalyst supported on GS showed the highest nitrate removal activity and nitrite was not found as by-product. The acidity of the reaction medium is associated with this behavior, attributing this effect to the chemical composition of the catalyst support. Control of pH through CO₂ addition to the reaction medium was beneficial in the case of the Pd–Cu catalyst prepared with CAC. However, no significant influence was observed in the case of the GS-supported catalyst. The concentration of promoting metal affects more strongly the catalyst performance than that of Pd. Low Cu contents (0.5 and 1.5wt.%) within the range tested (0.5–5wt.%) led to the highest selectivity towards the undesired ammonium ion. The catalysts supported on GS with 2.5% Cu and 5% Pd allowed achieving the European Standards for drinking water when a 100mg/L nitrate starting solution was treated, in terms of nitrate, nitrite and ammonium concentrations. The Pd–based bimetallic catalysts containing Sn and In as promoting metal showed a lower catalytic activity and significantly higher selectivity towards ammonium.

Keywords: Denitration; Nitrate; Activated carbon; Bimetallic Pd–Cu catalysts

Dechlorination of tetrachloro- o-benzoquinone by ozonation catalyzed by cesium loaded metal oxides by Suresh Maddila; Venkata D.B.C. Dasireddy; Sreekanth B. Jonnalagadda (pp. 149-160).

Display Omitted► Complete dechlorination of tetrachloro- o-benzoquinone (TCCD) is achieved. ► Complete mineralization of possible. ► % Conversion of TCCD and product selectivity depends on ozone ratio and ozonation duration.Ozone initiated oxidation of tetrachloro- o-benzoquinone (3,4,5,6-Tetrachlorocyclohexa-3,5-diene-1,2-dione, TCCD) in aqueous system catalyzed by different loadings of cesium oxide supported on metal oxides namely; Al₂O₃, SiO₂ and TiO₂ was investigated. Catalyst materials were characterized using different surface techniques including Raman, FT-IR, BET, SEM, TEM, ICP, TPD and XRD. XRD showed that cesium is in three different phases on the surface of the catalysts; and SEM and SEM-EDX indicated that cesium is well dispersed on the surface of the supports. Catalyst testing was done employing varying ozone molar ratios from 1 to 3 in the oxygen stream in a semi-batch reactor. 2,3-Dichloro-4,5-dioxohex-2-enedioic acid (DCA) was an intermediate and 2,3-dioxosuccinic acid (DSA) and oxalic acid (OA) were the main oxidation by-products. The oxidation products were characterized and confirmed by IR,¹H NMR and Mass spectral data. The product distribution was dependent on the acidity of the supports. Among all the catalysts while 5% Cs/TiO₂ showed good activity, 1% Cs/SiO₂ showed relatively poor catalytic activity.

Keywords: Key words; 3,4,5,6-Tetrachlorocyclohexa-3,5-diene-1,2-dione; Ozone; Cesium Oxide loaded; Alumina; Silica; Titania; 2,3-Dioxosuccinic acid; Oxalic acid

Polyoxometalate-based Ionic liquid as thermoregulated and environmentally friendly catalyst for starch oxidation by Xiaoli Chen; Bouasavanh Souvanhthong; Hang Wang; Hongwei Zheng; Xiaohong Wang; Mingxi Huo (pp. 161-166).

Display Omitted► Easily synthesis of POM-based ionic liquid catalyst [(CH₃)₃NCH₂CH₂OH]₅PV₂Mo₁₀O₄₀ ► Thermoregulated catalysis based on POMs, which means it could be used as a homogeneous catalyst for oxidation of starch when raising the temperature. ► Highly efficiency(0.59 molCO2Hper100g) and high selectivity on producing of polyhydroxycarboxylic acids. ► Easily handling of this catalyst for reuse.A new kind of polyoxometalate (POM) ionic liquid ([(CH₃)₃NCH₂CH₂OH]₅PV₂Mo₁₀O₄₀) (abbreviated as Ch₅PMo₁₀V₂O₄₀) has been synthesized by a precipitation/ion exchange method with choline chloride and H₅PMo₁₀V₂O₄₀ as precursors. The produced salt turned out to be an original ionic liquid (IL) catalyst and exhibited a novel switchable property based on temperature variation. In this regard, it refers to a thermoregulated feature that elevated temperature leads to the miscibility of catalyst and substrate. As decreasing the temperature, the catalyst precipitates and becomes heterogeneous form to be separated automatically from the reaction mixture. The combination of POMs with choline chloride was also proved to be effective in catalyzing the oxidation of starch, which showed higher or nearly identical performance with traditional catalysts, such as FeSO₄. Results demonstrated the catalyst was easily separated from the products and the retrieved Ch₅PMo₁₀V₂O₄₀ could be repeatedly used without appreciable loss of its performance, which highlighted the practical application of this important biomass.

Keywords: POMs; Ionic liquid; Oxidation; Starch; Thermoregulated catalyst

Green synthesis and catalytic properties of polyallylamine functionalized tetrahedral palladium nanocrystals by Gengtao Fu; Xian Jiang; Linfei Ding; Lin Tao; Yu Chen; Yawen Tang; Yiming Zhou; Shaohua Wei; Jun Lin; Tianhong Lu (pp. 167-174).

The water-soluble polyallylamine functionalized tetrahedral palladium nanocrystals with adjustable size and concavity are successfully achieved through a facile one-pot hydrothermal synthesis. Due to the facet effect, the concave tetrahedral palladium nanocrystals exhibit much superior catalytic activity for the reduction of 4-nitrophenol to flat tetrahedral palladium nanocrystals.•Tetrahedral Pd nanocrystals are facilely synthesized through hydrothermal method.•Concavity of nanocrystals can be tuned by controlling the reaction parameters.•Pd nanocrystals have excellent colloidal stability and anti-oxidation capability.•Pd{110} exhibits superior catalytic activity to Pd{111} for hydrogenation reduction.The water-soluble polyallylamine (PAH) functionalized tetrahedral palladium nanocrystals with adjustable size and concavity are successfully achieved through a one-pot hydrothermal synthesis. The size, morphology and surface composition of tetrahedral palladium nanocrystals are investigated by transmission electron microscopy (TEM), high angle annular dark field scanning TEM (HAADF-STEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The anchorage of PAH on palladium nanocrystals results in excellent colloidal stability and anti-oxidation capability of palladium nanocrystals. Both {110} and {111}-enclosed concave tetrahedral palladium nanocrystals ( c-Pd-TNCs) exhibit superior catalytic activity to only {111}-enclosed flat tetrahedral palladium nanocrystals ( f-Pd-TNCs) for the hydrogenation reduction of nitro functional groups and CN double bond.

Keywords: Green synthesis; Polyallylamine; Palladium nanocrystals; Tetrahedra; Catalytic activity

A facile approach to ZnO/CdS nanoarrays and their photocatalytic and photoelectrochemical properties by Chunmei Li; Taha Ahmed; Mingguo Ma; Tomas Edvinsson; Jiefang Zhu (pp. 175-183).

Display Omitted► A facile and controllable method to prepare ZnO/CdS nanoarrays is reported. ► Initial voltage pulse is very important for the fast nucleation and even distribution of ZnO on FTO glass during electrodeposition. ► The promoting effect between coupled ZnO and CdS is proved. ► The optimum composition of ZnO/CdS nanoarrays also varies with the circumstances of their testing and application.ZnO nanorods were successfully deposited on Transparent Conductive Oxide (TCO) glass by electrochemical deposition, during which initial pulse potential proves important for the fast nucleation and even distribution of ZnO. CdS nanoparticles were coated outside the as-prepared ZnO nanorods by chemical-bath deposition forming ZnO/CdS nanoarrays. The nanoarrays were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), ultraviolet–visible (UV–vis) spectroscopy, and photoelectrochemistry. The short-circuit current density ( J_sc) of some ZnO/CdS sample showed over 3.3mA/cm² under solar-simulated illumination. The ZnO/CdS nanoarrays showed promising photocatalytic activity with respect to the degradation of Eriochrome Black T (EBT). The relatively high photoelectrochemical properties and photocatalytic performance under visible light irradiation can be ascribed to the enhanced visible light harvest from CdS and charge separation by the coupling of the semiconductors. The combination of electrodeposition and chemical-bath deposition can provide a simple and facile approach to the fabrication of one-dimensional nanocomposites.

Keywords: ZnO; CdS; Nanoarray; Photocatalysis; Photoelectrochemistry

Ion-exchange synthesis and enhanced visible-light photocatalytic activities of CuSe-ZnSe flower-like nanocomposites by Weidong Shi; Jiaqi Shi; Shuai Yu; Pei Liu (pp. 184-190).

Display Omitted► The CuSe-ZnSe flower-like nanocomposite can be easily synthesized by using ion-exchange method. ► The content of CuSe in the nanocomposite influences the visible light photocatalytic activity.► IFCT effect can explain the cause of enhanced visible-light photocatalytic activities of the nanocomposite.CuSe-ZnSe flower-like nanocomposites with uniform diameters can be easily fabricated on a large scale by a controlled ion-exchange reaction between monodisperse ZnSe flower-like nanostructures and Cu²⁺ ions in solution. The difference of solubility products ( K_sp) of ZnSe and CuSe is the main driving force for the formation of these flower-like nanocomposites. The Cu content greatly influences the physical properties and photocatalytic activity of obtained CuSe-ZnSe nanocomposites. The as-produced CuSe-ZnSe nanocomposites show tremendous enhancements on the photocatalytic degradation ratio of organic dyes methylene orange (MO) and methylene blue (MB) under visible-light irradiation. The 8wt.% CuSe-ZnSe sample exhibits the highest degradation ratio for both MO (ca. 100%, 90min) and MB (ca. 96%, 60min), which are over 4 times and 2.5 times than that of the pure ZnSe sample, respectively. Based on the data of UV–vis diffuse reflection spectra, XPS and PL spectra, the enhancements of photocatalytic activities of CuSe-ZnSe flower-like nanocomposites are due to the effective separation of photo-electrons and holes induces by the direct initiates interfacial charge transfer (IFCT) from the valence band (VB) of ZnSe to CuSe, which results in the reduction of CuSe to Cu₂Se. This work not only highlights the potential use of visible-light-driven CuSe-ZnSe flower-like nanocomposites photocatalysts, but also emphasizes the simple ion-exchange in situ growth method for the preparation of selenides heterogeneous structures.

Keywords: CuSe-ZnSe nanocomposites; Ion-exchange reaction; Visible-light-driven; Photocatalytic activities; Organic dyes

Insights into the role of SO₂ and H₂O on the surface characteristics and de-N₂O efficiency of Pd/Al₂O₃ catalysts during N₂O decomposition in the presence of CH₄ and O₂ excess by M. Konsolakis; I.V. Yentekakis; G. Pekridis; N. Kaklidis; A.C. Psarras; G.E. Marnellos (pp. 191-198).

Display Omitted► The detrimental effects of H₂O and SO₂ on de-N₂O efficiency of Pd/Al₂O₃ revealed. ► H₂O inhibition on de-N₂O rate is reversible since it simply competes N₂O adsorption. ► Substantial irreversible deactivation is resulted by SO₂ presence in feed stream. ► SO₂ results in Brönsted acid sites on Al₂O₃ and hence in inactive Pd δ⁺ species. ► Correlation between surface chemistry and catalytic performance is demonstrated.The catalytic abatement of nitrous oxide (N₂O), a powerful greenhouse and ozone depletion gas, is an efficient end-of-pipe technology for N₂O emissions control. However, de-N₂O performance is notably suppressed by SO₂ and H₂O presence on the flue gases, whereas little is known about their influence on catalyst surface chemistry. In the present study, the impact of sulfur dioxide and water vapor on the catalytic performance of Pd/Al₂O₃ catalysts during the N₂O decomposition in the presence of CH₄ and O₂ excess is investigated, with particular emphasis on the corresponding surface chemistry modifications. Catalytic activity and stability measurements, in conjunction with a kinetic study, were carried out to elucidate the individual effect of each molecule on de-N₂O performance. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and Fourier transform infrared spectroscopy (FTIR) of pyridine adsorption are employed to evaluate the impact of SO₂ and H₂O molecules on catalyst surface chemistry, which is appropriately correlated with the achieved catalytic performance. The results revealed that the de-N₂O efficiency can be substantially improved by CH₄ under reducing (absence of O₂) conditions, due to the scavenging of strongly adsorbed O_ads species by the hydrocarbon; however, under O₂ excess conditions the beneficial effect of CH₄ is marginal. Water vapor in the feed has a detrimental influence on both N₂O and CH₄ conversions, which, however, is totally reversible; the latter is mainly ascribed to the competitive adsorption of H₂O molecules on catalyst surface. In contrast, SO₂ addition in feed stream results in a severe, irreversible deactivation; SO₂ leads to the creation of Brönsted acid sites on Al₂O₃ support, which in turn results in highly oxidized Pd entities, inactive for N₂O decomposition.

Keywords: N; ₂; O decomposition; Palladium; CH; ₄; SO; ₂; H; ₂; O; XPS; DRIFTS; FTIR-pyridine

Sulfation of Pt/Al₂O₃ catalyst for soot oxidation: High utilization of NO₂ and oxidation of surface oxygenated complexes by Shuang Liu; Xiaodong Wu; Duan Weng; Min Li; Jun Fan (pp. 199-211).

Display Omitted▶ Modification of sulfates enhances the soot oxidation activity of Pt/Al₂O₃ in NO+O₂. ▶ The sulfated Pt/Al₂O₃ promotes the preferential adsorption of NO₂ on soot. ▶ The accelerated decomposition of SOCs by sulfates is observed by in situ FTIR. ▶ Highly reactive NO₂⁺ species exits on the sulfated catalyst at high temperatures.The sulfated Pt/Al₂O₃ catalyst was synthesized by impregnating H₂SO₄ on the Pt/Al₂O₃ catalyst. It exhibits higher catalytic activity than Pt/Al₂O₃ for soot oxidation under loose contact conditions in a feed flow containing NO and O₂. Further studies ascribe its good activity to a synergistic effect between sulfate species and platinum. Firstly, the electronegative sulfate species may improve the oxidation-resistance of metallic platinum in the oxidizing atmosphere, which is important for achieving high NO↔NO₂↔soot recycling efficiency; Secondly, the sulfate species inhibit the NO_x adsorption on the alumina support, leading to a preferential adsorption of NO_x on the surface of soot rather than on the catalyst, and thus provide more chances for NO₂-soot reaction to generate the surface oxygenated complexes (SOCs); Finally, the sulfate species can promote the further decomposition of these SOCs species, resulting in a high catalytic efficiency for soot oxidation.

Keywords: Pt/Al; ₂; O; ₃; Sulfates; Diesel soot oxidation; Surface oxygenated complexes; NO; _x; preferential adsorption

Photocatalytic degradation of organic pollutants on surface anionized TiO₂: Common effect of anions for high hole-availability by water by Hua Sheng; Qin Li; Wanhong Ma; Hongwei Ji; Chuncheng Chen; Jincai Zhao (pp. 212-218).

•Specific-adsorbed anions such as F⁻, PO₄³⁻, and SO₄²⁻ cause similar effects on the photocatalytic process of TiO₂.•These effects originate from a common mechanism that is based on the anion-derived surface negative charges.•The anion-derived surface negative charges draw the photogenerated holes to the TiO₂ surface by the electrostatic force and consequently enhance the oxidation of the surface adsorbed water molecules.Effects of TiO₂ surface anionization by inorganic anions such as phosphate, fluoride and sulfate on the photocatalytic degradation behaviors of a series of model pollutants are systematically investigated. The degradation rate, accumulation of hydrogen peroxide, formation of hydroxyl radicals and zeta potential are compared in the presence of different anions. Our experimental results show that specific-adsorbed anions have similar effect on all the tested photocatalytic parameters in all the systems, although the extent is anion-dependent. These observations indicate that the previously studied effect of surface fluorination is not special, and it is only an example of anionization effects. In combination with DFT calculation, we propose a common mechanism for anionization effect. According to this mechanism, the anion-derived surface negative charges are able to draw the photogenerated holes to TiO₂ surface by electrostatic force. Thus, more holes are available at the interface, which accelerates remarkably the oxidation of surface-adsorbed solvent water to freeOH radicals.

Keywords: Anion; TiO; ₂; Photocatalysis; Charge separation; Hole-availability

Significant photocatalytic activity enhancement of titania inverse opals by anionic impurities removal in dye molecule degradation by Min Wu; Anmin Zheng; Feng Deng; Bao-Lian Su (pp. 219-228).

Display Omitted► Negative effect of sulfate impurities. ► Titania inverse opal photocatalysts. ► Removal of sulfate impurities by simple washing. ► Enhancement of photocatalytic activity. ► Theoretical calculations of dye molecule and sulfate anions adsorption.The photocatalytic behavior in dye molecule degradation of highly ordered three dimensional macroporous titania inverse opals prepared by the polystyrene spheres templating method has been investigated. The sulfate impurity stemming from K₂S₂O₈ used as initiator for the styrene polymerization and remaining in the final materials in a form of sulfate anions was found to strongly inhibit the photocatalytic process of titania inverse opals. The mechanism of the negative effect of sulfate anionic impurity has been studied by the theoretical calculations and the comparison of samples subject to a wash process or not, the artificial addition of sulfate anions to the reaction medium and cycle experiments of samples without the washing process. Raman spectroscopy confirmed that in TiO₂ inverse opal structures, sulfate ions are present in divalent forms. However, in aqueous photocatalytic medium, monovalent hydrosulfate anions can also be present. Theoretical calculations on the interaction of sulfate (mono and divalent) anions and Rhodamine B (RhB) with TiO₂ inverse opal indicated that the adsorption binding energy of divalent sulfate anions on the titania surface (168kcal/mol) is over four times as that of the Rhodamine B (36kcal/mol) in the photocatalytic system and that of hydrosulfate anions is around 53–57kcal/mol, still much higher than that of Rhodamine B. The strong adsorption of the anionic sulfate impurity on the surface of titania inverse opals would block the active sites and thus strongly affect the photocatalytic performance. A model of the negative action of sulfate anions has been proposed. This work leads to a new physic-chemical insight on the behavior of sulfate anions in the photocatalytic degradation of RhB and revealed that a single washing process to remove the impurity suggested significant promotion effect of the photocatalytic reaction without any surface modulations. This washing process dramatically suppressed the adsorption effect induced by the sulfate impurity and simplified the procedures, improving the photocatalytic performance.

Keywords: Inverse opal; TiO; ₂; , Photocatalysis; Sulfate anion effect; Dye molecule degradation

Crystalline palladium–cobalt alloy nanoassemblies with enhanced activity and stability for the formic acid oxidation reaction by Lu Zhang; Ling Wan; Yanrong Ma; Yu Chen; Yiming Zhou; Yawen Tang; Tianhong Lu (pp. 229-235).

Display Omitted► Pd–Co alloy nanoassemblies (Pd–Co ANAs) are obtained by cyanogel reduction. ► Pd–Co ANAs have particular 3D structure, abundant defects and high alloying degree. ► Pd–Co ANAs exhibit enhanced stability and activity for the formic acid oxidation.In this work, we conveniently synthesize the three-dimensionally (3D) networks-like palladium–cobalt alloy nanoassemblies (Pd–Co ANAs) through a simple simultaneous reduction reaction with sodium borohydride using inorganic K₂PdCl₄/K₃Co(CN)₆ cyanogel as reaction precursors, and clarify the formation mechanism of 3D networks structure and generation mechanism of Pd–Co alloy at room temperature. The morphology, structure, size and composition of the Pd–Co ANAs are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry, chronoamperometry and CO-stripping voltammetry tests demonstrate the Pd–Co ANAs have higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning over single-component Pd nanoparticles for the formic acid oxidation reaction (FAOR) owing to their unique 3D structure and alloy property.

Keywords: 3D network; Palladium–cobalt alloy nanoassemblies; Cyanogel; Electrocatalytic activity; Formic acid oxidation reaction

Transesterification of canola oil to biodiesel using calcium bentonite functionalized with K compounds by Nezahat Boz; Nebahat Degirmenbasi; Dihan M. Kalyon (pp. 236-242).

.Display Omitted► Highly active solid base catalysts were synthesized by using calcium bentonite as a convenient support material and employed for transesterification. ► A relatively high 98.2±1.4% methyl ester yield could be obtained by using 40% KF on calcium bentonite catalyst. ► The catalyst was recovered and tested for reusability and stability. ► Bentonite was found to be a suitable support material for the preparation of K-functionalized biodiesel catalysts for the canola oil transesterification reaction.The transesterification reaction of canola oil and methanol to biodiesel was investigated using a calcium bentonite based catalyst support that was functionalized with KF, KOH and K₂CO₃. Transesterification reaction time, methanol to oil molar ratio, temperature and catalyst loading level were the principal parameters. The activity of KF impregnated catalyst was superior to those of KOH and K₂CO₃ catalysts. Methyl ester yields which were as high as 98.2±1.4% could be obtained with KF impregnation.

Keywords: Biodiesel; FAME; Transesterification; Calcium Bentonite; Potassium compounds

Visible-light-driven photodegradation of acetaldehyde gas catalyzed by aluminosilicate nanotubes and Cu(II)-grafted TiO₂ composites by Ken-ichi Katsumata; Xiao Hou; Munetoshi Sakai; Akira Nakajima; Akira Fujishima; Nobuhiro Matsushita; Kenneth J.D. MacKenzie; Kiyoshi Okada (pp. 243-252).

•We succeeded to synthesize the imogolite with nanotube structure.•Cu(II)-grafted TiO₂-imogolite composite was developed.•Composite exhibited high activity under visible light than Cu(II)-grafted TiO_2.•High activity of composite was exhibited over the wide range of relative humidity.•Composite is effective visible-light-driven photocatalyst decompose or remove VOCs.Aluminosilicate nanotubes and Cu(II)-grafted TiO₂ composites were prepared, and the acetaldehyde degradation activity of the composites was evaluated at various relative humidities. The aluminosilicate nanotubes were synthesized hydrothermally and characterized by TEM, XRD,²⁷Al and²⁹Si NMR, FT-IR, N₂ and water vapor isotherms. Their morphology was nanotubular with 3–5nm outer diameter, and the specific surface area was 245m²/g. The aluminosilicate had a strong affinity for water molecules, and the structure was determined to be an imogolite by²⁷Al and²⁹Si NMR. TiO₂ and imogolite composites exhibited higher activity for the photodegradation of acetaldehyde under UV irradiation than TiO₂, but was dependent on the relative humidity. Cu(II)-grafted TiO₂ and imogolite composites exhibited higher activity for the photodegradation of acetaldehyde under visible light irradiation than Cu(II)-grafted TiO₂, and were less affected by the relative humidity. These results show that Cu(II)-grafted TiO₂ - imogolite composites exhibit very efficient absorption and photodecomposition of acetaldehyde in a variety of environments.

Keywords: Imogolite; TiO; ₂; Photocatalyst; Relative humidity; Interfacial charge transfer; Acetaldehyde

Catalytic removal of benzene over CeO₂–MnO_x composite oxides prepared by hydrothermal method by Zhen Wang; Genli Shen; Jiaqi Li; Haidi Liu; Qi Wang; Yunfa Chen (pp. 253-259).

The benzene catalytic oxidation process for Ce_xMn1−_x composite oxides was carried out according to three paths. The first path (I), benzene that had been adsorbed on Ce_xMn1−_x oxides is oxidized by the release of oxygen from CeO₂ phase; the second path (II), benzene is oxidized by the release of oxygen from Ce_xMn1−_x oxides; the third path (III), benzene is oxidized by the active oxygen species from gas oxygen molecules. Meanwhile, the synergistic effect between CeO₂ and Mn₂O₃ can enhance the migration of oxygen vacancy to improve the catalytic activity; therefore, the synergistic effect and oxygen vacancy play an important part in the whole process.Display Omitted► A series of Ce_xMn1−_x catalysts are synthesized through hydrothermal process. ► Their catalytic properties over benzene oxidation were studied. ► The difference was explained in view of synergistic effect and oxygen vacancy.A series of CeO₂–MnO_x composite oxides were synthesized through hydrothermal method and the complete catalytic oxidation of benzene were examined. The effects of the Ce_at/Mn_at atomic ratio on the features of catalyst structure and catalytic behavior were researched. The results exhibited that the catalytic properties of CeO₂–MnO_x composite oxides were higher than pure CeO₂ or MnO_x. When the Ce_at/Mn_at ratio was 3:7, the catalytic activity reached the best. By means of testing, the data revealed that the synergistic effects existed in the composite oxides, which resulted in the enhancement of catalytic abilities. In the main phase, MnO_x provided available oxygen species and CeO₂ enhanced oxygen mobility. In addition, the nature of oxygen vacancy of catalysts was also studied through positron annihilation spectrum. The results showed that the concentration of oxygen vacancy for CeO₂–MnO_x composite oxides changed comparing with pure CeO₂ or MnO_x, which also caused the activity differences over benzene.

Keywords: CeO; ₂; –MnO; _x; composite oxides; Oxygen vacancy; Synergistic effect; Benzene oxidation

Selective synthesis of TiO₂-based nanoparticles with highly active surface sites for gas-phase photocatalytic oxidation by Yijiao Jiang; Rose Amal (pp. 260-267).

Display Omitted► It corroborates surface hydroxyl groups is vital for defining TiO₂ photoactivity. ► We apply this understanding to the synthesis of highly active TiO₂ materials. ► The present bare TiO₂ exhibits 100% photodegradation of acetaldehyde and ethanol. ► Only stoichiometric CO₂ production was observed and no by-products were evolved.This work demonstrated the absence of surface terminal hydroxyl groups plays a key role in the photocatalytic oxidation of low concentration volatile organic compounds. Probed by¹H MAS NMR spectroscopy, we showed the synthesis of bare and F-TiO₂ nanoparticles with undetectably low content of terminal hydroxyl groups (TiOH) on the surface of TiO₂ could be obtained through a sol–gel process. The characterization results by N₂ adsorption, XRD, HRTEM, Raman, and XPS show that the bare TiO₂ and F-TiO₂ have almost identical bulk and surface structural properties. The photocatalytic activity was evaluated by photocatalytic oxidation of acetaldehyde and ethanol. Due to the absence of terminal TiOH in the bare TiO₂ and F-TiO₂, both materials exhibit 100% photodegradation of acetaldehyde and ethanol. No deactivation was observed during the experimental period of 8 days. The activities surpassed the photodegradation performance of the benchmarking Aeroxide P25 TiO₂ under similar conditions (93%). On the bare TiO₂, only stoichiometric CO₂ production was observed and no detectable by-product existed in the product stream, resulting in no expanded off-odor problems. On the contrary, ethanol photodegradation on F-TiO₂ produced minor acetaldehyde as a by-product, but the amount of acetaldehyde produced was still lower than that produced on Aeroxide P25.

Keywords: Photocatalytic oxidation; Titanium dioxide; Surface hydroxyl groups; ¹; H MAS NMR; Acetaldehyde; Ethanol

Comparison of UV/TiO₂ and UV/H₂O₂ processes in an annular photoreactor for removal of micropollutants: Influence of water parameters on metaldehyde removal, quantum yields and energy consumption by Olivier Autin; Julie Hart; Peter Jarvis; Jitka MacAdam; Simon A. Parsons; Bruce Jefferson (pp. 268-275).

Display Omitted► Whilst background organic matter and alkalinity act asOH scavengers during UV/H₂O₂, alkalinity inhibits the UV/TiO₂ process due to TiO₂ aggregation. ► UV/TiO₂ is a much more effective process than UV/H₂O₂ at absorbing photons. ► However, greater quantum yields are observed in the UV/H₂O₂ process. ► The electrical energy consumption can be reduced by improving the rate of photon absorption in the reaction space.Advanced oxidation processes have proven their efficacy in the removal of micropollutants but the role of background constituents on the kinetics of degradation is not well understood. Investigation into the role of alkalinity and background organic matter as defined by three surrogate compounds – serine, leucine and resorcinol – on the degradation of metaldehyde was conducted with a continuous flow photoreactor operated as either UV/TiO₂ or UV/H₂O₂. Background organic compounds inhibited the process through scavenging such that reaction rates were on average reduced by 19%. Modelling the radiation field enabled the quantum yield to be determined indicating that metaldehyde contributed to 0.1% of the total quantum yield under realistic background organic matter concentrations. Examination of models in term of electrical energy per order suggested that ideal reactor width of 9mm for TiO₂ and 11.7cm are required.

Keywords: Metaldehyde; Natural organic matter; Alkalinity; Quantum yield; Advanced oxidation processes

Fe/SiO₂ heterogeneous Fenton catalyst for continuous catalytic wet peroxide oxidation prepared in situ by grafting of iron released from LaFeO₃ by G. Satishkumar; M.V. Landau; T. Buzaglo; L. Frimet; M. Ferentz; R. Vidruk; F. Wagner; Y. Gal; M. Herskowitz (pp. 276-284).

Display Omitted► Selective extraction deposition (SED) method proposed to prepare solid catalyst containing isolated iron sites. ► CWPO of phenol with in situ deposition of iron ions demonstrated high TOC removal (90%) and stability. ► Dynamic behavior of iron that includes its SED–leaching–condensation along the catalysts layer was observed.Functionalization of silica-gel by immobilization of iron ions at its surface was carried out through a novel method – selective extraction–deposition (SED) in acidic solution using LaFeO₃ orthoferrite with perovskite structure as a solid precursor. Isolated Fe-ions produced as a result of precursors decomposition in acidic aqueous solution were trapped by silica surface silanols. The presence of iron in the only one state of isolated surface ions over 2wt%Fe/SiO₂ material at the Fe content corresponded to surface silanols concentration was confirmed using ESR, Mossbauer spectroscopy, UV Raman, FTIR and XPS techniques. Catalytic performance of 2wt% Fe/SiO₂ was examined toward catalytic wet peroxide oxidation (CWPO) of phenol in up flow fixed bed reactor at pH 4, 80°C, LHSV 6h⁻¹ with 200ppmw phenol and 1300ppmw hydrogen peroxide in water. It was demonstrated that mixing of LaFeO₃ with silica-gel gives an advanced catalytic material with high activity (TOC removal of 90%) and stability without iron leaching. This effect is due to dynamic behavior of iron that includes its SED–leaching–condensation along the catalysts layer. In this case, the LaFeO₃ has a multiple function–active catalytic component, precursor of iron ions and buffer controlling the pH along the catalysts layer.

Keywords: LaFeO; ₃; perovskite; Selective extraction-deposition; Silica; Isolated iron ions; Phenol wet peroxide oxidation

Silver palladium core–shell electrocatalyst supported on MWNTs for ORR in alkaline media by Ryan C. Sekol; Xiaokai Li; Peter Cohen; Gustavo Doubek; Marcelo Carmo; André D. Taylor (pp. 285-293).

Display Omitted•Create supported Ag-Pd core–shell catalyst on MWNTs using galvanic displacement.•Oxygen reduction reaction of 3 different galvanic displacement procedures.•Ag@Pd/MWNTs have greater current density for ORR than standard catalysts.•Ag@Pd/MWNTs show improved tolerance to alcohols present during ORR.•Ag@Pd/MWNTs have improved durability compared to standard Pd/C catalysts.We show that silver palladium core-shell catalysts supported on multiwalled carbon nanotubes (Ag@Pd/MWNTs) are highly active and alcohol tolerant for oxygen reduction reactions (ORR) in alkaline media. These electrocatalysts were synthesized by galvanic displacement of Pd on Ag nanoparticles deposited on MWNTs. The Ag@Pd/MWNTs are shown to be tolerant of the presence of methanol and ethanol in the electrolyte. In the presence of methanol, the Ag@Pd/MWNTs current density decreased by 0.18mA/cm², compared to Pt/C (0.97mA/cm²) and Pd/C (1.09mA/cm²). In the presence of ethanol, the Ag@Pd/MWNTs current density decreased by 0.12mA/cm², compared to Pt/C (0.87mA/cm²) and Pd/C (2.13mA/cm²). The Ag@Pd/MWNTs also show improved durability with an increased mass activity of ~3.5 times that of standard Pd/C, after durability testing in ethanol. The Ag@Pd/MWNTs are promising platinum free direct alcohol fuel cell cathode catalysts due to their high activities and durability, as well as their improved tolerance to methanol and ethanol from possible fuel crossover.

Keywords: Oxygen reduction reaction; Electrocatalysts; Core–shell catalyst; Alkaline fuel cells; Direct alcohol fuel cells

Influence of oxygen addition on photocatalytic oxidation of aqueous ammonia over platinum-loaded TiO₂ by Satoshi Shibuya; Satoshi Aoki; Yoshika Sekine; Ikko Mikami (pp. 294-298).

•The decomposition rate was significantly increased by the addition of oxygen.•The influence of DO concentration on selectivity for nitrite and nitrate was examined.•The selectivity for nitrite and nitrate was suppressed as the initial concentration of ammonia was increased.The oxidation of aqueous ammonia over a platinum-loaded TiO₂ photocatalyst was investigated for purification of wastewater. The reaction rate for the decomposition of aqueous ammonia was significantly increased by the addition of oxygen to the reaction system. The enhancement of charge separation efficiency due to consumption of photogenerated electrons by oxygen increased the decomposition rate. For dissolved oxygen (DO) concentrations below 0.09mM, the initial decomposition rate and the selectivity for nitrite and nitrate increased as DO concentration increased. Although the selectivity for nitrite and nitrate was over 90% for the initial concentration of ammonia ([NH₃]_i)=5.0mM under an air flow, the selectivity was suppressed as the initial concentration of ammonia was increased, e.g., 43% for [NH₃]_i=100mM.

Keywords: Photocatalysis; Water treatment; Aqueous ammonia; Titanium(IV) oxide

Hierarchical porous CdS nanosheet-assembled flowers with enhanced visible-light photocatalytic H₂-production performance by Quanjun Xiang; Bei Cheng; Jiaguo Yu (pp. 299-303).

Hierarchical porous CdS nanosheet-assembled flowers, synthesized by ion-exchange between Cd(OH)₂ and Na₂S, exhibited high visible-light photocatalytic H₂ production performance.•Hierarchical porous CdS nanosheet-assembled flowers were synthesized by a simple ion-exchange strategy using morphology-analogous Cd(OH)₂ and Na₂S as precursors.•The prepared CdS flowers exhibited high visible-light photocatalytic H₂ production activity and 24.7% quantum efficiency at 420nm.•The ion-exchange strategy of Cd(OH)₂ intermediates can be extended to the preparation of other porous oxides and sulfides with hierarchical nanostructures.•The hierarchical organization of nanosheets and porous nanosheet structures can efficiently enhance light-absorption ability and provide a greater number of active adsorption sites.Hierarchical porous CdS nanosheet-assembled flowers were synthesized by a simple ion-exchange strategy using morphology-analogous Cd(OH)₂ and Na₂S as precursors. The prepared CdS flowers exhibited high visible-light photocatalytic H₂-production activity with a rate of 468.7μmolh⁻¹ and the corresponding apparent quantum efficiency (QE) of 24.7% at 420nm, which exceeded that obtained on CdS nanoparticles by more than 3 times. This enhanced photocatalytic H₂-production activity was achieved because the hierarchical organization of nanosheets and porous nanosheet structures can efficiently enhance light-absorption ability and provide a greater number of active adsorption sites. This work shows a great potential of hierarchical porous CdS nanosheet-assembled flowers for photocatalytic H₂ production, and also demonstrates that the ion-exchange strategy of Cd(OH)₂ intermediates can be extended to the preparation of other porous oxides and sulfides with hierarchical nanostructures.

Keywords: Hierarchical; Porous CdS nanosheet; Ion-exchange strategy; Photocatalytic H; ₂; -production activity

Controllable synthesis of double layered tubular CdSe/ZnO arrays and their photoelectrochemical performance for hydrogen production by Meng Wang; Jiangang Jiang; Guanjie Liu; Jinwen Shi; Liejin Guo (pp. 304-310).

Display Omitted► Double layered CdSe/ZnO arrays were prepared by CBD approach. ► Structure of the samples could be controlled by tuning the experimental condition. ► Physicochemical and photoelectrochemical properties were investigated. ► CdSe/ZnO prepared at 60°C for 60min showed superior photocatalytic activity. ► Growth mechanism of this new structure was also forecasted.CdSe sensitized ZnO nanostructure arrays with double layered tubular structure were first synthesized by chemical bath deposition and chemical etch process with hydrothermal-synthesized ZnO nanorods as the template. CdSe/ZnO arrays with different micro-nanostructures like nanocable or double layered nanotube were obtained by changing chemical bath deposition conditions. Physicochemical and electrical properties of this novel material were investigated to describe its photoelectrochemical performance in an electrode cell. Under the irradiation of 100mW/cm², CdSe/ZnO with double layered tubular structure gave maximum photocurrent of 2.55mA/cm², which is over 12 times larger than that of bare ZnO. The high performance of this material was believed structure dependent. The structure effect and growth mechanism of the double layered nanostructure arrays were also discussed in this paper.

Keywords: CdSe/ZnO; Double layered structure; Photoelectrochemical; Hydrogen production

Kinetic enhancement in photocatalytic oxidation of organic compounds by WO₃ in the presence of Fenton-like reagent by Hongshin Lee; Jihyun Choi; Seokheon Lee; Seong-Taek Yun; Changha Lee; Jaesang Lee (pp. 311-317).

•Combination with Fenton-like reagent improves photocatalytic activity of WO₃.•Performance assessment with multiple organics confirms the synergistic combination.•The effects of reaction parameters on the synergistic enhancement are examined.•Neutral pH condition favors the production of OH radicals from the combined system.•The combined system enables the visible-light-induced oxidative degradation of organics.WO₃-mediated photocatalytic oxidation is achievable in the presence of electron acceptors as an alternative to O₂ or co-catalysts enabling O₂ reduction pathway. This study suggests the combination with Fenton-like reagent (Fe(III)/H₂O₂) as a strategy to improve the photocatalytic activity of WO₃. Under neutral pH condition where Fe(III) is present as iron oxide precipitate, photocatalytic degradation of 4-chlorophenol (4-CP) proceeded 3-fold faster in the WO₃/Fe(III)/H₂O₂ system relative to the WO₃/H₂O₂ system, while no noticeable oxidation occurred in the systems of Fe(III)/H₂O₂, WO₃, and WO₃/Fe(III). Such efficacy increase at circumneutral pH was observed in photocatalytic oxidation of diverse organics including phenol, bisphenol A, acetaminophen, and carbamazepine. Compatible with the pH dependence of photocatalytic activity of the WO₃/Fe(III)/H₂O₂ system, hydroxylation of benzoic acid and coumarin as indirect indication for OH radical production was drastically retarded with increasing pH. The pH effect indicates that OH radical as primary oxidant may be responsible for the kinetic enhancement in the WO₃/Fe(III)/H₂O₂ system. In that platinum deposits or Nafion layers as physical barriers possibly inhibit surface Fe(III) precipitation, use of platinized or Nafion-coated WO₃ caused the negligible photocatalytic improvement in the ternary system. Effective oxidative degradation in the presence of the UV cut-off filter corroborated visible light activation of the WO₃/Fe(III)/H₂O₂ system.

Keywords: Photocatalysis; Tungsten oxide; Fenton reaction; Advanced oxidation technology; Visible light activity

Sonophotocatalytic mineralization of antipyrine in aqueous solution by A. Durán; J.M. Monteagudo; I. Sanmartín; A. García-Díaz (pp. 318-325).

•The UV/H₂O₂/Fe/US process is an alternative for mineralization of antipyrine.•92% of TOC is removed after 50min.•Antipyirine photodegradation proceeds mainly through a radical mechanism.•Important synergistic effect (45.3%) between sonolysis and photoFenton.The mineralization of aqueous solutions of antipyrine, an emerging contaminant, using an innovative homogeneous sono-photocatalytic oxidation process (H₂O₂/UV/Fe/Ultrasound) was evaluated in an artificial UV lamp.At the selected operation conditions [H₂O₂]=1500ppm, pH=2.7, amplitude=100%, pulse length (cycles)=0.3 during 15min and then 1, 92% of TOC is removed after 50min treating an aqueous solution containing 50ppm of antipyrine. An important synergistic effect between sonolysis and photoFenton (UV/H₂O₂/Fe) of 45.4% was quantified using the first order rate constants for TOC.Comparison experiments of scavenger-loaded conditions demonstrate that the antipyirine photodegradation proceeds mainly through a radical mechanism probably beginning by the cleavage of the NN bond of penta heterocycle leading to the formation of aromatic acids (anthranilic and 1,4-benzenedicarboxylic acids) then followed by the opening of phenyl ring to form small molecular organic acids (mainly 2-butenedioic, 4-oxo-pentanoic and butanedioic acids), which may be decomposed further into CO₂.

Keywords: Abbreviations; ECs; emerging contaminants; k; _m; mineralization rate constant; NNs; neural networks; TOC; total organic carbon; US; ultrasound; US EPA; United States-Environmental Protection Agency; UV; ultraviolet; WWTPs; wastewater treatment plantsEmerging contaminant; Pharmaceuticals; TOC; Ultrasound; UV radiation

Recoverable visible light photocatalytic activity of wide band gap nanotubular titanic acid induced by H₂O₂-pretreatment by Yan Wang; Xiangjiang Meng; Xinluan Yu; Min Zhang; Jianjun Yang (pp. 326-332).

Ti-peroxide complexes are formed on the surface of NTA upon treatment with H₂O₂ functioning as visible light absorbing sensitizers. These surface complexes can be excited by visible light in association with the state change from ground state to excited state, while NTA functions as an electron acceptor to accept an electron which is injected from the excited state of Ti-peroxide complexes at its conduction band thereby generating TiOOH radical. TiOOH radical is highly active and tends to self-react to resume the original TiOH species in association with releasing O₂. Released O₂ captures a conduction band electron to generate O₂⁻ radical possessing strong oxidation ability thereby initiating the degradation of propylene.•NTA is endowed with visible light response by H₂O₂-pretreatment.•Ti-peroxide complexes is formed on the surface of NTA after H₂O₂-pretreatment. Ti-peroxide complexes serve as visible light absorbing sensitizers.•The excited state of Ti-complexes injects an electron to the conduction band of NTA.•The electron is captured by O₂ to generation of O₂⁻ for oxidation of propylene.Nanotubular titanic acid (denoted as NTA) with orthorhombic crystal structure was prepared by combining hydrothermal treatment of TiO₂ in alkaline medium with follow-up pickling. Resultant NTA was further treated with the aqueous solution of H₂O₂ to extend its light absorbance responses to visible light region thereby acquiring visible light photocatalytic activity. The photocatalytic performance of as-prepared NTA modified by H₂O₂ (denoted as H₂O₂-NTA) was evaluated by monitoring the oxidation of propylene under visible light irradiation. Moreover, as-fabricated H₂O₂-NTA was annealed at 300°C in air to examine its thermal stability, and used H₂O₂-NTA was retreated with aqueous H₂O₂ at the end of the third run of propylene oxidation tests to allow regeneration. Results indicate that pretreatment with aqueous H₂O₂ provides NTA with apparent visible light photocatalytic activity for the oxidation of propylene. H₂O₂-pretreatment results in a large amount of Ti-peroxide complexes on the surface of NTA; resultant Ti-peroxide complexes serve as visible light absorbing sensitizers and are excited by visible light in association with the state change from the ground state to the excited state. As a result, an electron is injected from the excited state of Ti-peroxide complexes to the conduction band of NTA, thereby generating O₂⁻ radical possessing strong oxidation ability to initiate the degradation of propylene. The visible light photocatalytic activity of H₂O₂-NTA gradually declines with extending photocatalytic reaction time, which is attributed to the gradual consumption of active Ti-peroxide complexes therewith. However, the lost visible light photocatalytic activity of H₂O₂-NTA can be regenerated by retreatment with aqueous H₂O₂. In this way, the visible-light-responses and photocatalytic activities of NTA, an orthorhombic crystalline rather than anatase or rutile phase TiO₂, is well regenerated.

Keywords: Nanotubular titanic acid; H; ₂; O; ₂; -pretreatment; Photocatalyst; Ti-peroxide complexes; Propylene oxidation

Heterogeneous photocatalysis of moxifloxacin: Identification of degradation products and determination of residual antibacterial activity by Xander Van Doorslaer; Kristof Demeestere; Philippe M. Heynderickx; Marieke Caussyn; Herman Van Langenhove; Frank Devlieghere; An Vermeulen; Jo Dewulf (pp. 333-341).

•Identification of photocatalytic degradation products of MOX at three pH levels.•Proposal of initial photocatalytic degradation pathway of MOX.•Evaluation of antibacterial activity after photocatalytic reaction at three pH levels.TiO₂-mediated heterogeneous photocatalysis of the fluoroquinolone antibiotic moxifloxacin in water is investigated with respect to both the formation of degradation products and the evaluation of residual antibacterial activity after photocatalytic treatment. High-resolution magnetic sector mass spectrometry coupled to high performance liquid chromatograph is used to determine the accurate mass of the measured degradation products. Eight main photoproducts are identified at both acidic, neutral and alkaline pH. A molecular structure is proposed by using the accurate mass, the double bond equivalent and by taking into account the structural formula of the parent compound. The photocatalytic degradation does not take place at the quinolone core and defluorination was not observed. A general initial photocatalytic pathway for moxifloxacin is proposed. Time profiles of the different degradation products reveal that the solution pH influences their relative abundance during reaction but the observed degradation products show no pH dependency. Residual antibacterial activity of the photocatalytic reaction solutions against Escherichia coli ( G⁻), Staphylococcus carnosus ( G⁺), Streptococcus mutans ( G⁺) and Klebsiella pneumoniae ( G⁻) is evaluated by means of agar diffusion tests. A reduction in antibacterial activity is noticed for all investigated pH levels with a complete inactivation at neutral pH after 12min of photocatalytic treatment.

Keywords: Heterogeneous photocatalysis; Fluoroquinolone; Pathway; Degradation products; Antibacterial activity

Sulphur tolerance of a P-doped Rh/γ-Al₂O₃ catalyst during the partial oxidation of methane to syngas by S. Cimino; G. Mancino; L. Lisi (pp. 342-352).

Display Omitted► P-doped Rh/γ-Al₂O₃ catalyst was tested for the first time in methane CPO to syngas. ► P-doped Rh catalyst shows enhanced tolerance against sulphur poisoning. ► A metallic Rh-P phase is formed by H₂-TPR for T>650°C. ► P increases Rh dispersion and its CO chemisorption capacity. ► P-doped Rh chemisorbs less S preserving a higher activity for steam reforming.A novel monolith catalyst with Rh supported on γ-Al₂O₃ and doped with phosphorous was prepared by temperature-programmed reduction of oxidic precursors and tested for the first time in the CPO of methane at short contact time and high temperature in the presence of sulphur. The catalyst was characterized by ICP-MS, XRD, TGA, SEM-EDS, BET, H₂-TPR, quantitative CO chemisorption measurements and in situ DRIFT of adsorbed CO, performed on freshly reduced samples or after exposures to sulphur species at temperatures and conditions close to those expected under actual CPO of methane. Results were compared with the reference undoped Rh/γ-Al₂O₃ catalyst and the P-γ-Al₂O₃ support. Both transient and steady state operation of the CPO reactor were investigated particularly with regards to the effect that the addition/removal of variable S quantities in the feed has on catalyst temperature, on the formation of main reaction products, on the approach to equilibrium and on the apparent reaction rate.

Keywords: Rh; Sulphur poisoning; Catalytic partial oxidation; Structured catalyst; DRIFT

Unravelling the structure and reactivity of supported Ni particles in Ni-CeZrO₂ catalysts by S. Gopalakrishnan; M.G. Faga; I. Miletto; S. Coluccia; G. Caputo; S. Sau; A. Giaconia; G. Berlier (pp. 353-361).

NiCeZrO₂ catalysts studied about surface chemistry and MSR reaction.Display Omitted► NiCeZrO₂ catalysts were prepared by optimisation of one pot co-precipitation method. ► High dispersion of supported Ni phases gives good stability to deactivation in low temperature MSR. ► Surface reactivity explained by easy oxygen transfer from/to support.We report about the synthesis and characterisation of two NiCeZrO₂ catalysts prepared by one pot-co-precipitation method. The two samples are characterised by similar chemical composition (15wt% Ni, Ce/Zr=80/20 atomic ratio) and properties of the CeZrO₂ support, which is a cubic phase solid solution with nanometer sized (5–6nm) crystalline hexagonal/roundish particles. The main differences between the samples are in the NiO particles dispersion and surface area, which were found to be affected by the synthesis pH. Both samples were characterised about their surface properties by employing FTIR spectroscopy of adsorbed CO probe, and tested about their activity and stability in methane steam reforming (MSR) reaction at relatively low temperature (793K). The results show a good activity in MSR irrespective of the NiO size and morphology, with negligible CO formation, but a strong dependence of the catalysts stability upon these parameters. Only the catalyst with smaller (5–10nm) NiO particles was found stable for 250h in MSR at relatively high steam to carbon ratio (S/C=2). This performance could be related to a positive effect of the CeZrO₂ support, allowing fast and easy oxygen transfer to and from the NiO/Ni⁰ active phase, most likely thanks to the occurrence of a strong metal–support interaction.

Keywords: Methane steam reforming; CeZrO; ₂; Ni carbonyls; FTIR spectroscopy; Solar energy

Cooperative effect of Ce and Mn in MnCe/Al₂O₃ environmental catalysts by N. Drenchev; I. Spassova; E. Ivanova; M. Khristova; K. Hadjiivanov (pp. 362-372).

•Manganese is better dispersed on MnCe/Al₂O₃ catalyst as compared to Mn/Al₂O₃.•MnCe/Al₂O₃ manifests higher catalytic activity than Ce/Al₂O₃ and Mn/Al₂O₃.•At low temperatures the NO+CO interaction occurs on NO_x-precovered surfaces.•At high temperatures the NO+CO interaction occurs on carbonate-precovered surfaces.Three samples, Mn/Al₂O₃, Ce/Al₂O₃ and MnCe/Al₂O₃ (containing 10wt.% metal) were prepared by impregnation and comparatively studied by means of FTIR spectroscopy, other characterization techniques and catalytic measurements. It was established that the active phase deposition led to (i) partial disappearance of all kinds of the alumina OH groups and (ii) blocking of part of the Al³⁺ Lewis acid sites. The results indicated that manganese was better dispersed on the MnCe/Al₂O₃ sample as compared to Mn/Al₂O₃. As a result, the bimetallic sample was the most active one in a series of catalytic reactions: NO decomposition, CO oxidation and CO+NO interaction.Interaction of all samples with CO leads to formation of carbonates and hydrogencarbonates increasing in amount with the temperature of interaction and in the sequence Al₂O₃2O₃2O₃≪MnCe/Al₂O₃. When the samples interacted with NO, different nitrogen oxo-compounds were formed and manganese nitrosyls appeared with the Mn-containing samples. In agreement with the higher Mn dispersion, the amount of the latter was larger with the bimetallic sample. Interaction between CO and NO results in formation of isocyanates, (hydrogen)carbonates and nitrogen oxo-compounds (nitrosyls, nitro-nitrito and nitrate species). When the interaction occurs at ambient temperature, the surfaces of the Al₂O₃, Ce/Al₂O₃ and Mn/Al₂O₃ are covered mainly by nitrates and nitro-nitrito species. With increase of the interaction temperature these species are gradually replaced by (hydrogen)carbonates. The temperature of this replacement decreases in the order Al₂O₃–Ce/Al₂O₃–Mn/Al₂O₃. With the MnCe/Al₂O₃ sample carbonates dominate even at 373K interaction. Consequently, the NO+CO catalytic conversion occurs in two regimes. The low temperature regime (the temperature interval depends on the catalyst) is associated with NO_x precovered surface, while at higher temperatures the catalysts surfaces are precovered with (hydrogen)carbonates.

Keywords: Adsorption; CO; NO; FTIR spectroscopy; Catalysis; NO decomposition; Oxidation of CO; NO; +; CO reaction

Improved low-temperature SCR activity for Fe-BEA catalysts by H₂-pretreatment by Radka Nedyalkova; Soran Shwan; Magnus Skoglundh; Louise Olsson (pp. 373-380).

•Improved low-temperature activity for Fe-BEA as NH₃-SCR catalyst.•H₂-pretreatment.•Catalyst regeneration after hydrothermal treatment.•Changes of the nature of the iron species.A series of iron-exchanged zeolite beta catalysts (0.5–4wt.% Fe) have been prepared by incipient wetness impregnation and tested for selective catalytic reduction (SCR) of NO_X with ammonia as reductant. The catalysts were characterized using BET, NH₃-TPD and XPS before and after H₂-pretreatment at 650°C for 5h. The NH₃-SCR activity tests show that the samples pretreated by hydrogen exhibit higher low-temperature SCR activity compared to the fresh samples, while the high-temperature activity remains almost constant. The results clearly show that the high-temperature H₂-treatment has a significant influence on the extent of different iron species formed in the zeolite. Furthermore, H₂-treatment of hydrothermally aged samples can recover some of the initial activity, although not completely due irreversible dealumination during the ageing. By H₂-pretreatment SCR catalysts with high iron loading and high activity can be prepared.

Keywords: H; ₂; -treatment; Catalyst regeneration; Low-temperature activity; Lean NO; _X; reduction; NH; ₃; -SCR; Fe-BEA; Zeolite catalyst

Effects of β-cyclodextrin introduction to zirconia supported-cobalt oxide catalysts: From molecule-ion associations to complete oxidation of formaldehyde by Lei Bai; Frédéric Wyrwalski; Jean-François Lamonier; Andrei Y. Khodakov; Eric Monflier; Anne Ponchel (pp. 381-390).

•β-CD as a novel additive for the design of Co₃O₄/ZrO₂ catalysts for the HCOH oxidation.•β-CD acts as an efficient scaffold molecule for the cobalt ions during preparation.•Controlled addition of β-CD improves both dispersion and reducibility of Co₃O₄.•Highest activity for β-CD to Co ratio of 0.1 with a 15°C drop in light-off temperature.The present paper deals with the impact of the addition of β-cyclodextrin on the genesis of cobalt active phases in zirconia-supported catalysts and on their performances in the complete oxidation of formaldehyde. With this aim, a series of cobalt catalysts supported on zirconia (5wt.%) is prepared by wet impregnation using mixtures of Co(NO₃)₂ and β-cyclodextrin as precursors. After the impregnation step, the materials are dried and calcined under air at 400°C. Different ratios of β-cyclodextrin to cobalt have been employed to obtain insight in the role of β-cyclodextrin, i.e. from 0.01 to 1. The ability of β-cyclodextrin to interact with the cobalt salt is investigated in solution by UV–vis spectroscopy, ion conductivity in water and dynamic light scattering measurements. After the impregnation step, the cobalt supported materials are characterized at different stages of the preparation (before and after calcination) by means of conventional techniques including UV–vis spectroscopy, thermogravimetry, N₂ adsorption/desorption, X-ray diffraction and temperature-programmed reduction analysis. Characterization results suggest that the carbohydrate ligand bound to the cobalt species retards the decomposition of the cobalt complexes into Co₃O₄. Finally, these cobalt oxide catalysts prepared from β-cyclodextrin are able to catalyze the oxidation of formaldehyde more efficiently than the control sample. The results are explained in terms of cobalt oxide dispersion and cobalt-support interactions. Indeed, the cobalt oxide particles generated by the thermal decomposition of β-cyclodextrin-Co(II) adducts are on the one hand smaller than those formed with cobalt nitrate alone and on the other hand reducible at lower temperatures, two key factors in the catalytic oxidation reactions.

Keywords: Cobalt catalysts; Cobalt precursor; Catalyst preparation; Cyclodextrins; VOC oxidation

Optimization of the degradation of imazalil by photocatalysis: Comparison between commercial and lab-made photocatalysts by Dunia E. Santiago; José M. Doña-Rodríguez; J. Araña; C. Fernández-Rodríguez; O. González-Díaz; J. Pérez-Peña; Adrián M.T. Silva (pp. 391-400).

•The efficiency of photocatalysis in the elimination of imazalil was proved.•Commercial and several home-made photocatalysts were studied.•The fastest degradation of imazalil was obtained with a home-made photocatalyst.•The degradation pathway was proposed and five by-products were confirmed by LC–MS.•The degradation pathway was confirmed by FTIR studies and ion chromatography.The elimination and mineralization of the fungicide imazalil and its by-products has been studied by means of heterogeneous photocatalysis. The activity of different photocatalysts, including the commercial TiO₂ benchmark photocatalyst (Evonik P25) and several TiO₂-based lab-made catalysts, is compared. The best results were achieved with the new lab-made photocatalyst synthesized by using sulphuric acid in the sol–gel process and calcined at a high temperature (EST-1023t). The apparent initial rate constant was up to 2 times faster for EST-1023t when compared to that obtained with Evonik P25. The effect of different operating parameters (pH, photocatalyst load and initial imazalil concentration) on the photocatalytic process were studied for these two photocatalysts and a degradation pathway was proposed considering data obtained from ion chromatography, LC–MS and FTIR studies. The formation of imidazole acetic acids was confirmed, as well as complete mineralization and release of stoichiometric nitrogen (as ammonium and nitrate) and chloride ions.

Keywords: Imazalil; Heterogeneous photocatalysis; Lab-made photocatalysts; TiO; ₂

Effect of Na content and thermal treatment of titanate nanotubes on the photocatalytic degradation of formic acid by Asma Turki; Hafedh Kochkar; Chantal Guillard; Gilles Berhault; Abdelhamid Ghorbel (pp. 401-415).

•Na retards the dehydration process during the transformation of titanate into TiO₂.•Presence of Na after calcination strongly impacts negatively photocatalysis.•Calcined Na-free titanate leads to highly active TiO₂ in formic acid degradation.•The enhancement of photoactivity results from improved textural properties.The influence of the sodium content on thermal stability and photocatalytic activity of calcined titanate nanotubes (TNT) was herein evaluated by preparing different samples through hydrothermal treatment of TiO₂ powder (P25) in a concentrated NaOH solution (11.25M) at 130°C during 20h followed by acid washing steps. Titanate nanotubes samples with sodium (Na-TNT) and sodium-free (H-TNT) were then obtained using different concentrations of HCl aqueous solutions namely 0.1M and 1M respectively. As synthesized nanomaterials with different Na percentages were then calcined at temperatures varying between 400°C and 700°C. Samples were characterized by means of nitrogen adsorption-desorption isotherms at 77K, thermal analysis (DTA, TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). The photocatalytic activities of Na-TNT and H-TNT derived nanomaterials were then evaluated through the photocatalytic degradation of formic acid (FA).Results show that the presence of sodium retards the dehydration process during the transformation of titanate into TiO₂ shifting the formation of anatase phase to higher temperatures. However, sodium is not necessary to preserve the nanotubular morphology. The presence of sodium after calcination strongly impacts negatively the photocatalytic properties. If sodium is completely removed from the initial titanate orthorhombic phase, calcination leads to TiO₂ anatase materials with enhanced photocatalytic properties compared to P25 in the degradation of formic acid, particularly if nanotubular morphology is preserved. The highest activity was therefore achieved for the H-TNT sample calcined at 400°C. The photodegradation activity of formic acid depends on the specific surface areas and TiO₂ crystallinity. In pure anatase nanoparticles the activity strongly decreases with coherent crystallographic domains ≥10nm.

Keywords: Titanates; Nanotubes; Sodium; Thermal stability; Photocatalytic activity

Degradation heterogeneities induced by repetitive start/stop events in proton exchange membrane fuel cell: Inlet vs. outlet and channel vs. land by Julien Durst; Adrien Lamibrac; Frédéric Charlot; Jérome Dillet; Luis F. Castanheira; Gaël Maranzana; Laetitia Dubau; Frédéric Maillard; Marian Chatenet; Olivier Lottin (pp. 416-426).

•The degradation rates induced by repeated start-ups are highly heterogeneous.•A first level of aging heterogeneity is between the H₂ inlet and outlet.•The second level of aging heterogeneity is between the land and the channel.This paper investigates aging heterogeneities that set up during PEMFC operation in start-up and shut down conditions. The spatially-resolved analyses were based on in situ measurements of local current densities, electrochemical surface area of Pt at the cathode in a segmented cell and overall CO₂ generation. In complement, ex situ physicochemical analyses were performed after the PEMFC testing, using scanning and transmission electron microscopy as well as focused ion beam scanning electron microscopy, to probe the micro and nano-scale of the cathode catalyst layer. In the present cell configuration (counter-flow mode, impact of the shut-down events negligible versus that of start-up), two kinds of aging heterogeneities are witnessed. Firstly, the performances loss at the air outlet/H₂ inlet is less important than at the air inlet/H₂ outlet; fuel starvation events are prevalent in this latter region; the resulting local loss of performances are linked to the distribution of the internal currents along the cell, and to larger physicochemical changes of the cathode catalyst layer in the air outlet/H₂ inlet region. The faradic part of the internal currents (generated during the fuel starvation events) was identified to not only come from the electrooxidation of the carbon support of the cathode catalytic layer (CL): internal currents may also originate from Pt dissolution, carbon corrosion in the gas diffusion layer (GDL) and/or water oxidation. Secondly, the degradations at the air inlet/H₂ outlet also depend on the position during the aging, either under a channel or a land. Fuel starvation events are more pronounced in land regions, due to slower removal of oxygen trapped under a land (the source of the fuel starvation) in the anode compartment during a start-up. Finally, it is wise pointing out that the particular degradation mechanism witnessed in this study would not have been observed if the MEA had been aged following a standardized stress test (potential cycling under N₂-atmosphere); therefore, one may question whether the DOE standardized stress-test procedure is relevant to mimic real fuel cell operation.

Keywords: Proton exchange membrane fuel cell; Platinum nanoparticles; Durability; Heterogeneities of ageing; Segmented cell; Channel and land

Hierarchically porous silicon with significantly improved photocatalytic oxidation capability for phenol degradation by Jingyang Su; Hongtao Yu; Xie Quan; Shuo Chen; Hua Wang (pp. 427-433).

Display Omitted•Oxidation capability of prepared porous silicon is elevated significantly due to quantum confinement effect.•Hierarchically porous silicon as a cathode displays good electrochemical stability.•Porous silicon can decompose phenol via oxidation approach under visible light irradiation for the first time.In this work, hierarchically porous silicon was fabricated through electro-assisted chemical etching using a silicon wafer as a substrate. Pores with an average diameter of ca. 1200nm (macropores) were observed and a large number of nanopores with a diameter of less than 5nm were uniformly distributed over the surface of the macropore, forming the hierarchically porous silicon with nanopores in macropores structure (NP-MPSi). UV–vis diffuse reflection measurements indicated that NP-MPSi has a bandgap of 2.12eV, which is 1.0eV higher than that of the original silicon wafer because of the quantum confinement effect caused by the nanopores. Mott–Schottky experiments further demonstrated that the increase in bandgap of NP-MPSi arises from a positive shift of the valence band potential, which improves its capability for photocatalytic oxidation. NP-MPSi exhibited higher photoelectrochemical stability than macroporous silicon (MPSi), a comparison sample lacking nanopores. Using phenol as an example, photocatalytic experiments under irradiation with a Xe lamp demonstrated that the kinetic constants of phenol degradation and total organic carbon removal using NP-MPSi were nearly 3.5 and 8.0 times larger, respectively, than those using MPSi. This unique porous silicon material is therefore an attractive photocatalyst for environmental applications.

Keywords: Porous silicon; Quantum confinement effect; Photocatalytic oxidation; Stability

BEA zeolite modified with iron as effective catalyst for N₂O decomposition and selective reduction of NO with ammonia by Paweł Boroń; Lucjan Chmielarz; Jacek Gurgul; Kazimierz Łątka; Tetsuya Shishido; Jean-Marc Krafft; Stanislaw Dzwigaj (pp. 434-445).

•Two-steps postsynthesis procedure allowed incorporating of iron in zeolite framework.•The isolated mononuclear Fe(III) was identified by DR UV–vis, XPS and XAS.•Mainly pseudo-tetrahedral Fe(III) was distinguished in FeSiBEA zeolite by Mössbauer.•FeSiBEA shows high activity (NO conversion>90%) and selectivity to N₂ (>95%).BEA zeolite is modified by a two-steps postsynthesis method allowing incorporate iron atoms into the zeolite framework. Two series of the zeolite samples with aluminium (Fe_xAlSiBEA) and without aluminium (Fe_xSiBEA), containing various iron content (0.5–4.0Fewt.%) are obtained. For low Fe content (<2Fewt.%), iron is incorporated into the framework of SiBEA zeolite as a framework pseudo-tetrahedral Fe(III) as evidenced by combined used of XRD, DR UV–vis, XAS,⁵⁷Fe Mössbauer and XPS investigations. In contrast, for higher iron content, the framework pseudo-tetrahedral Fe(III) and an extra-framework octahedral Fe(III) species are identified. For Fe_xAlSiBEA, significantly higher acidity than for Fe_xSiBEA is evidenced by FTIR with adsorption of CO and TPD of NH₃. Fe_xAlSiBEA and Fe_xSiBEA are found to be active and selective catalysts of N₂O decomposition and selective catalytic reduction of NO with ammonia. The highest catalytic activity in both processes are obtained for the Fe_4.0AlSiBEA sample containing iron mainly as the framework pseudo-tetrahedral Fe(III) and characterized by relatively high acidity.

Keywords: Iron; BEA zeolite; Ammonia; N; ₂; O decomposition; SCR of NO

HydrophobicW₁₀O₃₂⁴⁻/silica photocatalyst for toluene oxidation in water system by Alessandra Molinari; Giuliana Magnacca; Gabriele Papazzoni; Andrea Maldotti (pp. 446-452).

•A new hydrophobic silica containing Na₄W₁₀O₃₂ is prepared via sol–gel method.•Due to its high hydrophicity the material scavenges all the toluene present in water.•W₁₀O₃₂⁴⁻ photoassisted formation of OH radicals is responsible of the oxidizing ability.•More than 90% of the adsorbed toluene is converted to CO₂.•The heterogeneous photocatalyst is recyclable without any loss of activity.A new photocatalyst (Na₄W₁₀O₃₂/SiO₂/BTESE) has been prepared by simultaneous hydrolysis of tetraethyl orthosilicate (TEOS) and 1,2-bis(triethoxysilyl)ethane (BTESE) in the presence of Na₄W₁₀O₃₂. This material is able to scavenge and accumulate significant amounts of toluene from water solutions saturated with the hydrocarbon. This is due to its large specific surface area, micro and mesoporosity, and, above all, to the high hydrophobicity of its surface. Moreover, photoexcited Na₄W₁₀O₃₂/SiO₂/BTESE show savery strong oxidizing ability, allowing an almost complete mineralization of toluene to CO₂ through the formation and reactivity of OH radicals. Considering both the sorption capability and the photocatalytic activity, the efficiency of Na₄W₁₀O₃₂/SiO₂/BTESE is significantly higher than those of Na₄W₁₀O₃₂/SiO₂ and Na₄W₁₀O₃₂dissolved in homogeneous solution. At the end of a cycle of reaction, Na₄W₁₀O₃₂/SiO₂/BTESE is reusable without any loss of activity opening to the development of new efficient and stable photocatalytic systems addressed to clean wastewater containing aromatic hydrocarbons.

Keywords: Photocatalysis; Pollutionabatement; Polyoxoanion; Tolueneoxidation

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Applied Catalysis B, Environmental (v.138-139, #)

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Applied Catalysis B, Environmental (v.138-139, #)