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Applied Catalysis B, Environmental (v.125, #)

Editorial Board (pp. co2).

Editorial Board (pp. i).

Contents (pp. i-ii).

Contents (pp. co4).

Monometallic Pd/Fe₃O₄ catalyst for denitrification of water by Wuzhu Sun; Qi Li; Shian Gao; Jian Ku Shang (pp. 1-9).

Display Omitted► A magnetite supported monometallic Pd catalyst used in the denitrification of water. ► Fe₃O₄ was found to play multifunctional roles in this catalyst system. ► Fe₃O₄ was a good promoter for nitrate reduction with the Fe(II)/Fe(III) redox couple. ► Fe₃O₄ could also provide active sites for nitrite reduction. ► Different reduction mechanism from those in bimetallic catalysts was found.A magnetite supported monometallic Pd catalyst was synthesized by a co-precipitation process followed with the reduction in pure hydrogen at 453K. The catalyst was composed of ultrafine Pd nanoparticles (∼2nm) highly dispersed on the surface of superparamagnetic Fe₃O₄ nanoparticles. Aside from its roles as the catalyst support and the magnetic separation medium, Fe₃O₄ was found to be a good promoter for the nitrate reduction, where nitrate was firstly reduced to nitrite by the Fe(II)/Fe(III) redox couple, and subsequently reduced to nitrogen and ammonium. Further mechanistic studies demonstrated that besides the Pd sites, active sites for the nitrite reduction also exist on the surface of Fe₃O₄. Part of the nitrite reduction occurred on the surface of Fe₃O₄, which may also be attributed to the Fe(II)/Fe(III) redox couple. In the present study, ammonium was the main product because of the different denitrification mechanisms compared with bimetallic catalysts.

Keywords: Pd/Fe; ₃; O; ₄; Catalytic denitrification; Superparamagnetic catalyst; Fe(II)/Fe(III) redox couple

Corrigendum to “ZnO/La₂O₂CO₃ layered composite: A new heterogeneous catalyst for the efficient ultra-fast microwave biofuel production” [Appl. Catal. B: Environ. 103 (2011) 200–205] by Lei Jin; Yashan Zhang; James P. Dombrowski; Chun-Hu Chen; Anthony Provatas; Linping Xu; Christopher Perkins; Steven L. Suib (pp. 10-10).

Novel mesoporous Zn_xCd1−_xS nanoparticles as highly efficient photocatalysts by Xin Xu; Ruijuan Lu; Xiaofei Zhao; Yue Zhu; Sailong Xu; Fazhi Zhang (pp. 11-20).

Display Omitted► Uniform distributed mesoporous Zn_xCd1−_xS nanoparticles were fabricated. ► Using selective leaching of amorphous alumina from as-prepared Al-Zn_xCd1−_xS. ► The abundance of hydroxyl groups formed on the surface of mesoporous Zn_xCd1−_xS. ► Their photocatalytic activity increased with the decline of alumina content. ► The homogeneous mesoporous structure leading to the higher photocatalytic activity.Porous semiconductor photocatalysts which are active under illumination by visible light have attracted extensive attention recently due to their remarkable well-designed physical and chemical properties. Here, novel mesoporous Zn_xCd1−_xS nanoparticles have been successfully fabricated by a two-steps strategy: Al-Zn_xCd1−_xS nanoparticles which are homogeneously distributed within the confinement of an amorphous alumina matrix was first synthesized by in situ gas–solid reaction of a single precursor—a Zn²⁺,Cd²⁺,Al³⁺-containing layered double hydroxides (ZnCdAl-LDHs)—with gaseous H₂S; subsequently, selective leaching of amorphous alumina by sodium hydroxide solution from the as-prepared Al-Zn_xCd1−_xS nanoparticles was carried out, with the aim of achieving the introduction of mesopority in the chalcogenide semiconductor. The resulting mesoporous Zn_xCd1−_xS nanoparticles can retain the uniform distributed structure with a network-like manner after the selective leaching of amorphous alumina. The absorption edge of the mesoporous Zn_xCd1−_xS exhibit a monotonic blue shift within the visible light region as the amount of residual alumina decreased. The photocatalytic activities of the mesoporous Zn_xCd1−_xS samples for the photodegradation of methylene blue (MB) dye molecules increase with the decline of alumina. And, the mesoporous Zn_xCd1−_xS exhibits an enhanced photocatalytic performance compared to the pure CdS sample obtained from the same procedure without Zn²⁺, the unleached Al-Zn_xCd1−_xS sample and the sample obtained by a coprecipitation method with the same composition. The homogeneous structure of the mesoporous Zn_xCd1−_xS and the abundant surface hydroxyl groups are proposed to be beneficial to the generation of hydroxyl radicals, identified by electron spin resonance (ESR) spectra, leading to the higher photocatalytic activity.

Keywords: CdS; Layered double hydroxide; Photocatalysis; Mesoporous

The effect of TiO₂ doping on the catalytic properties of nano-Pd/SnO₂ catalysts during the reduction of nitrate by Yan-ni Guo; Jian-hua Cheng; Yong-you Hu; De-hao Li (pp. 21-27).

The XRD spectra of Pd/TiO₂–SnO₂ at different mol fraction of TiO₂ shows when the TiO₂ mol fraction exceeded 10%, the characteristic peaks of TiO₂ appeared at the diffraction angle 2 θ 48.03° and 75.04°, suggesting that TiO₂ had exceeded the maximum dispersion content on the surface of SnO₂ and was partly deposited on the surface of SnO₂ in the form of crystalline TiO₂.The catalytic activity of the doped Pd/TiO₂–SnO₂ catalysts was higher than that of the simple Pd/SnO₂ catalyst. Lattice distortion caused by introduced titanium ions which increase the redox active center oxygen vacancies is helpful for the improvement of the catalytic activity of Pd/TiO₂–SnO₂ composite catalysts.The monometallic catalysts Pd/TiO₂–SnO₂ and Pd/SnO₂ prepared by impregnation method were investigated for their ability to catalyze the reduction of nitrate with formic acid as the reducing agent and were characterized by X-ray diffraction (XRD), BET surface area, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Pd and TiO₂ were in high dispersion on the surface of the SnO₂ support when the mol fraction of TiO₂ was less than 15%. The SnO₂ crystal lattice was partially replaced by titanium ions, causing SnO₂ lattice distortion and resulting in the increase of oxygen vacancies as catalytic active sites. The best catalytic properties of the formic acid–Pd/TiO₂–SnO₂ system were achieved at a mol fraction of 10% TiO₂. Compared with the Pd/SnO₂ catalyst, the catalytic activity of Pd/TiO₂–SnO₂ increased by 48% from 2.08mg/(ming_cata) to 4.00mg/(ming_cata), while the NH₄⁺ concentration decreased from 13.0mg/L to 5.2mg/L. The catalytic activity, selectivity and stability of the Pd/TiO₂–SnO₂ catalyst were superior to those of Pd/SnO₂ with the same Pd loading and formic acid concentration. The results of the XPS analysis indicated that the catalysts Pd/SnO₂ and Pd/TiO₂–SnO₂ were of high oxygen vacancy. Pd/TiO₂–SnO₂ has better catalytic properties than Pd/SnO₂ may attribute to the increased amount of oxygen vacancy after TiO₂ doping.

Keywords: Palladium; Titanium dioxide; Tin dioxide; Nitrate; Catalytic reduction

Photocatalytic removal of 2,4-dichlorophenoxyacetic acid by using sol–gel synthesized nanocrystalline and commercial TiO₂: Operational parameters optimization and toxicity studies by E.I. Seck; J.M. Doña-Rodríguez; C. Fernández-Rodríguez; O.M. González-Díaz; J. Araña; J. Pérez-Peña (pp. 28-34).

Display Omitted► ECT-1023t showed higher photocatalytic activity than Evonik P25 at natural pH. ► Production of toxic of intermediates (2,4-DCP) was reduced by using ECT-1023t. ► Toxicity was eliminated before 1h of treatment using H₂O₂ as oxidizing agent.A comparative study of the photoefficiency of two different TiO₂ catalysts in the elimination, mineralization and detoxification of waters containing herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and toxic intermediates was performed at laboratory scale. Commercial TiO₂ (Degussa (Evonik) P25) and TiO₂ synthesized by citrate sol–gel method (ECT-1023t) were selected as photocatalysts. Adsorption studies, kinetic analysis and an analysis of the effect of adding oxidizing agents (H₂O₂ and S₂O₈²⁻) were carried out for both catalysts. The toxic effect of photocatalytic treatment at different reaction times was determined by marine bacteria Vibrio fischeri bioassay. The toxic effect on this organism of the main degradation intermediate 2,4-dichlorophenol (2,4-DCP) was higher than for the initial herbicide. The optimal operational variables to eliminate the herbicide and toxic intermediates were established for both catalysts. The most effective removal of 2,4-D and toxic intermediate 2,4-DCP was achieved using ECT-1023t as catalyst at pH 3 and pH 5. The inhibitory effect on V. fischeri growth in water containing 2,4-D after 2h of photocatalytic treatment was negligible when using ECT-1023t as catalyst. Longer times were necessary to obtain similar results when using P25 as catalyst. The addition of H₂O₂ significantly enhanced the degradation and mineralization rate, with different optimal H₂O₂ concentrations for the tested catalysts. When using H₂O₂ as oxidizing agent, toxicity on V. fischeri was eliminated before 1h of photodegradation treatment with both photocatalysts.

Keywords: 2,4-Dichlorophenoxyacetic acid; Photocatalysis; ECT-1023t; Vibrio fischeri; H; ₂; O; ₂; FTIR

Visible light induced photosensitized degradation of Acid Orange 7 in the suspension of bentonite intercalated with perfluoroalkyl perfluoro phthalocyanine zinc complex by Dominik Drozd; Krzysztof Szczubiałka; Łukasz Łapok; Michał Skiba; Hemantbhai Patel; Sergiu M. Gorun; Maria Nowakowska (pp. 35-40).

Display Omitted► A photosensitizer based on bentonite and fluorinated phthalocyanine was obtained. ► The hybrid photosensitizer can degrade Acid Orange 7, a model azo dye. ► The photodegradation occurs both in the absence and in the presence of oxygen. ► The hybrid photosensitizer may be reused.We report the intercalation of a perfluoroalkyl perfluoro phthalocyanine zinc complex (F₆₄PcZn) in bentonite (Ben) to generate a hybrid photosensitizer (F₆₄PcZn∈Ben) and demonstrate its ability to degrade a model azo dye, Acid Orange 7 (AO7), in aqueous solution using visible light. The F₆₄PcZn photosensitizer is active both in the presence and in the absence of O₂, via the photogeneration of singlet oxygen or via a photoinduced electron transfer from the azo dye, respectively. Both F₆₄PcZn and F₆₄PcZn∈Ben exhibit high photochemical stability. The heterogeneous system can be used cyclically by the removal and reutilization of the photocatalytic hybrid, thus highlighting possible technological applications.

Keywords: Bentonite; Perfluoroalkyl perfluoro-phthalocyanine; Azo dyes; Hybrid photosensitizer; Singlet oxygenAbbreviations; Ben; bentonite; F; ₆₄; PcZn; a perfluoroalkyl perfluoro phthalocyanine zinc complex; F; ₆₄; PcZn∈Ben; a hybrid photosensitizer based on a perfluoroalkyl perfluoro phthalocyanine zinc complex intercalated in bentonite; AO7; Acid Orange 7; XRD; X-ray diffraction; RNO; N,N-dimethyl-4-nitrosoaniline; RH; relative humidity; DMF; dimethylformamide; MeCN; acetonitrile; ANS; 2-anthracene sulfonate

CO₂ methanation on Rh/γ-Al₂O₃ catalyst at low temperature: “ In situ” supply of hydrogen by Ni/activated carbon catalyst by Colas Swalus; Marc Jacquemin; Claude Poleunis; Patrick Bertrand; Patricio Ruiz (pp. 41-50).

Display Omitted► Rh/γ-Al₂O₃ catalysts were studied in CO₂ methanation at low temperature. ► Enhancement of catalytic performances by mixing with nickel on activated carbon catalysts. ► Hydrogen migration from nickel catalysts to rhodium particles.Nowadays, the control of CO₂ emissions is still a challenge. A few alternatives exist but nothing concrete seems to be developed. Instead of catching and storing CO₂, one possibility would be its transformation into value added molecules as methane. Rhodium catalysts are active in CO₂ methanation reaction. But it seems that a competitive adsorption exist between the two reactants: CO₂ and hydrogen. In order to surpass this trouble and increase hydrogen adsorption, a known active catalyst in methanation (Rh/γ-Al₂O₃) was put into contact with a known active catalyst in hydrogen activation (Ni/activated carbon). Catalysts were prepared by the mechanical mixing of the latter two in different proportions. Catalysts were tested in the low temperature methanation reaction using CO₂ and H₂. Methane is produced in all cases with a 100% of selectivity. A significant synergy appears in the catalytic activity of this mixed catalyst. Production of methane in mixtures is largely higher than the theoretical predicted values considering the individual performances. Catalysts were characterized before and after reaction by ICP-AES, N₂ physisorption, XRD, CO₂ chemisorption, ToF-SIMS, XPS and TPR. The synergy is due to the increase of H₂ adsorption and promoting the carbon hydride formation. Furthermore the suggested hydrogen spill-over maintains Rh particles in a metallic state necessary for the reaction.

Keywords: CO; ₂; Methanation; Rhodium; γ-Al; ₂; O; ₃; Nickel; Hydrogen spill-over

Fe-zeolites as heterogeneous catalysts in solar Fenton-like reactions at neutral pH by Rafael Gonzalez-Olmos; Maria J. Martin; Anett Georgi; Frank-Dieter Kopinke; Isabel Oller; Sixto Malato (pp. 51-58).

Display Omitted► Fe-zeolites show high catalytic activity at neutral pH in photo-Fenton-like reactions. ► Contaminant degradation and efficiency of H₂O₂ utilization improved by contaminant adsorption in the zeolite frame. ► Catalytic activity of Fe-zeolites is significantly increased using solar light in a CPC pilot plant.This paper focuses on the study of photo-Fenton-like processes using two types of Fe-zeolites (Fe-ZSM5 and Fe-Beta) as heterogeneous catalysts in order to treat contaminated effluents with organic compounds at neutral pH. It was proved that light (solar and artificial) improves significantly the DOC removal in this kind of processes. A possible contribution by homogeneous photo-Fenton reaction catalyzed by the iron leached during the reaction was insignificant. This study also proves that the catalytic activity of Fe-zeolites is improved by photo Fenton-like processes using solar light in a pilot plant equipped with compound parabolic collectors (CPC).

Keywords: Heterogeneous catalyst; Photo-Fenton; Zeolites; Phenol; Imidacloprid; AOP

WS₂ nanosheets as a highly efficient electrocatalyst for hydrogen evolution reaction by Zhuangzhi Wu; Baizeng Fang; Arman Bonakdarpour; Aokui Sun; David P. Wilkinson; Dezhi Wang (pp. 59-66).

Unique separate WS₂ nanosheets (NSs) were produced through ball-milling S and WO₃ followed by an annealing at 600°C, which exhibit high electrocatalytic activity toward hydrogen evolution reaction due to their highly exposed active sites.Display Omitted► We report separate WS₂ nanosheets as a highly efficient electrocatalyst for hydrogen evolution reaction. ► WS₂ nanosheets were prepared by a mechanical activation strategy, followed by an annealing at an elevated temperature. ► Different annealing temperatures result in various nanostructures. ► Inorganic fullerene nanostructures can also be obtained at a high annealing temperature. ► The pretreatment of ball milling plays a crucial role in the formation of WS₂ nanosheets.Novel nanostructured material WS₂ nanosheets (NSs) were prepared through a simple and highly reproducible approach, namely, a mechanical activation strategy by using WO₃ and S as the starting materials, and were explored as electrocatalyst for hydrogen evolution reaction (HER). The as-prepared WS₂ NSs reveal separate NSs nanostructure with a sheet thickness of less than 10nm. On the basis of experimental results obtained under various synthesis conditions, a reasonable reaction process and formation mechanism is proposed, in which the pre-treatment of ball milling is assumed to play a key role for the formation of WS₂ NSs. Due to its large active sites originating from its unique structural characteristics such as loosely stacked layers, providing highly exposed rims particularly edges, WS₂ NSs catalyst has demonstrated high electrocatalytic activity toward HER, which considerably outperforms the commonly used MoS₂ (JDC) catalyst.

Keywords: Tungsten disulfide; Nanosheets; Preparation; Electrocatalyst; Hydrogen evolution reaction

Beneficial influence of EDTA on the structure and catalytic properties of sulfided NiMo/SBA-15 catalysts for hydrotreating of light gas oil by Sandeep Badoga; K. Chandra Mouli; Kapil K. Soni; A.K. Dalai; J. Adjaye (pp. 67-84).

Display Omitted► A detailed mechanism has been developed to explain the behavior of chelating agent. ► HRTEM results explain the high dispersion of NiMoS active phases in sulfided state. ► XANES reveals the delayed Ni²⁺ sulfidation is main cause of improvement in activity. ► EDTA helps in redistribution of big crystallite of MoO₃ during sulfidation.SBA-15 supported NiMo hydrotreating catalysts with different EDTA/Ni molar ratio were prepared by incipient wetness impregnation method. Hydrotreating activities of these catalysts were studied with Athabasca bitumen derived light gas oil and comparison was done with NiMo/SBA-15 and NiMo/γ-Al₂O₃ catalysts. A beneficial effect of chelating ligand was seen in hydrotreating activity and 28% increase in HDS of LGO was found as compared to NiMo/γ-Al₂O₃ in the case of EDTA/Ni molar ratio 4. Detailed mechanistic aspect of interaction between support – EDTA (ethylene diamine tetraacetic acid), EDTA-metallic species, support – metal, metallic species – metallic species at different reaction conditions is studied at different process parameters by using different characterization techniques such as X-ray absorption near-edge structure (XANES), Fourier transform infrared spectroscopy (FTIR), HRTEM, XRD, Raman, temperature programmed reduction (TPR), ICP-MS, CO chemisorption and N₂ adsorption. A detailed scheme has been developed to explain the behavior of chelating agent in mesoporous SBA-15 supported catalysts. HRTEM results explain the high dispersion of Ni and MoS₂ active phases in sulfided state even though big crystallite of MoO₃ was seen in oxide state characterized by XRD and Raman spectra which explains role of EDTA in redistribution of active phases during sulfidation. XANES technique is used as predominant method for atomic level study of various structural changes in sulfided and oxide catalysts to find out the appropriate mechanism of the reaction. Characterization by XANES reveals that the presence of chelating agent delayed Ni²⁺ sulfidation which is main cause of improvement in HDS and HDN activity of the catalysts prepared in presence of organic chelates. Nickel sulfidation starts only when the EDTA–Ni complex decomposes and released nickel atoms move to the reactive edges of the MoS₂ to form a finely dispersed sulfide NiMoS type II active phase.

Keywords: Key words; EDTA; SBA-15; Sulfidation mechanism; XANES; LGO; Hydrotreating

Electrocatalytic oxidation of ethylene glycol (EG) on supported Pt and Au catalysts in alkaline media: Reaction pathway investigation in three-electrode cell and fuel cell reactors by Le Xin; Zhiyong Zhang; Ji Qi; David Chadderdon; Wenzhen Li (pp. 85-94).

Display Omitted► Pt/C and Au/C with small particle size (2.4nm, 3.5nm) were prepared. ► Product generation sequence from EG electro-oxidation in high pH media was presented. ► Formic acid was favorably produced from CC bond breaking of EG not glycolic acid. ► >98% selectivity to glycolic acid was obtained in AEMFC with Au/C anode. ► Product distribution from EG electro-oxidation in AEMFC agreed with half cell tests.Carbon supported Pt and Au nanoparticles with small sizes (2.4nm for Pt/C, and 3.5nm for Au/C) and narrow size distributions were prepared though a modified solution-phase reduction method, and served as the working catalysts for an investigation of electrocatalytic oxidation of EG in alkaline media. Our three-electrode cell with an on-line sample collection system showed that with applied potential increasing, glycolic acid, oxalic acid and formic acid were sequentially produced from EG oxidation on Pt/C, while only glycolic acid and formic acid were detected on Au/C. Oxalic acid is a fairly stable product, and Pt/C is inactive to its further oxidation reaction. On Au/C, glycolic acid is the primary product, and no oxalic acid was found at specified test conditions. We clarified that formic acid was produced preferably from direct CC bond cleavage of EG not glycolic acid on both Pt/C and Au/C catalysts. The single anion exchange membrane-direct EG fuel cell (AEM-DEGFC) with Pt/C and Au/C anode catalysts showed consistent results with the three-electrode cell tests. The AEM-DEGC with Pt/C anode catalyst demonstrated a peak power density of 71.0mWcm⁻², which is much higher than that with the Au/C (only 7.3mWcm⁻²) at 50°C. With the fuel cell operation voltage decreasing (anode overpotential increasing), deeper-oxidized products oxalic acid and formic acid were generated in the Pt/C anode AEM-DEGFC with higher selectivity. No formic acid was detected in the Pt anode AEM-DEGFC when glycolic acid was employed as fuel. On Au/C anode catalyst, very high selectivity to glycolic acid (>98%) was achieved. The AEM-DEGFC results confirmed the EG electro-oxidation pathways proposed by using an on-line sample collection system.

Keywords: Electrocatalytic oxidation; Fuel cell; Alkaline electrolyte; Ethylene glycol; Reaction pathway

Establishing the trichloroethene dechlorination rates of palladium-based catalysts and iron-based reductants by Shujing Li; Yu-Lun Fang; Chris D. Romanczuk; Zhaohui Jin; Tielong Li; Michael S. Wong (pp. 95-102).

.Display Omitted► Trichloroethene degradation rates were quantified for Pd- and Fe-based materials. ► Room-temperature, atmospheric-pressure, buffered, H2-filled conditions were used. ► Pd-on-Au nanoparticles were 9 orders more active than commercial zerovalent iron. ► Unlike iron reductants, Pd-based catalysts did not form dechlorinated byproducts. ► These materials were tested under same reaction conditions for the first time.The removal of undesired chlorinated hydrocarbon contaminants through chemical destruction using ex situ Pd-based catalytic or in situ Fe-based reductive nanomaterials offers unique advantages over current physical displacement methods for groundwater treatment. While these two types of chemical methods has been studied in-depth in recent years, their respective hydrodechlorination and dechlorination transformations have not been analyzed together before. Here, the reactivities of Pd catalysts and Fe reductants were experimentally assessed for trichloroethene (TCE) degradation using room-temperature, atmospheric-pressure, dihydrogen-headspace-filled batch reactor studies under buffered and non-buffered conditions. Pseudo-first order reaction rate constants at pH 7 spanned 9 decades: 1.2×10⁴, 1.0×10³, 4.5×10², 2.41×10⁻⁴, 4.2×10⁻⁴, and 7.09×10⁻⁶L/g_active-metal/min for Pd-on-Au nanoparticles (Pd/Au NPs), Pd NPs, Pd-on-alumina powder, and two nano-sized forms and one micron-sized form of commercial zerovalent iron, respectively. With rates measured in the range of commonly reported values, the Fe-based materials produced ethane, ethene, and vinyl chloride; ethene hydrogenated into ethane at sufficiently long reaction times. The much more active Pd-based materials produced ethane as the primary TCE degradation reaction product. This study presents, for the first time, a quantitative comparison of TCE degradation rates determined under identical experimental conditions.

Keywords: Trichloroethene; Iron; Palladium; Gold; Hydrodechlorination; Nanoparticles

Molecular recognitive photocatalytic degradation of various cationic pollutants by the selective adsorption on visible light-driven SnNb₂O₆ nanosheet photocatalyst by Shijing Liang; Ruowen Liang; Linrui Wen; Rusheng Yuan; Ling Wu; Xianzhi Fu (pp. 103-110).

Display Omitted► SnNb₂O₆ nanosheet was applied into selective photocatalysis for the first time. ► Nanosheet exhibits very high selectivity and activity in mixture pollutants. ► Relationship between adsorption and photocatalytic activity was investigated. ► Roles of active species on the selective photocatalysis were discussed. ► Adsorption modes of cationic pollutants over nanosheet have also been proposed.Two-dimensional (2D) oxide nanosheet has attracted multidisciplinary study because of its unique physicochemical properties. In this work, a visible-light driven 2D nanosheet photocatalyst, SnNb₂O₆ nanosheet (SNNS), has been applied into the selective photocatalysis for the first time. It is found that the SNNS sample exhibits significantly higher selectivity and superior activity for the photocatalytic degradation of positively charged pollutants from a mixture solution compared with the bulk SnNb₂O₆, TiO₂, and N-doped TiO₂ under visible light irradiation, even when the concentrations of other pollutants are much higher than those of cationic pollutants. This high selectivity and activity may be explained by the integrative effect of the unique crystal structure, highly selective adsorption performance, and oxidation of the photogenerated holes. By analyzing the results of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy, as well as combining with the crystal structure of the nanosheet, the interaction between the SNNS sample and the pollutants has also been well investigated. In addition, the photocatalytic mechanism under visible light irradiation has also been discussed. Our current work may widen the application of the nanosheet and open promising prospects for the utilization of the nanosheet as visible light photocatalyst for selective degradation in environmental remediation.

Keywords: SnNb; ₂; O; ₆; Nanosheet; Visible light; Selective adsorption; Selective photocatalysis

Development of a catalytic ceramic foam for efficient tar reforming of a catalytic filter for hot gas cleaning of biomass-derived syngas by Manfred Nacken; Lina Ma; Steffen Heidenreich; Francis Verpoort; Gino V. Baron (pp. 111-119).

Display Omitted► Novel tar reforming catalytic filter with integrated catalytic foam developed. ► A MgO-Al₂O₃-NiO activated ceramic foam shows complete naphthalene conversion. ► In the presence of H₂S the catalytic filter achieves 98% naphthalene conversion.In order to improve the tar reforming performance of a catalytic filter in hot gas cleaning of biomass-derived syngas, as new approach, 45ppi ceramic foams of 10mm wall thickness were used as ceramic support for catalyst integration. Screening of this ceramic support was performed by varying the type of catalyst support, its loading and the NiO loading. As a result, a SiC ceramic foam with a MgO-Al₂O₃-NiO catalytic layer, a catalyst support density of 0.03g/cm³ and a NiO density of 0.02g/cm³ was identified as most active catalytic ceramic foam. After the transfer of the corresponding impregnation procedure to an Al₂O₃ based ceramic foam to be able to operate at the target filtration temperature of 850°C, a naphthalene conversion of 99% was achieved at a superficial velocity of 2.5cm/s in the presence of 100ppmv H₂S. At doubled superficial velocity the conversion still achieves 93%. The transfer of the catalyst integration procedure for the most active SiC candle supported MgO-Al₂O₃-NiO layer to an Al₂O₃ filter candle with 10mm wall thickness has led to a naphthalene conversion of 87% at 850°C at a superficial velocity of 2cm/s in the presence of 100ppmv H₂S being 8% higher than in the SiC based candle. The combined Al₂O₃ based catalytic filter and ceramic foam disk system shows an overall conversion of 99% at a superficial velocity of 2cm/s. Based on these results the corresponding overall conversion of an Al₂O₃ based catalytic filter candle with integrated catalytic ceramic foam was precalculated to 98% at 850°C in the presence of 100ppmv H₂S indicating the technical feasibility of efficient tar reforming using this novel catalytic filter candle design.

Keywords: Catalytic ceramic foam; Catalytic filter; NiO; Tar reforming; Biomass gasification; Hot gas cleaning

Electro-Fenton oxidation of pesticides with a novel Fe₃O₄@Fe₂O₃/activated carbon aerogel cathode: High activity, wide pH range and catalytic mechanism by Hongying Zhao; Yujing Wang; Yanbin Wang; Tongcheng Cao; Guohua Zhao (pp. 120-127).

.Display Omitted► Novel Fe₃O₄@Fe₂O₃/ACA composite cathode was reported for the first time. ► ACA with high surface area 2410m²g⁻¹ worked both as cathode and catalyst support. ► 90% of TOC removal was achieved after reaction 60min over wide pH rage of 3–9. ► Reasonable oxidation mechanisms were proposed when at acidic and basic condition.A novel electro-Fenton (E-Fenton) system with the Fe₃O₄@Fe₂O₃/activated carbon aerogel (ACA) composite cathode was firstly constructed in this study. Its application on degrading imidacloprid exhibited highly catalytic efficiency over a wide applicable pH range from 3 to 9. The removal of imidacloprid and TOC achieved to 90% within 30 and 60min, respectively. The nature of composite cathode was examined by BJH, XRD, SEM, TEM, XPS and FTIR techniques. ACA with high surface area of 2410m²g⁻¹ and multiplicated porosities composed of micropores and mesopores worked not only as cathode but also as Fenton catalyst support, enhancing oxidation activity. We proposed reasonable E-Fenton oxidation mechanisms with Fe₃O₄@Fe₂O₃/ACA cathode at acidic and basic conditions. At pH 3, it followed a Haber–Weiss mechanism that the dissolved iron ions and surface Fe(II) sites catalyzed the decomposition of H₂O₂ to generate hydroxyl radicals (OH). While at pH 9, it was expected the formation and deactivation of H₂O₂ complex as well as the catalytic decomposition of H₂O₂ with surface Fe(III) and Fe(II) sites to produce both superoxide anion (O₂⁻/HO₂) and hydroxyl radicals (OH), involving an in situ recycling of iron oxide (FeO·Fe₂O₃→Fe₂O₃).

Keywords: Composite iron oxide; Activated carbon aerogel electrode; Electro-Fenton; Surface reaction; Imidacloprid

Enhancement of nano titanium dioxide photocatalysis in transparent coatings by polyhydroxy fullerene by Wei Bai; Vijay Krishna; Jie Wang; Brij Moudgil; Ben Koopman (pp. 128-135).

Partially decomposed fungal spore on photocatalytic coating.Display Omitted► Polyhydroxy fullerene enhances TiO₂ photocatalysis in a thin, transparent coating. ► Polyhydroxy fullerene and TiO₂ self-assemble into a nanocomposite. ► Coating of the nanocomposite degraded dye 2× faster than TiO₂ alone under UVA. ► Fungal spores were killed by the coating 3 times faster than TiO₂ alone under UVA.Microbe transmission via surfaces is a common mode for the spreading of infectious diseases. A simple way to combat disease transmission via surfaces is to apply antimicrobial coatings. We have developed a thin, transparent, photocatalytic coating for rapid destruction of microbes. The coating uses polyhydroxy fullerene (PHF) as an enhancer for nano TiO₂ photocatalysis. A nanocomposite of PHF and TiO₂ was synthesized through physical mixing of the two components in aqueous suspension. The nanocomposite was characterized by dynamic light scattering, zeta potential and Langmuir adsorption isotherm. A coating of the PHF/TiO₂ nanocomposite was characterized by scanning electron microscopy. Photocatalytic activity of the nanocomposite coating, as indicated by degradation of organic dye (Procion red MX-5B) under UVA illumination, was optimal at a PHF/TiO₂ ratio of 0.01. The nanocomposite coating degraded the organic dye twice as fast as a coating of TiO₂ that contained no PHF. The nanocomposite coating was then applied to photocatalytically inactivate spores of Aspergillus niger, a household fungus commonly implicated in asthma. The nanocomposite inactivated spores three times as fast as a coating of TiO₂ containing no PHF. Changes to the morphology of A. niger spores due to photocatalysis were investigated using scanning electron microscopy.

Keywords: Abbreviations; PHF; polyhydroxy fullerene; TiO; ₂; titanium dioxide; UVA; ultraviolet A; CFU; colony forming unitProcion red MX-5B; TiO; ₂; UVA; Nanocomposite; Antimicrobial coatings; Aspergillus niger; Fungal spores; Fullerol; Fullerenol

Two stage pyrolysis-catalytic gasification of waste tyres: Influence of process parameters by Ibrahim F. Elbaba; Paul T. Williams (pp. 136-143).

.Display Omitted► Two-stage catalytic steam pyrolysis-gasification of waste tyres was investigated. ► Potential H₂ production was 20.0wt.% at the catalyst:waste tyres ratio of 2.0. ► Increased gasification temperature increased the potential H₂ production. ► Significant formation of coke was observed on the catalyst.The pyrolysis-catalytic steam gasification of waste tyres has been investigated using a two-stage fixed bed reactor. The catalyst used was Ni/Al₂O₃. The influence of the process parameters, catalyst:waste tyre ratio, gasification temperature and water injection rate on hydrogen production were investigated. The results indicated that the potential H₂ production (conversion of the hydrogen in the tyre to hydrogen gas) was 7.19wt.% when the catalyst:waste tyres ratio was 0.5 (g/g), which increased to 20.0wt.% at the catalyst:waste tyres ratio of 2.0 (g/g). Increasing the gasification temperature from 600 to 900°C was shown to increase gas yield from 14.3wt.% to 56.8wt.% and the potential H₂ production increased from 3.2 to 13.1wt.%. The steam flow rate, in terms of the amount of water injected, had a small but significant influence on the potential H₂ production. The characteristics of the carbon deposited on the reacted catalysts were examined by temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) and were shown to consist of be monoatomic carbon and filamentous carbon. The amount of carbon deposited on the catalyst was reduced with an increase in the amount of catalyst used and the water content. However, the highest amount of coke deposited on the catalyst was 20.8wt.% for the gasification temperature of 700°C.

Keywords: Hydrogen; Catalyst; Pyrolysis; Gasification; Tyre; Waste

Bi₂WO₆/SiO₂ photonic crystal film with high photocatalytic activity under visible light irradiation by Songmei Sun; Wenzhong Wang; Ling Zhang; Jiehui Xu (pp. 144-148).

Display Omitted► Bi₂WO₆/SiO₂ photonic crystal film is firstly realized. ► It is used for photocatalytic oxidation of organic contaminants. ► Its photocatalytic activity is significantly better than ordinary Bi₂WO₆ film. ► Its high photocatalytic performance is ascribed to its special film structure.Immobilized Bi₂WO₆ thin films were successfully synthesized by direct chemical deposition on SiO₂ photonic crystals. The as-prepared Bi₂WO₆/SiO₂ photonic crystal films exhibited excellent photocatalytic decomposition of RhB and phenol under visible light irradiation. Almost 99% of the RhB molecules were degraded within 60min and 64% of the phenol molecules were degraded within 2h along with the sharp decrease of total organic carbon (TOC) under visible light irradiation. Comparative studies indicated that the photocatalytic activity of the Bi₂WO₆/SiO₂ films is about 3 times higher than that of ordinary Bi₂WO₆ films under the same conditions. The transmission spectrum of the Bi₂WO₆/SiO₂ photonic crystal films exhibited an apparent transmission dip around 550nm originated from its photonic crystal structure. The different photocatalytic performance between the ordinary Bi₂WO₆ film and the Bi₂WO₆/SiO₂ photonic crystal film may be ascribed to their different film structures.

Keywords: Photocatalyst; Bi; ₂; WO; ₆; film; Phenol degradation; Photonic crystal

Stoichiometric and non-stoichiometric perovskite-based catalysts: Consequences on surface properties and on catalytic performances in the decomposition of N₂O from nitric acid plants by Y. Wu; X. Ni; A. Beaurain; C. Dujardin; P. Granger (pp. 149-157).

Display Omitted► Surface lanthanum enrichment for stoichiometric LaCoO₃ and LaCo_0.8Fe_0.2O₃ solids. ► Higher reaction rates in N₂O decomposition on aged non-stoichiometric perovskite. ► Improved stability for La_0.8CoO₃ and La_0.9Co_0.8Fe_0.2O₃ after ageing. ► Selective N₂O decomposition without NO_x losses.Catalytic activity for the N₂O decomposition into N₂ was investigated on perovskite-based materials in the presence of 5vol% NO, 6vol% O₂ and 15vol% H₂O. This feed is typical of industrial conditions for nitric acid plants operating at high temperature (850–900°C). The catalytic properties were found to be sensitive to the surface composition as revealed by XRD and XPS. Surface reconstructions on La and Co deficient perovskites induced surface La or Co enrichment. The latter governed the catalytic properties at medium and high temperature and was related to change in oxygen mobility. The presence of water was found as an outstanding parameter to speed up structural changes at the surface. However the presence of water had globally a negative impact in the catalytic activity in N₂O decomposition. Surface changes which determined the extent of deactivation were more accentuated on Co-deficient perovskites due to La₂O₃ segregation. Higher resistance to deactivation was obtained on La-deficient perovskites such as La_0.8CoO₃ and La_0.9Co_0.8Fe_0.2O₃. Surface reconstruction was evidenced at high temperature in severe reaction conditions.

Keywords: Perovskite; LaCoO; ₃; N; ₂; O decomposition; High temperature resistance; XPS

Study on the mechanism of the oxidation of soot on Fe₂O₃ catalyst by Steffen Wagloehner; Sven Kureti (pp. 158-165).

Display Omitted► Fe₂O₃ model catalyst was used for mechanistic studies on soot oxidation. ► Mechanistic studies showed transfer of surface and bulk oxygen of the catalyst to the soot. ► The contact of catalyst and soot is a crucial feature upon soot oxidation. ► The amount and heat capacity of the catalyst strongly affect the rate of soot oxidation.The present paper deals with the mechanism of the soot oxidation on Fe₂O₃ catalyst. The catalytic oxidation of soot is essential for the regeneration of diesel particulate filters already applied for vehicles and working machines. A series of mechanistic studies were conducted including systematic variation of reaction conditions, isotopic labelling (¹⁸O₂) and local temperature measurements by using an IR camera. These investigations provided knowledge on the transfer of oxygen from the gas-phase to catalyst and soot, the heat distribution on the surface of the catalyst/soot mixture and the effect of crucial parameters on the kinetics, i.e. heating rate, contact mode (tight vs. loose) and catalyst/soot ratio. From these examinations the following insights were derived: (1) Lattice oxygen of Fe₂O₃ is drastically involved in the soot oxidation by migration from the bulk to the soot. Therefore, the ratio of catalyst/soot directly affects the total amount of oxygen transported from catalyst to soot. (2) In another route, oxygen is “pumped” from the gas-phase via the Fe₂O₃ surface to the soot. (3) The oxygen transfer from Fe₂O₃ to soot mainly occurs by physical contact points. (4) The local temperature in the catalyst/soot mixture strongly depends on the amount and heat capacity of the catalyst, respectively, i.e. the catalyst acts as a temperature buffer. Thus, an optimum ratio of catalyst/soot exists reflecting a compromise of high number of contact points (high catalyst mass) and low heat capacity (low catalyst mass).Consequently, a global reaction mechanism of the catalytic soot oxidation on Fe₂O₃ was suggested. This mechanism implies the formation of oxygen defect sites as a result of the oxygen transfer to the soot. These defect sites are refilled either by migration of surface oxygen and re-oxidation by gas-phase oxygen, respectively, or by bulk oxygen. The resulting oxygen deficiency of the bulk is balanced by migration of oxygen from the surface or sub-surface.

Keywords: Soot oxidation; Fe; ₂; O; ₃; catalyst; Mechanism; Isotopic labelling

Ni supported on Mg–Al oxides for continuous catalytic wet air oxidation of Crystal Violet by Gabriel Ovejero; Araceli Rodríguez; Ana Vallet; Juan García (pp. 166-171).

Display Omitted► Ni/MgAlO catalyst. ► Catalytic wet air oxidation in trickle-bed reactor for Crystal Violet removal. ► Effect of the reaction variables was tested. ► The catalyst proved to be stable and efficient for the dye degradation.The continuous catalytic oxidation of aqueous Crystal Violet (CV) solutions has been investigated using a nickel catalysts (7wt%) supported over Mg–Al mixed oxides in a trickle-bed reactor. The influence of the temperature, pressure, gas flow and dye initial concentration were studied in the catalytic wet air oxidation of CV. The catalyst showed a very stable activity up to 350h on stream with an average total organic carbon (TOC) conversion of 64%. CV and TOC removal were very sensitive to the temperature. Dye conversion augmented from 44.7% at 120°C to 86.1% at 180°C. Dye conversion varied from 62.6 to 18.4%, TOC from 59.5 to 18.7% and TN from 66.6 to 14.0% within 10 to 50ppm of initial dye concentration. The leaching of Ni was 6wt% of the initial metal present in the catalyst and a 0.59% of carbonaceous deposit was formed onto the catalyst surface.

Keywords: Catalytic wet air oxidation; Crystal Violet; Nickel; Trickle-bed reactor; Wastewater

Enhanced selective hydrodechlorination of 1,2-dichloroethane to ethylene on Pt–Ag/TiO₂ catalysts prepared by sequential photodeposition by Yuxiang Han; Juan Zhou; Wenjuan Wang; Haiqin Wan; Zhaoyi Xu; Shourong Zheng; Dongqiang Zhu (pp. 172-179).

Display Omitted► TiO₂ supported Pt–Ag bimetallic catalysts ( pd-Pt–Ag/TiO₂) were prepared by a sequential photodeposition method. ► Photodeposition of Ag on Pt/TiO₂ led to preferential growth of Ag on Pt particle surface, which effectively blocked the adjacent Pt sites. ► Given similar Ag loading the pd-Pt–Ag/TiO₂ catalyst displayed much higher catalytic stability and ethylene selectivity than the catalyst prepared by the impregnation method.TiO₂ supported Pt–Ag bimetallic catalysts were prepared using a sequential photodeposition method (denoted as pd-Pt–Ag/TiO₂). For comparison, supported bimetallic catalysts were also prepared using the conventional impregnation method (denoted as im-Pt–Ag/TiO₂). The catalysts were characterized by X-ray diffraction, transition electron microscopy, CO chemisorption, IR spectroscopy of CO adsorption, and X-ray photoelectron spectroscopy. Characterization results indicated that photodeposition led to site-specific deposition of metallic Ag domain on the surface of Pt particles and thus to the formation of core–shell (Pt@Ag) like bimetallic species, which effectively blocked the adjacent Pt sites. However, Pt–Ag ensemble was predominant in im-Pt–Ag/TiO₂. Accordingly, hydrodechlorination of 1,2-dichloroethane exhibited substantially higher ethylene selectivity and catalytic stability on pd-Pt–Ag/TiO₂ than on im-Pt–Ag/TiO₂ at similar Ag loading levels. Findings from this study highlight the potential of using sequentially photodeposited core–shell like bimetallic catalysts to enhance the ethylene selectivity in hydrodechlorination of 1,2-dichloroethane.

Keywords: Catalytic hydrodechlorination; 1,2-Dichloroethane; Ethylene selectivity; Pt–Ag/TiO; ₂; catalyst; Sequential photodeposition

General strategy for one-pot synthesis of metal sulfide hollow spheres with enhanced photocatalytic activity by Man Luo; Yong Liu; Juncheng Hu; Jinlin Li; Jun Liu; Ryan M. Richards (pp. 180-188).

Display Omitted► A general strategy has enabled synthesis of a diverse portfolio of metal sulfide hollow spheres. ► These metal sulfide hollow spheres were synthesized by a simple one-step route. ► The shell of all hollow spheres is composed of single-crystal metal sulfide nanoparticles. ► The enhanced photoactivity can be ascribed to their unique hollow structure.A gas bubble-templating method has enabled synthesis of a diverse portfolio of hollow transition-metal sulfides microspheres (e.g., CdS, ZnS, CuS and Bi₂S₃) by a general one-step route. The products were characterized by X-ray powder diffraction, scanning and transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy analysis, N₂ adsorption and UV–vis diffuse reflectance spectroscopy. The shell of all hollow spheres is composed of single-crystal metal sulfide nanoparticles and the shell thickness can be readily controlled by changing the deposition time. These hollow microspheres are envisioned to have broad applications in catalysis, Li-ion batteries, microreactors, biomedicines, etc. As an example, here, we demonstrate that the prepared CdS and ZnS hollow sub-micrometer spheres are excellent photocatalysts with higher photodegradation efficiency of potential polluting agents than that of commercial CdS, ZnS and TiO₂ P25 under visible light and UV light illumination, respectively.

Keywords: Hollow spheres; Metal sulfide; CdS; ZnS; Photocatalysis

CO oxidation over graphene supported palladium catalyst by Yingzhi Li; Yue Yu; Jian-Guo Wang; Jie Song; Qiang Li; Mingdong Dong; Chang-Jun Liu (pp. 189-196).

Display Omitted► Highly dispersed Pd NPs on graphene were obtained via hydrogen reduction method. ► The interaction between Pd and graphene sheet was firstly proposed and confirmed. ► The Pd/graphene catalysts were applied for gas reaction. ► The Pd/graphene catalysts show very good activity and stability for CO oxidation. ► The L–H mechanism of CO oxidation over Pd/GE was confirmed.Graphene supported palladium (Pd) catalyst has been prepared using the conventional impregnation and hydrogen reduction method. Highly dispersed nano particles are formed on the support graphene. The density functional theory (DFT) study and the catalyst characterization using Raman and X-ray photoelectron spectroscopy confirm that the oxygen containing groups play an important role in stabilizing Pd clusters on graphene. The first layer of the metal particle mainly presents as PdO_x. The graphene supported Pd catalyst shows superior catalytic activity and high stability for CO oxidation. The kinetic studies indicate that CO oxidation over the graphene supported Pd catalyst follows the Langmuir–Hinshelwood (L–H) mechanism.

Keywords: Catalyst; CO oxidation; DFT; Graphene; Palladium

Using pyridine as nitrogen-rich precursor to synthesize Co-N-S/C non-noble metal electrocatalysts for oxygen reduction reaction by Jinli Qiao; Li Xu; Lei Ding; Lei Zhang; Ryan Baker; Xianfeng Dai; Jiujun Zhang (pp. 197-205).

Display Omitted► Novel non-precious metal catalyst Co-N-S/C with remarkable electroactivity for oxygen reduction was prepared. ► Pyridine is used as the nitrogen-rich ligand for precursor complex formation. ► Co-N-S/C derived from 10%Co30%Py/C showed a high onset potential of 0.014V and a well-defined limiting current plateau. ► The catalyst in alkaline solution with a KOH range of 0.1–3.0M catalyze the ORR via the four-electron pathway.The development of non-noble metal catalysts is of great interest due to their significant potential application in both fuel cell systems and metal–air batteries, particularly when considering long term commercial deployment. In this regard, novel Co-N-S/C non-noble metal catalysts supported on carbon, are synthesized in this study using a solvent-milling method followed by heat-treatment at elevated temperatures. Pyridine is used as the nitrogen-rich ligand for Co-N_x precursor complex formation. The morphology and composition of the catalyst are characterized by X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) as well as X-ray photoelectron spectroscopy (XPS). Several catalysts containing different amounts of Co are also synthesized. The optimal Co content is found to be in the range of 10–15wt% nominal, in terms of catalytic oxygen reduction reaction (ORR) activity. This catalyst shows high electroactivity for the ORR with a high stability in alkaline media. Using rotating disk electrode measurements, and Koutechy–Levich analysis, the overall electron transfer number in the catalyzed ORR is found to be 3.8–4.0, suggesting the catalyzed ORR is a four-electron transfer process from O₂ to H₂O.

Keywords: Non-noble metal catalysts; Cobalt; Pyridine; Oxygen reduction reaction; Fuel cells; Metal–air batteries

Effect of molybdenum addition on supported platinum catalysts for the water–gas shift reaction by W. Damion Williams; Luis Bollmann; Jeffrey T. Miller; W. Nicholas Delgass; Fabio H. Ribeiro (pp. 206-214).

Display Omitted► PtMo/Al₂O₃ and SiO₂ turnover frequencies are comparable to Pt/CeO_2. ► The increase in Pt TOF with Mo is lower on SiO₂ than on Al₂O_3. ► H₂ reduction forms PtMo bimetallic particles that are surface rich in Mo.The effect of molybdenum on water–gas shift (CO+H₂O↔CO₂+H₂) turnover frequencies was investigated for 2wt% platinum, up to 11wt% molybdenum, alumina and silica supported catalysts. The maximum PtMo turnover frequencies were observed for Mo weight loadings of 1.4% and 1.2% when supported on Al₂O₃ and SiO₂, respectively. Above these loadings, the exposed Pt surface area as measured by hydrogen chemisorption was reduced. The hydrogen chemisorption values and X-ray absorption spectroscopy of the reduced catalysts indicate the formation of PtMo bimetallic particles that are surface rich in Mo, yet increases in Pt–Mo coordination do not correlate with changes in turnover frequency, and most of the Mo is present in the form of Mo-oxide. The decrease in TOF from the optimum Mo loading is attributed to differences in surface coverages of intermediates that are observed in the changing reaction orders and ascribed to the interplay between the PtMo alloy metal function and the promotion of water activation by MoO_x promotion of the support. The decreased Pt dispersion and CO binding energy of Pt–Mo catalysts result in CO reaction orders as high as 0.8 at 300°C, and Mo addition resulted in apparent activation energies which were 20–40kJ/mol lower than the Mo free samples. The promoted catalysts achieved higher TOF than Pt/CeO₂ when calculated at or below 250°C with 6.8% CO, 8.5% CO₂, 21.9% H₂O, 37.4% H₂, and balance Ar at 1atm total pressure.

Keywords: Water–gas shift; X-ray absorption Spectroscopy; Platinum; Molybdenum oxide; PtMo Alloy

Time evolution of surface speciation during heterogeneous photocatalysis: Gallic acid on titanium dioxide by Paula Z. Araujo; Pedro J. Morando; Eduardo Martínez; Miguel A. Blesa (pp. 215-221).

TiO₂ surface populated by gallic acid with two adsorption isotherms is depleted sequentially by photocatalytic oxidation.Display Omitted► Adsorption of gallic acid onto TiO₂ proceeds via two diffusion steps. ► Photocatalytic oxidation depletes surface excess. ► (Undetected) intermediates are further oxidized either photochemically or thermally.Gallic acid adsorbs onto TiO₂ films deposited onto an ATR crystal in two steps, both described by the kinetic Langmuir equation, as shown by measuring the spectral changes due to adsorbed species. Both pathways lead to species with the same spectral signature.Upon irradiation for preset times, integrated spectral absorbance profiles (log( A/ A₀) vs time) for the adsorbate peaks coincides with the analogous profile of remnant concentration in solution (log( C/ C₀) vs time). In our experiments, initially there are similar amounts of adsorbed and dissolved gallic acid. Hence, the rate of destruction of surface complexed gallic acid is approximately twice as large as the net rate of ligand uptake from solution. Upon irradiation, ligand surface concentration falls below equilibrium values, as also shown by plotting spectral signal intensity as a function of solution concentration.Under intermittent irradiation, the original rates were the same, but at larger radiation doses, the overall conversion was higher. This result demonstrates that during the intervening dark periods thermal reactions contribute to the overall rate. These thermal reactions may include desorption of intermediates, dark oxidation of intermediates, and re-equilibration of the surface with increasing gallic acid surface concentration. A description of photocatalysis based in the concept of oxidation length is provided.

Keywords: Gallic acid adsorption kinetics; Photocatalysis; Titanium dioxide; Surface speciation; Intermittent irradiation

Supported gold catalysts for the total oxidation of volatile organic compounds by Salvatore Scirè; Leonarda Francesca Liotta (pp. 222-246).

Display Omitted► Au/metal oxide catalysts are receiving growing attention for the deep oxidation of VOC. ► VOC oxidation over Au/metal oxide catalysts is governed by both the support and the gold properties. ► The research focused on the understanding on how operative variables affect support and gold properties. ► The stability enhancement of Au/metal oxide catalysts and the application of photocatalysis deserve further studies.This review intends to describe and critically analyze the growing literature dealing with the use of supported gold catalysts in the catalytic deep oxidation of volatile organic compounds (VOC). Among the wide family of VOC, attention has been given to the oxidation of saturated (methane, ethane, propane, isobutane, n-hexane) and unsaturated (acetylene, ethylene, propene) aliphatic compounds, aromatic hydrocarbons (benzene, toluene, xylenes, naphthalene), alcohols (methanol, ethanol, n- and iso-propanol), aldehydes (formaldehyde), ketones (acetone), esters (ethylacetate). Moreover, the oxidation of chlorinated VOC (dichloromethane, o-dichlorobenzene, o-chlorobenzene), as well as of nitrogen- (trimethylamine) and sulphur-containing (dimethyldisulfide) compounds has been addressed.The reaction mechanism and the influence of different factors, such as the nature and the properties of the support, the Au particle size and shape, the electronic state of gold, the preparation method and the pretreatment conditions of catalysts, the nature and the concentration of the organic molecule, are discussed in detail.

Keywords: Au; VOC; Support; Preparation; Mechanism; Combustion; Environmental protection

Novel, efficient and recyclable silica based organic–inorganic hybrid Nickel catalyst for degradation of dye pollutants in a newly designed chemical reactor by R.K. Sharma; Shikha Gulati; Amit Pandey; Alok Adholeya (pp. 247-258).

Display Omitted► Synthesis of silica-based organic–inorganic hybrid Nickel catalyst.► Large scale degradation of dyes in a novel chemical reactor with automated modes.► Degradation followed pseudo-first order kinetics.► Catalyst achieved degradation efficiency up to 96%.► Reusability up to seven cycles without loss in its activity.In this paper, a novel organic–inorganic hybrid heterogeneous catalyst was prepared through the immobilization of nickel tetrasulfophthalocyanine (NiTSPc) complex onto silica. The synthetic route is facile, cost effective and green. The catalyst was characterized by elemental analysis, diffuse reflectance UV–visible spectroscopy,¹³C CPMAS and²⁹Si CPMAS NMR spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), BET surface area analysis, Energy dispersive X-ray fluorescence (ED-XRF) and Fourier transform Infrared (FT-IR) spectroscopic techniques. The catalytic performance of the novel organic–inorganic hybrid catalyst was evaluated in the oxidative degradation of azo dyes at room temperature using hydrogen peroxide as an environmentally benign oxidant. The conditions for maximum dye degradation were optimized in terms of catalyst loading, H₂O₂ dosage and initial pH of the solution. The dye degradation followed pseudo first order kinetics. GC–MS was used to analyze the products formed after the dye degradation. The hybrid catalyst showed up to 96% of degradation efficiency, and can be recovered and reused for multiple cycles without appreciable loss in its catalytic activity. In addition, a novel chemical reactor with automated modes has been designed for the first time which opens up a new avenue for the effective and large scale degradation of dyes at room temperature using recyclable organic-inorganic hybrid catalyst.

Keywords: Silica; Phthalocyanine; Recyclable catalyst; Azo dyes; Degradation

Influence of active metal loading and oxygen mobility on coke-free dry reforming of Ni–Co bimetallic catalysts by Petar Djinović; Ilja Gasan Osojnik Črnivec; Boštjan Erjavec; Albin Pintar (pp. 259-270).

Display Omitted► Carbon accumulation in the form of nanofilaments does not affect catalyst deactivation. ► Active NiCo bimetallic particles can be finely dispersed at loadings below 6wt.%. ► High oxygen mobility within the CeZr support is promoted by small crystallite size and highly defective structure. ► High oxygen mobility and finely dispersed active metal phase support long term coke-free operation.Two different techniques (precipitation with ammonia and hydrothermal synthesis with ethylene glycol, both followed by autoclave aging) were employed for the synthesis of CeO₂–ZrO₂ mixed oxides on a 80–20wt.% basis. Aging parameters, such as time and temperature, were systematically investigated in order to determine the optimal conditions to maintain high surface area and oxygen mobility of the prepared solids. Different loadings of nickel and cobalt (3, 6, 12 and 18wt.%) were subsequently deposited via homogeneous deposition precipitation method. Calcined bimetallic catalysts were characterized by N₂ adsorption–desorption, XRD, H₂-TPR, TPO-TGA and FE-SEM methods, and tested for activity, selectivity and stability in the reforming of equimolar CH₄–CO₂ gas streams. During temperature programmed methane reforming tests, syngas with a H₂/CO ratio between 0.3 and 0.79 was produced. Growth of carbon nanofilaments over the catalyst does not lead to deactivation, but can cause reactor plugging. Two conditions are vital and must be fulfilled simultaneously to avoid excessive carbon deposition: strong interaction between the NiCo bimetallic particles and CeZr support, which exists only at NiCo loadings up to 6wt.%, as well as high oxygen mobility within the highly defective CeO₂–ZrO₂ crystalline lattice for timely carbon oxidation.

Keywords: Methane dry reforming; Deactivation; CeO; ₂; –ZrO; ₂; Oxygen mobility; Nickel cobalt bimetallic catalysts

Ethanol electrocatalysis on gold and conducting polymer nanocomposites: A study of the kinetic parameters by Rakesh K. Pandey; V. Lakshminarayanan (pp. 271-281).

Display Omitted► A novel in situ approach of gold and different conjugated polymer nanocomposites formation. ► Kinetic parameters, i.e. activation energy, Tafel slope, reaction rate of the electrocatalytic reaction were studied in detail. ► Based on kinetic parameters different nanocomposites were judged. ► Effect of impurities and temperature on catalytic activity was also studied.The study attempts to compare the electrocatalytic effect of gold nanoparticles dispersed conjugated polymers using activation energy, Tafel slopes and reaction orders for the evaluation of their performance. A simple and rapid in situ chemical and electrochemical method was adopted for the synthesis of gold and different conducting polymers nanocomposites on electrode surfaces. The method involves the polymerization of the monomer to yield the polymer nanocomposite film with dispersed gold nanoparticles. Polyaniline, polypyrrole, polythiophene and poly(3,4-ethylenedioxythiophene) are the four polymers studied in this work. A systematic comparison among the nanocomposites reveals that although all the conducting polymers have good catalytic activity in alkaline medium however polyaniline dispersed with gold nanoparticles has the best catalytic properties among them as evidenced by its very low activation energy, low onset potential and reproducible currents.

Keywords: In situ electropolymerization; Catalysis; Electrochemistry; Conducting polymers; Nanocomposite

Efficient photocatalytic reduction of aqueous Cr(VI) over CaSb₂O₅(OH)₂ nanocrystals under UV light illumination by Guodong Chen; Meng Sun; Qin Wei; Zhenmin Ma; Bin Du (pp. 282-287).

Display Omitted► Cr(VI) can be effectively photocatalytic reduced over CaSb₂O₅(OH)₂. ► CaSb₂O₅(OH)₂ exhibits substantially higher catalytic activity than TiO₂(P25). ► Cr(VI) reduction rate increases with the decrease of initial pH.CaSb₂O₅(OH)₂ nanocrystals were synthesized via traditional and microwave-assisted hydrothermal methods from aqueous solution of CaCl₂ and KSb(OH)₆, respectively. The structures, Brunauer–Emmett–Teller (BET) specific surface areas and optical properties of the as-synthesized samples were characterized by X-ray diffraction, transmission electron microscopy, N₂ sorption–desorption isotherms, and UV–vis diffuse reflectance spectra. The results of photocatalytic reduction of aqueous Cr(VI) revealed that CaSb₂O₅(OH)₂ possessed a superior activity greatly larger than that of commercial P25 (Degussa Co.). It was shown that proton supply played a crucial role in the reduction reaction. The Cr(VI) photo-reduction rates were systematically accelerated as the proton concentration increased in the aqueous suspensions. Formate ions were also shown to exert a dramatic accelerating influence on Cr(VI) reduction in the system. This observation should be rationalized by considering that these species act as hole scavengers in the reduction process. The consequent improvement in quantum yield combines with the protons provided by H₂SO₄ result in the observed rate enhancement.

Keywords: Photocatalysis; Reduction; Cr(VI); Ultraviolet; CaSb; ₂; O; ₅; (OH); ₂

Low temperature-synthesis of BiVO₄ nanorods using polyethylene glycol as a soft template and the visible-light-activity for copper acetylacetonate decomposition by Sho-ichi Eda; Musashi Fujishima; Hiroaki Tada (pp. 288-293).

Monoclinic sheelite BiVO₄ nanorods ( ms-BiVO₄ NRs) have been synthesized from an aqueous solution of Bi(NO₃)₃ and NH₄VO₃ at 370K containing polyethylene glycol (PEG), while micron-sized BiVO₄ crystals ( ms-BiVO₄ MCs) are formed without PEG. The UV–vis absorption spectra of the PEG solutions of NH₄VO₃ suggested the formation of a complex consisting of VO₃⁻ ion and PEG. In this synthetic route, PEG can suppress the reactivity of VO₃⁻ ions by the stabilization to further act as a soft template for the formation of ms-BiVO₄ NRs. The as-grown ms-BiVO4 NRs exhibit a high level of photocatalytic activity for the degradation of Cu(acac)₂ without sacrificial agents under illumination of visible-light ( λ>430nm). The local symmetry of VO₄ tetrahedron affecting the light absorption intensity in addition to the large surface area and high crystallinity have been suggested to be a crucial factor to achieve the high visible-light-activity of ms-BiVO₄.Display Omitted► BiVO₄ nanorods (NRs) were synthesized at 370K from aqueous PEG solution. ► PEG acts as a soft template to yield BiVO₄ NRs with a specific surface area of 8.8m²g⁻¹. ► The BiVO₄ NR exhibits much higher visible-light-activity than the sample prepared without PEG. ► The compatibility of large surface area and high crystallinity is important for achieving high visible-light-activity. ► The local symmetry of VO₄ tetrahedron is another crucial factor for the high visible-light-activity.Monoclinic sheelite BiVO₄ nanorods ( ms-BiVO₄ NRs) have been synthesized from an aqueous solution of Bi(NO₃)₃ and NH₄VO₃ at 370K containing polyethylene glycol (PEG), while micron-sized BiVO₄ crystals ( ms-BiVO₄ MCs) are formed without PEG. The UV–vis absorption spectra of the PEG solutions of NH₄VO₃ suggested the formation of a complex consisting of VO₃⁻ ion and PEG. In this synthetic route, PEG can suppress the reactivity of VO₃⁻ ions by the stabilization to further act as a soft template for the formation of ms-BiVO₄ NRs. The as-grown ms-BiVO₄ NRs exhibit a high level of photocatalytic activity for the degradation of Cu(acac)₂ without sacrificial agents under illumination of visible-light ( λ>430nm). The local symmetry of VO₄ tetrahedron affecting the light absorption intensity in addition to the large surface area and high crystallinity have been suggested to be a crucial factor to achieve the high visible-light-activity of ms-BiVO₄.

Keywords: Bismuth vanadate; Nanoparticles; Low-temperature synthesis; Visible light photocatalysis

A new perspective for effect of Bi on the photocatalytic activity of Bi-doped TiO₂ by Yin Hu; Yuantao Cao; Peixian Wang; Danzhen Li; Wei Chen; Yunhui He; Xianzhi Fu; Yu Shao; Yi Zheng (pp. 294-303).

A simple approach, directly mixing Bi₂O₃ powder with TiO₂ sol, was developed to fabricate Bi-doped TiO₂ photocatalyst. The most attractive feature of this procedure was that a relatively high concentration of Bi₂O₃ was introduced into TiO₂ to understand the Bi species modification. During the photooxidation of gaseous benzene under visible light irradiation, the prepared catalysts exhibited higher activities than P25 and nitrogen-doped TiO₂. In particular, characterization results and a series of designs demonstrated that the amorphous Bi_xTiO_y microstructures contribute to the good photocatalytic activity. It was suggested that these Bi species could be preferable for forming more activated sites and bigger specific areas and improving the efficiency of the composites. This approach is very conductive to reshape human understanding about the condition of the bismuth in the binary Bi₂O₃–TiO₂ system and its role in the photocatalytic activity. The simple and low cost approach would be a highly efficient means for broadening the further industrial application.Display Omitted► A simple method is developed to fabricate Bi-doped TiO₂ with different Bi/Ti molar ratio. ► Gaseous benzene is chosen as a model VOC to investigate the activities of the photocatalysts. ► The amorphous Bi_xTiO_y microstructures contribute to the good photocatalytic activity. ► It gives a better understanding about the existence form of Bi in the Bi₂O₃–TiO₂ system.In the current work, a simple approach, directly mixing Bi₂O₃ powder with TiO₂ sol, was developed to fabricate Bi-doped TiO₂ photocatalyst. The obtained product was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectra analysis, X-ray photoelectron spectra (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). On the basis of the above characterization results, it was found that the excess Bi₂O₃ loading (>5mol%) and sol–gel processing route could lead to the formation of Bi_xTiO_y. The XRD data pointed out that Bi_xTiO_y remained amorphous up to 500°C and crystallized into the distinctive phase Bi₂Ti₄O₁₁ at higher temperature of 700°C. It was worth mentioning that the participation of the distinctive microstructures made the finishing point of the doped photocatalyst, that is, strong spectral response in visible region and marked activity during the photooxidation of gaseous benzene under visible light illumination ( λ>450nm). Furthermore, the calcination temperature also had an important effect on the photocatalytic activity. The optimal dosage of 10mol% Bi in TiO₂ and sintering temperature of 400°C achieved the best photocatalytic activity. Finally, the amorphous Bi_xTiO_y microstructures formed in TiO₂ crystal made a significant contribution in providing large specific surface area and more activated units regarding the photocatalytic process. It is hoped that our current work will contribute to a better understanding of the existence form of bismuth in TiO₂ crystal. More generally, it suggests the incorporation of bismuth into a simple oxide of wide band gap as a strategy to design photocatalysts with excellent properties.

Keywords: Bi-doped TiO; ₂; Amorphous; Visible light; Photocatalysis; Benzene

A facile synthesis of nearly monodisperse ruthenium nanoparticles and their catalysis in the hydrolytic dehydrogenation of ammonia borane for chemical hydrogen storage by Hasan Can; Önder Metin (pp. 304-310).

Display Omitted► A facile and novel method for preparation of nearly monodisperse Ru nanoparticles. ► Highly active heterogeneous Ru nanocatalyst for the hydrolytic dehydrogenation of H₃NBH₃. ► The record TOF value of 83.3min⁻¹ that is even higher than Pt-based catalyst. ► The rate law and apparent activation parameters for the catalytic dehydrogenation of AB in water.A facile method for the preparation of nearly monodisperse Ru nanoparticles (NPs) and their record catalytic activity in the hydrolytic dehydrogenation of ammonia borane (AB) for chemical hydrogen storage are reported herein. Ru NPs were prepared by a novel protocol comprising the thermal decomposition and concomitant reduction of ruthenium(III) acetylacetonate (Ru(acac)₃) in the presence of oleylamine (OAm) and benzylether (BE). In the protocol, OAm served as both a stabilizer and reducing agent and BE used as a solvent. Ru NPs were supported on aluminum oxide nanopowder (Ru@Al₂O₃) via a simple liquid impregnation method before their use as catalyst for the dehydrogenation of AB in water. Without any special treatment to remove the surfactants, Ru@Al₂O₃ showed high catalytic activity in the hydrolytic dehydrogenation of AB providing an initial turnover frequency (TOF) of 39.6molH₂(molRumin)⁻¹. Their catalytic performance was further enhanced dramatically by the acetic acid treatment and the initial TOF value is increased to 83.3molH₂(molRumin)⁻¹ that is the highest among the reusable Ru catalysts and even higher than Pt-based catalysts tested in the hydrolysis of AB. Additionally, the work reported here includes a wealth of kinetic data to determine the rate law and apparent activation parameters for the catalytic dehydrogenation of AB in water.

Keywords: Ruthenium nanoparticles; Al; ₂; O; ₃; nanopowder; Heterogeneous catalyst; Dehydrogenation; Ammonia borane

Isomorphous substitution of Zr in the framework of aluminosilicate HY by an electrochemical method: Evaluation by methylene blue decolorization by N. Sapawe; A.A. Jalil; S. Triwahyono; S.H. Adam; N.F. Jaafar; M.A.H. Satar (pp. 311-323).

.Display Omitted► Electrochemical method can generates nanosize zirconia in average of 8–18nm. ► Isomorphous substitution of Al with Zr was taken place. ► A new structural model for EGZrO₂/HY is proposed. ► SiOZr bonds were formed as evidenced by MAS NMR, XPS, and IR. ► 1wt% EGZrO₂/HY exhibited the best performance for the photodecolorization of MB.Isomorphous substitution of Zr in the framework of aluminosilicate HY occurred during the preparation of electrogenerated zirconia supported HY (EGZrO₂/HY) catalyst via a simple electrochemical method. Dealumination accompanied by an ion exchange with Zr⁴⁺ formed SiOZr bond, which controlled the formation of active species EGZrO₂ that influenced the efficiency of the photodecolorization of methylene blue (MB). An amount of 0.375gL⁻¹ 1wt% EGZrO₂/HY was found to be the optimum dosage for 10mgL⁻¹ MB, which resulted in 97% decolorization after 6h of contact time at pH 11. The kinetics study indicates that the reaction follows the Langmuir–Hinshelwood model, where the reaction may occur both on the surface of the catalyst and in the bulk solution. The mineralization of MB was measured by removal of chemical oxygen demand (COD), five days biochemical oxygen demand/chemical oxygen demand (BOD₅/COD), and total organic carbon (TOC/TOC₀), and the results obtained were 95%, 7.14, and 0.08, respectively. After five cycling runs, the catalyst was still stable and showed no leaching effect. This study is believed to be extendable to the synthesis of other catalysts with different characteristics and be used in various applications.

Keywords: Isomorphous substitution; EGZrO; ₂; /HY; Electrochemical; Photodecolorization; Methylene blue

Highly dispersed nickel loaded on mesoporous silica: One-spot synthesis strategy and high performance as catalysts for methane reforming with carbon dioxide by Zhicheng Liu; Jian Zhou; Kun Cao; Weimin Yang; Huanxin Gao; Yangdong Wang; Hexing Li (pp. 324-330).

Display Omitted► A new kind of Ni loaded mesoporous silica material was prepared by a one-spot co-assembly method. ► Ni species were highly dispersed into the pore walls during the self-assembly synthesis of mesoporous silica. ► The Ni metal particle sizes of the catalyst are less than 5nm. ► There is strong interaction of Ni with silica matrix. ► It has high catalytic performance and good anti-coke property for CO₂ reforming of CH₄.A kind of Ni containing mesoporous silica, Ni-KIT-6, was prepared by a one-spot co-assembly method, in which Ni species were highly dispersed into the pore walls during the self-assembly synthesis of the mesoporous silica. Compared with the catalyst prepared by conventional impregnation method, Ni-KIT-6 demonstrates extremely smaller Ni particles on the support and stronger interaction of Ni with silica matrix. As a result, it exhibits high catalytic activity and selectivity, and more importantly, good coke-resistant performance for the catalytic reaction of methane reforming with carbon dioxide.

Keywords: Nickel; Mesoporous silica; Methane reforming with carbon dioxide; Catalysis

A review on the visible light active titanium dioxide photocatalysts for environmental applications by Miguel Pelaez; Nicholas T. Nolan; Suresh C. Pillai; Michael K. Seery; Polycarpos Falaras; Athanassios G. Kontos; Patrick S.M. Dunlop; Jeremy W.J. Hamilton; J.Anthony Byrne; Kevin O'Shea; Mohammad H. Entezari; Dionysios D. Dionysiou (pp. 331-349).

Display Omitted► VLA-TiO₂ include non metal, metal doping, dye sensitized and coupling semiconductors. ► Physicochemical/photoelectrochemical methods to deduce VLA-TiO₂ reaction mechanisms. ► Examination of VLA-TiO₂ for water treatment, disinfection and air purification.Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO₂) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO₂ photocatalytic materials. In this review, a background on TiO₂ structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO₂ for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO₂, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO₂ are discussed and compared to conventional UV-activated TiO₂ nanomaterials. Recent advances in bacterial disinfection using VLA TiO₂ are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

Keywords: TiO; ₂; Visible; Solar; Water; Treatment; Air purification; Disinfection; Non-metal doping; Anatase; Rutile; N–TiO; ₂; Metal doping; Environmental application; Reactive oxygen species; Photocatalysis; Photocatalytic; EDCs; Cyanotoxins; Emerging pollutants

In₂O₃ nanoporous nanosphere: A highly efficient photocatalyst for decomposition of perfluorooctanoic acid by Zhenmin Li; Pengyi Zhang; Tian Shao; Xiaoyun Li (pp. 350-357).

Display Omitted► Uniform In₂O₃ nanospheres synthesized by a solvothermal method. ► In₂O₃ nanospheres were self-assembled with ultrathin nanoplates. ► In₂O₃ nanospheres possess high surface area (39m²g⁻¹) and nanopores at 6nm. ► In₂O₃ nanospheres are highly active for PFOA, 54.6 times higher than TiO₂. ► The half-life of PFOA decomposition was shorten to 7.1min.Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant and receives increasing concerns due to its global occurrence and resistance to most conventional decomposition methods. In₂O₃ nanoporous nanospheres (NPNSs) with uniform size (∼100nm) were obtained by calcining nanoporous InOOH/In(OH)₃ nanospheres and its photocatalytic activity for PFOA decomposition were evaluated. The InOOH/In(OH)₃ precursor was self-assembled from ultrathin nanoplates (∼2nm) in an ethylenediamine-assisted alcohol-thermal system. The In₂O₃ NPNSs possessed a high value of specific surface area (39.0m²g⁻¹) and a large number of nanopores (∼6nm). Compared with commercial In₂O₃ nanocrystals (NCs) and TiO₂ (Degussa P25), In₂O₃ NPNSs showed a remarkable photocatalytic activity to decompose PFOA with the half-life of 7.1min. The first-order rate constant of PFOA by In₂O₃ NPNSs was nearly 9 and 54.6 times higher than that by In₂O₃ NCs and TiO₂ respectively. The superior activity of In₂O₃ NPNSs for PFOA decomposition can be attributed to its nanoporous structure, large specific surface area, and direct reaction between the photogenerated hole and PFOA.

Keywords: Indium oxide; Self-assembly; Nanoporous nanostructure; Perfluorooctanoic acid; Photocatalysis

Coverage of carbon nanotubes with titania nanoparticles for the preparation of active titania-based photocatalysts by Sakae Takenaka; Takafumi Arike; Hideki Matsune; Masahiro Kishida (pp. 358-366).

Carbon nanotube with Pt metal particles in its cavity was covered with TiO₂ nanoparticles by hydrolysis of Ti(OC₃H₇)₄. The composite catalysts showed high activity for the photodegradation of organic impurities in water.Display Omitted► Uniform coverage of carbon nanotube (CNT) with TiO₂ particles. ► Hydrolysis of Ti(OC₃H₇)₄ in the presence of urea and CNT. ► Urea as linker molecules between TiO₂ particles and CNT. ► Stabilization of Pt particles in the CNT cavity in TiO₂-coated CNT. ► High catalytic activity for the photodegradation of organic impurities in water.TiO₂ nanoparticles were deposited on carbon nanotubes (CNTs) to improve their photocatalytic activity. The outer surface of the CNTs could be uniformly covered with TiO₂ nanoparticles using the hydrolysis of titanium tetraisopropoxide (Ti(OⁱPr)₄) in the presence of urea or glycine amide. The urea and glycine amide acted as linker molecules between the TiO₂ nanoparticles and the CNT surfaces. The TiO₂-coated CNTs showed a higher catalytic activity for the photodegradation of organic molecules than TiO₂ alone. The addition of the CNTs to the TiO₂ photocatalytic system retarded the recombination of the electron–hole pairs generated in the photo-irradiated TiO₂. When Pt metal particles were inserted in the cavities of the CNTs in the TiO₂-coated CNT catalyst system, further improvements in the photocatalytic activity were observed. The TiO₂-coated CNTs with Pt metal particles displayed a unique catalytic performance in the photocatalytic degradation of organic impurities in water.

Keywords: Carbon nanotube; Titania; Titania-coated carbon nanotube; Pt metal; Photocatalyst

Hierarchical SrTiO₃/TiO₂ nanofibers heterostructures with high efficiency in photocatalytic H₂ generation by Hongwei Bai; Jermyn Juay; Zhaoyang Liu; Xiaoxiao Song; Siew Siang Lee; Darren Delai Sun (pp. 367-374).

Display Omitted► Hierarchical SrTiO₃/TiO₂ nanofibers heterostructures were fabricated to integrate many merits. ► Promoting mass transfer and allowing light reflection and absorption. ► 1D long fibrous structure favorable electrons transfer. ► Close contact at their interphase suppressing the recombination of electrons and holes. ► Finally, high photocatalytic H₂ generation activity is resulted.Through hydrothermally growing SrTiO₃ cubics on the surface of electrospun TiO₂ nanofibers, SrTiO₃/TiO₂ nanofibers heterostructures were successfully fabricated in the present study. This process is able to ensure uniform distribution of SrTiO₃ on the surface of TiO₂ nanofibers and lead to close contact between SrTiO₃ and TiO₂, which is beneficial for the fast separation of photogenerated electrons and holes so as to suppress the recombination of photogenerated electrons and holes at the interphase of SrTiO₃ and TiO₂. Besides this, the long 1D fibrous structure easy for electron transfer, the hierarchical structure promoting mass transfer and allowing more light reflection and absorption, and the large specific surface area providing more reactions sites to facilitate the reactants to desired oxidation places all together create a synergistic effect on improving the photocatalytic activity of the hierarchical SrTiO₃/TiO₂ nanofibers heterostructures. Under the irradiation of UV light, in a water/methanol sacrificial reagent system, the SrTiO₃/TiO₂ nanofibers heterostructures generate five times more H₂ than bare TiO₂ nanofibers because of its high photocatalytic activity.

Keywords: Heterostructure; Hierarchical; H; ₂; Generation; SrTiO; ₃; TiO; ₂

Heterogenous photocatalytic inactivation of B. stearothermophilus endospores in aqueous suspensions under artificial and solar irradiation by Chrysanthi Berberidou; Ioannis Paspaltsis; Eleni Pavlidou; Theodoros Sklaviadis; Ioannis Poulios (pp. 375-382).

Display Omitted► B. stearothermophilus spores were inactivated by TiO₂/UV-A in aqueous suspensions. ► Surface modification of TiO₂ by Ag and Pt enhanced the photocatalytic efficiency. ► Solar photocatalysis led to results similar to the ones under UV-A. ► Photocatalysis caused severe damage of the cell structure.TiO₂ mediated photocatalytic disinfection constitutes an attractive emerging technology against waterborne diseases transmitted through pathogenic microorganisms. This study demonstrates the potential of TiO₂ suspensions to fully inactivate highly resistant microorganisms, Bacillus stearothermophilus endospores in water, in the presence of artificial and solar irradiation. Photo-inactivation, however, in the absence of TiO₂ led to twelve times lower reaction rates and in the inactivation of only 50% of the initial endospore population, in the same time intervals. The addition of limited amounts of ferric species, as well as catalyst surface modification by Ag and Pt deposition, clearly results in enhanced reaction rates. Furthermore, electron micrographs correlate endospore inactivation and inability to reactivate in the dark with extended morphological lesions of the spore structure, caused by the photocatalytically generated reactive oxygen species.

Keywords: AOPs; Photocatalysis; TiO; ₂; Solar; Disinfection/inactivation; Endospores

Synthesis of highly photoactive TiO₂ and Pt/TiO₂ nanocatalysts for substrate-specific photocatalytic applications by C. Fernández-Rodríguez; J.M. Doña-Rodríguez; O. González-Díaz; I. Seck; D. Zerbani; D. Portillo; J. Perez-Peña (pp. 383-389).

Display Omitted► Stabilizing the anatase phase at high calcination temperatures. ► Synthesis of highly photoactive TiO₂ nanoparticles. ► Design of TiO₂ photocatalysts for substrate-specific applications. ► Tailoring of structural properties by means of appropriate post-synthesis treatments.The relative activity of TiO₂ photocatalysts depends to a large extent on the type of test substrate. With this in mind, phenol, formic acid, 2,4-dichlorophenoxyacetic acid (2,4-D) and methyl orange (MO) were selected as test substrates due to their different degradation mechanisms. In this work, the aim behind the synthesis and subsequent surface modification of the nanocatalysts was to obtain the most efficient material for removing these test substrates from water. A series of nanocatalysts with different average particle size, specific surface area and anatase phase content were synthesized by sol–gel method followed by calcinations at different annealing temperatures or hydrothermal treatment. Subsequently, platinization of certain samples was carried out using a photodeposition method. The most efficient catalyst for phenol photodegradation was found to be that with the largest average particle size as well as the highest anatase phase ratio. The photodeposition of platinum on this sample had detrimental effects on phenol photodegradation. The platinized sample and anatase TiO₂ with the lowest average particle size were the most efficient catalysts for the removal of formic acid. Finally, the platinized material also showed the highest photoactivity in the removal of 2,4-D and in the methyl orange bleaching test.

Keywords: Sol–gel synthesis; Pt/TiO; ₂; TiO; ₂; Specific-substrate photoactivity

Synthesis and characterization Pt nanocatalysts on tungsten based supports for oxygen reduction reaction by N.R. Elezovic; B.M. Babic; P. Ercius; V.R. Radmilovic; Lj.M. Vracar; N.V. Krstajic (pp. 390-397).

Novel Pt catalysts on tungsten based supports for oxygen reduction, with improved catalytic activity and stability.Display Omitted► Two different tungsten carbide based supports were synthesized. ► Pt/WC catalysts were prepared and tested for oxygen reduction in HClO₄ solution. ► WC supports and Pt/WC catalysts were characterized by XRD, TEM and EELS techniques. ► Pt/WC catalysts, compared to Pt/C, showed better catalytic activity and stability.Platinum nanocatalysts on two tungsten based supports have been synthesized and characterized as catalysts for oxygen reduction reaction in 0.5moldm⁻³ HClO₄ solution, at 25°C. Tungsten based support assigned WCctabr has been synthesized by polycondensation of resorcinol and formaldehyde in the presence of CTABr surfactant. Support assignedWCWO3 was synthesized from resorcinol/formaldehyde gel, using WO₃ nanoparticles as starting material. Supporting materials have been characterized by BET (Brunauer, Emmett and Teller) technique and determined values of surface area were 80m²g⁻¹ for WCctabr and 175m²g⁻¹ forWCWO3.Platinum nanocatalysts (10% Pt) at tungsten based supports have been prepared by borohydride reduction method. Both synthesized supports and catalysts have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) techniques. Cyclic voltammetry was applied for determination of electrochemically active surface area (40m²g⁻¹ forPt/WCWO3 and 55m²g⁻¹ for Pt/WCctabr).Oxygen reduction reaction has been studied by cyclic voltammetry and linear sweep voltammetry at rotating disc electrode (RDE). These catalysts exhibited better catalytic activity, expressed in terms of kinetic current density per real surface area at the constant potential and better stability, in comparison with Pt/C catalyst, as well as with already reported catalytic activity values for Pt catalysts on tungsten based supports.

Keywords: Tungsten based support; Pt/WC catalyst; Oxygen reduction reaction; Acid solution

NO oxidation over nitrogen doped carbon xerogels by Juliana P.S. Sousa; Manuel F.R. Pereira; José L. Figueiredo (pp. 398-408).

The presence of pyridine (N6) and pyrrole (N5) groups in N-doped carbon xerogels favours the oxidation of NO.Display Omitted► Nitrogen-doped carbon xerogels were prepared using melamine and urea. ► The materials performed well as catalysts for NO oxidation at room temperature. ► The catalytic activity of the catalysts was maintained in consecutive runs. ► The presence of pyridine and pyrrole groups favours the oxidation of NO. ► The presence of surface oxygen inhibits NO oxidation.Carbon xerogels were prepared from a nitrogen-containing polymer precursor, using melamine and urea as nitrogen sources incorporated into the polymer matrix, by the sol–gel process. Materials with different contents of nitrogen were obtained and used as catalysts for NO oxidation at room temperature. The NO conversions obtained with nitrogen doped carbon xerogels were quite high, showing that carbon xerogels are efficient catalysts for NO oxidation. A maximum of 88% conversion for NO was obtained at NO initial concentration of 1000ppm and 20% of O₂. The presence of nitrogen-containing surface groups was shown to favour the oxidation of NO to NO₂. The catalytic activity of the catalysts is maintained in consecutive runs.

Keywords: NO oxidation; Nitrogen-doping; Carbon xerogels; Carbon catalysts; NO; _x; abatement

FeMo-based catalysts for H₂ production by NH₃ decomposition by Barbara Lorenzut; Tiziano Montini; Manuela Bevilacqua; Paolo Fornasiero (pp. 409-417).

Display Omitted► Nanostructured Fe–Mo catalysts are active in hydrogen production by ammonia decomposition. ► Bimetallic Fe–Mo catalysts are more active than the reference monometallic samples. ► Fe₅Mo₅/La–Al₂O₃ demonstrates promising catalytic performances. ► Formation of Fe/Mo nitrides is observed during NH₃ decomposition reaction.Active and stable catalysts for ammonia decomposition were obtained by deposition of Fe(5wt%)–Mo(5wt%) on commercial stabilized zirconia and modified aluminas. The adopted preparation methodology, combined with a severe reduction treatment, allowed obtaining highly dispersed nanoparticles of Fe–Mo alloy, as revealed by powder XRD. The bimetallic catalysts demonstrated a higher activity with respect to the monometallic ones with the same metal loading (10wt%). The best performances were obtained for a bimetallic Fe₅Mo₅/La₂O₃-modified Al₂O₃ sample. During ammonia decomposition reaction, the Fe–Mo alloy was progressively converted into a mixture of Fe/Mo nitrides, while good catalytic activity was maintained. The performances of the present catalysts well fit with the requirements of catalysts for application in ammonia-fueled SOFCs or for internal combustion engines.

Keywords: Hydrogen; Ammonia decomposition; Iron; Molybdenum; Nitrides

Enhanced Fenton degradation of Rhodamine B over nanoscaled Cu-doped LaTiO₃ perovskite by Lili Zhang; Yulun Nie; Chun Hu; Jiuhui Qu (pp. 418-424).

Display Omitted► LaTi_0.4Cu_0.6O₃ showed high Fenton activity and stability for the degradation of RhB. ► The introduction of Cu induced the formation of LaTiO₃ perovskite. ► The coexistence of Ti^3+/4+ and Cu^+/2+ in the perovskite structure enhanced Fenton activity. ► H₂O₂ was predominately converted intoOH and HO₂/O₂⁻ in LaTi_0.4Cu_0.6O₃ suspension.Cu-doped LaTiO₃ perovskite was prepared with a sol–gel method and characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The introduction of Cu induced the formation of LaTiO₃ perovskite in which titanium existed as Ti³⁺, resulting in the coexistence of Ti^3+/4+ and Cu^+/2+ in the perovskite structure. LaTi_0.4Cu_0.6O₃ showed highly Fenton activity and stability for the degradation of RhB with H₂O₂ in the initial pH range of 4–9. Moreover, the catalyst buffered the solution with the tested initial pH to around 7 during the adsorption process. The studies of electron spin resonance, the effect of radical scavengers and other experiments verified that H₂O₂ was predominately converted intoOH and HO₂/O₂⁻ in LaTi_0.4Cu_0.6O₃ suspension. A mechanism of heterogeneous Fenton catalysis was proposed on the basis of the both cycles of Ti³⁺/Ti⁴⁺ and Cu⁺/Cu²⁺ during the interaction of LaTi_0.4Cu_0.6O₃ with H₂O₂.

Keywords: Cu-doped LaTiO; ₃; perovskite; Fenton-like; Active radicals; Rhodamine B

Microwave-assisted non-aqueous route to deposit well-dispersed ZnO nanocrystals on reduced graphene oxide sheets with improved photoactivity for the decolorization of dyes under visible light by Yu Liu; Yong Hu; Mojiao Zhou; Haisheng Qian; Xiao Hu (pp. 425-431).

Display Omitted► rGO/ZnO nanohybrids were synthesized via a facile and rapid microwave-assisted route in a non-aqueous media. ► The nanohybrids exhibit well-dispersed ZnO nanocrystals loading. ► They also demonstrate improved photoactivity for the decolorization of self-photosensitized dyes under visible light.A new strategy is discussed for deposition of monodisperse ZnO nanocrystals on the surface of reduced graphene oxide (rGO) sheets to form rGO/ZnO nanohybrids via a microwave-assisted route in a non-aqueous media. This is a facile and rapid process, which only requires a proration of zinc salt and rGO sheets react in diethylene glycol (DEG) under a low level of microwave irradiation (300W) for 10min. The as-prepared nanohybrids demonstrate well-dispersed ZnO nanocrystals loading and powerful photocatalytic activity for the decolorization of self-photosensitized dyes (rhodamine-B and methylene blue) under visible-light illumination. Here, DEG does not only help to enhance dispersion of rGO sheets, but also play an important role of controlling the growth of ZnO. Furthermore, the average size and loading amount of ZnO nanocrystals can be conveniently varied or controlled by the concentration of zinc precursor. The result uncovers that the loading of ZnO nanocrystals in the as-prepared nanohybrids is crucial to obtain an optimal synergistic effect between ZnO and rGO sheets in the mediated photocatalysis process for the photosensitized dyes decolorization. Accordingly, the optimum matching for the best photocatalytic activity is investigated thoroughly and a reasonable mechanism is also proposed.

Keywords: Reduced graphene oxide; ZnO nanocrystals; Nanohybrids; Microwave-assisted method; Photoactivity

Synergetic effect by coupling photocatalysis with plasma for low VOCs concentration removal from air by Alina Maciuca; Catherine Batiot-Dupeyrat; Jean-Michel Tatibouët (pp. 432-438).

Display Omitted► VOC removal from air was enhanced by coupling non-thermal plasma and photocatalysis. ► A synergy effect was observed by coupling non-thermal plasma, catalyst and photocatalysis. ► Ozone activation by photocatalysis is mainly responsible of the synergy effect.By combining non-thermal plasma and photocatalysis a synergy effect has been observed in low concentrated gaseous isovaleraldehyde oxidation in air. The study of the behavior in isovaleraldehyde oxidation by the separate processes has shown that this synergy effect could be due to the activation by UV on TiO₂ of the ozone produced by the non-thermal plasma.According to the results, plasma–photocatalysis system significantly increases the efficiency of isovaleraldehyde removal and tends to favor the complete mineralization of isovaleraldehyde. It means that plasma–photocatalysis system could be a relevant method for the removal of low concentrated volatile organic compounds from air.

Keywords: Non-thermal plasma; Photocatalysis; VOCs oxidation; Isovaleraldehyde; Synergetic effect

Plasma-catalytic dry reforming of methane in an atmospheric dielectric barrier discharge: Understanding the synergistic effect at low temperature by X. Tu; J.C. Whitehead (pp. 439-448).

Display Omitted► Plasma-catalytic dry reforming of methane and carbon dioxide with a Ni/alumina catalyst to give syngas. ► Low temperature (<300°C) operation. ► Synergistic effect of combining plasma and catalyst gives increased conversions and improved energy efficiency.A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma-catalytic dry reforming of CH₄ into syngas over different Ni/γ-Al₂O₃ catalysts. Three different packing methods are introduced into the single-stage plasma-catalysis system to investigate the influence of catalysts packed into the plasma area on the physical properties of the DBD and determine consequent synergistic effects in the plasma-catalytic dry reforming reactions. Compared to the fully packed reactor, which strongly changes the discharge mode due to a significant reduction in the discharge volume, partially packing the Ni/γ-Al₂O₃ catalyst either in a radial or axial direction into the discharge gap still shows strong filamentary discharge and significantly enhances the physical and chemical interactions between the plasma and catalyst. Optical emission spectra of the discharge demonstrate the presence of reactive species (CO, CH, C₂, CO₂⁺ and N₂⁺) in the plasma dry reforming of methane. We also find the presence of the Ni/γ-Al₂O₃ catalyst in the plasma has a weak effect on the gas temperature of the CH₄/CO₂ discharge. The synergistic effect resulting from the integration of the plasma and catalyst is clearly observed when the 10wt% Ni/γ-Al₂O₃ catalyst in flake form calcined at 300°C is partially packed in the plasma, showing both the CH₄ conversion (56.4%) and H₂ yield (17.5%) are almost doubled. The synergy of plasma-catalysis also contributes to a significant enhancement in the energy efficiency for greenhouse gas conversion. This synergistic effect from the combination of low temperature plasma and solid catalyst can be attributed to both strong plasma–catalyst interactions and high activity of the Ni/γ-Al₂O₃ catalyst calcined at a low temperature.

Keywords: Plasma-catalysis; Synergistic effect; Dry reforming; Hydrogen; Optical emission spectroscopy

Preparation of multifunctional gas-diffusion electrode and its application to the degrading of chlorinated phenols by electrochemical reducing and oxidizing processes by Hui Wang; Zhaoyong Bian; Guang Lu; Lei Pang; Zhipeng Zeng; Dezhi Sun (pp. 449-456).

Display Omitted► Pd/C gas-diffusion cathode exhibits high electrocatalytic dechlorination activity. ► Pd particle is main active species for electrochemical degradation of chlorophenols. ► HNO₃ pretreatments of AC show great effects on catalytic properties of Pd/C. ► Chlorophenols degradation performed under a combination process of reduction and oxidation.Multifunctional gas-diffusion electrode with electrochemical reduction and oxidation properties was achieved based on the palladium-modified activated carbon (Pd/C). Pd/C catalysts were prepared using the formaldehyde reduction from nitric acid treated activated carbon and fully characterized by Boehm titration method, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cyclic voltammetry (CV) techniques. The electrochemical degradation of three typical chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) was investigated in a diaphragm electrolysis system with the Pd/C gas-diffusion electrode as a cathode, feeding firstly with hydrogen gas and then with air. The electrolysis system with 15% mass fraction nitric acid pretreated activated carbon showed better electrocatalytic activity compared to those from other mass fractions nitric acid, due to the active organic function groups increased on the surface of the activated carbon. When the ratio of Pd/C was low, Pd particles with an average size of 3.5nm were highly dispersed in the activated carbon with an amorphous structure. The Pd/C gas-diffusion cathode cannot only reductively dechlorinate chlorinated phenols by feeding hydrogen gas, but also accelerate the two-electron reduction of O₂ to H₂O₂ by feeding air. Therefore, the removal efficiency of chlorinated phenols reached almost 100%, conforming to the sequence of 4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol. The dechlorination of three chlorinated phenols exceeded 80% after 100min. For H₂O₂ and HO existed in the catholyte, the mineralization of organic pollutants in the cathodic compartment was better than that in the anodic compartment. Finally, chlorinated organic pollutants were efficiently degraded by the combined processes of reduction and oxidation in the present system.

Keywords: Chlorinated organic pollutants; Palladium-modified electrode; Reduction and oxidation processes; Reductive dechlorination

Optimisation of Ag loading and alumina characteristics to give sulphur-tolerant Ag/Al₂O₃ catalyst for H₂-assisted NH₃-SCR of NO_x by Sebastian Fogel; Dmitry E. Doronkin; Pär Gabrielsson; Søren Dahl (pp. 457-464).

Display Omitted► Sulphur tolerance of different Ag/Al₂O₃ catalysts for SCR of NO_x was tested. ► High S_BET and high Ag load are important for high sulphur tolerance. ► S_BET affects the NH₃ adsorption capacity, i.e. availability of NH₃ for SCR. ► A higher Ag load means more Ag clusters and particles that can be regenerated.A series of Ag/Al₂O₃ catalysts with different alumina precursors and different Ag loadings were tested for H₂ assisted NH₃-SCR of NO. The catalysts were characterised (BET, XRD, NH₃-TPD, ICP-OES, TEM and UV–vis spectroscopy) and tested as fresh catalyst, during long-term cycling tests with SO₂ present and after the sulphur testing. The aim was to find an optimal configuration of the Ag/Al₂O₃ catalyst for automotive applications. Catalysts with a high sulphur tolerance during long-term SO₂ cycling (1h with 10ppm SO₂ at 250°C followed by 10min regeneration at 670°C, repeated until no difference between cycles was seen) were demonstrated. The high sulphur tolerance and activity was attributed to high surface areas of the catalyst supports, together with a high Ag loading. The high surface area allows a larger NH₃ storage on the surface which is previously reported necessary for the SCR reaction. A higher Ag loading will affect the state of Ag by increasing the ratio of Ag-clusters and particles to highly dispersed Ag ions. SO₂-poisoned Ag-clusters and particles can be regenerated by the high temperature treatment in the deNO_x feed, highly dispersed Ag ions cannot.

Keywords: Ag/Al; ₂; O; ₃; NH; ₃; SCR; H; ₂; Sulphur tolerance

Photoelectrochemical degradation of azo dye over pulsed laser deposited nitrogen-doped TiO₂ thin film by Yen-Ping Peng; Emre Yassitepe; Yun-Ta Yeh; Inci Ruzybayev; S. Ismat Shah; C.P. Huang (pp. 465-472).

Display Omitted► Nitrogen was successfully doped into TiO₂ structure using PLD method. ► Nitrogen doping extended the band gap of TiO₂ from 400 to 595nm. ► NTTF had peak IPCE ( λ) of 26.77% under 2V bias potential 325nm light. ► Two-chamber PEC system improves photocatalytic oxidation of methyl orange.We investigated the synergetic effect of electrochemical and photocatalytic oxidation in photoelectrochemical (PEC) process for the degradation of hazardous organic compounds exemplified by methyl orange, an azo dye. Nitrogen doped TiO₂ thin film (NTTF) synthesized by the pulsed laser deposition (PLD) method, was used as the working anode. The crystalline, optical properties, surface morphology, and structure of the NTTF were characterized by XRD, UV–vis absorbance edges, SEM, and XPS. Results showed that the NTTF was dominated by anatase phase after sintered at 600°C with significant visible light response at 595nm. XPS analyses indicated nitrogen doping was mainly responsible for reducing the band gap as evidence of 3% N doping into the structure via the linkage of TiON and NTiO bond. SEM images illustrated the nitrogen-doped TiO₂ nanoparticles being attached firmly and spread evenly over the ITO glass surface, which is beneficial for PEC applications. The degradation efficiency of MO by photoelectrochemical, photocatalytic, electrochemical and photolysis methods were compared in terms of pseudo-first-order reaction rate. PEC was the most efficient in degrading MO at a bias potential of 2.0V (vs. SCE) under light at a wavelength of 325nm, which was consistent with results of IPCE (%) measurements. The synergetic effect was quantified at current/bias potential of 0.07mA/0.3V and 0.6mA/2.0V, respectively. Results demonstrated that the bias potential could separate photogenerated holes and electrons effectively and enhance the electrochemical-oxidation of MO. The mechanistic aspects of MO degradation by the PEC process were discussed.

Keywords: Photoelectrochemical; Pulsed laser deposition; N-doped TiO; ₂; Thin film; Synergetic effect

Comparison of the morphology and HDS activity of ternary Ni(Co)-Mo-W catalysts supported on Al-HMS and Al-SBA-16 substrates by R. Huirache-Acuña; B. Pawelec; C.V. Loricera; E.M. Rivera-Muñoz; R. Nava; B. Torres; J.L.G. Fierro (pp. 473-485).

.Display Omitted► HDS activity is markedly influenced by the type of promoter and support used. ► Ni promoter is much more effective than Co. ► Al-HMS is more effective than the Al-SBA-16 counterpart. ► The presence of extraframework AlNO₃ phases on catalyst surface favours the formation of a less active “onion-type” Mo(W)S₂ phases.This research compares the hydrodesulphurization (HDS) activity of supported Co(Ni)-Mo-W ternary catalysts with respect to the nature of the support (hexagonal mesoporous silica (HMS) versus SBA-16 material having cage-like mesoporous structure), the type of promoter (Co vs. Ni) and the nature of Al species formed after support modification with Al. Both Al-HMS and Al-SBA-16 mesoporous silica substrates were prepared by the one-pot sol–gel synthesis method via the neutral templating pathway using dodecylamine and Pluronic F127 as surfactants, respectively. The oxide precursors were characterized by a variety of techniques (N₂ adsorption–desorption isotherms, XRD, DRS UV–vis spectroscopy and²⁷Al NMR), whereas sulphided catalysts were characterized by XPS and HRTEM, and tested in the HDS of DBT conducted in a high-pressure batch reactor at T=350°C and P=3.1MPa. The activity results revealed that NiMoW/Al-HMS catalyst was more active than all Co-promoted catalysts (including a commercial CoMo/Al₂O₃ catalyst). The HDS activity was found to be markedly influenced by the textural properties of support and the dispersion of the active phases on the catalyst surface. It has been hypothesised that the presence of extraframework AlNO₃ phases on the surface of CoMoW/Al-SBA16 compromises its HDS activity because of the formation of a less active “onion-type” Mo(W)S₂ structure.

Keywords: Hydrodesulphurization; Mesoporous systems; Al-HMS; Al-SBA-16; CoMoW; NiMoW catalysts

Dimethyl carbonate via transesterification of propylene carbonate with methanol over ion exchange resins by Axel Pyrlik; Wolfgang F. Hoelderich; Karsten Müller; Wolfgang Arlt; Julia Strautmann; Daniela Kruse (pp. 486-491).

Display Omitted► We study the catalytic effect of strongly basic ion exchange resins. ► The transesterification is conducted batch-wise and in a continuous flow reactor. ► The catalyst is very active in the beginning but deactivates within one week. ► Washing of the catalyst with diluted bases result in complete regeneration.The transesterification of propylene carbonate with methanol to form dimethyl carbonate has been carried out in the presence of strong basic ion exchange resins as heterogeneous catalysts at low temperatures. Experiments have been carried out in a 75mL autoclave as well as in a continuous flow fixed bed reactor. Temperatures were varied between −20 and 40°C without any additional pressure. The molar ratio of methanol and propylene carbonate was adjusted between 8:1 and 4:1. The ion exchange resins showed a high activity even below 0°C when OH⁻ is used as counter ion. Leaching tests resulted in a complete hold of the conversion after removing the catalyst. In the continuous reactor the catalysts suffered from a rather fast deactivation within one week due to the transformation of the counter ion hydroxide to carbonate. However, a regeneration of the catalyst using different basic liquids was possible resulting in a complete recovery of its catalytic activity.

Keywords: Transesterification; Ion exchange resin; Dimethyl carbonate; Propylene carbonate; DMC

Catalytic decomposition of N₂O over Cu_xCe1−_xO_y mixed oxides by Haibo Zhou; Zhen Huang; Chao Sun; Feng Qin; Desheng Xiong; Wei Shen; Hualong Xu (pp. 492-498).

Display Omitted► The synergetic effect is demonstrated between Cu and Ce in the Cu_xCe1−_xO_y mixed oxides. ► The synergetic effect leads to an enhancement in the catalytic activity and stability. ► The amount of the Cu^I species correlates well with the N₂O decomposition performance. ► The synergy promotes the stability and the ability of regeneration of active site Cu^I.The catalytic N₂O decomposition was investigated over a series of Cu_xCe1−_xO_y mixed oxides with different Cu/Ce molar ratios. Effects of synergy over mixed oxides of CeO₂ and CuO were observed significantly, the catalyst of Cu_0.67Ce_0.33O_y exhibited the high activity among the Cu–Ce–O mixed oxides for N₂O decomposition. Characterizations of XRD, N₂-adsorption, XPS, and H₂-TPR were applied to correlate their properties with the corresponding catalytic performance, and reveal the synergetic effect between CuO and CeO₂ for N₂O decomposition. In situ DRIFTS investigation confirmed the presence of Cu^I species that was closely related with the activity of Cu_xCe1−_xO_y catalyst. The synergy of Cu_xCe1−_xO_y promoted the stability and the ability to regenerate the active Cu^I site.

Keywords: Synergetic effect; N; ₂; O decomposition; Cu; _x; Ce; 1−; _x; O; _y; catalyst; In situ DRIFTS

Recycling of waste plastics into fuels. LDPE conversion in FCC by Francisco J. Passamonti; Ulises Sedran (pp. 499-506).

Display Omitted► LDPE dissolved into VGO can be converted in FCC units operating under standard conditions. ► Conversions do not change substantially in comparison to those with VGO alone. ► Most important hydrocarbon groups such as LPG and gasoline increase their yields. ► Olefin yields in LPG and gasoline are increased, while coke loads would not interfere. ► Resid catalysts would show better global performances in co-processing waste polymers.In order to study the tertiary recycling of waste polymers in standard FCC units low density polyethylene (LDPE) was dissolved into a commercial vacuum gas oil at 2 and 6wt.% and converted over two equilibrium FCC catalysts of the octane-barrel and resid types in a CREC Riser Simulator laboratory reactor. The reaction temperatures were 500, 525 and 550°C, the mass catalyst to oil relationship was 6.35 and the contact times were from 3 to 30s. The study included the effect of the concentration of LDPE over conversion, the various product (dry gas, LPG, gasoline, LCO and coke) yields and selectivities. Results were very similar for the two concentrations. At typical conversions of 70wt.%, dry gas and gasoline yields increased about 10wt.%, LPG yields between 9 and 13wt.%, LCO yields decreased more than 15wt.% and coke yields were lower than 7.7wt.% The RON index of gasoline was improved slightly (up to one point), mainly due to significant increases in olefin concentrations, while the fuel quality of the LCO cut was not affected. LDPE is easily converted and seems to be subjected to primary reactions of catalytic cracking, thus increasing the yields of olefins in the LPG and gasoline boiling ranges. It was concluded that recycling waste LDPE by co-processing it as part of conventional feeds to the FCC would not interfere with the standard operation.

Keywords: Waste polymers; Polyethylene; Tertiary recycling; FCC; Fuels

Gold catalysts for low temperature water-gas shift reaction: Effect of ZrO₂ addition to CeO₂ support by Floriana Vindigni; Maela Manzoli; Tatyana Tabakova; Vasko Idakiev; Flora Boccuzzi; Anna Chiorino (pp. 507-515).

Display Omitted► Au/CeO₂–ZrO₂ catalysts were prepared and tested in WGS reaction at low temperature. ► The CeO₂–ZrO₂ solid solution is formed in the presence of ZrO₂. ► The new phase influences Au dispersion and the acid/base properties of ceria. ► The best activity of AuCe50Zr50 is partially correlated to the abundance of Au sites. ► The support acid/base properties influence the stability of carbonate-like species.New gold catalysts supported on ceria modified by addition of ZrO₂ have been synthesized and tested in the water-gas shift reaction (WGSR) at low temperature, where they displayed better catalytic activity than gold supported on pure ceria, following the trend: AuCe50Zr50>AuCe80Zr20>AuCe. Morphologic, textural, structural and spectroscopic characterisation showed that the addition of zirconia to ceria leads to the formation of mixture of tetragonal ceria–zirconia phases. Moreover, depending on the zirconia amount, a different Au dispersion is observed. Au agglomerates (10–20nm) and nanoparticles (about 2.5nm) have been detected by HRTEM on AuCe80Zr20, while only nanoparticles have been found on AuCe50Zr50. FTIR spectroscopy of CO adsorbed at 120K showed also the presence of Au clusters, more abundant on AuCe50Zr50 than on AuCe80Zr20. However, at low temperature the best catalytic activity of AuCe50Zr50 is correlated not only to the abundance of gold clusters and nanoparticles, but also to the effect of ZrO₂ addition that influences the acid/base surface properties of ceria, as successfully demonstrated by adsorption and surface reaction of acetone vapor at room temperature. FTIR measurements performed before and after reaction showed that the carbonate-like species have the lowest stability on the AuCe50Zr50 surface. This feature, along with the presence of a high gold dispersion, makes AuCe50Zr50 the best catalyst in terms of activity and stability.

Keywords: WGSR; Highly dispersed gold; Ceria; Zirconia; CeO; ₂; ⁻; ZrO; ₂; mixed phase; Acid/base properties; FTIR

A comparison of sol–gel and impregnated Pt or/and Ni based γ-alumina catalysts for bioglycerol aqueous phase reforming by M. El Doukkali; A. Iriondo; P.L. Arias; J. Requies; I. Gandarías; L. Jalowiecki-Duhamel; F. Dumeignil (pp. 516-529).

Display Omitted► Pt/Ni based γ-Al₂O₃ catalysts for H₂ production by APR of bioglycerol was studied. ► SGB method allows to PtNiAl catalyst with high surface area/porosity and good dispersion. ► Cooperative effect between Pt and Ni provide a better performance of PtNiAl catalysts. ► The APR behavior of the catalysts is more stable at moderate temperature/pressure reactions. ► Pt promotes H₂-rich gas, while Ni is more selective to alkanes, but PtNi led to an intermediate behavior.Two series of Pt or/and Ni-based γ-alumina catalysts were prepared using sol–gel and conventional impregnation methods. Their activities were tested in the aqueous phase reforming of glycerol. All catalysts were also characterized by different techniques such as: ICP, BET, TPR-H₂, in situ XPS and XRD to study their textural and physicochemical properties. The effect of preparation method, nature of active phase and possible cooperative effect between Pt and Ni in catalytic performance have been the focus of this investigation. The results obtained showed that sol–gel catalysts present better catalytic properties. TPR-H₂, XPS and XRD showed that sol–gel PtNiAl catalyst contain well dispersed active phases and present high resistance against sintering leading to better and more stable catalytic activities, especially at moderate temperature/pressure conditions. As a result, sol–gel PtNi catalysts allowed higher reforming rates (3–8 times) to gaseous products than PtNi catalysts prepared by incipient wetness impregnation. This better behavior can be explained by the enhancement of textural properties, higher active phases dispersion and cooperative effect between Pt and Ni elements.

Keywords: Platinum-nickel catalysts; Sol–gel method; Aqueous phase reforming; Bioglycerol; Hydrogen

How and to what extent do carbon materials catalyze solar hydrogen production from water? by Young Kwang Kim; Hyunwoong Park (pp. 530-537).

Display Omitted► CdSe particles were loaded on seven different kinds of carbon materials. ► The catalytic effects of carbon materials are enhanced by acid treatment by a factor of 3–7. ► The degrees of disordered carbon negatively influences the photocatalytic H₂ generation. ► The H₂ amounts have a correlation with the logarithmic electrical conductivities of carbon materials.The aim of this study is to find key physicochemical properties of carbon materials in catalyzing the photocatalytic H₂ production from visible light-irradiated aqueous suspensions of carbon/CdSe composites. For this, we have employed five different carbon materials (activated carbons, carbon fibers, multi- and single-walled nanotubes, and graphites) without and with acid treatment, and two carbon materials obtained from graphite (graphite oxides and reduced graphene oxides). Detailed surface analyses for the bare carbon materials and carbon/CdSe composites were completed to characterize their physicochemical properties. Most virgin (non-treated) carbon materials are beneficial in catalyzing the photocatalytic H₂ production of carbon/CdSe composites, and such catalytic effects are significantly enhanced by their acid treatment by a factor of 3–7. Systematic investigation indicates that the surface area, the degree of disordered carbon (i.e., I_D/ I_G ratios), and the electrical conductivity ( σ) of carbon materials display the correlations with H₂ production of carbon/CdSe composites. However, the first two factors could not explain well the enhanced H₂ production by acid treatment of carbon materials, whereas the last factor exhibits the linearity with the H₂ amounts even for the acid-treated carbon materials. High electrical conductivity appears to facilitate the photogenerated electron transfer from CdSe to neighboring carbon materials, leading to inhibition of charge pair recombination as evidenced by photoluminescence study.

Keywords: Photocatalyst; CdSe; Artificial photosynthesis; Water splitting; Heterojunction

In situ capture of active species and oxidation mechanism of RhB and MB dyes over sunlight-driven Ag/Ag₃PO₄ plasmonic nanocatalyst by Wei Teng; Xinyong Li; Qidong Zhao; Jijun Zhao; Dongke Zhang (pp. 538-545).

Display Omitted► The Ag/Ag₃PO₄ nanocatalyst was prepared by ethylene glycol reduction method. ► The nanocatalyst possesses excellent photocatalytic activity. ► The photocatalytic reaction was mainly governed by the holes direct oxidation. ► The calculation results clarified the origin of the photocatalytic activity.Sunlight-driven Ag/Ag₃PO₄ plasmonic nanocatalysts have been successfully prepared using an in situ ethylene glycol reduction method. The photocatalysts showed strong photocatalytic activity for decomposition of RhB and MB dyes under visible light irradiation ( λ>420nm). The excellent photocatalytic performance of Ag/Ag₃PO₄ came from the sensitivity of Ag₃PO₄ and the high separation efficiency of electron–hole pairs, which resulted in a large number of holes participating in the photocatalytic oxidation process. The results of density function theory calculation revealed that the visible-light absorption band in the Ag₃PO₄ catalyst is attributed to the band transition from the hybrid orbital of O 2p and Ag 4d to the Ag 5s and 5p orbital. The generation of active species in the photocatalytic system was evaluated using the fluorescence (FL) and electron spin resonance (ESR) techniques as well as in situ capture of active species by t-butanol and EDTA. The results indicated that the free hydroxyl radicals were not the major active oxidizing species in the photocatalytic process. The photocatalytic reaction process of the pollutants was mainly governed by the direct oxidation by the holes.

Keywords: Photocatalysis; Sunlight; Ag/Ag; ₃; PO; ₄; Calculation

Ageing analysis of a model Ir/CeO₂ catalyst in ethanol steam reforming by Fagen Wang; Weijie Cai; Tana; Hélène Provendier; Yves Schuurman; Claude Descorme; Claude Mirodatos; Wenjie Shen (pp. 546-555).

Display Omitted► Structure/morphology sensitivity of ethanol steam reforming over Ir/ceria catalyst. ► Initial and long term catalyst ageing mechanisms demonstrated. ► Fast initial deactivation due to ceria reduction and coating with reaction intermediates. ► Long term ageing due to ceria/metal sintering and not to encapsulating carbon.The ageing processes of a model Ir/CeO₂ catalyst during ethanol steam reforming was investigated. Various causes of deactivation were identified, depending on reaction temperature and time on stream. The initial, fast and but rather limited deactivation process was ascribed essentially to a loss of ceria surface (smoothing by loss of microporosity and/or roughness in the presence of steam), coinciding with an active phase build-up formed by a monolayer of carbonaceous reacting intermediates. In addition, a progressive and long-term deactivation was found to superimpose, originating from structural changes at the ceria/Ir interface linked to the Ir particles sintering and the ceria restructuring. The continuous build-up of an encapsulating layer of carbon at moderate temperature, coming from C₂ intermediate polymerization, was found not to contribute significantly to the catalyst deactivation, at least under the operating conditions investigated in this study.

Keywords: Ethanol steam reforming; Catalyst deactivation; Ir particle sintering; Ceria restructuring; Carbon deposition

Effect of the active metals on the selective H₂ production in glycerol steam reforming by M. Araque; L.M. Martínez T; J.C. Vargas; M.A. Centeno; A.C. Roger (pp. 556-566).

.Display Omitted► The presence of both Co anf Rh enhances the catalyst reduction capacity. ► Selective H₂ production related to the catalyst's capacity to activate water under the reaction conditions. ► Thermal decomposition of glycerol is superimposed with its steam reforming.The production of hydrogen by glycerol steam reforming was studied using CeZr(Co, CoRh) catalysts. The effect of Co and Rh presence on the properties of the mixed oxides and the effect on the catalytic behavior were considered. The catalysts were characterized before and after testing by XRD, Raman, TPR, H₂-TPD, TPD-TPO and HRTEM. It was observed that the presence of Co allowed the selective H₂ production related with the presence of a metallic phase at the beginning of the reaction. The presence of Rh favored even more the H₂ production and also increased the stability of the catalyst. For CeZrCoRh, the presence of both metals enhanced the catalyst reduction capacity, a characteristic that significantly improved the catalytic behavior for glycerol steam reforming. The selective H₂ production was related to the capacity of the catalyst to activate H₂O under the reaction conditions. The progressive loss of this capacity decreases the production of H₂, and glycerol decomposition is actually favored over glycerol steam reforming. According to the initial distribution of products, and its evolution with time on stream, two main reaction pathways were proposed.

Keywords: Hydrogen production; Glycerol; Steam reforming; Mixed oxides; Rhodium catalysts; Cobalt catalysts; Glycerol decomposition

Corrigendum to “Glycerol oxidation with gold supported on carbon xerogels: Tuning selectivities by varying mesopore sizes” [Appl. Catal. B: Environ. 115–116 (2012) 1–6] by Elodie G. Rodrigues; Manuel F.R. Pereira; José J.M. Órfão (pp. 567-568).

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Applied Catalysis B, Environmental (v.125, #)