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Applied Catalysis B, Environmental (v.123-124, #)

Contents (pp. i-ii).

Contents (pp. co4).

Editorial Board (pp. co2).

Editorial Board (pp. i).

Fast photocatalytic degradation of rhodamine B over [Mo₆Br₈(N₃)₆]²⁻ cluster units under sun light irradiation by Alexandre Barras; Stéphane Cordier; Rabah Boukherroub (pp. 1-8).

.Display Omitted► Water soluble Na₂[Mo₆Br₈(N₃)₆] was prepared by the reaction of Mo₆Br₁₂ with NaN₃. ► The cluster absorbs efficiently UV and visible light ( E_g=2.08eV). ► The photocatalytic activity of the cluster was studied under UV and visible light. ► The cluster shows a high performance for the photodegradation of RhB.The paper reports on the high photocatalytic activity of [Mo₆Br₈(N₃)₆]²⁻ cluster units for the degradation of rhodamine B under UV, visible or sun light irradiation. Water soluble Na₂[Mo₆Br₈(N₃)₆] inorganic compound built up from [Mo₆Br₈(N₃)₆]²⁻ anionic cluster units associated with Na⁺ counter cations investigated in this work is prepared in high yield by the interaction of Mo₆Br₁₂ with sodium azide in methanol. The high photocatalytic performance of the molybdenum cluster is demonstrated under real solar light excitation, suggesting that the photocatalyst could be used in broad daylight hours. Furthermore, the cluster is still highly active after ten successive cycling runs under UV or visible light irradiation without any apparent loss of its efficiency.

Keywords: [Mo; ₆; Br; ₈; (N; ₃; ); ₆; ]; ²⁻; cluster unit; Rhodamine B; Photodegradation; Sun light

Low temperature synthesis and photocatalytic properties of highly oriented ZnO/TiO2−_xN_y coupled photocatalysts by Yunfang Huang; Yuelin Wei; Jihuai Wu; Chongshen Guo; Ming Wang; Shu Yin; Tsugio Sato (pp. 9-17).

Display Omitted► A large-scale ZnO arrays were prepared via soft solution process without any polymer additives. ► TiO2−_xN_y was coupled with the ZnO arrays in order to give the visible-light responsiveness. ► The ZnO nanotube arrays/TiO2−_xN_y composites showed excellent photocatalytic activities.A novel photocatalysts, ZnO thin film with nanotube arrays was prepared via soft solution route without any polymer additives and subsequently using a facile chemical etching of ZnO nanorods arrays along the c-axis. The thin film of large-scale ZnO arrays could be produced directly on the glass substrates. Scanning electron microscopy, diffuse reflectance spectra and X-ray diffraction were systematically used to confirm the successful fabrication of the patterns and to characterize the structure and morphology. The possible mechanism to form the ZnO nanotube array via such a facile approach was also discussed. Moreover, nitrogen doped titania (TiO2−_xN_y) as sensitizers were coupled with the ZnO nanotube and nanotube arrays in order to give the visible-light responsiveness. The investigation of photocatalytic ability proved that the ZnO nanotube arrays/TiO2−_xN_y composites showed excellent photocatalytic activities for the decomposition of NO_x gas under both visible-light and UV light irradiation, being superior to that of ZnO nanorods, ZnO nanotube, TiO2−_xN_y, commercial TiO₂ (AEROXIDE^® P25) powders and ZnO nanorod arrays/TiO2−_xN_y composites.

Keywords: ZnO; Photocatalytic activity; Coupled catalyst; Nanotube array

One-step in situ solvothermal synthesis of SnS₂/TiO₂ nanocomposites with high performance in visible light-driven photocatalytic reduction of aqueous Cr(VI) by Yong Cai Zhang; Jing Li; Hai Yan Xu (pp. 18-26).

Display Omitted► SnS₂/TiO₂ nanocomposites are synthesized by a one-step in situ solvothermal route. ► Photocatalytic activities depend on compositions. ► Higher activity than SnS₂, TiO₂ and SnS₂/TiO₂ physical mixture at different doses. ► Good photocatalytic stability. ► Cr(VI) is reduced to Cr(III).SnS₂/TiO₂ nanocomposites with adjustable TiO₂ contents were synthesized directly via the solvothermal reactions of SnCl₄·5H₂O, thioacetamide and different amounts of tetrabutyl titanate in the mixed solvents of ethanol and acetic acid at 180°C for 12h. The structures, compositions, Brunauer–Emmett–Teller (BET) specific surface areas and optical properties of the as-synthesized products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, N₂ adsorption and UV–vis diffuse reflectance spectra, and their photocatalytic properties were tested for the reduction of aqueous Cr(VI) under visible light ( λ>420nm) irradiation. Furthermore, contrast photocatalytic experiments were also conducted for different doses of the as-synthesized SnS₂/TiO₂ nanocomposite, SnS₂ and physical mixture of SnS₂ and TiO₂. It was found that the as-synthesized SnS₂/TiO₂ nanocomposite with a suitable TiO₂ content (e.g., 44.5mass% TiO₂) not only exhibited extraordinary superior photocatalytic activity to SnS₂, TiO₂ and physical mixture of SnS₂ and TiO₂ (44.5mass%) at different catalyst doses, but also had good photocatalytic stability. Moreover, Cr(VI) can be reduced to Cr(III) by SnS₂/TiO₂-mediated photocatalysis. The tight heterojunction structure of the as-synthesized SnS₂/TiO₂ nanocomposite, which can facilitate interfacial electron transfer and reduce the separation and self-agglomeration of two components, was considered to play an important role in achieving its greatly improved photocatalytic performance.

Keywords: SnS; ₂; and TiO; ₂; Nanocomposites; Cr(VI) reduction; Photocatalysis; Stability

Cu-modified cryptomelane oxide as active catalyst for CO oxidation reactions by Willinton Y. Hernández; Miguel A. Centeno; Svetlana Ivanova; Pierre Eloy; Eric M. Gaigneaux; José A. Odriozola (pp. 27-35).

Display Omitted► Cryptomelane-type manganese dioxide materials for CO oxidation reactions. ► Mn–Cu interaction improves the catalytic activity of the cryptomelane structure. ► Catalytic activity in CO oxidation is related to the high lattice oxygen mobility. ► Application in the preferential oxidation of CO in presence of H₂.Manganese oxide octahedral molecular sieves (cryptomelane structure) were synthesized by a solvent-free method and tested in the total oxidation of CO (TOX), and preferential oxidation of CO in presence of hydrogen (PROX). The influence of Cu in the cryptomelane structure was evaluated by several characterization techniques such as: X-ray fluorescence (XRF), thermogravimetric analysis (TGA), hydrogen temperature programmed reduction (TPR-H₂) and X-ray photoelectron spectroscopy (XPS). The Cu-modified manganese oxide material (OMS-Cu) showed very high catalytic activity for CO oxidation in comparison to the bare manganese oxide octahedral molecular sieve (OMS). The improved catalytic activity observed in OMS-Cu catalyst was associated to a high lattice oxygen mobility and availability due to the formation of CuMnO bridges. In addition, under PROX reaction conditions the catalytic activity considerably decreases in the presence of 10% (v/v) CO₂ in the feed while the same amount of water provokes an improvement in the CO conversion and O₂ selectivity.

Keywords: CO oxidation; Manganese oxides; Octahedral molecular sieve (OMS); Cu-modified cryptomelane

Surface-modified anatase nanocrystalline building blocks for constructing catalytically highly active nanoporous titania materials by Chia-Hsiu Chen; Chun-Hsia Liu; Yu-Chung Su; Chia-Min Yang (pp. 36-42).

Display Omitted► Anatase nanocrystals with modified surface have been prepared. ► Pyridine retards anatase growth and modify the surface. ► The nanocrystals spontaneously assemble with anionic surfactant in water. ► The assembled material has high surface area and uniform mesoporosity. ► It exhibits excellent photocatalytic activity and epoxidation activity.Anatase nanocrystals with controlled size, shape and modified surface have been prepared and applied as nanocrystalline building blocks for surfactant-directed spontaneous assembly in aqueous solution. The nanocrystals were synthesized in a mixture of titanium tetrachloride and benzyl alcohol with the addition of pyridine as a modifying ligand. It was found that pyridine retarded the growth of anatase nanocrystals, preferentially along the c axis, and its addition resulted in nanocrystals with higher percentage of the high-energy {001} facets. Moreover, the nanocrystals was modified with pyridine chemisorbed at surface acid sites that were most likely to be associated to the five-coordinated titanium atoms. The pyridine-modified anatase nanocrystals interacted with sodium dodecyl sulfate in acidic aqueous solution, causing a spontaneous surfactant-directed assembly. After calcination, the surfactant-free nanoporous material exhibited high anatase crystallinity, high surface area, uniform mesoporosity and preferred surface properties. Owing to the textural and surface properties, the assembled material exhibited excellent catalytic activities in the photodegradation of methylene blue and in the epoxidation of cyclohexene with hydrogen peroxide as compared to reference titania samples.

Keywords: Anatase nanocrystal; Surface modification; Surfactant-directed assembly; Photodegradation; Epoxidation

Photodegradation of phenanthrene on cation-modified clays under visible light by Hanzhong Jia; Jincai Zhao; Xiaoyun Fan; Kamila Dilimulati; Chuanyi Wang (pp. 43-51).

Photodegradation of phenanthrene on cations-modified clays under visible light.Display Omitted► Clay minerals have great potential to act as catalysts for the photolysis of PAHs. ► Photolysis rate is determined by the interaction of phenanthrene with clay surfaces. ► Photodegradation rate are strongly dependent on the species of iron on clay surface. ► Phthalates were identified as intermediates during phenanthrene photodegradation.Transformation and fate of polycyclic aromatic hydrocarbons (PAHs) are critically influenced by natural conditions, especially their interactions with various components of soils and sediments. In the present study, phenanthrene was employed as a model to explore the potential photocatalysis effect of various cation-modified clay minerals in the soil under visible-light irradiation. For five types of cation-modified smectite clays, the photodegradation rates of phenanthrene follow the order: Fe³⁺>Cu²⁺>>Ca²⁺>K⁺>Na⁺, which is explained in terms of photo-Fenton-like catalysis. To further inspect the effect of clay type, additional two types of clays were paralleled. Among three types of Fe(III)-modified clays, Fe(III)-smectite shows the highest photodegradation rate followed by Fe(III)-vermiculite and Fe(III)-kaolinite. The photoactivity order is consistent with the iron content contained in the three clays, suggesting that Fe(III) content plays an important role in photocatalytic degradation of phenanthrene. The reactivity of iron species greatly depends on the interlayer microenvironment of smectite such as pH and water content. Moreover, phthalates, 9,10-phenanthrenequinone and alkanoic acids were identified by GC/MS analyses as the main intermediate compounds, and the organic compounds were mineralized finally. The overall results provide valuable insights on the transformation and fate of PAHs in the natural soil environment.

Keywords: Polycyclic aromatic hydrocarbons (PAHs); Phenanthrene; Clay minerals; Visible light photodegradation; Fenton-like reaction

Graphene as a new carbon support for low-temperature fuel cell catalysts by Ermete Antolini (pp. 52-68).

Display Omitted► Using graphene sheets as a support very low metal particle size can be obtained. ► The activity for methanol oxidation of Me/GNS is higher that that of Me/C and Me/CNT. ► Me/GNS catalysts have a similar activity for oxygen reduction than Me/C. ► Me/GNS catalysts show high durability in fuel cell operation conditions. ► Catalysts supported on composite GNS–CNT better perform than on single GNS and CNT.Highly dispersed catalysts on a conductive support, commonly platinum and platinum-based catalysts, are used as electrode materials in low-temperature fuel cells. Carbon blacks are commonly used as fuel cell catalysts supports, but their properties are not completely satisfactory. Thus, in the last years carbon black alternative materials such as nanostructured carbons, ceramic and polymer materials have been proposed as fuel cell catalyst supports. Very recently, in consideration of their high surface area, high conductivity, unique graphitized basal plane structure and potential low manufacturing cost, graphene nanosheets have been investigated as a support for low-temperature fuel cell catalysts. This paper presents an overview of graphene nanosheets used as supports for fuel cell catalysts. In particular, the catalytic activity and durability of catalysts supported on graphene are compared with those of catalysts supported on the commonly used carbon blacks and on carbon nanotubes, that is, on rolled graphene.

Keywords: Fuel cells; Catalyst supports; Graphene; Platinum

Optimization synthesis of carbon nanotubes-anatase TiO₂ composite photocatalyst by response surface methodology for photocatalytic degradation of gaseous styrene by Jiangyao Chen; Guiying Li; Yong Huang; Haimin Zhang; Huijun Zhao; Taicheng An (pp. 69-77).

Display Omitted► MWCNTs–TiO₂ composites were prepared by the method of multiple variable analysis. ► Photocatalytic degradation efficiency was obtained for gaseous styrene degradation. ► Optimum synthesis parameters were predicted by center composite design based on RSM.In present study, the center composite design in response surface methodology (RSM) was firstly applied to optimize the synthesis of multi-wall carbon nanotubes (MWCNTs)–TiO₂ composite photocatalyst. Twenty-eight composite photocatalysts were prepared by adjusting four operating parameters (amount of MWCNTs, amount of TiF₄, hydrothermal temperature and hydrothermal time) at five levels by the method of multiple variable analysis. The structural, optical and morphological properties of the prepared composite photocatalysts were characterized by X-ray diffraction, UV–visible absorption spectra and scanning electron microscopy, respectively. Based on the experimental design, a semi-empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation activity of the prepared composite photocatalysts to gaseous styrene in a cubic flow-through reactor. The results showed that the experimental photocatalytic degradation efficiencies using the differently prepared MWCNTs–TiO₂ composite photocatalysts matched with the theoretically predicted values very well with a high correlation ( R²=0.9790). Based on the theoretical and experimental results, the optimum synthesis parameters for the composite photocatalyst within the experimental ranges were 0.01g MWCNTs, 0.14g TiF₄, and 120°C hydrothermally treated for 87.2h. The photocatalytic degradation efficiency of gaseous styrene using the MWCNTs–TiO₂ composite photocatalyst synthesized under the optimum parameters reached 74.4%. All these demonstrates that the experimental design and theoretical prediction methods used in this work would have great significance in designing and developing high performance photocatalysts for environmental remediation and solar energy conversion.

Keywords: MWCNTs based composite photocatalyst; Optimization synthesis; Center composite design; Photocatalytic degradation; Gaseous styrene

Nanocrystalline pyrochlore AgSbO₃: Hydrothermal synthesis, photocatalytic activity and self-stable mechanism study by Wenjun Liu; Xiaobin Liu; Yanghe Fu; Qingqing You; Renkun Huang; Ping Liu; Zhaohui Li (pp. 78-83).

Display Omitted► Nanocrystalline pyrochlore AgSbO₃ can be synthesized by a facile hydrothermal method. ► Hydrothermally prepared AgSbO₃ exhibits a superior photocatalytic activity. ► Partial formation of metallic Ag and Ag₂O on the surface of pyrochlore AgSbO₃ during photocatalysis. ► Pyrochlore AgSbO₃ can maintain its photocatalytic activity during the photocatalytic reaction.Nanocrystalline pyrochlore AgSbO₃ has been successfully synthesized by a facile hydrothermal method and was fully characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The as-prepared pyrochlore AgSbO₃ showed a higher photocatalytic activity in the degradation of typical dye as compared to that prepared by the solid-state reaction. The photocatalytic mechanism of pyrochlore AgSbO₃ and its stability during photocatalytic reactions was investigated. It was found that pyrochlore AgSbO₃ can maintain its structure stability and photocatalytic activity under visible light irradiations by partial formation of metallic Ag and Ag₂O on its surface during the photocatalytic degradation of organic pollutants. This study provides some new insights into the photocatalytic mechanism of Ag-based multi-metal oxide photocatalysts.

Keywords: Hydrothermal; Pyrochlore AgSbO; ₃; Photocatalytic; Visible light; Self-stable mechanism

Ag-doped Mn–Cd sulfide as a visible-light-driven photocatalyst for H₂ evolution by Keita Ikeue; Yumeki Shinmura; Masato Machida (pp. 84-88).

Display Omitted► The photocatalytic activity of Mn–Cd sulfides was markedly improved by Ag doping. ► Metallic Ag was deposited on the Mn–Cd sulfide surface during the hydrothermal reaction. ► Metallic Ag on Ag-doped Mn–Cd sulfide could act as co-catalyst for photocatalytic hydrogen evolution.We have investigated the role of Ag in the Ag_yMn1− x−_yCd_xS during photocatalytic H₂ evolution under visible light irradiation ( λ>420nm). The rate of H₂ evolution increased with the amount of Ag doping, and reached a maximum at y=0.003 ( x=0.40). Ag_yMn1− x−_yCd_xS consisted of a highly crystalline solid solution phase over the range 0.48≤ x≤0.63 and 0≤y≤0.02, suggesting that the effect of Ag on the photocatalytic activity is not associated with crystallinity. UV–vis absorption spectra of Ag_yMn1− x−_yCd_xS showed a band gap absorption at 500nm and a flat absorption above 500nm. The latter absorption was caused by the presence of Ag₂S, which does not significantly contribute to the photocatalytic activity. X-ray photoelectron spectroscopy detected metallic Ag on the surface of Ag_0.003Mn_0.40Cd_0.60S, which could act as a co-catalyst in photocatalytic hydrogen evolution.

Keywords: H; ₂; production; Sulfide; Photocatalyst; Visible light response; Ag; Hydrothermal synthesis

Highly efficient photocatalyst Bi₂MoO₆ induced by blue light-emitting diode by Zhijie Zhang; Wenzhong Wang; Jia Ren; Jiehui Xu (pp. 89-93).

.Display Omitted► The applicability of LED as light source for environmental remediation is studied. ► Bi₂MoO₆ exhibits high photocatalytic activity under blue LED irradiation. ► The LED is a much more energy-saving light source than the generally used Xe lamp.The applicability of blue light-emitting diode (LED, λ=465nm) as the light source for environmental remediation by photocatalyst Bi₂MoO₆ was investigated. Two target compounds, phenol and ibuprofen (IBP), were selected as the model pollutants to evaluate the photocatalytic activities. The photocatalytic inactivation of Escherichia coli ( E. coli) was also conducted to check the feasibility of using blue LED as the light source for the disinfection of bacteria. The results showed that efficient elimination of phenol and IBP and inactivation of E. coli were realized under a 3W blue LED in the presence of Bi₂MoO₆. This demonstrates that LED is a competitive and promising alternative light source for the application in environmental remediation because the electrical energy consumption of LED decreased dramatically compared with other light source.

Keywords: LED; Bi; ₂; MoO; ₆; Ibuprofen; Phenol; E. coli

Mechanisms of catalytic ozonation on alumina and zeolites in water: Formation of hydroxyl radicals by Amir Ikhlaq; David R. Brown; Barbara Kasprzyk-Hordern (pp. 94-106).

Display Omitted► Coumarin was used as probe molecule to investigateOH formation during catalytic ozonation in water. ► The ZSM-5 zeolites act mainly as adsorbents of ozone and coumarin and do not generate hydroxyl radicals. ► Al₂O₃/O₃ leads to hydroxyl radicals formation due to interaction of ozone with surface hydroxyl groups of alumina.The mechanisms of catalytic ozonation of coumarin on ZSM-5 zeolites and γ-alumina in water have been studied. Coumarin is known to react with hydroxyl radicals to produce 7-hydroxycoumarin and is used to differentiate between radical and non-radical mechanisms. The effect of the radical scavenger (t-butanol) and phosphates has also been used to study the possible involvement of radicals and the role of surface hydroxyl groups of catalysts. Four ZSM-5 zeolites with varying silica to alumina ratios and with both hydrogen and sodium counter ions were used in the study (Z1000H:SiO₂/Al₂O₃=1000, Z900Na:SiO₂/Al₂O₃=900, Z25H:SiO₂/Al₂O₃=25 and Z25Na:SiO₂/Al₂O₃=25). The results show that both alumina and the zeolites catalyse the removal of coumarin from aqueous solution by ozonation, but that alumina is generally more active than zeolites and it catalyses a radical pathway involving hydroxyl radicals, showing its highest activity at pH close to the point of zero charge where surface hydroxyl groups are most susceptible to conversion of ozone to hydroxyl radicals. The zeolites operate through a simple adsorption process, leading to a direct reaction between adsorbed coumarin and adsorbed ozone. Activity depends to an extent on the silica to alumina ratio of the zeolite but is insensitive to the nature of the zeolite counter ion.

Keywords: Catalytic ozonation; Water treatment; Coumarin; 7-hydroxycoumarin; ZSM-5 zeolites; Alumina; Mechanism; AOPs; Advanced oxidation processes

Platinum oxide formation and reduction during NO oxidation on a diesel oxidation catalyst – Experimental results by K. Hauff; U. Tuttlies; G. Eigenberger; U. Nieken (pp. 107-116).

Experimental study of platinum oxide formation on a diesel oxidation catalyst.Display Omitted► Slow deactivation of DOC due to platinum oxidation in lean exhaust gas. ► The pretreatment of the catalyst influences strongly its activity. ► NO is able to reduce PtO in a lean exhaust gas <220°C. ► Thermal decomposition of PtO >300°C. ► Proof of PtO formation by H₂ titration.Experimental investigations clearly show that the activity of a diesel oxidation catalyst (DOC, Pt- γ-Al₂O₃) is changing during NO oxidation. This can be attributed to the reversible formation of platinum oxide. Therefore the activity depends strongly on the pretreatment and the operating conditions. In this paper, the impact of O₂ and NO₂ as oxidising agents and of NO as reductant for platinum as well as the influence of different pretreatments is experimentally studied under typical DOC conditions in an isothermal flat bed reactor with either constant temperature or with temperature ramps. Furthermore, a method to determine the platinum oxide fraction in situ is shown.An inverse hysteresis in NO conversion is observed if the temperature is linearly increased and subsequently decreased at constant gas composition, confirming the findings of Hauptmann et al. . A variation of the minimal temperature of the ramp shows that a reduction of PtO by NO is possible in a net oxidising atmosphere (500ppm NO, 12% O₂, 10% H₂O) below 220°C. Above 300°C, PtO becomes instable. Experiments with and without NO₂ prove that small NO₂ concentrations (<200ppm) have no influence on the progress of platinum oxidation in the presence of 12% O₂. Platinum oxidation is mainly driven by the high O₂ concentration, which is confirmed by an observed deactivation of CO oxidation after reductive pretreatment. In a mixture of CO and NO, the light-off and light-out behaviour of both components is strongly modified by the other component.

Keywords: Diesel oxidation catalyst; Platinum oxide; Catalyst deactivation

Fenton-like degradation of 2,4-dichlorophenol using Fe₃O₄ magnetic nanoparticles by Lejin Xu; Jianlong Wang (pp. 117-126).

Heterogeneous Fenton-like degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was investigated over Fe₃O₄ magnetic nanoparticles (MNPs) as catalyst. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption isotherms, and physical property measurement system (PPMS). The catalytic results showed that Fe₃O₄ MNPs presented good properties for the degradation and mineralization of 2,4-DCP, achieving complete decomposition of 2,4-DCP and 51% of TOC removal after 180min at reaction conditions of H₂O₂ 12mM, Fe₃O₄ MNPs 1.0g/L, 2,4-DCP 100mg/L, pH 3.0 and T 30°C. The effect of different reaction parameters such as initial pH, H₂O₂ dosage, Fe₃O₄ MNPs addition, initial concentration of 2,4-DCP and temperature on two-stage first-order kinetics of 2,4-DCP degradation was studied. A high utilization efficiency of H₂O₂ calculated as 73% was observed. According to the analyses of iron leaching, reactive oxidizing species and degradation intermediates, a possible mechanistic steps of 2,4-DCP degradation dominated byOH reactions (especially by freeOH in the bulk solution) were proposed. Besides, stability and reusability of Fe₃O₄ MNPs were tested.Display Omitted► Heterogeneous Fenton oxidation of 2,4-dichlorophenol using Fe₃O₄ magnetic nanoparticles. ► Fe₃O₄ magnetic nanoparticles show good catalytic activity and recyclability. ► Degradation of 2,4-dichlorophenol exhibits the two-stage first-order reaction kinetics. ► A high utilization efficiency of H₂O₂ is calculated as 73%. ►OH reactions (especially freeOH in the bulk solution) predominate in the process.Fenton-like degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was investigated over Fe₃O₄ magnetic nanoparticles (MNPs) as catalyst. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption isotherms, and physical property measurement system (PPMS). The catalytic results showed that Fe₃O₄ MNPs presented good properties for the degradation and mineralization of 2,4-DCP, achieving complete decomposition of 2,4-DCP and 51% of TOC removal after 180min at reaction conditions of H₂O₂ 12mM, Fe₃O₄ MNPs 1.0g/L, 2,4-DCP 100mg/L, pH 3.0 and T 30°C. The effect of different reaction parameters such as initial pH, H₂O₂ dosage, Fe₃O₄ MNPs addition, initial concentration of 2,4-DCP and temperature on two-stage first-order kinetics of 2,4-DCP degradation was studied. A high utilization efficiency of H₂O₂ calculated as 73% was observed. According to the analyses of iron leaching, reactive oxidizing species and degradation intermediates, a possible mechanistic steps of 2,4-DCP degradation dominated byOH reactions (especially by freeOH in the bulk solution) were proposed. Besides, stability and reusability of Fe₃O₄ MNPs were tested.

Keywords: Fe; ₃; O; ₄; magnetic nanoparticles; Hydrogen peroxide; Fenton-like; 2,4-Dichlorophenol; Hydroxyl radicals

Formation of core/shell structured polystyrene/anatase TiO₂ photocatalyst via vapor phase hydrolysis by Fuzhi Shi; Yaogang Li; Hongzhi Wang; Qinghong Zhang (pp. 127-133).

Display Omitted► Anatase TiO₂ nanocrystals were immobilized on the surface of PS microspheres via the vapor phase hydrolysis process. ► PS/TiO₂ showed better suspensible ability and improved light harvesting properties in the efficient degradation the MB dye and phenol. ► The crystallite size and the thickness of the TiO₂ shell in the composite could be tuned. ► The presence of SiO₂ was demonstrated to be against the photocatalytic oxidation of polymer core.The core/shell structured polystyrene/anatase TiO₂ (PS/A-TiO₂) photocatalyst is prepared via vapor phase hydrolysis method and characterized by X-ray diffraction, transmission electron microscopy (TEM), High resolution transmission electron microscopy (HRTEM), thermogravimetry, N₂ adsorption/desorption isotherm analysis and UV–vis spectra. TEM and HRTEM show that well crystalline A-TiO₂ nanocrystals are immobilized on the surface of PS microspheres with dimensions of 400nm. The TiO₂ crystallite size in the shell ranges from 7.5nm to 13.6nm, which is dependent on the temperature of vapor phase hydrolysis. The weight ratio of A-TiO₂ in the composite can be tuned by varying the content of titanium precursor. The composite density is lower than that of bare A-TiO₂ because of the light PS core, thus the composite has improved floating property. The photocatalytic performances of various catalysts in the degradation of methylene blue (MB) and phenol are evaluated, and the core/shell catalyst has a relatively higher activity than that of bare A-TiO₂ due to the improved floating and light harvesting ability. However, the PS core competitively consumes some active radicals, which are generally essential to the photocatalytic oxidation of MB, phenol or their intermediate derivatives. Then an insulating coating of SiO₂ between the PS core and A-TiO₂ shell is also introduced via vapor phase hydrolysis process, and the long-term stability of core/shell structured composite is enhanced.

Keywords: Polystyrene/TiO; ₂; Vapor phase hydrolysis; Photocatalysis; Phenol; Stability

Selective catalytic reduction of NO on single site FeSiBEA zeolite catalyst: Influence of the C₁ and C₂ reducing agents on the catalytic properties by Janusz Janas; Wojciech Rojek; Tetsuya Shishido; Stanislaw Dzwigaj (pp. 134-140).

Display Omitted► Iron is incorporated in framework of zeolite as mononuclear tetrahedral Fe(III). ► The single site FeSiBEA catalyst is active in SCR of NO with ethanol and ethylene. ► The selectivity towards N₂ exceeding 90% in the broad temperature range. ► FeSiBEA shows inferior activity with methanol and methane. ► The selectivity towards N₂ is inferior 65% with methanol and 10% with methane.FeSiBEA zeolite with 0.8 Fe wt% is prepared in acidic condition (pH 2.5) by a two-step postsynthesis method which allows to incorporate iron into framework of zeolite as mononuclear distorted tetrahedral Fe(III) species, as evidenced by XRD, diffuse reflectance UV–vis and X-ray absorption spectroscopy. The single site FeSiBEA catalyst with isolated and framework Fe centres is active in SCR of NO process with C₂ (ethanol and ethylene) reducing agents, with selectivity towards N₂ exceeding 90% in the broad temperature range from 573 to 723K for maximum NO conversion about 50 and 30% at 573K for ethanol and ethylene respectively. In contrast, this catalyst is much less active with C₁ (methanol and methane) reducing agents, with maximum selectivity towards N₂ not exceeding 65% with methanol and 10% with methane for maximum NO conversion of 10 and 23% respectively. The low activity in CH₄-SCR of NO on Fe_0.8SiBEA catalyst containing only isolated mononuclear distorted tetrahedral Fe(III) species in the framework zeolite could be explained by high energy of CH bond, which should be broken to activate methane molecule.

Keywords: Iron; SiBEA; SCR of NO; Methanol; Methane; Ethanol; Ethylene

Catalytic wet air oxidation of a high strength p-nitrophenol wastewater over Ru and Pt catalysts: Influence of the reaction conditions on biodegradability enhancement by Mariángel Martín-Hernández; Julián Carrera; María Eugenia Suárez-Ojeda; Michèle Besson; Claude Descorme (pp. 141-150).

Display Omitted► Conversion higher than 90% were systematically achieved, being temperature the most important parameter. ► Identification of oxidation intermediates allowed establishing a reaction pathway. ► In general, CWAO increased biodegradability by more than 50%. ► All the catalysts exhibited a similar behaviour. ► Carboxylic acid fraction was the key factor for biodegradability enhancement. p-Nitrophenol (PNP) is widely used as a raw material in several industries, therefore it can be released to the environment, being mandatory the treatment of the PNP-contaminated industrial wastewaters. In this sense, the influence of temperature, oxygen partial pressure, type of catalyst, pH and ionic strength on the wet air oxidation (WAO) of a highly concentrated PNP wastewater was studied. Several 480min batch tests have been performed and four Pt and Ru-based catalysts have been tested. The PNP elimination, total organic carbon (TOC) abatement and the intermediates distribution were monitored. Moreover, respirometric screening tests were completed after each experiment to assess the biodegradability enhancement of the catalytic WAO (CWAO) treated effluents. The results showed that PNP elimination was higher than 90% in most cases, being the temperature the most important operating parameter upon CWAO. Additionally, all the catalysts showed a similar behaviour in terms of PNP and TOC conversions. Besides, CWAO increased the biodegradability by more than 50% in most of the tested conditions, being the carboxylic acid fraction the key factor to be taken into account, as the best biodegradability enhancement was observed when this fraction was the highest. The partial pressure of oxygen had a negligible effect on the biodegradability enhancement. The ionic strength influence over the CWAO was studied and even though it did not affect the CWAO performances, the presence of NaCl in the solution resulted in a decrease of the effluent biodegradability. In terms of pH, the most suitable scenario was the one with no pH adjustment. Conclusively, this work demonstrated that an integrated CWAO and biological treatment would allow an easy removal of PNP and the intermediates formed during the first step of the treatment, being the best CWAO conditions for this pre-treatment to work at 180°C under stoichiometric oxygen pressure (i.e. 7.6bar of oxygen partial pressure) with a Ru/TiO₂ catalyst.

Keywords: p; -Nitrophenol degradation; CWAO; Biodegradability enhancement; Noble metal-based catalysts; Respirometry

Photo-assisted degradation of 2,4,5-trichlorophenoxyacetic acid by Fe(II)-catalyzed activation of Oxone process: The role of UV irradiation, reaction mechanism and mineralization by Y.R. Wang; W. Chu (pp. 151-161).

Display Omitted► Photo-assisted Fe(II)-catalyzed decomposition of Oxone process (FOU) was explored. ► Elucidated the role of UV by comparing real-time of [Fe(II)] between FO and FOU. ► Excellent performance of FOU is due to synergistic effect among Oxone, Fe²⁺ and UV. ► Decay pathways of 2,4,5-T by UV alone, UV/Oxone, and FOU were proposed.In this study, the potential of Fe(II)-catalyzed activation of Oxone process with UV irradiation (FOU) for the degradation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in aqueous solution was explored and compared with the Fe(II)/Oxone (FO) process. Experimental results show that the FO process was dramatically promoted upon the introduction of UV irradiation. As a result, the role of UV irradiation was elucidated in-depth by comparing the real-time of [Fe(II)] between the FO process and the FOU process. It was found that a beneficial Fe(III)/Fe(II) catalytic cycle is established in the presence of UV irradiation, thereby leading to the accelerated regeneration of Fe(II). Additionally, 2,4,5-T decay by the FOU process under various [Oxone] and [2,4,5-T] was also examined. Furthermore, the decay pathways for the transformation of 2,4,5-T by UV alone, Oxone/UV, and FOU processes were proposed by using LC-ESI/MS analysis. Distinct differences of intermediate distributions were observed among the three processes with or without the involvement of radicals (OH and SO₄⁻). Besides, the efficiencies of various processes (i.e., UV alone, Oxone/UV and FOU) were further examined in terms of mineralization and Cl⁻ ion accumulation.

Keywords: 2,4,5-Trichlorophenoxyacetic acid; Oxone; Hydroxyl radical; Sulfate radical; UV irradiation

Multidirectional porous NiO nanoplatelet-like mosaics as catalysts for green chemical transformations by Sherif A. El-Safty; Mohamed Khairy; Mohamd. Ismael; Hiroshi Kawarada (pp. 162-173).

Display Omitted► Fabrication of multidirectional porous NiO nanocrystals with hexagonal platelet-like mosaic catalyst. ► Green chemical transformation of phenolic pollutants to safe compounds was performed. ► The intrinsic properties of NiO nanoplatelets showed excellent catalytic activity and high reusability.The design of multidirectional porous metal oxide catalysts has attracted extensive attention because such materials have potential for environmental applications. To satisfy the requirements of these applications, large-scale production, low-cost manufacturing, and efficient transformation reactions are needed. The present paper reports the fabrication of hierarchical nickel oxide nanocrystals (NiO NCs) with hexagonal nanoplatelets and micro-, meso-, and macropore cavities through an eco-friendly method. The controlled size and shape of the NiO platelets in condensed orientation sequence “tesserae blocks” led to the formation of a hexagonal mosaic-like morphology. The NiO NCs could be recovered and reused without lost of activity over a number of batch reactions. In addition, theoretical models to predict the molecular structures of both the intermediate and transition states within the chemical transformation reactions were developed. The theoretical findings in the current study provide insight into the key factors that control the changes in the molecular structure throughout the transformation mechanism of the phenolic pollutants using NiO platelet nanocatalysts.

Keywords: Hexagonal NiO; Aminophenols; Oxidative cyclocondensation; Oxygen; Water treatment

Comparative study on the mechanism in photocatalytic degradation of different-type organic dyes on SnS₂ and CdS by Xi Li; Jian Zhu; Hexing Li (pp. 174-181).

Display Omitted► The rate is faster on SnS₂ than CdS in MO degradation but slower in RhB degradation. ► MO degradation follows a reduction mechanism on SnS₂ but an oxidation one on CdS. ► Photoreduction on SnS₂ results from electrons transfer via Sn^VI/Sn^II transition. ► Photoreduction reduces the photocorrosion of SnS₂ in MO degradation.The photocatalytic performances of the SnS₂ and the CdS under the irradiation of visible light were investigated by using different organic dyes as reactants. The photodegradation of organic dyes containing NN double bond on the SnS₂ followed a reduction mechanism with photoelectrons via the Sn^IV/Sn^II transition while the photodegradation of organic dyes containing NN double bond on the CdS and the photodegradation of organic dyes without NN double bond on either the SnS₂ or the CdS followed an oxidation mechanism withO₂⁻ andOH radicals. The SnS₂ exhibited much higher activity than the CdS during the photocatalytic degradation of organic dyes containing NN double bond, since the reduction of reactant molecules on the SnS₂ surface was much faster than the migration of either theO₂⁻ or theOH radicals. However, the SnS₂ displayed even lower activity than the CdS in the photocatalytic degradation of other organic dyes without NN double bond, since all these reactions followed the oxidation mechanism and the SnS₂ displayed a lower efficiency than the CdS in producingO₂⁻ orOH radicals due to the presence of the Sn^IV/Sn^II transition.

Keywords: SnS; ₂; CdS; Organic dye; Photoreduction; Photooxidation

Aging of photocatalytic coatings under a water flow: Long run performance and TiO₂ nanoparticles release by Josune Olabarrieta; Saioa Zorita; Iratxe Peña; Nerea Rioja; Oihane Monzón; Pablo Benguria; Lorette Scifo (pp. 182-192).

Display Omitted► Accelerated aging of two photocatalytic coatings under a water flow. ► Deactivation of photocatalytic active sites upon prolonged immersion. ► Release of TiO₂ nanoparticles even in absence of mechanical deterioration. ► Common pattern of aging for the two coatings. ► Strongest damages in presence sodium chloride.Although photocatalytic coatings may experience severe wearing in most of their application, little work has been done to investigate their aging in a comprehensive way. In this article, we present an original experimental protocol to simulate an accelerated aging of photocatalytic coatings under a water flow, and test it on two materials: a well-known commercial product, Pilkington Activ™, and an experimental coating. The influence of intrinsic properties of the coatings (chemical nature, thickness) as well as environmental parameters (water matrix, UV-light) is investigated while the consequences of aging are evaluated under three different endpoints, related either to the long run performance of photocatalytic coatings or their environmental impact: (i) loss of the photocatalytic activity, (ii) degradation of mechanical properties, and (iii) release of TiO₂ nanoparticles. It is observed that both photocatalytic coatings experienced a deactivation of their active sites upon prolonged immersion. The extent of deactivation varies depending on the coating, being around 20% for experimental coatings and 65% for Pilkington Activ™ but shows little dependency on water matrix or illumination. An alteration of mechanical properties is seen on experimental coatings, which was accompanied by TiO₂ emissions as high as 150.5μgL⁻¹. Although no reduction in film hardness or adhesion could be evidenced for Pilkington Activ™, TiO₂ concentrations up to 30.8μgL⁻¹ was detected in the aging water showing that some release of TiO₂ nanoparticles also took place on this material. Interestingly, a common mechanism of release, triggered by an interaction between TiO₂, NaCl and UVA could be identified. Most severe damages were observed in presence of sodium chloride. These results suggest that the use of photocatalytic coatings with surface-bound nanoparticles in environmental applications may entail new entries of nanomaterials into the aqueous medium. They also prove that aging assays are an effective way of assessing the emissions.

Keywords: Photocatalytic coatings; TiO; ₂; nanoparticles; Aging; Emissions; Water flow

Ag-AgCl/WO₃ hollow sphere with flower-like structure and superior visible photocatalytic activity by Bowen Ma; Jianfeng Guo; Wei-Lin Dai; Kangnian Fan (pp. 193-199).

We describe an effective route to synthesize Ag-AgCl/WO₃ hollow sphere with flower-like structure, which displayed excellent visible photocatalytic activity and recycling ability for the degradation of 4-chlorophenol.Display Omitted► Highly active Ag-AgCl/WO₃ hollow sphere with flower-like structure. ► This photocatalyst was prepared for the first time. ► This material displayed excellent visible photocatalytic activity. ► Good recycling ability for the degradation of 4-chlorophenol. ► The presence of surface plasmon resonance effect of Ag nanoparticles.In this work, we describe an effective route to synthesize Ag-AgCl/WO₃ hollow sphere with flower-like structure, which displayed excellent visible light response photocatalytic activity and recycling ability for the degradation of 4-chlorophenol. Its high photocatalytic activity can be attributed to the surface plasmon resonance effect of Ag nanoparticles, which were highly dispersed on the surface of Ag-AgCl/WO₃. N₂ adsorption and desorption isotherm spectra, X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy were used to determine the correlation between the micro-structure and the catalytic properties of the as-prepared photocatalysts.

Keywords: Photocatalyst; Ag-AgCl/WO; ₃; Plasmon resonance; photodegradation; 4-chlorophenol

Magnetically recoverable Fe_xO_y–MWNT Fenton's catalysts that show enhanced activity at neutral pH by Meherzad F. Variava; Tamara L. Church; Andrew T. Harris (pp. 200-207).

Magnetically recoverable Fe_xO_y–MWNT Fenton's catalysts active at neutral pH.Display Omitted► Rapid microwave-assisted synthesis of multiwalled-carbon-nanotube-supported Fe_xO_y. ► Fe_xO_y–MWNTs successfully employed for heterogeneous dye degradation at pH₀=7. ► Catalyst exhibited minimal leaching, thus was regenerated and reused.Known supported catalysts for the Fenton degradation of organic contaminants must be used in acidified solutions, where they leach Fe and consequently lose activity. In this study, Fe_xO_y nanoparticles (average diameter=3nm) were immobilized onto multiwalled carbon nanotubes using a facile microwave-assisted polyol method to produce a Fenton catalyst that was active at neutral pH. Despite an Fe content of only 1.5wt%, Fe_xO_y–MWNTs catalyzed the near-complete degradation of 50mgL⁻¹ of an organic dye contaminant in water at pH₀=7 in 30min. At neutral pH, Fe leaching from the catalyst was minimal. Factors affecting the activity and stability of the catalyst were studied and a method was developed to regenerate the catalyst, which could be separated and reused with a small loss in activity.

Keywords: MWNT; Fenton; Heterogeneous catalyst; Fe; _x; O; _y; Polyol functionalization; Advanced Oxidation Processes

A mechanistic study on photocatalysis by thiapyrylium salts. Photodegradation of dimethoate, alachlor and pyrimethanil under simulated sunlight by J. Gomis; A. Arques; A.M. Amat; M.L. Marin; M.A. Miranda (pp. 208-213).

Display Omitted► Photodegradation of the title pesticides occurs using a thiapyrilium salt (TPTP⁺). ► The photoreactivity order is: pyrimethanil>dimethoate>alachlor. ► Formation of TPTP⁺/pesticide complexes is involved in photodegradation. ► Quenching of TPTP⁺ singlet excited state by pesticides leads to photodegradation. ► A correlation exists between the missing fraction of triplets and photoreactivity.Photodegradation of dimethoate, alachlor, and pyrimethanil using a thiapyrilium salt (TPTP⁺) as photocatalyst was performed under simulated sunlight. The photocatalyst removes preferentially pyrimethanil (45% after 60min of irradiation), followed by dimethoate (20%) and alachlor (13%). In the three cases, an important to moderate decrease of the fluorescence intensity upon addition of the pollutants was observed. The active participation of the singlet excited state in the photodegradation of the pollutants was demonstrated; the corresponding dynamic quenching rate constants were found to be 1.9×10¹⁰M⁻¹s⁻¹ (pyrimethanil), 6.7×10⁹M⁻¹s⁻¹ (dimethoate) and 9.1×10⁹M⁻¹s⁻¹ (alachlor). Moreover, a decrease in the signal corresponding to the triplet excited state was observed immediately after the laser pulse; again a good correlation was observed between the missing fraction of triplets and the photodegradation rates under solar light. Detection of TPTP⁺, the reduced species derived from the photocatalyst, as well as Rehm–Weller calculations on the free energy changes, strongly support an electron transfer mechanism occurring from the singlet excited state.

Keywords: Pesticides; Fluorescence; Laser flash photolysis; Quenching; Singlet excited state; Triplet

Synthesis and characterization of carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst with high durability for PEMFCs application by Zheng-Zhi Jiang; Zhen-Bo Wang; Wei-Li Qu; Da-Ming Gu; Ge-Ping Yin (pp. 214-220).

Carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst (blue) performs similar activity to the Pt/C and Pt/TiO₂–C ones. It possesses 8.5 times stability as high as that of Pt/C. It exhibits 4.5 times life-span as long as that of carbon riveted Pt/TiO₂–C which was reported in our previous work.Display Omitted► Carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst was synthesized based on in situ carbonization of glucose. ► Carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst performs similar activity to the Pt/C and Pt/TiO₂–C ones. ► Carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst possesses 8.5 times stability as high as that of Pt/C. ► Carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst exhibits 4.5 times life-span as long as that of carbon riveted Pt/TiO₂–C.Pt/TiC, Pt/TiO₂–TiC, and Pt/MWCNTs@TiO₂–TiC catalysts have been synthesized by the microwave-assisted polyol process. Moreover, carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst based on in situ carbonization of glucose has also been prepared. X-ray diffraction, energy dispersive analysis of X-ray, transmission electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammograms, and accelerated potential cycling tests have been used to characterize the catalysts. Experimental results show that both of the activity and stability of Pt/TiC catalyst cannot meet the requirements of proton exchange membrane fuel cells. In comparison with Pt/TiC, Pt/TiO₂–TiC catalyst exhibits lower activity due to poor conductivity of TiO₂ and higher stability ascribed to strong metal–support interaction (SMSI) between Pt and TiO₂. However, compared with Pt/TiC, Pt/MWCNTs@TiO₂–TiC catalyst exhibits both higher activity and stability because of high electrical conductivity of the mixed support and SMSI between Pt nanoparticles and nanocapsule composite MWCNTs@TiO₂. Furthermore, the measurement results show that carbon riveted Pt/MWCNTs@TiO₂–TiC catalyst with similar activity to the Pt/C and Pt/TiO₂–C ones possesses 8.5 times stability as high as that of Pt/C and exhibits 4.5 times life-span as long as that of carbon riveted Pt/TiO₂–C reported in our previous study.

Keywords: Electrocatalysts; TiC; Multi-walled carbon nanotubes; Proton exchange membrane fuel cells

Structured fibrous carbon-based catalysts for continuous nitrate removal from natural water by T. Yuranova; C. Franch; A.E. Palomares; E. Garcia-Bordejé; L. Kiwi-Minsker (pp. 221-228).

Display Omitted► Bimetallic (Pd–Cu, Pd–Sn) supported nanoparticles were used for water denitrification. ► The catalysts were tested in both batch and continuous modes with natural water. ► The mesoporous CNF/SMF support allows avoiding internal diffusion limitations. ► (Pd–Cu) nanoparticles are probably alloyed, (Pd–Sn) nanoparticles have a core–shell structure. ► (Pd–Sn) catalysts are higher N₂ selective as compared to (Pd–Cu) catalysts.Bimetallic (Pd–Cu, Pd–Sn) nanoparticles supported on structured fibrous carbons (activated carbon fibers and carbon nanofibers grown on sintered metal fibers) were tested in nitrate removal of natural polluted water by hydrogen (a batch and continuous mode). Dependence of the activity/selectivity on catalyst chemical composition, promoter nature and metal particle size was studied. Sn-modified Pd nanoparticles showed higher N₂ selectivity as compared to Cu-modified ones. The structured (Pd–Sn) nanoparticles supported on carbon nanofibers grown on Inconel sintered metal fibers demonstrated the best catalytic performance in an open flow reactor, providing optimal hydrodynamics properties.

Keywords: Nitrate removal; Structured fibrous carbon-based catalysts; Bimetallic; Nanofibers; Nanoparticles

Low-temperature selective catalytic reduction of NO_x with NH₃ over Mn-containing catalysts by M. Stanciulescu; G. Caravaggio; A. Dobri; J. Moir; R. Burich; J.-P. Charland; P. Bulsink (pp. 229-240).

Display Omitted► Study of Mn mono- and bimetallic catalysts active for NH₃–SCR. ► Comparison of DeNO_x activity for catalysts with various supports. ► Mn on Fe-exchanged zeolite is more active than Fe on Mn-exchanged zeolite. ► 100% NO_x conversion to N₂ at low and high temperatures with Mn-containing catalysts.Mn-containing catalysts exhibit a high NO_x conversion in selective catalytic reduction (SCR) with NH_3. Their high activity (80–100%) covers a broad temperature range (195–600°C). 100% N₂ formation is reached at about 230°C for the catalysts prepared by Mn ion-exchanged in CBV-2314, a MFI zeolite. The catalysts obtained by Mn- or Fe-exchange zeolites are superior for N₂ formation compared to those prepared by wet impregnation of Mn precursors on the γ-Al₂O₃ (80%)-TiO₂ (20%) catalyst support.Since the Mn catalysts are active for NO_x reduction in the intermediate temperature range of diesel engine exhaust mainly, an effort was undertaken in this study to extend this temperature range by promoting Mn with Cu, Ce and Fe oxides. These catalysts with two metals in the active phase were prepared and tested for DeNO_x activity. All promoted catalysts showed higher formation of N₂ at either low or high temperatures. The Ce/MnCBV-2314 catalyst was more active and stable at high temperatures, close to 600°C, than those containing Fe or Cu oxides. Cu/MnCBV-2314 showed high activity at low temperature. 100% N₂ formation for 2.1Mn/3.8FeCBV ranged from 220 to beyond 450°C.

Keywords: NH; ₃; –SCR for NO; _x; Mn exchanged zeolites; Mn/(γ-Al; ₂; O; ₃; -TiO; ₂; ); Ce/MnCBV-2314; Fe/MnCBV-2314; Cu/MnCBV-2314; Low temperature SCR

Advanced nanostructured photocatalysts based on reduced graphene oxide–TiO₂ composites for degradation of diphenhydramine pharmaceutical and methyl orange dye by Luisa M. Pastrana-Martínez; Sergio Morales-Torres; Vlassis Likodimos; José L. Figueiredo; Joaquim L. Faria; Polycarpos Falaras; Adrián M.T. Silva (pp. 241-256).

Display Omitted► GOT photocatalytic activity exceeded that of P25, especially under visible light. ► Optimization of the GO–TiO₂ interface is crucial for the photocatalytic efficiency. ► Photogenerated holes were identified as the main reactive species. ► GO may operate as a visible light sensitizer of TiO₂. ► Enhanced contribution of radical mediated oxidation evidenced under visible light.Reduced graphene oxide–TiO₂ composites (GOT) were prepared by liquid phase deposition followed by post-thermal reduction at different temperatures. The composite materials were systematically evaluated as photocatalysts for the degradation of an important pharmaceutical water pollutant, diphenhydramine (DP), and an azo-dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation as a function of the graphene oxide (GO) content. A marked compositional dependence of the photocatalytic activity was evidenced for DP and MO pollutants degradation and mineralization under both UV/Vis and visible light. Especially under visible light, optimum photocatalytic performance was obtained for the composites treated at 200°C comprising 3.3–4.0wt.% GO, exceeding that of the benchmark P25 (Evonik) catalyst. According to scanning electron microscopy, Raman spectroscopy, and porosimetry analysis data, this was attributed to the optimal assembly and interfacial coupling between the reduced GO sheets and TiO₂ nanoparticles. Almost total degradation and significant mineralization of DP and MO pollutants (in less than 60min) was achieved under near-UV/Vis irradiation for the optimum GOT composites. However, higher GO content and calcination temperatures (350°C) led to detrimental effects due to the GO excess and the disruption of the GO–TiO₂ binding. Photocatalytic experiments employing sacrificial hole and radical scavenging agents revealed that photogenerated holes are the primary active species in DP degradation for both bare TiO₂ and GOT under UV/Vis irradiation, while an enhanced contribution of radical mediated DP oxidation was evidenced under visible light. These results combined with the distinct quenching of the GO photoluminescence under visible and NIR laser excitation, indicate that reduced GO acts either as electron acceptor or electron donor (sensitizer) of TiO₂ under UV and visible light, respectively. Fine-tuning of the reduced GO–TiO₂ interface is concluded as a very promising route to alleviate electron–hole recombination and circumvent the inherently poor light harvesting ability of TiO₂ in the visible range.

Keywords: Reduced graphene oxide; Titanium dioxide; Heterogeneous photocatalysis; Scavengers for holes and radicals; Photoluminescence quenching; Raman spectroscopy

Copper and iodine co-modified TiO₂ nanoparticles for improved activity of CO₂ photoreduction with water vapor by Qianyi Zhang; Tingting Gao; Jean M. Andino; Ying Li (pp. 257-264).

Display Omitted► TiO₂ is modified by Cu deposited on the surface and iodine doped in the lattice. ► CO₂ is photocatalytically reduced with water vapor and the major product is CO. ► The activity under UV and visible light is dependent on the catalyst composition. ► Cl species on the catalyst results in higher CO₂ reduction and CH₃Cl formation. ► Methyl (CH₃) radicals may be one of the reaction intermediates.Copper and iodine co-modified TiO₂ nanoparticles (Cu–I–TiO₂) were synthesized through a combined hydrothermal and wet-impregnation process. The structures and properties of the catalysts were characterized by XRD, BET, SEM/EDX, XPS, and UV–vis diffuse reflectance spectroscopy. Iodine ions were doped in the TiO₂ lattice by replacing Ti⁴⁺ and, consequently, Ti³⁺ was generated to balance the charge. Iodine doping reduced the TiO₂ crystal size and was responsible for visible light absorption. Cu species were found to deposit on the surface of TiO₂ and resulted in a slightly increased particle size. The activity of the Cu–I–TiO₂ catalyst was investigated by the photocatalytic reduction of CO₂ with water vapor, and CO was found to be the major reduction product with trace amounts of CH₄ generated. Under UV–vis irradiation, the activity of the co-modified catalyst (Cu–I–TiO₂) was higher than that of the single ion-modified catalysts (Cu–TiO₂ or I–TiO₂). Under visible light irradiation, the addition of Cu to I–TiO₂ did not lead to significant improvements in CO₂ reduction. Methyl chloride (CH₃Cl) was detected as a reaction product when CuCl₂ was used as the precursor in the synthesis, thus suggesting that methyl radicals are reaction intermediates. When CuCl₂ was used as the Cu precursor, a three-fold increase in CO₂ photoreduction activity was observed, as compared to when Cu(NO₃)₂ was used as the Cu precursor. These differences in activities were probably due to enhanced Cu dispersion and the hole-scavenging effects of the Cl ions. However, the formation of by-products (e.g., CH₃Cl) may be undesirable.

Keywords: Photocatalysis; CO; ₂; reduction; Solar energy; TiO; ₂; Copper; Iodine

Co₃O₄ nanocrystals on graphene oxide as a synergistic catalyst for degradation of Orange II in water by advanced oxidation technology based on sulfate radicals by Penghui Shi; Ruijing Su; Fengzhi Wan; Mincong Zhu; Dengxin Li; Shihong Xu (pp. 265-272).

Display Omitted► Cobalt oxide supported on GO successfully. ► The Co₃O₄ nanocrystals on GO is a synergistic catalyst for activation of PMS. ► The Co₃O₄/GO exhibits good heterogeneous activity in the degradation of Orange II. ► Very limited cobalt dissolved from Co₃O₄/GO.Graphene oxide and cobalt oxide nanocomposites (Co₃O₄/GO) are fabricated in situ as heterogeneous catalysts by the decomposition of cobalt nitrate through heat and crystal growth of Co₃O₄ on the surface of GO sheets in 1-hexanol solvent. The Co₃O₄/GO catalyst is characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Results show that the Co₃O₄/GO catalysts are large GO sheets decorated homogenously with well-dispersed Co₃O₄ nanoparticles. Although Co₃O₄ or GO alone exhibit little catalytic activity, their hybrid (Co₃O₄/GO) exhibits an unexpectedly high catalytic activity in the degradation of Orange II in water by advanced oxidation technology based on sulfate radicals, and 100% decomposition can be achieved in 6min. These phenomena suggest a synergistic catalytic activity of Co₃O₄ and GO in the hybrid.

Keywords: Graphene oxide; Cobalt oxide; Sulfate radical; Advanced oxidation processes; Orange II

Ceria-doped and TiO₂ nanocomposite coating on multiwalled carbon nanotubes for the photocatalytic remediation of agro-industrial wastewaters by D. Wilson; W. Wang; Rodrigo J.G. Lopes (pp. 273-281).

Field emission scanning electron microscopy photograph of CNT0.5/(TiO₂)9–(CeO₂)0.5 nanocomposite.Display Omitted► We investigate the photocatalytic oxidation of hazardous organic compounds. ► CNT/TiO₂–CeO₂ catalysts were characterized by means of FESEM, TEM, XRD, and BET. ► Ce-doped and TiO₂ coating nanocomposites on CNT were photocatalytically the most active. ► Multiwall CNT/TiO₂–CeO₂ exhibited worthy properties concerning long-term operation. ► The catalytic efficiency of the nanotube arrays was maintained for five reaction cycles.Aiming to gain further insights into the heterogeneous catalysis of carbon nanotubes (CNTs), several catalysts have been investigated by embedding TiO₂ and CeO₂ into CNTs for the photo-oxidation of high-strength liquid pollutants. First, the CNT/TiO₂–CeO₂ nanocomposites were synthetized by the surfactant wrapping sol–gel technique with titanium isopropoxide precursor. The photocatalytic activity in parent compound depletion was evaluated comparatively with the photocatalytic efficiency in total organic carbon (TOC) abatement at UV-254 and 420nm. Here, the higher photodegradation efficiencies in pollutant (88.2%) and TOC (61.9%) were achieved with the CNT_0.5/(TiO₂)₉–(CeO₂)_0.5 catalyst. Second, the nanocomposites have been characterized by FESEM and TEM techniques indicating a highly heterogeneous porous structure with equivalent nanotube length and wall thickness as well as confirming the existence of a continuous titanium and cerium oxide layer coating the surface of CNTs. Afterwards, the XRD structure and chemical composition has been used to query the effect of the calcination temperature. The CNT/TiO₂–CeO₂ nanocomposites exhibited remarkable differences concerning the crystalline morphology and the BET/porosity analysis pointed out the presence of mesopores in the nanoparticle matrix. Finally, several sequential mineralization trials were accomplished by recycling the most active catalyst, and CNT_0.5/(TiO₂)₉–(CeO₂)_0.5 has preserved 61% of TOC conversion for long-term photo-oxidation experiments.

Keywords: Photo-oxidation; Phenolic pollutants; CNT; TiO; ₂; CeO; ₂; FESEM; TEM; XRD

Study of Na/Cu/TiO₂ catalysts for the storage and reduction of NO by Sichem Guerrero; Igor Guzmán; Gonzalo Aguila; Boris Chornik; Paulo Araya (pp. 282-295).

Display Omitted► Na/Cu/TiO₂ catalysts were studied in the adsorption of NO under lean conditions. ► The adsorption of NO occurs with the gradual formation of nitrates/nitrites. ► An increase in Na loading increased the reduction temperature of the copper phase. ► The NO adsorption activity is facilitated by Cu and Na being in close interaction. ► CO and H₂ fully regenerated the catalysts in successive cycles of operation.A Pt-free system based on Na/Cu/TiO₂ catalysts was used to study the adsorption of NO under lean conditions. The results show that the NO adsorption activity dramatically increased when both sodium and copper are in intimate contact. Although copper is the active phase in the oxidation of NO to NO₂, it was found that the addition of sodium species is of vital importance on the subsequent adsorption of NO₂, which mainly occurs on the surface of the alkali in the form of nitrates and nitrites. It was found that a loading increase of the alkali led to an increase in the reduction temperature of the copper phase, which is ascribed to a close interaction between the copper and the sodium phases. Among the Na loadings that were studied, the addition of 5% Na gave the optimum adsorption of NO. After successive cycles of adsorption, the catalysts were fully regenerated at temperatures higher than 250°C using either CO or H₂ as a reducing agent.

Keywords: NO oxidation; NO storage; NO reduction; NSR; Cu/TiO; ₂; Na/Cu/TiO; ₂; Cu H; ₂; -TPR

Effect of C₃H₆ on selective catalytic reduction of NO_x by NH₃ over a Cu/zeolite catalyst: A mechanistic study by Jin-Yong Luo; Harry Oh; Cary Henry; William Epling (pp. 296-305).

Display Omitted► C₃H₆ oxidation intermediates and coke formation induced poisoning, depending on temperature. ► Poisoning caused non-monotonic NO changes due to NH₃ coverage changes along the catalyst. ► Changes in reaction pathways during fast and NO₂ SCR in the presence of C₃H₆ were observed.The effects of C₃H₆ on key SCR reactions over a model Cu/beta zeolite catalyst were characterized using step-response method reactor testing. Under standard SCR conditions, C₃H₆ clearly inhibited the reduction reaction at 200°C and above. The inhibition was not caused by competitive adsorption between C₃H₆ and NH₃, but by surface intermediate species formed during C₃H₆ oxidation, including acrolein-like and coke species as indicated by in situ DRIFTS. Similar to the standard SCR reaction, C₃H₆ also had a negative effect on the fast SCR reaction. Spaci-FTIR (spatially resolved capillary-inlet Fourier transform infrared spectroscopy) results indicated that NO₂ was quickly reduced to NO by C₃H₆, leading to the occurrence of some standard SCR instead of purely fast SCR. However, C₃H₆ had a positive effect on NO₂ SCR. The reduction of NO₂ to NO by C₃H₆ resulted in the occurrence of the fast SCR reaction combined with NO₂ SCR instead of pure NO₂ SCR. The reaction pathway change also decreased N₂O formation significantly.

Keywords: Selective catalytic reduction; NO; _x; control; Diesel emissions; Transient-response method; In situ DRIFTS; Catalyst poisoning

Photocatalysis/catalysis by innovative TiN and TiN-Ag surfaces inactivate bacteria under visible light by S. Rtimi; O. Baghriche; R. Sanjines; C. Pulgarin; M. Ben-Simon; J.-C. Lavanchy; A. Houas; J. Kiwi (pp. 306-315).

Display Omitted► When Ti was sputtered in N₂ atmosphere, the TiN films revealed semiconductor properties. ► TiN layers 50nm thick sputtered by DC for 3min led to complete inactivation of E. coli within 120min. ► The optical absorption of TiN-Ag films in Kubelka–Munk units was directly proportional to the E. coli inactivation kinetics. ► A TiN film has the potential to replace Ag-based disinfection films leaching Ag into the environment.This study presents the design, preparation, testing and characterization of TiN and TiN-Ag nanoparticulate films leading to photocatalytic and catalytic inactivation of Escherichia coli. When Ti was sputtered in N₂ atmosphere, the TiN films unexpectedly revealed semiconductor properties when irradiated under visible light due to the formation of TiO₂ showing absorption in the visible spectral region. In TiN-Ag films, Ag enhances the photocatalytic activity of TiN leading to faster bacterial inactivation. Evidence for the presence of TiO₂ and TiN in the films is presented by XPS. The TiN layers 50nm thick sputtered by DC for 3min led to complete inactivation of E. coli within 120min. But TiN layers with a thickness >50nm hinder the surface diffusion of charges reducing bacterial inactivation. The rate of TiN deposition was ∼1.4×10¹⁵atoms TiN/cm²s. For the TiN-polyester samples under visible light a 3log₁₀ bacterial reduction (99.9%) was observed within 30min while for TiN-Ag samples the same bacterial reduction was attained within ∼15min. The absorption of the TiN-Ag samples in Kubelka–Munk (KM) units was directly proportional to the E. coli inactivation kinetics. TiN-Ag plasmon nanostructures are concurrently formed under low intensity visible light and accelerated bacterial inactivation. This study shows that TiN films have the potential to replace Ag-based disinfection materials leaching Ag into the environment.

Keywords: TiN; E. coli; inactivation; Polyester; Visible light; TiN-Ag sputtering DC and DCP

Mesoporous tantalum phosphate as acidic catalyst for the methanolysis of sunflower oil by I. Jiménez-Morales; J. Santamaría-González; P. Maireles-Torres; A. Jiménez-López (pp. 316-323).

Display Omitted► Mesoporous tantalum phosphate is a solid acid with strong acidic character. ► It is active in the methanolysis of sunflower oil at 200°C, after 2h of reaction. ► No leaching of tantalum is detected and the catalyst can be reutilised. ► This solid catalyses the simultaneous FFAs esterification and sunflower oil transesterification.Mesoporous tantalum phosphate was prepared from tantalum tartrate complex and ammonium dihydrogenphosphate, by using hexadecyltrimethylammonium bromide as surfactant, and ulterior calcination at 550°C. It exhibits a high specific surface area (256m²g⁻¹) and strong acidity (1480μmolNH₃g⁻¹), and it can be successfully used as solid catalyst in the transesterification of sunflower oil with methanol. With only 5wt.% of this catalyst in relation to the oil, a 89wt.% of biodiesel formation was attained at 200°C and after only 2h of reaction. The catalyst is very stable and no leaching of tantalum or phosphorus species to the liquid medium was found. Moreover, this acid solid catalyst is able to simultaneously catalyse the esterification of free fatty acids (FFAs) and the transesterification of triglycerides, even in the presence of 9% of FFAs. Its catalytic performance is well maintained after three catalytic cycles, without any treatment and even in the presence of 5wt.% of water. The use of a co-solvent do not enhanced the biodiesel formation.

Keywords: Mesoporous tantalum phosphate; Transesterification; Sunflower oil; Acid catalysts

LaNiO₃ as a precursor of Ni/La₂O₃ for CO₂ reforming of CH₄: Effect of the presence of an amorphous NiO phase by Rosa Pereñiguez; Victor M. Gonzalez-delaCruz; Alfonso Caballero; Juan P. Holgado (pp. 324-332).

.Display Omitted► Four different methods were used for preparing the LaNiO₃ system, later characterized. ► NiO amorphous phase was detected in the four samples in different proportion NiO/LaNiO₃. ► The amount of NiO was modified with the conditions of calcinations. ► The final physico-chemical properties of the systems together with the NiO presence result in different performance for DRM.The objective of the present work has been the study of the physico-chemical and catalytic properties of Ni/La₂O₃ catalysts obtained by reduction of four LaNiO₃ samples prepared by different methods. The LaNiO₃ precursors as well as the resulting Ni/La₂O₃ catalysts, were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), temperature programmed reduction and oxidation (TPR, TPO). The catalytic performances of these systems for dry reforming of methane (DRM) were also tested. These samples show different physico-chemical properties resulting from the synthesis method used. The XAS and TPR measurements show that in all four LaNiO₃ samples there is, in addition of the crystalline LaNiO₃ rhombohedrical phase, a significant amount of an amorphous NiO phase, not detectable by XRD but evidenced by XAS. The amount of this NiO amorphous phase seems to play, together with some other microstructural parameters, an important role in the performance of the Ni/La₂O₃ samples for the DRM reaction.

Keywords: Hydrogen; Perovskite; Dry reforming of methane; XAS; Synthesis methods

Zeolite-promoted hydrolysis of cellulose in ionic liquid, insight into the mutual behavior of zeolite, cellulose and ionic liquid by Haile Cai; Changzhi Li; Aiqin Wang; Guoliang Xu; Tao Zhang (pp. 333-338).

.Display Omitted► H-type zeolites exhibited high activity for hydrolysis of cellulose in ionic liquid. ► Hydrolysis efficiency strongly depends on the pore size, the acid amount, the water amount and the timing of water addition. ► H⁺ generated in-situ from the Brönsted acid sites of zeolite was the key active species. ► The structure properties of zeolite in ionic liquid that unlike its usual state were well identified. ► After simple calcination of the catalyst, the activity was fully recovered.In this paper, a variety of H-type zeolites were demonstrated as efficient catalysts for hydrolysis of cellulose in ionic liquid (IL) to afford high yield of glucose under mild condition without a pretreatment process. By supplying water gradually as the reaction progresses, HY with the acid amount of 11.1mol% promoted the highest glucose yield of 50.0% at 130°C, and the yield of the three main products (glucose, cellobiose and 5-hydroxymethylfurfural) was up to 97.2%. It was found that the pore size, the acid amount, the water amount and the timing of water addition are critical factors for high hydrolysis efficiency. XRD characterization suggested that the framework structure of zeolite was particularly stable in 1-butyl-3-methylimidazolium chloride ([BMIm]Cl), while the cell parameter were enlarged due to the dilatation effect of [BMIm]Cl. Elemental analysis of the IL-treated HY demonstrated that IL entered the channel of HY. As such, part of the intra-channel space of HY was occupied, making the average pore diameter, pore volume and the BET surface area of IL-treated HY all decreased, which were demonstrated by physisorption characterization. FT-IR through pyridine adsorption showed that H⁺ cations generated in-situ from the Brönsted acid sites of zeolite were the key active species for the good hydrolysis performance, while the Lewis acid sites did not exhibit high activity. By simple calcination, the recovered HY showed excellent reusability. Finally, the proposed reaction pathway and recycle of the catalyst were presented.

Keywords: Cellulose; Zeolites; Ionic liquids; Hydrolysis; Glucose

Application of spaciMS to the study of ammonia formation in lean NO_x trap catalysts by Vencon Easterling; Yaying Ji; Mark Crocker; Mark Dearth; Robert W. McCabe (pp. 339-350).

Display Omitted► Ammonia formation in LNT catalysts was studied using spaciMS. ► Catalyst aging resulted in elongation of the NO_x storage–reduction zone. ► Ammonia emissions increased due to shortening of the OSC-only zone. ► After aging the rate of propagation of the reductant front increased. ► Increased H₂:NO_x ratios at the Pt/Rh sites resulted in increased selectivity to NH_3.SpaciMS was employed to understand the factors influencing the selectivity of NO_x reduction in two fully formulated LNT catalysts, both degreened and thermally aged. Both catalysts contained Pt, Rh, BaO and Al₂O₃, while one of them also contained La-stabilized CeO₂. The amount of reductant required to fully regenerate each catalyst was first determined experimentally based on the OSC of the catalyst and the NO_x storage capacity (NSC). In this way a correction was made for the change in catalyst OSC and NSC after aging, thereby eliminating these as factors which could affect catalyst selectivity to NH₃. For both catalysts, aging resulted in an elongation of the NO_x storage–reduction (NSR) zone due to a decrease in the concentration of NO_x storage sites per unit catalyst length. In addition to decreased lean phase NO_x storage efficiency, stretching of the NSR zone affected catalyst regeneration. Three main effects were identified, the first being an increase of the NO_x “puff” that appeared during the onset of the rich front as it traversed the catalyst. Spatially, NO_x release tracked the NSR zone, with the result that the NO_x concentration peaked closer to the rear of the aged catalysts. Hence the probability that NO_x could re-adsorb downstream of the reduction front and subsequently undergo reduction by NH₃ (formed in the reduction front) was diminished, resulting in higher rich phase NO_x slip. Second, the stretching of the NSR zone resulted in increased selectivity to NH₃ due to the fact that less catalyst (corresponding to the OSC-only zone downstream of the NSR zone) was available to consume NH₃ by either the NH₃-NO_x SCR reaction or the NH₃-O₂ reaction. Third, the loss of OSC and NO_x storage sites, along with the decreased rate of NO_x diffusion to Pt/Rh sites (as a result of Pt/Rh–Ba phase segregation), led to an increase in the rate of propagation of the reductant front after aging. This in turn resulted in increased H₂:NO_x ratios at the Pt/Rh sites and consequently increased selectivity to NH₃.

Keywords: SpaciMS; Lean NO; _x; trap; NO; _x; adsorber catalyst; Storage; Reduction; Ammonia; Aging

Quantitative analysis of active oxygen for soot oxidation over Ag/ZrO₂: Characterization with temperature-programmed reduction by NH₃ by Tetsuya Nanba; Shoichi Masukawa; Akira Abe; Junko Uchisawa; Akira Obuchi (pp. 351-356).

Display Omitted► There are two kinds of active oxygen species for soot oxidation on Ag/ZrO₂. ► Temperature-programmed reduction by NH₃ revealed the existence of oxygen having strong oxidation capacity. ► N₂O formation in NH₃-TPR reflected the amount of active oxygen for soot oxidation.Active oxygen species for soot oxidation over Ag/ZrO₂ were characterized by means of X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption and reduction methods. The temperature-programmed surface reaction (TPSR) between carbon black (CB), a model soot, and surface oxygen revealed that two kinds of adsorbed oxygen species were involved in CB oxidation over Ag/ZrO₂. The results of XPS, temperature-programmed desorption of O₂, and temperature-programmed reduction by H₂ were insufficient to distinguish the two kinds of active oxygen species. Temperature-programmed reduction by NH₃ (NH₃-TPR) resulted in N₂ and N₂O formation as products of reduction of the Ag/ZrO₂ surface and bulk oxygen. The N₂O formation profile in NH₃-TPR exhibited two peaks, corresponding to two kinds of oxygen species having a strong oxidation capacity. The effect of Ag loading on the total amount of N₂O formation was in good agreement with that on the amount of active oxygen species observed by TPSR-CB. We concluded that NH₃-TPR was an appropriate technique for quantitative characterization of the amount of active oxygen species for soot oxidation on Ag/ZrO₂.

Keywords: Soot; Oxidation; Ag; ZrO; ₂; H; ₂; -TPR; NH; ₃; -TPR

Deoxygenation of benzofuran in supercritical water over a platinum catalyst by Jacob G. Dickinson; Jack T. Poberezny; Phillip E. Savage (pp. 357-366).

Display Omitted► Pt/C catalyzes the hydrothermal deoxygenation of benzofuran to produce hydrocarbons. ► The main deoxygenated products of benzofuran are ethylbenzene and ethylcyclohexane. ► Benzofuran slows the rate of deoxygenation.This study reports the results of the catalytic deoxygenation of 2,3-benzofuran in supercritical water over a 5wt% platinum on activated carbon catalyst. We examine the effect of batch-holding time, water loading, hydrogen loading, and catalyst loading on the reaction products. The major products were 2-ethylphenol, ethylbenzene, ethylcyclohexanone, ethylcyclohexanol, and ethylcyclohexane. Increasing the water loading or decreasing the hydrogen loading decreases the selectivity to aromatic deoxygenated products (e.g. ethylbenzene) and increases the selectivity to hydrogenated deoxygenated products (e.g. ethylcyclohexane). Combining the results from these benzofuran experiments with results obtained in separate experiments with the above-mentioned reaction products as the starting reagent allowed for the development of the hydrothermal deoxygenation reaction network. The reaction network provided a foundation for a quantitative kinetic model that correlated the experimental results. The model showed that the experimental results were consistent with benzofuran having an inhibitory effect on the deoxygenation of ethylphenol to ethylbenzene.

Keywords: Hydrothermal; Hydrodeoxygenation; Kinetics; Benzofuran; Pt/C

Water gas shift reaction over multi-component ceria catalysts by Vijay M. Shinde; Giridhar Madras (pp. 367-378).

Display Omitted► Cu-Ni and Cu-Fe modified ceria catalysts were synthesized and characterized. ► Relation between catalyst activity and oxygen storage capacity was explored. ► Cyclic reoxidation and high oxygen storage capacity were observed. ► A new model was proposed to correlate the experimental data.This study reports the activity of ionic substituted bimetallic Cu-Ni-modified ceria and Cu-Fe-modified ceria catalysts for low-temperature water gas shift (WGS) reaction. The catalysts were synthesized in nano-crystalline size by a sonochemical method and characterized by XRD, TEM, XPS, TPR and BET surface analyzer techniques. Due to the ionic substitution of these aliovalent base metals, lattice oxygen in CeO₂ is activated and these catalysts show high activity for WGS at low temperature. An increase in the reducibility and oxygen storage capacity of bimetallic substituted CeO₂, as evidenced by H₂-TPR experiments, is the primary reason for the higher activity towards WGS reaction. In the absence of feed CO₂ and H₂, 100% conversion of CO with 100% H₂ selectivity was observed at 320°C and 380°C, for Cu-Ni-modified ceria and Cu-Fe-modified ceria catalysts. Notably, in the presence of feed H₂O, a reverse WGS reaction does not occur over these ceria modified catalysts. A redox reaction mechanism, involving oxidation of CO adsorbed on the metal was developed to correlate the experimental data and determine kinetic parameters.

Keywords: Water gas shift; Ceria supported catalyst; Oxygen storage capacity; Reaction mechanism

Influence of the shape of Ni catalysts in the glycerol steam reforming by L.F. Bobadilla; A. Álvarez; M.I. Domínguez; F. Romero-Sarria; M.A. Centeno; M. Montes; J.A. Odriozola (pp. 379-390).

Ni structured catalyst is active and stable for the hydrogen production from steam reforming of glycerol.Display Omitted► Coke formation was not observed in the structured catalyst. ► The blocking of the pores with carbon deactivated pellets and powder catalysts. ► The morphology is the responsible for the different behavior during reaction. ► Preparation of catalyst with high resistance to coke formation.Biomass is an alternative to replace the use of fossil fuels. Glycerol, a byproduct in the biodiesel production, can be used for obtaining hydrogen. The most efficient method for obtaining hydrogen from glycerol is the steam reforming (SR). So far all the published papers report the use of conventional catalyst. In this paper, a structured catalyst has been prepared and compared with the conventional ones (powder and spherical pellets). Results show that the structured catalyst (monolith) is more stable as formation of coke was not observed.

Keywords: Monoliths; Conventional catalyst; Glycerol steam reforming; Coke

Enhancement of photocatalytic activity of titania–titanate nanotubes by surface modification by Soonhyun Kim; Minsun Kim; Sung-Ho Hwang; Sang Kyoo Lim (pp. 391-397).

Display Omitted► Titanate nanotubes are modified with NaF or AdP during acid treatment. ► Surface modified titanate nanotubes were relatively stable under acid treatment. ► The crystalline phases were also strongly affected by the surface modifications. ► The BET surface area was also increased by surface modifications. ► The photocatalytic activities were strongly enhanced by the surface modifications.Hydrothermally prepared titanate nanotubes are known to be thermodynamically unstable and to be easily transformed to the titania phase by heat or acid treatment, which is accompanied by the destruction of the nanotube structures. Surface modification of titanate nanotubes is expected to retard the phase-transition reactions from titanate nanotubes to titania nanoparticles. In this study, we investigated the effects of surface modifications, such as fluorination or phosphation, on the phase-transition reactions of hydrothermally prepared titanate nanotubes under acidic conditions. After acid treatment, surface-modified titanate nanotubes maintained their nanotube structures, and spherical nanoparticles were partially formed in the titanate nanotubes. Unmodified titanate nanotubes, however, changed to elongated nanostructures and spherical nanoparticles. The surface modifications also strongly affected the crystalline phases and increased the BET surface area. The photocatalytic activities for methylene blue degradation and gaseous CH₃CHO oxidation were strongly enhanced by the surface modifications. These effects were attributed to the anatase crystalline phase and the high surface area. Therefore, these surface modifications are useful methods to improve the photocatalytic activities of titanate nanotubes.

Keywords: Photocatalysis; Titanate nanotubes; Titania; Hydrothermal reaction; Surface modification

WO₃ nanocrystals with tunable percentage of (001)-facet exposure by Dieqing Zhang; Songling Wang; Jian Zhu; Hexing Li; Yunfeng Lu (pp. 398-404).

Orthorhombic WO₃ nanocrystals with tunable percentage of (001)-facet exposure were synthesized. The preferable exposure of the high-energy (001) facets endows the nanocrystals with significantly enhanced photocatalytic activity.Display Omitted► Orthorhombic WO₃ nanocrystals. ► Novel high-energy (001)-facet exposure. ► Tunable percentage of (001)-facet exposure. ► Significantly enhanced photocatalytic activity.Orthorhombic WO₃ nanocrystals with tunable percentage of (001)-facet exposure were synthesized by hydrothermal reaction using BF₄⁻ as the guiding agent. The preferable exposure of the high-energy (001) facets endows the nanocrystals with significantly enhanced photocatalytic activity as probed by photodegradation of Rhodamine B and the electron spin resonance techniques.

Keywords: WO; ₃; High-energy; Facets; Photocatalysis

Support mediated promotional effects of rare earth oxides (CeO₂ and La₂O₃) on N₂O decomposition and N₂O reduction by CO or C₃H₆ over Pt/Al₂O₃ structured catalysts by M. Konsolakis; C. Drosou; I.V. Yentekakis (pp. 405-413).

Display Omitted► The promotional effect of rare earth oxides on de-N₂O over Pt/Al₂O₃ is demonstrated. ► The remarkable de-N₂O performance is related with the formation of Pt nanoparticles. ► Pt sites located on the metal–support interface are responsible for the superior de-N₂O activity.The N₂O decomposition and reduction by CO or C₃H₆ over rare earth oxides (REOs)-modified Pt/Al₂O₃ structured catalysts, i.e., coated on ceramic honeycomb monoliths, were comparatively investigated in a wide temperature interval of 100–600°C, either in the presence or in the absence of excess O₂ and H₂O. It was shown that the de-N₂O efficiency can be remarkably enhanced via modification of Al₂O₃ support with rare earth oxides (REOs). In specific, complete conversion of N₂O can be attained over REOs-modified catalysts at a relatively low temperature ( ca. 480°C) even in the presence of excess O₂, which in general depresses de-N₂O efficiency, in opposite to the unmodified Pt/Al₂O₃ catalyst, over which, 20% N₂O conversion is never exceeded for temperatures up to 600°C. In terms of turnover frequency (TOF), optimally modified (by REOs) Pt–Al₂O₃ catalyst exhibits one order of magnitude higher activity compared to that of the unpromoted Pt/Al₂O₃ sample. Under reducing conditions the N₂O conversion is strongly enhanced by C₃H₆ and especially by CO, whereas marginal inhibition is induced by reducing agents under excess oxygen conditions. Water was found to induce a detrimental influence on N₂O decomposition, with its effect however, to be partially reversible. An in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study, using CO as a probe molecule, was performed over both unmodified and REOs-modified Pt/Al₂O₃ catalysts to correlate their surface characteristics with their de-N₂O efficacy. The results revealed that the superior catalytic performance of promoted samples could be mainly attributed to the increase of Pt dispersion as well as to the development of Pt sites with exceptional electron density, located on the metal–support interfacial area.

Keywords: N; ₂; O decomposition; Platinum; Rare earth oxides; CeO; ₂; La; ₂; O; ₃; Cordierite monoliths; DRIFTS

Concurrent photoelectrochemical reduction of CO₂ and oxidation of methyl orange using nitrogen-doped TiO₂ by Yen-Ping Peng; Yun-Ta Yeh; S. Ismat Shah; C.P. Huang (pp. 414-423).

Concurrent photoelectrochemical reduction of CO₂ and oxidation of methyl orange using nitrogen-doped TiO₂.Display Omitted► Nitrogen-doped TiO₂ thin film (NTTF) was an effective photoanode. ► Bias potential isolating electrons from the photoanode enhanced redox reactions. ► Separating electrons from holes enhanced photocatalytic reaction efficiency. ► Methanol increased water solubility and photoelectrochemcial reduction of CO₂. ► PEC improves the degradation of Methyl Orange drastically.This study employed a novel material, nitrogen-doped TiO₂ thin film (NTTF), as a photoanode for the concurrent photoeletrochemical (PEC) reduction of CO₂ and oxidation of methyl Orange (MO). Under illumination, the onset potential of the total current was approximately 1.5V (vs. SCE) and the maximum total current was around 0.65mA at 2V (vs. SCE). The photocurrent can be effectively driven to the counter electrode at this positive potential, which will decrease the recombination of photo-generated holes and electrons, leading to more electrons available for CO₂ reduction in the cathodic chamber and more holes for the oxidation of hazardous chemicals in the anodic chamber simultaneously. Formic acid, formaldehyde, methanol and methane were detected as the CO₂ reduction products at a Cu electrode in the KHCO₃ electrolyte. The first-order kinetic model was successfully applied to simulate the NTTF PEC reduction of CO₂. The reaction rate constant were 6.68×10⁻⁷, 2.18×10⁻⁴, 8.62×10⁻⁴ and 2.27×10⁻⁴s⁻¹, for the formation of formic acid, formaldehyde, methanol, and methane, respectively. The maximum Faradaic efficiency was 5.01, 1.04, 5.41 and 7.83% for the generation of formic acid, formaldehyde, methanol, and methane, individually. In addition, the effect of initial CO₂ concentration on CO₂ reduction was also conducted in the presence of methanol (0, 20 and 40%). Results showed that methanol-containing electrolyte enhanced CO₂ solubility thereby suppressing hydrogen generation and favoring CO₂ reduction. Finally, the degradation of methyl orange was compared using PEC, photocatalytic (PC), electrochemical (EC) and direct photolysis (P) processes. The PEC process was able to achieve a 10-log versus less than 1-log of methyl orange degradation by all other methods studied within 60min under otherwise similar conditions of pH, temperature, intensity and wavelength of light source. Results clearly demonstrated the potential of a sustainable technology for the concurrent reduction of CO₂ and oxidation of hazardous chemicals by the PEC process using solar energy.

Keywords: Photoelectrochemical; CO; ₂; reduction; Nitrogen-doped TiO; ₂; Kinetics

CO–PROX reactions on copper cerium oxide catalysts prepared by melt infiltration by Xiaobo Li; Xian-Yang Quek; D.A.J. Michel Ligthart; Meiling Guo; Yi Zhang; Can Li; Qihua Yang; Emiel J.M. Hensen (pp. 424-432).

Display Omitted► Supported CuO–CeO₂ catalysts were synthesized by melt infiltration methods. ► CO/PROX activity of CuO–CeO₂ catalysts significantly depends on the Cu/Ce mole ratio. ► Finely dispersed CuO cluster on CeO₂ shows the highest activity in CO/PROX oxidation. ► The catalysts exhibit superior performance to catalyst prepared by solution impregnation.A series of copper cerium oxide catalysts was prepared by melt infiltration routes using silica hollow spheres (SHS) as the support material. Their catalytic activity in CO oxidation and preferential oxidation of CO in H₂ stream (PROX) strongly depend on the Cu/Ce ratio. Lower ratios resulted in higher activity, indicating that finely dispersed CuO clusters that strongly interact with ceria are the active sites. The highest activity is found for an atomic Cu/Ce ratio of 1/8. The catalysts prepared by melt infiltration are more active than their counterparts prepared by conventional solution impregnation methods. The difference is attributed to the higher proportion of finely dispersed CuO clusters strongly interacting with ceria in the melt infiltrated catalysts.

Keywords: Copper; Ceria; Melt infiltration; CO oxidation; CO–PROX

Remediation of 2,4-dichlorophenol contaminated water by visible light-enhanced WO₃ photoelectrocatalysis by E.O. Scott-Emuakpor; A. Kruth; M.J. Todd; A. Raab; G.I. Paton; D.E. Macphee (pp. 433-439).

Display Omitted► Degradation of 2,4-DCP was investigated using a WO₃ photoelectrocatalytic fuel cell. ► The WO₃ photoelectrocatalyst was active in the presence of visible light. ► The application of an external bias enhanced the degradation rate of the cell. ► Degradative progress was assessed by chemical and biosensor toxicity analyses. ► WO₃ is potentially an alternative photocatalyst for treatment of contaminated water.The application of semiconductor photocatalysis in waste water treatment has been intensively investigated over the past decade. Most studies involve titanium-based photocatalysts; however, practical applications are still limited by their poor visible light activity. As an alternative, a tungsten trioxide-based photoelectrocatalytic fuel cell (PECFC) with a cell configuration based on the proton exchange membrane fuel cell (PEMFC) technology has been employed for pollutant remediation. In this study, the degradation of a persistent chlorophenol (2,4-dichlorophenol) was assessed using a visible light active tungsten trioxide photocatalyst. The degradative progress of the 2,4-DCP was monitored over a period of 24h by both chemical analysis and a bacterial biosensor ( Escherichia coli HB101 pUCD607) toxicity assay. A 74% decrease in concentration of the 2,4-DCP was observed after a period of 24h, from which ca. 54% were accountable to degradation processes and 20% due to pollutant losses by adsorption or volatilisation. The biosensor toxicity response correlated well with the observed concentration reduction of 2,4-DCP, but also indicated the formation of more toxic intermediates. HPLC–MS analysis was carried out to study intermediate degradation products. There were indications of the occurrence of stable dimers within the first few hours of the degradation process and the formation of intermediate degradation products of higher bacterial toxicity than the parent compound. Although the potential of the PECFC, as a sustainable method for water treatment, has been demonstrated, further work is required to optimise this new technology for mineralisation of organic contaminants.

Keywords: Tungsten trioxide; 2,4-Dichlorophenol; Photoelectrocatalysis; Waste water; Bacterial biosensor

Synthesis of flower-like Co₃O₄–CeO₂ composite oxide and its application to catalytic degradation of 1,2,4-trichlorobenzene by Shijing Lin; Guijin Su; Minghui Zheng; Dekun Ji; Manke Jia; Yexuan Liu (pp. 440-447).

Display Omitted► A flower-like Co₃O₄–CeO₂ composite oxide was synthesized to degrade 1,2,4-trichlorobenzene. ► The Co₃O₄–CeO₂ composite oxide showed the best catalytic performance in the degradation of 1,2,4-trichlorobenzene, with an apparent activation energy of 27kJ/mol under pulsed conditions. ► The high activity was attributed to the composite oxide's structural features and synergistic catalytic effects between the two phases of the composite.A micrometer-sized, nanostructured, flower-like Co₃O₄–CeO₂ composite oxide was synthesized by an ethylene-glycol-mediated process. The composite oxide was an assembly of polycrystalline nanoparticles, with a typical mesoporous structure. The composite's catalytic activity in 1,2,4-trichlorobenzene degradation was evaluated using a pulsed-flow microreactor–gas chromatography system, and compared with that of quartz sand, commercial CeO₂, commercial Co₃O₄, and a Co₃O₄/CeO₂ equimass mixture. The composite oxide was a promising catalyst for 1,2,4-trichlorobenzene degradation. This is attributed to the structural features of the composite oxide with a high specific surface area and a high total pore volume, and the synergistic effect between the two composite phases. The easy creation of high-mobility active oxygen on CeO₂ and the easy cleavage of CoO bonds at the interface of the two components promote reactivity of Co₃O₄ in 1,2,4-trichlorobenzene degradation. Pulsed catalytic theory suggests a first-order reaction between the composite oxide and 1,2,4-trichlorobenzene, with an apparent activation energy of about 27kJ/mol, and degradation on the Co₃O₄–CeO₂ composite oxide would occur easily.

Keywords: Micro/nano composite material; 1,2,4-Trichlorobenzene; Catalytic degradation; Synergistic effect; Apparent activation energy

Ecofriendly production of ethylene by dehydration of ethanol over Ag₃PW₁₂O₄₀ salt in nitrogen and air atmospheres by L. Matachowski; M. Zimowska; D. Mucha; T. Machej (pp. 448-456).

Display Omitted► Relative humidity of atmosphere strongly influences structure of Ag₃PW₁₂O₄₀ salt. ► Catalytic activity of Ag₃PW₁₂O₄₀ salt depends on relative humidity of carrier gas. ► Very high yield of ethylene in ethanol dehydration on Ag₃PW₁₂O₄₀ catalyst.Neutral silver salt of tungstophosphoric acid Ag₃PW₁₂O₄₀·3H₂O (AgPW) was investigated as the catalyst in the gas-phase dehydration of ethanol, in the temperature range of 373–493K. The relative humidity of atmosphere (nitrogen or air) was changed from 2% to 10%. It was shown that relative humidity of both atmospheres strongly influences the catalytic activity of AgPW salt. The thermal stability of AgPW salt was determined with simultaneous DSC/TG analysis and high temperature XRD method. It was demonstrated that one molecule of water, which hydrates silver cation loses the salt structure in the temperature range of 473–523K. The stability of primary and secondary structure of AgPW salt after reaction was investigated using FT-IR and XRD techniques. The AgPW salt is stable, when relative humidity attains at least 10% independent of atmosphere in which reaction is performed. In such conditions and at 473K the AgPW catalyst exhibited the conversion of ethanol as well as the selectivity to ethylene about 99%. It can be concluded that Ag₃PW₁₂O₄₀·3H₂O salt can be used as an ‘ecofriendly’ catalyst for ethylene production by the dehydration of ethanol in nitrogen or air atmospheres in relatively low temperature and appropriate relative humidity.

Keywords: Silver tungstophosphate; Ethanol dehydration; Relative humidity; FT-IR; XRD

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Applied Catalysis B, Environmental (v.123-124, #)

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Applied Catalysis B, Environmental (v.123-124, #)