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Applied Catalysis B, Environmental (v.132-133, #)

Editorial Board (pp. co2).

Contents (pp. co4).

Contents (pp. i-ii).

Editorial Board (pp. i).

Oxidative reforming of model biogas over NiO–Y₂O₃–ZrO₂ catalysts by Yvan J.O. Asencios; Cristiane B. Rodella; Elisabete M. Assaf (pp. 1-12).

Display Omitted► NiO–Y₂O₃ and Y₂O₃–ZrO₂ solid solutions were formed in the catalysts. ► The mixture of both solid solutions favored the catalysis. ► Y₂O₃–ZrO₂ seemed to hinder the formation of filamentous carbon. ► Y₂O₃ stabilized the zirconia, with particles of rectangular parallelepiped form. ► Ni20YZ catalyst is promissory for the oxidative reforming of biogas.Catalysts composed of NiO/Y₂O₃/ZrO₂ mixtures were synthesized by the polymerization method in a single step. They were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), physisorption of N₂ (BET) and X-ray photoelectron spectroscopy (XPS) and then tested in the oxidative reforming of a model biogas (1.5CH₄:1CO₂) in the presence of oxygen (1.5CH₄+1CO₂+0.25O₂) at 750°C for 6h. It was observed that the catalysts Ni20YZ and Ni40YZ performed better in catalytic processes than NiO/ZrO₂ and NiO/Y₂O₃, synthesized under the same conditions. The formation of Y₂O₃–ZrO₂ and NiO–Y₂O₃ solid solutions increased the rates of conversion of the reactants (CH₄ and CO₂) into synthesis gas (H₂+CO). The formation of oxygen vacancies (in samples containing ZrO₂ and Y₂O₃) seemed to promote removal of the coke deposited on the nickel surface during the oxidative reforming of model biogas. The H₂/CO ratios in the reaction products formed on the best catalysts were 1:1, which is desirable for their direct use in the STD and in the Fischer–Tropsch processes.

Keywords: NiO–Y; ₂; O; ₃; –ZrO; ₂; catalysts; Polymerization method; Reforming reaction; Model biogas; Synthesis gas

The effect of carbon nanofiber properties as support for PtRu nanoparticles on the electrooxidation of alcohols by David Sebastián; Isabel Suelves; Elena Pastor; Rafael Moliner; María J. Lázaro (pp. 13-21).

Display Omitted► Small PtRu nanoparticles (2nm) were supported on different carbon nanofibers. ► The electrooxidation of methanol is favored on highly graphitic PtRu/CNF catalysts. ► The electrooxidation of ethanol is instead favored on highly porous PtRu/CNF. ► The CNF pore volume plays an determining role in the electrooxidation of ethanol.Carbon nanofibers (CNFs) characterized by different mean diameter, BET surface area, pore volume and crystallinity were prepared and studied as supports for PtRu nanoparticles to investigate the influence of the support characteristics on the performance for the electrooxidation of alcohols. A modified microemulsion procedure was used to deposit the metal nanoparticles minimizing the effect of the support on the catalyst particle size.PtRu nanoparticles of ca. 2nm size were obtained despite the relatively low surface area of CNFs (95–185m²g⁻¹) with a good distribution on the surface as confirmed by TEM micrographs and the high values of the electrochemically active surface areas (110–140m²g⁻¹) determined by electrochemical CO stripping. The most appropriate PtRu dispersion was achieved for those carbon nanofibers showing the best compromise in terms of BET surface area and graphicity.A cross-analysis of the supports physico-chemical properties, ECSA and mass activity for the methanol and ethanol oxidation reactions suggests that both PtRu dispersion and electronic properties as determined by the effect of CNF crystallinity play a significant role in determining the electrocatalytic activity. Different electrocatalytic activity behavior with CNF properties were found for methanol and ethanol. Methanol oxidation is favored using highly crystalline CNFs as PtRu support, despite their low surface area, whereas ethanol oxidation is hindered by diffusional problems when using highly graphitic CNFs due to their low pore volume, so the activity is maximized supporting PtRu on CNFs with a more accessible porosity.

Keywords: PtRu catalyst; Carbon nanofibers; Fuel cell; Methanol; Ethanol

Optimizing the synthesis of carbon nanofiber based electrocatalysts for fuel cells by David Sebastián; Isabel Suelves; Rafael Moliner; María Jesús Lázaro; Alessandro Stassi; Vincenzo Baglio; Antonino Salvatore Aricò (pp. 22-27).

Display Omitted► Synthesis of Pt catalyst on low surface area CNF was optimized using four methods. ► Colloidal and microemulsion were appropriate methods to obtain small Pt particles. ► A volcano-shaped curve was obtained for ORR mass activity vs. Pt particle size. ► Degradation tests highlighted the need for initial Pt particles smaller than 3nm.This work deals with an optimization of the platinum dispersion on low surface area carbon nanofibers (CNFs) by using different synthesis procedures and its electrocatalytic activity toward oxygen reduction. The selected CNFs were characterized by a BET surface area of ca. 100 m²g⁻¹ and were in-house synthesized by the decomposition of CH₄ at 700°C. Pt nanoparticles were deposited by using four different synthesis routes. A metal concentration of 20wt% was confirmed by EDX and TGA. Two classical impregnation routes were employed, one using NaBH₄ as reducing agent at 15°C and the second one using formic acid at 80°C. Two alternative processes consisted in a microemulsion procedure followed by reduction with NaBH₄ and a colloidal route by using the sulphite complex method followed by reduction with hydrogen. The main differences regarded the platinum crystal size varying from 2.5nm for the colloidal route to 8.1nm for the impregnation route (formic acid). The classical impregnation procedures did not result appropriate to obtain a small particle size in the presence of this support, whereas microemulsion and colloidal methods fit the requirements for the cathodic oxygen reduction reaction in polymer electrolyte fuel cells, despite the low surface area of CNFs. The catalysts were subjected to an accelerated degradation test by continuous potential cycling. Although the initial activity was the highest for the microemulsion based catalyst, after the accelerated degradation test the colloidal based catalyst experienced a relatively lower loss of performance.

Keywords: Carbon nanofibers supports; Durability; Fuel cells; Oxygen–reduction reaction; Platinum

Nanostructured Pd modified Ni/CeO₂ catalyst for water gas shift and catalytic hydrogen combustion reaction by Vijay M. Shinde; Giridhar Madras (pp. 28-38).

Display Omitted► Pd modified Ni/CeO₂ catalyst was synthesized and characterized. ► Catalyst is highly active and 100% selective for H₂ production. ► Enhancement in WGS activity is due to change in the reducibility of support. ► Redox reaction mechanism was used to correlate data.Nanostructured Pd-modified Ni/CeO₂ catalyst was synthesized in a single step by solution combustion method and characterized by XRD, TEM, XPS, TPR and BET surface analyzer techniques. The catalytic performance of this compound was investigated by performing the water gas shift (WGS) and catalytic hydrogen combustion (CHC) reaction. The present compound is highly active and selective (100%) toward H₂ production for the WGS reaction. A lack of CO methanation activity is an important finding of present study and this is attributed to the ionic substitution of Pd and Ni species in CeO₂. The creation of oxide vacancies due to ionic substitution of aliovalent ions induces dissociation of H₂O that is responsible for the improved catalytic activity for WGS reaction. The combined H₂-TPR and XPS results show a synergism exists among Pd, Ni and ceria support. The redox reaction mechanism was used to correlate experimental data for the WGS reaction and a mechanism involving the interaction of adsorbed H₂ and O₂ through the hydroxyl species was proposed for CHC reaction. The parity plot shows a good correspondence between the experimental and predicted reaction rates.

Keywords: Solution combustion; Ceria-supported catalyst; CO methanation; Redox mechanism

Visible-light photocatalysis with phosphorus-doped titanium(IV) oxide particles prepared using a phosphide compound by Motoki Iwase; Keiji Yamada; Tsutomu Kurisaki; Orlando Omar Prieto-Mahaney; Bunsho Ohtani; Hisanobu Wakita (pp. 39-44).

Display Omitted► Phosphorus-doped TiO₂ was prepared by doping TiO₂ with phosphorus having negative charges. ► The P-doped TiO₂ nanoparticles exhibited a pale yellow color. ► The action spectra for acetaldehyde decomposition revealed visible light activity of P-TiO₂. ► The photocatalytic activity of P-TiO₂ depended on calcination temperature.Doping titanium(IV) oxide(TiO₂) with phosphorus (P) having negative charges was attempted in order to obtain P-doped TiO₂ with a red shift of the absorption edge and visible-light photocatalytic activity. P-doped TiO₂ was synthesized through the hydrolysis of titanium tetraisopropoxide in a suspension containing phosphide. The P-doped TiO₂ nanoparticles exhibited a pale yellow color. The UV–vis diffuse reflection spectra of P-doped TiO₂, which was calcined at 450–600°C, showed a continuous and tailing absorption in the visible region. XRD patterns of P-doped TiO₂ showed the presence of anatase phase up to a temperature of 500°C and the appearance of rutile phase from a temperature over 550°C. The red shift of the absorption edge was not associated with the phase transformation from anatase to rutile. The XPS P2p spectra of P-doped TiO₂ indicated the decrease of P⁵⁺ and the increase of P³⁻ during sputtering. The results suggested the presence of phosphate on the surface and the presence of P³⁻ on the inner side of P-TiO₂. The action spectra of photocatalytic reaction for acetaldehyde decomposition revealed visible light activity of P-doped TiO₂. P-doped TiO₂ calcined at 475°C was the most active in degradation of phenol under visible light. The P-content was found to play a key role in determining the spectral response in visible area and the photocatalytic activity under visible light irradiation.

Keywords: Titania; Phosphorus; Photocatalysis; Phosphorus-doped titania; Phosphide

Ag₃PO₄/reduced graphite oxide sheets nanocomposites with highly enhanced visible light photocatalytic activity and stability by Pengyu Dong; Yuhua Wang; Baocheng Cao; Shuangyu Xin; Linna Guo; Jia Zhang; Fenghua Li (pp. 45-53).

Display Omitted► Ag₃PO₄/RGOs nanocomposites were firstly prepared by a facile approach. ► The composite shows high photocatalytic activity for organic dyes degradation. ► The composite exhibits enhanced photocatalytic and structural stability. ► RGOs could improve the stability of easily photocorroded photocatalysts.A series of Ag₃PO₄ and reduced graphite oxide sheets (RGOs) nanocomposites have been fabricated by a facile chemical precipitation approach in N,N -dimethylformamide (DMF) solvent without any hard/soft templates. The as-prepared Ag₃PO₄/RGOs composites were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared spectra (FTIR), Raman spectroscopy, field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS). It is found that the nano-sized Ag₃PO₄ particles are deposited on the surfaces of RGOs. The Ag₃PO₄/RGOs nanocomposites exhibit enhanced photocatalytic activity for the photodegradation of organic methyl orange (MO) and methylene blue (MB) under visible light irradiation. The photocatalytic rate of Ag₃PO₄/2.1wt% RGOs nanocomposite is 3 and 2 times of that of pure Ag₃PO₄ nanoparticles for the degradation of MO and MB, respectively. Furthermore, the photocatalytic and structural stability of Ag₃PO₄ is greatly enhanced. It is suggested that RGOs can be used as protective coatings that partially inhibit the photocorrosion of Ag₃PO₄. Overall, this work could provide a new approach to the improvement not only in the photocatalytic activity but also the stability of photocorrosion catalysts.

Keywords: Reduced graphite oxide sheets; Silver orthophosphate; Nanocomposite; Photocatalysis; Stability

Selective hydrogenation of CO₂ and CO to useful light olefins over octahedral molecular sieve manganese oxide supported iron catalysts by Boxun Hu; Samuel Frueh; Hector F. Garces; Lichun Zhang; Mark Aindow; Christopher Brooks; Eric Kreidler; Steven L. Suib (pp. 54-61).

Display Omitted► Porous Fe–Mn–K catalysts selectively hydrogenate CO₂ and CO to light olefins. ► Particle sizes and catalytic interfaces influence catalytic activity. ► DART MS spectra show strong readsorption of olefins on catalysts. ► Fe, Mn, and K synergistically improve catalytic activity and selectivity.Porous cryptomelane-type octahedral molecular sieve manganese oxide (K-OMS-2) supported iron nanocatalysts have been developed for selective hydrogenation of CO₂ and CO to light olefins. Surface coated iron (SCI) catalysts and frame-work doped iron (FDI) catalysts have different interfaces. The synergistic interactions of nano-size iron carbides, potassium promoters, and manganese oxides vary in these two types of the Fischer-Tropsch (F-T) catalysts with respect to their catalytic activities and selectivity. For example, the SCI catalysts have high selectivity (>95%) to light olefins but low catalytic activity with a CO conversion of 45% and a CO₂ conversion of 32%. The FDI catalysts showed higher catalytic activities with a CO conversion of 87% and a CO₂ conversion of 45%. Direct analyses in real time-mass spectra and temperature programmed reduction-mass spectra have been used to correlate temperature effects. These component–structure–activity relationships provide insight for CO₂ utilization and F-T syntheses.

Keywords: Carbon dioxide utilization; DART; Olefin; Fischer-Tropsch; Manganese oxide

Mixed metal nanoparticles loaded catalytic polymer membrane for solvent free selective oxidation of benzyl alcohol to benzaldehyde in a reactor by S. Prakash; Chumki Charan; Ajay K. Singh; Vinod K. Shahi (pp. 62-69).

Catalytic polymer membrane (CPM) was prepared by in situ loading of mixed (silver and lead) metal nanoparticles (MNPs) in sulfonated poly (ether sulfone) (SPES) matrix for selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (BzH) in ambient conditions without regeneration of catalysts, separation steps and waste generation.Display Omitted► Ag-Pb nanoparticles loaded on catalytic polymer membrane for low temperature. ► Catalytic membrane reactor for selective chemical transformations. ► Selective oxidation of benzyl alcohol without catalyst regeneration, waste generation and any separation steps.Catalytic polymer membrane (CPM) was prepared by in situ loading of mixed (silver and lead) metal nanoparticles (MNPs) in sulfonated poly(ether sulfone) (SPES) matrix. Developed membrane (SPES-Ag⁰(35)/Pb⁰(65)) was used as a catalyst (oxidant) loaded and separator, in two-compartment catalytic membrane reactor (CMR) for selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (BzH) in ambient conditions without regeneration of catalysts, separation steps and waste generation. CPM acts as barrier and contactor between organic and aqueous phase, which was characterized by FTIR, XRD EDX, SEM, and physicochemical properties. Reported SPES-Ag⁰(35)/Pb⁰(65) showed good solvent, chemical and thermal stabilities in compare with fluorinated membrane and assessed to be more suitable for CMR. Effects of various reaction parameters such as substituted BnOH, concentration, silver nanoparticles (AgNPs) load etc. were investigated. High performance, low cost and stability of reported SPES-Ag⁰(35)/Pb⁰(65) suggested its commercial viability for chemical transformations in CMR.

Keywords: Selective oxidation; Catalytic polymeric membranes; Catalytic membrane reactor; Metal nanoparticles, Solvent free reaction

Hydrogen and methane selectivity during alkaline supercritical water gasification of biomass with ruthenium-alumina catalyst by Jude A. Onwudili; Paul T. Williams (pp. 70-79).

Display Omitted► Ru/Al₂O₃ catalyst was effective in the gasification of biomass with CGE of more than 96% for glucose. ► Ru/Al₂O₃ and alkaline additives e.g. CaO gave higher selectivities towards H₂ and CH₄ production. ► With sodium formate and acetate, Ru/Al₂O₃ gave gas products rich in both methane and hydrogen gas. ► Results indicated that Ru/Al₂O₃ could catalyze the reversible Sabatier reaction for H₂ and/or CH₄.Ruthenium supported on alpha-alumina spheres has been employed as a catalyst for the gasification of glucose and other biomass-related samples in supercritical water at 550°C, 36MPa, in a batch Inconel reactor. Most of the reactions were conducted in the presence of alkaline additives particularly sodium hydroxide and calcium oxide (hydroxide). In general, over 96% carbon gasification efficiencies (CGE) were achieved in the presence of Ru/Al₂O₃, while hydrogen gasification efficiencies (HGE) based on result-derived reaction stoichiometries reached 87% for glucose. Both HGE and CGE approached 100% for the sodium carboxylates. Without alkaline additives, Ru/Al₂O₃ converted glucose into gas product with average yields of 10.8mol hydrogen/(kg of glucose), 8.6mol methane/(kg of glucose) and 17mol carbon dioxide/(kg of glucose), while carbon monoxide and C₂-C₄ hydrocarbons made up only 1mol//(kg of glucose). However, when the ruthenium catalyst was used in combination with sodium hydroxide and calcium hydroxide, the selectivity towards hydrogen gas increased, with the complete removal of carbon dioxide. Similar yields of hydrogen (14.7mol/kg of glucose) and methane (12.8mol/kg of glucose) were obtained with CaO and Ru/Al₂O₃. Reactions of sodium carboxylates (formate and acetate) suggested that the ruthenium catalyst was capable of catalyzing the Sabatier reversible reaction in both the forward and backward directions. The yield of each gas was found to be dependent on the concentrations of methane, hydrogen and carbon dioxide in the reactor.

Keywords: Biomass; Catalytic hydrothermal gasification; Sabatier reaction; Methane; Hydrogen

Enhanced electropromotion of methane combustion on palladium catalysts deposited on highly porous supports by F. Matei; C. Jiménez-Borja; J. Canales-Vázquez; S. Brosda; F. Dorado; J.L. Valverde; D. Ciuparu (pp. 80-89).

Display Omitted► Pd film was deposited on a combination of porous-dense Y₂O₃-stabilized-ZrO₂. ► The use of porous interlayer led to a more active catalyst due to high dispersion. ► Despite its high in-plane resistance, it shows a major enhancement in activity. ► NEMCA is observed at comparable performance with dense supported samples.The aim of the present study was to explore the potential to electrochemically promote the methane oxidation reaction over palladium catalyst-electrodes deposited on a combination of porous-dense Y₂O₃-stabilized-ZrO₂ (YSZ), an oxygen ion conductor. We have prepared for the first time an electro-active palladium catalyst on a highly porous support, which was successfully used to enhance the catalytic activity by electrochemical promotion (NEMCA effect or EPOC). The wet impregnation technique has been used over highly porous YSZ disks to achieve very active catalyst-electrodes, with a metal catalyst dispersion of 27% (up to 4.5 times higher than that obtained for catalysts supported on dense YSZ), and susceptible to be electropromoted, despite its relatively high in-plane electrical resistance. The sample impregnated on porous YSZ turned to be much more active in methane combustion than the sample prepared by impregnation on dense YSZ, reaching, under similar working conditions, one order of magnitude higher CO₂ formation rates. The catalyst supported on porous YSZ was characterized by XRD, XPS, SEM and TEM techniques, while galvanostatic transients and electrochemical current–potential curves were recorded in order to assess the electropromotion of the catalytic reaction in a temperature range from 350 to 430°C under reducing, stoichiometric and oxidizing conditions.

Keywords: Methane oxidation; Electrochemical promotion; NEMCA; Pd catalyst-electrode; Porous YSZ

Potocatalytic oxidative degradation of organic pollutant with molecular oxygen activated by a novel biomimetic catalyst ZnPz(dtn-COOH)₄ by Zehui Zhang; Mingjian Zhang; Jia Deng; Kejian Deng; Bingguan Zhang; Kangle Lv; Jie Sun; Lianqing Chen (pp. 90-97).

Display Omitted► A novel biomimetic catalyst ZnPz(dtn-COOH)₄ was synthesized by template method. ► ZnPz(dtn-COOH)₄ was used to activate oxygen for the degradation of Rhodamine B by 80%. ► The mechanism for the oxidative degradation of RhB involves both¹O₂ and HO. ► N,N-diehyl-N-ethyl-rhodamine was the main intermediate during RhB degradation. ► The catalyst can be reused several times without losing its catalytic activity.Zinc porphyrins and its analogs showing many excellent properties such as good potosensitivity, non-toxicity, high stability and facile preparation attract more and more attention of scientists. Here, a novel zinc porphyrazine, namely zinc(II) tetracarboxyl- tetra(1,4-dithiin) porphyrazine [abbreviated as ZnPz(dtn-COOH)₄] was successfully synthesized and its potocatalytic activity was studied. The ZnPz(dtn-COOH)₄ supported on an Amberlite CG-400 resin was used as a biomimetic catalyst for the activation of molecular oxygen under visible light to degrade a probe dye compound Rhodamine B (RhB) in aqueous solution. Interestingly, the mechanism for the oxidative degradation of RhB involves both¹O₂ and HO (Type II and Type I mechanisms, respectively). More hydroxyl radicals were produced at pH 3, which was responded for the highest degradation ratio. The catalyst can be reused several times without losing its catalytic activity, with an average RhB degradation ratio around 80% for 12h. The most probable mechanism of RhB degradation in this study was that N,N-diehyl-N-ethyl-rhodamine was the main intermediate, which was then cleaved to small molecule by reactive oxidizing species. This study demonstrated a promising approach for the activation of molecular oxygen by the newly developed biomimetic catalyst, in which the central metal to be unchangeable valence, for environmental remediation and oxidation catalysis.

Keywords: Zinc porphyrazine with sulfur; Biomimetic catalyst; Activating molecular oxygen; Photodegradation; Rhodamine B

Influence of the preparation method on the activity of ceria zirconia mixed oxides for naphthalene total oxidation by David R. Sellick; Asunción Aranda; Tomas García; José M. López; Benjamín Solsona; Ana M. Mastral; David J. Morgan; Albert F. Carley; Stuart H. Taylor (pp. 98-106).

Display Omitted► Ceria zirconia mixed oxide is an effective catalyst for naphthalene total oxidation. ► The influence of zirconia addition differs for carbonate and urea preparations. ► A range of factors including surface hydroxyls and residual carbonate influence catalyst activity.Cerium/zirconium mixed oxides, with different Ce/Zr ratios, have been synthesised by a co-precipitation method using two different precipitating agents (sodium carbonate and urea) and tested for the total oxidation of naphthalene. Catalysts were characterised by N₂ adsorption, XRD, Raman, TPR, XPS and DRIFTS. Ceria prepared by carbonate precipitation had low activity and this is likely to be related to the high concentration of residual surface carbonate that covers catalytic sites and inhibits reaction. For carbonate precipitation, increasing the Zr content to 1% resulted in a significant increase of activity, which is related to the decrease of surface carbonate. Increasing the Zr content up to 50% resulted in catalysts more active than ceria, but activity decreased as Zr content increased. This was in spite of increasing the number of oxygen vacancies, and this effect has been related to the decrease in the number of surface hydroxyl groups, which favours naphthalene adsorption. Ceria prepared by urea precipitation was markedly more active than that produced by carbonate precipitation. The urea-derived catalyst with 1% Zr is marginally more active than pure ceria, whilst for higher Zr contents activity was marginally lower. Two factors can account for these observations; they are the increase of oxygen vacancies contributing positively to activity and the opposing negative effect of decreasing the number of surface hydroxyl groups when the zirconium content increases.

Keywords: VOCs; Catalytic oxidation; Ceria; Zirconia; Naphthalene; PAHs

Gold nanoparticle decorated ceria nanotubes with significantly high catalytic activity for the reduction of nitrophenol and mechanism study by Jianming Zhang; Guozhu Chen; Mohamed Chaker; Federico Rosei; Dongling Ma (pp. 107-115).

Display Omitted► Surface “bare” Au nanoparticles (AuNPs) were easily coupled on CeO₂ nanotubes. ► The AuNP–CeO₂ coupling does not need any additional chemicals. ► The Au/CeO₂ catalyst shows superior activity in catalytic reduction of nitrophenol. ► The effect of AuNP surface and support on catalytic activity was investigated. ► Unique surface chemistry of AuNPs and Au–CeO₂ interaction contribute to catalysis.We report the preparation and catalytic properties of a new nanostructured catalyst, made of small (∼5nm in diameter) and uniform gold nanoparticles (AuNPs) and ceria nanotubes (CeO₂ NTs). “Surfactant-free” AuNPs fabricated by pulsed laser ablation in liquid (PLAL) on a bulk Au target are efficiently assembled onto the surface of CeO₂ NTs without performing any surface functionalization of either component to promote their coupling, thanks to the presence ofOH on the PLAL-AuNPs. The reduction reaction of 4-nitrophenol into 4-aminophenol catalyzed by our PLAL-AuNP/CeO₂-NT catalyst exhibits remarkably higher reaction rate in comparison to that catalyzed by similar catalysts composed of chemically prepared AuNPs (Chem-AuNPs) as an active phase and/or commercially available CeO₂ powder as support. Their superior catalytic activity is found to be due to the unique, relatively “bare” surface of the PLAL-AuNPs as well as oxidized Au species induced by the strong interaction between the “barrier-free” surface of PLAL-AuNPs and surface defects (oxygen vacancies) of CeO₂ NTs. The important role of unique surface chemistry of PLAL-AuNPs in catalysis was further demonstrated in CO oxidation reaction in gas phase. Our results suggest that the use of PLAL-AuNPs enables easy and efficient attachment of AuNPs onto the surface of the CeO₂ NTs and their unique combination leads to the development of highly efficient catalysts. Our design and fabrication of the nanocatalysts take full advantage of the unique features of the PLAL-AuNPs and potentially constitute a general and efficient route to prepare other metal-NP/metal-oxide-support catalysts, which can therefore largely expand the applications of PLAL-noble metal NPs in catalysis.

Keywords: Au nanoparticle; CeO; ₂; Hydrogenation; Nitrophenol reduction; Laser ablation

Shape-dependency activity of nanostructured CeO₂ in the total oxidation of polycyclic aromatic hydrocarbons by Laura Torrente-Murciano; Alexander Gilbank; Begoña Puertolas; Tomas Garcia; Benjamin Solsona; David Chadwick (pp. 116-122).

Display Omitted► Determination of the morphological phase diagram of CeO₂ nanostructures. ► Shape-dependency of physical properties on nanostructured ceria. ► Relationship between surface oxygen vacancies and VOC full oxidation activity.A morphological phase diagram is determined to relate the effect of base concentration and temperature during the hydrothermal synthesis with the final ceria nanostructured morphology. Representative samples of nanoparticles, nanorods and nanocubes have been characterized by XRD, N₂ adsorption, TEM, XPS and Raman and catalytically tested for the total oxidation of naphthalene as a model polycyclic aromatic hydrocarbon. Ceria nanoparticles present the highest surface area and smallest crystalline size, leading to the most active of these structures. However if the catalytic activity is normalized by unit of surface area, the observed reactivity trend (nanorods

Keywords: Ceria; Nanotubes; Nanorods; Nanocubes; Nanostructures; Catalytic total oxidation; VOC; Naphthalene; Morphological diagram

Supported CeO₂ catalysts in technical form for sustainable chlorine production by M. Moser; C. Mondelli; T. Schmidt; F. Girgsdies; M.E. Schuster; R. Farra; L. Szentmiklósi; D. Teschner; J. Pérez-Ramírez (pp. 123-131).

Display Omitted► HCl oxidation to Cl₂ is studied over supported ceria catalysts. ► ZrO₂ enables to attain high dispersion and tunes the electronic properties of CeO₂. ► CeO₂/ZrO₂ is a cost-effective alternative to RuO₂-based catalysts. ► Pilot tests over mm-sized bodies for 700h evidence outstanding performance.Bulk CeO₂ has been recently reported as a promising catalyst for the oxidation of HCl to Cl₂. In order to undertake the scale up of this system, various oxides (TiO₂, Al₂O₃, and low- and high-surface area ZrO₂) have been evaluated as carriers. Supported CeO₂ catalysts (3–20wt.% Ce) prepared by dry impregnation were isothermally tested at the lab scale. Their performance was ranked as: CeO₂/ZrO₂≫CeO₂/Al₂O₃≥CeO₂/TiO₂. Kinetic data revealed a lower activation energy and a similar activity dependence on the partial pressure of O₂ for CeO₂/ZrO₂ compared to bulk CeO₂. Pilot-scale testing over 3-mm pellets of this catalyst evidenced outstanding stability for 700h on stream. In-depth characterization of the carriers and fresh catalysts by N₂ sorption, Hg porosimetry, X-ray diffraction, temperature-programmed reduction with H₂, Raman spectroscopy, electron microscopy, and in situ prompt gamma activation analysis, enabled to rationalize the different catalytic behavior of the materials. ZrO₂ stabilizes nanostructures of CeO₂ and a Ce–Zr mixed oxide phase, which offer high dispersion and improved oxidation properties. The catalyst also shows reduced chlorine uptake, and overall stands as a better Deacon material compared to bulk CeO₂ and other supported systems. CeO₂ is present on Al₂O₃ predominantly as well-distributed nanoparticles. Still, alumina does not induce any electronic effect, thus the supported phase behaves similarly to bulk ceria. TiO₂, likely due to the structural collapse and dramatic sintering suffered during calcination, leads to the formation of very large ceria particles. Based on our results, CeO₂/ZrO₂ appears as a robust and cost-effective alternative to the current RuO₂-based catalysts for large-scale chlorine recovery.

Keywords: Chlorine production; HCl oxidation; Ceria; Support; CeO; ₂; /ZrO; ₂; Technical catalyst; Pilot test

N-butanol removal over alumina supported platinum catalysts by Henri-Joël Sedjame; Gwendoline Lafaye; Jacques Barbier Jr. (pp. 132-141).

Display Omitted► Pt/Al₂O₃ catalysts prepared by incipient wetness impregnation and sol–gel methods. ► Butanol dehydration and 1-butene isomerization are function of catalyst acidity. ► Excessive amount of Lewis acidic sites contributes to a deactivation of the catalyst. ► Inhibitor effect of water on butanol oxidation.Pure alumina and alumina supported platinum catalysts were used in n-butanol removal reaction. Platinum catalysts were prepared by two different methods and characterized by N₂ adsorption isotherms, ICP, H₂ chemisorption and TEM. Acid–base properties of catalysts were studied by pyridine and carbon dioxide adsorption–desorption followed by FTIR. Experiments were performed by changing conditions (with or without oxygen and/or water) to determine some correlation between the reactivity and the acid–base properties of the catalysts and to study the effect of water on the reactivity. In the absence of oxygen, dehydration of n-butanol occurs whereas in the presence of oxygen the n-butanol is oxidized. In presence of oxygen, butanal is the only by-product observed whereas in absence of oxygen butene isomerization products are also observed. N-butanol dehydration involves the catalyst acidity whereas the reaction of dehydrogenation involves the basic character of the catalyst. Platinum addition changes the properties of alumina and increases the activity of catalyst for all these reactions. In large amount, water appears as an inhibitor for n-butanol oxidation.

Keywords: Alumina; Platinum; N-butanol; Butanal; Butene; FTIR; Dehydration; Dehydrogenation; Oxidation

Solar photoelectrocatalytic degradation of Acid Orange 7 azo dye using a highly stable TiO₂ photoanode synthesized by atmospheric plasma spray by Sergi Garcia-Segura; Sergi Dosta; Josep M. Guilemany; Enric Brillas (pp. 142-150).

Display Omitted► Synthesis of a TiO₂ photoanode on stainless steel substrate by atmospheric plasma spray. ► Degradation of Acid Orange 7 by solar photoelectrocatalysis with a TiO₂/air-diffusion cell. ► 15mgL⁻¹ azo dye, pH 7.0 and anodic current density of 1.0mAcm⁻² as best operating variables. ► Fast azo dye removal and total solution decolorization, but poor mineralization achieved. ► Phthalic, tartaric, succinic, acetic and oxalic acids as main by-products at long-electrolysis time.A TiO₂ coating composed of 29% rutile, 9% anatase and 62% of Ti₇O₁₃ on stainless steel support has been prepared by atmospheric plasma spray technology. This novel photoanode was coupled to an air-diffusion cathode that generates H₂O₂ in a photoelectrochemical cell submitted to direct sunlight irradiation to degrade 100mL of Acid Orange 7 (AO7) azo dye solutions in 0.05M Na₂SO₄ by solar photoelectrocatalysis (SPEC). The photoanode presented excellent mechanical properties as well as large stability and long durability up to 2.0mAcm⁻². The decolorization process in SPEC was synergistic of the individual processes in solar photocatalysis and anodic oxidation with generated H₂O₂ under comparable conditions owing to the larger production ofOH from the higher amounts of photogenerated holes that can be separated of photogenerated electrons. The best operating variables for SPEC were 15mgL⁻¹ AO7, pH 7.0 and anodic current density ( j_anod) of 1.0mAcm⁻². Under these conditions, the azo dye disappeared in 100min and the solution was totally decolorized in 120min, but only 40% mineralization was attained after 240min of electrolysis. The AO7 decay followed a pseudo-first-order reaction as found by reversed-phase HPLC and it was accelerated with increasing j_anod due to the higher amounts ofOH generated from the production of more photogenerated holes and the enhancement of anodic oxidation of water. Ion-exclusion HPLC allowed the identification of generated carboxylic acids like phthalic, tartaric, succinic, acetic and oxamic, which were the main components of long-time electrolysis. Their persistence explains the low mineralization of AO7 in SPEC. The initial N of the azo dye was mineralized as NH₄⁺ ion, in larger proportion than NO₃⁻ ion, although it was mainly loss as volatile species.

Keywords: Acid Orange 7; Photocatalysis; Photoelectrocatalysis; Sunlight; Water treatment

The reduction of NO by CO under oxygen-rich conditions in a fixed-bed catalytic reactor: A mathematical model that can explain the peculiar behavior by Alexei G. Makeev; Nickolai V. Peskov (pp. 151-161).

Display Omitted► Three mathematical models of an isothermal catalytic reactor are used for calculation of CO and NO conversions. ► A decrease of the active catalyst surface area can improve the NO conversion and the overall reactor efficiency. ► An increase of the flow rate can also improve the NO conversion.A kinetic model of the NO+CO+O₂ catalytic reaction in the isothermal continuous stirred tank reactor (CSTR) has been introduced previously in [A.G. Makeev, N.V. Peskov, H. Yanagihara, Appl. Catal. B: Environ. 119–120 (2012) 273]. The present study implements the same kinetic mechanism but now it is combined with a more realistic model of the catalytic flow reactor – the axially dispersed plug flow reactor model. The resulting new model is compared with the CSTR-based model. The calculations demonstrate that back-mixing in the isothermal reactor can lead to the following effect. At sufficiently high temperatures, when the conversion of CO is close to 100%, an increase in NO-to-N₂ conversion can be induced by: (1) the decrease of the active catalyst surface area and (2) the increase of the space velocity of the feed gas. These items just represent the peculiar behavior, which seems to contradict with the physical intuition. In fact, such results have been observed experimentally, but probably they have not been properly explained. We demonstrate that these peculiar effects can be caused by the kinetics of competing reactions in a catalytic flow reactor. The vital step in the reaction mechanism appears to be the reversible dissociation of the adsorbed NO species. In particular, the calculations show that the overall reactor efficiency can decrease significantly when the catalyst surface area is increasing. This effect disappears if the ideal plug flow model (i.e., without dispersion/diffusion) is applied.

Keywords: Modeling; Catalytic reactor; NO reduction; Lean-burn conditions; Effect of catalyst loading and space velocity

Enhancement of pesticide photo-Fenton oxidation at high salinities by María M. Micó; Jordi Bacardit; Jorge Malfeito; Carme Sans (pp. 162-169).

Display Omitted► The performance of photo-Fenton at high salinity conditions has not be assessed enough. ► Salinity seems to have a noticeable effect over photo-Fenton parameters. ► Methomyl and imidacloprid depletions were enhanced by higher conductivities, while total organic carbon was worsened. ► Chloride anions seem to be the main causatives of the salts influence over the process. ► Organic substances can interact with Fe³⁺ affecting the whole process.The performance of the photo-Fenton reaction under high salinity conditions (up to 50mScm⁻¹) has been tested regarding the oxidation of two pesticides, imidacloprid and methomyl, in the shape of their commercial formulations. In opposition to what is commonly outlined in the literature, an enhancement in pesticides depletion has been found due to the positive participation of halogen radicals, Cl. However, this beneficial effect does not improve organic carbon elimination but rather displays worse total organic carbon (TOC) depletion. This effect is most likely due to the hydroxyl radicals scavenging and the complexation of Fe³⁺ by chloride salts, which reduce the availability of reagents. Although salts/Fe³⁺ interaction was observed, Fe³⁺ interaction with the organic content was revealed as more relevant, especially for imidacloprid.

Keywords: Advanced oxidation processes; Chloride; High conductivity; Imidacloprid; Methomyl; Water reuse

Glycerol conversion to acrylonitrile by consecutive dehydration over WO₃/TiO₂ and ammoxidation over Sb-(Fe,V)-O by Carsten Liebig; Sébastien Paul; Benjamin Katryniok; Cyrille Guillon; Jean-Luc Couturier; Jean-Luc Dubois; Franck Dumeignil; Wolfgang F. Hoelderich (pp. 170-182).

Display Omitted► Conversions of glycerol to acrolein and of acrolein to acrylonitrile were studied. ► Dehydration and ammoxidation steps were successfully combined in a tandem reactor. ► The presence of FeSbO₄ was correlated to the high selectivity to acrylonitrile. ► The performance increase with reaction time was due to in operando FeSbO₄ formation.The indirect ammoxidation of glycerol to acrylonitrile via intermediate formation of acrolein was studied using a tandem reactor coupling a dehydration step with an ammoxidation step. For the first step of dehydration of glycerol to acrolein, we used a previously optimized WO₃/TiO₂ catalyst, while Sb-V-O or Sb-Fe-O catalysts were developed and used for the subsequent ammoxidation step. Especially, the Sb-Fe-O catalysts were found highly selective and thus were more-deeply investigated. The corresponding catalysts were characterized by nitrogen physisorption, X-ray powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature-programmed reduction in the presence of H₂. We found that the presence of a FeSbO₄ mixed phase on the synthesized samples was correlated to a high selectivity to acrylonitrile. Further, we observed an increase in selectivity to acrylonitrile with the reaction time, which was explained by the progressive formation of additional amounts of FeSbO₄ on the catalysts during the reaction. Finally, the reaction parameters (temperature, catalyst amount, molar NH₃/AC ratio and molar O₂/AC ratio) for the catalyst with an Sb/Fe molar ratio of 0.6 were optimized, whereby a maximum yield in acrylonitrile of 40% (based on glycerol) could be achieved.

Keywords: Glycerol; Indirect ammoxidation; Acrolein; Acrylonitrile; Tandem-reactor

Core–shell Pt modified Pd/C as an active and durable electrocatalyst for the oxygen reduction reaction in PEMFCs by Geng Zhang; Zhi-Gang Shao; Wangting Lu; Feng Xie; Hui Xiao; Xiaoping Qin; Baolian Yi (pp. 183-194).

Display Omitted► Shell/core Pt/Pd/C catalysts are prepared by a facile chemical reduction method. ► Pt/Pd/C has better ORR activity and durability than that of Pt/C. ► Pd@Pt is converted to Pt-Pd alloy with Pt rich surface after potential cycling.A series of Pt modified Pd/C catalysts (Pt/Pd/C) with different Pt/Pd molar ratio (Pt:Pd=1:4, 1:2 and 1:1) are synthesized by a chemical reduction method for oxygen reduction reaction (ORR). X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV) measurements confirm that Pt is deposited on the Pd nanoparticles and the Pt/Pd/C catalysts have a Pd_core@Pt_shell structure. In the half cell testing, the catalytic ORR activity of Pt₁/Pd₂/C and Pt₁/Pd₄/C are superior to commercial Pt/C. Moreover, the electrochemical durability to potential cycling of Pt₁/Pd₂/C and Pt₁/Pd₁/C catalysts is better than Pt/C catalysts. The improved durability is believed to be associated with the dissolution of Pd and the corresponding structure transformation from core–shell structure to Pt-Pd alloy with Pt rich surface. The structure change is confirmed by TEM, CV, XRD and X-ray photoelectron spectroscopy (XPS). In addition, the electrochemical active surface area (ECSA) loss and polarization behavior in the single cell testing also suggest that the Pt/Pd/C show a much better durability than Pt/C catalysts. Similarly, the dissolution of Pd is observed by CV and scanning electron microscope-energy dispersive X-ray spectra (SEM-EDX). The Pt/Pd/C electrocatalysts have high ORR activity and this high activity can be further improved during potential cycling, that is, the activity and durability can be obtained simultaneously. This Pd_core@Pt_shell structure allows for the development of highly active and durable ORR electrocatalysts, with potential for the application in proton exchange membrane fuel cells (PEMFCs).

Keywords: Proton exchange membrane fuel cell; Oxygen reduction; Electrocatalyst; Core–shell; Platinum; Palladium

Reaction kinetics investigation of the selective oxidation of aqueous ethanol solutions with air over a Au/TiO₂ catalyst by Pedram Aghaei; Rob J. Berger / (pp. 195-203).

Display Omitted► Kinetics of selective oxidation of aqueous ethanol with air over Au/TiO₂ catalyst. ► The gold catalyst was characterized by N₂ physisorption, XRD, ICP-OES, and TEM. ► The experimental data were adequately fitted into a LHHW kinetic model. ► H abstraction by a surface hydroxyl species is assumed to be the RDS.The selective oxidation of aqueous ethanol solution with air over a powdered commercial 1wt% Au/TiO₂ catalyst was investigated in stirred mini-autoclaves. The catalyst was characterized by various techniques including N₂ physisorption, XRD, ICP-OES, and TEM. Temperature, pressure, initial ethanol concentration, catalyst concentration, and reaction time were varied in order to successfully determine the parameters of a Langmuir–Hinshelwood–Hougen–Watson type reaction kinetics model, which was derived from the surface reactions. It is assumed that hydrogen abstraction by surface hydroxyl species is the rate-determining step. The model adequately describes the decreasing conversion at higher ethanol concentration and also the selectivities towards the products acetaldehyde, acetic acid, ethyl acetate, and CO₂. The moderate description of the conversion at 180–200°C can be improved by expanding the model with a second reaction route.

Keywords: Aerobic oxidation of aqueous ethanol; Gold catalysts; Production of acetic acid; Reaction kinetics

Co₃O₄ nanoparticles assembled coatings synthesized by different techniques for photo-degradation of methylene blue dye by T. Warang; N. Patel; R. Fernandes; N. Bazzanella; A. Miotello (pp. 204-211).

Display Omitted► Co₃O₄ NPs assembled coatings synthesized by PLD, EBD, sol–gel, and electroless methods. ► Co₃O₄ NPs synthesized by PLD showed the best photo-degradation activity for MB dye. ► Morphological, structural, and optical properties of NPs (PLD) suit perfectly for catalysis.Co₃O₄ nanoparticles assembled coatings have been synthesized by physical (pulsed laser deposition (PLD) and electron beam deposition) and chemical (sol–gel and electroless) techniques. The morphological, structural, and optical properties of all the coatings were analyzed by SEM, XRD, Raman spectroscopy, XPS, and UV–vis spectroscopy. The catalytic activities of the several Co₃O₄ heterogeneous catalyst coatings have been compared by looking at their efficiency on degradation of methylene blue dye that occurs via photo Fenton reaction in presence of H₂O₂ or oxone oxidants. The coating synthesized by PLD exhibits the best photo-degradation rate of dye in presence of H₂O₂ (4h) or oxone (8min). The NPs produced by PLD process exhibit smaller average size (18nm), narrow size distribution ( σ=3nm), perfect spherical shape, low degree of agglomeration, and mixed amorphous-nanocrystalline phase. These special features of NPs, along with better visible light absorption, are the main factors responsible for the enhanced photocatalytic activity of the PLD Co₃O₄ NPs assembled coating. It is also observed that although the concentration of oxone (0.5mM) was very small as compared to H₂O₂ (100mM) the photo-degradation of MB dye solution is much faster for oxone.

Keywords: Pulsed laser deposition; Electron beam deposition; Sol–gel; Co-precipitation; Photocatalytic degradation

Effect of water vapor on the by-products and decomposition rate of ppb-level toluene by photocatalytic oxidation by Jinhan Mo; Yinping Zhang; Qiujian Xu (pp. 212-218).

Display Omitted► Water vapor has significant influence on the PCO by-products generation of toluene. ► Maximum decomposition efficiency does not always lead to minimum by-products. ► By-products make the typical L–H model unfeasible in real application. ► Health related index (HRI) was used to evaluate the health risk of by-products. ► Health risk assessment shall be included to evaluate the PCO performance.It was found that there were unwanted by-products in the photocatalytic oxidation (PCO) of indoor ppb-level toluene, a typical volatile organic compound (VOC) in indoor air. However, up to now the control mechanism of the generation of the products has not been clear. In this study we address the problem: a titania-coated glass-plate reactor was applied to study the by-products and decomposition rate; the by-products generated under a series of water vapor concentrations were instantaneously identified by proton transfer reaction-mass spectrometer (PTR-MS); the results indicate that water vapor has a significant effect not only on the photocatalytic decomposition rate of toluene, but also on its by-products generation; the competitive adsorption mechanism between water vapor, toluene and its by-products was analyzed. By-products may make the typical Langmuir–Hinshelwood model unfeasible in real application. A health risk assessment of the by-products was also introduced. The results show that the maximum decomposition efficiency does not always lead to minimal by-products and lowest health risk. What it does show is that when evaluating the performance of photocatalytic air purification, health risks posed by the by-products should be the primary concern rather than the decomposition efficiency.

Keywords: Photocatalytic oxidation (PCO); Volatile organic compounds (VOCs); Indoor air quality (IAQ); Air cleaning

A salt-assisted approach for the pore-size-tailoring of the ionic-liquid-templated TiO₂ photocatalysts exhibiting high activity by Sue-min Chang; Chung-yu Lee (pp. 219-228).

Display Omitted► Inorganic salts expand the pore sizes of IL-templated TiO₂ powders based on ionic strength, volume exclusion and Coulomb repulsion. ► The ions with large ionic radii and high charges are more capable of expanding the pores. ► Pore-expansion reduces steric hindrance and opens internal surface areas of mesoporous photocatalysts to reactants, thus greatly enhancing the photoactivity. ► The critical pore size for the adsorption of hydrated bisphenol A molecules within the pores is ca. 4.2nm.In this study, we develop a novel salt-assisted approach to adjusting the pore size of ionic-liquid-templated TiO₂ photocatalysts by simply changing the concentrations and types of the inorganic salts. Four types of salts, including NaCl, CaCl₂, NH₄Cl, and NH₄NO₃, are selected in order to investigate the effects of the ionic radii and the charges of the constituent ions on the resulting textures. In addition, a mechanism that the salts assist the self-assembly of hydrophilic 1-butyl-3-methylimidazolium chloride (C₄mimCl) molecules in hydrophobic benzyl alcohol is proposed. The templated TiO₂ powder, which incorporates phosphate species to enhance its structural stability, exhibits a small pore size of 4.2nm and a high surface area of 164m²g⁻¹. Small amounts of the salts increase the ionic strength, slightly shrinking the template and the pore size, and pore expansion results when the salt/Ti ratio is above 0.2. The salts at a salt/Ti ratio of 1.0 remarkably extend the pore size to 8.7–16.8nm in the order of NH₄NO₃ (16.8nm)>NH₄Cl (13.7nm)>CaCl₂ (12.4nm)>NaCl (8.7nm). Moreover, high surface areas of 154–199m²g⁻¹ are still achieved. The ions that have large radii and high valence numbers are more capable of expanding the pores because of strong volume exclusion and Coulomb repulsion. The critical pore size for the adsorption of hydrated bisphenol A molecules within the pores is ca. 4.2nm. Pore expansion facilitates mass diffusion in the channels and turns internal surface areas available for reactions, thus greatly enhancing the activity of the mesoporous photocatalyst by 2.7–5.5 times.

Keywords: Ionic liquids; Salt-assisting; Mesoporous materials; Pore expansion; Photocatalysis

Cornered silver and silverplatinum nanodisks: Preparation and promising activity for alkaline oxygen reduction catalysis by Chien-Liang Lee; Ciou-Mei Syu; Chun-Han Huang; Hsueh-Ping Chiou; Yi-Ju Chao; Chia-Chen Yang (pp. 229-236).

Display Omitted► A simple method for the efficient synthesis of cornered Ag and AgPt nanodisks has been developed. ► The cornered nanodisks were used as new catalysts in oxygen reduction reaction. ► The order of cornered AgPt nanodisk>cornered Ag nanodisk>Ag nanoplate in activity was obtained.A simple method for the efficient synthesis of cornered Ag and AgPt nanodisks by using triangular Ag nanoplates as reactants has been developed. The triangular Ag nanoplates are heated and reshaped to spherical nanodisks; in turn, through the introduction of PtCl₄²⁻ ions, the spherical nanodisks undergo sculpturing and a subsequent displacement reaction to form cornered Ag nanodisks and AgPt nanodisks with pores. The selected-area electron diffraction pattern shows that the cornered Ag nanodisks are composed of two basal Ag (111) planes, thus indicating the occurrence of selective etching on the spherical nanodisks by this method. The analyses provided by X-ray diffraction spectroscopy and line-scanned energy-dispersive spectroscopy confirm the compositions of these cornered nanodisks and the mixed alloy in the Ag–Pt nanodisks. For the investigation of the practical feasibility of the application of the proposed method, these cornered Ag and AgPt nanodisks were then used as methanol-tolerant electrocatalysts in the alkaline oxygen reduction reaction (ORR). Electrochemical measurements were performed using an ultrathin-film rotating ring-disk electrode. The two types of nanodisks are found to have high stabilities and improved activities in 1M NaOH electrolyte. In the electrolyte with free methanol, the mass activities at −0.1V (vs. Ag/AgCl; within kinetic control region) in terms of the currents normalized to Ag mass for the Ag nanodisks and AgPt nanodisks are 6.98×10⁻⁴ and 2.01×10⁻³mAμg⁻¹, respectively, which are greater than the value of 2.09×10⁻⁴mAμg⁻¹ for Ag nanoparticles. The order in terms of the ORR activity is found to be as follows: cornered AgPt nanodisks>cornered Ag nanodisks>Ag nanoparticles. Additionally, in the presence of methanol, all the cornered nanodisk catalysts experience cathodic currents, indicating that the ORR occurs despite the use of a methanol solution.

Keywords: Unsaturated-bonding catalyst; Fuel cell; Cathodic catalyst; Pt; Nanoprism

Nanostructure catalysts prepared by multi-sputtering deposition process for enhanced methanol electrooxidation reaction by Kyung-Won Park; Young-Woo Lee; Yung-Eun Sung (pp. 237-244).

Display Omitted► The Pt-based nanostructure catalysts were fabricated by multi-sputtering deposition process. ► The size and/or composition Pt-based nanostructure catalysts were controlled. ► The nanostructure catalysts exhibited improved electrocatalytic activity for methanol oxidation.We report size and/or composition-controlled nanostructure catalysts for direct methanol fuel cells fabricated by means of multi-sputtering deposition process. The size-controlled Pt nanophases ranging from 0.62±0.14nm to 3.07±0.34nm in average size with narrow size distribution are fabricated as a function of sputtering power ratio of targets. The composition-controlled PtRu alloy nanophases deposited at different RF power ratio of Pt and Ru targets with the same power of WO₃ target exhibit varied atomic percentages of PtRu, i.e. (79.8:21.2), (62.2:37.8) and (37.6:62.4). Furthermore, the PtRu nanophases deposited at a constant RF power ratio of Pt and Ru targets with different power of WO₃ target show controlled average sizes such as 3.62±0.15nm, 1.86±0.23nm, and 1.20±0.22nm with the same compositions. The specific maximum power density of the nanostructure catalyst (∼100Wg⁻¹) is superior to that of the conventional nanostructure catalyst (∼37Wg⁻¹), representing that the nanostructure catalyst has an excellent electrode structure for methanol electrooxidation as compared to the conventional catalyst.

Keywords: Electrocatalyst; Direct methanol fuel cells; Size-control; Composition-control; Sputtering deposition process

Catalytic removal of formaldehyde at room temperature over supported gold catalysts by Bing-Bing Chen; Chuan Shi; Mark Crocker; Yu Wang; Ai-Min Zhu (pp. 245-255).

Display Omitted► This paper firstly reported complete oxidation HCHO into CO₂ and H₂O over Au/CeO₂(DPU) catalyst at room temperature. ► Au/CeO₂(DPU) catalyst shows 100% conversion of HCHO even in the presence of water and at high GHSV (143,000h⁻¹). ► Charge transfer weakened the CeO bond and facilitated the generation of comparatively more active surface oxygen species. ► Consumption of the formate intermediates is the rate limiting step for catalytic oxidation of HCHO over Au/CeO₂ catalysts.Two kinds of Au/CeO₂, prepared by deposition–precipitation (DP) using urea (U) or NaOH (N) as precipitants were investigated as catalysts for HCHO oxidation. H₂-TPR and XPS techniques were used to characterize the Au/CeO₂ samples. Due to the generation of increased amounts of active surface oxygen species resulting from the strong Au–CeO₂ interaction, the Au/CeO₂ (DPU) catalyst showed higher activity than the DPN catalyst, achieving 100% conversion of HCHO into CO₂ and H₂O at room temperature, even in the presence of water and at high GHSV (143,000h⁻¹); moreover, the conversion was stable for at least 60h. The reaction mechanism and the rate limiting steps for HCHO oxidation over the Au/CeO₂ catalysts were identified by means of in situ DRIFTS studies. The influence of oxygen and water on the formation and consumption of the formate reaction intermediates was also investigated. Results suggest that Au/CeO₂ (DPU) is a promising catalyst for HCHO removal under real world conditions.

Keywords: Formaldehyde; Catalytic oxidation; Au/CeO; ₂; Room temperature

Comparison of different precious metals in activated carbon-supported catalysts for the gas-phase hydrodechlorination of chloromethanes by M. Martin-Martinez; L.M. Gómez-Sainero; M.A. Alvarez-Montero; J. Bedia; J.J. Rodriguez (pp. 256-265).

.Display Omitted► Pd/C, Pt/C, Rh/C and Ru/C were active in the HDC of MCM, DCM and TCM. ► The catalysts show significant differences in the activity and selectivity to reaction products. ► They are related to the different electronic structure and oxidation state of metals. ► Different reaction pathways were found depending on the catalyst and the starting CM.Four precious metals supported on activated carbon are compared as catalysts in the gas-phase hydrodechlorination (HDC) of chloromethanes. The intrinsic activity or turnover frequency (TOF) of the catalysts follows the order Pd/C>Rh/C>Pt/C>Ru/C in the HDC of dichloromethane (DCM) while the sequence Pd/C>Pt/C>Rh/C>Ru/C was found for the HDC of chloroform (TCM). High selectivities to non-chlorinated products were obtained in all cases except for the HDC of TCM with Rh/C and Ru/C where the selectivity to DCM greatly depends on the operating conditions. A wider diversity of non-chlorinated hydrocarbons was obtained as reaction products with these two catalysts, especially in the HDC of TCM, favoring the formation of carbonaceous deposits which provoked a marked deactivation of the catalysts. In contrast, CH₄ was the only non-chlorinated product obtained with the Pt/C catalysts which showed by far the highest stability. Different reaction pathways were found depending on the catalyst and the starting chloromethane. The different reactivity of the metals is explained in terms of their different electronic structure and the physicochemical properties of the catalysts.

Keywords: Hydrodechlorination; Residual gases; Chloromethanes; Carbon-supported metallic catalysts; Reaction scheme

Mechanistic investigations of the promoting role of Rh on the NSR performance of NO_x storage BaO-based catalysts by Stanislava Andonova; Valentina Marchionni; Marta Borelli; Radka Nedyalkova; Luca Lietti; Louise Olsson (pp. 266-281).

Display Omitted► Barium nitrates decomposes at lower temperature with Rh present compared to Pt. ► NO_x spill-over is increased using Rh compared to Pt, due to increased O₂ desorption. ► N₂O dissociation forming N₂ and O₂ occurs already at 373K on Rh, but 573K on Pt. ► NO_x storage in presence of water is much slower, but the storage capacity is larger. ► Water increases formation of bulk nitrates with higher stability.To determine the promoting effect of Rh on the overall NO_x storage and reduction (NSR) performance, the studies in the current work were directed toward investigating the storage and release ability over Rh NO_x storage BaO-based catalysts compared to Pt. In terms of the metal surface dispersion and the ability of the noble metals to release oxygen at lower temperatures, the synthesized catalysts were characterized by means of dynamic CO chemisorption (RT) and N₂O dissociation (RT - 773K). The NO_x storage capacity and the thermal stability of the NO_x adsorbed species formed on the surface were analyzed via NO_x storage tests and temperature programmed desorption (TPD) without and in the presence of CO₂ and H₂O. In addition, experiments with lean and rich cycling were conducted at 473, 573 and 673K. The results from the N₂O dissociation experiments showed the superior ability of Rh/Al and Rh/Ba/Al catalysts compared to Pt toward O₂ release from the catalytic surface at lower temperatures. In this work, we show that the presence of Rh into the BaO/γ-Al₂O₃ system has a considerable effect on the spill-over process of NO_x to the precious metal, controlling the subsequent desorption of NO_x to occur at lower temperatures in comparison with that of the Pt catalysts. It is suggested a mechanism of NO_x desorption where the lower temperature of O₂ release from the surface of Rh catalysts could leave a significant number of noble metal sites accessible for adsorption. Thus this could facilitate the rate of spill-over of NO_x from the storage site (the surface sites on γ-Al₂O₃ and those on BaO) to the noble metal and their desorption at lower temperatures. The limited NO_x storage ability of the Rh-based BaO/γ-Al₂O₃ catalysts under lean-burn conditions was found to originate from both low NO oxidation activity and NO_x reduction activity, while the main limiting factor for the low NSR performance of the Pt-based catalysts was the limited regeneration ability during rich period.

Keywords: NO; _x; storage/reduction; Pt; Rh; BaO; noble metal; TPD; N; ₂; O decomposition; CO chemisorption

Understanding the impact of aluminum oxide binder on Ni/HZSM-5 for phenol hydrodeoxygenation by Chen Zhao; Yanzhe Yu; Andreas Jentys; Johannes A. Lercher (pp. 282-292).

Display Omitted► Ni/Al₂O₃-HZSM-5 had almost three times more accessible Ni atoms than Ni/HZSM-5. ► TPR found that Ni oxide on Al₂O₃-HZSM-5 was more difficult to reduce due to the formation of NiO–Al₂O₃ ‘pseudo spinels’. ► The BAS concentration of Ni/Al₂O₃-HZSM-5 highly decreased because the small Ni nanoparticles nucleated at obstructed BAS sites. ► The in situ IR showed that Al₂O₃-HZSM-5 had higher adsorption capacities than HZSM-5 due to the added γ-Al₂O₃ binder.The properties of supported Ni particles on HZMS-5 and Al₂O₃-HZSM-5 were comparably investigated by diverse characteristic techniques. Ni/Al₂O₃-HZSM-5 had at least three times higher concentrations of accessible Ni atoms (average diameter Ni⁰: 8.8nm) compared to Ni/HZSM-5 (average diameter Ni⁰: 35nm), which are consistently evidenced by TEM and XRD as well as H₂ chemisorption and IR spectra of adsorbed CO. The Ni nanoparticles interacted strongly with the binder through the interaction between NiO and Al₂O₃, explored by the combined extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and H₂ temperature-programmed reduction (TPR) techniques. The Brønsted acid sites on two supports probed by IR of adsorbed pyridine were similar, but Lewis acid sites contributed by the γ-Al₂O₃ were more abundant on Al₂O₃-HZSM-5. The acid sites of the two catalysts responded differently to metal incorporation and subsequent treatments, reflecting changes in Al environments illuminated by²⁷Al MAS NMR. In situ IR spectra of adsorbed species demonstrates that Al₂O₃-HZSM-5 has higher adsorption capacity for phenol, cyclohexanone, and cyclohexanol due to stronger adsorption of these compounds on the γ-Al₂O₃ binder.

Keywords: Al; ₂; O; ₃; binder; ²⁷; Al and; ²⁹; Si MAS NMR; EXAFS; XANES

Lean NO_x reduction on LNT-SCR dual-layer catalysts by H₂ and CO by Yi Liu; Yang Zheng; Michael P. Harold; Dan Luss (pp. 293-303).

.Display Omitted► CO inhibition of LNT mitigated by adding ceria and adding top layer of SCR. ► Ceria zoning in LNT layer exhibits high NO_x conversion over wide temperature range. ► PGM loading in the LNT layer can be reduced by increasing the SCR loading. ► NO_x conversion is improved by optimizing the lean-rich cycle ratio and duration.Lean reduction of NO_x (NO & NO₂) by H₂ and CO was conducted over monolithic catalysts consisting of a selective catalytic reduction (SCR) catalyst layer deposited on top of a lean NO_x trap (LNT) catalyst. An increase in the CO/H₂ ratio decreased the cycle-averaged NO_x conversion for the ceria-free LNT catalyst. CO poisoning was especially significant below 250°C. The low-temperature NO_x reduction was increased either by use of an LNT-SCR dual-layer catalyst or deposition of CeO₂ on the LNT catalyst. However, the ceria decreased the high-temperature reductive conversion of NO_x due to promotion of the undesired NH₃ oxidation. Ceria zoning enhanced the monolith NO_x conversion. Downstream loading of ceria led to the highest NO_x reduction at both low- and high- temperatures due to the beneficial interaction of the ceria and H₂. The low-temperature NO_x conversion of an aged dual-layer catalyst could be increased by a higher SCR catalyst loading. However, at high temperatures NO_x reduction was independent of the SCR loading. The ratio of the lean to rich feed duration and the total cycle time were optimized to improve the NO_x conversion in a temperature range from 150 to 400°C. The highest cycle-averaged NO_x conversion was obtained with a 30s:5s lean-rich cycle containing 1.25% total reductant for all CO/H₂ ratios for a lean feed containing 500ppm NO and 5% O₂.

Keywords: Dual-layer catalyst; Monolith; Lean NO; _x; trap; NO; _x; Selective catalytic reduction; NO; _x; storage and reduction; Zoning ceria; Cu; ZSM-5; NH; ₃; Pt; CO; H; ₂

Bismuth vanadate hollow spheres: Bubble template synthesis and enhanced photocatalytic properties for photodegradation by Jingxue Sun; Gang Chen; Jingzhu Wu; Hongjun Dong; Guihong Xiong (pp. 304-314).

.Display Omitted► Hollow sphere m-BiVO₄ is simply synthesized via a simple hydrothermal method. ► Urea is used as bubble guiding surfactant. ► The formation process is bubble guiding attachment and repining. ► m-BiVO₄ shows optimalizing activity for degradation of RhB and 2-propanol.Hollow sphere monoclinic scheelite BiVO₄ ( m-BiVO₄) is simply synthesized via a simple hydrothermal method by using urea as guiding surfactant. The forming process is investigated to be the incorporation of bubble guiding, oriented attachment and Ostwald ripening. The heterostructured hollow spheres are built up of truncated octahedrons which are also found to be feasible based on theoretical calculation. The preferred truncated octahedron consists of {040}, {011}, and {110} crystal planes with multiplicities of 2, 2, and 4, respectively. Besides urea, different kinds of organic additives (citric acid, Vitamin C and oleic acid) are also chosen for the synthesis of m-BiVO₄ to clarify the role of urea. The photocatalytic activities with different morphologies are evaluated on the degradation of Rhodamine B. It is found out that the m-BiVO₄ with hollow structure shows the optimalizing activity and the reaction rate constant reaches up to 0.035min⁻¹ without adding H₂O₂ as hydroxyl radicals provider. Except for activity, the as-prepared samples have high stability and durability, after four cycling runs of photodegradation of RhB, the photocatalytic ability of as-synthesized m-BiVO₄ did not show any loss. The degradation of RhB is attributed to intrinsically strong photo-oxidation ability rather than photosensitization and the synthesized samples also shows efficient photocatalytic activity for the degradation of 2-propanol. Meanwhile, the reasons for the superior activity are also carefully investigated.

Keywords: Hollow spheres; Bubble template; Photodegradation; Formation mechanism

Water splitting from dye wastewater: A case study of BiOCl/copper(II) phthalocyanine composite photocatalyst by Ling Zhang; Wenzhong Wang; Songmei Sun; Yuanyuan Sun; Erping Gao; Jie Xu (pp. 315-320).

The overall water splitting reaction to H₂ and O₂ is realized on BiOCl/CuPc (copper phthalocyanine) composite from RhB (rhodamine B) solution under simulated solar light irradiation.Display Omitted► BiOCl/CuPc composite photocatalyst have been prepared by precipitation method. ► BiOCl/CuPc photoelectrode shows an enhanced photocurrent density. ► Photocatalytic activity of BiOCl/CuPc is much higher than that of BiOCl. ► Water splitting reaction on BiOCl/CuPc was achieved in methanol/H₂O/RhB solution.Oxygen evolution is frequently the bottleneck determining the efficiency in the overall photocatalytic water splitting. Herein, for the first time overall water splitting reaction to H₂ and O₂ is realized on BiOCl/CuPc (copper phthalocyanine) composite from RhB (rhodamine B) solution under simulated solar light irradiation. The photosensitized RhB dye molecules supplied photo-generated holes which took part in the reaction of O₂ evolution. By loading CuPc, the efficiency of H₂ evolution is improved. On the base of the greatly enhanced photocurrent density, the considerable enhancement of performance can be attributed to the quick transfer of photogenerated electrons from the photosensitizer to the CB (conduction band) of BiOCl. Furthermore, as active electron traps, the oxygen vacancies on the surface of the BiOCl photocatalyst promote the separation efficiency of photo-generated electrons and holes, resulting in high photoactivity. This study presents a way that organic dye wastewater will be a useful system for the overall photocatalytic water splitting reaction to H₂ and O₂.

Keywords: BiOCl; Copper phthalocyanine; Photocatalytic; Water splitting; Photosensitizer

Reactive adsorption of hydrogen sulfide on visible light photoactive zinc (hydr)oxide/graphite oxide and zinc (hydr)oxychloride/graphite oxide composites by Oluwaniyi Mabayoje; Mykola Seredych; Teresa J. Bandosz (pp. 321-331).

Display Omitted► H₂S capacity of the composites increases with an increase in the GO content. ► Terminal hydroxyl groups of zinc (hydr)oxide are active in the adsorption process. ► Exposure to visible light decreases the H₂S capacity as a result of its oxidation. ► High energy adsorption centers are formed on the composite surfaces.Composites of zinc (hydr)oxide and graphite oxide (GO) with 2, 5, and 20wt.% of the GO component were obtained by precipitating zinc hydroxide from zinc chloride with dispersed GO present in the solution. The materials were evaluated as adsorbents of hydrogen sulfide at ambient conditions. The surface properties of the initial and exhausted samples were studied by FTIR, XRD, SEM/EDX, TEM, nitrogen adsorption, potentiometric titration, microcalorimetry, and thermal analysis. The adsorption capacity increases with an increase in the content of GO in the composites studied. The lower adsorption capacities measured for the samples with 2 and 5wt.% of graphite oxide are linked to the zinc (hydr)oxychlorides phase present in these composites. The heats of H₂S adsorption on the zinc (hydr)oxide and its composites were measured in nitrogen and in air flow. The results indicate that highly energetic adsorption centers are formed on the composite surfaces. Exposure to visible light decreases the H₂S adsorption capacity. This behavior is linked to photoactivity that leads to the reduction of the composite and formation of sulfur and sulfites/sulfates. These processes involve active centers,OH groups, which react with hydrogen sulfide.

Keywords: Visible light activity; Graphite oxide; Zinc (hydr)oxide; Zinc (hydr)oxychlorides; Composites; H; ₂; S adsorption; Surface reactivity

A novel BiOCl thin film prepared by electrochemical method and its application in photocatalysis by Xiaochao Zhang; Xiaoxia Liu; Caimei Fan; Yawen Wang; Yunfang Wang; Zhenhai Liang (pp. 332-341).

The schematic diagrams of preparation process for BiOCl thin films and the possible synergistic mechanism for electrons and holes transport between BiOCl bulk states and (110) surface states.Display Omitted► A novel BiOCl thin film was prepared by electrochemical method for the first time. ► BiOCl with highly exposed (110) plane distributed uniformly on the Ti substrate. ► Synergistic effect of BiOCl bulk and (110) surface states enhanced carrier transport. ► As-prepared thin film exhibited wonderful photocatalytic activity and stability. ► BiOCl film shows a competitive and promising application in photocatalysis field.In this study, a novel BiOCl thin film with flakelike structures has been successfully prepared through electrochemical method composed of a cathodic electrodeposition and an anodic oxidation at room temperature. The samples obtained at the different oxidation voltages were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), electronic energy spectrum (EDS), and UV–vis diffuse reflectance spectra (UV–vis DRS). The analysis results show that the morphological, structural, and optical characteristics of BiOCl thin films depend markedly on the anode oxidation voltage and the lattice orientation of BiOCl thin film is transformed mainly into (110) surface with the increasing oxidation voltages. The observed results of high-resolution transmission electron microscopy (HRTEM) confirm that pure tetragonal BiOCl thin film with the highly exposed (110) surface is obtained at 2.0V and consists of interlaced nanosheets. First-principles calculations reveal that the existence of BiOCl (110) surface states enhances the electron transition and efficient separation of photo-induced electron–hole pairs. The optimized BiOCl thin film can not only guarantee the intrinsic photochemical properties of BiOCl bulk but also exhibit additional electronic characteristics of BiOCl (110) surface, and consequently the wonderful synergistic effect between BiOCl bulk and BiOCl (110) surface accelerates the efficient separation of electron–hole pairs and produces the high reducing superoxide radicals O₂⁻ and strong oxidizing hydroxyl radicalsOH required for the degradation of organic compounds. For as-prepared BiOCl thin film, the degradation ratio of methyl orange (MO) reaches 98% under 2.5h UV irradiation at the first cycle and still remains 90% at the fifth cycle, and the COD removal efficiency of 50mg/L MO solution over BiOCl thin film achieves 73.47% after 8h reaction time. The BiOCl thin film with highly exposed {110} facets exhibits the excellent photocatalytic performance and potential application in photocatalysis field.

Keywords: BiOCl thin film; Electrochemical method; Photocatalysis; Methyl orange

Catalytic wet air oxidation of bisphenol A model solution in a trickle-bed reactor over titanate nanotube-based catalysts by Boštjan Erjavec; Renata Kaplan; Petar Djinović; Albin Pintar (pp. 342-352).

Display Omitted► Hydrothermal synthesis route produced high surface area titanate nanotubes. ► Complete removal of bisphenol A was achieved in the CWAO process. ► Significant TOC conversions were attained over bare TiO₂-based catalysts. ► Negligible amount of carbonaceous deposits was accumulated on the catalyst surface.Titanate nanotube-based catalysts were prepared via alkaline hydrothermal synthesis route followed by heat-treatment at different temperatures, ranging from 300 to 700°C. The resulting metal-free solids were then applied as a catalyst in a three-phase trickle-bed reactor, where catalytic wet air oxidation (CWAO) reactions of model aqueous bisphenol A (BPA) solution were performed. Mainly, the CWAO experiments were conducted at 200°C with oxygen partial pressure of 10bar over 300mg of a catalyst. It was observed in the given range of operating conditions that BPA undergoes both non-catalytic as well as catalytic oxidation routes, while the latter is far more pronounced. At 210°C and in the presence of 0.5g of titanate nanotube-based catalyst, which was annealed at 600°C, complete BPA removal was obtained. From TOC point of view, approximately 70% conversion was achieved indicating the persistence of refractory intermediates of lower carboxylic acids. The cross-section of results derived from various analytical techniques, which were used to identify surface, textural and morphological properties, revealed that balanced physicochemical properties are required to achieve meaningful extent of BPA removal. During 2–4 day time on stream, no catalyst deactivation occurred that could be attributed to the dissolution of active powders, or to the carbonaceous deposits accumulated on the catalyst surface. Therefore, these nanotubular materials can be regarded as innocuous and efficient long-term catalysts for oxidation of hazardous organic compounds (such as BPA) in the CWAO process.

Keywords: Catalytic wet air oxidation; Bisphenol A; TiO; ₂; Water treatment; Titanate nanotubes; Hydrothermal synthesis

The improved reactivity of manganese catalysts by Ag in catalytic oxidation of toluene by Zhenping Qu; Yibin Bu; Yuan Qin; Yi Wang; Qiang Fu (pp. 353-362).

Display Omitted► Ag/Mn ratio of 1:3 is an appropriate ratio for high activity for toluene oxidation. ► Ag enters into MnO₂ phase and leads the formation of Ag_1.8Mn₈O₁₆ and Mn₂O₃. ► The ratios of Mn³⁺/Mn⁴⁺and O_latt/O_surf on the Mn catalyst are increased by Ag. ► The oxygen mobility and reducibility of manganese oxides are enhanced by Ag. ► The formation of benzaldehyde is closely related with lattice oxygen of the catalyst.The effects of Ag on Mn/SBA-15 catalysts have been investigated in the toluene catalytic oxidation. The reactivity of catalysts is related closely to the Ag/Mn molar ratio, and the sample with 1:3 of Ag/Mn molar ratio exhibits the highest reactivity for toluene oxidation, with a complete conversion at 260°C. Based on the characterization results, it is found that Ag enters into MnO₂ phase, and the Ag_1.8Mn₈O₁₆ mixed phase forms. Meanwhile Ag leads to parts of MnO₂ being transformed into Mn₂O₃. The Ag/Mn molar ratio has a strong influence on the molar ratio of the surface Mn⁴⁺ to Mn³⁺ and surface adsorbed oxygen (O_ads) to lattice oxygen (O_latt) through the interaction between silver and MnO_x. The coexistence of MnO₂, Mn₂O₃, Ag_1.8Mn₈O₁₆, and the strong interactions between Ag and Mn species exhibit a good synergetic interaction, which promotes the reducibility of catalysts and the formation of abundant active lattice oxygen, thus increasing the catalytic activity of toluene oxidation. And the formation of intermediate benzaldehyde should be closely link with the lattice oxygen of the Mn based catalyst.

Keywords: Toluene oxidation; Ag-Mn/SBA-15; Redox properties; Lattice oxygen; Interaction

Synthesis and catalysis of copper sulfide/carbon nanodots for oxygen reduction in direct methanol fuel cells by Zih-Yu Shih; Arun Prakash Periasamy; Pin-Che Hsu; Huan-Tsung Chang (pp. 363-369).

Cu2−_xS/carbon nanodot and Cu2−_xS/carbon nanotube nanomaterials were used as cathode catalysts for oxygen reduction reaction in acidic media.Display Omitted► Cu2−_xS (Cu₂S and Cu₉S₅)/carbon dots (C dots) were prepared. ► The Cu2−_xS/C dot electrode is active for oxygen reduction reaction in acidic media. ► The onset potential for the Cu2−_xS/C dot electrode is 0.92V (vs. Ag/AgCl). ► The Cu2−_xS/C dot electrode is durable and cost-effective. ► The Cu2−_xS/C dot is potential catalyst for direct methanol fuel cells.We have fabricated Cu2−_xS/carbon nanodot (C dot) electrodes for direct methanol fuel cells (DMFCs). To the best of our knowledge, this is the first time that Cu2−_xS/C dot nanomaterials (NMs) were proposed to be used as a cathode catalyst for oxygen reduction reaction (ORR) in acidic media. The structural characterizations revealed that Cu2−_xS alloy possessed two types of crystalline phases, such as Cu₉S₅ and Cu₂S in the structure of Cu2−_xS/C dot NMs. The onset potential of the ORR for Cu2−_xS/C dot NMs is 0.92V (vs. Ag/AgCl), revealing a good ORR activity of these NMs. The Cu2−_xS/C dot electrodes (mass loading: 2.26mgcm⁻²) provide a mean limiting density of −1.77mAcm⁻² at a scan rate of 5mVs⁻¹ and rotation rate of 3600rpm. Electrochemical impedance spectrometry (EIS) results revealed that the charge-transfer resistance ( R_ct) of the Cu2−_xS/C dots was smaller than that of Cu2−_xS/CNT. In addition, compared with Pt/C electrodes, Cu2−_xS/C dot electrodes were more tolerant against MeOH poisoning. The low-cost, electrochemically stable, and highly active Cu2−_xS/C dot electrode has great potential for use in DMFCs.

Keywords: Carbon nanodots; Cathode catalyst; Cu; 2−; _x; S; Fuel cells; Oxygen reduction reaction

Performance of layered birnessite-type manganese oxide in the thermal-catalytic degradation of polyamide 6 by Erdal Eren; Murat Guney; Bilge Eren; Huseyin Gumus (pp. 370-378).

Breaking of the hydrogen bonds between PA6 chains after BMO addition.Display Omitted► Synthesis, characterization, and catalytic properties of LMO were discussed. ► The LMO presented an excellent catalytic property to decomposition of PA6. ► A marked reduction in the degradation temperature in the presence of LMO. ► The thermal-catalytic degradation efficiency increased with increasing the amount of LMO. ► The thermal oxidation mechanisms were investigated by IR, XRD and TA techniques.The nature and the extent of degradation of polyamide 6 (PA6) in the presence of layered birnessite-type manganese oxide (LMO) were analysed by thermogravimetric analysis under static air atmosphere at several heating rates between 5°C/min and 20°C/min. The samples were characterized using infrared (IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ gas adsorption–desorption and thermal analysis (TA) techniques. XRD and DTA results for LMO showed that the oxidative transformation of MnO₂ was occured on heating from 300°C to 500°C. The IR spectra of Mn–O band proved the covalent character of oxygen bonding to the metal ions of the surface. The addition of LMO caused the change in the crystalline phase of PA6 from predominantly α to largely γ phase. The activation energy for degradation estimated by Kissinger method for PA6 and 10wt.% LMO/PA6 composite were found to be 213 and 118kJ/mol in static air atmosphere, respectively. The experimental results revealed that the addition of 10wt.% LMO decreased the thermal stability in static air of PA6 by about 80°C.

Keywords: Polyamide 6; Catalytic degradation; Birnessite; Layered oxides; Oxidation

Nitrogen-doped reduced graphene oxide supports for noble metal catalysts with greatly enhanced activity and stability by Daping He; Yulin Jiang; Haifeng Lv; Mu Pan; Shichun Mu (pp. 379-388).

.Display Omitted► N-doped reduced graphene oxide (NRGO) with high N content was created by lyophilization-assisted and mild N-doping method. ► Dominant pyridinic-N and quaternary-N forms in NRGO enhance dispersed state of Pt and electron density of supports. ► Pt/NRGO catalyst shows superior catalytic activity and nearly no loss of activity after 1000 potential cycles. ► Doped-N in NRGO would be exposed as bench-warmer active sites with potential cycles.Pt nanoparticles supported on nitrogen-doped reduced graphene oxide (NRGO) were investigated for use as proton exchange membrane fuel cell catalysts. Artfully, NRGO was synthesized using a lyophilisation-assisted N-doping method, and simultaneous reduction of graphene oxide (GO) was achieved. A nitrogen content as high as 5.06% was obtained with pyridinic-N as the dominant nitrogen species. Pt nanoparticles with an average diameter of 2.5nm were uniformly loaded on NRGO using impregnation methods. Both cyclic voltammetry and oxygen reduction reaction (ORR) measurements revealed a higher catalytic activity and lower losses of the electrochemically active surface area of this novel Pt/NRGO catalyst in comparison to those of the Pt/GO and conventional Pt/C catalysts. Significantly, the catalytic activity of the Pt/NRGO in ORR showed almost no degradation even after 1000 potential cycles, indicating that our new catalysts have excellent stability. A mechanism for improving the ORR activity and the stability of the Pt/NRGO was tentatively proposed and discussed.

Keywords: Catalysts; Reduced graphene oxide; Nitrogen-doping; Oxygen reduction reaction; Proton exchange membrane fuel cells

A search for alternative Deacon catalysts by Markus Hammes; Martin Valtchev; Marion B. Roth; Klaus Stöwe; Wilhelm F. Maier (pp. 389-400).

Display Omitted► Ru or Cr doped Co spinel catalysts stable Deacon catalysts. ► Catalysts are chlorinated during long term testing, but the STY is not affected. ► New corrosion resistant sequential 10-fold fixed bed gas phase reactor applied. ► Stability of mixed oxides correlates with bulk chlorination tendency. ► Best catalysts discovered were optimized through doping and composition variation.High-throughput methods, emissivity-corrected infrared thermography (ecIRT) and a sequential 10-fold fixed bed gas phase reactor have been used to accelerate the development of new catalysts for the Deacon process (4 HCl+O₂⇌2 Cl₂+2 H₂O). Both setups were modified to withstand the corrosive process conditions. Besides the reactor equipment also the catalysts themselves often suffered corrosion during the reaction. To consider the catalyst corrosion the tested oxides were typically aged for 24h under a HCl-O₂ atmosphere at reaction temperature. The experimentally observed stability of selected binary mixed-metal oxides is correlated with literature data for the bulk chlorination tendency of the pure oxides and the corresponding melting/sublimation point of the chloride. The starting binary mixed-metal oxides have been selected based on a set of thermodynamic data for bulk chlorination and chloride oxidation and doping of TiO₂ and SnO₂, which are preferentially used as catalyst supports in Deacon reactions. The best catalysts discovered were optimized through doping and composition variations. Characterization of the best materials is provided.

Keywords: Deacon catalyst; Chlorine Production; Catalyst stability; Catalyst corrosion; High throughput; Emissivity corrected IR-thermography

Heterogeneous catalytic reaction of elemental mercury vapor over cupric chloride for mercury emissions control by Xin Li; Zhouyang Liu; Jinsoo Kim; Joo-Youp Lee (pp. 401-407).

Display Omitted► CuCl₂ oxidizes Hg(0) vapor while oxidizing Hg(0) to HgCl₂ and reducing itself to CuCl. ► The reduced CuCl can be re-chlorinated to CuCl₂ with HCl and O₂ gases in flue gas. ► Hg(0) is oxidized by a heterogeneous reaction with surface Cl atom of CuCl₂. ► The Hg(0) oxidation follows a Mars–Maessen mechanism with CuCl₂ redox catalyst. ► CuCl₂ can continue to oxidize Hg(0) vapor under very high SO₂ concentrations.In this study, the reaction mechanism of Hg(0) vapor oxidation over cupric chloride (CuCl₂) was investigated using 10% (wt) CuCl₂/α-Al₂O₃ for mercury emissions control from coal-fired power plants. The CuCl₂/α-Al₂O₃ sample showed >90% Hg(0) oxidation with excellent resistance to SO₂ at 140°C in a simulated flue gas containing 10ppmv HCl, 2000ppmv SO₂, and 6% O₂ gases balanced with N₂ gas. In the absence of HCl and O₂ gases, Hg(0) vapor was found to be oxidized by consuming atomic Cl of CuCl₂ and reducing it to CuCl, following a Mars–Maessen mechanism. The reduced CuCl could be re-chlorinated back to CuCl₂ by replenishing empty Cl atoms under 10ppmv HCl and 6% O₂ gases readily present in coal combustion flue gases even under 2000ppmv SO₂ concentration for continuous Hg(0) oxidation. Cl₂ gas generation was not observed over CuCl₂ at 140°C, indicating a heterogeneous catalytic reaction. CuCl₂ shows potential that can be realized in a honeycomb or plate catalyst bed.

Keywords: Elemental mercury oxidation; Cupric chloride; Redox catalyst; Coal combustion flue gas

Heterogeneous photo-enhanced conversion of carbon dioxide to formic acid with copper- and gallium-doped titania nanocomposites by P.L. Richardson; Marisa L.N. Perdigoto; W. Wang; Rodrigo J.G. Lopes (pp. 408-415).

Display Omitted► The photocatalytic reduction of CO₂ into HCOOH has been investigated. ► Ga- and Cu-doped catalysts were characterized by means of XRD, TEM, XPS, XANES, and BET/BJH. ► Both dopants acted as electron trappers circumventing the recombination of hole and electron. ► Cu_x–Ga1−_x/TiO₂ catalysts exhibited bandgaps higher than 3eV. ► Cu_0.78–Ga_0.22/TiO₂ was photocatalytically the most active with the highest selectivity.Copper- and gallium-doped titania photocatalysts prepared by means of sol–gel technique were comparatively evaluated with commercial TiO₂ (P25) for the photo-reduction of carbon dioxide to formic acid. The laboratory-made Cu_x–Ga1−_x/TiO₂ nanocomposites have been thoroughly characterized in crystallographic, structural, morphological, and elemental composition analyses. XRD revealed photocatalysts owning the specific crystalline phases of anatase, β-Ga₂O₃ and Cu₂O, which allowed inferring on the doping phenomena of both transition and post-transition metals. The quasi-homogeneous deposition of a Ga and Cu layer has been identified from the TEM morphological characterization and the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda techniques unveiled quantitative differences in textural properties among the mesoporous Ga- and Cu-doped titania photocatalysts by underlining a decrease of surface area when augmenting the gallium dose. The laboratory-made photocatalysts presented bandgaps higher than 3eV and the DRS spectra underlined the optical absorption edge of the nanocomposites with a considerable shift to the visible light region. The elemental composition quantified by means of XPS reproduced the binding energies relative of Ti, Cu and Ga (2p_3/2, 2p_1/2), and the K-edge XANES characterization confirmed the effective doping and modulation of the electronic properties of the laboratory-made photocatalysts. Several experimental runs have been carried out with Cu_0.78–Ga_0.22/TiO₂ exhibiting the highest formic acid yields (394μmol/g_cat) as well as superior quantum efficiency (49%) and selectivity (0.84). Accordingly, the photo-reduction of CO₂ was considerably promoted by doping Ga and Cu into the titania substrate, which ultimately avoided the surface recombination of electron–hole pairs, thereby enhancing the photo-activity of Cu_x–Ga1−_x/TiO₂ nanocomposites.

Keywords: Photo-reduction; Carbon dioxide; Copper; Gallium; Titania; Formic acid

Halloysite–TiO₂ nanocomposites: Synthesis, characterization and photocatalytic activity by Dimitrios Papoulis; Sridhar Komarneni; Dionisios Panagiotaras; Elias Stathatos; Despina Toli; Konstantinos C. Christoforidis; Marcos Fernández-García; Huihui Li; Shu Yin; Tsugio Sato; Hiroaki Katsuki (pp. 416-422).

Display Omitted► Halloysite–TiO₂ nanocomposites were prepared under hydrothermal treatment at 180°C. ► The nanocomposites showed significantly higher activity in decomposing NO_x gas compared to P25. ► Composite photocatalyst showed larger catalytic activity in decomposing toluene compared to the P25.Two halloysite–TiO₂ nanocomposites were prepared with two different tubular halloysite clays by depositing anatase-TiO₂ on the halloysite surfaces using titanium isopropoxide under hydrothermal treatment at 180°C. The nanocomposites were characterized by X-Ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), attenuated total reflection using Fourier transform infrared spectroscopy (ATR-FTIR), absorption properties by UV–vis spectroscopy and N₂ specific surface area (SSA) analysis by BET method. Good dispersion of 3–10nm TiO₂ particles on halloysite external surfaces was achieved in both the halloysite–TiO₂ nanocomposites and ATR-FTIR results showed the formation of hydrogen bonding between TiO₂ and the outer surfaces of halloysite tubes. After treating with TiO₂, both halloysite samples largely showed interparticle mesopores of about 5.7nm. However, the macropores of halloysite (lumen or central hole in halloysite tubes) were not detected probably as a result of plugging of the lumens in halloysite tubes by TiO₂ nanoparticles. These nanocomposites were tested for their photocatalytic activities in decomposing NO_x gas and toluene. The halloysite–titania samples showed significantly higher activity in decomposing NO_x gas under visible-light irradiation ( λ>510nm) and UV–visible light irradiation ( λ>290nm) compared to that of the standard commercial titania photocatalyst, P25. In addition, composite photocatalyst showed larger catalytic activity either under sunlight or pure UV irradiation in decomposing toluene compared to the commercial titania, P25. Our experimental data suggest that the enhanced photocatalytic activity is related with the good dispersion of the TiO₂ nanocrystals on the surface of the clay minerals.

Keywords: Halloysite; Titania; Nanocomposite; Photocatalytic activity

Tungsten as an interface agent leading to highly active and stable copper–ceria water gas shift catalyst by Anna Kubacka; Rui Si; Piotr Michorczyk; Arturo Martínez-Arias; Wenqian Xu; Jonathan C. Hanson; José A. Rodriguez; Marcos Fernández-García (pp. 423-432).

Display Omitted► System prepared from an initial ternary oxide with fluorite structure. ► High activity and stability at temperatures above 300C and GHSV of 42,000h⁻¹. ► In situ XRD-XAS-Vibrational experiments show that presence of a W–Cu mixed oxide phase is key to enhance catalytic properties.A series of W–Cu–Ce mixed oxide catalysts prepared by microemulsion was evaluated in the water-gas shift (WGS) reaction. At low temperatures (<350°C), the total conversion of CO on the W–Cu–Ce systems was two times larger than on binary Cu–Ce mixed oxides which are well known catalysts for the WGS. In addition and in contrast with Cu–Ce, W–Cu–Ce catalysts were stable and no signs of deactivation were found after 10h of reaction time. The rationale for the excellent catalytic performance presented by the W–Cu–Ce ternary oxide was elucidated from the viewpoint of a complete structural (e.g. analysis of the long and short range order) and redox behavior characterization using in situ, time-resolved X-ray diffraction (XRD) as well as X-ray absorption (XAS), infrared (diffuse reflectance Fourier transform DRIFTS) and Raman spectroscopies. From a single phase fluorite-type structure, the catalysts show significant structure/redox evolution under reaction conditions as a function of the W and Cu content. As it occurs in the parent Cu–Ce system, the dominant presence of metallic Cu and fluorite-type oxide phases is detected under reaction conditions for the ternary systems. An outstanding promotion of catalytic properties is nevertheless evidenced for samples with W content above 10 at.% and is shown to be related to the presence of oxidized W–Cu local entities. Such local entities, which are obviously characteristic of the ternary system, greatly enhance fluorite redox properties and play an interfacial role between the main metallic Cu and fluorite-type oxide phases. As a consequence of all these effects, incorporation of W into the initial material leads to efficient WGS catalysts, most promising for their application in the so-called low temperature region, e.g. below 350°C.

Keywords: WGS catalyst; Mixed oxides; Ceria; Copper; Tungsten; In situ XRD; XAFS; Vibrational

Ni/Al–Mg–O solids modified with Co or Cu for the catalytic steam reforming of bio-oil by J. Remón; J.A. Medrano; F. Bimbela; L. García; J. Arauzo (pp. 433-444).

Display Omitted► Ni/AlMg catalysts modified with Cu or Co and prepared by impregnation and coprecipitation. ► Study of the catalyst performance using one-way ANOVA analysis and the multiple LSD test. ► Significant improvement with the NiCo/AlMg catalyst prepared by coprecipitation. ► Comparison of the catalyst performance in fixed bed and fluidized bed reactors.An environmentally friendly method of producing a hydrogen rich gas is the catalytic steam reforming of bio-oil. This requires the development of a catalyst appropriate for the process. In the present work, five different research catalysts have been prepared and tested. A Ni/AlMg catalyst was selected as a reference. Modifications to the catalyst were studied, incorporating Co or Cu by coprecipitation or by incipient wetness impregnation. The experiments took place at 650°C and atmospheric pressure in a fixed bed and in a fluidized bed reactor, using an aqueous fraction (S/C=7.6molH₂O/molC) of pine sawdust bio-oil. A spatial time ( W/ m_org) of 4g catalyst min/g organics and an u/ u_mf ratio of 10 (in fluidized bed) were used. In both reactors, the coprecipitated NiCo/AlMg catalyst showed the best performance. Over a period of 2h, 0.138g H₂/g organics and 80% carbon conversion to gas were obtained in the fixed bed reactor.The catalyst deactivation rate was higher when the steam reforming took place in the fixed bed reactor, although the initial H₂ and CO₂ yields were higher. In contrast, the stability of the catalysts was higher in the fluidized bed reactor. Elemental analysis, FESEM and TPO analyses of some of the catalysts revealed a relationship between their stability and the quantity and characteristics of the coke deposited on their surface.

Keywords: Hydrogen; Bio-oil; Steam reforming; Nickel; Copper; Cobalt; Fixed bed; Fluidized bed

A novel twin reactor for CO₂ photoreduction to mimic artificial photosynthesis by Wei-Hsuan Lee; Chi-Hung Liao; Min-Fei Tsai; Chao-Wei Huang; Jeffrey C.S. Wu (pp. 445-451).

Display Omitted► We demonstrated the photo CO₂ hydrogenation by a novel twin reactor to mimic photosynthesis. ► A twin reactor can separate H₂ and O₂ to prevent the backward oxidation reaction. ► The dual photocatalyst system was more efficient than single photocatalyst system under simulated sunlight AM1.5G.One of the best routes to covert CO₂ into energy and simultaneously reduce atmospheric CO₂ is photosynthesis. In natural photosynthesis, the first step is water splitting in which proton is generated and O₂ is released using solar energy. The second step is the Calvin cycle in which CO₂ is reduced to hydrocarbons. This study demonstrated the photocatalytic hydrogenation of CO₂ by using a novel twin reactor to mimic photosynthesis process in nature. The twin reactor, which divided H₂-generating photocatalyst and O₂-generating photocatalyst in two compartments using a membrane, first achieved separate H₂ and O₂ evolution to prevent the backward reaction to form water under visible light irradiation. The generated hydrogen was then used to perform CO₂ hydrogenation by CO₂ reduction photocatalyst. The advantage is that CO₂ hydrogenation is a spontaneous reaction based on the thermodynamics. The single photocatalyst system using Pt/CuAlGaO₄ as both H₂-generating photocatalyst and CO₂ reduction photocatalyst, was compared with the dual photocatalyst system using Pt/SrTiO₃:Rh and Pt/CuAlGaO₄ as H₂-generating photocatalyst and CO₂ reduction photocatalyst, respectively, under simulated sunlight AM1.5G. The dual photocatalyst system has demonstrated photoreduction quantum efficiency (PQE) of 0.0051%, which is more than doubled the PQE of the single photocatalyst system.

Keywords: CO; ₂; reduction; Photocatalysis; Photosynthesis; Solar; Renewable energy

One-step synthesis of easy-recycling TiO₂-rGO nanocomposite photocatalysts with enhanced photocatalytic activity by Ping Wang; Jin Wang; Xuefei Wang; Huogen Yu; Jiaguo Yu; Ming Lei; Yonggang Wang (pp. 452-459).

Display Omitted► A one-step green hydrothermal method has been developed for the fabrication TiO₂-GO nanocomposite. ► The formation mechanism was based on the initial formation of strong-coupling and the subsequent in situ reduction of GO to rGO during hydrothermal treatment. ► The prepared TiO₂-GO nanocomposite photocatalyst showed an enhanced photocatalytic performance. ► The suspensible TiO₂-rGO composite photocatalysts can be easily separated from the aqueous solution after photocatalytic reaction.The addition of reduced graphene oxide (rGO) in the TiO₂ has been demonstrated to be one of the effective methods to improve the photocatalytic performance of TiO₂ photocatalyst. Despite tremendous efforts, developing facile and green synthetic method of TiO₂-rGO nanocomposites still remains a great challenge. In this study, a one-step green hydrothermal method for the fabrication of easily recycled TiO₂-rGO composites, based on the initial formation of strong-coupling TiO₂-GO nanocomposite and the subsequent in situ reduction of GO to rGO during hydrothermal treatment, was developed in the pure water without using any reductant and surfactant. It is found that the TiO₂ nanoparticles with a clean surface and a good dispersion are highly required for the formation of the easy-recycling TiO₂-rGO composite photocatalyst. Photocatalytic experimental results indicated that compared with the high-efficiency P25 TiO₂ precursor, the photocatalytic performance could be obviously improved (about 23%) for the decomposition of phenol after coupling 1-wt% rGO. The enhanced photocatalytic performance can be attributed the cooperation effect of the effective separation of charge carriers via rGO cocatalyst, the enrichment of phenol molecular on the rGO, and the strong coupling interaction between TiO₂ nanoparticles and rGO nanosheets. Considering its completely green and facile preparation and recyclable feature from an aqueous solution, the present TiO₂-rGO nanocomposite photocatalyst can be regards as one of the ideal photocatalysts for various potential applications.

Keywords: Reduced graphene oxide; TiO; ₂; Photocatalytic activity; Easy recycling; Green method

Photocatalytic activity of N-doped and N–F co-doped TiO₂ and reduction of chromium(VI) in aqueous solution: An EPR study by A.E. Giannakas; E. Seristatidou; Y. Deligiannakis; I. Konstantinou (pp. 460-468).

Display Omitted► N-doped and N–F co-doped TiO₂ catalysts were characterized by EPR spectroscopy. ► N_b and O₂⁻ radicals were formed in N- and N–F TiO₂ and Ti³⁺ in N–F TiO₂ catalysts. ► Electron capturing by O₂ and generation of O₂⁻ was favored for N-doped catalyst. ► Cr(VI) reduction depends on the N_b quantity, crystal size, conduction band energy. ► TNF1 (Ti:N/F molar ratio of 1:1) showed higher photocatalytic reduction of Cr(VI).N-doped and N–F co-doped TiO₂ catalysts were prepared via a sol–gel method using NH₄Cl and NH₄F as N and N–F dopant precursors, respectively, having Ti:N and/or F molar ratios of 1:1, 1:2 and 1:3. The catalysts were tested for the photocatalytic reduction of Cr(VI) in the presence of oxalate ions. XRD analysis showed the formation of TiO₂ anatase phase in all cases. UV–vis DRS spectra showed that both N–F and N-doping resulted in a decrease in the band gap energy ( E_g), at the values of 2.81eV and 3.01eV, respectively. Thus, N–F doped TiO₂ showed enhanced absorption at visible wavelengths. The structure and photodynamics of the TiO₂ catalysts was investigated in detail by electron paramagnetic resonance (EPR) spectroscopy. The EPR data showed that: [i] NO centers, N_b and O₂⁻ radicals were formed. In addition, lattice Ti³⁺ ions were detected in N–F co-doped solids; [ii] the N_b and Ti³⁺ species were photoactive, while the NO species were non-photoactive.The photocatalytic efficiency for Cr(VI) reduction in the presence of oxalate ions, followed the trend TNF1>TN1>TNF2>TN3>TN2>TNF3. Importantly, an apparent correlation between the catalytic efficiency and the concentration of N_b species was revealed by EPR. The location of N_b in the crystal lattice of TiO₂ has been assessed also by measuring their microwave saturation parameters P_1/2. Electron capturing by O₂ and subsequent generation of O₂⁻ was favored for N-doped catalysts. In contrast, in N–F co-doped catalysts, O₂ could not compete efficiently with Cr(VI) for the photogenerated electrons in energy states below the conduction band of TiO₂, resulting in higher reduction efficiency for these catalysts.

Keywords: Photocatalysis; N-doped TiO; ₂; N–F co-doped TiO; ₂; Cr(VI) reduction; EPR; N; _b; species; Microwave saturation

Decomposition of methane over unsupported porous nickel and alloy catalyst by Aik Chong Lua; Hong Yan Wang (pp. 469-478).

FESEM micrographs of Ni and Ni-Cu alloy catalyst particles (top) and their catalytic activities under different reaction temperatures (bottom).Display Omitted► Unsupported NiO and NiO-CuO particles prepared from oxalate were used as catalyst precursors. ► Porous metallic Ni and Ni-Cu alloy are effective catalysts for methane decomposition. ► Nickel–copper alloy particles showed steady catalytic activities at high temperatures. ► Carbon nano-fibres act as living supports and prevent catalyst particles from sintering. ► Ni-Cu catalyst produced the highest methane conversion of 85% at 750°C.Unsupported NiO and NiO-CuO nano-particles were prepared by a facile method and these nano-particles showed promising catalytic activity towards methane decomposition. The decomposition of fibrous nickel (or mixed) oxalate precursors led to the formation of porous oxide aggregates with small primary oxide particles of 8–20nm. Similar to supported catalysts, nickel–copper alloy particles showed steady catalytic activities even at high reaction temperatures (>700°C). Unlike the supported catalysts, it was necessary to introduce methane to the reactor at lower temperatures to avoid catalyst particles sintering into bigger ones during the reaction. The initial carbon nano-fibres (CNFs) acted as living supports to take the catalyst particles away and prevent them from sintering with adjacent particles. The textural properties of the CNFs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and N₂ adsorption. The textural and micro-structural properties depended on the composition of the catalyst and the reaction temperature.

Keywords: Key words; Nickel catalyst; Nickel-copper catalyst; Unsupported catalyst; Methane decomposition; Hydrogen production; Carbon nano-fibre

Catalytic coating synthesized onto cordierite monolith walls. Its application to diesel soot combustion by E.D. Banús; V.G. Milt; E.E. Miró; M.A. Ulla (pp. 479-486).

Display Omitted► The catalytic coating on cordierite monolith exhibits excellent mechanical adherence. ► The thin ZrO₂ layer and the macropores of the monolith allow soot filtration. ► Co, Ba and K were deposited on the surface and inside of the cordierite walls. ► The developed catalyst is a potential candidate for a continuous regeneration filter.Co,Ba,K/ZrO₂ coating onto a cordierite monolith was produced using a sequential process. The first step involved the formation of a ZrO₂ layer using a colloidal suspension and the second, the incorporation of active metals. The coating morphology and its physicochemical properties were studied using different characterization techniques. The ZrO₂ colloidal suspension and the active ingredients, Co, Ba and K, penetrated through the macropores of the cordierite and their interconnections, both being retained inside the walls and on the external surface. After calcination, the active species were BaCO₃, KNO₃ and Co₃O₄.The catalytic performance for diesel soot combustion was analyzed through the loose deposition of soot onto the structured catalyst and the TPO experiments showed a maximum in combustion rate at about 400°C when NO (0.1%) was added.Cordierite monoliths are well known as wall-flow type soot filters and the morphology of their walls provides an optimum substrate for the anchoring of a thin catalytic coating, thus achieving an excellent mechanical stability. Moreover, the catalytic layer also covers internal pores of the channel walls, where some of the soot particles are trapped, enhancing the catalytic activity and preserving most of the original cordierite monolith macroporosity. Therefore, coating cordierite walls with a Co,Ba,K/ZrO₂ catalyst constitutes a potential catalytic filter for soot combustion. As the textural properties indicated, no changes in the pore volume were observed after the incorporation of the catalytic coating, which favors the potential application of this type of monoliths.

Keywords: Structured catalyst; Soot combustion; Cordierite monolith; Co,Ba,K/ZrO; ₂; coating

Efficient persistent photocatalytic decomposition of nitrogen monoxide over a fluorescence-assisted CaAl₂O₄:(Eu, Nd)/(Ta, N)-codoped TiO₂/Fe₂O₃ by Huihui Li; Shu Yin; Yuhua Wang; Tsugio Sato (pp. 487-492).

Display Omitted► Compensated codoped TiO₂ were prepared by microwave-assisted hydrothermal method. ► The photocatalytic activity was further increased by the interfacial charge transfer. ► CaAl₂O₄:(Eu, Nd)/(Ta, N)-TiO₂/Fe₂O₃ as a efficient fluorescence-emitting Photocatalyst. ► Degradation of pollutant gas proceeded in a continuous flow system or a closed system. ► Persistent catalytic ability after turning off light in dark was realized.An effective promoting approach was described to modify the photoelectrochemical properties of rutile TiO₂ by codoping with the nonmetal N and transition metal Ta ions, followed by loading with Fe₂O₃. Here, the charge compensated and coupled semiconductor systems were constructed, and their visible-light and persistent fluorescence assisted photocatalytic activities for NO destruction and CH₃CHO removal were evaluated. The results demonstrated that both the charge compensation of TiO₂ by co-doping with N³⁻ and Ta⁵⁺ and loading with a proper amount of Fe₂O₃ facilitated the enhancement of both the visible-light and persistent fluorescence induced photocatalytic ability. The TiO₂ co-doped with N³⁻ and Ta⁵⁺ followed by loading with Fe₂O₃ excellently met the criteria for the persistent photocatalysts, which can be functional for environmental purification even after turning off lamp irradiation.

Keywords: Compensated codoping; Loading; Coupling; Persistent fluorescence assisted; Visible-light; Photocatalyst

Transformation of dibenzothiophenes model molecules over CoMoP/Al₂O₃ catalyst in the presence of oxygenated compounds by M. Philippe; F. Richard; D. Hudebine; S. Brunet (pp. 493-498).

Display Omitted► Decrease of the activity of model sulfur compounds (DBT and 46DMDBT) whatever the oxygenated compounds. ► Most inhibiting effect by decanoic acid and CO oxygenated compounds. ► Competitive adsorption between sulfur and oxygenates compounds.Decanoic acid is one of the most inhibiting compounds with CO in the transformation of the most refractory sulfur compounds in gas oils. Unlike phenols compounds, decanoic acid and CO its main by-product present a strong inhibiting effect in the conversion of sulfur compounds. The effects are due to phenomena of competitive adsorption between sulfur and oxygen compounds on the catalyst surface. Furthermore, according to oxygenated molecules, the impact on both transformation pathways (HYD and DSD) mainly involved in HDS of gas oils is not the same. Decanoic acid and CO have a greater impact on the DSD way involved in the transformation of DBT than in HYD way involved in the transformation of 46DMDBT. These results confirmed that these two reactions require two different sites located in sulfur and metal edges of the catalyst.

Keywords: Deep hydrodesulfurization; 4,6-Dimethyldibenzothiophene; Dibenzothiophene; Carbon oxide; Carbon dioxide; CoMoP/Al; ₂; O; ₃; Biomass; Decanoic acid

Effect of Ce/Zr ratio in CeZr-CoRh catalysts on the hydrogen production by glycerol steam reforming by L.M. Martínez T; M. Araque; J.C. Vargas; A.C. Roger (pp. 499-510).

Display Omitted► Steam reforming of glycerol toward H₂ production with mixed oxide catalysts CeZrCoRh. ► The higher production of H₂ is favored with the increase of the ceria content. ► Higher ceria amount favors the re-oxidation capacity and the gasification ability. ► The increase of the ceria amount favors the activation of H₂O. ► Higher ceria amount allows the carbon gasification and delays the deactivation.The H₂ production by glycerol steam reforming has been studied using fluorite-type mixed oxides of CZCoRh. The effect of the Ce/Zr ratio on the catalytic properties and its influence on the catalytic behavior are discussed. The catalysts were characterized before and after catalytic test by XRD, Raman spectroscopy, BET surface area, HRTEM, H₂-TPR and TPD-TPO. The results show that an increase of the cerium amount enhances both the stability and the selectivity toward H₂ and CO₂. This is related to the improvement of the reducibility and re-oxidation properties, oxygen storage capacity and metal support interaction. The activity results demonstrate that selective H₂ production is related to the capacity of the catalysts to activate H₂O under reaction conditions. This step ensures the steam reforming of the by-products to H₂. The progressive loss of this capacity reduces the H₂ production, decreasing the steam reforming ability and the glycerol decomposition becomes predominant. In this last case the production of CO, CH₄ and C₂H₄ is promoted along with the formation of condensable products as hydroxyacetone, acetaldehyde and acrolein.

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

Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts by Atsushi Satsuma; Kaoru Osaki; Masatoshi Yanagihara; Junya Ohyama; Kenichi Shimizu (pp. 511-518).

Display Omitted► The activity-controlling factors of were discussed on CO oxidation over supported Pd catalysts. ► Both of two factors, (1) formation of metallic Pd and (2) oxygen storage property of metal oxide support, were clarified to be critical. ► The oxidation of CO proceeds on Pd/CeO₂ and Pd/TiO₂ even under nearly 100% coverage of CO over Pd.The effect of supports (CeO₂, TiO₂, Al₂O₃, ZrO₂, and SiO₂) on CO oxidation over Pd catalysts at low temperatures was investigated, and activity-controlling factors were discussed. The light-off temperature was in the order of Pd/CeO₂22O₃2≤Pd/SiO₂ which was fairly in agreement with the reduction temperature of supported Pd to metallic species in CO-Temperature programmed reduction (CO-TPR) profile. The result indicates that higher reducibility of supported Pd to metallic species is one of the activity-controlling factors for the oxidation activity. The activation of oxygen on metal oxide support is suggested to be another factor for the low temperature oxidation. Actually, in situ IR measurement revealed that the oxidation of CO proceeds on Pd/CeO₂ and Pd/TiO₂ even under nearly 100% coverage of CO over Pd, though Pd/Al₂O₃ showed CO oxidation activity below 50% coverage of CO. The supports having oxygen storage property, CeO₂ and TiO₂, contribute to the oxygen activation to proceed CO oxidation irrespective of self-poisoning of metallic Pd surface by adsorbed CO. It was concluded that both of the following two factors are essential for CO oxidation at low temperature: (1) formation of metallic Pd and (2) oxygen storage property of metal oxide support.

Keywords: Pd; Support effect; CO oxidation; Oxygen storage capacity; Activity-controlling factor

Optimization of imazalil removal in the system UV/TiO₂/K₂S₂O₈ using a response surface methodology (RSM) by R. Hazime; Q.H. Nguyen; C. Ferronato; T.K.X. Huynh; F. Jaber; J.-M. Chovelon (pp. 519-526).

Graphical presentation of the statistical evaluation of the interactions of two factors on the 90% of removal time of imazalil.Display Omitted► K₂S₂O₈ was used as electron scavenger to accelerate the degradation rate of imazalil. ► The photocatalytic degradation of imazalil was optimized in the system UV/TiO₂/K₂S₂O₈. ► An experimental design was used to accomplish this optimization. ► For the low concentration of imazalil, acidic pH, 2.5gL⁻¹of persulfate and 2.5gL⁻¹ of TiO₂, give the faster removal time.The optimization of the photocatalytic degradation of a carcinogen pesticide, imazalil, was carried out in an aqueous solution using TiO₂ as photocatalyst under UV irradiation in the presence of persulfate. Persulfate plays a double role; an electron scavenger and it promotes the formation of sulfate radicals which allow accelerating the removal of imazalil.For the optimization, experimental design was used based on the surface response methodology; it was applied to assess the individual and interaction effects of several operating parameters (pH, TiO₂ concentration, pesticide concentration and persulfate concentration) on the treatment efficiency (90% of pesticide removal time).Based on the experimental design data, a semi-empirical expression was obtained, permitting to predict and to optimize the pesticide removal time. This model was very consistent with experimental results (correlation factor: 99.15%). The strongest interactions between the parameters assessed were pH/[K₂S₂O₈] and [Imazalil]/[K₂S₂O₈]. Optimal experimental conditions found for imazalil (25mgL⁻¹) removal were acidic pH 3–4, persulfate concentration (≈2.5gL⁻¹) and TiO₂ loading (2.5gL⁻¹). By using tert-butanol as hydroxyl radical scavenger, it was found that sulfate radicals were predominant at acidic pH and as the pH increases the hydroxyl radicals are more and more produced.The experimental design allows obtaining the maximum of efficiency with the minimum amount of persulfate.This work demonstrates well the utility and benefits of the experimental design approach for screening and modeling the reaction parameters.Furthermore, it contributes significantly to the improvement and better understanding of photocatalytic processes using oxidants.

Keywords: Imazalil degradation; UV/TiO; ₂; /K; ₂; S; ₂; O; ₈; CCD; Experimental design; Persulfate

Carbon–NSR catalyst interaction: Impact on catalyst structure and NO_x storage efficiency by Jennifer Klein; Dongliang Wu; Valerie Tschamber; Ioana Fechete; Francois Garin (pp. 527-534).

Display Omitted► Effect of carbon–catalyst contact on the NO_x storage capacity of NSR catalysts. ► Contact between carbon and NO_x storage catalysts affect nitrate species formed far from Pt. ► Carbon oxidation process led to premature aging of the catalysts. ► Carbon oxidation process induces structural modifications of the catalysts. ► The structural modifications lead to a decrease of NO_x storage through the ‘nitrite’ route.The impact of the presence of carbon on the structure of model NO_x storage catalysts (NSR) and their ability to store NO_x were investigated. Three catalysts, composed of Pt and/or Ba supported on Al₂O₃, were prepared. Reactivity of the catalysts toward NO_x storage was studied during adsorption/TPD cycles. Comparison of the results obtained in the presence and absence of carbon in the catalytic bed revealed that a carbon–catalyst contact leads to a decrease in NO_x storage capacity attributed to a destabilization of nitrate species formed far from Pt sites. Both Al and Ba sites are affected. During the carbon oxidation process, an aging of the catalysts, caused by Pt sintering and Ba agglomeration, as observed using TEM technology. These structural modifications reduce the proximity between the Pt sites and adsorption sites (Ba and/or Al), which results in a decrease in the NO_x storage toward the ‘nitrite route’.

Keywords: NO; _x; storage capacity; Soot; Sintering; Platinum based catalyst; Barium nitrate

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO₂ supported on titanium anodes by Levent Özcan; Sedat Yurdakal; Vincenzo Augugliaro; Vittorio Loddo; Simonetta Palmas; Giovanni Palmisano; Leonardo Palmisano (pp. 535-542).

Display Omitted► Selective photoelectrocatalytic oxidation of 4-methoxybenzyl alcohol to 4-methoxybenzaldehyde was performed in aqueous medium. ► TiO₂/Ti anodes were prepared by either Ti thermal oxidation or dip-coating in a TiO₂ sol. ► The influence of the substituent group of the benzyl alcohol aromatic ring on selectivity and activity was investigated. ► Electron donor groups in para or ortho position positively affect the reactivity and selectivity to aldehyde.The photoelectrocatalytic partial oxidation of 4-methoxybenzyl alcohol in aqueous solution irradiated by near-UV light was carried out in a three-electrode batch reactor. TiO₂ films were either deposited by dip-coating of a TiO₂ sol onto a Ti foil and subsequent calcination or generated on Ti plates by thermal oxidation in air at 400–700°C. The effects of the anode preparation method and bias potential values on conversion and selectivity to the corresponding aldehyde were investigated. The photoelectrocatalytic results were compared with the photocatalytic and electrocatalytic ones. The results indicated that no reaction occurred during the electrocatalytic experiments, whereas the photocatalytic reactivity was positively influenced by the application of a small bias (0.75V vs. saturated calomel electrode). By applying the previous bias the highest initial degradation rates, r₀, and selectivities to 4-methoxybenzaldehyde, S, were obtained in photoelectrocatalytic experiments by using Ti plate calcined at 500°C ( r₀=0.1507mMh⁻¹, S=85%) or TiO₂ film prepared by dip-coating and calcined at 700°C ( r₀=0.1339mMh⁻¹, S=90%). In order to investigate the influence of the substituent groups on reactivity and selectivity, photoelectrocatalytic runs with benzyl alcohol, 2-methoxybenzyl alcohol, 3-methoxybenzyl alcohol, 2,4-dimethoxybenzyl alcohol, 2,3,4-trimethoxybenzyl alcohol, 4-nitrobenzyl alcohol and 4-hydroxybenzyl alcohol have been performed. The selectivity and reactivity values increased by increasing the electron-donor properties of the substituent groups. This positive effect, however, was obtained only if the electron-donor group is in para or ortho position with respect to the alcoholic group.

Keywords: Photoelectrocatalysis; Titanium; TiO; ₂; /Ti; 4-Methoxybenzaldehyde; Aromatic alcohols; Green synthesis

On the kinetics of photoelectrocatalytic water splitting on nanocrystalline TiO₂ films by Andreas K. Seferlis; Stylianos G. Neophytides (pp. 543-552).

Display Omitted► Partial electrochemical reduction enhances TiO₂ photoelectrocatalytic activity. ► This is attributed to the formation of defect states within the bandgap. ► Bandgap states at different energy levels induce two voltage dependent kinetic regions. ► Adsorbed water splitting proceeds through the photo activation of ‘wet electron’ state. ► Oxygen evolution is observed with selectivity ≤10% at the saturation current.Water splitting photoelectrocatalytic reaction mechanism on TiO₂ nano particulate polycrystalline film has been studied by means of potentiostatic and potentiodynamic measurements in alkaline solutions under UV irradiation peaking at 365nm. The TiO₂ photoelectrode is reduced by scanning to negative potentials and its photoelectrocatalytic activity is enhanced. This is attributed to the formation of defect states within the bandgap created while in negative potential. The defect states can be responsible for the appearance of the two kinetic regions observed in the potentiostatic experiments. These are located within the potential range −0.1 to 0.3V (region I) and 0.3–0.8V (region II) vs. RHE, respectively, and can be activated by different states positioned at different energy levels within the bandgap of TiO₂. For film thickness <5μm region I does not appear and the open circuit voltage (OCV) shifts to more positive values by 0.35V as compared to thicker electrodes. The splitting of adsorbed water can be realized through the activation of the ‘wet electron’ state of adsorbed water molecules, which is activated by photo-excited electrons originating from bandgap states positioned closer to the bottom of the conduction band. Based on the OH_ad reduction peak of the cyclic voltammograms (CV) and the BET surface area of the ∼5μm thick TiO₂ electrode, the electrochemical utilization of TiO₂ film specific surface area was found to be 100% and the maximum turn over frequency at the saturation photocurrent 0.7s⁻¹.

Keywords: Photo electrocatalysis; Water splitting; Wet electron state; TiO; ₂; nanocrystalline film

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Applied Catalysis B, Environmental (v.132-133, #)