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Applied Catalysis B, Environmental (v.130-131, #)

Editorial Board (pp. co2).

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Editorial Board (pp. i).

BiOI thin film via chemical vapor transport: Photocatalytic activity, durability, selectivity and mechanism by Liqun Ye; Junnian Chen; Lihong Tian; Jinyan Liu; Tianyou Peng; Kejian Deng; Ling Zan (pp. 1-7).

As-synthesized BiOI TF was prepared via a low temperature chemical vapor transport route, and composed of high symmetrical BiOI nanosheets with dominant exposed {001} facets. It displayed better photocatalytic activity, durative and selectivity. Photocatalytic mechanism results indicated that O₂⁻ and h⁺ are the main active species under high-pressure Xenon lamp irradiation. And corresponding reformed CBM photocatalytic mechanism was suggested.Display Omitted► This paper firstly reported chemical vapor transport route to prepare BiOI thin film. ► This paper firstly reported the photocatalytic selectivity of BiOI. ► Possible reformed CBM photocatalytic mechanism was suggested.BiOI thin film (BiOI TF) was prepared via a low temperature chemical vapor transport (CVT) route for the first time, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, fast-Fourier transform pattern and UV–vis diffuse reflectance. As-synthesized BiOI thin film was composed of high symmetrical BiOI nanosheets with dominant exposed {001} facets. It displayed better photocatalytic activity, durability and selectivity than benchmark P25 TiO₂ thin film and the origin come from the layered structure and good photoelectrochemical performance, CVT immobilization, the 100% terminal oxygen atoms of {001} facets, respectively. At end, the photocatalytic mechanism with O₂⁻ production was studied.

Keywords: BiOI; Photocatalytic; Durability; Selectivity; Mechanism

Nitrogen and copper doped solar light active TiO₂ photocatalysts for water decontamination by Mike B. Fisher; Donal A. Keane; Pilar Fernández-Ibáñez; John Colreavy; Steven J. Hinder; Kevin G. McGuigan; Suresh C. Pillai (pp. 8-13).

Schematic diagram of bacterial decontamination using visible light active catalyst.Display Omitted► A stable photocatalytic sun-light-active TiO₂ (VLAT) coating has been developed. ► Enhanced photocatalytic activity of coated bottles was observed. ► Visible light activated accelerated the degradation of methylene blue under natural sunlight. ► Doped TiO₂ films accelerated bacterial (e.g. E. coli) inactivation under natural sunlight.A novel class of photocatalytic coating capable of degrading bacterial and chemical contaminants in the presence of visible sunlight wavelengths was produced by depositing a stable photocatalytic TiO₂ film on the internal lumen of glass bottles via a sol–gel method. This coating was prepared in either undoped form or doped with nitrogen and/or copper to produce visible light-active TiO₂ films which were annealed at 600°C and were characterized by Raman and X-ray photoelectron spectroscopy. The presence of doped and undoped TiO₂ films was found to accelerate the degradation of methylene blue in the presence of natural sunlight, while copper-doped TiO₂ films were found to accelerate bacterial inactivation (of Escherichia coli and Enterococcus faecalis) in the presence of natural sunlight.

Keywords: Sunlight; Visible light; Titanium dioxide; Photocatalysis; Thin film; Emerging pollutants; SODIS; Disinfection; Bacterial deactivation; Contamination; Visible light; Depollution; Anatase

Inorganic–organic core–shell titania nanoparticles for efficient visible light activated photocatalysis by N.G. Moustakas; A.G. Kontos; V. Likodimos; F. Katsaros; N. Boukos; D. Tsoutsou; A. Dimoulas; G.E. Romanos; D.D. Dionysiou; P. Falaras (pp. 14-24).

Display Omitted► Combustion gel synthesis of composite titania photocatalysts. ► Optimization of urea content and calcination temperature. ► Core crystalline TiO₂ uniformly covered by thin porous carbonaceous shell. ► Visible light activated EPR signals from organic radicals. ► High photocatalytic performance under visible light illumination.Nanostructured modified TiO₂ (m-TiO₂) was synthesized using the gel combustion method based on the calcination of an acidified alkoxide solution mixed with urea. The materials were characterized by Raman, FT-IR and UV–vis diffuse reflectance spectroscopies, transmission (TEM) and scanning electron microscopies (SEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR), in comparison with reference material untreated with urea (ref-TiO₂). The effect of both the urea content and calcination temperature were optimized, providing the optimal absorption threshold of 2.19eV for solar light harvesting. The photocatalytic performance of the m-TiO₂ powder was tested for the degradation of methylene blue (MB) azo dye under UVA (350–365nm), visible (440–460nm), and daylight (350–750nm) illumination. The hybrid inorganic/organic material shows exceptional physicochemical properties and significant photocatalytic activity, especially in the visible, attributed to sensitization of the TiO₂ by a thin porous layer of carbonacious species in controlled core–shell morphology.

Keywords: Visible light active TiO; ₂; Core–shell structure; Solar photocatalysis; HRTEM; EPR

NH₃ decomposition and oxidation over noble metal-based FCC CO combustion promoters by Behnam Bahrami; Vasileios G. Komvokis; Michael S. Ziebarth; Oleg S. Alexeev; Michael D. Amiridis (pp. 25-35).

Display Omitted► Catalytic oxidation of NH₃ formed in reducing zones of FCC regenerators contributes to increased NO_x emissions. ► Below 350°C NH₃ oxidation over noble metal-based CO combustion promoters follows an iSCR-type pathway. ► NO_x and surface nitrite/nitrate species formed from NH₃ can react with the remaining NH₃ to form N₂. ► At 700°C and under excess O₂ conditions NH₃ is oxidized to NO_x. ► Optimal O₂ concentrations can be found for complete NH₃ conversion and high N₂ selectivity.The surface chemistry of NH₃ decomposition and oxidation was examined over M n⁺/Ce n⁺/Na⁺/γ-Al₂O₃ commercial catalysts incorporating Pt, Pd, and Rh in order to clarify the role of these materials in converting NH₃ into N₂ and NO_x within the dense phase of FCC regenerators. All catalysts were active in promoting the decomposition of NH₃ into N₂ in the 500–700°C temperature range, with the Rh containing catalyst being the most active at 700°C. Oxygen species activated on the surfaces of these materials significantly enhanced the selective conversion of NH₃ into N₂. When O₂ was present in the feed, complete conversion of NH₃ – with approximately 80% selectivity to N₂ – was observed over the reduced Pt-, Pd-, and Rh-containing materials at temperatures as low as 200, 300, and 350°C, respectively. At temperatures below 350°C, the NH₃ oxidation reaction follows an iSCR-type pathway, in which a fraction of NH₃ is converted into NO_x and subsequently into surface nitrite/nitrate species capable of reacting with the remaining portion of NH₃ to form N₂. Although the oxidation of NH₃ to NO_x prevails at 700°C under excess O₂ conditions, optimal O₂ concentrations can be found under which both complete NH₃ conversion and high N₂ selectivity are achieved. Under these conditions, the noble metal component of the M n⁺/Ce n⁺/Na⁺/γ-Al₂O₃ materials promotes the reaction of NH₃ with the NO_x formed, yielding N₂. Excess O₂ effectively hinders this reaction pathway at high temperatures. Overall, the results presented herein indicate that the significant increase in NO_x emissions, typically observed over conventional Pt-based FCC CO combustion promoters, could be directly attributed to the oxidation of NH₃ formed in the reducing zone of the FCC regenerators.

Keywords: NO; _x; reduction; NH; ₃; oxidation; FCC additives; Palladium; Platinum; Rhodium; Nitrates; Nitrites

Catalytic abatement of trichloroethylene over Mo and/or W-based bronzes by N. Blanch-Raga; M.D. Soriano; A.E. Palomares; P. Concepción; J. Martínez-Triguero; J.M. López Nieto (pp. 36-43).

Display Omitted► W,Mo-containing bronzes are active catalysts for the catalytic oxidation of TCE. ► Bronzes show higher catalytic activity than the zeolitic reference catalyst (H-MOR). ► The most active catalyst, i.e. MW-50, was achieved for a W/(Mo+W) ratio of ca. 0.50. ► The catalytic activity is strongly related to the W/(Mo+W) ratio of catalysts.In this paper we present the results of the synthesis, characterization and catalytic behaviour of Mo(W)–Nb–V–O mixed metal oxides bronzes for the catalytic oxidation of trichloroethylene. The catalysts were prepared hydrothermally with different Mo/W/Nb/V/P atomic ratio and heat-treated at 500 and 700°C. They were characterized by several techniques as N₂-adsorption, X-ray diffraction, FTIR, SEM-EDS, temperature programmed desorption, temperature programmed reduction, UV–vis, Fourier transformed infrared spectroscopy of adsorbed pyridine and¹⁸O/¹⁶O isotope exchange. X-ray diffraction patterns (XRD) of samples heat-treated at 500°C suggest the presence of a semi-crystalline material with a diffraction peak at ca. 2 θ=22.2°, while XRD patterns of samples heat-treated at 700°C show the formation of a tetragonal tungsten bronze (TTB) structure. The activity for the catalytic abatement of trichloroethylene strongly depends on the heat-treatment temperature and the catalyst composition. Thus, samples with W/(Mo+W) atomic ratios of 0.25-0.75 and heat-treated at 500°C are the most active ones. The enhanced activity has been related to the remarkable higher surface area of the catalyst and to the catalyst composition which influences the acid characteristics as well as the reducibility and reoxidation of the catalysts. The importance of the oxygen dissociation on the catalyst surface and the diffusion of oxygen species through the catalyst are also discussed.

Keywords: Catalytic oxidation; Chlorinated VOCs; Trichloroethylene; Mo–W–O mixed oxides bronzes

One-pot microwave mediated growth of heterostructured ZnO@AlSi as a potential dual-function eco-catalyst for treating hazardous pollutants in water resources by P.S. Suchithra; C.P. Shadiya; A. Peer Mohamed; P. Velusamy; S. Ananthakumar (pp. 44-53).

Mesoporous, hybrid ZnO@AlSi, consisted of nanoparticulate zinc oxide embedded in aluminosilicate matrix acted as a cost-effective ecocatalyst with dual function as adsorbent and photocatalyst. The catalyst was very effective for detoxification of multicomponent complex wastewater containing both hazardous organic and inorganic pollutants through synergic adsorption, photo reduction and photooxidation effects consecutively for three cycles.Display Omitted► Eco-catalyst via microwave assisted in situ intercalation and crystal growth. ► Mesoporous, heterostructured ZnO@aluminosilicate as adsorbent and photocatalyst. ► Photoreduction of carcinogenic Cr(VI) to non-toxic Cr(III). ► Mineralization of phenol and methylene blue via photodecomposition. ► Synergic photoeffect for treating multicomponent pollutant systems.Dual function, eco-catalyst material had been designed with nano ZnO@aluminosilicate mineral (ZnO@AlSi) and processed via microwave assisted in situ intercalation and crystal growth reactions. Dual function of ZnO@AlSi was confirmed by the simultaneous adsorption and UV photoreduction of carcinogenic Cr(VI) to non-toxic Cr(III) and photooxidation of phenol and methylene blue dye (MB); a co-existed model system was simulated and prepared together in laboratory conditions. Single phase nano ZnO and ion exchanged AlSi layered silicates were also separately prepared for comparisons with ZnO@AlSi system. All these materials were characterized for BET, DLS, TGA, SEM, TEM, UV–visible and fluorescence spectrophotometry to analyze structural, thermal, morphological, and optical properties. It was seen that the inherent silicate layered structure significantly restricted the growth of ZnO, resulting in mesoporous, UV-active ZnO@AlSi heterogeneous nanocatalyst. An effective adsorption of Cr(VI), phenol and MB to the extent of 99% and the transformation of Cr(VI) to Cr (III) through photoreduction, and decomposition of phenol and MB by photooxidation followed by mineralization were achieved at once. This synergic adsorption and photodecomposition effects could not be found together in single phase nano ZnO as well as ion exchanged AlSi system. The kinetic photo-experiments indicated that reduction of Cr(VI) and degradation of phenol and MB by ZnO@AlSi followed Langmuir–Hinshelwood first-order kinetic model. The investigation of ZnO@AlSi at Cr(VI)/phenol and Cr(VI)/MB binary systems displayed high decontamination performance of ZnO@AlSi than in single pollutant system due to the arresting of electron–hole pair recombination via consuming both the members in separate redox half-reactions. Alternatively, life time of catalyst was found decreased in organic–inorganic pollutant system compared to single component systems. In summary, a dual function catalyst was designed through a facile technique and validated for the cost-effective removal and decomposition of organic and inorganic pollutants simultaneously in the complex wastewater.

Keywords: ZnO; Aluminosilicates; Cr(VI) photoreduction; Phenol photooxidation; Methylene blue

NO_x storage capacity of yttria-stabilized zirconia-based catalysts by W.Y. Hernández; A. Hadjar; M. Klotz; J. Leloup; A. Princivalle; C. Tardivat; C. Guizard; P. Vernoux (pp. 54-64).

Display Omitted► Yttria-stabilized zirconia (YSZ) can store NO x on its surface oxygen vacancies. ► NO x conversion of 75% was achieved on Pt-Rh/YSZ powdered catalysts. ► YSZ-based catalysts were deposited in the porosity of mini SiC-DPFs. ► YSZ-based catalysts show high thermal resistance and sulfur tolerance.A NO x chemisorption study was performed on yttria-stabilized zirconia (YSZ), an O²⁻ ionically conducting ceramic. NO₂ chemisorption on YSZ as well as NO+O₂ interactions on Pt/YSZ catalyst were clearly correlated to the presence of surface oxygen vacancies. A remarkable NO x storage capacity was obtained on Pt/YSZ powdered catalysts, by combining nitrates formation and NO₂ adsorption on oxygen vacancies. Under cycling conditions (lean phase/rich phase: 3min/2min) and using propene as a reductant, powdered Pt-Rh catalyst exhibited overall NO x abatement conversion of around 75% at 250 and 300°C. Pt/Rh/YSZ catalysts were finely dispersed in the porosity of SiC mini diesel particulate filters (DPFs). Quite reproducible and stable NO x conversions were achieved in cycling conditions with values around 50% between 250 and 400°C. In addition, YSZ-based catalysts have shown high thermal resistance and sulfur tolerance.

Keywords: Yttria-stabilized zirconia; Oxygen vacancies; Ionic conductor; NO; _x; storage-reduction; Diesel particulate filters

RF-plasma pretreatment of surfaces leading to TiO₂ coatings with improved optical absorption and OH-radical production by O. Baghriche; S. Rtimi; C. Pulgarin; C. Roussel; J. Kiwi (pp. 65-72).

Display Omitted► Evidence is presented for RF-plasma pretreatment increasing the surface amount of TiO₂. ► The increased amount of surface TiO₂ led to an increase of OH-radicals under light irradiation. ► Redox catalysis on the TiO₂ coatings was involved during light induced bacterial inactivation.Evidence presented for the RF pretreatment of polyester enhances the TiO₂ coating generation of oxidative species/radicals under a low level actinic light irradiation. After 30min RF-plasma pretreatment of the polyester samples, the fastest bacterial inactivation was observed concomitant with (a) the largest ratio of surface oxidized to the reduced functionalities as determined by XPS, (b) a strong sample optical absorption as seen by DRS and (c) the highest concentration surface OH-radicals monitoring the fluorescence of the hydroxy-terephthalic acid. Evidence for the photocatalyst self-cleaning was found by XPS due to the lack of accumulation of bacterial residues on the polyester-TiO₂. A further proof of self-cleaning was the ability by the polyester-TiO₂ samples to inactivate again bacterial charge at the end of an inactivation cycle. By XPS evidence is presented for the Ti⁴⁺/Ti³⁺ related redox catalysis and the details of the C and O-functionalities. Surface techniques such as XRF, DRS, TEM, contact angle (CA), XRD and XPS were applied to relate the microstructure of the TiO₂ coatings with the destruction of Escherichia coli taken as a probe.

Keywords: Vacuum RF-plasma; TiO; ₂; photocatalysis; OH-radicals; Bacterial inactivation kinetics

Improving the DME steam reforming catalyst by alkaline treatment of the HZSM-5 zeolite by Jorge Vicente; Ana G. Gayubo; Javier Ereña; Andrés T. Aguayo; Martin Olazar; Javier Bilbao (pp. 73-83).

Display Omitted► HZSM-5 zeolite modified by alkaline treatment is used as acid function for the catalyst in the DME steam reforming. ► The treatment of the zeolite with NaOH enables to obtain high yields of H₂. ► The attenuation in acidity lowers the formation of undesired hydrocarbons and CO. ► The catalyst is stable and its kinetic behaviour remains constant with time on stream.Dimethyl ether (DME) steam reforming for hydrogen production has been studied on a bifunctional catalyst prepared by the (wet) physical mixing (at 50wt%) of a metallic function of CuO–ZnO–Al₂O₃ (Cu/Zn/Al atomic ratio=4.5:4.5:1.0, prepared by co-precipitation) and an acidic function of HZSM-5 zeolite modified by alkaline treatments of different severity. The runs have been carried out in a fluidized bed reactor. The results obtained by using treated HZSM-5 zeolites and γ-Al₂O₃ as acid functions have been compared. The alkaline treatment affects both the acid properties of the zeolite (attenuating total acidity and acid strength) and its porous structure (increasing the mesoporous surface and decreasing the microporous volume and BET surface area). The attenuation in acidity hinders the formation of undesired hydrocarbons from oxygenates (methanol+DME). Consequently, alkaline treatment (with 0.2–0.4M NaOH solutions for 300min) is suitable for improving the kinetic performance of the bifunctional catalyst, as it provides high selectivity and a high yield of H₂ at 300°C without hydrocarbon formation, as well as minimizing CO formation and avoiding deactivation by Cu sintering. The catalyst is stable, and its kinetic performance remains constant throughout long runs.

Keywords: Dimethyl ether; Hydrogen; Steam reforming; HZSM-5 zeolite; Alkaline treatment

Preparation of Cu₂(OH)₃NO₃/ZnO, a novel catalyst for methyl orange oxidation under ambient conditions by Assadawoot Srikhaow; Siwaporn Meejoo Smith (pp. 84-92).

Display Omitted► New synthetic route for copper hydroxide nitrate by a metal oxide assisted method. ► Catalytic wet oxidation of organic dye was promoted without addition of oxidizer. ► This cheap-to-produce catalyst has high performance under ambient conditions. ► The catalyst can be reused effectively, without regeneration requirement. ► Efficiency testing results suggested radical assisted oxidation of the organic dye.This work reports a novel process to synthesize copper hydroxyl nitrate/zinc oxide composites (Cu₂(OH)₃NO₃/ZnO), and their application as a highly effective and reusable catalyst for wet oxidation of methyl orange (MO) under ambient conditions. No additional air or oxygen flow is required. Using a metal oxide assisted method, the Cu₂(OH)₃NO₃/ZnO composites were hydrothermally obtained by varying the Cu:Zn mole ratio (2:1, 4:1, and 6:1) and the structural, chemical and surface properties of the composites were investigated. Decolorization of 500ppm MO can be effectively catalyzed by the Cu₂(OH)₃NO₃/ZnO composite (Cu:Zn=4:1) with the color, chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies being greater than 99%, 98% and 94%, respectively, after 20min treatments using the catalyst loading of 3gL⁻¹. Results from systematic catalytic activity tests strongly suggested that MO was oxidized by oxygen dissolved in the dye solution, and that the degradation pathway of MO possibly occurred through radical and H₂O₂ generation. The application of highly efficient Cu₂(OH)₃NO₃/ZnO catalysts in wastewater remediation may be attractive alternative to existing oxidation catalyst systems as they are low-cost, simple to prepare, feasible to operate under ambient conditions.

Keywords: Copper hydroxide nitrate; Zinc oxide; Layered hydroxyl salts; Catalytic wet oxidation; Wastewater treatment

Interfacial charge carrier dynamics of type-II semiconductor nanoheterostructures by Yi-Fang Lin; Yung-Jung Hsu (pp. 93-98).

Display Omitted► Interfacial charge carrier dynamics of type-II semiconductor nanoheterostructures have been comprehended. ► Carrier dynamics results are in good accordance with that of photoconversion performance evaluation. ► The counteraction effect associated with electron–hole recombination across interface is an essentially important factor.Semiconductor nanoheterostructures with type-II band offset have exhibited unique optoelectronic properties that are beneficial to photoconversion applications. Debatable arguments however exist in the literature for interpreting the most enhanced photocatalytic performance of type-II semiconductor nanoheterostructures when an optimal content of the constituents is employed. In this work, time-resolved photoluminescence is used to investigate the interfacial charge carrier dynamics for CdSnO₃-decorated CdS nanowires, a prototype type-II nanoheterostructures system, with varying CdSnO₃ contents. Our results show that the CdSnO₃ content of 2.5at% rendered CdS–CdSnO₃ NWs the most significant charge carrier separation, above which electron–hole recombination across CdS/CdSnO₃ interface mediated carrier transfer to compromise the overall charge separation efficiency. The carrier dynamics results are in good accordance with that of photoconversion performance evaluation in dye photodegradation, which assists in resolving the very critical but still controversial issue as to the factors causing the depressed photocatalytic efficiency of type-II nanoheterostructures when the constituent content exceeds the optimal value.

Keywords: Type-II semiconductor nanoheterostructures; Charge separation; Photoconversion; Photocatalysis; CdS nanowires

Development of a doped titania immobilised thin film multi tubular photoreactor by Morgan Adams; Nathan Skillen; Cathy McCullagh; Peter K.J. Robertson (pp. 99-105).

Display Omitted► Development of a thin film photoreactor, doped with a rare earth element. ► Photoreactor produced degradation of methyl orange equal to that of P25 TiO₂. ► Degradation rate of 95% after 90min under UV irradiation and 70% under visible irradiation. ► Use of lanthanide doping is thought to increase the electron hole separation. ► Increasing doping from 0.5% to 1.0% increased photocatalytic degradation by ∼17%.This paper describes a novel doped titania immobilised thin film multi tubular photoreactor which has been developed for use with liquid, vapour or gas phase media. In designing photocatalytic reactors measuring active surface area of photocatalyst within the unit is one of the critical design parameters. This dictate greatly limits the applicability of any semi-conductor photocatalyst in industrial applications, as a large surface area equates to a powder catalyst. This demonstration of a thin film coating, doped with a rare earth element, novel photoreactor design produces a photocatalytic degradation of a model pollutant (methyl orange) which displayed a comparable degradation achieved with P25 TiO₂. The use of lanthanide doping is reported here in the titania sol gel as it is thought to increase the electron hole separation therefore widening the potential useful wavelengths within the electromagnetic spectrum. Increasing doping from 0.5% to 1.0% increased photocatalytic degradation by ∼17% under visible irradiation. A linear relationship has been seen between increasing reactor volume and degradation which would not normally be observed in a typical suspended reactor system.

Keywords: Photocatalysis; Thin film; Titanium dioxide (TiO; ₂; ); Lanthanides; Surface area

Anti-bacterial activity of indoor-light activated photocatalysts by Damian W. Synnott; Michael K. Seery; Steven J. Hinder; Georg Michlits; Suresh C. Pillai (pp. 106-111).

Degradation rate of the bacteria in the presence of the photocatalyst.Display Omitted► Nanocrystalline photocatalysts, prepared under ambient conditions using a microwave assisted synthesis. ► These nanomaterials show indoor light photocatalytic activity for the degradation of S. aureus and E. coli. ► A novel energy efficient method (green synthesis) to produce anti-bacterial zinc sulphide. ► The mechanism for the indoor light antibacterial photocatalysis is proposed.Nanocrystalline photocatalysts, prepared under ambient conditions using a microwave assisted synthesis, show indoor light photocatalytic activity for the degradation of Staphylococcus aureus and Escherichia coli. The zinc sulphide (ZnS) nanomaterials, prepared by a microwave assisted synthesis, are shown to be cubic blende structure with an average crystallite size of 4–6nm. The anti-bacterial activity of these nanomaterials is investigated under irradiation from a 60W light bulb and photocatalytic activity is revealed to be due to the defects present in the crystal structure. The ZnS shows anti-bacterial action as both a bacteriostatic and bacteriocidal (88% reduction in the amount of bacteria in 5h) material and the methods of bacterial degradation on the ZnS is discussed. The anti-bacterial actions of these materials were also compared with commercial ZnS and Evonik-Degussa P-25. A detailed mechanism for the light absorption in the visible light region of the microwave prepared ZnS is proposed based on the luminescence spectroscopy.

Keywords: Gram positive and gram negative bacteria; Decontamination; Visible light; XPS; Solar; Anti-microbial; ZnO; MRSA; Green and energy efficient synthesis; Anti-MRSA coatings; Hospital acquired infections; Photo-activity; Emerging pollutants; TiO; ₂; Degussa P-25; Cell wall; Disinfection; Micro-biology; Doping; Band gap; Escherichia coli; P. aerginosa; Methicillin-resistant; Staphylococcus aureus; (MRSA)

Decontamination of real textile industrial effluent by strong oxidant species electrogenerated on diamond electrode: Viability and disadvantages of this electrochemical technology by Aline Maria Sales Solano; Cynthia K. Costa de Araújo; Jailson Vieira de Melo; Juan M. Peralta-Hernandez; Djalma Ribeiro da Silva; Carlos A. Martínez-Huitle (pp. 112-120).

Display Omitted► Electrogenerated strong oxidants on BDD surface improve the color and COD removals. ► Active chlorine species can generate organochlorinated compounds at the end of treatment. ► Chloroform is a recalcitrant and persistent by-product formed. ► Catalytic alternative processes to eliminate organic pollutants from industrial effluents.In a previous work [1], the treatment of dye solutions containing Remazol Red BR (RRB) and Novacron Blue C-D (NB) by anodic oxidation using boron doped diamond anode (BDD) demonstrated that the electrochemical treatment is an efficient alternative for removing color and chemical oxygen demand (COD) and this technology can be used for depuration of real effluents. More recently, these assumptions have been confirmed by oxidizing electrochemically a real textile effluent using BDD anode [2]. Then, as a further development of the research carried out in these previous studies [1,2], in the present work, it has been considered appropriate to extend the investigation to the anodic oxidation, using BDD anode, of a specific real effluent discharged by Brazilian textile industry, adding Na₂SO₄ or NaCl salts in order to verify the applicability of this treatment producing in situ strong oxidant species (peroxodisulfates or active chlorine, respectively).In this study, we also attempt to discuss critical evidence about the viability of peroxodisulfates or active chlorine. Results obtained in this research clearly demonstrated that the effect of the electrogenerated strong oxidant species, peroxodisulfates or active chlorine, depends on electrocatalytic mechanism followed on BDD surface, improving the color and COD removal. However, there is a limit of NaCl for treating real effluents avoiding the formation of organochloride compounds; and it is a subject of critical importance, from the environmental point of view, to apply this alternative treatment.

Keywords: Diamond electrode; Real effluent; Decolorization; Organic matter; Peroxodisulfates; Active chlorine; Strong oxidant species

Alcohol induced ultra-fine dispersion of Pt on tuned morphologies of CeO₂ for CO oxidation by Sumanta Kumar Meher; Matteo Cargnello; Horacio Troiani; T. Montini; G. Ranga Rao; Paolo Fornasiero (pp. 121-131).

Display Omitted► Microstructurization of CeO₂ is achieved by different anions during synthesis. ► Pt dispersion on CeO₂ is improved by slow reduction of H₂PtCl₆ with ethylene glycol. ► CeO₂ support prepared in the presence of Cl⁻ ion induces better Pt dispersion. ► More Pt-CeO₂ interfacial sites are responsible for low temperature CO oxidation.Controlling the structures of supports and supported phases is important for catalytic applications where synergic effects can play a main role. In this context, we present versatile methods for suitable microstructurization of CeO₂ support and improved dispersion of supported Pt crystallites in a Pt/CeO₂ system for enhanced catalytic oxidation of CO. The physicochemical properties investigated using SEM, BET, visible Raman, H₂-TPR and OSC measurements demonstrated the important role played by the precursor on the properties of CeO₂. Further, 0.5wt% Pt deposited over CeO₂ via ethylene glycol assisted reduction (EGR) was found to be more advantageous than conventional impregnation (IMP) in producing very finely dispersed Pt particles that did not noticeably sinter even after thermal treatment at 500°C for longer duration. H₂-chemisorption and H₂-TPR experiments further substantiated better Pt dispersion on CeO₂ prepared in the presence of Cl⁻ ions regardless of the method employed, thus suggesting a strong microstructural effect of support during growth and anti-sintering activity of Pt crystallites. The CO oxidation activity additionally demonstrates that samples prepared by EGR method show remarkably better performance (100% conversion in <100°C) as compared to their impregnated counterparts (100% conversion at ∼300°C). The present approach to improve the catalytic activity of Pt/CeO₂ based hetero-nanocomposites by finely dispersing low concentrations of Pt nanocrystallites over microstructurally tuned CeO₂ support is encouraging in the context of designing novel metal–metal oxide based catalysts for astute potential applicability under vibrantly testing conditions.

Keywords: CeO; ₂; Surface morphology; Alcohol assisted reduction; Pt dispersion; CO oxidation

Preparation and application of thermosensitive poly(NIPAM- co-MAH-β-CD)/(TiO₂-MWCNTs) composites for photocatalytic degradation of dinitro butyl phenol (DNBP) under visible light irradiation by Hui-Long Wang; Yan Li; Li Pang; Wen-Zhu Zhang; Wen-Feng Jiang (pp. 132-142).

Display Omitted► Simple UV light photoinitiating synthesis method for the composite photocatalysts. ► The photocatalysts had thermoreversibility with little loss of thermosensitivity. ► Exceptionally high activity in the photocatalytic degradation of DNBP. ► High adsorption capacity, visible light & thermo-response of the photocatalysts.Based on the unique temperature responsive characters of polymeric material based on N-isopropylacrylamide (NIPAM), a capacity for organic molecular inclusion of maleic anhydride (MAH) modified β-cyclodextrin (β-CD), and the enhancements in photocatalytic activity of TiO₂ doped with multi-walled carbon nanotubes (MWCNTs), the novel thermosensitive poly(NIPAM- co-MAH-β-CD)/(TiO₂-MWCNTs) composite photocatalysts were prepared by UV light photoinitiating method. Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), BET surface area and UV–Vis diffuse reflectance spectra (UV–Vis/DRS) were used to characterize the structure, morphology and composition of the as-prepared composites. Results showed that TiO₂-MWCNTs nanoparticles were embedded evenly within the thermally responsive copolymer of NIPAM and MAH-β-CD. The thermoresponsive property of the synthesized composites was investigated by using swelling ratio measurements. The photocatalytic performances of the thermosensitive composite catalysts were evaluated for the degradation of 2- sec-butyl-4,6-dinitrophenol (DNBP) solution under visible light irradiation. The effect of operational parameters, i.e. pH of the solution, catalyst concentration, irradiation time, initial DNBP concentration on the photocatalytic degradation efficiency was explored and the results obtained were fitted with modified Langmuir–Hinshelwood model to investigate the degradation kinetics and discussed in detail. The repeatability of photocatalytic activity was also tested. The thermosensitive composite photocatalysts exhibited easy separation and less deactivation after several runs. A plausible mechanism is proposed for the photocatalytic degradation pathway of DNBP. The results of this study showed the feasible and potential use of the thermosensitive composites in photodegradation of organic pollutants by controlling temperature simply.

Keywords: Titania; Thermosensitive composite; Photocatalyst; Photocatalytic degradation; Alkyl dinitro phenol

FeCo–N_x embedded graphene as high performance catalysts for oxygen reduction reaction by Xiaogang Fu; Yanru Liu; Xiaoping Cao; Jutao Jin; Qiao Liu; Junyan Zhang (pp. 143-151).

Display Omitted► Novel FeCo–N_x moieties embedded graphene was prepared. ► The catalyst shows high activity toward oxygen reduction reaction (ORR). ► The content of Fe–N_x moieties could affect ORR activity. ► Binary metal precursors assists embed FeCo–N_x moieties into graphene sheets.Graphene based non precious metal catalysts for oxygen reduction reaction (ORR) has been successfully fabricated through pyrolysis of a mixture of Fe, Co salts, polyaniline, and reduced graphene oxide (rGO). The transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectrum and X-ray photoelectron spectroscopy (XPS) analysis's indicated the transition metal nitrogen-containing moieties (M–N_x, M=Fe or/and Co, x=2 or 4) could be embedded into the graphene sheets. The electrochemical measurements showed that the embedded M–N_x moieties could act as catalytic sites and boost the activity of catalysts in both acidic and alkaline medium. The effects of Fe and Co on electrochemical properties toward ORR were also investigated, and the results showed the binary metal FeCo–N–rGO was the most active ORR catalyst. Rotating disk electrode measurements revealed that, compared to a commercial Pt/C electrocatalyst (loading: 52.6μgPtcm⁻²), the half-wave potential of the resultant FeCo–N–rGO was 46mV positive in alkaline medium and 119mV negative in acidic medium. In addition, the FeCo–N–rGO catalyst was much more stable and tolerant to crossover effect than Pt/C. The above superiorities make it a promising candidate for substituting Pt-based nanomaterials as a cathode catalyst for ORR in fuel cells.

Keywords: Embedded; Graphene; Electrocatalysts; Fuel cells; Oxygen reduction reaction

Selective catalytic oxidation of ammonia to nitrogen over Mg-Al, Cu-Mg-Al and Fe-Mg-Al mixed metal oxides doped with noble metals by Lucjan Chmielarz; Magdalena Jabłońska; Adam Strumiński; Zofia Piwowarska; Agnieszka Węgrzyn; Stefan Witkowski; Marek Michalik (pp. 152-162).

Display Omitted► Calcined Cu-Mg-Al hydrotalcite is active catalyst for low-temperature SCO of NH₃ to N₂. ► Calcined Fe-Mg-Al hydrotalcite is active catalyst for high-temperature SCO of NH₃ to N₂. ► Doping of the catalysts with Pt, Pd and Rh increased their activity and decreased selectivity to N₂. ► Performance of catalyst is determined by its activity in NH₃ oxidation to NO and NO reduction by NH₃.Mg-Al, Cu-Mg-Al and Fe-Mg-Al mixed oxides, were obtained by thermal decomposition of synthetic hydrotalcite-like materials and, in the next step, were modified with selected noble metals (Pt, Pd, Rh) by incipient wetness impregnation method. The process of thermal decomposition of hydrotalcite-like materials into metal oxide systems was studied by thermogravimetry method combined with the on-line analysis of gaseous products of the sample decomposition (TG–DTA-QMS). The obtained catalysts were studied with respect to chemical composition (EDS), structure (XRD, UV–vis–DRS), morphology (STEM), surface area (BET) and redox properties (H₂-TPR). Metal oxide catalysts obtained from the hydrotalcite-like precursors were characterized by high dispersion of transition metals (Cu, Fe), which were present mainly in the form of monomeric or small aggregated species dispersed in the Mg-Al oxide matrix. Noble metals, as it was shown by STEM studies, were rather uniformly dispersed on the surface of the samples. The obtained samples were tested as catalysts of the selective catalytic oxidation (SCO) of ammonia to nitrogen. The Cu-Mg-Al oxide catalyst was active in the low-temperature SCO process, while the Fe-containing sample was found to operate in the high temperature range. Modification of these catalysts with noble metals significantly decreased temperature of the ammonia oxidation but also decreased the selectivity to nitrogen. The best catalytic properties were obtained for the Cu-Mg-Al oxide catalyst modified with small amount of platinum (0.2wt%), which operated at relatively low temperature with high selectivity to nitrogen.

Keywords: Selective catalytic oxidation (SCO) of ammonia; Hydrotalcite-like materials; Mixed metal oxides; Noble metals

A new insight into the photocatalytic reduction of 4-nitroaniline to p-phenylenediamine in the presence of alcohols by Weiming Wu; Linrui Wen; Lijuan Shen; Ruowen Liang; Rusheng Yuan; Ling Wu (pp. 163-167).

Reduction of 4-nitroaniline to p-phenylenediamine via photocatalysis was observed in presence of alcohols (CH₃OH, C₂H₅OH and i-C₃H₇OH) upon purging with N₂. A mechanism was also proposed to explain the photoreduction of 4-nitroaniline to p-phenylenediamine in the present alcohols (CH₃OH, C₂H₅OH and i-C₃H₇OH).Display Omitted► Reduction of 4-nitroaniline via photocatalysis was observed in presence of CH₃OH. ► Methanol radical was found to be the main active species. ► Its formation was formed by the reaction between CH₃OH and hydroxyl radical. ► C₂H₅OH and i-C₃H₇OH were also efficient additives for the reduction reaction. ► The mechanism of the reduction of 4-nitroaniline in presence of alcohols was studied.Photoreduction of 4-nitroaniline to p-phenylenediamine over TiO₂, ZnO, PbBi₂Nb₂O₉ and CdS photocatalysts in the presence of CH₃OH was investigated under light irradiation ( hv≥band gap) upon purging with N₂. Compared with PbBi₂Nb₂O₉ and CdS, TiO₂ and ZnO showed photocatalytic activities for the photoreduction of 4-nitroaniline. Electron spin resonance analysis results revealed that a methanol radical could be detected in the present of TiO₂ and ZnO. Its formation was attributed to the reaction between the hydroxyl radical and CH₃OH molecule. The species had strong reductive ability, and therefore could reduce 4-nitroaniline to p-phenylenediamine. Other alcohols (C₂H₅OH and i-C₃H₇OH) were also found to be efficient additives for the photoreduction of 4-nitroaniline. The results of the²H-labeled experiments indicated that the p-phenylenediamine formation was formed by the hydrogen transfer reaction between the 4-nitroaniline and H₂O molecules. A mechanism was proposed to explain the photoreduction of 4-nitroaniline to p-phenylenediamine in the present alcohols.

Keywords: Nitro reduction; Photocatalysis; Electron spin resonance; Alcohol radicals

Olivine as tar removal catalyst in biomass gasification: Catalyst dynamics under model conditions by Hans O.A. Fredriksson; Remco J. Lancee; Peter C. Thüne; Hubert J. Veringa; J.W. (Hans) Niemantsverdriet (pp. 168-177).

Display Omitted► Olivine, a tar-removal catalyst in bio-mass gasification, was investigated. ► It is better seen as a supported Fe/FeO_x-catalyst than a homogeneous mineral. ► It causes substantial oxygen transport when used in dual fluidized bed reactors. ► It rapidly changes chemistry and catalytic function upon changes in gas environment. ► Olivine also shows carbon build-up in CO, and thus product gas destruction/catalyst deactivation.Olivine ((Mg,Fe)₂SiO₄) has been extensively explored as an active bed material for catalytic cracking of tars during gasification of biomass in dual fluidized bed reactors. It is known that both the elemental composition, addition of Fe and high temperature calcinations influence the catalytic properties of this mineral. However, it is not clear how olivine responds to the fairly hostile environments present during gasification or what chemical state Fe takes during operation. We have investigated the stability of Austrian olivine under model conditions, resembling those in a gasifier. Powder samples were heated to 750°C in a quartz-tube flow-reactor and sequentially exposed to oxidizing (O₂, H₂O, CO₂) or reducing gases (CO, H₂) or mixtures thereof, for various durations of time. Significant changes in phase composition of the material, depending on the gas composition and the duration of the treatments, were found using X-ray photo-electron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and scanning electron microscopy (SEM). A large fraction of the Fe in the investigated material is present as free Fe-phases, which are sensitive to changes in the gas environment. After exposure to oxidizing gases, the free Fe phases are: Fe₂O₃ and Fe₃O₄ or MgFe₂O₄. Upon exposure to reducing gases, the iron oxides are converted into Fe⁰ and Fe₃C and formation of graphitic carbon is observed. In addition, the elemental composition of the surface changes dramatically depending on the gas composition. After exposure to oxidizing environments, the amount of Fe at the surface is twice as high as after reduction. Both the change in chemical state of the Fe-phases, the amount of surface Fe and the build-up of surface carbon are fast processes under the applied conditions and significant changes are observed on the time scale of one minute. These observations have important implications for olivine as a tar cracking catalyst, especially when used in dual fluidized bed gasifiers. The fast reduction of the iron oxides upon switching from oxidizing to reducing conditions shows that olivine transports oxygen from the combustor into the gasifier. Furthermore, the catalytic properties of Fe depend strongly on its chemical state. Therefore, the catalytic function of olivine depends strongly on the gas environment and on the catalysts residence time in the gasifier. Finally, both the decreasing amount of surface-Fe and the carbon deposition observed after exposing olivine to reducing conditions can result in significant catalyst deactivation.

Keywords: Biomass; Gasification; Catalyst stability; Tar; Olivine

Hydrothermal fabrication and enhanced photocatalytic activity of hexagram shaped InOOH nanostructures with exposed {020} facets by Hua Zhao; Wenyan Yin; Mingyuan Zhao; Yuzhe Song; Heqing Yang (pp. 178-186).

Display Omitted► Hexagram shaped InOOH nanostructures were first obtained via a hydrothermal route. ► The InOOH hexagram shaped structures were formed via the oriented attachment process. ► Hexagram shaped InOOH nanostructures show higher photocatalysis than Degussa P25. ► The high intrinsic photocatalytic activity results from the exposed {020} facets.Hexagram shaped InOOH nanostructures with exposed {020} facets were synthesized in large quantities via the hydrothermal reaction of InCl₃ with NaAc, ethylene glycol and H₂O system at 180–220°C for 12h. The six constituent nanocones of the hexagram shaped nanostructure grew along the directions perpendicular to(200)/(2¯00),(101)/(1¯01¯) and(1¯01)/(101¯) facets of the orthorhombic InOOH through the oriented attachment process, and the top and bottom surfaces of the hexagrams were dominantly enclosed by the {020} facets. The {020} facets were stabilized by ethylene glycol, which was employed to control the growth of InOOH crystals. When the hydrothermal reaction temperature increased, the size of hexagram shaped InOOH nanostructures decreased, their specific surface area and the texture coefficient (TC) of (020) plane increased, and thus their photocatalytic activity was enhanced. The hexagram shaped InOOH nanostructures obtained at 220°C showed higher intrinsic photocatalytic activity than Degussa P25 TiO₂ for degradation of rhodamine B. The superior intrinsic photocatalytic activity was attributed to the high percentage of exposed {020} facets of the hexagram shaped nanostructures.

Keywords: InOOH; Hexagram shaped nanostructures; Exposed {0; 2; 0} facets; Photocatalytic activity; Rhodamine B

Tungstophosphoric acid immobilized on ammonium Y and ZSM5 zeolites: Synthesis, characterization and catalytic evaluation by Candelaria Leal Marchena; Romina A. Frenzel; Silvina Gomez; Liliana B. Pierella; Luis R. Pizzio (pp. 187-196).

Display Omitted► TPA immobilized over NH₄Y and NH₄ZSM5 zeolites were prepared by wet impregnation. ► S_BET of NH4YTPA and NH4ZSM5TPA samples decreased with the increase of TPA content. ► E_g values of NH4YTPA and NH4ZSM5TPA samples are similar to those reported for TiO₂. ► Irradiated NH4YTPA and NH4ZSM5TPA samples degraded efficiently 4-CP solutions.Two series of materials based on tungstophosphoric acid (TPA) immobilized on NH4Y and NH4ZSM5 zeolites were prepared by wet impregnation of the zeolite matrix with TPA aqueous solutions. Their concentration was varied in order to obtain TPA contents of 5, 10, 20 and 30% (w/w) in the solid. The materials were characterized by N₂ adsorption–desorption isotherms, XRD, FT-IR,³¹P MAS-NMR, TGA-DSC, DRS–UV–vis, and the acidic behavior was studied by potentiometric titration with n-butylamine.The specific surface area ( S_BET) decreased when the TPA content was raised as a result of the zeolite pore blocking. The X-ray diffraction patterns of the solids modified with TPA only presented the characteristic peaks of NH4Y and NH4ZSM5 zeolites, and an additional set of peaks assigned to the presence of (NH₄)₃PW₁₂O₄₀. According to the Fourier transform infrared and³¹P magic angle spinning-nuclear magnetic resonance spectra, the main species present in the samples (except for NH4YTPA05) is the [PW₁₂O₄₀]³⁻ anion, which was partially transformed into [P₂W₂₁O₇₁]⁶⁻ anion during the synthesis and drying steps. The thermal stability of the NH4YTPA and NH4ZSM5TPA materials is similar to that of their parent zeolites. Moreover, the samples with the higher TPA content present band gap energy values similar to those reported for TiO₂.The immobilization of TPA on NH4Y and NH4ZSM5 zeolites is a good method to obtain catalysts with high photocatalytic activity in the 4-chlorophenol degradation. They can be reused at least three times without an important decrease in the degradation degrees.

Keywords: Tungstophosphoric acid; Zeolites; 4-Chlorophenol; Photocatalytic degradation

Pt nanoparticles supported on SBA-15: Synthesis, characterization and applications in heterogeneous catalysis by Junjiang Zhu; Tao Wang; Xuelian Xu; Ping Xiao; Jinlin Li (pp. 197-217).

Display Omitted► High-surface-area SBA-15 was used as support of platinum catalysts. ► Various methods used for the preparation of Pt/SBA-15 were overviewed. ► Characterizations on Pt/SBA-15 prepared by different methods were conducted to indicate the feature of each method. ► Catalytic performances of Pt/SBA-15 for various reactions were discussed.This review gave a brief description on the synthesis, characterizations and applications of Pt/SBA-15 in heterogeneous catalysis. Pt/SBA-15 has attracted a great deal of interest in catalysis in the past decades due to its excellent catalytic performances exhibited in the reactions such as CO oxidation, aerobic alcohol oxidation, toluene hydrogenation. Whereas, the preparation of active and stable Pt/SBA-15 material for catalysis use is still a challenging topic, as the surface of SBA-15 is relatively inert and the surface Pt NPs tend to aggregation at high temperatures, or leaching in liquid medium. Thus, for a defined reaction, the selection of a proper method and an understanding to the features of the method are essential before synthesizing Pt/SBA-15 and using it for reactions. In this review, the synthesis method, physicochemical properties and catalytic performances of Pt/SBA-15 prepared by different methods were overviewed. These introductions are base for new researcher working in this field, but are also necessary for experienced scientists who want to explore new fields.

Keywords: Pt nanoparticles; SBA-15; Preparation method; Characterization; Catalytic performance

The role of interfacial lattice Ag⁺ on titania based photocatalysis by Hongyun Yang; Feng Chen; Yanchao Jiao; Jinlong Zhang (pp. 218-223).

Display Omitted► Ag⁺/TiO₂ was prepared by eluting the Ag⁰ cluster from the Ag⁰/Ag⁺/TiO₂. ► Ag⁺/TiO₂ shows higher photocatalytic activity than Ag⁰/Ag⁺/TiO₂. ► Interfacial lattice Ag⁺ is crucial for the superior activity of Ag⁺/TiO₂. ► Interfacial lattice Ag⁺ acts as recyclable catalytic sites in photocatalysis.Ag⁰/Ag⁺/TiO₂ composites were prepared via alkalescent hydrothermal process in aqueous ammonia, and Ag⁺/TiO₂ was prepared by eluting the Ag⁰ cluster from the Ag⁰/Ag⁺/TiO₂ composites with K₃[Fe(CN)₆]/aqueous ammonia. Methyl orange (MO) and Rhodamine B (RhB) were used to test the photocatalytic activity of the photocatalysts. The photocatalytic activity of the composites was greatly improved after eluting Ag⁰ clusters from the Ag⁰/Ag⁺/TiO₂ composites. Interfacial lattice Ag⁺ cations but not Ag⁰ clusters are responsible for improving the photocatalytic performance of the composites in this work. XPS measurement shows that the chemical state of the interfacial lattice Ag⁺ cation is different with the surface chemical adsorbed Ag⁺ cation. Surface chemical adsorbed Ag⁺ cation is invalid to promote the photocatalytic activity of TiO₂ while Na⁺ cation can cancel the promotional effect of the interfacial lattice Ag⁺ cation by competitively occupying the interfacial lattice defects. The 2h turn over numbers of the interfacial lattice Ag⁺ cations to the degradation of MO and RhB reach 8 and 10, respectively, which show that the interfacial lattice Ag⁺ cations act as recyclable catalytic sites but not one-time consumptive species.

Keywords: Ag; ⁰; Ag; ⁺; TiO; ₂; Photocatalysis; Interface

Preferential oxidation of CO in excess H₂ over CuO/CeO₂ catalysts: Characterization and performance as a function of the exposed face present in the CeO₂ support by D. Gamarra; A. López Cámara; M. Monte; S.B. Rasmussen; L.E. Chinchilla; A.B. Hungría; G. Munuera; N. Gyorffy; Z. Schay; V. Cortés Corberán; J.C. Conesa; A. Martínez-Arias (pp. 224-238).

Structure/activity relationships on the basis of multitechnique characterization and catalytic testing complemented by operando-DRIFTS analysis for the preferential oxidation of CO in H₂-rich streams demonstrate interactions of dispersed CuO with CeO₂ (100) faces in ceria nanocubes as most interesting for the process.Display Omitted► CO-PROX catalytic properties of CuO/CeO₂ as a function of the exposed face in CeO₂. ► Ceria nanocubes supported system shows most interesting CO-PROX performance. ► Redox and particle size properties of dispersed CuO particles appear most relevant.A series of oxidised copper-cerium nanostructured catalysts prepared by impregnation of copper over ceria supports synthesized by different methods (hydrothermal with varying preparation parameters, microemulsion/precipitation), in order to achieve different specific morphologies (nanocubes, nanorods and nanospheres), have been examined with respect to their catalytic properties for preferential oxidation of CO in excess H₂ (CO-PROX). The catalysts have been characterized in detail by XRD, Raman, S_BET measurement, HREM, XPS, TPR and EPR, which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of CO-PROX catalytic properties by means of catalytic activity measurements complemented by operando-DRIFTS. Structural dependence of the CO oxidation reaction on the dispersed copper oxide entities as a function of the exposed face present at the surface of the different ceria supports is revealed. An important overall enhancement of the CO-PROX performance is detected for the sample supported on ceria nanocubes which is proposed to be a consequence of the interaction between copper oxide and (100) faces of the ceria support.

Keywords: Nanostructured CuO-CeO; ₂; catalysts; CO-PROX; HREM; EPR; TPR; Operando-DRIFTS; XPS; Raman; XRD

Pt and Au/TiO₂ photocatalysts for methanol reforming: Role of metal nanoparticles in tuning charge trapping properties and photoefficiency by Alberto Naldoni; Massimiliano D’Arienzo; Marco Altomare; Marcello Marelli; Roberto Scotti; Franca Morazzoni; Elena Selli; Vladimiro Dal Santo (pp. 239-248).

Display Omitted► Pt nanoparticles loaded on TiO₂ highly active in hydrogen production. ► Pt nanoparticles loaded on TiO₂ highly active in the methanol complete oxidation. ► The amount of electron traps (Ti³⁺ centers) follows the order TiO₂≫Au/TiO₂>Pt/TiO₂. ► The amount of hole traps (O⁻ centers) is highest in Pt/TiO₂. ► Easier transfer of photopromoted electrons to Pt NPs accounts for higher performance.Metal-loaded TiO₂ is, by far, one of the most important class of photocatalysts in hydrogen production through photoreforming of organics and water photosplitting. In this study anatase loaded with Au and Pt nanoparticles (Au/TiO₂ and Pt/TiO₂) by an impregnation-reduction method was investigated as for morphological, electronic (XPS) and photocatalytic properties in hydrogen production by methanol photoreforming. The electron and hole trapping centers, Ti³⁺ and O⁻, respectively, formed under UV–vis irradiation of the photocatalysts, were studied by in situ electron spin resonance (ESR) spectroscopy. The nature of the loaded metal affected both the H₂ evolution rate and the distribution of the methanol oxidation products. The better performance of Pt/TiO₂ is attributable to the greater ability of Pt with respect to Au to act as electron sink, slowering the recombination of photoproduced electron–hole couples. Direct evidence of this effect was obtained by ESR analysis, showing that the amount of Ti³⁺ active sites follows the order TiO₂>Au/TiO₂≫Pt/TiO₂, thus confirming easier electron transfer from Ti³⁺ to Pt, where the H⁺ reduction to H₂ occurs.

Keywords: Photocatalytic hydrogen production; Titanium dioxide; Gold; Platinum; ESR; Charge trapping centers

Photolysis and TiO₂ photocatalysis of the pharmaceutical propranolol: Solar and artificial light by N. De la Cruz; R.F. Dantas; J. Giménez; S. Esplugas (pp. 249-256).

Display Omitted► We studied propranolol degradation by direct photolysis and photocatalysis. ► We employed and compared two different devices with artificial and solar light. ► Photolysis contributed significantly to transformation, but gave poor mineralization. ► Photocatalysis was useful on the removal and mineralization of PRO. ► Photocatalysis improved toxicity and oxidation of intermediates.This study focuses on the removal of the pharmaceutical propranolol (PRO) by direct photolysis and TiO₂ photocatalysis. Two different devices were employed, one at laboratory scale with artificial light (Xe-lamp) and the other one at pilot scale using solar irradiation. The solar plant was based on CPCs photoreactors. Solar radiation was quantified by a radiometer. To compare both devices, radiation was also measured using actinometries. PRO degradation and mineralization were assessed to establish the feasibility of both treatments.For direct photolysis, the influence of wavelength ranges was evaluated. In addition, reactors made with different materials (quartz and Duran) were also tested. Significant PRO degradation could be observed employing quartz reactors in both devices. PRO removal achieved after 240min was 77% and 71% for the solar and the laboratory device, respectively. However, mineralization accomplished resulted to be negligible (7% and 2%).For photocatalysis, different TiO₂ concentrations (0.1, 0.2, 0.4gL⁻¹) were tested. When 0.4gL⁻¹ was used, the best results could be observed in both installations. PRO degradation percentages achieved after 240min were 81% at the solar plant and 94% at laboratory. Meanwhile, mineralization reached was 30% and 41% in solar plant and laboratory device respectively.In order to compare the different catalyst loads at the two devices, kinetics were evaluated as a function of time and energy involved. As TiO₂ concentration increased, higher reaction rates were obtained in both devices. In general, the laboratory device gave rates 1.1–1.5 times higher than the solar installation.Biodegradability (BOD₅/COD), oxidation (COD) and toxicity (algae Chlorella vulgaris) evolution during solar photocatalysis were followed. Biodegradability improved slightly from 0 to 0.06 after 270min for the solar device, remaining non-biodegradable. Toxicity, measured in percentage of photosynthesis inhibition, decreased with treatment time. Oxidation of intermediates was observed, as COD underwent a reduction of 30% after 270min.This article also provides a section comparing different techniques found in literature employed for PRO abatement.

Keywords: Emerging contaminants; Propranolol; Advanced oxidation process; Direct photolysis; Photocatalysis; TiO; ₂; Solar; Xe-lamp

Highly stable and efficient Ag/AgCl core–shell sphere: Controllable synthesis, characterization, and photocatalytic application by Bowen Ma; Jianfeng Guo; Wei-Lin Dai; Kangnian Fan (pp. 257-263).

.Display Omitted► Highly active Ag/AgCl core–shell sphere with uniform morphology. ► Molar ratio of Fe:Ag in solution at room temperature controls the structure. ► The formation process of the sphere was proposed. ► Fe: Ag-1:1 shows the best activity in the photo-degradation of RhB. ► Outstanding stability and reusability was found.A new composite photocatalyst Ag/AgCl core–shell sphere was synthesized at room temperature by using a simple and generic approach. SEM images revealed that the as-prepared catalyst showed a uniform morphology with an average size of about 2μm. The photocatalytic activity was significantly dependent on the molar ratio of Ag⁰:Ag⁺ on the surface of the catalyst, the optimum ratio being 0.035. Recycling experiments confirmed the excellent stability of the catalysts, without any silver leaching from the surface of the catalyst, suggesting that the photocatalyst Ag/AgCl core–shell sphere was a form of active and stable visible-light driven plasmonic material.

Keywords: Ag/AgCl core–shell sphere; Photocatalysis; FeCl; ₃; oxidation; RhB degradation; Visible-light driven material

Improvement of visible light responsivity of rutile TiO₂ nanorods by site-selective modification of iron(III) ion on newly exposed faces formed by chemical etching treatment by Misa Nakamura; Asami Ono; Eunyoung Bae; Naoya Murakami; Teruhisa Ohno (pp. 264-269).

Display Omitted► Fe³⁺ were modified on newly exposed {001} and {11 n} ( n<1) as oxidation faces. ► Photocatalytic activity was evaluated by decomposition of toluene under visible light. ► Fe³⁺-modified rutile nanorods after etching with H₂SO₄ exhibited superior activity. ► Fe³⁺-modification on {001} faces increased in electron injection from Fe³⁺ into TiO₂. ► Activity depended on both surface area of reduction faces and amount of electrons.Site-selective modification of trivalent iron(III) (Fe³⁺) ions was applied to rutile titanium(IV) oxide (TiO₂) nanorods after chemical etching treatment in order to improve photocatalytic activity under visible-light irradiation. Chemical etching of rutile nanorods with {110} and {111} faces using aqueous sulfuric acid (H₂SO₄) or hydrogen (H₂O₂)–ammonia (NH₃) solution exposed {001} and {11 n} ( n<1) faces, respectively. Fe³⁺-modified rutile nanorods after chemical etching exhibited higher photocatalytic activity for degradation of toluene in gas phase than that before chemical etching. This improvement of photocatalytic activity was attributed to a large amount of site-selectively-modified Fe³⁺ ions, resulting in an increase in photoabsorption. Moreover, our results indicate that a rutile nanorod with large {001} and {110} exposed crystal faces is the most suitable structure for visible light response by site-selective modification of Fe³⁺ ions.

Keywords: Rutile TiO; ₂; nanorod; Exposed crystal faces; Site-selective modification of Fe; ³⁺; ions; Chemical etching; Visible-light responsive photocatalyst

One-pot synthesis of gold nanoparticle/molybdenum cluster/graphene oxide nanocomposite and its photocatalytic activity by Alexandre Barras; Manash R. Das; Rami Reddy Devarapalli; Manjusha V. Shelke; Stéphane Cordier; Sabine Szunerits; Rabah Boukherroub (pp. 270-276).

Display Omitted► A tri-component Au nanoparticles/molybdenum cluster/GO nanohybrid is synthesized. ► The photocatalytic activity of the composite was studied under visible irradiation. ► The nanocomposite shows a high performance for the photodegradation of RhB.The paper reports on a facile one-pot synthesis of a tri-component gold nanoparticle/molybdenum cluster/graphene oxide (AuNPs@Mo–GO) nanohybrid composite. The synthetic methodology consists on direct UV irradiation of an aqueous solution containing graphene oxide (GO), Na₂[Mo₆Br₈(N₃)₆], HAuCl₄·3H₂O and isopropanol at room temperature in air using a UV fiber lamp. The composite material exhibits very high photocatalytic activity for the degradation of rhodamine B under visible light irradation. The resulting nanohybrid material was characterized using Raman spectroscopy, UV–vis spectrometry, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

Keywords: [Mo; ₆; Br; ₈; (N; ₃; ); ₆; ]; ²⁻; cluster; Graphene oxide; Gold nanoparticles; Nanohybrid; Rhodamine B; Photodegradation; Visible light

Ordered mesoporous CeO₂-TiO₂ composites: Highly efficient photocatalysts for the reduction of CO₂ with H₂O under simulated solar irradiation by Yangang Wang; Bo Li; Chengli Zhang; Lifeng Cui; Shifei Kang; Xi Li; Lihui Zhou (pp. 277-284).

Ordered mesoporous CeO₂-TiO₂ composites with 2D hexagonal structure and varied compositions were synthesized through a simple nanocasting route using ordered mesoporous SBA-15 as the template. Due to the special composition and structure, these composite photocatalysts exhibited an exceptionally high activity in the photoreduction of CO2 with H2O under simulated solar irradiation.Display Omitted► Ordered mesoporous CeO₂-TiO₂ composites were synthesized by a nanocasting route. ► The obtained CeO₂-TiO₂ composites have a high surface area and hierarchical porosity. ► Induced CeO₂ in composites can extend the spectral response from UV to visible area. ► The enhanced surface chemisorbed oxygen species was observed in CeO₂-TiO₂ composites. ► These CeO₂-TiO₂ composites exhibit a high activity in the photoreduction of CO₂.Ordered mesoporous CeO₂-TiO₂ composites with 2D hexagonal structure and varied compositions were synthesized through a nanocasting route using ordered mesoporous SBA-15 as the template. X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectra analysis techniques were used to characterize the samples. It is observed that the obtained CeO₂-TiO₂ composites have ordered 2D hexagonal mesostructures with high specific surface area and hierarchical porosity. Introduction of CeO₂ species can effectively extend the spectral response from UV to visible area and enhance the surface chemisorbed oxygen of the ordered mesoporous TiO₂. Due to the peculiar composition and structural characteristics, these ordered mesoporous CeO₂-TiO₂ composites exhibited excellent photocatalytic activity in the reduction of CO₂ with H₂O under simulated solar irradiation.

Keywords: Ordered mesoporous; CeO; ₂; -TiO; ₂; composites; Nanocasting route; Photocatalyst; Reduction of CO; ₂

Photocatalytic degradation of carbamazepine by tailored BiPO₄: efficiency, intermediates and pathway by Jian Xu; Lei Li; Changsheng Guo; Yuan Zhang; Wei Meng (pp. 285-292).

Display Omitted► BiPO₄ was controllably synthesized via hydrothermal methods. ► BiPO₄ exhibited high photocatalytic activity to carbamazepine. ► The monoclinic phase BiPO₄ was proved to be more active than the hexagonal phase. ► Photogenerated holes and HO• dominated the reaction by BiPO₄. ► Ten reaction intermediate/products were identified by HPLC–MS/MS.This study firstly explored the photodegradation of carbamazepine, one of the most frequently detected pharmaceuticals, with tailored BiPO₄ nanomaterials. BiPO₄ was synthesized with a hydrothermal method. The physicochemical properties of the obtained samples were characterized and the results indicated that both the hydrothermal temperature and reaction time influenced the phase, morphology and optical properties of the BiPO₄ catalysts, which may further determine their specific photocatalytic performances. The intrinsic microstructure and optical properties reflected the crystal properties of the catalysts to some extent. The BiPO₄ prepared at 180°C for 72h (BPO-180-72) displayed the best photocatalytic activity under UV irradiation, during which carbamazepine was nearly completely eliminated from ultrapure water after 60min irradiation. The good photocatalytic activity was ascribed to the synergistic effect of monoclinic phase and relatively ordered morphology of the resulting BiPO₄. Particularly, the monoclinic phase was firstly proved to be more active than the hexagonal phase for BiPO₄ samples. BPO-180-72 removed approximately 72.4% of carbamazepine from lab-prepared simulated wastewater after 60min irradiation, suggesting the potential application of this material in wastewater treatment. Ten reaction intermediate products were observed and identified by HPLC–MS/MS, and a tentative reaction pathway was proposed. Results indicated that photogenerated holes and hydroxyl radicals were the main reactive species for the photodegradation of carbamazepine in the system.

Keywords: Photocatalysis; BiPO; ₄; Carbamazepine; Intermediates; Pathway

A comparative study of different doped metal cations on the reduction, adsorption and activity of CuO/Ce_0.67M_0.33O₂ (M=Zr⁴⁺, Sn⁴⁺, Ti⁴⁺) catalysts for NO+CO reaction by Xiaojiang Yao; Qiang Yu; Zeyang Ji; Yuanyuan Lv; Yuan Cao; Changjin Tang; Fei Gao; Lin Dong; Yi Chen (pp. 293-304).

Display Omitted► The electronegativity of dopant influences the reducibility of CuO/Ce_0.67M_0.33O₂ (M=Zr⁴⁺, Sn⁴⁺, Ti⁴⁺) catalysts and their catalytic performance significantly. ► Cu⁺/Cu⁰ species play a key role in NO reduction by CO. ► CuO/Ce_0.67Zr_0.33O₂ exhibits higher activity and selectivity than CuO/Ce_0.67Sn_0.33O₂ and CuO/Ce_0.67Ti_0.33O₂.A series of ceria-based solid solutions (Ce_0.67Zr_0.33O₂, Ce_0.67Sn_0.33O₂, Ce_0.67Ti_0.33O₂) were synthesized by inverse co-precipitation, and then used as supports to prepare CuO/Ce_0.67M_0.33O₂ (M=Zr⁴⁺, Sn⁴⁺, Ti⁴⁺) catalysts through wetness impregnation method. The obtained samples were investigated in detail by means of XRD, LRS, N₂-physisorption, H₂-TPR, XRF, XPS and in situ FT-IR techniques. The catalytic reduction of NO by CO as a model reaction was chosen to evaluate the catalytic performance of these samples. These results suggest that: (1) the reduction of CuO/Ce_0.67Zr_0.33O₂ is easier than CuO/Ce_0.67Sn_0.33O₂ and CuO/Ce_0.67Ti_0.33O₂ catalysts, which may be attributed to the difference in the electronegativity of dopant; (2) the reduced state Cu⁺ is present in CuO/Ce_0.67Zr_0.33O₂ at ambient temperature due to the shifting of redox equilibrium (Cu²⁺+Ce³⁺ ↔ Cu⁺+Ce⁴⁺) to right; (3) the adsorbed NO species on CuO/Ce_0.67Zr_0.33O₂ are more liable to desorb/transform/decompose than those on CuO/Ce_0.67Sn_0.33O₂ and CuO/Ce_0.67Ti_0.33O₂ samples. The results of catalytic performance show that Cu⁺/Cu⁰ species play a key role in NO reduction by CO, and the activity is mainly related to the electronegativity of dopant, the reduction and adsorption behaviors of these catalysts. Furthermore, a possible reaction mechanism (schematic diagram) is tentatively proposed to understand this reaction.

Keywords: Ceria-based solid solution; Dopant; Electronegativity; Copper-based catalyst; NO; +; CO reaction

Pronounced synergetic effect of the nano-sized PtSnNi/C catalyst for ethanol oxidation in direct ethanol fuel cell by Seden Beyhan; Jean-Michel Léger; Figen Kadırgan (pp. 305-313).

Display Omitted► Carbon supported Pt–Sn based nanoparticles synthesized by Bönnemann method. ► The promoted effect of Ni on the activity for PtSnNi/C towards ethanol oxidation. ► With the Pt₈₀Sn₁₀Ni₁₀/C anode catalyst six times higher DEFC performance than Pt/C.Carbon supported well-dispersed Pt, Pt₉₀Sn₁₀, Pt₉₀Ni₁₀ and Pt₈₀Sn₁₀Ni₁₀ nanoparticles were synthesized by co-reduction using Bönnemann's colloidal precursor method. X-ray diffraction (XRD) analysis showed that catalysts have the Pt face centred cubic (fcc) structure and their crystallite size are in the range 2–6nm. Regarding the ternary Pt₈₀Sn₁₀Ni₁₀/C catalyst, its lattice parameter is larger than that of Pt₉₀Ni₁₀/C and smaller than that of Pt₉₀Sn₁₀/C. The size of catalyst nanoparticles was observed via Transmission electron microscopy (TEM) and showed an average diameter of 3nm. X-ray photon electron spectroscopy (XPS) results indicate that the surface of Pt₉₀Sn₁₀/C catalyst is enriched in Sn as compared to bulk composition, whereas Pt₈₀Sn₁₀Ni₁₀/C catalyst is Pt-enriched. The onset potentials for ethanol oxidation on Pt₉₀Sn₁₀/C and Pt₈₀Sn₁₀Ni₁₀/C catalysts were significantly lower than that of Pt/C and Pt₉₀Ni₁₀/C. Single direct ethanol fuel cell (DEFC) performances obtained for the Pt₈₀Sn₁₀Ni₁₀/C is promising when compared to that obtained with Pt₉₀Sn₁₀/C catalyst. The effect of Ni by promoting the CC bond cleavage is confirmed by in situ IR measurements. These results suggest the presence of Ni in the Pt₈₀Sn₁₀Ni₁₀/C catalyst can facilitate CC bond cleavage reaction on its Pt-rich surface; however, Sn oxide species activates the adsorbed CO on the surface providing the necessary OH species for oxidation of ethanol at lower potentials.

Keywords: PtSnNi/C catalyst; PtSn-based catalyst; Ethanol oxidation; Direct ethanol fuel cell

Investigation of a molybdenum-containing silica catalyst synthesized by the sol–gel process in heterogeneous catalytic esterification reactions using methanol and ethanol by Alesandro Bail; Vannia Cristina dos Santos; Marianne Roque de Freitas; Luiz Pereira Ramos; Wido Herwig Schreiner; Gustavo Pimenta Ricci; Katia Jorge Ciuffi; Shirley Nakagaki (pp. 314-324).

Display Omitted► Preparation of solid catalyst based on Mo-containing silica by the sol–gel process. ► Catalyst based on Mo-containing silica for heterogeneous esterification reaction. ► Fatty acids catalytic heterogeneous esterification reaction using CH₃OH and CH₃CH₂OH. ► Activity is associated with Mo atoms sites displaying Brønsted acidity in the silica. ► Catalyst with efficiency and recyclability capacity.Molybdenum-containing silica easily synthesized by the sol–gel process was evaluated as catalyst for heterogeneous esterification reaction of fatty acids using methanol and ethanol. The molybdenum content depended on the conditions employed during the synthesis. The solids were characterized by X-ray powder diffraction, textural analysis, X-ray photoelectronic spectroscopy, and inductively coupled plasma optical emission spectroscopy. The strength and distribution of the acid sites were assessed by the adsorption–desorption of n-butylamine as monitored by Fourier transform infrared spectroscopy and thermogravimetric analysis. Kinetic studies revealed high fatty acid conversion for both alcohols and diminished activity upon decreasing concentration of acid sites. Monitoring of the acid sites during the recycling experiments indicated association of the catalytic activity with Mo oxide species on the surface and with the availability of molybdenum-active sites displaying Brønsted–Lowry acidity in the silica structure.

Keywords: Molybdenum; Heterogeneous catalysis; Esterification; Biodiesel; Acid sites; Silica; Sol–gel process

Nanostructured ceria supported Pt and Au catalysts for the reactions of ethanol and formic acid by Aysegul Ciftci; D.A.J. Michel Ligthart; Pietro Pastorino; Emiel J.M. Hensen (pp. 325-335).

Display Omitted► Pt and Au supported on ceria nanoshapes tested in ethanol and formic acid decomposition. ► Pt more active than Au in ethanol steam reforming, oxidation and decomposition. ► Rod-shaped ceria yields more active catalysts in ethanol steam reforming and WGS. ► Au on ceria selectively dehydrogenates formic acid. ► Decarbonylation of formic acid also takes places on Pt/ceria.Decomposition reactions of ethanol and formic acid were studied over a series of Au and Pt nanoparticle catalysts. CeO₂ nanorods and nanocubes served as model supports representing the {110} and {100} surfaces of CeO₂ nanocrystals. Pt was more active than Au in low temperature (below 400°C) steam reforming, oxidation and decomposition (without an oxygen source) of ethanol. Similar trends were observed in the WGS reaction. Different from Au, for Pt the initial step of ethanol dehydrogenation to acetaldehyde is followed by the cleavage of the CC bonds of acetaldehyde to CH₄ and CO due to the higher PtC bond strength when compared to that of AuC. The catalysts supported on nanorod-shaped ceria were more active than those derived from nanocube-shaped ones in ethanol steam reforming and WGS reactions due to the abundance of OH species formed by activation of water on the oxygen vacancies in the CeO₂{110} surfaces of ceria nanorod supported catalysts. Complete oxidation of ethanol to CO₂ and H₂O was observed over the Pt and Au supported CeO₂(rod) catalysts. For the former, complete oxidation took place starting from temperatures as low as 150°C. These catalysts were active for decomposition of formic acid starting from near-ambient temperatures ( T>50°C) up to 200°C, at which temperature formic acid was completely converted over all the catalysts. Au was more active and it selectively dehydrogenated formic acid into CO₂ and H₂. The intrinsic activity of the CN-leached Au/CeO₂(rod) catalyst containing highly dispersed sub-nanometer Au clusters was higher than the parent catalyst. Pt, on the other hand, showed lower selectivity toward the dehydrogenation pathway due to its higher activity in WGS reaction and enhanced PtO bond strength resulting in decarbonylation of formic acid.

Keywords: Gold; Platinum; Ceria; Ethanol conversion; Formic acid decomposition

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Applied Catalysis B, Environmental (v.130-131, #)

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Applied Catalysis B, Environmental (v.130-131, #)