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Applied Catalysis B, Environmental (v.136-137, #)

Contents (pp. co4).

Editorial Board (pp. i).

Contents (pp. i).

Editorial Board (pp. co2).

Nickel cobalt hydroxide nanoflakes as catalysts for the hydrogen evolution reaction by Stève Baranton; Christophe Coutanceau (pp. 1-8).

Display Omitted► NiCo alloys of different atomic ratio were synthesized and characterized. ► Ni_xCo1−_x(OH)₂ nanoflakes were obtained. ► The order of activity towards HER increases with Co content. ► The order of stability decreases with Co content. ► Ni₅Co₅ and Ni₇Co₃ are good compromises between activity and stability towards HER.The activity of Ni_xCo10−_x/C catalysts for the hydrogen evolution reaction (HER) was evaluated. The Ni_xCo10−_x/C (0≤ x≤ 10) nano-catalysts were synthesized by a water-in-oil microemulsion method and were then characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The control of a metal loading of ca. 30wt% on carbon was confirmed for all catalysts from TGA, while TEM images and XRD patterns revealed the formation of nickel cobalt hydroxide nano-flakes with a preferential growth along the (100) and (010) directions. The electrochemical investigations in 0.1M NaOH confirmed the interaction between nickel and cobalt in the catalytic materials, and their activity towards the HER. The catalytic activity increased regularly with the increase of the cobalt content in the Ni_xCo10−_x/C materials. The short term stability measurements performed by chronoamperometry revealed that dissolution of cobalt occurred. Hence, amongst the nickel cobalt hydroxides synthesized, Ni₅Co₅/C and Ni₇Co₃/C catalysts were found to present a good compromise between catalytic activity for the HER and stability.

Keywords: Alkaline medium; Alloys; Cobalt; Hydrogen evolution reaction; Nickel

Maghemite nanoparticles and maghemite/silica nanocomposite microspheres as magnetic Fenton catalysts for the removal of water pollutants by Nassira Ferroudj; Jimmy Nzimoto; Anne Davidson; Delphine Talbot; Emmanuel Briot; Vincent Dupuis; Agnès Bée; Mohamed Salah Medjram; Sébastien Abramson (pp. 9-18).

Display Omitted► Maghemite nanoparticles and maghemite–silica nanocomposite microspheres were designed. ► These materials were fully characterized and tested as magnetic Fenton catalysts. ► Both were active on three aqueous pollutants, which were quickly decomposed. ► The activity depends on the adsorption capacity and the accessibility to the catalyst. ► The microspheres can be easily removed with a magnet and were reused five times.Maghemite nanoparticles (γ-Fe₂O₃ NP) and maghemite/silica nanocomposite microspheres (γ-Fe₂O₃/SiO₂ MS) have been evaluated as magnetic heterogeneous Fenton catalysts. The catalysts were fully characterized by electronic microscopies, magnetometry, XRD, UV–vis–NIR spectroscopy, and sorption volumetry. It was found that the two materials differ in size, morphology, porosity and microstructure, although the maghemite nanoparticles are not modified by their encapsulation into the silica. Both catalysts have a strong magnetic susceptibility, but only the MS catalyst can be easily recovered by magnetic settlement. The mineralization and decolorization of aqueous solutions containing a model pollutant in presence of the catalysts were comparatively studied. Three model pollutants differing in their structure and their electrostatic charge were tested. The obtained reaction rates depend on the nature of the pollutant and catalyst. The results indicate the existence of a correlation between the amount of adsorbed pollutant and the decolorization rate. The free NP are usually more active than the MS catalyst, but larger velocity can also be obtained with the MS catalyst when the pollutant is strongly adsorbed on this material. Moderate mineralization rates were observed for both catalysts illustrating the larger stability towards oxidation of the uncoloured organic intermediates resulting from the primary degradation of the model pollutants. Moreover the efficiency and stability of the MS catalyst were established since this material showed an activity for a pollutant during five consecutive tests. This was also confirmed by characterization of the catalyst after these tests.

Keywords: Iron oxide nanoparticles; Silica microspheres; Magnetic nanocomposites; Fenton catalyst; Water-treatment

Novel effect of SO₂ on the SCR reaction over CeO₂: Mechanism and significance by Shijian Yang; Yongfu Guo; Huazhen Chang; Lei Ma; Yue Peng; Zan Qu; Naiqiang Yan; Chizhong Wang; Junhua Li (pp. 19-28).

.Display Omitted► The promotion of SO₂ on the SCR reaction was due to the sulfation of CeO₂. ► The SCR reaction over CeO₂ and sulfated CeO₂ followed the E–R mechanism. ► The SCR reaction through the E–R mechanism was promoted after CeO₂ sulfation. ► Catalytic oxidization of NH₃ to NO over CeO₂ was restrained after sulfation.Ceria (CeO₂) showed a poor activity for the selective catalytic reduction (SCR) of NO with NH₃, while CeO₂ showed an excellent SCR activity in the presence of SO₂ at 300–500°C. The promotion of SO₂ on the SCR reaction over CeO₂ was mainly due to the sulfation of CeO₂. The SCR reaction over CeO₂ and that over sulfated CeO₂ both followed the Eley–Rideal mechanism (i.e. the reaction between activated NH₃ with gaseous NO). Meanwhile, the catalytic oxidization of NH₃ to NO could simultaneously happen during the SCR reaction, resulting in a drop of NO_x conversion at high temperatures. The adsorption of NH₃ on CeO₂ was obviously promoted after the sulfation, resulting in an obvious promotion of the Eley–Rideal mechanism. Meanwhile, the adsorption sites forNH₂ adsorption and the oxidization agents forNH₂ oxidization on CeO₂ were separated after the sulfation. Thus, the probability of the collision betweenNH₂ and Ce⁴⁺ on sulfated CeO₂ was much less than that on CeO₂, resulting in an obvious repression of the catalytic oxidization of NH₃ to NO. As a result, the SCR activity of sulfated CeO₂ was much better than that over CeO₂.

Keywords: SO; ₂; effect; CeO; ₂; Sulfation; NH; ₃; adsorption; Eley–Rideal mechanism; Catalytic oxidization of NH; ₃; to NO

Supported Pt, Pd and Au nanoparticle anode catalysts for anion-exchange membrane fuel cells with glycerol and crude glycerol fuels by Zhiyong Zhang; Le Xin; Ji Qi; David J. Chadderdon; Wenzhen Li (pp. 29-39).

Display Omitted► Pt/C, Pd/C and Au/C catalysts with small diameters were synthesized. ► Electro-oxidation of glycerol activity in alkaline electrolyte: Pt/C>Pd/C>Au/C. ► The AEMFC performance was studied with both high purity and crude glycerol fuels. ► The effects of crude glycerol and KOH concentrations were investigated. ► Pt/C anode crude glycerol AEMFC exhibited a peak power density of 184.2mWcm⁻².Carbon supported Pt, Pd, and Au nanoparticles (NPs) catalysts with small diameters (2.4–3.5nm) were prepared through a solution-phase reduction method, and applied as the model catalysts for electro-oxidation of both high-purity glycerol and biodiesel-derived crude glycerol. The half cell investigations showed that Pt/C has the highest activity in the low potential range, which can be further facilitated at elevated temperatures. The anion-exchange membrane fuel cells (AEMFCs) investigations demonstrated no obvious drop in peak power density on Pt/C anode, when the fuel was switched from high-purity glycerol to crude glycerol, indicating a good stability of the Pt/C against poisoning/deactivation from the impurities in crude glycerol. The tests also showed that on all these three model catalysts, a volcano-type relationship exists between the fuel cell performance and crude glycerol concentration at a fixed KOH concentration, while with a given crude glycerol concentration, the performance monotonically increased with the KOH concentration increasing. The highest performances were achieved with 6.0M KOH+1.0M crude glycerol at 80°C, which are 184.2, 93.9, and 50.1mWcm⁻² on Pt/C, Pd/C, and Au/C anodes, respectively.

Keywords: Nanoparticle; Electro-oxidation; Crude glycerol; Alkaline electrolyte; Fuel cell

Photocatalytic nitrate reduction in water: Managing the hole scavenger and reaction by-product selectivity by K. Doudrick; T. Yang; K. Hristovski; P. Westerhoff (pp. 40-47).

Display Omitted► Stoichiometric evidence is provided showing formic acid acts as a two-hole scavenger and that nitrate/formate can be removed at a 1:1 ratio. ► Silver is present as a metallic core with an oxide shell and reduces the overpotential for nitrate reduction at neutral pH. ► Nitrate reduction occurs through a step-wise reduction via multi-electron transfers. ► Proton localization at the reaction site is necessary to move beyond nitrite.Nitrate contamination of groundwater limits it use as a drinking water supply unless the nitrate is removed. The aim of this study was to move toward implementing photocatalysis for nitrate treatment in drinking water systems by understanding the effects of experimental conditions and the mechanisms involved. Specifically, the photocatalytic reduction of nitrate in water was examined using titanium dioxide (Evonik P90) loaded with silver nanoparticles and formate as a hole scavenger (electron donor). Experimental conditions including pH, nitrate concentration, formate concentration, photocatalyst concentration, and silver loading were varied to demonstrate their effect on the rate of nitrate and formate removal as well as by-product selectivity. For drinking water applications, minimization of residual formate is essential to prevent adverse effects in potable water distribution systems (e.g., carbon source for biofilm growth). The experimental stoichiometric requirement for formate indicated that it acts as a two-hole scavenger, which suggests conduction band electrons, rather than radicals, are responsible for nitrate reduction. Using optimal operating conditions, nitrate and formate were efficiently removed at nearly a 1:1 ratio, showing that the residual hole scavenger concentration can be controlled while maintaining an acceptable rate. Compared to P90 alone, the addition of silver nanoparticles improved the rate of nitrate and formate removal significantly, reduced the overpotential for nitrate reduction, and provided a more positive surface charge. The removal rates decreased with increasing pH, which suggests that the reaction is a proton-coupled electron reaction and that adsorption of the constituents is necessary for effective charge transfer. Under acidic conditions (pH=2.5), nitrogen gases (∼85%) and ammonium (∼15%) were the final by-products. Between pH 3.5 and 4, a sudden by-product switch occurred to nitrite, suggesting that, at higher pH, a co-catalyst that is efficient at localizing protons is required to move beyond nitrite.

Keywords: Titanium dioxide; Photocatalysis; Silver; Nitrate; Formate; Hole scavenger

Aluminumphosphate molecular sieves supported Pt–Co catalysts for the preferential oxidation of CO in H₂-rich gases by ChangXu Wang; Lihong Zhang; Yutan Liu (pp. 48-55).

Display Omitted► Pt–Co alloy were formed and the particles were highly dispersed. ► Substitution of cobalt ions for aluminium ions has obvious influence on the interaction between the support and platinum/cobalt species. ► CoAPO supported Pt–Co catalysts showed very good catalytic performance for CO preferential oxidation. ► The enlarged temperature window for CO purification is supposed to be attributed to the loaded cobalt oxide.A series of aluminumphosphate molecular sieves supported platinum–cobalt catalysts were prepared and tested for the preferential oxidation of CO in H₂-rich gases. The catalysts were characterized by XRD, HRTEM, EDX, TPR and XPS techniques. The optimized catalysts were highly active and selective, CO could be purified below 10ppm in the reaction temperature range of 110°C–125°C under 1% CO, 1% O₂, 12.5% CO₂, 15% H₂O, 50% H₂ in volume and N₂ balance at the space velocity of 24,000mLg_cat⁻¹h⁻¹_. Pt–Co/CoAPO-5 exhibited the best catalytic performance and Pt–Co/AlPO-5 was the most active catalyst at low reaction temperature, in which particles of Pt–Co alloy were formed and the particles were highly dispersed on the surface of the support. The high activity could be attributed to the Pt–Co nano-partilces with small sizes. The enlarged temperature window for CO purification should be ascribed to the loaded cobalt oxide. Substitution of cobalt ions for aluminium ions has obvious influence on the interaction between the support and platinum/cobalt species.

Keywords: Aluminophosphate; AlPOs; Preferential oxidation; Platinum; Cobalt

TiO₂/Cu(II) photocatalytic production of benzaldehyde from benzyl alcohol in solar pilot plant reactor by Danilo Spasiano; Lucia del Pilar Prieto Rodriguez; Jaime Carbajo Olleros; Sixto Malato; Raffaele Marotta; Roberto Andreozzi (pp. 56-63).

Display Omitted► Use of the TiO₂/Cu(II) photocatalytic system in solar pilot plant. ► Selective oxidation of benzyl alcohol to the corresponding aldehyde. ► Partial conversion of aldehyde to the corresponding benzoic acid. ► Copper regeneration. ► Evaluation of figure of merit.The technical feasibility of selective photocatalytic oxidation of benzyl alcohol to benzaldehyde, in aqueous solutions, in presence of cupric ions has been investigated in a solar pilot plant with Compound Parabolic Collectors. Aldrich (pure anatase) and P25 Degussa TiO₂ have been used as photocatalysts. The influences of cupric species concentrations, solar irradiance and temperature are discussed too. The oxidation rates were strongly influenced by the initial cupric ions concentration, incident solar irradiance and temperatures.The best results found, in terms of yields and selectivities to benzaldehyde under acidic conditions were higher than 50% and 60%, respectively, under acidic conditions.Under deaerated conditions, the presence of reduced copper species was proved by XPS analysis. The results indicated that, at the end of the process, cupric species can be easily regenerated and reused, through a re-oxidation of reduced copper, produced during the photolytic run, with air or oxygen in dark conditions.A figure-of-merit ( A_CM), proposed by the International Union of Pure and Applied Chemistry (IUPAC) and based on the collector area, has been estimated, under the proposed conditions, with the aim to provide a direct link to the solar-energy efficiency independently of the nature of the system. Generally speaking, it can be considered that the lower A_CM values the higher the system efficiency.

Keywords: Selective oxidation; Benzyl alcohol; Benzaldehyde production; TiO; ₂; photocatalysis; Solar photocatalytic plant; Figure-of-merit

Effective pharmaceutical wastewater degradation by Fenton oxidation with zero-valent iron by Y. Segura; F. Martínez; J.A. Melero (pp. 64-69).

Display Omitted► Excellent removal of complex organic pollutants present in wastewater generated from a drug manufacturing plant. ► Up to 80% TOC removal reached in 1h treatment, using moderate loadings of ZVI and H₂O₂. ► Easy, economic and effective pre-treatment step.The pre-treatment of a pharmaceutical wastewater (PWW) by Fenton oxidation with zero-valent iron (ZVI) and hydrogen peroxide was investigated to improve the degradation of the complex-mixture of organic compounds present in the wastewater. The influence of different crucial parameters such as the initial hydrogen peroxide concentration, the ZVI concentration and the capacity of the ZVI/H₂O₂ system to treat different organic loading have been evaluated. The optimal conditions for degradation led to TOC reductions of up to 80% in only 1h of treatment. This degree of organic mineralization was reached by using moderate loadings of ZVI and hydrogen peroxide (ZVI/TOC weight and H₂O₂/TOC molar ratios of 12 and 3.2, respectively). Moreover, the use of waste-metallic iron shavings in terms of TOC removal compared to commercial ZVI powder may be a promising and cheaper development.

Keywords: Fenton processes; Zero valent iron (ZVI); Pharmaceutical wastewater

Influence of the preparation method and dopants nature on the WGS activity of gold catalysts supported on doped by transition metals ceria by T. Tabakova; L. Ilieva; I. Ivanov; R. Zanella; J.W. Sobczak; W. Lisowski; Z. Kaszkur; D. Andreeva (pp. 70-80).

Display Omitted► Au catalysts on ceria doped by Fe, Mn or Sn ions were prepared by different methods. ► A higher WGS activity exhibited the catalysts prepared by mechanical mixing. ► High and stable activity of doped by Fe or Mn ceria-based catalysts was established. ► The different activity is due to the preparation method and to the nature of dopant.Gold catalysts supported on ceria doped by different metal oxides (Me=Fe, Mn, Sn) were synthesized by two different methods: coprecipitation (CP) and mechanochemical activation (MA). Samples were characterized by means of XRD, HRTEM, TPR and XPS. Both XRD and HRTEM analyses reveal differences in the average size of the gold and ceria particles. As shown by TPR data, ceria doping improves oxygen mobility, i.e. a higher oxygen capacity was observed while compared with gold catalyst on undoped ceria. The method of preparation and the nature of dopant applied influence the catalytic performance in the water–gas shift (WGS) reaction. The differences in WGS activity between the MA and CP samples were significant. The MA catalysts, doped by Fe and Mn, manifested higher WGS activity than the undoped Au/ceria sample and the sample doped by Sn. A high concentration of Ce³⁺ ions in the highly active catalysts containing Fe or Mn was registered by XPS and found consistent with an earlier proposed model of the active sites for the WGS reaction.

Keywords: Gold catalysts; WGSR; Ceria doped by Fe, Mn and Sn oxides

H₂ and O₂ photocatalytic production on TiO₂ nanotube arrays: Effect of the anodization time on structural features and photoactivity by Marco Altomare; Michele Pozzi; Mattia Allieta; Luca Giacomo Bettini; Elena Selli (pp. 81-88).

Display Omitted► TiO₂ nanotube arrays were grown on titanium disks by different anodization times. ► Photoelectrodes were so prepared for separate H₂ and O₂ production from water. ► Short anodization led to best performing aligned 80–20 anatase-rutile nanotubes. ► Long anodization produced a detrimental anatase layer covering the nanotubes top. ► Photocatalytic water splitting was perfectly mirrored by photocurrent measurements.TiO₂ nanotube (NT) arrays of different lengths were prepared by electrochemical anodization of ca. 10cm² area titanium disks in NH₄F–H₂O–formamide solution for different times, followed by annealing at 450°C. After Pt deposition on the opposite side of the disk, the so obtained Ti-supported crystalline anodic oxides were employed as photoactive electrodes in a two compartments cell for separate H₂ and O₂ production through water photosplitting and characterized by SEM, XRD analysis and photocurrent measurements. The anodization time affected the phase composition and morphology of the growing NTs, which strictly influenced their photocatalytic activity. Short anodization times (40–60min) resulted in well aligned short tubes composed of anatase-rutile mixed phases. Longer anodization (>2.5h) yielded thicker NT arrays covered on top by a preferentially oriented anatase layer that limited their photoactivity. Photocurrent intensity measurements perfectly paralleled the water splitting activity results obtained with the different NT arrays. In particular, a square-shaped fast photoresponse was recorded with ordered and fully top-open nanotubular structures. On the other hand, clogged tubes not only yielded low current densities, but also showed delayed photocurrent transient signals due to the reduced mobility of the charge carriers within the preferentially oriented anatase layer. NT arrays obtained under optimized conditions had a ca. 80:20 anatase:rutile composition and ensured a hydrogen production rate of 83mmolh⁻¹m⁻² ( i.e. 1.9NLh⁻¹m⁻²) in the absence of any hole scavenger or external bias.

Keywords: Photocatalytic water splitting; H; ₂; production; TiO; ₂; nanotubes; Photocurrent; Photoelectrodes

The effect of Au cocatalyst loaded on La-doped NaTaO₃ on photocatalytic water splitting and O₂ photoreduction by Akihide Iwase; Hideki Kato; Akihiko Kudo (pp. 89-93).

Display Omitted► We achieved the increased water splitting over NaTaO₃ doped with La photocatalyst by loading Au cocatalyst. ► Impregnated Au worked better as cocatalyst for water splitting than photodeposited Au. ► The impregnated Au cocatalyst suppressed the O2 photoreduction more efficiently than the photodeposited Au cocatalyst.Photocatalytic water splitting over La-doped NaTaO₃ (NaTaO₃:La) was improved by loading with Au cocatalyst which works as H₂ evolution sites. NaTaO₃:La loaded with Au by an impregnation method showed higher and more steady activity for water splitting than that by a photodeposition method. This difference in the activity for water splitting was related to the O₂ photoreduction on the loaded Au cocatalyst, which is one of the backward reactions of water splitting. The impregnated spherical Au cocatalyst suppressed the O₂ photoreduction by photogenerated electrons more efficiently than the photodeposited hemispherical Au cocatalyst, because the perimeter of Au/NaTaO₃:La interface which produces activated O₂ molecules was smaller in the impregnated Au than the photodeposited Au.

Keywords: Photocatalyst; Water splitting; Au cocatalyst; Oxygen reduction

A high efficient photocatalyst Ag₃VO₄/TiO₂/graphene nanocomposite with wide spectral response by Jinxiu Wang; Peixian Wang; Yuantao Cao; Jing Chen; Wenjuan Li; Yu Shao; Yi Zheng; Danzhen Li (pp. 94-102).

In this work, Ag₃VO₄/TiO₂/graphene nanocomposite as a wide spectrum responsive photocatalyst was prepared first by a two-step process, which exhibited obviously increased visible light absorption and photocatalytic activity in degradation of organic pollutants. The transfer of photogenerated charges and photocatalytic mechanism for degradation of organic pollutants on Ag₃VO₄/TiO₂/graphene were proposed and discussed in detail.Display Omitted► Ag₃VO₄/TiO₂/graphene nanocomposite performs high photocatalytic activity. ► Graphene plays an important role in the enhancement of its photocatalytic activity. ► Transfer of photogenerated carriers and photocatalytic mechanism on samples are discussed. ► Our research presents a new idea for the design of efficient composite photocatalyst.Great efforts have been made to develop efficient visible light activated photocatalysts in recent years. In this work, Ag₃VO₄/TiO₂/graphene nanocomposite as a wide spectrum responsive photocatalyst was prepared first by a two-step process, which exhibited obviously increased visible light absorption and photocatalytic activity in degradation of organic pollutants including methyl orange and Rhodamine B, compared with Ag₃VO₄/TiO₂ and TiO₂/GR nanocomposites. For Ag₃VO₄/TiO₂/graphene nanocomposite, the introduction of graphene contributed to the uniform dispersion of Ag₃VO₄ and TiO₂ nanoparticles on graphene sheets. The capacity of graphene in storing and shuttling electrons and the formation of heterojunction between Ag₃VO₄ and TiO₂ facilitated together the enhancement of efficiency in the separation of photogenerated electron–hole pairs. Based on the results of photoelectrochemical measurement and the detection of active species in photocatalytic degradation process, the transfer of photogenerated carriers and photocatalytic degradation mechanism on Ag₃VO₄/TiO₂/graphene nanocomposite were proposed and discussed in detail.

Keywords: Visible light photocatalyst; Ag; ₃; VO; ₄; TiO; ₂; Graphene; Heterojunction

A cyclic reaction pathway triggered by ammonia for the selective catalytic reduction of NO_x by ethanol over Ag/Al₂O₃ by Yunbo Yu; Jiaojiao Zhao; Yong Yan; Xue Han; Hong He (pp. 103-111).

Ammonia originating from the hydrolysis of –NCO species can in turn react with enolic species to produce –NCO, creating a cyclic pathway for the reduction of NO_x by ethanol over Ag/Al₂O₃.Display Omitted► Ag/Al₂O₃ prepared from nordstrandite shows high activity for ethanol-SCR. ► Ammonia was inevitably produced by the hydrolysis of–NCO over Ag/Al₂O₃. ► In turn, the produced ammonia can react with enolic species to produce –NCO. ► This reaction involving ammonia creates a cyclic pathway for ethanol-SCR.Alumina-supported silver catalysts (Ag/Al₂O₃) prepared using nordstrandite as a precursor exhibited excellent activity for the selective catalytic reduction of NO_x by ethanol (ethanol-SCR). During the ethanol-SCR, the formation of NH₃ was observed over all Ag/Al₂O₃ catalysts, the amount of which was related to silver loading, reaction temperature, and the concentration of ethanol used, even when water was excluded from the inlet gas. Transient activity testing and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis showed that the reaction between isocyanate species (–NCO) and water is the main pathway of NH₃ formation. Addition of NH₃ enhanced the NO_x conversion for ethanol-SCR and the oxidation of ethanol over 3wt% Ag/Al₂O₃. DRIFTS analysis revealed for the first time that NH₃ reacted with enolic species to form –NCO over Ag/Al₂O₃, thus resulting in a novel and cyclic reaction pathway for ethanol-SCR.

Keywords: Selective catalytic reduction of NO; _x; Ammonia; Enolic species; Ag/Al; ₂; O; ₃; Isocyanate

Highly efficient photocatalytic removal of sodium pentachlorophenate with Bi₃O₄Br under visible light by Jiling Wang; Ying Yu; Lizhi Zhang (pp. 112-121).

Display Omitted► Sodium pentachlorophenate could be removed with Bi₃O₄Br under visible light. ► High efficiency is attributed to effective separation and transfer of charge carriers. ►O₂⁻ could inhibit photoinduced charge carriers recombination and benefit dechlorination.In this study we demonstrate that Bi₃O₄Br is a superior visible light driven photocatalyst for the decomposition and mineralization of a typical chlorinated phenol derivative sodium pentachlorophenate. It could remove more than 92% of sodium pentachlorophenate with concentration of 40mg/L under visible light irradiation from 500W Xe-lamp with a 420nm cut off filter in 15min, accompanying with 80% of mineralization. Density functional theory (DFT) calculation and systematical characterization reveal that high efficient visible light driven sodium pentachlorophenate removal with Bi₃O₄Br could be attributed to effective separation and transfer of photoinduced charge carriers in Bi₃O₄Br with narrower band gap and more negative conduction band position, which favors the photogenerated electrons trapping with molecular oxygen to produceO₂⁻. TheO₂⁻ radicals could not only inhibit the recombination of photoinduced charge carriers, but also benefit the dechlorination of chlorinated phenol derivative. The visible light induced degradation pathway of sodium pentachlorophenate was carefully investigated with high performance gas chromatography–mass spectrometry. This study provides a new photocatalyst for chlorinated phenol derivative removal with solar light.

Keywords: Bismuth oxybromide; Visible light; Photocatalysis; Sodium pentachlorophenate; Degradation

Reduction and catalytic behaviour of nanostructured Pd/gadolinia-doped ceria catalysts for methane combustion by Fernando F. Muñoz; Richard T. Baker; A. Gabriela Leyva; Rodolfo O. Fuentes (pp. 122-132).

Display Omitted► 1wt% and 5wt% Pd/GDC10 nanopowders were prepared by cation complexation (CC) and incipient wetness impregnation (WI). ► Reduction behaviour was studied by in situ synchrotron radiation techniques. ► The addition of Pd increased the reducibility of the Ce in the mixed oxide. ► Catalysts with 5wt% Pd loading exhibited the best performance for CH₄ combustion. ► 1wt% Pd nanopowders prepared by CC resulting in more active catalysts than those prepared by the WI method.In the present work, 1wt% and 5wt% Pd/GDC10 (Gd_0.1Ce_0.9O_1.95) nanopowders were prepared by two different methods: (a) cation complexation (CC) and (b) incipient wetness impregnation (WI) of an aqueous Pd²⁺ solution onto GDC10 nanopowders. All samples were characterised by X-ray diffraction (XRD), thermal analysis (TG/DTA), specific surface area determination and high resolution transmission electron microscopy (HRTEM). In order to study the oxidation state of Pd in samples with and without reducing treatments, XANES experiments at the Pd L₃-edge were carried out. In situ Ce L₃-edge XANES experiments were performed under reducing conditions in order to investigate the reduction behaviour of these materials. The addition of Pd to the GDC10 nanopowders increased the reducibility of Ce in the mixed oxide. Finally, catalytic tests for CH₄ combustion were performed on the Pd/GDC10 nanopowders. Catalysts with higher Pd loading (5wt%) exhibited the best performance for CH₄ combustion. The influence of preparation method was evident for catalysts with 1wt% Pd, the cation complexation method resulting in more active catalysts than the wetness impregnation method.

Keywords: Solid oxide fuel cells; Supported Pd catalysts; Nanostructured ceria-gadolinia catalyst supports; HRTEM; X-ray powder diffraction; X-ray absorption spectroscopy

Improvements to the photocatalytic efficiency of polyaniline modified TiO₂ nanoparticles by M. Radoičić; Z. Šaponjić; I.A. Janković; G. Ćirić-Marjanović; S.P. Ahrenkiel; M.I. Čomor (pp. 133-139).

Display Omitted► Surface modified TiO₂ nanocrystals by PANI synthesized without added acid/surfactants. ► The presence of subnanometer thick PANI layer on TiO₂ NPs was confirmed. ► Multiple increase of photocatalytic activity of PANI modified TiO₂ nanoparticles. ► Emeraldine salt and base forms of PANI- the best PANI/TiO₂ photocatalyst.Polyaniline/TiO₂ nanocomposite powders were successfully synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in water without the addition of acid, in the presence of colloidal TiO₂ nanoparticles ( d∼4.5nm). The morphological, structural, and optical properties of the synthesized nanocomposites prepared at initial TiO₂/aniline mole ratios of 50, 100, and 150 were studied using transmission electron microscopy, X-ray powder diffraction, Raman and UV–vis spectroscopies. The presence of emeraldine salt and the base form of linear polyaniline (PANI) chains as well as the presence of phenazine units, branched PANI chains, oligomeric structures and short PANI chains in PANI/TiO₂ nanocomposites was confirmed by Raman spectroscopy. The anatase crystal structure of TiO₂ nanoparticles in all the nanocomposites was confirmed by X-ray powder diffraction measurements and by Raman spectroscopy. The photocatalytic activities of PANI/TiO₂ nanocomposites were evaluated using the photocatalytic degradation of Rhodamine B and Methylene blue as model compounds and compared with the activity of bare colloidal TiO₂ nanoparticles. Enhanced degradation efficiencies in the dyes used were observed. A possible explanation for the PANI/TiO₂ photocatalytic activities was suggested, taking into account the influence of the molecular structures of the used dyes and PANI in PANI/TiO₂ nanocomposites.

Keywords: Photocatalysis; TiO; ₂; Polyaniline

Oxygen-removal of dibenzofuran as a model compound in biomass derived bio-oil on nickel phosphide catalysts: Role of phosphorus by J.A. Cecilia; A. Infantes-Molina; E. Rodríguez-Castellón; A. Jiménez-López; S.T. Oyama (pp. 140-149).

Display Omitted► Ni₂P catalysts with low Ni loading show good activity and stability in HDO of DBF. ► The main product (BCH) comes from HYD of both aromatic rings. ► Catalysts do not suffer from coke and water deactivation. ► Water interacts preferentially with the excess phosphorous, preserving Ni₂P phase.The hydrodeoxygenation (HDO) of dibenzofuran (DBF) was investigated over silica-supported nickel phosphide catalysts with low metallic loadings (2.5–10wt.%) and with different initial P/Ni atomic ratios. The formation of the nickel phosphide phase as well as the textural, structural and acidic properties of the catalysts were evaluated by X-ray fluorescence (XRFS), H₂-temperature programmed reduction (H₂-TPR), X-ray diffraction (XRD), CO chemisorption at 35°C, N₂ adsorption–desorption isotherms at −196°C, NH₃-temperature programmed desorption (NH₃-TPD) and elemental analysis (CNHS). The effect of metallic loading, the initial P/Ni molar ratio as well as the feed O-concentration on the catalytic activity were studied. Characterization results reveal that smaller particle sizes are formed at lower metallic loadings and high P/Ni atomic ratios, and that the acidity increases linearly with the metallic loading pointing to nickel and phosphorous species as the acidic centers in reduced catalysts. Nickel phosphide catalysts display good activity and stability in the HDO of DBF, reaching high DBF conversion values at moderate temperatures (300°C) and with high selectivity to bicyclohexane (BCH), the main deoxygenated product which was obtained by hydrogenation of both aromatic rings (HYD pathway). Catalyst deactivation due to coke was minimal due to the low strength of the acid sites, while the formation of water did not present an inhibiting effect even under high O-concentration. This behavior might occur because water interacts preferentially with the excess phosphorous present on the catalyst surface and thus nickel phosphide particles do not undergo oxidation.

Keywords: Nickel phosphide (Ni; ₂; P); Dibenzofuran; Hydrodeoxygenation; Hydrotreatment

A facile and efficient synthesis of styrene carbonate via cycloaddition of CO₂ to styrene oxide over ordered mesoporous MCM-41-Imi/Br catalyst by Jimmy Nelson Appaturi; Farook Adam (pp. 150-159).

Display Omitted► MCM-41 was synthesized from rice husk ash (RHA) via simple sol–gel technique. ► MCM-41-Imi/Br was prepared by post-grafting method. ► MCM-41-Imi/Br exhibited ordered mesoporous straight channels with S_BET of 130m²g⁻¹. ► The catalyst showed high activity in cycloaddition with 100% conversion.MCM-41 was successfully immobilized with imidazole using 3-chloropropyltriethoxysilane (CPTES) as the anchoring agent followed by alkylation with 1,2-dibromoethane at 110°C. The resulting catalyst was designated as MCM-41-Imi/Br. TEM showed the catalyst had ordered mesoporous straight-channels with average wall thickness of 2.14nm and average pore size of 1.56nm. The²⁹Si MAS NMR analysis confirmed the presence of T², T³, Q³ and Q⁴ silicon centers. The¹³C MAS NMR showed that MCM-41-Imi/Br had three chemical shifts corresponding to the three carbon atoms of the propyl group. The aromatic imidazole peaks were detected at 110–140ppm. The catalyst was used in the solvent-less synthesis of styrene carbonate (SC) from CO₂ and styrene oxide (SO) under ambient conditions. It was demonstrated that the synergistic effect due to the stronger nucleophilicity of Br⁻ and amine in the catalyst could lead to a maximum selectivity of 99.1%. Based on the results, a plausible reaction mechanism was proposed for the catalytic reaction. The catalyst could be recovered and reused several times without significant loss in the catalytic activity.

Keywords: Cycloaddition; Styrene oxide; Styrene carbonate; Carbon dioxide; Imidazole

Pt-Cu electrocatalysts for methanol oxidation prepared by partial galvanic replacement of Cu/carbon powder precursors by I. Mintsouli; J. Georgieva; S. Armyanov; E. Valova; G. Avdeev; A. Hubin; O. Steenhaut; J. Dille; D. Tsiplakides; S. Balomenou; S. Sotiropoulos (pp. 160-167).

Display Omitted► Bimetallic Pt–Cu nanoparticles, supported on fuel cell technology carbon supports, have been prepared by a combination of Cu chemical reduction followed by its partial galvanic replacement by Pt. ► The formation of a Pt–Cu alloy was confirmed by XRD whereas voltammetry points to the existence of a Pt-rich shell. ► The prepared Pt-Cu/C catalysts exhibited moderately enhanced catalytic activity for methanol electrooxidation in acid and significantly better Pt utilization.A bimetallic Pt-Cu carbon-supported catalyst (Pt(Cu)/C) has been prepared by a room temperature two-step procedure involving the chemical reduction of Cu ions by sodium borohydride in the presence of Vulcan XC72R carbon powder, followed by the partial galvanic replacement of Cu particle layers by Pt, upon immersion in a chloroplatinate solution. The characterization of the Pt(Cu)/C catalyst by XRD has proven the formation of a Pt–Cu alloy while cyclic voltammetry in deaerated acid revealed similar characteristics to those of pure Pt. These two findings point to the existence of Pt-rich outer layers and a Pt–Cu core. The electrocatalytic activity of the bimetallic Pt(Cu)/C catalyst towards methanol oxidation is comparable to or better than that of a commercial 20% Pt Vulcan XC72R catalyst (when assessed by voltammetric or prolonged chronoamperometric experiments respectively). This is attributed to the effect of Cu on CO poison adsorption and removal from Pt. Moreover, related to the same effect but also to the reduced Pt loading of the mixed Pt–Cu particles, the specific mass activity of the prepared catalyst is superior to that of the commercial catalyst.

Keywords: Platinum catalysts; Galvanic replacement; Binary catalysts; Methanol oxidation

The effect of the gas composition on hydrogen-assisted NH₃-SCR over Ag/Al₂O₃ by Stefanie Tamm; Sebastian Fogel; Pär Gabrielsson; Magnus Skoglundh; Louise Olsson (pp. 168-176).

Display Omitted► Ratio of converted NO:NH₃:H₂=1:1:2 without unselective oxidation of reductants. ► H₂ conversion is independent of NO and NH₃ concentrations. ► H₂ removes single O-atoms from silver to free sites for NO and NH₃ adsorption. ► NO conversion increases linearly with H₂ inlet concentrations below 250°C. ► NO conversion increases slightly because of mild aging of Ag/Al₂O₃ at 500°C.In addition to high activity in hydrocarbon-SCR, Ag/Al₂O₃ catalysts show excellent activity for NO_x reduction for H₂-assisted NH₃-SCR already at 200°C. Here, we study the influence of different gas compositions on the activity of a pre-sulfated 6wt% Ag/Al₂O₃ catalyst for NO_x reduction, and oxidation of NO and NH₃. The catalyst displays high initial activity for NO_x reduction with a maximum of about 85% at 250°C. Increasing the concentration of H₂ results in further increased NO_x reduction. Moreover, a global stoichiometry between NO:NH₃:H₂ equal to 1:1:2 is established during selective NO_x reduction conditions. When increasing the concentration of one of the reducing agents only an increase of the H₂ concentration leads to an increase in NO_x reduction, while an increase of the NH₃ concentration only is beneficial to a limit of an equimolar ratio between NO and NH₃. Under transient conditions at constant temperature, the concentration of NO reaches steady state fast, whereas it takes longer time for NH₃ due to accumulated surface species, probably on the alumina. The oxidation of NO to NO₂ is sensitive to the H₂ concentration in similarity to the SCR reaction, while higher amounts of H₂ suppress the oxidation of NH₃. Moreover, the dependency on the O₂ concentration is much higher for the NO and NH₃ oxidation than for the SCR reaction. To explain all these features a reaction mechanism is proposed in which the role of H₂ is to free silver from single oxygen atoms. Ammonia and nitric oxygen can adsorb on these sites and react probably on the border between the silver and alumina or on the alumina surface to N₂.

Keywords: Ag/Al; ₂; O; ₃; H; ₂; -effect; Reaction mechanism; Influence of gas mixture; H; ₂; -assisted NH; ₃; -SCR; Urea

Palladium on graphene as efficient catalyst for solvent-free aerobic oxidation of aromatic alcohols: Role of graphene support by Guangjun Wu; Xueming Wang; Naijia Guan; Landong Li (pp. 177-185).

Display Omitted► Palladium supported on graphene as active catalyst for aerobic oxidation of aromatic alcohols. ► Graphene promotes the adsorption of aromatic alcohols through π-electron interaction. ► Graphene promotes oxygen adsorption due to oxygen spill-over from palladium sites to graphene.Palladium catalysts supported on different carbon materials, i.e. graphene, carbon nanotube and activated carbon, have been prepared by improved wet impregnation and employed in the solvent-free aerobic oxidation of aromatic alcohols using molecular oxygen as oxidant. High catalytic activity as well as high selectivity to corresponding carbonyl compounds can be obtained on Pd/graphene. Typically, an extremely high turnover frequency of 30,137mol/hmol_Pd is observed in the aerobic oxidation of benzyl alcohol to benzaldehyde using Pd/graphene as catalyst. Palladium catalysts on different carbon supports are fully characterized by a series of techniques, e.g. Raman, XRD, SEM, TEM, TG, XPS, FTIR spectra of benzyl alcohol adsorption and O₂-TPD. Based on the catalytic and characterization results, the superior reactivity of Pd/graphene in the aerobic oxidation of aromatic alcohols is attributed to the promotion role of graphene support in the adsorption of reactant alcohol and oxygen.

Keywords: Pd catalysts; Graphene; Aerobic oxidation; Aromatic alcohols

Influence of the nature and environment of vanadium in VSiBEA zeolite on selective catalytic reduction of NO with ammonia by Rafal Baran; Thomas Onfroy; Teresa Grzybek; Stanislaw Dzwigaj (pp. 186-192).

Display Omitted► V(V) was incorporated in zeolite framework by two-steps postsynthesis method. ► VSiBEA zeolite was active in SCR of NO with ammonia. ► Product selectivity and NO conversion were depended on vanadium speciation. ► VSiBEA zeolite was stable in SCR process.The influence of the nature and environmental of vanadium on the catalytic properties of V_xSiBEA zeolite in selective catalytic reduction of NO with ammonia is investigated. Catalysts containing 1–7.5wt.% of vanadium were prepared by a two-step postsynthesis method which consists, in the first step, of dealumination of TEABEA zeolite to obtain SiBEA support and then, in the second step, of contacting the obtained material with an aqueous solution of NH₄VO₃ at pH 2.7. XRD and low temperature N₂ sorption results show that full dealumination of parent TEABEA zeolite by nitric acid treatment as well as incorporation of vanadium atoms in the framework of SiBEA zeolite do not change the crystallinity of BEA zeolite. The presence of isolated pseudo-tetrahedral V(V) species for low V content and pseudo-tetrahedral and octahedral V(V) species for high V content is evidenced by diffuse reflectance UV–vis, Raman and TPR. The catalytic activity of V_xSiBEA in selective catalytic reduction of nitric oxide with ammonia as reducing agent strongly depends on the nature and environmental of vanadium in BEA structure. The single site V_1.0SiBEA catalyst with isolated pseudo-tetrahedral V(V) species is active in SCR of NO process, with maximum NO conversion about 60% at 773K and with very low selectivity toward undesired N₂O. In contrast, V_3.0SiBEA and, especially, V_7.5SiBEA catalyst containing mainly extra-framework octahedral V(V) and vanadium oxide species are less active in SCR of NO process at higher temperature and big amount of N₂O is observed in the product stream.

Keywords: Vanadium; Ammonia; NO; BEA; FTIR; DR UV–vis; TPR; SCR

Design and synthesis of hydrophobic and stable mesoporous polymeric solid acid with ultra strong acid strength and excellent catalytic activities for biomass transformation by Fujian Liu; Anmin Zheng; Iman Noshadi; Feng-Shou Xiao (pp. 193-201).

Display Omitted► Introduction ofSO₂CF₃ group enhances acid strength of PDVB-SO₃H. ► Abundant mesoporosity is favorable for the fast diffusion of reactants. ► Strong acid strength results in excellent catalytic activity for biomass transformation. ► Hydrophobic–oleophilic network results in high exposition degree of active sites. ► The stable network of mesoporous solid strong acid results in its good recyclability.Novel and efficient mesoporous polydivinylbenzene (PDVB) based solid strong acid (PDVB-SO₃H-SO₂CF₃) has been successfully prepared by grafting of strong electron withdrawing group ofSO₂CF₃ onto the network of performed mesoporous solid acid of PDVB-SO₃H, which could be synthesized from sulfonation of superhydrophobic mesoporous PDVB or copolymerization of DVB with sodium p-styrene sulfonate. Characterizations of N₂ sorption isotherms, TG curves and contact angle tests show that PDVB-SO₃H-SO₂CF₃ has large Brunauer–Emmett–Teller (BET) surface area, superior thermal stability, good hydrophobicity and oleophilicity. Solid³¹P NMR spectra and NH₃–TPD curves show that the Brønsted acidic site in PDVB-SO₃H-SO₂CF₃ has been significantly enhanced and rather homogeneously distributed when compared with that of PDVB-SO₃H. Catalytic tests show that PDVB-SO₃H-SO₂CF₃ exhibits excellent catalytic activities and good recyclability in biomass transformation toward transesterification to biodiesel and depolymerization of crystalline cellulose to sugars when compared with those of PDVB-SO₃H, solid strong acids of SO₄/ZrO₂ and Nafion NR50. The excellent catalytic activity and good recyclability of PDVB-SO₃H-SO₂CF₃ result from its unique characters such as large surface area, ultra strong acid strength, adjustable hydrophobic–oleophilic and stable network.

Keywords: Solid strong acid; Mesoporous polymers; Hydrophobicity; Wettability; Biomass transformation

The impact of ZnO load, stability and morphology on the kinetics of the photocatalytic degradation of caffeine and resazurin by Marko Bitenc; Barbara Horvat; Blaž Likozar; Goran Dražić; Zorica Crnjak Orel (pp. 202-209).

Display Omitted► The photocatalytic activity of ZnO varied with its morphology; ZnHC was not photocatalytic. ► Rod-like crystals showed a better photocatalytic effect than flower- and hedgehog-like crystals. ► More profound photocatalytic effect was achieved with smaller crystals. ► The band gap of hydrozincite was 4.1eV, determined for the first time.Zinc oxide (ZnO) powders with diverse morphologies were synthesized with various solvothermal techniques. Water, 1-butanole and ethylene glycol were used as the solvents, while the temperature of the solvothermal synthesis was varied from 90°C to 120°C. Resazurin and caffeine were used for the evaluation of the photocatalytic activity of all the prepared samples, and in particular to compare ZnO with commercial titanium dioxide photocatalytic material (P25 Evonik Degussa) using UV–vis spectroscopy. The composition, crystallinity, and morphology of the prepared materials were investigated with FTIR, XRD, TEM and FEG-SEM techniques. The band gaps of the obtained semiconductors were measured because the band gap of hydrozincite, determined in this study to be 4.1eV, has not been reported previously. The specific surface area (BET) and the porosity of the prepared particles were estimated. The crystal size in one dimension was estimated and was found to play an important role in the photocatalytic activity, which increased with a smaller size. A higher degree of aggregation caused the opposite effect. Thus, a more aggregated material with a larger surface area than a less aggregated one exhibited a lower photocatalytic activity. The particle morphology strongly influenced the photocatalytic process, while the degree of crystallinity was not comparably significant. The external mass-transfer (diffusion to the catalytic surface) resistance was negligible, and consequently the first-order, second-order, and Langmuir–Hinshelwood mechanism kinetics of the photocatalysis were examined.

Keywords: Photocatalysis; ZnO; Hydrozincite; Kinetics; Band gap

The effect of lanthanum doping on activity of Zn-Al spinel for transesterification by Qianhe Liu; Lei Wang; Congxin Wang; Wei Qu; Zhijian Tian; Huaijun Ma; Donge Wang; Bingchun Wang; Zhusheng Xu (pp. 210-217).

Zinc aluminate doped with 5.5wt% lanthanum (5.5% La/ZnAl₂O₄) was a high active catalyst for the synthesis of biodiesel by transesterification of soybean oil with methanol. With this catalyst, the biodiesel yield exceeded 95% at 160°C, 2.0MPa, 0.9h⁻¹, and n_methanol/ n_oil of 24:1.Display Omitted► Lanthanum doped zinc aluminate shows high activity to the synthesis of biodiesel. ► Doping La increases the basicity and pore diameter of Zn-Al spinel. ► The basic sites of the catalyst are surface OH groups and isolated O²⁻ anions. ► No deactivation is happened on the catalyst in the reaction of about 500h.The transesterification of soybean oil with methanol to biodiesel using lanthanum doped zinc aluminate with spinel structure as catalyst is studied. The catalyst was characterized by X-ray diffraction (XRD), N₂ adsorption/desorption, temperature programmed desorption of CO₂ (CO₂-TPD) and infrared spectroscopy of CO₂ adsorption (CO₂-IR). The results of CO₂-IR show that the basic sites of La doped zinc aluminate are surface isolated O²⁻ anions and OH⁻ groups. The results of CO₂-TPD show that the total amount of basic sties of the catalyst improves with the increase of the La doping amount until which is to 18.5wt%. Doping La also enlarges the pore volume and diameter of zinc aluminate. It gets the largest pore volume (0.30cm³g⁻¹) and pore diameter (7.9nm) when doped with 5.5wt% La. Zinc aluminate doped with 5.5wt% La (5.5% La/ZnAl₂O₄) exhibits the highest activity, with which the biodiesel yield exceeds 95% at 160°C, 2.0MPa and 0.9h⁻¹. Furthermore, the transesterification reaction of about 500h in a fixed-bed reactor was carried out over 5.5% La/ZnAl₂O₄ catalyst. No deactivation and leaching of catalyst components were happened on the catalyst in reaction.

Keywords: Biodiesel; Transesterification; Lanthanum doping; Zinc aluminate; Spinel

A ferromagnetic γ-alumina-supported iron catalyst for CWPO. Application to chlorophenols by Macarena Munoz; Zahara M. de Pedro; Nieves Menendez; Jose A. Casas; Juan J. Rodriguez (pp. 218-224).

Display Omitted► Short and simple procedure for synthesizing a new magnetic catalyst (Fe₃O₄/γ-Al₂O₃). ► The ferromagnetic catalyst is highly active and stable upon CWPO of chlorophenols. ► The complete conversion and dechlorination of chlorophenols and 75% mineralization is reached. ► The catalyst shows ferromagnetic properties allowing easy separation and recovery from the liquid phase.A ferromagnetic γ-Al₂O₃-supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mössbauer spectroscopy. The behavior of these catalysts in CWPO of chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H₂O₂ leading to an increased degradation and mineralization of chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4h under stoichiometric H₂O₂ dose, 100mgL⁻¹ initial chlorophenol concentration, 1gL⁻¹ catalyst, pH 3 and 50°C temperature. Moreover, complete dechlorination of all the chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.

Keywords: Heterogeneous Fenton; Ferromagnetic catalyst; Chlorophenol

The effect of La³⁺-doping of CeO₂ support on the water-gas shift reaction mechanism and kinetics over Pt/Ce1−_xLa_xO2−_δ by Christos M. Kalamaras; Klito C. Petallidou; Angelos M. Efstathiou (pp. 225-238).

Display Omitted► 20at.% La³⁺-doping of ceria largely promotes WGS activity on Pt/Ce_xLa1−_xO₂. ► A reactive zone equivalent to one lattice constant of support is established around each Pt nanoparticle. ► The surface concentration of active species depends on Ce/La ratio in Ce_xLa1−_xO2−_δ chemical composition. ► The WGS on Pt/Ce_xLa1−_xO2−_δ ( x=0.0, 0.2 and 1.0) proceeds via the “redox” and “associative” mechanisms. ► The extent of each mechanism depends on the Ce/La ratio in support chemical composition.Platinum nanoparticles ( d_Pt=1.0–1.2nm) supported on single CeO₂ and La₂O₃ metal oxides and Ce_0.8La_0.2O2−_δ solid solution were prepared to investigate for the first time the effect of La³⁺-doping of ceria on important mechanistic and kinetic aspects of the water-gas shift (WGS) reaction, namely: (i) the concentration and chemical structure of active adsorbed reaction intermediates present in the C-path and H-path of WGS at 250 and 300°C, (ii) the chemical nature of inactive species formed during WGS, and (iii) the prevailing mechanistic path among “redox” and “associative” both proposed in the literature. For this, steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with in situ DRIFTS and mass spectrometry were performed to follow the H-path (use of D₂O) and C-path (use of¹³CO) of the WGS. In addition, other transient isotopic experiments using operando methodology (use of DRFTS and mass spectrometry) were designed to follow with time on stream the reactivity toward water of the various adsorbed species formed under WGS. It is proposed that on Pt/Ce1−_xLa_xO2−_δ ( x=0.0, 0.2 and 1.0) the WGS reaction follows both the “redox” and “associative” mechanisms but the extent of participation of each mechanism to the overall WGS reaction rate depends on the support chemical composition. The WGS kinetic rate (μmol COg⁻¹s⁻¹) increased by a factor of 2.0 and 2.8 at 300°C on 0.5wt% Pt supported on Ce_0.8La_0.2O2−_δ compared to CeO₂ and La₂O₃, respectively. This was explained by (i) the larger concentration of active surface intermediates formed around each Pt nanoparticle (larger extent of reactive zone) and (ii) the higher reactivity of sites ( k, s⁻¹) responsible for CO₂ and H₂ formation on Pt/Ce_0.8La_0.2O2−_δ compared to Pt/CeO₂ and Pt/La₂O₃. ActiveOH groups is suggested to be formed on defect sites (Ce³⁺□_s) of Ce_0.8La_0.2O2−_δ as a consequence of the introduction of La³⁺ into the ceria lattice, the latter enhancing the concentration of labile oxygen and its surface mobility, important characteristics of the “redox” mechanism.

Keywords: WGS reaction mechanism; La; ³⁺; -doping; Ceria-supported Pt; SSITKA-DRIFTS; SSITKA-MS; Operando; studies

Catalytic oxidation of toluene by ozone over alumina supported manganese oxides: Effect of catalyst loading by Ebrahim Rezaei; Jafar Soltan; Ning Chen (pp. 239-247).

Display Omitted► Oxidation state of Mn depends on loading of Mn on γ-alumina. ► Mn₂O₃ is formed at Mn loading lower than 10% while MnO₂ is dominant MnO_x phase at higher loadings. ► Lower oxidation states of Mn in catalysts with lower Mn loading lead to higher rate of toluene oxidation by ozone.This paper investigates effect of manganese loading on total oxidation of toluene by ozone using alumina-supported manganese oxide catalysts. Activities of four loadings of Mn (1, 5, 10 and 20%) were studied in the temperature range of 22–100°C. Catalysts were characterized by BET, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). All catalysts became deactivated at room temperature and their activities were improved by increase of temperature. CHNS and Fourier transform infra red (FT-IR) spectroscopy were used to study catalyst deactivation at room temperature. Alcohols and carboxylic acids were identified as deposited species on the catalysts responsible for catalyst deactivation. A direct relationship between Mn loading and average oxidation state of manganese was found. Catalysts at lower loadings up to 10% were mostly composed of Mn₂O₃ while a mixture of MnO₂ and Mn₂O₃ were present in catalysts with loadings higher than 10%. It was observed that lower Mn loadings have higher activity in oxidation of toluene. It was proposed that lower oxidation states of manganese are more favorable in decomposition of ozone resulting in higher rate of toluene oxidation.

Keywords: Toluene; Ozone; Manganese loading; XANES; EXAFS

Investigation of the role of platinum oxide for the degradation of phenol under simulated solar irradiation by Harrison S. Kibombo; Chia-Ming Wu; Rui Peng; Jonas Baltrusaitis; Ranjit T. Koodali (pp. 248-259).

Display Omitted► Control of the resultant oxidation state of Pt on TiO₂ was demonstrated. ► 100% PtO₂ on TiO₂ was obtained using a combination of phase transfer and hydrothermal treatment. ► The photocatalytic activities were investigated under solar simulated conditions. ► Pt⁰/PtO₂/TiO₂ exhibited superior photocatalytic performance with respect to TiO₂ and PtO₂/TiO₂.We demonstrate that a desired oxidation state can be achieved by synthetic colloidal methods and the choice of characterization technique is crucial for determining the physicochemical properties that influence the photocatalytic activities. XPS studies showed that PtO₂ was realized in this study, and the resultant crystalline PtO₂–TiO₂ prepared by subsequent hydrothermal treatment demonstrated activity for phenol degradation under simulated solar light irradiation. Preformed platinum based TiO₂ ensures control over the oxidation state and the crystallite size of titania. The role of Pt_ox in the form of stable Pt⁴⁺ is elucidated as a mild recombination center, whereas the crystallite size of Pt in surfactant free Pt⁰–TiO₂ appears to be the overriding factor for attaining enhanced photocatalytic performance.

Keywords: Platinum; Titania; Photocatalysis; Surface studies; Phenol degradation

High carbon-resistance Ni/CeAlO₃-Al₂O₃ catalyst for CH₄/CO₂ reforming by Wei Chen; Guofeng Zhao; Qingsong Xue; Li Chen; Yong Lu (pp. 260-268).

Dry reforming of methane on Ni/CeAlO₃-Al₂O₃ catalysts was studied to verify the cerium existing state under reaction condition and to probe the effects on carbon resistance improvement. The CeAlO₃ phase was identified and exhibited the ability to inhibit growth of filamentous carbon on nickel surface as a function of CeAlO₃ content.Display Omitted► High-performance Ni/Ce-AlO catalysts were developed for dry reforming of methane. ► Cerium is definitely identified to exist in the form of CeAlO₃ phase. ► CeAlO₃ can decompose CO₂ to form surface CeO₂ thereby inhibiting growth of graphene layers. ► Formation of amorphous carbon is independent of CeAlO₃ phase.High carbon-resistance Ni/Ce-AlO catalysts have been developed for dry reforming of methane (DRM) that is attracting growing attention for chemical recycling of CO₂ to fuels/chemicals. Cerium is definitely identified to exist in the form of CeAlO₃ phase after reduction at 900°C, and so is it under running conditions. The formation of CeAlO₃ phase significantly enhances the catalyst carbon-resistance without decreasing the activity. Whereas the catalysts with or without CeAlO₃ all show good activity maintenance within 250h testing at 800°C using 20,000mLh⁻¹g_cat⁻¹, their carbon deposition amounts exhibit significant decrease from 0.92 to 0.29gg_cat⁻¹ along with the increase of the CeAlO₃ phase. The presence of CeAlO₃ can inhibit growth of graphitic carbon on nickel surface while the formation of amorphous carbon is independent of the CeAlO₃. The CeAlO₃ species shows ability for decomposing CO₂ to form active surface oxygen and therefore the carbon-resistance promotion by nature is suggested to be contributed to an oxidative environment around Ni particles.

Keywords: Carbon dioxide; Methane; Syngas; Nickel catalyst; Cerium; Carbon

Well-dispersed g-C₃N₄ nanophases in mesoporous silica channels and their catalytic activity for carbon dioxide activation and conversion by Zhijun Huang; Fengbo Li; Bingfeng Chen; Tao Lu; Yin Yuan; Guoqing Yuan (pp. 269-277).

Display Omitted► Well-dispersed g-C₃N₄ nanophases were prepared in silica mesochannels through a two-step vapor condensation of dicyandiamide. ► Defect-containing, polymeric g-C₃N₄ nanophases were active catalysts for CO₂ activation. ► The active species were detected by XPS analysis. ► Activated CO2 can be steadily converted to target compounds with high selectivity. ► The catalytic materials have good stability and recyclability.Well-dispersed g-C₃N₄ nanophases in SBA-15 mesochannels were prepared by a two-step vapor condensation of dicyandiamide. Defect-containing g-C₃N₄ nanophases were active catalysts for CO₂ activation. Activated CO₂ species were steadily converted to target compounds with a high selectivity. The presence of doped metal ions markedly promoted the catalytic activity and selectivity. Zn²⁺-doped g-C₃N₄/SBA-15 showed a high activity in transferring CO₂ to epoxides. Fe³⁺-doped g-C₃N₄/SBA-15 was an efficient catalyst for the direct oxidative cycloadditon of CO₂ to olefins. Styrene was converted into 4-phenyl-1, 3-dioxolan-2-one. The process conversion was 34.1% and the selectivity to the oxidative cycloaddition product reached 93%. The recyclability of SBA-15 supported g-C₃N₄ nanophases was investigated through a five-run test. Their catalytic activity and microstructures were kept constant during the five-run recycling test. No marked metal leaching was detected during each test.

Keywords: Heterogeneous catalysis; Carbides; Nanomaterials; Fixation of carbon dioxide; Cycloaddition

Fabrication of novel SnO₂-Sb/carbon aerogel electrode for ultrasonic electrochemical oxidation of perfluorooctanoate with high catalytic efficiency by Hongying Zhao; Junxia Gao; Guohua Zhao; Jiaqi Fan; Yanbin Wang; Yujing Wang (pp. 278-286).

Display Omitted► Novel SnO₂-Sb/CA composite electrode with high efficiency was firstly fabricated. ► Optimal temperature for sinking micro SnO₂-Sb into CA as nanoparticles was 600°C. ► 91% and 86% of PFOA and TOC removal was respectively achieved after reaction 5h. ► Reasonable catalytic mechanism of US-EC process with SnO₂-Sb and CA was proposed.A novel SnO₂-Sb/CA electrode, possessing high surface area, strong adsorption capacity, good electrical conductivity and electrocatalytic activity, was firstly proposed for ultrasonic electrochemical oxidation (US-EC) of persistent high concentration perfluorooctanoate (PFOA) in this study. The optimal calcination temperature for sinking micro-sized SnO₂-Sb particles existed on the surface of CA into the structure of CA as nanoparticles was 600°C. Its application on degrading PFOA (60mL of 100mgL⁻¹) exhibited efficient electrocatalytic performance. After 5h electrolysis, over 91% of PFOA was degraded with a first-order kinetic constant of 0.52h⁻¹ and over 86% TOC removal was achieved, while 47% PFOA removal and 33% TOC removal were obtained in traditional electrochemical (EC) process. The main role of determining the decomposition efficiency, i.e., the mass transport, hydroxyl radical (·OH) generation and electrode surface reaction, were greatly enhanced in US-EC system. Additionally, the generated intermediates existing on electrode surface and in solution were separately detected after different electrolysis time and the proper mechanism for efficient removing PFOA in US-EC process was investigated in detail. At early reaction stage (<0.5h), the intermediate products on SnO₂-Sb/CA surface were C₅F₁₁COO⁻, C₄F₉COO⁻, C₃F₇COO⁻, C₂F₅COO⁻, CF₃COO⁻, while in solution were C₅F₁₁COO⁻, C₄F₉COO⁻, C₃F₇COO⁻. At late reaction stage (>5h), the intermediates either on electrode surface or in solution became the same including C₅F₁₁COO⁻, C₄F₉COO⁻, C₃F₇COO⁻.

Keywords: Sb-doped SnO; ₂; Carbon aerogel electrode; Electrochemical oxidation; Ultrasonic irradiation; Perfluorooctanoate

Sulfonic acid-functionalized aerogels as high resistant to deactivation catalysts for the etherification of glycerol with isobutene by María Dolores González; Pilar Salagre; Elena Taboada; Jordi Llorca; Elies Molins; Yolanda Cesteros (pp. 287-293).

Display Omitted► Silica aerogel and lyogel have been succesfully sulfonated by post-synthesis. ► Microwaves allowed loading higher amounts of sulfonic groups in aerogel and lyogel. ► Aerogel samples showed higher conversion and selectivity to h-GTBE than lyogel ones. ► Microwave-assisted sulfonated aerogel led the highest selectivity to h-GTBE (75%). ► Large porosity of functionalized aerogel makes this material high resistant to deactivation.Silica aerogel and lyogel have been successfully sulfonated in one step by a simple post-synthesis method using microwaves as well as conventional heating. The use of microwaves allowed loading higher amounts of sulfonic acid groups in both silicas, according to the higher S/Si atomic ratio determined by XPS, and the higher sulfur content determined by TGA, also exhibiting lower surface area and higher acidity. Sulfonated aerogels showed higher conversion and selectivity to h-GTBE (glycerol di- and tri-ethers) than sulfonated lyogels for the acid-catalyzed etherification of glycerol with isobutene. This was attributed to the higher content of sulfonic acid groups incorporated in aerogel. Microwave-assisted sulfonated aerogel yielded 75% of selectivity to h-GTBE, which can be used as fuel additive, for practically total conversion. Interestingly, larger porosity of aerogel avoided the partial blocking of pores by reaction products observed when other micro- and mesoporous catalysts were tested for this reaction. The combination of high conversion, high selectivity to h-GTBE, practically no formation of undesired di-isobutylenes and very high resistance to catalyst deactivation makes microwave-assisted sulfonic acid functionalized aerogel a promising catalyst for this etherification reaction.

Keywords: Aerogel; Lyogel; Sulfonic acid-functionalization; Microwaves; Glycerol etherification; Deactivation

Synergistic catalytic degradation of antibiotic sulfamethazine in a heterogeneous sonophotolytic goethite/oxalate Fenton-like system by Tao Zhou; Xiaohui Wu; Yanrong Zhang; Jianfeng Li; Teik-Thye Lim (pp. 294-301).

Display Omitted► A novel goethite catalyzed sonophotolytic Fenton-like (SP-FL) system was developed. ► Synergistic SMZ degradation, mineralization and detoxicity was achieved in the SP-FL system. ► In situ generation of H₂O₂ and fast regeneration of Fe(II) leads to the synergy achieved. ► The cleavage of SN bond in the SMZ molecule was dominant underOH attacking. ► Ultrasound achieved promotional role in the overall heterogeneous Fenton-like reactions.A novel heterogeneous sonophotolytic goethite/oxalate Fenton-like (SP-FL) system was developed in this study. Compared to the corresponding photochemical Fenton-like (P-FL) system and sonochemical Fenton-like system (S-FL) system, it was found that the SP-FL system could achieve synergistic degradation of antibiotic sulfamethazine (SMZ). A synergy factor of 2.2 based on pseudo-first-order degradation rate constant ( k_obs) was observed, along with great improvements in organic mineralization and wastewater detoxification. Examining the evolution of dissolved iron species and reactive oxygen species (H₂O₂ andOH) in the three systems revealed that the SMZ degradation strongly relied on the “in-situ” photochemical generation of H₂O₂ and fast regeneration of dissolved Fe(II) species. Identification of the organic intermediates and released inorganic ions suggested that the cleavage of SN bond in the SMZ molecule was dominant underOH attacking. The important synergistic role of ultrasound (US) in promoting SMZ degradation was proposed. Herein US could affect the system at multi-folds: (1) accelerating the goethite-chelating dissolution by reducing mass transfer barriers, (2) enhancing the radical reactions in the bulk solution with sonochemical cavitation effect, and (3) possible direct hydrolysis of amine intermediates inside the cavitation bubbles.

Keywords: Sonophotocatalysis; Fenton-like; Sulfamethazine; Iron–oxalate complexes; Goethite

Rationales for the selection of the best precursor for potassium doping of cobalt spinel based deN₂O catalyst by G. Maniak; P. Stelmachowski; A. Kotarba; Z. Sojka; V. Rico-Pérez; A. Bueno-López (pp. 302-307).

Display Omitted► K₂CO₃ is the best precursor for Co₃O₄ promotion. ► Catalytic activity in N₂O decomposition correlates with Co₃O₄ spinel work function. ► K promotes activation of N₂O via e- transfer and suprafacial oxygen recombination.Cobalt spinel Co₃O₄ catalysts promoted with different potassium precursors (K₂CO₃, KNO₃, CH₃COOK, KOH) were prepared and characterized by surface (XPS, work function, SEM) and structure (Raman, XRD, H₂-TPR) sensitive techniques. The stability of potassium promoter was determined by means of Species Resolved-Thermal Alkali Desorption method (SR-TAD). The N₂O decomposition mechanism on series of synthesized catalysts was studied by temperature programmed reaction and pulse experiments of isotopically labeled¹⁵N₂¹⁸O. The role of the octahedral cobalt ions as catalytic active sites was revealed. The most dispersed state of alkali promoter, obtained from K₂CO₃ precursor, results in its highest stability and lowest work function, leading to the highest catalytic activity in N₂O decomposition in the investigated K-Co₃O₄ series. The beneficial effect of potassium is discussed in terms of the facile activation of N₂O via dissociative electron transfer (N₂O +e⁻=N₂+O⁻) and promotion of the preferred fast suprafacial recombination of oxygen intermediates (revealed by the isotopic experiments).

Keywords: Cobalt spinel; Co; ₃; O; ₄; N; ₂; O decomposition; Potassium promotion; Potassium precursor; Nitrous oxide; Catalyst; Promoter dispersion; Isotopic labeling; Isotopic pulse; Work function

Co/Ce_xZr1−_xO₂ solid-solution catalysts with cubic fluorite structure for carbon dioxide reforming of methane by Shanghong Zeng; Xiaohong Zhang; Xiaojuan Fu; Lei Zhang; Haiquan Su; Hui Pan (pp. 308-316).

There were three kinds of deposition carbon on the catalysts according to the temperature of elimination carbon, named as α carbon (low temperature), β carbon (medium temperature) and γ carbon (high temperature). Only one-type carbon (β carbon) existed in the Co/ZrO₂ catalyst. For Co/CeO₂, there were two kinds of deposition carbon after the reaction, including β carbon and γ carbon. For Co/Ce_xZr1−_xO₂, α carbon and β carbon existed in the catalysts after the reaction, indicating that carbon was easy to eliminate from the Co/Ce_xZr1−_xO₂ catalysts at low and medium temperature, which was closely related with their reducibility.Display Omitted► Ce_xZr1−_xO₂ solid solution retained cubic fluorite structure of CeO₂ support. ► Good dispersion of Co₃O₄ crystallites on cubic fluorite Ce_xZr1−_xO₂ supports. ► Co/Ce_xZr1−_xO₂ catalysts had better reducibility compared with ZrO₂ and CeO₂. ► Catalytic performance was closely related with acidity, dispersion and reducibility. ► Deposition carbon of Co/Ce_0.6Zr_0.4O₂ mainly was low-temperature carbon.The Co/Ce_xZr1−_xO₂ catalysts were prepared by the impregnation method and characterized via BET, NH₃-TPD, XRD, H₂-TPD, H₂-TPR, TEM and TG–DSC techniques. The study showed that the Co₃O₄ crystallites had better dispersion on the cubic fluorite Ce_xZr1−_xO₂ supports compared with on the ZrO₂ and CeO₂, and the Co/Ce_0.6Zr_0.4O₂ retained the cubic fluorite structure after the reaction. The Ce_0.6Zr_0.4O₂ catalyst showed good catalytic performance, which was attributed to the alkalescence of support surface, better dispersion of active species, better textural property and reducibility. The deposition carbon over the Co/Ce_0.6Zr_0.4O₂ catalyst mainly existed in the form of low-temperature carbon.

Keywords: Ce; _x; Zr; 1−; _x; O; ₂; Cobalt catalyst; Carbon deposition; CH; ₄; /CO; ₂; reforming

Complete methanol oxidation in carbon monoxide streams over Pd/CeO₂ catalysts: Correlation between activity and properties by Yongjin Luo; Yihong Xiao; Guohui Cai; Yong Zheng; Kemei Wei (pp. 317-324).

Display Omitted► Three types of Pd/CeO₂ were compared in the co-oxidation of CO and methanol. ► An easier CO oxidation facilitates the complete methanol oxidation. ► High degree of defect sites connected with activated oxygen mobility is the key. ► Pd dispersion, stable PdO_x species and redox ability also affect the oxidation activity.Three different techniques, a hydrothermal process with impregnation, solution-combustion and common precipitation with impregnation, were employed for the synthesis of 1.5wt% Pd/CeO₂, and the resulting catalysts were denoted as Pd/HY, Pd/COM and Pd/PI, respectively. These catalysts have been investigated in terms of catalytic co-oxidation of CO and methanol and characterized by means of XRD, BET, SEM, STEM-EDS, CO chemisorption, XPS, Raman, O₂-TPD, H₂-TPR and CO-TPD measurements. Activity results show that a rapid catalytic oxidation of CO following the Mars-van Krevelen-type mechanism favors the complete methanol oxidation at low temperature. Consequently, the Pd/HY catalyst with the highest degree of defect sites connected with the mobility of activated oxygen shows the best catalytic performance. And the generation of more defect sites demonstrated by Raman is assumed for the low crystallinity and small crystallite size of CeO₂ synthesized through a hydrothermal process while the high mobility of activated oxygen is evidenced by O₂-TPD and H₂-TPR. Additionally, the outstanding catalytic performance of Pd/HY is also associated with its high Pd dispersion and stable PdO_x species as well as good redox behavior.

Keywords: Pd/CeO; ₂; Synthetic techniques; CO; Methanol; Defect sites

Effect of silver nanoparticles on TiO₂-mediated photodegradation of Alizarin Red S by Michele L. de Souza; Paola Corio (pp. 325-333).

Display Omitted► A simple wet chemistry method for immobilization of Ag NPs on the P25 surface leading to a catalytic composite was performed. ► P25-Ag composite photocatalytic efficiency was observed under UV/visible and visible excitation photodegradation of ARS. ► Distinct mechanisms were identified according with the radiation source and the degradation stage. ► Phototensitization and plasmonic effects showed to be incremental on the P25-Ag composite.Titanium oxide (TiO₂) is widely employed in photocatalysis and in organic solar cells despite certain efficiency shortcomings regarding the high e⁻/h⁺ pair recombination rate and wide E_gap. Wet chemistry immobilization of plasmonic Ag NPs onto commercial TiO₂ (P25) through a bifunctional linker molecule (3-mercaptopropionic acid) was employed as a strategy to overcome such shortcomings. This paper proposes the main photodegradation excitation mechanisms according to the irradiation energy source. The photodegradation of the textile dye Alizarin Red S (ARS) catalyzed by bare P25 and a P25-Ag composite was studied applying UV/visible and visible radiation. Under UV/visible radiation, the P25-Ag composite showed a 40% improvement in the photodegradation rate constant in comparison to the bare P25, a phenomenon assigned to the charge separation due to the Schottky barrier. After 180min under visible radiation the ARS degradation was 80%, i.e. low P25 photosensitization, while the P25-Ag composite showed a 7% increase in the percentage degradation of the unsaturated compounds, which was attributed to the plasmonic local field enhancement at the TiO₂ surface.

Keywords: AOPs; Catalytic photodegradation efficiency; Alizarin Red S; Plasmonic photodegradation

A dye-sensitized FeOOH–CNT photocatalyst with three electron transfer channels regulated by hydrogen bonding by Xi-Feng Shi; Na Li; Ke Zhao; Guan-Wei Cui; Ying-Qiang Zhao; Ming-Yue Ma; Ke-Hua Xu; Ping Li; Yu-Bin Dong; Bo Tang (pp. 334-340).

A RuL₂Cl₂–FeOOH–CNT catalyst with three electron transfer channels in cyclohexane performs better photocatalytic efficiency than those with one or two channels. Theoretical calculation results further explained the formation of three electron transfer channels driven by intermolecular hydrogen bonding.Display Omitted► A RuL₂Cl₂–FeOOH–CNT composite was constructed by esterification method. ► The composite was used as a visible light photocatalyst for 2-hydroxybenzoic acid. ► The photocatalyst possessed 3 electron transfer channels in nonpolar solvents. ► The activity of photocatalyst was much better than that of reported photocatalysts.A dye-sensitized photocatalyst with three electron transfer channels was constructed, in which FeOOH and photosensitizer RuL₂Cl₂·2H₂O were employed as the electron donor, carbon nanotubes were served as the electron container. The catalytic activities of the photocatalyst were evaluated by a model photocatalytic carboxylation reaction of phenol by CO₂. The photocatalytic efficiency and transient photocurrent density increased obviously when the catalysis reaction was carried out in cyclohexane compared to two electron activations in water, which suggested the formation of three electron transfer channels in the catalytic system. Moreover, time-dependent density functional theory (TD-DFT) calculation results also indicated the existence of three electron transfer channels assisted by intermolecular hydrogen bonding interaction.

Keywords: Photocatalysis; Electron transfer; Three channels; Hydrogen bonding

Solar Advanced Oxidation Processes as disinfection tertiary treatments for real wastewater: Implications for water reclamation by M. Agulló-Barceló; M.I. Polo-López; F. Lucena; J. Jofre; P. Fernández-Ibáñez (pp. 341-350).

Display Omitted► We assess the disinfection of a real secondary effluent using solar AOPs. ► We provide novel results on their effects in naturally occurring microorganisms. ► A single microbial indicator may not be enough to guarantee a low risk of infection. ► Viral indicators were more sensitive to TiO₂/solar than bacterial indicators. ► Photo-Fenton would provide high quality reclaimed water in a very short time.The aim of this study was to assess the disinfection of a real secondary effluent from a municipal wastewater treatment plant using added H₂O₂ (20 and 50mgL⁻¹), TiO₂ (100mgL⁻¹) and photo-Fenton under natural solar radiation in compound parabolic collector photo-reactors. For this purpose, the naturally occurring Escherichia coli, spores of sulphite-reducing clostridia (SRC), somatic coliphages (SOMCPH) and F-specific RNA bacteriophages (FRNA) were tested before and along the different solar treatments. Results for E. coli showed the different treatments efficiency rank: photo-Fenton pH 3>H₂O₂ (20mgL⁻¹)/solar>TiO₂/solar>solar photo-inactivation. On the other hand, for viral indicators the ranking was: photo-Fenton pH 3>TiO₂/solar>H₂O₂ (20mgL⁻¹)/solar>solar photo-inactivation. SRC was the most resistant indicator microorganism in all the evaluated processes. For the first time these solar processes have been evaluated for naturally occurring conventional indicators such as E. coli and alternative indicators such as SOMCPH and FRNA as viral indicators or spores of SRC as protozoan indicators. Some of the tested solar photo-oxidation treatments have shown their capability to reduce E. coli concentrations to a suitable level for water reuse (according to different reclaimed water guidelines) within affordable treatment times.

Keywords: Solar disinfection; AOP; E. coli; Bacteriophages; Reclaimed water

Synthesis of Pt-based hollow nanoparticles using carbon-supported Co@Pt and Ni@Pt core–shell structures as templates: Electrocatalytic activity for the oxygen reduction reaction by D.A. Cantane; F.E.R. Oliveira; S.F. Santos; F.H.B. Lima (pp. 351-360).

Display Omitted► Electrocatalysts exhibited hollow-induced lattice contraction. ► Ligand effect played important role on the activity for the ORR. ► Hollow@NiPt/C presented high specific activity. ► High activity of Hollow@NiPt/C associated to the faster reduction of oxygenated species.Pt-based hollow nanoparticles were investigated as electrocatalysts for the oxygen reduction reaction (ORR) in acid electrolyte. The electrocatalysts were synthesized via Ni or Co diffusion/dissolution, induced by the vacancy-mediated Kirkendall effect, during electrochemical potential cycling of Ni@Pt and Co@Pt core–shell nanoparticles in acid media. The nanoparticles were characterized by high resolution transmission electron microscopy, in situ X-ray absorption spectroscopy and X-ray diffraction measurements. The results show substantial differences in nanoparticle structure/composition and in the activity for the ORR, depending on the nature of the non-noble metal in the nanoparticle core. The Pt hollow nanostructures showed higher specific catalytic activity than that of the state-of-the-art Pt/C electrocatalyst. This was attributed to three main effects: (i) hollow-induced lattice contraction in the multilayer Pt shells, (ii) mismatch-induced lattice contraction of the thick Pt shell by the remaining Ni or Co atoms and (iii) a ligand effect, due to the electronic interaction of Pt with the remaining Ni or Co atoms in the Pt multilayers of the hollow structure. These three effects caused a Pt d-band center down-shift, which decreased the adsorption strength of oxygenated reaction intermediates and spectators, thus increasing the ORR rate.

Keywords: Pt hollow electrocatalysts; Core–shell nanoparticles; Oxygen reduction reaction

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Applied Catalysis B, Environmental (v.136-137, #)