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  Subjects -> ENGINEERING (Total: 2266 journals)
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ENGINEERING (1195 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Full-text available via subscription   (Followers: 5)
AASRI Procedia     Open Access   (Followers: 15)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 216)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 1)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 10)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
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Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
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Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 5)
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Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
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ASEE Prism     Full-text available via subscription   (Followers: 2)
Asian Engineering Review     Open Access  
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Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 7)
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Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
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ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 3)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
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Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 9)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
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Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
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Biomedical Microdevices     Hybrid Journal   (Followers: 8)
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Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
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Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 13)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 21)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 4)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
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Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 23)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 252)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 177)
Composites Part B : Engineering     Hybrid Journal   (Followers: 223)
Composites Science and Technology     Hybrid Journal   (Followers: 164)
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Concurrent Engineering     Hybrid Journal   (Followers: 3)
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Control and Dynamic Systems     Full-text available via subscription   (Followers: 7)
Control Engineering Practice     Hybrid Journal   (Followers: 40)
Control Theory and Informatics     Open Access   (Followers: 7)
Corrosion Science     Hybrid Journal   (Followers: 24)
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Journal Cover Catalysis Today
  [SJR: 1.348]   [H-I: 164]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [3032 journals]
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287


      PubDate: 2017-04-10T04:09:27Z
       
  • Contents list
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287


      PubDate: 2017-04-10T04:09:27Z
       
  • Introduction by guest editors
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Nicolas Keller, Didier Robert, Pilar Fernández-Ibañez, Sixto Malato


      PubDate: 2017-04-10T04:09:27Z
       
  • Photocatalytic treatment of saccharin and bisphenol-A in the presence of
           TiO2 nanocomposites tuned by Sn(IV)
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): K. Davididou, E. Hale, N. Lane, E. Chatzisymeon, A. Pichavant, J.-F. Hochepied
      This study deals with the photocatalytic treatment of saccharin (SAC) and bisphenol-A (BPA) under UV irradiation. For this purpose, novel submicronic anatase–rutile nanocomposite particles with tuned phase ratio, produced by thermohydrolysis of acidic Ti(IV) solutions in the presence of controlled amounts of Sn(IV), were used. These catalysts were then assessed regarding their efficiency to degrade SAC or BPA, which are contaminants of increased environmental and health concern. The effect of various operating conditions, such as the anatase-rutile ratio (100:0, 85:15, 70:30), catalyst concentration (50–600mg/L) and solute concentration (3–10mg/L) was investigated. Furthermore, catalyst reuse –an important but little studied aspect- was assessed. Anatase–rutile nanocomposites were successfully prepared presenting good crystallinity and surface quality. Their activity was about the same for removing SAC or BPA from water. It was found that photocatalytic performance was increased with catalyst loading up to 400mg/L. A further increase to 600mg/L did not significantly enhance BPA removal, thus associating this tendency with screening effects. Also, photocatalytic efficiency was increased with initial solute concentration decrease. Organics degradation followed a pseudo-first order kinetic rate in terms of both SAC and BPA removal. The reproducibility of catalyst activity was assessed in three successive reuse cycles, where the removal percentage of initially 5mg/L SAC was maintained as high as 70% at the end of the 3rd cycle, in the presence of initially 400mg/L anatase catalyst, and after 90min of treatment. Finally, additional experimental runs were carried out with ultrasound cleaning (US) being applied to the reactant mixture at the beginning of each reuse cycle, but it was found to have no significant effect on treatment efficiency.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Microcontaminant removal in secondary effluents by solar photo-Fenton at
           circumneutral pH in raceway pond reactors
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): I. De la Obra, L. Ponce-Robles, S. Miralles-Cuevas, I. Oller, S. Malato, J.A Sánchez Pérez
      This paper deals with raceway pond reactors (RPRs) as an alternative photoreactor for solar photo-Fenton applications. Raceway pond reactors are common low-cost reactors which can treat large volumes of water. The experiments were carried out with Fe3+:EDDS complex in the secondary effluent of a municipal wastewater treatment plant spiked with a mixture of 100 μg/L each of five pharmaceuticals (carbamazepine, flumequine, ibuprofen, ofloxacin and sulfamethoxazole) at circumneutral pH. In a preliminary stage, two operating strategies, sequential addition of iron sulfate and Fe3+:EDDS complex at a 1:2 molar ratio were compared, and Fe3+:EDDS complex was found to be the best option. The effect of liquid depth (10, 15 and 20 cm) was also explored. 90% pharmaceutical removal was achieved with accumulated solar UV energy of around 1kJ/L. Finally, RPRs and tubular photoreactors with compound parabolic collectors (CPC) were compared under realistic conditions. Pharmaceutical removal efficiency was four times higher, increasing from 0.26mg/kJ with CPC reactors to 1.07mg/kJ in the 15-cm-deep RPR. As far as the authors know, this is the first detailed study on the effect of liquid depth in RPRs at circumneutral pH.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Legionella jordanis inactivation in water by solar driven processes:
           EMA-qPCR versus culture-based analyses for new mechanistic insights
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): María Inmaculada Polo-López, María Castro-Alférez, Samira Nahim-Granados, Sixto Malato, Pilar Fernández-Ibáñez
      In this contribution, the validation of EMA-qPCR method for the quantification of viable Legionella spp. in water after solar treatments was carried out. EMA-qPCR was used to evaluate the different effects of several solar water disinfection processes over this bacterium, and furthermore their mode of action. Inactivation of Legionella jordanis in water by solar photocatalytic (TiO2 and TiO2/H2O2) and solar photochemical (solar/H2O2 and solar disinfection) processes have been investigated under natural sunlight. Culture-based and molecular (EMA-qPCR) techniques were systematically compared for the analysis of treated water samples. Solar tests were done under natural solar radiation (clear sky) and ambient temperature (20–35°C) for 2h, using H2O2/Solar (10, 20 and 50mg/L), TiO2/Solar (100, 200, 300, 400, and 500mg/L) and TiO2/H2O2/Solar (100/10, 200/10, 500/10mg/L). According to culture-based method, the best results of bacterial inactivation were obtained for 500/10mg/L of TiO2/H2O2. The order of efficiency to reach complete inactivation was: TiO2/H2O2/solar (5min)>TiO2/solar (15min)≈H2O2/solar (15min)>Solar only disinfection (90min). Moreover, EMA-qPCR and culturable counting results showed a direct correlation for samples treated with TiO2/solar for those catalyst concentrations that generate a strong oxidative attack over the cell wall. EMA-qPCR results demonstrated to be a good method to detect damaged and dead cells when the treatment affects the integrity of the cell’s membrane, as occurs under photocatalysis. Meanwhile for solar disinfection and solar/H2O2 (at non-toxic concentrations, <1.5mM), where membrane integrity remained unaltered, EMA-qPCR results couldn’t discriminate between alive and dead cells, even when the bacteria were not culturable.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Decahedral anatase titania particles immobilized on zeolitic materials for
           photocatalytic degradation of VOC
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): I. Jansson, K. Kobayashi, H. Hori, B. Sánchez, B. Ohtani, S. Suárez
      Decahedral anatase titania particles (DAPs) immobilized on zeolites (zeolite/DAP hybrids), have been prepared by the first time. DAPs have been synthesized from titanium chloride (TiCl4) through a gas-phase reaction process by rapid heating and quenching. DAPs with well-defined {101} and {001} facets were synthetized and dispersed onto the zeolites. The incorporation of an 8wt% of DAPs into the zeolites has been achieved by means of the freezing-drying technique. Two types of zeolites (ZSM-5 and zeolite Y) with different SiO2/Al2O3 contents have been selected as adsorbents. The photocatalytic properties for the degradation of representative volatile organic compounds (VOC), i.e. acetaldehyde, formaldehyde or trichloroethylene were analyzed under batch and continuous flow reactors. Raw materials and composites were characterized by SEM, N2 adsorption-desorption, UV–vis spectroscopy, XRD, zeta potential and the amount of VOC adsorbed was measured at dynamic conditions. Zeolite/DAP hybrids combine the textural and crystalline properties of zeolite and DAPs phases. The zeolite type (crystal structure, SiO2/Al2O3 ratio and surface net charge) play a relevant role in the dispersion of DAPs. Zeolite/DAP composites show better photocatalytic performance than those prepared with commercial TiO2 due to the presence of {001} facets in the former. The composites prepared with hydrophobic ZSM-5 and DAPs, are the most versatile materials for photooxidation of aldehydes and organochloride compounds, with substantially less formation of non-desirable reaction products respect to those based on benchmark TiO2.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • A simple non-aqueous route to nano-perovskite mixed oxides with improved
           catalytic properties
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Liwei Hou, Hui Zhang, Lihua Dong, Li Zhang, Daniel Duprez, Sébastien Royer
      Highly crystalline LaBxO3 (B=Co, Mn) perovskites are produced through a simple non-aqueous benzyl alcohol (BA) route. Textural properties of BA-derived materials were compared to those obtained for solids of comparable composition, prepared by classical citric acid complexation method. Oxygen mobility in synthesized materials was evaluated by oxygen isotopic (18O) exchange (OIE). Perovskites obtained with the BA route shows much larger specific surface area, smaller crystallite size and superior oxygen mobility. Such improvement in properties is in favor of low temperature catalytic oxidation, as evaluated by CO oxidation.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Delaminated kaolinites as potential photocatalysts: Tracking degradation
           of Na-benzenesulfonate test compound adsorbed on the dry surface of
           kaolinite nanostructures
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Péter Szabó, Balázs Zsirka, Dávid Fertig, Erzsébet Horváth, Tamás Csizmadia, János Kristóf
      Based on their bandgap values, kaolins can have semiconductive and photocatalytic properties enabling them to use as potential photocatalysts. Kaolinite nanostructures (Knano) and silver-coated kaolinite nanohybrids (Knano(Ag)) were made of ordered (Hinkley Index, HI=1.4) and disordered (HI=0.3) kaolins via intercalation/deintercalation. The book-type kaolin built up from tetrahedral(T)-octahedral(O) double layers has very low photocatalytic activity. At the same time the nanostructures made of individual TO layers show photochemical activity in spite of the fact that their bandgap values are comparable to those of the book-type ones. The presence of Ag on the surface significantly reduced the bandgap and shifted the excitation wavelength towards the visible range. This phenomenon supports the supposition that kaolinite has some semiconductive character. This work presents the connection between photocatalytic activity and morphology for the first time. The surface activity of kaolinite nanostructures and their Ag-hybrids was studied through the decomposition of sodium-benzenesulfonate (BS) test compound with attenuated total reflection Fourier transform infrared spectroscopy (FT-IR/ATR). BS decomposition can be detected on the Knano surface but with low efficiency. The presence of silver can significantly improve the mineralization efficiency. No correlation was found between the activity and the quantity of Ti and Fe contaminants and the amount of Ag on the surface. However, the activity could be correlated with the order-dependent morphology (mixture of semi-hexagonal and nanoscroll-type structures), the pore size and with the increase of the surface coverage.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Novel ‘Pickering’ modified TiO2 photocatalysts with high
           De-NOx efficiency
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): S. Karapati, T. Giannakopoulou, N. Todorova, N. Boukos, I. Papailias, D. Dimotikali, C. Trapalis
      Modified TiO2 nanoparticles were prepared by a Pickering emulsions route with the use of hydrophobic (oleylamine) and hydrophilic (polyethylene glycol) organic surfactants and their combination, as well. The attachment of modifiers to the TiO2 nanoparticles was proved via FT-IR and thermal analysis. Thicker modifier layer was formed on the TiO2 surface but lower average particle size was attained when amphiphilic modification was applied that was revealed by TEM analysis and dynamic light scattering, correspondingly. The amphiphilic modification permitted control of the hydrophobic properties of the TiO2 nanoparticles so that their incorporation in cement matrix led to preparation photocatalytic cement materials with superior De-NOx efficiency.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Titanium and zirconium-based mixed oxides prepared by using pressurized
           and supercritical fluids: On novel preparation, microstructure and
           photocatalytic properties in the photocatalytic reduction of CO2
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): K. Kočí, L. Matějová, I. Troppová, M. Edelmannová, T. Prostějovský, P. Peikertová, T. Brunátová, J. Lang, L. Čapek, L. Obalová
      The ZrxTi1-xOn mixed oxides with various Ti:Zr molar ratios and parent TiO2 and ZrO2 were prepared unconventionally, combining the reverse micelles-controlled sol-gel method with high-pressure processing by pressurized and supercritical fluids. The mixed oxides were characterized using several complementary characterization methods and investigated in the photocatalytic reduction of CO2. Applied novel unconventional processing affected significantly the (micro)structure of mixed oxides, which was further reflected to their optical and thus electronic properties. The Zr0.1Ti0.9On mixed oxide showed the best photocatalytic behavior in a consequence of the optimal crystallinity and the lowest band gap energy from all mixed oxides. The Zr0.1Ti0.9On mixed oxide was of bicrystalline TiO2 anatase-brookite structure (67:33wt.%) showing small crystallite-sizes, which allowed the optimal surface phase junction.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Anatase TiO2 nanotube arrays and titania films on titanium mesh for
           photocatalytic NOX removal and water cleaning
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Motola Martin, Satrapinskyy Leonid, Roch Tomáš, Šubrt Jan, Kupčík Jaroslav, Klementová Mariana, Jakubičková Michaela, Peterka František, Plesch Gustav
      An anodization method was developed for the preparation of highly photoactive titania nanotube arrays (TiNTs) on commercially available titanium mesh. The prepared material was characterized from the point of view of its structure and possible photocatalytic applications and was compared with titania films deposited on the Ti-mesh by liquid deposition (TiO2-LD) and sol-gel methods (TiO2-SG). The photoactivity was determined in gas phase using NOX decomposition according to the ISO standard no. 22 197-1 (2007) as well as in liquid phase by decolorization of organic dyes e.g. methylene blue (MB) and rhodamine B (RhB). The investigated anatase nanotube arrays on Ti mesh showed the highest photoactivity in both gaseous and liquid phases and are promising for applications in photocatalytic reactors for environmental purification.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Layered Dion-Jacobson type niobium oxides for photocatalytic hydrogen
           production prepared via molten salt synthesis
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Natalia Kulischow, Calin Ladasiu, Roland Marschall
      A class of Dion-Jacobson type layered perovskite niobium oxides (AB2Nb3O10 with A=K, Rb, Cs and B=Ca, Sr, Ba) was prepared via molten salt method for the first time. By dissolving oxide and carbonate precursors in A-cation chloride melts, this type of synthesis needs only two hours of preparation time resulting in highly crystalline layered niobates at a much shorter synthesis time compared to conventional syntheses, like the solid state reaction. Beside detailed materials characterization, we investigated the influence of A-cation and B-cation variation on the band gap and photocatalytic activity for hydrogen production. It was found that the band gap decreases with the increase in size of the B-cation. A strong dependence on interlayer spacing (influenced by the size of the A-cation) and lattice relaxation can be derived from the steady-state hydrogen evolution rates.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Selective photocatalytic oxidation of benzyl alcohol to benzaldehyde by
           using metal-loaded g-C3N4 photocatalysts
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Maria J. Lima, Pedro B. Tavares, Adrián M.T. Silva, Cláudia G. Silva, Joaquim L. Faria
      Replacement of traditional thermal synthesis of fine chemicals by selective photocatalysis can lead to more environmental friendly processes, carried out at milder conditions, using ambient temperature, atmospheric pressure, with more ecological and economic solvents such as water. Because benzaldehyde (BAL), as fine chemical building block, has an enormous range of applications in pharmaceutical, fragrance and agricultural industries, we analyzed its route of synthesis by the photocatalytic oxidation of benzyl alcohol (BA). In this work, we used graphitized-carbon nitride (g-C3N4) as photocatalyst for the selective synthesis of benzaldehyde from benzyl alcohol. The solid matrix of the photocatalyst was modified by loading different metals such as Au, Ru, Pd, Pt, Ir, Ag and Rh. Conversion, yield and selectivity were compared against benchmark commercial photocatalyst P25 TiO2 (by Evonik). The influence of the physical-chemical nature of the medium, by means of the pH, on the efficiency of the photocatalytic process was also evaluated. The 1wt.% Ru/g-C3N4 photocatalyst had the best compromise between conversion (73%) and selectivity (72%) for a 4h of irradiation time using 390nm activation by a light emitting diode source and it proved to be stable up to 3 consecutive runs.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Cu/TiO2 photocatalysts for the conversion of acetic acid into biogas and
           hydrogen
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Ana Amorós-Pérez, Laura Cano-Casanova, María Ángeles Lillo-Ródenas, M. Carmen Román-Martínez
      Photocatalytic decomposition of acetic acid into biogas and hydrogen was performed over Cu/TiO2 photocatalysts synthesized by the sol-gel method. Samples with different Cu loadings (0, 0.5, 1 and 10wt.%) were prepared by two different methods (in situ and impregnation), and then they were heat treated at 500°C either in air or in argon. Structural and surface characterization of the photocatalysts was carried out. The influence of the synthesis variables on their efficiency in the photocatalytic decomposition of acetic acid in aqueous solution was analyzed. The photodegradation results show that all the prepared materials are more active than commercial TiO2, used as a reference, and reveal that the presence of copper improves the activity of pure TiO2. Cu/TiO2 photocatalysts prepared by the in situ method and heat treated in argon show the best results. This can be explained considering that these synthesis conditions lead to more efficient interaction between Cu species and TiO2, to a more developed porosity and to a more suitable distribution of copper oxidation states (large contribution of Cu(I) and Cu(0) seem to give better activity). Catalysts with 0.5wt.% copper are the most active, likely because copper species are highly dispersed and interact efficiently with TiO2. Thus, the activity of a Cu/TiO2 catalyst produced in situ, heat treated in Ar atmosphere and with a 0.5wt.% Cu content is double than that of the TiO2 commercial catalyst.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Promoter effect of Ga in Pt/Ga-TiO2 catalysts for the photo-production of
           H2 from aqueous solutions of ethanol
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): A.C. Sola, M. Broch Gösser, P. Ramírez de la Piscina, N. Homs
      In this paper, the effect of Ga in Pt/Ga-TiO2 catalysts for photocatalytic H2 production from aqueous solutions of ethanol is studied. The fresh and post-reaction catalysts were characterized using different techniques including BET, XRD, TPR, SEM-EDX, XPS, CO chemisorption and in situ DRIFTS. The presence of Ga in Pt/TiO2-based catalysts increased the Pt dispersion and decreased the relative amount of surface oxidized Pt species. Pt/Ga-TiO2 catalysts showed more stable behaviour during the photocatalytic reaction than the reference Pt/TiO2. The Pt/0.2Ga-TiO2 catalyst showed a higher initial rate of production of H2 and produced a higher total amount of H2 than the monometallic Pt/TiO2. The promoter effect of Ga is analysed in the light of the surface characteristics of the catalysts.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Novel preparation of ZnS from Zn5(CO3)2(OH)6 by the hydro- or solvothermal
           method for H2 production
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Octavio Aguilar, Francisco Tzompantzi, Raúl Pérez‐Hernández, Ricardo Gómez, Agileo Hernández-Gordillo
      Mesoporous nanostructured zinc sulfide was prepared by the hydro or solvothermal method using synthesized Hydrozincite as a novel zinc precursor. ZnS from annealing ZnO and zinc nitrate as zinc sources was also investigated. Synthesized Hydrozincite, ZnO and the ZnS samples were characterized by XRD, UV–vis diffuse reflectance spectroscopy and FTIR analysis. The morphology and textural properties of the ZnS materials were investigated by SEM and N2 adsorption-desorption, respectively. The photocatalytic properties of the ZnS materials were evaluated in the photocatalytic production of H2 using a methanol-water solution at pH 6 (natural) under UV light irradiation. For the unique active mesoporous ZnS, an additional chemical stability test varying the pH solution (acid or alkaline media) using four reaction cycles was carried out and selected spent ZnS was characterized. The photoactiviy of synthesized mesoporous ZnS from Hydrozincite by solvothermal method was discussed as a function of the presence of ethylenediamine linked to ZnS.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Hematite photoanodes for solar water splitting: Directly sputtered vs.
           anodically oxidized sputtered Fe
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Josef Krýsa, Martin Zlámal, Šárka Paušová, Tomáš Kotrla, Štěpán Kment, Zdeněk Hubička
      Hematite iron oxide has been extensively studied for photoelectrochemical (PEC) water splitting. Nanostructuring of hematite-based photoanodes represents an effective strategy to supress the negative impact of a short diffusion length of photoexcited holes on the PEC performance. Here we present a comparative structural and photoelectrochemical study of hematite photoanodes fabricated in the forms of two-dimensional (2D) very thin (∼25nm) nanocrystaline films and one-dimensional (1D) nanostructures including nanotubes and nanorods. Hematite films on fluorine-doped tin oxide (FTO) coated glass were prepared by two methods (i) by reactive high-power impulse magnetron sputtering (HiPIMS) and (ii) by anodic oxidation of Fe films deposited on FTO by HiPIMS. While in the first case very thin, dense, compact hematite films were deposited, the second approach yielded transparent nanotubular or nanorod hematite nanostructures. In both cases, the photoelectrochemical response was crucially influenced by the post thermal treatment at 750°C resulting in the Sn4+ diffusion from the FTO substrate and the improvement of conductivity across the FTO/Fe2O3 interface. Fe2O3 films exhibit a photocurrent onset at potential 1.1V (RHE) with almost linear increase of photocurrent with applied potential. The highest photocurrents were obtained for planar thin hematite electrodes prepared directly by HIPIMS technique (0.55mAcm−2 at 0.5V vs. Ag/AgCl). The observed minimal bias for photoelectrochemical water splitting with hematite photoanode was 1.25V. For applied potential 0.25V (vs. Ag/AgCl) and bias 1.3V, the observed photocurrent density and hydrogen production rate was 0.305mA/cm2 and 5.8μmol/h/cm2, respectively.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Morphological effect of ZnO nanoflakes and nanobars on the photocatalytic
           dye degradation
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Nora S. Portillo-Vélez, Agileo Hernández-Gordillo, Monserrat Bizarro
      ZnO films with nanoflake and nanobar morphologies were obtained by spray pyrolysis by changing the precursor salt and without any structure-directing agents. Nanoflakes were obtained from zinc acetate while nanobars with zinc chloride. Both films presented ZnO hexagonal wurtzite structure, a transmittance above 80% and band gap of 3.2eV. The photocatalytic activity of the films was evaluated by the degradation of methyl orange and indigo carmine dyes in different concentrations. The film with nanoflake morphology showed the best performance in discoloration (96%) and it achieved a 51% in mineralization. The film with nanobars attained only a 67% in discoloration whereas it failed to mineralize the dye solution. The principal factors involved in the best performance of the nanoflake films were the less defective surface in the ZnO structure that diminished the electron-hole recombination, allowing the generation of hydroxyl radicals in a sufficient amount. The nanoflake film showed also a high stability after 10 degradation cycles, indicating a promising material for photocatalytic water treatment.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Growth of TiO2 nano-wall on activated carbon fibers for enhancing the
           photocatalytic oxidation of benzene in aqueous phase
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Ajit Sharma, Byeong-Kyu Lee
      In the present study, TiO2 nano-wall networks (TNWs) were successfully grown on the surface of activated carbon fibers (ACFs) pre-coated with TiO2 nanoparticles (TNPs) via a hydrothermal process. The TNWs with an average length of 0.7–0.9μm grew on the ACFs (ACF-TNW) surface in a three-dimensional direction to a complex structure with good uniformity and high crystallinity, as confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The maximum removal capacities of benzene in a combined process of photo-oxidation and sorption affinity were 111.6 and 144.8mg/g for ACF-TiO2 and ACF-TNW, respectively, at pH 5, under UV light irradiation within 80min. The highest benzene removal efficiency of 98.7% in the ACF-TNW system (in 100mL of 50mg/L), also confirmed by the CO2 emission results, was accompanied by total organic carbon (TOC) and chemical oxygen demand (COD) reductions of 79.5 and 82.3%, respectively. The ACF-TNW nanocomposite also showed a higher photocatalytic oxidation of benzene than that of TNPs due to the minimization of electron-hole recombination resulting from the transfer of photo-induced electrons through the ACFs surface. The ACF-TNW nanocomposite was also easily separated from aqueous solution for regeneration and showed good stability after multiple uses.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Self-supported Co-Ni-P ternary nanowire electrodes for highly efficient
           and stable electrocatalytic hydrogen evolution in acidic solution
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Wei Li, Dehua Xiong, Xuefei Gao, Wei-Guo Song, Fang Xia, Lifeng Liu
      Self-supported electrodes comprising densely-packed, vertically-aligned Co-Ni-P ternary nanowire arrays supported on a nickel foam current collector (Co-Ni-P/NF) have been fabricated through hydrothermal growth of Co-Ni precursor nanowires on nickel foam, followed by a facile phosphorization treatment using low-cost red phosphorous. The morphology, crystal structure, microstructure and chemical composition of the as-fabricated Co-Ni-P nanowires are comprehensively investigated using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The as-obtained Co-Ni-P nanowires are porous and composed of polycrystalline solid solution, and Co, Ni and P are uniformly distributed over nanowires. Moreover, these nanowires are firmly adhered to the nickel foam with excellent structural robustness, forming an integrated electrode. The self-supported integrated electrode exhibits outstanding catalytic activity towards the hydrogen evolution reaction (HER), which can deliver current densities of −10, −20 and −100mAcm−2 at small overpotentials of 68, 94 and 134mV, respectively. Furthermore, it is able to sustain continuous galvanostatic electrolysis at −10mAcm−2 for 40h without obvious degradation, showing good long-term stability. The excellent electrocatalytic performance can be attributed, on the one hand, to the intrinsically high catalytic activity of Co-Ni-P ternary nanowires; on the other hand, to the unique porous nanowire morphology and monolithic electrode structure that not only offer appreciable electrocatalytically active sites, but also provide efficient conductive paths and facilitate mass transport of electrolyte and release of the generated gas bubbles.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Photoelectrochemical and structural properties of TiO2 nanotubes and
           nanorods grown on FTO substrate: Comparative study between electrochemical
           anodization and hydrothermal method used for the nanostructures
           fabrication
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Hana Kmentova, Stepan Kment, Lingyun Wang, Sarka Pausova, Tereza Vaclavu, Radomir Kuzel, Hyungkyu Han, Zdenek Hubicka, Martin Zlamal, Jiri Olejnicek, Martin Cada, Josef Krysa, Radek Zboril
      Titanium dioxide in the form of one-dimensional (1D) nanostructure arrays represent widely studied morphological arrangement for light harvesting and charge transfer applications such as photocatalysis and photoelectrochemistry (PEC). Here we report a comparative structural and PEC study of variously grown 1D TiO2 nanostructures including i) nanorod arrays prepared by a hydrothermal method (TNR), ii) nanotube arrays fabricated by a two-step hydrothermal method using a ZnO nanorod array film as a template (THNT) and finally iii) nanotubes grown by self-organized electrochemical anodization of Ti films deposited on the FTO substrate (TNT). These nanostructures are assumed to be utilized as photoanodes in PEC water splitting devices. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), TEM images and UV–vis absorption spectra were used to characterize TiO2 nanostructures. The SEM and TEM morphology images revealed that the main difference among the nanostructures grown on the FTO are the shape and diameter of the individual nanotubes/nanorods and also the array’s density in the range of TNR>THNT>TNT and the degree of organization in the range of TNT>TNR>THNT. The obtained photocurrents at 0V vs. Ag/AgCl increased in the order of THNT (110μAcm−2)<TNT (185μAcm−2)<TNR (630μAcm−2). Extended electron lifetime and light absorption shifted to the longer wavelengths were attributed to the enhanced PEC performance of TNR.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Transparent α-Fe2O3/TiO2 nanotubular photoanodes
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Martin Zlámal, Šárka Paušová, Štěpán Kment, Zdeněk Hubička, Josef Krýsa
      This paper describes the formation and characterization of transparent mixed α-Fe2O3/TiO2 nanotubular layers. Mixed metal oxide nanostructured layers were prepared by two steps. At first, Fe-Ti alloy layer was prepared by a high-powered impulse magnetron sputtering (HiPIMS) deposition on fluorine doped tin oxide (FTO) glass substrate and then electrochemically oxidized in fluoride containing electrolyte. Prepared alloy layers and anodized layers were characterized by SEM/EDS, μXRD, UV–vis spectroscopy. Anodized layers consist of hematite nanotubes with the length around 1400nm and expansion factor close to 2.5. Titanium is present as amorphous TiO2. Photoelectrochemical properties of transparent mixed α-Fe2O3/TiO2 layer in aqueous electrolyte were evaluated. Presence of Ti in the Fe-Ti alloy results in a significant increase in photoresponse.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Transparent titania-zirconia-silica thin films for self-cleaning and
           photocatalytic applications
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Nives Vodišek, Kandalam Ramanujachary, Vlasta Brezová, Urška Lavrenčič Štangar
      Highly transparent thin films of TiO2-ZrO2-SiO2 composites on glass were prepared by sol-gel process, wherein different amounts of zirconia precursor were mixed with titania precursor solution (0–20mol% Zr with regard to Ti). For better adhesion of the films on glass supports, a silica binder was added to the mixture of alkoxides (27mol% Si vs. Ti). The prepared samples were characterized by various techniques to obtain information on their structural, optical and surface properties. The presence of anatase titania polymorph as the only crystalline phase was detected. Unexpectedly, the higher loading of Zr promoted the growth of anatase particles with progressive spherical shape and concomitant decrease of specific surface area, which adversely influenced the photocatalytic activity. Decrease of the photodegradation activity with increasing amount of Zr was evidenced by contact angle measurements of a fatty deposit, spectrofluorometrically using terephthalic acid probe and by EPR spectroscopy monitoring indirectly the non-persistent radicals generation. On the other hand, the higher content of Zr improved the mechanical stability of resulting thin films. An optimal Zr content around 10mol% appears to be a good compromise between photocatalytic activity and mechanical robustness of the films.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Aqueous ammonia abatement on Pt- and Ru-modified TiO2: Selectivity effects
           of the metal nanoparticles deposition method
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Maria Vittoria Dozzi, Sabrina Brocato, Gianluigi Marra, Gabriella Tozzola, Laura Meda, Elena Selli
      A series of TiO2–based photocatalysts obtained by deposition of Pt nanoparticles (NPs) has been tested in the photocatalytic decomposition of aqueous ammonia under UVA irradiation. Two main deposition routes were employed, i.e. (i) the deposition of surfactant-stabilized preformed metal NPs and (ii) a modified version of the well-known deposition-precipitation technique, employing urea as precipitating agent. The effects that the deposition route and the amount of deposited metal have on both ammonia conversion (X NH3 ) and selectivity (S Y) towards the different N-containing products (Y=N2, NO2 −, NO3 −) have been investigated systematically, in relation to the morphological distribution of NPs on TiO2, as evidenced by HR-TEM analysis. The combination of Pt (0.8wt.%) with a relatively low amount of Ru NPs (0.1wt.%) as co-catalysts, both deposited on TiO2 under optimized conditions, results in an exceptional stabilization of nitrite ions (S NO2 − ∼70%), from which N2, the most desired ammonia oxidation product, might subsequently be obtained catalytically.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Correlations between photocatalytic activity and chemical structure of
           Cu-modified TiO2–SiO2 nanoparticle composites
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): T. Čižmar, U. Lavrenčič Štangar, I. Arčon
      Copper-modified TiO2–SiO2 photocatalysts were prepared by sol–gel method based on organic copper, silicon and titanium precursors. Copper concentration varied from 0.1 to 3.0mol%. A widely applied model reaction of photocatalytic oxidation of terephtalic acid (TPA) in water solution was used in order to evaluate the catalytic activities of elaborated samples. The crystal structures of the titania components of all tested titania–silica species were studied using XRD analysis. The influence of Cu2+ cation incorporation on the crystal structure of titania, as well as the chemical states and the neighbouring structures of copper cations, have been examined by means of Cu K-edge EXAFS and XANES analysis. The experimental data show that there is a ten times increase in photocatalytic activity when TiO2–SiO2 matrix is modified with 0.1mol% of Cu. It can be supposed that an enhancement of photocatalytic activity of low-concentrated copper-modified titania–silica nanocomposites is probably due to a close attachment of Cu2+ cations to the surfaces of photocatalytically active TiO2 nanoparticles. In this case, Cu2+ cations may possibly act as free electron traps reducing the intensity of recombination between opposite free charge carriers (electrons, holes) available at the photocatalyst’s surface.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Assessing the photoelectrochemical properties of C, N, F codoped TiO2
           nanotubes of different lengths
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Athanasios Chatzitakis, Mathieu Grandcolas, Kaiqi Xu, Sen Mei, Juan Yang, Ingvild Julie Thue Jensen, Christian Simon, Truls Norby
      The aim of this work has been the photoelectrochemical (PEC) study of nanostructured photoanodes based on TiO2. Highly ordered and well adhered TiO2 nanotubes (TNTs) of different lengths (∼2–20μm) were prepared in a two-step process in ethylene glycol solutions containing fluorides, and detailed XPS analysis showed that they have become co-doped with C, N and F. PEC measurements revealed that increasing surface area is not followed by increase in the photoconversion efficiency, but rather that an optimal balance between electroactive surface area (ESA) and charge carrier concentration exists. TNTs of around 10μm show the optimum incident photon-to-current efficiency (IPCE) of ∼33% and an overall photoconversion efficiency of ∼6.3% under UV illumination of 4mWcm−2 light intensity. Finally, Mott-Schottky analysis revealed significant frequency dispersion of the estimated space charge layer capacitance, which renders the accurate estimation of the flatband position and charge carrier concentration unreliable. On the other hand, more realistic charge carrier concentrations can be obtained by normalizing the capacitance per ESA.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Photocatalytic decolorization of azo dyes on TiO2: Prediction of mechanism
           via conceptual DFT
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Nazli Turkten, Zekiye Cinar
      The aim of this study is to develop a shortcut method to predict the intermediates and the mechanism of decolorization reactions of azo dyes. To this purpose, Reactive Red 195 (RR195) was chosen as the representative member of azo dyes and photocatalytic decolorization reaction of RR195 in the presence of TiO2 under UV-A light irradiation was investigated. TiO2 was synthesized by an acid-catalyzed sol-gel method from an alkoxide precursor and characterized by XRD, XPS, ESEM-EDX and BET measurements. The decolorization reaction was monitored by UV–vis, FTIR, GC–MS and ESEM-EDX techniques. Conceptual Density Functional Theory was applied to the degradation reaction of the target molecule and reactivity descriptors were calculated by means of DFT/B3LYP/6-31G* level of theory. Eventually, the reactive sites of the molecule for OH radical attack were determined and the reaction mechanism was predicted by combining the results of the DFT calculations with the experimental FTIR and GC–MS analyses. The predicted mechanism was confirmed by comparison with the experimental results on simple structures reported in the literature. The results of the study suggest that TiO2/UV photocatalysis may be used as a method for treatment of diluted wastewaters in textile industries, adsorption on TiO2 surface occurs through sulfo and carbonyl groups of the dye molecule, while decolorization by the breaking of the NN double bond of the chromophore group.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Photocatalytic activity of TiO2-WO3 mixed oxides in formic acid oxidation
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Francesca Riboni, Maria Vittoria Dozzi, Maria Cristina Paganini, Elio Giamello, Elena Selli
      TiO2 and Ti-W mixed oxide photocatalysts, with W/Ti molar ratios in the 0–5% range, were prepared through a simple sol-gel method, followed by annealing at 500 or 700°C, and their photoactivity was tested in the photo-oxidation of formic acid in the aqueous phase under ambient aerobic conditions. XRPD analysis evidenced that in the presence of tungsten the anatase phase was stable even after calcination at 700°C, with a progressively larger surface area and smaller particle dimensions with increasing tungsten content. Tungsten can both enter the titania lattice, as demonstrated by HAADF-STEM analysis, and also segregate as amorphous WO3 on the photocatalysts surface, as suggested by XPS analysis. The best performing Ti/W oxide photocatalyst is that containing 1.0mol% W/Ti, mainly due to the tungsten-induced stabilization effect of the anatase phase, whereas electron transfer from TiO2 to WO3, though compatible with the here performed EPR measurements, appears to have no beneficial effect in the investigated reaction, likely due to the low energy level of the conduction band of WO3, from which electrons cannot efficiently transfer to adsorbed dioxygen.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Impact of the annealing temperature on Pt/g-C3N4 structure, activity and
           selectivity between photodegradation and water splitting
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Marine Caux, Federica Fina, John T.S. Irvine, Hicham Idriss, Russell Howe
      This work presents a systematic study of the effect of fabrication temperature (450 to 650°C) on the structure and electronic properties of g-C3N4 prepared from melamine. The work is conducted by X-ray diffraction, elemental analysis, BET nitrogen adsorption, UV–vis absorption, and electron paramagnetic resonance (EPR). The photocatalytic activity is tested for hydrogen production in the presence of oxalic acid (OA) as well as triethanolamine (TEOA). A considerable change in the morphology is observed with increasing the synthesis temperature resulting in an increase of the surface area, likely due to thermal etching. The decrease of charge carriers’ concentration, per unit surface area, with increasing annealing temperature may be due to the decrease of the conjugation of the polymer. Probing the activity of in situ reduced Pt/g-C3N4 for hydrogen evolution reinforced this conclusion, the rate of hydrogen evolution per unit area for OA as well as TEOA decreased with increasing annealing temperature. An interesting finding is the correlation between CO2:H2 ratio and the increase in the band gap of g-C3N4 prepared at different temperatures when using oxalic acid as an electron donor. This suggests that water oxidation becomes easier with increasing band gap energy, probably due to a lowering of the valence band edge.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Graphene oxide-TiO2 and reduced graphene oxide-TiO2 nanocomposites:
           Insight in charge-carrier lifetime measurements
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Ewelina Kusiak-Nejman, Agnieszka Wanag, Łukasz Kowalczyk, Joanna Kapica-Kozar, Christophe Colbeau-Justin, María G. Mendez Medrano, Antoni W. Morawski
      A hybrid nanocomposites containing nanocrystalline TiO2 and graphene related materials (graphene oxide and reduced graphene oxide) were successfully prepared elevated pressure using hydrothermal method. The structural and textural properties as well as the presence of different carbonaceous structures on the surface of obtained nanocomposites have been characterized by means of XRD, FTIR/DRS and Raman spectroscopy. FTIR/DRS analysis allowed to find characteristic peaks of graphene oxide: epoxy stretching at 1229cm−1 and alkoxy stretching vibration at 1059cm−1. In the spectrum of nanocomposites containing rGO, all the bands decreased or even disappear. It can be indicated that GO was successfully reduced to rGO. SEM studies showed difference between graphene oxide (aggregated, crumpled, non-transparent) and reduced graphene oxide (thin and transparent) flakes. The Time Resolved Microwave Conductivity analysis have been utilized to investigate the excess of charge-carrier lifetimes in TiO2-graphene oxide and TiO2-reduced graphene oxide hybrid nanocomposites. It was generally concluded that modification of starting TiO2 with carbonaceous precursors leads to the slight increase of intensity of the TRMC signals, indicating that more electrons are induced in the conduction band of hybrid nanocomposites. It is also worth mentioning that the decay of studied signals of modified powders depends on added carbon precursor, indicating that the type of deposited species may affect the slight or significant suppression of recombination or charge-carriers trapping.
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      PubDate: 2017-04-10T04:09:27Z
       
  • Durability of Cementitious Photocatalytic Building Materials
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Elia Boonen, Anne Beeldens, Inge Dirkx, Veerle Bams
      Photocatalytic building materials have been shown to be a promising remediation technique for air pollutants such as NOx and VOC’s. However, there are still doubts and questions about the durability of the air cleaning characteristic in time. In this respect, a pre-normative research is being undertaken at BRRC as a first step towards evaluation of the life time of these photo-active air purifying products. This is done by combining and adapting existing durability tests for cement-based materials with standardized test methods to determine the photocatalytic activity. First results of this research are presented here, including a state-of-the-art on accelerated ageing testing as well as the validation of applicable ageing procedures in combination with a normalized evaluation test for photocatalytic NOx abatement. Finally, recommendations for future work regarding durability testing on photocatalytic building materials are also given.
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      PubDate: 2017-04-10T04:09:27Z
       
  • TiO2 cement-based materials: Understanding optical properties and
           electronic band structure of complex matrices
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): E. Jimenez-Relinque, I. Llorente, M. Castellote
      Different mortar mixes using TiO2 P25 as photocatalyst have been prepared. The samples were characterized by UV–vis spectroscopy, X-ray photoelectron spectroscopy and Photoluminiscence spectroscopy. Also, determination of hydroxyl radicals and degradation tests of NOx under visible and UV light have been performed. The results obtained have allowed determining the band edges, Urbach energies and valence band tail sizes, directly related to the energy levels present in the TiO2-cement based materials. Therefore, the schema of the electronic structures of the reference TiO2-photocatalyst and the three TiO2-cement based samples have been constructed. The photocatalytic efficiency has been evaluated according to these energy levels, being able to conclude that in some cases, as the mortar with slags, the chemical composition seems to prevail over the effect of the optical parameter and electronic band structure.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286


      PubDate: 2017-03-20T13:51:00Z
       
  • Contents list
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286


      PubDate: 2017-03-20T13:51:00Z
       
  • Progress in the Electrochemical Synthesis of Ammonia
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): V. Kyriakou, I. Garagounis, E. Vasileiou, A. Vourros, M. Stoukides
      Ammonia is one of the most important and widely produced chemicals worldwide with a key role in the growth of human population. Nowadays, the main route for ammonia synthesis is the Haber-Bosch process, developed a century ago. In this process, Fe-based catalysts are usually employed at temperatures between 400 and 500°C and pressures between 130 and 170bar. As opposed to the industrial process, in nature, plants and bacteria have been producing ammonia for millions of years at mild conditions. Atmospheric nitrogen is reduced by solvated protons on the FeMo cofactor of the metalloenzyme nitrogenase. The natural method of nitrogen fixation has motivated several research groups to explore the electrochemical synthesis of ammonia at ambient pressure. Since it was first demonstrated in 1998, the electrochemical synthesis has been studied in a variety of experimental configurations over a wide temperature range (25–800°C). In the present review, the progress of this method in both solid and liquid electrolyte cells is reported. The experimental studies are divided into high (T>500°C), intermediate (500°C>T>100°C) and low (T<100°C) temperatures. The experimental observations are comparatively discussed with theoretical predictions based on DFT calculations. The techno-economic advantages and disadvantages of the electrochemical approach, as well as the requirements to be met in order to enable practical applications are also analyzed.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Role of alkali promoter in ammonia synthesis over ruthenium
           catalysts—Effect on reaction mechanism
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Ken-ichi Aika
      Previous research on ammonia synthesis over ruthenium catalysts is reviewed with a particular emphasis on the action of alkali promoters. The concept of electron donation and the nature of the adsorbed species are examined, and their relationship with electronic and structural factors related to dinitrogen activation is considered. A kinetic analysis is performed and the reaction mechanism involved in ammonia synthesis over ruthenium catalysts is investigated.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Coordination chemistry insights into the role of alkali metal promoters in
           dinitrogen reduction
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Gannon P. Connor, Patrick L. Holland
      The Haber-Bosch process is a major contributor to fixed nitrogen that supports the world's nutritional needs and is one of the largest-scale industrial processes known. It has also served as a testing ground for chemists' understanding of surface chemistry. Thus, it is significant that the most thoroughly developed catalysts for N2 reduction use potassium as an electronic promoter. In this review, we discuss the literature on alkali metal cations as promoters for N2 reduction, in the context of the growing knowledge about cooperative interactions between N2, transition metals, and alkali metals in coordination compounds. Because the structures and properties are easier to characterize in these compounds, they give useful information on alkali metal interactions with N2. Here, we review a variety of interactions, with emphasis on recent work on iron complexes by the authors. Finally, we draw conclusions about the nature of these interactions and areas for future research.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Electrocatalytic ammonia synthesis via a proton conducting oxide cell with
           BaCe0.5Zr0.3Y0.16Zn0.04O3-δ electrolyte membrane
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): S. Klinsrisuk, J.T.S. Irvine
      Ceramic membrane cells of BaCe0.5Zr0.3Y0.16Zn0.04O3-δ (BCZYZ) have been developed for electrocatalytic ammonia synthesis. Unlike the high-pressure Haber-Bosch process, an atmospheric synthesis of ammonia was attempted in this work. The membrane cells were fabricated by tape casting and the electrode materials were applied by ion impregnation. The impregnated electrodes comprised NiO/CeO2 composite anode and iron oxide cathode. The formation of ammonia was studied in the range of 400–500°C. The addition of Pd catalyst into the iron oxide cathode enhanced the ammonia formation rate while the addition of Ru improved only the electrochemical performance. The highest ammonia formation rate of 4×10−9 mols−1 cm−2 was obtained from Pd-modified cell at 450°C. The current efficiency of ammonia formation was in the range of 1–2.5% while that of H2 evolution varied from 0 to 60% depending on applied potentials. The total current efficiency close to 100% was obtained from Pd-modified cell.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Electrochemical synthesis of ammonia from wet nitrogen via a dual-chamber
           reactor using La0.6Sr0.4Co0.2Fe0.8O3−δ-Ce0.8Gd0.18Ca0.02O2−δ
           composite cathode
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Ibrahim A. Amar, Rong Lan, John Humphreys, Shanwen Tao
      A La0.6Sr0.4Co0.2Fe0.8O3−δ-Ce0.8Gd0.18Ca0.02O2−δ composite cathode was used to investigate the electrochemical synthesis of ammonia from wet nitrogen. Wet nitrogen was flown through a dual chamber reactor under atmospheric pressure leading to the successful synthesis of ammonia. Ammonia was synthesised at a rate of 1.5×10−10 mols−1 cm−2 at 400°C when applying a dc voltage of 1.4V, which is the highest reported to date. This rate is twice that of the observed ammonia formation rate (7×10−11 mols−1 cm−2) when Co-free cathode, La0.6Sr0.4FeO3−δ-Ce0.8Gd0.18Ca0.02O2−δ was used as the cathode catalyst. A higher catalytic activity for ammonia synthesis may be obtained when using a catalyst with high oxygen vacancies, with the introduction of oxygen vacancies at the cathode being a good strategy to improve the catalytic activity of ammonia synthesis.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Recent progress towards the electrosynthesis of ammonia from sustainable
           resources
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Michael A. Shipman, Mark D. Symes
      Ammonia (NH3) is a key commodity chemical of vital importance for fertilisers. It is made on an industrial scale via the Haber Bosch process, which requires significant infrastructure to be in place such that ammonia is generally made in large, centralized facilities. If ammonia could be produced under less demanding conditions, then there would be the potential for smaller devices to be used to generate ammonia in a decentralized manner for local consumption. Electrochemistry has been proposed as an enabling technology for this purpose as it is relatively simple to scale electrolytic devices to meet almost any level of demand. Moreover, it is possible to envisage electrosynthetic cells where water could be oxidised to produce protons and electrons at the anode which could then be used to reduce and protonate nitrogen to give ammonia at the cathode. If this nitrogen were sourced from the air, then the only required infrastructure for this process would be supplies of water, air and electricity, the latter of which could be provided by renewables. Hence an electrosynthetic cell for ammonia production could allow NH3 to be generated sustainably in small, low-cost devices requiring only minimal facilities. In this review, we describe recent progress towards such electrosynthetic ammonia production devices, summarizing also some of the seminal literature in the field. Comparison is made between the various different approaches that have been taken, and the key remaining challenges in the electrosynthesis of ammonia are highlighted.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Onset potentials for different reaction mechanisms of nitrogen activation
           to ammonia on transition metal nitride electro-catalysts
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Younes Abghoui, Egill Skúlason
      Recent theoretical calculations with DFT suggest that transition metal nitrides (TMNs) are promising materials to catalyze N2 electroreduction to ammonia at ambient conditions. To realize which mechanism is more favourable, we conduct DFT calculations to explore the catalytic activity of these materials in their most stable structures via conventional associative (AM) and dissociative (DM) mechanisms, and then compare the corresponding results with that of Mars-van Krevelen (MvK) mechanism we recently reported. The dissociation of N2 on the clean surfaces is endothermic on most of these nitrides and the activation barriers large in all cases, which is inhibitive of a DM on these materials. The onset potential predicted for ammonia formation on these TMNs is always less negative via MvK than with AM, except a few cases, where both mechanisms have similar onset potentials. In those cases, the AM is less favourable than MvK since the adsorption of N2 molecule is endothermic. Therefore, the MvK is almost always the favourable mechanism. We used the computational hydrogen electrode method and neglected any proton-electron transfer reaction barriers in this work but including those will be necessary to make a more definitive statement, which is the subject of future work.
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      PubDate: 2017-03-20T13:51:00Z
       
  • Electrochemical synthesis of ammonia via Mars-van Krevelen mechanism on
           the (111) facets of group III–VII transition metal mononitrides
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Younes Abghoui, Egill Skúlason
      Density functional theory (DFT) calculations were carried out on a new class of materials in pursuit of nitrogen activation and electrochemical ammonia formation at ambient conditions. The source of proton provided by the anode could be either water splitting or H2. But we focused only on the cathode reaction here where nitrogen is reduced to ammonia. The Mars-van Krevelen mechanism was studied on the (111) facets of the NaCl-type structure of earlier transition metal mononitrides of Sc, Ti, V, Cr, Mn, Y, Zr, Nb, Mo, Hf, Ta, W, and Re. The catalytic activity was investigated, free energy of all intermediates was calculated along the reaction path and free energy diagrams were constructed to explore the potential-determining steps of the reaction and accordingly estimate onset potential necessary for nitrogen activation on each different metal nitrides. The possibility of catalyst poisoning in electrochemical environment was also scrutinized at the bias needed for running the reaction. In addition, hydrogen production on all these nitride candidates was explicitly considered within our mechanistic model by removing the constraint of proton adsorption occurring only on surface nitrogen atoms and accordingly most of these candidates show capability for suppressing competitive hydrogen production, in contrast to metallic surfaces that almost exclusively evolve hydrogen gas. The likelihood of catalyst decomposition and catalyst regeneration was assessed for the most interesting nitrides. It was found that the only active and stable nitride catalyst that can regenerate itself and activate nitrogen to ammonia is NbN, and others should decompose to their parental metals under operational conditions.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • The inhibitor role of NH3 on its synthesis process at low temperature,
           over Ru catalytic nanoparticles
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Charles Leterme, Camila Fernández, Pierre Eloy, Eric M. Gaigneaux, Patricio Ruiz
      Single catalysts containing 3, 5 and 7wt.% of Ru (Ru3/Al2O3, Ru5/Al2O3 and Ru7/Al2O3) were prepared via impregnation of alumina with RuO2 colloidal suspensions. Two mechanical mixtures, containing Ru3/Al2O3 +Ru5/Al2O3 and Ru3/Al2O3 +Ru7/Al2O3, were also prepared. Catalytic activity was measured during low-temperature ammonia synthesis reaction. Three different tests were performed after reduction pretreatment of the catalysts: 1) Standard test, the catalytic activity of ammonia synthesis; 2) Test under NH3 +He treatment, following ammonia decomposition; 3) Test under NH3 +He+H2 treatment, following ammonia decomposition in presence of hydrogen. Standard tests were additionally used to study the effect of the different treatments (NH3 +He and NH3 +He+H2) on the catalytic activity of ammonia synthesis. Catalysts were characterized by N2 physisorption, XRD and XPS spectroscopy. The size of Ru nanoparticles influences their performance during ammonia synthesis. The important role of the average size and size distribution of Ru nanoparticles in their activity for ammonia synthesis has been confirmed. Catalysts having a broad size distribution of Ru nanoparticles are more active than those having a narrow size distribution of Ru nanoparticles. Ammonia treatment has a negative effect in ammonia synthesis: results suggest that NHx intermediates remaining strongly adsorbed on the surface inhibit the activity of catalysts during ammonia synthesis. The presence of hydrogen during NH3 treatment inhibits ammonia decomposition and induces weaker adsorption of NHx intermediates. The presence of large particles is necessary to reach and maintain a high catalytic activity during ammonia synthesis. Taking into account previous studies, it could be suggested that large Ru nanoparticles activates mobile hydrogen atoms that migrate towards small Ru nanoparticles, promoting NHx hydrogenation. When mixing two catalysts having different mean Ru sizes, there is a significant synergistic effect in the catalytic activity, due to a more effective hydrogenation of NHx intermediates.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Activity of iron pyrite towards low-temperature ammonia production
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Israel Temprano, Tao Liu, Stephen J. Jenkins
      In this work we report the characteristics of iron pyrite toward the production of ammonia at low temperatures under ultra-high vacuum conditions. We review (with additional unpublished details) our previous systematic study of nitrogen and hydrogen adsorption on single-crystal iron pyrite (FeS2) and summarise our earlier findings regarding the possibility of ammonia synthesis on this material. We also present new results concerning the adsorption of nitrogen and hydrogen on two related materials, namely molybdenum-treated iron pyrite surfaces and iron pyrite nanostructures deposited on a gold single-crystal. On the bare iron pyrite samples, ammonia is produced upon hydrogenation of preadsorbed N species at 230K, demonstrating that all hydrogenation steps are possible at low pressures and temperatures. Nitrogen adsorbs molecularly on FeS2{100} at low temperatures, desorbing at 130K, but does not adsorb dissociatively even at pressures up to 1bar. Adsorbed nitrogen species can, however, be obtained through exposure to excited nitrogen species. Hydrogen adsorbs on FeS2{100}, but only in the presence of an incandescent Ta filament. Recombinative desorption of H2 occurs at 225K and is accompanied by desorption of H2S at 260K. On the molybdenum-treated iron-pyrite, no appreciable Nads species were detected under the experimental conditions studied, and the same is true for iron pyrite nanostructures on Au{111}. We also provide further details of our efficient and reproducible method for preparing well-ordered stoichiometrically pure FeS2{100} suitable for surface science studies.
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      PubDate: 2017-03-20T13:51:00Z
       
  • Wustite based iron-cobalt catalyst for ammonia synthesis
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Łukasz Czekajło, Zofia Lendzion-Bieluń
      By way of melting, iron and iron-cobalt wustite based catalysts promoted with oxides of calcium, aluminium, and potassium were obtained. Measurements of the activity in the ammonia synthesis reaction at pressure of 10MPa were conducted. A positive effect of cobalt addition into the wustite structure of the iron catalyst on increasing in the catalyst catalytic activity in the ammonia synthesis reaction, lowering a temperature, at which catalysts achieved the maximum reduction rate, decreasing values of the apparent activation energy of obtained catalysts, and increasing resistance to the overheating process was observed. All the results were compared with the results obtained for the industrial magnetite-based iron catalyst.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • A method of determining nanoparticle size distribution in iron ammonia
           
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Rafał Pelka
      A new method for determination of nanoparticle size distribution, on the basis of measurements of nanomaterial conversion degree as a function of the chemical potential of gas reagent, was presented. The method was applied for determination of nanocrystallite size distribution in a pre-reduced iron catalyst for ammonia synthesis being an example of a nanomaterial. Samples were reduced with hydrogen at 500°C and then nitrided at 300°C in gaseous ammonia-hydrogen mixtures of different nitriding potentials. Conversion degree measurements, viz., measurements of mass changes of the catalyst were performed in a differential reactor equipped with systems that enable thermogravimetric measurements and analysis of gas phase chemical composition. Based on the performed measurements, a relationship binding the conversion degree with size distribution was proposed. The resulting size distribution of nanocrystallites was compared to distributions determined by known techniques based on XRD or on measurements of the nitriding reaction rate. The size distribution determined using the new method has a higher resolution, revealing more details of the sample morphology.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Computational screening of perovskite redox materials for solar
           thermochemical ammonia synthesis from N2 and H2O
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Ronald Michalsky, Aldo Steinfeld
      To circumvent the scaling relations of activation energies and adsorption energies at catalytic surfaces limiting their catalytic activity, perovskites are investigated for a solar-driven production of ammonia (NH3) from N2 and H2O via a two-step redox cycle. The cycle consists of an endothermal reduction of N2 at 1400°C using solar process heat, followed by an exothermal hydrolysis forming NH3 at 400°C. Both steps are carried out at ambient pressure. Electronic structure computations are employed to assess the stability and surface activity of oxygen vacancies and lattice nitrogen at the (001) facet of nitrogen-doped perovskites. The results are compared to the activities of Mo2N(100), Mo2N(111), and Mn2N(0001) reference models. We find producing oxygen vacancies at high temperature that are active in N2 reduction is the energetically limiting reaction step of the redox cycle. The redox energetics can be tuned by the perovskite composition and are most sensitive to the type of transition metal at the B site terminating the surface. Promising perovskites contain Co or Mn at the surface and Co doped with Mo or W in the bulk, such as CaCoO3-terminated La0.5Ca0.5Mo0.5Co0.5O3, SrCoO3-terminated Sr0.5La0.5Co0.5W0.5O3, and CaMnO3-terminated Sr0.5Ca0.5MnO3. Trade-offs in the redox energetics are quantified to guide future experimental work.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
  • Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon
           support and electron donating promoter on activity
    • Abstract: Publication date: 15 May 2017
      Source:Catalysis Today, Volume 286
      Author(s): Laura Torrente-Murciano, Alf K. Hill, Tamsin E. Bell
      This paper sets the new design parameters for the development of low temperature ammonia decomposition catalysts based on readily available cobalt as an alternative to scarce but highly active ruthenium-based catalysts. By using a variety of carbon materials as catalytic supports, we systematically demonstrate that microporous supports capable of stabilising small cobalt crystallites (∼2nm) lead to high catalytic activities compared to bigger nanoparticles. Additionally, the degree of graphitisation of the carbon support has a detrimental effect on the activity of the cobalt (0) active sites, likely due to their potential as an electron donator. Consequently, the addition of electron donating promoters such as cesium substantially decreases the activity of the cobalt catalysts. This relationship deviates from the trends observed for ruthenium-based catalysts with an optimum 3–5nm size where an increase of the graphitisation degree of the support and the addition of electron donating promoters increases the ammonia decomposition activity.
      Graphical abstract image

      PubDate: 2017-03-20T13:51:00Z
       
 
 
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