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  Subjects -> COMPUTER SCIENCE (Total: 1985 journals)
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COMPUTER SCIENCE (1153 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 872 Journals sorted alphabetically
3D Printing and Additive Manufacturing     Full-text available via subscription   (Followers: 12)
Abakós     Open Access   (Followers: 3)
Academy of Information and Management Sciences Journal     Full-text available via subscription   (Followers: 67)
ACM Computing Surveys     Hybrid Journal   (Followers: 23)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 8)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 13)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 16)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 6)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 11)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 4)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 18)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 12)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 3)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 1)
ACM Transactions on Economics and Computation     Hybrid Journal  
ACM Transactions on Embedded Computing Systems (TECS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Information Systems (TOIS)     Hybrid Journal   (Followers: 20)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 9)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 8)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 11)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 21)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Ad Hoc Networks     Hybrid Journal   (Followers: 11)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26)
Advanced Science Letters     Full-text available via subscription   (Followers: 6)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 8)
Advances in Artificial Intelligence     Open Access   (Followers: 15)
Advances in Artificial Neural Systems     Open Access   (Followers: 4)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 15)
Advances in Computer Science : an International Journal     Open Access   (Followers: 13)
Advances in Computing     Open Access   (Followers: 3)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 52)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
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Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
Advances in Human-Computer Interaction     Open Access   (Followers: 19)
Advances in Materials Sciences     Open Access   (Followers: 16)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access  
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 6)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Air, Soil & Water Research     Open Access   (Followers: 7)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 10)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 3)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 6)
American Journal of Sensor Technology     Open Access   (Followers: 2)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 5)
Analysis in Theory and Applications     Hybrid Journal  
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 8)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 6)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Software Engineering     Hybrid Journal   (Followers: 12)
Annual Reviews in Control     Hybrid Journal   (Followers: 6)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applied and Computational Harmonic Analysis     Full-text available via subscription   (Followers: 2)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 14)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Clinical Informatics     Hybrid Journal   (Followers: 1)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Computer Systems     Open Access   (Followers: 1)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 32)
Applied Medical Informatics     Open Access   (Followers: 9)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 16)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Architectural Theory Review     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 4)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 118)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 5)
Asia Pacific Journal on Computational Engineering     Open Access  
Asia-Pacific Journal of Information Technology and Multimedia     Open Access   (Followers: 1)
Asian Journal of Computer Science and Information Technology     Open Access  
Asian Journal of Control     Hybrid Journal  
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
Australian Educational Computing     Open Access  
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 3)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 9)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Basin Research     Hybrid Journal   (Followers: 3)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Bioinformatics     Hybrid Journal   (Followers: 301)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 45)
British Journal of Educational Technology     Hybrid Journal   (Followers: 121)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 2)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 13)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal  
Cell Communication and Signaling     Open Access   (Followers: 1)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access  
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
China Communications     Full-text available via subscription   (Followers: 7)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
CIN Computers Informatics Nursing     Full-text available via subscription   (Followers: 12)
Circuits and Systems     Open Access   (Followers: 16)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
CLEI Electronic Journal     Open Access  
Clin-Alert     Hybrid Journal   (Followers: 1)
Cluster Computing     Hybrid Journal   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Communication Methods and Measures     Hybrid Journal   (Followers: 11)
Communication Theory     Hybrid Journal   (Followers: 19)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Algebra     Hybrid Journal   (Followers: 3)
Communications in Partial Differential Equations     Hybrid Journal   (Followers: 3)
Communications of the ACM     Full-text available via subscription   (Followers: 53)
Communications of the Association for Information Systems     Open Access   (Followers: 18)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access  
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 9)
Computación y Sistemas     Open Access  
Computation     Open Access  
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 1)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 8)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 13)
Computational Linguistics     Open Access   (Followers: 23)
Computational Management Science     Hybrid Journal  
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 4)
Computational Methods and Function Theory     Hybrid Journal  
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Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Particle Mechanics     Hybrid Journal   (Followers: 1)
Computational Research     Open Access   (Followers: 1)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computational Science and Techniques     Open Access  
Computational Statistics     Hybrid Journal   (Followers: 13)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 28)
Computer     Full-text available via subscription   (Followers: 83)
Computer Aided Surgery     Hybrid Journal   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 7)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 22)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 10)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 1)
Computer Music Journal     Hybrid Journal   (Followers: 14)
Computer Physics Communications     Hybrid Journal   (Followers: 6)
Computer Science - Research and Development     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 17)
Computer Science and Information Technology     Open Access   (Followers: 11)
Computer Science Education     Hybrid Journal   (Followers: 12)
Computer Science Journal     Open Access   (Followers: 20)

        1 2 3 4 5 6 | Last

Journal Cover Chinese Journal of Catalysis
  [SJR: 0.6]   [H-I: 29]   [2 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 1872-2067
   Published by Elsevier Homepage  [3042 journals]
  • 2016 Impact Factor of Chinese Journal of Catalysis is 2.813
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Can Li, Tao Zhang
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Sell a dummy: Adjacent functional group modification strategy for the
           catalytic cleavage of lignin β–O–4 linkage
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Chaofeng Zhang, Feng Wang
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Metal–organic-framework-based catalysts for hydrogenation reactions
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Zhijie Chen, Junying Chen, Yingwei Li
      Metal–organic-framework (MOF)-based materials with novel physicochemical properties have emerged as promising catalysts for various hydrogenation reactions. In addition to metal clusters and multifunctional organic ligands, MOF-based catalysts can incorporate other functional species, and thus provide various active sites for hydrogenation processes. The structural properties of the catalysts play significant roles in enhancing the interactions among the reactants, products, and catalytic sites, which can be rationally designed. Because of the synergistic effects between the active sites and the structural properties, MOF-based catalysts can achieve higher activities and selectivities in hydrogenation reactions than can be obtained using traditional heterogeneous catalysts. This review provides an overview of recent developments in MOF-based catalysts in the hydrogenation of alkenes, alkynes, nitroarenes, cinnamaldehyde, furfural, benzene, and other compounds. Strategies for improving the catalytic performances of MOF-based catalysts are discussed as well as the different active sites and structural properties of the catalysts.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Highly dispersed Ni nanoparticles on 3D-mesoporous KIT-6 for CO
           methanation: Effect of promoter species on catalytic performance
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Hong-Xia Cao, Jun Zhang, Cheng-Long Guo, Jingguang G. Chen, Xiang-Kun Ren
      Promoter-modified Ni-based catalysts were synthesized by an incipient-wetness impregnation method using 3D-mesoporous KIT-6 as a support modified by ethylene glycol, and evaluated for the catalytic production of synthetic natural gas (SNG) from CO methanation. Characterization results suggested that the addition of promoter species could remarkably improve the low-temperature catalytic activity for CO methanation, which was due to a large dispersion of Ni nanoparticles, an enhanced interaction between metal and support as well as a confinement effect of 3D-mesopores. Among all catalysts, Ni-V/KIT-6 possessed the best catalytic performance, which was ascribed to the largest H2 uptake of 177.6 μmol/g and Ni dispersion of 26.5%, an intimate interaction with the support from the formation of Si–O–V linkage and an enhanced confinement effect of 3D-mesopores to effectively prevent the growth of Ni nanoparticles and carbon filaments. In consequence, Ni-V/KIT-6 displayed excellent catalytic performance as well as high catalytic stability, which can be regarded as a promising candidate for CO methanation.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • A DFT+U study of the structures and reactivities of polar CeO2(100)
           surfaces
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Su-Hong Zhong, Guanzhong Lu, Xue-Qing Gong
      Density functional theory calculations corrected by on-site Coulomb interactions were carried out to study the structures of polar CeO2(100) surfaces as well as activities during catalytic CO oxidation. The stabilities of various CeO2(100) termination structures are discussed, and calculated energetics are presented. The most stable CeO2(100) surface was obtained by removing half the outermost full layer of oxygen and the surface stability was found to decrease as the exposed oxygen concentration was increased. Assessing the reaction pathways leading to different final products during CO oxidation over the most stable CeO2(100) surface, we determined that the formation of carbonate species competed with CO2 desorption. However, during CO oxidation on the less stable CeO2(100) surfaces having more exposed oxygen, the CO is evidently able to react with surface oxygen, leading to CO2 formation and desorption. The calculation results and electronic analyses reported herein also indicate that the characteristic Ce 4ƒ orbitals are directly involved in determining the surface stabilities and reactivities.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • High-efficiency oxidative esterification of furfural to methylfuroate with
           a non-precious metal Co-N-C/MgO catalyst
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Na Huo, Hong Ma, Xinhong Wang, Tianlong Wang, Gang Wang, Ting Wang, Leilei Hou, Jin Gao, Jie Xu
      From both fundamental and practical perspectives, the production of chemicals from biomass resources using high-efficiency non-precious metal catalysts is important. However, many processes require addition of stoichiometric or excess quantities of base, which leads to high energy consumption, leaching problems, and side reactions. In this study, we investigated the high-efficiency oxidative esterification of furfural to methylfuroate by molecular oxygen with a Co-N-C/MgO catalyst. The catalyst was prepared by direct pyrolysis of a cobalt(II) phenanthroline complex on MgO at 800 °C under N2 atmosphere. From furfural, 93.0% conversion and 98.5% selectivity toward methylfuroate were achieved under 0.5 MPa O2 with reaction at 100 °C for 12 h without a basic additive. The conversion and selectivity were much higher than those obtained with cobalt catalysts produced by pyrolysis of a cobalt(II) phenanthroline complex on activated carbon or typical basic supports, including NaX, NaY, and CaO. X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and experimental results revealed that the high efficiency of Co-N-C/MgO for production of methylfuroate was closely related to the cobalt-nitrogen-doped carbon species and its catalytic ability in hydrogen abstraction. In contrast, Co-N-C(HCl) that synthesized by removing MgO with HCl from Co-N-C/MgO, as the catalyst produced mainly an acetal as a condensation product, and chloride ions had a negative effect on the oxidative esterification. Although the catalytic performance of the cobalt-nitrogen-doped carbon species was greatly affected by HCl treatment, it could be recovered to a great extent by addition of MgO. Moreover, changes in the oxygen pressure hardly affected the oxidative esterification of furfural with Co-N-C/MgO. This study not only provides an effective approach to prepare methylfuroate, but also for designing high-performance non-precious metal catalysts for the oxidative esterification of biomass-derived compounds.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Catalytic wet oxidation of aniline over Ru catalysts supported on a
           modified TiO2
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Mingguang Song, Yunsong Wang, Yun Guo, Li Wang, Wangcheng Zhan, Yanglong Guo, Guanzhong Lu
      The catalytic wet air oxidation of aniline over Ru catalysts supported on modified TiO2 (TiO2, Ti0.9Ce0.1O2, Ti0.9Zr0.1O2) is investigated. A series of characterization techniques are conducted to determine the relationship between the physico-chemical properties and the catalytic performance. As a result of the good metal dispersion and large number of surface oxygen species, the Ru/Ti0.9Zr0.1O2 catalyst presents the best catalytic activity among the tested samples. The effects of the operating conditions on the reaction are investigated and the optimal reaction conditions are determined. Based on the relationship between the by-products concentration and the reaction time, the reaction path for the catalytic oxidation of aniline is established. Carbonaceous deposits on the surface of the support are known to be the main reason for catalyst deactivation. The catalysts maintain a constant activity even after three consecutive cycles.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Ni/Al2O3 catalysts derived from spinel NiAl2O4 for low-temperature
           hydrogenation of maleic anhydride to succinic anhydride
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Jie Li, Yuanhang Ren, Bin Yue, Heyong He
      Ni/Al2O3 catalysts were derived from spinel NiAl2O4 with different Ni content ((2.5, 5 and 7.5) wt%). The catalysts were obtained by H2 reduction and were investigated for the low-temperature hydrogenation of maleic anhydride (MA) to produce succinic anhydride (SA). The characterization results showed that Ni0 active sites were mainly derived during the H2 reduction from spinel NiAl2O4. Among the catalysts studied, employing the optimum preparation and reaction conditions with Ni(5%)/Al2O3 yielded the highest catalytic performance. A near-100% conversion of MA and ∼90% selectivity to SA were achieved at 120 °C and 0.5 MPa of H2 with a weighted hourly space velocity (MA) of 2 h−1.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Enhanced plasmonic photocatalysis by SiO2@Bi microspheres with
           hot-electron transportation channels via Bi–O–Si linkages
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Zilin Ni, Wendong Zhang, Guangming Jiang, Xiaoping Wang, Zhenzhen Lu, Yanjuan Sun, Xinwei Li, Yuxin Zhang, Fan Dong
      The semimetal Bi has received increasing interest as an alternative to noble metals for use in plasmonic photocatalysis. To enhance the photocatalytic efficiency of metallic Bi, Bi microspheres modified by SiO2 nanoparticles were fabricated by a facile method. Bi–O–Si bonds were formed between Bi and SiO2, and acted as a transportation channel for hot electrons. The SiO2@Bi microspheres exhibited an enhanced plasmon-mediated photocatalytic activity for the removal of NO in air under 280 nm light irradiation, as a result of the enlarged specific surface areas and the promotion of electron transfer via the Bi–O–Si bonds. The reaction mechanism of photocatalytic oxidation of NO by SiO2@Bi was revealed with electron spin resonance and in situ diffuse reflectance infrared Fourier transform spectroscopy experiments, and involved the chain reaction NO → NO2 → NO3 − with •OH and •O2 − radicals as the main reactive species. The present work could provide new insights into the in-depth mechanistic understanding of Bi plasmonic photocatalysis and the design of high–performance Bi-based photocatalysts.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Strong visible absorption and excellent photocatalytic performance of
           brown TiO2 nanoparticles synthesized using one-step low-temperature
           process
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Ting Wang, Wanwen Li, Dandan Xu, Xuanmin Wu, Liwei Cao, Jianxin Meng
      We report a facile and modified sol-gel approach to synthesize brown TiO2 nanoparticles at low temperature (100–600 °C). The TiO2 nanoparticles dried at 180 °C (TiO2-180°C) possessed a small particle size (5.0 nm), large specific surface area (213.45 m2/g), and efficient response to broadband light over the entire ultraviolet-visible spectrum with a narrow band gap of 1.84 eV. In addition, TiO2-180°C exhibited the optimal reaction rate constant for the degradation of methylene blue (0.08287 mg/(L·min)), which is six times higher than that of the mixed rutile/anatase phase TiO2 photocatalytic standard P25 (0.01342 mg/(L·min)). Furthermore, cycling photodegradation experiments confirmed the stability and reusability of this catalyst. The unique physicochemical properties resulting from the low-temperature preparation of TiO2-180°C, including its broadband visible absorption associated with a high concentration of oxygen vacancies, large surface area, and enriched surface –OH/H2O may be responsible for this excellent photocatalytic performance. The use of as-prepared TiO2-180°C for practical applications is expected after further optimization.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Fabrication of a highly dispersed Pdcore@Ptshell electrocatalyst for the
           oxygen reduction reaction
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Longsheng Cao, Shangfeng Jiang, Geng Zhang, Xuejun Tang, Xiaoping Qin, Zhigang Shao, Baolian Yi
      Core-shell nanostructures have been widely investigated to improve the electrocatalytic performance of platinum. However, organic precursors, surfactants or high temperature are usually necessary during the preparation procedure. Unfortunately, these requirements limit the application of these methods on a large scale. Herein, a Pdcore@Ptshell nanostructure was fabricated through the reduction of K2PtCl4 by dissociated hydrogen at room temperature without the assistance of either a surfactant or a high-boiling point solvent. The shell thickness of this nanostructure was successfully controlled by varying the amount of K2PtCl4; core-shell nanoparticles with a shell thickness of 0.45, 0.75 and 0.90 nm were obtained, as determined by TEM. The remarkable crystallinity and epitaxial growth of the Pdcore@Ptshell nanostructure were revealed by HRTEM and EDS. According to ICP and XPS, surface segregation of Pt was established. The impressive ORR performance was attributed to the weak adsorption strength of the OHads species, which resulted from the electron transfer impact between the Pdcore and Ptshell. The facile and clean preparation method can be used to prepare other core-shell nanostructures under a mild atmosphere.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Synthesis of zeolite Beta containing ultra-small CoO particles for
           ethylbenzene oxidation
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Guanqun Zhang, Donge Wang, Pei Feng, Song Shi, Congxin Wang, Anda Zheng, Guang Lü, Zhijian Tian
      Zeolite Beta containing ultra-small CoO particles was synthesized from a one-step hydrothermal process. The synthesis route involves the pre-mixture of hydrofluoric acid with tetraethylammonium hydroxide (in a molar ratio of 1.3–1.5:1) before the addition of a silicon and cobalt source. Investigations by scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, H2-temperature-programmed reduction and transmission electron microscopy confirm the presence of ultra-small CoO particles in the zeolite Beta structure. The ultra-small CoO particles in zeolite Beta present high stability against both oxidation and reduction atmospheres at high temperatures. The catalytic performance of the CoO-containing zeolite Beta catalysts was compared with other Co-containing zeolites by evaluating ethylbenzene oxidation reactivity. The CoO-containing zeolite Beta exhibits high ethylbenzene conversion and high selectivity to acetophenone and 1-phenylethanol. The high activity of this catalyst system can be attributed to the high dispersion of the ultra-small CoO particles in the Beta structure.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Decomposition of a β-O-4 lignin model compound over solid Cs-substituted
           polyoxometalates in anhydrous ethanol: acidity or redox property
           dependence'
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Xuezhong Wu, Wenqian Jiao, Bing-Zheng Li, Yanming Li, Yahong Zhang, Quanrui Wang, Yi Tang
      Production of aromatics from lignin has attracted much attention. Because of the coexistence of C–O and C–C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone (2-PAP), was investigated over several cesium-exchanged polyoxometalate (Cs-POM) catalysts. Decomposition of 2-PAP can follow two different mechanisms: an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox properties of the catalysts. The catalysts of POMs perform the following functions: promoting active hydrogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen liberation and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP (>99%) with excellent selectivities to the desired products (98.6% for phenol and 91.1% for acetophenone) can be achieved.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • The effect of the support on the surface composition of PtCu alloy
           nanocatalysts: In situ XPS and HS-LEIS studies
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Junjie Huang, Yanying Song, Dongdong Ma, Yanping Zheng, Mingshu Chen, Huilin Wan
      Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area TiO2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribution, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 surface and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk composition were plotted and compared for the supported and unsupported materials.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Acidic alumina overcoating on platinum nanoparticles: Close metal–acid
           proximity enhances bifunctionality for glycerol hydrogenolysis
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Hongyi Du, Si Chen, Hengwei Wang, Junling Lu
      Bifunctional catalysts that contain both metal and acidic functions have been widely used in renewable biomass conversions. The bifunctionality closely depends on the distance between the metal and acid sites. However, the metal–acid proximity effect has rarely investigated in biomass conversions. In this work, we precisely deposited a porous Al2O3 overcoat onto a Pt/Al2O3 catalyst using atomic layer deposition to improve the proximity between the Pt metal and the alumina acid sites by increasing the area of the metal–acid interface. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of pyridine chemisorption confirmed that the overall catalyst acidity did not change considerably after applying the alumina overcoat. In the aqueous-phase, hydrogenolysis of glycerol was used to demonstrate that the alumina overcoat significantly improved the activity approximately 2.8-fold, as well as the selectivity to 1,2-propanediol (1,2-PD) at high conversions. DRIFTS measurements of CO chemisorption indicated that the Pt-alumina interface had greater area for alumina coated Pt/Al2O3 than for the uncoated analog. Moreover, we used the hydrogenation of acetol, the key reaction intermediate in glycerol hydrogenolysis, as a control experiment to confirm that the observed activity improvement in the hydrogenolysis of glycerol could be attributed to the enhancement of the dehydration reaction step, which requires acidic function. In brief, our work provides solid evidence that close metal–acid proximity enhances bifunctionality, thus improving the catalytic activity.
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      PubDate: 2017-07-09T09:13:53Z
       
  • Efficient synthesis of pyrano[2,3-d]pyrimidinone and
           pyrido[2,3-d]pyrimidine derivatives in presence of novel basic ionic
           liquid catalyst
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Omid Goli Jolodar, Farhad Shirini, Mohadeseh Seddighi
      A basic ionic liquid, namely 1,1′-(butane-1,4-diyl)bis(1,4-diazabicyclo [2.2.2]octan-1-ium) hydroxide, was prepared and characterized using Fourier-transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and pH measurements. The ionic liquid was used for efficient promotion of the synthesis of pyrano[2,3-d]pyrimidinone and pyrido[2,3-d]pyrimidine derivatives at room temperature under grinding conditions. A simple procedure, short reaction time, high yields, non-column chromatographic separation, commercial availability of the starting materials, and recyclability of the catalyst are attractive features of this process.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • N-doped ordered mesoporous carbon as a multifunctional support of
           ultrafine Pt nanoparticles for hydrogenation of nitroarenes
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Jifen Liang, Xiaoming Zhang, Lingyan Jing, Hengquan Yang
      Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported catalysts. Here, a N-doped ordered mesoporous carbon with a high N content (9.58 wt%), high surface area (417 m2/g), and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles (NPs). The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs (about 1.0 ± 0.5 nm) to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger (4.4 ± 1.7 nm) and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity (conversion 100%) and selectivity (>99%) in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst (conversion 89% and selectivity 90%). This outstanding catalytic performance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction activity and selectivity.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Comparative studies of leached Pt-Fe and Pt-Co catalysts for CO oxidation
           reactions
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Hong Xu, Ke Ni, Xiaokun Li, Sheng Zhu, Guohong Fan
      Leached Pt-Fe and Pt-Co catalysts were prepared by acid leaching the reduced catalysts in acid solution. Oxidation treatments of leached catalysts produced the structure of metal oxides decorating the surface of nanoparticles. The fully oxidized Fe2O3 and Co3O4 species on Pt nanoparticle surfaces result in the low performance of the CO complete oxidation (COOX) reaction. In contrast, unsaturated FeO and CoO surface species can be formed during exposure to the CO preferential oxidation (CO-PROX) reaction with an excess of H2, leading to a high O2 activation ability and enhancing the CO-PROX activity. The FeO x surface structures can be transformed between these two states by varying the reactive gas environments, exhibiting oscillating activity in these two reactions. Conversely, the CoO surface structure formed in the H2-rich atmosphere is stable when exposed to the COOX reaction and exhibits similar activity in these two reactions. It is hoped that this work may assist in understanding the important role of surface oxides in real reactions.
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      PubDate: 2017-07-09T09:13:53Z
       
  • Promotional effect of spherical alumina loading with manganese-based
           bimetallic oxides on nitric-oxide deep oxidation by ozone
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Fawei Lin, Zhihua Wang, Jiaming Shao, Dingkun Yuan, Yong He, Yanqun Zhu, Kefa Cen
      Nitric oxide (NO) deep oxidation to dinitrogen pentoxide (N2O5) by ozone together with wet scrubbing has become a promising technology for nitrogen-oxide (NO x ) removal in industrial boilers. Catalysts were introduced to enhance the N2O5 formation rate with less ozone injection and leakage. A series of monometallic catalysts (manganese, cobalt, cerium, iron, copper, and chromium) as prepared by the sol-gel method were tested. The manganese oxides achieved an almost 80% conversion efficiency at an ozone (O3)/NO molar ratio of 2.0 in 0.12 s. The crystalline structure and porous parameters were determined. The thermodynamic reaction threshold of NO conversion to N2O5 is oxidation with an O3/NO molar ratio of 1.5. Spherical alumina was selected as the support to achieve the threshold, which was believed to improve the catalytic activity by increasing the surface area and the gas-solid contact time. Based on the manganese oxides, cerium, iron, chromium, copper, and cobalt were introduced as promoters. Cerium and iron improved the deep-oxidation efficiency compared with manganese/spherical alumina, with less than 50 mg/m3 of outlet NO + nitrogen oxide, and less than 25 mg/m3 of residual ozone at an O3/NO molar ratio of 1.5. The other three metal oxides inhibited catalytic activity. X-ray diffraction, nitrogen adsorption, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy results indicate that the catalytic activity is affected by the synergistic action of NO x oxidation and ozone decomposition.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Co3O4 nanoparticles assembled on polypyrrole/graphene oxide for
           electrochemical reduction of oxygen in alkaline media
    • Abstract: Publication date: July 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 7
      Author(s): Suzhen Ren, Yanan Guo, Shaobo Ma, Qing Mao, Dandan Wu, Ying Yang, Hongyu Jing, Xuedan Song, Ce Hao
      The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co3O4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst (Co3O4/Ppy/GO) as an efficient catalyst for the oxygen reduction reaction (ORR) in alkaline media. The catalyst was prepared via the hydrothermal reaction of Co2+ ions with Ppy-modified GO. The GO, Ppy/GO, and Co3O4/Ppy/GO were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of Ppy into GO nanosheets resulted in the formation of a nitrogen-modified GO porous structure, which acted as an efficient electron-transport network for the ORR. With further anchoring of Co3O4 on Ppy/GO, the as-prepared Co3O4/Ppy/GO exhibited excellent ORR activity and followed a four-electron route mechanism for the ORR in alkaline solution. An onset potential of −0.10 V vs. a saturated calomel electrode and a diffusion limiting current density of 2.30 mA/cm2 were achieved for the Co3O4/Ppy/GO catalyst heated at 800 °C; these values are comparable to those for noble-metal-based Pt/C catalysts. Our work demonstrates that Co3O4/Ppy/GO is highly active for the ORR. Notably, the Ppy coupling effects between Co3O4 and GO provide a new route for the preparation of efficient non-precious electrocatalysts with hierarchical porous structures for fuel cell applications.
      Graphical abstract image

      PubDate: 2017-07-09T09:13:53Z
       
  • Preface to Special Issue on Nanoscience and Catalysis
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Zhiyong Tang, Huijun Zhao
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Recent advances in the rational design of electrocatalysts towards the
           oxygen reduction reaction
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Jianfei Kong, Wenlong Cheng
      The quest for low-cost yet efficient non-Pt electrocatalysts for the oxygen reduction reaction (ORR) has become one of the main focuses of research in the field of catalysis, which has implications for the development of the next generation of greener fuel cells. Here, we comprehensively describe the ‘big picture’ of recent advances made in the rational design of ORR electrocatalysts, including molecule-based, metal-oxide-based, metal-nanomaterial-based and two-dimensional electrocatalysts. Transition metals can fabricate molecular electrocatalysts with N4-macrocycles such as porphyrin-class compounds and the so-formed M–N–C active centre plays a crucial role in determining the catalytic performances towards the ORR. Group-IV and -V Transition metal oxides represent another class of promising alternative of Pt-based catalysts for the ORR which catalytic activity largely depends on the surface structure and the introduction of surface defects. Recent advances in synthesis of metallic nanoparticles (NPs) allow for precise control over particle sizes and shapes and the crystalline facets exposed to enhance the ORR performance of electrocatalysts. Two-dimensional materials such as functionalized grapheme or MoS2 are emerging as novel electrocatalysts for the ORR. This review covers various aspects towards the design of future ORR electrocatalysts, including the catalytic performance, stability, durability and cost. Some novel electrocatalysts even surpass commercial Pt/C systems, demonstrating their potential to be alternatives in industrial applications. Despite the encouraging progress, challenges, which are also described, remain to be overcome before the real-world application of novel ORR electrocatalysts.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Advanced yolk-shell nanoparticles as nanoreactors for energy conversion
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Meiwen Wang, Yash Boyjoo, Jian Pan, Shaobin Wang, Jian Liu
      Yolk-shell structured nanoparticles are of immense scientific and technological interests because of their unique architecture and myriad of applications. This review summarizes recent progresses in the use of yolk-shell structured nanoparticles as nanoreactors for various chemical reactions. A very brief overview of synthetic strategies is provided with emphasis on recent research progress in the last five years. Catalytic applications of these yolk-shell structured nanoreactors are then discussed by covering photocatalysis, methane reforming and electrochemical conversion. The state of the art research and perspective in future development are also highlighted.
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      PubDate: 2017-06-21T11:54:35Z
       
  • Earth-abundant amorphous catalysts for electrolysis of water
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Wence Xu, Hongxia Wang
      The generation of hydrogen through the electrolysis of water has attracted attention as a promising way to produce and store energy using renewable energy sources. In this process, a catalyst is very important to achieve a high-energy conversion efficiency for the electrolysis of water. A good catalyst for water electrolysis should exhibit high catalytic activity, good stability, low cost and good scalability. Much research has been devoted to developing efficient catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Traditionally, it has been accepted that a material with high crystallinity is important to serve as a good catalyst for HER and/or OER. Recently, catalysts for HER and/or OER in the electrolysis of water splitting based on amorphous materials have received much interest in the scientific community owing to the abundant unsaturated active sites on the amorphous surface, which form catalytic centers for the reaction of the electrolysis of water. We summarize the recent advances of amorphous catalysts for HER, OER and overall water splitting by electrolysis and the related fundamental chemical reactions involved in the electrolysis of water. The current challenges confronting the electrolysis of water and the development of more efficient amorphous catalysts are also discussed.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Cu nanoparticles supported on graphitic carbon nitride as an efficient
           electrocatalyst for oxygen reduction reaction
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Henan Li, Yanan Xu, Hansinee Sitinamaluwa, Kimal Wasalathilake, Dilini Galpaya, Cheng Yan
      High active and cost-effective electrocatalysts for the oxygen reduction reaction (ORR) are essential components of renewable energy technologies, such as fuel cells and metal/air batteries. Herein, we propose that ORR active Cu/graphitic carbon nitride (Cu/g-CN) electrocatalyst can be prepared via a facile hydrothermal reaction in the present of the ionic liquid (IL) bis(1-hexadecyl-3-methylimidazolium) tetrachlorocuprate [(C16mim)2CuCl4] and protonated g-CN. The as-prepared Cu/g-CN showed an impressive ORR catalytic activity that a 99 mV positive shift of the onset potential and 2 times kinetic current density can be clearly observed, comparing with the pure g-CN. In addition, the Cu/g-CN revealed better stability and methanol tolerance than commercial Pt/C (HiSPECTM 3000, 20%). Therefore, the proposed Cu/g-CN, as the inexpensive and efficient ORR electrocatalyst, would be a potential candidate for application in fuel cells.
      Graphical abstract image Highlights Cu supported on graphitic carbon nitride electrocatalyst was synthesized by a facile hydrothermal reaction and shows high catalytic activity for the oxygen reduction reaction in an alkaline electrolyte.

      PubDate: 2017-06-21T11:54:35Z
       
  • Platinum stabilized by defective activated carbon with excellent oxygen
           reduction performance in alkaline media
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Xuecheng Yan, Yi Jia, Longzhou Zhang, Xiangdong Yao
      The exploration of highly active and durable cathodic oxygen reduction reaction (ORR) catalysts with economical production cost is still the bottleneck to realize the large-scale commercialization of fuel cells and metal-air batteries. Given that carbon support is crucial to the electrocatalysts, and Pt is the best-known ORR catalyst so far, in this work, we employed a simple impregnation method for synthesizing a kind of defective activated carbon (D-AC) supported low Pt content electrocatalysts for the ORR. The reduction conditions of the Pt-containing precursor were firstly optimized, and the influence of the Pt loading amount on the ORR was investigated as well. The results show that the obtained D-AC@5.0%Pt sample (contains 5 wt% Pt) has surpassed the commercial Pt/C with 20 wt% Pt for the ORR in an alkaline solution. In the meantime, it is more stable than the commercial Pt/C. The outstanding ORR performance of the D-AC@5.0%Pt confirms that both the unique defects in the D-AC and the introduced Pt particles are indispensable to the ORR. Particularly, the ORR activity of the synthesized catalysts is superior to most of the reported counterparts, but with much easier preparation methods and lower production cost, making them more advantageous in practical fuel cell applications.
      Graphical abstract image Highlights A highly efficient and durable oxygen reduction reaction electrocatalyst was prepared by stabilizing the nano-sized Pt particles with a kind of defective activated carbon.

      PubDate: 2017-06-21T11:54:35Z
       
  • Hydrotalcite-wrapped Co–B alloy with enhanced oxygen evolution
           activity
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Xue Leng, Kuang-Hsu Wu, Bing-Jian Su, Ling-Yun Jang, Ian R. Gentle, Da-Wei Wang
      Water oxidation is one of the most attractive techniques for intermittent renewable energy conversion and storage. The oxygen evolution electrocatalytic performance of an amorphous Co–B alloy and its derivatives were studied. These materials were chemically synthesized by reducing a Co salt with NaBH4. The amorphous Co–B alloy showed good electrocatalytic activity in oxygen evolution but its stability was poor. A hydrotalcite-wrapped Co–B alloy was synthesized by mild oxidation. The electrocatalytic activity of this material in the oxygen evolution reaction was better than that of a commercially available Ir/C catalyst.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Highly dispersed few-layer MoS2 nanosheets on S, N co-doped carbon for
           electrocatalytic H2 production
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Shixin Hua, Dan Qu, Li An, Guangcheng Xi, Ge Chen, Fan Li, Zhijun Zhou, Zaicheng Sun
      Ultrathin small MoS2 nanosheets exhibit a higher electrocatalytic activity for the hydrogen evolution reaction. However, strong interactions between MoS2 layers may result in aggregation; together with the low conductivity of MoS2, this may lower its electrocatalytic activity. In this paper we present a method that we developed to directly produce solid S, N co-doped carbon (SNC) with a graphite structure and multiple surface groups through a hydrothermal route. When Na2MoO4 was added to the reaction, polymolybdate could be anchored into the carbon materials via a chemical interaction that helps polymolybdate disperse uniformly into the SNC. After a high temperature treatment, polymolybdate transformed into MoS2 at 800 °C for 6 h in a N2 atmosphere at a heating rate of 5 °C/min, owing to S2– being released from the SNC during the treatment (denoted as MoS2/SNC-800-6h). The SNC effectively prevents MoS2 from aggregating into large particles, and we successfully prepared highly dispersed MoS2 in the SNC matrix. Electrochemical characterizations indicate that MoS2/SNC-900-12h exhibits a low onset potential of 115 mV and a low overpotential of 237 mV at a current density of 10 mA/cm2. Furthermore, MoS2/SNC-900-12h also had an excellent stability with only ∼2.6% decay at a current density of 10 mA/cm2 after 5000 test cycles.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Fabrication, characterization and electrochemical properties of porous
           
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Qingquan Kong, Wei Feng, Xiaodong Zhu, Jing Zhang, Chenghua Sun
      In the present study, porous bulk palladium samples were prepared by sodium chloride salt powder spacer incorporation and removal combined with dealloying. The obtained porous Pd bulks were characterized by X-ray diffraction, field-emission scanning electron microscopy and N2 adsorption isotherm measurements. The prepared porous Pd bulk samples showed a hierarchical pore structure, a high porosity of ∼88%, a high surface area of ∼54 m2/g, and a compression strength of ∼0.5 MPa. Electrochemical measurements were performed to evaluate the electrocatalytic properties of the porous Pd bulk samples, revealing their effectiveness for ethanol oxidation.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Amorphous ferric oxide as a hole-extraction and transfer layer on
           nanoporous bismuth vanadate photoanode for water oxidation
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Ling Qian, Pengfei Liu, Le Zhang, Chongwu Wang, Shuang Yang, Lirong Zheng, Aiping Chen, Huagui Yang
      An amorphous ferric oxide layer was prepared on a bismuth vanadate photoanode. This resulted in improved charge carrier separation and surface catalytic performance compared with the photoanode without the oxide layer. The photocurrent of the oxide-layer-containing photoanode was 2.52 mA/cm2 at 1.23 V versus the reversible hydrogen electrode, in potassium phosphate buffer (0.5 mol/L, pH = 7.0). The amorphous ferric oxide layer on the photoanode contained low-valence-state iron species (FeII), which enabled efficient hole extraction and transfer.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Preparation of a p-n heterojunction BiFeO3@TiO2 photocatalyst with a
           core–shell structure for visible-light photocatalytic degradation
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Yazi Liu, Shanshan Ding, Jian Xu, Huayang Zhang, Shaogui Yang, Xiaoguang Duan, Hongqi Sun, Shaobin Wang
      Magnetically separable bismuth ferrite (BiFeO3) nanoparticles were fabricated by a citrate self-combustion method and coated with titanium dioxide (TiO2) by hydrolysis of titanium butoxide (Ti(OBu)4) to form BiFeO3@TiO2 core–shell nanocomposites with different mass ratios of TiO2 to BiFeO3. The photocatalytic performance of the catalysts was comprehensively investigated via photocatalytic oxidation of methyl violet (MV) under both ultraviolet and visible-light irradiation. The BiFeO3@TiO2 samples exhibited better photocatalytic performance than either BiFeO3 or TiO2 alone, and a BiFeO3@TiO2 sample with a mass ratio of 1:1 and TiO2 shell thickness of 50–100 nm showed the highest photo-oxidation activity of the catalysts. The enhanced photocatalytic activity was ascribed to the formation of a p-n junction of BiFeO3 and TiO2 with high charge separation efficiency as well as strong light absorption ability. Photoelectrochemical Mott–Schottky (MS) measurements revealed that both the charge carrier transportation and donor density of BiFeO3 were markedly enhanced after introduction of TiO2. The mechanism of MV degradation is mainly attributed to hydroxyl radicals and photogenerated electrons based on energy band theory and the formation of an internal electrostatic field. In addition, the unique core–shell structure of BiFeO3@TiO2 also promotes charge transfer at the BiFeO3/TiO2 interface by increasing the contact area between BiFeO3 and TiO2. Finally, the photocatalytic activity of BiFeO3@TiO2 was further confirmed by degradation of other industrial dyes under visible-light irradiation.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Surface-sulfurized Ag2O nanoparticles with stable full-solar-spectrum
           photocatalytic activity
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Haidong Li, Tinghan Chen, Yao Wang, Jianguo Tang, Yana Wang, Yuanhua Sang, Hong Liu
      Ag2O has attracted much recent attention, because of its high photocatalytic activity in the ultraviolet (UV)-visible region. However, there have been few reports on the near-infrared (NIR) photocatalytic activity of Ag2O. This paper reports the high NIR photocatalytic activity of Ag2O nanoparticles. Ag2O is unsuitable for application in full-solar-spectrum photocatalysis, because it is unstable under UV irradiation. A surface sulfurization process was carried out to address this issue. Specifically, a layer of Ag2S2O7 nanoparticles was grown on the surface of the Ag2O nanoparticles, to improve the stability of the Ag2O photocatalyst and enhance its photocatalytic activity in the UV, visible and NIR regions. The Ag2O/Ag2S2O7 heterostructure is a stable and efficient full-solar-spectrum photocatalyst. It has potential application in the photodegradation of organic pollutants, and more generally in environmental engineering where full utilization of the solar spectrum is required.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Synthesis of TiO2/g-C3N4 nanocomposites with phosphate–oxygen functional
           bridges for improved photocatalytic activity
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Chong Liu, Fazal Raziq, Zhijun Li, Yang Qu, Amir Zada, Liqiang Jing
      One of the most general methods to enhance the separation of photogenerated carriers for g-C3N4 is to construct a suitable heterojunctional composite, according to the principle of matching energy levels. The interface contact in the fabricated nanocomposite greatly influences the charge transfer and separation so as to determine the final photocatalytic activities. However, the role of interface contact is often neglected, and is rarely reported to date. Hence, it is possible to further enhance the photocatalytic activity of g-C3N4-based nanocomposite by improving the interfacial connection. Herein, phosphate–oxygen (P–O) bridged TiO2/g-C3N4 nanocomposites were successfully synthesized using a simple wet chemical method, and the effects of the P–O functional bridges on the photogenerated charge separation and photocatalytic activity for pollutant degradation and CO2 reduction were investigated. The photocatalytic activity of g-C3N4 was greatly improved upon coupling with an appropriate amount of nanocrystalline TiO2, especially with P–O bridged TiO2. Atmosphere-controlled steady-state surface photovoltage spectroscopy and photoluminescence spectroscopy analyses revealed clearly the enhancement of photogenerated charge separation of g-C3N4 upon coupling with the P–O bridged TiO2, resulting from the built P–O bridges between TiO2 and g-C3N4 so as to promote effective transfer of excited electrons from g-C3N4 to TiO2. This enhancement was responsible for the improved photoactivity of the P–O bridged TiO2/g-C3N4 nanocomposite, which exhibited three-time photocatalytic activity enhancement for 2,4-dichlorophenol degradation and CO2 reduction compared with bare g-C3N4. Furthermore, radical-trapping experiments revealed that the OH species formed as hole-modulated direct intermediates dominated the photocatalytic degradation of 2,4-dichlorophenol. This work provides a feasible strategy for the design and synthesis of high-performance g-C3N4-based nanocomposite photocatalysts for pollutant degradation and CO2 reduction.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • La1-xCaxMn1-yAlyO3 perovskites as efficient catalysts for two-step
           thermochemical water splitting in conjunction with exceptional hydrogen
           yields
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Lulu Wang, Mohammad Al-Mamun, Porun Liu, Yun Wang, Hua Gui Yang, Huijun Zhao
      Solar-driven thermochemical water splitting represents one efficient route to the generation of H2 as a clean and renewable fuel. Due to their outstanding catalytic abilities and promising solar fuel production capacities, perovskite-type redox catalysts have attracted significant attention in this regard. In the present study, the perovskite series La1-x Ca x Mn1-y Al y O3 (x, y = 0.2, 0.4, 0.6, or 0.8) was fabricated using a modified Pechini method and comprehensively investigated to determine the applicability of these materials to solar H2 production via two-step thermochemical water splitting. The thermochemical redox behaviors of these perovskites were optimized by doping at either the A (Ca) or B (Al) sites over a broad range of substitution values, from 0.2 to 0.8. Through this doping, a highly efficient perovskite (La0.6Ca0.4Mn0.6Al0.4O3) was developed, which yielded a remarkable H2 production rate of 429 μmol/g during two-step thermochemical H2O splitting, going between 1400 and 1000 °C. Moreover, the performance of the optimized perovskite was found to be eight times higher than that of the benchmark catalyst CeO2 under the same experimental conditions. Furthermore, these perovskites also showed impressive catalytic stability during two-step thermochemical cycling tests. These newly developed La1-x Ca x Mn1-y Al y O3 redox catalysts appear to have great potential for future practical applications in thermochemical solar fuel production.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • Acid-activated and WOx-loaded montmorillonite catalysts and their
           catalytic behaviors in glycerol dehydration
    • Abstract: Publication date: June 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 6
      Author(s): Weihua Yu, Pengpeng Wang, Chunhui Zhou, Hanbin Zhao, Dongshen Tong, Hao Zhang, Huimin Yang, Shengfu Ji, Hao Wang
      The use of H2SO4-, HCl-, H3PO4-, and CH3COOH-activated montmorillonite (Mt) and WO x /H3PO4-activated Mt as catalysts for the gas-phase dehydration of glycerol was investigated. The WO x /H3PO4-activated Mt catalysts were prepared by an impregnation method using H3PO4-activated Mt (Mt-P) as the support. The catalysts were characterized using powder X-ray diffraction, Fourier-transform infrared spectroscopy, N2 adsorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy, temperature-programmed desorption of NH3, and thermogravimetric analysis. The acid activation of Mt and WO x loaded on Mt-P affected the strength and number of acid sites arising from H+ exchange, the leaching of octahedral Al3+ cations from Mt octahedral sheets, and the types of WO x (2.7 ≤ x ≤ 3) species (i.e., isolated WO4/WO6-containing clusters, two-dimensional [WO6] polytungstates, or three-dimensional WO3 crystals). The strong acid sites were weakened, and the weak and medium acid sites were strengthened when the W loading on Mt-P was 12 wt% (12%W/Mt-P). The 12%W/Mt-P catalyst showed the highest catalytic activity. It gave a glycerol conversion of 89.6% and an acrolein selectivity of 81.8% at 320 °C. Coke deposition on the surface of the catalyst led to deactivation.
      Graphical abstract image

      PubDate: 2017-06-21T11:54:35Z
       
  • LSDA+U study on the electronic and anti-ferromagnetic properties of
           Ni-doped CuO and Cu-doped NiO
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Yujie Li, Fan Yang, Ying Yu
      Doping is an effective way to improve the activity of photocatalysts. The effect of doping on the magnetic properties of some photocatalysts that are easily recycled was studied using the local spin density approximation (LSDA)+U method on typical divalent metal oxide semiconductors CuO, NiO, Ni-doped CuO, and Cu-doped NiO. It is found that the influence of Ni doping on the spatial structure of CuO and that of Cu doping on the spatial structure of NiO are negligible because of the similar radii of Ni2+ and Cu2+. The valence band and conduction band for Ni-doped CuO are clearly spin-split, corresponding to a net effective magnetic moment of µ eff = 1.66 µB. This may improve the photocatalytic efficiency and raise the recycle rate of photocatalysts. In the Cu-doped NiO system, the presence of Cu 3d states near to the Fermi level increases the width of the valence band and narrows the band gap with respect to that in pure NiO. Beyond the Cu 3d states, within the band gap, appear two energy levels around the Fermi level, which may effectively separate the electron-hole pair and also lead to enhanced absorption of visible light and infrared light. It can be concluded that the observed changes in the band structure may be helpful for improving the activity of photocatalysts and the doped systems have net magnetic moments, meaning that they are easily recycled and can be reused.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Gold-catalyzed addition reaction between creatinine and isatin: A
           sustainable and green chemistry approach for the diastereoselective
           synthesis of 3-substituted-3-hydroxyisatins
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): K. Parthasarathy, T. Ponpandian, C. Praveen
      The aldolization of various isatins with creatinine under gold catalysis in water has been developed. The reaction is operationally simple as the products can be isolated by simple filtration without requiring tedious solvent extraction and column chromatographic techniques. The generality of this methodology is showcased through the reactions of a wide range of isatin derivatives with creatinine to afford the respective aldol products in excellent yields with complete syn-selectivity. The scope of this chemistry is further extended to a tandem reaction involving isatins, creatinine and malononitrile to afford multicomponent products in excellent yields with complete anti-selectivity. The antioxidant potency of the synthesized compound was assessed by a spectrophotometric method, which revealed that three compounds containing halogen atoms (2c, 2d and 2e) were the most active compared with the standard.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Enantioselective synthesis of quaternary α-aminophosphonates by
           organocatalytic Friedel–Crafts reactions of indoles with cyclic
           α-ketiminophosphonates
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Zhong Yan, Xiang Gao, Yong-Gui Zhou
      An efficient asymmetric Friedel–Crafts reaction has been developed for the synthesis of optically active quaternary α-aminophosphonates with up to 98% ee. The synthesis involves the reaction of cyclic α-ketiminophosphonates with indoles using an H8-BINOL-derived chiral phosphoric acid (CPA) catalyst that bears electron-withdrawing 3,5-ditrifluoromethylphenyl substituents on its 3- and 3′-positions. This Friedel–Crafts reaction of cyclic α-ketiminophosphonates was also successful with pyrrole.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • In-plasma catalytic degradation of toluene over different MnO2 polymorphs
           and study of reaction mechanism
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Ting Wang, Si Chen, Haiqiang Wang, Zhen Liu, Zhongbiao Wu
      α-, β-, γ- and δ-MnO2 catalysts were synthesized by a one-step hydrothermal method, and were utilized for the catalytic oxidation of toluene in a combined plasma-catalytic process. The relationship between catalytic performance and MnO2 crystal structures was investigated. It was noted that the toluene removal efficiency was 32.5% at the specific input energy of 160 J/L when non-thermal plasma was used alone. The α-MnO2 catalyst showed the best activity among the investigated catalysts, yielding a toluene conversion of 78.1% at the specific input energy of 160 J/L. For β-MnO2, γ-MnO2 and δ-MnO2, removal efficiencies of 47.4%, 66.1% and 50.0%, respectively, were achieved. By powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, Brunauer-Emmett-Teller, H2 temperature-programmed reduction and X-ray photoelectron spectroscopy analyses, it was concluded that the tunnel structure, the stability of the crystal in plasma, the Mn–O bond strength of MnO2 and the surface-chemisorbed oxygen species played important roles in the plasma-catalytic degradation of toluene. Additionally, the degradation routes of toluene in non-thermal plasma and in the plasma-catalytic process were also studied. It was concluded that the introduction of MnO2 catalysts enabled O3, O2, electrons and radical species in the gas to be adsorbed on the MnO2 surface via a facile interconversion among the Mn4+, Mn3+ and Mn2+ states. These four species could then be transported to the toluene or intermediate organic by-products, which greatly improved the toluene removal efficiency and decreased the final output of by-products.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Cobalt carbonyl ionic liquids based on the 1,1,3,3-tetra-alkylguanidine
           cation: Novel, highly efficient, and reusable catalysts for the
           carbonylation of epoxides
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Wei Zhang, Feng Han, Jin Tong, Chungu Xia, Jianhua Liu
      A series of novel cobalt carbonyl ionic liquids based on 1,1,3,3-tetra-alkyl-guanidine, such as [1,1-dimethyl-3,3-diethylguanidinium][Co(CO)4] (3a), [1,1-dimethyl-3,3-dibutylguanidinium][Co(CO)4] (3b), [1,1-dimethyl-3,3-tetramethyleneguanidinium][Co(CO)4] (3c), and [1,1-dimethyl-3,3-pentamethyleneguanidinium] [Co(CO)4] (3d), were synthesized in good yields and were also characterized using infrared spectroscopy, ultraviolet-visible spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, 13C NMR spectroscopy, high–resolution mass spectrometry, differential scanning calorimetry, and thermogravimetric analysis. The four compounds exhibited high thermal and chemical stability. In addition, the catalytic performance of these compounds was investigated in the carbonylation of epoxides, with 3a exhibiting the best catalytic activity without the aid of a base as the additive. The catalyst could be reused at least six times without significant decreases of the selectivity or conversion rate. Moreover, the catalyst system exhibited good tolerance with terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, and chloromethyl functional groups.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Effect of Pd doping on CH4 reactivity over Co3O4 catalysts from
           density-functional theory calculations
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Chengcheng Zhao, Yonghui Zhao, Shenggang Li, Yuhan Sun
      Palladium oxide (PdO x ) and cobalt oxide (Co3O4) are efficient catalysts for methane (CH4) combustion, and Pd-doped Co3O4 catalysts have been found to exhibit better catalytic activities, which suggest synergism between the two components. We carried out first-principles calculations at the PBE+U level to investigate the Pd-doping effect on CH4 reactivity over the Co3O4 catalyst. Because of the structural complexity of the Pd-doped Co3O4 catalyst, we built Pd-doped catalyst models using Co3O4(001) slabs with two different terminations and examined CH4 reactivity over the possible Pd–O active sites. A low energy barrier of 0.68 eV was predicted for CH4 dissociation over the more reactive Pd-doped Co3O4(001) surface, which was much lower than the 0.98 and 0.89 eV that was predicted previously over the more reactive pure Co3O4(001) and (011) surfaces, respectively. Using a simple model, we predicted CH4 reaction rates over the pure Co3O4(001) and (011) surfaces, and Co3O4(001) surfaces with different amounts of Pd dopant. Our theoretical results agree well with the available experimental data, which suggests a strong synergy between the Pd dopant and the Co3O4 catalyst, and leads to a significant increase in CH4 reaction rate.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Facile synthesis of S-doped reduced TiO2-x with enhanced visible-light
           photocatalytic performance
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Zhenyu Huang, Zhenggang Gao, Shanmin Gao, Qingyao Wang, Zeyan Wang, Baibiao Huang, Ying Dai
      A different approach to synthesize visible-light-active sulfur (S)-doped reduced titania (S-TiO2-x ) using thiourea dioxide as both the S source and reductant was developed. The structure, morphology, and optical and electronic properties of the as-prepared S-TiO2-x samples were examined by multiple techniques, such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller and photocurrent measurements, and electrochemical impedance spectroscopy. The photocatalytic activity of S-TiO2-x was evaluated by photodegradation of organic Rhodamine B under visible-light irradiation. The degradation rate of Rhodamine B by S-TiO2-x obtained by calcination was about 31, 2.5, and 3.6 times higher than those of pure TiO2, pristine TiO2-x , and S-doped TiO2, respectively. In addition, the as-prepared S-TiO2-x exhibited long-term stable photocatalytic performance in the degradation of Rhodamine B under visible-light illumination. This report reveals a new approach to prepare stable and highly efficient solar light-driven photocatalysts for water purification.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Synergetic photo-epoxidation of propylene with molecular oxygen over
           bimetallic Au–Ag/TS-1 photocatalysts
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Naixu Li, Bin Yang, Ming Liu, Yong Chen, Jiancheng Zhou
      Au–Ag bimetallic nanoparticle-supported microporous titanium silicalite-1 catalysts were prepared via a hydrothermal-immersion method, and their structures were examined. These materials serve as efficient catalysts for the photosynthesis of propylene oxide via the epoxidation of propene. The Au/Ag mass ratio and reaction temperature were demonstrated to have significant effects on the catalytic activity and selectivity of propylene oxide. The optimal formation rate (68.3 μmol/g·h) and selectivity (52.3%) toward propylene oxide were achieved with an Au:Ag mass ratio of 4:1. Notably, the strong synergistic effect between Au and Ag resulted in superior photocatalysis of the bimetallic systems compared with those of the individual systems. A probable reaction mechanism was proposed based on the theoretical and experimental results.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Performance enhancement mechanism of Mn-based catalysts prepared under N2
           for NOx removal: Evidence of the poor crystallization and oxidation of
           MnOx
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Kai Qi, Junlin Xie, De Fang, Fengxiang Li, Feng He
      Among multitudinous metal-oxide catalysts for the selective catalytic reduction of NO x with NH3 (NH3-SCR), Mn-based catalysts have become very popular and developed rapidly in recent years because of its superior low-temperature denitrification activity, mainly originating from multi-valence of Mn. Most studies suggest that the catalytic activity of multi-component oxides is superior to that of single-component catalysts owing to the synergistic effect among the metallic elements in such materials, of which more attentions have been given to Ce as an additive owing to its powerful oxygen storage capacity, redox ability and its ready availability. As the core of SCR technology, the research points in catalyst development at the present stage of all researchers in countries mainly centralize on the optimization of active components, carriers, calcination temperature, calcination time and temperature-raising procedure, giving little thought to the effects of the calcination atmosphere. In the present work, Ce-modified Mn-based catalysts were prepared by a simple impregnation method. The effects of the calcination atmosphere (N2, air or O2) on the performance of the resulting materials during NH3-SCR and its causes of the differences were subsequently investigated and characterized using various analytical methods. Data obtained from X-ray diffraction, thermogravimetry and temperature-programmed reduction with hydrogen show that calcination under N2 reduces both the degree of oxidation and crystallization of the MnO x . Scanning electron microscopy also demonstrates that the use of N2 inhibits the growth of grains and increases the dispersion of the catalysts. In addition, the results of temperature-programmed desorption with ammonia indicate that catalysts calcined under N2 exhibit a greater quantity of acid sites. Finally, X-ray photoelectron spectrometry and activity results demonstrate that MnO x in the lower valence states is more favorable for NH3-SCR reactions. In conclusion, catalysts calcined under N2 show superior performance during NH3-SCR for NO x removal, allowing NO conversions up to 94% at 473 K.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Brønsted-acidic ionic liquids as efficient catalysts for the synthesis of
           polyoxymethylene dialkyl ethers
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Heyuan Song, Meirong Kang, Fuxiang Jin, Guoqin Wang, Zhen Li, Jing Chen
      Acetalation of formaldehyde (HCHO) with dialkyl formal or aliphatic alcohol to prepare polyoxymethylene dialkyl ethers (RO(CH2O) n R, n ≥ 1) catalyzed by Brønsted-acidic ionic liquids has been developed. The correlation between the structure and acidity activity of various ionic liquids was studied. Among the ionic liquids investigated, 1-(4-sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate ([MIMBs]HSO4) exhibited the best catalytic performance in the reaction of diethoxymethane (DEM1) with trioxane. The influences of ionic liquid loading, molar ratio of DEM1 to HCHO, reaction temperature, pressure, time, and reactant source on the catalytic reaction were explored using [MIMBs]HSO4 as the catalyst. Under the optimal conditions of n([MIMBs]HSO4):n(DEM1):n(HCHO) = 1:80:80, 140 °C, and 4 h, the conversion of HCHO and selectivity for DEM2–8 were 92.6% and 95.1%, respectively. The [MIMBs]HSO4 catalyst could be easily separated and reused. A feasible mechanism for the catalytic performance of [MIMBs]HSO4 was proposed.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Quaternary-ammonium-immobilized polystyrenes as efficient and reusable
           heterogeneous catalysts for synthesis of cyclic carbonate: Effects of
           linking chains and pendent hydroxyl group
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Xiaoming Yan, Xuan Ding, Yu Pan, Xiaowei Xu, Ce Hao, Wenji Zheng, Gaohong He
      Spherical polystyrene-supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions of CO2 and epoxides. The effects of the length of the linking chains and a hydroxyl group pendent on the linking chain on the catalytic performance of ionic liquid immobilized catalysts and their mechanisms were studied through experiments and density functional theory calculations. It was found that, compared with a short linking chain, a long chain can make the halogen anion more negative and provide a larger contact area of the catalysts with the reactants, thus enhancing the reaction kinetics. The hydroxyl group can stretch the C–O bonds of the epoxides, promoting the reaction thermodynamics. As a result, for the cycloaddition of propylene oxide, the yield of propylene carbonate is much higher for the catalyst with a long linking chain (yield: 91.4%) compared with the yield for that with a short chain (yield: 70.9%), and is further increased in the presence of pendent hydroxyl groups (yield: 98.5%). The catalyst also shows a high catalytic activity even at mild temperature and good reusability (yield: ≥ 96% for 10 cycles), and the selectivity is always above 99%.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Synthesis of ZSM-5 monoliths with hierarchical porosity through a
           steam-assisted crystallization method using sponges as scaffolds
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Tiejing Hu, Jian Liu, Changyan Cao, Weiguo Song
      Self-supporting ZSM-5 crystals with hierarchical porosity were prepared through a steam-assisted crystallization method using sponges as rigid scaffolds. The synthesized materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, solid-state nuclear magnetic resonance spectroscopy and ammonia temperature-programmed desorption. The ZSM-5 monoliths exhibited high crystallinities, hierarchical porous structures and strong acidities. They showed superior catalytic performance in the liquid-phase esterification reaction between benzyl alcohol and hexanoic acid.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Synthesis of propylene glycol ethers from propylene oxide catalyzed by
           environmentally friendly ionic liquids
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Cong Zhao, Shengxin Chen, Ruirui Zhang, Zihang Li, Ruixia Liu, Baozeng Ren, Suojiang Zhang
      A series of acetate ionic liquids were synthesized using a typical two-step method. The ionic liquids were used as environmentally benign catalysts in the production of propylene glycol ethers from propylene oxide and alcohols under mild conditions. The basic strengths of the ionic liquids were evaluated by determination of their Hammett functions, obtained using ultraviolet-visible spectroscopy, and the relationship between their catalytic activities and basicities was established. The catalytic efficiencies of the ionic liquids were higher than that of the traditional basic catalyst NaOH. This can be attributed to the involvement of a novel reaction mechanism when these ionic liquids are used. A possible electrophilic-nucleophilic dual activation mechanism was proposed and confirmed using electrospray ionization quadrupole time-of-flight mass spectrometry. In addition, the effects of significant reaction parameters such as concentration of catalyst, molar ratio of alcohol to propylene oxide, reaction temperature, and steric hindrance of the alcohol were investigated in detail.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Chiral BINAP-based hierarchical porous polymers as platforms for efficient
           heterogeneous asymmetric catalysis
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Tao Wang, Yuan Lyu, Kai Xiong, Wenlong Wang, Hao Zhang, Zhuangping Zhan, Zheng Jiang, Yunjie Ding
      Two vinyl-functionalized chiral 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) ligands, (S)-4,4′-divinyl-BINAP and (S)-5,5′-divinyl-BINAP, were successfully synthesized. Chiral BINAP-based porous organic polymers (POPs), denoted as 4-BINAP@POPs and 5-BINAP@POPs, were efficiently prepared via the copolymerization of vinyl-functionalized BINAP with divinyl benzene under solvothermal conditions. Thorough characterization using nuclear magnetic resonance spectroscopy, thermogravimetric analysis, extended X-ray absorption fine structure analysis, and high-angle annular dark-field scanning transmission electron microscopy, we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores. Ru was introduced as a catalytic species into the POPs using different synthetic routes. Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous asymmetric hydrogenation of β-keto esters revealed their excellent chiral inducibility as well as high activity and stability. Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
  • Sr-doping effects on La2O3 catalyst for oxidative coupling of methane
    • Abstract: Publication date: May 2017
      Source:Chinese Journal of Catalysis, Volume 38, Issue 5
      Author(s): Linna Cong, Yonghui Zhao, Shenggang Li, Yuhan Sun
      Density-functional theory calculations were carried out to study the strontium (Sr)-doping effect on methane activation over a lanthanum-oxide (La2O3) catalyst for the oxidative coupling of methane (OCM) using the cluster model. Eight Sr-doped La2O3 cluster models were built from pure La2O3 clusters that were used previously to model the La2O3 catalyst. These form two distinct categories, namely, those without a radical character (LaSrO2(OH), La2SrO4, La3SrO5(OH), and La5SrO8(OH)) and those with a radical character (LaSrO3, La2SrO4(OH), La3SrO6, and La5SrO9). The potential-energy surface for CH4 activation to form a CH3 radical at different Sr–O and La–O pair sites on these Sr-doped La2O3 clusters was calculated to study the Sr-doping effect on the OCM catalytic activity. CH4 physisorption and chemisorption energies, and activation barriers, and CH3 desorption energies were predicted. Compared with the pure La2O3 clusters, in general, the Sr-doped La2O3 clusters are thermodynamically and kinetically more reactive with CH4. For the Sr-doped La2O3 clusters without the radical character, the Sr–O pair site is more reactive with CH4 than the La–O pair site, although a direct release of the CH3 radical is also highly endothermic as in the case of the pure La2O3 clusters. In contrast, for the Sr-doped La2O3 clusters with a radical character, the activation of CH4 at the oxygen radical site and the release of the CH3 radical are much easier. Thus, our calculations suggest that the Sr dopant prompts the OCM catalytic activity of the La2O3 catalyst by providing a highly active oxygen-radical site and by strengthening the basicity of the M–O pair site, which leads to lower CH4 activation energies and lower CH3 desorption energies.
      Graphical abstract image

      PubDate: 2017-05-22T08:35:24Z
       
 
 
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