单原子催化剂的制备、表征及催化性能（英文）

发布时间：2018-05-07 15:04

本文选题：单原子催化剂 + 制备方法　；参考：《催化学报》2017年09期

【摘要】：单原子催化剂(SACs)是指金属以单原子形式均匀分散在载体上形成的具有优异催化性能的催化剂.与传统载体型催化剂相比,SACs具有活性高、选择性好及贵金属利用率高等优点,在氧化反应、加氢反应、水煤气变换、光催化制氢以及电化学催化等领域都具有广泛应用,是目前催化领域的研究热点之一.常见的SACs制备方法有共沉淀法、浸渍法、置换反应法、原子层沉积法以及反奥斯瓦尔德熟化法等.实验及理论研究表明,单原子催化剂高的活性和选择性可归因于活性金属原子和载体之间的相互作用及由此引起的电子结构改变.载体是影响单原子催化剂性能的重要因素之一.目前常用的SACs载体有金属氧化物、二维材料和金属纳米团簇等,本文着重综述了这三种负载型SACs的制备、表征、催化性能及催化机理,并概述了SACs未来可能的发展方向和应用.研究表明,共沉淀法、湿浸渍法和反奥斯瓦尔德熟化法等方法可用来制备氧化物负载的SACs.高角环形暗场像-扫描透射电子显微镜(HAADF-STEM)表明金属是以单原子形式均匀分散在载体上,近边X射线吸收精细结构(XANES)结果表明金属原子与载体之间存在着强相互作用.实验和理论研究均表明该类催化剂在CO氧化反应、水煤气转化及乙炔加氢生成乙烯等反应中具有高的催化活性和稳定性.采用化学气相沉积法和原子层沉积法等方法可以将金属原子稳定地负载在具有缺陷活性位点的石墨烯、MXene及六方氮化硼等二维材料上并相应制备出SACs.X射线吸收精细结构谱(EXAFS)和XANES分析表明样品中金属以单原子形式存在,而且金属原子与载体之间也存在着强相互作用,理论计算表明金属原子与二维载体之间的电荷转移是SACs活性高的主要原因.置换反应法和连续还原法是制备溶胶型SACs的有效方法,其中置换反应法可将活性金属原子原位组装在金属模板团簇的顶点位置,连续还原法可将活性原子负载于金属模板团簇的表面.DFT计算表明活性原子和金属模板团簇之间存在电荷转移效应,这是溶胶型SACs具有非常高的催化活性的主要原因.SACs下一步的研究方向可能是:(1)研究开发新型SACs,尽可能提高催化剂中活性金属原子的含量;(2)深入研究SACs的结构、活性以及催化机理之间的关系;(3)尝试将SACs大规模应用于工业催化.
[Abstract]:Monatomic catalyst (SACs) is a kind of catalyst with excellent catalytic performance, which is formed by the uniform dispersion of metal on the support in the form of single atom. Compared with the traditional supported catalysts, SACs have many advantages, such as high activity, good selectivity and high utilization rate of precious metals. They are widely used in the fields of oxidation, hydrogenation, water gas shift, photocatalytic hydrogen production and electrochemical catalysis. It is one of the research hotspots in the field of catalysis. The common preparation methods of SACs are coprecipitation, impregnation, displacement reaction, atomic layer deposition and anti Oswald maturation. Experimental and theoretical studies show that the high activity and selectivity of monatomic catalysts can be attributed to the interaction between active metal atoms and the support and the resulting electronic structure changes. Support is one of the important factors affecting the performance of monatomic catalysts. Metal oxides, two-dimensional materials and metal nanoclusters are commonly used as SACs carriers. In this paper, the preparation, characterization, catalytic performance and catalytic mechanism of the three kinds of supported SACs are reviewed, and the possible development direction and application of SACs in the future are summarized. The results show that coprecipitation, wet impregnation and anti-Oswald aging can be used to prepare oxide supported SACs. The high angle ring dark field image-scanning transmission electron microscopy (SEM) shows that the metal is uniformly dispersed on the carrier in the form of a single atom, and the near edge X-ray absorption fine structure (XANES) shows that there is a strong interaction between the metal atom and the carrier. Both experimental and theoretical studies show that the catalysts have high catalytic activity and stability in CO oxidation, water gas conversion and acetylene hydrogenation to ethylene. By chemical vapor deposition and atomic layer deposition, metal atoms can be stably loaded on two dimensional materials, such as graphene and hexagonal boron nitride with defect active sites, and the fine SACs.X ray absorption can be prepared accordingly. The structure spectrum and XANES analysis showed that the metal in the sample existed in the form of a single atom. There is also a strong interaction between metal atoms and supports. Theoretical calculations show that the charge transfer between metal atoms and two-dimensional carriers is the main reason for the high SACs activity. Displacement reaction and continuous reduction are effective methods for the preparation of sol-like SACs, in which the active metal atoms can be assembled in situ at the top of the metal template cluster. The continuous reduction method can load the active atoms on the surface of the metal template cluster. DFT calculation shows that there is a charge transfer effect between the active atom and the metal template cluster. This is the main reason that sol type SACs has very high catalytic activity. The next research direction of SACs may be: 1) to develop new SACs, to increase the content of active metal atoms in the catalyst as much as possible and to further study the structure of SACs. The relationship between activity and catalytic mechanism is discussed. (3) A large scale application of SACs in industrial catalysis is attempted.
【作者单位】：武汉科技大学耐火材料与冶金国家重点实验室;武汉科技大学化学与化工学院;武汉科技大学冶金工业过程系统科学湖北省重点实验室;
【基金】：supported by the National Natural Science Foundation of China(51472184 and 51472185) the Science and Technology Support Program of Hubei Province(2013BHE003) the Program for Innovative Teams of Outstanding Young and Middle-Aged Researchers in the Higher Education Institutions of Hubei Province(T201602)~~
【分类号】：O643.36

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