First-principles Study On The Mechenism Of Coking Inhibition By The Nickle Based IB-group Metals Catalysis

The global energy crisis and environmental pollution are two major problems that the internationalcommunity has to face in21century. Scientists are trying to find the solution in the following two ways:(1)The development of new energy sources, such as the well known series of new green energies of solarphotovoltaic, wind and geothermal energies;(2) adopting new methods to improve the energy efficiency.At present solid oxide fuel cells (SOFCs) have attracted extensive attention due to their ability to achievehigh energy conversion efficiencies and their inherent fuel flexibility. To promote the applications of it,some related deficiencies still need to be overcome. For example, the nickel catalyst of the anode is proneto be deactivated by coke formation. Therefore, it is urgent to develop new nickel-based alloy catalystswith coke resistance, low cost and high efficiency.In this thesis, the first-principles methods based on the density functional theory are used toinvestigate the stability and catalytic activity of the nickel-based alloy catalyst (111) surface (abbreviated asNi/M (111)), as well as the resistance to carbon deposition on the catalyst surface. The work performed andmain results reached are as follows:(1) Structural stability of the Ni-based IB Group metal SOFC anode catalysts is systematicallyinvestigated. The uniformly doped Ni-based IB Group alloy catalysts are proved to be more stable. Tostudy the coke resistance of the catalysts, the adsorptions of carbon atoms and carbon dimers on differentsurfaces are investigated. Compared with the adsorptions on the monometallic Ni (111) or M(111) surfaces,the ones on the Ni/M (111) are proved to be stronger. And the adsorbed C atoms tend to stay away from theIB Group metal dopant atoms, and adsorb on the hollow sites consist of three Ni atoms (hcpNiand fccNi).Furthermore, the carbon atoms on the Ni/M (111) surface also tend to be adsorbed dispersedly. The stableadsorption sites for carbon atoms are separated from each other by the introduced IB metal atoms on thecatalyst surfaces, the adsorbed carbon atoms are bound to fccNiand hcpNisites. Therefore, the C atomsmigration barriers on the alloy catalyst surfaces are greatly enhanced, which effectively inhibits the carbondimmer or oligomer formation. Thereby, it is an effective way to fundamentally prevent the active sites onthe surface of the SOFC anode catalyst from covered by carbon clusters, which can inhibit the furtherreactions and lead to catalyst poisoning.(2) The structural stability and catalytic activity for the H2O decomposition of SOFC anode Ni/Au alloycatalyst doped in various non-uniform ways are investigated systematically. First, by comparing thestructural stability of the uniform doping alloy Ni/Au catalyst and the non-uniform doping ones, the formeris found to be more stable, which indicates Au atoms tend to be scattered on the surface. By optimizing H,O, OH and H2O adsorption on different surfaces, the stable adsorption sites are found. Finally, thedissociative process of water on different catalysts is studied. It is found that the linearly ordered Au atomscontaining lower Au concentration are excellent in catalytic hydrolysis.