| With the constant improvement of quantum chemistry and the rapid development of computer technology, density functional theory method has become a conventional research method in the fields of physics, chemistry, biology and so on. In this thesis, the catalystic properties of WC(0001) and Pt/WC(0001) surfaces are discussed. This thesis can be divided into two parts. In the first part, adsorption and dissociation of water on the W-and C-terminated WC(0001) surfaces surface have been studied with periodical slab model by PW91approach of GGA within the framework of density functional theory (DFT). For the W-terminated WC(0001) surface it was shown that the preferable adsorption sites are top, hcp, hcp and fcc for H2O, OH, O and H respectively, while for the C-terminated surface all adsorbates preferentially adsorb at the top site. H2O, OH and O bind preferentially on metal surface, while H prefers C termination over W termination due to the formation of stable C-H bond. The C-terminated surface has significantly higher activity toward water dehydrogenation reactions than the W-terminated surface, but H2(g) formation from this surface cannot happen. We also predict that WC(0001) is more active to decompose water than Pt(111), Pd(111) and Ru(0001), which would be very desirable for the fuel cells.In the second part, the Pt/WC(0001) surface is built on the basis of the first part. Subsequently, water decomposition and CO oxidation on the Pt/WC(0001) surface are calculated. Compared to Pt(111), the adsorption energy of H2O on the Pt/WC(0001) surface is larger, while the adsorption energy of CO is smaller, which is consistent the TPD result that the desorption temperature of CO from Pt/WC is lower than from Pt. Compared to Pt(111), the Pt/WC(0001) surface inhibit the decomposition of H2O, while significantly promot the reaction of CO oxidation to CO2. Our results here well explain the reason of the improvement in the good resistance to CO poisoning of Pt/WC catalysts. |
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