Theoretical Study On The Adsorption Of Methanol, Carbon Monoxide And Water Over The Pt (111), Pt-Sn (111)/C Surface

The direct methanol fuel cell (DMFC) is a variant of proton exchange membrane (PEM) fuel cell, which has been widely investigated in recent years because of its low pollution and high performance. Now finding an anode catalyst with low cost, high catalytic activity and better anti-poisoning ability is one of the research emphases of DMFC.The Pt/X binary metal has been proved to have a.high catalytic ability. The density functional theory (DFT) and self-consistent periodic calculation have been used to investigate the methanol, CO and H2O absorption and decomposing paths on Pt(111) and Pt-Sn(111)surface, respectively. The main contents are as follows:1.Dmol3 suit of programs has been used to optimize the geometry structures of the methanol, CO and water at the four types of sites on the Pt(111) surface, and has gotten the stable absorption energies at the different sites.CO and H2O are all the possible products getting from the absorption of methanol over the Pt (111)surface. And the absorption energies of CO and H2O are larger than that of CH3OH,, it indicates that the poisoning effect between CO and H2O tends to happen easily which may weaken the catalytic effect of catalyst. Then the change of the methanol's geometry structure after absorption is analyzed, the electron transfer process is discussed and the figures of density of states and band structures of the clean Pt(111) surface and the Pt(111) surface absorbed with methanol are compared.2.The optimized geometry structures and the stable absorption energies of the methanol, CO and water at the eight types of sites on the Pt-Sn(111) surface has been obtained by the same method. According to the analyses of absorption energies,band structures and density of states, the catalytic effect of Pt/Sn is better than that of pure Pt can be found. In addition, the absorption energies of CO and water on Pt-Sn(111) surface is lower than that of methanol,it indicates that the two component alloy Pt/Sn has certain ability of anti-poisoning of CO and water. So we can conclude that the two component alloy Pt/Sn is a better anode catalyst of the direct methanol fuel cell.The results are in agreement with the experimental data.