A Theoretical Study On Carbon Monoxide Poisoning Of Catalysts For Direct Methanol Fuel Cell

Direct methanol fuel cell (DMFC) is an ideal power source due to the high energy density of methanol and convenient fuel management and low system complexity. In the dissertation, carbon monoxide poisoning of the different single-crystal faces of platinum catalysts have been studied. The results provide the precision of Ab initio when it was used to calculate the adsorption of CO on the pure Pt surfaces. Based the precision of Ab initio. carbon monoxide poisoning of the Pt-Ru alloys have been studied.Using the ab initio, we theoretically study the adsorption of CO at the on-top site of the Pt(100) and Pt(111) surfaces in the first part of the dissertation. The binding energies calculated with the Pts cluster models and Pt7 cluster model are 222 kJ/mol and 175 kJ/mol. respectively. These results agree on the recently calorimetric measurements quite well. Our results indicate that Ab initio. which combine small clusters, can be used to simulate the adsorption CO on the pure platinum surface. According to the results, the adsorption CO on Pt(100) surface is more facile.In the second part of the dissertation, we have used the ab initio cluster model approach to study the adsorption of CO on the Pt-Ru alloys surfaces. The calculated equilibrium geometries and vibrational frequencies have been found to be rather in agreement with experimental study. The Pt-C bond length is slightly shorter in the Pt3Ru2CO cluster than in the Pt(1,4)CO cluster, and its adsorption energy is 147 kJ/mol below that for Pt91.4)CO cluster. It accounts that the Pt3Ru2 cluster is not more easily CO "poison". The analysis of the chemisorption bond has been carried out by means of projection operator techniques. These analyses reveal that the bonding interactions are dominated by the π-back-donation although σ-donation plays a significant role. The populations of 5σ and the 2π CO molecular orbitals are about 1.5 and 0.7 electrons expect the Pt3Ru2CO cluster.All these results illustrate the role in which theoretical methods can be used to provide data for combinatorial strategies for discovering and designing new catalysts.