Theoretical Study Of Carbon Monoxide Oxidation Reactions On Platinum And Its Alloy Surfaces

It is known to all, Metal Platinum (Pt) and its alloys have been used to oxidate CO for many years for their high reaction activity. The experiments can produce preferable catalysts with high activity, high selectivity and high stability, however, it can not describe the visible and detailed steps. Furthermore, the validity of the mechanism proposed according to experimental and fundamental chemical knowledge should be further confirmed. Theoretical studies on the other hand can provide the supplemental information and instruct to experimental findings through surveying the structures and possible transition states of considered reactions. In this thesis, the slab Pt(111) and alloy Pt3Sn(001) are chosen as the adsorbents models for studying the adsorption and reactions of CO and O_a, and the reactions are theoretically investigated using density functional theory (DFT). The calculations suggest that the hcp site is more active than fcc site for adsorbed O_a in initial structures on Pt(111) surface, and this structure for CO oxidation is in favor of producing CO₂ gas. The reaction barrier Ebarrier when O_a adsorbed in hcp site is 0.77 eV, lower 0.86 eV when O_a adsorbed in fcc site. For alloy Pt₃Sn(001), we optimize the structures of CO and O_a adsorbed on different atom terminations, and calculate the reaction pathways. We find that alloy Mixed atom termination is most active, the reaction barrier is only 0.60 eV, lower than system CO+O_a/Pt(100) and alloy's Pure-Pt termination surfaces. In conclusion, the higher the coadsorption energy of CO+O_a, the more difficult CO oxidation reaction, this result also applys the alloy Pt₃Sn(001) surface. Hirshfeld population for atoms of IS, TS, PS structures is also considered to study the transfer of charges from metal atoms to adsorbates. In oxidation reation, the more charges transfer, the higher activity metal surface has.