Steric Effects in CO Oxidation on Pt(111) by Impinging Oxygen Atoms Lead to an Exclusive Hot Atom Mechanism

摘要

Ab initio molecular dynamics calculations are performed to gain insights into the oxidation of CO adsorbed on Pt(111) by impinging O atoms. The calculation results indicate facile reactivity for forming desorbed CO2 products. Interestingly, this Eley-Rideal reaction is found exclusively via a hot-atom mechanism, in which the impinging O atom captured by the Pt surface attacks the carbon end in the CO adsorbate. This can be attributed to the strong steric effect of this reaction as the cone of acceptance for CO oxidation is located at its C end and facing the surface. As a result, direct collisions of incident O atoms onto the O end of the CO adsorbate are nonreactive. Consistent with experimental observations, the CO2 product was found to desorb near the surface normal, with high internal excitation. In addition, several previously unknown reactive and nonreactive channels have been identified.