Stability and Kinetics of Subsurface O on the Pt(111) Surface

Operating internal combustion engines under oxygen-rich conditions can significantly enhance fuel efficiency and lower the emissions of hydrocarbons and CO. Platinum based alloys are currently used in automotive catalysis, but there is a need to better understand the formation and reactivity of oxides that form on the transition metal surface. We are currently probing the initial stages of oxidation the Pt(111) surface using computational modeling. In particular, we have used Density functional theory (DFT), an accurate quantum mechanical method, to determine the oxygen coverages when subsurface oxygen becomes favorable on the Pt(111) surface. The formation of subsurface O is expected to be the initial step towards oxidation of the metal surface. We will report on the stability of surface versus subsurface O as a function of surface oxygen coverage. We have also probed the kinetics of subsurface O by determining the mechanism and energy barriers for O diffusion from the surface to the subsurface. Conclusions drawn about the initiation of oxide formation based on our DFT work will be compared to existing ultra-high vacuum experimental results.