High CO tolerance of Pt/Ru nanocatalyst: Insight from first principles calculations

Density functional theory based calculations of the energetics of adsorption and diffusion of CO on Pt islets and on the Ru(0001) substrate show that the CO has the lowest adsorption energy at the center of the islet and its bonding increases as it moves to the edge of the island and further onto the substrate. Activation energy barriers for CO diffusion from the islet to the Ru surface are found to be lower than 0.3 eV making the process feasible and leading to the conclusion that this hydrogen oxidation catalyst is CO tolerant because of the spillover of CO from active Pt sites to the Ru substrate. The rate of CO oxidation by OH is found to be substantially enhanced when the former is adsorbed on the edge of Pt islands and the latter on nearby Ru sites.