Influence of Support Effects on CO Oxidation Kinetics on CO-Saturated Graphene-Supported Pt13 Nanoclusters

Abstract

We investigate support effects on the CO oxidation reaction on graphene–supported Pt13 nanoclusters using first-principles density functional theory calculations. As CO adsorption on Pt13 clusters is found to be substantially stronger than O adsorption, we focus on understanding CO oxidation kinetics on CO-saturated Pt nanoclusters. For this high CO coverage regime, the relevant kinetic mechanism is shown to proceed via a CO*-assisted activation of the O2 molecule, resulting in the formation of an O*–O–C*–O transition state that eventually forms a CO2 molecule and a chemisorbed O* species. By sampling this particular reaction pathway at various surface sites on unsupported Pt13 nanoclusters as well as clusters bound at support point defects (vacancies/divacancies) in graphene, we show that strong support–cluster interactions substantially reduce the CO oxidation reaction barrier, on average, by about 0.5 eV. Our results suggest that defect engineering of carbon supports could serve to enhance the catalytic activity of ultrasmall Pt nanoclusters, opening up another dimension for rational design of catalytic materials.