Turnover frequencies and rates of CO oxidation on Pt single atomic sites on CeO₂ surfaces: an ab initio based KMC study

Our recent study on singly dispersed Pt single atoms on CeO₂ surfaces have shown that the Pt atoms bind at the Ce vacancy at the edge sites on CeO₂ support after calcination at 550^oC whereas they bind at the Ce vacancy sites on the terrace of CeO₂ after calcination at 800^oC. This difference in the local Pt geometry has substantial impact on CO oxidation such that the former exhibits higher CO turnover frequency (TOF) and reaches 100% CO conversion at lower temperature than the latter. To understand the rationale for this behavior, we have calculated the CO oxidation reaction pathways on both catalysts using density functional theory and then performing Kinetic Monte Carlo (KMC) simulations. Our KMC results show that the catalyst calcinated at 550^oC has a higher CO₂ TOF and conversion rate than the one calcinated at 800^oC, in good agreement with experiments. We track the difference in the performance of the catalysts to the activation energies for O₂ dissociation and CO-O combination.