Single-atom Pt on non-metal modified graphene sheets as efficient catalyst for CO oxidation
By density functional theory (DFT) calculations, the formation geometries, electronic structures and catalytic properties of metal Pt and nonmetal (NM) atoms co-modified graphene (Pt-3NM-graphene, NM=N, Si, P) as reactive substrates are investigated. Firstly, the formation energy of Pt-3N-graphene configuration is less than that of the Pt-3Si- and Pt-3P-graphene systems. The adsorbed O2 on Pt-3NM-graphene is more stable than that of CO molecule and their corresponding electronic and magnetic properties are analyzed in detail. Compared with the isolated O2 or CO molecule, the coadsorption of CO/O2 (or 2CO) has larger adsorption energies on Pt-3NM-graphene, which may facilitate the catalytic reactions for CO oxidation. Furthermore, the different reaction mechanisms of CO oxidation on Pt-3NM-graphene are systematically investigated. It is found that the Eley-Rideal (ER) mechanism (CO + O2 → CO3) as initial state on Pt-3NM-graphene sheets have larger energy barriers than those of the Langmuir-Hinshelwood (LH) and new termolecular Eley-Rideal (TER) mechanisms. For the Pt-3N- and Pt-3Si-graphene, the catalytic oxidation of CO reactions through LH and TER reactions have much small energy barriers (˂ 0.3 eV), which as the initial state is energetically more favorable. These results provide valuable guidance on selecting dopants in graphene to design the carbon-based catalysts with low price and high activity.