Formation, geometric properties, and surface activities of nSi clusters (n = 1 − 4) doped graphene as metal-free catalyst

Abstract

The formation processes, electronic, and catalytic properties of nSi (n = 1 − 4) atom-doped divacancy graphene (nSi-graphene) are discussed using density functional theory calculations. First, the formation mechanisms of nSi-graphene sheets are investigated in detail. According to the formation energies values, it is found that the tetrahedral 4Si cluster-anchored graphene has the least energy as compared with that of others. Second, the adsorption behaviors and electronic structures of adsorbed species on the 1Si-graphene and 4Si-graphene sheets are comparably analyzed. The adsorption of O2 molecule is more stable than that of the CO molecule; thus, the possible CO oxidation reactions on different nSi-graphene surfaces are investigated through Eley–Rideal. In the complete CO oxidation reactions, the formation process of CO3 complex on the 1Si-graphene sheet is the rate-controlling step, while the interaction between CO3 and CO on the 4Si-graphene has a relatively large energy barrier. This result illustrates that the different numbers of Si atoms can regulate the surface curvature and activities of graphene sheets, which provides a theoretical reference for designing the graphene-based metal-free catalyst in energy-related devices.