Effects of the Carbon-Doped BN Support on the Stability and Reactivity of Single-Atom Catalysts

Single-atom catalysts (SACs) on hexagonal boron nitride (h-BN) with boron vacancies (denoted as M@BN) exhibit high stability but limited activity for O 2 activation. Carbon doping can effectively tune the electronic structure of the BN support, enhancing catalytic performance. Using density functional theory (DFT) calculations, this study systematically investigates the stability, O 2 activation, and oxidative desulfurization (ODS) mechanisms of M@BN and M@BN- n C (M = Co, Ni, Cu) SACs. The findings indicate that the content and arrangement of carbon doping exert a substantial influence on the stability of the catalysts, and a compromise exists between stable performance and O 2 activation activity. Hexagonal carbon doping in BN ensures high stability but low activity, whereas triangular doping (e.g., M@BN-4C) enhances O 2 activation despite slightly reduced stability. Electronic structure analysis indicates that triangular C-doping narrows the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap by raising the HOMO energy via C 2p orbital contributions, facilitating electron transfer to O 2 and enhancing reactivity. Further evaluation of the M@BN-4C catalysts in ODS reactions shows that the oxidation of dibenzothiophene (DBT) to dibenzothiophene sulfoxide (DBTO) is the rate-determining step. By comparing the reaction energy barriers and reaction energies, Ni@BN-4C is identified as offering the best balance between stability and activity among the Co, Ni, and Cu SACs.