Catalytic oxidation mechanisms of carbon monoxide over single- and double-vacancy Mn-embedded graphene

Abstract

Single-atom catalysts (SACs) have been extensively investigated in recent times due to their highly dispersed atomic levels and the improved distribution of their metallic active sites, maximizing the specific activity of the catalysts. Through density functional theory (DFT) calculations, the carbon monoxide oxidation reaction (COOR) on Mn atoms embedded in single- and double-vacancy graphene was investigated (MnC₃ and MnC₄). For MnC₃, COOR may occur via the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms, and the corresponding energy barriers of the rate-determining step (RDS) at 0 K are 0.832 and 0.829 eV, respectively. COOR prefers to react via the LH mechanism and the energy barrier of the RDS is 0.761 eV at room temperature (298.15 K). For MnC₄, COOR prefers to follow the LH mechanism with an energy barrier of 0.568 eV at 0 K. The CO oxidation reaction on MnC₃ and MnC₄ has fast kinetics and the reaction time of the RDS is less than 1 s. These results indicate that MnC₃ and MnC₄ are promising CO oxidation catalysts.