▎ 摘　　要

With the advantages of maximum metal utilization, single-atom catalysts (SACs) are emerging as promising catalysts in the CO2 reduction reaction (CO2RR) field. Herein, first-principles calculation is performed to investigate the CO2-to-CO conversion mechanism by a serial of transition metal single transition metal atom supported on graphene systems (TM@Gr(s)) as a CO2 reduction catalyst. Among all SACs considered in this work, Cr@Gr(s) exhibits a low limiting potential of -0.21 V, showing remarkable performance for CO2RR. To understand activity origin of CO2RR, we analyzed the effect of d-band centers of TM@Gr(s) and investigated the charge transfer and bonding/antibonding states between the intermediates and TM atoms. These physical quantities provide a good explanation for the process of CO2RR and show the theoretical guidance for proper catalyst discovery and better carbon circulation.