▎ 摘　　要

Electrocatalytic reduction of harmful nitrate (NO3-) to valuable ammonia (eNO(3)RR) is critical and attractive for both environmental remediation and energy transformation. A single atom catalyst (SAC) based on graphene represents one of the most promising eNO(3)RR catalysts. However, the underlying catalytic mechanism and the intrinsic factors dictating the catalytic activity trend remain unclear. Herein, using first-principles calculations, eNO(3)RR on TMN3 and TMN4 (TM = Ti-Ni) doped graphene was thoroughly investigated. Our results reveal that FeN4 doped graphene exhibits excellent eNO(3)RR performance with a low limiting potential of -0.38 V, agreeing with the experimental finding, which can be ascribed to the effective adsorption and activation of NO(3)(-)via the charge "acceptance-donation" mechanism and its moderate binding due to the occupation of the d-p antibonding orbital. In particular, we found that eNO(3)RR activities are well correlated with the intrinsic properties of TM centers and their local environments. With the established activity descriptor, several other graphene-based SACs were efficiently screened out with excellent eNO(3)RR performance. Our studies could not only provide an atomic insight into the catalytic mechanism and activity origin of eNO(3)RR on graphene-based SACs, but also open an avenue for the rational design of SACs for eNO(3)RR towards ammonia by regulating the metal center and its local coordination environment.