The catalytic mechanism, activity trend, and activity origin of electroreduction of nitrate to ammonia on graphene-based single-atom catalysts was systematically studied and unrevealed.
Electrocatalytic reduction of harmful nitrate (NO 3 −) to valuable ammonia (eNO 3RR) 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 3RR catalysts. However, the underlying catalytic mechanism and the intrinsic factors dictating the catalytic activity trend remain unclear. Herein, using first-principles calculations, eNO 3RR on TMN 3 and TMN 4 (TM = Ti–Ni) doped graphene was thoroughly investigated. Our results reveal that FeN 4 doped graphene exhibits excellent eNO 3RR 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 3RR 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 3RR performance. Our studies could not only provide an atomic insight into the catalytic mechanism and activity origin of eNO 3RR on graphene-based SACs, but also open an avenue for the rational design of SACs for eNO 3RR towards ammonia by regulating the metal center and its local coordination environment.