Effect of oxygen coordination on the electrocatalytic nitrogen fixation of a vanadium single-atom catalyst embedded in graphene

The rational design of efficient electrocatalysts for nitrogen reduction reaction (NRR) to produce NH3 under ambient condition is a longstanding challenge. The graphene-based single-atom catalyst (SAC) has been revealed as a promising candidate. Previous studies mainly focused on the metal center coordinated with N atoms, while those coordinated with other heteroatoms were rarely reported. Herein, we theoretically investigated the effect of oxygen coordination on the performance of vanadium (V) SAC embedded in graphene (VO4/G) towards NRR owing to the fact that V with less d electrons usually exhibits high chemical activity. It is revealed that VO4/G with good stability can efficiently convert N-2 into NH3 through a distal mechanism with a low limiting potential of -0.60 V, which is superior to the experimentally synthesized FeN4/G and FeO4/G SACs. Moreover, the stronger adsorption of N-2 than the H atom renders the high NRR selectivity of VO4/G against the competing hydrogen evolution reaction, and the rapid removal of the produced NH3 endows VO4/G with excellent recyclability. The good stability, high catalytic activity and selectivity, and excellent recyclability make VO4/G a prospective NRR catalyst. This work provides a promising NRR electrocatalyst awaiting experimental exploration and will stimulate further studies on other coordination atoms beyond N for graphene-based SAC.