Asymmetric hydrogenation-driven enhancement of activity and selectivity in V-anchored N3-doped graphene catalysts for nitrogen reduction

Abstract

Simultaneously achieving high catalytic activity and selectivity remains a significant challenge for single-atom catalysts (SACs) in electrocatalytic nitrogen reduction reaction (NRR). In this study, we propose an asymmetric hydrogenation strategy to optimize the NRR performance of vanadium-anchored N₃-doped graphene catalysts (V@Hx-N₃G). Using density functional theory calculations combined with the constant potential method, we systematically investigate the impact of hydrogenation degree and configuration on catalyst performance. Among the partially hydrogenated catalysts, V@H_5A-N₃G exhibits outstanding activity, achieving a low NRR limiting potential of −0.42 V and favorable selectivity toward NRR over the hydrogen evolution reaction, with a 45.6 % improvement in selectivity compared to the unhydrogenated V@Graphene-N₃ system. Remarkably, under realistic electrochemical conditions, V@H_5A-N₃G achieves an ultralow limiting potential of −0.04 V vs. SHE at an optimal applied potential of 0.89 V. Additionally, the catalyst demonstrates strong pH stability, with minimal performance degradation across a broad pH range. The enhancement originates from asymmetric hydrogenation-induced modulation of electronic structure, d-band center, and N₂ adsorption strength. These results demonstrate that asymmetric hydrogenation is a powerful strategy for simultaneously enhancing catalytic activity and selectivity, providing valuable insights for the design of advanced electrocatalysts.