Copper Selenide Nanosheet with Adjustable Cation Vacancy for Boosting Nitrogen Electroreduction

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable pathway for ammonia synthesis under ambient conditions. Among these, vacancy engineering has emerged as an effective approach to accelerate nitrogen-to-ammonia conversion and enhance electrocatalytic performance. However, the controllable synthesis of catalysts with precise cation vacancy concentrations remains a significant challenge. In this study, we address this by employing a combined thermal treatment and plasma approach to fabricate copper selenide nanosheets with precisely tuned copper vacancy (V_Cu) concentrations. The resulting p-Cu_1.8Se/Cu₂Se/C-5 catalyst, possessing the highest V_Cu concentration, demonstrated superior NRR activity, achieving an NH₃ production rate of 21.81 μg h^-1 mg_cat.^-1 at -0.7 V vs the reversible hydrogen electrode (RHE), a value more than 3-fold higher than that of its vacancy-free counterpart. These results indicate that V_Cu sites serve as active centers that optimize nitrogen adsorption and activation, thereby significantly lowering the energy barrier of the rate-determining step. This work provides a new avenue for designing next-generation, high-performance NRR electrocatalysts through precise defect engineering.