Theory-Guided Construction of the Unsaturated V-N 2 Site with Carbon Defects for Highly Selective Electrocatalytic Nitrogen Reduction.

Renewable energy-driven, electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy for ammonia synthesis. However, improving catalyst activity and selectivity under ambient conditions has long been challenging. In this work, we obtained the potential active V-N center through theoretical prediction and successfully constructed the associated V-N 2 /N 3 structure on N-doped carbon materials. Surprisingly, such a catalyst exhibits excellent electrocatalytic NRR performance. The V-N 2 catalyst affords a remarkably high faradaic efficiency of 76.53% and an NH 3 yield rate of 31.41 μg NH 3 h -1 mg Cat. -1 at -0.3 V vs RHE. The structural characterization and density functional theory (DFT) calculations verified that the high performance of the catalyst originates from the tuned d-band upon coordination with nitrogen, in line with the original design intention as derived theoretically. Indeed, the V-N 2 center with carbon defects enhances dinitrogen adsorption and charge transfer, thereby lowering the energy barriers to form the *NNH intermediates. Such a strategy as a rational design─controllable synthesis─theoretical verification may prove effective as well for other chemical processes.