Spin‐State Modulation of Cobalt Centers for Boosting Electrochemical Ammonia Synthesis

Conventional low‐spin Co 3 O 4 suffers from weak orbital hybridization with oxygenates ( * NO x and * H 2 O), leading to slow reaction kinetics for ammonia synthesis during electrochemical nitrate reduction (NO 3 RR). Herein, we demonstrate the precise spin‐state engineering of octahedral Co 3+ sites in spinel Co 3 O 4 through a facile yet effective thermally induced lattice distortion. Spectroscopic and theoretical investigations reveal this lattice distortion reshapes the localized d‐orbital energy levels, thereby fundamentally driving a transition from the thermodynamically stable low‐spin configuration to a highly active high‐spin state. Mechanistically, the unpaired e g electrons of high‐spin Co 3+ strengthen orbital hybridization with oxygen‐containing intermediates ( * NO x and * H 2 O). This enhanced binding not only promotes the adsorption and cleavage of these species but also ensures a sustained supply of protons via accelerated water dissociation, thereby synergistically accelerating the NO 3 RR toward NH 3 . Consequently, the optimized high‐spin Co 3 O 4 delivers an exceptional Faradaic efficiency of 93.36% and an NH 3 yield rate of 1.17 mmol/h/cm 2 . Moreover, techno‐economic analysis shows a two‐electrode membrane‐electrode assembly (MEA) reactor coupling NO 3 RR with GOR (NO 3 RR//GOR) enables favorable economic performance with a total revenue of 7651 USD/t NH 3 . This work presents a facile synthetic route toward highly active electrocatalysts via distortion‐driven spin‐state regulation, providing a promising strategy for sustainable electrochemical ammonia synthesis.