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

Abstract

Conventional low‐spin Co3O4 suffers from weak orbital hybridization with oxygenates (*NOx and *H2O), leading to slow reaction kinetics for ammonia synthesis during electrochemical nitrate reduction (NO3RR). Herein, we demonstrate the precise spin‐state engineering of octahedral Co3+ sites in spinel Co3O4 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 eg electrons of high‐spin Co3+ strengthen orbital hybridization with oxygen‐containing intermediates (*NOx and *H2O). 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 NO3RR toward NH3. Consequently, the optimized high‐spin Co3O4 delivers an exceptional Faradaic efficiency of 93.36% and an NH3 yield rate of 1.17 mmol/h/cm2. Moreover, techno‐economic analysis shows a two‐electrode membrane‐electrode assembly (MEA) reactor coupling NO3RR with GOR (NO3RR//GOR) enables favorable economic performance with a total revenue of 7651 USD/t NH3. 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.