Fe single-atom catalysts with pre-organized coordination structure for efficient electrochemical nitrate reduction to ammonia

Single atom catalysts (SAC) have the potential to achieve large-scale production of NH3 through electrochemical nitrate reduction reaction (NO3-RR). Tailoring the coordination structure of the SAC can effectively tune their electronic structure and thus promote their catalytic selectivity and activity. In this work, Fe SAC with unique FeN2O2 coordination was fabricated through direct pyrolysis of metal-organic frameworks that have pre-organized FeN2O4 environment. Fe SAC exhibits both high faradaic efficiency (~92%) and high ammonia yield rate (46 mg h−1 mg cat.−1) in neutral electrolytes. Density functional theory calculations reveal that the O atoms in FeN2O2 can tune the d-band center of Fe and thus adjust the adsorption energies of the NO3-RR intermediates. Compared to FeN4, FeN2O2 structure has higher conductivity and selectivity to NH3 and can spontaneously trigger the transformation of *NOH to N * , thus promoting the NO3-RR. This work provides a simple method to fabricate O, N-coordinated Fe SAC and may stimulate the flourishing development of asymmetric SAC for electrocatalysis.