O-Induced Diatomic Fe–Mo Mimetic Enzyme for Efficient Electrocatalytic Nitrogen Reduction at Universal pH

Electrochemical nitrogen reduction reaction (ENRR) provides a sustainable route for the NH3 synthesis. However, designing catalysts that facilitate efficient electron/proton transfer and the hydrogenation of multiple intermediates remains a challenge. In this study, inspired by the natural nitrogenase proteins, a biomimetic Fe–Mo diatomic catalyst (FeMo-CDW(CT-3h)) was designed for efficient ENRR. The microenvironment of Fe–Mo diatomic sites was precisely tuned using the O-induced atomic confinement effect, where O atoms modulate the activity of the sites. FeMo-CDW(CT-3h) with four O atoms achieves a record-breaking NH3 yield at universal pH as well as high stability (250 h and 10 cycles) due to its optimal electron transfer efficiency. In particular, the NH3 yield of 336.03 μg h–1 cm–2 in 0.1 M HCl was over three times higher than the previously reported maximum. Theoretical calculations reveal that the hybridization of Fe–Mo d orbitals with N2* antibonding orbitals enhances electron transfer, extends and weakens the N≡N bond, and accelerates proton transfer and hydrogenation, thereby increasing NH* antibonding orbitals enhances electron transfer, extends and weakens the N≡N bond, and accelerates proton transfer and hydrogenation, thereby increasing NH3 generation.