Electronic Perturbation of Isolated Fe Coordination Structure for Enhanced Nitrogen Fixation

Abstract

Modulation of the local electronic structure of isolated coordination structures plays a critical role in electrocatalysis yet remains a grand challenge. Herein, we have achieved electron perturbation for the isolated iron coordination structure via tuning the iron spin state from a high spin state (FeN 4 ) to a medium state (FeN 2 B 2 ). The transition of spin polarization facilitates electron penetration into the antibonding π orbitals of nitrogen and effectively activates nitrogen molecules, thereby achieving an ammonia yield of 115 μg h –1 mg –1 cat. and a Faradaic efficiency of 24.8%. In situ spectroscopic studies and theoretical calculations indicate that boron coordinate sites, as electron acceptors, can regulate the adsorption energy of N x H y intermediates on the Fe center. FeN 2 B 2 sites favor the NNH* intermediate formation and reduce the energy barrier of rate-determining steps, thus accounting for excellent nitrogen fixation performance. Our strategy provides an effective approach for designing efficient electrocatalysts via precise electronic perturbation.