Electronic Perturbation of Isolated Fe Coordination Structure for Enhanced Nitrogen Fixation.

Chang, Bin; Cao, Zhen; Ren, Yuanfu; Chen, Cailing; Cavallo, Luigi; Raziq, Fazal; Zuo, Shouwei; Zhou, Weijia et al. · ACS Nano · 2024

basic_science · Level V

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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<sub>4</sub>) to a medium state (FeN<sub>2</sub>B<sub>2</sub>). 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<sup>-1</sup> mg<sup>-1</sup><sub>cat.</sub> and a Faradaic efficiency of 24.8%. <i>In situ</i> spectroscopic studies and theoretical calculations indicate that boron coordinate sites, as electron acceptors, can regulate the adsorption energy of N<sub><i>x</i></sub>H<sub><i>y</i></sub> intermediates on the Fe center. FeN<sub>2</sub>B<sub>2</sub> 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.