Identification of M‐NH₂‐NH₂ Intermediate and Rate Determining Step for Nitrogen Reduction with Bioinspired Sulfur‐Bonded FeW Catalyst

Abstract

Abstract The multimetallic sulfur‐framework catalytic site of biological nitrogenases allows the efficient conversion of dinitrogen (N 2 ) to ammonia (NH 3 ) under ambient conditions. Inspired by biological nitrogenases, a bimetallic sulfide material (FeWS x @FeWO 4 ) was synthesized as a highly efficient N 2 reduction (NRR) catalyst by sulfur substitution of the surface of FeWO 4 nanoparticles. Thus prepared FeWS x @FeWO 4 catalysts exhibit a relatively high NH 3 production rate of 30.2 ug h −1 mg −1 cat and a Faraday efficiency of 16.4 % at −0.45 V versus a reversible hydrogen electrode in a flow cell; these results have been confirmed via purified 15 N 2 ‐isotopic labeling experiments. In situ Raman spectra and hydrazine reduction kinetics analysis revealed that the reduction of undissociated hydrazine intermediates (M‐NH 2 ‐NH 2 ) on the surface of the bimetallic sulfide catalyst is the rate‐determing step for the NRR process. Therefore, this work can provide guidance for elucidating the structure–activity relationship of NRR catalysts.