Identification of M-NH2-NH2 Intermediate and Rate Determing Step for Nitrogen Reduction with Bioinspired Sulfur-bonded FeW Catalyst

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.