Nitrogenase-Inspired Atomically Dispersed Fe-S-C Linkages for Improved Electrochemical Reduction of Dinitrogen to Ammonia

The electrochemical nitrogen reduction reaction (NRR) provides a sustainable alternative to the Haber-Bosch process for ammonia (NH3) production. Transition metal catalysts have poor NRR performance due to the highly competitive hydrogen evolution reaction and the scaling relation between inert dinitrogen (N-2) and other reaction intermediates. Owing to the enhanced active sites and the anomalous quantum size effect, single-atom catalysts (SACs) have been proven to be effective in overcoming these limitations. Inspired by our understanding of metal- sulfur (M-S) linkages in the nitrogenase enzyme, we have modulated the electronic structure of iron by tethering to sulfur in a mesoporous carbon matrix. Theoretical calculations identified enhanced electron transfer and flexible coordination as important features of Fe-S-C linkages responsible for the improved NRR performance, which is achieved due to enhanced N-2 interaction with localized charge density sites formed by Fe-S-C linkages. A high faradaic efficiency (6.1 +/- 0.9%) with an improved rate of NH3 formation (8.8 +/- 1.3 mu g h(-1) mg(-1)) is obtained on the best-performing sample at -0.1 V versus RHE. Our work reveals the importance of M-S linkages for improved NRR performance and provides a strategy for the rational catalyst design.

Automated summary

The electrochemical nitrogen reduction reaction (NRR) can be an alternative to the Haber-Bosch process for ammonia production, and single-atom catalysts have been proven effective in improving the reaction. By modulating the electronic structure of iron and tethering it to sulfur, the NRR performance can be enhanced.