Nitrogenase-Inspired Atomically Dispersed Fe–S–C Linkages for Improved Electrochemical Reduction of Dinitrogen to Ammonia
Muhammad Ibrar Ahmed, Lakshitha Jasin Arachchige, Zhen Su, David Brynn Hibbert, Chenghua Sun, Chuan Zhao
Abstract
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 (N2) 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 N2 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 μg 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.