posted on 2022-01-10, 16:39authored byMuhammad
I. Ahmed, Lakshitha J. Arachchige, Zhen Su, David B. Hibbert, Chenghua Sun, Chuan Zhao
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.