Salt-Templated Construction of Ultrathin Cobalt Doped Iron Thiophosphite Nanosheets toward Electrochemical Ammonia Synthesis

Abstract

Exploiting efficient electrocatalysts for electrochemical nitrogen reduction (NRR) is highly desired and deeply meaningful for realizing sustainable ammonia (NH₃ ) production under ambient conditions. The Fe protein contains one [Fe₄ S₄ ] cluster and P cluster, which play an important role for transfer electron during the nitrogen fixing of nitrogenases. Based on the understanding of nitrogenase, the rising-star 2D iron thiophosphite (FePS₃ ) nanomaterials may be highly active electrocatalysts toward NRR due to the ideal elemental composition. In this work, 2D FePS₃ nanosheets are successfully synthesized by a facile salt-templated method. The FePS₃ nanosheets show better electrocatalytic NH₃ yield and faradaic efficiency (FE) than Fe₂ S₃ , which demonstrates that the P element indeed improves the NRR activity of Fe-S. Theoretically, Co incorporation not only effectively prompts the conductivity of FePS₃ , but also enhances the catalytic activities of Fe-edge sites. Experimentally, Co-doped FePS₃ (Co-FePS₃ ) nanosheets exhibit a remarkable electrocatalytic performance toward NRR, such as high NH₃ yield rate of 90.6 µg h^-1 mg_cat^-1 , high FE of 3.38%, and an excellent long-term stability. Being the first theoretical and experimental report regarding FePS₃ -based electrocatalyst toward NRR, this work represents an important beginning to the family of metal thiophosphite as advanced electrocatalysts toward NRR.

Keywords: Fe protein; electrocatalysis; nitrogen reduction reaction; salt-templated method; thiophosphite.