A MoFe nitrogenase-mimicking electrocatalyst for nitrogen fixation with high faradaic efficiency

Abstract

Electrochemical conversion of N₂ provides an eco-friendly approach for sustainable ammonia (NH₃) production, but most electrocatalysts still suffer from low selectivity. Herein, a new three dimensional (3D) graphene aerogel-supported MoO₂ and FeS₂ nanocomposite (MoO₂/FeS₂/GA) was developed through mimicking the elemental composition and proportion of MoFe nitrogenase. Herein, MoO₂ and FeS₂ can both act as active sites for nitrogen fixation, while FeS₂ plays the role of suppressing the competitive hydrogen evolution activity simultaneously. Moreover, the graphene aerogels can promote the charge transfer and increase the specific surface area of the nanocomposites. Based on the synergistic effects of such a ternary architecture, the electrocatalyst exhibits a high NH₃ yield of 40.18 μg h⁻¹ mg_cat.⁻¹ and outstanding faradaic efficiency of 37.44% at −0.25 V versus the reversible hydrogen electrode (RHE) in 0.1 M HCl. The selectivity of the as-proposed nanocomposite is superior to those of GA, FeS₂/GA, MoO₂/GA and most previously reported NRR electrocatalysts. Such a bioinspired strategy provides a new avenue to develop more high-efficiency catalysts with controllable activity for the NRR under ambient conditions.