Adsorption-dissociation-association mechanism for enhancing electrochemical nitrate to ammonia conversion

Abstract

The electrocatalytic nitrate reduction to ammonia is a promising strategy for efficient NH3 synthesis. In this study, we introduce an electrocatalyst comprising a Fe-Nx layer and porous carbon-dispersed Fe nanoparticles. This configuration achieves an exceptionally high ammonia yield rate and Faradaic efficiency of 30,151.4 ± 1060.6 µg‧h−1‧mgcat−1 and 98.4 %, respectively, via the nitrate reduction reaction. Our findings indicate that the porosity and electrical properties of the catalyst play a crucial role in NO3− adsorption, surpassing the importance of specific surface area. The abundant metal-nitrogen active sites preferentially adsorb NO3− over H2O, facilitating increased production of adsorbed hydrogen. Additionally, the elevated energy barrier from H to H2 reduces the formation of hydrogen evolution byproducts, thus favoring ammonia synthesis. This study offers valuable insights into designing highly selective catalysts for adsorption-dissociation-association mechanism and has implications for a wide range of applications.