Highly distributed amorphous copper catalyst for efficient ammonia electrosynthesis from nitrate

Abstract

Electroreduction of nitrate to ammonia, instead of N2, is beneficial toward pollution control and value-added chemical production. Metallic catalysts have been developed for enhancing ammonia evolution efficiency from nitrate based on the crystalline state of the catalyst. However, the development of amorphous metallic catalysts with more active sites is still unexplored. Herein, a highly distributed amorphous Cu catalyst exhibiting an outstanding ammonia yield rate of 1.42 mol h−1 g−1 and Faradaic efficiency of 95.7%, much superior to crystallized Cu, is demonstrated for nitrate-reduction to ammonia. Experimental and computational results reveal that amorphizing Cu increases the number of catalytic sites, enhances the NO3− adsorption strength with flat adsorption configurations, and facilitates the potential determining step of *NO protonation to *NHO. The amorphous Cu catalyst shows good electrochemical stability at − 0.3 V, while crystallization weakens the activity at a more negative potential. This study confirms the crystallinity-activity relationship of amorphous catalysts and unveils their potential-limited electrochemical stability.