Cu3P/CoP Heterostructure for Efficient Electrosynthesis of Ammonia from Nitrate Reduction Reaction

Electrocatalytic nitrate reduction (ENO3RR) for ammonia production is one of the potential alternatives to Haber–Bosch technology for the realization of artificial ammonia synthesis. However, efficient ammonia production remains challenging due to the complex electron transfer process in ENO3RR. In this study, we fabricated a Cu3P/CoP heterostructure on carbon cloth (CC) by electrodeposition and vapor deposition, which exhibits an exceptional ENO3RR performance in alkaline medium, and showcases a Faradaic efficiency of ammonia (FENH3) and an ammonia yield rate as high as 97.95% and 17,637.3 μg h–1 cm–2 at −0.9 V vs RHE. Moreover, Cu3P/CoP also has excellent catalytic activity for nitrite reduction to ammonia, with an FENH3 up to 98.31% at −0.7 V vs RHE. The experimental and theoretical calculations reveal and confirm that the formation of a heterogeneous interface between Cu3P and CoP effectively promotes the electron transfer, where Cu3P as an electron donor induces the decrease of electron density around Cu and results in an enhancement of NO2– adsorption, thereby accelerating the ENO3RR process while inhibiting the competitive hydrogen evolution reaction (HER). Moreover, the metal phosphide catalyst facilitates the water dissociation, which accelerates the abundant *H generation, thus enhancing the subsequent hydrogenation process toward ENO3RR.