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 (FE_NH₃) 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 FE_NH₃ 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.