Facile Construction of CuFe‐Based Metal Phosphides for Synergistic NOx−Reduction to NH3 and Zn‐Nitrite Batteries in Electrochemical Cell

The electrocatalytic nitrite/nitrate reduction reaction (eNO₂RR/eNO₃RR) offer a promising route for green ammonia production. The development of low cost, highly selective and long-lasting electrocatalysts for eNO₂RR/eNO₃RR is challenging. Herein, a method is presented for constructing Cu₃P-Fe₂P heterostructures on iron foam (CuFe-P/IF) that facilitates the effective conversion of NO₂ ^- and NO₃ ^- to NH₃. At -0.1 and -0.2 V versus RHE (reversible hydrogen electrode), CuFe-P/IF achieves a Faradaic efficiency (FE) for NH₃ production of 98.36% for eNO₂RR and 72% for eNO₃RR, while also demonstrating considerable stability across numerous cycles. The superior performance of CuFe-P/IF catalyst is due tothe rich Cu₃P-Fe₂P heterstuctures. Density functional theory calculations have shed light on the distinct roles that Cu₃P and Fe₂P play at different stages of the eNO₂RR/eNO₃RR processes. Fe₂P is notably active in the early stages, engaging in the capture of NO₂ ^-/NO₃ ^-, O─H formation, and N─OH scission. Conversely, Cu₃P becomes more dominant in the subsequent steps, which involve the formation of N─H bonds, elimination of OH^* species, and desorption of the final products. Finally, a primary Zn-NO₂ ^- battery is assembled using CuFe-P/IF as the cathode catalyst, which exhibits a power density of 4.34 mW cm^-2 and an impressive NH₃ FE of 96.59%.