Gradient Adsorption Energy Strategy Unlocks Ultra‐Long Stability and Efficient Electrocatalytic Ammonia Synthesis from Nitrate Over CoP/Cu ₃ P

Electrocatalytic nitrate (NO₃ ^-) reduction to ammonia (NRA) is an important approach for achieving both ammonia synthesis and wastewater treatment. However, its multi-step proton-electron transfer process and the difficulty in synergistically regulating the adsorption energy of intermediates limit the reaction efficiency. In this study, a self-supported CoP/Cu₃P composite nanotube array electrode (CoP/Cu₃P-CF) was fabricated on copper foam through in situ growth and phosphidation. By precisely regulating synergistic catalytic sites for multiple elementary reactions, the catalyst simultaneously enhances both adsorption and desorption processes through a gradient adsorption energy strategy. The catalyst utilizes the synergistic effect of Cu and Co dual sites to enhance the adsorption and conversion of NO₃ ^- and the directed transformation of *NO₂ intermediates to NH₃, respectively, while P atoms act as electron transfer bridges to promote charge transport. At -0.3 V vs. RHE, it achieved an exceptional ammonia production rate of 1.59 mmol h^-1 with a Faradaic efficiency of 96.35%. The strong interfacial interaction between CoP and Cu₃P effectively suppressed structural reconstruction, enabling stable operation for 150 h without significant performance degradation. Kelvin probe force microscopy and in situ characterization confirmed a broad adsorption energy distribution conducive to multi-site synergistic catalysis. This study provides new insights for the design and mechanistic understanding of highly active NRA catalysts.