Strong electron coupling of FeP₄/Ni₂P to boost highly-efficient electrochemical nitrate reduction to ammonia

Electrochemical reduction of contaminated nitrate to ammonia (NRA) opens a new window for mass production of ammonia and the alleviation of energy crises and environmental pollution. However, fabricating effective catalysts for the NRA still faces significant challenges. Herein, a highly-efficient NRA catalyst, FeP₄/Ni₂P, was successfully constructed. The strong electron coupling at heterointerfaces of FeP₄/Ni₂P promoted the generation of abundant active hydrogen *H, inhibited the competition of the HER, accelerated the hydrogenation of the NRA. Benefiting from these, the catalyst displays good NRA catalytic activity in the neutral electrolyte, with the NH₃ FE of 97.83 ± 0.091 %, NH₃ selectivity of 98.67 ± 0.50 %, NH₃ yield rate of 0.262 ± 0.01 mmol·h^-1·cm^-2, and NO₃^- conversion rate of 93.02 ± 0.14 %. The DFT theoretical calculations demonstrated that the FeP₄/Ni₂P heterointerfaces played a critical role in shearing the H-OH bonds of water, resulting in generating more active hydrogen as a key NRA hydrogenation source, and hindering the *H dimerization to form H₂, enhancing the NH₃ selectivity. This work has a certain reference value for designing excellent catalysts for the NRA.