Heterostructure Cu₃P-Ni₂P/CP catalyst assembled membrane electrode for high-efficiency electrocatalytic nitrate to ammonia

Electrochemical nitrate reduction reaction (NO₃RR) is a promising means for generating the energy carrier ammonia. Herein, we report the synthesis of heterostructure copper-nickel phosphide electrocatalysts via a simple vapor-phase hydrothermal method. The resultant catalysts were evaluated for electrocatalytic nitrate reduction to ammonia (NH₃) in three-type electrochemical reactors. In detail, the regulation mechanism of the heterogeneous Cu₃P-Ni₂P/CP-x for NO₃RR performance was systematically studied through the H-type cell, rotating disk electrode setup, and membrane-electrode-assemblies (MEA) electrolyzer. As a result, the Cu₃P-Ni₂P/CP-0.5 displays the practicability in an MEA system with an anion exchange membrane, affording the largest ammonia yield rate (R_NH3) of 1.9 mmol·h⁻¹·cm⁻², exceeding most of the electrocatalytic nitrate reduction electrocatalysts reported to date. The theoretical calculations and in-situ spectroscopy characterizations uncover that the formed heterointerface in Cu₃P-Ni₂P/CP is beneficial for promoting nitrate adsorption, activation, and conversion to ammonia through the successive hydrodeoxygenation pathway.