A 3D porous P-doped Cu–Ni alloy for atomic H* enhanced electrocatalytic reduction of nitrate to ammonia

Abstract

Electrocatalytic nitrate (NO₃⁻) reduction to ammonia (NH₃) (NRA) is of great significance for solving the problem of urgent NO₃⁻ pollution in the environment and opening up a new route to synthesize NH₃. However, NRA is limited by its multi-electron/proton transfer process and the NRA process relies heavily on atomic H* produced by H₂O splitting, undergirding the necessity for effective NRA catalysts. Herein, three-dimensional (3D) porous phosphorus (P)-doped Cu–Ni alloy materials are constructed through a one-step electrodeposition synthesis. 3D porous materials modulate hydrophilicity and enrich active sites. The Cu d-band center can be tuned through Ni alloying to modify the adsorption energies of intermediates such as *NO₃⁻, *NO₂⁻, and *NH₂. The hydrogenation evolution capacity of P promotes the hydrogenation process in the atomic H* path and effectively accelerates the NRA reaction rate. Density functional theory (DFT) calculations demonstrate that the charge transfer between the negatively charged P^δ− and the positively charged Ni^δ+ and Cu^δ+ assists in generating more atomic H* for coupling with reaction intermediates, showing an enhanced catalytic activity at low overpotential. The optimal sample exhibits an exceptional NRA performance with an ammonia yield rate of 848.1 μmol h⁻¹ cm⁻² and a faradaic efficiency of 96.1%. This work provides a strategy for creating effective NRA catalysts through enhancing the atomic H* reduction strategy.