Sev-rich NiO/Cu2Se heterostructure for efficient electrocatalytic ammonia oxidation to nitrite

The electrochemical ammonia oxidation reaction (AOR) offers a promising route for converting ammonia into value-added chemicals while enabling green hydrogen production. However, practical application is hindered by the high cost and limited stability of noble-metal catalysts. Herein, a selenium-vacancy-rich NiO/Cu 2 Se heterostructure (Se v –NiO/Cu 2 Se) is designed via solvothermal-calcination-selenization-annealing. The heterointerface modulates the electronic structure, while Sev activates lattice oxygen through Se O exchange to generate peroxy radical intermediates that facilitate AOR. In situ formed selenite anions suppress competitive OH − adsorption on Ni sites, inhibiting oxygen evolution. Consequently, Se v –NiO/Cu 2 Se achieves 10 mA cm −2 at 1.43 V and 96% nitrite selectivity at 1.6 V with over 96 h stability. When integrated with hydrogen evolution in a flow cell, the system enables simultaneous ammonia conversion (81% nitrite selectivity) and hydrogen production at 1.9 V, reducing cell voltage by 350 mV (at 20 mA cm −2 ) vs. conventional water splitting. This work demonstrates synergistic catalyst design via anion vacancies and heterojunctions for sustainable ammonia valorization and hydrogen production.