Universal synergistic Cu/Co3O4 heterostructure enables near-unity selectivity ammonia electrosynthesis from nitrate under various operational conditions

The electrocatalytic nitrate reduction reaction (NO 3 − RR) is a promising and economic green alternative to the traditional Haber-Bosch process for ammonia (NH 3 ) production. However, it suffers from high overpotential and poor NH 3 selectivity due to various competing reactions. In this study, we developed a CuO/Co 3 O 4 nanoneedle heterostructure catalyst grown on nickel foam. After electro-activation to Cu/Co 3 O 4 , it achieved nearly 100 % NH 3 selectivity in both alkaline and neutral electrolytes across a wide range of potentials. The catalyst showed a high NH 3 yield rate of 617.14 μmol h −1  cm −2 at −0.2 V vs. reversible hydrogen electrode along with an excellent stability over a 120-hour test. The mechanism involves CuO reducing to Cu, forming a heterostructure that modifies the electronic environment of Co sites, the synergistic Cu and Co 3 O 4 interfaces enhancing rapid *NO 3 adsorption and lowering the energy barriers for NH 3 production, thereby facilitating the overall efficiency even at low concentrations (0.01 M NO 3 − ).