Structural evolution-induced strong-coupling in CuRu-Cu2O nanocomposite enables low-overpotential electrocatalytic ammonia synthesis

Ammonia (NH3) synthesis via nitrate reduction offers a sustainable energy conversion and mitigates aquatic NO3− pollution, yet most catalysts require high overpotentials for appreciable NH3 yields. Here, we report a sulfur-leaching strategy to transform Cu1.8S/Ru heterostructures into a small CuRu-Cu2O nanocomposite with abundant heterointerfaces, enabling strong electronic coupling between CuRu and Cu2O particles, synergistically enhancing NO3– adsorption and reaction kinetics. The optimized catalyst achieves 95.4% NH3 Faradaic efficiency at a low potential of 0.0 V versus reversible hydrogen electrode, stable over 30 cycles. Operando spectroscopy and density functional theory calculations reveal the incorporation of Ru facilitates active hydrogen generation, alleviating the energy barrier for hydrogenation steps at heterointerfaces. The catalyst demonstrates high stability in a membrane electrode assembly at 450 mA cm–2 over 200 h and enables a Zinc-NO3– battery operation exceeding 50 h, offering a design model for durable, active nanocomposites in sustainable NH3 synthesis. Electrocatalytic nitrate reduction offers a sustainable route for ammonia synthesis but suffers from high overpotentials. Here, the authors report CuRu-Cu2O nanocomposites that achieve 95.4% ammonia Faradaic efficiency at 0 V (reversible hydrogen electrode) and operate stably for over 200 h.