Recent advances in Cu-based electrocatalysts for nitrate reduction to ammonia: from catalyst design to practical...

Ammonia is a vital industrial feedstock and a promising carbon-free energy carrier. However, its conventional production via the Haber-Bosch process is energy-intensive and is accompanied by significant CO₂ emissions. The electrocatalytic nitrate reduction reaction (NO₃RR) has emerged as a sustainable alternative, capable of converting nitrate pollutants in wastewater into valuable ammonia under ambient conditions, thereby integrating environmental remediation with green chemical synthesis. Among various electrocatalysts, Cu-based materials have garnered particular attention due to their tunable electronic structure, moderate adsorption strength for nitrogen intermediates, and inherent ability to suppress the competing hydrogen evolution reaction. This review provides a comprehensive overview of recent advances in Cu-based catalysts for the NO₃RR, encompassing monometallic nanostructures, alloys, oxides, single atoms, and metal-organic frameworks. We systematically discuss the fundamental reaction mechanisms, insights gained from in situ/operando characterization and theoretical computations, and key performance-governing factors such as electrolyte composition, pH, and applied potential. Furthermore, this article highlights the application potential of this technology in wastewater treatment, distributed ammonia synthesis, and metal-nitrate batteries. Finally, we outline current challenges related to catalyst stability in complex media, reactor engineering, and system integration, and offer perspectives on future research directions, aiming to promote the practical implementation of nitrate reduction technology, thereby contributing to closing the nitrogen cycle and establishing a sustainable ammonia economy.