Electrochemical nitrate reduction to ammonia using copper-based electrocatalysts

Ammonia (NH₃) is an ideal green fuel with high energy density and plays an indispensable role in fertilizer production. Electrochemical reduction of nitrate (NO₃^–), a toxic pollutant in groundwater, has shown promising as a viable approach to converting waste into valuable NH₃ under ambient conditions, offering an alternative to the energy-intensive Haber-Bosch process. Due to their high efficiency, copper (Cu)-based materials have shown great potential as electrocatalysts for the NO₃^– reduction reaction (NO₃^–RR) to NH₃. In this review, we provide a comprehensive summary of the fundamental principles underlying nitrate reduction over Cu-based electrocatalysts and discuss various strategies to enhance the performance of NO₃^– reduction, including facets, morphologies, size, surface functionalization, compositional engineering, and defect engineering. We also delve into the relationship between the electrocatalytic performance and structure characteristics of electrocatalysts and thoroughly examine the reaction mechanism involved in NO₃^–RR. Furthermore, we highlight the existing challenges and prospective paths forward in this area of study. This review offers valuable insights and guidance for the strategic design and optimization of Cu-based electrocatalysts for NO₃^–RR applications.