Electrochemical nitrate reduction for sustainable nitrogen and resource cycles: Progress and prospects

The accumulation of nitrates in water bodies caused by human activities poses a serious threat to human health and aquatic ecosystems. Electrocatalytic nitrate reduction reaction (eNO₃RR), as a promising green process, can convert nitrate (NO₃⁻) into high-value ammonia (NH₃), achieving the goal of “turning waste into resources”. However, eNO₃RR is a significantly complex process involving multiple influencing factors. Herein, we critically review the fundamental principles of NO₃⁻ reduction and selective NH₃ synthesis in eNO₃RR. The cathode engineering design for the NH₃ generation by eNO₃RR is systematically summarized, including a comparative analysis of precursor materials, such as precious metals, transition metals, and nonmetals. Moreover, the critical roles of reactor configuration, initial NO₃^- concentration, pH conditions, and competitive ions in determining the selectivity and yield of NH₃ from NO₃⁻ reduction are thoroughly analyzed. This review also evaluates the research on efficient and compatible ammonia recovery technologies, addressing the core post-reaction processing gap in the field. Finally, techno-economic assessments and key challenges of eNO₃RR are synthesized to examine the industrial potential and further implementation prospects.