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.