Neutral-pH Electrocatalysis for Nitrate Reduction to Ammonia: Toward Sustainable Nitrogen Management in Aquatic Systems

Anthropogenic disruption of the nitrogen cycle has led to pervasive nitrate (NO₃^-) contamination in aquatic systems, posing risks to environmental integrity and public health. Electrocatalytic nitrate reduction reaction (eNO₃^-RR) to ammonia (NH₃) offers simultaneous remediation and resource recovery under ambient conditions. However, most studies have mainly been conducted in strongly alkaline electrolytes for their high ionic conductivity and suppressed hydrogen evolution reaction, despite inducing corrosive degradation and scaling issues that limit practical deployment. Critically, the neutral pH characteristic of most natural and contaminated waters offers environmentally compatible conditions, spurring growing research interest in neutral media to bridge laboratory-to-field relevance. Given the absence of systematic understanding of neutral eNO₃^-RR, a timely and comprehensive review is urgently needed. This review provides a comprehensive synthesis of mechanistic understanding, catalyst development, and system-level advances specifically for neutral conditions. We summarize thermodynamic and kinetic insights into NO₃^--to-NH₃, outline the influence of environmental factors on mechanisms, evaluate strategies including doping, defect, phase control, interfacial engineering, microenvironment tuning, and surface reconstruction, and discuss recent progress in electrolyte optimization and reactor design. Eventually, application scenarios for neutral-pH eNO₃^-RR are discussed to bridge fundamental understanding with practical implementation, offering perspectives for its role in future sustainable nitrogen management.