Transition metal single-atom electrocatalytic reduction catalyst for nitrate to ammonia

Nitrates in aqueous solutions cause significant environmental stress due to their high stability and persistent accumulation. The electrocatalytic nitrate reduction reaction (NO3RR) is considered to be the best option for nitrate reduction in wastewater due to its high reliability and efficiency. The catalyst directly influences the reaction efficiency of nitrate removal and is considered one of the most critical factors. Single-atom catalysts (SACs) are notable for their high atom utilization, activity, and selectivity in nitrate reduction. This review provides a comprehensive discussion of the design, characterization, synthesis methods, and application of single-atom electrocatalysts for transition metals. The reaction mechanism of electrocatalytic nitrate reduction is summarised. Advances in experimental and theoretical studies on Cu, Co, and Fe catalysts are presented. The effects of various factors such as catalyst type, electrolyte side effects, pH, and overpotential on the catalytic activity and NO3RR are analyzed. Finally, strategies for performance modification of electrocatalytic nitrate reduction catalysts are summarised and the main challenges and opportunities for future research on single-atom electrocatalysts are presented. The performance enhancements summarised in this review will provide valuable insights into the design and fabrication of novel electrocatalysts for the efficient and green nitrogen cycle of single-atom electrocatalyst-catalyzed nitrate.