From Waste to Wealth: Single-Atom Catalysts for Green Ammonia Synthesis via Nitrate Electroreduction.
The electrochemical reduction of nitrate (NO3 -) offers a green and sustainable approach for treating nitrogen-containing wastewater and is regarded as a promising alternative to the energy-intensive Haber-Bosch process. However, this reaction entails multielectron transfer and complex reaction pathways, and its efficiency is often hampered by competing side reactions such as the hydrogen evolution reaction, as well as challenges related to the safe storage and transport of products. These limitations underscore the urgent need to develop electrocatalysts that exhibit high activity, stability, and selectivity. Since their emergence, single-atom catalysts (SACs) have attracted extensive interest due to their exceptional atomic utilization efficiency and relatively low cost. To elucidate the structure-performance relationships and underlying catalytic mechanisms of SACs in nitrate electroreduction, this review summarizes recent advances in SAC-based electrocatalysts, highlighting various categories of single-atom materials and their corresponding design strategies. Finally, we outline future research directions for SACs in this field, with the aim of providing valuable insights and guidance for the rational design of efficient, low-energy, and environmentally benign electrocatalytic nitrate reduction systems toward practical industrial applications.