Emerging Trends in Two-Dimensional Nanomaterials for Electrocatalytic Nitrate-to-Ammonia Conversion

Electrocatalytic nitrate reduction to ammonia (ENRA) has emerged as a promising strategy due to its dual functionality in wastewater treatment and sustainable ammonia synthesis. Two-dimensional (2D) nanomaterials offer the exposure of highly active sites, tunability of the electronic structure, and enhanced mass transfer capabilities, thereby optimizing the atomic-scale kinetics of the nitrate reduction reaction and improving the ammonia synthesis efficiency. This review provides a comprehensive overview of recent advances in the field of 2D nanomaterials. Initially, fundamental mechanisms are examined. Subsequently, the paper explores the advantages of 2D materials, including metallic variants (e.g., metals, metal oxides, metal hydroxides, metal carbides, metal nitrides, metal borides, and 2D-confined single-atom catalysts) as well as 2D nonmetallic materials, focusing on their roles in nitrate activation and proton-coupled electron transfer processes. Finally, this review provides a prospective development of 2D catalysts, addressing the challenges related to long-term stability under industrial-grade current densities and outlining potential avenues for future research in this area.