A Review of Advanced Nanomaterials for Electrochemical Nitrate Reduction to Ammonia

Ammonia (NH₃) is essential for global agriculture, chemical synthesis, and emerging as a sustainable energy vector. Conventional Haber–Bosch production, relying on fossil-derived hydrogen, is energy-intensive and a major source of CO₂ emissions. Electrochemical nitrate reduction (e-NO₃RR) has emerged as a promising alternative, offering the dual advantage of mitigating nitrate pollution while enabling sustainable NH₃ synthesis under ambient conditions. This review critically examines recent progress in electrocatalyst design across diverse classes, including carbon-based frameworks, non-noble and noble metals, metal oxides, and multifunctional composites. Advanced strategies such as defect engineering, electronic structure modulation, interfacial tuning, and hybridization are highlighted for their roles in enhancing activity, selectivity, and operational stability. The influence of electrolyte composition, electrode architecture, local reaction microenvironments, and competing pathways is systematically analyzed. Mechanistic insights obtained from in-situ characterization and density functional theory (DFT) calculations are integrated to guide rational catalyst development. Challenges in maximizing nitrogen conversion efficiency, minimizing side reactions, and ensuring long-term durability are discussed, alongside perspectives on system-level integration and scalability. By unifying materials innovation with mechanistic understanding, this review provides a strategic roadmap for advancing e-NO₃RR as an efficient, sustainable, and industrially viable platform for NH₃ production.