Tailoring the Delocalization State in Electrocatalysts for Efficient NO _<i>x</i> Reduction: Recent Advances and Perspectives

Electrocatalytic reduction of nitrogen oxides (NOx) into valuable chemicals and fuels is vital for environmental remediation and carbon–nitrogen cycle sustainability. Recent work has demonstrated that delocalization states tuning of the catalyst may enhance NOx reduction (NOxRR) by optimizing intermediate adsorption, cleavage, and electronic conductivity, thereby improving activity, selectivity, and stability. This comprehensive review details the fundamental definition, unique properties, and mechanistic role of delocalization states within the NOxRR pathway. It then synthesizes recent advances across the catalyst lifecycle: synthesis strategies, cutting-edge characterization techniques probing electronic structure, and diverse applications. Applications are systematically categorized into four key regulatory approaches: exploiting intrinsic material delocalization, modulation via tailored organic ligands, engineering through heteroatom doping and heterojunction formation, and external field activation using photo-, electric-, or magnetic fields. Finally, the review identifies key NOxRR delocalization engineering challenges (e.g., unclear dynamic evolution, imbalanced delocalization-activity-selectivity, poor catalyst scalability) and targeted solutions: (1) operando multicharacterization + machine learning-DFT; (2) ligand engineering + external fields for product-specific tuning. It aims to frame next-generation NOxRR catalyst design, advancing environmental remediation and carbon–nitrogen cycle sustainability.