Synthesis strategies, characterization techniques, and prospects of defect-engineered single-atom catalysts for electrocatalysis

• This article reviews the application of defect engineering in the synthesis of SACs. • The regulatory effect of defect engineering on SACs performance is summarized. • The characterization techniques for defect-engineered SACs is analyzed. • This review provides guidance for the application of defect-engineered SACs. Defect-engineered single-atom catalysts (SACs) not only provide unique active sites for catalytic reactions but also enable precise regulation of defect types, spatial distribution, and concentration through defect engineering strategies, thereby optimizing reaction pathways and significantly enhancing catalytic efficiency and selectivity. However, the atomic-scale precision in constructing defect-engineered SACs while maintaining high stability of active sites remains a critical challenge in this field. This review systematically summarizes the construction strategies and advanced characterization techniques for defect engineering in SACs, with a particular focus on their superior performance in key energy conversion reactions, including the oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO 2 RR), and water electrolysis. By integrating the latest research advances, we thoroughly discuss the regulatory mechanisms of defect engineering on synthesis methodologies, performance enhancement, and structure–activity relationships in SACs. Furthermore, we prospectively outline future research directions for defect-engineered SACs, aiming to inspire innovative rational design principles for advanced defect-engineered SACs and accelerate their broader applications in high-efficiency energy conversion and storage technologies.