Recent Progress in Halogen-Doped Single-Atom Catalysts for Electrochemical Reactions

Since the concept of single-atom catalysts (SACs) was first proposed in 2011, related research has grown exponentially, establishing SACs as a highly active research field. Compared to conventional supported nanoparticle catalysts, SACs have attracted significant attention due to their theoretically highest atomic utilization efficiency and tunable active sites. Halogen atoms, with their high electronegativity, possess strong electron-withdrawing ability, enabling them a powerful regulatory effect on the active sites. Although there are numerous comprehensive and high-quality reviews on SACs, specialized research on halogen-doped SACs is relatively scarce. Therefore, this article reviewed recent progress in halogen-doped SACs, categorizing them by the four halogen atoms: fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). We also discussed the application of halogen-doped SACs in several key electrochemical reactions commonly relevant to clean energy storage and conversion, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and CO2 reduction reaction (CO2RR), and elaborated on the corresponding reaction mechanisms. Finally, this paper presented prospects to promote the development of SACs with tunable catalytic activity.