Engineering electrocatalytic activity via fluorine doping in carbonaceous and non-carbonaceous materials

Electrocatalysis plays a crucial role in modern electrochemical energy technologies by governing key reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), which support sustainable hydrogen production, fuel cells, and metal-air batteries. However, achieving high catalytic activity, selectivity, and long-term stability under severe operating conditions remains a significant challenge, inspiring the development of advanced catalyst design strategies. Fluorination has attracted increasing attention as an effective strategy for tuning the electronic structure, surface chemistry, and interfacial properties of electrocatalytic materials. Due to the remarkably high electronegativity of fluorine, the formation of polarized C-F or M-F bonds induces charge redistribution and surface reconstruction, and promotes the in situ generation of catalytically active oxide, hydroxide, or oxyhydroxide species. These effects accelerate reaction kinetics in electrochemical processes. Fluorine incorporation may also improve electrical conductivity by increasing charge-carrier density and controlling electronic states near the Fermi level, while enhancing electrolyte penetration, reactant diffusion, and effective gas release. This review analyzes more than 80 representative studies and provides a systematic overview of fluorination strategies across three major classes of materials: (i) carbon-based materials as metal-free electrocatalysts; (ii) carbon-based conductive supports for electocatalysts; and (iii) non-carbonaceous materials including metal sulfides, oxides, ferro-oxides, perovskites, and layered hydroxides. For each category, fluorination conditions, fluorine incorporation modes, and key governing factors are discussed alongside the resulting structural and electronic modifications. Finally, future opportunities in controlled fluorination and defluorination are highlighted as promising routes for surface-selective modification, defect engineering, and active-site generation, positioning fluorination as a versatile platform for rational electrocatalyst design and next-generation electrochemical energy technologies.