Tailoring photocatalysts and elucidating mechanisms of photocatalytic degradation of perfluorocarboxylic acids (PFCAs) in water: a comparative overview

A perfluorooctanoic acid (PFOA), as the most important representative of perfluorocarboxylic acids (PFCAs), is environmentally persistent and bioaccumulative. Among treatment techniques for PFOA decomposition, photocatalytic degradation of PFOA has received considerable attention. A series of candidate photocatalytic materials, including TiO₂-, carbonaceous-, Ga₂O₃-, In₂O₃-based, etc., have been successfully proposed to eliminate PFOA. Overall, there are two types of mechanisms for photocatalytic degradation of PFCAs, including conventional mechanism and charge transfer mechanism. For a conventional mechanism, the mechanism of PFOA photodegradation over bulk TiO₂ via two pathways: photo-redox and β-scission. For the charge transfer mechanism, the PFOA degradation pathway in water-soluble H₃PW₁₂O₄₀ is mainly via charge-transfer excited complex ([PW₁₂O₄₀]^3−*). Finally, attention on critical challenges and prospects for photodegradation of PFOA are also intensified.