UV-induced photodegradation of PFAS using boron nitride: Structural compatibility, interfacial activation and...

Diverse per- and poly-fluoroalkyl substances (PFAS) can be effectively photodegraded over hexagonal boron nitride (hBN) under irradiation at 254 nm, but mechanistic understanding of interfacial activation and structural compatibility of PFAS remains insufficiently elucidated. Herein, four PFAS and three photocatalysts were selected to elucidate the key determinants influencing degradation of PFAS in UV/BN. From PFAS molecule insights, two perfluoroalkyl ether carboxylic acid (PFECA) exhibited worse photocatalytic degradation, compared to perfluorooctanoic acid, attributed to an interface steric hindrance of branched α-CF₃ moiety and substantial consumption equivalent of photogenerated hole to cleave terminal -COO^-. The transformation of intermediates and perfluoroalkyl radicals was more critical than the cleavage of 6:2 fluorotelomer sulfonic acid (FTS) for its defluorination. From material insights, interfacial binding of [PFAS-catalyst] complex was primary determinant governing PFECA degradation than photoelectric properties, comparing to UV/BiOCl. The enhanced nitrogen defects and >B-O sites on BN were observed during in-situ UV irradiation. In addition, ball milling approach was applied to amplify active sites, facilitating the interfacial binding and photodegradation of PFECA. Novel redox degradation pathways of C7 HFPO-TA and 6:2 FTS were proposed. This study highlighted the pivotal role of structural compatibility and proposed targeted modification strategies for BN to enhance photocatalytic degradation of diverse PFAS.