Recently we found that hexagonal-phase boron nitride (hBN) can photo-catalytically oxidize and degrade perfluorooctanoic acid (PFOA), a persistent and toxic water contaminant, under 254-nm light (UVC) illumination. hBN is widely used as a lubricant for paints, cosmetics, etc. due to its chemical stability and surface hydrophobicity. It is considered chemically inert and an insulator due to its wide bandgap (~ 6 eV). To more fully understand the higher activity of hBN compared to TiO<sub>2</sub> reference photocatalyst, we studied the electronic band structure of hBN that accounts for structural defects in the material through materials characterization and density functional theory calculations. We find that certain structural defects introduce midgap states in the band structure that enable light absorption and photoexcitation. We also find the surface hydrophobicity of hBN to contribute to its enhanced photocatalysis via greater PFOA sorption, leading to more reaction of the photogenerated holes with PFOA than with water. Surface hydrophobicity appears to play a greater role in photocatalysis than previously assumed, suggesting directions to engineer catalysts that can degrade other per- and polyfluoroalkyl substances (the "forever chemicals").

Surface defects and hydrophobicity of boron nitride contribute to efficient PFOA photocatalytic oxidation

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.