Mechanism of Z-scheme BN/BiOI heterojunction for efficient photodegradation of perfluorooctane sulfonate (PFOS)

Abstract

Perfluorooctane sulfonate (PFOS) poses a significant threat to human health and ecosystems throughout its lifecycle because of its PBT-LRT properties. In this study, a Z-scheme photocatalyst BN/BiOI was developed and evaluated for its efficacy in photodegrading PFOS. Notably, after 2 h of reaction, 100 % removal of PFOS (k_obs = 1.278 h⁻¹) was achieved, alongside a 100 % desulfurization rate and a 45.40 % defluorination rate after 6 h. Comparing the BN/BiOI system to BN, the remarkable enhancement observed in BN/BiOI heterojunction can be attributed primarily to the efficient separation and reduced recombination rate of photogenerated electrons and holes. Insights from Electron Paramagnetic Resonance (EPR) analysis shed light on the roles of e^-, h⁺, •OH, and •O₂H radicals in the PFOS degradation process facilitated by BN/BiOI. The proposed mechanism for photocatalytic PFOS degradation by the BN/BiOI system underscores the initial breaking of the C-S bond. Moreover, BN/BiOI showcases its effectiveness in degrading perfluorocarboxylic acids (PFOA, TA, C7, and Gen-X) as well as perfluoro sulfonic acids (F-53B, F-53, and 6:2 FTS), highlighting its potential for treating not only PFOS but also other PFAS contaminants across a broad pH range. To the best of our knowledge, this study is the first to demonstrate the Z-scheme BN/BiOI heterogeneous photocatalytic degradation of PFOS.