Surface chemical changes of polytetrafluoroethylene under sub-keV (10–500 eV) electron irradiation: An X-ray photoelectron spectroscopy analysis

Energy-dependent electron irradiation induces different surface modification mechanisms in polytetrafluoroethylene, ranging from deeper, multiple ionization at 500 eV to dissociative electron attachment (DEA)-dominated at 10 eV. • XPS reveals that sub-keV (10–500 eV) electrons induce surface chemical changes in PTFE. • Progressive defluorination (CF 2 → CF 3 → CF → C–CF) occurs with higher electron energies. • Lower-energy electrons (10 eV) may promote dissociative electron attachment (DEA) processes and enhance decomposition efficiency. • Results provide insight into degradation mechanisms and the potential role of sub-keV electrons in PFAS decomposition. Per- and polyfluoroalkyl substances (PFAS) are a significant environmental concern because of their extreme persistence. High-energy (keV-MeV) irradiation has the potential to cause complete PFAS decomposition; however, the surface chemical changes induced by sub-keV electrons remain poorly understood. In this study, we investigated sub-keV (10–500 eV) electron-induced surface chemical changes in polytetrafluoroethylene (PTFE, C n F 2n ), the simplest solid PFAS polymer, using X-ray photoelectron spectroscopy (XPS). At 500 eV, electron irradiation induced extensive ionization-driven reactions within the surface region, resulting in pronounced defluorination and backbone rearrangements of the polymer chains. The CF 2 component decreases while CF 3 , C–F, and C–CF species sequentially emerge, and the fluorine-to-carbon (F/C) ratio declines from 1.9 to 0.6 after 4 h of irradiation. At 70 eV, ionization-driven surface degradation of PTFE was milder than that observed at 500 eV. Even at 10 eV, irradiation induced both ionization and dissociative electron attachment (DEA), making its efficiency higher than that of 70 eV irradiation. These results provide direct experimental evidence that clarifies the role of sub-keV electrons in PFAS degradation, indicating the potential for using sub-keV electrons for controlled surface modifications.