Reusable standalone carbon photocatalyst for a complete and fast photodegradation of PFOA to fluorine ions under solar-simulated illumination

Per- and polyfluoroalkyl substances (PFAS), such as perfluorooctanoic acid (PFOA), pose significant risks to health and the environment due to their chemical resistance. Here, we compare the photocatalytic performance of standalone carbon photocatalysts based on diamond nanomaterials. We demonstrate the complete mineralization of PFOA under solar-simulated illumination using highly crystalline hydrogenated milled nanodiamonds (H-MND). Mechanism investigations reveal two distinct degradation pathways: chain-shortening and defluorination reaction through F/OH substitution which appears specific to H-MND and absent in other types of nanodiamonds. This selectivity is attributed to the unique negative electron affinity of H-MND and their enhanced surface hydrophobicity. Notably, PFOA photodegradation in presence of H-MND arises efficiently under 300–400 nm illumination, deep UV (254 nm) only accelerating the process. Under comparable conditions, H-MND outperforms conventional standalone photocatalysts, even in aerobic environments and under solar-type irradiation. These findings highlight the potential of H-MND to serve as an effective solution for PFAS remediation, whether used as a simple and reusable standalone photocatalyst or integrated into more advanced hybrid systems.