Efficient degradation of perfluorooctanoic acid by solar photo-electro-Fenton like system fabricated by MOFs/carbon nanofibers composite membrane

A solar photo-electro-Fenton like (SPEF) system constructed by MOFs/carbon nanofibers composite membrane (MOFs/CNF) was proposed for the efficient degradation of perfluorooctanic acid (PFOA). The bifunctional catalytic cathode, MOFs/CNF, was fabricated by solvothermal growth of Fe/Co bi-metal MOFs on CNF which synthesized from carbonization of electrospun PAN fibers, and exhibited both extraordinary photo-catalytic and electro-catalytic abilities. During the degradation, H2O2 was continuously generated on-site through the 2-electron pathway of ORR, and further be quickly photo-catalyzed to produce •OH on MOFs/CNF. Moreover, PFOA was not only be degraded effectively and rapidly (degradation efficiency of 99% in 120 min), but also highly mineralized as revealed by the total organic carbon removal efficiency reaching 91% in 120 min. The possible mechanism for PFOA mineralization was proposed on the basis of the intermediate analysis and illustrated by the valence state change of Co and Fe on MOFs, as determined through XPS before and after degradation. The EPR analysis of •OH with or without solar light radiation further confirmed the enhanced solar photo-electro-catalysis compared to common electro-Fenton process.