Electrochemical defluorination of PFAS from the perspective of electron fate: Input, partitioning, and competition

Per- and polyfluoroalkyl substances (PFAS) are highly resistant to transformation because of the exceptional strength of the C-F bond. The limitations of electrochemical PFAS degradation are largely governed by the interplay among multiple reaction pathways and electron-transfer processes at the electrode-electrolyte interface. In many cases, inefficient electron utilization resulting from electron redistribution and competition significantly limits PFAS conversion. In this work, PFAS electrochemical conversion is systematically interpreted through the lens of electron fate and generalized into a three-stage process: electron input, electron redistribution, and electron competition. From the perspective of electron fate, PFAS transformation can be interpreted as three coupled processes: electron input, electron partitioning, and electron competition. The overall degradation efficiency ultimately depends on how effectively electrons are delivered to, retained within, and utilized by PFAS transformation pathways. Collectively, these coupled processes prevent efficient and selective utilization of electrons for PFAS transformation, thereby accounting for the intrinsically high energy demand and low mineralization efficiency of electrochemical PFAS treatment. These observations indicate that improving PFAS degradation requires not only increasing electron supply but also regulating the destination of electrons after they enter the electrochemical system. Accordingly, electrode materials should be redefined not as passive conductors, but as active regulators of electron pathways, capable of directing electron transport and selectively releasing electrons through rational interfacial and energy-level engineering. This framework provides a unified electron-scale perspective for both oxidative and reductive PFAS transformation and offers a new theoretical basis for overcoming the efficiency and selectivity limitations of electrochemical treatment.