Photo-Electrochemical Reduction of PFAS in Complex Water Matrices

Per- and polyfluoroalkyl substances (PFAS) pose significant environmental threats due to their persistence and toxicity. Compared with oxidative approaches and homogeneous chemical reduction methods, electrochemical reduction (ER) and photoelectrochemical reduction (PER) offer promising chemical-free alternatives without concerns regarding harmful byproduct formation. However, fundamental challenges remain regarding unfavorable PFAS adsorption and defluorination on electrode surfaces under cathodic potentials. This study introduces a novel PER approach utilizing Pd-decorated TiO ₂ cathodes, demonstrating exceptional efficacy in degrading perfluorooctane sulfonic acid (PFOS) under ambient conditions. Detailed operando characterization and density functional theory (DFT) calculations reveal a unique mechanism in which cathodic potentials remarkably enhance PFAS adsorption on TiO ₂ , facilitating subsequent defluorination via photo-generated energetic electrons from Pd active sites. This PER method achieves substantial PFOS removal and defluorination, surpassing previously reported ER and PER processes even in complex water matrices containing competitive organic and inorganic species. Additionally, the study presents practical single-chamber reactor configurations and scalable cathode designs, demonstrating effective mesoscale treatment of various PFAS in reverse osmosis concentrates (ROC) and aqueous film-forming foam (AFFF)-impacted solutions.