Photoelectrocatalytic Degradation Mechanism of Fluorinated Pollutants Using a Bilayer WO ₃ Photoanode: Synergistic Role of Holes and Hydroxyl Radicals

Fluorinated organic pollutants pose significant environmental and health risks due to the high stability of C─F bonds, necessitating effective strategies for their degradation. Herein, we present a bilayer WO₃ photoelectrode (double-WO₃) incorporating an electron transport layer (ETL) and a hexagonal-monoclinic heterophase junction for PEC degradation of fluorinated pollutants. The double-WO₃ catalyst achieves a high photocurrent density (4.3 mA cm^-2 at 1.2 V_RHE) and nearly complete degradation (99.9%) of bisphenol AF (BPAF), 4-fluorophenol (4-FP), and pentafluorophenol (PFP), with 99.9% mineralization of PFP. Experimental and transient photocurrent (TPC) analyses confirm that the ETL-heterophase junction structure enhances electron extraction and surface reaction kinetics while minimizing electron-hole recombination. In this process, photogenerated h⁺ excites fluorinated pollutants, enhancing C─F bond susceptibility to ∙OH attack, which facilitates bond cleavage and subsequent oxidation into CO₂, H₂O, and F^-. This study offers a promising strategy for designing advanced PEC systems and effectively remediating persistent fluorinated contaminants.