Photoelectrocatalytic Degradation Mechanism of Fluorinated Pollutants Using a Bilayer WO3 Photoanode: Synergistic Role of Holes and Hydroxyl Radicals

Abstract

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 VRHE) 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.