Durable Ti₄O₇ Heterojunction Composite Membrane Encapsulating N-Doped Graphene Nanosheets for Efficient Electro-Oxidation of GenX and Other PFAS in Fluorochemical Wastewater

Rational interfacial engineering design of an electrocatalyst, such as a heterojunction structure, can effectively enhance its catalytic activity. This study aims to address a critical challenge associated with the use of carbon material@Ti₄O₇ heterojunction composite electrodes for wastewater treatment─electrode stability over long-term operation. Herein, we report a highly stabilized interfacial engineering strategy, i.e., the use of conductive inorganic CeO₂ as a "cement" to firmly encapsulate N-doped graphene oxide nanosheets (N-GS) on the Ti₄O₇ surface. The defect-rich N-GS encapsulated on the Ti₄O₇ surface significantly enhances interfacial charge transfer. This enhancement results in the N-GS/CeO₂@Ti₄O₇ heterojunction composite electrode exhibiting excellent efficiency in the electro-oxidation of hexafluoropropylene oxide dimer acid (HFPO-DA or GenX). Furthermore, a flow-through N-GS/CeO₂@Ti₄O₇ reactive electrochemical membrane system effectively mineralizes other 35 PFASs in a real fluorochemical wastewater sample, achieving a high defluorination rate of 70-90% and exhibiting better performance in PFAS destruction and energy efficiency compared to the UV/KI-SO₃^2- process. Results of this study enhance our understanding of the electrochemical oxidation of PFAS and offer valuable insight into the design of stabilized Ti₄O₇ heterojunction composites. These findings are instrumental in advancing the development of effective treatments for PFAS-contaminated environments.