Multifaceted Advances in TiO₂-Based Photocatalysts for PFAS Degradation: A Critical Review of Mechanisms, Modifications, and Challenges

Abstract

The global persistence of per- and polyfluoroalkyl substances (PFAS) poses significant environmental and human health risks, driving regulatory action and intensified research into effective remediation strategies. Photocatalysis has emerged as a promising, sustainable approach for PFAS degradation via light-driven redox processes. Titanium dioxide (TiO₂) remains the benchmark photocatalyst due to its chemical stability, low toxicity, and strong oxidative potential; however, its practical application is limited by rapid electron-hole recombination and restricted visible-light absorption, which reduce efficacy against the robust carbon-fluorine bonds characteristic of PFAS. Recent advances focus on multifunctional TiO₂-based systems, including metal and nonmetal doping, carbonaceous composites, heterojunction hybrids, molecularly imprinted polymers, and integration with advanced oxidation processes, which enhance charge separation, light harvesting, selective adsorption, and reactive species generation. This review provides a critical comparative assessment of these strategies, highlighting mechanistic insights, comparative performance, and structure-activity relationships, while addressing challenges such as catalyst stability, matrix effects, and scalability. By consolidating current innovations and practical considerations, this work provides guidance for the rational design of efficient, scalable, and sustainable photocatalytic technologies for global PFAS remediation.