Enhanced Electrochemical Dehalogenation via Direct Electron Transfer on Pd/Ti₄O₇ Flow Cathode

Electrochemical dehalogenation is a promising approach for removing persistent halogenated organic pollutants from water, but its practical application is often constrained by limited mass transfer and high energy demand in conventional batch reactors. Here, we report a self-separating flow cathode system using Pd-loaded Ti₄O₇ microparticles (Pd/Ti₄O₇), integrated with a porous Ti filter that enables in situ particle retention and recycling. With an optimized Pd loading of 0.5 wt %, the system achieved 93- and 13-fold faster diclofenac (DCF) dechlorination than systems without Pd/Ti₄O₇ and with Ti₄O₇ alone, respectively, while significantly reducing predicted biotoxicity. Efficient dehalogenation was further demonstrated for multiple chlorinated organic pollutants. Direct electron transfer (DET), rather than atomic hydrogen-mediated reduction, dominates the dehalogenation pathway, which confers strong resistance to common water matrix interferences. A single-pass system removed 99% of DCF from municipal wastewater within 7 min at an energy cost of 0.26 kWh·m^-3, comparable to or lower than state-of-the-art technologies. Collectively, these results establish Pd/Ti₄O₇ self-separating flow cathodes as a robust and scalable platform for electrochemical dehalogenation, while highlighting remaining challenges related to material cost and life-cycle impacts.