Enhanced atomic H* utilization on urchin-like TiO₂-supported palladium nanoparticles for efficient electrocatalytic detoxification of chlorinated organics

Improving the utilization of hydrogen radicals (H*) is of great significance for effective Pd-mediated electrocatalytic hydrodechlorination (EHDC) in detoxifying chlorinated organic pollutants (COPs). However, the limited H* utilization by single Pd arises from its inadequate performance in adsorbing/activating COPs and inferior mass transfer of low-concentration COPs. In this study, an urchin-like yolk/shell TiO2 spheres with mesoporous structure are developed for supporting Pd nanoparticles (Pd/U-TiO2), which exhibits superior EHDC activity and selectivity for 2,4-DCP reduction. Notably, the prepared Pd/U-TiO2 catalyst achieves a mass activity of 4.2 min(-1) g(Pd)(-1) and a specific activity of 1.94 min(-1) mol(Pd)(-1) when detoxifying 50 mg/L of 2,4-DCP at -0.85 V, surpassing the most reported catalysts. Furthermore, the Pd/U-TiO2 catalyst consistently demonstrates higher H* utilization efficiency compared to single Pd, regardless of the 2,4-DCP concentration or reaction mode (batch or continuous-flow). This enhanced H* utilization efficiency is attributed to two key factors: the urchin-like and yolk/shell structure of U-TiO2 enhances the mass diffusion of 2,4-DCP, and the strong interactions between Pd and U-TiO2 generate electron-rich Pd species that enhance the adsorption and activation of COPs. Overall, this work highlights the synergistic effects of strong metal-support interactions and mass diffusion in enhancing atomic H* utilization. This study lays a significant experimental and theoretical foundation for designing efficient electrocatalysts for the detoxification of chlorinated organic pollutants and various other halogenated organic pollutants.