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

The superior electrocatalytic hydrodechlorination (EHDC) performance on Pd/U-TiO2 catalyst is attributed to the electron-rich Pd regulated by urchin-like yolk/shell TiO2 support, enhanced adsorption and activation of 2,4-dichlorophenol, faster mass diffusion behavior and high current efficiency toward EHDC. [Display omitted] •Pd supported on urchin-like yolk/mesoporous shell TiO2 (Pd/U-TiO2) is prepared.•Pd/U-TiO2 affords high efficiency and durability in EHDC of 2,4-DCP.•Pd/U-TiO2 affords a higher H* utilization efficiency of 48.6 % than single Pd.•U-TiO2 support boosts the mass diffusion of 2,4-DCP around Pd nanoparticles.•The pollutant adsorption and activation are enhanced on U-TiO2-supported Pd. 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 gPd-1 and a specific activity of 1.94 min−1 molPd-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.