Electrodeposited Palladium Nanoparticles Enhancing Atomic Hydrogen-Mediated Electrochemical Recovery of Antimony

Electro-generated atomic hydrogen (H*) emerges as a potent species for water contaminant remediation, yet its short life span and confinement to the electrode–solution interface have restricted its broader application. Herein, we investigated the efficacy of palladium nanoparticles loaded onto a carbon cloth (hereafter the Pd/CC) electrode in stabilizing surface atomic H* and enhancing its electroreduction performance against toxic antimonite Sb(III). In comparison to the CC electrode, the Pd/CC electrode exhibited a 0.4 V increase in the onset potential of H+ electroreduction and a 5.5-fold improvement in electrochemically active surface area. Additionally, the Sb(III) removal rate constant and metallic antimony (Sb0) formation on the Pd/CC electrode surface were increased by 2.2- and 5.1-fold, respectively. Quenching experiments showed a 20% reduction ratio of atomic H* to Sb(III) at −1.0 V vs Ag/AgCl. Moreover, in situ trapping combined with semiquantification via electron spin resonance indicated that ca. 89% of atomic H* participated in Sb(III) reduction. The exposed crystal surface of Pd nanoparticles increased the electron transport capacity and atomic H* coverage on the electrode surface, which provided a large number of reduction sites for the direct and indirect reductions of Sb(III). Furthermore, accumulated reduction products were easily recovered in dilute H2SO4, rendering the electrode reusable. This work offers a practical and innovative solution for remediating heavy-metal-polluted wastewater and simultaneously recovering metal resources.