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.