Perchlorate decomposition on rhodium nanoclusters supported on copper crystallite (RhxCu) electrode in an electrodialysis-assisted bipolar electro-reduction system (ED-ER)

Abstract

Perchlorate (ClO4−) contamination in the aquatic environments presents challenges for remediation due to its high solubility and chemical inertness. A bimetallic RhxCu/Ti was synthesized by incorporating rhodium (Rh) nanoclusters onto the copper crystallites on a titanium mesh substrate for electro-reduction of perchlorate ions. Characterization, which included voltammetry, Raman spectroscopy, and constant potential electrolysis, elucidated the reduction mechanism of perchlorate. A reversible phase transition of Rh(0)⇌ Rh(II) was found to be an effective electron mediator of adsorbed ClO4−, where the neighboring Cu sites were responsible for hydrogenation of chlorinated intermediates. The dispersity of Rh clusters was influenced by the Rh-to-Cu ratio, thereby enhancing the electrochemical reactivity. The bimetallic electrode with around 30 % Rh coverage, i.e., Rh0.3Cu/Ti, possessed superior removal and faradaic efficiency within a potential range of −0.6 V to −0.8 V (vs. Ag/AgCl, at pH 3), which were 95 % and 78 %, respectively. The electro-reduction (ER) and the associated electrodialysis (ED) divided using ion exchange membrane were demonstrated for the treatment of perchlorate wastewater. The electrical field applied by the ED unit drove the migration of ClO4− ions to the surfaces of Rh0.3Cu/Ti cathode, further improving the removal efficiency of perchlorate and lowering energy consumption.