Electrode–gas interface-driven dechlorination of gaseous chlorobenzene: Mechanistic asymmetry between reductive and oxidative pathways

Chlorobenzene (CB), a volatile and toxic halogenated compound, is a significant atmospheric pollutant emitted from industrial sources. This study investigates the electrochemical dechlorination of gaseous CB at the electrode–gas interface using a CuNi alloy foam electrode under both reductive and oxidative conditions in a PVA-SPP gel membrane-divided electrochemical cell. To enable gas-solid interaction, one half-cell operated without liquid electrolyte at ambient temperature and pressure. Electrochemical treatment was conducted at applied potentials of −1.2 V and +1.2 V for reduction and oxidation, respectively. The oxidative pathway yielded a CB removal capacity of 24.68 mg cm⁻² min⁻¹, while the reductive route achieved 15.98 mg cm⁻² min⁻¹. Gas chromatography–mass spectrometry identified benzene as a major intermediate in both cases, but its presence in the gas phase during reduction and on the electrode surface during oxidation reflects a mechanistic divergence. Chloride ion analysis indicated approximately ∼80% total recovery, with 62% retained on the electrode and membrane in the oxidative case versus only 28% during reduction. These findings confirm that oxidative dechlorination proceeds via a surface-confined redox mechanism, whereas the reductive process involve gas-phase intermediates. Overall, this study demonstrates that the CuNi electrode–gas interface enables effective electrochemical dechlorination of gaseous CB and provides mechanistic insight into the contrasting reductive and oxidative pathways.