Electrochemical Generation of Reactive Chlorine Species via Chloride Oxidation on –COOH-Modified Graphite Electrode to Attain Dye Degradation

In this study, we investigate the electrochemical performance of a carboxyl-functionalized pencil graphite (CFPG) electrode for chloride ion oxidation and its subsequent application in dye degradation. The graphite electrode was chemically modified using acetic acid to introduce –COOH functional groups, enhancing surface polarity and chloride adsorption capacity. Surface characterization by SEM, EDX, and XPS confirmed morphological changes and oxygen enrichment following functionalization. Electrochemical measurements demonstrated a positive shift in open circuit potential (OCP) and significantly enhanced chloride oxidation activity, as evidenced by cyclic voltammetry (CV) in 0.1 M KCl. The functionalized electrode facilitated the in situ generation of reactive chlorine species (RCS), with spectral features near ~240 nm consistent with HOCl/ClO− and a broader band around ~450 nm attributable to chlorine-derived intermediates rather than exclusively to molecular chlorine. These species played a central role in degrading structurally diverse dyes—Kenacid Green and Brilliant Green—via oxidative pathways. The results highlight the potential of low-cost, –COOH-modified graphite electrodes as effective platforms for the RCS-mediated electrochemical treatment of organic contaminants.