Efficiently complete degradation of 2,4-DCP using sustainable photoelectrochemical reduction and sequential oxidation method

Halogenated organic compounds (HOCs) like chlorophenols (CPs) are one of persistent organic pollutants in environment, and it is an urgent issue to remove HOCs efficiently because they are detrimental to aquatic organisms and human beings. Electrocatalytic hydrodechlorination (ECH) technique has been widely studied to deal with chlorophenols. However, litter attention has been paid to the further treatment of the dechlorination product phenol. Meanwhile, photoelectrocatalysis is regarded as a promising method for contaminants elimination and water splitting using inexhaustible solar energy. Therefore, this study proposed a photoelectrochemical reductive hydrodechlorination and sequential oxidation method for thorough degradation of 2,4-dichlorophenol (2,4-DCP) using WO₃/Mo-doped BiVO₄ as photoanode and Pd/Ni foam as cathode. Several factors such as Pd-loading amount, initial pH, overpotential, and Cl⁻ that would influence the efficiency of 2,4-DCP hydrodechlorination and phenol oxidation have been investigated in detail. The 2,4-DCP could be completely hydrodechlorinated to phenol, and removal efficiency of the obtained phenol reached ~45% for 4 h reaction under optimized conditions. Additionally, there was no secondary chlorinated pollutant generated during the oxidation process even though the existence of Cl⁻. Lastly, the possible mechanism and degradation pathway were also explored based on LC-MS. This study proposed an efficient and environmental-friendly technique for complete degradation of chlorophenols, which might be also suitable for other HOCs and would be industrialized with the help of further studies.