Electrocatalytic dechlorination of 2,4-dichlorophenoxyacetic acid using a Pd-Co3O4/Ni foam electrode: Influencing factors and possible environmental applications

A hybrid electrode comprised of Pd and Co3O4 supported on Ni foam (Pd-Co3O4/Ni foam) was applied toward the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D). The effects of the reaction condition, such as Co3O4 and Pd loading, current density, initial concentration of 2,4-D, temperature and dissolved anions, on the electrochemical dechlorination process were investigated and interpreted based on an indirect reduction mechanism via active atomic H*. The optimal Pd and Co3O4 loading were determined to be 0.47 and 0.51 mg/cm(2), respectively. A highest current efficiency of 12.10% was obtained at a current density of 1.50 mA/cm(2), an initial 2,4-D concentration of 50 mg/L and reaction temperature of 298 K, and the apparent activation energy of 2,4-D dechlorination by the Pd-Co3O4/Ni foam electrode was calculated to be 42.33 x 10(3) J/mol. In addition, dissolved anions such as S2-, SO32- and NO(3)(- )suppress the catalytic activity, whereas HCO3- and Cl- have a negligible effect on the reaction process. The Pd-Co3O4/Ni foam electrode can also be applied to the dechlorination of 2,4-D in natural water bodies as well as other chlorinated organic compounds, such as chlorophenols.