Enhanced electrocatalytic dechlorination of 2,4-dichlorophenoxyacetic acid on in situ prepared Pd-anchored Ni(OH)2 bifunctional electrodes: synergistic effect between H* formation on Ni(OH)2 and dechlorination steps on Pd

Abstract

The reductive dechlorination of chlorinated organic compounds (COCs) is very important to reduce the toxicity of waste effluents produced from pharmaceutical, electronics, dyestuff, pesticide, paper, and plastics industries. Electrochemical dechlorination as a green technology under mild reaction conditions is widely used in the reductive dechlorination of COCs using Pd as the electrode. Currently, the challenges of this method are the need to use large Pd loadings and the low dechlorination efficiency. Efforts were made in this work to reduce the loading of Pd and improve the efficiency using 2,4-dichlorophenoxyacetic acid (2,4-D) as a probe molecule for COCs in dechlorination. In this study, Pd-anchored Ni(OH)₂/Ni-foam bifunctional electrodes were prepared in situ and for the first time applied in the reductive dechlorination of COCs. The results indicate that the dechlorination efficiency of 2,4-D can be enhanced on Pd-anchored Ni(OH)₂/Ni-foam bifunctional electrodes even at a low Pd loading (<2 mg cm⁻²). A synergistic effect is found for 2,4-D dechlorination: H* formation on Ni(OH)₂ and dechlorination steps on Pd. The enhanced dechlorination efficiency might be related to the shortened transport route between Ni(OH)₂ and Pd active centers for H*.