Electrochemical reductive removal of trichloroacetic acids by a three-dimensional binderless carbon nanotubes/ CoP/Co foam electrode: Performance and mechanism

Numerous chlorinated disinfection by-products (DBPs) are produced during the chlorination disinfection of water. Among them, chloroacetic acids (CAAs) are of great concern due to their potential human carcinogenicity. In this study, effective electrocatalytic dechlorination of trichloroacetic acids (TCAA), a typical CAAs was achieved in the electrochemical system with the three-dimensional (3D) self-supported CoP on cobalt foam modified by carbon nanotubes (CNT/CoP/CF) as the cathode. At a 10mAcm-2 current density, 74.5% of TCAA (500μgL-1) was converted into AA within 100min. In-situ growth of CoP increased the effective electrochemical surface area of the electrode. Electrodeposited CNT promoted electron transfer from the electrode surface to TCAA. Therefore, the production of surface-adsorbed atomic hydrogen (H⁎) on CNT/CoP/CF was improved, further resulting in excellent electrochemical dechlorination of TCAA. The dechlorination pathway of TCAA proceeded into acetic acids via direct electronic transfer and H⁎-mediated reduction on CNT/CoP/CF electrode. Additionally, the electroreduction efficiency of CNT/CoP/CF for TCAA exceeded 81.22% even after 20 cycles. The highly efficient TCAA reduction performance (96.57%) in actual water revealed the potential applicability of CNT/CoP/CF in the complex water matrix. This study demonstrated that the CNT/CoP/CF is a promising non-noble metal cathode to remove chlorinated DBPs in practice. Environmental Implication The contamination of chloroacetic acids (CAAs) has drawn great public concern because of their potential carcinogenicity to humans. Electrochemical dechlorination is an efficient method for CAAs removal. Herein, a novel 3D binderless CNT/CoP/CF cathode was constructed and exhibited excellent performance for the electrochemical reductive dechlorination of CAAs with trichloroacetic acids (TCAA) as the target pollutant, and the nontoxic end product acetic acid was successfully obtained. Moreover, the long-term stability of CNT/CoP/CF and the highly efficient TCAA reduction performance in actual water revealed the potential applicability of CNT/CoP/CF in complex water matrices.