Enhanced electrocatalytic cathodic degradation of 2,4-dichlorophenoxyacetic acid based on a synergistic effect obtained from Co single atoms and Cu nanoclusters

Electrochemical reduction-oxidation is an environmentally-friendly process of degrading 2,4-dichlorophenoxyacetic acid (2,4-D). However, the design of electrocatalysts having reductive dechlorination and oxygen-specific active sites remains challenging. In the present study, catalytic cathodes were made from single Co atoms and Cu nanoclusters on nitrogen-doped carbon to enhance the degradation of 2,4-D through a synergistic mechanism. In this process, 2,4-D was dechlorinated on the Cu nanoclusters and then oxidized by ·OH radicals produced by the conversion of O2 on the Co atoms. The Cu nanoclusters served as both conductive bridges and 2,4-D adsorption sites to improve the electron transfer of the circuit and so accelerate the direct electron transfer associated with dechlorination. The single Co atoms first reduced O2 to H2O2 and then continuously catalyzed the decomposition of this H2O2 to form ·OH. As a result of the synergistic combination of these two effects, complete efficient dechlorination and 93.4% total organic carbon removal were achieved after 2 h. The kinetics constant for this reaction was determined to be 546.4 min−1·gmetal−1, indicating exceptional performance relative to previous reports of organic pollutant degradation. This study demonstrates the rational design of a bifunctional electrocatalyst and elucidates the electron transfer pathway and O2 activation mechanism associated with 2,4-D removal by electrochemical reduction-oxidation. This process is likely to have potential applications in the remediation of polluted water.