Degradation of 4-chlorophenol through in situ generation of reactive chlorine species in a Zn2CoOx electrocatalytic system

Chloride ion significantly impacts the degradation efficiency of organic pollutants in chemical industrial wastewater during electrocatalytic process, therefore utilization of Cl− to in situ produce reactive chlorine species (RCS) is desired for electrocatalytic degradation of pollutants. We developed a novel catalyst by incorporating Zn into CoOx (ZnnCoOx) as anode for the electrocatalytic removal of 4-chlorophenols (4-cp) in Cl−-containing wastewater. Characterization and electrochemical performance of ZnnCoOx catalysts indicated that Zn incorporation increased Co2+/Co3+ ratio, resulting in lattice distortion and the formation of oxygen vacancy (OV). Electrocatalytic experiments showed that Zn2CoOx (i.e., ZnCo = 2:1) had the highest electrochemical reactivity, and the 4-cp degradation rates (kobs) showed a positive correlation with OV. The identified reactive species involved in 4-cp degradation included O2•− and RCS. The formation mechanism of reactive species and the degradation pathways of 4-cp during electrocatalytic process using the Zn2CoOx anode were proposed. Overall, the developed ZnnCoOx catalyst as anode can utilize Cl− to in situ produce RCS and exhibit an effective performance on the 4-cp degradation in Cl−-containing wastewater.