Fe-based layered double hydroxides carbon cathode modulates oxygen reduction pathways and HO formation mechanism in electro-peroxone system

Electro-peroxone (EP) is an emerging technology that combines electrochemistry and O 3 to remove contaminants. However, conventional carbon cathodes primarily contribute to the synthesis of H 2 O 2 in the system, which may scavenge HO . Herein, a series of Fe-based layered double hydroxides (LDH) was loaded onto graphite felt cathodes to strengthen the removal of organic contaminants. The EP system with CuFe-LDH/GF cathode (EP-CuFe-LDH/GF) demonstrated the highest removal rate (91.2 % within 20 min) of oxalic acid (OA), a typical ozone-resistance substance, approximately twice that of the EP-GF system. HO was identified the main reactive species. A new pathway for O 2 reduction and the generation of HO was found. The loading of CuFe-LDH altered the reduction pathway of O 2 on the GF cathode from 2e − to 1e − or 4e − process. As a result, HO was produced by the combination of O 3 and O 2 − instead of O 3 and H 2 O 2 , which avoided the quenching of HO by H 2 O 2 and enhanced the removal of OA. Moreover, the breaking complexation by O 3 , cathodic O 3 reduction and metal-OH catalyzed O 3 processes also contributed to the HO formation. Furthermore, the system could efficiently remove OA across a broad pH range of 3.0 to 9.0, addressing the poor performance of conventional EP systems under acidic conditions. Overall, the finding of this significant mechanism advances the understanding of organic pollutants removal and broadens the potential applications of EP system.