A novel Cu/Fe cathode prepared by a facile redox pathway for phenol degradation electrocatalytically via the electro-fenton assisted electro-chlorination process

Abstract

Electrochemical methods for treating phenolic wastewater have been widely studied, with most research focusing primarily on the anode, while the cathode has generally served as a counter electrode. This study aims to enhance the electrocatalytic process by developing a new Fe/Cu-based cathode using a simple redox method. We created a CuOCu@Fe-Fe₂O_3-x (0 < x < 1, combining Fe₂O₃ and FeO) electrode, referred to as CCFFO, to facilitate the electro-Fenton process without requiring additional H₂O₂ or Fe²⁺. In our electrolysis system with NaCl as the electrolyte for electro-chlorination process, phenol concentration was reduced from 100 mg/L to below 0.5 mg/L within 10 min. Optimal experimental conditions were determined by evaluating various parameters such as chloride electrolyte concentration, current density, electrode plate spacing, aeration, pH, and cathode types. Additionally, the role of chloride ions in phenol degradation was investigated through free radical quenching experiments. A 500-hour continuous flow experiment demonstrated the durability of the CCFFO cathode. GC/MS analysis identified intermediates formed during phenol degradation and the underlying catalytic mechanism was explored. The results indicate that the electro-chlorination process at the anode is the primary driver of phenol degradation, assisted by the electro-Fenton process on the CCFFO cathode. The CCFFO cathode effectively prevents the production of harmful by-products like perchlorate. The degradation efficiencies of chemical oxygen demand (COD) and total organic carbon (TOC) were 63.5 % and 80.25 %, respectively. Achieving a phenol degradation efficiency of 99.5 % within 10 min, the CCFFO cathode and electrolytic system show significant potential for wastewater treatment applications.