High-efficiency and low-energy hydrophilic cathode for heterogenous electro-Fenton wastewater purification

In this study, Cu was embedded within a carbonaceous layer via a sol-gel method, and the cathode’s conductivity was optimized at different carbonization temperatures. A hydrophilic cathode (Cu 4 -Fe@CTS/Ni foam) was fabricated using a tablet compression method. This cathode was employed in a heterogeneous electro-Fenton system to degrade 200   mg/L of fulvic acid (FA), enabling an assessment of its electro-Fenton performance. After 3.5   hours of operation, the cathode achieved an 82% of Chemical oxygen demand (COD) removal and a 73% of Total organic carbon (TOC) removal with an exceptionally low energy consumption of 21.34 kWh/kg COD. This high efficiency was attributed to the absence of excessive Polytetrafluoroethylene (PTFE) in the electrode fabrication, which significantly enhanced direct contact between the electrode, reactants, and electrolyte. Water contact angle measurements confirmed that the electrode remained hydrophilic during electrolysis. Mechanistic insights into organic pollutant degradation under hydrophilic conditions were elucidated through multiple characterization techniques. Unlike conventional electro-Fenton cathodes that require substantial PTFE incorporation to form a hydrophobic layer and forced aeration to supply oxygen for H₂O₂ generation, this cathode directly utilized dissolved oxygen in water to produce H₂O₂ under non-aerated conditions. The hydroxyl radicals responsible for organic pollutant degradation were catalytically generated by low-valence transition metals immobilized on the cathode surface. After five consecutive cycles, the degradation efficiency exhibited only a slight decline to 72%. These findings highlight the potential of this approach in advancing the practical application of heterogeneous electro-Fenton technology.