Activation of O2 within confined ultramicropores of carbon electrocatalyst for enhanced electrochemical oxidation of water contaminants

Electrochemical oxidation is effective for water decontamination, but its large-scale application is constrained by high energy demands. This work addresses this challenge by developing an ultramicroporous carbon (UMC) electrocatalyst to effectively activate molecular oxygen (O₂) for assisting the electrochemical oxidation of contaminants. Participation of O₂ switches the electrochemical oxidation pathway of 2,4-dichlorophenol from polymerization to degradation, allowing its deep mineralization at low potentials. Experimental findings and density functional theory (DFT) calculations attribute the UMC’s catalytic activity to the synergistic sp²-carbon conjugation and ultramicroporous structure. In the confined space of ultramicropores, O₂ convert into •OH by capturing electrons from the sp²-conjugated carbon wall. The ultramicropores supplies an inner surface exclusively available for O₂ activation, and the confinement effect enhances O₂ adsorption to the sp²-conjugated carbon wall and interfacial electron transfer. Taking advantage of the UMC electrocatalyst, the air-enhancing strategy reduces the energy consumption for electrochemical oxidation of phenolic compounds by over 50 %, and demonstrates stability across broad pH and real water conditions. These findings open up new opportunities for designing efficient O₂ activators towards more energy-efficient and less wasteful electrochemical oxidation processes.