Built-in electric field activates endogenous redox couple for self-sustained Fenton-like reaction

Heterogeneous catalyst systems hold significant potential for advanced water treatment, yet achieving sustainable catalytic processes capable of continuously generating reactive species remains a substantial challenge. In this work, we develop an integrated oxidation-reduction system that synergistically couples peracetic acid (PAA) with H2O2 under the guidance of an interfacial built-in electric field (BEF). Through a programmable self-assembly approach, a porous nitrogen-doped carbon (NC) layer encapsulating Co/CoO heterojunction was constructed. Experimental and theoretical results confirm that strong electronic coupling between metallic Co and semiconductor CoO spontaneously generates a robust BEF. This field not only optimizes the electronic configuration to enhance PAA adsorption and activation, but also enables the selective adsorption of H2O2 from the mixed oxidant solution. The adsorbed H2O2 acts as an electron donor to sustain the Co(II)/Co(III) redox cycle, facilitating continuous reactive oxygen species (ROS) generation for approximately 120 min. The system demonstrates exceptional catalytic performance, achieving high contaminant removal rate constants (0.3 to 0.6 min-1) with an ultralow catalyst dosage of 15 mg L-1 and significantly improved PAA utilization efficiency. This BEF-mediated “dual-enhancement” strategy offers a sustainable and efficient route for water purification by enabling high oxidant utilization while minimizing catalyst consumption. A Co/CoO@NC catalyst with an interfacial built-in electric field can activate the endogenous PAA-H₂O₂ redox couple, establishing a self-sustaining catalytic loop that overcomes the activity-stability trade-off in advanced oxidation processes.