| Summary: | This study presents an electrolysis system utilizing a novel self-circulation process of sulfate (SO<sub>4</sub><sup>2−</sup>) and persulfate (S<sub>2</sub>O<sub>8</sub><sup>2−</sup>) ions based on a boron-doped diamond (BDD) anode and an activated carbon fiber (ACF) cathode, which is designed to enable electrochemical remediation of environmental contaminants with reduced use of chemical reagents and minimized residues. The production of S<sub>2</sub>O<sub>8</sub><sup>2−</sup> and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) on the BDD anode and ACF cathode, respectively, is identified as the source of active radicals for the contaminant degradation. The initiator, sulfate, is identified by comparing the degradation efficiency in NaSO<sub>4</sub> and NaNO<sub>3</sub> electrolytes. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed that the SO<sub>4</sub><sup>−</sup>· and ·OH generated on the ACF cathode are the main reactive radicals. A comparison of the degradation efficiency and the generated S<sub>2</sub>O<sub>8</sub><sup>2−</sup>/H<sub>2</sub>O<sub>2</sub> of the divided/undivided electrolysis system is used to demonstrate the superiority of the synergistic effect between the BDD anode and ACF cathode. This work provides evidence of the effectiveness of the philosophy of “catalysis in lieu of supplementary chemical agents” and sheds light on the mechanism of the generation and transmission of reactive species in the BDD and ACF electrolysis system, thereby offering new perspectives for the design and optimization of electrolysis systems.
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