Electrochemically Activated Peroxymonosulfate on CeO₂/Sulfur-Doped Graphitic Carbon Nitride for Degradation of Tetracycline

Tetracycline (TC) is a class of broad-spectrum antibiotics which is difficult to degrade under natural conditions due to its stable molecular structure. A sulfur-doped g-C 3 N 4 decorated with CeO 2 nanoparticles (CeO 2 /2CNS) was synthesized as a composite catalyst for the electrochemical (EC) activation of peroxymonosulfate (PMS) to degrade TC. Degradation experiments revealed synergistic effects between CeO 2 and CNS, with the EC(CeO 2 /2CNS) + PMS system achieving the highest TC removal efficiency of 78.1% within 60 min, outperforming individual components and systems without EC. The first-order kinetic degradation constant was 2.1 and 3.6 times higher than those of CeO 2 and CNS, respectively. Moreover, CeO 2 /2CNS demonstrated excellent reusability, and the activity can be partially recovered by sintering the used electrode. The remarkable activation performance can be attributed to the combination of CeO 2 and CNS, which provides sufficient active sites and an enhanced electron transfer process. The PMS activation mechanism was explored by chemical quenching experiments, electron spin resonance analysis, and electrochemical studies. Singlet oxygen ( 1 O 2 ) was identified as the dominant species, while surface-bound radicals and electron transfer contributed marginally. This work provides a sustainable strategy for low-toxicity catalysts of PMS activation, offering broad potential for organic pollutant treatment.