Mechanistic Insights into Sulfamethazine Degradation\nby Defect-Rich MnO<sub>2</sub>‑Activated Peracetic Acid

Manganese\n(Mn)-based oxides, mainly MnO<sub>2</sub>, have garnered\nsignificant attention in catalytic applications due to their superior\nredox properties and structural flexibility. However, their saturated\ncoordination structure presents challenges in achieving an enhanced\nperformance. Herein, a defective MnO<sub>2</sub> catalyst (MnO<sub>2</sub>-D) was constructed, and for the first time, it was proven\nto effectively activate peracetic acid (PAA) for the complete degradation\nof sulfamethazine (SMT). Compared to MnO<sub>2</sub> with a saturated\ncoordination structure (i.e., the perfect MnO<sub>2</sub> structure,\nMnO<sub>2</sub>-P), the MnO<sub>2</sub>-D catalyst exhibited a higher\nsurface electron density and abundant surface oxygen vacancies (OVs),\nsignificantly improving its catalytic activity. Experimental evidence\nrevealed that the OVs and Mn<sup>3+</sup> on the surface of MnO<sub>2</sub>-D were considered as the primary active sites and that the\nMnO<sub>2</sub>-D/PAA system followed a singlet oxygen (<sup>1</sup>O<sub>2</sub>)-dominated nonradical pathway. The MnO<sub>2</sub>-D\ncatalyst can maintain its activity with minimal interference from\ninorganic anions, humic acid, varying pH levels, and real water environments.\nIn addition, the MnO<sub>2</sub>-D/PAA system was efficient in mitigating\nthe toxicity of SMT and eliminating diverse micropollutants. This\nwork presents an enhancement strategy for constructing defect-rich\nmetal oxide catalysts to advance future water treatment technologies.