Selective activation of peroxymonosulfate to singlet oxygen by engineering oxygen vacancy defects in TiCNT MXene for effective removal of micropollutants in water.

Defect engineering is an effective strategy to boost the catalytic activity of MXene towards heterogeneous peroxymonosulfate (PMS) activation for water decontamination. Herein, we developed a facile approach to fine-tune the generation of oxygen vacancies (OVs) on TiCNT crystals by Ce-doping (Ce-TiCNT) with the aim of mediating PMS activation for the degradation of micropollutants in water. By varying the dopant content, the OV concentrations of TiCNT could be varied to enable the activation of PMS to almost 100% singlet oxygen (O), and hence the effective degradation of sulfamethoxazole (SMX, a model micropollutant). Various advanced characterization techniques were employed to obtain detailed information on the microstructure, morphology, and defect states of the catalysts. The experimental results showed that SMX removal was proportional to the OVs level. Density functional theory (DFT) models demonstrated that, in contrast to pristine TiCNT, the OVs on 10%Ce-TiCNT could adsorb the terminal O of PMS, which facilitated the formation of SO as well as the generation of O. We further loaded the optimized catalysts onto a polytetrafluoroethylene microfiltration membrane and also demonstrated the efficient removal of SMX from water using a convection-enhanced mass transport flow-through configuration. This study provides new insights into the effective removal of micropollutants from water by integrating state-of-the-art defect engineering, advanced oxidation, and microfiltration techniques.