Oxygen Vacancy-Enriched Kaolinite/wo3-X Nanocomposites Exhibiting Enhanced Photo-Synergetic H2O2 Activation for Tetracycline Degradation Boosted by Hydroxyl Groups and Exciton

The efficient activation of H2O2 into hydroxyl and superoxide radicals with strong oxidizing power is an often overlooked but challenging issue. In this study, oxygen vacancy-enriched kaolinite/WO3-x composites (KW7) were prepared by a three-step method. Benefiting from abundant oxygen vacancies and surface hydroxyl groups, KW7 composite exhibited excellent photocatalytic H2O2 activation performance. The TC degradation experiments revealed that the KW7/H2O2/hv system exhibited the highest rate constant (k) of approximately 0.1561 min-1, which was 9.4, 5.3, and 5.1-fold greater than those of Kaol/H2O2/hv, WO3/H2O2/hv, and WO3-x/H2O2/hv, respectively. Furthermore, the k value was found to be 5.6 and 4.1 times higher than those observed in the KW7/ hv and KW7/H2O2 systems, respectively. The investigation into the underling mechanism of reactive oxygen species generation reveals that, the presence of a high concentration of oxygen vacancies in KW7 results in the increased number of defect energy levels, which leads to the predominance of excitonic effects-mediated O2 activation for the production of 1O2 within the photocatalytic system. On the contrast, in the photo-synergetic H2O2 activation system, due to the strong adsorption of H2O2 on the atoms around Ov, the exciton dissociation process is accelerated and the enhanced charge transfer process is dominant, which effectively activates H2O2 to generate a large amount of center dot OH and O2 center dot-. The present study provides valuable insights into the photocatalytic activation of H2O2 based on clay composites.