Fabrication of TiO₂ nanosheets: Via Ti³⁺ doping and Ag₃PO₄ QD sensitization for highly efficient visible-light photocatalysis

Visible-light photocatalysis has attracted much attention in environmental remediation and sustainable energy utilization, however, it is still a great challenge to develop highly efficient and stable visible-light photocatalyst. Herein, we developed Ag₃PO₄ quantum dots (QDs) sensitized and Ti³⁺-doped TiO₂ nanosheets (NS) via a solvothermal/in situ precipitation method. The TiO₂/Ag₃PO₄ ratio in the composite was tuned from 3:1 to 1:4 to optimize the dispersion and size of Ag₃PO₄ QDs, and the best dispersed Ag₃PO₄ QDs with the smallest size (ca. 2 nm) was obtained for TA1:3. The characterizations confirm that abundant Ti³⁺ defects are introduced into TiO₂, and the interaction between Ag₃PO₄ QDs and TiO₂ NS is in the form of Ag-O-Ti bonds, which benefit the visible-light absorption and accelerates the charge separation. Moreover, the well-matched band structures drive the electrons to Ag₃PO₄ and holes to TiO₂ {001} faces, respectively. Therefore, TA1:3 shows a 1.7-fold, 1.4-fold and 5-fold higher activity than bulk Ag₃PO₄ in MO, phenol photodegradation, and PEC water splitting, respectively. In addition, the sample shows relatively high photostability. Thus, we believe that the rational design of heterostructures based on the matched band and abundant defects can fabricate the highly reactive photocatalysts.