Facile synthesis of TiO2/Ag3PO4 composites with co-exposed high-energy facets for efficient photodegradation of rhodamine B solution under visible light irradiation

摘要

In this study, TiO _(2) /Ag _(3) PO _(4) composites based on anatase TiO _(2) nanocrystals with co-exposed {101}, {010}/{100}, {001} and [111]-facets and Ag _(3) PO _(4) microcrystals with irregular and cubic-like polyhedron morphologies were successfully synthesized by combining hydrothermal and ion-exchange methods. The anatase TiO _(2) nanocrystals with different high-energy facets were controllably prepared via hydrothermal treatment of the exfoliated [Ti _(4) O _(9) ] ~(2?) /[Ti _(2) O _(5) ] ~(2?) nanosheet solutions at desired pH values. The Ag _(3) PO _(4) microcrystal with different morphologies was prepared via the ion-exchange method in the presence of AgNO _(3) and NH _(4) H _(2) PO _(4) at room temperature, which was used as a substrate to load the as-prepared anatase TiO _(2) nanocrystals on its surface and to form TiO _(2) /Ag _(3) PO _(4) heterostructures. The apparent rate constant of the pH 3.5-TiO _(2) /Ag _(3) PO _(4) composite was the highest at 12.0 × 10 ~(?3) min ~(?1) , which was approximately 1.1, 1.2, 1.4, 1.6, 13.3, and 24.0 fold higher than that of pH 0.5-TiO _(2) /Ag _(3) PO _(4) (10.5 × 10 ~(?3) min ~(?1) ), pH 7.5-TiO _(2) /Ag _(3) PO _(4) (10.2 × 10 ~(?3) min ~(?1) ), pH 11.5-TiO _(2) (8.8 × 10 ~(?3) min ~(?1) ), Ag _(3) PO _(4) (7.7 × 10 ~(?3) min ~(?1) ), blank sample (0.9 × 10 ~(?3) min ~(?1) ), and the commercial TiO _(2) (0.5 × 10 ~(?3) min ~(?1) ), respectively. The pH 3.5-TiO _(2) /Ag _(3) PO _(4) composite exhibited the highest visible-light photocatalytic activity which can be attributed to the synergistic effects of its heterostructure, relatively small crystal size, large specific surface area, good crystallinity, and co-exposed high-energy {001} and [111]-facets. The as-prepared TiO _(2) /Ag _(3) PO _(4) composites still exhibited good photocatalytic activity after three successive experimental runs, indicating that they had remarkable stability. This study provides a new way for the preparation of TiO _(2) /Ag _(3) PO _(4) composite semiconductor photocatalysts with high energy crystal surfaces and high photocatalytic activity.