Facile synthesis of TiO2/Ag3PO4composites with co-exposed high-energy facets for efficient photodegradation of rhodamine B solution under visible light irradiation

In this study, TiO2/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 preparedviahydrothermal treatment of the exfoliated [Ti4O9](2-)/[Ti2O5](2-)nanosheet solutions at desired pH values. The Ag(3)PO(4)microcrystal with different morphologies was preparedviathe 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 TiO2/Ag(3)PO(4)heterostructures. The apparent rate constant of the pH 3.5-TiO2/Ag(3)PO(4)composite was the highest at 12.0 x 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-TiO2/Ag3PO4(10.5 x 10(-3)min(-1)), pH 7.5-TiO2/Ag3PO4(10.2 x 10(-3)min(-1)), pH 11.5-TiO2(8.8 x 10(-3)min(-1)), Ag3PO4(7.7 x 10(-3)min(-1)), blank sample (0.9 x 10(-3)min(-1)), and the commercial TiO2(0.5 x 10(-3)min(-1)), respectively. The pH 3.5-TiO2/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 TiO2/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 TiO2/Ag(3)PO(4)composite semiconductor photocatalysts with high energy crystal surfaces and high photocatalytic activity.