Towards efficient photocatalytic degradation of organic pollutants in hierarchical TiO2/SnO p–n heterojunction under visible-light irradiation

Abstract

Preparation of a p–n heterojunction with hierarchical structure is of great significance for photocatalysis due to its large specific surface area, abundant active sites and increased charge separation rate. Herein, we designed the novel p–n heterojunction photocatalyst TiO2/SnO microflower (TiO2/F-SnO) with hierarchical architecture by decorating TiO2 nanoparticles on the surface of the SnO microflower via a simple hydrothermal route. Compared to pure TiO2 and TiO2/SnO with a microplate structure (TiO2/P-SnO), TiO2/F-SnO heterojunctions exhibited significantly enhanced photocatalytic performances for organics removal such as toluidine blue O (TBO) and methylene blue (MB) under daylight fluorescent lamp irradiation (350–800 nm). The improved performance was not only ascribed to the promoted charge transfer and separation efficiency induced by the formation of p–n junction, but also attributed to the larger specific surface area, sufficient active sites and stronger redox ability provided by the hierarchical microflowers. Moreover, after three photocatalytic cycles (24 h), the TiO2/SnO heterojunction still exhibited a stable photocatalytic activity. Finally, the photocatalytic enhancement mechanism for the TiO2/SnO heterojunction was proposed based on band alignments calculation and the active species trapping experiments.