Synthesis, Analysis and Testing of Photoactive Heterojunction Semiconductors

Abstract

Photocatalysis is a growing area of study for a clean and renewable energy source, particularly for the purification of water and air. Researchers have studied the combination of various semiconductors to create photocatalysts with improved activities, but little has been reported in selecting semiconductors based on their extrinsic type – namely n-type or p-type. In this study, a BiOBr (p-type)-Bi2WO6 (n-type) heterojunction semiconductor was synthesized by the facile hydrothermal method. The new materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and diffuse-reflection spectroscopy (DRS). Degradation of Rhodamine B was employed to measure the photocatalytic activity of the as-prepared photocatalysts. On the basis of these techniques, the influence of the synthesis conditions (namely, hydrothermal reaction time and temperature) and the degradation conditions (namely, initial concentration, pH of the initial dye water and amount of catalysts dosage) have been explored and discussed. Furthermore, effect of concentrations of the dopants (the atomic ratio of BiOBr and Bi2WO6 were 1:4， 1:1， 4:1) was examined by measuring the degradation rate of Rhodamine B. Finally, the mechanism of the degradation process and the enhancement effect of heterojunction were also interpreted by analyzing the quenching effect of the scavengers and the band structure. Conclusively, this study shed light on the benefits of using heterojunction photocatalysts, and also on the importance of considering the semiconductor type when forming composite photocatalysts.