Preparation of a Core-Shell-Like TiO_2/Bi_2O_3Heterostructure and Qualitative Analysis of the Function of the Heterojunction Region in the Photocatalytic Process

摘要

A core-shell-like heterojunction structure was successfully fabricated on films by coating nano-sized Bi_2O_3 dots with TiO_2. By changing the dot density of the Bi_2O_3 dot layer, the effect of the heterojunction size on the photocatalytic performance of the composite film was studied. The morphology, structure, and properties of the samples were investigated via different techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and photolumines-cence (PL). The optical transmittance spectra and the photocatalytic degradation capacity of these samples for Rhodamine B (RhB) were determined via ultraviolet-visible (UV) spectroscopy. It was found that the particle size and dot density of Bi_2O_3 dot layer could be regulated by controlling the evaporation rate and evaporation quality of Bi powder. The results showed that the composite film with a greater heterojunction region had a better photocatalytic degradation ability. In addition, the TiO_2/Bi_2O_3 film with a Bi_2O_3 dot density of 20/μm~2 degraded 81.4 RhB in 120 min, which showed improved photocatalytic properties compared to TiO_2 films. The high photocatalytic performance was attributed to the appropriate particle size of the dot layer and the large heterojunction region, which hindered the recombination of electron-hole pairs and provided a greater area for carriers to transfer. This work provides effective results and ideas for the preparation of heterojunction films.