Photoelectrochemical property of the BiOBr-BiOI/ZnO heterostructures with tunable bandgap

Layered BiOBr-BiOI composites with tunable bandgap were deposited onto ZnO nanowire arrays by spin-coating. The prepared BiOBr-BiOI/ZnO heterostructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible absorption, and photoelectrochemical response. The bandgap of the BiOBr-BiOI can be tuned by varying the ratio of BiOBr/BiOI. The BiOBr-BiOI composites were proved to be n-type semiconductors, which serve as sensitizers in the BiOBr-BiOI/ZnO heterostructures. BiOBr-BiOI/ZnO heterostructures show much higher visible light photoelectrochemical activity than ZnO nanowire arrays because of the visible light absorption of BiOBr-BiOI and the formation of heterojunction between BiOBr-BiOI and ZnO, which reduces the recombination of photogenerated electrons and holes. In addition, the bandgap of BiOBr-BiOI directly affects the photoelectrochemical performance of the BiOBr-BiOI/ZnO heterojunctions. The smaller bandgap of the BiOBr-BiOI is, the more visible light is absorbed and the higher photoelectrochemical performance of the BiOBr-BiOI/ZnO heterojunctions achieves. The BiOBr-BiOI/ZnO heterostructures can be developed for application in water splitting and other optoelectrical devices.