Synthesis and photocatalytic properties of electrodeposited bismuth oxyiodide on rutile/anatase TiO2 heterostructure

Bismuth oxyiodide (BiOI) modified rutile/anatase TiO2 heterostructure was fabricated by a three-step process. Anatase TiO2 sheet was first formed on fluorine-doped tin oxide (FTO) glass substrate. Rutile TiO2 nanorods were then grown on anatase TiO2 sheet via a hydrothermal process. BiOI was finally coated on the surface of hierarchical TiO2 film using an electrochemical deposition method. Photocatalytic tests on degradation of methylene blue (MB) in water indicated that BiOI modified hierarchical TiO2 film possessed an excellent photocatalytic activity superior to those of the monophase anatase and rutile TiO2 films, commercial P25 film and hierarchical anatase/rutile TiO2 film. The enhanced photocatalytic performance was probably attributed to the synergetic effects of strong visible light absorption and formation of heterojunctions by the interfaces in the BiOI/rutile TiO2/anatase TiO2/FTO structure, which promoted efficient separation of photoinduced electron-hole pairs. In addition, the main active species during the degradation were confirmed to be hydroxyl radicals and superoxide radicals.