Preparation And Photoelectric Conversion Properties Of BiOI/TiO₂ Micro/Nano Composite Materials

Titanium dioxide (TiO2) has become a research hotspot in recent years due to its outstanding characteristics, such as low cost, nontoxicity, chemical inertness and long-term stability. However, TiO2 can only be excited by UV irradiation because of its large band gap energy of 3.2 eV. In addition, the quantum efficiency of TiO2can be decreased by the recombination of photoinduced electrons and holes. Therefore, it is of great significance to accelerate the generation and separation of photoinduced electron-hole pairs in TiO2 for further practical application.Bismuth oxyiodide (BiOI), an important II-VI semiconductor with a narrow band gap of 1.7-1.9 eV, has demonstrated excellent photocatalytic for the degradation of organic pollutants due to its unique optical properties and promising industrial applications in prior studies.In this article, three-dimensional mesoporous TiO2 was used to couple with BiOI to form a novel photoelectric functional micro/nano composite material. Main research results in this work can be summarized as following:1. A series of novel BiOI/mesoporous TiO2 photoanodes for solar cells were prepared, which were fabricated with BiOI attached onto a three-dimensional mesoporous TiO2 film by chemical bath deposition (CBD) method, displaying some excellent characteristics, such as low processing cost, easy fabrication, light scatter effect and environmental friendliness. The growth of BiOI particles can be controlled by varying cycles of deposition immersions. The mesoporous TiO2 with appropriate pore size made BiOI to be loaded more sufficiently and uniformly, and also can serve as light scattering layer. The Mesoporous TiO2-based solar cell sensitized by BiOI displayed good photovoltaic performance. Meanwhile, the photovoltaic performance of the solar cell was also optimized by adjust CBD cycles.2. A soft-chemical method was used to prepare BiOI-TiO2 heterostructures with different Bi to Ti molar ratios. Meanwhile, the photocatalytic activities of these BiOI-TiO2 heterostructures were evaluated on the degradation of methyl orange under visible-light irradiation which indicated that the photocatalytic activities of these BiOI-TiO2 heterostructures were much higher than pure BiOI and TiO2. These results revealed that the BiOI-TiO2 heterostructures can be used as a new type of visible-light-driven photocatalysts for practical applications.