Synthesis And Photocatalytic Properties Of Bismuth Based Heterojunction Photocatalyst

With the development of global industry, environment pollution was becoming more and more serious. Subsequently, photocatalytic technology was used to solve the problem of environmental pollution. However, traditional photocatalyst can only be excitated by ultraviolet light, due to its wide band gap, such as TiO₂. It can't meet the practical applications of photocatalysis. Developing the visible light catalyst is particularly important. In addition, the photocatalytic activity of the pristine semiconductor was limited, due to the rapid recombination of photogenerated electrons and holes. Hence, in this dissertation, we developed a novel and simple method namely ionic liquid assisted ultrasonic method to prepare bismuth-based heterojunctions photocatalysts at room temperature. The detail research contents were discussed as follows:1. The BiOI/BiOCl composites with high photocatalyitic and adsorption ablities were prepared via a facile ionic liquid assisted ultrasonic method in several hours at room temperature. The BiOI/BiOCl composites with different contents can be conveniently synthesized via changing the amount of 1-ethyl-3-methylimidazolium iodide precursor during the preparation process. Photocatalytic results suggest that the obtained BiOI/BiOCl composite with 40% BiOI has the highest photoactivity for the degradation of rhodamine-B and quinoline blue under visible light irradiation. Moreover, the first-principle investigation was carried out to explicate the impact of the composite electronic structures on the photocatalytic abilities.2. A simple method namely ionic liquid assisted ultrasonic method was developed to prepare BiOCl/m-BiVO₄ heterojunctions in one step at room temperature. Through this method, BiOCl/BiVO₄ heterojunctions with different contents of BiOCl can be conveniently synthesized via the simple change of the amount of 1-butyl-3-methylimidazolium chloride [EMIM]Cl. X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy were used to demonstrate the structures of the as-prepared BiOCl/m-BiVO₄ heterojunctions. And the morphologies were characterized via scanning electron microscopy and transmission electron microscopy. The photocatalytic activities of the as-synthesized BiOCl/m-BiVO₄ heterojunctions were tested via the degradation of RhB under visible light irradiation and sunlight irradiation. The results suggest that BiOCl/m-BiVO₄ heterojunctions exhibited high photocatalytic activity and stability. Moreover, a possible photocatalytic mechanism has been proposed.3. Bi₂WO₆/BiOCl heterojunctions were synthesized via an ionic-liquid assisted ultrasonic irradiation at room temperature. Bi₂WO₆/BiOCl heterojunctions with different structures and properties were obtained just by changing the amount of [BMIM]Cl. The photocatalytic activities of Bi₂WO₆/BiOCl heterojunctions were evaluated by the degradation of rhodamine B and quinoline blue under visible light and sunlight irradiation. The results suggest that the as-prepared Bi₂WO₆/BiOCl heterojunctions have high photocatalytic activities for the degradation of organic dyes. Furthermore, a possible photocatalytic mechanism was proposed4. BiVO₄/BixOyI heterojunctions were synthesized via an ionic-liquid assisted ultrasonic irradiation at room temperature. The experimental results showed that different reaction time and different amount of reactants have significant impacts on the synthesis of products. With increasing of the reaction time and the amount of [EMIM] I, the impurity peak of Bi₂O₃ was observed. The photocatalytic activity of BiVO₄/BixOyI was studied by the degradation of rhodamine B and quinoline blue. The results suggest that the as-prepared BiVO₄/Bi₅O₇ I heterojunctions have high photocatalytic activities.