还原助催化剂/Bi2MoO6复合体系的能带协同调控及其光催化烃类选择性氧化性能研究

The oxidation of hydrocarbons to produce aldehydes and ketones is an important way to produce bulk chemicals and fine chemicals. Photocatalytic reaction is the most ideal way of hydrocarbon conversion and utilization which is carried out under mild conditions. The uniqueness of photocatalytic oxidation of hydrocarbon is that the catalytic process requires the participation of holes and electrons. But it has the difficulty of the over-oxidation of desired products and the poor selectivity of the products which was caused by the strong oxidative ability •OH and O2- radicals derived from the holes and electrons. To solve this problem, this project intends to utilize a new type of composite photocatalyst constructed by reduction co-catalysts modified Bi2MoO6, realize a synergetic optimization of the valence band and conduction band simultaneously. The new catalyst leads to a high selective oxidation of the hydrocarbon by utilizing the holes and electrons, and avoiding the generation of •OH and O2- radicals. The effect of composition, structure and surface properties of reduction co-catalysts on the conduction band of Bi2MoO6, the reactivity and selectivity will be studied. To deeply understand the mechanism for the photocatalytic aerobic oxidation of hydrocarbons and the reaction pathway, the reactive species will be trapped and characterized. By theoretical calculation, construct gradually the way to adjust of the catalytic reaction pathway by the structure optimization of photocatalyst. This project would provide a theoretical basis and technology roadmap for promoting the environment-friendly, green utilization of hydrocarbon resources.

氧化烃类分子产生醛、酮等含氧化合物是生产大宗和精细化学品的重要途径。因反应条件温和，光催化反应是实现烃类化合物转化和利用的理想途径。光催化烃类氧化反应具有空穴和电子共同参与的优势，但光催化氧化过程中产生的强氧化性•OH和O2-自由基将导致目标产物过度氧化和选择性降低。本项目从光催化剂价带和导带位置的协同调控出发，以Bi2MoO6光催化剂为研究对象，其价带位置合适，避免生成•OH自由基；拟引入还原助催化剂，通过其调节半导体的导带位置，避免生成•O2-自由基，实现烃类分子的选择性氧化。研究还原助催化剂的组成、结构、表面性质对Bi2MoO6光催化剂导带位置的影响，探究其对反应活性和选择性的影响规律。通过活性中间体的表征和表面吸附物种的甄别，结合理论计算，揭示复合光催化剂中烃类氧化反应的路径和机理，开发出高效烃类选择性氧化的光催化体系。本项目的实施将为烃类选择性氧化反应提供技术路线和理论依据。

光催化选择性氧化烃类分子是一种理想的合成高附加值化学品的方式。构筑高活性和高选择性的光催化剂是实现光催化烃类选择性氧化反应的关键。本项目1）构筑了还原助催化剂/氧空位-双活性位点的钼酸铋催化剂，调节还原助催化剂的种类和负载量，实现还原助催化剂和氧空位的协同催化。在光催化苯甲醇氧化反应中，双活性位点的复合催化剂的活性约是含还原助催化剂或氧空位催化剂的5倍，获得99%苯甲醛的选择性。2）通过控制溶剂热合成中的pH值，构筑了暴露（010）和（001）晶面的钼酸铋催化剂。在光催化氧化甲苯反应中，暴露（010）晶面钼酸铋的活性是暴露（001）晶面钼酸铋活性的2.3倍。3）研究催化剂合成过程中煅烧的影响。相对于未煅烧的催化剂，煅烧后催化剂的乙苯氧化反应的活性和选择性均显著提升，且煅烧也能够有效的提升不同种类铋系半导体的活性。4）研究还原助催化剂对于钼酸铋性能的影响，发现不同种类的还原助催化剂均能提升乙苯氧化反应的活性和选择性，且还原助催化剂也能提升不同种类铋系半导体的活性。5）发展了一种利用机械能驱动的摩擦电等离子体克服半导体和底物能级不匹配的策略，有效的提升了CO2还原反应和CO氧化反应的活性。本项目的实施为理性的设计高效、高选择性的半导体基催化体系提供了一种有效的策略。