面向选择性氧化反应的石墨烯/铁酸盐晶体光催化材料的结构设计与性能调控

Solar photocatalysis plays a very important role in the field of environmental treatment and renewable energy utilization. But the application of most semiconductor photocatalytic materials comes to a bottle-neck due to low photon conversion efficiency and poor reaction controllability. Therefore, it becomes imperative to explore the intrinsic factors influencing the activity and selectivity of the catalytic materials. According to that, new method for controlling and optimizing the properties of the catalytic materials would be created, and the application of photocatalytic processes in the field of organic synthesis would be broadened. In this project, a new perspective is brought forward on the basis of existing work to understand and design the photocatalytic materials from the matching of charge carrier mobility efficiency and surface-interface properties, which takes sufficient account of factors such as band gap, energy level and crystal match of different semiconductors along with the periodic arrangement of atoms and the anisotropy in ferrite semiconductor crystals. The doping of heteroatom in semiconductor and the combination of which with graphene is desired to control the correspondence and correlation degree between the photocatalytic properties and the charge carrier mobility efficiency together with the micro chemical environment of the catalytic system, thereafter to explore their influence law and mechanism on the performance of photocatalytic materials. In consequence, more effective tuning on the microstructure of the photocatalytic materials and their catalytic properties can be fulfilled. Moreover, the nano-sized catalysts can be magnetically separated and recycled easily, which would solve the bottleneck recycling problem in industrial engineering application of nanomaterials. The research results of this project are expected to provide scientific support for the design and expansion of novel photocatalytic materials and the creation of highly efficient catalytic reaction system.

太阳能光催化技术在环境治理和可再生能源领域有着非常重要的应用，但当前半导体光催化材料普遍面临着光子转化效率低和反应可控性差的瓶颈，迫切需要揭示影响催化材料活性和选择性的内在因素，建立调控优化催化性能的新方法，从而拓宽光催化过程在有机合成领域应用的新途径。项目结合铁酸盐晶体原子排列周期性和各向异性的特点，充分考虑不同半导体禁带宽度、能级水平、晶型匹配等因素，提出以载流子迁移效率与催化剂表界面性质匹配性这一新视角来理解、设计光催化材料。利用异质原子介入和石墨烯固载来调控载流子迁移效率、催化体系微观化学环境与光催化性能之间的对应关系及关联度，旨在阐明它们的匹配性对光催化材料性能的影响机制，实现对光催化材料微观结构和催化性能的有效调控，并通过便捷的磁分离方法解决纳米材料工程应用中难回收再利用的瓶颈问题，为设计发展新型光催化材料和构建高效催化反应体系提供科学依据。

本项目以磁性尖晶石型铁酸铜晶体为主要研究对象，充分考虑不同半导体禁带宽度、价带、导带能级位置以及晶型的匹配因素，以及不同金属离子的配位及电荷等因素，选择了不同的异质原子（Fe、Co、Ni、Cr、Ag等）对铁酸铜进行了掺杂修饰。采用水热合成、溶胶凝胶等方法，制备了一系列以石墨烯为载体，含异质原子的尖晶石半导体纳米复合材料，如CuFe2O4-RGO、NiFe2O4 -RGO、CuFeO2-RGO、CuCr2O4/rGO、Fe3O4-CuCr2O4/rGO、CuCr LDH/RGO、NiCo LDH/RGO、Ag-NiCo LDH/RGO等。采用XRD、TEM、SEM、FTIR、UV-vis、XPS、Raman、BET等对所制得的复合材料晶体结构、尺寸大小、组成和形貌等进行了分析和表征。通过优化制备参数，调控复合物的形貌结构。.以选择性催化苯羟基化、环己烷氧化、甲苯氧化、苯乙烯氧化为探针反应考察了所得尖晶石半导体纳米复合物在选择性催化过程中的表现。通过原料转化率、产品选择性研究了复合物的催化活性。探索了复合物的组成、结构等因素对催化性能的影响规律，以及石墨烯的含量、催化剂用量、溶剂种类、反应温度、反应时间和物料配比等对催化剂活性的影响。研究了催化剂的回收效果以及循环稳定性。CuFe2O4-RGO20催化苯酚氧化的转化率达到35.5%，苯二酚的选择性大于95.2%；CuFeO2-RGO15催化下，苯酚的转化率提高至51.1%，反应时间缩短至25 min。CuCr2O4/rGO催化环己烷氧化，74.8 %的环己烷转化成环己酮。CuCr LDH/RGO10催化下，环己烷的转化率达到85.6%，环己酮的选择性为82.4%。Fe3O4-CuCr2O4/rGO催化下，61.2%的甲苯转化为苯甲醛。NiCo LDH/RGO5催化苯乙烯氧化的转化率达到95.1%，氧化苯乙烯的选择性达到73.9%。Ag-NiCo LDH/RGO5催化下，苯乙烯的转化率达到96.5%，氧化苯乙烯的选择性达到76.4%。相较于其他已报道的催化剂，所制备的催化剂具有循环稳定性好、活性高等特点，实现了高效选择性催化氧化和催化剂的便捷回收再利用，且使用廉价的过渡金属可以降低制备成本，具有较好的工业化应用前景。