不同形貌ZnO/C3N4复合光催化剂的制备及其可见光催化性能

In recent years, ZnO/C3N4 composite photocatalyst have been extensively investigated. Lots of exciting achievements have been achieved. But the ZnO/C3N4 composite has got with no certain morphologies of ZnO particles. Due to the ZnO particles agglomerate severely and are not fully loaded on the surface of the g-C3N4. Only a small amount of ZnO particles and g-C3N4 formed the heterostructure, thus affecting the enhancement of the visible photocatalytic activities.. The ZnO/C3N4 composite photocatalyst with different morphologies will be directly grown on the surface of g-C3N4 through a simple hydrothermal reaction or in-situ thermal oxidation method with the assistant of the complexing agent. The closely heterostructure between ZnO and g-C3N4 with a certain morphology will be built. The relationship is summarized between the reaction temperature, time, solvent, different complexing agent and ZnO/C3N4 composite material with different structure and morphologies. The visible photocatalytic properties of the prepared ZnO/C3N4 composite photocatalyst with different morphologies and content will be studied by degradation of dyes. The relationship between the photocatalytic activity and the photogeneration carriers separation and recombination with different structure and morphologies of ZnO/C3N4 composite photocatalyst will be revealed. The corresponding photocatalytic reaction mechanism is significantly studied as well. This project is proposed to provide the basis of how to design and build the high visible light driven catalytic activity and high stable composite photocatalyst.

目前，人们己经对ZnO/C3N4复合光催化剂进行了大量的研究，取得了一些可喜的成绩，但得到的是无一定形貌ZnO颗粒与g-C3N4的复合物，由于ZnO颗粒团聚严重，只有少量ZnO颗粒与g-C3N4形成了异质结构，因而影响了其可见光催化活性的提高。. 本项目预采用配位剂辅助水热法和原位热氧化法在g-C3N4表面原位制备出不同形貌、含量的ZnO/C3N4复合材料，构建出具有一定形貌且结合紧密的ZnO/C3N4异质结构。总结反应温度、时间、溶剂及不同配位剂对ZnO/C3N4复合材料结构、形貌的影响规律。研究不同形貌、含量ZnO/C3N4复合材料在可见光照射下对染料的光催化降解性能，探明其光生电荷分离-复合的行为与光催化降解性能之间的关系，揭示不同结构、形貌ZnO/C3N4复合材料光催化降解机理，为以后设计、构建高催化活性、高稳定性的的复合材料提供理论依据。

本项目基于不同形貌ZnO/g-C3N4复合材料的制备及其可见光催化性能研究，筛选出性能优良的可见光催化剂，为实现高活性的无贵金属可见光催化材料的太阳能转换和利用提供了前景。其主要成果包括：研究了热解法制备条件对g-C3N4可见光催化性能的影响，结果表明以尿素为源，570℃保温2 h制备的g-C3N4可见光催化性能最好；采用配位剂辅助水热法，在Zn(NO3)2•6H2O-NH3•H2O-NaBH4-g-C3N4体系制备出蜂窝形ZnO/g-C3N4复合光催化剂，提出了其生长机理，研究了蜂窝形ZnO/C3N4复合材料在可见光照射下对染料的光催化降解性能。结果表明：当ZnO的含量为28.3%时复合材料的光催化性能最佳，比单相g-C3N4提高了70%，揭示了复合材料的吸附能力和电子空穴分离是可见光催化性能提高的重要因素，得出了复合光催化剂在光催化过程中的主要活性物种是超氧自由基（•O2-）和空穴（h+）；在前期合成ZnO/ C3N4复合光催化剂的基础上，我们进行了2个扩展工作：采用配位剂辅助水热法在NiCl2•6H2O-NH3•H2O-C2H5OH-g-C3N4 体系中，制备出多孔片形g-C3N4/Ni(OH)2复合材料，研究了其电化学性能。结果表明电流密度为0.5 A g-1，其比电容为887 F g-1，比单相Ni(OH)2增加了46%。另外，将其与活性炭组装成非对称超级电容器，当电流密度为4 A g-1，其比电容为54.8 F g-1，经过6000次循环后，其比电容还保留原始比电容的83.9%，当功率密度为798.4和7991.9 W kg-1，其能量密度为28.3 和10.9 Wh kg-1，揭示了复合材料的形貌及g-C3N4和Ni(OH)2的协同作用是电极材料性能提高的主要因素；采用原位热解法制备出八面体NiO/C3N4复合材料，当电流密度为1 A g-1，其比电容为660 F g-1，当电流密度增加到20 A g-1，其比电容为356 F g-1。将其与活性炭组装成非对称超级电容器，当功率密度为800 W kg-1，其能量密度为24.0 Wh kg-1。本项目的研究成果为以后设计、构建高光电活性复合材料提供了技术路线和理论依据。