基于氧化物的多级结构光催化能源材料的设计、优化及性能研究

发布时间：2018-08-02 19:00

【摘要】：化石能源的大规模使用造成的环境问题,与其日趋枯竭引发的能源危机,以及化石能源燃烧产物CO_2所引起的温室效应,促使人类必须开发出清洁、无污染、可持续利用的替代能源。新一代太阳能技术是解决上述问题的关键,而其中关键材料的开发无疑成为重中之重。基于氧化物的多级结构光催化能源材料作为材料家族的重要一员具有广阔的应用前景。与此同时,基于氧化物发展的光催化能源材料实现水分解和CO_2还原已经备受科研工作者的青睐,但受限于材料的设计、优化以及先进的光催化体系开发,在提高光催化效率、设计优化新型高效的光催化剂、以及催化剂的回收和再生等方面还有待于进一步研究探索。基于以上研究现状,我们开展了本论文的研究工作。主要从优异光催化体系的构筑与优化出发,通过材料多级结构设计、表面缺陷控制,以及优化复合等途径获得系列多级结构无机光催化剂,并系统研究了它们的光催化产H_2、产O_2性能；与此同时,探索新型碳基复合类金属光催化材料,尤其是体系的构筑与优化,发现了MOF衍生复合材料在光催化CO_2还原方面的潜在应用。本论文主要包括以下几个方面内容：1.采用“自模板”合成策略制备多壳层空心CeO_2微纳材料。多壳层空心CeO_2微纳材料用于紫外光催化水分解制O_2,相比较与双壳层空心球,单壳层空心球和商业CeO_2光催化剂,催化活性和稳定剂均大大提高。进一步,在材料结构设计的同时,表面缺陷可调控的莹石型CeO_2纳米棒在可见光催化产O_2方面的研究。与空气中800℃下后处理得到的样品相比较,Ar-H_2混合气处理的CeO_2纳米棒的可见光催化分解水活性提高10倍。详细的表征和理论分析揭示：在CeO_2表面存在的氧空位和Ce~(3+)是其活性提高的关键因素。2.在控制材料结构及表面的基础上,采用一锅法水热将Cu_2O纳米团簇原位均匀生长于TiO_2纳米盘表面,并以其为催化剂进行光催化产H_2研究,当TiO_2纳米片表面负载纳米Cu_2O团簇后,加快表面电子传递,从而大大地提高电子空穴对分离效率。更为值得关注的是,Cu_2O/TiO_2表现出高于贵金属Au纳米颗粒负载的TiO_2纳米盘的光催化产H_2效果。极好的光催化稳定性,也说明廉价Cu_2O团簇负载形成的表面异质结是提高电子和空穴分离效率的重要方法。3.最后,尝试控制无机光催化复合材料的结构以及成分,通过超声法合成片层Co-MOF74,并在Ar气中碳化处理,制备Co@C/Co-C碳基复合材料,从而实现Co/C成分的调控。进一步,确定碳基复合材料1200-Co@C/Co-C结合Ru(bpy)32+在CO_2转化生成CO过程中,具有最高的活性。实验发现,这种类金属复合材料具有超高的电子传输能力,其中金属Co成分是CO_2还原的活性中心,而石墨化碳成分则在CO_2的吸附和光生电子传输能力的提高方面起到至关重要的作用。更重要的是,首次提出这种新型的高稳定性类金属材料结合金属配合物分子体系(Co-C结合Ru(bpy)32+)的概念,并将Co@C/Co-C复合材料成功应用在可见光催化CO_2还原中。
[Abstract]:The environmental problems caused by the large-scale use of fossil energy, the energy crisis caused by the increasing depletion of energy and the greenhouse effect caused by the burning product of fossil energy, CO_2, urge mankind to develop clean, pollution-free and sustainable alternative energy. The new generation of solar energy technology is the key to solve the above problems, and the key material is the key material. There is no doubt that the development of material has become the top priority. As an important member of the material family, the multi structure photocatalytic energy material based on oxide has a broad application prospect. At the same time, the photocatalytic energy materials based on oxide based photocatalytic energy materials have attracted more and more attention to the water decomposition and CO_2 reduction, but are limited to the design of materials. The optimization and the development of advanced photocatalytic system have yet to be further studied in improving the photocatalytic efficiency, designing and optimizing new and efficient photocatalysts, as well as the recovery and regeneration of the catalyst. Based on the above research status, we have carried out the research work in this paper. The construction and optimization of the excellent photocatalytic system is mainly carried out. A series of multistage structure inorganic photocatalysts are obtained through multi-stage structure design, surface defect control, and optimization of composite materials, and their photocatalytic production of H_2 and O_2 performance are studied systematically. At the same time, the construction and optimization of new type carbon based composite metal photocatalytic material, especially the system, have been found, and MOF derivation has been found. The potential applications of composites in photocatalytic CO_2 reduction are discussed. The main contents of this paper are as follows: 1. the multi shell hollow CeO_2 micronanomaterials are prepared by the "self template" synthesis strategy. The multi shell hollow CeO_2 micronano material is used for UV photocatalytic water decomposition to make O_2, compared with the hollow sphere, single shell hollow sphere and the hollow sphere. Commercial CeO_2 photocatalyst, catalytic activity and stabilizer are greatly improved. Further, in the design of material structure, the surface defects can be controlled by the crystal CeO_2 nanorods in the visible light catalytic production of O_2. Compared with the samples treated at 800 C in the air, the visible light of the CeO_2 nanorods treated with Ar-H_2 mixed gas Catalytic decomposition water activity increased by 10 times. Detailed characterization and theoretical analysis revealed that the presence of oxygen vacancy and Ce~ (3+) on the surface of CeO_2 was the key factor for the improvement of its activity. On the basis of the structure and surface of the material.2., the Cu_2O nanocluster was uniformly grown on the surface of the TiO_2 nanodisk by one pot method of hydrothermal heat, and the catalyst was used as the catalyst. The study of photocatalytic production of H_2 shows that when the surface of TiO_2 nanoparticles is loaded with nano Cu_2O clusters, the surface electron transfer is accelerated, which greatly improves the separation efficiency of the electron hole. It is more worthy of concern that Cu_2O/TiO_2 shows the effect of photocatalytic production of H_2 in the TiO_2 nanoscale disk which is higher than the Au nanoparticle load of precious metals. Excellent photocatalytic stability. It is also indicated that the surface heterojunction formed by the low cost Cu_2O cluster load is an important method to improve the efficiency of electron and hole separation,.3.. Finally, we try to control the structure and composition of the inorganic photocatalytic composite material, synthesize the layer Co-MOF74 by ultrasonic method, and carbonization in the Ar gas, and prepare the Co@C/Co-C carbon based composite, so as to realize the Co/C formation. Further, it is determined that the carbon based composite material 1200-Co@C/Co-C combined with Ru (bpy) 32+ has the highest activity in the process of CO_2 conversion and formation of CO. It is found that this kind of metal composite has super high electron transport capacity, in which the metal Co component is the living center of CO_2 reduction, while the graphite carbon composition is at CO_2 adsorption and light. The improvement of electronic transmission capacity plays an important role. More importantly, this new high stability metal like material is first proposed with the concept of metal complex molecular system (Co-C binding Ru (bpy) 32+), and the Co@C/Co-C composite is successfully applied to the visible photocatalytic CO_2 reduction.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36

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