贵金属/氧化物(ZnO,SnO2)复合材料的制备及其性能研究

IMR OpenIR

	贵金属/氧化物(ZnO,SnO2)复合材料的制备及其性能研究
	陈雪松
学位类型	硕士
导师	苏党生 ; 孙振华
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	Zno纳米结构 Sno2纳米结构贵金属形貌可控 Suzuki反应气敏 Zno Nanostructure Sno2 Nanostructure Noble Metals Morphology Control Suzuki Coupling Reaction Gas Sensing
其他摘要	" 半导体金属氧化物ZnO与SnO2都是良好的气敏材料，ZnO与SnO2纳米材料的合成与制备研究，是研究其特性与应用的基础，对于进一步加深理解晶体的形成过程与机理等物理和化学问题具有重要的意义。在气敏传感领域内，对它们的气敏特性进行研究以及改良，探索其相成分、形貌、结构与敏感性质之间的内在联系，同样也具有重要的理论意义与应用价值。从材料体系来看，改善半导体金属氧化物元件的性能主要依靠材料体系的重新设计与试验，而用贵金属对半导体金属氧化物进行修饰与复合可以显著提高其应用性能。同时，半导体金属氧化物对于负载的贵金属来说又具有了载体效应。实验中我们选用的贵金属为Pd、Pt和Au，其中Pd是Suzuki反应中重要的催化剂。然而，反应中所使用的催化剂Pd在自然界中数量稀少、价格昂贵，而且在反应中容易团聚、不易回收、循环使用性能较差，增加了生产所需要的成本。在本实验中，我们将Pd纳米粒子原位负载到ZnO载体上，不仅提高了Pd纳米粒子的分散度，增加了反应面积，提高了反应效率，而且因为负载后容易离心回收，大大提高了Pd催化剂的循环使用性能。在以前的研究报道中，有很多方法可以实现用贵金属对半导体金属氧化物的修饰，但通常采用两步甚至多步法，不仅工艺复杂，而且得到的复合材料中贵金属的修饰也不够均匀，从而限制了这类材料的广泛应用。本论文最大的亮点就在于，我们通过一步水热法，原位地将贵金属与半导体金属氧化物进行了复合，方法简单、能耗低、效率高，对相关研究具有一定的指导意义。本论文的主要研究内容及得出的主要结论： (1) 本论文通过水热法一步合成了贵金属/ZnO复合纳米材料，利用SEM、TEM、XPS和XRD等手段对样品进行了详细的表征，并考察了溶液的pH值、贵金属种类、贵金属与ZnO的质量比值等因素对ZnO形貌及贵金属纳米粒子负载情况的影响。 (2) 考察了Pd/ZnO对Suzuki反应的催化性能，结果表明，联苯产率几乎接近100%，循环后的产率也依然很高。由此可知，Pd/ZnO的催化活性非常高，Pd在ZnO上的负载即均匀又稳定。 (3) 初步分析了pH值对ZnO形貌影响的机理，对纳米ZnO材料的合成工作具有一定的指导意义。 (4) 利用上述水热法合成了Au/SnO2复合纳米材料，并对样品进行了详细的表征。 (5) 考察并讨论了Au的修饰对SnO2在气敏性能上的影响，结果表明，Au/SnO2对乙醇响应的灵敏度明显高于SnO2。这是由于Au的修饰使气敏材料的表面吸附了更多的氧，增加了与乙醇分子的反应量，从而提高了器件的灵敏度。同时，实验表明Au的修饰可以显著提高气敏元件对乙醇的选择性。" ; " ZnO and SnO2 as semiconductor metal oxides both were good gas sensing materials, the synthesis and preparation were the basis to study the characteristics and applications of ZnO and SnO2 nano-materials, and there was important significance for further understanding the formation process and mechanism and other physical and chemical problems of crystal. In gas sensing field, researching and improving their gas sensing properties and the internal relation between the gas sensing properties and the composition, morphology and structure also had important theoretical significance and application value. From the view of the material system, the new design and experiment could improve the performance of the semiconductor metal oxides, and its application performance could be significantly enhanced when the semiconductor metal oxides were decorated and compounded with noble metal. Meanwhile, the semiconductor metal oxides had carrier effect for the loaded noble metal. We choosed Pd, Pt and Au as samples in our experiments, and Pd was an important catalyst in Suzuki reaction. However, Pd was rare resources in nature, it was expensive, easy to reunite in reactions, hard to recover, bad in recycling reactions, and all of this raised the production cost. In our experiments, Pd nanoparticle be loaded to ZnO in situ, it not only improved the Pd nanoparticles dispersion, increased the reaction area, enhanced the reaction efficiency, but also greatly improved the circulation performance of Pd catalyst, because of its easyly centrifugal recovery after loaded. In previous study reports, there were many ways to decorate semiconductor metal oxides with noble metal, but it was usually by two step even more footwork, which not only be complicated, but also influenced the loaded effect, so limiting the wide application of this kind of material. The biggest advantage of this paper was that the noble metal nanoparticle be loaded to the semiconductor metal oxides in situ through one step hydrothermal synthesis, it had some instructive significance because of its simple method, low energy consumption and high efficiency. The main research contents and conclusions obtained were as follows: (1) We had synthetized noble metal/ZnO composite nano-materials through one step hydrothermal synthesis method, and carefully examined the attributes of the sample by means of SEM, TEM, XPS and XRD, and examined the influence between the ZnO morphology, the noble metal nanoparticles load effect and the pH value of the solution, the noble metals types, the ratio of noble metal to ZnO. (2) We had examined the catalytic performance of Pd/ZnO in Suzuki reaction, the results showed that the yield of biphenyl was close to 100%, and the circulation performance was very good. Therefore, the catalytic activity of Pd/ZnO was very high, the loaded Pd was uniform and stability. (3) We had preliminary analysed the influence mechanism of the pH value of the solution to the ZnO morphology, it had some instructive significance for the nano-ZnO synthesis work. (4) We had synthetized Au/SnO2 composite nano-materials through one step hydrothermal synthesis method, and carefully examined the attributes of the sample. (5) We had examined and discussed the influence of the SnO2 gas sensing performance because of the Au modification, the results showed that the response sensitivity to ethanol of Au/SnO2 was significantly higher than SnO2. This was because that the gas sensing materials adsorbed more oxygen for the Au modification, increased the reaction amount to ethanol molecular, thus improved the sensitivity of the device. At the same time, the experimental results showed that the Au modification could significantly improve the selectivity to ethanol of the gas sensors."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64514
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	陈雪松. 贵金属/氧化物(ZnO,SnO2)复合材料的制备及其性能研究[D]. 北京. 中国科学院金属研究所,2012.