【作者】 于文强；

【导师】 易清风；

【作者基本信息】 湖南科技大学 ， 物理化学， 2010， 硕士

【摘要】 小分子电催化氧化具有重要的理论和实际研究意义,世纪九十年代以来一直受到高度重视。随着小分子电氧化过程研究的深入,对电化学现象的认识、促进物理化学学科相关理论与实验研究方法的发展,具有重要的意义。铂、金等贵金属对小分子电氧化被广为研究。修饰电极在电催化以及电分析等领域具有很好的应用前景。水热反应法是以水或其它溶剂作为介质,在一定温度条件和自生压力作用下,进行反应的过程。本论文采用合适的实验条件,将金纳米颗粒负载在钛基体上,从而制备出负载金纳米颗粒的钛基电极,并通过电化学测试方法对各电极电催化性能进行了研究。论文的主要内容和研究结论如下:1.对纳米颗粒的制备方法和小分子的电氧化研究进展进行了概述,系统总结了金电极研究进展和应用。2.确定了制备纳米金修饰钛电极的具体实验条件。3.运用扫描电镜和能谱分析测试技术,对所制备催化剂的形貌、结构与成分等进行了分析。对nanoAu/Ti电极而言,SEM和EDS分析表明,在钛基表面沉积了尺寸均匀的Au球形小颗粒,直径大小约300nm,并且这些球形小颗粒相互连接,形成三维网络状结构,具有巨大的表面积。Au-Ru/Ti电极,则在钛基表面沉积了尺寸均匀的Au-Ru金属球形颗粒,球形颗粒表面由向外突出的纳米晶片组成,并且这些球形小颗粒相互紧密连接呈多孔状结构,具有数目巨大的活性位点。此外,利用电化学沉积技术,直接从无支持电解质的低浓度氯金酸溶液中,沉积Au纳米颗粒到钛基体表面上,并且研究了电极对葡萄糖、肼和甲醛的电催化氧化过程。4.采用循环伏安、电位阶跃和交流阻抗等电化学方法,在碱性介质中研究了电极对葡萄糖、肼和甲醛的电催化氧化过程,并对电极过程进行了动力学分析。主要结论如下:(1)伏安特性研究表明,在碱性溶液中,nanoAu/Ti电极对葡萄糖、肼和甲醛氧化表现出很好的电催化活性。nanoAu/Ti电极对葡萄糖、肼和甲醛电化学氧化起始电位与多晶金电极相比均有所提前;在电极几何面积相同的条件下,nanoAu/Ti电极上葡萄糖、肼和甲醛的氧化电流也大于多晶金电极。电位阶跃实验表明,稳态电流十分稳定,表明nanoAu/Ti电极具有良好的稳定性。(2)对所制备的双金属Au-Ru/Ti电极的电化学测试研究表明:这些电极对葡萄糖的催化活性与Au和Ru的比例有关,含5%Ru的Au95Ru5/Ti电极对葡萄糖氧化表现出最优异的催化性能。Ru的加入明显改善了电催化剂对葡萄糖的电化学氧化性能,可能是Ru与Au产生协同作用,促进了氧化反应的发生。目前关于小分子电催化氧化的研究报道虽然较多,但探索制备性能优良的催化剂仍是这一领域的研究难点。本文制备的金纳米颗粒催化剂,其颗粒具有新颖的微观结构,在电氧化反应中表现出优异的催化活性。这些工作对燃料电池阳极材料的研发、以及新型电化学传感器的研发具有一定的指导意义。更多还原

【Abstract】 We all know that, since the end of 20th century, the electrocatalytic oxidation of small molecules has been receiving extensive investigation. The electrocatalytic oxidation process is of significant application both in fundamental research as model systems and in the fuel cells (FC). Small molecule electrocatalytic oxidation on noble metals has been widely studied. Development of electrocatalysts with significantly activities was a much challenging problem.Hydrothermal method as a soft chemistry method, has been applied to preparing the novel electrode materials in this paper. The electrocatalytic properties of electrocatalysts made by hydrothermal method are different from that by the traditional method. Novel titanium-supported gold electrodes were synthesized in this paper. Electro-catalytic activities of the electrodes were investigated by voltammetric responses, chronoamperometric measurements and electrochemical impedance spectra, etc. The main contents are as follows:1. The electrooxidation mechanism of glucose, hydrazine and formaldehyde was elaborated. The application of gold electrodes and small molecules electrooxidation are reviewed briefly.2. The electrodes were synthesized by the hydrothermal process.3. To investigate the morphology and element compositions of the electrodes obtained by the hydrothermal process, scanning electron microscopy and energy disperse spectroscopy are employed in the process. SEM and EDS images of nanoAu/Ti show that the surface of Ti substrate is covered by gold particles. The gold particles were present as small balls with a size of around 300nm. The gold particles are connected with each other and form 3D structures. The surface of the Au-Ru/Ti was covered by dentritic particles. The roughened surface of the dentritic particles is made up of variform flakes protruding from the surface. These flakes exhibit a variety of shapes but they have a similar thickness of ca. 30～35 nm. The presence of nanoporous features and the protruded flakes results in the high surface area of the Au-Ru/Ti catalyst.Using an electrochemical deposition technique, the titanium-supported Au/Ti electrodes are fabricated using HAuCl4 solutions as raw materials. Results show that the electrode presented high catalytic activity for glucose (hydrazine, formaldehyde) oxidation.4. Cyclic voltammetry, pseudo-steady state polarization, chronoamperometry and electrochemical impedance spectroscopy (EIS) were used to study the electrooxidation of glucose (hydrazine, formaldehyde) in sodium hydroxide solution on the nanoAu/Ti electrode.(1) It can be seen from CVs in alkaline solutions that the nanoAu/Ti electrodehas high catalytic activity for glucose (hydrazine, formaldehyde) oxidation. Compared to the polycrystalline Au electrode, the onset potential for oxidation of glucose (hydrazine, formaldehyde) was more negative on the nanoAu/Ti. From chronoamperometric measurements, we find that the steady-state current on the nanoAu/Ti was high and without pronounced decay, indicating the high stability of the nanoAu/Ti electrode in the electrooxidation process.(2) Electrochemical measurements show that Au99Ru5/Ti electrode presented highest catalytic activity for glucose oxidation. The different catalytic activity gives evidence of the important role of Ru playing in the stable immobilization of Au particles on the Ti substrate. The prepared nanoporous Au and Au-Ru electrocatalysts present novel morphological structures and significantly high electroactivity.更多还原