【作者】 王珏；

【导师】 韩民；

【作者基本信息】 南京大学 ， 材料科学与工程， 2016， 博士

【摘要】 随着人类对环境和健康问题的关注,很多研究被投入到改善工业生产时产生的污染以及与健康问题密切相关的分析技术上。本论文结合Pd纳米粒子独特的催化特性,采用团簇束流沉积系统制备了尺寸及覆盖率可控的的Pd纳米粒子,沉积在不同衬底上。深入研究了Pd纳米粒子修饰电极的电化学传感性能以及对氢气-氧气直接反应生成H202的催化特性。论文研究结果如下：1.采用团簇束流沉积系统制备Pd纳米粒子,在高真空环境中修饰到玻碳电极表面,获得了Pd纳米粒子修饰的玻碳电极。该系列电极具有清洁的表面,Pd纳米粒子与玻碳电极可以不通过粘结剂而紧密结合,Pd纳米粒子有很好的分散性、有效的催化面积和快速的电子转移能力。通过调控沉积时间以得到不同覆盖率的Pd纳米粒子修饰GCE电极,通过线性扫描伏安法、循环伏安法及计时电流法研究了Pd纳米粒子的覆盖率及数密度对电极性能的影响。结果表明,Pd纳米粒子的传感性能随着纳米粒子的覆盖率增加而增大,但是当覆盖率逐步接近百分之百,传感性能开始下降。过高的沉积量会使纳米粒子堆叠在一起,比表面积变小,数密度变小。PdNPs修饰电极在覆盖率为85%即数密度最大的情况有最佳的性能。它的检测限为3.4×10-7M,灵敏度50.9μA mM-1,线性范围1.0×10-6到6.0×10-3M,同时它具有极低的过电位-0.12V,在这个电位下电化学传感器基本可以排除大部分的杂质干扰。2.通过化学气相沉积法制备了大片A-B堆垛的双层石墨烯,将制备获得的石墨烯转移到玻碳电极或ITO导电玻璃表面,获得具有高导电性能的石墨烯修饰电极。在此基础上,通过改变缓冲和溅射气体流量、冷凝距离、溅射功率等制备参数,制备了尺寸分布分别为～6.47nm、～10.56nm、～12.21nm的三种Pd纳米粒子。将这些尺寸不同的PdNPs分别修饰到A-B堆垛双层石墨烯修饰的玻碳电极表面。采用循环伏安法及电流时间法系统的研究了电极的性质。结果表明,随着纳米粒子的增大还原峰电位逐步正移,而还原峰电流则是在纳米粒子大小为10nm左右时最大,电极的响应速度均小于小于3S。Pd纳米粒子大小为10nm左右修饰的电极具有最佳的性能,灵敏度为115.14μA mM-1,线性范围为4μM-13555μM,响应时间为3s以内。将沉积后电极放置于空气中一个星期,电极均能够保持稳定,不发生衰减,表现了该结构传感器良好的稳定性。将平均尺寸为10nm的Pd纳米粒子沉积到A-B堆垛的双层石墨烯修饰的ITO表面,进行对H2O2的传感性能测试。结果表明,该电极有极快的传感速度即小于3s,极高的灵敏度186.114μA mM-1,这与之前的工作一同证明了CVD法制备的石墨烯具有极高的电子传递能力。在碱性介质中测试了钯纳米粒子修饰电极、钯纳米粒子与石墨烯复合修饰电极的循环伏安曲线,结果显示,加入双层石墨烯的复合材料比未加石墨烯修饰电极具有更高的有效活性面积,故而有更好的传感效果。3.采用电化学氧化的方法制备获得Al203多孔模板以及孔壁光滑排列整齐的TiO2纳米管。利用团簇束流沉积系统在SiO2/Si、Al2O3、TiO2上沉积了相同量的钯纳米粒子。自主搭建了超高真空测试系统,采用程序升温脱附研究钯纳米粒子与不同载体结合对双氧水直接合成的催化性能。结果表明Pd NPs/TiO2对氢气和氧气均有极强的吸附,并且吸附于Pd的不同的活性点位上。而Pd NPs/SiO2/Si和Pd NPs/Al2O3对氢气和氧气均没有明显的吸附。程序升温表面反应显示Pd NPs/TiO2在68℃下有一个H2O2尖峰,Pd NPs/SiO2/Si在429℃出现了一个H2O2脱附峰,Pd NPs/Al2O3在471℃下出现了一个H2O2脱附峰,结合O2-TPD、 H2-TPD、TPSR三个实验结果,提出Pd纳米粒子/TiO2纳米管阵列对氢氧低温直接反应生成H2O2的催化机理。更多还原

【Abstract】 With more attention to health and environment, many researches have been put into reducing the pollution from industrial production and analysis techniques. In this thesis, we combine the unique catalytic properties of palladium nanoparticles, Pd NPs with controlled size and coverage were deposited on different substrates by using gas phase cluster beam deposition for non-enzymatic hydrogen peroxide detection and heterogeneous catalysis. respectively. The main research results are as follows:1. The Pd nanoparticles (PdNPs) were fabricated on glass carbon electrodes (GCEs) by using gas phase cluster beam deposition. The Pd NPs fabricated by this method have the advantages of clean surface, good adhesion ability and nice dispersion. Pd NPs/GCEs possess high specific surface area, allow free access of analytes to the electrode surface, and enable the enhanced electron transfer reaction between H2O2 and the electrodes. To examine the effects of the coverage of the Pd NPs on the reduction of the H2O2, a series of Pd NPs with different deposition time have been fabricated. We have shown that the electrocatalytic ability of the Pd NPs/GCEs changes with the nanoparticle coverage. The coverage of 85% is the optimal coverage to achieve both the best sensitivity and linearity. With such optimal nanoparticle coverage, a high selective nonenzyme sensing platform for stable detection of H2O2 with a low detection limit (3.4×10-7M), high sensitivity (50.9μA mM-1) as well as a wide linear range (from 1.0×10-6 to 6.0×10-3M) has been demonstrated. All these features provide a favorable environment for the electrocatalytic reduction of H2O2 and allow the detection of H2O2 at a sufficient low applied potential (-0.12V), which effectively minimizes the interference. The fabricated device is promising for the development of sensor and biosensor based on nonenzymatic H2O2 detection.2. Bilayer graphene films (BGF) were synthesized by chemical vapor deposition(CVD) with copper foil as the growth substrate, the BGFs have transferred on GCE and indium tin oxide(ITO) glass to obtained graphene modified electrodes with good electrical conductivity. A series of Pd NPs with three different size distribution～6.47nm,～10.56nm,～12.21nm were prepared by gas phase cluster beam deposition. An investigation about electrocatalytic ability of the nanoparticle with different size distribution has been finished. The result shows that the size about 10nm of Pd nanoparticles is optimum for the reduction of H2O2. The nonenzye sensing platform shows wide linear range (4μM-13555μM), response time (typically less than 3 second) and high sensitivity (115.14μA mM-1). Pd NPs/BGF/GCEs were stored in air at room temperature for 1 week. The CV showed their response to 0.01M H2O2 retains 100%. This could be attributed to the Pd NPs which produced by the gas phase clusters beam deposition system can closely integrated with bilayer graphene. This structure could stabilize the nanoparticle. The PdNPs with size distribution-10.56nm were fabricated on BGF/ITO/glass. The Pd NPs/BGF/ITO/glass electrode shows enhanced electrocatalytic activity toward the reduction of H2O2 with response time (typically less than 3 second) and high sensitivity (186.11μA mM-1), The electrochemical activity surface area was confirmed by the cyclic voltammetry (CV) for 0.1M NaOH. The result shows that the active surface area was promoted by BGF, and the Pd NPs/BGF/GCE exhibited better electrochemical reduction of H2O2 than Pd NPs/GCE.3. Anodic alumina membranes and highly ordered TiO2 nanotube arrays were prepared by potentiostatic anodization method in a two-electrode electrochemical cell. The same amount of Pd NPs was fabricated on SiO2/Si, Al2O3, and TiO2 by using gas phase cluster beam deposition. The ultra high vacuum test system was builded. To understand the activities of catalysts, temperature programmed desorption (TPD) have been used for the direct synthesis of H2O2. The result shows that Pd NPs/TiO2 has strong adsorption for H2 and O2, but the Pd NPs/SiO2/Si and Pd NPs/Al2O3 do not have apparent adsorption. The temperature programmed surface reaction shows that Pd NPs/TiO2/Ti has a H2O2 desorption peak at 68℃, at 429℃ for Pd NPs/SiO2/Si and at 471℃ for Pd NPs/Al2O3. Combined with O2-TPD, H2-TPD and TPSR, we proposed a possible catalytic mechanism of the direct synthesis of H2O2 by Pd NPs/TiO2.更多还原