【作者】 卞琳艳；

【导师】 王艳辉； 臧建兵；

【作者基本信息】 燕山大学 ， 材料学， 2011， 博士

【摘要】 纳米金刚石作为一种功能性碳材料,兼具金刚石和纳米材料的双重特性。它具有很高的机械强度,化学惰性和热稳定性,可以承受较强的电化学负荷,而且具有很强的抗中毒、抗污染能力,可以在强腐蚀的介质中长期稳定工作,在电分析领域有着很好的应用前景;另一方面它作为纳米材料,具有巨大的比表面积和较高的表面活性,是极具潜力的电催化剂载体材料。本文通过循环伏安曲线研究了纳米金刚石粉末电极的基本电化学性质。纳米金刚石粉末电极在KCl底液中电势窗口范围约为2.2 V,背景电流在10-6 A数量级上。典型氧化还原对[Fe（CN）₆]^3-/4-在纳米金刚石粉末电极上的电极反应属于准可逆反应,电极动力学过程属平面扩散控制的传质过程。通过循环伏安曲线和稳态极化曲线考察了亚硝酸盐在纳米金刚石粉末电极上的氧化行为,结果表明纳米金刚石粉末电极对亚硝酸盐的检测限为1.2×10-4 mol/L。为了提高纳米金刚石电极对亚硝酸盐的检测能力,本文使用循环真空充气气相沉积法通过H₂还原TiCl₄在纳米金刚石表面沉积金属钛层,之后在空气中加热至500°C,使钛层氧化为锐钛矿晶型的二氧化钛涂层,获得纳米二氧化钛修饰的纳米金刚石。通过透射电子显微镜和拉曼光谱表征了纳米金刚石表面的二氧化钛涂层。TiO2/ND电极在亚硝酸盐溶液中的电化学性质表明表面修饰的二氧化钛涂层促进了亚硝酸盐的氧化,亚硝酸盐的检测限达到5.5×10-7 mol/L。采用恒电位沉积法在1.1 mmol/L H2PtCl6 + 0.5 mol/L H₂SO₄溶液中,-0.2 V电位下,电沉积1200 s,制备了纳米金刚石负载的铂催化剂。使用场发射扫描电子显微镜和X射线谱表征了样品的形貌和结构,纳米金刚石表面的铂颗粒尺寸在10 nm左右,分布均匀。Pt/ND催化剂对于甲醇氧化反应表现出了很好的催化性能。相同电沉积条件下,以爆轰合成的纳米金刚石为载体的Pt/ND5电极上的甲醇氧化峰电流高于以机械破碎制备的纳米金刚石为载体的Pt/ND100电极,前者表现出更好的催化性能。使用微波辅助乙二醇还原法制备了以纳米金刚石作为载体的铂催化剂,使用透射电子显微镜和X射线谱表征了样品的形貌和结构,铂颗粒尺寸为3⁵ nm,比电沉积法制备的铂颗粒尺寸小,且尺寸非常均一,分布均匀。Pt/ND催化剂对于甲醇氧化反应表现出了良好的催化性能。相同载铂量时,比较于Pt/ND100和Pt/ND250,Pt/ND5表现出最好的电催化活性。更多还原

【Abstract】 Nanodiamond, as a kind of functional materials, has both properties of diamond and nanomaterials. On the one hand, nanodiamond has high mechanical strength, thermal and chemical stability, so it can stably work in a strong corrosive solution, poisonous or high potential environments for a long time. These properties make it has potential to be a kind of good electrode material. On the other hand, as a kind of nanomaterials nanodiamond has large surface areas and high surface activity. So it has the potential to be a new catalyst support material.The electrochemical properties of nanodiamond powder electrode were studied by cyclic voltammetry. The results showed that nanodiamond powder electrode was electrochemically stable in KCl electrolytes, its potential window was 2.2 V and background current in magnitude was 1×10-6 A. The electrode reaction was quasi-reversible and diffusion-controlled in ferricyanide–ferrocyanide redox couple solution.The electrochemical properties of nanodiamond powder electrode toward nitrite oxidation were also studied with cyclic voltammetry and Tafel curves. The detection limit was 1.2×10^-4 mol/L. Coating nanodiamond with Titania could improve the electrochemical activity of nanodiamond. Cycled vacuum-feeding chemical vapour deposition was utiltzed to coat nanodiamond with titanium from gaseous TiCl₄ and H₂, and then an oxidation treatment was carried out in the air. Titania coating was obtained on the surface of nanodiamond particles. The structure and the morphology of the TiO2/ND were characterized by Raman spectrum and Transmission Electron Microscopy. Anatase coated nanodiamond powder electrode could catalyse the oxidation of nitrite, and improve the detection limit to 5.5×10^-7 mol/L.Nanodiamond powder with average particle sizes of 5 and 100 nm （ND5 and ND100） were modified with Pt nanoparticles by electrodeposition from 1.1 mmol/L H2PtCl6+0.5 mol/L H₂SO₄ aqueous solution for 1200 s under -0.2 V. The structure and morphology of the composite were characterized by Field Emission-Scanning Electron Microscope and X-ray Diffraction. The results showed that Pt nanoparticles with particle sizes of 10 nm were well-dispersed on the facet surfaces of nanodiamond particles. The electrooxidation of methanol on Pt-modified nanodiamond powders was investigated by cyclic voltammetry, which indicated its good electrocatalytic activity. Compared with ND100, ND5 modified with Pt nanoparticles exhibited better electrocatalytic activity on the same deposition conditions.Pt-modified nanodiamond was prepared by a microwave heating polyol method. The structure and morphology of the composite were characterized by Transmission Electron Microscopy and X-ray Diffraction. It was found that the Pt nanoparticles were small and uniform in size, and highly dispersed on nanodiamond supports. The mean size of the Pt particles was 3⁵ nm, which is smaller than that obtained by electrodeposition. The Pt-modified nanodiamond exhibited good electrocatalytic activity for methanol electrooxidation. Compared with Pt/ND100 and Pt/ND250, Pt/ND5 with same Pt loading exhibited a much higher electrocatalytic activity for methanol electrooxidation.更多还原