【作者】 徐国荣；

【导师】 任凤莲； 司士辉；

【作者基本信息】 中南大学 ， 应用化学， 2006， 博士

【摘要】 本文在综述纳米材料在电化学催化领域中的应用、纳米材料的模板合成、多孔阳极氧化铝模板（PAA）的结构、制备条件的基础上,研究了以铝作基体,借助阳极氧化形成的PAA模板组装一些金属、过镀金属铁氰化物和导电聚合物等纳米材料。用扫描电镜（SEM）表征了纳米材料的表面形貌,用X-射线粉末衍射（XRD）测定了它们的晶体结构,用电化学方法研究了它们的电催化性能。主要内容和结果如下:1.制备了不同孔径的PAA,研究了PAA的电化学性质。结果表明,铝纯度越高,纳米孔的有序性和均匀性越好;氧化电压与模板的孔径大小存在线性关系;循环伏安实验表明,PAA具有单向导电性的原因是氢离子能够穿过阻挡层在铝基体上发生还原。2.首次提出了一种在中性电解质溶液中以PAA作阴极,通过电解还原产生碱溶解阻挡层的新方法。最适宜的电解条件为温度在15℃以下,电解电位在-1.8～2.3 V之间,电解时间为5～15 min。在此条件下,电解法可以有效地去除PAA的阻挡层而不扩大模板孔径和减薄模板厚度。利用这种模板制备一系列的新型的纳米材料修饰电极用于电分析等领域。3.用直流电沉积的方法制备了nano-sized Cu/PAA电极。结果显示铜纳米线直径为22 nm,沿（111）晶面择优取向。与本体铜电极相比,亚硝酸根在Nano-sized Cu/PAA电极上的催化还原峰电位正移80 mV,峰电流明显增加。检测亚硝酸根的灵敏度、检测限和线性范围分别是216μA mmol^-1cm^-2,5×10^-6molL^-1,2×10^-5molL^-1～2×10^-2molL^-1。4.通过两步化学修饰法制备了纳米铁氰化镍（NiHCF）修饰PAA电极（Nano-sized NiHCF/PAA）。NiHCF纳米颗粒大小为25 nm左右。与本体NiHCF/Al电极相比,抗坏血酸在Nano-sized NiHCF/PAA电极上的电催化氧化峰电位低69 mV,氧化峰电流大2倍。用安培法测定抗坏血酸,线性范围和检测限分别是1×10^-6molL^-1～1.5×10^-2molL^-1,2.4×10^-7molL^-1。5.用两步无电沉积的方法制备了nano-sized PB/Pd-PAA电极。nano-sized PB/Pd-PAA电极稳定性好于PB/Pd-Al电极。nano-sizedPB/Pd-PAA电极测定过氧化氢的线性范围、检测限和灵敏度分别为1×10^-5～1×10^-2molL^-1、363.5μA mmol^-1cm^-2和0.8μmolL^-1。6.用直流电制备了Pt/nano-sized Ni催化剂。Pt/nano-sized Ni催化剂颗粒大小为70～80 nm。甲醇在Pt/nano-sized Ni催化剂上的氧化起始电位比在光滑铂上低100 mV,峰电位低70 mV,峰电流大40倍。以纳米镍作催化剂载体,能大大降低铂用量。7.用直流电沉积的方法制备的镍钼合金纳米线。镍钼合金纳米线的直径在20～30 nm之间。镍-钼共沉积的伏安图上在-1.4 V左右出现一个扩散电流平台,光电子能谱（XPS）试验表明钼的完全还原电位应小于-1.4 V。钼镍离子浓度比,柠檬酸盐,氨盐浓度比均影响镍钼合金纳米线的共沉积。优化条件下制备的镍钼合金纳米线的析氢过电位比本体镍钼合金正移210 mV。通过对镍钼合金纳米线共沉积条件分析,提出了镍钼形成中间物种放电的共沉积机理。8.用直流电沉积一层镍作催化层后,用电化学方法合成了聚苯胺（PANI）纳米线薄膜电极。制备的PANI纳米线的直径大约22 nm,循环伏安法制备的纳米线呈网状,而恒电位法制备的纳米线较规则呈直立状。充放电实验表明,聚苯胺纳米线薄膜电极的放电容量大于本体聚苯胺薄膜电极的放电容量。通过本文的研究,建立了一种新型的纳米材料修饰电极与纳米材料电催化剂组装和应用的有效方法。更多还原

【Abstract】 The application of nano-sized materials to the field of electro catalyst,the preparation of nano-sized materials with template method and the preparation of porous anodic aluminua（PAA）template were reviewed in this thesis.Based on the summary,some nano-sized materials such as metals and alloy,transition-metal ferricyanide and conductive polymer were fabricated in PAA and were characterize by Scanning electron Microscope（SEM）,X-ray power diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）and FT-IR spectroscopy.Their electrocatalytic properties also were studied.The main contents and results are as follows:1.The PAA with a different diameter of pores were prepared.The result showed the more the purity of aluminum is high,the more the homogeneity and ordering are good.The relationship between nanohole diameter and anodizing voltage was almost linear.The Cyclic voltammo -grams of PAA indicated the H⁺ ion（H₂O）could transit the barrier layer.2.Based on rectifying properties of PAA,an electrochemical method to remove barrier of PAA is presented firstly.The barrier of PAA was dissolved by electrolysis in a three-electrode cell with PAA as cathode in neutral potassium chloride solution.The most suitable experimental conditions for removing barrier layer are the applied potential at -1.8～2.3 V,temperature at below 15℃and electrolytic time for 7～15 min. Electro -chemical method can effectively remove barrier of PAA and doesn’t enlarge the nanohole diameter.Based on this kind of template, some novel nano-sized materials modified-electrodes were prepared.3.Nano-sized Cu modified PAA electrodes are fabricated by direct currents electrodeposition.The prepared Cu wires had an average diameter of 22 nm with the cubic face-centered copper structure,highly oriented along the（111）direction.Electrochemical experiments revealed that the peak currents obtained on nano-sized Cu/PAA electrodes toward catalytic reduction of nitrite were 2 times higher than those obtained on the bulk Cu electrodes,the peak potential was 80 mV higher than that at the bulk Cu electrodes.The calibration plot is linear over the nitrite concentration range 2×10^-5molL^-1to 2×10^-2molL^-1using amperometric method.The detection limit and sensitivity were 5×10^-6 molL^-1and 216μA mmol^-1cm^-2,respectively.4.Nano-sized nickel hexacyanoferrate（NiHCF）modified PAA electrodes（Nano-sized NiHCF/PAA）are fabricated by two-step electroless dipping method.The prepared Nano-sized NiHCF had an average diameter of 25 nm.The peak currents obtained on nano-sized NiHCF/PAA electrodes toward catalytic oxidation of ascorbic acid（AA） were two times bigger than those obtained on the bulk NiHCF/Al electrodes,and the peak potential was 69 mV lower than that at the bulk NiHCF/Al electrodes.The calibration plot is linear over the AA concentration range 1×10^-6to1.5×10^-2mol L^-1using amperometric method.The detection limit of the ampeorometric method is 2.4×10^-7 molL^-1.The presented method was used for determination of AA in fresh fruit and vegetable juices,and the results were consistent with those results obtained using Iodine titration method.5.A kind of nano-sized Prussian blue（PB）thin film electrode was prepared based on a two-step electroless deposition method.This kind of PB thin film electrode possessed a good electrochemical and mechanical stability,a good storage and operational stability.The modified electrode showed an excellent catalytic activity towards hydrogen peroxide reduction.The linear range of detection is found to lie between 10μM and 10 mM.The detection limit（signal to noise is 3）and sensitivity are 0.8μM and 363.5μA cm^-2mM^-1,respectively.6.Pt/Nano-sized Ni catalysts were prepared by direct current electrodeposition.The diameter of Pt/Nano Ni particle was about 70～80 nm.Cyclic voltammograms of Pt/Nano-sized Ni/PAA electrode exhibited the onset of electro-oxidation of methanol shifted to less anodic potential values（by 100 mV）and current enhanced up to 40 times,compared with pure Pt sheet electrode.When Pt loading amount was 42.6μg cm^-2,the highest electrocatalytic activity of Pt/Nano-sized Ni /PAA could be obtained.7.Ni-Mo alloy nanowires were fabricated.The SEM micrographs revealed that the diameter of the Ni-Mo alloy nanowires was about 20～ 30 nm.Voltammetric gram of the Ni-Mo alloy codeposition presented a pronounced plateau of a limiting current.XPS indicated the potential of complete reduction of Mo ion occurs at -1.4 V,correspond -ing to the potential where plateau of limiting currents occurred.The concentration ratios of citrate salt and the ammonia salt,concentration ratios of molybdate salt and nickel salt and the electrolyte acidity had considerable effects on codeposition of Ni-Mo alloy.The as-prepared Ni-Mo alloy nanowires exhibits a better catalytic activity for hydrogen evolution reaction.8.Polyaniline nanowire thin film electrodes were fabricated by electrochemical methods.Prior to electro polymerization of aniline,a layer of metallic nickel was deposited in PAA to provide a suitable electrocatalytic layer for the electro polymerization of aniline.The PANI wires had an average diameter of 22 nm corresponding to the pore diameter of the template.The charge-discharge curves showed the charge determined for PANI nanowire/PAA is higher than for bulk PANI film grown directly on Ni/Al.Based on the present study,a new effective method has been established for fabrication and application of new nano-sized materials modified electrodes and nano-sized electrocatalyst.更多还原