乙二醇的电化学分析方法研究

本文制备了介孔碳/纳米铂复合材料修饰玻碳电极,并采用循环伏安法研究了乙二醇在该电极上的电化学行为,与乙二醇在裸玻碳电极上的电化学行为进行相应的对比,发现乙二醇在修饰电极上的氧化峰电流较大,且氧化峰电势电位较低,表明乙二醇在该修饰的电极上具有良好的电催化氧化效应。乙二醇在浓度范围为1.0×10~(-5)~1.0×10~(-3)mol/L之间与峰电流ip呈良好的线性关系,据此建立了乙二醇的电化学分析方法,可用于实际样品中乙二醇的测定。     

介孔炭修饰玻碳电极的制备及其分析特性研究

利用硼氢化钠的还原性从氯铂酸钾溶液中还原出了纳米铂,然后利用介孔炭的吸附性制备了介孔炭/纳米铂离子复合电极材料,用该复合材料制备了介孔炭/铂纳米粒子复合修饰电极。经过实验研究发现,介孔炭/铂纳米粒子复合修饰电极对过氧化氢有电催化作用,过氧化氢在该修饰玻碳电极上可产生较大的还原峰电流,表明介孔炭/铂纳米粒子对过氧化氢有很好的催化性能,据此建立了过氧化氢的电化学分析方法。     

甲醛的电化学检测方法研究

甲醛是一种电活性不活泼的有机物质,其很难在电极表面直接电催化氧化,所以利用复合纳米材料对甲醛的催化作用,将复合纳米材料修饰在玻碳电极表面制成修饰电极,进而利用修饰电极对甲醛的电催化活性,从而建立甲醛的电化学检测分析方法。以玻碳电极为基础电极,将氧化石墨烯用滴涂法滴涂于基础电极表面,再在饱和的氯化钾溶液中还原,随后采用电沉积法将纳米铂粒子沉积于还原的氧化石墨烯表面,制备出纳米铂/石墨烯复合电极,依据甲醛在电极表面反应时,产生了电流的改变,甲醛的浓度与产生的氧化电流成线性关系,从而建立了甲醛的电化学分析方法,并对其条件优化进行了探究。     

Ag纳米粒子修饰的玻碳电极及对甲醛的检测研究

采用三乙醇胺化学还原制备Ag纳米颗粒,尺寸约为108±6 nm,将其修饰到玻碳电极上作为甲醛的电催化氧化电极。电化学研究结果发现,Ag纳米粒子可提高玻碳电极的电化学活性表面积,并改善对甲醛的电催化氧化作用。在碱性介质中,氧化峰电流与甲醛浓度呈良好的线性关系,检出限可达9.4×10~(-5) mol/L,且多次测量中甲醛氧化峰电流相对标准偏差仅为6.8%,显示出良好的稳定性和实用性。     

L-半胱氨酸/纳米金修饰电极对硒的电化学检测

利用纳米金修饰玻碳电极,再自组装上L-半胱氨酸制得L-半胱氨酸/纳米金复合修饰电极(L-cys/GNPs/GCE)。在硫酸介质中,采用循环伏安法(CV)考察硒(Ⅳ)在电极上的电化学行为。研究表明,L-cys/GNPs/GCE对硒(Ⅳ)的氧化还原具有较好的电催化作用,在峰电位0. 917 V处有灵敏的氧化溶出峰。此修饰电极的LSV响应与硒(Ⅳ)在0. 02～20μM范围内呈线性关系,检出限为5 n M(S/N=3)。此修饰电极具有良好的选择性、重现性和稳定性,可应用于实际样品中硒的测定。     

金纳米粒子修饰玻碳电极的电化学行为研究

利用层层自组装技术,通过有机偶联层胱胺将金纳米粒子修饰在玻碳电极上,得到金纳米粒子/胱胺/玻碳电极,并通过循环伏安法和电化学阻抗谱对修饰电极的电化学行为进行研究,结果表明该修饰电极具有优于裸玻碳电极的良好的电化学性能,可用于进一步的应用。     

铋-卟啉复合电极电化学检测研究

将卟啉与铋膜复合到玻碳电极表面,用制得的铋-卟啉复合玻碳电极对亚硝酸盐进行检测,与未修饰和只修饰卟啉的玻碳电极比对,通过方波伏安法对同等浓度的亚硝酸盐进行检测,峰电流明显升高,说明该复合电极对亚硝酸盐有较大的电催化作用.通过对镀铋的方法、缓冲溶液和pH值等测定条件进行优化,选取最佳的测定条件.结果 表明,在8 ～ 20...     

介孔炭/铂纳米粒子复合材料修饰电极的制备及其应用

本文利用介孔炭的吸附性制备了介孔炭/铂纳米粒子的复合材料修饰电极,然后用循环伏安法,用该电极测定对苯二酚。结果显示对苯二酚溶液在裸玻碳电极上的峰电流最小,然后是介孔炭修饰电极,复合材料修饰电极的峰电流最大,表明铂纳米粒子对对苯二酚溶液有很好的催化性。复合材料修饰电极在1.0×10~(-5)~1.0×10~(-3) mol/L范围内的对苯二酚溶液中浓度c与峰电流ip有良好的线性关系。     

金-铂纳米空球催化甲醇氧化的行为

介绍了以硒溶胶为模板,研制金-铂纳米空球[(Au-Pt)HN]及其修饰玻碳(GC)电极[(Au-Pt)HN/GC]的方法;用SEM、HR-TEM、UV-Vis、XRD和电化学循还伏安等方法检测了(Au-Pt)HN的表面形貌、结构与组成;碱性介质中,利用常规电化学方法研究了(Au-Pt)HN/GC对甲醇的电催化氧化行为,考察了金、铂配比不同的(Au-Pt)HN对催化甲醇氧化性能的影响,得出金、铂配比不同的(Au-Pt)HN对催化甲醇氧化的活性顺序为:20∶150∶1100∶110∶15∶1。     

玻碳电极表面修饰的应用研究进展

裸玻碳电极的性质、功能较为单一,应用较为有限。为了拓展其应用领域,对玻碳电极进行表面修饰,玻碳电极表面修饰已经成为当前电化学研究的一个热点。文章在研究玻碳电极表面修饰相关文献的基础上,主要对当前玻碳电极表面修饰的应用领域及表面修饰剂的种类进行简要综述,以期为该领域的深入研究提供参考。     

Electro-oxidation of glycerol on platinum dispersed in polyaniline matrices

Films of polyaniline (PAni) were electrosynthesized on gold and glassy carbon substrates. The morphology of the films was verified using scanning electron microscopy (SEM) and, as expected, the PAni film formed on glassy carbon presented fibrillar morphology, while that formed on gold presented fibrils on top of a more compact structure. Different amounts of platinum were electrodeposited into the polymer matrices at constant potential and the electrocatalytic activities of the electrodes were evaluated for glycerol electro-oxidation in acidic medium. Furthermore, the active areas of such modified electrodes were determined from the charges involved in the electro-oxidation of an adsorbed carbon monoxide monolayer. Considering the real active areas, the modified electrode with the gold substrate presents higher electrocatalytic activity for glycerol oxidation than that with the glassy carbon substrate. This difference is mainly related to their morphological characteristics and platinum particle sizes.     

Anodic Oxidation of Polyhydric Alcohols on a Pt Electrode in Alkaline Solution

The electrochemical oxidation of various polyhydric alcohols, ethylene glycol, glycerol, meso-erythoritol, and xylitol, on a platinum electrode was investigated systemematically in acidic H₂SO₄, and in alkaline KOH and K₂CO₃ solutions to evaluate the potential of these polyhydric alcohols as fuels in micro-fuel cells for portable electronic devices. All polyhydric alcohols tested in the present study showed high reactivities in both alkaline solutions. Ethylene glycol showed the highest reactivity. Although the reactivity of ethylene glycol was lower in K₂CO₃ than in KOH, the carbonate solution is a potential candidate as an electrolyte solution due to its resistance to solution carbonation. Furthermore, ethylene glycol showed much less significant electrode poisoning by adsorbed CO upon oxidation in alkaline solution.     

Electrochemical Oxidation of Phenol on Metal‐Impregnated Zeolite Electrodes

Nanodispersed metallic clusters of platinum, silver and cobalt were incorporated into NaX zeolite cavities by impregnation with acetone solution of corresponding acetylacetonates and solvent evaporation followed by acetylacetonate thermal decomposition. The mixture of modified zeolites and 10 wt % of carbon black, in the form of a thin layer, was pasted onto a glassy carbon surface by Nafion. With such electrode materials, the phenol oxidation in neutral, alkaline and acid solution was studied by cyclovoltammetry. Deactivation of all electrodes in both neutral and alkaline medium was observed, indicating that polymerization reaction might be the main reaction pathway of phenol at higher pH values. Formation of quinine‐type structures was obtained during electro‐oxidation at lower pH values, being more significant in acidic solutions.     

Platinum modification of gold and electrocatalytic oxidation of ethylene glycol on Pt-modified Au electrodes

The surface modification of gold electrodes with platinum and the electrocatalytic oxidation of ethylene glycol on Pt-modified Au electrodes are investigated by cyclic voltammetry. Platinum modification is performed by the electrochemical deposition of platinum on polycrystalline gold electrodes, and the Pt-modified Au electrodes with different amount of the deposited platinum are used for the ethylene glycol oxidation in alkaline and acidic solutions. It is shown that oxidation potential for the ethylene glycol oxidation on the Pt-modified Au electrodes shifts significantly negative compared with that on Au electrodes, nearly same oxidation potentials as that on Pt electrodes are observed, and peak current density of the ethylene glycol oxidation is dependent on the amounts of the deposited platinum on gold surface, much higher peak current densities than that on Au and Pt electrodes can be obtained. The low oxidation potential and high peak current density indicate the enhanced reactivity of Au electrodes by the platinum modification. The characteristics of the Pt-modified Au electrodes are found to be similar to that of Pt electrodes, and the reactivity of the Pt-modified Au electrodes is mainly attributed to the deposited platinum.     

Electro-oxidation of methanol and ethylene glycol on platinum in alkaline solution: Poisoning effects and product analysis

The electrochemical oxidation of ethylene glycol on platinum was investigated and compared with that of methanol in alkaline solution by using various electrochemical and analytical measurements. Ethylene glycol showed much less significant electrode poisoning than methanol at low potential (400 mV). This phenomenon was clarified by analyzing the products of ethylene glycol oxidation. In ethylene glycol oxidation, partial oxidation to glycolate was much faster than complete oxidation to CO₂. In addition, there were two paths for ethylene glycol oxidation: poisoning and non-poisoning paths. The poisoning path led to the production of C1 compounds and the non-poisoning path gave oxalate. The non-poisoning path prevented the formation of poisonous species on platinum.     

A glassy carbon electrode modified by a copolymer of Co-tetrakis (para-aminophenyl)porphyrin and ortho-phenylenediamine. Characterization and electrocatalytic sulfite oxidation behavior of a basic extract from red wine

In this work, we present a comparison among three glassy carbon electrodes modified by Co-porphyrin, ortho-phenylenediamine, or both simultaneously. This comparison shows the differences among the electrochemical behavior, morphological characteristics and electrocatalytic behavior toward the sulfite oxidation of these electrodes. The electrode modified by Co-porphyrin, ortho-phenylenediamine and copolymer has been investigated in detail for the comparision of electrocatalytic activity towards the sulfite oxidation. In the case of the glassy carbon-modified electrodes, the presence of the copolymer enhances the electrocatalytic performance of the modified electrodes in spite of the non-catalytic response (compared to the bare glassy carbon) of both homopolymer-modified electrodes toward the oxidation of sulfite. Additionally, the oxidation of sulfite extracted from red wine is shown. The copolymer-modified electrode is capable of oxidizing the extracted free sulfite in a 0.02 M NaOH solution. Through the addition of standards method, a concentration of free sulfite in a Chilean red wine sample was determined to be 44 ppm.     

Electrochemical behavior of cysteine at a CuGeO3 nanowires modified glassy carbon electrode

A CuGeO₃ nanowire modified glassy carbon electrode was fabricated and characterized by scanning electron microscopy. The results of electrochemical impedance spectroscopy reveal that electron transfer through nanowire film is facile compared with that of bare glassy carbon electrode. The modified electrode exhibited a novel electrocatalytic behavior to the electrochemical reactions of l-cysteine in neutral solution, which was not reported previously. Two pairs of semi-reversible electrochemical peaks were observed and assigned to the processes of oxidation/reduction and adsorption/desorption of cysteine at the modified electrode, respectively. The electrochemical response of cysteine is poor in alkaline condition and is enhanced greatly in acidic solution, suggesting that hydrogen ions participate in the electrochemical oxidation process of cysteine. The intensities of two anodic peaks varied linearly with the concentration of cysteine in the range of 1 × 10⁻⁶ to 1 × 10⁻³ mol L⁻¹, which make it possible to sensitive detection of cysteine with the CuGeO₃ nanowire modified electrode. Furthermore, the modified electrode exhibited good reproducibility and stability.     

A comparative study of the electrocatalytic oxidation of ethylene glycol on PtAu nanocomposite catalysts in alkaline, neutral and acidic media

Electrocatalytic oxidation of ethylene glycol on platinum-gold nanocomposite catalysts is investigated by cyclic voltammetry. Platinum-gold nanoparticles are prepared by chemical reduction, and cyclic voltammograms of carbon-supported platinum-gold nanocomposite catalysts show significant differences in alkaline, neutral and acidic solutions. The catalysts exhibit high electrocatalytic activity and stability in alkaline solution, showing oxidation peaks at low potentials with high current densities. Oxidation peaks at higher potentials with significant current declines are observed in neutral solution, and further positive shifts in peak potential are observed in acidic solution. The concentrations of ethylene glycol and the supporting electrolytes also affect the reaction. A higher alkaline concentration is favorable for oxidation at low potential with high current density. Increased phosphate concentration in neutral buffer solution yields a negative shift in peak potential and minor enhancement in peak current density. Changes in the sulfuric acid concentration mainly affect peak current density. Factors such as the synergic catalysis effect and increased active surface area are thought to be responsible for the reactivity of the platinum-gold nanocomposite catalysts.     

Green bio-synthesis of Ni/montmorillonite nanocomposite using extract of Allium jesdianum as the nano-catalyst for electrocatalytic oxidation of methanol

In this work, synthesis of Ni nanoparticles was carried out successfully by water extract of Allium jesdianum as a biochemical reducing agent in the presence of montmorillonite clay (MMT) as a natural solid support for the first time. Then the electrochemical activity of the synthesized nanocomposite was investigated in methanol electrocatalytic oxidation. MMT with high cation exchange capacity and nano layer structure was exposed to ion exchange conditions in nickel solution. Then Ni²⁺ ion exchanged form was used in this process as a source of ions and also capping agent. Water extract of Allium jesdianum used as a reducing agent due to abundant availability of phenolic and flavonoid contents. The synthesized Ni/MMT nanocomposite was characterized using UV-Vis spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDX). The surface of prepared modified electrode has been characterized using SEM to evaluate the morphology, showing uniform dispersion of Ni nanoparticles with mean diameter of 12 to 20 nm. The modified carbon paste electrode was then used in methanol electrocatalytic oxidation reaction. Methanol oxidation on the proposed modified electrode surface occurs at 0.6 V and 0.3 V in alkaline and acidic medium respectively. Also, the results showed the better performance of modified electrode toward methanol electrocatalytic oxidation in comparison with carbon paste electrode that is modified by ion exchanged MMT. Charge transfer coefficients and apparent charge transfer rate constant for the modified electrode in the absence of methanol in alkaline medium were respectively found as: α_a = 0.53, α_c = 0.37 and k_s = 1.6×10^-1 s^-1. Also, the average value of catalytic rate constant for the electrocatalytic oxidation of methanol by the prepared nano-catalyst was estimated to be about 0.9 L·mol^-1·s^-1 by chronoamperometry technique. The prepared electrode was also effective for electrocatalytic oxidation of ethanol and formaldehyde in alkaline medium.     

Electrocatalytic Activity of Platinum modified Polypyrrole Films for the Methanol Oxidation reaction

The catalytic activity of platinum modified polypyrrole films prepared in different ways was studied for the methanol oxidation reaction. Surprisingly, no catalytic activity was observed for films modified with colloidal platinum particles incorporated into the film during its synthesis or for the film synthesised with tetrachloroplatinate complex as a nucleophilic counter-ion, which was subsequently cathodically reduced. On the other hand, high catalytic activity was observed for platinum deposited onto pre-synthesised polypyrrole film. The platinum load, film thickness and potential of platinum deposition were found to be important parameters. High electrocatalytic activity was also observed for platinum layers deposited directly onto the glassy carbon (GC) support. However, in the latter case the stability of the electrocatalytic activity was lower when compared with the polypyrrole film modified by cathodically deposited Pt.