YSZ粉末对多孔铂电极活性的影响

多孔铂电极的活性对氧传感器的使用性能起着决定作用,通过电化学循环伏安测试(CV)和扫描电镜分析,研究了YSZ(氧化钇稳定的氧化锆)粉末对铂浆法制得的多孔铂电极活性的影响,其中,以循环伏安测试中的电流密度来表征多孔铂电极的活性.结果表明:随着铂浆中YSZ粉末的含量升高,所制得的多孔铂电极孔隙率和电化学反应活性明显升高,这可能是由于YSZ粉末的加入提高了多孔铂电极O2(g),Pt/YSZ体系的三相界面面积造成的.     

亚硝酸根离子在聚中性红膜修饰玻碳电极上的电化学行为

用循环伏安法研究了电化学聚合中性红过程中聚合方式对聚合物膜的形成及电化学性能的影响.通过观察亚硝酸根离子在聚中性红薄膜修饰玻碳电极上的电化学响应行为,找到了中性红在玻碳电极上聚合的最佳条件以及该修饰电极对亚硝酸根离子检测的最佳实验条件.循环伏安实验结果表明,该修饰电极对亚硝酸根离子的电化学氧化具有一定的催化作用,NO-2的氧化峰电流值与NO-2 浓度在1.0×10-5～1.0×10-3mol/L范围内呈现良好的线性关系,相关系数r=0.9988,检测限为2.0×10-6mol/L.实验结果还表明,该修饰电极对亚硝酸根离子的测定具有较好的重现性,有望用于以电化学分析法现场监测实际水样中的NO-2.     

半微分循环伏安法

循环伏安法不仅能提供有关电极反应可逆性的信息,而且对于反应机理的研究,特别是对逐级反应的研究也很有价值。在许多情况下,可以用来直接研究活性中间产物。但循环伏安曲线的峰状对称性较差。近年新发展起来的半微分电分析法,比线性扫描伏安法有更良好的特性。K.B.Oldham指出了半积分循环伏安法用于动力学分析的优点。董绍俊用各类新极谱对聚乙烯二茂铁化学修饰电极进行了循环伏安法的研究。K.B.Oldham分别用摸拟技     

3,5-二溴水杨醛缩甲硫氨基酸席夫碱镍(Ⅱ)配合物修饰碳糊电极的制备及对甲醇的电催化氧化研究

制备了3,5-二溴水杨醛缩甲硫氨基酸席夫碱镍(Ⅱ)配合物修饰碳糊电极,研究了该电极催化甲醇的电化学行为。实验结果表明,电极材料组成中电活性物质BrTMSBNi为0.06g、石墨用量为0.30g时,电极有最大的氧化峰电流值;电极反应主要受扩散控制。利用循环伏安法测定了氧化峰电流值与甲醇浓度的关系,在1.2～2.0g/L范围内线性关系良好,相关系数为0.9997,检出限为0.04g/L。加标回收实验表明,该电极测定溶液中的甲醇具有较高的准确度。     

金属电极材料对YSZ氧传感器性能的影响

借助循环伏安和计时电流方法,研究了金属电极材料对YSZ氧传感器性能的影响。结果表明,在500℃和空气条件下,Ag-1%Pd/YSZ电极由于具有合适的微观结构以及较强的氧扩散能力,使其无论是作为YSZ氧传感器的阳极还是阴极,性能均为最好,而Au/YSZ电极最差;各金属/YSZ电极具有相似的阳极极化计时电流曲线,其电流密度值在10 s之内即可达到平稳;随着阳极阶跃极化电位增大,使得参加电极还原反应的氧原子数量增加,从而导致Ag-1%Pd/YSZ电极电流密度稳定值亦增大。     

基于COMSOL的微带电极阵列关键结构优化

为了研究不同特征尺寸对微带电极阵列电化学性能的影响,首先使用COMSOL有限元软件对不同特征尺寸微带电极阵列进行建模,分析了微带电极阵列表面电活性物质的浓度分布与循环伏安性能;然后,利用微加工技术制作了集成有不同特征尺寸微带电极阵列的微流控芯片,在亚铁氰化钾(K_4[Fe(CN)_6])溶液中对微带电极阵列的循环伏安性能进行测试;最后,根据仿真与实验结果推导修正公式,并验证修正公式的可靠性。结果表明,在0.5 mmol/L K4[Fe(CN)6]溶液进行扫速为1 V/s的循环伏安测试时,对于宽度为20μm和10μm的微带电极阵列,间距取40μm可避免屏蔽效应。优化后的结构对设计微带电极阵列具有指导意义。     

管式玻碳电极安培法流动注射分析测定药物异烟肼

报导一种管式玻碳电极流动注射电化学检测系统。用该系统测定了药物异烟肼,考察了各种底液的效果,以HAc-NaAc溶液(pH=5.6)较理想。在该溶液中可获得异烟肼良好的循环伏安波形,阳极峰电位为+950mV(以Ag/AgCl为参考电极)。检测限为1.0ppb。在10ppb～100ppm范围内,浓度与峰高有良好的线性关系。     

钢箱梁正交异性板抗疲劳加固试验研究

针对钢箱梁正交异性板的疲劳损伤,提出采用碳玻混杂纤维布(C/GFRP)加固和裂纹焊合法加固2种方法对疲劳裂纹进行维修加固,以提高其抗疲劳性能。试验结果表明,碳玻混杂纤维布加固和裂纹焊合法加固试验件与未加固试验件疲劳破坏表现形式几乎相同;结构钢度退化均可分为循环前期、循环中期和循环后期等3个阶段;2种加固方法均可有效地提升结构寿命。     

用聚合亚甲蓝修饰的酶电极对牛奶中青霉素残留测定研究

将青霉素酶与亚甲蓝用循环伏安法共聚合在玻碳电极上,制成青霉素酶电极,通过交流阻抗谱对酶电极表征。在一定电位范围内,青霉素微小浓度变化与亚甲蓝还原峰电流成正比,据此可间接测定了牛奶中残留青霉素含量,在磷酸缓冲溶液和牛奶中,线性范围分别为2.81×10-4～2.81×10-3mmol·L-1和1.12×10-3～2.81×10-3mmol·L-1。     

Ag/AgCl和碳纤维海洋电场电极的探测特性研究

使用烧结法制备了Ag/AgCl固态不极化海洋电场电极,利用聚丙烯腈碳纤维T300制备了电容型海洋电场电极。研究了不极化电极和电容型电极探测海洋电场的原理,提出了两种电极的使用方法并研究了其探测性能。使用电化学工作站对两种电极进了循环伏安测量和电极对极差跟踪;使用低频低噪声放大器对两种电极的自噪声稳定速度和大小进行对比测量;在自制水槽中测试了两种电极在不同频率下的响应性能。试验结果表明两种电极均可测量1 m Hz以上的交变海洋电场;相比于Ag/AgCl电极,碳纤维电极具有极差小和自噪声稳定速度快的特点;稳定后两种电极的自噪声均为1 n V/√Hz@1 Hz。     

质子交换膜燃料电池膜电极组件的制备

采用直接涂膜技术,利用40%的Pt/C催化剂制备质子交换膜燃料电池的核心部分膜电极组件.通过优化催化层中催化剂与Nafion的最佳质量比以及扩散层的微孔层的聚四氟乙烯与碳粉的质量比以改进燃料电池的性能,并利用循环伏安、电化学阻抗谱等技术对电池的电化学性能进行了表征.研究表明催化层中催化剂与Nafion的最佳质量比为3∶1时,对应的电池的活性面积最大,欧姆阻抗和电荷传递阻抗最小.另外,研究还发现在恒电流条件下,当扩散层的微孔层中碳粉质量分数为2 mg/cm2,碳粉与PTFE的质量比为7∶3时,放电性能最佳.     

Electrochemical characterization of a Porphyridium cruentum-modified carbon paste electrode by cyclic voltammetry

A carbon paste electrode was modified with red algal specie of Porphyridium cruentum and then characterization of its electrocatalytic activity was demonstrated with cyclic voltammetric studies of potassium ferricyanide (K₃[Fe(CN)₆]) system. Stable and fast response of modified electrode to redox couple of [Fe(CN)₆]^3?/[Fe(CN)₆]^4? was highlighted by performing experiments in comparison to bare carbon paste electrode. Fourier transform infrared spectra revealed the functional moieties of bare and modified electrode. Electrochemical surface area and surface coverage capacity were calculated for both electrodes. The effect of scan rate helped evaluate the nature of electrode process, electron transfer mechanism, and kinetic parameters (rate constant, charge transfer coefficient).     

Electrochemical determination of hydrogen peroxide using a novel prussian blue–polythiophene–graphene oxide membrane-modified glassy carbon electrode

A polythiophene–graphene oxide compound membrane and Prussian blue were deposited sequentially on the surface of a glassy carbon electrode by cyclic voltammetry. Due to its excellent electrocatalysis and its analogy with peroxidase enzymes, Prussian blue has been widely used in amperometric biosensors. The polythiophene–graphene oxide compound membrane exhibited good electroconductibility and a large specific surface area. The fabricated Prussian blue/polythiophene/graphene oxide/glassy carbon electrode was characterized by transmission electron microscopy, scanning electron microscopy, and cyclic voltammetry. Under the optimal experimental conditions, the detection of hydrogen peroxide was studied by its amperometric current–time curve. Due to the presence of polythiophene–graphene oxide compound membrane and Prussian blue, the hydrogen peroxide sensor shows a linear calibration range of 1.0?×?10^?6–1.0?×?10^?4?mol?L^?1, detection limits of 3.2?×?10^?7?mol?L^?1 at a signal-to-noise ratio of 3, and recoveries from 95.0 to 105.0%. The results show that the modified glassy carbon electrode has potential practical application for the determination of hydrogen peroxide based on its sensitivity and long-term stability.     

Glassy carbon electrode modified with glucose oxidase–graphene–nano-copper composite film for glucose sensing

We report on the modification of a glassy carbon electrode with graphene and Cu nanoparticles (Cu_nano), and how this electrode can serve as a platform for the construction of a novel electrochemical biosensor for the study of the direct electrochemistry of glucose oxidase and then application for glucose detection. To obtain the biosensor, the glucose oxidase was immobilized on the surface of the graphene and Cu_nano modified electrode, and this process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. A sensitive biosensor with a detection limit of 5 μM glucose was achieved, which was thought to result from a combination of beneficial effects including the biocompatibility and large surface area of the Cu_nano, the high conductivity of the graphene, the synergistic effects of composite film, and the increased quantity of glucose oxidase adsorbed on the electrode surface. The voltammetric responses were proportional to the concentration of glucose in the range from 0.05 mM to 12 mM. The biosensor was sensitive and stable.     

Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals.     

Influence of PTFE on electrode structure for performance of PEMFC and 10-cells stack

Water plays a critical role on the performance, stability and lifetime of proton exchange membrane fuel cells(PEMFCs). The addition of poly tetrafluoroethylene(PTFE) to the gas diffusion layer, especially, the cathode side, would optimize the transportation of water, electron and gas and thus improve the performance of the fuel cell. But until now, the studies about directly applying the PTFE to the catalyst layer are rarely reported. In this paper, the membrane electrode is fabricated by using directly coating catalyst to the membrane method(CCM) and applying PTFE directly to the cathode electrode catalyst layer. The performance of the single cell is determined by polarization curves and durability tests. Electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM) techniques are used to characterize the electrochemical properties of PEMFC. Also the performance of a 10-cells stack is detected. Combining the performance and the physical-chemistry characterization of PEMFC shows that addition of appropriate content of PTFE to the electrode enhances the performance of the fuel cell, which may be due to the improved water management. Addition of appropriate content of PTFE enhances the interaction between the membrane and the catalyst layer, and bigger pores and highly textured structure form in the MEA, which favors the oxygen mass transfer and protons transfer in the fuel cell. While superfluous addition of PTFE covers the surface of catalysts and hindered the contact of catalyst with Nafion, which leads to the reduction of electrochemical active area and the decay of the fuel cell performance. The proposed research would optimize the water management of the fuel cell and thus improve the performance of the fuel cell.     

Potential step study of electrooxidation of methanol in 1-butyl-3-methylimidazolium tetrafluoroborate

A potential step method was used to characterize the electrooxidation of methanol on a chemically modified electrode in an ionic liquid solvent. Two major findings were reported from this study. Firstly, the oxidation was dominant 2.2 s after the potential step. Before that, the double layer charging and adsorption were dominant. Therefore, there should be a waiting time of a few seconds if a methanol sensor is developed with a potential step method. Secondly, the oxidation of methanol on the electrode was diffusion controlled. The concentration of methanol affected the diffusion. The diffusion constant D₀ was 8.37 × 10⁻¹⁷ m²/s when the concentration was lower than 0.5 M and was 2.66 × 10⁻¹³ m²/s when the concentration was higher than 1.0 M. This suggests that the methanol concentration should be kept higher than a threshold in an ionic liquid based fuel cell.     

Application of L-DOPA modified carbon nanotubes as a bifunctional electrocatalyst for simultaneous determination of ascorbic acid,adrenaline, acetaminophen and tyrosine

L-DOPA multi-wall carbon nanotube modified glassy carbon electrode (DOPA-MWCNT-GCE) was used as a bifunctional electrocatalyst for simultaneous quantitative determination of ascorbic acid (AA) and adrenaline (AD). Electrochemical experiments show that the modified electrode plays the role of an excellent bifunctional electrocatalyst for the oxidation of AA and AD in two different potentials. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k′, for the electrocatalytic oxidation of AA and AD at the DOPA-MWCNT-GCE surface were estimated. Through a different pulse voltammetric (DPV) method, the plot of the electrocatalytic current versus AA and AD concentrations emerged to be constituted of two linear segments with different sensitivities. In addition, detection limits of 1.5 μM for AA and 0.62 μM for AD were obtained. In DPV, the proposed bifunctional electrocatalyst could separate the oxidation peak potentials of AA, AD, acetaminophen (AC) and tyrosine (Tyr) present in a mixture though, at the bare GCE, the peak potentials overlap. Finally, DOPA-MWCNT-GCE was satisfactorily used for the determination of AA, AD, AC and Tyr in pharmaceutical preparations.     

A Chitosan-Graphene Electrochemical Sensor for the Determination of Copper(II)

Graphite oxide was prepared by oxidizing graphite powder, reduced to graphene using hydrazine hydrate, and the grapheme was mixed with chitosan to form a composite that was used to modify a glassy carbon electrode for the determination of copper(II). The electrochemical behavior of the modified electrode was studied by cyclic and square wave voltammetries. The morphology and structure of the composite were characterized by infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. In addition, the proportion of composite material, pH, and adsorption time was optimized. Under the optimized experimental conditions, the sensor showed a linear dynamic range from 1.0 × 10^?9 to 1.5 × 10^?8 mol · L^?1 for copper(II) with a limit of detection of 4.3 × 10^?10 mol · L^?1 at a signal-to-noise ratio of three. The sensor displayed excellent electrochemical response and high sensitivity.