多相高分子快离子导体阻抗谱的研究

研究了以ＬｉＣｌＯ４掺杂的聚乙二醇聚氨酯双离子导体及磺酸型聚乙二醇聚氨酯离聚物单一离子导体的阻抗谱，给出了多相快离子导体交流阻抗测试系统的等效电路．通过阻抗谱计算机解析，计算得出了样品的基本电学参数．通过讨论界面阻抗的色散现象，计算出样品的离子电导率，和阻抗谱解析法得到的结果相一致．     

旋转铂盘电极上Cu(phen)_2~(2 )与6-巯基嘌呤的相互作用

在Tris-NaC1*(pH=7.2)缓冲溶液中,应用循环伏安法,微分脉冲伏安法、旋转圆盘电极实验、交流阻抗法及其数据模拟等技术研究了Cu(phen)2 25(phcn=1.10-邻菲咯啉)与6-巯基嘌呤(6-MP)的相互作用.结果显示.Cu(phen)2 2MP与6-MP无论在扩散控制过程或电化学控制过程都发生了相互作用.Cu(phen)2 2及其与6-MP的作用产物于铂电极上均呈现一对氧化还原峰,但后者呈现的氧化还原峰负移.峰电流减小.交流阻抗结果显示,无论6-MP存在与否,Cu(phen)2 2在交流阻抗谱上均呈现两个清晰的电容弧,但当6-MP存在时,电化学反应电阻和电化学吸脱附电阻均增大.Cu(phen)2 2在不同转速下的阻抗拟合结果显示.随转速增大.电化学反应电阻和电化学吸脱附电阻均减小.双电层电容呈增大趋势,而吸脱附电容呈减小趋势:当6-MP存在时.仍然呈现此变化规律.     

All Solid‐State pH Electrode Based on Titanium Nitride Sensitive Film

Titanium nitride was used as pH‐sensitive material to fabricate all solid‐state pH electrode. The fabrication and the response performance of the pH electrode were described in the paper. The TiN film electrode showed a linear response in the pH range of 2–12 with a near‐Nenstian response (?55 mV/pH). The response time was within 1 min, and the electrode had good reproducibility, stability and low sensitivities for different species. Compared with the glass pH electrode, the electrode exhibited some advantages, for example, without activation, rapid response and high mechanical strength. In addition, the electrode performed excellently in a corrosion medium containing F^?(1 M). Electrochemical behaviors of TiN electrode in Britton‐Robinson buffers were studied with Electrochemical Impedance Spectroscopy (EIS).     

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

Effect of the protonation level of poly(o-phenylenediamine) (PoPD) on the ac impedance of humidity-sensitive PoPD/poly(vinyl alcohol) composite film

A composite film consisting of poly(o-phenylenediamine) (PoPD) and poly(vinyl alcohol) (PVA) has been prepared, and the effect of the protonation level of PoPD on the response of the composite to humidity been investigated by ac impedance measurements. The electrochemical system of the PoPD/PVA composite in a humid atmosphere is represented by an electrochemical equivalent circuit containing film (R_film, C_film), Warburg (W) and interfacial (R_ct, C_dl) impedance. R_film was increased with decreasing protonation level of the PoPD in relative humidity regions higher than 40%, but it was almost independent of the protonation level in humidity regions lower than this percentage.     

Physical properties and electrochemical performance of LiMn2O4 cathode materials prepared by a precipitation method

LiMn₂O₄ powder for lithium-ion batteries was prepared by a precipitation method, and the effects of calcination temperature on the physical properties and electrochemical performance of the samples were investigated by various methods. The results of X-ray diffraction (XRD) showed that the lattice parameter (a) and the unit cell volume (v) decrease with the increasing calcination temperature, and the LiMn₂O₄ sample calcined at 750°C has smaller particle size and higher crystallinity than other samples. The results of the electrochemical experiments showed that the sample calcined at 750°C has larger peak currents, higher initial capacity, and better cycling capability, because of its lower charge-transfer resistance and larger diffusion coefficient of Li⁺ ions than those of other samples.     

Assessment of corrosion resistance of surface-coated galvanized steel by analysis of the AC impedance spectra measured on the salt-spray-tested specimen

In the present work, corrosion resistance of surface-coated galvanized steel was quantitatively determined by an analysis of the alternating current (AC) impedance spectra measured on the salt-spray-tested specimen. To evaluate the corrosion resistance of the surface-coated galvanized steel, AC impedance spectroscopy was performed on the salt-spray-tested specimen previously exposed to salt-sprayed corrosive environment. From the analysis of the impedance spectra, the area fraction transient of white rust θ ₂(t) was theoretically derived from the equivalent circuit equation by using two fitting parameters. The values of the two fitting parameters were determined by fitting the empirical transient equations to the area fraction of the resin coating layer and to the total resistance obtained from the impedance spectra measured, respectively. From the analyses of θ ₂(t) for four kinds of surface-coated galvanized steels with various resin coating layers, it is indicated that as the values of the two fitting parameters decrease in the order of CP, GI, OD and OM (commercial trade names) specimens, the corrosion resistance increases in that order as well. Furthermore, from the quantitative comparison of the two fitting parameters with the polarization resistance of the upper resin coating layer R _p determined from the potentiodynamic polarization curve, it is suggested that the two fitting parameters decrease in value as well with increasing R _p.     

镀金和碳纳米管修饰金电极上吸附态葡萄糖氧化酶比活性的EQCM研究

采用石英晶体微天平(EQCM)技术监测了裸金电极、镀金和碳纳米管修饰金电极上葡萄糖氧化酶(GOD)的吸附过程. 通过EQCM测量吸附固定的GOD质量, 并实时检测酶反应产物H2O2的氧化电量, 求算了各表面上吸附态GOD的比活性(ESAi). 结果表明, 各表面上均可吸附一定的GOD, 且吸附态GOD均有一定的酶活性; 修饰CNTs可增大酶吸附量和酶电极对葡萄糖的响应电流, 但ESAi随CNTs修饰量的增大而降低; Au电极上电镀金后, 酶吸附量和酶电极对葡萄糖的响应电流亦增大, 但ESAi与裸金电极上的基本一致.     

Effect of the Structure of Nonuniform Conducting Polymer Films on Their Electrochemical Impedance Response

Electrochemical impedance spectroscopy is used to characterize thin p-doped polypyrrole (PPy) films in propylene carbonate (PC) solutions and poly(trifluorophenyl)thiophene (PTFPT), in solutions based on sulfolane (SF). It appears that the latter film is much less swelled compared to the former one. One consequence of this difference is that the PTFPT film shows a much higher bulk resistance compared to that for the PPy film. Another important consequence is that the swelling of the PTFPT film is essentially physically non-homogeneous. Two parallel, uncoupled paths, with different chemical diffusion coefficients, model the experimental results adequately. In order to quantify the impedance spectra for both polymer films, we use a model proposed by Rubinstein et al. explaining the difference in the diffusion coefficients of Ru(bpy)^3+/2+ ₃ within a thin Nafion film. The model can also predict the impedance spectra for composite powdery electrodes containing different particle sizes, such as composite cathodes and graphite anodes used in lithium batteries.     

靛红掺杂聚吡咯膜修饰电极的电荷传输

利用交流阻抗法研究了靛红掺杂聚吡咯膜内的电荷传输，通过非线性最小二乘法拟合，得出了体系的等效电路，并计算出其电荷扩散系数和异相电子传递反应速率常数。实验结果表明，随着膜厚的增加，活性点增多，异相电子传递反应速率常数增大，同时表观扩散系数也增大。