关于变价态奎宁电极的研制与Ph对电极斜率影响的探讨

本文研究在两种质子化状态存在时奎宁的电极行为与特点,证明在不同pH溶液中变价态奎宁电极电位不能直接用能斯脱公式或Nicolsky-eisenman公式表出,提出了变价态电极的S-σ经验或,并依据此式,用奎宁选择性电极测出20℃下I=0.5McIlvaine缓冲液双质子化奎宁,辛可宁、硫胺的Ka1分别为(8.37±0.96)x10[-5],(8.00±0.92)x10[-5].(8.37±0.96)x10[-6].指出:同系列溶剂介电常数增大,液膜电极斜率增大,存在S-1/ε线性关系,电极可用于奎宁的电位滴定法或直接电位法测定。     

不受电极斜率限制的离子电极标准加入法算图

格兰图在离子选择电极法中应用广泛,但该图要求电极响应的能斯特斜率为一定值。对电极斜率偏离理论值的情况进行修正已有报道。 本文提出一种不需任何电极斜率校正步骤的算图,即以加入标准溶液后电位的变化值△E与实际斜率S的比值△pe对加入标准溶液体积Vs作图的计算图(简称为△pe格兰图)。在实际操作中,根据测得的△E值和S值,经换算为△pe后,即可在标准算图上作图进行结果计算。克服了作空白溶液线或共线图线时可能引进的误差,简化了结果处理过程。此外,对不同价态离子的测定,该算图纵坐标标度△pe不变,不必扩大或缩小,作图十分方便。     

长链四烷基锡作中性载体的亚硝酸根选择性电极的研究

用亲脂的长链四烷基锡作中性载体制备亚硝酸根选择性电极. 其选择性模式与经典的阴离子交换剂相比有显著不同, 相对硝酸根的电位选择性系数改善约4个数量级. 线性响应区间为1x10^-^1-2x10^-^5mol.dm^-^3, 检测下限为5x10^-^6mol.dm^-^3. 电极斜率在弱性介质中为Nernst响应, 在弱酸性介质中为两倍Nernst响应. 紫外光谱研究发现酸度影响载体与阴离子的多级配位平衡. 电极斜率的变化与此平衡密切相关, 在此基础上给出了对电极斜率的异常变化及电位-pH     

直接电位分析法的定位校准和斜率校准

本文阐述了直接电位分析法定位和斜率校准的理论与测量原理。Eemf pM标准曲线法不必考虑定位和斜率校准问题 ;单点定位pMX 直读法 ,只进行定位校准 ,没有完全校正电极理论与实际斜率不一致所产生的测量误差 ;双点定位pMX 直读法在pMS1～pMS2 之间同时进行定位与斜率校准 ,测量的相对误差较小     

键参数拓扑指数与常用元素的标准电极电位

采用元素键参数拓扑指数关联了第一、二和七主族元素的标准电极电位;采用无机化合物键参数拓扑指数关联了第四周期过渡元素和标准电极电位,结果显示,键参数拓扑指数与元素的标准电极电位之间有较好的线性相关性。     

电位传感器聚(1,2-二氨基苯)膜化学修饰电极——Ⅰ.电极制备方法的研究

本文报道在[NiFe(CN)_6]~(2-/1)化学修饰膜上电化学聚合生成聚(1,2-二氨基苯)膜化学修饰电极的制备方法,实验结果表明该电极制备方法简便、性能稳定、电极电位对溶液pH值变化敏感,在pH4～10范围内电位响应与pH呈直线关系,斜率为54mV,具有作为pH传感器的前景。     

多孔与平面硅电极界面的电化学行为

研究了重掺杂n-型单晶硅(CSi)在氢氟酸体系中生成多孔硅(PSi)的电化学行为,根据线性极化曲线,选取不同的电流密度,采用恒电流阳极极化法,制备了一系列多孔硅层。利用扫描电子显微镜对其进行了表面和断面形貌的表征,通过线性扫描极化技术和计时电位法,比较了单晶硅电极和多孔硅电极的电化学行为,分析了多孔硅形成前后的塔菲尔曲线和计时电位曲线,给出了多孔硅形成过程中的重要电化学参数,如腐蚀电流、开路电位、塔菲尔斜率等。并对其进行深入分析,根据实验结果,提出了单晶硅电极/电解质界面和多孔硅电极/电解质界面的结构模型,并利用该模型讨论了两种电极界面的电化学特性。     

采用循环伏安与Tafel曲线比较不同阳极的电催化性能

采用循环伏安和Tafel曲线两种方法评价了Pt电极、钛基二氧化钌电极(Ti/RuO2)及钛基二氧化锡电极(Ti/SnO2)的电催化氧化性能.结果表明,在500 mg/L的苯酚溶液中,Pt,Ti/RuO2和Ti/SnO2电极氧化苯酚的峰电位依次为0.93,0.95和1.40 V(vsAg/AgCl).Tafel曲线表明,三种电极析氧过电位的顺序依次是Ti/RuO2相似文献   

稀土离子选择电极的研制

(一)本文首次提出一类新型离子选择电极——水膜电极。推导了水膜电极遵循的能斯特方程式。具体研制了氯化钕水膜电极,用于测定环己酮中Na(PMBP)₃螯合物。结果与理论相符合。研究了参比电极电位在非水介质中保持稳定的条件。发现了两不相溶溶液界面上的电位响应可以是双向的,而且响应曲线斜率的绝对值基本相同。水膜离子选择电极可以做到完全不受有机溶剂的腐蚀,这是水膜电极的优点。     

流动注射-流通式电极法对阳离子表面活性剂的测定

将流动注射、管状流通式电极与电位计连接,测定水体中阳离子表面活性剂的含量.以二次蒸馏水作为载液,在流速1.5 mL·min-1,进样体积340 μL,管路长度为15 cm的条件下对水样进行测定.结果表明电极在6.4×10-7 ～1.6×10-4 mol·L-1范围内对阳离子表面活性剂具有良好的能斯特响应,响应斜率为-53.07 mV/pcCTMAB,相关系数为0.999 2,加标样品的平均回收率为100%.     

An electrochemical study of safranin O binding to DNA at the surface

The interaction of safranin O (SO) with double-stranded calf thymus DNA was investigated electrochemically, using a DNA-modified glassy carbon (GC-DNA) electrode. The results were compared with those obtained using a bare GC electrode. The formal potential of SO was more negative when using the GC-DNA electrode, although the rate of heterogeneous electron transfer was not altered. The GC-DNA electrode enabled preconcentration of the SO on the electrode surface, despite the fact that the mass transfer effects in the thin DNA layer adsorbed on the surface were still observed. The diffusion coefficient of SO and the binding ratio for the oxidized and reduced forms of the bound species were obtained. A binding isotherm for SO at the GC-DNA electrode was plotted from coulometric titrations, giving a binding constant of 5.8×10⁴ L mol⁻¹.     

Impedance Studies of Spinel LiMn2O4 Electrode/electrolyte Interfaces

The formation process of solid electrolyte interphase（SEI） film on spinel LiMn2O4 electrode surface was studied by electrochemical impedance spectroscopy（EIS） during the initial storage in 1 mol/L LiPF6-EC：DMC：DEC electrolyte and in the subsequent first charge-discharge cycle. It has been demonstrated that the SEI film thickness increased with the increase of storage time and spontaneous reactions occurring between spinel LiMn2O4 electrode and electrolyte can be prevented by the SEI film. In the first charge-discharge cycle succeeding the storage, the electrolyte oxidation coupled with Li-ion insertion is evidenced as the main origin to increase the resistance of SEI film. The results also confirm that the variations of the charge transfer resistance（Rot） with the electrode potential（E） can be well described using a classical equation.     

Keggin型缺位硅钨杂多阴离子的电化学性质及电催化还原H2O2

应用循环伏安、方波伏安和交流阻抗法研究了Keggin型缺位硅钨杂多阴离子SiW11O398-(SiW11)在0.1mol.L-1NaHSO4+Na2SO4溶液中的电化学性质及其对H2O2还原的间接电催化作用.结果表明,SiW11的酸性水溶液在玻碳(GC)电极上显示两对可逆的还原-氧化波,对应的电荷迁移数均为1,且有2个质子参与反应.根据第1对波的还原峰电流与扫描速率平方根关系得到SiW11在溶液中的扩散系数DO为8.92×10-6cm2.s-1.SiW11对H2O2的还原具有明显的电催化活性,催化峰电位随溶液pH的降低而正移,峰电流增大.质子H+在催化反应中起协同促进作用.实验测定该电催化过程的均相准一级反应速率常数为0.30 s-1.SiW11电催化还原H2O2的机理被认为是经过形成所谓"七配位过氧化物"而发生的.     

The effect of partial charge transfer on the electrochemical turbulent noise

Theoretical analysis of the effect of electrode potential on the spectral density of random alternating current emerged in electrochemical cell under the action of turbulent pulsations of the electrolyte solution velocity is carried out. An impedance model of metal electrode dissolution reaction, including two adsorption stages, is suggested, with allowance for the oxidized ion diffusion in electrolyte solution. It is known that in terms of the Ershler-Randles model, at low frequencies the experimentally measured slope of bilogarithmic frequency dependence of spectral density equals 3, which is characteristic of the diffusion control; at high frequencies the slope equals 4, which is characteristic of the kinetic control. It is shown that for the model of impedance of the two-stage adsorption oxidation process, in the middle segment of the spectrum the local slope must decrease down to 2, provided the first oxidation stage, which proceeds within the inner electrical double layer, is slow; the local slope must increase up to 6 (or 5, for diffusion control), provided the second oxidation stage (the partially oxidized ion desorption to solution) is slow. The “height” and “width” of the slope local changes appeared explicitly depending on the parameters of the partial charge transfer. This makes the turbulent noise method somewhat superior to the impedance method in the studying of the above-specified reaction type.     

Determination of the number of electrons by chronoamperometry at small electrodes

The number of electrons transferred, n, was determined by taking the ratio of the square of the slope to the intercept of Cottrell plots by chronoamperometry at a small disk electrode without knowing values of diffusion coefficients. The intercept is ascribed to the contribution of spherical diffusion. This technique is useful for estimating reaction mechanisms of unstable species of which lifetime is shorter than the period of bulk electrolysis. It takes advantage not only of getting the simultaneous acquisition of two independent variables (the slope and the intercept) in one chronoamperometric curve but also of evaluating the dependence of n for multi-step charge transfer reactions on electrode potentials. Ferrocene and N,N′-bis(4-methoxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine were used for redox species at n = 1 and 2, respectively. Chronoamperometric currents were obtained at the platinum disk electrode 50 μm in radius for the time less than 3 s, responding to the various stepped potential values. Values of n were obtained at each potential even for sluggish charge transfer reactions.     

Kinetics of multiple electron transfer reactions at porous electrodes under stationary and flow conditions

The kinetics of consecutive two-electron transfer reactions at porous flooded electrodes are investigated under both stationary and flow conditions, where mass transfer is due respectively to diffusion and forced convection. The current-polarization relations were calculated for both modes of mass transfer as a function of the specific surface area of the electrode, the rates of the respective steps of the electron transfer reaction and the appropriate mass transfer coefficients. The computed solutions degenerate to the known limiting cases of single electron transfer control under conditions of very high or very low polarizations. Thus, at high anodic polarization, the electrochemical reaction is controlled by a single electron transfer step, the other step being too fast. Under conditions of 0.1<i/i_L<1, the overall reaction rate is controlled by both mass transfer and electrochemical activation. For flooded diffusion electrodes, the current-voltage curves follow the Tafel equation with a slope of double the normal value. This is attributed to mass transfer control in agreement with previous work. Experimental results, obtained on the porous flow-through electrode, agreed well with the theoretical predictions. The calculations presented here enable a quantitative evaluation of the relative influence of the rate of any step on the overall behaviour of the electrode under the appropriate experimental conditions.     

Electrochemical formation and reduction of silver oxides in alkaline media

The anodic oxidation of silver electrodes in NaOH solution and the reduction of the silver oxides formed were studied by potential step chronoamperometry. Oxidation of Ag to Ag₂O is a diffusion-controlled reaction, the diffusion control being established in the solid phase. Oxidation of Ag₂O to AgO proceeds via a nucleation and growth-controlled process. The amount of AgO decreased with increasing step height. The current—time curves for this reaction have been analysed with the Kolmogoroff—Avrami equation. Reduction of AgO to Ag₂O occurs initially on the outside of the electrode, and the rate of the reaction is limited by diffusion of ions across the thickening layer of Ag₂O. Reduction of Ag₂O to Ag proceeds via a nucleation and growth reaction.     

How Water Accelerates Bivalent Ion Diffusion at the Electrolyte/Electrode Interface

The effect of H₂O in electrolytes and in electrode lattices on the thermodynamics and kinetics of reversible multivalent‐ion intercalation chemistry based on a model platform of layered VOPO₄ has been investigated. The presence of H₂O at the electrolyte/electrode interface plays a key role in assisting Zn²⁺ diffusion from electrolyte to the surface, while H₂O in the lattice structure alters the working potential. More importantly, a dynamic equilibrium between bulk electrode and electrolyte is eventually reached for H₂O transport during the charge/discharge cycles, with the water activity serving as the key parameter determining the direction of water movement and the cycling stability.     

尖晶石锂锰氧化物电极首次脱锂过程的EIS研究

研究了尖晶石锂锰氧化物电极首次脱锂过程中的电化学阻抗特征. 通过选取适当的等效电路拟合实验所得的电化学阻抗谱数据, 获得了首次脱锂过程中固体电解质相界面膜(SEI膜)的电阻、电容以及电荷传递电阻、双电层电容等随电极极化电位的变化规律.     

Direct electron transfer and bioelectrocatalysis of hemoglobin on nano-structural attapulgite clay-modified glassy carbon electrode

Direct electrochemistry of hemoglobin (Hb) on natural nano-structural attapulgite clay film-modified glassy carbon (GC) electrode was investigated. The interaction between Hb and attapulgite was examined using UV-vis, FTIR spectroscopy, and electrochemical methods. The immobilized Hb displayed a couple of well-defined and quasi-reversible redox peaks with the formal potential (E(0')) of about -0.366 V (versus SCE) in 0.1 M phosphate buffer solution of pH 7.0. The current was linearly dependent on the scan rate, indicating that the direct electrochemistry of Hb in that case was a surface-controlled electrode process. The formal potential changed linearly from pH 5.0 to 9.0 with a slope value of -48.2 mV/pH, which suggested that a proton transfer was accompanied with each electron transfer in the electrochemical reaction. The immobilized Hb exhibited excellent electrocatalytic activity for the reduction of hydrogen peroxide without the aid of an electron mediator. The electrocatalytic response showed a linear dependence on the H(2)O(2) concentration ranging from 5.4 x 10(-6) to 4.0 x 10(-4) M with the detection of 2.4 x 10(-6) M at a signal-to-noise ratio of 3. The apparent Michaelis-Menten constant K(M)(app) for the H(2)O(2) sensor was estimated to be 490 microM, showing a high affinity.