圆环电极上计时电流理论及其验证

本文推导得到了圆环电极上计时电流方程式。该式形式简单、计算方便、适用于任何电极半径和时间。用微金环电极在K4Fe(CN)6-KCl体系中对该理论进行验证,实验结果与理论十分符合。     

Hydrodynamic voltammetry at channel electrodes: Part III. Theory of kinetic currents

A theory of kinetic currents at a channel electrode is developed without any assumption on the magnitude of the rate constant of the preceding chemical reaction. An approximate equation with reasonable accuracy which relates the limiting current to the rate constant, flow velocity and the electrode geometries, is presented. The validity of the equation derived from the concept of the thin reaction layer is also discussed.     

Derivation of a general theory for reversible multistep electrode processes in voltammetry with constant potential at spherical electrodes

The rigorous theory for a reversible multistep electrode process in voltammetry with constant potential at spherical electrodes is derived. The expressions for the surface concentrations, the concentration profiles of species participating in the different steps and the current as a function of time have been deduced. These expressions are valid for any number of steps in which the initial species is oxidized/reduced, whatever the relative values of the formal potentials of the different steps and for any electrode radius value, including plane electrodes and ultra-microelectrodes.     

Determining the thermodynamic electrode potential in the presence of a mixed potential using EQCM technique

We give the theory explaining how to use Electrochemical Quartz Crystal Microbalance (EQCM) to determine the thermodynamic equilibrium electrode potential in a system where the open circuit potential is a mixed potential. The approach is applicable to electrodes of the first or the second kind in the presence of one or more soluble redox couples, at least one of which is irreversible. The key insight to be gained is that if the mass of an electrode of the first or the second kind does not change, its electrode potential is the thermodynamic equilibrium potential. This is true regardless of any other redox processes involving only soluble species that may be occurring at the electrode/solution interface. The model system used to test and confirm the theory was an electrode of the first kind, NiH_x,solid/Ni(II) undergoing active corrosion caused by hydrogen peroxide. The electrochemical quartz crystal microbalance method can be applied in fundamental and applied studies, e.g., of electroless deposition and corrosion systems containing multiple redox systems.     

A statistical study of the potential dependence of a transfer coefficient supports the Marcus theory

Cyclic voltammograms for the reduction of 2-methyl-2-nitropropane at a mercury electrode in acetonitrile solvent have been analyzed carefully by the “global” method. The dependence of the logarithm of the heterogeneous rate constant on the potential is only mildly parabolic, but statistical analysis shows that the curvature is nonetheless genuine and cannot be explained by random errors. The sign of the curvature is that predicted by the Marcus theory and the magnitude of the effect is also compatible with theory. No trend with scan rate is observed in any of the measured kinetic, thermodynamic or transport parameters.     

The Influence of Electrode Porosity on Diffusional Cyclic Voltammetry

A simple generic model to predict the influence of electrode porosity on the cyclic voltammetric response of an electrode is presented. The conditions under which deviation from the behavior of a perfectly flat, planar electrode can be expected are predicted. The scope for misinterpretation when conventional flat electrode theory is applied to porous electrodes is highlighted, especially in respect to the extraction of electrode kinetic parameters and the influence of ‘electrocatalysis’.     

Computer simulation of single-ion trajectories in paul-type ion traps

The computer simulation of single-ion trajectories using a number of computer programs is described together with associated theory. The programs permit calculation of ion trajectories while the ion is subjected to collisions with buffer gas of variable pressure, resonance excitation in any of three modes, and static or ramped DC and radiofrequency levels. Initially, the programs were designed for the calculation of ion trajectories in a quadrupole ion trap. The programs now permit such calculations for ions confined in traps having electrodes shaped to include percentages of hexapole and octupole components in the electric field as well as electrode surface geometries for which there is no closed-form expression. The Langevin collision theory is reviewed and a theoretical treatment of the multipole trap is presented.     

用单次电化学实验求电极邻近区域三维扩散方程的通解

电化学问题中的三维扩散方程一般都很难求解,即使是微园盘电极,也多采用数值计算或近似方法来处理。若电极形状不规则,严格求解将更困难,即便借助计算机也是件耗时而麻烦的工作。为解决这一困难,本文提出用单次电化学实验求电极邻近区域三维扩散方程通解的设想:     

Electrochemical Sensitive Determination of Nanomolar Guanine from ZnO Nanorods Coated on Platinum Electrode

The crystalline ZnO nanorods, grown on Si‐substrate (100) at a low temperature using a hydrothermal process were used for modification of platinum electrode using PVC and THF for in order to test their chemosensor activity. The modified electrode can be used for selective nanomolar determination of guanine in aqueous media without any interference from other biomolecules. The prepared chemosensor has a lower detection limit of 40 nM for guanine, and a modification of the electrodes with ZnO nanorods increases the reproducibility by reducing the fouling effect caused by the oxidation of biomolecules on the electrode surface as the prepared electrode can be used for more than 30 consecutive scans and can be used for 5 days without any change in current intensity or sensitivity.     

超微带电极上准稳态可逆波及其微分,半微分理论

本文推导了超微带电极上准稳态过程可逆波及其微分、半微分伏安曲线方程式，对曲线的性质进行了详细的讨论。在Ｋ４Ｆｅ（ＣＮ）６·ＫＣｌ体系中用超微金带电极对理论进行了验证，结果表明，理论与实验相符。     

Anodic stripping voltammetry with the florence mercury film electrode. determination of copper,lead and cadmium in sea water

The use of the rotating glassy carbon electrode mercury plated in situ for anodic stripping voltammetry has been investigated. The choice of electrode material is discussed. The effect of instrumental parameters on the stripping response for copper, lead and cadmium in sea water is studied, the results being in accordance with the theory of thin film electrodes. The variation in the observed sensitivity for the three metals in sea water is discussed in terms of complex-forming ligands. Lastly the performance of the film electrode is compared to that of the hanging mercury drop electrode.     

Continuous-time random-walk theory of interfering diffusion and chemical reaction with an application to electrochemical impedance spectra of oxidized Zr-1%Nb

A microscopic theory is developed for the interplay of diffusion and chemical reaction and the results are compared with electrode impedance measurements on an oxide electrode. The theory is based on the ideas of continuous-time random walk and accounts for the interference of diffusion and recombination of the charge carriers in the oxide. The treatment results in a dispersive diffusivity with two time constants, one of them corresponding to the random walk, the other to the reaction. Combining this diffusivity with the Warburg electrode admittance expression, which refers to cases where the rate-limiting step is diffusion in a semi-infinite medium bounded by a plane, an admittance function is obtained. The phase angle is found to be higher than 45 degrees distinguishing it from the Gerischer impedance which was developed for a related problem. The oxides were produced by hydrothermal oxidation of Zr-l%Nb alloy, a metal used as cladding material for nuclear fuel elements. The electrode impedance spectra of Zr/Zr-oxide electrodes in aqueous SO(3) (2-) solutions were taken at various anodic voltages between 1 Hz and 100 kHz and temperatures between 278 and 333 K. The theoretical admittance functions could be successfully compared with the observed spectra. Both the functional forms and the fitted parameter values support our theory which is also in keeping with Macdonald's point-defect model.     

Comparison of fundamental and second-harmonic a.c., and normal,derivative and differential pulse linear-sweep and stripping voltammetric methods

Linear-sweep and stripping a.c. and pulse voltammetric methods have been compared for a variety of electrodes and electrode processes. Each of the linear-sweep techniques is readily used systematically because, in contrast to d.c. linear-sweep voltammetry, the theory for reversible electrode processes is basically analogous to that for polarography at a dropping mercury electrode. In stripping analysis, some departures are found at a hanging mercury drop electrode because of spherical diffusion effects. For reversible electrode processes, the limits of detection for a.c. and pulse methods are comparable. However, a.c. methods offer advantages over pulse methods in discriminating against irreversible electrode processes and permit the ready use of faster scan rates. Pulse methods are more sensitive for irreversible electrode process. Normal pulse polarography is particularly favourable in minimizing undesirable phenomena arising from adsorption or deposition of material on electrodes.     

Current transients at a channel electrode produced by a potential step

A theory is presented which describes the transient current response to a potential step at a channel (or tubular) electrode for a reversible electrode reaction. Experimental results for a wide range of solution flow velocities are found to be in good agreement with theory.     

超微盘电极线性扫描准稳态可逆波及其导数波理论

提出超微盘电极线性扫描准稳态可逆波理论, 对伏安曲线性质进行了研究,利用铂超微盘电极及K~4Fe(CN)~6-KCl体系进行了验证, 此外, 还对超微盘电极线性扫描可逆波的一次, 二次, 三次微分进行了理论探讨。     

A multilayer model for the study of space distributed redox modified electrodes: Part II. Theory and application of linear potential sweep voltammetry for a simple reaction

The theory of linear potential sweep voltammetry for a simple redox system in the case of a space distributed redox modified electrode (redox polymer electrode, or adsorption of an electroactive substance in several layers) is established on the basis of the model discussed in Part I of this series. When the rate of the reaction of electron exchange inside the coating is rapid, the theory for a monolayer adsorption is directly applicable. When it is slow, the peaks have a particular shape, with a “tailing” of the current; their characteristics are discussed. The theory is applied to the study of the multilayer adsorption of benzo(c)-cinnoline.     

An improved cell for in-situ electrochemical ESR

An improved cell for simultaneous electrochemical ESR based on a coaxial cylindrical cavity is described and shown to have high sensitivity whilst behaving as a satisfactory hydrodynamic electrode as evidenced by Tafel analysis, by Levich analysis and comparison with theory for the dependence of the ESR signal on electrode currents and electrolyte flow rate.     

A Novel Process for the Fabrication of a Silver‐Nanoparticle‐Modified Electrode and Its Application in Nonenzymatic Glucose Sensing

In this work, we present a novel process for fabrication of a silver‐nanoparticle‐modified electrode using silver ion implantation. This method is facile, low‐cost and environmental friendly without the use of any other chemicals. The obtained AgNPs on the electrode surface, which were free from any reagents surrounding or binding to them, showed prominent electrocatalytic activity towards the oxidation of glucose, leading to a nonenzymatic glucose sensor with a wide linear range and a detection limit of 0.5 µM. In addition, the modified electrode also exhibited acceptable reproducibility and long‐term stability.     

Thermal fluctuations of total and free electrode charges

Using the Nyquist fluctuation-dissipation theorem, the analysis of thermal fluctuations in a complex electrochemical system is carried out for the case of slow discharge accompanied by surfactant adsorption. It is shown that the dispersion of thermal fluctuations of the total and free charges of a reversible electrode obey an equation general for both Gibbs and Einstein-Landau approaches to the theory of thermal fluctuations of extensive values and also the noise approach based on the Nyquist fluctuation-dissipation theorem. Thus, in contrast to the higher correlations of the fluctuating electrode charge, the Gibbs theory of squared correlations is in complete agreement with the Nyquist fluctuation-dissipation theorem.     

A Mercury-free Electrode for Determining Amalgam-forming Elements by Stripping Voltammetry

A mercury-free modified screen-printed electrode was proposed for the preconcentration and determination of Cu(II), Pb(II), Cd(II), and Zn(II). The simplicity of design, compactness, and low cost of the developed electrode; the possibility of using it as a disposable electrode; and no need in any operations on the mechanical treatment of the electrode surface make this electrode a candidate for portable transducers in flow and discrete analyses.