Linear scanning voltammetry

Equation (25) is general in that it does not depend on the electrochemical method employed to obtain the i-E data. Moreover, unlike conventional electrochemical methods such as cyclic or linear scan voltammetry, all of the experimental i-E data are used in kinetic analysis (as opposed to using limited information such as the peak potentials and half-widths when using cyclic voltammetry). Finally, and of particular importance, the convolution analysis has the great advantage that the heterogeneous ET kinetics can be analyzed without the need of defining a priori the ET rate law. By contrast, in conventional voltammetric analyses, a specific ET rate law (as a rule, the Butler-Volmer rate law) must be used to extract the relevant kinetic information. 

The convolution analysis is based on the use of convolution data and further manipulation to obtain information on the ET mechanism, standard potentials, intrinsic barriers, and also to detect mechanism transitions. It is worth noting that the general outlines of the methodology were first introduced in the study of the kinetics of reduction of terf-nitrobutane in dipolar aprotic solvents, under conditions of chemical stability of the generated anion radical. For the study of concerted dissociative ET processes, linear scan voltammetry is the most useful electrochemical technique. 

Linear scan voltammetry (LSV) — It is an experimental method when the -> electrode potential is varied linearly with time (t) with a scan (sweep) rate v = dE/dt and the current (I) vs. E curve (which is equivalent with E vs. t curve) is recorded. Usually scan rates ranging from 1 mV s-1 to 1V s-1 are applied in the case of conventional electrodes with surface area between 0.1 and 2 cm2, however, at -> ultramicroelectrodes 1000 or even 106 V s-1 can also be used. The scan is started at a potential where no electrochemical reaction occurs. At the potential where the charge transfer begins, a current can be observed which increases with the potential, however, after a maximum value (current peak) it starts to decrease due to the depletion of the reacting species at the -> interface. 

Linear sweep voltammetry - linear scan voltammetry... 

Peak height (in -> voltammetry) — It is the maximum current in - linear scan voltammetry, -> cyclic voltammetry, - staircase voltammetry, - differential staircase voltammetry, -> alternating current polarography... 

In linear scan voltammetry (LSV) the peak current of fast and reversible electrode reactions controlled by semi-infinite planar diffusion is given by the following equation [i] ... 

See also -> linear scan voltammetry, and - cyclic voltammetry. 

Potential at half-height — (in voltammetry) This is a diagnostic criterion in -> linear scan voltammetry. The potential at half-height Ep/2 is the potential at which the current is equal to one-half of the peak current fp Ep/2 = h (/=/p/2)- I he first of two potentials at half-height, the one that precedes the peak potential (Ep) is considered only. If a simple electrode reaction is reversible (- reversibility) and controlled by the planar, semi-infinite - diffusion, the absolute value of the difference between Ep/2 and Ep is equal to 56.6/n mV and independent of the - scan rate. If the -> electrode reaction of dissolved reactant is totally irreversible (-> reversibility), the difference Ep/2 - Ep is equal to 47.7/an mV for the cathodic process and -47.7/(l - a)n mV for the anodic process. 

Potentiodynamictechniques— are all those techniques in which a time-dependent -> potential is applied to an - electrode and the current response is measured. They form the largest and most important group of techniques used for fundamental electrochemical studies (see -> electrochemistry), -> corrosion studies, and in -> electroanalysis, -+ battery research, etc. See also the following special potentiodynamic techniques - AC voltammetry, - DC voltammetry, -> cyclic voltammetry, - linear scan voltammetry, -> polarography, -> pulse voltammetry, - reverse pulse voltammetry, -> differential pulse voltammetry, -> potentiodynamic electrochemical impedance spectroscopy, Jaradaic rectification voltammetry, - square-wave voltammetry. 

Randles-5>evcik equation — An equation introduced by - Randles [i] and - Sevcik [ii] describing the magnitude of the voltammetric peak current /p (in - linear scan voltammetry or in - cyclic voltammetry) for a reversible electron transfer ( rev mechanism -> Erev diagnostics in cyclic voltammetry). 

Linear scan voltammetry Electroanalytical methods that involve measurement of the current in a cell as the electrode potential is linearly increased or decreased with time the basis for hydrodynamic voltammetry and polarography. 

We begin by considering linear-scan voltammetry (LSV). The voltage is rapidly scanned at the working electrode (Fig. 1), and the resulting current is monitored and plotted as a function of either time or (usually) potential. The experiment is performed at a small stationary electrode in an unstirred solution. The most popular working electrodes are the hanging mercury-drop electrode (hmde) and either a flat disk or small... 

Figure 2. Plot of X (at) (ordinate) vs. n(E — E, ) for a reversible system studied by linear-scan voltammetry. [Reproduced with permission from A. J. Bard, L. Faulkner, Electrochemical Methods. J. Wiley, New York, 1980, p. 219.]...

The theory for linear-scan voltammetry (LSV) and cyclic voltammetry (CV) for the CE mechanism uses a terminology in which ... 

That there is no peak observed in the linear-scan voltammetry (LSV) scan can be understood because under the experimental conditions (rapid feeding of a small equilibrium amount of Yq to the electrode) there will be no depletion of Y near the electrode as the reduction proceeds. Also (2) i is independent of v, and (3) Ep shifts positive by 29/n mV for each tenfold increase in v through ... 

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