Voltammetry reverse pulse

NPV does not allow direct examination of the product of the electrode reaction. To do this, a technique complementary to NPV may be employed. Reverse pulse voltammetry (RPV) is such a technique [5,10,11]. It is based on the waveform shown in Fig. II.2.7. 

A typical shape of a reverse pulse voltammogram is presented in Fig. II.2.8. The corresponding normal pulse voltammogram is added to the figure as a reference. The DC part of the RP voltammogram, foc is positive as is the normal pulse current, i p. The reverse pulse current, /rp, is of opposite sign, since the product of the electrode reaction is oxidized now. 

If the working electrode is sufficiently large and the diffusion to its surface is planar, and the initial concentrations at the electrode surface are renewed after each pulse, the limiting DC current of the reverse pulse wave will be given by  

For a reaction where Red is the primary substrate and Ox is reduced in the reverse going pulses to Red, Dqx and Cox should be replaced in Eqs. (II.2.8) and (II.2.9)byDRed andCRed. 

Another useful equation is that describing the ratio iiim,Dc/ iim,RP  

If the experimental data do not fit Eqs. (n.2.10) and (II.2.11), this means that the electrode reaction in the first-generation step is not of stoichiometry 1 1, or simply the product of the first step is transferred in a chemical process to an electroinactive compound. The deviations may also be caused by the adsorption of either Ox or Red. Similar to NPV, the adsorption of Red at the electrode surface will make the RP voltammogram peak-shaped, and the adsorption of Ox will produce a pre-wave. 

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Osteryoung J and Murphy M M 1991 Normal and reverse pulse voltammetry at small electrodes Microelectrodes Theory and Applications (Nate ASI Series E vol 197) ed M I Montenegro, M A Queiros and J L Daschbach (Dordrecht Kluwer)... 

A related technique, reverse-pulse voltammetry, has a pulse sequence that is a mirror image of that of normal-pulse voltammetry (5). hi this case, the initial potential is on the plateau of the wave (i.e., where reduction occurs), and a series of positive-going pulses of decreasing amplitude is applied. 

Here, the electrode reaction is followed by a first-order irreversible chemical reaction in solution that consumes the primary product B and forms the final product C. The rate of this chemical reaction can be measured conveniently with cyclic voltammetry, double-potential-step chronoamperometry, reverse pulse voltammetry, etc. However, this is only true if the half-life of B is greater than or equal to the shortest attainable time scale of the experiment. 

They are applicable to electrodes of any shape and size and are extensively employed in electroanalysis due to their high sensitivity, good definition of signals, and minimization of double layer and background currents. In these techniques, both the theoretical treatments and the interpretation of the experimental results are easier than those corresponding to the multipulse techniques treated in the following chapters. Four double potential pulse techniques are analyzed in this chapter Double Pulse Chronoamperometry (DPC), Reverse Pulse Voltammetry (RPV), Differential Double Pulse Voltammetry (DDPV), and a variant of this called Additive Differential Double Pulse Voltammetry (ADDPV). A brief introduction to two triple pulse techniques (Reverse Differential Pulse Voltammetry, RDPV, and Double Differential Triple Pulse Voltammetry, DDTPV) is also given in Sect. 4.6. 

Scheme 4.2 Reverse Pulse Voltammetry, (a) Potentialtime program (b) RPV response. /Rpv.rcd and /ri V.ox are the limiting currents corresponding to...

This section deals with the solution corresponding to an EC mechanism (see reaction scheme 4.IVc) in Reverse Pulse Voltammetry technique under conditions of kinetic steady state (i.e., the perturbation of the chemical equilibrium is independent of time see Sect. 3.4.3). In this technique, the product is electrogenerated under diffusion-limited conditions in the first period (0 < t < ) and then exam-... 

Appendix G. Application of Two Potential Pulses to a Non-reversible Charge Transfer Differential Double Pulse Voltammetry and Reverse Pulse Voltammetry... 

Solution for the Second Current in Reverse Pulse Voltammetry... 

Fig. 10.12. Scheme of reverse pulse voltammetry (RPV). base corresponds to electrolysis of the electroactive species in solution. 

See -> differential pulse voltammetry, - normal pulse voltammetry, and -> reverse pulse voltammetry. 

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. 

Pulse voltammetry — A technique in which a sequence of potential pulses is superimposed to a linear or staircase voltage ramp. The current is usually measured at the end of the pulses to depress the - capacitive (charging) current. Depending on the way the pulses are applied and the current is sampled we talk about - normal pulse voltammetry, reverse pulse voltammetry and - differential pulse voltammetry. Several other, less popular pulse techniques are offered in commercial voltammetric instrumentation. Some people consider - square-wave voltammetry as a pulse technique. 

We will consider five subtopics tast polarography and staircase voltammetry, normal pulse voltammetry, reverse pulse voltammetry, differential pulse voltammetry, and square wave voltammetry. Tast polarography, normal pulse voltammetry, and differential pulse voltammetry form a sequence of development rooted historically in polarography at the DME. To illustrate the motivating concepts, we will introduce each of these methods within the polarographic context, but in a general way, applicable to both the DME and SMDE. Then we will turn to the broader uses of pulse methods at other electrodes. Reverse pulse voltammetry and square wave voltammetry were later innovations and will be discussed principally outside the polarographic context. 

In reverse pulse voltammetry or reverse pulse polarography (47), the potential waveform and sampling scheme are identical with those of the normal pulse method (Figure... 

Figure 7.3.8 Reverse pulse voltammetry V5. normal pulse voltammetry in a simple reversible one-electron system.

Osteryoung J and Murphy M M 1991 Normal and reverse pulse voltammetry at small electrodes Microelectrodes ... 

Normal and reverse pulse voltammetries are often employed for the studies of stepwise or chemically complicated processes where the direct product of electrode reaction is unstable and undergoes transformations into other species - either elec-troinactive or active in a different potential range. Reverse pulse voltammetry allows a direct examination of the product generated between pulse applications thus it is simply a short electrolysis (seconds) followed by recording the produa of electrooxidation or reduction on the time-scale of milliseconds. 

REVERSE PULSE VOLTAMMETRY AT MICROELECTRODES. NEW POSSIBILITIES IN ANALYTICAL CHEMISTRY... 

Reverse pulse voltammetry (rpv) is a very useful elect roan alyti cal technique in the cases where current measurements of direct reduction or oxidation of substrated is complicated due to poorly defined waves. It is also very useful in investigations of chemical reactions coupled with electrode processes. The potential waveform is presented in Fig.l. 

L. Camacho, J. J. Ruiz, C. Serna, A. Molina, and F. Martinez-Ortiz. Reverse pulse voltammetry and polarography A general analytical solution. Can. J. Chem. 72, 2369 (1994). 

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