Multipulse chronoamperometry

It is of interest at this point to compare the study of Multipulse Chronoamperometry and Staircase Voltammetry with those corresponding to Single Pulse Chronoamperometry and Normal Pulse Voltammetry (NPV) developed in Chaps. 2 and 3 in order to understand how the same perturbation (i.e., a staircase potential) leads to a sigmoidal or a peak-shaped current-potential response as the equilibrium between two consecutive potential pulses is restored, or not. This different behavior is due to the fact that in SCV the current corresponding to a given potential pulse depends on the previous potential pulses, i.e., its history. In contrast, in NPV, since the equilibrium is restored, for a reversible process the current-potential curve is similar to a stationary one, because in this last technique the current corresponding to any potential pulse is independent of its history [8]. 

Scheme 5.1 Multipulse Chronoamperometry and Chronocoulometry. (a) Potential-time program (b) Current-time response (c) Charge-time response...

The general electrochemical behavior of surface-bound molecules is treated in Sect. 6.4. The response of a simple electron transfer reaction in Multipulse Chronoamperometry and Chronocoulometry, CSCV, CV, and Cyclic Staircase Voltcoulometry and Cyclic Voltcoulometry is also presented. Multielectronic processes and first- and second-order electrocatalytic reactions at modified electrodes are also discussed extensively. 

The different assumptions needed to make a statement of this problem will be presented in the following section. Then the general solution corresponding to the application of a sequence of potential pulses to attached molecules giving rise to simple charge transfer processes and particular solution corresponding to Multipulse Chronoamperometry and Chronocoulometry and Staircase Voltammetry will be deduced. Cyclic Voltammetry has a special status and will be discussed separately. Finally, some effects that cause deviation from the ideal behavior and more complex reaction schemes like multielectronic processes and chemical reactions in the solution coupled to the surface redox conversion will be discussed. 

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. 

The simplest case of a multipulse technique corresponds to the record of the current time (chronoamperometry) or the charge time (chronocoulometry) curves obtained when a given sequence of successive potential pulses Eu E2,. .Ep is applied for times 0 < tn < t , with n= 1, 2,. .., p, as shown in Scheme 5.1. 

For the sake of simplicity we will tackle the case of a one-electron transfer (7.1), although the same methodology here described has been successfully applied to the study of a munber of systems with different mechanisms, including comproportionation reactions [3] and amalgamation processes [5], and using different electrochemical techniques chronoamperometry [4], cyclic voltammetry [6] and multipulse voltammetries [7]. 

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