Differential double pulse voltammetry DDPV

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. 

In this section, the analytical expressions given by Eqs. (4.171) and (4.172) are applied to differential double pulse voltammetry (DDPV) [63,64]. In this technique the duration of the second pulse is usually much shorter than that of the first i > 50 x t2. Under these conditions, fc,(j + r2,<7c) /g(ti, <7g) so equation for A ddpv simplifies to ... 

In the case of DMPV (see Scheme 7.2), the treatment followed in Sect. 4.2.4.1 for Differential Double Pulse Voltammetry (DDPV) for one and two polarizable interfaces can be used because the equilibrium is quickly reestablished during the longer period Therefore, the peak potential of the DMPV curves when the current is plotted versus the index potential is... 

With respect to the peak potentials, their value are independent of all the technique parameters (including the pulse amplitude) and it is corroborated that it coincides with the peak potential in Differential Double Pulse Voltammetry (DDPV) and Differential Multipulse Voltammetry (DMPV). So, by imposing the condition dy/ vw/dE = 0 in Eq. (7.65), the three following roots are obtained in terms of K [49] ... 

Differential Double Pulse Voltammetry (DDPV), where the length of the second pulse (t2) is much shorter than the length of the first pulse (t/), t//t2 = 50-100 (Fig. 2.36a), which leads to very high sensitivity. Differential Double Normal Pulse Voltammetry (DDNPV) is where both pulses have similar durations tj x t2 (Fig. 2.36b). 

Equation (4.77) corresponds to the normal mode of Differential Double Pulse Voltammetry for which the duration of the second applied pulse is not restricted as in the case of DDPV [35]. From this equation, the expression of the current A/dndpv at very negative and positive potentials valid for any electrode geometry can be directly obtained,... 

This technique is based on the derivative of the NPV curve introduced by Barker and Gardner [2]. In DDPV, two consecutive potentials E and E2 are applied during times 0 < fi < ti and 0 < t2 < z2. respectively, with the length of the second pulse being much shorter than the first (t /t2 = 50 100). The difference AE = E2 — E is kept constant during the experiment and the difference A/DDPV = h h is plotted versus E or versus an average potential E y2 = (E +E2)/2. When the two pulses are of similar duration, the technique is known as Differential Normal Double Pulse Voltammetry (DNDPV) (Scheme 4.3). 

Double Pulse Square Wave Voltammetry (DPSWV) is where both pulses are equal tj — t2 and the pulse height (AE — E2—E1) is opposite from the scan direction (Fig. 2.36c). Because of its analogy with the potential-time program applied in Square Wave Voltammetry, it is referred to as Double Pulse Square Wave Voltammetry. Differential Multi Pulse Voltammetry (DMPV) is as a variant of DDPV where the initial conditions are not recovered during the experiment (Fig. 2.36d). Thus, the pulse length (tp) is much shorter than the period between pulses (ti), tj/tp — 50—100. 

It is necessary to mention that there is no universal and unambiguous nomenclature for the different differential pulse techniques, something which can lead to inaccurate analyses and misinterpretations. The DDPV technique is usually called Differential Pulse Voltammetry (DPV) referring to the double pulse... 

As in the case of differential double potential pulse techniques like DDPV, slow electrochemical reactions lead to a decrease in the peak height and a broadening of the response of differential multipulse and square wave voltammetries as compared with the response obtained for a Nemstian process. Moreover, the peak potential depends on the rate constant and is typically shifted toward more negative potentials (when a reduction is considered) as the rate constant or the pulse length decreases. SWV is the most interesting technique for the analysis of non-reversible electrochemical reactions since it presents unique features which allow us to characterize the process (see below). Hereinafter, unless expressly stated, a Butler-Volmer potential dependence is assumed for the rate constants (see Sect. 1.7.1). 

---