Linear Sweep Voltammetry Simulations

The summary given by this author rests on the work of several theorists who followed the work of Sevcik. Among the most outstanding of these is Paul Delahay who. with Strassner and others in 1951 1953 contributed much to the basic theory of linear sweep voltammetry with partial interfacial control. Students interested in programs for such simulations should contact Prof. David K. Gosser, Chemistry Department, City College of New York, NY, 10031. 

To see how one might incorporate the effect of a changing electrode potential into the boundary value problem, let us consider the simulation of Nernstian linear sweep voltammetry. One first selects an appropriate potential scan range... 

Saveant and coworkers [87-89, 123-125] introduced this approach for determining kc in linear sweep voltammetry. The experimental voltammograms were compared with simulations to determine cleavage rate constants for radical anions ranging from 10 to 5 x 10 s . The indirect approach is therefore a very useful supplement to direct techniques such as cyclic voltammetry [126-130], pulse radiolysis [131-135], and flash photolysis [136], which have proven to be convenient and effective tools when the cleavage rate constant of RX is lower than 10 s . ... 

Recently new methods, based on petturbations on the linear sweep voltammetry response of the mediator in the presence of the protein," a mediated thin-layer voltammetry technique, cyclic voltammetric simulation apphed to an electrochemically mediated enzyme reaction" have been setded to gain information on the protein-mediator interactions. More recendy the Scanning Electrochemical Microscopy (SECM) was used to probe the red-ox activity of individual cells of purple bacteria, by using two groups of mediators (hydrophilic and hydrophobic species) in order to gain information on the dependence of measured rate constant on the formal potential of the mediator in solution. By this technique an evaluation of the intracellular potential was also performed. ... 

The diffusional behaviour observed in each case is illustrated schematically in Figure 10.4, accompanied by an example of the simulated linear sweep voltammetry that can be expected under each regime. The example voltammograms are simulated based on a system with a surface coverage 0 = 0.01, disc radius re = 1 /um and diffusion coefficient Da = 10 cm s and vary only in terms of the voltammetric scan rate,... 

Abstract Recent advances in molecular modeling provide significant insight into electrolyte electrochemical and transport properties. The first part of the chapter discusses applications of quantum chemistry methods to determine electrolyte oxidative stability and oxidation-induced decomposition reactions. A link between the oxidation stability of model electrolyte clusters and the kinetics of oxidation reactions is established and compared with the results of linear sweep voltammetry measurements. The second part of the chapter focuses on applying molecular dynamics (MD) simulations and density functional theory to predict the structural and transport properties of liquid electrolytes and solid elecfiolyte interphase (SEI) model compounds the free energy profiles for Uthium desolvation from electrolytes and the behavior of electrolytes at charged electrodes and the electrolyte-SEl interface. 

Klymenko OV, Gavaghan DJ, Harriman KE, Compton RG (2002) Finite element simulation of electrochemically reversible, quasireversible and irreversible linear sweep voltammetry at the wall tube electrode. J Electroanal Chem 531 25-31... 

Harriman K, Gavaghan DJ, Siili E (2004) Simulation of linear sweep voltammetry using an... 

Very recently, Viswanathan et al. " developed a multiscale model for simulating linear sweep voltammetry of electrochemical solid-liquid interfaces of H2O on Pt(l 11) and on Pt3Ni(l 11) facets. In the model, DFT was used to parameterize the reaction kinetics KMC was used to capture the kinetic steps of the electrochemical oxidation, and conventional MC was used to equilibrate the surface between kinetic steps. The calculated cyclic voltammograms are in good agreement with experimental CV - CS d the experimental XPS results (Figure 8). 

V. Viswanathan, H. A. Hansen, J. Rossmeisl, T. F. Jaramillo, H. Pitsch, and J. K. Norskov, /. Phys. Chem. C, 116, 4698 (2012). Simulating Linear Sweep Voltammetry from First-Principles Application to Electrochemical Oxidation of Water on Pt(lll) and PtjNidll). 

The task now at hand is to find solutions to these second-order differential equations under theboundary conditions defined by the electroanalytical method in question. Nowadays, this is most often accomplished by numerical integration, known in electroanalytical chemistry as digital simulation. It is beyond the scope of this chapter to go into the mathematical details, and the interested reader is referred to the specialist literature [33]. Commercial user-friendly software for linear sweep and cyclic voltammetry is available (DigiSim ) software for other methods has been developed and is available through the Internet. 

One of the main uses of digital simulation - for some workers, the only application - is for linear sweep (LSV) or cyclic voltammetry (CV). This is more demanding than simulation of step methods, for which the simulation usually spans one observation time unit, whereas in LSV or CV, the characteristic time r used to normalise time with is the time taken to sweep through one dimensionless potential unit (see Sect. 2.4.3) and typically, a sweep traverses around 24 of these units and a cyclic voltammogram twice that many. Thus, the explicit method is not very suitable, requiring rather many steps per unit, but will serve as a simple introduction. Also, the groundwork for the handling of boundary conditions for multispecies simulations is laid here. 

Strutwolf J, SchoeUer WW (1996) Linear and cyclic sweep voltammetry at a rotating disk electrode. A digital simulation. Electroanalysis 8 1034-1039... 

In theory, D, c, or n can be calculated from the peak current (Ip) of a dc linear-sweep or cyclic voltammogram by employing the relationships described by the Randles-Sevcik equation for a reversible electron-transfer process of the kind Ox+ne" Red, when the effect of is negligible [6]. When woiking in a viscous RTIL, however, very few of the electrochemical systems of interest fulfill these criteria, which severely limits the direct application of dc voltammetry for this purpose. Assuming the Randles-Sevcik equation is not applicable, a best-fit approach with numerical simulation may be a viable alternative, although even this method has its limitations, as mechanistic complexities or other uncertainties can make the modeling process difficult [10]. 

FIGURE 1.34. PiHar distribution obtained by Monte Carlo simulation of the phase propagation problem in the context of linear potential sweep (Ips) voltammetry for ( = 0.01 (A), 0.279 (B), and 3.0 (C), assuming that a = 0.5. (Adapted from Ref. 114.)... 

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