Current-potential plot

The main goal of the molecular dynamics computer simulation of ionic solvation and adsorption on a metal surface has been to test the above model and to provide more quantitative information about the different factors that influence the structure of hydrated ions at the interface. Unfortunately, most of the experimental information about these issues has been obtained from indirect measurements such as capacity and current-potential plots, although in recent years in situ experimental techniques have begun to provide an accurate test of the above model. For a recent review of experimental techniques and the theory of ionic adsorption at the water/metal interface, see the excellent paper by Philpott. ... 

Fig. 1.5 Current-potential plot for polarizable and non-polarizable interphases...

Fig. 2E Current-potential plots for a single step charge-transfer process, for three values of P, at low overpotentials. Note that linearity is maintained longer for P = 0.50 than for other values of the symmetry factor.

Fig. 14G Current-potential plots obtained at different sweep rates, for a system having a faradaic current in addition to the doublelayer charging current. Using the difference Ai, rather than the individual values of i or i, eliminates most of the...

In connection with the foregoing, double layers of course also play an important role in electroanalysis. Transfer of. say, electroactive ions through the polarized mercury-solution interface is preceded by passage through the double layer. Therefore current-potential plots depend in principle on double layer properties. Historically, it was his interest In charge-transfer and corrosion problems that induced Grahame to start his seminal double layer Investigations. 

DPP and DPV are probably the most analytically useful of all the voltammetric methods. DPP and DPV produce current-potential plots in the typical peak form familiar to, and readily interpretable by, the analyst. DPP and DPV result from a variation in the pattern of the applied voltage. 

The advantages of cyclic voltammetry versus stationary current-potential plots is... 

Figure 1 shows a current-potential plot of DIN 1.4301 stainless steel in 0.01 M sulfuric acid and of iron in a boron buffer solution (at pH 8.4). As seen, the current density resulting from corrosion attacks drops by several orders of magnitude for a certain potential value E = -550 mV and E = -300 mV respectively). 

Figure 1.2.11 Current-time and current-potential plots resulting from a cyclic linear potential sweep (or triangular wave) applied to an RC circuit.

Figure 2. Typical current-potential plot for membrane type sensor. characteristic of a particular species and is the potential at which the current is half the diffusion limited value.

If iron is made a part of the electrochemical cell, a test electrode, and placed in a potentiostatic circuit. Figure 1, the experimental current-potential plots show an interesting pattern. Figure 2 with an increase of potential, starting from the corrosion potential, the dissolution current Increases, just as expected. Metal ions go into the solution... 

Fig. 4 Quasi-stationary current-potential plots for HCOOH (0.5 M) oxidation on sputtered Pt modified by Pb adlayer and HCOOH adsorbates in 0.1 M HCIO4. Current taken 2 min after stepping the potential. The current density is given with respect to the free-Pt surface (16% of the whole surface).

An example is shown in Figure 6.16. The reciprocal current is plotted versus the reciprocal value of the rotation frequency of a rotating disc electrode. The currents taken from the extrapolation to 1/Vf = 0 (rotation frequency/ = 00) are represented versus the potential in Figure 6.17. The current-potential plot shows a current-potential curve in the sub-Tafel region. An approximate current-potential line is shown in Figure 6.17. An approximate value of the charge transfer resistance and of the exchange current density... 

Figure 6.17 Current-potential plot of the extrapolated current data from Figure 6.15, Fe CN)l -Fe CN) redox system, charge transfer resistance = 5.6 il cm", and exchange current density /q = 5.2 mA cm . ...

Figure 10.10 Current-potential plot of an iron electrode in an acid electrolyte (schematic representation). passivation potential, passivation current density, E-p Flade potential, and passive current density.

Figure 10.13 Thickness of a passive fihn of iron as a function of the potential. Comparison with the current-potential plot. (Reproduced with permission from Ref. [25], 1980, Elsevier.)...

Indeed, Figure 3 reports normalized current-potential plots, in order to make voltammograms independent of the experimental variables typical of the particular redox process considered. This is accomplished by replacing current with the dimensionless quantity i.e., a function of both a... 

This technique represents the most direct way for getting the real current-potential plots of both reversible and irreversible electrode processes. With use of microelectrodes or ultramicroelectrodes this procedure has become an effective tool for electroanalysis and for biological research. This topic has been recently reviewed in an impressive paper [9]. Under appropriate circumstances (see section 1) the relationship between the electrode potential, E, and the Faradaic current, If, is established not involving time. This situation is termed the steady state and the graph I vs. E is called a steady-state voltammogram. 

Fig. 24. Comparison of the faradaic currents in the DCP, NPP, and DPP. 1, the mean diffusion limited DCP current 2, Ip and Ep the coordinates of the DPP peak 3, the current-potential plot in the NPP technique I, the NPP (sampled) diffusion-limited current i, the DCP (sampled) limiting current. Note the shift of Ep vs. Ej/2 and the mutual heights of the limiting (peak) currents i, Ij, and Ip under identical experimental conditions.

A hydrodynamic voltammogram is a current-potential curve which shows the dependence of the chromatographic peak height on the detection potential. The technique used to obtain the necessary information is voltammetric flow injection analysis. in which an aliquot of the analyte is injected into the flowing eluent prior to the detector and the peak current recorded. This is repeated many times, the detector potential being changed after each injection, until the peak current - potential plot reaches a plateau or a maximum, as shown... 

The reduced species (that is, the metal) is then oxidized out of the film by making the electrode increasingly anodic. A peak appears on the current-potential plot, and the peak current can be shown to be ... 

Online observation of mass signals from volatile reaction partners offers, in addition to a current-potential plot, use-fiil information on the studied reaction (DEMS technique, in Ref [18-20]). Eor... 

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