Square-wave amplitude peak current

Fig. 2.2 The dependence of the dimensionless net peak current (i) and the ratio of the dimensionless net peak current and the half-peak width (2) on the product of number of electrons and the square-wave amplitude...

Table 3.2 Peak current ratios for commercial iron oxide (FeiO-, Aldrich) and earth pigments from Kremer. From square-wave voltammograms of sample-modified PlGEs immersed into 0.10 M HCl. Potential step increment 4 mV square wave amplitude 25 mV frequency 5 Hz. Adapted from ref. [139]...

The peak height of the SWV net current increases in all the cases with the square wave amplitude until it reaches a constant value (plateau) for sw > lOOmV. This value depends on the electrode shape and size and also on the catalytic rate constants. Under steady-state conditions, the plateau current at microspheres and microdiscs is given by... 

The splitting of the SWV net current appears on increasing the square wave amplitude and the ratio co. For example, for E sw = 50 mV, the splitting appears for surface electrode reactions with co > 3. Therefore, the values of the peak... 

The second procedure is based on the effect of the square wave amplitude on the peak potential separation between the anodic and cathodic components of the SWV response. This separation depends on both the reversibility of the surface charge transfer (through co and Sw- Thus, by plotting the differences AEp = Epc — E pl>, with Ep c and EpA being the peak potentials of the forward and reverse currents measured versus the index potential, or AE p = Ef c — E p a with h p c and h p a being the peak potentials of the forward and reverse currents measured versus the real potential that is applied in each case (potential-corrected voltammograms), it is possible to obtain linear dependences between the peak potentials separation and... 

In square-wave voltammetry of diffusion-controlled, reversible, and totally irreversible electrode reactions, the peak current is a linear function of the square root of frequency, but its relationship with square-wave amplitude is not linear. 

The peak currents and potentials of the forward and backward components are listed in Table II.3.2. If the square-wave amplitude is not too small nEsw > 10 mV), the backward component indicates the reversibility of the electrode reaction. In the... 

The peak current depends on the square-wave amplitude E, and the potential increment AE in the same way as in the case of the simple reaction (Eq. II.3.1) (see Table II.3.1). The half-peak width also depends on the amplitude and has no diagnostic value. However, the response of the reversible reaction (II.3.5) is narrower than the response of the reversible reaction (Eq. II.3.1). If nE y = 50 mV and tiAE = 10 mV, the half-peak widths are 100 mV and 125 mV, respectively [88]. 

Table 2.1 Square-wave voltammetry of fast and reversible electrode reaction (1.1). The dimensionless net peak current, the ratio of peak currents of the forward and backward components, the peak potentials of the components and the half-peak width as functions of SW amplitude ...

The dimensionless net peak current A p primarily depends on the product nEsw [31]. This is shown in Table II.3.1. With increasing nfsw the slope BA pIdnEsv, continuously decreases, while the half-peak width increases. The maximum ratio between Ahalf-peak width appears for nEv, = 50mV [6]. This is the optimum amplitude for analytical measurements. If sw = 0, the square-wave signal turns into the signal of differential staircase voltammetry, and A[Pg.124]

In principle, this method is a combination of the DC and the NP mode. Square-wave DC pulses of small and constant amplitude (AU = 5-100 mV) during 40-60 msec ate superimposed on the continuously changing DC voltage. The application of the pulses and the measurements of the currents must be correctly synchronized. For every pulse the current is measured twice during precisely defined identical intervals (e.g., 20 msec). The first measurement ends just before the start of the pulse, the second with the end of the pulse. The current of the first measurement is subtracted from that of the second and the resulting derivative AilAU is plotted in function of the DC voltage ramp. The shape of the curve shows rather sharp peaks on a smooth baseline. 

In EIS one can use potential or current sinusoidal perturbations. In practice, the potential perturbation of 10 mV peak to peak or a 5 mV amphtude is usually used because EIS is based on the linearization of nonlinear electrochemical equations. This also means that as the sum of sine waves is appUed, its total amplitude cannot exceed 5 mV. In practice amplitude of 5 mV rms is usually used for diffusion and adsorption limited processes, see Sect. 13.2, but in certain cases of surface processes where sharp voltammetric peaks appear the amplitude should be much lower. The linearity can be simply checked by decreasing amplitude and comparing the obtained results. Sect. 13.2. It should be kept in mind that the apparatus used in electrochemistry displays the root-mean-squared (rms) amplitude, which is the effective amplitude measured by an ac voltmeter. This rms amplitude is equal to the real amplitude divided by V ... 

CV peak current in the backward process, Eq. (92) CV peak current in the forward process, Eq. (92) quasi-reversible LSV current, Eq. (88) reduction current, Eq. (6) ring current, Eq. (121) sampled current, Eq. (42) staircase current square-wave current, Eq. (64) steady state current transformed LSV current, Eq. (94) alternating current, Eq. (56) amplitude of the AC peak-to-peak distance in the 2nd derivative DCP current density, Eq. (2) exchange current density, Eq. (9) limiting current density, Eq. (119)... 

Square-wave voltammetry The potential-time waveform and current measuring scheme for this technique is shown in Fig. 10. The waveform consists of a symmetrical square-wave (peak to peak amplitude 2Es ) superimposed on a staircase wave of step height AE and a period t. The response current is sampled at the end of both the forward (If) and reverse (If) half cycle. A difference current dl is determined as... 

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