Sinusoidal potential excitation

If a sinusoidal potential excitation is applied to the electrode/solution interface, the potential, current and impedance can be predicted as per Bam and Faulkner mathematical models [6]. Thus,... 

In spite of the fact that the decay after excitation of the hard-potential itinerant oscillator is similar to the experimental computer simulation result of Figs. 7 and 8, we do not believe that it is the reduced model equivalent to the one-dimensional many-particle model under study. As remarked above, indeed, the e(r) function is not correctly reproduced by this reduced model. The choice of a virtual potential softer than the linear one seems also to be in line with the point of view of Balucani et al. They used an itinerant oscillator with a sinusoidal potential, which is the simplest one (to be studied via the use of CFP) to deal with the soft-potential itinerant oscillator. Note that the choice... 

One can envision three types of perturbation an infinitesimally narrow light pulse (a Dirac or S-functional), a rectangular pulse (characteristic of chopped or interrupted irradiation), or periodic (usually sinusoidal) excitation. All three types of excitation and the corresponding responses have been treated on a common platform using the Laplace transform approach and transfer functions [170]. These perturbations refer to the temporal behavior adopted for the excitation light. However, classical AC impedance spectroscopy methods employing periodic potential excitation can be combined with steady state irradiation (the so-called PEIS experiment). In the extreme case, both the light intensity and potential can be modulated (at different frequencies) and the (nonlinear) response can be measured at sum and difference frequencies. The response parameters measured in all these cases are many but include... 

The transfer functions depend on the angular frequency and are expressed as impedance Z (u>) and admittance Y (u>). It should be emphasized that Z (ta) is the frequency-dependent proportionality factor of the transfer function between the potential excitation and the current response. Thus, for a sinusoidal current... 

The potential excitation and its current response are schematically shown in Figure 35 as sinusoidal excitations. The electrochemical impedance spectroscopy method is conducted according to the ASTM G-106 standard practice, in which a range of smaU-amphtude sinusoidal potential perturbation is applied to the electrode/sohition interface at discrete frequencies. These frequencies cause an out of phase current response with respect to the applied sinusoidal potential waveform. 

Sinusoidal voltammetry (SV) is an EC detection technique that is very similar to fast-scan cyclic voltammetry, differing only in the use of a large-amplitude sine wave as the excitation waveform and analysis performed in the frequency domain. Selectivity is then improved by using not only the applied potential window but also the frequency spectrum generated [28]. Brazill s group has performed a comparison between both constant potential amperometry and sinusoidal voltammetry [98]. 

To this point, we have found that excitation of an electrochemical system by a signal, E c — AE sin produces a sinusoidal current response at the same frequency. That result rests on the fact that only the linearized current-potential relation has been used. The remaining terms in the Taylor expansion of current v. potential were dropped (Section... 

When a pure sinusoidal voltage is applied to an electrochemical cell, the waveform of the resulting current is very often distorted due to this nonlinear current-potential relationship unless the excitation voltage is sufficiently small. The response signal can be described as... 

Fig. 6.2. Schematic model of nearly sinusoidal two-well potential with asymmetry A for hydrogen in metals, showing ground and first excited eigenstates. Heavy tines for the states show where the particle is likely to be.

This term is used to cover a range of techniques in which the mean potential is controlled potentiostatically and swept over a range while a small amplitude, relatively high frequency alternating potential superimposed on the slowly-varying sweep is used to excite a sinusoidal response in the current, which is... 

It is now our task to calculate the response coefficient associated with an excitation of a concentration wave with wave vector k. Imagine that this excitation is due to the action of a sinusoidally varying potential which interacts exclusively with the A s. If this potential has the amplitude the response is described by... 

As the first approximation, impedance of a porous electrode can always be considered as a series combination of two processes—a mass-transport resistance inside the pores and impedance of electrochemical reactions inside the pores. De Levie was the first to develop a transmission line model to describe the frequency dispersion in porous electrodes in the absence of internal diffusion limitations [66]. De Levie s model is based on the assumption that the pores are cylindrical, of uniform diameter 2r and semi-infinite length /, not intercoimected, and homogeneously filled with electrolyte. The electrode material is assumed to have no resistance. Under these conditions, a pore behaves like a imiform RC transmission line. If a sinusoidal excitation is applied, the transmission line behavior causes the amplitude of the signal to decrease with the distance from the opening of the pore, and concentration and potential gradients may develop inside the pore. These assumptions imply that only a fraction of the pore is effectively taking part in the double-layer charging process. The RpQi i- [ohm] resistance to current in a porous electrode structure with number of pores n, filled with solution with resistivity p, is ... 

---