Photoelectrochemical impedance

In an IMPS experiment the light intensity is modulated to produce an ac photocurrent that is analysed to obtain kinetic information. An alternative approach is to modulate the electrode potential while keeping the illumination intensity constant. This method is called PhotoElectrochemical Impedance Spectroscopy (PEIS). 

D. B. Bonham and M. E. Orazem, "A Mathematical Model for the Influence of Deep-Level Electronic States on Photoelectrochemical Impedance Spectroscopy 1. Theoretical Development," Journal of The Electrochemical Society, 139 (1992) 118-126,... 

EIS measurements can also be carried out under conditions where illumination of the semiconductor generates a photocurrent. The technique is then referred to as photoelectrochemical impedance spectroscopy, PEIS. Interpretation of the results in terms of passive RC circuit elements is no longer appropriate since the system contains a current source. A more satisfactory approach is to relate the impedance response directly to the physical processes responsible for the photocurrent (Ponomarev and Peter, 1995 Peter, 1999 Peter and Vanmaekelbergh, 1999). 

Bonham D. B. and Orazem M. E. (1992), A mathematical model for the influence of deep-level electronic states on photoelectrochemical impedance spectroscopy 1. Theoretical development , 7. Electrochem. Soc. 139, 118-126. 

FerminD. J., Ponomarev E. A. and Peter L. M. (1999), A kinetic stndy of CdS photocorrosion by intensity-modnlated ph otocurrent and photoelectrochemical impedance spectroscopy , J. Electroanal Chem. 473, 192-203. 

Relationship between IMPS and Photoelectrochemical Impedance Spectroscopy (PEIS)... 117... 

The terminology used for the transfer function requires some care. If the input function is an intensive quantity such as voltage (also called an across function), and the output function is an extensive quantity such as current (also called a through function), the ratio of output to input can be referred to as an admittance. If the type of input and output functions are reversed, then the ratio becomes an impedance. If the input and output functions are both of the same type, the ratio of output to input can be referred to as a gain function. However, these conventions, which are usually employed in network analysis, have not always been followed consistently in the development of new photoelectrochemical techniques. For example, the frequency dependent photocurrent efficiency, O, shown in Table 1 is often referred to as the opto-electrical admittance and its inverse as the opto-electrical impedance [62, 64-66], in spite of the fact that it is the ratio of two through functions. It would be preferable to use the term opto-electrical transfer function. The inverse of has also been called the photoelectrochemical impedance [53, 70]. To avoid confusion, the use... 

IMPS uses modulation of the light intensity to produce an ac photocurrent that is analysed to obtain kinetic information. An alternative approach is to modulate the electrode potential while keeping the illumination intensity constant. This method has been referred to as photoelectrochemical impedance spectroscopy (PEIS), and it has been widely used to study photoelectrochemical reactions at semiconductors [30-35]. In most cases, the impedance response has been fitted using equivalent circuits since this is the usual approach used in electrochemical impedance spectroscopy. The relationship between PEIS and IMPS has been discussed by a number of authors [35, 60, 64]. Vanmaekelbergh et al. [64] have calculated both the IMPS transfer function and the photoelectrochemical impedance from first principles and shown that these methods give the same information about the mechanism and kinetics of recombination. Recombination at CdS and ZnO electrodes has been studied by both methods [62, 77]. Ponomarev and Peter [35] have shown how the equivalent circuit components used to fit impedance data are related to the physical properties of the electrode (e.g. the space charge capacitance) and to the rate constants for photoelectrochemical processes. 

Under these conditions, the modulation of the minority carrier flux by the applied ac voltage can be neglected and g = 7(0). The main effect of the ac potential perturbation is to change the density of majority carriers at the surface and consequently the value of ktec- The modulation of knc about a mean (dc) value results in a corresponding frequency dependent ac photocurrent. The photoelectrochemical impedance is determined by the ratio of the perturbing ac voltage to the ac component of the total photocurrent. For the simple competition mechanism discussed in section... 

In their chapter on time- and frequency-resolved studies of photoelectrochemical kinetics, Peter and Vanmaekelbergh give an extensive survey of how modulation techniques such as photoelectrochemical impedance spectroscopy or intensity-modulated photocurrent spectroscopy can yield valuable information on the time dependence of reactions at semiconducting surfaces over a broad range of time scales. Kinetic studies with single crystals as well as porous or nanocrystalline material reveal the important role that is played by the bulk structure of semiconductor electrodes. 

A comparison of this method with photoelectrochemical impedance spectroscopy" as applied to photoelectrochemical hydrogen evolution at p-lnP has been reported [728]. Intensity modulated photocurrent spectroscopy has been compared with intensity-modulated photo voltage spectroscopy (IMVS) [729]. Intensity modulated photocurrent spectroscopy has been applied in a study of the silicon dissolution in aqueous solutions of NH4F [730] and n-GaAs electrodes [731] a general review is available [732]. Photocorrosion of CdS has been investigated with IMPS and photoelectrochemical impedance spectroscopy (PEIS) [733] a mechanism could be de-... 

Wijayan a, K.G.U., Saremi-Yarahmadi, S. and Peter, L.M. (2011) Kinetics of oxygen evolution at alpha-Fe203 photoanodes a study by photoelectrochemical impedance spectroscopy. Physical Chemistry Chemical Physics, 13, 5264-5270. 

Song, H. and Macdonald, D.D. (1991) Photoelectrochemical impedance spectroscopy I. Validation of the transfer function by Kramers-Kronig transformation. Journal of The Electrochemical... 

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