Impedance spectroscopy, photoelectrochemical

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). 

In a PEIS experiment, the flux of minority carriers generated by illumination is constant to a good approximation, and if the condition 1/a dSc + L is fulfilled, then g 7(0). The ac potential perturbs the density of majority carriers at the surface and therefore modulates knc about a mean (dc) value, giving rise to an ac photocurrent. The photoelec-trochemical admittance, (VVeis = 1/ZPE1S), is the ratio of the ac component of the total photocurrent to the ac voltage. For competition between recombination and electron transfer, the photoelectrochemical admittance is given by [29] 

The complex plane plot of VpEis exhibits two semicircles, and it can be fitted using the series/parallel circuit shown in Fig. 8.19. 

The R and C values for the low frequency semicircle, which depend on the dc illumination, 7(0), are given by 

The frequency of the maximum of the low-frequency semicircle, wmax(LF) is equal to kXr and is independent of light intensity. 

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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... 

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. 

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... 

Owing to its extraordinary chemical stability, diamond is a prospective electrode material for use in theoretical and applied electrochemistry. In this work studies performed during the last decade on boron-doped diamond electrochemistry are reviewed. Depending on the doping level, diamond exhibits properties either of a superwide-gap semiconductor or a semimetal. In the first case, electrochemical, photoelectrochemical and impedance-spectroscopy studies make the determination of properties of the semiconductor diamond possible. Among them are the resistivity, the acceptor concentration, the minority carrier diffusion length, the flat-band potential, electron phototransition energies, etc. In the second case, the metal-like diamond appears to be a corrosion-stable electrode that is efficient in the electrosyntheses (e.g., in the electroreduction of hard to reduce compounds) and electroanalysis. Kinetic characteristics of many outer-sphere... 

A consistent picture for dynamics of heterogeneous ET has been emerging in the last 5 years with the development of new experimental approaches. Techniques such as AC impedance, modulated and time-resolved spectroscopy, SECM, and photoelectrochemical methods have extended our knowledge of charge-transfer kinetics to a wide range of time scales. This can be exemplified by comparing impedance analysis, which is limited to k of... 

The basic measurement technique for intensity-modulated photovoltage spectroscopy (IMVS) is the same as for IMPS. In principle, IMVS measurements can be made for any constant current condition, but in practice it is usual to make measurements under conditions where the net current is zero. In the case of a photoelectrochemical solar cell, this corresponds to the open-circuit condition, and a high impedance voltage amplifier is used to ensure that a negligible current is drawn from the illuminated device. The output of the voltage amplifier is fed to the FRA, and the remainder of the set up is the same as for IMPS (cf. Fig. 12.26). 

Koshida N, Nagasu M, Sakusabe T, Kiuchi Y (1985) The current voltage characteristics of a photoelectrochemical cell using p-type porous silicon. J Electrochem Soc 132(2) 346-349 Koshida N, Nagasu M, Echizenya K, Kiuchi Y (1986) Impedance spectra of p-type porous Si-electrolyte interfaces. J Electrochem Soc 133(11) 2283-2287 Mamykin AI, Moshnikov VA, Ilin AY (1998) Magnetic resonance spectroscopy of porous quantum-size structures. Semiconductors 32(3) 322-324... 

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