On the Diffusion Impedance at Semiconductor Electrodes

Abstract

It is well known that at metal electrodes, mass transport limitations introduce a Warburg impedance in the electrochemical impedance of an electrode process. Semiconductor electrodes, however, react differently from metal electrodes to variations of the applied potential, so that the influence of diffusion on the electrochemical impedance is less straightforward. In this paper, we propose a general approach of this problem, allowing to describe both the metal and semiconductor electrode behavior by using appropriate kinetical models. When discussing the diffusion impedance at ideal semiconductor/electrolyte contacts, distinction must be made between direct capture reactions and direct injection reactions. Whereas the former result in a Randles-like equivalent circuit, no Warburg component is present in the impedance spectrum of the latter if the reverse reaction is negligible. Thus, the electrochemical impedance provides a clear distinction between both reaction types. At nonideal semiconductor/electrolyte contacts, the situation is different because of the unpinning of the band edges. This may result in a Warburg impedance appearing in the electrochemical impedance of an injection reaction as well, i.e. if the shift of the band edges influences the rate constant of the injection reaction.

Impedance Study of GaN and InGaN Semiconductor Anion Selective Electrodes

“…Similar shapes of the impedance diagrams were obtained by other researchers who performed EIS measurements with semiconductor electrodes such as iron oxides (Fe 1 [14]), boron-doped diamond films on molybdenum substrates [20], and Si, Sn and Zn-doped n-GaAs, n-InP and p-InP electrodes [18]. Aroutiounian [13,14] also suggested that the main contribution to the impedance at high frequencies (> 10 kHz) is the space charge layer of the semiconductor, while at low frequencies (< 10 kHz) a slow diffusion process dominates the impedance spectra.…”

“…As the surface of the In 0.2 Ga 0.8 N electrode is covered by a layer of specifically and nonspecifically adsorbed anions, the electroactive ion species in the solution must diffuse through this layer in order to reach the surface of the electrode and participate in a charge transfer reaction (oxidation or reduction through exchange of electrons via the conduction band of the semiconductor). As the small potential perturbation applied during the EIS experiments affects the rate of this diffusion process, it in turn influences the electrochemical impedance of the system [18].…”

Fundamentals of Semiconductor Electrochemistry and Photoelectrochemistry

“…The theoretically predicted AC impedance response was compared with experiments on n-GaAs rotating disk electrodes in sulfuric acid media [79]. The equivalent circuit in Fig.…”

“…As in the latter case, hydrodynamic voltammetry is best suited to study mass transport. AC impedance spectroscopy can be another useful tool in this regard [105].…”

Generalization of Randles-Ershler admittance for an arbitrary topography electrode: application to random finite fractal roughness

“…Their influence on the electrochemical responses and its application lies at the heart of modern day electrochemical devices like batteries [6,7], fuel cells [8,9], electrochromic smart windows [10], ion exchange membranes [11], solar cells [12], capacitive deionization cells [13], supercapacitors [13], nanostructured semiconductor electrodes [14], electrochromic films [10,15], and ion intercalation in nanostructured materials [7,16]. It is well known that the geometrical and morphological characteristics like non-uniformities of the surface, viz.…”