Specific adsorption of halide ions at the germanium electrolyte-solution interface; frequency dispersion of interfacial impedance☆

Abstract The specific effect of halide ions at germanium/electrolyte-solution interfaces has been studied by means of the frequency dispersion of the interfacial impedance, which was measured by ac bridge over the frequency range 100 Hz-1 MHz. Anomalous dispersions occur in the presence of halides (except fluoride) under anodic polarization. Characteristic peaks for each halide appear in tan δ/frequency curves at various pds. The equivalent circuit of the germanium electrode in contact with halide has been determined. The dispersion behaviour is discussed in terms of the charge relaxation due to surface states produced by the specific adsorption of halides, and relaxation-time spectra describing the interaction of halides with the surface atoms have been obtained. From kinetic considerations of the relaxation time, the rate of chemisorption-desorption process of halide can be estimated.