IMPEDANCE OF PLATINUM-ELECTRODES IN SOLID CERIUM(IV) SULFATE HYDRATE

The impedance of the electrochemical solid-state cell Pt \ Ce(SO4)2.4H 2O \ Pt was measured in argon at temperatures between -20 and +60-degr ees-C over the frequency range from 0.11 to 100 kHz. It was shown that the frequency dependence of impedance is in good agreement with the m odel of adsorptive double-layer relaxation at reversible electrodes. T he double-layer capacitance, electrolyte conductivity, exchange curren t density of the charge transfer reaction, and Warburg constant for di ffusional relaxation were determined. The results obtained were interp reted in terms of concepts that charge transport in the electrolyte is accomplished by virtual protons arising from dynamical dissociation o f water. Large exchange current densities were determined at the plati num electrodes; these may be due to the Ce(IV) = Ce(III) redox reactio n. It was suggested that double-layer relaxation is due to the diffusi on of SO42- ions.