Electrochemical investigations of the redox conducting solid electrolytes

Various experimental strategies and results are presented for electrochemical measurements of mixed conductors, ionic and mixed-valence electron hopping materials, such as Prussian Blue films and silicono-12-tungstic acid single crystals, in the absence of deliberately added liquid electrolyte phase. These inorganic solids contain chemically identifiable, Fe(III, II) or W(VI, V), redox sites and mobile (hydrated), potassium or hydronium counterions. Their population is extensive enough to support diffusive mass transport of electrons (redox conduction). The simple experimental approaches include two-electrode sandwich cells (without reference electrode), in which the investigated material is introduced between a pair of equivalent electrodes. Both closed and open sandwich cells, as well as thick and thin coatings of Prussian Blue, have been considered. The most successful design utilizes an ultramicrodisk electrode facing a silver rod semi reference/counter electrode within a two-electrode cell. Fast potential scan rate (20 V s-1) cyclic voltammetry of silicono-tungstic acid single crystals is possible. (author). 24 refs, 5 figs