ELECTROCHEMICAL INVESTIGATIONS OF THE REDOX CONDUCTING SOLID ELECTROLYTES

Various experimental strategies and results are presented for electroc hemical measurements of mixed conductors, ionically and mixed-valence electron hopping materials, such as Prussian Blue films and silico-12- tungstic acid single crystals, in the absence of deliberately added li quid electrolyte phase. These inorganic solids contain chemically iden tifiable, Fe(III,II) or W(VI,V), redox sites and mobile (hydrated), po tassium or hydronium counterions. Their population is extensive enough to support diffusive mass transport of electrons (redox conduction). The simplest experimental approaches include two-electrode sandwich ce lls (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 B lue, have been considered. The most successful design utilizes an ultr amicrodisk electrode facing a silver rod semireference/counter electro de within a two-electrode cell. Fast potential scan rate (20 V s-1) cy clic voltammetry of silicotungstic acid single crystals is possible.