A thin film of Prussian blue (KFeFe(CN6)), on a platinum or gold substrate, is reduced to Everitt's salt (K2FeFe(CN6)) at 0.195 V (vs. SCE) or is oxidized to Berlin green (K1/3Fe(FeIII(CN)6)2/3(Fe II(CN)6)1/3) at 0.870 V in 1 N KCl or K2SO4 solutions. It is shown that potassium ion migrates into or out of the film during the electrolysis. Both reactions are reversible at sweep rates of <5 mV/s in 1 N potassium ion solutions. Partial oxidation or reduction of Prussian blue leads to the formation of solid solutions. For the reduction reaction the solid solution formed is nonideal, and the voltammograms are explained in terms of the theory of strictly regular solutions with a negative interaction energy. For the oxidation reaction the solid solution appears to be almost ideal, but approximately one-third of the ferrocyanide ions remain unoxidized in the stable form of the completely oxidized compound.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry