Four decades of electrochemical investigation of Prussian blue

Abstract

Prussian blue and its analogues are well known nowadays as promising substances for energy storage, capable of electrochemical insertion of Li+, Na+, Ca2+, and other ions. A huge amount of experimental data obtained recently is in evident contradiction with the postulates declared in the early investigations on Prussian blue electrochemistry. Nevertheless, some of these old postulates are widely in use up to now. On the basis of the data on the chemistry and the composition of the Prussian blue not previously involved in the discussion, this article examines the possible participation of hydrated ions in the redox process, the composition of the electrodeposited films of this compound, and some other important problems. Analytical data on Prussian blue, obtained in the nineteenth century and underestimated by twentieth century chemists, suggests that it is a non-stoichiometric compound. Equations describing electrochemical processes of this substance have been proposed.