Based on three-phase electrode models, we study to access the Gibbs energy contributions for the transfer of ions and electrons in Prussian blue analogs since they have long life cycles and high energy efficiency. Ni[Fe(CN)₆] (HCFNi) and Cu[Fe(CN)₆] (HCFCu) were preliminarily synthesized by a hydrothermal process. The obtained HCFNi powders were supported on a paraffin-impregnated graphite electrode in contact with an organic electrolyte, producing solid-state oxidation-reduction electrochemical reactions, which have been monitored by cyclic voltammetry and open circuit potential measurements in the presence of potassium as intercalating ion. The results show a behavior according to the Nernst equation as the potassium ion concentration varies, with a slope of 61.2 mV/dec. These experiments make it possible to access Gibbs free energy values for both transfers separately and replicate them for different insertion ions, such as Na⁺ and Li⁺.

Figure: (Left) Open circuit potential measurements; (center) mid-peak potential measurements; and (right) cyclic voltammetry for Ni[Fe(CN)6] in potassium media.