Dependence of redox characteristics in Prussian blue-modified electrode on pH of electrolytic solution

Redox characteristics in Prussian blue (PB) film were studied from a viewpoint of dependency of apparent diffusion coefficient (Dapp) on pH of electrolytic solution. The PB film was electrodeposited on Pt foil in electrolysis bath of FeCl3 and K3Fe(CN)6 mixed solution. Electrolytic solution for measurements was 1.0 mol dm−3 KCl solution with various pH which was adjusted by 0.1 mol dm−3 HCl. Cyclic voltammograms of the PB-modified electrode suggested that redox reactions proceeded by diffusion-controlled mode. Chronoamperometry and chronocoulometry with potential step range between 0.5 and 0.0 V showed that maximum arcs of Dapp were present at redox reactions in pH 2–3 of electrolytic solution. In order to analyze the Dapp behavior of the PB film, concentrations of K+ ion and Cl− ion were measured by ionchromatography, and configuration of the ions in the soluble PB lattice was discussed. Steric hindrance for K+ ion diffusion in the PB film was considered to arise chiefly from interstitial K+ ion among K+ ion, H+ ion, and Cl− ion in the PB lattice.