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

Abstract

Redox characteristics in Prussian blue (PB) film were studied from a viewpoint of dependency of apparent diffusion coefficient ( D app) on pH of electrolytic solution. The PB film was electrodeposited on Pt foil in electrolysis bath of FeCl 3 and K 3Fe(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 D app were present at redox reactions in pH 2–3 of electrolytic solution. In order to analyze the D app 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.