Electrochemical impedance spectroscopy and UV–vis reflectance spectroelectrochemistry of cobalt hexacyanoferrate films

Electrochemical impedance spectroscopy (EIS) was used in conjunction with cyclic voltammetry and UV–vis spectroelectrochemistry to study the influence of growth history on compounds formed in the cobalt hexacyanoferrate (CoHCF) family and their redox inter-relationships. The CoHCF films were potentiodynamically grown via precipitation on polycrystalline gold substrates from a 1 M KNO3 medium dosed with Co2+ and Fe(CN)63- precursor species. The growth variables were the precursor concentration ratio: [Co2+]/[Fe(CN)63-], potential window for film growth, delay time (between precursor mixing and potential cycling), and the number of potentiodynamic cycles for film growth. The combined use of the data from the three techniques identified above has afforded identification of the various CoHCF compounds that constitute the films and their redox inter-relationships.