Quartz crystal microbalance study of the growth of indium hexacyanoferrate films during electrodeposition and coagulation

An electrochemical quartz crystal microbalance and cyclic voltammetry have been used to monitor fabrication of indium(III) hexacyanoferrate(III,II) films by electrodeposition through potential cycling and by interfacial coagulation during ageing in the modification solution containing potassium electrolyte, indium(III) and hexacyanoferrate(III). We have chosen indium hexacyanoferrate as a model system since its cyclic voltammetry shows a single set of reversible, well-defined peaks significantly separated from the solution responses. Simultaneous estimations of charge and mass have been used to characterize the efficiency of the deposition processes. Microgravimetry is particularly attractive for monitoring the film growth due to interfacial coagulation (at open circuit). Electrodeposition by potential cycling permits fast preparation of thin films. The coagulation method is useful for fabrication of thick films. We also discuss the response of the resulting indium hexacyanoferrate film in the supporting electrolyte. The data are consistent with the insertion and exclusion of K+ countercations during the system's reduction and oxidation respectively.