Electrochemical study of microcrystalline solid Prussian blue particles mechanically attached to graphite and gold electrodes: Electrochemically induced lattice reconstruction

The voltammetric behavior of solid Prussian blue mechanically attached to graphite, glassy carbon, or gold electrodes as an array of microscopically small particles is extremely well defined when the electrode is placed in aqueous media containing suitable electrolytes. Electron microscopy, electron microprobe analysis, and in situ electrochemical quartz crystal microbalance techniques have been used in addition to the voltammetric data, to characterize the redox and ion-transport processes of solids attached to the electrode. The results compare favorably with published studies based on electrogenerated films, although, as expected, the scan rate dependence is different when solid particles are used. Ion-exchange reactions accompanying redox processes have been examined in K⁺ and Cd²⁺ containing aqueous electrolyte solutions, and two types of ion exchange can be distinguished. These are based on replacement of interstitial positions and replacement of lattice positions. An overall reaction scheme based on electrochemically initiated lattice reconstruction is presented to explain the generation of cadmium hexacyanoferrate when oxidation or reduction of Prussian blue occurs at the electrode-solid-K⁺/Cd²⁺ containing aqueous electrolyte interface.