A comparative study of Prussian-Blue-modified graphite paste electrodes and solid graphite electrodes with mechanically immobilized Prussian Blue

Abstract

The cyclic voltammetry of Prussian Blue was studied using two different types of electrodes. In one case microcrystalline particles of Prussian Blue were mechanically immobilized on the surface of a paraffin-impregnated solid graphite electrode, whereas in the other the Prussian Blue was added to a paste of graphite and silicone oil. The overall behaviour of Prussian Blue in both electrodes is very similar to the well-known behaviour for electrodes with an electrochemically synthesized Prussian Blue film. Differences were observed for the modified paste electrode, particularly in acid-containing solutions. Prussian Blue exhibits pronounced ion-exchange properties in acid solutions. New voltammetric peaks are observed which are clearly related to an exchange of protons between Prussian Blue and the solution. In mixed solutions containing potassium ions and protons competition between these cations is visible. Scanning electron microscopy in conjunction with energy dispersive X-ray analysis supports a reaction scheme which includes both cations. This study provides evidence for the ability of protons to undergo a chemically reversible intercalation in the Prussian Blue lattice. An additional aim of this study was to assess the reliability of experiments using graphite paste electrodes with an organic binder. The results show that the binder affects the electrochemistry of Prussian Blue, but the similarities between “pure” Prussian Blue and that in the paste electrode are clearly dominant.