A COMPARATIVE-STUDY OF PRUSSIAN-BLUE-MODIFIED GRAPHITE PASTE ELECTRODES AND SOLID GRAPHITE-ELECTRODES WITH MECHANICALLY IMMOBILIZED PRUSSIAN-BLUE

The cyclic voltammetry of Prussian Blue was studied using two differen t types of electrodes. In one case microcrystalline particles of Pruss ian Blue were mechanically immobilized on the surface of a paraffin-im pregnated solid graphite electrode, whereas in the other the Prussian Blue was added to a paste of graphite and silicone oil. The overall be haviour of Prussian Blue in both electrodes is very similar to the wel l-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 ex hibits pronounced ion-exchange properties in acid solutions. New volta mmetric peaks are observed which are clearly related to an exchange of protons between Prussian Blue and the solution. In mixed solutions co ntaining potassium ions and protons competition between these cations is visible. Scanning electron microscopy in conjunction with energy di spersive X-ray analysis supports a reaction scheme which includes both cations. This study provides evidence for the ability of protons to u ndergo a chemically reversible intercalation in the Prussian Blue latt ice. An additional aim of this study was to assess the reliability of experiments using graphite paste electrodes with an organic binder. Th e results show that the binder affects the electrochemistry of Prussia n Blue, but the similarities between ''pure'' Prussian Blue and that i n the paste electrode are clearly dominant.