Potentiodynamic study of the intercalation compounds of graphite with chromium trioxide in sulphuric acid solution

✍ Scribed by J.M. Skowroński

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 517 KB
• Volume: 30
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(85)80161-4

✦ Synopsis

The electrochemical behaviour of the dilute intercalation compounds prepared in the reaction of graphite with molten 00, has been examined in 0.25 M H,SO, using a slow (1 mVs_') potentiodynamic method. The measurements were carried out in a potential range between 0.4 and 1.5 V. Due to deintercalation occurring when the compounds are pressed and/or heat treated, al1 experiments were performed with the electrodes being the bed of the intercalation compound particles. The curves demonstrated the cathodic peak around 1 V attributed to the reduction of hexavalent chromium ions formed during the previous anodic sweep. Because chemical analysis of electrolyte after several cycles revealed no detectable amount of chromium, it was suggested that the electrochemical reactions take place in the buik of the compound. It was shown that the oxidation of the lower oxides ofchromium occurs in a potential range of oxygen evolution and, therefore, no anodic peak is perceptible. The potentioclynamic results supported by non-electrochemical data allowed us to assume that the lower oxides remaining in the intercalation compounds after washing with both hot water and 6 M HCl tie bounded with the graphite host and are electrochemically active. The reaSons for the electrochemical inertness of the intercalated Cr03 are considered.