The influence of oxidative pretreatment of graphite electrodes on the catalysis of the Cr3+Cr2+ and Fe3+Fe2+ redox reactions

Cyclic voltammetry was applied to investigate the Cr3+Cr2+ and Fe3+Fe2+ redox couple reactions in HCI electrolytes on highly oriented pyrographite electrodes activated by oxidative pretreatment. The activation effect observed after the oxidative pretreatment was very unstable for the Cr3+Cr2+ reaction in comparison to the Fe3+ reduction. It is thus concluded that acidic surface oxides are participating in the redox reaction. These oxides are reduced, however, in the case of Cr3+ reduction near the potential of hydrogen evolution.