The oxidation of trivalent chromium at polycrystalline gold electrodes

The electrochemical oxidation of Cr(III) to Cr(VI) species was examined in aqueous solution. The responses of boron doped diamond, glassy carbon and gold electrodes were probed towards the oxidation of trivalent chromium over a wide pH range (1.0–13.0). High quality voltammetric profiles were found to appear only at a gold electrode and in solutions of pH greater than 12. It was found that the oxidation reaction proceeds via a multi-step mechanism, where the first electron transfer is electrochemically irreversible and rate-determining, followed by two fast electron transfers. DIGISIM was successfully utilized to model the experimentally obtained data. The oxidation was additionally found to involve OH− ions, at potentials where these are adsorbed at the gold electrode surface. AFM measurements were carried out to complement these findings.