Electrochemical behaviour of oxocarbons on single crystal platinum electrodes .4. Rhodizonic acid in 0.5 M sulphuric acid medium

The electrochemical behaviour of rhodizonic acid on Pt(111), Pt(100) and Pt(110) surfaces has been studied in sulphuric acid solutions by cyclic voltammetry and in situ FTIR spectroscopy. The direct oxidation process takes place at potentials positive to the desorption of strongly bonded adsorbates. For the three orientations, polyketonic compounds and finally carbon dioxide are the oxidation products. Reduction processes can cake place at lower potentials, leading to the formation of tetrahydroxyquinone and hexahydroxybenzene, also detected by FTIR. These species seem to be adsorption intermediates in the case of Pt(111), transforming from one to another depending on potential. A small amount of carbon monoxide is observed on this orientation. Significantly higher CO adsorptions have been obtained for Pt(110) (linear CO) and Pt(100) (linearly and bridge bonded). Other adsorbates seem to be formed after adsorption experiments, which give no detectable infrared absorption.