Electrooxidation of xylitol on platinum single crystal electrodes: A voltammetric and in situ FTIRS study

The adsorption and oxidation reactions of xylitol at platinum single crystal electrodes with basal orientations have been studied by cyclic voltammetry and in situ FTIR spectroscopy. Cyclic voltammetric results have shown that, even if oxidation takes place at higher potentials, Pt(1 0 0) surface is the more active as far as current densities are concerned, and also the less poisonable surface. The electrocatalytic activity evaluated from the first sweep follows the order Pt(1 0 0) > Pt(1 1 1) > Pt(1 1 0). FTIR spectroscopic experiments have indicated that CO is formed upon xylitol dissociative adsorption on the three basal platinum surfaces. This adsorbed intermediate, which was identified as the main poisoning species, is bonded to the platinum surface both in a linearly and bridge bonding mode on a ratio which depends on the electrode surface orientation. Besides the formation of carbon dioxide, the presence of some other reaction products containing carbonyl groups can also be inferred from the obtained spectra. The electrooxidation process was found to be strongly dependent on the platinum crystalline surface structure. Moreover, experiments performed on two sets of platinum stepped surfaces have shown that the adsorption and oxidation reactions of xylitol are sensitive to the symmetry of the bidimensional domains as well as to the distribution of orientated defects (monatomic steps) on the platinum surfaces. Increasing the density of steps hinders the catalytic activity.