The electrochemical oxidation of xylitol on Pt(111) in acid medium

A voltammetric and spectroscopic study of the oxidation of xylitol, in acid medium, on a platinum single crystal, Pt (111) and on polycrystalline platinum, Pt (poly), electrodes is presented in this paper. The superior electrocatalytic activity of the Pt (111) electrode surface in comparison with that of the Pt (poly) was clearly demonstrated. The oxidation of xylitol on the Pt (111) electrode surface has been studied by varying the scan potential rate and the xylitol concentration. The CVs show a shoulder and a well-defined anodic peak. It was concluded that both peaks are due to an irreversible one-electron transfer reaction and that the most positive peak presents a diffusion control. The reactions are of the order of 1/2 with respect to the initial polyol concentration. FTIRS data of the system Pt (111) in 0.1 M HClO4 + 0.01 M xylitol, either in water or D2O, have shown the existence of bands corresponding to adsorbed CO, bridge and linearly bonded, both involved in the surface poisoning in the range from 0.325 to 0.625 V vs. reversible hydrogen electrode (RHE). At E > 0.625 V vs. RHE, bands, which may be attributed to acid groups and to a lactone, have been observed. Thus, the rather probable reaction products are, besides CO2, xylonic acid (and the corresponding lactone, xylonolactone) and other short-chain aliphatic carboxylic acids resulting from the breaking of the initial molecular carbon skeleton. (C) 2004 Elsevier B.V. All rights reserved.