Electro-oxidation of D-xylose on platinum and gold electrodes in alkaline medium

The electrocatalytic oxidation of D-xylose was performed in alkaline medium at both platinum and gold electrodes. The higher catalytic activity of gold was clearly demonstrated. Cyclic voltammetric studies were performed in a wide range of sweep rates (0.010-1.00Vs^-1), various concentrations of D-xylose and of hydroxide. The influence of temperature was also studied. Kinetic data was obtained. The chromatographic analysis has identified xylonic acid (0.5 to 5×10^-3moldm^-3) as the main oxidation product produced during the electrolysis of D-xylose, on Pt and Au electrodes, respectively, at potentials corresponding to the main oxidation peaks. The D-xylose conversion yield was found to be higher on Au than on Pt (98% against 26%). Other carboxylic acids, in concentrations lower than 10 ^-3moldm^-3, were identified by high-performance liquid chromatography (HPLC), as secondary products, namely glyceric; glycolic and formic acids, during the electrolysis on both electrode materials. On the other hand, tartaric (4.6%) and glyoxilic acids (14.0%) have been identified during the electrolysis on Au and Pt electrodes, respectively. Traces of tartronic and of oxalic acids have also been identified. HPLC studies have demonstrated the higher selectivity of Au electrodes for the production of xylonic acid.