Abstract

The electro-oxidation of gamma-hydroxybutyric acid (GHB) on a polycrystalline platinum electrode in acidic medium has been studied using chronoamperometry. The study has been performed in a wide interval of potentials and at different concentrations. It was found that at longer times the density currents reached stationary values at more
anodic potentials, whereas it is zero at lower potentials. These characteristics in the j-t curves suggest a different mechanism for the electro-oxidation of GHB, potential dependent, with a catalytic process at high potentials and an adsorption process controlled by mass transport at low potential.
The change in the stationary current obtained at +0.9 V with variable GHB concentrations also suggests an oxidation mechanism catalysed by the platinum surface with platinum hydroxides acting as reaction intermediates to make the final oxidation product for GHB. The results obtained using chronoamperometry are in good agreement with those obtained using cyclic voltammetry where the alcohol group is oxidised at different potentials.
In situ Surface Enhanced Raman Scattering (SERS) spectra corresponding to GHB intermediates and water adsorbed species being formed/consumed at the potentialdependent adsorption processes have been analyzed using spectro-electrochemistry. A peak at 1590 cm-1, corresponding to the asymmetric stretching of carboxylic group in a bridge configuration, increases with the potential. This supports the hypothesis of a mechanism of formation of the succinic acid on the platinum surface as reaction product under the experimental conditions studied.