Impedance spectroscopy of the low potential range electro-oxidation of glucose on a polycrystalline gold electrode undergoing surface reconstruction

Abstract

The glucose electro-oxidation on a reconstructed surface gold electrode was studied using voltammetry and electrochemical impedance spectroscopy in an alkaline medium. The study deals with the low potential range where different works have attributed a voltammetric signal to the direct oxidation of glucose to gluconolactone, which hydrolyzes to gluconate. In the sampled i vs. E curve obtained from EIS measurements data, the presence of at least two peaks is identified in this range of potential, indicating two different processes and interaction of glucose with the metallic surface. These findings are in agreement with EIS results that reinforce the existence of these two behaviors within this short potential range. By comparing sampled i vs. E curve to changes in Rct with potential, it is found that an inhibiting behavior starts at a potential where the gold surface reconstruction occurs and is also apparently related to the beginning of the OH− adsorption zone. An analysis of previous facts given by different authors led us to conclude that OH− adsorption hinders somehow the aldehyde group oxidation to give gluconolactone, but radically promotes its more energetic oxidation in the opposite C-6 end.