Insight into the Electro-Oxidation Mechanism of Glucose and Other Carbohydrates by CuO-Based Electrodes

In this work, a new hypothesis for the electrocatalytic behavior of CuO electrodes is presented. Different from the established mechanism, here we discuss why Cu-III species do not participate in the oxidation mechanism of carbohydrates. We show that hydroxyl ion adsorption and the semiconductive properties of the material play a more significant role in this process. The relationship between the flat band potential and the potential that begin oxidation suggests that the concentration of vacancies in the charge region acts upon the reactivity of the adsorbed hydroxyl ions through a partial charge transfer reaction. In the presence of carbohydrate molecules, the electron transfer is facilitated and involves the transfer of electrons from the adsorbed hydroxyl ions to the CuO film. This mechanism is fundamentally relevant since it helps the understanding of several experimental misleads. The results can also lead to obtaining better catalysts, since improvements in the material should focus on enhancing the semiconductive properties rather than the Cu-II/Cu-III redox transition. The results shed light on different aspects of carbohydrate molecules oxidation that could lead to novel applications and possibly a better description of other semiconductor mechanisms in electrocatalysis.