Revisited Mechanisms for Glucose Electrooxidation at Platinum and Gold Nanoparticles

The electrooxidation of glucose on gold (Au) and platinum (Pt) nanoparticles (NPs) is investigated in alkaline medium by cyclic voltammetry after chronoamperometry at different potentials (+0.100 V, +0.200 V, and +0.400 V vs the reversible hydrogen electrode, RHE), in situ Fourier transform infrared spectroscopy, and differential electrochemical mass spectrometry measurements. We show that glucose can adsorb on both metallic Au and Pt surfaces at low potentials, but that the adsorbed species are different: hydrogen atoms, carbon monoxide (CO), lactones and gluconate species on Pt-NPs, and only hydrogen atoms and gluconate species on Au-NPs. On Pt-NPs, the first oxidation peak between +0.050 V vs RHE and +0.250 V vs RHE is due to glucose adsorption and hydrogen atoms oxidation into protons (H+), whereas the second electrochemical feature between +0.250 V vs RHE and +0.800 V vs RHE is due to the oxidation of glucose into lactone and gluconate and of adsorbed CO into carbon dioxide (CO2). For Au-NPs, adsorbed hydrogen atoms are not oxidized into H+ but transformed into molecular hydrogen H-2, and glucose is adsorbed as gluconate species that are desorbed into gluconates for potentials higher than +0.300 V vs RHE.