Enhancement Effect of Chemisorbed Sulfate toward Electrochemical Oxidation of Ethanol on Platinum Electrodes

The influence of sulfate on ethanol oxidation reaction at a polyoriented Pt electrode has been investigated using cyclic voltammetry (CV) and combining chronoamperometry with high-performance liquid chromatography (HPLC) and in situ surface-enhanced Raman spectroscopy (SERS). In addition to the well-known inhibitory role, sulfate adsorption has also been found to increase the activity of Pt for ethanol oxidation under certain conditions, resulting from the strengthening adsorption of the substrate on Pt and inhibiting the formation of CO. Onset potential of ethanol oxidation moves to a lower value, and a new current peak at around 0.55 V (RHE) appears in the presence of sulfate in a potential range at which sulfate adsorption takes place. Also, the distributions of product concentration are consistent with CV, indicating that the sulfate adsorbed on Pt has a positive effect on ethanol electro-oxidation under certain conditions. Adsorption energy and geometric parameters calculated from density functional theory (DFT) further explain the positive role of sulfate adsorption in ethanol electrochemical oxidation.