Infrared study of the electrooxidation of ethanol in alkaline electrolyte with Pt/C, PtRu/C and Pt3Sn

Abstract

The electrooxidation of ethanol with Pt/C, PtRu/C and Pt3Sn in alkaline electrolyte has been studied using electrochemical coupled infrared spectroscopy. In order to identify the evolution of the species formed during the electrooxidation of ethanol infrared spectra have been collected in KOH/H2O and KOD/D2O electrolytes. Whereas the electrochemical studies show different catalytic performance for the EOR (Ethanol Oxidation Reaction) over the three catalysts in terms of onset potential and actual current density, especially at low potentials, the IR spectra show that carbonates and acetates are the main species formed during the EOR with all catalysts. The infrared spectra reveal that the scission of the C–C bond of ethanol takes place at the surface of Pt/C, PtRu/C and Pt3Sn catalysts at potentials as low as 20 mV vs RHE yielding carbonates. At higher potentials, C2 species resulting from the partial oxidation of ethanol to acetates are the main species detected with all catalysts. Upon the progress of the ethanol oxidation, the electrolyte becomes acidified and acetaldehyde and acetic acid (C2 species typically formed during the EOR at acid electrolyte) are observed.