In situ study of methanol oxidation on Pt and Pt/Ru-mixed with Nafion® anodes in a direct methanol fuel cell by means of FTIR spectroscopy

Abstract

Methanol and carbon monoxide (CO) oxidation on unsupported Pt- and Pt/Ru-mixed with Nafion® anodes in the direct methanol fuel cell (DMFC) were studied by in situ Fourier transform infrared spectroscopy. IR measurements were performed using a specially constructed DMFC by diffuse reflection and on-line transmittance techniques at different potentials applied to anodes under cell operating conditions. The experiments show that the major products of the methanol oxidation are methylformate, carbon monoxide and carbon dioxide. No other products could be discerned. This fact is in contrast with the results reported for smooth/single crystal electrodes in a supporting electrolyte environment, where other products (COHads, formaldehyde, formic acid and dimethoxymethane) were found. This can reflect a difference in the electrochemical conditions in the real DMFC and those which are set on the model electrodes. Inverse and bipolar IR band shapes of the linearly bound CO (COL) were observed. The exact reason for the anomalous shape is not understood, however, the influence of the mixed or supporting material on the optical response of the COL is obvious. The COL experiences reduced influence from the applied potential. The possible reasons are discussed.