Methanol generation by CO2 reduction at a Pt-Ru/C electrocatalyst using a membrane electrode assembly

We have investigated the CO2 electroreduction at a Pt-Ru/C-based catalyst using a membrane electrode assembly (MEA) in a single cell to realize a methanol-based reversible fuel cell. Cyclic voltammograms were measured under N2 and CO2 atmospheres using the Pt-Ru/C-based MEA. For comparison, the Pt/C-based MEA was used. A typical voltammogram attributed to the Pt electrode has been obtained using Pt/C under an N2 atmosphere, and an extra oxidation peak appeared at 0.60 V vs. DHE under a CO2 atmosphere. This peak has been considered to be caused by the re-oxidation of the CO2 reductant. For the Pt-Ru/C, the re-oxidation peak has been observed at 0.50 V vs. DHE which is more negative than Pt/C. The limiting cathode potential of the cyclic voltammogram was changed from 0.06 to 0.35 V vs. DHE under a CO2 atmosphere, and the magnitude of the re-oxidation peak decreased. To quantitatively analyze the product of the CO2 reduction, a gas chromatograph and methanol- and CO-stripping voltammograms were measured. Based on these results, methanol has been found to be the main product of the CO2 reduction at the Pt-Ru/C. Finally, the methanol yield and coulombic efficiency were calculated resulting in 7.5% and 75% at the Pt-Ru/C, respectively.