Novel O2-enhancing Methanol Oxidation at Pt-Ru-C Sputtered Electrode: Direct Methanol Fuel Cell Power Generation Performance

In this study, novel Pt-C and Pt-Ru-C electrodes were prepared by a co-sputtering technique to improve the methanol oxidation reaction. The methanol oxidation was first compared for Pt, Pt0.56C0.44 and Pt0.61Ru0.34C0.05 electrodes in N2-and O2-saturated 0.5 mol dm–3 H2SO4 + 1 mol dm–3 CH3OH solutions. An O2-enhancing methanol oxidation at the Pt0.56C0.44, which never occurs for the Pt, was observed and compared to that for the Pt0.61Ru0.34C0.05. The results demonstrated that the addition of Ru to the Pt-C increases the methanol oxidation current and leads to a negative shift in the onset potential (Eonset) in both the N2 and O2 atmospheres. Based on these results, the O2-enhancing methanol oxidation with a negative Eonset is evidently achieved by the Pt-Ru-C sputtered electrode. Next, an MEA containing the Pt0.61Ru0.34C0.05 was prepared and installed in a DMFC single cell. Methanol oxidation voltammograms were measured by feeding the N2- and O2-saturated methanol solutions to the Pt-Ru-C electrode and humidified H2 to the Pt-based counter-electrode. As a result, a higher cell temperature and a higher methanol concentration accelerated the methanol oxidation reaction in the N2 and O2 atmospheres. This also points out the fact that the O2-enhancing methanol oxidation takes place under these conditions. The DMFC power generation performance was then assessed by changing the counter-electrode reactant from H2 to O2. When 1 mol dm–3 CH3OH was fuelled, the generated power successfully increased with an increase in the cell temperature. Also, the O2-enhancing methanol oxidation was clearly observed. However, the DMFC power generation decreased when 5 and 10 mol dm–3 CH3OH solutions were used. By comparing the results of the methanol oxidation voltammogram and DMFC power generation performance, the degraded DMFC power generation was determined to be due to methanol crossover.