Ethanol oxidation on a high temperature PBI-based DEFC using Pt/C, PtRu/C and Pt3Sn/C as catalysts

A high temperature ethanol-fed polymer electrolyte membrane fuel cell has been implemented by using H₃PO₄-doped m-polybenzimidazole as polymeric electrolyte. Commercial Pt/C, PtRu/C and Pt₃Sn/C catalysts are used in the anode. The performance was assessed in terms of polarization curves at different temperatures, feeding the cell with a high concentration ethanol solution (water/ethanol mass ratio of 2). The product distribution was measured with the support of a gas chromatograph. The use of bimetallic catalysts increased the current density. PtRu/C showed the best performance up to 175 °C, but it is outperformed by Pt₃Sn/C at 200 °C. In terms of oxidation products, higher temperatures and current densities favour the oxidation of ethanol. However, Pt₃Sn/C promoted the generation of more oxidized products compared to PtRu/C (in which most of the ethanol is oxidized to acetaldehyde), especially at high temperature. This accounts for the large current density. In terms of complete oxidation of ethanol to CO₂, Pt/C was by far the most efficient catalyst for C–C scission, achieving percentages of 56 % of CO₂, although operating above 175 °C dramatically boosted an undesirable methanation process that slashed the efficiency. The combination of fuel cell results and product distribution helped to suggest the different oxidation routes on the surface of the different catalysts.