| Platinum-based particles are synthesized via the polyol process in an effort to include various metal oxides in a multi-phase catalyst for the direct ethanol fuel cell anode. Among Eu, In, La and Nb, no single metal oxide with platinum yields open circuit potentials or maximum current densities as high as tin oxide with platinum. For this reason, particles with platinum, tin oxide and the oxide of a third metal were developed. Platinum tin/indium oxide slightly outperforms platinum tin oxide. The particles are characterized by TEM, EDX, XRD and ICP. The metal oxides and the platinum are located together in one particle, uniformly 5.3 nm in diameter. ICP analysis indicates that the catalysts are 20% platinum on carbon and the metals of the oxides are on the order of 1-2% by mass. The catalytic abilities of the particles were evaluated in a single cell direct ethanol fuel cell where polarization curves were taken up to 130°C, and oxidation products were analyzed by gas chromatography. Open circuit voltages of as high as 0.82 V were obtained for platinum tin/indium oxide catalysts and current densities as high as 0.4 A cm-2 were seen. The cells produced large amounts of acetaldehyde and acetic acid, as well as small amounts of methanol and carbon dioxide. A spillover mechanism is proposed for the oxidation of ethanol to CO2 on these platinum/metal oxide catalysts. |
