Abstract
Pt nanoparticle catalysts supported on carbon black coated with mixtures of Ru and Sn oxides (Pt/Ru-Sn oxide/C) have been screened for their activity and stoichiometry for ethanol oxidation. The compositions, loadings, and properties of the mixed Ru + Sn oxide support layers were varied by changing the concentration of base used during their deposition. Cyclic voltammetry at ambient temperature showed that Ru oxide alone provided a significant increase in activity at low potentials over Pt/C, while a small amount of Sn provided a large additional benefit. The most active catalyst had Ru and Sn loadings of 17% and 1.2% by mass, respectively. This was also the most active catalyst for ethanol oxidation at 80°C in proton exchange membrane electrolysis cells, where it provided four times more current than a commercial Pt/C catalyst at 0.25 V vs. a hydrogen evolving cathode. This is comparable to the performance of commercial PtRu/C, and the Pt/Ru-Sn oxide/C catalyst was more selective for the complete oxidation of ethanol to CO2. Thus, in direct ethanol fuel cells, Pt/Ru-Sn oxide/C catalysts would provide greatly increased current and power densities over Pt/C, and improved efficiencies over PtRu/C.
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