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The platinum solubility in a polymer electrolyte would be a key issue in order to improve and guarantee the durability of PEFCs. In this study, the platinum solubility has been determined in acidic electrolytes as a function of temperature and pH. The solubility was ca. 3 x 10-6 mol dm-3 at 25oC in 1 mol dm-3 of H2SO4, HClO4, and CF3SO3H under air, and increased with temperature and with the decrease in pH. The platinum solubility in oxygen was slightly larger than that in air. However, the solubility in nitrogen was much smaller than the mixtures. Based on these results, the dissolution of platinum in an acidic medium would follow an acidic dissolution mechanism.

The Pt-Ru alloy is used as an electrocatalyst for stationary polymer electrolyte fuel cells (PEFCs) and direct methanol fuel cells because of its anti -CO poisoning property. Degradation of the Pt-Ru anode is one of the important problems for the durability of PEFC systems. In this study, the dissolution of Ru and RuO 2 has been investigated in sulfuric acid as a fundamental study of the stability of the Pt-Ru anode. The stability of Ru was very sensitive to the history of the surface treatment. The steadystate concentration of Ru ions from RuO 2 /Ti was less than 2 μmol dm −3 and slightly increased with potential in the range from 0.2 to 0.5 V vs. RHE. On the other hand, the concentration of Ru ions from Ru-black/Au was a several times greater than that from RuO 2 /Ti up to 0.3 V. vs. RHE and significantly increased above 0.5 V vs. RHE. The maximum concentration was 16 μmol dm −3 at 0.6 V vs. RHE. The surface of Ru might be irreversible with a potential change, and the steady-state concentration would be affected by the surface property.

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