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Palladium-based alloys, such as Pd–Co, Ni, and Cr, have been developed as a novel methanol-tolerant oxygen reduction electrocatalyst for direct methanol fuel cells. The Pd alloy electrocatalysts were fabricated by a rf sputtering method. Their electrochemical characteristics for the oxygen reduction reaction (ORR) were determined in sulfuric acid solution with and without methanol at 30°C . The Pd alloys showed a higher ORR electrocatalytic activity than Pd, although lower than Pt. The Pd alloys also had no electrocatalytic activity for methanol oxidation in the presence of methanol. The maximum electrocatalytic activities for ORR were observed for the alloy composition of ca. 60 atom % Pd in all the Pd alloys. Based on the X-ray photoelectron surface analysis, it was confirmed that the filling of the Pd d-band by alloying decreased the density of states (DOS) at the Fermi level. The decreased DOS inhibited the formation of Pd oxide on the surface of the electrocatalyst. This result should contribute to the improvement of the ORR activity of the Pd alloy electrocatalysts.

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Nickel-titanium (NiTi) alloy derives its biocompatibility and good corrosion resistance from a homogeneous oxide layer mainly composed of TiO(2), with a very low concentration of nickel. In this article, we described the corrosion behavior of NiTi alloys after mechanical polishing, electropolishing, and sterilization processes using cyclic polarization and atomic absorption. As a preparative surface treatment, electropolishing decreased the amount of nickel on the surface and remarkably improved the corrosion behavior of the alloy by increasing the mean breakdown potential value and the reproducibility of the results (0.99 +/- 0.05 V/SCE vs. 0.53 +/- 0. 42). Ethylene oxide and Sterrad(R) sterilization techniques did not modify the corrosion resistance of electropolished NiTi, whereas a steam autoclave and, to a lesser extent, peracetic acid sterilization produced scattered breakdown potential. In comparing the corrosion resistance of common biomaterials, NiTi ranked between 316L stainless steel and Ti6A14V even after sterilization. Electropolished NiTi and 316L stainless-steel alloys released similar amounts of nickel after a few days of immersion in Hank's solution. Measurements by atomic absorption have shown that the amount of released nickel from passive dissolution was below the expected toxic level in the human body. Auger electron spectroscopy analyses indicated surface contamination by Ca and P on NiTi during immersion, but no significant modification in oxide thickness was observed.

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