The dissolution of Fe and Ni from Pt 1Ϫx M x ͑M ϭ Fe, Ni; 0 Ͻ x Ͻ 1͒ oxygen reduction electrocatalysts was studied under simulated operating conditions ͑low pH, 80°C͒ of proton exchange membrane ͑PEM͒ fuel cells. The alloys were prepared combinatorially by sputtering Pt and M ͑M ϭ Fe, Ni͒ onto thin films of nanostructured whisker-like supports, and mapped over the entire composition range of the binary systems. For 0 Ͻ x Ͻ 1.0, we observe the formation of randomly ordered substitutional solid solutions of Pt 1Ϫx Fe x and Pt 1Ϫx Ni x alloys. Electron microprobe measurements show that transition metals are removed from all compositions during acid treatment, but that the percentage removed increases with x, acid strength, and temperature. For small values of x (x Ͻ 0.6) no substantial changes in the lattice size are observed upon dissolution of Fe or Ni suggesting that the dissolved transition metals originate from the surface. However, for electrocatalysts with x Ͼ 0.6, the lattice constant expands indicating that transition metals dissolve also from the bulk. X-ray photoelectron spectroscopy results show complete removal of surface Ni ͑Fe͒ after acid treatment at 80°C for all compositions. The results of the acid treatments compare well to the composition changes that occur when a Pt 1Ϫx Fe x or Pt 1Ϫx Ni x combinatorial catalyst library is used in an operating PEM fuel cell.

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Macroporous a-Al 2 O 3 hollow fibers are used as supports for thin dense Pd membranes; these membranes show a high and stable H 2 flux in permeance studies.The increasing demand for H 2 as an energy carrier or chemical in the petroleum industry has promoted research interest in H 2 production, purification and utilization all over the world. 1 As an advanced technology with a compact apparatus and high efficiency, metallic Pd-based membranes have occasionally been applied to separate and purify H 2 for electronic, metallurgic and fine chemical applications. 2 However, the commercialization of Pd-based technology on a large scale does not appear to be likely in the near future, although this technology has been shown to have great potential 3-5 in last four decades.

Pt 1−x Ta x ͑0 Յ x Յ 1͒ thin-film libraries were prepared using combinatorial dc magnetron sputtering on a variety of substrates. For x Ͻ 0.5, the materials adopted a face-centered cubic structure and for x Ͼ 0.5 a nanocrystalline phase of Pt 1−x Ta x was observed. The bulk composition of the films obtained by electron microprobe before and after treatment in 0.5 M H 2 SO 4 at 80°C showed no detectable dissolution of Ta at any x in Pt 1−x Ta x . X-ray photoelectron spectroscopy of acid-treated samples revealed that for regions with high Ta content ͑x Ͼ 0.5͒, full oxidation of surface Ta had occurred. The samples, when used as oxygen-reduction electrocatalysts, also showed corrosion stability; however, the addition of Ta significantly lowered the activity towards oxygen reduction reaction for x Ͼ 0.1 in Pt 1−x Ta x .