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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.

Nanostructured thin film catalysts (NSTF) with widely varying compositions of Pt x M y and Pt x M y N z (M, N ¼ Ni, Co, Zr, Hf, Fe, Mn) have been evaluated for 0 x, y, z < 1. The catalysts' activity for oxygen reduction (ORR) was measured in 50 cm 2 fuel cell membrane electrode assemblies. Pt 1-x Ni x was found to be unique in showing an extraordinarily sharp peak in ORR activity as a function of the as-made composition around x ¼ 0.69 6 0.02 determined gravimetrically. This composition gave a corresponding fcc lattice parameter of 3.71 Angstroms and a grain size of 7.5 nm. Both surface area and specific activity increases contribute to the increased mass activity of the resultant dealloyed films. The ORR mass activity of the Pt 3 Ni 7 is 60% higher than for the NSTF standard Pt 68 Co 29 Mn 3 alloy. Rotating disk electrode measurements of a Pt 1-x Ni x series on NSTF coated glassy carbon disks show a similar large and sharp peak in activity. In contrast, PtCo shows a diminished but still sharply peaked mass activity in 50 cm 2 tests near x ¼ 0.62 by electron microprobe over the 0 < x < 0.7 range examined.

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Water based electrolyzers offer a promising approach for generating hydrogen gas for renewable energy storage. 3M's nanostructured thin film (NSTF) catalyst technology platform has been shown to significantly reduce many of the performance, cost and durability barriers standing in the way of H 2 /air PEM fuel cells for vehicles. In this paper we describe results from the first evaluations of low loaded NSTF catalysts in H 2 /O 2 electrolyzers at Proton OnSite and Giner, Inc. Over two dozen membrane electrode assemblies comprising nine different NSTF catalyst types were tested in 11 short stack durability tests at Proton OnSite and 14 performance tests in 50 cm 2 single cells at Giner Electrochemical Systems. NSTF catalyst alloys of Pt 68 Co 29 Mn 3 , Pt 50 Ir 50 and Pt 50 Ir 25 Ru 25 , with Pt loadings in the range of 0.1 to 0.2 mg/cm 2 , were investigated for beginning-of-life performance and durability up to 4000 hours as both electrolyzer cathodes and anodes. Catalyst composition, deposition and process conditions were found to be important for meeting the performance of standard PGM blacks on electrolyzer anodes while using only 10% as much PGM catalyst. Analyses of MEA's after the durability tests by multiple techniques document changes in catalyst alloy composition, loading, crystallite structure and support stability.Pure pressurized hydrogen gas offers a convenient and predictable means for storing and transporting convertible energy from renewable or other energy sources for powering fuel cells for vehicle, portable and back-up power applications. Renewable energy sources such as wind and solar will require large, efficient and versatile energy storage means for load leveling over wide periods of time covering seconds to days for which electrochemical storage means offer many advantages. Regenerative fuel cells and H 2 /O 2 electrolyzers used for energy storage are key examples. Water based electrolyzers with higher heating value voltage efficiencies of 75% are projected to be able to produce H 2 in the $3-$4/kg range, competitive with current gasoline prices, at reasonable electricity costs on the order of $0.05/kW-Hr. [1][2][3][4] Proton exchange membrane (PEM) based water electrolyzers offer a promising pathway to efficient hydrogen production because of a small installation footprint, ease of handling the solid polymer electrolyte and ability to generate high pressure hydrogen with only deionized water and electricity as inputs. Commercial PEM electrolyzer costs based on current technology are excessive due both to low volume (batch) system assembly and high stack component material costs. However, the electrolyzer stacks and their internal components, viz. separator plates, PEM's and catalysts have cost factors that could benefit significantly from the technology improvements that PEM fuel cell development has enabled over the past decade or more. With respect to the electrocatalysts, current commercial PEM electrolyzers use 2 mg/cm 2 or more of precious group metals (PGM) on their anodes (oxygen ev...