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...

The fungal pathogen Histoplasma capsulatum evades the innate and adaptive immune responses and thrives within resting macrophages (Mφ). Cytokines that induce antimicrobial activity such as granulocyte macrophage-colony stimulating factor (GM-CSF) inhibit H. capsulatum growth in Mφ. Conversely, interleukin 4 (IL-4) inhibits the killing of intracellular pathogens. Using inductively coupled plasma mass spectrometry, we examined alterations in metal homeostasis of murine H. capsulatum-infected Mφ infected that were exposed to activating cytokines. Restriction of iron (Fe2+/3+) and zinc (Zn2+) was observed in infected, GM-CSF-treated Mφ compared to infected controls. IL-4 reversed the anti-fungal activity of GM-CSF-activated Mφ and was associated with increased intracellular Zn2+. Chelation of Zn2+ inhibited yeast replication both in the absence and presence of Mφ. Treatment of cells with GM-CSF altered the host Zn2+ binding species profile. These results establish that Zn2+ deprivation may be a host defense mechanism utilized by Mφ.

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This paper describes a comprehensive investigation of particle number concentrations including a multi-method comparison, theoretical modeling, and cellular dosimetry.