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Browsing by Author "Tsai, Chih-Fang"

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    Effect of platinum present in multi-element nanoparticles on methanol oxidation
    (2009-06-10)
    Tsai, Chih-Fang
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    Yeh, Kung-Yu
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    Wu, Pu-Wei
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    Hsieh, Yi-Fan
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    Lin, Pang
    Nanoparticles of Pt(x)Fe((100-x)/5)Co((100-x)/5)Ni((100-x)/5)Cu((100-x)/5)Ag((100-x)/5) (x = 22, 29, 52, 56) were prepared by the sputter depositions on pretreated carbon clothes with their electrocatalytic abilities for the methanol oxidation investigated. XRD analysis of the deposited nanoparticles indicated crystalline fcc phases and SEM images revealed apparent growths of nanoparticulate nodules. Their average sizes were found to increase with the deposition time. Cyclic voltammetry of the deposited samples demonstrated enhancements in the current responses with increasing Pt amount and deposition time. In mass activity, the Pt(52)Fe(11)Co(10)Ni(11)Cu(10)Ag(8) exhibited the highest values of 462-504 mA/mg. Identical process was conducted to fabricate electrodes with sputtered Pt and Pt(43)Ru(57). In comparison, the Pt(52)Fe(11) Co(10)Ni(11)Cu(10)Ag(8) showed moderate improvements over that of Pt but was still outperformed by the Pt(43)Ru(57). (C) 2008 Elsevier B.V. All rights reserved.
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    Sputter deposition of multi-element nanoparticles as electrocatalysts for methanol oxidation
    (2008-07-01)
    Tsai, Chih-Fang
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    Wu, Pu-Wei
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    Lin, Pang
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    Chao, Cheun-Guang
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    Yeh, Kung-Yu
    Fabrication of multi-element nanoparticles on noncatalyzed gas diffusion electrodes (GDEs) by radio frequency sputter deposition was reported. X-ray diffraction analysis of the as-deposited films indicated crystalline fee phases while energy dispersive X-ray spectroscope confirmed their composition as Pt(50)Fe(11)Co(10)Ni(11)Cu(10)Ag(8). Scanning electron microscopy images revealed nanoparticulate nodules growing on the carbon particles. Cyclic voltammetry (CV) was employed to analyze their methanol oxidation abilities for direct methanol fuel cells. The CV responses improved upon cycling and became stabilized after 70 cycles. The areas under the CV curves were proportional to the amount of nanoparticles deposited. In mass activities the GDE with 5 nm nanoparticles demonstrated the highest values of 400-600 mA/mg. In comparing with Pt and Pt(43)Ru(57), the Pt(43)Ru(57) exhibited the lowest onset potential with the highest mass activities. Our work presents preliminary information on the catalytic behaviors of multi-element nanoparticles which is likely to bring new directions in catalyst design.