Browsing by Author "Yeh, Kung-Yu"

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Effect of anodic dissolution in multi-element nanoparticles on methanol electro-oxidation
(2009-11-03)
Hsieh, Yi-Fan
;
Yeh, Kung-Yu
;
Wu, Pu-Wei
;
Hsieh, Yu-Chi
;
Lin, Pang
Radio frequency sputter deposition was used to deposit multi-element nanoparticles on carbon clothes for methanol electro-oxidation. Results from energy dispersive spectroscope confirmed the composition was Ft(35)Fe(12)Co(12)Ni(20)Cu(12)Ag(9). X-ray diffraction pattern suggested a fcc phase. An electrochemical de-alloying treatment was conducted in an acidic electrolyte with multiple potential sweeps at a scan rate of 20 mV/s for 0-0.3,0-0.5, and 0-0.7 V, respectively. Images from scanning electron microscope after anodic dissolutions demonstrated considerable variations in surface morphologies. Measurements on hydrogen desorption also revealed substantial increase in electrochemical active surface area. Current responses from cyclic voltammetry indicated the sample of 0-0.5 V anodic dissolution with notable enhancement. In mass activities, the same sample exhibited a comparable value to that Of Pt(43)Ru(57) (C) 2009 Elsevier B.V. All rights reserved.
Effect of platinum present in multi-element nanoparticles on methanol oxidation
(2009-06-10)
Tsai, Chih-Fang
;
Yeh, Kung-Yu
;
Wu, Pu-Wei
;
Hsieh, Yi-Fan
;
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.
Sputter deposition of multi-element nanoparticles as electrocatalysts for methanol oxidation
(2008-07-01)
Tsai, Chih-Fang
;
Wu, Pu-Wei
;
Lin, Pang
;
Chao, Cheun-Guang
;
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.