Browsing by Author "Lu, Yung-Jean"

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Displacement Reaction in Pulse Current Deposition of PtRu for Methanol Electro-Oxidation
(2009)
Hsieh, Yu-Chi
;
Wu, Pu-Wei
;
Lu, Yung-Jean
;
Chang, Yun-Min
;
材料科學與工程學系
Galvanostatic depositions in rectangular pulses and nitrosol precursors were employed to prepare PtRu nanoparticles on carbon clothes in various sizes and compositions. Variables including current on-time (T(on)), current off-time (T(off)), and current density were explored to identify the optimized catalytic performances for methanol electro-oxidation. Electrochemical characterizations including cyclic voltammetry and hydrogen desorption were carried out. Images from a transmission electron microscope on the PtRu nanoparticles revealed a moderate size distribution. Signals from X-ray patterns indicated a slight shift of diffraction peaks, suggesting that the Ru was alloyed successfully in the Pt lattice. In addition, the amount of alloyed Ru was found to decrease with reduced duty cycles. Composition determinations from inductively coupled plasma mass spectrometry and analysis on the oxidation states from X-ray photoelectron spectroscopy suggested a displacement reaction in which the Ru was alternately deposited and dissolved during T(on) and T(off), while the Pt was deposited continuously. As a result, we observed substantial enrichment of Pt in the PtRu nanoparticles when the duty cycle was shortened.
Galvanostatic Pulse Plating of PtRu Nanoparticles for Direct Methanol Fuel Cells
(2008)
Hsieh, Yu-Chi
;
Lu, Yung-Jean
;
Wu, Pu-Wei
;
Chang, Yun-Min
;
Chiu, Yu-Fan
A galvanostatic pulse electrodeposition technique of preparing nanoparticulate PtRu electrocatalyst for direct methanol fuel cells has been demonstrated. After extensive cyclic voltammetric analysis, we determined the optimized parameters for the methanol oxidation to be current on-time on 50 ms, current off-time of 400 ms, current density of 50 mA/cM, and total charge of 9.0 C/cm(2) In addition, the catalyst loading was measured at 68 mu g/cm(2) resulting in a mass activity of 213 mA/Pt. mg. The composition for the nanoparticles was confirmed as Pt(65)RU(35). High-magnification images on the specimen indicated fine particles in 4-20 nm with uniform distributions.