Browsing by Author "Chen, Chieng-Ming"

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Improved Catalytic Performance of Pt Supported on Multi-Wall Carbon Nanotubes as Cathode for Direct Methanol Fuel Cell Applications Prepared by Dual-stepped Surface Thiolation Processes
(2009-12-01)
Chen, Tsan-Yao
;
Lin, Tsang-Lang
;
Chen, Chien-Chung
;
Chen, Chieng-Ming
;
Chen, Chia-Fu
This study develops a simple surface modification process for modifying the MWCNT surface by thiolation reaction after the conventional nitric acid treatment for strong interface attachment of Pt NPs and improved dispersion onto MWCNTs. The thiolated MWCNTs (Pt/MWCNTs) showed significant improvement of methanol electro-oxidation activity compared with that treated only by nitric acid solution. The prepared electrode with thiolated MWCNTs was used as the cathode for assembling MEA for DMFC single-cell applications. Testing results indicate that the thiolated MWCNT cathode can improve the power density of MEA by more than 300% (from 4.6 to 20.6 mW cm(-2)) compared with that treated only by conventional nitric acid reactions. The dual-step modification process for MWCNT surface treatment showed significant improvement over the convention nitric acid treatment and can be successfully used in DMFC applications.
Modification of multi-walled carbon nanotubes by microwave digestion method as electrocatalyst supports for direct methanol fuel cell applications
(2007-01-01)
Chen, Chien-Chung
;
Chen, Chia-Fu
;
Chen, Chieng-Ming
;
Chuang, Fang-Tzu
;
材料科學與工程學系
Multi-walled carbon nanotubes (MWCNTs) which were directly synthesized on carbon cloth were modified by a microwave digestion method in 5 M HNO3 for supporting Pt nanoparticles. The characterizations of modified CNTs were carried out by TEM, XPS, FTIR and Raman spectroscopy. The HRTEM image shows the caps of MWCNTs are opened after modifying by microwave digestion method. The open-end and undamaged MWCNTs can provide a larger surface area for supporting more catalysts. Furthermore, the methanol electrocatalytic oxidation of microwave digestion treated Pt/MWCNTs electrode shows higher current density than pristine and nitric acid-treated MWCNTs from cyclic voltammograms. This can be an effective and undamaged method for modifying CNTs. (c) 2006 Elsevier B.V. All rights reserved.
Rapid and homogeneous dispersion of pt catalyst particles on multi-walled carbon nanotubes by temperature-controlled microwave polyol method
(2008-04-01)
Chen, Chieng-Ming
;
Chen, Mi
;
Yu, Hung-Wei
;
Lu, Su-Chen
;
Chen, Chia-Fu
Fuel cells, particularly direct methanol fuel cells (DMFCs), have great potential as mobile power sources. It has been extensively reported that the DMFC performance strongly depends on the electrode catalyst, and many research groups have focused on the preparation of high efficiency cathode catalysts using all types of metal nanoparticle and support. However, most of these methods are either time-consuming with multiple-steps or there is low loading of the nanocatalyst dispersed on the supports. In this study, platinum nanoparticles of uniform diameter (approximately 4.3 nm) were efficiently dispersed on multi-walled carbon nanotubes (MWCNTs) by the temperature-control led, microwave-assisted polyol method with the addition of sodium dodecyl sulfate (SDS) and [poly(vinyl pyrrolidone)] (PVP). The addition of SDS and PVP in chloroplatinic acid/ethylene glycol (EG) solution can cause the efficient and homogeneous dispersion of the catalyst particles on MWCNTs, enhance the adsorption of platinum particles, and reduce the residue of platinum particles. Moreover, temperature was determined to be the most important factor affecting the reduction of Pt in the process, and large amounts of Pt particles were characterized when the temperature ranged from 140 to 160 degrees C. The results indicate that the optimum temperature ranges from 140 to 160 degrees C, and that the loading amount of Pt/CNTs can reach more than 50 wt % in only 90 s of processing time. The significant improvements in dispersion and loading are due to the ability of SDS, to wrap the PVP-stabilized Pt nanoparticles around the surface of the carbon nanotubes. The characterization analyses were conducted by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and thermal gravinnetric analysis (TGA).