2003.07a
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PtRu alloy and
$PtRu-WO_3$ nanocomposite thin-film electrodes for methanol electrooxidation were fabricated by means of a sputtering method. The structural and electrochemical properties of well-defined PtRu alloy thin-film electrodes were characterized using X-ray diffraction, Rutherford backscattering spectroscopy. X-ray photoelectron spectroscopy, and electrochemical measurements. The alloy thin-film electrodes were classified as follows: Pt-based and Ru-based alloy structure. Based on structural and electrochemical understanding of the PtRu alloy thin-film electrodes, the well-controlled physical and (electro)chemical properties of$PtRu-WO_3$ , showed superior specific current to that of a nanosized PtRu alloy catalyst, The homogeneous dispersion of alloy catalyst and well-formed nanophase structure would lead to an excellent catalytic electrode reaction for high-performance fuel cells. In addition, the enhanced catalytic activity in nanocomposite electrode was found to be closely related to proton transfer in tungsten oxide using in-situ electrochemical transmittance measurement. -
Fuel processing is an enabling technology for faster commercialization under lack of hydrogen infrastructures. It has been reported that the development of novel catalysts that are active and selective for hydrocarbon reforming reactions. It has been realized, however, that with pellet or conventional honeycomb catalysts, the reforming process is mass transport limited. This paper reports the development of catalyst structures with microchannels that are able to reduce the diffusion resistance and thereby achieve the same production rate within a smaller reactor bed. These microchannel reforming catalysts were prepared and tested with natural gas and gasoline-type fuels in a microreactor (1-cm dia.) at space velocities of up to 250,000 per hour. These catalysts have also been used in engineering-scale reactors (10 kWe, 7-cm dia.) with similar product qualities. Compared to pellet catalysts. the microchannel catalysts enable a nearly 5-fold reduction in catalyst weight and volume.
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The lap-top with a integrated fuel cell system presented here proves that these solutions have a great potential. Though, there are things that have to be improved before they are introduced to the marked. In this system, heat and water management as well as dead end operation are critical issues which must be directly addressed in further research. Both modified stack design and other new cooling techniques are possible ways to continue the work.
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Organic/inorganic hybrid membranes have been prepared and evaluated as polymer electrolytes in a polymer electrolyte membrane fuel cell (PEMFC). Previously, partially fluorinated poly (arylenether) was synthesized and the polymer was sulfonated by fuming sulfuric acid
$(30\%\;SO_3)$ . Modification of these polymers with coupling agent and inorganic materials was carried out to prepare membranes. Membranes cast from these materials were investigated in relation to the proton conductivity and weight loss at the room temperature. It was found that these membranes had a higher conductivity of$10^{-2}\;Scm^{-1}$ at the room temperature. But inorganic materials have leaked out from the hybrid membrane. If this problem is resolved, organic/inorganic hybrid membranes will become satisfactory Polymer electrolytes for the PEMFC. -
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Kim Ki-hwan;Ahn Sang-yeoul;Ryu Jung;Oh In-hwan;Ha Heung Yong;Hong Seong-Ahn;Kim Moon-Sun;Lee Yong-Chul 177
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Carbon nanotubes, prepared by the catalytic decomposition of acetylene at
$700^{\circ}C$ over a Mm based$AB_5$ hydrogen storage alloy hydride catalysts, have been used as a support for platinum electrocatalysts. The performance of this electrocatalyst In proton exchange membrane fuel cells has been studied and discussed. -
In this work, we have prepared platinum catalyst by various methods, investigated fuel cell performance and compared performance with commercially available
$20\%$ Pt supported on carbon (Pt/C) catalyst. We have found that Pt/C prepared by reduction of chloroplatinic acid in mixed solvent (water+ethylene glycol) gives better performance compared to that produced by reduction of aqueous chloroplatinic acid, which can be attributed to smaller catalyst particle size and lower agglomeration in the mixed solvent. We have also prepared a novel platinum electrocatalyst by depositing platinum on Nafion coated carbon powder and it shows great promise. The performance of electrode prepared using$20\%Pt$ onn Nafion coated carbon mixed with Pt/C was found to be higher than the performance of electrodes using commercially available$20\%$ Pt/C, up to a current density of about$1100mA/cm^2$ . The cell voltages obtained were respectively 621 and 603mV, at a current density of:$1000mA/cm^2$ , in a single cell using$0.25mgPt/cm^2$ and Nafion 10035 membrane at$80^{\circ}C$ using hydrogen/oxygen reactants at 1 atm pressure. -
Mixture of
$Ni(OH)_2-Mg(OH)_2$ used as the precurs was treated by mechnochemical(MC) and hand grinding process. Carbon nanofibers(CNF) were prepared using CVD process with the above prepared catalyst. CNFs with a uniform diameter were obtained with MC process treated catalyst, and the diameter could be controlled by tuning the grinding time. CNF bundles with close coalescence were produced with MC treated catalyst. After purification of CNFs and loading with Pt, they were used in fuel cell as the cathode catalyst support. The performance with carbon nanofibers prepared using ground mixture was found to be better than that prepared using unground mixture, which is attributed to the homogeneous CNFs with small diameter and specific interaction between Pt and CNFs. -
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