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Ansan, South Korea

Jung J.-H.,University of Ulsan | Cha M.-S.,Ordeg Co | Kim J.-B.,University of Ulsan
Journal of Nanoscience and Nanotechnology

In this study, carbon nano?ber (CNF) was used as a support in which 47.5 wt% Pt/CNFs catalyst was prepared by a modi?ed polyol method. The platinum particle size and dispersion on the CNFs are approximately 2-4 nm as determined by X-ray diffractometry and transmission electron microscopy. The speci?c surface area was approximated as 55.90 m 2 /g by BET analysis. Electrodes were prepared by the spray method and have a size of 5 cm 2 . A commercial catalyst (TKK, 46 wt% Pt/C) was used as the anode and the cathode was Pt/CNFs. Different amounts of Na?on ionomer (Aldrich, 5 wt% solution, in the range of 0-20 wt%) were coated on a membrane (Dupont, Na?on 212) with 0.4 mg/cm 2 of Pt catalyst at the cathode side. The resulting polarization, ohmic and mass transfer resistances changed signi?cantly based on the Na?on ionomer content. Optimum Na?on ionomer content in the 47.5 wt% Pt/CNFs was 5 wt%. The well-dispersed Na?on ionomer was observed on the catalyst surface area using SEM-EDAX analysis. A suf?cient triple-phase boundary was formed by a small amount of Na?on ionomer due to the BET surface area of the Pt/CNFs. © 2012 American Scientific Publishers. Source

Jung J.H.,University of Ulsan | Park B.I.,Ordeg Co | Kim J.,University of Ulsan
Nanoscale Research Letters

In this study, a catalyst was synthesized on carbon nanofibers [CNFs] with a herringbone-type morphology. The Pt/CNF catalyst exhibited low hydrophilicity, low surface area, high dispersion, and high graphitic behavior on physical analysis. Electrodes (5 cm 2) were prepared by a spray method, and the durability of the Pt/CNF was evaluated by fuel starvation. The performance was compared with a commercial catalyst before and after accelerated tests. The fuel starvation caused carbon corrosion with a reverse voltage drop. The polarization curve, EIS, and cyclic voltammetry were analyzed in order to characterize the electrochemical properties of the Pt/CNF. The performance of a membrane electrode assembly fabricated from the Pt/CNF was maintained, and the electrochemical surface area and cell resistance showed the same trend. Therefore, CNFs are expected to be a good support in polymer electrolyte membrane fuel cells. © 2012 Jung et al. Source

Jung J.,University of Ulsan | Kwon M.,University of Ulsan | Kim H.-R.,Ordeg Co | Kim J.,University of Ulsan
International Journal of Hydrogen Energy

Research on membrane electrode assemblies (MEA) is focused on reducing cost and increasing durability in polymer electrolyte membrane fuel cells (PEMFC). Development of the electrode structure and reduction of platinum (Pt) contents are studied to improve the efficiency of Pt catalysts. We studied the combined effects of improved electrode structure and reduced Pt loading. To enhance the performance of an MEA, a commercial Pt/C catalyst with micro graphite (MG) was used. The 40 wt% Pt/C catalyst content was reduced about 5, 15, 30 and 60 wt% at the cathode. MG was added as a reduced weight percent of Pt/C. Cell performance was significantly dependent on the content of MG. The MEA with 15 wt% of MG was seen to best performance compare with other MEA. These results showed that the catalyst with mixed MG improved both performance and cost savings with reduced Pt content of PEMFC. Copyright © 2013, Hydrogen Energy Publications, LLC. Source

Wang T.J.,Korea Advanced Institute of Science and Technology | Wang T.J.,Doosan Infracore | Baek S.W.,Korea Advanced Institute of Science and Technology | Kwon H.J.,Pohang University of Science and Technology | And 5 more authors.
Industrial and Engineering Chemistry Research

In this work, an in-house computational code capable of simulating highly coupled physicochemical phenomena occurring in ammonia/urea SCR (selective catalytic reduction) was developed. On the basis of this computational code, the kinetic parameters of catalytic reactions were newly calibrated using the experimental results obtained over a commercial ammonia/urea SCR washcoated Fe-ion-exchanged zeolite-based catalyst. Powder-phase NH3 TPD (temperature-programmed desorption) experiments were performed to calibrate the kinetic parameters of NH3 adsorption and desorption, and core-out monolith experiments were conducted to estimate the kinetic parameters of various deNOx reactions as well as NH3 oxidation. The currently established SCR model and kinetic parameters gave a good prediction for both steady-state and transient experimental results for a wide range of operating conditions. The main objectives of this study were to develop numerical tools and their implementation methodologies that can be cost-effectively applied to the design and development of real-world ammonia/urea SCR systems. Details of the procedures and techniques in numerical modeling and kinetic parameter calibration are described step-by-step in this article. © 2011 American Chemical Society. Source

Choung S.-J.,Kyung Hee University | Kim J.,Kyung Hee University | Kim H.-R.,Ordeg Co
International Journal of Photoenergy

The photocatalytic production of hydrogen from water using solar energy is potentially a clean and renewable source for hydrogen fuel. This study examines the production of hydrogen over In, P-TiO2s photocatalysts. 1mol% In-TiO2 and P-TiO2 were produced using the solvothermal method and were treated at 500 and 800°C to obtain anatase and rutile structure, respectively. The photocatalysts were characterized by X-ray diffraction, photoluminescence spectra, X-ray spectroscopy, UV-visible spectroscopy, and scanning electron microscopy. The production of H2 from methanol photodecomposition was greater over the rutile structure than over the anatase structure of TiO2. Moreover, the amount of hydrogen was enhanced over In-TiO2 and P-TiO2 compared to that over pure TiO2; the production increased by about 30%. The structural effect and the addition of In, P have significant influence on the H2 production from methanol/water decomposition. Copyright © 2011 Joonwoo Kim et al. Source

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