Publications by authors named "Byungrok Lee"

4 Publications

  • Page 1 of 1

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells.

Nanomaterials (Basel) 2016 Aug 15;6(8). Epub 2016 Aug 15.

Fuel Cell Research Center, Korea Institute of Energy Research (KIER), Daejeon 305-343, Korea.

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF-supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.
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http://dx.doi.org/10.3390/nano6080148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5224627PMC
August 2016

Preparation and Characteristics of SiO Coated Carbon Nanotubes with High Surface Area.

Nanomaterials (Basel) 2012 Jun 18;2(2):206-216. Epub 2012 Jun 18.

Fuel Cell Research Center, Korea Institute of Energy Research, Daejeon 305-343, Korea.

An easy method to synthesize SiO coated carbon nanotubes (SiO-CNT) through thermal decomposition of polycarbomethylsilane adsorbed on the surface of CNTs is reported. Physical properties of SiO-CNT samples depending on various Si contents and synthesis conditions are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen isotherm, scanning electron microscope (SEM), and transmission electron microscope (TEM). Morphology of the SiO-CNT appears to be perfectly identical to that of the pristine CNT. It is confirmed that SiO is formed in a thin layer of approximately 1 nm thickness over the surface of CNTs. The specific surface area is significantly increased by the coating, because thin layer of SiO is highly porous. The surface properties such as porosity and thickness of SiO layers are found to be controlled by SiO contents and heat treatment conditions. The preparation method in this study is to provide useful nano-hybrid composite materials with multi-functional surface properties.
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http://dx.doi.org/10.3390/nano2020206DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5327897PMC
June 2012

Electrochemical catalytic activity for oxygen reduction reaction of nitrogen-doped carbon nanofibers.

J Nanosci Nanotechnol 2011 Jul;11(7):6350-8

Advanced Energy Technology, University of Science and Technology (UST), Daejeon 305-333, Republic of Korea.

The electrocatalytic activity of nitrogen-doped carbon nanofibers (N-CNFs), which are synthesized directly from vaporized acetonitrile over nickel-iron based catalysts, for oxygen reduction reaction (ORR), was investigated. The nitrogen content and specific surface area of N-CNFs can be controlled through the synthesis temperature (300-680 degrees C). The graphitization degree of N-CNFs also are significantly affected by the temperature, whereas the chemical compositions of nitrogen species are similar irrespective of the synthesis conditions. From measurement of the electrochemical double layer capacitance, the surface of N-CNFs is found to have stronger interaction with ions than undoped-carbon surfaces. Although N-CNFs show higher over-potential than Pt catalysts do, N-CNFs were observed to have a noticeable ORR activity, as opposed to the carbon samples without nitrogen doping. The activity dependency of N-CNFs on the content of the nitrogen with which they were doped is discussed, based on the experiment results. The single cell of the direct methanol fuel cell (DMFC) was tested to investigate the performance of a membrane-electrode assembly that includes N-CNFs as the cathode catalyst layer.
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http://dx.doi.org/10.1166/jnn.2011.4443DOI Listing
July 2011

Characteristics of porous carbon nano-fibers synthesized by selective catalytic gasification.

J Nanosci Nanotechnol 2011 Jul;11(7):5775-80

Advanced Energy Technology, University of Science and Technology (UST), 113 Gwahangno, Yuseong-gu, Daejeon, 305-333, Republic of Korea.

Carbon nanofibers (CNFs) with uniquely oriented channels were prepared via selective catalytic gasification in air at 450 and 500 degrees C, using Pt or Ru nano particles as catalysts. Catalytic gasification was chosen because it can selectively generate channels in the vicinity of the catalyst particles at relatively low temperatures, where thermal oxidation does not intensively occur. The structures and surface properties of the CNFs were examined via X-ray diffraction, analysis of the nitrogen adsorption-desorption isotherms, and high-resolution transmission electron microscopy. The effects of the catalyst species and loading amount on the formation of pores (channels) were investigated. The gasification mechanism, especially the channeling direction, throught the selection of the gasification catalysts, is discussed based on the results. This process can be effectively utilized for preparation of porous carbons, which have a well-aligned graphitic structure, and also channel-type pores can be designed by selection of gasification catalysts and conditions. The present porous CNF can be applied for catalyst support in fuel cells, without further treatment (e.g., acid treatment for the removal of metallic components).
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http://dx.doi.org/10.1166/jnn.2011.4452DOI Listing
July 2011
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