• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.836-844
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• 2009

A denitrification bacterium was isolated from riverbed soil and identified as Ochrobactrum sp., whose specific enzymes for denitrification metabolism were biochemically assayed or confirmed with specific coding genes. The denitrification activity of strain G3-1 was proportional to glucose/nitrate balance, which was consistent with the theoretical balance (0.5). The modified graphite felt cathode with neutral red, which functions as a solid electron mediator, enhanced the electron transfer from electrode to bacterial cell. The porous carbon anode was coated with a ceramic membrane and cellulose acetate film in order to permit the penetration of water molecules from the catholyte to the outside through anode, which functions as an air anode. A non-compartmented electrochemical bioreactor (NCEB) comprised of a solid electron mediator and an air anode was employed for cultivation of G3-1 cells. The intact G3-1 cells were immobilized in the solid electron mediator, by which denitrification activity was greatly increased at the lower glucose/nitrate balance than the theoretical balance (0.5). Metabolic stability of the intact G3-1 cells immobilized in the solid electron mediator was extended to 20 days, even at a glucose/nitrate balance of 0.1.

• Transactions on Electrical and Electronic Materials
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• v.15 no.4
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• pp.189-192
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• 2014

Yttria-stablized zirconia (YSZ) is the most commonly used electrolyte material, but the reduction in working temperature leads to insufficient ionic conductivity. Ceria based electrolytes (GDC) are more attractive in terms of conductivity at low temperature, but these materials are well known to be reducible at very low oxygen partial pressure. The reduction of electrolyte resistivity is necessary to overcome cell performance losses. So, thin YSZ/GDC bilayer technology seems suitable for decreasing the electrolyte resistance at lower operating temperatures. Bilayer electrolytes composed of a galdolinium-doped $CeO_2$ ($Ce_{0.9}Gd_{0.1}O_{1.95}$, GDC) layer and yttria-stabilized $ZrO_2$ (YSZ) layer with various thicknesses were deposited by RF sputtering and E-beam evaporation. The bilayer electrolytes were deposited between porous Ni-GDC anode and LSM cathode for anode-supported single cells. Thin film structure and surface morphology were investigated by X-ray diffraction (XRD), using $CuK{\alpha}$-radiation in the range of 2ce morphol$^{\circ}C$. The XRD patterns exhibit a well-formed cubic fluorite structure, and sharp lines of XRD peaks can be observed, which indicate a single solid solution. The morphology and size of the prepared particles were investigated by field-emission scanning electron microscopy (FE-SEM). The performance of the cells was evaluated over $500{\sim}800^{\circ}C$, using humidified hydrogen as fuel, and air as oxidant.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.146-151
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• 2013

This paper reveals the performance decrease and recovery of PEMFC when the contaminated fuel gas and air source with sulfur impurities such as hydrogen sulfide and sulfur dioxide were simultaneously introduced to anode and cathode, respectively. Three different GDLs were fabricated with different carbon black and activated carbon to prevent an introduction of sulfur compound impurities into MEA. components. The severity of $SO_2$ and $H_2S$ poisoning was depended on concentrations(3 ppm - 10 ppm) of sulfur impurities. Especially, cell performance degradation rate was rapid when MEA fabricated with CN-2 GDL because it had little porosity on GDL surface. Moreover, the cell performance can be recovered up to 90%-95% only with neat hydrogen and fresh air feeding.. Conclusively, MEA fabricated with porous CN-1 GDL showed the best cell performance and recovery efficiency during exposure to poisoning condition by simultaneous sulfur impurities.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.172-175
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• 2001

Nanophase catalyst layer for direct methanol fuel cell has been fabricated by magnetron sputtering method. Catalyst metal targets and carbon were sputtered simultaneously on the Nafion membrane surface at abnormally higher gas (Ar/He mixture) pressure than that of normal thin film processing. They could be coated as a novel structure of catalyst layer containing porous PtRu or Pt and carbon particles both in nanometer range. Membrane electrode assembly made with this layer led to a reduction of the catalyst loading. At the catalyst loading of 1.5mg $PtRu/cm^2$ for anode and 1mg $Pt/cm^2$ for cathode, it could provide $45 mW/cm^2$ in the operation at 2 M methanol, 1 Bar Air at 80"C. It is more than $30\%$ increase of the power density performance at the same level of catalyst loading by conventional method. This was realized due to the ultra fine particle sizes and a large fraction of the atoms lie on the grain boundaries of nanophase catalyst layer and they played an important role of fast catalyst reaction kinetics and more efficient fuel path. Commercialization of direct methanol fuel cell for portable electronic devices is anticipated by the further development of such design.