• Journal of Hydrogen and New Energy
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• v.20 no.4
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• pp.309-316
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• 2009

The effect of gas diffusion layers (GDLs) on the freeze/thaw condition durability in polymer electrolyte fuel cells (PEFCs) were investigated. For this purpose, three kinds of GDLs, such as, felt, paper and cloth types with different basic properties have been first prepared, then the changes in the properties and performance of cells was observed during the freeze/thaw cycles ranging from -30 to $70^{\circ}C$. The performance evaluations were conducted by using the single cells consisting of different GDLs. The performance degradation and the cell resistance increase could be directly correlated. The physical destruction of electrode was shown by SEM analysis. The mechanically supporting ability on the interface between the cell components can help enhancing the durability of PEFCs in the freeze/thaw condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1070-1073
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• 2003

We have studied the characteristics of organic light-emitting diodes(OLEDs) with the PTFE buffer layer. The OLEDs have been based on the molecular compounds, N,N'-diphenyl-N,N'-bis (3-methylphenyl)-1, 1'- biphenyl-4, 4'-diamine (TPD) as a hole transport, tris(8-hydroxyquinolinoline) aluminum (III) ($Alq_3$) as an electron transport and the Polytetrafluoroethylene (PTFE) as a buffer layer. The devices of structure were fabricated ITO/PTFE/TPD(40nm)/$Alq_3$(60nm)/Al( 150nm) to see the effects of the PTFE buffer layer in organic EL devices. The thickness of the PTFE layer varied from 0.5 to 10[nm]. We were measured Current-Voltage-Luminance Characteristics and Luminance efficiency due to the variation of PTFE thickness. the PTFE layer was reported that helped to enhance the hole tunneling injection and effectively impede induim diffusion from the ITO electrode. We have obtained an improvement of luminance efficiency when the PTFE thickness is 0.5[nm] is used. The improvement of efficiency of is expected due to a function of hole-blocking of PTFE in OLEDs.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.473.1-473.1
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• 2014

We report on the characteristics of Zr-doped $In_2O_3$ (IZrO) films prepared by DC-RF magnetron cosputtering of $In_2O_3$ and $ZrO_2$ targets for use as a transparent electrode for high efficient organic solar cells (OSCs). The effect of $ZrO_2$ doping power on electrical, optical, structural, and surface morphology of the IZrO film was investigated in detail. At optimized $ZrO_2$ RF power of 50 W, the IZrO film exhibited a low sheet resistance of 20.71 Ohm/square, and a high optical transmittance of 83.9 %. Furthermore, the OSC with the IZrO anode showed a good cell-performance: fill factor of 61.71 %, short circuit current (Jsc) of $8.484mA/cm^2$, open circuit voltage (Voc) of 0.593 V, and power conversion efficiency (PCE) of 3.106 %. In particular, the overall OSC characteristics of the cell with the IZrO anode were comparable to those of the OSC with the conventional Sn-doped $In_2O_3$ (FF of 65.03 %, Jsc of $8.833mA/cm^2$, Voc of 0.608 V, PCE of 3.495 %), demonstrating that the IZrO anode is a promising alternative to ITO anode in OSCs.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.478-482
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• 2017

Humidity control of proton exchange membrane fuel cell(PEMFC) is very important control condition during driving. In terms of water management, low humidification conditions are advantageous, and high humidification is advantageous in terms of drainage utilization and energy efficiency. In this study, the characteristics of outlet water in low humidification and high humidification process were studied in terms of utilization of discharged water. Since the impurities in the effluent are generated during the degradation of the membrane and the electrode assembly(MEA), degradation of the MEA under low humidification and high humidification conditions was also studied. The rate of radical generation was high at low humidification condition of the anode RH 0%, which showed that it was the main cause of the degradation of the polymer membrane. Analysis of effluent showed low concentration of fluoride ion concentration of about 20 ppb at high humidification (both electrodes RH 100%) and 0.6 V, which was enough to be used as the feed water for electrolysis. Very low concentration of platinum below 0.2 ppb was detected in the condensate discharged from the high humidification condition.

• Journal of Surface Science and Engineering
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• v.48 no.4
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• pp.158-162
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• 2015

To substitute indium tin oxide (ITO), many substituents have been studied such as metal nanowires, carbon based materials, 2D materials, and conducting polymers. These materials are not good enough to apply to an electrode because theses exhibit relatively high resistance. So metal grids are required as an additionalelectrode to improve the conductivities of substituents. The metal grids were printed by electrohydrodynamic printing system using Ag nanoparticle based ink. The Ag grids showed high uniformity and the line width was about $10{\mu}m$. The Ag nanoparticles are surrounded by dispersants such as unimolecular and polymer to prevent aggregation between Ag nanoparticles. The dispersants lead to low conductivity of Ag grids. Thus, the sintering process of Ag nanoparticles is strongly recommended to remove dispersants and connect each nanoparticles. For sintering process, the interface and microstructure of the Ag grid were controlled in 1.0 torr Ar atmosphere at aound $400^{\circ}C$ of temperature. From the sintering process, the uniformity of the Ag grid was improved and the defects on the Ag grids were reduced. As a result, the resistivity of Ag grid was greatly reduced up to $5.03({\pm}0.10){\times}10^{-6}{\Omega}{\cdot}cm$. The metal grids embedded substrates containing low pressure Ar sintered Ag grids showed 90.4% of transmittance in visible range with $0.43{\Omega}/{\square}$ of sheet resistance.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.554-560
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• 1998

Vinylbenzyl triphenyl phosphonium chloride(VTPC)/styrenes=3.7 copolymer was prepared for the moisture-absorptive polyelectrolyte dew sensor containing phosphonium salts. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $11M{\Omega}$, $980k{\Omega}$, $50k{\Omega}$, and $11k{\Omega}$ at 70%RH, 80%RH, 90%RH and 95%RH, respectively, at $25^{\circ}C$ and the humidity-sensitive charactristic was suitable for the dew sensor. The temperature-dependent coefficient between $15^{\circ}C$ and $35^{\circ}C$ was found to be $-0.25%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 45 sec for the relative humidity ranging from 70%RH to 98%RH at $25^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a dew sensor.

• Carbon letters
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• v.11 no.1
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• pp.38-40
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• 2010

Carbon supported electrocatalysts are commonly used as electrode materials for polymer electrolyte membrane fuel cells(PEMFCs). These kinds of electrocatalysts provide large surface area and sufficient electrical conductivity. The support of typical PEM fuel cell catalysts has been a traditional conductive type of carbon black. However, even though the carbon particles conduct electrons, there is still significant portion of Pt that is isolated from the external circuit and the PEM, resulting in a low Pt utilization. Herein, new types of carbon materials to effectively utilize the Pt catalyst are being evaluated. Carbon nanofiber/activated carbon fiber (CNF/ACF) composite with multifunctional surfaces were prepared through catalytic growth of CNFs on ACFs. Nickel nitrate was used as a precursor of the catalyst to synthesize carbon nanofibers(CNFs). CNFs were synthesized by pyrolysising $CH_4$ using catalysts dispersed in acetone and ACF(activated carbon fiber). The as-prepared samples were characterized with transmission electron microscopy(TEM), scanning electron microscopy(SEM). In TEM image, carbon nanofibers were synthesized on the ACF to form a three-dimensional network. Pt/CNF/ACF was employed as a catalyst for PEMFC. As the ratio of prepared catalyst to commercial catalyst was changed from 0 to 50%, the performance of the mixture of 30 wt% of Pt/CNF/ACF and 70wt% of Pt/C commercial catalyst showed better perfromance than that of 100% commercial catalyst. The unique structure of CNF can supply the significant site for the stabilization of Pt particles. CNF/ACF is expected to be promising support to improve the performance in PEMFC.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3109-3114
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• 2010

Flexible composite films of $V_2O_5$ and conductive polypyrrole ($V_2O_5$/PPy) were grown by facile electrochemical polymerization, wherein an anodization potential was applied to the substrate electrode in an electrolyte solution containing pyrrole monomer and dispersed $V_2O_5$ particles. The coating of polypyrrole (PPy) on the surface of $V_2O_5$ particles was induced by the oxidative catalytic action of $V_2O_5$ during the electrochemical polymerization of pyrrole. PPy in the composite film connects the isolated $V_2O_5$ particles. This results in the formation of conductive networks in the composite film cathode, thereby enhancing the Li+ ion diffusion to the surface of the isolated $V_2O_5$ particles and thus increasing the accessibility of the $Li^+$ ions. The specific capacity tests of the Li rechargeable batteries revealed that the discharge capacity of this composite film cathode was higher, i.e., $497\;mAhg^{-1}$, than that of $V_2O_5$/PPy powder or pristine $V_2O_5$.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1153-1159
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• 2013

A novel solid-contact indium(III)-selective sensor based on bis-(1H-benzimidazole-5-methoxy-2-[(4-methoxy-3, 5-dimethyl-1-pyridinyl) 2-methyl]) thiosulfinate, known as an omeprazole dimer (OD) and a neutral ionophore, was constructed, and its performance characteristics were evaluated. The sensor was prepared by applying a membrane cocktail containing the ionophore to a graphite rod pre-coated with polyethylene dioxythiophene (PEDOT) conducting polymer as the ion-to-electron transducer. The membrane contained 3.6% OD, 2.3% oleic acid (OA) and 62% dioctyl phthalate (DOP) as the solvent mediator in PVC and produced a good potentiometric response to indium(III) ions with a Nernstian slope of 19.09 mV/decade. The constructed sensor possessed a linear concentration range from $3{\times}10^{-7}$ to $1{\times}10^{-2}$ M and a lower detection limit (LDL) of $1{\times}10^{-7}$ M indium(III) over a pH range of 4.0-7.0. It also displayed a fast response time and good selectivity for indium(III) over several other ions. The sensor can be used for longer than three months without any considerable divergence in potential. The sensor was utilized for direct and flow injection potentiometric (FIP) determination of indium(III) in alloys. The parameters that control the flow injection method were optimized. Indium(III) was quantitatively recovered, and the results agreed with those obtained using atomic absorption spectrophotometry, as confirmed by the f and t values. The sensor was also utilized as an indicator electrode for the potentiometric titration of fluoride in the presence of chloride, bromide, iodide and thiocyanate ions using indium(III) nitrate as the titrant.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.65-70
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• 2006

An amperometric glucose biosensor has been developed based on the use of the nanoporous composite film of sol-gel-derived zirconia and perfluorosulfonated ionomer, Nafion, for the encapsulation of glucose oxidase (GOx) on a platinized glassy carbon electrode. Zirconium isopropoxide (ZrOPr) was used as a sol-gel precursor for the preparation of zirconia/Nafion composite film and the performance of the resulting glucose biosensor was tuned by controlling the water content in the acid-catalyzed hydrolysis of sol-gel stock solution. The presence of Nafion polymer in the sol-gel-derived zirconia in the biosensor resulted in faster response time and higher sensitivity compared to those obtained at the pure zirconia- and pure Nafion-based biosensors. Because of the nanoporous nature of the composite film, the glucose biosensor based on the zirconia/Nafion composite film can reach 95% of steady-state current less than 5 s. In addition, the biosensor responds to glucose linearly in the range of 0.03-15.08 mM with a sensitivity of 3.40 $\mu$A/mM and the detection limit of 0.037 mM (S/N = 3). Moreover, the biosensor exhibited good sensor-to-sensor reproducibility (~5%) and long-term stability (90% of its original activity retained after 4 weeks) when stored in 50 mM phosphate buffer at pH 7 at 4 ${^{\circ}C}$.