• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.793-799
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• 2005

A composite cathode of LSCF$(La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3)\;and\;GDC\; (Gd_2O_3-doped\;CeO_2:Ce_{0.9}Gd_{0.1}O_{1.95_})$ was characterized in terms of an electrode response, using a point contact in an Yttria-Stabilized Zirconia (YSZ) electrolyte incorporated into AC two-point impedance spectroscopy. The point-contacted configuration amplifies the responses occurring near the YSZ/cathode interface through the aligned point contact on the planar LSCF/GDC electrode. The point contact interface increases the bulk resistance allowing the estimation of the point contact geometry and resolving the electrode-related responses. The resultant impedance spectra are analyzed through an equivalent circuit model constructed by resistors and constant phase elements. The bulk responses can be resolved from the electrode-related portions in terms of spreading resistance. The electrode-related polarizations are measured in terms of temperature and oxygen partial pressure. The modified impedance spectroscopy is discussed in terms of methodology and analytical aspects, toward resolving the electrode-polarization issues in solid oxide fuel cells.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.197-204
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• 2019

An electrochemical oxygen permeating membrane (OPM) is fabricated using Zr_0.895Sc_0.095Ce_0.005Gd_0.005O_2-δ (ScCeGdZ) as the solid electrolyte and aLa_0.7Sr_0.3MnO₃-bScCeGdZ composite (LZab, electrode) as the electrode. The crystal phase of the electrode and the microstructure of the membrane is investigated with X-ray diffraction and scanning electron microscopy. The electrochemical resistance of the membrane is examined using 2-p ac impedance spectroscopy, and LZ55 shows the lowest electrode resistance among LZ82, LZ55 and LZ37. The oxygen permeation is studied with an oxygen permeation cell with a zirconia oxygen sensor. The oxygen flux of the OPM with LZ55 is nearly consistent with the theoretical value calculated from Faraday's Law below a critical current. However, it becomes saturated above the critical current due to the limit of the oxygen ionic conduction of the OPM. The OPM with LZ55 has a very high oxygen permeation flux of ~ 3.5 × 10^-6 mol/㎠s in I = 1.4 A/㎠.

• Journal of Surface Science and Engineering
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• v.57 no.3
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• pp.214-220
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• 2024

In this study, three-dimensional (3D) networks structure using single-walled carbon nanotubes (SWCNTs) for Si-graphite composite electrode was developed and studied about effects on the electrochemical performances. To investigate the effect of SWCNTs on forming a conductive 3D network structure electrode, zero-dimensional (0D) carbon black and different SWCNTs composition electrode were compared. It was found that SWCNTs formed a conductive network between nano-Si and graphite particles over the entire area without aggregation. The formation of 3D network structure enabled to effective access for lithium ions leading to improve the c-rate performance, and provided cycle stability by alleviating the Si volume expansion from flexibility and buffer space. The results of this study are expected to be applicable to the electrode design for high-capacity lithium-ion batteries.

• Macromolecular Research
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• v.17 no.10
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• pp.746-749
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• 2009

Poly(ethylene terephthalate) (PET) fabric/poly(3,4-ethylenedioxythiophene) (PEDOT) composite with stable and high electrochemical activity was fabricated by chemical and electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on a PET fabric in sequence. Effects of polymerization conditions on the following characteristics of the composite were studied: electrical conductivity and surface morphology. The electrochemical properties were also investigated by cyclic voltammetry and cyclic charge/discharge experiments. The specific volume resistivity, electrical conductivity and specific discharge capacitance of the composite were 0.034 $\Omega-cm$ and 25 S/cm, and 54.5 F/g, respectively.

• Journal of Powder Materials
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• v.10 no.5
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• pp.337-343
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• 2003

Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

• Carbon letters
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• v.15 no.2
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• pp.113-116
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• 2014

Due to their morphology, electrochemical stability, and function as a conducting carbon matrix, graphene nanosheets (GNS) have been studied for their potential roles in improving the performance of sulfur cathodes. In this study, a GNS/sulfur (GNS/S) composite was prepared using the infiltration method with organic solvent. The structure, morphology and crystallinity of the composites were examined using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The electrochemical properties were also characterized using cyclic voltammetry (CV). The CV data revealed that the GNS/S composites exhibited enhanced specific-current density and ~10% higher capacity, in comparison with the S-containing, activated-carbon samples. The composite electrode also showed better cycling performance for multiple charge/discharge cycles. The improvement in the capacity and cycling stability of the GNS/S composite electrode is probably related to the fact that the graphene in the composite improves conductivity and that the graphene is well dispersed in the composites.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.99-103
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• 2019

A derivative of 1,4-Naphthoquinone coded HBU671 was synthesized and used in addition to activated carbon as composite electrode for supercapacitor application. From the electrochemical properties analysis, a specific capacitance of about $300F\;g^{-1}$ exhibited almost two times of that of activated carbon at a scan rate of $100mV\;s^{-1}$ and a potential window of - 0.2 - 1V. This improvement is due to the inherent redox reaction in HBU671. Cycle test also proved that this composite is still stable even after 1000 cycle within the applied potential window and it is highly recommended for practical application.

• Analytical Science and Technology
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• v.27 no.6
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• pp.308-313
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• 2014

The effect of electrochemical characteristics of dye-sensitized solar cells (DSSC) upon employing multi-wall carbon nanotube (MWCNT) on both working electrode and counter electrode were examined with using EIS, J-V curves and UV-Vis absorption spectrometry. When 0.1 wt% of MWCNT was employed in the $TiO_2$-MWCNT composit on working electrode, the energy conversion efficiency increased about 12.5% compared to the $TiO_2$ only working electrode. The higher light conversion efficiency may attribut to the high electrical conductivity of MWCNT in $TiO_2$-MWCNT composite which improves the electron transport in the working electrode. However, higher amount of MWCNT than 0.1 wt% in the $TiO_2$-MWCNT composite decreases the light conversion efficiency, which is mainly ascribed to the decreased transmittance of light by MWCNT and to the decreased adsorption of dye onto $TiO_2$. The MWCNT employed counter electrode exhibited much lower light conversion efficiency of DSSC than the Pt-counter electrode, while the MWCNT-Pt counter electrode showed similar in light conversion efficiency to that of Pt-counter electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1226-1229
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• 2004

Supercapacitors, also known as electrochemical capacitors, are being extensively studied due to an increasing demand for energy-storage systems. These devices offer many advantages over conventional secondary batteries, which include the ability of fast charge propagation, long cycle-life and better storage efficiency. That is to say supercapacitor bridges the gap between conventional capacitors and batteries. A new type electric double layer capacitor (EDLC) also called supercapacitors. Recently, supercapacitors concerns about their high power density and energy density. So we experiment with EDLC by using carbon nanofibers (CNFs) and DAAQ(1,5-diaminoanthraquinone) electrode. The electrode for supercapacitor was prepared by synthesis of DAAQ covered CNFs. CNFs could be covered with very thin DAAQ oligomer from the results of CV, XRD, DSC, SEM images, and TEM images. Dissolved electrode active material in NMP solution has been drop-coated on carbon plate. Its electrochemical characteristics were investigated by cyclic voltammograms. And compared with different electrolyte of aqueous type. As a result, CNFs coated by DAAQ composite electrode showed relatively good electrochemical behaviors with respect to specific capacity and scan rate dependency.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.169-175
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• 2018

Cu-Salen complex was prepared and attached into chitosan (Cs) polymer backbone. Nanocomposite of the synthesized polymer was prepared with functionalized carbon nano-particles (Cs-Cu-sal/C) to modify the electrode surface. The surface morphology of (Cs-Cu-sal/C) nanocomposite film showed a homogeneous distribution of carbon nanoparticles within the polymeric matrix. The cyclic voltammogram of the modified electrode exhibited a redox behavior at -0.1 V vs. Ag/AgCl (3 M KCl) in 0.1 M PB (pH 7) and showed an excellent hydrogen peroxide reduction activity. The Cs-Cu-sal/C electrode displays a linear response from $5{\times}10^{-6}$ to $5{\times}10^{-4}M$, with a correlation coefficient of 0.993 and detection limit of $0.9{\mu}M$ (at S/N = 3). The sensitivity of the electrode was found to be $0.356{\mu}A\;{\mu}M^{-1}\;cm^{-2}$.