• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2022-2024
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• 2005

Electrical double-layer capacitor (EDLC) is an electrochemical energy storage device in which electric charges only accumulated by a pure electrostatic attraction force are stored on the electrolyte-electrode interface in a form of double layer and separated by the electrolyte. The composite was prepared by mixing nanosize $TiO_2$ and activated carbon through a means of ultrasonic vibration in ethanol solution for 30 min in various mass ratios of $AC:TiO_2$ to form activated carbone-semiconducting oxide composites. Either 1.0 M $LiClO_4/EC-DEC$ or $Et_4NBF_4$/EC-DEC was used as the electrolyte. It was found that with modification of $TiO_2$, the specific capacitance of activated carbon measured at $1mA/cm^2$ was increased from 40 to 50 F/g. This method is unique in comparison the conventional method because it uses semiconducting TiO2 other than electrochemically active materials such as $RuO_2$. The increase in specific capacitance could be attributed to the decrease in electric polarization, caused by the introduction of $RuO_2$.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.52-55
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• 2000

Structually organized mono- and multilayers were developed on gold for the catalytic and affinity biosensing using hyper-branched dendrimers. For the catalytic biosensing interface, a new approach to construct a multilayered enzyme film on the electrode surface was developed. The film was prepared by layer-by-layer depositions of dendrimers and periodate-oxidized glucose oxidase. The voltammograms obtained from the GOx/dendrimer multilayered electrodes revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers. From the analysis of voltammetric and ellipsometric signals, the coverage of active enzyme per layer during the layering steps was estimated, demonstrating the spatially-ordered multilayer formation. As an extension of the study, dendrimers having various degrees of ferrocenyl modification were prepared and used. The resulting electrodes were electrochemically characterized, and the density of ferrocenyl groups, active enzyme coverage, and sensitivity were estimated. For the affinity-sensing surrface, a biosensor system based on avidin-biotin interaction was developed. As the building block of affinity monolayer, G4 dendrimer having partial ferrocenyl-tethered surface groups was prepared and used. And the biotinylated and electroactive dendritic monolayer was used for the affinity-sensing surface interacting with avidin. Electrochemical characterization of the resulting biosensor was conducted using free enzyme in electrolyte in terms of degree of surface coverage with avidin and subsequent surface shielding.

• 한국표면공학회지
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• 제49권2호
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• pp.191-195
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• 2016

Among the lithium metal oxides for hybrid-capacity, $Li_4Ti_5O_{12}(LTO)$ is an emerging electrode material as zero-stain material in volume change during the with the charging and discharging processes. However, LTO has a limitation of low ionic and electronic conductivity. To enhance the ionic and electronic properties of $Li_4Ti_5O_{12}(LTO)$, we synthesized the spherical LTO/CNT composite by sol-gel process for hybrid capacitors. CNT interconnection networks between CNT-LTO particles enhanced electronic conductivity and electrochemical charging/discharging properties. All of the LTO samples was observed to show the spinel structure and spherical morphology with the diameter of $5{\sim}10{\mu}m$. Especially, spherical LTO/CNT composite of the CNT-3 wt% showed the enhanced capacity from 110 mAh/g to 140 mAh/g at 10 C.

• 한국재료학회지
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• 제15권1호
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• pp.66-72
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• 2005

Surface modification of the silicon-coated graphite was carried out at $200^{\circ}C\~800^{\circ}C$ under hydrogen atmosphere. The silicon-coated graphites were prepared by fluidized-bed spray coating method. The components of silicon films prepared on the graphite consist of SiO, $SiO_x\;(1. The components of silicon films at $200^{\circ}C$ of heat treatment brought on the higher fraction of SiO and $SiO_x$ than that of $SiO_2$. However, inactive $SiO_2$ fraction increases with increase of the heat treatment temperature. The high content of SiO and $SiO_x$ in the silicon film on graphite leads to the higher discharge capacity in our experimental range.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2004년도 추계 학술발표회 논문집
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• pp.133-138
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• 2004

Proton exchange membrane fuel cell (PEMFC) is considered as a clean and efficient energy conversion det ice for mobile and stationary applications. Anions all the components of the PEMFC, the interface between the electrolyte ,and electrode catalyst plays an important role in determining tile cell performance since the electrochemical reactions take place at the interface in contact with tile reactant gases. Therefore, to increase the interface area and obtain a high-performance PEMFC, surface of the electrolyte membrane was roughened by Ar$^{+}$ beam bombardment. The results imply that by modifying surface of the electrolyte membrane, platinum loading can be reduced significantly without performance loss. To optimize the surface treatment condition, effects of ion dose density on characteristics of the membrane/electrode interface were examined by measuring the cell performance, impedance spectroscopy, and cyclic voltammograms. Surface of the modified membranes were characterized using scanning electron microscopy and FT-IR.R.

• 한국분말재료학회지
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• 제28권5호
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• pp.429-434
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• 2021

Magnetic nanoparticles have a significant impact on the development of basic sciences and nanomedical, electronic, optical, and biotech industries. The development of magnetic structures with size homogeneity, magnetization, and particle dispersibility due to high-quality process development can broaden their utilization for separation analysis, structural color optics using surface modification, and energy/catalysts. In addition, magnetic nanoparticles simultaneously exhibit two properties: magnetic and plasmon resonance, which can be self-assembled and can improve signal sensitivity through plasmon resonance. This paper reports typical examples of the synthesis and properties of various magnetic nanoparticles, especially magnetoplasmonic nanoparticles developed in our laboratory over the past decade, and their optical, electrochemical, energy/catalytic, and bio-applications. In addition, the future value of magnetoplasmonic nanoparticles can be reevaluated by comparing them with that reported in the literature.

• 전기화학회지
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• 제17권2호
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• pp.94-102
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• 2014

바나듐 레독스 흐름 전지 (Vanadium redox flow battery, VRB) 시스템 운전 중 양이온 교환막을 통한 바나듐이온의 투과로 인하여 성능이 저하되는 문제점을 보완하기 위해 판상형태의 탄소물질인 산화그라핀 (Graphene Oxide, GO)을 기존에 사용하였던 양이온 교환막인 Nafion 양이온 교환막 표면에 열압착 방식으로 코팅하여 양이온 교환막 개선 및 VRB 성능 향상을 도모하였다. 개선된 양이온 교환막의 물리화학적 특성분석을 위하여 SEM (Scanning Electron Microscopy)분석, 이온 교환 용량, 수분 흡수 및 수소이온 전도도를 측정하였다. 산화그라핀층을 코팅한 결과, SEM 분석을 통해 양이온 교환막 표면에 약 $0.93{\mu}m$의 산화그라핀층이 형성된 것을 확인할 수 있었다. 산화그라핀을 코팅하여 개선된 양이온 교환막의 수소이온 전도도 측정 결과, 상용 양이온 교환막의 27% 수준으로 감소하였음을 확인하였으며, 동시에 바나듐이온 투과실험을 실시한 결과, 개선된 양이온 교환막의 바나듐이온 투과도가 기존 상용 양이온 교환막의 25% 이하 수준으로 감소하였음을 확인할 수 있었다. VRB 단위전지 성능실험을 실시하여 충-방전 특성을 분석한 결과, 산화그라핀을 코팅하여 개선된 양이온 교환막을 VRB 시스템에 적용하였을 경우, 바나듐이온의 투과도 감소로 인하여 쿨롱효율이 증가하였음을 확인할 수 있었고, 그로 인하여 전체적인 에너지효율이 상용막을 적용하였을 때 보다 증가하였음을 확인할 수 있었다. 따라서, 본 연구를 통해 양이온 교환막 표면에 판상형태의 탄소물질인 산화그라핀을 코팅하는 방법이 바나듐이온 투과도를 저하시키고 VRB의 시스템성능을 향상시킬 수 있는 효과적인 방법임을 제시할 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.424-432
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• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• 전기화학회지
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• 제11권4호
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• pp.256-261
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• 2008

본 연구에서는 나피온 막을 통한 메탄올 투과도를 감소시키기 위하여 양전하를 띠는 polyaniline(PANi)와 음전하를 갖는 sulfonated Poly(ether sulfone)(SPES)으로부터 다층 자기조립 박막법으로 나피온 막의 표면을 개질하였다. PANi과 SPES는 열적 화학적으로 안정하며 매우 강직한 특성을 띄고 있어, 나피온 막 표면에 다층 자기조립 박막 형성시 메탄올 투과도 감소 및 치수 안정성의 향상을 기대할 수 있다. 자외선-가시광선 흡광분석에 의하여 PANi와 SPES의 다층박막의 형성이 균일하게 이루어짐을 확인 하였다. TEM 분석을 통하여 다층 자기조립 박막의 bilayer당 두께가 약 10 nm 정도임을 확인 하였다. 개질된 나피온 막은 순수한 나피온 막에 비하여 15%의 이온전도도 감소가 일어났지만 67%의 높은 메탄올 투과도 감소를 나타내어 2.5배 높은 선택도를 보였다. 5 M 메탄올을 연료로 사용한 연료전지 성능시험에서 개질된 나피온 막은 순수한 나피온 막에 비해 최대 전력 밀도가 $30^{\circ}C$에서는 2.4배 증가, $60^{\circ}C$에서는 1.4배 향상을 나타내었다.

• 전기화학회지
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• 제5권2호
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• pp.52-56
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• 2002

졸-겔법을 이용하여 주석산화물을 흑연입자 표면에 도포하고 $400-600^{\circ}C$에서 열처리하여 미세결정구조를 갖는 리튬이온 전지용 주석산화물 전극을 제조하였다. 도포 된 주석산화물의 양은 $2.25 wt\%\~11.1 wt\%$로 조절하여 실험한 결과 주석산 화물의 함량에 따라 방전용량이 증가하고 또한 초기의 비가역 용랑도 증가함을 알 수 있었다. 싸이클에 따른 주석 산화물 전극의 방전용량은 propylene carbonate(PC) 계 전해액에서도 초기 싸이클에서 350mAh/g 이상, 30 싸이클 후 에서는 300mAh/g을 나타낸 반면, 표면개질이 되지 않은 흑연전극의 경우에는 140mAh/g의 방전용량을 나타내었다. 충방전 속도를 C/5에서 C/2로 빠르게 했을 때 주석산화물 전극과 흑연전극의 방전용량은 초기 용량의 $92\%,\;77\%$로 각각 나타났다. 이러한 전극 특성의 향상은 주석산화물이 리튬이온과 반응하여 형성된 리튬 옥사이드$(Li_2O)$부동태 피막이 흑연전극의 탈리 현상을 막고 또한 환원된 주석이 흑연입자간의 전기전도를 원활하게 하여 전극의 전류분포를 향상시키기 때문인 것으로 해석되었다.