• Korean Chemical Engineering Research
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• 제56권1호
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• pp.24-28
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• 2018

산화환원흐름전지(Redox Flow Battery, RFB)는 대용량 에너지 저장장치로 바나듐 산화환원흐름전지가 대표적인 RFB인데, VRFB는 고가인 점이 문제다. 철-크롬RFB는 저가의 활물질을 사용해 경제적인 점이 장점인데, 성능이 낮은 점이 해결해야할 과제다. 낮은 성능의 한 원인이 활물질의 크로스오버인데, 본 연구에서 철과 크롬 이온의 Nafion 막 크로스오버 및 Nafion 막의 안정성에 대해 실험하였다. 철과 크롬이온의 Nafion 막 투과도는 각각 $5.5{\times}10^{-5}$, $6.0{\times}10^{-5}cm^2/min$ 이었다. Nafion 막에서 바나듐 이온의 투과도 $2.9{\times}10^{-6}cm^2/min$ 보다 18.9~20.7배 높아 철과 크롬 이온의 Nafion 막 크로스오버가 성능 저하의 한 원인임을 보였다. 온도 증가에 따라 크로스오버가 급증(활성화 에너지 38.8 kJ/mol)하므로 낮은 온도에서 구동하는 것이 크로스오버에 의한 성능감소를 저하시키는 방법임을 나타냈다. Nafion막은 3M HCl용액에서 비교적 안정적이었다.

• 폴리머
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• 제35권6호
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• pp.593-598
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• 2011

본 연구에서는 전바나듐 레독스-흐름 전지용 음이온교환막의 제조를 위하여 isophthalic acid (IPA), 1,6-hexanediol(HDO), terephthalic acid(TPA), maleic anhydride(MA)의 용융 축합중합 방법에 의해 IPA-co-HDO-co-(TPA/MA)(IHTM) 공중합체를 합성하였다. 합성된 IHTM 공중합체 아민화 반응을 trimethylamine으로 하였으며, UV 가교 반응을 통하여 음이온교환막을 제조하였다. IHTM 공중합체의 구조 및 열안정성을 FTIR, $^1H$ NMR, TGA 분석을 통하여 확인하였다. 또한 IHTM 음이온교환막의 함수율, 이온교환용량, 전기저항, 전기전도도를 중량법, 적정법 및 LCR 미터로 측정하였으며, 전바나듐 레독스-흐름 전지의 효율 실험을 하였다. 막의 이온교환용량, 전기저항, 전기전도도는 각각 1.10 meq/g, $1.98{\Omega}{\cdot}cm^2$, 0.009 S/cm로 우수하게 나타났으며, 전바나듐 레독스-흐름 전지의 충 방전효율, 전압효율 및 에너지효율은 각각 96.5, 74.6, 70.0%이었다.

• 한국전기전자재료학회논문지
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• 제31권5호
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• pp.345-350
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• 2018

Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and $CH_4$ fuel running. Using Pd-doped perovskite, $La(Sr)Fe(Mn,Pd)O_3$, as an anode, fairly high maximum power densities of 0.5 and $0.2cm^{-2}$ were achieved at 1,073 K in $H_2$ and $CH_4$ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in $CH_4$ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

• Journal of Electrochemical Science and Technology
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• 제6권3호
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• pp.106-110
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• 2015

This study investigates Cu(II) complexes of cyclam, propylene cross-bridged cyclam (PCB-cyclam), and propylene cross-bridged cyclam diacetate (PCB-TE2A) as homogeneous electrocatalysts for CO₂ reduction in comparison with Ni(II)-cyclam. It is found that Cu(II)-cyclam can catalyze CO₂ reduction at the potential close to its thermodynamic value (0.75 V vs. Ag/AgCl) in tris-HCl buffer (pH 8.45) on a glassy carbon electrode. Cu(II)-cyclam, however, suffers from severe demetalation due to the insufficient stability of Cu(I)-cyclam. Cu(II)-PCB-cyclam and Cu(II)-PCB-TE2A are revealed to exhibit much less demetalation behavior, but poor CO₂ reduction activities as well. The inferior electrocatalytic ability of Cu(II)-PCB-cyclam is ascribed to its redox potential that is too high for CO₂ reduction, and that of Cu(II)-PCB-TE2A to the steric hindrance preventing facile contact with CO₂ molecules. This study suggests that in addition to the redox potential and chemical stability, the stereochemical aspect has to be considered in designing efficient electrocatalysts for CO₂ reduction.

• Environmental Engineering Research
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• 제10권3호
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• pp.131-137
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• 2005

The catalytic activity of precious metals(Rh, Pd, Pt) and nickel catalysts supported on ${\gamma}-Al_2O_3\;and\;CeO_2$ in the partial combustion of methane(PCM) to syngas was investigated based on the product distribution in a fixed bed now reactor under atmospheric condition and also on analysis results by SEM, XPS, TPD, BET, and XRD. The activity of the catalysts based on the syngas yield increased in the sequence $Rh(5)/CeO_2{\geq}Ni(5)/CeO_2>>Rh(5)/Al_2O_3>Pd(5)/Al_2O_3>Ni(5)/Al_2O_3$. Compared to the precious catalysts, the syngas yield and stability of the $Ni(5)/CeO_2$ catalyst were almost similar to $(5)/CeO_2$ catalyst, and superior to these of any other catalysts. The syngas yield of $Ni(5)/CeO_2$ catalyst was 90.66% at 1023 K. It could be suggested to be the redox cycle of the successive reaction and formation of active site, $Ni^{2-}$ and the lattice oxygen, $O^{2-}$ produced due to reduction of $Ce^{4-}$ to $Ce^{3-}$.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3143-3155
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• 2014

This tutorial review provides a general account of the electrochemical behavior of quinones and their various applications. Quinone electrochemistry has been investigated for a long time due to its complexity. A simple point of view is developed that considers the relative stability of the reduced quinone species and the values of the first and second reduction potentials. The 9-membered square scheme in buffered aqueous solutions is explained and semiquinone radical stability is discussed in this context. Quinone redox reaction has also been employed in various studies. Diverse examples are presented under three broad categories defined by the roles of quinone: molecular tool for physical chemistry, versatile electron mediator, and charge storage for energy conversion devices.

• Bulletin of the Korean Chemical Society
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• 제8권5호
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• pp.362-366
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• 1987

Modification of n-Si electrodes coated by photogalvanostatically with polyaniline and polypyrrole in aqueous solutions considerably enhanced the stability and the spectral response of the photoelectrodes. A polypyrrole coated electrode incorporated with redox couple $Fe(CN)_{6}^{3-_6}$ / $Fe(CN)_{6}^{4-_6}$ yielded a photocurrent density of 400${\mu}A/cm^2$ for about 120 hours. Broad spectral responses over 300-850 nm were observed for both polymer coated electrodes of which polypyrrole coated one showed better current conversion efficiency.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.145-151
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• 2023

Planer-type electrolyte substrates are often utilized for stack manufacturing of electrolyte-supported solid oxide fuel cells (ES-SOFCs) to fulfill necessary requirements such as a high mechanical strength and redox stability. This work did an electrochemical analysis of ES-SOFC with different NiO-YSZ anode thicknesses to find the optimal value for the high performance of the fuel cell. The cell resistivities were constant at anode thickness between 25-58 ㎛, but a thick anode (74 ㎛) caused a high electrode resistivity leading to a dramatic reduction in cell performance. A stability test was performed for 50 hours at 700℃, and the results showed a degradation rate of 0.3% per 1000 h by extrapolated fitting.

• Journal of Microbiology and Biotechnology
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• 제33권12호
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• pp.1681-1691
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• 2023

Flavin mononucleotide-binding proteins or domains emit cyan-green fluorescence under aerobic and anaerobic conditions, but relatively low fluorescence and less thermostability limit their application as reporters. In this work, we incorporated the codon-optimized fluorescent protein from Chlamydomonas reinhardtii with two different linkers independently into the redox-responsive split intein construct, overexpressed the precursors in hyperoxic Escherichia coli SHuffle T7 strain, and cyclized the target proteins in vitro in the presence of the reducing agent. Compared with the purified linear protein, the cyclic protein with the short linker displayed enhanced fluorescence. In contrast, cyclized protein with incorporation of the long linker including the myc-tag and human rhinovirus 3C protease cleavable sequence emitted slightly increased fluorescence compared with the protein linearized with the protease cleavage. The cyclic protein with the short linker also exhibited increased thermal stability and exopeptidase resistance. Moreover, induction of the target proteins in an oxygen-deficient culture rendered fluorescent E. coli BL21 (DE3) cells brighter than those overexpressing the linear construct. Thus, the cyclic reporter can hopefully be used in certain thermophilic anaerobes.

• 전기화학회지
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• 제12권3호
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• pp.263-270
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• 2009

레독스 흐름 전지의 전극으로 사용하기 위해 탄소펠트를 열처리와 산처리 방법으로 산화 개질하였다. 열중량 분석결과 열처리 또는 산처리에 의하여 탄소펠트의 섬유 표면에 고분자 물질이 제거되고 산소 관능기가 도입된 것을 확인할 수 있었으며 습식 방법인 산처리 방법보다 건식방법인 열처리 방법이 기계적 안정성을 유지하는데 효과적인 처리 방법으로 나타났다. XPS, 원소분석을 통하여 500$^{\circ}C$에서 4시간 열처리한 탄소펠트의 표면에 산소 관능기가 부가된 것을 확인하였으며 질소흡착실험에서 거의 없던 표면적이 96 $m^2/g$로 증가한 것을 알 수 있었다. CV실험 및 분극 실험을 수행한 결과 500$^{\circ}C$ 열처리 전극의 활성화 저항이 가장 낮게 나타났다. 산처리한 탄소펠트와 400$^{\circ}C$, 500$^{\circ}C$에서 열처리한 탄소펠트를 이용하여 바나듐 레독스 흐름 전지를 구성하고 충/방전 실험을 실시한 결과 충/방전 전압효율이 산처리 전극의 경우 86.6%, 400$^{\circ}C$ 열처리 전극의 경우 89.6%, 500$^{\circ}C$ 열처리 전극의 경우 90.6%로 500$^{\circ}C$ 열처리 전극이 가장 우수하였다.