• 생명과학회지
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• 제15권2호
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• pp.304-310
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• 2005

생체세포에 대한 paraquat의 독작용은 superoxide dismutase 활성저해에 기인하는 것으로 알려져 있다. 그러나 세균이 paraquat에 매우 짧은 시간동안의 노출에 의하여서도 독작용을 받을 수 있는 것으로 검토됨에 따라 paraquat의 독작용의 하나로서 전자전달에 미치는 영향 중 NAD(H)의 산화 및 환원반응에 미치는 영향을 검토한 결과는 다음과 같다. 공시균의 원형질막 획분, rat mitocondria분산액 및 NAD-dependent dehydrogenase에 의한 산화 및 환원시 paraquat 첨가구에서 반응 Graph의 경사도가 더 컸으며, 반응 개시점 및 종결점이 대조구에 비해 낮은 결과로 반응이 가속화되는 결과를 볼 수 있었다. 반응을 경시적으로 NAD(H)의 함량변화로 검토한 결과에서도 원형질 막 획분과 rat mitocondria 분산액을 이용한 경우에 10분간의 NADH산화량이 대조구는 각각 960 mM, 1,187 mM이었으나 Paraquat 처리구는 각각 1,200 mM, 1,434 mM로 Paraquat 처리구가 반응 가속화 경향을 보였다. NAD(H) dependent dehydrogenase에 의한 NAD(H)의 산화 및 환원 반응에서도 대조구에 비하여 Paraquat 처리구가 초기반응의 가속화 및 총산화량의 증가를 보였다.

• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.305-312
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• 2008

ZnO/Zn redox cycle is the one of the promising thermochemical cycles for hydrogen production via water splitting with high temperature heat source like a concentrated solar energy. This paper reports the particle size effect of Zinc on water splitting behavior. Water splitting reaction experiments were carried out at isothermal conditions of 350 and 400$^{\circ}C$ in TGA (Thermo Gravimetric Analyzer) using four commercial Zinc powders (nano, <10 ${\mu}m$, <150 ${\mu}m$ and $150{\sim}600\;{\mu}m$ particle sizes). Before the experiments, average particle size of Zinc powders was analyzed by PSA (Particle Size Analysis). After the experiments, XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscope) analyses were conducted on the samples. The experimental results showed that particle size had a effect on the conversion of Zinc to ZnO. Zinc conversion was increased, as the particle size decreased. Especially, the nano size particles were aggregated and the particle's morphology changed on the surface during hydrolysis reaction.

• 전기화학회지
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• 제14권4호
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• pp.214-218
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• 2011

납이 용해된 수용성메탄술폰산을 전해액으로 사용하는 레독스 플로우 전지의 전기화학적 특성과 성능을 평가하였다. 납과 이산화납의 부착, 용해과정을 평가하기 위해 전압전류법을 실시하였다. 음전위쪽으로 순방향 주사에서 뚜렷한 환원피크는 관찰되지 않고, 전류는 서서히 증가하였다. 음전위 구간에서 역방향 주사에서 산화피크의 on-set potential은 -0.47 V(vs SCE)에서 관찰되었다. 양전위 구간에서는 순방향과 역방향에서 뚜렷한 피크가 나타났다. 비이커 셀내에 설치된 전극으로 충방전 실험을 실시하였다. 납의 충전(부착)은 약 0.5 V(vs SCE), 납의 방전(용해)는 약 0.25 V(vs SCE)에서 진행되었으며, 충전 및 방전시의 전위 차이는 약 0.25 V이다. 이산화납의 초기 충전(부착)은 1.7 V(vs SCE)에서 진행되었고, 방전(용해)은 0.95 V 부근의 일정전위에서 진행되었다. 두번째 사이클에서, 충전은 1.5 V(vs SCE)이하에서 시작되고, 이후 전위가 1.7 V(vs SCE)로 증가하였다. 방전 전위는 약 1.0 V로 안정적으로 유지하였다.

• Journal of Electrochemical Science and Technology
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• 제9권3호
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• pp.220-228
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• 2018

This study introduced a carbon-free electrode for $Li-O_2$ cells with the aim of suppressing the side reactions activated by carbon material. Micro-particles of poly(3,4-ethylenedioxythiophene) (PEDOT), a conducting polymer, were used as the base material for the air electrode of $Li-O_2$cells. The PEDOT micro-particles were treated with $H_2SO_4$ to improve their electronic conductivity, and LiBr and CsBr were used as the redox mediators to facilitate the dissociation of there action products in the electrode and reduce the over-potential of the $Li-O_2$ cells. The capacity of the electrode employing PEDOT micro-particles was significantly enhanced via $H_2SO_4$ treatment, which is attributed to the increased electronic conductivity. The considerable capacity enhancement and relatively low over-potential of the electrode employing $H_2SO_4$-treated PEDOT micro-particles indicate that the treated PEDOT micro-particles can act as reaction sites and provide storage space for the reaction products. The cyclic performance of the electrode employing $H_2SO_4$-treated PEDOT micro-particles was superior to that of a carbon electrode. The results of the Fourier-transform infrared spectroscopic analysis showed that the accumulation of residual reaction products during cycling was significantly reduced by introducing the carbon-free electrode based on $H_2SO_4$-treated PEDOT micro-particles, compared with that of the carbon electrode. The cycle life was improved owing to the effect of the redox mediators. The refore, the use of the carbon -free electrode combined with redox mediators could realize excellent cyclic performance and low over-potential simultaneously.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.152-161
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• 2023

Vanadium redox flow batteries (VRFBs) have been considered one of promising power sources for large scale energy storage systems (ESS) because of their excellent cycle performance and good safety. However, VRFBs still have a few challenging issues, such as poor Coulombic efficiency due to vanadium crossover between catholyte and anolyte, although recent efforts have shown promise in electrochemical performance. Herein, the vanadium complexes with various glyme ligands have been examined as active materials to suppress vanadium crossover between catholyte and anolyte, thus improving the Coulombic efficiency of VRFBs. The conventional Nafion membrane has a channel size of ca. 10 Å, whereas vanadium cation species are small compared to the Nafion membrane channel. For this reason, vanadium cations can permeate through the Nafion membrane, resulting in significant vanadium crossover during cycling, although the Nafion membrane is a kind of ion-selective membrane. In this regard, various glyme additives, such as 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), and tetraethylene glycol dimethyl ether (tetraglyme) have been examined as complexing agents for vanadium cations to increase the size of vanadium-ligand complexes in electrolytes. Since the size of vanadium-glyme complexes is proportional to the chain length of glymes, the vanadium permeability of the Nafion membrane decreases with increasing the chain length of glymes. As a result, the vanadium complexes with tetraglyme shows the excellent electrochemical performance of VRFBs, such as stable capacity retention (90.4% after 100 cycles) and high Coulombic efficiency (98.2% over 100 cycles).

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.260-266
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• 2012

Syngas and hydrogen from the $CeO_2/ZrO_2$ coated foam devices were investigated under simulated solar radiation. The $CeO_2/ZrO_2$ coated SiC, Ni and Cu foam device were prepared using drop-coating method. Syngas production step was performed at $900^{\circ}C$, and hydrogen production process was performed for ten repeated cycles to compare the CeO2 conversion in syngas production step, $H_2$ yield in hydrogen production step and cycle reproducibility. The produced syngas had the $H_2$/CO ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. In addition, syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. After ten cycles of redox reaction, the $CeO_2/ZrO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

• 방사성폐기물학회지
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• 제20권1호
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• pp.33-41
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• 2022

Liquid Bi pool is a candidate electrode for an electrometallurgical process in the molten LiCl-KCl eutectic to treat the spent nuclear fuels from nuclear power plants. The electrochemical behavior of Bi³⁺ ions and the electrode reaction on liquid Bi pool were investigated with the cyclic voltammetry in an environment with or without BiCl₃ in the molten LiCl-KCl eutectic. Experimental results showed that two redox reactions of Bi³⁺ on inert W electrode and the shift of cathodic peak potentials of Li⁺ and Bi³⁺ on liquid Bi pool electrode in molten LiCl-KCl eutectic. It is confirmed that the redox reaction of lithium with respect to the liquid Bi pool electrode would occur in a wide range of potentials in molten LiCl-KCl eutectic. The obtained data will be used to design the electrometallurgical process for treating actinide and lanthanide from the spent nuclear fuels and to understand the electrochemical reactions of actinide and lanthanide at liquid Bi pool electrode in the molten LiCl-KCl eutectic.

• BMB Reports
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• 제56권7호
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• pp.385-391
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• 2023

Aspartate-glutamate carrier 2 (AGC2, citrin) is a mitochondrial carrier expressed in the liver that transports aspartate from mitochondria into the cytosol in exchange for glutamate. The AGC2 is the main component of the malate-aspartate shuttle (MAS) that ensures indirect transport of NADH produced in the cytosol during glycolysis, lactate oxidation to pyruvate, and ethanol oxidation to acetaldehyde into mitochondria. Through MAS, AGC2 is necessary to maintain intracellular redox balance, mitochondrial respiration, and ATP synthesis. Through elevated cytosolic Ca²⁺ level, the AGC2 is stimulated by catecholamines and glucagon during starvation, exercise, and muscle wasting disorders. In these conditions, AGC2 increases aspartate input to the urea cycle, where aspartate is a source of one of two nitrogen atoms in the urea molecule (the other is ammonia), and a substrate for the synthesis of fumarate that is gradually converted to oxaloacetate, the starting substrate for gluconeogenesis. Furthermore, aspartate is a substrate for the synthesis of asparagine, nucleotides, and proteins. It is concluded that AGC2 plays a fundamental role in the compartmentalization of aspartate and glutamate metabolism and linkage of the reactions of MAS, glycolysis, gluconeogenesis, amino acid catabolism, urea cycle, protein synthesis, and cell proliferation. Targeting of AGC genes may represent a new therapeutic strategy to fight cancer.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.239-243
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• 2019

본 연구에서는 Anthraquinone-2,7-disulfonic acid (2,7-AQDS)와 Tiron을 수계 레독스 흐름 전지 음극 및 양극 활물질로 사용하며 기존의 황산 전해질 대신 중성인 염화암모늄 ($NH_4Cl$)을 전해질로 도입하였다. 이렇게 전해질을 변경함으로써, 황산 전해질의 낮은 셀 전압(0.76 V)을 1.01 V까지 향상시킬수 있다. 성능 최적화를 위해 염화암모늄 전해질에 0.1 M로 활물질 농도를 맞춰 컷-오프 전압에 변화를 주며 완전지셀 성능을 평가하였다. 0.2~1.6 V 구간의 컷-오프 전압으로 $40mA/cm^2$ 하에서 20 사이클 동안 완전지셀을 테스트한 결과, 충전 동안 수소가 발생하였다. 이에 컷-오프 전압 조절로 충전 전압을 낮춰서 수소 발생을 제한하고자 0.2~1.2 V 구간으로 $40mA/cm^2$ 하에서 완전지셀 테스트를 진행하였다. 수소 발생은 없었으며, 전류 효율 99%, 방전 용량 3.3 Ah/L의 성능을 보였다.

• 한국수소및신에너지학회논문집
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• 제13권2호
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• pp.143-150
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• 2002

The thermal behavior of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ prepared by a co-precipitation wasinvestigated for Hz generation by the thermochemical cycle. The reduction reaction of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ started from $480^{\circ}C$, and the weight loss was 1.6 wt% up to $1100^{\circ}C$. At this reaction, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ was reduced by release of oxygen bonded with the $Fe^{3+}$ ion in the B site of ($CO_{0.5}$ $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidationof reduced $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. The crystal structure of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ for reduction reaction maintained spinel structure and the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ ($8.41\AA$) was enlarged to $8.45\AA$. But the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ after $H_2O$ decomposition reaction did not change to $8.45\AA$. Then, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ is excellent material in the thermochemical cyclic reaction due to release oxygen at low temperature for the reduction reaction and produce $H_2$ maintaining crystal structure for redox reaction.