• Korean Chemical Engineering Research
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• 제53권6호
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• pp.690-694
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• 2015

최근에 직접 액체 연료전지 중에서 직접 개미산 연료전지(Direct Formic Acid Fuel Cells, DFAFC)가 활발히 연구되고 있다. 불소계막을 대신할 저가의 탄화수소막이 DFAFC막으로 주목받고 있다. 본 연구에서는 sulfonated poly(ether ether ketone ketone, sPEEK)막과 Poly(arylene ether sulfone)(PAES)막을 사용해 Nafion 막과 그 특성을 DFAFC 조건에서 비교하였다. 탄화수소계막의 개미산 투과 전류밀도가 $240{\sim}250mA/cm^2$로 불소계인 Nafion 211 막의 $600mA/cm^2$보다 낮았다. sPEEK MEA(Membrane and Electrode Assembly)와 Nafion 211 MEA의 막 저항이 서로 비슷해 I-V 성능도 거의 같았다. 개미산 투과도가 낮은 sPEEK MEA가 Nafion 211 MEA보다 안정함을 보였다.

• 한국재료학회지
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• 제33권1호
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• pp.21-28
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• 2023

The electromembrane process, which has advantages such as scalability, sustainability, and eco-friendliness, is used in renewable energy fields such as fuel cells and reverse electrodialysis power generation. Most of the research to visualize the internal flow in the electromembrane process has mainly been conducted on heterogeneous ion exchange membranes, because of the non-uniform swelling characteristics of the homogeneous membrane. In this study, we successfully visualize the electro-convective vortices near the Nafion homogeneous membrane in PDMS-based microfluidic devices. To reinforce the mechanical rigidity and minimize the non-uniform swelling characteristics of the homogeneous membrane, a newly developed swelling supporter was additionally adapted to the Nafion membrane. Thus, a clear image of electroconvective vortices near the Nafion membrane could be obtained and visualized. As a result, we observed that the heterogeneous membrane has relatively stronger electroconvective vortices compared to the Nafion homogeneous membranes. Regarding electrical response, the Nafion membrane has a higher limiting current and less overlimiting current compared to the heterogeneous membrane. Based on our visualization, it is assumed that the heterogeneous membrane has more activated electroconvective vortices, which lower electrical resistance in the overlimiting current regime. We anticipate that this work can contribute to the fundamental understanding of the ion transport characteristics depending on the homogeneity of ion exchange membranes.

• 센서학회지
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• 제22권3호
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• pp.207-211
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• 2013

In this research, the pH sensor was developed using CNT nanosheet with Nafion coating for the advanced medical sensor such as a blood gas analyzer. The CNT nanosheet was formed by dielectrophoresis and water-meniscus between cantilever-type electrodes. Then, the process of the heat annealing and the Nafion coating was conducted for reducing contact resistance and giving proton selectivity respectively. We measured the response of the pH sensor as the electrolyte-gated CNT-nanosheet field effect transistor. The sensor showed a linear current ratio in a similar range of the normal blood pH. A calibration method for decreasing of the response variation among sensors has also been introduced. Coefficient of variance of the pH sensor was decreased by applying the calibration method. A linear relation between the calibrated response of the sensors and pH variance was also obtained. Finally, the pH sensor with a high resolution was fabricated and we verify the feasibility of the sensor by applying the calibration method.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.579-584
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• 2011

Sulfonated poly (ether sulfone)s containing BFBN were prepared from 2,3-bis(4-fluorophenyl)-2-butenedinitrile , 4,4-sulfonyldiphenol and sulfonated 4,4'-difluorodiphenylsulfone sodium salt using potassium carbonate, and followed acidification reaction with 1M $H_2SO_4$. BFBN was prepared from 4-fluorobenzylcyanide, $CCl_4$, NaOH using trimethylbenzylammoniumchloride . Sulfonated poly(ether sulfone)s containing BFBN were studied by FT-IR, $^1H$-NMR spectroscopy, and thermo gravimetric analysis (TGA). The water uptake of synthesized S-PBFBN membranes exhibit 31~62% compared with 28% of Nafion 211. The S-PBFBN membranes exhibit proton conductivities ($80^{\circ}C$, RH 100) of 53.8~117.4 mS/cm compared with 137.4 mS/cm of Nafion 211.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.673-681
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• 2023

Hydrocarbon-based polymer membranes to replace perfluorinated polymer membranes are being continuously researched. However, hydrocarbon-based membranes have a problem in that they are less durable than fluorine-based membranes. In this study, we sought to compare the annealing effect to improve the durability of sulfonated poly(ether ether ketone) (SPEEK). After membranes formation, thermogravimetric analysis and tensile strength were measured to compare changes in membranes properties due to annealing. After manufacturing the membrane and electrode assembly (MEA), the initial performance and chemical durability was compared with unit cell operation. During the 24-hour annealing process, the strength increased due to the increase in-S-O-S-crosslinking, and the sulfonic acid group decreased, leading to a decrease in I-V performance. By annealing, the hydrogen permeability was reduced to less than 1/10 of that of the nafion membrane, and as a result, open circuit voltage (OCV) and durability was improved. The SPEEK membranes annealed for 24 hours showed higher durability than the nafion 211 membranes of the same thickness.

• Korean Chemical Engineering Research
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• 제49권2호
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• pp.211-217
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• 2011

본 연구는 high impact polystyrene (HIPS)의 가교 및 술폰화시간을 달리하여 이온교환막을 제조하였다. 술폰화 HIPS(SHIPS) 이온교환막의 술폰화도는 술폰화시간이 증가함에 따라 증가하였고, 가교시간이 증가함에 따라 감소하였으며 이때 최대 술폰화도는 66%였다. 또한, SHIPS 이온교환막의 이온교환용량과 함수율은 가교율이 증가할수록 감소하였고 술폰화시간이 증가할수록 우수한 성능을 나타냈으며 가장 우수한 함수율과 이온교환용량은 35.2%와 1.55 meq/g이였다. SHIPS 이온교환막의 전기저항 및 이온전도도는 술폰화시간이 증가할수록 우수한 성능을 나타냈으며 가장 우수한 값은 각각 $0.4\Omega{\cdot}cm^{2}$와 0.1 S/cm으로 나타났으며 Nafion 117보다 성능이 우수하였다. SHIPS 이온교환막의 유기용매에서의 내구성은 가교시간이 증가할수록 증가하였으며 SEM 관찰 결과 술폰화시간이 진행됨에 따라 표면이 불균일하게 변화되는 것을 확인할 수 있었다.

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.517-522
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• 2023

고분자전해질 연료전지 (PEMFC)에 공기와 수소를 공급하고 개회로전압 (OCV) 상태에서 가습/건조를 반복하는 고분자막의 화학적/기계적 내구성 평가법이 사용되고 있다. 이 프로토콜에서 가습/건조가 반복되면 전압 상승/감소가 반복되어 전극 열화도 발생한다. 막 내구성이 우수한 경우 전압 변화 횟수가 증가해, 전극 열화에 의해 평가가 종료되어 원래 목적인 막 내구성 평가를 할 수 없는 문제가 발생하기도 한다. 본 연구에서는 미국 에너지부 (DOE)와 동일한 프로토콜을 사용하되 cathode 가스로 공기대신 산소를 사용하고 가습/건조시간과 유량도 증가시켜 막의 화학적/기계적 열화 속도를 증가시켜서 고분자막 내구 평가 시간을 단축시킴으로서 이와 같은 문제를 개선하고자 하였다. Nafion 211 막전극접합체(MEA) 내구성 평가를 공기 대신 산소를 사용해서 가속화도를 2.6배 증가시켜 2,300 사이클만에 평가 종료하였다. 본 프로토콜에 의해 고분자막도 가속 열화되고, 전극 촉매도 가속 열화되어 고분자막과 전극의 내구성을 동시에 평가할 수 있는 이점도 있었다.