• Membrane Journal
• /
• v.25 no.5
• /
• pp.456-463
• /
• 2015

In this study, we synthesize novel silane based inorganics for preparation of the polymer electrolyte membrane with high proton conductivity under high temperature condition and developed membranes are characterized. SPAES, hydrocarbon based polymer are synthesized and used as main polymeric material. We used sol-gel method to prepare inorganic material with high performance using silica, phosphate and zirconium. Three types of inorganics were prepared by control of the mole ration of each component. As a result of EDX analysis, the inorganic materials are well dispersed in the polymer membrane. The water uptake of the composite membrane is increased by introduction of the hydrophilic inorganic material in the membrane. When the content of the zirconium in the membrane is increased, the proton conductivity of the composite membrane shows the higher value than pure SPAES membrane at the high temperature. And the silica based inorganics effect to increase the proton conductivity under low temperature condition.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.135.1-135.1
• /
• 2010

최근 고온에서 사용 가능한 PEMFC용 고분자전해질 막 개발에 대한 연구가 활발히 진행되고 있다. PEMFC가 고온에서 작동하게 되면 높은 성능과 많은 장점을 갖게 된다. PEMFC를 $100^{\circ}C$ 이상에서 운전하게 될 경우 백금 전극 반응을 향상시켜 고가의 백금 촉매 양을 줄일 수 있게 되고, 수소연료 속에 미량 포함된 CO에 의한 촉매표면 피독현상에 대한 내구성을 높일 수 있어 저 순도 수소연료 사용이 가능해 진다. 또한 가습장치와 수소 연료 개질장치의 부피를 줄일 수 있게 되어 전체적인 PEMFC 시스템이 단순화 된다. 현재 연료전지용 고분자 전해질막으로 DuPont사의 과-불소계 고분자 전해질막인 Nafion$^{(R)}$이 가장 널리 사용되고 있다. Nafion$^{(R)}$은 유연한 분자구조 안에 소수성이 강한 주사슬과 친수성을 나타내는 술폰산이 결합된 곁사슬이 존재하여 술폰화 곁사슬의 클러스터 둘레에는 친수성 영역이 형성이 되기때문에 소수/친수 상 분리가 잘되어 이온 클러스터 형성이 용이하지만 제조비용이 높은 단점을 갖고 있다. 특히, 전해질 막내에서 Bronsted base 역할을 하는 물에 의해 이온전도가 이루어지기 때문에 고온에서는 수분증발로 인해 성능이 급격히 감소된다. 따라서, 본 연구에서는 고온 저가습 조건에서 운전이 가능하고 Nafion이 갖는 문제점을 해결하고자, 내열특성이 뛰어나며 높은 수소이온 전도도 학보가 용이한 Sulfonated Poly(aryl ether)sulfone(SPAES) 고분자 전해질에, 고온에서도 수화성이 유지될 수 있도록 지르코니아를 황산화한 sulfated zirconia(s-$ZrO_2$)를 함침하여 복합 고분자전해질막을 제조하여 고온 저가습 조건에서의 수소이온 전도 특성에 관한 연구를 수행하였다. 개발된 막의 물리/화학적 특성은 water content(Wup%), 이온교환 용량(IEC, meq $g^{-1}$), 수소이온전도도(s $cm^{-1}$) 열 중량 분석(TGA), X선 회절분석(XRD) 등을 통하여 분석 및 관찰하였다. 내화학 및 열적 특성분석 결과, 황산화 반응공정으로 $ZrO_2$에 술폰산기가 안정적으로 결합하고 있음이 관찰되었으며, 본 연구에서 개발된 유 무기 복합막이 $250^{\circ}C$이상 열적안정성을 확보하고 있는 것으로 판단되었다. $100^{\circ}C$ 이하의 저온 영역에서, 일정 비율의 s-$ZrO_2$/SPAES막에서 이온교환용량(IEC)이 순수 SPAES 막보다 낮음에도 불구하고, water uptake가 증가함과 동시에 수소이온 전도도가 향상된 것을 관찰하였다. 또한, 고온에서는 수소이온이 자유롭게 이동할 수 있는 water channel을 형성하는 free water는 증발 하지만 s-$ZrO_2$와 SPAES의 술폰산기 사이에 강력하게 결합하고 있는 bound Water는 $100^{\circ}C$ 이상의 고온 영역에서도 존재하여, 비록 무가습 조건에서도 일정 비율의 s-$ZrO_2$/SPAES50 전해질 막의 경우, 높은 전도도를 나타냄을 관찰할 수 있었다. 따라서 본 연구를 통해 저가습 고온 적용을 목적으로 개발된 s-$ZrO_2$/SPAES50막은 우수한 내열 특성을 나타냄과 동시에 저가습 고온 영역($120^{\circ}C$, $50RH{\downarrow}$)에서 높은 수소이온 전도도를 유지하여, 고온 저가습 연료전지 운전에 적합할 것으로 사료된다.

• Journal of Hydrogen and New Energy
• /
• v.29 no.6
• /
• pp.620-626
• /
• 2018

Recently, fuel cell field is receiving much attention as an environmentally friendly energy in the world. Among the various types of fuel cells, in the case of PEMFC, ions move through the membrane in the middle of the unit cell. Therefore, proper moisture is required inside the PEMFC. In the case of membrane type humidifier, flat membrane or hollow fiber membrane is mainly used. Since various parameters can change the performance, the performance investigation has to be carried out with parameters. In this study, water transport of hollow fiber membrane was investigated in terms of principle operating conditions such as temperature and flow rate.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.149-149
• /
• 2009

Generally, Nafion ionomer is used in the polymer electrolyte fuel cell (PEFC) electrodes to achieve high power density. At the high temperature operation of PEFC, however, ionic conductivity of Nafion remarkably decreased due to the evaporation of water in Nafion polymer. Recently, many researchers have focused on using the Ionic Liquids(ILs) instead of water in Nafion polymer. ILs have intrinsic properties such as good electrochemical stability, high ionic conductivity, and non-flammability. Especially, ILs play a crucial role in proton conduction by the Grottuss mechanism and act as water in water-free Nafion polymer. However, it was found that the ILs was leached out of the polymer matrix easily. In this study, we prepared membrane electrode assemblies with various contents of ILs. The effect of ILs in the electrode of each designed was investigated by a cyclic voltammetry measurement and the cell performance obtained through a single cell test using H2/Air gases. Electrodes with different contents of ILs in catalyst layer were examined at high temperature and low humidified condition.

• Membrane Journal
• /
• v.26 no.1
• /
• pp.1-13
• /
• 2016

Fuel cells are regarded as a representative energy source expected to replace fossil fuels particularly used in internal combustion engines. One of the most important components is polymer electrolyte membranes (PEMs) acting as a proton conducting barrier to prevent fuel gas crossover. Since water channels act as proton pathways through PEMs, many researchers have been focused on the 'good phase-separation of hydrophilic moiety' which ensures high water retention under low humidity enough to keep the water channel for good proton conduction. Here, we summarized the strategies which have been adopted to synthesize sulfonated PEMs having high proton conductivities even under low humidified conditions, and hope this review will be helpful to design high performance hydrocarbon PEMs.

• Applied Chemistry for Engineering
• /
• v.23 no.5
• /
• pp.445-449
• /
• 2012

The activation process of the membrane-electrode assembly (MEA) is important for the mass production of the polymer electrolyte membrane fuel cell. The conventional activation process for the MEA requires excessive time and hydrogen gas and it might become the barrier for the commercialization of the fuel cell. The conventional activation process is based on hydrolysis of ion conducting membrane. In the study, we suggest the cyclic voltammetry (CV) technique as an on-line activation process and the CV activation process consists of two steps : 1) the humidification of the polymer electrolyte membrane and the electrode with 100% RH humidified nitrogen ($N_{2}$) gas, and 2) the removal step of the oxide layer on the surface of the Pt catalyst with CV cycling. The cycling reduces the activation time of the MEA by 2.5 h and use of hydrogen gas by 1/4.

• Membrane Journal
• /
• v.18 no.4
• /
• pp.282-293
• /
• 2008

Partially sulfonated poly(aryl ether sulfone) membranes were prepared from the sulfonated sulfone monomer, which was synthesized by a nucleophilic substitution, non-sulfonated monomers and potassium carbonate by a direct polymerization method and a subsequent solution casting technique with mixed solvents of N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). To investigate the effect of mixed solvent, the volume ratios of NMP and DMAc were varied in the range of $0{\sim}100%$ and the degrees of sulfonation of the copolymers were fixed as 50%. The surface properties of the resulting membranes were examined by scanning electron microscope (SEM) and atomic force microscope (AFM), and a comparative study of the morphology changes and the physicochemical properties such as proton conductivity and methanol permeability was achieved. It was found that proton conductivities depend on the volume ratio of NMP-DMAc mixed solvents, and the proton conductivity determined at the condition of $25^{\circ}C$ and 100% relative humidity was $1.38{\times}10^{-1}\;S/cm$ for the membrane prepared in the 50:50 v/v-% of NMP : DMAc mixed solvent.

• Applied Chemistry for Engineering
• /
• v.29 no.5
• /
• pp.489-496
• /
• 2018

Fuel cells are seen as eco-friendly energy resources that convert chemical energy into electrical energy. However, proton exchange membrane fuel cells (PEMFCs) have problems such as the use of expensive platinum catalysts for the reduction of conductivity under high temperature humidification conditions. Thus, an anion exchange membrane fuel cell (AEMFC) is attracting a great attention. Anion exchange fuel cells use non - Pt catalysts and have the advantage of better efficiency because of the lower activation energy of the oxygen reduction reaction. However, there are various problems to be solved including problems such as the electrode damage and reduction of ion conductivity by being exposed to the carbon dioxide. Therefore, this mini review proposes various solutions for different problems of anion exchange fuel cells through a wide range of research papers.

• Membrane Journal
• /
• v.27 no.5
• /
• pp.389-398
• /
• 2017

The most important characteristic of the polymer electrolyte membranes (PEMs) for fuel cells, the proton conducting ability is mainly influenced by the distribution and morphology of the water channels inside the PEMs. Non-perfluorinated hydrocarbon PEMs are known to have weaker water channels than perfluorinated PEM, Nafion, and thus relatively low proton conducting ability. In this study, we used a mesoscale simulation technique to observe the water channel formation and phase separation behavior of hydrocarbon PEM, sulfonated polyimides, under the humidification condition. It was observed that the water molecules were distributed evenly through the entire hydrophilic region, and clear water clusters were formed only in the sulfonated polyimide having high sulfonation degree. In addition, it was observed that sulfonated polyimides have a difficulty in forming water channel under the low hydrated condition. These results clearly support the theories of the formation of water channels in non-perfluorinated hydrocarbon PEMs, and also well explain the tendency of proton conducting abilities of sulfonated polyimides. Thus, it is confirmed that mesoscale simulation techniques can be very effective in analyzing phase separation behavior and water channel formation in PEMs for fuel cells and elucidating the ion conducting abilities.