Perfluorinated sulfonic acid (PFSA) ionomers have been widely used for renewable energy generation, including polymer electrolyte fuel cells (PEFCs), owing to their excellent resistance to harsh chemicals and good ion-transport properties. PFSA materials experience critical chemical decomposition to radical attacks, and fast hydrogen crossover leading to fairly reduced electrochemical performances, when they are used as membrane materials. Similar chemical degradation also occurs in PEFC electrodes containing PFSA ionomer binders used as both mechanical supporters and proton conductors and shortens PEFC lifetime. In this study, several approaches based on their morphological rearrangement to overcome these economical and technical issues are proposed. They include pore-filling membrane formation, nanodispersion, and their combination.

Perfluorinated sulfonic acid ionomers have been used as representative membrane materials in a wide range of applications. Though PFSA ionomers have been well known as chemically durable materials, their chemical resistances should be improved further to apply them to practical fuel cell systems operated under harsh conditions. One plausible solution would be to fabricate reinforced membranes composed of proton-conducting ionomers and chemically durable porous support films. In this study, pore-filling membranes are prepared via the impregnation of PFSA ionomers into porous PTFE support films. The objective of this study is to systematically investigate the influences of pore characteristics on proton transport behavior and electrochemical single performances.

Perfluorinated sulfonic acid (PFSA) ionomers have been widely used as membranes in the fields of green power generation and electrolysis. In spite of their high ion-conducting properties, it is difficult to apply them in the freestanding membrane state to harsh operation conditions owing to their chemical and electrochemical degradation issues. A promising membrane concept to satisfy this purpose would be “pore-filling membrane” composed of PFSA ionomers and porous PTFE support films. In this study, the porous PTFE support film treated with a cheap hydrophilic polymer is used as a reinforced material. Interestingly, the resulting PFSA-PTFE pore-filling membranes exhibit an extremely high proton conductivity with a fairly reduced ionomer content, which may give a valuable information to design a desirable pore-filling membrane.

과불소계 술폰화 이오노머(perfluorinated sulfonic acid ionomers; PFSAs)는 뛰어난 수소이온전도성과 높은 내화학성으로 인해 고분자 전해질 연료전지(polymer electrolyte fuel cells)용 고체전해질로 널리 사용되고 있다. 그러나 PFSA 전해질은 가습-건조조건에서 연료전지가 구동에 따라 반복적인 팽윤-수축으로 인해 전극층이 전해질로부터 탈리되어 전기화학적 수명특성이 감소되는 문제점을 가지고 있다. 본 연구에서는 다공성 PTFE support film의 기공특성에 대한 이해를 바탕으 로 기공구조 내 나피온 이오노머를 함침시키는 강화막을 제조하였고, 기본특성을 평가하였다. 제조된 강화막은 매우 높은 수 소이온전도도(~0.5 S cm-1@90°C in liquid water)를 나타내었다.

This study is aimed to increase the activity of cathodic catalysts for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). we investigated the temperature effect of 20wt% Pt/C catalysts at five different temperatures. The catalysts were synthesized by using chemical reduction method. Before adding the formaldehyde as reducing agent, process was undergone for 2 hours at the room temperature (RT), 40˚C, 60˚C, 80˚C and 100˚C, respectively. The performances of synthesize catalysts are compared. The electrochemical oxygen reduction reaction (ORR) was studied on 20wt% Pt/C catalysts by using a glassy carbon electrode through cyclic voltammetric curves (CV) in a 1M H2SO4 solution. The ORR specific activities of 20wt% Pt/C catalysts increased to give a relative ORR catalytic activity ordering of 80˚C > 100˚C > 60˚C > 40˚C > RT. Electrochemical active surface area (EAS) was calculated with cyclic voltammetry analysis. Prepared Pt/C (at 80˚C, 100˚C) catalysts has higher ESA than other catalysts. Physical characterization was made by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The TEM images of the carbon supported platinum electrocatalysts (80˚C, 100˚C) showed homogenous particle distribution with particle size of about 2~3.5 nm. We found that a higher reaction temperature resulted in more uniform particle distribution than lower reaction temperature and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.

친전자성 치환반응을 통하여 제조된 술폰화 단량체와 비(非)술폰화 단량체의 직접 중합법을 통하여 서로 다른 술폰화도를 나타내는 술폰화 폴리아릴에테르술폰 공중합체를 합성하고, 이들로부터 직접 메탄올 연료전지용 이중층(層) 고분자 전해질 막을 제조하였다. 우수한 이온 전도특성을 나타내는 술폰화도 50%의 공중합체를 사용하여 전해질 막의 모체(母體) 전도층을 제조하고, 이들의 한쪽 표면에 술폰화도 10%의 공중합체를 도포한 후 건조하여 낮은 메탄올 투과 특성의 코팅층을 형성시켰다. 도포되는 공중합체의 질량비를 5~20%로 조절함으로써 코팅 층 두께에 따른 전해질 막의 특성 변화를 고찰하였으며, 형성된 코팅 층을 막-전극 접합체의 음극 면에 접합시켜 운전 시 메탄올 연료와 직접 접촉하도록 하였다. 이중층 형성 공정을 통하여, 단일 전해질 막과 동등한 수준의 이온 전도 특성을 유지하면서도, 전해질 막을 통한 메탄올 투과 특성이 현저히 개선된 우수한 효율의 고분자 전해질 막 제조가 가능하였다. 작동 온도 60°C, 2 M의 메탄올 공급 환경에서 수행된 연료 전지 성능 평가 결과, 막-전극 접합체 출력 밀도는 5%의 질량비에서 최대 134.01 mW/cm2였으며, 이로부터 상용 나피온 115 대비 105.5%의 향상된 성능 효율을 확인할 수 있었다.

Novel bisphenol-based wholly aromatic poly(ether sulfone-ketone) copolymer containing pendant sulfonate groups were prepared by direct aromatic nucleophilic substitution polycondensation of 4,4-difluorobenzophenone, 2,2'-disodiumsulfonyl-4,4'-fluorophenylsulfone (40mole% of bisphenol A) and bisphenol A. Polymerization proceeded quantitatively to high molecular weight in N-methyl-2-pyrrolidinone at . Organic-inorganic composite membranes were obtained by mixing organic polymers with hydrophilic (ca. 20nm) obtained by sol-gel process. The polymer and a series of composite membranes were studied by FT-IR, , differential scanning calorimetry (DSC) and thermal stability. The proton conductivity as a function of temperature decreased as content increased, but methanol permeability decreased. The nano composite membranes were found to posse all requisite properties; Ion exchange capacity (1.2meq./g), glass transition temperatures , and low affinity towards methanol .

본 연구에서는 흑연, 열경화성 수지, 그리고 카본 블랙을 사용하여 조성과 제조 조건을 달리하여서 탄소 복합체를 제조하였다. 제조된 탄소 복합체의 고분자 전해질 연료전지용 bipolar plate로의 응용 가능성을 살펴보기 위하여 연속 흐름 기체 투과 장치를 사용하여서 산소의 투과도를 측정하였다 실험 결과 카본 블랙의 양이 증가할수록 산소 투과도가 증가하였으며, 탄소 복합체의 성형 시간이 증가할수록 투과도가 감소하였다 반면에 성형 압력은 산소 투과도에 큰 영향을 미치지 않음을 알 수 있었다.