고온 구동형 고분자 전해질 막 연료전지(high temperature polymer electrolyte membrane fuel cell, HT-PEMFC)는 전극의 빠른 활성과 피독 현상에 대한 높은 저항성으로 인해 저온 구동형 PEMFC의 대안으로 많은 연구가 진행되고 있다. 폴리벤즈이미다졸(polybenzimidazole, PBI)을 기반으로 한 PEM의 경우 고온 구동 조건에서 이온 전도성 물질과의 높은 상호 작용과 우수한 열적ㆍ기계적 안정성 특징으로 인해 HT-PEMFC용 PBI 기반 전해질 막 개발과 관련된 다양한 연구들이 진행 되고 있다. 본 총설에서는 고성능/고내구성의 PBI 기반 PEM을 개발하기 위해 1) 인산 및 다양한 이온전도성 물질이 도핑된 PBI 막의 특성 분석과 막 제조법에 따른 PBI 막의 물성 비교에 관한 연구를 우선적으로 살펴본 후 2) 다공성 폴리테트라플루 오르에틸렌 지지체 및 무기 입자 혼입을 통한 PBI 복합 막의 성능 개선 연구 및 3) 고분자 블렌딩을 통해 가교 구조가 도입 된 PBI 기반 가교 막의 내구성 향상에 관한 연구 동향에 대하여 소개하고자 한다.

국제해사기구(IMO)는 국제해운 분야의 온실가스(Green House Gas, GHG) 감축을 위하여 각국의 기술 개발 및 에너지 효율성 제 고에 관한 정책 시행을 적극적으로 권장하고 있다. 이러한 IMO의 환경규제와 관련된 정책들은 해운 분야 전반에 큰 영향을 미치고 있으 며, 선주들에게도 막대한 부담으로 작용하고 있다. 선박에서 발생하는 GHG 배출을 억제하기 위한 가장 합리적인 방안은 탄소제로배출 (Zero Emission) 선박의 개발로 귀결된다. 즉 친환경 연료로 추진하는 연료전지선박(Fuel Cell Ship, FCS)의 개발이 IMO의 규제를 벗어날 수 있는 대안인 것이다. 아시아, 북미, 유럽 등의 각국에서는 독자적으로 PEMFC를 개발 및 생산하여 국제공인등록 기관으로부터 형식승인 인증을 획득함으로써 국제표준화의 선점을 추구하고 있다. 현재 다양한 연료전지(Fuel Cell, FC) 중에서 선박용으로 권장하는 것은 크게 고 분자전해질 연료전지(PEMFC), 용융 탄산염 연료전지(MCFC) 및 고체산화물형 연료전지(SOFC) 등의 세종류가 있다. 본 연구에서는 글로벌 FC 시장에서 지속적인 성장이 예상되는 PEMFC를 대상으로 하여 국내외 개발 동향, 제조업체별 규격, 성능 및 선박에 적용한 실증적 사례 를 분석하였다. 그리고 PEMFC를 선박에 적용할 경우, 고려해야 할 사항과 개발 방향에 관하여 제안하고자 하였다.

Polymer electrolyte membrane fuel cells (PEFCs) are eco-friendly energy conversion systems to convert hydrogen directly into electricity via an electrocatalytic reaction. Representative membrane materials of PEFCs are Perfluorinated sulfonic acid (PFSA) ionomers including Nafion® and 3M ionomers. In spite of high proton conductivity, it is difficult to apply PFSA free-standing membranes in real PEFC applications owing to their weak mechanical failures and thermo-chemical decomposition during PFEC operations, in addition to a relatively high production cost. In this study, Nafion nanodispersions in water-alcohol mixtures are fabricated using a supercritical fluid technique. The fundamental membrane characteristics are compared with those of counterpart membranes obtained from a commercially available Nafion emulsion.

Sulfonated poly(arylene ether sulfone) (SPAES)random copolymers have been perceived as alternatives to perfluorinated sulfonic acid (PFSA) ionomers owing to their cheap production cost and low hydrogen permeability. In spite of their advantages, there are some issues to overcome such as membrane durability and relatively low proton conductivity in the low humidity range. An approach to solve these problems is to fill SPAES copolymers into porous support films (e.g., poly(tetra fluoro ethylene), PTFE). However, it is difficult to make defect-free pore-filling membranes. In this study, SPAES nanodispersion in a water-alcohol mixture is made under a modified supercritical condition and used to make highly proton conductive and chemical durable SPAES-PTFE pore-filling membranes.

Ionomers are polymeric materials containing fixed charged ions (e.g., – SO3 -) to transport their counter ions (e.g., H+, Li+, Na+ and so on) selectively and have been widely used as key components for membrane and unit cell formation targeted for renewable energy generation (e.g., polymer electrolyte membrane fuel cells(PEMFC), redox flow batteries, and reverse electrodialyses) and valued chemical production (e.g., water and brine electrolysis). There are advantages such as high processability, easy solvent evaporation, and chemical inertness, when the ionomers are in the dissolved or dispersed states in water-alcohol mixtures to be applied for these applications. Unfortunately, it is difficult to make homogeneous solution or dispersion using the ionomers with hydrophilic levels undissolved in water. In this study, water-alcohol nanodipsersion with perfluorinated or hydrocarbon sulfonic acid ionomers are fabricated and their feasibilities as PEMFC and electrolysis materials are evaluated.

Sulfonated poly(arylene ether sulfone)(SPAES) random copolymers are representative alternatives to perfluorinated sulfonic acid(PFSA) ionomers used as the state-of-the-art polymer electrolyte membranes for fuel cells. SPAES copolymers have advantages such as low hydrogen permeability, low production cost. However, it is difficult to demonstrate high electrochemical single cell performances for a long period time, since SPAES membranes have critical interfacial issues with catalyst layers containing PFSA ionomers, particularly in the repeated hydrated and dehydrated cycles. In this study, called as radiation grafting of proton conductive polymers on SPAES membranes, is tried in order to improve proton conductivity without a severe loss in dimensional stability and to reduce interfacial resistance with PFSA catalyst layers at the same time.

Sulfonated poly(arylene ether sulfone) (SPAES) random copolymers have been perceived as membrane materials alternative to perfluorinated sulfonic acid (PFSA) ionomers, since they are cheap and chemically tunable when compared with PFSA. Moreover, their relatively low gas permeability, particularly to hydrogen, contributes to reduced thermal decomposition of membrane-electrode assemblies. In spite of their advantages, freestanding SPAES copolymers have critical issues associated with chemical/electrochemical durability as well as interfacial resistance with electrodes. In this study, SPAES-PTFE reinforced membranes are fabricated using consecutive membrane formation protocols, (e.g., SPAES nanodispersion in water-alcohol mixtures, spontaneous pore-filling, and solvent-assisted thermal treatment techniques) and systematically evaluated.

Polymer electrolyte membrane fuel cells (PEFCs) are eco-friendly energy conversion systems to convert hydrogen directly into electricity via an electrocatalytic reaction. Representative membrane materials of PEFCs are Perfluorinated sulfonic acid (PFSA) ionomers including NafionⓇ and 3M ionomers. In spite of high proton conductivity, it is difficult to apply PFSA free-standing membranes in real PEFC applications owing to their weak mechanical failures and thermo-chemical decomposition during PFEC operations, in addition to a relatively high production cost. In this study, Nafion nanodispersions in water-alcohol mixtures are fabricated using a supercritical fluid technique. The fundamental membrane characteristics are compared with those of counterpart membranes obtained from a commercially available Nafion emulsion.