• Title, Summary, Keyword: Proton conductivity

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Improvement of Oxidative Stability for Non-fluorinated Membranes Prepared by Substituted Styrene Monomers (스티렌 유도체를 이용한 비불소계 고분자 전해질막의 산화적 안정성 개선)

  • Moon, Seung-Hyeon;Woo, Jung-Je;Fu, Rong-Qiang;Seo, Seok-Jun;Yun, Sung-Hyun
    • Membrane Journal
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    • v.17 no.4
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    • pp.294-301
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    • 2007
  • To improve oxidative stability of non-fluorinated styrene-based polymer electrolyte membranes, copolymerized membranes were prepared using styrene derivatives such as p-methylstyrene, t-butylstyrene, and ${\alpha}-methylstyrene$ by monomer sorption method. Prepared membrane was characterized by measurement of weight gain ratio, water content, ion-exchange capacity, proton conductivity, and oxidative stability under the accelerated condition. It was found that each step of monomer sorption method including sorption, polymerization and sulfonation could be affected by the properties and the structures of styrenederivatives. Due to difficulty of polymerization, ${\alpha}$-methylstyrene was copolymerized with styrene or p-methylstyrene. Prepared membrane using ${\alpha}-methylstyrene$ and styrene showed higher performance and stability comparing to copolymerized membrane with styrene. However, copolymerized membranes with ${\alpha}-methylstyrene$ did not showed much improved oxidative stability comparing to styrene membrane due to their lower molecular weight. The t-butylstyrene membrane showed a low performance due to substituted bulky-butyl group which prevents sorption and sulfonation reaction. However, copolymerized t-butylstyrene membranes with p-methylstyrene showed good performance and much improved stability than the styrene membranes.

Perfluorinated Sulfonic Acid based Composite Membranes for Vanadium Redox Flow Battery (바나듐 레독스 흐름 전지를 위한 과불소화 술폰산 복합막)

  • Cho, Kook-Jin;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.19 no.1
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    • pp.21-27
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    • 2016
  • Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

Poly(arylene ether ketone) block copolymer prepared through sulfonation process for polymer electrolyte membrane fuel cell (술폰화 공정을 통해 제조한 고분자 전해질형 연료전지용 폴리(아릴렌 이서 케톤) 블록 코폴리머)

  • Jang, Hyeri;Nahm, Keesuk;Yoo, Dongjin
    • Journal of Energy Engineering
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    • v.25 no.3
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    • pp.66-72
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    • 2016
  • In this study, a sulfonated poly(arylene ether ketone) block copolymer was prepared from hydrophilic oligomer and hydrophobic oligomer. The structure of the prepared membrane was characterized by $^1H$-NMR, FT-IR and GPC. The $M_w$(weight-average molecular weights) of the polymer was $209,700g\;mol^{-1}$ and the molecular weight distribution($M_w/M_n$) of 1.25 was obtained. The prepared membrane showed excellent thermal stability with gradual weight loss up to $200^{\circ}C$. The proton conductivity of SPAEK block copolymer reached the maximum of $9.0mS\;cm^{-1}$ at $90^{\circ}C$ under 100% relative humidity (RH). From the observed results, it is necessary to do more aggressive attempt to study the possibility of application as an ion-conductive composite electrolyte.