成果報告書詳細
管理番号20090000000593
タイトル*平成20年度中間年報 固体高分子形燃料電池実用化戦略的技術開発 次世代技術開発 無加湿中温形燃料電池をめざした電解質および電極設計
公開日2010/3/13
報告書年度2008 - 2008
委託先名国立大学法人横浜国立大学
プロジェクト番号P05011
部署名燃料電池・水素技術開発部 燃料電池グループ
和文要約以下本編抜粋:1. 研究開発の内容及び成果等 無加湿中温形燃料電池を開発するために、非水系のプロトン伝導体であるイオン液体に注目している。これまでに80種類以上のブレンステッド酸及び塩基の組み合わせから選別された、diethylmethylammonium trifluoromethanesulfonate [dema][TfO]が開発目標値であるイオン伝導率:10-2-10-1 S/cm、耐熱性:200 °C、開回路での空気極の電位低下が2 mV/h以下を満足する優れた特性を有することを見出した(120 °C におけるイオン導電率43 mScm-1、融点-13 °C、分解温度360 °C、空気極の電位低下は300 h観測されず)。
英文要約In this year, in order to apply diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], to non-humidified intermediated temperature fuel cell as electrolyte, the following research subjects have been explored. (1) Estimation of cluster structure of [dema][TfO] by MD calculation and FT-IR spectrum: We measured FT-IR spectrum of [dema][TfO] and found the absorption peaks corresponding to N-H at 3069 cm-1 and 2799 cm-1. In order to find corresponding structure to these peaks, bulk structure was estimated by MD simulation after calculating the molecular structure of [dema][TfO] by ab initio method. It was found that two cluster structures can be estimated and observed N-H can be reproduced in these structures. (2) Determination of solubility and diffusion coefficient of the reaction gases, H2 and O2, by chronoamperometry: Choronoamperometry was conducted using a Pt electrode at various temperatures to investigate temperature dependence of solubility and diffusion coefficient of the reaction gases (H2 and O2) in [dema][TfO]. The solubility of H2 was lower than that of O2 while the opposite tendency was observed for the diffusion coefficient. In comparison with those of O2 in Nafion, O2 shows lower solubility and higher diffusion coefficient in [dema][TfO]. On the other hand, both solubility and diffusion coefficient of O2 in 1M H2SO4aq are lower. These results suggest that gas crossover of the composite membrane based on [dema][TfO] can be one of the serious drawback. (3) The fabrication of ion gels based on N-phentylmaleimide/styrene alternating copolymer and [dema][TfO]: First, hydroxyl groups was introduced in the end of the phenyl groups to improve the compatibility of the polymer with [dema][TfO]. We found that maximum content of [dema][TfO] increased from 60wt% to 66wt% when all of the phenylmaleimide groups are substituted. However, the ionic conductivity could not be improved. We assumed that strong interaction between polymer chains derived from the hydroxyl groups prevents diffusion of ionic species. Next, oligo-ethylene oxide groups were partially introduced. As increasing the introducing amount, the ionic conductivity at low temperature improved. This may be due to the lower glass transition temperature of oligo-ethylene oxide groups than that of main chain. We confirmed that the ion gels can be obtained until introducing amount of 30% without serious loss in mechanical stability. (4) Non-humidified operation of H2/O2 fuel cell at 120 °C: Conventional composite membranes that we reported were based on sulfonated 5-membered polyimide. Thus, fuel cell could not be operated at high temperature due to its low hydrolytic stability. In this year, sulfonated six-membered polyimide membranes which have better hydrolytic stability were synthesized and employed as a matrix for composite membranes with [dema][TfO]. The composite membranes fabricated by casting method are tough and flexible and show good thermal stability (Td >240 °C) and ionic conductivity. ( = 20 mS cm-1 at 160 °C when [dema][TfO] contents are 67wt%.) On the operation of H2/O2 fuel cell using the composite membrane containing 75wt% of [dema][TfO] at 120 °C, the current density of 200 mA cm-2 could be achieved with the maximum power density of 44 mW cm-2. Further, fuel cell performance at low temperature was also improved.
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