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Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamamoto, Kazuya*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
Journal of the Electrochemical Society, 161(9), p.F889 - F893, 2014/06
Times Cited Count：21 Percentile：61.11(Electrochemistry)Graft-type anion-conducting electrolyte membranes (AEMs) with imidazolium cations on graft polymers were synthesized through radiation-induced graft polymerization of 
-vinylimidazole (NVIm) on poly(ethylene-co-tetrafluoroethylene) (ETFE) films, followed by -propylation and ion-exchange reactions. The -propylation proceeded quantitatively, whereas the ion-exchange reactions in 1 M KOH at 60
C were accompanied by partial 
-elimination of the imidazolium cations(AEM2), which exhibited an ion-exchange capacity (IEC) of 0.85 mmol g
and ionic conductivity of 10 mS cm. AEM2 showed alkaline stability at 60C but it gradually degraded at 80C for ca. 150 h. The copolymer-type AEM (AEM3) with an IEC of 1.20 mmol g was prepared through the copolymerization of NVIm with styrene on ETFE films, followed by the same -propylation and ion-exchange reactions. AEM3 was shown higher alkaline durability in 1 M KOH at 80C. As a result, it exhibited higher conductivity (
10 mS cm) for 250 h. Therefore, alkylimidazolium cations in copolymer grafts are a promising anion conducting group for alkaline-durable AEMs. A maximum power density of 75 mW cm
is obtained for AEM3 in a direct hydrazine hydrate fuel cell.
Koshikawa, Hiroshi; Yoshimura, Kimio; Sinnananchi, W.; Yamaki, Tetsuya; Asano, Masaharu; Yamamoto, Kazuya*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
Macromolecular Chemistry and Physics, 214(15), p.1756 - 1762, 2013/08
Times Cited Count：15 Percentile：45.22(Polymer Science)Graft-type anion-conducting polymer electrolyte membranes were prepared by the radiation-induced graft polymerization of chloromethylstyrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization with trimethylamine to evaluate the counter anion effects on fuel cell properties. The hydroxide form was maintained in -saturated water to prevent the bicarbonate formation. The hydroxide form showed conductivity and water uptake four and two times higher than the chloride and bicarbonate forms. The hydroxide form is thermally and chemically less stable, resulting in the tendency to absorb water and to convert to the bicarbonate form.
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
ECS Transactions, 50(2), p.2075 - 2081, 2012/10
no abstracts in English
-ray pre-irradiation graftingKoshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.240 - 241, 2011/06
The anion-exchange membranes (AEM) for fuel cells were prepared by the radiation-induced graft polymerization of chloromethylstyrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization of the grafts with trimethylamine. When the AEM were treated in 1M-KOH and washed with N
-saturated water, the membranes with chloride form can be converted quantitatively to hydroxide form. However, the hydroxide form was easily converted to the bicarbonate form by the treatment in non-bubbled (CO dissolved) water. When we introduced the crosslinkers in polymer grafts, which is proved to be very effective in the proton conducting PEM having a poly(styrenesulfonic acid) grafts, the grafted AEM with both chloride and hydroxide forms showed only slight decrease of water uptake. It should be noted that AEM with hydroxide form showed very high tendency to absorb water.
Asazawa, Koichiro*; Yamamoto, Kazuya*; Yamada, Koji*; Tanaka, Hirohisa*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Atanassov, P.*
ECS Transactions, 33(1), p.1751 - 1755, 2010/10
CoPPyC were analyzed with X-ray adsorption fine structure (XAFS) measurements. Acid-treated CoPPyC (CoPPyC-AT) has higher activity than PPyC for oxygen reduction reaction. From the analysis of EXAFS of Co, CoPPyC electrocatalysts as synthesized consist of two peaks. The peak around 1.6 
was assigned to Co-N and/or Co-O shells. The second peak around 2.6 was assigned to Co-O-Co shells originated from cobalt hydroxide. CoPPyC-AT showed only one peak of assigned to Co-N and/or Co-O, and it indicates that cobalt hydroxide is removed by acid treatment. It is clear that a coexistence of cobalt and nitrogen in CoPPyC-AT shows specific performance, and pyrolysis is not necessary to make correlation of Co-N.
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on an ethylene-tetrafluoroethylene copolymer by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. The crosslinker effect was investigated in terms of membrane preparation and performance of a hydrazine fuel cell. The quaternization ratio appeared to decrease as the concentration of divinylbenzene (DVB) in the CMS grafting solution increased. Importantly, the crosslinker lowered the water uptake of the resulting membranes in the Cl
and OH forms, possibly thereby restricting excessive swelling during the fuel-cell operation.
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on an ethylene-tetrafluoroethylene copolymer by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. The crosslinker effect was investigated in terms of membrane preparation and performance of a hydrazine fuel cell. The quaternization ratio appeared to decrease as the concentration of divinylbenzene (DVB) in the CMS grafting solution increased. Importantly, the crosslinker lowered the water uptake of the resulting membranes in the Cl and OH forms, possibly thereby restricting excessive swelling during the fuel-cell operation.
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on -ray crosslinked ethylene-tetrafluoroethylene copolymer (ETFE) by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. Little effect of radiation crosslinking was observed for the degree of CMS grafting and the quaternization ratio. Interestingly, however, the crosslinking structure in ETFE was found to lower water uptake of the resulting membranes in the OH form, thereby restricting excessive swelling during hydrazine-fuel-cell operation.
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on an ethylene-tetrafluoroethylene copolymer by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. The crosslinker effect was investigated in terms of membrane preparation and performance of a hydrazine fuel cell. The quaternization ratio appeared to decrease as the concentration of divinylbenzene (DVB) in the CMS grafting solution increased. Importantly, the crosslinker lowered the water uptake of the resulting membranes in the Cl and OH forms, possibly thereby restricting excessive swelling during the fuel-cell operation.
Maekawa, Yasunari; Koshikawa, Hiroshi; Sinnananchi, W.; Yamamoto, Kazuya*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non-expensive platinum free metals are used as a electrode catalysts, can be prepared using radiation techniques. The grafted AEM were prepared by the radiation-induced graft polymerization of chloromethylstyrene (CMS) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization of the grafts with trimethylamine. When the grafted AEM with different counter anions, Cl, OH, and HCO
(AEM-Cl, AEM-OH, AEM-HCO) were prepared; then, the polymer electrolyte properties were compared with each other. Compared with proton conducting PEM such as Nafion, AEM-Cl showed almost the same conductivity, while the AEM-OH showed two times higher conductivity and water uptake. The conductivity and water uptakes of the grafted AEM increased drastically with the decreases of acidity of the counter anions.
Maekawa, Yasunari; Sinnananchi, W.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non precious metals are used as a electrode catalyst, were prepared using radiation techniques. The grafted AEM were prepared by the radiation-induced graft polymerization of chloromethylstyrene (CMS) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization of the grafts with trimethylamine. When the grafted AEM were treated in 1M-KOH and washed with N-saturated water, the membranes with chloride form (ETFE-TMAMS(Cl)) can be converted quantitatively to hydroxide form (ETFE-TMAMS(OH)) without the formation of the bicarbonate form. The grafted AEM with IEC of 2.0 mmol/g showed the maximum power density of more than 300 mW/cm
with stability for 400 hours under the operation at 80C.
-ray pre-irradiation grafting; Effect of the structure of quaternary ammonium ionsKoshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We investigated the effect of the length of the linear chain on the structure of quaternary ammonium ions on the membrane properties such as durability of ion conductivity. Graft polymerization was performed by immersing the pre-irradiated ETFE film in the CMS solution. The ETFE-g-CMS film was then quaternized in four different tertiary amines, that is, trimethylamine (n = 1), dimethylethylamine (n = 2), n-butyldimethylamine (n = 4) and n-hexyldimethylamine (n = 6) solutions. The n dependence of the OH conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution. When n increased from 1 to 6, the OH conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. The chemical durability seemed to increase eight-fold at the same time. The chemical attack by hydroxyl radicals on the quaternary ammonium ions would be controlled by hydrophobicity and steric hindrance of the alkyl group.
Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We prepared new membrane materials by radiation techniques for application in alkaline fuel cells, especially in direct hydrazine fuel cells. Our unique method based on radiation-induced crosslinking and grafting, which previously proved to be an effective way of obtaining high-performance proton exchange membranes, has been used for developing anion-exchange membranes superior to those by the conventional radiation grafting. New attempts here were the -ray crosslinking of the poly(ethylene-co-tetrafluoroethylene) base film and chloromethylstyrene grafting with addition of a chemical crosslinker, divinylbenzene. The crosslinked anion-exchange membranes exhibited high OH conductivity in their fully hydrated state and low water uptake, implying practical usefulness of our method.
Yoshimura, Kimio; Sinnananchi, W.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
Yoshimura, Kimio; Sinananwanich, W.*; Koshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
