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Journal Articles

Structure of active sites of Fe-N-C nano-catalysts for alkaline exchange membrane fuel cells

Kishi, Hirofumi*; Sakamoto, Tomokazu*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Kato, Takeshi*; Zulevi, B.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Matsumura, Daiju; et al.

Nanomaterials (Internet), 8(12), p.965_1 - 965_13, 2018/12

 Times Cited Count:7 Percentile:44.73(Chemistry, Multidisciplinary)

Journal Articles

Study of catalytic reaction at electrode-electrolyte interfaces by a CV-XAFS method

Kusano, Shogo*; Matsumura, Daiju; Asazawa, Koichiro*; Kishi, Hirofumi*; Sakamoto, Tomokazu*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Mizuki, Junichiro*

Journal of Electronic Materials, 46(6), p.3634 - 3638, 2017/06

 Times Cited Count:2 Percentile:16.8(Engineering, Electrical & Electronic)

Journal Articles

Operando XAFS study of carbon supported Ni, NiZn, and Co catalysts for hydrazine electrooxidation for use in anion exchange membrane fuel cells

Sakamoto, Tomokazu*; Matsumura, Daiju; Asazawa, Koichiro*; Martinez, U.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Tamura, Kazuhisa; Nishihata, Yasuo; Tanaka, Hirohisa*

Electrochimica Acta, 163, p.116 - 122, 2015/05

 Times Cited Count:47 Percentile:82.38(Electrochemistry)

Journal Articles

In situ XAFS and HAXPES analysis and theoretical study of cobalt polypyrrole incorporated on carbon (CoPPyC) oxygen reduction reaction catalysts for anion-exchange membrane fuel cells

Asazawa, Koichiro*; Kishi, Hirofumi*; Tanaka, Hirohisa*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Saputro, A. G.*; Nakanishi, Hiroshi*; Kasai, Hideaki*; Artyushkova, K.*; et al.

Journal of Physical Chemistry C, 118(44), p.25480 - 25486, 2014/11

 Times Cited Count:14 Percentile:47.31(Chemistry, Physical)

Journal Articles

Electrooxidation of hydrazine hydrate using Ni-La catalyst for anion exchange membrane fuel cells

Sakamoto, Tomokazu*; Asazawa, Koichiro*; Martinez, U.*; Halevi, B.*; Suzuki, Toshiyuki*; Arai, Shigeo*; Matsumura, Daiju; Nishihata, Yasuo; Atanassov, P.*; Tanaka, Hirohisa*

Journal of Power Sources, 234, p.252 - 259, 2013/07

 Times Cited Count:64 Percentile:88.65(Chemistry, Physical)

Journal Articles

Alkaline durable anion exchange membranes based on graft-type fluoropolymer films for hydrazine hydrate fuel cell

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

Journal Articles

Preparation of anion-exchange membranes for fuel cell applications by $$gamma$$-ray pre-irradiation grafting

Koshikawa, 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$$_{2}$$-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$$_{2}$$ 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.

Journal Articles

XAFS analysis of unpyrolyzed CoPPyC oxygen reduction catalysts for Anion-Exchange Membrane Fuel Cells (AMFC)

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 ${AA}$ was assigned to Co-N and/or Co-O shells. The second peak around 2.6 ${AA}$ 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.

Oral presentation

Preparation of anion-exchange membranes by radiation grafting and their fuel cell performance

Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*

no journal, , 

no abstracts in English

Oral presentation

Preparation of anion-exchange membranes using ionizing radiation and their cell testing

Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamaguchi, Susumu*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*

no journal, , 

Anion-exchange membranes based on poly(ethylene-co-tetrafluoroethylene) (ETFE) were prepared by the $$gamma$$-ray graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization. The degree of grafting increased during the course of reaction for up to 8 h. We obtained higher degree of grafting as the pre-irradiation dose became higher. The highest degree of grafting reached 101% at a dose of 50 kGy for 8 h. The hydroxide ion conductivity was 0.044 S/cm at room temperature and a relative humidity of 100%. This value is higher than or comparable to that of the previous radiation-grafted anion-exchange membranes.

Oral presentation

Preparation of anion-exchange membranes by radiation grafting

Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*

no journal, , 

no abstracts in English

Oral presentation

Preparation of anion-exchange membranes by radiation grafting and their cell testing; Effect of crosslinker

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 $$gamma$$-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.

Oral presentation

Preparation of anion-exchange membranes using ionizing radiation and their cell testing

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 $$gamma$$-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.

Oral presentation

Preparation of anion-exchange membranes by radiation grafting

Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*

no journal, , 

no abstracts in English

Oral presentation

Development of anion-exchange membranes by using crosslinked ETFE films

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

Oral presentation

Preparation of anion-exchange membranes using ionizing radiation and their cell testing; Swelling-suppression effect due to crosslinking of ETFE base films

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 $$gamma$$-ray crosslinked ethylene-tetrafluoroethylene copolymer (ETFE) by $$gamma$$-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.

Oral presentation

Development of anion-exchange ETFE membranes by radiation grafting

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 $$gamma$$-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.

Oral presentation

Fuel cell performance of anion exchange polymer electrolyte membranes prepared by radiation-induced grafting

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$$_{2}$$-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$$^{2}$$ with stability for 400 hours under the operation at 80$$^{circ}$$C.

Oral presentation

Preparation of anion-exchange membranes for fuel cell applications by $$gamma$$-ray pre-irradiation grafting; Effect of the structure of quaternary ammonium ions

Koshikawa, 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.

Oral presentation

Development of anion-exchange polymer electrolyte membranes by radiation techniques; Radiation-induced crosslinking and grafting

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 $$gamma$$-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.

29 (Records 1-20 displayed on this page)