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

https://doi.org/10.1007/s11664-016-5259-x

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

https://doi.org/10.1021/jp507534f

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

https://doi.org/10.1149/05002.2075ecs

no abstracts in English

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

https://doi.org/10.1149/1.3484664

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.

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 -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.

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 -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.

Synthesis of alkaline durable anion exchange membranes by radiation-induced grafting for hydrazine hydrate fuel cell

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

Development of anion-exchange membranes by radiation grafting; Effect of crosslinker for swelling

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

Graft-type anion conducting membranes consisting of iminium cation for alkaline durable fuel cells

Maekawa, Yasunari; Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*

no journal, , 

Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non precious metals are used as an electrode catalyst, have been developing by radiation techniques. AEMs having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole or the copolymerizaiton with styrene onto ETFE film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 80 C. The AEM consisting of the homopolymer grafts showed alkaline stability at 80 C for ca. 150 hours. In contrast, the copolymer (1:1 molar ratio) grafts type AEM kept its ion conductivity above 10 mS/cm in 1M KOH at 80 C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.

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

Koshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*

no journal, , 

We investigated the effect of a linear carbon chain length (n) in quaternary ammonium ions, on the durability of ion conductivity of anion exchange membrane. The poly(ethylene-co-tetrafluoroethylene) grafted chloromethylstyrene film was 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 ion conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution (3% hydrogen peroxide+ 4 ppm iron sulfate) at 80 C for 2 h. When n increased from 1 to 6, the ion conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. Interestingly, 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.