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Nagase K.,Yamanashi University | Nagase K.,Takahata Precision Japan Co. | Motegi H.,Mizuho Information and Research Institute | Yoneda M.,Mizuho Information and Research Institute | And 6 more authors.
ChemElectroChem | Year: 2015

Visualization of the oxygen partial pressure (pO(2)) was performed at the surface of a gas diffusion layer (GDL) and the upper part of the gas-flow channel of the cathode of an operating polymer electrolyte fuel cell (PEFC) with straight flow channels by using an oxygen-sensitive luminescent dye film. The gradient of pO(2) inside a channel was clearly observed, even on the GDL surface across the channel. A numerical simulation was performed to understand the reaction distributions inside the PEFC. By visualization and numerical simulation, the distributions of pO(2), the current density, water concentration, and temperature in the operating PEFC were obtained, and the relationships between the parameters were studied. Supersaturated water inside the cell was found both experimentally and computationally. pO(2) and the water concentration were concluded to be the two most important factors in determining the distribution of power generation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yokota N.,Yamanashi University | Yokota N.,Takahata Precision Japan Co. | Yokota N.,Japan Science and Technology Agency | Ono H.,Yamanashi University | And 10 more authors.
ACS Applied Materials and Interfaces | Year: 2014

A novel series of aromatic block copolymers composed of fluorinated phenylene and biphenylene groups and diphenyl ether (QPE-bl-5) or diphenyl sulfide (QPE-bl-6) groups as a scaffold for quaternized ammonium groups is reported. The block copolymers were synthesized via aromatic nucleophilic substitution polycondensation, chloromethylation, quaternization, and ion exchange reactions. The block copolymers were soluble in organic solvents and provided thin and bendable membranes by solution casting. The membranes exhibited well-developed phase-separated morphology based on the hydrophilic/hydrophobic block copolymer structure. The membranes exhibited mechanical stability as confirmed by DMA (dynamic mechanical analyses) and low gas and hydrazine permeability. The QPE-bl-5 membrane with the highest ion exchange capacity (IEC = 2.1 mequiv g-1) exhibited high hydroxide ion conductivity (62 mS cm-1) in water at 80 °C. A noble metal-free fuel cell was fabricated with the QPE-bl-5 as the membrane and electrode binder. The fuel cell operated with hydrazine as a fuel exhibited a maximum power density of 176 mW cm-2 at a current density of 451 mA cm-2. © 2014 American Chemical Society.

Nishino E.,Daihatsu Motor Co. | Yamada J.,Daihatsu Motor Co. | Asazawa K.,Daihatsu Motor Co. | Yamaguchi S.,Daihatsu Motor Co. | And 4 more authors.
Chemistry Letters | Year: 2016

The properties of anion-exchange membranes composed of fluorinated block copoly(arylene ether)s, QPE-bl-3, were investigated. QPE-bl-3 membranes exhibited high chemical stability under accelerated testing conditions. Reasonably high fuel cell performance was obtained with QPE-bl-3, hydrazine hydrate as a fuel, and non-platinum catalysts. © 2016 The Chemical Society of Japan.

Nagase K.,Yamanashi University | Nagase K.,Takahata Precision Japan Co. | Suga T.,Waseda University | Nagumo Y.,Shimadzu Corporation | And 4 more authors.
Journal of Power Sources | Year: 2015

(Figure Presented). Visualization inside polymer electrolyte fuel cells (PEFCs) for elucidating the reaction distributions is expected to improve the performance, durability, and stability. An oxygen-sensitive film of a luminescent porphyrin was used to visualize the oxygen partial pressures in five straight gas-flow channels of a running PEFC with liquid-water blockages formed at the end of the channels. The blockage greatly lowered and unstabilized the cell voltage. The oxygen partial pressure decreased nearly to 0 kPa in the blocked channel. With a water blockage in a channel, the oxygen partial pressures in the adjacent channels were lowered due to an extra demand of oxygen consumption. When the number of the blocked channels increased, the oxygen partial pressure in the unblocked channels became much lowered. When the water blockages disappeared, the oxygen partial pressures quickly returned to the values before plugging. The influence of the cross flows of air through the gas diffusion layers in straight channels was much smaller than that in serpentine flow channels. © 2014 Elsevier B.V. All rights reserved.

Akiyama R.,Yamanashi University | Yokota N.,Takahata Precision Japan Co. | Nishino E.,Daihatsu Motor Co. | Asazawa K.,Daihatsu Motor Co. | Miyatake K.,Yamanashi University
Macromolecules | Year: 2016

A novel series of anion conductive aromatic copolymers were synthesized from preaminated monomers (2,5-, 3,5-, or 2,4-dichloro-N,N-dimethylbenzylamine), and their properties were investigated for alkaline fuel cell applications. The targeted copolymers (QPE-bl-11a, -11b, and -11c) were synthesized via nickel-mediated Ullmann coupling polymerization, followed by quaternization and ion exchange reactions. Unlike the conventional method involving chloromethylation or bromination, this method provided copolymers with well-defined chemical structure. The hydrophilic components of the copolymers were composed of chemically stable phenylene main chain modified with high-density ammonium groups. Oligo(arylene ether sulfone ketone)s were employed as a hydrophobic block. QPE-bl-11a gave tough and bendable membranes by solution casting. The obtained membrane with the highest ion exchange capacity value (IEC = 2.47 mequiv g-1) showed high hydroxide ion conductivity (130 mS cm-1) in water at 80 °C. The QPE-bl-11a membrane showed reasonable alkaline stability in 1 M KOH aqueous solution for 1000 h at 60 °C. A platinum-free fuel cell was successfully operated with hydrazine as a fuel, the QPE-bl-11a as a membrane, and an electrode binder. The maximum power density of 380 mW cm-2 was achieved at a current density of 1020 mA cm-2 with O2. © 2016 American Chemical Society.

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