Honda Giken Kogyo Kabushiki Kaisha

Honda Motor Co., Ltd.

Teruaki Komiya

Yuji Saito

Masaru Iguchi

Hiroshi Akita

Yoshikatsu Higuchi

Ushio Harada

Tadahiro Shiba

Masahiro Ise

A free-standing membrane electrolyte electrode assembly (ESC) comprises an electrolyte, an anode electrode formed at one end face of the electrolyte, and a cathode electrode formed at the other. The electrolyte is a single crystal having a surface along with oxide ions move or a direction in which the ions move or a polycrystal oriented along a surface along which oxide ions move or in a direction in which the ions move. The surface or the direction is parallel to the thickness direction. The thickness of the electrolyte is 50 to 800 &#x3bc;m and the quotient of the division of the total thickness of the anode electrode and the cathode electrode by the thickness of the electrolyte is 0.1 or less,. The thickness of the ESC is 1 mm or less.

Free-standing membrane electrolyte electrode assembly

An acidic group-containing polymer which has an acidic group such as sulfonic acid group, phosphoric acid group, and phosphonic acid group, and a proton acceptor which has a boiling point at 1 atmosphere higher than 100&#xb0; C. and which functions as a medium for conducting proton dissociated from the acidic group are retained in pores of a porous member. Preferred examples of the proton acceptor include a salt structure composed of an anion and a cation derived from a basic organic compound, a basic organic compound, and a dissociation-facilitating polymer which facilitates dissociation of proton. Any one of the acidic group-containing polymer and the proton acceptor may be retained first, or both may be retained simultaneously.

Proton conductor

A material such as imidazole (nitrogen-containing heterocyclic compound), which has at least one lone pair, is dispersed in a basic solid polymer such as polybenzimidazole. The mole number of imidazole per gram of polybenzimidazole is less than 0.0014 mol, preferably less than 0.0006 mol. The basic solid polymer is impregnated with an acidic inorganic liquid such as phosphoric acid and sulfuric acid to prepare a proton conductive solid polymer electrolyte.

Proton conductive solid polymer electrolyte

A monomer to produce polybenzimidazole is dissolved in polyphosphoric acid. For example, polysulfated phenylene sulfonic acid (acidic group-possessing polymer) is further dissolved in this solution. In this procedure, the acidic group-possessing polymer and the monomer are adsorbed to one another in accordance with the acid-base interaction. When the monomer is polymerized, for example, by means of dehydration polymerization in this state, then polybenzimidazole is synthesized, and the polybenzimidazole and the acidic group-possessing polymer are compatibilized with each other to produce a compatibilized polymer. When the compatibilized polymer is deposited as a solid, and the solid is separated from polyphosphoric acid, then the compatibilized polymer is obtained. A proton conductive solid polymer electrolyte as a final product is manufactured by forming the compatibilized polymer to have a predetermined shape.

Proton conductive solid polymer electrolyte and method for producing the same

The operating condition is set so that a phosphoric acid concentration, at which an amount of reaction product water to lower a concentration of phosphoric acid and an amount of water evaporated from phosphoric acid are equilibrated, can be not less than a reference phosphoric acid concentration to maintain desired performance, when a phosphoric acid fuel cell is operated under a condition where the reaction product water exists as liquid water. Specifically, an equilibrium phosphoric acid concentration-setting system is used to control, if necessary, gas flow rate control systems, gas temperature control systems, and pressure control systems so as to effectively prevent the performance of the phosphoric acid fuel cell and its power generation from being worsened. Accordingly, it is possible to suitably operate the phosphoric acid fuel cell at a low temperature without additional equipments.

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Fujimi, Japan

Teruaki Komiya