Electrode for solid polymer fuel cell

• US 20040115517A1
• Filed: 11/07/2003
• Published: 06/17/2004
• Est. Priority Date: 11/08/2002
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Inai, Shigeru, Watanabe, Shinya, Kohyama, Katsuhiko, Iwasawa, Chikara, Tani, Masaki, Fukuda, Kaoru, Shinkai, Hiroshi, Kaji, Hayato, Muro, Takeshi
• Granted Patent: US 7,232,627 B2
• Time in Patent Office: Days
• US Class Current: 429/44
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/8636 with a gradient in another property than porosity H01M4/861 takes precedence
• CPC Class Codes: H01M 4/8821 Wet proofing
• CPC Class Codes: H01M 4/921 Alloys or mixtures with metallic elements
• CPC Class Codes: H01M 4/926 on carbon or graphite
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04104 Regulation of differential pressures
• CPC Class Codes: H01M 8/04291 Arrangements for managing water in solid electrolyte fuel cell systems H01M8/04119 takes precedence
• CPC Class Codes: H01M 8/1007 with both reactants being gaseous or vaporised H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An electrode for a solid polymer fuel cell includes a gas diffusion layer, an electrode catalyst layer disposed between a solid polymer membrane of the fuel cell and the gas diffusion layer, and a water-holding layer disposed between the gas diffusion layer and the electrode catalyst layer. Under high-relative humidity conditions of reaction gases, flooding can be prevented because the electrode catalyst layer is made porous, while under low-relative humidity conditions of reaction gases, sufficient water contents can be stably provided thanks to the water-holding layer so that proton conductivity of the solid polymer membrane can be maintained appropriately. Consequently, high-performance and high-durability electrode and membrane electrode assembly for a solid polymer fuel cell can be provided such that the performance and the durability thereof are not affected by change in relative humidity in reactant gases supplied to the solid polymer fuel cell.

Claims

1. An electrode for a solid polymer fuel cell comprising:

a gas diffusion layer for uniformly diffusing reactant gases;

an electrode catalyst layer disposed between a solid polymer membrane of the fuel cell and the gas diffusion layer to support a catalyst for reaction of the diffused reactant gases; and

a water-holding layer disposed between the gas diffusion layer and the electrode catalyst layer to enhance a water-retaining capability of the gas diffusion layer,

wherein the electrode catalyst layer is made porous to facilitate drainage of water from the electrode catalyst layer.

2. An electrode according to claim 1, wherein the gas diffusion layer has a moisture content ranging between 50% and 90% inclusive, the moisture content being obtained by an equation:

3. An electrode according to claim 1, wherein a differential pressure of the reactant gases calculated from two pressures measured at places upstream and downstream of the gas diffusion layer when a predetermined flow rate of the reactant gases pass through the gas diffusion layer ranges between 60 mmH₂O and 120 mmH₂O inclusive.

4. An electrode according to claim 1, fiber including a water-repellent layer provided between the water-holding layer and the gas diffusion layer to facilitate drainage of water from the gas diffusion layer.

5. An electrode according to claim 1, wherein the electrode catalyst layer includes a catalyst, a carbon powder for supporting the catalyst, an ion conductive polymer, and a crystalline carbon fiber;

and

wherein the gas diffusion layer includes, in sequence from an electrode catalyst layer side;

a water-repellent layer containing an ion conductive polymer, a carbon powder and a crystalline carbon fiber; and

a carbon cloth layer.

6. A membrane electrode assembly for a solid polymer fuel cell comprising:

a pair of electrodes; and

a solid polymer membrane disposed between the electrodes, wherein at least one of the electrodes includes;

a gas diffusion layer for uniformly diffusing reactant gases;

an electrode catalyst layer disposed between the solid polymer membrane and the gas diffusion layer to support a catalyst for reaction of the diffused reactant gases; and

a water-holding layer disposed between the gas diffusion layer and the electrode catalyst layer to enhance a water-retaining capability of the gas diffusion layer,

wherein the electrode catalyst layer is made porous to facilitate drainage of water from the electrode catalyst layer.

7. A membrane electrode assembly according to claim 6, wherein the gas diffusion layer has a moisture content ranging between 50% and 90% inclusive, the moisture content being obtained by an equation:

8. A membrane electrode assembly according to claim 6, wherein a differential pressure of the reactant gases calculated from two pressures measured at places upstream and downstream of the gas diffusion layer when a predetermined flow rate of the reactant gases pass through the gas diffusion layer ranges between 60 mmH₂O and 120 mmH₂O inclusive.

9. A membrane electrode assembly according to claim 6, further including a water-repellent layer provided between the water-holding layer and the gas diffusion layer to facilitate drainage of water from the gas diffusion layer.

10. A membrane electrode assembly according to claim 6, wherein the electrode catalyst layer includes a catalyst, a carbon powder for supporting the catalyst, an ion conductive polymer, and a crystalline carbon fiber;

and

wherein the gas diffusion layer includes, in sequence from an electrode catalyst layer side;

a water-repellent layer containing an ion conductive polymer, a carbon powder and a crystalline carbon fiber; and

a carbon cloth layer.

11. A membrane electrode assembly according to claim 6, a percentage of a charge amount of catalytic substances existing on an interface between the solid polymer membrane and the electrode catalyst layer to a charge amount of all catalytic substances existing in the electrode catalyst layer is 15% or greater, the charge amounts being determined by a cyclic voltammetry.