# US 7,745,037 B2 · Membrane electrode assembly for solid polymer electrolyte fuel cell

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- Number: US 7,745,037 B2
- Document ID: US7745037B2
- Status: Granted
- Kind: B2
- Application number: 11/265,463
- Filed: 2005-11-01
- Published: 2006-05-04
- Granted: 2010-06-29
- Earliest claimed: 2004-11-04
- Assignees: Honda Motor Co., Ltd.
- Inventors: Junji Matsuo; Kaoru Fukuda
- Web page: https://patentgrep.com/patent/US7745037B2

## CPC

- H01M 8/1004: characterised by membrane-electrode assemblies [MEA] (H01M8/12 takes precedence)
- H01M 4/881: {Electrolytic membranes}
- H01M 4/921: {Alloys or mixtures with metallic elements}
- H01M 4/926: {on carbon or graphite}
- H01M 4/625: {Carbon or graphite}
- H01M 4/8657: {layered}
- H01M 2004/021: {Physical characteristics, e.g. porosity, surface area}
- Y02E 60/10: Energy storage using batteries
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A membrane electrode assembly for a solid polymer electrolyte fuel cell includes an anode electrode, a cathode electrode, and a polymer electrolyte membrane sandwiched by the electrodes, the catalyst layer of the cathode electrode containing a catalyst supporting particle in which a precious metal is supported on heat-treated carbon black or activated carbon, an ion conductive material, and a crystalline carbon fiber. Heat treatment is preferably applied at 2,500 to 3,000° C. (degrees Celsius). The membrane electrode assembly provides superior power generation performance.

## Claims

### Claim 1

A membrane electrode assembly of a solid polymer electrolyte fuel cell, comprising:
an anode electrode;
a cathode electrode; and
a polymer electrolyte membrane sandwiched by the electrodes;
wherein each electrode is formed from a catalyst layer adjacent the polymer electrolyte membrane, and from a gas diffusion layer adjacent the catalyst layer, and
wherein the catalyst layer of the cathode electrode contains a catalyst supporting particle in which a precious metal is supported on heat-treated carbon black or activated carbon subjected to heat processing at a temperature in a range of 2,500 to 3,000° C., an ion conductive material, and crystalline carbon fibers,
wherein an amount of the crystalline carbon fibers is 20 to 60% by mass relative to an overall mass of the catalyst supporting particle, and
wherein the catalyst layer of the cathode electrode has a pore volume for pores with a diameter in a range of 0.01 to 2.0 μm of at least 2.8 μl/cm2/mg•metal, and has a pore volume for pores with a diameter in a range of 0.01 to 0.15 μm of at least 1.7 μl/cm2/mg•metal.

### Claim 2 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein the crystalline carbon fibers are filamentous carbon fibers.

### Claim 3 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein, for the crystalline carbon fiber, the mean lattice plane spacing of the [002] plane is 0.69 nm or less, the fiber diameter is 0.1 to 0.5 the fiber length is 10 to 40 μm, the bulk density is 0.02 to 0.10 g/cm3, the specific surface area is 5 to 20 m2/g, and the specific resistance is 0.025 Ω•cm or less.

### Claim 4 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein the specific surface area is 300 to 1,600 m2/g before the carbon black or activated carbon is heat-treated, it is 160 m2/g or less after it is heat-treated, and the reduction rate of the specific surface area before and after it is heat-treated is 80% or more.

### Claim 5 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein the [002] mean lattice plane spacing of the carbon black or activated carbon is 0.340 to 0.349 nm and one or two crystallization peaks exist between 24 to 28 in 2θ/degree, in the X-ray diffraction measurement.

### Claim 6 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein the precious metal is platinum or a platinum alloy, and the support rate of the precious metal relative to overall mass of the catalyst supporting particle is 40 to 60% by mass after the support, the particle size of the supported platinum or platinum alloy is 2 to 5 nm, the specific surface area is 75 to 100 m2/g, and one or two crystallization peaks exist between 24 to 28 in 2θ/degree in the X-ray diffraction measurement.

### Claim 7 (depends on 1)

The membrane electrode assembly of the solid polymer electrolyte fuel cell according to claim 1 wherein the metal surface area is 40 to 120 m2/g when the precious metal supports platinum or a platinum alloy.