# US 2016/0064755 A1 · Self-wetting membrane electrode unit and fuel cell having such a unit

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- Number: US 2016/0064755 A1
- Document ID: US20160064755A1
- Status: Published application
- Kind: A1
- Application number: 14/888,361
- Filed: 2014-03-17
- Published: 2016-03-03
- Earliest claimed: 2013-04-30
- Assignees: Aktiengesellschaft
- Applicants: Aktiengesellschaft
- Inventors: Gerold HUBNER; Hannes SCHOLZ
- Web page: https://patentgrep.com/patent/US20160064755A1

## CPC

- H01M 8/04291: Arrangements for managing water in solid electrolyte fuel cell systems (H01M8/04119 takes precedence)
- H01M 4/861: {with a gradient in the porosity}
- H01M 4/8636: {with a gradient in another property than porosity (H01M4/861 takes precedence)}
- H01M 4/8657: {layered}
- H01M 8/0241: Composites
- H01M 8/1004: characterised by membrane-electrode assemblies [MEA] (H01M8/12 takes precedence)
- H01M 8/1016: characterised by the electrolyte material (H01M8/12 takes precedence)
- H01M 8/1053: consisting of layers of polymers with at least one layer being ionically conductive
- H01M 8/1067: characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
- H01M 2008/1095: {Fuel cells with polymeric electrolytes}
- H01M 2300/0082: Organic polymers
- H01M 2300/0094: in the form of layered products, e.g. coatings
- 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 and fuel cell having such assembly. The membrane electrode assembly has a polymer electrolyte membrane, two catalytic electrodes in contact with the polymer electrolyte membrane on both sides, namely an anode and a cathode, and two gas diffusion layers directly or indirectly adjoining the electrodes, namely an anode-side gas diffusion layer and a cathode-side gas diffusion layer. At least one of the gas diffusion layers may optionally feature a microporous layer facing the polymer electrolyte membrane. The sequence of layers is anode-side gas diffusion layer, anode-side microporous layer, anode, polymer electrolyte membrane, cathode, cathode-side microporous layer, cathode-side gas diffusion layer. A relative hydrophobicity of at least two of these components and/or a hydrophobicity gradient within at least one of these components, and a relative pore structure having pore size and/or porosity of at least two of these components and/or a gradient within the pore structure of at least one of these components, is designed in such a way that it promotes the transport of water via the polymer electrolyte membrane, preferably from the cathode side to the anode side.

## Claims

### Claim 1

A membrane electrode assembly for a fuel cell comprising
a polymer electrolyte membrane,
two catalytic electrodes in contact with the polymer electrolyte membrane on both sides, namely an anode and a cathode, and
two gas diffusion layers directly or indirectly adjoining the electrodes, namely an anode-side gas diffusion layer and a cathode-side gas diffusion layer, wherein at least one of the gas diffusion layers may optionally feature a microporous layer facing a polymer electrolyte membrane,
wherein
in the sequence of layers, comprising anode-side gas diffusion layer anode-side microporous layer/anode/polymer electrolyte membrane/cathode/cathode-side microporous layer/cathode-side gas diffusion layer:
a relative hydrophobicity of at least two of these components and/or a hydrophobicity gradient within at least one of these components and/or
a relative pore structure, comprising porosity and/or pore size, of at least two of these components and/or a gradient within the pore structure of at least one of these components
is designed in such a way that it promotes the transport of water via the polymer electrolyte membrane.

### Claim 2 (depends on 1)

The membrane electrode assembly according to claim 1, wherein at least one of the hydrophobicity and pore structure within the layer sequence is designed in such a way that it promotes the transport of water via the polymer electrolyte membrane from the cathode side to the anode side.

### Claim 3 (depends on 1)

The membrane electrode assembly according to claim 1 wherein at least one of the relative hydrophobicity and hydrophobicity gradient is designed in such a way that the hydrophobicity increases in the direction of the cathode-side gas diffusion layer.

### Claim 4 (depends on 1)

The membrane electrode assembly according to claim 1, wherein at least one of the relative porosity, pore size, and their gradient is designed in such a way that at least one of the porosity and pore size increases in the direction of the cathode-side gas diffusion layer.

### Claim 5 (depends on 1)

The membrane electrode assembly according to claim 1, wherein at least one of the hydrophobicity, porosity, and pore size of at least one of the anode-side components, comprising the anode-side gas diffusion layer, the anode-side microporous layer, the anode, and one anode side of the polymer electrolyte membrane, is smaller than at least one of the hydrophobicity, porosity, and pore size of the corresponding cathode-side component, comprising the cathode-side gas diffusion layer, the cathode-side microporous layer, the cathode, and the cathode side of the polymer electrolyte membrane.

### Claim 6 (depends on 1)

The membrane electrode assembly according to claim 1, wherein the polymer electrolyte membrane features at least two membrane layers, wherein at least one of the hydrophobicity, pore size, and porosity of an anode-side membrane layer is smaller than at least one of the hydrophobicity, pore size, and porosity of a cathode-side membrane layer.

### Claim 7 (depends on 6)

The membrane electrode assembly according to claim 6, wherein the different hydrophobicities of the at least two membrane layers are generated by at least one of various concentrations of ionic groups in the polymer electrolyte material of the membrane layers and various concentrations of a non-ionic, particularly hydrophobic, material that is admixed to the polymer electrolyte material.

### Claim 8 (depends on 1)

The membrane electrode assembly according to claim 1, wherein the cathode features at least two layers, wherein at least one of the hydrophobicity, pore size, and porosity of a layer facing the polymer electrolyte membrane smaller than those of a layer facing away from the polymer electrolyte membrane and/or that the anode features at least two layers, wherein at least one of the hydrophobicity, pore size, and porosity of a layer facing the polymer electrolyte membrane is larger than those of a layer facing away from the polymer electrolyte membrane.

### Claim 9 (depends on 1)

The membrane electrode assembly according to claim 1, wherein the hydrophobicity of at least one of the anode and cathode, or their layers is adjusted with the use of a polymer binder with the corresponding hydrophobicity and/or with a variable share of a non-ionic, particularly hydrophobic, material, which is admixed to the polymer binder.

### Claim 10 (depends on 1)

The membrane electrode assembly according to claim 1, wherein the hydrophobicity of at least one of the gas diffusion layers and their microporous layers is adjusted by coating at least one of the substrate of the gas diffusion layers and their microporous layers with a material of the corresponding hydrophobicity or by selecting a substrate for at least one of the gas diffusion layers and their microporous layers that is made of a material with the corresponding hydrophobicity.

### Claim 11 (depends on 1)

A fuel cell comprising at least one membrane electrode assembly according to claim 1.