Gas diffusion layer for a fuel cell

Abstract

The invention relates to a gas diffusion layer (100) for a fuel cell (101, 303), said gas diffusion layer (100) comprising: - a main part (103, 201, 207), and - a hydrophobic layer (105), wherein the hydrophobic layer (105) overlaps solely with parts of the surface of the main part (103, 201, 207), and one part of the surface of the main part (103, 201, 207) is not overlapped by the hydrophobic layer (105).

Description

[0001] Description

[0002] title

[0003] Gas diffusion layer for a fuel cell

[0004] The presented invention relates to a gas diffusion layer for a fuel cell, a manufacturing method for a gas diffusion layer and a fuel cell system.

[0005] State of the art

[0006] A fuel cell typically contains a gas diffusion layer (GDL). The GDL's function is to uniformly deliver reaction gases to a membrane or catalytic layer of the fuel cell and to remove any water produced.

[0007] For this purpose, a base body of the GDL is coated with a hydrophobic material to prevent water droplets from accumulating in the base body. This has the disadvantage that only water vapor can be used to humidify the membrane. Liquid water in the cathode supply air cannot therefore be used to maintain membrane humidity.

[0008] Especially at low loads, the usual measures for moistening the membrane are not sufficient.

[0009] Disclosure of the invention

[0010] Within the scope of the invention presented, a gas diffusion layer, a manufacturing method for producing the gas diffusion layer, and a fuel cell system are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the gas diffusion layer according to the invention naturally also apply in connection with the manufacturing method according to the invention and the fuel cell system according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0011] The invention presented serves in particular to provide an improved gas diffusion layer.

[0012] Thus, according to a first aspect of the invention presented, a gas diffusion layer for a fuel cell is presented.

[0013] The proposed gas diffusion layer comprises a base body and a hydrophobic layer, wherein the hydrophobic layer only partially overlies a surface of the base body and a part of the surface of the base body is not overlaid by the hydrophobic layer.

[0014] In the context of the present invention, a base body of a gas diffusion layer is understood to mean, in particular, a porous layer made of, for example, carbon fiber or carbon particles. In particular, a base body can consist of a hydrophilic material, such as carbon paper or carbon fleece.

[0015] In the context of the invention presented, a hydrophobic layer is understood to mean a layer made of a hydrophobic material, such as a plastic.

[0016] The presented invention is based on the principle that only a part or a region of the base body is coated or will be coated with a hydrophobic layer, so that at least one region of the base body is free of the hydrophobic material and, as a result, permeable to liquid water. Accordingly, finely dispersed liquid water, such as that found in a cathode air mass flow, can penetrate the gas diffusion layer and / or humidify it and / or prevent the gas diffusion layer and, if applicable, a membrane connected to the gas diffusion layer from drying out. Accordingly, the presented gas diffusion layer prevents damage to a fuel cell system due to drying out.

[0017] It can be provided that at least one end region of the base body is not overlaid by the hydrophobic layer.

[0018] Since respective end regions, in particular a region of a gas diffusion layer facing a cathode inlet, dry out particularly quickly during operation of a fuel cell system, these regions can be selectively humidified by omitting the hydrophobic layer.

[0019] Accordingly, it can be provided that the gas diffusion layer is permeable to liquid water in an area whose surface is not overlaid by the hydrophobic layer.

[0020] In order to ensure permeability for liquid water and, for example, to wet a membrane in contact with the gas diffusion layer with liquid water, the base body of the gas diffusion layer can consist of a porous material that is in particular not sealed with an additional layer.

[0021] According to a second aspect, the presented invention relates to a manufacturing method for a gas diffusion layer.

[0022] The presented manufacturing process involves coating only a part of a base body with a hydrophobic material.

[0023] The coating of only a part of a base body with a hydrophobic material, i.e. the partial coating of the base body, can be carried out, for example, by spraying, painting, printing or by any other technically suitable application method.

[0024] For example, by printing a pattern of the hydrophobic material onto the base body, particularly precise and selective moistening of the gas diffusion layer by penetrating liquid water can be achieved. In particular, the coating process can involve immersing the base body in a bath of the hydrophobic material, with the base body only being partially immersed in the bath, so that the hydrophobic material only partially covers a surface of the base body, and a portion of the base body's surface is not covered by the hydrophobic material.

[0025] A bath of hydrophobic material enables a continuous coating process, in which, for example, a substrate is unrolled from a roll, cut to a specified size, and pulled through the bath. Of course, the substrate can also be pulled through the bath first and then cut to a specified size.

[0026] It can be provided that the base body is folded at least once and is moved through the hydrophobic material in the folded state.

[0027] By folding the base body into, for example, a U-shape or a V-shape, the respective ends of the base body protrude from the bath when the base body is moved through the bath and therefore cannot be coated.

[0028] It can further be provided that the base body is folded several times so that a large number of areas of the base body are not overlaid by the hydrophobic material.

[0029] A large number of folds enables a complex geometry in which many areas protrude from the bath when the base body is moved through it and therefore cannot be coated.

[0030] According to a third aspect, the presented invention relates to a fuel cell system for converting energy.

[0031] The proposed fuel cell system comprises a plurality of fuel cells, each of which incorporates a possible configuration of the proposed gas diffusion layer. The proposed gas diffusion layer makes the fuel cells of the proposed fuel cell system particularly robust against drying out and / or particularly suitable for partial load operation.

[0032] It may be provided that respective gas diffusion layers in the region of a cathode inlet are not overlaid by the hydrophobic layer.

[0033] Since a gas diffusion layer dries out particularly in the area of ​​a cathode inlet, an area that is not covered by the hydrophobic layer compensates for any drying out behavior in this area.

[0034] Advantages described in detail with respect to the gas diffusion layer for a fuel cell according to the first aspect of the invention equally apply to the manufacturing method for a gas diffusion layer according to the second aspect of the invention and the fuel cell system for converting energy according to the third aspect of the invention.

[0035] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0036] They show:

[0037] Figure 1 is a schematic representation of a fuel cell with a possible design of the presented gas diffusion layer,

[0038] Figure 2 shows a possible embodiment of the presented manufacturing process, and

[0039] Figure 3 shows a possible design of the presented fuel cell system.

[0040] Figure 1 shows a fuel cell 101 with gas diffusion layers 100. The gas diffusion layers 100 each comprise a base body 103, which is partially coated with a hydrophobic layer 105

[0041] Accordingly, the gas diffusion layer 100 comprises a first region 107 in which no hydrophobic layer 105 rests or is present on the base body 103 and a second region 109 which is coated with the hydrophobic layer 105.

[0042] Accordingly, water particles 111 migrate from a bipolar plate 113 through the area 107 to a membrane 117 coated with catalyst layers 115 and keep it moist.

[0043] The first region 107 can, for example, be left out at a cathode inlet, or in a region where an active region of the membrane ends and where no catalyst is present, since no production of liquid water takes place in this region.

[0044] Figure 2 shows a manufacturing method 200.

[0045] In the manufacturing method 200, a first base body 201 is moved through a bath of hydrophilic material 203. The base body 201 is held at its free end 205 so that it protrudes from the hydrophilic material 203 and is therefore not coated with the hydrophilic material 203.

[0046] A second base body 207 was folded in a V-shape so that two free ends 209, 211 protrude from the hydrophilic material 203 and are therefore not coated with the hydrophilic material 203.

[0047] Figure 3 shows a fuel cell system 300. The fuel cell system 300 comprises a fuel cell stack 301 with fuel cells 303, each of which has a gas diffusion layer 100 as shown in Figure 1.

Claims

Claims 1. A gas diffusion layer (100) for a fuel cell (101, 303), the gas diffusion layer (100) comprising: a base body (103, 201, 207), a hydrophobic layer (105), the hydrophobic layer (105) only partially overlying a surface of the base body (103, 201, 207) and a part of the surface of the base body (103, 201, 207) not being overlaid by the hydrophobic layer (105).

2. Gas diffusion layer (100) according to claim 1, characterized in that at least one end region (205, 209, 211) of the base body (103, 201, 207) is not overlaid by the hydrophobic layer (105).

3. Gas diffusion layer (100) according to claim 1 or 2, characterized in that the gas diffusion layer (100) is permeable to liquid water in a region (107) whose surface is not overlaid by the hydrophobic layer (105).

4. Manufacturing method (200) for a gas diffusion layer (100), the manufacturing method (200) comprising: Coating only a part of a base body (103, 201, 207) with a hydrophobic material (203).

5. Manufacturing method (200) according to claim 4, characterized in that the coating comprises: Immersing the base body (103, 201, 207) in a bath of the hydrophobic material (203), wherein the base body (103, 201, 207) is immersed in the bath only in certain regions, so that the hydrophobic material (203) only partially overlies a surface of the base body (103, 201, 207) and a part of the surface of the base body (103, 201, 207) is not overlaid by the hydrophobic material (203).

6. Manufacturing method (200) according to claim 4 or 5, characterized in that the base body (103, 201, 207) is folded at least once and is moved through the hydrophobic material (203) in the folded state.

7. Manufacturing method (200) according to one of claims 4 to 6, characterized in that the base body (103, 201, 207) is folded several times so that a plurality of regions of the base body (103, 201, 207) are not overlaid by the hydrophobic material (203).

8. Manufacturing method (200) according to one of claims 4 to 7, characterized in that the base body (103, 201, 207) is unrolled from a roll.

9. A fuel cell system (300) for converting energy, wherein the fuel cell system (300) comprises a plurality of fuel cells (101, 303), each comprising a gas diffusion layer (100) according to one of claims 1 to 3.

10. Fuel cell system (300) according to claim 9, characterized in that respective gas diffusion layers (100) in the region of a cathode inlet are not overlaid by the hydrophobic layer (105).

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