KR102288898B1 - Gas diffusion layer of polymer electrolyte membrane fuel cell - Google Patents

Abstract

The gas diffusion layer of the polymer electrolyte membrane according to the present invention is formed so that the contact angle of the reaction product water increases from the air inlet to the air outlet in consideration of the change in the concentration of the reactant and the product in the plane, thereby improving the performance of the fuel cell. can be improved In addition, in the gas diffusion layer according to the present invention, by depositing a hydrophilic material in the region close to the air inlet in the gas diffusion layer, the contact angle is relatively small compared to other regions, so that the reaction product improves the water retention function, so that the electrolyte membrane is formed even under low humidity conditions. Can be well hydrated. In addition, in the gas diffusion layer according to the present invention, the area close to the air outlet in the gas diffusion layer is formed by including a hydrophobic material, so that the contact angle is relatively large compared to other areas, so that water can be easily discharged even if the concentration of water, which is the reaction product, is high. can In addition, the gas diffusion layer according to the present invention maintains a uniform porosity, but by forming only a different contact angle of water, it is easier to manufacture than when the porosity is changed, and there is an advantage in that both the water retention function and the water discharge function can be secured. .

Description

Gas diffusion layer of polymer electrolyte membrane fuel cell

The present invention relates to a gas diffusion layer of a polymer electrolyte membrane fuel cell, and more particularly, the gas diffusion layer is formed so that the contact angle of water increases from an air inlet to an air outlet. It relates to a gas diffusion layer.

In general, a fuel cell is a power generation device that directly converts chemical energy generated by oxidation of fuel into electrical energy. The fuel cell is classified into a solid oxide fuel cell, a molten carbonate fuel cell, and a polymer electrolyte membrane fuel cell according to the type of electrolyte.

The polymer electrolyte membrane fuel cell (PEMFC) is a fuel cell using a polymer capable of permeating hydrogen ions as an electrolyte membrane. The polymer electrolyte membrane fuel cell stack includes a membrane-electrode assembly (MEA) having an electrode layer including an anode and a cathode around an electrolyte membrane, and a gas diffusion layer (GDL) for evenly distributing reactive gases. , and a bipolar plate for supplying reaction gases to the gas diffusion layer and discharging the generated water.

In order to improve the output and efficiency of the polymer electrolyte membrane fuel cell, smooth mass transfer of reactants must be ensured, and management of water resulting from the reaction is very important.

Conventionally, since the concentration change of the reactant and the product is not taken into account by applying a uniform gas diffusion layer, the current density distribution within the reaction area is non-uniform, so there is a negative problem in the performance and durability of the fuel cell.

Korean Patent No. 10-1836648

An object of the present invention is to provide a gas diffusion layer for a polymer electrolyte membrane fuel cell having an in-plane contact angle gradient.

In the gas diffusion layer of the polymer electrolyte membrane fuel cell according to the present invention, the first surface is opposed to the air flow path of the cathode plate, the second surface is disposed to face the membrane electrode assembly, and air is introduced from the first surface The inlet and the air outlet from which air is discharged are provided to be spaced apart from each other, and a gas diffusion layer is formed so that the contact angle of water increases from the air inlet to the air outlet from the first surface, the gas diffusion layer comprising: , The first surface is partitioned by a predetermined first area including the air inlet portion, and a hydrophilic region formed by deposition of a hydrophilic material, and spaced apart from the hydrophilic region by a predetermined distance on the first surface, the air outlet portion It includes a hydrophobic region that is partitioned by a preset second preset area, and is formed of a hydrophobic material so that the contact angle is greater than that of the hydrophilic region.

The hydrophobic region is formed such that the content of the hydrophobic material is gradually increased along the direction of the air flow path so that the contact angle is gradually increased.

The hydrophobic region is formed so that the content of the hydrophobic material increases as the region near the air outlet portion increases, so that the contact angle gradually increases.

The second surface is formed to increase the contact angle from the air inlet to the air outlet.

The porosity of the gas diffusion layer is uniformly formed from the air inlet to the air outlet.

The hydrophilic material includes titanium oxide.

The hydrophobic material includes 5 wt% or more of polytetrafluoroethylene (PTFE).

In the gas diffusion layer of the polymer electrolyte membrane fuel cell according to another aspect of the present invention, the first surface is opposed to the air flow path of the cathode plate, the second surface is disposed to face the membrane electrode assembly, and the air from the first surface is A gas diffusion layer formed so that the inlet air inlet and the air outlet air outlet are diagonally spaced apart from each other, and the contact angle of water increases from the air inlet to the air outlet in the first surface. and, the gas diffusion layer is partitioned by a preset first width including the air inlet on the first surface, and a hydrophilic region formed by depositing a hydrophilic material to have a first contact angle, and in the first surface It is spaced apart from the hydrophilic region by a preset distance, is divided by a preset second preset area including the air outlet, and is formed to include a hydrophobic material to have a third contact angle greater than the first contact angle of the hydrophilic region. a hydrophobic region and an intermediate region disposed between the hydrophilic region and the hydrophobic region to have a second contact angle greater than the first contact angle and smaller than the third contact angle, wherein the hydrophobic region is at the air outlet portion The closer the region is, the more the content of the hydrophobic material increases, so that the contact angle gradually increases, the hydrophilic material includes titanium oxide, and the hydrophobic material contains 5 to 40 wt% of polytetrafluoroethylene (PTFE) and the gas diffusion layer includes a gas diffusion support layer facing the cathode plate and a thin porous layer facing the membrane electrode assembly, and the porosity of the thin porous layer is constant from the air inlet to the air outlet. do.

The gas diffusion layer of the polymer electrolyte membrane according to the present invention is formed so that the contact angle of the reaction product water increases from the air inlet to the air outlet in consideration of the change in the concentration of the reactant and the product in the plane, thereby improving the performance of the fuel cell. can be improved

In addition, in the gas diffusion layer according to the present invention, by depositing a hydrophilic material in the region close to the air inlet in the gas diffusion layer, the contact angle is relatively small compared to other regions, so that the reaction product improves the water retention function, so that the electrolyte membrane is formed even under low humidity conditions. Can be well hydrated.

In addition, in the gas diffusion layer according to the present invention, the area close to the air outlet in the gas diffusion layer is formed by including a hydrophobic material, so that the contact angle is relatively large compared to other areas, so that water can be easily discharged even if the concentration of water, which is the reaction product, is high. can

In addition, the gas diffusion layer according to the present invention maintains a uniform porosity, but by forming only a different contact angle of water, it is easier to manufacture than when the porosity is changed, and there is an advantage in that both the water retention function and the water discharge function can be secured. .

1 is a side view showing a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.
2 is a view showing an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.
3 is a view showing another example of an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.
4 is a view showing another example of an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.

Hereinafter, a gas diffusion layer having an in-plane contact angle gradient according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a side view showing a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention. 2 is a view showing an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.

1 and 2 , the gas diffusion layer 30 according to the present invention is disposed between the cathode plate 10 and the membrane electrode assembly 20 .

The first surface 30a of the gas diffusion layer 30 is disposed to face the air passage 11 of the cathode plate 10 , and the second surface 30b is disposed to face the membrane electrode assembly 30 . do.

The gas diffusion layer 30 is formed by stacking the gas diffusion support layer 31 and the porous thin layer 32 in the thickness direction. The gas diffusion support layer 31 is formed to include carbon fibers, and the porous thin layer 32 is formed to include carbon powder.

In the gas diffusion layer 30 , at least one of the first surface 30a and the second surface 30b is formed to have a contact angle (θc, Contact angle) gradient of water as a reaction product within the surface. Hereinafter, in this embodiment, since the concentration of water, which is a reaction product, is more important on the first surface 30a in contact with air, the first surface 30a is formed to have a contact angle gradient of water. However, the present invention is not limited thereto, and it is of course also possible to form the second surface 30b to increase the contact angle along the air flow direction.

In the gas diffusion layer 30, only the contact angle changes along the air flow path direction, and the porosity is uniformly formed. Therefore, manufacturing is easier compared to the case of changing the porosity.

The first surface 30a is provided with an air inlet portion 33 through which air is introduced and an air outlet portion 34 through which air is discharged. The air inlet part 33 and the air outlet part 34 are disposed to be spaced apart from each other in a diagonal direction from the first surface 30a.

The gas diffusion layer 30 is formed so that the contact angle θc of water increases from the air inlet portion 33 toward the air outlet portion 34 in the first surface 30a. That is, it is formed so that the contact angle θc increases in-plane rather than in the thickness direction.

The gas diffusion layer 30 is divided into a hydrophilic region 100 , an intermediate region 200 , and a hydrophobic region 300 .

The hydrophilic region 100 is a region in which a hydrophilic material is deposited on the first surface 30a by a predetermined first preset area including the air inlet 33 . The first preset area may be set to an area in which the concentration of water is less than the first preset concentration through an experiment on a conventional gas diffusion layer. If the concentration of water is less than the first set concentration, there is a problem in that the electrolyte membrane is not sufficiently hydrated, so that the resistance is large and a relatively small current is produced. Accordingly, the hydrophilic region 100 may improve the degree of hydration such that the concentration of water is equal to or greater than the first preset concentration.

The hydrophilic material is _{described as including titanium oxide (TiO 2} ), but is not limited thereto, and it is of course possible to use other hydrophilic materials in addition to this.

The hydrophilic material may be deposited using an atomic layer deposition (ALD) method or a chemical vapor deposition (CVD) method.

The hydrophilic region 100 is formed by depositing the hydrophilic material so that the contact angle of water is the first contact angle θ _{c1 .} However, the present invention is not limited thereto, and it is of course possible to form the contact angle to have a gradient even in the hydrophilic region 100 .

_{Referring to FIG. 2 , the first contact angle θ c1} of the hydrophilic region 100 , which is the region closest to the air inlet 33 , is expressed as 100%. The smaller the contact angle of water, the stronger the property of retaining water on the surface, so that the electrolyte membrane can be sufficiently hydrated in the hydrophilic region 100 close to the air inlet 33 under low humidity conditions.

The intermediate region 200 is a region partitioned between the hydrophilic region 100 and the hydrophobic region 300 , and is a region that is not subjected to hydrophilic or hydrophobic treatment. The width of the intermediate region 200 may be determined according to the widths of the hydrophilic region 100 and the hydrophobic region 300 , and it is also possible that the intermediate region 200 does not exist.

Since the hydrophilic material is not deposited in the intermediate region 200 , the second contact angle θ _c2 of the intermediate region 200 is greater than the first contact angle θ _{c1 of the hydrophilic region 100 .}

Herein, the increase rate of the contact angle from the hydrophilic region 100 to the intermediate region 200 is described as 30% as an example, but it is not limited thereto and can be adjusted according to the hydration characteristics or the current production level.

Referring to FIG. 2 , the second contact angle θ _c2 of the intermediate region 200 is expressed as 130%.

The hydrophobic region 300 is a region spaced apart from the hydrophilic region 100 by a preset distance on the first surface 30a and partitioned by a preset second preset width including the air outlet 34 . . The second set area may be set to an area in which the concentration of water is equal to or greater than the second set concentration through an experiment on a conventional gas diffusion layer. Although the concentration of the reactant in the region close to the air outlet portion 34 is small, if the concentration of water is higher than the second set concentration, the water may prevent the reactant from diffusing toward the electrolyte membrane, and the diffusion of the reactant may not be smoothly achieved. Failure to do so may increase resistance and reduce current production. The hydrophobic region 300 may facilitate the discharge of water, thereby lowering the concentration of water to less than the second set concentration.

The hydrophobic region 300 includes a hydrophobic material, and is a region in which a contact angle θc of water is greater than that of the hydrophilic region 100 and the intermediate region 200 .

When the gas diffusion layer 30 is manufactured, the hydrophobic material may be mixed only in a portion corresponding to the hydrophobic region 300 to change the contact angle of the hydrophobic region 300 . The gas diffusion layer 30 is formed of carbon fiber or carbon powder, and 5 wt% or more of polytetrafluoroethylene (PTFE) may be mixed as the hydrophobic material. In this embodiment, polytetrafluoroethylene is described as an example used in the range of 5 to 40 wt%. However, the present invention is not limited thereto, and a material other than the polytetrafluoroethylene may be used as the hydrophobic material.

By adjusting the addition ratio of the polytetrafluoroethylene, the contact angle θc of the hydrophobic region 300 may be changed. As the addition ratio of the polytetrafluoroethylene increases, the contact angle θc may increase to increase hydrophobicity.

The hydrophobic region 300 may be formed such that the content of the hydrophobic material gradually increases along the direction of the air flow path 11 so that the contact angle θc gradually increases, and within the hydrophobic region 300 It is also possible that the contact angle θc is formed to be constant.

Hereinafter, in the present embodiment, the contact angle θc in the hydrophobic region 300 will be described as an example that is set to be constant as _{the third contact angle θ c3 .} The third contact angle θ _c3 of the hydrophobic region 300 is greater than the second contact angle θ _{c2 of the intermediate region 200 .}

Referring to FIG. 2 , the third contact angle θ _c3 of the hydrophobic region 300 is expressed as 160%. The increase rate of the contact angle from the intermediate region 200 to the hydrophobic region 300 is described as 30% as an example, but is not limited thereto and can be adjusted according to hydration characteristics or current production level.

Since the larger the contact angle of the water, the stronger the property of discharging water from the surface, the better the diffusion of the reactant into the electrolyte membrane can occur, and thus the performance degradation due to the decrease in the concentration of the reactant at the air outlet part 34 can be prevented. there is.

Meanwhile, in the above embodiment, it has been described as an example that the content of the hydrophobic material is formed to increase in the direction of the air passage only in the hydrophobic region 300 , but the present invention is not limited thereto. A material may be included, and the content of the hydrophobic material included in the hydrophilic region 100 is preferably set to be less than the content of the hydrophobic material included in the hydrophobic region 300 . For example, the hydrophilic region 100 may contain the hydrophobic material in an amount of 5 wt% or less.

Meanwhile, FIG. 3 is a view showing another example of an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.

Referring to FIG. 3 , the gas diffusion layer 30 may be divided into five first, second, third, and fourth regions A1 to A5 having different contact angles θc.

However, the present invention is not limited thereto, and the number and size of regions in the gas diffusion layer 30 having different contact angles θc may be variously adjusted.

Among the first, second, third, and fourth regions A1 to A5, the closer to the air inlet 33, the smaller the contact angle θc, and the closer to the air outlet 34, The contact angle θc is formed to increase.

For example, by depositing the hydrophilic material in the first area A1, which is the area closest to the air inlet 33 among the first, second, third, and fourth areas A1 to A5, The first contact angle θ _c1 of the first area A1 may be the smallest. Here, the first contact angle θ _c1 was expressed as 100%.

Among the first, second, third, and fourth regions (A1 to A5), the remaining second, 3, 4, and 5 regions (A2 to A5) except for the first region (A1) include the hydrophobic material. However, it can be formed by increasing the content of the hydrophobic material as it is closer to the air outlet part 34 . Accordingly, the contact angle θc may gradually increase in the second, 3, 4, and 5 (A2 to A5) regions as it approaches the air outlet 34 . Here, the second contact angle θ _c2 of the second area A2 is 115%, the third contact angle θ _c3 of the third area A3 is 130%, and the fourth area A4 is The fourth contact angle θ _c4 is 145%, and the fifth contact angle θ _c5 of the fifth area A5 is 160%.

The contact angle θc has been described as an example of increasing by 15%, but the present invention is not limited thereto, and the increase rate can be adjusted differently, and of course it is also possible to adjust the increase rate to vary for each region.

In the above, it has been described as an example that the contact angle is different by adjusting the ratio of the hydrophobic material, but it is not limited thereto, and it is of course possible to change the contact angle by adjusting the deposition degree of the hydrophilic material.

Meanwhile, FIG. 4 is a view showing another example of an in-plane contact angle gradient of a gas diffusion layer of a polymer electrolyte membrane fuel cell according to an embodiment of the present invention.

Referring to FIG. 4 , the gas diffusion layer 30 may be divided into nine first to ninth regions B1 to B9 having different contact angles θc along the direction of the air flow path.

That is, the gas diffusion layer 30 may be partitioned into a plurality of matrices, and it will be described as an example of partitioning the gas diffusion layer 30 into three rows and three columns and partitioning a total of nine regions.

However, the present invention is not limited thereto, and the number and size of regions in the gas diffusion layer 30 having different contact angles θc may be variously adjusted.

In the first to ninth regions B1 to B9, the contact angle θc gradually decreases as it approaches the air inlet 33, and the contact angle θc decreases as it approaches the air outlet 34. is formed to grow larger.

_{The contact angles θ c1} , θ _c2 , and θ _{c3 of} the first, second, and third regions B1 , B2 and B3 arranged in the same first row among the first to ninth regions B1 to B9 are also formed differently. do. The contact angles of the first, second, and third regions B1, B2, and B3 are gradually increased along the direction of the air flow path.

_{In addition, the contact angles θ c4} , θ _c5 , θ _{c6 of} the 4,5 and 6th regions B4 , B5 , and B6 arranged in the same second row among the first to ninth regions B1 to B9 are It is larger than the contact angle of the first row, and the contact angles θ _c4 , θ _c5 , θ _{c6 of} the fourth, fourth, and sixth regions B4 , B5 and B6 are formed differently. _{The contact angles θ c4} , θ _c5 , and θ _{c6 of} the fourth, fourth, and sixth regions B4 , B5 and B6 are formed to gradually increase in contact angle along the direction of the air flow path.

_{In addition, the contact angles θ c7} , θ _c8 , θ _{c9 of} the 7th, 8th, and 9th regions B7, B8 and B9 arranged in the same third row among the 1st to 9th regions B1 to B9 are It is larger than the contact angle of the second row, and the contact angles θ _c7 , θ _c8 , and θ _{c9 of} the seventh, eighth, and ninth regions B7 , B8 and B9 are formed to be different from each other. _{The contact angles θ c7} , θ _c8 , and θ _{c9 of} the seventh, eighth, and ninth regions B7 , B8 and B9 are formed to gradually increase in the direction of the air flow path.

The first to ninth regions B1 to B9 may have different contact angles by varying at least one of the deposition degree of the hydrophilic material and the content of the hydrophobic material.

In addition, at least a portion of the first to ninth regions B1 to B9 may have a hydrophilic material deposited thereon and may also contain a hydrophobic material. At this time, the content of the hydrophobic material is set to gradually increase along the direction of the air flow path.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is merely exemplary, it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

10: cathode plate 20: membrane electrode assembly
30: gas diffusion layer 31: gas diffusion support layer
32: porous thin layer 100: hydrophilic region
200: middle region 300: hydrophobic region

Claims (8)

The first surface is opposed to the air flow path of the cathode plate, the second surface is disposed to be opposite to the membrane electrode assembly, and the air inlet through which air is introduced and the air outlet through which air is discharged are spaced apart from each other. and a gas diffusion layer formed to increase hydrophobicity by increasing a contact angle of water from the air inlet to the air outlet on the first surface,
The gas diffusion layer,
a hydrophilic region partitioned by a preset first preset area including the air inlet on the first surface and formed by depositing a hydrophilic material;
A hydrophobic region that is spaced apart from the hydrophilic region by a set distance on the first surface, is partitioned by a preset second preset area including the air outlet, and is formed including a hydrophobic material so that the contact angle is greater than that of the hydrophilic region. including,
The gas diffusion layer,
a gas diffusion support layer facing the cathode plate;
a porous thin layer opposite the membrane electrode assembly;
The porosity of the porous thin layer is formed uniformly from the air inlet to the air outlet,
The hydrophobic region,
The gas diffusion layer of the polymer electrolyte membrane fuel cell is formed such that the content of the hydrophobic material is gradually increased along the direction of the air flow path and the contact angle is gradually increased. delete The first surface is opposed to the air flow path of the cathode plate, the second surface is disposed to be opposite to the membrane electrode assembly, and the air inlet through which air is introduced and the air outlet through which air is discharged are spaced apart from each other. and a gas diffusion layer formed to increase hydrophobicity by increasing a contact angle of water from the air inlet to the air outlet on the first surface,
The gas diffusion layer,
a hydrophilic region partitioned by a preset first preset area including the air inlet on the first surface and formed by depositing a hydrophilic material;
A hydrophobic region that is spaced apart from the hydrophilic region by a set distance on the first surface, is partitioned by a preset second preset area including the air outlet, and is formed including a hydrophobic material so that the contact angle is greater than that of the hydrophilic region. including,
The gas diffusion layer,
a gas diffusion support layer facing the cathode plate;
a porous thin layer opposite the membrane electrode assembly;
The porosity of the thin porous layer is formed uniformly from the air inlet to the air outlet,
The hydrophobic region,
The gas diffusion layer of the polymer electrolyte membrane fuel cell is formed such that the content of the hydrophobic material increases as the area near the air outlet increases, so that the contact angle gradually increases. 4. The method according to claim 1 or 3,
A gas diffusion layer of a polymer electrolyte membrane fuel cell formed so that the contact angle increases from the air inlet to the air outlet on the second surface. delete 4. The method according to claim 1 or 3,
The hydrophilic material is a gas diffusion layer of a polymer electrolyte membrane fuel cell comprising titanium oxide. 4. The method according to claim 1 or 3,
The hydrophobic material is a gas diffusion layer of a polymer electrolyte membrane fuel cell comprising 5 wt% or more of polytetrafluoroethylene (PTFE). The first surface is opposite to the air flow path of the cathode plate, the second surface is disposed to be opposite to the membrane electrode assembly, and the air inlet part through which air is introduced and the air outlet part through which air is discharged are diagonally from each other in a diagonal direction. A gas diffusion layer provided to be spaced apart and formed to increase hydrophobicity by increasing a contact angle of water from the air inlet to the air outlet on the first surface,
The gas diffusion layer,
a hydrophilic region partitioned by a preset first width including the air inlet on the first surface and formed by depositing a hydrophilic material to have a first contact angle;
A third spaced apart from the hydrophilic region by a preset distance on the first surface, divided by a preset second preset width including the air outlet, and formed including a hydrophobic material, which is larger than the first contact angle of the hydrophilic region A hydrophobic region formed to have a contact angle;
It is disposed between the hydrophilic region and the hydrophobic region, is a region that is not subjected to hydrophilic treatment or hydrophobic treatment, and includes an intermediate region formed to have a second contact angle greater than the first contact angle and smaller than the third contact angle;
The hydrophobic region is formed such that the content of the hydrophobic material increases as the region close to the air outlet increases, so that the contact angle gradually increases,
The hydrophilic material includes titanium oxide,
The hydrophobic material contains 5 to 40 wt% of polytetrafluoroethylene (PTFE),
The gas diffusion layer,
a gas diffusion support layer facing the cathode plate;
a porous thin layer opposite the membrane electrode assembly;
The porosity of the porous thin layer is a gas diffusion layer of a polymer electrolyte membrane fuel cell formed uniformly from the air inlet to the air outlet.

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