JP7272318B2 - Laminates for fuel cells - Google Patents

Description

The present invention relates to laminates for fuel cells.

Fuel cells are known that generate electricity by chemically reacting an anode gas such as hydrogen and a cathode gas such as oxygen.

In a fuel cell, an anode gas (fuel gas) such as hydrogen and a cathode gas (oxidant gas) such as oxygen are supplied to two electrically connected electrodes, respectively, to electrochemically oxidize the fuel. directly converts chemical energy into electrical energy.

At the anode (fuel electrode) to which hydrogen is supplied as the anode gas, the reaction of the following formula (a) proceeds.
H ₂ → 2H ⁺ + 2e ^- (a)

The electrons (e ⁻ ) generated in the above formula (1) reach the cathode (oxidant electrode) after going through an external circuit and working on an external load. On the other hand, the protons (H ⁺ ) generated in the above formula (a) move from the anode side to the cathode side in the electrolyte membrane sandwiched between the anode and the cathode by electroosmosis while being hydrated with water. do.

On the other hand, at the cathode, the protons (H ⁺ ) generated by the above formula (a) that passed through the electrolyte membrane, the oxygen supplied as the cathode gas, and the electrons (e ^- ) advances the reaction of the following formula (b).
2H ⁺ + 1/2O ₂ + 2e ⁻ → H ₂ O (b)

Therefore, the chemical reaction represented by the following formula (c) proceeds in the entire battery, an electromotive force is generated, and electrical work is performed on the external load.
H ₂ + 1/2O ₂ → H ₂ O (c)

Such a fuel cell is generally constructed by stacking a plurality of unit cells each having a basic structure of a membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes. Among them, a solid polymer electrolyte fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane has advantages such as easy miniaturization and low temperature operation, and is particularly useful in mobile devices. It is expected to be used as a portable power source or a power source for mobile objects such as electric vehicles.

Here, the configuration of a single cell of a solid polymer electrolyte fuel cell includes, for example, an anode-side separator, an anode-side gas diffusion layer, an anode-side catalyst layer, an electrolyte membrane, a cathode-side catalyst layer, a cathode-side gas diffusion layer, and A laminate in which cathode-side separators are laminated in this order is known.

Here, in a fuel cell, the anode tends to dry out under high temperature and low humidity conditions. As drying progresses, resistive polarization increases and cell performance deteriorates. In addition, a decrease in output at high temperatures cannot be avoided. In response to this, it has been proposed to send the water generated at the cathode to the anode side for use (see Patent Document 1).

In Patent Document 1, among the layers constituting the laminate, the thickness of the cathode-side catalyst layer is made larger than the thickness of the anode-side catalyst layer, and the thickness of the anode-side gas diffusion layer is made larger than the thickness of the cathode-side gas diffusion layer. A technique has been proposed in which the thickness of each layer constituting the laminate is increased and the thickness of each layer constituting the laminate is set in a specific relationship to promote the movement of water from the cathode side to the anode side.

JP 2016-081581 A

In addition, the fuel cell may generate hydrogen peroxide during the reaction process. The generated hydrogen peroxide decomposes the ionomer, which is an electrolyte component. As a result, an electrolyte membrane containing ionomer as a main component and a catalyst layer containing ionomer as a component are deteriorated, causing a problem in durability of the battery.

On the other hand, it is known to add a cerium-containing oxide to the material of the laminate constituting the fuel cell. Cerium-containing oxides generate cerium ions that act as catalysts for decomposing hydrogen peroxide.

However, the present inventors have found that in a fuel cell in which a cerium-containing compound, which is a decomposition catalyst for hydrogen peroxide, is contained in the microporous layer (MPL) of the gas diffusion layer, the flow from the cathode side to the anode side during endurance The inventors have found that the movement of generated water becomes insufficient, and as a result, the gas diffusion layer on the cathode side becomes hydrophilic due to the cerium ions dissolved in the generated water, and the battery performance after endurance may deteriorate.

The present invention has been made in view of the above background, and is capable of ensuring output performance after endurance even in a fuel cell containing a cerium-containing compound in the microporous layer (MPL) of the gas diffusion layer. It is an object of the present invention to provide a laminate for a fuel cell that can

The inventor of the present invention has made intensive studies to solve the above problems. In the gas diffusion layer for a fuel cell, if the thickness of the diffusion layer substrate layer and the thickness of the microporous layer (MPL) have a specific relationship, the microporous layer (MPL) contains a cerium-containing compound. The inventors have found that even a battery can ensure output performance after endurance, and have completed the present invention. That is, the present invention is as follows.

A laminate for a fuel cell in which an anode-side gas diffusion layer, an electrolyte membrane, and a cathode-side gas diffusion layer are laminated in this order,
The anode-side gas diffusion layer comprises an anode-side microporous layer and an anode-side diffusion layer substrate layer laminated in this order from the electrolyte membrane side,
In the cathode-side gas diffusion layer, a cathode-side microporous layer and a cathode-side diffusion layer base layer are laminated in this order from the electrolyte membrane side,
the anode-side microporous layer and the cathode-side microporous layer comprise a cerium-containing compound;
D1 is the thickness of the anode-side diffusion layer substrate layer, D2 is the thickness of the anode-side microporous layer, D3 is the thickness of the cathode-side diffusion layer substrate layer, and D4 is the thickness of the cathode-side microporous layer. sometimes satisfying the following formulas (1), (2), and (3) below,
Laminates for fuel cells.
D1/D2<D3/D4 (1)
D1/D2>3.0 (2)
D3/D4>3.0 (3)

According to the fuel cell laminate of the present invention, even if the fuel cell contains a cerium-containing compound in the microporous layer (MPL) of the gas diffusion layer, it realizes a fuel cell that can ensure output performance after endurance. can do.

1 is a cross-sectional view of a laminate for a fuel cell of the present invention according to one embodiment; FIG. 4 is a graph showing the relationship between the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) on the anode side and the cathode side, and the ratio of the output after temperature change endurance to the initial output. The ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) on the cathode side to the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) on the anode side, and the initial output 3 is a graph showing the relationship between the ratio of output after temperature change endurance to .

Embodiments of the present invention will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be implemented in various modifications.

《Laminates for fuel cells》
A fuel cell laminate of the present invention is at least a part of a laminate constituting a fuel cell, and is a laminate in which an anode-side gas diffusion layer, an electrolyte membrane, and a cathode-side gas diffusion layer are laminated in this order. is the body. Each of the gas diffusion layers on the anode side and the cathode side has a microporous layer and a diffusion layer substrate layer laminated in this order from the electrolyte membrane side.

In the laminate for a fuel cell of the present invention, the anode-side microporous layer and the cathode-side microporous layer contain a cerium-containing compound, and the anode-side diffusion layer substrate layer, the anode-side microporous layer, and the cathode-side diffusion layer are composed of: The respective thicknesses of the substrate layer and the cathode-side microporous layer have a specific relationship.

In the fuel cell laminate of the present invention, the respective thicknesses of the anode-side diffusion layer substrate layer, the anode-side microporous layer, the cathode-side diffusion layer substrate layer, and the cathode-side microporous layer have specific relationships. As a result, even if the anode-side microporous layer and the cathode-side microporous layer contain a cerium-containing compound, it is possible to realize a fuel cell capable of ensuring output performance after endurance.

The fuel cell laminate of the present invention may contain other layers as long as the anode-side gas diffusion layer, the electrolyte membrane, and the cathode-side gas diffusion layer are essential components. Other layers include, for example, separators and catalyst layers, but are not limited to these.

The structure of a laminate stored in a general fuel cell includes, for example, an anode-side separator, an anode-side gas diffusion layer, an anode-side catalyst layer, an electrolyte membrane, a cathode-side catalyst layer, a cathode-side gas diffusion layer, and a cathode. A laminate in which the side separators are laminated in this order can be mentioned.

FIG. 1 is a cross-sectional view of a fuel cell stack according to one embodiment of the present invention. A laminate 100 according to an embodiment of the present invention comprises an anode-side gas diffusion layer 10, an anode-side catalyst layer 15, and an electrolyte membrane 30, which are formed by laminating an anode-side diffusion layer substrate layer 11 and an anode-side microporous layer 12. , the cathode catalyst layer 25, the cathode diffusion layer substrate layer 21, and the cathode microporous layer 22 are laminated in this order.

In the laminate 100 shown in FIG. 1, a catalyst layer is present on each of the anode side and the cathode side between the gas diffusion layer and the electrolyte membrane, which are essential components of the fuel cell laminate of the present invention. are doing. The anode-side and cathode-side microporous layers face the catalyst layer.

In the fuel cell laminate of the present invention, the anode-side microporous layer and the cathode-side microporous layer contain a cerium-containing compound. That is, in the laminate 100 shown in FIG. 1, the anode-side microporous layer 12 and the cathode-side microporous layer 22 contain a cerium-containing compound.

Further, in the fuel cell laminate of the present invention, the respective thicknesses of the anode-side diffusion layer substrate layer, the anode-side microporous layer, the cathode-side diffusion layer substrate layer, and the cathode-side microporous layer have specific relationships. have That is, in the laminate 100 shown in FIG. 1, each of the anode-side diffusion layer base layer 11, the anode-side microporous layer 12, the cathode-side diffusion layer base layer 21, and the cathode-side microporous layer 22 has a thickness of , has a specific relationship.

<Gas diffusion layer>
In the fuel cell laminate of the present invention, the anode-side gas diffusion layer and the cathode-side gas diffusion layer are essential constituent layers. In the present invention, an electrolyte membrane exists between them.

The gas diffusion layer has the function of diffusing and uniformizing the reactant gas to be supplied, and spreading the gas over the adjacent catalyst layers in the case of a single cell of the fuel cell.

In the present invention, the gas diffusion layer is a laminate in which a microporous layer is laminated on a diffusion layer base material layer. Then, when incorporated into a fuel cell, the microporous layer is positioned to face the adjacent catalyst layer.

(Diffusion layer base layer)
The diffusion layer substrate layer in the gas diffusion layer is a porous layer that supplies a reaction gas to the adjacent catalyst layer in the case of a single cell of a fuel cell. The diffusion layer substrate layer is preferably made of a material having gas permeability and electrical conductivity.

In the laminate for a fuel cell of the present invention, any material that is generally used as a diffusion layer substrate layer can be used without particular limitation. A material, or a metal porous material such as a metal mesh or a foamed metal can be used. Incidentally, the carbon porous body such as carbon paper or carbon cloth may be formed of, for example, carbon fiber and a binder such as polytetrafluoroethylene.

In the fuel cell laminate of the present invention, the pore diameter, density, thickness, etc. of the diffusion layer base material layer constituting the gas diffusion layer are not particularly limited on either the anode side or the cathode side. However, it can be appropriately set according to the required performance of the fuel cell to be formed.

(Microporous layer (MPL))
The microporous layer in the gas diffusion layer is present on the diffusion layer substrate layer, and becomes a layer adjacent to the catalyst layer in the case of a single cell of the fuel cell. By forming the MPL on the gas diffusion layer that constitutes the fuel cell laminate, the gas diffusion property in the fuel cell is improved.

The method for producing the microporous layer (MPL) is not particularly limited. A method of applying by discharging from a working head, followed by drying and baking may be mentioned.

The microporous layer in the gas diffusion layer in the fuel cell laminate of the present invention contains a cerium-containing compound that generates cerium ions that serve as hydrogen peroxide decomposition catalysts on both the anode side and the cathode side. Therefore, the MPL-forming slurry or MPL-forming paste is a composition containing a cerium-containing compound as an essential component on both the anode side and the cathode side.

The cerium-containing compound that generates cerium ions serving as a hydrogen peroxide decomposition catalyst is not particularly limited, and may be a cerium-containing oxide or complex, such as cerium oxide (CeO ₂ ).

In addition, other components constituting the microporous layer in the gas diffusion layer are not particularly limited, but generally carbon particles and a water-repellent resin can be mentioned as main components.

Examples of carbon particles include particles of carbon black, graphene, graphite, and the like.

The carbon particles may have an average primary particle size of 25 nm to 70 nm. The average primary particle size of the carbon particles may be 25 nm or more, 45 nm or more, or 65 nm or more, and may be 70 nm or less, 60 nm or less, or 50 nm or less.

The average primary particle diameter of the carbon particles is determined by using an electron microscope such as a transmission electron microscope (TEM) or a scanning electron microscope (SEM) to determine the directional diameter (Feret diameter), and the arithmetic mean of the obtained measured values.

Examples of water-repellent resins include fluorine-based polymer materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer, polypropylene, Polyethylene etc. can be mentioned.

In the fuel cell laminate of the present invention, the thickness of the microporous layer (MPL) constituting the gas diffusion layer is not particularly limited on either the anode side or the cathode side, and the fuel cell formed is can be appropriately set according to the required performance. For example, it may be 20 μm or more.

(Relationship between the thickness of the diffusion layer base layer and the thickness of the microporous layer (MPL))
In the gas diffusion layer of the fuel cell laminate of the present invention, the thickness of each of the anode-side diffusion layer substrate layer, the anode-side microporous layer, the cathode-side diffusion layer substrate layer, and the cathode-side microporous layer is specified. have a relationship of

Specifically, the thickness of the anode-side diffusion layer substrate layer is D1, the thickness of the anode-side microporous layer is D2, the thickness of the cathode-side diffusion layer substrate layer is D3, and the thickness of the cathode-side microporous layer is D4. Then, the following formulas (1), (2), and (3) are satisfied.
D1/D2<D3/D4 (1)
D1/D2>3.0 (2)
D3/D4>3.0 (3)

The above formula (1) indicates that the ratio of the thickness of the diffusion layer base material layer to the thickness of the microporous layer (MPL) on the cathode side is the ratio of the thickness of the diffusion layer base material layer to the thickness of the microporous layer (MPL) on the anode side. means greater than the ratio.

By satisfying the above formula (1), the drainage properties of the cathode-side diffusion layer can be improved.

The thickness D1 of the anode-side diffusion layer substrate layer, the thickness D2 of the anode-side microporous layer, the thickness D3 of the cathode-side diffusion layer substrate layer, and the thickness D4 of the cathode-side microporous layer are related by the following formula (1a). may be the relationship of the following formula (1b).
1.5×(D1/D2)<D3/D4 (1a)
2.0×(D1/D2)<D3/D4 (1b)

Further, the thickness D1 of the anode-side diffusion layer substrate layer, the thickness D2 of the anode-side microporous layer, the thickness D3 of the cathode-side diffusion layer substrate layer, and the thickness D4 of the cathode-side microporous layer are related by the following formula (1c). or the relationship of the following formula (1d).
3.0×(D1/D2)>D3/D4 (1c)
2.5×(D1/D2)>D3/D4 (1d)

The above formula (2) means that the ratio of the thickness of the diffusion layer substrate layer on the anode side to the thickness of the microporous layer (MPL) on the anode side is greater than 3. Moreover, the above formula (3) means that the ratio of the thickness of the diffusion layer substrate layer on the cathode side to the thickness of the microporous layer (MPL) on the cathode side is greater than 3.

By satisfying the above formulas (2) and (3), the effect of ionization of the cerium-containing compound contained in the microporous layer (MPL) and dissolution into the generated water can be reduced, and the water repellency of the diffusion layer can be reduced. can be suppressed.

The thickness D1 of the anode-side diffusion layer substrate layer and the thickness D2 of the anode-side microporous layer may have the relationship of the following formula (2a) or the following formula (2b).
D1/D2>3.5 (2a)
D1/D2>4.0 (2b)

Further, the thickness D1 of the anode-side diffusion layer substrate layer and the thickness D2 of the anode-side microporous layer may have the relationship of the following formula (2c) or the following formula (2d).
D1/D2<5.0 (2c)
D1/D2<4.5 (2d)

The thickness D3 of the cathode-side diffusion layer substrate layer and the thickness D4 of the cathode-side microporous layer may have the relationship of the following formula (3a) or the following formula (3b).
D3/D4>3.5 (3a)
D3/D4>4.0 (3b)

Further, the thickness D3 of the cathode-side diffusion layer substrate layer and the thickness D4 of the cathode-side microporous layer may have the relationship of the following formula (3c) or the following formula (3d).
D3/D4<5.0 (3c)
D3/D4<4.5 (3d)

In the present invention, the thickness of the anode-side diffusion layer substrate layer, the thickness of the anode-side microporous layer, the thickness of the cathode-side diffusion layer substrate layer, and the thickness of the cathode-side microporous layer can be any 10 It may be the average value of the points measured.

<Electrolyte membrane>
The electrolyte membrane is an essential constituent layer in the fuel cell laminate of the present invention, and is arranged between the anode-side gas diffusion layer and the cathode-side gas diffusion layer. The electrolyte membrane has the function of blocking the flow of electrons and gases, and of transferring protons (H ⁺ ) generated at the anode from the anode-side catalyst layer to the cathode-side catalyst layer.

The electrolyte membrane is not particularly limited, and known membranes as electrolyte membranes used in fuel cells can be used. In the case of a solid polymer electrolyte fuel cell using a solid polymer electrolyte membrane as the electrolyte membrane, for example, an ion-conducting polymer electrolyte resin formed of a polymer electrolyte resin containing sulfonic acid groups such as perfluorosulfonic acid (PFSA) ionomer. an ion-exchange membrane having properties. The membrane is not limited to sulfonic acid groups, and may include other ion exchange groups (electrolyte components) such as phosphoric acid groups and carboxylic acid groups.

A commercially available ion exchange membrane may be applied, and a polymer membrane having ion conductivity formed of a polymer electrolyte resin, which is a solid polymer material such as perfluorosulfonic acid (PFSA) ionomer, is used as the electrolyte. It consists of an ion exchange membrane with Examples of commercially available fluororesin-based ion exchange membranes containing sulfonic acid groups include Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, and Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd. etc.

The thickness of the electrolyte membrane is not particularly limited, and can be appropriately set according to the required performance of the fuel cell to be formed. The thickness of the electrolyte membrane may be, for example, 10 μm or less.

<Other layers>
The fuel cell laminate of the present invention may contain other layers as long as the anode-side gas diffusion layer, the electrolyte membrane, and the cathode-side gas diffusion layer are essential components. Other layers include, for example, separators and catalyst layers, but are not limited to these.

(catalyst layer)
The catalyst layer that is an arbitrary layer of the fuel cell laminate of the present invention is not particularly limited, and a known catalyst layer can be applied.

The anode-side catalyst layer has a function of decomposing hydrogen (H ₂ ), which is a reaction gas, into protons (H ⁺ ) and electrons (e ⁻ ). On the other hand, the cathode-side catalyst layer has the function of generating water (H ₂ O) from protons (H ⁺ ), electrons (e ⁻ ), and oxygen (O ₂ ).

The catalyst layers on the anode side and cathode side can be made of similar materials. For example, a conductive carrier supporting a catalyst such as platinum or a platinum alloy is used, and more specifically, a catalyst-supporting carbon in which a catalyst is supported on carbon particles such as carbon black that functions as a conductive substance. Examples include a layer composed of particles and an electrolyte component that exhibits proton conductivity due to ion exchange groups, which is a component of the electrolyte membrane described above. A layer formed by coating the catalyst-supporting carbon particles with an electrolyte component such as an ionomer having proton conductivity may be used.

The thickness of the catalyst layer is not particularly limited, and can be appropriately set according to the required performance of the fuel cell to be formed.

Hereinafter, the present invention will be described in more detail by showing experimental results.

<<Experimental Example 1>> The relationship between the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) and the ratio of the output after temperature change endurance to the initial output In Experimental Example 1, the anode side diffusion layer substrate The thickness of the layer (D1) and the thickness of the cathode-side diffusion layer substrate layer (D3) are fixed, and the thickness of the anode-side microporous layer (D2) and the thickness of the cathode-side microporous layer (D4) are changed at the same thickness. 6 fuel cells were produced. The six fuel cells obtained were evaluated for initial output and output after temperature change endurance.

<Fabrication of fuel cell>

(Preparation of gas diffusion layer)
Twelve sheets of carbon paper were prepared as porous substrates. A slurry for forming a microporous layer (MPL) containing cerium oxide (CeO ₂ ), carbon particles, and polytetrafluoroethylene (PTFE) is applied to the surface of each carbon paper by a die coater, dried and then baked. By doing so, a gas diffusion layer in which a microporous layer (MPL) was laminated on the diffusion layer substrate layer was produced.

At this time, the thickness of the formed microporous layer (MPL) was formed so that each set of two microporous layers had the same thickness, and six sets of gas diffusion layers were produced.

(Preparation of laminate)
Using one set of gas diffusion layers obtained above as a cathode-side gas diffusion layer and an anode-side gas diffusion layer, anode-side gas diffusion layer/anode-side catalyst layer/electrolyte membrane/cathode-side catalyst layer/cathode-side gas Diffusion layers were laminated in this order to form a laminate, which was sandwiched between a pair of separators to produce six types of fuel cells having microporous layers with different thicknesses.

The anode-side catalyst layer and the cathode-side catalyst layer were arranged so that the microporous layers (MPL) of the adjacent gas diffusion layers faced each other.

<Battery evaluation>
(initial output)
The initial output was evaluated for the 6 types of fuel cells produced. The initial output was defined as the output at the maximum output point when the reaction gas was passed through the fabricated fuel cell and the current was swept.

(output after temperature change endurance)
Output after temperature change endurance was evaluated for the six types of fuel cells that were produced. As the temperature change endurance test, an operation was performed in which the temperature was repeatedly raised and lowered for the number of times assumed to be used while sweeping the current at a constant low current density. After the endurance test, the output at the maximum output point was evaluated in the same manner as the initial output.

<Evaluation results>
FIG. 2 is a diagram showing the relationship between the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layers (MPL) on the anode side and the cathode side, and the ratio of the output after temperature change endurance to the initial output. The horizontal axis of the graph is the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL), and the vertical axis of the graph is the ratio of the post-endurance output to the initial output of the obtained fuel cell. The vertical axis of the graph is a relative value based on the case where the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) is 3 as a reference.

From FIG. 2, if the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) is greater than 3 on both the anode side and the cathode side, the ratio of the output after temperature change endurance to the initial output is high. Therefore, it can be seen that the output performance after endurance can be ensured even in a fuel cell containing a cerium-containing compound in the microporous layer (MPL) of the gas diffusion layer.

<<Experimental Example 2>> The ratio of the thickness of the diffusion layer base material layer to the thickness of the microporous layer (MPL) on the cathode side with respect to the ratio of the thickness of the diffusion layer base material layer to the thickness of the microporous layer (MPL) on the anode side. Relationship between the ratio and the ratio of output after temperature change endurance to initial output , the thickness (D2) of the anode-side microporous layer and the thickness (D4) of the cathode-side microporous layer were varied to fabricate five fuel cells. The five fuel cells thus obtained were evaluated for initial output and output after temperature change endurance.

<Fabrication of fuel cell>
(Fabrication of anode-side gas diffusion layer)
Six sheets of carbon paper were prepared as porous substrates. A slurry for forming a microporous layer (MPL) containing cerium oxide (CeO ₂ ), carbon particles, and polytetrafluoroethylene (PTFE) is applied to the surface of each carbon paper by a die coater, dried and then baked. By doing so, a gas diffusion layer in which a microporous layer (MPL) was laminated on the diffusion layer substrate layer was produced.

At this time, by varying the thickness of the formed microporous layer (MPL), five types of anode-side gas diffusion layers having different thicknesses (D2) of the anode-side microporous layer were produced.

(Fabrication of cathode-side gas diffusion layer)
Five sheets of carbon paper were prepared as diffusion layer substrates. A slurry for forming a microporous layer (MPL) containing cerium oxide (CeO ₂ ), carbon particles, and polytetrafluoroethylene (PTFE) is applied to the surface of each carbon paper by a die coater, dried and then baked. By doing so, a gas diffusion layer in which a microporous layer (MPL) was laminated on the diffusion layer substrate layer was produced.

At this time, by varying the thickness of the formed microporous layer (MPL), five kinds of cathode-side gas diffusion layers having different cathode-side microporous layer thicknesses (D4) were produced.

(Preparation of laminate)
Using the cathode-side gas diffusion layer and the anode-side gas diffusion layer obtained above, the anode-side gas diffusion layer/anode-side catalyst layer/electrolyte membrane/cathode-side catalyst layer/cathode-side gas diffusion layer are laminated in this order. By constructing a stacked body and sandwiching it between a pair of separators, five types of fuel cells having different thicknesses (D2) of the anode-side microporous layer and (D4) of the cathode-side microporous layer were produced.

The anode-side catalyst layer and the cathode-side catalyst layer were arranged so that the microporous layers (MPL) of the adjacent gas diffusion layers faced each other.

<Battery evaluation>
In the same manner as in Experimental Example 1, the initial output and the output after temperature change endurance were evaluated for the five types of fuel cells produced.

<Evaluation results>
FIG. 3 shows the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) on the cathode side to the ratio of the thickness of the diffusion layer substrate layer to the thickness of the microporous layer (MPL) on the anode side. and the ratio of output after temperature change endurance to initial output.

The horizontal axis of the graph is the ratio of the thickness (D1) of the diffusion layer substrate layer to the thickness (D2) of the microporous layer (MPL) on the anode side versus the thickness (D4) of the microporous layer (MPL) on the cathode side. It is the ratio of the thickness (D3) of the diffusion layer substrate layer, and the vertical axis of the graph indicates the ratio of the output after temperature change endurance to the initial output of the obtained fuel cell.

The vertical axis of the graph represents the thickness (D4 ) to the thickness (D3) of the diffusion layer base material layer is set as a relative value based on the case where the ratio is 0.5.

From FIG. 3, the ratio of the thickness (D1) of the diffusion layer base layer to the thickness (D2) of the microporous layer (MPL) on the anode side is compared to the thickness (D4) of the microporous layer (MPL) on the cathode side. If the ratio of the thickness (D3) of the substrate layer is greater than 1, that is, the ratio of the thickness (D3) of the diffusion layer substrate layer to the thickness (D4) of the microporous layer (MPL) on the cathode side is larger than the ratio of the thickness (D1) of the diffusion layer base layer to the thickness (D2) of the microporous layer (MPL) on the anode side, the ratio of the output after temperature change endurance to the initial output is high. Therefore, it can be seen that the output performance after endurance can be ensured even in a fuel cell containing a cerium-containing compound in the microporous layer (MPL) of the gas diffusion layer.

REFERENCE SIGNS LIST 100 laminate 10 anode-side gas diffusion layer 11 anode-side diffusion layer substrate layer 12 anode-side microporous layer 15 anode-side catalyst layer 20 cathode-side gas diffusion layer 21 cathode-side diffusion layer substrate layer 22 cathode-side microporous layer 25 cathode Side catalyst layer 30 Electrolyte membrane

Claims (1)

A laminate for a fuel cell in which an anode-side gas diffusion layer, an electrolyte membrane, and a cathode-side gas diffusion layer are laminated in this order,
The anode-side gas diffusion layer comprises an anode-side microporous layer and an anode-side diffusion layer substrate layer laminated in this order from the electrolyte membrane side,
In the cathode-side gas diffusion layer, a cathode-side microporous layer and a cathode-side diffusion layer base layer are laminated in this order from the electrolyte membrane side,
the anode-side microporous layer and the cathode-side microporous layer comprise a cerium-containing compound;
D1 is the thickness of the anode-side diffusion layer substrate layer, D2 is the thickness of the anode-side microporous layer, D3 is the thickness of the cathode-side diffusion layer substrate layer, and D4 is the thickness of the cathode-side microporous layer. sometimes satisfying the following formulas (1), (2), and (3) below,
Laminates for fuel cells.
D1/D2<D3/D4 (1)
D1/D2>3.0 (2)
D3/D4>3.0 (3)

Images