JP4788130B2 - Gas diffusion layer for fuel cell and fuel cell manufacturing method - Google Patents

Description

  The present invention relates to a gas diffusion layer for a fuel cell, a fuel cell, and a manufacturing method thereof.

  At the time of power generation of the fuel cell, generated water is generated at one electrode along with power generation. Therefore, in order to maintain the power generation performance of the fuel cell well, it is important to prevent retention of the generated water inside the fuel cell. . In particular, when the fuel cell is a solid polymer fuel cell, it is necessary to always keep the solid polymer membrane as the electrolyte layer in a sufficiently wet state in order to maintain proton conductivity in the electrolyte layer. is there. As described above, in the fuel cell, it is important to appropriately maintain the water supply / discharge state around the electrolyte layer and the electrode.

  As a configuration for maintaining a good water supply / discharge state around the electrolyte layer and the electrode, for example, in the gas diffusion layer provided adjacent to the electrode formed on the electrolyte layer, the region facing the gas flow path is repellent. It is known that water is provided and other regions have hydrophilicity (see Patent Document 1). Here, in order to form the water-repellent region and the hydrophilic region as described above, a dispersion containing a hydrophobic substance is applied to a predetermined region of the hydrophilic carbon porous body. . By forming the water-repellent region and the hydrophilic region as described above, the water distribution in the plane is made uniform.

JP 2003-197203 A

  However, when applying a dispersion containing a hydrophobic substance on a hydrophilic carbon porous body, the hydrophilic group and water-repellent substance of the carbon porous body as a base material are difficult to become familiar with each other, The strength with which the water repellent layer adheres to the porous body becomes insufficient, and the durability may be insufficient. Furthermore, there may be a step between the formed water-repellent region and the surrounding hydrophilic region that is the base material. Thus, when a step is generated on the surface in contact with the electrode in the gas diffusion layer, the contact resistance increases in a low region where the water repellent layer is not formed, which may cause a decrease in battery performance. In addition, even if a water-repellent region is formed in a predetermined region, a dispersion containing a hydrophobic substance spreads on the hydrophilic base material, and accuracy in forming the water-repellent region may be insufficient. is there. Furthermore, even with the above configuration, when the generated water becomes excessive, such as at low temperatures or when the amount of power generated in the fuel cell is large, there is a possibility that the generated water may stay in the vicinity of the electrode, and further improvement in drainage is desired. It was.

  The present invention has been made to solve the above-described conventional problems, and can maintain a good supply / discharge state of water around the electrolyte layer and the electrode without deteriorating durability and battery performance. An object is to provide a gas diffusion layer.

In order to achieve the above object, the present invention provides a method for producing a fuel cell gas diffusion layer provided adjacent to an electrode formed on an electrolyte layer,
(A) preparing a conductive porous body to be a base material of the fuel cell gas diffusion layer;
(B) The oxidizing electrolyte layer and the conductive porous material so that the other surface of the oxidizing electrolyte layer having an electrode layer formed on one surface faces the one surface of the conductive porous body. A step of laminating the material,
(C) The difference between the electrode potential in the electrode layer and the potential in the conductive porous body is such that the electrochemical oxidation reaction that generates a hydrophilic group on the surface of the conductive porous body can proceed. And a step of applying a voltage between the electrode layer and the conductive porous body.

  According to the method for producing a gas diffusion layer for a fuel cell of the present invention configured as described above, a hydrophilic group is introduced into the surface of the conductive porous body by utilizing electrochemical oxidation. The hydrophilic group can be firmly fixed on the surface, and the durability of the gas diffusion layer can be improved. In addition, since a step is not generated on the surface of the gas diffusion layer by introducing a hydrophilic group, the contact resistance between the gas diffusion layer and the electrode is reduced in the fuel cell including the gas diffusion layer manufactured in this way. There is nothing to do. Furthermore, it becomes possible to introduce a hydrophilic group accurately at a desired position in the gas diffusion layer.

In the method for producing a fuel cell gas diffusion layer of the present invention,
The conductive porous body includes carbon on at least the one surface,
The step (c) applies a voltage while supplying water vapor to the conductive porous body, and oxidizes the carbon using the water vapor to form hydrophilic groups on the surface of the conductive porous body. It may be introduced.

  With such a configuration, by supplying water vapor to the conductive porous body when a voltage is applied, the carbon on the surface of the conductive porous body can be oxidized and a hydrophilic group can be easily introduced.

In such a method for producing a gas diffusion layer for a fuel cell of the present invention,
The oxidation electrolyte layer is an electrolyte layer having proton conductivity,
The step (c)
(C-1) supplying a predetermined gas to the electrode layer while supplying an inert gas containing water vapor to the conductive porous body;
(C-2) The electrode in the electrode layer when the conductive porous body is connected to the positive electrode of a predetermined external power source, the electrode layer is connected to the negative electrode of the external power source, and the predetermined gas is supplied Applying a voltage having a magnitude determined based on a potential between the electrode layer and the conductive porous body by the external power source to oxidize the carbon.

  With such a configuration, a voltage determined based on the electrode potential in the electrode layer when a predetermined gas is supplied to the electrode layer side is applied between the electrode layer and the conductive porous body, thereby providing a conductive property. It is possible to efficiently introduce a hydrophilic group to the surface of the porous porous body.

  At this time, the predetermined gas supplied to the electrode layer may be hydrogen.

  By using hydrogen as the predetermined gas, the voltage to be applied between the electrode layer and the conductive porous body can be set more easily.

In such a method for producing a gas diffusion layer for a fuel cell of the present invention,
The step (b) is a step of introducing a hydrophilic group into a predetermined region on the one surface of the conductive porous body, and when the oxidation electrolyte layer and the conductive porous body are laminated. A non-proton that does not allow proton transfer between the conductive porous body and the oxidizing electrolyte layer in a region other than the predetermined region at the interface between the oxidizing electrolyte layer and the conductive porous body A conductive region may be provided.

  With such a configuration, electrochemical oxidation in which hydrophilic groups are introduced does not occur in the non-proton conducting region, so that the hydrophilic groups are accurately introduced into the desired region on the surface of the fuel cell gas diffusion layer. Can do. Such a non-proton conductive region can be formed, for example, by providing a non-proton conductive layer made of a material having no proton conductivity at the interface. Further, it is desirable that such a non-proton conductive layer further exhibits non-electron conductivity.

In the method for producing a fuel cell gas diffusion layer of the present invention,
The step (a) may include a step of subjecting the one surface of the conductive porous body to a water repellent treatment in advance.

  With such a configuration, it is possible to obtain a gas diffusion layer in which the region corresponding to the non-proton conduction region has water repellency and the predetermined region not corresponding to the non-proton conduction region has hydrophilicity. As described above, when forming the water-repellent region and the hydrophilic region in the gas diffusion layer, the hydrophilic group can be firmly fixed by introducing the hydrophilic group by electrochemical oxidation. In addition, the above-described effect that no step is generated on the surface of the gas diffusion layer can be obtained particularly remarkably.

  Further, in the method for producing a fuel cell gas diffusion layer according to the present invention, the fuel cell gas diffusion layer is formed on the electrode side where generated water is generated by an electrochemical reaction. It is good also as a gas diffusion layer for arrange | positioning and using the surface which introduce | transduced the said hydrophilic group in a diffusion layer so that the said electrode may be touched.

  By arranging the gas diffusion layer so that the surface where the hydrophilic group is introduced is in contact with the electrode on the electrode side where the generated water is generated, it is possible to efficiently drain the generated water and prevent the generated water from staying in the vicinity of the electrode. it can.

The first fuel cell manufacturing method of the present invention comprises:
(A) forming an electrode including a catalyst on both surfaces of an electrolyte layer having proton conductivity;
(B) providing a conductive porous body as a gas diffusion layer through which a gas to be subjected to an electrochemical reaction flows so as to sandwich the electrolyte layer on which the electrode is formed;
The said (B) process WHEREIN: The said gas for fuel cells manufactured by the manufacturing method of the gas diffusion layer for fuel cells in any one of Claim 1 thru | or 9 as at least one of the said electroconductive porous body which clamps the said electrolyte layer The gist is that the diffusion layer is used and the gas diffusion layer for a fuel cell is disposed so that the surface into which the hydrophilic group has been introduced is in contact with the electrode.

The second fuel cell production method of the present invention comprises:
(A) forming an electrode including a catalyst on both surfaces of an electrolyte layer having proton conductivity;
(B) disposing a conductive porous body as a gas diffusion layer through which a gas to be subjected to an electrochemical reaction flows so as to sandwich the electrolyte layer on which the electrode is formed;
(C) Further, the conductive porous body has a predetermined concavo-convex shape on the outer surface, abuts the conductive porous body at the end of the concavo-convex convex portion, and between the convex portions Disposing a gas separator that forms a flow path for the gas between the conductive porous body and a recess formed in
The said (B) process WHEREIN: The said gas for fuel cells manufactured by the manufacturing method of the gas diffusion layer for fuel cells in any one of Claim 5 thru | or 8 as at least one of the said electroconductive porous body which clamps the said electrolyte layer A step of using a diffusion layer and disposing the fuel cell gas diffusion layer so that the surface into which the hydrophilic group is introduced is in contact with the electrode;
The step (C) is a step of arranging the gas separator while aligning the predetermined region where the hydrophilic group is introduced in the gas diffusion layer for the fuel cell and the recess. Is the gist.

  According to the first and second fuel cell manufacturing methods of the present invention configured as described above, a fuel cell having a hydrophilic group introduced into the surface of the gas diffusion layer in contact with the electrode can be obtained. In the fuel cell, even if generated water is generated along with power generation, it can be quickly drained from the vicinity of the electrode. Therefore, it is possible to prevent a decrease in battery performance due to water remaining in the vicinity of the electrode. Further, the effect of using the fuel cell gas diffusion layer, that is, the durability of the entire fuel cell is improved, and the deterioration of the cell performance due to the increase in contact resistance between the electrode and the gas diffusion layer is prevented. An effect can be obtained.

  Furthermore, according to the second fuel cell manufacturing method of the present invention, the gas separator is aligned so that the concave portion corresponds to the predetermined region where the hydrophilic group is introduced in the gas diffusion layer. In the manufactured fuel cell, the distance that the water drained by the action of the hydrophilic group in the predetermined region moves to the gas flow path may be short. Therefore, the drainage efficiency by the hydrophilic group can be further improved.

In the second method for producing a fuel cell of the present invention,
9. The fuel cell gas diffusion produced by the method of producing a fuel cell gas diffusion layer according to claim 5 at the step (B) at least on the electrode side where produced water is generated by an electrochemical reaction. A layer may be used.

  In such a case, by using the gas diffusion layer on the electrode side where the produced water is generated, the produced water can be efficiently drained in the manufactured fuel cell, and retention of the produced water in the vicinity of the electrode can be prevented. .

The gas diffusion layer for a fuel cell of the present invention is disposed between an electrode formed on an electrolyte layer made of a solid polymer membrane having proton conductivity and a gas separator having a predetermined uneven shape, A gas diffusion layer for a fuel cell that is in contact with an end of a convex portion having a shape and forms a space for a gas flow path for an electrochemical reaction between the concave portion formed between the convex portions. ,
A region corresponding to the concave portion of the gas separator on the surface in contact with the electrode is a hydrophilic region showing hydrophilicity, and a region corresponding to the convex portion of the gas separator is a region showing water repellency. This is the summary.

The fuel cell of the present invention comprises
An electrolyte layer made of a solid polymer membrane having proton conductivity;
Electrodes formed on both surfaces of the electrolyte layer and provided with a catalyst;
A gas diffusion layer formed by a porous body having electron conductivity, the electrode being disposed so as to sandwich the electrolyte layer formed on the surface;
It is disposed further outside the gas diffusion layer, has a predetermined uneven shape on the surface, is in contact with the gas diffusion layer at the end of the uneven portion, and is formed between the protrusions. A gas separator that forms a gas flow path for an electrochemical reaction between the gas diffusion layer and the gas diffusion layer,
In the gas diffusion layer, the region corresponding to the concave portion of the gas separator on the surface in contact with the electrode is a hydrophilic region showing hydrophilicity, and the region corresponding to the convex portion of the gas separator is The gist is that the region exhibits water repellency.

  According to the fuel cell using the gas diffusion layer for a fuel cell of the present invention configured as described above or the fuel cell of the present invention, a hydrophilic region is provided on the surface of the gas diffusion layer on the side in contact with the electrode. Therefore, water can be guided by this hydrophilic region and drained quickly from the vicinity of the electrode. Here, since the hydrophilic region is formed in a region corresponding to the concave portion of the separator that forms the gas flow path, the moving distance when draining the water guided from the vicinity of the electrode by the hydrophilic region to the gas flow path is small. It is short and can improve drainage efficiency. In addition, on the surface of the gas diffusion layer, the water repellency region is provided in the region corresponding to the convex portion of the gas separator, so that water is pushed back to the electrolyte side and the electrolyte layer made of the solid polymer film lacks moisture. Therefore, it is possible to prevent the battery performance from being deteriorated.

  The present invention can be realized in various forms other than those described above. For example, a gas separator manufactured by the method for manufacturing a fuel cell gas separator according to the present invention, and a fuel manufactured by the method for manufacturing a fuel cell according to the present invention. It can be realized in the form of a battery or the like.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Fuel cell configuration:
B. Manufacturing method of gas diffusion layer 17:
C. Operation during power generation:
D. effect:
E. Other examples of electrochemical oxidation:
F. Variations:

A. Fuel cell configuration:
A fuel cell according to an embodiment of the present invention is a polymer electrolyte fuel cell and has a stack structure in which a plurality of single cells are stacked. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a single cell 10 constituting the fuel cell of the embodiment. The single cell 10 includes an MEA (Membrane Electrode Assembly) 12 containing an electrolyte, gas diffusion layers 16 and 17 that sandwich the MEA 12 from both sides to form a sandwich structure, and the sandwich structure from both sides. Separators 20 and 21 are provided. Here, between the separator 20 and the gas diffusion layer 16, a fuel gas flow path 22 in the single cell through which the fuel gas containing hydrogen passes is formed. Further, between the separator 21 and the gas diffusion layer 17, an in-single cell oxidizing gas flow path 23 through which an oxidizing gas containing oxygen passes is formed.

  The MEA 12 includes an electrolyte layer 13 and an anode 14 and a cathode 15 that are electrodes formed on the surface of the electrolyte layer 13 with the electrolyte layer 13 interposed therebetween. The electrolyte layer 13 is a proton conductive ion exchange membrane formed of a solid polymer material, for example, a fluororesin, and exhibits good electrical conductivity in a wet state. In this example, a Nafion membrane (manufactured by DuPont) was used. The anode 14 and the cathode 15 include a catalyst that promotes an electrochemical reaction, such as platinum or an alloy made of platinum and other metals. In order to form the anode 14 and the cathode 15, for example, carbon powder carrying platinum or an alloy made of platinum and another metal is produced, and the carbon powder carrying the catalyst is dispersed in a suitable organic solvent, and an electrolyte is prepared. A paste may be prepared by adding an appropriate amount of a solution (for example, Aldrich Chemical, Nafion Solution). By applying this paste onto the electrolyte layer 13 by a method such as screen printing, the anode 14 and the cathode 15 can be formed.

  The gas diffusion layers 16 and 17 are constituted by members having gas permeability and electron conductivity. In this embodiment, the gas diffusion layers 16 and 17 are formed of a carbon porous body such as carbon cloth or carbon paper. Such gas diffusion layers 16 and 17 serve as a flow path for gas to be subjected to an electrochemical reaction and collect current. That is, the fuel gas is supplied to and discharged from the above-described single-cell fuel gas flow channel 22 through the gas diffusion layer 16 to the anode 14, and the single-cell oxidizing gas flow channel 23 through the gas diffusion layer 17. The oxidizing gas is supplied to and discharged from the cathode 15.

  The separators 20 and 21 are gas-impermeable members formed of a material having electronic conductivity, and can be formed of, for example, a metal member such as stainless steel or a carbon member. On the surfaces of the separators 20 and 21, predetermined uneven shapes for forming the above-described single-cell fuel gas flow path 22 and single-cell oxidizing gas flow path 23 are formed.

  In the present embodiment, the gas diffusion layer 17 includes a water repellent layer 30 exhibiting water repellency and a hydrophilic layer 32 exhibiting hydrophilicity on the surface in contact with the cathode 15. The hydrophilic layer 32 is formed on the surface of the gas diffusion layer 17 and in a region corresponding to the recess formed in the separator 21, that is, a region corresponding to the oxidizing gas flow path 23 in the single cell. In addition, the water repellent layer 30 is formed in a region other than the region where the hydrophilic layer 19 is formed, that is, a region corresponding to the end of the convex portion of the separator 21 where the separator 21 and the gas diffusion layer 17 are in contact. In contrast, the gas diffusion layer 17 includes a water repellent layer 34 over the entire surface in contact with the anode 14.

  In addition, a sealing member such as a gasket is disposed on the outer peripheral portion of the single cell 10 in order to ensure gas sealing properties in the single-cell fuel gas flow path 22 and the single-cell oxidizing gas flow path 23. In addition, a plurality of gas manifolds (not shown) through which fuel gas or oxidant gas flows are provided in the outer peripheral portion of the stack structure in which the single cells 10 are stacked in parallel with the stacking direction of the single cells 10. . The fuel gas flowing through the fuel gas supply manifold among the plurality of gas manifolds is distributed to each single cell 10 and passes through each single cell fuel gas flow path 22 while being subjected to an electrochemical reaction. Collect in the gas exhaust manifold. Similarly, the oxidant gas flowing through the oxidant gas supply manifold is distributed to each single cell 10, passes through the oxidant gas flow path 23 in each single cell while being subjected to an electrochemical reaction, and then gathers in the oxidant gas discharge manifold. To do.

  As the fuel gas supplied to the fuel cell, a hydrogen-rich gas obtained by reforming a hydrocarbon-based fuel may be used, or a high-purity hydrogen gas may be used. For example, air can be used as the oxidizing gas supplied to the fuel cell.

  Although illustration is omitted, in order to adjust the internal temperature of the stack structure, a refrigerant flow path through which the refrigerant passes may be provided between the single cells or every time a predetermined number of single cells are stacked. good. The refrigerant flow path may be provided between adjacent single cells and between the separator 21 provided in one single cell and the separator 20 of the other single cell provided adjacent thereto.

B. Manufacturing method of gas diffusion layer 17:
FIG. 2 is a process diagram showing a manufacturing method of the gas diffusion layer 17 used on the cathode side. When manufacturing the gas diffusion layer 17, first, a carbon porous body such as the carbon cloth described above is prepared (step S100). Next, one surface of the carbon porous body prepared in step S100 is subjected to water repellent treatment to form a water repellent layer (step S110). Specifically, this water-repellent treatment can be performed, for example, by applying a paste containing carbon powder and a water-repellent resin such as a fluorine-based resin on one surface of the carbon porous body. As the gas diffusion layer 16 used on the anode side, a carbon porous body similar to the carbon porous body on which the water repellent layer is formed in step S110 is used as it is.

  Thereafter, in the carbon porous body, a partial region of the surface on the side subjected to the water-repellent treatment in step S110 is hydrophilized using electrochemical oxidation (step S120), and the gas diffusion layer 17 is completed. Here, the partial region is a region where the hydrophilic layer 32 shown in FIG. 1 is to be formed, and when the fuel cell is assembled, it is formed in the recess of the separator 21 that forms the single-cell oxidizing gas flow path 23. The corresponding area. Electrochemical oxidation refers to changing the potential state of a member to be processed by an electric method such as voltage application to advance an oxidation reaction (a reaction that emits electrons). Specifically, a hydrophilic group is introduced into the carbon porous body by applying a predetermined voltage to the carbon porous body and oxidizing the carbon on the surface of the carbon porous body with water (water vapor). To do.

  FIG. 3 is an explanatory diagram showing members involved in the hydrophilic treatment by electrochemical oxidation. The structure 40 used for performing the hydrophilic treatment by electrochemical oxidation and the surface having been subjected to water repellent treatment in step S110 described above. The carbon porous body (the carbon porous body 117 in which the water repellent layer 118 is formed) is shown. The structure 40 shown in FIG. 3 has a structure similar to the structure on the anode side of the MEA 12 in the single cell 10 shown in FIG. For this reason, members common to the single cell 10 in the structure 40 are given reference numbers obtained by adding 100 to the reference numbers of the corresponding members in the single cell 10, and only the configuration different from the single cell 10 will be described below. . The structure 40 has a layer composed of a catalyst layer 42 and an insulating layer 43 on the electrolyte layer 113 instead of the cathode 15. The catalyst layer 42 is the same layer as the anode 14 and the cathode 15 and has proton conductivity and electron conductivity. The insulating layer 43 is a layer that does not have proton conductivity. The insulating layer 42 preferably has non-electron conductivity in addition to non-proton conductivity. For example, when the porous carbon body is subjected to an electrochemical oxidation treatment, such as a fluororesin, In addition, it is desirable to form with a material that is not oxidized. Here, the structure 40 is for oxidizing the surface of the carbon porous body 117 by applying a voltage by further superposing the carbon porous body 117, and the catalyst layer 42 provided in the structure 40. Has a shape corresponding to the hydrophilic layer 19 to be formed on the carbon porous body 117.

  FIG. 4 is an explanatory diagram showing a state in which the surface of the carbon porous body 117 is electrochemically oxidized using the structure 40. As shown in FIG. 4, when performing the hydrophilic treatment by electrochemical oxidation, the structure 40 and the carbon porous body 117 are overlapped so that the water repellent layer 118 is in contact with the structure 40. Then, a separator 121 similar to the separator 21 shown in FIG. 1 is further laminated on the outside of the carbon porous body 117. In addition, the separator 121 used here does not necessarily need to be the same shape as the separator 21, and should just be able to form a gas flow path between the carbon porous bodies 117.

  Thereafter, humidified hydrogen is supplied to the flow path 122 formed between the separator 120 and the gas diffusion layer 116, and humidified nitrogen is supplied to the flow path 123 formed between the separator 121 and the carbon porous body 117. A predetermined voltage is applied between the separators 120 and 121. In this embodiment, the applied voltage was 1.5V. The reason why the hydrogen supplied to the flow path 122 is humidified is to maintain the wet state of the electrolyte layer 113 provided in the structure 40 and to ensure proton conductivity in the electrolyte layer. The reason why the nitrogen supplied to the flow path 123 is humidified is to ensure proton conductivity in the electrolyte layer 113 and to supply water used when electrochemically oxidizing carbon.

  FIG. 5 is an explanatory diagram showing an example of a reaction that proceeds on the surface of the porous carbon body 117 in contact with the structure 40 when a voltage is applied as described above. FIG. 5A shows a reaction in which carbon that forms a benzene ring structure reacts with water to form a quinone group. FIG. 5B shows a reaction in which carbon forming a benzene ring structure reacts with water to form a phenol group. The quinone group has a carbonyl group which is a hydrophilic group, and the phenol group has a hydroxyl group which is a hydrophilic group. Since the carbon porous body is generally a continuum of six-membered rings, the oxidation reaction as described above proceeds on the surface of the carbon porous body 117. Thus, the hydrophilic treatment by electrochemical oxidation is to introduce a hydrophilic group to the surface of the carbon porous body 117 by oxidizing the carbon with water vapor when a voltage is applied. When the reaction shown in FIG. 5 proceeds on the surface of the carbon porous body 117, protons generated along with the formation of quinone groups and the like are transferred to the electrolyte layer 113 provided in the structure 40.

  Here, the carbon oxidation reaction described above is performed when the carbon porous body 117 exhibits a predetermined potential difference with respect to the electrode potential at the other electrode (the catalyst layer 114 adjacent to the gas diffusion layer 116 in FIG. 4). It becomes possible to proceed. The potential difference necessary for the progress of such an oxidation reaction can be theoretically determined thermodynamically. In this embodiment, the other electrode is a hydrogen electrode to which hydrogen is supplied, and the electrode potential at the hydrogen electrode can be considered to be approximately 0 V (vs. RHE and RHE are reversible hydrogen electrode potentials). At this time, the theoretical potential difference required for the oxidation reaction shown in FIG. 5 to proceed in the carbon porous body is about 0.2 V (vs. RHE), and a voltage larger than this is applied. As a result, the oxidation reaction can proceed on the surface of the carbon porous body 117. In this embodiment, the separator 121 adjacent to the carbon porous body 117 is connected to the positive electrode of the external power source 44, and the other separator 120 is connected to the negative electrode of the external power source 44, so that a voltage of 1.5V is applied. Since it is applied, the reaction for generating a hydrophilic group as shown in FIG. 5 can be advanced. As a result, in the carbon porous body 117, the hydrophilic layer 32 is formed in the region in contact with the catalyst layer 42, and the remaining region in contact with the insulating layer 43 remains in a state of being subjected to water repellency treatment. It becomes the water layer 30 and the gas diffusion layer 17 is completed. In the structure 40 of FIG. 4, in the catalyst layer 114, a reaction for generating hydrogen proceeds from protons transmitted from the carbon porous body 117 through the electrolyte layer 113 and electrons supplied from an external power source. .

  Below, the relationship between the applied voltage at the time of performing electrochemical oxidation and the degree of introduction of hydrophilic groups is shown. When electrochemical oxidation is performed on a carbon porous body similar to the base material of the gas diffusion layer 17, oxidation is performed with various applied voltages, and the properties of the obtained hydrophilic carbon porous body are investigated. The results are shown in FIG. FIG. 6 is a cyclic voltammogram showing the result of cyclic voltammetry performed on the hydrophilic carbon porous material oxidized by the various applied voltages. Cyclic voltammetry is a method of applying a cyclic potential change to an object and measuring the current value at that time to measure the oxidation-reduction potential of the reactant in the object (how much reaction occurs at what potential). ) Is a known method. Here, when performing electrochemical oxidation of the carbon porous body, the treatment time is fixed to 10 minutes, and the applied voltage is varied in 8 steps from 0.6 V to 1.5 V to make the hydrophilic carbon porous body. And potential sweep was performed for each. As shown in FIG. 6, all the hydrophilic carbon porous bodies showed a peak at a common electrode potential. The peak is indicated by an arrow in FIG. The electrode potential shown as a peak in the cyclic voltammogram is a value corresponding to the reaction product, and it is considered that the oxidation-reduction reaction of the quinone group is detected from the value of the electrode potential in the obtained peak. The oxidation-reduction reaction of the quinone group is shown in FIG. Here, the height of the peak in the cyclic voltammogram is considered to indicate the concentration of the reactant that performs the oxidation-reduction reaction. As shown in FIG. 6, it is applied when electrochemically oxidizing the carbon porous body. It can be seen that the higher the voltage is, the larger the peak current value is, and that more quinone groups are introduced, that is, the degree of hydrophilicity is large.

  The peak detected by cyclic voltammogram is considered to be a quinone group as described above. Under the above applied voltage, in addition to the quinone group having a carbonyl group, the phenol having the hydroxyl group described above is used. It is considered that a carboxyl group and an aldehyde group are also formed. For this reason, it is considered that the oxidation reaction in which these other hydrophilic groups occur is similarly activated by sufficiently increasing the applied voltage.

  After the electrochemical oxidation as shown in FIG. 4, the obtained gas diffusion layer 17 is separated from the structure 40 and laminated with a predetermined member such as the MEA 12 to produce the single cell 10. At that time, the gas diffusion layer 17 and the separator 21 are overlapped so that the position of the hydrophilic layer 32 of the gas diffusion layer 17 corresponds to the position of the recess formed in the separator 21.

C. Operation during power generation:
When the fuel cell generates power, the reaction expressed by the following formula (1) proceeds at the anode 14 and the reaction expressed by the following formula (2) proceeds at the cathode 15, and the following (3 ) The reaction shown in the formula proceeds.

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  FIG. 8 is an explanatory diagram showing an enlarged view of the vicinity of the cathode 15 during power generation of the fuel cell. At the time of power generation of the fuel cell, water is generated at the cathode 15 as shown in the formula (2). The generated water is pushed back to the electrolyte layer 13 side by the water repellent layer 30 formed on the surface of the gas diffusion layer 17. . A state in which water is pushed back on the surface of the water repellent layer 30 is indicated by a black arrow in FIG. The generated water is pushed back by the water repellent layer 30 in this manner, so that the electrolyte layer 13 is kept in a sufficiently wet state and good proton conductivity is maintained.

  Further, the generated water generated in the cathode 15 is guided into the gas diffusion layer 17 by the hydrophilic layer 32 formed on the surface of the gas diffusion layer 17 and discharged into the oxidizing gas flow path 23 in the single cell. . That is, since the surface of the hydrophilic layer 32 having a hydrophilic group has a property of being easily adapted to water, the generated water is quickly taken into the gas diffusion layer 17 and vaporized into the oxidizing gas, and is oxidized in the single cell. The gas is discharged outside by the oxidizing gas passing through the gas flow path 23. A state in which the produced water generated at the cathode 15 is guided to the oxidizing gas flow path 23 in the single cell is indicated by a white arrow in FIG.

  A water repellent layer 34 is formed on the entire surface of the gas diffusion layer 16 in contact with the anode 14, and this water repellent layer 34 has a function of pushing water back to the electrolyte layer 13 side. This contributes to the maintenance of 13 wet states.

D. effect:
According to the fuel cell of the present embodiment configured as described above, the gas diffusion provided with the hydrophilic layer 32 and the water-repellent layer 30 in order to achieve both drainage around the electrode and supply of water to the electrolyte layer 13. When the layer 17 is formed, the hydrophilic layer 32 is formed by oxidizing the carbon on the surface of the carbon porous body 117 on which the water-repellent layer 118 is formed by electrochemical oxidation. There is no step on the surface of the diffusion layer 17. Therefore, due to the provision of the hydrophilic layer, a region having a large contact resistance is not partially generated between the gas diffusion layer 17 and the cathode 15, and the battery performance is not deteriorated. Furthermore, since hydrophilic groups are introduced into the surface of the gas diffusion layer 17 by electrochemical oxidation, the adhesion strength of the hydrophilic layer 32 to the gas diffusion layer 17 is not insufficient, and the hydrophilic layer is provided. As a result, the durability of the fuel cell does not deteriorate. In particular, in the present embodiment, the hydrophilic layer 32 is formed on the surface of the gas diffusion layer 17 once subjected to the water repellent treatment. When the hydrophilic layer is formed using oxidation, unlike the case where the hydrophilic layer is formed by applying a hydrophilic substance, a step is generated in the region where the hydrophilic layer 32 is provided or the fixing strength of the hydrophilic layer 32 is increased. It will not be insufficient.

  Further, according to the fuel cell of the present embodiment, since the hydrophilic layer 32 is formed by electrochemical oxidation using the structure 40 having a fuel cell-like structure, the hydrophilic layer introduced into the surface of the gas diffusion layer 17 is used. The effect that the amount of the group can be adjusted with higher accuracy is obtained. Here, when the hydrophilic group is introduced by electrochemical oxidation, the amount of the hydrophilic group to be introduced is controlled as a value obtained by integrating the current value flowing through the gas diffusion layer 17 with time during the electrochemical oxidation treatment. Can do. Therefore, compared with the case where the hydrophilic layer is formed by applying a hydrophilic substance, the amount of introduced hydrophilic groups, that is, the degree of hydrophilicity can be adjusted with high accuracy. The hydrophilic group introduced to the surface of the gas diffusion layer 17 contributes to quick drainage from the periphery of the electrode. However, if the hydrophilicity in the gas diffusion layer is too high, the water retention capacity of the gas diffusion layer is increased too much. There is a possibility that the generated water will be excessively stored inside when generating electricity. Thus, when introducing a hydrophilic group into the gas diffusion layer, in order to obtain high battery performance, the gas diffusion layer may be hydrophilized to such an extent that sufficient drainage is achieved and water is not excessively retained. is important. In this embodiment, it is easy to adjust the degree of hydrophilization to a desired level by introducing a hydrophilic group by electrochemical oxidation.

  Furthermore, according to the fuel cell of the present embodiment, the gas diffusion layer 17 is provided with the hydrophilic layer 32 in the region corresponding to the separator recess forming the single cell oxidizing gas flow path, and the water repellent layer in the other region. 30 is provided, it is possible to effectively achieve both improvement in drainage near the cathode 15 and prevention of water shortage in the electrolyte layer 13. That is, as described above, both the effect of guiding the generated water to the side of the oxidizing gas flow path 23 in the single cell by the hydrophilic layer 32 and the effect of pushing the generated water back to the electrolyte layer 13 side by the water repellent layer 30. Obtainable. By improving the drainage of the produced water at the cathode 15, the produced water does not stay on the surface of the cathode 15 and the supply of the oxidizing gas to the catalyst is not delayed, and the electrochemical reaction can proceed smoothly. . In addition, by maintaining the wet state of the electrolyte layer 13 by pushing the generated water back to the electrolyte layer 13 side, the performance of the fuel cell can be favorably maintained during power generation.

  In particular, on the surface of the gas diffusion layer 17, the region corresponding to the concave portion of the separator 21 can be said to be the region having the shortest distance to the oxidizing gas flow path 23 in the single cell, and the hydrophilic layer 32 is provided in such a region. As a result, the generated water can be discharged to the oxidizing gas flow path 23 in the single cell more efficiently. In the region corresponding to the convex portion of the separator 21 on the surface of the gas diffusion layer 17, the gas diffusion layer 17 is more strongly pressed toward the cathode 15, and the contact area between the gas diffusion layer 17 and the cathode 15 becomes larger. It can be called an area. Therefore, by providing the water repellent layer 30 in such a region, the generated water can be pushed back to the electrolyte layer 13 side more efficiently.

  The effect of improving drainage in the vicinity of the cathode 15 is not only when the amount of water generated increases due to an increase in the amount of power generation, but also when the fuel cell is restarted at low temperatures or after the fuel cell temperature has decreased after the fuel cell is stopped. Can be obtained particularly remarkably. For example, when the amount of power generation in the fuel cell increases rapidly, it is possible that excessive generated water remains in the vicinity of the cathode 15 even if the water repellent layer 30 pushes the generated water back to the electrolyte layer 13 side. In such a case, there is a possibility that the gas supply to the cathode 15 may be insufficient. However, in this embodiment, the generated water is quickly removed from the vicinity of the cathode 15 by the action of the hydrophilic layer 32, so that the amount of power generation is increased. Even if there is a sudden increase, power generation can be continued well.

  Furthermore, even during the power generation of the fuel cell, when the ambient temperature of the fuel cell decreases, the saturated water vapor pressure in the oxidizing gas decreases and water condenses in the oxidizing gas, and the condensed water stays in the vicinity of the cathode 15. there's a possibility that. When the degree of temperature drop is large, the condensed water staying in this way may be frozen in the vicinity of the electrode. On the other hand, in the fuel cell of this embodiment, even if condensed water is generated due to a temperature drop, the condensed water can be quickly removed from the vicinity of the cathode 15 by the hydrophilic layer 32. Therefore, even when the ambient temperature is low at the time of power generation, it is possible to prevent the battery performance from being deteriorated due to water remaining on the surface of the cathode 15 and the supply of oxygen to the catalyst being delayed.

  In addition, when water stays on the surface of the cathode 15 when the operation of the fuel cell is stopped, the surface of the cathode 15 is changed when the ambient temperature decreases after the operation stops and the internal temperature of the fuel cell becomes below freezing point. May be covered with ice. In such a state, the next time the fuel cell is started, the oxidizing gas cannot be supplied to the ice-covered catalyst, and power generation cannot be started. In the fuel cell of the present embodiment, water such as produced water and condensed water is quickly removed from the vicinity of the cathode 15 by the action of the hydrophilic layer 32. Therefore, when the operation of the fuel cell is stopped, Will not stay. Therefore, even when the temperature falls while the fuel cell is stopped, it is possible to prevent inconvenience at the start of power generation due to the cathode 15 being covered with ice when the fuel cell is restarted.

  Note that the above-described effects due to the positional relationship between the hydrophilic layer 32 and the water-repellent layer 30 are the same effects that can be obtained when a gas diffusion layer is produced by a method other than introducing a hydrophilic group by electrochemical oxidation. . For example, a conductive paste containing a hydrophilic group and a conductive paste containing a water-repellent group are applied on the conductive porous body, and the hydrophilic layer and the water-repellent layer are disposed at the same position as the gas diffusion layer 17 of the example. Even when the gas diffusion layer is formed by providing the layer, the above-described effect due to the positional relationship between the hydrophilic layer and the water repellent layer can be obtained in the same manner.

  FIG. 9 is an explanatory diagram showing the results of examining the performance of the fuel cell of this example under low temperature conditions. As shown in FIG. 1, the fuel cell of the example includes a gas diffusion layer 17 having a hydrophilic layer 32 and a water repellent layer 30 formed on the surface thereof on the cathode side. Moreover, the Example of a comparative example is equipped with the gas diffusion layer which has only a water repellent layer without forming the hydrophilic layer 32 in the cathode side. Using the fuel cells of these examples and comparative examples, power generation was performed under a predetermined low temperature condition, and the cell performance was compared. When investigating the performance, the fuel cells of the above Examples and Comparative Examples were used in a single cell state.

Conditions for comparing battery performance under low temperature conditions are as follows. That is, hydrogen was supplied to the anode side at a flow rate of 300 cc / min, and air was supplied to the cathode side at a flow rate of 300 cc / min. At this time, the cell temperature was maintained at −10 ° C., and a current was swept by connecting a load to the fuel cell so that the current density was maintained at 50 mA / cm ² at normal pressure. In FIG. 9, the horizontal axis indicates the elapsed time from the start of power generation, and the vertical axis indicates the output voltage of the fuel cell.

  As shown in FIG. 9, even in the low temperature condition of −10 ° C., the fuel cell of the example can maintain an output voltage comparable to that at the start of power generation for a longer period, specifically 5 minutes or more. did it. On the other hand, in the fuel cell of the comparative example, the output voltage suddenly decreased after about 2 minutes from the start of power generation. Here, in the fuel cell of the comparative example, the cell voltage was decreased because the generated water generated on the cathode side was frozen to cover the cathode surface, and oxygen supply to the cathode was delayed. In contrast, in the fuel cell of the example, by providing the hydrophilic layer 32 on the surface of the gas diffusion layer 17, the generated water is efficiently removed from the surface of the cathode 15, and the coating of the surface of the cathode 15 with the frozen generated water is suppressed. Therefore, it is considered that a good output voltage can be maintained for a longer time.

E. Other examples of electrochemical oxidation:
When the hydrophilic layer 32 is formed on the carbon porous body 117 having the water repellent layer 118 formed on the surface, a configuration other than that shown in FIG. 4 may be adopted. For example, in FIG. 4, the catalyst layer 42 is provided in the structure 40 so as to be in contact with the region where the hydrophilic layer 32 is to be formed, but such a catalyst layer 42 may not be provided. FIG. 10 shows a state in which electrochemical oxidation is performed using the structure 140 that does not include the catalyst layer 42. The structure 140 shown in FIG. 10 has a configuration similar to that of the structure 40 shown in FIG. 4, and thus the same reference numerals are given to portions common to FIG. 4 and description thereof is omitted. In FIG. 10, the insulating layer 43 similar to that in FIG. 4 is provided on the electrolyte layer 113 of the structure 140. However, since the catalyst layer 42 is not provided, the hydrophilic layer 32 on the surface of the carbon porous body 117. And the electrolyte layer 113 are in direct contact with each other. Here, contact between the carbon porous body 117 and the electrolyte layer 113 is ensured by the pressing force applied in the stacking direction between the structure 140, the carbon porous body 117, and the separator 121. Even when such a structure 140 is used, the gas diffusion layer 17 similar to that of the above-described embodiment can be produced. Thus, in order for the electrochemical oxidation to proceed, the catalyst layer 42 is not necessarily required. If the surface of the carbon porous body 117 and the electrolyte layer 113 are in contact with each other, the catalyst layer 42 is generated along with the electrochemical oxidation. Protons can be transferred to the electrolyte layer 113 to form the hydrophilic layer 32.

  In the structure that performs electrochemical oxidation, the electrolyte layer does not need to be formed on the entire surface, and may be formed only in a region corresponding to the hydrophilic layer 32. FIG. 11 shows a state in which electrochemical oxidation is performed using the structure 240 including the electrolyte layer 213 having such a shape. Since structure 240 shown in FIG. 11 has a configuration similar to that of structure 140 in FIG. 10, the same reference numerals are given to portions common to FIG. In FIG. 11, an electrolyte layer 213 similar to the electrolyte layer 113 is formed on the catalyst layer 114 of the structure 240 only in a region corresponding to the region where the hydrophilic layer 32 is to be formed on the surface of the carbon porous body 117. Yes. In addition, an insulating layer 243 similar to the insulating layer 43 is formed on the catalyst layer 114 in a region other than the region where the electrolyte layer 213 is formed. That is, the insulating layer 243 having non-proton conductivity and non-electron conductivity is formed. Even when such a structure 240 is used, the gas diffusion layer 17 similar to that of the above-described embodiment can be produced.

  Here, in the structure used for electrochemical oxidation, an insulating layer is not necessarily provided in a region corresponding to a region to be left as the water repellent layer 30 in the carbon porous body. When the electrolyte layer 113 is provided on the entire surface in contact with the carbon porous body 117 as in the structure of FIGS. 4 and 10, the carbon porous body 117 is in a region where the hydrophilic layer 32 is not provided in the carbon porous body 117. As long as proton conduction is prevented between the electrolyte layer 113 and the electrolyte layer 113. In addition, as shown in FIG. 11, when the electrolyte layer 213 is provided only in a limited region, the region between the carbon porous body 117 and the catalyst layer 114 is not provided in the carbon porous body 117 where the hydrophilic layer 32 is not provided. Therefore, it is sufficient that the conduction of protons and electrons is prevented.

  In the embodiment described above, hydrogen is supplied to the flow path 122 between the separator 120 and the gas diffusion layer 116 when performing the electrochemical oxidation, but other types of gases can also be used. . In the case of using hydrogen, it is desirable that the voltage control during the electrochemical oxidation becomes easier, but for example, even if oxygen or an inert gas is used instead of hydrogen, the electrochemical oxidation process is the same. Can be done. As described above, in order to proceed the electrochemical oxidation in the carbon porous body 117, the potential difference with respect to the electrode potential on the catalyst layer 114 side is a potential difference exceeding a predetermined value determined thermodynamically. What is necessary is just to apply a voltage to the carbon porous body 117 side. Therefore, when a gas other than hydrogen is allowed to flow through the flow path 122, the required potential difference is determined thermodynamically based on the electrode potential on the catalyst layer 114 side determined by the gas used, so that a sufficient potential difference is realized. The voltage may be applied by the external power supply 44.

  Further, a gas other than nitrogen may be used as the gas supplied to the flow path 123 between the separator 121 and the carbon porous body 117. For example, other types of inert gases such as helium (He) and argon (Ar) can be used.

  Furthermore, although the structure 40 for performing electrochemical oxidation has a structure similar to the structure on the anode side of the MEA 12 in the single cell 10, it may have a different configuration. For example, the electrolyte layer 113 included in the structure 40 may be formed of an electrolyte other than the solid polymer. If an electrolyte having proton conductivity is used, electrochemical oxidation can be carried out in the same manner using other types of electrolytes such as solid oxides. Since the solid polymer film is softer than a solid oxide or the like, when the electrolyte layer 113 is formed of a solid polymer film like the structure 40, the gap between the carbon porous body 117 and the structure is determined. It is possible to secure a larger contact area. Thus, if the contact area between the carbon porous body 117 and the structure is increased, it becomes possible to introduce hydrophilic groups from the surface to a deeper region in the carbon porous body. The molecular film is particularly desirable as an electrolyte constituting the electrolyte layer 113 of the structure.

F. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

F1. Modification 1:
In the gas diffusion layer 17 of the embodiment, the hydrophilic layer 32 is provided in the groove portion of the separator 21, that is, the region corresponding to the oxidizing gas flow path 23 in the single cell. However, the present invention is not limited to this. As described above, it is preferable to provide the hydrophilic layer 32 in the region corresponding to the groove portion because the generated water travel distance when draining the generated water is short, and drainage efficiency is increased. However, even when a hydrophilic layer is partially provided in other regions on the surface of the gas diffusion layer, the effect of suppressing the retention of water on the electrode surface by guiding the generated water into the gas diffusion layer by the hydrophilic layer, The effect of pushing the generated water back to the electrolyte layer 13 side by the water repellent layer can be similarly obtained.

F2. Modification 2:
In the embodiment, the gas diffusion layer 17 is provided with the hydrophilic layer 32 and the water repellent layer 30 on the surface thereof, but a configuration without the water repellent layer is also possible. That is, in the manufacturing process of the gas diffusion layer 17 shown in FIG. 2, only the electrochemical oxidation process of step S120 may be performed without performing the water repellent process of step S110. Even in such a case, it is possible to obtain an effect of improving drainage near the electrode by providing the hydrophilic layer. Further, by using electrochemical oxidation to form a hydrophilic layer, the conditions of electrochemical oxidation treatment are adjusted to precisely adjust the degree of hydrophilicity, and a gas diffusion layer having a desired hydrophilicity The effect of producing is obtained.

  Here, the gas diffusion layer 17 produced using the electrochemical oxidation treatment is a fuel cell of a type other than the polymer electrolyte fuel cell shown in the embodiment, for example, a solid electrolyte type including a ceramic layer as an electrolyte layer. It is also possible to apply to a fuel cell. Also when applied to other types of fuel cells, if a gas diffusion layer similar to the gas diffusion layer 17 is used as a gas diffusion layer provided on the electrode side where generated water is generated, drainage from the electrode is enhanced, particularly at low temperatures. The battery performance in can be improved. Thus, in a fuel cell including an electrolyte layer other than a solid polymer membrane, it is not necessary to maintain the wet state of the electrolyte layer for the purpose of maintaining the proton conductivity of the electrolyte layer, so that the generated water is pushed back to the electrolyte layer side. The effect of providing a water layer is small. Therefore, when the present invention is applied to other types of fuel cells, the effect of improving the cell performance can be sufficiently obtained even when the water repellent layer is not provided.

F3. Modification 3:
In the embodiment, the space formed between the gas diffusion layer and the recess on the separator surface is used as the gas flow path in the single cell. However, the present invention can be applied to fuel cells having different configurations. For example, a flat plate-like separator having no unevenness is disposed outside the flat plate-like gas diffusion layer, and the entire internal space of the gas diffusion layer, which is a porous body, is disposed inside the single cell. It is good also as a structure. Also in this case, the surface of the gas diffusion layer in contact with the catalyst layer may be partially hydrophilized, and other regions may be subjected to water repellent treatment in advance. Further, in the case of a fuel cell other than a solid polymer type, the hydrophilic layer may be formed wider, and the other region may not be subjected to aggressive water repellent treatment, or the catalyst layer and A hydrophilic layer may be provided on the entire surface of the gas diffusion layer in contact therewith.

F4. Modification 4:
In the examples, the gas diffusion layer that forms the hydrophilic layer by electrochemical oxidation is formed of a carbon porous body. However, the gas diffusion layer may be formed of a conductive material other than carbon, for example, metal porous The body may be used. In this case, if the carbon is supported at least on the surface of the porous body formed of the gas diffusion layer and subjected to the hydrophilic treatment by electrochemical oxidation, the hydrophilic treatment by the electrochemical oxidation of carbon is similarly performed. Can be applied. For example, carbon can be supported by applying a paste containing carbon particles to the surface of the metal porous body. When the water repellent layer is formed on the surface of the metal porous body in advance, a paste containing a water repellent substance such as a fluororesin together with the carbon particles is applied to the surface of the metal porous body, and the carbon particles and the water repellent substance are applied. May be deposited on the porous metal body.

F5. Modification 5:
In the embodiment, the gas diffusion layer 17 in which the hydrophilic layer 32 is formed is disposed on the cathode side. However, a similar gas diffusion layer may be disposed on the anode side, that is, the side where generated water is not generated. When the fuel gas supplied to the anode side contains a certain amount of water vapor, water in the fuel gas may condense at the low temperature and cover the anode surface. By providing, the condensed water can be discharged quickly and the battery performance can be prevented from deteriorating. In particular, in the polymer electrolyte fuel cell as in the example, the fuel gas may be actively humidified in order to maintain the wet state of the electrolyte layer, and from the cathode side to the anode side through the electrolyte layer. Therefore, the effect of improving the drainage by providing a hydrophilic layer on the surface of the anode-side gas diffusion layer can be obtained.

It is a cross-sectional schematic diagram showing the outline of a structure of the fuel cell of an Example. 3 is a process diagram illustrating a method for manufacturing a gas diffusion layer 17. FIG. It is explanatory drawing showing the member in connection with the hydrophilic process by electrochemical oxidation. It is explanatory drawing showing a mode that the surface of the carbon porous body 117 is oxidized. It is explanatory drawing showing an example of the oxidation reaction which progresses on the carbon porous body 117 surface. It is a cyclic voltammogram showing the result of having investigated the property of the gas diffusion layer by cyclic voltammetry. It is explanatory drawing which shows the oxidation-reduction reaction of a quinone group. It is explanatory drawing showing the mode of the vicinity of the cathode 15 at the time of electric power generation. It is explanatory drawing which shows the result of having investigated the performance of the fuel cell of a present Example on low temperature conditions. FIG. 5 is an explanatory diagram illustrating a state in which electrochemical oxidation is performed using a structure 140. FIG. 10 is an explanatory diagram illustrating a state in which electrochemical oxidation is performed using a structure 240.

Explanation of symbols

10 ... Single cell 12 ... MEA
DESCRIPTION OF SYMBOLS 13 ... Electrolyte layer 14 ... Anode 15 ... Cathode 16, 17 ... Gas diffusion layer 19 ... Hydrophilic layer 20, 21 ... Separator 22 ... Fuel gas flow path in single cell 23 ... Oxidation gas flow path in single cell 30 ... Water-repellent layer 32 ... hydrophilic layer 34 ... water repellent layer 40, 140, 240 ... structure 42 ... catalyst layer 43, 243 ... insulating layer 44 ... external power source 113, 213 ... electrolyte layer 114 ... catalyst layer 116 ... gas diffusion layer 117 ... carbon porous Body 118 ... Water repellent layer 120 ... Separator 121 ... Separator 122 ... Channel 123 ... Channel

Claims (12)

A method for producing a fuel cell gas diffusion layer provided adjacent to a fuel cell electrode formed on a fuel cell electrolyte layer, comprising:
(A) preparing a conductive porous body having carbon molecules on one surface, which is a base material for the fuel cell gas diffusion layer;
(B) preparing an oxidation electrolyte layer having proton conductivity;
On one surface of the oxidation electrolyte layer, an oxidation electrode layer containing a catalyst that promotes a reaction that generates hydrogen from protons and electrons is formed,
Laminating the oxidizing electrolyte layer and the conductive porous body so that the carbon molecules are in contact with the other surface of the oxidizing electrolyte layer,
Connecting the conductive porous body to a positive electrode of a predetermined external power source, and connecting the oxidation electrode layer to a negative electrode of the external power source;
(C) supplying water vapor to the conductive porous body and applying a voltage between the oxidation electrode layer and the conductive porous body by the external power source;
With
In the step (c), the carbon molecule is oxidized by the water vapor to generate a hydrophilic group, and protons and electrons generated by the oxidation pass through the oxidation electrolyte layer or the external power source, respectively. A method for producing a gas diffusion layer for a fuel cell, to which a voltage is applied to cause an electrochemical oxidation reaction that moves to the oxidation electrode layer and generates hydrogen by the catalyst. It is a manufacturing method of the gas diffusion layer for fuel cells according to claim 1,
The step (c)
(C-1) The potential of the oxidation electrode layer is set to a predetermined value with respect to the oxidation electrode layer while supplying the inert gas containing water vapor to the conductive porous body. Supplying a predetermined gas for
(C-2) The difference between the electrode potential in the electrode layer for oxidation when the predetermined gas is supplied and the potential in the conductive porous body when the inert gas containing water vapor is supplied, Applying a voltage between the electrode layer for oxidation and the conductive porous body so that the electrochemical oxidation reaction can proceed to a value, a method for producing a gas diffusion layer for a fuel cell . A method for producing a gas diffusion layer for a fuel cell according to claim 2,
The predetermined gas supplied to the oxidation electrode layer is hydrogen. A method for producing a gas diffusion layer for a fuel cell. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 1 to 3,
In the step (b), in order to introduce a hydrophilic group into a predetermined region on the one surface of the conductive porous body, the oxidation electrolyte layer and the conductive porous body are laminated, Gas diffusion for fuel cells, comprising a step of providing an aprotic conductive layer made of a material having no proton conductivity in a region other than the predetermined region between the oxidation electrolyte layer and the conductive porous body Layer manufacturing method. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 1 to 3,
In the step (b), in order to introduce a hydrophilic group into a predetermined region on the one surface of the conductive porous body, as an operation of stacking the oxidation electrolyte layer and the conductive porous body, The oxidation electrolyte layer is formed in the predetermined region, and a layer in which a non-proton conductive layer made of a material having no proton conductivity is formed in a region other than the predetermined region, and the conductive porous layer A method for producing a gas diffusion layer for a fuel cell, wherein the gas diffusion layer is laminated with a material. A method for producing a gas diffusion layer for a fuel cell according to claim 4 or 5,
The method for producing a gas diffusion layer for a fuel cell, wherein the non-proton conductive layer further exhibits non-electron conductivity. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 4 to 6,
The step (a) includes a step of subjecting the one surface of the conductive porous body to a water repellent treatment in advance. A method for producing a gas diffusion layer for a fuel cell. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 1 to 7,
The gas diffusion layer for a fuel cell is a gas for disposing and using the surface of the gas diffusion layer where the hydrophilic group is introduced so as to be in contact with the electrode on the electrode side where generated water is generated by an electrochemical reaction. A method for producing a gas diffusion layer for a fuel cell, which is a diffusion layer. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 1 to 8,
The oxidation electrolyte layer has a structure common to the fuel cell electrolyte layer, and the oxidation electrode has a structure common to the fuel cell electrode. . A fuel cell manufacturing method comprising:
(A) forming a fuel cell electrode provided with a catalyst on both surfaces of a fuel cell electrolyte layer having proton conductivity;
(B) disposing a conductive porous body as a gas diffusion layer through which a gas to be subjected to an electrochemical reaction flows so as to sandwich the fuel cell electrolyte layer on which the fuel cell electrode is formed. ,
In the step (B), a gas diffusion layer is manufactured by the method for manufacturing a fuel cell gas diffusion layer according to any one of claims 1 to 9, and the manufactured gas diffusion layer is separated from the oxidation electrolyte layer. And the separated gas diffusion layer as at least one of the conductive porous bodies sandwiching the fuel cell electrolyte layer so that the surface into which the hydrophilic group is introduced is in contact with the fuel cell electrode. A fuel cell manufacturing method. A fuel cell manufacturing method comprising:
(A) forming a fuel cell electrode provided with a catalyst on both surfaces of a fuel cell electrolyte layer having proton conductivity;
(B) disposing a conductive porous body as a gas diffusion layer through which a gas to be subjected to an electrochemical reaction flows so as to sandwich the fuel cell electrolyte layer on which the fuel cell electrode is formed;
(C) Further, the conductive porous body has a predetermined concavo-convex shape on the outer surface, abuts the conductive porous body at the end of the concavo-convex convex portion, and between the convex portions Disposing a gas separator that forms a flow path for the gas between the conductive porous body and a recess formed in
The step (B) includes a step of producing a gas diffusion layer by the method for producing a fuel cell gas diffusion layer according to any one of claims 4 to 7, and separating the produced gas diffusion layer from the oxidation electrolyte layer. And disposing the separated gas diffusion layer as at least one of the conductive porous bodies sandwiching the fuel cell electrolyte layer so that the surface into which the hydrophilic group is introduced is in contact with the electrode. And comprising
The step (C) is a step of arranging and arranging the gas separator so that the predetermined region into which the hydrophilic group is introduced in the gas diffusion layer for the fuel cell and the concave portion correspond to each other. Battery manufacturing method. A method of manufacturing a fuel cell according to claim 11,
The said (B) process is the said gas diffusion for fuel cells manufactured by the manufacturing method of the gas diffusion layer for fuel cells in any one of Claim 4 thru | or 7 in the electrode side in which produced water produces | generates with an electrochemical reaction at least. A method of manufacturing a fuel cell using a layer.

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