JP5405783B2 - Fuel cell catalyst layer, fuel cell catalyst layer transfer sheet, fuel cell gas diffusion electrode, fuel cell membrane electrode assembly, and fuel cell - Google Patents

Description

  The present invention relates to a catalyst layer for a polymer electrolyte fuel cell.

  A polymer electrolyte fuel cell (PEFC) using a polymer electrolyte having a proton-conducting group can be operated at a low temperature and can be reduced in size and weight. Application to small portable devices for private use is being considered and is expected as one of the pillars of new energy technology.

  The PEFC has a structure in which a membrane electrode assembly (MEA) of a gas diffusion electrode and a polymer electrolyte membrane formed from a catalyst layer and a gas diffusion layer is sandwiched between gas flow plates from both sides. The MEA includes an anode, a cathode, and a polymer electrolyte membrane that separates them. A gas flow path is processed in the gas flow plate. Electric power can be obtained by supplying hydrogen as fuel to the anode and oxygen or air as oxidant to the cathode.

However, since this PEFC cannot obtain a desired output unless the supplied fuel and oxidant are sufficiently humidified, a humidifier or the like must be installed. For this reason, since the entire PEFC system becomes larger, it is indispensable to downsize or remove the humidifier in recent years to reduce the size of the PEFC system, and the PEFC can be operated even by supplying low-humidified fuel and oxidant. There is a strong demand for technology to do this. In order to solve the above-mentioned problem, for example, Patent Literature 1 discloses a technique for improving moisture retention by disposing a hydrophilic layer in a catalyst layer. This technique is disclosed on the anode side. Nothing is said about the cathode side, which is specialized and highly sensitive to the humidity of the oxidant.
JP2007-329036

  There is a strong desire to produce a catalyst layer that exhibits good PEFC power generation characteristics even when a low-humidifying oxidant is supplied, particularly a catalyst layer that can be applied to a cathode. The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell catalyst layer that exhibits good PEFC power generation characteristics even when a low-humidifying oxidant is supplied. .

  As a result of intensive studies to solve the above problems, the present inventor manufactured a catalyst layer using at least a polymer compound having an aromatic unit having a proton conductive group introduced therein and a fuel cell catalyst. The present invention has found that by controlling the water contact angle of the catalyst layer to 0 ° <X <90 °, good power generation characteristics of PEFC can be expressed even when a low-humidified gas, particularly an oxidizing agent is supplied. It came to complete.

  That is, according to the present invention, the contact angle of water of the catalyst layer for a fuel cell including at least the polymer compound having an aromatic unit having a proton conductive group introduced therein and the catalyst for the fuel cell is 0 ° <X <90 °. A catalyst layer for a fuel cell, characterized in that

Further, the ratio Y of the polymer compound into which the proton conductive group is introduced relative to the catalyst carrier in the catalyst layer (Y = weight of solid content of polymer compound into which the proton conductive group is introduced / weight of the catalyst carrier) is 0. It is preferable that 1 ≦ Y ≦ 1.0.
The catalyst layer is preferably a fuel cell catalyst layer transfer sheet formed on a polymer film.

The catalyst layer is preferably a fuel cell catalyst layer transfer sheet formed on an inorganic film.
Moreover, it is preferable that the said catalyst layer is a gas diffusion electrode for fuel cells formed on the electroconductive porous sheet.
The catalyst layer is preferably used as a cathode, and the catalyst layer is preferably a fuel cell membrane electrode assembly bonded to a polymer electrolyte membrane having proton conductivity. The catalyst layer is preferably used for a fuel cell.

According to another aspect of the present invention, there is provided a power generation method characterized in that a gas containing at least an oxidant containing oxygen and water vapor of 90% RH or less is supplied to the fuel cell catalyst layer.
According to another aspect of the present invention, there is provided a fuel cell system in which a gas containing at least an oxidizing agent containing oxygen and water vapor of 90% RH or less is supplied to the fuel cell catalyst layer.

According to the present invention, a catalyst layer including at least a polymer compound having an aromatic unit into which a proton conductive group is introduced and a catalyst for a fuel cell is prepared, and the contact angle of water of the catalyst layer is 0 ° < By controlling X <90 °, good power generation characteristics of PEFC can be expressed even when a low-humidified fuel and an oxidant are supplied. Therefore, the PEFC using the fuel cell catalyst layer of the present invention showed excellent power generation characteristics even under low humidification conditions.

An embodiment of the present invention will be described as follows. Note that the present invention is not limited to the following description.

  The fuel cell catalyst layer of the present invention will be specifically described.

  The water contact angle X of the fuel cell catalyst layer of the present invention is 0 ° <X <90 °. In the case of X in the above range, even if a low-humidified fuel and an oxidizer are supplied, an appropriate amount of water can be maintained in the catalyst layer, so that good power generation characteristics can be exhibited.

  The low-humidifying oxidant in the present invention preferably contains at least oxygen. In the present invention, the amount of water vapor in the low-humidifying oxidant is usually 90% RH or less, preferably 85% RH or less, more preferably 80% RH or less.

  The control of the water contact angle of the fuel cell catalyst layer of the present invention is as follows: “the ratio Y of the polymer compound into which the proton conductive group is introduced to the catalyst carrier in the catalyst layer (Y = a high proton conductive group introduced ratio). Solid content weight of molecular compound / weight of catalyst support) "or" a ratio of the polymer compound in which the proton conductive group is not introduced to the catalyst support in the catalyst layer or an inorganic compound Z (Z = proton conductivity) " The weight of the polymer compound or inorganic compound into which the group is not introduced / the weight of the solid content / the weight of the catalyst carrier) can be controlled. When the water contact angle X of the fuel cell catalyst layer is larger than 90 °, the water repellency is too large, and the catalyst layer and the polymer electrolyte membrane are discharged out of the system up to the amount of water necessary for proton conduction. This is not preferable because the power generation characteristics are significantly deteriorated.

  The method for measuring the contact angle of the catalyst layer is not particularly limited. For example, a certain amount of deionized water (eg, 1 μL to 1 mL) is dropped on the surface of the catalyst layer, and after a certain time (1 second to 1 minute) has elapsed, A method of measuring the shape by visually observing the shape with a CCD camera is exemplified.

  The polymer compound having an aromatic unit having at least a proton conductive group used in the present invention is not particularly limited as long as it can introduce a proton conductive group into the aromatic unit in the polymer compound. For example, polyetherketone, polyetheretherketone, polyetherketoneketone, polyetheretherketoneketone, polysulfone, polyethersulfone, polyetherethersulfone, polyarylethersulfone, poly1,4-biphenyleneetherethersulfone, polyarylene Ether sulfone, polyparaphenylene, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfoxide, polyphenylene sulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, polystyrene, Ndiotactic polystyrene, polyethylene-graft-polystyrene copolymer, styrene- (ethylene-propylene) -styrene block copolymer, styrene- (ethylene-butylene) -styrene block copolymer, styrene-isobutylene-styrene block copolymer Examples of the polymer include polyimide, polyetherimide, polybenzimidazole, polybenzoxazole, polybenzothiazole, cyanate ester resin, and derivatives thereof. The polymer compound used in the present invention may be a copolymer using one or more of these compounds, or a compound using these compounds in a graft chain. Moreover, in order to produce the copolymer of these compounds, the coupling agent which connects compounds may be used.

  As a method for obtaining a polymer compound in which a proton conductive group is introduced into a polymer compound having an aromatic unit of the present invention, a monomer having a proton conductive group and a monomer having no proton conductive group are copolymerized. Known methods such as a method of introducing a proton conductive group by a polymer reaction with a polymer compound having an aromatic unit, and the like can be applied. Examples of the former include, for example, a method in which a monomer having a proton conductive group into which an appropriate protective group is introduced as necessary and a monomer having no proton conductive group are copolymerized and then deprotected. . Examples of the latter include a method of reacting a polymer compound having an aromatic unit with a sulfonating agent such as chlorosulfonic acid in a solvent, a method of reacting in concentrated sulfuric acid or fuming sulfuric acid, and the like. .

  The proton conductive group of the present invention is not particularly limited as long as it can dissociate protons in a water-containing state, and examples thereof include sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, carboxyl groups, and phenolic hydroxyl groups. These may be used alone or in combination. Among these, a sulfonic acid group is particularly preferable in view of ease of introduction of a proton conductive group and proton conductivity of the resulting polymer compound.

  The ion exchange capacity of the polymer compound in which a proton conductive group is introduced into the polymer compound having an aromatic unit of the present invention is preferably 0.9 meq / g or more and 6 meq / g or less. If it is less than 0.9 meq / g, the proton conductivity required for PEFC power generation may not be obtained, and if it is greater than 6 meq / g, the polymer compound is decomposed by the reaction having the ion exchange capacity. There is a fear.

  In order to improve the chemical durability of the polymer compound used in the present invention, a crosslinking material may be used. Although the said crosslinking material is not specifically limited, It is preferable that two or more functional groups of Formula (1) exist in 1 molecule. When the number of functional groups is less than 1, it is not preferable because crosslinking of the polymer compound may not proceed.

  The R of the functional group present in two or more molecules in the cross-linking material is not particularly limited as long as it is any one of hydrogen, an alkyl group, and an acyl group, and the Rs of the functional groups are independent and the same. Or different. Considering the availability of the compound and the ease of removing the compound by-produced by the reaction with the above-mentioned “polymer compound having an aromatic unit having a proton conductive group introduced”, hydrogen, methyl group or acetyl group It is preferable that

  Examples of such a crosslinking material include 1,2-bis (hydroxymethyl) benzene, 1,3-bis (hydroxymethyl) benzene, 1,4-bis (hydroxymethyl) benzene, and 2,6-bis (hydroxy). Methyl) phenol, 3,5-bis (hydroxymethyl) phenol, 4,6-bis (hydroxymethyl) -o-cresol, 2,6-bis (hydroxymethyl) -p-cresol, 2,6-bis (hydroxy) Methyl) -4-t-butylphenol, 2,2′-bis (hydroxymethyl) diphenyl ether, 4,4′-bis (hydroxymethyl) diphenyl ether, 1,2,4-benzenetrimethanol, 1,3,5-benzene Trimethanol, 4,4′-methylenebis [2,6-di (hydroxymethyl)] phenol, oxybis ( , 4-Dihydroxymethyl) benzene, 1,2-bis (methoxymethyl) benzene, 1,3-bis (methoxymethyl) benzene, 1,4-bis (methoxymethyl) benzene, 2,6-bis (methoxymethyl) -P-cresol, 2,6-bis (methoxymethyl) -4-tert-butylphenol, 2,4,6-tris [bis (methoxymethyl) amino] -1,3,5-triazine, Cymel (registered trademark, Nippon Cytec Industries Co., Ltd.), DML-PC (Honshu Chemical Industry Co., Ltd.), TML-BPA-MF (Honshu Chemical Industry Co., Ltd.), TML-BPAF-MF (Honshu Chemical Industry Co., Ltd.), DML- OC (manufactured by Honshu Chemical Industry Co., Ltd.), Dimethymethyl p-CR (manufactured by Honshu Chemical Industry Co., Ltd.), DML-MBPC ( State Chemical Industry Co., Ltd.), DML-BPC (Honshu Chemical Industry Co., Ltd.), TML-BP (Honshu Chemical Industry Co., Ltd.), TMOM-BP (Honshu Chemical Industry Co., Ltd.), DML-PEP (Honshu Chemical Co., Ltd.) Industrial Co., Ltd.), DML-34X (Honshu Chemical Industry Co., Ltd.), DML-PSBP (Honshu Chemical Industry Co., Ltd.), DML-PTBP (Honshu Chemical Industry Co., Ltd.), DML-PCHP (Honshu Chemical Industry Co., Ltd.) Company), DML-POP (Honshu Chemical Industry Co., Ltd.), DML-PFP (Honshu Chemical Industry Co., Ltd.), DML-MBOC (Honshu Chemical Industry Co., Ltd.), HML-TPPHBA (Honshu Chemical Industry Co., Ltd.) ), HMOM-TPPHBA (manufactured by Honshu Chemical Industry Co., Ltd.), 26DMPC (manufactured by Asahi Organic Materials Co., Ltd.), 46DMOC (Asahi Organic Material Industries Co., Ltd.) ), DM-BIPC-F (Asahi Organic Material Industries Co., Ltd.), DM-BIOC-F (Asahi Organic Material Industries Co., Ltd.), TM-BIP-A (Asahi Organic Material Industries Co., Ltd.), Nikarak (Stock) (Manufactured by Sanwa Chemical Co., Ltd.) can be exemplified, but is not limited thereto. Furthermore, although partially overlapping with the above, examples of the crosslinking material include compounds represented by the following chemical formula. That is, 10 types of the following structural formulas (2)-(11), 15 types of (12)-(26), 15 types of (27)-(41), and 4 types of (42)-(45) Although a compound can be illustrated, it is not limited only to these.

  These compounds may be one kind or plural. Among these, availability, reactivity with the above-mentioned “polymer compound having an aromatic unit into which a proton-conducting group is introduced”, and “polymer having an aromatic unit into which a proton-conducting group is introduced” In consideration of the heat resistance of the reaction product with the “compound” and the effect of suppressing the swelling / solubility and permeability to liquids such as water, ten types of compounds represented by the following structural formulas (2) to (11)

からなる群から選択される少なくとも１種以上であることが特に好ましい。

Particularly preferred is at least one selected from the group consisting of

  The blending ratio of the “polymer compound having an aromatic unit into which a proton conductive group is introduced” and the cross-linking material is 100 wt% of the “polymer compound having an aromatic unit into which a proton conductive group is introduced”. The crosslinking material is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight with respect to parts. When the cross-linking material is less than 1 part by weight, the effect of improving the heat resistance of the reaction product with the “polymer compound having an aromatic unit into which a proton conductive group is introduced” and the swelling property with respect to a liquid such as water There is a risk that the effect of suppressing solubility and permeability is lowered. On the other hand, if the cross-linking material exceeds 50 parts by weight, the proton conductivity and mechanical strength of the reaction product with the “polymer compound having an aromatic unit having a proton conductive group introduced” may be lowered. .

  The reaction product of the polymer electrolyte and the crosslinking material can be obtained by heating the mixture. In addition, this chemical reaction can occur sufficiently in air as long as it is heated. The heating temperature usually needs to be in the range of the temperature at which the chemical reaction proceeds to the decomposition temperature of the polymer electrolyte and the boiling point and decomposition temperature of the compound X. In order to obtain a fuel cell catalyst layer and a fuel cell electrode in which these chemical reactions proceed rapidly and can exhibit excellent performance, heating is performed at a temperature not lower than the temperature at which the chemical reaction proceeds and not higher than 300 ° C. Is preferred. Here, the temperature at which the chemical reaction proceeds can be confirmed by a change in the amount of heat generated before and after the reaction by a differential scanning calorimeter (DSC) or a change in mechanical characteristics by a thermomechanical analyzer (TMA) or the like. . When the heating temperature is lower than the above temperature range, the reaction may not occur, the reaction may be insufficient, or the reaction time may be prolonged. On the other hand, when the heating temperature is higher than the above temperature range, there is a risk that side reactions or decomposition reactions that cause performance degradation may occur, or proton conductive groups of the polymer electrolyte may be decomposed and eliminated. The heating conditions are preferably 130 ° C. or higher and 200 ° C. or lower, and the time is 1 minute or longer and 180 minutes or shorter, preferably 5 minutes or longer and 60 minutes or shorter. By selecting such heating conditions, the production method is excellent in terms of both characteristics and productivity. In the present invention, the heating method at the time of the chemical reaction is not particularly limited, and examples thereof include heating by a normal oven, heating by a vacuum oven, heating by a press machine, and the like, but are not limited thereto. Moreover, you may heat at the time of the heating press-contact at the time of the membrane electrode assembly for fuel cells mentioned later.

  The fuel cell catalyst used in the present invention is not particularly limited, and a catalyst that can use an active catalyst for the electrode reaction of the fuel cell, for example, a catalyst carrier on which a catalyst metal is supported is preferable. The catalyst carrier of the present invention refers to a member that supports a catalyst that is active for the electrode reaction of a fuel cell. However, the polymer compound into which the proton conductive group is introduced or the proton conductive group is introduced. High molecular compounds not included are not included.

  The catalyst carrier may be, for example, a high surface area carbon material such as furnace black, acetylene black, ketjen black, activated carbon, carbon nanohorn, or carbon nanotube, or a high surface area inorganic compound such as titanium dioxide or silicon oxide. preferable. Examples of the catalyst metal include platinum. Furthermore, a composite or alloy catalyst made of platinum and an arbitrary catalyst metal can be used for improving the reduction ability, stabilizing the catalyst metal, or extending the life. Further, the component may be three or more components using iron, tin, rare earth elements and the like. Further, the weight ratio of the catalyst metal to the fuel cell catalyst is preferably 20 wt% or more and 95 wt% or less. If it is less than 20 wt%, when a catalyst layer having a desired amount of catalyst metal is formed, the thickness of the catalyst layer is increased, and the diffusibility of the fuel and the oxidant is decreased. On the other hand, if it is 95 wt% or more, the catalyst metal cannot be finely supported on the surface of the catalyst carrier, and the total surface area of the catalyst metal is reduced, so that the activity of the catalyst is lowered.

  In the catalyst layer of the present invention, the ratio Y of the polymer compound into which the proton conductive group is introduced with respect to the catalyst carrier (Y = solid content weight of the polymer compound into which the proton conductive group is introduced / weight of the catalyst carrier) is 0. It is preferable that 1 ≦ Y ≦ 1.0. If it is less than 0.1, the polymer compound having a proton conductive group introduced in the catalyst layer is less connected, so that the proton conduction path is interrupted and the power generation characteristics of the PEFC are deteriorated. On the other hand, when the ratio is larger than 1.0, the pores in the catalyst layer are filled with the polymer compound into which the proton conductive group is introduced, so that the diffusion of the fuel and the oxidant is inhibited and the power generation characteristics of the PEFC are deteriorated. It is not preferable.

  Further, the solid content weight of the polymer compound into which the proton conductive group is introduced means only the solid content weight of the polymer compound when the cross-linking material is not used. Moreover, when the said crosslinking material is used, the total solid content weight of the said high molecular compound and the said crosslinking material is said.

  In order to control the contact angle of the catalyst layer of the present invention, the catalyst layer may contain a polymer compound into which no proton conductive group is introduced or an inorganic compound. The polymer compound into which the proton conductive group is not introduced is preferably a fluorine-based polymer compound such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Inorganic compounds such as titanium dioxide and silicon oxide are preferred. The polymer compound in which the proton conductive group is not introduced to the catalyst carrier in the catalyst layer of the present invention, or the ratio Z in which the inorganic compound is contained (Z = polymer compound or inorganic compound in which no proton conductive group is introduced) The weight of solid content / weight of the catalyst carrier is preferably 0.05 or more and 1.0 or less. If it is less than 0.05, it is impossible to control the contact angle of the catalyst layer, and if it is more than 1.0, diffusion of gas in the catalyst layer is hindered.

  The catalyst layer for a fuel cell of the present invention comprises, on a substrate, a catalyst layer forming material for a fuel cell comprising at least a polymer compound having an aromatic unit having a proton conductive group introduced therein and the fuel cell catalyst. Manufactured by applying. The catalyst layer forming material may contain a solvent, a polymer compound into which a proton conductive group is not introduced, an inorganic compound, a dispersant, a thickener, a pore forming agent, and the like, as necessary. . In addition, those additives conventionally known to those skilled in the art can be used, and other specific configurations are not particularly limited.

  As a method for applying the catalyst layer forming material to the base material, the following application methods can be used depending on the viscosity and the type of the base material. The method for applying the catalyst layer forming material onto the base material may be any conventionally known application method for those skilled in the art, and other specific configurations are not particularly limited. For example, methods using a knife coater, a bar coater, a spray, a dip coater, a spin coater, a roll coater, a die coater, a curtain coater, screen printing, and the like can be listed, but are not limited to the present invention.

  In the present invention, when a polymer sheet and an inorganic sheet are used as a base material, a fuel cell catalyst layer transfer sheet is used, and when a conductive porous sheet is used, a fuel cell gas diffusion electrode is used. Can be manufactured.

  The polymer sheet used in the method for producing a fuel cell catalyst layer transfer sheet of the present invention is literally a polymer film conventionally known to those skilled in the art, and other specific configurations are not particularly limited. Such polymer sheets include polyimide, polyethylene terephthalate, polyparvanic acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherimide, polyarylate, polyethylene naphthalate, ethylenetetrafluoro. Selected from the group consisting of ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), and polytetrafluoroethylene (PTFE). Including at least one kind is preferable because it can withstand the heating conditions in the production process and is easily available industrially.

  The inorganic sheet used in the method for producing a catalyst layer transfer sheet for a fuel cell according to the present invention may literally be an inorganic sheet conventionally known to those skilled in the art, and the other specific configurations are not particularly limited. The inorganic sheet preferably contains at least one selected from the group consisting of titanium, stainless steel, aluminum, and copper because of excellent durability and easy industrial availability.

  The conductive porous sheet used in the method for producing a gas diffusion electrode for a fuel cell of the present invention may literally be a conductive porous sheet conventionally known to those skilled in the art, and other specific configurations are particularly limited. Not. In the method for producing an electrode for a fuel cell of the present invention, the conductive porous sheet includes carbon paper, carbon cloth, and the like, because of the diffusibility of fuel and oxidant, electrochemical stability, industrial availability, and the like. It is preferably at least one selected from the group consisting of carbon felt. The conductive porous sheet is preferably subjected to a water repellent treatment because it easily controls the amount of water in the catalyst layer. In addition, the conductive porous sheet is provided on the surface on which the fuel cell catalyst layer forming material is applied from the viewpoint that electrical contact between the catalyst layer and the conductive porous sheet can be improved and moisture management can be appropriately performed. It is preferable to provide a layer made of a water-repellent conductive material. Examples of the water repellent conductive material include conductive fine particles such as carbon black and a fluorine-based polymer compound such as tetrafluoroethylene (PTFE), but the present invention is not limited thereto. .

  The catalyst layer for a fuel cell of the present invention is preferably used on the cathode side where the influence of humidity of the oxidant is large. When the catalyst layer is used for the cathode, it is preferable to reduce the humidity of the oxidant supplied to the cathode, that is, to reduce the influence of the humidity of the cathode, because the amount of water in the catalyst layer can be appropriately maintained. As a result, the humidifier or the like can be downsized or removed, and the PEFC system can be downsized.

  The fuel cell membrane electrode assembly (MEA) of the present invention comprises a fuel cell catalyst layer, a fuel cell catalyst layer transfer sheet, and a fuel cell gas diffusion electrode disposed on at least one surface of the polymer electrolyte membrane, What is necessary is just to be heat press-contacted, and it does not specifically limit about specific structures, such as other manufacturing conditions, a component, material, and a mixture ratio.

  In the MEA of the present invention, the catalyst layer obtained by the production method of the present invention is disposed on both surfaces of the polymer electrolyte membrane, the polymer electrolyte membrane and the catalyst layer are joined, and then the polymer film is peeled off. Thus, a three-layer membrane electrode assembly (three-layer MEA: Membrane Electrode Assembly, CCM: Catalyst Coating Membrane) comprising a polymer electrolyte membrane, an anode-side catalyst layer, and a cathode-side catalyst layer can be produced.

  In addition, when a gas diffusion electrode for a fuel cell obtained by the production method of the present invention is used instead of the catalyst layer, a five-layer membrane electrode assembly in which a diffusion layer is formed outside the three-layer membrane electrode assembly (5-layer MEA) can be manufactured.

  Furthermore, at least a layer made of a water repellent conductive material composed of conductive carbon particles and a water repellent agent is provided between the diffusion layer and the catalyst layer as needed, and the electrolyte at the periphery of the diffusion layer It is added that a seven-layer membrane electrode assembly formed by arranging a pair of gaskets on the membrane is also within the scope of the present invention.

  The polymer electrolyte membrane used for the fuel cell membrane electrode assembly of the present invention may be literally a polymer electrolyte membrane conventionally known to those skilled in the art, and other specific configurations are not particularly limited. Examples of perfluorocarbon sulfonic acid polymer electrolyte membranes include Nafion manufactured by DuPont, Flemion manufactured by Asahi Glass Co., Ltd., Aciplex manufactured by Asahi Kasei Co., Ltd., and Gore Select manufactured by Gore. As the non-fluorine polymer electrolyte membrane, those conventionally known to those skilled in the art can be used. For example, a polymer electrolyte film exemplified in the present invention, a pore filling film in which a nonelectrolytic porous support is filled with a polymer electrolyte, or a composite electrolyte film in which a polymer electrolyte and a nonelectrolyte are combined Etc. are preferably used.

  In the production of the fuel cell membrane / electrode assembly of the present invention, the conditions of the heat-pressure welding may literally be those conventionally known to those skilled in the art, and the other specific configurations are not particularly limited. The optimum conditions need to be set as appropriate according to the type of polymer electrolyte contained in each of the electrolyte membrane, the anode side catalyst layer, and the cathode side catalyst layer. Generally, the temperature of the heating and pressure welding is equal to or lower than the thermal deterioration or thermal decomposition temperature of the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer, and the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer. It is preferable to carry out the reaction at a temperature above the glass transition point or softening point of the polymer electrolyte, or at a temperature above the glass transition point or softening point of the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer. In addition, the pressurizing condition of the heat pressure contact is generally in the range of 0.1 MPa or more and 20 MPa or less, and the polymer electrolyte membrane and the catalyst layer are in sufficient contact with each other, and there is no deterioration in characteristics due to significant deformation of the material used. preferable. Further, at the time of the heating and pressure welding, the above-mentioned “step of obtaining a reaction product by chemically reacting the polymer electrolyte and a crosslinking agent” may be used.

  In the fuel cell of the present invention, the membrane electrode assembly of the present invention is inserted between a pair of separators in which a flow path for feeding fuel and an oxidant is formed. A fuel cell containing is obtained. The separator is not particularly limited, and for example, a conductive material such as carbon graphite or stainless steel can be used. In particular, when a metal material such as stainless steel is used, it is preferable to perform a corrosion resistance treatment.

  In the fuel cell of the present invention, hydrogen is not particularly limited as a fuel for the anode, but oxygen or air can be used for the cathode as an oxidant, although not particularly limited. The humidity of the oxidant supplied to the cathode is preferably 90% RH or less. If it is higher than 90% RH, the amount of water supplied to the cathode is too large, which is not preferable because flooding occurs and power generation characteristics deteriorate, and a large humidifier must be installed. The humidity is a value calculated from the ratio of the saturated water vapor at the temperature of the water in the humidifier to the saturated water vapor amount at the operating temperature of the fuel cell. The humidity of the fuel supplied to the anode is preferably 100% RH or less.

  It should be noted that the polymer electrolyte fuel cells according to the present embodiment can be used alone or in a stacked manner to form a stack, or a fuel cell system incorporating them.

  Hereinafter, the present invention will be described in more detail with reference to examples. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

Example 1
<Preparation of Aromatic Polymer Compound (Sulfonated PEEK) Introduced with Proton Conducting Group>
First, 552.0 g of sulfuric acid was placed in a reaction vessel equipped with a mechanical stirrer, a reflux pipe, and a calcium chloride pipe, and then 22.2 g of PEEK450PF (polyether ether ketone manufactured by Victorex MC) was added with stirring. For 48 hours. The reaction solution was dropped into ion-exchanged water to precipitate a reaction product, followed by filtration, and washed with ion-exchanged water until the filtrate became neutral. The obtained reaction product was dried under vacuum at 105 ° C. for 8 hours to obtain 26.94 g of an aromatic polymer compound (sulfonated PEEK) into which a proton conductive group was introduced. The compound had an IEC of 2.2 meq / g and a proton conductivity of 6.0 × 10 ⁻² S / cm.

<Manufacture of gas diffusion electrode with cathode catalyst layer>
Cathode of ratio Y = 0.1 of polymer compound having proton conductive group introduced to catalyst carrier in catalyst layer (Y = weight of solid content of polymer compound having proton conductive group introduced / weight of catalyst carrier) The gas diffusion electrode on which the side catalyst layer was formed was produced by the following procedure. Here, the solid content weight of the polymer compound into which the proton conductive group was introduced was the total weight of the polymer compound into which the proton conductive group was introduced and the cross-linking material.

First, as a fuel cell composition, the sulfonation as a polymer compound of “a polymer compound in which a proton conductive group is introduced into a polymer compound having an aromatic unit in a solvent (methanol, 3.240 g)”. PEEK (0.300 g) and compound (6) as a cross-linking material: “5,5 ′-[2,2,2-Trifluoro-1-ethyl (triethylene)] bis [2-hydroxy-1,3-benzenediethanol] (Hereinafter, TML-BPAF-MF, 0.060 g) was added to prepare a uniform solution, thereby preparing a 10 wt% polymer electrolyte solution used in this example. Next, after adding platinum-supported carbon catalyst powder (ratio of catalyst metal in the catalyst: 50 wt%, 0.5 g) to deionized water (2.500 g), methanol (2.500 g) was added as described above. A molecular electrolyte solution (10 wt%, 0.25 g) was added in order, and the mixture was stirred for 30 minutes using a magnetic stirrer. Next, PTFE dispersion (60 wt%, 0.125 g) was added as a polymer compound into which no proton conductive group was introduced, and a catalyst layer forming material was produced using a disperser. In the catalyst layer, the ratio Y of the polymer compound into which the proton conductive group is introduced to the catalyst carrier in the catalyst layer is 0.1 (Y = weight of solid content of the polymer compound into which the proton conductive group is introduced / weight of the catalyst carrier) The ratio Z of the polymer compound in which no proton conductive group is introduced to the catalyst carrier in the catalyst layer is 0.3 (Z = weight of solid content of polymer compound in which no proton conductive group is introduced / catalyst carrier weight) Weight). Finally, the fuel cell catalyst layer forming material is applied to carbon paper with a microporous layer (GDL24BC, manufactured by SGL) using air spray, and finally dried in a blowing oven (80 ° C.) for 1 hour. Thus, a gas diffusion electrode on which a cathode catalyst layer having a platinum loading of 0.5 mg Pt / cm ² was formed was manufactured.

<Production of gas diffusion electrode with anode catalyst layer>
First, as a fuel cell composition, after adding platinum ruthenium alloy-supported carbon catalyst powder (ratio of catalyst alloy metal in the catalyst: 55 wt%, 0.833 g) to deionized water (8.330 g), A molecular electrolyte solution (Nafion solution, manufactured by DuPont, 5 wt%, 5.250 g) was sequentially added, and the mixture was stirred for 30 minutes using a magnetic stirrer. Next, PTFE dispersion (60 wt%, 0.188 g) was added as a polymer compound into which no proton conductive group was introduced, and a catalyst layer forming material was produced using a disperser. In the catalyst layer, the ratio Y of the polymer compound into which the proton conductive group is introduced to the catalyst carrier in the catalyst layer is 0.7 (Y = weight of solid content of polymer compound into which the proton conductive group is introduced / weight of the catalyst carrier) The ratio Z of the polymer compound in which no proton conductive group is introduced to the catalyst carrier in the catalyst layer is 0.3 (Z = weight of solid content of polymer compound in which no proton conductive group is introduced / catalyst carrier weight) Weight). Finally, the fuel cell catalyst layer forming material is applied to carbon paper with a microporous layer (GDL24BC, manufactured by SGL) using air spray, and finally dried in a blowing oven (80 ° C.) for 1 hour. Thus, a gas diffusion electrode in which an anode catalyst layer having a platinum loading of 0.5 mg Pt / cm ² was formed was produced.

<Measurement method of water contact angle of catalyst layer>
The cathode side gas diffusion electrode was made of a SUS plate, a polyimide sheet (100 mm × 100 mm × 0.05 mm), an anode side gas diffusion electrode (22 mm × 22 mm), and a PTFE sheet (100 mm × 100 mm × 0.00 mm) cut out from the gas diffusion electrode portion. 2 mm), a polyimide sheet (100 mm × 100 mm × 0.05 mm), and a SUS plate were laminated in this order, and placed on a pressure plate heated to 150 ° C., followed by heat treatment under conditions of 50 kgf / cm ² and holding for 30 minutes. 1 μL of deionized water was dropped on the heat-treated gas diffusion electrode catalyst layer, and the contact angle of the catalyst layer with water was measured by photographing the shape of the water drop with a CCD camera.

<Manufacture of membrane electrode assembly>
The membrane electrode assembly was manufactured by the following procedure using a heating and pressure welding machine (Tester Sangyo Co., Ltd.). First, a SUS plate, a PTFE sheet (100 mm × 100 mm × 0.05 mm), an anode side gas diffusion electrode (22 mm × 22 mm), a PTFE sheet (100 mm × 100 mm × 0.2 mm) cut out from the gas diffusion electrode, and a polymer PTFE sheet (100 mm × 100 mm × 0.2 mm), cathode side gas diffusion electrode (22 mm × 22 mm), PTFE sheet (100 mm × 100 mm × 0.05 mm) cut out from the electrolyte membrane (NRE212CS, manufactured by DuPont) catalyst layer Laminated in the order of SUS plates. After this laminate was placed on a pressure plate heated to 150 ° C., it was produced by heating and pressing under conditions of holding at 50 kgf / cm ² for 30 minutes.

<PEFC power generation characteristics evaluation>
A single fuel cell was assembled using the membrane electrode assembly. First, an anode side end plate, a gas flow plate, a PTFE gasket (0.20 mm), a membrane electrode assembly, a PTFE gasket (0.20 mm), a gas flow plate, and an end plate were laminated in this order. Next, a fuel cell single cell used in this example was manufactured by tightening with M3 bolts at 2 Nm.

Subsequently, after the single cell was installed in an evaluation apparatus equipped with an electronic load device (PLZ164WA, manufactured by Kikusui Electronics Co., Ltd.), the cell temperature was 80 ° C., and the fuel (hydrogen, 84 ml / min, 100% RH) was supplied to the anode side. Supplied to. Further, an oxidizing agent (air, 400 ml / min, 100% RH) was supplied to the cathode side. Next, the electronic load device was set to a constant current mode, and the potential of the fuel cell including the membrane electrode assembly was held at 0.5 A / cm ² for 24 hours to condition the PEFC. Finally, the cell temperature is 80 ° C., the fuel (hydrogen, 84 ml / min, 100% RH) is supplied to the anode side, and the oxidant (air, 400 ml / min, 80% RH, 40% RH) is supplied to the cathode side. The polarization characteristics at 0.3 A / cm ² were evaluated. Evaluation of power generation characteristics of PEFC under low humidification conditions is based on the maximum power density of oxidant (air, 400 ml / min, 40% RH) relative to the maximum power density of oxidant (air, 400 ml / min, 80% RH). This was done by calculating the ratio.

(Example 2)
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced relative to the catalyst carrier in the cathode catalyst layer was 0.25.

(Example 3)
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced with respect to the catalyst support in the cathode catalyst layer was 0.5.

Example 4
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced to the catalyst support in the cathode catalyst layer was 0.7.

(Example 5)
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced with respect to the catalyst support in the cathode catalyst layer was 1.0.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced to the catalyst support in the cathode catalyst layer was 0.08.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the ratio Y of the polymer compound into which the proton conductive group was introduced with respect to the catalyst support in the cathode catalyst layer was 1.2.

(Comparative Example 3)
Instead of a polymer compound having an aromatic unit into which a proton conductive group is introduced used for the cathode catalyst layer, a polymer compound having no aromatic unit into which a proton conductive group is introduced (Nafion solution, manufactured by DuPont) ) Was used in the same manner as in Example 4.

  FIG. 1 shows the “contact angle of water on the cathode side catalyst layer” prepared in Examples 1, 2, 3, 4, 5, and Comparative Examples 1, 2, and 3, and “oxidant (air, 400 ml / min, The ratio of the maximum power density at the oxidizing agent (air, 400 ml / min, 40% RH) to the maximum power density at 80% RH) is summarized. In this evaluation, “the ratio of the maximum power density in the oxidant (air, 400 ml / min, 40% RH) to the maximum power density in the air (400 ml / min, 80% RH)” is 0.65. The above values are considered to be excellent in power generation characteristics under low humidification conditions. From this result, it was found that the PEFC having the catalyst layer produced in the example has a small decrease in power generation characteristics even when the oxidizer is low humidified, that is, the power generation characteristics of PEFC under low humidification conditions are excellent.

  The catalyst layer for PEFC according to the present invention has various industrial applicability including PEFC.

Ratio of contact angle of water and maximum power density of catalyst layer

Claims (9)

At least a polymer compound having an aromatic unit having a proton conductive group introduced therein and the formula (1)
-CH ₂ OR (1)
(In the formula, R is hydrogen, an alkyl group, or an acyl group, and a plurality of R's are independent and may be the same or different from each other.)
The contact angle of water of the reaction product with the cross-linking material having two or more functional groups in a molecule and the fuel cell catalyst layer containing the fuel cell catalyst is 0 ° <X <90 °, A catalyst layer for a fuel cell, which is used for a cathode. The ratio Y of the polymer compound into which the proton conductive group is introduced with respect to the catalyst carrier in the catalyst layer according to claim 1 (Y = solid content weight of the polymer compound into which the proton conductive group is introduced / weight of the catalyst carrier) The fuel cell catalyst layer according to claim 1, wherein 0.1 ≦ Y ≦ 1.0. 3. A fuel cell catalyst layer transfer sheet, wherein the fuel cell catalyst layer according to claim 1 is formed on a polymer film. 3. A fuel cell catalyst layer transfer sheet, wherein the fuel cell catalyst layer according to claim 1 is formed on an inorganic film. A fuel cell gas diffusion electrode, wherein the fuel cell catalyst layer according to claim 1 or 2 is formed on a conductive porous sheet. The fuel cell catalyst layer according to claim 1, the fuel cell catalyst layer peeled off from the fuel cell catalyst layer transfer sheet according to claim 3, or the fuel cell catalyst layer according to claim 5. A fuel cell membrane electrode assembly comprising a gas diffusion electrode, wherein a fuel cell catalyst layer is joined to a polymer electrolyte membrane having proton conductivity. The fuel cell catalyst layer according to claim 1, the fuel cell catalyst layer peeled off from the fuel cell catalyst layer transfer sheet according to claim 3, or the fuel cell gas diffusion according to claim 5. A fuel cell comprising the electrode or the membrane electrode assembly for a fuel cell according to claim 6. A power generation method comprising supplying a gas containing an oxidizing agent containing at least oxygen and water vapor of 90% RH or less to the fuel cell catalyst layer according to claim 1. The fuel cell system according to claim 1, wherein a gas containing at least an oxidizing agent containing oxygen and water vapor of 90% RH or less is supplied to the fuel cell catalyst layer.

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