JP4882225B2 - Water-repellent electrode catalyst layer, catalyst layer transfer sheet and catalyst layer-electrolyte assembly for polymer electrolyte fuel cell - Google Patents

Description

The present invention relates to an electrode catalyst layer for a polymer electrolyte fuel cell, a catalyst layer transfer sheet, and a catalyst layer-electrolyte assembly.

  Conventionally, fuel cells have been mainly used in the fields of space development and marine development. In recent years, expectations for fuel cells have increased rapidly from the viewpoint of protecting the global environment and from the viewpoint of high energy conversion efficiency when hydrogen is used directly as a fuel. Then, instead of an automobile engine, it has been developed into a home power generator, and the possibility of being widely used is increasing.

  A fuel cell simply refers to a device that continuously supplies fuel (reducing agent) and oxygen or air (oxidant) from the outside and reacts them electrochemically to extract electrical energy.

  The classification of the fuel cell is performed on the basis of the operating temperature, the type of fuel used, the application, and the like, and is mainly performed on the basis of the type of electrolyte used. Specifically, the types of electrolytes are classified into solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), and polymer electrolyte fuel cells (PEFC: Polymer Electrolyte Fuel Cell) and alkaline aqueous fuel cell (AFC). These five types use hydrogen gas generated from methane or the like as fuel. Furthermore, a direct methanol fuel cell (DMFC) that directly uses an aqueous methanol solution as a fuel is also known.

  Among such fuel cells, in particular, a polymer electrolyte fuel cell having a structure in which a solid polymer membrane is sandwiched between two types of electrodes and these members are sandwiched between separators has attracted attention. In this polymer electrolyte fuel cell, an electrode such as an air electrode (oxygen electrode) and a fuel electrode (hydrogen electrode) are usually arranged on both sides of a solid polymer membrane to constitute a unit cell. Both sides are sandwiched between fuel cell separators. In other words, a fuel electrode and an air electrode made of a catalyst layer are formed on both sides of the solid polymer film and integrated, and a porous support layer (carbon paper) is attached to the outside of the catalyst layer as a current collector, and hydrogen, oxygen, etc. It is clamped by a separator (partition plate) that also serves as a reaction gas supply path. In this polymer electrolyte fuel cell, it is necessary to isolate the fuel (hydrogen) and oxidant (air) from each other and to transport hydrogen ions (protons) generated at the fuel electrode to the air electrode side. is there.

  One of the required functions of the electrode catalyst layer is that the generated water generated in the power generation process is quickly discharged from the catalyst layer to ensure the flow path of the fuel gas and oxidant gas.

  Fuel gas and oxidant gas are supplied while being humidified according to the operating conditions. For this reason, if humidification increases too much, dew condensation due to water vapor occurs in the electrode catalyst layer. When the amount of water droplets increases, there arises a problem that the water droplets block the voids in the electrode catalyst layer and the gas supply decreases.

  The rapid discharge of generated water and condensed water depends on the wettability of the electrode catalyst layer with respect to water, and greatly affects the performance of the fuel cell (cell maximum output density, resistance value, etc.). For this reason, various efforts have been made to provide the characteristic of quickly discharging generated water and condensed water from the electrode catalyst layer.

For example, there is a method of using a porous material made of carbon paper or carbon fiber as an electrode and forming a layer in which a conductive material such as carbon black or graphite and a fluororesin that is a binder and water repellent material are mixed. (Patent Document 1, Patent Document 2)
Also, a water repellent treatment method of mixing a conductive material such as carbon black and carbon paper with a silane coupling agent in the presence of ethanol, and a water repellent treatment method of mixing with a silane coupling agent while being dispersed in a cyclic silicone oil Is provided (Patent Document 3).

  However, in the former case, if the amount of the water repellent is large, the electrical resistance value increases, so that sufficient conductivity cannot be maintained. Conversely, if the water repellent material is small, sufficient water repellency cannot be obtained and gas permeation is hindered. As a result, there arises a problem that the battery performance is lowered.

In the latter case, since the carbonaceous material such as carbon black is dispersed in alcohol or liquid silicone, the entire carbonaceous material is covered with a resistor. The water-repellent substance is limited to a specific substance such as a silane coupling agent that easily reacts with a functional group on the surface of the carbonaceous material.
JP-A-10-261421 JP 2001-43865 A JP 2000-239704 A

  Thus, although development of a technique for efficiently discharging generated water and the like without impairing battery characteristics is desired, it has not yet been developed.

  Accordingly, the present invention has been made in view of these problems of the prior art, and in particular, for forming an electrode catalyst layer and an electrode catalyst layer of a polymer electrolyte fuel cell having excellent water repellency without impairing battery characteristics. And a catalyst layer-electrolyte membrane assembly.

  In light of the problems of the prior art described above, the present inventor has found that the object can be achieved by using an electrode catalyst layer having a specific configuration, and has completed the present invention.

That is, the present invention provides catalyst layer catalyst are shown in the following - according to the manufacturing method of the electrolyte membrane assembly.
1 . Using a transfer sheet obtained by forming an electrocatalyst layer on a transfer substrate and then forming a water-repellent layer on a part or all of the surface of the electrocatalyst layer by a thermal CVD method using a self-assembled monolayer A method for producing a catalyst layer-electrolyte membrane assembly, comprising a step of transferring the transfer sheet to a solid polymer electrolyte membrane so that the water-repellent layer contacts the surface of the solid polymer electrolyte membrane.
2 . The self-assembled monolayer has the following general formula (1):
R ¹ XR ² (1)
(Wherein, R ¹ is, .R ² represents an alkyl group or aryl group, hydrogen, halogen, or -OR ³ (R ³ is an alkyl group, an allyl group, or an aryl group.) With a substituent represented by X represents Si, Ti, Al, C or S.)
Item 2. The method according to Item 1, wherein the method is formed by a compound represented by the formula:
3 . Item 3. The method according to Item 1 or 2 , wherein the water repellent layer has a contact angle with water of 70 to 170 °.

  According to the electrode catalyst layer of the present invention, it is possible to form a water repellent layer without impairing the conductivity of the carbon powder and without closing the voids of the catalyst layer. Therefore, it is possible to form an electrode catalyst layer having high water repellency while maintaining gas permeability and conductivity.

  Furthermore, according to the water-repellent catalyst layer-electrolyte assembly of the present invention, since the water-repellent layer is present in the vicinity of the electrolyte membrane, water generated during the battery reaction generated between the electrolyte membrane and the catalyst layer is efficiently removed. it can.

  The fuel cell comprising these prevents the supply of fuel gas from being lowered due to long-time operation, and at the same time maintains high conductivity. As a result, it is possible to prevent the deterioration of the battery and improve the fuel cell performance, that is, to supply a high maximum output density and to reduce the resistance value of the battery.

The water-repellent electrode catalyst layer of the present invention is
An electrode catalyst layer for a polymer electrolyte fuel cell,
1) The electrode catalyst layer includes a solid polymer electrolyte and a catalyst material,
2) The catalyst material has a catalytically active component supported on part or all of the surface of the carbon material,
3) The electrode catalyst layer is formed by forming a water repellent layer on a part or all of at least one surface thereof.
It is characterized by that.
(Solid polymer electrolyte)
The solid polymer electrolyte of the present invention is not particularly limited as long as it has hydrogen ion conductivity, and a known one can be used. Examples thereof include perfluorosulfonic acid-based fluorine ion exchange resins; hydrocarbon-based membranes and glass membranes into which phosphoric acid groups, sulfonic acid groups and the like are introduced. Among these, perfluorosulfonic acid-based fluorine ion exchange resins are preferable.
(Catalyst material)
The catalyst material is formed by supporting a catalytically active component on part or all of the surface of the carbon material.

  A carbon material in particular is not restrict | limited, A well-known thing can be used. For example, carbon black such as channel black, furnace black, ketjen black, acetylene black, and lamp black, graphite, activated carbon, carbon fiber, carbon nanotube, and the like can be used alone or in combination of two or more.

  The structure, surface shape, etc. of the carbon material are not particularly limited, and can be appropriately selected according to the purpose.

  The shape of the carbon material is not particularly limited, and examples thereof include a bead shape, a pellet shape, a powder shape, and a flake shape, and a powder shape is particularly preferable.

  The particle size of the carbon material is about 1 nm to 200 nm, preferably 10 nm to 100 nm, more preferably about 10 nm to 50 nm as primary particles.

Usually 10m ² / g~2000m ² / g as a specific surface area of the carbon material, preferably 200m ² / g~1500m ² / g.

  The catalytically active component to be supported is not particularly limited as long as it causes a fuel cell reaction at the fuel electrode or air electrode of the fuel cell. For example, platinum, a platinum compound, etc. are mentioned. Examples of the platinum compound include an alloy of platinum and at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, iron and the like.

  The particle size of the catalytically active component is usually about 1 nm to 20 nm, preferably about 1 nm to 10 nm, and more preferably about 1 nm to 5 nm.

Usually 50m ² / g~1000m ² / g as specific surface area of the catalytically active component, preferably 100m ² / g~500m ² / g.
(Electrode catalyst layer)
The electrode catalyst layer of the present invention includes the catalyst material and the electrolyte.

The electrode catalyst layer is usually produced from a catalyst paste dispersed by mixing the carbon particles and the electrolyte in at least one solvent selected from alcohols, ethers, dialkyl sulfoxides and water.
The thickness of the electrode catalyst layer is usually 1 μm to 50 μm, preferably 5 μm to 20 μm.
(Water repellent layer)
The water repellent layer of the present invention is formed on a part or all of at least one surface of the electrode catalyst layer described above.

The substance constituting the water repellent layer is not particularly limited as long as it has water repellency. For example, organic mechanization compound having a carbon-containing group; include nitrogen-containing compounds, and the like; hydrocarbon compounds; fluorine-containing compounds. Among these, organic mechanization compound having a carbon-containing group; hydrocarbon compounds; fluorine-containing compounds are preferred.

Hereinafter, organic mechanization compound having a carbon-containing group, a hydrocarbon compound, and the fluorine-containing compound, will be described respectively.
(1) Yes mechanization Gobutsu having a chromatic mechanization compound carbon-containing group which has a carbon-containing machine, at least one central element in the molecule - so long as it has a carbon bond is not particularly limited.

The central element is not particularly limited, and examples thereof include Si, Ti, Al, Zn, Cu, Ni, Co, Fe, and combinations thereof. Among these, at least one of Si, Ti, and Al is preferable.

  The number of carbon atoms in the carbon-containing group is not particularly limited. In the present invention, those having 1 to 30 carbon atoms are preferred, and among them, a methyl group having 1 to 6 carbon atoms, especially 1 carbon atom, or an ethyl group having 2 carbon atoms is most preferred.

Specific examples include organosilicon materials represented by Si _x O _y C _z Hα (1 ≦ x ≦ 10, 0 ≦ y ≦ 10, 1 ≦ _z ≦ 50, 1 ≦ α ≦ 122) or their weight. Coalescence is mentioned.

More specifically, hexamethyldisiloxane (HMDSO; (CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ ), tetramethyldisiloxane (TMDSO; (CH ₃ ) ₂ HSiOSiH (CH ₃ ) ₂ ), tetramethylsilane ( TMS; Si (CH ₃ ) ₄ ) and the like.
(2) Hydrocarbon compound The hydrocarbon compound is not particularly limited as long as it is composed of C and H, and examples thereof include a hydrocarbon-based material or a polymer thereof.

Specific examples include polyolefin materials such as polyethylene resins and cyclic polyolefin resins and / or polymers thereof, C ₂ H ₂ , C ₂ H ₄ , CH ₄ , C ₂ H _{6 and the} like.
(3) Fluorine-containing compound The fluorine-containing compound is not particularly limited as long as it contains fluorine. For example, an organic film represented by Si _x O _y C _z HαFβ (where 1 ≦ x ≦ 10, 0 ≦ y ≦ 10, 1 ≦ z ≦ 50, 1 ≦ α ≦ 122, 1 ≦ β ≦ 122) is shown. Silicon fluoride material or polymer thereof; Si _x O _y HαFβ (where 1 ≦ x ≦ 10, 0 ≦ y ≦ 10, 1 ≦ α ≦ 21, 1 ≦ β ≦ 22) Fluorine-containing hydrocarbon represented by C _x O _y H _z Fα (where 1 ≦ x ≦ 50, 0 ≦ y ≦ 10, 0 ≦ z ≦ 102, 0 ≦ α ≦ 102) Examples thereof include fluorine-containing carbon-hydrogen materials and polymers thereof represented by C _x F _y (where 1 ≦ x ≦ 50, 0 ≦ y ≦ 10). Among these, Si _x O represented by _{Si x O y HαFβ; y C} z organic fluoride represented by Harufaefubeta silicon material or a polymer Kka silicon material or a polymer thereof; C _x O _y H _z fluorine-containing hydrocarbon represented by Fα material or a polymer thereof are preferable.

Specific examples include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoroethylene), PVF (polyvinyl fluoride), ETFE (ethylene / tetrafluoroethylene copolymer), CF ₄ , C ₂ F ₂ , C ₂ F ₄ , C ₂ F _{6 and the} like can be mentioned.

  Here, when the water repellent layer is a silicon oxide layer containing oxygen atoms and silicon atoms, the concentration of oxygen atoms in the water repellent layer is not particularly limited, but there is an upper limit for the number of Si atoms of 100. Preferably it is about 50, more preferably about 25.

  Since oxygen atoms easily form hydrogen bonds with water molecules, having oxygen atoms in the water repellent layer causes water molecules to be attracted, resulting in a decrease in water repellency. In the water-repellent layer, since the concentration of oxygen atoms is within the above-described range, it is possible to suppress a decrease in water repellency due to oxygen atoms and to make the laminate highly water-repellent.

  Here, the component ratio in each part of the water-repellent layer of the present invention is a value measured by XPS (X-ray Photoelectron Spectroscopy). The analysis method by XPS will be described below. When a solid surface is irradiated with X-rays in a vacuum, electrons are scattered from the surface atoms given energy by the X-rays. These electrons are called photoelectrons because they are generated by irradiation with light such as X-rays. Since this photoelectron has energy specific to the element, qualitative analysis and quantitative analysis of the element can be performed by measuring the energy distribution. In addition, photoelectrons generated deep from the surface lose their energy before coming out to the surface and are difficult to measure. The escape depth of electrons having a kinetic energy of 1000 eV is several nm (tens of atomic layers). Therefore, it is possible to obtain information on the outermost surface.

  Furthermore, in order to measure the depth, the surface may be sputtered with ions such as argon. Since selective sputtering occurs depending on the type of element, a known correction method may be performed for quantification.

  Furthermore, the water-repellent layer in the present invention may be a self-assembled monomolecular film in addition to the above. Hereinafter, the self-assembled monolayer will be described.

  A self-assembled monolayer usually forms a monolayer spontaneously while organic molecules gather spontaneously at the solid / liquid interface or solid / gas interface to form an aggregate. An organic thin film. For example, when a substrate made of a specific material is exposed to a solution or vapor of an organic molecule having a high chemical affinity with the substrate material, the organic molecule is chemically reacted and adsorbed on the surface of the substrate. If the organic molecule consists of two parts: a functional group with high chemical affinity and an alkyl group that does not cause any chemical reaction with the substrate, and the functional group with high affinity is at its end, the molecule The reactive terminal is adsorbed with the substrate side facing and the alkyl group facing the outside. When alkyl groups gather together, the whole becomes stable, so organic molecules gather spontaneously during the process of chemisorption. Since molecular adsorption requires a chemical reaction between the substrate and the terminal functional group, once the surface of the substrate is covered with organic molecules to form a monolayer, molecular adsorption is performed thereafter. Does not happen. As a result, an organic monomolecular film in which molecules are densely gathered and aligned is formed. In the present invention, such a film is a self-assembled monolayer. Here, the reactive terminal group bonded to the substrate is an adsorbing group, and the group oriented to the outside is an aligning group.

  When the water repellent layer is the self-assembled monomolecular film, it is possible to form a film with monomolecules along the unevenness of the substrate (in the present invention, the electrode catalyst layer). Due to the water repellency of the unevenness and the orientation group of the self-assembled monomolecular film, a highly water-repellent laminate can be obtained.

Here, the self-assembled monolayer is preferably formed of a compound represented by the following general formula (1).
R ¹ XR ² (1)
(Where R ¹ represents an alkyl group, an aryl group, etc .; R ² represents hydrogen, halogen, —OR ³ (R ³ represents an alkyl group, an allyl group, an aryl group, etc.), etc.) X is Si, Ti, Al, C or S.
R ¹ is an orientation group such as an alkyl group or an aryl group (benzene ring). Although carbon number is not specifically limited, Preferably it is 1-50, More preferably, it is 1-30. Further, it may partially contain a branched chain, multiple bonds and the like. Further, the group bonded to carbon may contain halogen such as fluorine and chlorine, hydrogen, nitrogen and the like. When R ¹ is the above-mentioned orientation group, the self-assembled monomolecular film of the present invention has high water repellency.

R ² is an adsorbing group such as hydrogen, halogen, or —OR ³ . Here, the group bonded to carbon may contain halogen such as fluorine and chlorine, hydrogen, nitrogen and the like.

  Examples of the self-assembled monolayer forming material shown above include octadecyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrichlorosilane, octadecylmethyldiethoxysilane, octadecyldimethylmethoxysilane, octadecylmethyldimethoxysilane, and octadecylmethoxydichlorosilane. , Octadecylmethyldichlorosilane, octadecyldimethyl (dimethylamino) silane, octadecyldimethylchlorosilane, nonylchlorosilane, octenyltrichlorosilane, octenyltrimethoxysilane, octylmethyldichlorosilane, octylmethyldiethoxysilane, octyltrichlorosilane, octyltriethoxy Silane, octyltrimethoxysilane, pentafluorophenylpropyl trichloro Silane, pentafluorophenylpropyltrimethoxysilane, pentyltriethoxysilane, pentyltrichlorosilane, phenethyltrichlorosilane, phenethyltrimethoxysilane, phenyldichlorosilane, phenyldiethoxysilane, phenylethyldichlorosilane, phenylmethyldimethoxysilane, phenyltrimethoxysilane , Phenyltrichlorosilane, phenyltriethoxysilane, propyltriethoxysilane, propyltrimethoxysilane, propyltrichlorosilane, tetradecyltrichlorosilane, (3,3,3-trifluoropropyl) dimethylchlorosilane, (3,3,3- (Trifluoropropyl) trichlorosilane, (3,3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trif Olopropyl) triethoxysilane, 3,3,4,4,5,5,6,6,6-nonafluorohexylmethyldichlorosilane, 3,3,4,4,5,5,6,6,6-nona Fluorohexyltrichlorosilane, isooctyltrimethoxysilane, isobutylmethyldichlorosilane, isobutyltriethoxysilane, isobutyltrichlorosilane, hexyltrichlorosilane, hexyltriethoxysilane, hexyltrimethoxysilane, hexenyltrichlorosilane, hexyldichlorosilane, hexadecyltri Chlorosilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, heptyltrichlorosilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane, (heptadecafluoro-1, 1,2,2-tetrahydrodecyl) trichlorosilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) methyldichlorosilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) dimethylchlorosilane , Eicosyltrichlorosilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, dodecyltrichlorosilane, dodecylmethyldichlorosilane, dodecyldimethylchlorosilane, diphenyldiethoxysilane, diphenyldichlorosilane, diphenyldiethoxysilane, diphenyldimethoxysilane, dimethoxymethyl- 3,3,3-trifluoropropylsilane, decylmethyldichlorosilane, decyltrichlorosilane, decyltriethoxysilane, decyltrimethoxysilane, decyldimethyl Lorosilane, cyclohexylmethyltrichlorosilane, cyclohexyltrichlorosilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltrichlorosilane, chlorophenyltrichlorosilane, butyltrimethoxysilane And butyltrichlorosilane.

  In the present invention, among them, octadecyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrichlorosilane, nonylchlorosilane, octenyltrichlorosilane, octenyltrimethoxysilane, octyltrichlorosilane, octyltriethoxysilane, octyltrimethoxysilane, pentafluoro Phenylpropyltrichlorosilane, pentafluorophenylpropyltrimethoxysilane, pentyltriethoxysilane, pentyltrichlorosilane, phenethyltrichlorosilane, phenethyltrimethoxysilane, phenyltrimethoxysilane, phenyltrichlorosilane, phenyltriethoxysilane, propyltriethoxysilane, propyltri Methoxysilane, propyltrichlorosilane, tetradecylto Chlorosilane, (3,3,3-trifluoropropyl) trichlorosilane, (3,3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trifluoropropyl) triethoxysilane, 3,3, 4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, isooctyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrichlorosilane, hexyltrichlorosilane, hexyltriethoxysilane, hexyltrimethoxysilane, hexenyl Trichlorosilane, hexadecyltrichlorosilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, heptyltrichlorosilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane, (heptadeca (Luoro-1,1,2,2-tetrahydrodecyl) trichlorosilane, eicosyltrichlorosilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, dodecyltrichlorosilane, dimethoxymethyl-3,3,3-trifluoropropylsilane, decyl Trichlorosilane, decyltriethoxysilane, decyltrimethoxysilane, decyldimethylchlorosilane, cyclohexylmethyltrichlorosilane, cyclohexyltrichlorosilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltrichlorosilane, chlorophenyl Trichlorosilane, butyltrimethoxysilane, and butyltrichlorosilane are preferred.

  In particular octadecyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrichlorosilane, octyltriethoxysilane, phenyltriethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane, isobutyltrimethoxysilane, (Heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane, dodecyltriethoxysilane, and 3-chloropropyltrimethoxysilane are more preferable.

  When the water repellent layer alone forms a planar layer, the contact angle between water and the planar layer is shown in FIG. From the viewpoint of high water repellency, the planar layer preferably has a contact angle with water of 70 to 120 °, more preferably 100 to 120 °.

  The contact angle is measured using a contact angle measuring device (model number CA-Z, manufactured by Kyowa Interface Chemical Co., Ltd.). Specifically, one drop (a constant amount) of pure water is dropped on the flat layer surface of the object to be measured, and the shape of the water drop is visually observed using a microscope or a CCD camera after a predetermined time (about 10 seconds). The contact angle is physically obtained by observing.

(Transfer substrate)
The transfer substrate of the present invention is not particularly limited, and known materials can be used. For example, polyimide, polyethylene terephthalate, polyparvanic acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene naphthalate, and ethylene tetrafluoro as a fluororesin Examples include heat-resistant resins such as ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), and polytetrafluoroethylene (PTFE). It is done. Among these, polyethylene terephthalate is preferable.

The thickness of the transfer substrate is usually about 1 μm to 100 μm, preferably about 10 μm to 50 μm. If it is thinner than the above range, the handleability of the film at the time of coating or transferring may be deteriorated. When it is too thick, it is disadvantageous in terms of cost because it is discarded after transfer.
(Water repellent electrode catalyst layer)
In the water-repellent electrode catalyst layer of the present invention, the water-repellent layer is formed on a part or all of at least one surface of the electrode catalyst layer. In particular, by using the vapor phase method, the water repellent material, which is usually non-conductive, can be formed so as not to cover at least the entire surface of the carbon material, so electrons move to the separator via the carbon material. can do. As a result, the electrode catalyst layer of the present invention can obtain water repellency while having conductivity.

The average amount of the water-repellent material constituting the water-repellent layer with respect to the surface of the electrode catalyst layer is not particularly limited, and may be determined as appropriate according to the desired material of the water-repellent layer and the electrode catalyst layer. Usually at ^{0.01mg / cm 2 ~3000mg / cm 2} , 0.05mg / cm 2 ~500mg / cm 2 is preferred.

  The average thickness of the water repellent layer is usually within the range of 1 nm to 50 nm, preferably 1 nm to 20 nm, and more preferably 1 nm to 5 nm. When the average thickness of the water-repellent layer is smaller than the above range, there is a possibility that the function as the water-repellent layer cannot be exhibited, for example, a portion where the water-repellent material is not formed. Moreover, even if the average thickness is increased from the above range, the water repellency is saturated.

  In the present invention, when water is present on the surface of the water-repellent electrode catalyst layer, the electrode catalyst layer preferably has a contact angle with water of 70 to 170 °, and is 100 ° or more. Is more preferable, and more preferably 150 ° or more. In addition, the measurement method of the contact angle with water here is measured by the method mentioned above.

  The gas phase method is not particularly limited as long as it is a method via a gas phase, and a known method can be used. For example, physical vapor deposition methods (PVD method) such as reactive sputtering method, reactive vapor deposition method, ion plating method, etc., chemical vapor deposition methods (CVD method) such as plasma CVD method, thermal CVD method, laser CVD method, etc. ) And the like. Among these, the CVD method is preferable from the viewpoints of three-dimensional deposition, adhesion to a substrate, and productivity. Furthermore, a plasma CVD method and a thermal CVD method are more preferable. The plasma CVD method may be any method that generates plasma from the reaction gas in the reaction apparatus by discharging. The thermal CVD method may be any method that evaporates the reaction gas in the reaction apparatus by increasing the temperature.

In particular, organic mechanization compound having the alkyl group, a hydrocarbon compound, a fluorine-containing compound such as water-repellent carbon material formed by a plasma CVD method using, or thermal CVD method using the self-assembled monolayer The water-repellent carbon material formed by is preferable.
(Water repellent electrode catalyst layer transfer sheet)
The water repellent electrode catalyst layer transfer sheet in the present invention is formed by laminating a transfer substrate so that the water repellent layer is exposed.
(Water repellent catalyst layer-electrolyte assembly)
In the water-repellent catalyst layer-electrolyte assembly, an electrode catalyst layer and a gas diffusion layer are sandwiched in order on both sides of the electrolyte membrane.

  In the water-repellent catalyst layer-electrolyte assembly of the present invention, at least one of the two electrode catalyst layers sandwiched may be the above-described water-repellent catalyst layer. The water repellent catalyst layer is sandwiched so that the water repellent layer is in contact with the electrolyte membrane.

  The electrolyte membrane is not particularly limited as long as it has hydrogen ion conductivity, and can be appropriately employed depending on the purpose. For example, a perfluorocarbon sulfonic acid polymer (PFS polymer) in which the C—H bond of a hydrocarbon ion exchange membrane is substituted with fluorine may be mentioned. The introduction of fluorine atoms having a high electronegativity into the PFS-based polymer makes it very chemically stable and has a high degree of sulfonic acid group dissociation, so that high ionic conductivity can be realized. Among these, specifically, Nafion (registered trademark, manufactured by DuPont), Flemion (registered trademark, manufactured by Asahi Glass), and Aciplex (registered trademark, manufactured by Asahi Kasei) are preferable.

  The thickness of the electrolyte membrane is usually 10 μm to 250 μm, preferably 15 μm to 175 μm.

The gas diffusion layer is not particularly limited as long as it has gas permeability and conductivity, and examples thereof include carbon paper made of carbon paper using conductive fibers, carbon cloth, carbon felt, and the like.
(Unit cell)
The unit cell for the solid fuel cell of the present invention may be any unit cell provided with the membrane-electrode assembly.

  The unit cell of the present invention is obtained by sandwiching the membrane-electrode assembly with a separator.

A separator in particular is not restrict | limited, A well-known thing can be used. Examples of the material of the separator include metals such as stainless steel, copper, titanium, aluminum, rhodium, tantalum, tungsten, and gold, or at least one alloy thereof; graphite; a carbon compound in which carbon is kneaded into a resin. Among these, from the viewpoints of strength, thinning of the fuel cell, etc., the above metals or at least one of these alloys are preferable, and stainless steel and titanium are more preferable.
The separator may be subjected to a surface treatment such as plating. These surface treatments can be performed according to known methods.
(Fuel cell)
The polymer electrolyte fuel cell is formed by stacking unit cells, and the polymer electrolyte fuel cell of the present invention only needs to have one or more unit cells.
2. Method for producing water repellent catalyst layer ( method for producing water repellent catalyst layer)
The method for producing a water-repellent catalyst layer of the present invention is a method for producing an electrode catalyst layer for a polymer electrolyte fuel cell, comprising a solid polymer electrolyte, a catalyst material in which a catalytic material is supported on a carbon material, A step of forming a water-repellent layer by a vapor phase method on part or all of the surface of the electrode catalyst layer.

The gas phase method for forming the water repellent layer on the surface of the catalyst layer is not particularly limited as long as it is performed via the gas phase. For example, film forming methods such as a reactive sputtering method, a reactive vapor deposition method, a PVD method such as an ion plating method, a CVD method such as a thermal CVD method, a plasma CVD method, and a laser CVD method can be given. In the present invention, the CVD method is preferable.
(1) In particular, a layer of a desired material can be formed at a low temperature (in the range of about -20 to 200 ° C.) that does not cause thermal damage to the base material. From the viewpoint that the type and physical properties of the obtained layer can be controlled by electric power or the like, the plasma CVD method is preferable.

  Specific conditions for forming the water repellent layer in the plasma CVD method of the present invention will be described.

  The temperature of the catalyst layer as a substrate is not particularly limited, but is usually in the range of -20 to 100 ° C, preferably in the range of -10 to 50 ° C.

  The source gas is not particularly limited as long as it is a gas containing a component contained in a desired water-repellent layer.

  The energy band of the plasma CVD method is not particularly limited, and high frequency, super high frequency, microwave, or the like may be used.

Here, when forming the water-repellent layer by the plasma CVD method, the water repellent layer, at least one organic mechanization compound (ii) a hydrocarbon compound and (iii) a fluorine-containing compound having (i) a carbon-containing group Preferably it is a seed. Thereby, a water-repellent layer having high water repellency can be formed on a part or all of the surface of the catalyst layer. Hereinafter, the source gas used for these will be described.
(I) As the gas for forming the water-repellent layer made of organic mechanization compound having a chromatic mechanization compound carbon-containing group which has a carbon-containing group, those containing alkyl groups and Si, Ti, the original elements of Al, If it is, it will not be restrict | limited in particular.

  Specific examples of the organosilicon compound gas include hexamethyldisiloxane (HMDSO), 1,1,3,3-tetramethyldisiloxane (TMDSO), tetramethylsilane (TMS), vinyltrimethoxysilane, and vinyltrimethyl. Silane, tetramethoxysilane (TMOS), methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, tetraethoxysilane (TEOS), dimethyldiethoxysilane, methyldimethoxysilane, methyldiethoxysilane, hexamethyldisilazane, etc. are preferred In addition to these, one or more conventionally known ones such as tetramethyldisiloxane and normal methyltrimethoxysilane can be used.

  Among these, from the viewpoint of further improving water repellency, an organosilicon compound having a large number of carbon-silicon bonds in the molecule is preferably used. Specifically, hexamethyldisiloxane (HMDSO), 1,1,3,3-tetramethyldisiloxane (TMDSO), tetramethylsilane (TMS), vinyltrimethoxysilane, vinyltrimethylsilane, methyltrimethoxysilane, Examples thereof include dimethyldimethoxysilane, trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, methyldiethoxysilane, and hexamethyldisilazane.

Furthermore, from the viewpoint of having more carbon-silicon bonds in the molecule, hexamethyldisiloxane (HMDSO; (CH ₃ ) ₃ SiOSi (CH ₃ ) ₃ ), tetramethyldisiloxane (TMDSO; (CH ₃ ) ₂ HSiOSiH (CH ₃ ) ₂ ) and tetramethylsilane (TMS; Si (CH ₃ ) ₄ ) are more preferred.
(Ii) Hydrocarbon-based material The hydrocarbon-based material is not particularly limited as long as it is composed of C and H. Preferable materials include CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₃ H _8, or a mixed gas thereof, more preferably C ₂ H ₂ or C ₂ H _4. it can.
(Iii) Fluorine-containing compound material The fluorine-containing compound material is not particularly limited as long as it contains fluorine, but is preferably a fluorine-containing organic compound, for example, CF ₄ , C ₂ F ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₃ F ₈ , C ₅ F ₈ or a mixed gas thereof can be exemplified, and among these, C ₂ F ₄ or C ₃ F ₈ is particularly preferable.

An organic compound having many carbon-silicon bonds is used as the organic silicon compound gas in the source gas, and the temperature of the base material at the start, the input power in the plasma generating means, the film forming pressure, etc. are within the above range as described above. Thus, a more excellent water-repellent layer can be obtained. This is because the compounds (i) and (iii) have low decomposability of the organosilicon compound gas, and an alkyl group (usually in the range of 1 to 30 carbon atoms) or fluorine is taken into the film. This is based on the reason that it becomes easier. The compound (ii) is based on the reason that a film having a high water repellent effect can be obtained as a result of the layer being composed of only CH bonds.
(2) It is also preferable to form the water repellent layer by the thermal CVD method among the CVD methods.

  This is because, in the thermal CVD method, the material as a raw material is vaporized, the material is fed uniformly on the base material, and reactions such as oxidation, reduction, and substitution are performed. Is also based on the reason that it is possible to form a self-assembled monolayer uniformly.

  As preferable conditions for the thermal CVD method in the present invention, the higher the heat resistance temperature of the electrode catalyst layer to be used, the better. However, it is particularly preferable that the temperature is within the range of 50 ° C to 200 ° C. This is based on the reason that the presence of moisture or oxygen in the reaction system further promotes the hydrolysis reaction of the alkoxy group of the water-repellent layer-constituting substance and increases the reactivity with the substrate.

The water repellent layer formed by the thermal CVD method in the present invention is preferably a self-assembled monomolecular film. The material for the self-assembled monolayer is the same as the above-described self-assembled monolayer-forming substance.
(Catalyst layer-electrolyte membrane assembly production method)
The method for producing a catalyst layer-electrolyte membrane assembly of the present invention is obtained by forming an electrode catalyst layer on a transfer substrate and then forming a water-repellent layer on part or all of the surface of the electrode catalyst layer by a vapor phase method. And a step of transferring the transfer sheet to the solid polymer electrolyte membrane so that the water-repellent layer is in contact with the surface of the solid polymer electrolyte membrane.

  The electrode catalyst layer can be formed on the transfer substrate by, for example, applying the catalyst paste to the transfer substrate method.

  About the application method of a catalyst paste, the application method according to the viscosity, solid content, etc. of a catalyst paste can be selected, and it is not specifically limited. Examples thereof include knife coaters, bar coaters, sprays, dip coaters, spin coaters, roll coaters, die coaters, curtain coaters, and screen printing.

  The method for forming the water repellent layer by the vapor phase method is the same as described above in the method for producing the electrode catalyst layer.

  The transfer method is not particularly limited, and a known method can be used. As a specific example of the transfer, a base material on which two electrode catalyst layers are formed is arranged so as to face the electrolyte membrane by a roll press machine, a flat plate press machine, etc., and then transferred by a hot press method or the like. Can be mentioned.

The present invention will be described more specifically with reference to the following examples and comparative examples. The present invention is not limited to the following embodiment.
Example 1
(Production of electrode catalyst layer and electrode catalyst layer transfer sheet)
In the preparation of the catalyst layer, 10 g of platinum catalyst-supporting carbon (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and 100 g of 5 wt% Nafion solution (trade name: Nafion SE20042, manufactured by DuPont) are used as an alcohol that is 1-propanol. The electrode catalyst layer preparation paste was prepared by mixing in 100 g of solvent.

Next, the electrode catalyst preparation paste prepared above was applied onto a PET film (E3120, manufactured by Toyobo Co., Ltd., thickness 12 μm) with a doctor blade so that the thickness after drying was 10 μm. Thereafter, this was dried at 90 ° C. for 30 minutes in an air atmosphere to form an electrode catalyst layer, thereby producing an electrode catalyst layer transfer sheet.
(Water repellent material formation by thermal CVD process)
The catalyst layer transfer sheet and about 0.2 ml of octadecyltrimethoxysilane (00256 manufactured by Tokyo Chemical Industry Co., Ltd.) placed in a glass container were placed in a Teflon (registered trademark) container. This was left in an oven at 100 ° C. for 5 hours to form a water repellent layer by thermal CVD on the surface of the electrode catalyst layer.

After the formation of the water repellent layer, the water repellent layer characteristics were evaluated by XPS. As a result, the presence of Si was confirmed in the water repellent layer. The evaluation by XPS was performed using XPS220iXL (manufactured by ESCALAB) under the conditions of using MgKα, 15 kV, 20 mA (300 W).
(Production of catalyst layer-electrolyte membrane assembly)
In producing the electrode catalyst layer (air electrode), the PET film on which the electrode catalyst layer was formed was transferred. That is, the PET film and the electrolyte membrane were joined by peeling the PET film from the PET film after sandwiching the PET film at a hydrogen ion conductive polymer electrolyte membrane (Nafion 112, manufactured by DuPont) at 150 ° C. and 10 Mpa.

In the production of the electrode catalyst layer (fuel electrode), 10 g of catalyst material particles (PtRu 53.3 wt%, TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) carrying a platinum ruthenium alloy as a catalyst, and a 5 wt% Nafion solution (manufactured by Dupont, A catalyst paste (for fuel electrode) for preparing an electrode catalyst layer was prepared by stirring and mixing 100 g of solvent propanol) with a disperser. This catalyst paste was hot pressed to obtain an electrode catalyst layer-electrolyte membrane assembly.
Example 2
The electrode catalyst layer and the electrode catalyst layer transfer sheet were produced in the same manner as in Example 1.
(Water-repellent layer formation by plasma CVD process; silica-based layer formation)
Prepared catalyst layer transfer sheet silica layer is water-repellent layer (SiC _x H _y based thin: octadecyl trimethoxysilane) was formed by capacitively coupled RF plasma CVD. That is, the electrode catalyst layer was installed in the chamber, and the degree of vacuum inside the chamber was set to 1.0 × 10 ⁻⁴ Pa or less. Thereafter, a source gas was introduced into the reaction chamber, and the total pressure was 10 Pa. As a source gas, tetramethylsilane (T2050 manufactured by Chisso Corporation) was used as an organosilicon compound. Plasma generation and raw material decomposition were performed using a high frequency of 13.56 MHz. A silica-based layer as a water-repellent layer was formed on the electrode catalyst layer with a power of 200 W for a formation time of 30 seconds. During the formation, the metal plate surface temperature was 50 ° C. or lower. After the formation of the silica-based layer, it was confirmed that a water-repellent layer was formed by water droplet contact angle measurement and XPS composition analysis.

Then, it carried out similarly to Example 1 and created the electrode catalyst layer-electrolyte membrane assembly.
Comparative Example 1
An electrode catalyst layer was formed in the same manner as in Example 1 except that a water-repellent electrode catalyst sheet was not used, and an electrode catalyst layer-electrolyte membrane assembly was prepared.
(Test evaluation)
After placing an electrode base material (carbon paper made of carbon fiber, TGP-H-090, manufactured by Toray Industries, Inc.) on both sides of the electrode catalyst layer-electrolyte membrane laminate, a single cell was produced by sandwiching it with a separator. The unit cell was continuously operated for 500 hours at a constant current of 300 mA, and the battery performance of the catalyst layer-electrolyte membrane laminate prepared using each catalyst layer transfer sheet was evaluated.

  As a result, Examples 1 and 2 showed a small decrease in battery current even after 500 hours, while Comparative Example 1 showed a large decrease in current. This is because the water-repellent layer allows the water generated by the battery reaction to be discharged out of the system, thus improving the performance.

FIG. 1 shows the contact angle between a layer and a water droplet.

Explanation of symbols

1 water 2 layers

Claims (3)

Using a transfer sheet obtained by forming an electrocatalyst layer on a transfer substrate and then forming a water-repellent layer on a part or all of the surface of the electrocatalyst layer by a thermal CVD method using a self-assembled monolayer A method for producing a catalyst layer-electrolyte membrane assembly, comprising a step of transferring the transfer sheet to a solid polymer electrolyte membrane so that the water-repellent layer contacts the surface of the solid polymer electrolyte membrane. The self-assembled monolayer has the following general formula (1):
R ¹ XR ² (1)
(Wherein, R ¹ is, .R ² represents an alkyl group or aryl group, hydrogen, halogen, or -OR ³ (R ³ is an alkyl group, an allyl group, or an aryl group.) With a substituent represented by X represents Si, Ti, Al, C or S.)
The method of claim 1 which is formed by in a compound represented. Water-repellent layer A method according to claim 1 or 2 contact angle with water is 70 to 170 °.

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