WO2014126002A1 - 燃料電池用ガス拡散層、およびその製造方法 - Google Patents
燃料電池用ガス拡散層、およびその製造方法 Download PDFInfo
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- WO2014126002A1 WO2014126002A1 PCT/JP2014/052846 JP2014052846W WO2014126002A1 WO 2014126002 A1 WO2014126002 A1 WO 2014126002A1 JP 2014052846 W JP2014052846 W JP 2014052846W WO 2014126002 A1 WO2014126002 A1 WO 2014126002A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0239—Organic resins; Organic polymers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
- H01M4/8803—Supports for the deposition of the catalytic active composition
- H01M4/8807—Gas diffusion layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0234—Carbonaceous material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0241—Composites
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0241—Composites
- H01M8/0245—Composites in the form of layered or coated products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a gas diffusion layer suitably used for a fuel cell, particularly a polymer electrolyte fuel cell. More specifically, in order to enhance the power generation performance, it has high gas diffusibility and high drainage in the thickness direction, and prevents gas shortcuts between the grooves of the separator, so that the gas (hydrogen, oxygen) supplied from the separator can be reduced.
- the present invention relates to a gas diffusion layer having low air permeability in the planar direction and further excellent mechanical properties, electrical conductivity, and thermal conductivity so that the catalyst layer can be supplied uniformly.
- a polymer electrolyte fuel cell that supplies a fuel gas containing hydrogen to an anode and an oxidizing gas containing oxygen to a cathode to obtain an electromotive force by an electrochemical reaction occurring at both electrodes is generally a separator, gas diffusion A layer, a catalyst layer, an electrolyte membrane, a catalyst layer, a gas diffusion layer, and a separator are sequentially laminated.
- the gas diffusion layer has a high gas diffusibility for diffusing the gas supplied from the separator to the catalyst, a high drainage property for discharging water generated by the electrochemical reaction to the separator, and taking out the generated current. Therefore, a gas diffusion layer (hereinafter referred to as a gas diffusion layer) made of carbon fiber or the like is widely used.
- Patent Document 1 proposes a means for reducing the bulk density of the porous carbon fiber substrate
- Patent Document 2 proposes a means for reducing the thickness of the porous carbon fiber substrate.
- the gas (hydrogen, oxygen) supplied from the separator in order for the gas (hydrogen, oxygen) supplied from the separator to be supplied uniformly to the catalyst layer, the air permeability in the planar direction in the gas diffusion layer in order to suppress a gas shortcut between the grooves of the separator. It is necessary to reduce (in-plane air permeability).
- Patent Document 3 proposes means for increasing the bulk density of the porous carbon fiber substrate
- Patent Document 4 discloses means for soaking the porous layer into the porous carbon fiber substrate. Proposed.
- increasing gas diffusivity and drainage in the thickness direction and reducing the air permeability in the planar direction are in a trade-off relationship, making it difficult to balance both at a higher level.
- Patent Document 5 proposes a means for intentionally putting a concave shape on the surface of the porous layer in order to improve the gas diffusivity in the thickness direction. There may be a problem with durability.
- the inventors of the present invention have intensively studied to solve the above problems, and have found that the above problems can be solved by using the gas diffusion layer for fuel cells of the present invention and the manufacturing method thereof.
- the gas diffusion layer for a fuel cell of the present invention has the following configuration. That is, a gas diffusion layer for a fuel cell comprising a porous carbon fiber base material in which discontinuous carbon fibers are bound with a carbide, and a porous layer containing at least carbonaceous particles, the porous layer (A) is disposed on one surface A of the porous carbon fiber base material with a thickness t1 of 10 to 55 ⁇ m, and the porous layer (J) penetrates into the porous carbon fiber base material and at least a part of it is infiltrated.
- the ratio of the cross-sectional area in the cross section in the thickness direction of the voids held inside the porous carbon fiber substrate is 5 to 40%, and at least the porous layer ( The porosity of both A) and the porous layer (J) is 50 to 85%, the thickness of the porous carbon fiber substrate is 60 to 300 ⁇ m, and the volume of the porous carbon fiber substrate is density of 0.20 ⁇ 0.45g / cm 3, a fuel collector A use gas diffusion layer.
- the porous layer (A) and the porous layer (J) have different compositions.
- the porous layer (A) and the porous layer (J) have the same composition.
- the method for producing a gas diffusion layer for a fuel cell of the present invention has the following configuration. That is, in the above-described method for producing a fuel cell gas diffusion layer, a dispersion comprising at least carbonaceous particles and a dispersion medium on a porous carbon fiber base material in which discontinuous carbon fibers are bound with carbides ( 1) impregnation step (I) for impregnating, and an arrangement step for disposing a dispersion liquid (2) comprising at least carbonaceous particles and a dispersion medium on one surface A of the porous carbon fiber substrate that has undergone the impregnation step (I). It is a manufacturing method of the gas diffusion layer for fuel cells which heats and sinters the porous carbon fiber base material containing (II) which passed through arrangement process (II).
- discontinuous carbon fibers A porous liquid (2) composed of at least carbonaceous particles and a dispersion medium is placed on one surface A of the porous carbon fiber base material bound with carbide, and the porous carbon fiber base material is soaked into the porous carbon fiber base material. It is also possible to employ a method for producing a gas diffusion layer for a fuel cell, which includes a disposition impregnation step (II-3) and heats and sinters the porous carbon fiber base material that has undergone the disposition impregnation step (II-3). .
- high power generation performance is achieved by enhancing gas diffusibility and drainage in the thickness direction, and gas shortcuts between the grooves of the separator are suppressed by reducing the air permeability in the planar direction. Furthermore, it is possible to provide a gas diffusion layer having excellent smoothness on the surface of the porous layer.
- FIG. 1 is a schematic sectional view of a gas diffusion layer for a fuel cell according to the present invention.
- a porous carbon fiber substrate (hereinafter also abbreviated as CP) in which discontinuous carbon fibers are bound with carbide, and a porous layer (hereinafter abbreviated as MPL) containing at least carbonaceous particles.
- a gas diffusion layer for a fuel cell (hereinafter sometimes abbreviated as GDL), and the porous layer (A) is formed on one surface A of the porous carbon fiber substrate.
- GDL gas diffusion layer for a fuel cell
- GDL gas diffusion layer for a fuel cell
- the porous layer (A) is formed on one surface A of the porous carbon fiber substrate.
- t1 average thickness
- J is infiltrated into the porous carbon fiber base material, and voids are maintained inside the porous carbon fiber base material. It consists of Hereinafter, each component will be described.
- porous carbon fiber substrate that is a component of the present invention will be described.
- the porous carbon fiber base material has a high gas diffusibility for diffusing the gas supplied from the separator to the catalyst, and a high drainage property for discharging water generated by the electrochemical reaction to the separator. It is necessary to have high conductivity for taking out the generated current. Therefore, it is preferable to use a porous carbon fiber base material having conductivity and an average pore diameter of 10 to 100 nm. More specifically, for example, it is preferable to use a carbon fiber nonwoven fabric or a carbon fiber nonwoven fabric such as a carbon fiber papermaking body.
- a base material formed by binding a carbon fiber papermaking body with a carbide that is, “carbon paper”, because of its excellent property of absorbing a dimensional change in the thickness direction of the electrolyte membrane, that is, “spring property”.
- a substrate formed by binding a carbon fiber papermaking body with a carbide is usually obtained by impregnating a carbon fiber papermaking body with a resin and carbonizing it, as will be described later.
- Examples of the carbon fiber include polyacrylonitrile (hereinafter abbreviated as PAN), pitch, rayon, and vapor growth carbon fibers.
- PAN polyacrylonitrile
- pitch rayon
- vapor growth carbon fibers examples of the carbon fiber.
- PAN-based and pitch-based carbon fibers are preferably used in the present invention because of excellent mechanical strength.
- the average diameter of the single yarn is preferably in the range of 3 to 20 ⁇ m, and more preferably in the range of 5 to 10 ⁇ m.
- the average diameter is 3 ⁇ m or more, the pore diameter is increased, drainage is improved, and flooding can be suppressed.
- the average diameter is 20 ⁇ m or less, the water vapor diffusibility becomes small, and dry-up can be suppressed.
- the average diameter of the single fiber in the carbon fiber is measured with a microscope such as a scanning electron microscope, the carbon fiber is magnified 1,000 times or more, and photography is performed, and 30 different single fibers are selected at random. The diameter is measured and the average value is obtained.
- a microscope such as a scanning electron microscope
- S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.
- the carbon fiber in the present invention is discontinuous.
- the average length of the single yarn is preferably in the range of 3 to 20 mm, and more preferably in the range of 5 to 15 mm. .
- the porous carbon fiber substrate is preferable because it has excellent mechanical strength, electrical conductivity, and thermal conductivity.
- the average length is 20 mm or less, the dispersibility of carbon fibers during papermaking is excellent, and a homogeneous porous carbon fiber substrate is obtained.
- Carbon fibers having such an average length can be obtained by a method of cutting continuous carbon fibers into a desired length.
- the average length of the carbon fiber is taken with a microscope such as a scanning electron microscope, the carbon fiber is magnified 50 times or more, and 30 different single fibers are selected at random. Is measured and the average value is obtained.
- a microscope such as a scanning electron microscope
- S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used as the scanning electron microscope.
- the average diameter and average length of the single fiber in the carbon fiber are usually measured by directly observing the carbon fiber as a raw material, but by observing and measuring the porous carbon fiber substrate. Also good.
- the pore diameter of the porous carbon fiber substrate is preferably in the range of 20 to 80 ⁇ m, more preferably in the range of 25 to 75 ⁇ m, and further preferably in the range of 30 to 70 ⁇ m. preferable.
- the pore diameter is 20 ⁇ m or more, drainage performance is improved and flooding can be suppressed.
- the pore diameter is 80 ⁇ m or less, the conductivity is high, and the power generation performance is improved at both high and low temperatures.
- the pore diameter of the porous carbon fiber base material is obtained by determining the peak diameter of the pore diameter distribution obtained by measuring in the measurement pressure range of 6 kPa to 414 MPa (pore diameter 30 nm to 400 ⁇ m) by mercury porosimetry. is there. When a plurality of peaks appear, the peak diameter of the highest peak is adopted.
- Autopore 9520 manufactured by Shimadzu Corporation or an equivalent product thereof can be used as a measuring device.
- the porous carbon fiber base material preferably contains carbonaceous particles.
- the conductivity of the porous carbon fiber substrate itself is improved.
- the average particle size of the carbonaceous particles is preferably 0.01 to 10 ⁇ m, more preferably 1 to 8 ⁇ m, and even more preferably 3 to 6 ⁇ m.
- the carbonaceous particles are preferably graphite or carbon black powder, more preferably graphite powder.
- the average particle size of the carbonaceous particles can be obtained from the number average of the obtained particle size distribution by performing dynamic light scattering measurement.
- the porous carbon fiber substrate has a thickness of 60 to 300 ⁇ m, preferably 70 to 250 ⁇ m, more preferably 80 to 200 ⁇ m, and a bulk density of 0.20 to 0.45 g / cm 3 , preferably It is 0.22 to 0.43 g / cm 3 , more preferably 0.24 to 0.40 g / cm 3 .
- the thickness of the porous carbon fiber substrate is 60 ⁇ m or more, the mechanical strength becomes high and handling becomes easy.
- the amount of gas through which liquid water flows in the flow path can be reduced by reducing the cross-sectional area of the porous carbon fiber substrate because the thickness is 300 ⁇ m or less, thereby suppressing the gas that passes through from the flow path to the adjacent flow path.
- the porous carbon fiber base material has a bulk density of 0.20 g / cm 3 or more, the mechanical strength increases and handling becomes easy. It is preferable that the bulk density is 0.45 g / cm 3 or less because drainage and gas diffusibility are enhanced.
- the thickness of the porous carbon fiber substrate is indicated by the thickness when the porous carbon fiber substrate is pressed at a surface pressure of 0.15 MPa. Specifically, 20 or more different locations were selected at random, and a surface pressure of 0.15 MPa was applied in the thickness direction of the sheet using a micrometer having a circular cross section of the measuring element at a diameter of 5 mm. Then, individual thicknesses can be measured, and the measured individual thicknesses can be averaged.
- the bulk density of the porous carbon fiber substrate was determined by weighing and averaging 10 pieces of 10 cm ⁇ 10 cm square cut out from the sheet using an electronic balance (per unit area per unit area). Mass) can be obtained by dividing by the thickness of the porous carbon fiber substrate described above.
- porous carbon fiber base material is carbon paper
- a paper body containing carbon fibers impregnated with a resin composition is referred to as “pre-impregnated body”.
- controlling the basis weight of the carbon fiber in the pre-impregnated body and the amount of the resin component with respect to the carbon fiber is effective for obtaining a porous carbon fiber base material suitable for the present invention.
- a low bulk density substrate is obtained by reducing the carbon fiber basis weight in the pre-impregnated body, and a high bulk density substrate is obtained by increasing the carbon fiber basis weight.
- a low bulk density base material is obtained by reducing the blending amount of the resin component relative to the carbon fiber, and a high bulk density base material is obtained by increasing the blending amount of the resin component.
- a low bulk density base material can be obtained by increasing the thickness of the porous carbon fiber base material, and a high bulk density base material can be obtained by reducing the thickness. It is done.
- the porous carbon fiber base material having such a bulk density is to control the carbon fiber basis weight in the pre-impregnated body, the blending amount of the resin component with respect to the carbon fiber, and the thickness of the porous carbon fiber base material in the production method described later. Is obtained.
- the porous layer that is a component of the present invention will be described.
- the porous layer is classified into a porous layer (A), a porous layer (J), and a porous layer (B).
- the porous layer usually contains 5 to 95% of carbonaceous particles by mass fraction with respect to the total amount.
- the porous layer (A) is a porous layer disposed on one surface A of the porous carbon fiber base material with a finite average thickness t1, and is high for diffusing the gas supplied from the separator to the catalyst. It is necessary to have gas diffusivity, high drainage to discharge the water generated by the electrochemical reaction to the separator, and high conductivity to take out the generated current, and in addition, the reverse of moisture to the electrolyte membrane It is necessary to have a function of promoting diffusion. For this reason, the porous layer (A) is preferably a porous body having conductivity and an average pore diameter of 1 to 10 nm. More specifically, for example, a mixture of carbonaceous particles and a water-repellent resin is mixed. It is preferable that it is formed.
- Examples of the carbonaceous particles in the present invention include graphite, carbon black, graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers such as vapor-grown carbon fibers, and carbon fiber milled fibers. Black is preferred.
- the particle size of the carbonaceous particles is more preferably 10 to 200 nm.
- the particle diameter of carbonaceous particles means the particle diameter calculated
- the outer diameter represents the maximum diameter of the particles (that is, the long diameter of the particles and indicates the longest diameter in the particles).
- JEM-4000EX manufactured by JEOL Ltd. or an equivalent thereof can be used.
- carbon black refers to carbon fine particles having a carbon atom ratio of 80% or more and a primary particle diameter of about 3 to 500 nm.
- carbon black having a carbon atom ratio of 80% or more the conductivity and corrosion resistance of the porous layer are further improved.
- carbon black having a primary particle diameter of 500 nm or less the conductivity and mechanical properties of the porous layer (A) are further improved due to the increase in particle density per unit mass and the development of the structure.
- examples of carbon black include furnace black, channel black, acetylene black, and thermal black. Among them, it is preferable to use acetylene black having high conductivity and low impurity content.
- the porous layer (A) preferably contains carbon nanofibers in order to improve conductivity. By including the carbon nanofiber, the porosity of the porous layer (A) is increased, and the conductivity is also improved.
- the fiber diameter of the carbon nanofiber is preferably 1 to 1,000 nm, and more preferably 10 to 500 nm. When carbon nanofibers having a fiber diameter of less than 1 nm are used, the porosity of the porous layer (A) decreases, and the drainage performance may not be improved as expected. In addition, when carbon nanofibers having a fiber diameter exceeding 1,000 nm are used, the smoothness of the porous layer (A) may be lowered, the plugging property may not be improved as expected, and the contact resistance may be increased. is there.
- the carbon nanofiber refers to those having a carbon atom ratio of 90% or more and an aspect ratio of 10 or more. Since carbon nanofibers have a carbon atom ratio of 90% or more and an aspect ratio of 10 or more, the use of carbon nanofibers improves the conductivity and mechanical properties of the porous layer.
- the aspect ratio of the carbon nanofiber refers to the ratio between the fiber diameter and the fiber length determined by a transmission electron microscope.
- the measurement magnification is 500,000 times, observation with a transmission electron microscope is performed, the diameter and length of 100 fibers present on the screen are measured, and the aspect ratio is calculated by dividing the average fiber length by the average fiber diameter.
- As the transmission electron microscope JEM-4000EX manufactured by JEOL Ltd. or an equivalent thereof can be used.
- the carbon nanofibers in the present invention include single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanohorns, carbon nanocoils, cup-stacked carbon nanotubes, bamboo-like carbon nanotubes, vapor-grown carbon fibers, and graphite nanofibers. Is mentioned. Of these, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and vapor-grown carbon fibers are preferably used because of their large aspect ratio and excellent electrical conductivity and mechanical properties. Vapor-grown carbon fiber is obtained by growing carbon in a gas phase with a catalyst, and those having an average diameter of 5 to 200 nm and an average fiber length of 1 to 20 ⁇ m are preferably used.
- the porous layer (A) can be used in combination with a water-repellent resin in addition to the carbonaceous particles such as carbon black and carbon nanofibers in order to impart a water-repellent resin to the porous layer (A) to improve drainage.
- a water repellent resin polychlorotrifluoroethylene resin (PCTFE), polytetrafluoroethylene resin (PTFE), polyvinylidene fluoride resin (PVDF), a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) And fluoropolymers such as a copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) and a copolymer of tetrafluoroethylene and ethylene (ETFE).
- the fluororesin refers to a water repellent resin containing a fluorine atom in its structure.
- the blending amount is preferably 1 to 70 parts by mass with respect to 100 parts by mass of the carbonaceous particles in the porous layer (A). More preferably, it is part by mass.
- the blending amount of the water repellent resin is 1 part by mass or more, the porous layer (A) is excellent in drainage and mechanical strength, and when the blending amount of the water repellent resin is 70 parts by mass or less, the porous layer (A) is porous.
- the layer (A) becomes more excellent in conductivity.
- a carbonaceous particle which comprises a porous layer (A) what mixed carbon black and carbon nanofibers, such as acetylene black, may be used, for example.
- the average thickness t1 of the porous layer (A) is in the range of 10 to 55 ⁇ m, preferably 15 to 50 ⁇ m, more preferably 20 to 45 ⁇ m.
- t1 is 10 ⁇ m or more, carbon monofilaments of the porous carbon fiber base material can be prevented from piercing the electrolyte membrane, and when t1 is 55 ⁇ m or less, the electrical resistance of the porous layer (A) can be reduced.
- the presence frequency of cracks on the surface of the porous layer (A) can be 1 place or less in 1 mm square.
- the average thickness t1 of the porous layer (A) is the porous carbon fiber in which the porous layer (J) and the porous layer (B) measured in advance from the average thickness of the entire gas diffusion layer are arranged. It can be determined by subtracting the average thickness of the substrate. Further, the thickness of the entire gas diffusion layer and the thickness of the porous carbon fiber base material on which the porous layer (J) and the porous layer (B) are arranged are the same method as the thickness of the porous carbon fiber base material described above. Can be measured.
- the number of cracks on the surface of the porous layer (A) was selected by randomly selecting 5 different locations on the surface of the porous layer (A) with a microscope such as an optical microscope, and enlarged by about 50 to 100 times.
- the number of independent cracks existing in an arbitrary 1 mm square area is counted, and the average value of the number of cracks in each image is calculated.
- an optical microscope a digital microscope manufactured by Keyence Corporation or an equivalent thereof can be used.
- the porous layer (J) is a porous layer soaked in the porous carbon fiber base material, and has high gas diffusibility and electrochemical reaction for diffusing the gas supplied from the separator to the catalyst.
- the porous layer (J) is preferably a porous body having conductivity and an average pore diameter of 1 to 10 nm.
- the porous layer (J) is the same as the porous layer (A).
- it is preferably formed by mixing carbonaceous particles and a water-repellent resin.
- the carbonaceous particles those described above can be used.
- the porous layer (J) may have the same composition as the porous layer (A) or a different composition, but when the expected function is different between the porous layer (J) and the porous layer (A). It can be said that it is a preferable aspect to have a different composition. That is, the porous layer (A) requires a sparse structure in order to achieve particularly high gas diffusivity, and the porous layer (J) has a dense structure in order to achieve particularly high conductivity and moisture retention. May be necessary. For this reason, it can be said that it is preferable to prescribe different compositions suitable for each as described above.
- the porous layer (J) preferably has the same composition as the porous layer (A).
- the porous layer (A) and the porous layer (J) only one type of dispersion liquid needs to be used, and there is an advantage that the gas diffusion layer can be produced efficiently.
- the porous layer (J) contains carbon nanofibers in order to improve the conductivity, like the porous layer (A).
- the fiber diameter of the carbon nanofiber is preferably 1 to 1,000 nm, and more preferably 10 to 500 nm.
- carbon nanofibers having a fiber diameter of less than 1 nm are used, the porosity of the porous layer (J) decreases, and drainage may not be improved as expected.
- carbon nanofibers having a fiber diameter exceeding 1,000 nm are used, the amount of the porous layer (J) penetrating into the porous carbon fiber substrate decreases, and the in-plane air permeability does not decrease as expected.
- the porous layer (J) imparts a water-repellent resin and improves drainage, so that the carbon black or carbon nanofiber and the water-repellent resin are used in combination. it can.
- the water repellent resin include the same fluororesins as described above.
- the blending amount of the water-repellent resin in the porous layer (J) is preferably 1 to 70 parts by mass with respect to 100 parts by mass of the carbonaceous particles in the porous layer (J), as in the porous layer (A). It is more preferably 5 to 60 parts by mass.
- the blending amount of the water repellent resin is within this range, there are advantages similar to those described for the porous layer (A).
- the carbonaceous particles constituting the porous layer (J) include those similar to the porous layer (A). For example, a mixture of carbon black such as acetylene black and carbon nanofibers may be used.
- the porosity of the porous layer (J) is preferably 50 to 85%, more preferably 60 to 80%.
- the porosity of the porous layer (J) is 50% or more, drainage properties and gas diffusibility from the gas diffusion layer become higher, and the porosity of the porous layer (J) is 85% or less.
- the porous layer (J) has excellent mechanical strength.
- the porosity can be adjusted by the mixing ratio of the carbonaceous particles and the mixing ratio of the water repellent resin.
- the porous layer (J) soaks into the porous carbon fiber base material, and at least a part thereof also exists on the opposite surface B.
- the porous layer (J) is soaked in the porous carbon fiber substrate, but the ratio of the cross-sectional area in the cross section in the thickness direction of the voids held in the porous carbon fiber substrate is 5 to 40. It must be%.
- maintained inside the porous carbon fiber base material is hereafter called the porosity. When the porosity is 5% or more, drainage from the gas diffusion layer and gas diffusibility are enhanced.
- the porosity when the porosity is 40% or less, the in-plane air permeability is lowered, and plugging can be prevented.
- the porosity can be controlled by adjusting the concentration of the carbonaceous particles and the concentration of the water-repellent resin in the dispersion liquid (1) composed of the carbonaceous particles and the dispersion medium. Further, since at least a part of the porous layer (J) is also present on the opposite surface B, the contact resistance between the gas diffusion layer and the separator can be reduced, and the power generation efficiency can be increased.
- the porous layer (J) soaks into the porous carbon fiber base material and at least a part of the porous layer (J) is also present on the opposite surface B, it can be checked with a microscope such as a scanning electron microscope. This can be confirmed by magnifying the gas diffusion layer and observing the cross section of the gas diffusion layer.
- the porous layer (J) soaks into the porous carbon fiber substrate, and at least a part thereof is also present on the opposite surface B. This means that the cross section and the opposite surface of the porous carbon fiber substrate are present. It means that the porous layer (J) is visible in at least a part of B.
- the porosity is randomly selected from five sections perpendicular to the sheet surface of the gas diffusion layer, photographed with a scanning electron microscope, etc., magnified at a magnification of about 400 times, and binarized by image processing. It can obtain
- the image processing can be performed by the following method, for example. Calculate the area of the processing region (vertical pixel number ⁇ horizontal pixel number) and set it as the total area. The image is averaged over 9 pixels (vertical pixel count 3 ⁇ horizontal pixel count 3), and image 1 is obtained by removing noise in pixel units.
- image 1 a region (porous layer and carbon fiber cross section) having a luminance equal to or higher than an arbitrary average luminance value in which portions other than the voids are detected or lower than the average luminance value is extracted as an image 2.
- image 2 only an island having an area of 100 pixels or more is left, and image 3 is set.
- Image 3 is subjected to a circular closing process with a radius of 2.5 pixels (fills a small hole) to form image 4.
- -Divide the area of the void obtained by subtracting the area of the image 4 from the total area by the total area to calculate the individual void ratio.
- the frequency of occurrence of cracks in the porous layer (A) is smaller than the frequency of occurrence of cracks in the porous layer (J). Since the porous layer (J) is present in the porous carbon fiber base material, it is difficult to directly receive the load due to the expansion and contraction of the electrolyte membrane when used as a fuel cell, but the porous layer (A) is directly affected by the load. From the viewpoint of durability, the porous layer (A) is preferably less cracked, particularly from the viewpoint of durability. On the other hand, from the viewpoint of gas diffusibility, it is preferable that the presence frequency of cracks is high.
- the frequency of cracks in the porous layer (A) is smaller than the frequency of cracks in the porous layer (J).
- the presence of cracks in the porous layer is randomly selected from five cross-sections of the porous layer orthogonal to the sheet surface of the gas diffusion layer, and magnified by a magnification of about 400 times with a scanning electron microscope or the like. And the number of independent cracks with a continuous length of 10 ⁇ m or more can be counted and obtained.
- a porous layer (B) is a porous layer arrange
- the porous layer (B) has a high gas diffusibility for diffusing the gas supplied from the separator to the catalyst, and discharges water generated in association with the electrochemical reaction to the separator. It is necessary to have high drainage and high conductivity for taking out the generated current. Therefore, the porous layer (B) is preferably a porous body having conductivity and an average pore diameter of 1 to 10 nm. More specifically, the same thing as a porous layer (A) is mentioned.
- the porous layer (B) preferably contains carbon nanofibers in order to improve the conductivity, like the porous layer (A). By including the carbon nanofiber, the porosity of the porous layer (B) is large and the conductivity is also good.
- the fiber diameter of the carbon nanofiber is preferably 1 to 1,000 nm, and more preferably 10 to 500 nm. When carbon nanofibers having a fiber diameter of less than 1 nm are used, the porosity of the porous layer (B) decreases, and the drainage performance may not be improved as expected. In addition, when carbon nanofibers having a fiber diameter exceeding 1,000 nm are used, the smoothness of the porous layer (B) is lowered, and the plugging property may not be improved as expected, and the contact resistance may be increased. is there.
- the porous layer (B) is provided with a water-repellent resin to improve drainage, so that the carbon black or carbon nanofiber and the water-repellent resin are used in combination. Can do.
- the water repellent resin include the same fluororesins as described above.
- the blending amount of the water-repellent resin in the porous layer (B) is preferably 1 to 70 parts by mass with respect to 100 parts by mass of the carbonaceous particles in the porous layer (B), as in the porous layer (A). It is more preferably 5 to 60 parts by mass.
- the blending amount of the water repellent resin is within this range, there are advantages similar to those described for the porous layer (A).
- the carbonaceous particles constituting the porous layer (B) include those similar to the porous layer (A), and may be a mixture of carbon black such as acetylene black and carbon nanofibers.
- the average thickness t2 of the porous layer (B) is preferably in the range of 0 to 20 ⁇ m, and more preferably 3 to 10 ⁇ m. As shown in FIG. 1 (a), if the porous layer (J) soaks into the porous carbon fiber substrate and at least a part thereof is also present on the opposite surface B, the porous layer (B) The average thickness is substantially 0 ⁇ m, that is, the porous layer (B) may not be disposed. Further, as shown in FIG.
- the thickness is 3 ⁇ m or more over the entire surface of the opposite surface B, when the porous layer (B) is used facing the separator side, the separator and the gas diffusion layer It is possible to reduce the gap between the interfaces and not only increase the effect of preventing plugging due to a decrease in the in-plane air permeability, but also can further reduce the contact resistance with the separator as described above, further increasing the power generation efficiency. Can do.
- the average thickness t2 of the porous layer (B) is obtained by subtracting the thickness of the porous carbon fiber substrate and the average thickness t1 of the porous layer (A) from the average thickness of the entire gas diffusion layer. Can do.
- the porous layer (B) preferably has the same composition as the porous layer (J).
- the step of applying the porous layer (B) can be omitted.
- the porosity of both the porous layer (A) and the porous layer (J) needs to be 50 to 85%, preferably 60 to 80%.
- the porosity is 50% or more, drainage and gas diffusibility from the gas diffusion layer are enhanced, and when the porosity is 85% or less, the porous layer has excellent mechanical strength.
- the porosity of the porous layer (B) is more preferably within the above-described range.
- the porosity of a porous layer (A) is larger than the porosity of either a porous layer (B) or a porous layer (J).
- the porosity of the porous layer (A) is larger than the porosity of the porous layer (J). Since the porosity of the porous layer (A) is larger than the porosity of either the porous layer (B) or the porous layer (J), it is preferable because gas diffusibility can be sufficiently maintained. .
- the porosity can be adjusted by the mixing ratio of the carbonaceous particles and the mixing ratio of the water repellent resin.
- each porosity of a porous layer (A), a porous layer (B), and a porous layer (J) is a cross section orthogonal to the sheet
- the image processing can be performed by the following method, for example. Calculate the area of the processing region (vertical pixel number ⁇ horizontal pixel number) and set it as the total area.
- the image is averaged over 9 pixels (vertical pixel count 3 ⁇ horizontal pixel count 3), and image 1 is obtained by removing noise in pixel units.
- image 1 a region (porous layer cross section) having a luminance equal to or higher than an arbitrary average luminance value in which a portion other than pores is detected is extracted as an image 2.
- image 2 only an island having an area of 100 pixels or more is left, and image 3 is set.
- Image 3 is subjected to a circular closing process with a radius of 2.5 pixels (fills a small hole) to form image 4.
- the individual porosity is obtained at five locations, and the average value is calculated to obtain the porosity.
- S-4800 manufactured by Hitachi, Ltd. or an equivalent product thereof is used.
- image processing software “HALCON” (registered trademark) 9.0 manufactured by MVTec Co., Ltd. or an equivalent product thereof is used. be able to.
- ⁇ Carbon fiber nonwoven fabric> In order to obtain a non-woven fabric containing carbon fibers, a wet method in which carbon fibers are dispersed in a liquid, a dry method in which carbon fibers are dispersed in air, and a dry method are used. Among these, a wet papermaking method that can obtain a thin carbon fiber nonwoven fabric is preferably used. A carbon fiber nonwoven fabric obtained by a wet papermaking method is referred to as a carbon fiber papermaking body.
- pulp For the purpose of reducing the in-plane air permeability, it is also preferable to make paper by mixing pulp with carbon fiber.
- pulp natural pulp such as wood pulp, bagasse pulp, and straw pulp
- synthetic fiber such as fibrillated polyethylene fiber, vinylon fiber, polyacetal fiber, polyester fiber, polyamide fiber, rayon fiber, acrylic fiber, and aramid fiber may be used. it can.
- the carbon fiber nonwoven fabric is preferably in the form of a sheet in which carbon fibers are randomly dispersed in a two-dimensional plane for the purpose of isotropic in-plane conductivity and thermal conductivity.
- the pore size distribution in the nonwoven fabric is affected by the carbon fiber content and dispersion state, it can be formed in a size of about 20 to 100 ⁇ m.
- the nonwoven fabric preferably has a carbon fiber basis weight in the range of 10 to 60 g / m 2 , and more preferably in the range of 20 to 50 g / m 2 .
- the basis weight of the carbon fiber is 10 g / m 2 or more, the porous carbon fiber substrate has excellent mechanical strength, and when it is 60 g / m 2 or less, the porous carbon fiber substrate has gas diffusibility and drainage. It becomes more excellent by the property.
- the basis weight of the carbon fibers is within the above range after the bonding.
- the weight per unit area of the carbon fiber in the porous carbon fiber substrate is held in an electric furnace at a temperature of 450 ° C. in a nitrogen atmosphere for 15 minutes in a non-woven fabric, and the residue mass is set to the area of the nonwoven fabric (0 .01 m 2 ).
- a nonwoven fabric containing carbon fibers is impregnated with a resin composition to prepare a pre-impregnated body.
- a method of impregnating a resin composition into a nonwoven fabric containing carbon fibers a method of immersing the nonwoven fabric in a solution containing the resin composition, a method of applying a solution containing the resin composition to the nonwoven fabric, and a film made of the resin composition
- a method of transferring on a non-woven fabric is used.
- productivity since productivity is excellent, the method of immersing a nonwoven fabric in the solution containing a resin composition is used preferably.
- a resin composition a resin composition that is carbonized upon firing to become a conductive carbide is used. Thereby, it can take the structure where the discontinuous carbon fiber was bound by the carbide after firing.
- a resin composition means what added the solvent etc. to the resin component as needed.
- a resin component contains resin, such as a thermosetting resin, and also contains additives, such as a carbon-type filler and surfactant, as needed.
- the carbonization yield of the resin component contained in a resin composition is 40 mass% or more.
- a carbonization yield of 40% by mass or more is preferable because the porous carbon fiber base material has excellent mechanical properties, electrical conductivity, and thermal conductivity. The higher the carbonization yield, the better.
- the current state of the art is generally 70% by mass or less.
- Resins constituting the resin component include thermosetting resins such as phenol resin, epoxy resin, melamine resin, furan resin. Of these, a phenol resin is preferably used because of its high carbonization yield.
- a carbon-based filler typified by the above-mentioned carbonaceous particles Can be included.
- the carbon-based filler carbon black, carbon nanotube, carbon nanofiber, milled fiber of carbon fiber, graphite, or the like can be used.
- the resin composition can use the resin component having the above-described configuration as it is, and can contain various solvents as necessary for the purpose of improving the impregnation property of the papermaking body.
- water, methanol, ethanol, isopropyl alcohol, acetone, or the like can be used as the solvent.
- the resin component is preferably impregnated with 30 to 400 parts by mass, more preferably 50 to 300 parts by mass with respect to 100 parts by mass of the carbon fiber.
- the porous carbon fiber base material is preferable because it has excellent mechanical properties, electrical conductivity, and thermal conductivity.
- the porous carbon fiber base material is preferable because it has excellent gas diffusibility.
- the pre-impregnated body After forming the pre-impregnated body, prior to carbonization, the pre-impregnated body can be bonded or heat-treated.
- a plurality of pre-impregnated bodies can be bonded together for the purpose of setting the porous carbon fiber substrate to a predetermined thickness.
- a plurality of pre-impregnated bodies having the same properties can be bonded together, or a plurality of pre-impregnated bodies having different properties can be bonded together.
- a plurality of pre-impregnated bodies having different average diameters and average lengths of carbon fibers, carbon fiber basis weight of the papermaking body, impregnation amount of the resin component, and the like can be bonded together.
- the pre-impregnated body can be heat-treated for the purpose of thickening and partially cross-linking the resin composition.
- a heat treatment method a method of blowing hot air, a method of heating by sandwiching between hot plates such as a press device, a method of heating by sandwiching between continuous belts, or the like can be used.
- ⁇ Carbonization> After impregnating the carbon fiber nonwoven fabric with the resin composition, firing is performed in an inert atmosphere in order to carbonize the carbon fiber nonwoven fabric.
- a batch-type heating furnace can be used, or a continuous-type heating furnace can be used.
- the inert atmosphere can be obtained by flowing an inert gas such as nitrogen gas or argon gas in the furnace.
- the maximum temperature for firing is preferably in the range of 1,300 to 3,000 ° C., more preferably in the range of 1,700 to 2,850 ° C., and in the range of 1,900 to 2,700 ° C. More preferably, it is within.
- the maximum temperature is 1,300 ° C. or higher, the carbonization of the resin component proceeds, and the porous carbon fiber base material is preferably excellent in conductivity and thermal conductivity.
- the maximum temperature of 3,000 ° C. or lower is preferable because the operating cost of the heating furnace is reduced.
- porous carbon fiber substrate what is carbonized after impregnating a resin composition into a nonwoven fabric containing carbon fibers.
- the porous carbon fiber base material may be subjected to water repellent treatment for the purpose of improving drainage.
- the water repellent process can be performed by applying a water repellent resin to the porous carbon fiber substrate.
- a water repellent resin for example, the above fluororesins can be illustrated.
- the amount of the water-repellent resin applied is preferably 1 to 50 parts by mass and more preferably 3 to 40 parts by mass with respect to 100 parts by mass of the porous carbon fiber substrate.
- the applied amount of the water-repellent resin is 1 part by mass or more, the porous carbon fiber substrate is superior in drainage, and when it is 50 parts by mass or less, the porous carbon fiber substrate is more excellent in conductivity. It will be a thing.
- the gas diffusion layer cross section is enlarged about 400 times with a microscope such as a scanning electron microscope, and the energy dispersion type
- the fluorine concentration distribution in the cross-sectional direction may be analyzed with an X-ray analyzer or an electron beam microanalyzer.
- the porous layer (J) is formed by soaking a dispersion liquid (1) in which carbonaceous particles are dispersed in a dispersion medium such as water or an organic solvent into the porous carbon fiber substrate.
- the dispersion (1) is usually mixed with the same water-repellent resin as used in the above-described water-repellent processing. Dipping method, die coater coating, kiss coater coating, screen printing, rotary screen printing, spray spraying, intaglio printing, gravure printing, bar coating, blade coating, etc. can be used, but the inside is uniform. It is preferred to use a dip method that can be soaked. In order to impregnate so that the porosity is 5 to 40%, the composition and solid content of the dispersion can be appropriately adjusted.
- the dispersion liquid (1) and the dispersion liquid (2) and dispersion liquid (3) described later may contain a dispersion aid such as a surfactant.
- a dispersion aid such as a surfactant.
- the dispersion medium used in the dispersion liquid (1) and the dispersion liquid (2) and dispersion liquid (3) described below is preferably water, and more preferably a nonionic surfactant is used as the dispersion aid.
- step (I) the excess dispersion liquid (1) adhering to the surface of the porous carbon fiber substrate is removed using a blade or a squeeze roll so that the porosity is adjusted to 5 to 40%. May be.
- the blade can be appropriately selected from rubber, plastic, metal and the like.
- the squeezing roll can be appropriately selected from rubber, plastic, metal and the like, and can be appropriately selected from nip method, clearance method and the like.
- the porous carbon fiber base material that has been subjected to the impregnation step (I) and, if necessary, the drawing step (I-2) is heated at a temperature of 80 to 200 ° C. before being put into the next step. It is preferable to remove (dry) the dispersion medium.
- the porous layer (A) is formed by applying a dispersion liquid (2) in which carbonaceous particles are dispersed in a dispersion medium such as water or an organic solvent on one surface A of a porous carbon fiber substrate.
- the dispersion (2) is usually mixed with the same water-repellent resin as used in the above-described water-repellent processing.
- the coating method die coater coating, kiss coater coating, screen printing, rotary screen printing, spray spraying, intaglio printing, gravure printing, bar coating, blade coating, etc. can be used. Since the coating amount can be quantified regardless of the surface roughness, it is preferable to use a die coater coating.
- the porous carbon fiber substrate that has undergone the placement step (II) can be heated at a temperature of 80 to 200 ° C. to remove (dry) the dispersion medium in the dispersion liquid (2) before being put into the next step. preferable.
- the gas diffusion layer for a fuel cell according to a preferred embodiment of the present invention in which the porous layer (A) and the porous layer (J) have the same composition is used.
- the second method including the following arrangement impregnation step (II-3) can be adopted instead of the above step.
- a dispersion liquid (2) in which carbonaceous particles are dispersed in a dispersion medium such as water or an organic solvent is applied to one surface A of the porous carbon fiber base material, and the dispersion liquid (2) The remaining part of the dispersion liquid (2) is soaked into the porous carbon fiber base material while leaving a part of the surface on the surface.
- the dispersion (2) is usually mixed with the same water-repellent resin as used in the above-described water-repellent processing.
- the coating method die coater coating, kiss coater coating, screen printing, rotary screen printing, spray spraying, intaglio printing, gravure printing, bar coating, blade coating, etc. can be used.
- a die coater coating that can accurately control the coating amount regardless of the surface roughness and easily control the degree of penetration into the porous carbon fiber substrate.
- the coating speed, the discharge speed, the clearance between the discharge port and the porous carbon fiber base material And the viscosity of the dispersion liquid may be adjusted.
- the porous carbon fiber base material that has undergone the placement and impregnation step (II-3) is heated at a temperature of 80 to 200 ° C. to remove the dispersion medium (2) in the dispersion liquid (2) before being put into the next step. Is preferred.
- ⁇ Opposite surface arrangement step (II-2) Formation of porous layer (B)> A porous layer (B) is formed on the porous carbon fiber substrate that has undergone the placement step (II) or the placement impregnation step (II-3), if necessary.
- the carbonaceous particles are dispersed in a dispersion medium such as water or an organic solvent on the surface B which is opposite to the one surface A of the porous carbon fiber substrate coated with the porous layer (A). It can be formed by coating the dispersion (3).
- the dispersion (3) is usually mixed with the same water-repellent resin as used in the above-described water-repellent processing.
- the coating method can be die coater coating, kiss coater coating, screen printing, rotary screen printing, spray spraying, intaglio printing, gravure printing, bar coating, blade coating, etc.
- kiss coater coating or screen Printing is preferably employed in the present invention because the amount of coating can be adjusted more easily than other methods.
- a porous layer having the same composition as the porous layer (J) is formed on at least one surface of the porous carbon fiber substrate when forming the porous layer (J). It is also preferable to form (B). In this case, the opposite surface arrangement step (II-2) and the drying step (II-2 ') can be omitted.
- the porous carbon fiber base material that has undergone the opposite surface placement step (II-2) is heated at a temperature of 80 to 200 ° C. to remove the dispersion medium in the dispersion liquid (3) before being put into the next step (drying). Is preferable.
- the porous carbon fiber base material that has undergone the placement step (II) or the placement impregnation step (II-3) is optionally subjected to a drying step (II ′), an opposite surface placement step (II-2), and a drying step (II). -2 '), drying step (II-3'), etc., and then put in or pass through a muffle furnace, a baking furnace or a high-temperature dryer and heat at 300 to 380 ° C. for 1 to 30 minutes for baking. Conclude.
- sintering when a water-repellent resin is used, it melts and becomes a binder between carbonaceous particles to form a porous layer.
- MEA membrane electrode assembly
- a membrane electrode assembly can be constituted by bonding the gas diffusion layer described above to at least one surface of the solid polymer electrolyte membrane 8 having the catalyst layers 9 on both surfaces.
- a fuel cell is configured by having separators (not shown) on both sides of such a membrane electrode assembly.
- a polymer electrolyte fuel cell is constructed by laminating a plurality of such membrane electrode assemblies on both sides sandwiched by a separator via a gasket.
- the catalyst layer 9 is composed of a layer containing a solid polymer electrolyte and catalyst-supporting carbon.
- platinum is usually used.
- a fuel cell in which a reformed gas containing carbon monoxide is supplied to the anode side, it is preferable to use platinum and ruthenium as the catalyst on the anode side.
- the solid polymer electrolyte it is preferable to use a perfluorosulfonic acid polymer material having high proton conductivity, oxidation resistance, and heat resistance.
- Such a fuel cell unit and the configuration of the fuel cell itself are well known.
- the thickness of the porous carbon fiber substrate, the thickness of the entire gas diffusion layer, and the thickness of the porous carbon fiber substrate on which the porous layer (J) and the porous layer (B) are arranged were determined as follows. . In other words, 20 different points were selected at random from the sheet-like specimen to be measured, and the surface of each part was measured using a Nikon Micrometer MF-501 having a circular cross section of 5 mm in diameter. The thickness was determined by measuring individual thicknesses under pressure of 0.15 MPa and averaging the measured individual thicknesses.
- the average thickness t1 of the porous layer (A) is determined from the average thickness of the entire gas diffusion layer of the porous carbon fiber substrate on which the porous layer (J) and the porous layer (B) measured in advance are arranged. It was determined by subtracting the average thickness.
- the average thickness t2 of the porous layer (B) was determined by subtracting the thickness of the porous carbon fiber substrate and the average thickness t1 of the porous layer (A) from the average thickness of the entire gas diffusion layer.
- the bulk density of the porous carbon fiber substrate was determined by dividing the basis weight (mass per unit area) of the porous carbon fiber substrate weighed using an electronic balance by the thickness of the porous carbon fiber substrate.
- the image was magnified 400 times and the thickness direction of the gas diffusion layer entered the entire surface of the image.
- the porous layer (A) is disposed on one surface of the porous carbon fiber substrate, and further the porous layer (J) soaks into the porous carbon fiber substrate so that at least a part thereof is the opposite surface B. It was also confirmed that voids were retained inside the porous carbon fiber substrate. Five different locations were selected at random from the cross section, and for each location, the individual porosity was obtained by binarization by the following image processing using image processing software HALCON 9.0 manufactured by MVTec.
- image processing The area of the processing region (vertical pixel number ⁇ horizontal pixel number) was calculated and defined as the total area. Image 9 was averaged (number of vertical pixels: 3 ⁇ number of horizontal pixels: 3), and image 1 was obtained by removing noise in pixel units.
- image 1 a region (porous layer and carbon fiber cross section) having a luminance equal to or higher than an arbitrary average luminance value where a portion other than voids is detected or lower than the average luminance value was extracted and used as image 2.
- Image 3 was subjected to a circular closing process with a radius of 2.5 pixels (filling a small hole) to obtain an image 4.
- the area of the image 4 ( part which is not a space
- image 1 a region (porous layer cross section) having a luminance equal to or higher than an arbitrary average luminance value in which a portion other than pores is detected is extracted as image 2.
- image 3 was subjected to a circular closing process with a radius of 2.5 pixels (filling a small hole) to obtain an image 4.
- image 4 was subjected to a circular closing process with a radius of 2.5 pixels (filling a small hole) to obtain an image 4.
- ⁇ Evaluation of power generation performance of polymer electrolyte fuel cells > 1.00 g of platinum-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum support: 50% by mass), 1.00 g of purified water, “Nafion” (registered trademark) solution (“Nafion” (registered trademark) 5 manufactured by Aldrich) (0.0 mass%) 8.00 g and isopropyl alcohol (manufactured by Nacalai Tesque) 18.00 g were sequentially added to prepare a catalyst solution.
- a catalyst solution was applied to 9001 (manufactured by Nichias Co., Ltd.) by spraying and dried at room temperature to prepare a PTFE sheet with a catalyst layer having a platinum amount of 0.3 mg / cm 2 .
- a solid polymer electrolyte membrane “Nafion” (registered trademark) NRE-211cs (manufactured by DuPont) cut to 10 cm ⁇ 10 cm is sandwiched between two PTFE sheets with a catalyst layer, and pressed to 5 MPa with a flat plate press.
- the catalyst layer was transferred to a solid polymer electrolyte membrane by hot pressing at ° C. After pressing, the PTFE sheet was peeled off to produce a solid polymer electrolyte membrane with a catalyst layer.
- the solid polymer electrolyte membrane with the catalyst layer was sandwiched between two gas diffusion layers cut to 7 cm ⁇ 7 cm, and hot pressed at 130 ° C. while pressing to 3 MPa with a flat plate press to produce a membrane electrode assembly.
- the gas diffusion layer was arranged so that the surface having the porous layer (A) was in contact with the catalyst layer side.
- the obtained membrane electrode assembly was incorporated into a single cell for fuel cell evaluation, and the voltage when the current density was changed was measured.
- a serpentine type single groove having a groove width of 1.5 mm, a groove depth of 1.0 mm, and a rib width of 1.1 mm was used.
- evaluation was performed by supplying hydrogen pressurized to 210 kPa to the anode side and air pressurized to 140 kPa to the cathode side. Both hydrogen and air were humidified using a humidification pot set at 70 ° C. The utilization rates of hydrogen and oxygen in the air were 80% and 67%, respectively.
- the output voltage was measured when the operating temperature was maintained at 65 ° C. and the current density was set at 2.2 A / cm 2, and used as an index of flooding resistance (low temperature performance). Plugging resistance was evaluated by looking at the frequency of instantaneous decrease in power generation performance when held at this current density of 2.2 A / cm 2 for 30 minutes. That is, count the number of times the output voltage became 0.2V or less in 30 minutes, C for 7 times or more, B for 5-6 times, A for 3-4 times, 2 times The following was designated S.
- the current density is set to 1.2 A / cm 2 , the operating temperature is maintained from 80 ° C. for 5 minutes, the output voltage is measured while repeatedly raising 2 ° C. over 5 minutes, and the limit temperature at which power generation is possible is obtained. It was used as an index of dry-up resistance (high temperature performance).
- Example 1 Toray Co., Ltd. polyacrylonitrile-based carbon fiber “Torayca” (registered trademark) T300 (average single fiber diameter: 7 ⁇ m) was cut to a length of 12 mm, and continuously made with water as a papermaking medium. A long carbon fiber paper having a carbon fiber weight per unit area of 16 g / m 2 was obtained through a paper making process of dipping in a 10% by mass aqueous solution and drying. The added amount of the added polyvinyl alcohol was equivalent to 20 parts by mass with respect to 100 parts by mass of the carbon fiber.
- a dispersion in which flaky graphite (average particle size 5 ⁇ m), phenol resin, and methanol were mixed at a mass ratio of 1: 9: 50 was prepared.
- the carbon fiber paper was continuously impregnated with the dispersion so that the resin impregnation amount was 104 parts by mass of phenol resin with respect to 100 parts by mass of carbon fiber, and the resin impregnation step was performed at a temperature of 90 ° C. Thereafter, a resin-impregnated carbon fiber paper (preliminarily impregnated body) was obtained.
- the phenol resin a resin obtained by mixing a resol type phenol resin and a novolac type phenol resin at a mass ratio of 1: 1 was used.
- a press machine was set so that the upper and lower hot plates were parallel to each other, and the resin-impregnated carbon fiber paper was compressed and heated at a hot plate temperature of 170 ° C and a surface pressure of 0.8 MPa.
- the carbon fiber paper subjected to the compression treatment is used as a precursor fiber sheet, introduced into a heating furnace having a maximum temperature of 2400 ° C. maintained in a nitrogen gas atmosphere, and through a carbonization step, a thickness of 100 ⁇ m, a basis weight of 24 g / m 2 , and a bulk density A porous carbon fiber substrate of 0.24 g / cm 3 was obtained.
- Dispersion liquid (2) was coated on an impregnated substrate using a die coater, and heated and dried at 120 ° C. to obtain a coated substrate.
- a gas diffusion layer having a porous layer (J) inside a porous carbon fiber substrate and a porous layer (A) on one surface of the porous carbon fiber substrate by heating the dried coating substrate at 380 ° C. was made.
- the average thickness t1 ( ⁇ m) of the porous layer (A) was 40 ⁇ m, and the basis weight of the porous layer (A) was 20 g / m 2 .
- the porous layer (J) was exposed on a part of the opposite surface B of the porous carbon fiber substrate.
- the porous layer (J) present on the opposite surface B was a porous layer (B) having an average thickness t2 ( ⁇ m) of 0 ⁇ m.
- the porosity of the obtained gas diffusion layer was calculated to be 31%, and the porosity of the porous layer (J) and porous layer (A) of the obtained gas diffusion layer was calculated to be porous.
- the porous layer (J) was 52% and the porous layer (A) was 75%.
- the output voltage is 0.38 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 91 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1 As described above, both flooding resistance and dry-up resistance were good.
- Example 2 In ⁇ Formation of porous layer (A), porous layer (J), porous layer (B)> in Example 1, after sintering, the average thickness t1 ( ⁇ m) of the porous layer (A) is 15 ⁇ m, A gas diffusion layer was obtained in the same manner as in Example 1 except that the basis weight of the porous layer (A) was changed to 8 g / m 2 . As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was good.
- the output voltage is 0.37 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1 As described above, both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 3 In ⁇ Formation of porous layer (A), porous layer (J), porous layer (B)> in Example 1, after sintering, the average thickness t1 ( ⁇ m) of the porous layer (A) is 52 ⁇ m, A gas diffusion layer was obtained in the same manner as in Example 1 except that the basis weight of the porous layer (A) was changed to 26 g / m 2 . As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was extremely good.
- the output voltage is 0.36 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1 As described above, both flooding resistance and dry-up resistance were good.
- the number of cracks on the surface of the porous layer (A) was 1.
- Example 4 In Example 1 ⁇ Formation of Porous Layer (A), Porous Layer (J), and Porous Layer (B)>, Dispersion (1) was placed in a stainless steel vat to disperse the porous carbon fiber substrate. The liquid adhering completely to the liquid (1), the liquid adhering to the surface is not dried off with a stainless steel spatula, but is heated and dried at 120 ° C., and the average thickness t2 is formed on the entire opposite surface (B) of the porous carbon fiber substrate.
- a gas diffusion layer was obtained in the same manner as in Example 1 except that an impregnated base material having an impregnation amount of 29 g / m 2 in terms of after sintering was obtained.
- the porosity of this gas diffusion layer was 10%.
- the output voltage is 0.33 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 92 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1
- both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- a gas diffusion layer was obtained in the same manner as in Example 1 except that an impregnated base material having an impregnation amount of 8 g / m 2 in terms of after sintering was obtained.
- the porosity of this gas diffusion layer was 38%.
- the output voltage is 0.38 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1
- both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- the average thickness t1 ( ⁇ m) of the porous layer (A) obtained using this dispersion liquid (2) was 43 ⁇ m, the basis weight was 20 g / m 2 , and the porosity was 80%.
- the plugging resistance was extremely good.
- the output voltage is 0.39 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1 As described above, both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- the average thickness t1 ( ⁇ m) of the porous layer (A) obtained using this dispersion liquid (2) was 30 ⁇ m, the basis weight was 20 g / m 2 , and the porosity was 52%. As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was extremely good.
- the output voltage is 0.32 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 1 As described above, both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 9 A porous carbon fiber substrate having a thickness of 75 ⁇ m, a basis weight of 24 g / m 2 and a bulk density of 0.32 g / cm 3 was obtained in the same manner as in Example 1 except that the molding thickness was set thin. Thus, a water-repellent treatment substrate was obtained.
- Example 10 In the paper making process of carbon fiber paper in Example 1, carbon fiber paper having a carbon fiber basis weight of 32 g / m 2 was obtained, and in the resin impregnation process, phenol resin was 290 with respect to 100 parts by mass of carbon fiber.
- a porous material having a thickness of 200 ⁇ m, a weight per unit area of 80 g / m 2 , and a bulk density of 0.40 g / cm 3 obtained as the same resin impregnation conditions as in Example 1 except that the resin impregnation amount is part by mass.
- the carbon fiber substrate was subjected to water repellent treatment in the same manner as in Example 1 to obtain a water repellent treated substrate.
- Example 11 A porous layer was formed on the water-repellent treated substrate obtained in Example 1 as shown in ⁇ Formation of Porous Layer> to obtain a gas diffusion layer.
- the heat-dried coated substrate was heated at 380 ° C. to produce a gas diffusion layer in which the porous layer (A) and the porous layer (J) had the same composition. That is, the porous layer (A) and the porous layer (J) were formed by the dispersion liquid (2).
- the average thickness t1 ( ⁇ m) of the porous layer (A) was 19 ⁇ m, and the basis weight of the porous layer (A) was 20 g / m 2 . Further, the porous layer (J) was exposed on a part of the opposite surface B of the porous carbon fiber substrate.
- the porosity of the obtained gas diffusion layer was calculated to be 31%, and the porosity of the porous layer (A) and porous layer (J) of the obtained gas diffusion layer was calculated respectively. 75%.
- the output voltage is 0.39 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 2
- both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 12 Except for changing the water-repellent treated base material to the water-repellent treated base material obtained in Example 9 and adjusting the coating amount so that the porosity in the CP becomes equivalent to that of Example 9, all the examples and Similarly, a gas diffusion layer was obtained.
- the average thickness t1 ( ⁇ m) of the porous layer (A) was 25 ⁇ m.
- the output voltage is 0.39 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 2
- both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 13 In the water repellent treated substrate obtained in Example 10, the basis weight of the porous layer (A) in ⁇ Formation of porous layer> is 29 g / m 2 , and the porosity in CP is equal to that in Example 10.
- a gas diffusion layer was obtained in the same manner as Example 11 except that the coating amount was adjusted. As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was good.
- the output voltage is 0.32 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 92 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 2 As described above, both flooding resistance and dry-up resistance were good. Cracks on the surface of the porous layer (A) were not confirmed.
- Tables 1 and 2 summarize the configurations and evaluation results of Examples 1 to 13.
- Example 1 Comparative Example 1 Except that the dispersion liquid (1) was not impregnated in ⁇ Formation of porous layer (A), porous layer (J), porous layer (B)> in Example 1, it was the same as Example 1. A gas diffusion layer was obtained. As a result of evaluating the power generation performance of this gas diffusion layer, the resistance to plugging was greatly reduced. The output voltage is 0.38 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 88 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 3 As described above, the flooding resistance was good, but the dry-up resistance was lowered.
- the reason why the high temperature performance is low is that the porous carbon fiber base material is not impregnated with the porous layer (J), and water vapor easily escapes to the separator side, and drying of the electrolyte membrane becomes remarkable. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 2 In ⁇ Formation of Porous Layer (A), Porous Layer (J), Porous Layer (B)> in Example 1, the average thickness t1 ( ⁇ m) of the porous layer (A) is 60 ⁇ m, A gas diffusion layer was obtained in the same manner as in Example 1 except that the coating amount of the dispersion liquid (2) was changed so that the basis weight of A) was 30 g / m 2 . As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was extremely good.
- the output voltage is 0.29 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 86 ° C.
- Example 1 Similarly, after coating on the surface of the porous carbon fiber substrate to obtain a coated substrate, the dispersion (3) was applied to the opposite surface B using a die coater and dried, then Example 1 And a gas diffusion layer having a porous layer (A) and a porous layer (B).
- the average thickness t2 ( ⁇ m) of the porous layer (B) was 30 ⁇ m, the basis weight was 15 g / m 2 , and the porosity was 66%.
- the plugging resistance was extremely good.
- the output voltage could not be taken out (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ).
- the flooding resistance was greatly reduced and the dry-up resistance was good.
- the low-temperature performance is low because the porous layer (B) is thick and the discharge of water to the separator is suppressed. Cracks on the surface of the porous layer (A) were not confirmed.
- the mixture is heat-dried to form a porous layer (B) having an average thickness t2 ( ⁇ m) of 11 ⁇ m on the entire opposite surface (B) of the porous carbon fiber substrate, and an impregnation amount of 43 g / m in terms of post-sintering 2
- a gas diffusion layer was obtained in the same manner as in Example 1 except that an impregnated base material (porous layer (J) 35 g / m 2 + porous layer (B) 8 g / m 2 ) was obtained.
- the plugging resistance was extremely good.
- the porosity of this gas diffusion layer was 2%.
- the output voltage is 0.25 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 89 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ), Table 3
- both the flooding resistance and the dry-up resistance decreased.
- the low temperature performance is low because the porous carbon fiber base material is filled with a dense porous layer (J), and the discharge of water vapor from the catalyst layer is suppressed, and the high temperature performance is low. This is because the gas diffusion layer has a low in-plane gas diffusibility due to the porous layer (J), and fuel cannot be sufficiently supplied to the catalyst.
- the number of cracks on the surface of the porous layer (A) was 1.
- the output voltage could not be taken out (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 88 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm 2 ).
- both flooding resistance and dry-up resistance decreased.
- the low temperature performance is low because the porosity of the porous layer (A) is low and the discharge of water vapor from the catalyst layer is suppressed, and the low temperature performance is low because of the porosity of the porous layer (A). This is because the gas diffusion layer has a low in-plane gas diffusibility and cannot sufficiently supply fuel to the catalyst. Cracks on the surface of the porous layer (A) were not confirmed.
- Example 6 In the paper making process of the raw fiber paper in Example 1, after obtaining 28 g / m 2 of carbon fiber paper, in the resin impregnation process, the resin impregnation amount is 403 parts by mass of phenol resin with respect to 100 parts by mass of carbon fiber.
- a resin-impregnated carbon fiber paper was obtained as described above, and the resin impregnation conditions were the same as in Example 1 except that two sheets of the resin-impregnated carbon fiber paper were stacked and compressed in the pressing step. The thickness was 350 ⁇ m and the basis weight was 175 g / m. 2.
- a porous carbon fiber substrate having a bulk density of 0.50 g / cm 3 was obtained.
- a water repellent treatment was performed in the same manner as in Example 1 to obtain a water repellent treated substrate.
- Example 1 ⁇ Formation of porous layer (A), porous layer (J), porous layer (B)> A gas diffusion layer was obtained in the same manner as in Example 1 except that the impregnation base material having an impregnation amount of J) was 38 g / m 2 . The porosity of this gas diffusion layer was 30%. As a result of evaluating the power generation performance of this gas diffusion layer, the plugging resistance was good. In the evaluation of flooding resistance, the output voltage could not be taken out (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 90 ° C.
- Table 3 summarizes the configurations and evaluation results of Comparative Examples 1 to 6.
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Abstract
Description
・処理領域の面積(縦画素数×横画素数)を計算し、全面積とする。
・画像を9画素平均(縦画素数3×横画素数3)し、画素単位のノイズを除去した画像1とする。
・画像1のうち、空隙以外の部分が検出される任意の平均輝度値以上または平均輝度値以下の輝度を持つ領域(多孔質層および炭素繊維断面)を抽出し、画像2とする。
・画像2のうち、面積100画素以上の島のみを残し、画像3とする。
・画像3を半径2.5画素の円形クロージング処理し(小さな穴を埋める)、画像4とする。
・画像4 (=空隙でない部分)の面積を求める。
・全面積から画像4の面積を引いた空隙の面積を全面積で割り、個別の空隙率を算出する。
・処理領域の面積(縦画素数×横画素数)を計算し、全面積とする。
・画像を9画素平均(縦画素数3×横画素数3)し、画素単位のノイズを除去した画像1とする。
・画像1のうち、空孔以外の部分が検出される任意の平均輝度値以上の輝度を持つ領域(多孔質層断面)を抽出し、画像2とする。
・画像2のうち、面積100画素以上の島のみを残し、画像3とする。
・画像3を半径2.5画素の円形クロージング処理し(小さな穴を埋める)、画像4とする。画像4を写した一例を図2に示す。
・画像4 (=空孔でない部分)の面積を求める。
・全面積から画像4の面積を引いた空孔の面積を全面積で割り、個別の空孔率を算出する。
炭素繊維を含む不織布を得るためには、炭素繊維を液中に分散させて製造する湿式法や、空気中に分散させて製造する乾式法などが用いられる。なかでも、薄肉の炭素繊維不織布が得られる湿式の抄紙法が好ましく用いられる。湿式の抄紙法で得られた炭素繊維不織布を炭素繊維抄紙体と称する。
炭素繊維を含む不織布に樹脂組成物を含浸して予備含浸体を作製する。炭素繊維を含む不織布に樹脂組成物を含浸する方法として、樹脂組成物を含む溶液中に不織布を浸漬する方法、樹脂組成物を含む溶液を不織布に塗工する方法、樹脂組成物からなるフィルムを不織布に重ねて転写する方法などが用いられる。なかでも、生産性が優れることから、樹脂組成物を含む溶液中に不織布を浸漬する方法が好ましく用いられる。
予備含浸体を形成した後、炭素化を行うに先立って、予備含浸体の張り合わせや、熱処理を行うことができる。多孔質炭素繊維基材を所定の厚みにする目的で、複数枚の予備含浸体を張り合わせることができる。この場合、同一の性状を有する予備含浸体を複数枚張り合わせることもできるし、異なる性状を有する予備含浸体を複数枚張り合わせることもできる。具体的には、炭素繊維の平均直径、平均長さ、抄紙体の炭素繊維目付、樹脂成分の含浸量などが異なる複数枚の予備含浸体を張り合わせることもできる。
炭素繊維不織布に樹脂組成物を含浸した後、炭素化するために、不活性雰囲気下で焼成を行う。斯かる焼成は、バッチ式の加熱炉を用いることもできるし、連続式の加熱炉を用いることもできる。また、不活性雰囲気は、炉内に窒素ガス、アルゴンガスなどの不活性ガスを流すことにより得ることができる。
本発明において、排水性を向上する目的で、多孔質炭素繊維基材に撥水加工を施しても良い。撥水加工は、多孔質炭素繊維基材に撥水性樹脂を付与することにより行うことができる。撥水性樹脂としては特に限定されないが、たとえば、前記したようなフッ素樹脂が例示できる。撥水性樹脂の付与量は、多孔質炭素繊維基材100質量部に対して1~50質量部であることが好ましく、3~40質量部であることがより好ましい。撥水性樹脂の付与量が1質量部以上であると、多孔質炭素繊維基材が排水性により優れたものとなり、50質量部以下であると、多孔質炭素繊維基材が導電性により優れたものとなる。
多孔質層(J)は、炭素質粒子を水や有機溶媒などの分散媒に分散した分散液(1)を多孔質炭素繊維基材の内部に染み込ませることによって形成する。分散液(1)には通常、上述した撥水加工で用いたのと同様の撥水性樹脂を混合する。染み込ませる方法は、ディップ法、ダイコーター塗工、キスコーター塗工、スクリーン印刷、ロータリースクリーン印刷、スプレー噴霧、凹版印刷、グラビア印刷、バー塗工、ブレード塗工などが使用できるが、内部に均一に染み込ませることができるディップ法を使用することが好ましい。空隙率が5~40%となるように含浸させるために、分散液の組成や固形分率は適宜調製することができる。
工程(I)の後に、多孔質炭素繊維基材の表面に付着した余分な分散液(1)をブレードまたは絞りロールを用いて取り除くことで、空隙率が5~40%となるように調整しても良い。ブレードはゴム製、プラスチック製、金属製など適宜選択することができる。絞りロールもゴム製、プラスチック製、金属製など適宜選択することができ、ニップ法、クリアランス法など適宜選択することができる。
含浸工程(I)および必要に応じて絞り工程(I-2)を経た多孔質炭素繊維基材は、次工程に投入する前に80~200℃の温度で加熱して分散液(1)における分散媒を除去する(乾燥する)ことが好ましい。
多孔質層(A)は、多孔質炭素繊維基材の片表面Aに、炭素質粒子を水や有機溶媒などの分散媒に分散した分散液(2)を塗工することによって形成する。分散液(2)には、通常、上述した撥水加工で用いたのと同様の撥水性樹脂を混合する。塗工方法は、ダイコーター塗工、キスコーター塗工、スクリーン印刷、ロータリースクリーン印刷、スプレー噴霧、凹版印刷、グラビア印刷、バー塗工、ブレード塗工などが使用できるが、多孔質炭素繊維基材の表面粗さによらず塗工量の定量化を図ることができるため、ダイコーター塗工を使用することが好ましい。
配置工程(II)を経た多孔質炭素繊維基材は、次工程に投入する前に、80~200℃の温度で加熱して分散液(2)における分散媒を除去する(乾燥する)ことが好ましい。
多孔質層(A)は、多孔質炭素繊維基材の片表面Aに、炭素質粒子を水や有機溶媒などの分散媒に分散した分散液(2)を塗工し、分散液(2)の一部を表面に残しつつ、残りの一部の分散液(2)を多孔質炭素繊維基材内部へ染み込ませることによって形成する。分散液(2)には、通常、上述した撥水加工で用いたのと同様の撥水性樹脂を混合する。塗工方法は、ダイコーター塗工、キスコーター塗工、スクリーン印刷、ロータリースクリーン印刷、スプレー噴霧、凹版印刷、グラビア印刷、バー塗工、ブレード塗工などが使用できるが、多孔質炭素繊維基材の表面粗さによらず塗工量を精度良く制御でき、多孔質炭素繊維基材内部への染み込み程度を制御し易いダイコーター塗工を使用することが好ましい。多孔質炭素繊維基材内部へ分散液(2)を染み込ませる量を制御するためには、ダイコーター塗工の場合は、塗工速度、吐出速度、吐出口と多孔質炭素繊維基材のクリアランス、及び分散液粘度などを調整すればよい。
配置含浸工程(II-3)を経た多孔質炭素繊維基材は、次工程に投入する前に、80~200℃の温度で加熱して分散液(2)における分散媒を除去する(乾燥する)ことが好ましい。
配置工程(II)または配置含浸工程(II-3)を経た多孔質炭素繊維基材に、必要に応じて多孔質層(B)を形成する。多孔質層(B)は、多孔質層(A)を塗工した多孔質炭素繊維基材の片表面Aの反対側にあたる表面Bに、炭素質粒子を水や有機溶媒などの分散媒に分散した分散液(3)を塗工することによって形成できる。分散液(3)には、通常、上述した撥水加工で用いたのと同様の撥水性樹脂を混合する。塗工方法は、ダイコーター塗工、キスコーター塗工、スクリーン印刷、ロータリースクリーン印刷、スプレー噴霧、凹版印刷、グラビア印刷、バー塗工、ブレード塗工などが使用できるが、なかでもキスコーター塗工やスクリーン印刷は他の方法よりも裏面塗工の際の塗工量の調整が行いやすいため本発明では好ましく採用される。
反対表面配置工程(II-2)を経た多孔質炭素繊維基材は、次工程に投入する前に、80~200℃の温度で加熱して分散液(3)における分散媒を除去する(乾燥する)ことが好ましい。
配置工程(II)または配置含浸工程(II-3)を経た多孔質炭素繊維基材は、必要に応じて、乾燥工程(II’)、反対表面配置工程(II-2)、乾燥工程(II-2’)、乾燥工程(II-3’)などを経た後、マッフル炉や焼成炉または高温型の乾燥機に投入、あるいは通過させ、300~380℃にて1~30分間加熱して焼結する。焼結により、撥水性樹脂を用いた場合にはそれが溶融し、炭素質粒子同士のバインダーとなって多孔質層が形成される。
多孔質炭素繊維基材の厚み、ガス拡散層全体の厚み、ならびに多孔質層(J)及び多孔質層(B)を配置した多孔質炭素繊維基材の厚みは、次のようにして求めた。すなわち、測定すべきシート状の検体から、無作為に異なる20箇所を選び、それぞれの箇所について、測定子断面が直径5mmの円形である(株)ニコン製 マイクロメーター MF-501を用いて、面圧0.15MPaで加圧した状態で個別の厚みを測定し、測定した個別の厚みを平均することにより求めた。
多孔質層(A)の平均厚みt1は、ガス拡散層全体の平均厚みから、予め測定しておいた多孔質層(J)及び多孔質層(B)を配置した多孔質炭素繊維基材の平均厚みを差し引くことで求めた。
多孔質層(B)の平均厚みt2は、ガス拡散層全体の平均厚みから、多孔質炭素繊維基材の厚み、及び多孔質層(A)の平均厚みt1を差し引くことで求めた。
多孔質炭素繊維基材の嵩密度は、電子天秤を用いて秤量した多孔質炭素繊維基材の目付(単位面積当たりの質量)を、多孔質炭素繊維基材の厚みで除して求めた。
ガス拡散層をシート面に直交する面で切断して前加工した後、日本電子(株)製クロスセクションポリッシャー SM-9010を用いて作製した断面を観察試料とした。
(画像処理)
・処理領域の面積(縦画素数×横画素数)を計算し、全面積とした。
・画像を9画素平均(縦画素数3×横画素数3)し、画素単位のノイズを除去した画像1とした。
・画像1のうち、空隙以外の部分が検出される任意の平均輝度値以上または平均輝度値以下の輝度を持つ領域(多孔質層および炭素繊維断面)を抽出し、画像2とした。
・画像2のうち、面積100画素以上の島のみを残し、画像3とした。
・画像3を半径2.5画素の円形クロージング処理し(小さな穴を埋める)、画像4とした。
・画像4 (=空隙でない部分)の面積を求めた。
・全面積から画像4の面積を引いた空隙の面積を全面積で割り、個別の空隙率を算出した。
空隙率と同様の観察試料を用いた。
(画像処理)
・処理領域の面積(縦画素数×横画素数)を計算し、全面積とした。
・画像を9画素平均(縦画素数3×横画素数3)し、画素単位のノイズを除去した画像1とした。
・画像1のうち、空孔以外の部分が検出される任意の平均輝度値以上の輝度を持つ領域(多孔質層断面)を抽出し、画像2とした。
・画像2のうち、面積100画素以上の島のみを残し、画像3とした。
・画像3を半径2.5画素の円形クロージング処理し(小さな穴を埋める)、画像4とした。
・画像4 (=空孔でない部分)の面積を求めた。
・全面積から画像4の面積を引いた空孔の面積を全面積で割り、個別の空孔率を算出した。
(株)キーエンス製デジタルマイクロスコープを用い、50倍に拡大し、任意の1mm四方のエリアに存在する独立したクラック数をカウントし求めた。
白金担持炭素(田中貴金属工業(株)製、白金担持量:50質量%)1.00g、精製水 1.00g、“Nafion”(登録商標)溶液(Aldrich社製 “Nafion”(登録商標)5.0質量%)8.00g、イソプロピルアルコール(ナカライテスク社製)18.00gを順に加えることにより、触媒液を作成した。
東レ(株)製ポリアクリロニトリル系炭素繊維“トレカ”(登録商標)T300(平均単繊維径:7μm)を12mmの長さにカットし、水を抄造媒体として連続的に抄造し、さらにポリビニルアルコールの10質量%水溶液に浸漬し、乾燥する抄紙工程を経て、炭素繊維の目付が16g/m2の長尺の炭素繊維紙を得た。炭素繊維100質量部に対して、添加したポリビニルアルコールの付着量は20質量部に相当した。
多孔質層(J)を形成するための分散液を分散液(1)、多孔質層(A)を形成するための分散液を分散液(2)、多孔質層(B)を形成するための分散液を分散液(3)と称する。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、焼結後に、多孔質層(A)の平均厚みt1(μm)が15μm、多孔質層(A)の目付が8g/m2となるよう変更した以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は良好であった。出力電圧0.37V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、焼結後に、多孔質層(A)の平均厚みt1(μm)が52μm、多孔質層(A)の目付が26g/m2となるよう変更した以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.36V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラック数は1であった。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(1)をステンレス製バットに入れ、多孔質炭素繊維基材を分散液(1)に完全に浸漬させ、表面に付着した液はステンレス製ヘラで掻き落とさずに、120℃で加熱乾燥させ、多孔質炭素繊維基材の反対表面(B)の全面に平均厚みt2(μm)が10μmの多孔質層(B)を形成するとともに、焼結後換算で含浸量22g/m2(多孔質層(J)15g/m2+多孔質層(B)7g/m2)の含浸基材を得た以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.33V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度92℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(1)として、配合比をカーボンブラック/PTFE樹脂=75質量部/25質量部、固形分が21%となるように調整したものを用いた。この分散液(1)をB型粘度計で粘度測定したところ、46mPa・sであった。この分散液(1)をステンレス製バットに入れ、多孔質炭素繊維基材をこの分散液(1)に完全に浸漬させ、表面に付着した液はステンレス製ヘラで掻き落とし、120℃で加熱乾燥させ、焼結後換算で含浸量29g/m2の含浸基材を得た以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の空隙率は、10%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.33V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度92℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1の<多孔質層(A)、多孔質層(J、多孔質層(B))の形成>において、分散液(1)として、配合比をカーボンブラック/PTFE樹脂=75質量部/25質量部、固形分が7%となるように調整したものを用いた。この分散液(1)をB型粘度計で粘度測定したところ、16mPa・sであった。この分散液(1)をステンレス製バットに入れ、多孔質炭素繊維基材をこの分散液(1)に完全に浸漬させ、表面に付着した液はステンレス製ヘラで掻き落とし、120℃で加熱乾燥させ、焼結後換算で含浸量8g/m2の含浸基材を得た以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の空隙率は、38%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は良好であった。出力電圧0.38V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(2)として、配合比をカーボンブラック/PTFE樹脂/界面活性剤/精製水=75質量部/25質量部、固形分が22%となるように調整したものを用いた以外は、実施例1と同様にしてガス拡散層を得た。この分散液(2)を用いて得られた多孔質層(A)の平均厚みt1(μm)は43μm、目付は20g/m2、空孔率は80%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.39V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(2)として、配合比をカーボンブラック/PTFE樹脂/界面活性剤/精製水=75質量部/25質量部、固形分が23%となるように調整したものを用いた以外は、実施例1と同様にしてガス拡散層を得た。この分散液(2)を用いて得られた多孔質層(A)の平均厚みt1(μm)は30μm、目付は20g/m2、空孔率は52%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.32V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表1に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
成形厚みを薄く設定する以外は実施例1と同様にして得た、厚み75μm、目付24g/m2、嵩密度0.32g/cm3の多孔質炭素繊維基材に、実施例1と同様にして撥水処理を行い撥水処理基材を得た。
実施例1における炭素繊維紙の抄紙工程において、炭素繊維の目付を32g/m2とした炭素繊維紙を得たこと、および、樹脂含浸工程において、炭素繊維100質量部に対してフェノール樹脂が290質量部である樹脂含浸量になるように含浸したこと以外は、実施例1と同様の樹脂含浸条件として得た、厚み200μm、目付80g/m2、嵩密度0.40g/cm3の多孔質炭素繊維基材に、実施例1と同様にして撥水処理を行い撥水処理基材を得た。
実施例1で得た撥水処理基材に、次に示す<多孔質層の形成>のようにして多孔質層を形成し、ガス拡散層を得た。
分散液(2)として実施例1と同じものを用い、ダイコーターを用いて前記撥水処理基材上に塗工した。その際、多孔質炭素繊維基材内部に分散液(2)が染み込むようにダイコーターの吐出口を前記撥水処理基材に近づけ、CP中の空隙率が実施例1と同等になるように調整した。塗工後、120℃で加熱乾燥させ、塗工基材を得た。
撥水処理基材を、実施例9で得た撥水処理基材に変更し、CP中の空隙率が実施例9と同等になるように塗工量を調整した以外は全て実施例11と同様にしてガス拡散層を得た。多孔質炭素繊維基材を変えたことで、多孔質層(A)の平均厚みt1(μm)は25μmとなった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.39V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表2に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例10で得た撥水処理基材に、<多孔質層の形成>における多孔質層(A)の目付けが29g/m2、CP中の空隙率が実施例10と同等になるように塗工量を調整した以外は全て実施例11と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は良好であった。出力電圧0.32V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度92℃(加湿温度70℃、電流密度1.2A/cm2)であり、表2に記載のように、耐フラッディング性、耐ドライアップ性ともに良好であった。多孔質層(A)表面のクラックは確認されなかった。
実施例1における<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(1)を含浸しなかった以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は大きく低下した。出力電圧0.38V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度88℃(加湿温度70℃、電流密度1.2A/cm2)であり、表3に記載のように、耐フラッディング性は良好であったが、耐ドライアップ性は低下した。高温性能が低いのは多孔質炭素繊維基材に多孔質層(J)が含浸されておらず、水蒸気がセパレータ側へ逃げやすく電解質膜の乾燥が顕著になったためである。多孔質層(A)表面のクラックは確認されなかった。
実施例1における<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、多孔質層(A)の平均厚みt1(μm)が60μm、多孔質層(A)の目付が30g/m2になるように分散液(2)の塗工量を変更したこと以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。出力電圧0.29V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度86℃(加湿温度70℃、電流密度1.2A/cm2)であり、表3に記載のように、耐フラッディング性、耐ドライアップ性ともに低下した。低温性能が低いのは、多孔質層(A)を厚くしたことで触媒層からの水蒸気の排出が抑制されたためであり、高温性能が低いのは、ガス拡散層の面直ガス拡散性が低く触媒への燃料が十分に供給できないためである。多孔質層(A)表面のクラック数は6であった。
実施例1における<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(3)として、配合比をカーボンブラック/PTFE樹脂=75質量部/25質量部、固形分が24%となるように調整したものを準備した。実施例1の<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(1)を含浸せず、分散液(2)を実施例1と同様に多孔質炭素繊維基材の表面に塗工して塗工基材を得た後、その反対表面Bにダイコーターを用いて分散液(3)を塗工、乾燥した後に、実施例1と同じ条件で焼結して多孔質層(A)及び多孔質層(B)を有するガス拡散層を得た。多孔質層(B)の平均厚みt2(μm)は30μm、目付は15g/m2、空孔率は66%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。耐フラッディング性評価では出力電圧が取り出せず(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度90℃(加湿温度70℃、電流密度1.2A/cm2)であり、表3に記載のように、耐フラッディング性は大幅に低下し、耐ドライアップ性は良好であった。低温性能が低いのは多孔質層(B)が厚いので、セパレータへの水の排出が抑制されたためである。多孔質層(A)表面のクラックは確認されなかった。
実施例1における<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(1)として、配合比をカーボンブラック/PTFE樹脂=75質量部/25質量部、固形分が23%となるように調整したものを用いた。この分散液(1)をB型粘度計で粘度測定したところ、50mPa・sであった。この分散液(1)をステンレス製バットに入れ、撥水処理基材をこの分散液(1)に完全に浸漬させ、表面に付着した液はステンレス製ヘラで掻き落とさずに、120℃で10分加熱乾燥させ、多孔質炭素繊維基材の反対表面(B)の全面に平均厚みt2(μm)が11μmの多孔質層(B)を形成するとともに、焼結後換算で含浸量43g/m2(多孔質層(J)35g/m2+多孔質層(B)8g/m2)の含浸基材を得た以外は、実施例1と同様にしてガス拡散層を得た。このガス拡散層の発電性能評価をした結果、耐プラッギング性は極めて良好であった。このガス拡散層の空隙率は、2%であった。出力電圧0.25V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度89℃(加湿温度70℃、電流密度1.2A/cm2)であり、表3に記載のように、耐フラッディング性、耐ドライアップ性ともに低下した。低温性能が低いのは多孔質炭素繊維基材が密な多孔質層(J)で充填されているため、触媒層からの水蒸気の排出が抑制されたためであり、高温性能が低いのは密な多孔質層(J)のためガス拡散層の面直ガス拡散性が低く、触媒への燃料が十分に供給できないためである。多孔質層(A)表面のクラック数は1であった。
実施例1における<多孔質層(A)、多孔質層(J)、多孔質層(B)の形成>において、分散液(2)として、配合比をカーボンブラック/PTFE樹脂=75質量部/25質量部、固形分が23%となるように調整したものを用いた以外は、実施例1と同様にしてガス拡散層を得た。この分散液(2)を用いて得られた多孔質層(A)の平均厚みt1(μm)は25μm、目付は20g/m2、空孔率は45%であった。このガス拡散層の発電性能評価をした結果、耐プラッギング性は良好であった。耐フラッディング性評価では出力電圧が取り出せず(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度88℃(加湿温度70℃、電流密度1.2A/cm2)であり、表3に記載のように、耐フラッディング性、耐ドライアップ性ともに低下した。低温性能が低いのは多孔質層(A)の空孔率が低く、触媒層からの水蒸気の排出が抑制されたためであり、高温性能が低いのは多孔質層(A)の空孔率が低いため、ガス拡散層の面直ガス拡散性が低く、触媒への燃料が十分に供給できないためである。多孔質層(A)表面のクラックは確認されなかった。
実施例1における素繊維紙の抄紙工程において、28g/m2の炭素繊維紙を得た後、樹脂含浸工程において、炭素繊維100質量部に対してフェノール樹脂が403質量部である樹脂含浸量になるように樹脂含浸炭素繊維紙を得て、プレス工程で該樹脂含浸炭素繊維紙を2枚重ねて圧縮処理した以外は、実施例1と同様の樹脂含浸条件として、厚み350μm、目付175g/m2、嵩密度0.50g/cm3の、多孔質炭素繊維基材を得た。次いで、実施例1と同様にして撥水処理を行い撥水処理基材を得た。
2 多孔質層(J)
3 多孔質層(B)
4 炭素繊維
5 空隙
6 空孔
7 炭素質粒子(または撥水性樹脂)
8 電解質膜
9 触媒層
Claims (18)
- 不連続の炭素繊維が炭化物で結着されている多孔質炭素繊維基材と、少なくとも炭素質粒子を含む多孔質層とから構成される燃料電池用ガス拡散層であって、多孔質層(A)が、多孔質炭素繊維基材の片表面Aに平均厚みt1を10~55μmとして配置され、さらに多孔質層(J)が多孔質炭素繊維基材の内部に染み込んで少なくともその一部が反対表面Bにも存在しており、多孔質炭素繊維基材の内部に保持されている空隙の、厚み方向断面に占める断面積の割合が5~40%であり、且つ、少なくとも多孔質層(A)および多孔質層(J)のいずれの空孔率も50~85%であり、且つ、多孔質炭素繊維基材の厚みが60~300μmであり、且つ、多孔質炭素繊維基材の嵩密度が0.20~0.45g/cm3である、燃料電池用ガス拡散層。
- 前記多孔質層(A)と前記多孔質層(J)とが異なる組成である、請求項1に記載の燃料電池用ガス拡散層。
- 前記多孔質層(A)と前記多孔質層(J)とが同一の組成である、請求項1に記載の燃料電池用ガス拡散層。
- 前記反対表面Bに平均厚みt2=0~20μmの多孔質層(B)が更に配置されている、請求項1~3のいずれかに記載の燃料電池用ガス拡散層。
- 前記多孔質層(B)と、前記多孔質層(J)とが同一の組成である、請求項1~4のいずれかに記載の燃料電池用ガス拡散層。
- 前記多孔質炭素繊維基材および前記多孔質層が、更に撥水性樹脂を含む、請求項1~5のいずれかに記載の燃料電池用ガス拡散層。
- 前記撥水性樹脂が、前記多孔質炭素繊維基材の中で、前記多孔質層(A)側に偏在して配置されている、請求項6に記載の燃料電池用ガス拡散層。
- 前記多孔質層に含まれる炭素質粒子の質量分率が5~95%である、請求項1~7のいずれかに記載の燃料電池用ガス拡散層。
- 前記炭素質粒子が、少なくともカーボンブラックを含む、請求項1~8のいずれかに記載の燃料電池用ガス拡散層。
- 前記多孔質層(A)の空孔率が、前記多孔質層(B)または前記多孔質層(J)のいずれかの空孔率よりも大きいものである、請求項1~9のいずれかに記載の燃料電池用ガス拡散層。
- 前記多孔質層(A)の内部のクラックの存在頻度が、前記多孔質層(J)の内部のクラックの存在頻度よりも小さい、請求項1~10のいずれかに記載の燃料電池用ガス拡散層。
- 前記多孔質層(A)のクラックの存在頻度が、1mm四方に1箇所以下である、請求項1~11のいずれかに記載の燃料電池用ガス拡散層。
- 請求項1~12のいずれかに記載の燃料電池用ガス拡散層の製造方法であって、不連続の炭素繊維が炭化物で結着されている多孔質炭素繊維基材に、少なくとも炭素質粒子と分散媒からなる分散液(1)を含浸させる含浸工程(I)、および、含浸工程(I)を経た多孔質炭素繊維基材の片表面Aに少なくとも炭素質粒子と分散媒からなる分散液(2)を配置する配置工程(II)を含み、配置工程(II)を経た多孔質炭素繊維基材を加熱して焼結する、燃料電池用ガス拡散層の製造方法。
- 請求項3~12のいずれかに記載の燃料電池用ガス拡散層の製造方法であって、不連続の炭素繊維が炭化物で結着されている多孔質炭素繊維基材に、少なくとも炭素質粒子と分散媒からなる分散液(2)を片表面Aに配置するとともに、前記多孔質炭素繊維基材の内部に染み込ませる配置含浸工程(II-3)を含み、配置含浸工程(II-3)を経た多孔質炭素繊維基材を加熱して焼結する、燃料電池用ガス拡散層の製造方法。
- 前記分散液(1)、(2)の少なくともいずれかに、更に撥水性樹脂を含む、請求項13または14に記載の燃料電池用ガス拡散層の製造方法。
- 前記配置工程(II)または前記配置含浸工程(II-3)を経た多孔質炭素繊維基材の反対表面Bに少なくとも炭素質粒子と分散媒からなる分散液(3)を配置する反対表面配置工程(II-2)を含む、請求項13~15のいずれかに記載の燃料電池用ガス拡散層の製造方法。
- 前記各工程後、次工程に投入する前に、多孔質炭素繊維基材を加熱して分散媒を除去する、請求項13~16のいずれかに記載の燃料電池用ガス拡散層の製造方法。
- 前記分散液(3)が、更に撥水性樹脂を含む、請求項16または17に記載の燃料電池用ガス拡散層の製造方法。
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Also Published As
Publication number | Publication date |
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US20150372332A1 (en) | 2015-12-24 |
EP2958174A1 (en) | 2015-12-23 |
CN104981929B (zh) | 2017-07-04 |
KR102150653B1 (ko) | 2020-09-01 |
TW201448339A (zh) | 2014-12-16 |
JPWO2014126002A1 (ja) | 2017-02-02 |
CA2892918C (en) | 2023-03-14 |
KR20150118087A (ko) | 2015-10-21 |
EP2958174B1 (en) | 2017-09-20 |
EP2958174A4 (en) | 2016-10-05 |
CA2892918A1 (en) | 2014-08-21 |
CN104981929A (zh) | 2015-10-14 |
US10249886B2 (en) | 2019-04-02 |
JP5621949B1 (ja) | 2014-11-12 |
TWI597889B (zh) | 2017-09-01 |
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