WO2014030553A1 - 燃料電池用ガス拡散電極基材 - Google Patents
燃料電池用ガス拡散電極基材 Download PDFInfo
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- WO2014030553A1 WO2014030553A1 PCT/JP2013/071623 JP2013071623W WO2014030553A1 WO 2014030553 A1 WO2014030553 A1 WO 2014030553A1 JP 2013071623 W JP2013071623 W JP 2013071623W WO 2014030553 A1 WO2014030553 A1 WO 2014030553A1
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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
- H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
- H01M4/8657—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites layered
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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
- H01M4/96—Carbon-based electrodes
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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
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
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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
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
- H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
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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
- H01M8/0243—Composites in the form of mixtures
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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
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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 electrode base material suitably used for a fuel cell, particularly a polymer electrolyte fuel cell. More specifically, it is excellent in flooding resistance and dry-up resistance, can exhibit high power generation performance over a wide temperature range from low temperature to high temperature, and further has a gas diffusion electrode base with excellent mechanical properties, electrical conductivity, and thermal conductivity. Regarding materials.
- a polymer electrolyte fuel cell that supplies a fuel gas containing hydrogen to the anode and an oxidizing gas containing oxygen to the cathode to obtain an electromotive force by an electrochemical reaction occurring at both electrodes is generally a separator, gas diffusion An electrode base material, a catalyst layer, an electrolyte membrane, a catalyst layer, a gas diffusion electrode base material, and a separator are laminated in order.
- the gas diffusion electrode base material has high in-plane direction gas diffusivity and high in-plane direction gas diffusivity for diffusing the gas supplied from the separator to the catalyst layer, and liquid water generated with electrochemical reaction Therefore, high drainage for discharging the gas to the separator and high conductivity for taking out the generated current are required, and electrode substrates made of carbon fiber or the like are widely used.
- Patent Document 1 proposes a gas diffusion electrode substrate in which a microporous layer made of carbon black and a water-repellent resin is formed on the catalyst layer side of a high-weight electrode substrate of 167 g / m 2 .
- the microporous layer forms a small pore structure having water repellency, discharge of liquid water to the cathode side is suppressed, and flooding tends to be suppressed. It is in. Further, since the generated water is pushed back to the electrolyte membrane side (hereinafter referred to as reverse diffusion), the electrolyte membrane tends to be wet and dry-up tends to be suppressed. However, there is a problem that flooding and dry-up are still insufficiently controlled.
- Patent Document 2 a gas in which a microporous layer made of carbon black and a water-repellent resin is formed on the catalyst layer side of an electrode base material from a relatively low basis weight to a relatively high basis weight within a range of 44 to 92 g / m 2. Diffusion electrode substrates have been proposed. According to the fuel cell using these gas diffusion electrode base materials, it was expected that the flooding was suppressed because the gas diffusion property and drainage of the electrode base material were improved, but the suppression of flooding was still insufficient. However, there was a problem that dry-up could not be suppressed.
- Patent Document 3 proposes a gas diffusion electrode substrate in which a microporous layer made of carbon black, linear carbon, and a water-repellent resin is formed on the catalyst layer side of a relatively high basis weight electrode substrate of 84 g / m 2. Yes. According to the fuel cell using this gas diffusion electrode substrate, the gas diffusibility and drainage of the microporous layer were improved, so that flooding was expected to be suppressed, but the flooding suppression was still insufficient. However, there was a problem that dry-up could not be suppressed.
- the object of the present invention is excellent in flooding resistance and dry-up resistance, and can exhibit high power generation performance over a wide temperature range from low temperature to high temperature.
- An object of the present invention is to provide a gas diffusion electrode substrate having excellent thermal conductivity.
- the gas diffusion electrode substrate of the present invention employs the following means in order to solve such problems.
- a gas diffusion electrode base material for a fuel cell in which a microporous layer is disposed on one side of an electrode base material, the microporous layer containing linear carbon having an aspect ratio in the range of 30 to 5000,
- a gas diffusion electrode substrate for a fuel cell wherein the basis weight of the gas diffusion electrode substrate is in the range of 30 to 60 g / m 2 .
- the microporous layer contains carbon black, and the mixing mass ratio of carbon black to linear carbon having an aspect ratio in the range of 30 to 5000 is in the range of 0.5 to 20 (1) to ( 5)
- flooding can be suppressed by promoting the discharge of liquid water at the gas diffusion electrode substrate, and further, dry-up can be suppressed by suppressing water vapor diffusion. For this reason, when the gas diffusion electrode substrate of the present invention is used, high power generation performance can be expressed over a wide temperature range from low temperature to high temperature.
- the gas diffusion electrode substrate of the present invention also has good mechanical strength, electrical conductivity, and thermal conductivity.
- the gas diffusion electrode substrate of the present invention is a gas diffusion electrode substrate for a fuel cell in which a microporous layer is disposed on one side of the electrode substrate, and the microporous layer has an aspect ratio in the range of 30 to 5000. It includes certain linear carbon, and the basis weight of the gas diffusion electrode substrate is in the range of 30 to 60 g / m 2 .
- a substrate made of only carbon paper and not provided with a microporous portion is referred to as an “electrode substrate”, and a substrate provided with a microporous layer on an electrode substrate is referred to as a “gas diffusion electrode substrate”. Called.
- the present inventors have performed gas diffusion in the in-plane direction of the electrode substrate. Although the flooding was expected to be improved due to the improvement of the property and drainage, the suppression of flooding is still insufficient, and the reason why the dry-up could not be suppressed was considered as follows.
- a carbon coating liquid containing carbon black and a water-repellent resin is usually used as a precursor of the microporous layer. Since the electrode base material is used, the carbon coating liquid permeates into the electrode base material remarkably, and the carbon coating liquid escapes to the back surface of the electrode base material (hereinafter referred to as back-through). For this reason, the inside of the electrode base material is filled with the carbon coating liquid, and not only the gas diffusibility in the in-plane direction of the electrode base material is lowered, but also the drainage property is lowered, and the flooding is not sufficiently suppressed. I thought.
- the thickness of the microporous layer to be formed on the surface layer of the electrode substrate was insufficient, the back diffusion of generated water was insufficient, the electrolyte membrane was dried, and the dry-up could not be suppressed.
- the conductivity of the gas diffusion electrode base material would be reduced if the electrode base material was made thick with a relatively low weight.
- the microporous layer when a microporous layer is formed on a low basis weight electrode substrate, the microporous layer contains linear carbon having an aspect ratio in the range of 30 to 5000, so that a carbon coating that is a precursor of the microporous layer is formed. It has been found that flooding can be suppressed because the penetration of the liquid into the electrode substrate is moderately suppressed and the gas diffusibility and drainage in the in-plane direction at the electrode substrate portion are improved. Furthermore, it has been found that a microporous layer having a sufficient thickness is formed on the surface layer of the electrode substrate, and the reverse diffusion of the generated water is promoted, so that dry-up can be suppressed.
- the microporous layer when a microporous layer is formed using an electrode base material having a relatively low basis weight, the microporous layer contains linear carbon having an aspect ratio in the range of 30 to 5000, and further, a gas diffusion electrode base material It has been found that by setting the basis weight within a range of 30 to 60 g / m 2 , the gas diffusibility in the in-plane direction, the gas diffusibility in the direction perpendicular to the plane, and the drainage are improved, and thus flooding can be suppressed. Furthermore, it has been found that a microporous layer having a sufficient thickness is formed on the surface layer of the electrode substrate, and the reverse diffusion of the generated water is promoted, so that dry-up can be suppressed.
- the electrode substrate in the present invention is a high in-plane gas diffusivity for diffusing the gas supplied from the separator to the catalyst, a gas diffusivity in the direction perpendicular to the surface, and liquid water generated with an electrochemical reaction. High drainage for discharging to the separator and high conductivity for taking out the generated current are required.
- a porous metal body such as carbon fiber woven fabric, carbon fiber nonwoven fabric, carbon fiber papermaking body, and the like, a porous metal body such as a fired sintered metal, a metal mesh, and an expanded metal as the electrode base material.
- a porous body containing carbon fiber because of its excellent corrosion resistance.
- a substrate formed by binding a carbon fiber papermaking body with a carbide that is, “carbon” It is preferable to use “paper”.
- 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 (PAN), pitch, and rayon carbon fibers.
- PAN polyacrylonitrile
- pitch rayon carbon fibers.
- PAN-based and pitch-based carbon fibers are preferably used in the present invention because of excellent mechanical strength.
- the average diameter of single fibers 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 taken with a microscope such as a scanning electron microscope, the carbon fiber is magnified 1000 times or more, and 30 different single fibers are randomly selected. The diameter was measured and the average value was obtained.
- a microscope such as a scanning electron microscope
- S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.
- the average length of single fibers is preferably in the range of 3 to 20 mm, and more preferably in the range of 5 to 15 mm.
- the electrode base material 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 electrode substrate is obtained, which is preferable.
- 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.
- the average diameter and average length of the single fiber in carbon fiber are normally measured by observing the carbon fiber directly about the carbon fiber used as a raw material, you may observe and measure an electrode base material.
- the basis weight of the electrode base material is preferably a low basis weight within a range of 20 to 50 g / m 2 , more preferably 45 g / m 2 or less, and further preferably 40 g / m 2 or less. preferable. Further, it is more preferably 25 g / m 2 or more, and further preferably 30 g / m 2 or more.
- the basis weight of the electrode substrate is 20 g / m 2 or more, the amount per unit area of the carbon fibers constituting the electrode substrate becomes more preferable, the conductivity is further improved, and the conductivity of the obtained gas diffusion electrode substrate. The power generation performance is improved at both high and low temperatures.
- the mechanical strength of the electrode base material is further improved, and the electrolyte membrane and the catalyst layer can be supported more preferably.
- the basis weight of the electrode substrate is 50 g / m 2 or less
- the gas permeation diffusibility in the direction perpendicular to the surface of the electrode substrate is further improved, and the gas diffusibility in the direction perpendicular to the surface of the obtained gas diffusion electrode substrate is improved.
- the power generation performance is improved at both high and low temperatures.
- the electrode base material having such a basis weight can be obtained by controlling the carbon fiber basis weight in the pre-impregnated body and the blending amount of the resin component with respect to the carbon fiber in the production method described later.
- a paper body containing carbon fibers impregnated with a resin composition is referred to as a “pre-impregnated body”.
- a low basis weight base material is obtained by reducing the carbon fiber basis weight of the pre-impregnated body, and a high basis weight base material is obtained by increasing the carbon fiber basis weight.
- a low basis weight base material is obtained by reducing the blending amount of the resin component with respect to the carbon fiber, and a high basis weight base material is obtained by increasing the blending amount of the resin component.
- the basis weight means the mass per unit area.
- the basis weight of the electrode base material is obtained by dividing the mass of the electrode base material weighed using an electronic balance by the area of the XY plane of the electrode base material.
- the basis weight of the gas diffusion electrode base material needs to be a low basis weight within a range of 30 to 60 g / m 2 . It is preferably 55 g / m 2 or less, more preferably 50 g / m 2 or less. Further, it is preferably 35 g / m 2 or more, more preferably 40 g / m 2 or more.
- the basis weight of the gas diffusion electrode substrate is less than 30 g / m 2 , the amount of carbon fiber constituting the gas diffusion electrode substrate, the amount per area of the carbon-based filler is small, and the gas diffusion electrode substrate has low conductivity. The power generation performance may be degraded at both high and low temperatures.
- both the in-plane direction gas diffusivity and the perpendicular direction gas diffusibility of the gas diffusion electrode substrate decrease.
- the power generation performance may decrease.
- a gas diffusion electrode substrate having such a basis weight can be obtained by controlling the basis weight of the electrode substrate and the basis weight of the microporous layer.
- the basis weight of the gas diffusion electrode substrate is obtained by dividing the mass of the gas diffusion electrode substrate weighed using an electronic balance by the area of the XY plane of the gas diffusion electrode substrate.
- the electrode substrate preferably has a pore diameter in the range of 30 to 80 ⁇ m, more preferably in the range of 40 to 75 ⁇ m, and still more preferably in the range of 50 to 70 ⁇ m.
- the pore diameter is 30 ⁇ m or more, drainage performance is further improved, and flooding can be further suppressed.
- the pore diameter is 80 ⁇ m or less, the conductivity is higher, and the power generation performance is further improved at both high and low temperatures.
- it is effective to include both carbon fibers having an average single fiber diameter of 3 ⁇ m to 8 ⁇ m and carbon fibers having an average single fiber diameter exceeding 8 ⁇ m.
- the pore diameter of the electrode base material is obtained by determining the peak diameter of the pore diameter distribution obtained by measurement in the measurement pressure range of 6 kPa to 414 MPa (pore diameter 30 nm to 400 ⁇ m) by mercury porosimetry. 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 thickness of the electrode substrate is preferably in the range of 50 to 160 ⁇ m, more preferably 140 ⁇ m or less, and even more preferably 120 ⁇ m or less. Moreover, it is more preferable that it is 60 micrometers or more, and it is still more preferable that it is 70 micrometers or more.
- the thickness of the electrode substrate is 50 ⁇ m or more, gas diffusion in the in-plane direction becomes more preferable, and gas can be more easily supplied to the catalyst under the ribs of the separator. Power generation performance is further improved. Further, the mechanical strength of the electrode base material is further improved, and the electrolyte membrane and the catalyst layer can be supported more preferably.
- the thickness of the electrode substrate is 150 ⁇ m or less, the drainage path is shortened, so that the drainage performance is further improved, flooding can be further suppressed, and the conductivity path is shortened, and the conductivity is further improved.
- the power generation performance is further improved at both high and low temperatures.
- the electrode substrate having such a thickness can be obtained by controlling the thickness at the time of heat treatment in the production method described later.
- the thickness of the electrode base material can be determined using a micrometer in a state of being pressurized at a surface pressure of 0.15 MPa.
- the thickness of the gas diffusion electrode substrate is preferably 70 to 190 ⁇ m, more preferably 170 ⁇ m or less, and even more preferably 150 ⁇ m or less. Further, it is preferably 70 ⁇ m or more, more preferably 80 ⁇ m or more, and further preferably 90 ⁇ m or more.
- the thickness of the gas diffusion electrode substrate is 70 ⁇ m or more, gas diffusion in the in-plane direction becomes more preferable, and gas can be more easily supplied to the catalyst under the ribs of the separator. The power generation performance is further improved.
- the thickness of the gas diffusion electrode substrate is 190 ⁇ m or less, the drainage property is further improved, flooding can be further suppressed, the path for conduction is shortened, the conductivity is further improved, the high temperature, The power generation performance is further improved at any low temperature.
- a gas diffusion electrode substrate having such a thickness can be obtained by controlling the thickness of the electrode substrate and the thickness of the microporous layer.
- the thickness of the gas diffusion electrode base material can be obtained using a micrometer in a state where the surface pressure is 0.15 MPa.
- a microporous layer is disposed on one side of the electrode substrate.
- the microporous layer has high gas diffusivity in the vertical direction for diffusing the gas supplied from the separator to the catalyst, and high drainage for discharging the liquid water generated by the electrochemical reaction to the separator. High electrical conductivity is needed to extract the measured current. Furthermore, it has a function of promoting the reverse diffusion of moisture into the electrolyte membrane and moistening the electrolyte membrane.
- the basis weight of the microporous layer is preferably in the range of 10 to 35 g / m 2 , more preferably 30 g / m 2 or less, and further preferably 25 g / m 2 or less. Further, more preferably 14 g / m 2 or more, more preferably 16g / m 2 or more.
- the basis weight of the microporous layer is 10 g / m 2 or more, the surface of the electrode substrate can be covered more, the back diffusion of generated water is further promoted, and the dry-up can be further suppressed.
- the basis weight of the microporous layer is 35 g / m 2 or less, drainage performance is further improved, and flooding can be further suppressed.
- a porous body containing linear carbon and a water repellent material for the microporous layer.
- linear carbon having an aspect ratio of 30 to 5000 it is necessary to use linear carbon having an aspect ratio of 30 to 5000 as linear carbon in the microporous layer.
- penetration of the carbon coating liquid, which is a precursor of the microporous layer, into the electrode substrate is moderately suppressed, and in-plane direction gas diffusibility and drainage are improved.
- a microporous layer having a sufficient thickness is formed on the surface layer of the electrode base material and the reverse diffusion of the generated water is promoted, dry-up can be suppressed.
- the aspect ratio of the linear carbon is less than 30, the entanglement of the linear carbon in the carbon coating liquid is reduced, the viscosity of the carbon coating liquid is lowered, and the back-through of the carbon coating liquid cannot be suppressed.
- the linear carbon has an aspect ratio of preferably 3000 or less, and more preferably 1000 or less. Further, the aspect ratio of the linear carbon is more preferably 35 or more, and further preferably 40 or more.
- the aspect ratio of linear carbon means average length ( ⁇ m) / average diameter ( ⁇ m).
- the average length is taken with a microscope such as a scanning electron microscope or a transmission electron microscope, taking a picture with a magnification of 1000 times or more, selecting 10 different linear carbons at random, and measuring the length.
- the average diameter was obtained by taking a photograph with a microscope such as a scanning electron microscope and a transmission electron microscope at a magnification of 10,000 times or more, and randomly varying 10 linear carbons. Is selected, the diameter is measured, and the average value is obtained.
- As the scanning electron microscope S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.
- linear carbon having a specific aspect ratio it is preferable to use linear carbon having a specific aspect ratio as the linear carbon having a specific aspect ratio.
- the linear carbon include vapor grown carbon fiber, single-walled carbon nanotube, double-walled carbon nanotube, multi-walled carbon nanotube, carbon nanohorn, carbon nanocoil, cup-stacked carbon nanotube, bamboo-shaped carbon nanotube, and graphite nanofiber. .
- vapor-grown carbon fibers, single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes are suitable as linear carbon for use in the present invention because the aspect ratio can be increased and the electrical conductivity and mechanical properties are excellent.
- Vapor-grown carbon fiber is obtained by growing carbon in a gas phase with a catalyst, and preferably has an average diameter of 5 to 200 nm and an average fiber length of 1 to 20 ⁇ m.
- the average length thereof is preferably in the range of 0.1 to 30 ⁇ m, more preferably in the range of 1 to 20 ⁇ m, and 2 to 15 ⁇ m. More preferably, it is in the range.
- the average length is 0.1 ⁇ m or more, the viscosity of the carbon coating liquid becomes higher, the back-through is further suppressed, and the gas diffusibility and drainage in the in-plane direction of the electrode substrate are suppressed. Can be further improved and flooding can be further suppressed.
- the microporous layer needs to contain linear carbon having a specific aspect ratio, but may further contain various carbon-based fillers other than the linear carbon.
- Carbon fillers that do not have a specific aspect ratio include carbon black such as furnace black, acetylene black, lamp black, thermal black, scaly graphite, scaly graphite, earthy graphite, artificial graphite, expanded graphite, flake graphite, etc.
- Graphite having an aspect ratio not in the range of 30 to 5000 and linear carbon such as CNT and having an aspect ratio not in the range of 30 to 5000.
- the mixing mass ratio of carbon black to linear carbon having a specific aspect ratio is preferably within a range of 0.5 to 20. More preferably, it is in the range of 2 to 10, and more preferably in the range of 2 to 10.
- the mixing mass ratio is 0.5 or more, the porosity of the microporous layer containing linear carbon and carbon black having a specific aspect ratio becomes a more appropriate size. It can be suppressed more.
- the mixing mass ratio is 20 or less, penetration of the carbon coating liquid, which is a precursor of the microporous layer, into the electrode base material is moderately suppressed due to the effect of blending the linear carbon having a specific aspect ratio.
- the microporous layer preferably contains a water repellent material in combination with linear carbon.
- a fluorine-based polymer as the water repellent material because of its excellent corrosion resistance.
- the fluorine-based polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).
- various materials can be used in combination with linear carbon for the microporous layer from the viewpoint of promoting the discharge of liquid water and suppressing the diffusion of water vapor.
- a disappearing material can be used for the purpose of increasing the pore size of the microporous layer and promoting drainage of liquid water.
- the disappearing material is heated at 300 to 380 ° C. for 5 to 20 minutes to melt the water-repellent material and burn away when forming a microporous layer as a binder between linear carbons.
- the porosity of the microporous layer is preferably in the range of 60 to 85%, more preferably in the range of 65 to 80%, and further preferably in the range of 70 to 75%. preferable.
- the porosity is 60% or more, drainage is further improved, and flooding can be further suppressed.
- the porosity is 85% or less, water vapor diffusibility is smaller, and dry-up can be further suppressed.
- the conductivity is high, and the power generation performance is improved at both high and low temperatures.
- the microporous layer having such a porosity is obtained by adjusting the basis weight of the microporous layer, the water repellent material, the blending amount of the carbon-based filler with respect to other materials, the type of the carbon-based filler, and the thickness of the microporous layer in the manufacturing method described later. It is obtained by controlling. Among them, it is effective to control the blending amount of the carbon-based filler with respect to the water repellent material and other materials and the type of the carbon-based filler.
- a high porosity microporous layer can be obtained, and by reducing the blending amount of the carbon-based filler with respect to the water-repellent material and other materials.
- a low porosity microporous layer is obtained.
- the porosity of the microporous layer is measured by using a sample for cross-sectional observation using an ion beam cross-section processing apparatus, and taking a photograph with a microscope such as a scanning electron microscope with a cross-section magnified 1000 times or more. The area of the portion was measured, and the ratio of the area of the void portion to the observation area was obtained.
- a microscope such as a scanning electron microscope with a cross-section magnified 1000 times or more.
- S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.
- a microporous layer be disposed on one side of the electrode base material. From the viewpoint that the electrical resistance between the separator and the gas diffusion electrode base material can be reduced, the microporous layer is used. Is preferably impregnated in the electrode substrate.
- the gas permeation resistance in the perpendicular direction is used as an index of the gas diffusivity in the perpendicular direction.
- the gas permeation resistance in the direction perpendicular to the plane is preferably in the range of 15 to 190 mmAq, more preferably 180 mmAq or less, and even more preferably 170 mmAq or less. Moreover, it is more preferable that it is 25 mmAq or more, and it is further more preferable that it is 50 mmAq or more.
- the surface gas permeation resistance of the gas diffusion electrode substrate was determined by using a circular sample with a diameter of 4.7 cm cut out from the gas diffusion electrode substrate, and air was supplied from the surface on the microporous layer side to the opposite surface at 58 cc / min / cm. The differential pressure between the surface on the microporous layer side and the opposite surface when it was permeated at a flow rate of 2 was measured with a differential pressure gauge to obtain a surface direct gas permeation resistance.
- the microporous portion is disposed on the surface of the electrode substrate opposite to the surface on which the microporous layer is disposed.
- the microporous portion serves as a conductive path, so that the conductivity can be improved.
- the microporous portion preferably contains a carbon-based filler, and the carbon-based filler is preferably flake graphite.
- the area ratio of the microporous portion is preferably in the range of 5 to 70%.
- the area ratio refers to the ratio of the projected area covered with the microporous portion to the projected area of one surface of the electrode base when the gas diffusion electrode base is photographed with a digital camera or the like.
- the area ratio may be obtained using the following method. Using a microscope such as a scanning electron microscope, select 100 different locations at random from the gas diffusion electrode substrate cross section, and take a photograph at a magnification of about 40 times. In each image, the electrode substrate surface is a microporous part. The ratio of the projected area covered is measured, and the average value of the area ratio of the microporous portion in each image is indicated.
- S-4800 manufactured by Hitachi, Ltd. or an equivalent product can be used as a scanning electron microscope.
- the microporous part preferably forms a pattern.
- a pattern or pattern is a pattern that is repeated at a constant period. It is preferable that there is a repetition period in an area of 100 cm 2 or less, and it is more preferable that there is a repetition period in an area of 10 cm 2 or less. Since the period is small, in-plane performance variations such as conductivity and drainage can be reduced.
- the presence or absence of a period may be confirmed by comparing between sheets. Examples of patterns include lattices, stripes, concentric circles, and island shapes.
- the microporous portion forming the pattern on the separator side from the viewpoint that the electrical resistance between the separator and the gas diffusion electrode substrate can be reduced, it is preferable to dispose the microporous portion forming the pattern on the separator side.
- a wet papermaking method in which carbon fibers are dispersed in a liquid and a dry yarn making method in which the fibers are dispersed in air are used.
- the wet papermaking method is preferably used because of its excellent productivity.
- the present invention for the purpose of improving the drainage of the electrode base material and the gas diffusibility in the in-plane direction, it is possible to make paper by mixing organic fibers with carbon fibers.
- organic fiber polyethylene fiber, vinylon fiber, polyacetal fiber, polyester fiber, polyamide fiber, rayon fiber, acetate fiber, or the like can be used.
- an organic polymer can be included as a binder for the purpose of improving the shape retention and handling properties of the papermaking body.
- the organic polymer polyvinyl alcohol, polyvinyl acetate, polyacrylonitrile, cellulose or the like can be used.
- the paper body in the present invention 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 obtained from the paper body can be formed to a size of about 20 to 500 ⁇ m, although it is affected by the carbon fiber content and dispersion state.
- the paper body preferably has a carbon fiber basis weight in the range of 10 to 40 g / m 2 , more preferably in the range of 15 to 35 g / m 2 , and 20 to 30 g / m 2. More preferably, it is in the range. It is preferable that the basis weight of the carbon fiber is 10 g / m 2 or more because the electrode base material has excellent mechanical strength. It is preferable that the basis weight of the carbon fiber is 40 g / m 2 or less because the electrode base material has excellent in-plane gas diffusibility and drainage. In addition, when bonding a plurality of paper bodies, it is preferable that the basis weight of the carbon fibers after the bonding is in the above range.
- the weight per unit area of the carbon fiber in the electrode base material is the weight of the residue obtained by removing the organic matter by holding the paper body cut to 10 cm square in an electric furnace at a temperature of 450 ° C. for 15 minutes in a nitrogen atmosphere. , Divided by the area of the paper body (0.1 m 2 ).
- a method of impregnating a paper composition containing carbon fibers with a resin composition a method of immersing a papermaking article in a solution containing a resin composition, a method of applying a solution containing a resin composition to a papermaking article, a resin
- a method of transferring a film made of the composition on a paper body is used.
- productivity is excellent, the method of immersing a papermaking body in the solution containing a resin composition is used preferably.
- the resin composition used in the present invention is preferably one that is carbonized upon firing to become a conductive carbide.
- a resin composition means what added the solvent etc. to the resin component as needed.
- the resin component includes a resin such as a thermosetting resin, and further includes additives such as a carbon-based filler and a surfactant as necessary.
- the carbonization yield of the resin component contained in the resin composition is preferably 40% by mass or more.
- the electrode base material is preferable because it has excellent mechanical properties, electrical conductivity, and thermal conductivity.
- examples of the resin constituting the resin component include thermosetting resins such as phenol resin, epoxy resin, melamine resin, and furan resin.
- a phenol resin is preferably used because of high carbonization yield.
- a carbon-type filler can be included in order to improve the mechanical characteristics, electroconductivity, and thermal conductivity of an electrode base material.
- carbon-based filler carbon black, carbon nanotube, carbon nanofiber, carbon fiber milled fiber, graphite, flake graphite and the like can be used.
- the resin composition used in the present invention can use the resin component obtained by the above-described configuration as it is, and can contain various solvents as needed for the purpose of improving the impregnation property to the papermaking body.
- various solvents as needed for the purpose of improving the impregnation property to the papermaking body.
- methanol, ethanol, isopropyl alcohol, or the like can be used as the solvent.
- the resin composition used in the present invention is preferably liquid at 25 ° C. and 0.1 MPa.
- it is liquid, it is preferable because the paper body has excellent impregnation properties and the electrode base material has excellent mechanical properties, electrical conductivity, and thermal conductivity.
- 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 electrode base material is preferable because it has excellent mechanical properties, electrical conductivity, and thermal conductivity.
- the electrode base material is preferable because it has excellent in-plane direction gas diffusibility and in-plane direction gas diffusibility.
- the pre-impregnated body after a pre-impregnated body impregnated with a resin composition is formed on a papermaking body containing carbon fibers, 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 electrode 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 with a hot plate such as a press device, a method of heating with a continuous belt, or the like can be used.
- ⁇ Carbonization> after impregnating the paper composition containing carbon fibers with the resin composition, firing is performed in an inert atmosphere in order to carbonize the paper composition.
- 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 firing temperature is preferably in the range of 1300 to 3000 ° C, more preferably in the range of 1700 to 3000 ° C, and still more preferably in the range of 1900 to 3000 ° C.
- the maximum temperature is 1300 ° C. or higher, the carbonization of the resin component proceeds, and the electrode base material is preferably excellent in conductivity and thermal conductivity.
- the maximum temperature of 3000 ° C. or lower is preferable because the operating cost of the heating furnace is reduced.
- the rate of temperature rise be in the range of 80 to 5000 ° C./min for firing.
- a temperature increase rate of 80 ° C. or higher is preferable because productivity is excellent.
- the electrode base material is preferably excellent in conductivity and thermal conductivity.
- a carbonized paper body impregnated with a resin composition and then carbonized is referred to as a “carbon fiber fired body”.
- the carbon fiber fired body is preferably subjected to water repellent treatment for the purpose of improving drainage.
- the water-repellent processing can be performed by applying a water-repellent material to the carbon fiber fired body and heat-treating it.
- the water repellent material it is preferable to use a fluorine-based polymer because of its excellent corrosion resistance.
- the fluorine-based polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).
- the application amount of the water repellent material 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 carbon fiber fired body.
- the electrode substrate is preferable because it has excellent drainage.
- the electrode base material is preferably excellent in conductivity.
- the water-repellent processing of the carbon fiber fired body is preferably performed so that the amount of the water repellent material is different between the front and back surfaces of the carbon fiber fired body. That is, it is preferable that the fluorine ratio with respect to carbon is different on one side of the electrode base material used for the gas diffusion electrode base material and the opposite side, and the microporous layer is disposed on the surface on the side having a large fluorine ratio with respect to carbon. By disposing the microporous layer on the surface having a higher fluorine ratio to carbon, the carbon coating liquid for forming the microporous layer is less likely to penetrate into the electrode base material, and the back-through is further suppressed.
- the gas diffusibility in the in-plane direction of the electrode base material is further improved, and the power generation performance of the fuel cell is further improved.
- the carbon coating liquid is less likely to penetrate into the electrode base material, and the microporous layer is formed on the electrode base material surface layer with a more preferable thickness, the back diffusion of the generated water further suppresses drying of the electrolyte membrane, Dry-up is further suppressed.
- the fact that the ratio of fluorine to carbon is different on one side of the electrode substrate and the opposite side means that the water repellent material distribution index in the electrode substrate described later is greater than 1.5.
- the index of the water repellent distribution is more preferably in the range of 2 to 10, and still more preferably in the range of 4 to 8.
- the index of the water repellent material distribution is less than 10 and the microporous layer is disposed on the surface on the side having a large fluorine ratio to carbon, the water repellency on the separator side is further maintained. Drainage is further promoted at the interface.
- the index of the water repellent distribution is obtained as follows. First, a scanning electron microscope (SEM) -EDX measurement was performed using a sample for cross-sectional observation in the thickness direction of an electrode substrate produced by an ion beam cross-section processing apparatus under conditions of an acceleration voltage of 10 kV and an enlargement magnification of 400 times. Elemental mapping images of carbon and fluorine in the cross section in the vertical direction are obtained.
- SEM scanning electron microscope
- the obtained elemental mapping image of the cross section in the thickness direction is divided into two in the middle of the surface on one side of the electrode substrate and the surface on the opposite side, and the side on which the microporous layer is arranged (microporous layer side) And the other side (separator side), the ratio of the average value of the signal intensity of fluorine to the average value of the signal intensity of carbon (F / C ratio) is calculated.
- the ratio of the F / C ratio on the porous layer side (microporous layer side / separator side) is calculated and used as an index of the water repellent distribution.
- the result of SEM-EDX line scan measurement may be used.
- measurement is performed five or more times with a scan width of 20 ⁇ m and a line scan interval of 50 ⁇ m, and the F / C ratio is calculated on each of the microporous layer side and the separator side. If it is difficult to distinguish between the microporous layer side and the separator side surface when dividing into two in the thickness direction, that is, the microporous layer side and the separator side, the acceleration voltage
- the thickness of the electrode substrate can be determined using a scanning electron microscope image taken under conditions of 10 kV and an enlargement magnification of 400 times.
- S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.
- an energy dispersive X-ray analyzer HORIBA, Ltd. EX-220SE, or its equivalent can be used. If the index of water repellency distribution in the electrode substrate cannot be obtained due to reasons such as the electrode substrate not being available, a sample for cross-sectional observation in the thickness direction of the gas diffusion electrode substrate or membrane electrode assembly is used. The water repellent distribution index obtained by the method described above can be used instead.
- a method of changing the amount of water repellent material on the front and back of the carbon fiber fired body a method of applying the water repellent material to the carbon fiber fired body from one side with a die coater, etc., dipping the carbon fiber fired body in the water repellent dispersion, There is a method of uniformly applying and impregnating in the thickness direction and then wiping one side.
- the low-weight electrode base material used in the present invention has a large porosity, a small thickness, and the water-repellent material tends to spread throughout the electrode base material during the water-repellent processing.
- a method of immersing in a dispersion, uniformly applying and impregnating in the thickness direction, and then wiping off one side is more preferable.
- the carbon fiber fired body As a method of immersing the carbon fiber fired body in the water repellent dispersion, uniformly applying and impregnating in the thickness direction, and then wiping one side, the carbon fiber fired body is immersed in the water repellent dispersion and the thickness direction Applying and impregnating the fabric with a cloth, etc., dipping the carbon fiber fired body in the water-repellent dispersion, uniformly applying and impregnating in the thickness direction, and then sucking the water-repellent material from one side with a suction pump And a method in which a carbon fiber fired body is immersed in a water repellent dispersion, uniformly coated and impregnated in the thickness direction, and then contacted with a roll on one side.
- the carbon fiber fired body corresponds to an “electrode substrate”.
- the carbon fiber fired body is subjected to water-repellent finishing as necessary, but in the present invention, the carbon fiber fired body subjected to water-repellent finishing also corresponds to the “electrode substrate”. (A carbon fiber fired body that is not subjected to water repellent treatment naturally corresponds to an “electrode substrate”).
- the microporous layer can be formed by applying a carbon coating solution containing linear carbon having at least an aspect ratio in the range of 30 to 5000 on one surface of the electrode substrate.
- the carbon coating liquid may contain a dispersion medium such as water or an organic solvent, or may contain a dispersion aid such as a surfactant.
- a dispersion medium such as water or an organic solvent
- a dispersion aid such as a surfactant.
- Water is preferable as the dispersion medium, and a nonionic surfactant is more preferably used as the dispersion aid.
- you may contain various carbon-type fillers and water repellent materials other than the linear carbon of a specific aspect ratio as mentioned above.
- the coating of the carbon coating liquid on the electrode substrate can be performed using various commercially available coating apparatuses.
- As the coating method screen printing, rotary screen printing, spray spraying, intaglio printing, gravure printing, die coater coating, bar coating, blade coating and the like can be used.
- the coating methods exemplified above are only for illustrative purposes, and are not necessarily limited thereto.
- the coating liquid it is preferable to dry the coating liquid at a temperature of 80 to 120 ° C. after coating the carbon coating liquid on the electrode substrate. That is, the coated product is put into a drier set at a temperature of 80 to 120 ° C. and dried in a range of 5 to 30 minutes.
- the amount of drying air may be determined as appropriate, but rapid drying is undesirable because it may induce micro cracks on the surface.
- solids (carbon filler, water repellent material, surfactant, etc.) in the carbon coating liquid remain after drying to form a microporous layer.
- the microporous layer and the microporous part When placing the microporous layer and the microporous part on the electrode substrate, after drying the coated material coated on one side with the carbon coating solution, apply the carbon coating solution on the other side and dry again. It is preferable to do. Drying is performed in a range of 5 to 30 minutes by putting the coated product in a drier set at a temperature of 80 to 120 ° C. The amount of drying air may be determined as appropriate, but rapid drying is undesirable because it may induce micro cracks on the surface.
- the dried coated product is put into a muffle furnace, a baking furnace or a high-temperature dryer, heated at 300 to 380 ° C. for 5 to 20 minutes to melt the water repellent material, and a binder of carbon fillers. Thus, it is preferable to form a microporous layer.
- a membrane electrode assembly can be comprised by joining the above-mentioned gas diffusion electrode base material to at least one side of a solid polymer electrolyte membrane having a catalyst layer on both sides. At that time, by arranging the microporous layer on the catalyst layer side, the back diffusion of the generated water is more likely to occur, and the contact area between the catalyst layer and the gas diffusion electrode substrate increases, reducing the contact electrical resistance. can do.
- the microporous layer and the microporous portion are disposed on the electrode base material, the microporous portion functions as a conductive path by disposing the microporous portion on the separator side, so that the conductivity can be improved. Moreover, since the area ratio of a microporous part is small, the drainage from an electrode base material is not inhibited and flooding can be suppressed.
- the fuel cell of the present invention has separators on both sides of the membrane assembly. That is, a fuel cell is constituted by having separators on both sides of the membrane electrode assembly.
- a polymer electrolyte fuel cell is constructed by laminating a plurality of sandwiched electrode separators on both sides of such a membrane electrode assembly.
- the catalyst layer 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.
- ⁇ Preparation of electrode substrate> Preparation of electrode base material with a basis weight of 25 g / m 2
- the paper was continuously dispersed by wet papermaking. Further, a 10% by mass aqueous solution of polyvinyl alcohol as a binder was applied to the paper and dried to prepare a paper body having a carbon fiber basis weight of 15.5 g / m 2.
- the coating amount of polyvinyl alcohol was 22 parts by mass with respect to 100 parts by mass of the papermaking body.
- thermosetting resin using a resin in which a resol type phenolic resin and a novolac type phenolic resin are mixed at a weight ratio of 1: 1 as a thermosetting resin, scaly graphite (average particle size 5 ⁇ m) as a carbon filler, and methanol as a solvent.
- Carbon-based filler / solvent 10 parts by mass / 5 parts by mass / 85 parts by mass
- the paper body cut into 15 cm ⁇ 12.5 cm is immersed in a resin composition filled with aluminum bat, and the resin component (thermosetting resin + carbon filler) becomes 130 parts by mass with respect to 100 parts by mass of the carbon fibers. After impregnating in this manner, it was dried by heating at 100 ° C. for 5 minutes to prepare a pre-impregnated body. Next, it heat-processed for 5 minutes at 180 degreeC, pressing with a flat plate press. In addition, a spacer was disposed on the flat plate press during the pressurization, and the interval between the upper and lower press face plates was adjusted so that the thickness of the pre-impregnated body after the heat treatment was 130 ⁇ m.
- the base material obtained by heat-treating the pre-impregnated body was introduced into a heating furnace having a maximum temperature of 2400 ° C. maintained in a nitrogen gas atmosphere in a heating furnace to obtain a carbon fiber fired body.
- Water repellent processing method A Carbon fiber fired body was dispersed in PTFE resin aqueous dispersion ("Polyflon” (registered trademark) PTFE dispersion D-1E (Daikin Industries Co., Ltd.)) with respect to 95 parts by weight of the carbon fiber fired body.
- the carbon fiber fired body is coated with and impregnated with PTFE resin by dipping in 5 parts by mass of a PTFE resin diluted to an appropriate concentration to give 5 parts by weight of PTFE resin. Heat to dry for minutes. When drying, the carbon fiber fired body was arranged vertically, and the vertical direction was changed every minute so that the distribution in the in-plane direction of the PTFE resin was not biased.
- Water repellent processing method B Carbon fiber fired product was dispersed in a PTFE resin dispersion (“Polyflon” (registered trademark) PTFE dispersion D-1E (Daikin Industries, Ltd.)) with respect to 95 parts by mass of the carbon fiber fired product. 100mm diameter stainless steel roll coated with PTFE resin, impregnated and hard chrome plated by dipping in carbon fiber fired body by dipping in a suitable concentration to give part by weight of PTFE resin) One side was brought into contact with the surface and the PTFE resin on one side was wiped off, and then dried by heating in a dryer furnace having a temperature of 100 ° C. for 5 minutes. When drying, the carbon fiber fired body was placed horizontally such that the surface of the carbon fiber fired body from which the PTFE resin had been wiped was down.
- a PTFE resin dispersion (“Polyflon” (registered trademark) PTFE dispersion D-1E (Daikin Industries, Ltd.)
- electrode base material having a basis weight of 20 g / m 2 Except for the carbon fiber basis weight being 15.5 g / m 2 , the basis weight is 20 g / m according to the method described in the preparation of the electrode base material having a basis weight of 25 g / m 2. 2. An electrode substrate having a thickness of 90 ⁇ m was prepared. In addition, the water repellent processing followed the method described in the water repellent processing method B.
- VGCF Linear carbon / vapor-grown carbon fiber “VGCF” (registered trademark) having an aspect ratio in the range of 30 to 5000 (manufactured by Showa Denko KK, average diameter: 0.15 ⁇ m, average fiber length: 8 ⁇ m, (Aspect ratio: 50, a kind of linear carbon) Vapor growth carbon fiber “VGCF-S” (registered trademark) (manufactured by Showa Denko KK, average diameter: 0.10 ⁇ m, average fiber length: 11 ⁇ m, aspect ratio: 110, a kind of linear carbon) ⁇ Multi-walled carbon nanotubes (Cheap Tubes, average diameter: 0.015 ⁇ m, average fiber length: 20 ⁇ m, aspect ratio: 1300, a kind of linear carbon) ⁇ Flake graphite “xGnP” (registered trademark) grade M (manufactured by XG Science, average particle size: 5
- the carbon coating liquid used here a carbon-based filler, a water repellent material, a surfactant, and purified water are used, so that the composition of the carbon coating liquid is shown in Tables 1 to 4 with the blending amounts described in parts by mass. What was adjusted to was used.
- the blending amounts of PTFE resin shown in Tables 1 to 4 represent the blending amount of the PTFE resin itself, not the blending amount of the aqueous PTFE resin dispersion.
- a carbon coating solution was applied to the electrode substrate using a die coater, and then heated at 120 ° C. for 10 minutes and at 380 ° C. for 10 minutes to form a microporous layer.
- a microporous layer was formed on the surface on the side where the index of the water repellent distribution was large.
- the microporous portion on the catalyst layer side was formed after the microporous portion on the separator side was formed and dried.
- a carbon coating solution was applied to the electrode substrate using a screen printing plate, and then heated at 120 ° C. for 10 minutes to form a microporous portion.
- ⁇ 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 Corporation) 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. Pressing at 5 ° C. for 5 minutes transferred the catalyst layer to the solid polymer electrolyte membrane. 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 a catalyst layer is sandwiched between two gas diffusion electrode substrates cut to 7 cm ⁇ 7 cm, and pressed at 130 ° C. for 5 minutes while being pressurized to 3 MPa with a flat plate press, and a membrane electrode assembly was made.
- the gas diffusion electrode base material was disposed so that the surface having the microporous layer 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 separator having a single flow path 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 non-pressurized hydrogen to the anode side and non-pressurized air 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 humidifying temperature was set to 70 ° C.
- the current density was set to 2.2 A / cm 2
- the output voltage was measured and used as an indicator of flooding resistance (low temperature performance).
- the electrical resistance of the gas diffusion electrode substrate is as follows: 1. When a uniform surface pressure of 1.0 MPa is applied with a gas diffusion electrode substrate cut to 2.23 mm ⁇ 2.23 mm sandwiched between two gold-plated plates. An electric current of 0 A was passed, and the electric resistance was measured to obtain the area. If the surface pressure is high, the structure of the gas diffusion electrode substrate is destroyed and the resistance value cannot be measured accurately. Therefore, it is preferable to measure and compare the electrical resistance at a relatively low surface pressure.
- the electrical resistance is preferably made of a 9.0m ⁇ ⁇ cm 2 or less, 7.5m ⁇ ⁇ cm 2 or less being more preferred.
- the surface gas permeation resistance of the gas diffusion electrode base material is a circular sample with a diameter of 4.7 cm cut out from the gas diffusion electrode base material, and air is supplied from the surface on the microporous side to the opposite surface at 58 cc / min / cm 2.
- the differential pressure between the surface on the microporous side and the opposite surface when measured at a flow rate of 5 mm was measured with a differential pressure gauge to obtain a straight gas permeation resistance.
- the index of the water repellent distribution of the electrode substrate was determined as follows. First, a scanning electron microscope (SEM) -EDX measurement was performed using a sample for cross-sectional observation in the thickness direction of an electrode substrate produced by an ion beam cross-section processing apparatus under conditions of an acceleration voltage of 10 kV and an enlargement magnification of 400 times. Element mapping images of carbon and fluorine in the cross section in the vertical direction were obtained.
- SEM scanning electron microscope
- the obtained elemental mapping image of the cross section in the thickness direction is divided into two in the middle of the surface on one side of the electrode substrate and the surface on the opposite side, and the side on which the microporous layer is arranged (microporous layer side) And the other side (separator side), the ratio of the average value of the signal intensity of fluorine to the average value of the signal intensity of carbon (F / C ratio) is calculated.
- the ratio of the F / C ratio on the porous layer side (microporous layer side / separator side) was calculated and used as an index of the water repellent distribution.
- S-4800 manufactured by Hitachi, Ltd. was used as the scanning electron microscope, and EX-220SE, Horiba, Ltd.
- an index of water repellency distribution was determined by the method described above.
- the part of the electrode base material in the cross section of the gas diffusion electrode base material was identified using a scanning electron microscope image taken under conditions of an acceleration voltage of 10 kV and an enlargement magnification of 400 times.
- Example 1 According to the method described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, a surface containing vapor-grown carbon fibers having a specific aspect ratio on the catalyst layer side of the electrode substrate shown in Table 1 A gas diffusion electrode base material having a shaped microporous layer was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 90 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electrical resistance was 8.6 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all good.
- Example 2 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 1, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 91 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 8.5 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all good.
- Example 3 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 1, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained. As a result of evaluating the power generation performance of this gas diffusion electrode substrate, an output voltage of 0.40 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 92 ° C.
- the index of the water repellent material distribution was 1.
- the index of the water repellent distribution was 1.2.
- Example 4 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 1, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.38 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 90 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 9.0 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all good.
- Example 5 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 1, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.40 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 92 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 7.4 m ⁇ ⁇ cm 2
- the flooding resistance and conductivity were extremely good
- the dry-up resistance was also good.
- the catalyst layer side of the electrode substrate includes multi-walled carbon nanotubes and acetylene black having a specific aspect ratio shown in Table 1.
- a gas diffusion electrode substrate having a planar microporous layer was obtained.
- an output voltage of 0.41 V operation temperature: 65 ° C., humidification temperature: 70 ° C., current density: 2.2 A / cm 2
- limit temperature: 92 ° C. humidity temperature: 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 7.3 m ⁇ ⁇ cm 2
- the flooding resistance and conductivity were extremely good
- the dry-up resistance was also good.
- Example 7 According to the methods described in ⁇ Preparation of Electrode Base> and ⁇ Formation of Microporous Layer and Microporous Portion>, a vapor-grown carbon fiber having a specific aspect ratio on the catalyst layer side of the electrode base, furnace black shown in Table 1 Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.40 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 92 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 7.4 m ⁇ ⁇ cm 2
- the flooding resistance and conductivity were extremely good
- the dry-up resistance was also good.
- Example 8 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 91 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 8.9 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all good.
- Example 9 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.42 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 93 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electrical resistance was 6.4 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all very good.
- Example 10 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 90 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 6.2 m ⁇ ⁇ cm 2
- the flooding resistance and the dry-up resistance were good
- the conductivity was very good.
- Example 11 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.38 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 92 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 6.4 m ⁇ ⁇ cm 2
- the flooding resistance and the dry-up resistance were good
- the conductivity was very good.
- Example 12 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing and having a microporous portion with an area ratio of 36% on the separator side was obtained.
- an output voltage of 0.40 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 93 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electrical resistance was 6.4 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all very good.
- Example 13 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing and having a microporous portion with an area ratio of 36% on the separator side was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 93 ° C. (humidification temperature 70 ° C., The current density was 1.2 A / cm 2 ), the electric resistance was 5.6 m ⁇ ⁇ cm 2 , the flooding resistance was good, the dry-up resistance and the conductivity were very good.
- Example 14 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black on the catalyst layer side of the electrode substrate, shown in Table 2, Thus, a gas diffusion electrode substrate having a planar microporous layer containing and having a microporous portion with an area ratio of 36% on the separator side was obtained.
- an output voltage of 0.42 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 93 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 5.3 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all very good.
- Example 15 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black, on the catalyst layer side of the electrode substrate, shown in Table 3, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.41 V operation temperature: 65 ° C., humidification temperature: 70 ° C., current density: 2.2 A / cm 2 ), limit temperature: 92 ° C. (humidification temperature: 70 ° C., The current density was 1.2 A / cm 2 ), the electric resistance was 7.4 m ⁇ ⁇ cm 2 , the flooding resistance and conductivity were extremely good, and the dry-up resistance was also good.
- Example 16 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black, on the catalyst layer side of the electrode substrate, shown in Table 3, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.38 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 89 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electrical resistance was 9.1 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all good.
- Example 17 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black, on the catalyst layer side of the electrode substrate, shown in Table 3, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained.
- an output voltage of 0.39 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 89 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 5.8 m ⁇ ⁇ cm 2
- the flooding resistance and the dry-up resistance were good
- the conductivity was very good.
- Example 18 According to the method described in ⁇ Preparation of Electrode Base> and ⁇ Formation of Microporous Layer and Microporous Portion>, a surface containing vapor-grown carbon fibers having a specific aspect ratio on the catalyst layer side of the electrode base as shown in Table 3 A gas diffusion electrode base material having a shaped microporous layer was obtained. As a result of evaluating the power generation performance of this gas diffusion electrode substrate, an output voltage of 0.40 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 92 ° C.
- Example 19 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black, on the catalyst layer side of the electrode substrate, shown in Table 3, Thus, a gas diffusion electrode substrate having a planar microporous layer containing was obtained. As a result of evaluating the power generation performance of this gas diffusion electrode substrate, an output voltage of 0.41 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2 ), limit temperature 93 ° C.
- Example 20 According to the methods described in ⁇ Preparation of electrode substrate> and ⁇ Formation of microporous layer and microporous portion>, vapor-grown carbon fibers having a specific aspect ratio, acetylene black, on the catalyst layer side of the electrode substrate, shown in Table 3, Thus, a gas diffusion electrode substrate having a planar microporous layer containing and having a microporous portion with an area ratio of 36% on the separator side was obtained.
- an output voltage of 0.41 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 93 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electrical resistance was 6.0 m ⁇ ⁇ cm 2
- the flooding resistance, dry-up resistance, and conductivity were all very good.
- the electrode substrate has a planar microporous layer containing acetylene black on the catalyst layer side shown in Table 4.
- a gas diffusion electrode substrate was obtained.
- an output voltage of 0.30 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 85 ° C. humidity temperature 70 ° C., Current density was 1.2 A / cm 2
- electric resistance was 7.5 m ⁇ ⁇ cm 2
- the conductivity was very good, but the flooding resistance and the dry-up resistance were insufficient.
- the electrode substrate has a planar microporous layer containing acetylene black on the catalyst layer side shown in Table 4.
- a gas diffusion electrode substrate was obtained.
- an output voltage of 0.35 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 88 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 9.2 m ⁇ ⁇ cm 2
- the flooding resistance was good, the dry-up resistance and the conductivity were insufficient.
- the electrode substrate has a planar microporous layer containing acetylene black on the catalyst layer side shown in Table 4.
- a gas diffusion electrode substrate was obtained.
- an output voltage of 0.35 V operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.2 A / cm 2
- limit temperature 88 ° C. humidity temperature 70 ° C.
- the current density was 1.2 A / cm 2
- the electric resistance was 9.2 m ⁇ ⁇ cm 2
- the flooding resistance was good, the dry-up resistance and the conductivity were insufficient.
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Abstract
Description
(1)電極基材の片面にマイクロポーラス層が配置されてなる燃料電池用ガス拡散電極基材であって、マイクロポーラス層にアスペクト比が30~5000の範囲内である線状カーボンを含み、ガス拡散電極基材の目付が30~60g/m2の範囲内であることを特徴とする燃料電池用ガス拡散電極基材。
(2)マイクロポーラス層の目付が10~35g/m2の範囲内である前記(1)に記載の燃料電池用ガス拡散電極基材。(3)ガス拡散電極基材の厚さが70~190μmの範囲内である前記(1)または(2)に記載の燃料電池用ガス拡散電極基材。
(4)面直方向のガス透過抵抗が15~190mmAqの範囲内である前記(1)~(3)のいずれかに記載の燃料電池用ガス拡散電極基材。
(5)ガス拡散電極基材に用いる電極基材の片面とその反対側の面でカーボンに対するフッ素比率が異なり、カーボンに対するフッ素比率が多い面にマイクロポーラス層が配置されてなる前記(1)~(4)のいずれかに記載の燃料電池用ガス拡散電極基材。
(6)マイクロポーラス層にカーボンブラックを含み、アスペクト比が30~5000の範囲内である線状カーボンに対するカーボンブラックの混合質量比が0.5~20の範囲内である前記(1)~(5)のいずれかに記載の燃料電池用ガス拡散電極基材。
(7)電極基材のマイクロポーラス層を配置した面とは別のもう一方の面に面積率が5~70%の範囲内であるマイクロポーラス部が配置されてなる前記(1)~(6)のいずれかに記載の燃料電池用ガス拡散電極基材。
本発明において、炭素繊維を含む抄紙体を得るためには、炭素繊維を液中に分散させて製造する湿式抄紙法や、空気中に分散させて製造する乾式抄糸法などが用いられる。中でも、生産性が優れることから、湿式抄紙法が好ましく用いられる。
本発明において、炭素繊維を含む抄紙体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抄紙体を浸漬する方法、樹脂組成物を含む溶液を抄紙体に塗布する方法、樹脂組成物からなるフィルムを抄紙体に重ねて転写する方法などが用いられる。中でも、生産性が優れることから、樹脂組成物を含む溶液中に抄紙体を浸漬する方法が好ましく用いられる。
本発明においては、炭素繊維を含む抄紙体に樹脂組成物を含浸した予備含浸体を形成した後、炭素化を行うに先立って、予備含浸体の貼り合わせや、熱処理を行うことができる。
本発明において、炭素繊維を含む抄紙体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。かかる焼成は、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、炭素繊維焼成体に撥水加工を施すことが好ましい。撥水加工は、炭素繊維焼成体に撥水材を塗布、熱処理することにより行うことができる。ここで、撥水材としては、耐腐食性が優れることから、フッ素系のポリマーを用いることが好ましい。フッ素系のポリマーとしては、ポリテトラフルオロエチレン(PTFE)、テトラフルオロエチレン-ヘキサフルオロプロピレン共重合体(FEP)、テトラフルオロエチレン-パーフルオロアルキルビニルエーテル共重合体(PFA)などが挙げられる。撥水材の塗布量は、炭素繊維焼成体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。撥水材の塗布量が1質量部以上であると、電極基材が排水性に優れたものとなり好ましい。一方、50質量部以下であると、電極基材が導電性の優れたものとなり好ましい。
マイクロポーラス層は、電極基材の片面に、少なくともアスペクト比が30~5000の範囲内である線状カーボンを含むカーボン塗液を塗布することによって形成することができる。
本発明において、前記したガス拡散電極基材を、両面に触媒層を有する固体高分子電解質膜の少なくとも片面に接合することで膜電極接合体を構成することができる。その際、触媒層側にマイクロポーラス層を配置することで、より生成水の逆拡散が起こりやすくなるのに加え、触媒層とガス拡散電極基材の接触面積が増大し、接触電気抵抗を低減することができる。電極基材にマイクロポーラス層とマイクロポーラス部を配置する場合は、マイクロポーラス部をセパレータ側に配置することでマイクロポーラス部が導電パスとして働き、導電性を向上できる。また、マイクロポーラス部の面積率が小さいため、電極基材からの排水が阻害されずフラッディングを抑制できる。
本発明の燃料電池は、上述の膜接合体の両側にセパレータを有するものである。すなわち、上述の膜電極接合体の両側にセパレータを有することで燃料電池を構成する。通常、かかる膜電極接合体の両側にガスケットを介してセパレータで挟んだものを複数個積層することによって固体高分子型燃料電池を構成する。触媒層は、固体高分子電解質と触媒担持炭素を含む層からなる。触媒としては、通常、白金が用いられる。アノード側に一酸化炭素を含む改質ガスが供給される燃料電池にあっては、アノード側の触媒としては白金およびルテニウムを用いるのが好ましい。固体高分子電解質は、プロトン伝導性、耐酸化性、耐熱性の高い、パーフルオロスルホン酸系の高分子材料を用いるのが好ましい。かかる燃料電池ユニットや燃料電池の構成自体は、よく知られているところである。
・目付25g/m2の電極基材の作製
東レ(株)製ポリアクリルニトリル系炭素繊維“トレカ(登録商標)”T300(平均炭素繊維径:7μm)を平均長さ12mmにカットし、水中に分散させて湿式抄紙法により連続的に抄紙した。さらに、バインダーとしてポリビニルアルコールの10質量%水溶液を当該抄紙に塗布し、乾燥させ、炭素繊維目付15.5g/m2の抄紙体を作製した。ポリビニルアルコールの塗布量は、抄紙体100質量部に対して、22質量部であった。
炭素繊維目付を15.5g/m2とした以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付20g/m2、厚さ90μmの電極基材を作製した。なお、撥水加工は撥水加工方法Bに記載した方法に従った。
樹脂成分を210質量部とした以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付33g/m2、厚さ100μmの電極基材を作製した。なお、撥水加工は撥水加工方法Aに記載した方法に従った。
樹脂成分を250質量部とした以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付37g/m2、厚さ100μmの電極基材を作製した。なお、撥水加工は撥水加工方法Aに記載した方法に従った。
炭素繊維目付を20g/m2、樹脂成分を210質量部に変えた以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付44g/m2、厚さ110μmの電極基材を作製した。なお、撥水加工は撥水加工方法Aに記載した方法に従った。
炭素繊維目付を20g/m2、樹脂成分を190質量部に変えて作製した予備含浸体2枚を積層し、平板プレスで加圧しながら熱処理を行った以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付84g/m2、厚さ190μmの電極基材を作製した。なお、撥水加工は撥水加工方法Aに記載した方法に従った。
<材料>
C:アスペクト比が30~5000の範囲内である線状カーボン
・気相成長炭素繊維“VGCF”(登録商標)(昭和電工(株)製、平均直径:0.15μm、平均繊維長:8μm、アスペクト比:50、線状カーボンの一種)
・気相成長炭素繊維“VGCF-S”(登録商標)(昭和電工(株)製、平均直径:0.10μm、平均繊維長:11μm、アスペクト比:110、線状カーボンの一種)
・多層カーボンナノチューブ(チープ チューブス社製、平均直径:0.015μm、平均繊維長:20μm、アスペクト比:1300、線状カーボンの一種)
・薄片グラファイト“xGnP”(登録商標)グレードM(XG サイエンス社製、平均粒子径:5μm、平均厚さ:0.006μm、アスペクト比:830)
D:アスペクト比が30~5000の範囲内に含まれない炭素系フィラー
・アセチレンブラック“デンカブラック”(登録商標)(電気化学工業(株)製、平均粒子径:0.035μm、アスペクト比:1、カーボンブラックの一種)
・ファーネスブラック“バルカン”(登録商標)XC72C(キャボット社製、平均粒子径:0.030μm、アスペクト比:1、カーボンブラックの一種)
F:撥水材
・PTFE樹脂(PTFE樹脂を60質量部含む水分散液である“ポリフロン”(登録商標)PTFEディスパージョンD-1E(ダイキン工業(株)製)を使用)
G:その他
・界面活性剤“TRITON”(登録商標)X-100(ナカライテスク(株)製)
(触媒層側)
スリットダイコーターを用いて電極基材に面状のマイクロポーラス層を形成した。ここで用いたカーボン塗液には、炭素系フィラー、撥水材、界面活性剤、精製水を用い、表1~4に示す、配合量を質量部で記載したカーボン塗液の組成となるように調整したものを用いた。なお、表1~4に示すPTFE樹脂の配合量は、PTFE樹脂の水分散液の配合量ではなく、PTFE樹脂自体の配合量を表す。ダイコーターを用いて電極基材にカーボン塗液を塗工後、120℃で10分、380℃で10分加熱し、マイクロポーラス層を形成した。撥水加工方法Bの電極基材を用いる場合は、撥水材分布の指標が大きい側の面にマイクロポーラス層を形成した。セパレータ側にマイクロポーラス部を配置する場合は、セパレータ側のマイクロポーラス部を形成して乾燥した後に触媒層側のマイクロポーラス層を形成した。
線幅0.5mm、線間隔2mmの直線が直交する格子状のパターン部分以外を樹脂でマスクしたスクリーン印刷版を用いて電極基材のセパレータ側に面積率36%の格子状のパターン様のマイクロポーラス部を形成した。ここで用いたカーボン塗液には、炭素系フィラーとして薄片グラファイトとアセチレンブラック、撥水材、界面活性剤、精製水を用い、薄片グラファイト/アセチレンブラック/撥水材/界面活性剤/精製水=5.8質量部/1.9質量部/2.5質量部/14質量部/75.8質量部となるように調整したものを用いた。スクリーン印刷板を用いて電極基材にカーボン塗液を塗工後、120℃で10分加熱し、マイクロポーラス部を形成した。
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。
ガス拡散電極基材の電気抵抗は、2.23mm×2.23mmにカットしたガス拡散電極基材を2枚の金メッキ板の間に挟んで1.0MPaの一様な面圧をかけたとき、1.0Aの電流を流して、電気抵抗を測定して面積をかけて求めた。面圧が高ければガス拡散電極基材の構造が破壊されて抵抗値が正確に測定できないので、比較的低い面圧で電気抵抗を測定し比較を行うのがよい。燃料電池用のガス拡散電極基材として用いるとき、電気抵抗は、9.0mΩ・cm2以下になることが好ましく、7.5mΩ・cm2以下がより好ましい。
ガス拡散電極基材の面直ガス透過抵抗は、ガス拡散電極基材から切り出した直径4.7cmの円形のサンプルを用い、マイクロポーラス側の面からその反対面に空気を58cc/min/cm2の流速で透過させたときの、マイクロポーラス側の面とその反対面の差圧を差圧計で測定し、面直ガス透過抵抗とした。
電極基材の撥水材分布の指標は以下のように求めた。まず、イオンビーム断面加工装置により作製した電極基材の厚さ方向の断面観察用サンプルを用い、加速電圧10kV、拡大倍率400倍の条件で走査型電子顕微鏡(SEM)-EDX測定を行い、厚さ方向の断面の炭素、およびフッ素の元素マッピング像を得た。次に、得られた厚さ方向の断面の元素マッピング像を電極基材の片側の面とその反対側の面の中間で2分割し、マイクロポーラス層が配置される側(マイクロポーラス層側)とその反対側(セパレータ側)の各々において、炭素のシグナル強度の平均値に対するフッ素のシグナル強度の平均値の比率(F/C比)を算出し、さらに、セパレータ側のF/C比に対するマイクロポーラス層側のF/C比の比率(マイクロポーラス層側/セパレータ側)を算出し、撥水剤分布の指標とした。走査型電子顕微鏡としては、(株)日立製作所製S-4800、エネルギー分散型X線分析装置としては、(株)堀場製作所EX-220SEを用いた。ガス拡散電極基材についても上述する方法により撥水分布の指標を求めた。ガス拡散電極基材の断面における電極基材の部分の識別は、加速電圧10kV、拡大倍率400倍の条件で撮影した走査型電子顕微鏡像を用いて行った。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維を含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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)、電気抵抗8.6mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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91℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗8.5mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.40V(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)、電気抵抗は7.5mΩ・cm2であり、耐フラッディング性と導電性は極めて良好であり、耐ドライアップ性も良好であった。カーボン塗液を塗布する前の電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は1であった。カーボン塗液を塗布、乾燥した後にガス拡散電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は1.2であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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)、電気抵抗は9.0mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.40V(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)、電気抵抗は7.4mΩ・cm2であり、耐フラッディング性と導電性は極めて良好であり、耐ドライアップ性も良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の多層カーボンナノチューブ、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.41V(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)、電気抵抗は7.3mΩ・cm2であり、耐フラッディング性と導電性は極めて良好であり、耐ドライアップ性も良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表1に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、ファーネスブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.40V(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)、電気抵抗は7.4mΩ・cm2であり、耐フラッディング性と導電性は極めて良好であり、耐ドライアップ性も良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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91℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は8.9mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.42V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.4mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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)、電気抵抗は6.2mΩ・cm2であり、耐フラッディング性、耐ドライアップ性が良好、導電性が極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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92℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.4mΩ・cm2であり、耐フラッディング性、耐ドライアップ性が良好、導電性が極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有し、セパレータ側に面積率36%のマイクロポーラス部を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.40V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.4mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有し、セパレータ側に面積率36%のマイクロポーラス部を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は5.6mΩ・cm2であり、耐フラッディング性が良好であり、耐ドライアップ性、導電性が極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表2に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有し、セパレータ側に面積率36%のマイクロポーラス部を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.42V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は5.3mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.41V(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)、電気抵抗は7.4mΩ・cm2であり、耐フラッディング性と導電性は極めて良好であり、耐ドライアップ性も良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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89℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は9.1mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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89℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は5.8mΩ・cm2であり、耐フラッディング性、耐ドライアップ性が良好、導電性が極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維を含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.40V(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)、電気抵抗は8.2mΩ・cm2であり、耐フラッディング性が極めて良好、耐ドライアップ性、導電性がともに良好であった。カーボン塗液を塗布する前の電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は5.0であった。カーボン塗液を塗布、乾燥した後にガス拡散電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は5.5であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.41V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は7.1mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに極めて良好であった。カーボン塗液を塗布する前の電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は5.0であった。カーボン塗液を塗布、乾燥した後にガス拡散電極基材の断面の撥水材分布を測定したところ、撥水材分布の指標は5.5であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表3に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有し、セパレータ側に面積率36%のマイクロポーラス部を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.41V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度93℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.0mΩ・cm2であり、耐フラッディング性、耐ドライアップ性、導電性がともに極めて良好であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側にアセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.30V(運転温度65℃、加湿温度70℃、電流密度2.2A/cm2)、限界温度85℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は7.5mΩ・cm2であり、導電性は極めて良好であるが、耐フラッディング性、耐ドライアップ性が不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側にアセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.35V(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)、電気抵抗は9.2mΩ・cm2であり、耐フラッディング性は良好、耐ドライアップ性、導電性がともに不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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86℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.3mΩ・cm2であり、導電性は極めて良好であるが、耐フラッディング性はやや低下し、耐ドライアップ性は不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維、アセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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87℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は5.8mΩ・cm2であり、導電性は極めて良好、耐フラッディング性は良好、耐ドライアップ性は不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維を含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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86℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は7.4mΩ・cm2であり、導電性は極めて良好であるが、耐フラッディング性はやや低下し、耐ドライアップ性は不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側に特定アスペクト比の気相成長炭素繊維を含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、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86℃(加湿温度70℃、電流密度1.2A/cm2)、電気抵抗は6.9mΩ・cm2であり、導電性は極めて良好であるが、耐フラッディング性は良好、耐ドライアップ性は不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、表4に示す、電極基材の触媒層側にアセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材を得た。このガス拡散電極基材の発電性能を評価した結果、出力電圧0.35V(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)、電気抵抗は9.2mΩ・cm2であり、耐フラッディング性は良好、耐ドライアップ性、導電性がともに不十分であった。
<電極基材の作製>および<マイクロポーラス層、マイクロポーラス部の形成>に記載した方法に従って、炭素繊維目付を7.8g/m2とした以外は、上記した目付25g/m2の電極基材の作製に記載した方法に従って、目付10g/m2の電極基材、表4に示す、電極基材の触媒層側にアセチレンブラックを含む面状のマイクロポーラス層を有するガス拡散電極基材の作製を試みたが、抄紙工程で基材が破れ、炭素繊維抄紙体を得ることができなかった。
Claims (7)
- 電極基材の片面にマイクロポーラス層が配置されてなる燃料電池用ガス拡散電極基材であって、マイクロポーラス層にアスペクト比が30~5000の範囲内である線状カーボンを含み、ガス拡散電極基材の目付が30~60g/m2の範囲内であることを特徴とする燃料電池用ガス拡散電極基材。
- マイクロポーラス層の目付が10~35g/m2の範囲内である請求項1に記載の燃料電池用ガス拡散電極基材。
- ガス拡散電極基材の厚さが70~190μmの範囲内である請求項1または2に記載の燃料電池用ガス拡散電極基材。
- 面直方向のガス透過抵抗が15~190mmAqの範囲内である請求項1~3のいずれかに記載の燃料電池用ガス拡散電極基材。
- ガス拡散電極基材に用いる電極基材の片面とその反対側の面でカーボンに対するフッ素比率が異なり、カーボンに対するフッ素比率が多い面にマイクロポーラス層が配置されてなる請求項1~4のいずれかに記載の燃料電池用ガス拡散電極基材。
- マイクロポーラス層にカーボンブラックを含み、アスペクト比が30~5000の範囲内である線状カーボンに対するカーボンブラックの混合質量比が0.5~20の範囲内である請求項1~5のいずれかに記載の燃料電池用ガス拡散電極基材。
- 電極基材のマイクロポーラス層を配置した面とは別のもう一方の面に面積率が5~70%の範囲内であるマイクロポーラス部が配置されてなる請求項1~6のいずれかに記載の燃料電池用ガス拡散電極基材。
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JP7129751B2 (ja) | 2014-10-17 | 2022-09-02 | 東レ株式会社 | 炭素シート、ガス拡散電極基材、および燃料電池 |
JPWO2016060045A1 (ja) * | 2014-10-17 | 2017-07-27 | 東レ株式会社 | 炭素シート、ガス拡散電極基材、および燃料電池 |
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JP2017091712A (ja) * | 2015-11-06 | 2017-05-25 | 凸版印刷株式会社 | 電極触媒層、膜電極接合体、固体高分子形燃料電池、および、電極触媒層の製造方法 |
CN106876743B (zh) * | 2017-03-16 | 2019-07-23 | 厦门大学 | 一种燃料电池气体扩散层结构 |
CN106876743A (zh) * | 2017-03-16 | 2017-06-20 | 厦门大学 | 一种燃料电池气体扩散层结构 |
JP2020155386A (ja) * | 2019-03-22 | 2020-09-24 | トヨタ自動車株式会社 | 燃料電池セル |
JP2021072270A (ja) * | 2019-11-01 | 2021-05-06 | 株式会社豊田中央研究所 | 自立型マイクロポーラス層 |
JP7234902B2 (ja) | 2019-11-01 | 2023-03-08 | 株式会社豊田中央研究所 | 自立型マイクロポーラス層 |
Also Published As
Publication number | Publication date |
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CA2879283C (en) | 2020-08-04 |
EP2889939B1 (en) | 2018-07-04 |
US20150207151A1 (en) | 2015-07-23 |
KR102121822B1 (ko) | 2020-06-11 |
JP6206186B2 (ja) | 2017-10-04 |
CA2879283A1 (en) | 2014-02-27 |
KR20150046102A (ko) | 2015-04-29 |
TWI573313B (zh) | 2017-03-01 |
CN104584292B (zh) | 2017-08-22 |
TW201415702A (zh) | 2014-04-16 |
JPWO2014030553A1 (ja) | 2016-07-28 |
EP2889939A1 (en) | 2015-07-01 |
EP2889939A4 (en) | 2016-01-13 |
US9972847B2 (en) | 2018-05-15 |
CN104584292A (zh) | 2015-04-29 |
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