WO2011096355A1 - 固体高分子型燃料電池用膜電極構造体および固体高分子型燃料電池 - Google Patents
固体高分子型燃料電池用膜電極構造体および固体高分子型燃料電池 Download PDFInfo
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- WO2011096355A1 WO2011096355A1 PCT/JP2011/051899 JP2011051899W WO2011096355A1 WO 2011096355 A1 WO2011096355 A1 WO 2011096355A1 JP 2011051899 W JP2011051899 W JP 2011051899W WO 2011096355 A1 WO2011096355 A1 WO 2011096355A1
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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
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
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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
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
- H01M8/1025—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon and oxygen, e.g. polyethers, sulfonated polyetheretherketones [S-PEEK], sulfonated polysaccharides, sulfonated celluloses or sulfonated polyesters
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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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
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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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1067—Polymeric electrolyte materials characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
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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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
- H01M2250/20—Fuel cells in motive systems, e.g. vehicle, ship, plane
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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
- H01M8/0247—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the form
- H01M8/0254—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the form corrugated or undulated
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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
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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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/40—Application of hydrogen technology to transportation, e.g. using fuel cells
Definitions
- the present invention relates to a membrane electrode structure for a polymer electrolyte fuel cell and a polymer electrolyte fuel cell using the same.
- Fuel cells generate power using hydrogen and oxygen as reaction gases, and since the product produced by the electrode reaction is only water, it has come to be widely used as a clean power generation system with almost no adverse impact on the environment. I came. Its main applications are diverse, such as fuel cell vehicles, household fuel cells, and mobile devices.
- the polymer electrolyte fuel cell (PEFC) has an operating temperature of about room temperature to about 90 ° C. and can generate electric power quickly. Therefore, it is frequently used in fuel cell vehicles.
- the internal environment of a polymer electrolyte fuel cell used in a fuel cell vehicle, particularly in the vicinity of an electrode (hereinafter, the proton conductive membrane, the electrode catalyst layer, and the gas diffusion layer may be collectively referred to in this manner (see FIG. 3 of the present application). ).
- the electrode for example, immediately after the start of the polymer electrolyte fuel cell or when the humidifier cannot keep up with the amount of power generated, it becomes highly dry, and if the operation continues for a while after the start, the electrochemical reaction will proceed. Water is generated in the electrode catalyst layer, resulting in a highly moist state. If the polymer electrolyte fuel cell continues to generate electricity in a highly dry state, the ionic conductivity of the proton conducting membrane (electrolyte membrane) will decrease and the resistance will increase, resulting in reduced power generation performance. Then, the pores of the gas diffusion layer and the electrode catalyst layer are prevented and the reaction gas is inhibited, so that the power generation performance is lowered.
- the proton conducting membrane electrolyte membrane
- Patent Documents 1 to 3 disclose techniques that can reduce the influence of changes in the humidity environment on solid polymer fuel cells.
- a cathode (air electrode) 620 having a catalyst layer 622, an intermediate layer 624, and a gas diffusion layer 626 in order, a catalyst layer 632, an intermediate layer 634, and a gas diffusion layer 636 are sequentially provided.
- a polymer electrolyte corresponding to the proton conducting membrane 2 (see FIG. 3 of the present application) disposed between the anode (fuel electrode) 630, the catalyst layer 622 of the cathode 620, and the catalyst layer 632 of the anode 630.
- a membrane electrode assembly 610 for a polymer electrolyte fuel cell provided with a membrane 640 is described.
- At least one of the catalyst layers 622 and 632 of the cathode 620 and the anode 630 includes a catalyst containing platinum, and the intermediate layers 624 and 634 include carbon fibers, and at least one of them includes ( a) The condition that the ratio of platinum contained in the intermediate layer is 3 to 20 atomic% with respect to 100 atomic% of the total amount of platinum contained in the catalyst layer and platinum contained in the intermediate layer, and (b) At least one of the conditions in which 90 atomic% or more of platinum contained in the intermediate layer exists in a region from the interface between the catalyst layer and the intermediate layer to 1 ⁇ 2 of the thickness of the intermediate layer is satisfied. It is stated that it is necessary. Further, it is described that platinum is preferably a supported catalyst in which platinum or a platinum alloy is supported on a carbon support.
- Patent Document 2 As shown in FIG. 7, on the cathode side of an electrolyte membrane 715 corresponding to the proton conducting membrane 2 in the present invention (see FIG. 3 of the present application), a cathode catalyst layer 716, a cathode underlayer 717, A cathode diffusion layer 718 is laminated, an oxygen gas flow path 724 is provided outside the cathode diffusion layer 718, and an anode catalyst layer 721, an anode base layer 722, and an anode diffusion layer 723 are laminated on the anode side of the electrolyte membrane 715, A fuel cell membrane electrode assembly 712 is described in which a hydrogen gas flow path 725 is provided outside the diffusion layer 723 and each layer and the electrolyte membrane 715 are arranged in a direction in which gravity acts.
- the cathode underlayer 717 describes that a water absorbing material is added and that Nafion (registered trademark) is specifically used as the water absorbing material, and that the water absorbing material functions as an adhesive
- Patent Document 3 As shown in FIG. 8, a fuel electrode (anode) 808 and an air electrode (cathode) 817 which are electrodes used in a fuel cell 810 and include a fuel electrode side catalyst layer 804 and a diffusion layer 805. A fuel cell electrode is described.
- the air electrode 817 includes a first catalyst layer 813a, a second catalyst layer 813b, and an electrolyte membrane 802 corresponding to the proton conducting membrane 2 (see FIG. 3 of the present application) in the present invention.
- the first catalyst layer 813a has a higher gas movement resistance than the second catalyst layer 813b, and the first catalyst layer 813a moves the hydrogen that has passed through the electrolyte membrane 802.
- the first catalyst layer 813a is a layer containing a Pt-supported carbon catalyst
- the second catalyst layer 813b is a noble metal nanoparticle 51 according to the present invention (see FIG. 3 of the present application).
- JP 2009-199915 A (Claim 1, paragraph 0007, paragraph 0014, paragraph 0028, paragraph 0033, FIG. 1)
- JP 2006-107752 (Claim 1, paragraph 0027, paragraph 0068, FIG. 2)
- Japanese Patent No. 4492037 (Claim 1, paragraph 0018, paragraph 0019, FIG. 5, FIG. 6)
- the platinum contained in the catalyst layer and the intermediate layer of Patent Document 1 has a high affinity with water and a small contact angle with water, it can retain water due to the nature of platinum. Since the form contained in the layer, that is, the shape and size, is unknown and cannot be said to be appropriate, it absorbs water from the proton conducting membrane (electrolyte membrane) when the vicinity of the electrode is in a high humidity state. It is not possible to ensure that the humidity condition is high and the humidity condition is good by supplying water to the proton conducting membrane when the vicinity of the electrode is in a highly dry state. There was a problem.
- Patent Document 2 since a water absorbing material is added to the cathode underlayer 717, as in Patent Document 1, water generated by power generation is quickly absorbed, and the humidity near the electrode is reduced. Although it can be lowered, there is a problem that it is difficult to supply water once absorbed to the proton conducting membrane when the vicinity of the electrode becomes highly dry.
- Patent Documents 1 and 2 still do not solve the conventional problem that the power generation performance becomes unstable due to the change in the power generation environment, that is, the change in the humidity conditions near the electrodes.
- the present invention has been made to solve the above-mentioned problem, and even if there is a change in the power generation environment, that is, a change in the humidity conditions near the electrode, the power generation performance is not likely to be unstable, the initial performance is high, and the It is an object of the present invention to provide a membrane electrode structure for a polymer electrolyte fuel cell that can suppress performance degradation due to use, and a polymer electrolyte fuel cell using the same.
- the present inventors have absorbed water into the proton conducting membrane when the vicinity of the electrode becomes highly dry in the power generation environment of the polymer electrolyte fuel cell, and the vicinity of the electrode is highly wetted. It is ideal to dehydrate from the proton conducting membrane when it reaches the state, and in order to realize this, an intermediate layer serving as a water buffer is provided between the electrode catalyst layer and the gas diffusion layer.
- the functions required for the intermediate layer to be provided firstly, the water storage capacity for supplying and dehydrating water is large, and secondly, there is little volume change due to the power generation environment in order to reliably supply water.
- a membrane electrode structure for a polymer electrolyte fuel cell according to the present invention that solves the above-described problems is a proton conductive membrane that conducts protons, an electrode that is provided on both sides of the proton conductive membrane, and that has catalyst particles and an electrode electrolyte.
- a membrane electrode structure for a polymer electrolyte fuel cell comprising: a catalyst layer; and a gas diffusion layer provided on the electrode catalyst layer and having a porous base material, wherein at least one of the electrode catalyst layers An intermediate layer having noble metal nanoparticles, an electrode electrolyte, and carbon powder and having a thickness of 2 to 6 ⁇ m is provided between the gas diffusion layer and the gas diffusion layer.
- the noble metal nanoparticles (for example, platinum black) included in the intermediate layer are nanoparticles having a small particle diameter, the surface area is remarkably large as compared with the case where the same amount of noble metal particles that are not nanoparticles are included.
- the noble metal nanoparticles 51 such as platinum black have a high affinity with the water W and a small contact angle with the water W as compared with carbon black or the like, so that a large amount of the water W is physically attached to the surface. (See FIG. 1A).
- water-absorbing material WA such as Nafion (registered trademark) and conventionally used electrode electrolytes, it does not adsorb water W between molecules (see FIG. 1B). There is no change, and water absorption and dehydration can be performed quickly and in large quantities on the electrode catalyst layer.
- the membrane electrode structure for a polymer electrolyte fuel cell according to the present invention has noble metal nanoparticles (not shown in FIG. 2A) in the intermediate layer 5, FIG. As shown, the water W held by the noble metal nanoparticles when the vicinity of the electrode is in a highly dry state can be supplied (supplied) from the intermediate layer 5 to the electrode catalyst layer 3 and the proton conducting membrane 2. The proton conductivity of the conductive membrane 2 can be increased.
- the membrane electrode structure for a polymer electrolyte fuel cell according to the present invention has noble metal nanoparticles (not shown in FIG. 2B) in the intermediate layer 5, so that FIG.
- the water W generated in the electrode catalyst layer 3 when the vicinity of the electrode is in a highly wet state can be drawn into the intermediate layer 5 to dehydrate the electrode catalyst layer 3. Therefore, it is possible to suppress a decrease in power generation performance (decrease in cell voltage) and deterioration of the electrode catalyst layer 3 due to the pores of the electrode catalyst layer 3 being blocked by water generated by power generation.
- the intermediate layer contains carbon powder, the gas diffusibility in the intermediate layer and the gas permeability to the electrode catalyst layer can be kept good. And since the thickness of an intermediate
- the membrane electrode structure for a polymer electrolyte fuel cell according to the present invention can stably generate power in a wide humidity range, and there is a change in power generation environment, that is, a change in humidity conditions near the electrode.
- power generation performance is unlikely to be unstable.
- the initial performance is high, and performance degradation due to long-term use can be suppressed.
- At least one of the electrode catalyst layer and the intermediate layer has fibrous carbon.
- the fibrous carbon included in at least one of the electrode catalyst layer and the intermediate layer serves as a support column, the layer having fibrous carbon can impart more pores.
- the reaction gas of the layer having fibrous carbon and the water generated by power generation can be easily entered and exited, and the power generation characteristics are improved.
- the proton conductive membrane is preferably a sulfonated polyarylene polymer. Since the sulfonated polyarylene polymer has a large change in proton conductivity performance depending on the amount of water retained, the effect of improving the power generation characteristics can be further obtained.
- the proton exchange membrane preferably has an ion exchange capacity IEC of 1.9 to 2.4 meq / g. If the ion exchange capacity IEC of the proton conducting membrane is in such a specific range, the water content of the proton conducting membrane can be sufficiently secured, so that power generation characteristics at low humidity can be maintained and the moisture content is excessive. Therefore, flooding can be suppressed and power generation characteristics at high humidity can be maintained.
- the content of the noble metal nanoparticles is preferably 0.1 to 0.5 mg / cm 2 in unit projected area.
- the noble metal nanoparticles having the above-described features can be contained in a sufficient amount. Therefore, as described above, when the vicinity of the electrode is in a highly dry state, the water retained by the noble metal nanoparticles can be supplied (supplied) to the electrode catalyst layer 3 and the proton conducting membrane 4, and the proton conduction Not only can the proton conductivity of the membrane 4 be improved, but also performance degradation due to long-term use can be suppressed.
- the content of the carbon powder is preferably 15 to 45% by mass with respect to the content of the noble metal nanoparticles. If the content of the carbon powder is in such a specific range, the pores in the intermediate layer can be sufficiently secured, so that the gas diffusibility in the intermediate layer and the gas permeability to the electrode catalyst layer are improved. be able to. Therefore, not only can the initial performance be improved, but also the performance degradation due to long-term use can be suppressed.
- the content of the electrode electrolyte is preferably 20 to 25% by mass with respect to the content of the noble metal nanoparticles.
- the content of the electrode electrolyte is in such a specific range, a sufficient amount of the electrode electrolyte is contained, so that protons can be reliably conducted. Therefore, the initial performance can be increased.
- the average particle diameter of the noble metal nanoparticles is preferably 4 to 7 nm.
- the average particle diameter of the noble metal nanoparticles is in such a specific range, the noble metal nanoparticles are difficult to elute even when the specific surface area of the noble metal nanoparticles is large and a high potential is generated. Therefore, the initial performance can be further enhanced, and the performance degradation due to long-term use can be suppressed.
- the polymer electrolyte fuel cell according to the present invention is a polymer electrolyte fuel cell using the membrane electrode structure for a polymer electrolyte fuel cell described above, and the membrane electrode structure for a polymer electrolyte fuel cell. And a separator provided between adjacent membrane electrode structures for a polymer electrolyte fuel cell, and the separator is arranged vertically, and the separator introduces a gas introduction unit so as to flow a reaction gas in the vertical direction. Is formed in the upper part, and the gas outlet part is formed in the lower part.
- the polymer electrolyte fuel cell according to the present invention uses the membrane electrode structure for a polymer electrolyte fuel cell described above, and has noble metal nanoparticles, an electrode electrolyte, and carbon powder in an intermediate layer, Since an intermediate layer with a thickness of 2 to 6 ⁇ m is provided, power can be generated stably over a wide range of humidity, and power generation performance is not affected even if the power generation environment changes, that is, the humidity conditions near the electrodes. It is difficult to become stable. Further, the initial performance is high, and performance degradation due to long-term use can be suppressed.
- the membrane electrode structure for the polymer electrolyte fuel cell and the separator are arranged vertically, and the gas introduction part is formed in the upper part of the separator, and the gas outlet part is formed in the lower part. Water flows downward by gravity and is discharged from the gas outlet. Therefore, an excessively high wet state can be prevented, and the pores of the electrode catalyst layer and the intermediate layer can be prevented from being clogged with water. As a result, the polymer electrolyte fuel cell according to the present invention can stably generate power in a wide humidity range.
- an intermediate layer having noble metal nanoparticles, an electrode electrolyte, and carbon powder and having a thickness of 2 to 6 ⁇ m is provided in the intermediate layer. Therefore, the water produced
- the polymer electrolyte fuel cell according to the present invention has the membrane electrode structure for a polymer electrolyte fuel cell described above, and is disposed vertically together with the separator, so that it can stably generate power in a wide humidity range. Even if there is a change in the power generation environment, that is, a change in the humidity conditions near the electrodes, the power generation performance is unlikely to become unstable. Further, the initial performance is high, and performance degradation due to long-term use can be suppressed.
- FIG. (A) is explanatory drawing which shows a mode that the noble metal nanoparticle (platinum black) has adhered water
- (b) is a description which shows a mode that the conventional water absorbing material has adsorbed water between molecules.
- FIG. (A) is explanatory drawing explaining the effect
- (b) is the polymer electrolyte fuel concerning this invention in a wet state
- FIG. 7 It is a cross-sectional schematic diagram explaining the structure of the polymer electrolyte fuel cell which concerns on this invention.
- (A) And (b) is a top view explaining the separator used in Example 7 and Comparative Example 7.
- FIG. It is sectional drawing which shows an example of the conventional membrane electrode structure for polymer electrolyte fuel cells. It is sectional drawing which shows another example of the conventional membrane electrode structure for polymer electrolyte fuel cells. It is sectional drawing which shows another example of the conventional membrane electrode structure for polymer electrolyte fuel cells.
- a membrane electrode structure 1 for a polymer electrolyte fuel cell includes a proton conducting membrane 2, an electrode catalyst layer 3, and a gas diffusion layer 4, and at least one of the electrode catalysts. Between the layer 3 and the gas diffusion layer 4, an intermediate layer 5 having noble metal nanoparticles 51, an electrode electrolyte 52, and carbon powder (not shown in FIG. 3) and having a thickness of 2 to 6 ⁇ m is provided. It has a provided structure.
- the intermediate layers 5a and 5b are provided between the gas diffusion layer 4b and the anode gas AnG.
- the proton conducting membrane 2 is a membrane that can conduct proton H + .
- a conventionally known solid polymer electrolyte membrane can be used.
- a sulfonated polyarylene polymer represented by the following formula (1), a fluorine-containing ion exchange resin, or the like can be used.
- the sulfonated polyarylene polymer represented by the following formula (1) can be produced by the method described in paragraphs [0066] to [0079] of JP-A-2005-158265.
- the ion exchange capacity IEC of the proton conducting membrane 2 is preferably 1.9 to 2.4 meq / g. If the ion exchange capacity IEC of the proton conducting membrane is in such a specific range, the water content of the proton conducting membrane 2 can be sufficiently secured, so that the power generation characteristics at low humidity can be maintained and the water content can be reduced. Since it is not excessive, flooding can be suppressed and the power generation characteristics at high humidity can be maintained.
- the electrode catalyst layer 3 is provided on both surfaces of the proton conducting membrane 2 and has catalyst particles and an electrode electrolyte.
- the catalyst particles used for the electrode catalyst layer 3 it is preferable to use a noble metal that is chemically stable and has good electrical conductivity, or a carbon or an oxide carrying a noble metal.
- a noble metal that is chemically stable and has good electrical conductivity
- a carbon or an oxide carrying a noble metal for example, Pt (platinum), palladium, or an alloy with another metal containing these can be used.
- the application amount of the catalyst particles can be, for example, 0.2 to 0.5 mg / cm 2, but is not limited thereto.
- a conventionally known ion conductive resin can be used.
- ion conductive resin Nafion (registered trademark) which is a perfluorocarbon material composed of a perfluoro side chain having a carbon-fluorine skeleton and a sulfonic acid group can be used.
- the electrode catalyst layer 3 may contain a base material for ensuring pores and functioning as a support column together with the above-described catalyst particles and the electrode electrolyte.
- a substrate for example, fibrous carbon such as vapor grown carbon fiber can be used.
- the electrode catalyst layer 3 is made uniform by stirring after adding an arbitrary solvent, for example, a solvent in which NPA (normal propyl alcohol) and water are mixed at a mass ratio of 1: 2 to 2: 1. This is formed by screen-printing on a PET film, etc., heating and drying, then bringing the coated surface into close contact with the proton conducting membrane 2 and hot-pressing and integrating, and then peeling off the PET sheet can do.
- an arbitrary solvent for example, a solvent in which NPA (normal propyl alcohol) and water are mixed at a mass ratio of 1: 2 to 2: 1.
- the electrode catalyst layer 3a functioning as the cathode Ca and the electrode catalyst layer 3b functioning as the anode An can be prepared by using the same composition and method, or can be prepared by using different compositions and methods. It can also be used.
- the gas diffusion layer 4 is provided on the electrode catalyst layer 3 directly or via an intermediate layer 5 as described later, and has a porous substrate.
- a porous substrate for example, carbon paper, carbon cloth, carbon felt or the like can be used. These porous substrates may be used alone, or may be subjected to a water repellent treatment by attaching a fluororesin, or may be subjected to a hydrophilic treatment with titanium oxide, silicone, metal, or the like.
- the gas diffusion layer 4 may form a base layer (not shown) having a water-repellent fluororesin and carbon having water repellency and conductivity alone or in combination, and the surface of the gas diffusion layer 4 is water-repellent.
- Water repellent treatment may be carried out with a solution or dispersion containing a fluororesin or carbon having water repellency and conductivity.
- water-repellent fluororesin for example, polytetrafluoroethylene (PTFE) can be used
- carbon having water repellency and conductivity for example, carbon black can be used.
- the gas diffusion layer 4 is made of, for example, a mixture of carbon having water repellency and conductivity and a water repellent fluororesin at an arbitrary mass ratio, and then uniformly dispersed in ethylene glycol or the like to form a porous group such as carbon paper. It can produce as a gas diffusion layer with a foundation layer by making it dry after apply
- the intermediate layer 5 having noble metal nanoparticles 51, an electrode electrolyte 52, and carbon powder (not shown in FIG. 3) and having a thickness of 2 to 6 ⁇ m is provided.
- the thickness of the intermediate layer 5 is less than 2 ⁇ m, a sufficient amount of the noble metal nanoparticles 51 cannot be contained. For this reason, it is not possible to suppress a decrease in performance due to long-term use.
- the thickness of the intermediate layer 5 exceeds 6 ⁇ m, gas diffusibility in the intermediate layer 5 is hindered, so that the initial performance is deteriorated. Therefore, the thickness of the intermediate layer 5 is 2 to 6 ⁇ m.
- middle layer 5 can be measured by analysis of the cross-sectional image with an electron microscope, for example.
- the noble metal nanoparticles 51 include Pt—Co, Pt—Fe, Pt—Zn, Pt—Cu, Pt—Ni, Pt—Ru, Pt—V, Pt—Pd, Pt—Ir, Pt—Lu, Au—Pd. Nanoparticles made of an alloy such as or an alloy containing two or more selected from these, or nanoparticles made of a metal element such as Pd, Au, Ru, Fe, Co, etc. can be used. Most preferably, (Pt) is used.
- Platinum black is also called platinum black or platinum black.
- E. PtBlack powder (BL-1901) manufactured by CHEMCAT (Hi-spec 1000), Hi-spec1000 manufactured by Johnson Matthey, etc. can be used.
- platinum black can also select and use 1 type selected from these, and can also select and use 2 or more types together.
- Platinum black has excellent oxidation resistance among the noble metal nanoparticles, and not only excels in power generation by assisting the action of the electrode catalyst layer 3, but also conducts electrons e ⁇ as shown in FIG. Since it functions as a conductive path and has a low ionization tendency and is difficult to elute, it is suitable as the noble metal nanoparticles 51.
- the content of the noble metal nanoparticles 51 is preferably 0.05 to 1 mg / cm 2 in unit projected area.
- the unit projected area is a size that serves as a reference in evaluating performance with current density.
- the content of the noble metal nanoparticles 51 is less than 0.05 mg / cm 2 in unit projected area, when the vicinity of the electrode is in a highly dry state, water can be absorbed quickly and in large quantities with respect to the electrode catalyst layer, When the vicinity of the electrode is in a highly wet state, the electrode catalyst layer cannot be dehydrated quickly and in large quantities.
- the effect obtained even when the content of the noble metal nanoparticles 51 exceeds 1 mg / cm 2 in unit projected area is not preferable because the effect is not only saturated but also the cost increases. Therefore, the content of the noble metal nanoparticles 51 is preferably 0.05 to 1 mg / cm 2 in unit projected area.
- the content of the noble metal nanoparticles 51 in the intermediate layer 5a used on the cathode Ca side in the intermediate layer 5 is preferably 0.1 to 0.5 mg / cm 2 in unit projected area.
- the content of the noble metal nanoparticles 51 in the intermediate layer 5a used on the cathode Ca side is within this range, in addition to the above-described action, it is possible to suppress performance degradation due to long-term use.
- the content of the noble metal nanoparticles 51 of the intermediate layer 5a used on the cathode Ca side is less than 0.1 mg / cm 2 in unit projected area, a sufficient amount of the noble metal nanoparticles 51 cannot be contained. It becomes difficult to suppress performance degradation due to long-term use.
- the content of the noble metal nanoparticles 51 in the intermediate layer 5a used on the cathode Ca side exceeds 0.5 mg / cm 2 in unit projected area, the thickness of the intermediate layer 5 increases, and thus the electrode catalyst layer 3a has a large thickness. Gas permeability is lowered and initial performance is degraded. Therefore, the content of the noble metal nanoparticles 51 in the intermediate layer 5a used on the cathode Ca side in the intermediate layer 5 is preferably 0.1 to 0.5 mg / cm 2 in unit projected area.
- the average particle diameter of the noble metal nanoparticles 51 is preferably 4 to 20 nm, for example. If the average particle diameter of the noble metal nanoparticles 51 is in this range, when the vicinity of the electrode is in a highly dry state, the effect of absorbing water quickly and in large quantities with respect to the electrode catalyst layer, or the vicinity of the electrode is in a highly wet state. The effect of dehydrating the electrode catalyst layer quickly and in large quantities can be more reliably obtained. Moreover, since the specific surface area is large, the activity is high, and the noble metal nanoparticles 51 are not easily eluted even when a high potential is generated, it is possible to suppress the performance deterioration due to long-term use.
- the average particle diameter of the noble metal nanoparticles 51 is less than 4 nm, the noble metal nanoparticles 51 are likely to be eluted when a high potential is generated, and the initial performance may be deteriorated by use.
- the average particle diameter of the noble metal nanoparticles 51 exceeds 20 nm, the specific surface area is decreased and the water absorption performance is lowered. It is not possible to obtain the effect of absorbing water and the effect of dehydrating the electrode catalyst layer quickly and in large quantities when the vicinity of the electrode is in a highly wet state. Therefore, even if there is a change in the power generation environment, that is, a change in the humidity conditions near the electrodes, the power generation performance tends to be unstable. Therefore, the average particle diameter of the noble metal nanoparticles 51 is preferably 4 to 20 nm.
- the average particle diameter of the noble metal nanoparticles 51 used in the intermediate layer 5a on the cathode Ca side in the intermediate layer 5 is preferably 4 to 7 nm.
- the average particle diameter of the noble metal nanoparticles 51 used for the intermediate layer 5a on the cathode Ca side is within this range, the specific surface area is large, the activity is high, and the noble metal nanoparticles 51 are not easily eluted even when a high potential is generated. , Performance degradation due to long-term use can be suppressed.
- the average particle diameter of the noble metal nanoparticles 51 used for the intermediate layer 5a on the cathode Ca side is less than 4 nm, the specific surface area increases and the activity is improved, so that the initial performance is expected to be improved.
- the average particle diameter of the noble metal nanoparticles 51 used for the intermediate layer 5a on the cathode Ca side is preferably 4 to 7 nm.
- the same electrode electrolyte as that of the electrode catalyst layer 3 can be used, or a different one can be used.
- an electrode electrolyte (ion conductive polymer) used for the electrode electrolyte 52 for example, powder and dispersion solution of Nafion (registered trademark) manufactured by DuPont, Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd., manufactured by Asahi Glass Co., Ltd. Mention may be made of Flemion® powders and dispersions.
- the electrode electrolyte used for the electrode electrolyte 52 one selected from these can be selected and used, or two or more can be selected and used together.
- the content of the electrode electrolyte 52 is preferably 20 to 25% by mass with respect to the content of the noble metal nanoparticles 51.
- the content of the electrode electrolyte 52 is within this range, a sufficient amount of the electrode electrolyte is contained, so that protons can be reliably conducted. Therefore, the initial performance can be increased.
- the content of the electrode electrolyte 52 is less than 20% by mass with respect to the content of the noble metal nanoparticles 51, the conduction of proton H + becomes insufficient and the initial performance is deteriorated.
- the noble metal nanoparticles 51 and the carbon powder cannot be bound, they fall off and it is difficult to form the intermediate layer 5.
- the content of the electrode electrolyte 52 exceeds 25% by mass with respect to the content of the noble metal nanoparticles 51, the pores in the intermediate layer 5 become insufficient. Therefore, the gas diffusibility in the intermediate layer 5 and the gas permeability to the electrode catalyst layer 3 are lowered, and the initial performance is lowered. Therefore, the content of the electrode electrolyte 52 is preferably 20 to 25% by mass with respect to the content of the noble metal nanoparticles 51.
- the electrode electrolyte 52 contains a carbon powder (not shown in FIG. 3), that is, carbon black.
- a carbon powder (not shown in FIG. 3), that is, carbon black.
- Examples of the carbon powder include furnace black, acetylene black, glassy carbon pulverized products, vapor grown carbon fibers, and those obtained by graphitizing them.
- furnace black include Ketjen Black EC, Ketjen Black EC-600JD, Cabot Vulcan (registered trademark) XC-72, Tokai Carbon Co., Ltd. Toka Black (trade name).
- Examples of acetylene black include Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo Kabushiki Kaisha.
- Examples of vapor grown carbon fibers include VGCF (registered trademark) and VGCF (registered trademark)- H can be mentioned.
- the carbon powder used for the electrode electrolyte 52 can be used by selecting one type selected from these, or two or more types can be selected and used together. Among these, it is preferable to use fibrous carbon such as vapor-grown carbon fiber in order to secure pores and function as a support column.
- the content of the carbon powder is preferably 15 to 45% by mass with respect to the content of the noble metal nanoparticles 51.
- the pores in the intermediate layer 5 can be sufficiently secured, so that the gas diffusibility in the intermediate layer 5 and the gas permeability to the electrode catalyst layer 3 are improved. Can do. Therefore, not only can the initial performance be improved, but also a decrease in performance due to long-term use can be suppressed.
- the content of the carbon powder is less than 15% by mass with respect to the content of the noble metal nanoparticles 51, the pores in the intermediate layer 5 are insufficient. Therefore, the gas diffusibility in the intermediate layer 5 and the gas permeability to the electrode catalyst layer 3 are lowered, and the initial performance is lowered.
- the carbon corrodes when a high potential is generated, the ratio of the electrode electrolyte 52 is increased, and the hydrophilicity is increased.
- the content of the carbon powder exceeds 45% by mass with respect to the content of the noble metal nanoparticles 51, the intermediate layer 5 becomes thick and the gas permeability to the electrode catalyst layer 3 is lowered, so that the initial performance is descend. Therefore, the content of the carbon powder is preferably 15 to 45% by mass with respect to the content of the noble metal nanoparticles 51.
- the polymer electrolyte fuel cell 10 includes a membrane electrode structure 1 for a polymer electrolyte fuel cell described above and a membrane electrode structure for an adjacent polymer electrolyte fuel cell (not shown).
- a plurality of separators 11 provided between the bodies are arranged vertically.
- the separator 11 has a gas introduction part formed at the upper part and a gas outlet part formed at the lower part so that the reaction gas flows in the vertical direction.
- the membrane electrode structure 1 for a polymer electrolyte fuel cell and the separator 11 are arranged vertically as described above, the water generated in the electrode catalyst layer 3 is pushed downward because a gas flow and gravity act on it, It is easily discharged out of the system. As a result, the membrane electrode structure 1 for a polymer electrolyte fuel cell tends to be in a highly dry state.
- the intermediate layer 5 is configured using the membrane electrode structure 1 for the polymer electrolyte fuel cell having the noble metal nanoparticles 51 in the intermediate layer 5. Sufficient water can be retained. Therefore, even when the membrane electrode structure 1 for a polymer electrolyte fuel cell and the separator 11 are arranged vertically, it is difficult to achieve a highly dry state.
- a membrane electrode structure for a polymer electrolyte fuel cell and a polymer electrolyte fuel cell according to the present invention are specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention. I will explain it.
- Example 1 A membrane electrode structure for a polymer electrolyte fuel cell of Example 1 was produced as follows (1) to (7).
- (1) Preparation of proton conducting membrane A proton conducting membrane was prepared according to the method described in paragraph [0066] to paragraph [0079] of JP-A-2005-158265. Specifically, it was prepared as follows.
- Preparation of the compound represented by the formula (2) was performed as follows. First, 137.3 g (400 mmol) of 2,5-dichloro-4′-phenoxybenzophenone was added to a 3 l (3 liter) three-necked flask equipped with a stirrer and a condenser tube, and then 500 ml of 1,2-dichloroethane was added and dissolved. I let you. Further, a 2 mol / l acetylsulfuric acid solution newly prepared from 56 ml of concentrated sulfuric acid, 152 ml of acetic anhydride and 400 ml of 1,2-dichloroethane was added with stirring, and the mixture was reacted in an oil bath at 60 ° C.
- Preparation of the compound represented by the formula (3) was performed as follows. First, 300 ml of acetonitrile and 200 ml of sulfolane as solvents were added to 215 g (about 400 mmol) of crude sodium salt of 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonic acid, and phosphoryl trichloride 245. 3 g (1.6 mol) was added and reacted at 70 ° C. Further, 5 ml of N, N-dimethylacetamide was added and the yellow suspension was stirred at 71-73 ° C. for 40 minutes and cooled to 3 ° C.
- Preparation of the oligomer represented by Formula (5) was performed as follows. First, 2,2-bis (4-hydroxyphenyl) -1,1,1,3 was added to a 1-liter three-necked flask equipped with a stirrer, thermometer, cooling tube, Dean-Stark tube, and three-way cock for introducing nitrogen.
- Preparation of the sulfonated polyarylene represented by the formula (6) was performed as follows. First, 15.34 g (32 mmol) of iso-butyl 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonate represented by the formula (4), an oligomer represented by the formula (5) (Average molecular weight 7940) 10.52 g (1.33 mmol), bis (triphenylphosphine) nickel dichloride 0.65 g (1 mmol), triphenylphosphine 33.50 g (13.33 mmol), sodium iodide 0.65 g ( 4.83 mmol) and 5.45 g (83.33 mmol) of zinc dust were added 60 ml of dry N-methylpyrrolidone under a nitrogen atmosphere.
- the reaction system was heated with stirring, finally heated to 74 ° C., and reacted for 3 hours. During the reaction, an increase in viscosity in the reaction system was observed.
- the obtained polymerization reaction solution was diluted with 250 ml of tetrahydrofuran, stirred for 30 minutes, filtered using Celite as a filter aid, and then the filtrate was poured into a large excess of methanol (1500 ml) to be solidified.
- the coagulated product was collected by filtration, air-dried, redissolved in a mixed solvent of 200 ml of tetrahydrofuran / 30 ml of N-methylpyrrolidone, and then coagulated and precipitated with a large excess of methanol (1500 ml). After air-drying, it was heat-dried to obtain 20.54 g (yellow flaky, yield 78%) of the sulfonated polyarylene represented by the target formula (6).
- the light green transparent solution was cast into a glass plate to form a film.
- the membrane was immersed in water for 3 days, air-dried, and vacuum-dried to obtain a proton conductive membrane having a dry film thickness of 50 ⁇ m (shown as PEM species “HC system” in Table 2 described later).
- the ion exchange capacity IEC of the obtained proton conducting membrane was measured by a neutralization titration method and found to be 2.2 meq / g (milli equivalent / g).
- anode electrode ink was screen-printed on a PET film so that the amount of platinum was 0.2 mg / cm 2 , heated at 60 ° C. for 10 minutes, and then heated at 100 ° C. for 15 minutes under reduced pressure. Then, an anode electrode sheet (electrode catalyst layer) was produced by drying.
- the mixed solution was stirred and homogenized using a planetary ball mill at 80 rpm ⁇ 60 minutes to prepare an intermediate layer ink.
- the prepared intermediate layer ink was applied by screen printing on the base layer portion of the gas diffusion layer prepared in (5) so that the amount of platinum was 0.2 mg / cm 2 in unit projected area, and dried to be intermediate. A layer was made.
- Comparative Example 1 was produced by the same composition and method as Example 1 except that platinum black powder was not used in the production of the intermediate layer of (1) of Example 1.
- Example 2 is an example of iso-butyl 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonate represented by the above formula (5) in the preparation of the proton conducting membrane of Example 1 (1).
- An MEA was produced in the same manner as in Example 1 except that the amount was changed to 13.04 g.
- Comparative Example 2 was produced by the same composition and method as Example 2 except that platinum black powder was not used in producing the intermediate layer of Example 1 (6).
- Example 3 is an example of iso-butyl 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonate represented by the above formula (5) in the preparation of the proton conducting membrane of (1) of Example 1.
- An MEA was produced in the same manner as in Example 1 except that the weight was changed to 11.82 g.
- Comparative Example 3 was produced by the same composition and method as Example 3 except that platinum black powder was not used in producing the intermediate layer of Example 1 (6).
- Example 4 is an example of iso-butyl 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonate represented by the above formula (5) in the preparation of the proton conducting membrane of (1) of Example 1.
- An MEA was produced in the same manner as in Example 1 except that the weight was changed to 16.87 g.
- Comparative Example 4 was produced by the same composition and method as Example 4 except that platinum black powder was not used in producing the intermediate layer of Example 1 (6).
- Example 5 is an example of iso-butyl 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonate represented by the above formula (5) in the preparation of the proton conducting membrane of (1) of Example 1.
- a MEA was produced in the same manner as in Example 1 except that the weight was changed to 17.64 g.
- Comparative Example 5 was prepared by the same composition and method as Example 5 except that platinum black powder was not used in the preparation of the intermediate layer of Example 1 (6).
- Example 6 in the preparation of the proton conducting membrane of Example 1 (1), a commercially available fluorine-based electrolyte membrane (Nafion (registered trademark) N112 manufactured by DuPont) was used as the proton conducting membrane (PEM in Table 2 below).
- An MEA was prepared in the same manner as in Example 1 except that it was referred to as “F-type”.
- Comparative Example 6 was produced by the same composition and method as Example 6 except that platinum black powder was not used in producing the intermediate layer of Example 1 (6). Note that Nafion (registered trademark) N112 manufactured by DuPont was used as the proton conductive membrane.
- Example 7 was placed vertically between the separators 11 shown in FIGS. 5A and 5B using the same MEA as in Example 1 (that is, vertically arranged) (PEM species in Table 2 below) It is indicated as “HC system; vertical”). In addition, it installed so that the gas introduction part 11a of the reactive gas might be located in the upper part of the separator 11, and it installed so that the gas derivation
- Comparative Example 7 was the same as Example 7 except that platinum black powder was not used in the production of the intermediate layer (6) of Example 1.
- Comparative Example 8 an MEA was produced in the same manner as in Example 1 except that the production of the intermediate layer (6) in Example 1 was performed as follows.
- a solvent having a mass ratio of NPA to water of 1: 2 was prepared, and 18 g of platinum-supported carbon powder (catalyst for fuel cell TEC10EA30E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was added to 50 g of this solvent. Further, 3 g of vapor grown carbon fiber (manufactured by Showa Denko KK, trade name: VGCF) was added.
- an ion conductive resin solution (20% solution, manufactured by DuPont, trade name: DE2020) was added and stirred for 10 minutes with a three-dimensional stirrer. Thereafter, the mixed solution was stirred and homogenized using a planetary ball mill at 80 rpm ⁇ 60 minutes to prepare an intermediate layer ink.
- the produced intermediate layer ink was screen-printed on the base layer portion of the gas diffusion layer produced by the same method as in Example 1 (5) so that the platinum amount was 0.2 mg / cm 2 in unit projected area.
- the intermediate layer was produced by coating and drying.
- the gas pressures of the anode gas and the cathode gas were both 100 kPa, and the humidification conditions of these reaction gases were 50/50% Rh, 75/75% Rh, and 100/100% Rh, respectively, at the anode / cathode. Then, the cell voltage at the time of power generation at a current density of 1 A / cm 2 was read under each humidification condition, and the standard deviation (mV) of each cell voltage was calculated and used as an index for evaluating the stability of the power generation performance.
- Table 2 below shows the evaluation of the stability of power generation performance.
- the standard deviation (mV) in Table 2 indicates how far from the cell voltage (mV) when the humidity condition of the reaction gas is 75/75% Rh, and this is referred to. This shows the magnitude of the effect of suppressing fluctuation under each humidity condition.
- the ion exchange capacities IEC in Examples 2 to 7 and Comparative Examples 1 to 8 were measured in the same manner as in Example 1 and will be described together.
- the standard deviation was smaller in all examples than in the comparative example indicated by the corresponding number. In other words, it was found that any example had a larger fluctuation suppressing effect than the comparative example.
- those having a low IEC for example, IEC 1.7 meq / g
- Example 7 was found to decrease in voltage due to flooding at high humidity (100/100% Rh). Furthermore, in Example 7, although the cell was placed vertically, it was found that the fluctuation suppressing effect was greater than that of Comparative Example 1. In Comparative Example 8, the voltage at low humidity decreased. This is presumably because the carbon in the platinum-supporting carbon powder has water repellency, so that the generated water was quickly discharged and became dry.
- anode electrode ink was screen-printed on a PET film so that the amount of platinum was 0.2 mg / cm 2 , heated at 60 ° C. for 10 minutes, and then heated at 100 ° C. for 15 minutes under reduced pressure. Then, an anode electrode sheet (electrode catalyst layer) was produced by drying.
- an ion conductive resin solution (20% solution, manufactured by DuPont, trade name: D2020) was added in the amount [g (solution)] shown in Table 3 below, and stirred for 10 minutes with a three-dimensional stirrer. Thereafter, the mixed solution was stirred and homogenized using a planetary ball mill at 80 rpm ⁇ 60 minutes to prepare an intermediate layer ink.
- the produced intermediate layer ink was screen-printed on the base layer portion of the gas diffusion layer produced in (4) so that the amount of platinum was the unit projected area shown in Table 3 below [mg / cm 2 ]. Then, the intermediate layers according to Examples 8 to 10 and Comparative Examples 9 to 12 were produced.
- the cell temperature is set to 70 ° C.
- the anode humidification condition is set to 65% Rh
- the cathode humidification condition is set to 75% Rh
- the gas pressure is set to 100 kPa for every 200 start cycles.
- the cell voltage during power generation at a current density of 1 A / cm 2 was measured. This was performed until the number of activations reached 3000, and the cell voltage drop transition was calculated by linear approximation. The reason why the number of activations is 3000 times is that a cell voltage drop amount of about 40 mV is required to accurately evaluate the performance drop rate, and a cell voltage drop of 40 mV or more has conventionally occurred.
- the initial performance [mV] and performance degradation rate [mV / 1000 times] of Examples 8 to 10 and Comparative Examples 9 to 12 are listed in Table 4.
- 600 mV or more was set as the pass ((circle)), and less than 600 mV was set as the disqualification (x).
- 20 mV / 1000 times or less was set to pass ((circle)), and the thing exceeding 20 mV / 1000 times was set to rejection (x).
- the thickness of the intermediate layer was less than 2 ⁇ m, and the content of platinum black powder (noble metal nanoparticles) was less than 0.1 mg / cm 2 in unit projected area.
- Comparative Example 10 since the thickness of the intermediate layer exceeded 6 ⁇ m and the content of platinum black powder (noble metal nanoparticles) exceeded 0.5 mg / cm 2 in unit projected area, the initial performance was rejected ( ⁇ )
- Comparative Example 11 the thickness of the intermediate layer exceeded 6 ⁇ m, and the content of carbon black (carbon powder) exceeded 45% by mass with respect to the content of platinum black powder (noble metal nanoparticles). The performance was rejected (x).
- the thickness of the intermediate layer was less than 2 ⁇ m, and the content of carbon black (carbon powder) was less than 15% by mass with respect to the content of platinum black powder (noble metal nanoparticles). Both initial performance and performance degradation rate were rejected (x).
- the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.
- the embodiment has shown the form in which the intermediate layer is disposed on both sides of the anode and the cathode, and the form in which the intermediate layer is disposed only on the cathode side. Is obtained.
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Abstract
Description
なお、固体高分子型燃料電池は、高乾燥状態で発電を続けると、プロトン伝導膜(電解質膜)などのイオン導電性が低下して抵抗が大きくなるため発電性能が低下する一方、高湿潤状態となると、ガス拡散層や電極触媒層の細孔を防ぎ、反応ガスを阻害するため発電性能が低下する。
このようにすれば、電極触媒層および中間層のうち少なくとも一方が有する繊維状カーボンが支持柱の役割を果たすため、繊維状カーボンを有する層は、より多くの細孔を付与することができる。その結果、繊維状カーボンを有する層の反応ガスおよび発電により生成した水の出入りが容易になり、発電特性が向上する。
スルホン化ポリアリーレンポリマーは、保水量によるプロトン導電性能の変化が大きいため、発電特性の向上効果をさらに得ることができる。
プロトン伝導膜のイオン交換容量IECをこのような特定の範囲とすれば、プロトン伝導膜の含水量を十分に確保できるため、低湿度での発電特性を維持することができるとともに、含水量が過度ではないため、フラッディングを抑制して、高湿度での発電特性を維持することができる。
貴金属ナノ粒子の含有量をこのような特定の範囲とすれば、前記した特長を有する貴金属ナノ粒子を十分な量で含有させることができる。そのため、前記したように、電極付近が高乾燥状態となったときに、貴金属ナノ粒子が保持している水を電極触媒層3およびプロトン伝導膜4に供給(給水)することができ、プロトン伝導膜4のプロトン伝導性を高めることができるようになるだけでなく、長期間使用による性能低下を抑制することができる。
カーボン粉末の含有量をこのような特定の範囲とすれば、中間層内の細孔を十分に確保することができるため、中間層内のガス拡散性や電極触媒層へのガス透過性を高めることができる。そのため、初期性能を高くすることができるだけでなく、長期間使用による性能低下を抑制することができる。
電極電解質の含有量をこのような特定の範囲とすれば、十分な量の電極電解質を含有するので、プロトンを確実に伝導させることができる。そのため、初期性能を高くすることができる。
貴金属ナノ粒子の平均粒径をこのような特定の範囲とすれば、貴金属ナノ粒子の比表面積が大きくかつ高電位発生時であっても貴金属ナノ粒子が溶出し難い。そのため、より一層、初期性能を高くすることができ、また、長期間使用による性能低下を抑制することができる。
そのため、本発明に係る固体高分子型燃料電池用膜電極構造体によれば、幅広い湿度範囲で安定して発電を行うことができ、発電環境の変化、つまり電極付近の湿度条件の変化があっても発電性能が不安定となり難い。また、初期性能が高く、かつ長期間使用による性能低下を抑制することができる。
はじめに、図3を参照して本発明に係る固体高分子型燃料電池用膜電極構造体について説明する。
以下、各構成について詳細に説明する。
多孔質基材としては、例えば、カーボンペーパー、カーボンクロス、カーボンフェルトなどを用いることができる。これらの多孔質基材は単独の使用の他、フッ素樹脂を付着させて撥水処理を施したり、酸化チタンやシリコーン、金属等によって親水化処理を施したりしてもよい。
下地層を形成したり、ガス拡散層4の表面を撥水処理したりすることにより、電極触媒層3で生成した水が移動し易くなるため、水によってガス拡散層4の細孔が塞がれるのを防止することができる。
一方で、中間層5の厚みが6μmを超えると、中間層5内におけるガス拡散性が妨げられるので、初期性能が低下する。
よって、中間層5の厚みは2~6μmとする。
なお、中間層5の厚みは、例えば電子顕微鏡による断面画像の解析によって測定することができる。
貴金属ナノ粒子51の含有量が、単位投影面積で0.05mg/cm2未満となると、電極付近が高乾燥状態となったときに、電極触媒層に対して迅速かつ大量に吸水することや、電極付近が高湿潤状態となったときに、電極触媒層に対して迅速かつ大量に脱水することができない。
一方、貴金属ナノ粒子51の含有量が、単位投影面積で1mg/cm2を超えても得られる効果は飽和するばかりかコストが上昇し、好ましくない。
よって、貴金属ナノ粒子51の含有量は、単位投影面積で0.05~1mg/cm2とするのが好ましい。
カソードCa側に用いられる中間層5aの貴金属ナノ粒子51の含有量がこの範囲であると、前記した作用に加えて、長期間使用による性能低下を抑制することができるようになる。
カソードCa側に用いられる中間層5aの貴金属ナノ粒子51の含有量が、単位投影面積で0.1mg/cm2未満となると、十分な量の貴金属ナノ粒子51を含有させることができなくなるため、長期間使用による性能低下を抑制することが難しくなる。
一方、カソードCa側に用いられる中間層5aの貴金属ナノ粒子51の含有量が、単位投影面積で0.5mg/cm2を超えると、中間層5の厚みが大きくなるため電極触媒層3aへのガス透過性が低くなり、初期性能が低下する。
よって、中間層5のうち、カソードCa側に用いられる中間層5aの貴金属ナノ粒子51の含有量については、単位投影面積で0.1~0.5mg/cm2とするのが好ましい。
貴金属ナノ粒子51の平均粒径が4nm未満であると、高電位発生時に貴金属ナノ粒子51が溶出し易く、使用により初期性能が低下するおそれがある。
一方、貴金属ナノ粒子51の平均粒径が20nmを超えると、比表面積が減少して吸水性能が低下するため、電極付近が高乾燥状態となったときに、電極触媒層に対して迅速かつ大量に吸水する効果や、電極付近が高湿潤状態となったときに、電極触媒層に対して迅速かつ大量に脱水する効果を得ることができない。そのため、発電環境の変化、つまり電極付近の湿度条件の変化があっても発電性能が不安定となり易い。
よって、貴金属ナノ粒子51の平均粒径は、4~20nmとするのが好ましい。
カソードCa側の中間層5aに用いる貴金属ナノ粒子51の平均粒径がこの範囲であると、比表面積が大きく、活性も高く、高電位発生時であっても貴金属ナノ粒子51が溶出し難いため、長期間使用による性能低下を抑制することができる。
カソードCa側の中間層5aに用いる貴金属ナノ粒子51の平均粒径が4nm未満であると、比表面積が増加し、活性も向上するため初期性能の向上が見込まれるものの、高電位発生時に貴金属ナノ粒子51が溶出し易くなるため、長期間使用による性能低下が進み易い。
一方、カソードCa側の中間層5aに用いる貴金属ナノ粒子51の平均粒径が7nmを超えると、高電位発生時に貴金属ナノ粒子51が溶出し難いため、長期間使用による性能低下が緩和されるものの、比表面積が減少し、活性も低下するため、初期性能が低下する。
よって、カソードCa側の中間層5aに用いる貴金属ナノ粒子51の平均粒径については、4~7nmとするのが好ましい。
電極電解質52に用いられる電極電解質(イオン導電性ポリマー)としては、例えばデュポン社製ナフィオン(登録商標)の粉末および分散溶液、旭化成社製アシプレックス(商品名)の粉末および分散溶液、旭硝子社製フレミオン(登録商標)の粉末および分散溶液を挙げることができる。電極電解質52に用いられる電極電解質は、これらの中から選択される1種を選択して使用することもできるし、2種以上を選択して併用することもできる。
電極電解質52の含有量がこの範囲であると、十分な量の電極電解質を含有するので、プロトンを確実に伝導させることができる。そのため、初期性能を高くすることができる。
電極電解質52の含有量が、貴金属ナノ粒子51の含有量に対して20質量%未満であると、プロトンH+の伝導が不十分となるため初期性能が低下する。また、貴金属ナノ粒子51やカーボン粉末を結着することができないためこれらの脱落が生じ、中間層5を形成することが困難となる。
一方、電極電解質52の含有量が、貴金属ナノ粒子51の含有量に対して25質量%を超えると、中間層5内の細孔が不十分となる。そのため、中間層5内のガス拡散性や電極触媒層3へのガス透過性が低下し、初期性能が低下する。
よって、電極電解質52の含有量は、貴金属ナノ粒子51の含有量に対して20~25質量%とするのが好ましい。
カーボン粉末の含有量がこの範囲であると、中間層5内の細孔を十分に確保することができるため、中間層5内のガス拡散性や電極触媒層3へのガス透過性を高めることができる。そのため、初期性能を高くすることができるだけでなく、長期間使用による性能低下を抑制することができる。
カーボン粉末の含有量が、貴金属ナノ粒子51の含有量に対して15質量%未満となると、中間層5内の細孔が不十分となる。そのため、中間層5内のガス拡散性や電極触媒層3へのガス透過性が低下し、初期性能が低下する。また、高電位発生時にカーボンが腐食するので電極電解質52の比率が高くなり、親水性が高くなるため長期間使用による性能低下が進み易くなる。
一方、カーボン粉末の含有量が、貴金属ナノ粒子51の含有量に対して45質量%を超えると、中間層5が厚くなり、電極触媒層3へのガス透過性が低下するため、初期性能が低下する。
よって、カーボン粉末の含有量は、貴金属ナノ粒子51の含有量に対して15~45質量%とするのが好ましい。
図4に示すように、本発明に係る固体高分子型燃料電池10は、前記した固体高分子型燃料電池用膜電極構造体1と、図示しない隣り合う固体高分子型燃料電池用膜電極構造体の間に挟まれて設けられるセパレータ11と、を鉛直に複数配置してなる。
ここで、セパレータ11は、反応ガスを鉛直方向に流すようにガス導入部を上部に形成するとともに、ガス導出部を下部に形成されている。
[実施例1]
実施例1の固体高分子型燃料電池用膜電極構造体を下記(1)~(7)のようにして作製した。
(1)プロトン伝導膜の準備
プロトン伝導膜は、特開2005-158265号公報の段落[0066]~段落[0079]に記載の方法に従って準備した。具体的には次のようにして準備した。
次に、前記淡緑色透明溶液をガラス板状にキャストして製膜した。製膜後、水中に3日間浸漬し、風乾、真空乾燥し、乾燥膜厚50μmのプロトン伝導膜を得た(後記する表2においてPEM種「HC系」と示す。)。
得られたプロトン伝導膜のイオン交換容量IECを中和滴定法によって測定したところ、2.2meq/g(ミリ当量/g)であった。
まず、NPA(ノルマルプロピルアルコール)と水の比率を質量比で1:2とした溶媒を準備した。この溶媒180gに燃料電池用白金触媒(田中貴金属工業社製、燃料電池用触媒TEC36F52)を30g投入し、さらに気相成長炭素繊維(昭和電工社製、商品名:VGCF)を10g投入した。
その後、イオン導伝性樹脂溶液(20%溶液、デュポン社製、商品名:DE2020)を80g投入し、3次元攪拌機で10分間攪拌した。
その後、この混合溶液に対し、遊星ボールミルを用いて80rpm×120分攪拌して均一化し、カソード電極インクを作製した。
(2)で作製したカソード電極インクの白金量が0.5mg/cm2となるようにPETフィルム上にスクリーン印刷して塗工し、60℃で10分間加熱した後、減圧下、100℃で15分間加熱して、乾燥させることによりカソード電極シート(電極触媒層)を作製した。
まず、NPAと水の比率が質量比で2:1の溶媒を準備した。この溶媒180gに燃料電池用白金触媒(田中貴金属工業社製、燃料電池用触媒TEC36F52)を30g投入し、さらに気相成長炭素繊維(昭和電工社製、商品名:VGCF)を7g投入した。
その後、イオン導伝性樹脂溶液(20%溶液、デュポン社製、商品名:DE2020)を70g投入し、3次元攪拌機で10分間攪拌した。
その後、この混合溶液に対し、遊星ボールミルを用いて80rpm×120分攪拌して均一化し、アノード電極インクを作製した。
作製したアノード電極インクの白金量が0.2mg/cm2となるようにPETフィルム上にスクリーン印刷して塗工し、60℃で10分間加熱した後、減圧下、100℃で15分間加熱して、乾燥させることによりアノード電極シート(電極触媒層)を作製した。
カーボンブラック(三菱化学製ケッチェンブラックEC)とポリテトラフルオロエチレン(PTFE)粒子(三井・デュポンフロロケミカル製テフロン(登録商標)640J)とを4:6の質量比で混合して得られた混合物をエチレングリコールに均一に分散させ、スラリーを作製した。
その後、作製したスラリーを東レ製カーボンペーパーTGP-H060の平坦面に塗布し、乾燥させて下地層を形成し、カーボンペーパーと下地層とからなるガス拡散層を作製した。
NPAと水の比率が質量比で1:2の溶媒を準備した。この溶媒50gに白金ブラック粉末(田中貴金属工業社製燃料電池用触媒TEC90400)を10g投入し、さらに気相成長炭素繊維(昭和電工社製、商品名:VGCF)を2g投入した。なお、白金ブラック粉末の平均粒径は4.6nmだった。
その後、イオン導伝性樹脂溶液(20%溶液、デュポン社製、商品名:DE2020)を10g投入し、3次元攪拌機で10分間攪拌した。
その後、この混合溶液に対し、遊星ボールミルを用いて80rpm×60分攪拌して均一化し、中間層インクを作製した。
作製した中間層インクを、(5)で作製したガス拡散層の下地層部分に白金量が単位投影面積で0.2mg/cm2となるようにスクリーン印刷して塗工し、乾燥させて中間層を作製した。
(1)で作製したプロトン伝導膜を、アノード電極シートの電極塗工面とカソード電極シートの電極塗工面に接するように挟持し、120℃、2.0MPaの条件下、8分間のホットプレスを行い、その後、アノード電極シートおよびカソード電極シートのPETシートを剥がすことでプロトン伝導膜に電極層が形成された接合体(CCM)を作製した。
次に、(6)で作製した中間層を有するガス拡散層を2枚用意し、これらガス拡散層の中間層の間にCCMを挟持して150℃、2.5MPaの条件下、12分間のホットプレスを行って一体化し、固体高分子型燃料電池用膜電極構造体(MEA)を製造した。
比較例1は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例1と同様の組成および手法で作製した。
実施例2は、実施例1の(1)のプロトン伝導膜の準備において、前記式(5)で表される4-〔4-(2,5-ジクロロベンゾイル)フェノキシ〕ベンゼンスルホン酸iso-ブチルを13.04gにした以外は、実施例1と全て同じ手法でMEAを作製した。
比較例2は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例2と同様の組成および手法で作製した。
実施例3は、実施例1の(1)のプロトン伝導膜の準備において、前記式(5)で表される4-〔4-(2,5-ジクロロベンゾイル)フェノキシ〕ベンゼンスルホン酸iso-ブチルを11.82gにした以外は、実施例1と全て同じ手法でMEAを作製した。
比較例3は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例3と同様の組成および手法で作製した。
実施例4は、実施例1の(1)のプロトン伝導膜の準備において、前記式(5)で表される4-〔4-(2,5-ジクロロベンゾイル)フェノキシ〕ベンゼンスルホン酸iso-ブチルを16.87gにした以外は、実施例1と全て同じ手法でMEAを作製した。
比較例4は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例4と同様の組成および手法で作製した。
実施例5は、実施例1の(1)のプロトン伝導膜の準備において、前記式(5)で表される4-〔4-(2,5-ジクロロベンゾイル)フェノキシ〕ベンゼンスルホン酸iso-ブチルを17.64gにした以外は、実施例1と全て同じ手法でMEAを作製した。
比較例5は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例5と同様の組成および手法で作製した。
実施例6は、実施例1の(1)のプロトン伝導膜の準備において、プロトン伝導膜に市販のフッ素系電解質膜(デュポン社製ナフィオン(登録商標)N112)を用いた(下記表2においてPEM種「F系」と示す。)以外は、実施例1と全て同じ手法でMEAを作製した。
比較例6は、実施例1の(6)の中間層の作製で白金ブラック粉末を使用しない以外、実施例6と同様の組成および手法で作製した。
なお、プロトン伝導膜には、デュポン社製ナフィオン(登録商標)N112を用いた。
実施例7は、実施例1と同じMEAを用いて図5(a)および(b)に示すセパレータ11の間に配置して縦置きした(すなわち鉛直に配置した)(下記表2においてPEM種「HC系;縦」と示す。)。なお、セパレータ11の上部に反応ガスのガス導入部11aが位置するように設置するとともに、セパレータ11の下部に反応ガスのガス導出部11bが位置するように設置した。
比較例7は、実施例1の(6)の中間層の作製において、白金ブラック粉末を使用しない以外、実施例7と同様した。
比較例8は、実施例1の(6)の中間層の作製を次のようにした以外は、実施例1と全て同じ手法でMEAを作製した。
比較例8における中間層は、NPAと水の比率が質量比で1:2の溶媒を準備し、この溶媒50gに白金担持カーボン粉末(田中貴金属工業社製燃料電池用触媒TEC10EA30E)を18g投入し、さらに気相成長炭素繊維(昭和電工社製、商品名:VGCF)を3g投入した。
その後、イオン導伝性樹脂溶液(20%溶液、デュポン社製、商品名:DE2020)を20g投入し、3次元攪拌機で10分間攪拌した。
その後、この混合溶液に対し、遊星ボールミルを用いて80rpm×60分攪拌して均一化し、中間層インクを作製した。
作製した中間層インクを、実施例1の(5)と同様の手法で作製したガス拡散層の下地層部分に白金量が単位投影面積で0.2mg/cm2となるようにスクリーン印刷して塗工し、乾燥させて中間層を作製した。
作製した実施例1~7および比較例1~8について、発電性能の安定性の評価を行った。評価は以下の条件にて行った。
発電性能の安定性の評価は、電極面積25cm2(実施例7および比較例7においては電極面積50cm2)としたJARI標準セルにて行った(図5(a)および(b)参照)。セル温度は70℃とし、アノードガスとして純水素を用い、カソードガスとして空気を用い、ガス流は平行流とした。なお、セパレータの材質はカーボンであり、ガス流路の山幅を2mm、溝幅を2mmとした。
アノードガスとカソードガスのガス圧はともに100kPaとし、これらの反応ガスの加湿条件はアノード/カソードでそれぞれ50/50%Rh、75/75%Rhおよび100/100%Rhとした。そして、それぞれの加湿条件にて1A/cm2の電流密度の発電時のセル電圧を読み取り、それぞれのセル電圧の標準偏差(mV)を算出して発電性能の安定性の評価の指標とした。
なお、IECが1.9meq/gのものと2.2meq/gのものは、中間層に白金黒を添加することでセル電圧の変動抑制効果がより大きくなることがわかった。
また、IECが低い(例えばIEC1.7meq/g)ものは、低湿度(50/50%Rh)となると水不足によって導電性が悪化するため電圧が低下すること、およびIECが高い(例えばIEC2.5meq/g)ものは、高湿度(100/100%Rh)となるとフラッディングにより電圧が低下することがわかった。
さらに、実施例7ではセルを縦置きとしたにも関わらず、比較例1よりも変動抑制効果が大きいことがわかった。
また、比較例8は、低湿度における電圧が低下した。これは、白金担持カーボン粉末中のカーボンが撥水性を有するため、生成した水が速やかに排出され、乾燥状態になったことが原因だと考えられる。
次に、カソード側の中間層について、当該中間層の厚み、貴金属ナノ粒子の含有量、カーボン粉末の含有量、電極電解質の含有量、および貴金属ナノ粒子の平均粒径を対象とした好適条件の検討を行った。
かかる好適条件の検討は、下記に示す実施例8~10および比較例9~12を用いて行った。実施例8~10および比較例9~12は下記(1)~(10)のようにして作製した。
NPAと水の比率を質量比で1:2とした溶媒を準備し、当該溶媒を燃料電池用白金触媒(田中貴金属工業社製、燃料電池用触媒TEC36F52)の質量比で10倍量となるように加えた。
その後、イオン導伝性樹脂溶液としてパーフルオロアルキレンスルホン酸高分子化合物(デュポン社製、ナフィオン(登録商標)D2020)溶液を用い、燃料電池用白金触媒:イオン導伝性樹脂溶液中のポリマー分=1:1.5の質量比となるように投入した。
その後、所定のインク粘度となるまで攪拌して得られた混合溶液を、遊星ボールミルを用いて80rpm×120分攪拌して均一化し、カソード電極インクを作製した。
(1)で作製したカソード電極インクの白金量が0.5mg/cm2となるようにPETフィルム上にスクリーン印刷して塗工し、60℃で10分間加熱した後、減圧下、100℃で15分間加熱して、乾燥させることによりカソード電極シート(電極触媒層)を作製した。
NPAと水の比率を質量比で1:2とした溶媒を準備し、当該溶媒を燃料電池用白金触媒(田中貴金属工業社製、燃料電池用触媒TEC10EA50E)の質量比で10倍量となるように加えた。
その後、イオン導伝性樹脂溶液としてパーフルオロアルキレンスルホン酸高分子化合物(デュポン社製、ナフィオン(登録商標)D2020)溶液を用い、燃料電池用白金触媒:イオン導伝性樹脂溶液中のポリマー分=1:1の質量比となるように投入した。
その後、所定のインク粘度となるまで攪拌して得られた混合溶液を、遊星ボールミルを用いて80rpm×120分攪拌して均一化し、アノード電極インクを作製した。
作製したアノード電極インクの白金量が0.2mg/cm2となるようにPETフィルム上にスクリーン印刷して塗工し、60℃で10分間加熱した後、減圧下、100℃で15分間加熱して、乾燥させることによりアノード電極シート(電極触媒層)を作製した。
ガス拡散層は、前記1.(5)ガス拡散層の作製で記載したのと同様にして作製した。
NPAと水の比率が質量比で1:2の溶媒を準備し、この溶媒25gに白金ブラック粉末(田中貴金属工業社製燃料電池用触媒TEC90300)を5g投入した。さらに、カーボンブラック(Cabot社製、商品名:VulcanXC-72)を、下記表3の実施例8~10および比較例9~12に示す量[g]投入した。なお、白金ブラック粉末の平均粒径は4.6nmであった。
その後、イオン導伝性樹脂溶液(20%溶液、デュポン社製、商品名:D2020)を下記表3に示す量[g(溶液)]投入し、3次元攪拌機で10分間攪拌した。
その後、この混合溶液に対し、遊星ボールミルを用いて80rpm×60分攪拌して均一化し、中間層インクを作製した。
作製した中間層インクを、(4)で作製したガス拡散層の下地層部分に白金量が単位投影面積で下記表3に示す量[mg/cm2]となるようにスクリーン印刷して塗工し、乾燥させて、実施例8~10および比較例9~12に係る中間層を作製した。
プロトン伝導膜は、市販のフッ素系電解質膜(デュポン社製ナフィオン(登録商標)N112)を用いた。
当該プロトン伝導膜を、アノード電極シートの電極塗工面とカソード電極シートの電極塗工面に接するように挟持し、120℃、2.0MPaの条件下、8分間のホットプレスを行い、その後、アノード電極シートおよびカソード電極シートのPETシートを剥がすことでプロトン伝導膜に電極層が形成された接合体(CCM)を作製した。
次に、(5)で作製した実施例8~10および比較例9~12に係る中間層をそれぞれ1枚用意し、これらのアノード側ガス拡散層、CCM、前記(5)で作製した中間層(カソード側中間層)、カソード側ガス拡散層の順に積層して150℃、2.5MPaの条件下、12分間のホットプレスを行って一体化し、固体高分子型燃料電池用膜電極構造体(MEA)を製造した。
なお、電子顕微鏡による断面写真を解析することによりMEAの中間層の厚みを測定したところ、その厚み[μm]は下記表3に示すとおりとなった。
実施例8~10および比較例9~12について、初期のセル電圧[mV]を測定するとともに、所定回数起動した後の電圧低下推移を線形近似で算出した。それぞれ、初期性能および性能低下速度として後記する表4に記載する。
なお、初期性能の測定および性能低下速度の算出は次のようにして行った。
なお、起動回数を3000回としたのは、性能低下速度を精度よく評価するためには40mV程度のセル電圧低下量が必要とされており、従来40mV以上のセル電圧低下が発生していた3000回の起動を実施することにより、長期間使用による性能低下を的確に判断できると考えられたためである。
実施例8~10および比較例9~12の初期性能[mV]および性能低下速度[mV/1000回]として表4に記載する。
なお、表4に示す初期性能については、600mV以上を合格(○)、600mV未満を不合格(×)とした。また、性能低下速度については、20mV/1000回以下を合格(○)、20mV/1000回を超えるものを不合格(×)とした。
一方、比較例9~12は、本発明の要件のうちの少なくとも1つを満たさないため、初期性能および性能低下速度うちの少なくとも一方の結果が不合格となった。
比較例10は、中間層の厚みが6μmを超えており、白金ブラック粉末(貴金属ナノ粒子)の含有量が単位投影面積で0.5mg/cm2を超えていたため、初期性能が不合格(×)となった。
比較例11は、中間層の厚みが6μmを超えており、カーボンブラック(カーボン粉末)の含有量が、白金ブラック粉末(貴金属ナノ粒子)の含有量に対して45質量%を超えていたため、初期性能が不合格(×)となった。
また、比較例12は、中間層の厚みが2μm未満であり、カーボンブラック(カーボン粉末)の含有量が、白金ブラック粉末(貴金属ナノ粒子)の含有量に対して15質量%未満であったため、初期性能および性能低下速度の両方が不合格(×)となった。
例えば、実施形態として中間層をアノード、カソード両側に配置した形態、カソード側にのみ配置した形態を示したが、アノード側のみに配置をしても前記形態ほどではないにしても本発明の効果は得られる。
2 プロトン伝導膜
3 電極触媒層
4 ガス拡散層
5 中間層
51 貴金属ナノ粒子
52 電極電解質
10 固体高分子型燃料電池
Claims (9)
- プロトンを伝導するプロトン伝導膜と、
前記プロトン伝導膜の両面に設けられ、触媒粒子と電極電解質とを有する電極触媒層と、
前記電極触媒層の上に設けられ、多孔質基材を有するガス拡散層と、
を備えた固体高分子型燃料電池用膜電極構造体であって、
少なくとも一方の前記電極触媒層と前記ガス拡散層との間に、貴金属ナノ粒子と、電極電解質と、カーボン粉末と、を有し、厚みが2~6μmである中間層を設けた
ことを特徴とする固体高分子型燃料電池用膜電極構造体。 - 前記電極触媒層および前記中間層のうち少なくとも一方が繊維状カーボンを有することを特徴とする請求の範囲第1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記プロトン伝導膜がスルホン化ポリアリーレンポリマーであることを特徴とする請求の範囲第1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記プロトン伝導膜のイオン交換容量IECが1.9~2.4meq/gであることを特徴とする請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記貴金属ナノ粒子の含有量が単位投影面積で0.1~0.5mg/cm2であることを特徴とする請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記カーボン粉末の含有量が、前記貴金属ナノ粒子の含有量に対して15~45質量%であることを特徴とする請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記電極電解質の含有量が、前記貴金属ナノ粒子の含有量に対して20~25質量%であることを特徴とする請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体。
- 前記貴金属ナノ粒子の平均粒径が4~7nmであることを特徴とする請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体。
- 請求の範囲第1項から請求の範囲第3項のうちのいずれか1項に記載の固体高分子型燃料電池用膜電極構造体を用いた固体高分子型燃料電池であって、
前記固体高分子型燃料電池用膜電極構造体と、隣り合う前記固体高分子型燃料電池用膜電極構造体の間に挟まれて設けられるセパレータと、を鉛直に配置し、かつ
前記セパレータは、反応ガスを鉛直方向に流すようにガス導入部を上部に形成するとともに、ガス導出部を下部に形成した
ことを特徴とする固体高分子型燃料電池。
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US10851237B2 (en) | 2016-08-05 | 2020-12-01 | Japan Science And Technology Agency | Block copolymer, multilayered structure, solid polymer membrane, fuel cell, method for producing multilayered structure, and method for producing multilayered structure including inorganic nanoparticles |
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US9716279B2 (en) * | 2013-05-15 | 2017-07-25 | Brookhaven Science Associates, Llc | Core-shell fuel cell electrodes |
JP6427215B2 (ja) * | 2017-03-07 | 2018-11-21 | 本田技研工業株式会社 | 固体高分子型燃料電池用フィルム成形品のプレス加工方法及びプレス加工装置 |
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