Classifications

• • 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
  • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
• • 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
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
  • H01M8/0625—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material in a modular combined reactor/fuel cell structure
• • 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
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
  • H01M8/0656—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants by electrochemical means
• • 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 is suitable for a fuel cell including an anode catalyst layer to which vaporized fuel obtained by vaporizing liquid fuel is supplied.
• Fuel cells have the advantage that they can generate electricity simply by supplying fuel and oxidant, and can generate electricity continuously by replenishing and replacing only the fuel. For this reason, if the size can be reduced, it can be said that the system is extremely advantageous for the operation of portable electronic devices.
• the direct methanol fuel cell can be miniaturized because it has high energy density and uses methanol as the fuel, and can extract current directly on the methanol-powered electrocatalyst.
• the fuel is easier to handle than hydrogen gas fuel.
• DMFC fuel supply methods include gas supply type DMFC that vaporizes liquid fuel and feeds it into the fuel cell with a force blower, etc., and liquid supply type DMFC that sends liquid fuel directly into the fuel cell with a pump or the like, An internal vaporization type DMFC that vaporizes liquid fuel in a cell is known.
• JP-A-2003-132931 and JP-A-2003-346862 relate to a liquid supply type D MFC.
• a reaction product storage chamber for storing a reaction product (water) generated by power generation is provided on the negative electrode separator side, and unreacted methanol is contained in a container having the reaction product storage chamber.
• a catalyst for detoxifying harmful substances such as by-product formaldehyde formic acid is arranged.
• 2003-346862 discloses that a catalyst for oxidizing these as a means for removing formaldehyde, formic acid, carbon monoxide, and the like produced by incomplete oxidation of fuel is used as a negative electrode current collector. It discloses disposing at the carbon dioxide outlet.
• organic substances for example, methanol, formaldehyde, etc.
• An object of the present invention is to prevent organic substances from flowing out.
• it is suitable for a fuel cell having a fuel vaporization means for supplying a vaporized component of a liquid fuel to an anode catalyst layer.
• a fuel cell according to the present invention comprises a force sword
• a proton conducting membrane disposed between the force sword and the anode
• An oxidation catalyst layer having an oxidation catalyst disposed on a side opposite to the surface of the force sword facing the proton conductive membrane and oxidizing an organic substance;
• FIG. 1 is a schematic cross-sectional view showing a direct methanol fuel cell according to a first embodiment of the present invention.
• FIG. 2 is a schematic cross-sectional view showing a direct methanol fuel cell according to a second embodiment of the present invention.
• the fuel vaporization means power Of the vaporized fuel supplied to the anode, most of organic components such as methanol are consumed by power generation, but some of them are intermediates (for example, formaldehyde) by partial oxidation or the like. Such as ketones, carboxylic acids such as formic acid) or permeate the power sword in its original form.
• An oxidation catalyst layer with an oxidation catalyst that oxidizes organic substances is placed on the opposite side of the force sword opposite to the proton conductive membrane, so that methanol and these intermediates are oxidized and harmless by the catalytic reaction. It is possible to prevent the organic matter from flowing out of the cell.
• the fuel cell of the present invention is particularly effective for a fuel cell in which fuel is supplied to the anode by a fuel vaporization unit that supplies a vaporized component of liquid fuel.
• a moisturizing plate is disposed between the oxidation catalyst layer and the force sword to suppress the evaporation of water generated in the force sword, and an insulating layer is disposed on the opposite surface of the oxidation catalyst layer. Therefore, it is possible to avoid a decrease in the cell voltage due to the oxidation catalyst layer and to promote water diffusion from the power sword to the anode, thereby improving the output characteristics of the fuel cell. Can do.
• FIG. 1 is a schematic cross-sectional view showing a direct methanol fuel cell according to the first embodiment of the present invention.
• a membrane electrode assembly (MEA) 1 includes a force sword composed of a force sword catalyst layer 2 and a force sword gas diffusion layer 4, an anode catalyst layer 3 and an anode gas diffusion layer 5.
• the node and the proton conductive electrolyte membrane 6 disposed between the force sword catalyst layer 2 and the anode catalyst layer 3 are omitted.
• Examples of the catalyst contained in the force sword catalyst layer 2 and the anode catalyst layer 3 include platinum group element simple metals (Pt, Ru, Rh, Ir, Os, Pd, etc.) and platinum group elements. Alloys can be mentioned. It is desirable to use Pt—Ru, which is highly resistant to methanol and carbon monoxide, as the anode catalyst, and platinum as the power sword catalyst, but it is not limited to this. Further, a supported catalyst using a conductive support such as a carbon material may be used, or an unsupported catalyst may be used.
• Proton conductive materials constituting the proton conductive electrolyte membrane 6 include, for example, a fluorine-based resin having a sulfonic acid group (for example, a perfluorosulfonic acid polymer) and a hydrate having a sulfonic acid group. Mouth carbon-based resin, inorganic such as tungstic acid and phosphotungstic acid Forces including things etc. It is not limited to these.
• the force sword catalyst layer 2 is laminated on the force sword gas diffusion layer 4, and the anode catalyst layer 3 is laminated on the anode gas diffusion layer 5.
• the force sword gas diffusion layer 4 plays a role of uniformly supplying the oxidizing agent to the force sword catalyst layer 2, but also serves as a current collector for the force sword catalyst layer 2.
• the anode gas diffusion layer 5 serves to uniformly supply fuel to the anode catalyst layer 3 and also serves as a current collector for the anode catalyst layer 3.
• the force sword conductive layer 7a and the anode conductive layer 7b are in contact with the force sword gas diffusion layer 4 and the anode gas diffusion layer 5, respectively.
• porous layers for example, meshes
• a rectangular frame-shaped force sword seal material 8 a is located between the force sword conductive layer 7 a and the proton conductive electrolyte membrane 6 and surrounds the force sword catalyst layer 2 and the force sword gas diffusion layer 4. Yes.
• the rectangular frame-shaped anode sealing material 8b is located between the anode conductive layer 7b and the proton conductive electrolyte membrane 6, and surrounds the anode catalyst layer 3 and the anode gas diffusion layer 5.
• the force sword seal material 8a and the anode seal material 8b are O-rings for preventing fuel leakage and oxidant leakage from the membrane electrode assembly 1.
• a liquid fuel tank 9 is disposed below the membrane electrode assembly 1.
• liquid methanol or aqueous methanol solution is accommodated.
• the fuel vaporization means selectively permeates a vaporized component of liquid fuel (hereinafter referred to as vaporized fuel) and supplies it to the anode.
• a gas-liquid separation membrane 10 that allows only vaporized fuel to permeate but does not allow liquid fuel to permeate is disposed as fuel vaporization means.
• the vaporized fuel means vaporized methanol when liquid methanol is used as the liquid fuel.
• the vaporized component of methanol and the vaporized component of water are used. It means mixed gas.
• a frame 11 made of resin is laminated.
• the space surrounded by the frame 11 functions as a vaporized fuel storage chamber 12 (so-called vapor reservoir) that temporarily stores the vaporized fuel that has diffused through the gas-liquid separation membrane 10. Due to the effect of suppressing the amount of permeated methanol in the vaporized fuel storage chamber 12 and the gas-liquid separation membrane 10, a large amount is obtained at once. It is possible to prevent the vaporized fuel from being supplied to the anode catalyst layer 3 and to suppress the occurrence of methanol crossover.
• the frame 11 is a rectangular frame, and is formed from a thermoplastic polyester resin such as PET (polyethylene terephthalate).
• an oxidation catalyst layer 14 is laminated on the force sword conductive layer 7 a laminated on the upper part of the membrane electrode assembly 1 via an insulating layer 13.
• the oxidation catalyst layer 14 includes an acid catalyst for acidifying organic substances derived from gas fuel that has not been consumed by power generation.
• organic substances include unused methanol and methanol intermediates (eg, ketones such as formaldehyde, carboxylic acids such as formic acid, etc.).
• the catalyst having such a function that it is desirable to convert these organic substances into acid and harmless water and diacid carbon by catalytic reaction include the above-mentioned power sword catalyst and anode catalyst. .
• an anode catalyst such as a Pt—Ru alloy is desirable.
• the type of oxidation catalyst used can be one or more. Further, a supported catalyst in which the catalyst is supported on a fine powder may be used, or an unsupported catalyst may be used.
• the oxidation catalyst layer 14 is formed, for example, by supporting a mixture containing an acid catalyst and a binder on a porous plate.
• the insulating layer 13 is for insulating the acid catalyst layer 14 and the force sword. As a result, it is possible to avoid the generation of a hybrid potential between the acid catalyst layer 14 and the force sword, thereby preventing the voltage characteristics of the fuel cell from being impaired.
• the insulating layer 13 is formed of a porous insulating plate so as not to impair air diffusion. Examples of the insulating material forming the insulating plate include a porous body having a resin skeleton such as polyethylene and polypropylene, and a porous plate made of ceramics such as alumina and silica.
• a moisturizing plate 15 is laminated on the acid catalyst layer 14.
• the moisturizing plate 15 serves to suppress the transpiration of the water generated in the force sword catalyst layer 2 and uniformly introduces an oxidizing agent into the force sword gas diffusion layer 4 to thereby oxidize the force sword catalyst layer 2. It also plays a role as an auxiliary diffusion layer that promotes uniform diffusion.
• the moisturizing plate 15 is preferably made of an insulating material that is inert to methanol and resistant to dissolution.
• an insulating material include polyethylene and polypropylene. Polyolefins such as ren can be mentioned.
• the moisture retention plate 15 has an air permeability specified by JIS P-8117-1998 of 50 seconds ZlOOcm 3 or less. This is because if the air permeability exceeds 50 seconds / 100 cm 3 , the air inlet 16 force may interfere with the air diffusion to the force sword, and high output may not be obtained. A more preferable range of the air permeability is 10 seconds or less ZlOOcm 3 .
• the moisture retention plate 15 has a water vapor transmission rate of 6000 gZm as defined by the JIS L-1099-1993 A-1 method.
• the value of moisture permeability is JIS L-1099-1993.
• the temperature value is 40 ⁇ 2 ° C. This is because if the water vapor permeability exceeds 60 00 gZm 2 24h, the amount of water evaporated from the power sword increases, and the effect of promoting water diffusion to the power sword force anode may not be obtained sufficiently. Also, if the moisture permeability is less than 500gZm 2 24h, excess water may be supplied to the anode and high output may not be obtained, so the moisture permeability is in the range of 500 to 6000gZm 2 24h. That force S is desirable. A more preferable range of moisture permeability is 1000 to 4000 gZm 2 24 h.
• a cover 17 on which a plurality of air inlets 16 for taking in air as an oxidant is formed is laminated on the moisture retaining plate 15. Since the cover 17 also plays a role of increasing the adhesion by pressing the stack including the membrane electrode assembly 1, the cover 17 is formed of a metal such as SUS304, for example.
• the liquid fuel for example, aqueous methanol solution
• the liquid fuel tank 9 is vaporized, and the vaporized methanol and water are discharged.
• the gas-liquid separation membrane 10 is diffused, temporarily stored in the vaporized fuel storage chamber 12, and then gradually diffused through the anode gas diffusion layer 5 and supplied to the anode catalyst layer 3, and methanol shown in the following reaction formula (1) The internal reforming reaction occurs.
• the air taken in from the air inlet 16 of the cover 17 diffuses through the moisture retention plate 15, the oxidation catalyst layer 14, the insulating layer 13 and the power sword gas diffusion layer 4 and is supplied to the force sword catalyst layer 2.
• water is generated by the reaction shown in the following formula (2).
• the moisturizing plate 15 since the water retention from the power sword to the anode can be promoted by the moisturizing plate 15, a high output is obtained even when a methanol aqueous solution or a pure methanol having a concentration exceeding 50 mol% is used as the liquid fuel. Characteristics can be obtained. Furthermore, the liquid fuel tank can be reduced in size by using these high-concentration liquid fuels.
• the purity of pure methanol is desirably 95% by weight or more and 100% by weight or less.
• the moisturizing plate 15 is disposed outside the oxidation catalyst layer 14, the methanol and the intermediate in the oxidation catalyst layer 14 are dissolved in water without being oxidized and flow backward to the power sword. Can be suppressed.
• the arrangement of the insulating layer, the oxidation catalyst layer, and the moisture retention plate is different from that of the direct methanol fuel cell according to the first embodiment described above.
• the moisturizing plate 15 is laminated on the force sword conductive layer 7 a laminated on the upper part of the membrane electrode assembly 1.
• the oxidation catalyst layer 14 is disposed on the moisture retention plate 15.
• the cover 17 is laminated on the oxidation catalyst layer 14 via the insulating layer 18.
• the oxidation catalyst layer 14 is disposed outside the moisture retention plate 15, and water is generated by a catalytic reaction in the oxidation catalyst layer 14, the evaporation of water from the moisture retention plate 15 is suppressed. be able to. As a result, the force sword force can further improve the return of water to the anode, so that the cell characteristics can be further improved.
• the insulating layer 18 is for insulating the acid catalyst layer 14 and the metal cover 17.
• the insulating layer 18 is preferably formed from a porous insulating plate so as not to impair air diffusion! Examples of the insulating material forming the insulating plate include the same materials as those described in the first embodiment.
• the obtained paste was applied to porous carbon paper as an anode gas diffusion layer to obtain an anode having a thickness of 450 ⁇ m.
• a paste was prepared by adding a perfluorocarbonsulfonic acid solution, water and methoxypropanol to a power sword catalyst (Pt) -supported carbon black, and dispersing the catalyst-supported carbon black.
• the obtained paste was applied to porous carbon paper as a force sword gas diffusion layer to obtain a force sword having a thickness of 400 m.
• a perfluorocarbon sulfonic acid membrane (nafion membrane, having a thickness of 30 ⁇ m and a water content of 10 to 20% by weight as a proton conductive electrolyte membrane between the anode catalyst layer and the force sword catalyst layer.
• Membrane / electrode assembly (ME A) was obtained by placing them and subjecting them to hot pressing.
• An oxidation catalyst layer was produced by the method described below.
• PTFE polytetrafluoroethylene
• rayon as a binder was added to the same type of catalyst as the anode catalyst, kneaded, and formed into a 5 m thick sheet.
• the obtained sheet was pressure-bonded to a porous force single-bon paper having a thickness of 50 m to obtain an acid catalyst layer.
• a polypropylene porous film having a thickness of 50 ⁇ m was prepared.
• the frame is made of PET and has a thickness of 25 ⁇ m.
• a 200 ⁇ m thick silicone rubber sheet was prepared as a gas-liquid separation membrane.
• a direct methanol fuel cell having the same configuration as that described in Example 1 was prepared except that the insulating layer was not provided.
• a direct methanol fuel cell having the same configuration as that described in Example 3 was prepared except that the insulating layer was not provided.
• a direct methanol fuel cell having the same configuration as described in Example 1 was prepared except that the type of catalyst used in the oxidation catalyst layer was changed to platinum (Pt).
• a direct methanol fuel cell having the same configuration as described in Example 1 was prepared except that the type of catalyst used in the oxidation catalyst layer was changed to Ir Ru.
• An internal vaporization type direct methanol fuel cell was assembled in the same manner as described in Example 1 except that the acid catalyst layer and the insulating layer were not provided.
• Example 1 has a higher cell voltage.
• the voltage drop is suppressed by providing an insulating layer between the acid catalyst layer and the force sword.
• the same tendency was obtained in Examples 3 and 4 in which the arrangement of the oxidation catalyst layer was different from that in Example 1.

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• 2006
  • 2006-09-15 WO PCT/JP2006/318418 patent/WO2007034756A1/ja not_active Ceased
  • 2006-09-15 US US12/067,743 patent/US20100203427A1/en not_active Abandoned
  • 2006-09-15 JP JP2007536476A patent/JPWO2007034756A1/ja active Pending
  • 2006-09-21 TW TW095134966A patent/TW200740016A/zh not_active IP Right Cessation

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