CA1171903A - Fuel cell - Google Patents
Fuel cellInfo
- Publication number
- CA1171903A CA1171903A CA000398513A CA398513A CA1171903A CA 1171903 A CA1171903 A CA 1171903A CA 000398513 A CA000398513 A CA 000398513A CA 398513 A CA398513 A CA 398513A CA 1171903 A CA1171903 A CA 1171903A
- Authority
- CA
- Canada
- Prior art keywords
- fuel cell
- matrix
- phosphoric acid
- cell according
- gas diffusion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000446 fuel Substances 0.000 title claims abstract description 42
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 102
- 239000011159 matrix material Substances 0.000 claims abstract description 57
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 51
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 27
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 27
- 238000009792 diffusion process Methods 0.000 claims abstract description 19
- 239000011230 binding agent Substances 0.000 claims abstract description 16
- 239000003792 electrolyte Substances 0.000 claims abstract description 11
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 10
- 229910052726 zirconium Inorganic materials 0.000 claims description 10
- 229910052845 zircon Inorganic materials 0.000 claims description 8
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical group [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 claims description 8
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 6
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 6
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 6
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 229910001887 tin oxide Inorganic materials 0.000 claims description 5
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 claims description 4
- QHGNHLZPVBIIPX-UHFFFAOYSA-N tin(ii) oxide Chemical class [Sn]=O QHGNHLZPVBIIPX-UHFFFAOYSA-N 0.000 claims description 4
- 229940058401 polytetrafluoroethylene Drugs 0.000 claims 2
- 230000015556 catabolic process Effects 0.000 abstract description 3
- 238000006731 degradation reaction Methods 0.000 abstract description 3
- 238000009413 insulation Methods 0.000 abstract description 3
- 239000007789 gas Substances 0.000 description 13
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 12
- 229910010271 silicon carbide Inorganic materials 0.000 description 12
- 239000002245 particle Substances 0.000 description 8
- 229910019142 PO4 Inorganic materials 0.000 description 6
- 229920001568 phenolic resin Polymers 0.000 description 6
- 239000005011 phenolic resin Substances 0.000 description 6
- 235000021317 phosphate Nutrition 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 5
- 239000004811 fluoropolymer Substances 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 4
- 239000010452 phosphate Substances 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 229920002313 fluoropolymer Polymers 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000005871 repellent Substances 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 239000004094 surface-active agent Substances 0.000 description 3
- 238000007864 suspending Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000004812 Fluorinated ethylene propylene Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229920009441 perflouroethylene propylene Polymers 0.000 description 2
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000001846 repelling effect Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
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
- H01M8/02—Details
- H01M8/0289—Means for holding the electrolyte
- H01M8/0293—Matrices for immobilising electrolyte solutions
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0002—Aqueous electrolytes
- H01M2300/0005—Acid electrolytes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/44—Fibrous material
-
- 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
- Y02E60/10—Energy storage using batteries
-
- 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
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Fuel Cell (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A fuel cell comprising a pair of gas diffu-sion electrodes, an electrolyte retaining matrix disposed between said gas diffusion electrodes, and a phosphoric acid electrolyte disposed within said matrix, characterized by using as matrix that compris-ing one or more metal oxides having electronic insula-tion and insolubility in phosphoric acid and a binder is excellent in phosphoric acid retaining ability and can be used for a long period of time without degrada-tion of the performance of fuel cell.
A fuel cell comprising a pair of gas diffu-sion electrodes, an electrolyte retaining matrix disposed between said gas diffusion electrodes, and a phosphoric acid electrolyte disposed within said matrix, characterized by using as matrix that compris-ing one or more metal oxides having electronic insula-tion and insolubility in phosphoric acid and a binder is excellent in phosphoric acid retaining ability and can be used for a long period of time without degrada-tion of the performance of fuel cell.
Description
~719~3 l This invention relates to a fuel cell using liquid phosphoric acid as electrolyte, particularly to a fuel cell having a structure wherein a matrix retaining phosphoric acid is disposed between a pair of gas diffusion electrodes.
As the matrix for retaining the electrolyte in a phosphoric acid fuel cell, there have been used phenolic resin fiber cloth, a material obtained by binding silicon carbide particles with a water-repellent binder, and the like. A fuel cell having such a matrix is disclosed in U.S. Patent No. 4,017,664. According to said U.S. patent, the difficulty with a phenollc resin type of matrix is that over a long period of time there is a reaction between the phosphoric acid and the organic material at temperatures greater than about 250F~ and the reaction produces a molecule which adsorbs onto the electrode catalyst and poisons the catalyst, resulting in performance degradation. On the other hand, when there is used a matrix made from silicon carbide particles and a water-repellent binder, the above-mentioned problem taking place in the case of using the phenolic resin matrix does not take place according to said U.S. patent, which is not completely satisfactory for retaining phosphoric acid.
It is an ob~ect of this invention to provide 1 1~7~9~3 a fuel cell having a matrix which is superior in retaining phosphoric acid to silicon carbide.
This invention provides a fuel cell comprising a paix of gas diffusion electrodes, a matrix for retaining phosphoric acid electrolyte disposed between said gas diffusion electrodes, characterized in that said matrix consists essentially of one or more metal oxides which are electron-insulative and insoluble in phosphoric acid and selected from complex oxides containing zirconium, titanium oxides and tin oxides, and one or more binders.
In the attached drawings, FIG. 1 is a cross-sectional view of a fuel cell having the special matrix according to this invention, each of FIGS. 2, 4 and 6 is a graph showing a relationship between a current density and a voltage in fuel cells using the matrix according to this invention and a conventional matrix, and each of FIGS. 3, 5 and 7 is a graph showing a relationship between an operation time and a voltage in fuel cells using the matrix according to this invention and a conventional matrix.
This invention is explained referring to FIG. 1.
The fuel cell of this invention comprises a pair of spaced apart gas diffusion electrodes 2 and 3, and disposed therein a matrix 1 retaining phosphoric acid. Said one pair of gas diffusion electrodes and the matrix are disposed in a pair of conventional separators 4 and 5. The gas diffusion electrodes may be conventional ones and can be obtained, for example, by coating carbon powders supporting platinum on a 11719(13 1 carbon paper. In the gas diffusion electrodes, numeral
As the matrix for retaining the electrolyte in a phosphoric acid fuel cell, there have been used phenolic resin fiber cloth, a material obtained by binding silicon carbide particles with a water-repellent binder, and the like. A fuel cell having such a matrix is disclosed in U.S. Patent No. 4,017,664. According to said U.S. patent, the difficulty with a phenollc resin type of matrix is that over a long period of time there is a reaction between the phosphoric acid and the organic material at temperatures greater than about 250F~ and the reaction produces a molecule which adsorbs onto the electrode catalyst and poisons the catalyst, resulting in performance degradation. On the other hand, when there is used a matrix made from silicon carbide particles and a water-repellent binder, the above-mentioned problem taking place in the case of using the phenolic resin matrix does not take place according to said U.S. patent, which is not completely satisfactory for retaining phosphoric acid.
It is an ob~ect of this invention to provide 1 1~7~9~3 a fuel cell having a matrix which is superior in retaining phosphoric acid to silicon carbide.
This invention provides a fuel cell comprising a paix of gas diffusion electrodes, a matrix for retaining phosphoric acid electrolyte disposed between said gas diffusion electrodes, characterized in that said matrix consists essentially of one or more metal oxides which are electron-insulative and insoluble in phosphoric acid and selected from complex oxides containing zirconium, titanium oxides and tin oxides, and one or more binders.
In the attached drawings, FIG. 1 is a cross-sectional view of a fuel cell having the special matrix according to this invention, each of FIGS. 2, 4 and 6 is a graph showing a relationship between a current density and a voltage in fuel cells using the matrix according to this invention and a conventional matrix, and each of FIGS. 3, 5 and 7 is a graph showing a relationship between an operation time and a voltage in fuel cells using the matrix according to this invention and a conventional matrix.
This invention is explained referring to FIG. 1.
The fuel cell of this invention comprises a pair of spaced apart gas diffusion electrodes 2 and 3, and disposed therein a matrix 1 retaining phosphoric acid. Said one pair of gas diffusion electrodes and the matrix are disposed in a pair of conventional separators 4 and 5. The gas diffusion electrodes may be conventional ones and can be obtained, for example, by coating carbon powders supporting platinum on a 11719(13 1 carbon paper. In the gas diffusion electrodes, numeral
2 denotes an anode (a ruel electrode) and numeral 3 dentoes a cathode (an air electrode) and the anode 2 is so designed as to contact with hydrogen and the cathode 3 is so designed as to contact with air.
As for the matrix for retaining phosphoric acid as the electrolyte, it must have the following properties, which are also disclosed in U.S. Patent No. 4,017,664: (1) it is stable against the phosphoric acid at high temperatures (190 - 200C), that is~
it is not soluble in the phosphoric acid; (2) it has a larger phosphoric acid retaining ability; and (3) it has no electronic conductivity (i.e., it is an electronic insulator).
If the matrix is soluble in phosphoric acid, the properties of phosphoric acid as the electrolyte are damaged and the matrix dissolved in the phosphoric acid migrates to the electrode sides, which has a bad influence upon the properties of the electrodes.
Further, if the matrix has electronic conductivity, there takes place a short-circuit within the fuel cell In order to prevent the short-circuit caused by the matrix, it is preferable to use a matrix having a resistivity of 10 ohm-cm or more at the operation temperature of the fuel cell. In this invention, the electronic insulation is ~udged whether or not it has a resistivity of 10 ohm-cm or more at the operation temperature of the fuel cell.
11719~3 It was found for the first time that metal oxides that are electron-insulative and insoluble in phosphoric acid are larger in phosphoric acid retaining ability and superior to silicon carbide. In a matrix having one or more such metal oxides, since the metal oxide is well wettable to phosphoric acid, phosphoric acid is easily retained.
Further, the phosphoric acid once retained in the matrix is hardly released therefrom. Therefore, a fuel cell having such a matrix hardly loses the phosphoric acid and is very little degraded in performance.
As the metal oxides that are electron-insulative and insoluble in phosphoric acid, there can be used, for example, complex oxides containing zirconium, titanium oxides and tin oxides. Among them, preferable metal oxides are TiO2 and SnO2. Examples of the complex oxides containing zirconium are a compound containing zirconium and selenium, a compound containing zirconium and phosphorus, a compound containing zirconium and silicon, etc. Among them, zircon (ZrSiO4) is particularly preferable.
When resistivities were measured as to complex oxides containing zirconium, titanium oxides and tin oxides, these oxides had larger values than 108 ohm-cm at the operation temperature (190-200C) of the fuel cell and was more excellent in electron-insulating property than silicon carbide.
, .
~ 1'71~(~3 In addition, as the metal oxides, those which can form a phosphate when reacted with phosphoric acid in addition to having the electronic insulation and insolubility in phosphoric acid can also preferably be used. In the matrix having such a metal oxide, a part or whole of the metal oxide is converted into a phosphate while retaining the phosphoric acid electrolyte. When there is formed a phosphate, which is very wettable to phosphoric acid, the phosphoric acid retaining ability is further enhanced. Examples of such metal oxides which can form phosphates are TiO2 and SnO2.
The matrix containing zircon which is difficult to form a phosphate has the same phosphoric acid retaining ability as those containing phosphates formed.
The electrolyte retaining matrix may comprise either one kind of metal oxide and a binder or, two or more kinds of metal oxides and one or more binders. The matrix may further contain a small amount of conventional matrix material such as silicon carbide, phenolic resin fibers, etc.
The metal oxide has a tendency to shift around within the fuel cell and a short-circuit is caused by the shifting around. In order to prevent the shifting around, a binder is mixed with the metal oxide. The binder may be either water-repellent or hydrophilic.
11719~3 1 As the binder, there can be used, for example, a fluoropolymer such as polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, etc., or a phenolic resin. Among the fluoropolymers, polytetra-f:Luoroethylene is more preferable than fluorinatedethylene-propylene copolymer, since the former is stronger than the latter in binding force of metal oxide at the operation temperature of the fuel cell. It is preferable to use as the binder at least one member selected from the group consisting of the fluoro-polymers and phenolic resins mentioned above in an amount of preferably 15% by weight or-less based on the weight of the matrix (the amount of the metal oxide being preferably 85~ by weight or-more). Since the fluoropolymer is hydrophobic and has a property of repelling phosphoric acid, the use of too large amount of it is not preferable for making the phosphoric acid difficult to enter into pores in the matrix.
It is preferable to use a matrix consisting of 95 to 98~ by weight of one or more metal oxides and the balance of a binder, that is, the binder is contained in an amount of 2 to 5% by weight.
The metal oxide which is a matrix material can be used in any form such as fibers, particles, and the like. As to the particle size of the metal oxide, since phosphoric acid easily passes through pores formed between the metal oxide particles when these particle sizes become larger, a smaller partlcle 1~7196~3 l size is preferable. A particle size which can pass a 200-mesh sieve (Tyler standardj is particularly preferable.
With the progress of operation of the fuel cell, the phosphoric acid retained in the mat~ix tends to be losed gradually by absorption into the electrodes and the separators. But the loss of phosphoric acid in the fuel cell of this invention is smaller than that in the conventional fuel cells using silicon carbide or a phenolic resin as the matrix. Therefore, the degradation of cell performance with the lapse of time is very little.
This invention is illustrated by way of the following Examples, in which all percents are by weight unless otherwise specified.
Example l As the complex oxides containing zirconium as a major component, zircon (ZrSiO4) was used in the form of particles which can pass a 200-mesh sieve.
To 98 g of the zircon fine particles, 30 ml of a suspension obtained by suspending about 2 g of polytetrafluoroethylene fine powders in water with a surface active agent was added to give a paste. The resulting mixture was heated at 200C for about 8 hours to remove the water, followed by addition of 98~
concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was li719~3 1 about 50%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon. Subsequently, a fuel cell having a structure as shown in FIG. 1 was produded by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve A in FIG. 2 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm2 was also measured and plotted as the curve A in FIG. 3. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No.
4,017,664 were also measured and plotted as the curve X in FIGS. 2 and 3.
As is clear from FIGS, 2 and 3, excellent performance can be obtained when zircon is used as a matrix material compared with the case of using silicon cabide. This seems to be derived from properties of zircon that it has no electronic conductivity, it has a large phosphoric acid retaining ability and it is stable to phosphoric acid.
Example 2 To 98 g of titanium oxide fine powders (passing a 200-mesh sieve) obtained by pyrolyzing m-titanic acid at 900~C, was added 30 ml of a suspension obtained by suspend-ing about 2 g of polytetrafluoroethylene fine powders in 1~19(?3 l water with a surface active agent to give a paste.
The resulting mixture was heated at 200C for about 8 hours to remove the water, followed ~y addition of 98~
concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was about 70%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon. Subsequently, a fuel cell having a structure as shown in FIG. l was produced by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve B in FIG. 4 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm2 was also measured and plotted as the curve B ln FIG. 5. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No. 4,017~664 were also measured and ~lotted as the curve X in FIGS. 4 and 5.
As is clear from FIGS. 4 and 5, excellent performance can be obtained when the matrix according to this invention is used compared with the case of using silicon carbide.
Example 3 To 98 g of stannic oxide fine powders (passing a 200-mesh sieve), was added 30 ml of a suspension obtained by suspending about 2 g of polytetrafluoroethylene fine 11719~3 1 powders in water with a surface active agent to give a paste. The resulting mixture was heated at 200C for about 8 hours to remove the water, followed by addition of 98% concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was about 70%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon.
Subsequently, a fuel cell having a structure as shown in FIG. 1 was produced by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve C in FIG. 6 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm was also measured and plotted as the curve C ln FIG. 7. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No. 4,017,664 were also measured and plotted as the curve X in FIGS. 6 and 7.
As is clear from FIGS. 6 and 7, excellent performance can be obtained when the matrix according to this invention is used compared with the case of using silicon carbide.
As for the matrix for retaining phosphoric acid as the electrolyte, it must have the following properties, which are also disclosed in U.S. Patent No. 4,017,664: (1) it is stable against the phosphoric acid at high temperatures (190 - 200C), that is~
it is not soluble in the phosphoric acid; (2) it has a larger phosphoric acid retaining ability; and (3) it has no electronic conductivity (i.e., it is an electronic insulator).
If the matrix is soluble in phosphoric acid, the properties of phosphoric acid as the electrolyte are damaged and the matrix dissolved in the phosphoric acid migrates to the electrode sides, which has a bad influence upon the properties of the electrodes.
Further, if the matrix has electronic conductivity, there takes place a short-circuit within the fuel cell In order to prevent the short-circuit caused by the matrix, it is preferable to use a matrix having a resistivity of 10 ohm-cm or more at the operation temperature of the fuel cell. In this invention, the electronic insulation is ~udged whether or not it has a resistivity of 10 ohm-cm or more at the operation temperature of the fuel cell.
11719~3 It was found for the first time that metal oxides that are electron-insulative and insoluble in phosphoric acid are larger in phosphoric acid retaining ability and superior to silicon carbide. In a matrix having one or more such metal oxides, since the metal oxide is well wettable to phosphoric acid, phosphoric acid is easily retained.
Further, the phosphoric acid once retained in the matrix is hardly released therefrom. Therefore, a fuel cell having such a matrix hardly loses the phosphoric acid and is very little degraded in performance.
As the metal oxides that are electron-insulative and insoluble in phosphoric acid, there can be used, for example, complex oxides containing zirconium, titanium oxides and tin oxides. Among them, preferable metal oxides are TiO2 and SnO2. Examples of the complex oxides containing zirconium are a compound containing zirconium and selenium, a compound containing zirconium and phosphorus, a compound containing zirconium and silicon, etc. Among them, zircon (ZrSiO4) is particularly preferable.
When resistivities were measured as to complex oxides containing zirconium, titanium oxides and tin oxides, these oxides had larger values than 108 ohm-cm at the operation temperature (190-200C) of the fuel cell and was more excellent in electron-insulating property than silicon carbide.
, .
~ 1'71~(~3 In addition, as the metal oxides, those which can form a phosphate when reacted with phosphoric acid in addition to having the electronic insulation and insolubility in phosphoric acid can also preferably be used. In the matrix having such a metal oxide, a part or whole of the metal oxide is converted into a phosphate while retaining the phosphoric acid electrolyte. When there is formed a phosphate, which is very wettable to phosphoric acid, the phosphoric acid retaining ability is further enhanced. Examples of such metal oxides which can form phosphates are TiO2 and SnO2.
The matrix containing zircon which is difficult to form a phosphate has the same phosphoric acid retaining ability as those containing phosphates formed.
The electrolyte retaining matrix may comprise either one kind of metal oxide and a binder or, two or more kinds of metal oxides and one or more binders. The matrix may further contain a small amount of conventional matrix material such as silicon carbide, phenolic resin fibers, etc.
The metal oxide has a tendency to shift around within the fuel cell and a short-circuit is caused by the shifting around. In order to prevent the shifting around, a binder is mixed with the metal oxide. The binder may be either water-repellent or hydrophilic.
11719~3 1 As the binder, there can be used, for example, a fluoropolymer such as polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, etc., or a phenolic resin. Among the fluoropolymers, polytetra-f:Luoroethylene is more preferable than fluorinatedethylene-propylene copolymer, since the former is stronger than the latter in binding force of metal oxide at the operation temperature of the fuel cell. It is preferable to use as the binder at least one member selected from the group consisting of the fluoro-polymers and phenolic resins mentioned above in an amount of preferably 15% by weight or-less based on the weight of the matrix (the amount of the metal oxide being preferably 85~ by weight or-more). Since the fluoropolymer is hydrophobic and has a property of repelling phosphoric acid, the use of too large amount of it is not preferable for making the phosphoric acid difficult to enter into pores in the matrix.
It is preferable to use a matrix consisting of 95 to 98~ by weight of one or more metal oxides and the balance of a binder, that is, the binder is contained in an amount of 2 to 5% by weight.
The metal oxide which is a matrix material can be used in any form such as fibers, particles, and the like. As to the particle size of the metal oxide, since phosphoric acid easily passes through pores formed between the metal oxide particles when these particle sizes become larger, a smaller partlcle 1~7196~3 l size is preferable. A particle size which can pass a 200-mesh sieve (Tyler standardj is particularly preferable.
With the progress of operation of the fuel cell, the phosphoric acid retained in the mat~ix tends to be losed gradually by absorption into the electrodes and the separators. But the loss of phosphoric acid in the fuel cell of this invention is smaller than that in the conventional fuel cells using silicon carbide or a phenolic resin as the matrix. Therefore, the degradation of cell performance with the lapse of time is very little.
This invention is illustrated by way of the following Examples, in which all percents are by weight unless otherwise specified.
Example l As the complex oxides containing zirconium as a major component, zircon (ZrSiO4) was used in the form of particles which can pass a 200-mesh sieve.
To 98 g of the zircon fine particles, 30 ml of a suspension obtained by suspending about 2 g of polytetrafluoroethylene fine powders in water with a surface active agent was added to give a paste. The resulting mixture was heated at 200C for about 8 hours to remove the water, followed by addition of 98~
concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was li719~3 1 about 50%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon. Subsequently, a fuel cell having a structure as shown in FIG. 1 was produded by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve A in FIG. 2 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm2 was also measured and plotted as the curve A in FIG. 3. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No.
4,017,664 were also measured and plotted as the curve X in FIGS. 2 and 3.
As is clear from FIGS, 2 and 3, excellent performance can be obtained when zircon is used as a matrix material compared with the case of using silicon cabide. This seems to be derived from properties of zircon that it has no electronic conductivity, it has a large phosphoric acid retaining ability and it is stable to phosphoric acid.
Example 2 To 98 g of titanium oxide fine powders (passing a 200-mesh sieve) obtained by pyrolyzing m-titanic acid at 900~C, was added 30 ml of a suspension obtained by suspend-ing about 2 g of polytetrafluoroethylene fine powders in 1~19(?3 l water with a surface active agent to give a paste.
The resulting mixture was heated at 200C for about 8 hours to remove the water, followed ~y addition of 98~
concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was about 70%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon. Subsequently, a fuel cell having a structure as shown in FIG. l was produced by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve B in FIG. 4 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm2 was also measured and plotted as the curve B ln FIG. 5. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No. 4,017~664 were also measured and ~lotted as the curve X in FIGS. 4 and 5.
As is clear from FIGS. 4 and 5, excellent performance can be obtained when the matrix according to this invention is used compared with the case of using silicon carbide.
Example 3 To 98 g of stannic oxide fine powders (passing a 200-mesh sieve), was added 30 ml of a suspension obtained by suspending about 2 g of polytetrafluoroethylene fine 11719~3 1 powders in water with a surface active agent to give a paste. The resulting mixture was heated at 200C for about 8 hours to remove the water, followed by addition of 98% concentrated phosphoric acid to give a matrix retaining the phosphoric acid. The phosphoric acid content was about 70%. The thus produced matrix was coated on a gas diffusion electrode in 0.3 mm thick and another gas diffusion electrode was placed thereon.
Subsequently, a fuel cell having a structure as shown in FIG. 1 was produced by a conventional process.
The current density-voltage properties of the resulting fuel cell were measured and plotted as the curve C in FIG. 6 and the change of cell voltage with the lapse of time when continuously operated at a current density of 200 mA/cm was also measured and plotted as the curve C ln FIG. 7. For comparison, the properties of fuel cell obtained by using silicon carbide as the matrix according to U.S. Patent No. 4,017,664 were also measured and plotted as the curve X in FIGS. 6 and 7.
As is clear from FIGS. 6 and 7, excellent performance can be obtained when the matrix according to this invention is used compared with the case of using silicon carbide.
Claims (10)
1. In a fuel cell comprising a pair of gas diffusion electrodes, a matrix for retaining phosphoric acid electrolyte, disposed between said gas diffusion electrodes, the improvement wherein said matrix consists essentially of one or more metal oxides which are electron-insulative and insoluble in phosphoric acid and selected from complex oxides containing zirconium, titanium oxides and tin oxides, and one or more binders.
2. A fuel cell according to claim 1, wherein the metal oxide is contained in the matrix in an amount of 85% by weight or more.
3. A fuel cell according to claim 1, wherein the binder is contained in the matrix in an amount of 15% by weight or less.
4. A fuel cell according to claim 1, wherein the metal oxide is a complex oxide containing zirconium.
5. A fuel cell according to claim 4, wherein the complex oxide is zircon.
6. A fuel cell according to claim 1, wherein the metal oxide is a titanium oxide.
7. A fuel cell according to claim 1, wherein the metal oxide is a tin oxide.
8. A fuel cell according to claim 1, wherein the matrix consists essentially of 95 to 98% by weight of the metal oxide and 2 to 5% by weight of the binder.
9. A fuel cell according to claim 1, wherein the binder is polytetrafluoroethylene.
10. In a fuel cell comprising a pair of gas diffusion electrodes, a matrix for retaining phosphoric acid electrolyte disposed between said gas diffusion electrodes, the improvement wherein said matrix consists essentially of 95 to 98% by weight of zircon and 2 to 5% by weight of poly-tetrafluoroethylene.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56037846A JPS57152680A (en) | 1981-03-18 | 1981-03-18 | Fuel cell |
| JP37844/1981 | 1981-03-18 | ||
| JP37845/1981 | 1981-03-18 | ||
| JP56037844A JPS57152678A (en) | 1981-03-18 | 1981-03-18 | Fuel cell |
| JP37846/1981 | 1981-03-18 | ||
| JP56037845A JPS57152679A (en) | 1981-03-18 | 1981-03-18 | Fuel cell |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171903A true CA1171903A (en) | 1984-07-31 |
Family
ID=27289610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398513A Expired CA1171903A (en) | 1981-03-18 | 1982-03-16 | Fuel cell |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4493879A (en) |
| EP (1) | EP0060560A1 (en) |
| CA (1) | CA1171903A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57191962A (en) * | 1981-05-20 | 1982-11-25 | Hitachi Ltd | Fuel cell |
| JPH0777130B2 (en) * | 1984-04-11 | 1995-08-16 | 株式会社日立製作所 | Fuel cell |
| FR2584867A1 (en) * | 1985-07-15 | 1987-01-16 | Innolab | Ceramic separators for electrical accumulator batteries |
| EP0267342A1 (en) * | 1986-11-12 | 1988-05-18 | Innolab | Ceramic separators for electrical accumulator batteries |
| US4687715A (en) * | 1985-07-26 | 1987-08-18 | Westinghouse Electric Corp. | Zirconium pyrophosphate matrix layer for electrolyte in a fuel cell |
| US4639401A (en) * | 1986-02-26 | 1987-01-27 | The United States Of America As Represented By The United States Department Of Energy | Surfactant addition to phosphoric acid electrolyte |
| EP0306567A1 (en) * | 1986-08-19 | 1989-03-15 | Japan Gore-Tex, Inc. | A fuel cell electrolyte matrix and a method for its manufacture |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3276910A (en) * | 1961-10-12 | 1966-10-04 | Standard Oil Co | Ion transfer medium for electrochemical reaction apparatus |
| NL6612494A (en) * | 1965-09-30 | 1967-03-31 | ||
| SE347273B (en) * | 1965-09-30 | 1972-07-31 | Leesona Corp | |
| US3453149A (en) * | 1965-10-01 | 1969-07-01 | Engelhard Ind Inc | Fluorocarbon matrix membrane containing free acid and method of fabricating |
| US3407096A (en) * | 1966-01-25 | 1968-10-22 | American Cyanamid Co | Fuel cell and method for preparing the electrodes |
| FR1474667A (en) * | 1966-04-06 | 1967-03-24 | Gen Electric | Matrix fuel cell |
| US3567666A (en) * | 1968-02-02 | 1971-03-02 | Carl Berger | Separation means |
| US3575718A (en) * | 1968-09-23 | 1971-04-20 | Engelhard Min & Chem | Composite electrolyte member for fuel cell |
| US3953237A (en) * | 1971-07-06 | 1976-04-27 | Brunswick Corporation | Electric energy sources such as fuel cells and batteries |
| US4066823A (en) * | 1973-09-11 | 1978-01-03 | Armstrong William A | Method for a low temperature oxygen electrode |
| US4017664A (en) * | 1975-09-02 | 1977-04-12 | United Technologies Corporation | Silicon carbide electrolyte retaining matrix for fuel cells |
| CH608310A5 (en) * | 1976-05-28 | 1978-12-29 | Raffinage Cie Francaise | |
| FR2423065A1 (en) * | 1978-04-12 | 1979-11-09 | Battelle Memorial Institute | PROCESS FOR MANUFACTURING ELECTRODES FOR FUEL CELLS, DEVICE FOR IMPLEMENTING THE PROCESS AND ELECTRODES RESULTING FROM THIS PROCESS |
| US4322482A (en) * | 1980-06-09 | 1982-03-30 | United Technologies Corporation | Electrolyte matrix for molten carbonate fuel cells |
| US4317865A (en) * | 1980-09-24 | 1982-03-02 | United Technologies Corporation | Ceria matrix material for molten carbonate fuel cell |
| US4345008A (en) * | 1980-12-24 | 1982-08-17 | United Technologies Corporation | Apparatus for reducing electrolyte loss from an electrochemical cell |
-
1982
- 1982-03-11 US US06/357,278 patent/US4493879A/en not_active Expired - Lifetime
- 1982-03-16 CA CA000398513A patent/CA1171903A/en not_active Expired
- 1982-03-16 EP EP82102131A patent/EP0060560A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0060560A1 (en) | 1982-09-22 |
| US4493879A (en) | 1985-01-15 |
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