CA2732240C - Method for preparing fuel cell electrode catalyst and solid polymer fuel cell - Google Patents
Method for preparing fuel cell electrode catalyst and solid polymer fuel cell Download PDFInfo
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- CA2732240C CA2732240C CA2732240A CA2732240A CA2732240C CA 2732240 C CA2732240 C CA 2732240C CA 2732240 A CA2732240 A CA 2732240A CA 2732240 A CA2732240 A CA 2732240A CA 2732240 C CA2732240 C CA 2732240C
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- nitrogen
- fuel cell
- catalyst
- metal complex
- baking
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- 239000003054 catalyst Substances 0.000 title claims abstract description 95
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000000446 fuel Substances 0.000 title claims abstract description 20
- 239000007787 solid Substances 0.000 title description 5
- 229920000642 polymer Polymers 0.000 title description 4
- 229910052751 metal Inorganic materials 0.000 claims abstract description 37
- -1 nitrogen-containing metal complex Chemical class 0.000 claims abstract description 32
- 238000010306 acid treatment Methods 0.000 claims abstract description 31
- NGCDGPPKVSZGRR-UHFFFAOYSA-J 1,4,6,9-tetraoxa-5-stannaspiro[4.4]nonane-2,3,7,8-tetrone Chemical compound [Sn+4].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O NGCDGPPKVSZGRR-UHFFFAOYSA-J 0.000 claims abstract description 22
- 239000002184 metal Substances 0.000 claims abstract description 18
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000010828 elution Methods 0.000 claims abstract description 11
- 239000011261 inert gas Substances 0.000 claims abstract description 9
- 150000002894 organic compounds Chemical class 0.000 claims abstract description 9
- 239000000203 mixture Substances 0.000 claims abstract description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 34
- 150000004032 porphyrins Chemical class 0.000 claims description 17
- 229910052697 platinum Inorganic materials 0.000 claims description 16
- 229910052723 transition metal Inorganic materials 0.000 claims description 15
- 238000002604 ultrasonography Methods 0.000 claims description 11
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 claims description 10
- 150000003624 transition metals Chemical class 0.000 claims description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 6
- 239000010949 copper Substances 0.000 claims description 4
- 239000011572 manganese Substances 0.000 claims description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052763 palladium Inorganic materials 0.000 claims description 2
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 claims description 2
- 239000013522 chelant Substances 0.000 abstract description 9
- 150000002678 macrocyclic compounds Chemical class 0.000 abstract description 9
- 150000004033 porphyrin derivatives Chemical class 0.000 abstract description 5
- QBCIMRXPMLWVML-UHFFFAOYSA-N cobalt(2+);5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin-22,24-diide Chemical compound [Co+2].C1=CC(OC)=CC=C1C(C1=CC=C([N-]1)C(C=1C=CC(OC)=CC=1)=C1C=CC(=N1)C(C=1C=CC(OC)=CC=1)=C1C=CC([N-]1)=C1C=2C=CC(OC)=CC=2)=C2N=C1C=C2 QBCIMRXPMLWVML-UHFFFAOYSA-N 0.000 description 21
- 238000011156 evaluation Methods 0.000 description 19
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 14
- 238000002360 preparation method Methods 0.000 description 14
- 239000007789 gas Substances 0.000 description 12
- 239000006185 dispersion Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 238000001914 filtration Methods 0.000 description 10
- 238000002525 ultrasonication Methods 0.000 description 9
- 238000002156 mixing Methods 0.000 description 8
- 239000011148 porous material Substances 0.000 description 8
- 238000005406 washing Methods 0.000 description 8
- 238000001035 drying Methods 0.000 description 7
- 239000007864 aqueous solution Substances 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 238000010248 power generation Methods 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910001260 Pt alloy Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052798 chalcogen Inorganic materials 0.000 description 3
- 150000001787 chalcogens Chemical class 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
- 125000001424 substituent group Chemical group 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 238000001132 ultrasonic dispersion Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000003377 acid catalyst Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000004088 foaming agent Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 150000003839 salts Chemical group 0.000 description 2
- 229910000904 FeC2O4 Inorganic materials 0.000 description 1
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 230000010757 Reduction Activity Effects 0.000 description 1
- 239000002262 Schiff base Substances 0.000 description 1
- 150000004753 Schiff bases Chemical class 0.000 description 1
- QGKVXWDADKTZHW-UHFFFAOYSA-N azaporphyrin Chemical compound C1=C(N=2)C=CC=2C=C(N=2)C=CC=2C=C(N2)C=CC2=CC2=CNC1=N2 QGKVXWDADKTZHW-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000002134 carbon nanofiber Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000004700 cobalt complex Chemical class 0.000 description 1
- 150000004696 coordination complex Chemical class 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 229920000867 polyelectrolyte Polymers 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 239000012925 reference material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000001291 vacuum drying Methods 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
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9008—Organic or organo-metallic compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
- H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
- H01M4/8882—Heat treatment, e.g. drying, baking
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
- H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/923—Compounds thereof with non-metallic elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
- H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Catalysts (AREA)
- Inert Electrodes (AREA)
Abstract
According to the present invention, the catalyst performance of a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative is improved.
Also, the following method is provided: a method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of: adding tin oxalate to the nitrogen-containing metal complex; and baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere, wherein elution of metal tin is carried out via acid treatment.
Also, the following method is provided: a method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of: adding tin oxalate to the nitrogen-containing metal complex; and baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere, wherein elution of metal tin is carried out via acid treatment.
Description
DESCRIPTION
METHOD FOR PREPARING FUEL CELL ELECTRODE CATALYST AND SOLID
POLYMER FUEL CELL
Technical Field The present invention relates to a method for preparing a fuel cell electrode catalyst having excellent oxygen reduction activity. Further, the present invention relates to a solid polymer fuel cell in which the electrode catalyst is contained in a catalyst layer of an electrode.
Background Art A catalyst used to promote a reaction is essential for a solid polymer electrolyte fuel cell. Platinum and platinum alloys have been mainly examined as catalysts that can be used in both hydrogen and oxygen electrodes. A large overvoltage is generated particularly in an oxygen electrode (cathode). In order to reduce such overvoltage, it would be possible to increase the amount of supported platinum or platinum alloy that is used as a catalyst. However, such increase in the catalyst amount is not effective enough to cause overvoltage reduction. On the other hand, the problem of cost increase along with an increase in the catalyst amount is further intensified.
Thus, it has been a major objective to strike a balance between cost and catalyst performance.
As an aside, a complex of a macrocyclic compound containing metal such as porphyrin (PP), phthalocyanine (Pc), or tetraazaannulene (TAA) has been examined as a catalyst that has oxygen-reducing ability. The basic idea is that such complex of a metal macrocyclic compound has the capacity to adsorb oxygen molecules so that such capacity can be utilized and applied to a reaction for electrochemically reducing oxygen molecules. It would be possible to apply, as a catalyst, such nitrogen-containing-platinum-based complex having a PtN4 chelate structure in which platinum (Pt) is coordinated with 4 nitrogen atoms to a practical electrode.
For instance, W02003/004156 filed by the present applicant discloses a platinum-free chelate catalyst containing metal porphyrin. In addition, in W02003/004156, the chelate catalyst comprises a nitrogen-containing organic transition metal complex, which contains a transition metal that differs from the aforementioned transition metal, and a chalcogen component, in addition to at least one unsupported transition metal salt. It is described that when an unsupported transition metal salt is used as a filler during carbon matrix formation, a highly porous material is formed upon thermal decomposition of the salt due to the forming effect. Patent Document 1 discloses, in the Examples, a nitrogen-containing organic transition metal complex, in which cobalt tetramethoxyphenylporphyrin (CoTMPP) serving as metal porphyrin, sulfur serving as a chalcogen component, and an unsupported iron oxalate serving as transition metal salt were used. In such case, Fe contained in iron oxalate reacted with sulfur such that iron sulfide was formed, followed by acid elution. Thus, sulfur, which serves as a chalcogen component, is an essential component in W02003/004156.
Disclosure of the Invention Problem to Be Solved by the Invention In the case of the chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156, a salt of an unsupported transition metal functions as a "foaming agent" for a nitrogen-containing organic transition metal complex. Accordingly, it is thought that a carbon matrix becomes porous and thus the activity surface area is extended, contributing to an improvement in catalyst activity.
However, a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156 is problematic in terms of the following (a) and (b): (a): a foaming agent (pore-forming material) cannot be completely removed; (b): the pore size is not optimized.
Therefore, further improvement in catalyst activity has been awaited.
Thus, it is an objective of the present invention to improve the catalyst performance of a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156.
Means for Solving the Problem The present inventors focused on the impossibility of achieving sufficient pore formation with the use of a "forming agent" used for a conventional chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative.
Accordingly, they have found that sufficient pore formation can be achieved by carrying out a specific treatment with the use of a specific compound. This has led to the completion of the present invention.
Specifically, firstly, the present invention relates to a method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of: adding tin oxalate to the nitrogen-containing metal complex;
and baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere (hereafter to be referred to as the 1st baking). Tin oxalate functions as a pore-forming material and becomes metal tin when reduced via baking.
At such time, tin oxalate also forms pores in a substrate comprising a nitrogen-containing metal complex. Thus, an electrode catalyst material having a large specific surface area can be obtained.
According to the present invention, elution of metal tin is carried out via acid treatment following the step of baking a mixture of the above nitrogen-containing metal complex and tin oxalate. As a result, metal tin generated from tin oxalate removed, and thus catalyst activity can be further improved. In such case, it is preferable to carry out ultrasound irradiation upon elution of metal tin or before or simultaneously such elution such that removal of the metal tin is promoted and thus the pore size can be adequately adjusted.
In addition, according to the present invention, it is preferable to carry out baking at least once (hereafter to be referred to as, for example, the 2nd baking) in an atmosphere containing N2 and H2 following the aforementioned elution of metal tin for , .
=
the improvement of catalyst activity.
Further, it is preferable to further carry out elution of metal tin via acid treatment or to carry out acid treatment and ultrasonication in combination following the above step of 2n1 baking in an atmosphere containing N2 and H2 for the improvement of catalyst activity.
Preferred examples of the above nitrogen-containing metal complex include a nitrogen-containing metal complex in which at least one transition metal selected from the group consisting of cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), copper (Cu), manganese (Mn), and palladium (Pd) is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
In addition, the above nitrogen-containing metal complex is not limited to the above transition metal complex. Thus, it may be a nitrogen-containing metal complex comprising a platinum metallic element. Specifically, preferred examples thereof include a nitrogen-containing metal complex in which a platinum metallic element or a platinum metallic element combined with other elements, which serves as a metal, is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
Secondly, the present invention relates to a solid polymer fuel cell comprising a fuel cell electrode catalyst prepared by the above method.
Effects of the Invention When a mixture of tin oxalate that serves as a pore-forming material and a nitrogen-containing macrocyclic compound is baked, porous parts are adequately formed in a catalyst substrate such that the catalyst substrate has a high specific surface area.
Thus, catalyst activity can be improved. Accordingly, a fuel cell electrode catalyst having excellent properties can be obtained. In particular, the current density in a high electric potential region can be improved in the case of such catalyst.
METHOD FOR PREPARING FUEL CELL ELECTRODE CATALYST AND SOLID
POLYMER FUEL CELL
Technical Field The present invention relates to a method for preparing a fuel cell electrode catalyst having excellent oxygen reduction activity. Further, the present invention relates to a solid polymer fuel cell in which the electrode catalyst is contained in a catalyst layer of an electrode.
Background Art A catalyst used to promote a reaction is essential for a solid polymer electrolyte fuel cell. Platinum and platinum alloys have been mainly examined as catalysts that can be used in both hydrogen and oxygen electrodes. A large overvoltage is generated particularly in an oxygen electrode (cathode). In order to reduce such overvoltage, it would be possible to increase the amount of supported platinum or platinum alloy that is used as a catalyst. However, such increase in the catalyst amount is not effective enough to cause overvoltage reduction. On the other hand, the problem of cost increase along with an increase in the catalyst amount is further intensified.
Thus, it has been a major objective to strike a balance between cost and catalyst performance.
As an aside, a complex of a macrocyclic compound containing metal such as porphyrin (PP), phthalocyanine (Pc), or tetraazaannulene (TAA) has been examined as a catalyst that has oxygen-reducing ability. The basic idea is that such complex of a metal macrocyclic compound has the capacity to adsorb oxygen molecules so that such capacity can be utilized and applied to a reaction for electrochemically reducing oxygen molecules. It would be possible to apply, as a catalyst, such nitrogen-containing-platinum-based complex having a PtN4 chelate structure in which platinum (Pt) is coordinated with 4 nitrogen atoms to a practical electrode.
For instance, W02003/004156 filed by the present applicant discloses a platinum-free chelate catalyst containing metal porphyrin. In addition, in W02003/004156, the chelate catalyst comprises a nitrogen-containing organic transition metal complex, which contains a transition metal that differs from the aforementioned transition metal, and a chalcogen component, in addition to at least one unsupported transition metal salt. It is described that when an unsupported transition metal salt is used as a filler during carbon matrix formation, a highly porous material is formed upon thermal decomposition of the salt due to the forming effect. Patent Document 1 discloses, in the Examples, a nitrogen-containing organic transition metal complex, in which cobalt tetramethoxyphenylporphyrin (CoTMPP) serving as metal porphyrin, sulfur serving as a chalcogen component, and an unsupported iron oxalate serving as transition metal salt were used. In such case, Fe contained in iron oxalate reacted with sulfur such that iron sulfide was formed, followed by acid elution. Thus, sulfur, which serves as a chalcogen component, is an essential component in W02003/004156.
Disclosure of the Invention Problem to Be Solved by the Invention In the case of the chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156, a salt of an unsupported transition metal functions as a "foaming agent" for a nitrogen-containing organic transition metal complex. Accordingly, it is thought that a carbon matrix becomes porous and thus the activity surface area is extended, contributing to an improvement in catalyst activity.
However, a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156 is problematic in terms of the following (a) and (b): (a): a foaming agent (pore-forming material) cannot be completely removed; (b): the pore size is not optimized.
Therefore, further improvement in catalyst activity has been awaited.
Thus, it is an objective of the present invention to improve the catalyst performance of a chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative described in W02003/004156.
Means for Solving the Problem The present inventors focused on the impossibility of achieving sufficient pore formation with the use of a "forming agent" used for a conventional chelate catalyst comprising a complex of a macrocyclic compound such as a porphyrin derivative.
Accordingly, they have found that sufficient pore formation can be achieved by carrying out a specific treatment with the use of a specific compound. This has led to the completion of the present invention.
Specifically, firstly, the present invention relates to a method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of: adding tin oxalate to the nitrogen-containing metal complex;
and baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere (hereafter to be referred to as the 1st baking). Tin oxalate functions as a pore-forming material and becomes metal tin when reduced via baking.
At such time, tin oxalate also forms pores in a substrate comprising a nitrogen-containing metal complex. Thus, an electrode catalyst material having a large specific surface area can be obtained.
According to the present invention, elution of metal tin is carried out via acid treatment following the step of baking a mixture of the above nitrogen-containing metal complex and tin oxalate. As a result, metal tin generated from tin oxalate removed, and thus catalyst activity can be further improved. In such case, it is preferable to carry out ultrasound irradiation upon elution of metal tin or before or simultaneously such elution such that removal of the metal tin is promoted and thus the pore size can be adequately adjusted.
In addition, according to the present invention, it is preferable to carry out baking at least once (hereafter to be referred to as, for example, the 2nd baking) in an atmosphere containing N2 and H2 following the aforementioned elution of metal tin for , .
=
the improvement of catalyst activity.
Further, it is preferable to further carry out elution of metal tin via acid treatment or to carry out acid treatment and ultrasonication in combination following the above step of 2n1 baking in an atmosphere containing N2 and H2 for the improvement of catalyst activity.
Preferred examples of the above nitrogen-containing metal complex include a nitrogen-containing metal complex in which at least one transition metal selected from the group consisting of cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), copper (Cu), manganese (Mn), and palladium (Pd) is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
In addition, the above nitrogen-containing metal complex is not limited to the above transition metal complex. Thus, it may be a nitrogen-containing metal complex comprising a platinum metallic element. Specifically, preferred examples thereof include a nitrogen-containing metal complex in which a platinum metallic element or a platinum metallic element combined with other elements, which serves as a metal, is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
Secondly, the present invention relates to a solid polymer fuel cell comprising a fuel cell electrode catalyst prepared by the above method.
Effects of the Invention When a mixture of tin oxalate that serves as a pore-forming material and a nitrogen-containing macrocyclic compound is baked, porous parts are adequately formed in a catalyst substrate such that the catalyst substrate has a high specific surface area.
Thus, catalyst activity can be improved. Accordingly, a fuel cell electrode catalyst having excellent properties can be obtained. In particular, the current density in a high electric potential region can be improved in the case of such catalyst.
Brief Description of the Drawings Fig. 1 shows power generation performance results based on RDE evaluation in the case of the Co/Sn catalyst of the present invention (Example 1) and that in the case of a Co/Fe/S catalyst obtained by a conventional method (Comparative example).
Fig. 2 shows the results of performance evaluation of different Co/Sn catalysts prepared by changing the baking temperature when baking a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate in an inert gas atmosphere.
Fig. 3 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking followed by acid treatment (initial catalyst, Ref.1) and followed by 2nd backing with changing gas species without acid treatment (labeled without acid treatment) or followed by acid treatment (labeled; with acid treatment). Ref.1: catalyst prepared following the step lto 4 of the preparation procedure.
step 1 step 2 step 3 to 4 CoTMPP/ ist backing Acid treatm. in USo. Co/Sn catalyst Sn oxalate (750 C in Ar or N2) bath, Filtration... (Ref. 1 for 2nd backing) Performance of 2nd backing:
Co/Sn catalyst 2nd backing (750 C) catalyst labelled changing gas species "without acid treatment" (in Fig. 3) Co/Sn catal yst 2nd backing (750 C) acid catalyst labelled changing gas species treatment "with acid treatment" (in Fig.
3) Fig. 4 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking followed by acid treatment and changing gas species upon the 2" baking. Ref.2: catalyst prepared following the step lto 7 of the preparation procedure.
step 1 step 2 step 3 to 4 step 5 to 7 CoTMPP/ 1st backing Acid treatm. in US0. US dispersion 0. Co/Sn catalyst Sn oxalate (750 C in Ar or N2) bath, Filtration... with US stick, (Ref. 2 for 2' backing) H20, 4h Performance of 2nd backing:
Co/Sn catalyst 2nd backing (750 C) catalyst labelled changing gas species "without acid treatment" (in Fig. 4) Co/Sn catal St 2nd backing (750 C) acid catalyst labelled changing gas species treatment "with acid treatment" (in Fig.
4) Fig. 5 shows the results of performance evaluation of different Co/Sn catalysts subjected to acid treatment without ultrasonication, such catalysts each having a different mixing ratio.
CoTM PP/ 1st backing acid Co/Sn catalyst 10.
Sn oxalate (750 C in Ar or N2) treatment (without ultrasonication) Fig. 6 shows the results of performance evaluation of different Co/Sn catalysts subjected to ultrasonication during the acid treatment, such catalysts each having a different mixing ratio.
CoTM PP/ 1st backing acid treatm. in Co/Sn catalyst Sn oxalate (750 C in Ar or N2) UltraSonic bath (with ultrasonication) Fig. 7 shows the results of performance evaluation of catalyst prepared using a 2nd baking in different gas species ( A and B: N2/H2; C and D CO2) and followed by an acid treatment in some cases ( B and D). Catalysts are compared to reference catalyst where Co/Sn catalyst was prepared by carrying out 1st baking followed by acid treatment where 30 min were performed in an ultrasonic bath followed by filtration, washing . . .
drying and a second reference Co/Sn catalyst was prepared by carrying out the 1st baking followed by an acid treatment where 30 min where performed in ultrasonic bath followed by filtration, washing and drying and followed by an ultrasonic dispersion in 1-120 using an ultrasonic stick.
Best Mode for Carrying Out the Invention The following is a schematic view of a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound. A
transition metal, a platinum metallic element, or a platinum metallic element combined with other elements, which serves as the main element (M), is coordinated with nitrogen atoms in a macrocyclic organic compound such that a complex of a macrocyclic compound (MCC) is formed.
N
N---M---N
, i N
Preferred examples of a macrocyclic organic compound used in the present invention that constitutes a metal complex include the following compounds having the N4-chelate structure: porphyrin and derivatives thereof; phthalocyanine and derivatives thereof; azaporphyrin and derivatives thereof; tetraazaannulene and derivatives thereof;
and a Schiff base.
The following chemical formulae are examples of a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound. In the examples porphyrin and a derivative thereof are used.
' = =
I \ R5 N N
¨N N
Rii \ R7 (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R1 to R12 each represent hydrogen or a substituent);
R ¨( N N¨
, =. ,-R22 __ M
N _________________________ / _____ R17 ¨N-R21 Ri R a (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R13 to R22 each represent hydrogen or a substituent); and . = . .
RNIA rx R27 / ( N¨
N,s, R36 = I
M
/ _________________________________ R29 I ==
----N' N __ ,..3z ..31 (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R23 to R36 each represent hydrogen or a substituent).
According to the present invention, a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound may be carried on a support. Even without the use of a support, such complex can exhibit catalyst performance. A macrocyclic organic compound used in the present invention is carbonized via baking so as to serve as a carrier, and thus a support is not necessarily used, which is advantageous. In a case in which a carrier is used, the conductive carrier used is not particularly limited. Examples thereof include carbon black, carbon nanotube, and carbon nanofiber.
Examples Hereafter, the present invention is described based on the Examples and the Comparative example.
(Example 1) [Preparation of Co/Sn catalysts]
A cobalt complex catalyst (hereafter to be referred to as Co/Sn) in which pores were formed were prepared from cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate as described below.
1. Mixing of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate with a mortar 2. Baking in an inert gas atmosphere (750 C, 45 min) 3. Cooling of the resultant, followed by 12h in a 1 M hydrochloric acid aqueous solution (with ultrasound dispersion for 30 min) 4. Filtration, washing, and drying 5. Ultrasound dispersion in H20 at 10 C for 30 min - 6 h 6. Addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min - 2h) 7. Filtration, washing, and drying 8. Baking at 750 C in an N2/H2 atmosphere 9. After cooling down, addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min) 10. Baking at 600 C for 45 min in an N2/H2 atmosphere (Comparative example) [Preparation of Co/Fe/S catalysts]
A tetramethoxyphenylporphyrin cobalt complex/iron oxalate/ sulfur catalyst (hereafter to be referred to as Co/Fe/S) was prepared as described below in accordance with W02003/004156.
1. Mixing of cobalt tetramethoxyphenylporphyrin /iron oxalate (FeC204=2H20)/S
(at a molar ratio of 1:22.7:0.95) with a mortar 2. Baking in an inert gas atmosphere (450 C for 1 h, 750 C for 1 h) 3. Cooling of the resultant followed by immersion in 1N hydrochloric acid (12 h) 4. Filtration and washing followed by vacuum drying [MEA performance evaluation]
MEA performance evaluation was carried out by assembling an MEA mixed with Nafion (trade name) serving as a polyelectrolyte under the following conditions.
Gas species: anode: H2; cathode: Air Cell temperature: anode: 80 C; cathode: 80 C
Humidification rate: anode: 75%; cathode: 60%
Fig. 1 shows power generation performance results based on RDE evaluation in the case of the Co/Sn catalyst of the present invention (Example 1) and in the case of a Co/Fe/S catalyst obtained by a conventional method (Comparative example).
As is apparent from the results shown in fig. 1, power generation performance can be improved, particularly in a high electric potential region, by carrying out a baking treatment with the use of tin oxalate as a pore forming material.
(Example 2: optimization of a temperature for the 1st baking) Different Co/Sn catalysts were prepared in the manner described in Example 1 by changing the baking temperature when baking a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate (SnC204) in an inert gas atmosphere. The obtained catalysts were subjected to performance evaluation.
Fig. 2 shows the results of performance evaluation. As is apparent from the results shown in fig. 2, the optimal baking temperature range is 660 C to 800 C.
(Example 3: Gas species used for the 2nd baking) Different Co/Sn catalysts were prepared in the manner described in Example 1 by carrying out the 1st baking of a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate (SnC204) in an inert gas atmosphere with or with an acid treatment and changing gas species upon the 2nd baking. The obtained catalysts were subjected to performance evaluation.
Fig. 3 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking with acid treatment and followed by a second backing in changing gas species. In Fig.3, Ref.1 referes to a catalyst prepared following the preparation steps lto 4 of the example.
Fig. 4 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking with acid treatment and followed by a second baking in changing gas species. In Fig.4 Ref.2: catalyst was prepared following the preparation steps lto 7 of the example.
Based on the results of figs. 3 and 4, the effectiveness of ultrasound dispersion ( step5 to 7 of the preparation), the N2/H2 baking (step 8) and acid treatment (step9) are understood.
(Example 4: Optimization of the porphyrin/tin oxalate ratio) Different Co/Sn catalysts were prepared in the manner described in Example 1 by changing the mixing ratio of cobalt tetramethoxyphenylporphyrin (CoTMPP) to tin oxalate. The obtained catalysts were subjected to performance evaluation.
Fig. 5 shows the results of performance evaluation of different Co/Sn catalysts, each having a different mixing ratio. Catalyst preparation followed the preparation procedure steps 1 to 4 but without ultrasonic dispersion named in step 3. In addition, Fig.
6 shows the results of performance evaluation of different Co/Sn catalysts, each having a different mixing ratio. Catalyst preparation followed the preparation procedure steps 1 to 4 but with ultrasonic dispersion named in step 3.
As is apparent from fig. 5, the optimal range of CoTMPP is 0.5 to 0.8 g or more relative to 3.88 g of tin oxalate in the case without ultrasonication. In addition, as is apparent from the results of fig. 6, the optimal range of CoTMPP is 0.5 to 0.9 g relative to 3.88 g of tin oxalate in the case involving ultrasonication.
(Example 5: Effectiveness of acid treatment and of ultrasonication) As Reference material a Co/Sn catalysts subjected to acid treatment in an ultrasonic bath (steps 1 to 4 of the preparation procedure) and one subjected additional to an ultrasonification step (step 5 to 7 in the preparation procedure) were used.
Fig. 7 shows the results of performance evaluation of these reference catalysts and different 2" baking in changing atmospheres with or without an acid treatment. In the case of treatment method A, the 2" baking was carried out in an N2/H2 atmosphere at 750 C for 30 min. In the case of a treatment method B, the 2" baking was carried out in an N2/H2 atmosphere at 750 C for 30 min, followed by a treatment with 1 M HC1.
In the case of a treatment method C, the 2" baking was carried out in a CO2 atmosphere at 750 C for 30 min. In the case of a treatment method D, the 2" baking was carried out in a CO2 atmosphere at 750 C for 30 min, followed by a treatment with 1 M
HC1.
As is apparent from the results shown in fig. 7, the catalyst activity is preferably improved as a result of ultrasonication and acid treatment (steps 5 to 7). In particular, it is understood that performance improvement is significantly observed in the case of baking in an N2/H2 atmosphere followed by an acid treatment.
Based on the above findings, it is thought that the currently best mode for preparation of a Co/Sn catalyst is as follows.
1. Mixing 0.64g of cobalt tetramethoxyphenylporphyrin (CoTMPP) and 3.88 of tin oxalate (SnC204) in a mortar 2. Baking in an inert gas atmosphere (750 C, 45 min) 3. Cooling of the resultant, followed by 12h in a 1 M hydrochloric acid aqueous solution (with ultrasound dispersion for 30 min) 4. Filtration, washing, and drying 5. Ultrasound dispersion in H20 at 10 C for 30 min - 6 h 6. Addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min - 2h) 7. Filtration, washing, and drying 8. Baking at 750 C in an N2/H2 atmosphere 9. After cooling down, addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min), followed by filtration, washing and drying 10. Baking at 600 C for 45 min in an N2/H2 atmosphere Industrial Applicability According to the present invention, a fuel cell electrode catalyst having excellent properties can be obtained. In particular, the current density in a high electric potential region can be improved in the case of such catalyst. Thus, the present invention contributes to improvement in fuel cell power generation characteristics.
Fig. 2 shows the results of performance evaluation of different Co/Sn catalysts prepared by changing the baking temperature when baking a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate in an inert gas atmosphere.
Fig. 3 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking followed by acid treatment (initial catalyst, Ref.1) and followed by 2nd backing with changing gas species without acid treatment (labeled without acid treatment) or followed by acid treatment (labeled; with acid treatment). Ref.1: catalyst prepared following the step lto 4 of the preparation procedure.
step 1 step 2 step 3 to 4 CoTMPP/ ist backing Acid treatm. in USo. Co/Sn catalyst Sn oxalate (750 C in Ar or N2) bath, Filtration... (Ref. 1 for 2nd backing) Performance of 2nd backing:
Co/Sn catalyst 2nd backing (750 C) catalyst labelled changing gas species "without acid treatment" (in Fig. 3) Co/Sn catal yst 2nd backing (750 C) acid catalyst labelled changing gas species treatment "with acid treatment" (in Fig.
3) Fig. 4 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking followed by acid treatment and changing gas species upon the 2" baking. Ref.2: catalyst prepared following the step lto 7 of the preparation procedure.
step 1 step 2 step 3 to 4 step 5 to 7 CoTMPP/ 1st backing Acid treatm. in US0. US dispersion 0. Co/Sn catalyst Sn oxalate (750 C in Ar or N2) bath, Filtration... with US stick, (Ref. 2 for 2' backing) H20, 4h Performance of 2nd backing:
Co/Sn catalyst 2nd backing (750 C) catalyst labelled changing gas species "without acid treatment" (in Fig. 4) Co/Sn catal St 2nd backing (750 C) acid catalyst labelled changing gas species treatment "with acid treatment" (in Fig.
4) Fig. 5 shows the results of performance evaluation of different Co/Sn catalysts subjected to acid treatment without ultrasonication, such catalysts each having a different mixing ratio.
CoTM PP/ 1st backing acid Co/Sn catalyst 10.
Sn oxalate (750 C in Ar or N2) treatment (without ultrasonication) Fig. 6 shows the results of performance evaluation of different Co/Sn catalysts subjected to ultrasonication during the acid treatment, such catalysts each having a different mixing ratio.
CoTM PP/ 1st backing acid treatm. in Co/Sn catalyst Sn oxalate (750 C in Ar or N2) UltraSonic bath (with ultrasonication) Fig. 7 shows the results of performance evaluation of catalyst prepared using a 2nd baking in different gas species ( A and B: N2/H2; C and D CO2) and followed by an acid treatment in some cases ( B and D). Catalysts are compared to reference catalyst where Co/Sn catalyst was prepared by carrying out 1st baking followed by acid treatment where 30 min were performed in an ultrasonic bath followed by filtration, washing . . .
drying and a second reference Co/Sn catalyst was prepared by carrying out the 1st baking followed by an acid treatment where 30 min where performed in ultrasonic bath followed by filtration, washing and drying and followed by an ultrasonic dispersion in 1-120 using an ultrasonic stick.
Best Mode for Carrying Out the Invention The following is a schematic view of a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound. A
transition metal, a platinum metallic element, or a platinum metallic element combined with other elements, which serves as the main element (M), is coordinated with nitrogen atoms in a macrocyclic organic compound such that a complex of a macrocyclic compound (MCC) is formed.
N
N---M---N
, i N
Preferred examples of a macrocyclic organic compound used in the present invention that constitutes a metal complex include the following compounds having the N4-chelate structure: porphyrin and derivatives thereof; phthalocyanine and derivatives thereof; azaporphyrin and derivatives thereof; tetraazaannulene and derivatives thereof;
and a Schiff base.
The following chemical formulae are examples of a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound. In the examples porphyrin and a derivative thereof are used.
' = =
I \ R5 N N
¨N N
Rii \ R7 (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R1 to R12 each represent hydrogen or a substituent);
R ¨( N N¨
, =. ,-R22 __ M
N _________________________ / _____ R17 ¨N-R21 Ri R a (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R13 to R22 each represent hydrogen or a substituent); and . = . .
RNIA rx R27 / ( N¨
N,s, R36 = I
M
/ _________________________________ R29 I ==
----N' N __ ,..3z ..31 (where M represents a transition metal element, a platinum metallic element, or a platinum metallic element combined with other elements, and R23 to R36 each represent hydrogen or a substituent).
According to the present invention, a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound may be carried on a support. Even without the use of a support, such complex can exhibit catalyst performance. A macrocyclic organic compound used in the present invention is carbonized via baking so as to serve as a carrier, and thus a support is not necessarily used, which is advantageous. In a case in which a carrier is used, the conductive carrier used is not particularly limited. Examples thereof include carbon black, carbon nanotube, and carbon nanofiber.
Examples Hereafter, the present invention is described based on the Examples and the Comparative example.
(Example 1) [Preparation of Co/Sn catalysts]
A cobalt complex catalyst (hereafter to be referred to as Co/Sn) in which pores were formed were prepared from cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate as described below.
1. Mixing of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate with a mortar 2. Baking in an inert gas atmosphere (750 C, 45 min) 3. Cooling of the resultant, followed by 12h in a 1 M hydrochloric acid aqueous solution (with ultrasound dispersion for 30 min) 4. Filtration, washing, and drying 5. Ultrasound dispersion in H20 at 10 C for 30 min - 6 h 6. Addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min - 2h) 7. Filtration, washing, and drying 8. Baking at 750 C in an N2/H2 atmosphere 9. After cooling down, addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min) 10. Baking at 600 C for 45 min in an N2/H2 atmosphere (Comparative example) [Preparation of Co/Fe/S catalysts]
A tetramethoxyphenylporphyrin cobalt complex/iron oxalate/ sulfur catalyst (hereafter to be referred to as Co/Fe/S) was prepared as described below in accordance with W02003/004156.
1. Mixing of cobalt tetramethoxyphenylporphyrin /iron oxalate (FeC204=2H20)/S
(at a molar ratio of 1:22.7:0.95) with a mortar 2. Baking in an inert gas atmosphere (450 C for 1 h, 750 C for 1 h) 3. Cooling of the resultant followed by immersion in 1N hydrochloric acid (12 h) 4. Filtration and washing followed by vacuum drying [MEA performance evaluation]
MEA performance evaluation was carried out by assembling an MEA mixed with Nafion (trade name) serving as a polyelectrolyte under the following conditions.
Gas species: anode: H2; cathode: Air Cell temperature: anode: 80 C; cathode: 80 C
Humidification rate: anode: 75%; cathode: 60%
Fig. 1 shows power generation performance results based on RDE evaluation in the case of the Co/Sn catalyst of the present invention (Example 1) and in the case of a Co/Fe/S catalyst obtained by a conventional method (Comparative example).
As is apparent from the results shown in fig. 1, power generation performance can be improved, particularly in a high electric potential region, by carrying out a baking treatment with the use of tin oxalate as a pore forming material.
(Example 2: optimization of a temperature for the 1st baking) Different Co/Sn catalysts were prepared in the manner described in Example 1 by changing the baking temperature when baking a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate (SnC204) in an inert gas atmosphere. The obtained catalysts were subjected to performance evaluation.
Fig. 2 shows the results of performance evaluation. As is apparent from the results shown in fig. 2, the optimal baking temperature range is 660 C to 800 C.
(Example 3: Gas species used for the 2nd baking) Different Co/Sn catalysts were prepared in the manner described in Example 1 by carrying out the 1st baking of a mixture of cobalt tetramethoxyphenylporphyrin (CoTMPP) and tin oxalate (SnC204) in an inert gas atmosphere with or with an acid treatment and changing gas species upon the 2nd baking. The obtained catalysts were subjected to performance evaluation.
Fig. 3 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking with acid treatment and followed by a second backing in changing gas species. In Fig.3, Ref.1 referes to a catalyst prepared following the preparation steps lto 4 of the example.
Fig. 4 shows the results of performance evaluation of different Co/Sn catalysts prepared by carrying out the 1st baking with acid treatment and followed by a second baking in changing gas species. In Fig.4 Ref.2: catalyst was prepared following the preparation steps lto 7 of the example.
Based on the results of figs. 3 and 4, the effectiveness of ultrasound dispersion ( step5 to 7 of the preparation), the N2/H2 baking (step 8) and acid treatment (step9) are understood.
(Example 4: Optimization of the porphyrin/tin oxalate ratio) Different Co/Sn catalysts were prepared in the manner described in Example 1 by changing the mixing ratio of cobalt tetramethoxyphenylporphyrin (CoTMPP) to tin oxalate. The obtained catalysts were subjected to performance evaluation.
Fig. 5 shows the results of performance evaluation of different Co/Sn catalysts, each having a different mixing ratio. Catalyst preparation followed the preparation procedure steps 1 to 4 but without ultrasonic dispersion named in step 3. In addition, Fig.
6 shows the results of performance evaluation of different Co/Sn catalysts, each having a different mixing ratio. Catalyst preparation followed the preparation procedure steps 1 to 4 but with ultrasonic dispersion named in step 3.
As is apparent from fig. 5, the optimal range of CoTMPP is 0.5 to 0.8 g or more relative to 3.88 g of tin oxalate in the case without ultrasonication. In addition, as is apparent from the results of fig. 6, the optimal range of CoTMPP is 0.5 to 0.9 g relative to 3.88 g of tin oxalate in the case involving ultrasonication.
(Example 5: Effectiveness of acid treatment and of ultrasonication) As Reference material a Co/Sn catalysts subjected to acid treatment in an ultrasonic bath (steps 1 to 4 of the preparation procedure) and one subjected additional to an ultrasonification step (step 5 to 7 in the preparation procedure) were used.
Fig. 7 shows the results of performance evaluation of these reference catalysts and different 2" baking in changing atmospheres with or without an acid treatment. In the case of treatment method A, the 2" baking was carried out in an N2/H2 atmosphere at 750 C for 30 min. In the case of a treatment method B, the 2" baking was carried out in an N2/H2 atmosphere at 750 C for 30 min, followed by a treatment with 1 M HC1.
In the case of a treatment method C, the 2" baking was carried out in a CO2 atmosphere at 750 C for 30 min. In the case of a treatment method D, the 2" baking was carried out in a CO2 atmosphere at 750 C for 30 min, followed by a treatment with 1 M
HC1.
As is apparent from the results shown in fig. 7, the catalyst activity is preferably improved as a result of ultrasonication and acid treatment (steps 5 to 7). In particular, it is understood that performance improvement is significantly observed in the case of baking in an N2/H2 atmosphere followed by an acid treatment.
Based on the above findings, it is thought that the currently best mode for preparation of a Co/Sn catalyst is as follows.
1. Mixing 0.64g of cobalt tetramethoxyphenylporphyrin (CoTMPP) and 3.88 of tin oxalate (SnC204) in a mortar 2. Baking in an inert gas atmosphere (750 C, 45 min) 3. Cooling of the resultant, followed by 12h in a 1 M hydrochloric acid aqueous solution (with ultrasound dispersion for 30 min) 4. Filtration, washing, and drying 5. Ultrasound dispersion in H20 at 10 C for 30 min - 6 h 6. Addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min - 2h) 7. Filtration, washing, and drying 8. Baking at 750 C in an N2/H2 atmosphere 9. After cooling down, addition of the resultant to a 1 M hydrochloric acid aqueous solution (12 h) (with ultrasound dispersion for 30 min), followed by filtration, washing and drying 10. Baking at 600 C for 45 min in an N2/H2 atmosphere Industrial Applicability According to the present invention, a fuel cell electrode catalyst having excellent properties can be obtained. In particular, the current density in a high electric potential region can be improved in the case of such catalyst. Thus, the present invention contributes to improvement in fuel cell power generation characteristics.
Claims (6)
1. A method for preparing a fuel cell electrode catalyst comprising a nitrogen-containing metal complex in which a metallic element is coordinated with a macrocyclic organic compound, such method comprising the steps of adding tin oxalate to the nitrogen-containing metal complex, baking a mixture of the nitrogen-containing metal complex and tin oxalate in an inert gas atmosphere and elution of generated metal tin is carried out.
2. The method for preparing a fuel cell electrode catalyst according to claim 1, wherein the elution of metal tin is carried out via acid treatment.
3. The method for preparing a fuel cell electrode catalyst according to claim 2, wherein ultrasound irradiation is carried out upon the elution of metal tin in the acid treatment.
4. The method for preparing a fuel cell electrode catalyst according to claim 2 or 3, wherein further baking is carried out at least once in an atmosphere containing N2 and H2 following the elution of metal tin in the acid treatment.
5. The method for preparing a fuel cell electrode catalyst according to any one of claims 1 to 4, wherein the nitrogen-containing metal complex is a nitrogen-containing metal complex in which at least one transition metal selected from the group consisting of cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), copper (Cu), manganese (Mn), and palladium (Pd) is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
6. The method for preparing a fuel cell electrode catalyst according to any one of claims 1 to 4, wherein the nitrogen-containing metal complex is a nitrogen-containing metal complex in which platinum metallic element or platinum metallic element combined with other elements, which serves as a metal, is coordinated with at least one nitrogen-containing macrocyclic compound selected from the group consisting of porphyrin (PP) and derivatives thereof, phthalocyanine (Pc) and derivatives thereof, and tetraazaannulene (TAA) and derivatives thereof.
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|---|---|---|---|---|
| JPS5228498A (en) * | 1975-08-28 | 1977-03-03 | Matsushita Electric Ind Co Ltd | Producing method for stannic oxide whiskers |
| DE3068641D1 (en) * | 1979-02-27 | 1984-08-30 | Asahi Glass Co Ltd | GAS DIFFUSION ELECTRODE |
| JPS5644784A (en) * | 1979-09-21 | 1981-04-24 | Asahi Glass Co Ltd | Preparation of cathode for electrolysis of alkali chloride |
| JPS6021690B2 (en) * | 1979-12-13 | 1985-05-29 | 株式会社東芝 | Manufacturing method of urethane foam |
| DE10132490B4 (en) * | 2001-07-03 | 2007-04-12 | Hahn-Meitner-Institut Berlin Gmbh | Platinum-free chelate catalyst material for selective oxygen reduction and process for its preparation |
| EP1277826A1 (en) * | 2001-07-18 | 2003-01-22 | ATOFINA Research | Hydrogenation and dehydrogenation processes and catalysts therefor |
| WO2004058633A2 (en) * | 2002-12-20 | 2004-07-15 | Honda Giken Kogyo Kabushiki Kaisha | Platinum-free ruthenium-cobalt catalyst formulations for hydrogen generation |
| JP2005230648A (en) * | 2004-02-18 | 2005-09-02 | Toyota Motor Corp | Fuel cell cathode electrode catalyst |
| DE112006000983A5 (en) * | 2005-02-20 | 2008-01-24 | Hahn-Meitner-Institut Berlin Gmbh | Production of a platinum-free chelate catalyst material as an intermediate and its further processing into an electrocatalytic coating as end product |
| JP2006314871A (en) * | 2005-05-10 | 2006-11-24 | Toyota Motor Corp | Porphyrin-based electrocatalyst |
| JP2007237092A (en) * | 2006-03-09 | 2007-09-20 | Toyota Motor Corp | Method for producing catalyst material |
| KR100754380B1 (en) * | 2006-09-18 | 2007-08-31 | 삼성에스디아이 주식회사 | Catalyst for fuel cell and fuel cell using same |
| CN101855011B (en) * | 2007-05-31 | 2015-07-22 | 开利公司 | Anti-deactivation photocatalyst and preparation method thereof |
-
2008
- 2008-07-29 US US13/056,362 patent/US8455384B2/en not_active Expired - Fee Related
- 2008-07-29 JP JP2011502174A patent/JP5328888B2/en not_active Expired - Fee Related
- 2008-07-29 WO PCT/JP2008/063935 patent/WO2010013353A1/en not_active Ceased
- 2008-07-29 CA CA2732240A patent/CA2732240C/en not_active Expired - Fee Related
- 2008-07-29 AT AT08792141T patent/ATE551740T1/en active
- 2008-07-29 EP EP08792141A patent/EP2329551B1/en not_active Not-in-force
- 2008-07-29 CN CN200880130557XA patent/CN102113155B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2732240A1 (en) | 2010-02-04 |
| EP2329551B1 (en) | 2012-03-28 |
| US8455384B2 (en) | 2013-06-04 |
| ATE551740T1 (en) | 2012-04-15 |
| JP5328888B2 (en) | 2013-10-30 |
| EP2329551A1 (en) | 2011-06-08 |
| JP2011528482A (en) | 2011-11-17 |
| CN102113155A (en) | 2011-06-29 |
| CN102113155B (en) | 2013-11-13 |
| US20110130270A1 (en) | 2011-06-02 |
| WO2010013353A1 (en) | 2010-02-04 |
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