JP2009125666A - Catalyst body, its manufacturing method, and solid polymer type membrane/electrode assembly for fuel cell using it - Google Patents
Catalyst body, its manufacturing method, and solid polymer type membrane/electrode assembly for fuel cell using it Download PDFInfo
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- JP2009125666A JP2009125666A JP2007303425A JP2007303425A JP2009125666A JP 2009125666 A JP2009125666 A JP 2009125666A JP 2007303425 A JP2007303425 A JP 2007303425A JP 2007303425 A JP2007303425 A JP 2007303425A JP 2009125666 A JP2009125666 A JP 2009125666A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 93
- 239000012528 membrane Substances 0.000 title claims description 37
- 239000000446 fuel Substances 0.000 title claims description 29
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000007787 solid Substances 0.000 title claims description 11
- 229920000642 polymer Polymers 0.000 title claims description 10
- MUMZUERVLWJKNR-UHFFFAOYSA-N oxoplatinum Chemical compound [Pt]=O MUMZUERVLWJKNR-UHFFFAOYSA-N 0.000 claims abstract description 38
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910003446 platinum oxide Inorganic materials 0.000 claims abstract description 38
- 239000002245 particle Substances 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 21
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 19
- 239000011148 porous material Substances 0.000 claims abstract description 16
- 239000005518 polymer electrolyte Substances 0.000 claims description 50
- 239000000126 substance Substances 0.000 claims description 32
- 239000000243 solution Substances 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 15
- 239000002243 precursor Substances 0.000 claims description 13
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 10
- 239000004202 carbamide Substances 0.000 claims description 10
- 150000003058 platinum compounds Chemical class 0.000 claims description 6
- 229910017053 inorganic salt Inorganic materials 0.000 claims description 4
- 239000007789 gas Substances 0.000 abstract description 15
- 238000009792 diffusion process Methods 0.000 abstract description 12
- 239000003795 chemical substances by application Substances 0.000 abstract description 9
- 239000001257 hydrogen Substances 0.000 abstract description 9
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 9
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 7
- 239000001301 oxygen Substances 0.000 abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 239000000463 material Substances 0.000 abstract description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 239000000758 substrate Substances 0.000 description 7
- 239000002244 precipitate Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 230000006911 nucleation Effects 0.000 description 5
- 238000010899 nucleation Methods 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 125000006297 carbonyl amino group Chemical group [H]N([*:2])C([*:1])=O 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- -1 perfluoroalkyl sulfonic acid Chemical compound 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 description 4
- 235000011152 sodium sulphate Nutrition 0.000 description 4
- 229920000557 Nafion® Polymers 0.000 description 3
- 229920002125 Sokalan® Polymers 0.000 description 3
- 239000006229 carbon black Substances 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000007606 doctor blade method Methods 0.000 description 2
- 238000007731 hot pressing Methods 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000005304 joining Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 229910021642 ultra pure water Inorganic materials 0.000 description 2
- 239000012498 ultrapure water Substances 0.000 description 2
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229920003934 Aciplex® Polymers 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 229920003935 Flemion® Polymers 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- RJTANRZEWTUVMA-UHFFFAOYSA-N boron;n-methylmethanamine Chemical compound [B].CNC RJTANRZEWTUVMA-UHFFFAOYSA-N 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000010411 electrocatalyst Substances 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000008098 formaldehyde solution Substances 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000002429 nitrogen sorption measurement Methods 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 229920000867 polyelectrolyte Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 229910001379 sodium hypophosphite Inorganic materials 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
Classifications
-
- 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
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
本発明は、触媒体、その製造方法、およびそれを用いた固体高分子型燃料電池用膜／電極接合体に関する。 The present invention relates to a catalyst body, a production method thereof, and a membrane / electrode assembly for a polymer electrolyte fuel cell using the catalyst body.
固体高分子型燃料電池は、室温付近の低温において高出力が得られ、小型・軽量化が可能であるため、家庭用、自動車用およびモバイル機器用電源としての応用が期待されている。 The polymer electrolyte fuel cell is expected to be applied as a power source for home use, automobile use, and mobile equipment because it can obtain high output at a low temperature around room temperature and can be reduced in size and weight.
一般的に、固体高分子型燃料電池の発電部位である膜／電極接合体（Ｍｅｍｂｒａｎｅ Ｅｌｅｃｔｒｏｄｅ Ａｓｓｅｍｂｌｙ；ＭＥＡ）は、高分子電解質膜の両面にアノードおよびカソードとして一対の電極触媒層を接合することにより構成されている。アノードにおいては、燃料として供給された水素がプロトンと電子に解離し、プロトンは高分子電解質膜中を、電子は外部回路を通りカソードへ移動する。一方、カソードにおいては、アノードより前記径路を通り移動してきたプロトンおよび電子と外部より供給された酸素の反応により水が生成する。固体高分子型燃料電池は、このような一連の電気化学反応により発電を行う。 In general, a membrane / electrode assembly (MEA), which is a power generation site of a polymer electrolyte fuel cell, is formed by joining a pair of electrode catalyst layers as an anode and a cathode on both sides of a polymer electrolyte membrane. It is configured. In the anode, hydrogen supplied as fuel dissociates into protons and electrons, and the protons move in the polymer electrolyte membrane, and the electrons move through the external circuit to the cathode. On the other hand, in the cathode, water is generated by the reaction of protons and electrons that have moved along the path from the anode and oxygen supplied from the outside. A polymer electrolyte fuel cell generates power through such a series of electrochemical reactions.
固体高分子型燃料電池においては、高分子電解質膜としては、ＤｕＰｏｎｔ社製のＮａｆｉｏｎ（登録商標）に代表されるパーフルオロアルキルスルフォン酸膜が用いられている。一方、電極触媒層は、微細に混合された触媒体と高分子電解質の間に空隙が形成されている多孔質構造を有し、水素や酸素のような気体および発生した水分は該空隙中を拡散する。電極触媒層は主に高分子電解質と触媒体より構成されるが、水分管理対策としてポリテトラフルオロエチレン粒子を含有する場合もある。触媒体としては、白金等の微粒子を担持した高比表面積を有するカーボンブラックが広く利用されている。 In a polymer electrolyte fuel cell, a perfluoroalkyl sulfonic acid membrane represented by NaPotion (registered trademark) manufactured by DuPont is used as a polymer electrolyte membrane. On the other hand, the electrode catalyst layer has a porous structure in which voids are formed between the finely mixed catalyst body and the polymer electrolyte, and a gas such as hydrogen and oxygen and generated moisture are contained in the voids. Spread. The electrode catalyst layer is mainly composed of a polymer electrolyte and a catalyst body, but may contain polytetrafluoroethylene particles as a measure for moisture management. As the catalyst body, carbon black having a high specific surface area carrying fine particles such as platinum is widely used.
上記電極触媒層を作製する方法としては、高分子電解質の分散溶液と触媒体を混合したインクを膜状に成形する方法、または、触媒体を任意の溶媒に分散させたインクを膜状に成形した後に高分子電解質の分散溶液を含浸する方法が一般的である。該インクは、多孔質カーボン電極または高分子電解質膜または基体上に製膜され、一対の電極触媒層を高分子電解質膜の両面に配置し、ホットプレス等により熱圧着することにより膜／電極接合体が得られる。 The electrode catalyst layer can be produced by forming a film of an ink in which a polymer electrolyte dispersion and a catalyst body are mixed, or by forming an ink in which a catalyst body is dispersed in an arbitrary solvent into a film. After that, a method of impregnating with a dispersion solution of a polyelectrolyte is generally used. The ink is formed on a porous carbon electrode, a polymer electrolyte membrane or a substrate, a pair of electrode catalyst layers are arranged on both sides of the polymer electrolyte membrane, and thermo-compression bonding is performed by hot pressing or the like to form a membrane / electrode joint. The body is obtained.
しかしながら、前記製造方法のように、白金担持カーボンブラックのようなナノメートルオーダーの微粒子を触媒体として用いた場合、水素や酸素のような気体および水分が拡散する空隙を有する多孔質構造を再現性良く形成することは困難である。そこで、この問題を解決する手段として、高分子電解質と触媒体より構成されるインクに造孔剤を混合し、電極触媒層の製膜後または高分子電解質との接合後に造孔剤のみを溶出し、造孔剤が存在していた位置に空隙が形成される方法が提案されている。造孔剤としては、例えば、無機塩（特許文献１参照）、水溶性繊維（特許文献２参照）、三次元構造を有する亜鉛粉末（特許文献３参照）などが用いられている。
しかし、上記の発明のように、所望の多孔質構造を形成する目的で、造孔剤のように最終的には電極触媒層を構成しない物質を含有させると、該物質を除去した後も該物質の一部が不純物として電極触媒層中に残存する場合がある。また、造孔剤として、溶解時にイオン生成する物質を用いた場合は、該イオンが高分子電解質の特性を劣化させるという問題がある。 However, as in the case of the above-mentioned invention, for the purpose of forming a desired porous structure, if a substance that does not ultimately constitute an electrode catalyst layer, such as a pore-forming agent, is contained, the substance is removed even after the substance is removed. Part of the substance may remain as impurities in the electrode catalyst layer. In addition, when a substance that generates ions when dissolved is used as the pore-forming agent, there is a problem that the ions deteriorate the characteristics of the polymer electrolyte.
本発明は、上記課題を解決するために、造孔剤のように最終的には電極触媒層を構成しない物質を用いることなく、水素や酸素のような気体の拡散径路および水分の拡散径路としての空隙を有する触媒体を提供するものである。 In order to solve the above-mentioned problems, the present invention uses a gas diffusion path and a moisture diffusion path such as hydrogen and oxygen without using a material that does not eventually constitute an electrode catalyst layer, such as a pore-forming agent. The catalyst body which has the space | gap of this is provided.
また、本発明は、上記の触媒体を容易且つ再現性良く製造することができる方法を提供するものである。
また、本発明は、上記の触媒体を用いた固体高分子型燃料電池用膜／電極接合体を提供するものである。
The present invention also provides a method by which the above catalyst body can be produced easily and with good reproducibility.
The present invention also provides a membrane / electrode assembly for a polymer electrolyte fuel cell using the above catalyst body.
上記の課題を解決する触媒体は、三次元的に相互に連結した粒子より構成され、該粒子の間隙に細孔を有する多孔質構造体からなることを特徴とする。
上記の課題を解決する触媒体の製造方法は、三次元的に相互に連結した粒子より構成され、該粒子の間隙に細孔を有する酸化白金多孔質構造体を作製する第一の工程と、該酸化白金多孔質構造体を還元する第二の工程を含むことを特徴とする。
A catalyst body that solves the above-mentioned problems is composed of particles that are three-dimensionally connected to each other, and is composed of a porous structure having pores in the gaps between the particles.
A method for producing a catalyst body that solves the above problems includes a first step of producing a platinum oxide porous structure composed of particles three-dimensionally interconnected and having pores in the gaps between the particles, A second step of reducing the platinum oxide porous structure is included.
上記の課題を解決する固体高分子型燃料電池用膜／電極接合体は、上記の触媒体と固体高分子電解質を含有する一対の電極触媒層を、固体高分子電解質膜の両面に配置してなることを特徴とする。 A membrane / electrode assembly for a polymer electrolyte fuel cell that solves the above-mentioned problems is obtained by arranging a pair of electrode catalyst layers containing the above catalyst body and a solid polymer electrolyte on both sides of the solid polymer electrolyte membrane. It is characterized by becoming.
本発明により、造孔剤のように、最終的には電極触媒層を構成しない物質を用いることなく、水素や酸素のような気体の拡散径路および水分の拡散径路としての空隙を有する触媒体を提供できる。 According to the present invention, a catalyst body having voids as a gas diffusion path and a moisture diffusion path such as hydrogen and oxygen can be obtained without using a material that does not eventually constitute an electrode catalyst layer, such as a pore-forming agent. Can be provided.
また、本発明は、上記の触媒体を容易且つ再現性良く製造することができる方法を提供できる。
また、本発明は、上記の触媒体を用いた固体高分子型燃料電池用膜／電極接合体を提供できる。
In addition, the present invention can provide a method capable of easily and reproducibly producing the above catalyst body.
The present invention can also provide a membrane / electrode assembly for a polymer electrolyte fuel cell using the above catalyst body.
以下、本発明を詳細に説明する。
本発明に係る触媒体は、三次元的に相互に連結した粒子より構成され、該粒子の間隙に細孔を有する多孔質構造体からなることを特徴とする。
Hereinafter, the present invention will be described in detail.
The catalyst body according to the present invention is composed of a three-dimensionally interconnected particle, and a porous structure having pores in the gap between the particles.
前記触媒体が、白金からなることが好ましい。
また、本発明に係る触媒体の製造方法は、三次元的に相互に連結した粒子より構成され、該粒子の間隙に細孔を有する酸化白金多孔質構造体を作製する第一の工程と、該酸化白金多孔質構造体を還元する第二の工程を含むことを特徴とする。
The catalyst body is preferably made of platinum.
Further, the method for producing a catalyst body according to the present invention comprises a first step of producing a platinum oxide porous structure composed of particles interconnected three-dimensionally and having pores in the gaps between the particles, A second step of reducing the platinum oxide porous structure is included.
前記第一の工程が、白金または白金化合物と尿素を溶解した水溶液に、第二の物質と第三の物質または第二の物質と第三の物質の少なくとも一方を添加した前駆溶液を加熱して酸化白金多孔質構造体を作製する工程であることが好ましい。 In the first step, a precursor solution obtained by adding at least one of the second substance and the third substance or the second substance and the third substance to an aqueous solution in which platinum or a platinum compound and urea are dissolved is heated. A step of producing a platinum oxide porous structure is preferred.
前記第二の物質が、無機塩であることが好ましい。
前記第三の物質が、高分子であることが好ましい。
また、本発明に係る固体高分子型燃料電池用膜／電極接合体は、上記の触媒体と固体高分子電解質を含有する一対の電極触媒層を、固体高分子電解質膜の両面に配置してなることを特徴とする。
The second substance is preferably an inorganic salt.
The third substance is preferably a polymer.
The membrane / electrode assembly for a polymer electrolyte fuel cell according to the present invention comprises a pair of electrode catalyst layers containing the catalyst body and the solid polymer electrolyte disposed on both sides of the solid polymer electrolyte membrane. It is characterized by becoming.
以下、本発明に係る触媒体、その製造方法、およびそれを用いた固体高分子型燃料電池用膜／電極接合体の最良の形態について詳細に説明する。
（触媒体の形態および構造）
一般的には、触媒は高活性であることが求められる。そのため、固体高分子型燃料電池用の触媒体としては、数ナノメートルの白金微粒子を数十ナノメートルのカーボンブラックに担持した触媒体を用いる場合が多い。一方、固体高分子型燃料電池においては、水素および酸素のような気体、および生成した水分の拡散径路となる空隙が電極触媒層内に形成されていることが重要である。しかし、前記のようなナノメートルオーダーの粒子状の触媒体を用いて、そのような多孔質構造を容易且つ再現性良く形成することは困難である。
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a catalyst body according to the present invention, a production method thereof, and a best mode of a membrane / electrode assembly for a polymer electrolyte fuel cell using the same will be described in detail.
(Catalyst body form and structure)
In general, the catalyst is required to be highly active. Therefore, as a catalyst body for a polymer electrolyte fuel cell, a catalyst body in which several nanometers of platinum fine particles are supported on carbon black of several tens of nanometers is often used. On the other hand, in a polymer electrolyte fuel cell, it is important that voids serving as diffusion paths for gases such as hydrogen and oxygen and generated moisture are formed in the electrode catalyst layer. However, it is difficult to form such a porous structure easily and with good reproducibility using the nanometer-order particulate catalyst body as described above.
また、一般的には、比表面積と粒子径は負の相関を示す。しかし、本発明に係る触媒体は、多孔質構造体であり、三次元的に相互に連結したナノメートルオーダーの粒子を最小単位とするため、サブマイクロメートルからマイクロメートルオーダーの大きさの多孔質構造体であるにも関わらず高比表面積が実現される。このような比較的大きな形状を有する多孔質構造体は、最密充填した場合においても、該多孔質構造体間に空隙が形成される。さらに、前記多孔質構造体はナノメートルオーダーの最小単位より構成され、高比表面積を有するため、高い触媒活性を示す。 In general, the specific surface area and the particle size have a negative correlation. However, the catalyst body according to the present invention is a porous structure and has a nanometer-order particle interconnected three-dimensionally as a minimum unit, so that the porous body has a size of submicrometer to micrometer order. Despite being a structure, a high specific surface area is realized. In the porous structure having such a relatively large shape, voids are formed between the porous structures even when the porous structure is closely packed. Furthermore, since the porous structure is composed of a minimum unit of nanometer order and has a high specific surface area, it exhibits high catalytic activity.
本発明に係る触媒体を構成する最小単位としての粒子の形状としては、球状、ロッド状、ワイヤ状、薄片状などが挙げられるが特にこれらに制限されず、高比表面積を示すものであれば良く、これらの粒子は三次元的に相互に連結し、該粒子の間隙には細孔が形成されていることが好ましい。また、多孔質構造体の巨視的な形状も特に制限されないが、最密充填した場合においても嵩高い形状が好ましい。 Examples of the shape of the particles as the minimum unit constituting the catalyst body according to the present invention include a spherical shape, a rod shape, a wire shape, and a flake shape. However, the shape is not particularly limited as long as it shows a high specific surface area. It is preferable that these particles are three-dimensionally connected to each other, and pores are formed in the gaps between the particles. Further, the macroscopic shape of the porous structure is not particularly limited, but a bulky shape is preferable even when the porous structure is packed closely.
前記触媒体の平均細孔径は、１０ｎｍ以上１００ｎｍ以下、好ましくは２０ｎｍ以上８０ｎｍ以下であることが好ましい。
前記触媒体の直径は、１００ｎｍ以上１０μｍ以下、好ましくは５００ｎｍ以上５μｍ以下であることが好ましい。
The catalyst body has an average pore diameter of 10 nm to 100 nm, preferably 20 nm to 80 nm.
The catalyst body has a diameter of 100 nm to 10 μm, preferably 500 nm to 5 μm.
前記触媒体のＢＥＴ比表面積が、１０ｍ２／ｇ以上１００ｍ２／ｇ以下、好ましくは２０ｍ２／ｇ以上８０ｍ２／ｇ以下であることが好ましい。
（触媒体の製造方法）
本発明に係る触媒体は、最終生成物である白金より成る触媒体と実質的に同等の微細構造、形状、大きさを有する酸化白金の多孔質構造体を作製する第一の工程と、該酸化白金の多孔質構造体を還元して白金よりなる触媒体を作製する第二の工程により製造される。
The catalyst body has a BET specific surface area of 10 m 2 / g or more and 100 m 2 / g or less, preferably 20 m 2 / g or more and 80 m 2 / g or less.
(Method for producing catalyst body)
The catalyst body according to the present invention includes a first step of producing a porous structure of platinum oxide having a microstructure, shape, and size substantially equivalent to a catalyst body made of platinum as a final product, It is manufactured by a second step of producing a catalyst body made of platinum by reducing a porous structure of platinum oxide.
先ず、酸化白金の多孔質構造体を作製する第一の工程について説明する。
前記酸化白金の多孔質構造体の作製には、白金または白金化合物と尿素の溶解した水溶液に第二の物質と第三の物質または第二の物質と第三の物質の少なくとも一方を添加した水溶液を前駆溶液として用いる。白金または白金化合物と尿素を溶解した水溶液を７０〜８０℃に加熱し、尿素の分解により水溶液のｐＨが塩基性側へ移行すると、水溶液は酸化白金に対して過飽和である準安定状態となる。この酸化白金に対して過飽和である水溶液中では、均一核生成およびそれに続く成長により酸化白金の多孔質構造体が生成する。
First, the first step of producing a platinum oxide porous structure will be described.
For producing the porous structure of platinum oxide, an aqueous solution in which at least one of the second substance and the third substance or the second substance and the third substance is added to an aqueous solution in which platinum or a platinum compound and urea are dissolved. Is used as a precursor solution. When an aqueous solution in which platinum or a platinum compound and urea are dissolved is heated to 70 to 80 ° C. and the pH of the aqueous solution shifts to the basic side due to decomposition of urea, the aqueous solution becomes a metastable state that is supersaturated with respect to platinum oxide. In an aqueous solution that is supersaturated with respect to platinum oxide, a porous structure of platinum oxide is formed by homogeneous nucleation and subsequent growth.
このような生成過程において、前駆溶液中に第二の物質も第三の物質も共存していない時は、生成する物質固有の結晶晶癖にも依存するものの、図１に示すように、核１１は比較的等方的に成長して粒子１２を形成する。 In such a production process, when neither the second substance nor the third substance coexists in the precursor solution, it depends on the crystal habit of the substance to be produced, but as shown in FIG. 11 grows relatively isotropically to form particles 12.
しかしながら、前駆溶液中に共存種として第二の物質と第三の物質または第二の物質と第三の物質の少なくとも一方が存在する時は、図２に示すように、共存種の核２１の表面への吸着により一部の核表面の粒成長が抑制されるため、非常に複雑且つ精緻な多孔質構造体の粒子２４が形成される。 However, when there is at least one of the second substance and the third substance or the second substance and the third substance as coexisting species in the precursor solution, as shown in FIG. Since the grain growth on the surface of some of the nuclei is suppressed by the adsorption to the surface, particles 24 of a very complicated and fine porous structure are formed.
第二の物質としては、無機塩を用いることができる。より具体的には、水に可溶である硫酸塩、塩化物、硝酸塩、リン酸塩、フッ化物、次亜塩素酸塩、次亜リン酸塩、クロム酸塩、酢酸塩等を用いることが好ましい。一種類の無機塩を単独で用いても、これらの中から選択される二種類以上の無機塩を混合して用いても構わない。 An inorganic salt can be used as the second substance. More specifically, it is possible to use sulfate, chloride, nitrate, phosphate, fluoride, hypochlorite, hypophosphite, chromate, acetate, etc. that are soluble in water. preferable. One kind of inorganic salt may be used alone, or two or more kinds of inorganic salts selected from these may be mixed and used.
第三の物質としては、高分子を用いることができる。より具体的には、ポリビニルピロリドン、ポリビニルアルコール、ポリアクリル酸、ポリエチレングリコール、ポリエチレンオキサイド等の水溶性ポリマーが好適に用いられる。一種類の高分子を単独で用いても、これらの中から選択される二種類以上の高分子を混合して用いても構わない。 A polymer can be used as the third substance. More specifically, water-soluble polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polyethylene glycol, and polyethylene oxide are preferably used. One kind of polymer may be used alone, or two or more kinds of polymers selected from these may be mixed and used.
また、前駆溶液の白金の濃度、尿素の濃度、第二の物質の濃度および種類、第三の物質の濃度および種類、加熱温度、加熱時間等を変化させることにより、過飽和度、均一核生成頻度、成長速度が変化するため、多孔質構造体の巨視的な大きさや形状および最小単位としての微視的な粒子の大きさや形状を制御することができる。さらに、低過飽和度の前駆溶液中に任意の基体を浸漬させると、不均一核生成が優先的に生じるため、該基体表面に上記多孔質構造体を膜状に被覆することも可能である。 Also, by changing the concentration of platinum in the precursor solution, the concentration of urea, the concentration and type of the second substance, the concentration and type of the third substance, the heating temperature, the heating time, etc., the degree of supersaturation, the frequency of uniform nucleation Since the growth rate changes, the macroscopic size and shape of the porous structure and the microscopic particle size and shape as the minimum unit can be controlled. Further, when an arbitrary substrate is immersed in a precursor solution having a low supersaturation degree, non-uniform nucleation occurs preferentially, and thus the porous structure can be coated on the surface of the substrate in the form of a film.
次に、第一の工程で得た酸化白金の多孔質構造体を還元して白金より成る触媒体を作製する第二の工程について説明する。
上記酸化白金の多孔質構造体を還元する方法としては、還元性気体の雰囲気中で還元する方法および還元剤を含有する水溶液中で還元する方法を用いることができる。より具体的には、還元性気体としては、水素、一酸化炭素、硫化水素、メタン、アンモニア等が好適に用いられるが、特にこれに限定されない。また、還元剤を含有する水溶液としては、水素化ホウ素ナトリウム、次亜リン酸ナトリウム、アンモニア、ホルムアルデヒド、ジメチルアミンボラン、ヒドラジン等を含有する水溶液が好ましいが、これらに限定されるものではない。
Next, the second step of producing a catalyst body made of platinum by reducing the porous structure of platinum oxide obtained in the first step will be described.
As a method for reducing the platinum oxide porous structure, a method of reducing in a reducing gas atmosphere and a method of reducing in an aqueous solution containing a reducing agent can be used. More specifically, hydrogen, carbon monoxide, hydrogen sulfide, methane, ammonia and the like are preferably used as the reducing gas, but are not particularly limited thereto. The aqueous solution containing the reducing agent is preferably an aqueous solution containing sodium borohydride, sodium hypophosphite, ammonia, formaldehyde, dimethylamine borane, hydrazine, or the like, but is not limited thereto.
（固体高分子型燃料電池用膜／電極接合体）
本発明に係る触媒体を用いて作製された固体高分子型燃料電池用膜／電極接合体について説明する。
(Membrane / electrode assembly for polymer electrolyte fuel cells)
A membrane / electrode assembly for a polymer electrolyte fuel cell produced using the catalyst body according to the present invention will be described.
図３は、本発明に係る固体高分子型燃料電池の模式的な構成図である。本発明に係る膜／電極接合体を備えた固体高分子型燃料電池のセルは、高分子電解質膜３１の両面にアノード３２およびカソード３３として高分子電解質と、本発明の触媒体より成る一対の電極触媒層を配置した膜／電極接合体３４と、アノード側ガス拡散層３５、カソード側ガス拡散層３６、アノード側セパレータ３７、カソード側セパレータ３８より構成される。 FIG. 3 is a schematic configuration diagram of a polymer electrolyte fuel cell according to the present invention. A cell of a polymer electrolyte fuel cell having a membrane / electrode assembly according to the present invention comprises a pair of a polymer electrolyte as anodes 32 and cathodes 33 on both sides of a polymer electrolyte membrane 31 and a catalyst body of the present invention. A membrane / electrode assembly 34 having an electrode catalyst layer disposed thereon, an anode-side gas diffusion layer 35, a cathode-side gas diffusion layer 36, an anode-side separator 37, and a cathode-side separator 38.
高分子電解質膜は、例えば、高プロトン伝導性および気体不透過性など一般的に固体高分子型燃料電池用高分子電解質として要求される性能を具備したものであれば良く、Ｎａｆｉｏｎ（ＤｕＰｏｎｔ製）、Ｆｌｅｍｉｏｎ（旭硝子製）、Ａｃｉｐｌｅｘ（旭化成製）のような市販品を用いても良い。 The polymer electrolyte membrane only needs to have a performance generally required as a polymer electrolyte for a solid polymer fuel cell, such as high proton conductivity and gas impermeability, and Nafion (manufactured by DuPont) Commercial products such as Flemion (Asahi Glass) and Aciplex (Asahi Kasei) may also be used.
ガス拡散層は、主に電極触媒層への燃料の速やかな供給と生成した水分の外部への放出を目的として装備されるが、電子の外部回路への輸送も行わなければならないため、高い導電性を有する多孔質体である必要があり、例えば、カーボンクロスやカーボンペーパーなどが好適に用いられる。 The gas diffusion layer is equipped mainly for the purpose of promptly supplying fuel to the electrocatalyst layer and releasing the generated water to the outside, but it must also transport electrons to an external circuit, so it has high conductivity. For example, carbon cloth or carbon paper is preferably used.
また、セパレータは、燃料供給流路の確保、燃料気体の混合防止、隣接するセル同士の電気的接続を目的として配置され、高導電性、高強度、気体不透過性を有するカーボン製または金属製のものを用いることが好ましい。 The separator is arranged for the purpose of securing the fuel supply flow path, preventing mixing of fuel gas, and electrical connection between adjacent cells, and is made of carbon or metal having high conductivity, high strength, and gas impermeability. It is preferable to use those.
次に、本発明に係る固体高分子型燃料電池用膜／電極接合体の製造方法について説明する。固体高分子型燃料電池用膜／電極接合体の製造方法は特に限定されるものではなく、公知の技術により製造することできる。 Next, a method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell according to the present invention will be described. The method for producing the membrane / electrode assembly for a polymer electrolyte fuel cell is not particularly limited, and can be produced by a known technique.
先ず、電極触媒層の作製方法について説明する。電極触媒層は、作製した触媒体と高分子電解質を分散させた溶液を混合したインクを膜状に成形する方法と、作製した触媒体を分散させたインクより作製された膜状の成形体に高分子電解質を分散させた溶液を含浸する方法がある。前記触媒体と高分子電解質より成るインクまたは前記触媒体より成るインクは、多孔質カーボン電極、高分子電解質膜、または、基体上に成形される。前記基体としては、シート状のポリテトラフルオロエチレン、ポリエチレンテレフタレート、またはポリイミドを用いることができる。電極触媒層の成形方法は、ドクターブレード法、スクリーンプリント法、スプレー法のような一般的な方法で良い。 First, a method for producing an electrode catalyst layer will be described. The electrode catalyst layer is formed on a film-shaped molded body made from an ink in which a prepared catalyst body and a solution in which a polymer electrolyte is dispersed are mixed, and a film-shaped molded body made from an ink in which the produced catalyst body is dispersed. There is a method of impregnating a solution in which a polymer electrolyte is dispersed. The ink composed of the catalyst body and the polymer electrolyte or the ink composed of the catalyst body is formed on a porous carbon electrode, a polymer electrolyte membrane, or a substrate. As the substrate, sheet-like polytetrafluoroethylene, polyethylene terephthalate, or polyimide can be used. The electrode catalyst layer may be formed by a general method such as a doctor blade method, a screen printing method, or a spray method.
次に、前記電極触媒層を備えた固体高分子型燃料電池用膜／電極接合体の作製方法について説明する。形成された電極触媒層を高分子電解質膜と熱圧着すると膜／電極接合体が得られる。電極触媒層を基体上に成形した場合は、電極触媒層を基体ごと高分子電解質膜と熱圧着することにより転写する。また、電極触媒層を高分子電解質膜上に直接成形した場合は、そのまま熱圧着する。熱圧着による接合方法は、例えば、ホットプレスやロールプレスのような方法を用いることができる。 Next, a method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell having the electrode catalyst layer will be described. When the formed electrode catalyst layer is thermocompression bonded to the polymer electrolyte membrane, a membrane / electrode assembly is obtained. When the electrode catalyst layer is formed on the substrate, the electrode catalyst layer is transferred by thermocompression bonding with the polymer electrolyte membrane together with the substrate. When the electrode catalyst layer is directly formed on the polymer electrolyte membrane, it is directly thermocompression bonded. As a joining method by thermocompression bonding, for example, a method such as hot pressing or roll pressing can be used.
以下、実施例により、本発明を更に詳細に説明するが、本発明はこれら実施例に限定されるものではない。
実施例１
本実施例は、白金化合物、尿素、硫酸ナトリウム、ポリアクリル酸ナトリウムの溶解した水溶液を加熱して酸化白金の多孔質構造体を作製した後、該酸化白金の多孔質構造体を還元して、多孔質構造を有する白金の触媒体を製造するものである。
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
Example 1
In this example, a platinum oxide porous structure was prepared by heating an aqueous solution in which a platinum compound, urea, sodium sulfate, and sodium polyacrylate were dissolved, and then reducing the platinum oxide porous structure. A platinum catalyst body having a porous structure is produced.
テトラクロロ白金酸カリウム（Ｋ２ＰｔＣｌ４）を超純水に溶解させた水溶液に尿素（ＮＨ２ＣＯＮＨ２）、硫酸ナトリウム（Ｎａ２ＳＯ４）、ポリアクリル酸ナトリウム（ＰＡＡ；重量平均分子量２１００）を順に添加したものを前駆溶液とした。前駆溶液の組成は、Ｋ２ＰｔＣｌ４：ＮＨ２ＣＯＮＨ２：Ｎａ２ＳＯ４：ＰＡＡ：Ｈ２Ｏ＝２：１：１０：０．２：１０００のモル比となるようにした。この前駆溶液を８０℃の恒温槽で４８時間保持したところ、黒褐色の沈殿が生成した。前記黒褐色の沈殿は、水洗と遠心分離を数回繰返した後、室温で乾燥した。 In an aqueous solution in which potassium tetrachloroplatinate (K 2 PtCl 4 ) is dissolved in ultrapure water, urea (NH 2 CONH 2 ), sodium sulfate (Na 2 SO 4 ), sodium polyacrylate (PAA; weight average molecular weight 2100) Were added in order as a precursor solution. The composition of the precursor solution was set to a molar ratio of K 2 PtCl 4 : NH 2 CONH 2 : Na 2 SO 4 : PAA: H 2 O = 2: 1: 10: 0.2: 1000. When this precursor solution was kept in a constant temperature bath at 80 ° C. for 48 hours, a blackish brown precipitate was formed. The black-brown precipitate was dried at room temperature after being repeatedly washed with water and centrifuged several times.
走査型電子顕微鏡による観察の結果を図４Ａ，Ｂに示す。図４Ａは、実施例１の酸化白金からなる多孔質構造体のマクロ構造を示す走査型電子顕微鏡写真である。図４Ｂは、実施例１の酸化白金からなる多孔質構造体のミクロ構造を示す走査型電子顕微鏡写真である。 The results of observation with a scanning electron microscope are shown in FIGS. 4A and 4B. 4A is a scanning electron micrograph showing the macro structure of the porous structure made of platinum oxide of Example 1. FIG. 4B is a scanning electron micrograph showing the microstructure of the porous structure made of platinum oxide of Example 1. FIG.
生成した沈殿は直径約１μｍの球状粒子であり、約２０ｎｍの球状のユニットが互いに数珠状に連結し、その間隙に細孔を有する多孔質構造体であった。また、Ｘ線回折測定により、この多孔質構造体は酸化白金であることが確認された。 The produced precipitate was a spherical particle having a diameter of about 1 μm, and a porous structure having spherical units having a diameter of about 20 nm connected to each other in a bead shape and having pores in the gaps. Further, it was confirmed by X-ray diffraction measurement that the porous structure was platinum oxide.
この粒子を３７％ホルムアルデヒド水溶液の入った耐圧容器に加え、１００℃で２４時間還元した。還元後の粒子の形態を走査型電子顕微鏡により観察したところ、還元前の酸化白金粒子の巨視的および微視的形態を維持していた。Ｘ線回折測定の結果、酸化白金は白金に還元されていることが確認され、窒素吸着測定法によるＢＥＴ比表面積は約２０ｍ２／ｇであった。 The particles were added to a pressure vessel containing a 37% aqueous formaldehyde solution and reduced at 100 ° C. for 24 hours. When the morphology of the particles after reduction was observed with a scanning electron microscope, the macroscopic and microscopic morphology of the platinum oxide particles before reduction were maintained. As a result of the X-ray diffraction measurement, it was confirmed that platinum oxide was reduced to platinum, and the BET specific surface area by the nitrogen adsorption measurement method was about 20 m 2 / g.
前記白金触媒体１ｇと５％Ｎａｆｉｏｎ（登録商標）分散溶液２ｍｌを混合してインクを調製し、ＰＴＦＥシート上にドクターブレード法で製膜して電極触媒層を作製した。前記電極触媒層をＮａｆｉｏｎ（登録商標）１１２（ＤｕＰｏｎｔ製）の両面に配置し、１５０℃でホットプレスすることにより固体高分子型燃料電池用膜／電極接合体を作製した。 An ink was prepared by mixing 1 g of the platinum catalyst body and 2 ml of a 5% Nafion (registered trademark) dispersion solution, and forming an electrode catalyst layer on a PTFE sheet by a doctor blade method. The electrode catalyst layer was placed on both sides of Nafion (registered trademark) 112 (manufactured by DuPont), and hot-pressed at 150 ° C. to prepare a membrane / electrode assembly for a polymer electrolyte fuel cell.
実施例２
本実施例は、白金化合物、尿素、硫酸ナトリウムの溶解した水溶液を加熱して酸化白金粒子を作製した後、該酸化白金の多孔質構造体を還元して、多孔質構造を有する白金の触媒体を製造するものである。
Example 2
In this example, platinum oxide particles were prepared by heating an aqueous solution in which a platinum compound, urea, and sodium sulfate were dissolved to produce platinum oxide particles, and then reducing the platinum oxide porous structure to obtain a platinum catalyst having a porous structure. Is to be manufactured.
テトラクロロ白金酸カリウム（Ｋ２ＰｔＣｌ４）を超純水に溶解させた水溶液に尿素（ＮＨ２ＣＯＮＨ２）と硫酸ナトリウム（Ｎａ２ＳＯ４）を順に添加したものを前駆溶液とした。前駆溶液の組成は、Ｋ２ＰｔＣｌ４：ＮＨ２ＣＯＮＨ２：Ｎａ２ＳＯ４：Ｈ２Ｏ＝２：１：１０：１０００のモル比となるようにした。この前駆溶液を６０℃の恒温槽で９６時間保持したところ、黒褐色の沈殿が生成した。得られた沈殿は、水洗と遠心分離を数回繰返した後、室温で乾燥した。 A precursor solution was obtained by sequentially adding urea (NH 2 CONH 2 ) and sodium sulfate (Na 2 SO 4 ) to an aqueous solution in which potassium tetrachloroplatinate (K 2 PtCl 4 ) was dissolved in ultrapure water. The composition of the precursor solution was set to a molar ratio of K 2 PtCl 4 : NH 2 CONH 2 : Na 2 SO 4 : H 2 O = 2: 1: 10: 1000. When this precursor solution was kept in a constant temperature bath at 60 ° C. for 96 hours, a blackish brown precipitate was formed. The obtained precipitate was repeatedly washed with water and centrifuged several times, and then dried at room temperature.
走査型電子顕微鏡による観察の結果を図５Ａ，Ｂに示す。図５Ａは、実施例２の酸化白金からなる多孔質構造体のマクロ構造を示す走査型電子顕微鏡写真である。図５Ｂは、実施例２の酸化白金からなる多孔質構造体のミクロ構造を示す走査型電子顕微鏡写真である。 The results of observation with a scanning electron microscope are shown in FIGS. 5A and 5B. 5A is a scanning electron micrograph showing the macro structure of the porous structure made of platinum oxide of Example 2. FIG. 5B is a scanning electron micrograph showing the microstructure of the porous structure made of platinum oxide of Example 2. FIG.
生成した沈殿は直径約２μｍの粒子状物質であり、約１０ｎｍの厚さの花弁状ユニットが集合し、その間隙に細孔を有する多孔質構造体であった。また、Ｘ線回折測定により、この多孔質構造体は酸化白金であることが確認された。 The produced precipitate was a particulate material having a diameter of about 2 μm, and was a porous structure in which petal-like units having a thickness of about 10 nm were assembled and pores were formed in the gaps. Further, it was confirmed by X-ray diffraction measurement that the porous structure was platinum oxide.
この粒子を水素雰囲気中で２００℃、１時間加熱還元した。還元後の粒子の走査型電子顕微鏡による観察の結果、還元前の酸化白金粒子の巨視的および微視的形態を維持していた。また、Ｘ線回折測定により酸化白金は白金に還元されていることが確認され、窒素吸着等温線測定より算出されたＢＥＴ比表面積は約３０ｍ２／ｇであった。 The particles were reduced by heating at 200 ° C. for 1 hour in a hydrogen atmosphere. As a result of observing the particles after reduction with a scanning electron microscope, the macroscopic and microscopic morphology of the platinum oxide particles before reduction were maintained. Further, it was confirmed by X-ray diffraction measurement that platinum oxide was reduced to platinum, and the BET specific surface area calculated from nitrogen adsorption isotherm measurement was about 30 m 2 / g.
前記白金触媒体を用いて、実施例１と同様の方法で固体高分子型燃料電池用膜／電極接合体を作製した。 Using the platinum catalyst, a membrane / electrode assembly for a polymer electrolyte fuel cell was produced in the same manner as in Example 1.
本発明に係る触媒体は、携帯電話、ノート型パソコンのようなモバイル機器用の小型の固体高分子型燃料電池へ利用可能である。 The catalyst body according to the present invention can be used for small solid polymer fuel cells for mobile devices such as mobile phones and notebook computers.
１１ 不均一核生成により生成した核
１２ 成長後の粒子
２１ 不均一核生成により生成した核
２２ 第二の物質
２３ 第三の物質
２４ 成長後の粒子
３１ 高分子電解質膜
３２ アノード
３３ カソード
３４ 膜／電極接合体
３５ アノード側ガス拡散層
３６ カソード側ガス拡散層
３７ アノード側セパレータ
３８ カソード側セパレータ
11 Nuclei generated by heterogeneous nucleation 12 Particles after growth 21 Nuclei generated by heterogeneous nucleation 22 Second material 23 Third material 24 Particles after growth 31 Polymer electrolyte membrane 32 Anode 33 Cathode 34 membrane / Electrode assembly 35 Anode side gas diffusion layer 36 Cathode side gas diffusion layer 37 Anode side separator 38 Cathode side separator
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