JP2016088763A - Carbon nanofiber/carbon nanoparticle composite and method for producing the same, and catalyst using carbon nanofiber/carbon nanoparticle composite - Google Patents
Carbon nanofiber/carbon nanoparticle composite and method for producing the same, and catalyst using carbon nanofiber/carbon nanoparticle composite Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 71
- 239000011852 carbon nanoparticle Substances 0.000 title claims abstract description 55
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 239000002131 composite material Substances 0.000 title claims abstract description 48
- 239000002134 carbon nanofiber Substances 0.000 title claims abstract description 44
- 238000004519 manufacturing process Methods 0.000 title claims description 20
- 239000006229 carbon black Substances 0.000 claims abstract description 71
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000000446 fuel Substances 0.000 claims abstract description 35
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 26
- 239000011148 porous material Substances 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 41
- 229910052799 carbon Inorganic materials 0.000 claims description 38
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 26
- 239000007789 gas Substances 0.000 claims description 22
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 17
- 150000003839 salts Chemical class 0.000 claims description 13
- 230000003197 catalytic effect Effects 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 10
- 229910045601 alloy Inorganic materials 0.000 claims description 9
- 239000000956 alloy Substances 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 9
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 8
- 239000005977 Ethylene Substances 0.000 claims description 8
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 8
- 239000012298 atmosphere Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- CLBRCZAHAHECKY-UHFFFAOYSA-N [Co].[Pt] Chemical compound [Co].[Pt] CLBRCZAHAHECKY-UHFFFAOYSA-N 0.000 claims description 4
- 239000010931 gold Substances 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 229910052763 palladium Inorganic materials 0.000 claims description 4
- CFQCIHVMOFOCGH-UHFFFAOYSA-N platinum ruthenium Chemical compound [Ru].[Pt] CFQCIHVMOFOCGH-UHFFFAOYSA-N 0.000 claims description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 3
- ATYMFSXXDJFCKP-UHFFFAOYSA-N [Co].[Mn].[Pt] Chemical compound [Co].[Mn].[Pt] ATYMFSXXDJFCKP-UHFFFAOYSA-N 0.000 claims description 3
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 3
- WTNQAVHULAZUFR-UHFFFAOYSA-N antimony;oxotin;platinum Chemical compound [Sb].[Pt].[Sn]=O WTNQAVHULAZUFR-UHFFFAOYSA-N 0.000 claims description 3
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 3
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 claims description 3
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 229910052741 iridium Inorganic materials 0.000 claims description 3
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052749 magnesium Inorganic materials 0.000 claims description 3
- 239000011777 magnesium Substances 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 3
- HWLDNSXPUQTBOD-UHFFFAOYSA-N platinum-iridium alloy Chemical class [Ir].[Pt] HWLDNSXPUQTBOD-UHFFFAOYSA-N 0.000 claims description 3
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 claims description 3
- 229910052709 silver Inorganic materials 0.000 claims description 3
- 239000004332 silver Substances 0.000 claims description 3
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 3
- 229910001887 tin oxide Inorganic materials 0.000 claims description 3
- 229910000531 Co alloy Inorganic materials 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 2
- 229910000914 Mn alloy Inorganic materials 0.000 claims description 2
- 229910001252 Pd alloy Inorganic materials 0.000 claims description 2
- 229910000566 Platinum-iridium alloy Inorganic materials 0.000 claims description 2
- 229910000929 Ru alloy Inorganic materials 0.000 claims description 2
- 229910001245 Sb alloy Inorganic materials 0.000 claims description 2
- 239000002140 antimony alloy Substances 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
- 229910000457 iridium oxide Inorganic materials 0.000 claims description 2
- 150000002739 metals Chemical class 0.000 claims description 2
- 229910001925 ruthenium oxide Inorganic materials 0.000 claims description 2
- 229910001936 tantalum oxide Inorganic materials 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims 2
- 239000003575 carbonaceous material Substances 0.000 abstract description 10
- 239000000835 fiber Substances 0.000 abstract description 4
- 230000006866 deterioration Effects 0.000 abstract 2
- 239000002657 fibrous material Substances 0.000 abstract 1
- 235000019241 carbon black Nutrition 0.000 description 67
- 230000015572 biosynthetic process Effects 0.000 description 26
- 238000003786 synthesis reaction Methods 0.000 description 26
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- 229910002555 FeNi Inorganic materials 0.000 description 7
- 239000002086 nanomaterial Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000010453 quartz Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 239000001307 helium Substances 0.000 description 5
- 229910052734 helium Inorganic materials 0.000 description 5
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 5
- 229910021392 nanocarbon Inorganic materials 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229920000557 Nafion® Polymers 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 229910006404 SnO 2 Inorganic materials 0.000 description 2
- YNMICVQQTIWUQI-UHFFFAOYSA-N [Sb].[Pt] Chemical compound [Sb].[Pt] YNMICVQQTIWUQI-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000010411 electrocatalyst Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000002121 nanofiber Substances 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000011883 electrode binding agent Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical group 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000976 ink Substances 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000001947 vapour-phase growth Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Abstract
Description
本発明はカーボン系材料に関し、特にカーボンナノファイバー−カーボンナノ粒子複合体及びその製造方法に関する。本発明は更に当該複合体を触媒担体として使用した燃料電池用の触媒にも関する。 The present invention relates to a carbon-based material, and particularly to a carbon nanofiber-carbon nanoparticle composite and a method for producing the same. The present invention further relates to a catalyst for a fuel cell using the composite as a catalyst carrier.
カーボンは今、いろんな産業分野で重要な材料として使用されている。カーボン材料は現在多くの種類のものが広範に使用され、科学技術の発展により現在も新規なカーボン材料の開発が続いている（特許文献１〜５）。 Carbon is now used as an important material in various industrial fields. Many types of carbon materials are widely used at present, and new carbon materials are still being developed due to the development of science and technology (Patent Documents 1 to 5).
カーボン材料は形状によって異なる特徴を持ち、様々な産業分野で使用されている。その中で最も広く使用されているカーボン材料がカーボンブラックである。カーボンブラックは炭化水素を不完全燃焼あるいは熱分解することによって大量生産が可能な材料である。原料ガス、製造方法及び製造条件によってそれぞれのカーボンブラック特性が異なるため様々なカーボンブラックに分類されている。このカーボンブラックは黒色顔料（インク、コピートナーなど）やゴム製品への添加剤、石油の脱硫などの吸着剤、リチウム二次電池で負極材料の導電材及び燃料電池の電極触媒担体など幅広い用度に用いられている。特に低コスト性、優れた伝導性及び化学的安定性を有するとともに、大きな比表面積を有していて電極触媒である白金貴金属触媒を分撒させることができ、また触媒活性を向上することができるため、カーボンブラックは燃料電池電極触媒担体としても広く利用されている。 Carbon materials have different characteristics depending on their shapes, and are used in various industrial fields. Among them, the most widely used carbon material is carbon black. Carbon black is a material that can be mass-produced by incomplete combustion or thermal decomposition of hydrocarbons. Since the characteristics of each carbon black differ depending on the raw material gas, the production method and the production conditions, they are classified into various carbon blacks. This carbon black is widely used for black pigments (inks, copy toners, etc.), additives for rubber products, adsorbents for petroleum desulfurization, conductive materials for negative electrode materials in lithium secondary batteries, and electrode catalyst carriers for fuel cells. It is used for. In particular, it has low cost, excellent conductivity and chemical stability, has a large specific surface area, can separate the platinum noble metal catalyst which is an electrode catalyst, and can improve the catalytic activity. Therefore, carbon black is widely used as a fuel cell electrode catalyst carrier.
しかし、カーボンブラックは以下のような問題も有している。すなわち、カーボンブラックは多くの気孔を有するため、径が４０ｎｍ以上の一次孔（primary pore）を持っている。白金が一次孔内部に担持された電極触媒を燃料電池等に使用した場合には、電極バインダーが一次孔内部の白金に接触しなくなり、これによって一次孔中の白金が触媒活性を発揮できなくなってしまうことがある。 However, carbon black also has the following problems. That is, since carbon black has many pores, it has primary pores with a diameter of 40 nm or more. When an electrode catalyst in which platinum is supported in the primary hole is used in a fuel cell or the like, the electrode binder does not come into contact with the platinum in the primary hole, which prevents the platinum in the primary hole from exhibiting catalytic activity. May end up.
燃料電池電極触媒担体としてのカーボンブラックの問題点を解消するため、カーボン材料としてカーボンナノチューブ（ＣＮＴ）、カーボンナノファイバー（ＣＮＦ）などのカーボンナノ材料を使用することが検討されている（特許文献４、５）。カーボンナノ材料の形状はカーボンブラックとは異なり、線径が数ｎｍから数十ｎｍ程度の繊維状であるため、カーボンブラックのような多くの気孔を持っていない。更に、これらのカーボンナノ材料は高い結晶性、高電気伝導性、高熱伝導性及び高い有効比表面積などの優れた性質を有している。しかし、合成したカーボンナノ材料は通常は互いに絡み合った凝集体として得られるため、この種のナノ材料は分散性が悪く、良好な性能を有する電極触媒を作製することは困難であるという問題がある。 In order to solve the problem of carbon black as a fuel cell electrode catalyst carrier, the use of carbon nanomaterials such as carbon nanotubes (CNT) and carbon nanofibers (CNF) as carbon materials has been studied (Patent Document 4). 5). Unlike carbon black, the shape of the carbon nanomaterial is a fiber having a diameter of several nanometers to several tens of nanometers, and therefore does not have many pores like carbon black. Furthermore, these carbon nanomaterials have excellent properties such as high crystallinity, high electrical conductivity, high thermal conductivity, and high effective specific surface area. However, since synthesized carbon nanomaterials are usually obtained as aggregates intertwined with each other, this type of nanomaterial has poor dispersibility, and it is difficult to produce an electrocatalyst having good performance. .
本発明の課題は、カーボンブラックで代表されるカーボンナノ粒子を触媒単体として使用する際に問題を引き起こす一次孔が少なく、またカーボンナノ材料を使用する際に問題となる繊維の低分散性を改善したカーボン材料を提供することである。 The object of the present invention is to reduce the number of primary pores that cause problems when using carbon nanoparticles represented by carbon black as a single catalyst, and to improve the low dispersibility of fibers that are problematic when using carbon nanomaterials. Is to provide an improved carbon material.
本発明の一側面によれば、カーボンナノ粒子表面にカーボンナノファイバーが設けられている、カーボンナノファイバー−カーボンナノ粒子複合体が与えられる。
ここで、前記カーボンナノ粒子はカーボンブラックであってよい。
また、前記カーボンナノファイバーは前記カーボンナノ粒子表面上の一次孔の少なくとも一部を塞いでいてよい。
また、前記カーボンナノ粒子の直径は６０ｎｍ〜１２０ｎｍであり、前記カーボンナノファイバーの直径は１０ｎｍから１００ｎｍ、長さは１０ｎｍ〜１０μｍであってよい。
また、前記カーボンナノファイバーは前記カーボンナノ粒子から屈曲して伸びてよい。
本発明の他の側面によれば、表面に金属が担持されたカーボンナノ粒子に炭素源を含む原料ガスを供給して加熱することにより、カーボンナノ粒子表面にカーボンナノファイバーを成長させる、カーボンナノファイバー−カーボンナノ粒子複合体の製造方法が与えられる。
ここで、前記炭素源はエチレン、アセチレン及びメタンからなる群から選択された一または複数のガスであってよい。
また、前記金属はニッケル、鉄、銅、マグネシウム及びコバルトからなる群から選択された複数の金属の組み合わせであってよい。
また、金属塩が担持されたカーボンナノ粒子を還元性雰囲気中で加熱することにより前記表面に金属が担持されたカーボンナノ粒子を得てよい。
また、前記還元性雰囲気は水素を含んでよい。
また、前記加熱を６１０℃から１０００℃の温度範囲で１０分から２時間行ってよい。
本発明の更に他の側面によれば、上記何れかのカーボンナノ繊維−カーボンナノ粒子複合体に触媒活性を有する物質を担持させた触媒が与えられる。
ここで、前記触媒活性を有する物質は白金、パラジウム、イリジウム、金、銀、ニッケル、鉄、白金−ルテニウム合金、白金−パラジウム合金、白金−イリジウム合金、白金−コバルト合金、白金−コバルト−マンガン合金、白金−アンチモン合金、白金−アンチモン−酸化スズ合金、酸化ルテニウム、酸化イリジウム、酸化スズ、ジルコニア、チタニア、セリア、酸化タンタル及び酸化アルミニウムからなる群から選択されてよい。
本発明の更に他の側面によれば、上記何れかの触媒からなる燃料電池電極用触媒が与えられる。
According to one aspect of the present invention, a carbon nanofiber-carbon nanoparticle composite is provided in which carbon nanofibers are provided on the surface of the carbon nanoparticle.
Here, the carbon nanoparticles may be carbon black.
The carbon nanofibers may block at least a part of primary pores on the surface of the carbon nanoparticles.
The carbon nanoparticles may have a diameter of 60 nm to 120 nm, the carbon nanofibers may have a diameter of 10 nm to 100 nm, and a length of 10 nm to 10 μm.
The carbon nanofibers may be bent and extend from the carbon nanoparticles.
According to another aspect of the present invention, a carbon nanofiber is grown on the surface of a carbon nanoparticle by supplying a source gas containing a carbon source to the carbon nanoparticle having a metal supported on the surface and heating the carbon nanoparticle. A method for producing a fiber-carbon nanoparticle composite is provided.
Here, the carbon source may be one or more gases selected from the group consisting of ethylene, acetylene, and methane.
The metal may be a combination of a plurality of metals selected from the group consisting of nickel, iron, copper, magnesium and cobalt.
Moreover, the carbon nanoparticle carrying a metal salt may be obtained by heating the carbon nanoparticle carrying a metal salt in a reducing atmosphere.
The reducing atmosphere may contain hydrogen.
The heating may be performed at a temperature range of 610 ° C. to 1000 ° C. for 10 minutes to 2 hours.
According to still another aspect of the present invention, there is provided a catalyst in which a substance having catalytic activity is supported on any of the above carbon nanofiber-carbon nanoparticle composites.
Here, the substance having catalytic activity is platinum, palladium, iridium, gold, silver, nickel, iron, platinum-ruthenium alloy, platinum-palladium alloy, platinum-iridium alloy, platinum-cobalt alloy, platinum-cobalt-manganese alloy. , Platinum-antimony alloy, platinum-antimony-tin oxide alloy, ruthenium oxide, iridium oxide, tin oxide, zirconia, titania, ceria, tantalum oxide and aluminum oxide.
According to still another aspect of the present invention, a fuel cell electrode catalyst comprising any one of the above catalysts is provided.
本発明により、分散性が良好であり、また触媒をその活性を失わせることなく担持できるカーボンナノファイバー−カーボンナノ粒子複合体が与えられる。 The present invention provides a carbon nanofiber-carbon nanoparticle composite having good dispersibility and capable of supporting a catalyst without losing its activity.
本発明の材料であるＣＮＦとＣＢ等のカーボンナノ粒子との複合体（ＣＮＦ−カーボンナノ粒子複合体）は、図１に示すように、ＣＢ等のカーボンナノ粒子の表面に繊維状のナノサイズのカーボンを結合させ、または成長させた構造を有する。このナノ繊維がＣＢ等のカーボンナノ粒子表面の一次孔を覆うなどして塞ぐため、一次孔内に白金等が入りこむことによる触媒活性の低下が防止される。更に、カーボンナノ粒子表面に所要の金属を比較的一様に分布させてから、この金属を起点としてＣＮＦの成長を開始させるため、ＣＢ表面上の特定の箇所で集中してＣＮＦが成長あるいは結合する場合に比べてＣＮＦ同士の絡み合いの程度が小さくなる。更には、成長するＣＮＦは、遠方に向かって直線状に伸びるよりは、図１に示すように屈曲しながら成長して成長開始点周囲を取り囲むようになる傾向が強いため、他のＣＢ上のような遠方で成長を開始したＣＮＦと接触して絡み合う確率が低くなる。これらの要因により、ＣＮＦだけからなる従来の材料に比べて、本発明の複合体はＣＮＦ相互の絡み合いが少なくなり、従って従来の材料に比べて分散性が向上する。また、ＣＮＦが屈曲してカーボンナノ粒子表面を覆うように伸びることにより、ＣＮＦが効率よく一次孔を塞ぐことができる。 As shown in FIG. 1, a composite of CNF and carbon nanoparticles such as CB (CNF-carbon nanoparticle composite), which is a material of the present invention, has a fibrous nanosize on the surface of carbon nanoparticles such as CB. It has a structure in which carbon is bonded or grown. Since the nanofibers cover and block the primary pores on the surface of the carbon nanoparticle such as CB, the catalytic activity is prevented from being lowered due to platinum or the like entering the primary pores. Furthermore, after a required metal is distributed relatively uniformly on the surface of the carbon nanoparticle, CNF growth starts from this metal as a starting point, so that CNF grows or binds at a specific location on the CB surface. The degree of entanglement between the CNFs is smaller than that in the case of doing so. Further, since the growing CNF tends to grow while bending as shown in FIG. 1 to surround the growth start point rather than linearly extending toward the far side, Thus, the probability of entanglement with the CNF that has started to grow at a far distance becomes low. Due to these factors, the composite of the present invention is less entangled with each other than the conventional material consisting only of CNF, and thus the dispersibility is improved as compared with the conventional material. In addition, CNF can bend and extend so as to cover the carbon nanoparticle surface, so that CNF can efficiently close the primary hole.
従来の燃料電池用電極触媒の製造方法の多くは、高温、長時間、製造プロセスが複雑なプロセスで構成されている（特許文献６〜１０）。その結果、燃料電池用電極触媒のコストは高くなる。これに対して、本発明では低温、短時間かつ単純な製造プロセスにより燃料電池用電極触媒のコスト低減を達成する燃料電池用電極触媒等の触媒の製造方法が提供される。具体的には、本発明ではＣＮＦ−カーボンナノ粒子複合体を化学蒸着法により直接合成し、これを白金金属触媒等の触媒活性を有する物質の担体として利用する。触媒活性を有する物質としては、他にパラジウム（Ｐｄ）、イリジウム（Ｉｒ）、金（Ａｕ）、銀（Ａｇ）、ニッケル（Ｎｉ）、鉄（Ｆｅ）、白金−ルテニウム（Ｐｔ−Ｒｕ）合金、白金−パラジウム（Ｐｔ−Ｐｄ）合金、白金−イリジウム（Ｐｔ−Ｉｒ）合金、白金−コバルト（Ｐｔ−Ｃｏ）合金、白金−コバルト−マンガン（Ｐｔ−Ｃｏ−Ｍｎ）合金、白金−アンチモン（Ｐｔ−Ｓｂ）合金、白金−アンチモン−酸化スズ（Ｐｔ−Ｓｂ−ＳｎＯ２）合金、酸化ルテニウム（ＲｕＯ２）、酸化イリジウム（ＩｒＯ２）、酸化スズ（ＳｎＯ２）、ジルコニア（ＺｒＯ２）、チタニア（ＴｉＯ２）、セリア（ＣｅＯ２）、酸化タンタル（Ｔａ２Ｏ５）、酸化アルミニウム（Ａｌ２Ｏ３）等を使用することができる。 Many of the conventional methods for producing an electrode catalyst for a fuel cell are composed of a high temperature, a long time, and a complicated production process (Patent Documents 6 to 10). As a result, the cost of the fuel cell electrode catalyst increases. In contrast, the present invention provides a method for producing a catalyst such as a fuel cell electrode catalyst that achieves cost reduction of the fuel cell electrode catalyst by a simple production process at a low temperature for a short time. Specifically, in the present invention, a CNF-carbon nanoparticle composite is directly synthesized by a chemical vapor deposition method and used as a carrier for a substance having catalytic activity such as a platinum metal catalyst. Other materials having catalytic activity include palladium (Pd), iridium (Ir), gold (Au), silver (Ag), nickel (Ni), iron (Fe), platinum-ruthenium (Pt-Ru) alloy, Platinum-palladium (Pt-Pd) alloy, platinum-iridium (Pt-Ir) alloy, platinum-cobalt (Pt-Co) alloy, platinum-cobalt-manganese (Pt-Co-Mn) alloy, platinum-antimony (Pt- Sb) alloy, platinum-antimony-tin oxide (Pt—Sb—SnO 2 ) alloy, ruthenium oxide (RuO 2 ), iridium oxide (IrO 2 ), tin oxide (SnO 2 ), zirconia (ZrO 2 ), titania (TiO 2 ) 2 ), ceria (CeO 2 ), tantalum oxide (Ta 2 O 5 ), aluminum oxide (Al 2 O 3 ), and the like can be used.
なお、本発明ではＣＢに限らず、カーボンナノ材料等のカーボン材料一般の上にカーボンナノ繊維を成長させることができるが、本願明細書ではカーボン材料の一例としてＣＢについて説明を行っていることに注意されたい。 In the present invention, carbon nanofibers can be grown not only on CB but on carbon materials such as carbon nanomaterials in general. In the present specification, CB is described as an example of a carbon material. Please be careful.
以下の実施例においては、カーボンナノ粒子としてＣＢを用い、本発明の単純な触媒製造方法を利用して燃料電池用電極触媒を製造し、分析及び評価を行なった。 In the following examples, CB was used as carbon nanoparticles, and an electrode catalyst for a fuel cell was produced using the simple catalyst production method of the present invention, and was analyzed and evaluated.
［二元金属をＣＢの表面に担持した触媒の製造］
ＣＢとしてVulcan XC-72R（ＶＣ）を使用し、ＦｅＮｉ二元金属触媒の前駆体である二元金属塩としてＮｉ（ＮＯ３）６Ｈ２Ｏ（Nacalai tesque社）及びＦｅ（ＮＯ３）３９Ｈ２Ｏ（Aldrich社）を使用してＣＢの表面に当該二元金属塩を担持し、これを還元性雰囲気中で加熱することにより、ＣＮＦ−ＣＢ複合体の合成に必要な触媒を製造した。製造方法としては、先ずエタノール（Wako社）１００ｍｌにＦｅ及びＮｉを金属換算で１ｇ（ＦｅとＮｉとの重量比は２：８、上記金属塩の量としては、Ｆｅ塩を３．９６２ｇ、Ｎｉ塩を０．７６９ｇ）添加して１時間攪拌した。その後、ＣＢを９ｇ添加して２４時間攪拌を行なった。攪拌終了後、蒸発装置を利用して８０℃の温度で攪拌することによってエタノールを蒸発させ、Ｆｅ及びＮｉの塩（二元金属塩、ＦｅＮｉ塩とも称する）を担持したＣＢを得た。その後、ＦｅＮｉ塩を担持しているＣＢ粉末を１００℃の乾燥装置で２４時間乾燥させた。なお、ＣＢとしては、一次粒子サイズが６０ｎｍ〜１２０ｎｍ、二次粒子サイズが５００ｎｍ〜数μｍのものが好適に使用できる。
[Production of catalyst with binary metal supported on CB surface]
Vulcan XC-72R (VC) is used as CB, and Ni (NO 3 ) 6 H 2 O (Nacalai tesque) and Fe (NO 3 ) 3 9H 2 are used as the binary metal salt that is the precursor of the FeNi bimetallic catalyst. The catalyst required for the synthesis | combination of a CNF-CB composite_body | complex was manufactured by carrying | supporting the said binary metal salt on the surface of CB using O (Aldrich), and heating this in reducing environment. As a production method, first, 1 g of Fe and Ni in terms of metal is added to 100 ml of ethanol (Wako) (Fe: Ni weight ratio is 2: 8, the amount of the metal salt is 3.962 g of Fe salt, Ni 0.769 g of salt) was added and stirred for 1 hour. Thereafter, 9 g of CB was added and stirred for 24 hours. After the completion of stirring, ethanol was evaporated by stirring at a temperature of 80 ° C. using an evaporator to obtain CB carrying Fe and Ni salts (also referred to as binary metal salt and FeNi salt). Thereafter, the CB powder carrying the FeNi salt was dried for 24 hours with a drying apparatus at 100 ° C. As CB, those having a primary particle size of 60 nm to 120 nm and a secondary particle size of 500 nm to several μm can be suitably used.
［ＣＮＦ−ＣＢ複合体の合成］
上述の通り製造した、ＦｅＮｉの二元金属塩を担持しているＣＢをＣＮＦ−ＣＢ複合体の種として使用し、気相成長法を利用して合成を行なった。この時、石英チューブ内部には圧力を掛けず、常圧の状態でＣＮＦ−ＣＢ複合体の合成を行なった。この合成の間に供給するガスにはヘリウム、水素及びエチレンガスの混合ガスを使用した。それぞれのガスの役割は、ヘリウムガスは不活性ガスとして使用し、水素ガスはこれを石英チューブ内部に導入することによって触媒表面から酸素又は水分を除去して、ＦｅＮｉ触媒を活性化させる還元ガスとして使用した。また、エチレンガスは還元されたＦｅＮｉ触媒の表面で触媒と反応してＣＮＦを成長させ、ＣＮＦ−ＣＢ複合体を合成させる原料ガス（炭素源）として使用した。
[Synthesis of CNF-CB Complex]
Synthesis was carried out using the vapor phase growth method using CB carrying the FeNi binary metal salt produced as described above as the seed of the CNF-CB composite. At this time, the CNF-CB composite was synthesized under normal pressure without applying pressure to the inside of the quartz tube. As a gas supplied during the synthesis, a mixed gas of helium, hydrogen and ethylene gas was used. The role of each gas is that helium gas is used as an inert gas, and hydrogen gas is used as a reducing gas to activate the FeNi catalyst by removing oxygen or moisture from the catalyst surface by introducing it into the quartz tube. used. Further, ethylene gas was used as a source gas (carbon source) for reacting with the catalyst on the surface of the reduced FeNi catalyst to grow CNF and synthesize a CNF-CB composite.
ＣＮＦ−ＣＢ複合体の合成に当たって、先ずＦｅＮｉ／ＶＣ触媒を石英などの基板上に配置して加熱炉の石英チューブに接続した。次に、石英チューブにヘリウムガスを２００ｍｌ／分の流量で３０分間導入して、石英チューブ内部のガス雰囲気を、空気雰囲気からヘリウム雰囲気へ置換した。その後、６１０℃または６４０℃の温度まで４℃／分の速度で昇温しながらヘリウムガス（１６０ｍｌ／分）と水素ガス（４０ｍｌ／分）との混合ガスを導入して、ＦｅＮｉ二元金属塩触媒を還元し、ＣＢの表面上にＮｉ及びＦｅ金属（ＮｉＦｅ）を形成した。このようにしてＣＢ表面上にＮｉＦｅからなる微粒子をほぼ一様に分布させた後、６１０℃、６４０℃の温度でそれぞれ１０分、２０分、３０分間維持しながら水素（１００ｍｌ／分）及びエチレンガス（１００ｍｌ／分）を導入してＣＮＦ−ＣＢ複合体の合成を行った。 In synthesizing the CNF-CB composite, first, an FeNi / VC catalyst was placed on a substrate such as quartz and connected to a quartz tube of a heating furnace. Next, helium gas was introduced into the quartz tube at a flow rate of 200 ml / min for 30 minutes to replace the gas atmosphere inside the quartz tube from an air atmosphere to a helium atmosphere. Thereafter, a mixed gas of helium gas (160 ml / min) and hydrogen gas (40 ml / min) is introduced while raising the temperature to a temperature of 610 ° C. or 640 ° C. at a rate of 4 ° C./min. The catalyst was reduced to form Ni and Fe metal (NiFe) on the surface of CB. After NiFe fine particles were distributed almost uniformly on the CB surface in this way, hydrogen (100 ml / min) and ethylene were maintained at temperatures of 610 ° C. and 640 ° C. for 10 minutes, 20 minutes and 30 minutes, respectively. Gas (100 ml / min) was introduced to synthesize a CNF-CB complex.
［ＣＮＦ−ＣＢ複合体の分析］
ＣＮＦ−ＣＢ複合体の合成が行なわれたか否かに関しては日立電子社製走査電子顕微鏡（ＳＥＭ；Ｓ−４８００）を利用して観察し、確認した。ＣＮＦ−ＣＢ複合体の繊維状ナノカーボンは日本電子社製透過型電子顕微鏡（ＴＥＭ；ＪＥＭ−２１００Ｆ）を利用して観察し、確認した。合成されたＣＮＦ−ＣＢ複合体の比表面積はQuantachrome社のＢＥＴ（ＡＳＩＺＭ０００２−４）を利用して測定を行なった。
[Analysis of CNF-CB Complex]
Whether or not the synthesis of the CNF-CB complex was performed was confirmed by observation using a scanning electron microscope (SEM; S-4800) manufactured by Hitachi Electronics. The fibrous nanocarbon of the CNF-CB composite was observed and confirmed using a transmission electron microscope (TEM; JEM-2100F) manufactured by JEOL. The specific surface area of the synthesized CNF-CB composite was measured using BET (ASIZM0002-4) manufactured by Quantachrome.
［ＣＮＦ−ＣＢ複合体及びＣＢを用いた燃料電池電極触媒の製造］
燃料電池電極触媒は単純な方法で製造した。すなわち、上述のようにして合成した本発明のＣＮＦ−ＣＢ複合体及び比較対象としてのＣＢ（ＣＮＦ−ＣＢの原料と同じＣＢを単独で使用）を燃料電池電極触媒の担体として利用し、ＰｔＣｌ６９Ｈ２Ｏ（Wako社）を金属触媒として利用した。ここで、ＮａＢＨ４（Wako社）を金属触媒の還元剤として用いた。これにより、２０ｗｔ％Ｐｔ／ＣＮＦ−ＣＢ及び２０ｗｔ％Ｐｔ／ＣＢの燃料電池電極触媒を製造した。更に、本発明の上記実施例の燃料電池電極触媒と比較するために、市販されているJohnson Matthey社の２０ｗｔ％Ｐｔ／Ｃ（Hispec 1000）を使用した。
[Production of fuel cell electrode catalyst using CNF-CB composite and CB]
The fuel cell electrode catalyst was produced by a simple method. That is, the CNF-CB composite of the present invention synthesized as described above and CB as a comparison target (using the same CB as the raw material of CNF-CB alone) are used as a support for the fuel cell electrode catalyst, and PtCl 6 9H 2 O (Wako) was used as the metal catalyst. Here, NaBH 4 (Wako) was used as a reducing agent for the metal catalyst. As a result, 20 wt% Pt / CNF-CB and 20 wt% Pt / CB fuel cell electrode catalysts were produced. In addition, a commercially available 20 wt% Pt / C (Hispec 1000) from Johnson Matthey was used for comparison with the fuel cell electrocatalysts of the above examples of the present invention.
本発明のＣＮＦ−ＣＢを利用した燃料電池電極触媒及び比較対象としての従来から使用されているＣＢを利用した燃料電池電極触媒を製造するに当たって、先ず脱イオン水（DI Water）１００ｍｌとエタノール（Wako社）２０ｍｌとの混合液にＣＮＦ−ＣＢ複合体またはＣＢ（以下、カーボンと総称する）をそれぞれ０．５ｇ添加して、超音波を５分間照射した。その後、温度を３〜１０℃に設定した攪拌機で攪拌を行った。 In producing a fuel cell electrode catalyst using CNF-CB of the present invention and a fuel cell electrode catalyst using CB conventionally used as a comparison object, first, 100 ml of deionized water (DI Water) and ethanol (Wako) 0.5 g of a CNF-CB complex or CB (hereinafter collectively referred to as carbon) was added to a mixed solution of 20 ml and irradiated with ultrasonic waves for 5 minutes. Then, it stirred with the stirrer which set temperature to 3-10 degreeC.
その後、以下に示す手順により、燃料電池触媒となる貴金属（Ｐｔ）の担持を行った。先ず、カーボンに対して２０ｗｔ％となる重量のＰｔＣｌ６９Ｈ２Ｏ（Wako社）を脱イオン水１００ｍｌに添加することにより、ＰｔＣｌ６９Ｈ２Ｏ水溶液を調整した。次に、上述のようにして準備したところのカーボンが入っている脱イオン水１００ｍｌとエタノール２０ｍｌとの混合液中に、上記ＰｔＣｌ６９Ｈ２Ｏ水溶液をビューレットを用いて１０分間で２０ｍｌ滴下した。その後、ＮａＢＨ４（Wako社）還元剤の粉末を０．１９ｇを投入した。このＰｔＣｌ６９Ｈ２Ｏ水溶液２０ｍｌの滴下とその後のＮａＢＨ４粉末０．１９ｇの投入のサイクルを全部で５回繰り返した。その後、Ｐｔへの還元が完全に行われるように、１０分〜２０分程度攪拌した。このようにしてＰｔＣｌ６９Ｈ２Ｏを還元して、触媒金属であるＰｔをカーボンに担持させた。上述の燃料電池電極触媒製造の全工程は約１時間３０分を要した。その後、洗浄し、ろ過し、９０℃で２４時間乾燥することで、本発明及び比較対象の燃料電池電極触媒を得た。 Thereafter, a noble metal (Pt) serving as a fuel cell catalyst was supported by the following procedure. First, a PtCl 6 9H 2 O aqueous solution was prepared by adding PtCl 6 9H 2 O (Wako) having a weight of 20 wt% to carbon to 100 ml of deionized water. Next, 20 ml of the above PtCl 6 9H 2 O aqueous solution was dropped into a mixed solution of 100 ml of deionized water containing carbon prepared as described above and 20 ml of ethanol using a buret for 10 minutes. . Thereafter, 0.19 g of NaBH 4 (Wako) reducing agent powder was added. The cycle of dropping 20 ml of this PtCl 6 9H 2 O aqueous solution and then adding 0.19 g of NaBH 4 powder was repeated a total of 5 times. Then, it stirred for about 10 minutes-20 minutes so that the reduction | restoration to Pt might be performed completely. In this way, PtCl 6 9H 2 O was reduced, and Pt as a catalyst metal was supported on carbon. The entire process for producing the fuel cell electrode catalyst described above took about 1 hour 30 minutes. Then, it wash | cleaned, filtered, and obtained the fuel cell electrode catalyst of this invention and a comparison object by drying at 90 degreeC for 24 hours.
［製造した２０ｗｔ％Ｐｔ／ＣＮＦ−ＣＢ及び２０ｗｔ％Ｐｔ／ＣＢ並びに市販触媒２０ｗｔ％Ｐｔ／Ｃの活性評価］
上述のようにして製造した実施例の２０ｗｔ％Ｐｔ／ＣＮＦ−ＣＢ、並びに比較例としての上述のようにして製造した２０ｗｔ％Ｐｔ／ＣＢ及び市販触媒２０ｗｔ％Ｐｔ／Ｃ（Johnson Matthey）にそれぞれNafion（登録商標）バインダー（Wako社；４０ｗｔ％）を添加してスラリー化し、カーボンペーパーの上にこれらのスラリーである電極触媒を塗布し（Ｐｔ換算で０．３ｍｇ／ｃｍ２）、それぞれ燃料電池のアノード電極として利用した。カソード電極は、Johnson Matthey（２０ｗｔ％Ｐｔ／Ｃ）にNafionバインダー（Wako社；４０ｗｔ％）を添加してスラリー化し、カーボンペーパーの上に電極触媒（Ｐｔ換算で０．３ｍｇ／ｃｍ２）を塗布して製造した。このようにして製造したアノード電極とカソード電極との間にNafion 電解質膜（Dupon社；Nafion 115）を挟んで１５５℃、０．８ＭＰａの状態で１０分間ホットプレスを行なうことで、燃料電池電極を製造した。この電極を用いて単電池を作成し、Ｉ−Ｖ特性を利用して実施例及び比較例の触媒の活性を評価した。Ｉ−Ｖ測定条件としては７０℃、１００％加湿の状態で評価し、東陽テクニカ社製の燃料電池テストシステムを使用して分析を行なった。
[Activity evaluation of produced 20 wt% Pt / CNF-CB and 20 wt% Pt / CB and commercially available catalyst 20 wt% Pt / C]
Example 20 wt% Pt / CNF-CB prepared as described above, and 20 wt% Pt / CB prepared as described above as a comparative example and commercially available catalyst 20 wt% Pt / C (Johnson Matthey), respectively. (Registered trademark) Binder (Wako; 40 wt%) was added to form a slurry, and the electrode catalyst as a slurry was applied on carbon paper (0.3 mg / cm 2 in terms of Pt). Used as an anode electrode. The cathode electrode was made into a slurry by adding a Nafion binder (Wako; 40 wt%) to Johnson Matthey (20 wt% Pt / C), and an electrode catalyst (0.3 mg / cm 2 in terms of Pt) was applied on the carbon paper. And manufactured. A fuel cell electrode is formed by performing hot pressing at 155 ° C. and 0.8 MPa for 10 minutes with a Nafion electrolyte membrane (Dupon; Nafion 115) sandwiched between the anode electrode and the cathode electrode thus manufactured. Manufactured. A single cell was prepared using this electrode, and the activity of the catalysts of Examples and Comparative Examples was evaluated using IV characteristics. The IV measurement conditions were evaluated at 70 ° C. and 100% humidification, and the analysis was performed using a fuel cell test system manufactured by Toyo Technica.
ＣＮＦ−ＣＢ複合体のモデルを図１に示す。ＣＢの表面にＦｅ−Ｎｉ金属触媒を担持させてエチレンガスを投入すると、ＣＢの表面から繊維状ナノカーボンが成長してＣＢを覆う形態のＣＮＦ−ＣＢ複合体が合成される。 A model of the CNF-CB complex is shown in FIG. When an Fe-Ni metal catalyst is supported on the surface of CB and ethylene gas is introduced, fibrous nanocarbon grows from the surface of CB and a CNF-CB composite in a form covering CB is synthesized.
合成されたＣＮＦ−ＣＢ複合体をＳＥＭとＴＥＭを利用して観察した。そのＳＥＭ像及びＴＥＭ像をそれぞれ図２及び図３に示す。図２はＣＢ（図２（ａ））及びＣＮＦ−ＣＢ複合体（図２（ｂ））のＳＥＭ像である。ＣＮＦ−ＣＢ複合体ではＣＢから直径が２０ｎｍ〜４０ｎｍ、長さが１０ｎｍ〜１００ｎｍのＣＮＦが成長していることが確認された。なお、直径よりも長さの短いＣＮＦも観察されたが、これは成長のごく初期段階のものであると考えられる。図３はＣＢ（図３（ａ））及びＣＮＦ−ＣＢ複合体（図３（ｂ））のＴＥＭ像である。図３（ａ）からわかるように、ＣＢは球状の粒子が連結してミクロン単位の二次粒子を形成している。一方、ＣＮＦ−ＣＢ複合体では、図３（ｂ）からわかるように、ＣＢの表面からＣＮＦが成長してＣＢを覆っている形態のＣＮＦ−ＣＢ複合体が合成されている。それと共に、ＣＢの一次孔部分をＣＮＦが塞いでいる（つまり、一次孔自体は残っているとしても、その上からＣＮＦで蓋をした状態になっている）ことも確認した。 The synthesized CNF-CB complex was observed using SEM and TEM. The SEM image and TEM image are shown in FIGS. 2 and 3, respectively. FIG. 2 is an SEM image of CB (FIG. 2 (a)) and CNF-CB complex (FIG. 2 (b)). In the CNF-CB complex, it was confirmed that CNF having a diameter of 20 nm to 40 nm and a length of 10 nm to 100 nm was grown from CB. Although CNF having a length shorter than the diameter was also observed, it is considered that this is an extremely early stage of growth. FIG. 3 is a TEM image of CB (FIG. 3A) and CNF-CB complex (FIG. 3B). As can be seen from FIG. 3A, spherical particles are connected to form secondary particles in units of microns. On the other hand, in the CNF-CB complex, as can be seen from FIG. 3B, a CNF-CB complex in a form in which CNF grows from the surface of the CB and covers the CB is synthesized. At the same time, it was also confirmed that CNF was blocking the primary hole portion of CB (that is, even if the primary hole itself remained, it was covered with CNF from above).
図４は様々な温度及び時間の条件下で合成されたＣＮＦ−ＣＢ複合体のＳＥＭ写真を示す。ＣＮＦ−ＣＢ複合体の合成温度は６１０℃及び６４０℃とし、また合成時間は１０分、２０分及び３０分として、二通りの温度と三通りの合成時間の組み合わせである六通りの条件で合成処理を行った。合成温度及び合成時間が増加するにつれて繊維状ナノカーボンの長さも増大することがわかった。また、それにつれて、以下の表１に示すようにＣＮＦ−ＣＢ複合体の重量も増加した。 FIG. 4 shows SEM photographs of CNF-CB composites synthesized under various temperature and time conditions. The synthesis temperature of the CNF-CB complex is 610 ° C. and 640 ° C., and the synthesis time is 10 minutes, 20 minutes, and 30 minutes. The synthesis is performed under six conditions, which are combinations of two temperatures and three synthesis times. Processed. It has been found that the length of the fibrous nanocarbon increases with increasing synthesis temperature and synthesis time. In addition, the weight of the CNF-CB complex also increased as shown in Table 1 below.
図５に、様々な合成温度と合成時間との組み合わせにより合成したＣＮＦ−ＣＢ複合体及びそれらの原料として使用したＣＢのＢＥＴ法による比表面積測定の結果を示す。ＣＢの比表面積は２６１ｍ２／ｇと測定された。ＣＢ上で繊維状ナノカーボンが合成されたＣＮＦ−ＣＢ複合体の比表面積は、合成温度が６１０℃の場合は合成時間１０分で３０６ｍ２／ｇ、２０分で３３４ｍ２／ｇ及び３０分で３５５ｍ２／ｇとなった。合成温度が６４０℃の場合は合成時間１０分で３１９ｍ２／ｇ、２０分で３４８ｍ２／ｇ及び３０分で３７８ｍ２／ｇとなった。このようにして合成されたＣＮＦ−ＣＢ複合体は何れの合成条件のものもＣＢに比べて大きな比表面積を有することが示された。その中でも、６４０℃で３０分間合成したＣＮＦ−ＣＢ複合体はＣＢに比べて比表面積が４０％以上増加した。 FIG. 5 shows the results of measurement of the specific surface area by the BET method of CNF-CB composites synthesized by various combinations of synthesis temperatures and synthesis times and CBs used as raw materials thereof. The specific surface area of CB was measured to be 261 m 2 / g. The specific surface area of CNF-CB composite fibrous nanocarbon is synthesized on CB, if the synthesis temperature is 610 ° C. at synthesis time 10 min 306m 2 / g, 20 min 334m 2 / g and at 30 minutes It became 355 m < 2 > / g. If the synthesis temperature of 640 ° C. became 378m 2 / g at 348m 2 / g and 30 min at 319m 2 / g, 20 minutes at synthesis time 10 minutes. It was shown that the CNF-CB complex synthesized in this way has a larger specific surface area than that of CB under any synthesis condition. Among them, the specific surface area of the CNF-CB composite synthesized at 640 ° C. for 30 minutes increased by 40% or more compared to CB.
２０ｗｔ％Ｐｔ／Ｃ、２０ｗｔ％Ｐｔ／ＣＢ及び２０ｗｔ％Ｐｔ／ＣＮＦ−ＣＢを燃料電池触媒として上述のようにして作製した燃料電池のＩ−Ｖ特性を評価した。その結果を図６に示す。上述の単純な燃料電池電極触媒プロセスで製造した本発明の比較例としての２０ｗｔ％Ｐｔ／ＣＢ触媒を使用した燃料電池の電力密度は４５０ｍＷ／ｃｍ２となり、市販されている２０ｗｔ％Ｐｔ／Ｃ触媒を使用した燃料電池の電力密度４２７ｍＷ／ｃｍ２に比べて少し高い触媒活性を得ることができた。本発明の実施例のＣＮＦ−ＣＢ複合体を触媒担体とした２０ｗｔ％Ｐｔ／ＣＮＦ−ＣＢ触媒を使用して同様に作製した燃料電池は４６８ｍＷ／ｃｍ２の電力密度を達成し、上述の２０ｗｔ％Ｐｔ／Ｃ触媒に基づく燃料電池に比べて４１ｍＷ／ｃｍ２だけ高い電力密度を達成できた。 The IV characteristics of the fuel cells prepared as described above using 20 wt% Pt / C, 20 wt% Pt / CB and 20 wt% Pt / CNF-CB as fuel cell catalysts were evaluated. The result is shown in FIG. The power density of a fuel cell using a 20 wt% Pt / CB catalyst as a comparative example of the present invention manufactured by the above simple fuel cell electrode catalyst process is 450 mW / cm 2 , and a commercially available 20 wt% Pt / C catalyst. As a result, it was possible to obtain a slightly higher catalytic activity than the power density of 427 mW / cm 2 of the fuel cell using NO. A fuel cell similarly produced using a 20 wt% Pt / CNF-CB catalyst using the CNF-CB composite of the example of the present invention as a catalyst support achieved a power density of 468 mW / cm 2 , and the above-mentioned 20 wt% A power density higher by 41 mW / cm 2 was achieved compared to fuel cells based on Pt / C catalysts.
燃料電池触媒担体として使用できる本発明のＣＮＦ−ＣＢ複合体は、ＣＢの表面に繊維状のナノカーボンを成長させてＣＢを覆う形態を有すること及びＣＢの一次孔部分をナノ繊維が塞いでいることを、ＳＥＭ、ＴＥＭで確認した。また、温度範囲としては常圧の状態で６１０℃〜１０００℃の範囲、合成温度は１０分以上の組み合わせで所望の形態を有するＣＮＦ−ＣＢ複合体が合成されることもＳＥＭで確認した。更に、合成温度及び時間を調節することによって有効比表面積を制御できることが分かった。なお、合成時間を長くするとＣＮＦ−ＣＢ複合体を形成するＣＮＦを実質的にいくらでも長くすることができるが、ＣＮＦが過度に長くなるとカーボンナノ繊維同士の絡み合いが甚だしくなってＣＮＦ−ＣＢ複合体の分散性が低下する。そのため、実用的には合成時間を２時間以下とするのが望ましい。 The CNF-CB composite of the present invention that can be used as a fuel cell catalyst support has a form in which a fibrous nanocarbon is grown on the surface of the CB to cover the CB, and the primary fibers of the CB are blocked with the nanofibers. This was confirmed by SEM and TEM. It was also confirmed by SEM that a CNF-CB complex having a desired form was synthesized in a combination of a temperature range of 610 ° C. to 1000 ° C. under normal pressure and a synthesis temperature of 10 minutes or more. Furthermore, it was found that the effective specific surface area can be controlled by adjusting the synthesis temperature and time. In addition, if the synthesis time is lengthened, CNF forming the CNF-CB composite can be made virtually any length, but if CNF becomes excessively long, the entanglement between the carbon nanofibers becomes excessive and the CNF-CB composite Dispersibility decreases. Therefore, in practice, it is desirable that the synthesis time is 2 hours or less.
上述した実施例ではＣＢ上にＣＮＦを成長させるためにＣＢにＮｉとＦｅとの組み合わせを担持させた。しかし、ＣＮＦのこのような成長に使用できるための金属触媒としてはこれに限定されるものではなく、Ｎｉ、Ｆｅ、Ｃｕ、Ｍｇ及びＣｏから選択された二またはもっと多くの金属種の組み合わせを使用しても、ＣＮＦを同様に成長させることができる。更に、上述したように、ＣＮＦはＣＢ以外のカーボンナノ粒子の上にも成長させることができる。また、実施例ではＣＢとしてVulcan XC-72R（ＶＣ）を使用したが、もちろんこれに限定されるものではない。アセチレンブラック、ケッチェンブラックなど、他の多くの種類のカーボンブラックも使用することができる。また、実施例ではＣＮＦの原料となる炭素源としてエチレンを使用したが、炭素源はこれに限定されるものではなく、例えばエチレン、アセチレンまたはメタン等のガス、あるいはこれらのうちから選択した二種もしくはもっと多くのガスを混合したものを使用することができる。更に、カーボンナノ粒子上のＣＮＦの長さは概ね１０ｎｍ〜１００ｎｍ、また直径は概ね１０ｎｍ〜数μｍ（例えば１０μｍ）の範囲である。 In the embodiment described above, a combination of Ni and Fe was supported on the CB in order to grow CNF on the CB. However, the metal catalyst that can be used for such growth of CNF is not limited to this and uses a combination of two or more metal species selected from Ni, Fe, Cu, Mg and Co. Even so, CNF can be grown similarly. Furthermore, as described above, CNF can be grown on carbon nanoparticles other than CB. In the embodiment, Vulcan XC-72R (VC) is used as the CB, but the present invention is not limited to this. Many other types of carbon black such as acetylene black and ketjen black can also be used. In the examples, ethylene was used as a carbon source as a raw material for CNF, but the carbon source is not limited to this. For example, a gas such as ethylene, acetylene or methane, or two kinds selected from these gases Alternatively, a mixture of more gases can be used. Furthermore, the length of CNF on the carbon nanoparticles is generally in the range of 10 nm to 100 nm, and the diameter is in the range of approximately 10 nm to several μm (for example, 10 μm).
本発明のＣＮＦ−カーボンナノ粒子複合体はＣＢ等のカーボンナノ粒子に比較して表面の一次孔が少ないために、その表面にＰｔ等の触媒を担持させた場合にその利用効率が高く、また分散性が良いためにその利用に当たっての取り扱いが容易になる。また、本複合体は低温かつ短時間で合成することが可能であり、更に製造方法が単純であることにより、これを利用した製品の低コスト化に貢献できる。従って、本発明は例えば燃料電池触媒分野に大いに利用されることが期待される。 Since the CNF-carbon nanoparticle composite of the present invention has fewer primary pores on the surface than carbon nanoparticles such as CB, its utilization efficiency is high when a catalyst such as Pt is supported on the surface. Since the dispersibility is good, the handling in the use becomes easy. In addition, the composite can be synthesized at a low temperature and in a short time, and the manufacturing method is simple, which can contribute to cost reduction of a product using the composite. Therefore, the present invention is expected to be used greatly in the field of fuel cell catalysts, for example.
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