JP5534394B2 - Fuel cell catalyst using platinum-foreign metal composite nanoparticles encapsulated in phenylazomethine dendrimer - Google Patents
Fuel cell catalyst using platinum-foreign metal composite nanoparticles encapsulated in phenylazomethine dendrimer Download PDFInfo
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- 229920000736 dendritic polymer Polymers 0.000 title claims description 78
- 239000000412 dendrimer Substances 0.000 title claims description 64
- 239000003054 catalyst Substances 0.000 title claims description 35
- 239000002105 nanoparticle Substances 0.000 title claims description 33
- 239000000446 fuel Substances 0.000 title claims description 28
- 239000002905 metal composite material Substances 0.000 title claims description 22
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 115
- 229910052697 platinum Inorganic materials 0.000 claims description 42
- 229910052751 metal Chemical group 0.000 claims description 18
- 239000002184 metal Chemical group 0.000 claims description 18
- 150000002466 imines Chemical class 0.000 claims description 16
- 150000004696 coordination complex Chemical class 0.000 claims description 15
- 150000002736 metal compounds Chemical class 0.000 claims description 14
- 150000003058 platinum compounds Chemical class 0.000 claims description 14
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- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 7
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 6
- 125000004429 atom Chemical group 0.000 claims description 5
- 125000001424 substituent group Chemical group 0.000 claims description 5
- 229910052723 transition metal Inorganic materials 0.000 claims description 3
- 150000003624 transition metals Chemical class 0.000 claims description 3
- 125000003545 alkoxy group Chemical group 0.000 claims description 2
- 125000000217 alkyl group Chemical group 0.000 claims description 2
- 125000003277 amino group Chemical group 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 125000004093 cyano group Chemical group *C#N 0.000 claims description 2
- 125000002147 dimethylamino group Chemical group [H]C([H])([H])N(*)C([H])([H])[H] 0.000 claims description 2
- 229910052733 gallium Inorganic materials 0.000 claims description 2
- 125000005843 halogen group Chemical group 0.000 claims description 2
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- 125000002950 monocyclic group Chemical group 0.000 claims description 2
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- 125000000524 functional group Chemical group 0.000 claims 1
- 239000000243 solution Substances 0.000 description 35
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 14
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- 238000007254 oxidation reaction Methods 0.000 description 7
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 7
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- 150000003839 salts Chemical class 0.000 description 6
- 238000002484 cyclic voltammetry Methods 0.000 description 5
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- FBEIPJNQGITEBL-UHFFFAOYSA-J tetrachloroplatinum Chemical compound Cl[Pt](Cl)(Cl)Cl FBEIPJNQGITEBL-UHFFFAOYSA-J 0.000 description 5
- 238000001075 voltammogram Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
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- 235000011150 stannous chloride Nutrition 0.000 description 3
- AXZWODMDQAVCJE-UHFFFAOYSA-L tin(II) chloride (anhydrous) Chemical compound [Cl-].[Cl-].[Sn+2] AXZWODMDQAVCJE-UHFFFAOYSA-L 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
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- PEQHIRFAKIASBK-UHFFFAOYSA-N tetraphenylmethane Chemical compound C1=CC=CC=C1C(C=1C=CC=CC=1)(C=1C=CC=CC=1)C1=CC=CC=C1 PEQHIRFAKIASBK-UHFFFAOYSA-N 0.000 description 2
- AQRLNPVMDITEJU-UHFFFAOYSA-N triethylsilane Chemical compound CC[SiH](CC)CC AQRLNPVMDITEJU-UHFFFAOYSA-N 0.000 description 2
- 238000012795 verification Methods 0.000 description 2
- CSDQQAQKBAQLLE-UHFFFAOYSA-N 4-(4-chlorophenyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine Chemical compound C1=CC(Cl)=CC=C1C1C(C=CS2)=C2CCN1 CSDQQAQKBAQLLE-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000005749 Copper compound Substances 0.000 description 1
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000012448 Lithium borohydride Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910021551 Vanadium(III) chloride Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- CUJRVFIICFDLGR-UHFFFAOYSA-N acetylacetonate Chemical compound CC(=O)[CH-]C(C)=O CUJRVFIICFDLGR-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- WGHCVSYNPVNMID-UHFFFAOYSA-N alumane;sodium Chemical compound [Na].[AlH3].[AlH3] WGHCVSYNPVNMID-UHFFFAOYSA-N 0.000 description 1
- SIPUZPBQZHNSDW-UHFFFAOYSA-N bis(2-methylpropyl)aluminum Chemical compound CC(C)C[Al]CC(C)C SIPUZPBQZHNSDW-UHFFFAOYSA-N 0.000 description 1
- UORVGPXVDQYIDP-BJUDXGSMSA-N borane Chemical class [10BH3] UORVGPXVDQYIDP-BJUDXGSMSA-N 0.000 description 1
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- 230000008859 change Effects 0.000 description 1
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- XOYLJNJLGBYDTH-UHFFFAOYSA-M chlorogallium Chemical compound [Ga]Cl XOYLJNJLGBYDTH-UHFFFAOYSA-M 0.000 description 1
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- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 1
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 1
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- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- AASUFOVSZUIILF-UHFFFAOYSA-N diphenylmethanone;sodium Chemical compound [Na].C=1C=CC=CC=1C(=O)C1=CC=CC=C1 AASUFOVSZUIILF-UHFFFAOYSA-N 0.000 description 1
- 238000012678 divergent method Methods 0.000 description 1
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- 150000002259 gallium compounds Chemical class 0.000 description 1
- UPWPDUACHOATKO-UHFFFAOYSA-K gallium trichloride Chemical compound Cl[Ga](Cl)Cl UPWPDUACHOATKO-UHFFFAOYSA-K 0.000 description 1
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- 125000000623 heterocyclic group Chemical group 0.000 description 1
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- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
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- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 1
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- 150000003606 tin compounds Chemical class 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
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- CMHHITPYCHHOGT-UHFFFAOYSA-N tributylborane Chemical compound CCCCB(CCCC)CCCC CMHHITPYCHHOGT-UHFFFAOYSA-N 0.000 description 1
- DBGVGMSCBYYSLD-UHFFFAOYSA-N tributylstannane Chemical compound CCCC[SnH](CCCC)CCCC DBGVGMSCBYYSLD-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 150000003682 vanadium compounds Chemical class 0.000 description 1
- HQYCOEXWFMFWLR-UHFFFAOYSA-K vanadium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[V+3] HQYCOEXWFMFWLR-UHFFFAOYSA-K 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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Description
本発明は、フェニルアゾメチンデンドリマー金属錯体と白金−異種金属複合ナノ微粒子並びに燃料電池用触媒に関するものである。 The present invention relates to a phenylazomethine dendrimer metal complex, platinum-foreign metal composite nanoparticles, and a fuel cell catalyst.
近年において新たなエネルギー源として期待されている燃料電池の触媒として、白金が使用されている。具体的には、燃料電池の電極表面で、空気極における酸素還元反応、あるいは燃料極における水素、メタノールなどの酸化反応のための触媒として、導電性カーボンに担持した白金微粒子（白金ナノ粒子）が用いられている。 In recent years, platinum has been used as a fuel cell catalyst that is expected as a new energy source. Specifically, platinum fine particles (platinum nanoparticles) supported on conductive carbon are used as a catalyst for the oxygen reduction reaction at the air electrode or the oxidation reaction of hydrogen, methanol, etc. at the fuel electrode on the electrode surface of the fuel cell. It is used.
従来、白金ナノ粒子は、単純な濃度制御や担体の添加などの条件下で、還元法により白金錯体などの金属塩から合成している。従来、燃料電池用の白金触媒としては粒径が2〜5nm、白金原子数に換算すると1000原子以上のものが知られている。 Conventionally, platinum nanoparticles are synthesized from a metal salt such as a platinum complex by a reduction method under conditions such as simple concentration control and addition of a carrier. Conventionally, platinum catalysts for fuel cells having a particle diameter of 2 to 5 nm and 1000 atoms or more in terms of the number of platinum atoms are known.
しかし、白金の希少さによる高コストなどの問題を解決するためにも、燃料電池用触媒としての白金の使用量を低減する技術の開発が望まれている。近年のナノテクノロジーの進歩に伴い、ナノ粒子の触媒活性が粒子のサイズ（構成金属原子の数）に強く依存する現象や、微粒子化に伴う量子サイズ効果の発現などが報告されているが、白金触媒の高活性化により白金使用量の低減を図る手段としては、更なる微粒子化などが考えられる。 However, in order to solve the problems such as high cost due to the scarcity of platinum, it is desired to develop a technique for reducing the amount of platinum used as a catalyst for a fuel cell. As nanotechnology advances in recent years, it has been reported that the catalytic activity of nanoparticles strongly depends on the size of particles (number of constituent metal atoms) and the manifestation of quantum size effects associated with micronization. As a means for reducing the amount of platinum used by increasing the activation of the catalyst, further fine particle formation and the like can be considered.
ところが、白金イオンのバルク還元などによる手法では、生成した白金微粒子の凝集などのため、微小かつ均一な白金微粒子、たとえば粒径2nm未満の白金微粒子の合成は困難であった。 However, in the method using platinum ion bulk reduction or the like, it is difficult to synthesize fine and uniform platinum particles, for example, platinum particles having a particle diameter of less than 2 nm, due to aggregation of the generated platinum particles.
一方、ナノ微粒子の製造方法として、デンドリマーを鋳型として用いる方法が知られている。不対電子対を有する窒素などを骨格に持つデンドリマーは、ルイス酸との錯形成が可能となり内側にさまざまな分子を取り込むことができる。さらに、デンドリマーの構造は中心部が疎、外側が密であるといった特徴を有していることから金属や有機分子などを内包することができる。 On the other hand, a method of using a dendrimer as a template is known as a method for producing nanoparticles. A dendrimer having nitrogen or the like having an unpaired electron pair as a skeleton can form a complex with a Lewis acid and can incorporate various molecules inside. Furthermore, the dendrimer structure is characterized in that the center is sparse and the outside is dense, so that it can enclose metals and organic molecules.
近年本発明者らにより開発され、その検討が続けられているフェニルアゾメチンデンドリマーは、骨格に高い配位性を示すイミン部位を多数有していることからルイス酸と錯形成が可能である。フェニルアゾメチンデンドリマーは、イミンからの電子供与が末端から中心に向けて増加することで、末端のイミンから中心に向かってイミンの電子密度が増加するという電子勾配を有している。 In recent years, phenylazomethine dendrimers, which have been developed by the present inventors and have been studied, have a number of imine sites exhibiting high coordinating properties in the skeleton, and thus can be complexed with a Lewis acid. The phenylazomethine dendrimer has an electron gradient in which the electron density of the imine increases from the terminal imine toward the center as the electron donation from the imine increases from the terminal to the center.
このような電子勾配は自然の光合成を模した機構であり、フェニルアゾメチンデンドリマー独自のユニークな特徴である。この電子勾配に起因して、ルイス酸と錯形成させた場合にはデンドリマーの内側から順に錯形成させることが可能となり、デンドリマーの各層に順に金属錯体を錯形成させることで、金属錯体の数と位置を正確に制御することが可能となる。そのため、デンドリマー金属錯体を還元することで、粒径の分布が極めて小さい精密に制御されたナノクラスターの形成が可能となる（たとえば特許文献１〜３参照）。 Such an electron gradient is a mechanism that mimics natural photosynthesis and is a unique feature unique to phenylazomethine dendrimers. Due to this electron gradient, when complexed with a Lewis acid, it is possible to form a complex in order from the inside of the dendrimer. By complexing a metal complex sequentially to each layer of the dendrimer, the number of metal complexes and The position can be accurately controlled. Therefore, by reducing the dendrimer metal complex, it is possible to form a precisely controlled nanocluster having a very small particle size distribution (see, for example, Patent Documents 1 to 3).
さらに、フェニルアゾメチンデンドリマーは、π共役による剛直な構造であるため、薄膜とした際に、構造が変形することなく緻密に並んだ状態が観測されている。従来のデンドリマーでは、構造が溶媒などの周辺環境により変化し、内包された微粒子がデンドリマーの外へ排出され易い。しかし、フェニルアゾメチンデンドリマーでは、剛直な骨格に内包されることでデンドリマーのシェル効果が向上する。これにより、内包された微粒子同士の凝集を抑制し、微粒子の触媒活性の安定性、耐久性を期待することができる。 Furthermore, since the phenylazomethine dendrimer has a rigid structure due to π conjugation, when the film is formed into a thin film, it is observed that the structure is closely arranged without deformation. In the conventional dendrimer, the structure changes depending on the surrounding environment such as a solvent, and the encapsulated fine particles are easily discharged out of the dendrimer. However, in the case of phenylazomethine dendrimer, the shell effect of dendrimer is improved by being encapsulated in a rigid skeleton. Thereby, aggregation of the encapsulated fine particles can be suppressed, and the stability and durability of the catalytic activity of the fine particles can be expected.
本発明者らによる検討の過程から以上のような知見が得られており、フェニルアゾメチンデンドリマーと金属との錯体については大きな可能性が見込まれ、燃料電池用触媒への応用も期待される。しかし、その詳細についての検証は依然として多くの未踏の課題として残されており、たとえば、フェニルアゾメチンデンドリマーに2種以上の金属錯体を配位させた場合の詳細な知見は得られていないのが現状である。 The above findings have been obtained from the process of study by the present inventors, and a great potential is expected for the complex of phenylazomethine dendrimer and metal, and application to a fuel cell catalyst is also expected. However, verification of the details still remains as a number of unexplored issues. For example, detailed knowledge about the coordination of two or more metal complexes with phenylazomethine dendrimers has not been obtained. It is.
本発明は、以上の通りの事情に鑑みてなされたものであり、従来のバルク白金触媒に代わるスケールの燃料電池用触媒として利用可能な、新規な白金−異種金属複合ナノ微粒子およびそれを用いた燃料電池用触媒と、その前駆体である新規なフェニルアゾメチンデンドリマー金属錯体を提供することを課題としている。 The present invention has been made in view of the circumstances as described above, and uses a novel platinum-dissimilar metal composite nanoparticle that can be used as a fuel cell catalyst of a scale in place of a conventional bulk platinum catalyst and the same. An object of the present invention is to provide a catalyst for a fuel cell and a novel phenylazomethine dendrimer metal complex which is a precursor thereof.
本発明は、上記の課題を解決するために、以下のことを特徴としている。 The present invention is characterized by the following in order to solve the above problems.
第１：次式（I） 1: The following formula (I)
（式中のR1は有機分子基を示し、R2は1以上の置換基を有していてもよいフェニル基を示す。Mはそれぞれ独立に白金化合物または白金とは異種の遷移金属による異種金属化合物を示し、全体として白金化合物および異種金属化合物の両方を含有している。mはデンドリマーの世代数を表す1以上の整数を示し、nは有機分子基R1に対するデンドロン部位の結合数を示す。）で表されることを特徴とするフェニルアゾメチンデンドリマー金属錯体。 (In the formula, R 1 represents an organic molecular group, R 2 represents a phenyl group which may have one or more substituents. M is independently a platinum compound or a heterogeneous transition metal different from platinum. This represents a metal compound, and contains both a platinum compound and a heterogeneous metal compound as a whole, m represents an integer of 1 or more representing the number of generations of dendrimers, and n represents the number of bonds of the dendron site to the organic molecular group R 1 . A phenylazomethine dendrimer metal complex characterized by being represented by:
第２：デンドリマーの第1世代から第m世代未満までのイミン部位に異種金属化合物が配位しており、その外側のイミン部位に白金化合物が配位していることを特徴とする上記第１のフェニルアゾメチンデンドリマー金属錯体。 Second: The first feature characterized in that a heterogeneous metal compound is coordinated to an imine site from the first generation to less than the mth generation of a dendrimer, and a platinum compound is coordinated to an imine site outside the dendrimer. Phenylazomethine dendrimer metal complex.
第３：上記第１または第２のフェニルアゾメチンデンドリマー金属錯体が還元されたものであることを特徴とする白金−異種金属複合ナノ微粒子。 Third: Platinum-foreign metal composite nanoparticle, wherein the first or second phenylazomethine dendrimer metal complex is reduced.
第４：上記第３の白金−異種金属複合ナノ微粒子からなることを特徴とする燃料電池用触媒。 Fourth: A fuel cell catalyst comprising the third platinum-foreign metal composite nanoparticle.
本発明によれば、従来のバルク白金触媒に代わるスケールの燃料電池用触媒として利用可能な、新規な白金−異種金属複合ナノ微粒子およびそれを用いた燃料電池用触媒と、その前駆体である新規なフェニルアゾメチンデンドリマー金属錯体が提供される。 INDUSTRIAL APPLICABILITY According to the present invention, a novel platinum-foreign metal composite nanoparticle that can be used as a fuel cell catalyst on a scale that replaces a conventional bulk platinum catalyst, a fuel cell catalyst using the same, and a novel precursor thereof A phenylazomethine dendrimer metal complex is provided.
以下、本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail.
式（I）で表されるフェニルアゾメチンデンドリマー金属錯体において、符号R1は、1価または多価の有機分子基であり、置換基を有していてもよい炭化水素基あるいは複素環基などの各種のものが対象とされる。その具体例としては、単環または多環の芳香族基、ポルフィリン基、フタロシアニン基、サイクロン基またはこれらの誘導基などを挙げることができ、下記のものが例示される。 In the phenylazomethine dendrimer metal complex represented by the formula (I), the symbol R 1 is a monovalent or polyvalent organic molecular group, such as a hydrocarbon group or a heterocyclic group which may have a substituent. Various things are targeted. Specific examples thereof include monocyclic or polycyclic aromatic groups, porphyrin groups, phthalocyanine groups, cyclone groups, and derivatives thereof, and the following are exemplified.
（上記において、Mは2つの水素原子または任意の金属原子を示し、Dはデンドロン結合部位を示す。）
式（I）の符号R2は、置換基を1つ以上有していてもよいフェニル基であり、全てが同一のものであっても互いに異なっていてもよい。置換基を有するフェニル基R2の具体例としては、ハロゲン原子、アルキル基、アルコキシ基、フェニル基、アミノ基、シアノ基またはジメチルアミノ基などの置換基がo位、m位、p位のいずれか1ヶ所または2ヶ所以上に置換した置換フェニル基が挙げられる。
(In the above, M represents two hydrogen atoms or any metal atom, and D represents a dendron binding site.)
The symbol R 2 in the formula (I) is a phenyl group which may have one or more substituents, and all may be the same or different from each other. Specific examples of the phenyl group R 2 having a substituent include a halogen atom, an alkyl group, an alkoxy group, a phenyl group, an amino group, a cyano group, a dimethylamino group, Or a substituted phenyl group substituted at one or more sites.
式（I）の符号mはデンドリマーの世代数を表し、1以上の整数であり、たとえば1〜4の範囲の整数である。 The sign m in the formula (I) represents the number of generations of dendrimers and is an integer of 1 or more, for example, an integer in the range of 1 to 4.
式（I）の符号nは有機分子基R1に対するデンドロン部位の結合数を示すものである。なお、有機分子基R1に複数のデンドロンが結合する場合、各デンドロンの世代は同一であっても異なっていてもよい。また、本発明において使用されるフェニルアゾメチンデンドリマーは、部分的に分岐ユニットの欠陥をもつハイパーブランチ型高分子であってもよい。 The symbol n in the formula (I) indicates the number of dendron sites bonded to the organic molecular group R 1 . In the case of combining a plurality of dendrons in the organic molecular group R 1, generation of the dendron may be the same or different. In addition, the phenylazomethine dendrimer used in the present invention may be a hyperbranched polymer partially having a branch unit defect.
本発明において使用されるフェニルアゾメチンデンドリマーは、たとえば、デンドリマーの中心から外に向かって合成するDivergent法や、デンドリマー末端から中心に向かって合成するConvergent法、あるいはこれらを組み合わせた方法などにより合成することができる。 The phenylazomethine dendrimer used in the present invention can be synthesized by, for example, the divergent method of synthesizing from the center of the dendrimer toward the outside, the convergent method of synthesizing from the end of the dendrimer toward the center, or a combination thereof. Can do.
式（I）の符号Mは、それぞれ独立に、1価もしくは多価の白金化合物または、白金とは異種の遷移金属による１価もしくは多価の異種金属化合物を示し、全体として白金化合物および異種金属化合物の両方を含有している。 The symbol M in the formula (I) represents each independently a monovalent or polyvalent platinum compound or a monovalent or polyvalent heterometallic compound of a transition metal different from platinum. Contains both compounds.
白金化合物は、イミン部位に対して錯形成することができるものであれば特に制限はないが、その具体例としては塩化白金（IV）などの白金塩または白金錯体が挙げられる。 The platinum compound is not particularly limited as long as it can form a complex with an imine moiety, and specific examples thereof include a platinum salt such as platinum (IV) chloride or a platinum complex.
異種金属化合物の具体例としては、SnCl2等の錫化合物、VCl3等のバナジウム化合物、FeCl3等の鉄化合物、CuCl2等の銅化合物、GaCl3等のガリウム化合物、CoCl3等のコバルト化合物、RhCl3等のロジウム化合物、RuCl3等のルテニウム化合物、Ti(acac)Cl3等のチタン化合物などの異種金属塩または異種金属錯体が挙げられる。 Specific examples of the dissimilar metal compounds, tin compounds such as SnCl 2, a vanadium compound such as VCl 3, iron compounds such as FeCl 3, a copper compound such as CuCl 2, gallium compounds such as GaCl 3, cobalt compounds such as CoCl 3 And a different metal salt or a different metal complex such as a rhodium compound such as RhCl 3 , a ruthenium compound such as RuCl 3 , and a titanium compound such as Ti (acac) Cl 3 .
デンドリマーにおける一部のイミン部位に白金化合物が配位し、他のイミン部位に異種金属化合物が配位した本発明のデンドリマー錯体は、たとえば、最初にイミン部位を有するフェニルアゾメチンデンドリマーに他の金属化合物を滴下することで錯形成させ、次いで白金化合物を滴下することで錯形成させることにより得ることができる。 The dendrimer complex of the present invention in which a platinum compound is coordinated to some imine sites in the dendrimer and a heterogeneous metal compound is coordinated to other imine sites is, for example, a phenylazomethine dendrimer having an imine site first. It can be obtained by complexing by dropping and then complexing by dropping a platinum compound.
この際、滴下した化合物は、内側から外側へと段階的に規則正しく錯形成により集積されていく。上記のように異種金属化合物を滴下させ次いで白金化合物を滴下させた場合には、最初に滴下した異種金属化合物はデンドリマーの第1世代のイミン部位から外側に世代順に配位し、次いで滴下した白金化合物は、異種金属化合物が配位したイミン部位からさらに外側に世代順に配位する。 At this time, the dropped compound is accumulated in a regular and stepwise fashion from the inside to the outside. When a foreign metal compound is dropped as described above and then a platinum compound is dropped, the first dropped foreign metal compound is coordinated from the first generation imine site of the dendrimer to the outside in order of generation, and then dropped platinum The compound is coordinated in order of generation further outward from the imine site coordinated with the different metal compound.
白金化合物と異種金属化合物は、滴下量などにより当量を制御することで、意図した数をデンドリマーの内部に集積させることができ、一分子内に白金と異種金属の両方を精密に制御して錯形成させることができる。これは、フェニルアゾメチンデンドリマーが分子構造内に電子密度勾配を有しているためと考えられる。 By controlling the equivalent amount of the platinum compound and the dissimilar metal compound by controlling the amount of dripping, etc., the intended number can be accumulated in the dendrimer. Can be formed. This is presumably because phenylazomethine dendrimer has an electron density gradient in the molecular structure.
本発明の白金−異種金属複合ナノ微粒子は、上述したデンドリマー錯体を還元することで製造することができる。デンドリマー錯体の還元は、一般に白金塩に対して還元作用を有し、これを0価の状態まで還元することができる試薬を用いて行うことができる。このような試薬の具体例としては、水素化ホウ素ナトリウム（NaBH4）、水素化シアノホウ素ナトリウム（NaBH3CN）、水素（H2）、ヒドラジン類、水素化アルミニウムリチウム、水素化ジイソブチルアルミニウム、水素化ホウ素リチウム、水素化トリエチルホウ素リチウム、ボラン錯体類、トリエチルシラン、水素化ビスアルミニウムナトリウム、水素化ホウ素ニッケル、水素化トリアセトキシホウ素ナトリウム、水素化ホウ素亜鉛、水素化トリブチルホウ素リチウム、水素化トリブチルホウ素カリウム、Schwartz試薬、Stryker試薬、水素化トリブチルスズ、水素化ナトリウム、水素化リチウム、水素化カルシウム、ナトリウムベンゾフェノンケチル、過酸化水素などが挙げられる。 The platinum-foreign metal composite nanoparticle of the present invention can be produced by reducing the above-described dendrimer complex. The reduction of the dendrimer complex can be performed using a reagent that generally has a reducing action on a platinum salt and can reduce this to a zero-valent state. Specific examples of such reagents include sodium borohydride (NaBH 4 ), sodium cyanoborohydride (NaBH 3 CN), hydrogen (H 2 ), hydrazines, lithium aluminum hydride, diisobutylaluminum hydride, hydrogen Lithium borohydride, lithium triethylborohydride, borane complexes, triethylsilane, sodium bis-aluminum hydride, nickel borohydride, sodium triacetoxyborohydride, zinc borohydride, lithium tributylborohydride, tributyl boron hydride Examples include potassium, Schwartz reagent, Stryker reagent, tributyltin hydride, sodium hydride, lithium hydride, calcium hydride, sodium benzophenone ketyl, hydrogen peroxide, and the like.
水素化ホウ素ナトリウムを用いた場合、その使用量は、たとえば1.5〜5.5当量の範囲である。 When sodium borohydride is used, the amount used is, for example, in the range of 1.5 to 5.5 equivalents.
このようにしてデンドリマー錯体を還元することで、下記の概念図に例示するように、配位させた金属錯体の数に相当する大きさのナノ微粒子を、デンドリマーに内包されたものとして調製することができる。 By reducing the dendrimer complex in this way, as illustrated in the conceptual diagram below, nanoparticle having a size corresponding to the number of coordinated metal complexes is prepared as being encapsulated in the dendrimer. Can do.
たとえば、ベンゼンをコアとするDPA G4デンドリマーは、内層のイミン部位から2、6、14、30個の白金化合物もしくは異種金属化合物を集積可能であり、テトラフェニルメタン(TPM)をコアとするTPM-DPA G4デンドリマーは、内層のイミン部位から4、12、28、60個の白金化合物もしくは異種金属化合物を集積可能であり、これを化学的に還元することで個数を精密に制御した微粒子の合成が可能である。このように、コアの有機分子基Ｒ１およびデンドロン(分岐鎖)の世代を適宜のものとすることで、たとえば構成原子数2〜124個の白金−異種金属複合ナノ微粒子を合成することができる。 For example, DPA G4 dendrimer with benzene as the core can accumulate 2, 6, 14, 30 platinum compounds or different metal compounds from the imine site of the inner layer, and TPM- with tetraphenylmethane (TPM) as the core. DPA G4 dendrimer can accumulate 4, 12, 28, 60 platinum compounds or heterogeneous metal compounds from the imine site of the inner layer, and by chemically reducing this, the synthesis of fine particles with precisely controlled numbers can be achieved. Is possible. In this way, for example, platinum-dissimilar metal composite nanoparticles having 2 to 124 constituent atoms can be synthesized by appropriately selecting the generation of the core organic molecular group R 1 and the dendron (branched chain). .
本発明の白金−異種金属複合ナノ微粒子を燃料電池用触媒として使用する場合、白金−異種金属複合ナノ微粒子の組成は、好ましくはPty‐xMx（X＝2〜59、Y＝3〜60、Y＞X）である。本発明の燃料電池用触媒は、燃料電池の電極表面や活性炭素表面などに担持して利用することができる。 When the platinum-foreign metal composite nanoparticle of the present invention is used as a fuel cell catalyst, the composition of the platinum-foreign metal composite nanoparticle is preferably Pt y-x M x (X = 2 to 59, Y = 3 to 60, Y> X). The catalyst for a fuel cell of the present invention can be used by being supported on the electrode surface or activated carbon surface of the fuel cell.
本発明の燃料電池用触媒に使用される白金−異種金属複合ナノ微粒子は、分子量分布を有しておらず、精密に金属の個数と比率が制御された原子集合体（クラスター）である。そして粒径は従来の製法では不可能であった1nm以下と大幅に小さくすることもでき、白金量当たりの比表面積を大幅に増大させることができる。しかも、デンドリマーのある程度閉鎖された空間内に白金含有微粒子が包接されることで、ナノ粒子同士の凝集が抑制され、かつ、完全に白金含有微粒子を被覆しているのではないため触媒活性の低下を最小限に抑えることができ、高活性触媒として使用できる。したがって、本発明の白金−異種金属複合ナノ微粒子は、燃料電池の酸素還元触媒や、その他メタノール酸化、水素酸化、および炭化水素燃料の酸化の触媒に使用することができる。 The platinum-foreign metal composite nanoparticles used in the fuel cell catalyst of the present invention are atomic aggregates (clusters) that do not have a molecular weight distribution and whose number and ratio of metals are precisely controlled. The particle size can be greatly reduced to 1 nm or less, which was impossible with the conventional manufacturing method, and the specific surface area per platinum amount can be greatly increased. In addition, the inclusion of platinum-containing fine particles in a space where the dendrimer is closed to some extent suppresses aggregation of the nanoparticles and does not completely cover the platinum-containing fine particles. The decrease can be minimized, and it can be used as a highly active catalyst. Therefore, the platinum-foreign metal composite nanoparticle of the present invention can be used as an oxygen reduction catalyst for a fuel cell, a catalyst for methanol oxidation, hydrogen oxidation, and hydrocarbon fuel oxidation.
以下、実施例により本発明をさらに詳しく説明するが、本発明はこれらの実施例に何ら限定されるものではない。
＜実施例１＞
3.3μMのTPM-DPA G4 dendrimer（クロロホルム：アセトニトリル=１：１）溶液2mlに、塩化錫（II）アセトニトリル溶液を、dendrimer：Sn=1：4の比率となるように加え、さらに塩化白金（IV）アセトニトリル溶液をdendrimer：Pt=1：24の比率となるように加えて十分に錯形成させた。
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.
<Example 1>
To 2 ml of a 3.3 μM TPM-DPA G4 dendrimer (chloroform: acetonitrile = 1: 1) solution, a tin (II) chloride acetonitrile solution was added so as to have a ratio of dendrimer: Sn = 1: 4, and platinum chloride (IV ) Acetonitrile solution was added at a ratio of dendrimer: Pt = 1: 24 to allow sufficient complexation.
このようにして得られた（(PtCl4)24(SnCl2)4@dendrimer含有溶液に、還元剤として20mg/Lの水素化ホウ素ナトリウム−メタノール溶液を10ml加えて、約50分間攪拌した。 10 ml of a 20 mg / L sodium borohydride-methanol solution as a reducing agent was added to the ((PtCl 4 ) 24 (SnCl 2 ) 4 @ dendrimer-containing solution thus obtained, and the mixture was stirred for about 50 minutes.
紫外可視吸収スペクトルの変化の収束により、反応の終了を確認した。得られたPt24Sn4@dendrimerのTEM像を図１に示す。同図のTEM像にも示されるように、クラスターの粒度分布が全くないことが確認された。
＜実施例２＞
実施例１において合成したPt24Sn4@dendrimer、および同様の方法で合成した異なる組成の金属複合ナノ粒子(PtnSn28-n@dendrimer)について、燃料電池用触媒としての活性を評価した。撹拌終了後のナノ微粒子を分散させた溶液を、炭素基板(グラッシーカーボン)上に少量(1μL〜5μL)滴下し、溶媒を揮発させることによって微粒子修飾電極を作成した。
The completion of the reaction was confirmed by the convergence of the change in the UV-visible absorption spectrum. A TEM image of the obtained Pt 24 Sn 4 @dendrimer is shown in FIG. As shown in the TEM image in the figure, it was confirmed that there was no cluster size distribution.
<Example 2>
The activity as a fuel cell catalyst was evaluated for the Pt 24 Sn 4 @dendrimer synthesized in Example 1 and the metal composite nanoparticles (Pt n Sn 28-n @dendrimer) having different compositions synthesized by the same method. A small amount (1 μL to 5 μL) of a solution in which nanoparticles after dispersion were dispersed was dropped on a carbon substrate (glassy carbon), and the solvent was volatilized to prepare a fine particle modified electrode.
この得られた電極の電解酸素還元反応に対する触媒活性をサイクリックボルタンメトリー法によって解析した。図２は、Pt24Sn4@dendrimer担持グラッシーカーボン電極を作用極として測定した酸素飽和状態におけるサイクリックボルタモグラムである。各曲線は、異なる白金担持量で測定したボルタモグラムに対応する。図３は、グラッシーカーボン電極に担持する白金の重量と、得られるサイクリックボルタモグラムのピーク電流値との関係を示すグラフである。各プロットは、本発明の方法で作成した異なる組成の金属複合ナノ粒子(PtnSn28-n@dendrimer)および、市販の燃料電池触媒として入手可能なカーボン担持白金ナノ粒子(粒径分散2-5 nm)に対応する。 The catalytic activity of the obtained electrode for the electrolytic oxygen reduction reaction was analyzed by cyclic voltammetry. FIG. 2 is a cyclic voltammogram in an oxygen saturated state measured using a Pt 24 Sn 4 @ dendrimer-supported glassy carbon electrode as a working electrode. Each curve corresponds to a voltammogram measured at a different platinum loading. FIG. 3 is a graph showing the relationship between the weight of platinum carried on the glassy carbon electrode and the peak current value of the obtained cyclic voltammogram. Each plot shows metal composite nanoparticles (Pt n Sn 28-n @dendrimer) having different compositions prepared by the method of the present invention and carbon-supported platinum nanoparticles (particle size dispersion 2- 5 nm).
図２より、酸素を飽和させた電解質溶液(1 mol/L 硫酸)に浸した修飾電極にて、0.4 V vs. Ag/AgCl付近より不可逆な還元波が観測され、本電極が酸素に対して触媒活性を有していることが確認された。なお試験条件は次のとおりである。
対極：白金
参照極：Ag/AgCl 3M NaCl
作用極：GCE(Φ=6mm)にPt24Sn4@dendrimerを担持
電解質：1 N H2SO4 (O2飽和)
スキャンレート：5 mV/s
同様の手法によって得た白金単独からなる微粒子(Pt28@dendrimer)で観測される酸素還元の開始電位は0.40 Vであるが、これと比較してPt24Sn4@dendrimerでは開始電位が0.41 Vに向上し、Pt16Sn12@dendrimerでは0.44 Vとさらに向上した。この開始電位の向上は、酸素還元反応に必要な過電圧の低下に対応しており、燃料電池触媒として用いた場合には起電力の向上に寄与する。
Figure 2 shows that an irreversible reduction wave is observed near 0.4 V vs. Ag / AgCl at the modified electrode immersed in an oxygen-saturated electrolyte solution (1 mol / L sulfuric acid). It was confirmed to have catalytic activity. The test conditions are as follows.
Counter electrode: Platinum Reference electrode: Ag / AgCl 3M NaCl
Working electrode: GCE (Φ = 6mm) carrying Pt 24 Sn 4 @dendrimer Electrolyte: 1 NH 2 SO 4 (O 2 saturated)
Scan rate: 5 mV / s
The onset potential of oxygen reduction observed with fine particles of platinum alone (Pt 28 @dendrimer) obtained by the same method is 0.40 V, but compared with this, the onset potential of Pt 24 Sn 4 @dendrimer is 0.41 V. Pt 16 Sn 12 @dendrimer further improved to 0.44 V. This improvement in the starting potential corresponds to a decrease in overvoltage necessary for the oxygen reduction reaction, and contributes to an improvement in electromotive force when used as a fuel cell catalyst.
一方、CVのピーク電流値を各微粒子間で比較したところ、同量の白金使用量においてはPt24Sn4@dendrimerが白金単独であるPt28@dendrimerより高い値を示すことが確認された（図３）。このことは、燃料電池において取り出せる電流値の大きさが大きいことを示している。
＜実施例３＞
上記において得られた金属複合ナノ微粒子について、メタノールの酸化反応に対する触媒活性を評価した(図４)。図４の試験条件は次のとおりである。
対極：白金
参照極：Ag/AgCl 3M NaCl
作用極：GCE(Φ=6mm) にPt24Sn4@dendrimer等を担持
電解質：1 N H2SO4 + 1.5 M ethanol
スキャンレート：5 mV/s
図４より、上記において得られた金属複合ナノ微粒子は、メタノールの酸化反応に対しても高い触媒活性を示した。即ち、実施例２の結果と併せて、本発明の金属複合ナノ微粒子は、燃料電池において、酸素還元反応が生起する空気極、酸化反応が生起する燃料極のいずれにおいても高い触媒活性を発揮することが示された。
＜実施例４＞
Pt16M12(Mはバナジウム、鉄、銅、ガリウム、スズいずれかの金属元素を示す。)の組成を有する白金-異種金属複合ナノ微粒子を調製した。
On the other hand, when the peak current value of CV was compared between the fine particles, it was confirmed that Pt 24 Sn 4 @dendrimer showed a higher value than Pt 28 @dendrimer, which is platinum alone, at the same amount of platinum used ( FIG. 3). This indicates that the current value that can be taken out in the fuel cell is large.
<Example 3>
About the metal composite nanoparticle obtained in the above, the catalytic activity with respect to the oxidation reaction of methanol was evaluated (FIG. 4). The test conditions in FIG. 4 are as follows.
Counter electrode: Platinum Reference electrode: Ag / AgCl 3M NaCl
Working electrode: GCE (Φ = 6mm) with Pt 24 Sn 4 @dendrimer, etc. Electrolyte: 1 NH 2 SO 4 + 1.5 M ethanol
Scan rate: 5 mV / s
From FIG. 4, the metal composite nanoparticle obtained in the above showed high catalytic activity even for the oxidation reaction of methanol. That is, in combination with the results of Example 2, the metal composite nanoparticle of the present invention exhibits high catalytic activity in both the air electrode where the oxygen reduction reaction occurs and the fuel electrode where the oxidation reaction occurs in the fuel cell. It was shown that.
<Example 4>
Platinum-dissimilar metal composite nanoparticles having a composition of Pt 16 M 12 (M represents a metal element of vanadium, iron, copper, gallium, or tin) were prepared.
金属塩(三塩化バナジウム、三塩化鉄、二塩化銅、三塩化ガリウム、二塩化スズ)をアセトニトリル溶媒に溶解し、3mmolL-1の濃度となるように溶液を調製した。同様に、四塩化白金のアセトニトリル溶液を3mmolL-1の濃度となるように調製した。 A metal salt (vanadium trichloride, iron trichloride, copper dichloride, gallium trichloride, tin dichloride) was dissolved in an acetonitrile solvent to prepare a solution having a concentration of 3 mmol L- 1 . Similarly, an acetonitrile solution of platinum tetrachloride was prepared to have a concentration of 3 mmol L- 1 .
実施例１と同様のデンドリマーをアセトニトリル/クロロホルムの混合溶媒(体積比1:1)に溶解し、3μmol-1の濃度となるように溶液を調製した。 The same dendrimer as in Example 1 was dissolved in a mixed solvent of acetonitrile / chloroform (volume ratio 1: 1), and a solution was prepared so as to have a concentration of 3 μmol −1 .
上記のデンドリマー溶液1mLに、上記で調製した金属塩(M)の溶液をモル濃度比でデンドリマー:M = 1:12となるように加えた。5分間室温で撹拌を行い、デンドリマーの金属錯体を得た。 The metal salt (M) solution prepared above was added to 1 mL of the above dendrimer solution so that the molar concentration ratio of dendrimer: M = 1: 12. Stirring was performed at room temperature for 5 minutes to obtain a dendrimer metal complex.
この金属錯体溶液にさらに、上記において調製した四塩化白金の溶液をデンドリマー:M:Pt = 1:12:16のモル濃度比となるように加え、60分間撹拌を行った。 Further, the platinum tetrachloride solution prepared above was added to this metal complex solution so as to have a molar concentration ratio of dendrimer: M: Pt = 1: 112: 16, and the mixture was stirred for 60 minutes.
還元剤である水素化ホウ素ナトリウム(NaBH4)のメタノール溶液(20mgmL-1の濃度で調製)を10μL分の間、上記の溶液に加えて金属塩の還元を行い、合金クラスターの分散溶液を得た。
＜実施例５＞
実施例４において得られた白金-異種金属複合ナノ微粒子の評価を行った。市販の電気化学測定用グラッシーカーボン電極(φ=6mm)に、各異種金属(M)を含む複合ナノ微粒子の分散溶液を均等に載せ、乾燥させた。この際の分散溶液積載量は、均一分散した複合ナノ微粒子の質量のうち、白金相当量がそれぞれ17.1, 25.7, 34.3ngとなるように設定した。
A reducing agent, sodium borohydride (NaBH 4 ) in methanol (prepared at a concentration of 20 mgmL- 1 ) is added to the above solution for 10 μL for metal salt reduction to obtain a dispersed alloy cluster solution. It was.
<Example 5>
The platinum-foreign metal composite nanoparticle obtained in Example 4 was evaluated. A dispersion solution of composite nanoparticles containing each different metal (M) was evenly placed on a commercially available glassy carbon electrode for electrochemical measurement (φ = 6 mm) and dried. The amount of the dispersion solution loaded at this time was set such that the platinum equivalent amounts were 17.1, 25.7, and 34.3 ng among the mass of the uniformly dispersed composite nanoparticles, respectively.
以下の条件において、回転ディスクボルタンメトリー(RDV)法によって測定を行った。
作用極：白金触媒を担持したグラッシーカーボンディスク電極(φ=6mm)
参照電極：Ag/AgCl (3molL-1NaCl)
対極：Ptコイル
電解質溶液：0.5molL-1硫酸水溶液 (O2ガスパージによる酸素飽和)
電極回転数ω=120, 180, 300rpm
それぞれの異種金属種(M)、白金積載量、電極回転数におけるボルタモグラムより、参照電極(Ag/AgCl)基準で0.0V, 0.35Vのそれぞれにおける電流値を読み取り、図５(0.0V)、図６(0.35V)にそれぞれ得られたデータをもとに以下の手順で速度論的限界電流値(jK)を算出し、プロットした。
The measurement was performed by the rotating disk voltammetry (RDV) method under the following conditions.
Working electrode: Glassy carbon disc electrode carrying platinum catalyst (φ = 6mm)
Reference electrode: Ag / AgCl (3molL -1 NaCl)
Counter electrode: Pt coil electrolyte solution: 0.5 molL -1 sulfuric acid aqueous solution (oxygen saturation by O 2 gas purge)
Electrode rotation speed ω = 120, 180, 300rpm
The current values at 0.0V and 0.35V on the reference electrode (Ag / AgCl) standard were read from the voltammogram of each different metal species (M), platinum loading, and electrode rotation speed. Figure 5 (0.0V), Figure The kinetic limit current value (j K ) was calculated and plotted according to the following procedure based on the data obtained at 6 (0.35 V).
Koutecky-Levich式にて、観測された電流密度jobsより、基質である酸素の拡散過程を取り除いた界面反応速度成分jKを算出した。この際、Fはファラデー定数(9.65×104Cmol-1)、C0は電解質溶液への大気圧下における酸素分子飽和濃度(1.1×10-6molL-1)、D0は酸素分子の拡散係数(1.9×10-5cm2s-1)、ωは電極の回転数(単位rpm)、νは水溶液の動粘度(1.0×10-2cm2s-1)である。 From the observed current density j obs by the Koutecky-Levich equation, the interfacial reaction rate component j K was calculated by removing the diffusion process of oxygen as a substrate. At this time, F is the Faraday constant (9.65 × 10 4 Cmol −1 ), C 0 is the oxygen molecule saturation concentration (1.1 × 10 −6 molL −1 ) under atmospheric pressure into the electrolyte solution, and D 0 is the diffusion of oxygen molecules. The coefficient (1.9 × 10 −5 cm 2 s −1 ), ω is the rotation speed of the electrode (unit: rpm), and ν is the kinematic viscosity of the aqueous solution (1.0 × 10 −2 cm 2 s− 1 ).
図５より、同一サイズの白金単一触媒(Pt28)と比較して、速度論的限界電流値が合金化に伴って維持もしくは向上することが示された。また、図６では、触媒の開始電位が大幅に向上することが明らかとなった。これは酸素還元反応に必要な過電圧の低下に対応しており、燃料電池触媒として用いた場合には起電力の向上に寄与する。
＜実施例６＞
バイメタリッククラスター(Pt16Sn12)と、ホモクラスター(Pt28)の触媒活性の比較検証実験を行った。実施例４と同様に、二塩化スズおよび四塩化白金のアセトニトリル溶液を3mmolL-1の濃度となるように調製した。
FIG. 5 shows that the kinetic limit current value is maintained or improved as a result of alloying as compared with a single platinum catalyst (Pt 28 ) of the same size. Moreover, in FIG. 6, it became clear that the starting potential of a catalyst improves significantly. This corresponds to a decrease in overvoltage necessary for the oxygen reduction reaction, and contributes to improvement of electromotive force when used as a fuel cell catalyst.
<Example 6>
A comparative verification experiment of the catalytic activity of bimetallic cluster (Pt 16 Sn 12 ) and homocluster (Pt 28 ) was conducted. In the same manner as in Example 4, an acetonitrile solution of tin dichloride and platinum tetrachloride was prepared to a concentration of 3 mmol L- 1 .
実施例４と同様のデンドリマーをアセトニトリル/クロロホルムの混合溶媒(体積比1:1)に溶解し、3μmol-1の濃度となるように溶液を調製した。 The same dendrimer as in Example 4 was dissolved in a mixed solvent of acetonitrile / chloroform (volume ratio 1: 1), and a solution was prepared so as to have a concentration of 3 μmol −1 .
このデンドリマー溶液1mLに、上記において調製した四塩化白金の溶液をモル濃度比でデンドリマー:Pt=1:28となるように加えた(溶液A)。同様に、二塩化スズについてもモル濃度比でデンドリマー:Sn=1:28となるように加えた(溶液B)。それぞれの溶液について、5分間室温で撹拌を行い、デンドリマーの金属錯体を得た。 To 1 mL of this dendrimer solution, the solution of platinum tetrachloride prepared above was added so that the molar ratio of dendrimer: Pt = 1: 28 (solution A). Similarly, tin dichloride was also added so that the molar ratio of dendrimer: Sn = 1: 28 (solution B). Each solution was stirred at room temperature for 5 minutes to obtain a dendrimer metal complex.
溶液Aと溶液Bを、それぞれ16:12の比率で混合した溶液Cを調製した。溶液Cに還元剤である水素化ホウ素ナトリウム(NaBH4)のメタノール溶液(20mgmL-1の濃度で調製)を10μL加え、金属塩の還元を行い、合金クラスターの分散溶液を得た。これをPt16Sn12とした。 Solution C was prepared by mixing solution A and solution B in a ratio of 16:12, respectively. 10 μL of a methanol solution of sodium borohydride (NaBH 4 ) as a reducing agent (prepared at a concentration of 20 mg mL −1 ) was added to Solution C to reduce the metal salt to obtain a dispersion solution of alloy clusters. This was designated as Pt 16 Sn 12 .
溶液A、溶液Bのそれぞれについて、還元剤である水素化ホウ素ナトリウム(NaBH4)のメタノール溶液を別個に加え、ホモクラスター(Pt28, Sn28)を合成した。そしてそれぞれのホモクラスター分散溶液を16:12の比率で混合しホモクラスター混合物16/28Pt28+12/28Sn28を得た。 For each of Solution A and Solution B, a methanol solution of sodium borohydride (NaBH 4 ) as a reducing agent was added separately to synthesize a homocluster (Pt 28 , Sn 28 ). Each homocluster dispersion was mixed at a ratio of 16:12 to obtain a homocluster mixture 16 / 28Pt 28 + 12 / 28Sn 28 .
ヘテロバイメタリッククラスター溶液(Pt16Sn12)とホモクラスター混合溶液(16/28Pt28+12/28Sn28)に含まれるそれぞれの元素の質量は全く同一であると見なせる。これらのそれぞれについて、実施例５と同様に触媒活性評価を行った。その結果を図７に示す。 It can be considered that the masses of the respective elements contained in the heterobimetallic cluster solution (Pt 16 Sn 12 ) and the homocluster mixed solution (16 / 28Pt 28 + 12 / 28Sn 28 ) are exactly the same. About each of these, catalytic activity evaluation was performed similarly to Example 5. The result is shown in FIG.
図７より、Pt16Sn12ではクラスター混合物に比べて、酸素還元が開始する電位がより高電位側に観測される。このことは酸素還元に必要な過電圧が低下していることを意味しており、0.35Vにおける触媒活性の差として明確に現れている。一方で、バイメタリッククラスターになることで、十分な過電圧(0.0V)を印加した場合の電流値は殆ど失われず、十分な触媒活性を保った。 From FIG. 7, the potential at which oxygen reduction starts is observed on the higher potential side in Pt 16 Sn 12 as compared with the cluster mixture. This means that the overvoltage required for oxygen reduction is decreasing, and this clearly appears as a difference in catalyst activity at 0.35V. On the other hand, by becoming a bimetallic cluster, the current value when a sufficient overvoltage (0.0 V) was applied was hardly lost, and sufficient catalytic activity was maintained.
Claims (3)
（式中のMは2つの水素原子または任意の金属原子を示し、Dはデンドロン結合部位を示す。）のいずれかで表わされる請求項１に記載の燃料電池用触媒。 R 1 in the formula (I) is represented by the following formula:
2. The fuel cell catalyst according to claim 1, wherein M is a hydrogen atom or any metal atom, and D is a dendron binding site.
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