JP2011021250A - Metallic material composed of metal nanoparticle, and method for producing the same - Google Patents
Metallic material composed of metal nanoparticle, and method for producing the same Download PDFInfo
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 36
- 239000007769 metal material Substances 0.000 title claims abstract description 31
- 239000002082 metal nanoparticle Substances 0.000 title description 10
- 239000007864 aqueous solution Substances 0.000 claims abstract description 64
- 229910052751 metal Inorganic materials 0.000 claims abstract description 51
- 239000010419 fine particle Substances 0.000 claims abstract description 42
- 150000001413 amino acids Chemical class 0.000 claims abstract description 32
- 239000003054 catalyst Substances 0.000 claims abstract description 31
- 239000002244 precipitate Substances 0.000 claims abstract description 31
- 238000001354 calcination Methods 0.000 claims abstract description 26
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- 150000002500 ions Chemical class 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 12
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 106
- 239000002184 metal Substances 0.000 claims description 49
- 229910052697 platinum Inorganic materials 0.000 claims description 9
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- 150000004681 metal hydrides Chemical class 0.000 claims description 4
- 229940024606 amino acid Drugs 0.000 abstract description 32
- 235000001014 amino acid Nutrition 0.000 abstract description 32
- QNAYBMKLOCPYGJ-REOHCLBHSA-N L-alanine Chemical compound C[C@H](N)C(O)=O QNAYBMKLOCPYGJ-REOHCLBHSA-N 0.000 abstract description 19
- 229960003767 alanine Drugs 0.000 abstract description 19
- 235000004279 alanine Nutrition 0.000 abstract description 19
- QNAYBMKLOCPYGJ-UHFFFAOYSA-N Alanine Chemical compound CC([NH3+])C([O-])=O QNAYBMKLOCPYGJ-UHFFFAOYSA-N 0.000 abstract description 8
- 229950010030 dl-alanine Drugs 0.000 abstract description 4
- 239000000243 solution Substances 0.000 abstract description 3
- 108090000765 processed proteins & peptides Proteins 0.000 description 31
- 229920001184 polypeptide Polymers 0.000 description 28
- 102000004196 processed proteins & peptides Human genes 0.000 description 28
- 239000000463 material Substances 0.000 description 26
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- 238000002156 mixing Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 239000003125 aqueous solvent Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- -1 ion compound Chemical class 0.000 description 4
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- 238000001228 spectrum Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 239000002638 heterogeneous catalyst Substances 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000002923 metal particle Substances 0.000 description 3
- 239000011859 microparticle Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000012279 sodium borohydride Substances 0.000 description 3
- 229910000033 sodium borohydride Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910001111 Fine metal Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- SIPUZPBQZHNSDW-UHFFFAOYSA-N bis(2-methylpropyl)aluminum Chemical compound CC(C)C[Al]CC(C)C SIPUZPBQZHNSDW-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
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- YMAWOPBAYDPSLA-UHFFFAOYSA-N glycylglycine Chemical compound [NH3+]CC(=O)NCC([O-])=O YMAWOPBAYDPSLA-UHFFFAOYSA-N 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
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- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 108010069941 DNA receptor Proteins 0.000 description 1
- 108010008488 Glycylglycine Proteins 0.000 description 1
- FFEARJCKVFRZRR-BYPYZUCNSA-N L-methionine Chemical compound CSCC[C@H](N)C(O)=O FFEARJCKVFRZRR-BYPYZUCNSA-N 0.000 description 1
- COLNVLDHVKWLRT-QMMMGPOBSA-N L-phenylalanine Chemical compound OC(=O)[C@@H](N)CC1=CC=CC=C1 COLNVLDHVKWLRT-QMMMGPOBSA-N 0.000 description 1
- 229910010082 LiAlH Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
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- 230000002378 acidificating effect Effects 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- PBAYDYUZOSNJGU-UHFFFAOYSA-N chelidonic acid Natural products OC(=O)C1=CC(=O)C=C(C(O)=O)O1 PBAYDYUZOSNJGU-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
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- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
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- 150000004687 hexahydrates Chemical class 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 239000012280 lithium aluminium hydride Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229930182817 methionine Natural products 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- COLNVLDHVKWLRT-UHFFFAOYSA-N phenylalanine Natural products OC(=O)C(N)CC1=CC=CC=C1 COLNVLDHVKWLRT-UHFFFAOYSA-N 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- UQDJGEHQDNVPGU-UHFFFAOYSA-N serine phosphoethanolamine Chemical compound [NH3+]CCOP([O-])(=O)OCC([NH3+])C([O-])=O UQDJGEHQDNVPGU-UHFFFAOYSA-N 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- FBEIPJNQGITEBL-UHFFFAOYSA-J tetrachloroplatinum Chemical compound Cl[Pt](Cl)(Cl)Cl FBEIPJNQGITEBL-UHFFFAOYSA-J 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Abstract
Description
本発明は、触媒として用いられ得る構造を備えた金属微粒子（金属ナノ粒子）からなる金属材料と、その製造方法に関する。 The present invention relates to a metal material composed of metal fine particles (metal nanoparticles) having a structure that can be used as a catalyst, and a method for producing the metal material.
白金（Ｐｔ）、パラジウム、銀等の金属は、燃料電池（例えば固体高分子電解質形燃料電池）の電極反応や、自動車の排ガス成分の分解、浄化反応等を始めとする種々の化学反応を促進する不均一触媒として利用されている。不均一触媒は、多くの場合、触媒表面で触媒反応が進行する。このことから、粒子径（典型的には平均粒子径）が数ナノメートル〜数十ナノメートル程度（すなわちナノメートルサイズ）である金属ナノ粒子を触媒体として利用すれば、粉末状触媒体（すなわち該ナノ粒子の集合体）全体の表面積（すなわち反応面積）が従来のミクロンサイズの金属粒子を用いた場合と比較して増大し、触媒効率が向上するので触媒体として高い利用価値を有することが期待される。 Metals such as platinum (Pt), palladium, and silver promote various chemical reactions including electrode reactions of fuel cells (for example, solid polymer electrolyte fuel cells), decomposition of automobile exhaust gas components, and purification reactions. It is used as a heterogeneous catalyst. In many cases, a heterogeneous catalyst undergoes a catalytic reaction on the catalyst surface. From this, if metal nanoparticles having a particle size (typically an average particle size) of about several nanometers to several tens of nanometers (that is, nanometer size) are used as a catalyst body, a powdery catalyst body (that is, The aggregate of the nanoparticles) has a high surface area (ie, reaction area) as compared to the case of using conventional micron-sized metal particles, and the catalyst efficiency is improved, so that it has a high utility value as a catalyst body. Be expected.
ところで、金属ナノ粒子は、その粒子の形態（形状）により導電性、耐熱性、触媒活性等の種々の物性（性能）が異なり得ることが知られている。このため、かかる金属ナノ粒子の製造にあたっては、平均粒子径をナノメートルサイズ（好ましくは数ナノメートルレベル）に制御するとともに、該金属ナノ粒子を使用目的（例えば触媒体）に対して好適な物性を有し得る形態で再現性高く生成し、その形態を長期にわたり安定的に維持し得るように製造することが好ましい。 By the way, it is known that various physical properties (performance) such as conductivity, heat resistance, and catalytic activity may vary depending on the shape (shape) of the metal nanoparticles. Therefore, in the production of such metal nanoparticles, the average particle diameter is controlled to a nanometer size (preferably several nanometer level), and the physical properties suitable for the intended use (for example, catalyst body) are used. It is preferable to produce so that it can be produced in a form having high reproducibility and can be stably maintained over a long period of time.
触媒として機能し得る金属ナノ粒子から構成される金属材料の製造方法として、種々の方法が提案されている。特に近年では、有機化合物（典型的には高分子化合物）を鋳型として所定形状の金属ナノ粒子を製造したり、あるいは、有機化合物で形成される構造（空間）内に収容された状態の金属材料（例えば界面活性剤として機能する複数の有機化合物と結合することで該有機化合物に取り囲まれた金属ナノ粒子）を製造する方法が提案されている。なお、非特許文献１〜３では、医学や薬学分野での利用を目的として、ポリペプチドまたは側鎖にアミノ酸を備えたポリマーが結合している金属材料が提案されている。 Various methods have been proposed as a method for producing a metal material composed of metal nanoparticles that can function as a catalyst. In particular, in recent years, metal materials of a predetermined shape are produced using an organic compound (typically a polymer compound) as a template, or a metal material that is housed in a structure (space) formed of an organic compound. There has been proposed a method for producing (for example, metal nanoparticles surrounded by an organic compound by binding to a plurality of organic compounds functioning as a surfactant). In Non-Patent Documents 1 to 3, a metal material in which a polypeptide or a polymer having an amino acid in a side chain is bonded is proposed for the purpose of use in the medical or pharmaceutical fields.
本発明の主な目的は、触媒として機能し得る新規な形態の金属微粒子から構成される金属材料を製造する方法を提供することである。また、このような方法を用いて得られる金属材料を提供することを他の目的とする。 The main object of the present invention is to provide a method for producing a metal material composed of a novel form of metal fine particles that can function as a catalyst. Another object is to provide a metal material obtained by using such a method.
本発明者は、従来のナノ粒子とは異なる新規な形状、特に触媒として好適に機能し得ると考えられる形状を備えた金属ナノ粒子、およびその製造方法を開発するべく、ある種のアミノ酸を用いて金属微粒子を製造する方法を検討したところ、かかるアミノ酸からなるポリペプチドを鋳型として金属微粒子が析出し、かかる析出物をか焼すると触媒体として用いられ得る多孔質構造を有する好適な金属材料を生成することができ、本発明を完成するに至った。 The present inventor has used a certain amino acid to develop a metal nanoparticle having a novel shape different from that of a conventional nanoparticle, particularly a shape that can be suitably used as a catalyst, and a method for producing the metal nanoparticle. As a result of examining the method for producing metal fine particles, a metal material having a porous structure that can be used as a catalyst body is obtained by depositing metal fine particles using a polypeptide comprising such an amino acid as a template and calcining the precipitate. The present invention has been completed.
すなわち、本発明により提供される触媒体として好適に機能し得る金属材料の製造方法は、触媒として機能し得る金属元素を含むイオンを含有する水溶液を用意すること、該用意した水溶液に、所定の種類のアミノ酸を添加すること、上記水溶液に還元剤を添加すること、および上記金属微粒子を含む析出物を生じさせること、を包含する。
本発明に係る金属材料の製造方法では、上記アミノ酸同士が結合してなるポリペプチドと上記金属元素を含むイオンとが結合（例えば、かかるポリペプチドの末端基におけるアミノ酸のアミノ基および／またはカルボキシル基と上記金属元素を含むイオンとの結合、またはポリペプチドと上記金属イオンとの水素結合）することにより、還元剤を添加すると上記ポリペプチドの周囲にナノメートルサイズの金属微粒子（金属ナノ粒子）を凝集、析出させることができる。このように金属微粒子が上記ポリペプチドの表面に析出した形態の金属微粒子から構成される金属材料は、触媒体として好ましく用いられ得る。
したがって、本発明に係る製造方法によると、触媒として機能し得る構造を備えた金属微粒子からなる金属材料を、上記のような工程により容易に製造することができる。
That is, a method for producing a metal material that can suitably function as a catalyst body provided by the present invention includes preparing an aqueous solution containing an ion containing a metal element that can function as a catalyst. It includes adding a kind of amino acid, adding a reducing agent to the aqueous solution, and producing a precipitate containing the metal fine particles.
In the method for producing a metal material according to the present invention, a polypeptide formed by bonding the amino acids and an ion containing the metal element are bonded (for example, an amino group and / or a carboxyl group of an amino acid at a terminal group of the polypeptide). When the reducing agent is added, the nanometer-sized metal fine particles (metal nanoparticles) are formed around the polypeptide. Aggregation and precipitation are possible. Thus, the metal material comprised from the metal fine particle of the form which metal fine particle precipitated on the surface of the said polypeptide can be preferably used as a catalyst body.
Therefore, according to the production method of the present invention, a metal material composed of metal fine particles having a structure that can function as a catalyst can be easily produced by the above-described steps.
ここで開示される金属材料の製造方法の好ましい一態様では、上記金属微粒子を含む析出物をか焼すること、をさらに包含する。
かかる構成の製造方法によると、上記のようにして得られた金属微粒子を含む析出物をか焼することにより、か焼後に残った金属微粒子は、上記ポリペプチドを鋳型とした繊維状（糸状）のような形状で表面積が大きい多孔質構造（海綿状に孔が形成された立体構造）を有し得る。このことにより、得られた金属材料は、該材料を構成する金属微粒子の表面積がより一層増大して触媒効率が向上するので、高触媒活性のより一層好適な触媒体として用いられ得る。
In a preferred embodiment of the method for producing a metal material disclosed herein, the method further includes calcining the precipitate containing the metal fine particles.
According to the manufacturing method having such a configuration, the metal fine particles remaining after calcination are obtained by calcining the precipitate containing the metal fine particles obtained as described above, so that the fibrous (thread-like) shape using the polypeptide as a template. It is possible to have a porous structure (three-dimensional structure in which pores are formed in a spongy shape) having a large surface area. Thus, the obtained metal material can be used as a more suitable catalyst body with high catalytic activity because the surface area of the metal fine particles constituting the material is further increased and the catalyst efficiency is improved.
ここで開示される金属材料の製造方法のより好ましい一態様では、上記還元剤として、金属水素化物を用いる。
かかる構成の製造方法によると、還元剤として金属水素化物（例えば水素化ホウ素ナトリウム）を用いることにより、金属微粒子を含む析出物をより好適に生じさせることができるので好ましい。
In a more preferred embodiment of the method for producing a metal material disclosed herein, a metal hydride is used as the reducing agent.
According to the manufacturing method having such a configuration, it is preferable to use a metal hydride (for example, sodium borohydride) as a reducing agent because a precipitate containing metal fine particles can be generated more suitably.
ここで開示される金属材料の製造方法の別の好ましい一態様では、上記アミノ酸としてアラニンを用いる。
かかる構成の製造方法では、アラニン（ＣＨ３ＣＨ（ＣＯＯＨ）ＮＨ２；例えばＤＬ−アラニン）を用いることにより、生成する金属微粒子の鋳型となるポリペプチドをより好ましく形成することができる。また、かかるアラニンは、安価で入手可能であるとともに、炭素（Ｃ）、窒素（Ｎ）、および水素（Ｈ）元素のみからなる単純な構成であるため、通常のか焼条件でのか焼であれば有害物質の発生がなく環境への負荷も小さいので、好ましく用いることができる。
In another preferable embodiment of the method for producing a metal material disclosed herein, alanine is used as the amino acid.
In the production method having such a configuration, by using alanine (CH 3 CH (COOH) NH 2 ; for example, DL-alanine), a polypeptide serving as a template for the generated metal fine particles can be more preferably formed. In addition, such alanine is available at a low price and has a simple structure composed only of carbon (C), nitrogen (N), and hydrogen (H) elements, so that it can be calcined under normal calcination conditions. Since there is no generation of harmful substances and the load on the environment is small, it can be preferably used.
また、ここで開示される金属材料の製造方法は、触媒活性の高い金属元素である白金に対して好ましく適用することができる。したがって、かかる製造方法によると、触媒として好適に用いられ得る形状の白金微粒子からなる白金材料を好ましく製造することができる。 Moreover, the manufacturing method of the metal material disclosed here can be preferably applied with respect to platinum which is a metal element with high catalytic activity. Therefore, according to such a production method, a platinum material composed of platinum fine particles having a shape that can be suitably used as a catalyst can be preferably produced.
また、ここで開示される金属材料の製造方法の別の好ましい一態様では、上記アミノ酸を、上記金属元素を含むイオン１モルに対して１モル〜２０モルの割合で添加する。
かかる構成の製造方法では、アミノ酸を上記のような配合比で添加することにより、より高い触媒活性を有する好適な金属材料を得ることができる。
Moreover, in another preferable one aspect | mode of the manufacturing method of the metal material disclosed here, the said amino acid is added in the ratio of 1 mol-20 mol with respect to 1 mol of ions containing the said metal element.
In the production method having such a configuration, a suitable metal material having a higher catalytic activity can be obtained by adding amino acids at the blending ratio as described above.
また、本発明は、他の側面として、ここで開示される製造方法を用いることにより製造される金属微粒子を提供することができる。 Moreover, this invention can provide the metal microparticle manufactured by using the manufacturing method disclosed here as another side surface.
以下、本発明の好適な実施形態を説明する。なお、本明細書において特に言及している事項（例えば、触媒として機能し得る金属元素を含むイオンを含有する水溶液にアミノ酸および／または還元剤を添加する方法）以外の事項であって本発明の実施に必要な事柄（例えば、生成した金属微粒子を含む析出物を取り出す方法）は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。 Hereinafter, preferred embodiments of the present invention will be described. It should be noted that items other than those specifically mentioned in this specification (for example, a method of adding an amino acid and / or a reducing agent to an aqueous solution containing an ion containing a metal element that can function as a catalyst) Matters necessary for implementation (for example, a method of taking out a precipitate containing generated fine metal particles) can be grasped as a design matter of a person skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
本発明に係る金属材料の製造方法は、アミノ酸が結合したポリペプチドを鋳型として形成された形状の金属微粒子であって触媒体として用いられ得る金属微粒子からなる金属材料を生成する方法である。かかる製造方法は、触媒として機能し得る金属元素を含むイオンを含有する水溶液を用意すること、該用意した水溶液にアミノ酸を添加すること、該水溶液に還元剤を添加すること、該水溶液中に上記金属元素の微粒子を含む析出物を生じさせること、および該金属微粒子を含む析出物をか焼すること、を包含することによって特徴づけられるものである。したがって、上記目的を達成し得る限りにおいて、その他の構成成分の内容や組成については、種々の基準に照らして任意に決定することができる。 The method for producing a metal material according to the present invention is a method for producing a metal material composed of metal fine particles that are formed using a polypeptide to which an amino acid is bound as a template and can be used as a catalyst body. Such a production method includes preparing an aqueous solution containing an ion containing a metal element that can function as a catalyst, adding an amino acid to the prepared aqueous solution, adding a reducing agent to the aqueous solution, and adding the reducing agent to the aqueous solution. It is characterized by including producing a precipitate containing fine particles of a metal element and calcining the precipitate containing the fine metal particles. Therefore, as long as the above object can be achieved, the content and composition of other components can be arbitrarily determined in light of various standards.
本発明に係る金属材料の製造方法では、該金属材料を構成する金属微粒子の構成元素として白金族元素、すなわち周期表の第５〜６周期、第８〜１０族に位置する元素、すなわち、ルテニウム（Ｒｕ）、ロジウム（Ｒｈ）、パラジウム（Ｐｄ）、オスミウム（Ｏｓ）、イリジウム（Ｉｒ）および白金（Ｐｔ）の少なくとも一種を用いることができる。かかる白金族元素の中でも不均一触媒として利用頻度が高く、燃料電池（典型的には固体高分子電解質形燃料電池（ＰＥＦＣ））における電極触媒や自動車の排ガス浄化用触媒として好適に用いられているＰｔがより好ましい。
以下では、特に限定することを意図しないが、Ｐｔ微粒子からなるＰｔ材料を製造する場合を例として、本発明に係る金属材料の製造方法について詳細に説明する。
In the method for producing a metal material according to the present invention, a platinum group element, that is, an element located in the fifth to sixth periods and the eighth to tenth groups of the periodic table, that is, ruthenium as a constituent element of the metal fine particles constituting the metal material. At least one of (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) can be used. Among such platinum group elements, it is frequently used as a heterogeneous catalyst, and is suitably used as an electrode catalyst in a fuel cell (typically a solid polymer electrolyte fuel cell (PEFC)) or an exhaust gas purification catalyst for an automobile. Pt is more preferable.
In the following, although not specifically limited, the method for producing a metal material according to the present invention will be described in detail by taking as an example the case of producing a Pt material composed of Pt fine particles.
まず、触媒として機能するＰｔを含むイオンを含有する水溶液を用意（典型的には調製）する。かかる水溶液としては、例えばＰｔのインゴットを所定の酸性媒体（例えば塩酸や王水）に溶解させたもの（例えば塩化白金（ＩＶ）水溶液）を用いることができる。好ましくは、上記水溶液の溶質（Ｐｔ源）として、後述のペプチド鎖と結合可能なＰｔ化合物であって水系溶媒に対する溶解度が高いＰｔイオン化合物であり、より好ましくはＰｔを含む錯イオンから構成される白金錯体であり、さらに好ましくはかかる錯イオンが陰イオンである白金錯体である。このような白金錯体の一好適例として、塩化白金酸（典型的にはその六水和物；Ｈ２［ＰｔＣｌ６］・６Ｈ２Ｏ）を好ましく用いることができる。以下、Ｐｔ源としてＨ２［ＰｔＣｌ６］を用いる場合を例として説明する。 First, an aqueous solution containing ions containing Pt that functions as a catalyst is prepared (typically prepared). As such an aqueous solution, for example, a Pt ingot dissolved in a predetermined acidic medium (for example, hydrochloric acid or aqua regia) (for example, a platinum (IV) chloride aqueous solution) can be used. Preferably, the solute (Pt source) of the aqueous solution is a Pt ion compound that is capable of binding to a peptide chain described later and has high solubility in an aqueous solvent, and more preferably composed of a complex ion containing Pt. It is a platinum complex, more preferably a platinum complex in which such a complex ion is an anion. As a preferred example of such a platinum complex, chloroplatinic acid (typically its hexahydrate; H 2 [PtCl 6 ] · 6H 2 O) can be preferably used. Hereinafter, the case where H 2 [PtCl 6 ] is used as the Pt source will be described as an example.
Ｈ２［ＰｔＣｌ６］水溶液（以下、単に「Ｐｔ水溶液」ということもある。）を調製する。かかるＰｔ水溶液の濃度としては、該Ｐｔ水溶液中のＰｔ錯イオンが後述のポリペプチドと効率よく反応し得る量で存在する程度の濃度であることが好ましい。例えばＰｔイオン（すなわち［ＰｔＣｌ６］２−）が凡そ２．５ｍＭ〜２６０ｍＭ（より好ましくは凡そ５０ｍＭ〜１６０ｍＭ、例えば凡そ１００ｍＭ±３０ｍＭ）となるように調製されることが好ましい。あるいは、Ｈ２［ＰｔＣｌ６］水溶液中のＰｔの含有率が凡そ０．０５質量％〜５質量％（より好ましくは凡そ１質量％〜３質量％、例えば凡そ２質量％±０．５質量％）となるように調製されることが好ましい。なお、かかるＨ２［ＰｔＣｌ６］水溶液については、例えば上記濃度範囲よりも１０倍程度高い濃度の水溶液を調製し、その後適宜上記濃度範囲に希釈してから用いてもよい。また、市販されている所定濃度の水溶液を用意し、この水溶液を所望の濃度に希釈してから用いてもよい。 An H 2 [PtCl 6 ] aqueous solution (hereinafter, simply referred to as “Pt aqueous solution”) is prepared. The concentration of the Pt aqueous solution is preferably such a concentration that the Pt complex ions in the Pt aqueous solution are present in an amount capable of efficiently reacting with the polypeptide described below. For example, it is preferable that the Pt ion (ie, [PtCl 6 ] 2− ) is prepared to be about 2.5 mM to 260 mM (more preferably about 50 mM to 160 mM, for example, about 100 mM ± 30 mM). Alternatively, the content of Pt in the H 2 [PtCl 6 ] aqueous solution is about 0.05% by mass to 5% by mass (more preferably about 1% by mass to 3% by mass, for example, about 2% by mass ± 0.5% by mass). It is preferable to prepare so that it may become. As for the H 2 [PtCl 6 ] aqueous solution, for example, an aqueous solution having a concentration about 10 times higher than the above concentration range may be prepared and then diluted to the above concentration range as appropriate. Alternatively, a commercially available aqueous solution having a predetermined concentration may be prepared and used after being diluted to a desired concentration.
次に、上記Ｐｔ水溶液に、アミノ酸を添加する。ここで用いられるアミノ酸としては、水系溶媒に可溶であり、上記Ｐｔ水溶液中で互いにペプチド結合して容易にポリペプチドを形成し得るものが好ましい。このようなアミノ酸として、アラニンが挙げられる。アラニンの光学異性体についてはＤ体であってもＬ体であっても特に限定されず、両異性体が混在するＤＬ−アラニンでもよい。アラニンは、安価で入手できるとともに、構成元素が炭素（Ｃ）、窒素（Ｎ）、および水素（Ｈ）元素のみの単純な構成であり、通常のか焼条件（例えば十分量の酸素雰囲気下で完全燃焼可能な条件）でのか焼であれば有害物質の発生がなく、また生分解可能であることから環境への負荷が小さく好ましい。アラニンは、常温下では固体（粉末状）であるので、粉末状のアラニンを上記Ｐｔ水溶液に添加してもよいし、あるいは所定量の水系溶媒に予めアラニンを溶解しておき、このアラニン水溶液を上記Ｐｔ水溶液に添加してもよく、添加方法に特に制限はない。 Next, an amino acid is added to the Pt aqueous solution. The amino acid used here is preferably an amino acid that is soluble in an aqueous solvent and can easily form a polypeptide by peptide bonding to each other in the aqueous Pt solution. Examples of such amino acids include alanine. The optical isomer of alanine is not particularly limited as it is a D-form or an L-form, and DL-alanine in which both isomers are mixed may be used. Alanine is available at a low cost and has a simple structure with only carbon (C), nitrogen (N), and hydrogen (H) elements as constituent elements, and can be used under normal calcination conditions (for example, under a sufficient amount of oxygen atmosphere). The calcination under the combustible condition) is preferable because it generates no harmful substances and can be biodegraded, so the load on the environment is small. Since alanine is solid (powder) at room temperature, powdery alanine may be added to the Pt aqueous solution, or alanine is dissolved in a predetermined amount of an aqueous solvent in advance, You may add to the said Pt aqueous solution, and there is no restriction | limiting in particular in the addition method.
上記アミノ酸の添加量については、上記Ｐｔ水溶液におけるＰｔ含有イオン（すなわち［ＰｔＣｌ６］２−）１モルに対して、上記アミノ酸は１モル〜２０モルの割合で添加することが好ましく、より好ましくは１モル〜１５モル、特に好ましくは１モル〜１０モルである。このような割合で上記アミノ酸を添加することにより、適当な長さのポリペプチドが形成され得るとともに、かかるポリペプチドの周囲に触媒体として機能し得る適当量のＰｔが凝集、析出し得るので好ましい。 Regarding the amount of amino acid added, the amino acid is preferably added at a ratio of 1 to 20 moles, more preferably 1 mole relative to 1 mole of Pt-containing ions (that is, [PtCl 6 ] 2− ) in the Pt aqueous solution. 1 to 15 mol, particularly preferably 1 to 10 mol. By adding the amino acid at such a ratio, a polypeptide having an appropriate length can be formed, and an appropriate amount of Pt capable of functioning as a catalyst can be aggregated and precipitated around the polypeptide. .
上記アミノ酸を上記のような添加量で上記Ｐｔ水溶液に添加し、上記Ｐｔ含有イオン［ＰｔＣｌ６］２−とアミノ酸との混合水溶液を調製する。ここで、上記アミノ酸を添加する際には、室温（典型的には常温とされる温度領域をいい、２０℃±１５℃を指すものとする。）下で上記Ｐｔ水溶液を攪拌しながら実施するのが好ましい。攪拌速度としては、添加したアミノ酸が十分にＰｔ水溶液中に拡散して十分に溶解することができる限りにおいて特に制限されないが、例えば１００ｒｐｍ〜１０００ｒｐｍが適当であり、好ましくは３００ｒｐｍ〜８００ｒｐｍであり、例えば５００ｒｐｍ±１００ｒｐｍである。 The amino acid is added to the Pt aqueous solution in the above-described addition amount to prepare a mixed aqueous solution of the Pt-containing ion [PtCl 6 ] 2− and the amino acid. Here, when the amino acid is added, it is carried out while stirring the Pt aqueous solution at room temperature (typically a temperature range that is normal temperature, which indicates 20 ° C. ± 15 ° C.). Is preferred. The stirring speed is not particularly limited as long as the added amino acid can be sufficiently diffused and sufficiently dissolved in the Pt aqueous solution. For example, 100 rpm to 1000 rpm is suitable, and preferably 300 rpm to 800 rpm. 500 rpm ± 100 rpm.
また、上記Ｐｔ水溶液に上記アミノ酸を添加して混合水溶液を調製した後、例えば１時間〜１００時間（より好ましくは５０時間〜８０時間、例えば７０時間±５時間））程度の間、上記混合水溶液の攪拌を持続させることが好ましい。このように十分な攪拌を行った後は、上記混合水溶液を例えば９０時間〜１００時間の間で静置しておくことが好ましい。このような処理により、上記アミノ酸は互いにペプチド結合をしてポリペプチドを構成し、かかるポリペプチドに上記Ｐｔ含有イオン［ＰｔＣｌ６］２−が結合（例えば、かかるポリペプチドの末端基におけるアミノ酸のアミノ基との結合および／または上記ポリペプチドの側鎖との水素結合）し得る。この結果、上記Ｐｔ含有イオンは、かかるポリペプチドのポリペプチド鎖の周囲（該ポリペプチドが折りたたまれて立体構造を構成している場合には該立体構造の内部空間を含む）に存在することとなる。 Further, after preparing the mixed aqueous solution by adding the amino acid to the Pt aqueous solution, the mixed aqueous solution is for about 1 hour to 100 hours (more preferably 50 hours to 80 hours, for example 70 hours ± 5 hours), for example. It is preferable to continue the stirring of. After sufficiently stirring as described above, the mixed aqueous solution is preferably allowed to stand for 90 hours to 100 hours, for example. By such treatment, the amino acids form peptide bonds with each other to form a polypeptide, and the Pt-containing ion [PtCl 6 ] 2− is bound to the polypeptide (for example, the amino acid amino acid at the terminal group of the polypeptide). Group and / or hydrogen bond to the side chain of the polypeptide). As a result, the Pt-containing ions are present around the polypeptide chain of such a polypeptide (including the internal space of the three-dimensional structure when the polypeptide is folded to form a three-dimensional structure). Become.
次に、上記混合水溶液に還元剤を添加する。還元剤としては、金属水素化物を好適に用いることができる。より好ましくは、水素化ホウ素化合物または水素化アルミニウム化合物であり、例えば水素化ホウ素ナトリウム（ＮａＢＨ４）、水素化ジイソブチルアルミニウム（ＤＩＢＡＨまたはＤＩＢＡＬ‐Ｈと呼ばれる。）、あるいは水素化アルミニウムリチウム（ＬｉＡｌＨ４）が挙げられる。特に好ましくはＮａＢＨ４である。かかる還元剤の添加量としては、上記Ｐｔ水溶液におけるＰｔ含有イオン（すなわち［ＰｔＣｌ６］２−）１モルに対して、該還元剤が０．５モル〜２モル程度（例えば１モル±０．２モル）で添加されることが好ましい。かかる添加量が０．５モルよりも低い場合には、金属Ｐｔ微粒子の生成に長時間を要する虞がある。また、上記添加量が２モルより大幅に高い場合には、金属Ｐｔ微粒子が生成される還元反応以外に別の副反応が起こり得る虞がある。
また、かかる還元剤は、好ましくは水系溶媒に溶解して水溶液として上記混合水溶液に添加される。このような還元剤の水溶液は、一定の滴下速度（例えば凡そ２ｍＬ／分）で上記混合水溶液に添加（滴下）されることが好ましい。また、かかる滴下の際には、上記還元剤が良好に拡散し、上記混合水溶液中のＰｔ含有イオンと該還元剤とが良好に反応し得るように、所定の攪拌速度（例えば５０ｒｐｍ〜２５０ｒｐｍ）で上記混合水溶液を攪拌することが好ましい。このように還元剤水溶液を滴下していくと、徐々に上記混合水溶液の液色（黄金色）が消えていき、黒色の析出物が観察される。上記還元反応終了後、上記還元剤添加後の混合水溶液を１時間〜５時間（例えば３時間±１時間）程度静置することにより上記黒色析出物を完全に沈殿させる。例えば、少なくとも３週間〜１か月程度の長期にわたり上記混合水溶液を静置しておいても、上記析出物は安定的に存在し得る。以上のようにして、金属Ｐｔ微粒子を含む上記黒色析出物を、沈殿物として得ることができる。
沈殿物として得られた上記黒色析出物は、従来の沈殿物の取出し方法と同様の方法を用いることにより取り出すことができる。例えば、上記沈殿物を純水等で複数回（例えば３回〜６回）洗浄して副生成物その他塩類を除去した後に、残った残渣を乾燥する。このような工程を経て精製された金属Ｐｔ微粒子を含む析出物をここで開示されるＰｔ材料として得ることができる。
Next, a reducing agent is added to the mixed aqueous solution. As the reducing agent, a metal hydride can be suitably used. More preferably, it is a borohydride compound or an aluminum hydride compound, such as sodium borohydride (NaBH 4 ), diisobutylaluminum hydride (referred to as DIBAH or DIBAL-H), or lithium aluminum hydride (LiAlH 4 ). Is mentioned. And particularly preferably NaBH 4. The amount of the reducing agent to be added is about 0.5 to 2 moles (for example, 1 mole ± 0.0.1) with respect to 1 mole of Pt-containing ions (that is, [PtCl 6 ] 2− ) in the Pt aqueous solution. 2 mol) is preferably added. When the added amount is lower than 0.5 mol, it may take a long time to form the metal Pt fine particles. Moreover, when the said addition amount is significantly higher than 2 mol, there exists a possibility that another side reaction may occur besides the reductive reaction in which metal Pt microparticles | fine-particles are produced | generated.
The reducing agent is preferably dissolved in an aqueous solvent and added as an aqueous solution to the mixed aqueous solution. Such an aqueous solution of a reducing agent is preferably added (dropped) to the mixed aqueous solution at a constant dropping rate (for example, approximately 2 mL / min). Further, at the time of such dripping, a predetermined stirring speed (for example, 50 rpm to 250 rpm) is used so that the reducing agent diffuses well and the Pt-containing ions in the mixed aqueous solution can react well with the reducing agent. It is preferable to stir the mixed aqueous solution. When the reducing agent aqueous solution is dropped in this manner, the liquid color (golden color) of the mixed aqueous solution gradually disappears, and a black precipitate is observed. After completion of the reduction reaction, the black precipitate is completely precipitated by allowing the mixed aqueous solution after addition of the reducing agent to stand for about 1 hour to 5 hours (for example, 3 hours ± 1 hour). For example, even if the mixed aqueous solution is allowed to stand for a long period of at least about 3 weeks to about 1 month, the precipitate can exist stably. As described above, the black precipitate containing metal Pt fine particles can be obtained as a precipitate.
The black precipitate obtained as a precipitate can be taken out by using a method similar to the conventional method for taking out a precipitate. For example, the precipitate is washed several times (for example, 3 to 6 times) with pure water to remove by-products and other salts, and then the remaining residue is dried. A precipitate containing metal Pt fine particles refined through such steps can be obtained as the Pt material disclosed herein.
また、上記のようにして得られた金属Ｐｔ微粒子を含む析出物をか焼することにより、触媒体として用いられ得るより一層好適な形状を有するＰｔ材料を製造することができる。すなわち、上記析出物を一般的な焼成炉を用いて３００℃〜５００℃（好ましくは３５０℃〜４５０℃、例えば４００℃±１０℃）の焼成温度でか焼する。ここで、昇温速度および降温速度条件については特に制限されないが、例えば、６０℃／時間で上記最高温度（例えば４００℃）まで昇温し、該最高温度を凡そ３時間維持した後、放冷すればよい。か焼時間（上記最高温度を維持する時間）は上記析出物の量によって適宜変えればよいが、例えば２．５ｇ程度の析出物であれば３時間±１時間程度が適当である。 Further, by calcining the precipitate containing the metal Pt fine particles obtained as described above, a Pt material having a more suitable shape that can be used as a catalyst body can be produced. That is, the precipitate is calcined at a firing temperature of 300 ° C. to 500 ° C. (preferably 350 ° C. to 450 ° C., for example, 400 ° C. ± 10 ° C.) using a general firing furnace. Here, the temperature increase rate and temperature decrease rate conditions are not particularly limited. For example, the temperature is increased to 60 ° C./hour up to the maximum temperature (for example, 400 ° C.), and the maximum temperature is maintained for about 3 hours. do it. The calcination time (the time for maintaining the maximum temperature) may be appropriately changed depending on the amount of the precipitate. For example, if the precipitate is about 2.5 g, about 3 hours ± 1 hour is appropriate.
このようにして得られたか焼後の上記析出物（すなわちか焼後のＰｔ材料）は、ＳＥＭ観察に基づく顕微鏡像によると、金属Ｐｔ微粒子から構成されており、かかる金属Ｐｔ微粒子は、上記ポリペプチドを鋳型とするような繊維状（糸状）に細長い形状を有し、またかかる糸状部分を微視的にみると海綿状に孔が形成された多孔質構造をなした二次粒子（集合体または凝集体）の形態で上記Ｐｔ材料を構成し得る。また、凡そ１０ｎｍ以下の粒子径（シェラー（Ｓｃｈｅｒｒｅｒ）の式に基づくＸ線回折ピークの線幅から算出される粒子径）を有し得る金属Ｐｔ微粒子からなる上記Ｐｔ材料を得ることができる。なお、このような形態のＰｔ材料には、上記Ｐｔ微粒子とともに一部上記ポリペプチドが含まれて（残存して）いてもよい。 According to a microscopic image based on SEM observation, the precipitate after calcination obtained in this way (that is, the Pt material after calcination) is composed of metal Pt fine particles. Secondary particles (aggregate) having a porous structure with a fiber-like (thread-like) shape that uses peptide as a template, and when the thread-like part is microscopically formed with spongy pores Alternatively, the Pt material can be configured in the form of an aggregate. In addition, the Pt material can be obtained which is composed of metal Pt fine particles that can have a particle size of about 10 nm or less (particle size calculated from the line width of the X-ray diffraction peak based on the Scherrer equation). The Pt material in such a form may partially contain (remain) the polypeptide together with the Pt fine particles.
以下、本発明に関する実施例を図１〜図９を参照して説明するが、本発明を以下の実施例に示すものに限定することを意図したものではない。ここで、図１は以下に示す実施例の例２におけるサンプル１の走査型電子顕微鏡（ＳＥＭ）写真である。図２は、以下の実施例の例２におけるサンプル１のＳＥＭ写真である。図３は、以下の実施例の例４におけるサンプル１１のＳＥＭ写真である。図４は、以下の実施例の例４におけるサンプル１１の異なるＳＥＭ写真である。図５は、以下の実施例の例４におけるサンプル１１のＳＥＭ写真である。図６は、以下の実施例の例５におけるサンプル１〜３のＸ線回折（ＸＲＤ）スペクトルである。図７は、以下の実施例の例５におけるサンプル１１〜１３のＸ線回折（ＸＲＤ）スペクトルである。図８は、以下の実施例の例６におけるサンプル４の走査型電子顕微鏡（ＳＥＭ）写真である。図９は、以下の実施例の例６におけるサンプル４の異なる走査型電子顕微鏡（ＳＥＭ）写真である。 Embodiments relating to the present invention will be described below with reference to FIGS. 1 to 9, but the present invention is not intended to be limited to those shown in the following embodiments. Here, FIG. 1 is a scanning electron microscope (SEM) photograph of sample 1 in Example 2 of the embodiment shown below. FIG. 2 is an SEM photograph of Sample 1 in Example 2 of the following example. FIG. 3 is an SEM photograph of sample 11 in Example 4 of the following example. FIG. 4 is a different SEM photograph of sample 11 in Example 4 of the following example. FIG. 5 is an SEM photograph of sample 11 in Example 4 of the following example. FIG. 6 is an X-ray diffraction (XRD) spectrum of Samples 1 to 3 in Example 5 of the following example. FIG. 7 is an X-ray diffraction (XRD) spectrum of Samples 11 to 13 in Example 5 of the following example. FIG. 8 is a scanning electron microscope (SEM) photograph of Sample 4 in Example 6 of the following example. FIG. 9 shows different scanning electron microscope (SEM) photographs of sample 4 in Example 6 of the following example.
＜例１：か焼前のＰｔ材料の作製＞
以下のような手順でか焼前のＰｔ材料を作製した。
まず、Ｐｔ源として、塩化白金酸（Ｈ２［ＰｔＣｌ６］）（ノリタケ機材株式会社製品）を用意し、所定量を純水に溶解させることにより、濃度０．１ＭのＨ２［ＰｔＣｌ６］水溶液を１００ｍＬ調製した。
次に、アミノ酸として、市販（Ａｃｒｏｓ Ｏｒｇａｎｉｃｓ株式会社製）のＤＬ−アラニン（純度９９％）を用意した。このアラニンを０．０１モル分（０．８９ｇ）量り取り、これを上記Ｈ２［ＰｔＣｌ６］水溶液を攪拌しながら該水溶液に添加した。
次いで、室温条件下で、上記Ｈ２［ＰｔＣｌ６］とアラニンの混合水溶液を５００ｒｐｍの攪拌速度で７２時間攪拌した。
<Example 1: Preparation of Pt material before calcination>
A Pt material before calcination was prepared by the following procedure.
First, as a Pt source, chloroplatinic acid (H 2 [PtCl 6 ]) (manufactured by Noritake Equipment Co., Ltd.) is prepared, and a predetermined amount is dissolved in pure water, whereby a concentration of 0.1 M H 2 [PtCl 6 ] is obtained. 100 mL of an aqueous solution was prepared.
Next, commercially available (Acros Organics Co., Ltd.) DL-alanine (99% purity) was prepared as an amino acid. The alanine was weighed out in 0.01 mol (0.89 g), and this was added to the aqueous solution while stirring the H 2 [PtCl 6 ] aqueous solution.
Subsequently, the mixed aqueous solution of H 2 [PtCl 6 ] and alanine was stirred at a stirring speed of 500 rpm for 72 hours under room temperature conditions.
次いで、還元剤として、市販（アジア パシフィック スペシャルティ ケミカルズ株式会社製）の水素化ホウ素ナトリウム（ＮａＢＨ４）を用意し、１１２ｍＭのＮａＢＨ４水溶液を調製した。このＮａＢＨ４水溶液９０ｍＬを、滴下速度２ｍＬ／分で上記混合水溶液に所定量滴下した。このとき、上記混合水溶液を攪拌速度１００ｒｐｍ程度で攪拌させながら上記滴下を行った。かかる滴下により、混合水溶液の液色は黄金色が消失するとともに、黒色の析出物が生じた。その後、上記混合水溶液を３時間放置して、上記黒色析出物を沈殿させた。
沈殿した上記黒色析出物を純水で数回洗浄して精製した。このようにして、ＰｔとアラニンとＮａＢＨ４の配合比が１：１：１である「か焼前のＰｔ材料」を得た。これをサンプル１とする。
上記Ｈ２［ＰｔＣｌ６］水溶液に対して、アミノ酸と還元剤の添加量が異なる以外は、上記手順と同様にして、ＰｔとアラニンとＮａＢＨ４の配合比が１：１０：１であるか焼前のＰｔ材料（サンプル２）、およびＰｔとアラニンとＮａＢＨ４の配合比が１：５：１であるか焼前のＰｔ材料（サンプル３）を作製した。
Subsequently, commercially available sodium borohydride (NaBH 4 ) (manufactured by Asia Pacific Specialty Chemicals Co., Ltd.) was prepared as a reducing agent, and a 112 mM NaBH 4 aqueous solution was prepared. A predetermined amount of 90 mL of this NaBH 4 aqueous solution was dropped into the mixed aqueous solution at a dropping rate of 2 mL / min. At this time, the dropping was performed while stirring the mixed aqueous solution at a stirring speed of about 100 rpm. By such dripping, the liquid color of the mixed aqueous solution disappeared from the golden color, and a black precipitate was generated. Thereafter, the mixed aqueous solution was allowed to stand for 3 hours to precipitate the black precipitate.
The black precipitate thus precipitated was purified by washing several times with pure water. In this way, a “Pt material before calcination” in which the blending ratio of Pt, alanine and NaBH 4 was 1: 1: 1 was obtained. This is designated as sample 1.
Calcination in which the blending ratio of Pt, alanine and NaBH 4 is 1: 10: 1 in the same manner as in the above procedure except that the addition amounts of amino acid and reducing agent are different from the aqueous H 2 [PtCl 6 ] solution. The previous Pt material (sample 2) and the Pt material before calcination (sample 3) in which the blending ratio of Pt, alanine and NaBH 4 was 1: 5: 1 were prepared.
＜例２：サンプル１および２のＳＥＭ観察＞
上記サンプル１に対して、走査型電子顕微鏡（ＳＥＭ）の観察を実施した。この観察結果を図１および図２に示した。図１および図２に示されるように、サンプル１では、凹凸のある塊状、および繊維状のポリペプチド（図面における暗く写っている部分）の表面にＰｔ微粒子（図面における白く写っている部分）が凝集して付着していることが確認された。なお、このＳＥＭ観察に基づくＥＤＸによる元素分析を行ったところ、図１および図２において暗く写っている部分からは炭素（Ｃ）が主に検出されるとともに、白く写っている部分からはＰｔが検出されていた。
<Example 2: SEM observation of samples 1 and 2>
The sample 1 was observed with a scanning electron microscope (SEM). The observation results are shown in FIG. 1 and FIG. As shown in FIG. 1 and FIG. 2, in sample 1, Pt fine particles (portion shown in white in the drawing) are formed on the surface of the concavo-convex lump and fibrous polypeptide (portion shown in dark in the drawing). Aggregation and adhesion were confirmed. In addition, when elemental analysis by EDX based on this SEM observation was performed, carbon (C) was mainly detected from the dark portion in FIGS. 1 and 2, and Pt was detected from the white portion. It was detected.
＜例３：か焼後のＰｔ材料の作製＞
か焼前のＰｔ材料であるサンプル１を、焼成炉に入れ、６０℃／時間で４００℃まで昇温し、この温度を凡そ３時間維持した後、放冷した。このようにして上記サンプル１をか焼することにより「か焼後のＰｔ材料」を作製した。この触媒体をサンプル１１とした。上記サンプル２およびサンプル３についても、上記と同様にそれぞれか焼し、か焼後のＰｔ材料であるサンプル１２およびサンプル１３を得た。
<Example 3: Production of Pt material after calcination>
Sample 1 which is Pt material before calcination was placed in a firing furnace, heated to 400 ° C. at 60 ° C./hour, maintained at this temperature for about 3 hours, and then allowed to cool. The sample 1 was calcined in this manner to produce a “calcined Pt material”. This catalyst body was designated as Sample 11. Sample 2 and sample 3 were also calcined in the same manner as above to obtain sample 12 and sample 13 which were Pt materials after calcination.
＜例４：サンプル１１のＳＥＭ観察＞
上記サンプル１１に対して、ＳＥＭの観察を実施した。この観察結果を図３〜図５に示した。図３〜図５に示されるように、サンプル１１では、金属Ｐｔ微粒子が凝集して繊維状（糸状）に細長い形状をなしており、かかる糸状部分を微視的にみると海綿状に孔が形成された多孔質構造を形成していることが分かった。なお、このＳＥＭ観察に基づくＥＤＸによる元素分析の結果、Ｃが一部検出されており、上記アラニンからなるポリペプチドが若干残存し得ることがわかった。
<Example 4: SEM observation of sample 11>
The sample 11 was observed by SEM. The observation results are shown in FIGS. As shown in FIGS. 3 to 5, in the sample 11, the metal Pt fine particles are aggregated to form a fibrous (thread-like) elongated shape, and when the thread-like portion is viewed microscopically, pores are formed in a spongy shape. It was found that the formed porous structure was formed. In addition, as a result of elemental analysis by EDX based on this SEM observation, a part of C was detected, and it was found that the alanine polypeptide could remain a little.
＜例５：サンプル１〜３およびサンプル１１〜１３のＸＲＤ測定＞
上記例１および例３においてそれぞれ得られたサンプル１〜３（か焼前のＰｔ材料）およびサンプル１１〜１３（か焼後のＰｔ材料）のＸ線回折（ＸＲＤ）測定を実施した。サンプル１〜３の各ＸＲＤスペクトルを図６に、サンプル１１〜１３の各ＸＲＤスペクトルを図７に示した。なお、図６および図７の横軸は２θ、縦軸はピーク強度（任意単位）を示している。この結果、図６に示されるように、サンプル１〜３の全てからＰｔに由来するピーク（すなわち、Ｐｔ（１１１），（２００），（２２０）および（３１１）に帰属するピーク）が検出され、金属Ｐｔが存在していることが確認された。また、このＸＲＤピークの線幅からシェラー（Ｓｃｈｅｒｒｅｒ）の式に基づいてかかる金属Ｐｔの粒子径を算出したところ、約１０ｎｍ以下であることがわかった。
<Example 5: XRD measurement of samples 1 to 3 and samples 11 to 13>
X-ray diffraction (XRD) measurements of Samples 1 to 3 (Pt material before calcination) and Samples 11 to 13 (Pt material after calcination) obtained in Example 1 and Example 3 were performed. The XRD spectra of Samples 1 to 3 are shown in FIG. 6, and the XRD spectra of Samples 11 to 13 are shown in FIG. 6 and 7, the horizontal axis represents 2θ, and the vertical axis represents peak intensity (arbitrary unit). As a result, as shown in FIG. 6, peaks derived from Pt (that is, peaks attributed to Pt (111), (200), (220), and (311)) are detected from all of samples 1 to 3. It was confirmed that metal Pt was present. Further, when the particle diameter of the metal Pt was calculated based on the Scherrer equation from the line width of the XRD peak, it was found to be about 10 nm or less.
一方、サンプル１１〜１３についても、図７に示されるように、金属Ｐｔ微粒子が存在していることが確認された。ここで、図７に示される２本のピーク（すなわちＰｔ（１１１）および（２００）に帰属するピーク）の線幅が上記図６に示されるピークの線幅よりも小さくなっていた。このことにより、サンプル１１〜１３に係る金属Ｐｔ微粒子は焼結はしてないが、該微粒子の粒子径はサンプル１〜３に係る金属Ｐｔ微粒子の粒子径に比べて若干増大していることがわかった。 On the other hand, it was confirmed that Samples 11 to 13 also had metal Pt fine particles as shown in FIG. Here, the line width of the two peaks shown in FIG. 7 (that is, the peak attributed to Pt (111) and (200)) was smaller than the line width of the peak shown in FIG. Thus, the metal Pt fine particles according to Samples 11 to 13 are not sintered, but the particle diameter of the fine particles is slightly increased as compared with the particle diameters of the metal Pt fine particles according to Samples 1 to 3. all right.
＜例６：Ｐｔ材料の安定性評価＞
次に、上記例１におけるＰｔ材料の作製手順において、黒色析出物が沈殿した混合水溶液を静置する時間を３時間から２３日間に変更する以外は例１と同様にして、ＰｔとアラニンとＮａＢＨ４の配合比が１：１０：１であるか焼前のＰｔ材料（サンプル４）を作製した。このようにして得られたサンプル４のＳＥＭ観察を実施した。その結果を図８および図９に示した。図８および図９に示されるように、Ｐｔ微粒子はアラニンからなる細長い繊維状のポリペプチドの表面をコーティングするように付着していた。このことにより、上記混合水溶液を２０日以上の長期にわたり静置しておいても、Ｐｔ微粒子が安定的にポリペプチドに凝集、付着したＰｔ材料を好ましく得られることが確認された。
<Example 6: Stability evaluation of Pt material>
Next, in the procedure for preparing the Pt material in Example 1 above, Pt, alanine, and NaBH were performed in the same manner as in Example 1 except that the time for standing the mixed aqueous solution in which the black precipitates were settled was changed from 3 hours to 23 days. A pre-calcination Pt material (Sample 4) having a mixing ratio of 4 of 1: 10: 1 was prepared. SEM observation of the sample 4 thus obtained was performed. The results are shown in FIG. 8 and FIG. As shown in FIG. 8 and FIG. 9, the Pt microparticles were attached so as to coat the surface of an elongated fibrous polypeptide composed of alanine. Thus, it was confirmed that a Pt material in which Pt fine particles stably aggregate and adhere to a polypeptide can be preferably obtained even when the mixed aqueous solution is allowed to stand for a long period of 20 days or longer.
上述のように、本実施例によると、Ｐｔ源としてのＨ２［ＰｔＣｌ６］水溶液に対して、アミノ酸としてアラニン、および還元剤としてＮａＢＨ４を添加することにより、金属Ｐｔ微粒子をポリペプチドの周囲に凝集、析出した（ポリペプチドの表面に付着した）状態で容易に得ることができた。またこのような金属Ｐｔ微粒子を４００℃でか焼することにより、上記ポリペプチドを鋳型とした繊維状のような形状で、微視的には海綿状に孔が形成された多孔質構造の金属ナノ粒子からなる金属Ｐｔ材料を作製することができた。このようにして得られた金属Ｐｔ材料は、上記のような触媒機能が高い高機能性構造を備えていることから、触媒活性が高い優れた触媒体として種々の工業分野で利用され得るものである。
As described above, according to this example, by adding alanine as an amino acid and NaBH 4 as a reducing agent to an aqueous solution of H 2 [PtCl 6 ] as a Pt source, the metal Pt fine particles are surrounded by a polypeptide. It was easily obtained in the state of being aggregated and precipitated (attached to the surface of the polypeptide). Further, by calcining such metal Pt fine particles at 400 ° C., a metal having a porous structure in which pores are microscopically formed in a fibrous shape using the polypeptide as a template. A metal Pt material composed of nanoparticles could be produced. Since the metal Pt material thus obtained has a high-functional structure having a high catalytic function as described above, it can be used in various industrial fields as an excellent catalyst body having a high catalytic activity. is there.
Claims (6)
触媒として機能し得る金属元素を含むイオンを含有する水溶液を用意すること、
前記用意した水溶液に、所定の種類のアミノ酸を添加すること、
前記水溶液に還元剤を添加すること、および
前記水溶液中に前記金属元素の微粒子を含む析出物を生じさせること、
を包含する、金属材料の製造方法。 A method for producing a metal material, comprising:
Preparing an aqueous solution containing ions containing a metal element that can function as a catalyst;
Adding a predetermined type of amino acid to the prepared aqueous solution;
Adding a reducing agent to the aqueous solution, and generating a precipitate containing fine particles of the metal element in the aqueous solution,
A method for producing a metal material, comprising:
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| KR101736578B1 (en) | 2015-06-15 | 2017-05-17 | 부산대학교 산학협력단 | Nano particle for a reduction catalyst, method of manufacturing the nano particle, and method of reducing a compound using the nano particle |
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