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JP2011038158A - Metallic fine particle and method for producing the same - Google Patents

Metallic fine particle and method for producing the same Download PDF

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Publication number
JP2011038158A
JP2011038158A JP2009187350A JP2009187350A JP2011038158A JP 2011038158 A JP2011038158 A JP 2011038158A JP 2009187350 A JP2009187350 A JP 2009187350A JP 2009187350 A JP2009187350 A JP 2009187350A JP 2011038158 A JP2011038158 A JP 2011038158A
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metal
fine particles
metal fine
metal ions
metallic fine
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Takehisa Yamaguchi
猛央 山口
Kakade Bhalchandra
バラチャンドラ カカデ
Hideo Ohashi
秀伯 大橋
Hirobumi Konno
博文 紺野
Yoshihiro Kobori
良浩 小堀
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Tokyo Institute of Technology NUC
Japan Petroleum Energy Center JPEC
Eneos Corp
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Petroleum Energy Center PEC
Tokyo Institute of Technology NUC
JX Nippon Oil and Energy Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing metallic fine particles, in a reaction system where, in a liquid phase comprising metal ions or a metal salt to be the precursor thereof, the metal ions are reduced so as to produce metallic fine particles, the particle structure of the metallic fine particles can be sufficiently controlled, and also, the yield of the metallic fine particles can be improved, and to provide metallic fine particles obtained by the production method. <P>SOLUTION: In a solution comprising metal ions or a metal salt giving the metal ions, polyvinylpyrrolidone and an organic solvent having an amide group, the metal ions are reduced to precipitate metallic fine particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、燃料電池触媒等に好適に利用することができる金属微粒子の製造方法に関する。   The present invention relates to a method for producing metal fine particles that can be suitably used for a fuel cell catalyst or the like.

金属微粒子、特に貴金属微粒子は、燃料電池触媒や廃ガス浄化触媒、または種々の有機合成反応用触媒への適用において良好な性能を有することから、産業上有用な材料として期待されている。   Metal fine particles, particularly noble metal fine particles, are expected as industrially useful materials because they have good performance in application to fuel cell catalysts, waste gas purification catalysts, or various organic synthesis reaction catalysts.

金属の触媒作用はその表面において起こるため、触媒性能を維持しつつ金属使用量を削減する観点からは、金属の粒径を小さくし、同一金属量あたりの外表面積の割合を増やすことが有効である。   Since metal catalysis occurs on the surface, it is effective to reduce the metal particle size and increase the ratio of the outer surface area per the same metal amount from the viewpoint of reducing the metal usage while maintaining the catalyst performance. is there.

また、触媒の性能は粒子の構造によっても変化する。例えば、(111)面は原子の密度が他の面に比べて高いことや、電子状態が種々の反応に優れていることから、高い反応性を有していることが知られている(一例として、パラジウムのアルキンの水素付加反応がある。)。(非特許文献1等参照)。   The performance of the catalyst also varies depending on the particle structure. For example, the (111) plane is known to have high reactivity because the density of atoms is higher than other planes and the electronic state is excellent in various reactions (an example) As a hydrogenation reaction of palladium alkynes). (Refer nonpatent literature 1 grade | etc.,).

また、貴金属元素は、地球上に存在する量が限られており、その生産国が偏在していることから、その使用量を極力減らすことが求められている。上記のような微粒子化および粒子の構造制御は、貴金属の使用量を削減する技術としても有意義である。   Further, since the amount of noble metal elements existing on the earth is limited and the producing countries are unevenly distributed, it is required to reduce the amount of use as much as possible. Fine particle formation and particle structure control as described above are also significant as a technique for reducing the amount of noble metal used.

金属微粒子の製造法は、気相合成法と液相合成法の2つに大別される。気相合成法とは、気相中に導入した金属蒸気から固体の金属微粒子を生成させる方法である。一方、液相合成法とは溶液中に存在する金属イオンを還元することにより金属微粒子を生成させる方法である。   The method for producing metal fine particles is roughly divided into a gas phase synthesis method and a liquid phase synthesis method. The gas phase synthesis method is a method of generating solid metal fine particles from metal vapor introduced into the gas phase. On the other hand, the liquid phase synthesis method is a method of generating metal fine particles by reducing metal ions present in a solution.

従来、液相合成法において、粒子構造を制御する技術に関して種々検討が行われており、多くの場合、金属粒子の成長に制約を与える目的で、種々の高分子、DNA、RNAといった化合物を反応系に添加する方法が用いられている。特に、水溶液中に前駆体金属イオンが存在した系に対して、ポリビニルピロリドン(PVP)を添加する方法が、粒子構造の制御の面において有効であることが報告されている(非特許文献2〜4参照。)。   Conventionally, in liquid phase synthesis methods, various studies have been conducted on techniques for controlling the particle structure, and in many cases, various polymers, DNA, RNA and other compounds are reacted for the purpose of limiting the growth of metal particles. A method of adding to the system is used. In particular, it has been reported that a method of adding polyvinylpyrrolidone (PVP) to a system in which precursor metal ions are present in an aqueous solution is effective in terms of controlling the particle structure (Non-Patent Documents 2 to 2). 4).

Catal. Lett. 127(2009)334頁Catal. Lett. 127 (2009) 334 J.Am.Chem.Soc. 127(2005)17118項J. et al. Am. Chem. Soc. 127 (2005) 17118 Adv.Mater.19(2007)3385項Adv. Mater. 19 (2007) 3385 Langmuir 22(2006)8563項Langmuir 22 (2006) 8563

上記の非特許文献4には、反応系において、PVPが金属粒子の成長を制約するだけでなく、PVP末端のヒドロキシル基が還元剤として機能していると報告されている。このことから、当該反応系においては、PVPがマイルドな速度で反応速度を緩やかに抑えることにより、金属微粒子の粒子構造の制御がなされていると考えられる。   Non-Patent Document 4 reports that, in the reaction system, PVP not only restricts the growth of metal particles, but also the hydroxyl group at the end of PVP functions as a reducing agent. From this, it is considered that in the reaction system, the particle structure of the metal fine particles is controlled by moderately suppressing the reaction rate of PVP at a mild rate.

しかし、このような反応系においては、生成する金属微粒子の粒子構造を制御すると、金属微粒子の収率が不十分となるという問題がある。   However, in such a reaction system, there is a problem that the yield of the metal fine particles becomes insufficient when the particle structure of the generated metal fine particles is controlled.

そこで本発明は、金属イオンまたはその前駆体となる金属塩を含有する液相中で金属イオンを還元することで金属微粒子を製造する反応系において、金属微粒子の粒子構造を十分に制御し、且つ、金属微粒子の収率を向上させることが可能な金属微粒子の製造方法、並びに該製造方法によって得られる金属微粒子を提供することを目的とする。   Therefore, the present invention sufficiently controls the particle structure of metal fine particles in a reaction system for producing metal fine particles by reducing metal ions in a liquid phase containing metal ions or a metal salt serving as a precursor thereof, and An object of the present invention is to provide a method for producing metal fine particles capable of improving the yield of metal fine particles, and metal fine particles obtained by the production method.

上記課題を解決するために、本発明は、金属イオンまたは該金属イオンを与える金属塩と、ポリビニルピロリドン(PVP)と、アミド基を有する有機溶媒と、を含有する溶液中で、上記金属イオンを還元して金属微粒子を析出させることを特徴とする金属微粒子の製造方法を提供する。   In order to solve the above-described problems, the present invention provides a metal ion or a metal salt that provides the metal ion, polyvinylpyrrolidone (PVP), and an organic solvent having an amide group in a solution containing the metal ion. Provided is a method for producing metal fine particles, characterized in that metal fine particles are precipitated by reduction.

上記製造方法によれば、PVPとアミド基を有する有機溶媒とを併用することで、PVPの金属微粒子の粒子構造の制御機能と、アミド基を有する有機溶媒の還元剤としての機能が相俟って、金属微粒子の粒子構造を十分に制御しつつ、金属微粒子の収率を向上させることが可能となる。このようにして得られる金属微粒子は、十分に微細化されたものであり、また、通常、その粒子構造が(111)面を多く有する構造に制御されたものである。   According to the above production method, by using PVP and an organic solvent having an amide group in combination, the function of controlling the particle structure of the metal particles of PVP and the function as a reducing agent of the organic solvent having an amide group are combined. Thus, the yield of the metal fine particles can be improved while sufficiently controlling the particle structure of the metal fine particles. The metal fine particles obtained in this way are sufficiently miniaturized, and usually the particle structure is controlled to a structure having many (111) planes.

上記金属は、パラジウム、白金、ルテニウム、ロジウム、イリジウム、金および銅からなる群より選ばれる少なくとも1種であることが好ましい。   The metal is preferably at least one selected from the group consisting of palladium, platinum, ruthenium, rhodium, iridium, gold and copper.

アミド基を有する化合物は、N−メチルピロリドン、N,N−ジメチルホルムアミドおよびN,N−ジメチルアセトアミドからなる群より選ばれる少なくとも1種であることが好ましい。   The compound having an amide group is preferably at least one selected from the group consisting of N-methylpyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide.

また、本発明は、上記本発明の金属微粒子の製造方法によって製造され、平均1次粒子径が1〜100nmであることを特徴とする金属微粒子を提供する。   The present invention also provides metal fine particles produced by the method for producing metal fine particles of the present invention, wherein the average primary particle size is 1 to 100 nm.

上記金属微粒子は、上記本発明の金属微粒子の製造方法によって製造されるものであるため、(111)面を多く有する構造に制御されたものである。X線回折において、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)が2.5より大きいことが好ましい。   Since the metal fine particles are produced by the method for producing metal fine particles of the present invention, the metal fine particles are controlled to have a structure having many (111) planes. In X-ray diffraction, the ratio I (111) / I (200) of the peak intensity I (111) attributed to the (111) plane to the peak intensity I (200) attributed to the (200) plane is 2. Is preferably greater than .5.

以上の通り、本発明の金属微粒子の製造方法によれば、金属イオンまたはその前駆体となる金属塩を含有する液相中で金属イオンを還元することで金属微粒子を製造する反応系において、金属微粒子の粒子構造を十分に制御し、且つ、金属微粒子の収率を向上させることが可能となる。   As described above, according to the method for producing metal fine particles of the present invention, in a reaction system for producing metal fine particles by reducing metal ions in a liquid phase containing a metal ion or a metal salt serving as a precursor thereof, It becomes possible to sufficiently control the particle structure of the fine particles and improve the yield of the metal fine particles.

また、本発明の金属微粒子は、平均1次粒子径が1〜100nmと十分に微細であり、且つ、(111)面を多く有する構造に制御されたものである。   In addition, the metal fine particles of the present invention are controlled to a structure having an average primary particle diameter of 1 to 100 nm and sufficiently fine and having many (111) planes.

実施例1で得られた金属微粒子のTEM像を示す図である。2 is a diagram showing a TEM image of metal fine particles obtained in Example 1. FIG.

以下、本発明の好適な実施形態について詳細に説明する。   Hereinafter, preferred embodiments of the present invention will be described in detail.

本実施形態に係る金属微粒子の製造方法においては、金属イオンまたは該金属イオンを与える金属塩と、ポリビニルピロリドン(PVP)と、アミド基を有する有機溶媒と、を含有する溶液中で、金属イオンを還元して金属微粒子を析出させる。   In the method for producing metal fine particles according to the present embodiment, metal ions are added in a solution containing metal ions or a metal salt that gives the metal ions, polyvinylpyrrolidone (PVP), and an organic solvent having an amide group. Reduction to deposit metal fine particles.

金属イオン、金属塩および金属微粒子の金属種は、特に限定されるものではないが、パラジウム、白金、ルテニウム、ロジウム、金および銅からなる少なくとも1種以上の金属からなることが好ましく、パラジウムおよび/または白金がより好ましい。   The metal species of the metal ions, metal salts and metal fine particles are not particularly limited, but are preferably composed of at least one metal composed of palladium, platinum, ruthenium, rhodium, gold and copper, and palladium and / Or platinum is more preferable.

金属塩は、いわゆる金属の前駆体である。金属塩としては、所望の金属イオンを与えるものであれば特に限定されないが、当該金属の塩化物、硝酸塩、炭酸塩、酸化物、リン酸塩、ホウ酸塩、スルホン酸塩、硫酸塩など無機酸塩や、酢酸塩などの有機酸塩を好適に用いることができる。   The metal salt is a so-called metal precursor. The metal salt is not particularly limited as long as it gives a desired metal ion, but inorganic such as chloride, nitrate, carbonate, oxide, phosphate, borate, sulfonate, sulfate of the metal. Organic acid salts such as acid salts and acetates can be preferably used.

溶液中の金属イオンまたは金属塩の濃度は、特に限定されるものではないが、0.01〜100mMの範囲にあることが好ましい。当該濃度が0.01mM未満であると、同一量の溶媒に対する生成物の収量が低下する傾向にある。また、当該濃度が100mMを超えると、金属前駆体を均一に溶解させることが困難となる傾向にある。同様の理由から、当該濃度は、0.1〜50mMの範囲にあることがより好ましく、1mM〜20mMの範囲にあることが特に好ましい。   The concentration of the metal ion or metal salt in the solution is not particularly limited, but is preferably in the range of 0.01 to 100 mM. When the concentration is less than 0.01 mM, the yield of the product with respect to the same amount of solvent tends to decrease. Further, when the concentration exceeds 100 mM, it tends to be difficult to uniformly dissolve the metal precursor. For the same reason, the concentration is more preferably in the range of 0.1 to 50 mM, and particularly preferably in the range of 1 mM to 20 mM.

本実施形態において、PVPは、構造規定剤としての役割を担うものであり、還元剤としての機能および金属微粒子の粒子構造の制御機能を有する。PVPの重量平均分子量は、特に限定されるものではないが。平均分子量として、3000〜500000の範囲にあることが好ましい。分子量があまりに小さいと構造制御性が低下し、また分子量があまりに大きいと、粒子径が増大し、また収率が低下してしまうことから、5000〜100000の範囲にあることがより好ましく、8000〜50000の範囲にあることが特に好ましい。   In this embodiment, PVP plays a role as a structure directing agent, and has a function as a reducing agent and a function of controlling the particle structure of metal fine particles. The weight average molecular weight of PVP is not particularly limited. The average molecular weight is preferably in the range of 3000 to 500000. When the molecular weight is too small, the structure controllability is lowered, and when the molecular weight is too large, the particle diameter is increased and the yield is decreased. Therefore, the molecular weight is more preferably in the range of 5000 to 100,000. A range of 50,000 is particularly preferable.

本実施形態におけるPVPの使用量は、特に限定されるものではないが、溶液に含まれる金属(金属イオンまたは金属塩に由来する金属)とのモル比(PVP/金属比)が、0.01〜100の範囲にあることが好ましい。PVP/金属比が0.01未満であると、得られる金属微粒子の粒子径や構造が不均一になる傾向にある。また、PVP/金属比が100を超えると、得られる金属微粒子の収率が低下する傾向にある。同様の理由から、PVP/金属比は、0.1〜50の範囲にあることがより好ましく、0.2〜20の範囲にあることが特に好ましい。なお、ここでいうPVPのモル量は、使用するPVPの質量を数平均分子量で除した値を意味する。   Although the usage-amount of PVP in this embodiment is not specifically limited, The molar ratio (PVP / metal ratio) with the metal (metal derived from a metal ion or a metal salt) contained in a solution is 0.01. It is preferable to be in the range of ~ 100. When the PVP / metal ratio is less than 0.01, the particle diameter and structure of the obtained metal fine particles tend to be non-uniform. On the other hand, when the PVP / metal ratio exceeds 100, the yield of the obtained metal fine particles tends to decrease. For the same reason, the PVP / metal ratio is more preferably in the range of 0.1 to 50, and particularly preferably in the range of 0.2 to 20. In addition, the molar amount of PVP here means the value which remove | divided the mass of PVP to be used by the number average molecular weight.

アミド基を有する有機溶媒は、特に限定されるものではないが、金属イオンまたは金属塩を十分に溶解できるものが好ましい。アミド基を有する有機溶媒は、下記式(1):
−C(=O)−NR (1)
[式(1)中、R、RおよびRは同一でも異なっていてもよく、それぞれ水素原子または有機基を示す。]
で表すことができる。好ましい例として、N−メチルピロリドン、N−メチルアセトアミド、N−メチルホルムアミド、N−メチルプロパンアミド、ホルムアミド、N,N−ジメチルアセトアミド、N,N−ジメチルホルムアミド、アセトアミド、ε−カプロラクタム、またはこれらの2種以上の混合溶媒が挙げられる。さらに、製造条件下で液体であることが作業上望ましいことから、N−メチルピロリドン、N,N−ジメチルホルムアミド、N−メチルアセトアミドがより好ましく、N−メチルピロリドンが特に好ましい。
Although the organic solvent which has an amide group is not specifically limited, What can melt | dissolve a metal ion or a metal salt fully is preferable. The organic solvent having an amide group is represented by the following formula (1):
R 1 —C (═O) —NR 2 R 3 (1)
[In Formula (1), R 1 , R 2 and R 3 may be the same or different and each represents a hydrogen atom or an organic group. ]
Can be expressed as Preferred examples include N-methylpyrrolidone, N-methylacetamide, N-methylformamide, N-methylpropanamide, formamide, N, N-dimethylacetamide, N, N-dimethylformamide, acetamide, ε-caprolactam, or these 2 or more types of mixed solvents are mentioned. Furthermore, N-methylpyrrolidone, N, N-dimethylformamide, and N-methylacetamide are more preferable, and N-methylpyrrolidone is particularly preferable because it is desirable for the operation to be liquid under production conditions.

本実施形態において、金属イオンの還元の際の反応温度は、特に限定されるものではないが、60〜250℃の範囲にあることが好ましい。反応温度が60℃未満であると、反応が十分進まずに収率が低下する傾向にある。また、反応温度が250℃を超えると、得られる金属微粒子の粒子径や構造が不均一となる傾向にある。同様の理由から、反応温度は、80〜200℃の範囲にあることがより好ましく、100〜150℃の範囲にあることが特に好ましい。   In the present embodiment, the reaction temperature during the reduction of the metal ions is not particularly limited, but is preferably in the range of 60 to 250 ° C. If the reaction temperature is less than 60 ° C., the reaction does not proceed sufficiently and the yield tends to decrease. On the other hand, when the reaction temperature exceeds 250 ° C., the particle diameter and structure of the obtained metal fine particles tend to be non-uniform. For the same reason, the reaction temperature is more preferably in the range of 80 to 200 ° C, and particularly preferably in the range of 100 to 150 ° C.

また、還元の際の反応時間は、特に限定されるものではなく、使用する前駆体やアミド化合物、PVPの種類、反応温度等の条件に応じて適宜選択可能である。金属微粒子の粒子径分布の均一性および生産性の向上の観点からは、反応時間を24時間以内とすることが好ましい。   Moreover, the reaction time in the case of a reduction | restoration is not specifically limited, According to conditions, such as the precursor to be used, an amide compound, PVP, reaction temperature, it can select suitably. From the viewpoint of improving the uniformity of the particle size distribution of the metal fine particles and improving the productivity, the reaction time is preferably within 24 hours.

上記製造方法によれば、PVPとアミド基を有する有機溶媒とを併用することで、金属微粒子の粒子構造を十分に制御しつつ、金属微粒子の収率を向上させることが可能となる。したがって、本実施形態に係る金属微粒子は、様々な用途に適用することができる。かかる用途としては、燃料電池触媒、廃ガス浄化触媒、または種々の有機合成反応用触媒などが挙げられる。   According to the production method described above, the combined use of PVP and an organic solvent having an amide group makes it possible to improve the yield of the metal fine particles while sufficiently controlling the particle structure of the metal fine particles. Therefore, the metal fine particles according to the present embodiment can be applied to various uses. Examples of such applications include fuel cell catalysts, waste gas purification catalysts, and various organic synthesis reaction catalysts.

このようにして得られる金属微粒子について、透過型電子顕微鏡(TEM)を用いることにより、粒子の平均1次粒子径を求めることができる。金属微粒子は同一金属量あたりで比較した際には、粒子径が小さいほど、表面に存在する金属の割合が多くなることから触媒性能が良好になる。本実施形態に係る金属微粒子の粒子径は、従来の手法により製造される金属粒子と比較して触媒性能等の特性を一層向上させることができることから、1〜100nmの範囲であることが好ましく、1〜20nmの範囲であることがより好ましい。   By using a transmission electron microscope (TEM) for the metal fine particles thus obtained, the average primary particle diameter of the particles can be obtained. When the metal fine particles are compared per amount of the same metal, the smaller the particle diameter, the higher the ratio of the metal present on the surface, and the better the catalyst performance. The particle diameter of the metal fine particles according to the present embodiment is preferably in the range of 1 to 100 nm, since the characteristics such as the catalyst performance can be further improved as compared with the metal particles produced by the conventional method, A range of 1 to 20 nm is more preferable.

また、本実施形態に係る金属微粒子の粒子構造の制御の度合いは、X線回折における(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を指標とすることができる。例えば金属種がパラジウムである場合には、2θ=40°付近に(111)面に由来するピークを、2θ=52°付近に(200)面に由来するピークを観測することができる。(111)面は原子の密度が他の面に比べて高いことや、電子状態が種々の反応に優れていることから高い反応性を示すことが知られており、(111)面を多く有する金属微粒子は、それらの反応に対して良好な触媒性能を示すため望ましいといえる。   In addition, the degree of control of the particle structure of the metal fine particles according to the present embodiment depends on the peak intensity I (111) attributed to the (111) plane and the peak intensity I attributed to the (200) plane in X-ray diffraction. The ratio I (111) / I (200) with (200) can be used as an index. For example, when the metal species is palladium, a peak derived from the (111) plane near 2θ = 40 ° and a peak derived from the (200) plane near 2θ = 52 ° can be observed. The (111) plane is known to show high reactivity because the density of atoms is higher than other planes, and the electronic state is excellent in various reactions, and has many (111) planes. Metal fine particles are desirable because they exhibit good catalytic performance for these reactions.

本実施形態に係る金属微粒子のI(111)/I(200)は、2.5より大きいことが好ましく、3.0以上であることがより好ましい。なお、従来法において、構造規定剤を用いずに製造した金属微粒子が一般に(I(111)/I(200))の値が1.6〜2.0の範囲に見られるのに対し、本実施形態に係る金属微粒子は、上記の製造方法によって得られるものであるため、I(111)/I(200)を上記のように飛躍的に大きくすることができ、触媒性能等の特性を向上させる上で非常に有用である。   I (111) / I (200) of the metal fine particles according to this embodiment is preferably larger than 2.5, more preferably 3.0 or more. In the conventional method, metal fine particles produced without using a structure directing agent generally have a value of (I (111) / I (200)) in the range of 1.6 to 2.0. Since the metal fine particles according to the embodiment are obtained by the above-described manufacturing method, I (111) / I (200) can be dramatically increased as described above, and characteristics such as catalyst performance are improved. It is very useful in making it happen.

以下、実施例および比較例に基づき本発明をさらに具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。   EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[実施例1]
0.35gの塩化パラジウムに対し、濃塩酸を1mlずつ溶解するまで加え、10mMの溶液200mlを得た。塩化パラジウムを十分溶解させるために、当該溶液を室温で1晩静置した。この10mM塩化パラジウム溶液2mLに対して、N−メチルピロリドン(NMP)3mLを加えて4mMの溶液を調製し、さらにこの溶液にPVP(重量平均分子量:55,000)26mgを添加した(PVP/Pdモル比12.5)。この混合溶液を140℃で10分攪拌することでパラジウム微粒子溶液を得た。この溶液に30mlの過剰量のアセトンを添加し、24時間置くことで、パラジウム微粒子は容器下部に沈殿する。上澄みを捨て残った沈殿をアセトンを用いて3〜4回程度同様に洗浄した。最終的な沈殿物を1時間ドラフト内で置くことでアセトンを蒸発させ、清浄なパラジウム微粒子を回収した。得られた微粒子について透過型顕微鏡による分析(TEM分析)を行い、平均1次粒子径を測定した。また、X線回折分析を行い、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を求めた。
[Example 1]
Concentrated hydrochloric acid was added to 0.35 g of palladium chloride until 1 ml was dissolved, and 200 ml of a 10 mM solution was obtained. In order to sufficiently dissolve palladium chloride, the solution was allowed to stand overnight at room temperature. To 2 mL of this 10 mM palladium chloride solution, 3 mL of N-methylpyrrolidone (NMP) was added to prepare a 4 mM solution, and 26 mg of PVP (weight average molecular weight: 55,000) was further added to this solution (PVP / Pd Molar ratio 12.5). This mixed solution was stirred at 140 ° C. for 10 minutes to obtain a palladium fine particle solution. To this solution, 30 ml of an excess amount of acetone is added and left for 24 hours, so that the palladium fine particles are precipitated at the bottom of the container. The remaining precipitate was discarded and washed with acetone about 3 to 4 times in the same manner. The final precipitate was placed in a fume hood for 1 hour to evaporate acetone and collect clean palladium particles. The obtained fine particles were analyzed by a transmission microscope (TEM analysis), and the average primary particle size was measured. Further, X-ray diffraction analysis was performed, and the ratio I (111) / I () of the peak intensity I (111) attributed to the (111) plane and the peak intensity I (200) attributed to the (200) plane. 200).

[実施例2]
NMPに代えてN,N−ジメチルホルムアミド(DMF)を用いたこと以外は実施例1と同様にして、パラジウム微粒子を合成した。さらに、得られた微粒子についてTEM分析を行い、平均1次粒子径を測定した。また、X線回折分析を行い、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を求めた。
[Example 2]
Palladium fine particles were synthesized in the same manner as in Example 1 except that N, N-dimethylformamide (DMF) was used instead of NMP. Further, the obtained fine particles were subjected to TEM analysis, and the average primary particle size was measured. Further, X-ray diffraction analysis was performed, and the ratio I (111) / I () of the peak intensity I (111) attributed to the (111) plane and the peak intensity I (200) attributed to the (200) plane. 200).

[実施例3]
塩化パラジウムに代えて塩化白金を用いたこと以外は実施例1と同様にして、白金微粒子を合成した。さらに、得られた微粒子についてTEM分析を行い、平均1次粒子径を測定した。また、X線回折分析を行い、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を求めた。
[Example 3]
Platinum fine particles were synthesized in the same manner as in Example 1 except that platinum chloride was used instead of palladium chloride. Further, the obtained fine particles were subjected to TEM analysis, and the average primary particle size was measured. Further, X-ray diffraction analysis was performed, and the ratio I (111) / I () of the peak intensity I (111) attributed to the (111) plane and the peak intensity I (200) attributed to the (200) plane. 200).

[比較例1]
PVPを添加しなかったこと以外は実施例1と同様にして、パラジウム微粒子を合成した。さらに、得られた微粒子についてTEM分析を行い、平均1次粒子径を測定した。また、X線回折分析を行い、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を求めた。
[Comparative Example 1]
Palladium fine particles were synthesized in the same manner as in Example 1 except that PVP was not added. Further, the obtained fine particles were subjected to TEM analysis, and the average primary particle size was measured. Further, X-ray diffraction analysis was performed, and the ratio I (111) / I () of the peak intensity I (111) attributed to the (111) plane and the peak intensity I (200) attributed to the (200) plane. 200).

[比較例2]
NMPに代えて水を用いたこと以外は実施例1と同様にして、パラジウム微粒子を合成した。さらに、得られた微粒子についてTEM分析を行い、平均1次粒子径を測定した。また、X線回折分析を行い、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)を求めた。
[Comparative Example 2]
Palladium fine particles were synthesized in the same manner as in Example 1 except that water was used instead of NMP. Further, the obtained fine particles were subjected to TEM analysis, and the average primary particle size was measured. Further, X-ray diffraction analysis was performed, and the ratio I (111) / I () of the peak intensity I (111) attributed to the (111) plane and the peak intensity I (200) attributed to the (200) plane. 200).

実施例1〜3および比較例1、2で得られた各金属微粒子について、TEM分析により求めた平均1次粒子径、X線回折分析により求めたピーク強度比I(111)/I(200)、および得られた金属微粒子の収率を表1にまとめた。また、実施例1で得られた金属微粒子のTEM像を図1に示した(倍率2万倍)。なお、TEM分析にはHitachiH−7000(装置名)を用い、TEM像(倍率2〜5万倍)の300nm×300nmの範囲に観察される50個の金属微粒子の1次粒子径の平均値を平均1次粒子径とした。また、X線回折分析にはRigaku RINT−2000(装置名)を用いた。   For each of the metal fine particles obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the average primary particle diameter determined by TEM analysis and the peak intensity ratio I (111) / I (200) determined by X-ray diffraction analysis Table 1 summarizes the yields of the obtained metal fine particles. Further, a TEM image of the metal fine particles obtained in Example 1 is shown in FIG. 1 (magnification 20,000 times). In addition, HitachiH-7000 (device name) was used for TEM analysis, and the average value of primary particle diameters of 50 metal fine particles observed in a 300 nm × 300 nm range of a TEM image (magnification: 2 to 50,000 times) was calculated. The average primary particle size was used. In addition, Rigaku RINT-2000 (device name) was used for X-ray diffraction analysis.

表1に示した通り、実施例1〜3においては、いずれも、十分に微細化されており、且つ、金属微粒子の粒子構造が十分に制御された金属微粒子を高収率で得ることができた。   As shown in Table 1, in each of Examples 1 to 3, metal fine particles that are sufficiently miniaturized and in which the particle structure of the metal fine particles is sufficiently controlled can be obtained in high yield. It was.

また、実施例1と比較例1との比較により、溶媒としてNMPを用いても、溶液がPVPを含まない場合には、得られる金属微粒子の平均1次粒子径が増大し、I(111)/I(200)が低下し、収率が低下することが確認された。   In addition, when NMP is used as a solvent by comparison between Example 1 and Comparative Example 1, when the solution does not contain PVP, the average primary particle diameter of the obtained metal fine particles increases, and I (111) / I (200) was reduced, and it was confirmed that the yield was reduced.

さらに、実施例1と比較例2との比較により、溶液がPVPを含んでも、溶媒が水である場合には、収率が顕著に低下することが確認された。   Furthermore, it was confirmed by comparison with Example 1 and Comparative Example 2 that even if the solution contains PVP, when the solvent is water, the yield is significantly reduced.

本発明の金属微粒子およびその製造方法は、燃料電池触媒や廃ガス浄化触媒、または種々の有機合成反応用触媒に使用される金属微粒子の製造において有用である。   The metal fine particles and the production method thereof of the present invention are useful in the production of metal fine particles used in fuel cell catalysts, waste gas purification catalysts, or various organic synthesis reaction catalysts.

Claims (5)

金属イオンまたは該金属イオンを与える金属塩と、ポリビニルピロリドンと、アミド基を有する有機溶媒と、を含有する溶液中で、前記金属イオンを還元して金属微粒子を析出させることを特徴とする金属微粒子の製造方法。   Metal fine particles characterized by reducing metal ions and precipitating metal fine particles in a solution containing metal ions or a metal salt that gives the metal ions, polyvinylpyrrolidone, and an organic solvent having an amide group Manufacturing method. 前記金属が、パラジウム、白金、ルテニウム、ロジウム、イリジウム、金および銅からなる群より選ばれる少なくとも1種であることを特徴とする、請求項1に記載の金属微粒子の製造方法。   2. The method for producing fine metal particles according to claim 1, wherein the metal is at least one selected from the group consisting of palladium, platinum, ruthenium, rhodium, iridium, gold and copper. 前記アミド基を有する有機溶媒が、N−メチルピロリドン、N,N−ジメチルホルムアミドおよびN,N−ジメチルアセトアミドからなる群より選ばれる少なくとも1種であることを特徴とする、請求項1または2に記載の金属微粒子の製造方法。   The organic solvent having an amide group is at least one selected from the group consisting of N-methylpyrrolidone, N, N-dimethylformamide, and N, N-dimethylacetamide. The manufacturing method of the metal microparticle of description. 請求項1〜3のいずれか一項に記載の製造方法によって製造され、平均1次粒子径が1〜100nmであることを特徴とする金属微粒子。   Metal fine particles produced by the production method according to any one of claims 1 to 3, and having an average primary particle diameter of 1 to 100 nm. X線回折において、(111)面に帰属されるピークの強度I(111)と(200)面に帰属されるピークの強度I(200)との比I(111)/I(200)が2.5より大きいことを特徴とする、請求項4に記載の金属微粒子。   In X-ray diffraction, the ratio I (111) / I (200) of the peak intensity I (111) attributed to the (111) plane to the peak intensity I (200) attributed to the (200) plane is 2. The fine metal particles according to claim 4, wherein the fine metal particles are larger than .5.
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