JP2007190454A - PtRu BASED CATALYST FOR METHANOL OXIDIZATION AND ITS PRODUCTION METHOD - Google Patents

PtRu BASED CATALYST FOR METHANOL OXIDIZATION AND ITS PRODUCTION METHOD Download PDF

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JP2007190454A
JP2007190454A JP2006008712A JP2006008712A JP2007190454A JP 2007190454 A JP2007190454 A JP 2007190454A JP 2006008712 A JP2006008712 A JP 2006008712A JP 2006008712 A JP2006008712 A JP 2006008712A JP 2007190454 A JP2007190454 A JP 2007190454A
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fine particles
metal fine
ptru
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JP4009731B2 (en
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Tadaoki Mitani
忠興 三谷
Yong-Tae Kim
容兌 金
Kazuyoshi Oshima
和佳 大島
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Japan Advanced Institute of Science and Technology
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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    • Y02E60/50—Fuel cells

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PtRu base catalyst reducing ununiformness of a size of Pt fine particles by preventing a coagulation of the Pt fine particles and having a catalytic ability even if an amount of Pt used is less. <P>SOLUTION: In the PtRu base catalyst, the Ru metal fine particles are dispersed on a carrier surface, the Pt metal fine particles having an average particle diameter of 0.5-15 nm are dispersed on a surface of the Ru metal fine particles and a standard deviation of the average particle diameter of the Pt metal fine particles is 7-13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は燃料電池等に好適に使用できるＰｔＲｕ系触媒及びその製造方法に関する。   The present invention relates to a PtRu-based catalyst that can be suitably used for fuel cells and the like and a method for producing the same.

近年、電気自動車の動力源である燃料電池の触媒活性の向上が重要な課題の一つとなっている。このようなメタノールを使用する燃料電池の電極材料として、従来から白金系触媒をカーボンに担持させたものが用いられている。しかし、白金単体をメタノール極の触媒に用いると、メタノールの酸化反応中間物であるＣＯやアルデヒドによって白金が被毒される問題がある。
そこで、白金−ルテニウム（Ｐｔ−Ｒｕ）合金触媒が用いられてきている（例えば、特許文献１、２参照）。Ｒｕは、Ｐｔ上に吸着したＣＯをＣＯ２に酸化し、Ｐｔの被毒を防止する。しかし、これらの技術の場合、担体上でＰｔやＲｕの微粒子が凝集して粗大化し、触媒の有効表面積が向上し難いという問題がある。
このようなことから、担体上にアルコール還元法で生成したＰｔＲｕ合金を、３００〜５００℃で加熱処理することにより、ＰｔとＲｕの金属微粒子の原子間距離を更に接近させて合金化する技術が開発されている（例えば、特許文献３参照）。この技術によれば、粒子径１ｎｍ〜５０ｎｍのＰｔＲｕ触媒微粒子が得られるとされる。
特開平２−１１１４４０号公報 特開２００４−２６７９６１号公報 特開２００５−１７７６６１号公報（段落００２３） In recent years, improvement of the catalytic activity of a fuel cell, which is a power source of an electric vehicle, has become one of important issues. As an electrode material of a fuel cell using such methanol, a material in which a platinum-based catalyst is supported on carbon has been conventionally used. However, when platinum alone is used as a catalyst for the methanol electrode, there is a problem that platinum is poisoned by CO or aldehyde which is an intermediate of methanol oxidation reaction.
Accordingly, platinum-ruthenium (Pt—Ru) alloy catalysts have been used (see, for example, Patent Documents 1 and 2). Ru oxidizes CO adsorbed on Pt to CO 2 to prevent Pt poisoning. However, these techniques have a problem that the fine particles of Pt and Ru are aggregated and coarsened on the support and it is difficult to improve the effective surface area of the catalyst.
For this reason, there is a technique in which a PtRu alloy produced by an alcohol reduction method on a support is heat-treated at 300 to 500 ° C. to make the interatomic distance between the Pt and Ru metal fine particles closer to each other. It has been developed (see, for example, Patent Document 3). According to this technique, PtRu catalyst fine particles having a particle diameter of 1 nm to 50 nm are obtained.
JP-A-2-111440 Japanese Patent Application Laid-Open No. 2004-267961 Japanese Patent Laying-Open No. 2005-177661 (paragraph 0023)

しかしながら、上記した特許文献３記載の技術を用いても、触媒となるＰｔ微粒子の凝集を防止することは難しく、Ｐｔ微粒子の大きさのばらつきが生じて触媒能が低下する問題がある。
本発明は上記の課題を解決するためになされたものであり、Ｐｔ微粒子の凝集を防止してＰｔ微粒子の大きさのばらつきを低減し、Ｐｔの使用量が少なくても触媒能が高いＰｔＲｕ系触媒の提供を目的とする。 However, even if the technique described in Patent Document 3 described above is used, it is difficult to prevent the aggregation of Pt fine particles serving as a catalyst, and there is a problem that variations in the size of Pt fine particles occur and the catalytic performance is lowered.
The present invention has been made to solve the above-mentioned problems, and prevents the Pt fine particles from agglomerating to reduce the variation in the size of the Pt fine particles, and has a high catalytic ability even if the amount of Pt used is small. The purpose is to provide a catalyst.

上記の目的を達成するために、本発明のＰｔＲｕ系触媒は、担体表面にＲｕ金属微粒子が分散し、該Ｒｕ金属微粒子の表面に平均粒径０．５〜１５ｎｍのＰｔ金属微粒子が分散し、かつ前記Ｐｔ金属微粒子の平均粒径の標準偏差が７〜１３である。   In order to achieve the above object, in the PtRu-based catalyst of the present invention, Ru metal fine particles are dispersed on the surface of the support, and Pt metal fine particles having an average particle diameter of 0.5 to 15 nm are dispersed on the surface of the Ru metal fine particles. And the standard deviation of the average particle diameter of the Pt metal fine particles is 7-13.

本発明のＰｔＲｕ系触媒の製造方法は、表面にチオール基を有する担体と、Ｒｕ前駆体と、Ｐｔ前駆体とを共存させた状態で、前記Ｒｕ前駆体及びＰｔ前駆体を還元させ、前記担体表面にＲｕ金属微粒子とＰｔ金属微粒子とを担持させる工程と、前記Ｒｕ金属微粒子とＰｔ金属微粒子とを担持させた担体を、非酸化雰囲気で熱処理する工程とを有する。
上記製造方法において、前記熱処理の温度を３００℃未満とすることが好ましい。 The method for producing a PtRu-based catalyst according to the present invention comprises reducing the Ru precursor and the Pt precursor in a state where a carrier having a thiol group on the surface, a Ru precursor, and a Pt precursor coexist. A step of supporting Ru metal fine particles and Pt metal fine particles on the surface, and a step of heat-treating the carrier supporting the Ru metal fine particles and Pt metal fine particles in a non-oxidizing atmosphere.
In the manufacturing method, the temperature of the heat treatment is preferably less than 300 ° C.

本発明によれば、Ｐｔ微粒子の凝集を防止してＰｔ微粒子の大きさのばらつきを低減し、Ｐｔの使用量が少なくても触媒能が高いＰｔＲｕ系触媒が得られる。   According to the present invention, it is possible to obtain a PtRu-based catalyst having high catalytic ability even if the amount of Pt used is small by preventing aggregation of Pt fine particles and reducing variation in the size of Pt fine particles.

以下、本発明の実施形態について説明する。   Hereinafter, embodiments of the present invention will be described.

本発明の実施形態に係るＰｔＲｕ系触媒は、担体表面にＲｕ金属微粒子が分散し、該Ｒｕ金属微粒子の表面に平均粒径０．５〜１５ｎｍのＰｔ金属微粒子が分散し、かつ前記Ｐｔ金属微粒子の平均粒径の標準偏差が７〜１３である。   In the PtRu-based catalyst according to the embodiment of the present invention, Ru metal fine particles are dispersed on the surface of the support, Pt metal fine particles having an average particle size of 0.5 to 15 nm are dispersed on the surface of the Ru metal fine particles, and the Pt metal fine particles The standard deviation of the average particle size is 7-13.

１）担体
担体としては、例えば、炭素、酸化物が挙げられるが炭素を用いることが好ましい。
炭素担体としては、一般に触媒に用いられるものであれば特に限定されないが、例えば、多層カーボンナノチューブ（ＭＷＮＴ）、単層カーボンナノチューブ（ＳＷＮＴ）、カーボンナノ繊維（ＣＮＦ）、カーボンブラック（ＣＢ）、活性炭（ＡＣ）、活性カーボンナノ繊維（ＡＣＦ）が例示される。
酸化物担体としては、一般に触媒に用いられるものであれば特に限定されないが、例えばシリカ、アルミナ、ゼオライト等の無機酸化物が例示される。
その他、一般に電極基板として用いられる金属、半導体等の導電性材料を担体として用いることができる。単体の大きさ及び形状も特に限定されない。 1) Carrier Examples of the carrier include carbon and oxides, but carbon is preferably used.
The carbon support is not particularly limited as long as it is generally used for a catalyst. For example, multi-walled carbon nanotube (MWNT), single-walled carbon nanotube (SWNT), carbon nanofiber (CNF), carbon black (CB), activated carbon (AC) and activated carbon nanofiber (ACF) are exemplified.
Although it will not specifically limit if it is generally used for a catalyst as an oxide support | carrier, For example, inorganic oxides, such as a silica, an alumina, a zeolite, are illustrated.
In addition, a conductive material such as a metal or a semiconductor generally used as an electrode substrate can be used as a carrier. The size and shape of the single body are not particularly limited.

２）Ｒｕ金属微粒子
担体表面にはＲｕ金属微粒子が分散している。Ｒｕは、メタノールの酸化反応中間物であるＣＯやアルデヒドによって白金が被毒されることを防止し、Ｐｔの触媒活性を維持するものである。Ｒｕ金属微粒子の平均粒径は０．５〜１５ｎｍ程度であることが好ましい。Ｒｕ金属微粒子の平均粒径が０．５ｎｍ未満であるものは製造することが困難であり、平均粒径が１５ｎｍを超えると、Ｒｕによる白金の被毒防止効果が改善されない。 2) Ru metal fine particles Ru metal fine particles are dispersed on the surface of the carrier. Ru prevents platinum from being poisoned by CO or aldehyde, which is an intermediate of methanol oxidation reaction, and maintains the catalytic activity of Pt. The average particle size of the Ru metal fine particles is preferably about 0.5 to 15 nm. The Ru metal fine particles having an average particle size of less than 0.5 nm are difficult to produce, and if the average particle size exceeds 15 nm, the effect of preventing the poisoning of platinum by Ru is not improved.

３）Ｐｔ金属微粒子
Ｒｕ金属微粒子の表面には平均粒径０．５〜１５ｎｍのＰｔ金属微粒子が分散している。Ｐｔは触媒反応を生じさせるものである。Ｐｔ金属微粒子の平均粒径が０．５ｎｍ未満であるものは製造することが困難であり、又、以下のＴＥＭ像で確認することが困難である。一方、平均粒径が１５ｎｍを超えると、Ｐｔ粒が粗大となって触媒活性が向上せず、触媒反応に有効に寄与するPtの割合が低減する。
なお、Ｒｕ及びＰｔ金属微粒子の平均粒径は、例えばＴＥＭ（透過型電子顕微鏡）像から求めることができる。 3) Pt metal fine particles Pt metal fine particles having an average particle diameter of 0.5 to 15 nm are dispersed on the surface of the Ru metal fine particles. Pt causes a catalytic reaction. It is difficult to produce a Pt metal fine particle having an average particle size of less than 0.5 nm, and it is difficult to confirm with the following TEM image. On the other hand, if the average particle size exceeds 15 nm, the Pt particles are coarse and the catalytic activity is not improved, and the proportion of Pt that effectively contributes to the catalytic reaction is reduced.
In addition, the average particle diameter of Ru and Pt metal fine particles can be calculated | required from a TEM (transmission electron microscope) image, for example.

本発明の触媒においては、以下に示すようにＰｔ金属微粒子がＲｕ金属微粒子の殆ど表面に存在し、Ｒｕの内部にＰｔが殆ど存在しないことが確認されている。通常のPtRu合金電極材料は、Ru内部にPtが取り込まれてしまうため、Ｐｔのうち触媒として機能しない部分があるが、本発明においてはRuの表面上にPt粒子が分散して存在することで、触媒反応に有効に寄与するPtの割合が増大する。
図１、図２は、シンクロトロン放射光（SPring-8）を利用した、後述する実施例の試料についてのＸＡＦＳ(X線吸収微細構造；X-ray Absorption Fine Structure)スペクトルを示す。ＸＡＦＳは、着目する元素のＸ線吸収エネルギー近傍のエネルギーを物質に照射し、吸収スペクトルから着目元素の近傍元素の情報を得るものである。 In the catalyst of the present invention, it has been confirmed that Pt metal fine particles are present on almost the surface of Ru metal fine particles and Pt is hardly present inside Ru as shown below. In the normal PtRu alloy electrode material, Pt is taken into Ru. Therefore, there is a part of Pt that does not function as a catalyst. In the present invention, Pt particles are dispersed on the surface of Ru. The proportion of Pt that contributes effectively to the catalytic reaction increases.
FIG. 1 and FIG. 2 show XAFS (X-ray Absorption Fine Structure) spectra of samples of Examples described later using synchrotron radiation (SPring-8). XAFS irradiates a substance with energy in the vicinity of the X-ray absorption energy of the element of interest, and obtains information on the element near the element of interest from the absorption spectrum.

図１は、Ｐｔを着目元素とした場合のＸＡＦＳスペクトルを示す。この図において、着目するＰｔ元素からの距離Ｒが約1.9×10-10ｍのピークＰ１は、Ｐｔの第１近接元素（1NN:first nearest neighbor）がＳ（イオウ）である（以下、「Ｐｔ−Ｓ」のように1NNを表記する）ピークである。このＳはチオール基に由来しており、図の矢印に示す方向に試料の熱処理温度が高くなるほど、チオールが蒸発してＰ１の高さも減少する。なお、距離Ｒは正確には着目原子からの距離ではなく、スペクトルのフーリエ（Fourier）変換で得られたパラメータである。例えば、Ｒが1.9×10-10ｍである場合、実際の距離は位相差を考慮すると2.2×10-10ｍ程度になる。
Ｐ２はＰｔ−Ｒｕのピークを示し、熱処理温度が高くなるほどＰ２も高くなる。つまり、熱処理温度が高くなるほど、Ｒｕの凝集クラスターが大きくなることを示唆する。
Ｐ３はＰｔ−Ｐｔのピークを示し、熱処理温度が高くなるほどＰ２も高くなる。しかしながら、Ｐ３の高さはＰ２の高さより低い。つまり、Ｐｔの近傍にはＲｕがより多く存在することを示唆する。
つまり、図１から、ＰｔはＲｕのクラスター上に分散して存在することが考えられる。 FIG. 1 shows an XAFS spectrum when Pt is the element of interest. In this figure, a peak P1 having a distance R from the Pt element of interest of about 1.9 × 10 −10 m has a first nearest neighbor (1NN: SNN) of Pt (hereinafter referred to as “Pt”). It is a peak). This S is derived from a thiol group, and as the heat treatment temperature of the sample increases in the direction indicated by the arrow in the figure, the thiol evaporates and the height of P1 decreases. Note that the distance R is not a distance from the target atom, but a parameter obtained by Fourier transform of the spectrum. For example, when R is 1.9 × 10 −10 m, the actual distance is about 2.2 × 10 −10 m considering the phase difference.
P2 shows a peak of Pt—Ru, and P2 increases as the heat treatment temperature increases. That is, it is suggested that the higher the heat treatment temperature, the larger the aggregated clusters of Ru.
P3 shows a peak of Pt-Pt, and P2 increases as the heat treatment temperature increases. However, the height of P3 is lower than the height of P2. That is, it is suggested that more Ru exists in the vicinity of Pt.
That is, from FIG. 1, it can be considered that Pt exists in a distributed manner on a Ru cluster.

図２は、Ｒｕを着目元素とした場合のＸＡＦＳスペクトルを示す。この図において、Ｐ４はＲｕ−Ｒｕのピークを示し、熱処理温度が高くなるほどＰ２も高くなる。そして、Ｒｕ−Ｐｔのピークは殆ど見られない。つまり、図２から、ＰｔはＲｕのクラスター上に分散して存在することがより強く示唆される。   FIG. 2 shows an XAFS spectrum when Ru is used as the element of interest. In this figure, P4 shows a Ru-Ru peak, and P2 increases as the heat treatment temperature increases. The Ru—Pt peak is hardly observed. That is, FIG. 2 strongly suggests that Pt exists in a distributed manner on Ru clusters.

又、本発明のＰｔＲｕ系触媒においては、Ｐｔ金属微粒子の平均粒径の標準偏差が７〜１３である。上記した標準偏差はＰｔ金属微粒子の大きさのばらつきを示し、標準偏差が大きくなると、粒子の大きさにばらつきが生じて粒子が凝集していることを示す。ここで、標準偏差を上記範囲に規定した理由は、標準偏差が７未満のものを製造するのは困難であるからである。又、標準偏差が１３を超えると、Ｐｔ金属微粒子の大きさがばらつき、粒子に凝集が生じて触媒能が低下するとともに、Ｐｔ使用量の低減を図ることができなくなる。   In the PtRu-based catalyst of the present invention, the standard deviation of the average particle diameter of the Pt metal fine particles is 7 to 13. The standard deviation described above indicates variation in the size of the Pt metal fine particles. When the standard deviation increases, the particle size varies and indicates that the particles are aggregated. Here, the reason why the standard deviation is defined in the above range is that it is difficult to manufacture a standard deviation of less than 7. On the other hand, when the standard deviation exceeds 13, the size of the Pt metal fine particles varies, the particles are aggregated, the catalytic ability is lowered, and the amount of Pt used cannot be reduced.

５）ＰｔとＲｕの原子比
ＰｔとＲｕの原子比は特に制限はないが、Ｐｔ／Ｒｕ＝０．０１〜５であることが好ましい。本発明においては、Ｐｔ金属微粒子がＲｕ金属微粒子の表面に存在し、かつＰｔ金属微粒子の大きさのばらつきが小さいため、触媒反応に有効に寄与するPtの割合が高くなるため、Ｐｔ／Ｒｕの比が小さくても触媒活性を維持することができる。
Ｐｔ／Ｒｕ＝０．０１未満であると、Ｐｔの触媒活性が低下する場合があり、Ｐｔ／Ｒｕ＝５を超えると、Ｐｔの使用量が多くなってコスト増となる場合がある。 5) Atomic ratio of Pt and Ru The atomic ratio of Pt and Ru is not particularly limited, but is preferably Pt / Ru = 0.01-5. In the present invention, since the Pt metal fine particles are present on the surface of the Ru metal fine particles and the variation in the size of the Pt metal fine particles is small, the ratio of Pt that effectively contributes to the catalytic reaction is increased. Even if the ratio is small, the catalytic activity can be maintained.
If Pt / Ru = less than 0.01, the catalytic activity of Pt may decrease, and if it exceeds Pt / Ru = 5, the amount of Pt used may increase and the cost may increase.

本実施形態に係るＰｔＲｕ系触媒は、燃料電電池の触媒電極、キャパシター、二次電池の複合電極などに好適に使用できる。   The PtRu-based catalyst according to this embodiment can be suitably used for a catalyst electrode of a fuel cell, a capacitor, a composite electrode of a secondary battery, and the like.

本実施形態に係るＰｔＲｕ系触媒は、例えば以下のようにして製造することができる。   The PtRu-based catalyst according to this embodiment can be produced, for example, as follows.

Ａ）担体のチオール化
まず、担体表面にチオール基を修飾する。本発明者らの検討によれば、従来の液状還元法で担体にＰｔやＲｕを担持させた場合、担持の際にＰｔやＲｕが凝集してその粒子径が大きくなることが判明している。そこで、本発明者らは、担体にチオール基を分散させて修飾させ、チオール基にＰｔやＲｕを担持させることとした。これにより、担体上に分散したチオール基に選択的にＰｔやＲｕが析出するので、これら粒子の凝集を抑制し、粒子径を微細化することに成功した、この理由としては、チオール基がＰｔやＲｕの金属微粒子の表面に強く吸着され、金属微粒子の凝集が効果的に阻止されることが考えられる。
なお、Ｒｕ及びＰｔと相互作用する官能基であれば、チオール基以外の基を用いてもよい。このような官能基としては、アミド基、シアン基、カルボキシル基などが挙げられる。 A) Thiolation of carrier First, a thiol group is modified on the surface of the carrier. According to the study by the present inventors, when Pt or Ru is supported on a carrier by the conventional liquid reduction method, it has been found that Pt and Ru are aggregated during the loading and the particle diameter is increased. . Therefore, the present inventors decided to disperse the thiol group on the carrier for modification, and to support Pt or Ru on the thiol group. As a result, Pt and Ru are selectively deposited on the thiol group dispersed on the carrier, and thus the aggregation of these particles was suppressed and the particle diameter was successfully reduced. The reason for this is that the thiol group is Pt. It is considered that the particles are strongly adsorbed on the surface of the metal fine particles of Ru and Ru, and the aggregation of the metal fine particles is effectively prevented.
A group other than a thiol group may be used as long as it is a functional group that interacts with Ru and Pt. Examples of such a functional group include an amide group, a cyan group, and a carboxyl group.

Ａ−１）酸化処理
チオール化に先立ち、担体表面に酸化処理を施す。酸化処理は、次工程で担体表面をハロゲン化するための前処理である。酸化処理は、担体に酸処理を施すか、又は担体を含酸素雰囲気（例えば空気）中で加熱して行うことができる。
担体に酸処理を行う場合、例えば、硫酸、硝酸、塩酸等の無機酸；ベンゼンスルホン酸等の有機酸；過マンガン酸カリウム、過酸化水素、クロム酸カリウム、二酸化鉛、酸化銅等の酸化剤；を単独で使用し又は２種以上を併用することができる。これらのうち、硫酸、硝酸、塩酸等の無機酸、及び過マンガン酸カリウムを用いることが好ましい。
酸処理の効率を高めると共に安全性を考慮し、酸処理の温度は、通常は好ましくは３００〜７００℃、より好ましくは４００〜５００℃とする。酸処理の時間は特に制限されないが、通常、２時間以内である。
含酸素雰囲気中で担体を加熱する際の温度は、担体の材質にもよるが、例えば担体が炭素である場合は、通常、好ましくは３００〜７００℃、より好ましくは４００〜５００℃とする。このように、担体を空気中で所定温度で、所定時間（通常、１２時間以内）で加熱処理することにより、担体表面にカルボキシル基を導入することができる。 A-1) Oxidation treatment Prior to thiolation, the support surface is subjected to an oxidation treatment. The oxidation treatment is a pretreatment for halogenating the support surface in the next step. The oxidation treatment can be performed by subjecting the support to an acid treatment or by heating the support in an oxygen-containing atmosphere (for example, air).
When performing acid treatment on the carrier, for example, inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, etc .; organic acids such as benzenesulfonic acid; oxidizing agents such as potassium permanganate, hydrogen peroxide, potassium chromate, lead dioxide, copper oxide Can be used alone or in combination of two or more. Among these, it is preferable to use inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and potassium permanganate.
In consideration of increasing the efficiency of the acid treatment and considering safety, the temperature of the acid treatment is usually preferably 300 to 700 ° C, more preferably 400 to 500 ° C. Although the acid treatment time is not particularly limited, it is usually within 2 hours.
Although the temperature at which the carrier is heated in an oxygen-containing atmosphere depends on the material of the carrier, for example, when the carrier is carbon, it is usually preferably 300 to 700 ° C, more preferably 400 to 500 ° C. Thus, a carboxyl group can be introduce | transduced on the support | carrier surface by heat-processing a support | carrier at predetermined temperature in air for predetermined time (usually within 12 hours).

Ａ−２）ハロゲン化処理
ハロゲン化処理は、チオール化処理の前処理であり、ハロゲン化にはハロゲン化剤を用いることができる。
ハロゲン化剤としては、例えば、塩化チオニル、塩化アルミニウム、塩化水銀等が挙げられるがこれらに限定されない。そして、担体及びハロゲン化剤を適当な温度、時間で攪拌することによってハロゲン化処理を行うことができる。ハロゲン化処理の温度は、通常５０〜１００℃程度とすることができ、処理時間は特に限定されないが、通常、１２時間以内であればよい。 A-2) Halogenation treatment The halogenation treatment is a pretreatment for the thiolation treatment, and a halogenating agent can be used for the halogenation.
Examples of the halogenating agent include, but are not limited to, thionyl chloride, aluminum chloride, mercury chloride and the like. And a halogenation process can be performed by stirring a support | carrier and a halogenating agent at appropriate temperature and time. The temperature of the halogenation treatment can usually be about 50 to 100 ° C., and the treatment time is not particularly limited, but it may usually be within 12 hours.

Ａ−３）チオール化
ハロゲン化させた担体表面をチオール化することにより、チオール基を導入する。チオール化の方法は特に限定されないが、有機化学的方法、機械化学的方法を用いることができる。
有機化学的方法としては、担体とチオール化剤とを反応させる方法が挙げられる。この場合、チオール化剤として、アミノメタンチオール、アミノエタンチオール、アミノドデカンチオール等の炭素数１〜１２のアミノアルカンチオール；メルカプトメタノール、メルカプトエタノール、メルカプトドデカノール等の炭素数１〜１２のメルカプトアルコール；アミノチオフェノール、メルカプトフェノール等のベンゼン誘導体；等が挙げられるがこれらに限定されない。
担体とチオール化剤との反応は、例えば両者を接触させて行うことができ、反応効率の点から反応温度は５０〜１００℃であることが好ましい。反応時間は特に限定されないが、通常、２４時間以内であればよい。 A-3) Thiolation A thiol group is introduced by thiolation of the halogenated carrier surface. The method for thiolation is not particularly limited, and an organic chemical method or a mechanochemical method can be used.
Examples of the organic chemical method include a method of reacting a carrier with a thiolating agent. In this case, as the thiolizing agent, aminoalkanethiol having 1 to 12 carbon atoms such as aminomethanethiol, aminoethanethiol, aminododecanethiol; mercaptoalcohol having 1 to 12 carbon atoms such as mercaptomethanol, mercaptoethanol, mercaptododecanol Benzene derivatives such as aminothiophenol and mercaptophenol; and the like.
The reaction between the carrier and the thiolating agent can be carried out, for example, by bringing both into contact, and the reaction temperature is preferably 50 to 100 ° C. from the viewpoint of reaction efficiency. Although reaction time is not specifically limited, Usually, what is necessary is just within 24 hours.

Ｂ）担体表面へのＲｕ及びＰｔの担持
次に、チオール化した担体と、Ｒｕ前駆体と、Ｐｔ前駆体とを共存させた状態で、Ｒｕ前駆体及びＰｔ前駆体を還元させ、担体表面にＲｕ金属微粒子とＰｔ金属微粒子とを担持させる。これは、金属前駆体を液状還元法で還元させる方法である。
Ｒｕ及びＰｔの前駆体としては、これらの金属の塩又は錯体を用いることができ、たとえば、塩化ルテニウム水溶液及び塩化白金水溶液が挙げられる。そして、これらの水溶液に担体を浸漬し、超音波を与えたり、攪拌することにより、担体と水溶液とを充分に接触させた後、還元剤を添加して前駆体を還元する。
還元剤としては、例えば、水素化ホウ素ナトリウム、水素化アルミニウムリチウム、水素等が挙げられるが、これらに限定されない。還元剤の量は、通常、上記Ｒｕ及びＰｔの前駆体の合計に対して過剰量（例えば、上記前駆体の合計１moL当り1.5〜10moL）となるように調整することが好ましい。 B) Loading Ru and Pt on the support surface Next, in the state where the thiolated support, the Ru precursor, and the Pt precursor coexist, the Ru precursor and the Pt precursor are reduced, Ru metal fine particles and Pt metal fine particles are supported. This is a method of reducing a metal precursor by a liquid reduction method.
As the precursor of Ru and Pt, a salt or complex of these metals can be used, and examples thereof include an aqueous ruthenium chloride solution and an aqueous platinum chloride solution. Then, the carrier is immersed in these aqueous solutions, and ultrasonic waves are applied or stirred to bring the carrier and the aqueous solution into sufficient contact, and then the reducing agent is added to reduce the precursor.
Examples of the reducing agent include, but are not limited to, sodium borohydride, lithium aluminum hydride, hydrogen, and the like. Usually, the amount of the reducing agent is preferably adjusted so as to be an excess amount (for example, 1.5 to 10 moL per 1 mol of the total precursor) relative to the total of the precursors of Ru and Pt.

以上のようにして、表面がチオール化した担体に、Ｒｕ及びＰｔの金属微粒子が担持される。これらの金属微粒子は凝集せず、担体上に微細に分散することができる。
なお、担体上に担持されるＲｕ金属微粒子とＰｔ金属微粒子との割合は、Ｒｕ前駆体及びＰｔ前駆体の濃度割合を変化させて調整することができる。
Ｒｕ及びＰｔの担持量は、担体表面のチオール基の数、Ｒｕ及びＰｔ前駆体の液濃度等によって異なるが、触媒活性を維持する点から、通常、担体の１０〜６０質量％程度とすることが好ましい。 As described above, Ru and Pt metal fine particles are supported on a carrier having a thiolated surface. These metal fine particles do not aggregate and can be finely dispersed on the carrier.
The ratio of the Ru metal fine particles and the Pt metal fine particles supported on the carrier can be adjusted by changing the concentration ratio of the Ru precursor and the Pt precursor.
The supported amount of Ru and Pt varies depending on the number of thiol groups on the surface of the support, the liquid concentration of the Ru and Pt precursors, etc., but is generally about 10 to 60% by mass of the support from the viewpoint of maintaining catalytic activity. Is preferred.

Ｃ）熱処理
次に、Ｒｕ金属微粒子とＰｔ金属微粒子とを担持させた担体を、非酸化雰囲気で熱処理することにより、担体表面のチオール基が除去されると共に、担体上に担持された隣接する金属微粒子同士が一体化し、所定の粒径となる。
熱処理はチオール基が分解する温度である２００℃以上とする必要がある。熱処理を行うと、チオール基が除去され、Ｒｕ及びＰｔの金属原子が担体上に存在する。この状態で、まず融点の低いＲｕの金属微粒子が担体上を移動して凝集し、上記した所定の粒径となる。Ｐｔ金属微粒子は凝集せず、隣接するＲｕの移動に伴って移動する。Ｒｕの凝集が完了すると、Ｐｔ金属微粒子は周囲をＲｕの凝集体で囲まれているために、他のＰｔ金属微粒子と凝集することが難しく、チオール化した担体に担持された時の粒径をほぼ維持すると考えられる。 C) Heat treatment Next, the support on which the Ru metal fine particles and the Pt metal fine particles are supported is heat-treated in a non-oxidizing atmosphere, thereby removing the thiol group on the support surface and adjoining the metal supported on the support. Fine particles are integrated into a predetermined particle size.
The heat treatment needs to be 200 ° C. or higher, which is the temperature at which the thiol group decomposes. When heat treatment is performed, the thiol group is removed and Ru and Pt metal atoms are present on the support. In this state, Ru metal fine particles having a low melting point first move on the carrier and aggregate to form the predetermined particle size described above. Pt metal fine particles do not aggregate and move with the movement of adjacent Ru. When the aggregation of Ru is completed, since the Pt metal fine particles are surrounded by the Ru aggregates, it is difficult to aggregate with other Pt metal fine particles, and the particle size when supported on the thiolated carrier is reduced. It is thought that it is almost maintained.

従って、チオール化の時点で担持されるＰｔの量（原子比）を、Ｒｕの量より少なくすることにより、熱処理によるＰｔ金属微粒子の凝集を防止し、Ｒｕ表面にＰｔを分散させることができる。
熱処理温度は、２００〜６００℃の範囲とすることが好ましく、２００℃以上３００℃未満とすることがより好ましく、２００〜２５０℃とすることが最も好ましい。熱処理温度が６００℃を超えると、Ｒｕ及びＰｔ金属微粒子が凝集して粗大化し、触媒活性が低下する場合がある。
熱処理時間は特に制限されないが、通常、１時間程度とすることができる。
非酸化雰囲気としては、例えば水素雰囲気が挙げられる。 Therefore, by making the amount (atomic ratio) of Pt supported at the time of thiolation smaller than the amount of Ru, aggregation of Pt metal fine particles due to heat treatment can be prevented, and Pt can be dispersed on the Ru surface.
The heat treatment temperature is preferably in the range of 200 to 600 ° C, more preferably 200 ° C or more and less than 300 ° C, and most preferably 200 to 250 ° C. When the heat treatment temperature exceeds 600 ° C., Ru and Pt metal fine particles aggregate and become coarse, and the catalytic activity may be reduced.
The heat treatment time is not particularly limited, but can usually be about 1 hour.
Examples of the non-oxidizing atmosphere include a hydrogen atmosphere.

次に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらに限定されるものではない。   EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.

１．担体のチオール化
直径１０〜２０ｎｍの多層カーボンナノチューブ１００ｍｇを硫酸と硝酸の混合物（３：１）で７０℃で１時間酸化処理した後、この多層カーボンナノチューブに塩化チオニル２５ｍＬを加えて７０℃で１２時間攪拌することにより、多層カーボンナノチューブの表面を塩素化させた。
次に、塩素化された多層カーボンナノチューブとアミノエタンチオールとを７０℃で２４時間反応させることによって多層カーボンナノチューブの表面をチオール化させ、表面にチオール基が導入された炭素担体を得た。
２．Ｒｕ及びＰｔの担持
チオール化した担体に、３．１２５ｍｍｏｌ／Ｌの塩化ルテニウム水溶液５ｍＬと、３．０５４ｍｍｏｌ／Ｌの塩化白金酸水溶液５ｍＬとを加え、１時間超音波を与えた後、ＲｕとＰｔの合計量に対し過剰量となるよう、１００ｍｍｏｌ／Ｌの水素化ホウ素ナトリウム水溶液を加えてＲｕとＰｔを還元させ、担体表面にＲｕ及びＰｔ金属微粒子を担持させた。 1. Thiolation of carrier 100 mg of multi-walled carbon nanotubes having a diameter of 10 to 20 nm were oxidized with a mixture of sulfuric acid and nitric acid (3: 1) at 70 ° C. for 1 hour, and then 25 mL of thionyl chloride was added to the multi-walled carbon nanotubes and 12 ° C. at 70 ° C. The surface of the multi-walled carbon nanotube was chlorinated by stirring for a period of time.
Next, the surface of the multi-walled carbon nanotube was thiolated by reacting the chlorinated multi-walled carbon nanotube with aminoethanethiol at 70 ° C. for 24 hours to obtain a carbon support having a thiol group introduced on the surface.
2. Supporting Ru and Pt 5 mL of a 3.125 mmol / L ruthenium chloride aqueous solution and 5 mL of a 3.054 mmol / L chloroplatinic acid aqueous solution were added to the thiolated support, and after applying ultrasonic waves for 1 hour, Ru and Pt A 100 mmol / L sodium borohydride aqueous solution was added to reduce the amount of Ru and Pt so as to be excessive with respect to the total amount of Ru, and Ru and Pt metal fine particles were supported on the support surface.

３．熱処理
Ｒｕ及びＰｔを担持した担体を、水素雰囲気下で２００℃〜６００℃の範囲の所定温度で１時間熱処理し、触媒を得た。 3. Heat treatment The support carrying Ru and Pt was heat-treated at a predetermined temperature in the range of 200 ° C. to 600 ° C. for 1 hour in a hydrogen atmosphere to obtain a catalyst.

４．評価
得られた触媒のＴＥＭ像を図３〜図８に示す。各図において、ＣＮＴの担体１０の表面にＲｕ粒２が析出しているのがわかる（例えば,図６の符号参照）。但し、このＴＥＭ像では倍率が低いため、Ｐｔ粒子を確認することはできない。
図９〜図１３は、それぞれ図４〜図８に対応した試料のＰｔ微粒子の平均粒径分布を示す。Ｐｔ微粒子の平均粒径は、高倍率のＴＥＭ像から個々のＰｔ微粒子の最大径を目視判定した値を採用した。
図９〜図１３の粒径分布をもとに、各試料におけるＰｔ金属微粒子の平均粒径の標準偏差を求めた。その結果を表１に示す。 4). Evaluation TEM images of the obtained catalyst are shown in FIGS. In each figure, it can be seen that Ru particles 2 are deposited on the surface of the CNT carrier 10 (for example, see the reference numerals in FIG. 6). However, since the magnification is low in this TEM image, Pt particles cannot be confirmed.
9 to 13 show average particle size distributions of the Pt fine particles of the samples corresponding to FIGS. 4 to 8, respectively. As the average particle diameter of the Pt fine particles, a value obtained by visually determining the maximum diameter of each Pt fine particle from a high-magnification TEM image was adopted.
Based on the particle size distributions of FIGS. 9 to 13, the standard deviation of the average particle size of the Pt metal fine particles in each sample was determined. The results are shown in Table 1.

表１から明らかなように、各試料のＰｔ金属微粒子の平均粒径の標準偏差は７〜１３の範囲内にあり、Ｐｔ金属微粒子の大きさのばらつきを低減できることが確認された。   As is clear from Table 1, the standard deviation of the average particle diameter of the Pt metal fine particles in each sample is in the range of 7 to 13, and it was confirmed that the variation in the size of the Pt metal fine particles can be reduced.

本発明の実施形態に係るＰｔＲｕ系触媒の金属微粒子のＸＡＦＳスペクトルを示す図である。It is a figure which shows the XAFS spectrum of the metal fine particle of the PtRu type catalyst which concerns on embodiment of this invention. 本発明の実施形態に係るＰｔＲｕ系触媒の金属微粒子のＸＡＦＳスペクトルを示す別の図である。It is another figure which shows the XAFS spectrum of the metal fine particle of the PtRu type catalyst which concerns on embodiment of this invention. チオール化後の熱処理を行わなかった場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type | system | group catalyst which concerns on embodiment of this invention at the time of not performing the heat processing after thiolation. チオール化後の熱処理を５２３Ｋとした場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type catalyst which concerns on embodiment of this invention when heat processing after thiolation is 523K. チオール化後の熱処理を５７３Ｋとした場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type catalyst which concerns on embodiment of this invention when the heat processing after thiolation is 573K. チオール化後の熱処理を６７３Ｋとした場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type catalyst which concerns on embodiment of this invention when the heat processing after thiolation is 673K. チオール化後の熱処理を７７３Ｋとした場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type catalyst which concerns on embodiment of this invention when the heat processing after thiolation is 773K. チオール化後の熱処理を８７３Ｋとした場合の本発明の実施形態に係るＰｔＲｕ系触媒のＴＥＭ像を示す図である。It is a figure which shows the TEM image of the PtRu type catalyst which concerns on embodiment of this invention when the heat processing after thiolation is 873K. 図４に示すＰｔＲｕ系触媒のＰｔ微粒子の平均粒径分布を示す図である。FIG. 5 is a diagram showing an average particle size distribution of Pt fine particles of the PtRu-based catalyst shown in FIG. 4. 図５に示すＰｔＲｕ系触媒のＰｔ微粒子の平均粒径分布を示す図である。FIG. 6 is a diagram showing an average particle size distribution of Pt fine particles of the PtRu-based catalyst shown in FIG. 5. 図６に示すＰｔＲｕ系触媒のＰｔ微粒子の平均粒径分布を示す図である。FIG. 7 is a diagram showing an average particle size distribution of Pt fine particles of the PtRu-based catalyst shown in FIG. 6. 図７に示すＰｔＲｕ系触媒のＰｔ微粒子の平均粒径分布を示す図である。FIG. 8 is a diagram showing an average particle size distribution of Pt fine particles of the PtRu-based catalyst shown in FIG. 7. 図８に示すＰｔＲｕ系触媒のＰｔ微粒子の平均粒径分布を示す図である。FIG. 9 is a diagram showing an average particle size distribution of Pt fine particles of the PtRu-based catalyst shown in FIG. 8.

符号の説明Explanation of symbols

２ Ｒｕ金属微粒子
１０ 担体 2 Ru metal fine particles 10 Carrier

Claims (3)

担体表面にＲｕ金属微粒子が分散し、該Ｒｕ金属微粒子の表面に平均粒径０．５〜１５ｎｍのＰｔ金属微粒子が分散し、かつ前記Ｐｔ金属微粒子の平均粒径の標準偏差が７〜１３であるＰｔＲｕ系触媒。 Ru metal fine particles are dispersed on the surface of the carrier, Pt metal fine particles having an average particle diameter of 0.5 to 15 nm are dispersed on the surface of the Ru metal fine particles, and the standard deviation of the average particle diameter of the Pt metal fine particles is 7 to 13 A PtRu catalyst. 表面にチオール基を有する担体と、Ｒｕ前駆体と、Ｐｔ前駆体とを共存させた状態で、前記Ｒｕ前駆体及びＰｔ前駆体を還元させ、前記担体表面にＲｕ金属微粒子とＰｔ金属微粒子とを担持させる工程と、
前記Ｒｕ金属微粒子とＰｔ金属微粒子とを担持させた担体を、非酸化雰囲気で熱処理する工程とを有するＰｔＲｕ系触媒の製造方法。 In a state where a carrier having a thiol group on the surface, a Ru precursor, and a Pt precursor coexist, the Ru precursor and the Pt precursor are reduced, and Ru metal fine particles and Pt metal fine particles are formed on the carrier surface. A supporting step;
A method for producing a PtRu-based catalyst, comprising a step of heat-treating a support carrying the Ru metal fine particles and Pt metal fine particles in a non-oxidizing atmosphere. 前記熱処理の温度を３００℃未満とする請求項２記載のＰｔＲｕ系触媒の製造方法。 The method for producing a PtRu-based catalyst according to claim 2, wherein the temperature of the heat treatment is less than 300 ° C.
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JP2010010623A (en) * 2008-06-30 2010-01-14 Chubu Electric Power Co Inc Electrochemical capacitor and its production process
JP2010236989A (en) * 2009-03-31 2010-10-21 Toyota Motor Corp Method of creating particle size distribution model, method of predicting degradation of fuel cell catalyst using the method of creating particle size distribution model, and method of controlling fuel cell using the method of predicting degradation of fuel cell catalyst
JP2011065792A (en) * 2009-09-16 2011-03-31 Hitachi Ltd PtRu-BASED CATALYST, MANUFACTURING METHOD OF THE SAME, MEMBRANE ELECTRODE ASSEMBLY, AND FUEL CELL

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010010623A (en) * 2008-06-30 2010-01-14 Chubu Electric Power Co Inc Electrochemical capacitor and its production process
JP2010236989A (en) * 2009-03-31 2010-10-21 Toyota Motor Corp Method of creating particle size distribution model, method of predicting degradation of fuel cell catalyst using the method of creating particle size distribution model, and method of controlling fuel cell using the method of predicting degradation of fuel cell catalyst
US8660827B2 (en) 2009-03-31 2014-02-25 Toyota Jidosha Kabushiki Kaisha Method of creating particle size distribution model, method of predicting degradation of fuel cell catalyst using the method of creating particle size distribution model, and method of controlling fuel cell using the method of predicting degradation of fuel cell catalyst
US8843355B2 (en) 2009-03-31 2014-09-23 Toyota Jidosha Kabushiki Kaisha Method of controlling fuel cell using the method of predicting degradation of fuel cell catalyst
US9002689B2 (en) 2009-03-31 2015-04-07 Toyota Jidosha Kabushiki Kaisha Method of predicting degradation of fuel cell catalyst using the method of creating particle size distribution model
JP2011065792A (en) * 2009-09-16 2011-03-31 Hitachi Ltd PtRu-BASED CATALYST, MANUFACTURING METHOD OF THE SAME, MEMBRANE ELECTRODE ASSEMBLY, AND FUEL CELL

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