JP2004087426A - Conductive polymer-alloy cluster conjugate electrode and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive polymer-alloy cluster conjugate electrode for a solid polymer fuel cell in which nanoscale alloy particulates are homogeneously dispersed in an electroconductive polymer without causing agglomeration. <P>SOLUTION: This electroconductive polymer-alloy cluster conjugate electrode is constituted such that a metal complex containing a metal complex (A) expressed by the following formula 1 (in the formula, R is a methyl group or the like, X is a triphenylsiloxo group or the like, and M is platinum or palladium), and a metal complex (B) having one or more organic ligands selected from 1,5-cyclooctadiene, 1,3,5-cyclooctatriene or the like (however, a metal element is a different metal from the M) is made to contact hydrogen and to be reduced, and the obtained particulates are made to be homogeneously dispersed in the conductive polymer. <P>COPYRIGHT: (C)2004,JPO

Description

【００１８】
（式中、Ｒは、メチル基、エチル基またはフェニル基であり、Ｘは、トリフェニルシロキソ基、トリフェニルカルビノキシ基またはフェノキソ基であり、Ｍは、白金またはパラジウムである）で表される金属錯体（Ａ）を、水素を用いて還元して得られる微粒子を含む、導電性高分子−合金クラスタ複合体電極である。
【００１９】
本発明はまた、合金微粒子が、この金属錯体（Ａ）と、メチル基、エチル基、１，５−シクロオクタジエン、１，３，５−シクロオクタトリエン、ジベンジリデンアセトン、アセタト基、アセチルアセタト基およびトリフェニルシロキソ基から選択される１以上の有機配位子を有する金属錯体（Ｂ）（但し、金属元素は、白金、金、銀、銅、パラジウム、ロジウム、ニッケル、亜鉛、チタン、ルテニウム、鉄、コバルト、モリブデン、錫、レニウム、バナジウムまたはクロムであり、前記Ｍとは異なる金属である）と、を含む金属錯体を、水素を用いて還元して得られる微粒子である、導電性高分子−合金クラスタ複合体電極である。
【００２０】
１００ｎｍ以下の金属微粒子を導電性高分子の溶液中に均一に分散させるために、本発明では、金属錯体（Ａ）と、金属錯体（Ａ）とは異なる金属を含有する金属錯体（Ｂ）とを有機溶媒中に溶解した導電性高分子溶液中に加え、この溶液をまたは有機溶媒を留去した後の混合物を水素と接触させて、金属錯体（Ａ）と金属錯体（Ｂ）とを還元する。
【００２１】
【発明の実施の形態】
以下に、本発明に係る導電性高分子−合金クラスタ複合体電極について、具体的に説明する。
【００２２】
本発明の導電性高分子−合金クラスタ複合体電極では、２種類の金属錯体（Ａ）および（Ｂ）を原料として、合金微粒子を調製する。金属錯体（Ａ）は、下記式：
【００２３】
【化４】

【００２４】
（式中、Ｒは、メチル基、エチル基またはフェニル基であり、Ｘは、トリフェニルシロキソ基、トリフェニルカルビノキシ基またはフェノキソ基であり、Ｍは、白金またはパラジウムである）で表わせる金属種を１種含む錯体である。金属種が同一である限り、上記式中のＲまたはＸが異なる錯体を２以上併用することができる。金属錯体（Ａ）は、例えば、Ｉｎｏｒｇａｎｉｃａ　Ｃｈｅｍｉｃａ　Ａｃｔａ　２９４（１９９９）　ｐｐ．２６６−２７４で示されている方法により製造することができる。
【００２５】
また金属錯体（Ｂ）は、メチル基、エチル基、１，５−シクロオクタジエン（以下「ｃｏｄ」という）、１，３，５−シクロオクタトリエン（以下「ｃｏｔ」という）、ジベンジリデンアセトン、アセタト基、アセチルアセタト基およびトリフェニルシロキソ基から選択される１以上の有機配位子を有する金属錯体（Ｂ）（但し、金属元素は、白金、金、銀、銅、パラジウム、ロジウム、ニッケル、亜鉛、チタン、ルテニウム、鉄、コバルト、モリブデン、錫、レニウム、バナジウムまたはクロムであり、前記Ｍとは異なる金属である）である。金属種が金属錯体（Ａ）の金属種と異なるかぎり、２以上の錯体であることができる。
【００２６】
金属錯体（Ｂ）は、例えば、（ｃｏｄ）（ｃｏｔ）ルテニウムは、Ｊ．　Ｃｈｅｍ．　Ｓｏｃ．，　Ｄａｌｔｏｎ　Ｔｒａｎｓ．　（１９８０）　ｐ１９６１に記載された方法で、ビス（ジベンジリデンアセトン）白金は、Ｊ．　Ｃｈｅｍ．　Ｓｏｃ．，　Ｃｈｅｍ．　Ｃｏｍｍｕｎ．　（１９７１）　ｐ９８２に記載された方法で、ビス（ジベンジリデンアセトン）パラジウムは、Ｊ．　Ｏｒｇａｎｏｍｅｔ．　Ｃｈｅｍ．　６５（１９７４）　ｐ２５３に記載された方法で、製造することができる。
【００２７】
金属錯体（Ａ）と金属錯体（Ｂ）との物質量比は、２０：１〜１：１が好ましく、１０：１〜２：１がより好ましい。金属錯体（Ａ）と金属錯体（Ｂ）の比がこの範囲にあると、触媒作用の低下あるいは合金触媒の効果の低下を防止することができる。
【００２８】
本発明は、有機溶媒に溶解した導電性高分子中に、この金属触媒（Ａ）および（Ｂ）を加える。導電性高分子を溶解させる有機溶媒としては、非プロトン性溶媒、またははプロトン性溶媒であってもフェノール系の溶媒であれば用いることができる。例えば、非プロトン性溶媒としては、四塩化炭素、アセトン、ジメチルスルホキシド、アセトニトリル、ジメチルホルムアミド、テトラヒドロフラン、ジグリム、２−ブタノン、１−メチル−２−ピロリドン、シクロヘキサノン、トルエン、クロロホルム等が、フェノール系のプロトン性溶媒としてはメタクレゾール等があげられる。これらの有機溶媒は、単独で又は２以上を併用して使用することができる。またこれらの有機溶媒は、金属錯体を還元する条件で金属錯体が完全に溶解する量以上、かつ金属錯体と導電性高分子を混ぜ合わせる条件で導電性高分子が有機溶媒に溶解し、導電性高分子の固相が消失する量以上の溶媒を使用する。溶解は、例えば１００℃以下の温度で行うことができる。
【００２９】
本発明では、高分子−合金クラスタ複合体電極として、導電性高分子を使用する。電極の用途において、金属微粒子の触媒を担持する高分子材料として、非電導性の高分子と導電性高分子が考えられる。一般に非導電性の高分子でも金属を十数重量％から数十重量％まで含有させることによって導電性の材料を得ることができる。しかしながら、非導電性高分子を金属微粒子の分散マトリックスとして用いて電極を作成し酸化反応に用いると、流れる電流は微量である。一方、導電性高分子を担体に用いると、アノード反応により大きな電流が流れ、金属微粒子上で酸化反応が進み、高い触媒活性を得ることができる。
【００３０】
本発明に使用する導電性高分子としては、特に限定されず、例えば、ポリアセチレン、ポリチアジル、ポリピロール、ポリチオフェン、ポリフラン、ポリセレノフェン、ポリテルロフェン、ポリイソチオナフテン、ポリイソチオフェンビニレン、ポリアズレン、ポリインデン、ポリインドール、ポリフェニレン、ポリナフテン、ポリアントラセン、ポリアニリン、ポリアセンとそれらの置換体等があげられる。これらの導電性高分子は、単独で又は２以上を併用して使用することができる。
【００３１】
導電性高分子の量は、金属錯体（Ａ）および金属錯体（Ｂ）の合計量１モルに対し、０．４〜１５０ｃｍ^３が好ましく、０．７〜１００ｃｍ^３がより好ましい。金属錯体の合計量に対して導電性高分子の量が少ないと、合金微粒子の凝集化が起こり、触媒能力が低下するからである。
【００３２】
金属錯体（Ａ）および（Ｂ）は、有機溶媒中に溶解した導電性高分子中に、固体状態で加えて溶解させてもよいし、またはこれらの錯体を同じ有機溶媒中に一旦溶解させて、溶液状態で高分子溶液に加えることもできる。このとき、これらの金属錯体を溶解する溶媒は、導電性高分子を溶解する有機溶媒と同一であっても、また異なってもよく、さらに金属錯体ごとに有機溶媒を変えてもよい。なお、金属錯体（Ｂ）の場合、金属錯体に溶媒が配位していてもよい。
【００３３】
一方、導電性高分子−合金クラスタ複合体を導電体上に担持させる場合は、上記で得た導電性高分子−錯体溶液を導電体上に塗布し、溶媒を留去することによって錯体を含む導電性高分子を導電体上に担持させる。
【００３４】
導電体としては特に限定されず、金、銀、銅、鉄等の金属、黒鉛等の炭素、酸化インジウムスズまたは導電性高分子等が例示できる。これらの導電体は、単独でまたは２以上併用して使用することもできる。
【００３５】
次に、金属錯体（Ａ）および（Ｂ）と導電性高分子が溶解した有機溶媒との混合物を、水素と接触させて、金属錯体（Ａ）および（Ｂ）を還元すると、還元反応によりゼロ価の合金微粒子が生成する。このとき、導電性高分子が溶解した溶媒を留去した後に水素による還元を行うと、金属錯体の反応にともなう物質移動が抑制されるので、合金粒子の微細化が進み好ましい。溶媒を留去する方法は、真空留去、１００℃以下の加熱、窒素等の不活性雰囲気下での自然乾燥、またはこれらの方法を併用することができる。
【００３６】
水素還元温度は、−５０℃以上１００℃以下が好ましく、−３０℃以上６０℃以下がより好ましい。−５０℃以上であると、還元反応が非常に遅くなるか、または還元反応が停止することが防止でき、また、１００℃以下であると、生成する合金微粒子の凝集が起こり難く、粒子径の粗大化を防止できる。
【００３７】
水素還元は減圧下、常圧または加圧下で、還元に必要な水素量を供給することによって行うことできる。
【００３８】
また、導電性高分子−金属錯体溶液を水素と接触させて、金属錯体を還元して導電性高分子溶液−合金クラスタ複合体とした後、上記の導電体上にキャストすることも可能である。
【００３９】
【実施例】
以下に本発明を実施例により説明するが、本発明はこれらの実施例に限定されるものではない。また、金属錯体の調製および導電性高分子−合金クラスタ複合体電極の作製は、特に断らない限り窒素雰囲気下で行った。使用した導電性高分子であるポリアニリンは、重量平均分子量（ポリスチレン基準）５６０００の高分子を使用した。
【００４０】
得られた導電性高分子−合金クラスタ複合体電極は、サイクリックボルタンメトリーによって電極特性を評価した。ここでサイクリックボルタンメトリーは、基準電極を銀−塩化銀電極とし、電解液として０．５ｍｏｌ／Ｌの硫酸２５ｍＬを使用し、電圧を０．５ｍＶ／秒で変化させて測定した。また、合金微粒子の粒子径は、走査型プローブ顕微鏡または透過電子顕微鏡を用いて測定した。
【００４１】
メチル（トリフェニルシロキソ）（ｃｏｄ）白金の調製
窒素で置換したシュレンクに、ＰｔＭｅＣｌ（ｃｏｄ）（ここで「Ｍｅ」はメチル基を表す）３４９．２ｍｇ、ＮａＳｉＰｈ_３３５６．５ｍｇおよびテトラヒドロフラン１５ｍＬを入れ、室温で３時間撹拌した。溶媒を真空留去し、トルエンで抽出した。濾過を行った後、再び真空留去し、残った固体からジエチルエーテルを用いて抽出した。ヘキサンを加え、無色の固体である標記化合物：メチル（トリフェニルシロキソ）（ｃｏｄ）白金（金属錯体（Ａ））３６３．１ｍｇを得た。
【００４２】
（ｃｏｄ）（ｃｏｔ）ルテニウムの調製
亜鉛粉末８０．０ｇに、メタノール７０ｍＬおよび１，５−シクロオクタジエン１４０ｍＬを加えた。７０℃で還流しながら、メタノール７０ｍＬに溶解したＲｕＣｌ_３・３Ｈ_２Ｏ７．０３ｇを滴下した。滴下終了後３時間加熱還流した。還流終了後、濾過を行い赤色の溶液を得た。溶媒を真空留去した後、ヘキサンで抽出を行い、得られた赤色の溶液を中性アルミナカラムで精製した。さらに、ペンタンを用いて再結晶を行い、黄色の結晶である標記物質：（ｃｏｄ）（ｃｏｔ）ルテニウム（金属錯体（Ｂ））５．５１ｇを得た。
【００４３】
実施例１（白金−ルテニウム合金触媒電極）
ポリアニリン１０ｍｇを１−メチル−２−ピロリドン１００ｍＬに溶解した。上記調製で得たメチル（トリフェニルシロキソ）（ｃｏｄ）白金５９．４ｍｇおよびＲｕ（ｃｏｄ）（ｃｏｔ）３．２ｍｇに、このポリアニリン１−メチル−２−ピロリドン溶液２ｍＬを加えて溶解した。この溶液の一部を、酸化インジウムスズの基板に塗布し、真空乾燥した。次いで常圧、室温で水素雰囲気下に２４時間曝すことによって、導電性高分子−合金クラスタ複合体電極を得た。この電極は、膜厚１０μｍ、ポリアニリン５μｇ／ｃｍ^２、塗布面積１ｃｍ^２であり、合金中のＲｕは０．０２ｍｇ／ｃｍ^２、Ｐｔは０．４ｍｇ／ｃｍ^２であった。
【００４４】
得られた導電性高分子−合金クラスタ複合体電極を用いて、電解液に一酸化炭素を１０分間吹き込むことにより一酸化炭素を溶解し、一酸化炭素雰囲気下でサイクリックボルタングラムの測定を行った。結果を図１に示す。また、得られた電極を用いて、電解液中にメタノールの非存在下および０．５ｍｏｌ／Ｌの存在下でサイクリックボルタングラムを測定した。結果を図２に示す。
【００４５】
実施例２（白金−ルテニウム合金触媒電極）
上記調製で得たＲｕ（ｃｏｄ）（ｃｏｔ）を６．３ｍｇ使用した以外は、実施例１と同様にして導電性高分子−合金クラスタ複合体電極を得た。この電極は、膜厚１０μｍ、ポリアニリン５μｇ／ｃｍ^２、塗布面積１ｃｍ^２であり、合金中のＲｕは０．０４ｍｇ／ｃｍ^２、Ｐｔは０．４ｍｇ／ｃｍ^２であった。得られた導電性高分子−合金クラスタ複合体電極を用いて、実施例１と同様にして、一酸化炭素雰囲気下でサイクリックボルタングラムの測定を行った。結果を図１に示す。
【００４６】
実施例３（白金−ルテニウム合金触媒電極）
上記調製で得たＲｕ（ｃｏｄ）（ｃｏｔ）を１５．６ｍｇ使用した以外は、実施例１と同様にして導電性高分子−合金クラスタ複合体電極を得た。この電極は、膜厚１０μｍ、ポリアニリン５μｇ／ｃｍ^２、塗布面積１ｃｍ^２であり、合金中のＲｕは０．１ｍｇ／ｃｍ^２、Ｐｔは０．４ｍｇ／ｃｍ^２であった。得られた合金微粒子の粒径は、２０〜３０ｎｍであった。こうして得られた導電性高分子−合金クラスタ複合体電極を用いて、実施例１と同様にして、一酸化炭素雰囲気下でサイクリックボルタングラムの測定を行った。結果を図１に示す。
【００４７】
比較例１（白金触媒電極）
ポリアニリン１０ｍｇを１−メチル−２−ピロリドン１００ｍＬに溶解した。上記調製で得たメチル（トリフェニルシロキソ）（ｃｏｄ）白金３０ｍｇに、このポリアニリン１−メチル−２−ピロリドン溶液１ｍＬを加えて溶解した。この溶液の一部を、酸化インジウムスズの基板に塗布し、真空乾燥した。次いで常圧、室温で水素雰囲気下に２４時間曝すことによって導電性高分子−金属（白金）クラスタ複合体電極を得た。この電極は、膜厚１０μｍ、ポリアニリン５μｇ／ｃｍ^２、塗布面積１ｃｍ^２、Ｐｔ０．４ｍｇ／ｃｍ^２であった。また、白金微粒子の粒子径は１２ｎｍであった。
【００４８】
得られた導電性高分子−金属（白金）クラスタ複合体電極を用いて、実施例１と同様にして、一酸化炭素雰囲気下でサイクリックボルタングラムおよびメタノールの非存在下、存在下でサイクリックボルタングラムを測定した。結果を図１、図２に示す。
【００４９】
図１から明らかなように、本発明の導電性高分子−合金クラスタ複合体電極は、白金のみを含む導電性高分子−金属クラスタ複合体電極を用い測定したサイクリックボルタングラムに比べて、Ｐｔ−Ｒｕ合金触媒とすることにより、酸化電流ピークを約０．１〜０．２Ｖ低電圧側にすることができた。また、図２に示すように、導電性高分子−合金クラスタ複合体電極は、白金のみを含む導電性高分子−金属クラスタ複合体電極よりも、メタノールの存在下で、酸化電流ピークが０．５ｍＡ増大した。
【００５０】
【発明の効果】
本発明の導電性高分子−合金クラスタ複合体電極は、ナノスケールの合金微粒子を凝集を起こさずに導電性高分子中に分散したものであり、これにより、白金のみを含む導電性高分子−金属クラスタ複合体電極に比べて、触媒上での電極反応が促進し、また合金化により一酸化炭素に被毒され難くなる等の触媒機能を改善するという効果を奏する。
【図面の簡単な説明】
【図１】本発明の実施例１〜３および比較例の導電性高分子−合金（金属）複合体電極の一酸化炭素雰囲気下でのサイクリックボルタングラムの測定結果を示す図である。
【図２】本発明の実施例１および比較例の導電性高分子−合金（金属）複合体電極における、メタノールの非存在下および０．５ｍｏｌ／Ｌの存在下電解液中でのサイクリックボルタングラムの測定結果を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive polymer-alloy cluster composite electrode in which alloy fine particles of 100 nm or less are dispersed in a conductive polymer, and a method for producing the same. More specifically, a conductive polymer-alloy cluster composite in which alloy fine particles obtained by reducing a metal complex, which can be applied as an electrode, a fuel cell catalyst or a sensor, are uniformly dispersed in a conductive polymer. The present invention relates to an electrode or a conductive polymer-alloy cluster composite electrode in which the composite is supported on a conductor and a method for producing the same.
[0002]
[Prior art]
As other methods for obtaining metal fine particles uniformly dispersed in a polymer, Japanese Patent No. 261888 and Japanese Patent No. 2521638 disclose a method of forming an unstable polymer layer by a method such as heat treatment or desolvation. A method has been disclosed in which a metal vapor-deposited film is formed on the surface of a molecular film and the film is thermally stabilized, so that the metal is finely divided and uniformly dispersed in a polymer. Japanese Patent Application Laid-Open No. Hei 10-273774 discloses a method in which a metal is vapor-deposited on a polymer or oligomer having a specific functional group and then heated to disperse metal fine particles. Discloses a method of obtaining a metal-polymer dispersion by dissolving a noble metal complex in a monomer, followed by polymerization and solidification.
[0003]
In addition to the problem that it is difficult to increase the dispersion concentration of the metal fine particles, these methods are limited to avoiding aggregation of the metal fine particles caused by polymerization conditions, reduction conditions, and the like, and to using a polymer having a specific functional group. Had problems.
[0004]
On the other hand, in recent years, fuel cells have attracted attention, and in particular, polymer electrolyte fuel cells have attracted attention. This polymer electrolyte fuel cell can operate at a lower temperature and has a higher energy density than a phosphoric acid fuel cell, a molten carbonate fuel cell, or a solid electrolytic fuel cell. Therefore, it is considered to be promising as a power source for a fuel cell hybrid vehicle because it is suitable for a mobile power source and a small-capacity power source.
[0005]
A polymer electrolyte fuel cell uses hydrogen or a hydrocarbon such as methanol or natural gas as a fuel, and uses a polymer ion exchange membrane represented by a perfluorosulfonic acid membrane as an electrolyte. This is a device that joins an anode electrode and a cathode electrode and supplies hydrogen to the anode and oxygen to the cathode to cause an electrochemical reaction to generate power. The electrodes are composed of an electron conductor, a catalyst substance and a proton conductor. As the catalyst material, zero-valent platinum or a platinum-ruthenium alloy which is an active metal is used, and these catalyst materials are supported on carbon particles as an electron conductor. The same polymer as the ion exchange membrane covers the catalyst substance and the carbon particles as a binder polymer, and plays a role of a proton conductor.
[0006]
The catalyst in the electrode contributes to the promotion of the next reaction.
Anode: H ₂ → 2H ⁺ + 2e ⁻
Cathode: 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O
Total reaction: H ₂ + 1 / 2O ₂ → H ₂ O
[0007]
The catalyst promotes the anodic reaction at the gas-liquid-solid three-phase interface in the fuel cell, thereby oxidizing hydrogen to generate electric current, and is an important factor directly controlling power generation efficiency. is there. For this reason, the catalyst is required to support metal particles of appropriate particles on carbon particles, and that the metal particles be an active zero-valent metal. By satisfying these requirements, the amount of platinum in the entire catalyst can be reduced, so that the cost of the apparatus can be reduced.
[0008]
On the other hand, when hydrocarbons are used as fuel for fuel cells, the platinum catalyst is poisoned by carbon monoxide as an oxide generated from the fuel. Prevent the decline. When a single metal is used as the catalyst metal, this metal is generally prepared by mixing a metal chloride with carbon particles as a carrier and reducing the mixture. However, when an alloy is used as the metal for the catalyst, aggregation of the reduced alloy fine particles is likely to occur, which makes the preparation difficult.
[0009]
The alloy catalyst is required to be alloy fine particles having an appropriate particle size not too large and not too small, and to be a zero-valent active alloy. Alloy catalysts are generally prepared by melting and mixing two or more metals at a high temperature to form an alloy, a method of thermally decomposing in a reducing atmosphere to form an alloy, or a method of alloying by a physical method such as sputtering. Has been manufactured by However, in these alloying methods, since the metal to be alloyed is once melted or exposed to a high temperature, it is difficult to obtain an alloy of fine particles. Furthermore, since these methods require a high-temperature process, there is a problem that they are not suitable for producing a polymer-alloy cluster composite material having an organic polymer or the like as a matrix.
[0010]
JP-A-2001-72881 discloses a method for producing fine particles of a single metal, in which a solution obtained by dissolving a thermoplastic polymer or a thermosetting polymer in an organic solvent is combined with an MO-Si bond (M is a metal atom). the organic metal complex MMe a (OSiPh ₃₎ (cod) were dispersed with, for example ambient temperature, by thereafter hydrogen contacted at atmospheric pressure to reduce the metal complex uniformly in a polymer matrix nanoscale metal clusters A method for producing a dispersed polymer-metal cluster composite is disclosed. However, this method is a method of obtaining a single kind of metal fine particles, and it is completely described whether alloy fine particles can be produced or agglomeration of the produced alloy fine particles can be avoided when an alloy catalyst is used. It has not been.
[0011]
JP-A-2000-12040 discloses a method of reducing chloroplatinic acid or the like with a reducing agent of hydrogen gas or anhydrous hydrazine as a catalyst substance used for an electrode for a polymer electrolyte fuel cell. . This method not only produces a platinum catalyst which is a single metal, but also makes it possible to form a platinum-ruthenium alloy using a mixture of a platinum compound and a ruthenium compound. However, regarding metal fine particles having an appropriate particle diameter required for a catalyst, not only alloys but also single metals have not been studied at all, and it is not clear whether alloy fine particles can be produced.
[0012]
Further, an alloy colloid solution is prepared by simultaneously adding two or more metal salts dissolved in water to an aqueous solution of a reducing agent comprising an organic acid such as sodium citrate, and the alloy colloid particles are mixed with a carrier powder. A method for producing an alloy catalyst to be supported on a polymer and a method for producing a polymer electrolyte fuel cell using the same are disclosed in JP-A-2001-224969. According to this method, alloy fine particles having an average particle diameter of 2 to 5 nm can be produced. However, since an aqueous solution is used as a solvent, a wide range of polymers cannot be dissolved, and alloy fine particles are dissolved in the polymer. It is difficult to produce a uniformly dispersed composite, and there is a problem of poor versatility.
[0013]
By supporting metal (alloy) fine particles on a polymer, it is possible to easily support a substrate or the like by using a technique such as spin coating or printing by a casting method, and it is easy to achieve a film thickness, a metal content, and a carrier amount. Can be controlled. In particular, in the case of electrodes using ITO (indium tin oxide) as a substrate, there is a concern that the conductivity may be reduced due to a change in the molecular arrangement and bonding state of ITO due to firing. A method in which metal (alloy) fine particles are supported on a polymer material at a relatively low temperature, which cannot be adopted, is essential. In addition, non-conductive polymers and conductive polymers can be considered as polymers for supporting metal (alloy) fine particles. In the case of a non-conductive polymer, it is possible to obtain a conductive material by adding a large amount of a dozen or more to several tens of weight percent of a conductive fine-particle metal (alloy), but it is possible to obtain a conductive material. The flowing current is very small and has a practical problem. By comparison, conductive polymer typified by polyacetylene, some have a 1 to 10 5 S / ^cm metal and same high conductivity. However, there has been no attempt to use a conductive polymer as a carrier.
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems of the prior art relating to the alloy catalyst or an electrode for a polymer electrolyte fuel cell using the alloy catalyst. An electrode, a fuel cell catalyst, a conductive polymer-alloy cluster composite electrode that can be applied as a sensor, or an electrode that promotes an electrode reaction on a catalyst by uniformly dispersing It is an object of the present invention to provide a conductive polymer-alloy cluster composite electrode supported on a substrate and a method for producing the same. Specifically, the electrode obtained in the present invention can be easily reduced using hydrogen, the obtained alloy fine particles can obtain nanoscale-level fine particles without causing aggregation, and the hydrogen reduction temperature range is It is characterized by being near room temperature so as to avoid agglomeration of fine particles, having a high proportion of an alloy that can be reduced to a zero-valent metal, and having a simple apparatus used for the reduction reaction.
[0015]
[Means for Solving the Problems]
The present invention for solving the above problems is a conductive polymer-alloy cluster composite electrode in which alloy fine particles of 100 nm or less are dispersed in a conductive polymer. The present invention is also a conductive polymer-alloy composite electrode in which the composite is supported on a conductor.
[0016]
The present invention further provides the alloy fine particles having the following formula:
[0017]
Embedded image

[0018]
(Wherein, R is a methyl group, an ethyl group or a phenyl group, X is a triphenylsiloxo group, a triphenylcarbinoxy group or a phenoxo group, and M is platinum or palladium). A conductive polymer-alloy cluster composite electrode containing fine particles obtained by reducing the metal complex (A) to be used with hydrogen.
[0019]
According to the present invention, the alloy fine particles may be prepared by combining the metal complex (A) with a methyl group, an ethyl group, 1,5-cyclooctadiene, 1,3,5-cyclooctatriene, dibenzylideneacetone, an acetate group, or an acetylacetate group. And a metal complex (B) having one or more organic ligands selected from triphenylsiloxo groups (where the metal element is platinum, gold, silver, copper, palladium, rhodium, nickel, zinc, titanium, ruthenium) , Iron, cobalt, molybdenum, tin, rhenium, vanadium or chromium, which is a metal different from the above M). It is a molecule-alloy cluster composite electrode.
[0020]
In order to uniformly disperse metal fine particles of 100 nm or less in a conductive polymer solution, in the present invention, a metal complex (A) and a metal complex (B) containing a metal different from the metal complex (A) are used. Is added to a conductive polymer solution dissolved in an organic solvent, and this solution or a mixture obtained by distilling off the organic solvent is brought into contact with hydrogen to reduce the metal complex (A) and the metal complex (B). I do.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the conductive polymer-alloy cluster composite electrode according to the present invention will be specifically described.
[0022]
In the conductive polymer-alloy cluster composite electrode of the present invention, alloy fine particles are prepared using two types of metal complexes (A) and (B) as raw materials. The metal complex (A) has the following formula:
[0023]
Embedded image

[0024]
(Wherein R is a methyl group, an ethyl group or a phenyl group, X is a triphenylsiloxo group, a triphenylcarbinoxy group or a phenoxo group, and M is platinum or palladium). Complex containing one kind of metal species. As long as the metal species is the same, two or more complexes having different R or X in the above formula can be used in combination. The metal complex (A) is described, for example, in Inorganica Chemical Acta 294 (1999) pp. 266-274.
[0025]
The metal complex (B) includes a methyl group, an ethyl group, 1,5-cyclooctadiene (hereinafter, referred to as “cod”), 1,3,5-cyclooctatriene (hereinafter, referred to as “cot”), dibenzylideneacetone, A metal complex (B) having one or more organic ligands selected from an acetato group, an acetylacetato group and a triphenylsiloxo group (provided that the metal element is platinum, gold, silver, copper, palladium, rhodium, nickel, Zinc, titanium, ruthenium, iron, cobalt, molybdenum, tin, rhenium, vanadium or chromium, and is a metal different from M). As long as the metal species is different from the metal species of the metal complex (A), it can be two or more complexes.
[0026]
The metal complex (B) is, for example, (cod) (cot) ruthenium is described in J. Am. Chem. Soc. , Dalton Trans. (1980) Bis (dibenzylideneacetone) platinum was prepared according to the method described in p1961. Chem. Soc. Chem., Chem. Commun. (1971) Bis (dibenzylideneacetone) palladium was prepared according to the method described in p982. Organomet. Chem. 65 (1974), page 253.
[0027]
The substance ratio of the metal complex (A) to the metal complex (B) is preferably from 20: 1 to 1: 1 and more preferably from 10: 1 to 2: 1. When the ratio of the metal complex (A) to the metal complex (B) is within this range, it is possible to prevent a reduction in the catalytic action or a reduction in the effect of the alloy catalyst.
[0028]
In the present invention, the metal catalysts (A) and (B) are added to a conductive polymer dissolved in an organic solvent. As the organic solvent for dissolving the conductive polymer, an aprotic solvent or a protic solvent can be used as long as it is a phenol-based solvent. For example, as the aprotic solvent, carbon tetrachloride, acetone, dimethyl sulfoxide, acetonitrile, dimethylformamide, tetrahydrofuran, diglyme, 2-butanone, 1-methyl-2-pyrrolidone, cyclohexanone, toluene, chloroform and the like, phenol-based Examples of the protic solvent include metacresol. These organic solvents can be used alone or in combination of two or more. In addition, these organic solvents are used in an amount not less than the amount in which the metal complex is completely dissolved under the condition of reducing the metal complex, and the conductive polymer is dissolved in the organic solvent under the condition of mixing the metal complex and the conductive polymer. Use more solvent than the amount by which the solid phase of the polymer disappears. The dissolution can be performed, for example, at a temperature of 100 ° C. or less.
[0029]
In the present invention, a conductive polymer is used as the polymer-alloy cluster composite electrode. In the use of the electrode, non-conductive polymers and conductive polymers are considered as the polymer material supporting the catalyst of the metal fine particles. In general, even a non-conductive polymer can obtain a conductive material by containing a metal in an amount of more than ten to several tens of weight%. However, when an electrode is prepared using a non-conductive polymer as a dispersion matrix of metal fine particles and used for an oxidation reaction, a small amount of current flows. On the other hand, when a conductive polymer is used for the carrier, a large current flows due to the anodic reaction, the oxidation reaction proceeds on the metal fine particles, and high catalytic activity can be obtained.
[0030]
The conductive polymer used in the present invention is not particularly limited. , Polyindole, polyphenylene, polynaphthene, polyanthracene, polyaniline, polyacene, and their substituted products. These conductive polymers can be used alone or in combination of two or more.
[0031]
The amount of the conductive polymer is preferably 0.4 to 150 cm ³ , more preferably 0.7 to 100 cm ³ , based on 1 mol of the total amount of the metal complex (A) and the metal complex (B). This is because if the amount of the conductive polymer is smaller than the total amount of the metal complex, agglomeration of the alloy fine particles occurs, and the catalytic ability decreases.
[0032]
The metal complexes (A) and (B) may be added and dissolved in a solid state in a conductive polymer dissolved in an organic solvent, or these complexes may be once dissolved in the same organic solvent. Alternatively, it can be added to the polymer solution in a solution state. At this time, the solvent for dissolving these metal complexes may be the same as or different from the organic solvent for dissolving the conductive polymer, and the organic solvent may be changed for each metal complex. In the case of the metal complex (B), a solvent may be coordinated with the metal complex.
[0033]
On the other hand, when the conductive polymer-alloy cluster complex is supported on a conductor, the conductive polymer-complex solution obtained above is applied on the conductor, and the solvent is distilled off to contain the complex. A conductive polymer is supported on a conductor.
[0034]
The conductor is not particularly limited, and examples thereof include metals such as gold, silver, copper, and iron; carbon such as graphite; indium tin oxide; and conductive polymers. These conductors can be used alone or in combination of two or more.
[0035]
Next, a mixture of the metal complexes (A) and (B) and an organic solvent in which the conductive polymer is dissolved is brought into contact with hydrogen to reduce the metal complexes (A) and (B). Valent alloy fine particles are produced. At this time, it is preferable to perform reduction with hydrogen after distilling off the solvent in which the conductive polymer is dissolved, since mass transfer accompanying the reaction of the metal complex is suppressed, and the alloy particles are refined, which is preferable. As a method for distilling off the solvent, vacuum distillation, heating at 100 ° C. or lower, natural drying under an inert atmosphere such as nitrogen, or a combination of these methods can be used.
[0036]
The hydrogen reduction temperature is preferably from -50C to 100C, more preferably from -30C to 60C. When the temperature is −50 ° C. or more, the reduction reaction becomes very slow or the reduction reaction can be prevented from being stopped. When the temperature is 100 ° C. or less, the alloy fine particles to be formed hardly aggregate, and the particle diameter is reduced. Coarsening can be prevented.
[0037]
Hydrogen reduction can be performed by supplying the amount of hydrogen required for reduction under reduced pressure, normal pressure, or increased pressure.
[0038]
Alternatively, the conductive polymer-metal complex solution may be brought into contact with hydrogen to reduce the metal complex to form a conductive polymer solution-alloy cluster composite, and then cast on the above conductor. .
[0039]
【Example】
Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. Preparation of the metal complex and preparation of the conductive polymer-alloy cluster composite electrode were performed in a nitrogen atmosphere unless otherwise specified. As the conductive polymer used, polyaniline used was a polymer having a weight average molecular weight (based on polystyrene) of 56,000.
[0040]
The electrode properties of the obtained conductive polymer-alloy cluster composite electrode were evaluated by cyclic voltammetry. Here, the cyclic voltammetry was measured by using a silver-silver chloride electrode as a reference electrode, using 25 mL of 0.5 mol / L sulfuric acid as an electrolytic solution, and changing the voltage at 0.5 mV / sec. The particle diameter of the alloy fine particles was measured using a scanning probe microscope or a transmission electron microscope.
[0041]
Preparation of Methyl (triphenylsiloxo) (cod) platinum In a Schlenk substituted with nitrogen, 349.2 mg of PtMeCl (cod) (where “Me” represents a methyl group), 356.5 mg of NaSiPh ₃ and 15 mL of tetrahydrofuran were put. And stirred at room temperature for 3 hours. The solvent was removed in vacuo and extracted with toluene. After filtration, the residue was vacuum distilled again, and the remaining solid was extracted with diethyl ether. Hexane was added to obtain 363.1 mg of the title compound as a colorless solid: methyl (triphenylsiloxo) (cod) platinum (metal complex (A)).
[0042]
(Cod) (cot) Preparation of ruthenium 70 mL of methanol and 140 mL of 1,5-cyclooctadiene were added to 80.0 g of zinc powder. While refluxing at 70 ° C., 7.03 g of RuCl ₃ .3H ₂ O dissolved in 70 mL of methanol was added dropwise. After completion of the dropwise addition, the mixture was heated under reflux for 3 hours. After the completion of the reflux, filtration was performed to obtain a red solution. After the solvent was distilled off in vacuo, extraction was performed with hexane, and the obtained red solution was purified with a neutral alumina column. Further, recrystallization was performed using pentane to obtain 5.51 g of the title substance: (cod) (cot) ruthenium (metal complex (B)) as yellow crystals.
[0043]
Example 1 (platinum-ruthenium alloy catalyst electrode)
10 mg of polyaniline was dissolved in 100 mL of 1-methyl-2-pyrrolidone. To 59.4 mg of platinum of methyl (triphenylsiloxo) (cod) and 3.2 mg of Ru (cod) (cot) obtained in the above preparation, 2 mL of this polyaniline 1-methyl-2-pyrrolidone solution was added and dissolved. A portion of this solution was applied to a substrate of indium tin oxide and vacuum dried. Then, the conductive polymer-alloy cluster composite electrode was obtained by exposing it to hydrogen atmosphere at normal pressure and room temperature for 24 hours. The electrode has a film thickness 10 [mu] m, polyaniline 5 [mu] g / cm ^2, a coating area 1 cm ^2, Ru in the alloy is 0.02 mg / ^cm 2, Pt was 0.4 mg / cm ^2.
[0044]
Using the obtained conductive polymer-alloy cluster composite electrode, carbon monoxide was dissolved in the electrolyte by blowing carbon monoxide for 10 minutes, and the cyclic voltammogram was measured in a carbon monoxide atmosphere. Was. The results are shown in FIG. Using the obtained electrode, a cyclic voltammogram was measured in the absence of methanol and in the presence of 0.5 mol / L in the electrolytic solution. FIG. 2 shows the results.
[0045]
Example 2 (platinum-ruthenium alloy catalyst electrode)
A conductive polymer-alloy cluster composite electrode was obtained in the same manner as in Example 1, except that 6.3 mg of Ru (cod) (cot) obtained in the above preparation was used. The electrode has a film thickness 10 [mu] m, polyaniline 5 [mu] g / cm ^2, a coating area 1 cm ^2, Ru in the alloy is 0.04 mg / ^cm 2, Pt was 0.4 mg / cm ^2. Using the obtained conductive polymer-alloy cluster composite electrode, a cyclic voltammogram was measured in a carbon monoxide atmosphere in the same manner as in Example 1. The results are shown in FIG.
[0046]
Example 3 (Platinum-ruthenium alloy catalyst electrode)
A conductive polymer-alloy cluster composite electrode was obtained in the same manner as in Example 1, except that 15.6 mg of Ru (cod) (cot) obtained in the above preparation was used. This electrode had a thickness of 10 μm, polyaniline of 5 μg / cm ² , and a coating area of 1 cm ^2. Ru in the alloy was 0.1 mg / cm ² and Pt was 0.4 mg / cm ² . The particle size of the obtained alloy fine particles was 20 to 30 nm. Using the conductive polymer-alloy cluster composite electrode thus obtained, a cyclic voltammogram was measured in a carbon monoxide atmosphere in the same manner as in Example 1. The results are shown in FIG.
[0047]
Comparative Example 1 (platinum catalyst electrode)
10 mg of polyaniline was dissolved in 100 mL of 1-methyl-2-pyrrolidone. 1 mL of this polyaniline 1-methyl-2-pyrrolidone solution was added to and dissolved in 30 mg of the methyl (triphenylsiloxo) (cod) platinum obtained in the above preparation. A portion of this solution was applied to a substrate of indium tin oxide and vacuum dried. Then, the conductive polymer-metal (platinum) cluster composite electrode was obtained by exposing to a hydrogen atmosphere at normal pressure and room temperature for 24 hours. This electrode had a thickness of 10 μm, a polyaniline of 5 μg / cm ² , an application area of 1 cm ² , and a Pt of 0.4 mg / cm ² . Further, the particle diameter of the platinum fine particles was 12 nm.
[0048]
Using the obtained conductive polymer-metal (platinum) cluster composite electrode, in the same manner as in Example 1, cyclic voltammogram and cyclic voltammogram in the absence of methanol and in the presence of methanol were used. The voltammogram was measured. The results are shown in FIGS.
[0049]
As can be seen from FIG. 1, the conductive polymer-alloy cluster composite electrode of the present invention has a higher Pt than a cyclic voltammogram measured using a conductive polymer-metal cluster composite electrode containing only platinum. By using a -Ru alloy catalyst, the oxidation current peak could be set to a low voltage side of about 0.1 to 0.2 V. Further, as shown in FIG. 2, the conductive polymer-alloy cluster composite electrode has an oxidation current peak of 0.1 in the presence of methanol more than the conductive polymer-metal cluster composite electrode containing only platinum. Increased by 5 mA.
[0050]
【The invention's effect】
The conductive polymer-alloy cluster composite electrode of the present invention is obtained by dispersing nanoscale alloy fine particles in a conductive polymer without causing aggregation, and thereby, a conductive polymer containing only platinum. Compared with the metal cluster composite electrode, the present invention has the effect of promoting the electrode reaction on the catalyst and improving the catalytic function such as being less likely to be poisoned by carbon monoxide due to alloying.
[Brief description of the drawings]
FIG. 1 is a diagram showing the measurement results of cyclic voltammograms in a carbon monoxide atmosphere of conductive polymer-alloy (metal) composite electrodes of Examples 1 to 3 of the present invention and Comparative Example.
FIG. 2 shows cyclic volatility in an electrolytic solution in the absence of methanol and in the presence of 0.5 mol / L at the conductive polymer-alloy (metal) composite electrode of Example 1 and Comparative Example of the present invention. It is a figure which shows the measurement result of a tangram.

Claims (7)

A conductive polymer-alloy cluster composite electrode, wherein alloy fine particles of 100 nm or less are dispersed in a conductive polymer. The conductive polymer-alloy cluster composite electrode according to claim 1, wherein the composite is carried on a conductor. The alloy fine particles have the following formula:

(Wherein, R is a methyl group, an ethyl group or a phenyl group, X is a triphenylsiloxo group, a triphenylcarbinoxy group or a phenoxo group, and M is platinum or palladium). The conductive polymer-alloy cluster composite electrode according to claim 1 or 2, comprising fine particles obtained by reducing the metal complex (A) using hydrogen. When the alloy fine particles are mixed with the metal complex (A), a methyl group, an ethyl group, 1,5-cyclooctadiene, 1,3,5-cyclooctatriene, dibenzylideneacetone, an acetato group, an acetylacetato group and a triphenylsiloxy group A metal complex (B) having one or more organic ligands selected from the group consisting of platinum, gold, silver, copper, palladium, rhodium, nickel, zinc, titanium, ruthenium, iron, cobalt , Molybdenum, tin, rhenium, vanadium or chromium, which is a metal different from M)), wherein the fine particles are obtained by reducing a metal complex containing hydrogen with hydrogen. The conductive polymer-alloy cluster composite electrode according to claim 1. The conductive polymer-alloy cluster composite electrode according to claim 4, wherein a substance ratio of the metal complex (A) to the metal complex (B) is 20: 1 to 1: 1. A method for producing a conductive polymer-alloy cluster composite electrode, comprising:
(A) The following formula:

(Wherein, R is a methyl group, an ethyl group or a phenyl group, X is a triphenylsiloxo group, a triphenylcarbinoxy group or a phenoxo group, and M is platinum or palladium). Step of preparing the metal complex (A) and (b) methyl group, ethyl group, 1,5-cyclooctadiene, 1,3,5-cyclooctatriene, dibenzylideneacetone, acetato group, acetylacetato group and triphenylsiloxy A metal complex (B) having one or more organic ligands selected from the group consisting of platinum, gold, silver, copper, palladium, rhodium, nickel, zinc, titanium, ruthenium, iron, cobalt , Molybdenum, tin, rhenium, vanadium or chromium, which is a different metal from M).
(C) dissolving the conductive polymer in an organic solvent;
(D) adding the metal complexes (A) and (B) to the dissolved conductive polymer;
(E) optionally distilling off the organic solvent;
(F) reducing the metal complexes (A) and (B) in the conductive polymer with hydrogen;
A method comprising: The method according to claim 6, wherein the step of adding the metal complexes (A) and (B) adds the metal complex (A) and the metal complex (B) in a mass ratio of 20: 1 to 1: 1.

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