JP2004220962A - Catalyst composition, zygote containing catalyst layer using it and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst composition providing a fuel cell with excellent generating property. <P>SOLUTION: (1) This invention provides the catalyst composition containing three components of a metal catalyst (a), carbon fine particles (b) and aromatic polymer (c) having a ultra-strong acid group in a side chain.(2) The aromatic polymer (c) having the ultra-strong acid group in the side chain of the composition of (1) is represented by general formula (I) :-(A-Z)m-(A'-Z')n-. In the general formula (I), A is a divalent aromatic group and A' is a divalent aromatic group replaced by the ultra-strong acid group. Z and Z' are a direct coupling or a divalent group independently, respectively. m and n are numbers of repeating units, n is 10 to 100,000, n repeating units may be the same or different, m is 0 to 100,000, and m repeating units may be the same or different. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１４】
また上記（２ｂ）の超強酸基の好ましい例としては、例えばＬ−６〜Ｌ−３０等が挙げられる。

【００１５】

【００１６】

【００１７】
また上記（２ｃ）の超強酸基の好ましい例としては、例えばＬ−３１〜Ｌ−３５等が挙げられる。

【００１８】
また上記（２ｄ）の超強酸基の好ましい例としては、例えばＬ−３６〜Ｌ−６０等が挙げられる。

【００１９】

上記のようなＬ−１〜Ｌ−６０のなかでは、Ｌ−１〜Ｌ−３０が好ましく使用される。
【００２０】
本発明における（ｃ）成分は、主鎖が前記のような芳香族系高分子からなるものであって、側鎖に上記のような超強酸基を有するものである。かかる高分子の代表例としては、例えば下記一般式（１）で表される構造を含む高分子が挙げられる。
−（Ａ−Ｚ）_ｍ−（Ａ’−Ｚ’）_ｎ− （１）
（式中、Ａは２価の芳香族基を、Ａ’は超強酸基が置換している２価の芳香
族基を表す。Ｚ、Ｚ’はそれぞれ独立に直接結合または２価の基を表わす。ｍ、ｎは繰返し単位の数を表し、ｎは１０〜１０００００の範囲であり、ｎ個ずつある繰り返し単位は同じであっても異なっていてもよく、ｍは０〜１０００００の範囲でありｍ個ずつある繰り返し単位は同じであっても異なっていてもよい。）
【００２１】
ここで、Ａは、２価の芳香族基を表し、その代表例としては、例えば下記式（３ａ）〜（３ｃ）より選ばれる２価の芳香族基が挙げられる。

（式中、Ｒは、水酸基、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、炭素数７〜１２のアラルキル基、アリール基、ハロゲンを表す。ｐ、ｒ、ｓ、ｔはそれぞれ独立に０〜４の、ｑは０〜６の数を表わし、Ｒが複数ある場合は、これらは同一でも異なっていてもよい。ｊは０または１の数を表わす。Ｙは直接結合または２価の基を表し、Ｙが複数ある場合は、これらは同一でも異なっていてもよい。）
【００２２】
Ｒにおける炭素数１〜６のアルキル基としては、例えばメチル基、エチル基、プロピル基等が、炭素数１〜６のアルコキシ基としては、例えばメトキシ基、エトキシ基等が、炭素数７〜１２のアラルキル基としては、例えば、ベンジル基、トルイル基等が、アリール基としては、例えば、フェニル基、ナフチル基等が、ハロゲンとしては、例えばフッ素原子、塩素原子、臭素原子等が挙げられる。
またＹは、直接結合または２価の基を表すが、Ｙとして具体的には、例えば、直接結合、−Ｏ−、−Ｓ−、−ＣＯ−、−ＳＯ_２−、炭素数１〜２０のアルキレン基、炭素数１〜２０のアルキレンジオキシ基等が挙げられる。好ましくは、直接結合、−Ｏ−、−Ｓ−、−ＳＯ_２−、炭素数１〜１０のアルキレン基、炭素数１〜１０のアルキレンジオキシ基等である。Ｙが複数ある場合は、これらは同一であっても異なっていてもよい。ここで、炭素数１〜２０のアルキレン基としては例えばメチレン基、エチレン基、プロピレン基、ブチレン基等が挙げられる。炭素数１〜２０のアルキレンジオキシ基としては例えばメチレンジオキシ基、エチレンジオキシ基などが挙げられる。
【００２３】
また式（１）におけるＡ’は超強酸基が置換している２価の芳香族基を表し、その代表例としては、例えば下記式（３ｄ）〜（３ｇ）より選ばれる２価の芳香族基が挙げられる。

（式中、Ｒは、水酸基、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、炭素数７〜１２のアラルキル基、アリール基又はハロゲンを表す。Ｚ’’およびＹは互いに独立に直接結合または２価の基を表わし、Ｚ’’が複数ある場合は、それらは同一でも異なっていてもよく、Ｙが複数ある場合は、それらは同一でも異なっていてもよい。Ｄは、超強酸基を表し、Ｄが複数ある場合は、それらは同一でも異なっていても良い。ｈ、ｈ’’、ｈ’’’はそれぞれ独立に１〜４の、ｈ’は１〜６の、（ｐ’＋ｈ）、（ｒ’＋ｈ’’）、（ｓ’’＋ｈ’’’）はそれぞれ独立に１〜４の、ｓ’、ｔ’、ｒ’’、ｔ’’はそれぞれ独立に０〜４の、
（ｑ’＋ｈ’）は１〜６のの数を表わし、Ｒが複数ある場合は、これらは同一でも異なっていてもよい。ｊは０または１の数を表わす。）
【００２４】
ここで、Ｒ、Ｙは、前記Ａにおいて記載したとおりである。Ｄは、超強酸基を表し、かかる超強酸基としては、例えば前記（２ａ）〜（２ｄ）から選ばれる超強酸基が挙げられる。またＺ’’は、直接結合または２価の基を表すが、Ｚ’’として具体的には、例えば、直接結合、−Ｏ−、−Ｓ−、−ＣＯ−、−ＳＯ_２−、炭素数１〜２０程度のアルキレン基、または炭素数１〜２０程度のアルキレンジオキシ基等のＹと同様な２価の基のほかに、フッ素で置換されている炭素数１〜２０程度のアルキレン基、フッ素で置換されている炭素数１〜２０程度のアルキレンジオキシ基、フッ素で置換されていることもある炭素数６〜１２程度のアリーレン基、フッ素で置換されていることもある炭素数６〜１２程度のアリーレンオキシ基、フッ素で置換されていることもある炭素数１〜２０程度のアルキレンオキシ基等が挙げられる。
好ましくは、直接結合、−Ｏ−、−Ｓ−、−ＳＯ_２−、炭素数１〜１０のアルキレン基、炭素数１〜１０のアルキレンジオキシ基、フッ素で置換されている炭素数１〜１０のアルキレン基、フッ素で置換されている炭素数１〜１０のアルキレンジオキシ基、フッ素で置換されていることもある炭素数６〜１０のアリーレン基、フッ素で置換されていることもある炭素数６〜１０のアリーレンオキシ基、フッ素で置換されていることもある炭素数１〜１０のアルキレンオキシ基が挙げられる。
【００２５】
ここで、炭素数１〜２０のアルキレン基としては例えばメチレン基、エチレン基、プロピレン基、ブチレン基等が挙げられる。炭素数１〜２０のアルキレンジオキシ基としては例えばメチレンジオキシ基、エチレンジオキシ基等が挙げられる。フッ素で置換されている炭素数１〜２０程度のアルキレン基としては例えば、ジフルオロメチレン基、テトラフルオロエチレン基、ヘキサフルオロプロピレン基、オクラフルオロブチレン基が挙げられる。フッ素で置換されている炭素数１〜２０のアルキレンジオキシ基としては２，２，３，３−テトラフルオロブチレンジオキシ基、２，２−ビス（トリフルオロメチル）プロピレンジオキシ基等が挙げられる。フッ素で置換されていることもある炭素数６〜１２程度のアリーレン基としては例えばフェニレン基、テトラフルオロフェニレン基等が挙げられる。フッ素で置換されていることもある炭素数６〜１２程度のアリーレンオキシ基としては例えばフェニレンオキシ基、テトラフルオロフェニレンオキシ基等が挙げられる。フッ素で置換されていることもある炭素数１〜２０程度のアルキレンオキシ基としては、例えば、メチレンオキシ基、ジフルオロメチレンオキシ基、エチレンオキシ基、テトラフルオロエチレンオキシ基等が挙げられる。
【００２６】
また式（１）におけるＺ、Ｚ’は、それぞれ独立に直接結合または２価の基を表わすが、Ｚ、Ｚ’としては、例えば前記Ｙと同様な２価の基が挙げられる。ｍ、ｎは繰返し単位の数を表し、ｎは通常１０〜１０００００の範囲であり、ｎ個ずつある繰り返し単位は同じであっても異なっていてもよく、ｍは通常０〜１０００００の範囲であり、ｍ個ずつある繰り返し単位は同じであっても異なっていてもよい。好ましくはｎが１５〜５００００の範囲、ｍが０〜５００００の範囲、特に好ましくはｎが２０〜１００００の範囲、ｍが０〜１００００の範囲である。ｎ個ずつある繰り返し単位とｍ個ずつある繰り返し単位は、ブロック共重合体、ランダム共重合体、交互共重合体、マルチブロック共重合体、またはグラフト共重合体のいずれの結合様式であってもよい。
本発明における側鎖に超強酸基を有する芳香族系高分子の分子量は、数平均分子量で通常５０００〜５０００００、好ましくは１００００〜３０００００の範囲、特に好ましくは１５０００〜１０００００である。
【００２７】
上記のような側鎖に超強酸基を有する芳香族系高分子は、例えば、下記一般式（４）
−（Ａ−Ｚ）_ｍ−（Ａ’’−Ｚ’）_ｎ− （４）
（式中、Ａ、Ｚ、Ｚ’、ｍ、ｎは前記と同じ意味を有し、Ａ’’は下記一般式（４ａ）〜（４ｄ）から選ばれる基を示す。）
および下記一般式（５）
Ｅ−Ｄ （５）
（式中、Ｄは、前記と同じ意味を有し、Ｅは、Ｚ’’’と反応して、前記Ｚ’’を形成する基を表わす。）
を反応させることにより得ることができる。
【００２８】

（上記式中、Ｒ、Ｚ’’、Ｙ、ｐ’、ｑ’、ｒ’、ｓ’、ｔ’、ｒ’’、ｓ’’、
ｔ’’、ｈ、ｈ’、ｈ’’、ｈ’’’、ｊは前述と同じ意味を表わす。Ｚ’’’は、Ｅと反応することにより前記Ｚ’’を形成する基を表わす。）
【００２９】
上記の方法としては特に制限を受けることはないが例えば、Ｅがハロゲン、Ｚ’’’がハロゲンである組み合わせを金属存在下において反応させて、直接結合を形成する方法などが挙げられる。ハロゲンとしてはフッ素、塩素、臭素、ヨウ素が挙げられ、好ましくは塩素、臭素、ヨウ素が挙げられる。この反応は通常、溶媒を用いない状態でも行うことは可能であるが、適当な溶媒中で行うことが好ましい。溶媒としては、炭化水素系溶媒、エーテル系溶媒、ケトン系溶媒、アミド系溶媒、スルホン系溶媒、スルホキシド系溶媒などを用いることができる。テトラヒドロフラン、ジエチルエーテル、ジメチルスルホキシド、スルホラン、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチルピロリドン、Ｎ，Ｎ’−ジメチルイミダゾリジノン等が好ましく用いられる。金属としては銅、ナトリウム、リチウム、カリウム、亜鉛、鉄、クロム、ニッケル、マグネシウムなどが挙げられ、好ましくは銅、亜鉛またはナトリウムである。用いる金属の量はハロゲン化アルキルおよび／またはハロゲン化アリールの合計の１／２当量以上が用いられる。反応温度は−１０℃〜２５０℃が好ましく、より好ましくは０℃〜２００℃である。
【００３０】
本発明における一般式（４）で表わされる高分子、すなわちＺ’’’を有する芳香族系高分子は、例えば、芳香族系高分子に、高分子反応でＺ’’’を導入する方法等で得ることができる。
この方法としては例えば、Ｎ−ブロモスクシンイミドを作用させて臭素を導入する方法、塩素ガス、臭素、ヨウ素などを直接作用させてハロゲンを導入する方法、三臭化リンを用いて水酸基を臭素基に変換する方法、塩化チオニルを用いて水酸基を塩素化する方法などが挙げられる。（マクマリー有機化学（上）、２９１〜２９６ページ、東京化学同人、１９９２年）
【００３１】
ここで、高分子反応により、Ｚ’’’が導入される芳香族系高分子としては、前述のように主鎖が主として芳香族環で構成されているものであれば特に限定はなく、例えば、ポリフェニレンエーテル系、ポリナフチレン系、ポリフェニレン系、ポリエーテルスルホン系、ポリフェニレンスルフィド系、ポリエーテルエーテルケトン系、ポリエーテルエーテルスルホン系、ポリスルホン系、ポリエーテルスルホン系、ポリエーテルケトン系、ポリベンズイミダゾール系などの高分子が挙げられる。この中でも特にポリフェニレンエーテル系、ポリナフチレン系、ポリフェニレン系、ポリエーテルスルホン系高分子が好ましく使用される。これらの高分子は任意の２種類以上の高分子からなる、ブロック共重合体、ランダム共重合体、交互共重合体、マルチブロック共重合体、またはグラフト共重合体などの共重合体であってもよい。
これらの高分子はＡｌｄｒｉｃｈ社、住友化学工業株式会社などのメーカーなどから入手することができる。例えば、住友化学工業株式会社からはスミカエクセル ＰＥＳ３６００Ｐ 、ＰＥＳ４１００Ｐ、ＰＥＳ４８００Ｐ、ＰＥＳ５２００Ｐ、ＰＥＳ５００３Ｐ（いずれも住友化学工業株式会社の登録商標、以下同様）の商品名で市販されているポリエーテルスルホン類を入手することができる。
【００３２】
本発明の触媒組成物は、上記のような側鎖に超強酸基を有する芳香族系高分子（ｃ）の他に、金属触媒（ａ）及び炭素微粒子（ｂ）を含有することを特徴とするものである。
ここで、金属触媒（ａ）としては、水素の酸化反応または酸素の還元反応を活性化できるものであれば特に制限はなく、公知のものも用いることができる。その代表例としては、例えば白金、ルテニウム、パラジウム、ニッケル、鉄およびこれら２種以上の合金または組成物等が挙げられる。なかでも白金、ルテニウムおよびこれら２種以上の合金または組成物が好ましく、より好ましくは、白金、白金を必須成分とする合金または白金を必須成分とする組成物である。ここで、合金とは２種類以上の金属が実質的に均一な状態となったものを示し、組成物とは２種類以上の金属が単に混合されたものを示す。これらの触媒としては金属塩を還元して得られたものを使用することもできる。
また炭素微粒子（ｂ）としては、例えば活性炭や黒鉛などの粒子状のカーボン、繊維状のカーボン、カーボンナノチューブ、カーボンナノホーンまたはフラーレンなどの炭素原子を主成分とするものを用いることができる。
なお、上記のような成分（ａ）、（ｂ）は、（ａ）が（ｂ）に担持された触媒担持炭素微粒子（ｇ）の形のものも使用できることはいうまでもない。
【００３３】
本発明における成分（ｃ）の成分（ａ）に対する使用比率は、重量基準で、通常（ｃ）／（ａ）＝０．０１〜１００程度、好ましくは０．０５〜５０程度、より好ましくは０．１〜１０程度、特に好ましくは０．５〜５である。
また成分（ｂ）の成分（ａ）に対する比率として、重量基準で、通常（ｂ）／（ａ）＝０．０１〜１００程度、好ましくは０．０５〜５０程度、より好ましくは０．１〜１０程度である。
【００３４】
本発明の触媒組成物は、上記のような側鎖に超強酸基を有する芳香族系高分子（ｃ）の他に、金属触媒（ａ）及び炭素微粒子（ｂ）を含有することを特徴とするものであるが、これら以外の成分を含有することもできる。例えばパーフルオロアルキルスルホン酸系高分子（ｄ）、ポリ（テトラフルオロエチレン）、ポリ（ビニリデンフルオリド）などを含有することもできる。
ここで、パーフルオロアルキルスルホン酸系高分子（ｄ）としては、主鎖が主としてパーフルオロアルキレンからなり、側鎖にパーフルオロアルキルエーテルスルホン酸からなるイオン交換基が導入された高分子が挙げられ、その代表例としては例えば、デュポン社のＮａｆｉｏｎなどが挙げられる。この（ｄ）成分を用いる場合は、成分（ｃ）に対して、重量比で、通常（ｄ）／（ｃ）＝０．０１〜１００程度、好ましくは０．０５〜５０程度、より好ましくは０．１〜１０程度、特に好ましくは０．５〜５程度である。
【００３５】
また本発明における触媒層の製造方法としては、例えば各成分を溶剤に分散させてペーストとした触媒組成物を調製し、これを乾燥させる方法、（ａ）が（ｂ）に担持された触媒担持炭素微粒子（ｇ）と成分（ｄ）とを溶剤に分散させてペーストとし、これを乾燥させた後、これに成分（ｃ）の溶液を塗布し、乾燥させる方法、成分（ｇ）と成分（ｃ）とを溶剤に分散させてペーストとし、これを乾燥させた後、これに成分（ｄ）の溶液を塗布し、乾燥させる方法等が挙げられる。
【００３６】
次に本発明における触媒層と集電体との接合体について説明する。
ここで、集電体とは電気伝導性およびガス拡散性を有する材料のことを示し、公知の材料を用いることができるが、原料ガスを効率よく触媒に輸送し得ることから、多孔質性のカーボン織布、カーボン不織布またはカーボンペーパーが好ましく用いられる。これらの集電体に撥水処理が施されたものも用いることもできる。
触媒層と集電体との接合体としては、通常、集電体上に触媒層が積層されたものが使用される。なかでも集電体の空孔内に触媒層の一部が入り込んだ状態のものが好ましく用いられる。
集電体上に触媒層を積層する方法としては、例えば、前記の触媒層の製造方法において示したペーストを集電体に塗布する以外は前記と同様に触媒層を製造する方法等が挙げられる。また触媒が塗布されているカーボン織布やカーボンペーパーが市販されているが、これらに成分（ｃ）の溶液を塗布し、乾燥させることにより集電体−触媒層接合体を得ることもできる。
【００３７】
塗布方法としては、例えばペーストをへらなどで塗布する方法、スプレーで塗布する方法、スクリーン印刷法で塗布する方法、ペーストに集電体を浸漬して塗布する方法、基材上に塗布したあと転写することにより塗布する方法、スピンコートで塗布する方法などが挙げられ、ペーストをへらなどで塗布する方法、スプレーで塗布する方法、スクリーン印刷法で塗布する方法が好ましく用いられる。得られた集電体−触媒層接合体は、必要に応じて、熱処理および／またはプレス処理を行うことも可能である。
また塗布する触媒層の量としては、集電体単位面積当りの乾燥重量として、通常０．０１〜１００ｍｇ／ｃｍ^２程度、好ましくは０．０５〜５０ｍｇ／ｃｍ^２程度、より好ましくは０．１〜１０ｍｇ／ｃｍ^２程度である。
かくして得られた集電体−触媒層接合体は、必要に応じて、熱処理および／またはプレス処理を行うことも可能である。
【００３８】
次に本発明の触媒層と電解質膜との接合体について説明する。
本発明の触媒層と電解質膜との接合体としては、高分子電解質膜と触媒層が積層された状態のものが通常使用される。触媒層は高分子電解質膜の片面、または両面に積層されていても良いが、燃料電池を作動させる場合には、両面に触媒層が積層された触媒層／高分子電解質膜／触媒層の３層からなることが好ましい。ここで、高分子電解質膜は、高分子電解質からなるものであり、該電解質としてはイオン交換基として、例えば、−ＳＯ_３Ｈ、−ＣＯＯＨ、−ＰＯ（ＯＨ）_２、−ＰＯＨ（ＯＨ）、−ＳＯ_２ＮＨＳＯ_２−、−Ｐｈ（ＯＨ）（Ｐｈはフェニル基を表す）等の陽イオン交換基を有する高分子が挙げられる。イオン交換基は、その一部または全部が対イオンとの塩を形成していても良い。
【００３９】
かかる高分子電解質の代表例としては、例えば（Ａ）主鎖が脂肪族炭化水素からなる高分子であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質；（Ｂ）主鎖の一部または全部の水素原子がフッ素で置換された脂肪族炭化水素からなる高分子であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質；（Ｃ）主鎖が芳香環を有する高分子であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質；（Ｄ）主鎖に実質的に炭素原子を含まないポリシロキサン、ポリホスファゼンなどの高分子であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質；（Ｅ）（Ａ）〜（Ｄ）のスルホン酸基および／またはホスホン酸基導入前の高分子を構成する繰り返し単位から選ばれるいずれか２種以上の繰り返し単位からなる共重合体であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質；（Ｆ）主鎖あるいは側鎖に窒素原子を含み、硫酸やリン酸等の酸性化合物がイオン結合により導入された形の高分子電解質等が挙げられる。
上記（Ａ）の高分子電解質としては、例えば、ポリビニルスルホン酸、ポリスチレンスルホン酸、ポリ（α−メチルスチレン）スルホン酸、等が挙げられる。
【００４０】
また上記（Ｂ）の高分子電解質としては、Ｎａｆｉｏｎに代表される、側鎖にパーフルオロアルキルスルホン酸を有し、主鎖がパーフルオロアルカンである高分子、水素原子の一部または全部がフッ素原子に置換されたビニルモノマと炭化水素系ビニルモノマとの共重合によって作られた主鎖と、スルホン酸基を有する炭化水素系側鎖とから構成されるスルホン酸型ポリスチレン−グラフト−エチレン−テトラフルオロエチレン共重合体（ＥＴＦＥ、例えば特開平９−１０２３２２号公報）や、炭化フッ素系ビニルモノマと炭化水素系ビニルモノマとの共重合によって作られた膜に、α，β，β−トリフルオロスチレンをグラフト重合させ、これにスルホン酸基を導入して固体高分子電解質膜とした、スルホン酸型ポリ（トリフルオロスチレン）−グラフト−ＥＴＦＥ膜（例えば、米国特許第４，０１２，３０３号及び米国特許第４，６０５，６８５号）等が挙げられる。
【００４１】
上記（Ｃ）の高分子電解質としては、主鎖が酸素原子等のヘテロ原子で中断されているものであってもよく、例えば、ポリエーテルエーテルケトン、ポリスルホン、ポリエーテルスルホン、ポリ（アリーレンエーテル）、ポリイミド、ポリ（（４−フェノキシベンゾイル）−１，４−フェニレン）、ポリフェニレンスルフィド、ポリフェニルキノキサレン等の（共）重合体のそれぞれにスルホン酸基が導入されたもの、スルホアリール化ポリベンズイミダゾール、スルホアルキル化ポリベンズイミダゾール、ホスホアルキル化ポリベンズイミダゾール、ホスホン化ポリ（フェニレンエーテル）、および先述の側鎖に超強酸基を有する芳香族系高分子（ｃ）などを挙げることができる。
【００４２】
また上記（Ｄ）の高分子電解質としては例えば、ポリホスファゼンにスルホン酸基が導入されたもの、Ｐｏｌｙｍｅｒ Ｐｒｅｐ．， ４１， Ｎｏ．１， ７０ （２０００） に記載の、ホスホン酸基を有するポリシロキサン等が挙げられる。
上記（Ｅ）の高分子電解質としては、ランダム共重合体にスルホン酸基および／またはホスホン酸基が導入されたものでも、交互共重合体にスルホン酸基および／またはホスホン酸基が導入されたものでも、ブロック共重合体にスルホン酸基および／またはホスホン酸基が導入されたものでもよい。ランダム共重合体にスルホン酸基が導入されたものとしては、例えば、スルホン化ポリエーテルスルホン−ジヒドロキシビフェニル共重合体が挙げられる（例えば、特開平１１−１１６６７９号公報）。上記（Ｅ）の高分子電解質に含まれるブロック共重合体において、スルホン酸基および／またはホスホン酸基を持つブロックの具体例としては、例えば特開２００１−２５０５６７号公報に記載のスルホン酸基および／またはホスホン酸基を持つブロックが挙げられる。
【００４３】
また上記（Ｆ）の高分子電解質としては例えば、特表平１１−５０３２６２号公報に記載の、リン酸を含有せしめたポリベンズイミダゾール等が挙げられる。本発明に使用される高分子電解質の重量平均分子量は、通常１０００〜１００００００程度であり、イオン交換基当量重量は、通常５００〜５０００ｇ／モル程度である。
上記（Ａ）〜（Ｇ）の高分子電解質の中でも（Ｃ）の主鎖が芳香環を有する高分子であり、スルホン酸基および／またはホスホン酸基が導入された形の高分子電解質が好ましく用いられる。
【００４４】
本発明に用いられる高分子電解質膜は、上記のような高分子電解質からなるものであるが、その製法としては、例えば溶媒キャスト法等を使用することができる。具体的には、上記のような高分子電解質の溶液を基材に流延製膜した後、溶媒を除去することにより、高分子電解質膜を製造し得る。
ここで、基材としては、溶媒への耐性があり、製膜後に膜が剥離できるものであれば特に制限はなく、通常ガラス板、ＰＥＴ（ポリエチレンテレフタレート）フィルム、ステンレス板、ステンレスベルト、シリコンウエハ等が用いられる。これらの基材は、必要に応じて、表面が離型処理、エンボス加工、つや消し加工がされてるものも使用し得る。高分子電解質膜の厚みは、特に制限はないが１０〜３００μｍが好ましい。実用に耐える膜の強度を得るには１０μｍより厚い方が好ましく、膜抵抗の低減つまり発電性能の向上のためには３００μｍより薄い方が好ましい。かかる膜厚は溶液濃度あるいは基板上への塗布厚により制御できる。
【００４５】
高分子電解質の溶液は、通常、高分子電解質を溶解可能であり、その後に除去し得る溶媒を用いて調製される。係る溶媒としては、例えばＮ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン、ジメチルスルホキシド等の非プロトン性極性溶媒、ジクロロメタン、クロロホルム、１，２−ジクロロエタン、クロロベンゼン、ジクロロベンゼン等の塩素系溶媒、メタノール、エタノール、プロパノール等のアルコール類、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル等のアルキレングリコールモノアルキルエーテルが好適に用いられる。これらは単独で用いることもできるが、必要に応じて２種以上の溶媒を混合して用いることもできる。中でも、ジメチルアセトアミド、塩化メチレン／メタノール混合溶媒、ジメチルホルムアミド、ジメチルスルホキシドが溶解性が高く好ましい。
高分子電解質膜を製膜する方法としては、バーコーター法やスピンコーター法を用いると均一な層ができるため好ましい。
【００４６】
上記のような電解質膜に触媒層を積層する方法としては、ペーストを集電体に塗布する方法として挙げた前述の方法と同様な方法を挙げることができる。また、前述のように燃料電池として用いる場合には両面に触媒層が積層された触媒層／高分子電解質膜／触媒層の３層からなる電解質膜−触媒層接合体を用いることが好ましい。
また塗布する触媒層の量としては、集電体単位面積当りの乾燥重量として、通常０．０１〜１００ｍｇ／ｃｍ^２程度、好ましくは０．０５〜５０ｍｇ／ｃｍ^２程度、より好ましくは０．１〜１０ｍｇ／ｃｍ^２程度である。
かくして得られた電解質膜−触媒層接合体は、必要に応じて、熱処理および／またはプレス処理を行うことも可能である。
【００４７】
次に本発明の集電体と触媒層と電解質膜との接合体について説明する。
集電体と触媒層と電解質膜との接合体としては、通常、集電体、触媒層および高分子電解質膜が積層されているものが使用される。これを用いて燃料電池として作動させることを目的とする場合には集電体／触媒層／高分子電解質膜／触媒層／集電体の順番に５層からなる接合体であることが好ましい。
積層方法としては、例えば▲１▼前述の集電体−触媒層接合体と高分子電解質膜を接合する方法、▲２▼前述の高分子電解質膜−触媒層接合体と集電体を接合させて得る方法を挙げることができる。上記５層からなる接合体は、例えば高分子電解質膜の両面を、触媒層が高分子電解質側になるようにした集電体−触媒層接合体で挟むことにより得ることができるし、高分子電解質膜の両面に触媒層が積層された、触媒層／高分子電解質膜／触媒層の３層からなる接合体の両面に集電体を挟むことにより得ることもできる。
かくして得られた集電体−触媒層−高分子電解質膜接合体は、必要に応じて、熱処理および／またはプレス処理を行うことも可能である。
【００４８】
次に本発明の燃料電池について説明する。
上記で得られた集電体−触媒層−高分子電解質膜接合体の一面に酸素ガス、他面に水素ガスを流すことによって燃料電池として作動させることが可能である。この際に、酸素ガスおよび／または水素ガスを加湿して供給することも可能である。 作動させる温度範囲に特に制限はないが０〜１５０℃が好ましく、３０〜１２０℃がより好ましく、５０〜１００℃が特に好ましい。
【００４９】
【実施例】
以下、実施例を挙げて本発明を説明するが、本発明はこれらの実施例によりなんら限定されるものではない。
【００５０】
参考例１ 側鎖に超強酸基を有する芳香族系高分子の製造
フラスコに、ポリ（オキシ−４，４’−ビフェニレンオキシ−４，４’−ジフェニルスルホン）（アルドリッチ社製）１５ｇと塩化メチレン８０ｍｌを入れて溶解し、０℃に保ちながら臭素４６．５ｇを１０分間で加えた。室温で４時間攪拌した後、反応液を過剰のＮａ_２ＳＯ_３を溶解した水溶液に加えた。その後、塩化メチレンを減圧留去、ろ過、乾燥を行うことにより、重合体（ａ）２０．５ｇを得た。元素分析、^１Ｈ ＮＭＲ、^１３Ｃ ＮＭＲ測定を行った結果、得られた重合体（ａ）のフェニル環にはブロモ基が導入されていることがわかった。重合体（ａ）中にブロモ基は２７．７重量％導入されていた。ＤＭＡｃを展開溶媒としたＧＰＣ測定による分子量の測定結果、数平均分子量はポリスチレン換算で３４０００であった。
フラスコに５−ヨード−オクタフルオロペンチル−３−オキサペンタンスルホニルフルオリド１５．０１ｇ、水５ｍｌ、塩化メチレン５ｍｌ、２，６−ルチジン４．８０ｇ、テトラｎ−ブチルアンモニウムフルオリドの１ＭＴＨＦ溶液を０．１ｍｌ入れ、室温で４日間反応させた。塩化メチレンで３回抽出し、溶媒を減圧留去した後、ＴＨＦ３０ｍｌ、炭酸カリウム２．８２ｇを入れて室温で１０ｈ攪拌した。固体をろ別し、ろ液を濃縮したところ白色固体が析出した。白色固体をＴＨＦ／トルエン混合溶媒より再結晶して白色固体１２．３ｇ得た。得られた白色固体は^１９Ｆ−ＮＭＲ、元素分析の結果より５−ヨード−オクタフルオロ−３−オキサペンタンスルホン酸カリウム（ｂ）であることが確認された。
窒素置換したフラスコに重合体（ａ）０．５００ｇ、銅紛末０．５００ｇ（７．８７ｍｍｏｌ）、Ｎ，Ｎ−ジメチルスルホキシド１０ｍｌを入れ、１２０℃で２時間攪拌した。次いで１２０℃に保ったまま（ｂ）１．００ｇ（２．１６ｍｍｏｌ）のＮ，Ｎ−ジメチルスルホキシド１０ｍｌ溶液を加えた。１２０℃で４０時間反応を行った後に１Ｎ‐ＨＣｌ水溶液１００ｍｌに加えて重合体を沈殿させた。沈殿したポリマーを乾燥させて側鎖に超強酸基を有する芳香族系高分子（ｃ）を得た。
【００５１】
参考例２ スルホン化ポリエーテルエーテルケトンの製造
特表２００１−５２５４７１に準拠し製造した。具体的には、フラスコに、市販のポリエーテルエーテルケトン（アルドリッチ社製）２５ｇと濃硫酸１２５ｍｌを仕込み、窒素気流下、室温にて４８時間攪拌して該ポリマーをスルホン化した。反応溶液を３リットルの脱イオン水にゆっくりと滴下することでスルホン化ポリエーテルエーテルケトンを析出させ、ろ過回収した。析出した沈殿は、ミキサーを用いた脱イオン水洗浄と吸引ろ過器による回収操作を、洗液が中性になるまで繰り返した後、乾燥することによりスルホン化ポリエーテルエーテルケトン（ｄ）を得た。
【００５２】
実施例１ 燃料電池特性評価
市販の白金担持炭素微粒子（白金担持量＝３０ｗｔ％）１０ｍｇを参考例１で製造した（ｃ）の塩化メチレン／メタノール＝８０／２０（ｗｔ／ｗｔ）５ｗｔ％溶液０．０７１ｍｌと混合してペースト状とし、５ｃｍ^２の多孔質性のカーボン織布にへらで塗布し、乾燥して電極を作成した。この電極を２枚作成し、特開２００１−２５０５６７号公報の実施例１に準拠して得た高分子電解質膜の両面に１枚ずつ接合し、集電体／触媒層／高分子電解質膜／触媒層／集電体の５層からなる集電体−触媒層−高分子電解質膜接合体を得た。該接合体の一面に０．１ＭＰａの加湿酸素ガス、他面に０．１ＭＰａの加湿水素ガスを流し、該接合体を８０℃に保ち、その発電特性を測定することによって行った。結果を表１に示す。
【００５３】
実施例２ 燃料電池特性評価
市販の白金担持炭素微粒子（白金担持量＝３０重量％）１０ｍｇをＮａｆｉｏｎ（アルドリッチ社製、５ｗｔ％、アルコール／水混合溶液）０．１ｍｌと混合してペースト状とし、５ｃｍ^２の多孔質性のカーボン織布にスクリーン印刷法で塗布し、乾燥した。さらに参考例１で合成した（ｃ）を塩化メチレン／メタノール＝８０／２０（ｗｔ／ｗｔ）に溶解させて１ｗｔ％溶液として、スプレーで塗布して電極としての集電体−触媒層接合体を作成した。（ｃ）はカーボン織布５ｃｍ^２あたり、２．２ｍｇ塗布されていた。この電極を２枚作成し、特開２００１−２５０５６７号公報の実施例１で得られた高分子電解質膜の両面に１枚ずつ接合し、さらに温度１００℃、圧力１０ＭＰａで９０分間プレスを行うことにより集電体／触媒層／高分子電解質膜／触媒層／集電体の５層からなる集電体−触媒層−高分子電解質膜接合体を得た。該接合体の一面に０．１ＭＰａの加湿酸素ガス、他面に０．１ＭＰａの加湿水素ガスを流し、該接合体を８０℃に保ち、その発電特性を測定することによって行った。結果を表１に示す。
【００５４】
比較例１ 燃料電池特性評価
市販の白金担持炭素微粒子（白金担持量＝３０ｗｔ％）１０ｍｇを参考例２で合成した（ｄ）の塩化メチレン／メタノール＝８０／２０（ｗｔ／ｗｔ）２ｗｔ％溶液０．１４３ｍｌと混合してペースト状とし、５ｃｍ^２の多孔質性のカーボン織布にへらで塗布し、乾燥して電極を作成した以外は実施例１と同様に集電体−触媒層−高分子電解質膜接合体の作製および燃料電池特性評価を行った。結果を表１に示す。
【００５５】
【表１】
燃料電池特性試験の結果

【００５６】
【発明の効果】
本発明によれば、燃料電池の触媒層におけるプロトン伝導性材料として、側鎖に超強酸基を有する芳香族系高分子を用いることにより、燃料電池の発電性能等を向上し得る。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalyst composition, and more specifically, is characterized by containing three components: a metal catalyst (a), carbon fine particles (b), and an aromatic polymer (c) having a super strong acid group in a side chain. It relates to a catalyst composition.
[0002]
2. Description of the Related Art
2. Description of the Related Art In recent years, fuel cells have attracted attention as highly efficient and clean energy conversion devices. Among them, a solid polymer fuel cell using a polymer membrane having proton conductivity as an electrolyte has a compact structure, high output can be obtained, and can be operated with a simple system. Attention has been paid.
The polymer electrolyte fuel cell generally includes a polymer electrolyte membrane, a catalyst layer used to sandwich the membrane, and a current collector used to sandwich the outside of the catalyst layer. Among them, the catalyst layer is composed of a metal catalyst (a), carbon fine particles (b), a proton conductive material and the like.
As the proton conductive material used for the catalyst layer, a perfluoroalkylsulfonic acid-based polymer has been widely used. In recent years, sulfonated polyetheretherketone (Patent Document 1), aromatic polymers in which a sulfonic acid group is bonded to an aromatic ring via an alkyl group (Patent Document 2), and sulfonated polyethersulfone (Non-Patent Document 1) ) Have also been proposed.
However, when these proton conductive materials are used for the catalyst layer, the power generation performance is not sufficient, and improvement in this point has been demanded.
[0003]
[Patent Document 1]
JP-A-2002-75403
[0004]
[Patent Document 2]
JP-A-2002-110174
[0005]
[Non-patent document 1]
Posters from Fuel Cells for Transportation and Fuels for Four Cells Lab R & D Review Meetings, May 9-10, 2002.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above problems, and as a result, by using an aromatic polymer having a super strong acid group in a side chain as a proton conductive material in a catalyst layer, a fuel cell has been developed. The inventors have found that the power generation performance and the like can be improved, and have further studied variously to complete the present invention.
That is, the present invention is practically characterized in that it contains three components: (1) a metal catalyst (a), carbon fine particles (b), and an aromatic polymer (c) having a superacid group in a side chain. An excellent catalyst composition, (2) the composition of the above (1), further comprising a perfluoroalkylsulfonic acid polymer (d), (3) the above (1) or (2). (4) a joined body of a catalyst layer containing each component described in (1) or (2) above and a polymer electrolyte membrane, And (6) a joined body of a current collector and a polymer electrolyte containing a catalyst layer containing each component described in (1) or (2) above, and (6) a fuel cell or the like using them.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The catalyst composition of the present invention is characterized by containing three components: a metal catalyst (a), carbon fine particles (b), and an aromatic polymer (c) having a superacid group in a side chain. It may also contain a perfluoroalkylsulfonic acid-based polymer (d) or the like.
Further, the catalyst layer in the present invention may be composed of the above-mentioned catalyst composition, that is, a mixture of the above-described components, or may be composed of a laminate of the respective components.
[0008]
Here, as the aromatic polymer in the aromatic polymer having a super strong acid group in the side chain as the component (c), the main chain is mainly an aromatic ring, for example, a monocyclic aromatic ring such as benzene, Polymers composed of a polycyclic aromatic ring such as naphthalene and biphenyl, a heterocyclic aromatic ring such as a pyridine group, and a polycyclic heteroaromatic ring such as benzimidazole are exemplified.
The polymer is not particularly limited as long as its main chain is mainly composed of an aromatic ring, and typical examples thereof include polyphenylene ether, polynaphthylene, polyphenylene, polyphenylene sulfide, and polyphenylene sulfide. Polymers of ether ether ketone type, polyether ether sulfone type, polysulfone type, polyether sulfone type, polyether ketone type, polybenzimidazole type, polyimide type and the like can be mentioned. Among these, polymers such as polyphenylene ether, polyphenylene, polyether ketone, polyether ether ketone, polyether ether sulfone, and polyether sulfone are preferred.
[0009]
The aromatic ring in these polymers may have a substituent in addition to the super-strong acid group as a side chain. Examples of such a substituent include a hydroxyl group, a methyl group, an ethyl group, and a propyl group. An alkyl group having 1 to 6 carbon atoms such as a group, an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group, an aralkyl group having 7 to 12 carbon atoms such as a benzyl group, an aryl group such as a phenyl group and a naphthyl group; And halogen such as fluorine atom, chlorine atom and bromine atom. It may have a plurality of substituents, in which case they may be different. Among them, those substituted with a fluorine atom are preferably used.
[0010]
In the present invention, the aromatic polymer having a super strong acid group in the side chain is one having a super strong acid group in the side chain in addition to the aromatic polymer having a main chain as described above. Here, the super-strong acid group means an acid substantially stronger than 100% sulfuric acid.
Examples of such a super strong acid group include groups represented by the following general formulas (2a) to (2d).
-G-SO₃ ⁻W⁺                  (2a)
-G-SO₂N⁻W⁺SO₂-E (2b)
-GP (O) (O⁻W⁺)₂        (2c)
-GP (O) O⁻W⁺-E (2d)
(Where G is an alkylene group in which part or all of hydrogen is substituted with fluorine, an aralkylene group in which part or all of hydrogen is substituted with fluorine, or an arylene group in which part or all of hydrogen is substituted with fluorine. And W⁺Represents a cation, E represents an alkyl group in which part or all of hydrogen is substituted with fluorine, an aralkyl group in which part or all of hydrogen is substituted with fluorine, or E in which part or all of hydrogen is substituted with fluorine. Represents an aryl group. )
[0011]
Where W⁺Representative examples thereof include alkali metal ions such as hydrogen ions, sodium ions, and lithium ions. When used for a fuel cell, it is preferably hydrogen ion.
The alkylene group in G usually has about 1 to 6 carbon atoms, the aralkylene group usually has about 7 to 12 carbon atoms, and the arylene group usually has about 6 to 10 carbon atoms. Among them, G is preferably an alkylene group in which all of the hydrogen is substituted with fluorine, an aralkylene group in which all of the hydrogen is substituted with fluorine, or an arylene group in which all of the hydrogen is substituted with fluorine. Preferred examples of G include a difluoromethylene group, a tetrafluoroethylene group, a hexafluoropropylene group, a hexafluorobenzylene group, a tetrafluorophenylene group, and a hexafluoronaphthylene group.
[0012]
The alkyl group in E generally has about 1 to 6 carbon atoms, the aralkyl group usually has about 7 to 12 carbon atoms, and the aryl group usually has about 6 to 10 carbon atoms. Among them, E is preferably an alkyl group in which all of hydrogen is substituted with fluorine, an aralkyl group in which all of hydrogen is substituted with fluorine, or an aryl group in which all of hydrogen is substituted with fluorine. Preferred examples of E include, for example, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a heptafluorobenzyl group, a pentafluorophenyl group, a heptafluoronaphthyl group.
[0013]
Preferred examples of the super strong acid group (2a) include, for example, L-1 to L-5.

[0014]
Preferred examples of the super strong acid group (2b) include L-6 to L-30.

[0015]

[0016]

[0017]
Preferred examples of the super strong acid group (2c) include, for example, L-31 to L-35.

[0018]
Preferred examples of the super strong acid group (2d) include, for example, L-36 to L-60.

[0019]

Among the above L-1 to L-60, L-1 to L-30 are preferably used.
[0020]
The component (c) in the present invention has a main chain composed of the aromatic polymer as described above, and has a superacid group as described above in a side chain. Representative examples of such polymers include, for example, polymers having a structure represented by the following general formula (1).
-(AZ)_m-(A'-Z ')_n-(1)
(Wherein A represents a divalent aromatic group, and A ′ represents a divalent aromatic group substituted by a superacid group.
Represents a group. Z and Z 'each independently represent a direct bond or a divalent group. m and n represent the number of repeating units, n is in the range of 10 to 100,000, and n repeating units may be the same or different, m is in the range of 0 to 100,000 and m Each repeating unit may be the same or different. )
[0021]
Here, A represents a divalent aromatic group, and typical examples thereof include a divalent aromatic group selected from the following formulas (3a) to (3c).

(In the formula, R represents a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, an aryl group, or halogen. P, r, s, t. Each independently represents a number from 0 to 4, q represents a number from 0 to 6, and when there are a plurality of Rs, these may be the same or different, j represents a number of 0 or 1, and Y represents a direct bond Or, when it represents a divalent group and has a plurality of Y's, these may be the same or different.)
[0022]
Examples of the alkyl group having 1 to 6 carbon atoms for R include a methyl group, an ethyl group, and a propyl group, and examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group and an ethoxy group. Examples of the aralkyl group include benzyl group and toluyl group; examples of the aryl group include phenyl group and naphthyl group; examples of the halogen include a fluorine atom, a chlorine atom, and a bromine atom.
Y represents a direct bond or a divalent group, and specific examples of Y include, for example, a direct bond, -O-, -S-, -CO-, -SO₂-, An alkylene group having 1 to 20 carbon atoms, an alkylenedioxy group having 1 to 20 carbon atoms, and the like. Preferably, a direct bond, -O-, -S-, -SO₂-, An alkylene group having 1 to 10 carbon atoms, an alkylenedioxy group having 1 to 10 carbon atoms, and the like. When there are a plurality of Ys, these may be the same or different. Here, examples of the alkylene group having 1 to 20 carbon atoms include a methylene group, an ethylene group, a propylene group, and a butylene group. Examples of the alkylenedioxy group having 1 to 20 carbon atoms include a methylenedioxy group and an ethylenedioxy group.
[0023]
A ′ in the formula (1) represents a divalent aromatic group substituted by a superacid group, and a typical example thereof is a divalent aromatic group selected from the following formulas (3d) to (3g). Groups.

(In the formula, R represents a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, an aryl group, or halogen. Z ″ and Y represent each other. And independently represents a direct bond or a divalent group, and when there are a plurality of Z ″, they may be the same or different, and when there are a plurality of Y, they may be the same or different. , Represents a super strong acid group, and when there are a plurality of D, they may be the same or different, and h, h ″, and h ′ ″ each independently represents 1 to 4, and h ′ represents 1 to 6. , (P ′ + h), (r ′ + h ″) and (s ″ + h ′ ″) are independently 1 to 4; s ′, t ′, r ″ and t ″ are each independently 0-4,
(Q '+ h') represents a number of 1 to 6, and when there are a plurality of Rs, these may be the same or different. j represents a number of 0 or 1. )
[0024]
Here, R and Y are as described in the above A. D represents a super strong acid group, and examples of the super strong acid group include a super strong acid group selected from the above (2a) to (2d). Z ″ represents a direct bond or a divalent group. Specific examples of Z ″ include a direct bond, —O—, —S—, —CO—, and —SO—.₂-In addition to a divalent group similar to Y such as an alkylene group having about 1 to 20 carbon atoms or an alkylenedioxy group having about 1 to 20 carbon atoms, about 1 to 20 carbon atoms substituted with fluorine Alkylene dioxy group having about 1 to 20 carbon atoms substituted with fluorine, an arylene group having about 6 to 12 carbon atoms sometimes substituted with fluorine, and sometimes substituted with fluorine Examples thereof include an aryleneoxy group having about 6 to 12 carbon atoms and an alkyleneoxy group having about 1 to 20 carbon atoms which may be substituted with fluorine.
Preferably, a direct bond, -O-, -S-, -SO₂-, An alkylene group having 1 to 10 carbon atoms, an alkylenedioxy group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms substituted by fluorine, and an alkylene having 1 to 10 carbon atoms substituted by fluorine. A dioxy group, an arylene group having 6 to 10 carbon atoms which may be substituted by fluorine, an aryleneoxy group having 6 to 10 carbon atoms which may be substituted by fluorine, and may be substituted by fluorine Examples thereof include an alkyleneoxy group having 1 to 10 carbon atoms.
[0025]
Here, examples of the alkylene group having 1 to 20 carbon atoms include a methylene group, an ethylene group, a propylene group, and a butylene group. Examples of the alkylenedioxy group having 1 to 20 carbon atoms include a methylenedioxy group and an ethylenedioxy group. Examples of the alkylene group having about 1 to 20 carbon atoms substituted with fluorine include a difluoromethylene group, a tetrafluoroethylene group, a hexafluoropropylene group, and an oclafluorobutylene group. Examples of the C1-C20 alkylenedioxy group substituted by fluorine include a 2,2,3,3-tetrafluorobutylenedioxy group and a 2,2-bis (trifluoromethyl) propylenedioxy group. Can be Examples of the arylene group having about 6 to 12 carbon atoms that may be substituted with fluorine include, for example, a phenylene group and a tetrafluorophenylene group. Examples of the aryleneoxy group having about 6 to 12 carbon atoms which may be substituted with fluorine include, for example, a phenyleneoxy group and a tetrafluorophenyleneoxy group. Examples of the alkyleneoxy group having about 1 to 20 carbon atoms which may be substituted with fluorine include, for example, a methyleneoxy group, a difluoromethyleneoxy group, an ethyleneoxy group, a tetrafluoroethyleneoxy group and the like.
[0026]
Z and Z 'in Formula (1) each independently represent a direct bond or a divalent group. Examples of Z and Z' include the same divalent groups as those described above for Y. m and n each represent the number of repeating units, n is generally in the range of 10 to 100,000, n repeating units may be the same or different, and m is usually in the range of 0 to 100,000. , M repeating units may be the same or different. Preferably, n is in the range of 15 to 50,000, m is in the range of 0 to 50,000, particularly preferably n is in the range of 20 to 10,000, and m is in the range of 0 to 10,000. The repeating unit having n units and the repeating unit having m units may be any of a bonding mode of a block copolymer, a random copolymer, an alternating copolymer, a multi-block copolymer, or a graft copolymer. Good.
The molecular weight of the aromatic polymer having a super strong acid group in the side chain in the present invention is generally in the range of 5,000 to 500,000, preferably 10,000 to 300,000, and particularly preferably 15,000 to 100,000 in terms of number average molecular weight.
[0027]
The aromatic polymer having a super strong acid group in the side chain as described above is, for example, represented by the following general formula (4)
-(AZ)_m-(A "-Z ')_n-(4)
(In the formula, A, Z, Z ′, m, and n have the same meaning as described above, and A ″ represents a group selected from the following general formulas (4a) to (4d).)
And the following general formula (5)
ED (5)
(Wherein, D has the same meaning as described above, and E represents a group which reacts with Z ″ ′ to form the above-mentioned Z ″).
Can be obtained by reacting
[0028]

(Where R, Z '', Y, p ', q', r ', s', t', r '', s' ',
t ″, h, h ′, h ″, h ″ ″, and j have the same meanings as described above. Z "" represents a group which forms the aforementioned Z "by reacting with E. )
[0029]
The method is not particularly limited, and examples thereof include a method in which a combination in which E is a halogen and Z ″ ′ is a halogen is reacted in the presence of a metal to form a direct bond. Halogen includes fluorine, chlorine, bromine and iodine, preferably chlorine, bromine and iodine. This reaction can usually be performed without using a solvent, but is preferably performed in an appropriate solvent. As the solvent, a hydrocarbon solvent, an ether solvent, a ketone solvent, an amide solvent, a sulfone solvent, a sulfoxide solvent, or the like can be used. Tetrahydrofuran, diethyl ether, dimethyl sulfoxide, sulfolane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolidinone and the like are preferably used. Examples of the metal include copper, sodium, lithium, potassium, zinc, iron, chromium, nickel, magnesium and the like, and preferably copper, zinc or sodium. The amount of the metal used is at least 1/2 equivalent of the total of the alkyl halide and / or the aryl halide. The reaction temperature is preferably from -10C to 250C, more preferably from 0C to 200C.
[0030]
The polymer represented by the general formula (4) in the present invention, that is, the aromatic polymer having Z ′ ″ is, for example, a method of introducing Z ′ ″ into the aromatic polymer by a polymer reaction. Can be obtained at
As this method, for example, a method of introducing bromine by acting N-bromosuccinimide, a method of introducing halogen by directly acting chlorine gas, bromine, iodine, or the like, a method of converting a hydroxyl group to a bromine group using phosphorus tribromide. A conversion method, a method of chlorinating a hydroxyl group using thionyl chloride, and the like can be mentioned. (McMurray Organic Chemistry (above), pp. 291-296, Tokyo Kagaku Doujin, 1992)
[0031]
Here, the aromatic polymer into which Z ″ ′ is introduced by the polymer reaction is not particularly limited as long as the main chain is mainly composed of an aromatic ring as described above. , Polyphenylene ether, polynaphthylene, polyphenylene, polyether sulfone, polyphenylene sulfide, polyether ether ketone, polyether ether sulfone, polysulfone, polyether sulfone, polyether ketone, polybenzimidazole, etc. Polymer. Of these, polyphenylene ether, polynaphthylene, polyphenylene, and polyethersulfone polymers are preferably used. These polymers are copolymers such as block copolymers, random copolymers, alternating copolymers, multi-block copolymers, or graft copolymers comprising any two or more polymers. Is also good.
These polymers can be obtained from manufacturers such as Aldrich and Sumitomo Chemical Co., Ltd. For example, from Sumitomo Chemical Co., Ltd., polyether sulfones which are commercially available under the trade name of Sumika Excel PES3600P, PES4100P, PES4800P, PES5200P, PES5003P (all are registered trademarks of Sumitomo Chemical Co., Ltd., hereinafter the same) are obtained. be able to.
[0032]
The catalyst composition of the present invention contains a metal catalyst (a) and fine carbon particles (b) in addition to the aromatic polymer (c) having a super strong acid group in the side chain as described above. Is what you do.
Here, the metal catalyst (a) is not particularly limited as long as it can activate a hydrogen oxidation reaction or an oxygen reduction reaction, and a known catalyst can be used. Representative examples include platinum, ruthenium, palladium, nickel, iron and alloys or compositions of two or more of these. Among them, platinum, ruthenium, and alloys or compositions of two or more thereof are preferable, and platinum, an alloy containing platinum as an essential component, or a composition containing platinum as an essential component are more preferable. Here, an alloy refers to an alloy in which two or more metals are in a substantially uniform state, and a composition refers to an alloy in which two or more metals are simply mixed. As these catalysts, those obtained by reducing a metal salt can also be used.
Further, as the carbon fine particles (b), for example, those mainly containing carbon atoms such as particulate carbon such as activated carbon and graphite, fibrous carbon, carbon nanotube, carbon nanohorn or fullerene can be used.
It goes without saying that, as the above components (a) and (b), those in the form of catalyst-supported carbon fine particles (g) in which (a) is supported on (b) can also be used.
[0033]
The use ratio of component (c) to component (a) in the present invention is usually (c) / (a) = about 0.01 to 100, preferably about 0.05 to 50, and more preferably 0, on a weight basis. About 0.1 to 10, particularly preferably 0.5 to 5.
Further, as a ratio of the component (b) to the component (a), (b) / (a) = about 0.01 to 100, preferably about 0.05 to 50, more preferably about 0.1 to 100 on a weight basis. It is about 10.
[0034]
The catalyst composition of the present invention contains a metal catalyst (a) and fine carbon particles (b) in addition to the aromatic polymer (c) having a super strong acid group in the side chain as described above. However, components other than these can also be contained. For example, a perfluoroalkylsulfonic acid-based polymer (d), poly (tetrafluoroethylene), poly (vinylidene fluoride), or the like can be contained.
Here, as the perfluoroalkylsulfonic acid polymer (d), a polymer having a main chain mainly composed of perfluoroalkylene and an ion exchange group composed of perfluoroalkylethersulfonic acid introduced into a side chain is exemplified. Typical examples thereof include Nafion of DuPont. When this component (d) is used, it is usually about (d) / (c) = about 0.01 to 100, preferably about 0.05 to 50, more preferably about 0.05 to 50% by weight based on the component (c). It is about 0.1 to 10, particularly preferably about 0.5 to 5.
[0035]
The method for producing the catalyst layer in the present invention includes, for example, a method in which each component is dispersed in a solvent to prepare a catalyst composition as a paste, and the paste is dried. A method in which the carbon fine particles (g) and the component (d) are dispersed in a solvent to form a paste, which is dried, and then a solution of the component (c) is applied thereto, followed by drying, a method of drying the component (g) and the component ( c) is dispersed in a solvent to form a paste, which is dried, and then a solution of the component (d) is applied thereto, followed by drying.
[0036]
Next, the joined body of the catalyst layer and the current collector in the present invention will be described.
Here, the current collector refers to a material having electric conductivity and gas diffusibility, and a known material can be used. However, since a raw material gas can be efficiently transported to a catalyst, a porous material is used. Carbon woven fabric, carbon nonwoven fabric or carbon paper is preferably used. Those obtained by subjecting these current collectors to a water-repellent treatment can also be used.
As a joined body of the catalyst layer and the current collector, a product in which a catalyst layer is laminated on a current collector is usually used. Among them, a collector in which a part of the catalyst layer has entered the pores of the current collector is preferably used.
Examples of the method of laminating the catalyst layer on the current collector include, for example, a method of manufacturing the catalyst layer in the same manner as described above except that the paste shown in the method for manufacturing the catalyst layer is applied to the current collector. . Also, carbon woven fabric and carbon paper coated with a catalyst are commercially available, and a current collector-catalyst layer assembly can be obtained by applying a solution of the component (c) to these and drying the solution.
[0037]
Examples of the coating method include a method of applying a paste with a spatula, a method of applying with a spray, a method of applying with a screen printing method, a method of immersing a current collector in a paste and applying, and a method of applying a paste on a substrate and then transferring the paste. And a method of applying the paste by a spin coater. A method of applying the paste by a spatula, a method of applying by a spray, and a method of applying by a screen printing method are preferably used. The obtained current collector-catalyst layer assembly can be subjected to a heat treatment and / or a press treatment, if necessary.
The amount of the catalyst layer to be applied is usually 0.01 to 100 mg / cm as a dry weight per unit area of the current collector.²Degree, preferably 0.05 to 50 mg / cm²Degree, more preferably 0.1 to 10 mg / cm²It is about.
The current collector-catalyst layer assembly thus obtained can be subjected to a heat treatment and / or a press treatment, if necessary.
[0038]
Next, the joined body of the catalyst layer and the electrolyte membrane of the present invention will be described.
As the bonded body of the catalyst layer and the electrolyte membrane of the present invention, a bonded body in which the polymer electrolyte membrane and the catalyst layer are laminated is usually used. The catalyst layer may be laminated on one side or both sides of the polymer electrolyte membrane. However, when the fuel cell is operated, the catalyst layer having the catalyst layers laminated on both sides / polymer electrolyte membrane / catalyst layer may be used. It preferably comprises a layer. Here, the polymer electrolyte membrane is made of a polymer electrolyte, and the electrolyte may be, for example, -SO₃H, -COOH, -PO (OH)₂, -POH (OH), -SO₂NHSO₂Polymers having a cation exchange group such as-, -Ph (OH) (Ph represents a phenyl group) are exemplified. Part or all of the ion exchange group may form a salt with a counter ion.
[0039]
Representative examples of such a polymer electrolyte include, for example, (A) a polymer having a main chain composed of an aliphatic hydrocarbon and having a sulfonic acid group and / or a phosphonic acid group introduced therein; (C) a polymer electrolyte comprising an aliphatic hydrocarbon in which some or all of the hydrogen atoms in the main chain are substituted with fluorine, and a sulfonic acid group and / or a phosphonic acid group are introduced; A polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group is introduced, which is a polymer having an aromatic ring in the chain; (D) polysiloxane, polyphosphazene, etc. having substantially no carbon atom in the main chain And a polymer electrolyte having a sulfonic acid group and / or a phosphonic acid group introduced therein; (E) the polymer before the introduction of the sulfonic acid group and / or the phosphonic acid group of (A) to (D) Make up (F) a polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group is introduced; and Examples include a polymer electrolyte containing an atom and in which an acidic compound such as sulfuric acid or phosphoric acid is introduced by ionic bonding.
Examples of the polymer electrolyte (A) include polyvinyl sulfonic acid, polystyrene sulfonic acid, and poly (α-methylstyrene) sulfonic acid.
[0040]
Examples of the polymer electrolyte (B) include a polymer represented by Nafion, having a perfluoroalkylsulfonic acid in a side chain and a perfluoroalkane in the main chain, and a part or all of hydrogen atoms being fluorine. Sulfonic acid type polystyrene-graft-ethylene-tetrafluoroethylene composed of a main chain produced by copolymerization of an atom-substituted vinyl monomer and a hydrocarbon vinyl monomer, and a hydrocarbon side chain having a sulfonic acid group Α, β, β-trifluorostyrene is graft-polymerized to a copolymer (ETFE, for example, JP-A-9-102322) or a film formed by copolymerization of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer. A sulfonic acid type poly (trifluorostyrene) by introducing sulfonic acid groups into the polymer electrolyte membrane. - graft -ETFE film (e.g., U.S. Patent No. 4,012,303 and U.S. Pat. No. 4,605,685), and the like.
[0041]
The polymer electrolyte of the above (C) may be one in which the main chain is interrupted by a hetero atom such as an oxygen atom, for example, polyether ether ketone, polysulfone, polyether sulfone, poly (arylene ether) , Poly ((4-phenoxybenzoyl) -1,4-phenylene), polyphenylene sulfide, polyphenylquinoxalene, and other (co) polymers each having a sulfonic acid group introduced therein, sulfoarylated poly Examples thereof include benzimidazole, sulfoalkylated polybenzimidazole, phosphoalkylated polybenzimidazole, phosphonated poly (phenylene ether), and the above-mentioned aromatic polymer (c) having a super strong acid group in the side chain. .
[0042]
Examples of the polymer electrolyte (D) include those in which a sulfonic acid group is introduced into polyphosphazene, Polymer Prep. , 41, No. 1, 70 (2000), polysiloxane having a phosphonic acid group, and the like.
As the polymer electrolyte (E), even when a sulfonic acid group and / or a phosphonic acid group is introduced into a random copolymer, a sulfonic acid group and / or a phosphonic acid group is introduced into an alternating copolymer. Or a block copolymer in which a sulfonic acid group and / or a phosphonic acid group are introduced. Examples of the random copolymer having a sulfonic acid group introduced therein include a sulfonated polyethersulfone-dihydroxybiphenyl copolymer (for example, JP-A-11-116679). Specific examples of the block having a sulfonic acid group and / or a phosphonic acid group in the block copolymer contained in the polymer electrolyte (E) include, for example, a sulfonic acid group described in JP-A-2001-250567. And / or a block having a phosphonic acid group.
[0043]
Examples of the polymer electrolyte (F) include polybenzimidazole containing phosphoric acid described in JP-T-11-503262. The weight average molecular weight of the polymer electrolyte used in the present invention is generally about 1,000 to 1,000,000, and the equivalent weight of the ion exchange group is usually about 500 to 5,000 g / mol.
Among the polymer electrolytes (A) to (G), a polymer electrolyte in which the main chain of (C) is an aromatic ring and a sulfonic acid group and / or a phosphonic acid group is introduced is preferable. Used.
[0044]
The polymer electrolyte membrane used in the present invention is made of the above-mentioned polymer electrolyte, and as a manufacturing method thereof, for example, a solvent casting method or the like can be used. Specifically, a polymer electrolyte membrane can be produced by casting the above-mentioned polymer electrolyte solution on a substrate and then removing the solvent.
Here, the substrate is not particularly limited as long as it has resistance to a solvent and can peel off the film after film formation, and is usually a glass plate, a PET (polyethylene terephthalate) film, a stainless steel plate, a stainless steel belt, a silicon wafer. Are used. As these substrates, those having a surface subjected to release treatment, embossing, and matting may be used as necessary. The thickness of the polymer electrolyte membrane is not particularly limited, but is preferably from 10 to 300 μm. It is preferable that the thickness be larger than 10 μm to obtain a film strength that can withstand practical use, and it is preferable that the thickness be smaller than 300 μm to reduce the film resistance, that is, to improve the power generation performance. Such a film thickness can be controlled by a solution concentration or a coating thickness on a substrate.
[0045]
The polymer electrolyte solution is usually prepared using a solvent capable of dissolving the polymer electrolyte and subsequently removing the same. Examples of such a solvent include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, Chlorinated solvents such as dichlorobenzene, alcohols such as methanol, ethanol and propanol, and alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether are preferably used. Can be These can be used alone, but if necessary, a mixture of two or more solvents can be used. Among them, dimethylacetamide, a mixed solvent of methylene chloride / methanol, dimethylformamide, and dimethylsulfoxide are preferable because of high solubility.
As a method for forming a polymer electrolyte membrane, a bar coater method or a spin coater method is preferable because a uniform layer can be formed.
[0046]
As a method of laminating the catalyst layer on the electrolyte membrane as described above, a method similar to the method described above as a method of applying the paste to the current collector can be used. In addition, when used as a fuel cell as described above, it is preferable to use an electrolyte membrane-catalyst layer assembly composed of three layers of catalyst layer / polymer electrolyte membrane / catalyst layer in which catalyst layers are laminated on both sides.
The amount of the catalyst layer to be applied is usually 0.01 to 100 mg / cm as a dry weight per unit area of the current collector.²Degree, preferably 0.05 to 50 mg / cm²Degree, more preferably 0.1 to 10 mg / cm²It is about.
The thus obtained electrolyte membrane-catalyst layer assembly can be subjected to a heat treatment and / or a press treatment, if necessary.
[0047]
Next, the joined body of the current collector, the catalyst layer, and the electrolyte membrane of the present invention will be described.
As the joined body of the current collector, the catalyst layer, and the electrolyte membrane, one in which a current collector, a catalyst layer, and a polymer electrolyte membrane are laminated is usually used. When it is intended to operate as a fuel cell using this, it is preferable that the joined body is composed of five layers in the order of current collector / catalyst layer / polymer electrolyte membrane / catalyst layer / current collector.
Examples of the laminating method include (1) a method of bonding the above-described current collector-catalyst layer assembly to the polymer electrolyte membrane, and (2) a method of bonding the above-described polymer electrolyte membrane-catalyst layer assembly to the current collector. Can be obtained. The joined body composed of the five layers can be obtained, for example, by sandwiching both surfaces of a polymer electrolyte membrane with a collector / catalyst layer joined body in which the catalyst layer is on the polymer electrolyte side. It can also be obtained by sandwiching current collectors on both sides of a joined body composed of three layers of a catalyst layer / polymer electrolyte membrane / catalyst layer in which catalyst layers are laminated on both sides of an electrolyte membrane.
The current collector-catalyst layer-polymer electrolyte membrane assembly thus obtained can be subjected to heat treatment and / or press treatment as necessary.
[0048]
Next, the fuel cell of the present invention will be described.
A fuel cell can be operated by flowing oxygen gas on one surface and hydrogen gas on the other surface of the current collector-catalyst layer-polymer electrolyte membrane assembly obtained above. At this time, the oxygen gas and / or the hydrogen gas can be supplied after being humidified. The operating temperature range is not particularly limited, but is preferably 0 to 150 ° C, more preferably 30 to 120 ° C, and particularly preferably 50 to 100 ° C.
[0049]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0050]
Reference Example 1Preparation of aromatic polymer having super strong acid group in side chain
15 g of poly (oxy-4,4′-biphenyleneoxy-4,4′-diphenylsulfone) (manufactured by Aldrich) and 80 ml of methylene chloride were dissolved in a flask, and 46.5 g of bromine was added at 10 ° C. while maintaining the temperature at 0 ° C. Minutes. After stirring for 4 hours at room temperature, the reaction was₂SO₃Was added to the dissolved aqueous solution. Thereafter, methylene chloride was distilled off under reduced pressure, filtered and dried to obtain 20.5 g of a polymer (a). Elemental analysis,¹H NMR,^ThirteenAs a result of C NMR measurement, it was found that a bromo group was introduced into the phenyl ring of the obtained polymer (a). In the polymer (a), 27.7% by weight of a bromo group was introduced. As a result of measuring the molecular weight by GPC using DMAc as a developing solvent, the number average molecular weight was 34,000 in terms of polystyrene.
A flask was charged with 15.01 g of 5-iodo-octafluoropentyl-3-oxapentane sulfonyl fluoride, 5 ml of water, 5 ml of methylene chloride, 4.80 g of 2,6-lutidine, and a 1MTHF solution of tetra-n-butylammonium fluoride in 0.1 ml. 1 ml was added and reacted at room temperature for 4 days. After extraction with methylene chloride three times, the solvent was distilled off under reduced pressure, 30 ml of THF and 2.82 g of potassium carbonate were added, and the mixture was stirred at room temperature for 10 h. The solid was separated by filtration and the filtrate was concentrated, whereby a white solid precipitated. The white solid was recrystallized from a mixed solvent of THF / toluene to obtain 12.3 g of a white solid. The resulting white solid is¹⁹From the results of F-NMR and elemental analysis, the powder was confirmed to be potassium 5-iodo-octafluoro-3-oxapentanesulfonic acid (b).
0.500 g of the polymer (a), 0.500 g (7.87 mmol) of copper powder, and 10 ml of N, N-dimethylsulfoxide were placed in a flask purged with nitrogen, and stirred at 120 ° C. for 2 hours. Next, a solution of 1.00 g (2.16 mmol) of (b) in 10 ml of N, N-dimethylsulfoxide was added while maintaining the temperature at 120 ° C. After performing the reaction at 120 ° C. for 40 hours, the mixture was added to 100 ml of a 1N aqueous HCl solution to precipitate a polymer. The precipitated polymer was dried to obtain an aromatic polymer (c) having a super strong acid group in a side chain.
[0051]
Reference Example 2Production of sulfonated polyetheretherketone
It was manufactured in accordance with JP-T-2001-525471. Specifically, 25 g of commercially available polyetheretherketone (manufactured by Aldrich) and 125 ml of concentrated sulfuric acid were charged into a flask, and the polymer was sulfonated by stirring at room temperature for 48 hours under a nitrogen stream. The reaction solution was slowly dropped into 3 liters of deionized water to precipitate a sulfonated polyetheretherketone, which was collected by filtration. The precipitated precipitate was repeatedly washed with deionized water using a mixer and a collection operation using a suction filter until the washing liquid became neutral, and then dried to obtain a sulfonated polyetheretherketone (d). .
[0052]
Example 1Evaluation of fuel cell characteristics
A paste obtained by mixing 10 mg of commercially available platinum-supported carbon fine particles (amount of platinum supported = 30 wt%) with 0.071 ml of a 5 wt% methylene chloride / methanol = 80/20 (wt / wt) solution prepared in Reference Example 1 5cm²Was applied to a porous carbon woven fabric with a spatula and dried to form an electrode. Two electrodes were prepared and joined one by one to both sides of the polymer electrolyte membrane obtained according to Example 1 of JP-A-2001-250567, and the current collector / catalyst layer / polymer electrolyte membrane / A current collector-catalyst layer-polymer electrolyte membrane assembly comprising five layers of catalyst layer / current collector was obtained. This was performed by flowing a humidified oxygen gas of 0.1 MPa to one surface of the joined body and a humidified hydrogen gas of 0.1 MPa to the other surface, keeping the joined body at 80 ° C., and measuring the power generation characteristics thereof. Table 1 shows the results.
[0053]
Example 2Evaluation of fuel cell characteristics
10 mg of commercially available platinum-supported carbon fine particles (amount of platinum supported = 30% by weight) was mixed with 0.1 ml of Nafion (5% by weight, alcohol / water mixed solution, manufactured by Aldrich) to form a paste into a paste of 5 cm.²Was applied by a screen printing method to a porous carbon woven fabric, and dried. Further, (c) synthesized in Reference Example 1 was dissolved in methylene chloride / methanol = 80/20 (wt / wt) to form a 1 wt% solution, which was applied by spraying to form a collector-catalyst layer assembly as an electrode. Created. (C) is a carbon woven cloth 5cm²2.2 mg was applied. Two electrodes were prepared, joined one by one to both sides of the polymer electrolyte membrane obtained in Example 1 of JP-A-2001-250567, and further pressed at a temperature of 100 ° C. and a pressure of 10 MPa for 90 minutes. As a result, a current collector-catalyst layer-polymer electrolyte membrane assembly comprising five layers of current collector / catalyst layer / polymer electrolyte membrane / catalyst layer / current collector was obtained. This was performed by flowing a humidified oxygen gas of 0.1 MPa to one surface of the joined body and a humidified hydrogen gas of 0.1 MPa to the other surface, keeping the joined body at 80 ° C., and measuring the power generation characteristics thereof. Table 1 shows the results.
[0054]
Comparative Example 1Evaluation of fuel cell characteristics
A paste obtained by mixing 10 mg of commercially available platinum-supported carbon fine particles (platinum supported amount = 30 wt%) with 0.143 ml of a 2 wt% methylene chloride / methanol = 80/20 (wt / wt) solution of (d) synthesized in Reference Example 2. 5cm²Preparation of a current collector-catalyst layer-polymer electrolyte membrane assembly and fuel cell property evaluation were performed in the same manner as in Example 1 except that an electrode was prepared by applying a spatula to a porous carbon woven fabric and drying the electrode. went. Table 1 shows the results.
[0055]
[Table 1]
Result of fuel cell characteristic test

[0056]
【The invention's effect】
According to the present invention, the power generation performance and the like of the fuel cell can be improved by using an aromatic polymer having a superacid group in a side chain as the proton conductive material in the catalyst layer of the fuel cell.

Claims (14)

A catalyst composition comprising three components: a metal catalyst (a), carbon fine particles (b), and an aromatic polymer (c) having a super strong acid group in a side chain. The composition according to claim 1, further comprising a perfluoroalkylsulfonic acid polymer (d). The aromatic polymer (c) having a super strong acid group in the side chain is represented by the following general formula (1)
− (AZ) _m − (A′−Z ′) _n − (1)
(In the formula, A represents a divalent aromatic group, A ′ represents a divalent aromatic group substituted by a super strong acid group. Z and Z ′ each independently represent a direct bond or a divalent group. And m and n represent the number of repeating units, n is in the range of 10 to 100,000, n repeating units may be the same or different, and m is in the range of 0 to 100,000. The m repeating units may be the same or different.)
The composition according to claim 1, wherein the composition is represented by: A is a divalent aromatic group selected from the following general formulas (3a) to (3c), and A ′ is a divalent aromatic group selected from (3d) to (3g). 3. The composition according to 3.

(In the formula, R represents a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, an aryl group, or halogen. P, r, s, t. Each independently represents a number from 0 to 4, q represents a number from 0 to 6, and when there are a plurality of Rs, these may be the same or different, j represents a number of 0 or 1, and Y represents a direct bond Or a divalent group, and when there are a plurality of Y, these may be the same or different, and Z ″ and Y independently represent a direct bond or a divalent group, and there are a plurality of Z ″ In the case, they may be the same or different, and when there are a plurality of Y, they may be the same or different.D represents a superacid group, and when there are a plurality of D, they may be the same. H, h ″ and h ′ ″ each independently represent 1 to 4, and h ′ represents 1 (P ′ + h), (r ′ + h ″), and (s ″ + h ′ ″) are independently 1 to 4, s ′, t ′, r ″, and t ″ are (Q '+ h') represents a number of 1 to 6 independently, and j represents a number of 0 or 1. Z, Z ′ and Y are each independently a direct bond, —O—, —S—, —CO—, —SO ₂ —, an alkylene group having 1 to 12 carbon atoms, an alkylenedioxy group having 1 to 12 carbon atoms. Z ′ is a group selected from the group consisting of a direct bond, —O—, —S—, —CO—, —SO ₂ —, and an alkylene having about 1 to 20 carbon atoms which may be substituted with fluorine. Group, an alkylenedioxy group having about 1 to 20 carbon atoms which may be substituted with fluorine, an arylene group having about 6 to 12 carbon atoms which may be substituted with fluorine, and which may be substituted with fluorine. The composition according to claim 3, wherein the composition is a group selected from an aryleneoxy group having about 6 to 12 carbon atoms and an alkyleneoxy group having about 1 to 20 carbon atoms which may be substituted with fluorine. object. The super strong acid group has the following general formula (2a) to (2d)
^{_{-G-SO 3 - W + (}} 2a)
^{_{-G-SO 2 N - W +}} SO 2 -E (2b)
-GP (O) (O ^- W ⁺ ) ₂ (2c)
-GP (O) O ^- W ⁺ -E (2d)
(Where G is an alkylene group in which part or all of hydrogen is substituted with fluorine, an aralkylene group in which part or all of hydrogen is substituted with fluorine, or an arylene group in which part or all of hydrogen is substituted with fluorine. W ⁺ represents a cation; E is an alkyl group in which part or all of hydrogen is substituted with fluorine, an aralkyl group in which part or all of hydrogen is substituted with fluorine, or part or all of hydrogen. Represents an aryl group substituted with fluorine.)
The composition according to claim 1, wherein the composition is selected from the group consisting of: The composition according to claim 6, wherein W is a hydrogen ion. 8. The composition according to claim 1, wherein the amount of component (c) is (c) / (a) = 0.01 to 100 on a weight basis relative to component (a). 9. The composition according to claim 1, wherein the amount of component (b) is (b) / (a) = 0.01 to 100 on a weight basis relative to component (a). The composition according to any one of claims 1 to 9, wherein the component (a) is platinum, an alloy containing platinum as an essential component, or a composition containing platinum as an essential component. A current collector-catalyst layer assembly comprising a current collector and a catalyst layer containing each component according to claim 1. A catalyst layer-electrolyte membrane assembly comprising an electrolyte membrane and a catalyst layer containing each of the components according to claim 1. A current collector-catalyst layer-electrolyte membrane assembly comprising an electrolyte membrane, a current collector, and a catalyst layer containing each of the components according to claim 1. A fuel cell comprising the composition according to any one of claims 1 to 10 or the joined body according to any one of claims 11 to 13.