JP3601753B2 - Highly functional material holding ultrafine metal particle-supported photocatalyst and method for producing the same - Google Patents
Highly functional material holding ultrafine metal particle-supported photocatalyst and method for producing the same Download PDFInfo
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- JP3601753B2 JP3601753B2 JP24588597A JP24588597A JP3601753B2 JP 3601753 B2 JP3601753 B2 JP 3601753B2 JP 24588597 A JP24588597 A JP 24588597A JP 24588597 A JP24588597 A JP 24588597A JP 3601753 B2 JP3601753 B2 JP 3601753B2
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- metal
- photocatalyst
- ultrafine
- particles
- fine particles
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Images
Description
【０００１】
【発明の属する技術分野】
本発明は光触媒微粒子を素材表面に保持した高機能性素材に関し、更に詳細には、金属超微粒子を光触媒微粒子に担持した金属超微粒子担持光触媒を繊維や窓ガラス等の素材表面に保持させた自浄分解力のある高機能性素材およびその製造方法に関する。
【０００２】
【従来の技術】
二酸化チタンの光触媒反応は１９７２年にネイチャーに発表され、本田・藤島効果として世界に知られるところとなった。それ以来、光照射下での二酸化チタンによる水の分解、また有機物水溶液の分解を通して水素と二酸化炭素の生成研究が行われ、現在ではタイルや窓ガラスに二酸化チタンの微粒子を薄膜状に保持させて環境汚染物質、即ちタバコのヤニや細菌あるいは細菌が作った毒素等の有機物の分解に実用化されつつある。
【０００３】
二酸化チタンは粉末状の金属酸化物であり、水や溶液の分解では溶液中に分散して使用する。しかし、窓ガラスや風呂タイル、建材表面には粒子状であっても均一な薄膜状に付着することが望まれる。そのためにゾルーゲル法、チタンアセテートなどのスプレーパイロリシス法やディップコーティング法等が開発されるに至った（応用物理第６４巻８（１９９５）ｐｐ８０３、化学と工業第４８巻１０（１９９５）ｐｐ１２５６、化学と工業第４９巻６（１９９６）ｐｐ７６４）。これらの二酸化チタン保持ガラス等を用いて、紫外線照射下で付着した油やタバコのヤニも分解できることが示された。チリ・ホコリ等の無機物を分解することは難しいが、油などの有機物がバインダーとなって無機物が付着していたため、有機物の分解によって無機物も付着しにくくなったことが報告されている。
【０００４】
タイル等の素材上における二酸化チタン微粒子の作用原理は、二酸化チタンの半導体としての光触媒特性である。二酸化チタンにバンドギャップ・エネルギーより大きな光、例えば紫外線を照射すると、価電子帯にある電子が励起されて伝導帯に遷移し、価電子帯には正電荷の正孔が残されて電子−正孔の対が生成される。この電子と正孔は二酸化チタン中を動きながら表面に到達し、電子は空気中の酸素に与えられてＯ２ −（スーパーオキサイドアニオン）を作って他の物質を還元する。正孔は有機物を直接酸化分解するだけでなく表面に付着する水分子を酸化して水酸ラジカルという強酸化物を作り、この水酸ラジカルの酸化力により他物質を酸化する。前記Ｏ２ −はこの酸化過程にも関与していると云われるが、その詳細な反応回路は現在もなお研究対象となっている。このようにして光により誘起された電子−正孔対により有機物は二酸化炭素と水にまで分解される。
【０００５】
この研究の中で、二酸化チタン単体では電子と正孔が外部物質を酸化還元する前に再結合して消滅する場合があるから、その光触媒効率に限界があることが指摘されていた。二酸化チタンは常態が粉末であり、その一粒を考えてみると、その表面及び内部には無数の点欠陥・面欠陥等の格子欠陥が入っている。紫外線により二酸化チタンに誘起された電子と正孔はその移動過程で格子欠陥に遭遇すると、その格子欠陥に捕獲されて再結合してしまう。また表面に移動できても電子と正孔が接近すると再結合する場合もある。これを改善するには格子欠陥のない二酸化チタンの作製技術と表面で電子−正孔を分離する技術を開発しなければならない。前者については結晶成長技術の改良が逐次なされてきており、また本発明とは直接関係しないのでここではその詳細を省略する。
【０００６】
表面で電子−正孔を分離する技術に関しては、励起電子を集電する電極を二酸化チタン上に形成して、二酸化チタン表面に正孔を、金属電極表面に電子をそれぞれ分離集電する光触媒が提案された。このようにすれば金属電極上に効率的に電子を集電でき、しかも正孔と電子を分離できるので再結合の確率が低くなると考えられたのである。この種の光触媒を金属担持光触媒といい、従来から触媒として用いられているＰｔ（白金）やＣｕ（銅）等の金属を二酸化チタン上に形成して作製された。金属単体でも触媒作用を有するものならば、二酸化チタンの触媒作用と相乗効果を発揮できるだろうというアイデアである。
【０００７】
このような金属担持光触媒の製法として、光析出法、混合法、含浸法、化学析出法、同時沈澱法が開発されてきたが、担持される金属粒子の粒径はミクロン程度と大きく、しかも二酸化チタン粒子１個当りに担持される金属微粒子の個数（担持密度）も数十個の範囲に留まっていた。担持密度が小さいのは、金属微粒子の粒径が大きいために多くの金属微粒子が１個の二酸化チタン粒子上に付着しないことも原因の一つである。従って、金属担持の光触媒効果については二酸化チタン単体よりも２〜４倍に程度に増強されるに過ぎなかった。
【０００８】
発明者等はなぜミクロンサイズの金属微粒子では触媒効率がそれほど増強されないかについて、図１７を参照しながら理論的に検討してみた。
二酸化チタン中に生じた電子を金属電極中に効率的に取り込むためには、二酸化チタンと金属の界面における電子遷移の障壁をできるだけ小さくすることが望まれる。ところが金属微粒子の粒径がミクロンサイズ（約０．１μｍ以上）の場合には、その電子状態は大きな固体結晶（バルク結晶）とほぼ同じバンド構造となる。つまり、価電子帯と伝導帯が一定のバンドギャップを隔てて画然と形成され、伝導帯では自由電子が底から最上端のフェルミ準位まで順に密に詰まった構造となる。他方、二酸化チタンはバルクな結晶であるからその電子状態は当然バンド構造をとる。バンド構造においては、バンドを構成するエネルギー準位はほぼ連続的に密に配置され、各準位に対応した波動関数はその物質内に鋭く局在している。換言すると、波動関数がその物質外に裾をはみ出すことがないため、その準位に滞在する電子は物質外に放出される確率がかなり小さくなる。
【０００９】
この状態で、二酸化チタンが紫外線照射を受けて電子が伝導帯に励起され電子−正孔対が生成されたとしよう。この電子が外部物質Ａを還元したりスーパーオキサイドアニオンを生成するためには、電子が迅速に二酸化チタンから金属中に移動し、更に金属から金属外の外部物質Ａに移動する必要がある。ところが上述したように金属微粒子はミクロンサイズであるから、電子状態が大きな結晶と同様のバンド構造をとるだけでなく、波動関数も金属微粒子内に鋭く局在した構造をとる。従って、二酸化チタンの伝導帯に上った電子は金属の波動関数に乗ることが容易でないから、金属の伝導帯に移動することも簡単ではない。また電子が金属に何とか移動できても、金属から外部物質に移動することも同様に容易でないため、金属の外部に出る前に金属の伝導帯にあるフェルミ準位ＥＦの上に素早く落ちてしまう事が多く、外部物質と反応する機会は更に少なくなる。
【００１０】
つまり、バンド構造のように伝導帯の準位密度が大きい場合には、電子がフェルミ準位の上にまで落ちる時間（緩和時間）が極端に短くなり、波動関数の局在性とともに電子の外部への移動を阻止するのである。換言すると、ミクロンサイズでは電子は外部に出にくいから金属内に電子が過剰に蓄積されることとなり、その反発電場によって逆に二酸化チタン内の電子が金属中に移動することを阻止する結果となる。結局、金属微粒子の粒径がミクロンサイズの領域では、エネルギーのバンド構造と波動関数の局在性によって電子が二酸化チタン又は金属微粒子中に留まり、金属外部に放出される確率が小さくなると結論できる。同時に、ミクロンサイズの金属微粒子の場合には、１個の二酸化チタン粒子上に担持される金属微粒子の個数も数十個が限界であり、これらのことが金属担持光触媒の触媒効率を制限していた理由である。
【００１１】
光触媒は環境汚染物質の分解作用を有するが、これに吸着作用を付加しようとするアイデアが現れた。吸着作用を有する物質には活性炭、活性炭素繊維、ゼオライト等の多孔性材料がある。図１８の活性炭素繊維を説明すると、この繊維の表面には直径０．５ｎｍ程度の無数の孔、いわゆるミクロポアが開いている。このミクロポアに有機物等の環境汚染物質を吸着するのである。この活性炭素繊維は種々の形状に加工できるので浄水器や空気清浄機に多用されている。
【００１２】
この活性炭素繊維を素材として光触媒を保持させれば、活性炭素繊維が環境汚染物質を吸着し、光触媒が環境汚染物質を分解することができるはずである。特許第２５７４８４０号公報には活性炭に光触媒を保持させた脱臭装置が記載されている。これをより具体的に、活性炭素繊維にアナターゼ型二酸化チタンを保持させた光触媒と考えると、図１９がその想像図になる。ミクロポアに吸着された有機物が総て光触媒により分解されれば、効率１００％の吸着・分解力を有することになる。ところが、前述したように二酸化チタン単体の分解力には限界があるため、ミクロポアに有機物が残留するようになる。従って、活性炭素繊維の吸着力は次第に低下し、いずれアナターゼ型二酸化チタンの分解力だけが残存し、当初に予想した効果を発揮できないことが分かってきた。この主たる原因はアナターゼ型二酸化チタンの光触媒効率の限界であり、光触媒効率の画期的な向上が望まれていた。
【００１３】
二酸化チタンには結晶構造の違いからアナターゼ型とルチル型が存在する。このうちルチル型が安定構造で、約６００℃以上に加熱するとアナターゼ型の全てはルチル型に相転移し、冷却後の低温ではルチル型になる。６００℃以下でもアナターゼ型の一部はルチル型になる。従って、ルチル型がアナターゼ型よりも安価に量産できる二酸化チタンである。しかし従来、光触媒として用いられてきた二酸化チタンは全てアナターゼ型であり、安価なルチル型は全く使用されなかった。その理由はバンド構造から理解できる。
【００１４】
図２０にはルチル型二酸化チタンのバンド構造が示されている。そのギャップエネルギーは３．０５ｅＶである。紫外線により伝導帯に励起した電子は緩和によりエネルギーを一部消費しながら伝導帯の底に到達する。還元電位である酸素電位は３．１３ｅＶに位置しているから、伝導帯の底から酸素電位に登ることは外部エネルギーをもらう以外になく、自然には起こりにくい。従って、ルチル型ではスーパーオキサイドアニオンを生成することが困難である。
一方、図２１にはアナターゼ型二酸化チタンのバンド構造が示されている。そのギャップエネルギーは３．２０ｅＶであり、紫外線励起後、伝導帯の底に落ちてきても３．１３ｅＶの酸素を十分に還元でき、スーパーオキサイドアニオンを生成できる能力を有している。従って、現在の技術では高価なアナターゼ型二酸化チタンを光触媒として使用せざるを得なかった。
【００１５】
【発明が解決しようとする課題】
従って、本発明の課題は二酸化チタンの光触媒効率を格段に増強できる方法を見いだすことである。また従来安価であるにも拘らず光触媒として利用されなかったルチル型二酸化チタンを、光触媒として活用できる方法を見いだすことである。更に、活性炭素繊維等の吸着力を消失させないで分解力を格段に向上できる光触媒を実現し、吸着・分解のサイクルの長寿命化を達成することである。
【００１６】
【課題を解決するための手段】
本発明は上記欠点を解消するためになされたものであり、本発明に係る金属超微粒子担持光触媒を保持した高機能性素材は、金属超微粒子を光触媒微粒子に担持させ、この金属超微粒子担持光触媒を素材の表面に保持させることを基本構成としている。二酸化チタンの光触媒機能を格段に増強するためにナノスケールの金属超微粒子にまで金属粒子を極少化している。
金属超微粒子は量子サイズ効果を顕著に発現する１〜１０ｎｍの粒径を有し、光触媒微粒子１個当りに金属超微粒子を１００個以上担持させることに特徴を有している。金属超微粒子の材質は遷移金属であり、特にｐｔ、Λｕ、Ｐｄ、Ｒｈ又はＡｇが適当である。
光触媒微粒子は紫外線照射により水酸ラジカルおよび／またはスーパーオキサイドアニオンの生成能力を有する金属酸化物半導体であり、特に二酸化チタンが好適である。
素材は１次元、２次元又は３次元素材が利用でき、その中でも１次元素材としての繊維が利用できる。中でも活性炭素繊維は好適である。また、これらの繊維を編成・織成等により成形して作られた高機能性繊維製品も素材になる。
【００１７】
高機能性素材の製造方法には金属超微粒子担持光触媒を素材の表面に静電吸着させる方法がある。
コロイド焼成法として、光触媒微粒子に有機金属化合物コロイドを付着させる第１工程と、このコロイド付着光触媒微粒子を素材に添着させる第２工程と、この素材を焼成することにより有機金属化合物を還元して金属超微粒子を光触媒微粒子に強固に担持させ、同時にこの光触媒微粒子を素材に強固に保持させる第３工程から構成される製造方法がある。
また、別のコロイド焼成法として光触媒微粒子に有機金属化合物コロイドを付着させる第１工程と、このコロイド付着光触媒微粒子を焼成して金属超微粒子を光触媒微粒子に強固に担持させる第２工程と、この金属超微粒子担持光触媒を素材に添着させて焼成により光触媒微粒子を素材に強固に保持させる第３工程から構成される製造方法がある。
更に、原料繊維を炭化処理及び賦活化処理して活性炭素繊維に変成し、この活性炭素繊維を素材として上記のコロイド焼成法を適用する。
また膜状素材の製造方法として、溶媒上で薄膜状に展開する性質を有する物質に金属超微粒子を担持させた光触媒微粒子を混入させた後、この物質を溶媒上に展開して薄膜を形成し、この薄膜を２次元素材又は３次元素材の表面に保持させる方法がある。
【００１８】
【発明の実施の形態】
本発明者は金属担持二酸化チタンの光触媒機能を増強するために鋭意研究した結果、ナノスケールの金属超微粒子を二酸化チタン表面に担持させることにより、二酸化チタン単体よりも光触媒機能を約１００倍以上にまで増強できることが分かった。従って、ミクロンスケールの金属微粒子を担持した二酸化チタンと比較した場合でも、触媒効率を約３〜２５倍位にまで増強することができる。これは金属を微粒子から超微粒子へ転換すること、即ち粒径をミクロンスケールからナノスケールに、換言すれば粒径をミクロンスケール（約０．１μｍ以上）の１／１０〜１／１００程度にまで極小化することによって達成できるのである。本発明で用いられる金属超微粒子の平均粒径は１〜１０ｎｍ、より好ましくは１〜５ｎｍである。これより大きくすると後述する量子サイズ効果の発現が小さくなって光触媒効率の増強が顕著でなくなり、また粒径を更に小さくすると原子サイズに近接するため金属超微粒子の作製が技術的に困難になると同時に極めてコスト高になってしまう。
【００１９】
光触媒物質として二酸化チタン等の微粒子状の粉末を利用した場合には、光触媒微粒子１個に担持できる金属超微粒子の個数、つまり金属超微粒子の担持密度がその粒径とともに重要な要素となる。本発明ではナノスケールにまで極少化された金属超微粒子を用いることにより、光触媒微粒子１個に多数の金属超微粒子を担持させることを可能にした。即ち、ミクロンスケールの金属微粒子からナノスケールの金属超微粒子へと粒径の極少化を実現したことにより、担持密度の劇的な向上を達成したのである。本発明者等の研究によれば、光触媒微粒子１個当りに担持される金属超微粒子の平均個数は１００個以上、好ましくは２００個以上に設定することが望まれる。担持密度が１００個以上であれば量子サイズ効果との相乗効果により光触媒効率を従来より顕著に増大化できる。２００個以上であれば光触媒効率の格段の増加を達成できる。もちろん担持密度を更に増加できれば、光触媒効率の更なる増大化を図ることが可能となる。
【００２０】
金属超微粒子により初めて発現する量子サイズ効果について以下に検討する。例えば直径１ｎｍの超微粒子を考えると、その中に金属原子は原子のサイズに依存するが約１０〜１００個程度しか存在しない。又直径１０ｎｍの金属超微粒子になると約１００００〜１０００００個の原子を含有すると考えられる。このように原子数の少ない金属超微粒子では、金属の電子エネルギー状態はバンド構造から次第に離散的になり始め、エネルギー準位が広範囲に分布する。例えば伝導帯を考えてみると、伝導帯を構成する多数のエネルギー準位が密に固まった状態から互いに離散しながら上下に広範囲に分布するようになる。この準位の離散化は電子の緩和時間、即ちその準位からフェルミ準位に落ちるまでの時間を長くする効果を奏する。つまり、電子が準位に滞在する時間が長くなるのである。同時に、エネルギー準位に対応した波動関数が左右に裾を延ばしながら金属外部にもはみ出し、同時にピークが低くなる効果も有する。つまりこの波動関数に乗った電子は量子トンネル効果により容易に外部に移動できることになる。本発明において量子サイズ効果という場合には、上記したようにエネルギー準位の離散化と波動関数の非局在化による量子トンネル効果の発現を意味する。
【００２１】
図１には金属超微粒子担持光触媒が活性炭素繊維に保持されている状態が示されている。金属超微粒子担持光触媒の重量は繊維重量の少なくとも１％以上、好ましくは３％以上あればよい。１％以下だと金属超微粒子担持光触媒の効果が十分ではなくなる。光触媒はルチル型二酸化チタンであり、数ｎｍの粒径の金属超微粒子がルチル型二酸化チタンに高密度に担持されている。まず、活性炭素繊維が環境汚染物質である有機物を吸着し、そのミクロポアに有機物が詰め込まれてゆく。次に、金属超微粒子担持光触媒が有機物の分解を始める。
【００２２】
金属超微粒子を担持した二酸化チタンが如何に有機物に対し効率的に酸化還元を行うかを見てみよう。図２は金属超微粒子を二酸化チタン上に担持した場合のエネルギー状態を示している。二酸化チタンに紫外線を照射すると電子−正孔対が形成され、価電子帯に正孔を残して伝導帯に電子が励起される。エネルギーの大きな紫外線で励起された場合には電子は伝導帯の高い位置に遷移するが、次第にエネルギーを失いながら伝導帯の底に落ちてくる。金属のエネルギー準位はある程度密に離散化しているため、二酸化チタンの伝導帯の底に対応したエネルギー準位が必ず存在する。しかもその準位の波動関数は左右に長く裾を引いており、左端は二酸化チタン中に右端は金属外部にまで延びている。つまり、二酸化チタンと金属のエネルギー準位は金属の波動関数を介して共鳴的に連続していることになる。二酸化チタンの伝導帯にある励起電子はその金属の波動関数に乗って一気に金属を介して外部に量子トンネル効果により放出される。二酸化チタンと金属が共鳴状態にあるため、この量子トンネル効果を共鳴トンネリングと称する。このとき金属中の準位は離散化しているので電子の緩和時間は長く、従って電子は金属のフェルミ準位の上に落ちる前に容易に金属外に放出されるのである。
【００２３】
二酸化チタンの価電子帯にある正孔は二酸化チタン表面に移動し、外部物質Ｄを酸化する。また外部物質を酸化するだけでなく、表面に付着した水を酸化して水酸ラジカルという強酸化物を生成し、この水酸ラジカルが外部物質を酸化分解しているとも考えられている。一方、金属外に共鳴トンネリングで放出された電子は外部物質Ａを直接還元するだけでなく、空気中の酸素を還元してＯ２ −というスーパーオキサイドアニオンを生成し、このアニオンが前記外部物質Ｄの分解にも関与していると考えられている。
特に、本発明では二酸化チタンから金属に移動した励起電子は金属中に蓄積されずに直ちに外部に放出されるから外部に反発電場が形成されず、紫外線照射による励起電子を次々と吸引することができる点で優れた還元力を有している。
【００２４】
二酸化チタンに限らず、本発明で用いられる光触媒の種類は、酸化還元しようとする分解対象物質によって決まる。この分解対象物質が還元される物質の場合には還元電位が存在し、酸化される物質の場合には酸化電位が存在する。これらの還元電位と酸化電位が光触媒物質の価電子帯と伝導帯の間にあるエネルギーギャップ内に位置している必要がある。詳しく述べると、図２に示すように、還元電位はギャップ内の上側に位置し、酸化電位はギャップ内の下側に位置するような光触媒物質を選択することが望まれる。この場合に、励起電子は伝導帯の底から還元電位に落ちて対象物質を還元し、正孔は価電子帯の上端から酸化電位に登って対象物質を酸化できる。但し、本発明では金属超微粒子の共鳴トンネリングが効力を発揮するから、還元電位は伝導帯の底の位置または少し上側にあってもよい。
【００２５】
図２ではルチル型二酸化チタンを用いているから、図２０と同じように還元電位は伝導帯の底より０．０８ｅＶ上に位置している。それでも励起電子はその位置の金属準位から共鳴トンネリングにより素早く外部物質を還元できる。この共鳴トンネリングによってルチル型二酸化チタンも光触媒として利用できるようになった意義は画期的である。量産性のある安価なルチル型二酸化チタンが本発明によって初めて光触媒として脚光を浴びることになる。
【００２６】
又、近年の研究では、電子はＯ２を還元してスーパーオキサイドアニオンＯ２−にし、正孔は水を酸化して水酸ラジカルを形成し、これらのＯ２ −と水酸ラジカルが対象物質を分解すると考えられている。従って、還元電位としてＯ２電位、酸化電位としてＯＨ電位を選んで光触媒物質を選択することもできる。即ち、紫外線の照射によって電子−正孔対が生成され、電子によって空気中や水中の酸素を還元してスーパーオキサイドアニオンを生成し、正孔によって表面に付着した水を酸化して水酸ラジカルを生成する光触媒物質であればよい。
【００２７】
光触媒物質としては半導体が適当である。絶縁体ではギャップエネルギーが大きすぎて通常の紫外線では電子−正孔対を生成するのが困難であり、またギャップエネルギーの小さな物質では禁制帯内に酸化および還元電位を配置させることが困難になるととも、水溶液に溶解し易くなるために不適である。
半導体の中でも金属酸化物半導体が本発明には適切である。金属酸化物は金属単体と比較して極めて安定な物質であるため、他物質との反応性が低くて安全でもあり、しかも電子の授受を十分に行うことができる物質である。従って、これらの性質を満足する金属酸化物半導体が本発明の光触媒物質として利用でき、例えば、ＷＯ３、ＣｄＯ３、Ｉｎ２Ｏ３、Ａｇ２Ｏ、ＭｎＯ２、ＣＵ２Ｏ３、Ｆｅ２Ｏ３、Ｖ２Ｏ５、ＴｉＯ２、ＺｒＯ２、ＲｕＯ２，Ｃｒ２Ｏ３、ＣｏＯ３、ＮｉＯ、ＳｎＯ２、ＣｅＯ２、Ｎｂ２Ｏ３、ＫＴａＯ３、ＳｒＴｉＯ３、Ｋ４ＮｂＯ１７等を含む公知の物質から分解対象物質に応じて選択することができる。この中でも、生成される電子−正孔密度やスーパーオキサイドアニオン・水酸ラジカル密度および材質としての耐腐食性・安全性等の観点からＴｉＯ２、ＳｒＴｉＯ３、Ｋ４ＮｂＯ１７が好ましく、特に二酸化チタンであるＴｉＯ２が最も望ましい。
【００２８】
本発明に利用できる光触媒物質は微粒子である。微粒子はその表面積が極めて大きいから環境汚染物質と接触する確率が大きくなると同時に、多数の金属超微粒子を表面に担持することができる。また、微粒子の方が紫外線等の有効受光面積が大きくなり、光触媒効率がバルク物質より格段に高くなる。通常、金属酸化物は粉体であるから、二酸化チタンのような金属酸化物半導体が本発明には適する。粒径としては３０ｎｍ〜１０００ｎｍ、より好ましくは５０ｎｍ〜５００ｎｍである。これより小さいと超微粒子に近づいて行くため製造に特殊な技術とコストがかかり、これより大きいと比表面積が小さくなって環境汚染物質・人体毒性物質・悪臭物質等との反応性が悪くなる。
例えば二酸化チタンを１０ｎｍ程度に超微粒子化することは可能であるが、独立した粒子として存在せず、二酸化チタン超微粒子が集合して団子状に固まり、結局前述のような大きな二酸化チタンの塊となる。この場合にはゴツゴツしているため表面積は単一固体よりは大きくなるから、反応性はより高くなる。本発明はこのような光触媒微粒子も包含する。光触媒微粒子の形態は金属超微粒子を担持できる限り特に制限されず、例えば球状・ペレット状・粒状などの形態で使用できる。
【００２９】
本発明において利用できる光源は、光触媒のバンドギャップ・エネルギー以上のエネルギーを有する光源であればよく、通常は紫外線灯が用いられる。特に二酸化チタンを用いる場合には、ルチル型とアナターゼ型があり、各々のギャップエネルギーを波長に換算すると、ルチル型は４０７ｎｍ、アナターゼ型は３８８ｎｍである。従って、二酸化チタンに対する光源の波長分布は４００ｎｍをピーク付近に有することが望ましい。図３の波長分布を有する誘蛾灯は、４００ｎｍがピーク近傍にあるためルチル型およびアナターゼ型両方に有効で極めて好ましい。
【００３０】
図４の波長分布を有する自然太陽光線は、可視光線が中心であるが、４００ｎｍを含んでいるために十分に利用できる。特に自然太陽光線では３８８ｎｍより４０７ｎｍの方が光強度が高いのでルチル型の方がアナターゼ型よりも有効である。従って、本発明によりルチル型二酸化チタンを光触媒として利用できることは自然太陽光線を活用できる大きな道を開いたものである。このことは、従来のアナターゼ型の場合には紫外線灯を利用できても、自然太陽光線の場合には触媒効率が極めて低かったことと対照的である。また、従来の光触媒では、屋外での太陽光線の利用は光強度が強いために可能であったが、屋内利用では光強度が弱いため弱点となっていた。しかし、本発明では光触媒効率が格段に増強されているため、太陽光線を光源として屋内における光触媒の利用の拡大を図ることが可能となる。
【００３１】
担持される金属超微粒子は遷移金属であればよい。遷移金属元素とは不完全なｄ殻を有する元素で原子番号２１（Ｓｃ）〜２９（Ｃｕ）、３９（Ｙ）〜４７（Ａｇ）、５７（Ｌａ）〜７９（Ａｕ）および８９（Ａｃ）〜理論的には１１１までの４グループからなる金属元素である。ｄ殻が不完全であるために最外殻がｄ電子により方向性を有し、その結果光触媒物質からやってくる励起電子を金属超微粒子表面で捕まえ易く、スーパーオキサイドアニオンを生成し易い。
金属単体で触媒として利用できる金属が望ましく、また安全性の観点から考えるとＡｕ、ｐｔ、Ａｇ、Ｐｄ、Ｒｈが好ましく、金属としての安定性の観点からＡｕ、Ｐｔ、Ｐｄがより好ましい。
【００３２】
本発明の特徴は、微粒子からなる光触媒物質の表面に金属超微粒子を担持形成する方法を確立したことである。従来の製法ではミクロンサイズの金属微粒子を担持させることはできたが、ナノスケールの金属超微粒子を形成担持することは不可能であった。この従来製法の限界が光触媒効率の向上を阻害していた原因でもあった。
従来製法が金属塩または金属粉を原料として使用していたのに対し、本発明では加熱により還元可能な有機金属化合物を用いることにより、光触媒効率の飛躍的な向上を達成したのである。加熱により還元可能とは、加熱すると有機金属化合物から金属だけが単離でき、換言すれば他の有機物部分が分離されてしまうことである。有機金属化合物の中でも、特に有機金属錯体が本発明の目的に適している。しかし、加熱により還元可能な有機金属化合物で有れば特に制限されないことは云うまでもない。
【００３３】
この中でも金属としての安定性および安全性の観点から、特にＡｕ系化合物、Ａｇ系化合物、Ｐｄ系化合物、Ｒｈ系化合物又はｐｔ系化合物の少なくとも１種を用いることが好ましい。より好ましくはＡｕ、Ａｇ、Ｐｄ、Ｒｈ又はｐｔと硫黄含有有機物との化合物であり、更に最も好ましくはＡｕ、Ｐｄ、Ｒｈ又はｐｔと硫黄含有有機物との化合物である。例えば、メチルメルカプタン、エチルメルカプタン、プロピルメルカプタン、ブチルメルカプタン、オクチルメルカプタン、ドデシルメルカプタン、ヘキサデシルメルカプタン、オクタデシルメルカプタン等のアルキルメルカプタン、チオグリコール酸ブチル等のチオグリコール酸類、そのほかトリメチロールプロパントリスチオグリコレート、チオグリセロール、チオ酢酸、チオ安息香酸、チオグリコール、チオジプロピオン酸、チオ尿素、ｔ−ブチルフェニルメルカプタン、ｔ−ブチルベンジルメルカプタン等が挙げられる。更にその他、バルサム金（Ｃ１０Ｈ１８ＳＡｕＣｌ１−３）、バルサム白金（Ｃ１０Ｈ１８ＳｐｔＣ１１−３）、バルサムパラジウム（Ｃ１０Ｈ１８ＳＰｄＣｌ１−３）、バルサムロジウム（Ｃ１０Ｈ１８ＳＲｈＣｌ１−３）等が利用できる。
【００３４】
上記の有機金属化合物と二酸化チタン等の光触媒物質の粉末を適当な公知の親水溶媒中に分散させると有機金属化合物の疎水コロイド等が形成でき、この有機金属化合物コロイド粒子が光触媒粉末粒子の表面に多数付着する。この混合液を乾燥させ、残った固体残留物を焼成すると、有機金属化合物のうち有機物は逃散し、金属だけがナノスケールの超微粒子となって光触媒微粒子の表面に担持されるのである。混合液自体を加熱して溶媒を蒸発させ、更に加熱により固形の残留物を焼成する等、乾燥・焼成が一連の工程となる場合も含む。
また別の製法として、上記の有機金属化合物のコロイド溶液と光触媒粉末を互いに対向させて噴霧すると、光触媒粉末粒子の表面にコロイドが多数付着し、このコロイド付着光触媒粉末粒子を落下する途中で加熱処理すると、金属超微粒子担持光触媒微粒子を連続的に製造することができる。
【００３５】
有機金属化合物の溶液濃度は、最終製品等に応じて適宜設定できるが、通常は０．１重量％以上とし、好ましくは０．５〜５０重量％とする。溶媒は有機金属化合物の種類により適宜選択でき、アルコール類、エステル類、芳香族類等の公知の有機溶媒を使用することができる。
【００３６】
本発明における焼成温度は、通常は有機金属化合物の還元析出温度以上であって、且つ還元されて析出する金属の融点未満の温度範囲内で適宜変更することができる。更に具体的に述べると、有機金属錯体のような有機金属化合物から金属を単離するためには、有機金属化合物を完全に分解して金属原子だけを残して他の有機物原子を逃散させなければならない。この温度を金属の還元析出温度と定義している。次に、単離された金属原子を集合させて金属超微粒子にまで再配列させなければならない。この上限温度はバルクの金属の融点以下であればよく、好ましくは、析出金属の融点の８０％以下、特に７０％以下とする。また、焼成雰囲気は酸化雰囲気、また希薄空気でもよく最終製品に応じて適宜選択できる。
【００３７】
本発明の最大の特徴は極めて優れた光触媒能力を有する金属超微粒子担持光触媒微粒子を素材に保持させる点にある。二酸化チタンだけを素材に保持させた場合には、二酸化チタンの分解力の限界が素材の自浄分解力の限界になり、商品としての素材の品質の限界になっていた。本発明では金属超微粒子担持光触媒を素材に保持させることにより、商品である素材の品質を格段に向上させたものである。生活環境には環境汚染物質や人体有害物質が充満しており、この空間内に本発明に係る素材を置いておくだけで、素材の自浄分解機能が作用して前記物質を水と二酸化炭素にまで分解し、環境の清浄化を期することができる。無機物質の分解は有機物質より困難性を有するが、有機物質が分解されることにより、従来有機物質がバインダーとなってチリ等の無機物質が素材に付着していた現象がなくなり、素材の長期清浄化を図ることもできる。
【００３８】
本発明で用いられる素材は１次元素材、２次元素材および３次元素材に分類できるが、１次元素材の典型例は繊維である。
繊維には天然繊維と化学繊維が含まれ、化学繊維には無機繊維、再生繊維、半合成繊維および合成繊維が包含される。天然繊維には動物繊維、植物繊維、鉱物繊維（石綿など）が含まれ、無機繊維には金属繊維、ガラス繊維、炭素繊維、活性炭素繊維等があり、合成繊維にはポリエステル系、ポリアクリル系、ポリアミド系、ポリプロピレン系、ポリエチレン系、ポリビニルアルコール系、ポリ塩化ビニル系、ポリ塩化ビニリデン系、ポリウレタン系、ポリアルキルパラオキシべンゾエート系、ポリテトラフルオロエチレン系などがあるが、近年のスーパー繊維、例えばアラミド系、全芳香族ポリエステル系、ヘテロ環系なども包含される。
【００３９】
金属超微粒子担持光触媒を保持した繊維と単なる活性炭素繊維を混紡した場合には活性炭素繊維が環境汚染物質を吸着し、他方の繊維上の金属担持光触媒微粒子によって分解できるという利点がある。また、金属担持光触媒微粒子を保持した炭素繊維を単なる活性炭素繊維と混紡した場合には吸着分解効果に繊維の色調も同一である点で用途が拡大する利点がある。更に、金属担持光触媒微粒子を活性炭素繊維の表面に形成した場合には、この繊維単独で吸着分解能力を有する点で優れている。
繊維だけでなく、これらの繊維を編成してできた編物、織成してできた織物および不織布状に成形したフェルト等の不織布、更にフィルターその他の繊維製品も本発明の素材に含まれる。フィルターは空気清浄器、浄水器、トイレ脱臭器、室内脱臭器、冷蔵庫脱臭器などに利用できる。
【００４０】
平面状の２次元素材としては窓ガラス、鏡、テーブル、壁材、タイル、障子、ふすま等があり、立体状の３次元素材としてはトイレの便器、家具、置物などがある。これらの表面に本発明の金属超微粒子担持光触媒を保持させれば、有機性の環境阻害物質・人体に有害な物質・悪臭などを自然の太陽光、蛍光灯、あるいは紫外線灯からの紫外線により自然に自浄分解することができる。有機物を分解するから、いままで有機物をバインダーにして付着していた無機汚れも付着しにくくなる。
【００４１】
金属超微粒子担持光触媒を素材に保持させる各種の方法がある。例えば、金属超微粒子担持光触媒からなる粉末を適当な溶媒中に分散させ、この溶媒中に素材を浸漬して金属担持光触媒微粒子を添着する浸漬法。また金属超微粒子担持光触媒を分散させた溶媒を素材に噴霧するスプレー法。２次元素材・３次元素材の場合にはローラーや刷毛での塗着法。
更に金属超微粒子担持光触媒を素材上に静電吸着させる方法がある。金属超微粒子担持光触媒微粒子も素材も自然状態で静電気を帯びており、この静電吸着力により金属超微粒子担持光触媒微粒子の粉末を素材に噴霧添着する方法や粉末中に素材を押し付けて添着させる方法等がある。又、電気集塵の原理によりまず金属超微粒子担持光触媒微粒子をコロナ放電により強制帯電させておき、極板間の電界力で極板間又は極板上にある素材表面に添着することもできる。
【００４２】
これらの方法により金属超微粒子担持光触媒微粒子を添着した素材を適当温度に加熱して素材に強固に保持させることもできる。より効果的には、加熱により硬化するバインダーを予め素材表面に塗着し、この上に前記方法で金属担持光触媒微粒子を添着し、加熱硬化させれば金属担持光触媒微粒子を強固に保持させることができる。
【００４３】
炭素繊維や活性炭素繊維の表面に金属超微粒子担持光触媒を保持させるには、予め素材として準備された炭素繊維や活性炭素繊維の表面に上記の方法で金属超微粒子担持光触媒微粒子を添着し、その後これらの繊維を所定温度で焼成すれば金属超微粒子担持光触媒を炭素繊維や活性炭素繊維上に強固に保持できる。
また、原料繊維を炭化処理して炭素繊維にし、あるいは賦活化処理により活性炭素繊維にした後、金属超微粒子担持光触媒を前述の方法で炭素繊維または活性炭素繊維に保持することもできる。
【００４４】
炭素繊維の原料にはレーヨン繊維や石油ピッチ・石炭ピッチを溶融紡糸したピッチ繊維、アクリル繊維、その他多くの繊維があり、これらの繊維を炭素繊維や活性炭素繊維に変成するのもほぼ同じ焼成法を適用できる。中でも炭素繊維の原料の主力はＰＡＮ（ポリアクリロニトリル）で、これを紡糸したものがアクリル繊維である。このアクリル繊維について以下説明すると、このアクリル繊維を不活性雰囲気中で１０００〜１８００℃の温度で加熱すると、アクリル繊維が炭素繊維になる。
この炭素繊維を水蒸気と二酸化炭素と窒素等の混合ガス中で賦活化処理すると無数のミクロポア（微小孔）が形成された活性炭素繊維を形成でき、この活性炭素繊維に金属超微粒子担持光触媒を保持させるのである。活性炭素繊維の吸着力と金属超微粒子担持光触媒の分解力により、自浄分解能力を格段に向上させることができる。
【００４５】
金属超微粒子と光触媒微粒子とアクリル等の原料繊維から連続処理により金属超微粒子担持光触媒を保持した活性炭素繊維を製造することもできる。即ち、原料繊維を加熱炉内に走行させて炭化処理と賦活化処理を行って活性炭素繊維を製造する。反応塔では有機金属錯体コロイドと光触媒微粒子を相互に噴霧してコロイド付着光触媒微粒子を空間中で生成し、この微粒子が落下する途中に前記活性炭素繊維を走行させると活性炭素繊維の表面にコロイド付着光触媒微粒子が添着する。この活性炭素繊維を約５００℃の加熱炉内に走行させると、金属超微粒子担持光触媒を強固に保持した活性炭素繊維が連続的に製造できる。
【００４６】
【実施例】
以下に本発明に係る金属超微粒子担持光触媒を保持した素材およびその製造方法の実施例を示し、本発明の特徴とするところを一層明確にする。
【００４７】
実施例１
［２種類のｐｔ超微粒子担持光触媒の調製］
有機金属錯体であるバルサムＰｔの疎水コロイドを親水性のアセトンに分散させて、濃度が２．５重量％の有機金属錯体コロイド溶液を調製した。このコロイド溶液に光触媒微粒子として結晶構造がルチル型で平均粒径３００ｎｍの二酸化チタン粉末を混入させて、二酸化チタン微粒子にコロイドを付着させた。このコロイド溶液をパイレックスガラス板に塗布して乾燥し、５００℃で３０分間焼成し、ガラス板から剥がして金属超微粒子担持光触媒Ａを得た。同様に結晶構造がルチル型で平均粒径７０ｎｍの二酸化チタン粉末を用いて金属超微粒子担持光触媒Ｂを得た。
図５はＡの、図６はＢの透過型電子顕微鏡写真であり、二酸化チタン微粒子上におけるＰｔ超微粒子の担持状態を示している。又、図７はＡの高分解能透過型電子顕微鏡による格子像を示し、その格子間隔からＰｔがルチル型二酸化チタン上に担持されていることを証明している。図８はＡおよびＢのＰｔ超微粒子の粒径分布を示し、Ａの平均粒径が３ｎｍ、Ｂの平均粒径が１．５ｎｍであることを示す。コロイド焼成法によれば平均粒径の小さな金属超微粒子を二酸化チタン上に担持させることができ、本発明の核心部である量子サイズ効果を最も効果的に発現させることができる。
【００４８】
実施例２
［実施例１のＰｔ超微粒子担持光触媒の担持密度の測定］
実施例１により得られたサンプルＡおよびＢのＰｔ超微粒子の担持密度を測定した。この際、二酸化チタン微粒子およびＰｔ超微粒子を球形に近似した。図５のＡの電子顕微鏡写真から、直径２００ｎｍの二酸化チタン微粒子１個の表面には約１２０個のＰｔ超微粒子が存在し、１ｃｍ２当りの担持密度は２×１０１１個であった。同様に、図６のＢの電子顕微鏡写真から、直径５０ｎｍの二酸化チタン１個の表面には約３００個のＰｔ超微粒子が存在し、担持密度は４×１０１２個／ｃｍ２であった。分かりやすさの観点から、本発明では担持密度を光触媒微粒子１個当りの金属超微粒子の個数で表現することにする。
【００４９】
実施例３
［Ｐｔ超微粒子担持光触媒を保持させたアクリル繊維］
実施例１で調製したサンプルＢ、即ち平均粒径７０ｎｍのルチル・Ｐｔ型の金属超微粒子担持光触媒からなる粉末をアクリル繊維にスプレーにより噴霧して、両者の静電気力で保持させた。過剰な粉末は少し叩くことによって落下させた。図９は金属超微粒子担持光触媒がアクリル繊維に静電気により保持されている状態の電子顕微鏡写真で、図１０はそれを更に拡大した電子顕微鏡写真である。金属超微粒子担持光触媒が繊維表面全体に保持されているのが分かる。保持させた金属超微粒子担持光触媒の重量はアクリル繊維重量の３％である。少なくとも１％以上あれば光触媒の効果があり、迅速な実験を行う場合には５％又は１０％にする場合もある。
【００５０】
実施例４
［Ｐｔ担持と従来の光触媒微粒子との比較］
別の製法によって平均粒径７０ｎｍのルチル型二酸化チタンに平均粒径１．５ｎｍのＰｔ超微粒子を担持させて、金属超微粒子担持光触媒を作製した。Ｐｔ超微粒子の担持密度は二酸化チタン微粒子１個当り６００個とかなり高密度であった。このＰｔ超微粒子担持光触媒０．５ｇ（１０重量％の場合）を実施例３と同様にアクリル繊維５ｇに保持させた。全く同条件で、平均粒径７０ｎｍのアナターゼ型二酸化チタン単体と平均粒径７０ｎｍのルチル型二酸化チタン単体を保持させたアクリル繊維を作製した。反応雰囲気として酸素とアルゴンガスの２種類を用意し、スーパーオキサイドアニオンの効果も確かめた。Ｐｔ超微粒子担持光触媒微粒子・Ｏ２をＩ、アナターゼ・Ｏ２をＪ、アナターゼ・ＡｒをＫ、ルチル・Ｏ２をＬとする。
アセトアルデヒドの酢酸への分解効率を見るため、密封容器内のアセトアルデヒド濃度が１００ｐｐｍから測定を開始し、１ｐｐｍになるまで計測を続けた。結果は図１１に片対数グラフで示されている。測定開始から同一時刻でのＩとＪの比較から、Ｐｔ担持はアナターゼ単体より触媒効率が約１００倍以上も高いことが分かる。この理由は、金属担持密度がかなり大きいこと及びＰｔ超微粒子の粒径が粒ぞろいでかなり小さく、量子サイズ効果が顕著に現れていることが原因である。また、ＪとＫの比較から、アルゴンガスでは分解が促進せず酸素の存在が効果的であることが証明された。即ち、スーパーオキサイドアニオンの存在が酸化還元過程に有効に作用しているのである。さらに、ルチル単体の場合には酸素中でも触媒効率が一番悪いことが分かった。
【００５１】
実施例５
［金属超微粒子担持光触媒を保持した活性炭素繊維の連続製造装置］
図１２は活性炭素繊維を製造しながら、これに金属超微粒子担持光触媒を連続的に保持させる装置を示している。反応塔は噴霧部２、第１加熱槽８および第２加熱槽１２から構成され、第１加熱槽８は第２加熱槽１２に第１フランジ部１０で接続されている。スプレー機構４から有機金属錯体コロイド溶液を、微粒子ノズル６から光触媒微粒子を対向して相互に噴霧する。粒子間の衝突により光触媒微粒子の表面に有機金属錯体コロイドが多数付着し、それらの粒子は重力によって下方に落下してゆく。まず第１加熱槽８で約１００℃に加熱されて水分を蒸発させる。次に、送流ファン１１により５００℃の第２加熱槽に送られ、邪魔板１３の間を通過しながらコロイドから金属が還元され、次第に金属超微粒子へと成長する。
他方、アクリル繊維等の原料繊維又はその繊維成形体からなる繊維体１４を１０００℃以上で炭化処理をしながら走行させ、その後賦活化ガスＧとヒーター１６により賦活化処理が行われて、原料繊維は活性炭素繊維にまで仕上がる。この段階で反応塔の下を走行し、上方から落下してくる金属超微粒子担持光触媒が活性炭素繊維の表面に添着する。約５００℃で加熱されながら、金属超微粒子担持光触媒は強固に活性炭素繊維上に保持される。この活性炭素繊維は図示しないロールに巻回されて完成となる。添着しなかった金属超微粒子担持光触媒はファン１８により吸引されて、ホッパー２０から容器２１に収納される。
【００５２】
実施例６
［活性炭素繊維と光触媒の吸着分解効果］
活性炭素繊維にルチル７０／Ｐｔ１．５の金属超微粒子担持光触媒を保持させたものと、平均粒径７０ｎｍのアナターゼ型二酸化チタンだけを保持させたものと、活性炭素繊維だけの３種類を比較した。活性炭素繊維５ｇに光触媒を０．５ｇ保持させている。まず最初に、アセトアルデピド濃度が２００ｐｐｍから出発し、濃度の経時変化を測定した。活性炭素繊維は１ｐｐｍまで吸着した後は吸着平衡に到達して濃度はそれ以上低下しなかった。ルチル７０／Ｐｔ１．５は急激に低下し、アナターゼ７０と比較しても１０倍から１００倍の吸着分解力を有することが分かる。特にルチル７０／Ｐｔ１．５は低濃度領域においてほぼ垂直に濃度が低下し、大きな分解力を有していることが分かる。
【００５３】
実施例７
［活性炭素繊維とルチル７０／Ｐｔ１．５の反復効果］
アセトアルデヒド濃度が１００ｐｐｍから出発し、１ｐｐｍにまで低下したときに外部からアセトアルデヒドを注入して再び１００ｐｐｍにまで戻す。この反復操作によって活性炭素繊維の吸着力と光触媒の分解効果を調べてみた。１１回の反復効果をみたが、１００ｐｐｍから１ｐｐｍに低下する周期は８０分でほとんど変化しなかった。５回目と１１回目の周期が長くなっているが、それはアセトアルデヒドを約３００ｐｐｍないし４００ｐｐｍにまで過剰に注入したからに他ならない。劣化が起こっていないということは、活性炭素繊維によってアセトアルデヒドが吸着され、同時に吸着されたアセトアルデヒドのほとんどが光触媒で分解されていることを示している。即ち、金属超微粒子担持光触媒を保持した活性炭素繊維は極めて効果的な吸着分解力を有していると云える。
【００５４】
比較例１
［活性炭素繊維だけの反復効果］
比較例として活性炭素繊維だけの反復効果を調べてみた。濃度が低下して飽和するのに約２０分の周期を有しているが、飽和値は次第に増加し、９回目にはほとんど濃度低下が起こらなくなっていることが分かる。このことはミクロポアがアセトアルデヒドにより充満してしまうと活性炭素繊維の吸着力は無くなってしまうことを示している。
【００５５】
比較例２
［活性炭素繊維とアナターゼ７０の反復効果］
従来の平均粒径７０ｎｍのアナターゼ型二酸化チタン（アナターゼ７０）を活性炭素繊維に保持させたときの反復効果を調べてみた。方法は実施例７と全く同様に行った。周期は１３時間と極めて長いため３回しか実験できなかった。その周期はルチル７０／Ｐｔ１．５の８０分と比較して約１０倍の長さである。人間の生活環境を浄化するのには長くかかりすぎである。
【００５６】
比較例１および比較例２に対して、本発明の実施例７が如何に優れた効果を示しているかが理解できる。
【００５７】
本発明は上記実施例に限定されるものではなく、本発明の技術的思想を逸脱しない範囲における種々の変形例・設計変更等をその技術的範囲内に包含するものである。
【００５８】
【発明の効果】
本発明は上記詳述したように、金属超微粒子担持光触媒の光触媒特性、即ち有機物分解力が光触媒微粒子単体のそれより格段に優れている事に着眼してなされたものである。この金属超微粒子担持光触媒を単独で各種の素材に保持させることにより、環境汚染物質、人体有害物質や悪臭等を強力に自浄分解し、優れた環境衛生を作り出すことが出来る。また、この金属超微粒子担持光触媒を活性炭素繊維に保持させた場合には極めて優れた吸着分解効果を示し、今後の住環境の改善に飛躍的な光明を与えるものである。
【図面の簡単な説明】
【図１】金属超微粒子担持光触媒を活性炭素繊維に保持させた状態の模式図である。
【図２】金属超微粒子の量子サイズ効果を説明するバンド構造の説明図である。
【図３】二酸化チタンのルチル型とアナターゼ型の両方を効率的に励起できる誘蛾灯の紫外線の波長分布図である。
【図４】自然な太陽光線の波長分布図である。
【図５】平均粒径３００ｎｍの二酸化チタンにＰｔ超微粒子を担持させた状態の透過型電子顕微鏡写真である。
【図６】平均粒径７０ｎｍの二酸化チタンにＰｔ超微粒子を担持させた状態の透過型電子顕微鏡写真である。
【図７】図５の状態の高分解能透過型電子顕微鏡による格子像である。
【図８】図５及び図６のＰｔ超微粒子の粒径分布図である。
【図９】アクリル繊維に金属超微粒子担持光触媒の粉末を静電吸着させている電子顕微鏡写真である。
【図１０】図９を更に拡大した電子顕微鏡写真である。
【図１１】Ｐｔ担持二酸化チタンと二酸化チタン単体によるアセトアルデヒド分解の時間経過図である。
【図１２】金属超微粒子担持光触媒を保持した活性炭素繊維の連続製造装置の概略図である。
【図１３】活性炭素繊維と光触媒の吸着分解効果を示したアセトアルデヒド濃度の時間経過図である。
【図１４】活性炭素繊維にルチル７０／Ｐｔ１．５の金属超微粒子担持光触媒を保持させた場合のアセトアルデヒド濃度の反復効果図である。
【図１５】活性炭素繊維だけのアセトアルデヒド濃度の反復効果図である。
【図１６】活性炭素繊維にアナターゼ７０の光触媒を保持させた場合のアセトアルデヒド濃度の反復効果図である。
【図１７】従来の金属担持光触媒のバンド構造の説明図である。
【図１８】活性炭素繊維の吸着状態の模式図である。
【図１９】アナターゼ型二酸化チタンを活性炭素繊維に保持させた状態の模式図である。
【図２０】ルチル型二酸化チタンが酸素を還元しにくいことを説明するバンド構造の概略図である。
【図２１】アナターゼ型二酸化チタンが酸素を容易に還元できることを説明するバンド構造の概略図である。
【符号の説明】
２・・噴霧部
４・・スプレー機構
６・・微粒子ノズル
８・・第１加熱槽
１０・・第１フランジ部
１１・・送流ファン
１２・・第２加熱槽
１３・・邪魔板
１４・・繊維体
１６・・ヒーター
１８・・ファン
２０・・ホッパー
２１・・容器
２４・・容器
Ｇ・・賦活化ガス[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-performance material having photocatalyst fine particles held on a material surface, and more particularly, to a self-cleaning method in which a metal ultrafine particle-supported photocatalyst having metal ultrafine particles supported on photocatalyst fine particles is held on a material surface such as fiber or window glass. The present invention relates to a high-functional material having decomposability and a method for producing the same.
[0002]
[Prior art]
The photocatalytic reaction of titanium dioxide was announced to Nature in 1972 and became known worldwide as the Honda-Fujishima effect. Since then, research on the generation of hydrogen and carbon dioxide through the decomposition of water by titanium dioxide under light irradiation and the decomposition of aqueous solutions of organic substances has been carried out.Currently, titanium dioxide fine particles are kept in thin films on tiles and window glasses. It is being put to practical use in decomposing environmental pollutants, that is, organic substances such as tobacco tar and bacteria or toxins produced by bacteria.
[0003]
Titanium dioxide is a powdered metal oxide, and is used by dispersing in a solution when decomposing water or a solution. However, it is desired that the particles adhere to the surface of window glass, bath tiles, and building materials in a uniform thin film even if they are in the form of particles. For this purpose, a sol-gel method, a spray pyrolysis method such as titanium acetate, a dip coating method, and the like have been developed (Applied Physics Vol. 64, 8 (1995) pp803, Chemistry and Industry Vol. 48, 10 (1995) pp1256, Chem. And Kogyo Vol. 49, 6 (1996) pp 764). It was shown that oil and tobacco tar adhering under ultraviolet irradiation can also be decomposed using these titanium dioxide-supporting glasses and the like. Although it is difficult to decompose inorganic substances such as dust and dirt, it has been reported that inorganic substances adhered due to decomposition of organic substances because organic substances such as oil acted as binders to adhere the inorganic substances.
[0004]
The principle of action of titanium dioxide fine particles on a material such as a tile is a photocatalytic property of titanium dioxide as a semiconductor. When the titanium dioxide is irradiated with light larger than the band gap energy, for example, ultraviolet light, electrons in the valence band are excited and transit to the conduction band, and positively charged holes are left in the valence band to make electrons-positive. A pair of holes is created. The electrons and holes move through the titanium dioxide and reach the surface, and the electrons are given to oxygen in the air and2 −(Superoxide anion) to reduce other substances. The holes not only directly oxidize and decompose organic substances, but also oxidize water molecules adhering to the surface to form strong oxides called hydroxyl radicals, and oxidize other substances by the oxidizing power of the hydroxyl radicals. Said O2 −Is said to be involved in this oxidation process, but its detailed reaction circuit is still being studied. The organic matter is decomposed into carbon dioxide and water by the electron-hole pairs induced by the light.
[0005]
In this study, it was pointed out that the photocatalytic efficiency of titanium dioxide alone is limited because electrons and holes may recombine and disappear before redoxing an external substance. Titanium dioxide is a powder in a normal state, and when one particle is considered, a lattice defect such as countless point defects and plane defects is present on the surface and inside thereof. When electrons and holes induced in titanium dioxide by ultraviolet rays encounter a lattice defect in the course of their movement, they are captured by the lattice defect and recombined. Even when the electrons and holes can move to the surface, recombination may occur when electrons and holes approach. In order to improve this, it is necessary to develop a technique for producing titanium dioxide without lattice defects and a technique for separating electrons and holes at the surface. Regarding the former, the improvement of the crystal growth technique has been successively made, and since it is not directly related to the present invention, the details are omitted here.
[0006]
Regarding the technology of separating electrons and holes at the surface, an electrode that collects excited electrons is formed on titanium dioxide, and a photocatalyst that separates and collects holes on the titanium dioxide surface and electrons on the metal electrode surface is used. was suggested. It was considered that this would allow electrons to be efficiently collected on the metal electrode, and furthermore, to separate holes and electrons, thereby reducing the probability of recombination. This type of photocatalyst is called a metal-supported photocatalyst, and was produced by forming a metal such as Pt (platinum) or Cu (copper), which has been conventionally used as a catalyst, on titanium dioxide. The idea is that if a metal alone has a catalytic action, it will have a synergistic effect with the catalytic action of titanium dioxide.
[0007]
As a method for producing such a metal-supported photocatalyst, a photoprecipitation method, a mixing method, an impregnation method, a chemical precipitation method, and a simultaneous precipitation method have been developed. The number of metal particles supported per titanium particle (supporting density) was also in the range of several tens. The low loading density is one of the reasons that many metal fine particles do not adhere to one titanium dioxide particle because the particle size of the metal fine particles is large. Therefore, the photocatalytic effect of metal loading was only enhanced about 2 to 4 times as compared with titanium dioxide alone.
[0008]
The inventors have theoretically studied why the catalytic efficiency is not so enhanced with micron-sized metal fine particles with reference to FIG.
In order to efficiently take in the electrons generated in titanium dioxide into the metal electrode, it is desirable to minimize the barrier of electron transition at the interface between titanium dioxide and the metal. However, when the particle size of the metal fine particles is a micron size (about 0.1 μm or more), the electronic state has the same band structure as that of a large solid crystal (bulk crystal). That is, the valence band and the conduction band are clearly formed with a certain band gap, and the conduction band has a structure in which free electrons are densely packed from the bottom to the uppermost Fermi level. On the other hand, since titanium dioxide is a bulk crystal, its electronic state naturally takes a band structure. In the band structure, the energy levels forming the band are arranged almost continuously and densely, and the wave function corresponding to each level is sharply localized in the substance. In other words, since the wave function does not protrude out of the material, the probability that electrons staying at that level are emitted out of the material is significantly reduced.
[0009]
In this state, suppose that the titanium dioxide is irradiated with ultraviolet rays to excite electrons into the conduction band and generate electron-hole pairs. In order for the electrons to reduce the external substance A or to generate a superoxide anion, it is necessary for the electrons to rapidly move from the titanium dioxide into the metal and further from the metal to the external substance A outside the metal. However, as described above, since the fine metal particles have a micron size, not only do they have a band structure similar to that of a crystal having a large electronic state, but also a wave function has a sharply localized structure in the fine metal particles. Therefore, it is not easy for electrons that have risen to the conduction band of titanium dioxide to ride on the wave function of the metal, and it is not easy to move to the conduction band of the metal. Also, even if the electrons can somehow move to the metal, it is not easy to move from the metal to the external substance, so the Fermi level E in the conduction band of the metal before exiting the metal.FOften fall quickly on the surface, and the chance of reacting with external substances is further reduced.
[0010]
In other words, when the level density of the conduction band is large as in the band structure, the time for the electron to fall above the Fermi level (relaxation time) becomes extremely short, and the localization of the wave function and the external It blocks movement to In other words, in the micron size, electrons are unlikely to escape to the outside, so electrons are excessively accumulated in the metal, and the anti-power generation field prevents electrons in the titanium dioxide from moving into the metal. . As a result, it can be concluded that in the region where the particle size of the metal fine particles is in the micron size, the probability that electrons stay in the titanium dioxide or the metal fine particles due to the energy band structure and the localization of the wave function and are emitted to the outside of the metal is reduced. At the same time, in the case of micron-sized metal fine particles, the number of metal fine particles supported on one titanium dioxide particle is limited to several tens, which limits the catalytic efficiency of the metal-supported photocatalyst. That's why.
[0011]
The photocatalyst has a function of decomposing environmental pollutants, and an idea to add an adsorption function to this has appeared. Substances having an adsorbing action include porous materials such as activated carbon, activated carbon fiber and zeolite. Explaining the activated carbon fiber of FIG. 18, the surface of the fiber has countless pores having a diameter of about 0.5 nm, so-called micropores. The micropores adsorb environmental pollutants such as organic substances. Since the activated carbon fiber can be processed into various shapes, it is frequently used in water purifiers and air purifiers.
[0012]
If the activated carbon fiber is used as a material to hold a photocatalyst, the activated carbon fiber should adsorb environmental pollutants and the photocatalyst should be able to decompose environmental pollutants. Japanese Patent No. 2,574,840 describes a deodorizing apparatus in which a photocatalyst is held in activated carbon. If this is more specifically considered as a photocatalyst in which an activated carbon fiber holds anatase type titanium dioxide, FIG. 19 is an imaginary diagram thereof. If all the organic substances adsorbed on the micropores are decomposed by the photocatalyst, the organic substance has an adsorption / decomposition power of 100%. However, as described above, since the decomposition power of titanium dioxide alone is limited, organic substances remain in the micropores. Therefore, it has been found that the adsorptive power of the activated carbon fiber gradually decreases, and only the decomposition power of the anatase type titanium dioxide eventually remains, and the initially expected effect cannot be exerted. The main reason for this is the limit of the photocatalytic efficiency of anatase type titanium dioxide, and there has been a demand for an epoch-making improvement in photocatalytic efficiency.
[0013]
Titanium dioxide has anatase type and rutile type due to the difference in crystal structure. Among them, the rutile type has a stable structure, and when heated to about 600 ° C. or more, all of the anatase type undergoes a phase transition to the rutile type, and becomes a rutile type at a low temperature after cooling. Even at a temperature of 600 ° C. or less, a part of the anatase type becomes rutile. Therefore, the rutile type is titanium dioxide which can be mass-produced at a lower cost than the anatase type. However, all titanium dioxides conventionally used as photocatalysts are anatase type, and inexpensive rutile type has not been used at all. The reason can be understood from the band structure.
[0014]
FIG. 20 shows the band structure of rutile type titanium dioxide. Its gap energy is 3.05 eV. Electrons excited in the conduction band by ultraviolet rays reach the bottom of the conduction band while partially consuming energy by relaxation. Since the oxygen potential, which is the reduction potential, is located at 3.13 eV, climbing from the bottom of the conduction band to the oxygen potential is not likely to occur naturally except for receiving external energy. Therefore, it is difficult to generate a superoxide anion in the rutile type.
On the other hand, FIG. 21 shows a band structure of anatase type titanium dioxide. Its gap energy is 3.20 eV, and it has the ability to sufficiently reduce 3.13 eV of oxygen even if it falls to the bottom of the conduction band after excitation with ultraviolet light, and to generate superoxide anion. Therefore, in the current technology, expensive anatase-type titanium dioxide had to be used as a photocatalyst.
[0015]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to find a method that can significantly enhance the photocatalytic efficiency of titanium dioxide. Another object of the present invention is to find a method that can utilize rutile-type titanium dioxide which has not been used as a photocatalyst despite its low cost. Another object of the present invention is to realize a photocatalyst capable of remarkably improving the decomposing power without losing the adsorbing power of activated carbon fibers and the like, and to achieve a longer life of the adsorption / decomposition cycle.
[0016]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned drawbacks, and a high-functional material holding a metal ultrafine particle-supported photocatalyst according to the present invention is a method in which metal ultrafine particles are supported on photocatalyst fine particles, Is basically held on the surface of the material. To significantly enhance the photocatalytic function of titanium dioxide, the number of metal particles has been reduced to nanoscale ultrafine metal particles.
The metal ultrafine particles have a particle size of 1 to 10 nm that remarkably exhibits the quantum size effect, and are characterized in that 100 or more metal ultrafine particles are supported per one photocatalyst fine particle. The material of the ultrafine metal particles is a transition metal, and particularly, pt, Δu, Pd, Rh, or Ag is suitable.
The photocatalyst fine particles are metal oxide semiconductors capable of generating hydroxyl radicals and / or superoxide anions by irradiation with ultraviolet light, and titanium dioxide is particularly preferable.
As the material, a one-dimensional, two-dimensional or three-dimensional material can be used, and among them, fiber as a one-dimensional material can be used. Among them, activated carbon fibers are preferred. Highly functional fiber products formed by knitting or weaving these fibers are also used as materials.
[0017]
As a method for producing a highly functional material, there is a method in which a photocatalyst supporting ultrafine metal particles is electrostatically adsorbed on the surface of the material.
As a colloid firing method, a first step of adhering an organometallic compound colloid to photocatalyst fine particles, a second step of attaching the colloid-adhered photocatalyst fine particles to a material, and firing the material to reduce the organometallic compound to reduce the metal There is a manufacturing method including a third step in which ultrafine particles are firmly supported on photocatalytic fine particles, and at the same time, the photocatalytic fine particles are strongly held in a material.
Further, as another colloid firing method, a first step of adhering an organometallic compound colloid to the photocatalyst fine particles, a second step of firing the colloid-adhered photocatalyst fine particles to strongly support the ultrafine metal particles on the photocatalyst fine particles, There is a manufacturing method including a third step in which a photocatalyst carrying ultrafine particles is attached to a material and the photocatalyst fine particles are firmly held in the material by firing.
Further, the raw material fiber is carbonized and activated to transform it into activated carbon fiber, and the activated carbon fiber is used as a raw material and the above-mentioned colloid firing method is applied.
Also, as a method of manufacturing a film-like material, after mixing photocatalyst fine particles carrying metal ultrafine particles into a material having a property of developing into a thin film on a solvent, the material is developed on a solvent to form a thin film. There is a method of holding this thin film on the surface of a two-dimensional material or a three-dimensional material.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have conducted intensive studies to enhance the photocatalytic function of metal-supported titanium dioxide.As a result of supporting nanoscale metal ultrafine particles on the surface of titanium dioxide, the photocatalytic function was more than 100 times higher than titanium dioxide alone. It was found that it could be increased. Therefore, even when compared with titanium dioxide supporting micron-scale metal fine particles, the catalyst efficiency can be enhanced to about 3 to 25 times. This involves converting metal from fine particles to ultrafine particles, that is, reducing the particle size from a micron scale to a nanoscale, in other words, reducing the particle size to about 1/10 to 1/100 of the micron scale (about 0.1 μm or more). It can be achieved by minimizing it. The average particle diameter of the ultrafine metal particles used in the present invention is 1 to 10 nm, more preferably 1 to 5 nm. If it is larger than this, the expression of the quantum size effect, which will be described later, will be reduced, and the enhancement of the photocatalytic efficiency will not be remarkable. It becomes extremely expensive.
[0019]
When a fine powder of titanium dioxide or the like is used as the photocatalyst substance, the number of ultrafine metal particles that can be supported by one photocatalyst fine particle, that is, the loading density of the ultrafine metal particles is an important factor together with the particle diameter. In the present invention, it is possible to support a large number of metal ultrafine particles on one photocatalyst fine particle by using ultrafine metal particles reduced to the nanoscale. In other words, a dramatic increase in the carrying density has been achieved by realizing a reduction in the particle size from micron-scale metal fine particles to nanoscale metal ultrafine particles. According to the study of the present inventors, it is desired that the average number of ultrafine metal particles carried per photocatalyst fine particle is set to 100 or more, preferably 200 or more. If the carrier density is 100 or more, the photocatalytic efficiency can be significantly increased by the synergistic effect with the quantum size effect. If the number is 200 or more, a remarkable increase in photocatalytic efficiency can be achieved. Of course, if the loading density can be further increased, the photocatalytic efficiency can be further increased.
[0020]
The quantum size effect first manifested by ultrafine metal particles is discussed below. For example, in the case of ultrafine particles having a diameter of 1 nm, only about 10 to 100 metal atoms exist therein, though depending on the size of the atoms. It is considered that ultrafine metal particles having a diameter of 10 nm contain about 10,000 to 100,000 atoms. In such a metal ultrafine particle having a small number of atoms, the electron energy state of the metal gradually starts to be discrete from the band structure, and the energy levels are distributed over a wide range. For example, when considering a conduction band, a large number of energy levels constituting the conduction band are distributed over a wide range up and down while being discrete from each other from a state of being tightly consolidated. This level discretization has the effect of increasing the electron relaxation time, that is, the time required for the electron to fall from that level to the Fermi level. That is, the time during which electrons stay at the level becomes longer. At the same time, the wave function corresponding to the energy level protrudes to the outside of the metal while extending the tail to the left and right, and also has the effect of reducing the peak at the same time. That is, the electrons on the wave function can easily move to the outside due to the quantum tunnel effect. In the present invention, the term “quantum size effect” means the occurrence of the quantum tunnel effect due to the discretization of the energy level and the delocalization of the wave function as described above.
[0021]
FIG. 1 shows a state in which the photocatalyst supporting ultrafine metal particles is held by activated carbon fibers. The weight of the ultrafine metal particle-supported photocatalyst should be at least 1% or more, preferably 3% or more of the fiber weight. If it is less than 1%, the effect of the photocatalyst supporting ultrafine metal particles is not sufficient. The photocatalyst is rutile-type titanium dioxide, and ultrafine metal particles having a particle diameter of several nm are supported on the rutile-type titanium dioxide at a high density. First, the activated carbon fiber adsorbs organic substances, which are environmental pollutants, and the organic substances are packed into the micropores. Next, the photocatalyst supporting ultrafine metal particles starts to decompose the organic matter.
[0022]
Let's see how titanium dioxide carrying ultrafine metal particles can efficiently redox organic substances. FIG. 2 shows an energy state when the ultrafine metal particles are supported on titanium dioxide. When titanium dioxide is irradiated with ultraviolet light, electron-hole pairs are formed, and electrons are excited in the conduction band while leaving holes in the valence band. When excited by ultraviolet light having a large energy, electrons transition to a higher position in the conduction band, but gradually fall to the bottom of the conduction band while losing energy. Since the energy levels of the metal are discretely dense to some extent, an energy level corresponding to the bottom of the conduction band of titanium dioxide always exists. In addition, the wave function of the level has a long tail at the left and right, and the left end extends into the titanium dioxide and the right end extends to the outside of the metal. That is, the energy levels of titanium dioxide and the metal are resonantly continuous via the wave function of the metal. Excited electrons in the conduction band of titanium dioxide are emitted at once by a quantum tunnel effect via the metal on the wave function of the metal. Since the titanium dioxide and the metal are in a resonance state, this quantum tunnel effect is called resonance tunneling. At this time, since the levels in the metal are discretized, the relaxation time of the electrons is long, so that the electrons are easily emitted out of the metal before falling on the Fermi level of the metal.
[0023]
Holes in the valence band of titanium dioxide move to the surface of titanium dioxide and oxidize the external substance D. In addition, it is considered that not only the external substance is oxidized, but also the water attached to the surface is oxidized to generate a strong oxide called a hydroxyl radical, and this hydroxyl radical oxidizes and decomposes the external substance. On the other hand, the electrons emitted by resonance tunneling outside the metal not only directly reduce the external substance A, but also reduce oxygen in the air to reduce oxygen.2 −It is thought that this anion is also involved in the decomposition of the external substance D.
In particular, in the present invention, the excited electrons transferred from the titanium dioxide to the metal are immediately discharged to the outside without being accumulated in the metal, so that no anti-power generation field is formed outside, and it is possible to successively attract the excited electrons by ultraviolet irradiation. It has excellent reducing power in that it can be used.
[0024]
Not only titanium dioxide but also the type of photocatalyst used in the present invention is determined by the decomposition target substance to be redox-reduced. When the decomposition target substance is a substance to be reduced, a reduction potential exists, and when the decomposition target substance is a substance to be oxidized, an oxidation potential exists. These reduction and oxidation potentials need to be located in the energy gap between the valence band and the conduction band of the photocatalytic substance. Specifically, as shown in FIG. 2, it is desired to select a photocatalytic substance in which the reduction potential is located above the gap and the oxidation potential is located below the gap. In this case, the excited electrons fall to the reduction potential from the bottom of the conduction band to reduce the target substance, and the holes rise to the oxidation potential from the top of the valence band to oxidize the target substance. However, in the present invention, since the resonance tunneling of the ultrafine metal particles is effective, the reduction potential may be at the bottom of the conduction band or slightly above.
[0025]
In FIG. 2, since the rutile type titanium dioxide is used, the reduction potential is located 0.08 eV above the bottom of the conduction band as in FIG. Nevertheless, the excited electrons can quickly reduce external substances from the metal level at that position by resonance tunneling. The significance of this resonance tunneling that rutile-type titanium dioxide can be used as a photocatalyst is epoch-making. According to the present invention, mass-produced and inexpensive rutile-type titanium dioxide will be spotlighted as a photocatalyst for the first time.
[0026]
In recent studies, electrons are O2To reduce the superoxide anion O2−The holes oxidize water to form hydroxyl radicals, and these O2 −And hydroxyl radicals are thought to degrade the target substance. Therefore, the reduction potential is O2The photocatalytic substance can be selected by selecting the OH potential as the potential and the oxidation potential. That is, electron-hole pairs are generated by the irradiation of ultraviolet rays, electrons reduce oxygen in the air or water to generate superoxide anions, and holes oxidize water attached to the surface to generate hydroxyl radicals. Any photocatalytic substance may be used.
[0027]
Semiconductors are suitable as photocatalytic substances. If insulators have too large a gap energy, it is difficult to generate electron-hole pairs with ordinary ultraviolet light, and if it is difficult to arrange oxidation and reduction potentials within the forbidden band with a material having a small gap energy. Both are unsuitable because they are easily dissolved in an aqueous solution.
Among the semiconductors, metal oxide semiconductors are suitable for the present invention. Metal oxide is a substance that is extremely stable as compared with a simple substance of metal, and therefore has low reactivity with other substances, is safe, and can sufficiently exchange electrons. Therefore, a metal oxide semiconductor satisfying these properties can be used as the photocatalyst substance of the present invention.3, CdO3, In2O3, Ag2O, MnO2, CU2O3, Fe2O3, V2O5, TiO2, ZrO2, RuO2, Cr2O3, CoO3, NiO, SnO2, CeO2, Nb2O3, KTaO3, SrTiO3, K4NbO17It can be selected from known substances including, for example, the substance to be decomposed. Among these, from the viewpoints of the density of generated electrons and holes, the density of superoxide anions and hydroxyl radicals, and the corrosion resistance and safety of the material, TiO2, SrTiO3, K4NbO17TiO, particularly titanium dioxide2Is most desirable.
[0028]
Photocatalytic substances that can be used in the present invention are fine particles. Since the fine particles have an extremely large surface area, the probability of contact with environmental pollutants increases, and at the same time, a large number of metal ultrafine particles can be supported on the surface. Also, the fine particles have a larger effective light receiving area for ultraviolet rays and the like, and the photocatalytic efficiency is much higher than that of the bulk substance. Since the metal oxide is usually a powder, a metal oxide semiconductor such as titanium dioxide is suitable for the present invention. The particle size is 30 nm to 1000 nm, more preferably 50 nm to 500 nm. If the particle size is smaller than this, the particles approach the ultrafine particles, so that a special technique and cost are required for the production. If the particle size is larger than this, the specific surface area is reduced and the reactivity with environmental pollutants, human toxic substances, malodorous substances, etc. is deteriorated.
For example, it is possible to make titanium dioxide into ultra-fine particles of about 10 nm, but it does not exist as independent particles, and ultra-fine particles of titanium dioxide are aggregated and solidified in a dumpling shape. Become. In this case, the reactivity is higher because the surface area is larger than that of a single solid due to the ruggedness. The present invention also includes such photocatalyst fine particles. The form of the photocatalyst fine particles is not particularly limited as long as the ultrafine metal particles can be supported, and can be used in the form of, for example, spheres, pellets, or particles.
[0029]
The light source that can be used in the present invention may be any light source having energy equal to or higher than the band gap energy of the photocatalyst, and usually an ultraviolet lamp is used. In particular, when titanium dioxide is used, there are a rutile type and an anatase type, and when the gap energy of each is converted into a wavelength, the rutile type is 407 nm and the anatase type is 388 nm. Therefore, it is desirable that the wavelength distribution of the light source for titanium dioxide has 400 nm near the peak. The attractant lamp having the wavelength distribution of FIG. 3 is effective for both the rutile type and the anatase type, and is extremely preferable since 400 nm is near the peak.
[0030]
The natural sunlight having the wavelength distribution shown in FIG. 4 is mainly visible light, but can be used sufficiently because it includes 400 nm. In particular, in the case of natural sunlight, the light intensity at 407 nm is higher than that at 388 nm, so that the rutile type is more effective than the anatase type. Therefore, the fact that rutile-type titanium dioxide can be used as a photocatalyst according to the present invention opens a great way to utilize natural sunlight. This is in contrast to the conventional anatase type, in which ultraviolet light can be used, but in the case of natural sunlight, the catalyst efficiency is extremely low. Further, in the conventional photocatalyst, it is possible to use sunlight outdoors because of the high light intensity, but it is a weak point in indoor use because the light intensity is low. However, in the present invention, since the photocatalytic efficiency is remarkably enhanced, it is possible to expand the use of the photocatalyst indoors using sunlight as a light source.
[0031]
The supported ultrafine metal particles may be transition metals. The transition metal element is an element having an incomplete d-shell and having atomic numbers 21 (Sc) to 29 (Cu), 39 (Y) to 47 (Ag), 57 (La) to 79 (Au), and 89 (Ac). -Theoretically, it is a metal element consisting of four groups up to 111. Since the d-shell is incomplete, the outermost shell has directionality due to d-electrons. As a result, excited electrons coming from the photocatalytic substance are easily captured on the surface of the metal ultrafine particles, and a superoxide anion is easily generated.
A metal that can be used alone as a catalyst is desirable, and from the viewpoint of safety, Au, pt, Ag, Pd, and Rh are preferable, and Au, Pt, and Pd are more preferable from the viewpoint of stability as a metal.
[0032]
A feature of the present invention is to establish a method of carrying and forming ultrafine metal particles on the surface of a photocatalytic substance composed of fine particles. In the conventional manufacturing method, micron-sized metal fine particles could be supported, but it was impossible to form and support nanoscale ultrafine metal particles. This limitation of the conventional production method was also a factor that hindered improvement in photocatalytic efficiency.
Whereas the conventional production method uses a metal salt or metal powder as a raw material, the present invention achieves a dramatic improvement in photocatalytic efficiency by using an organic metal compound that can be reduced by heating. Reducible by heating means that only metal can be isolated from the organometallic compound by heating, in other words, other organic substances are separated. Among the organometallic compounds, organometallic complexes are particularly suitable for the purpose of the present invention. However, it goes without saying that there is no particular limitation as long as the organic metal compound can be reduced by heating.
[0033]
Among them, from the viewpoint of stability and safety as a metal, it is particularly preferable to use at least one of an Au compound, an Ag compound, a Pd compound, a Rh compound, and a pt compound. More preferably, it is a compound of Au, Ag, Pd, Rh or pt and a sulfur-containing organic material, and most preferably a compound of Au, Pd, Rh or pt and a sulfur-containing organic material. For example, methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, octyl mercaptan, dodecyl mercaptan, hexadecyl mercaptan, alkyl mercaptan such as octadecyl mercaptan, thioglycolic acids such as butyl thioglycolate, and other trimethylolpropane tristhioglycolate, Thioglycerol, thioacetic acid, thiobenzoic acid, thioglycol, thiodipropionic acid, thiourea, t-butylphenylmercaptan, t-butylbenzylmercaptan and the like. Furthermore, balsam gold (C10H18SAuCl1-3), Balsam platinum (C10H18SptC11-3), Balsam palladium (C10H18SPdCl1-3), Balsam rhodium (C10H18SRhCl1-3) Etc. can be used.
[0034]
By dispersing the above-mentioned organometallic compound and a powder of a photocatalytic substance such as titanium dioxide in an appropriate known hydrophilic solvent, a hydrophobic colloid or the like of the organometallic compound can be formed. Many adhere. When this mixed solution is dried and the remaining solid residue is fired, the organic matter among the organometallic compounds escapes, and only the metal is converted into nanoscale ultrafine particles and carried on the surface of the photocatalytic fine particles. Drying and firing may be a series of steps, such as heating the mixed solution itself to evaporate the solvent, and further firing the solid residue by heating.
As another manufacturing method, when the above-mentioned colloidal solution of the organometallic compound and the photocatalyst powder are sprayed facing each other, a large number of colloids adhere to the surface of the photocatalyst powder particles, and the colloid-adhered photocatalyst powder particles are subjected to heat treatment while falling. Then, it is possible to continuously produce photocatalyst fine particles carrying metal ultrafine particles.
[0035]
The solution concentration of the organometallic compound can be appropriately set according to the final product or the like, but is usually 0.1% by weight or more, preferably 0.5 to 50% by weight. The solvent can be appropriately selected depending on the type of the organic metal compound, and a known organic solvent such as alcohols, esters, and aromatics can be used.
[0036]
The firing temperature in the present invention can be appropriately changed within a temperature range that is usually equal to or higher than the reduction precipitation temperature of the organometallic compound and lower than the melting point of the metal that is reduced and deposited. More specifically, in order to isolate a metal from an organometallic compound such as an organometallic complex, the organometallic compound must be completely decomposed to leave only metal atoms and allow other organic atoms to escape. No. This temperature is defined as the reduction precipitation temperature of the metal. Next, the isolated metal atoms must be assembled and rearranged into ultrafine metal particles. The upper limit temperature may be not more than the melting point of the bulk metal, and is preferably not more than 80%, especially not more than 70% of the melting point of the deposited metal. The firing atmosphere may be an oxidizing atmosphere or diluted air, and may be appropriately selected according to the final product.
[0037]
The greatest feature of the present invention resides in that photocatalyst fine particles carrying ultrafine metal particles having extremely excellent photocatalytic ability are held on a material. When only titanium dioxide is retained in the material, the limit of the decomposition power of titanium dioxide becomes the limit of the self-cleaning decomposition power of the material, and the limit of the quality of the material as a product. In the present invention, the quality of the commercial material is significantly improved by holding the ultrafine metal particle-supported photocatalyst on the material. The living environment is full of environmental pollutants and human harmful substances, and by simply placing the material according to the present invention in this space, the self-cleaning decomposition function of the material acts to convert the substance into water and carbon dioxide. It can be decomposed to clean the environment. Decomposition of inorganic substances is more difficult than organic substances, but the decomposition of organic substances eliminates the phenomenon that conventional organic substances have become a binder and inorganic substances such as dust have adhered to the material. Purification can also be achieved.
[0038]
The materials used in the present invention can be classified into one-dimensional materials, two-dimensional materials, and three-dimensional materials. A typical example of the one-dimensional material is a fiber.
The fibers include natural fibers and chemical fibers, and the chemical fibers include inorganic fibers, regenerated fibers, semi-synthetic fibers, and synthetic fibers. Natural fibers include animal fibers, plant fibers, and mineral fibers (such as asbestos). Inorganic fibers include metal fibers, glass fibers, carbon fibers, and activated carbon fibers. Synthetic fibers include polyester and polyacrylic fibers. , Polyamide-based, polypropylene-based, polyethylene-based, polyvinyl alcohol-based, polyvinyl chloride-based, polyvinylidene chloride-based, polyurethane-based, polyalkylparaoxybenzoate-based, polytetrafluoroethylene-based, and the like. Aramid-based, wholly aromatic polyester-based, heterocyclic, and the like are also included.
[0039]
When a fiber holding a photocatalyst carrying metal ultrafine particles and a simple activated carbon fiber are blended, there is an advantage that the activated carbon fibers adsorb environmental pollutants and can be decomposed by the photocatalyst fine particles carrying metal on the other fiber. Further, when the carbon fiber holding the metal-supported photocatalyst fine particles is blended with a mere activated carbon fiber, there is an advantage that the use is expanded in that the color tone of the fiber is the same as the adsorption and decomposition effect. Further, when the metal-supported photocatalyst fine particles are formed on the surface of the activated carbon fiber, the fiber alone is excellent in that it has an adsorption / decomposition ability.
Not only fibers but also knits formed by knitting these fibers, woven and woven fabrics, nonwoven fabrics such as felt formed into a nonwoven fabric, and filters and other fiber products are also included in the material of the present invention. The filter can be used for air purifiers, water purifiers, toilet deodorizers, indoor deodorizers, refrigerator deodorizers, and the like.
[0040]
Flat two-dimensional materials include window glass, mirrors, tables, wall materials, tiles, shoji, bran, and the like, and three-dimensional three-dimensional materials include toilet bowls, furniture, and figurines. By holding the metal ultrafine particle-supported photocatalyst of the present invention on these surfaces, organic environmental inhibitors, substances harmful to the human body, and foul odors are naturally emitted by natural sunlight, fluorescent light, or ultraviolet light from ultraviolet light. Self-cleaning can be decomposed. Since organic substances are decomposed, inorganic dirt that has been adhered using organic substances as a binder is less likely to adhere.
[0041]
There are various methods for holding a photocatalyst supporting metal ultrafine particles on a material. For example, an immersion method in which a powder made of a photocatalyst supporting ultrafine metal particles is dispersed in an appropriate solvent, and a material is immersed in the solvent to attach the photocatalyst fine particles carrying metal. A spray method in which a solvent in which a photocatalyst supporting metal ultrafine particles is dispersed is sprayed onto a material. For two-dimensional and three-dimensional materials, apply with a roller or brush.
Further, there is a method in which a photocatalyst supporting ultrafine metal particles is electrostatically adsorbed on a material. Both the ultrafine metal particle-supported photocatalyst microparticles and the material are naturally charged with static electricity, and the method of spraying and applying the powder of the ultrafine metal particle-supported photocatalyst microparticles to the material by this electrostatic attraction force and the method of pressing the material into the powder to adhere the powder Etc. Alternatively, the photocatalyst particles carrying ultrafine metal particles may be forcibly charged by corona discharge according to the principle of electric dust collection, and may be attached to the surface of the material between the electrodes or on the electrodes by the electric field force between the electrodes.
[0042]
By these methods, the material to which the ultrafine metal particle-supported photocatalyst fine particles are attached can be heated to an appropriate temperature and firmly held on the material. More effectively, a binder that is cured by heating is applied to the surface of the material in advance, and the metal-supported photocatalyst fine particles are attached to the material by the above-described method, and when heated and cured, the metal-supported photocatalyst fine particles can be firmly held. it can.
[0043]
In order to hold the metal ultrafine particle-supported photocatalyst on the surface of the carbon fiber or the activated carbon fiber, the metal ultrafine particle-supported photocatalyst fine particles are attached to the surface of the carbon fiber or the activated carbon fiber prepared as a material in advance by the above method, and then If these fibers are fired at a predetermined temperature, the photocatalyst supporting ultrafine metal particles can be firmly held on carbon fibers or activated carbon fibers.
Further, after the raw material fiber is carbonized by a carbonizing treatment or activated carbon fiber by an activation treatment, the photocatalyst supporting ultrafine metal particles can be held on the carbon fiber or the activated carbon fiber by the above-mentioned method.
[0044]
Raw materials for carbon fiber include rayon fiber, pitch fiber obtained by spinning petroleum pitch / coal pitch, acrylic fiber, and many other fibers, and these fibers are converted to carbon fiber or activated carbon fiber using almost the same firing method. Can be applied. Above all, the main raw material of carbon fiber is PAN (polyacrylonitrile), which is spun into acrylic fiber. The acrylic fiber will be described below. When the acrylic fiber is heated at a temperature of 1000 to 1800 ° C. in an inert atmosphere, the acrylic fiber becomes a carbon fiber.
By activating this carbon fiber in a mixed gas of water vapor, carbon dioxide and nitrogen, activated carbon fibers having countless micropores can be formed, and the activated carbon fibers hold the photocatalyst supporting ultrafine metal particles. To make it happen. The self-cleaning decomposition ability can be remarkably improved by the adsorption power of the activated carbon fiber and the decomposition power of the photocatalyst supporting ultrafine metal particles.
[0045]
Activated carbon fibers holding metal ultrafine particle-supported photocatalysts can also be produced by continuous processing from metal ultrafine particles, photocatalyst fine particles, and raw fibers such as acrylic. That is, the raw fiber is run in a heating furnace to perform a carbonization treatment and an activation treatment to produce an activated carbon fiber. In the reaction tower, the organometallic complex colloid and the photocatalyst fine particles are mutually sprayed to generate colloid-adhered photocatalyst fine particles in a space, and when the activated carbon fibers run while the fine particles fall, the colloid adheres to the surface of the activated carbon fibers. Photocatalytic fine particles adhere. When this activated carbon fiber is run in a heating furnace at about 500 ° C., an activated carbon fiber in which a photocatalyst supporting metal ultrafine particles is strongly held can be continuously produced.
[0046]
【Example】
Examples of a material holding a photocatalyst carrying ultrafine metal particles according to the present invention and a method for producing the same will be described below to further clarify features of the present invention.
[0047]
Example 1
[Preparation of two types of pt ultrafine particle-supported photocatalysts]
A hydrophobic colloid of balsam Pt as an organometallic complex was dispersed in hydrophilic acetone to prepare an organometallic complex colloid solution having a concentration of 2.5% by weight. Titanium dioxide powder having a rutile crystal structure and an average particle diameter of 300 nm was mixed with the colloid solution as photocatalyst fine particles, and the colloid was attached to the titanium dioxide fine particles. This colloid solution was applied to a Pyrex glass plate, dried, baked at 500 ° C. for 30 minutes, and peeled off the glass plate to obtain a photocatalyst A carrying ultrafine metal particles. Similarly, photocatalyst B carrying ultrafine metal particles was obtained using titanium dioxide powder having a rutile crystal structure and an average particle size of 70 nm.
5 is a transmission electron micrograph of FIG. 5A and FIG. 6 is a transmission electron micrograph of B, showing the state of Pt ultrafine particles being supported on titanium dioxide fine particles. FIG. 7 shows a lattice image of the sample A by a high-resolution transmission electron microscope, which proves that Pt is supported on rutile-type titanium dioxide from the lattice spacing. FIG. 8 shows the particle size distribution of Pt ultrafine particles of A and B, showing that the average particle size of A is 3 nm and the average particle size of B is 1.5 nm. According to the colloid firing method, ultrafine metal particles having a small average particle diameter can be supported on titanium dioxide, and the quantum size effect, which is the core of the present invention, can be most effectively exerted.
[0048]
Example 2
[Measurement of Loading Density of Pt Ultrafine Particle-Supported Photocatalyst of Example 1]
The carrying density of the Pt ultrafine particles of the samples A and B obtained in Example 1 was measured. At this time, the titanium dioxide fine particles and the Pt ultrafine particles approximated to a spherical shape. From the electron micrograph of FIG. 5A, about 120 Pt ultrafine particles exist on the surface of one titanium dioxide fine particle having a diameter of 200 nm, and 1 cm2Loading density per unit is 2 × 1011Was individual. Similarly, from the electron micrograph of FIG. 6B, about 300 Pt ultrafine particles are present on the surface of one titanium dioxide having a diameter of 50 nm, and the carrying density is 4 × 1012Pieces / cm2Met. From the viewpoint of easy understanding, in the present invention, the loading density is expressed by the number of ultrafine metal particles per photocatalyst fine particle.
[0049]
Example 3
[Acrylic fiber holding Pt ultrafine particle-supported photocatalyst]
The sample B prepared in Example 1, that is, a powder made of a photocatalyst carrying rutile / Pt type metal ultrafine particles having an average particle diameter of 70 nm was sprayed onto acrylic fibers by spraying, and both were held by electrostatic force. Excess powder was dropped by tapping slightly. FIG. 9 is an electron micrograph showing a state in which the ultrafine metal particle-supported photocatalyst is held on acrylic fibers by static electricity, and FIG. 10 is an electron micrograph showing a further enlarged view thereof. It can be seen that the photocatalyst supporting ultrafine metal particles is held on the entire fiber surface. The weight of the held metal ultrafine particle-supported photocatalyst is 3% of the weight of the acrylic fiber. If it is at least 1% or more, the effect of the photocatalyst is obtained, and in the case of performing a rapid experiment, it may be 5% or 10%.
[0050]
Example 4
[Comparison between Pt loading and conventional photocatalyst fine particles]
By another manufacturing method, ultrafine Pt particles having an average particle size of 1.5 nm were supported on rutile titanium dioxide having an average particle size of 70 nm to prepare a photocatalyst supporting metal ultrafine particles. The loading density of Pt ultrafine particles was as high as 600 per titanium dioxide fine particle. 0.5 g of this Pt ultrafine particle-supported photocatalyst (in the case of 10% by weight) was held on 5 g of acrylic fiber in the same manner as in Example 3. Under exactly the same conditions, an acrylic fiber holding an anatase-type titanium dioxide alone having an average particle diameter of 70 nm and a rutile-type titanium dioxide alone having an average particle diameter of 70 nm was produced. Oxygen and argon gas were prepared as reaction atmospheres, and the effect of superoxide anion was also confirmed. Pt ultrafine particle-supported photocatalyst fine particles / O2To I, anatase O2Is J, anatase / Ar is K, rutile / O2Is L.
In order to check the efficiency of decomposition of acetaldehyde into acetic acid, the measurement was started from a concentration of acetaldehyde in the sealed container of 100 ppm, and the measurement was continued until the concentration became 1 ppm. The results are shown in FIG. 11 as a semilogarithmic graph. From the comparison of I and J at the same time from the start of the measurement, it can be seen that the catalytic efficiency of Pt loading is about 100 times higher than that of anatase alone. The reason for this is that the metal carrying density is quite large, and the particle size of the ultrafine Pt particles is fairly small due to the uniformity of the particles, and the quantum size effect is remarkably exhibited. From the comparison between J and K, it was proved that decomposition was not promoted with argon gas and the presence of oxygen was effective. That is, the presence of the superoxide anion effectively acts on the oxidation-reduction process. Further, it was found that the catalyst efficiency was the worst in the case of rutile alone even in oxygen.
[0051]
Example 5
[Continuous production apparatus of activated carbon fiber holding photocatalyst supporting ultrafine metal particles]
FIG. 12 shows an apparatus for continuously holding a photocatalyst supporting ultrafine metal particles while producing activated carbon fibers. The reaction tower is composed of a
On the other hand, the raw material fiber such as an acrylic fiber or the
[0052]
Example 6
[Adsorption and decomposition effect of activated carbon fiber and photocatalyst]
Three types of activated carbon fibers were compared: one holding
[0053]
Example 7
[Repeated effect of activated carbon fiber and
Acetaldehyde concentration is started from 100 ppm, and when it drops to 1 ppm, acetaldehyde is injected from the outside and returned to 100 ppm again. By repeating this operation, the adsorption power of activated carbon fiber and the decomposition effect of photocatalyst were examined. An effect of eleven repetitions was observed, but the period from 100 ppm to 1 ppm was hardly changed at 80 minutes. The fifth and eleventh cycles are longer, only because of the excess injection of acetaldehyde from about 300 ppm to 400 ppm. The fact that the deterioration has not occurred indicates that acetaldehyde is adsorbed by the activated carbon fiber, and at the same time, most of the adsorbed acetaldehyde is decomposed by the photocatalyst. That is, it can be said that the activated carbon fiber holding the photocatalyst supporting ultrafine metal particles has an extremely effective adsorption / decomposition power.
[0054]
Comparative Example 1
[Repeated effect of activated carbon fiber only]
As a comparative example, the repetition effect of only activated carbon fiber was examined. Although it takes about 20 minutes for the density to decrease and saturate, the saturation value gradually increases, and it can be seen that the density does not substantially decrease at the ninth time. This indicates that when the micropores are filled with acetaldehyde, the adsorptive power of the activated carbon fibers is lost.
[0055]
Comparative Example 2
[Repeated effect of activated carbon fiber and anatase 70]
The repetitive effect when a conventional anatase-type titanium dioxide having an average particle size of 70 nm (anatase 70) was held on activated carbon fibers was examined. The method was performed exactly as in Example 7. The cycle was as long as 13 hours, so that only three experiments could be performed. The period is about 10 times longer than that of
[0056]
It can be understood that Example 7 of the present invention shows an excellent effect over Comparative Examples 1 and 2.
[0057]
The present invention is not limited to the embodiments described above, but includes various modifications and design changes within the technical scope thereof without departing from the technical idea of the present invention.
[0058]
【The invention's effect】
As described in detail above, the present invention has been made by focusing on the fact that the photocatalytic properties of the ultrafine metal particle-supported photocatalyst, that is, the ability to decompose organic substances is much better than that of the photocatalyst fine particles alone. By holding the metal ultrafine particle-supported photocatalyst alone on various materials, environmental pollutants, harmful substances to the human body, and offensive odors can be strongly decomposed and self-decomposed to produce excellent environmental hygiene. Further, when the photocatalyst supporting ultrafine metal particles is held on activated carbon fibers, it exhibits an extremely excellent adsorptive decomposition effect, and provides a dramatic brightening for the improvement of the living environment in the future.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a state in which a photocatalyst supporting metal ultrafine particles is held by activated carbon fibers.
FIG. 2 is an explanatory diagram of a band structure for explaining a quantum size effect of ultrafine metal particles.
FIG. 3 is a diagram showing the wavelength distribution of ultraviolet light of an attractant lamp capable of efficiently exciting both rutile type and anatase type of titanium dioxide.
FIG. 4 is a wavelength distribution diagram of natural sunlight.
FIG. 5 is a transmission electron micrograph of a state in which ultrafine Pt particles are supported on titanium dioxide having an average particle diameter of 300 nm.
FIG. 6 is a transmission electron micrograph of a state in which ultrafine Pt particles are supported on titanium dioxide having an average particle diameter of 70 nm.
7 is a lattice image of the state shown in FIG. 5 using a high-resolution transmission electron microscope.
8 is a particle size distribution diagram of the Pt ultrafine particles of FIGS. 5 and 6. FIG.
FIG. 9 is an electron micrograph of a powder of a photocatalyst supporting ultrafine metal particles electrostatically adsorbed on an acrylic fiber.
FIG. 10 is a further enlarged electron micrograph of FIG. 9;
FIG. 11 is a time course of acetaldehyde decomposition by Pt-supported titanium dioxide and titanium dioxide alone.
FIG. 12 is a schematic view of an apparatus for continuously producing activated carbon fibers holding a photocatalyst supporting ultrafine metal particles.
FIG. 13 is a time course of acetaldehyde concentration showing the effect of adsorbing and decomposing activated carbon fibers and a photocatalyst.
FIG. 14 is a repetition effect diagram of acetaldehyde concentration when a photocatalyst supporting ultrafine metal particles of
FIG. 15 is a repetition effect diagram of acetaldehyde concentration of only activated carbon fiber.
FIG. 16 is a repetitive effect diagram of acetaldehyde concentration when an activated carbon fiber holds a photocatalyst of
FIG. 17 is an explanatory diagram of a band structure of a conventional metal-supported photocatalyst.
FIG. 18 is a schematic view of the state of adsorption of activated carbon fibers.
FIG. 19 is a schematic diagram showing a state in which anatase type titanium dioxide is held on activated carbon fibers.
FIG. 20 is a schematic view of a band structure for explaining that rutile-type titanium dioxide hardly reduces oxygen.
FIG. 21 is a schematic diagram of a band structure illustrating that anatase type titanium dioxide can easily reduce oxygen.
[Explanation of symbols]
2. Spray section
4. Spray mechanism
6 ・ ・ Particle nozzle
8. First heating tank
10. First flange part
11 ・ ・ Sending fan
12. Second heating tank
13. Baffle plate
14. Fiber body
16. Heater
18. Fan
20 ・ Hopper
21 ... Container
24 ・ ・ Container
G ... activation gas
Claims (13)
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24588597A JP3601753B2 (en) | 1997-08-06 | 1997-08-06 | Highly functional material holding ultrafine metal particle-supported photocatalyst and method for producing the same |
| US09/068,831 US6121191A (en) | 1996-09-20 | 1997-08-22 | Ultrafine metal particle carrying photocatalyst, highly function material loaded with the photocatalyst, and method of manufacturing them |
| PCT/JP1997/002958 WO1998011984A1 (en) | 1996-09-20 | 1997-08-22 | Ultrafine metal particle carrying photocatalyst, highly function material loaded with the photocatalyst, and method of manufacturing them |
| EP97936863A EP0882504B1 (en) | 1996-09-20 | 1997-08-22 | Ultrafine metal particle carrying photocatalyst, highly function material loaded with the photocatalyst, and method of manufacturing them |
| DE69735209T DE69735209T2 (en) | 1996-09-20 | 1997-08-22 | PHOTOCATALYZER WITH ULTRA-FINE METAL PARTICLES, HIGH-FUNCTIONAL MATERIAL CHARGED WITH THE PHOTO CATALYST AND METHOD FOR THEIR PRODUCTION |
| US09/477,061 US6265341B1 (en) | 1996-09-20 | 2000-01-03 | Highly functional base material and a method of manufacturing the same |
| US09/717,652 US6365545B1 (en) | 1996-09-20 | 2000-11-21 | Highly functional base material |
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| JP24588597A JP3601753B2 (en) | 1997-08-06 | 1997-08-06 | Highly functional material holding ultrafine metal particle-supported photocatalyst and method for producing the same |
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| JPH1147611A JPH1147611A (en) | 1999-02-23 |
| JP3601753B2 true JP3601753B2 (en) | 2004-12-15 |
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| JP24588597A Expired - Fee Related JP3601753B2 (en) | 1996-09-20 | 1997-08-06 | Highly functional material holding ultrafine metal particle-supported photocatalyst and method for producing the same |
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| JP3916799B2 (en) * | 1999-03-19 | 2007-05-23 | 晃雄 小松 | Metal-supported titanium dioxide photocatalyst and method for mass production thereof |
| KR20010057595A (en) * | 1999-12-22 | 2001-07-05 | 김무강 | a silver application light catalyst making a method |
| JP4564263B2 (en) * | 2004-01-16 | 2010-10-20 | 日本板硝子株式会社 | Ultrafine metal particle-containing photocatalyst and method for producing the same |
| JP4586385B2 (en) * | 2004-03-11 | 2010-11-24 | 株式会社大林組 | Method for producing porous material provided with photocatalyst |
| JP4940421B2 (en) * | 2005-01-17 | 2012-05-30 | 国立大学法人東京工業大学 | Oxide composite material, method for producing the same, electrochemical device, and catalyst containing oxide composite material |
| JP2006326530A (en) * | 2005-05-27 | 2006-12-07 | Hiroshima Univ | Nanoporous titanium oxide membrane and method for treating volatile organic compound using the same |
| JP2007069093A (en) * | 2005-09-06 | 2007-03-22 | Mitsui Chemicals Inc | Rutile type titanium dioxide ultrafine particle photocatalyst |
| CN104190411A (en) * | 2008-04-11 | 2014-12-10 | 株式会社爱入府 | Water processing device |
| JP2012112053A (en) * | 2010-11-19 | 2012-06-14 | Josho Gakuen | Fiber coated with polypyrrole-palladium nanocomposite and method for manufacturing the same |
| IN2014DN07512A (en) | 2012-03-08 | 2015-04-24 | Univ Tokyo | |
| JP5999548B2 (en) * | 2012-04-27 | 2016-09-28 | 国立大学法人 東京大学 | Photocatalyst and method for producing the same |
| US9144237B2 (en) * | 2012-08-10 | 2015-09-29 | Tsukasa Sakurada | Sterilizing and deodorizing agents, their method of manufacture and uses |
| CN105944709B (en) * | 2016-06-03 | 2019-04-05 | 济南大学 | A kind of three-dimensional grapheme-nanometer titanium dioxide compound photocatalyst and preparation method thereof |
| CN107042065A (en) * | 2017-02-23 | 2017-08-15 | 苏州优函信息科技有限公司 | Visible ray near infrared band solid-state light catalytic purifying thin-film device |
| TWI767812B (en) * | 2021-07-30 | 2022-06-11 | 臺灣塑膠工業股份有限公司 | Carbon fiber composites and method for producing the same |
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