JP2004237267A - Photocatalyst activated by visible light - Google Patents
Photocatalyst activated by visible light Download PDFInfo
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- JP2004237267A JP2004237267A JP2003064162A JP2003064162A JP2004237267A JP 2004237267 A JP2004237267 A JP 2004237267A JP 2003064162 A JP2003064162 A JP 2003064162A JP 2003064162 A JP2003064162 A JP 2003064162A JP 2004237267 A JP2004237267 A JP 2004237267A
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- photocatalyst
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- titanium oxide
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- 229910052751 metal Inorganic materials 0.000 claims abstract description 58
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- 238000010521 absorption reaction Methods 0.000 claims abstract description 40
- 229910052737 gold Inorganic materials 0.000 claims abstract description 38
- 239000002245 particle Substances 0.000 claims abstract description 35
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- 229910052703 rhodium Inorganic materials 0.000 abstract description 3
- 230000004913 activation Effects 0.000 abstract 1
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- 239000000243 solution Substances 0.000 description 41
- 239000010931 gold Substances 0.000 description 38
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- 239000000084 colloidal system Substances 0.000 description 26
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- 239000010949 copper Substances 0.000 description 23
- 238000000862 absorption spectrum Methods 0.000 description 19
- 239000000203 mixture Substances 0.000 description 18
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- 239000007864 aqueous solution Substances 0.000 description 14
- 238000000034 method Methods 0.000 description 14
- 239000002253 acid Substances 0.000 description 13
- 238000003756 stirring Methods 0.000 description 13
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 12
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- 239000010944 silver (metal) Substances 0.000 description 11
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- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 10
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- 238000010992 reflux Methods 0.000 description 7
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- 239000001267 polyvinylpyrrolidone Substances 0.000 description 6
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- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 description 2
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- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、可視光にて活性化可能な光触媒に関する。
【０００２】
【従来の技術】
従来、光触媒としてはアナターゼやルチル型の酸化チタンが知られているが、約３８０ｎｍ以下の紫外線でしか活性化しないため、太陽光または紫外線放射ランプ等を用いる必要があった。このため、光触媒が活性化できる波長を可視光領域にまで広げる研究が活発に行われている。
【０００３】例えば、様々な金属を光触媒にドーピングしたりイオン注入する試み（特開平９−１９２４９６号公報や表面化学２０巻２号６０〜６５項１９９９年など）や、酸素欠陥または構造欠陥を発生させて可視光活性化させる試み（工業材料４８巻６号２６〜４４項２０００年など）が行われている。しかし、吸収波長が限られており、高活性を示す可視光活性光触媒は得られていない。
【０００４】特開平１１−１０４５００号公報には、可視光領域でプラズマ共鳴による吸収（プラズモン吸収）を示すクラスター状態の金属を光触媒物質中に分散させた光触媒が記載されている。しかし、金属微粒子が媒体となる光触媒中に分散しているため、媒体との相互作用を誘起し光電場による分極に影響を与え、プラズモン吸収が不鮮明になる欠点がある。また、プラズモン吸収はそれぞれの金属に固有の波長しか吸収できないため、例えば、媒体中または空気中で安定で明確なプラズモン吸収を示す金属であるＡｇ，Ａｕ，Ｃｕの微粒子の場合、４２０、５２０、５７０ｎｍ付近の波長は吸収できるが、６００〜８００ｎｍの領域の光では活性化できない欠点がある。
【０００５】特開平１０−１４６５３１号公報には、平均粒径１〜１０ｎｍの金属微粒子を光触媒表面に担持する事により触媒活性を向上させた光触媒が記載されているが、紫外線による活性向上のみしか得られていない。
【０００６】一方、光触媒中に半導体微粒子を分散させて、半導体微粒子のサブバンド吸収を利用した可視光活性光触媒も報告されている。しかし、吸収強度が低く、 ＣｄＳｅ、ＣｄＴｅ等の半導体のように、６９０、７６０ｎｍ付近の光を吸収できるが、水の存在下で光をあてると自己溶解現象を起こし、光触媒表面を覆ってしまうような不安定なものがほとんどで、高活性な可視光活性光触媒は得られていない。
【０００７】
【発明が解決しようとしている課題】
本発明の目的は、可視光領域の光を効率良く吸収して高い触媒活性を示す可視光活性光触媒を提供することにある。
【０００８】
【課題を解決するための手段】
明確なプラズモン吸収を示す金属としては、Ｌｉ，Ｎａ，Ｋ，Ａｕ，Ａｇ，Ｃｕなどが知られているが、媒体中または空気中で安定な金属としてはＡｕ、ＡｇおよびＣｕが挙げられる。これらの金属のプラズモン吸収波長は５２０、４２０、５７０ｎｍである。このようなプラズモン吸収は、一般に数ｎｍ〜数十ｎｍ程度の金属微粒子において見られる。しかし、これらの金属微粒子を２個以上凝集させて二次粒子化すると異なる吸収波長ピークが出現し、Ａｕは５２０と７２０ｎｍ、Ａｇは４２０と６２０ｎｍ、Ｃｕは５７０と８００ｎｍの吸収波長ピークを示すことが判った。
【０００９】また、ＡｕとＡｇからなる二次粒子には５２０と４２０ｎｍの吸収ピークの他に６６０ｎｍの吸収ピークが出現し、ＡｇとＣｕからなる二次粒子には４２０と５７０ｎｍの吸収ピークの他に６９０ｎｍの吸収ピークが出現し、ＡｕとＣｕからなる二次粒子には５２０と５７０ｎｍの吸収ピークの他に７６０ｎｍの吸収ピークが出現し、ＡｕとＡｇとＣｕからなる二次粒子には５２０と４２０と５７０ｎｍの吸収ピークの他に７００ｎｍの吸収ピークが出現することが判った。
【００１０】このように、Ａｕ，Ａｇ，Ｃｕなどの金属微粒子を２個以上凝集させた二次粒子化金属微粒子を光触媒中に分散または光触媒表面に担持することにより、可視光領域の光を効率良く吸収して活性化できる可視光活性光触媒が得られることを見い出した。
【００１１】二次粒子化金属微粒子は、光触媒中に分散させても可視光域の光を吸収して光触媒活性を示すが、光触媒表面に担持した方が活性が高いことを確認した。詳しい触媒反応機構は不明だが、光触媒中に分散させた金属微粒子は媒体との相互作用により、光電場による分極に影響が生じることが考えられ、また、金属微粒子で分極した電荷が実際に反応が起こる光触媒表面に十分に達していない事が考えられる。金属微粒子を光媒触表面に担持した場合は、プラズマ共鳴により金属微粒子表面に生じた分極の電荷が光触媒に有効に移行して光触媒表面に電子と正孔を生じるため、高い活性が得られると考えられる。
【００１２】さらに、金属微粒子の組成や粒径を変化させることによってプラズモン吸収ピークを変化させることができる。Ａｕ，Ａｇ，またはＣｕに、Ｐｔ、Ｒｈ、Ｐｄ、Ｉｒ、Ｚｎ、ＰｂまたはＢｉ等の金属を３０重量％まで混合して合金化することによりプラズモン吸収波長ピークを約５０ｎｍ長波長側にシフトさせることが可能であることを見い出した。このように合金化した金属微粒子を二次粒子化した場合に新たに発生する吸収ピークも同様に長波長側にシフトすることも見い出した。
【００１３】Ａｕ，ＡｇおよびＣｕの微粒子の粒径を、６０ｎｍ以上にするとプラズモン吸収ピークが長波長側にシフトし、１７０ｎｍ以上になるとプラズモン吸収ピークが見られなくなることも見い出した。このような６０〜１６０ｎｍの粒径の金属微粒子を二次粒子化した場合に発生する吸収ピークも同様に長波長側にシフトすることも見い出した。
【００１４】以下、本発明の詳細について説明する。光触媒にはチタンテトライソプロポキシドを加水分解して合成した酸化チタン粉末を用いたが、これ以外にも、粉砕により粉末化したのもや、テルミット法やＣＶＤ等で合成した酸化チタン粉末やコーティング膜、チョコラルスキー法やスカル・メルティング法等で合成された酸化チタン単結晶や多結晶も用いる事ができる。Ａｕ，Ａｇ，Ｃｕの金属微粒子の合成には多くの方法が提案されており、どのような方法で合成した金属微粒子を用いても良い。例えば、クエン酸、アスコルビン酸、ＰＶＡ、ポリビニルピロリドン等のコロイド安定化剤を加えた水溶液中で金属塩化物等の金属化合物を還元する方法等がある。金属微粒子の粒径を変化させるには、コロイド安定化剤や金属化合物の濃度を変化させる事により７．５ｎｍから１８０ｎｍ以上の粒径の金属微粒子が得られる。
【００１５】金属微粒子を二次粒子化するには、塩や電解質を少量添加する方法や、一度乾燥凝集させたものを再度分散させる再分散法などを用いる事ができる。例えば、Ａｕ微粒子が分散したコロイド溶液に硝酸アルミニウムを０．００２〜０．００５％程度添加する事により２から３個のＡｕ微粒子が凝集した二次粒子分散コロイド溶液が得られる。
【００１６】二次粒子化金属微粒子を酸化チタン光触媒上に担持する方法としては、酸化チタン分散溶液に二次粒子化金属微粒子コロイド溶液を混合して酸化チタンに吸着担持させたのち乾燥させる方法や、粉末状酸化チタンに二次粒子化金属微粒子コロイド溶液を含浸または噴霧させたのち乾燥させる方法等を用いて担持できる。
【００１７】二次粒子化した金属微粒子を酸化チタン光触媒中に分散させる方法としては、二次粒子化金属微粒子オルガノゾルにチタンテトライソプロポキシドを加えた後、加水分解して、二次粒子化金属微粒子分散酸化チタン光触媒を合成する方法等を用いる事ができる。二次粒子化金属微粒子オルガノゾルは、エタノール等の有機溶媒中で二次粒子化金属微粒子を合成する方法や、一度乾燥凝集した金属微粒子を有機溶媒中で再分散させる方法等で作成できる。
【００１８】
【発明の実施の形態】
発明の実施の形態を実施例にもとづき説明する。
【００１９】金属微粒子の粒径や凝集状態は透過型電子顕微鏡にて測定した。可視光活性光触媒の吸収スペクトルはダブルモノクロメータ可視紫外近赤外分光光度計を用いて測定した。
【００２０】本発明の実施例および比較例で用いる酸化チタンコロイド溶液は、エタノール２００ｃｃに純水０．７２ｇを加えて良く混合した後、チタンテトライソプロポキシド６．２６ｇを添加し、１０℃で撹拌してゆっくりと加水分解を行うことにより作成した。
【００２１】可視光活性光触媒の浄化能力測定には、シリカウール２．５ｇに本発明の可視光活性光触媒を０．１ｇ担持したものを用いた。外表面を紫外線吸収膜で覆った１ｌガラス容器中に、アセトアルデヒドを３０００ｐｐｍ含有させた標準空気（酸素２１％、窒素７９％）と可視光活性光触媒担持シリカウールを密閉し、紫外線カットガラスを介して４０Ｗの白熱灯を照射した。アセトアルデヒドの濃度変化はガスクロマトグラフにて測定した。比較にはシリカウール２．５ｇに酸化チタンのみを０．１ｇ担持したものを用いた。
【００２２】実施例１
９５ｇの純水にテトラクロロ金酸４水和物２０．５９ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金庫微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図１に示す。酸化チタン上に担持した二次粒子化金微粒子は、約４０ｎｍの金微粒子が２から３個凝集した二次粒子を形成していた。
【００２３】実施例２
テトラクロロ金酸４水和物２０．５９ｍｇの代わりに塩素酸銀９．５７ｍｇを用いたこと以外は、実施例１と同様にして、酸化チタン粒子上に二次粒子化銀微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図１に示す。酸化チタン上に担持した二次粒子化銀微粒子は、約４０ｎｍの銀微粒子が２から３個凝集した二次粒子を形成していた。
【００２４】実施例３
９０ｇの純水に塩化銅（ＩＩ）二水和物８．５２ｍｇと分子量１００００のポリビニルピロリドン５５．５ｍｇを加えて十分に容解した後、水素化ホウ素ナトリウム３．７８ｍｇを純水１０ｇに溶解した水溶液を加えて良く撹拌した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化銅微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図１に示す。酸化チタン上に担持した二次粒子化銅微粒子は、約３５ｎｍの銅微粒子が２から３個凝集した二次粒子を形成していた。
【００２５】実施例４
９５ｇの純水にテトラクロロ金酸４水和物２０．５９ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却して金微粒子コロイドを得た。９５ｇの純水に塩素酸銀９．５７ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却して銀微粒子コロイドを得た。得られた金微粒子コロイドと銀微粒子コロイドを混合した後、硝酸アルミニウム９水和物１０ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液２００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金属微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図２に示す。酸化チタン上に担持した金と銀の複合二次粒子化金属微粒子は、約４０ｎｍの金属微粒子が２から３個凝集した二次粒子を形成していた。
【００２６】実施例５
９５ｇの純水にテトラクロロ金酸４水和物２０．５９ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却して金微粒子コロイドを得た。９０ｇの純水に塩化銅（ＩＩ）二水和物８．５２ｍｇと分子量１００００のポリビニルピロリドン５５．５ｍｇを加えて十分に溶解した後、水素化ホウ素ナトリウム３．７８ｍｇを純水１０ｇに溶解した水溶液を加えて良く撹拌して銅微粒子コロイドを得た。得られた金微粒子コロイドと銅微粒子コロイドを混合した後、硝酸アルミニウム９水和物１０ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液２００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金属微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図２に示す。酸化チタン上に担持した金と銅の複合二次粒子化金属微粒子は、約３５ｎｍの金属微粒子が２から３個凝集した二次粒子を形成していた。
【００２７】実施例６
９５ｇの純水に塩素酸銀９．５７ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却して銀微粒子コロイドを得た。９０ｇの純水に塩化銅（ＩＩ）二水和物８．５２ｍｇと分子量１００００のポリビニルピロリドン５５．５ｍｇを加えて十分に溶解した後、水素化ホウ素ナトリウム３．７８ｍｇを純水１０ｇに溶解した水溶液を加えて良く撹拌して銅微粒子コロイドを得た。得られた銀微粒子コロイドと銅微粒子コロイドを混合した後、硝酸アルミニウム９水和物１０ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶２００ｃｃ液とを混合し、酸化チタン粒子上に二次粒子化金属微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図２に示す。酸化チタン上に担持した銀と銅の複合二次粒子化金属微粒子は、約３５ｎｍの金属微粒子が２から３個凝集した二次粒子を形成していた。
【００２８】実施例７
９５ｇの純水にテトラクロロ金酸４水和物６９．４９ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物２９．４ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図３に示す。酸化チタン上に担持した二次粒子化金微粒子は、約６０ｎｍの金微粒子が２から３個凝集した二次粒子を形成していた。
【００２９】実施例８
９５ｇの純水にテトラクロロ金酸４水和物１．３２ｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物１４．７ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図３に示す。酸化チタン上に担持した二次粒子化金微粒子は、約１６０ｎｍの金微粒子が２から３個凝集した二次粒子を形成していた。
【００３０】実施例９
合成後の金属微粒子の組成が金７０重量％、白金３０重量％となる様に、９５ｇの純水にテトラクロロ金酸４水和物１４．３７ｍｇとヘキサクロロ白金酸６水和物７．８３ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金属微粒子を吸着担持し、可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図３に示す。酸化チタン上に担持した二次粒子化金属微粒子は、約４０ｎｍの金属微粒子が２から３個凝集した二次粒子を形成していた。
【００３１】実施例１０
７９．３ｇのエタノールに分子量１００００のポリビニルピロリドン５５．５ｍｇとテトラクロロ金酸４水和物２０．５９ｍｇを加えて加熱し、１０分間還流沸騰させた後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液にチタンテトライソプロポキシド３．１３ｇを加えて良く混合した後、エタノール１００ｃｃと純水０．３６ｇを添加し、１０℃で撹拌してゆっくりと加水分解を行い、酸化チタン粒子中に２次粒子化金微粒子が分散した可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図３に示す。酸化チタン中に分散した二次粒子化金微粒子は、約４０ｎｍの金微粒子が２から３個凝集した二次粒子を形成していた。
【００３２】比較例１
９５ｇの純水にテトラクロロ金酸４水和物１．５８ｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物１０ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金微粒子を吸着担持して可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図４に示す。酸化チタン上に担持した二次粒子化金微粒子は、約１７０ｎｍの金微粒子が２から３個凝集した二次粒子を形成していた。
【００３３】比較例２
合成後の金属微粒子の組成が金６０重量％、白金４０重量％となる様に、９５ｇの純水にテトラクロロ金酸４水和物１２．３１ｍｇとヘキサクロロ白金酸６水和物１０．４２ｍｇを加えて加熱し、還流沸騰させながら、５ｇの純水にクエン酸ナトリウム２水和物５８．８ｍｇを溶解した水溶液を加え、１０分間撹拌した後、室温まで冷却した。その後、硝酸アルミニウム９水和物５ｍｇを加えて撹拌し、２次粒子化金属微粒子コロイド溶液を作成した。この２次粒子化金属微粒子コロイド溶液と酸化チタンコロイド溶液１００ｃｃとを混合し、酸化チタン粒子上に二次粒子化金属微粒子を吸着担持し、可視光活性光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図４に示す。酸化チタン上に担持した二次粒子化金属微粒子は、約４０ｎｍの金属微粒子が２から３個凝集した二次粒子を形成していた。
【００３４】比較例３
エタノール１００ｃｃに純水０．３６ｇを加えて良く混合した後、チタンテトライソプロポキシド３．１３ｇを添加し、１０℃で撹拌してゆっくりと加水分解を行い、酸化チタン光触媒を作成した。得られた酸化チタン光触媒の可視光域での吸収スペクトルを測定した結果を図４に示す。
【００３５】比較例４
７９．３ｇのエタノールに分子量１００００のポリビニルピロリドン５５．５ｍｇとテトラクロロ金酸４水和物２０．５９ｍｇを加えて加熱し、１０分間還流沸騰させた後、室温まで冷却して金属微粒子コロイド溶液を作成した。この金属微粒子コロイド溶液にチタンテトライソプロポキシド３．１３ｇを加えて良く混合した後、エタノール１００ｃｃと純水０．３６ｇを添加し、１０℃で撹拌してゆっくりと加水分解を行い、酸化チタン粒子中に金微粒子が分散した光触媒を作成した。可視光域での吸収スペクトルを測定した結果を図４に示す。酸化チタン中に分散した金微粒子の粒径は約４０ｎｍであった。
【００３６】実施例１から３で作成した可視光活性光触媒の浄化能力測定を行った結果を図５に、実施例４から６で作成した可視光活性光触媒の浄化能力測定を行った結果を図６に、実施例７から１０で作成した可視光活性光触媒の浄化能力測定を行った結果を図７に、比較例１から４で作成した光触媒および可視光活性光触媒の浄化能力測定を行った結果を図８に示す。このように、実施例１から１０の可視光活性光触媒は、可視光にて高い光触媒活性を示した。一方、比較例１から４の光触媒は、可視光にて低い光触媒活性を示した。
【００３７】
【発明の効果】
以上説明した様に、プラズモン吸収を示すＡｕ、Ａｇ、Ｃｕの金属微粒子が２個以上凝集した二次粒子を、酸化チタン等の光触媒中に分散または光触媒表面に担持する事により、今まで吸収が困難であった６００〜８００ｎｍの光を吸収して高い触媒活性を示す可視光活性光触媒を作成した。
【００３８】Ａｕ，Ａｇ，またはＣｕに、 Ｐｔ、Ｒｈ、Ｐｄ、Ｉｒ、Ｚｎ、ＰｂまたはＢｉ等の金属を３０重量％まで混合して合金化することによりプラズモン吸収波長ピークを約５０ｎｍ長波長側にシフトさせることが可能であり、このように合金化した金属微粒子を二次粒子化した場合に新たに発生する吸収ピークも同様に長波長側にシフトすることも見い出した。
【００３９】さらに、Ａｕ，ＡｇまたはＣｕの微粒子の粒径を、６０ｎｍ以上１６０ｎｍ以下にすることにより、波長吸収ピークが最大で約１００ｎｍ長波長側にシフトし、このように粒径を多きくした金属微粒子を二次粒子化した場合に新たに発生する吸収ピークも同様に長波長側にシフトすることも見い出した。これらの可視光活性光触媒を組み合わせる事により、可視光域全体で効率良く光を吸収でき、高い触媒活性を示す可視光活性光触媒を作成できる。この可視光活性光触媒は可視光で活性化できるため、蛍光灯や白熱灯の様に紫外線をほとんど含まない光源でも使用でき、近年問題となっているシックハウス症候群の原因物質や悪臭等を、室内の光だけで分解除去できる様になる。
【図面の簡単な説明】
【図１】実施例１、２、３の可視光吸収スペクトルを示す図である。
【図２】実施例４、５、６の可視光吸収スペクトルを示す図である。
【図３】実施例７、８、９、１０の可視光吸収スペクトルを示す図である。
【図４】比較例１、２、３、４の可視光吸収スペクトルを示す図である。
【図５】実施例１、２、３の可視光活性光触媒のアセトアルデヒド浄化能力測定結果を示す図である。
【図６】実施例４、５、６の可視光活性光触媒のアセトアルデヒド浄化能力測定結果を示す図である。
【図７】実施例７、８、９、１０の可視光活性光触媒のアセトアルデヒド浄化能力測定結果を示す図である。
【図８】比較例１、２、３、４の光触媒のアセトアルデヒド浄化能力測定結果を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photocatalyst that can be activated by visible light.
[0002]
[Prior art]
Conventionally, anatase or rutile type titanium oxide has been known as a photocatalyst, but since it is activated only by ultraviolet rays of about 380 nm or less, it was necessary to use sunlight or an ultraviolet radiation lamp. For this reason, research has been actively conducted to extend the wavelength at which the photocatalyst can be activated to the visible light region.
For example, attempts to dope various metals into a photocatalyst or perform ion implantation (Japanese Patent Application Laid-Open No. 9-192496, Surface Chemistry, Vol. 20, No. 60-65, 1999, etc.), or to generate oxygen defects or structural defects Attempts have been made to activate visible light (industrial materials Vol. 48, No. 6, pp. 26-44, 2000, etc.). However, the absorption wavelength is limited, and a visible light active photocatalyst showing high activity has not been obtained.
Japanese Patent Application Laid-Open No. 11-104500 describes a photocatalyst in which a metal in a cluster state exhibiting absorption by plasma resonance (plasmon absorption) in the visible light region is dispersed in a photocatalytic substance. However, since the metal fine particles are dispersed in the photocatalyst serving as a medium, there is a disadvantage that the interaction with the medium is induced to affect the polarization due to the electric field, and the plasmon absorption becomes unclear. Further, since plasmon absorption can only absorb a wavelength specific to each metal, for example, in the case of fine particles of Ag, Au, and Cu, which are stable and clear plasmon absorption in a medium or air, 420, 520, Although the wavelength around 570 nm can be absorbed, there is a drawback that it cannot be activated by light in the region of 600 to 800 nm.
Japanese Patent Application Laid-Open No. Hei 10-146531 discloses a photocatalyst in which the catalytic activity is improved by supporting fine metal particles having an average particle size of 1 to 10 nm on the photocatalyst surface. Not obtained.
On the other hand, there has been reported a visible light active photocatalyst in which semiconductor fine particles are dispersed in a photocatalyst and utilizing the sub-band absorption of the semiconductor fine particles. However, it has a low absorption intensity and can absorb light near 690 and 760 nm like semiconductors such as CdSe and CdTe. However, when light is applied in the presence of water, a self-dissolution phenomenon occurs and the photocatalyst surface is covered. Most of them are unstable and no highly active visible light active photocatalyst has been obtained.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a visible light active photocatalyst that efficiently absorbs light in the visible light region and exhibits high catalytic activity.
[0008]
[Means for Solving the Problems]
Li, Na, K, Au, Ag, Cu, and the like are known as metals exhibiting clear plasmon absorption. Au, Ag, and Cu are listed as metals stable in a medium or in air. The plasmon absorption wavelengths of these metals are 520, 420, and 570 nm. Such plasmon absorption is generally found in metal fine particles of several nm to several tens nm. However, when two or more of these metal fine particles are agglomerated to form secondary particles, different absorption wavelength peaks appear; Au shows absorption wavelength peaks of 520 and 720 nm, Ag shows 420 and 620 nm, and Cu shows absorption wavelength peaks of 570 and 800 nm. I understood.
The secondary particles of Au and Ag have an absorption peak of 660 nm in addition to the absorption peaks of 520 and 420 nm, and the secondary particles of Ag and Cu have absorption peaks of 420 and 570 nm. An absorption peak of 690 nm appears, secondary particles of Au and Cu have an absorption peak of 760 nm in addition to the absorption peaks of 520 and 570 nm, and secondary particles of Au, Ag and Cu have an absorption peak of 520 nm. It was found that an absorption peak at 700 nm appeared in addition to the absorption peaks at 420 and 570 nm.
[0010] As described above, by dispersing or carrying on the photocatalyst the secondary particulate metal fine particles obtained by aggregating two or more metal fine particles such as Au, Ag, and Cu, the light in the visible light region can be efficiently emitted. It has been found that a visible light active photocatalyst that can be well absorbed and activated is obtained.
Although the secondary metal particles are dispersed in the photocatalyst, they absorb light in the visible light range and exhibit photocatalytic activity, but it has been confirmed that the activity is higher when supported on the photocatalyst surface. Although the detailed catalytic reaction mechanism is unknown, it is considered that the fine metal particles dispersed in the photocatalyst may affect the polarization due to the electric field due to the interaction with the medium, and the charge polarized by the fine metal particles may actually react. It is conceivable that the photocatalyst surface does not reach the surface sufficiently. When the metal fine particles are carried on the surface in contact with the optical medium, the charge of polarization generated on the surface of the metal fine particles due to plasma resonance is effectively transferred to the photocatalyst to generate electrons and holes on the photocatalyst surface, so that high activity is obtained. Conceivable.
Further, the plasmon absorption peak can be changed by changing the composition and the particle size of the metal fine particles. Au, Ag, or Cu is mixed with a metal such as Pt, Rh, Pd, Ir, Zn, Pb, or Bi up to 30% by weight and alloyed to shift the plasmon absorption wavelength peak to a longer wavelength of about 50 nm. Has found that it is possible. It has also been found that when the alloyed metal fine particles are converted into secondary particles, the newly generated absorption peak similarly shifts to longer wavelengths.
It has also been found that when the particle size of the fine particles of Au, Ag and Cu is 60 nm or more, the plasmon absorption peak shifts to the longer wavelength side, and when it is 170 nm or more, the plasmon absorption peak disappears. It has also been found that the absorption peak generated when such metal fine particles having a particle size of 60 to 160 nm are converted into secondary particles is similarly shifted to the longer wavelength side.
Hereinafter, the present invention will be described in detail. For the photocatalyst, titanium oxide powder synthesized by hydrolyzing titanium tetraisopropoxide was used.In addition to this, titanium oxide powder or a coating film synthesized by pulverization, thermite method, CVD, etc. Titanium oxide single crystals or polycrystals synthesized by the Czochralski method or the skull melting method can also be used. Many methods have been proposed for synthesizing Au, Ag, and Cu metal fine particles, and metal fine particles synthesized by any method may be used. For example, there is a method of reducing a metal compound such as a metal chloride in an aqueous solution to which a colloid stabilizer such as citric acid, ascorbic acid, PVA, or polyvinylpyrrolidone is added. In order to change the particle size of the metal fine particles, metal fine particles having a particle size of 7.5 nm to 180 nm or more can be obtained by changing the concentration of the colloid stabilizer or the metal compound.
In order to convert the metal fine particles into secondary particles, a method of adding a small amount of a salt or an electrolyte or a redispersion method of re-dispersing once dried and agglomerated particles can be used. For example, by adding about 0.002 to 0.005% of aluminum nitrate to a colloid solution in which Au fine particles are dispersed, a secondary particle-dispersed colloidal solution in which two to three Au fine particles are aggregated can be obtained.
As a method for supporting the secondary particulate metal fine particles on the titanium oxide photocatalyst, a method of mixing a secondary particulate metal fine particle colloidal solution with a titanium oxide dispersed solution, adsorbing and supporting the titanium oxide on the titanium oxide photocatalyst, and drying. Alternatively, the powdery titanium oxide may be supported by impregnating or spraying the colloidal solution of the secondary metal particles into fine particles, followed by drying.
As a method for dispersing the secondary fine metal particles in the titanium oxide photocatalyst, titanium tetraisopropoxide is added to the secondary fine metal organosol and then hydrolyzed to form the secondary fine metal particles. A method of synthesizing a fine particle-dispersed titanium oxide photocatalyst or the like can be used. The secondary particle-formed metal fine particle organosol can be prepared by a method of synthesizing the secondary particle-formed metal fine particles in an organic solvent such as ethanol or a method of re-dispersing once dried and aggregated metal fine particles in an organic solvent.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described based on examples.
The particle size and the state of aggregation of the metal fine particles were measured with a transmission electron microscope. The absorption spectrum of the visible light active photocatalyst was measured using a double monochromator visible ultraviolet near infrared spectrophotometer.
The titanium oxide colloid solution used in the examples and comparative examples of the present invention was mixed with 200 cc of ethanol, 0.72 g of pure water and mixed well, and then 6.26 g of titanium tetraisopropoxide was added. It was prepared by stirring and slowly hydrolyzing.
In the measurement of the purifying ability of the visible light active photocatalyst, a silica wool having 2.5 g of the visible light active photocatalyst of the present invention supported thereon was used. Standard air (21% oxygen, 79% nitrogen) containing 3000 ppm of acetaldehyde and silica wool supporting a visible light active photocatalyst are sealed in a 1-liter glass container whose outer surface is covered with an ultraviolet absorbing film, and the ultraviolet light cut glass is used to seal the air. A 40 W incandescent lamp was applied. The change in the concentration of acetaldehyde was measured by gas chromatography. For comparison, a sample in which only 0.1 g of titanium oxide was supported on 2.5 g of silica wool was used.
20.59 mg of tetrachloroauric acid tetrahydrate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution obtained by dissolving 58.8 mg of sodium citrate dihydrate in 5 g of pure water was added thereto. After stirring for minutes, the mixture was cooled to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a secondary particle safe colloidal solution. The colloidal solution of the secondary particulate metal fine particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary particulate gold fine particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 1 shows the result of measuring the absorption spectrum in the visible light region. The secondary particle-formed gold fine particles supported on titanium oxide formed secondary particles in which two to three gold fine particles of about 40 nm were aggregated.
In the same manner as in Example 1 except that 9.57 mg of silver chlorate was used instead of 20.59 mg of tetrachloroauric acid tetrahydrate, secondary silver particles were adsorbed and supported on titanium oxide particles. Thus, a visible light active photocatalyst was prepared. FIG. 1 shows the result of measuring the absorption spectrum in the visible light region. The secondary silver fine particles supported on the titanium oxide formed secondary particles in which two to three silver fine particles of about 40 nm were aggregated.
To 90 g of pure water, 8.52 mg of copper (II) chloride dihydrate and 55.5 mg of polyvinylpyrrolidone having a molecular weight of 10,000 were added and sufficiently dissolved, and 3.78 mg of sodium borohydride was dissolved in 10 g of pure water. The aqueous solution was added and stirred well. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary particulate metal fine particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary particulate copper fine particles were adsorbed and supported on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 1 shows the result of measuring the absorption spectrum in the visible light region. The secondary particulate copper fine particles supported on the titanium oxide formed secondary particles in which two to three copper fine particles of about 35 nm were aggregated.
20.59 mg of tetrachloroauric acid tetrahydrate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution obtained by dissolving 58.8 mg of sodium citrate dihydrate in 5 g of pure water was added thereto. After stirring for minutes, the mixture was cooled to room temperature to obtain a colloidal gold particle. 9.57 mg of silver chlorate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution of 58.8 mg of sodium citrate dihydrate dissolved in 5 g of pure water was added thereto while stirring under reflux, followed by stirring for 10 minutes. After cooling to room temperature, a silver fine particle colloid was obtained. After mixing the obtained colloidal gold particles and colloidal silver particles, 10 mg of aluminum nitrate nonahydrate was added and stirred to prepare a secondary particulate metal colloid solution. The colloidal solution of the secondary metal particles and 200 cc of the titanium oxide colloid solution were mixed, and the secondary metal particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 2 shows the result of measuring the absorption spectrum in the visible light region. The composite metal particles of gold and silver supported on titanium oxide were formed into secondary particles in which two to three metal fine particles of about 40 nm were aggregated.
20.59 mg of tetrachloroauric acid tetrahydrate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution obtained by dissolving 58.8 mg of sodium citrate dihydrate in 5 g of pure water was added thereto. After stirring for minutes, the mixture was cooled to room temperature to obtain a colloidal gold particle. To 90 g of pure water, 8.52 mg of copper (II) chloride dihydrate and 55.5 mg of polyvinylpyrrolidone having a molecular weight of 10,000 were added and sufficiently dissolved, and then an aqueous solution in which 3.78 mg of sodium borohydride was dissolved in 10 g of pure water. Was added and stirred well to obtain a copper fine particle colloid. After mixing the obtained gold fine particle colloid and copper fine particle colloid, 10 mg of aluminum nitrate 9 hydrate was added and stirred to prepare a secondary fine particle metal colloid solution. The colloidal solution of the secondary metal particles and 200 cc of the titanium oxide colloid solution were mixed, and the secondary metal particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 2 shows the result of measuring the absorption spectrum in the visible light region. The composite secondary metal particles of gold and copper supported on titanium oxide formed secondary particles in which two to three metal particles of about 35 nm were aggregated.
9.57 mg of silver chlorate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution of 58.8 mg of sodium citrate dihydrate dissolved in 5 g of pure water was added thereto while stirring under reflux, followed by stirring for 10 minutes. After cooling to room temperature, a silver fine particle colloid was obtained. To 90 g of pure water, 8.52 mg of copper (II) chloride dihydrate and 55.5 mg of polyvinylpyrrolidone having a molecular weight of 10,000 were added and sufficiently dissolved, and then an aqueous solution in which 3.78 mg of sodium borohydride was dissolved in 10 g of pure water. Was added and stirred well to obtain a copper fine particle colloid. After mixing the obtained silver fine particle colloid and the copper fine particle colloid, 10 mg of aluminum nitrate nonahydrate was added and stirred to prepare a secondary fine particle metal colloid solution. The colloidal solution of the secondary metal particles and the 200 cc solution of the titanium oxide colloid solution were mixed, and the secondary metal particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 2 shows the result of measuring the absorption spectrum in the visible light region. The composite secondary metal particles of silver and copper supported on titanium oxide formed secondary particles in which two to three metal particles of about 35 nm were aggregated.
To 95 g of pure water, 69.49 mg of tetrachloroauric acid tetrahydrate was added, and the mixture was heated and refluxed, and an aqueous solution of 29.4 mg of sodium citrate dihydrate dissolved in 5 g of pure water was added thereto. After stirring for minutes, the mixture was cooled to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary particulate metal fine particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary particulate gold fine particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 3 shows the result of measuring the absorption spectrum in the visible light region. The secondary particle-formed gold fine particles supported on the titanium oxide formed secondary particles in which two to three gold particles of about 60 nm were aggregated.
Embodiment 8
To 95 g of pure water, 1.32 g of tetrachloroauric acid tetrahydrate was added and heated, and while refluxing and boiling, an aqueous solution in which 14.7 mg of sodium citrate dihydrate was dissolved in 5 g of pure water was added. After stirring for minutes, the mixture was cooled to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary particulate metal fine particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary particulate gold fine particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 3 shows the result of measuring the absorption spectrum in the visible light region. The secondary particle-formed gold fine particles supported on titanium oxide formed secondary particles in which two to three gold particles of about 160 nm were aggregated.
Embodiment 9
To 37 g of pure water, 14.37 mg of tetrachloroauric acid tetrahydrate and 7.83 mg of hexachloroplatinic acid hexahydrate were added to 95 g of pure water so that the composition of the synthesized metal fine particles would be 70% by weight of gold and 30% by weight of platinum. In addition, while heating and reflux boiling, an aqueous solution in which 58.8 mg of sodium citrate dihydrate was dissolved in 5 g of pure water was added, followed by stirring for 10 minutes and then cooling to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary metal particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary metal particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 3 shows the result of measuring the absorption spectrum in the visible light region. The secondary fine metal particles supported on titanium oxide formed secondary particles in which two to three metal fine particles of about 40 nm were aggregated.
Embodiment 10
To 79.3 g of ethanol, 55.5 mg of polyvinylpyrrolidone having a molecular weight of 10,000 and 20.59 mg of tetrachloroauric acid tetrahydrate were added, heated, boiled under reflux for 10 minutes, and then cooled to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. After adding 3.13 g of titanium tetraisopropoxide to the colloidal solution of the secondary metal particles and mixing well, 100 cc of ethanol and 0.36 g of pure water were added, and the mixture was stirred at 10 ° C. and slowly hydrolyzed. Then, a visible light active photocatalyst in which secondary fine particles of gold were dispersed in titanium oxide particles was prepared. FIG. 3 shows the result of measuring the absorption spectrum in the visible light region. The secondary fine-particled gold fine particles dispersed in the titanium oxide formed secondary particles in which two to three gold fine particles of about 40 nm were aggregated.
Comparative Example 1
1.58 g of tetrachloroauric acid tetrahydrate was added to 95 g of pure water, and the mixture was heated and refluxed, and an aqueous solution obtained by dissolving 10 mg of sodium citrate dihydrate in 5 g of pure water was added thereto, followed by stirring for 10 minutes. Then, it was cooled to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary particulate metal fine particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary particulate gold fine particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 4 shows the result of measuring the absorption spectrum in the visible light region. The secondary fine-particled gold fine particles supported on titanium oxide formed secondary particles in which two to three gold fine particles of about 170 nm were aggregated.
Comparative Example 2
12.31 mg of tetrachloroauric acid tetrahydrate and 10.42 mg of hexachloroplatinic acid hexahydrate were added to 95 g of pure water so that the composition of the synthesized metal fine particles would be 60% by weight of gold and 40% by weight of platinum. In addition, while heating and reflux boiling, an aqueous solution in which 58.8 mg of sodium citrate dihydrate was dissolved in 5 g of pure water was added, followed by stirring for 10 minutes and then cooling to room temperature. Thereafter, 5 mg of aluminum nitrate 9-hydrate was added and stirred to prepare a colloidal solution of secondary particulate metal fine particles. The colloidal solution of the secondary metal particles and 100 cc of the titanium oxide colloid solution were mixed, and the secondary metal particles were adsorbed and carried on the titanium oxide particles to prepare a visible light active photocatalyst. FIG. 4 shows the result of measuring the absorption spectrum in the visible light region. The secondary fine metal particles supported on titanium oxide formed secondary particles in which two to three metal fine particles of about 40 nm were aggregated.
Comparative Example 3
After adding 0.36 g of pure water to 100 cc of ethanol and mixing well, 3.13 g of titanium tetraisopropoxide was added, and the mixture was stirred at 10 ° C. and slowly hydrolyzed to prepare a titanium oxide photocatalyst. FIG. 4 shows the result of measuring the absorption spectrum in the visible light region of the obtained titanium oxide photocatalyst.
Comparative Example 4
To 79.3 g of ethanol, 55.5 mg of polyvinylpyrrolidone having a molecular weight of 10,000 and 20.59 mg of tetrachloroauric acid tetrahydrate were added, heated and boiled under reflux for 10 minutes, and then cooled to room temperature to obtain a colloidal solution of fine metal particles. Created. After adding 3.13 g of titanium tetraisopropoxide to the metal fine particle colloid solution and mixing well, 100 cc of ethanol and 0.36 g of pure water were added, and the mixture was stirred at 10 ° C. and slowly hydrolyzed to obtain titanium oxide particles. A photocatalyst in which gold fine particles were dispersed was prepared. FIG. 4 shows the result of measuring the absorption spectrum in the visible light region. The particle size of the fine gold particles dispersed in the titanium oxide was about 40 nm.
FIG. 5 shows the results of measuring the purifying ability of the visible light active photocatalysts prepared in Examples 1 to 3, and FIG. 5 shows the results of measuring the purifying ability of the visible light active photocatalysts prepared in Examples 4 to 6. 6 shows the results of measuring the purifying ability of the visible light active photocatalysts prepared in Examples 7 to 10, and FIG. 7 shows the results of measuring the purifying ability of the photocatalysts and visible light active photocatalysts produced in Comparative Examples 1 to 4. Is shown in FIG. Thus, the visible light active photocatalysts of Examples 1 to 10 exhibited high photocatalytic activity in visible light. On the other hand, the photocatalysts of Comparative Examples 1 to 4 exhibited low photocatalytic activity in visible light.
[0037]
【The invention's effect】
As described above, by absorbing secondary particles of two or more metal particles of Au, Ag, and Cu exhibiting plasmon absorption in a photocatalyst such as titanium oxide or by carrying the particles on the photocatalyst surface, the absorption has been achieved up to now. A visible light-active photocatalyst was prepared that absorbs light of 600 to 800 nm, which was difficult, and exhibits high catalytic activity.
By mixing a metal such as Pt, Rh, Pd, Ir, Zn, Pb or Bi with Au, Ag, or Cu up to 30% by weight and alloying the same, the plasmon absorption wavelength peak becomes about 50 nm longer wavelength side. It has also been found that the absorption peak newly generated when the metal fine particles thus alloyed are converted into secondary particles also shifts to the longer wavelength side.
Further, by setting the particle size of the fine particles of Au, Ag, or Cu to 60 nm or more and 160 nm or less, the wavelength absorption peak shifts up to a longer wavelength of about 100 nm at the maximum, and thus the particle size is increased. It was also found that the absorption peak newly generated when the metal fine particles were converted into secondary particles similarly shifted to the longer wavelength side. By combining these visible light active photocatalysts, light can be efficiently absorbed in the entire visible light region, and a visible light active photocatalyst exhibiting high catalytic activity can be produced. Since this visible light active photocatalyst can be activated by visible light, it can be used even with a light source that hardly contains ultraviolet rays such as fluorescent lamps and incandescent lamps. It can be decomposed and removed only by light.
[Brief description of the drawings]
FIG. 1 is a diagram showing visible light absorption spectra of Examples 1, 2, and 3.
FIG. 2 is a view showing visible light absorption spectra of Examples 4, 5, and 6.
FIG. 3 is a diagram showing visible light absorption spectra of Examples 7, 8, 9, and 10.
FIG. 4 is a view showing visible light absorption spectra of Comparative Examples 1, 2, 3, and 4.
FIG. 5 is a graph showing the results of measuring the acetaldehyde purification ability of the visible light active photocatalysts of Examples 1, 2, and 3.
FIG. 6 is a graph showing the results of measuring the acetaldehyde purification ability of the visible light active photocatalysts of Examples 4, 5, and 6.
FIG. 7 is a graph showing the results of measuring the acetaldehyde purification ability of the visible light active photocatalysts of Examples 7, 8, 9, and 10.
FIG. 8 is a diagram showing the results of measuring the acetaldehyde purification ability of the photocatalysts of Comparative Examples 1, 2, 3, and 4.
Claims (3)
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Cited By (7)
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| JP2007190528A (en) * | 2006-01-23 | 2007-08-02 | Doshisha | Metal particulate fixed photocatalyst substance and its production method |
| JP2008104996A (en) * | 2006-10-27 | 2008-05-08 | Central Japan Railway Co | Photocatalyst, coating liquid for forming photocatalyst and method for manufacturing photocatalyst |
| JP2012217970A (en) * | 2011-04-13 | 2012-11-12 | Toyota Motor Corp | Catalyst for exhaust purification |
| KR101249885B1 (en) * | 2011-03-16 | 2013-04-03 | 한국광기술원 | Photocatalyst water purifier using plasmon |
| JP2014169210A (en) * | 2013-03-05 | 2014-09-18 | Hokkaido Univ | Hydrogen generator and hydrogen generation method |
| JP2014195797A (en) * | 2013-03-07 | 2014-10-16 | 学校法人神奈川大学 | Preparation method of visible light-responsive photocatalyst and visible light-responsive photocatalyst intermediate, usage of visible light-responsive photocatalyst, and visible light-responsive photocatalyst |
| WO2015146830A1 (en) * | 2014-03-26 | 2015-10-01 | 新日鉄住金化学株式会社 | Photocatalyst and method for producing same |
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- 2003-02-04 JP JP2003064162A patent/JP3790222B2/en not_active Expired - Lifetime
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007190528A (en) * | 2006-01-23 | 2007-08-02 | Doshisha | Metal particulate fixed photocatalyst substance and its production method |
| JP2008104996A (en) * | 2006-10-27 | 2008-05-08 | Central Japan Railway Co | Photocatalyst, coating liquid for forming photocatalyst and method for manufacturing photocatalyst |
| KR101249885B1 (en) * | 2011-03-16 | 2013-04-03 | 한국광기술원 | Photocatalyst water purifier using plasmon |
| JP2012217970A (en) * | 2011-04-13 | 2012-11-12 | Toyota Motor Corp | Catalyst for exhaust purification |
| JP2014169210A (en) * | 2013-03-05 | 2014-09-18 | Hokkaido Univ | Hydrogen generator and hydrogen generation method |
| JP2014195797A (en) * | 2013-03-07 | 2014-10-16 | 学校法人神奈川大学 | Preparation method of visible light-responsive photocatalyst and visible light-responsive photocatalyst intermediate, usage of visible light-responsive photocatalyst, and visible light-responsive photocatalyst |
| WO2015146830A1 (en) * | 2014-03-26 | 2015-10-01 | 新日鉄住金化学株式会社 | Photocatalyst and method for producing same |
| JPWO2015146830A1 (en) * | 2014-03-26 | 2017-04-13 | 新日鉄住金化学株式会社 | Photocatalyst and method for producing the same |
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