JP4352681B2 - Photocatalyst production method - Google Patents
Photocatalyst production method Download PDFInfo
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- JP4352681B2 JP4352681B2 JP2002299288A JP2002299288A JP4352681B2 JP 4352681 B2 JP4352681 B2 JP 4352681B2 JP 2002299288 A JP2002299288 A JP 2002299288A JP 2002299288 A JP2002299288 A JP 2002299288A JP 4352681 B2 JP4352681 B2 JP 4352681B2
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- Prior art keywords
- titanium dioxide
- photocatalyst
- silicon
- forbidden band
- band width
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000011941 photocatalyst Substances 0.000 title claims description 59
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 134
- 239000004408 titanium dioxide Substances 0.000 claims description 57
- 229910052710 silicon Inorganic materials 0.000 claims description 26
- 239000010703 silicon Substances 0.000 claims description 26
- 239000010419 fine particle Substances 0.000 claims description 20
- 238000005422 blasting Methods 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 9
- 238000005507 spraying Methods 0.000 claims description 8
- 238000002347 injection Methods 0.000 claims description 5
- 239000007924 injection Substances 0.000 claims description 5
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 34
- 239000004065 semiconductor Substances 0.000 description 30
- 239000000463 material Substances 0.000 description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 23
- 239000013078 crystal Substances 0.000 description 23
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 22
- 230000003197 catalytic effect Effects 0.000 description 22
- 239000010408 film Substances 0.000 description 22
- 239000000758 substrate Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 15
- 229910021529 ammonia Inorganic materials 0.000 description 11
- 230000035484 reaction time Effects 0.000 description 10
- 229910010271 silicon carbide Inorganic materials 0.000 description 9
- 230000001443 photoexcitation Effects 0.000 description 8
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- 239000010409 thin film Substances 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 5
- 238000000354 decomposition reaction Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- 238000013032 photocatalytic reaction Methods 0.000 description 5
- 230000004075 alteration Effects 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 230000001699 photocatalysis Effects 0.000 description 4
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910005540 GaP Inorganic materials 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- 229910000673 Indium arsenide Inorganic materials 0.000 description 2
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 229910021431 alpha silicon carbide Inorganic materials 0.000 description 2
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 2
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- WPYVAWXEWQSOGY-UHFFFAOYSA-N indium antimonide Chemical compound [Sb]#[In] WPYVAWXEWQSOGY-UHFFFAOYSA-N 0.000 description 2
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 description 2
- HTUMBQDCCIXGCV-UHFFFAOYSA-N lead oxide Chemical compound [O-2].[Pb+2] HTUMBQDCCIXGCV-UHFFFAOYSA-N 0.000 description 2
- YEXPOXQUZXUXJW-UHFFFAOYSA-N lead(II) oxide Inorganic materials [Pb]=O YEXPOXQUZXUXJW-UHFFFAOYSA-N 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910052724 xenon Inorganic materials 0.000 description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 2
- SKJCKYVIQGBWTN-UHFFFAOYSA-N (4-hydroxyphenyl) methanesulfonate Chemical compound CS(=O)(=O)OC1=CC=C(O)C=C1 SKJCKYVIQGBWTN-UHFFFAOYSA-N 0.000 description 1
- PFNQVRZLDWYSCW-UHFFFAOYSA-N (fluoren-9-ylideneamino) n-naphthalen-1-ylcarbamate Chemical compound C12=CC=CC=C2C2=CC=CC=C2C1=NOC(=O)NC1=CC=CC2=CC=CC=C12 PFNQVRZLDWYSCW-UHFFFAOYSA-N 0.000 description 1
- IHGSAQHSAGRWNI-UHFFFAOYSA-N 1-(4-bromophenyl)-2,2,2-trifluoroethanone Chemical compound FC(F)(F)C(=O)C1=CC=C(Br)C=C1 IHGSAQHSAGRWNI-UHFFFAOYSA-N 0.000 description 1
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 1
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 1
- 229910017115 AlSb Inorganic materials 0.000 description 1
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 1
- 229910004613 CdTe Inorganic materials 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 229910005542 GaSb Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910007709 ZnTe Inorganic materials 0.000 description 1
- DUSBUJMVTRZABV-UHFFFAOYSA-M [O-2].O[Nb+4].[O-2] Chemical compound [O-2].O[Nb+4].[O-2] DUSBUJMVTRZABV-UHFFFAOYSA-M 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- LVQULNGDVIKLPK-UHFFFAOYSA-N aluminium antimonide Chemical compound [Sb]#[Al] LVQULNGDVIKLPK-UHFFFAOYSA-N 0.000 description 1
- MDPILPRLPQYEEN-UHFFFAOYSA-N aluminium arsenide Chemical compound [As]#[Al] MDPILPRLPQYEEN-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- -1 band gap: 1.4 eV) Chemical compound 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- WMWLMWRWZQELOS-UHFFFAOYSA-N bismuth(III) oxide Inorganic materials O=[Bi]O[Bi]=O WMWLMWRWZQELOS-UHFFFAOYSA-N 0.000 description 1
- DVRDHUBQLOKMHZ-UHFFFAOYSA-N chalcopyrite Chemical class [S-2].[S-2].[Fe+2].[Cu+2] DVRDHUBQLOKMHZ-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
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- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 1
- 229940112669 cuprous oxide Drugs 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- VTGARNNDLOTBET-UHFFFAOYSA-N gallium antimonide Chemical compound [Sb]#[Ga] VTGARNNDLOTBET-UHFFFAOYSA-N 0.000 description 1
- HZXMRANICFIONG-UHFFFAOYSA-N gallium phosphide Chemical compound [Ga]#P HZXMRANICFIONG-UHFFFAOYSA-N 0.000 description 1
- 239000002638 heterogeneous catalyst Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- JCDAAXRCMMPNBO-UHFFFAOYSA-N iron(3+);oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Ti+4].[Fe+3].[Fe+3] JCDAAXRCMMPNBO-UHFFFAOYSA-N 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 239000011859 microparticle Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 125000005375 organosiloxane group Chemical group 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 238000006303 photolysis reaction Methods 0.000 description 1
- SBIBMFFZSBJNJF-UHFFFAOYSA-N selenium;zinc Chemical compound [Se]=[Zn] SBIBMFFZSBJNJF-UHFFFAOYSA-N 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
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- QXKXDIKCIPXUPL-UHFFFAOYSA-N sulfanylidenemercury Chemical compound [Hg]=S QXKXDIKCIPXUPL-UHFFFAOYSA-N 0.000 description 1
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Description
【0001】
【発明の属する技術分野】
本発明は光触媒に関するものである。
【0002】
【従来の技術】
光励起により触媒活性を示す不均一系触媒として種々の半導体材料が知られている。例えば二酸化チタン(TiO2)は、紫外線などの短波長の光を照射することにより励起され、エチレンや有臭の有機ガスの分解反応などにおいて触媒活性を示すことが知られている。また、ゲルマニウム(Ge)やシリコン(Si)は、二酸化チタンの場合よりも長波長の光により励起される性質を有することが知られている。しかし、これらの半導体材料の1種を単独で用いたときの触媒活性は必ずしも十分とは言えない。
【0003】
そこで、光触媒の触媒活性の向上を図るべく、2種以上の半導体材料を組み合わせた光触媒が提案されている。例えば、二酸化チタンなどの半導体粒子と、銀(Ag)などの金属粒子またはケイ素粒子とを基材上に溶射して得られる光触媒機能体(例えば特許文献1)、シリコンとシリコンカーバイド(SiC)とを組み合わせることで水の光分解などを促進する光触媒(例えば特許文献2)などが知られている。
【0004】
【特許文献1】
特開2000−334311号公報
【0005】
【特許文献2】
特開昭61−222542号公報
【0006】
【発明が解決しようとする課題】
しかしながら、上記特許文献1に記載の光触媒機能体のように二酸化チタンなどのバンドギャップエネルギーの大きい半導体材料を用いるものは、触媒活性の発現のために紫外線などの短波長の光を照射する必要がある。従って、例えば太陽光を利用した光反応にかかる光触媒機能体を適用しても、光励起に寄与するのは太陽光のうちのごく一部の光であり、その反応効率は極めて低いものとなる。
【0007】
また、上記特許文献1には、二酸化チタンを溶射した後急冷することによって二酸化チタン中のアナターゼ型結晶の割合を増加することができ、これにより触媒活性が向上することが記載されている。しかし、このように二酸化チタンを溶融する方法ではアナターゼ型結晶からルチル型結晶への変質を十分に防止することができず、二酸化チタンと他の半導体材料との複合型触媒において十分な触媒活性を得ることは非常に困難である。
【0008】
また、特許文献2に記載の光触媒は、二酸化チタンを利用する場合に比べて長波長の光の照射により触媒活性を示すという利点を有するが、その触媒活性は必ずしも高いものではない。さらに、かかる光触媒においては、シリコン層とシリコンカーバイド層とを積層して薄膜状とし、さらに2層間に導電層を介在させる必要があるなどの構成上の制限があり、コスト高にならざるを得ず取扱いも不便である。
【0009】
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、幅広い波長領域の光に対して十分に高い光触媒活性を示し、コストや取扱い性の点で有用な光触媒およびその製造方法を提供することを目的とする。
【0010】
【課題を解決するための手段】
上記課題を解決するために、本発明の光触媒は、二酸化チタンと、シリコンとを含有し、該二酸化チタンと該シリコンとが接触していることを特徴とする。
【0011】
本発明の光触媒においては、二酸化チタンと、その禁制帯幅(3.2eV)よりも狭い禁制帯幅を有するシリコンとの相互作用によって、十分に広い波長領域において光励起が発現すると共に、光励起により生じる電子−正孔対が両者の接触部位を介して触媒活性点に伝導されて触媒反応に寄与することとなる。従って、紫外線のような短波長の光だけでなく比較的長波長の光によっても光触媒反応を行うことができ、また、かかる反応における触媒活性を十分に高めることができる。
【0013】
また、本発明の光触媒の製造方法は、二酸化チタンおよびシリコンの少なくとも一方にショットブラスト処理により機械的エネルギーを付与して、該二酸化チタンと該シリコンとが接触した光触媒を得ることを特徴とする。これにより、アナターゼ型結晶からルチル型結晶への変質が十分に防止されるので、本発明の光触媒を容易に且つ確実に得ることができる。
【0014】
本発明の光触媒の製造方法においては、二酸化チタンとして平均粒径1〜100μmの二酸化チタン微粒子を用い、該二酸化チタン微粒子を噴射圧力0.1〜0.6MPaのショットブラストでシリコンに吹き付けることが好ましい。かかる方法によれば、アナターゼ型結晶からルチル型結晶への変質をより確実に防止することができる。また、二酸化チタンとシリコンとの間にバインダーを介在させなくとも、二酸化チタンがシリコンの表面に安定的に保持されるので、二酸化チタンとシリコンとの接触効率が増加して光触媒の触媒活性をより向上させることができる。
【0015】
【発明の実施の形態】
以下、本発明の好適な実施形態について詳細に説明する。
【0016】
本発明の光触媒に含まれる二酸化チタンにおいては、アナターゼ型結晶の割合が60重量%以上であることが好ましく、80重量%以上であることが好ましい。該二酸化チタン中のアナターゼ型結晶の割合が60%未満であると触媒活性が不十分となる傾向にある。なお、アナターゼ型結晶以外の二酸化チタンは、通常、ルチル型結晶である。
【0017】
また、本発明の光触媒は、上記の二酸化チタンに加えて、該二酸化チタンの禁制帯幅(3.2eV)よりも狭い禁制帯幅を有する第2の半導体材料を含有するものであり、二酸化チタンと第2の半導体材料とは接触した状態で保持される。これにより、十分に広い波長領域において光励起が発現すると共に、光励起により生じる電子−正孔対が両者の接触部位を介して触媒活性点に伝導されて触媒反応に寄与することとなるので、紫外線などの短波長の光だけでなく可視光などの長波長の光によっても光触媒反応を行うことができ、また、かかる反応における触媒活性を十分に高めることができる。
【0018】
第2の半導体材料としては、シリコン(Si、禁制帯幅:1.1eV)、α−シリコンカーバイド(α−SiC、禁制帯幅:3.0eV)、β−シリコンカーバイド(β−SiC、禁制帯幅:2.2eV)、酸化タングステン(WO3、禁制帯幅:2.7eV)、酸化第二鉄(Fe2O3、禁制帯幅:2.2eV)、酸化第一銅(Cu2O、禁制帯幅:2.2eV)、酸化インジウム(In2O3)、チタン酸鉄(FeTiO3、禁制帯幅:2.8eV)、一酸化鉛(PbO、禁制帯幅:2.8eV)、五酸化バナジウム(V2O5、禁制帯幅:2.8eV)、三酸化ビスマス(Bi2O3、禁制帯幅:2.8eV)、三酸化ニオブ(Nb2O3、禁制帯幅:3.0eV)、砒化ガリウム(GaAs、禁制帯幅:1.4eV)、セレン化カドミウム(CdSe、禁制帯幅:1.7eV)、リン化ガリウム(GaP、禁制帯幅:2.3eV)、硫化カドミウム(CdS、禁制帯幅:2.4eV)、リン化アルミニウム(AlP、禁制帯幅:2.5eV)、砒化アルミニウム(AlAs、禁制帯幅:2.1eV)、セレン化亜鉛(ZnSe、禁制帯幅:2.7eV)、アンチモン化アルミニウム(AlSb、禁制帯幅:1.6eV)、テルル化亜鉛(ZnTe、禁制帯幅:2.3eV)、テルル化カドミウム(CdTe、禁制帯幅:2.3eV)、アンチモン化ガリウム(GaSb、禁制帯幅:0.7eV)、硫化水銀(HgS、禁制帯幅:2.5eV)、リン化インジウム(InP、禁制帯幅:1.4eV)、砒化インジウム(InAs、禁制帯幅:0.4eV)、アンチモン化インジウム(InSb、禁制帯幅:0.2eV)、ゲルマニウム(Ge、禁制帯幅:0.7eV)、その他、Mg2Si、Ca2Siなどの金属シリサイド(禁制帯幅:0.1〜2.3eV)、CuAlS2などのカルコパイライト型化合物(禁制帯幅:0.2〜3.0eV)などが挙げられる。これらは1種を単独で用いてもよく、2種以上を組み合わせて用いてもよい。これらの半導体材料の中でも、より高い触媒活性向上効果が得られる点で、禁制帯幅が0.5〜3.0eVのものを用いることが好ましく、シリコンおよび/またはシリコンカーバイドを用いることが特に好ましい。
【0019】
二酸化チタンと第2の半導体材料との含有割合は、光触媒の触媒活性が損なわれない限り特に制限されないが、5:95〜95:5の範囲内であることが好ましく、30:70〜70:30の範囲内であることがより好ましい。当該含有割合が前記の範囲外であると、二酸化チタンと第2の半導体材料との接触効率が低下して、光励起における相乗効果、並びに電子−正孔対の触媒活性点への伝導による触媒活性向上効果が不十分となる傾向にある。
【0020】
本発明の光触媒においては、二酸化チタンと第2の半導体材料とが相互に接触している限り、アルミナ、ジルコニア、金属アルコキシド、オルガノシロキサン系化合物、ケイ酸塩系化合物などの無機バインダー、アクリル系化合物、エポキシ系化合物、フッ素系化合物などの有機バインダー、無機成分を有機バインダーに分散させたものなどを用いて両者を保持してもよい。しかしながら、二酸化チタンと第2の半導体材料との接触効率の点から、二酸化チタンまたは第2の半導体材料の一方を他方に直接担持することが好ましい。より具体的には、二酸化チタンまたは第2の半導体材料のうちの一方を所定の基板上に薄膜状に成形し、その薄膜上に他方を積層したものが好ましい。また、二酸化チタンまたは第2の半導体材料のうちの一方が微粒子である場合には、その微粒子の表面に他方を担持して微粒子状の光触媒としてもよい。これらの光触媒は、後述する本発明の光触媒の製造方法により得ることができる。
【0021】
すなわち、本発明の光触媒の製造方法は、二酸化チタンおよび該二酸化チタンの禁制帯幅よりも狭い禁制帯幅を有する第2の半導体材料の少なくとも一方に機械的エネルギーを付与して、該二酸化チタンと該第2の半導体材料とが接触した光触媒を得ることを特徴とするものである。これにより、二酸化チタンにおけるアナターゼ型結晶からルチル型結晶への変質が十分に防止されるので、十分に高濃度のアナターゼ型結晶を含有する本発明の光触媒を容易に且つ確実に得ることができる。
【0022】
本発明の製造方法における温度は、好ましくは700℃以下であり、より好ましくは500℃以下である。温度が前記上限値を超えると、アナターゼ型結晶からルチル型結晶への変質を十分に防止することができない。
【0023】
また、二酸化チタンおよび/または第2の半導体材料への機械的エネルギーの付与は、いわゆるショットブラスト処理により好適に行うことができる。ショットブラスト処理とは、一方の微粒子を所定の圧力で他方に吹き付けて両者を高速で衝突させるものであり、これによりバインダーを用いずとも二酸化チタンおよび第2の半導体材料を安定的に保持することができ、両者の接触効率を高めることができる。
【0024】
ここで、ショットブラスト処理においては、二酸化チタンまたは第2の半導体材料のうち硬い(硬度の大きい)成分を軟らかい(硬度の小さい)成分に向けて吹き付けることが好ましい。例えば第2の半導体材料がシリコンおよび/またはシリコンカーバイドである場合には、二酸化チタン微粒子をシリコンおよび/またはシリコンカーバイドに吹き付けることが好ましい。
【0025】
また、ショットブラスト処理において用いられる微粒子の平均粒径は、1〜100μmが好ましく、5〜20μmがより好ましい。微粒子の平均粒径が前記上限値を超えると、二酸化チタンと第2の半導体材料との接触効率が低下する傾向にある。他方、微粒子の平均粒径が前記下限値未満であると、製造効率が低下する傾向にある。また、微粒子の噴射圧力および投射速度は、それぞれ二酸化チタンと第2の半導体材料との組み合わせなどに応じて適宜選定されるものであるが、噴射圧力は0.1〜0.6MPaであることが好ましく、投射速度は20〜240m/秒であることが好ましい。
【0026】
また、微粒子が吹き付けられる側の成分の形状は、薄膜状であっても微粒子状であってもよいが、吹き付ける微粒子を均一に且つ確実に担持できる点で薄膜状であることが好ましい。この薄膜も、ショットブラスト処理、すなわち当該成分を所定の圧力で基板上に吹き付けることにより成形することができる。
【0027】
より具体的には、先ず、第2の半導体材料からなる微粒子を基板の一方面に吹き付けることで、当該基板上に第2の半導体材料からなる膜が形成される。かかる基板としては、アルミニウム製基板、ステンレス鋼製基板などが好ましく用いられる。次いで、二酸化チタン微粒子を第2の半導体材料からなる膜に向けて吹き付けることで、第2の半導体材料からなる膜上に二酸化チタン膜が形成されて目的の光触媒が得られる。このようにして、二酸化チタン膜/シリコン膜、二酸化チタン膜/シリコンカーバイド膜などの構成を有する光触媒の製造を有効に実施することができる。
【0028】
上記のショットブラスト処理は、例えば空気雰囲気下で行ってもよいが、アナターゼ型結晶からルチル型結晶への変質を防止する点から、窒素、アルゴンなどの不活性ガス雰囲気下で行うことが好ましい。
【0029】
上記の製造方法により得られる本発明の光触媒が薄膜状である場合、二酸化チタンおよび第2の半導体材料の各層の膜厚は、0.01〜30μmであることが好ましい。当該膜厚が前記上限値を超えると、光励起により生じる電子−正孔対の触媒活性点への伝導効率が低下する傾向にある。他方、膜厚が前記下限値未満である層を均一に形成することは必ずしも容易でなく、製造効率の点で好ましくない。
【0030】
本発明の光触媒は、上述のように優れた触媒活性を有するものであり、様々な光触媒反応に好適に適用することができる。かかる光触媒反応としては、具体的には、アンモニアの分解反応、水の分解による水素発生反応などが挙げられる。また、さび止め、汚れ成分の付着防止、空気清浄(例えばアセトアルデヒドなどの悪臭成分の除去)などの用途にも本発明の光触媒は非常に有用である。
【0031】
【実施例】
以下、実施例および比較例に基づいて本発明をさらに具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。
【0032】
[実施例1]
(光触媒の調製)
先ず、シリコン微粒子(平均粒径:50μm)をショットブラスト装置(直圧型空気圧縮方式、以下同様である)に充填し、室温下、噴射圧力0.4MPa、投射速度150m/秒でアルミニウム製基板(縦:18mm、横:20mm、厚み:4mm)の一方の面の全体に吹き付けて、膜厚0.1〜5μm、表面積3600mm2のシリコン膜を成形した。
【0033】
次に、二酸化チタン(アナターゼ型結晶:100重量%、平均粒径:10μm)をショットブラスト装置に充填し、室温下、噴射圧力0.4MPa、投射速度150m/秒で上記のシリコン膜上に吹き付けた。これにより膜厚0.1〜5μm、表面積3600mm2の二酸化チタン膜(アナターゼ型結晶の含有割合:80重量%)を成形し、目的の光触媒を得た。
【0034】
(悪臭除去性能評価試験)
得られた光触媒を反応管に入れて閉鎖系循環ラインの所定の位置に装着し、アセトアルデヒドと空気との混合ガス(アセトアルデヒドの初期濃度:20ppm、全量:10l)を4l/分で循環させながら光照射を行い、ガス検知管(光明理化学工業製)を用いてアセトアルデヒド濃度を測定した。本実施例では、光源1としてキセノンランプ(ウシオ電機製、出力:500W)、光源2として光源1の後段にシャープカットフィルタ(スルガ精機製)を配置して波長420nm以下の光を遮蔽したもの、の2種を使用した。また、装置内に光源以外の光が照射しないように遮光した状態とし、温度は室温に維持した。
【0035】
本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0036】
[実施例2]
実施例1におけるシリコン微粒子の代わりにシリコンカーバイド(平均粒径:50μm)を用いたこと以外は実施例1と同様にして、光触媒の調製を行った。二酸化チタン膜中のアナターゼ型結晶の含有率は80重量%であった。
【0037】
次に、得られた光触媒を用い、実施例1と同様にして悪臭除去性能試験を行った。本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0038】
[比較例1]
実施例1で用いたアルミニウム製基板をそのまま光触媒として用い、実施例1と同様の悪臭除去性能試験を行った。本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0039】
[比較例2]
シリコン膜の成形を行わず、アルミニウム製基板上に二酸化チタンを吹き付けて二酸化チタン膜を成形したこと以外は実施例1と同様にして光触媒を調製した。
【0040】
次に、得られた光触媒を用い、実施例1と同様にして悪臭除去性能試験を行った。本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0041】
[比較例3]
実施例1と同様にしてアルミニウム製基板上にシリコン膜を成形した後、二酸化チタン膜の成形を行わなかったものを光触媒として用い、実施例1と同様の悪臭除去性能試験を行った。本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0042】
[比較例4]
実施例2と同様にしてアルミニウム製基板上にシリコンカーバイド膜を成形した後、二酸化チタン膜の成形を行わなかったものを光触媒として用い、実施例1と同様の悪臭除去性能試験を行った。本試験における反応時間(光照射時間)とアセトアルデヒド濃度との相関について、光源1を使用した場合を図1、光源2を使用した場合を図2にそれぞれ示す。
【0043】
図1に示したように、光源1を使用した試験では、実施例1、2においてはいずれもアセトアルデヒド濃度が十分に低減されており、各光触媒が十分に高い触媒活性を有していることが確認された。また、光源2を使用した試験でも、波長420nm以下の光を遮蔽したことによる影響がほとんどなく、実施例1、2においてはいずれもアセトアルデヒド濃度が十分に低減されており、各光触媒がが十分に高い触媒活性を有していることが確認された。
【0044】
これに対して、比較例1、3、4においては、光源1、2のいずれを使用した場合にもアセトアルデヒド濃度を低減することができなかった。また、比較例2においては、光源1を使用した場合にはアセトアルデヒド濃度の低減効果は実施例1、2に劣るものであり、さらに、光源2を使用した場合にはアセトアルデヒドの低減効果が認められなかった。
【0045】
(アンモニアの分解反応)
実施例1、2および比較例1〜4の光触媒を用い、以下の手順に従ってアンモニアの分解反応を行った。
【0046】
すなわち、各光触媒を反応管に入れて閉鎖系循環ラインの所定の位置に装着し、アンモニアと空気との混合ガス(アンモニアの初期濃度:100ppm、全量:10l)を5l/分で循環させながら光照射を行い、ガス検知管(光明理化学工業製)を用いてアンモニア濃度を測定した。本実施例では、光源としてキセノンランプ(ウシオ電機製、出力:500W)を使用した。また、装置内に光源以外の光が照射しないように遮光した状態とし、温度は室温に維持した。
【0047】
本試験における反応時間(光照射時間)とアンモニア濃度との相関を図3に示す。図3に示したように、実施例1、2においてはいずれもアンモニア濃度が十分に低減されており、各光触媒が十分に高いアンモニア分解能を有していることが確認された。
【0048】
[実施例3、4、比較例5〜8]
(光触媒の調製)
実施例3、4及び比較例5〜8においては、それぞれアルミニウム製基板の代わりにステンレス鋼(SUS304)製基板を用いたこと以外は実施例1、2及び比較例1〜4と同様にして光触媒を調製した。
【0049】
(沿岸地区での大気中暴露試験)
実施例3、4及び比較例5〜8の各光触媒を用いて沿岸地区での大気中暴露試験を行った。具体的には、海岸から500m離れた建物の屋上で、各光触媒をステンレス鋼製基板上に形成されたまま大気中に放置し、1年又は2年経過時におけるステンレス鋼製基板表面の錆の有無を観察した。得られた結果を表1に示す。なお、表1中、「+」は錆が顕著に認められたもの、「±」は薄い錆が認められたもの、「−」は錆が全く認められなかったものをそれぞれ意味する。
【0050】
【表1】
【0051】
表1に示したように、実施例3、4の光触媒の場合は、暴露試験開始から2年経過しても錆の発生が認められず、触媒活性に起因する優れた防錆効果が得られることが確認された。
【0052】
【発明の効果】
以上説明した通り、本発明の光触媒によれば、紫外線のような短波長の光だけでなく比較的長波長の光によっても光触媒反応を行うことができ、また、かかる反応における触媒活性を十分に高めることができる。
【0053】
また、本発明の光触媒の製造方法によれば、二酸化チタンにおけるアナターゼ型結晶からルチル型結晶などへの変質が十分に防止されるので、本発明の光触媒を容易に且つ確実に得ることができる。
【図面の簡単な説明】
【図1】実施例1、2及び比較例1〜4の光触媒について、光源1を用いて悪臭除去性能評価試験を行ったときの反応時間とアセトアルデヒド濃度との相関を示すグラフである。
【図2】実施例1、2及び比較例1〜4の光触媒について、光源2を用いて悪臭除去性能評価試験を行ったときの反応時間とアセトアルデヒド濃度との相関を示すグラフである。
【図3】実施例1、2及び比較例1〜4の光触媒について、光源1を用いてアンモニアの分解反応を行ったときの反応時間とアンモニア濃度との相関を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst.
[0002]
[Prior art]
Various semiconductor materials are known as heterogeneous catalysts that exhibit catalytic activity by photoexcitation. For example, titanium dioxide (TiO 2 ) is known to be excited by irradiating light with a short wavelength such as ultraviolet rays and exhibit catalytic activity in a decomposition reaction of ethylene or odorous organic gas. Further, it is known that germanium (Ge) and silicon (Si) have a property of being excited by light having a longer wavelength than that of titanium dioxide. However, the catalytic activity is not always sufficient when one of these semiconductor materials is used alone.
[0003]
Therefore, a photocatalyst combining two or more kinds of semiconductor materials has been proposed in order to improve the catalytic activity of the photocatalyst. For example, a photocatalytic functional body obtained by spraying semiconductor particles such as titanium dioxide and metal particles such as silver (Ag) or silicon particles on a substrate (for example, Patent Document 1), silicon and silicon carbide (SiC), A photocatalyst (for example, Patent Document 2) that promotes photodecomposition of water or the like by combining these is known.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-334111
[Patent Document 2]
Japanese Patent Application Laid-Open No. 61-222542 [0006]
[Problems to be solved by the invention]
However, in the case of using a semiconductor material having a large band gap energy such as titanium dioxide such as the photocatalytic functional body described in Patent Document 1, it is necessary to irradiate light having a short wavelength such as ultraviolet rays in order to exhibit catalytic activity. is there. Therefore, for example, even if a photocatalytic functional body related to a photoreaction using sunlight is applied, only a part of the sunlight contributes to photoexcitation, and the reaction efficiency is extremely low.
[0007]
Moreover, the said patent document 1 can increase the ratio of the anatase type crystal | crystallization in titanium dioxide by carrying out rapid cooling after spraying titanium dioxide, and this describes that catalyst activity improves. However, such a method of melting titanium dioxide cannot sufficiently prevent the transformation from anatase type crystals to rutile type crystals, and has sufficient catalytic activity in a composite catalyst of titanium dioxide and other semiconductor materials. It is very difficult to get.
[0008]
In addition, the photocatalyst described in Patent Document 2 has an advantage of exhibiting catalytic activity by irradiation with light having a longer wavelength than when titanium dioxide is used, but the catalytic activity is not necessarily high. Furthermore, in such a photocatalyst, there are structural limitations such as the necessity of laminating a silicon layer and a silicon carbide layer to form a thin film, and further interposing a conductive layer between the two layers, resulting in an increase in cost. The handling is also inconvenient.
[0009]
The present invention has been made in view of the above-described problems of the prior art. A photocatalyst exhibiting sufficiently high photocatalytic activity for light in a wide wavelength region and useful in terms of cost and handleability and a method for producing the photocatalyst are provided. The purpose is to provide.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, an optical catalyst of the present invention, the titanium dioxide, containing silicon, characterized in that the said titanium dioxide and the silicon is in contact.
[0011]
In the photocatalyst of the present invention, photoexcitation occurs in a sufficiently wide wavelength region and is caused by photoexcitation due to the interaction between titanium dioxide and silicon having a forbidden band narrower than its forbidden band (3.2 eV). The electron-hole pair is conducted to the catalytic active point through the contact site between the two and contributes to the catalytic reaction. Therefore, the photocatalytic reaction can be performed not only with short-wavelength light such as ultraviolet rays but also with relatively long-wavelength light, and the catalytic activity in such reaction can be sufficiently enhanced.
[0013]
The method for producing a photocatalyst of the present invention is characterized in that mechanical energy is applied to at least one of titanium dioxide and silicon by shot blasting to obtain a photocatalyst in which the titanium dioxide and the silicon are in contact. As a result, the transformation from the anatase crystal to the rutile crystal is sufficiently prevented, so that the photocatalyst of the present invention can be obtained easily and reliably.
[0014]
In the method for producing a photocatalyst of the present invention, titanium dioxide fine particles having an average particle diameter of 1 to 100 μm are used as titanium dioxide, and the titanium dioxide fine particles are preferably sprayed onto silicon by shot blasting at an injection pressure of 0.1 to 0.6 MPa. . According to this method, alteration from anatase crystal to rutile crystal can be prevented more reliably. In addition, since titanium dioxide is stably held on the surface of silicon without interposing a binder between titanium dioxide and silicon, the contact efficiency between titanium dioxide and silicon is increased, and the catalytic activity of the photocatalyst is further increased. Can be improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail.
[0016]
In the titanium dioxide contained in the photocatalyst of the present invention, the proportion of anatase type crystals is preferably 60% by weight or more, and more preferably 80% by weight or more. If the proportion of anatase type crystals in the titanium dioxide is less than 60%, the catalytic activity tends to be insufficient. In addition, titanium dioxide other than the anatase type crystal is usually a rutile type crystal.
[0017]
The photocatalyst of the present invention contains a second semiconductor material having a forbidden band width narrower than the forbidden band width (3.2 eV) of the titanium dioxide in addition to the above titanium dioxide. And the second semiconductor material are held in contact with each other. As a result, photoexcitation occurs in a sufficiently wide wavelength region, and electron-hole pairs generated by photoexcitation contribute to the catalytic reaction through conduction to the catalytically active site via both contact sites. The photocatalytic reaction can be carried out not only by the short wavelength light but also by the long wavelength light such as visible light, and the catalytic activity in the reaction can be sufficiently enhanced.
[0018]
As the second semiconductor material, silicon (Si, forbidden band width: 1.1 eV), α-silicon carbide (α-SiC, forbidden band width: 3.0 eV), β-silicon carbide (β-SiC, forbidden band) Width: 2.2 eV), tungsten oxide (WO 3 , forbidden band width: 2.7 eV), ferric oxide (Fe 2 O 3 , forbidden band width: 2.2 eV), cuprous oxide (Cu 2 O, Forbidden band width: 2.2 eV), indium oxide (In 2 O 3 ), iron titanate (FeTiO 3 , forbidden band width: 2.8 eV), lead monoxide (PbO, forbidden band width: 2.8 eV), five Vanadium oxide (V 2 O 5 , forbidden band width: 2.8 eV), bismuth trioxide (Bi 2 O 3 , forbidden band width: 2.8 eV), niobium trioxide (Nb 2 O 3 , forbidden band width: 3. 0 eV), gallium arsenide (GaAs, band gap: 1.4 eV), cadmium selenide (CdSe, forbidden band width: 1.7 eV), gallium phosphide (GaP, forbidden band width: 2.3 eV), cadmium sulfide (CdS, forbidden band width: 2.4 eV), aluminum phosphide (AlP, forbidden band) Width: 2.5 eV), aluminum arsenide (AlAs, forbidden band width: 2.1 eV), zinc selenide (ZnSe, forbidden band width: 2.7 eV), aluminum antimonide (AlSb, forbidden band width: 1.6 eV) Zinc telluride (ZnTe, forbidden band width: 2.3 eV), cadmium telluride (CdTe, forbidden band width: 2.3 eV), gallium antimonide (GaSb, forbidden band width: 0.7 eV), mercury sulfide (HgS) Forbidden band width: 2.5 eV), Indium phosphide (InP, Forbidden band width: 1.4 eV), Indium arsenide (InAs, Forbidden band width: 0.4 eV), Indium antimonide (InSb, forbidden band width: 0.2 eV), germanium (Ge, forbidden band width: 0.7 eV), and other metal silicides such as Mg 2 Si and Ca 2 Si (forbidden band width: 0.1-2. 3 eV), chalcopyrite type compounds such as CuAlS 2 (forbidden band width: 0.2 to 3.0 eV), and the like. These may be used individually by 1 type and may be used in combination of 2 or more type. Among these semiconductor materials, those having a forbidden band width of 0.5 to 3.0 eV are preferably used, and silicon and / or silicon carbide is particularly preferably used in that a higher catalytic activity improvement effect can be obtained. .
[0019]
The content ratio of titanium dioxide and the second semiconductor material is not particularly limited as long as the catalytic activity of the photocatalyst is not impaired, but is preferably in the range of 5:95 to 95: 5, and 30:70 to 70: More preferably, it is within the range of 30. When the content ratio is out of the above range, the contact efficiency between titanium dioxide and the second semiconductor material decreases, and a synergistic effect in photoexcitation and catalytic activity due to conduction of electron-hole pairs to the catalytic active point. The improvement effect tends to be insufficient.
[0020]
In the photocatalyst of the present invention, as long as titanium dioxide and the second semiconductor material are in contact with each other, inorganic binders such as alumina, zirconia, metal alkoxides, organosiloxane compounds, silicate compounds, and acrylic compounds Both of them may be held using an organic binder such as an epoxy compound or a fluorine compound, or an organic binder in which an inorganic component is dispersed. However, from the viewpoint of contact efficiency between titanium dioxide and the second semiconductor material, it is preferable to directly carry one of titanium dioxide or the second semiconductor material on the other. More specifically, it is preferable to form one of titanium dioxide or the second semiconductor material in a thin film on a predetermined substrate and laminate the other on the thin film. Further, when one of titanium dioxide and the second semiconductor material is a fine particle, the other may be supported on the surface of the fine particle to form a fine particle photocatalyst. These photocatalysts can be obtained by the method for producing the photocatalyst of the present invention described later.
[0021]
That is, in the method for producing a photocatalyst of the present invention, mechanical energy is applied to at least one of titanium dioxide and a second semiconductor material having a forbidden band width narrower than the forbidden band width of the titanium dioxide, A photocatalyst in contact with the second semiconductor material is obtained. This sufficiently prevents alteration of titanium dioxide from anatase-type crystals to rutile-type crystals, so that the photocatalyst of the present invention containing a sufficiently high concentration of anatase-type crystals can be obtained easily and reliably.
[0022]
The temperature in the production method of the present invention is preferably 700 ° C. or lower, more preferably 500 ° C. or lower. If the temperature exceeds the upper limit, it is not possible to sufficiently prevent the transformation from the anatase crystal to the rutile crystal.
[0023]
Further, the application of mechanical energy to titanium dioxide and / or the second semiconductor material can be suitably performed by so-called shot blasting. Shot blasting is a process in which one fine particle is sprayed onto the other at a predetermined pressure to cause both to collide at high speed, thereby stably holding titanium dioxide and the second semiconductor material without using a binder. The contact efficiency between the two can be increased.
[0024]
Here, in the shot blasting process, it is preferable to spray a hard (high hardness) component of the titanium dioxide or the second semiconductor material toward a soft (low hardness) component. For example, when the second semiconductor material is silicon and / or silicon carbide, it is preferable to spray titanium dioxide fine particles on silicon and / or silicon carbide.
[0025]
Moreover, 1-100 micrometers is preferable and, as for the average particle diameter of the microparticles | fine-particles used in a shot blast process, 5-20 micrometers is more preferable. When the average particle diameter of the fine particles exceeds the upper limit, the contact efficiency between titanium dioxide and the second semiconductor material tends to be reduced. On the other hand, when the average particle size of the fine particles is less than the lower limit, the production efficiency tends to decrease. Further, the injection pressure and the projection speed of the fine particles are appropriately selected according to the combination of titanium dioxide and the second semiconductor material, respectively, but the injection pressure may be 0.1 to 0.6 MPa. Preferably, the projection speed is 20 to 240 m / sec.
[0026]
Moreover, the shape of the component on the side to which the fine particles are sprayed may be a thin film or a fine particle, but is preferably a thin film in that the fine particles to be sprayed can be uniformly and reliably supported. This thin film can also be formed by shot blasting, that is, by spraying the component onto the substrate at a predetermined pressure.
[0027]
More specifically, first, a film made of the second semiconductor material is formed on the substrate by spraying fine particles made of the second semiconductor material onto one surface of the substrate. As such a substrate, an aluminum substrate, a stainless steel substrate or the like is preferably used. Next, by spraying titanium dioxide fine particles toward the film made of the second semiconductor material, a titanium dioxide film is formed on the film made of the second semiconductor material, and the target photocatalyst is obtained. In this way, it is possible to effectively produce a photocatalyst having a configuration of titanium dioxide film / silicon film, titanium dioxide film / silicon carbide film, or the like.
[0028]
The shot blast treatment may be performed, for example, in an air atmosphere, but is preferably performed in an inert gas atmosphere such as nitrogen or argon from the viewpoint of preventing alteration from anatase crystal to rutile crystal.
[0029]
When the photocatalyst of the present invention obtained by the above production method is in the form of a thin film, the thickness of each layer of titanium dioxide and the second semiconductor material is preferably 0.01 to 30 μm. When the film thickness exceeds the upper limit, the conduction efficiency of the electron-hole pair generated by photoexcitation to the catalytic active point tends to be reduced. On the other hand, it is not always easy to form a layer having a film thickness less than the lower limit value, which is not preferable in terms of production efficiency.
[0030]
The photocatalyst of the present invention has excellent catalytic activity as described above, and can be suitably applied to various photocatalytic reactions. Specific examples of the photocatalytic reaction include ammonia decomposition reaction, hydrogen generation reaction by water decomposition, and the like. The photocatalyst of the present invention is also very useful for applications such as rust prevention, prevention of adhesion of dirt components, and air cleaning (for example, removal of malodorous components such as acetaldehyde).
[0031]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
[0032]
[Example 1]
(Preparation of photocatalyst)
First, silicon fine particles (average particle size: 50 μm) are filled in a shot blasting apparatus (direct pressure type air compression method, the same applies hereinafter), and an aluminum substrate (at a jetting pressure of 0.4 MPa and a projection speed of 150 m / sec at room temperature). A silicon film having a film thickness of 0.1 to 5 μm and a surface area of 3600 mm 2 was formed by spraying on the entire surface of one side (vertical: 18 mm, horizontal: 20 mm, thickness: 4 mm).
[0033]
Next, titanium dioxide (anatase type crystal: 100% by weight, average particle size: 10 μm) is filled into a shot blasting apparatus and sprayed onto the silicon film at room temperature, an injection pressure of 0.4 MPa, and a projection speed of 150 m / sec. It was. As a result, a titanium dioxide film having a film thickness of 0.1 to 5 μm and a surface area of 3600 mm 2 (anatase-type crystal content ratio: 80% by weight) was formed to obtain the target photocatalyst.
[0034]
(Odor removal performance evaluation test)
The obtained photocatalyst is put in a reaction tube and mounted at a predetermined position in a closed circulation line, and light is mixed while circulating a mixed gas of acetaldehyde and air (initial concentration of acetaldehyde: 20 ppm, total amount: 10 l) at 4 l / min. Irradiation was performed, and the concentration of acetaldehyde was measured using a gas detector tube (manufactured by Komyo Chemical Co., Ltd.). In this example, a xenon lamp (manufactured by USHIO INC., Output: 500 W) is used as the light source 1, and a sharp cut filter (manufactured by Suruga Seiki) is disposed behind the light source 1 as the light source 2 to shield light having a wavelength of 420 nm or less. Two types of were used. Further, the apparatus was shielded from light so as not to be irradiated with light other than the light source, and the temperature was maintained at room temperature.
[0035]
Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0036]
[Example 2]
A photocatalyst was prepared in the same manner as in Example 1 except that silicon carbide (average particle size: 50 μm) was used instead of the silicon fine particles in Example 1. The content of anatase type crystals in the titanium dioxide film was 80% by weight.
[0037]
Next, a malodor removal performance test was conducted in the same manner as in Example 1 using the obtained photocatalyst. Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0038]
[Comparative Example 1]
Using the aluminum substrate used in Example 1 as a photocatalyst, the same malodor removal performance test as in Example 1 was performed. Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0039]
[Comparative Example 2]
A photocatalyst was prepared in the same manner as in Example 1 except that a silicon dioxide film was formed by spraying titanium dioxide onto an aluminum substrate without forming a silicon film.
[0040]
Next, a malodor removal performance test was conducted in the same manner as in Example 1 using the obtained photocatalyst. Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0041]
[Comparative Example 3]
In the same manner as in Example 1, a silicon film was formed on an aluminum substrate, and then a titanium dioxide film that was not formed was used as a photocatalyst. Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0042]
[Comparative Example 4]
After a silicon carbide film was formed on an aluminum substrate in the same manner as in Example 2, a malodor removal performance test similar to that in Example 1 was performed using a photocatalyst that was not formed with a titanium dioxide film. Regarding the correlation between the reaction time (light irradiation time) and the acetaldehyde concentration in this test, FIG. 1 shows the case where the light source 1 is used, and FIG. 2 shows the case where the light source 2 is used.
[0043]
As shown in FIG. 1, in the test using the light source 1, in both Examples 1 and 2, the acetaldehyde concentration is sufficiently reduced, and each photocatalyst has a sufficiently high catalytic activity. confirmed. Further, even in the test using the light source 2, there was almost no influence by shielding light with a wavelength of 420 nm or less, and in both Examples 1 and 2, the acetaldehyde concentration was sufficiently reduced, and each photocatalyst was sufficiently It was confirmed to have a high catalytic activity.
[0044]
In contrast, in Comparative Examples 1, 3, and 4, the acetaldehyde concentration could not be reduced when any of the light sources 1 and 2 was used. In Comparative Example 2, when the light source 1 is used, the effect of reducing the acetaldehyde concentration is inferior to that of Examples 1 and 2, and when the light source 2 is used, the effect of reducing acetaldehyde is recognized. There wasn't.
[0045]
(Ammonia decomposition reaction)
Using the photocatalysts of Examples 1 and 2 and Comparative Examples 1 to 4, ammonia was decomposed according to the following procedure.
[0046]
That is, each photocatalyst is put in a reaction tube and attached to a predetermined position of a closed system circulation line, and light is mixed while circulating a mixed gas of ammonia and air (initial concentration of ammonia: 100 ppm, total amount: 10 l) at 5 l / min. Irradiation was performed, and the ammonia concentration was measured using a gas detector tube (manufactured by Komyo Chemical Co., Ltd.). In this example, a xenon lamp (manufactured by USHIO INC., Output: 500 W) was used as the light source. Further, the apparatus was shielded from light so as not to be irradiated with light other than the light source, and the temperature was maintained at room temperature.
[0047]
FIG. 3 shows the correlation between the reaction time (light irradiation time) and the ammonia concentration in this test. As shown in FIG. 3, in Examples 1 and 2, the ammonia concentration was sufficiently reduced, and it was confirmed that each photocatalyst has a sufficiently high ammonia resolution.
[0048]
[Examples 3 and 4, Comparative Examples 5 to 8]
(Preparation of photocatalyst)
In Examples 3 and 4 and Comparative Examples 5 to 8, a photocatalyst was obtained in the same manner as in Examples 1 and 2 and Comparative Examples 1 to 4, except that a stainless steel (SUS304) substrate was used instead of the aluminum substrate. Was prepared.
[0049]
(Air exposure test in coastal area)
Using the photocatalysts of Examples 3 and 4 and Comparative Examples 5 to 8, an atmospheric exposure test was conducted in the coastal area. Specifically, on the rooftop of a building 500 m away from the coast, each photocatalyst is left in the atmosphere as it is formed on the stainless steel substrate, and the surface of the stainless steel substrate after 1 year or 2 years has passed. The presence or absence was observed. The obtained results are shown in Table 1. In Table 1, “+” means that rust was remarkably recognized, “±” means that thin rust was recognized, and “−” means that no rust was recognized.
[0050]
[Table 1]
[0051]
As shown in Table 1, in the case of the photocatalysts of Examples 3 and 4, rust was not generated even after 2 years from the start of the exposure test, and an excellent antirust effect due to the catalytic activity was obtained. It was confirmed.
[0052]
【The invention's effect】
As described above, according to the photocatalyst of the present invention, the photocatalytic reaction can be performed not only with short-wavelength light such as ultraviolet rays but also with relatively long-wavelength light. Can be increased.
[0053]
In addition, according to the method for producing a photocatalyst of the present invention, the alteration of titanium dioxide from an anatase type crystal to a rutile type crystal is sufficiently prevented, so that the photocatalyst of the present invention can be obtained easily and reliably.
[Brief description of the drawings]
FIG. 1 is a graph showing the correlation between reaction time and acetaldehyde concentration when a malodor removal performance evaluation test is performed using a light source 1 for the photocatalysts of Examples 1 and 2 and Comparative Examples 1 to 4.
FIG. 2 is a graph showing the correlation between reaction time and acetaldehyde concentration when a malodor removal performance evaluation test is performed using the light source 2 for the photocatalysts of Examples 1 and 2 and Comparative Examples 1 to 4.
FIG. 3 is a graph showing a correlation between reaction time and ammonia concentration when ammonia decomposition reaction is performed using the light source 1 for the photocatalysts of Examples 1 and 2 and Comparative Examples 1 to 4.
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