JP4868417B2 - Semiconductor photocatalyst - Google Patents
Semiconductor photocatalyst Download PDFInfo
- Publication number
- JP4868417B2 JP4868417B2 JP2008033160A JP2008033160A JP4868417B2 JP 4868417 B2 JP4868417 B2 JP 4868417B2 JP 2008033160 A JP2008033160 A JP 2008033160A JP 2008033160 A JP2008033160 A JP 2008033160A JP 4868417 B2 JP4868417 B2 JP 4868417B2
- Authority
- JP
- Japan
- Prior art keywords
- semiconductor
- photocatalyst
- light
- secondary structure
- semiconductor photocatalyst
- 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.)
- Active
Links
- 239000004065 semiconductor Substances 0.000 title claims description 101
- 239000011941 photocatalyst Substances 0.000 title claims description 100
- 239000000843 powder Substances 0.000 claims description 38
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 33
- 239000002243 precursor Substances 0.000 claims description 26
- 239000007787 solid Substances 0.000 claims description 19
- 150000002978 peroxides Chemical class 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 8
- 229910052721 tungsten Inorganic materials 0.000 claims description 7
- 239000010937 tungsten Substances 0.000 claims description 7
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 229910052797 bismuth Inorganic materials 0.000 claims description 4
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 230000032683 aging Effects 0.000 claims description 3
- 229910052738 indium Inorganic materials 0.000 claims description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 3
- 230000000717 retained effect Effects 0.000 claims description 3
- 239000010409 thin film Substances 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims 1
- 230000000052 comparative effect Effects 0.000 description 40
- 238000000034 method Methods 0.000 description 34
- 239000000243 solution Substances 0.000 description 29
- 230000031700 light absorption Effects 0.000 description 26
- 230000000694 effects Effects 0.000 description 17
- 239000002245 particle Substances 0.000 description 16
- 238000010521 absorption reaction Methods 0.000 description 12
- 239000010408 film Substances 0.000 description 12
- 239000007864 aqueous solution Substances 0.000 description 11
- 238000010298 pulverizing process Methods 0.000 description 11
- 239000000758 substrate Substances 0.000 description 11
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 10
- 229910010413 TiO 2 Inorganic materials 0.000 description 10
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 10
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 9
- 150000001875 compounds Chemical class 0.000 description 9
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 9
- 239000011164 primary particle Substances 0.000 description 9
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 8
- 230000008859 change Effects 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000004570 mortar (masonry) Substances 0.000 description 8
- 238000003786 synthesis reaction Methods 0.000 description 8
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 8
- 230000003197 catalytic effect Effects 0.000 description 7
- 238000000354 decomposition reaction Methods 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 230000001699 photocatalysis Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 6
- 239000010419 fine particle Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 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 5
- 229910000416 bismuth oxide Inorganic materials 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 5
- 229910003437 indium oxide Inorganic materials 0.000 description 5
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 5
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 5
- 229910000480 nickel oxide Inorganic materials 0.000 description 5
- 238000006864 oxidative decomposition reaction Methods 0.000 description 5
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 5
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 5
- 229910001935 vanadium oxide Inorganic materials 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 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 4
- 230000003287 optical effect Effects 0.000 description 4
- 230000000737 periodic effect Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 239000011163 secondary particle Substances 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 229910001930 tungsten oxide Inorganic materials 0.000 description 4
- CMPGARWFYBADJI-UHFFFAOYSA-L tungstic acid Chemical compound O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000005979 thermal decomposition reaction Methods 0.000 description 3
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 241000511976 Hoya Species 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- 229910003071 TaON Inorganic materials 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 238000000149 argon plasma sintering Methods 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000011022 opal Substances 0.000 description 2
- -1 organic acid salts Chemical class 0.000 description 2
- 238000013032 photocatalytic reaction Methods 0.000 description 2
- 239000004038 photonic crystal Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 239000012508 resin bead Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 150000003658 tungsten compounds Chemical class 0.000 description 2
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten trioxide Chemical compound O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 239000005749 Copper compound Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910021617 Indium monochloride Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910002367 SrTiO Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008033 biological extinction Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 150000001880 copper compounds Chemical class 0.000 description 1
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- LKRFCKCBYVZXTC-UHFFFAOYSA-N dinitrooxyindiganyl nitrate Chemical class [In+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O LKRFCKCBYVZXTC-UHFFFAOYSA-N 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- MMBMIVSDYYPRHH-UHFFFAOYSA-N hydrogen peroxide Chemical compound OO.OO MMBMIVSDYYPRHH-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- APHGZSBLRQFRCA-UHFFFAOYSA-M indium(1+);chloride Chemical compound [In]Cl APHGZSBLRQFRCA-UHFFFAOYSA-M 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000006303 photolysis reaction Methods 0.000 description 1
- 230000015843 photosynthesis, light reaction Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
Images
Landscapes
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Description
本発明は、入射光を無駄なく吸収し触媒活性に優れた半導体光触媒に関するものである。 The present invention relates to a semiconductor photocatalyst that absorbs incident light without waste and has excellent catalytic activity.
近年、環境汚染物質を吸着し太陽光や室内光によって分解除去する半導体光触媒が注目され、その研究が精力的に行われている。酸化チタンはその代表的なものであり強力な光触媒活性を示す。 In recent years, semiconductor photocatalysts that adsorb environmental pollutants and decompose and remove them with sunlight or room light have attracted attention, and their research has been vigorously conducted. Titanium oxide is a typical example and exhibits strong photocatalytic activity.
しかし、酸化チタンはバンドギャップが大きく、紫外光には活性を示すが太陽光の大部分を占める可視光には吸収性がなく、可視光に対する触媒活性を示さないため、太陽光を十分に利用することができず、また紫外光が極めて弱い室内では機能しないことなどの問題があった。 However, since titanium oxide has a large band gap and is active in ultraviolet light, it does not absorb visible light, which occupies most of sunlight, and does not show catalytic activity for visible light. In addition, there is a problem that it cannot function in a room where ultraviolet light is extremely weak.
このための対策として、窒素や硫黄、金属ドープなどで可視光を吸収できるようにするなどの酸化チタンの改良研究や可視光で光触媒として活性を示す化合物半導体の探索研究などが行われている。 As countermeasures for this, studies on improvement of titanium oxide such as allowing visible light to be absorbed by nitrogen, sulfur, metal dope, etc., and research on compound semiconductors that are active as a photocatalyst by visible light are being conducted.
化合物半導体としては、たとえば、酸化チタンに比較してバンドギャップが小さいために可視光を吸収することができる、酸化タングステン、酸化鉄、酸化インジウム、酸化バナジウム、酸化ビスマス、酸化モリブデン、酸化ニッケルなどの酸化物や複合酸化物、TaONやTa3N5などの非酸化物などの半導体化合物、さらには色素やバンドギャップの小さな物質をワイドバンドギャップ半導体に接合した増感型半導体も可視光活性な光触媒（可視光応答性光触媒）として期待されている。さらにこのような半導体を基板に成膜した膜状の光触媒や導電性基板に成膜した光電極への応用も期待されている。 As the compound semiconductor, for example, tungsten oxide, iron oxide, indium oxide, vanadium oxide, bismuth oxide, molybdenum oxide, nickel oxide and the like that can absorb visible light because the band gap is smaller than titanium oxide. Visible light-active photocatalysts include oxides, complex oxides, semiconductor compounds such as non-oxides such as TaON and Ta 3 N 5, and sensitized semiconductors in which dyes and small band gap materials are bonded to wide band gap semiconductors. It is expected as a (visible light responsive photocatalyst). Furthermore, application to such a film-like photocatalyst formed on a substrate and a photoelectrode formed on a conductive substrate is also expected.
しかしながら、これらの半導体化合物は、可視光触媒活性がまだ十分ではない場合があり、光触媒活性や光電変換効率の向上が課題であった。 However, the visible light catalytic activity of these semiconductor compounds may not be sufficient yet, and improvement of the photocatalytic activity and photoelectric conversion efficiency has been a problem.
光触媒の活性や光電極効率を向上させる最も単純な方法は、入射光を無駄なく吸収することである。しかし、バンドギャップの吸収端付近やドーピングによる吸収部分、増感型光触媒の吸収端付近などでは吸光係数が低く、多くの光子は反射されて反応に利用できないために、これが活性のロスの大きな原因になっていた。ドープ型の場合はドープ量を増やすと電荷再結合が促進されて活性が低下する欠点があり、大幅に吸収を増やせなかった。 The simplest method for improving the photocatalytic activity and photoelectrode efficiency is to absorb incident light without waste. However, the absorption coefficient is low near the absorption edge of the bandgap, the absorption part due to doping, and the absorption edge of the sensitized photocatalyst, and many photons are reflected and cannot be used for the reaction. It was. In the case of the doped type, there is a defect that the charge recombination is promoted and the activity is lowered when the doping amount is increased, and the absorption cannot be increased greatly.
そこで、入射光を無駄なく光学的に吸収する方法がいくつか検討されている。
例えば、ポリスチレン人工オパールを鋳型にしてTiO2膜を形成しての光閉じ込め法（非特許文献１，２）、TiO2/SiO2/Al多層膜をスパッタ法で作成して反射率を下げる方法（非特許文献３）や、シリコン基板などのエッチングにより周期構造を形成して光を閉じ込める方法（特許文献１、２）、陽極酸化した周期構造孔基板を用いた光閉じ込め法（特許文献３）などが報告されている。
Thus, several methods for optically absorbing incident light without waste have been studied.
For example, the optical confinement method by forming a TiO 2 film using polystyrene artificial opal as a mold (Non-patent Documents 1 and 2), and the method of reducing the reflectance by creating a TiO 2 / SiO 2 / Al multilayer film by sputtering (Non-patent Document 3), a method of confining light by forming a periodic structure by etching a silicon substrate or the like (Patent Documents 1 and 2), an optical confinement method using an anodized periodic structure hole substrate (Patent Document 3) Etc. have been reported.
しかし、非特許文献１や２の方法では、ポリスチレンビーズの周りの空間が狭いので半導体層が薄くさらにビーズを焼き飛ばした部分が完全な空孔になるので、構造全体の強度が極めて弱く、またその性能向上効果は充分とは言えない。また、非特許文献３の方法では、スパッタ法を用いているため、製造コストが大きく、さらに大面積の応用には不向きである。特許文献１〜３の方法では、同様に、製造コストがかかりすぎ、大面積の応用には不向きである。 However, in the methods of Non-Patent Documents 1 and 2, since the space around the polystyrene beads is narrow, the portion where the semiconductor layer is thin and the beads are burned out becomes complete vacancies, so the strength of the entire structure is extremely weak, The performance improvement effect is not sufficient. Further, since the method of Non-Patent Document 3 uses a sputtering method, the manufacturing cost is high and it is not suitable for a large area application. Similarly, the methods of Patent Documents 1 to 3 are too expensive to manufacture and are not suitable for large area applications.
本発明は、光吸収効率が著しく増大すると共にその光触媒活性が向上し、しかも簡便に大量に調製することが可能な工業的に極めて有利な半導体光触媒を提供することを目的とする。 An object of the present invention is to provide an industrially extremely advantageous semiconductor photocatalyst that can significantly prepare light absorption efficiency and improve its photocatalytic activity and can be easily prepared in large quantities.
本発明者らは、上記課題を解決するために鋭意検討した結果、たとえばＷＯ3やドープ型ＴｉＯ2などの可視光応答性光触媒の光吸収効率を向上させる方法について検討した結果、従来の物理的手法や樹脂ビーズ等を用いる二次構造の形成手法に代え、半導体光触媒の前駆体溶液の酸化的熱分解過程での発生ガスを利用すると、湿式法で自己組織化により二次構造が自発的に形成できることを発明者は見いだし、本発明を完成するに至った。
すなわち、この出願は、以下の発明を提供するものである。
〈１〉半導体光触媒前駆体溶液を過酸化物の存在下で加熱熟成し、その後乾燥させ、得られた固形物を焼成することにより光を閉じこめる二次構造を形成することを特徴とする半導体光触媒の製造方法。
〈２〉過酸化物が過酸化水素であることを特徴とする〈１〉に記載の半導体光触媒の製造方法。
〈３〉半導体光触媒がチタン、タングステン、ビスマス、モリブデン、ニッケル、バナジウム、鉄及びインジウムから選ばれた少なくとも一つの元素を含むことを特徴とする〈１〉又は〈２〉に記載の半導体光触媒の製造方法。
〈４〉〈１〉〜〈３〉のいずれかに記載された製造方法により形成された半導体光触媒であって、少なくとも光を閉じこめる二次構造を有し、その二次構造が保持されていることを特徴とする可視光応答性の半導体光触媒。
〈５〉その形状が粉末又は薄膜であることを特徴とする〈４〉に記載の半導体光触媒。
As a result of intensive studies to solve the above problems, the present inventors have studied a method for improving the light absorption efficiency of a visible light-responsive photocatalyst such as WO 3 or doped TiO 2. If the gas generated during the oxidative thermal decomposition of the precursor solution of the semiconductor photocatalyst is used instead of the secondary structure formation method using a technique or resin beads, the secondary structure is spontaneously formed by self-organization by a wet method. The inventors have found that it can be formed, and have completed the present invention.
That is, this application provides the following invention.
<1> A semiconductor photocatalyst characterized in that a semiconductor photocatalyst precursor solution is heated and aged in the presence of a peroxide, then dried, and the resulting solid is fired to form a secondary structure that traps light. Manufacturing method .
<2> The method for producing a semiconductor photocatalyst according to <1>, wherein the peroxide is hydrogen peroxide.
<3> The production of a semiconductor photocatalyst according to <1> or <2>, wherein the semiconductor photocatalyst contains at least one element selected from titanium, tungsten, bismuth, molybdenum, nickel, vanadium, iron and indium. Way .
<4> A semiconductor photocatalyst formed by the production method according to any one of <1> to <3>, having at least a secondary structure that confines light, and the secondary structure being retained. A visible light responsive semiconductor photocatalyst.
< 5 > The semiconductor photocatalyst according to <4> , wherein the shape is a powder or a thin film.
本発明の半導体光触媒は、従来のものに比べ光吸収効率が著しく向上し、その触媒活性に優れたものであり、またその調製法も極めて簡便なものである。したがって、光触媒としての活性も飛躍的に増大することから、環境汚染物質を分解・除去するための光触媒反応や水分解エネルギー変換のための触媒等として応用することができる。
また、本発明に係る半導体光触媒は主に可視光によって機能するため、太陽光を有効に利用したり、紫外光が極めて弱い室内・車内において使用したりすることが期待できる。更に本発明の半導体光触媒は半導体の光吸収を向上させるので、光触媒だけでなく、半導体光電極や色素増感太陽電池用の半導体膜電極にも応用できる。
The semiconductor photocatalyst of the present invention has a significantly improved light absorption efficiency as compared with conventional ones, has excellent catalytic activity, and its preparation method is extremely simple. Therefore, since the activity as a photocatalyst is also dramatically increased, it can be applied as a photocatalytic reaction for decomposing / removing environmental pollutants and a catalyst for water splitting energy conversion.
In addition, since the semiconductor photocatalyst according to the present invention mainly functions by visible light, it can be expected to use sunlight effectively or use it indoors or in a vehicle where ultraviolet light is extremely weak. Furthermore, since the semiconductor photocatalyst of the present invention improves the light absorption of the semiconductor, it can be applied not only to the photocatalyst but also to a semiconductor photoelectrode or a semiconductor film electrode for a dye-sensitized solar cell.
本発明の半導体光触媒は、少なくとも光を閉じこめる二次構造からなり、当該二次構造が半導体光触媒の前駆体溶液を過酸化物の存在下で加熱酸化分解することによって得られたものであることを特徴とする。
ここで、半導体光触媒とは、光照射により電子と正孔が生じ、それぞれが還元および酸化反応を引き起こす物質を意味する。また、二次構造とは一次構造（＝一次粒子）の不均一な集合構造を意味し、光閉じ込めとは、光の散乱と屈折を効果的に利用し、（光吸収経路が長くなることで、）一次構造の均一な集合構造に比べて、光吸収効率が大きく向上した状態を意味する。
The semiconductor photocatalyst of the present invention comprises at least a secondary structure that confines light, and the secondary structure is obtained by subjecting a precursor solution of a semiconductor photocatalyst to thermal oxidative decomposition in the presence of a peroxide. Features.
Here, the semiconductor photocatalyst means a substance that generates electrons and holes by light irradiation and causes reduction and oxidation reactions, respectively. The secondary structure means a non-uniform assembly structure of primary structures (= primary particles), and light confinement effectively uses light scattering and refraction (by increasing the light absorption path). )) This means a state in which the light absorption efficiency is greatly improved as compared with the uniform aggregate structure of the primary structure.
一般に、半導体光触媒の一次粒子が小さくて均一に分散していると屈折や散乱はあまり起こらないので、入射光が単純に透過または表面反射する一次構造を形成する。しかし、それらが凝集した構造部分では半導体密度や屈折率が異なるので光の屈折や散乱が大きくなる。半導体密度や屈折率が急に変わる部分がある構造部分の例としては、強く凝集した二次粒子や、部分的に結晶成長が進んだ巨大粒子、空孔構造、高多孔性構造などがある。そのような構造部分の大きさは、光の波長の半分程度の大きさで最も良く起こる。 In general, when primary particles of a semiconductor photocatalyst are small and uniformly dispersed, refraction and scattering do not occur so much, so that a primary structure in which incident light is simply transmitted or reflected on the surface is formed. However, since the density of the semiconductor and the refractive index are different in the structure portion in which they are aggregated, the refraction and scattering of light increase. Examples of the structure part where the semiconductor density and refractive index change abruptly include strongly agglomerated secondary particles, giant particles that have undergone partial crystal growth, pore structures, and highly porous structures. The size of such a structure portion most often occurs at about half the wavelength of light.
この場合、光吸収を増大させるには、光の入射方向に対して、半導体密度や屈折率が異なる構造を半導体粉末光触媒または多孔質半導体膜の内部に保有していることが重要である。このような、半導体一次粒子が異なる凝集形態を作っている構造全体が前記でいう二次構造である。 In this case, in order to increase the light absorption, it is important that the semiconductor powder photocatalyst or the porous semiconductor film has a structure having different semiconductor density and refractive index with respect to the incident direction of light. The entire structure in which the semiconductor primary particles form different aggregated forms is the secondary structure described above.
このような光を効率的に吸収する二次構造は、従来法では物理的手法や樹脂ビーズ等を使用することにより形成されていたが、本発明によれば、このような煩雑な手法や試薬を用いることなく、半導体前駆体溶液の加熱酸化分解（固体化過程またはその焼成過程）でのガス発生を利用することで、湿式法で自己組織化により自発的に形成することができる。 The secondary structure that efficiently absorbs such light has been formed by using a physical method or resin beads in the conventional method. However, according to the present invention, such a complicated method or reagent is used. By using gas generation in the thermal oxidative decomposition (solidification process or firing process thereof) of the semiconductor precursor solution without using the metal, it can be spontaneously formed by self-organization by a wet method.
すなわち、半導体前駆体溶液に過酸化物を混合しておくと、半導体前駆体溶液が加熱酸化分解する過程で気泡が半導体前駆体の固体粒子内部に残存し、その部分が低密度になり、二次構造が形成される。
ここで、半導体前駆体溶液とは、半導体を構成する金属を含む溶液であり、加熱により溶媒蒸発やガス発生が起こり、最終的に半導体触媒を形成することができる溶液を意味する。
このような半導体前駆体としては、後記する半導体光触媒の金属として、例えば、チタン、タングステン、ビスマス、モリブデン、ニッケル、バナジウム、鉄及びインジウムの硝酸塩、塩化物塩、有機酸塩などが挙げられる。特にタングステン化合物と、ドーピングしたチタン化合物が好ましい。
過酸化物としては、過酸化水素、および過酸化水素が半導体光触媒の金属と結合した化合物が用いられる。
特に過酸化水素（H2O2）の添加が非常に有効である。溶媒としては蒸発して固化する温度付近で分解してガスを発生しやすい化合物や溶媒を選択するのが望ましい。このような溶媒としては、たとえば、水やアルコール、有機酸などが挙げられるが、水が最も好ましい。また、ガスが取り込まれやすい条件としては固化する直前の溶液の粘度が高いことが望ましい。
That is, if a peroxide is mixed in the semiconductor precursor solution, bubbles remain in the solid particles of the semiconductor precursor during the process of thermal oxidative decomposition of the semiconductor precursor solution, and the portion becomes low density. The following structure is formed.
Here, the semiconductor precursor solution is a solution containing a metal constituting the semiconductor, and means a solution capable of finally forming a semiconductor catalyst by causing solvent evaporation and gas generation by heating.
Examples of such a semiconductor precursor include a metal of a semiconductor photocatalyst described later, such as titanium, tungsten, bismuth, molybdenum, nickel, vanadium, iron and indium nitrates, chloride salts, and organic acid salts. In particular, a tungsten compound and a doped titanium compound are preferable.
As the peroxide, hydrogen peroxide and a compound in which hydrogen peroxide is bonded to the metal of the semiconductor photocatalyst are used.
In particular, the addition of hydrogen peroxide (H 2 O 2 ) is very effective. As the solvent, it is desirable to select a compound or solvent that is likely to decompose and generate gas near the temperature at which it evaporates and solidifies. Examples of such a solvent include water, alcohol, organic acid and the like, and water is most preferable. Further, as a condition for easily taking in the gas, it is desirable that the viscosity of the solution immediately before solidification is high.
また、半導体前駆体溶液が蒸発する過程で、複数の種類の半導体前駆体の固体粒子が析出し、これらが二次粒子内部で混在していると、焼成時のそれぞれの半導体前駆体の分解挙動が異なるために、密度の異なる二次粒子が形成され、これらの混在によって効率的に光吸収する半導体の二次構造が形成される。半導体前駆体の固体粒子の種類によってその構造だけでなく、そこに含まれている水や塩やアニオンの種類や量が異なるため、半導体前駆体の固体粒子の分解後の密度が異なると考えられる。 In addition, when the semiconductor precursor solution evaporates, solid particles of multiple types of semiconductor precursors are precipitated, and if they are mixed inside the secondary particles, the decomposition behavior of each semiconductor precursor during firing Therefore, secondary particles having different densities are formed, and a semiconductor secondary structure that efficiently absorbs light is formed by mixing these secondary particles. Depending on the type of solid particles of the semiconductor precursor, not only its structure, but also the type and amount of water, salt, and anion contained in it, the density after decomposition of the solid particles of the semiconductor precursor is considered to be different .
再現性良く安定な二次構造を調製するには、半導体前駆体溶液を長時間熟成することが望ましい。熟成期間中に自己組織的に准安定な組成が溶液中にも形成される。熟成は数時間程度、静置または撹拌したり、溶媒の沸点以下で加熱する。 In order to prepare a stable secondary structure with good reproducibility, it is desirable to age the semiconductor precursor solution for a long time. A self-organizing metastable composition is also formed in the solution during the aging period. Aging is allowed to stand or stir for about several hours or heated below the boiling point of the solvent.
加熱および焼成温度としては、ガス分解成分がほぼ放出される温度以上であり、かつ半導体結晶が通常のX線回折（XRD）測定で観測される温度以上が必要である。例えば、チタンやタングステン化合物とH2O2の組み合わせでは常圧では300℃以上が望ましい。 The heating and calcination temperature needs to be not less than the temperature at which the gas decomposition component is almost released and not less than the temperature at which the semiconductor crystal is observed by ordinary X-ray diffraction (XRD) measurement. For example, a combination of titanium or a tungsten compound and H 2 O 2 is preferably 300 ° C. or higher at normal pressure.
半導体光触媒の調製法の代表例として、酸化タングステン（ＷＯ３）および窒素ドープ酸化チタン（Ｎ−ＴｉＯ２）の調製法を以下に具体的に説明する。 As a representative example of a method for preparing a semiconductor photocatalyst, a method for preparing tungsten oxide (WO 3 ) and nitrogen-doped titanium oxide (N—TiO 2 ) will be specifically described below.
図１に光閉じこめを効果的に行う二次構造を有するWO3半導体の調製法の例を示す。
図１に示されるように、H2WO4またはタングステンメタルをH2O2 水溶液に溶解させると無色透明溶液になる。これをホットスターラー上で熟成させると透明黄色溶液に変色する。この溶液を蒸発乾固させると濃いオレンジ色のタングステン過酸化物になる。この過酸化物を焼成すると、光閉じこめを効果的に行う二次構造を有する酸化タングステンになる。
図２に光閉じこめを効果的に行う二次構造を有するNドープTiO2半導体の調製法の例をに示す。TiCl4をHCｌ水溶液に溶解させ、次にアンモニア水とH2O2を添加すると褐色溶液になる。これをホットスターラー上で熟成させる。この溶液を蒸発乾固させると白色のチタン過酸化物になる。この過酸化物を焼成すると、光閉じこめを効果的に行う二次構造を有する酸化チタンになる。
FIG. 1 shows an example of a method for preparing a WO 3 semiconductor having a secondary structure that effectively performs light confinement.
As shown in FIG. 1, when H 2 WO 4 or tungsten metal is dissolved in an H 2 O 2 aqueous solution, a colorless transparent solution is obtained. When this is aged on a hot stirrer, it turns into a clear yellow solution. When this solution is evaporated to dryness, it becomes a dark orange tungsten peroxide. When this peroxide is baked, it becomes tungsten oxide having a secondary structure that effectively performs light confinement.
FIG. 2 shows an example of a method for preparing an N-doped TiO 2 semiconductor having a secondary structure that effectively performs optical confinement. When TiCl 4 is dissolved in HCl aqueous solution and then ammonia water and H 2 O 2 are added, a brown solution is obtained. This is aged on a hot stirrer. When this solution is evaporated to dryness, white titanium peroxide is obtained. When this peroxide is baked, it becomes titanium oxide having a secondary structure that effectively performs light confinement.
本発明に係る半導体光触媒の構造は、粒子状態でも良いし、膜状態でも良い。また、基板に対して膜状態で二次構造を形成した光触媒膜を剥離させてからごく軽く粉砕して粒子状態にしても良い。膜状にする場合の基板は平滑面でも、凸凹の大きな表面でも、多孔質でも良い。また、セラミックフィルターのような多孔性基板に対しては、該基板に前駆体溶液を染み込ませたり、スピンコートなどにより付着させ、これを焼成する方法を採ることが望ましい。
膜状態で用いるの場合、本発明の膜の上に屈折・散乱のほとんど無い透明膜を積層させることで光閉じこめ効果を増大させることもできる。
ここで、重要なことは、その二次構造が保持された状態を維持することである。あまりに強い衝撃を与えて二次構造を強く破壊すると、光吸収効果が大きく失われる。
The structure of the semiconductor photocatalyst according to the present invention may be in a particle state or a film state. Alternatively, the photocatalyst film in which the secondary structure is formed in a film state with respect to the substrate may be peeled and then pulverized very lightly to be in a particle state. The substrate in the form of a film may be a smooth surface, a rough surface, or a porous surface. For a porous substrate such as a ceramic filter, it is desirable to employ a method of impregnating the substrate with a precursor solution or attaching it to the substrate by spin coating or the like and firing it.
When used in a film state, the light confinement effect can be increased by laminating a transparent film almost free of refraction and scattering on the film of the present invention.
Here, what is important is to maintain a state in which the secondary structure is maintained. If the secondary structure is strongly destroyed by applying an excessively strong impact, the light absorption effect is greatly lost.
半導体光触媒の具体例としては、酸化チタン（TiO2）などの紫外線応答性光触媒の他、タングステン、ビスマス、モリブデン、ニッケル、バナジウム、鉄、インジウムなどの有色元素などを含有する化合物半導体、ドープ型光触媒などの多くの可視光応答性光触媒など挙げることができる。例えば、MドープTiO2（M=S,C,N,金属）やMドープSrTiO3などドープ型光触媒は、ドープ量を増やすと再結合が多くなり活性が低下するために、ドープ量を少なめにしている。そのため、ドープ準位の密度が低く、その光吸収励起効率が低いものが多い。このような光触媒に対して本発明は特に有効性を発揮する。
ドーピングは、そのドープ種前駆体を半導体前駆体に混ぜておいても良いし、光吸収効率の高い半導体構造を作ってから、後でアンモニア加熱などのドーピング処理をしても良い。また、ドープ型ではないが、通常の化合物型半導体光触媒においても、その吸収端は吸収効率が悪いので、本発明を充分に使える。例えば、酸化タングステン、酸化鉄、酸化インジウム、酸化バナジウム、酸化ビスマス、酸化モリブデン、酸化ニッケルなどを含む化合物半導体である。具体的には、WxMoyO3-z、BiVO4,TaON,Bi2WO6などがある。さらに本発明は光吸収する物質が半導体の表面に存在する色素増感型の反応でも効果的に利用することができる。
Specific examples of semiconductor photocatalysts include compound semiconductors containing colored elements such as tungsten, bismuth, molybdenum, nickel, vanadium, iron, and indium in addition to UV-responsive photocatalysts such as titanium oxide (TiO 2 ), doped photocatalysts And many visible light responsive photocatalysts. For example, doped photocatalysts such as M-doped TiO 2 (M = S, C, N, metal) and M-doped SrTiO 3 increase the amount of recombination and decrease their activity. ing. Therefore, many of the doped levels have a low density and a low light absorption excitation efficiency. The present invention is particularly effective for such a photocatalyst.
Doping may be performed by mixing the doped seed precursor with a semiconductor precursor, or after forming a semiconductor structure with high light absorption efficiency, a doping process such as heating with ammonia may be performed later. Moreover, although it is not a dope type, even in a normal compound semiconductor photocatalyst, the absorption edge has poor absorption efficiency, so that the present invention can be used sufficiently. For example, a compound semiconductor containing tungsten oxide, iron oxide, indium oxide, vanadium oxide, bismuth oxide, molybdenum oxide, nickel oxide, or the like. Specifically, W x Mo y O 3- z, BiVO 4, TaON, and the like Bi 2 WO 6. Furthermore, the present invention can be effectively used in a dye-sensitized reaction in which a light-absorbing substance is present on the surface of a semiconductor.
また、半導体光触媒は表面積が高い方が好ましいが、高すぎると結晶性が不十分で欠陥やアモルファスが多くなり、活性低下の原因となる。結晶性が高く且つ表面積が高い光触媒が望ましいが、その表面積の最適値は触媒密度や反応基質により多少異なる。有機物酸化分解では表面積は多め、酸素発生では少なめがよい。酸化タングステン（WO3）の炭化水素分解の場合、好ましくは1-50m2/g、より好ましくは2-40m2/g、更に好ましくは4-35m2/gである。XRDやTEM観察から推察される結晶性は、同じ表面積で比べれば結晶性ができるだけ高い方が望ましい。 In addition, the semiconductor photocatalyst preferably has a high surface area, but if it is too high, the crystallinity is insufficient and defects and amorphousness increase, causing a decrease in activity. A photocatalyst having a high crystallinity and a high surface area is desirable, but the optimum value of the surface area varies somewhat depending on the catalyst density and reaction substrate. For organic oxidative decomposition, a larger surface area is required, and for oxygen generation, a smaller surface area is better. In the case of hydrocarbon decomposition of tungsten oxide (WO 3 ), it is preferably 1-50 m 2 / g, more preferably 2-40 m 2 / g, and still more preferably 4-35 m 2 / g. The crystallinity inferred from XRD or TEM observation is preferably as high as possible when compared with the same surface area.
半導体光触媒を構成する半導体の一次粒子径に関しては、それ自体が可視光を含む入射光をできるだけ散乱しない大きさとすることが望ましい。光散乱は光の波長の半分程度の粒子径で最も良く起こる。可視光の波長は400〜800nmであり、その半分の粒子径は200〜400nmであるが、光散乱を全くしないこと、およびある程度の広い表面積を持つのが望ましいことを考慮すれば平均粒子径は200nm以下、好ましくは60nm以下が望ましい。そのような細かい粒子が単一分散していれば、散乱はなくほぼ透明であるので垂直入射光はほぼ直線的に透過できる。一次粒子径は、顕微鏡撮影や、XRD半値幅法、表面積からの計算法などで測定できる。一次粒子径の大きさは、調製時間や調整雰囲気で大きく異なるが、調製温度に最も影響を受けるので、上記の適切な粒子径になるように低温で調製する。 Regarding the primary particle diameter of the semiconductor constituting the semiconductor photocatalyst, it is desirable that the semiconductor itself has a size that does not scatter incident light including visible light as much as possible. Light scattering occurs most often with particle sizes about half the wavelength of light. The wavelength of visible light is 400 to 800 nm, and its half particle size is 200 to 400 nm, but considering that it does not scatter light at all and it is desirable to have a certain large surface area, the average particle size is 200 nm or less, preferably 60 nm or less is desirable. If such fine particles are monodispersed, they are almost transparent without scattering, so that normal incident light can be transmitted almost linearly. The primary particle diameter can be measured by microscopic photography, XRD half-width method, calculation method from surface area, and the like. The size of the primary particle size varies greatly depending on the preparation time and the adjustment atmosphere, but since it is most affected by the preparation temperature, it is prepared at a low temperature so as to have the above appropriate particle size.
上記のように、可視光の波長は400-800nmであり、その半分の粒子径は200-400nmであるが、二次構造の大きさはそれ以上の大きさでも十分屈折や散乱を起こすことができるし、多少小さくても屈折散乱を起こす。このような二次構造自体の大きさは実質的には150-20000nmが望ましい。 As mentioned above, the wavelength of visible light is 400-800nm, and its half particle size is 200-400nm. However, even if the secondary structure is larger than that, it can cause refraction and scattering sufficiently. Yes, even if it is a little small, it causes refraction scattering. The size of the secondary structure itself is desirably 150 to 20000 nm.
屈折や散乱反射が起こりにくい表面部分を光が通過し、光子を光触媒内部に導いた後で、その内部には屈折・散乱反射を起こしやすい二次構造が存在することが望ましい。その結果、光子は散乱で斜め方向に進行するため、屈折や散乱反射が起こらない部分の距離が短くても、光の通過距離が長くなり、吸収効率が増大できる。屈折や散乱反射が起こりにくい部分の距離は吸光係数(a)に依存するので一概に言えないが、好ましくはそこを通過した光子の10-50%が吸収される距離が良い。 It is desirable that after passing light through a surface portion where refraction and scattering reflection do not easily occur and guiding a photon into the photocatalyst, a secondary structure that easily causes refraction and scattering reflection exists inside. As a result, since the photon travels in an oblique direction due to scattering, even if the distance where the refraction or scattering reflection does not occur is short, the light passing distance becomes long and the absorption efficiency can be increased. The distance of the portion where refraction or scattering / reflection hardly occurs depends on the extinction coefficient (a) and cannot be generally stated. However, it is preferable that 10-50% of the photons passing therethrough are absorbed.
さらに、二次構造が整列して周期構造を形成していると、フォトニック結晶のような強い光閉じ込め効果が期待できる。周期的な構造を形成していると、光の干渉作用によりオパールのような虹色模様（遊色）が見られることがある。 Further, when the secondary structure is aligned to form a periodic structure, a strong light confinement effect like a photonic crystal can be expected. If a periodic structure is formed, a rainbow-colored pattern (play color) like an opal may be seen due to the interference of light.
光吸収効率の高い半導体光触媒構造が調製できたかどうかの判断は、反射・吸収スペクトルを測定して判断する。光吸収効率の高い半導体構造ができていれば、通常の半導体や市販品より反射率が小さく、光吸収が増大している。特に吸収の少ない部分でその効果が顕著に観測される。逆に、乳鉢等で物理的にすりつぶして吸収が小さくなり短波長化すれば、その構造が壊れたことになるので、その光吸収効率の高い半導体構造が存在する証明となる。 Whether or not a semiconductor photocatalyst structure with high light absorption efficiency has been prepared can be determined by measuring a reflection / absorption spectrum. If a semiconductor structure with high light absorption efficiency is made, the reflectance is smaller than that of a normal semiconductor or a commercially available product, and light absorption is increased. In particular, the effect is remarkably observed in a portion with little absorption. On the contrary, if the absorption is reduced by shortening the wavelength by physically grinding with a mortar or the like, the structure is broken, which proves that a semiconductor structure having a high light absorption efficiency exists.
半導体光触媒は通常助触媒を担持すると性能は大きくなる場合が多い。白金やパラジウム、ルテニウムなどの貴金属や銅化合物等を半導体粒子に担持しても良い。また、活性炭のような吸着特性の高い物質と共存させても良い。 The performance of semiconductor photocatalysts is usually increased when a cocatalyst is supported. You may carry | support a noble metal, copper compounds, etc., such as platinum, palladium, and ruthenium, to a semiconductor particle. Further, it may coexist with a substance having high adsorption characteristics such as activated carbon.
本発明に係る半導体光触媒を薄膜化した光触媒膜は、導電性基板上に形成すれば、半導体光電極となり、色素増感太陽電池用の電極やエネルギー変換用の光電極にも応用できる。 When the photocatalytic film obtained by thinning the semiconductor photocatalyst according to the present invention is formed on a conductive substrate, it becomes a semiconductor photoelectrode and can be applied to an electrode for a dye-sensitized solar cell and a photoelectrode for energy conversion.
以下、本発明を実施例によりさらに具体的に説明するが、本発明はこの実施例によって何ら限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
実施例１
WO3微粒子はタングステン酸(H2WO4、Ｗａｋｏ製)の過酸化物の熱分解法で調製した。タングステン酸２．５ｇを過酸化水素（H2O2,３０％水溶液）３０ｍｌにビーカー中で３００ｒｐｍ以上で２時間程度強く撹拌しながら溶解させた。得られた透明溶液を撹拌しながらゆっくりホットスターラー上で加熱しながら、水分と過酸化水素を蒸発させる。1/5程度に濃縮した溶液が透明な黄色溶液になるまで乾留熟成させる。この状態の溶液になってからこれを乾燥させると、溶液粘度が高くなりつつガス発生が観測され、最後にオレンジ色のキラキラした固体が析出する。この固体粉末はタングステンの水酸化物または過酸化物(過酸化ポリタングステン酸)と思われる。これを粉砕せずにスパチュラで取り出し、電気炉で空気中４００℃で０．５時間焼成して黄緑色のWO3微粒子を作製した。WO3微粒子の表面積は33ｍ２/ｇであった。最後に0.03〜0.3mm程度の粒子径に乳鉢で軽く粉砕する。この粉砕では、その粒子の表面は、合成過程で自然に形成された、平滑な表面でほとんどできている。この粉末光触媒を実施例１の光触媒とする。
Example 1
WO 3 fine particles were prepared by a thermal decomposition method of a peroxide of tungstic acid (H 2 WO 4 manufactured by Wako). 2.5 g of tungstic acid was dissolved in 30 ml of hydrogen peroxide (H 2 O 2, 30% aqueous solution) in a beaker with strong stirring at 300 rpm or more for about 2 hours. Moisture and hydrogen peroxide are evaporated while the resulting clear solution is slowly heated on a hot stirrer while stirring. Aged by dry distillation until the solution concentrated to about 1/5 becomes a clear yellow solution. When the solution is dried in this state, gas generation is observed while the viscosity of the solution is increased, and finally an orange glittering solid is deposited. This solid powder appears to be a hydroxide or peroxide of tungsten (polytungstic peroxide). This was taken out with a spatula without pulverization, and baked in an electric furnace at 400 ° C. in air for 0.5 hours to produce yellow-green WO 3 fine particles. The surface area of the WO 3 fine particles was 33 m 2 / g. Finally, pulverize lightly in a mortar to a particle size of about 0.03 to 0.3 mm. In this pulverization, the surface of the particles is almost made of a smooth surface that is naturally formed during the synthesis process. This powder photocatalyst is referred to as the photocatalyst of Example 1.
比較例１−１
実施例１において、過酸化水素を添加しない以外は 実施例１と同様にしてWO3粉末の作成を試みた。タングステン酸は過酸化水素を添加しない水にはほとんど溶解しないため、タングステン酸の粉末を電気炉で空気中４００℃で０．５時間焼成して黄緑色のWO3微粒子を作製した。この光触媒の表面積は22ｍ２/ｇであった。この粉末光触媒を比較例１−１の光触媒とする。
Comparative Example 1-1
In Example 1, an attempt was made to prepare WO 3 powder in the same manner as in Example 1 except that hydrogen peroxide was not added. Since tungstic acid hardly dissolves in water to which hydrogen peroxide is not added, the powder of tungstic acid was baked in an electric furnace at 400 ° C. for 0.5 hours to produce yellow-green WO 3 fine particles. The surface area of this photocatalyst was 22 m 2 / g. This powder photocatalyst is referred to as the photocatalyst of Comparative Example 1-1.
比較例１−２
実施例１において、二次構造が保持されない状態の光触媒の調製を試みた。すなわち、この実施例１の粉末を乳鉢で更に力をかけて0.01mm以下、大部分は0.003mm以下に粉砕し、二次構造を壊した粉末光触媒を比較例１−２とする。この粉砕では、その粒子の表面は、合成過程で自然に形成された表面よりも、破断した凸凹した面で大部分できている。表面積は粉砕によって変化しておらず、一次粒子自体は変化していないものと考えられる。
Comparative Example 1-2
In Example 1, an attempt was made to prepare a photocatalyst in a state where the secondary structure was not retained. That is, the powder of Example 1 was further pulverized to 0.01 mm or less, most of which was pulverized to 0.003 mm or less with a mortar, and a powder photocatalyst having a broken secondary structure was designated as Comparative Example 1-2. In this pulverization, the surface of the particle is mostly made up of a fractured uneven surface rather than the surface naturally formed during the synthesis process. It is considered that the surface area did not change by pulverization, and the primary particles themselves did not change.
実施例１と比較例１−１および比較例１−２で得た光触媒の反射スペクトルを図３に示す。図３から実施例１の触媒が比較例１−１や１−２のものより可視光領域で反射率が大幅に低下し、吸収率が増加していることがわかる。比較例１−１の粉末は比較例１−２と同様に粉砕しても、吸収スペクトルに大きな変化がなかったことから、比較例１−１の粉末では光吸収を増大させる二次構造はほとんどできていないことが分かった。
光吸収率＝１−反射率 と定義すると、図３から、450nmの光吸収率は、実施例１で７９％、比較例１−１では４５％、比較例１−２では５４％、であった。
The reflection spectrum of the photocatalyst obtained in Example 1, Comparative Example 1-1, and Comparative Example 1-2 is shown in FIG. It can be seen from FIG. 3 that the reflectance of the catalyst of Example 1 is significantly lower in the visible light region than that of Comparative Examples 1-1 and 1-2, and the absorption rate is increased. Even if the powder of Comparative Example 1-1 was pulverized in the same manner as in Comparative Example 1-2, there was no significant change in the absorption spectrum. Therefore, the powder of Comparative Example 1-1 had almost no secondary structure that increased light absorption. I knew it was n’t done.
When the light absorption rate is defined as 1−reflectance, the light absorption rate at 450 nm is 79% in Example 1, 45% in Comparative Example 1-1, and 54% in Comparative Example 1-2. It was.
＜ヘキサン分解反応法＞
これらの光触媒をそれぞれ4.4mlのバイアルびんにおよそ１５０mg入れ、これにヘキサンの液体を２μlを加えて、300WのＸｅランプで光照射し（波長>300nm）、ガスクロマトグラフィーにより光分解で生じる二酸化炭素の量の時間変化をモニターした。
図４にその反応結果を示す。実施例１では１２０分で53000ppmのCO2が発生したが、比較例１−１や１−２では、21000ppmと33000ppm程度しか発生しなかった。このことから、実施例１の光触媒活性は比較例１のものより高いことが分かる。
また、紫外線だけ照射した場合は、実施例１と比較例１−２ではあまり活性に変化はなかった。これは紫外線領域では両者の触媒とも十分光を吸収しているので、本質的には両者とも活性が等しく、単なる乳鉢粉砕では一次粒子としての活性は変化していないことを示している。
一方、Y-44フィルター（HOYA製、440nm以下の光をカット）で440nm以上光のみを照射した場合には、その触媒活性は実施例１が比較例１−２より１．８倍程度高かった。Y-48フィルター（HOYA製、480nm以下の光をカット）で480nm以上光のみを照射した場合には、その触媒活性は実施例１が比較例１−２より４倍程度高かった。これは、実施例１に係る光触媒は二次構造（多孔質）を有するために可視光応答性光触媒機能が大幅に向上することに起因するものと結論できる。
<Hexane decomposition reaction method>
Approximately 150 mg of each of these photocatalysts is placed in a 4.4 ml vial, to which 2 μl of hexane liquid is added, irradiated with a 300 W Xe lamp (wavelength> 300 nm), and carbon dioxide generated by photolysis by gas chromatography The amount of time was monitored over time.
FIG. 4 shows the reaction result. In Example 1, 53000 ppm of CO 2 was generated in 120 minutes, but in Comparative Examples 1-1 and 1-2, only about 21000 ppm and 33000 ppm were generated. From this, it can be seen that the photocatalytic activity of Example 1 is higher than that of Comparative Example 1.
In addition, when only ultraviolet rays were irradiated, there was not much change in activity in Example 1 and Comparative Example 1-2. This indicates that both catalysts absorb light sufficiently in the ultraviolet region, so that both have essentially the same activity, and mere mortar grinding does not change the activity as primary particles.
On the other hand, when only light of 440 nm or more was irradiated with a Y-44 filter (made by HOYA, cut light of 440 nm or less), the catalytic activity of Example 1 was about 1.8 times higher than that of Comparative Example 1-2. . When only light of 480 nm or more was irradiated with a Y-48 filter (made by HOYA, cut light of 480 nm or less), the catalytic activity of Example 1 was about 4 times higher than that of Comparative Example 1-2. It can be concluded that this is because the photocatalyst according to Example 1 has a secondary structure (porous) and thus the visible light-responsive photocatalytic function is greatly improved.
実施例２
NドープTiO2微粒子は四塩化チタン溶液(Ｗａｋｏ製、16%水溶液)と過酸化水素およびアンモニアの混合溶液の熱分解法で調製した。水３０ｍｌに塩酸３ｍｌを希釈し、撹拌しながらアンモニア水を１ｍｌゆっくり滴下する。これに過酸化水素過酸化水素（３０％水溶液）を３ｍｌゆっくり滴下すると溶液は濃いオレンジ色になる。この溶液をホットスターラー上でゆっくりと３時間加熱しながら、水分と過酸化水素、アンモニアを蒸発させる。最終的には白色固体が析出する。これをフタ付き蒸発皿で４００℃で２０分間焼成してNドープTiO2を合成した。この粉末光触媒を実施例２の光触媒とする。
Example 2
N-doped TiO 2 fine particles were prepared by a thermal decomposition method of a mixed solution of titanium tetrachloride solution (manufactured by Wako, 16% aqueous solution), hydrogen peroxide and ammonia. Dilute 3 ml of hydrochloric acid in 30 ml of water, and slowly drop 1 ml of aqueous ammonia with stirring. When 3 ml of hydrogen peroxide hydrogen peroxide (30% aqueous solution) is slowly added dropwise thereto, the solution becomes dark orange. While slowly heating this solution on a hot stirrer for 3 hours, water, hydrogen peroxide and ammonia are evaporated. Eventually a white solid precipitates. This was baked in an evaporating dish with a lid at 400 ° C. for 20 minutes to synthesize N-doped TiO 2 . This powder photocatalyst is referred to as the photocatalyst of Example 2.
比較例２
実施例２の粉末を乳鉢で更に力をかけて、二次構造を壊した粉末光触媒を比較例２の光触媒とする。図５に反射スペクトルを示す。実施例２の方が比較例２より可視光領域で反射率が低下していることがわかる。この図５から、４２０nmの光吸収率は、実施例２で２３％、比較例２で１６％、であるが、ベースラインを考慮すると両者の吸収の差はこの数字以上に大きいものと推定される。
つまり実施例２の光触媒の方が比較例２より可視光領域で光吸収の効率が高いことが分かる。比較例２の光触媒の光吸収率の低下の原因は、現時点では定かではないが、TiO2の一次粒子の物性がこのような単なる乳鉢の粉砕で変化するとはいないので、該光触媒の二次構造の崩壊が主たる原因と考えている。
Comparative Example 2
A powder photocatalyst having a secondary structure broken by applying further force to the powder of Example 2 in a mortar is used as the photocatalyst of Comparative Example 2. FIG. 5 shows the reflection spectrum. It can be seen that the reflectance of Example 2 is lower than that of Comparative Example 2 in the visible light region. From FIG. 5, the optical absorptance at 420 nm is 23% in Example 2 and 16% in Comparative Example 2. However, considering the baseline, the difference in absorption between the two is estimated to be larger than this figure. The
That is, it can be seen that the photocatalyst of Example 2 has higher light absorption efficiency in the visible light region than Comparative Example 2. The cause of the decrease in the light absorption rate of the photocatalyst of Comparative Example 2 is not clear at the present time, but since the physical properties of the primary particles of TiO 2 are not changed by such simple mortar grinding, the secondary structure of the photocatalyst The main reason is the collapse of.
＜アセトアルデヒド分解反応法＞
これらの光触媒を4.4mlのバイアルびんにおよそ１５mg入れ、これにアセトアルデヒド9000ppmを加えて、紫外線カットフィルター（HOYA、L-42）をつけた300WのＸｅランプで光照射し、ガスクロマトグラフィーにより光分解で生じる二酸化炭素の量の時間変化をモニターした。図６に反応結果を示す。実施例２では１２０分で1600ppmのCO2が発生したが、乳鉢で粉砕した比較例２では400ppm程度しか発生しなかった。実施例２の方が活性は非常に高いことが分かる。以上の結果から、比較例２のものと異なり実施例２の光触媒は光を効率的に吸収できる二次構造が存在するために活性が高かったものと結論できる。
また、実施例２においてH2O2を添加せずに合成したN-ドープTiO2では、１２０分で300ppm程度のCO2しか発生せず、しかも粉砕後の活性は１２０分で250ppmであり、粉砕による活性低下はH2O2添加無しのものと比べると極めて小さかったことから、H2O2添加の光閉じこめ効果の有効性がわかる。
<Acetaldehyde decomposition reaction method>
About 15 mg of these photocatalysts are put in a 4.4 ml vial, and 9000 ppm of acetaldehyde is added to the bottle. The amount of carbon dioxide produced over time was monitored over time. FIG. 6 shows the reaction results. In Example 2, 1600 ppm of CO 2 was generated in 120 minutes, but in Comparative Example 2 pulverized with a mortar, only about 400 ppm was generated. It can be seen that the activity of Example 2 is much higher. From the above results, it can be concluded that, unlike Comparative Example 2, the photocatalyst of Example 2 was highly active due to the presence of a secondary structure capable of efficiently absorbing light.
Also, the H 2 O 2 synthesized N- doped TiO 2 without adding in Example 2, only 300ppm of about CO 2 does not occur at 120 minutes, yet active after grinding is 250ppm at 120 minutes, The decrease in activity due to pulverization was extremely small compared to that without H 2 O 2 addition, indicating the effectiveness of the light confinement effect of H 2 O 2 addition.
実施例３
実施例１のWO3にCuOを0.1wt%担持した。担持方法は蒸発皿上で硝酸銅水溶液をWO3粉末に含浸法で担持し、３００度で３０分空気焼成した。この粉末の450nmの光吸収率は、７５％であった。この粉末を用いて、実施例２と同様にアセトアルデヒド分解を行った。１２０分で5700ppmのCO2発生が観測された。
Example 3
In WO 3 of Example 1, 0.1 wt% of CuO was supported. As a supporting method, a copper nitrate aqueous solution was supported on WO 3 powder by an impregnation method on an evaporating dish, and air-baked at 300 ° C. for 30 minutes. The light absorption rate at 450 nm of this powder was 75%. Using this powder, acetaldehyde decomposition was carried out in the same manner as in Example 2. CO 2 generation of 5700ppm was observed at 120 minutes.
比較例３
実施例３の粉末を乳鉢で更に力をかけて、二次構造を壊した粉末光触媒を比較例３の光触媒とする。450nmの光吸収率は５７％であり、実施例３と比較して小さくなった。１２０分で3000ppmのCO2発生が観測され、実施例３と比較して小さくなった。この比較結果も、光閉じこめできる二次構造が存在する状態では光吸収が増大し、活性が向上できることを示している。
Comparative Example 3
The powder photocatalyst having a secondary structure broken by applying further force to the powder of Example 3 in a mortar is used as the photocatalyst of Comparative Example 3. The light absorption rate at 450 nm was 57%, which was smaller than that in Example 3. 3000 ppm CO 2 generation was observed in 120 minutes, which was smaller than that in Example 3. This comparison result also indicates that light absorption increases and activity can be improved in the presence of a secondary structure capable of confining light.
実施例４−９、比較例４−９
多くの各種酸化物半導体について、半導体調製時に過酸化物を添加することで光吸収効率増大効果が発現するかどうか検討を行った。
実施例４のモリブデン酸化物の合成では、前駆体のH2MoO4をアンモニアとH2O2の混合水溶液に溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、薄黄色の固形物を得、この固形物を５００℃で１時間焼成し、モリブデン酸化物半導体粉末を得た。粉砕前の二次構造が保持された粉末を実施例４の光触媒とした。実施例４において過酸化水素を用いない以外は実施例４と同様にして合成したものを比較例４の光触媒とした。
実施例５のビスマス酸化物の合成では、前駆体のBiCl3をH2O2の水溶液に懸濁・溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、白色の固形物を得、この固形物を５００℃で１時間焼成し、ビスマス酸化物半導体粉末を得た。粉砕前の二次構造が保持された粉末を実施例５の光触媒とした。実施例５において過酸化水素を用いない以外は実施例５と同様にして合成したものを比較例５の光触媒とした。
実施例６のニッケル酸化物の合成では、前駆体のNiCl2をH2O2の水溶液に溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、黄色の固形物を得、この固形物を５００℃で１時間焼成し、ニッケル酸化物半導体粉末を合成した。粉砕前の二次構造が保持された粉末を実施例６の光触媒とした。実施例６において過酸化水素を用いない以外は実施例６と同様にして合成したものを比較例６の光触媒とした。
実施例７のバナジウム酸化物の合成では、前駆体のVOCl2をH2O2とHClの混合水溶液に溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、深緑色の固形物を得、この固形物を５００℃で１時間焼成し、バナジウム酸化物半導体粉末を得た。粉砕前の二次構造が保持された粉末を実施例７の光触媒とした。実施例７において過酸化水素を用いない以外は実施例７と同様にして合成したものを比較例７の光触媒とした。
実施例８の鉄酸化物の合成では、前駆体のFeCl3をH2O2水溶液に溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、褐色の固形物を得、この固形物を６００℃で１時間焼成し、鉄酸化物半導体粉末を得た。粉砕前の二次構造が保持された粉末を実施例８の光触媒とした。実施例８において過酸化水素を用いない以外は実施例８と同様にして合成したものを比較例８の光触媒とした。
実施例９のインジウム酸化物合成では、前駆体のInCl3をH2O2水溶液に溶解後、ホットスターラー上で５０℃で３時間熟成し、その後乾燥させ、白色の固形物を得、この固形物を６００℃で１時間焼成し、インジウム酸化物半導体粉末を得た。粉砕前の二次構造が保持された粉末を実施例９の光触媒とした。実施例９において過酸化水素を用いない以外は実施例９と同様にして合成したものを比較例９の光触媒とした。
Example 4-9, Comparative Example 4-9
With respect to many types of oxide semiconductors, it was examined whether or not the effect of increasing the light absorption efficiency was exhibited by adding peroxide during semiconductor preparation.
In the synthesis of the molybdenum oxide of Example 4, the precursor H 2 MoO 4 was dissolved in a mixed aqueous solution of ammonia and H 2 O 2 , then aged at 50 ° C. for 3 hours on a hot stirrer, then dried, and light yellow The solid was fired at 500 ° C. for 1 hour to obtain molybdenum oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 4. A photocatalyst of Comparative Example 4 was synthesized in the same manner as in Example 4 except that hydrogen peroxide was not used in Example 4.
In the synthesis of the bismuth oxide of Example 5, the precursor BiCl 3 was suspended and dissolved in an aqueous solution of H 2 O 2 and then aged at 50 ° C. for 3 hours on a hot stirrer and then dried to obtain a white solid. The solid was fired at 500 ° C. for 1 hour to obtain a bismuth oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 5. A photocatalyst of Comparative Example 5 was synthesized in the same manner as in Example 5 except that hydrogen peroxide was not used in Example 5.
In the synthesis of the nickel oxide of Example 6, the precursor NiCl 2 was dissolved in an aqueous solution of H 2 O 2 and then aged at 50 ° C. for 3 hours on a hot stirrer and then dried to obtain a yellow solid. This solid was fired at 500 ° C. for 1 hour to synthesize a nickel oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 6. A photocatalyst of Comparative Example 6 was synthesized in the same manner as in Example 6 except that hydrogen peroxide was not used in Example 6.
In the synthesis of the vanadium oxide of Example 7, the precursor VOCl 2 was dissolved in a mixed aqueous solution of H 2 O 2 and HCl, then aged for 3 hours at 50 ° C. on a hot stirrer, and then dried to obtain a dark green solid The solid was fired at 500 ° C. for 1 hour to obtain a vanadium oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 7. A photocatalyst of Comparative Example 7 was synthesized in the same manner as in Example 7 except that hydrogen peroxide was not used in Example 7.
In the synthesis of the iron oxide of Example 8, the precursor FeCl 3 was dissolved in an H 2 O 2 aqueous solution, then aged for 3 hours at 50 ° C. on a hot stirrer, and then dried to obtain a brown solid. The solid was fired at 600 ° C. for 1 hour to obtain an iron oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 8. A photocatalyst of Comparative Example 8 was synthesized in the same manner as in Example 8 except that hydrogen peroxide was not used in Example 8.
In the indium oxide synthesis of Example 9, the precursor InCl 3 was dissolved in an aqueous H 2 O 2 solution, then aged at 50 ° C. for 3 hours on a hot stirrer, and then dried to obtain a white solid. The product was fired at 600 ° C. for 1 hour to obtain an indium oxide semiconductor powder. The powder retaining the secondary structure before pulverization was used as the photocatalyst of Example 9. A photocatalyst of Comparative Example 9 was synthesized in the same manner as in Example 9 except that hydrogen peroxide was not used in Example 9.
上記各光触媒粉末の600nmにおける反射率を測定し、光吸収率を計算した結果を表１に示す。いずれの場合も、実施例の粉末の方が比較例より可視光領域で光吸収の効率が高いことが分かる。 Table 1 shows the results of measuring the reflectance at 600 nm of each photocatalyst powder and calculating the light absorption rate. In any case, it can be seen that the powder of the example has higher light absorption efficiency in the visible light region than the comparative example.
このように、対応する前駆体溶液の過酸化物の存在下での加熱酸化分解により二次構造が形成された、モリブデン酸化物、ビスマス酸化物、ニッケル酸化物、バナジウム酸化物、鉄酸化物、インジウム酸化物などが、従来の相応する酸化物に比べ可視光吸収が高くなり、半導体光触媒の触媒特性の効率が向上することが明らかとなったことから、これら以外の他の半導体光触媒も上記のような二次構造の改質手法によりその半導体光触媒の特性が向上することは極く自然に理解できることである。 Thus, molybdenum oxide, bismuth oxide, nickel oxide, vanadium oxide, iron oxide, whose secondary structure was formed by thermal oxidative decomposition in the presence of peroxide of the corresponding precursor solution, It has become clear that indium oxide and the like have higher visible light absorption than conventional corresponding oxides, and the efficiency of the catalytic properties of the semiconductor photocatalyst is improved. It can be understood very naturally that the characteristics of the semiconductor photocatalyst are improved by such a secondary structure modification technique.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2008033160A JP4868417B2 (en) | 2008-02-14 | 2008-02-14 | Semiconductor photocatalyst |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2008033160A JP4868417B2 (en) | 2008-02-14 | 2008-02-14 | Semiconductor photocatalyst |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2009189952A JP2009189952A (en) | 2009-08-27 |
| JP4868417B2 true JP4868417B2 (en) | 2012-02-01 |
Family
ID=41072468
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2008033160A Active JP4868417B2 (en) | 2008-02-14 | 2008-02-14 | Semiconductor photocatalyst |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4868417B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103007950A (en) * | 2012-12-31 | 2013-04-03 | 南京大学 | Nickel ion-doped tungsten trioxide catalyst, and preparation method and application thereof |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5775248B2 (en) * | 2008-03-21 | 2015-09-09 | 国立大学法人 東京大学 | Photocatalyst material, organic matter decomposition method, interior member, air cleaning device, oxidizer manufacturing device |
| JP5537356B2 (en) * | 2009-10-14 | 2014-07-02 | 積水樹脂株式会社 | Photocatalyst, coating agent, interior material, and method for producing photocatalyst |
| US9061272B2 (en) | 2010-02-16 | 2015-06-23 | Showa Denko K.K. | Tungsten oxide photocatalyst modified with copper ion, and process for production thereof |
| US9533284B2 (en) | 2011-02-16 | 2017-01-03 | National Institute Of Advanced Industrial Science And Technology | Visible-light-responsive photocatalyst with environmental resistance |
| JP2018167151A (en) * | 2017-03-29 | 2018-11-01 | 日東電工株式会社 | Porous filter, gas purifying device and gas purifying method |
| CN115254187B (en) * | 2022-08-03 | 2023-06-30 | 江苏理工学院 | Preparation method and application of mesoporous amorphous bismuth tungstate photocatalytic material |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3137623B1 (en) * | 1999-12-14 | 2001-02-26 | エフエム技研株式会社 | Dispersed gel and solution of titanium oxide fine particles and methods for producing them |
| JP2002177775A (en) * | 2000-12-14 | 2002-06-25 | Himeka Engineering Kk | Visible ray reaction type photocatalyst and manufacturing method thereof |
| JP2006000781A (en) * | 2004-06-18 | 2006-01-05 | National Institute Of Advanced Industrial & Technology | Photocatalyst for efficient purification of environment |
-
2008
- 2008-02-14 JP JP2008033160A patent/JP4868417B2/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103007950A (en) * | 2012-12-31 | 2013-04-03 | 南京大学 | Nickel ion-doped tungsten trioxide catalyst, and preparation method and application thereof |
| CN103007950B (en) * | 2012-12-31 | 2015-04-08 | 南京大学 | Nickel ion-doped tungsten trioxide catalyst, and preparation method and application thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2009189952A (en) | 2009-08-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Pany et al. | Plasmon induced nano Au particle decorated over S, N-modified TiO2 for exceptional photocatalytic hydrogen evolution under visible light | |
| Mudhoo et al. | Fabrication, functionalization and performance of doped photocatalysts for dye degradation and mineralization: a review | |
| JP4868417B2 (en) | Semiconductor photocatalyst | |
| Choi et al. | Effects of single metal-ion doping on the visible-light photoreactivity of TiO2 | |
| Sayed et al. | Photochemical hydrogen generation using nitrogen-doped TiO2–Pd nanoparticles: facile synthesis and effect of Ti3+ incorporation | |
| Zang et al. | Amorphous microporous titania modified with platinum (IV) chloride a new type of hybrid photocatalyst for visible light detoxification | |
| Fu et al. | Photocatalytic degradation of RhB by fluorinated Bi2WO6 and distributions of the intermediate products | |
| Wang et al. | Improved hydrogen production from glycerol photoreforming over sol-gel derived TiO2 coupled with metal oxides | |
| Ganesh et al. | Preparation and Characterization of Ni‐Doped TiO2 Materials for Photocurrent and Photocatalytic Applications | |
| Chi et al. | One-step template-free route for synthesis of mesoporous N-doped titania spheres | |
| Zhang et al. | Ta3N5 nanoparticles with enhanced photocatalytic efficiency under visible light irradiation | |
| KR100945035B1 (en) | Tungstates based visible-light induced oxides photocatalysts and synthesis methods thereof | |
| Di Paola et al. | Coupled semiconductor systems for photocatalysis. Preparation and characterization of polycrystalline mixed WO3/WS2 powders | |
| Parida et al. | Green synthesis of fibrous hierarchical meso-macroporous N doped TiO2 nanophotocatalyst with enhanced photocatalytic H2 production | |
| WO2015146830A1 (en) | Photocatalyst and method for producing same | |
| US20060283701A1 (en) | Photocatalyst and use thereof | |
| Khatamian et al. | Visible‐light response photocatalytic water splitting over CdS/TiO2 and CdS–TiO2/metalosilicate composites | |
| US20170072391A1 (en) | Photocatalytic hydrogen production from water over mixed phase titanium dioxide nanoparticles | |
| JP2015199065A (en) | Photocatalyst and production method therefor | |
| Huang et al. | Facile in situ synthesis of Ag and Bi co-decorated BiOCl heterojunction with high photocatalytic performance over the full solar spectrum | |
| Mokhtarifar et al. | Fabrication of dual-phase TiO 2/WO 3 with post-illumination photocatalytic memory | |
| Devi et al. | Effective band gap engineering by the incorporation of Ce, N and S dopant ions into the SrTiO 3 lattice: Exploration of photocatalytic activity under UV/solar light | |
| May Ix et al. | Effective electron–hole separation over N‐doped TiO2 materials for improved photocatalytic reduction of 4‐nitrophenol using visible light | |
| Ribeiro et al. | Enhanced photocatalytic activity of Bi2WO6 with PVP addition for CO2 reduction into ethanol under visible light | |
| Štengl et al. | TiO 2/ZnS/CdS nanocomposite for hydrogen evolution and orange II dye degradation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20100210 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20110622 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20110705 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20110902 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20111108 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20111109 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 4868417 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20141125 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20141125 Year of fee payment: 3 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |