Visible radiation type photocatalyst and production method thereof

• US 6,908,881 B1
• Filed: 08/13/1999
• Issued: 06/21/2005
• Est. Priority Date: 08/21/1998
• Status: Expired due to Fees

• Current Assignee: Asukatec Co., Ltd.
• Original Assignee: Ecodevice Laboratory Co., Ltd.
• Inventors: Sugihara, Shinichi
• Primary Examiner(s): Silverman, Stanley S.
• Assistant Examiner(s): Johnson, Edward M.
• Application Number:
  US09/763,394
• Time in Patent Office: 2,139 Days
• Field of Search: 502/350, 423/239.1
• US Class Current: 502/350
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 53/8678 Removing components of undefined structure
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 37/349 making use of flames, plasmas or lasers
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/043 Titanium sub-oxides
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/86 by NMR- or ESR-data
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: H01G 9/2031 comprising titanium oxide, e.g. TiO2 H01G9/2036 takes precedence
• CPC Class Codes: Y02E 10/542 Dye sensitized solar cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

The invention is directed to a catalyst having activity under the irradiation of a visible light, the catalyst being an oxide semiconductor such as an anatase type titanium dioxide, having stable oxygen defects. A method for producing a catalyst having activity under the irradiation of a visible light which comprises treating an oxide semiconductor with hydrogen plasma or with a plasma of a rare gas element, comprising performing the treatment in a state substantially free from the intrusion of air into the treatment system is also provided. An article comprising a base material having the catalyst above provided on the surface thereof and a method for decomposing a substance, comprising bringing an object to be decomposed into contact with the catalyst above under the irradiation of a light containing at least a visible radiation are disclosed. A novel photocatalyst which enables use of a visible radiation is provided, as well as a method utilizing the photocatalyst for removing various substances containing an organic matter or bacteria by photodecomposition.

Claims

1. A catalyst having activity under an irradiation of visible light in a wavelength region from about 400 to 600 nm, comprising titanium dioxide having stable oxygen defects and exhibiting NOx oxidation activity under the irradiation of a visible light at least in the wavelength region of from about 400 to 600 nm;

and said titanium dioxide further having a peak area ratio (O1s/Ti2p) of a peak area obtained by X-ray photoelectron spectroscopy assigned to the 1s electrons of oxygen (O1s) participating in the bonds with titanium to a peak area obtained by X-ray photoelectron spectroscopy assigned to the 2p electrons of titanium (Ti2p) of 1.99 or lower.

2. The catalyst according to claim 1, wherein said titanium dioxide component comprises titanium dioxide of an anatase type or a rutile type.

3. The catalyst according to claim 1, wherein the titanium dioxide has a primary particle size of 10 nm or less in diameter.

4. The catalyst according to claim 1, comprising titanium dioxide that is characterized by an X-ray diffraction (XRD) pattern that is substantially free from patterns other than patterns assigned to anatase type titanium dioxide.

5. The catalyst according to claim 1, wherein said catalyst is in a substantially granular, thin-film, or sheet shape.

6. The catalyst of claim 1, wherein said catalyst material has been provided on the surface of a base material substrate.

7. The catalyst article according to claim 6, wherein said base material is an exterior wall of a building, an exterior plane of a roof or a ceiling, an outer plane or an inner plane of a window glass, an interior wall of a room, a floor or a ceiling, a blind, a curtain, a protective wall of highway roads, an inner wall inside a tunnel, an outer plane or a reflective plane of an illuminating light, an interior surface of a vehicle, or a plane of a mirror.

8. A catalyst having activity under an irradiation of visible light, said catalyst comprising titanium dioxide having stable oxygen defects and a peak area ratio (O1s/Ti2p) of a peak area obtained by X-ray photoelectron spectroscopy assigned to the 1Is electrons of oxygen (O1s) participating in the bonds with titanium to a peak area obtained by X-ray photoelectron spectroscopy assigned to the 2p electrons of titanium (Ti2p) of 1.99 or lower.

9. The catalyst according to claim 8, wherein said peak area ratio (O1s/Ti2p) is in a range of from 1.5 to 1.95.

10. The catalyst according to claim 8, wherein said peak area ratio (O1s/Ti2p) remains substantially constant for time durations of 1 week or longer.

11. The catalyst according to claim 8, wherein said activity under the irradiation of visible light is an oxidation activity or a reduction activity.

12. The catalyst according to claim 8, wherein said activity under the irradiation of visible light is a decomposition activity for inorganic and organic substances, or a bactericidal activity.

13. A method for producing a catalyst comprising titanium dioxide having stable oxygen defects and a ratio of a peak area obtained by X-ray photoelectron spectroscopy assigned to the Is electrons of oxygen participating in the bonds with titanium to a peak area obtained by X-ray photoelectron spectroscopy assigned to the 2p electrons of titanium (O1s/Ti2p) of 1.99 or lower and having activity under an irradiation of a visible light, said method comprising treating the titanium dioxide with hydrogen plasma, characterized by performing said treatment in a state substantially free from an intrusion of air into a treatment system.

14. The method for producing a catalyst according to claim 13, wherein said treatment is performed in a tightly sealed system and said state substantially free from the intrusion of air into the treatment system is a state in which a vacuum degree inside the tightly sealed system takes at least 10 minutes to make a change of 1 Torr.

15. The method for producing a catalyst according to claim 13, wherein said oxide semiconductor is selected from the group consisting of titanium dioxide, zirconium oxide, hafnium oxide, strontium titanate, a titanium oxide-zirconium oxide based complex oxide, and a silicon oxide-titanium oxide based complex oxide.

16. The method for producing a catalyst according to claim 13, wherein said oxide semiconductor is an anatase type titanium dioxide.

17. A catalyst produced by the method of claim 13 and having activity under the irradiation of a visible light.

18. The catalyst according to claim 17, wherein said oxide semiconductor is titanium dioxide, zirconium oxide, hafnium oxide, strontium titanate, a titanium oxide-zirconium oxide based complex oxide, or a silicon oxide-titanium oxide based complex oxide.

19. A method for producing a catalyst comprising titanium dioxide having stable oxygen defects and a ratio of a peak area obtained by X-ray photoelectron spectroscopy assigned to the 1s electrons of oxygen participating in the bonds with titanium to a peak area obtained by X-ray photoelectron spectroscopy assigned to the 2p electrons of titanium (O1s/Ti2p) of 1.99 or lower and having activity under an irradiation of a visible light, said method comprising treating the titanium dioxide with a plasma of rare gas, and performing said treatment in a state substantially free from an intrusion of air into a treatment system.

20. The method for producing a catalyst according to claim 19, wherein said state substantially free from the intrusion of air into the treatment system is a state in which a vacuum degree inside a tightly sealed system takes at least 10 minutes to make a change of 1 Torr.

21. The method for producing a catalyst according to claim 19, wherein said oxide semiconductor is selected from the group consisting of titanium dioxide, zirconium oxide, hafnium oxide, strontium titanate, a titanium oxide-zirconium oxide based complex oxide, and a silicon oxide-titanium oxide based complex oxide.

22. The method for producing a catalyst according to claim 19, wherein said oxide semiconductor is an anatase type titanium dioxide.

23. A catalyst produced by the method of claim 19 and having activity under the irradiation of a visible light.

24. The catalyst according to claim 23, wherein said oxide semiconductor is titanium dioxide, zirconium oxide, hafnium oxide, strontium titanate, a titanium oxide-zirconium oxide based complex oxide, or a silicon oxide-titanium oxide based complex oxide.

25. A method for producing a catalyst comprising titanium dioxide having stable oxygen defects and a ratio of a peak area obtained by X-ray photoelectron spectroscopy assigned to the 1s electrons of oxygen participating in the bonds with titanium to a peak area obtained by X-ray photoelectron spectroscopy assigned to the 2p electrons of titanium (O1s/Ti2p) of 1.99 or lower and having activity under an irradiation of visible light, comprising the step of introducing ions of a rare gas on at least a portion of the surface of the titanium dioxide by means of ion implantation.