Titanium dioxide fine particles and method for producing the same, and method for producing visible light activatable photocatalyst

• US 20040058149A1
• Filed: 09/17/2003
• Published: 03/25/2004
• Est. Priority Date: 09/18/2002
• Status: Active Grant

• Current Assignee: Covalent Materials Corporation
• Original Assignee: Toshiba Carrier Company Limited (Toshiba Corporation)
• Inventors: Ito, Yugo, Yamaguchi, Hiroshi, Kondo, Hiroyuki, Zhou, Zhonghua, Tokuoka, Fumio, Ishii, Tatsuya, Shimai, Shunzo
• Granted Patent: US 7,175,911 B2
• Time in Patent Office: Days
• US Class Current: 428/328
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 53/86 Catalytic processes
• CPC Class Codes: B01J 21/06 Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 21/063 Titanium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 27/02 Sulfur, selenium or tellurium; Compounds thereof
• CPC Class Codes: B01J 27/20 Carbon compounds
• CPC Class Codes: B01J 27/24 Nitrogen compounds
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 37/08 Heat treatment B01J37/0009, B01J37/0018 take precedence
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/047 Titanium dioxide
• CPC Class Codes: C01G 23/08 Drying; Calcining ; After treatment of titanium oxide
• CPC Class Codes: C01P 2002/70 defined by measured X-ray, neutron or electron diffraction data
• CPC Class Codes: C01P 2002/82 by IR- or Raman-data
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

The invention provides titanium dioxide fine particles, wherein nitrogen and at least one element selected from carbon, hydrogen, sulfur doped in titanium dioxide by heat-treating fine particles of a material of titanium dioxide at 500° C. or more and 600° C. or less in a reducing gas atmosphere containing nitrogen. The titanium fine particles exhibit a high photocatalytic activity than in the conventional art by irradiating a visible light such that they exhibit an isopropanol oxidation activity induced by visible light irradiation with a wavelength of 400 nm or more and 600 nm or less with excellent stability and durability of the photocatalytic activity.

Claims

1. Titanium dioxide fine particles, wherein at least two members selected from carbon, hydrogen, nitrogen and sulfur are doped in titanium dioxide.

4. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein the concentration of doped nitrogen is 700 ppm by weight or more and 10,000 ppm by weight or less.

5. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein doped nitrogen is bonded to titanium of titanium dioxide as Ti—

N—

O bonds or Ti—

N—

Ti bonds.

6. Titanium dioxide fine particles according to claim 5, wherein the Ti—

N—

Ti bonds are the majority of the nitrogen-titanium bonds.

7. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein doped nitrogen is desorbed as N₂ by heating the titanium dioxide fine particles to show an N₂ desorption peak at a temperature of 700°

C. or more.

8. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein doped hydrogen is desorbed as H₂ by heating the titanium dioxide fine particles to show an H₂ desorption peak at a temperature of 700°

C. or more.

9. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein doped carbon is desorbed as CO₂ by heating the titanium dioxide fine particles to show a CO₂ desorption peak at a temperature of 700°

C. or more.

10. Titanium dioxide fine particles according to any one of claims 1 to 3, wherein a component having a m/e ratio between the mass number (m) and ionic charge number (e) of 68 is desorbed by heating the fine particles to show a desorption peak at a temperature of the component of 700°

C. or more.

15. The titanium dioxide fine particles according to any one of claims 1 to 3, 11 and 14, wherein a particle diameter thereof is 1 μ

m or less.

16. The titanium dioxide fine particles according to any one of claims 1 to 3, 11 and 14, wherein each particle has a ellipsoidal shape with a major axis length of 10 nm or more and 60 nm or less.

18. Titanium dioxide fine particles according to any one of claims 1 to 3, 11, 14 and 17, wherein an isopropanol oxidation activity is exhibited under visible light irradiation with a wavelength of 400 nm or more and 600 nm or less.

19. Titanium dioxide fine particles according to any one of claims 1 to 3, 11, 14 and 17,

wherein an acetone gas is formed in a concentration of 500 ppm or more using the titanium dioxide fine particles by the steps comprising:

placing 0.2 g of the titanium dioxide fine particles as a sample formed into a uniform 10 cm square layer in a gas bag with a volume of 1 liter;

filling an isopropanol gas in the bag by adjusting the initial concentration to 1,500 ppm±

150 ppm; and

irradiating a light from a UV-shielded fluorescent lamp to the sample at an intensity of 0.5 W/cm² at an wavelength of 420 nm for 1 hour.

20. Titanium dioxide fine particles according to any one of claims 1 to 3, 11, 14 and 17, used as a visible light activatable photocatalyst.

2. Titanium dioxide fine particles, wherein nitrogen and at least one member selected from carbon, hydrogen and sulfur are doped in titanium dioxide.

3. Titanium dioxide fine particles, wherein carbon, hydrogen and nitrogen are doped in titanium dioxide.

11. Titanium dioxide fine particles, wherein two kinds or more of anions including at least nitrogen and carbon are doped in titanium dioxide.

12. Titanium dioxide fine particles according to claim 11, wherein the content of the titanium dioxide component in the fine particles is 80% by weight or more.

13. Titanium dioxide fine particles according to claim 11, wherein the concentration of doped nitrogen is 700 ppm by weight or more relative to titanium dioxide, and the concentration of doped carbon is 50 ppm by weight or more relative to titanium dioxide.

14. Titanium dioxide fine particles, wherein 700 ppm by weight or more and 10,000 ppm by weight or less of nitrogen anions and carbon anions in a concentration of 1/30 or more and 1/3 or less of the concentration of nitrogen are doped in titanium dioxide.

17. Titanium dioxide fine particles, wherein an IR spectrum measured by Fourier transform IR spectroscopy exhibits absorption peaks at 340±

10 cm<sup>−

1</sup> and 580±

50 cm<sup>−

1</sup>.

21. A method for producing titanium dioxide fine particles obtained by heat-treating a material of the titanium dioxide fine particles at 500°

C. or more and 620°

C. or less in a reducing gas atmosphere containing a nitrogen containing gas.

24. The method for producing titanium dioxide fine particles according to any one of claims 21 to 23, wherein the material of the titanium dioxide fine particles has an average particle diameter of 10 nm or less and a specific surface area of 300 m²/g or more.

22. A method for producing titanium dioxide fine particles obtained by heat-treating a material of the titanium dioxide fine particles at 500°

C. or more and 620°

C. or less in an atmosphere of a nitrogen, carbon and hydrogen containing gas.

23. A method for producing titanium dioxide fine particles obtained by heat-treating a material of the titanium dioxide fine particles at 500°

C. or more and 620°

C. or less in an atmosphere of an NH₃ gas and carbon containing gas.

25. A method for producing a visible light activatable photocatalyst obtained by heat-treating a molded body, a sintered body or a film of titanium dioxide at 500°

C. or more and 620°

C. or less in a reducing gas atmosphere containing nitrogen gas.

26. A method for producing a visible light activatable photocatalyst obtained by heat-treating a molded body, a sintered body or a film of titanium dioxide at 500°

C. or more and 620°

C. or less in an atmosphere of a nitrogen, carbon and hydrogen containing gas.

27. A method for producing a visible light activatable photocatalyst obtained by heat-treating a molded body, a sintered body or a film of titanium dioxide at 500°

C. or more and 620°

C. or less in an atmosphere of an NH₃ gas and carbon containing gas.