Photocatalyst element, method and device for preparing the same

• US 20040248725A1
• Filed: 07/22/2004
• Published: 12/09/2004
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Shibaura Mechatronics Corporation
• Original Assignee: Shibaura Mechatronics Corporation
• Inventors: Noguchi, Daisuke, Haraga, Hisato, Hiraoka, Junji, Kawamata, Yoshio, Doke, Takahiro
• Granted Patent: US 7,799,731 B2
• Time in Patent Office: Days
• US Class Current: 502/4
• CPC Class Codes: B01J 33/00 Protection of catalysts, e.g. by coating
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 35/60 characterised by their surface properties or porosity
• CPC Class Codes: B01J 37/0215 Coating
• CPC Class Codes: B01J 37/0244 Coatings comprising several layers
• CPC Class Codes: B01J 37/347 Ionic or cathodic spraying; Electric discharge
• CPC Class Codes: C01G 23/04 Oxides; Hydroxides
• CPC Class Codes: C01G 23/047 Titanium dioxide
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/74 by peak-intensities or a ratio thereof only
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/86 Thin layer coatings, i.e. the coating thickness being less than 0.1 time the particle radius
• CPC Class Codes: C23C 14/083 of refractory metals or yttrium

Abstract

A photocatalyst according to the invention comprises a photocatalytic film of a compound of titanium and oxygen and is characterized in that the photocatalytic film is made porous and has 0.02 or higher value as a value calculated by dividing the arithmetical mean deviation of profile Ra with the film thickness. The photocatalytic film can also be specified by the intensity ratio between x-ray diffraction peaks of the anatase structure of titanium oxide. Such a porous photocatalytic material can be obtained by a reactive sputtering method in conditions of adjusting film formation parameters such as the film formation rate, the sputtering pressure, the substrate temperature, the oxygen partial pressure and the like in proper ranges, respectively, and the photocatalyst material is provided with excellent decomposition and hydrophilization capability.

Claims

1. A photocatalyst comprising a photocatalytic film of a compound of titanium and oxygen, wherein the photocatalytic film is an agglomerate of a number of grains, is formed to be porous including gaps among the number of grains at a surface of the photocatalytic film, and has 0.02 or higher value as a value calculated by dividing the arithmetical mean deviation of profile Ra with the film thickness, and the film thickness of the photocatalytic film is not thinner than 40 nm and not thicker than 100 nm.

2. The photocatalyst according to claim 1, wherein the arithmetical mean deviation of profile Ra of the photocatalytic film is 1.3 nm or more.

5. The photocatalyst according to claim 1, wherein the film thickness of the photocatalytic film is not thinner than 40 nm and not thicker than 80 nm.

6. The photocatalyst according to claim 1, further comprising a buffer layer of silicon oxide formed under the photocatalytic film.

7. The photocatalyst according to claim 1, wherein the refractive index of the photocatalytic film is 2.7 or lower.

8. The photocatalyst according to claim 1, wherein a silicon oxide film is formed on the photocatalytic film.

9. The photocatalyst according to claim 8, wherein the thickness of the silicon oxide film is not thinner than 3 nm and not thicker than 7 nm.

3. A photocatalyst comprising a photocatalytic film of a compound of titanium and oxygen, wherein the photocatalytic film is an agglomerate of a number of grains, is formed to be porous including gaps among the number of grains at a surface of the photocatalytic film, and has 5 or less value as the intensity ratio of the (101) diffraction peak of the anatase structure of titanium oxide to the (112) diffraction peak of the anatase structure of titanium oxide measured using a Kα

1 characteristic X-ray of copper.

22. The photocatalyst according to claim 3, wherein the film thickness of the photocatalytic film is not thinner than 40 nm and not thicker than 80 nm.

24. The photocatalyst according to claim 3, further comprising a buffer layer of silicon oxide formed under the photocatalytic film.

26. The photocatalyst according to claim 3, wherein the refractive index of the photocatalytic film is 2.7 or lower.

28. The photocatalyst according to claim 3, wherein a silicon oxide film is formed on the photocatalytic film.

4. A photocatalyst comprising a photocatalytic film of a compound of titanium and oxygen, wherein the photocatalytic film is an agglomerate of a number of grains, is formed to be porous including gaps among the number of grains at a surface of the photocatalytic film, and has 100 or less value as the intensity ratio of the (101) diffraction peak of the anatase structure of titanium oxide to the (215) diffraction peak of the anatase structure of titanium oxide measured using a Kα

1 characteristic X-ray of copper.

23. The photocatalyst according to claim 4, wherein the film thickness of the photocatalytic film is not thinner than 40 nm and not thicker than 80 nm.

25. The photocatalyst according to claim 4, further comprising a buffer layer of silicon oxide formed under the photocatalytic film.

27. The photocatalyst according to claim 4, wherein the refractive index of the photocatalytic film is 2.7 or lower.

29. The photocatalyst according to claim 4, wherein a silicon oxide film is formed on the photocatalytic film.

10. The method for producing a photocatalyst comprising a photocatalytic film of a compound of titanium and oxygen, wherein the method includes a step of depositing a porous photocatalytic film at a film formation rate not lower than 0.2 nm/s and not higher than 0.6 nm/s by sputtering a titanium-containing target in oxygen-containing atmosphere at not lower than 3 Pa and not higher than 5 Pa containing oxygen not less than 100 and not more than 30%,and the deposition is carried out at a temperature satisfying the following inequality:

R≦

2.36 exp(−

410(1/T)

where R denotes the deposition rate and T denotes a temperature of the surface to deposit the photocatalytic film thereon.

11. The method for producing a photocatalyst according to claim 10, wherein the sputtering is carried out by a DC sputtering.

12. The method for producing a photocatalyst according to claim 10, wherein the film thickness of the photocatalyst film is in not thinner than 40 nm and not thicker than 100 nm.

13. The method for producing a photocatalyst according to claim 10, wherein the film thickness of the photocatalyst film is not thinner than 40 nm and not thicker than 80 nm.

14. The method for producing a photocatalyst according to claim 10, wherein a buffer layer of silicon oxide is deposited prior to the deposition of the photocatalytic film.

15. The method for producing a photocatalyst according to claim 10, wherein the method further includes a step of depositing silicon oxide on the photocatalytic film.

16. An apparatus for producing a photocatalyst comprising a photocatalytic film of a compound of titanium and oxygen, the apparatus comprising:

a first film formation chamber capable of keeping atmosphere at a reduced pressure lower than the atmospheric pressure;

an electric power source for applying voltage to a target installed in the first film formation chamber;

heating means for heating a substrate;

a gas introduction mechanism for introducing a reaction gas containing oxygen into the first film formation chamber; and

a controller capable of controlling the heating means and the gas introduction mechanism,

wherein, at the time of forming the photocatalytic film of a compound of titanium and oxygen on the substrate by sputtering in the first film formation chamber, the controller controls the gas introduction mechanism so as to keep the pressure of the first film formation chamber at not lower than 3 Pa and not higher than 5 Pa and to keep the oxygen content in the first film formation chamber not less than 10% and not more than 30%, and controls the heating means so as to satisfy the following inequality;

R≦

2.36 exp(−

410(1/T);

between the film formation rate R of the photocatalytic film and the surface temperature T of the substrate at a formation rate not lower than 0.2 nm/s and not higher than 0.6 nm/s.

17. The photocatalyst production apparatus according to claim 16, wherein the electric power source is a DC power source.

18. The photocatalyst production apparatus according to claim 16, wherein the controller controls so as to make the film thickness of the photocatalyst not thinner than 40 nm and not thicker than 100 nm.

19. The photocatalyst production apparatus according to claim 16 further comprising:

a heating chamber having the heating means; and

a transporting mechanism for transporting the substrate from the heating chamber to the first film formation chamber,

wherein the substrate can be transported to the first film formation chamber by the transporting mechanism after the substrate is heated in the heating chamber to carry out the formation of the photocatalytic film by sputtering.

20. The photocatalyst production apparatus according to claim 19, further comprising a second film formation chamber capable of forming a silicon oxide film,

wherein a silicon oxide can be formed on the substrate prior to the formation of the photocatalytic film by sputtering.

21. The photocatalyst production apparatus according to claim 19, further comprising a third film formation chamber capable of forming a silicon oxide film,

wherein a silicon oxide can be formed on the photocatalytic film after the formation of the photocatalytic film by sputtering.