Photocatalyst materials having semiconductor characteristics and methods for manufacturing and using the same

• US 20070193875A1
• Filed: 02/16/2007
• Published: 08/23/2007
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Kwang Min, Ham, Dong Seok, Ihm, Son Ki, Jeong, Kwang Eun, Park, Joo Il
• Granted Patent: US 7,846,864 B2
• Time in Patent Office: Days
• US Class Current: 204/157.15
• CPC Class Codes: B01D 2255/20707 Titanium
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 2257/708 Volatile organic compounds V.O.C.'s
• CPC Class Codes: B01D 53/8687 Organic components
• 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 23/22 Vanadium
• CPC Class Codes: B01J 23/30 Tungsten
• CPC Class Codes: B01J 23/34 Manganese
• CPC Class Codes: B01J 23/745 Iron
• CPC Class Codes: B01J 23/80 with zinc, cadmium or mercury
• CPC Class Codes: B01J 23/835 with germanium, tin or lead
• CPC Class Codes: B01J 35/23 in a colloidal state
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 37/30 Ion-exchange
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

New types of photocatalyst materials are disclosed together with methods for preparing and using these materials, as well as air treatment systems incorporating such materials. The photocatalyst materials of this invention consist essentially of very small particles of a first-metal oxide, the first-metal being a metal that exhibits photo-induced semiconductor properties, having ions of a second-metal dispersed throughout its lattice structure, the second-metal being selected from the group of dopant metals. Such photocatalyst materials are prepared by the steps of mixing first-metal and second-metal precursors, removing nonessential ions from the mixture, drying the resulting product, and calcinating the dried product to produce the completed photocatalyst material.

Claims

1. A method for preparing a photocatalyst material comprising the sequential steps of:

(a) forming a mixture of a first-metal precursor and a second-metal precursor in a predetermined molar ratio of said second-metal relative to said first-metal, wherein said first-metal is a metal that exhibits photo-induced semiconductor properties and said second-metal is a dopant;

(b) treating the mixture of first-metal precursor and second-metal precursor to remove nonessential ion(s) from the mixture thereby to form a preliminary product comprising an oxide of the first-metal having ions of the second-metal dispersed therethrough;

(c) drying the preliminary product to form a dried first-metal oxide product doped with ions of said second-metal, said dried product comprising very small particles; and

,

(d) calcinating the dried first-metal oxide product by applying heat to form the photocatalyst material.

2. A method according to claim 1 wherein the photocatalyst material is formed of very small particles having a mean particle diameter of about 10 nm or less.

3. A method according to claim 1 wherein:

(a) said first-metal precursor has the general chemical formula M¹_xCl_y, where M¹ is a metal that exhibits photo-induced semiconductor properties, Cl is chloride ion, and x and y are positive integers; and

also (b) said second-metal precursor has the general chemical formula M²_xCl_y, where M² is a dopant, Cl is chloride ion, and x and y are positive integers.

4. A method according to claim 3 wherein M¹ is selected from the group consisting of titanium (Ti), zirconium (Zr), tin (Sn), zinc (Zn), and alloys and combinations thereof.

5. A method according to claim 3 wherein M² is selected from the group consisting of iron (Fe), tungsten (W), manganese (Mn), vanadium (V), and alloys and combinations thereof.

6. A method according to claim 1 wherein said first-metal precursor is selected from the group consisting of TiCl₄, ZrCl₂, SnCl₄, ZnCl₂ and mixtures thereof, and also said second-metal precursor is selected from the group consisting of Fe_xCl_y, W_xCl_y, Mn_xCl_y, V_xCl_y and mixtures thereof, where x and y are positive integers.

7. A method according to claim 1 wherein step (a) comprises the substeps of:

forming a solution of said second-metal precursor in a suitable solvent;

adding the first-metal precursor to the solution of second-metal precursor; and

, mixing the solution to form a substantially homogeneous mixture of the first-metal and second-metal precursors.

8. A method according to claim 7 wherein said second-metal precursor is selected from the group consisting of Fe_xCl_y, W_xCl_y, Mn_xCl_y, V_xCl_y and mixtures thereof, where x and y are positive integers, and also wherein said solvent is selected from the group consisting of water, hydrochloric acid, acetone, ether and ethanol.

9. A method according to claim 7 wherein the step of forming a solution of the second-metal precursor in a solvent is carried out at a temperature of about 0°

C. to about 1°

C.

10. A method according to claim 7 wherein the molar concentration of the second-metal in the solution of said second-metal precursor is in the range of about 0.1-10 mol %.

11. A method according to claim 1 wherein step (b) is a dialysis-type of ion removal treatment.

12. A method according to claim 1 wherein step (b) removes chloride ions from the mixture of first-metal precursor and second-metal precursor.

13. A method according to claim 1 wherein step (b) comprises the substeps of:

placing the mixture of first-metal precursor and second-metal precursor in a container comprising a semi-permeable membrane that is permeable to chloride ions but is not permeable to the first-metal or the second-metal;

floating the container with the precursor mixture in a fresh water bath for a sufficient length of time substantially to remove the chloride ions from the mixture; and

, recovering the preliminary product from the container.

14. A method according to claim 13 wherein the container is floated in the water bath for at least about one hour.

15. A method according to claim 13 wherein the water bath is at a temperature of about room temperature.

16. A method according to claim 1 wherein step (c) is a vacuum drying step carried out at about room temperature and at a pressure of about 1 torr to about 1 torr.

17. A method according to claim 1 wherein step (d) is carried out at a temperature in the range of about 50°

C. to about 600°

C.

18. A method according to claim 1 wherein step (d) is carried out at a temperature in the range of about 100°

C. to about 500°

C.

19. A method according to claim 1 wherein step (d) is carried out at a temperature in the range of about 300°

C. to about 500°

C.

20. A method according to claim 1 wherein step (d) is carried out for a period of about 1 to 3 hours.

21. A method according to claim 1 wherein step (d) is carried out at a temperature and for a length of time that is sufficient significantly to enhance the effectiveness of the photocatalyst in decomposing volatile organic compounds relative to the effectiveness of the product of step (c) prior to any calcination.

22. A photocatalyst material prepared according to the method of claim 1.

23. A photocatalyst material prepared according to the method of claim 2.

24. A method of decomposing volatile organic contaminants contained in an air stream comprising the steps of:

(a) activating a bed of a photocatalyst material prepared according to the method of claim 1 by exposing the photocatalyst material to light; and

(b) passing the air stream containing the volatile organic contaminants into contact with the bed of activated photocatalyst material.

25. An air treatment system for purifying an air stream containing volatile organic contaminants comprising in combination:

(a) a bed of a photocatalyst material prepared according to the steps of;

(i) forming a mixture of a first-metal precursor and a second-metal precursor in a predetermined molar ratio of said second-metal relative to said first-metal, wherein said first-metal is a metal that exhibits photo-induced semiconductor properties and said second-metal is a dopant;

(ii) treating the mixture of first-metal precursor and second-metal precursor to remove nonessential ion(s) from the mixture thereby to form a preliminary product comprising an oxide of the first-metal having ions of the second-metal dispersed therethrough;

(iii) drying the preliminary product to form a dried first-metal oxide product doped with ions of said second-metal, said dried product comprising very small particles; and

,

(iv) calcinating the dried first-metal oxide product by applying heat to form the photocatalyst material;

(b) a light source for producing light that is directed onto said bed of photocatalyst material sufficient to activate the photocatalyst; and

,

(c) a circulation system for circulating the air stream containing the organic contaminants such that the air stream contacts the activated bed of photocatalyst material.

26. An air treatment system according to claim 25 wherein the photocatalyst material is coated on a surface of a support member.

27. An air treatment system according to claim 25 wherein the photocatalyst material is formed of very small particles having a mean particle diameter of about 10 nm or less.

28. An air treatment system according to claim 25 wherein:

(a) said first-metal precursor has the general chemical formula M¹_xCl_y, where M¹ is a metal that exhibits photo-induced semiconductor properties, Cl is chloride ion, and x and y are positive integers; and

also (b) said second-metal precursor has the general chemical formula M²_xCl_y, where M² is a dopant, Cl is chloride ion, and x and y are positive integers.

29. An air treatment system according to claim 25 wherein M¹ is selected from the group consisting of titanium (Ti), zirconium (Zr), tin (Sn), zinc (Zn), and alloys and combinations thereof.

30. An air treatment system according to claim 25 wherein M² is selected from the group consisting of iron (Fe), tungsten (W), manganese (Mn), vanadium (V), and alloys and combinations thereof.

31. An air treatment system according to claim 25 wherein said first-metal precursor is selected from the group consisting of TiCl₄, ZrCl₂, SnCl₄, ZnCl₂ and mixtures thereof, and also said second-metal precursor is selected from the group consisting of Fe_xCl_y, W_xCl_y, Mn_xCl_y, V_xCl_y and mixtures thereof, where x and y are positive integers.

32. An air treatment system according to claim 25 wherein step (i) comprises the substeps of:

forming a solution of said second-metal precursor in a suitable solvent;

adding the first-metal precursor to the solution of second-metal precursor; and

, mixing the solution to form a substantially homogeneous mixture of the first-metal and second-metal precursors.

33. An air treatment system according to claim 25 wherein said second-metal precursor is selected from the group consisting of Fe_xCl_y, W_xCl_y, Mn_xCl_y, V_xCl_y and mixtures thereof, where x and y are positive integers, and also wherein said solvent is selected from the group consisting of water, hydrochloric acid, acetone, ether and ethanol.

34. An air treatment system according to claim 25 wherein the step of forming a solution of the second-metal precursor in a solvent is carried out at a temperature of about 0°

C. to about 1°

C.

35. An air treatment system according to claim 25 wherein the molar concentration of the second-metal in the solution of said second-metal precursor is in the range of about 0.1-10 mol %.

36. An air treatment system according to claim 25 wherein step (ii) is a dialysis-type of ion removal treatment.

37. An air treatment system according to claim 25 wherein step (ii) removes chloride ions from the mixture of first-metal precursor and second-metal precursor.

38. An air treatment system according to claim 25 wherein step (iii) is a vacuum drying step carried out at about room temperature and at a pressure of about 10³ torr to about 1 torr.

39. An air treatment system according to claim 25 wherein step (iv) is carried out at a temperature in the range of about 50°

C. to about 600°

C.

40. An air treatment system according to claim 25 wherein step (iv) is carried out at a temperature in the range of about 100°

C. to about 500°

C.

41. An air treatment system according to claim 25 wherein step (iv) is carried out at a temperature in the range of about 300°

C. to about 500°

C.

42. An air treatment system according to claim 25 wherein step (iv) is carried out for a period of about 1 to 3 hours.