PREPARATION OF NANO-TUBULAR TITANIA SUBSTRATE WITH OXYGEN VACANCIES AND THEIR USE IN PHOTO-ELECTROLYSIS OF WATER

• US 20090183994A1
• Filed: 09/11/2006
• Published: 07/23/2009
• Est. Priority Date: 09/09/2005
• Status: Abandoned Application

• Current Assignee: University of Nevada Reno (State of Nevada)
• Original Assignee: University of Nevada Reno (State of Nevada)
• Inventors: Mohapatra, Susant Kumar, Mahajan, Vishal Khamdeo, Misra, Manoranjan, Raja, Krishnan Selva
• Application Number:
  US12/066,102
• Publication Number:
  US 20090183994A1
• Time in Patent Office: Days
• US Class Current: 205/340
• CPC Class Codes: C25B 1/55 Photoelectrolysis
• CPC Class Codes: C25D 11/26 of refractory metals or alloys based thereon
• CPC Class Codes: C25D 3/56 of alloys
• CPC Class Codes: C25D 5/18 Electroplating using modulated, pulsed or reversing current
• CPC Class Codes: C25D 5/617 Crystalline layers
• 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: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• CPC Class Codes: Y02P 20/133 Renewable energy sources, e.g. sunlight
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof

Abstract

The invention relates to a method of making a nanotubular titania substrate having a titanium dioxide surface comprised of a plurality of vertically oriented titanium dioxide nanotubes containing oxygen vacancies, including the steps of anodizing a titanium metal substrate in an acidified fluoride electrolyte and annealing the titanium oxide surface in a non-oxidating atmosphere. The invention further relates to a nanotubular titania substrate having an annealed titanium dioxide surface comprised of self-ordered titanium dioxide nanotubes containing oxygen vacancies. The invention further relates to a photo-electrolysis method for generating H₂ wherein the photo-anode is a nanotubular titania substrate of the invention. The invention also relates to an electrochemical method of synthesizing CdZn/CdZnTe nanowires, wherein a nanoporous TiO₂ template was used in combination with non-aqueous electrolyte. The invention also relates to a nanotubular titania substrate having CdTe or CdZnTe nanowires extending therefrom.

Claims

1. A method of making a nanotubular titania substrate having a titanium dioxide surface comprised of a plurality of vertically oriented titanium dioxide nanotubes containing oxygen vacancies, the method comprising the steps of

anodizing a titanium metal substrate in an acidified fluoride electrolyte under conditions sufficient to form a titanium oxide surface comprised of self-ordered titanium oxide nanotubes, and

annealing the titanium oxide surface in a non-oxidating atmosphere.

2. The method of claim 1, wherein the non-oxidating atmosphere is a reducing atmosphere.

3. The method of claim 2, wherein the reducing atmosphere is an atmosphere comprising at least one of nitrogen, hydrogen, and cracked ammonia.

4. The method of claim 1 further comprising the step of doping the titanium oxide surface with a Group 14 element, a Group 15 element, a Group 16 element a Group 17 element, or mixtures thereof.

5. The method of claim 1, wherein the electrolyte includes a fluoride compound selected from the group consisting of HF, LiF, NaF, KF, NH₄F, and mixtures thereof.

6. The method of claim 1, wherein the electrolyte is an aqueous solution.

7. The method of claim 1, wherein the electrolyte is an organic solution.

8. The method of claim 7, wherein the organic solution is a polyhydric alcohol selected from the group consisting of glycerol, EG, DEG, and mixtures thereof.

9. The method of claim 1, wherein the electrolyte is ultrasonically stirred.

10. A nanotubular titania substrate having an annealed titanium dioxide surface comprised of self-ordered titanium dioxide nanotubes containing oxygen vacancies.

11. The nanotubular titania substrate of claim 10 having a band gap ranging from about 1.9 eV to about 3.0 eV.

12. The nanotubular titania substrate of claim 10, wherein the titanium dioxide nanotubes are doped with a Group 14 element, a Group 15 element, a Group 16 element, a Group 17 element, or mixtures thereof.

13. The nanotubular substrate of claim 10, wherein the titanium dioxide nanotubes are nitrogen doped.

14. The nanotubular substrate of claim 10, wherein the titanium dioxide nanotubes are carbon doped.

15. The nanotubular substrate of claim 10, wherein the titanium dioxide nanotubes are phosphorous doped.

16. The nanotubular substrate of claim 10, wherein the titanium dioxide nanotubes are doped in at least two of carbon, nitrogen, and phosphorous.

17. The nanotubular substrate of claim 10, wherein the titanium dioxide nanotubes are further modified with carbon under conditions suitable to form carbon modified titanium dioxide nanotubes.

18. A photo-electrochemical cell having the nanotubular titania substrate of claim 10 as an electrode.

19. A photo-electrolysis method for generating H₂ comprising the step of irradiating a photo-anode and a photo-cathode with light under conditions suitable to generate H₂,

wherein the photo-anode is a nanotubular titania substrate of claim 10.

20. The photo-electrolysis method of claim 19, wherein the light is solar light.

21. The photo-electrolysis method of claim 19, wherein an acidic solution is used in the photo-cathode compartment.

22. The photo-electrolysis method of claim 19, wherein a basic solution is used in the photo-anode compartment.

23. The photo-electrolysis method of claim 19, wherein the photo-cathode is at least one substance selected from the groups consisting of a cadmium telluride (CdTe) coated platinum foil, a cadmium zinc telluride (CdZnTe) coated platinum foil, and anodized TiO₂ nanotubes coated with nanowires of CdTe or CdZnTe.

24. An electrochemical method of synthesizing CdZn or CdZnTe nanowires comprising pulsing cathodic and anodic potentials to grow the nanowires, wherein a nanoporous TiO₂ template was used in combination with non-aqueous electrolyte.

25. The method of claim 24, wherein the non-aqueous electrolyte is propylene carbonate.

26. A nanotubular titania substrate having CdTe or CdZnTe nanowires extending therefrom.