Photolysis of water using rhodate semiconductive electrodes

• US 4,144,147 A
• Filed: 09/26/1977
• Issued: 03/13/1979
• Est. Priority Date: 09/26/1977
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Sleight, Arthur W., Kung, Harold H. C., Jarrett, Howard S.
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Weisstuch, Aaron
• Application Number:
  US05/836,839
• Time in Patent Office: 533 Days
• Field of Search: 204/129, 204/266, 204/278, 204/290 R, 204/290 F, 204/291-293, 429/111, 252/62.3 V, 252/62.3 BT, 252/501, 252/521, 250/527, 423/592, 423/593
• US Class Current: 205/340
• CPC Class Codes: C25B 1/55 Photoelectrolysis
• CPC Class Codes: H01G 9/2031 comprising titanium oxide, e.g. TiO2 H01G9/2036 takes precedence
• CPC Class Codes: H01M 14/005 Photoelectrochemical storage cells light sensitive devices H01G9/20, semiconductors sensitive to light H01L31/00
• 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: Y10S 204/03 Auxiliary internally generated electrical energy

Abstract

Decomposition of water into hydrogen and oxygen by sunlight is accomplished by using a rhodate p-type semiconductor as cathode and an n-type semiconductor or a metal as anode. A cell exposed to sunlight using a rhodate cathode and an n-type TiO₂ anode decomposes the contained water and also generates electric power.

Claims

1. In a photoelectrochemical cell comprising an anode and a p-type semiconducting cathode the improvement wherein the said cathode comprises an oxide of trivalent rhodium.

2. A sunlight-permeable device for decomposing water into hydrogen and oxygen when filled with a sunlight-permeable aqueous electrolyte and exposed to sunlight comprising

a container permeable to sunlight

having within it an anode and a cathode so spaced that entering sunlight will impinge on both simultaneously,

the anode being a metallic conductor or an n-type semiconductor,

the cathode being a p-type semiconducting oxide of trivalent rhodium having a resistivity less than 10⁵ ohm-cm, and

an external electrical circuit connecting the anode and cathode, the said circuit containing an applied voltage of zero to 1.23 volts.

3. A device as in claim 2 wherein the cathode is a p-type semiconducting rhodate of the formula Rh₂ O₃ or ARhO₃ wherein A is a trivalent rare earth.

4. A device as in claim 3 wherein the said rhodate is p-Rh₂ O₃.

5. A device as in claim 3 wherein the said rhodate is ARhO₃, where A is a rare earth.

6. A device as in claim 3 wherein the said rhodate is p-LuRhO₃.

7. A device as in claim 3 wherein the said rhodate is p-LaRhO₃.

8. A device as in claim 3 wherein the said rhodate is p-DyRhO₃.

9. A device as in claim 2 wherein the anode is an n-type semiconductor whose anodic photopotential is more cathodic than -0.3 volt vs S.C.E.

10. A device as in claim 9 wherein the anode is n-TiO₂.

11. A device as in claim 2 wherein the anode is a metallic conductor.

12. A device as in claim 2 wherein the cathode is a p-type semiconducting rhodate of the formula Rh₂ O₃ or ARhO₃ where A is a rare earth and the anode is an n-type semiconductor whose anodic photopotential is more cathodic than -0.3 volt vs S.C.E.

13. A device as in claim 12 wherein the cathode is p-LuRhO₃ and the anode is n-TiO₂.

14. A device as in claim 12 wherein the cathode is p-LaRhO₃ and the anode is n-TiO₂.

15. A device as in claim 12 wherein the cathode is p-DyRhO₃ and the anode is n-TiO₂.

16. A device as in claim 12 wherein the cathode is p-Rh₂ O₃ and the anode is n-TiO₂.

17. In the process of photoelectrochemically hydrolyzing water wherein an anode and p-type semiconducting cathode are used the improvement wherein the said cathode comprises an oxide of trivalent rhodium.

18. In the process of claim 17 the improvement wherein the said cathode comprises p-LuRhO₃.

19. In the process of claim 17 the improvement wherein the said cathode is p-LaRhO₃.

20. In the process of claim 17 the improvement wherein the said cathode is p-DyRhO₃.

21. In the process of claim 17 the improvement wherein the said cathode is p-Rh₂ O₃.

22. In the process of claim 17 the improvement wherein the anode is n-TiO₂ and the cathode is p-LuRhO₃.

23. In the process of claim 17 the improvement wherein the anode is n-TiO₂ and the cathode is p-LaRhO₃.

24. In the process of claim 17 the improvement wherein the anode is n-TiO₂ and the cathode is p-DyRhO₃.

25. In the process of claim 17 the improvement wherein the anode is n-TiO₂ and the cathode is p-Rh₂ O₃.