Integrated photoelectrochemical cell and system having a liquid electrolyte

• US 20050211290A1
• Filed: 05/23/2005
• Published: 09/29/2005
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: University of Toledo
• Original Assignee: University of Toledo
• Inventors: Deng, Xunming, Xu, Liwei
• Granted Patent: US 7,750,234 B2
• Time in Patent Office: Days
• US Class Current: 136/252
• CPC Class Codes: C25B 1/55 Photoelectrolysis
• CPC Class Codes: H01G 9/2045 comprising a semiconductor electrode comprising elements of the fourth group of the Periodic System (C, Si, Ge, Sn, Pb) with or without impurities, e.g. doping materials
• CPC Class Codes: H01G 9/2054 comprising a semiconductor electrode comprising AII-BVI compounds, e.g. CdTe, CdSe, ZnTe, ZnSe, with or without impurities, e.g. doping materials H01G9/2027 takes precedence
• CPC Class Codes: H01G 9/2068 Panels or arrays of photoelectrochemical cells, e.g. photovoltaic modules based on photoelectrochemical cells
• CPC Class Codes: H01M 14/005 Photoelectrochemical storage cells light sensitive devices H01G9/20, semiconductors sensitive to light H01L31/00
• CPC Class Codes: H01M 8/0656 by electrochemical means H01M8/065 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: Y02E 60/50 Fuel cells
• 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

Abstract

An integrated photoelectrochemical (PEC) cell generates hydrogen and oxygen from water while being illuminated with radiation. The PEC cell employs a liquid electrolyte, a multi-junction photovoltaic electrode, and a thin ion-exchange membrane. A PEC system and a method of making such PEC cell and PEC system are also disclosed.

Claims

1. A photoelectrochemical (PEC) cell, comprising:

at least one photovoltaic electrode that generates voltage under radiation;

at least one electrolyte;

a container that confines electrolyte;

a top cover that is substantially transparent to radiation;

at least one mechanism that separates the container into two compartment for oxidation and reduction reactions; and

a structure that allows sufficient radiation to reach the active area of the photoelectrode.

2. The PEC cell as in claim 1, wherein the photovoltaic electrode comprises at least one of the following solar cell types:

amorphous silicon (a-Si), cadmium telluride (CdTe), copper indium diselenide (CuInSe₂), copper indium gallium diselenide (CIGS), III-V (GaAs, InP etc), crystalline silicon (c-Si), thin film silicon (thin-Si), or variations and combinations thereof.

3. The PEC cell as in claim 2, wherein the photovoltaic electrode has multiple junctions including two-junctions, three junctions and more junctions wherein sufficient voltage is generated for electrolysis.

4. The PEC cell as in claim 3, wherein at least one of the photovoltaic junctions in the multiple-junction photoelectrode uses amorphous silicon.

5. The PEC cell as in claim 3, wherein a top-most junction is closest to the radiation in the photovoltaic electrode and the top-most junction comprises a liquid junction between a semiconductor and the electrolyte.

6. The PEC cell as in claim 5, wherein the semiconductor that forms a junction with the electrolyte comprises at least one metal oxide that is stable in the electrolyte.

7. The PEC cell as in claim 6, wherein the metal oxide comprises TiO₂, WO₃ or Fe₂O₃ and combinations thereof

8. The PEC cell as in claim 6, wherein the metal oxide is alloyed with at least one another material, including Ca and/or Mg, to increase radiation absorption.

9. The PEC cell as in claim 5, wherein the semiconductor that forms a junction with the electrolyte comprises at least one III-V compound semiconductor that is stable in electrolyte.

10. The PEC cell as in claim 9, wherein the III-V compound semiconductor includes at least one of:

InGaN, GaPN, GaAsPN, GaP and combinations thereof.

11. The PEC cell as in claim 5, wherein the semiconductor that forms a junction with the electrolyte comprises at least one Group IV semiconductor or semiconductor alloy that is stable in electrolyte.

12. The PEC cell as in claim 11, wherein the Group IV semiconductor or semiconductor alloy includes at least one of:

Si, C, Ge, Sn, SiC, GeC and combinations thereof.

13. The PEC cell as in claim 3 wherein a top-most junction is closest to the radiation in the photovoltaic electrode and comprises a solid-state junction generated between p-type and n-type semiconductors.

14. The PEC cell as in claim 13, wherein the photoelectrode is coated with a layer of transparent, conducting and corrosion-resistant (TCCR) layer.

15. The PEC cell as in claim 14, wherein the TCCR layer comprises a metal oxide based material.

16. The PEC cell as in claim 15, wherein the metal oxide TCCR layer comprises TiO₂, WO₃ and Fe₂O₃, and combination thereof.

17. The PEC cell as in claim 15, wherein the metal oxide TCCR layer is doped with at least on other element, including F, Cl and mixtures thereof, to increase resistance to corrosion.

18. The PEC cell as in claim 15, where in the metal oxide TCCR layer is doped with at least one other element to reduce or remove a rectifying junction between the oxide and the electrolyte and to reduce junction resistance.

19. The PEC cell as in claim 14, wherein the TCCR layer comprises a nitride compound.

20. The PEC cell as in claim 19, wherein the nitride compound comprises InGaN, GaPN, GaAsPN or variations and combinations of thereof, including both crystalline and amorphous forms.

21. The PEC cell as in claim 14, wherein the TCCR layer comprises a carbide compound.

22. The PEC cell as in claim 21, wherein the carbide compound comprises SiC, GeC, or variations and combinations of thereof, including both crystalline and amorphous forms.

23. The PEC cell as in claim 14, wherein the TCCR layer comprises a polymer based composite.

24. The PEC cell as in claim 23, wherein the TCCR polymer based composite comprises nanocomposite materials with a fraction of metal embedded inside to increase electrical conductivity.

25. The PEC cell as in claim 3, wherein the radiation comprises photons, electrons or other energy-carrying radiations and particles.

26. The PEC cell as in claim 25, wherein the radiation comprises solar radiation.

27. The PEC cell as in claim 3, wherein the mechanism that separates the container into two compartments comprises at least one thin ion-exchange membrane.

28. The PEC cell as in claim 27, wherein the membrane comprises at least one of a cation exchange membrane or an anion-exchange membrane.

29. The PEC cell as in claim 27, wherein the ion-exchange membrane is installed perpendicular to the photoelectrode to allow for maximum radiation to reach the photoelectrode.

30. The PEC cell as in claims 27, wherein the ion-exchange membrane is installed behind the photoelectrode and away from the radiation to allow for maximum radiation to reach the photoelectrode.

31. The PEC cell as in claim 30, wherein the membrane comprises a perfluorinated polymer that contains small proportions of sulfonic or carboxylic ionic functional groups

32. The PEC cell as in claim 31 wherein the membrane is applied onto a support.

33. The PEC cell as in claim 32 wherein the support comprises micro-porous polypropylene.

34. The PEC cell as in claim 3, wherein the electrolyte is acidic.

35. The PEC cell as in claim 3, wherein the electrolyte is alkaline.

36. The PEC system comprising the PEC cell as in claim 3 and further comprising at least one collecting mechanism to collect gases generated by the PEC cell.

37. The PEC system as in claim 36 comprising at least one end adaptor that delivers electrolyte to the PEC cell.

38. The PEC system as in claim 36 comprising collecting electrolyte mixed with oxygen or hydrogen bubbles from the PEC cell.

39. The PEC system as in claim 37, wherein the end adaptor comprises a top opening operatively connected to a top compartment and a bottom compartment opening operatively connected to a bottom compartment, wherein electrolyte flows out of the PEC cell into both the top opening and the bottom opening, through a first channel and a second channel operatively connected to the top and bottom openings, respectively, and out of first and second outlet tubes operatively connected to the first and second outlet tubes, respectively.

40. The PEC system as in claim 39, wherein the photoelectrode is an nipnip type cell with positive voltage generated on a radiation side.

41. The PEC system as in claim 39, wherein the photoelectrode is an pinpin type cell with negative voltage generated on a radiation side.

42. The PEC system as in claim 40, wherein hydrogen gas is generated in the bottom compartment and exits from the first outlet tube, and wherein oxygen is generated in the top compartment and exits from the second outlet tube.

43. The PEC system as in claim 41, wherein oxygen gas is generated in the bottom compartment and exits from the first outlet tube, and wherein hydrogen is generated in the top compartment and exits from the second outlet tube.

44. The PEC system as in claim 42, further comprising first and second pumps for circulating electrolyte wherein gases and electrolyte are circulated by the pumps through first and second gas collection containers, respectively, so that hydrogen is collected at a first collection port in a first gas collection container and oxygen is collected at a second collection port in a second gas collection container;

and wherein electrolyte flows from the first and second recycling ports, respectively, back into the bottom and top compartments respectively, through third and fourth inlet tubes operatively connected to a second end adaptor on and opposing end of the PEC cell.

45. The PEC system as in claim 43, further comprising first and second pumps for circulating electrolyte wherein gases and electrolyte are circulated by the pumps through first and second gas collection containers, respectively, so that oxygen is collected at a first collection port in a first gas collection container and hydrogen is collected at a second collection port in a second gas collection container;

and wherein electrolyte flows from the first and second recycling ports, respectively, back into the bottom and top compartments respectively, through third and fourth inlet tubes operatively connected to a second end adaptor on and opposing end of the PEC cell.

46. The PEC system as in claim 44, further comprising first and second water inlet valves and switches operatively connected via first and second ports, respectively, to the first and second gas collection containers to allow additional water to flow into the system.

47. The PEC system as in claim 45, further comprising first and second water inlet valves and switches operatively connected via first and second ports, respectively, to the first and second gas collection containers to allow additional water to flow into the system.

48. A method of making the PEC cell described in claim 3, comprising:

depositing a catalyst on a substrate,

depositing a reflective metal layer and a first transparent conducting oxide (TCO) layer on the metal substrate via at least one suitable thin film deposition process,

depositing a plurality of semiconductor layers on the TCO layer, and

depositing at least a second TCO layer deposited on a topmost layer of the semiconductor layers.

49. The method of making the PEC cell described in claim 48, wherein the substrate comprises a metal foil or plate.

50. The method of making the PEC cell described in claim 48, wherein the reflective metal layer comprises an aluminum layer.

51. The method of making the PEC cell described in claim 48, wherein the first transparent conducting oxide (TCO) layer comprises at least one of tin oxide or zinc oxide.

52. The method of making the PEC cell described in claim 48, wherein the thin film deposition process including at least one of evaporation, sputtering or other suitable deposition method.

53. The method of making the PEC cell described in claim 48, wherein the plurality of semiconductor layers comprises a-Si based semiconductor layers.

54. The method of making the PEC cell described in claim 48, wherein a thin layer of catalyst is deposited on the second TCO layer.

55. The method of making the PEC cell described in claim 48, wherein the catalyst comprises a thin layer of carbon powder with micrometer sized spheres that support nanometer sized Pt particles.

56. The method of making the PEC cell described in claim 48, wherein the carbon powder is pressed or bonded to the TCO layer.

57. The method of making the PEC cell described in claim 48, wherein the catalyst is applied to selected regions so that the catalyst does not substantially block incoming radiation.

58. The method of making the PEC system described in claim 32, comprising operatively connecting an end adaptor comprises a top opening to a top compartment and a bottom opening to a bottom compartment, wherein electrolyte flows out of the PEC cell into both the top opening and the bottom opening, through a first channel and a second channel operatively connected to the top and bottom openings, respectively, and out of first and second outlet tubes operatively connected to the first and second outlet tubes, respectively.

59. The method as in claim 58 wherein the photoelectrode is an nipnip type cell with positive voltage generated on a radiation side.

60. The method as in claim 58, wherein the photoelectrode is an pinpin type cell with negative voltage generated on a radiation side.

61. The method as in claim 59, wherein hydrogen gas is generated in the bottom compartment and exits from the first outlet tube, and wherein oxygen is generated in the top compartment and exits from the second outlet tube.

62. The method as in claim 60, wherein oxygen gas is generated in the bottom compartment and exits from the first outlet tube, and wherein hydrogen is generated in the top compartment and exits from the second outlet tube.

63. The method as in claim 61, further comprising circulating electrolyte wherein gases and electrolyte are circulated by the pumps through first and second gas collection containers, respectively, so that hydrogen is collected at a first collection port in a first gas collection container and oxygen is collected at a second collection port in a second gas collection container;

and wherein electrolyte flows from the first and second recycling ports, respectively, back into the bottom and top compartments respectively, through third and fourth inlet tubes operatively connected to a second end adaptor on and opposing end of the PEC cell.

64. The method as in claim 62, further comprising circulating electrolyte wherein gases and electrolyte are circulated by the pumps through first and second gas collection containers, respectively, so that oxygen is collected at a first collection port in a first gas collection container and hydrogen is collected at a second collection port in a second gas collection container;

and wherein electrolyte flows from the first and second recycling ports, respectively, back into the bottom and top compartments respectively, through third and fourth inlet tubes operatively connected to a second end adaptor on and opposing end of the PEC cell.

65. The method as in claim 63, further comprising adding additional water via first and second water inlet valves and switches operatively connected via first and second ports, respectively, to the first and second gas collection containers to allow additional water to flow into the system.

66. The method as in claim 64, further comprising adding additional water via first and second water inlet valves and switches operatively connected via first and second ports, respectively, to the first and second gas collection containers to allow additional water to flow into the system.

67. The PEC cell of claim 1, wherein the electrode comprises:

metal substrate, metal reflector, transparent conducting oxide (TCO), n-type a-Si layer, intrinsic a-SiGe layer or microcrystalline silicon layer, p-type a-Si based layer, n-type a-Si layer, intrinsic a-Si layer or a-SiGe layer, p-type a-Si based layer, n-type a-Si layer, intrinsic a-Si layer, p-type a-Si based layer (nipnipnip layers), TCO layer.

68. The PEC cell of claim 67 wherein the substrate is coated with a hydrogen evolution catalyst and the top TCO layer is covered with an oxygen evolution catalyst 11.

69. The PEC cell of claim 68 wherein top TCO layers comprise at least one of tin oxide and fluorine-doped tin oxide.

70. The PEC cell of claim 1, wherein the electrode comprises:

metal substrate, metal reflector, transparent conducting oxide (TCO) layer, p-type a-Si based layer, intrinsic a-SiGe layer or microcrystalline silicon layer, n-type a-Si layer, p-type a-Si based layer, intrinsic a-Si layer or a-SiGe layer, n-type a-Si layer, p-type a-Si based layer, intrinsic a-Si layer, n-type a-Si layer (pinpinpin layers), TCO layer.

71. The PEC cell of claim 70, wherein the substrate is coated with an oxygen evolution catalyst and the top TCO layer is covered with a hydrogen evolution catalyst.