Integrated photoelectrochemical cell and system having a liquid electrolyte

• US 7,750,234 B2
• Filed: 05/23/2005
• Issued: 07/06/2010
• Est. Priority Date: 11/27/2002
• Status: Expired due to Fees

• Current Assignee: University of Toledo
• Original Assignee: University of Toledo
• Inventors: Xu, Liwei, Deng, Xunming
• Primary Examiner(s): Wilkins, III; Harry D.
• Assistant Examiner(s): Smith; Nicholas A.
• Application Number:
  US11/134,929
• Publication Number:
  US 20050211290A1
• Time in Patent Office: 1,870 Days
• Field of Search: 136/252, 136/258, 204/252, 204/263, 204/266
• 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 Table 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:

a) at least one integrated photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of;

i) a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and ii) a transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, the polarity depending on the sequence of p-type and n-type doped layers in the semiconductor layers;

b) at least one electrolyte;

c) a container that confines electrolyte and the photovoltaic electrode;

d) top cover that is substantially transparent to radiation; and

,

e) at least one membrane that separates the container into two compartments for separate oxidation and reduction reactions, the membrane conducting ions and separating generated oxygen and hydrogen gases, the membrane being installed in a generally perpendicular orientation relative to the photovoltaic cell in order to allow for maximum radiation to reach the photovoltaic electrode,

wherein the PEC cell facilitates the interaction of gravity and fluid flow, and

wherein gravity drives gas bubbles out of the PEC cell and circulates the electrolyte.

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), (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 photovoltaic electrode 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 other 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 compound semiconductor that is stable in electrolyte.

10. The PEC cell as in claim 9, wherein the 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 one 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.

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 behind the photoelectrode and away from the radiation to allow for maximum radiation to reach the photoelectrode.

30. The PEC cell as in claim 29, wherein the membrane comprises a perfluorinated polymer that contains small proportions of sulfonic or carboxylic ionic functional groups.

31. The PEC cell as in claim 30 wherein the membrane is applied onto a support.

32. The PEC cell as in claim 31 wherein the support comprises micro-porous polypropylene.

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

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

35. 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.

36. The PEC system as in claim 35 comprising at least one end adaptor that delivers electrolyte to the PEC cell.

37. The PEC system as in claim 35 comprising collecting electrolyte mixed with oxygen or hydrogen bubbles from the PEC cell.

38. The PEC system as in claim 36, 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 channels, respectively.

39. The PEC system as in claim 38, wherein the photoelectrode is an nipnip type cell with positive voltage generated on a radiation side.

40. The PEC system as in claim 38, wherein the photoelectrode is an pinpin type cell with negative voltage generated on a radiation side.

41. The PEC system as in claim 39, 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.

42. The PEC system as in claim 40, 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.

43. The PEC system as in claim 41, 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 an opposing end of the PEC cell.

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 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 an opposing end of the PEC cell.

45. The PEC system as in claim 43, 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.

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 cell described in claim 1, wherein the substrate comprises a metal foil or plate.

48. The PEC cell described in claim 1, wherein the reflective metal layer comprises an aluminum layer.

49. The PEC cell described in claim 1, wherein the first transparent conducting oxide (TCO) layer comprises at least one of tin oxide or zinc oxide.

50. The PEC cell described in claim 1, wherein the thin film deposition process including at least one of evaporation, sputtering or other suitable deposition method.

51. The PEC cell described in claim 1, wherein the plurality of semiconductor layers comprises a-Si based semiconductor layers.

52. The PEC cell described in claim 1, wherein a thin layer of catalyst is deposited on the second TCO layer.

53. The PEC cell described in claim 1, wherein the catalyst comprises a thin layer of carbon powder with micrometer sized spheres that support nanometer sized Pt particles.

54. The PEC cell described in claim 1, wherein the carbon powder is pressed or bonded to the TCO layer.

55. The PEC cell described in claim 52, wherein the catalyst is applied to selected regions so that the catalyst does not substantially block incoming radiation.

56. 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.

57. The PEC cell of claim 56 wherein the substrate is coated with a hydrogen evolution catalyst and the top TCO layer is covered with an oxygen evolution catalyst.

58. The PEC cell of claim 57 wherein top TCO layers comprise at least one of tin oxide and fluorine-doped tin oxide.

59. 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.

60. The PEC cell of claim 59, wherein the substrate is coated with an oxygen evolution catalyst and the top TCO layer is covered with a hydrogen evolution catalyst.

72. The PEC cell as in claim 1, wherein the photovoltaic electrode comprises at least two multilayered photovoltaic cells.

73. The PEC cell as in claim 1, having at least two independent photovoltaic electrodes within the container.

24. A photoelectrochemical (PEC) cell, comprising:

at least one integrated 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 compartments for oxidation and reduction reactions; and

at least one membrane mechanism that separates the container into two compartments for oxidation and reduction reactions, the membrane conducting ions and separating generated gases, the membrane being installed in a generally perpendicular orientation relative to the photovoltaic cell in order to allow for maximum radiation to reach the PEC cell,

wherein the PEC cell facilitates the interaction of gravity and fluid flow, and

wherein gravity drives gas bubbles out of the PEC cell and circulates the electrolyte 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), (GaAs, InP etc.), crystalline silicon (c-Si), thin film silicon (thin-Si), or variations and combinations thereof;

wherein the photovoltaic electrode has multiple junctions including two-junctions, three junctions and more junctions wherein sufficient voltage is generated for electrolysis;

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;

wherein the photovoltaic electrode is coated with a layer of transparent, conducting and corrosion-resistant (TCCR) layer;

wherein the TCCR layer comprises a polymer based composite, and

wherein the TCCR polymer based composite comprises nanocomposite materials with a fraction of metal embedded inside to increase electrical conductivity.

61. A photoelectrochemical (PEC) cell system, comprising:

a) at least one integrated photoelectrochemical (PEC) cell 10 that generates voltage under radiation, the photovoltaic electrode being comprised of;

a-i) a multilayer semiconductor material deposited on a conducting substrate 21, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer 2 on a side opposing the conducting substrate;

wherein a first side of the PEC cell 1 serves as an anode and a second side of the PEC cell serves as a cathode,

the polarity depending on the sequence of p-type and n-type doped layers in the semiconductor materials;

whereby sufficient voltage is generated for electrolysis;

a-ii) at least one electrolyte E;

a-iii) a container 6 that confines electrolyte E and the PEC cell 10;

a-iv) a top cover 2 that is substantially transparent to radiation; and

,

a-v) at least one thin ion-exchange membrane 7 that separates the container 6 into a top compartment 3 and a bottom compartment 5, the thin ion-exchange membrane 7 positioned in a generally perpendicular orientation relative to the PEC cell 1,

wherein oxidation and reduction reactions occur in separate compartments, the thin ion exchange membrane 7 allowing exchange of ions while separating gases generated in each compartment; and

,

b) a least one end adapter collecting mechanism 23 for collecting gases generated by the PEC cell, comprising;

b-i) a top opening 24 operatively connected to the top compartment 3 for receiving a first supply of electrolyte, and

b-ii) a bottom opening 25 operatively connected to the bottom compartment 5 for receiving a second supply of electrolyte,

wherein electrolyte flows out of the PEC cell into both the top opening 24 and the bottom opening 25;

b-iii) a first channel 26 operatively connected to the top opening 24,

wherein the first supply of electrolyte flows from the first channel 26 to a first outlet tube 28; and

,

b-iv) a second channel 27 operatively connected to the bottom opening 25,

wherein the second supply of electrolyte flows from the second channel 27 to a second outlet tube 29.

62. The photoelectrochemical (PEC) cell system of claim 61, the system further including:

c) a first end adaptor mechanism 23 operatively connected to a first end of the photovoltaic electrode;

d) a second end adaptor mechanism 23 operatively connected to a second end of the photovoltaic electrode; and

e) a first electrolyte circulation system comprising;

e-i) a first pump 31 operatively connected to the first outlet tube 28 for circulating a first supply of electrolyte and a first gas,

e-ii) a first gas collection container 34 operatively connected to the first outer tube 28 through a first gas collection inlet 36,

e-iii) a first collection port 38 on the first gas collection container 34 for collecting the first gas; and

e-iv) a first recycling port 37 operatively connected to the first gas collection container 34 for recycling the first supply of electrolyte into a first inlet tube 28′

that is operatively connected to the second end adaptor 23′

; and

f) a second electrolyte circulation system comprising;

f-i) a second pump 31 operatively connected to the second outlet tube 29 for circulating a second supply of electrolyte and a second gas,

f-ii) a second gas collection container 42 operatively connected to the second outer tube 29 through a second gas collection inlet 43,

f-iii) a second collection port 46 on the second gas collection container 42 for collecting the second gas; and

f-iv) a second recycling port 45 operatively connected to the second gas collection container 42 for recycling the second supply of electrolyte into a second inlet tube 29′

that is operatively connected to the second end adaptor 23′

.

63. The photoelectrochemical (PEC) cell system of claim 62, wherein the first electrolyte circulation system further includes:

e-v) a first water inlet valve and switch system 32 configured to supply additional water to flow into the first electrolyte circulation system via a first water inlet port 33; and

f-v) a second water inlet valve and switch system 40 configured to supply additional water to flow into the second electrolyte circulation system via a second water inlet port 41.

64. The photoelectrochemical (PEC) cell system of claim 61, wherein the photoelectrode is an nipnip type cell with positive voltage generated on a radiation side, and

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.

65. The photoelectrochemical (PEC) cell system of claim 61, wherein the photoelectrode is an pinpin type cell with negative voltage generated on a radiation side;

and

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.

66. The photoelectrochemical (PEC) cell of claim 61, wherein the PEC cell is tilted so that the top cover facilitates the interaction of gravity and fluid flow, and

wherein gravity drives gas bubbles out of the PEC cell and circulates the electrolyte.

67. A photoelectrochemical (PEC) cell, comprising:

i) at least one photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, and

wherein the photoelectrode is an nipnip type cell with positive voltage generated on a radiation side;

ii) at least one electrolyte;

iii) a container that confines electrolyte and the photovoltaic electrode;

iv) a top cover that is substantially transparent to; and

,

v) at least one mechanism that separates the container into two compartments for oxidation and reduction reactions and positioned in a generally perpendicular orientation relative to the photovoltaic cell, the mechanism allowing an exchange of ions while separating gases generated.

68. A photoelectrochemical (PEC) cell, comprising:

i) at least one photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, and

wherein the photoelectrode is an pinpin type cell with negative voltage generated on a radiation side;

ii) at least one electrolyte;

iii) a container that confines electrolyte and the photovoltaic electrode;

iv) a top cover that is substantially transparent to radiation;

v) a first collection container configured to accumulate hydrogen gas and a second container configured to accumulate oxygen gas; and

,

vi) at least one mechanism that separates the container into two compartments for oxidation and reduction reactions and positioned in a generally perpendicular orientation relative to the photovoltaic cell, the mechanism allowing an exchange of ions while separating gases generated.

69. A photoelectrochemical (PEC) cell, comprising:

i) at least one photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, and

wherein the photoelectrode comprises;

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);

ii) at least one electrolyte;

iii) a container that confines electrolyte and the photovoltaic electrode;

iv) a top cover that is substantially transparent to radiation and is comprised of a conductive material; and

,

v) at least one mechanism that separates the container into two compartments for oxidation and reduction reactions and positioned in a generally perpendicular orientation relative to the photovoltaic cell, the mechanism allowing an exchange of ions while separating gases generated.

70. A photoelectrochemical (PEC) cell, comprising:

i) at least one photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, and

wherein the photoelectrode comprises;

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);

ii) at least one electrolyte;

iii) a container that confines electrolyte and the photovoltaic electrode;

iv) a top cover that is substantially transparent to radiation and is comprised of a conductive material; and

,

v) at least one mechanism that separates the container into two compartments for oxidation and reduction reactions and positioned in a generally perpendicular orientation relative to the photovoltaic cell, the mechanism allowing an exchange of ions while separating gases generated.

71. A photoelectrochemical (PEC) cell, comprising:

i) at least one photovoltaic electrode that generates voltage under radiation, the photovoltaic electrode being comprised of a multilayer photovoltaic cell having a stack of semiconductor layers deposited on a conducting substrate, and a layer of transparent, conducting and corrosion-resistant (TCCR) layer on an opposing side of the multilayer material;

wherein a first side of the photovoltaic electrode serves as an anode and a second side of the photovoltaic electrode serves as a cathode, the polarity depending on the sequence of p-type and n-type doped layers in the semiconductor materials;

ii) at least one electrolyte;

iii) a container that confines electrolyte and the photovoltaic electrode;

iv) a top cover that is substantially transparent to radiation;

v) a membrane configured to separate gases and positioned in a generally perpendicular orientation relative to the photovoltaic cell, the membrane being supported by a mounting mechanism having at least one via hole to permit electrolyte flow therethrough; and

,

wherein the PEC cell is oriented so that the flow of the electrolyte and separation of gases generated by oxidation and reduction reactions is aided by gravity.