Photoelectrochemical Cell and Energy System Using Same

• US 20120276464A1
• Filed: 11/04/2010
• Published: 11/01/2012
• Est. Priority Date: 11/10/2009
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kuroha, Tomohiro, Nomura, Takaiki, Hato, Kazuhito, Taniguchi, Noboru, Suzuki, Takahiro, Tokuhiro, Kenichi
• Granted Patent: US 8,821,700 B2
• Time in Patent Office: Days
• US Class Current: 429/418
• CPC Class Codes: C01B 3/042 Decomposition of water
• CPC Class Codes: C25B 1/55 Photoelectrolysis
• CPC Class Codes: H01M 14/005 Photoelectrochemical storage cells light sensitive devices H01G9/20, semiconductors sensitive to light H01L31/00
• CPC Class Codes: H01M 8/0606 with means for production of gaseous reactants
• 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

Abstract

A photoelectrochemical cell (100) includes: a semiconductor electrode (120) including a conductor (121), a first n-type semiconductor layer (122) having a nanotube array structure, and a second n-type semiconductor layer (123); a counter electrode (130) connected to the conductor (121); an electrolyte (140) in contact with the second n-type semiconductor layer (123) and the counter electrode (130); and a container (110) accommodating the semiconductor electrode (120), the counter electrode (130) and the electrolyte (140). Relative to a vacuum level, (I) band edge levels of a conduction band and a valence band in the second n-type semiconductor layer (123), respectively, are higher than band edge levels of a conduction band and a valence band in the first n-type semiconductor layer (122), (II) a Fermi level of the first n-type semiconductor layer (122) is higher than a Fermi level of the second n-type semiconductor layer (123), and (III) a Fermi level of the conductor (121) is higher than the Fermi level of the first n-type semiconductor layer (122).

Claims

1. A photoelectrochemical cell comprising:

a semiconductor electrode including a conductor, a first n-type semiconductor layer that is disposed on the conductor and has a nanotube array structure, and a second n-type semiconductor layer disposed on the first n-type semiconductor layer;

a counter electrode connected electrically to the conductor;

an electrolyte in contact with surfaces of the second n-type semiconductor layer and the counter electrode; and

a container accommodating the semiconductor electrode, the counter electrode and the electrolyte, wherein;

in the semiconductor electrode, relative to a vacuum level,

(I) band edge levels of a conduction band and a valence band in the second n-type semiconductor layer, respectively, are higher than band edge levels of a conduction band and a valence band in the first n-type semiconductor layer,

(II) a Fermi level of the first n-type semiconductor layer is higher than a Fermi level of the second n-type semiconductor layer, and

(III) a Fermi level of the conductor is higher than the Fermi level of the first n-type semiconductor layer; and

the photoelectrochemical cell generates hydrogen by irradiation of the second n-type semiconductor layer with light.

2. The photoelectrochemical cell according to claim 1, wherein

in the case of the electrolyte at a pH of 0 and a temperature of 25°

C.,

the Fermi level of the first n-type semiconductor layer is −

4.44 eV or more and the band edge level of the valence band in the second n-type semiconductor layer is −

5.67 eV or less, relative to the vacuum level.

3. The photoelectrochemical cell according to claim 1, wherein the first n-type semiconductor layer is formed of a titanium oxide nanotube array.

4. The photoelectrochemical cell according to claim 1, wherein the second n-type semiconductor layer is composed of one selected from the group consisting of oxide, nitride and oxynitride.

8. The photoelectrochemical cell according to claim 1, wherein the counter electrode is disposed on the conductor.

9. An energy system comprising:

the photoelectrochemical cell according to claim 1;

a hydrogen storage that is connected to the photoelectrochemical cell by a first pipe and that stores hydrogen generated in the photoelectrochemical cell; and

a fuel cell that is connected to the hydrogen storage by a second pipe and that converts the hydrogen stored in the hydrogen storage into electricity.

5. A photoelectrochemical cell comprising:

a semiconductor electrode including a conductor, a first p-type semiconductor layer that is disposed on the conductor and has a nanotube array structure, and a second p-type semiconductor layer disposed on the first p-type semiconductor layer;

a counter electrode connected electrically to the conductor;

an electrolyte in contact with surfaces of the second p-type semiconductor layer and the counter electrode; and

a container accommodating the semiconductor electrode, the counter electrode and the electrolyte, wherein;

in the semiconductor electrode, relative to a vacuum level,

(I) band edge levels of a conduction band and a valence band in the second p-type semiconductor layer, respectively, are lower than band edge levels of a conduction band and a valence band in the first p-type semiconductor layer,

(II) a Fermi level of the first p-type semiconductor layer is lower than a Fermi level of the second p-type semiconductor layer, and

(III) a Fermi level of the conductor is lower than the Fermi level of the first p-type semiconductor layer; and

the photoelectrochemical cell generates hydrogen by irradiation of the second p-type semiconductor layer with light.

6. The photoelectrochemical cell according to claim 5, wherein

in the case of the electrolyte at a pH of 0 and a temperature of 25°

C.,

the Fermi level of the first p-type semiconductor layer is −

5.67 eV or less and the band edge level of the conduction band in the second p-type semiconductor layer is −

4.44 eV or more, relative to the vacuum level.

7. The photoelectrochemical cell according to claim 5, wherein the second p-type semiconductor layer is composed of one selected from the group consisting of oxide, nitride and oxynitride.

10. The photoelectrochemical cell according to claim 5, wherein the counter electrode is disposed on the conductor.

11. An energy system comprising:

the photoelectrochemical cell according to claim 5;

a hydrogen storage that is connected to the photoelectrochemical cell by a first pipe and that stores hydrogen generated in the photoelectrochemical cell; and

a fuel cell that is connected to the hydrogen storage by a second pipe and that converts the hydrogen stored in the hydrogen storage into electricity.