Semiconductor photoelectrode, photoelectrochemical cell, hydrogen generation method, and energy system

Patent metadata

Field	Value
Publication number	US-9644276-B2
Application number	US-201414509361-A
Country	US
Kind code	B2
Filing date	Oct 8, 2014
Priority date	Oct 17, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

Provided is a semiconductor photoelectrode comprising a first conductive layer; a first n-type semiconductor layer disposed on the first conductive layer; and a second conductive layer covering the first n-type semiconductor layer. The first n-type semiconductor layer has a first n-type surface region and a second n-type surface region. The first n-type surface region is in contact with the first conductive layer. The second n-type surface region is in contact with the second conductive layer. The first n-type semiconductor layer is formed of at least one selected from the group consisting of a nitride semiconductor and an oxynitride semiconductor. The second conductive layer is light-transmissive. The second conductive layer is formed of a p-type oxide conductor.

First claim

The invention claimed is:

1. A semiconductor photoelectrode, comprising:
a first conductive layer;
a first n-type semiconductor layer disposed on the first conductive layer; and
a second conductive layer covering the first n-type semiconductor layer,
wherein
the first n-type semiconductor layer has a first n-type surface region and a second n-type surface region;
the first n-type surface region is in contact with the first conductive layer;
the second n-type surface region is in contact with the second conductive layer;
a band edge level E C2a of a conduction band of the first n-type surface region is not higher than a band edge level E C2b of a conduction band of the second n-type surface region;
a band edge level E V2a of a valence band of the first n-type surface region is not higher than a band edge level E V2b of a valence band of the second n-type surface region;
a Fermi level E F2b of the second n-type surface region is not higher than a Fermi level E F2a of the first n-type surface region;
the Fermi level E F2a of the first n-type surface region is lower than a Fermi level E F1 of the first conductive layer;
a Fermi level E F3 of the second conductive layer is lower than the Fermi level E F2b of the second n-type surface region;
the first n-type semiconductor layer is formed of at least one selected from the group consisting of a nitride semiconductor and an oxynitride semiconductor;
the second conductive layer is light-transmissive; and
the second conductive layer is formed of a p-type oxide conductor.

2. The semiconductor photoelectrode according to claim 1 , wherein
the nitride semiconductor and the oxynitride semiconductor each contain a metal selected from the group consisting of Ti, Nb, and Ta.

3. The semiconductor photoelectrode according to claim 1 , wherein
the first n-type semiconductor layer is composed of two or more kinds of elements; and
a concentration of the at least one kind of the element included in the first n-type semiconductor layer is increased or decreased along a thickness direction of the first n-type semiconductor layer.

4. The semiconductor photoelectrode according to claim 1 , further comprising:
a second n-type semiconductor layer,
wherein
the second n-type semiconductor layer is interposed between the first conductive layer and the first n-type semiconductor layer;
a band edge level of a conduction band E C22 of the second n-type semiconductor layer is lower than a band edge level of a conduction band E C21 of the first n-type semiconductor layer;
a band edge level of a valence band E V22 of the second n-type semiconductor layer is lower than a band edge level of a valence band E V21 of the first n-type semiconductor layer;
a Fermi level E F21 of the first n-type semiconductor layer is lower than a Fermi level E F22 of the second n-type semiconductor layer;
the Fermi level E F22 of the second n-type semiconductor layer is lower than the Fermi level E F1 of the first conductive layer; and
the Fermi level E F3 of the second conductive layer is lower than the Fermi level E F22 of the first n-type semiconductor layer.

5. The semiconductor photoelectrode according to claim 4 , wherein
the first n-type semiconductor layer is formed of a nitride or oxynitride semiconductor containing a metal selected from the group consisting of Ti, Nb and Ta.

6. The semiconductor photoelectrode according to claim 5 , wherein
the second n-type semiconductor layer is formed of an oxide, nitride, or oxynitride semiconductor containing a metal selected from the group consisting of Ti, Nb and Ta.

7. The semiconductor photoelectrode according to claim 6 , wherein
the metal selected from the group consisting of Ti, Nb, and Ta contained in the first n-type semiconductor layer is the same as the metal selected from the group consisting of Ti, Nb, and Ta contained in the second n-type semiconductor layer.

8. The semiconductor photoelectrode according to claim 1 , wherein
the p-type oxide conductor is formed of a material selected from the group consisting of p-type nickel oxide, p-type copper oxide, p-type cobalt oxide, p-type zinc oxide, p-type CuNbO 3 , p-type SrCu 2 O 2 , p-type BaCuSeF, and p-type CuAlO 2 .

9. The semiconductor photoelectrode according to claim 8 , wherein
the p-type oxide conductor is formed of p-type nickel oxide.

10. A photoelectrochemical cell, comprising:
the semiconductor photoelectrode according to claim 1 ;
a counter electrode electrically connected to the first conductive layer included in the semiconductor photoelectrode;
an electrolyte aqueous solution in contact with surfaces of the semiconductor photoelectrode and the counter electrode; and
a container containing the semiconductor photoelectrode, the counter electrode, and the electrolyte aqueous solution.

11. A method for generating hydrogen, the method comprising:
(a) preparing the photoelectrochemical cell according to claim 10 ; and
(b) irradiating the semiconductor photoelectrode included in the photoelectrochemical cell with light to generate hydrogen on the counter electrode included in the photoelectrochemical cell.

12. An energy system, comprising:
the photoelectrochemical cell according to claim 10 ;
a hydrogen reservoir for storing hydrogen generated in the photoelectrochemical cell,
a first pipe for connecting the hydrogen reservoir to the photoelectrochemical cell;
a fuel cell for converting hydrogen stored in the hydrogen reservoir into electric power; and
a second pipe for connecting the fuel cell to the hydrogen reservoir.

Assignees

• Panasonic Ip Man Co Ltd
• Panasonic Corp

Inventors

• Tamura Satoru
• Hato Kazuhito
• Nomura Takaiki
• Suzuki Takahiro
• Kozawa Yoshihiro
• Kikuchi Ryosuke

Classifications

• C25B1/04

  by electrolysis of water · CPC title

• Y02P20/135

  Cross-Sectional Technologies · mapped topic

• Y02E60/368

  Cross-Sectional Technologies · mapped topic

• H01M8/0656 Primary

  by electrochemical means (H01M8/065 takes precedence) · CPC title

• C25B11/0478

  Chemistry & Metallurgy · mapped topic