Semiconductor photocatalyst and artificial photonic synthesis device having the same

Patent metadata

Field	Value
Publication number	US-9951429-B2
Application number	US-201514748399-A
Country	US
Kind code	B2
Filing date	Jun 24, 2015
Priority date	Aug 1, 2014
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A semiconductor photocatalyst includes first and second layers made of first and second materials, respectively. Band gaps of the first and second materials are equal to or smaller than 1.5 eV and 2.5 eV, respectively. A lower electric potential of a conduction band of the second material is disposed on a positive side from the first material. An upper electric potential of a valence band of the second material is disposed on a positive side from the first material and from an oxidation electric potential of water when the first and second layers are bonded to each other in the hetero junction manner. The lower electric potential of the conduction band of the first layer is disposed on a negative side from a reduction electric potential of hydrogen when the first and second layers are bonded to each other in the hetero junction manner.

First claim

What is claimed is:

1. A semiconductor photocatalyst comprising:
a first layer made of a first material having a band gap equal to or smaller than 1.5 eV; and
a second layer made of a second material having a band gap equal to or smaller than 2.5 eV, wherein
the band gap of the second material is larger than the first material,
a lower electric potential of a conduction band of the second material is disposed on a positive side from a lower electric potential of a conduction band of the first material,
an upper electric potential of a valence band of the second material is disposed on a positive side from an upper electric potential of a valence band of the first material,
the first layer and the second layer are bonded to each other in a hetero junction manner,
the upper electric potential of the valence band of the second layer is disposed on a positive side from an oxidation electric potential of water under a condition that the first layer and the second layer are bonded to each other in the hetero junction manner,
the lower electric potential of the conduction band of the first layer is disposed on a negative side from a reduction electric potential of hydrogen under a condition that the first layer and the second layer are bonded to each other in the hetero junction manner,
the conduction band of the first material is bent to the negative side toward a hetero junction,
the valence band of the first material is bent to the negative side toward the hetero junction,
the conduction band of the second material is bent to the positive side toward the hetero junction, and
the valence band of the second material is bent to the positive side toward the hetero junction.

2. The semiconductor photocatalyst according to claim 1 ,
wherein the first material is a first semiconductor material having a P conductive type,
wherein the second material is a second semiconductor material having a N conductive type, and
wherein the hetero junction between the first layer and the second layer provides a tunnel diode.

3. The semiconductor photocatalyst according to claim 2 ,
wherein the first layer includes a first high impurity concentration layer, which is disposed on the hetero junction side,
wherein the first high impurity concentration layer has an impurity concentration higher than a part of the first layer disposed apart from the hetero junction,
wherein the second layer includes a second high impurity concentration layer, which is disposed on the hetero junction side, and
wherein the second high impurity concentration layer has an impurity concentration higher than a part of the second layer disposed apart from the hetero junction.

4. The semiconductor photocatalyst according to claim 1 ,
wherein the first layer includes a N conductive type layer and a P conductive type layer, which provide a PN junction,
wherein the P conductive type layer is disposed on a second layer side, and
wherein the N conductive type layer is disposed on a side opposite to the second layer side.

5. The semiconductor photocatalyst according to claim 1 , wherein
the first material is silicon, and
the second material is 3C—SiC.

6. The semiconductor photocatalyst according to claim 5 , wherein
the first layer of silicon has a 111-plane surface in which the silicon has a 111-plane orientation crystal structure located at the hetero junction between the silicon of the first layer and the 3C—SiC of the second layer.

7. The semiconductor photocatalyst according to claim 1 , further comprising:
a catalyst promoting material arranged on at least one of the first layer and the second layer, wherein
the catalyst is made of nickel oxide, rhodium oxide, ruthenium oxide, cobalt oxide, iridium oxide, or platinum.

8. The semiconductor photocatalyst according to claim 1 , wherein
the first layer includes an N conductive type layer and a P conductive type layer,
the P conductive type layer is bonded to the second layer, and
a part of the N conductive type layer is exposed to an external environment.

9. The semiconductor photocatalyst according to claim 1 , wherein
the first layer includes an N conductive type layer, a P conductive type layer, and a PN junction formed between the N conductive type layer and the P conductive type layer,
the conduction band of the first material is bent in the negative direction towards both the PN junction formed between the N conductive type layer and the P conductive type layer and the hetero junction between the first material and the second material, and
the valence band of the first material is bent in the negative direction towards both the PN junction formed between the N conductive type layer and the P conductive type layer and the hetero junction between the first material and the second material.

10. The semiconductor photocatalyst according to claim 1 , wherein
a bandgap between the conduction band of the second material and the valance band of the first material at the hetero junction is equal to, or less than, 0.2 eV.

11. An artificial photonic synthesis device comprising:
a semiconductor photocatalyst according to claim 1 ; and
a casing that accommodates water, in which the semiconductor photocatalyst is dipped,
wherein, when a sun light is irradiated on the semiconductor photocatalyst from a second layer side, the photocatalyst promotes to produce oxygen and hydrogen using the water, or produce carbon hydride using the water and carbon dioxide.

12. The artificial photonic synthesis device according to claim 11 , further comprising:
an anode electrode including the first layer and the second layer, which are arranged in the semiconductor photocatalyst;
a cathode electrode electrically connected to the first layer in the anode electrode;
a wiring electrically connecting the anode electrode and the cathode electrode; and
an electrolyte film that partitions the casing into a first casing and a second casing,
wherein the first casing accommodates the anode electrode,
wherein the second casing accommodates the cathode electrode,
wherein the oxygen is produced on the anode electrode, and
wherein at least one of the hydrogen or the carbon hydride is produced on the cathode electrode.

13. An artificial photonic synthesis device comprising:
a semiconductor photocatalyst according to claim 4 ;
a casing that accommodates water, in which the semiconductor photocatalyst is dipped;
an anode electrode including the first layer and the second layer, which are arranged in the semiconductor photocatalyst;
a cathode electrode electrically connected to the first layer in the anode electrode;
a wiring electrically connecting the anode electrode and the cathode electrode; and
an electrolyte film that partitions the casing into a first casing and a second casing,
wherein the first layer includes a N conductive type layer and a P conductive type layer, which provide a PN junction,
wherein the P conductive type layer is disposed on a second layer side,
wherein the N conductive type layer is disposed on a side opposite to the second layer side,
wherein the first casing accommodates the anode electrode,
wherein the second casing accommodates the cathode electrode,
wherein, when a sun light is irradiated on the anode electrode from a second layer side, the oxygen is produced on the anode electrode using the water, and at least one of the hydrogen or the carbon hydride is produced on the cathode electrode using the water and carbon dioxide.

14. The artificial photonic synthesis device according to claim 13 , further comprising:
a pad,
wherein the P conductive type layer is dis

Assignees

• Denso Corp

Inventors

• Yamaguchi Hitoshi

Classifications

• C25B11/0447

  Chemistry & Metallurgy · mapped topic

• C25B9/08

  Chemistry & Metallurgy · mapped topic

• C25B1/003 Primary

  Chemistry & Metallurgy · mapped topic

• Y02E60/368

  Cross-Sectional Technologies · mapped topic

• C25B13/04

  characterised by the material · CPC title