Photocatalyst electrode and method for producing photocatalyst electrode

Patent metadata

Field	Value
Publication number	US-2021238758-A1
Application number	US-201917053500-A
Country	US
Kind code	A1
Filing date	Apr 26, 2019
Priority date	May 7, 2018
Publication date	Aug 5, 2021
Grant date	—

Abstract

The present invention is to provide a photocatalyst electrode less likely to suffer from peeling of hematite-based crystal particles from a substrate and having higher catalytic activity than ever before. A method for producing a photocatalyst electrode includes: an in-process particle of heating a raw material solution to form in-process particles, the raw material solution including a raw material solvent and a hematite raw material dispersed therein, the in-process particle forming step including heating the raw material solution in a closed vessel for more than 12 hours; and a burning step of burning the in-process particles. In this way, a photocatalyst electrode with high catalytic activity can be produced.

First claim

1 - 21 . (canceled)

22 . A photocatalyst electrode comprising:
a substrate; and a plurality of hematite-based crystal particles stacked on a first main surface of the substrate, wherein the plurality of hematite-based crystal particles have a spherical shape or a shape with rounded corners and form a hematite layer covering the first main surface of the substrate, wherein the plurality of hematite-based crystal particles include a first and a second hematite-based crystal particles, the first and the second hematite-based crystal particles adjacently located, wherein a part of an outer surface of the first hematite-based crystal particle is fixed to an outer surface of the second hematite-based crystal particle, and wherein the first hematite-based crystal particle has a cavity inside the particle.

23 . The photocatalyst electrode according to claim 22 , wherein the first hematite-based crystal particle and the second hematite-based crystal particle are fixed to each other in a direction intersecting a direction orthogonal to the first main surface.

24 . The photocatalyst electrode according to claim 22 ,
wherein the plurality of hematite-based crystal particles include a third hematite-based crystal particle adjacent to the first hematite-based crystal particle, and wherein the outer surface of the first hematite-based crystal particle is fixed to a part of an outer surface of the third hematite-based crystal particle at a part different from the part where the first hematite-based crystal particle is fixed to the second hematite-based crystal particle.

25 . The photocatalyst electrode according to claim 22 , wherein the first hematite-based crystal particle has two or more cavities inside the particle.

26 . The photocatalyst electrode according to claim 22 , wherein the cavity communicates outside.

27 . The photocatalyst electrode according to claim 22 , wherein in the hematite layer, four or more cavities provided in the hematite-based crystal particles exist in an area of 500 nm square on a cross-section orthogonal to the first main surface of the substrate.

28 . The photocatalyst electrode according to claim 22 , wherein the hematite layer has a gap extending from the outer surface toward the substrate through spaces between the hematite-based crystal particles.

29 . The photocatalyst electrode according to claim 22 ,
wherein the plurality of hematite-based crystal particles constitute a crystal aggregation, and wherein the crystal aggregation has a hole formed at an interface between adjacent hematite-based crystal particles.

30 . The photocatalyst electrode according to claim 22 , wherein the hematite-based crystal particles are doped with titanium.

31 . The photocatalyst electrode according to claim 22 , wherein the hematite layer has an average thickness of 1.0 μm or more.

32 . The photocatalyst electrode according to claim 22 ,
wherein there is a difference between a number average particle diameter of the hematite-based crystal particles observed with a scanning electron microscope and a crystallite diameter calculated from the Scherrer formula on the basis of half width of a diffraction peak in X-ray diffraction measurement, and wherein a ratio of the number average particle diameter of the hematite-based crystal particles to the crystallite diameter is 3 or more and 20 or less.

33 . The photocatalyst electrode according to claim 22 ,
wherein the substrate is a transparent conductive substrate having a transparent conductive layer laminated on a transparent substrate, wherein the transparent conductive layer has irregularities on a surface thereof, and wherein the plurality of hematite-based crystal particles include a hematite-based crystal particle that has a particle diameter smaller than a depth of a recessed section of the transparent conductive layer and that is fixed to the transparent conductive layer in the recessed section.

34 . The photocatalyst electrode according to claim 22 , wherein when the photocatalyst electrode is immersed in water together with a counter electrode, the water is oxidized with irradiation of light.

35 . A photocatalyst electrode comprising:
a substrate; and a plurality of hematite-based crystal particles stacked on a first main surface of the substrate, wherein the plurality of hematite-based crystal particles form a hematite layer covering the first main surface of the substrate, wherein the hematite-based crystal particles each include a plurality of crystalline particles aggregated therein and fixing together in a planar shape, wherein there is a difference between a number average particle diameter of the hematite-based crystal particles observed with a scanning electron microscope and a crystallite diameter calculated from the Scherrer formula on the basis of half width of a diffraction peak in X-ray diffraction measurement, wherein a number average particle diameter of the hematite-based crystal particles is 200 nm or less, and
wherein the crystallite diameter is 25 nm or less.

36 . A method for producing a photocatalyst electrode, the photocatalyst electrode comprising:
a substrate; and a plurality of hematite-based crystal particles stacked on a first main surface of the substrate, the method comprising: an in-process particle forming step of heating a raw material solution to form in-process particles, the raw material solution including a raw material solvent and a hematite raw material dispersed therein, the in-process particle forming step including heating the raw material solution in a closed vessel for more than 12 hours at a temperature equal to or higher than a boiling point of the raw material solvent; a coating step of dispersing the in-process particles in a dispersion solvent to form a dispersion solution and coating the substrate with the dispersion solution; and a burning step of burning the in-process particles with which the substrate is coated in the coating step.

37 . A method for producing a photocatalyst electrode, the photocatalyst electrode comprising:
a substrate; and a plurality of hematite-based crystal particles stacked on a first main surface of the substrate, the method comprising: an in-process particle forming step of heating a raw material solution to form in-process particles, the raw material solution including a raw material solvent and a hematite raw material dispersed therein, the in-process particle forming step including heating the raw material solution in a closed vessel for more than 12 hours at a temperature equal to or higher than a boiling point of the raw material solvent; and a burning step of burning the in-process particles, wherein the in-process particle forming step includes: introducing the raw material solution into the closed vessel; and heating the substrate in the closed vessel in a state that the substrate is partially or totally immersed in the raw material solution, and wherein the burning step includes: taking out the substrate from the raw material solution; and burning the substrate outside the closed vessel.

38 . The method according to claim 36 , wherein the hematite raw material includes a titanium-containing compound.

39 . The method according to claim 36 , wherein the raw material solvent is alcohol.

40 . The method according to claim 37 , wherein the raw material solvent is water.

Assignees

• Univ Kobe Nat Univ Corp
• Kaneka Corp

Inventors

• Tachikawa Takashi
• Tozawa Tomokazu

Classifications

• B01J35/77

  Compounds characterised by their crystallite size · CPC title

• B01J2235/15

  X-ray diffraction · CPC title

• B01J2235/30

  Scanning electron microscopy; Transmission electron microscopy · CPC title

• B01J35/40

  characterised by dimensions, e.g. grain size (in a colloidal state B01J35/23; crystallite size B01J35/77) · CPC title

• B01J35/51

  Spheres · CPC title