Photochemical electrode and method for producing photochemical electrode

Abstract

A photochemical electrode includes: an electrically conductive layer; and a photoexcitation material layer provided over the electrically conductive layer and including a photoexcitation material, wherein the photoexcitation material layer is one of a first photoexcitation material layer in which a potential of the conduction band minimum decreases from a second surface opposite to a first surface on the side of the electrically conductive layer toward the first surface and a second photoexcitation material layer in which a potential of the valence band maximum decreases from the second surface toward the first surface.

What is claimed is: 
     
         1 . A photochemical electrode comprising:
 an electrically conductive layer; and   a photoexcitation material layer provided over the electrically conductive layer and including a photoexcitation material,   wherein the photoexcitation material layer is one of a first photoexcitation material layer in which a potential of the conduction band minimum decreases from a second surface opposite to a first surface on the side of the electrically conductive layer toward the first surface and a second photoexcitation material layer in which a potential of the valence band maximum decreases from the second surface toward the first surface.   
     
     
         2 . The photochemical electrode according to  claim 1 , wherein the photoexcitation material layer has a multilayer structure including a plurality of layers. 
     
     
         3 . The photochemical electrode according to  claim 2 , wherein the multilayer structure is one of a first multilayer structure in which the potential of the conduction band minimum decreases stepwise from the second surface toward the first surface and a second multilayer structure in which the potential of the valence band maximum decreases stepwise from the second surface toward the first surface. 
     
     
         4 . The photochemical electrode according to  claim 2 , wherein at least one of the plurality of the layers contains a photoexcitation material of a solid solution. 
     
     
         5 . The photochemical electrode according to  claim 4 , wherein the photoexcitation material is a solid solution of MN (M is at least one of Ga, Al, and In) and ZnO. 
     
     
         6 . The photochemical electrode according to  claim 5 , wherein the content of the ZnO in the solid solution is 30 mole percent or more. 
     
     
         7 . A method for producing a photochemical electrode, comprising:
 preparing an electrically conductive layer including a metal or a metal oxide;   forming a first layer by spraying a powder of a first photoexcitation material over the electrically conductive layer; and   forming a second layer by spraying a solid solution of a second photoexcitation material including the first material and a second material at a ratio over the first layer.   
     
     
         8 . The method for producing the photochemical electrode according to  claim 7 , wherein the first material is GaN and the second material is ZnO. 
     
     
         9 . The method for producing the photochemical electrode according to  claim 7 , wherein the spraying is performed by an aerosol-type nanoparticle deposition (NPD) process.