Reduction electrode and manufacturing method thereof, and electrolytic device

Abstract

A reduction electrode of an embodiment includes a metal base material and a plurality of metal nanowires provided on the metal base material. The plurality of metal nanowires include metal nanowires whose average height of contour curve of surface is 20 nm or less for 50% or more in a number ratio. The plurality of metal nanowires are formed by reducing a plurality of metal oxides each having a nanowire shape formed on the metal base material by an electrochemical reduction method. A reduction process of the metal oxides includes a first process of passing a current under a constant current condition where an absolute value is 5 mA/cm 2 or more through the plurality of metal oxides, and a second process of passing a current under a constant potential condition through the plurality of metal oxides.

What is claimed is: 
     
         1 . A reduction electrode of carbon dioxide, comprising:
 a metal base material; and   a plurality of metal nanowires which are provided on the metal base material,   wherein the plurality of metal nanowires include metal nanowires whose an average height of a contour curve of surface is 20 nm or less for 50% or more in a number ratio.   
     
     
         2 . The reduction electrode of  claim 1 , wherein the metal nanowire contains at least one selected from the group consisting of copper, silver, gold, platinum, palladium, nickel, cobalt, iron, manganese, titanium, cadmium, zinc, indium, gallium, lead, and tin. 
     
     
         3 . The reduction electrode of  claim 1 , wherein the metal nanowire is made up of at least one selected from the group consisting of copper, an alloy containing copper, and an intermetallic compound containing copper. 
     
     
         4 . A method for manufacturing of a reduction electrode, comprising:
 preparing a metal base material;   forming a plurality of metal oxides each having a nanowire shape on the metal base material by thermally oxidizing a surface of the metal base material; and   forming a plurality of metal nanowires on the metal base material by reducing the plurality of metal oxides by an electrochemical reduction method, wherein the plurality of metal nanowires forming includes a first process of passing a current under a constant current condition where an absolute value is 5 mA/cm 2  or more through the plurality of metal oxides, and a second process of passing a current under a constant potential condition through the plurality of metal oxides.   
     
     
         5 . The manufacturing method of  claim 4 , wherein the plurality of metal nanowires include metal nanowires whose an average height of a contour curve of surface is 20 nm or less for 50% or more in a number ratio. 
     
     
         6 . The manufacturing method of  claim 4 , wherein the current in the second process is passed at a potential capable of passing the current whose an absolute value is 5 mA/cm 2  or more. 
     
     
         7 . The manufacturing method of  claim 4 , wherein the metal nanowire contains at least one selected from the group consisting of copper, silver, gold, platinum, palladium, nickel, cobalt, iron, manganese, titanium, cadmium, zinc, indium, gallium, lead, and tin. 
     
     
         8 . The manufacturing method of  claim 4 , wherein the metal nanowire is made up of at least one selected from the group consisting of copper, an alloy containing copper, and an internetallic compound containing copper. 
     
     
         9 . An electrolytic device, comprising:
 an electrolytic tank which stores an electrolytic solution containing water and carbon dioxide;   the reduction electrode according to  claim 1  immersed in the electrolytic solution and producing a carbon compound by reducing the carbon dioxide; and   an oxidation electrode immersed in the electrolytic solution and producing oxygen by oxidizing the water.   
     
     
         10 . The electrolytic device of  claim 9 , wherein an organic compound is mainly produced as the carbon compound. 
     
     
         11 . The electrolytic device of  claim 9 ,
 wherein the electrolytic solution contains at least one anion selected from the group consisting of hydrogen carbonate ion, chloride ion, and bromide ion, and   wherein ethanol is mainly produced as the carbon compound.   
     
     
         12 . The electrolytic device of  claim 9 ,
 wherein the electrolytic solution contains iodide ion as anion, and   wherein formic acid is mainly produced as the carbon compound.   
     
     
         13 . The electrolytic device of  claim 11 , wherein a concentration of the anion in the electrolytic solution is 0.5 M or more. 
     
     
         14 . The electrolytic device of  claim 11 , wherein the electrolytic solution contains potassium ion as cation.