Electrode for electrolysis, and method for producing electrode for electrolysis

Abstract

An electrically conductive substrate contains at least titanium. An intermediate layer is provided on a primary surface of the electrically conductive substrate. A composite layer is provided on the intermediate layer. The composite layer includes tantalum layers and catalyst layers. Each of the catalyst layers contains platinum and iridium. Each of the tantalum layers is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum. The tantalum layers and the catalyst layers are alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate. A bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate is constituted by one tantalum layer of the tantalum layers. A top layer of the composite layer furthest from the electrically conductive substrate is constituted by one catalyst layer of the catalyst layers.

1 . An electrode for electrolysis, comprising:
 an electrically conductive substrate containing at least titanium;   an intermediate layer on a primary surface of the electrically conductive substrate; and   a composite layer on the intermediate layer,   the composite layer including
 a plurality of tantalum layers each of which is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum, and 
 a plurality of catalyst layers each of which contains platinum and iridium, 
   the plurality of tantalum layers and the plurality of catalyst layers being alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate,   a bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate being constituted by one tantalum layer of the plurality of tantalum layers, and   a top layer of the composite layer furthest from the electrically conductive substrate being constituted by one catalyst layer of the plurality of catalyst layers.   
     
     
         2 . The electrode for electrolysis of  claim 1 , wherein
 the composite layer has a main surface away from the intermediate layer,   the electrode for electrolysis has a plurality of recesses recessed from the main surface of the composite layer,   each of the plurality of recesses has a depth which is:
 greater than a distance between the main surface of the composite layer and a catalyst layer, second furthest from the electrically conductive substrate, of the plurality of catalyst layers; and also 
 smaller than or equal to a distance between the main surface of the composite layer and the intermediate layer. 
   
     
     
         3 . The electrode for electrolysis of  claim 2 , wherein
 the depth of each of the plurality of recesses is smaller than or equal to a distance between the main surface and the bottom layer of the composite layer.   
     
     
         4 . The electrode for electrolysis of  claim 2 , wherein
 each of the plurality of recesses is a crack extending linearly in a plan view as seen in the thickness direction.   
     
     
         5 . The electrode for electrolysis of  claim 4 , wherein
 each of the plurality of recesses has a width within a range of 0.3 μm to 3 μm.   
     
     
         6 . The electrode for electrolysis of  claim 4 , wherein
 a percentage of S 2  with respect to S 1 +S 2  falls within a range of 5% to 50%, where S 1  denotes an area of the main surface of the composite layer in the plan view as seen in the thickness direction of the electrically conductive substrate, and S 2  denotes a total area of opening areas of the plurality of recesses in the main surface of the composite layer in the plan view as seen in the thickness direction of the electrically conductive substrate.   
     
     
         7 . The electrode for electrolysis of  claim 6 , wherein
 at least one recess of the plurality of recesses is present in a 0.01 mm 2  square region in the plan view as seen in the thickness direction of the electrically conductive substrate, a total length of each opening edge of the at least one recess present in the 0.01 mm 2  square region being greater than or equal to 1 mm.   
     
     
         8 . The electrode for electrolysis of  claim 1 , wherein
 each of the plurality of catalyst layers is a porous layer.   
     
     
         9 . The electrode for electrolysis of  claim 1 , wherein
 the primary surface of the electrically conductive substrate is uneven.   
     
     
         10 . A method for producing an electrode for electrolysis, comprising:
 an intermediate layer formation process including forming an intermediate layer on a primary surface of an electrically conductive substrate containing titanium; and   a composite layer formation process including forming a composite layer on the intermediate layer, the composite layer having a stacked structure alternating a plurality of tantalum layers and a plurality of catalyst layers one layer by one layer,   each of the plurality of tantalum layers being made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum,   each of the plurality of catalyst layers containing platinum and iridium,   the composite layer formation process including a first process, a second process, and a third process,   the first process including applying a solution containing tantalum onto the intermediate layer and subsequently firing at a first prescribed temperature to form a tantalum layer, of the plurality of tantalum layers, that constitutes a bottom layer of the stacked structure,   the second process including repeating a first step and a second step to form a stacked body serving as a basis of a remaining part, other than the tantalum layer that constitutes the bottom layer, of the stacked structure,
 the first step including applying a solution containing platinum and iridium and subsequently heating and drying at a second prescribed temperature to form a layer serving as a basis of one catalyst layer of the plurality of catalyst layers, 
 the second step including applying a solution containing tantalum and subsequently heating and drying at a third prescribed temperature to form a layer serving as a basis of one, but other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers, 
   the third process including firing the stacked body at a fourth prescribed temperature, which is higher than each of the second prescribed temperature and the third prescribed temperature, to form the plurality of catalyst layers and tantalum layers, other than the tantalum layer that constitutes the bottom layer, of the plurality of tantalum layers together with a plurality of cracks recessed from a main surface of the catalyst layer, the main surface being a surface away from the intermediate layer.   
     
     
         11 . An electrode for electrolysis, comprising:
 an electrically conductive substrate containing at least titanium;   an intermediate layer on a primary surface of the electrically conductive substrate; and   a composite layer on the intermediate layer,   the composite layer including
 a plurality of tantalum layers each of which is made from tantalum oxide, tantalum, or a mixture of tantalum oxide and tantalum, and 
 a plurality of catalyst layers each of which contains platinum and iridium, 
   the plurality of tantalum layers and the plurality of catalyst layers being alternately stacked one layer by one layer in a thickness direction of the electrically conductive substrate,   a bottom layer of the composite layer closest to the primary surface of the electrically conductive substrate being constituted by one tantalum layer of the plurality of tantalum layers,   a top layer of the composite layer furthest from the electrically conductive substrate being constituted by another one tantalum layer of the plurality of tantalum layers,   the composite layer having a main surface away from the intermediate layer,   the electrode for electrolysis having a plurality of recesses recessed from the main surface of the composite layer,   each of the plurality of recesses having a depth such that each of the plurality of recesses is made to go completely through at least one catalyst layer of the plurality of catalyst layers.