CN114787423A

CN114787423A - Electrolysis electrode

Info

Publication number: CN114787423A
Application number: CN202080082972.3A
Authority: CN
Inventors: M·埃尔曼; 神农奎敏; 足立博史
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2019-12-13
Filing date: 2020-09-18
Publication date: 2022-07-22
Also published as: JP7153887B2; WO2021117311A1; EP4074864A1; US20230008403A1; JPWO2021117311A1

Abstract

An electrolytic electrode having improved durability is provided. The electrolytic electrode (1) comprises a conductive substrate (2), a catalyst layer (4) and a tantalum oxide layer (5). The conductive substrate (2) comprises at least titanium. The catalyst layer (4) is disposed on the conductive substrate (2). The catalyst layer (4) contains platinum and iridium oxide. A tantalum oxide layer (5) is provided on the catalyst layer (4). In the electrolysis electrode (1), the catalyst layer (4) is partially exposed.

Description

Electrolysis electrode

Technical Field

The present disclosure relates to electrolytic electrodes, and in particular to electrolytic electrodes comprising iridium oxide and platinum.

Background

There is known a technique for producing hypochlorous acid by causing a reaction between water and chlorine gas generated by electrolysis of a dilute sodium chloride solution obtained by adding a salt to tap water (patent document 1).

Patent document 1 discloses an electrode for electrolysis, which includes: an electrode body made of titanium or a titanium alloy; a titanium oxide layer provided on the electrode body; an intermediate oxide layer disposed on the titanium oxide layer, the intermediate oxide layer being made of a composite material containing 3 to 30 mol% of iridium oxide and 70 to 97 mol% of tantalum oxide, in terms of metal; and a composite body disposed on the intermediate oxide layer, the composite body containing, in metal terms, 2 to 35 mol% rhodium oxide, 30 to 80 mol% iridium oxide, 6 to 35 mol% tantalum oxide, and 12 to 62 mol% platinum.

It is desired to improve the durability of the electrolytic electrode.

Reference list

Patent literature

Patent document 1: JP 2009-52069A

Disclosure of Invention

It is an object of the present disclosure to provide an electrolytic electrode having improved durability.

An electrolysis electrode according to one aspect of the present disclosure includes a conductive substrate, a catalyst layer, and a tantalum oxide layer. The conductive substrate comprises at least titanium. The catalyst layer is disposed on a conductive substrate. The catalyst layer comprises platinum and iridium oxide. The tantalum oxide layer is disposed on the catalyst layer. In the electrolysis electrode, the catalyst layer is partially exposed.

Drawings

FIG. 1A is a cross-sectional view of an electrolysis electrode according to one embodiment;

FIG. 1B is a schematic view of a main part of an electrolysis electrode;

FIG. 2 is a schematic view of particles contained in a catalyst layer of an electrolysis electrode;

fig. 3A to 3D are sectional views showing respective steps in the manufacturing method of the electrolytic electrode;

FIG. 4 is a sectional view of an electrolysis electrode according to comparative example 2; and

fig. 5 is a graph of the results of durability tests performed on the electrolytic electrode according to the example of the embodiment, the electrolytic electrode according to comparative example 1, and the electrolytic electrode according to comparative example 2.

Detailed Description

Fig. 1A, 1B, 2, 3A to 3D, and 4 described in the following embodiments and the like are schematic diagrams, and the size ratio and the thickness ratio of components in the drawings do not necessarily reflect an actual size ratio.

(embodiments)

The electrolytic electrode 1 according to the embodiment will be described below with reference to fig. 1A to 3D.

(1) Overview

The electrolysis electrode 1 is an electrode for generating chlorine gas by electrolyzing brine. In this case, the brine is, for example, a sodium chloride solution. Assuming that the electrolysis electrode 1 is used for the application of electrolysis brine, and in this case, the electrolysis electrode 1 is used as an anode, a direct current voltage is applied from a power supply to a cathode and the anode, thereby electrolyzing a sodium chloride solution to generate chlorine gas, and hypochlorous acid water can be generated by the reaction of the chlorine gas with water.

(2) Component of an electrolysis electrode

As shown in fig. 1A, the electrolysis electrode 1 includes a conductive substrate 2, a catalyst layer 4, and a tantalum oxide layer 5. A catalyst layer 4 is provided on the conductive substrate 2. A tantalum oxide layer 5 is provided on the catalyst layer 4. The electrolysis electrode 1 also comprises an intermediate layer 3 arranged between the electrically conductive substrate 2 and the catalyst layer 4.

These components of the electrolysis electrode 1 will be described in more detail below.

(2.1) conductive substrate

The conductive substrate 2 has a first main surface 21 and a second main surface 22 opposite to the first main surface 21. The shape of the conductive substrate 2 in plan view (the outer peripheral shape of the conductive substrate 2 when viewed in the thickness direction defined with respect to the conductive substrate 2) is a rectangle. The thickness of the conductive substrate 2 is, for example, 100 μm or more and 2mm or less, for example, 500 μm. The conductive substrate 2 has dimensions of, for example, 25mm × 60mm in plan view.

The conductive substrate 2 comprises at least titanium. The conductive substrate 2 is, for example, a titanium substrate. The material of the conductive substrate 2 is titanium or an alloy including titanium as a main component (hereinafter referred to as a titanium alloy). The titanium alloy is, for example, a titanium-palladium alloy, a titanium-nickel-ruthenium alloy, a titanium-tantalum alloy, a titanium-aluminum alloy, or a titanium-aluminum-vanadium alloy.

The first major surface 21 of the conductive substrate 2 is preferably a rough surface to improve adhesion to the intermediate layer 3. In the electrolytic electrode 1 according to this embodiment, the first main surface 21 of the conductive substrate 2 is roughened before the intermediate layer 3 is provided. As for the surface roughness of the first main surface 21 of the conductive substrate 2, the arithmetic average roughness Ra is, for example, 0.7 μm, and the maximum height Rz is 7 μm. The arithmetic average roughness Ra and the maximum height Rz are specified in, for example, JIS B0601-2001 (ISO 4287-1997). The arithmetic average roughness Ra and the maximum height Rz are values measured by, for example, a cross-sectional Scanning Electron Microscope (SEM) image.

(2.2) intermediate layer

The intermediate layer 3 is arranged on the conductive substrate 2. More specifically, the intermediate layer 3 is provided on the first main surface 21 of the conductive substrate 2. The electrolytic electrode 1 has an interface between the conductive substrate 2 and the intermediate layer 3. The intermediate layer 3 is preferably made of a material having corrosion resistance to brine and chlorine gas and having higher corrosion resistance than the conductive substrate 2. Further, in order to increase the conductivity of the electrolytic electrode 1 as a whole, the material for the intermediate layer 3 is preferably a conductive material having high conductivity. The material of the intermediate layer 3 is, for example, a transition metal or a mixture including a transition metal, and is, for example, platinum; mixtures of tantalum, platinum and iridium; iridium; iridium oxide; or nickel. The material for the intermediate layer 3 is, for example, platinum. The thickness of the intermediate layer 3 is, for example, 0.2 μm or more and 5 μm or less, for example, 0.6 μm.

(2.3) catalyst layer

The catalyst layer 4 is provided on the intermediate layer 3. The electrolysis electrode 1 has an interface between the catalyst layer 4 and the intermediate layer 3. That is, the catalyst layer 4 is provided on the intermediate layer 3 on the conductive substrate 2.

The catalyst layer 4 contains platinum and iridium oxide. As shown in fig. 1B, the catalyst layer 4 is a porous layer including a plurality of composite particles 41 and a plurality of pores 42. As shown in fig. 2, each of the plurality of composite particles 41 includes a platinum particle 411 and an iridium oxide particle 412. In each of the plurality of composite particles 41, for example, a plurality of iridium oxide particles 412 are bonded to one platinum particle 411. In the catalyst layer 4, iridium oxide is dispersed by platinum. Iridium oxide is used as a catalyst for producing chlorine. In catalyst layer 4, the molar ratio of platinum to iridium oxide is, for example, but not limited to, 8: 5. In order to suppress agglomeration of iridium with time when the electrolytic electrode 1 is used, the molar amount of iridium oxide is preferably less than or equal to the molar amount of platinum. In addition to platinum and iridium oxide, the catalyst layer 4 may also include iridium. In this case, each of the composite particles 41 may include at least one iridium particle bonded to the platinum particle 411 in addition to the iridium oxide particle 412. Further, in the catalyst layer 4, the platinum particles 411 may be bonded to each other. The bonding state in the catalyst layer 4 is not particularly limited.

Catalyst layer 4 has a plurality of concave portions 45 recessed from main surface 40 on the side of catalyst layer 4 opposite to conductive substrate 2. In the electrolysis electrode 1, the catalyst layer 4 is partially exposed in the plurality of recesses 45. Each of the plurality of recesses 45 is, for example, a crack formed in the catalyst layer 4. More specifically, each of the plurality of recesses 45 is a crack that is linear in a thickness direction defined with respect to the catalyst layer 4 in a plan view. The plurality of cracks (recesses 45) have different shapes. Further, each crack may be formed in the thickness direction defined with respect to the catalyst layer 4, or may have a bend in the thickness direction defined with respect to the catalyst layer 4.

The depth of each of the plurality of concave portions 45 is, for example, 0.1 μm or more. The depth of each of the plurality of recesses 45 may be a depth reaching the intermediate layer 3, or may be a depth not reaching the intermediate layer 3. In the electrolytic electrode 1 according to this embodiment, the plurality of recesses 45 do not extend through the intermediate layer 3, and the entire first main surface 21 of the conductive substrate 2 is covered with the intermediate layer 3. The width of each of the plurality of concave portions 45 is greater than or equal to 0.1 μm and less than or equal to 10 μm, and preferably greater than or equal to 0.3 μm and less than or equal to 3 μm in a plan view in the thickness direction defined with respect to the conductive substrate 2. The width of each concave portion 45 is an opening width in a short direction (a direction orthogonal to the length direction) on the main surface 40 of the catalyst layer 4 in a plan view in the thickness direction defined with respect to the conductive substrate 2. In a plan view in the thickness direction defined with respect to the conductive substrate 2, the length of each of the plurality of concave portions 45 is shorter than the length of each side of the conductive substrate 2.

The thickness of the catalyst layer 4 is, for example, 0.1 μm to 10 μm.

Further, in a plan view in the thickness direction defined with respect to the conductive substrate 2, the percentage of the S2 ratio (S1+ S2) is, for example, higher than or equal to 5% and lower than or equal to 50%, where S1 is the area of the main surface 40 of the catalyst layer 4, and S2 is the total area of the opening areas of the plurality of recesses 45 in the main surface 40 of the catalyst layer 4. The percentage of S2 to (S1+ S2) is preferably greater than or equal to 5% to improve the efficiency of chlorine production. Further, the percentage of the S2 ratio (S1+ S2) is preferably less than or equal to 50%, more preferably less than or equal to 20%, in order to suppress, for example, peeling of the catalyst layer 4. That is, the percentage of S2 to (S1+ S2) is more preferably higher than or equal to 5% and lower than or equal to 20%.

(2.4) tantalum oxide layer

The tantalum oxide layer 5 has a function of suppressing elution of iridium oxide from the catalyst layer 4.

As shown in fig. 1B, tantalum oxide layer 5 has a first portion 51 provided on main surface 40 of catalyst layer 4 and a second portion 52 provided on inner surface 451 of at least one recess 45 of the plurality of recesses 45 in catalyst layer 4. The tantalum oxide layer 5 preferably has a second portion 52 on the inner surface 451 of each of the plurality of recesses 45 in the catalyst layer 4.

The molar amount of tantalum in the tantalum oxide layer 5 and iridium in the iridium oxide is preferably less than or equal to 60% of the total molar amount of iridium and platinum.

(2.5) tantalum oxide

The electrolysis electrode 1 further includes tantalum oxide 43 disposed in at least one hole 42 of the plurality of holes 42, and the tantalum oxide 43 is in contact with the catalyst layer 4. For example, the tantalum oxide 43 is formed when the tantalum oxide layer 5 is formed. The tantalum oxide 43 is in contact with the composite particles 41 of the catalyst layer 4.

(3) Method for producing electrolytic electrode

Referring to fig. 3A to 3D, an example of a manufacturing method of the electrolytic electrode 1 will be described.

In the manufacturing method of the electrolytic electrode 1, the conductive substrate 2 is first prepared, and then the surface roughening step, the intermediate layer forming step, the catalyst layer forming step, and the tantalum oxide layer forming step are sequentially performed.

The surface roughening step includes, for example, immersing the conductive substrate 2 in an aqueous oxalic acid solution, thereby roughening the first main surface 21 of the conductive substrate 2 (see fig. 3A). The surface roughening step is not an essential step. Regarding the surface roughness of the first main surface 21 of the conductive substrate 2 after the surface roughening step, the arithmetic average roughness Ra is, for example, 0.7 μm, and the maximum height Rz is 7 μm. The arithmetic average roughness Ra and the maximum height Rz may be values measured with a surface roughness meter of ZygoCo.

The intermediate layer forming step includes forming the intermediate layer 3 on the first main surface 21 of the conductive substrate 2 (see fig. 3B). The intermediate layer 3 is, for example, a platinum layer. The intermediate layer forming step includes applying a solution to be the intermediate layer 3, then performing a heating process, and thereafter baking the solution, thereby forming the intermediate layer 3. The solution is a solution obtained by dissolving a platinum compound in a solvent. The solvent is, for example, a liquid obtained by mixing ethylene glycol monoethyl ether with hydrochloric acid and ethanol. The platinum compound is, for example, but not limited to, chloroplatinic acid, and the platinum compound may be, for example, platinum chloride. The formation method of the intermediate layer 3 is not limited to the above-described example, but may be, for example, a vapor deposition method, a sputtering method, a CVD method, or an electroplating method.

The catalyst layer forming step includes forming a catalyst layer 4 on the intermediate layer 3 (see fig. 3C). The catalyst layer forming step includes a first step and a second step.

The first step of the catalyst layer formation step includes performing at least one application step and at least one drying step, thereby forming a catalyst material layer to be the catalyst layer 4 on the intermediate layer 3 on the conductive substrate 2. The number of times the application step and the drying step are carried out is determined based on, for example, the prescribed thickness of the catalyst layer 4. As for the number of times of carrying out the application step and the drying step, the number of times of carrying out the application step and the drying step increases at least with an increase in the prescribed thickness of the catalyst layer 4. For example, in the catalyst layer forming step, the application step and the drying step are alternately repeated a first prescribed number of times (for example, eight times) one after another, thereby forming a catalyst material layer to be the catalyst layer 4 on the intermediate layer 3 on the conductive substrate 2.

In the first step of the catalyst layer forming step, a solution containing an iridium compound and a platinum compound to be the catalyst layer 4 (hereinafter referred to as a first solution) is directly or indirectly applied onto the intermediate layer 3 on the conductive substrate 2 (the applying step is performed), and then, a heating process (drying step) of drying the first solution by heating under first conditions is performed at least once (for example, eight times), thereby forming a catalyst material layer to be the catalyst layer 4. The first solution is a solution obtained by dissolving a platinum compound and an iridium compound in a solvent (hereinafter referred to as a first solvent). The first solvent is, for example, a liquid obtained by mixing ethylene glycol monoethyl ether with hydrochloric acid and ethanol. The platinum compound is, for example, but not limited to, chloroplatinic acid, and the platinum compound may be, for example, platinum chloride. Chloroplatinic acid is, for example, hydrogen hexachloroplatinate (IV) n hydrate. The iridium compound is, for example, but not limited to, chloroiridic acid, and the iridium compound may be, for example, iridium chloride or iridium nitrate. Chloroiridic acid is, for example, hexachloroiridate (IV) n hydrate. The metal concentration (total concentration of platinum and iridium) of the first solution is, for example, 50 mg/mL. Further, the application amount of the first solution is, for example, 2. mu.L/cm². The first condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature under the first condition is, for example, 100 ℃ to 400 ℃, as a practical matterAn example may be 220 deg.c. Further, the heat treatment time under the first condition is, for example, 5 minutes to 15 minutes, and may be 10 minutes as an example.

In the second step of the catalyst layer forming step, a heat treatment of baking the catalyst material layer under prescribed baking conditions is carried out, thereby forming the catalyst layer 4 and a plurality of cracks (recesses 45) (see fig. 3C). The baking conditions include baking temperature and baking time. The baking temperature is, for example, 500 ℃ to 700 ℃, and 560 ℃ may be mentioned as an example. The baking time is, for example, 5 minutes to 20 minutes, and may be 10 minutes as an example.

The tantalum oxide layer forming step includes forming a tantalum oxide layer 5 on the catalyst layer 4 (see fig. 3D). The tantalum oxide layer forming step includes a first step and a second step.

The first step of the tantalum oxide layer step includes performing at least one application step and at least one drying step, thereby forming a material layer to be the tantalum oxide layer 5 on the catalyst layer 4. The number of times the application step and the drying step are carried out is determined based on, for example, the prescribed thickness of the tantalum oxide layer 5. As to the number of times of performing the applying step and the drying step, the number of times of performing the applying step and the drying step at least increases as the prescribed thickness of the tantalum oxide layer 5 increases. For example, in the tantalum oxide layer forming step, the application step is performed a second specified number of times (e.g., one time), and the drying step is performed a second specified number of times, thereby forming a material layer to be the tantalum oxide layer 5 on the catalyst layer 4.

In the first step of the tantalum oxide layer formation step, a solution including a tantalum compound to be the tantalum oxide layer 5 (hereinafter referred to as a second solution) is applied onto the catalyst layer 4 (i.e., the application step is performed), and then heat treatment (drying step) of drying the second solution by heating under a second condition is performed at least once (for example, once), thereby forming a metal layer to be the tantalum oxide layer 5. The second solution is a solution obtained by dissolving the tantalum compound in a solvent (hereinafter referred to as a second solvent). The second solvent is, for example, a liquid obtained by mixing ethylene glycol monoethyl ether with hydrochloric acid and ethanol. The tantalum compound is, for example and without limitation, tantalum chloride, and the tantalum compound may be, for example, tantalum ethoxide. Metal concentration of the second solution(tantalum concentration) is, for example, 50 mg/L. Further, the application amount of the second solution is, for example, 1. mu.L/cm². The second condition includes a heat treatment temperature and a heat treatment time. The heat treatment temperature in the second condition is, for example, 100 ℃ to 400 ℃, and may be 220 ℃ as an example. Further, the heat treatment time in the second condition is, for example, 5 minutes to 15 minutes, and may be 10 minutes as an example.

In the second step of the tantalum oxide layer formation step, heat treatment for baking the material layer under prescribed baking conditions is performed, thereby forming a tantalum oxide layer 5 (see fig. 3D). The baking conditions include baking temperature and baking time. The baking temperature is, for example, 500 ℃ to 700 ℃, and 560 ℃ may be mentioned as an example. The baking time is, for example, 5 minutes to 20 minutes, and may be 10 minutes as an example.

In the above-described method of manufacturing the electrolytic electrode 1, the tantalum oxide 43 in at least one of the holes 42 in the catalyst layer 4 is formed in the tantalum oxide layer forming step.

(4) Examples and comparative examples

Fig. 5 is a graph of the results of durability tests performed on the electrolytic electrode 1 according to the example of the embodiment, the electrolytic electrode according to comparative example 1, and the electrolytic electrode 1r according to comparative example 2 (see fig. 4).

The electrolytic electrode according to comparative example 1 is different from the electrolytic electrode 1 according to the example in that comparative example 1 does not include the tantalum oxide layer of the electrolytic electrode 1 according to the example. The electrolysis electrode 1r according to comparative example 2 includes 15 tantalum oxide layers 6 and 15 catalyst layers 7 alternately stacked one after another instead of the catalyst layer 4 and tantalum oxide layer 5 of the electrolysis electrode 1 according to the present embodiment. In fig. 4, only three tantalum oxide layers 6 and three catalyst layers 7 are shown. In the electrolysis electrode 1r according to comparative example 2, the total catalyst amount of the 15 catalyst layers 7 was the same as that of the electrolysis electrode 1 according to the example. The catalyst layer 7 contains platinum and iridium oxide. In the electrolysis electrode 1r according to comparative example 2, the composite layer including 15 tantalum oxide layers 6 and 15 catalyst layers 7 had a plurality of cracks.

The durability test is an accelerated test. Carrying out a durability test using the same conditionsThe two electrolysis electrodes 1 (or two electrolysis electrodes 1r) formed below serve as a pair of electrodes, and the pair of electrodes is immersed in brine in an electrolytic bath in a durability test apparatus. In the durability test, polarity inversion was performed every time the pair of electrodes was energized for a predetermined time (3 minutes). In this case, the polarity inversion means that the combination of the anode and the cathode in the pair of electrodes is inverted. In other words, the polarity inversion means that the electrode on the high potential side of the pair of electrodes is changed so that the electrode serving as the anode and the electrode serving as the cathode function as the cathode and the anode, respectively. The electrolytic cell in the durability testing apparatus has a water inlet and a water outlet for brine. In the durability test, brine was added so that the conductivity of the brine in the electrolytic cell was 1650. + -. 165. mu.S/cm. Further, in the durability test, the electrolytic cell in the durability test apparatus was drained while tap water was constantly supplied to the electrolytic cell at a flow rate of 2L/min. The brine supplied to the electrolytic cell in the durability test apparatus is a sodium chloride solution obtained by dissolving salt (sodium chloride) in tap water. The current value of the energization current in the durability test was 400 mA. In order to measure the hypochlorous acid water concentration, the electrode was taken out from the electrolytic bath in the durability test apparatus when measuring the hypochlorous acid water concentration, and the hypochlorous acid water concentration was measured as described below. As the brine in the electrolytic cell for measuring the hypochlorous acid water concentration, a brine produced by dissolving 4.5g of a salt (sodium chloride) in 800mL of pure water was used. The current value of the energization current for measuring the hypochlorous acid water concentration was 400 mA. Further, in the initial aging, the polarity inversion is performed every time the pair of electrodes is energized for a predetermined time (3 minutes), and in this way, the pair of electrodes is energized for a total of 12 minutes. After the initial aging, electrolysis was performed under the same conditions as the initial aging for 12 minutes, and then some of the electrolytic water was taken out every 3 minutes, and the hypochlorous acid water concentration was measured. For hypochlorous acid water concentration, free chlorine concentration (HOCl, OCl) was measured by a bag-type residual chlorine tester (HACH, bag-type colorimeter II 58700-00) based on the DPD method^－). In this case, the polarity inversion means that the combination of the anode and the cathode in the pair of electrodes is inverted. In other words, it is possible to use a single-layer structureThe polarity inversion means that the electrode on the high potential side of the pair of electrodes is changed so that the electrode serving as the anode and the electrode serving as the cathode function as the cathode and the anode, respectively.

The abscissa in fig. 5 represents the durability test time (elapsed time). The ordinate in fig. 5 represents the hypochlorous acid water concentration measured after energization was performed for a unit time (3 minutes). In this case, the chlorine gas generated in the vicinity of the anode contributes to the generation of hypochlorous acid, and therefore, the hypochlorous acid water concentration is basically determined based on the amount of chlorine gas generated per unit time.

As can be seen from fig. 5, in the electrolytic electrode 1 according to the example, the hypochlorous acid water concentration was higher, and the time until the hypochlorous acid water concentration decreased to or below a prescribed value (for example, 5mg/L) was longer (the durability was more improved) than in the electrolytic electrode according to comparative example 1 and the electrolytic electrode 1r according to comparative example 2. Note that the durability is determined based on elution caused by consumption of the catalyst layer 4, peeling of the catalyst layer 4, or the like. In the electrolysis electrode 1r according to comparative example 2, the tantalum oxide layer 6 and the catalyst layer 7 were alternately stacked, and therefore, the conduction path and the gas path were narrow, the amount of chlorine gas generated per unit time was small, and the number of unused active sites was large, and therefore, it was presumed that the electrolysis electrode 1r had a reduced service life. In the electrolytic electrode according to comparative example 1, chlorine gas was more easily generated than in the electrolytic electrode 1r according to comparative example 2, but the catalyst was more likely to be desorbed than in the electrolytic electrode 1 according to example, and therefore, it is presumed that the electrolytic electrode according to comparative example 1 had a shorter service life than the electrolytic electrode 1 according to example. In other words, as can be seen from fig. 5, the electrolysis electrode 1 according to the example was able to generate a larger amount of chlorine gas, and thus had a longer service life than the electrolysis electrode according to comparative example 1 and the electrolysis electrode 1r according to comparative example 2.

(5) Effect

The electrolytic electrode 1 according to the present embodiment includes the tantalum oxide layer 5 provided on the catalyst layer 4 containing platinum and iridium oxide, and the catalyst layer 4 is partially exposed, which results in improved durability. This enables the electrolysis electrode 1 according to this embodiment to enable the catalyst layer 4 to contribute to the generation of chlorine gas, and to have improved durability as compared with the case where the entire major surface 40 of the catalyst layer 4 is in contact with brine. The electrolysis electrode 1 according to the present embodiment includes the tantalum oxide layer 5 and the tantalum oxide 43, which can suppress platinum iridium from being excessively consumed (eluted) from the catalyst layer 4 during use, thereby suppressing a rapid structural change in the catalyst layer 4, and can suppress partial desorption of the catalyst layer 4 and peeling of the catalyst layer 4. Further, in the electrolytic electrode 1 according to this embodiment, agglomeration of iridium can be suppressed.

Further, the electrolysis electrode 1 according to the present embodiment includes the tantalum oxide 43, the tantalum oxide 43 being provided in the plurality of pores 42 in the catalyst layer 4 and being in contact with the catalyst layer 4, which makes it possible to improve the mechanical strength of the catalyst layer 4 and to suppress excessive consumption of iridium oxide, agglomeration of iridium oxide, and the like.

This embodiment is merely an example of various embodiments of the present disclosure. The present embodiment can be variously modified according to design and the like as long as the object of the present disclosure is achieved.

For example, the shape of the conductive substrate 2 in plan view is not limited to a rectangle, but may be, for example, a square.

Further, the catalyst layer 4 is not limited to the porous layer, but may be a non-porous layer.

Further, the plurality of concave portions 45 may have the same shape. In this case, for example, in the manufacturing method of the electrolytic electrode 1, the plurality of concave portions 45 may be formed by an etching technique, a laser processing technique, or the like. Using these techniques provides the following advantages: the degree of freedom in design in terms of the layout and size of the plurality of concave portions 45 increases, and the reproducibility of the formation positions of the plurality of concave portions 45 increases.

Further, in the electrolysis electrode 1, the catalyst layer 4 does not necessarily have a plurality of recesses 45, and in this case, for example, the tantalum oxide layer 5 has at least a plurality of holes (for example, pinholes or cracks) through which the main surface 40 of the catalyst layer 4 is partially exposed.

Further, in the electrolytic electrode 1, even in the case where the catalyst layer 4 has a plurality of recesses 45, the tantalum oxide layer 5 may have a plurality of cracks through which the catalyst layer 4 is partially exposed. In the above-described method for manufacturing the electrolytic electrode 1, if the tantalum oxide layer 5 has a thickness of 50nm or more, cracks through which the catalyst layer 4 is partially exposed may be formed in the tantalum oxide layer 5 in the second step of the tantalum oxide layer forming step. In the above-described method for producing the electrolytic electrode 1, cracks may be formed in the tantalum oxide layer in the second step of the tantalum oxide layer forming step, and cracks continuous with the cracks in the tantalum oxide layer may be formed in the catalyst layer 4. The plurality of holes in the tantalum oxide layer 5 may be formed by an etching technique, a laser processing technique, or the like.

The electrolysis electrode 1 may comprise a titanium oxide layer disposed between the conductive substrate 2 and the intermediate layer 3.

The tantalum oxide layer 5 may include tantalum in addition to tantalum oxide. In other words, the tantalum oxide layer 5 may be a layer including tantalum oxide and tantalum therein.

Further, the electrolysis electrode 1 may further include, on the second main surface 22 of the conductive substrate 2, a structural member similar to the structural member including the intermediate layer 3, the catalyst layer 4 and the tantalum oxide layer 5 at the first main surface 21 side.

(conclusion)

The above embodiments and the like disclose the following aspects in the present specification.

An electrolysis electrode (1) of the first aspect comprises a conductive substrate (2), a catalyst layer (4) and a tantalum oxide layer (5). The conductive substrate (2) contains at least titanium. The catalyst layer (4) is disposed on the conductive substrate (2). The catalyst layer (4) contains platinum and iridium oxide. A tantalum oxide layer (5) is provided on the catalyst layer (4). In the electrolysis electrode (1), the catalyst layer (4) is partially exposed.

The electrolytic electrode (1) of the first aspect has improved durability.

In the electrolysis electrode (1) of the second aspect with reference to the first aspect, the catalyst layer (4) is a porous layer including: a plurality of composite particles (41), each of which includes platinum (platinum particles 411) and iridium oxide (iridium oxide particles 412); and a plurality of holes (42). The electrolysis electrode (1) further comprises tantalum oxide (43) disposed in at least one hole (42) of the plurality of holes (42), and the tantalum oxide (43) is in contact with the catalyst layer (4).

The electrolysis electrode (1) according to the second aspect has increased chlorine gas production efficiency and improved durability.

In an electrolysis electrode (1) of a third aspect referring to the first or second aspect, the catalyst layer (4) has a plurality of recesses (45) recessed from a main surface (40) on a side of the catalyst layer (4) opposite to the conductive substrate (2). The tantalum oxide layer (5) has: a first portion (51) provided on the main surface (40) of the catalyst layer (4); and a second portion (52) provided on an inner surface (451) of at least one recess (45) of the plurality of recesses (45) in the catalyst layer (4).

The electrolysis electrode (1) according to the third aspect has improved chlorine gas production efficiency and improved durability.

In an electrolysis electrode (1) of a fourth aspect referring to the third aspect, the catalyst layer (4) is partially exposed in the plurality of recesses (45).

In the electrolysis electrode (1) of the fourth aspect, the brine easily enters the catalyst layer (4) through the inner surface (451) of the at least one recess (45) in the in-plane direction of the catalyst layer (4), and the inner surface (451) is exposed through the at least one recess (45). Therefore, it is presumed that in the electrolysis electrode (1) of the fourth aspect, the catalyst layer (4) easily contributes to the generation of chlorine gas, which enables improvement in durability.

The electrolytic electrode (1) of the fifth aspect with reference to any one of the first to fourth aspects further includes an intermediate layer (3). The intermediate layer (3) is arranged between the electrically conductive substrate (2) and the catalyst layer (4). The intermediate layer (3) contains platinum.

In the electrolysis electrode (1) of the fifth aspect, peeling of the plurality of catalyst layers (4) is suppressed, which enables improvement in durability.

In an electrolysis electrode (1) of a sixth aspect with reference to the fifth aspect, the electroconductive substrate (2) has a main surface (first main surface 21) facing the catalyst layer (4), and the main surface is a rough surface.

In the electrolysis electrode (1) of the sixth aspect, the adhesion between the conductive substrate (2) and the intermediate layer (3) is improved, which makes it possible to suppress the peeling of the catalyst layer (4) from the conductive substrate (2) side, thereby improving the durability.

List of reference numerals

1 electrolytic electrode

2 conductive substrate

21 first major surface

3 intermediate layer

4 catalyst layer

40 major surface

41 composite particle

411 platinum particles

412 iridium oxide particles

42 holes

43 tantalum oxide

45 concave part

451 inner surface

5 tantalum oxide layer

51 first part

52 second part

Claims

1. An electrolytic electrode, comprising:

a conductive substrate comprising at least titanium;

a catalyst layer disposed on the conductive substrate and comprising platinum and iridium oxide; and

a tantalum oxide layer disposed on the catalyst layer,

the catalyst layer is partially exposed.

2. The electrolysis electrode according to claim 1, wherein the catalyst layer is a porous layer including:

a plurality of composite particles each comprising platinum and iridium oxide, and

a plurality of holes, and

the electrolysis electrode further includes tantalum oxide disposed in at least one of the plurality of pores, the tantalum oxide in contact with the catalyst layer.

3. The electrolysis electrode according to claim 1 or 2, wherein the catalyst layer has a plurality of concave portions that are recessed from a main surface on a side of the catalyst layer opposite the electrically conductive substrate,

the tantalum oxide layer has:

a first portion disposed on the major surface in the catalyst layer, and

a second portion provided on an inner surface of at least one of the plurality of recesses in the catalyst layer.

4. The electrolysis electrode of claim 3, wherein the catalyst layer is partially exposed in the plurality of recesses.

5. The electrolysis electrode according to any one of claims 1 to 4, further comprising:

an intermediate layer disposed between the electrically conductive substrate and the catalyst layer, the intermediate layer comprising platinum.

6. The electrolysis electrode according to claim 5, wherein the electrically conductive substrate has a major surface facing the catalyst layer, the major surface being a roughened surface.