Electrode structure, electrolytic cell, electrolytic cell, and method for manufacturing electrolytic cell

Abstract

To provide an electrode structure etc. that can suppress the wear of a catalyst layer of an existing electrode and can maintain the electrolytic performance for a long period of time.SOLUTION: An electrode structure comprises an anode, and an electrolysis electrode arranged on the anode. The electrolysis electrode comprises a conductive substrate, and a catalyst layer arranged on at least one surface of the conductive substrate. A thickness of the electrolysis electrode is 150 μm or more and 1,000 μm or less. A BET specific surface area of the electrolysis electrode is 200 mm2 / mm2 or more and 5,000 mm2 / mm2 or less. A ventilation resistance of the electrolysis electrode is 0.005 kPa g / m or more and 0.350 kPa g / m or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode structure, an electrolytic cell, an electrolytic cell, and a method for manufacturing an electrolytic cell. [Background technology]

[0002] The electrolysis of aqueous alkali metal chloride solutions such as saline and the electrolysis of water (hereinafter collectively referred to as "electrolysis") utilizes a method using an electrolytic cell equipped with a diaphragm, more specifically, an ion exchange membrane or a microporous membrane. This electrolytic cell often contains a large number of electrolytic cells connected in series. Electrolysis is carried out with a diaphragm interposed between each electrolytic cell. In the electrolytic cell, a cathode chamber having a cathode and an anode chamber having an anode are arranged back-to-back via a partition (back panel) or by being pressed together by press pressure, bolting, or the like. Conventionally, the anodes and cathodes used in these electrolytic cells are fixed to the anode and cathode chambers of the electrolytic cell by welding, folding, or other methods, respectively, and then stored and transported to the customer. Meanwhile, the diaphragms are stored and transported to the customer in a state where they are wound up in a polyvinyl chloride pipe or the like. At the customer's site, the electrolytic cells are arranged on the frame of the electrolytic cell, and the diaphragms are sandwiched between the electrolytic cells to assemble the electrolytic cell. In this manner, the electrolytic cells are manufactured and the electrolytic cells are assembled at the customer's site.

[0003] As electrolysis operation continues after starting, various factors cause deterioration of each component, resulting in a corresponding decline in electrolysis performance. Therefore, at some point, each component must be replaced. Conventionally, when an anode or cathode fixed to an electrolytic cell deteriorates, the electrolytic cell is removed from the electrolytic cell, transported to a dedicated factory, and the old electrodes are removed by welding or other fastening methods. New electrodes are then installed in the electrolytic cell, fixed by welding or other methods, transported to the electrolytic factory, and returned to the electrolytic cell. This is a very cumbersome process. In light of this situation, for example, Patent Document 1 proposes the use of electrodes that have a small mass per unit area and can be weakly bonded to diaphragms such as ion exchange membranes and microporous membranes and to deteriorated electrodes. Specifically, the electrodes proposed in Patent Document 1 are capable of bonding to diaphragms and deteriorated electrodes with weak forces, such as the surface tension of water, and are said to be able to improve the performance of deteriorated electrodes to the same level as new ones or even higher, while maintaining the components of the existing electrolytic cell. In this specification, the term "updating" refers to an operation of improving the performance of an existing electrode to a level similar to or higher than that of a new electrode without removing the existing electrode. In addition, in this specification, the term "existing electrode" refers to an "electrode in an electrolytic cell that has already been subjected to electrolysis operation" and refers to an electrode that has inferior electrolytic performance compared to the electrolytic performance that an electrode (a new electrode) can exhibit at the time of assembly of the electrolytic cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 174199 Summary of the Invention [Problem to be solved by the invention]

[0005] When the electrode described in Patent Document 1 is used, for example, to replace an anode, that is, when the electrode described in Patent Document 1 is placed as a new electrode on an existing electrode (existing anode) fixed to an electrolysis cell and electrolysis operation is continued, not only does deterioration of the new electrode progress, but deterioration of the existing electrode also progresses. If deterioration of the existing electrode progresses excessively in this way, there is a problem that electrolysis performance does not fully recover even if the electrode described in Patent Document 1 is replaced with a new one. Here, deterioration of the existing electrode is thought to be mainly due to wear and tear of the catalyst layer in the existing electrode. In other words, there is still room for improvement in the technology described in Patent Document 1 from the perspective of suppressing wear and tear of the catalyst layer in the existing electrode and maintaining electrolysis performance for a longer period of time.

[0006] The present invention has been made in view of the above problems, and has an object to provide an electrode structure or the like that can suppress the wear of the catalyst layer in existing electrodes and maintain electrolysis performance for a long period of time. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by setting the thickness, air flow resistance, and BET specific surface area of ​​the electrode for electrolysis within each of predetermined ranges, and have thus completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] An electrode structure including an anode and an electrode for electrolysis disposed on the anode, the electrode for electrolysis comprises a conductive substrate and a catalyst layer disposed on at least one surface of the conductive substrate; The thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less, The BET specific surface area of ​​the electrode for electrolysis is 200 mm 2 / mm 2 More than 5000mm 2 / mm 2 is as follows: The air resistance of the electrolysis electrode is 0.005 kPa· s / m or more 0.350kPa· s / m or less electrode structure. [2] The catalyst loading of the catalyst layer is 0.050 mol / m 2 More than 2.000mol / m 2 The electrode structure according to [1], [3] The electrode structure according to [1] or [2], wherein the catalyst layer contains a platinum group element. [4] The electrode structure according to any one of [1] to [3], wherein the conductive base material contains titanium. [5] The electrode structure according to any one of [1] to [4], wherein the conductive substrate contains a fibrous metal. [6] The electrode structure according to [5], wherein the wire diameter of the fibrous metal is 10 μm or more and 150 μm or less. [7] The electrode structure according to any one of [1] to [6], wherein the conductive substrate has a porosity of 40% or more and 90% or less. [8] The electrode structure according to any one of [1] to [7], a cathode facing the anode; An electrolysis cell comprising: The electrolysis cell, wherein the electrode for electrolysis functions as an anode electrode. [9] [8] The electrolytic cell according to [8], a diaphragm disposed between the anode and the cathode; An electrolytic cell comprising:

[10] A method for producing a new electrolytic cell from an existing electrolytic cell comprising an anode, a cathode facing the anode, and a diaphragm disposed between the anode and the cathode, comprising: The method includes a step (A) of placing an electrode for electrolysis on an anode in the existing electrolytic cell, the electrode for electrolysis comprises a conductive substrate and a catalyst layer disposed on at least one surface of the conductive substrate; The thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less, The BET specific surface area of ​​the electrode for electrolysis is 200 mm2 / mm 2 More than 5000mm 2 / mm 2 is as follows: The air resistance of the electrolysis electrode is 0.005 kPa· s / m or more 0.350kPa· s / m or less, the electrode for electrolysis functions as an anode, The method for producing an electrolytic cell, wherein the electrode for electrolysis and the anode are electrically connected. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electrode structure or the like that can suppress the depletion of the catalyst layer in an existing electrode and maintain electrolysis performance for a long period of time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 10 is an explanatory diagram showing an example of an opening in an expanded metal. [Figure 2] FIG. 2 is a schematic diagram showing an example of a cross section of the electrolytic cell of the present embodiment. [Figure 3] 10 is a graph showing the relationship between the voltage rise value and the Ru amount observed in a reference example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0012] [Electrode structure] The electrode structure of this embodiment is an electrode structure comprising an anode and an electrode for electrolysis arranged on the anode, wherein the electrode for electrolysis comprises a conductive substrate and a catalyst layer arranged on at least one surface of the conductive substrate, the thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less, and the BET specific surface area of ​​the electrode for electrolysis is 200 mm 2 / mm 2 More than 5000mm 2 / mm 2 or less, and the air flow resistance of the electrode for electrolysis is 0.005 kPa· s / m or more 0.350kPa· s / m or less. Because the electrode structure of this embodiment is configured in this manner, it is possible to suppress wear of the catalytic layer in the existing electrodes and maintain electrolysis performance over the long term. The electrode structure of this embodiment can be said to be an electrode structure that suppresses wear of the catalytic layer in the existing electrodes, particularly when performing the renewal described below, and thereby contributes to maintaining electrolysis performance over the long term.

[0013] (Conductive base material) The conductive substrate is used in a chlorine gas generating atmosphere in a highly concentrated saline solution close to saturation. Therefore, the material of the conductive substrate is preferably a corrosion-resistant valve metal. Examples of the valve metal include, but are not limited to, titanium, tantalum, niobium, and zirconium. Among the valve metals, titanium is preferred from the viewpoints of economy and affinity with the catalyst layer.

[0014] The conductive substrate preferably has a flat shape having holes, and examples thereof include nonwoven fabric, mesh, expanded metal, and punched metal. Here, mesh refers to a wire mesh formed by weaving metal wires, and expanded metal refers to a mesh-like metal plate formed by expanding a metal plate while making staggered cuts using an expander, and then shaping the cuts into a diamond or tortoiseshell shape. In this embodiment, a shape formed of fibrous metal such as nonwoven fabric or mesh is more preferred, and nonwoven fabric is even more preferred. When the conductive substrate contains fibrous metal, the wire diameter of the fibrous metal is preferably 10 μm or more and 150 μm or less, more preferably 15 μm or more and 100 μm or less, and even more preferably 20 μm or more and 50 μm or less, from the viewpoints of surface area and strength. When preparing a conductive substrate as a product, the wire diameter of the fibrous metal may be a known value as is, or may be measured using, for example, an optical microscope.

[0015] The thickness of the conductive base material is not particularly limited as long as it is a value that makes the thickness of the electrode for electrolysis 150 μm or more and 1000 μm or less. From the viewpoint of maintaining long-term electrolysis performance and ensuring ease of renewal, the thickness is preferably 160 μm or more and 800 μm or less, more preferably 180 μm or more and 700 μm or less, and even more preferably 200 μm or more and 500 μm or less. The thickness of the conductive substrate can be measured, for example, based on the method described in the examples below.

[0016] (catalyst layer) In the electrode for electrolysis, a catalyst layer is disposed on at least one surface of the conductive substrate. The catalytic layer in the existing electrode is thought to be gradually worn away due to competition with the electrode for electrolysis, and a lower chlorine generation overvoltage of the catalytic layer in the electrode for electrolysis tends to suppress the electrolytic reaction in the existing electrode and maintain electrolytic performance over the long term. From the above viewpoint, the catalytic layer preferably contains an electrode catalytic material such as a platinum group element. It is more preferable that the platinum group metal element contains ruthenium. From the viewpoint of further reducing the voltage during electrolysis, it is more preferable that ruthenium is contained in the catalytic layer in the form of an oxide. Ruthenium oxides include, but are not limited to, RuO2.

[0017] The catalyst layer may contain only the above-described electrode catalyst material as a constituent element, or may contain other components. Specific examples of other components include, but are not limited to, iridium and titanium. When the catalyst layer of this embodiment contains other components, the content ratio thereof is preferably 0.5 to 1.5 mol of iridium and 1.5 to 2.5 mol of titanium per 1 mol of ruthenium.

[0018] The catalyst layer may be a single layer or may be two or more layers. In either case, the thickness of the catalyst layer in this embodiment is not particularly limited as long as it is a value that makes the thickness of the electrolysis electrode 150 μm or more and 1000 μm or less. However, from the viewpoints of electrolysis performance and economy, it is preferably 0.1 μm or more and 20 μm or less, and more preferably 0.5 μm or more and 10 μm or less. Here, the thickness of the catalyst layer refers to the thickness of a catalyst layer formed on a single fibrous metal, and does not take into account the thickness of a catalyst layer formed across multiple fibrous metals. The thickness of the catalyst layer can be measured by a cross-sectional image taken with a scanning electron microscope or the like.

[0019] The catalyst loading in the catalyst layer of the electrolysis electrode is set to 0.050 mol / m from the viewpoint of lowering the electrolysis voltage and maintaining the electrolysis performance for a long period of time. 2 More than 2.000mol / m 2The catalyst loading is preferably 0.050 mol / m or less. 2 In the above cases, since a sufficient amount of catalyst is supported on the electrode for electrolysis, the electrolysis reaction proceeds preferentially on the electrode for electrolysis, suppressing the electrolysis reaction on the surface of the existing electrode, which tends to suppress the wear of the catalyst coating on the existing electrode. 2 When the catalyst loading is less than 0.100 mol / m, there is no clogging of the electrolysis electrode due to the catalyst layer, the desorption of gas generated by electrolysis is high, and the supply of the electrolyte is high, so that the electrolysis voltage tends to be able to be lowered after renewal. 2 More than 1.800mol / m 2 More preferably, it is 0.160 mol / m or less. 2 More than 1.650mol / m 2 Here, the catalyst loading (mol / m 2 ) means the total amount of catalytic metal elements supported on the conductive substrate per apparent unit area. The catalyst loading can be measured by the method described in the Examples below. The catalyst loading can be adjusted to the above range by, for example, adjusting the concentration of the coating solution or the number of cycles of coating, drying, and baking.

[0020] (Electrode thickness for electrolysis) The electrode for electrolysis is preferably used for the purpose of updating the electrolysis performance by being disposed on an electrode (existing electrode) in an existing electrolysis cell. That is, the electrode structure of this embodiment is preferably an electrode structure in which the electrode for electrolysis is disposed on an anode as the existing electrode. The electrolysis performance can be evaluated based on the level of the electrolysis voltage, and specifically, can be evaluated based on the method described in the examples below. In this embodiment, the existing electrode and the electrode for electrolysis typically function as anodes. The thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less from the viewpoint of maintaining electrolysis performance for a long period of time even after renewal and from the viewpoint of ensuring ease of renewal. A thickness of 150 μm or more ensures a sufficient distance between the reaction field of the electrolysis reaction on the surface of the electrolysis electrode and the existing electrode. The inventors' investigations revealed that if the distance is small, the electrolysis reaction is likely to proceed not only on the surface of the electrolysis electrode but also on the surface of the existing electrode, resulting in a tendency for the catalytic coating on the existing electrode to wear away. Based on this knowledge, the inventors' further investigations revealed that as the wear of the catalytic coating progresses, a voltage increase over time after replacement tends to become more pronounced. Therefore, by making the thickness of the electrolysis electrode 150 μm or more, it becomes possible to maintain electrolysis performance for a long period of time even after replacement. Furthermore, by making the thickness 1000 μm or less, the electrode tends to adhere to the diaphragm and deteriorated electrodes more easily with a weak force such as the surface tension of water, ensuring ease of renewal. From the above viewpoint, the thickness is preferably 160 μm or more and 800 μm or less, more preferably 180 μm or more and 700 μm or less, and even more preferably 200 μm or more and 500 μm or less. The thickness can be measured by the method described in the Examples below. The thickness can be adjusted to the above range by adjusting the thickness of the conductive substrate to be used, for example.

[0021] (BET specific surface area of ​​electrolysis electrode) The BET specific surface area of ​​the electrolysis electrodes is set to 200 mm from the viewpoint of maintaining electrolysis performance for a long period even after renewal and from the viewpoint of sufficiently lowering the electrolysis voltage. 2 / mm 2 More than 5000mm 2 / mm 2 Here, the BET specific surface area is the apparent area of ​​the electrode (mm 2 BET pore surface area (mm 2 ) means The above BET specific surface area is 200mm 2 / mm 2If the electrode surface area is less than 100mV, it suggests that the surface area of ​​the electrode for electrolysis is insufficient. If electrolysis is performed after replacement using such electrodes, the electrolysis reaction will likely proceed on the surface of the existing electrodes, resulting in significant wear of the catalyst coating on the existing electrodes. The above BET specific surface area is 5000mm 2 / mm 2 The fact that the value exceeds 100% suggests that there are many excessively small pores in the electrolysis electrodes. If electrolysis is performed after renewal using such electrodes, the electrolysis voltage will increase. From the above viewpoint, the BET specific surface area is 200 mm 2 / mm 2 More than 5000mm 2 / mm 2 and 700mm 2 / mm 2 Over 4500mm 2 / mm 2 It is preferable that the length is equal to or less than 1000 mm, and more preferably, 1000 mm 2 / mm 2 Over 4000mm 2 / mm 2 The following is the result. The BET specific surface area can be measured by the method described below. The BET specific surface area can be adjusted to fall within the above range, for example, by employing a preferred production method described below.

[0022] (Air flow resistance of electrolysis electrode) The air flow resistance of the electrolysis electrodes is set to 0.005 kPa· from the viewpoint of preventing the accumulation of gas generated during electrolysis and maintaining electrolysis performance over the long term. s / m or more 0.350kPa· s / m or less. Air resistance is 0.005 kPa· s / m or more, it is more strongly suggested that there are no excessively large pores in the electrolysis electrodes, and as a result, the wear of the catalyst coating on the existing electrodes can be further suppressed even after replacement. s / m or less, it is more strongly suggested that the proportion of excessively small pores in the electrode for electrolysis is small, and as a result, an increase in the electrolysis voltage can be more effectively prevented. From the same viewpoint as above, it is more preferably 0.006 kPa· s / m or more 0.3kPa· s / m or less, and more preferably 0.01 kPa· s / m or more 0.1kPa· s / m or less. The airflow resistance can be measured by the method described in the Examples below. The airflow resistance can be adjusted to the above range, for example, by employing a preferred manufacturing method described below.

[0023] (Porosity of conductive substrate) From the viewpoint of preventing retention of gas generated during electrolysis, the porosity of the conductive substrate is preferably 40% or more and 90% or less, more preferably 50% or more and 85% or less, and even more preferably 60% or more and 80% or less. The porosity can be measured based on the method described in the Examples below. The porosity can be adjusted to the above range, for example, by employing a preferred production method described below.

[0024] The porosity is the proportion of voids per unit volume, and in this embodiment, the proportion of the conductive substrate in the apparent volume was calculated using the weight and density as follows: The apparent volume V was calculated from the gauge thickness, width, and length of the conductive substrate, and the weight W was then measured, and the porosity ε was calculated using the following formula: ε=(1-(W / (V×ρ))×100 ρ is the density of the conductive substrate material (g / cm 3 ) For example, the density of nickel is 8.908 g / cm 3 , and 4.506g / cm for titanium 3 is.

[0025] (anode) The anode in the electrode structure of this embodiment is not particularly limited as long as it functions as an anode, and various known electrodes can be used. The catalyst loading amount of the catalyst layer in the anode is not particularly limited, but from the viewpoint of maintaining electrolysis performance for a longer period of time, it is preferably 0.032 mol / m 2 More than 0.167mol / m 2 Preferably, 0.035 mol / m or less 2 More than 0.167mol / m 2 The following is more preferable: The catalyst loading amount can be measured based on the method described in the examples below, and can be adjusted to fall within the above-mentioned range by, for example, adjusting the concentration of the coating solution or adjusting the number of cycles of coating, drying, and baking.

[0026] [Method of manufacturing electrode structure] A method for manufacturing the electrode structure according to this embodiment will be described below. The electrode structure according to this embodiment can be manufactured by disposing the electrode for electrolysis according to this embodiment on an anode. Here, the method for fixing the electrode for electrolysis on the anode is not particularly limited, but from the viewpoint of a more efficient renewal operation, it is preferable to fix the electrode for electrolysis on the anode by using a liquid such as water as an intervening liquid and the surface tension of the liquid. The method for producing the electrode for electrolysis in the present embodiment is not particularly limited, but the electrode for electrolysis can be produced, for example, by preparing a conductive base material in a desired shape and forming a catalyst layer containing an electrode catalyst material such as a ruthenium element on the conductive base material. The conductive substrate is preferably produced as follows. That is, when a mesh is used as the conductive substrate, it can be obtained by weaving together a plurality of metal wires for producing the mesh obtained by various known methods. In this case, for example, by appropriately selecting the wire diameter of the metal wires for producing the mesh and the number of metal wires woven per unit area of ​​the mesh (number of meshes), the BET specific surface area, air flow resistance, and the like of the electrode for electrolysis can be adjusted within appropriate ranges. When a nonwoven fabric is used as the conductive substrate, it can be obtained by using metal wires for producing nonwoven fabrics obtained by various known methods. In this case, the BET specific surface area, air flow resistance, and the like of the electrode for electrolysis can be adjusted within appropriate ranges by, for example, appropriately selecting the wire diameter of the metal wires for producing the nonwoven fabric and the amount of metal wires used per unit area of ​​the nonwoven fabric (basis weight). When a perforated plate such as a punched metal is used as the conductive substrate, the electrode can be obtained by punching holes in a metal plate using a punching press die. In this case, the BET specific surface area, air flow resistance, and the like of the electrode for electrolysis can be adjusted within appropriate ranges by, for example, appropriately selecting the shape and arrangement of the die or the thickness of the metal plate to be used. When an expanded metal is used as the conductive substrate, it can be obtained by expanding a metal flat plate while making slits with an upper blade and a lower blade. In this process, the BET specific surface area, flow resistance, and the like of the electrolysis electrode can be adjusted within an appropriate range by adjusting, for example, the thickness of the metal flat plate, the size of the upper blade, the pressing amount of the upper blade, and the like. In particular, in the case of expanded metal or perforated metal, the BET specific surface area and flow resistance of the electrolysis electrode can be adjusted within the above-mentioned ranges by, for example, adjusting the size and spacing of the openings. The spacing of the openings in expanded metal refers to the center-to-center distance between the holes in the short direction of the mesh (SW) and the center-to-center distance between the holes in the long direction of the mesh (LW) (see Figure 1). The spacing of the openings in perforated metal refers to the center-to-center distance between the nearest holes. The catalyst layer can be formed, for example, as follows. That is, the catalyst layer can be formed on the electrode base material for electrolysis by a coating step of coating a coating liquid containing a catalyst, a drying step of drying the coating liquid, and a pyrolysis step of performing pyrolysis. By repeating the above steps, multiple new catalyst layers may be formed on an existing catalyst layer. Here, from the viewpoint of preventing clogging of the conductive base material by the catalyst, i.e., from the viewpoint of preventing the clogging from excessively affecting the BET specific surface area and through-flow resistance of the electrode for electrolysis, the catalyst loading amount can be adjusted within a suitable range by adjusting the concentration of the coating liquid used in the coating step and the number of times the catalyst layer is formed. Here, thermal decomposition refers to the heating of a precursor metal salt to decompose it into a metal or metal oxide and a gaseous substance. The decomposition products vary depending on the metal species used, the type of salt, the atmosphere in which thermal decomposition is performed, and other factors, but many metals tend to form oxides in an oxidizing atmosphere. In industrial electrode manufacturing processes, thermal decomposition is usually carried out in air, and in many cases, metal oxides or metal hydroxides are formed.

[0027] [Electrolytic cells and electrolytic baths] The electrolytic cell of this embodiment includes the electrode structure of this embodiment. Typically, the electrolytic cell of this embodiment is an electrolytic cell that includes the electrode structure of this embodiment and a cathode facing the anode, and the electrode for electrolysis functions as an anode electrode. In this embodiment, the anode and cathode can each be treated as existing electrodes, and in the electrolytic cell of this embodiment, the electrode for electrolysis of this embodiment is disposed on the anode as the existing electrode, so that the electrolysis performance derived from the anode can be treated as having been updated. The electrolytic cell of this embodiment includes the electrolytic cell of this embodiment. Typically, the electrolytic cell of this embodiment includes the electrolytic cell of this embodiment and a diaphragm disposed between the anode and the cathode. An example of a cross section of the electrolytic cell of this embodiment is shown schematically in FIG. 2.

[0028] The electrolytic cell 200 includes an electrolytic solution 210, a container 220 for storing the electrolytic solution 210, an electrode 230 and a cathode 240 immersed in the electrolytic solution 210, an ion exchange membrane 250, and wiring 260 for connecting the electrode 230 and the cathode 240 to a power source. In the electrolytic cell 200 illustrated in FIG. 2 , the space on the anode side separated by the ion exchange membrane 250 is referred to as the anode chamber, and the space on the cathode side is referred to as the cathode chamber. The electrolytic cell of this embodiment can be used for various electrolysis applications. As a representative example, use of the electrolytic cell for electrolysis of an alkaline chloride aqueous solution will be described below. The electrolytic solution 210 to be supplied to the electrolytic cell of this embodiment can be, for example, a 2.5 to 5.5 normal (N) aqueous solution of alkali chloride such as an aqueous sodium chloride solution (saline) or an aqueous potassium chloride solution in the anode chamber, and a diluted aqueous solution of alkali hydroxide (for example, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, etc.) or water in the cathode chamber.

[0029] The electrode 230 functions as an anode, and the electrode structure of this embodiment can be applied thereto. That is, a laminate of various known anodes (existing anodes) and the electrode for electrolysis of this embodiment can be applied. In this embodiment, an electrode that can function as an electrode for electrolysis alone can be used as the electrode for electrolysis of this embodiment, or two or more such electrodes integrated together using the surface tension of water, etc., can be used as the electrode for electrolysis of this embodiment, from the viewpoint of separately adjusting the thickness, airflow resistance, and / or BET specific surface area of ​​the electrode for electrolysis. In the latter aspect, the number of electrodes that can function as an electrode for electrolysis alone when integrated is not particularly limited, and may be two, three, four, or more. In this case, these multiple electrodes may be the same or different in terms of shape, material, size, etc.

[0030] As the ion exchange membrane 250, for example, a fluororesin membrane having ion exchange groups can be used. Among the ion exchange membranes, it is preferable to use an ion exchange membrane having protrusions (micro-protrusions: delta-shaped) made of a polymer that forms the ion exchange membrane on the anode side of the ion exchange membrane in combination with the electrolysis electrode according to this embodiment as an electrolytic cell. A specific example of such a membrane is "Aciplex" (registered trademark) F6801 (manufactured by Asahi Kasei Corporation).

[0031] The use of a delta-shaped ion exchange membrane promotes the supply of brine between the ion exchange membrane and the anode, which tends to suppress damage to the ion exchange membrane and an increase in the salt concentration in the caustic soda. Combining a delta-shaped ion exchange membrane with the electrolysis electrode according to this embodiment makes it possible to maintain stable electrolysis performance. The method for forming the protrusions is not particularly limited, but can be, for example, formed by the methods described in Japanese Patent Nos. 4,573,715 and 4,708,133.

[0032] The cathode 240 is a cathode for generating hydrogen, and may be an electrode in which a catalyst is coated on a conductive substrate. Known cathodes may be used, and specific examples include a cathode in which a nickel substrate is coated with nickel, nickel oxide, an alloy of nickel and tin, a combination of activated carbon and an oxide, ruthenium oxide, platinum, or the like; a cathode in which a ruthenium oxide coating is formed on a nickel mesh substrate, and the like.

[0033] The configuration of the electrolytic cell of this embodiment is not particularly limited and may be a mono-electrode type or a bi-electrode type. The materials constituting the electrolytic cell are not particularly limited, but for example, the material of the anode chamber is preferably titanium, which is resistant to alkali chlorides and chlorine, and the material of the cathode chamber is preferably nickel, which is resistant to alkali hydroxides and hydrogen.

[0034] The electrode for electrolysis (electrode 230) may be disposed with an appropriate gap between it and the ion exchange membrane 250, or may be disposed in contact with the ion exchange membrane 250 without any problems. The cathode 240 may be disposed with an appropriate gap between it and the ion exchange membrane 250, or may be used without any problems in a contact-type electrolytic cell (zero-gap electrolytic cell) with no gap between it and the ion exchange membrane 250.

[0035] The electrolysis conditions of the electrolytic cell of this embodiment are not particularly limited, and the electrolysis cell can be operated under known conditions. For example, the electrolysis temperature is 50 to 120°C, and the current density is 0.5 to 10 kA / m 2 It is preferable to carry out electrolysis by adjusting the temperature to the range of 100°C to 120°C.

[0036] [Electrolytic cell manufacturing method] The method for producing an electrolytic cell according to this embodiment is not particularly limited as long as the electrode structure according to this embodiment is used, but it is preferable to adopt the following method. That is, a preferred method for producing an electrolytic cell according to this embodiment is a method for producing a new electrolytic cell from an existing electrolytic cell comprising an anode, a cathode facing the anode, and a diaphragm disposed between the anode and the cathode, the method comprising step (A) of disposing an electrode for electrolysis on the anode in the existing electrolytic cell, the electrode for electrolysis comprising a conductive substrate and a catalyst layer disposed on at least one surface of the conductive substrate, the thickness of the electrode for electrolysis being 150 μm or more and 1000 μm or less, and the BET specific surface area of ​​the electrode for electrolysis being 200 mm 2 / mm 2 More than 5000mm 2 / mm 2 The electrolysis electrode functions as an anode, and the electrolysis electrode and the anode are electrically connected to each other.

[0037] In this embodiment, the new electrolytic cell further comprises the electrodes for electrolysis in this embodiment in addition to the components that already function as anodes and cathodes in the existing electrolytic cell. That is, the "electrodes for electrolysis" provided when manufacturing the new electrolytic cell function as anodes and are separate from the anodes in the existing electrolytic cell. In this embodiment, even if the electrolysis performance of the anodes deteriorates during operation of the existing electrolytic cell, the performance of the anodes (i.e., the existing anodes) can be updated by providing electrodes for electrolysis that are separate from these. In this embodiment, the existing electrolytic cell is assumed to be an "electrolytic cell that has already been put into operation," and the new electrolytic cell is assumed to be an "electrolytic cell that has not yet been put into operation." In other words, once an electrolytic cell manufactured as a new electrolytic cell is put into operation, it becomes an "existing electrolytic cell in this embodiment," and this existing electrolytic cell to which the electrolysis electrodes of this embodiment are further provided becomes a "new electrolytic cell in this embodiment." [Example]

[0038] The present embodiment will be described in more detail below based on examples, but the present embodiment is not limited to these examples.

[0039] [Reference example] Three substrate anodes (sample A without a catalytic layer; the amount of Ru in the catalytic layer was 0.52 g / m) were prepared as follows: 2 Sample B: The amount of Ru in the catalyst layer is 1.16 g / m 2A sample C was prepared using the same method. The base anode in this reference example was an anode with a small initial catalyst loading, intended to replicate an existing anode with a depleted catalyst layer. Specifically, a titanium expanded metal with a larger mesh size (LW) of 6 mm, a smaller mesh size (SW) of 3 mm, and a thickness of 1.0 mm was used as the conductive substrate. This expanded metal was fired in air at 540°C for 4 hours to form an oxide film on the surface, followed by acid treatment in 25% by mass sulfuric acid at 85°C for 4 hours. This pretreatment provided fine irregularities on the surface of the conductive substrate, yielding sample A. Sample A, prepared separately in the same manner, was subjected to the following treatment to obtain samples B and C. Next, an aqueous ruthenium chloride solution (Tanaka Kikinzoku K.K., ruthenium concentration 100 g / L) was cooled to below 5°C with dry ice and stirred while titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) was added little by little so that the element ratio (molar ratio) of ruthenium to titanium became 35:65, thereby obtaining Coating Solution 1. This coating solution 1 was poured into a liquid receiving tray, and the first EPDM sponge roll was rotated to absorb and impregnate the coating solution 1. A second EPDM sponge roll was placed in contact with the top of the first sponge roll. Furthermore, a PVC roll was placed in contact with the top of the second sponge roll. Then, the pretreated conductive substrate was passed between the second EPDM sponge roll and the PVC roll and coated. Thereafter, the coated substrate was dried at 50°C for 10 minutes and then baked in the air at 520°C for 10 minutes. The above cycle of roll coating, drying, and calcination was repeated until the desired catalyst loading was reached, forming a blackish-brown catalyst layer on the conductive substrate to produce Samples B and C. The catalyst loadings of these samples were determined based on the method described in Example 1 below, and the catalyst loadings of Samples B and C were each 0.015 mol / m 2 and 0.033 mol / m 2 It was. Electrolytic cells were assembled using various base anodes obtained as described above as follows. Specifically, an electrolytic cell consisted of a titanium anode cell (anode cell) in which the base anode was fixed to the rib of the anode chamber by welding, and a cathode cell having a nickel cathode chamber (cathode cell) in which a cathode was installed, arranged facing each other. The electrolysis electrode (Example 20) described in Patent Document 1 was stacked on the base anode of the anode cell. A pair of gaskets was placed between the cells, and an ion exchange membrane was sandwiched between the pair of gaskets. The anode cell, gasket, ion exchange membrane, gasket, and cathode cell were then tightly attached to prepare an electrolytic cell including an electrolytic cell and an ion exchange membrane. A nickel mesh substrate coated with a catalyst consisting of ruthenium oxide and cerium oxide was used as the cathode. A nickel expanded metal was used as the current collector for the cathode chamber. A mattress woven with thin nickel wires was used as the elastic metal body. The elastic metal mattress was placed on the current collector. A cathode was placed on top of it, and the four corners of the cathode were fixed to the current collector with strings made of Teflon (registered trademark). This electrolysis cell has a zero-gap structure, utilizing the repulsive force of the mattress, which is a metallic elastic body. A rubber gasket made of EPDM (ethylene propylene diene) was used as the gasket. "Aciplex" (registered trademark) F6801 (manufactured by Asahi Kasei Corporation) was used as the ion exchange membrane. The electrolytic cell obtained as above was electrolyzed at a current density of 6 kA / m 2 The electrolysis cell was operated at 40°C for 5 hours, and the voltage was measured after 5 hours. The brine concentration (sodium chloride concentration) in the anode chamber was adjusted to 205 g / L. The sodium hydroxide concentration in the cathode chamber was adjusted to 32 mass%. The temperatures of the anode chamber and cathode chamber were adjusted so that the temperature inside each electrolysis cell was 90°C. The voltage measured for the electrolytic cell using sample C was set as the reference (voltage rise of 0 mV), and the voltage difference from this was used as the voltage rise value for the electrolytic cells using samples A and B. The relationship with the amount of Ru was plotted in Figure 3. From this figure, it can be seen that the voltage tends to rise as the amount of Ru in the base anode decreases.

[0040] (Ru content in catalyst layer) The amount of Ru in the catalytic layer of the base anode was evaluated using a portable X-ray fluorescence analyzer (Rigaku, Niton XL3t800+PM). Specifically, with the base anode welded to the cell, the detector of the analyzer was pressed against the center of the base anode, closest to the ion exchange membrane, and measurements were taken in precious metal mode for 20 seconds. The average of two measurements was used as the measured value of the amount of Ru in the catalytic layer of the base anode.

[0041] (Voltage) The potential difference between the anode and the cathode was measured as the electrolysis voltage. That is, the conductive parts of the anode and the cathode were clamped with two tester clips, and the tester clips were connected to a data logger (TR-V1000, manufactured by KEYCENCE Corporation) to measure the electrolysis voltage.

[0042] [Example 1] (Conductive base material) A nonwoven fabric was obtained using a pure titanium wire with a wire diameter of 20 μm as the conductive substrate. When manufacturing the nonwoven fabric, the conductive substrate had a substrate thickness of 200 μm and a basis weight of 200 g / m 2 The titanium wire was made into a sheet with the goal of 198.49 g / m². The actual thickness of the substrate was measured using a Digimatic Sixness Gauge to measure three uniform points on the surface of the obtained nonwoven fabric, and the average value was used. The substrate thickness was 208 μm. The actual basis weight was obtained by cutting the obtained nonwoven fabric into a piece of 15.0 cm x 15.0 cm, measuring its weight on an electronic balance, and dividing the weight by the area. The basis weight was 198.49 g / m². 2 Furthermore, the porosity ε was measured by the following method and was found to be 79%. ε=(1-(W / (V×ρ))×100 ρ is the density of the conductive substrate material (g / cm 3 ), and in this example, the value for titanium is 4.506 g / cm 3 was used. The apparent volume V was calculated from the gauge thickness, width, and length of the conductive substrate, and the weight W was measured to calculate the porosity ε. The following porosities were calculated in the same manner. When the electrolysis electrode contained multiple conductive substrates, the average value of the porosities measured for each conductive substrate was used. (catalyst layer) Titanium tetrachloride (manufactured by Wako Pure Chemical Industries, Ltd.) was added little by little to an aqueous ruthenium chloride solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) cooled to 5°C or below with dry ice and stirred so that the element ratio (molar ratio) of ruthenium, iridium, and titanium became 25:25:50, and then an aqueous iridium chloride solution (manufactured by Tanaka Kikinzoku Co., Ltd., iridium concentration 100 g / L) was further added to obtain Coating Solution 2, which was an aqueous solution with a total metal concentration of 100 g / L. The nonwoven fabric was coated with Coating Liquid 2 in the same manner as in Reference Example. The coating was then dried at 50°C for 10 minutes and then baked in the air at 440°C for 10 minutes. The cycle of roll coating, drying, and baking was repeated two more times, with the baking temperature increased to 475°C, and finally, baking was further performed at 520°C for 1 hour, thereby forming a black-brown catalyst layer on the conductive substrate. A catalyst layer was further formed on this catalyst layer using Coating Liquid 1 in the same manner as Reference Example, and the resulting electrode was used as the electrolysis electrode of Example 1. The weight (g) of the supported catalyst was calculated by subtracting the weight before coating from the weight after coating. Furthermore, the total amount of substance (mol) of the supported catalytic metal elements was calculated from the catalyst composition. The amount of substance was divided by the apparent area of ​​the electrode for electrolysis to determine the amount of catalyst supported (mol / m 2 The catalyst loading of the catalyst layer consisting of coating liquid 2 and coating liquid 1 was 0.400 mol / m 2 When the electrode for electrolysis includes a plurality of catalyst layers, the total amount of catalyst carried measured for each catalyst layer was used. Using the above electrodes for electrolysis, an electrolysis test was carried out as follows. (Electrolytic Test) The electrolysis cell consisted of a titanium anode cell (anode cell) having an anode chamber in which a base anode was installed, and a cathode cell having a nickel cathode chamber (cathode cell) in which a cathode was installed, arranged facing each other. An electrode for electrolysis was stacked on the base anode of the anode cell. A pair of gaskets was placed between the cells, and an ion exchange membrane was sandwiched between the pair of gaskets. The anode cell, gasket, ion exchange membrane, gasket, and cathode cell were then tightly attached to prepare an electrolysis cell including the electrolysis cell and the ion exchange membrane. The base anode was prepared using the same conductive substrate and coating solution 1 as those used in the reference example, and in the same manner. When this base anode itself was subjected to the measurements described below, it was found to have a thickness of 1.004 mm and a BET specific surface area of ​​82 mm. 2 / mm 2 The amount of Ru in the catalyst layer was 4.06 g / m 2 The catalyst loading was 0.115 mol / m 2 It was. The base anode was fixed to the anode chamber by welding. The electrolysis electrodes were laminated to the base anode using the surface tension of water without welding. A nickel mesh substrate with a ruthenium oxide catalyst coating was used as the cathode. Nickel expanded metal was used as the current collector in the cathode chamber. A mattress woven with thin nickel wires was used as the elastic metal body. The elastic metal mattress was placed on the current collector. The cathode was placed on top of it, and the four corners of the cathode were fixed to the current collector with strings made of Teflon (registered trademark). This electrolysis cell achieved a zero-gap structure by utilizing the repulsive force of the elastic metal mattress. An EPDM (ethylene propylene diene) rubber gasket was used. An "Aciplex" (registered trademark) F6801 (manufactured by Asahi Kasei Corporation) was used as the ion exchange membrane. Electrolysis of salt was carried out using the above electrolytic cell. The brine concentration (sodium chloride concentration) in the anode chamber was adjusted to 205 g / L. The sodium hydroxide concentration in the cathode chamber was adjusted to 32 mass %. The temperatures of the anode chamber and cathode chamber were adjusted so that the temperature in each electrolytic cell was 90°C. The current density was 10 kA / m 2 Brine electrolysis was carried out for 7 days.

[0043] (Electrode thickness for electrolysis) The electrode for electrolysis was cut into a size of 36 mm x 49 mm. Using a Digimatic Sixth Gauge (manufactured by Mitutoyo Corporation, minimum display 0.001 mm), measurements were taken uniformly at three points on the surface, and the average value was calculated. This was the thickness of the electrode for electrolysis (gauge thickness).

[0044] (BET specific surface area of ​​electrolysis electrode) The BET specific surface area of ​​the electrolysis electrode was measured using the multipoint BET method based on JIS Z 8830:2001, Method for measuring the specific surface area of ​​powders (solids) by gas adsorption. Krypton was used as the adsorption gas. The multipoint BET measurement was carried out in accordance with "6. Procedure" of the JIS. The specific surface area was calculated in accordance with "7.2. Multipoint method." Specifically, the electrolysis electrode (approximately 1 g) obtained in each example was placed in a glass tube and degassed under vacuum at approximately 100 mTorr for 18 hours. The adsorption isotherm was then measured at -196°C using krypton gas as the adsorption gas using a multi-sample high-performance specific surface area and pore distribution analyzer (product name: 3Flex, manufactured by Micromeritics), and the specific surface area was calculated from a multipoint BET plot. The BET plot was performed in the krypton relative pressure (p / p0) range of 0.05 < (p / p0) < 0.2. The BET plot was performed using seven or more measurement points under conditions where the correlation coefficient of the fitted line was 0.999 or higher. The occupied cross section of krypton gas was 0.210 nm 2 was calculated using the values ​​of The obtained BET specific surface area (m 2 / g), convert the unit to (mm 2 / mm 2 ) was converted to BET specific surface area (mm 2 / mm 2 ) = BET specific surface area (m 2 / g)×10 6 × weight of sample used for measurement (g) ÷ apparent area of ​​sample used for measurement (mm 2 )

[0045] (Ru content in catalyst layer) The loss of the catalytic layer on the base anode was evaluated using a portable X-ray fluorescence analyzer (Rigaku, Niton XL3t800+PM). Specifically, with the base anode welded to the cell, the detector of the analyzer was pressed against the center of the base anode, closest to the ion exchange membrane, and measurements were taken in precious metal mode for 20 seconds. The average of two measurements was used as the measured value of the Ru content. The amount of depletion in the catalyst layer was calculated by subtracting the amount of Ru in the catalyst layer of the base anode after 7 days of electrolysis from the amount of Ru in the catalyst layer of the base anode before electrolysis.

[0046] (Voltage) The potential difference between the anode and the cathode was measured as the electrolysis voltage. That is, the conductive parts of the anode and the cathode were clamped with two tester clips, and the tester clips were connected to a data logger (TR-V1000, manufactured by KEYCENCE Corporation) to measure the electrolysis voltage.

[0047] (Airflow resistance) The airflow resistance of the electrolysis electrodes was measured using a KES-F8 air permeability tester (product name, Kato Tech Co., Ltd.). The unit of airflow resistance was kPa·s / m. The measurement was performed five times, and the average value is shown in Table 1. The measurement was performed under the following conditions: the temperature in the measurement room was 24°C, and the relative humidity was 32%. Piston speed: 2cm / s Airflow: 4cc / cm 2 / s Measurement range: SENSE M (medium) or H (high) Sample size: 50mm x 50mm

[0048] [Example 2] Three electrodes obtained in Example 1 were prepared, and an electrolysis test was carried out in the same manner as in Example 1, except that a laminate formed by combining three electrodes by the surface tension of water was used as the electrode for electrolysis.

[0049] [Example 3] An electrolysis test was carried out in the same manner as in Example 1, except that four electrodes obtained in Example 1 were prepared, and a laminate united by the surface tension of water was used as the electrode for electrolysis.

[0050] [Example 4] (Conductive base material) A mesh was obtained using pure titanium wire with a wire diameter of 100 μm as the conductive substrate. When manufacturing the mesh, the titanium wire was woven with the goal of a mesh count of 100 for the conductive substrate. The thickness of the conductive substrate was measured uniformly at three points on the surface using a Digimatic Sixness Gauge, and the average value was used. The thickness of the conductive substrate was 270 μm. The basis weight was obtained by cutting the conductive substrate into a piece of 11.0 cm x 9.5 cm, measuring its weight on an electronic balance, and dividing the weight by the area. The basis weight was 299.52 g / m 2 The porosity was 75%. (catalyst layer) An electrode obtained in the same manner as in Example 1, except that the mesh was used as the conductive substrate, was used as the electrode for electrolysis in Example 4. The catalyst loading was 0.165 mol / m 2 An electrolysis test was carried out in the same manner as in Example 1, except that such an electrode for electrolysis was used.

[0051] [Example 5] An electrolysis test was carried out in the same manner as in Example 1, except that two electrodes obtained in Example 4 were prepared, and a laminate formed by combining them using the surface tension of water was used as the electrode for electrolysis.

[0052] [Example 6] An electrolysis test was carried out in the same manner as in Example 1, except that three electrodes obtained in Example 4 were prepared, and a laminate united by the surface tension of water was used as the electrode for electrolysis.

[0053] [Comparative Example 1] The conductive substrate was a punched metal made of pure titanium (hole diameter 2 mm, pitch 3 mm, 60-degree staggered arrangement). The substrate thickness was measured uniformly at three points on the surface using a Digimatic thickness gauge, and the average value was used. The substrate thickness was 26 μm. The porosity was 39%. An electrode for electrolysis of Comparative Example 1 was obtained in the same manner as in Example 1, except that the punched metal was used as the conductive substrate. The catalyst loading was 0.0299 mol / m 2 An electrolysis test was carried out in the same manner as in Example 1, except that such an electrode for electrolysis was used.

[0054] Comparative Example 2 An electrolysis test was carried out in the same manner as in Example 1, except that the electrode for electrolysis in Example 1 was not used.

[0055] Table 1 shows the evaluation results of Examples 1 to 6 and Comparative Examples 1 and 2.

[0056] [Table 1] [Explanation of symbols]

[0057] 200 electrolytic cell 210 Electrolyte 220 Container 230 electrode 240 Cathode 250 Ion Exchange Membrane 260 Wiring

Claims

1. An electrode structure including an anode and an electrode for electrolysis disposed on the anode, the electrode for electrolysis comprises a conductive substrate and a catalyst layer disposed on at least one surface of the conductive substrate; The thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less, The BET specific surface area of ​​the electrode for electrolysis is 200 mm 2 in terms of the BET pore surface area per apparent area (mm 2 ) of the electrode for electrolysis. 2 / mm 2 Over 5000mm 2 / mm 2 is as follows: The electrode structure, wherein the electrolysis electrode has an air flow resistance of 0.005 kPa·s / m or more and 0.350 kPa·s / m or less.

2. The catalyst loading amount of the catalyst layer is 0.050 mol / m 2 2.000mol / m or more 2 2. The electrode structure of claim 1, wherein:

3. The electrode structure according to claim 1 or 2, wherein the catalyst layer contains a platinum group element.

4. 4. The electrode structure according to claim 1, wherein the conductive substrate comprises titanium.

5. The electrode structure according to any one of claims 1 to 4, wherein the conductive substrate comprises a fibrous metal.

6. The electrode structure according to claim 5 , wherein the wire diameter of the fibrous metal is 10 μm or more and 150 μm or less.

7. 7. The electrode structure according to claim 1, wherein the conductive substrate has a porosity of 40% or more and 90% or less.

8. The electrode structure according to any one of claims 1 to 7, a cathode facing the anode; An electrolysis cell comprising: The electrolysis cell, wherein the electrode for electrolysis functions as an anode electrode.

9. The electrolytic cell of claim 8; a diaphragm disposed between the anode and the cathode; An electrolytic cell comprising:

10. A method for producing a new electrolytic cell from an existing electrolytic cell comprising an anode, a cathode facing the anode, and a diaphragm disposed between the anode and the cathode, comprising: The method includes a step (A) of placing an electrode for electrolysis on an anode in the existing electrolytic cell, the electrode for electrolysis comprises a conductive substrate and a catalyst layer disposed on at least one surface of the conductive substrate; The thickness of the electrode for electrolysis is 150 μm or more and 1000 μm or less, The BET specific surface area of ​​the electrode for electrolysis is 200 mm 2 in terms of the BET pore surface area per apparent area (mm 2 ) of the electrode for electrolysis. 2 / mm 2 Over 5000mm 2 / mm 2 is as follows: The air flow resistance of the electrode for electrolysis is 0.005 kPa s / m or more and 0.350 kPa s / m or less, the electrode for electrolysis functions as an anode, The method for producing an electrolytic cell, wherein the electrode for electrolysis and the anode are electrically connected.

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