JP6956842B2 - Electrode for electrolysis, electrolytic cell, electrode laminate and electrode renewal method - Google Patents

Description

The present invention relates to an electrode for electrolysis, an electrolytic cell, an electrode laminate, and a method for renewing the electrode.

Ion exchange membrane method salt electrolysis is a method for producing caustic soda, chlorine, and hydrogen by electrolyzing (electrolyzing) salt water using an electrode for electrolysis. In the ion exchange membrane method salt electrolysis process, from the viewpoint of environmental load and energy problems, a technique capable of maintaining a low electrolysis voltage for a long period of time is required in order to reduce power consumption.
A detailed analysis of the breakdown of the electrolytic voltage shows that, in addition to the theoretically required electrolytic voltage, the voltage due to the resistance of the ion exchange film and the structural resistance of the electrolytic tank, the overvoltage of the anode and cathode, which are the electrodes for electrolysis, and the anode and cathode. It has been clarified that the voltage caused by the distance between the two is included. Further, if electrolysis is continued for a long period of time, a voltage increase or the like caused by various causes such as impurities in salt water may occur.

Among the above-mentioned electrolytic voltages, various studies have been conducted for the purpose of reducing the overvoltage of the anode for generating chlorine. For example, Patent Document 1 discloses a technique of an insoluble anode formed by coating an oxide of a platinum group metal such as ruthenium on a titanium base material. This anode is called DSA (Registered Trademark, Dimension Table Anode). Further, Non-Patent Document 1 describes the transition of soda electrolysis technology using DSA.

Various improvements have been made to the above-mentioned DSA, and studies have been conducted to improve its performance.
For example, Patent Document 2 describes an anode using a metallic porous plate having a predetermined thickness, pore diameter, and aperture ratio, or an expanded metal having a predetermined thickness, major axis, minor axis, and aperture ratio. A method of electrolyzing the anode surface of the cation exchange membrane as close as possible has been proposed. Patent Document 3 proposes an anode made of a substantially diamond-shaped metal mesh and having a predetermined ratio of mesh strands and openings, a longitudinal spacing LWD of openings, and a width spacing SWD. Patent Document 3 discloses that a platinum group metal oxide, magnetite, ferrite, cobalt spinel, or a mixed metal oxide can be used as a coating on the surface of a metal mesh having the shape.
Further, in Patent Document 4, a titanium expanded metal or a titanium wire net is used as the anode base material, the aperture ratio and thickness of the anode base material are set within a predetermined range, and after the catalyst is applied to the anode base material. A technique for improving the electrolytic performance has been proposed by setting the maximum value of the unevenness height difference on the surface of the anode of Titanium within a predetermined range.
Further, in Patent Document 5, it is stated that the cell voltage at the time of electrolysis can be lowered by reducing the thickness of the anode to about half or less of the conventional one and adjusting the ratio of the opening in the vertical direction and the horizontal direction of the opening. Attempts have been made to reduce the amount of impurity gas, that is, oxygen gas, generated by the reaction of hydroxide ions diffused from the cathode chamber through the ion exchange membrane with this electrode.
As described above, in the prior art, a measure of lowering the voltage during electrolysis is adopted in the direction of reducing the thickness of the anode and increasing the aperture ratio of the anode base material.

Special Publication No. 46-021884 Japanese Unexamined Patent Publication No. 58-130286 Special Table No. 62-502820 Japanese Patent No. 4453973 International Publication No. 2015/108115

Hiroaki Aikawa, "National Museum of Nature and Science Technology Systematization Survey Report Vol. 8", published by National Museum of Nature and Science, March 30, 2007, p32

However, in the conventional anode such as DSA described in Patent Document 1, the overvoltage immediately after the start of electrolysis is high, and it takes a certain period of time to settle to a low overvoltage due to the activation of the catalyst, so that power consumption loss occurs during electrolysis. There is a problem that it ends up.
Further, in Patent Documents 2 to 4, the aperture ratio of the expanded metal, the intervals in the longitudinal direction and the width direction of the mesh, and the like are examined, but the relationship between the shape of the anode and the electrolytic voltage is sufficiently examined. There is a demand for further reduction of the electrolytic voltage. In particular, an anode having a thin anode mesh and a high aperture ratio causes problems such as insufficient practical strength.
In Patent Document 5, a method of trying to reduce the voltage of the anode and the amount of oxygen gas generated by reducing the thickness of the anode to about half or less of the conventional one is adopted, but an ion exchange membrane electrolytic cell at an industrial level is adopted. Then, since it is operated by applying pressure from the cathode chamber, if the thickness of the anode mesh is too thin, the strength cannot be maintained, and it is necessary to use two expanded metals in layers, which satisfies the reduction of the anode strength and the electrolytic voltage. Needs further improvement.

The present invention has been made to solve the above-mentioned problems. Therefore, an object of the present invention is to provide an electrolysis electrode having practical strength and an electrolysis tank provided with the electrolysis electrode, which can suppress the voltage and power consumption during electrolysis to a low level. do.

The present inventors have conducted intensive studies to solve the above problems. As a result, the thickness of the electrode for electrolysis is set to a specific range, and the value obtained by dividing the total peripheral length of the openings of the electrodes for electrolysis by the opening ratio of the electrode for electrolysis is set to a specific range during electrolysis. The present invention has been made by finding that an electrode for electrolysis, which can suppress the voltage and power consumption of the above-mentioned material to be low and has practical strength, is provided. Further, the present inventors have found that the above-mentioned problems can be solved by forming the opening of the electrode for electrolysis into a specific shape, and have completed the present invention.
That is, the present invention is as follows.
[1]
A conductive base material made of a perforated metal plate and
With at least one catalyst layer formed on the surface of the conductive substrate,
Electrode for electrolysis
The thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less.
An electrolysis electrode having a value C obtained by dividing the sum total B of the peripheral lengths of the openings of the electrolysis electrodes by the aperture ratio A of the electrolysis electrodes of more than 2 and 5 or less.
[2]
The electrode for electrolysis according to [1], wherein the aperture ratio A is 5% or more and less than 25%.
[3]
The distance SW between the centers in the short direction of the mesh of the opening is 1.5 or more and 3 or less, and the distance LW between the centers in the long direction of the mesh is 2.5 or more and 5 or less, [1] or [ 2] The electrode for electrolysis.
[4]
The electrode for electrolysis according to any one of [1] to [3], wherein the thickness of the electrode for electrolysis is more than 0.5 mm and 0.9 mm or less.
[5]
The electrode for electrolysis according to any one of [1] to [4], wherein the value E represented by the following formula (1) is 0.5 or more.
E = B / (A × (SW ² + LW ² ) ^1/2 ) (1)
[6]
An anode chamber including the electrode for electrolysis according to any one of [1] to [5] as an anode, and an anode chamber.
A cathode chamber containing a cathode and
An ion exchange membrane that separates the anode chamber from the cathode chamber,
Equipped with an electrolytic cell.
[7]
The electrolytic cell according to [6], which has a protruding portion made of a polymer constituting the ion exchange membrane on the surface on the anode side of the ion exchange membrane.
[8]
The electrode for electrolysis according to any one of [1] to [3] and
A base electrode different from the electrode for electrolysis and
An electrode laminate.
[9]
The electrode laminate according to [8], wherein the thickness of the electrode for electrolysis is more than 0.5 mm and 0.65 mm or less.
[10]
A method for updating an electrode, which comprises a step of welding the electrode for electrolysis according to any one of [1] to [3] onto an existing electrode in an electrolytic cell.
[11]
A conductive base material made of a perforated metal plate and
With at least one catalyst layer formed on the surface of the conductive substrate,
Electrode for electrolysis
The shape of the opening of the electrolytic electrode is symmetrical with respect to the first virtual center line extending in the short direction of the mesh, and is symmetrical with respect to the second virtual center line extending in the long direction of the mesh. It is vertically asymmetric and
An electrode for electrolysis in which the thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less.
[12]
When the opening is divided into one portion a and the other portion b by the second virtual center line, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b is 1.15 or more. The electrode for electrolysis according to [11], which is 2.0 or less.
[13]
The value St obtained by subtracting the maximum opening in the short direction of the mesh of the opening from the distance SW between the centers in the short direction of the mesh of the opening is divided by the SW, and the value is 0.4 or more. ] Or the electrode for electrolysis according to [12].

INDUSTRIAL APPLICABILITY According to the present invention, an electrode for electrolysis which can suppress the voltage and power consumption during electrolysis to a low level and has practical strength is provided.

FIG. 1 is a schematic diagram for explaining the relationship between the total peripheral length of the openings and the aperture ratio of the electrolysis electrodes, assuming that the electrodes for electrolysis and the openings are square. FIG. 2 is a schematic view showing a typical example of a projection surface in which an electrode for electrolysis according to one aspect of the present embodiment is observed with a microscope. FIG. 3 is an explanatory diagram showing the relationship between the short-direction center-to-center distance SW of the mesh of the opening in the present embodiment, the long-direction center-to-center distance LW of the mesh, and the distance d, based on the schematic diagram of FIG. FIG. 4A is an explanatory diagram schematically showing a typical example of the shape of the opening of the electrode for electrolysis according to another aspect of the present embodiment. FIG. 4B is an explanatory diagram showing a portion a and a portion b in FIG. 4A. FIG. 4C is an explanatory diagram schematically showing a typical example of the shape of the opening of the conventional electrolytic electrode. FIG. 5 is an explanatory diagram schematically showing an example of the positional relationship of adjacent openings in the electrode for electrolysis according to another aspect of the present embodiment. FIG. 6 is a schematic view showing an example of a cross section of the electrolytic cell of the present embodiment.

Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist thereof.

The electrode for electrolysis according to the first aspect of the present embodiment (hereinafter, also simply referred to as “first electrode for electrolysis”) is a conductive base material made of a perforated metal plate and the conductive base material. An electrode for electrolysis provided with at least one catalyst layer formed on the surface, the thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less, and the sum of the peripheral lengths of the openings of the electrodes for electrolysis. The value C obtained by dividing B by the opening ratio A of the electrode for electrolysis is more than 2 and 5 or less. Since it is configured in this way, the first electrode for electrolysis can suppress the voltage and power consumption during electrolysis to a low level, and also has practical strength. The first electrolysis electrode can be used as a chlorine generation electrode particularly suitable for ion exchange membrane method salt electrolysis.

The electrode for electrolysis according to the second aspect of the present embodiment (hereinafter, also simply referred to as “second electrode for electrolysis”) is a conductive base material made of a perforated metal plate and the conductive base material. An electrolysis electrode including at least one layer of a catalyst layer formed on the surface, wherein the shape of the opening of the electrolysis electrode is left and right with respect to the first virtual center line extending in the short direction of the mesh. It is symmetric and vertically asymmetric with respect to the second virtual center line extending in the long direction of the mesh, and the thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less. Since it is configured in this way, the second electrode for electrolysis can also suppress the voltage and power consumption during electrolysis to a low level, and also has practical strength. The second electrode for electrolysis can also be used as a chlorine generating electrode particularly suitable for ion exchange membrane method salt electrolysis.
Hereinafter, when the term "electrolysis electrode according to the present embodiment" is used, the first electrolysis electrode and the second electrolysis electrode are included.

(Conductive base material)
In the electrode for electrolysis according to the present embodiment, the conductive base material is made of a perforated metal plate and is used in a chlorine gas generating atmosphere in a high concentration salt solution near saturation. Therefore, as the material of the conductive base material, a valve metal having corrosion resistance is preferable. The valve metal is not limited to the following, and examples thereof include titanium, tantalum, niobium, and zirconium. Among the valve metals, titanium is preferable from the viewpoint of economy and affinity with the catalyst layer.
The shape of the conductive base material is not particularly limited as long as it is made of metal and has a flat shape with holes. Examples thereof include expanded metal, perforated plate, wire mesh, and the like. In the present embodiment, the shape of the conductive base material is expanded metal. Is preferably used. Expanded metal is generally a metal flat plate or metal leaf that is spread out while making slits with the upper and lower blades to form a mesh, and then flattened to a desired thickness by rolling rolls or the like. Is. Since continuous hoop processing is possible, production efficiency is high, there is no waste loss of the original plate material, and it is economical, and because of the integrated structure, complete electrical conductivity is secured unlike wire mesh, and it does not unravel. ..

The electrode for electrolysis according to the present embodiment is configured by forming at least one layer of a catalyst layer on the surface of the above-mentioned conductive base material. The thickness of the electrode for electrolysis according to this embodiment is more than 0.5 mm and 1.2 mm or less. When the thickness of the electrode for electrolysis is a thin base material of 0.5 mm or less, the pressure difference between the anode chamber and the cathode chamber generated during electrolysis and the pressing pressure of the cathode cause the anode to drop due to the pressure of the ion exchange film pressing the anode, resulting in the electrode. Since the distance is widened, the electrolytic voltage becomes high. When the thickness of the electrode for electrolysis is more than 1.2 mm, the aperture ratio and the SW (distance between the centers of the mesh of the opening in the short direction) and LW (the length of the mesh of the opening) are suitable for this embodiment. Expanded metal with eye direction center distance) cannot be formed. From the same viewpoint as above, the thickness of the electrode for electrolysis is preferably more than 0.5 mm and 1.0 mm or less, more preferably more than 0.5 mm and 0.9 mm or less, and further preferably 0.7 mm or more and 0. It is 9 mm or less.

In the first electrode for electrolysis, the value C (= B / A) obtained by dividing the total peripheral length B of the openings of the electrodes for electrolysis by the aperture ratio A of the electrode for electrolysis is preferably more than 2 and 5 or less. Is 2.5 or more and 4.5 or less, and more preferably 3 or more and 4 or less.
The opening ratio A as used herein means a percentage of the total area S _B of the opening in the projected area S _A of one of the surfaces of the electrode for electrolysis (S _B / S _A). The total area S _B of the opening, in the electrode for electrolysis, it is possible that the sum of the projected area of the region cations or electrolytes, etc. is not blocked by the conductive substrate (perforated metal plate).
Further, the total B of the peripheral lengths of the openings referred to here is the length Li of the periphery of the openings per unit area of the electrode for electrolysis, and the peripheral lengths are integrated by the number n per unit area. The value (ΣLi, i = 1 to n).

The relationship between the total peripheral length of the opening and the aperture ratio will be described with reference to FIG. Although the opening is assumed to be square in FIG. 1 for convenience of explanation, it is different from the shape of the opening formed in the electrode for electrolysis according to the present embodiment. As shown in FIG. 1A, when one square (2 mm × 2 mm) opening 2 is formed in the square (4 mm × 4 mm) electrode 1, the opening area is 4 mm ² and the aperture ratio is 25%, the total peripheral length of the opening is 8 mm. On the other hand, as shown in FIG. 1 (b), when four square (1 mm × 1 mm) openings 3 are formed in the electrodes 1 having the same shape, the opening area is 4 mm ² and is different from that in FIG. 1 (a). The same is true, and the aperture ratio is 25%, which is the same as in FIG. 1 (a), but the total peripheral length of the openings is 16 mm, which is larger than that in FIG. 1 (a). As described above, when compared at the same aperture ratio, the larger the total peripheral length of the openings, the larger the number of openings. That is, it means that the number of openings increases as the value obtained by dividing the sum of the peripheral lengths of the openings by the aperture ratio increases. As the number of openings increases, the gas flow path is dispersed, so that stagnant bubbles are reduced, which contributes to suppressing the voltage rise.

The method for measuring the aperture ratio and the total peripheral length of the opening is not limited to the following, but for example, (I) the electrode for electrolysis is cut into a square having a length of 10 cm and a width of 10 cm and copied by a copying machine. A method of cutting out an opening portion from the cut paper and measuring the weight and peripheral length of the cut out portion as the opening portion; (II) Observe the surface of either one of the electrolysis electrodes with an image observation device such as a microscope. Examples thereof include a method of measuring by analyzing image data obtained by photographing a projection surface. FIG. 2 shows a diagram schematically showing a typical example of such image data. As shown in FIG. 2, it can be seen that a plurality of openings 20 are formed in the electrolysis electrode 10.
Regarding the above (I), the aperture ratio (%) is calculated by 100 × (w1-w2) / w1 from the weight w1 of the paper before cutting out the opening portion and the weight w2 of the paper after cutting out all the opening portions. can. Further, the total sum of the peripheral lengths can be obtained as the sum of the peripheral lengths of those cut out as the opening portion.
Regarding (II) above, as a method for analyzing image data, for example, the use of "Image J" developed by the National Institutes of Health (NIH) and publicly owned for image processing can be mentioned.
When the value C (= B / A) obtained by dividing the total peripheral length B of the peripheral lengths of the openings of the electrolytic electrodes by the opening ratio A of the electrolytic electrodes is 2 or less, the opening ratio becomes large or a small number of large openings. As the electrode for electrolysis has a portion and the specific surface area of the electrode for electrolysis is reduced, the apparent current density is increased and the electrolysis voltage is increased. Further, when the value of C described above is more than 5, the aperture ratio becomes low or the conductive base material has a large number of small openings, which adversely affects the circulation of the electrolytic solution and the desorption of the gas generated at the electrodes. By causing it, the electrolytic voltage may rise.

In the prior art, various techniques for lowering the electrolytic voltage by setting the thickness of the electrode to 0.5 mm or less have been disclosed, but in the first electrode for electrolysis, the thickness of the electrode for electrolysis is more than 0.5 mm 1. The voltage and power consumption during electrolysis are set to .2 mm or less, and the value C (= B / A) obtained by dividing the total peripheral length B of the openings of the electrodes for electrolysis by the opening ratio A is more than 2 and 5 or less. It is an electrode for electrolysis that keeps the amount low and has practical strength.

In the electrode for electrolysis according to the present embodiment, the aperture ratio of the electrode for electrolysis is preferably 5% or more and less than 25%, more preferably 7% or more and 20% or less, and 10% or more and 18% or less. It is particularly preferable to have. When the aperture ratio of the electrode for electrolysis is 5% or more, there is a tendency that adverse effects such as retention of gas generated at the electrode during electrolysis can be effectively eliminated without adversely affecting the liquid circulation of the electrolytic solution. There is a tendency that the electrolytic voltage can be reduced. Further, when the opening ratio of the electrolysis electrode is less than 25%, the specific surface area of the electrolysis electrode can be sufficiently secured, that is, a substantial electrode surface facing the ion exchange membrane tends to be sufficiently secured, and as a result. As a result, the apparent current density can be lowered, and the electrolytic voltage tends to be reduced.

In the electrode for electrolysis according to the present embodiment, the peripheral length of one opening of the electrode for electrolysis is preferably 1 mm or more, more preferably 2.5 mm or more. When the peripheral length of one opening of the electrode for electrolysis is 1 mm or more, the pressure loss of the electrolyte flow in the opening can be suppressed, and the electrolysis voltage tends to be reduced. The peripheral length of one opening of the electrode for electrolysis is preferably 4.8 mm or less, more preferably 4.55 mm or less, from the viewpoint of sufficiently securing the specific surface area of the electrode for electrolysis. The peripheral length of one opening of the electrode for electrolysis is measured by observing the surface of one of the electrodes for electrolysis described above with an image observation device such as a microscope and analyzing the image data obtained by photographing the projection surface. It can be measured by (image analysis).

In the electrode for electrolysis according to the present embodiment, the short diameter SW which is the distance between the centers in the short direction of the opening of the electrode for electrolysis is 1.5 mm or more and 3 mm or less, and the distance between the centers in the long direction of the mesh. It is preferable that a certain major axis LW is 2.5 mm or more and 5 mm or less, a minor axis SW is 1.5 mm or more and 2.5 mm or less, and a major axis LW is 3 mm or more and 4.5 mm or less.
The SW and LW can be specified as shown in FIG. That is, the SW can be specified as the distance connecting the centers of two openings adjacent to each other in the short direction of the mesh. Further, LW can be specified as a distance connecting the centers of two openings adjacent to each other in the long direction of the mesh.
When the SW is 1.5 mm or more and the LW is 2.5 mm or more, it becomes easy to secure a suitable thickness and aperture ratio in this embodiment. Further, when the SW is 3 mm or less and the LW is 5 mm or less, it becomes easy to secure a range of an aperture ratio suitable for this embodiment, that is, it becomes easy to secure a specific surface area of the electrode for electrolysis. ..
Further, as shown in FIG. 3, it is preferable to adjust the distance d between the openings. The distance d is calculated by the square root of the value obtained by adding the square of LW to the square of SW, and the smaller this value is, the more the movement of substances such as gas tends to be promoted. From this point of view, the value of d is preferably 2.9 to 5.8 mm, more preferably 3.4 to 5.1 mm.

In the electrode for electrolysis according to the present embodiment, it is obtained from the total peripheral length B of the opening, the aperture ratio A of the opening, the minor axis SW of the opening, and the major axis LW of the opening, and is represented by the following formula (1). The value E is preferably 0.5 or more, more preferably 0.69 or more, and further preferably 0.69 or more and 1.5 or less.
E = B / (A × (SW ² + LW ² ) ^1/2 ) (1)
In equation (1), (SW ² + LW ² ) ^1/2 corresponds to the above-mentioned d. By adjusting the relationship between A, B, and d in an appropriate range in this way, the degree of spatial dispersion of the openings becomes suitable, and the electrolytic voltage tends to be reduced. That is, when the value of E in the electrode for electrolysis is 0.5 or more and 1.5 or less, the degree of spatial dispersion of the opening of the electrode for electrolysis becomes preferable with respect to the liquid circulation of the electrolytic solution, and the electrolysis voltage is reduced. There is a tendency to be able to do it.

Next, the second electrode for electrolysis will be described in detail. The second electrode for electrolysis is an electrode for electrolysis including a conductive base material made of a perforated metal plate and at least one layer of a catalyst layer formed on the surface of the conductive base material. The shape of the opening of the electrode for use is symmetrical with respect to the first virtual center line extending in the short direction of the mesh, and is vertically asymmetric with respect to the second virtual center line extending in the long direction of the mesh. The thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less.
A typical example of the shape of the opening in the second electrode for electrolysis is shown in FIG. 4 (A). The opening 100 in FIG. 4A is symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Symmetry means that when the opening is divided into a right part and a left part with reference to the first virtual center line, the shape of the right part matches the shape of the left part, that is, the first virtual center line is used as a reference. It means that the right part and the left part are line symmetric. The left-right symmetry can be confirmed by the above-mentioned image analysis.
Further, the opening 100 is vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Vertical asymmetry means that when the opening is divided into an upper part and a lower part with reference to the second virtual center line, the shape of the upper part does not match the shape of the lower part, that is, the second virtual center line is used as a reference. It means that the upper part and the lower part are not line-symmetrical. The left-right symmetry can be confirmed by the above-mentioned image analysis. For example, in the example shown in FIG. 4B, the opening 100 can be divided into an upper portion a and a lower portion b with reference to the second virtual center line 102 extending in the long direction β of the mesh. , It can be easily confirmed by comparing the shapes of the portion a and the portion b.

It is not clear why the second electrode for electrolysis can suppress the voltage and power consumption during electrolysis low, but the present inventors presume that it is due to the following. However, the present invention is not limited to this speculation, and is included in the second electrolytic electrode as long as it is an electrolytic electrode having the above-described configuration.
Typical shapes of the openings in the conventional electrode for electrolysis include those that are symmetrical with respect to the first virtual center line and vertically symmetrical with respect to the second virtual center line. Be done. For example, in the example shown in FIG. 4C, the opening 100'is symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, in the opening 100', when the second virtual center line 102 extending in the long direction β of the mesh is used as a reference, the upper portion a and the lower portion b are line-symmetrical with respect to the virtual center line 102. It has become. In the case of such a shape, the opening is typically rhombic, and the four sides forming the opening are located substantially equidistant from the center point of the opening. In such a conventional electrode for electrolysis, when the generated gas (typically spherical) tries to pass through the opening, the gas comes into contact with the four sides (that is, four points) constituting the opening. It is presumed that the passage resistance tends to increase by doing so. That is, the gas generated at the electrode during electrolysis tends to inscribe in the opening and easily stay there, which may adversely affect the liquid circulation of the electrolytic solution and cause a problem that the electrolysis voltage rises.
On the other hand, the second electrode for electrolysis is symmetrical with respect to the first virtual center line and vertically asymmetric with respect to the second virtual center line, so that the gas generated at the electrode is generated. It is presumed that the passage resistance (typically spherical) when trying to pass through the opening tends to be reduced. That is, since the number of contact points between the gas generated at the electrode during electrolysis and each side constituting the opening tends to decrease, the gas tends to be effectively desorbed, which leads to liquid circulation of the electrolytic solution. The electrolytic voltage can be reduced without adversely affecting it.

In the second electrode for electrolysis, ^{the area of the opening with respect to the projected area of 1 cm 2 on either surface is not particularly limited, but is 0.05 cm 2} or more from the viewpoint of further reducing the voltage and power consumption during electrolysis. Is preferable. The number of openings with respect to the projected area of 1 cm ^{2 is} also not particularly limited, but is preferably 15 or more from the viewpoint of further reducing the voltage and power consumption during electrolysis. The values of the area of the openings and the number of openings can be measured by the image analysis described above.

In the second electrode for electrolysis, when the opening is divided into one portion a and the other portion b by the second virtual center line, the area Sa of the portion a is divided by the area Sb of the portion b. The value (Sa / Sb) is preferably 1.15 or more and 2.0 or less. In this case, the vertical asymmetry of the processed portion described above tends to be more remarkable. That is, it can be said from the value of Sa / Sb that the shape of the opening of the electrode for electrolysis is vertically asymmetric with respect to the second virtual center line extending in the long direction of the mesh. Further, when the value of Sa / Sb is 1.15 or more and 2.0 or less, the gas generated at the electrode during electrolysis tends to be effectively desorbed without adversely affecting the liquid circulation of the electrolytic solution. There is a tendency that the electrolytic voltage can be reduced. In the example of FIG. 4B, Sa and Sb correspond to the area of the portion a and the area of the portion b, respectively, and Sa> Sb. The values of Sa and Sb can be measured by the image analysis described above.

In the second electrode for electrolysis, the value St obtained by subtracting the maximum opening in the short direction of the mesh of the opening from the distance SW between the centers in the short direction of the mesh of the opening is divided by the SW (St / SW) is preferably 0.4 or more, and more preferably more than 0.67 and less than 1.0. In the example shown in FIG. 5, a plurality of openings are formed in the electrode 300 for electrolysis, and the SW is specified by the distance between the centers in the short direction of the mesh of the openings from the two adjacent openings. .. The "two adjacent openings" here mean an opening in which the first virtual center line first touches when the first virtual center line is extended from a certain opening. Further, the LW is specified by the distance between the centers in the long direction of the mesh of the openings from the two adjacent openings. The "two adjacent openings" here mean an opening in which the second virtual center line first touches when the second virtual center line is extended from a certain opening. In FIG. 5, in the electrode 300 for electrolysis, the second virtual center line 330 divides the opening into a portion a and a portion b, and the portion a (340) is referred to with the virtual center line 330 as a reference. Part b (350) is shown to be vertically asymmetric. Further, in FIG. 5, the distance 360 between two openings adjacent to each other in the short direction of the mesh of the opening is the maximum in the short direction of the mesh of the opening from the distance SW between the centers in the short direction of the mesh of the opening. Corresponds to the value St with the spread reduced. The maximum opening of the mesh of the opening in the short direction corresponds to the length of the first virtual center line 101 in the example shown in FIG. 4 (A). When St / SW is 0.4 or more, the specific surface area of the electrolytic electrode can be sufficiently secured without adversely affecting the liquid circulation of the electrolytic solution, and the electrolytic voltage tends to be reduced. The St and SW values can be measured by the image analysis described above.

The electrode for electrolysis according to the present embodiment is formed by forming at least one layer of a catalyst layer on the surface of the above-mentioned conductive base material, and the contact surface of the conductive base material with the catalyst layer is with the catalyst layer. In order to improve the adhesion, it is preferable to carry out a treatment for increasing the surface area of the conductive base material. The surface area increasing treatment method is not limited to the following, and examples thereof include blast treatment using cut wire, steel grid, alumina grid, etc .; acid treatment using sulfuric acid or hydrochloric acid, and the like. Among these treatments, a method of forming irregularities on the surface of the conductive base material by blasting and then further treating with acid is preferable.

(Catalyst layer)
The catalyst layer formed on the surface of the conductive base material in the electrode for electrolysis according to the present embodiment, preferably on the surface of the conductive base material subjected to the above-mentioned treatment, is a platinum group in order to lower the electrolytic voltage. It preferably contains an electrode catalytic material such as a metal oxide, magnetite, ferrite, cobalt spinel, or a mixed metal oxide. From the viewpoint of suppressing the voltage during electrolysis, it is more preferable that the ruthenium element, the iridium element and the titanium element are each in the form of an oxide among the above-mentioned electrode catalyst substances.
The ruthenium oxide is not limited to the following, and examples thereof include RuO ₂ .
Examples of the iridium oxide include, but are not limited to, IrO ₂ .
Examples of the titanium oxide include, but are not limited to, TiO _{2 and the} like.

In the catalyst layer of the electrode for electrolysis according to the present embodiment, it is preferable that the ruthenium oxide, the iridium oxide, and the titanium oxide form a solid solution. By forming a solid solution of ruthenium oxide, iridium oxide, and titanium oxide, the durability of ruthenium oxide is further improved, and the electrolytic voltage tends to be kept low for a long period of time.
A solid solution generally means a substance in which two or more kinds of substances are dissolved in each other to form a uniform solid phase as a whole. Examples of the substance forming the solid solution include simple substances of metal and metal oxides. In particular, in the case of a solid solution of a metal oxide suitable for the present embodiment, two or more kinds of metal atoms are irregularly arranged on equivalent lattice points in a unit lattice in an oxide crystal structure. Specifically, the ruthenium oxide, the iridium oxide, and the titanium oxide are mixed with each other, and when viewed from the ruthenium oxide side, the ruthenium atom is replaced by the iridium atom, the titanium atom, or both of them. It is preferably a solid solution. The solid solution state is not particularly limited, and a partially solid solution region may exist.
Due to the solid solution, the size of the unit cell in the crystal structure changes slightly. The degree of this change can be confirmed, for example, from the fact that the diffraction pattern due to the crystal structure does not change and the peak position due to the size of the unit cell changes in the measurement of powder X-ray diffraction.

In the catalyst layer of the electrode for electrolysis according to the present embodiment, the content ratios of the ruthenium element, the iridium element, and the titanium element are 0.2 to 3 mol of the iridium element and 0.2 to 3 mol of the titanium element with respect to 1 mol of the ruthenium element. It is preferably 0.2 to 8 mol; more preferably 0.3 to 2 mol of the iridium element and 0.2 to 6 mol of the titanium element with respect to 1 mol of the ruthenium element; It is particularly preferable that the amount of iridium element is 0.5 to 1.5 mol and the amount of titanium element is 0.2 to 3 mol with respect to 1 mol. By setting the content ratio of the three types of elements within the above range, the long-term durability of the electrode for electrolysis tends to be further improved. Iridium, ruthenium, and titanium may each be contained in the catalyst layer in a form other than oxide, for example, as a simple metal.

The catalyst layer in the electrode for electrolysis according to the present embodiment may contain only the above-mentioned ruthenium element, iridium element, and titanium element as constituent elements, or may contain other metal elements in addition to these elements. May be good. Specific examples of other metal elements include, but are not limited to, elements selected from tantalum, niobium, tin, platinum, vanadium and the like. Examples of the existence form of these other metal elements include the existence as a metal element contained in an oxide.
When the catalyst layer in the present embodiment contains other metal elements, the content ratio thereof may be 20 mol% or less as the molar ratio of the other metal elements to all the metal elements contained in the catalyst layer. It is preferably 10 mol% or less, and more preferably 10 mol% or less.
The thickness of the catalyst layer in the present embodiment is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm. By setting the thickness of the catalyst layer to the above lower limit value or more, the initial electrolysis performance tends to be sufficiently maintained. Further, by setting the thickness of the catalyst layer to be equal to or less than the above-mentioned upper limit value, an electrode for electrolysis having excellent economic efficiency tends to be obtained. The thickness of the catalyst layer can be measured by cutting a cross section of the base material and using an optical microscope or an electron microscope.

The catalyst layer may consist of only one layer, or may have two or more layers.
When there are two or more catalyst layers, at least one of them may be the catalyst layer in the present embodiment. When there are two or more catalyst layers, it is preferable that at least the innermost layer is the catalyst layer in the present embodiment. Since at least the innermost layer is a solid solution formed of ruthenium oxide, iridium oxide, and titanium oxide, the durability of the catalyst layer tends to be further improved. It is also preferable that the catalyst layer in the present embodiment has two or more layers having the same composition or different compositions.
Even when the number of catalyst layers is two or more, the thickness of the catalyst layer in the present embodiment is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm, as described above. preferable.

(Manufacturing method of electrode for electrolysis)
Next, the method for manufacturing the electrode for electrolysis according to the present embodiment will be described in detail by taking as an example the case where expanded metal is used as the conductive base material.
The electrode for electrolysis according to the present embodiment is used as a conductive base material and is expanded by expanding the valve metal flat plate with slits by the upper and lower blades to form a mesh, and is rolled to a desired thickness by rolling or rolling. The conductive base material is subjected to the above-mentioned surface area increasing treatment using the expanded metal flattened, and then a catalyst layer containing ruthenium element, iridium element, and titanium element is formed on the conductive base material. By forming, it can be manufactured.

As a method for producing expanded metal in the present embodiment, a step of forming a mesh by expanding the valve metal flat plate while making slits with an upper blade and a lower blade, and then a step of rolling and flattening by rolling or the like. When the electrode for electrolysis is formed by forming at least one layer of a catalyst layer on the surface of the conductive base material, the thickness is more than 0.5 mm and 1.2 mm or less, and the peripheral length of the opening is long. The value C (= B / A) obtained by dividing the total B of the above by the aperture ratio A of the electrode for electrolysis is greater than 2 and 5 or less to produce an expanded metal.

The thickness of the electrode for electrolysis is within a range suitable for this embodiment by adjusting the thickness of the valve metal flat plate used as the material of the conductive base material and the rolling strength at the time of flattening by rolling or the like. Can be adjusted.
Further, the aperture ratio of the electrode for electrolysis and the short-diameter SW, which is the distance between the centers of the mesh in the short direction in the opening, are a series of forming a mesh by expanding the valve metal flat plate while making slits with the upper and lower blades. In the above step, the step size for continuously feeding forward by the feed roller in conjunction with the vertical movement of the upper blade can be adjusted to a range suitable for the present embodiment. That is, from the viewpoint of adjusting the degree of dispersion of the openings of the present embodiment, it is preferable to adjust the step size when slitting the valve metal flat plate with the upper and lower blades to 0.8 mm or less. Further, from the viewpoint of maintaining the shape of the opening of the present embodiment, 0.5 mm or more is preferable.
Further, the major axis LW, which is the distance between the centers in the long mesh direction of the opening, is adjusted to a range suitable for the present embodiment by appropriately selecting the types of the upper blade and the lower blade for slitting the valve metal flat plate. can do.
Furthermore, since the total peripheral length of the openings of the electrode for electrolysis increases or decreases depending on the increase or decrease in the number of openings, it can be adjusted by the number of upper and lower blades to be slit.
On the other hand, when a perforated plate such as a punching metal is used as a conductive base material, it can be obtained by punching a metal flat plate with a punching press die. By appropriately selecting the shape and arrangement of the mold, the aperture ratio, the sum of the peripheral lengths of the openings, SW and LW can be adjusted to a suitable range of the present embodiment.
Further, when a wire mesh is used as a conductive base material, it can be obtained by weaving a plurality of metal wires for wire mesh production obtained by various known methods, and at that time, for example, for wire mesh production. By appropriately selecting the weight per unit length of the metal wire (equivalent to denier and thickness of the metal wire) and the number of metal wires to be woven per unit area of the wire mesh (number of meshes), the opening ratio and opening The sum of the peripheral lengths of the portions, SW and LW can be adjusted to a suitable range of the present embodiment. Further, by the same control as described above, the shape related to the second electrode for electrolysis tends to be easily obtained.

The formation of the catalyst layer on the above-mentioned conductive substrate is preferably performed by a thermal decomposition method.
In the production method by the thermal decomposition method, a coating liquid containing a mixture of compounds (precursors) containing the above elements is coated on a conductive base material, and then fired in an oxygen-containing atmosphere in the coating liquid. A catalyst layer can be formed by thermally decomposing the components of. According to this method, the electrode for electrolysis can be manufactured with high productivity with a smaller number of steps than the conventional manufacturing method.

The term "pyrolysis" as used herein means that a metal salt or the like as a precursor is fired in an oxygen-containing atmosphere to decompose it into a metal oxide or a metal and a gaseous substance. The obtained decomposition product can be controlled by the type of metal contained in the precursor mixed in the coating liquid as a raw material, the type of metal salt, the atmosphere in which thermal decomposition is performed, and the like. Usually, in an oxidizing atmosphere, many metals tend to form oxides. In the industrial manufacturing process of electrolytic electrodes, thermal decomposition is usually carried out in air. Also in this embodiment, the range of oxygen concentration at the time of firing is not particularly limited, and it is sufficient to carry out in air. However, if necessary, air may be circulated in the firing furnace or oxygen may be supplied.

In the compound contained in the coating liquid, the ruthenium compound, the iridium compound, and the titanium compound may be oxides, but are not necessarily oxides. For example, it may be a metal salt or the like. Examples of these metal salts include, but are not limited to, any one selected from the group consisting of chloride salts, nitrates, sulfates, and metal alkoxides.
The metal salt of the ruthenium compound is not limited to the following, and examples thereof include ruthenium chloride and ruthenium nitrate.
The metal salt of the iridium compound is not limited to the following, and examples thereof include iridium chloride and iridium nitrate.
The metal salt of the titanium compound is not limited to the following, and examples thereof include titanium tetrachloride.

The above compound is appropriately selected and used according to a desired metal element ratio in the catalyst layer.
The coating liquid may further contain a compound other than the compound contained in the above compound. Other compounds include, but are not limited to, metal compounds containing metal elements such as tantalum, niobium, tin, platinum, rhodium and vanadium; metal elements such as tantalum, niobium, tin, platinum, rhodium and vanadium. Examples thereof include organic compounds containing.
The coating liquid is preferably a liquid composition in which the above-mentioned compound group is dissolved or dispersed in an appropriate solvent. The solvent of the coating liquid used here can be selected according to the type of the above compound. For example, water; alcohols such as butanol can be used. The total compound concentration in the coating liquid is not particularly limited, but is preferably 10 to 150 g / L from the viewpoint of appropriately controlling the thickness of the catalyst layer.

The method of applying the coating liquid to the surface on the conductive base material is not limited to the following, but for example, a dip method in which the conductive base material is immersed in the coating liquid, or a coating method on the surface of the conductive base material. A method of applying the liquid with a brush, a roll method in which a conductive base material is passed through a sponge-like roll impregnated with the coating liquid, and a static charge method in which the conductive base material and the coating liquid are charged in the opposite charge and spray sprayed. An electric coating method or the like can be used. Among these coating methods, the roll method and the electrostatic coating method are preferable from the viewpoint of excellent industrial productivity. By these coating methods, a coating film of the coating liquid can be formed on at least one surface of the conductive base material.
After applying the coating liquid to the conductive base material, it is preferable to carry out a step of drying the coating film, if necessary. By this drying step, the coating film can be formed more firmly on the surface of the conductive base material. The drying conditions can be appropriately selected depending on the composition of the coating liquid, the solvent type, and the like. The drying step is preferably carried out at a temperature of 10 to 90 ° C. for 1 to 20 minutes.

After forming a coating film of the coating liquid on the surface of the conductive base material, it is fired in an oxygen-containing atmosphere. The firing temperature can be appropriately selected depending on the composition of the coating liquid and the solvent type. The firing temperature is preferably 300 to 650 ° C. If the firing temperature is less than 300 ° C., the decomposition of the precursor such as the ruthenium compound becomes insufficient, and the catalyst layer containing ruthenium oxide or the like may not be obtained. If the firing temperature exceeds 650 ° C., the conductive base material may be oxidized, so that the adhesion between the catalyst layer and the base material may decrease. This tendency should be emphasized especially when a titanium base material is used as the conductive base material.
The firing time is preferably longer. On the other hand, from the viewpoint of electrode productivity, it is preferable to adjust so that the firing time does not become excessively long. In consideration of these, the firing time at one time is preferably 5 to 60 minutes.

If necessary, the above-mentioned steps of coating, drying, and firing the catalyst layer can be repeated a plurality of times to form the catalyst layer to a desired thickness. After forming the catalyst layer, firing for a longer period of time can be performed if necessary to further improve the stability of the catalyst layer, which is extremely stable chemically, physically, and thermodynamically. The conditions for long-term firing are preferably about 30 minutes to 4 hours at 400 to 650 ° C.

The electrode for electrolysis according to the present embodiment has a low overvoltage even in the initial stage of electrolysis, and can be electrolyzed with a low voltage and a low power consumption for a long period of time. Therefore, it can be used for various electrolysis. In particular, it is preferably used as an anode for chlorine generation, and more preferably used as an anode for salt electrolysis in the ion exchange membrane method.

(Electrolytic cell)
The electrolytic cell of the present embodiment includes an electrode for electrolysis according to the present embodiment. That is, the electrolytic cell of the present embodiment includes an anode chamber including the electrode for electrolysis according to the present embodiment as an anode, a cathode chamber including the cathode, and an ion exchange film that separates the anode chamber and the cathode chamber. Be prepared. In this electrolytic cell, the initial voltage at the time of electrolysis is reduced. An example of the cross section of the electrolytic cell of this embodiment is schematically shown in FIG.

The electrolytic cell 200 connects the electrolytic solution 210, the container 220 for accommodating the electrolytic solution 210, the anode 230 and the cathode 240 immersed in the electrolytic solution 210, the ion exchange film 250, and the anode 230 and the cathode 240 to the power source. The wiring 260 for this is provided. In the electrolytic cell 200, the space on the anode side separated by the ion exchange membrane 250 is called the anode chamber, and the space on the cathode side is called the cathode chamber. The electrolytic cell of this embodiment can be used for various types of electrolysis. The case where it is used for electrolysis of an aqueous alkali chloride solution will be described below as a typical example.
As the electrolytic solution 210 supplied to the electrolytic tank of the present embodiment, for example, in the anode chamber, an alkaline chloride aqueous solution such as a sodium chloride aqueous solution (salt solution) or a potassium chloride aqueous solution of 2.5 to 5.5 (N) is specified. A diluted alkaline aqueous solution of alkali hydroxide (for example, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, etc.) or water can be used in the cathode chamber.

As the anode 230, the electrode for electrolysis according to this embodiment is used.
As the ion exchange membrane 250, for example, a fluororesin membrane having an ion exchange group or the like can be used. Among the ion exchange membranes, the electrode for electrolysis according to the present embodiment is an ion exchange membrane in which a protrusion (microprojection: delta shape) made of a polymer forming the ion exchange membrane is formed on the surface of the ion exchange membrane on the anode side. It is preferable to use it as an electrolytic cell in combination with. As a specific example thereof, for example, "Aciplex" (registered trademark) F6801 (manufactured by Asahi Kasei Corporation) and the like can be mentioned.

By using an ion exchange membrane having a delta shape, the supply of salt water between the ion exchange membrane and the anode is promoted, and damage to the ion exchange membrane and an increase in salt concentration in caustic soda tend to be suppressed. By combining the ion exchange membrane having a delta shape and the electrode for electrolysis according to the present embodiment, stable electrolysis performance can be maintained. The method for forming the protruding portion is not particularly limited, but can be formed by, for example, the methods described in Japanese Patent No. 4573715 and Japanese Patent No. 4708133.

As the cathode 240, an electrode or the like which is a cathode for hydrogen generation and in which a catalyst is coated on a conductive base material is used. A known cathode can be used. Specifically, for example, nickel, nickel oxide, an alloy of nickel and tin, a combination of activated carbon and an oxide, ruthenium oxide, platinum, etc. can be used on a nickel substrate. Coated cathode; Examples thereof include a cathode in which a coating of ruthenium oxide is formed on a nickel wire mesh base material.

The configuration of the electrolytic cell of the present embodiment is not particularly limited, and may be a single pole type or a double pole type. The material constituting the electrolytic cell is not particularly limited, but for example, the material of the anode chamber is preferably titanium which is resistant to alkali chloride and chlorine; the material of the cathode chamber is resistant to alkali hydroxide and hydrogen. Nickel or the like is preferable.
The electrode for electrolysis (anode 230) according to the present embodiment may be arranged at an appropriate distance from the ion exchange membrane 250, or may be arranged in contact with the ion exchange membrane 250. Can be used without problems. The cathode 240 may be arranged at an appropriate distance from the ion exchange membrane 250, or may be a contact type electrolytic cell (zero gap type electrolytic cell) having no space between the cathode 240 and the ion exchange membrane 250. It can be used without any problem.
The electrolysis conditions of the electrolytic cell of the present embodiment are not particularly limited, and the operation can be performed under known conditions. For example, it is preferable to perform electrolysis by adjusting the electrolysis temperature to 50 to 120 ° C. and the current density to 0.5 to 10 kA / m ^2.

(Reactivation of electrolytic electrodes)
The electrode for electrolysis according to the present embodiment can be suitably used for the purpose of renewing the electrode when the activity of the catalyst-coated electrode existing in the electrolytic cell decreases. That is, the electrode renewal method in the present embodiment includes a step of welding the electrode for electrolysis according to the present embodiment onto the existing electrode in the electrolytic cell. In this way, simply by newly welding the electrode for electrolysis according to the present embodiment onto the existing electrode, the electrolysis performance of the existing electrode whose activity has decreased can be returned to the level before deterioration or further improved, that is, easily. Can be reactivated. Therefore, conventionally, when renewing an existing electrode having reduced activity, the load at the time of electrode renewal has undergone two steps: a step of peeling the existing electrode from the electrolytic cell and a step of welding a new electrode. Can be reduced.
The electrode for electrolysis according to the present embodiment welded as described above and the existing electrode in the electrolytic cell can be regarded as a laminated body. That is, the electrode laminate of the present embodiment includes an electrode for electrolysis according to the present embodiment and a base electrode different from the electrode for electrolysis. The base electrode referred to here is not particularly limited, but typically, an existing electrode in the above-mentioned electrolytic cell and having reduced activity can be mentioned.
The electrode for electrolysis according to the present embodiment, which is suitable for reactivating the electrode for electrolysis, has a thickness of more than 0.5 mm and 0.65 mm or less, and the total peripheral length B of the opening is the aperture ratio A. The value C (= B / A) divided by 3 is preferably greater than 2 and 5 or less. When the thickness is within the above range, it is easy to weld when newly welding on the existing electrode, and the electrolytic performance is returned to the level before deterioration without changing the internal structure and used parts of the existing electrolytic cell. It can be returned or further improved, i.e. reactivated. That is, in the electrode laminate of the present embodiment, the thickness of the electrode for electrolysis is preferably more than 0.5 mm and 0.65 mm or less.

The electrode for electrolysis according to the present embodiment can lower the electrolysis voltage in salt electrolysis as compared with the conventional case. Therefore, according to the electrolytic cell of the present embodiment provided with the electrode for electrolysis, the power consumption required for salt electrolysis can be reduced.
Further, the electrode for electrolysis according to the present embodiment has an extremely stable catalyst layer chemically, physically and thermally, and therefore has excellent long-term durability. Therefore, according to the electrolytic cell of the present embodiment provided with the electrode for electrolysis, the catalytic activity of the electrode is maintained high for a long period of time, and high-purity chlorine can be stably produced.

Hereinafter, the present embodiment will be described in more detail based on the examples. The present embodiment is not limited to these examples.
First, each evaluation method in Examples and Comparative Examples is shown below.

(Ion exchange membrane method salt electrolysis test)
As the electrolytic cell, an electrolytic cell including an anode cell having an anode chamber and a cathode cell having a cathode chamber was prepared.
The electrode for electrolysis prepared in each Example and Comparative Example was cut out to a predetermined size (95 × 110 mm = 0.01045 m ² ) and used as a test electrode, and the test electrode was welded to the rib of the anode chamber of the anode cell. It was attached to and used as an anode.
As the cathode, a nickel wire mesh base material coated with ruthenium oxide catalyst was used. First, on the rib of the cathode chamber of the cathode cell, an expanded base material made of metallic nickel as a current collector is cut out to the same size as the anode and welded, and then a cushion mat woven with nickel wire is placed on it. A cathode was placed.
As the gasket, a rubber gasket made of EPDM (ethylene propylene diene) was used, and an ion exchange membrane was sandwiched between the anode cell and the cathode cell. As this ion exchange membrane, a cation exchange membrane "Aciplex" (registered trademark) F6801 (manufactured by Asahi Kasei Corporation) for salt electrolysis was used.

The measurement of the electrolytic voltage was carried out by measuring the potential difference between the cathode and the anode. In order to measure the initial electrolysis performance of the anode, the electrolysis voltage was measured 5 days after the start of electrolysis. The electrolysis conditions were a current density of 6 kA / m ² , a salt water concentration of 205 g / L in the anode cell, a NaOH concentration of 32% by mass in the cathode cell, and a temperature of 90 ° C. As a rectifier for electrolysis, "PAD36-100LA" (manufactured by Kikusui Electronics Co., Ltd.) was used.

[Example 1]
As the conductive base material, a titanium expanded metal having a mesh short distance center-to-center distance (SW) of 2.1 mm, a mesh long-direction center-to-center distance (LW) of 3 mm, and a plate thickness of 0.81 mm was used. The plate thickness was measured with a thickness gauge. Further, the values of SW, LW, St, aperture ratio, and the sum of the peripheral lengths of the openings are obtained by observing a predetermined range of the surface of the conductive base material with an image observation device such as a microscope and photographing the projection surface. Obtained by analyzing the data. As a method for analyzing image data, the publicly owned "Image J" developed by the National Institutes of Health (NIH) was used for image processing. The image size used for the image processing was in the range of 8.0 × 5.3 mm of the conductive base material. That is, for the openings existing in this range, the distance between the centers in the short direction of the mesh specified for each of the adjacent openings, the distance between the centers in the long direction of the mesh, and the mesh of the openings. The values obtained by subtracting the maximum opening in the short direction of the mesh of the opening from the distance between the centers in the short direction were measured, and the average values thereof were calculated and used as SW, LW, and St, respectively. Hereinafter, for the conductive base material and the electrode for electrolysis in each Example and Comparative Example, SW, LW, St, aperture ratio A, total peripheral length of the opening B, peripheral length of one opening, as described above. It was decided to obtain the values of E (= B / (A × (SW ² + LW ² ) ^{1/2)) and the thickness.} This expanded metal is calcined in the air at 540 ° C. for 4 hours to form an oxide film on the surface, and then acid-treated in 25% by mass sulfuric acid at 85 ° C. for 4 hours to cause fine irregularities on the surface of the conductive substrate. Pretreatment was performed.
Next, reduce the ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) to 5 ° C or lower with dry ice so that the element ratio (molar ratio) of ruthenium, iridium, and titanium is 25:25:50. While cooling and stirring, add titanium tetrachloride (manufactured by Kishida Chemical Co., Ltd.) little by little, and then add an aqueous solution of iridium chloride (manufactured by Tanaka Kikinzoku Co., Ltd., iridium concentration 100 g / L) little by little to bring the total metal concentration to 100 g / L. A coating liquid CL1 which is an aqueous solution of L was obtained. On the other hand, the ruthenium chloride aqueous solution and titanium tetrachloride were mixed in the same manner as described above so that the element ratio (molar ratio) of ruthenium and titanium was 35:65, and the total metal concentration was 100 g / L. A coating liquid CL2, which is an aqueous solution, was obtained.

This coating liquid CL1 is injected into the liquid receiving vat of the coating machine, and the coating liquid CL1 is sucked up and impregnated by rotating the EPDM sponge roll, and the PVC roll is placed in contact with the upper part of the sponge roll. Placed. Then, a pretreated conductive base material was passed between the EPDM sponge roll and the PVC roll for coating. Immediately after coating, the conductive substrate after coating was passed between two EPDM sponge rolls wrapped with cloth, and excess coating liquid was wiped off. Then, it was dried at 50 ° C. for 10 minutes, and then calcined in the air at 475 ° C. for 10 minutes.
The cycle consisting of roll coating, drying, and firing was repeated 7 times in total, and then firing at 520 ° C. for 1 hour was further performed to form a dark brown first catalyst layer on the conductive substrate. On the base material on which the first catalyst layer was formed, roll coating was performed in the same manner as when coating with the coating liquid CL1 except that the coating liquid was replaced with CL2, and then drying was performed in the air. Baking was carried out at 440 ° C. for 10 minutes. Finally, it was calcined in the air at 440 ° C. for 60 minutes to prepare an electrode for electrolysis.
The obtained electrolytic electrode has a thickness of 0.81 mm, an aperture ratio of 7.4%, the number of openings per projected area of the electrode is more ^{than 20 / cm 2} , and the total peripheral length of the openings is divided by the aperture ratio. Was 4.54. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.28, and the value obtained by dividing St by SW was 0.76.

[Comparative Example 1]
The conductive base material in Example 1 was a titanium expanded metal having a mesh with a short center-to-center distance (SW) of 3 mm, a mesh with a long-direction center-to-center distance (LW) of 6 mm, and a plate thickness of 1.0 mm. Except for the above, an electrode for electrolysis was produced by the same method as in Example 1.
The obtained electrolytic electrode has a thickness of 1.0 mm, an aperture ratio of 37.8%, the number of openings per projected area of the electrode is 13 / cm ² , and the sum of the peripheral lengths of the openings divided by the aperture ratio is the value. It was 1.06. Further, the shape of the opening was observed to be the same as that shown in FIG. 4C, and the opening 100'was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100'was vertically symmetrical with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.03, and the value obtained by dividing St by SW was 0.667.

[Example 2]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.2 mm, a mesh with a long-direction center-to-center distance (LW) of 4.2 mm, and a plate thickness of 0.8 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The obtained electrolytic electrode has a thickness of 0.80 mm, an aperture ratio of 10.9%, the number of openings per projected area of the electrode is 20 / cm ² , and the total peripheral length of the openings is divided by the aperture ratio. It was 3.26. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.64, and the value obtained by dividing St by SW was 0.73.

[Example 3]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.3 mm, a mesh with a long-direction center-to-center distance (LW) of 3.3 mm, and a plate thickness of 0.83 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The resulting electrode for electrolysis has a thickness 0.83 mm, opening ratio 9.25%, the opening parts per projected area of the electrode is 20 / cm ^2, greater than a value obtained by dividing the sum of the perimeter of the opening by an aperture Was 3.65. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.27, and the value obtained by dividing St by SW was 0.70.

[Example 4]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.3 mm, a mesh with a long-direction center-to-center distance (LW) of 3.3 mm, and a plate thickness of 0.81 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The obtained electrolytic electrode has a thickness of 0.81 mm, an aperture ratio of 22.1%, the number of openings per projected area of the electrode is more ^{than 20 / cm 2} , and the total peripheral length of the openings is divided by the aperture ratio. Was 2.05. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.28, and the value obtained by dividing St by SW was 0.43.

[Example 5]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 1.6 mm, a mesh with a long-direction center-to-center distance (LW) of 3.0 mm, and a plate thickness of 0.56 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The obtained electrolytic electrode has a thickness of 0.56 mm, an aperture ratio of 17.5%, the number of openings per projected area of the electrode is 43 / cm ² , and the total peripheral length of the openings is divided by the aperture ratio. It was 3.30. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.88, and the value obtained by dividing St by SW was 0.65.

[Example 6]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.1 mm, a mesh with a long-direction center-to-center distance (LW) of 3.1 mm, and a plate thickness of 0.81 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The resulting electrode for electrolysis has a thickness 0.81 mm, opening ratio 15.5%, the opening parts per projected area of the electrode is 20 / cm ^2, greater than a value obtained by dividing the sum of the perimeter of the opening by an aperture Was 2.72. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.42, and the value obtained by dividing St by SW was 0.67.

[Example 7]
The coating liquid CL1 in Example 1 was applied to the titanium expanded metal (SW: 2.2 mm, LW: 3.2 mm, plate thickness 0.82 mm) produced in the same manner as in Example 6 in the same manner as in Example 1. A first catalyst layer was formed on the conductive substrate.
Next, an aqueous ruthenium nitrate solution (manufactured by Furuya Metal Co., Ltd., ruthenium concentration 100 g /) so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 21.25: 21.25: 42.5: 15. While cooling and stirring L) with dry ice to 5 ° C. or lower, titanium tetrachloride (manufactured by Wako Pure Chemical Industries, Ltd.) was added little by little, and then an aqueous solution of iridium chloride (manufactured by Tanaka Kikinzoku Co., Ltd., iridium concentration 100 g / L) and Vanadium (III) chloride (manufactured by Kishida Chemical Co., Ltd.) was added little by little to obtain a coating liquid CL3 which is an aqueous solution having a total metal concentration of 100 g / L. On the base material on which the first catalyst layer was formed, the first firing temperature was set to 400 ° C. in a cycle consisting of roll coating, drying, and firing using the coating liquid CL3 in the same manner as in Example 1. Then, the temperature was raised to 450 ° C. and repeated three times, and finally, firing at 520 ° C. for 1 hour was further carried out to prepare an electrode for electrolysis.
The obtained electrolytic electrode has a thickness of 0.82 mm, an aperture ratio of 16.1%, the number of openings per projected area of the electrode is more ^{than 20 / cm 2} , and the total peripheral length of the openings is divided by the aperture ratio. Was 2.73. Further, the shape of the opening was observed to be the same as that shown in FIG. 4A, and the opening 100 was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100 was vertically asymmetric with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.38, and the value obtained by dividing St by SW was 0.63.

[Comparative Example 2]
The conductive substrate according to Example 1 is rolled with a mesh with a short center-to-center distance (SW) of 2.3 mm, a mesh with a long-direction center-to-center distance (LW) of 3.0 mm, and a plate thickness of 0.6 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that the expanded metal was made of titanium which was not flattened by a roll.
The obtained electrode for electrolysis had a thickness of 0.6 mm, an aperture ratio of 43.3%, and a value obtained by dividing the total peripheral length of the openings by the aperture ratio was 1.07. Further, the shape of the opening was observed to be the same as that shown in FIG. 4C, and the opening 100'was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100'was vertically symmetrical with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 0.90, and the value obtained by dividing St by SW was 0.45.

[Comparative Example 3]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.1 mm, a mesh with a long-direction center-to-center distance (LW) of 4.0 mm, and a plate thickness of 0.5 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The obtained electrode for electrolysis had a thickness of 0.5 mm, an aperture ratio of 35.7%, and a value obtained by dividing the total peripheral length of the openings by the aperture ratio was 1.78. Further, the shape of the opening was observed to be the same as that shown in FIG. 4C, and the opening 100'was symmetrical with respect to the first virtual center line 101 extending in the short direction α of the mesh. Further, the opening 100'was vertically symmetrical with respect to the second virtual center line 102 extending in the long direction β of the mesh. Furthermore, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b was 1.10, and the value obtained by dividing St by SW was 0.48.

[Ion exchange membrane method salt electrolysis test]
The ion exchange membrane method salt electrolysis test was carried out using the electrodes for electrolysis prepared in Examples 1 to 6 and Comparative Examples 1 to 3, respectively. The results are shown in Table 1.
In Table 1, the expanded metal used as the conductive base material was flattened by a rolling roll as “FR ○” and not flattened as “FR ×”. Further, the amount of reduction in the electrolytic voltage based on Comparative Example 1 was set as a positive value of "effect: ΔV".

At a current density of 6 kA / m ² , the reduction in electrolytic voltage based on Comparative Example 1 was 35 mV in Example 1, 43 mV in Example 2, 41 mV in Example 3, 8 mV in Example 4, and in Example 5. It was 42 mV and 19 mV in Example 6, and it was found that the electrolytic voltage could be reduced as compared with Comparative Example 1.
On the other hand, in Comparative Examples 2 and 3, the electrolytic voltage was increased by 23 mV and 19 mV, respectively, as compared with Comparative Example 1.

In addition, an ion exchange membrane method salt electrolysis test was carried out using the electrodes for electrolysis prepared in Examples 6 to 7 and Comparative Example 1, respectively. The results are shown in Table 2 together with the types of coating liquids for the catalyst layer.

At a current density of 6 kA / m ² , the amount of reduction in the electrolytic voltage based on Comparative Example 1 is 19 mV in Example 6 and 39 mV in Example 7, and both can reduce the electrolytic voltage as compared with Comparative Example 1. Do you get it. In particular, from the comparison between Example 6 and Example 7, it was found that when the electrode for electrolysis according to this embodiment has a vanadium-containing catalyst layer, the effect of reducing the electrolysis voltage is further increased.

[Example 8]
The electrode for electrolysis of Example 5 was used for reactivation of the electrode having reduced activity. As an electrode with reduced activity, an electrode for electrolysis produced in the same manner as in Comparative Example 1 energized for 6.9 years in an electrolytic cell of a semi-commercial plant was cut out ^{to a predetermined size (95 × 110 mm = 0.0145 m 2).} Was used as a base electrode, and this base electrode was attached to the rib of the anode chamber of the anode cell by welding. The electrolytic voltage of this base material electrode at a current density of 6 kA / m ² increased by 32 mV with reference to Comparative Example 1. The electrode for electrolysis of Example 5 was welded onto the base electrode as an electrode for renewal to form an electrolytic cell containing an electrode laminate.

[Example 9]
The conductive base material in Example 1 is made of titanium having a mesh with a short center-to-center distance (SW) of 2.2 mm, a mesh with a long-direction center-to-center distance (LW) of 3.0 mm, and a plate thickness of 0.52 mm. An electrode for electrolysis was produced by the same method as in Example 1 except that it was made of expanded metal.
The obtained electrode for electrolysis had a thickness of 0.52 mm, an aperture ratio of 23.3%, and a value obtained by dividing the total peripheral length of the openings by the aperture ratio was 2.36.
The above-mentioned electrode for electrolysis was used for reactivation of the electrode having reduced activity. As an electrode with reduced activity, an electrode for electrolysis produced in the same manner as in Comparative Example 1 energized for 7.1 years in an electrolytic cell of a manufacturing plant was cut out ^{to a predetermined size (95 × 110 mm = 0.0145 m 2).} It was used as a material electrode, and this base electrode was attached to the rib of the anode chamber of the anode cell by welding. The electrolytic voltage of this base material electrode at a current density of 6 kA / m ² increased by 35 mV with reference to Comparative Example 1. The above-mentioned electrode for electrolysis was welded onto the base electrode as a renewal electrode to form an electrolytic cell containing an electrode laminate.

The ion exchange membrane method salt electrolysis test was carried out using the electrolytic cells prepared in each of Examples 8 to 9. The results are shown in Table 3.

At a current density of 6 kA / m ² , the amount of reduction in the electrolytic voltage based on Comparative Example 1 was 33 mV in Example 8 and 24 mV in Example 9, both of which the electrolytic voltage was reduced as compared with Comparative Example 1. It was found that when the existing electrode with reduced activity is renewed, the electrolytic performance can be returned to the pre-deterioration level or further improved, that is, reactivated.

Since the electrode for electrolysis of the present invention can suppress the voltage and power consumption during electrolysis to a low level and has practical strength, it can be suitably used in the field of salt electrolysis. In particular, it is useful as an anode for ion exchange membrane method salt electrolysis, and makes it possible to produce high-purity chlorine gas having a low oxygen gas concentration for a long period of time with a low voltage and low power consumption.

1 Electrode 2, 3 Opening 10 Electrode for electrolysis 20 Opening 100 Opening 100'Opening 101 First virtual center line 102 Second virtual center line a Part a
b part b
200 Electrolytic cell for electrolysis 210 Electrolyte 220 Container 230 Anode (electrode for electrolysis)
240 Cathode 250 Ion exchange membrane 260 Wiring 300 Electrode electrode 310 Distance between centers in the short direction of the mesh of the opening (short diameter SW)
320 Distance between centers in the long direction of the mesh of the opening (major axis LW)
330 Second virtual centerline 340 Part a
350 part b
The distance between the shortest openings of the 360 opening mesh

Claims (3)

A conductive base material made of a perforated metal plate and
With at least one catalyst layer formed on the surface of the conductive substrate,
Electrode for electrolysis
The shape of the opening of the electrolytic electrode is symmetrical with respect to the first virtual center line extending in the short direction of the mesh, and is symmetrical with respect to the second virtual center line extending in the long direction of the mesh. It is vertically asymmetric and
An electrode for electrolysis in which the thickness of the electrode for electrolysis is more than 0.5 mm and 1.2 mm or less. When the opening is divided into one portion a and the other portion b by the second virtual center line, the value obtained by dividing the area Sa of the portion a by the area Sb of the portion b is 1.15 or more. The electrode for electrolysis according to claim 1 , which is 2.0 or less. The value St obtained by subtracting the short-time direction maximum mesh opening of mesh of the opening from the short-time direction center distance SW of the mesh of the opening, divided by the SW is 0.4 or more, claim The electrode for electrolysis according to 1 or 2.

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