JP6670948B2 - Electrode for electrolysis - Google Patents

Description

  The present invention relates to an electrode for electrolysis and a method for producing the same, and an electrolytic cell provided with the electrode for electrolysis.

The ion exchange membrane method salt electrolysis is a method of electrolyzing (electrolyzing) salt water using an electrode for electrolysis to produce caustic soda, chlorine, and hydrogen. In the ion exchange membrane salt electrolysis process, a technology capable of maintaining a low electrolysis voltage for a long period of time is required to reduce power consumption.
When the breakdown of the electrolysis voltage is analyzed in detail, in addition to the theoretically required electrolysis voltage, the voltage caused by the resistance of the ion exchange membrane and the structural resistance of the electrolytic cell, the overvoltage of the anode and the cathode, and the anode and cathode It has been clarified that a voltage or the like due to the distance between the two is included. Further, if the electrolysis is continued for a long time, a voltage rise or the like caused by various causes such as impurities in the salt water may occur.

  Among the above-mentioned electrolysis voltages, various studies have been made for the purpose of reducing the overvoltage of the anode for generating chlorine. For example, Patent Literature 1 discloses a technique of an insoluble anode in which an oxide of a platinum group metal such as ruthenium is coated on a titanium substrate. This anode is called DSA (registered trademark, Dimension Stable Anode: dimensionally stable anode). Non-Patent Document 1 describes the transition of soda electrolysis technology using DSA.

Regarding the above-mentioned DSA, various improvements have been made so far, and studies for improving the performance have been made.
For example, Patent Literature 2 focuses on a low chlorine overvoltage and a high oxygen overvoltage of palladium in the platinum group, and reports a chlorine generation electrode in which platinum and palladium are alloyed. Patent Literature 3 and Patent Literature 4 propose an electrode in which the surface of a platinum-palladium alloy is oxidized to form palladium oxide on the surface. Patent Literature 5 proposes an electrode which is mainly composed of a tin oxide and is covered with an external catalyst layer containing ruthenium, iridium, palladium, and niobium oxides. In order to obtain high-purity chlorine having a low oxygen concentration by using this electrode, attempts have been made to suppress the oxygen generation reaction at the anode, which occurs simultaneously with the generation of chlorine.

Japanese Patent Publication No. 46-021884 Japanese Patent Publication No. 45-11014 Japanese Patent Publication No. 45-11015 JP-B-48-3954 JP 2012-508326 A

Hiroaki Aikawa, "National Science Museum, Technology Systematization Survey Report Vol. 8", published by The National Science Museum, March 30, 2007, p. 32

However, in the conventional anode such as DSA described in Patent Literature 1, the overvoltage is high immediately after the start of electrolysis, and it takes a certain period of time to settle to a low overvoltage due to activation of the catalyst. Problem.
Further, the electrodes for chlorine generation described in Patent Documents 2 to 4 have high overvoltage and low durability in some cases. Furthermore, in the production of the electrodes described in Patent Documents 3 and 4, it is necessary to use an alloy for the base material itself, and after forming an oxide on the base material by thermal decomposition, alloying by reduction and further electrolytically A complicated process such as palladium oxide conversion by oxidation is required, and significant improvements are required both in practical use and in manufacturing methods.
Although the electrode described in Patent Document 5 has a certain effect in improving the electrolysis duration (electrode life) of palladium having poor chemical resistance, the chlorine generation overpotential cannot be said to be sufficiently low.
As described above, in the techniques described in Patent Literatures 1 to 5 and Non-Patent Literature 1, an electrolysis electrode capable of performing electrolysis with a sufficiently low overvoltage at the initial stage of electrolysis and low voltage and low power consumption for a long time is used. Can not be realized.

  The present invention has been made to solve the above-mentioned problem. Accordingly, the present invention provides an electrode for electrolysis that can reduce overvoltage at the initial stage of electrolysis and can perform electrolysis with low voltage and low power consumption for a long period of time, a method for manufacturing the same, and an electrolytic cell provided with the electrode for electrolysis. The purpose is to:

The present inventors have intensively studied to solve the above-mentioned problems. As a result, by adjusting the numerical value which is an index of the electric double layer capacity of the electrode for electrolysis having a catalyst layer containing a predetermined metal element in a predetermined ratio to a specific range, it is possible to reduce the overvoltage at the beginning of electrolysis, and The present inventors have found that electrolysis can be performed with low voltage and low power consumption over a long period of time, and have accomplished the present invention.
That is, the present invention is as follows.
[1]
A conductive substrate;
A catalyst layer formed on the surface of the conductive substrate,
An electrode for electrolysis comprising:
The catalyst layer contains a ruthenium element, an iridium element, a titanium element, and at least one first transition metal element selected from the group consisting of Sc, V, Cr, Fe, Co, Ni, Cu, and Zn,
A content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the titanium element is 0.25 mol% or more and less than 3.4 mol%,
The D values indicative of the electric double layer capacity of the electrode for electrolysis is 120C / ^{m 2} or more 420C / ^{m 2} or less, the electrode for electrolysis.
[2]
The electrode for electrolysis according to [1], wherein the first transition metal element forms a solid solution with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide.
[3]
The electrode for electrolysis according to [1] or [2], wherein the first transition metal element includes at least one metal element selected from the group consisting of vanadium, cobalt, copper, and zinc.
[4]
The electrode for electrolysis according to any one of [1] to [3], wherein the first transition metal element includes a vanadium element.
[5]
The electrode for electrolysis according to any one of [1] to [4], wherein a content of the first transition metal element with respect to all metal elements included in the catalyst layer is 10 mol% or more and 30 mol% or less.
[6]
The electrode for electrolysis according to any one of [1] to [5], wherein a content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the ruthenium element is 0.3 mol or more and less than 2 mol. .
[7]
The electrode for electrolysis according to any one of [1] to [6], wherein the D value is 120 C / m ² or more and 380 C / m ² or less.
[8]
A method for producing an electrode for electrolysis according to any one of [1] to [7],
Ruthenium compound, iridium compound, titanium compound, and a step of preparing a coating solution containing a compound containing the first transition metal element,
A step of applying the coating liquid on at least one surface of the conductive substrate to form a coating film,
Baking the coating film under an oxygen-containing atmosphere to form the catalyst layer,
A method for producing an electrode for electrolysis, comprising:
[9]
An electrolytic cell comprising the electrode for electrolysis according to any one of [1] to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the electrode for electrolysis which can reduce the overvoltage of the initial stage of electrolysis and can perform electrolysis with low voltage and low power consumption for a long period of time is provided.

FIG. 1 is a schematic cross-sectional view according to an example of the electrolytic cell of the present embodiment. FIG. 2 is a plot of the measured V / Ti value obtained by XPS depth direction analysis and the V / Ti value of the charge in the coating liquid for four samples having different element ratios (molar ratios) of V and Ti. 4 is a graph showing the result of linear approximation.

  Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiment is an exemplification for describing the present invention, and is 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 invention.

The electrode for electrolysis of the present embodiment is an electrode for electrolysis comprising a conductive substrate and a catalyst layer formed on the surface of the conductive substrate, wherein the catalyst layer is a ruthenium element, an iridium element. , Titanium element, and at least one first transition metal element selected from the group consisting of scandium, vanadium, chromium, iron, cobalt, nickel, copper and zinc (hereinafter, these transition metal elements are collectively referred to as A transition metal element "). Furthermore, in the electrode for electrolysis of the present embodiment, the content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the titanium element is 0.25 mol% or more and less than 3.4 mol%. D values indicative of the electric double layer capacity of use electrodes are configured to be 120C / ^{m 2} or more 420C / ^{m 2} or less.
In the present embodiment, in the catalyst layer, elemental ruthenium, in addition to the iridium and titanium element, by using a first transition metal element, from RuO ₂ as measured by X-ray photoelectron spectroscopy (XPS) Ru3d5 / 2 is an electrode for electrolysis in which the peak position of the peak attributed to No. ₂ is shifted from 280.5 eV of RuO ₂ to the higher binding energy side. Note that the XPS charging correction is performed so that the binding energy of Ti2p3 / 2 becomes 458.4 eV. The shift of the peak position of Ru3d5 / 2 to the higher binding energy side indicates a state in which Ru is electrically oxidized, which is considered to be due to the addition of the first transition metal element. For example, when vanadium is added as the first transition metal element, the following polarization occurs.
RuO ₂ + VO ₂ → RuO ₂ ^δ ++ VO ₂ ^δ−
RuO ₂ ^{δ +} becomes an active adsorption site for adsorbing chlorine, and by promoting chlorine adsorption, the overvoltage of chlorine generation can be reduced.
Although not intended to be limited to the above-described mechanism of action, the electrode for electrolysis of the present embodiment has the above-described configuration.When electrolysis is performed using the electrode for electrolysis, the overvoltage at the beginning of electrolysis can be reduced, and Electrolysis can be performed for a long time with low voltage and low power consumption. The electrode for electrolysis of the present embodiment can be suitably used as an electrode for chlorine generation particularly in ion exchange membrane method salt electrolysis.

(Conductive substrate)
The electrode for electrolysis of this embodiment is used in a chlorine gas generating atmosphere in a saline solution having a high concentration close to saturation. Therefore, as a material of the conductive substrate in the present embodiment, a valve metal having corrosion resistance is preferable. Examples of the valve metal include, but are not limited to, titanium, tantalum, niobium, and zirconium. Titanium is preferred from the viewpoint of economy and affinity with the catalyst layer.
The shape of the conductive substrate is not particularly limited, and an appropriate shape can be selected depending on the purpose. For example, an expanded shape, a perforated plate, a wire mesh or the like is suitably used. The thickness of the conductive substrate is preferably 0.1 to 2 mm.
The surface of the conductive substrate that is in contact with the catalyst layer is preferably subjected to a surface area increasing treatment in order to improve the adhesion to the catalyst layer. The method of the surface area increasing treatment is not limited to the following, but includes, for example, a blast treatment using a cut wire, a steel grid, an alumina grid, or the like; an 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 substrate by blast treatment and further performing an acid treatment is preferable.

(Catalyst layer)
The catalyst layer formed on the surface of the conductive substrate subjected to the above-described treatment contains a ruthenium element, an iridium element, a titanium element, and a first transition metal element.
The ruthenium element, the iridium element, and the titanium element are preferably each in the form of an oxide.
Examples of the ruthenium oxide include, but are not limited to, RuO _{2 and the} like.
Examples of the iridium oxide include, but are not limited to, IrO _{2 and the} like.
Examples of the titanium oxide include, but are not limited to, TiO _{2 and the} like.

In the catalyst layer of this embodiment, it is preferable that ruthenium oxide, iridium oxide, and titanium oxide form a solid solution. When the ruthenium oxide, the iridium oxide, and the titanium oxide form a solid solution, the durability of the ruthenium oxide is further improved.
A solid solution generally refers to a substance in which two or more types of substances are dissolved with each other and the whole is a uniform solid phase. Examples of the substance forming the solid solution include simple metals and metal oxides. In particular, in the case of a solid solution of a metal oxide suitable for the present embodiment, two or more types of metal atoms are irregularly arranged on equivalent lattice points in a unit cell in the oxide crystal structure. Specifically, ruthenium oxide, iridium oxide, and titanium oxide are mixed with each other, and when viewed from the ruthenium oxide side, a substitution type in which a ruthenium atom is replaced by an iridium atom or a titanium atom or both of them. It is preferably a solid solution. The solid solution state is not particularly limited, and a partial solid solution region may be present.
The solid solution slightly changes the size of the unit cell in the crystal structure. The degree of this change can be confirmed, for example, by measurement of the powder X-ray diffraction that the diffraction pattern caused by the crystal structure does not change and the peak position caused by the size of the unit cell changes.

  In the catalyst layer of the present embodiment, the content ratio of the ruthenium element, the iridium element, and the titanium element is 0.06 to 3 mol of the iridium element per 1 mol of the ruthenium element, and the titanium element is 0.2 to 8 mol. Mol; preferably 1 to 2 mol of ruthenium element, more preferably 0.2 to 3 mol of iridium element and 0.2 to 8 mol of titanium element; 1 mol of ruthenium element , The iridium element is preferably from 0.3 to 2 mol, and the titanium element is more preferably from 0.2 to 6 mol; the iridium element is from 0.5 to 1.5 mol per 1 mol of the ruthenium element; It is particularly preferable that the amount of the titanium element is 0.2 to 3 mol. When the content ratio of the three elements is 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 included in the catalyst layer in a form other than the oxide, for example, as a simple metal.

  The catalyst layer of the present embodiment contains a first transition metal element together with the ruthenium element, the iridium element, and the titanium element. The form in which the first transition metal element is present is not particularly limited. For example, whether it is in the form of an oxide, a simple metal, or an alloy, the first transition metal element may be contained in the catalyst layer. In the present embodiment, it is preferable that the first transition metal element forms a solid solution with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide from the viewpoint of durability of the catalyst layer. The formation of such a solid solution can be confirmed by, for example, XRD. In addition, the above solid solution can be formed by adjusting the firing temperature and the amount of the first transition metal element added when forming the catalyst layer to an appropriate range.

  In the present embodiment, the first transition metal element preferably contains a metal element selected from the group consisting of vanadium, cobalt, copper and zinc, from the viewpoint of compatibility between voltage and durability of the catalyst layer. More preferably, the metal element contains a vanadium element.

In the present embodiment, the content of the first transition metal element with respect to all the metal elements contained in the catalyst layer is preferably 10 mol% or more and 30 mol% or less, more than 10 mol% and 22.5 mol% or less. More preferably, it is 12 mol% or more and 20 mol% or less. When the first transition metal element contains vanadium, it is particularly preferable that the content of vanadium with respect to all metal elements contained in the catalyst layer satisfies the above range.
The above content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the method for producing a preferable electrode for electrolysis described later, but is described later in section STEM-EDX or X-ray photoelectron spectroscopy. It can be confirmed by a depth direction analysis using the XPS method.
When the content ratio of the first transition metal element is 10 mol% or more, the chlorine overvoltage or the electrolysis voltage tends to be reduced from the initial stage of electrolysis. When the content ratio of the first transition metal element is 30 mol% or less, the durability of the ruthenium oxide tends to be sufficiently ensured.

In the present embodiment, the content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the ruthenium element is preferably 0.3 mol or more and less than 2 mol, and is 0.5 mol or more and less than 2 mol. More preferably, it is 0.5 mol or more and less than 1.8 mol. When the first transition metal element contains vanadium, it is particularly preferable that the content ratio of vanadium to 1 mol of the ruthenium element contained in the catalyst layer satisfies the above range.
The above content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the method for producing a preferable electrode for electrolysis described later, but is described later in section STEM-EDX or X-ray photoelectron spectroscopy. It can be confirmed by a depth direction analysis using the XPS method.
When the content ratio of the first transition metal element is 0.3 mol or more per mol of the ruthenium element, the chlorine generation overvoltage or the electrolysis voltage tends to be reduced from the beginning of electrolysis, and the electric double layer capacity described later There is a tendency that the D value as an index of can be sufficiently increased. If the amount is less than 2 mol, the durability of the ruthenium oxide tends to be sufficiently ensured.

In the present embodiment, the content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the titanium element is from 0.25 mol to less than 3.4 mol, and from 0.25 mol to less than 2.6 mol. Preferably, there is. When the first transition metal element contains vanadium, it is particularly preferable that the content ratio of vanadium to 1 mol of the titanium element contained in the catalyst layer satisfies the above range.
The above content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the method for producing a preferable electrode for electrolysis described later, but is described later in section STEM-EDX or X-ray photoelectron spectroscopy. It can be confirmed by a depth direction analysis using the XPS method.
When the content ratio of the first transition metal element is 0.25 mol or more per 1 mol of the titanium element, the chlorine overvoltage or the electrolysis voltage tends to be reduced from the initial stage of electrolysis, and the electric double layer capacity to be described later is reduced. There is a tendency that the D value as an index of can be sufficiently increased. When the amount is less than 3.4 mol, the durability of the ruthenium oxide tends to be sufficiently secured.

The element ratio (molar ratio) between V and Ti in the catalyst layer in the electrode for electrolysis can be confirmed by, for example, cross-sectional STEM-EDX or depth direction analysis by X-ray photoelectron spectroscopy (XPS). For example, a method for obtaining an element ratio (molar ratio) between V and Ti in a catalyst layer containing a ruthenium element, an iridium element, a titanium element, and a vanadium element as a first transition metal element by XPS depth direction quantitative analysis is described below. . Here, a Ti base is used as the conductive base.
The XPS measurement conditions can be as follows.
Apparatus: PHI5000VersaProbeII manufactured by ULVAC-PHI,
Excitation source: monochromatic AlKα (15 kV × 0.3 mA),
Analysis size: about 200 μmφ,
Photoelectron extraction angle: 45 °
PassEnergy: 46.95 eV (Narrow scan)
Ar ⁺ sputtering conditions can be as follows.
Acceleration voltage: 2 kV,
Raster range: 2mm square,
There is Zalar rotation.

Regarding the method of calculating the concentration, the spectral levels of the photoelectron peaks used for quantification of Ru, Ir, Ti, and V are Ru3d, Ir4f, Ti2p, and V2p3 / 2. Since Ru3p3 / 2 overlaps with Ti2p and Ti3s overlaps with Ir4f, quantification can be performed by the following procedure.
(1) Ru3d, Ir4f (including Ti3s), Ti2p (including Ru3p3 / 2), and V2p3 / 2 peak area intensity at each sputtering time (each depth) using the analysis software “MaltiPak” attached to the apparatus. (Hereinafter, peak area intensity).
(2) Calculate the peak area intensity of Ru3p3 / 2 based on the peak area intensity of Ru3d. The calculation is performed using the ratio of the corrected RSF (relative sensitivity factor corrected by the value of the path energy) of the MultiPak. This is subtracted from the peak area intensity of Ti2p containing Ru3p3 / 2, and the peak area intensity of only Ti2p is calculated.
(3) Based on the corrected peak area intensity of Ti2p, the peak area intensity of Ti3s is calculated using the ratio of Corrected RSF. This is subtracted from the peak area intensity of Ir4f containing Ti3s, and the peak area intensity of Ir4f alone is calculated.

  The actual measured value of the element ratio (molar ratio) between V and Ti in the catalyst layer obtained by the XPS depth direction quantitative analysis is based on the following formula, and the respective depths in the depth range of the catalyst layer in which V is detected. And the ratio of the value obtained by integrating the peak area intensity of V2p3 / 2 and the value divided by the corrected RSF of V2p3 / 2 and the value obtained by integrating the peak area intensity of Ti2p at each depth and dividing by the corrected RSF of Ti2p. I do. The depth range of the catalyst layer in which the peak area intensity of each element is integrated is, for example, in the case where the catalyst layer is a single layer, the depth range from the start of detection of the signal of Ti derived from the Ti base material from the outermost surface. I do. Here, when the catalyst layer is a multilayer, the layers other than the catalyst layer directly formed on the surface of the Ti base are defined as the depth ranges of the respective catalyst layers, and the thickness of the catalyst layer directly formed on the surface of the Ti base is determined. Is a depth range until a signal of Ti derived from the Ti base material starts to be detected.

With respect to the following four samples a to d having different element ratios (molar ratios) of V and Ti, the actually measured values of V / Ti obtained by the XPS depth direction analysis by the above-described measurement method and the values of V / Ti in the coating liquid FIG. 2 shows the results of plotting the charged V / Ti values.
(Sample a) Electrode for Electrolysis with V / Ti Charge Ratio of 0.11 The element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 23.75: 23.75: 47.5: 5, respectively. An electrode for electrolysis obtained by a method similar to that of Example 1 described later, except that the conductive liquid was applied to the conductive substrate using the coating liquid a prepared as follows.
(Sample b) Electrode for Electrolysis with V / Ti Charge Ratio of 0.22 The element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 22.5: 22.5: 45: 10, respectively. An electrode for electrolysis obtained by the same method as in Example 1 except that the conductive liquid was applied to the conductive substrate using the coating liquid b prepared in Example 1.
(Sample c) Electrode for Electrolysis with V / Ti Charge Ratio of 0.35 An electrode for electrolysis obtained by the same method as in Example 1 described later.
(Sample d) Electrode for Electrolysis with V / Ti Charge Ratio of 1.13 An electrode for electrolysis obtained by the same method as in Example 3 described later.

As shown in FIG. 2, since the measured value of V / Ti and the value of the charge show a positive correlation, the calibration curve shows the relationship between V and Ti in the catalyst layer containing the ruthenium, iridium, titanium and vanadium elements. The element ratio (molar ratio) can be determined. When the components contained in the catalyst layer are changed, a calibration curve of the actually measured value of V / Ti and the charged value is prepared in the same manner to obtain an element ratio (molar ratio) of V and Ti in the catalyst layer. ).
In the electrode for electrolysis of the present embodiment, the catalyst layer may be composed of only one layer, or may have a multilayer structure of two or more layers. In the case of a multi-layer structure, the content ratio of the first transition metal element contained in at least one layer to 1 mol of the titanium element may be 0.25 mol or more and less than 3.4 mol. May not satisfy the content ratio.

Electrode for electrolysis of this embodiment, D values indicative of the electric double layer capacitor is characterized in that at 120C / ^{m 2} or more 420C / ^{m 2} or less. Further, more preferably 120C / ^{m 2} or more 380C / ^{m 2} or less, and more preferably 150C / ^{m 2} or more 360C / ^{m 2} or less. When the D value is 120 C / m ² or more, the chlorine generation overvoltage can be suppressed, and the electrolysis voltage can be reduced. Further, when the content is 420 C / m ² or less, the durability of the ruthenium oxide can be maintained.

The D value as an index of the electric double layer capacity here is a value calculated using the concept of the electric double layer capacity, and the surface area of the electrode (that is, the specific surface area of the catalyst layer on the electrode) is large. It is considered that the value increases as the value increases. Further, for example, by adjusting the content of the first transition metal element to the above-described preferable range, the D value can be set to the above-described range. In particular, increasing the content of the first transition metal element tends to increase the D value. Further, the D value tends to decrease by increasing the firing temperature (post-bake temperature) when forming the catalyst layer. Specifically, the calculation is performed using the value of the electrolytic current density (A / m ² ) measured for a certain sweep speed (V / sec) by the method described in the example described later, that is, cyclic voltammetry. can do. More specifically, a unique current density difference (a difference between the current density at the time of forward sweep and the current density at the time of reverse sweep) is obtained for each sweep speed, and the vertical axis represents the current density difference and the sweep range of 0.3 V. , The horizontal axis is the sweep speed, the respective data are plotted, and the slope when each plot is linearly approximated is the D value. Here, since the product of the current density difference and the sweep range of 0.3 V is well proportional to the sweep speed, the D value can be expressed by the following equation (a). By setting the D value, which is an index of the electric double layer capacity, in the above range, it is possible to reduce the overvoltage at the beginning of electrolysis without impairing the durability of the obtained electrode for electrolysis.
D (C / m ² ) = [difference in electrolytic current density (A / m ² ) × 0.3 (V)] ÷ [sweep speed (V / sec)] (a)

  The catalyst layer in the present embodiment contains a ruthenium element, an iridium element, a titanium element and a first transition metal element, and further has a content ratio of the first transition metal element and the titanium element in a specific range. The function as an electrocatalyst is improved with an increase in the D value, which is an index of the capacity, and the overvoltage at the beginning of electrolysis can be reduced.

The catalyst layer in the present embodiment may contain only the ruthenium element, the iridium element, the titanium element, and the first transition metal element described above as constituent elements, or may include other metal elements in addition to these. You may go out. Specific examples of other metal elements include, but are not limited to, elements selected from tantalum, niobium, tin, platinum, and the like. Examples of the form of the presence of these other metal elements include the presence as metal elements contained in oxides.
When the catalyst layer in the present embodiment contains another metal element, the content ratio may be 20 mol% or less as a molar ratio of the other metal element to all of the metal elements contained in the catalyst layer. It is more preferably at most 10 mol%.
In the present embodiment, the thickness of the catalyst layer is preferably from 0.1 to 5 μm, and more preferably from 0.5 to 3 μm. When the thickness of the catalyst layer is equal to or more than the above lower limit, the initial electrolytic performance tends to be sufficiently maintained. When the thickness of the catalyst layer is equal to or less than the above upper limit, an electrode for electrolysis having excellent economic efficiency tends to be obtained.

The catalyst layer may be composed of only one layer or 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, at least the outermost layer is preferably the catalyst layer in the present embodiment. A mode in which the catalyst layer in the present embodiment has two or more layers of the same composition or different compositions is also preferable.
Even when the number of the catalyst layers is two or more, as described above, the thickness of the catalyst layer in the present embodiment is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm. preferable.

(Method of manufacturing electrode for electrolysis)
Next, an example of the method for manufacturing the electrode for electrolysis of the present embodiment will be described in detail.
The electrode for electrolysis of the present embodiment, for example, by forming a catalyst layer containing a ruthenium element, an iridium element, a titanium element and a first transition metal element on a conductive substrate subjected to the surface area increasing treatment described above. , Can be manufactured. The formation of the catalyst layer is preferably performed by a thermal decomposition method.
In the production method based on the thermal decomposition method, a coating solution containing a mixture of compounds (precursors) containing the above elements is applied on a conductive substrate, and then fired in an oxygen-containing atmosphere, and By thermally decomposing the above component, a catalyst layer can be formed. According to this method, the electrode for electrolysis can be manufactured with high productivity with fewer steps than the conventional manufacturing method.

  The term “thermal decomposition” as used herein means that a metal salt or the like serving as a precursor is fired in an oxygen-containing atmosphere to be decomposed into a metal oxide or metal and a gaseous substance. The decomposition products obtained can be controlled by the type of metal, the type of metal salt, the atmosphere in which the thermal decomposition is carried out, and the like contained in the precursor mixed in the coating solution as a raw material. Usually, in an oxidizing atmosphere, many metals tend to easily form oxides. In an industrial production process of an electrode for electrolysis, thermal decomposition is usually performed in air. Also in the present embodiment, the range of the oxygen concentration at the time of firing is not particularly limited, and it is sufficient to perform the firing in air. However, if necessary, air may be circulated in the firing furnace or oxygen may be supplied.

  As a preferable mode of the method for producing an electrode for electrolysis according to the present embodiment, a step of preparing a coating liquid containing a ruthenium compound, an iridium compound, a titanium compound, and a compound containing a first transition metal element; The method preferably includes a step of applying a liquid on at least one surface of the conductive substrate to form a coating film; and a step of firing the coating film in an oxygen-containing atmosphere to form a catalyst layer. Note that the ruthenium compound, the iridium compound, the titanium compound, and the compound containing the first transition metal element correspond to the precursor containing the metal element contained in the catalyst layer in the present embodiment. By the above method, an electrode for electrolysis having a uniform catalyst layer can be manufactured.

In the compounds contained in the coating liquid, the ruthenium compound, the iridium compound, and the titanium compound may be oxides, but need not necessarily be oxides. For example, a metal salt or the like may be used. Examples of these metal salts include, but are not limited to, any one selected from the group consisting of chloride salts, nitrates, dinitrodiammine complexes, nitrosyl nitrates, sulfates, acetates, and metal alkoxides.
Examples of the metal salt of the ruthenium compound include, but are not limited to, ruthenium chloride and ruthenium nitrate.
Examples of the metal salt of the iridium compound include, but are not limited to, iridium chloride and iridium nitrate.
Examples of the metal salt of the titanium compound include, but are not limited to, titanium tetrachloride and the like.

  Among the compounds contained in the coating liquid, the compound containing the first transition metal element may be an oxide, but is not necessarily required to be an oxide. For example, it is preferably at least one selected from the group consisting of vanadium oxo acids and salts thereof; vanadium chlorides; vanadium nitrates.

The counter cation in the oxo acid salt is not limited to the following, but examples thereof include Na ⁺ , K ⁺ , and Ca ²⁺ .

  Specific examples of such a compound include oxo acid or a salt thereof, for example, sodium metavanadate, sodium orthovanadate, potassium orthovanadate; chloride; for example, vanadium chloride; nitrate; And vanadium nitrate.

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 other compounds other than the compounds contained in the above-mentioned compounds. Examples of other compounds include, but are not limited to, a metal compound containing a metal element such as tantalum, niobium, tin, platinum, and rhodium; and an organic compound containing a metal element such as tantalum, niobium, tin, platinum, and rhodium. And the like.
The coating liquid is preferably a liquid composition in which the above 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 compound. For example, water; alcohols such as butanol and the like can be used. The total compound concentration in the coating solution is not particularly limited, but is preferably from 10 to 150 g / L from the viewpoint of appropriately controlling the thickness of the catalyst layer.

The method of applying the coating liquid on the surface of the conductive substrate is not limited to the following. For example, a dipping method in which the conductive substrate is immersed in the coating liquid, a method of coating the surface of the conductive substrate A method of applying a liquid with a brush, a roll method of passing a conductive substrate through a sponge-like roll impregnated with a coating liquid, and a method of spraying by charging the conductive substrate and the coating liquid to opposite charges. An electrocoating method or the like can be used. Among these coating methods, a roll method and an electrostatic coating method are preferred 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 substrate.
After applying the coating liquid to the conductive substrate, it is preferable to perform a step of drying the coating film, if necessary. By this drying step, a coating film can be more firmly formed on the surface of the conductive substrate. Drying conditions can be appropriately selected depending on the composition of the coating solution, the type of solvent, and the like. The drying step is preferably performed 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 substrate, firing is performed in an oxygen-containing atmosphere. The firing temperature can be appropriately selected depending on the composition of the coating liquid and the type of solvent. The firing temperature is preferably from 300 to 650 ° C. If the firing temperature is lower than 300 ° C., the decomposition of the precursor such as a ruthenium compound becomes insufficient, and a catalyst layer containing ruthenium oxide or the like may not be obtained. If the firing temperature exceeds 650 ° C., the conductive substrate may be oxidized, and thus the adhesion at the interface between the catalyst layer and the substrate may be reduced. 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 the firing time so as not to be excessively long. Considering these, it is preferable that one firing time is 5 to 60 minutes.

  If necessary, the above-described steps of coating, drying, and firing the catalyst layer may be repeated a plurality of times to form the catalyst layer to a desired thickness. After the formation of the catalyst layer, baking may be performed for a longer time if necessary to further improve the stability of the catalyst layer, which is extremely chemically, physically, and thermally stable. As the conditions for the long-term firing, it is preferable that the firing time is about 30 minutes to 4 hours at 400 to 650 ° C.

  The electrode for electrolysis of the present embodiment has a low overvoltage even in the initial stage of electrolysis, and is capable of electrolysis with low voltage and 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 as an anode for salt electrolysis in an ion exchange membrane method.

(Electrolyzer)
The electrolytic cell of the present embodiment includes the electrode for electrolysis of the present embodiment. This electrolyzer has a reduced initial voltage at the time of electrolysis. FIG. 1 shows a schematic cross-sectional view according to an example of the electrolytic cell of the present embodiment.

The electrolytic cell 200 connects the electrolytic solution 210, a container 220 for containing the electrolytic solution 210, the anode 230 and the cathode 240 immersed in the electrolytic solution 210, the ion exchange membrane 250, and the anode 230 and the cathode 240 to a power source. Wiring 260 is provided. In the electrolytic cell 200, the space on the anode side divided by the ion exchange membrane 250 is called an anode room, and the space on the cathode side is called a cathode room. The electrolytic cell of the present embodiment can be used for various types of electrolysis. Hereinafter, as a typical example, a case where the present invention is used for electrolysis of an aqueous alkali chloride solution will be described.
As the electrolytic solution 210 to be supplied to the electrolytic cell of the present embodiment, for example, an aqueous solution of an alkali chloride such as a 2.5 to 5.5 N (N) aqueous solution of sodium chloride (brine) or an aqueous solution of potassium chloride is provided in the anode chamber. In the cathode chamber, a diluted alkali hydroxide aqueous solution (for example, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution or the like) or water can be used.

The electrode for electrolysis of the present embodiment is used as the anode 230.
As the ion exchange membrane 250, for example, a fluororesin membrane having an ion exchange group can be used. Specific examples thereof include, for example, “Aciplex” (registered trademark) F6801 (manufactured by Asahi Kasei Corporation). As the cathode 240, an electrode or the like, which is a cathode for generating hydrogen and has a catalyst coated on a conductive substrate, is used. As the cathode, known ones can be adopted. Specifically, for example, for example,
A cathode coated with nickel, nickel oxide, an alloy of nickel and tin, a combination of activated carbon and oxide, ruthenium oxide, platinum, etc. on a nickel substrate;
A cathode in which a ruthenium oxide coating is formed on a nickel-made wire netting substrate is exemplified.

The configuration of the electrolytic cell of the present embodiment is not particularly limited, and may be a monopolar type or a bipolar type. The material constituting the electrolytic cell is not particularly limited. For example, as a material for the anode chamber, titanium or the like having resistance to alkali chloride and chlorine is preferable; As a material for the cathode chamber, resistance to alkali hydroxide and hydrogen is preferable. Is preferred.
The electrode for electrolysis (anode 230) of the present embodiment may be disposed with an appropriate interval between the electrode and the ion exchange membrane 250, or may be disposed in contact with the ion exchange membrane 250 without any problem. Can be used without. The cathode 240 may be disposed with an appropriate interval from the ion exchange membrane 250, or may be a contact type electrolytic cell (zero gap type electrolytic cell) having no interval between the ion exchange membrane 250 and the cathode 240. Can be used without any problem.
The electrolysis conditions of the electrolyzer of this embodiment are not particularly limited, and the electrolyzer can be operated under known conditions. For example, it is preferable to perform electrolysis while adjusting the electrolysis temperature to 50 to 120 ° C. and the current density to 0.5 to 10 kA / m ² .

The electrode for electrolysis of the present embodiment can lower the electrolysis voltage in salt electrolysis as compared with the related art. Therefore, according to the electrolytic cell of the present embodiment including the electrode for electrolysis, the power consumption required for the salt electrolysis can be reduced.
Furthermore, the electrode for electrolysis of the present embodiment has a catalyst layer that is extremely chemically, physically, and thermally stable, and thus has excellent long-term durability. Therefore, according to the electrolytic cell of this embodiment including the electrode for electrolysis, the catalytic activity of the electrode is kept high for a long time, and high-purity chlorine can be stably produced.

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

(Ion exchange membrane method salt electrolysis test)
As the electrolysis cell, an electrolysis 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 of Examples and Comparative Examples was cut into a predetermined size (95 × 110 mm = 0.01045 m ² ) to be used as a test electrode, and the test electrode was welded to a rib in the anode chamber of the anode cell. And used as an anode.
The cathode used was a nickel wire mesh base material coated with ruthenium oxide catalyst. First, on the rib of the cathode chamber of the cathode cell, an expanded base made of metal nickel as a current collector was cut out and welded in the same size as the anode, and then a cushion mat knitted with a nickel wire was placed thereon, and placed thereon. A cathode was placed.
As a gasket, a rubber gasket made of EPDM (ethylene propylene diene) was used, and an ion exchange membrane was sandwiched between an anode cell and a cathode cell. As the ion exchange membrane, a cation exchange membrane for salt electrolysis “Aciplex” (registered trademark) F6801 (manufactured by Asahi Kasei Corporation) was used.

In order to measure the chlorine overvoltage, the platinum wire coated with PFA (tetrafluoroethylene / perfluoroalkylvinyl ether copolymer) was exposed at about 1 mm at the end to remove the platinum, and the platinum wire was removed from the anode. The surface opposite to the ion-exchange membrane was fixed by binding with a polytetrafluoroethylene thread and used as a reference electrode. During the electrolysis test, the reference electrode is in a saturated atmosphere with the generated chlorine gas, and thus exhibits a chlorine generation potential. Therefore, the value obtained by subtracting the potential of the reference electrode from the potential of the anode was evaluated as the chlorine overvoltage of the anode.
On the other hand, a potential difference between the cathode and the anode was measured as an electrolysis voltage.
In order to measure the initial electrolysis performance of the anode, the overvoltage and the electrolysis voltage were each measured 7 days after the start of electrolysis. The electrolysis was performed at 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 Corporation) was used.

(Accelerated test)
As a test electrode to be attached to the anode cell, except that used was a cut to a size of 58 × 48mm = 0.002748m ^2, using the same electrolytic cell and the ion exchange membrane process sodium chloride electrolytic test described above.
The electrolysis was performed at 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. In order to confirm the durability of the test electrode, a series of operations of stopping electrolysis, rinsing water in the electrolysis cell (for 10 minutes), and starting electrolysis are performed once every seven days. The overvoltage (anode overvoltage) was measured. Further, the residual ratio of Ru and Ir in the catalyst layer in the test electrode after electrolysis (100 × content before electrolysis / content after electrolysis;%) was measured by X-ray fluorescence measurement of each metal component before and after electrolysis ( XRF). Niton XL3t-800 or XL3t-800s (trade name, manufactured by Thermo Scientific) was used as the XRF measurement device.

(D value as an index of electric double layer capacity)
The test electrode was cut out into a size of 30 × 30 mm = 0.0009 m ² and fixed to the electrolytic cell with titanium screws. The counter electrode was a platinum mesh, 85-90 ° C., the NaCl aqueous solution of brine concentration 205g / L, the electrolytic current density ^{1kA / m 2, 2kA / m} 2 and 3 kA / ^{m 2} at 5 minutes each, 4 kA / m Electrolysis was performed for 30 minutes at ^{2 so} that the test anode generated chlorine.
After the above-described electrolysis, using Ag / AgCl as a reference electrode and applying an electric potential in a range of 0 V to 0.3 V, sweep speeds of 10 mV / sec, 30 mV / sec, 50 mV / sec, 80 mV / sec, 100 mV / sec, and The cyclic voltammogram was measured at 150 mV / sec, and the electrolytic current density at 0.15 V, which is the center of the applied potential range during the forward sweep from 0 V to 0.3 V, and the reverse sweep from 0.3 V to 0 V The electrolytic current density at 0.15 V, which is the center of the applied potential range at the time, was measured, and the difference between the two electrolytic current densities was obtained at each of the above-described sweep speeds. The product of the difference between the electrolytic current densities obtained at each sweep speed and the sweep range of 0.3 V is substantially directly proportional to the sweep speed, and its slope is represented by a D value (C / m) which is an index of the electric double layer capacity. ² ).

[Example 1]
As the conductive base material, a titanium expanded base material having a larger opening (LW) of 6 mm, a smaller opening (SW) of 3 mm, and a plate thickness of 1.0 mm was used. This expanded base material is baked at 540 ° C. for 4 hours in the atmosphere to form an oxide film on the surface, and then subjected to an acid treatment at 25 ° C. for 4 hours in 25% by mass sulfuric acid to form a fine surface on the conductive base material. A pretreatment for providing irregularities was performed.
Next, an aqueous ruthenium nitrate solution (manufactured by Furuya Metal Co., Ltd., ruthenium concentration: 100 g / mol) was prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 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 iridium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., iridium concentration 100 g / L) and Vanadium (III) chloride (manufactured by Kishida Chemical Co.) was added little by little to obtain a coating liquid A1 which was an aqueous solution having a total metal concentration of 100 g / L.

The coating liquid A1 is poured into a liquid receiving vat of a coating machine, and the coating liquid A1 is sucked up and impregnated by rotating an EPDM sponge roll, and a PVC roll is brought into contact with an upper part of the sponge roll. Placed. Then, between the EPDM sponge roll and the PVC roll, a pretreated conductive base material was applied. Immediately after coating, the conductive substrate after the coating was passed between two EPDM sponge rolls wound with cloth, and excess coating liquid was wiped off. Then, after drying at 50 ° C. for 10 minutes, baking was performed at 400 ° C. for 10 minutes in the air.
The cycle consisting of the above-mentioned roll coating, drying and baking is repeated three more times with the baking temperature raised to 450 ° C., and finally baking at 520 ° C. for one hour is further performed. A black-brown catalyst layer was formed on the upper surface to produce an electrode for electrolysis.

[Comparative Example 1]
Cool and stir a ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., ruthenium concentration 100 g / L) with dry ice to 5 ° C or less so that the element ratio (molar ratio) of ruthenium, iridium, and titanium is 25:25:50. While adding titanium tetrachloride (manufactured by Wako Pure Chemical Industries, Ltd.) little by little, an iridium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., iridium concentration 100 g / L) was added little by little, and the total metal concentration was 100 g / L. A coating solution B1 as an aqueous solution was obtained. The cycle consisting of using this coating liquid B1, and roll coating, drying, and firing was repeated three more times by setting the first firing temperature to 440 ° C., then raising the temperature to 475 ° C., and finally An electrode for electrolysis was produced in the same manner as in Example 1 except that the firing at 520 ° C. was further performed for 1 hour.

[Example 2]
Using a coating liquid A2 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 25.45: 25.45: 30: 19.1, the conductive base material is coated. An electrode for electrolysis was produced in the same manner as in Example 1 except that the above procedure was performed.

[Example 3]
Using a coating liquid A3 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 28.75: 28.75: 20: 22.5, coating is performed on a conductive substrate. An electrode for electrolysis was produced in the same manner as in Example 1 except that the above procedure was performed.

[Example 4]
The conductive substrate was coated using a coating liquid A4 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 32.05: 32.05: 10: 25.9. Except for this, an electrode for electrolysis was produced in the same manner as in Example 1.

[Example 5]
Except that the conductive base material was coated using a coating liquid A5 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 17.5: 17.5: 35: 30. Produced an electrode for electrolysis in the same manner as in Example 1.

  Table 1 shows the configuration (metal composition of the coating solution used for forming the catalyst layer) of each of the electrodes for electrolysis prepared in Examples 1 to 5 and Comparative Example 1 together with the measured D value as an index of the electric double layer capacity. Shown in The unit “mol%” in the table means a molar percentage (charge ratio) based on all metal elements contained in the formed catalyst layer. Further, the value of the first transition metal element / Ru and the value of the first transition metal element / Ti are values calculated from the charging ratio.

[Ion exchange membrane salt electrolysis test]
Using the electrodes for electrolysis prepared in Examples 1 to 5 and Comparative Example 1, a salt electrolysis test using an ion exchange membrane method was performed. Table 2 shows the results.

The electrolysis voltage at a current density of 6 kA / m ² was 2.94 V in Examples 1 and 2, 2.92 V in Examples 3 and 4, and 2.91 V in Example 5, respectively. In each case, the value was extremely low as compared with 0.99V.
The anode overvoltage was 0.032 V in Example 1, 0.034 V in Example 2, 0.032 V in Examples 3 and 4, and 0.031 V in Example 5, respectively. In each case, the value was lower than 0.057V.

[Example 6]
The conductive substrate was coated using a coating liquid A6 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 37: 33.35: 11.15: 18.5. And a cycle consisting of roll coating, drying, and baking, the first baking temperature was set to 310 ° C., then the temperature was raised to 520 ° C., and the cycle was repeated three more times, and further baking was performed at 520 ° C. for one hour. An electrode for electrolysis was prepared in the same manner as in Example 1 except for this.

[Example 7]
Coating the conductive substrate with the coating liquid A7 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 31.25: 28.1: 9.4: 31.25. The first baking temperature was set to 380 ° C., then the temperature was increased to 450 ° C., and the cycle consisting of roll coating, drying, and baking was repeated three more times, followed by baking at 450 ° C. for one hour. An electrode for electrolysis was produced in the same manner as in Example 1 except that the above was performed.

Example 8
A ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) was used instead of the ruthenium nitrate aqueous solution, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 19.6: 20.2: 47. 0.09: 13.11 The first to eighth firings were performed on the conductive substrate using the coating liquid A8 prepared in such a manner that the coating was performed on the conductive substrate, and the cycle of roll coating, drying, and firing was performed. An electrode for electrolysis was produced in the same manner as in Example 1, except that the temperature was set to 393 ° C., and then firing was performed at 485 ° C. for 1 hour.

[Example 9]
Ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) was used instead of ruthenium nitrate aqueous solution, and cobalt (II) chloride hexahydrate (manufactured by Wako Pure Chemical Industries) was used instead of vanadium (III) chloride. Coating on a conductive substrate using a coating solution A9 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and cobalt is 50: 3: 30: 17; and , A cycle consisting of roll coating, drying and baking was repeated at the first baking temperature of 440 ° C., then raised to 475 ° C., and further repeated three times. Finally, baking at 520 ° C. for one hour was further performed. Except for this, an electrode for electrolysis was produced in the same manner as in Example 1.

[Example 10]
Copper (II) nitrate trihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium (III) chloride, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and copper was 32.05: 32. An electrode for electrolysis was prepared in the same manner as in Example 1, except that the conductive substrate was coated with the coating liquid A10 prepared so that the ratio became 05: 10: 25.9.

[Example 11]
Zinc (II) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium (III) chloride, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and zinc was 32.05: 32. An electrode for electrolysis was prepared in the same manner as in Example 1, except that the coating solution was applied to the conductive base material using the coating liquid A11 prepared so as to be 05: 10: 25.9.

[Comparative Example 2]
Coating on a conductive substrate using a coating liquid B2 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 20: 18: 60: 2; A ruthenium chloride aqueous solution (Tanaka Kikinzoku Co., ruthenium concentration 100 g / L) was used for the preparation, and a cycle consisting of roll coating, drying, and baking was performed at a first baking temperature of 450 ° C. and subsequently at 450 ° C. An electrode for electrolysis was prepared in the same manner as in Example 1, except that the process was repeated three more times, and firing was further performed at 450 ° C. for one hour.

[Comparative Example 3]
The conductive base material is coated using a coating liquid B3 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium becomes 22.7: 20.5: 34.1: 22.7. The first baking temperature was set to 380 ° C., and the cycle consisting of roll coating, drying, and baking was repeated three more times at 380 ° C., and finally, baking at 590 ° C. for one hour was further performed. An electrode for electrolysis was prepared in the same manner as in Example 1 except for this.

[Comparative Example 4]
The conductive base material is coated using a coating liquid B4 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium becomes 28.6: 25.7: 42.8: 2.9. The first baking temperature was 450 ° C., the temperature was raised to 520 ° C., and the cycle consisting of roll coating, drying, and baking was repeated three more times, followed by baking at 520 ° C. for one hour. An electrode for electrolysis was produced in the same manner as in Example 1 except that the above was performed.

[Comparative Example 5]
The conductive substrate is coated using a coating liquid B5 prepared such that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 18.5: 16.7: 55.55: 9.25. The process of using a ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) for the preparation of the coating liquid, and a cycle consisting of roll coating, drying, and firing were performed at the first firing temperature. An electrode for electrolysis was produced in the same manner as in Example 1 except that the temperature was raised to 310 ° C., then the temperature was raised to 380 ° C., and the process was repeated three more times. Finally, firing was further performed at 590 ° C. for 1 hour. .

[Comparative Example 6]
Manganese nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium (III) chloride in Example 1, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and manganese was 21.25: 21.25: 42. An electrode for electrolysis was prepared in the same manner as in Example 1, except that the coating was applied to the conductive substrate using the coating liquid B6 prepared so that the ratio became 0.5: 15.

[Comparative Example 7]
Instead of vanadium (III) chloride in Example 1, zinc nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and zinc was 21.25: 21.25: 42. An electrode for electrolysis was prepared in the same manner as in Example 1, except that the coating liquid B7 prepared to give a ratio of 0.5: 15 was applied to the conductive substrate.

[Comparative Example 8]
Palladium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium (III) chloride in Example 1, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and palladium was 16.9: 15.4: 50. .8: 16.9 was applied to the conductive substrate using the coating liquid B8, and a cycle consisting of roll coating, drying, and firing was performed at a first firing temperature of 450. ° C, then raised to 520 ° C and repeated three more times. Finally, an electrode for electrolysis was produced in the same manner as in Example 1, except that firing was further performed at 590 ° C for 1 hour.

[Comparative Example 9]
Coating on a conductive substrate using a coating solution B9 prepared such that the element ratio (molar ratio) of ruthenium, titanium and vanadium is 40:40:20, and ruthenium chloride for preparing the coating solution An aqueous solution (manufactured by Tanaka Kikinzoku Co., ruthenium concentration 100 g / L) was used, and the cycle consisting of roll coating, drying, and firing was performed by setting the first firing temperature to 440 ° C., and then raising the temperature to 475 ° C. An electrode for electrolysis was produced in the same manner as in Example 1, except that the process was repeated three more times, and finally, firing was further performed at 520 ° C. for one hour.

  The configuration of the electrode for electrolysis (the metal composition of the coating solution used for forming the catalyst layer) prepared in each of Examples 6 to 11 and Comparative Examples 2 to 9 was determined as an index of the measured electric double layer capacity. The values are shown in Table 3 together with the values. The unit “mol%” in the table means a molar percentage (charge ratio) based on all metal elements contained in the formed catalyst layer. Further, the value of the first transition metal element / Ru and the value of the first transition metal element / Ti are values calculated from the charging ratio.

[Accelerated test]
Acceleration tests were performed using the electrodes for electrolysis prepared in Examples 1 to 11 and Comparative Examples 1 to 9, respectively. Table 4 shows the results. Comparative Example 9 is an evaluation result when the test was stopped after 14 days because the durability of ruthenium was low.

When the accelerated test was performed for 21 days, the following was found.
In the electrodes for electrolysis of Examples 1 to 11, the anode overvoltage one day after the start of the test was 0.030 to 0.045 V, and the anode overvoltage after 21 days was 0.030 to 0.039 V. On the other hand, in the electrodes for electrolysis of Comparative Examples 1 to 8, the anode overvoltage one day after the start of the test was 0.042 to 0.110 V, and the anode overvoltage after 21 days was 0.043 to 0.093 V. there were. As described above, it was verified that the examples can perform electrolysis with low voltage and low power consumption in the initial stage of electrolysis and over a long period of time, as compared with the comparative example.
Further, in Examples 1 to 11, the Ru and Ir residual ratios were both high even after 21 days from the start of the test, as compared with Comparative Example 9 in which the anode overvoltage was almost the same. It was verified that the durability was sufficient.

  This application is based on Japanese Patent Application No. 2006-227066 filed on November 22, 2016, the contents of which are incorporated herein by reference.

  INDUSTRIAL APPLICABILITY The electrode for electrolysis of the present invention exhibits a low chlorine overvoltage and can be electrolyzed with low voltage and low power consumption, and thus 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 with low voltage and low power consumption over a long period of time.

200 electrolytic cell for electrolysis 210 electrolytic solution 220 container 230 anode (electrode for electrolysis)
240 Cathode 250 Ion exchange membrane 260 Wiring

Claims (9)

A conductive substrate;
A catalyst layer formed on the surface of the conductive substrate,
An electrode for electrolysis comprising:
The catalyst layer contains a ruthenium element, an iridium element, a titanium element, and at least one first transition metal element selected from the group consisting of Sc, V, Cr, Fe, Co, Ni, Cu, and Zn,
A content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the titanium element is 0.25 mol% or more and less than 3.4 mol%,
The D values indicative of the electric double layer capacity of the electrode for electrolysis is 120C / ^{m 2} or more 420C / ^{m 2} or less, the electrode for electrolysis.   The electrode for electrolysis according to claim 1, wherein the first transition metal element forms a solid solution with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide.   3. The electrode for electrolysis according to claim 1, wherein the first transition metal element includes at least one metal element selected from the group consisting of vanadium, cobalt, copper, and zinc.   The electrode for electrolysis according to any one of claims 1 to 3, wherein the first transition metal element includes a vanadium element.   The electrode for electrolysis according to any one of claims 1 to 4, wherein a content of the first transition metal element with respect to all metal elements included in the catalyst layer is 10 mol% or more and 30 mol% or less.   The electrode for electrolysis according to any one of claims 1 to 5, wherein a content ratio of the first transition metal element contained in the catalyst layer to 1 mol of the ruthenium element is 0.3 mol or more and less than 2 mol. . The electrode for electrolysis according to any one of claims 1 to 6, wherein the D value is 120 C / m ² or more and 380 C / m ² or less. A method for producing an electrode for electrolysis according to any one of claims 1 to 7,
Ruthenium compound, iridium compound, titanium compound, and a step of preparing a coating solution containing a compound containing the first transition metal element,
A step of applying the coating liquid on at least one surface of the conductive substrate to form a coating film,
Baking the coating film under an oxygen-containing atmosphere to form the catalyst layer,
A method for producing an electrode for electrolysis, comprising:   An electrolytic cell comprising the electrode for electrolysis according to any one of claims 1 to 7.