WO2018097069A1

WO2018097069A1 - Electrode for electrolysis

Info

Publication number: WO2018097069A1
Application number: PCT/JP2017/041559
Authority: WO
Inventors: 豊光宮阪; 誠西澤; 佳典角
Original assignee: 旭化成株式会社
Priority date: 2016-11-22
Filing date: 2017-11-17
Publication date: 2018-05-31
Also published as: JP6670948B2; KR102272749B1; JPWO2018097069A1; KR20190067859A; ES2850501T3; EP3546619A4; EP3546619B1; CN109891002A; TW201819687A; RU2720309C1; EP3546619A1; CN109891002B; US20190338429A1; TWI661091B; BR112019010219A2

Abstract

This electrode for electrolysis is provided with a conductive base material and a catalyst layer that is formed on the surface of the conductive base material. The catalyst layer contains elemental ruthenium, elemental iridium, elemental titanium and at least one first transition metal element selected from the group consisting of Sc, V, Cr, Fe, Co, Ni, Cu and Zn; the content ratio of the first transition metal element contained in the catalyst layer relative to 1 mole of the elemental titanium is 0.25% by mole or more but less than 3.4% by mole; and the D value serving as an index for the electric double layer capacity of this electrode for electrolysis is from 120 C/m² to 420 C/m² (inclusive).

Description

Electrode for electrolysis

The present invention relates to an electrode for electrolysis, a method for producing the same, and an electrolyzer equipped with the electrode for electrolysis.

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 salt electrolysis process, a technique capable of maintaining a low electrolysis voltage over a long period of time is required in order to reduce power consumption.
A breakdown of the breakdown of the electrolysis voltage reveals that, in addition to the theoretically required electrolysis voltage, the voltage resulting from the resistance of the ion exchange membrane and the structure resistance of the electrolytic cell, the overvoltage of the anode and cathode as electrolysis electrodes, the anode and cathode It has been clarified that a voltage or the like due to the distance between is included. Further, when 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 electrolysis voltages described above, 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 obtained by coating a platinum base metal oxide such as ruthenium on a titanium substrate. This anode is called DSA (registered trademark, Dimension Stable Anode). Non-Patent Document 1 describes the transition of soda electrolysis technology using DSA.

Various improvements have been made to the above-described DSA so far, and studies for improving the performance have been made.
For example, Patent Document 2 reports an electrode for chlorine generation in which platinum and palladium are alloyed by paying attention to a low chlorine overvoltage and a high oxygen overvoltage of palladium in the platinum group. Patent Documents 3 and 4 propose electrodes in which the surface of a platinum-palladium alloy is oxidized and palladium oxide is formed on the surface. Patent Document 5 proposes an electrode that is mainly composed of an oxide of tin and is covered with an external catalyst layer containing each of oxides of ruthenium, iridium, palladium, and niobium. In order to obtain high-purity chlorine having a low oxygen concentration with this electrode, an attempt has been made to suppress the oxygen generation reaction at the anode that occurs simultaneously with the generation of chlorine.

Japanese Examined Patent Publication No. 46-021884 Japanese Examined Patent Publication No. 45-11014 Japanese Examined Patent Publication No. 45-11015 Japanese Patent Publication No. 48-3954 Special table 2012-508326 gazette

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 down to a low overvoltage due to the activation of the catalyst. There is a problem of end.
The electrodes for generating chlorine described in Patent Documents 2 to 4 may have high overvoltage and low durability. Furthermore, in the manufacture of the electrodes described in Patent Documents 3 and 4, it is necessary to use an alloy for the base material itself. In addition, an oxide is formed on the base material by thermal decomposition, then alloyed by reduction, and further electrolyzed. It requires complicated steps such as oxidation to palladium oxide, and a great improvement is required both in practical use and in manufacturing.
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, it cannot be said that the chlorine generation overvoltage is sufficiently low.
As described above, in the techniques described in Patent Documents 1 to 5 and Non-Patent Document 1, an electrode for electrolysis that can be electrolyzed with a low voltage and low power consumption over a long period of time while the overvoltage at the initial stage of electrolysis is sufficiently low. It cannot be realized.

The present invention has been made to solve the above-described problems. Accordingly, the present invention provides an electrode for electrolysis capable of reducing overvoltage in the initial stage of electrolysis and capable of electrolysis with low voltage and low power consumption over a long period of time, a method for producing the same, and an electrolytic cell equipped with the electrode for electrolysis For the purpose.

The inventors of the present invention have made extensive studies to solve the above problems. As a result, by adjusting a numerical value that 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 overvoltage at the initial stage of electrolysis, and It has been found that electrolysis is possible with a low voltage and low power consumption over a long period of time, and the present invention has been made.
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 includes 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;
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%,
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 contains a vanadium element.
[5]
The electrode for electrolysis according to any one of [1] to [4], wherein the content of the first transition metal element with respect to all the metal elements contained 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 the 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 the electrode for electrolysis according to any one of [1] to [7],
A step of preparing a coating liquid containing a ruthenium compound, an iridium compound, a titanium compound, and a compound containing the first transition metal element;
Applying the coating liquid onto at least one surface of the conductive substrate to form a coating film;
Baking the coating film in an oxygen-containing atmosphere to form the catalyst layer;
The manufacturing method of the electrode for electrolysis which has these.
[9]
An electrolytic cell comprising the electrode for electrolysis according to any one of [1] to [7].

The present invention provides an electrode for electrolysis that can reduce overvoltage at the initial stage of electrolysis and that can be electrolyzed with low voltage and low power consumption over a long period of time.

FIG. 1 is a schematic sectional view according to an example of the electrolytic cell of the present embodiment. FIG. 2 is a plot of measured V / Ti values obtained by XPS depth direction analysis and V / Ti values of preparations in the coating solution for four samples having different element ratios (molar ratios) between V and Ti. It 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 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 implemented with appropriate modifications within the scope of the gist thereof.

The electrode for electrolysis of this embodiment is an electrode for electrolysis comprising a conductive substrate and a catalyst layer formed on the surface of the conductive substrate, and the catalyst layer is composed of a ruthenium element or 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 “first Also referred to as “one transition metal element”). Furthermore, in the electrode for electrolysis of this 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%, and the electrolysis 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, in addition to the ruthenium element, the iridium element, and the titanium element, the first transition metal element is used, whereby Ru3d5 / derived from RuO ₂ measured by X-ray photoelectron spectroscopy (XPS). The peak position of the peak attributed to 2 is an electrode for electrolysis shifted from 280.5 eV of RuO ₂ to the high binding energy side. XPS charging correction is performed so that the binding energy of Ti2p3 / 2 is 458.4 eV. The shift of the peak position of Ru3d5 / 2 to the high binding energy side indicates a state in which Ru is oxidized by charge, which is considered to be caused by 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 the adsorption of chlorine, the overvoltage of chlorine generation can be reduced.
Although not intended to limit to the above-described mechanism of action, the electrode for electrolysis of the present embodiment has the above-described configuration, and therefore, when electrolysis is performed using the electrode for electrolysis, overvoltage at the initial stage of electrolysis can be reduced, and Electrolysis can be performed at low voltage and low power consumption over a long period of time. The electrode for electrolysis of the present embodiment can be suitably used as an electrode for generating chlorine, particularly for ion exchange membrane salt electrolysis.

(Conductive substrate)
The electrode for electrolysis of the present embodiment is used in a chlorine gas generating atmosphere in a highly concentrated saline solution 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, zirconium, and the like. Titanium is preferable 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 preferably used. The thickness of the conductive substrate is preferably 0.1 to 2 mm.
The surface of the conductive substrate that contacts the catalyst layer is preferably subjected to a surface area increasing treatment in order to improve the adhesion with the catalyst layer. Examples of the method for increasing the surface area include, but are not limited to, blasting using a cut wire, steel grid, alumina grid or the like; acid treatment using sulfuric acid or hydrochloric acid, or the like. Among these treatments, an acid treatment method is preferred after forming irregularities on the surface of the conductive substrate by blast treatment.

(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, iridium element, and titanium element are each preferably 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 the ruthenium oxide, iridium oxide, and titanium oxide form a solid solution. The ruthenium oxide, iridium oxide, and titanium oxide form a solid solution, thereby further improving the durability of the ruthenium oxide.
A solid solution generally refers to a substance in which two or more kinds of substances are dissolved in each other and the whole is a uniform solid phase. Examples of the substance forming the solid solution include a metal simple substance and a metal oxide. In particular, in the case of a metal oxide solid solution suitable for the present embodiment, two or more types of metal atoms are irregularly arranged on equivalent lattice points in the unit lattice in the oxide crystal structure. Specifically, a substitution type in which ruthenium oxide, iridium oxide and titanium oxide are mixed with each other, and when viewed from the ruthenium oxide side, the ruthenium atom is substituted by iridium atom or titanium atom or both of them. A solid solution is preferred. The solid solution state is not particularly limited, and a partial 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, by measuring the powder X-ray diffraction without changing the diffraction pattern due to the crystal structure and changing the peak position due to the size of the unit cell.

In the catalyst layer of this 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 with respect to 1 mol of the ruthenium element, and 0.2 to 8 of the titanium element. Preferably, it is 0.2 to 3 moles of the iridium element and more preferably 0.2 to 8 moles of the titanium element with respect to 1 mole of the ruthenium element; More preferably, the iridium element is 0.3 to 2 mol and the titanium element is 0.2 to 6 mol; the iridium element is 0.5 to 1.5 mol with respect to 1 mol of the ruthenium element; In particular, the titanium element is particularly preferably 0.2 to 3 mol. By setting the content ratio of the three kinds of elements in the above range, the long-term durability of the electrode for electrolysis tends to be further improved. Each of iridium, ruthenium, and titanium may be included in the catalyst layer as a form other than an oxide, for example, as a simple metal.

The catalyst layer of the present embodiment includes the first transition metal element together with the above-described ruthenium element, iridium element, and titanium element. The presence form of the first transition metal element is not particularly limited. For example, the first transition metal element may be in the form of an oxide, a simple metal, or an alloy, as long as it is contained in the catalyst layer. In the present embodiment, from the viewpoint of durability of the catalyst layer, the first transition metal element preferably forms a solid solution with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide. The formation of such a solid solution can be confirmed by, for example, XRD. Moreover, said solid solution can be formed by adjusting the calcination temperature at the time of forming a catalyst layer, the addition amount of a 1st transition metal element, etc. 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 the voltage and durability of the catalyst layer. More preferably, the metal element contains a vanadium element.

The content of the first transition metal element with respect to all the metal elements contained in the catalyst layer in the present embodiment is preferably 10 mol% or more and 30 mol% or less, and 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 vanadium content with respect to all the metal elements contained in the catalyst layer satisfy the above range.
The above-mentioned content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the preferable method for producing an electrode for electrolysis described later, but the cross-sectional STEM-EDX and X-ray photoelectron spectroscopy described later are used. It can be confirmed by depth direction analysis by the method (XPS).
When the content ratio of the first transition metal element is 10 mol% or more, the chlorine generation overvoltage or the electrolysis voltage tends to be reduced from the initial stage of electrolysis. Moreover, when the content rate of a 1st transition metal element is 30 mol% or less, it exists in the tendency for durability of a ruthenium oxide to fully be ensured.

The content ratio of the first transition metal element contained in the catalyst layer in the present embodiment 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. It is more preferable that the amount 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 vanadium content with respect to 1 mole of the ruthenium element contained in the catalyst layer satisfies the above range.
The above-mentioned content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the preferable method for producing an electrode for electrolysis described later, but the cross-sectional STEM-EDX and X-ray photoelectron spectroscopy described later are used. It can be confirmed by depth direction analysis by the method (XPS).
When the content ratio of the first transition metal element is 0.3 mol or more as 1 mol of the ruthenium element, the chlorine generation overvoltage or the electrolysis voltage tends to be reduced from the initial stage of electrolysis, and the electric double layer capacity described later It tends to be possible to sufficiently increase the D value, which is an index of. Moreover, when it is less than 2 mol, the durability of the ruthenium oxide tends to be sufficiently secured.

The content ratio of the first transition metal element contained in the catalyst layer in the present embodiment with respect to 1 mol of the titanium element is 0.25 mol or more and less than 3.4 mol, and 0.25 mol or more and less than 2.6 mol. Preferably there is. When the first transition metal element contains vanadium, it is particularly preferable that the content of vanadium with respect to 1 mole of titanium element contained in the catalyst layer satisfies the above range.
The above-mentioned content ratio is mainly derived from the charging ratio of each element in the coating liquid prepared in the preferable method for producing an electrode for electrolysis described later, but the cross-sectional STEM-EDX and X-ray photoelectron spectroscopy described later are used. It can be confirmed by depth direction analysis by the method (XPS).
When the content ratio of the first transition metal element is 0.25 mol or more per 1 mol of titanium element, the chlorine generation overvoltage or the electrolysis voltage tends to be reduced from the initial stage of electrolysis, and the electric double layer capacity described later It tends to be possible to sufficiently increase the D value, which is an index of. Moreover, when it is less than 3.4 mol, the durability of the ruthenium oxide tends to be sufficiently secured.

The elemental ratio (molar ratio) of 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 shown below. . Here, a Ti substrate is used as the conductive substrate.
The XPS measurement conditions can be as follows.
Apparatus: PHI5000 VersaProbeII 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 spectroscopic levels of the photoelectron peaks used for the determination of Ru, Ir, Ti, and V are Ru3d, Ir4f, Ti2p, and V2p3 / 2. Since Ru3p3 / 2 overlaps Ti2p and Ti3s overlaps Ir4f, quantification can be performed by the following procedure.
(1) Using the analysis software “MaltiPak” attached to the apparatus, the peak area intensity of Ru3d, Ir4f (including Ti3s), Ti2p (including Ru3p3 / 2), and V2p3 / 2 at each sputtering time (each depth) (Hereafter, peak area intensity) is obtained.
(2) The peak area intensity of Ru3p3 / 2 is calculated based on the peak area intensity of Ru3d. The calculation is performed using the ratio of the MaltiPak Corrected RSF (relative sensitivity factor modified by the path energy value). This is subtracted from the peak area intensity of Ti2p containing Ru3p3 / 2 to calculate the peak area intensity of Ti2p only.
(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 to calculate the peak area intensity of only Ir4f.

The actual value of the element ratio (molar ratio) between V and Ti in the catalyst layer determined by XPS depth direction quantitative analysis is based on the following calculation formula, and each depth in the catalyst layer depth range where V is detected: The sum of V2p3 / 2 peak area intensity at V2p3 / 2 and divided by V2p3 / 2 Corrected RSF and the ratio of Ti2p peak area intensity at each depth divided by Ti2p Corrected RSF To do. For example, when the catalyst layer is a single layer, the depth range of the catalyst layer that integrates the peak area intensity of each element is the depth range from the outermost surface until the Ti signal derived from the Ti base material starts to be detected. To do. Here, when the catalyst layer is multi-layered, the layers other than the catalyst layer directly formed on the surface of the Ti base material are set to the depth range of each catalyst layer, and the catalyst layer directly formed on the surface of the Ti base material. Is a depth range until a Ti signal derived from the Ti base material starts to be detected.

For the following four samples a to d having different element ratios (molar ratios) between V and Ti, the actual measurement value of V / Ti obtained by XPS depth direction analysis by the above-described measurement method, and the coating solution The result of plotting the V / Ti value of the feed is shown in FIG.
(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. The electrode for electrolysis obtained by the method similar to Example 1 mentioned later except having applied to the electroconductive base material using the coating liquid a prepared so that it might become.
(Sample b) Electrolysis electrode having a V / Ti feed ratio of 0.22 The element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 22.5: 22.5: 45: 10, respectively. The electrode for electrolysis obtained by the method similar to Example 1 except having applied to the electroconductive base material using the coating liquid b mix | blended.
(Sample c) Electrolysis electrode having a V / Ti charge ratio of 0.35 Electrolysis electrode obtained by the same method as in Example 1 described later.
(Sample d) Electrolysis electrode having a V / Ti charge ratio of 1.13 Electrolysis electrode 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 charged value show a positive correlation, the calibration curve shows the relationship between V and Ti in the catalyst layer containing ruthenium element, iridium element, titanium element and vanadium element. The element ratio (molar ratio) can be determined. When the components contained in the catalyst layer change, an element ratio (molar ratio) of V and Ti in the catalyst layer is prepared by preparing a calibration curve of the measured value of V / Ti and the charged value by the same method. ).
In the electrode for electrolysis of this 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 multilayer structure, the content ratio of the first transition metal element contained in at least one of the layers to the 1 mol of the titanium element may be 0.25 mol or more and less than 3.4 mol, and the other layers 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 lowered. Moreover, durability of a ruthenium oxide can be maintained because it is 420 C / m < ² > or less.

The D value as an index of the electric double layer capacity here is a value calculated using the concept of 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. The value is expected to increase. For example, the D value can be set to the above-described range by adjusting the content of the first transition metal element to the above-described preferable range. In particular, the D value tends to increase by increasing the content of the first transition metal element. Further, the D value tends to decrease by increasing the firing temperature (post-bake temperature) when forming the catalyst layer. Specifically, calculation is performed using the value of electrolytic current density (A / m ² ) measured for a certain sweep rate (V / sec) by the method described in the examples described later, that is, by cyclic voltammetry. can do. More specifically, a unique current density difference (difference between the current density during forward sweep and the current density during 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, each data is 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, within the above-mentioned range, it is possible to reduce overvoltage at the initial stage 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 sets the content ratio of the first transition metal element and the titanium element to a specific range, thereby providing an electric double layer. The function as an electrocatalyst accompanying an increase in the D value, which is an index of capacity, can be improved, and an overvoltage in the initial 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 contain other metal elements in addition to these elements. 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 existence form of these other metal elements include existence as a metal element contained in an oxide.
When the catalyst layer in the present embodiment contains other metal elements, the content ratio is 20 mol% or less as the molar ratio of the other metal elements to the entire metal elements contained in the catalyst layer. Preferably, it is 10 mol% or less.
In the present embodiment, the thickness of the catalyst layer is preferably 0.1 to 5 μm, and 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 electrolytic performance tends to be sufficiently maintained. Moreover, it is in the tendency for the electrode for electrolysis excellent in economical efficiency to be obtained by making thickness of this catalyst layer below into the above-mentioned upper limit.

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. The aspect which has two or more catalyst layers in this embodiment by the same composition or a different composition is also preferable.
Even when there are two or more catalyst layers, the thickness of the catalyst layer in this embodiment is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm, as described above. preferable.

(Method for producing electrode for electrolysis)
Next, an example of the method for manufacturing the electrode for electrolysis according to the present embodiment will be described in detail.
The electrode for electrolysis of this embodiment is formed by, for example, forming a catalyst layer containing a ruthenium element, an iridium element, a titanium element, and a first transition metal element on the conductive base material that has been 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 liquid containing a mixture of the above-described elements (precursor) is applied on a conductive substrate, and then baked in an oxygen-containing atmosphere. The catalyst layer can be formed by thermally decomposing these components. 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 "thermal decomposition" as used herein means that a precursor metal salt or the like is fired in an oxygen-containing atmosphere and decomposed into a metal oxide or metal and a gaseous substance. The decomposition product obtained can be controlled by the metal species contained in the precursor blended 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 an industrial production process of an electrode for electrolysis, thermal decomposition is usually performed in air. Also in this embodiment, the range of the oxygen concentration at the time of firing is not particularly limited, and it is sufficient to perform in the air. However, if necessary, air may be circulated in the firing furnace or oxygen may be supplied.

A preferred aspect of the method for producing an electrode for electrolysis according to the present embodiment includes 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; It is preferable to have a step of coating the liquid on at least one surface of the conductive substrate to form a coating film; and a step of baking the coating film in an oxygen-containing atmosphere to form a catalyst layer. In addition, 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-described method, an electrode for electrolysis having a uniform catalyst layer can be produced.

In the compound contained in the coating solution, the ruthenium compound, the iridium compound, and the titanium compound may be oxides, but are not necessarily 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.
The metal salt of the ruthenium compound is not limited to the following, and examples thereof include 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.
Although it does not limit to the following as a metal salt of a titanium compound, For example, titanium tetrachloride etc. are mentioned.

In the compound contained in the coating solution, the compound containing the first transition metal element may be an oxide, but is not necessarily an oxide. For example, the oxo acid of vanadium and the salt thereof; vanadium chloride; and one or more selected from the group consisting of vanadium nitrate are preferable.

Examples of the counter cation in the oxo acid salt include, but are not limited to, Na ⁺ , K ⁺ , Ca ^{2+ and the} like.

Specific examples of such compounds include oxoacids or salts thereof such as sodium metavanadate, sodium orthovanadate, potassium orthovanadate and the like; chlorides such as vanadium chloride and the like; , Vanadium nitrate, and the like.

The above compounds are appropriately selected and used according to the desired metal element ratio in the catalyst layer.
The coating liquid may further contain a compound other than the compounds contained in the above-described compound. Examples of other compounds include, but are not limited to, metal compounds containing metal elements such as tantalum, niobium, tin, platinum, and rhodium; organics containing metal elements such as tantalum, niobium, tin, platinum, and rhodium Compounds 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 for the coating solution used here can be selected according to the type of the compound. For example, water; alcohols such as butanol can be used. The total compound concentration in the coating solution 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 coating the coating liquid on the surface of the conductive substrate is not limited to the following, but, for example, a dipping method in which the conductive substrate is immersed in the coating liquid, or coating on the surface of the conductive substrate. 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 static spraying by charging the conductive base material and the coating liquid to opposite charges An electrocoating 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 substrate.
After applying the coating liquid to the conductive substrate, it is preferable to perform a step of drying the coating film as necessary. By this drying step, the coating film can be more firmly formed on the surface of the conductive substrate. 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 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, baking is performed 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. When the firing temperature is less than 300 ° C., the precursor such as ruthenium compound is not sufficiently decomposed, and a catalyst layer containing ruthenium oxide or the like may not be obtained. When the firing temperature exceeds 650 ° C., the conductive base material may be oxidized, so that the adhesion at the interface between the catalyst layer and the base material may be lowered. This tendency should be emphasized particularly when a titanium substrate is used as the conductive substrate.
A longer firing time is preferred. 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. Taking these into consideration, it is preferable that one baking time is 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 in a desired thickness. After the formation of the catalyst layer, firing can be performed for a longer time if necessary to further improve the stability of the catalyst layer that is extremely chemically, physically and thermally stable. The conditions for the long-term firing are preferably about 30 minutes to 4 hours at 400 to 650 ° C.

The electrode for electrolysis of this embodiment has a low overvoltage even in the initial stage of electrolysis, and can be electrolyzed with a low voltage and low power consumption over a long period. 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.

(Electrolysis tank)
The electrolytic cell of this embodiment includes the electrode for electrolysis of this embodiment. This electrolytic cell has a reduced initial voltage during electrolysis. FIG. 1 shows a schematic sectional view according to an example of the electrolytic cell of the present embodiment.

The electrolytic bath 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, a space on the anode side partitioned by the ion exchange membrane 250 is referred to as an anode chamber, and a space on the cathode side is referred to as a cathode chamber. The electrolytic cell of this embodiment can be used for various electrolysis. Below, the case where it uses for electrolysis of alkali chloride aqueous solution is demonstrated as the representative example.
As the electrolytic solution 210 to be supplied to the electrolytic cell of the present embodiment, for example, in the anode chamber, an aqueous alkali chloride solution such as a 2.5 to 5.5 N (N) aqueous sodium chloride solution (saline solution) or an aqueous potassium chloride solution is provided. In the cathode chamber, diluted alkali hydroxide aqueous solution (for example, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, etc.) or water can be used.

As the anode 230, the electrode for electrolysis of this embodiment is used.
As the ion exchange membrane 250, for example, a fluororesin membrane having an ion exchange group can be used. Specific examples thereof include “Aciplex” (registered trademark) F6801 (manufactured by Asahi Kasei Corporation). As the cathode 240, a cathode for hydrogen generation, which is an electrode in which a catalyst is coated on a conductive substrate, or the like is used. As this cathode, a known one can be adopted, and specifically, 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;
Examples thereof include a cathode in which a ruthenium oxide coating is formed on a nickel wire mesh substrate.

The structure of the electrolytic cell of this embodiment is not specifically limited, A monopolar type or a bipolar type may be sufficient. The material constituting the electrolytic cell is not particularly limited. For example, the material for the anode chamber is preferably titanium or the like resistant to alkali chloride and chlorine; the material for the cathode chamber is resistant to alkali hydroxide and hydrogen. Nickel or the like 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 even if it is disposed in contact with the ion exchange membrane 250, there is no problem. Can be used without The cathode 240 may be arranged with an appropriate interval from the ion exchange membrane 250, or even if it is a contact type electrolytic cell (zero gap type electrolytic cell) with no gap between the ion exchange membrane 250, Can be used without any problems.
The electrolysis conditions of the electrolytic cell of the present embodiment are not particularly limited, and can be operated 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 .

The electrode for electrolysis of this embodiment can lower the electrolysis voltage in salt electrolysis than before. Therefore, according to the electrolytic cell of this embodiment provided with this electrode for electrolysis, the power consumption required for salt electrolysis can be reduced.
Furthermore, since the electrode for electrolysis of this embodiment has a chemically, physically, and thermally stable catalyst layer, it has excellent long-term durability. Therefore, according to the electrolytic cell of this embodiment provided with the electrode for electrolysis, the catalytic activity of the electrode is maintained high for a long time, and it becomes possible to stably produce high-purity chlorine.

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

(Ion exchange membrane salt electrolysis test)
As an electrolytic cell, an electrolytic cell comprising 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 into a predetermined size (95 × 110 mm = 0.01045 m ² ) as a test electrode, and the test electrode was welded to the rib of the anode chamber of the anode cell. And used as an anode.
As the cathode, a nickel wire mesh base material coated with a 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 was cut out and welded at the same size as the anode, and then a cushion mat knitted with nickel wire was placed on it. A cathode was placed.
A rubber gasket made of EPDM (ethylene propylene diene) was used as the gasket, and an ion exchange membrane was sandwiched between the anode cell and the cathode cell. As the ion exchange membrane, a cation exchange membrane “Aciplex” (registered trademark) F6801 (manufactured by Asahi Kasei Co., Ltd.) for salt electrolysis was used.

In order to measure the chlorine overvoltage, the platinum wire exposed by removing the coating of about 1 mm from the tip of the platinum wire coated with PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) was used as the anode. The surface opposite to the ion exchange membrane was fixed with a polytetrafluoroethylene thread and used as a reference electrode. During the electrolysis test, the reference electrode is saturated with the generated chlorine gas, and thus exhibits a chlorine generation potential. Therefore, a 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, the potential difference between the cathode and the anode was measured as the electrolysis voltage.
In order to measure the initial electrolysis performance of the anode, the overvoltage and the electrolysis voltage were measured after 7 days from 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.

(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 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. In order to confirm the durability of the test electrode, a series of operations of stopping electrolysis, rinsing in the electrolysis cell (10 minutes), and starting electrolysis were performed once every 7 days, and chlorine was removed every 7 days after electrolysis was started. Overvoltage (anode overvoltage) was measured. Furthermore, 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 fluorescent X-ray measurement of each metal component before and after electrolysis ( XRF) was used for calculation. Niton XL3t-800 or XL3t-800s (trade name, manufactured by Thermo Scientific) was used as the XRF measurement apparatus.

(D value as an index of electric double layer capacity)
The test electrode was cut into a size of 30 × 30 mm = 0.0009 m ² and fixed to the electrolytic cell with a titanium screw. The counter electrode was a platinum mesh, 85 ~ 90 ℃, 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 ² for 30 minutes so that the test anode generated chlorine.
After the electrolysis described above, Ag / AgCl is used for the reference electrode, the applied potential is in the range of 0 V to 0.3 V, the sweep speed is 10 mV / second, 30 mV / second, 50 mV / second, 80 mV / second, 100 mV / second, and Cyclic voltammogram was measured at 150 mV / second, 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 sweep rates. The product of the difference in electrolytic current density obtained at each sweep rate and the sweep range of 0.3 V is substantially directly proportional to the sweep rate, and the slope is a D value (C / m) that serves as an index of electric double layer capacity. ² ).

[Example 1]
As the conductive base material, an expanded base made of titanium having a large opening (LW) of 6 mm, a small opening (SW) of 3 mm, and a plate thickness of 1.0 mm was used. This expanded substrate was baked at 540 ° C. in the atmosphere for 4 hours to form an oxide film on the surface, and then subjected to an acid treatment in 25% by mass sulfuric acid at 85 ° C. for 4 hours, so that the surface of the conductive substrate was fine. A pretreatment for providing irregularities was performed.
Next, an aqueous ruthenium nitrate solution (manufactured by Furuya Metals Co., Ltd., ruthenium concentration 100 g / wt) so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 21.25: 21.25: 42.5: 15. L) Titanium tetrachloride (manufactured by Wako Pure Chemical Industries, Ltd.) was added little by little while cooling and stirring to 5 ° C. or less with dry ice, and then an aqueous iridium chloride solution (manufactured by Tanaka Kikinzoku Co., Ltd., iridium concentration 100 g / L) and Vanadium chloride (III) (manufactured by Kishida Chemical Co., Ltd.) 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.

This coating liquid A1 is poured into a liquid receiving vat of the coating machine, and the EPDM sponge roll is rotated to suck up and impregnate the coating liquid A1, and the PVC roll is brought into contact with the upper part of the sponge roll. Arranged. And it applied through the electroconductive base material which gave the pre-treatment between the said EPDM sponge roll and the said PVC roll. Immediately after the coating, the conductive substrate after the coating was passed between two EPDM sponge rolls wound with cloth, and the excess coating solution was wiped off. Then, after drying at 50 ° C. for 10 minutes, firing was performed in the air at 400 ° C. for 10 minutes.
The above-mentioned cycle comprising roll coating, drying and firing is repeated 3 times by raising the firing temperature to 450 ° C., and finally by further firing for 1 hour at 520 ° C. A black-brown catalyst layer was formed thereon to produce an electrode for electrolysis.

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

[Example 2]
Coating on conductive substrate using 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 An electrode for electrolysis was produced in the same manner as in Example 1 except that.

[Example 3]
Application to conductive substrate using coating liquid A3 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium and vanadium is 28.75: 28.75: 20: 22.5 An electrode for electrolysis was produced in the same manner as in Example 1 except that.

[Example 4]
The conductive base material was coated using the coating liquid A4 prepared so 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]
Other than coating on conductive substrate using coating liquid A5 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium and vanadium is 17.5: 17.5: 35: 30 Produced an electrode for electrolysis by the same method as in Example 1.

Table 1 shows the configurations of the electrodes for electrolysis prepared in Examples 1 to 5 and Comparative Example 1 (metal composition of the coating solution used for forming the catalyst layer) together with the D value serving as an index of the measured electric double layer capacity. Shown in The unit “mol%” in the table means the mole percentage (feeding ratio) with respect to all the 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 preparation ratio.

[Ion exchange membrane method salt electrolysis test]
Using the electrode for electrolysis produced in each of Examples 1 to 5 and Comparative Example 1, an ion exchange membrane method salt electrolysis test was conducted. The results are shown in Table 2.

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. All showed extremely low values compared to .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. Comparative Example 1 As compared with 0.057 V in the case, all showed low values.

[Example 6]
The conductive base material was coated using the 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 firing is performed by setting the first firing temperature to 310 ° C., then raising the temperature to 520 ° C. and repeating three more times, and further firing at 520 ° C. for 1 hour. An electrode for electrolysis was produced in the same manner as in Example 1 except that.

[Example 7]
A conductive base material is coated with a 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. And the cycle consisting of roll coating, drying, and firing was performed at a first firing temperature of 380 ° C., then raised to 450 ° C. and repeated three more times, and further fired at 450 ° C. for 1 hour. The electrode for electrolysis was produced by the same method as Example 1 except having performed.

[Example 8]
The use of an aqueous ruthenium chloride solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) instead of an aqueous ruthenium nitrate solution, and an element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium of 19.6: 20.2: 47 .09: 13.11 The coating liquid A8 prepared so as to be 1311. 11 was applied to the conductive substrate, and the cycle consisting of roll coating, drying, and firing was performed from the first to the eighth firing. 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 baking was performed at 485 ° C. for 1 hour.

[Example 9]
Use of ruthenium chloride aqueous solution (Tanaka Kikinzoku Co., Ltd., ruthenium concentration 100 g / L) instead of ruthenium nitrate aqueous solution, and cobalt (II) chloride hexahydrate (manufactured by Wako Pure Chemical Industries) instead of vanadium (III) chloride Coating the conductive substrate using the coating liquid A9 prepared so that the elemental ratio (molar ratio) of ruthenium, iridium, titanium and cobalt is 50: 3: 30: 17; and The cycle consisting of roll coating, drying and firing was carried out at a first firing temperature of 440 ° C., then heated to 475 ° C. and repeated three more times, and finally fired at 520 ° C. for 1 hour. Except for this, an electrode for electrolysis was produced in the same manner as in Example 1.

[Example 10]
Use of copper nitrate (II) trihydrate (manufactured by Wako Pure Chemical Industries) 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 produced in the same manner as in Example 1 except that the coating liquid A10 prepared to be 05: 10: 25.9 was applied to the conductive substrate.

[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 produced in the same manner as in Example 1 except that the coating liquid A11 prepared so that the ratio was 05: 10: 25.9 was applied to the conductive substrate.

[Comparative Example 2]
The coating liquid B2 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium was 20: 18: 60: 2 was applied to the conductive substrate. Using a ruthenium chloride aqueous solution (manufactured by Tanaka Kikinzoku Co., Ltd., ruthenium concentration: 100 g / L) for the preparation, and a cycle consisting of roll coating, drying, and firing, the first firing temperature was set to 450 ° C., and subsequently at 450 ° C. An electrode for electrolysis was produced in the same manner as in Example 1 except that the treatment was further repeated three times and further baked at 450 ° C. for 1 hour.

[Comparative Example 3]
The conductive base material is coated with the coating liquid B3 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium, and vanadium is 22.7: 20.5: 34.1: 22.7. And the cycle consisting of roll coating, drying, and firing was repeated at 380 ° C. three more times, followed by further one-hour firing at 590 ° C., with the first firing temperature being 380 ° C. An electrode for electrolysis was produced in the same manner as in Example 1 except that.

[Comparative Example 4]
Coating on a conductive substrate using coating liquid B4 prepared so that the element ratio (molar ratio) of ruthenium, iridium, titanium and vanadium is 28.6: 25.7: 42.8: 2.9. And a cycle consisting of roll coating, drying, and firing is performed by setting the first firing temperature to 450 ° C., then raising the temperature to 520 ° C. and repeating three more times, and further firing at 520 ° C. for 1 hour The electrode for electrolysis was produced by the same method as Example 1 except having performed.

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

[Comparative Example 6]
Manganese nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium chloride (III) in Example 1, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and manganese was 21.25: 21.25: 42. The electrode for electrolysis was produced in the same manner as in Example 1 except that the coating liquid B6 prepared so as to have a ratio of 5:15 was applied to the conductive substrate.

[Comparative Example 7]
Zinc nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of vanadium chloride (III) in Example 1, and the element ratio (molar ratio) of ruthenium, iridium, titanium, and zinc was 21.25: 21.25: 42. An electrode for electrolysis was produced in the same manner as in Example 1 except that the coating liquid B7 prepared to have a ratio of 5:15 was applied to the conductive substrate.

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

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

The structure of the electrode for electrolysis produced in each of Examples 6 to 11 and Comparative Examples 2 to 9 (metal composition of the coating solution used for forming the catalyst layer) is an index of the measured electric double layer capacity D It shows in Table 3 with a value. The unit “mol%” in the table means the mole percentage (feeding ratio) with respect to all the 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 preparation ratio.

[Accelerated test]
An acceleration test was carried out using the electrodes for electrolysis produced in each of Examples 1 to 11 and Comparative Examples 1 to 9. The results are shown in Table 4. Comparative Example 9 shows the evaluation results when the test was stopped after 14 days because ruthenium had low durability.

When the 21-day acceleration test was conducted, the following was found.
The electrodes for electrolysis of Examples 1 to 11 had an anode overvoltage of 0.030 to 0.045 V one day after the start of the test, and an anode overvoltage of 0.030 to 0.039 V after 21 days. On the other hand, in the electrodes for electrolysis of Comparative Examples 1 to 8, the anode overvoltage after 1 day from the start of the test was 0.042 to 0.110 V, and the anode overvoltage after 21 days was from 0.043 to 0.093 V. there were. As described above, it was verified that the example can be electrolyzed at a low voltage and low power consumption in the initial stage of electrolysis and for a long period of time as compared with the comparative example.
In Examples 1 to 11, compared to Comparative Example 9 in which the anode overvoltage was comparable, both Ru and Ir residual ratios were high even after 21 days from the start of the test, and in the long-term electrolysis while maintaining the anode overvoltage low. It was verified that the durability was sufficient.

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

The electrode for electrolysis of the present invention exhibits a low chlorine generation overvoltage and can be electrolyzed with low voltage and low power consumption, and therefore can be suitably used in the field of salt electrolysis. In particular, it is useful as an anode for salt exchange electrolysis by ion exchange membrane method, and enables high-purity chlorine gas having a low oxygen gas concentration to be produced at low voltage and low power consumption over a long period of time.

200 Electrolysis Cell for Electrolysis 210 Electrolyte 220 Container 230 Anode (Electrode for Electrolysis)
240 Cathode 250 Ion exchange membrane 260 Wiring

Claims

A conductive substrate;
A catalyst layer formed on the surface of the conductive substrate;
An electrode for electrolysis comprising:
The catalyst layer includes 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;
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%,
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.
The electrode for electrolysis according to claim 1 or 2, wherein the first transition metal element contains 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 contains a vanadium element.
The electrode for electrolysis according to any one of claims 1 to 4, wherein the content of the first transition metal element with respect to all the metal elements contained 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 the electrode for electrolysis according to any one of claims 1 to 7,
A step of preparing a coating liquid containing a ruthenium compound, an iridium compound, a titanium compound, and a compound containing the first transition metal element;
Applying the coating liquid onto at least one surface of the conductive substrate to form a coating film;
Baking the coating film in an oxygen-containing atmosphere to form the catalyst layer;
The manufacturing method of the electrode for electrolysis which has these.
An electrolytic cell comprising the electrode for electrolysis according to any one of claims 1 to 7.