JP2023081781A - Electrode, water electrolysis tank, water electrolysis apparatus, carbon dioxide reduction electrolysis tank, and carbon dioxide electrolysis apparatus - Google Patents

Abstract

To provide an electrode that shows a low activation voltage in a neutral pH range.SOLUTION: The electrode contains a catalyst including at least one first metal element selected from the group consisting of nickel, iron, and cobalt and at least one second metal element selected from the group consisting of copper, silver, and gold.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to an electrode, a water electrolyzer, a water electrolyzer, a carbon dioxide reduction electrolyzer, and a carbon dioxide electrolyzer that exhibit a low activation overvoltage in the neutral pH range.

The effective use of renewable energy is an urgent social need for the realization of a sustainable society. This inability is an obstacle to large-scale use.
From this point of view, hydrogen is produced by electrolyzing water (water electrolysis) from electricity derived from renewable energy, and the hydrogen is stored and transported and used when needed by using hydrogen power generation equipment and fuel cells. Methods have been proposed to level the energy supply by extracting energy at different locations.

As industrial water electrolysis methods, alkaline water electrolysis using a concentrated aqueous solution of sodium hydroxide or potassium hydroxide and proton exchange membrane (PEM) type water electrolysis using a proton exchange membrane are mainly used. there is Since these techniques use a strongly basic or strongly acidic electrolyte, the materials of the members constituting the electrolytic device are required to have high corrosion resistance.

Therefore, if water electrolysis can be carried out in a neutral pH range of weakly acidic to weakly basic, it will be possible to construct a water electrolysis device with general-purpose materials, and it will be possible to extend the life of the electrolysis device. , the development of water electrolysis in the neutral pH region is being considered.
However, water electrolysis in the neutral pH range tends to have lower energy efficiency, ie, higher electrolysis voltage, than under strongly basic or strongly acidic conditions. One of the reasons for the low energy efficiency of water electrolysis is the low activity of the oxygen evolution reaction in the neutral pH range.

Therefore, a technique for improving the activity of the oxygen evolution reaction in the neutral pH range, that is, a technique for developing an oxygen evolution electrode with a low activation overvoltage, has been studied. By creating an electrode on which an iridium oxide catalyst is electrodeposited and performing water electrolysis in an electrolytic solution with a buffering action such as a phosphate buffer, a low activation overvoltage can be obtained even in a neutral pH range. is disclosed.

In Non-Patent Document 2, a nickel foam is oxidized and reduced by applying a predetermined potential to form a nanostructure on its surface to increase the electric double layer capacity, thereby producing an oxygen generating electrode with a low activation overvoltage. It is disclosed to obtain

In addition, Non-Patent Document 3 discloses a technology of a carbon dioxide reduction electrolytic cell in which a carbon dioxide reduction reaction is performed at the cathode and an oxygen evolution reaction is performed at the anode. In the carbon dioxide reduction electrolytic cell, when a strongly acidic electrolyte is used, the hydrogen generation reaction tends to take precedence over the carbon dioxide reduction reaction at the cathode, and when a strongly basic electrolyte is used, the base and carbon dioxide The acid-base reaction of the electrolyte may neutralize it.
For these reasons, even carbon dioxide reduction electrolytic cells are often operated in the neutral pH range (Non-Patent Document 3 also uses an aqueous potassium bicarbonate solution as the electrolyte), so activation is performed in the neutral pH range. An oxygen generating electrode with a low overvoltage is an important technology not only for water electrolysis but also for carbon dioxide reduction electrolysis.

T. Nishimoto, et al. , Chem Sus Chem 2021, 14, 1554-1564 T. Shinagawa, et al. , Angew. Chem. Int. Ed. 2017, 56, 5061-5065 R. Krause, et al. , Chem. Ing. Tech. 2020, 92, 53-61

However, even when water electrolysis or carbon dioxide reduction electrolysis is performed using the techniques of Non-Patent Documents 1 to 3, the energy efficiency of water electrolysis or carbon dioxide reduction electrolysis in the neutral pH region is still low. It was not enough, and further improvement of the technology was desired.

Therefore, an object of the present invention is to provide an electrode, a water electrolyzer, a water electrolyzer, a carbon dioxide reduction electrolyzer, and a carbon dioxide electrolyzer that exhibit a low activation overvoltage in the neutral pH range.

The present inventors have conducted studies to solve the above problems, and as a result, at least one first metal element selected from the group consisting of nickel, iron and cobalt, and selected from the group consisting of copper, silver and gold By containing a catalyst containing at least one second metal element in the electrode, high oxygen generation activity, that is, oxygen generation, is achieved in a neutral pH region (pH is 1.5 to 12.6 during non-electrolysis) The inventors have found that a low activation overvoltage can be exhibited in the reaction, and have completed the present invention.

The present invention was made based on the above findings, and the gist thereof is as follows.
1. Characterized by containing a catalyst containing at least one first metal element selected from the group consisting of nickel, iron and cobalt and at least one second metal element selected from the group consisting of copper, silver and gold and electrodes.
2. 2. The electrode according to 1 above, wherein the catalyst is a metal oxide containing the first metal element and the second metal element.
3. 3. The electrode described in 1 or 2 above, wherein the catalyst is supported on a conductive substrate.
4. 4. The electrode according to 3 above, wherein the conductive substrate contains a transition metal.
5. 5. The electrode as described in 3 or 4 above, wherein the conductive substrate is a porous body.
6. 6. The electrode as described in any one of 3 to 5 above, wherein the transition metal is at least one selected from the group consisting of nickel, titanium and iron.
7. 7. The electrode as described in any one of 3 to 6 above, wherein the conductive base material is produced by an activation treatment of electrochemical oxidation-reduction.
8. 8. The electrode as described in any one of 3 to 7 above, wherein the conductive substrate has an electric double layer capacity of 1.25 mF/cm ² or more.
9. The catalyst is obtained by immersing the conductive substrate in an electrolytic solution containing a soluble salt of the first metal element and a soluble salt of the second element and subjecting the substrate to electrodeposition. An electrode according to any one of the preceding claims.
10. 10. The electrode according to any one of 1 to 9 above, which is an electrode for generating oxygen.
11. 11. A water electrolytic cell, wherein the electrode according to any one of 1 to 10 is used as an oxygen generating electrode.
12. 12. The water electrolysis cell according to 11 above, wherein a buffer solution having a pH of 1.5 to 12.6 when not electrolyzed is used as the electrolyte solution.
13. 13. A water electrolysis apparatus comprising the water electrolysis cell according to 11 or 12 above.
14. 11. A carbon dioxide reduction electrolytic cell, characterized in that the electrode according to any one of 1 to 10 above is used as an oxygen generating electrode.
15. 15. The carbon dioxide reduction electrolytic cell as described in 14 above, wherein a buffer solution having a pH of 1.5 to 12.6 during non-electrolysis is used as the electrolytic solution.
16. 16. A carbon dioxide electrolyzer comprising the carbon dioxide reduction electrolytic cell according to 14 or 15 above.

According to the present invention, it is possible to provide an electrode, a water electrolyzer, a water electrolyzer, a carbon dioxide reduction electrolyzer, and a carbon dioxide electrolyzer that exhibit a low activation overvoltage in the neutral pH range.

FIG. 4 is a diagram showing the relationship between the current density and the potential of the working electrode (iR correction) when the electrodes of Examples and Comparative Examples are used. FIG. 4 is a diagram showing changes in potential (iR correction) in an on-off test (on: 400 mA/cm ² for 15 minutes, off: 5 minutes) when the electrodes of Examples and Comparative Examples were used as oxygen generating electrodes. . 1 is a photograph of an oxygen generating electrode of Example 1, observed with a scanning electron microscope, showing (a) activated nickel foam and (b) iron-copper oxide supported on it. 2 shows (a) a photograph of iron-copper oxide observed with a transmission electron microscope and (b) a partially enlarged photograph of the oxygen generating electrode of Example 1. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing the electrode which concerns on this invention is demonstrated in detail.
In addition, this embodiment is an illustration for demonstrating this invention, and this invention is not limited only to the embodiment. That is, the present invention can be modified in various ways without departing from the scope of the invention.

<Electrode>
The electrode of this embodiment contains at least one first metal element selected from the group consisting of nickel, iron and cobalt, and at least one second metal element selected from the group consisting of copper, silver and gold. Contains a catalyst.
By using the catalyst containing the first metal element and the second metal element as the electrode material, high reaction activity can be obtained, and as a result, a low activation overvoltage can be obtained in the neutral pH region.

(catalyst)
The catalyst used in the electrode of the present embodiment contains the first metal element and the second metal element. The first metal element is at least one selected from the group consisting of nickel, iron and cobalt, and preferably contains at least iron from the viewpoint of reaction activity.
Also, the second metal element is at least one selected from the group consisting of copper, silver and gold. High reaction activity can be obtained by including the first metal element and the second metal element in the catalyst.

The form of existence of the first metal element and the second metal element is not particularly limited, but from the viewpoint of reaction activity and chemical stability, it is preferable to exist as a metal element or a metal oxide.
In the case of the metal oxide, for example, it may have a stoichiometric composition such as FeO, Fe ₃ O ₄ and Fe ₂ O ₃ , or a non-chemical composition such as oxygen ion or metal ion deficiency. It may be a stoichiometric composition.
Moreover, the first metal element and the second metal element may be in a state of being mixed at the atomic level as an alloy or a composite metal oxide. For example, iron oxide particles and gold particles may be mixed. It can also be set as a form.

The element ratio (A ₁ /A _{2 ) between the first metal element (A 1 ) and the second metal element (A 2 ) is} preferably 0.05 to 10, more preferably 0.1 to 5. and more preferably 0.15 to 3.

Among the above-mentioned catalysts, from the viewpoint of reaction activity and chemical stability, iron-copper oxide, iron-silver oxide, iron-gold oxide, nickel-iron-copper oxide, nickel-silver-copper Oxides, nickel-iron-gold oxides and the like are preferred.

Furthermore, from the viewpoint of ensuring higher conductivity, the catalyst is preferably carried on a conductive substrate, which will be described later.
The method of supporting the conductive substrate is not particularly limited, but from the viewpoint of simple and uniform support, the conductive substrate is electrolyzed containing a soluble salt of the first metal element and a soluble salt of the second element. A method of immersing in a liquid and electrodepositing can be preferably used.

Although the soluble salt of the first metal element and the soluble salt of the second metal element are not particularly limited, they are preferably water-soluble salts. Examples of the water-soluble salt of the first metal element and the water-soluble salt of the second metal element include fluorides, chlorides, bromides, iodides, nitrates, sulfates and acetates.
In addition, it is preferable to use water as a solvent for the electrolytic solution. can also be added.

(Conductive substrate)
For the electrode of the present embodiment, the catalyst is preferably supported on a conductive substrate for the purpose of ensuring higher conductivity.
Although the material of the conductive substrate is not particularly limited, it is preferably a transition metal from the viewpoint of conductivity and chemical durability. The transition metal is at least one selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, molybdenum, ruthenium, rhodium, palladium, silver, iridium, platinum and gold. It is more preferably at least one selected from the group consisting of titanium, chromium, manganese, iron, cobalt and nickel, and particularly preferably at least one selected from the group consisting of nickel, titanium and iron. .
The conductive base material may be made of one type of transition metal, or may be an alloy or mixture of two or more types of transition metals. Furthermore, in addition to transition metals, typical elements such as carbon, oxygen, nitrogen, silicon, phosphorus, and sulfur can also be included.

Moreover, the conductive substrate is preferably a porous body from the viewpoint of increasing the surface area capable of supporting the catalyst. Furthermore, from the same viewpoint, the electric double layer capacitance of the conductive substrate is preferably 1.25 mF/cm ² or more, more preferably 1.30 mF/cm ² or more, and 1.35 mF/cm 2 or more. cm ² or more is more preferable.
The electric double layer capacity mentioned above means a value exhibited by a conductive substrate on which no catalyst is supported. The electric double layer capacitance is determined by the measuring method described in Examples.
The method for producing such a conductive substrate is not particularly limited, but for example, a method of performing an activation treatment by electrochemical oxidation-reduction of a nickel foam can be preferably used.

<Water electrolyzer>
The water electrolyzer of this embodiment uses the electrode of the present invention as an oxygen generating electrode.
In the water electrolysis cell of this embodiment, the cathode and the anode are immersed in the electrolytic solution, and the cathode and the anode are connected to the power source. Here, the anode is the oxygen generating electrode, and may have a structure in which a diaphragm or an ion exchange membrane (proton exchange membrane or anion exchange membrane) is sandwiched between the cathode and the anode.

The electrolytic solution used in the water electrolytic cell of the present embodiment has a pH in the neutral range (1.5 to 12.6) during non-electrolysis.
In water electrolysis, the substrate protons (H ⁺ ) or hydroxide ions (OH ⁻ ) are supplied to the electrode and the reaction proceeds. be restricted. In this case, the maximum operable current density is called "diffusion limiting current density". In industrial water electrolysis, from the viewpoint of productivity, it is usually operated at a current density of 100 mA/cm ² or ^more . ⁺ concentration or OH ⁻ concentration is insufficient, that is, it is considered to be in the neutral pH range, and an electrolyte solution having a pH in the range of 1.5 to 12.6 when not electrolyzed is called an electrolyte solution in the neutral pH range. Defined. For the calculation method of numerical values, refer to T.T. Shinagawa, and K.; Takanabe, Phys. Chem. Chem. Phys. 2015, 17, 15111-15114.

As described above, the electrolytic solution of the present embodiment has a pH in the range of 1.5 to 12.6 when not electrolyzed. The pH during non-electrolysis is preferably 4 to 12, more preferably 5 to 11.5.

From the viewpoint of keeping the pH of the electrolyte constant and promoting the supply of protons or hydroxide ions to the electrode, the electrolyte is preferably a buffer solution.
The type of buffer solution is not particularly limited. For example, carbonate-bicarbonate in combination with alkali metal (ie, lithium (Li), sodium (Na), potassium (K), cesium (Cs) and rubidium (Rb)) carbonates and alkali metal bicarbonates A buffer can preferably be used.

From the viewpoint of increasing the surface area, the cathode constituting the water electrolytic cell of the present embodiment preferably contains a conductive porous body of metal or carbon material. Examples of the metal porous body include plain weave mesh, punching metal, expanded metal, and metal foam. As the porous body of the carbon material, a woven fabric obtained by weaving carbon fibers, a non-woven fabric obtained by binding carbon fibers with a binder, carbon foam, or the like can be used.

For the cathode, the porous metal or carbon porous body described above may be used as it is. Although an electrode having a catalyst layer formed thereon can be used as an electrode, from the viewpoint of reducing the electrolysis voltage, it is preferable to form a catalyst layer having high reaction activity on the surface of the electrode substrate.

Here, the material of the electrode base material is not particularly limited, but mild steel, stainless steel, nickel, nickel alloy, titanium, titanium alloy, and carbon material are preferably used from the viewpoint of chemical and electrochemical durability.

In addition, the catalyst layer formed on the cathode preferably has a high ability to generate hydrogen, and nickel, cobalt, iron, platinum group elements (e.g., ruthenium, rhodium, palladium, osmium, iridium, etc.), etc. are used. can do. In order to achieve desired activity and durability, these materials can form catalyst layers as simple metals, compounds such as oxides, composite metal oxides or alloys composed of multiple metal elements, or mixtures thereof. Specifically, Raney nickel, Raney alloys composed of a combination of multiple materials such as nickel and aluminum, or nickel and tin, porous coatings produced by plasma spraying using nickel compounds and cobalt compounds as raw materials, nickel and cobalt , iron, molybdenum, silver, copper, etc., alloys and composite compounds with elements selected from, etc., metals and oxides of platinum group elements such as platinum and ruthenium with high hydrogen generating ability, and metals and oxides of these platinum group elements and mixtures with compounds of other platinum group elements such as iridium and palladium, compounds of rare earth metals such as lanthanum and cerium, and carbon materials such as graphene. In order to achieve high catalytic activity and durability, a plurality of the above materials may be laminated, or a plurality of them may be mixed in the catalyst layer. An organic substance such as a polymer material may be contained in order to improve durability and contact with the substrate.

The method for forming the catalyst layer on the electrode substrate includes a plating method, a thermal spraying method such as a plasma thermal spraying method, a thermal decomposition method in which a precursor solution is applied onto the substrate and then heat is applied, and a catalyst material is used as a binder component. Techniques such as a method of mixing and fixing to a substrate and a vacuum film forming method such as a sputtering method can be used.

The water electrolysis cell of the present embodiment is preferably operated in a temperature range of 60°C to 110°C, more preferably in a temperature range of 65°C to 105°C, and more preferably in a temperature range of 70°C to 100°C. is more preferred. By operating at a temperature near or above the boiling point of water, the reaction rate of water electrolysis can be greatly improved.

<Carbon dioxide reduction electrolytic cell>
The carbon dioxide reduction electrolytic cell of the present embodiment uses the above-described electrode of the present invention as an oxygen generating electrode.
In the carbon dioxide reduction electrolytic cell of the present embodiment, the cathode and the anode are immersed in the electrolytic solution, and the cathode and the anode are connected to the power supply. Here, said anode is an oxygen evolution electrode. Further, the carbon dioxide reduction electrolytic cell of the present embodiment may have a structure in which a diaphragm or an ion exchange membrane (proton exchange membrane or anion exchange membrane) is sandwiched between the cathode and the anode, A gas diffusion electrode can also be used as the cathode.

The carbon dioxide reduction electrolytic cell of the present embodiment can preferably use the same electrolytic solution as the water electrolytic cell described above.
Also, the cathode of the carbon dioxide reduction electrolytic cell of the present embodiment is preferably a conductive porous body of metal or carbon material, as in the water electrolytic cell described above.
The material constituting the metal porous body and the catalyst layer preferably has high carbon dioxide reduction activity. When the target product is carbon monoxide, gold, silver, and zinc are preferable, and formic acid is preferable. Indium, tin, and lead are preferable in the case of ethylene or ethanol, and copper is preferable in the case of ethylene or ethanol.

The operating conditions of the carbon dioxide electrolytic cell of the present embodiment are preferably in the temperature range of 40 to 100 ° C., more preferably in the temperature range of 50 to 90 ° C., from the balance between the reaction rate and the solubility of carbon dioxide. More preferably, the temperature range is from 55 to 80°C.

<Electrolyzer>
The electrolytic device of this embodiment includes a water electrolytic cell or a carbon dioxide reduction electrolytic cell using the above-described electrode of the present invention as an oxygen generating electrode.
According to such an electrolysis system, even when an electrolytic solution in the neutral pH range is used, the electrolysis voltage can be suppressed during water electrolysis or carbon dioxide reduction, and efficient electrolysis can be performed. .

The conditions of the electrolytic cell in the electrolytic device of this embodiment are the same as those of the water electrolytic cell or the carbon dioxide reduction electrolytic cell of this embodiment described above.

EXAMPLES The present invention will be described below with specific examples and comparative examples, but the present invention is not limited to the following examples.

(Manufacture of conductive substrate)
Two pieces of 1 cm × 1 cm nickel foam (manufactured by Nilaco Corporation, pore size 0.5 mm, thickness 1.6 mm) were used as the working electrode and the counter electrode, respectively, and a mercury/mercury chloride electrode was used as a reference electrode. It was prepared by mixing an aqueous potassium solution and an aqueous potassium hydrogencarbonate solution so that the total concentration of carbonate anion species was 1.5 mol/kg and pH = 10.5 at 25 ° C.), and heated to 67 ° C. Then, electrochemical treatment was performed with a three-electrode system.
First, after maintaining the open circuit voltage for 20 minutes, the process of applying an oxidation current of 50 mA for 25 minutes was repeated three times. After that, after holding the working electrode at 1.0 V (based on the reversible hydrogen electrode) for 10 minutes, the process of applying an oxidation current of 50 mA for 25 minutes was repeated twice in total to perform an activation treatment, and the conductive group of the sample. got the wood.

(Measurement of electric double layer capacity)
Using an activated conductive substrate as a working electrode, a nickel foam before electrochemical treatment as a counter electrode, and a mercury/mercury chloride electrode as a reference electrode, immerse in a potassium carbonate buffer and heat to 80°C. Then, electrochemical measurements were performed using a three-electrode system. Cyclic voltammetry is measured by sweeping the range of 0.3 to 0.9 V (reversible hydrogen electrode standard) at 200, 100, 50, 25, 10 mV / s, and the electric double layer capacity is measured from a current of 0.60 V. bottom. Here, the value of the electric double layer capacitance was the average value of the values obtained from the anode scan and the cathode scan. The electric double layer capacity of the nickel foam before the activation treatment is 1.06±0.15 mF (1.06±0.15 mF/cm ² per unit electrode area), and the electric double layer capacity of the nickel foam after the activation treatment is It was 1.90±0.17 mF (1.90±0.17 mF/cm ² per unit electrode area).

[Comparative Example 1: Electrodeposited iron oxide electrode]
A conductive substrate (nickel _foam ) activated as described above was used as _the working electrode, and a platinum wire was used as the _counter electrode. and electrodeposited at −10 mA/cm ² for 1 hour to obtain an oxygen generating electrode.
Using the above-described oxygen generating electrode supporting iron oxide as a working electrode, a platinum wire as a counter electrode, and mercury/mercury chloride as a reference electrode, immerse in a potassium carbonate-potassium hydrogen carbonate buffer (1.5 M, pH = 10.5). The mixture was heated to 80° C. in this state, and oxygen generation reaction was evaluated by a three-electrode method.
The relationship between the obtained current density and the potential of the working electrode (iR correction) is shown in ^FIG . ) is shown in FIG.

[Comparative Example 2: Oxygen Evolving Electrode Not Supporting Catalyst]
An oxygen evolution reaction was carried out under the same conditions as in Comparative Example 1, except that the conductive substrate (nickel foam) that had been activated as described above was directly used as the oxygen evolution electrode. FIG. 1 shows the relationship between the current density and the potential of the working electrode. FIG. 2 shows changes in potential (iR correction) when an on-off test was performed under the same conditions as in Comparative Example 1. In FIG.

[Comparative Example 3: Oxygen generating electrode in which titanium mesh supports iridium oxide]
T. Naito, et al. , ChemSusChem 2020, 13, 5921-5933, a 1 cm × 1 cm iridium oxide-supported titanium mesh was prepared. Then, an oxygen evolution reaction was carried out under the same conditions as in Comparative Example 1, except that this iridium oxide-supported titanium mesh was used as an oxygen evolution electrode. FIG. 1 shows the relationship between the current density and the potential of the working electrode, and FIG. 2 shows the transition of the potential during the on-off test.

[Example 1: Oxygen generating electrode supporting iron-copper oxide]
5 mM iron nitrate nonahydrate (Fe(NO ₃ ) _{3.9H 2} O) and 5 mM copper nitrate nonahydrate (Cu(NO ₃ ) _{2.9H 2} O) were added for electrodeposition of the catalyst. An oxygen evolution reaction was carried out under the same conditions as in Comparative Example 1, except that an oxygen evolution electrode supporting iron-copper oxide was obtained by using the aqueous solution containing the iron-copper oxide. FIG. 1 shows the relationship between the current density and the potential of the working electrode, and FIG. 2 shows the transition of the potential during the on-off test.
Scanning electron micrographs of the oxygen generating electrode obtained in Example 1 are shown in FIGS. 3(a) and 3(b). From FIG. 3, it can be seen that the iron-copper oxide forms a nanostructure. 4(a) and 4(b) are photographs of the iron-copper oxide collected from the surface of the oxygen generating electrode obtained in Example 1 and observed with a transmission electron microscope. From FIG. 4, it can be seen that fine black spots of several nm are present in the structure of several tens of nm, and nanoparticles are locally formed.

[Example 2: Oxygen generating electrode supporting iron-silver oxide]
For electrodeposition of the catalyst, an aqueous solution containing 5 mM iron nitrate nonahydrate (Fe(NO ₃ ) _{3.9H 2} O) and 5 mM silver nitrate (AgNO ₃ ) was used to support iron-silver oxide. An oxygen evolution reaction was carried out under the same conditions as in Comparative Example 1, except that an oxygen evolution electrode was obtained. FIG. 1 shows the relationship between the current density and the potential of the working electrode.

[Example 3: Oxygen generating electrode supporting iron-gold oxide]
An aqueous solution containing 5 mM iron nitrate nonahydrate (Fe(NO ₃ ) _{3.9H 2} O) and 5 mM tetrachloroauric acid (HAuCl ₄ ) was used for electrodeposition of the catalyst, and iron-gold oxide was deposited. An oxygen evolution reaction was carried out under the same conditions as in Comparative Example 1, except that an oxygen evolution electrode supporting was obtained. FIG. 1 shows the relationship between the current density and the potential of the working electrode.

From the results shown in FIGS. 1 and 2, by using the catalyst containing the first metal species and the second metal species for the oxygen generating electrode, the electrode containing the catalyst consisting only of the first metal species and the catalyst supported can be obtained. It can be seen that the activation overvoltage can be further reduced as compared with the case of using an electrode made of a conductive base material that is not exposed.
In Comparative Example 3, an iridium oxide catalyst known to have high oxygen generation activity in a wide pH range from strongly acidic to strongly basic is used for the oxygen generating electrode. Although the activation overvoltage is lower than that of the oxygen generating electrode, it is unstable in the neutral pH ^region and the activation overvoltage tends to gradually increase. It can be seen that the electrode exhibits a lower activation overvoltage.

According to the present invention, it is possible to provide an electrode, a water electrolyzer, a water electrolyzer, a carbon dioxide reduction electrolyzer, and a carbon dioxide electrolyzer that exhibit a low activation voltage in the neutral pH range. can be used in the neutral pH range, it can be suitably used in the field of water electrolysis.

Claims (16)

Characterized by containing a catalyst containing at least one first metal element selected from the group consisting of nickel, iron and cobalt and at least one second metal element selected from the group consisting of copper, silver and gold and electrodes. 2. The electrode according to claim 1, wherein said catalyst is a metal oxide containing said first metal element and said second metal element. 3. The electrode according to claim 1, wherein said catalyst is supported on a conductive substrate. 4. Electrode according to claim 3, characterized in that the conductive substrate contains a transition metal. 5. The electrode according to claim 3, wherein said conductive substrate is a porous body. The electrode according to any one of claims 3 to 5, wherein the transition metal is at least one selected from the group consisting of nickel, titanium and iron. The electrode according to any one of claims 3 to 6, characterized in that the conductive substrate is produced by an activation treatment of electrochemical redox. The electrode according to any one of claims 3 to 7, characterized in that said conductive substrate has an electric double layer capacitance of 1.25 mF/cm ² or more. Claims 3 to 8, characterized in that the catalyst is obtained by immersing the conductive substrate in an electrolytic solution containing the soluble salt of the first metal element and the soluble salt of the second element and subjecting it to electrodeposition. The electrode according to any one of . The electrode according to any one of claims 1 to 9, characterized in that it is an electrode for oxygen evolution. A water electrolyzer, characterized in that the electrode according to any one of claims 1 to 10 is used as an oxygen generating electrode. 12. The water electrolytic cell according to claim 11, wherein a buffer solution having a pH of 1.5 to 12.6 when not electrolyzed is used as the electrolyte. A water electrolysis apparatus comprising the water electrolysis cell according to claim 11 or 12. A carbon dioxide reduction electrolytic cell, wherein the electrode according to any one of claims 1 to 10 is used as an oxygen generating electrode. 15. The carbon dioxide reduction electrolytic cell according to claim 14, wherein a buffer solution having a pH of 1.5 to 12.6 during non-electrolysis is used as the electrolyte. A carbon dioxide electrolyzer comprising the carbon dioxide reduction electrolytic cell according to claim 14 or 15.

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