WO2018180517A1

WO2018180517A1 - Electrode base material, and electrode catalyst and electrolysis apparatus each using same

Info

Publication number: WO2018180517A1
Application number: PCT/JP2018/010104
Authority: WO
Inventors: 可織関根; 俊夫谷; 英樹會澤; 吉則風間; 稲森　康次郎
Original assignee: 古河電気工業株式会社
Priority date: 2017-03-29
Filing date: 2018-03-15
Publication date: 2018-10-04
Also published as: TW201903209A; JP6902375B2; TWI753143B; JP2018168410A

Abstract

The purpose of the present invention is to provide: a copper-based base material which is suitable for use as a base material for catalysts for hydrogen generation by means of electrolysis of water or catalysts for conversion of carbon dioxide into a carbon-containing substance by means of cathodic reduction, and which is capable of improving the catalytic performance of the catalysts; and an electrode catalyst and an electrolysis apparatus, each of which uses this copper-based base material. An electrode base material according to the present invention comprises: a substrate which is formed of copper or a copper alloy; and a diffusion prevention layer which is formed on the surface of the substrate directly or with an oxide layer being interposed therebetween, and which is formed from an organic material.

Description

Electrode base material, and electrode catalyst and electrolysis apparatus using the same

The present invention relates to an electrode base material, and an electrode catalyst and an electrolysis apparatus using the same.

In Japan, where energy resources are scarce, there are plans to make hydrogen for various fuels in the future. By increasing the renewable energy from solar cells, hydropower and wind power, we will produce hydrogen by electrolysis of water and water vapor and use it in place of fossil fuels.

Also, the recent adverse effects of global warming have brought about changes in the global environment, and many problematic phenomena have been recognized. The cause is said to be an increase in the concentration of greenhouse gases, particularly carbon dioxide, which accounts for the majority. To reduce carbon dioxide concentration, not only increase the amount of photosynthesis by new land plantations and marine algae, but also actively absorb and recover carbon dioxide, and use that carbon as a raw material carbon source for organic compounds for 10 years. It is necessary to fix to the valuables over the above. Specifically, it is necessary to reduce carbon dioxide and convert it into carbon monoxide, methane, methanol, formic acid, etc., and use it as a material that can be used as a raw material for organic synthesis.

In recent years, a catalyst such as a photocatalyst or an electrode catalyst has been widely used in the reduction reaction of carbon dioxide as described above, and the development of a catalyst having more excellent catalytic performance has been demanded.

The catalyst used for the reduction reaction of carbon dioxide requires not only the reaction efficiency but also selectivity for a specific reaction. From such a viewpoint, selection of a material is important (Non-patent Document 1). For example, gold and silver are effective in reducing and producing carbon monoxide efficiently, and copper is the catalyst material in efficiently reducing and producing hydrocarbons such as methane, ethane and ethylene. Recommended as. In particular, copper attracts attention as a cathode reduction electrode catalyst for carbon dioxide because it can produce higher-order organic substances such as ethylene.

As such a copper reduction electrode catalyst, a flat type such as a copper plate or a copper foil, a mesh or a porous one has been proposed (Patent Documents 1 and 2), and a catalyst is formed by electrodeposition or vapor deposition on a substrate. A copper electrode catalyst having a fixed material is also used. However, in such a copper electrode catalyst, the catalyst material fixedly formed on the base material reacts or interdiffuses with the atoms constituting the base material over time, and is integrated with the base material or altered. However, the desired catalyst performance as a catalyst material may not be exhibited.

JP 2001-97889 A Japanese Patent No. 5683883

The present invention has been made in view of the above problems, and is suitably used as a base material of a catalyst for generating hydrogen by electrolysis of water, or for converting carbon dioxide into a carbon-containing substance by cathodic reduction of carbon dioxide, An object of the present invention is to provide an electrode base material capable of improving the catalytic performance of the catalyst, and an electrode catalyst and an electrolysis apparatus using the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found out from a base made of copper or a copper-based alloy and an organic material formed on the surface of the base directly or via an oxide layer. A copper-based substrate having a diffusion barrier layer formed on the substrate by using hydrogen as an electrolysis of water, or as a catalyst substrate for cathodic reduction of carbon dioxide to convert it to a carbon-containing material. It has been found that a catalyst capable of suppressing or preventing a change in the formed catalyst material with time and exhibiting excellent catalyst performance can be obtained, and the present invention has been completed based on such knowledge.

That is, the gist configuration of the present invention is as follows.
[1] An electrode substrate comprising: a substrate made of copper or a copper-based alloy; and a diffusion prevention layer containing an organic material formed directly or via an oxide layer on the surface of the substrate. Wood.
[2] An electrode base material used as a base material constituting a catalyst for producing hydrogen by electrolysis of water or catalyzing carbon dioxide to convert it into a carbon-containing substance.
[3] The electrode substrate according to [1] or [2], wherein the organic material is an azole compound.
[4] The electrode substrate according to any one of [1] to [3] above, wherein the reciprocal value of the electric double layer capacity is 0.3 to 5 cm ² / μF.
[5] The electrode base material according to any one of the above [1] to [4], and a catalyst layer containing a catalyst material containing a metal cluster formed on the diffusion prevention layer of the electrode base material. An electrode catalyst.
[6] The electrode catalyst according to [5], wherein the metal cluster is a cluster made of copper or a copper-based alloy.
[7] An electrolysis apparatus comprising the copper base material according to any one of [1] to [4] above or the electrode catalyst according to [5] or [6] above.
[8] A cathode using the copper base material according to any one of [1] to [4], a cathode electrolyte, an anode, the anode electrolyte, and between the cathode and the anode. And an ion exchange membrane.

According to the present invention, it can be suitably used as a base material for a catalyst for generating hydrogen by electrolysis of water or for converting carbon dioxide into a carbon-containing substance by cathodic reduction. According to such an electrode base material, a catalyst capable of exhibiting good catalytic performance for electrolysis of water and cathode reduction of carbon dioxide can be obtained.

FIG. 1 is a schematic cross-sectional view showing an example of the copper-based substrate of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the copper-based substrate of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of a catalyst using the copper base material of the present invention. FIG. 4 is a configuration diagram schematically showing the electrolysis apparatus. FIG. 5 is a schematic cross-sectional view showing a configuration of an electrolysis cell (carbon dioxide reduction cell or water decomposition cell device) in the electrolysis apparatus shown in FIG.

Embodiments of an electrode substrate according to the present invention, and an electrode catalyst and an electrolysis apparatus using the electrode substrate will be described in detail below.

The electrode base material according to the present embodiment has a base made of copper or a copper-based alloy, and a diffusion prevention layer made of an organic material formed directly on the surface of the base or through an oxide layer. . Such a copper-based electrode base material is preferably used as a copper-based electrode base material constituting a catalyst for hydrogen generation by electrolysis of water, or cathodic reduction of a carbon dioxide base material to convert it to a carbon-containing material. It is done.

As an example of a copper base material according to the present embodiment, FIG. 1 shows a schematic cross-sectional view schematically showing a cross section of the copper base material according to the present embodiment. As shown in FIG. 1, a copper-based substrate 1 a according to the present invention includes a base 11 and a diffusion prevention layer 13 formed directly on the base 11. 2 is another example of the copper base material according to the present embodiment, and the copper base material 1b shown in FIG. 2 includes an oxide layer between the base 11 and the diffusion prevention layer 13. Twelve. In the following description, the copper-based substrate 1a shown in FIG. 1 and the copper-based substrate 1b shown in FIG. 2 are simply referred to as “copper-based substrate 1” unless otherwise distinguished.

Moreover, when using the copper base material which concerns on this Embodiment as a base material which comprises a catalyst, the usage condition as shown, for example in FIG. 3 is mentioned. FIG. 3 is an example when the copper base material according to the present embodiment is used as a catalyst base material, and schematically shows a cross section of the catalyst 3 using the copper base material 1a shown in FIG. It is sectional drawing. In the catalyst 3 of FIG. 3, the catalyst layer 31 is formed on the diffusion preventing layer 13 of the copper-based substrate 1a. In addition, although not shown in particular, when the copper base material 1b shown in FIG. 2 is used as the base material, the catalyst layer 31 is the same as the catalyst 3 shown in FIG. Formed on layer 13.

The copper-based substrate 1 according to the present embodiment used in this way has a diffusion prevention layer 13 formed directly on the substrate 11 or through the oxide layer 12, thereby providing a substrate for the catalyst 3. When used, the catalyst performance of the catalyst layer 31 is not deteriorated. That is, according to the copper-based substrate 1, since the catalyst layer 31 is formed on the diffusion preventing layer 13, the catalyst material constituting the catalyst layer 31 and the constituent components of the substrate 11 and the oxide layer 12 are in direct contact with each other. There is nothing. Therefore, it is possible to effectively prevent reaction or mutual diffusion over time with the atoms constituting the substrate 11 and the oxide layer 12. As a result, if the copper base material 1 according to the present embodiment is used, it is possible to effectively suppress deterioration over time due to integration and alteration of the catalyst material and the base material, which has been a problem with conventional base materials. Therefore, the catalyst performance peculiar to the catalyst material can be sufficiently and continuously exhibited.

The diffusion preventing layer 13 is made of an organic material. Here, as the organic material, when the copper base material 1 is used as the base material of the catalyst 3, the catalyst material constituting the catalyst layer 31 is between the constituents of the base material 11 and the oxide layer 12. Any organic material that can effectively prevent reaction or interdiffusion with time can be used, and in particular, it is a material that inhibits the movement of components between the substrate 11 and the oxide layer 12 and the catalyst layer 31. Is preferred. Examples of such a material include compounds such as azoles such as triazoles, thiazoles and imidazoles, mercaptans and triethanolamines. Among these, azoles are preferable because they have good affinity with copper (for example, coordinate bond to copper), more preferably triazoles, and still more preferably benzotriazoles. In addition, as a compound of benzotriazoles, for example, benzotriazole is preferable.

The formation state of the diffusion preventing layer 13 is not particularly limited and can be appropriately selected according to the shape of the base body 11 and the usage pattern, and may be formed on at least one surface of the base material 11. It may be formed so as to cover the entire surface.

Further, the thickness of the diffusion preventing layer 13 is quantitatively expressed by an inverse value of the electric double layer capacity.
Specifically, the reciprocal value of the electric double layer capacity expressing the thickness of the diffusion preventing layer 13 is obtained using a commercially available direct-reading type electric double layer capacity measuring instrument (for example, impedance analyzer C meter, manufactured by Hioki Electric Co., Ltd.). Then, the electric double layer capacity (C: μF) on the surface of the substrate is measured and calculated as the reciprocal value (1 / C) as shown by the following formula (1).
1 / C = A · d + B (1)
(D is the thickness of the electric double layer formed on the substrate, A and B are constants)

The reciprocal value of the electric double layer capacity obtained by the above formula (1) is induced in proportion to the thickness d of the electric double layer formed on the substrate, that is, the thickness of the diffusion prevention layer 13. Accordingly, the reciprocal value of the electric double layer capacitance is preferably 0.3 to 5 cm ² / μF, and more preferably 0.5 to 1.5 cm ² / μF. By setting it as the above range, a catalyst capable of exhibiting excellent catalyst performance can be obtained when used as a catalyst substrate. When the reciprocal value of the electric double layer capacity is 0.3 to 5 cm ² / μF, the thickness of the diffusion prevention layer 13 is measured with an electron microscope, and the average is about 4 to 75 nm.

The substrate 11 is made of copper or a copper-based alloy. In the case where the substrate 11 is made of copper (pure copper), for example, variously processed tough pitch copper TPC, phosphorus deoxidized copper PDC, oxygen-free copper OFC, or electrolytic copper foil can be used. When the substrate 11 is made of a copper alloy, a copper-based dilute alloy such as a copper-tin alloy, a copper-iron alloy, a copper-zirconium alloy, or a copper-chromium alloy can be used. It is also possible to use a solid solution or precipitation strengthened copper-based dilute alloy in which the component after the second component such as a Corson alloy system is about 0.01 to 5% by mass. In addition, in the case of an alloy-based electrode, as the additive amount of components other than silver increases, the conductivity tends to decrease and the basic characteristics as a base electrode tend to be reduced, so the additive amount of components other than silver is small. The more preferable. Moreover, the shape of the base | substrate 11 is not specifically limited, A thing of a mesh and a porous shape other than flat form can also be used, and a flat thing is preferable especially.

The oxide layer 12 is an arbitrary layer and is formed between the base 11 and the diffusion prevention layer 12. Such an oxide layer 12 is preferably composed of, for example, a metal oxide layer, and is preferably an oxide containing at least one metal selected from transition metals, in particular, copper. The oxide containing is preferable. Examples of the copper oxide include non-stoichiometric copper oxide in addition to cuprous oxide (Cu ₂ O) and cupric oxide (CuO). In particular, the oxide layer 12 preferably contains at least one of cuprous oxide and cupric oxide.

Further, the oxide layer 12 may be a single layer composed of one oxide layer, or may be a multilayer composed of two or more oxide layers. Further, when the oxide layer 12 is a single layer composed of one oxide layer, it may be a layer composed of one kind of oxide, or may be a layer in which two or more kinds of oxides are mixed. Good. Further, when the oxide layer 12 is a multi-layer composed of two or more oxide layers, each layer does not necessarily have to be clearly separate layers, and each layer is configured at the boundary between the two layers. Each of the oxides may be mixed. In addition to the various oxides, the oxide layer 12 may contain about 500 to 1000 ppm of the above-described organic materials, metals and alloys constituting the substrate.

The oxide layer 12 preferably contains at least cuprous oxide or cupric oxide. As such an oxide layer 12, a single layer containing at least one of cuprous oxide and cupric oxide, a layer made of cuprous oxide (hereinafter referred to as "cuprous oxide layer") and A multilayer including at least one of layers made of cupric oxide (hereinafter referred to as “cupric oxide layer”) may be mentioned.

The oxide layer 12 is preferably composed of two or more copper oxide layers having different copper oxidation numbers, and more preferably composed of a cuprous oxide layer and a cupric oxide layer. . Moreover, it is more preferable that the copper oxide layer of such two or more layers has a higher copper oxidation number as the layer is located on the surface side.

As an example when the oxide layer 12 is a multilayer, FIG. 2 shows a schematic cross-sectional view schematically showing a cross section of the copper-based substrate 1b according to the present embodiment. In the copper-based substrate 1b shown in FIG. 2, the oxide layer 12 is composed of a first copper oxide layer 121 and a second copper oxide layer 122 having different copper oxidation numbers. Yes. Here, it is preferable that the second copper oxide layer 122 located on the surface side of the first copper oxide layer 121 has a copper oxidation number larger than that of the first copper oxide layer 121.

For example, in FIG. 2, the cupric oxide layer is oxidized as in the case where the first copper oxide layer 121 is a cuprous oxide layer and the second copper oxide layer 122 is a cupric oxide layer. It is preferable that it is an outer layer rather than a 1st copper layer. Further, the ratio of the thickness of the cuprous oxide layer to the cupric oxide layer is preferably 0.0001 to 10,000, and more preferably 1 to 10,000.

Next, the preferable manufacturing method of the copper-type base material which concerns on this Embodiment is demonstrated.
The manufacturing method of the copper base material which concerns on this embodiment has the process of forming a diffusion prevention layer in the surface of a base | substrate. Moreover, you may have further the process of forming a pre-processing process and an oxide layer as needed. This will be specifically described below.

(Pretreatment process)
First, a base made of copper or a copper-based alloy is prepared, and the surface of the base is cleaned. By cleaning the surface of the substrate, a diffusion preventing layer can be formed uniformly on the substrate surface in a later step, and adhesion between the substrate and the diffusion preventing layer can be improved. The surface cleaning can be performed by a known method, but it is desirable to perform acid cleaning (neutralization) after immersion degreasing or cathode electrolytic degreasing.

(Step of forming a diffusion prevention layer)
A diffusion prevention layer is formed on the surface of the substrate after the pretreatment. Specifically, the diffusion preventing layer is formed on the substrate by immersing the substrate in a solution containing an organic material to be formed as the diffusion preventing layer and drying it.

The organic material described above can be used as the organic material. Moreover, as a solvent of the solution containing an organic material, for example, a known solvent such as water or alcohol can be used. In addition, when the substrate is immersed, the temperature of the solution containing the organic material may be 60 to 100 ° C., the immersion time may be about 1.5 to 4 minutes, and the drying temperature may be 60 to 90 ° C. . The thickness of the diffusion preventing layer can be adjusted by the number of organic materials, the concentration of the solution, and the steps of immersion and drying.

Further, when an oxide layer is formed between the base and the diffusion preventing layer, a step of forming the oxide layer is performed prior to the step of forming the diffusion preventing layer. The step of forming the oxide layer is preferably a step of performing any one of immersion treatment, anodic oxidation treatment and heat oxidation treatment on the substrate before forming the diffusion prevention layer.

Next, the catalyst using the copper base material according to the present embodiment will be described.
The catalyst according to the present embodiment preferably includes the above-described copper-based substrate according to the present embodiment and a catalyst layer including a catalyst material formed on the diffusion-preventing layer of the copper-based substrate. . FIG. 3 shows a catalyst 3 using the copper base material 1a shown in FIG. 1 as an example of the catalyst according to the present embodiment.

As shown in FIG. 3, the catalyst 3 according to the present embodiment has a catalyst layer 31 containing a catalyst material on the diffusion prevention layer 13 of the copper base material 1. In the catalyst 3, the catalytic reaction mainly occurs on the surface of the catalyst layer 31 or in the vicinity of the surface. According to such a catalyst 3, the constituent component of the catalyst layer 31 reacts with or diffuses with the constituent component of the base 11 constituting the copper base material 1 and the oxide layer 12 that is arbitrarily formed. Therefore, the reaction efficiency of the catalytic reaction by the catalyst layer 31 does not decrease with time.

Examples of the catalyst material constituting the catalyst layer 31 include a cluster catalyst including metal clusters and nanoparticles. Especially, the catalyst material containing a metal cluster is especially preferable from the high catalyst performance.

However, when the catalyst material includes a metal cluster, when a conventional base material that does not have the diffusion prevention layer 13 according to the present embodiment is used, the metal cluster included in the catalyst layer 31 and the copper component that forms the base material Inter-diffusion and fusion with each other, and the performance specific to the cluster catalyst is not fully exhibited.

On the other hand, according to the copper-based substrate 1 having the diffusion prevention layer 13 according to the present embodiment, even when the catalyst material includes a metal cluster, it is possible to effectively prevent the diffusion of atoms, and thus the cluster catalyst. As the performance does not deteriorate. That is, the copper-based substrate 1 according to the present embodiment can be particularly suitably used as a substrate for forming a catalyst layer made of a catalyst material containing a metal cluster.

In the present invention, the cluster means an aggregate of about 2 to 100 metal atoms. Of these, an aggregate of 10 to 40 metal atoms is preferable. In addition, the metal cluster includes one or more metals selected from platinum (Pt), gold (Au), silver (Ag), copper (Cu), palladium (Pd), and iron (Fe). Among them, those containing copper are preferable, and those made of copper or a copper-based alloy are more preferable. The catalyst material containing a metal cluster may contain about 30% by mass of metal particles other than the cluster in the catalyst material.

Next, the manufacturing method of the catalyst using the copper base material which concerns on this Embodiment is demonstrated. Below, an example of the manufacturing method of a catalyst is demonstrated to the case where the catalyst layer which consists of a catalyst material containing a metal cluster is formed as an example.
The method for producing a catalyst according to the present embodiment includes a step of forming a catalyst layer on the surface of the diffusion preventing layer of the copper-based substrate according to the present embodiment. Moreover, you may have further the process of forming a surface protective layer on the surface of a catalyst layer as needed. This will be specifically described below.

First, a copper base material according to the present embodiment is prepared. Next, a catalyst layer made of a catalyst material containing a metal cluster is formed on the diffusion preventing layer of the copper base material. Such a catalyst layer can be formed by vapor-depositing a cluster catalyst on the diffusion preventing layer of the copper base material. Although the formation method of a cluster catalyst is not specifically limited, For example, the method etc. which are described in the specification of international publication 2014/192703 are mentioned.

Specifically, it can be formed by a magnetron sputtering method using a DC power source. In such a method, a cluster catalyst is produced by using an apparatus including a vacuumed chamber, a cluster growth cell installed in the chamber, and a sputtering source (magnetron sputtering source) installed in the cluster growth cell. create. The cluster growth cell is surrounded by a liquid nitrogen jacket, and liquid nitrogen (N ₂ ) flows through the liquid nitrogen jacket. In order to generate plasma, argon gas (Ar) is supplied to the sputtering source, and helium gas (He) is supplied into the cluster growth cell. Pulse power is supplied from a pulse power source for the sputtering source, and sputtered particles such as neutral atoms and ions derived from the target are released from the target into the helium gas. Metal atoms and metal ions generated from these sputtering sources are cooled and agglomerated with the aforementioned helium gas to produce a cluster catalyst.

Such a catalyst according to the present invention is particularly suitable as an electrode catalyst. That is, the electrode catalyst according to the present embodiment is a catalyst layer made of a copper-based substrate according to the present embodiment and a catalyst material including a metal cluster formed on the diffusion-preventing layer of the copper-based substrate. It is preferable to have. Such an electrode catalyst can be suitably used as a cathode electrode of a carbon dioxide reduction apparatus described later. In particular, when used as a cathode electrode, the reaction overvoltage in the cathode reduction can be reduced, so that the required external bias voltage (external power) is reduced. That is, in cathodic reduction, the current efficiency of the reaction is increased, and the yield and productivity are improved.

The electrolysis apparatus according to the present embodiment preferably uses the copper base material according to the present embodiment or the electrode catalyst according to the present embodiment. The method for forming the device is not particularly limited, and can be performed by a known method. Examples of the electrolysis device include a carbon dioxide reduction device and a water electrolysis device.

Hereinafter, an example in which the electrode catalyst using the copper base material according to the present embodiment is used as a cathode electrode for electrochemical reduction (electrolytic reduction, cathode reduction) of carbon dioxide will be described.

FIG. 4 is a block diagram showing the configuration of the electrolysis apparatus 3 that performs electrochemical reduction of carbon dioxide. The electrolyzer 3 mainly includes a power supply 31, an electrolysis cell 33, a gas recovery device 35, an electrolyte solution circulation device 37, a carbon dioxide supply unit 39, and the like.

The electrolysis cell 33 is a part that reduces the target substance, and is also a part that includes the cathode electrode according to the present embodiment, and includes carbon dioxide (in the solution, in addition to dissolved carbon dioxide, hydrogen carbonate ions are included. Hereinafter, it is a site that simply reduces carbon dioxide. Electric power is supplied from the power source 31 to the electrolysis cell 33.

The electrolytic solution circulation device 37 is a part that circulates the cathode side electrolytic solution with respect to the cathode electrode of the electrolytic cell 33. The electrolytic solution circulation device 37 is, for example, a tank and a pump. Carbon dioxide or the like is supplied from the carbon dioxide supply unit 39 so as to have a predetermined carbon dioxide concentration and is dissolved in the electrolytic solution. It is possible to circulate the electrolyte.

The gas recovery device 35 is a part that recovers the gas generated by reduction by the electrolytic cell 33. The gas recovery device 35 can collect gas such as hydrocarbons generated at the cathode electrode of the electrolytic cell 33. In the gas recovery device 35, the gas may be separable for each gas type.

The electrolyzer 3 functions as follows. As described above, an electrolytic potential from the power source 31 is applied to the electrolytic cell 33. The electrolytic solution is supplied to the cathode electrode of the electrolytic cell 33 by the electrolytic solution circulation device 37 (arrow A in the figure). At the cathode electrode of the electrolytic cell 33, carbon dioxide or the like in the supplied electrolytic solution is reduced. When carbon dioxide and the like are reduced, hydrocarbons such as ethane and ethylene are mainly produced.

The hydrocarbon gas generated at the cathode electrode is recovered by the gas recovery device 35 (arrow B in the figure). The gas recovery device 35 can separate and store the gas as necessary.

As the carbon dioxide is reduced and consumed at the cathode electrode, the concentration of carbon dioxide and the like in the electrolyte decreases. Carbon dioxide or the like that has been reduced by the reduction reaction is always replenished, and its concentration is always kept within a predetermined range. Specifically, a part of the electrolytic solution is collected by the electrolytic solution circulation device 37 (arrow C in the figure), and an electrolytic solution having a predetermined concentration is always supplied (arrow A in the figure). As described above, in the electrolytic cell 33, hydrocarbons can always be generated under certain conditions.

Next, the electrolytic cell 33 will be described. FIG. 5 is a diagram showing the configuration of the electrolysis cell 33. The electrolysis cell 33 mainly includes a tank 316a which is a cathode tank, a metal mesh 317, a cathode electrode 319, a cation exchange membrane 321, an anode electrode 320, a tank 316b which is an anode tank, and the like.

Electrolytes

315a and 315b are held in the

tanks

316a and 316b, respectively. In the upper part of the tank 316a on the cathode electrode side, a hole for recovering the generated gas is formed and connected to a gas recovery device (not shown). That is, the gas generated at the cathode electrode is recovered from the hole. Moreover, piping etc. are connected to the tank 316a, and it connects with the electrolyte solution circulation apparatus 37 which abbreviate | omitted illustration. That is, the electrolytic solution 315a in the tank 316a can always be circulated by the electrolytic solution circulating device 37. If necessary, the electrolytic solution on the tank 315b side may be circulated in the same manner.

The electrolyte 315a that is a cathode electrolyte is preferably an electrolyte that can dissolve a large amount of carbon dioxide and the like. For example, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, carbonic acid An alkaline solution such as potassium hydrogen, monomethanolamine, methylamine, other liquid amines, or a mixture of these liquid amines and an aqueous electrolyte solution may be used. In addition, acetonitrile, benzonitrile, methylene chloride, tetrahydrofuran, propylene carbonate, dimethylformamide, dimethyl sulfoxide, methanol, ethanol, and the like can be used. In the case of water electrolysis for the purpose of generating hydrogen, an appropriate aqueous solution or pure water may be used.

Further, as the electrolytic solution 315b which is an anode electrolytic solution, the above-described cathode electrolytic solution can be used, or an appropriate pure water or aqueous solution can be used.

The metal mesh 317 is a member that is connected to the negative electrode side of the power supply 31 together with the reference electrode 318 and energizes the cathode electrode 319. The metal mesh 317 is, for example, a copper mesh or a stainless steel mesh, and a silver / silver chloride electrode can be used as the reference electrode 318.

As the cation exchange membrane 321, for example, a known Nafion system can be used. Hydrogen ions generated together with oxygen in the anode reaction can be moved to the cathode side.

The anode electrode 320 is connected to the positive electrode of the power source 31. As the anode electrode 320, an electrode having a small oxygen generation overvoltage, for example, an electrode in which a base material such as titanium or stainless steel is coated with iridium oxide, platinum, rhodium, or the like, an oxide electrode, a stainless electrode, a lead electrode, or the like is used. be able to.

In addition, the anode electrode 320 can also be comprised with a photocatalyst or a semiconductor electrode catalyst. That is, an electromotive force can be generated by irradiating light. By doing so, an electromotive force is generated by irradiating the anode electrode with light such as sunlight, and this electromotive force can be used as an electrolysis potential in the electrolysis cell 33.

At the cathode electrode 319, carbon dioxide or the like in the electrolyte is reduced. Carbon dioxide is dissolved in water, exists in the electrolyte in the form of dissolved carbon dioxide and hydrogen carbonate ions, and is supplied to the cathode electrode. Usually, in the case of a cathode electrode made of a material other than copper, a large amount of hydrogen and carbon monoxide tends to be generated, and almost no hydrocarbon is generated. On the other hand, in the case of a cathode electrode made of a copper-based material, hydrocarbons can be generated relatively efficiently.

The cathode electrode 319 according to the present embodiment is composed of the electrode catalyst according to the present embodiment. That is, the cathode electrode 319 is formed by forming a catalyst layer on the copper base material according to the present embodiment. By using such a cathode electrode, carbon dioxide can be efficiently decomposed and reduced, and hydrocarbons useful as energy can be generated with high energy efficiency.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and includes all aspects included in the concept and claims of the present embodiment. Various modifications can be made within the range described above.

Next, in order to further clarify the effects of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

Example 1
First, a TPC copper plate (10 mm × 10 mm × 0.1 mm, manufactured by Furukawa Electric Co., Ltd.) was prepared as a base. Next, as a pretreatment, the prepared substrate is degreased by cathode using a cleaner 160 (Meltex Co., Ltd.) aqueous solution, washed with water, and then acidified using a dilute sulfuric acid aqueous solution (sulfuric acid concentration 10 mass%). Wash neutralization and further water washing.
Next, a 2% by mass aqueous solution of benzotriazole (manufactured by Johoku Chemical Industry Co., Ltd.) (hereinafter simply referred to as “2% by mass BTA solution”) was prepared, and the substrate after the above pretreatment was added to the 2% by mass BTA solution. Immersion treatment was carried out under conditions of 80 ° C. for 2 minutes and then dried at 80 ° C. to prepare a copper base material having a diffusion prevention layer on the surface of the substrate.
Thereafter, copper nanocluster ions are generated by magnetron sputtering using Cu pellets as a raw material according to the method described in the specification of International Publication No. 2014/192703 on the diffusion-preventing layer of the obtained copper-based substrate. An electrode catalyst was obtained.

(Example 2)
In Example 2, instead of the 2% by mass BTA solution, a 0.5% by mass aqueous solution of benzotriazole (manufactured by Johoku Chemical Co., Ltd.) (hereinafter simply referred to as “0.5% by mass BTA solution”) was used. Except for the above, a copper-based substrate and an electrode catalyst using the same were prepared in the same manner as in Example 1.

(Example 3)
In Example 3, except that the immersion treatment using the 0.5 mass% BTA solution was repeated a plurality of times until the reciprocal of the electric double layer capacity shown in Table 1 was obtained with 80 ° C. drying in between. A copper base material and an electrode catalyst using the same were prepared in the same manner as in Example 2.

(Examples 4 to 6)
In Examples 4 to 6, except that the immersion treatment using the 2% by mass BTA solution was repeated a plurality of times until the reciprocal number of each electric double layer capacity shown in Table 1 was obtained with 80 ° C. drying in between. A copper-based substrate and an electrode catalyst using the same were prepared in the same manner as in Example 1.

(Example 7)
In Example 7, instead of the 2% by mass BTA solution, a 2.5% by mass aqueous solution of tolyltriazole (manufactured by Johoku Chemical Co., Ltd.) (hereinafter simply referred to as “2.5% by mass TTA solution”) was used. The copper base material and this were used in the same manner as in Example 1 except that the conditions for the immersion treatment using the 2.5 mass% TTA solution were 60 ° C. for 2 minutes and the subsequent drying conditions were 60 ° C. The electrode catalyst was prepared.

(Example 8)
In Example 8, a copper base material was prepared in the same manner as in Example 7 except that a 2.5% by mass aqueous solution of imidazole (manufactured by Johoku Chemical Co., Ltd.) was used instead of the 2.5% by mass TTA solution. And the electrode catalyst using this was produced.

Example 9
In Example 9, instead of the 2.5% by mass TTA solution, an aqueous solution containing 1% by mass of benzotriazole (manufactured by Johoku Chemical Industry Co., Ltd.) and 1.5% by mass of triazole (manufactured by Johoku Chemical Industry Co., Ltd.) was used. Except for the above, a copper-based substrate and an electrode catalyst using the same were prepared in the same manner as in Example 7.

(Comparative Example 1)
In Comparative Example 1, an electrode catalyst was obtained in the same manner as in Example 1 except that the diffusion prevention layer was not formed and copper clusters were directly deposited on the surface of the pretreated substrate.

(Comparative Example 2)
In Comparative Example 2, instead of the 2% by mass BTA solution, a 5% by mass aqueous solution of silica fine powder, which is an inorganic material, was prepared, and the substrate after the above pretreatment was added to this silica solution at 30 ° C. for 1 minute. A copper base material and an electrode catalyst using the same were prepared in the same manner as in Example 1, except that the diffusion prevention layer was formed on the surface of the substrate by dipping the substrate at 80 ° C.

(Example 10)
In Example 10, a copper base material was produced by the same method as in Example 1, and the diffusion preventive layer of the obtained copper base material was subjected to the method described in the specification of International Publication No. 2014/192703. Pd nanocluster ions were generated by magnetron sputtering using palladium (Pd) pellets as a raw material to obtain a Pd cluster electrode catalyst.

[Evaluation]
Using the copper base materials and electrode catalysts according to the above Examples and Comparative Examples, the following characteristic evaluation was performed. The evaluation conditions for each characteristic are as follows. The results are shown in Tables 1 and 2.

[1] Reciprocal value of electric double layer capacity For the copper base materials of Examples 1 to 10 and Comparative Example 2, the surface before and after the formation of the diffusion prevention layer (before formation of the diffusion prevention layer: the surface of the substrate after the pretreatment, After the formation of the diffusion prevention layer: the electric double layer capacity of the prepared copper-based substrate was measured, and the reciprocal (1 / C) was calculated. As a measuring device, a direct-reading type electric double layer capacitance measuring device (impedance analyzer C meter, manufactured by Hioki Electric Co., Ltd.) is used, and an electrolytic solution is a 0.1N potassium nitrate aqueous solution, and the step current is 50 μA / cm ² . Then, two points were measured for each sample (N = 2), and the average value was obtained. In Comparative Example 2, the electric double layer capacity could not be detected due to the measurement limit.

[2] Carbon dioxide reduction test Carbon dioxide reduction tests were conducted using the electrode catalysts of Examples 1 to 10 and Comparative Examples 1 and 2 as the cathode electrode of a carbon dioxide cathode reduction apparatus. The outline of the cathode reduction device for carbon dioxide is as described above (FIG. 5). The electrolyte used was a 50 mM aqueous solution of potassium hydrogen carbonate, and 30 mL each was used for each

tank

316a, 316b. As the anode electrode 320, a platinum electrode (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which a titanium base material was coated with platinum was used. The electrolysis was performed for 60 minutes under the conditions of a current of 2 mA and a voltage of 2.8V. During electrolysis, carbon dioxide gas was bubbled from the supply pipe at 10 mL / min (in the direction of arrow A in the figure). The gas generated from the cathode was collected by the analysis tube 323 (in the direction of arrow B in the figure) and analyzed by gas chromatography. SUPELCO CARBOXEN 1010PLOT 30m × 032mlD was used as the column, and FID (manufactured by Sigma-Aldrich) was used as the detector.

As the reaction at the cathode, attention was paid to the generation of methane, ethylene, and ethane as shown below.
CO ₂ + 8H ⁺ + 8e ⁻ → CH ₄ + 2H ₂ O
CO ₂ + 12H ⁺ + 12e ⁻ → C ₂ H ₄ + 4H ₂ O
CO ₂ + 14H ⁺ + 14e ⁻ → C ₂ H ₆ + 4H ₂ O
The results are shown in Table 3. In this example, methane gas concentrations of 40 ppm or higher, ethylene gas concentrations of 30 ppm or higher, and ethane gas concentrations of 10 ppm or higher were evaluated as acceptable levels.

[3] Water electrolysis test The electrolysis test of water was performed by changing the electrolyte solution to ion-exchanged water using the apparatus used in the carbon dioxide reduction test. In addition, this test was done about the case where Example 1, 2, and 6 are each used as a cathode electrode. The electrolysis conditions were a current of 2 mA, a voltage of 2.8 V, and 60 minutes. The results are shown in Table 2.

As shown in Table 1, since the copper base materials according to Examples 1 to 10 according to the above embodiment have a diffusion prevention layer made of an organic material directly formed on a base made of copper, When this was used as the base material of the catalyst electrode, it was confirmed that an electrode catalyst exhibiting good catalytic performance was obtained for the cathode reduction of carbon dioxide. Furthermore, as shown in Table 2, the catalyst electrode using the copper base material of the present invention (Examples 1, 2 and 6) is a good catalyst having a hydrogen gas concentration of 600 ppm or more even in the electrolysis of water. It was confirmed that the characteristics were developed.

On the other hand, since the copper base materials according to Comparative Examples 1 and 2 do not have a diffusion prevention layer made of an organic material on a base made of copper, an electrode catalyst using the same is an embodiment of the present invention. Compared with the electrode catalysts according to Examples 1 to 10, it was confirmed that the catalytic activity was inferior in the cathode reduction of carbon dioxide. This is because the copper base material according to Comparative Examples 1 and 2 does not have an organic material diffusion prevention layer, so the copper constituting the base and the Cu cluster are fused, and the activity as a cluster catalyst is reduced. It is guessed that it was because

DESCRIPTION OF SYMBOLS 1 ......... Copper base material 11 ......... Base 12 ......... Oxide layer 121 ......... Copper oxide layer 122 ......... Copper oxide layer 13 ......... Diffusion protective layer 3 ………… Electrolysis device 31 ………… Power supply 33 ………… Electrolysis cell (CO ₂ cathode reduction test device)
35 ………… Gas recovery device 37 ………… Electrolyte circulation device 39 ………… Carbon

dioxide supply unit

315a, 315b ………

Electrolyte

316a, 316b ……… Bath 317 ……… Metal mesh 318 …… ... Reference electrode (silver / silver chloride)
319 ......... Cathode electrode 320 ......... Anode electrode 321 ......... Cation exchange membrane 323 ......... Analysis tube 325 ......... Supply tube 327 ......... Seal member

Claims

An electrode base material comprising: a base made of copper or a copper-based alloy; and a diffusion prevention layer containing an organic material formed directly or through an oxide layer on the surface of the base.
The electrode base material according to claim 1, which is a copper base material used as a base material constituting a catalyst for hydrogen generation by electrolysis of water or a catalyst for cathodic reduction of carbon dioxide to convert it to a carbon-containing substance.
The electrode substrate according to claim 1 or 2, wherein the organic material is an azole compound.
The electrode substrate according to any one of claims 1 to 3, wherein the reciprocal value of the electric double layer capacity is 0.3 to 5 cm 2 / µF.
An electrode catalyst comprising: the electrode base material according to any one of claims 1 to 4; and a catalyst layer containing a catalyst material including a metal cluster formed in the diffusion prevention layer of the electrode base material. .
The electrode catalyst according to claim 5, wherein the metal cluster is a cluster made of copper or a copper-based alloy.
An electrolysis apparatus comprising the electrode substrate according to any one of claims 1 to 4 or the electrode catalyst according to claim 5 or 6.
A cathode comprising the copper-based substrate according to any one of claims 1 to 4, a cathode electrolyte, an anode, the anode electrolyte, and an ion provided between the cathode and the anode. An electrolysis apparatus comprising an exchange membrane.