Copper alloy catalyst

Abstract

To provide a copper alloy catalyst which is composed of an easy-to-handle bulk material and which enables production of C2 or higher organic compounds from CO2 with high Faradaic efficiency.SOLUTION: A copper alloy catalyst is composed of a bulk material of a copper alloy which contains one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, and Sn, and has a Cu content of 50 atom% or more. When a droplet of ion exchange water is dropped on the surface of the bulk material, the contact angle measured by θ / 2 method is 95° or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a copper alloy catalyst used for producing ethanol by electroreduction of CO2.

Background Art

[0002] At present when global warming is accelerating, reduction of GHGs such as CO2 gas in the atmosphere is a common global issue. In recent years, the development of CCU (Carbon dioxide Capture, Utilization) technology that uses carbon dioxide in the atmosphere as a raw material to produce useful chemical products has been accelerating. Carbon dioxide is in the highest oxidation state with an oxidation number of +4 for carbon and is a very stable compound with a standard Gibbs free energy of formation of about 400 kJ / mol. In order to convert carbon dioxide into useful chemical products, it is necessary to reduce carbon with a large amount of energy. Development of technologies capable of efficiently reducing carbon dioxide is required.

[0003] In recent years, co-electrolysis using an electrolytic cell composed of a polymeric ion exchange membrane has attracted attention (see, for example, Patent Documents 1 and 2). Co-electrolysis is a technique in which electrolysis by an oxidation reaction is performed at the anode and electrolysis by a reduction reaction is performed at the cathode simultaneously in an electrochemical cell. For example, by using water at the anode and an aqueous solution of KHCO3 or CO2 gas at the cathode as raw materials, CO2 can be reduced using protons generated from the electrolysis of H2O. Here, when Cu is used as a catalyst, organic compounds having two or more carbon atoms (for example, ethanol) can be obtained from CO2 with high Faraday efficiency.

[0004] In addition, in a copper catalyst, since the production efficiency of organic compounds having two or more carbon atoms is low in a bulk material, it has conventionally been provided as a powder or a sputtered thin film. In addition, Non-Patent Document 1 reports that in a copper catalyst composed of a sputtered thin film, by forming a polymer film on the surface to enhance the water repellency, it is possible to produce organic compounds with two or more carbon atoms from CO2 with a higher Faraday efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, in a copper catalyst, it is known that the catalytic properties are improved by adding a specific alloy element. However, in conventional powders and sputtered thin films, the alloy elements cannot be uniformly mixed, and the effect of improving the catalytic properties by alloying cannot be fully obtained. In addition, copper catalysts composed of powders or sputtered thin films have problems such as poor handleability, high cost, and poor energy efficiency during production. Furthermore, in Non-Patent Document 1, although the water repellency is enhanced by forming a polymer film on the surface of the sputtered thin film, the process cost is high and there are problems with stability.

[0008] The present invention has been made against the background of the above circumstances, and an object thereof is to provide a copper alloy catalyst made of a bulk material that is easy to handle and can generate organic compounds having two or more carbon atoms from CO2 with high Faradaic efficiency.

Means for Solving the Problems

[0009] In order to solve such problems and achieve the above object, the copper alloy catalyst of Aspect 1 of the present invention is composed of a bulk material of a copper alloy containing one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, and Sn, and having a Cu content of 50 atomic% or more. When water droplets of ion-exchanged water are dropped onto the surface of the bulk material, the contact angle measured by the θ / 2 method is 95° or more.

[0010] According to the copper alloy catalyst of Aspect 1 of the present invention, since it is composed of a bulk material of a copper alloy containing one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, and Sn and having a Cu content of 50 atomic% or more, it has excellent handleability and can sufficiently exhibit the effect of improving the catalyst characteristics by alloying. And when water droplets of ion-exchanged water are dropped onto the surface of the bulk material, the contact angle measured by the θ / 2 method is 95° or more, so it has high water repellency and can generate organic compounds having two or more carbon atoms from CO2 with high Faradaic efficiency.

[0011] The copper alloy catalyst of Aspect 2 of the present invention is characterized in that, in the copper alloy catalyst of Aspect 1 of the present invention, the spreading area ratio Sdr of the surface of the bulk material is 1% or more. According to the copper alloy catalyst of Aspect 2 of the present invention, the spreading area ratio Sdr of the surface of the bulk material is 1% or more, and fine irregularities are formed on the surface layer, so that the reactivity can be improved, the water repellency is increased, and it is possible to generate organic compounds having two or more carbon atoms from CO2 with higher Faradaic efficiency.

[0012] The copper alloy catalyst of Aspect 3 of the present invention is the copper alloy catalyst of Aspect 1 or Aspect 2 of the present invention, in which, by the EBSD method, a measurement area of 5000 μm 2 or more is measured at a measurement interval of 0.1 μm steps, and the average value of KAM excluding measurement points where the CI value analyzed by the data analysis software OIM is 0.1 or less is 0.30° or more. According to the copper alloy catalyst of Aspect 3 of the present invention, since the average value of the aforementioned KAM is 0.30° or more, strain energy is accumulated, and it becomes possible to improve reactivity.

[0013] The copper alloy catalyst of Aspect 4 of the present invention contains 2 atomic% or more of one or more alloy elements selected from Zn, Al, Ca, and Mg in any one of the copper alloy catalysts of Aspects 1 to 3 of the present invention, and the surface layer of the bulk material is a surface treatment layer treated with an acid or a basic solution. According to the copper alloy catalyst of Aspect 4 of the present invention, since it contains 2 atomic% or more of one or more alloy elements selected from Zn, Al, Ca, and Mg, and the surface layer of the bulk material is a surface treatment layer treated with an acid or a basic solution, Zn, Al, Ca, and Mg, which are metals less noble than copper, are preferentially dissolved, a fine structure is formed on the surface layer, the water repellency is increased, and it becomes possible to produce organic compounds of C2 or higher from CO2 with a high Faradaic efficiency.

[0014] The copper alloy catalyst of Aspect 5 of the present invention is characterized in that, in any one of the copper alloy catalysts of Aspects 1 to 4 of the present invention, the Faradaic efficiency of ethanol production is 0.8% or more. According to the copper alloy catalyst of Aspect 5 of the present invention, the Faradaic efficiency of ethanol production is as high as 0.8% or more, and it becomes possible to efficiently produce ethanol.

[0015] The electrochemical reaction device of Aspect 6 of the present invention is characterized by using any one of the copper alloy catalysts of Aspects 1 to 5 of the present invention. According to the electrochemical reaction device of Aspect 6 of the present invention, since any one of the copper alloy catalysts of Aspects 1 to 5 of the present invention is used, it is possible to produce organic compounds having two or more carbon atoms from CO2 with high Faraday efficiency.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a copper alloy catalyst made of a bulk material that is easy to handle and can produce organic compounds having two or more carbon atoms from CO2 with high Faraday efficiency.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0018] Hereinafter, a copper alloy catalyst and an electrochemical reaction device, which are embodiments of the present invention, will be described with reference to the attached drawings.

[0019] The copper alloy catalyst 10 of the present embodiment is used, for example, in an electrochemical reaction device that electrochemically reduces CO2 gas to produce organic compounds having two or more carbon atoms.

[0020] As shown in FIG. 1, the copper alloy catalyst 10 of the present embodiment is a bulk material having a substantially rectangular shape. Note that FIG. 1(a) is a mesh material obtained by processing a copper alloy wire, and FIG. 1(b) is a perforated metal in which a plurality of holes are formed in a copper alloy plate. The copper alloy catalyst 10 according to this embodiment is composed of a copper alloy containing one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, and Sn, and having a Cu content of 50 atomic% or more.

[0021] Also, in the copper alloy catalyst 10 according to this embodiment, it is preferable that the developed area ratio Sdr of the surface of the bulk material is 1% or more. Furthermore, in the copper alloy catalyst 10 according to this embodiment, when measuring an area of 5000 μm or more at a measurement interval of 0.1 μm step by the EBSD method and excluding the measurement points where the CI value analyzed by the data analysis software OIM is 0.1 or less, it is preferable that the average value of KAM is 0.30° or more. 2 Moreover, in the copper alloy catalyst 10 according to this embodiment, it preferably contains 2 atomic% or more of one or more alloy elements selected from Zn, Al, Ca, and Mg, and the surface layer of the bulk material is a surface treatment layer treated with an acid or a basic solution.

[0022] In addition, in the copper alloy catalyst 10 according to this embodiment, it is preferable that the ethanol production Faraday efficiency is 0.8% or more.

[0023] Hereinafter, in the copper alloy catalyst 10 according to this embodiment, the reasons for defining the composition, the contact angle of water, the average value of KAM, the surface treatment layer, the ethanol production Faraday efficiency, the formic acid production Faraday efficiency, and the ratio of the formic acid production Faraday efficiency to the ethanol production Faraday efficiency as described above will be explained.

[0024] (Alloy elements: one or more selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, Sn) In the copper alloy catalyst 10 made of a copper alloy containing the above alloy elements, the CO2 decomposition reaction and the ethanol production reaction occurring on its surface are promoted, and the production efficiency of ethanol is improved. Here, in the present embodiment, since the copper alloy catalyst 10 is a bulk material, the alloy elements are uniformly dispersed, and the catalyst characteristics are stabilized. In addition, the total content of the above alloy elements is preferably 0.03 atomic% or more, and more preferably 1.00 atomic% or more.

[0025] (Content of Cu: 50 atomic% or more) As described above, the production efficiency of ethanol is improved by containing alloy elements. However, if the content of Cu is less than 50 atomic%, it may not be possible to obtain the catalyst characteristics of the Cu main body. For this reason, in the present embodiment, the content of Cu is defined to be 50 atomic% or more. In addition, the content of Cu is preferably 52 atomic% or more, and more preferably 55 atomic% or more.

[0026] (Contact angle of water: 95° or more) When a water droplet of ion-exchanged water is dropped on the surface of the copper alloy catalyst 10 made of a bulk material, if the contact angle measured by the θ / 2 method is 95° or more, it has sufficient water repellency, a gas-liquid reaction site is secured, the reaction can be promoted, and the production efficiency of ethanol is improved. In addition, the contact angle of water is preferably 97° or more, and more preferably 100° or more.

[0027] (Surface development area ratio Sdr: 1% or more) The development area ratio Sdr is a value indicating the increment of the developed area of the measurement region with respect to the area of the measurement region. The Sdr of a completely flat surface is 0, and the larger the Sdr, the larger the surface area of the material. When the Sdr is 1% or more, the surface area where the CO2 decomposition reaction occurs increases, and the reactivity can be improved. Furthermore, the fact that the developed area ratio Sdr is as large as 1% or more also means that a fine shape is formed on the surface layer, and the water repellency can be improved. Therefore, the production efficiency of organic compounds with two or more carbon atoms, which have a high added value, can be improved. In addition, the developed area ratio Sdr of the surface of the copper alloy catalyst 10 made of the bulk material is more preferably 1.5% or more, and even more preferably 2.0% or more.

[0028] (Average value of KAM: 0.30° or more) The KAM (Kernel Average Misorientation) value measured by EBSD is a value calculated by averaging the orientation differences between one pixel and the pixels surrounding it. Since the shape of the pixel is a regular hexagon, when the proximity order is 1, the average value of the orientation differences with the six adjacent pixels is calculated as the KAM value. By using this KAM value, local orientation differences, that is, the distribution of strain, can be visualized. By setting the average value of KAM to 0.30° or more, strain energy is accumulated on the material surface, and the reactivity can be improved. In addition, as will be described later, when the surface layer of the bulk material is surface-treated with a basic solution or an acidic solution, fine structures are likely to be formed, and the water repellency is improved. In addition, the above-mentioned average value of KAM is more preferably 0.35° or more, and even more preferably 0.40° or more.

[0029] (Surface treatment layer) In the present embodiment, when the bulk material contains 2 atomic% or more of one or more alloy elements selected from Zn, Al, Ca, and Mg, and the surface layer of the bulk material is a surface treatment layer treated with an acid or a basic solution, one or more alloy elements selected from Zn, Al, Ca, and Mg, which are less noble than copper, are preferentially dissolved by the surface treatment, fine structures are formed on the surface layer of the bulk material, and the water repellency is improved.

[0030] (Faradaic efficiency for ethanol production) In this embodiment, if the Faradaic efficiency for ethanol production is 0.8% or more, application to a catalyst for converting carbon dioxide into a useful chemical product can be expected. Note that the Faradaic efficiency for ethanol production is more preferably 1.0% or more, and even more preferably 1.2% or more.

[0031] Next, an example of a method for manufacturing a copper alloy catalyst according to this embodiment configured as described above will be described with reference to the flowchart shown in FIG. 2.

[0032] (Melting and casting process S01) First, the aforementioned elements are added to the molten copper obtained by melting an oxygen-free copper raw material to adjust the composition, and a copper alloy molten metal is produced. Note that for the addition of various elements, elemental substances, master alloys, etc. can be used. Further, a raw material containing the aforementioned elements may be melted together with the copper raw material. Here, each element is preferably so-called 3N copper having a purity of 99.9 mass% or more, or so-called 4N copper having a purity of 99.99 mass% or more. In the melting process, for reducing the hydrogen concentration, atmospheric melting is performed in an inert gas atmosphere (for example, Ar gas) with a low vapor pressure of H2O, and the holding time during melting is preferably minimized. Then, the component-adjusted copper alloy molten metal is poured into a mold to produce an ingot. Note that when considering mass production, it is preferable to use a continuous casting method or a semi-continuous casting method.

[0033] (Hot working process S02) By performing hot working on the obtained ingot, strain is introduced and the shape is deformed into a predetermined size. By introducing strain through hot working, high strain can be applied in a state where the crystals are coarse, and the homogeneity of the material can be improved. Here, since it is necessary to break the as-cast structure, a certain reduction ratio is required, preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. The plastic working method is not particularly limited, but when the final shape is in the form of foil or strip, it is preferable to adopt rolling. In the case of wire, it is preferable to adopt extrusion or groove rolling, and in the case of bulk shape, it is preferable to adopt forging or pressing.

[0034] (Rough machining process S03) Next, rough machining is performed on the obtained hot-worked material to introduce strain and deform the shape into a predetermined size. Here, the processing method is not particularly limited, but when the final form is foil or strip, rolling is adopted, and when it is bar or wire, extrusion or groove rolling is adopted. The temperature during processing is not particularly limited, but -200 to 400 °C, which is cold or warm, is preferable. The total reduction ratio is not particularly limited either, but preferably 30% or more for the purpose of improving the efficiency of rough machining.

[0035] (Heat treatment process S04) For homogenization and / or solution treatment, heat treatment is performed in an Ar gas atmosphere and water quenching is carried out. Here, the heat treatment method is not particularly limited, but it is preferably carried out in a non-oxidizing or reducing atmosphere. The heat treatment temperature is not particularly limited, but when the temperature is low, a large amount of precipitates may be generated, making the processing process difficult. In addition to the possibility that sufficient recovery and recrystallization may not occur, and the diffusion may be insufficient, resulting in concentration spots of added elements, the heat treatment temperature is preferably 400 °C or more, and since the melting point of the material may be exceeded if the temperature is too high, the heat treatment temperature needs to be 1000 °C or less. The cooling method requires a method such as water quenching with a cooling rate of 200 °C / min. If the cooling rate is slow, precipitates may appear during cooling. Also, for further improvement of rough machining efficiency and homogenization of the structure, hot working may be carried out after heat treatment. The processing method is not particularly limited, but when the final form is foil or strip, rolling is adopted, and when it is rod or wire, extrusion or groove rolling is adopted. Note that the rough machining step S03 and the heat treatment step S04 may be repeatedly carried out.

[0036] (Cold working step S05) Next, cold working with a working rate of 50% or more is performed on the copper material after the heat treatment step S04 to accumulate high energy on the surface of the copper material. In order to prevent the release of energy due to dynamic recrystallization and recovery, working is carried out at -200 to 200 °C. The processing method is not particularly limited, but when the final form is foil or strip, rolling is adopted, and when it is wire, wire drawing or the like is adopted. The final thickness and wire diameter are not particularly limited, but for example, thicknesses and wire diameters such as 1 mm, 0.5 mm, 0.1 mm, 0.05 mm, 0.01 mm, etc. are applicable. Also, heat treatment may be carried out for tempering after cold working.

[0037] (Shape - giving step S06) Processing is carried out to form a flow path for flowing the raw material gas or solution required for the catalytic reaction. The processing method is not limited, but for foil or strip materials, punching processing, expanded metal processing, etc. are adopted. For wire materials, a mesh shape or the like can be adopted.

[0038] (Surface treatment step S07) Next, surface treatment is carried out by immersion in an acid or basic solution. When it contains 2 atomic% or more of one or more alloying elements selected from Zn, Al, Ca, Mg, which are metals nobler than Cu, the metal nobler than Cu is preferentially dissolved, a fine structure is formed on the surface, and the contact angle of the surface becomes larger. The acid solution is not particularly limited, but nitric acid, sulfuric acid, hydrochloric acid, etc. can be used. The basic solution is not particularly limited, but sodium hydroxide, ammonia solution, etc. can be used.

[0039] Through each of the above steps, the copper alloy catalyst according to the present embodiment will be produced.

[0040] Next, FIG. 3 shows a schematic diagram of an electrochemical reaction device 30 using the copper alloy catalyst 10 according to the present embodiment. Note that the electrochemical reaction device 30 of the present embodiment is a solid polymer type co-electrolysis device.

[0041] As shown in FIG. 3, the electrochemical reaction device 30 of the present embodiment includes an electrolytic cell 31 having an anode electrode 32 and a cathode electrode 33 arranged opposite to each other, an ion permeable membrane 34 arranged between the anode electrode 32 and the cathode electrode 33, and catalyst layers 35 and 36. Here, for the anode electrode 32, the cathode electrode 33, the ion permeable membrane 34, and the catalyst layer 35, those used in a conventional general solid polymer type water electrolysis device can be applied.

[0042] And the catalyst layer 36 disposed on the cathode electrode 33 side is composed of the copper alloy catalyst 10 according to the present embodiment. In the above-described electrochemical reaction device 30 (electrolytic cell 31), as shown in FIG. 3, water (H2O) is supplied to the anode electrode 32 side, and CO2 is supplied to the cathode electrode 33 side. Then, the anode electrode 32 and the cathode electrode 33 are energized. Then, water is electrolyzed at the anode electrode 32, the generated oxygen (O2) is discharged from the anode electrode 32, and hydrogen (H2) moves to the cathode electrode 33. And at the cathode electrode 33, CO2 is reduced, and organic compounds having two or more carbon atoms such as ethanol are generated. Note that the generated organic compounds having two or more carbon atoms such as ethanol are discharged to the outside of the electrolytic cell 31 through the pores 13 of the member main body 11.

[0043] According to the copper alloy catalyst 10 of the present embodiment configured as described above, it contains one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, Sn, and is composed of a bulk material of a copper alloy with a Cu content of 50 atomic% or more. Therefore, it has excellent handleability and can sufficiently exhibit the effect of improving the catalytic properties by alloying. And when water droplets of ion-exchanged water are dropped on the surface of the bulk material, the contact angle measured by the θ / 2 method is 95° or more. Therefore, it has high water repellency and can produce organic compounds of C2 or higher from CO2 with high Faradaic efficiency.

[0044] In the present embodiment, when the developed area ratio Sdr of the surface of the bulk material constituting the copper alloy catalyst 10 is 1% or more, fine irregularities are formed on the surface layer of the bulk material, the reactivity can be improved, the water repellency is increased, and it is possible to produce organic compounds of C2 or higher from CO2 with higher Faradaic efficiency.

[0045] In the present embodiment, by measuring an area of 5000 μm 2 or more at a measurement interval of 0.1 μm step and excluding the measurement points where the CI value analyzed by the data analysis software OIM is 0.1 or less, when the average value of KAM is 0.30° or more, strain energy is accumulated inside the bulk material, the reactivity can be improved, and it is possible to produce organic compounds of C2 or higher from CO2 with higher Faradaic efficiency.

[0046] In the present embodiment, when it contains 2 atomic% or more of one or more alloy elements selected from Zn, Al, Ca, Mg and the surface layer of the bulk material is a surface treatment layer treated with an acid or basic solution, Zn, Al, Ca, Mg, which are base metals more electropositive than copper, are preferentially dissolved, a fine structure is formed on the surface, the water repellency is increased, and it is possible to produce organic compounds of C2 or higher from CO2 with higher Faradaic efficiency.

[0047] In this embodiment, when the Faradaic efficiency of ethanol production is 0.8% or more, it becomes possible to surely and efficiently produce ethanol.

[0048] According to the electrochemical reaction device 30 of this embodiment, since the copper alloy catalyst 10 of this embodiment described above is used as the catalyst layer 36 disposed on the cathode electrode 33 side, it is possible to produce organic compounds of C2 or higher from CO2 with high Faradaic efficiency.

[0049] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention.

Example

[0050] The results of the confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0051] By the zone melting purification method, a raw material made of pure copper with a purity of 99.999 mass% or more and each additive element of 99.9% or more were prepared, loaded into a high-purity graphite crucible, and high-frequency melted in an atmosphere furnace with an Ar gas atmosphere. It was prepared to have the component composition shown in Table 1, poured into a heat insulating material (isowool) mold, and an ingot was produced. The size of the ingot was about 15 mm thick × about 50 mm wide × about 150 to 200 mm long.

[0052] The obtained ingot was heated in an Ar gas atmosphere at the temperature shown in Table 2 for 4 hours and hot-rolled at the rolling ratio shown in Table 2. The final pass temperature was confirmed by measuring the final temperature of the hot rolling with a radiation thermometer. Next, surface grinding was performed to remove the oxide film of the hot rolling, and cutting was performed to a predetermined size. Thereafter, the thickness was adjusted as appropriate to the final thickness and cutting was performed. Each of the cut samples after hot rolling was repeatedly subjected to rough machining and heat treatment under the conditions described in Table 1, and then cold rolling was performed to produce foil materials with a thickness of 0.04 to 0.06 mm and a width of about 50 mm.

[0053] Also, casting was performed in the same manner as described above to produce ingots with a diameter of 15 mm and a length of approximately 150 to 200 mm. This ingot was subjected to hot working, heat treatment, and cold working under the conditions described in Table 2 to produce a copper alloy wire with a wire diameter of 0.09 mm.

[0054] As a shape-giving process, the obtained copper alloy foil was subjected to punching. At this time, the hole diameter was about 0.6 mm and the pitch was 1.5 mm. The obtained copper alloy wire was processed into a mesh with a mesh number of 120 and a mesh opening of 0.12 mm. Then, the obtained punched metal and mesh material were immersed in the acid or basic solution shown in Table 2, and surface treatment was performed under the conditions described in Table 1.

[0055] Regarding the copper alloy catalyst obtained through the above processes, the component composition, contact angle of the surface, spreading area ratio Sdr, average value of KAM, and carbon dioxide reduction characteristics were evaluated by the following procedures. The evaluation results are shown in Table 3.

[0056] (Component composition) A measurement sample was taken from the obtained ingot and measured using a high-frequency induction emission analyzer (ICP).

[0057] (Contact angle) For the copper alloy catalyst (copper alloy foil or mesh material), 2 μL of ion-exchanged water was dropped using a contact angle meter (DMo-702 manufactured by Kyowa Interface Science Co., Ltd.), and the contact angle 1 second later was measured. The θ / 2 method was used for the measurement of the contact angle. The measurement environment was set at a temperature of 23 ± 5°C and a humidity of 65% ± 10%. After surface treatment, the sample was washed with ethanol, dried in the air for 1 day or more, and measured within 30 days. The measurement was performed 5 times or more, and the average value was taken as the contact angle.

[0058] (Spreading area ratio) The spreading area ratio was measured using a laser microscope (OLS5100 manufactured by OLYMPUS). 0.01 mm 2The above area was measured in three or more fields of view, and the developed area ratio Sdr was determined. At this time, the λc filter that defines the boundary between the roughness component and the waviness component was set to 25 μm, and the wavelength components longer than 80 μm were removed to calculate the developed area ratio. The average value of each field of view was defined as the developed area ratio Sdr.

[0059] (Average value of KAM) Samples were cut out from a copper alloy catalyst (copper alloy foil or mesh material). For the foil material, a cross-section perpendicular to the processing direction was prepared, and for the mesh material, a cross-section in the wire processing direction was prepared. After mechanical polishing using waterproof abrasive paper and diamond abrasive grains, finish polishing was performed using a colloidal silica solution. This sample was measured with an EBSD measurement device (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX / TSL (currently AMETEK)) and analysis software (OIM Data Analysis ver. 8.6 manufactured by EDAX / TSL (currently AMETEK)) at an acceleration voltage of the electron beam of 15 kV and a measurement interval of 0.1 μm step over a measurement area of 5000 μm 2 From the KAM values of each pixel, the average value was calculated excluding the measurement points where the CI value was 0.1 or less over the above measurement area.

[0060] (Carbon dioxide reduction test) Examples obtained at the cathode of an electrochemical cell of the 1 cm 2 class equipped with an anion exchange type ion exchange membrane were incorporated. The current density was controlled by a potentiostat (HCP-803 manufactured by BioLogic) to flow between the electrodes at 16 mA / cm 2 A titanium porous body plated with iridium oxide was used as the anode electrode. Pure water as a raw material was flowed through the anode at 10 cc / min using a precision diaphragm pump (Smooth Flow Pump Q series manufactured by Tacmina). Pure CO2 gas was controlled to 10 cc / min at the cathode using a mass flow controller (manufactured by KOFLOC), and further, a 0.1 M aqueous solution of KHCO3 was controlled to 1 cc / min and flowed using a precision diaphragm pump (FLOM; KP21).

[0061] (Faradaic efficiency of ethanol production) The solution after the reaction discharged from the cathode was separated from the gas, and the ethanol concentration contained in the obtained liquid was measured by high-performance liquid chromatography (Extrema manufactured by JASCO). Using the ethanol concentration obtained by high-performance liquid chromatography as C, the Faradaic efficiency FE was calculated from the following formula. FE=n×C×F / (I×t×M) Here, I (A): Constant current passed through the electrode during electrolysis t (s): Electrolysis time C (g / L): Ethanol concentration measured by high-performance liquid chromatography F (As / mol): Faraday constant n: Number of reaction electrons (in the CO2 → ethanol production reaction, 12) M (g / mol): Molecular weight That is.

[0062]

Table 1

[0063]

Table 2

[0064]

Table 3

[0065] In Comparative Example 1, it was composed of pure copper, the contact angle of the surface was as small as 94°, and the Faradaic efficiency of ethanol production was as low as 0.24%. In Comparative Example 2, it was composed of a copper alloy containing Zn and Ni, but the Cu content was less than 50%, the contact angle of the surface was as small as 90°, and the Faradaic efficiency of ethanol production was as low as 0.33%. In Comparative Example 3, it was composed of a copper alloy containing Al and Mg, but the contact angle of the surface was as small as 90°, and the ethanol production Faraday efficiency was as low as 0.35%.

[0066] On the other hand, in Examples 1 to 20 of the present invention, it is composed of a copper alloy containing one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, Sn, and the content of Cu is 50 atomic% or more. The contact angle of the surface is 95° or more, the production efficiency of ethanol is as high as 0.86% or more, and it was possible to efficiently produce ethanol by reducing CO2.

[0067] From the results of the above confirmation experiments, it was confirmed that according to the examples of the present invention, it is possible to provide a copper alloy catalyst made of a bulk material with easy handleability and capable of producing organic compounds having two or more carbon atoms from CO2 with high Faraday efficiency.

Explanation of symbols

[0068] 10 Copper alloy catalyst

Claims

1. The bulk material is a copper alloy containing one or more alloy elements selected from Zn, Al, Ca, Mg, Ni, Si, Mn, In, Fe, Co, Ag, and Sn, and containing 50 atomic % or more of Cu; A copper alloy catalyst characterized in that when a droplet of ion-exchanged water is dropped onto the surface of the bulk material, the contact angle measured by the θ / 2 method is 95° or more.

2. 2. The copper alloy catalyst according to claim 1, wherein the developed surface area ratio Sdr of the bulk material is 1% or more.

3. 5000μm by EBSD method ２ The copper alloy catalyst according to claim 1, characterized in that the average KAM value is 0.30° or more when the above measurement areas are measured at measurement intervals of 0.1 μm and measurement points having a CI value of 0.1 or less analyzed by data analysis software OIM are excluded.

4. The copper alloy catalyst according to claim 1, characterized in that it contains 2 atomic % or more of one or more alloy elements selected from Zn, Al, Ca, and Mg, and the surface layer of the bulk material is a surface treatment layer treated with an acid or basic solution.

5. 2. The copper alloy catalyst according to claim 1, characterized in that the faradaic efficiency of ethanol production is 0.8% or more.

6. An electrochemical reaction device using the copper alloy catalyst according to any one of claims 1 to 5.

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