Device of reducing carbon dioxide and method of reducing carbon dioxide

Abstract

To provide a device of reducing carbon dioxide and a method of reducing carbon dioxide, capable of obtaining only methane from carbon dioxide.SOLUTION: The device 100 of reducing carbon dioxide to generate methane from carbon dioxide being supplied to an electrolytic unit, comprises a first electrode 111 and a second electrode 112, an electrolytic membrane 113 disposed between the first electrode 111 and the second electrode 112, and an electrolysis unit comprising the first electrode 111 disposed on one side of the electrolytic membrane 113 to be supplied with carbon dioxide, and the second electrodes 112 disposed on the other side of the electrolytic membrane 113 to be supplied with one species selected from water, hydrogen and water vapor. The first electrode includes catalytic metal particles consisting of catalytic metal of a mean particle diameter of 1 to 10 nm, and carrier particles consisting of metal oxide supporting the catalytic metal particles, and the electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide reduction device and a carbon dioxide reduction method. [Background technology]

[0002] In recent years, there has been a worldwide demand for the reduction of carbon dioxide emissions, due to the possibility that carbon dioxide emissions resulting from the combustion of fossil fuels into the atmosphere could have a significant impact on ecosystems and the global environment. In response to this, technologies are being developed to fix carbon dioxide or convert it into other substances.

[0003] Furthermore, in completely closed environments such as space stations and rockets, it is not easy to replenish materials, and it is necessary to limit replenishment and emission to the minimum necessary at the elemental level. For this reason, it is necessary to increase the amount of materials that can be recovered by converting the generated carbon dioxide into other substances, and to reduce the amount of materials replenished and emitted as much as possible at the elemental level. It is thought that the above-mentioned technology for fixing carbon dioxide or converting it into other substances can be effectively used even in such environments.

[0004] As a carbon dioxide fixation system, a carbon dioxide reduction fixation system described in Patent Document 1 is known. The system described in Patent Document 1 includes a reaction section having a cathode and an anode arranged with an electrolyte therebetween, and a power supply section that applies a voltage between the anode and the cathode, and both the anode and the cathode include a catalyst material, a material having electrical conductivity, and a solid electrolyte capable of transporting cations. At the anode, electrons are generated by an oxidation reaction, and at the cathode, gaseous carbon dioxide is fixed by a reduction reaction, and cations or anions are transported through the electrolyte so as to compensate for the charge imbalance between the electrodes accompanying the oxidation reaction or the reduction reaction. In addition, the carbon dioxide reduction fixation system described in Patent Document 2 is further configured such that the onset potential of the oxidation reaction of a substance at the anode at the operating temperature is more negative than the onset potential of the reduction reaction of carbon dioxide at the cathode under the same operating conditions.

[0005] In addition, in the technology of reducing carbon dioxide with a catalyst and converting it into other substances such as carbon monoxide and organic acids, catalysts have also been proposed to obtain desired substances more efficiently. For example, in Patent Document 3, formic acid is selectively obtained by using an electrode material having a structure in which simple substances and / or compounds of metal elements of Groups 6 to 16 of the periodic table are supported on a powdered titanium suboxide support. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Patent Publication No. 2012118065 [Patent Document 2] International Patent Publication No. 2012128148 [Patent Document 3] Patent Publication No. 2019-173130 Summary of the Invention [Problem to be solved by the invention]

[0007] In both Patent Documents 1 and 2, carbon monoxide and methanol are produced as hydrocarbon compounds by the reduction of carbon dioxide, and in Patent Document 3, formic acid is produced as a hydrocarbon compound. However, in Patent Documents 1 to 3, it is not possible to selectively obtain only methane. Although methane, carbon monoxide, formic acid, and methanol are all carbon resources, there has been no carbon dioxide reduction system that obtains only methane.

[0008] The present invention has been made in view of the above problems, and provides a carbon dioxide reduction device and a carbon dioxide reduction method that are capable of obtaining only methane from carbon dioxide. [Means for solving the problem]

[0009] The carbon dioxide reduction device of the present invention comprises an electrolysis section having a first electrode and a second electrode, an electrolyte membrane provided between the first electrode and the second electrode, the first electrode being an electrode on one side of the electrolyte membrane and to which carbon dioxide is supplied, and a second electrode being an electrode on the other side of the electrolyte membrane and to which at least one selected from water, hydrogen and water vapor is supplied, carbon dioxide supplying means for supplying carbon dioxide to the first electrode side of the electrolysis section, water supplying means for supplying the at least one selected from water, hydrogen and water vapor to the second electrode side, a humidifying means provided between the carbon dioxide supplying means and the electrolysis section, and a voltage applying means for applying a voltage to the electrolysis section, and the carbon dioxide reduction device produces methane from the carbon dioxide supplied to the electrolysis section, wherein the first electrode comprises catalytic metal particles made of a catalytic metal having an average particle size of 1 to 10 nm and support particles made of a metal oxide supporting the catalytic metal particles, and the electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity. The first electrode includes catalytic metal particles made of a catalytic metal having an average particle size of 1 to 10 nm and support particles made of a metal oxide supporting the catalytic metal particles, and the electrolyte membrane is configured to be a solid polymer membrane having hydrogen ion conductivity, making it possible to obtain only methane from carbon dioxide in a high yield. It is preferable that the catalytic metal is at least one selected from ruthenium, nickel, copper, platinum, and iridium, or an alloy containing at least any of these, and the metal oxide is at least one selected from titanium oxide, silicon dioxide, magnesium oxide, aluminum oxide, zirconium oxide, niobium oxide, zeolite, and calcium phosphate. The first electrode preferably further contains a solid electrolyte. The first electrode preferably further contains a conductive material. The weight ratio of the catalyst particles, the conductive material, and the solid electrolyte is preferably 1-5:1-5:1-5, and more preferably 5-2:5-2:1. The metal oxide is preferably at least one selected from titanium oxide, silicon oxide, aluminum oxide, zeolite, and calcium phosphate. The titanium oxide is preferably of the anatase type or rutile type. The carbon dioxide reduction method of the present invention is a carbon dioxide reduction device that humidifies and supplies carbon dioxide to the first electrode side of an electrolysis unit having an electrolyte membrane, a first electrode on one side of the electrolyte membrane to which carbon dioxide is supplied, and a second electrode on the other side of the electrolyte membrane to which carbon dioxide is supplied, and humidifies and supplies water or water vapor to the second electrode side, and generates methane from the supplied carbon dioxide while applying a voltage to the electrolysis unit, wherein the first electrode includes catalytic metal particles having a diameter of 1 to 10 nm and carrier particles made of metal oxide that support the catalytic metal particles, the electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity, and a voltage higher than -400 mV is applied to the electrolysis unit. The carbon dioxide reduction device includes catalytic metal particles having a diameter of 1 to 10 nm and carrier particles made of metal oxide that support the catalytic metal particles, and the electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity, and by applying a voltage higher than -400 mV to the electrolysis unit, only methane can be obtained from carbon dioxide with a high yield. The temperature during the humidification is preferably maintained at 40 to 90°C. The temperature of the electrolysis section is preferably maintained at 40 to 90°C. It is preferable that a voltage of −400 mV to 100 mV is applied to the electrolysis section. Effect of the Invention

[0010] According to the carbon dioxide reduction device and carbon dioxide reduction method of the present invention, it is possible to obtain only methane from carbon dioxide at a high yield. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a carbon dioxide reduction device according to the present invention. [Diagram 2]Schematic diagram of the electrolysis section of a carbon dioxide reduction device. [Diagram 3] Graph showing the results of mass spectrum analysis in Example 1. [Figure 4] FIG. 2 is a partially enlarged view of a graph showing the results of mass spectrum analysis in Example 1. [Diagram 5] Graph showing current-voltage characteristics in Examples 1 to 9. [Figure 6] 1 is a graph showing characteristics of current vs. amount of methane produced in Examples 1 to 9. [Figure 7] 1 is a graph showing characteristics of voltage versus amount of methane produced in Examples 1 to 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Carbon dioxide reduction device) An embodiment of a carbon dioxide reduction device 1 according to the present invention will be described with reference to the drawings. 1 and 2, the carbon dioxide reduction device 1 according to an embodiment of the present invention includes an electrolysis unit 110, a carbon dioxide supply means 120 for supplying carbon dioxide to the first electrode 111 side of the electrolysis unit 110, a water supply means 130 for supplying water or water vapor to the second electrode 112 side of the electrolysis unit 110, and gas-liquid separation means 140, 150 for separating and recovering products, a carrier gas described below, and the like. The electrolysis unit 110 will be described in detail later.

[0013] The carbon dioxide supplying means 120 is filled with a raw material gas consisting of carbon dioxide such as carbon dioxide gas, and a humidifying means 121 for supplying water to humidify the raw material gas is provided in the path from the carbon dioxide supplying means 120 to the electrolysis unit 110.

[0014] The water supply means 130 is configured to supply water or water vapor to the electrolysis unit 110 by humidifying the carrier gas supplied from the carrier gas supply means 132 with the humidification means 131. The carrier gas may be any gas, such as nitrogen, argon, or helium, as long as it is stable to the reactions and products in the electrolysis unit. Furthermore, the carrier gas may contain hydrogen. In this case, hydrogen can be supplied without electrolysis in the electrolysis unit 110, so that even less energy input is required, and depending on the amount of hydrogen supplied, energy recovery is also possible.

[0015] The gas-liquid separation means 140 is provided on the first electrode 111 side, and has a circulation path 141 that circulates the unreacted gas again to a path (not shown) from the carbon dioxide supply means 120 to the electrolysis section 110, and the circulation path 141 is provided with a circulation pump 142.

[0016] The gas-liquid separation means 150 is provided on the second electrode 112 side, and has a circulation path 151 that circulates the carrier gas and unreacted water vapor back to the path from the water supply means 130 to the electrolysis section 110, and the circulation path 151 is provided with a circulation pump 152.

[0017] Electricity is supplied to the electrolysis unit 110 from a power supply unit (not shown), and the carbon dioxide reduction device 1 controls the voltage from the power supply unit. Specifically, the voltage applied between the first electrode 111 and the second electrode 112 of the electrolysis unit 110 is configured to be controllable by a voltage control means 161. Note that, in this embodiment, the voltage applied between the first electrode 111 and the second electrode 112 of the electrolysis unit 110 is controlled by controlling the current flowing between the first electrode 111 and the second electrode 112 of the electrolysis unit 110.

[0018] The temperatures of the gas-liquid separation means 140, 150 can be controlled independently by gas-liquid separation temperature control means 163, 166, respectively.

[0019] The temperature and humidification amount of the humidification means 121, 131 can be controlled independently by humidification temperature control means 164, 167 and humidification control means 165, 168. The humidification means 121, 131 each use a bubbling type humidification means that humidifies gas introduced into pure water by bubbling it. This makes it possible to easily humidify the source gas and carrier gas. In this case, the humidification temperature control means 164, 167 can adjust the temperature of the introduced gas by setting the temperature by bubbling.

[0020] Furthermore, the voltage control means 161, the electrolysis section temperature control means 162, the gas-liquid separation temperature control means 166, the humidification temperature control means 164, 167 and the humidification control means 165, 168 are configured to be able to be centrally controlled by the central control means 160 according to the type and amount of the product to be recovered. (Electrolytic part)

[0021] The following describes the configuration of the electrolysis unit 110. The electrolysis unit 110 includes a first electrode 111, a second electrode 112, and an electrolyte membrane 113 that separates the second electrode 111 and the first electrode 112.

[0022] The first electrode 111 has an electrode plate 114 and a first electrode portion 115. A voltage is applied to the electrode plate 114 from a voltage control means 161 (see FIG. 1). The electrode plate 114 is provided on the back side (outside) of the first electrode portion 115. A path 118 is formed in the electrode plate 114, and a gas (carbon dioxide) is supplied to the first electrode 111 through this path. An inlet and an outlet of this path are each connected to a circulation path 141 (see FIG. 1).

[0023] The first electrode section 115 is composed of a gas diffusion layer and an electrode layer. The electrode layer is adjacent to the electrolyte membrane 113 and contains a catalyst material and other materials. The catalyst material may be, for example, at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Ru, Bi, Mo, Pd, Ag, Ir, and Pt. Preferably, any of Ru, Ni, Cu, Pt, and Ir is used, and most preferably Ru. In this embodiment, Ru is used. Alternatively, the catalyst material may be an alloy containing at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Ru, Bi, Mo, Pd, Ag, Ir, and Pt, and a precious metal catalyst including Pt and a Pt alloy is preferred.

[0024] The catalyst material is preferably particulate to increase the surface area. The average particle size is 1 nm to 1 μm, preferably 1 to 10 nm, and more preferably 1 to 5 nm. If the average particle size is less than 1 nm, the catalyst material will not have sufficient crystallinity and will not perform adequately, whereas if it exceeds 1 μm, the surface area will be too small to perform adequately. If the average particle size is 1 to 5 nm, the catalyst performance can be preferably exhibited.

[0025] Other materials contained in the first electrode portion 115 include a carrier for supporting the catalyst. Examples of the carrier include oxides having properties as a semiconductor with electronic conductivity, such as metal oxides. Examples of the metal oxide include silicon dioxide, magnesium oxide, titanium oxide, zirconium oxide, niobium oxide, zeolite, and calcium phosphate. These may be used alone or in combination of two or more. The shape of the carrier may be spherical, polyhedral, amorphous, flaky, or scaly. The average particle size of the carrier is not particularly limited, but may be, for example, 0.01 to 30 μm, preferably 0.02 to 2.0 μm, and more preferably 100 nm to 300 nm. In particular, it is preferable to use anatase or rutile titanium oxide as the titanium oxide, and in this embodiment, anatase titanium oxide is used.

[0026] Other materials include conductive materials and solid electrolytes. The conductive material may be a highly corrosion-resistant metal micropowder or a carbon-based conductive assistant. As the carbon-based conductive assistant, for example, acetylene black, ketjen black, or carbon black (microcarbon, nanoparticle carbon, fullerene, etc.) may be used. As the metal micropowder, an oxidation-resistant metal particle may be used, and such a metal may be at least one selected from Au, Pt, Fe, Cu, and Cr. The conductivity of the metal micropowder is 1×10 -8 Ωcm~3×10 -8 Ωcm, preferably 1.2×10 -8 Ωcm~2.0×10 -8 Ωcm, most preferably 1.4×10 -8 Ωcm~1.8×10 -8 It is preferable that the metal powder has a resistivity of 1.6×10 -8 Gold particles with a conductivity of 1000.0×10 Ωcm are also examples of carbon-containing materials. -8 Ωcm~2000×10 -8 Ωcm, preferably 1200×10 -8 Ωcm~1500.0×10 -8 Ωcm, most preferably 1300.0×10 -6 Ωcm~14000×10 -6 Such a material has a conductivity of 1375.0×10 -6 Examples of the particles include carbon black particles having a viscosity of Ωcm and a particle size of 3 to 500 nm.

[0027] As the solid electrolyte, a polymeric material with ion exchange capability, such as NAFION (registered trademark) with cation exchange capability or a proton conductive material with a structure similar to NAFION, can be used, or a hydroxide ion conductive material with anion exchange capability can be used. Specifically, a fluorine-based material, such as Nafion, is used. When a conductive material and a solid electrolyte are included, the weight ratio of the catalytic metal particles, the conductive material, and the solid electrolyte is preferably 1-5:1-5:1-5, more preferably 5-2:5-2:1, and most preferably 2:2:1. By being in this range, methane can be preferably produced. If the weight ratio of the solid electrolyte is less than 1, the coating property is poor. On the other hand, if it exceeds 1, the coating property is good, but the exposed surface area of ​​the catalytic metal particles is reduced, resulting in a low reactivity. The electrode layer is formed on the solid electrolyte membrane or the gas diffusion layer using a dispersion liquid containing these. The formation method is not particularly limited, and the dispersion liquid may be directly sprayed or applied, or may be applied and then transferred.

[0028] The second electrode 112 has an electrode plate 116 and a second electrode portion 117. A voltage is applied to the electrode plate 116 from a voltage control means 161. The electrode plate 116 is provided on the second electrode portion 117. A path (not shown) is formed in the electrode plate 116, and at least one of water, hydrogen, and water vapor is supplied to the first electrode portion via this path. An inlet and an outlet of this path are each connected to a circulation path 151.

[0029] The second electrode portion 117 includes a catalytic material and may further include other materials. Examples of the catalytic material and other materials include the same materials as those used for the first electrode 111. In this embodiment, the second electrode 112 uses Pt as the catalytic material, and the support as the other material includes carbon.

[0030] The electrolyte membrane 113 is a solid polymer membrane having hydrogen ion conductivity. As such a solid polymer membrane, a fluorine-based membrane material, for example, NAFION (registered trademark), which is perfluorosulfonic acid, can be used. By using a membrane that is internally reinforced with polytetrafluoro fiber or the like contained in the fluorine-based membrane material, it is possible to prevent direct mixing of hydrogen and carbon dioxide. The thickness of the electrolyte membrane 113 is 5 μm to 300 μm, and preferably 5 μm to 50 μm.

[0031] (Carbon dioxide reduction method) A carbon dioxide reduction method using the above carbon dioxide reduction device 1 will be described.

[0032] First, the raw material gas (carbon dioxide gas) is humidified by the humidification means 121 from the carbon dioxide supply means 120 to the first electrode 111, and is supplied via the circulation path 141 and the inlet of the electrolysis section 110. The supply rate of the raw material gas is 1 to 60 cc / min, preferably 5 to 40 cc / min. If the flow rate is outside this range, the reaction will decrease. The temperature and humidification amount of the humidification means 121 are set to 10 to 120°C, preferably 40 to 90°C, by the humidification temperature control means 164 and the humidification control means 165. If the humidification temperature and humidification amount are not within this range, the reaction will decrease. In addition, the carrier gas supplied from the carrier gas supply means 132 is humidified by the humidifying means 131, and at least one of the obtained water, hydrogen, and water vapor is supplied to the second electrode 112 via the circulation path 151 and the inlet of the electrolysis section 110. The temperature of the humidifying means 131 is set to 10 to 120°C, preferably 40 to 90°C, by the humidification temperature control means 167 and the humidification control means 168. If the humidification temperature is not within this range, the reaction will be reduced. The supply amount of the carrier gas is 1 to 60 cc / min, preferably 5 to 40 cc / min. If the flow rate is outside this range, the reaction will be reduced.

[0033] In this embodiment, a voltage lower than −1200 mV, preferably lower than −400 mV, and most preferably a voltage of −400 mV to 100 mV is applied between the first electrode 111 and the second electrode 112 by the voltage control means 161 with respect to the first electrode 111 based on a hydrogen electrode. At this time, the temperature of the electrolysis unit 110 is controlled by the electrolysis unit temperature control means 162 to be 10 to 120° C., preferably 40 to 90° C.

[0034] In this case, the following carbon dioxide reduction reaction occurs at the first electrode 111. CO 2 +8H ++8e ー →CH 4 +2H 2 O …(1)

[0035] On the other hand, at the second electrode 112, the following oxidation reaction occurs: H 2 → 2H + +2e ー …(2)

[0036] In this way, only methane among the hydrocarbons is selectively produced from carbon dioxide on the first electrode 111 side of the electrolysis unit 110. Since water is also produced at the same time in the electrolysis unit 110 as described above, the produced methane and water are introduced into the gas-liquid separation means 140, which is a condensation means, via the circulation path 141, and are separated into water and methane by the gas-liquid separation means.

[0037] Furthermore, on the second electrode 112 side of the electrolysis section 110 , hydrogen ions are generated from hydrogen and introduced into the gas-liquid separation means 150 .

[0038] In this case, the temperatures of the gas-liquid separation means 140, 150 are controlled by gas-liquid separation temperature control means 163, 166, respectively, to be equal to or lower than the operating temperature of the electrolysis section. (Example)

[0039] The present invention will now be described in more detail with reference to examples. Example 1 The following materials were mixed to form a dispersion: Catalyst particles: Ru particles (Ru particles fixed on anatase-type titanium oxide particles by sputtering, with a particle size of 5 to 200 nm), 1 g Conductive material: Carbon black, 1g Solid electrolyte: 5% Nafion dispersion (registered trademark, manufactured by Wako Pure Chemical Industries, Ltd.), 10 g Dispersion liquid material: Water 0.1g, Methanol 1g, 2-propanol 1g Next, two pieces of carbon paper (TGP-H-060H) manufactured by Toray Industries, Inc., to be used as the anode diffusion layer and the cathode diffusion layer, were cut into squares each having a side length of 30 mm (area: 5 cm 2 The above dispersion liquid was sprayed onto one surface of each of the cut-out carbon papers and then dried to prepare a first electrode 111 and a second electrode 112, respectively.

[0040] First, the carbon dioxide reduction device 1 using the first electrode 111 and the second electrode 112 and NAFION's NR212 (thickness 50 μm) as the electrolytic membrane 113 was used, and carbon dioxide gas was supplied from the carbon dioxide supply means 120 to the first electrode 111 through the circulation path 141 and the inlet of the electrolysis unit 110 at 40 cc / min. In addition, the carrier gas (for example, nitrogen or argon) supplied from the carrier gas supply means 132 was humidified by the humidification means 131, and water or water vapor was supplied from the water supply means 130 to the electrolysis unit 110 at 40 cc / min through the circulation path 151 and the inlet of the electrolysis unit 110. The temperature of the humidification means 131 was set to 60°C.

[0041] The voltage control means 161 was set to apply a current of 0.805 A to the electrolysis unit 110 and apply a voltage of -297 mV. At this time, the temperature of the electrolysis unit 110 was controlled to 90°C by the electrolysis unit temperature control means 162.

[0042] The products in this case were analyzed using a mass spectrometer (Shimadzu Corporation, product name: GCMS-QP2010) and the results are shown in Figures 3 and 4. The individual peaks are as follows: Peak 1 3.214min: Hydrogen Peak 2 3.288min: Nitrogen (2.65591%) Peak 3: 3.533 min: Methane (0.00371%) Peak 4: 4.907 min: Carbon dioxide (72.49692%) FIG. 4 is a partial enlarged view of the region surrounded by the dotted line in FIG. 3, and furthermore, in FIG. 4, only the region showing methane and carbon dioxide is shown.

[0043] 3 and 4, mass spectrum analysis showed no peaks indicating the generation of hydrocarbon compounds such as aldehydes and ethanols, and only methane was selectively generated according to the reduction method using the carbon dioxide reduction device 1 of the present invention. In this case, it was found that 37.1 ppm of methane was generated. (Examples 2 to 9)

[0044] In Examples 2 to 9, methane production was carried out under the same conditions as in Example 1 except for the conditions shown in Table 1. (Table 1) TIFF2025086056000002.tif85136 The current-voltage characteristics of the electrolysis unit 110 in this case are shown in FIG. 5, the current-amount of methane produced is shown in FIG. 6, and the voltage-amount of methane produced is shown in FIG.

[0045] As shown in FIG. 5, when the current was gradually increased from 0A, the voltage decreased at a constant rate in all the examples, but especially in Example 1, the voltage decreased significantly from about 1.0A. As shown in FIG. 6, when the current increased in all the examples, the amount of methane produced increased. It was also found that the lower the supply gas flow rate, the greater the amount of methane produced. As shown in FIG. 7, when the voltage gradually decreased from 0mV, the amount of methane produced gradually increased up to -400mV, but from about -400mV, the amount of methane produced saturated at about 40ppm, and thereafter, the amount of methane produced tended not to increase even if the voltage decreased.

[0046] From the above, it was found that when the voltage range applied to the electrolysis unit 110 is -400 mV or more, methane is produced according to equation (1), but when the voltage range applied to the electrolysis unit 110 is lower than -400 mV, the reaction according to equation (2) proceeds, and more hydrogen is formed without increasing the amount of methane produced. [Industrial Applicability]

[0047] According to the method and system for solid polymer electrolysis of the present invention, it is possible to convert carbon dioxide into useful methane with little energy input and without the need to maintain high temperatures, and it is possible to solve environmental, energy and resource problems. Furthermore, it can be effectively used as a control technology for completely closed environments such as space stations and rockets from the viewpoints of carbon dioxide removal, circulation at the elemental level, energy generation, etc. [Explanation of symbols]

[0048] 1 Carbon dioxide reduction device 110 Electrolytic section 111 First electrode 112 Second electrode 113 Electrolyte membrane 114 Electrode Plate 115 First electrode section 116 Electrode Plate 117 Second electrode section 118 Routes 120 Carbon dioxide supply means 121, 131 Humidification means 130 Water supply means 132 Carrier gas supply means 140, 150 Gas-liquid separation means 141, 151 Circulation route 142, 152 Circulation pump 160 Central Control Means 161 Voltage control means 162 Electrolysis section temperature control means 163, 166 Temperature control means for gas-liquid separation 164, 167 Humidification temperature control means 165, 168 Humidification control means 166 Temperature control means for gas-liquid separation

Claims

1. an electrolysis section including a first electrode and a second electrode, an electrolyte membrane provided between the first electrode and the second electrode, the first electrode being an electrode on one side of the electrolyte membrane and to which carbon dioxide is supplied, and the second electrode being an electrode on the other side of the electrolyte membrane and to which at least one selected from water, hydrogen, and water vapor is supplied; a carbon dioxide supplying means for supplying carbon dioxide to the first electrode side of the electrolysis unit; and a water supplying means for supplying at least one selected from the water, hydrogen, and water vapor to the second electrode side of the electrolysis unit. A humidifying means provided between the carbon dioxide supplying means and the electrolysis unit; A voltage application means for applying a voltage to the electrolysis unit, A carbon dioxide reduction device for generating methane from carbon dioxide supplied to the electrolysis unit, the first electrode includes catalytic metal particles made of a catalytic metal having an average particle size of 1 to 10 nm and support particles made of a metal oxide supporting the catalytic metal particles, The electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity. A carbon dioxide reduction device characterized by:

2. 2. The carbon dioxide reduction device according to claim 1, characterized in that the catalytic metal is at least one selected from the group consisting of ruthenium, nickel, copper, platinum and iridium, or an alloy containing at least any of these, and the metal oxide is at least one selected from the group consisting of titanium oxide, silicon dioxide, magnesium oxide, aluminum oxide, zirconium oxide, niobium oxide, zeolite and calcium phosphate.

3. 2. The carbon dioxide reduction device according to claim 1, wherein the first electrode further includes a solid electrolyte.

4. 4. The carbon dioxide reduction device according to claim 3, wherein the first electrode further comprises a conductive material.

5. 5. The carbon dioxide reduction device according to claim 4, wherein a weight ratio of the catalyst particles, the conductive material, and the solid electrolyte is 1-5:1-5:1-5.

6. 3. The carbon dioxide reduction device according to claim 2, wherein the metal oxide is at least one selected from the group consisting of titanium oxide, silicon oxide, aluminum oxide, zeolite, and calcium phosphate.

7. 7. The carbon dioxide reduction device according to claim 6, wherein the titanium oxide is of anatase type or rutile type.

8. 6. The carbon dioxide reduction device according to claim 5, wherein a weight ratio of the catalyst particles, the conductive material, and the solid electrolyte is 5 to 2:5 to 2:

1.

9. an electrolysis unit including an electrolyte membrane, a first electrode on one side of the electrolyte membrane to which carbon dioxide is supplied, and a second electrode on the other side of the electrolyte membrane to which carbon dioxide is supplied, the electrolysis unit supplies humidified carbon dioxide to a first electrode side and humidified water or water vapor to a second electrode side; A carbon dioxide reduction device that generates methane from carbon dioxide supplied while applying a voltage to the electrolysis unit, the first electrode includes catalytic metal particles having a diameter of 1 to 10 nm and support particles made of metal oxide supporting the catalytic metal particles, the electrolyte membrane is a solid polymer membrane having hydrogen ion conductivity; A carbon dioxide reduction method, comprising applying a voltage higher than −400 mV to the electrolysis section.

10. 10. The carbon dioxide reduction method according to claim 9, wherein the temperature during the humidification is maintained at 40 to 90°C.

11. The carbon dioxide reduction method according to claim 9, wherein the temperature of the electrolysis section is maintained at 40 to 90°C.

12. 10. The carbon dioxide reduction method according to claim 9, wherein a voltage of −400 mV to 100 mV is applied to the electrolysis unit.

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