Carbon dioxide electrolysis cell

Abstract

To provide a carbon dioxide electrolysis cell that can electrolytically reduce carbon dioxide stably for a long period of time.SOLUTION: A carbon dioxide electrolysis cell (1) comprises: a cathode (10) including cobalt phthalocyanine; a gas passage (20); a cathode chamber (30) that can contain a catholyte (31); an anode (40); an anode chamber (50) that can contain an anolyte (51); and an anion exchange membrane (60).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an electrolytic cell for carbon dioxide. [Background technology]

[0002] In recent years, the electrolytic reduction of carbon dioxide (CO2) has attracted attention as a way to store surplus electrical energy obtained from renewable energy generation. By storing carbon compounds such as carbon monoxide (CO) generated by the electrolytic reduction of carbon dioxide, storage costs and storage losses can be reduced compared to storing electrical energy in batteries.

[0003] Patent Document 1 discloses an electrolytic reduction method for carbon dioxide using a gas diffusion electrode. Patent Document 2 discloses an electrolytic cell for carbon dioxide in which the anode is in contact with a separator.

[0004] Furthermore, Non-Patent Document 1 suggests that in the diffusion-rate limit range of an oxygen reduction reaction, the reduction current is smaller the higher the hydrophilicity of the cathode, indicating that gas diffusivity is reduced as the hydrophilicity of the cathode increases. Non-Patent Document 2 discloses an anion exchange membrane used in an alkali membrane fuel cell. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 1-205088 [Patent Document 2] Japanese Patent Publication No. 2018-123390 [Non-patent literature]

[0006] [Non-Patent Document 1] S. Takase et. al., "Investigation of the Effect of Hydrophilicity on Oxygen Reduction Reaction Property with Measurement of Water Vapor Specific Surface Area" Electrochemistry, 89(6), 597-601 (2021) [Non-Patent Document 2] Hiroyuki Yanagi et al., "Development of Electrolyte Materials and Power Generation Performance for Alkali Membrane Fuel Cells (AMFCs)," Hydrogen Energy Systems, Vol. 35, No. 2 (2010). [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the prior art described in Patent Documents 1 and 2 has the problem that it cannot stably electrolytically reduce carbon dioxide for a long period of time. One aspect of the present invention aims to realize an electrolytic cell for carbon dioxide that can stably electrolytically reduce carbon dioxide for a long period of time. [Means for solving the problem]

[0008] To solve the above problems, an electrolytic cell for carbon dioxide according to one aspect of the present invention comprises a cathode containing cobalt phthalocyanine for reducing carbon dioxide, a gas channel for supplying carbon dioxide to the cathode, a cathode chamber capable of containing a cathode electrolyte in contact with the cathode, an anode paired with the cathode, an anode chamber capable of containing an anode electrolyte in contact with the anode, and an anion exchange membrane for separating the cathode electrolyte and the anode electrolyte.

[0009] As a result of diligent research by the inventors, it was discovered that by including cobalt phthalocyanine in the cathode, the production of carbon monoxide through the reduction of carbon dioxide is promoted, while the production of formic acid is reduced. Therefore, fluctuations in the pH of the cathode electrolyte and anode electrolyte are reduced, and carbon dioxide can be electrolytically reduced stably for a long period of time.

[0010] Also, by separating the cathode electrolyte and the anode electrolyte with an anion exchange membrane, hydroxide ions (OH - ) generated by the reduction of carbon dioxide can move from the cathode chamber through the anion exchange membrane into the anode chamber. At this time, at the anode, for example, hydrogen ions (H + ) are generated by the oxidation of water or hydroxide ions. Therefore, the hydroxide ions (OH - ) that have moved from the cathode chamber into the anode chamber can neutralize at least a part of the surplus hydrogen ions (H + ) in the anode chamber. Therefore, fluctuations in the pH of the cathode electrolyte and the anode electrolyte can be reduced, and carbon dioxide can be electrochemically reduced stably for a long time.

Advantages of the Invention

[0011] According to one aspect of the present invention, an electrolytic cell for carbon dioxide that can stably electrochemically reduce carbon dioxide for a long time can be realized.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing an electrolytic cell for carbon dioxide according to one aspect of the present invention. [Figure 2] It is a schematic diagram explaining the operation of the electrolytic cell according to FIG. 1. [Figure 3] It is a diagram showing the relationship between the elapsed time after the start of electrolysis and the current of the electrolytic cell according to the example.

Modes for Carrying Out the Invention

[0013] Hereinafter, one aspect of the present invention will be described in detail. The following description is for better understanding of the gist of the invention and does not limit the present invention unless otherwise specified.

[0014] 〔Structure of the Electrolytic Cell for Carbon Dioxide〕 Figure 1 is a schematic diagram showing a carbon dioxide electrolytic cell 1 according to one aspect of the present invention. The electrolytic cell 1 comprises a cathode 10, a gas flow path 20, a cathode chamber 30, an anode 40, an anode chamber 50, and an anion exchange membrane 60.

[0015] The cathode 10 is an electrode containing cobalt phthalocyanine (hereinafter abbreviated as "CoPc") that reduces carbon dioxide. At the cathode 10, carbon monoxide may be produced by the reduction of carbon dioxide. The cathode 10 may also be a gas diffusion electrode containing a hydrophobic binder on its surface. An example of a hydrophobic binder is polytetrafluoroethylene (PTFE). The cathode 10 may not contain a hydrophilic binder in order to further improve its hydrophobicity. The cathode 10 may further contain carbon material in order to improve its conductivity.

[0016] By making the cathode 10 a gas diffusion electrode containing a hydrophobic binder on its surface, the diffusivity of the gas can be improved. Therefore, contact between the cathode 10 and carbon dioxide can be promoted. Furthermore, if the carbon compound generated at the cathode 10 is a gas, the detachment of the gaseous carbon compound from the cathode 10 can be promoted. Consequently, the current density at the cathode 10 during electrolytic reduction can be improved.

[0017] Furthermore, the increased hydrophobicity reduces wettability, thereby decreasing the contact area between the cathode electrolyte 31 and the cathode 10, and thus reducing the amount of carbon dioxide dissolved in the cathode electrolyte 31.

[0018] When the cathode 10 is a gas diffusion electrode, the concentration distribution of CoPc in the cathode 10 may be uniform within the cathode 10, or the concentration of CoPc may be higher closer to the surface on the gas flow side of the cathode 10.

[0019] Cathode 10 has a BET specific surface area (SA) with water as the adsorbed species. H2O ) and BET specific surface area (SA) with nitrogen as the adsorbent species N2 ) ratio (SA H2O / SA N2(hereinafter abbreviated as "hydrophilicity") may be 0.010 or less.

[0020] By setting the hydrophilicity of the cathode 10 to 0.010 or less, the diffusibility of gas can be improved. Therefore, the current density at the cathode 10 during electrolytic reduction can be further improved. In addition, since the contact area between the cathode electrolyte 31 and the cathode 10 can be further reduced, the voltage required for electrolytic reduction can be further decreased.

[0021] The gas flow path 20 supplies carbon dioxide to the cathode 10. As the gas flow path 20, a known one can be used. When the cathode 10 is a gas diffusion electrode, the gas flow path 20 may be continuous with the gas diffusion layer of the cathode 10.

[0022] The cathode chamber 30 can contain the cathode electrolyte 31 that contacts the cathode 10. The pH of the cathode electrolyte 31 is not particularly limited. For example, the pH may be 12 or more, and preferably 13 or more. Examples of the electrolyte that can be used as the cathode electrolyte 31 include, but are not limited to, an aqueous solution of potassium hydroxide (KOH), an aqueous solution of sodium hydroxide (NaOH), and an aqueous solution of potassium hydrogen carbonate (KHCO3).

[0023] When an aqueous solution of KHCO3 is used as the cathode electrolyte 31, in a solution where carbonate ions (CO3 2- ) are sufficiently present, the reaction in which CO2 dissolves and ionizes hardly proceeds. On the other hand, the condition is such that there are few OH - in the solution, and the oxygen generation reaction, which is the counter electrode reaction, hardly proceeds. Therefore, the current during electrolytic reduction is reduced compared to the case where a strong base electrolyte is used as the cathode electrolyte 31.

[0024] The anode 40 is an electrode paired with the cathode 10. As the anode 40, a known one such as a platinum electrode can be used. At the anode 40, for example, oxygen (O2) and hydrogen ions (H - ) can be generated by the oxidation of water (H2O) or hydroxide ions (OH + ).

[0025] The anode chamber 50 can contain the anode electrolyte 51 that comes into contact with the anode 40. The pH of the anode electrolyte 51 is not particularly limited, but for example, it may be 12 or higher, preferably 13 or higher. The anode electrolyte 51 may be the same electrolyte as the cathode electrolyte 31.

[0026] The anion exchange membrane 60 separates the cathode electrolyte 31 and the anode electrolyte 51. The anion exchange membrane 60 prevents oxygen generated at the anode 40 from moving to the cathode electrolyte 31, thereby preventing the reduction of oxygen generated at the anode 40 at the cathode 10 (oxygen crossover). Since the overpotential for carbon dioxide reduction is greater than that for oxygen reduction, it would be difficult to prevent such oxygen crossover without the anion exchange membrane 60.

[0027] The anion exchange membrane 60 may have an ionic conductivity of 1 mS / cm or more, preferably 3 mS / cm or more, and more preferably 5 mS / cm or more. The higher the ionic conductivity of the anion exchange membrane 60, the lower the voltage required during electrolytic reduction can be.

[0028] Furthermore, the anion exchange film 60 has a film resistance of 1 Ω·cm. 2 The following may also be acceptable, preferably 0.7Ω·cm 2 It may be less than or equal to 0.5Ω·cm, and more preferably 0.5Ω·cm 2 The following may also be true: The lower the film resistance of the anion exchange film 60, the lower the voltage required during electrolytic reduction can be.

[0029] [Ionic conductivity of anion exchange membrane] In this specification, the "ionic conductivity" of an anion exchange membrane means the ionic conductivity calculated as follows.

[0030] First, the anion exchange membrane was left in the air in a dry state for more than 24 hours, then moistened with deionized water at 40°C, and cut into a rectangle approximately 6 cm wide and 2.0 cm long. The film thickness L of the anion exchange membrane in the state moistened with deionized water was also measured.

[0031] Next, an insulating substrate is prepared on which five platinum wires with a wire width of 0.3 mm are arranged in a straight line parallel to the vertical direction (the same direction as the vertical direction of the anion exchange film), with a spacing of 0.5 cm in the horizontal direction (the same direction as the horizontal direction of the anion exchange film). Then, a sample for measurement is prepared by pressing the platinum wires on the insulating substrate against a strip-shaped anion exchange film.

[0032] The five platinum wires of the measurement sample are designated Pt1, Pt2, Pt3, Pt4, and Pt5, starting from the wire closest to one of the shorter sides of the rectangularly cut anion exchange membrane. The AC impedance is measured between Pt1 and Pt2 (spacing = 0.5 cm), between Pt1 and Pt3 (spacing = 1.0 cm), between Pt1 and Pt4 (spacing = 1.5 cm), and between Pt1 and Pt5 (spacing = 2.0 cm). The AC impedance is measured by holding the measurement sample in a constant temperature and humidity chamber at 40°C and 90% RH with droplets of ion-exchanged water on the surface of the anion exchange membrane, and applying a 1 kHz AC current between the platinum wires.

[0033] Then, with the horizontal axis representing the spacing of the platinum wires and the vertical axis representing the AC impedance, each measured value is plotted, and by performing a linear approximation using the least squares method, the gradient R3 between the resistive electrodes, which represents the resistivity of the anion exchange film, is determined as the slope of the line. From the gradient R3 between the resistive electrodes, the ionic conductivity σ is calculated based on the following equation (2). In the right-hand side of equation (2), "2.0" represents the vertical length of the anion exchange film, and the unit is cm.

[0034] σ = 1 / (R3 × 2.0 × L) ... (2) σ: Ionic conductivity [S / cm] L: Film thickness [cm] R3: Resistance gradient [Ω / cm] The y-intercept of the above approximate line represents the contact resistance between the platinum wire and the anion exchange film in the measurement sample. In this measurement, the ionic conductivity σ of the anion exchange film is calculated based on the gradient R3 between the resistive electrodes, so the effect of the above contact resistance can be excluded.

[0035] [Film resistance of anion exchange films] In this specification, the "membrane resistance" of an anion exchange membrane means the membrane resistance calculated as follows.

[0036] Membrane resistance (Ω cm 2 ) = Film thickness (cm) / Ionic conductivity (1 / (Ω·cm)) [Operation of a carbon dioxide electrolysis cell] Figure 2 is a schematic diagram illustrating the operation of electrolytic reduction of carbon dioxide using carbon dioxide electrolytic cell 1. In the example in Figure 2, aqueous KOH solution is used as the cathode electrolyte 31 and the anode electrolyte 51, but the present invention is not limited to this, and other electrolytes may be used. At the cathode 10, the reactions of formulas (3) and (4) below proceed.

[0037] [ka]

[0038] Furthermore, at cathode 10, the reaction shown in equation (5) below may also proceed.

[0039] [ka]

[0040] Meanwhile, at anode 40, the reaction shown in equation (6) below proceeds.

[0041] [ka]

[0042] In the cathode electrolyte 31, the above reactions (3) and (4) produce OH -An excess of ions occurs. On the other hand, in the anodic electrolyte 51, the reaction of formula (6) above produces H + An excess of ions occurs. Here, in electrolytic cell 1, the anion exchange membrane 60 separates the cathode electrolyte 31 and the anode electrolyte 51, so the excess hydroxide ions (OH) in the cathode electrolyte 31 are removed. - The hydroxide ions (OH) that have moved from the cathode chamber 30 to the anode chamber 50 can move through the anion exchange membrane 60. - ) is the excess hydrogen ions (H) in the anode chamber 50. + At least a portion of the solution can be neutralized. Therefore, fluctuations in the pH of the cathode electrolyte 31 and the anode electrolyte 51 are reduced, and carbon dioxide can be electrolytically reduced stably for a long period of time.

[0043] Furthermore, if the pH of the cathode electrolyte 31 is set to 12 or higher, the generation of hydrogen (H2) according to formula (5) above can be reduced, and the generation of CO according to formula (4) above can be promoted. Also, if the pH of the anode electrolyte 51 is set to 12 or higher, the anodic reaction according to formula (6) above can be promoted, and the voltage required during electrolytic reduction can be reduced.

[0044] According to the above configuration, surplus electrical energy obtained from renewable energy generation, for example, can be efficiently stored. Such effects can contribute to achieving goals such as Goal 7 of the United Nations' Sustainable Development Goals (SDGs), "Ensure access to affordable, reliable, sustainable, and modern energy for all."

[0045] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0046] [Examples] Examples of the present invention will be described below. Note that the electrolytic cells described in these examples are merely examples and do not limit the electrolytic cells to any particular aspect of the present invention. First, electrolytic cells Ex1 to Ex3 according to the examples and electrolytic cell CE1 according to the comparative example were prepared using the combinations shown in Table 1 below.

[0047] [Table 1]

[0048] As the cathode, an electrode was used, which was prepared by mixing the cathode catalyst, hydrophobic carbon powder, and PTFE listed in Table 1 above and hot-pressing the mixture. As the anode, a platinum electrode was used.

[0049] As the anion exchange membrane listed in Table 1 above, a sample product manufactured by Tokuyama Corporation (sample name: A201) was used. In addition, Nafion (product number: 117) manufactured by DuPont was used as the cation exchange membrane.

[0050] Using the fabricated electrolytic cell, a constant potential of -1600mV was applied to the cathode, and electrolytic reduction of carbon dioxide was performed using either (i) carbon dioxide alone (gas flow rate: 30mL / min) or (ii) carbon dioxide + saturated water vapor (total gas flow rate: 30mL / min) as the introduced gas. The results are shown in Table 2 below. In Table 2, "CO2" indicates that the introduced gas is (i) carbon dioxide alone, and "CO2 + H2O" indicates that the introduced gas is (ii) carbon dioxide + saturated water vapor. "ND" indicates that no substance was detected. In some cases, the Faraday efficiency exceeds 100%. This is thought to be due to measurement errors caused by analyzing only a portion of the generated gas, and the effect of reactions with fewer electrons than expected. An example of a reaction with fewer electrons is the one-electron CO generation reaction between a CO2 radical and CO2.

[0051] [Table 2]

[0052] As shown in Table 2 above, it was found that formic acid was not produced or was produced in very small amounts in the electrolytic cells related to Ex1 to Ex3. Therefore, it was shown that formic acid production can be reduced by including CoPc in the cathode.

[0053] Furthermore, it was shown that the electrolytic cells related to Ex1 to Ex2 produced a larger amount of electricity and more carbon monoxide than the electrolytic cell related to Ex3. This is presumed to be because the electrolytic cells related to Ex1 to Ex2 use a strong base with a pH of 12 or higher as the anodic electrolyte, so the anodic reaction represented by the above formula (6) proceeds rapidly.

[0054] In the electrolytic cells related to Ex1 and Ex3, using (ii) carbon dioxide + saturated water vapor as the introduction gas increased the amount of CO produced compared to using (i) carbon dioxide alone as the introduction gas. Therefore, it was suggested that when CoPc is contained in the cathode, the CO production reaction proceeds even if sufficient liquid water is not supplied to the reaction field.

[0055] Furthermore, the inventors have found that in the electrolytic cell according to Ex1, under conditions where the amount of gas generated becomes too large, morphological changes are observed that are thought to be caused by stress due to gas generation from inside the electrode. From this, it is suggested that when CoPc is supported throughout the reaction layer of the cathode, the reduction reaction of carbon dioxide proceeds not only at the interface between the cathode and the cathode electrolyte, but also inside the cathode.

[0056] On the other hand, metal catalysts other than CoPc, such as gold, are generally placed at the interface between the electrode and the electrolyte, and it is generally believed that a sufficient amount of water as liquid is necessary for the reaction. This is presumably because, in the case of metal catalysts such as gold, the bond strength between the reaction intermediate and the metal catalyst is strong, requiring the promotion of the elimination reaction.

[0057] Figure 3 shows the relationship between the elapsed time after the start of electrolytic reduction and the current for electrolytic cells Ex1 and CE1. To confirm reproducibility, measurements were performed using two electrolytic cells for each of electrolytic cells Ex1 and CE1. Both Ex1-1 and Ex1-2 shown in Figure 3 have the structure of electrolytic cell Ex1, and both CE1-1 and CE1-2 have the structure of electrolytic cell CE1.

[0058] As shown in Figure 3, electrolytic reduction stopped in CE1-1 at 9180 seconds and in CE1-2 at 8280 seconds, and no current flowed even when voltage was applied. On the other hand, electrolytic reduction could be continuously performed in Ex1-1 at 21600 seconds and in Ex1-2 at 18000 seconds until the voltage application was stopped.

[0059] Table 3 below shows the pH and potential difference of the electrolyte before and after electrolytic reduction for electrolytic cells Ex1 and CE1. As shown in Table 3, the pH fluctuation before and after electrolytic reduction was small for electrolytic cells Ex1-1 and Ex1-2, and the pH was 13.0 or higher at all times. On the other hand, for electrolytic cells CE1-1 and CE1-2, the pH of the anodic electrolyte decreased to 12.5 or lower after the completion of electrolytic reduction.

[0060] [Table 3]

[0061] As described above, the electrolytic cell related to Ex1, by incorporating an anion exchange membrane as an ion exchange membrane, reduces pH fluctuations and enables stable electrolytic reduction of carbon dioxide over a long period of time.

[0062] 〔summary〕 The carbon dioxide electrolytic cell according to embodiment 1 of the present invention comprises a cathode containing cobalt phthalocyanine for reducing carbon dioxide, a gas channel for supplying carbon dioxide to the cathode, a cathode chamber capable of containing a cathode electrolyte in contact with the cathode, an anode paired with the cathode, an anode chamber capable of containing an anode electrolyte in contact with the anode, and an anion exchange membrane for separating the cathode electrolyte and the anode electrolyte.

[0063] Based on the above configuration, the inventors' diligent research revealed that by including cobalt phthalocyanine in the cathode, the production of carbon monoxide through the reduction of carbon dioxide is promoted, while the production of formic acid is reduced. Therefore, pH fluctuations are reduced, and carbon dioxide can be electrolytically reduced stably for a long period of time.

[0064] Furthermore, by separating the cathode electrolyte and anodic electrolyte with an anion exchange membrane, hydroxide ions (OH) generated by the reduction of carbon dioxide are removed. - ) can move from the cathode chamber through the anion exchange membrane into the anode chamber. At this time, at the anode, hydrogen ions (H) can be generated by oxidation of water or hydroxide ions, for example. + ) is being generated. Therefore, hydroxide ions (OH) move from the cathode chamber to the anode chamber. - ) are excess hydrogen ions (H) in the anode chamber. + It can neutralize at least a portion of the ions. Therefore, it reduces fluctuations in the pH of the cathode electrolyte and anodic electrolyte, allowing for stable electrolytic reduction of carbon dioxide over a long period of time.

[0065] In the electrolytic cell according to aspect 2 of the present invention, the cathode may be configured to be a gas diffusion electrode containing a hydrophobic binder on its surface, as described in aspect 1 above.

[0066] According to the above configuration, by making the cathode a gas diffusion electrode containing a hydrophobic binder on its surface, the diffusivity of the gas can be improved. Therefore, contact between the cathode and carbon dioxide can be promoted. Furthermore, if the carbon compound generated at the cathode is a gas, the detachment of the gaseous carbon compound from the cathode can be promoted. Consequently, the current density at the cathode during electrolytic reduction can be improved.

[0067] Furthermore, since the contact area between the cathode electrolyte and the cathode can be reduced, the amount of carbon dioxide dissolved in the cathode electrolyte can be reduced. Therefore, the ionization of carbon dioxide into carbonate ions (CO3) 2- This reduces the amount of ) produced and the voltage (overvoltage) required for reduction. Therefore, it is possible to suppress the rise in overvoltage during electrolytic reduction.

[0068] The electrolytic cell according to embodiment 3 of the present invention, in embodiment 1 or 2 above, has a BET specific surface area (SA) with water as the adsorbent species. H2O ) and BET specific surface area (SA) with nitrogen as the adsorbent species N2 ) ratio (SA H2O / SA N2 A configuration in which ) is 0.010 or less is also acceptable.

[0069] According to the above configuration, SA is the cathode. H2O / SA N2 By setting the coefficient to 0.010 or less, the diffusivity of the gas can be improved. Therefore, the current density at the cathode during electrolytic reduction can be further improved. In addition, the contact area between the cathode electrolyte and the cathode can be further reduced, so the voltage required for electrolytic reduction can be further lowered.

[0070] In the electrolytic cell according to embodiment 4 of the present invention, in any one of embodiments 1 to 3 described above, the cathode electrolyte and the anode electrolyte may be configured to have a pH of 12 or higher.

[0071] According to the above configuration, by setting the pH of the cathode electrolyte to 12 or higher, the generation of hydrogen (H2) at the cathode during electrolytic reduction can be reduced, and the generation of CO can be promoted. Furthermore, by setting the pH of the anodic electrolyte to 12 or higher, the anodic reaction can be promoted. Therefore, the voltage required during electrolytic reduction can be further reduced.

[0072] In the electrolytic cell according to embodiment 5 of the present invention, in any one of embodiments 1 to 4 described above, the anion exchange membrane may be configured to have an ionic conductivity of 1 mS / cm or more.

[0073] With the above configuration, by setting the ionic conductivity of the anion exchange membrane to 1 mS / cm or higher, the voltage required during electrolytic reduction can be reduced. [Industrial applicability]

[0074] This invention can be used, for example, to store excess electrical energy. [Explanation of Symbols]

[0075] 1 electrolytic cell 10 cathode 20 Gas flow path 30 Cathode Chamber 31 Catholyte 40 Anode 50 Anode chamber 51 Anolyte 60 Anion exchange membrane

Claims

1. It contains cobalt phthalocyanine and is a cathode that reduces carbon dioxide, A gas channel for supplying carbon dioxide to the cathode, A cathode chamber capable of containing a cathode electrolyte that comes into contact with the cathode, The cathode is paired with an anode, An anode chamber capable of containing an anode electrolyte that comes into contact with the anode, The system comprises an anion exchange membrane for separating the cathode electrolyte and the anode electrolyte, The cathode is a carbon dioxide electrolytic cell in which the ratio of the BET specific surface area with water as the adsorbent species (SA H2O) to the BET specific surface area with nitrogen as the adsorbent species (SA N2) (SA H2O / SA N2) is 0.010 or less.

2. The electrolytic cell according to claim 1, wherein the cathode is a gas diffusion electrode containing a hydrophobic binder on its surface.

3. The electrolytic cell according to claim 1 or 2, wherein the cathode electrolyte and the anode electrolyte have a pH of 12 or higher.

4. The electrolytic cell according to claim 1 or 2, wherein the anion exchange membrane has an ionic conductivity of 1 mS / cm or more.

5. A cathode containing cobalt phthalocyanine that reduces carbon dioxide, A gas channel for supplying carbon dioxide to the cathode, A cathode chamber capable of containing a cathode electrolyte that comes into contact with the cathode, The cathode is paired with an anode, An anode chamber capable of containing an anode electrolyte that comes into contact with the anode, The system comprises an anion exchange membrane for separating the cathode electrolyte and the anode electrolyte, The anion exchange membrane is an electrolytic cell for carbon dioxide, having an ionic conductivity of 1 mS / cm or more.

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