Electrolytic cell

Abstract

To provide an electrolytic cell that has high airtightness to reaction gases and reaction solutions, and excellent long-term reliability. [Solution] The electrolytic cell of the present invention comprises a membrane electrode assembly including a positive electrode, a negative electrode, and an ion-conducting membrane. A reaction gas introduction plate is disposed on the positive electrode side of the membrane electrode assembly, and a reaction liquid introduction plate is disposed on the negative electrode side. The reaction gas introduction plate includes a reaction gas introduction hole in contact with the positive electrode, and the reaction liquid introduction plate includes a reaction liquid introduction hole in contact with the negative electrode. A sealing member is disposed between the reaction gas introduction plate and the reaction liquid introduction plate. The sealing member includes a resin film layer and a rubber layer, and the resin film layer and the rubber layer are laminated together.

Description

[Technical Field]

[0001] This application relates to an electrolytic cell that has excellent airtightness to reaction gases and reaction solutions. [Background technology]

[0002] In recent years, the concentration of carbon dioxide in the atmosphere has risen sharply due to the use of fossil fuels such as oil and coal. Therefore, expectations for renewable energy sources, which do not emit carbon dioxide, are increasing. Examples of renewable energy sources include solar cells and wind power, but because their power generation depends on weather and natural conditions, a stable supply of electricity is difficult to guarantee.

[0003] In this situation, a technology is being considered that uses electricity generated from renewable energy sources to electrochemically reduce carbon dioxide (CO2) and convert it into carbon compounds such as carbon monoxide (CO), methane (CH4), and ethylene (C2H4), which are then stored and used as fuel for power generation when electricity supply becomes tight.

[0004] Various electrolytic cells for carbon dioxide used in the above technology have been proposed (e.g., Patent Documents 1-4). For example, an electrolytic cell comprises a membrane electrode assembly having a positive electrode that reduces carbon dioxide to produce a carbon compound, a negative electrode that oxidizes an aqueous solution containing an electrolyte to produce oxygen, and an ion-conducting membrane disposed between the positive electrode and the negative electrode. Furthermore, the positive electrode is positioned in contact with a reaction gas containing carbon dioxide, and the negative electrode is positioned in contact with a reaction solution consisting of an aqueous solution. For this reason, the electrolytic cell requires high airtightness to prevent leakage of the reaction gas and the reaction solution.

[0005] Conventionally, in order to ensure the airtightness of the electrolytic cell, a sealing member made of an insulating material such as rubber or resin was placed around the membrane electrode assembly. However, conventional sealing members made of rubber had the problem of low thickness accuracy and low strength. On the other hand, sealing members made of resin had the problem of low flexibility and poor adhesion, although they had high strength and excellent durability.

[0006] To solve the above problem, it is conceivable to use a sealing member made of rubber-based material and a sealing member made of resin-based material in combination. However, simply combining rubber-based material and resin-based material to form a sealing member makes it difficult to improve the thickness accuracy, strength, and adhesion of the sealing member.

[0007] Furthermore, Non-Patent Document 1 is a prior art document related to this application. Non-Patent Document 1 discloses high-speed bonding between polymer materials by homogeneous electron beam irradiation. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2019-157252 [Patent Document 2] Japanese Patent Publication No. 2020-045509 [Patent Document 3] Japanese Patent Publication No. 2021-063267 [Patent Document 4] Japanese Patent Publication No. 2021-063292 [Non-patent literature]

[0009] [Non-Patent Document 1] "High-speed bonding between polymer materials by homogeneous electron beam irradiation," Journal of the Japan Institute of Metals, Vol. 72, No. 7 (2008) 526-531. [Overview of the project] [Problems that the invention aims to solve]

[0010] The problem to be solved by the present application is to provide an electrolytic cell having high airtightness with respect to reaction gases and reaction liquids and excellent long-term reliability.

Means for Solving the Problem

[0011] The electrolytic cell of the present application includes a positive electrode for reducing a reaction gas, a negative electrode for oxidizing a reaction liquid, and an ion conductive membrane disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the ion conductive membrane constitute a membrane electrode assembly. A reaction gas introduction plate is disposed on the positive electrode side of the membrane electrode assembly, and a reaction liquid introduction plate is disposed on the negative electrode side of the membrane electrode assembly. The reaction gas introduction plate includes a reaction gas introduction hole that contacts the positive electrode, and the reaction liquid introduction plate includes a reaction liquid introduction hole that contacts the negative electrode. A seal member is disposed between the reaction gas introduction plate and the reaction liquid introduction plate. The membrane electrode assembly and the seal member are sandwiched between the reaction gas introduction plate and the reaction liquid introduction plate. The seal member seals at least the outer peripheral portions of the positive electrode and the negative electrode of the membrane electrode assembly. The seal member includes a resin film layer and a rubber layer, and the resin film layer and the rubber layer are laminated.

Advantages of the Invention

[0012] According to the present application, it is possible to provide an electrolytic cell having high airtightness with respect to reaction gases and reaction liquids and excellent long-term reliability, using a seal member having high thickness accuracy, excellent strength, and excellent adhesion.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an overview of an electrolytic cell. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of an electrolytic cell according to an embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an example of a seal member according to an embodiment.

Mode for Carrying Out the Invention

[0014] An embodiment of the electrolytic cell of the present invention will now be described. The electrolytic cell of this embodiment comprises a positive electrode for reducing a reaction gas, a negative electrode for oxidizing a reaction solution, and an ion-conducting membrane disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the ion-conducting membrane constitute a membrane electrode assembly. A reaction gas introduction plate is disposed on the positive electrode side of the membrane electrode assembly, and a reaction solution introduction plate is disposed on the negative electrode side of the membrane electrode assembly. The reaction gas introduction plate includes a reaction gas introduction hole in contact with the positive electrode, and the reaction solution introduction plate includes a reaction solution introduction hole in contact with the negative electrode. A sealing member is disposed between the reaction gas introduction plate and the reaction solution introduction plate. The membrane electrode assembly and the sealing member are sandwiched between the reaction gas introduction plate and the reaction solution introduction plate. The sealing member seals at least the outer periphery of the positive electrode and the outer periphery of the negative electrode of the membrane electrode assembly. The sealing member comprises a resin film layer and a rubber layer, and the resin film layer and the rubber layer are laminated together.

[0015] The sealing member used in the electrolytic cell of this embodiment can be made into a thin film, has high thickness accuracy, and exhibits excellent gas barrier properties and leakage resistance. Furthermore, the sealing member includes a resin film layer and a rubber layer, and since the resin film layer and the rubber layer are laminated and bonded together, it has high strength, durability, flexibility, and excellent adhesion. Therefore, by using this sealing member, an electrolytic cell with high airtightness to reaction gases and reaction liquids and excellent long-term reliability can be realized.

[0016] The electrolytic cell of this embodiment will be described below, but first, an overview of the electrolytic cell for electrolyzing carbon dioxide will be described based on the drawings.

[0017] <Overview of electrolytic cells> FIG. 1 is a schematic diagram for explaining the outline of an electrolytic cell. In FIG. 1, a membrane electrode assembly 10 of the electrolytic cell includes a proton conductive membrane 11, a negative electrode 12 disposed on one main surface of the proton conductive membrane 11, and a positive electrode 13 disposed on the other main surface of the proton conductive membrane 11. The outside of the negative electrode 12 is in contact with an aqueous solution (electrolyte solution) 14 containing an electrolyte. Also, the outside of the positive electrode 13 is in contact with a reaction gas 15 containing carbon dioxide.

[0018] In FIG. 1, when a current is supplied between the negative electrode 12 and the positive electrode 13, at the negative electrode 12, 2H2O → 4H + + O2 + 4e - The oxidation reaction of water (H2O) occurs, generating protons H + and electrons e - This proton H + moves through the proton conductive membrane 11 to the positive electrode 13. On the other hand, at the positive electrode 13, due to the protons H + and electrons e - from the negative electrode 12, the following reduction reaction of carbon dioxide (CO2) occurs, generating carbon compounds 16 such as carbon monoxide (CO), methane (CH4), and ethylene (C2H4).

[0019] 2CO2 + 4H + + 4e - → 2CO + 2H2O CO + 6H + + 6e - → CH4 + H2O 2CO + 8H + + 8e - → C2H4 + 2H2O

[0020] Thus, in the electrolytic cell, carbon dioxide (CO2) is electrochemically reduced and converted into carbon compounds such as carbon monoxide (CO), methane (CH4), and ethylene (C2H4), and the carbon compounds can be used as fuel for power generation.

[0021] <The electrolytic cell of the present embodiment> Next, embodiments of the electrolytic cell of the present application will be described with reference to the drawings. Figure 2 is a schematic cross-sectional view showing an example of a carbon dioxide electrolytic cell of this embodiment. In Figure 2, the electrolytic cell 30 includes a membrane electrode assembly 31, which is composed of a positive electrode 21, a negative electrode 22, and an ion-conducting membrane 23.

[0022] The positive electrode 21 comprises a gas diffusion layer 21a and a catalyst layer 21b. The negative electrode 22 comprises a liquid diffusion layer 22a and a catalyst layer 22b, but the negative electrode 22 may consist only of the catalyst layer 22b.

[0023] A reaction gas introduction plate 24 is positioned on the positive electrode 21 side of the film electrode assembly 31. The reaction gas introduction plate 24 is provided with a reaction gas introduction hole 24a for taking in reaction gas (gas containing carbon dioxide), and the reaction gas introduction hole 24a is in contact with the positive electrode 21. The reaction gas introduction plate 24 is made of a conductive material and functions as a positive electrode current collector plate, so a lead body 24b is connected to the reaction gas introduction plate 24. In addition, a reaction gas introduction section 26 is provided on the outside of the reaction gas introduction plate 24. The reaction gas introduction section 26 includes a reaction gas inlet 26a and a reaction gas outlet 26b.

[0024] Furthermore, a reaction solution introduction plate 25 is positioned on the negative electrode 22 side of the membrane electrode assembly 31. The reaction solution introduction plate 25 is provided with a reaction solution introduction hole 25a for taking in the reaction solution (aqueous solution containing an electrolyte), and the reaction solution introduction hole 25a is in contact with the negative electrode 22. The reaction solution introduction plate 25 is made of a conductive material and functions as a negative electrode current collector, so a lead body 25b is connected to the reaction solution introduction plate 25. In addition, a reaction solution container 27 is provided on the outside of the reaction solution introduction plate 25 and is filled with the reaction solution (electrolyte) 28.

[0025] A sealing member 29 is positioned between the reaction gas introduction plate 24 and the reaction liquid introduction plate 25, and the membrane electrode assembly 31 and the sealing member 29 are sandwiched between the reaction gas introduction plate 24 and the reaction liquid introduction plate 25. The sealing member 29 seals at least the outer periphery of the positive electrode 21 and the outer periphery of the negative electrode 22 of the membrane electrode assembly 31.

[0026] In the membrane electrode assembly 31, the area of ​​the main surface of the ion-conducting membrane 23 is formed to be larger than the area of ​​the main surfaces of the positive electrode 21 and the negative electrode 22, and the ion-conducting membrane 23 has an overhang portion 23a that extends beyond the main surfaces of the positive electrode 21 and the negative electrode 22. As a result, a sealing member 29 is placed between the overhang portion 23a and the reaction gas introduction plate 24, and between the overhang portion 23a and the reaction liquid introduction plate 25, and the sealing member 29 sandwiches the overhang portion 23a of the ion-conducting membrane 23 from both sides. Therefore, the sealing member 29 can more reliably seal the outer periphery of the positive electrode 21 and the outer periphery of the negative electrode 22 of the membrane electrode assembly 31.

[0027] In this embodiment, an example is shown in which the area of ​​the main surface of the ion-conducting film 23 is formed to be larger than the area of ​​the main surfaces of the positive electrode 21 and the negative electrode 22. However, the ion-conducting film 23 can also be formed to be the same size as the area of ​​the main surfaces of the positive electrode 21 and the negative electrode 22 without having an overhang portion 23a. In this case, the sealing member can be formed as a single sealing member by integrating the upper and lower sealing members 29 shown in Figure 2. As a result, the integrated sealing member can seal the outer periphery of the positive electrode 21, the outer periphery of the negative electrode 22, and the outer periphery of the ion-conducting film 23 of the film electrode assembly 31.

[0028] The following describes in detail each component of the electrolytic cell 30.

[0029] <Sealing material> Figure 3 is a schematic cross-sectional view showing an example of a sealing member of this embodiment. In Figure 3, the sealing member 29 is composed of a resin film layer 29a and rubber layers 29b, 29b laminated on both sides of the resin film layer 29a. A through hole 29c is formed in the center of the sealing member 29 to house and seal the electrode portion of the membrane electrode assembly. The shape of the sealing member 29 in plan view is not particularly limited, but for example, it is formed in a rectangular shape to match the outer shape of the membrane electrode assembly.

[0030] The sealing member 29 has a three-layer structure consisting of a resin film layer 29a and rubber layers 29b, 29b arranged on both sides of the resin film layer 29a, and the rubber layers arranged on both sides provide high sealing performance.

[0031] As the material for the resin film layer 29a, for example, polyester resins (polyethylene terephthalate: PET, polyethylene naphthalate: PEN, polybutylene terephthalate: PBT, polybutylene naphthalate: PBN, etc.), polyolefin resins (polyethylene, polypropylene, etc.), polyimide resins, polyamide resins, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, polyurethane resins, polyetherketone resins, polyether resins (polyetherimide: PEI, etc.), polyethersulfone resins, polystyrene resins (polystyrene, etc.), polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl alcohol resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymers, polycarbonate resins, fluororesins, and crosslinked versions of these resins can be used. Among these, polyester resins are more preferred because they have excellent mechanical properties such as strength and durability, as well as excellent moldability. Furthermore, the above resin material may have functional groups as needed. Functional monomers or modifier monomers may also be grafted onto the resin material.

[0032] As the material for the rubber layer 29b, for example, chloroprene rubber (CR), isoprene rubber (IR), butyl rubber (IIR), nitrile-butadiene rubber (NBR), natural rubber, styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), urethane rubber, fluororubber, acrylic rubber, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), urethane rubber, silicone rubber, etc. can be used. Among these, ethylene-propylene rubbers such as EPM and EPDM, and silicone rubber are more preferred because they have excellent adhesion. The rubber layers 29b, 29b arranged on both sides of the resin film layer 29a may be formed from the same material or from different materials. Furthermore, it is preferable that the above rubber material does not contain additives such as crosslinking agents or plasticizers. This prevents the elution of impurities from the rubber layer and suppresses side reactions with electrolytic reaction products and electrolyte.

[0033] Furthermore, in the sealing member 29, it is preferable that the resin film layer 29a and the rubber layer 29b are composited at their interface. By compositing, the strength of the sealing member can be improved compared to the case where only lamination is performed. The tensile strength of the sealing member is preferably 10 MPa or more, and more preferably 20 MPa or more. In addition, by using a composite material for the resin film layer 29a and the rubber layer 29b, a sealing member with less expansion and contraction in the planar direction and excellent dimensional stability can be realized. As for the method of measuring the above tensile strength, a measurement method in accordance with JIS K-6251 can be mentioned.

[0034] Furthermore, it is preferable that the composite formation is carried out by an activation treatment at the interface between the resin film layer and the rubber layer by electron beam irradiation. This allows the resin film layer 29a and the rubber layer 29b to be joined without the use of an adhesive, so that even during the electrolytic reaction when the electrolytic cell is operated, the elution of impurities from the sealing member is reduced, and side reactions with the electrolytic reaction products and electrolyte can be suppressed. The conditions for composite formation of the resin film layer and the rubber layer by electron beam irradiation are not particularly limited, but for example, electron beam irradiation using an electron beam irradiation device can be performed with an acceleration voltage of 200 to 700 kV and an irradiation dose of 15 to 60 Mrad.

[0035] The width W of the sealing member 29 is preferably 1 mm or more in order to ensure high airtightness to the reaction gas and reaction liquid. On the other hand, if the width W is too large, the ratio of the area of ​​the sealing member 29 to the limited area of ​​the ion conductive film 23 becomes large, and the area of ​​the electrode is sacrificed. Therefore, the width W is preferably 50 mm or less, and more preferably 20 mm or less.

[0036] The thickness T of the sealing member 29 is not particularly limited and can be adjusted according to the thickness of the electrode. For example, if the electrode thickness is 200 to 300 μm, the thickness is set to 100 to 400 μm. On the other hand, it is preferable that the tolerance of the thickness T of the sealing member 29 be within ±10%. This is because if the tolerance of the thickness T exceeds ±10%, the airtightness to the reaction gas and reaction liquid will decrease. The thickness T of the sealing member is measured using a digital micrometer, and the tolerance of the thickness T is calculated from the measured values ​​obtained by measuring the thickness of the sealing member at 10 points.

[0037] Next, the manufacturing method of the sealing member 29 will be described. First, one resin film which will become the resin film layer 29a and a rubber coating which will become the rubber layer 29b are prepared. Next, the rubber coating is applied to one side of the resin film and irradiated with an electron beam using an electron beam irradiation device to composite and bond the resin film and the rubber layer at their interface. After that, the same process is performed on the opposite side of the resin film to create a three-layer composite film in which rubber layers are composited on both sides of the resin film. Finally, the film is cut to the size of the electrolytic cell and through holes 29c are formed by punching, thereby producing the sealing member 29 shown in Figure 3.

[0038] <Positive electrode> The positive electrode 21 functions as a reducing electrode that reduces carbon dioxide in the reaction gas to produce reduction products (carbon compounds), and comprises a gas diffusion layer 21a and a catalyst layer 21b. The gas diffusion layer 21a can be made of a porous electronically conductive material, such as a porous carbon sheet that has been treated with a water-repellent coating.

[0039] The catalyst layer 21b can be formed from a catalyst material and a binder. As catalyst materials used in the positive electrode catalyst layer, for example, metal nanoparticles such as copper (Cu), tin (Sn), manganese (Mn), iron (Fe), nickel (Ni), titanium (Ti), cobalt (Co), zinc (Zn), indium (In), molybdenum (Mo), tungsten (W), yttrium (Y), zirconium (Zr), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), platinum (Pt), cerium (Ce), iridium (Ir), and bismuth (Bi) can be used, but in the case of a carbon dioxide electrolytic cell, Cu nanoparticles are particularly preferred. This is because using Cu nanoparticles as the positive electrode catalyst material allows for the reduction of carbon dioxide to hydrocarbon-based carbon compounds such as methane and ethylene.

[0040] The particle size of the metal nanoparticles used in the positive electrode catalyst material is preferably 1 to 500 nm in order to enhance catalytic activity. Furthermore, the positive electrode catalyst material can also be used by being supported on the surface of a conductive material, similar to the negative electrode catalyst material described later.

[0041] As the binder mentioned above, proton-conducting organic materials such as polyperfluorocarbon sulfonic acid, polystyrene, polyether ketone, polyether ether ketone, polysulfone, and polyether sulfone can be used, but polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, and polyimide can also be used.

[0042] The binder content in the positive electrode catalyst layer should be 2 to 100 parts by mass per 100 parts by mass of the positive electrode catalyst material.

[0043] The catalyst layer 21b can be formed by preparing a catalyst coating containing the catalyst material, the binder, and the solvent, applying this catalyst coating to the gas diffusion layer 21a, and then drying and removing the solvent.

[0044] <Negative electrode> The negative electrode 22 functions as an oxidizing electrode that oxidizes the reaction solution (electrolyte) to produce oxidation products (oxygen), and comprises a liquid diffusion layer 22a and a catalyst layer 22b, although the negative electrode 22 may consist only of the catalyst layer 22b. The liquid diffusion layer 22a can be made of a porous electronically conductive material, such as a porous carbon sheet that has been treated with a water-repellent coating.

[0045] The catalyst layer 22b can be formed from a catalyst material, a conductive material, and a binder. As the catalyst material used for the negative electrode catalyst layer, for example, metal nanoparticles such as platinum (Pt) and palladium (Pd) can be used.

[0046] The conductive material is not particularly limited, but considering electronic conductivity, electrochemical stability, etc., carbon material powders with a high surface area such as carbon black, activated carbon, carbon nanohorns, and carbon nanotubes are preferred.

[0047] The particle size of the metal nanoparticles used in the negative electrode catalyst material is preferably 1 to 50 nm in order to enhance catalytic activity. Furthermore, it is preferable that the negative electrode catalyst material is supported on the surface of the conductive material powder, as this improves the electronic conductivity of the negative electrode catalyst material. The content of the negative electrode catalyst material in the conductive material on which the negative electrode catalyst material is supported is not particularly limited, but for example, it can be 10 to 500 parts by mass per 100 parts by mass of the conductive material.

[0048] The same binder used in the positive electrode catalyst layer can be used as the binder mentioned above. Furthermore, the binder content in the negative electrode catalyst layer should be 2 to 100 parts by mass per 100 parts by mass of the negative electrode catalyst material.

[0049] The negative electrode catalyst layer can be formed by preparing a catalyst coating containing a support in which the catalyst material is supported on the conductive material, the binder, and a solvent, applying this catalyst coating to the negative electrode diffusion layer, or, if a negative electrode diffusion layer is not provided, applying this catalyst coating directly to the ion-conductive film 23, and then removing the solvent.

[0050] <Ion-conducting film> As the ion-conducting membrane 23, a cation exchange membrane can be used. The cation exchange membrane preferably contains a proton-conducting organic material such as polyperfluorocarbon sulfonic acid, polystyrene, polyether ketone, polyether ether ketone, polysulfone, or polyether sulfone. This is because the material stability of these organic materials can be enhanced by creating a cross-linked structure or by partial fluorination. In particular, as the proton-conducting organic material, polyperfluorocarbon sulfonic acid, which exhibits good proton conductivity in a wet state, is preferred.

[0051] Anion exchange membranes can also be used as ion-conducting membranes. Anion exchange membranes, for example, are made of anions (OH -It can be formed using hydrotalcite or other materials with selective permeability. Furthermore, as anion exchange membranes, a membrane can be used in which a polymer is used as the matrix and metal compound particles are dispersed within that matrix.

[0052] <Electrolyte> As the electrolyte 28, an aqueous solution containing an electrolyte is used, and as the electrolyte, for example, hydroxide ions (OH) - ), hydrogen ions (H + ), potassium ions (K + ), sodium ions (Na + ), chloride ions (Cl - ), bromide ions (Br - ), iodide ion (I - ), nitrate ion (NO3 - ), sulfate ions (SO4 2- ), phosphate ion (PO4 2- ), bicarbonate ions (HCO3) - ), carbonate ions (CO3 2- Examples include the following. Typically, a weakly alkaline aqueous solution such as potassium bicarbonate is used as the electrolyte 28. This is because a weakly alkaline aqueous solution has little corrosive effect on the components of the electrolytic cell.

[0053] <Reaction gas introduction plate and reaction liquid introduction plate> As described above, the reaction gas introduction plate 24 and the reaction liquid introduction plate 25 also serve as current collector plates, and their material is, for example, a precious metal such as platinum or gold, a corrosion-resistant metal such as stainless steel, or a conductive material such as carbon material. Furthermore, these materials may be plated or painted on the surface to improve corrosion resistance. [Examples]

[0054] The present application will be described below with reference to examples, but the present application is not limited to the following examples.

[0055] (Example 1) <Fabrication of sealing components for electrolytic cells> A 0.1 mm thick, 300 mm square PEN film was coated with a 0.1 mm thick silicone rubber coating on one side. Electron beam irradiation (acceleration voltage: 200 kV, irradiation dose: 15 Mrad) was performed using an electron beam irradiation device to bond the PEN film and the silicone rubber layer at their interface. The same process was then performed on the opposite side of the PEN film to create a three-layer composite film with silicone rubber layers on both sides of the PEN film. Finally, the composite film was cut into 70 mm squares, and a 30 mm square through-hole was formed in the center by punching to create the electrolytic cell sealing member of Example 1.

[0056] (Example 2) The electrolytic cell sealing member for Example 2 was manufactured in the same manner as in Example 1, except that a two-layer composite film was used, in which a silicone rubber coating was applied to one side of a 0.1 mm thick, 300 mm square PEN film to a thickness of 0.2 mm, and the silicone rubber layer was compounded on only one side of the PEN film.

[0057] (Comparative Example 1) A sealing member for an electrolytic cell of Comparative Example 1 was manufactured in the same manner as in Example 1, except that a single layer sheet consisting of one 0.3 mm thick, 300 mm square silicone rubber sheet was used instead of a PEN film.

[0058] Using the sealing members from Examples 1 and 2 and Comparative Example 1 prepared above, electrolytic cells as shown in Figure 2 were assembled, and the following characteristics were evaluated.

[0059] <Reaction gas leak rate> CO2 gas was introduced as the reaction gas at a rate of 80 ml / min into each assembled electrolytic cell. The flow rate at the gas inlet and the gas outlet were measured using a flow meter, and the leak rate was calculated using the following formula. A lower leak rate indicates a more effective sealing material. Leak rate (%) = [(Inlet flow rate - Outlet flow rate) / Inlet flow rate] × 100

[0060] <Deformation rate of sealing material> The thickness of the sealing material before it was incorporated into the electrolytic cell was measured using a digital micrometer. Furthermore, after incorporating it into the electrolytic cell, the sealing material was tightened with a torque wrench at a pressure of 4N in the stacking direction of the electrolytic cell, and its compressed thickness was measured using calipers. Next, the deformation rate of the sealing material was calculated using the following formula. Deformation rate (%) = [(Thickness before assembly - Thickness after compression) / Thickness before assembly] × 100

[0061] Since the electrolytic cell described above uses two sealing members, the average value of the deformation rates of each sealing member was used as the deformation rate.

[0062] It is clear that a lower deformation rate of the sealing member is advantageous for the design of the electrolytic cell. Specifically, since the sealing member is usually placed around the electrode, as shown in Figure 2, to improve the airtightness of the electrolytic cell, the thickness of the sealing member is designed to match the thickness of the electrode. Therefore, when the sealing member is assembled into the electrolytic cell and fastened, if the deformation rate of the sealing member is large, the thickness of the sealing member will decrease, which will compress the electrode more, potentially changing the electrode characteristics or causing the electrode to crack. For this reason, a lower deformation rate of the sealing member is advantageous in the design of the electrolytic cell.

[0063] <Durability of sealing material> The sealing member was assembled into an electrolytic cell, tightened with a pressure of 4N, and then removed from the electrolytic cell. This process was repeated 50 times, after which the appearance of the sealing member was observed, and its durability was evaluated according to the following criteria. Evaluation A: No stretching or cracking occurred in either of the two sealing materials. Rating B: If stretching or cracking occurs in one or both of the two sealing materials.

[0064] The results are shown in Table 1.

[0065] [Table 1]

[0066] As shown in Table 1, the sealing member of Example 1 received high marks in terms of leak rate, deformation rate, and durability. The sealing member of Example 2, which had a two-layer structure of PEN film and silicone rubber layer, exhibited excellent deformation rate and durability, but inferior leak rate. On the other hand, the sealing member of Comparative Example 1, which did not use PEN film, had a low leak rate due to the action of the silicone rubber sheet, but despite having the same thickness as Example 1, its deformation rate and durability were inferior. Furthermore, electrolytic testing was confirmed to function without problems under all conditions. [Industrial applicability]

[0067] As described above, the electrolytic cell of this application uses a sealing member with high thickness accuracy, excellent strength and adhesion, and therefore provides an electrolytic cell with high airtightness to reaction gases and reaction liquids, as well as excellent long-term reliability. [Explanation of Symbols]

[0068] 10 Membrane electrode assembly 11 Proton-conducting film 12 Negative electrode 13 Positive electrode 14 Electrolyte 15 Reaction gas 16 Carbon compounds 21 Positive electrode 21a Gas diffusion layer 21b Catalyst layer 22 Negative electrode 22a Liquid diffusion layer 22b Catalyst layer 23 Ion-conducting film 23a Overhang 24 Reaction gas introduction plate 24a Reaction gas introduction port 24b Lead 25 Reaction solution introduction plate 25a Reaction solution introduction port 25b Lead 26 Reaction gas introduction section 27 Reaction solution container 28 Electrolyte 29. Sealing member 29a Resin film layer 29b Rubber layer 29c through hole 30 electrolytic cells 31 Membrane electrode assembly

Claims

1. An electrolytic cell comprising a positive electrode for reducing the reaction gas, a negative electrode for oxidizing the reaction solution, and an ion-conducting membrane disposed between the positive electrode and the negative electrode, The positive electrode, the negative electrode, and the ion-conducting film constitute a film electrode assembly. A reaction gas introduction plate is placed on the positive electrode side of the aforementioned film electrode assembly. A reaction solution introduction plate is placed on the negative electrode side of the aforementioned membrane electrode assembly. The reaction gas introduction plate includes a reaction gas introduction hole in contact with the positive electrode, The reaction liquid introduction plate includes a reaction liquid introduction hole in contact with the negative electrode, A sealing member is placed between the reaction gas introduction plate and the reaction liquid introduction plate. The membrane electrode assembly and the sealing member are sandwiched between the reaction gas introduction plate and the reaction liquid introduction plate. The sealing member seals at least the outer periphery of the positive electrode and the outer periphery of the negative electrode of the film electrode assembly. The sealing member includes a resin film layer and a rubber layer. An electrolytic cell characterized in that the resin film layer and the rubber layer are laminated together.

2. The electrolytic cell according to claim 1, wherein the resin film layer and the rubber layer are composited at their interface.

3. The electrolytic cell according to claim 2, wherein the composite formation is carried out by an activation treatment at the interface between the resin film layer and the rubber layer by electron beam irradiation.

4. The electrolytic cell according to claim 1, wherein the thickness tolerance of the sealing member is within ±10%.

5. The electrolytic cell according to claim 1, wherein the tensile strength of the sealing member is 10 MPa or more.

6. The electrolytic cell according to claim 1, wherein the resin film layer is formed from a polyester resin.

7. The electrolytic cell according to claim 1, wherein the rubber layer is formed from silicone rubber or ethylene-propylene rubber.

8. The electrolytic cell according to claim 1, wherein the sealing member has a three-layer structure in which the rubber layer is arranged on both sides of the resin film layer.

9. In the aforementioned film electrode assembly, the area of ​​the main surface of the ion-conducting film is formed to be larger than the area of ​​the main surfaces of the positive electrode and the negative electrode. The ion-conducting film includes protruding portions that extend beyond the main surfaces of the positive electrode and the negative electrode. The sealing member is positioned between the protruding portion and the reaction gas introduction plate, and between the protruding portion and the reaction liquid introduction plate. The electrolytic cell according to claim 1, wherein the sealing member clamps the protruding portion of the ion-conducting film from both sides.

10. The electrolytic cell according to claim 1, wherein the reaction gas introduction plate and the reaction liquid introduction plate are each formed of a conductive material and function as current collectors.

11. The electrolytic cell according to claim 1, wherein a reaction gas introduction section is arranged on the outside of the reaction gas introduction plate, and a reaction liquid container is arranged on the outside of the reaction liquid introduction plate.

12. The electrolytic cell according to claim 1, wherein the reaction gas comprises carbon dioxide.

13. The electrolytic cell according to claim 1, wherein the reaction solution is an aqueous solution containing an electrolyte.

14. The electrolytic cell according to claim 1, wherein the positive electrode reduces carbon dioxide to produce a carbon compound.

15. The electrolytic cell according to claim 1, wherein the negative electrode oxidizes an aqueous solution containing an electrolyte to produce oxygen.

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