Ion-conducting membrane, method for manufacturing the same, cell containing the membrane, and plant containing the cell.

Abstract

The present invention relates to an ion-conducting membrane for an electrochemical device, comprising a layer of a material containing ceramic, the ceramic comprising boron carbide (B4C). The present invention also relates to a method for producing the membrane and a cell for the electrochemical device. Application to electrolysis of water.

Description

Technical Field

[0001] The present invention relates to ion-conducting membranes, especially those used in electrolytic cells, but not only those.

Background Art

[0002] Document D1 = FR2916906 describes various types of ceramic-based membranes, especially membranes containing boron nitride. When used in the electrolysis of water, such membranes are involved in the activation of chemical reactions and make it possible to obtain purer hydrogen and oxygen gases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention provides a novel membrane having improved ion-conducting properties and improved chemical, mechanical and conducting properties as compared to the membranes described in document D1.

Means for Solving the Problems

[0005] More specifically, the present invention proposes an ion-conducting membrane for an electrochemical device, the membrane comprising a layer of a material containing a ceramic, characterized in that the ceramic contains boron carbide (B4C).

[0006] Boron carbide is a ceramic with multipolar molecular bonds, making it possible to manufacture films with good conductivity. Films containing boron carbide exhibit relatively high chemical resistance, particularly in basic media. Film durability is improved, achieving a service life of 4-5 years, in corrosive media (e.g., potassium hydroxide), and especially in alkaline media, meeting current requirements for water electrolysis applications. Furthermore, in water electrolysis applications using boron carbide films, the phenomenon of H2 gas dissolved in water passing through the film (known as "crossover") is less pronounced than with known films, resulting in the acquisition of higher purity gas.

[0007] The materials of the present invention preferably include the following: - Ceramic powder containing boron carbide in an amount of 60% to 95% by weight, and Polymer binders ranging from -5% by weight to 40% by weight.

[0008] The polymer binder provides bonding between the particles of the ceramic powder. The binder also allows for the creation of a film that is impermeable to gases, particularly hydrogen. The "crossover" phenomenon is further attenuated.

[0009] The present invention also relates to a method for producing the above-described membrane and an electrochemical cell containing the membrane.

[0010] Finally, the present invention relates to a water electrolysis plant comprising at least one electrochemical cell as described above. [Brief explanation of the drawing]

[0011] By describing embodiments of the present invention below, the present invention can be better understood and other features and advantages of the present invention can be revealed. These embodiments are not limited. The description should be read with reference to the accompanying drawings. The accompanying drawings depict the following:

[0012] [Figure 1] This shows a cell suitable for water electrolysis applications. [Figure 2] This shows a simplified diagram of a water electrolysis apparatus. [Modes for carrying out the invention]

[0013] As described above, the present invention relates to an ion-conducting film for electrochemical devices, characterized in that it comprises a layer of material containing a ceramic, wherein the ceramic contains boron carbide (B4C).

[0014] The aforementioned material preferably includes the following: - Ceramic powder containing boron carbide in an amount of 60% to 95% by weight, and Polymer binders ranging from -5% by weight to 40% by weight.

[0015] The ceramic powder may be pure boron carbide powder. The ceramic powder may also be a mixture of boron carbide powder and boron nitride powder. The presence of boron nitride improves the film manufacturing process because boron nitride has a greater affinity for bonding with polymer binders. Furthermore, boron nitride is a dry lubricant that can make the film easier to use and provide greater mechanical flexibility. However, to maintain the chemical properties and performance of the boron carbide film over time, the amount of boron nitride must be limited. Therefore, for films manufactured from powder mixtures, the most effective film was obtained when the amount of boron carbide was greater by weight than the amount of boron nitride.

[0016] The polymer binders used are as follows: -Polytetrafluoroethylene (PTFE), or Polyethersulfone (PES), or Polyethersulfone derivatives such as sulfonated polyethersulfone (SPES), aminochlorinated polyethersulfone (PES-Cl-NH2), or A mixture of polytetrafluoroethylene (PTFE), polyethersulfone (PES), and / or polyethersulfone derivatives.

[0017] For PTFE (polytetrafluoroethylene)-type polymer binders, the best results were obtained with binder amounts of 5% to 25% by weight (of the finished product). PTFE was selected due to its exceptional resistance to strong oxidizing agents such as pure oxygen under pressure.

[0018] For polymer binders of the polyethersulfone (PES) type, polymer binders of the polyethersulfone derivative type such as sulfonated polyethersulfone (SPES) or aminated chlorinated polyethersulfone (PES-Cl-NH2), or polymer mixtures containing polytetrafluoroethylene (PTFE), polyethersulfone (PES) and / or polyethersulfone derivatives, the best results were obtained with binder amounts of 15% to 40% by weight (of the finished material). PES and its derivatives were selected for their better compatibility with large-scale membrane manufacturing processes. To produce a membrane as described above, the process according to the invention essentially comprises the following steps: - Activating by dispersing a large amount of ceramic powder in a basic solution, such as a solution of potassium hydroxide KOH; - Adding a binder polymer in an amount from 5% to 40% by weight to the solution.

[0019] During the activation step, the solution is stirred for 1 hour to 24 hours. The activation step by immersion in a basic solution makes it possible to remove contaminant molecular bonds on the pendant bonds of the molecules of the ceramic powder particles. The use of a basic medium makes it possible to obtain a more chemically resistant membrane, and thus to have a longer service life for membranes that more easily meet the current resistance requirements for 4 to 5 years in corrosive media for applications such as water hydrolysis.

[0020] The addition of the binder polymer makes it possible to bind the powder particles to form a membrane without open pores that are impermeable to H2 gas dissolved in the electrolyte water.

[0021] Depending on the polymer binder used and the amount of binder used, the polymer binder can be mixed by stirring for a period ranging from several minutes to several hours. Also, in order to facilitate mixing, it can be mixed under a temperature-controlled atmosphere of about 40°C to 60°C.

[0022] Also, the process can include a step of shaping the mixture.

[0023] According to one embodiment, particularly in the case of a mixture containing PES, the shaping process can include a step of casting the mixture onto a support, such as a glass plate. If necessary to facilitate casting, before the casting step, it can include a step of adjusting the viscosity of the mixture and adding a solvent such as water or ethanol to make the mixture liquid enough to be castable. Then, after the shaping process, the solvent may be removed followed by a drying process (crosslinking) to form the polymer network. This embodiment is particularly suitable for large-scale membrane production.

[0024] According to another embodiment, particularly in the case of a mixture containing PTFE, the shaping process includes one or more lamination steps, and each lamination step includes a rolling step and a folding step that are performed continuously. The lamination step enables the long carbon chains of the PTFE polymer binder to be folded and connected to form a network in which ceramic powder particles are trapped. Depending on the viscosity of the mixture, the lamination step can be preceded by a filtration step and / or a drying step to obtain a paste that is flexible but not liquid.

[0025] According to yet another embodiment, the process of shaping the mixture can include a step of hot-extruding the mixture at a temperature on the order of 120°C to 180°C, preferably 150°C. If necessary, a lamination step can follow the extrusion step.

[0026] Finally, when a particularly flat membrane is desired, the process can include a final rolling step.

[0027] For example, membranes used in water electrolysis plants typically have a thickness on the order of 0.2 mm to 0.4 mm.

[0028] The membrane according to the present invention described above can be used in particular to manufacture an electrochemical cell comprising the following: - Anode 30 - Cathode 20, and - Between the anode and the cathode is a film 10 as described above.

[0029] Figure 1 shows a diagram of a known cell in a water electrolysis plant for producing gaseous hydrogen (H2) and oxygen (O2). Figure 2 shows a diagram of the principle of a membrane water electrolysis plant. A membrane 10 divides a tank containing a mixture of water and electrolyte into two sections, with a cathode 20 and an anode 30 positioned on opposite sides of the membrane and connected to the negative and positive terminals of a power supply, respectively. The membrane 10 allows for good separation of hydrogen gas produced at the cathode and oxygen gas produced at the anode. The cathode and anode, particularly on the anode side, are metals, such as nickel, stainless steel, or metal oxides. Nickel and stainless steel form oxides on their surfaces, which act as catalysts for the release of oxygen. 316L stainless steel is particularly effective due to its molybdenum content.

[0030] Furthermore, to improve the chemical reaction, catalyst layers 40 and 50 may be deposited on both sides of the film, between the cathode and the film on one side, and between the anode and the film on the other side. Additionally, the catalyst layer may be deposited on the anode and / or cathode. The catalyst layer may contain nickel powder. Furthermore, the catalyst material used may differ between the film and the electrodes.

[0031] A single cell is shown in Figure 1. However, in reality, an industrial plant can contain multiple cells, or even around 100 cells.

Claims

1. An ion-conducting membrane (10) for an electrochemical device used in water electrolysis to separate hydrogen gas and oxygen gas, It includes a layer of material containing ceramic that separates hydrogen gas and oxygen gas, A film characterized in that the ceramic contains boron carbide (B4C).

2. The aforementioned material, - Ceramic powder containing 60% to 95% by weight of boron carbide, and The film according to claim 1, comprising -5% to 40% by weight of a polymer binder.

3. The aforementioned ceramic powder - Boron carbide, or - The film according to claim 2, comprising a mixture of boron carbide and boron nitride, wherein the amount of boron carbide is greater by weight than the amount of boron nitride.

4. The polymer binder is - Polytetrafluoroethylene (PTFE) type polymer, or - Polyethersulfone (PES) type polymers, - Polyethersulfone derivative type polymers such as sulfonated polyethersulfone (SPES), aminochlorinated polyethersulfone (PES-Cl-NH2), or - The film according to claim 2 or 3, which is a mixture of polytetrafluoroethylene (PTFE), polyethersulfone (PES), and / or a polyethersulfone derivative.

5. The polymer binder is The film according to claim 4, wherein the film is a polytetrafluoroethylene (PTFE) type polymer in an amount of 5% to 25% by weight.

6. The polymer binder is The film according to claim 4, comprising a polyethersulfone (PES) type polymer, a polyethersulfone derivative type polymer such as sulfonated polyethersulfone (SPES) or aminochlorinated polyethersulfone (PES-Cl-NH2), or a polymer mixture containing polytetrafluoroethylene (PTFE), polyethersulfone (PES) and / or a polyethersulfone derivative, wherein the amount of polymer binder is 15% to 40% by weight.

7. A method for producing an ion-conducting film according to any one of claims 1 to 6, - A process of dispersing and activating ceramic powder containing boron carbide in a basic solution. - A step of adding a polymer binder to a solution to obtain a mixture. - A method including a molding step of molding a mixture.

8. The method according to claim 7, wherein the molding step includes a casting step of casting the mixture onto a support and a drying step.

9. The method according to claim 8, wherein the molding step includes a step of adding a solvent before the casting step.

10. The method according to claim 7, wherein the molding step includes at least one lamination step which includes a rolling step and a folding step performed in succession.

11. The method according to claim 10, wherein the molding step includes a filtration step and / or a drying step for obtaining a paste before the lamination step.

12. The method according to any one of claims 8 to 11, further comprising a final step of rolling the paste.

13. A cell for electrochemical devices, - Anode (30), - Cathode (20), - A cell comprising a membrane (10) according to any one of claims 1 to 6 between the anode and the cathode.

14. A water electrolysis plant comprising at least one cell as described in claim 13.

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