Composite film of polyethersulfone and zirconium oxide particles of formula ZrO2, and its use as an ion-conducting membrane.

Abstract

The invention relates to a composite film of polyethersulfone, poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), and zirconium oxide particles of formula ZrO2, the content of zirconium oxide particles in the composite film being greater than 40% by mass of the composite film. After impregnation with an aqueous solution, the composite film can be used as an ion-conducting membrane, particularly for protons or hydroxide anions, in a fuel cell or electrolyzer.

Description

Title of the invention: Composite film of polyethersulfone and zirconium oxide particles of formula ZrO2, and its use as an ion-conducting membrane.

[0001] The field of the present invention is that of composite films intended to be used as ion-conducting membranes in electrochemical devices such as fuel cells and electrolyzers.

[0002] Numerous composite materials have been proposed for use as ion-conducting membranes in electrochemical devices. These composite materials may consist of polymers in which particles of inorganic materials, such as metal oxides, are dispersed.

[0003] For example, Vermeiren et al. describe in the document "Hydrogen Power: Theoretical and Engineering Solutions, 179-184, 1998", a porous membrane conducting hydroxide anions, known as "Zirfon", prepared from polysulfone and zirconium oxide. The porosity of the membrane results from the use of the phase inversion technique which is precisely described in patent application WO 9315529 and which proves to be quite complex, since it requires the use of several solvents, including a solvent for the polysulfone and a non-solvent for the polysulfone, and that of a porogenous agent, as well as an immersion extraction operation.

[0004] US patent application 20050106469 describes a process for obtaining a composite film that appears less complex, since it comprises a simple step of mixing a solution of a polyarylene bearing sulfonate functionalities and a filler, a coating step, followed by a drying step. The filler is selected from hydrates of metal oxides, phyllosilicates, and hygroscopic inorganic porous compounds such as silica, zeolites, and oxides of titanium, aluminum, zirconium, or yttrium. When the filler is a hygroscopic inorganic porous compound, it is desirable to use no more than 60 parts, preferably no more than 30 parts, per 100 parts of functional polyarylene, in order to preserve the proton transport properties. Despite its apparent simplicity, the process requires the custom synthesis of a polyarylene bearing sulfonate functions, which is not a commercially available product.Furthermore, the prepared membrane is only effective for proton transport.

[0005] The Applicant has discovered a new process for obtaining a composite film intended for use as an ion-conducting membrane. The process does not have the drawbacks of the processes mentioned. Indeed, the elementary operations which The definitions are very simple, particularly with the use of a single solvent, and the raw materials needed to manufacture the film are all commercially available. Furthermore, the new composite film prepared according to the invention can be used, after impregnation with an aqueous solution, as an ion-conducting membrane, in particular for protons or hydroxide anions.

[0006] Thus, a first object of the invention is a composite film of polyethersulfone, poly(oxy-l,4-phenylenesulfonyl-l,4-phenylene), and zirconium oxide particles of formula ZrO2, the content of zirconium oxide particles in the composite film being greater than 40% by mass of the mass of the composite film.

[0007] A second object of the invention is an ion-conducting membrane comprising a composite film according to the invention and impregnated with water or an aqueous solution containing an electrolyte.

[0008] A third object of the invention is a method for preparing a composite film according to the invention.

[0009] A fourth object of the invention is a method for preparing a membrane according to the invention.

[0010] The invention also relates to a fuel cell which includes a membrane according to the invention.

[0011] The invention also relates to an electrolyzer which includes a membrane according to the invention. Detailed description of the invention

[0012] The polymers mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, they may also come from the recycling of materials already used, that is to say, they may be partially or totally derived from a recycling process, or even obtained from raw materials themselves derived from a recycling process.

[0013] The constituent elements of the composite film according to the invention are polyethersulfone and zirconium oxide.

[0014] Polyethersulfone is well known as poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), and its constituent units have the formula (Ci2H8O3S). Polyethersulfone is typically a commercially available product, generally in granular form, for example from BASF, Solvay, Sumitomo, and Goodfellow, under the respective trade names Ultrason® E, Varadel®, and Sumikaexcel®. It is used without prior chemical modification in the preparation process. of the composite film. Polyethersulfone preferably has a weight average molar mass (Mw) greater than 5,000 g / mol and less than 500,000 g / mol, more preferably greater than 10,000 g / mol and less than 200,000 g / mol, and even more preferably greater than 15,000 g / mol and less than 100,000 g / mol.

[0015] The zirconium oxide particles useful for the purposes of the invention have the chemical structure ZrO2. They are generally spherical or nearly spherical. They are typically commercially available products, for example from Sigma-Aldrich, Thermo Fischer Chemicals, or Saint-Gobain (ZirPro®) under the trade names "ZirPro CC", "ZirPro CS", "ZirPro CZE", or from Inframat under the trade names "40R-0803CF", "40R-0801", "40R-0802". They are present in the composite film at a concentration greater than 40% by mass of the composite film and preferably at a concentration less than 95% by mass of the composite film. Advantageously, the content of zirconium oxide particles in the composite film is greater than 50% by mass of the mass of the composite film and less than 95% by mass of the mass of the composite film.Preferably, the zirconium oxide particles have a median volume size, D50, of less than 10 pm. Preferably also, the zirconium oxide particles have a median volume size, D50, greater than or equal to 1 pm.

[0016] Preferably, the composite film has a thickness of 15 pm to 200 pm. These dimensions are particularly advantageous for use of the composite film in a conductive membrane for ions, protons or hydroxide anions, in an electrochemical device such as a fuel cell or an electrolyzer.

[0017] The composite film is typically a non-porous film.

[0018] Preferably, the polyethersulfone constituting the composite film according to the invention is not cross-linked.

[0019] Most preferably, the composite film is a non-porous film in which the polyethersulfone is not cross-linked.

[0020] The composite film is typically prepared by mixing polyethersulfone and zirconium oxide particles. The mixing can be carried out according to a first variant in the absence of solvent by melting or according to a second variant in the presence of solvent.

[0021] According to the first embodiment, the process for preparing the composite film comprises a mixing operation of polyethersulfone and zirconium oxide particles in a screw conveyor, followed by extrusion of the mixture. The mixing temperature in the screw conveyor can vary from 250°C to 350°C.

[0022] According to the second variant, the process for preparing the composite film comprises the following steps a) to f): - a) Dissolve the polyethersulfone in dimethyl sulfoxide, DMSO, to form a solution, - b) add the zirconium oxide particles to the solution to obtain a suspension, - c) shake the suspension, - d) deposit the suspension onto a support to form a layer, - e) dry the layer on the support to obtain the composite film, - f) peel the composite film from the support.

[0023] The support typically takes the form of a plate with a surface onto which a layer of the suspension is deposited. The dimensions of this surface are chosen by those skilled in the art, generally according to the desired dimensions of the composite film. They may be comparable to the desired dimensions of the composite film or, alternatively, larger, in which case the step of peeling the composite film from the support may be followed by cutting to obtain the composite film to the desired dimensions. The support may be made of an organic material such as PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), or an inorganic material, particularly a metallic one such as aluminum, stainless steel, preferably aluminum.

[0024] In step a), the concentration of the polyethersulfone solution in the DMSO is adjusted by a person skilled in the art so that the suspension formed by mixing the polyethersulfone solution and the zirconium oxide particles can be poured onto a support at near-ambient temperature to form a layer. It preferably varies from 5% to 20% by weight. Step a) is generally carried out at near-ambient temperature (23°C), typically from 22°C to 25°C. In step c), the suspension is stirred to obtain a suspension in which the zirconium oxide particles are homogeneously distributed.

[0025] Step e) can be carried out in an oven, in a drying cabinet called a fume hood, under ambient atmosphere, under an inert atmosphere such as nitrogen or under vacuum.

[0026] Typically, at the end of step e) the film is considered dry for a residual DMSO rate of less than 5% by mass of the mass of the film, preferably less than 2% by mass of the mass of the film.

[0027] The composite film according to the invention, whether obtained by the first variant of the process or the second variant of the process, is typically a non-porous film in which the polyethersulfone is not cross-linked.

[0028] The membrane, another object of the invention, has as its essential characteristic the inclusion of the composite film according to the invention, which is impregnated with water or an aqueous solution containing an electrolyte, which is preferably an aqueous solution of a strong acid or a strong base. It is intended to be used in a electrochemical device, such as a fuel cell or electrolyzer, containing two electrodes, the anode and the cathode, to ensure the transport of ions, in particular protons or hydroxide anions, from one electrode to the other.

[0029] According to a first embodiment of the invention, the membrane typically consists of a composite film according to the invention that is impregnated with water. When ions resulting from redox reactions, such as those resulting from an electrolysis reaction, come into contact with the surface of the water-impregnated composite film, the water-impregnated composite film, in this case the membrane, has the property of conducting the ions. The ions are preferably protons or hydroxide anions.

[0030] According to a second embodiment of the invention, the membrane consists of a composite film according to the invention which is impregnated with an aqueous solution of a strong acid or a strong base. When the composite film is impregnated with an aqueous solution of a strong acid, the membrane is a proton-conducting membrane. When the composite film is impregnated with an aqueous solution of a strong base, the membrane is a hydroxide anion-conducting membrane. Suitable strong bases include potassium hydroxide and sodium hydroxide, preferably potassium hydroxide. Suitable strong acids include hydrochloric acid, bromic acid, sulfuric acid, and nitric acid, preferably sulfuric acid.

[0031] The membrane according to the invention therefore has the advantage of exhibiting ion transport properties that can be selected according to the nature of the ions in the aqueous solution impregnating the composite film or according to the nature of the ions generated during the redox reactions. It also has the advantage of being usable under both alkaline and acidic conditions, particularly in electrochemical devices such as fuel cells and electrolyzers.

[0032] The membrane according to the first variant of the invention can be prepared by a process which contains the steps of the process described for preparing the composite film, which steps are followed by a step which consists of impregnating the composite film with water.

[0033] The membrane according to the second variant of the invention can be prepared by a process which contains the steps of the process described for preparing the composite film, which steps are followed by a step which consists of impregnating the composite film with an aqueous solution of an electrolyte which is preferably an aqueous solution of a strong acid or a strong base.

[0034] Whether it is the first variant or the second variant for preparing the membrane, the steps of the process described for preparing the composite film are indifferently those implemented in the absence of solvent or in the presence of solvent, respectively described in the first variant and in the second variant for preparing the composite film.

[0035] The impregnation rates are preferably less than 25%, a percentage calculated in relation to the mass of the membrane, to minimize the impact of the dimensional change of the membrane on the operation of an electrochemical device such as a fuel cell or an electrolyzer which would contain the membrane.

[0036] According to the invention, the composite film after impregnation with an aqueous solution can be used as an ion-conducting membrane, in particular of protons or hydroxide anions, in a fuel cell or electrolyzer.

[0037] In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 17:

[0038] Mode 1: Composite film of polyethersulfone, poly(oxy-l,4-phenylenesulfonyl-l,4-phenylene), and zirconium oxide particles of formula ZrO2, the content of zirconium oxide particles in the composite film being greater than 40% by mass of the mass of the composite film.

[0039] Mode 2: Composite film according to mode 1 in which the content of zirconium oxide particles is less than 95% by mass of the mass of the composite film.

[0040] Mode 3: Composite film according to mode 1 or 2 in which the content of zirconium oxide particles is greater than 50% by mass of the mass of the composite film and less than 95% by mass of the mass of the composite film.

[0041] Mode 4: Composite film according to any one of modes 1 to 3 in which the zirconium oxide particles have a median volume size, D50, less than 10 pm.

[0042] Mode 5: Composite film according to any one of modes 1 to 4 in which the zirconium oxide particles have a median volume size, D50, greater than or equal to 1 pm.

[0043] Mode 6: Composite film according to any one of modes 1 to 5 in which the polyethersulfone has a weight average molar mass greater than 5,000 g / mol and less than 500,000 g / mol.

[0044] Mode 7: Composite film according to any one of modes 1 to 6 in which the polyethersulfone has a weight average molar mass greater than 10,000 g / mol and less than 200,000 g / mol.

[0045] Mode 8: Composite film according to any one of modes 1 to 7 in which the polyethersulfone has a weight average molar mass greater than 15,000 g / mol and less than 100,000 g / mol.

[0046] Mode 9: Composite film according to any one of modes 1 to 8, which composite film has a thickness of 15 pm to 200 pm.

[0047] Mode 10: Composite film according to any one of modes 1 to 9, which film is non-porous.

[0048] Mode 11: Composite film according to any one of modes 1 to 10 in which the po- Lyethersulfone is not cross-linked.

[0049] Mode 12: Ion-conducting membrane comprising a composite film defined in any one of modes 1 to 11 and impregnated with water or an aqueous solution containing an electrolyte.

[0050] Mode 13: Ion-conducting membrane according to mode 12 in which the composite film is impregnated with an aqueous solution of a strong acid or a strong base.

[0051] Mode 14: A method for preparing a composite film defined in any one of modes 1 to 11 comprising the following successive steps a) to f): - a) Dissolve the polyethersulfone in dimethyl sulfoxide, DMSO, to form a solution, - b) add the zirconium oxide particles to the solution to obtain a suspension, - c) shake the suspension, - d) deposit the suspension onto a support to form a layer, - e) dry the layer on the support to obtain the composite film, - f) peel the composite film from the support.

[0052] Mode 15: A method for preparing a membrane defined in any one of modes 12 to 13, comprising the following successive steps: - a) Dissolve the polyethersulfone in dimethyl sulfoxide, DMSO, to form a solution, - b) add the zirconium oxide particles to the solution to obtain a suspension, - c) shake the suspension, - d) deposit the suspension on a support to form a layer, - e) dry the layer on the support to obtain the composite film, - f) peel the composite film from the support, then impregnate the composite film with water or an aqueous solution of an electrolyte which is preferably an aqueous solution of a strong acid or a strong base.

[0053] Mode 16: Fuel cell comprising a membrane according to mode 12 or 13 or a membrane capable of being obtained by the process according to mode 15.

[0054] Mode 17: Electrolyzer comprising a membrane according to mode 12 to 13 or a membrane capable of being obtained by the process according to mode 15.

[0055] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration. Examples

[0056] The values ​​of D50 are determined by laser diffraction, which allows us to determine the particle size distribution in volume percentage by means of a dry granulometer, the Mw values ​​by SEC / MALS (size exclusion chromatograph coupled to a differential refractometer and a multi-angle light scattering photometer). Preparation of composite films:

[0057] The composite films Fl to F3 are prepared according to the following procedure: In a beaker, polyethersulfone (Mw 58000 g / mol, "Goodfellow", commercial reference "SU30-GL-000111") is dissolved at room temperature with stirring in dimethyl sulfoxide (DMSO) to prepare an 18% wt. Zirconium particles (ZrO2, D5O 5 µm, supplier Sigma-Aldrich, commercial reference 230693) are added to the stirred PESU solution in DMSO to obtain a homogeneous suspension. The suspension is then deposited onto an aluminum plate measuring 150 mm x 300 mm to form a 500 µm thick layer. To remove the DMSO, the coated substrate is placed in a fume hood on a hot plate at 80°C for 2 hours under ambient air, then at 60°C for at least 12 hours in a vacuum oven. The composite film is considered dry when the residual DMSO content is less than 2% by mass of the composite film. The composite film is recovered by peeling it off the substrate.The contents of zirconium oxide and PESU in the composite film are given in Table 1 and are expressed as mass percentages relative to the mass of the composite film.

[0058] A film F0 is prepared according to the procedure described for preparing films Fl to F3 with the difference that the step of adding zirconium particles is omitted.

[0059] Table 1: F0 Fl F2 F3 % PESU 100 34 18 9 % ZrO2 0 66 82 91

[0060] The Fl to F3 composite films all conform to the invention. The F0 film does not conform to the invention. The thickness of the films varies from 100 to 150 µm.

[0061] Preparation of the ML M2 and M3 membranes by impregnation of the respective composite films FL F2 and F3:

[0062] The membranes are prepared according to the following procedure: The composite film is immersed for 24 hours in an aqueous potassium hydroxide (MI) solution to form the membrane. The membrane is then removed from the solution and its surface is wiped. The membrane's impregnation rate is calculated by the difference in mass between the mass of the membrane and the mass of the composite film before immersion. immersion in the solution. The impregnation rate is given in Table 2 as a percentage of the mass of the composite film before its immersion in the solution. Membranes M1 to M3 conform to the invention.

[0063] To determine the ionic conductivity of the prepared membrane, its electrochemical impedance is measured across the plane of the membrane at 23 °C, the measurement parameters being an amplitude variation of 10 mV and an applied potential of 0 V. The ionic conductivity results are shown in Table 2.

[0064] A control T1 is prepared by immersing the film F0 in place of the composite film according to the impregnation procedure described for preparing a membrane. Its ionic conductivity is also measured in the same way as that of membranes M1 to M3. The measurement shows that the control is not conductive.

[0065] Table 2: Composite film / Membrane Fl / Ml F2 / M2 F3 / M3 Impregnation rate (%) * <1 <1 17 Ionic conductivity θ (S / cm) 107 104 103

[0066] * 100 x (mass of the membrane - mass of the composite film before its immersion in the solution) / (mass of the composite film before its immersion in the solution).

[0067] The results show that the membranes prepared M1 to M3 are conductive of hydroxide anions unlike the control TL. It is also noted that the ionic conductivity increases with the mass content of zirconium oxide.

[0068] The ionic conductivity of a membrane M4 obtained by impregnating the composite film F3 in an aqueous solution of sulfuric acid (0.1M) instead of the aqueous potassium hydroxide solution is also measured, and its ionic conductivity is measured under the same conditions as those of membranes M1 to M3. The membrane M4 conforms to the invention. Its ionic conductivity is 10⁴ S / cm.

[0069] The ionic conductivity of a T2 control obtained by impregnating the F0 film in an aqueous solution of sulfuric acid (0.1M) instead of the aqueous potassium hydroxide solution is also measured, and its ionic conductivity is measured under the same conditions as those of the M1 to M3 membranes. The T2 control is not conductive.

[0070] The results show that the composite films according to the invention allow the production of ion-conducting membranes after impregnation of the composite films with an aqueous solution. The membranes according to the invention can be used in both acidic and alkaline media and allow the transfer of both protons and hydroxide anions, depending on the nature of the electrolyte present in the membrane.

[0071] The ionic conductivity property is obtained for relative impregnation rates tively weak, which makes it possible to limit changes in the dimension of the membrane and suggests better dimensional stability of an assembly (in English "stack") of a fuel cell or electrolyzer during its operation, which assembly includes a membrane according to the invention.

Claims

Demands

1. Composite film of polyethersulfone, poly(oxy-l,4-phenylenesulfonyl-l,4-phenylene), and zirconium oxide particles of formula ZrO2, the content of zirconium oxide particles in the composite film being greater than 40% by mass of the mass of the composite film.

2. Composite film according to claim 1 in which the content of zirconium oxide particles is less than 95% by mass of the mass of the composite film.

3. Composite film according to claim 1 or 2 in which the zirconium oxide particles have a median volume size, D50, of less than 10 pm.

4. Composite film according to any one of claims 1 to 3 in which the zirconium oxide particles have a median volume size, D50, greater than or equal to 1 pm.

5. Composite film according to any one of claims 1 to 4 wherein the polyethersulfone has a weight average molar mass greater than 5,000 g / mol and less than 500,000 g / mol, preferably greater than 10,000 g / mol and less than 200,000 g / mol, more preferably greater than 15,000 g / mol and less than 100,000 g / mol.

6. Composite film according to any one of claims 1 to 5, which composite film has a thickness of 15 pm to 200 pm.

7. Ion-conducting membrane comprising a composite film as defined in any one of claims 1 to 6 and impregnated with water or an aqueous solution containing an electrolyte.

8. Ion-conducting membrane according to claim 7 in which the composite film is impregnated with an aqueous solution of a strong acid or a strong base.

9. A method for preparing a composite film as defined in any one of claims 1 to 6, comprising the following successive steps a) to f): - a) dissolving polyethersulfone in dimethyl sulfoxide, DMSO, to form a solution, - b) adding zirconium oxide particles to the solution to obtain a suspension, - c) agitating the suspension, - d) depositing the suspension onto a support to form a layer, - e) dry the layer on the support to obtain the composite film, - f) peel the composite film from the support.

10. A method for preparing a membrane as defined in any one of claims 7 to 8 comprising the following successive steps: - a) dissolving polyethersulfone in dimethyl sulfoxide, DMSO, to form a solution, - b) adding zirconium oxide particles to the solution to obtain a suspension, - c) stirring the suspension, - d) depositing the suspension onto a support to form a layer, - e) drying the layer on the support to obtain the composite film, - f) peeling the composite film from the support, then impregnating the composite film with water or an aqueous solution of an electrolyte which is preferably an aqueous solution of a strong acid or a strong base.

11. Fuel cell comprising a membrane according to claim 7 or 8 or a membrane obtainable by the process defined in claim 10.

12. Electrolyzer comprising a membrane according to claim 7 or 8 or a membrane capable of being obtained by the process defined in claim 10.