Membrane for alkaline water electrolysis

Abstract

Disclosed are a membrane suitable for alkaline water electrolysis and an alkaline water electrolysis device comprising the same. A method for producing hydrogen and a method for producing a membrane for alkaline water electrolysis are also disclosed.

Description

[0001] Citation of Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 411,209, filed on September 29, 2022, and European Patent Application No. 22209371.8, filed on November 24, 2022, the entire contents of each of which are incorporated by reference into this application for all purposes. Technical Field

[0003] The present invention relates to a membrane suitable for alkaline water electrolysis, an alkaline water electrolysis device, a method for producing hydrogen, and a method for producing a membrane for alkaline water electrolysis. Background Art

[0004] Hydrogen has been used in a variety of industrial applications, such as in petroleum refining, chemical synthesis materials, metal refining, and stationary fuel cells. Today, the use of hydrogen is expected to grow in hydrogen stations for fuel cell vehicles (FCVs), smart communities, and hydrogen power plants. In view of this, attention is focused on technologies for producing high-purity hydrogen.

[0005] One industrial method for producing hydrogen is through water electrolysis. The advantage of this process is that it can be combined with electricity generation using renewable resources, such as wind and solar, which are needed to maintain a balance between supply and demand in the power grid.

[0006] In a typical water electrolysis process, an aqueous solution containing an electrolyte (such as sodium hydroxide or potassium hydroxide) is used as an electrolyte solution to obtain improved conductivity. A direct current is applied to the electrolyte solution through a cathode and an anode to initiate the water electrolysis process.

[0007] An electrolytic cell for an electrolysis process (which may be referred to hereinafter as "electrolysis") is divided into an anode chamber and a cathode chamber by a membrane. Oxygen is produced in the anode chamber, and hydrogen is produced in the cathode chamber. The membrane is required to have gas impermeability to prevent mixing of oxygen and hydrogen, and at the same time have high ion permeability to allow ions to flow within the electrolytic cell to generate electricity. Therefore, a membrane having a porous structure and high ion permeability is required.

[0008] WO 93 / 15529A1 discloses a diaphragm for alkaline water electrolysis, which is a porous membrane formed by incorporating zirconium oxide or magnesium oxide into polysulfone as an aromatic polymer resin and performing a non-solvent-induced phase separation process. It has been observed that as electrolysis continues, inorganic particles tend to separate from the pores, with the result that the number of inorganic particles on the surface of the porous membrane decreases. In the long run, this degrades the performance of the membrane by causing bubbles to adhere to the surface of the porous membrane and hindering the permeation of ions.

[0009] The existing technical solutions still have room for improvement. For example, when a diaphragm in the form of a porous film is sandwiched between electrodes (anode and cathode), hydrogen and oxygen released from the electrodes adhere to the surface of the porous film in the form of bubbles and close the pores in the surface of the porous film. This leads to an increase in voltage loss caused by the diaphragm during electrolysis because ions cannot penetrate through the pores closed by the bubbles. If the surface of the porous film is hydrophobic, the problem of increased voltage loss is quite serious because, in this case, bubbles can easily adhere to the surface.

[0010] Therefore, there is still a need to provide a membrane for alkaline water electrolysis which is not affected by the deterioration of ion permeability caused by the attachment of bubbles and is not affected by the deterioration of characteristics caused by the loss of hydrophilic inorganic particles. Summary of the invention

[0011] The problem faced by the Applicant is to provide a membrane which does not have the above-mentioned disadvantages and which can be manufactured in the form of a flat sheet and which is suitable for alkaline electrolysis. The Applicant has found that the above-mentioned problem can be solved by a membrane comprising at least one poly(aryletherketone) polymer, said membrane having a contact angle of at least 155° measured according to the trapped bubble contact angle test and / or a static contact angle characterized by a decrease over time. The membrane is a porous membrane. The membrane comprises at least one surface comprising a functionalized poly(aryletherketone) polymer having hydroxyl groups bonded to aromatic rings of the poly(aryletherketone) chains.

[0012] Poly(aryletherketone)s represent a class of semicrystalline engineering thermoplastics with excellent thermal properties and chemical resistance. Poly(aryletherketone) polymers are virtually insoluble in all common solvents at room temperature. These properties make poly(aryletherketone)s attractive materials for the preparation of porous membranes. DETAILED DESCRIPTION

[0013] In this application:

[0014] - even any description related to a specific embodiment is applicable to and interchangeable with other embodiments of the present disclosure;

[0015] - When an element or component is said to be included in and / or selected from a list of listed elements or components, it should be understood that in the relevant embodiments explicitly considered herein, the element or component may also be any of these listed independent elements or components, or may also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component listed in the list of elements or components may be omitted from this list; and

[0016] - Any recitation of numerical ranges by endpoints herein includes all numbers subsumed within the recited range as well as the endpoints of that range and equivalents thereof.

[0017] A first object of the present invention is a membrane as defined in the appended claims. The membrane has a contact angle of at least 155° measured according to the Captured Bubble Contact Angle Test.

[0018] The trapped air bubble (CAB) contact angle test provides a measure of the hydrophilicity of the film. It can be measured by a contact angle goniometer as described in detail in the experimental section. High hydrophilicity is associated with a high contact angle. In this specification, a fully wettable surface has a contact angle of 180° according to the trapped air bubble contact angle test.

[0019] Without being bound by theory, it is believed that increased hydrophilicity of the membrane, particularly at the membrane surface, can reduce the tendency of gases such as hydrogen and oxygen to adhere to the membrane surface and thereby close the pores of the membrane and hinder the passage of ions during electrolysis.

[0020] The membranes of the present invention are characterized by a contact angle of at least 155°, even at least 157°, measured according to a trapped bubble contact angle test. The trapped bubble contact angle test comprises immersing the membrane in deionized water at room temperature, dropping 2 pL of bubbles at the surface of the membrane using a J-shaped syringe, and measuring the contact angle between the bubbles and the membrane surface using an optical tensiometer equipped with a high-quality monochromatic cold LED light and a high-resolution digital camera. The bubbles are dropped at the surface of the membrane comprising a functionalized poly(aryletherketone) polymer.

[0021] The films of the invention may alternatively or additionally be characterized by a static contact angle that decreases over time.The static contact angle is measured according to ASTM D 5725-99.

[0022] The film of the present invention is characterized by a static contact angle of at least 15° lower than the initial value when measured after 60 seconds. In certain advantageous embodiments, the static contact angle is at least 10° lower after 10 seconds, even 20° lower after 10 seconds. The expression "initial value" means the static contact angle value determined at the initial time when a water droplet is placed on the surface of the film.

[0023] The change in static contact angle over time is determined by measuring the static contact angle according to ASTM D 5725-99 at an initial time, waiting a certain time interval, and taking a new contact angle measurement on the same sample under the same experimental conditions.

[0024] The trapped bubble contact angle and the static contact angle are conveniently measured on at least one surface comprising a functionalized poly(aryletherketone) polymer.

[0025] The film comprises at least one poly(aryletherketone) polymer.

[0026] The expression "poly(aryletherketone) polymer" is used herein to refer to a polymer comprising at least 50 mol % of repeating units (R PAEK ) wherein Ar and Ar' are the same or different from each other and are aromatic groups, preferably phenyl groups.

[0027] The poly(aryletherketone) polymer has at least 60 mol%, at least 80 mol%, at least 90 mol%, at least 95 mol%, or at least 98 mol% of the repeating units (R PAEK ). Repeating unit (R PAEK ) is selected from the group consisting of formulae (JA) to (JO) below:

[0028]

[0029]

[0030]

[0031] in:

[0032] - each R' is the same as or different from each other and is selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali metal or alkaline earth metal sulfonate, alkyl sulfonate, alkali metal or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium; and

[0033] -j' is zero or an integer from 1 to 4.

[0034] Repeating unit (R PAEK ) can independently have 1,2-, 1,4-, or 1,3-linkages to other moieties different from R' in the repeating unit. The phenylene moieties can have 1,3- or 1,4-linkages. Typically, the phenylene moieties have 1,4-linkages.

[0035] Furthermore, in some embodiments, the repeating unit (R PAEK ) is zero at each occurrence; that is, the phenylene moieties have no substituents other than those that enable linkage in the backbone of the polymer. In some such embodiments, the repeating unit (R PAEK ) may be represented by a formula selected from the group consisting of the following formulae (J'-A) to (J'-O):

[0036]

[0037]

[0038] The poly(aryletherketone) polymer may be a homopolymer, a random copolymer, an alternating copolymer or a block copolymer. When the poly(aryletherketone) polymer is a copolymer, it may contain (i) repeating units (R) having at least two different formulae selected from formulae (JA) to (JO) or (J'-A) to (J'-O) PAEK ), or (ii) having one or more repeating units (R) of formula (JA) to (JO) or (J'-A) to (J'-O) PAEK ) and the repeating unit (R PAEK ) different repeating units (R* PAEK ).

[0039] Repeating unit (R PAEK ) is conveniently selected from the group consisting of units of formula (J'-A) to (J'-D) and (J"-B):

[0040]

[0041] The membrane comprises at least one surface comprising a functionalized poly(aryletherketone) polymer. In the remainder of this document, the expression "functionalized poly(aryletherketone) polymer" is used to refer to a poly(aryletherketone) polymer comprising a hydroxyl group bonded to an aromatic ring of the poly(aryletherketone) polymer backbone. Preferably, the hydroxyl group is directly bonded to a carbon atom of the aromatic ring.

[0042] The functionalized poly(aryletherketone) polymer comprises repeating units (R PAEK-OH ), these repeating units are selected from the group consisting of units having the following formulae (KA) to (KD):

[0043]

[0044] wherein each of Q' is -OH and, independently at each occurrence, i is zero or an integer from 1 to 4, provided that in a given repeat unit, the sum of all i's is different from zero.

[0045] The functionalized poly(aryletherketone) polymer may further comprise repeating units (R PAEK ), these repeating units are selected from the group consisting of units of formula (J'-A) to (J'-D) and (J"-B) as defined above.

[0046] In the repeating unit (R PAEK-OH ), the phenylene moieties may independently have up to PAEK-OH ) is 1,2-, 1,4- or 1,3-linked to other moieties that are different from Q' in ).

[0047] The functionalized poly(aryletherketone) polymer comprises a combined amount of repeating units (R) of at least 50 mol % relative to the total number of repeating units in the functionalized poly(aryletherketone) polymer. PAEK-OH ) and repeating units (R PAEK The functionalized poly(aryletherketone) polymer typically comprises a combined amount of repeating units (R) of at least 60 mol%, at least 65 mol%, at least 70 mol%, at least 75 mol%, at least 80 mol%, at least 85 mol%, at least 90 mol%, at least 95 mol%, or at least 99.9 mol%, relative to the number of repeating units in the functionalized poly(aryletherketone) polymer. PAEK-OH ) and repeating units (R PAEK ).

[0048] In some cases, the functionalized poly(aryletherketone) polymer may contain 0.001 mol % or more, even 0.005 mol % or more, and in some cases 0.01 mol % or more of the repeating unit (R) relative to the number of repeating units in the functionalized poly(aryletherketone) polymer. PAEK-OH ).

[0049] Advantageously, the functionalized poly(aryletherketone) polymer is selected from the group comprising, preferably consisting of, functionalized poly(etheretherketone) (f-PEEK) and functionalized copolymers of PEEK and poly(diphenyletherketone) (f-PEEK-PEDEK copolymers) and blends thereof.

[0050] The expression "functionalized poly(etheretherketone) (f-PEEK)" denotes any polymer comprising repeating units having the above formulae (KA) and (J'-A). Preferably, the phenylene moieties in the repeating units (KA) and (J'-A) have 1,4-linkages.

[0051] Preferably at least 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%, 99 mol% and most preferably all repeating units are a combination of repeating units (KA) and (J'-A). The amount of repeating unit (KA) is different from zero.

[0052] The expression functionalized copolymer of PEEK and poly(diphenyl ether ketone) (f-PEEK-PEDEK copolymer) means any polymer comprising repeating units having formula (KA) and / or (J'-A) (PEEK repeating units) and repeating units having formula (KD) and / or (J'-D) (poly(diphenyl ether ketone) (PEDEK) repeating units):

[0053]

[0054]

[0055] wherein R', j', Q' and i are as defined above. Preferably, the phenylene moieties in the repeating units (KA), (J'-A), (KD) and (J'-D) have 1,4-linkages.

[0056] The f-PEEK-PEDEK copolymer may comprise PEEK repeating units and PEDEK repeating units in a relative molar ratio ranging from 95 / 5 to 60 / 40. Preferably, the sum of repeating units (KA), (J'-A), (KD) and (J'-D) accounts for at least 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%, 99 mol% of the repeating units in the functionalized poly(aryletherketone) polymer, provided that the amount of repeating units (KA)+(KD) is different from zero.

[0057] Most preferably, the functionalized poly(aryletherketone) polymer is f-PEEK or f-PEEK-PEDEK or a blend of f-PEEK and f-PEEK-PEDEK as defined above.

[0058] The membrane of the present invention comprises at least one surface comprising at least one functionalized poly(aryletherketone) polymer comprising hydroxyl groups bonded to aromatic rings of the poly(aryletherketone) polymer backbone. The remainder of the membrane may comprise a poly(aryletherketone) polymer having the same functionalized poly(aryletherketone) polymer backbone or a different backbone.

[0059] The membrane of the invention may have two surfaces comprising at least one functionalized poly(aryletherketone) polymer as defined above.

[0060] The membrane of the invention may have throughout its thickness the same composition comprising at least one functionalized poly(aryletherketone) polymer as defined above.

[0061] The term "membrane" is intended to mean a discrete, usually thin interface which slows the permeation of chemical species in contact with it, said membrane containing pores of finite size. The membrane of the present invention is a porous membrane.

[0062] Membranes containing pores uniformly distributed throughout their thickness are generally referred to as symmetric (or isotropic) membranes. Membranes containing pores non-uniformly distributed throughout their thickness are generally referred to as asymmetric (or anisotropic) membranes.

[0063] The membranes of the invention may be symmetric or asymmetric membranes.Asymmetric membranes may comprise a thin selective layer (0.1-1.0 μm thick) and a highly porous thick layer (100-200 μm thick) which acts as a support and has little effect on the separation characteristics of the membrane.

[0064] The membranes of the present invention have an average pore size of 50 to 200 nm, typically 60 to 150 nm.

[0065] The membrane has a bubble point (ie a measure of the largest pores) of from 100 nm to 400 nm, typically from 150 nm to 300 nm. The membrane has a minimum pore size of from 40 nm to 120 nm, typically from 50 to 100 nm.

[0066] Pore ​​size and bubble point can be measured according to ASTM F316.

[0067] Suitable techniques for determining the average pore size in the porous membranes of the present invention are described, for example, in Handbook of Industrial Membrane Technology, edited by PORTER, Mark C, Noyes Publications, 1990, pp. 70-78. The pore size of the membrane can be estimated by a variety of techniques including scanning electron microscopy (SEM), and / or measurement of bubble point, gas flux, water flux and molecular weight cut-off.

[0068] The membrane of the present invention may be a free-standing porous membrane consisting of one porous layer, or preferably a multilayer membrane comprising at least one porous layer supported on a substrate. The substrate is preferably composed of one or more materials that have a minimal effect on the selectivity of the porous membrane.

[0069] The film of the present invention preferably has a structure in which the porous polymer film surrounds the porous substrate, and more preferably has a structure in which the porous polymer film is laminated on both surfaces of the porous substrate. The inclusion of the substrate can enhance the strength of the film. For example, defects such as cutting and tearing in the film and stretching of the film due to mechanical stress can be prevented.

[0070] The material of substrate is preferably but not limited to the material that can not significantly reduce the permeability of film to electrolyte solution ions.The example of the material of porous substrate includes but is not limited to poly (phenylene sulfide), polyethylene, polypropylene, poly (vinylidene fluoride), polytetrafluoroethylene, poly (p-phenylene benzobisoxazole), poly (ether ketone), polyimide and polyetherimide. Among these, preferably containing polyphenylene sulfide. The use of poly (phenylene sulfide) allows porous substrate to show high tolerance to high temperature, high concentration alkaline solution, and shows high chemical stability to active oxygen released from anode during water electrolysis. In addition, when using poly (phenylene sulfide), the porous substrate can be easily processed into various forms, such as woven fabrics and nonwoven fabrics, and therefore can be appropriately modified according to expected application or expected use environment. The above materials can be used alone or in combination with two or more thereof.

[0071] Examples of porous substrates include, but are not limited to, nets, porous membranes, nonwoven fabrics, woven fabrics. These can be used alone or in combination with two or more thereof. Examples of more preferred forms of porous substrates include net substrates consisting of monofilaments of poly(phenylene sulfide) and composite fabrics comprising nonwoven fabrics and woven fabrics enclosed in the nonwoven fabrics.

[0072] The membrane of the present invention may be flat or tubular in shape, depending on its intended end use.

[0073] Flat membranes are generally preferred for use in electrolytic cells.

[0074] However, the scope of the invention is not limited to flat membranes, but also covers tubular and hollow fiber membranes. These are particularly advantageous in applications where compact modules with high surface area are required.

[0075] When the film is flat, its thickness is advantageously between 10 and 800 microns, even between 25 and 600 microns, preferably between 200 and 500 microns.

[0076] When the membrane is tubular, its outer diameter may be up to 15.0 mm. When the membrane has an outer diameter comprised between 0.5 mm and 3.0 mm, it is referred to as a hollow fiber membrane. When the membrane has a diameter less than 0.5 mm, it is referred to as a capillary membrane.

[0077] In certain embodiments, the membrane may comprise a composition comprising at least one poly(aryletherketone) polymer and / or at least one functionalized poly(aryletherketone) polymer and a radical scavenger. The radical scavenger is preferably selected from the group of inorganic scavengers, in particular from the group consisting of cerium salts and oxides.

[0078] Method for producing a membrane

[0079] The membranes of the present invention may be prepared from poly(aryletherketone) polymers as defined above.

[0080] In certain embodiments, it can be prepared starting from a functionalized poly(aryletherketone) polymer as defined above, which is a poly(aryletherketone) polymer comprising hydroxyl groups bonded to aromatic rings of the poly(aryletherketone) polymer backbone.

[0081] In the described embodiments, the functionalized poly(aryletherketone) polymer may provide only one surface layer of the membrane, both surface layers or it may be used to make the entire membrane. The functionalized poly(aryletherketone) polymer may be used alone or in a composition with another polymer (typically a polymer selected from the group of poly(aryletherketone) polymers as detailed above).

[0082] Alternatively, in a preferred embodiment, the membrane is obtained by chemically treating a film comprising a poly(aryletherketone) polymer and having a contact angle of less than 155° measured according to the trapped bubble contact angle test and / or a static contact angle that does not decrease over time (hereinafter referred to as the "precursor film"). The precursor film has at least one surface made of a poly(aryletherketone) polymer. The step of chemically treating the precursor film provides a membrane having at least one surface comprising hydroxyl groups bonded to aromatic rings in the poly(aryletherketone) polymer backbone. In other words, the step of chemically treating the precursor film provides a membrane having at least one surface comprising a functionalized poly(aryletherketone) polymer as defined above. The hydroxyl groups are generally directly bonded to carbon atoms of the aromatic rings.

[0083] In a first step, the method includes providing a precursor film comprising a poly(aryletherketone) polymer and having a contact angle less than 155° as measured according to the Captured Bubble Contact Angle Test and / or a static contact angle that does not decrease over time.

[0084] The precursor membrane can be prepared according to any method known in the art for preparing porous membranes comprising poly(aryletherketone) polymers.

[0085] Suitable methods for preparing porous membranes by processing poly(aryletherketone) polymers are, for example, those described in US 4,957,817, US 5,200,078, US 5,205,968 and US 4,755,540.

[0086] More advantageously, the precursor film may be prepared according to any of the methods described in WO 2018065526A1, WO 2021018868A1 or WO2022096373A1.

[0087] In a first embodiment, a precursor film is prepared according to a method comprising:

[0088] (i) processing a polymer composition into a solid article, the polymer composition comprising a poly(aryletherketone) polymer and at least 28 wt. %, based on the total weight of the polymer composition, of at least one additive having formula (I):

[0089] R a -Ar-X b (I)

[0090] Wherein: Ar is selected from the group consisting of: a substituted or unsubstituted monocyclic or polycyclic aromatic group having 5 to 18 carbon atoms, each R is the same as or different from each other and is selected from the group consisting of: halogen, hydroxyl, C1-C18 aliphatic group, C1-C18 alicyclic group and C1-C18 aromatic group; a is zero or an integer ranging from 1 to 5; X is (SO3- ),(M p+ ) 1 / p or (COO - ) , (M p+ ) 1 / p , where M p+ is a p-valent metal cation; and b is an integer from 1 to 4, and

[0091] (ii) immersing the solid article in water to obtain a porous article.

[0092] The additive of formula (I) is preferably selected from the group consisting of alkali metal salts of benzoate, methylbenzoate, ethylbenzoate, propylbenzoate, benzenesulfonate, benzenedisulfonate, p-toluenesulfonate, xylenesulfonate, cumenesulfonate, p-cymenesulfonate and dodecylbenzenesulfonate.

[0093] In a preferred embodiment, the precursor film is prepared according to a method comprising:

[0094] (I) providing a composition comprising at least one poly(aryl ether ketone) polymer, at least one poly(aryl ether sulfone) polymer, and at least one compound comprising a sulfonate or carboxylate of a metal selected from the group consisting of alkali metals, alkaline earth metals, aluminum, iron, zinc, nickel, copper, palladium, and silver;

[0095] (II) processing the composition to provide pellets;

[0096] (III) melt-extruding the pellets obtained in step (II) to provide a precursor layer;

[0097] (IV) contacting the precursor layer with at least one organic solvent or with water and subsequently with at least one organic solvent, thereby providing an intermediate porous layer;

[0098] (V) contacting the intermediate porous layer obtained in step (IV) with water to provide a porous membrane.

[0099] The poly(aryl ether sulfone) polymer is preferably selected from polyphenylsulfone (PPSU), polyethersulfone (PES) or polysulfone (PSU).

[0100] The compound containing sulfonate or carboxylate is selected from benzoate, methyl benzoate, ethyl benzoate, propyl benzoate, benzene sulfonate, benzene disulfonate, p-toluene sulfonate, xylene sulfonate, isopropyl benzene sulfonate, p-cymene sulfonate and dodecylbenzene sulfonate. Preferably, it is selected from the group consisting of sodium or potassium benzoate, sodium or potassium methyl benzoate, sodium or potassium ethyl benzoate, sodium or potassium butyl benzoate, sodium or potassium benzene sulfonate, sodium or potassium benzene-1,3-disulfonate, sodium or potassium p-toluene sulfonate, sodium or potassium xylene sulfonate, sodium or potassium isopropyl benzene sulfonate, sodium or potassium p-cymene sulfonate, sodium or potassium n-butylbenzene sulfonate, sodium or potassium isobutylbenzene sulfonate, sodium or potassium tert-butylbenzene sulfonate and sodium or potassium dodecylbenzene sulfonate.

[0101] In a second step, the method for preparing the membrane of the present invention comprises chemically treating the precursor membrane to obtain a contact angle of at least 155° as measured by the Captured Bubble Contact Angle Test and / or a static contact angle that decreases over time.

[0102] The chemical treatment provides a membrane having at least one surface comprising hydroxyl groups bonded to aromatic rings in the poly(aryletherketone) polymer backbone, ie, a membrane having at least one surface comprising a functionalized poly(aryletherketone) polymer.

[0103] The chemical treatment comprises contacting the precursor film with a peroxide in the presence of an oxidation catalyst comprising iron (II) or iron (III) ions to obtain hydroxyl groups that are bonded to aromatic rings of the poly(aryletherketone) polymer backbone. The hydroxyl groups are bonded to aromatic rings of the poly(aryletherketone) polymer backbone at least on the surface of the film.

[0104] The chemical treatment is typically carried out in an aqueous medium. The chemical treatment may be conveniently carried out by dipping or immersing the precursor film in a bath or tank containing an aqueous solution containing an oxidizing catalyst and a peroxide.

[0105] The peroxide is typically hydrogen peroxide.The concentration of hydrogen peroxide in the aqueous medium is typically from 0.5 to 15.0 wt%, even from 1.0 to 10.0 wt% relative to the aqueous medium.

[0106] The oxidation catalyst is preferably in the form of a salt. A notable example of a suitable salt is Fe(NH4)2(SO4)2*6H2O. The concentration of iron(II) or iron(III) ions in the aqueous medium is not limited. It is typically at least 1.0 x 10 -4 M.

[0107] The treatment is typically carried out under acidic conditions; preferably at a pH of the aqueous medium of less than 6.0, more preferably at a pH of 3.0 to 5.0.

[0108] The treatment is typically carried out at a temperature of 30 to 95°C, preferably 40 to 90°C.

[0109] If the precursor film is immersed, it may remain in the aqueous medium for a period of time ranging from one second to 10 hours, typically from 5 to 60 minutes.

[0110] The method may additionally comprise the step of washing the membrane followed by drying.

[0111] Due to the inherent chemical stability of the poly(aryletherketone) polymers, combined with the increased hydrophilicity, the membranes of the present invention are particularly suitable for use as diaphragms in alkaline water electrolysis devices.

[0112] The alkaline water electrolysis device comprises an anode, a cathode and a porous membrane as described in detail above, which is placed between the anode and the cathode. In a more specific example, the interior of the alkaline water electrolysis device is divided into an anode chamber including an anode and a cathode chamber including a cathode by the porous membrane of the present invention, and the oxygen and hydrogen released from these electrodes remain unmixed.

[0113] The configuration of the alkaline water electrolysis device of the present invention is not particularly limited as long as it includes the membrane of the present invention. When used as a diaphragm in an alkaline water electrolysis device, the membrane of the present invention is typically in the form of a flat membrane. It is advantageously in the form of a flat membrane comprising a porous substrate. Advantageously, it is a porous substrate in the form of a net, preferably a poly(phenylene sulfide) net.

[0114] When used as a diaphragm in an alkaline water electrolysis device, the membrane is characterized by a contact angle of at least 155°, even at least 157°, measured according to the Captured Bubble Contact Angle Test, and / or is characterized by a static contact angle that decreases over time, preferably a static contact angle that decreases by 15° relative to the initial value when measured after 60 seconds.

[0115] The method and conditions for electrolysis using the alkaline water electrolysis device of the present invention are not particularly limited, and known methods and conditions can be used. For example, the interior of the alkaline water electrolysis device is filled with an alkaline solution, and direct current is applied between the anode and the cathode. For example, an aqueous solution of sodium hydroxide or potassium hydroxide is used as the electrolyte solution.

[0116] Hydrogen can be produced industrially by a water electrolysis process using an alkaline water electrolysis device of the present invention and wherein a variable power source is applied to the device. That is, the method for producing hydrogen according to an embodiment of the present invention includes a step of electrolyzing alkaline water by applying a voltage to an alkaline water electrolysis device according to an embodiment of the present invention using a variable power source. With the method for producing hydrogen according to an embodiment of the present invention, a variable power source derived from renewable energy (such as large-scale wind power generation or photovoltaic power generation) can be efficiently and stably converted into hydrogen and stored as hydrogen.

[0117] Thus, an exemplary beneficial use of an electrolysis cell incorporating the membrane of the present invention allows electricity derived from renewable energy sources to be converted to and stored as hydrogen.

[0118] The porous membrane of the present invention can also be conveniently used in a filtration device, such as a microfiltration or ultrafiltration device.

[0119] Therefore, the object of the present invention is also a method for filtering at least one fluid, said method comprising contacting said fluid with at least one porous membrane of the present invention. The at least one fluid is a gas or a liquid and is preferably selected from the group consisting of: biological solutions, buffer solutions, oil / water emulsions, water, hydrocarbons. Among oil / water emulsions, notable examples are fracturing water and so-called "produced water", or in other words, water from oil wells, water with a high solids content, waste water.

[0120] Hereinafter, the present invention will be described in more detail with reference to various examples and comparative examples.

[0121] The above embodiments are intended to be illustrative rather than restrictive. Additional embodiments are within the inventive concept. In addition, although the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the present invention.

[0122] Examples

[0123] Material

[0124] The following was obtained from Solvay Specialty Polymers USA, LLC.:

[0125] PEEK: KT-820NL PEEK polymer (MFR = 3 g / 10 min measured at 400°C and 2.16 Kg);

[0126] PSU: P1700 PSU polymer (MFR measured at 343°C / 2.16Kg = 6.5 g / 10 min);

[0127] Dimethyl sulfoxide (DMSO) and isopropyl alcohol (IPA) were purchased from Sigma get.

[0128] Micronized sodium benzoate is commercially available from Fluid Energy, Telford, Pennsylvania.

[0129] Bubble point and pore size determination

[0130] The membrane bubble point (ie a measure of the largest pore), minimum pore size and average pore size were determined according to the ASTM F316 method using a capillary flow porosimeter PoroluxTM 1000 (Porometer-Belgium).

[0131] For each test, Fluorinert C 43 (fluorinated fluid with a surface tension of 16 dyn / cm) was initially used to completely wet the membrane sample. Nitrogen (inert gas) was used.

[0132] Measurement of static contact angle (CA)

[0133] According to ASTM D 5725-99, the The static water contact angle was evaluated at 25°C by ELISA (Electronics, Inc., Germany). The contact angle was measured only on one side of the flat film. The results shown in Table 2 are the average of at least 10 drops of water. The volume of the water droplet was 2 μL. The contact angle was measured immediately after the water droplet was deposited and the contact angle was re-measured on the same sample after the time indicated in Table 2 under the same experimental conditions.

[0134] Captured Air Bubble (CAB) Method

[0135] This method measures the contact angle of an air bubble at a surface immersed in a liquid (in this case water). Since the measurement is performed on an already wetted film, swelling and water absorption are suppressed. The instrument layout for this measurement is described in WO 2021 / 12262S A1 (page 40 and Figure I). Air contact angle (ACA) measurements were performed at room temperature using an adapted environmental control chamber filled with deionized water (I) (DI water). Prior to analysis, the wet sample was supported on a 15×5 mm glass substrate and fixed to the sample holder with double-sided tape. The sample was then immersed in DI water, and 2pL bubbles were dropped onto the sample surface using a J-type syringe. Contact angle measurements were performed using an optical tensiometer (Attension Theta Flex provided by BIOLIN) equipped with high-quality monochromatic cold LED light and a high-resolution (1984×1264) digital camera. Image acquisition parameters were set to 5 frames per second (FPS) and a minimum acquisition time of 60s. The instrument was calibrated using a calibration sphere (CA=143.15') with an acceptable error of 0.03. The contact angle value obtained was the average of 5 measurements on the same sample.

[0136] Preparation of precursor film (PQ)

[0137] PEEK and sodium benzoate were blended using a ZSK-26 twin-screw extruder (Coperion GmbH, Stuttgart, Germany) equipped with 12 barrel zones and a heated exit die operating at up to 450°C.

[0138] The barrel overview is as follows:

[0139]

[0140] The pre-blend was fed into one or more feed sections of the extruder using a K-Tron T-35 gravimetric feeder (from Coperion AG, Stuttgart, Germany) to produce the appropriate mass ratios of the components.

[0141] The components were melted and mixed with a screw designed to achieve a homogenous melt composition. The actual melt temperature at the exit die was measured with a handheld device and found to be between 390°C and 400°C.

[0142] The melt stream was air cooled and fed into a Maag Primo 60E pelletizer (from Maag Automatik GmbH, Stuttgart, Germany). The pellets were collected and used to prepare a compound comprising (all amounts are expressed in wt % relative to the total weight of the composition):

[0143] PEEK: 40.6wt%

[0144] PSU: 38.5wt%

[0145] Sodium benzoate: 20.9wt%.

[0146] The pellets were collected and stored in sealed plastic buckets until used for melt film extrusion. The pellets were dried at 130°C overnight and then fed into a single screw extruder and extruded into a film with a profile temperature of 360°C-390°C using a film die. The film was wound onto a cooled godet roll running at a speed of 0.5 to 2 m / min and a temperature of 90°C to 170°C.

[0147] The precursor layer obtained in the above step was soaked in DMSO at 120°C overnight, allowed to settle, and fresh DMSO was added under stirring over 2 hours. Washing was repeated by adding clean DMSO under stirring at room temperature over 2 hours, and then transitioned to water by 3 water washes, each with stirring for 1 hour.

[0148] Example: Preparation and Testing of Films 1 to 3

[0149] The precursor film sample obtained in the previous step was pre-wetted in alcohol and then immersed in 0.8 L of hydrogen peroxide and Fe(NH4)2(SO4)2*6H2O (9.1 x 10 -4 M) in aqueous solution glass dish. The pH of the solution was set at 4.0 by adding 0.05 M H2SO4. The temperature was set at 75°C and the reaction was allowed to proceed for 30 minutes. Different concentrations of hydrogen peroxide were used. The results are summarized in Table 1.

[0150] Table 1

[0151]

[0152] The static contact angle, its variation with time, and the trapped bubble contact angle were determined and summarized in Table 2.

[0153] Table 2

[0154]

[0155] (*) Measurement not possible: The gas droplets do not adhere to the surface of the film.

[0156] The contact angle results in Table 2 show an increase in hydrophilicity of membranes 1 to 3. Higher hydrogen peroxide concentrations during the membrane preparation process resulted in a more hydrophilic character of the membranes.

[0157] Membrane 3 shows the highest hydrophilicity characteristics: in the case of a static contact angle, a water droplet is adsorbed in less than 30 seconds. In the trapped bubble test, bubbles cannot even settle on the surface of the membrane due to its hydrophilicity. This is a particularly advantageous result, since such measurements simulate the real conditions of using the membrane in an alkaline electrolyser.

[0158] Determination of the presence of hydroxyl groups in membrane 3

[0159] The sample of film 3 (4×4 cm 2 The surface) was treated with a solution of trifluoroacetic anhydride (4 ml) in diethyl ether (60 ml) overnight, rinsed twice with acetonitrile and then dried at 40°C under vacuum.

[0160] The samples thus obtained in the form of thin flakes were characterized by solid-state NMR spectroscopy. The data were recorded at room temperature on an Agilent DD2 400 MHz NB spectrometer using a 1.6 mm T3MAS dedicated HFXY probe. 19 F MAS NMR spectra were acquired at a spinning speed of 34 kHz using a 4.2 μs 90° pulse, a 20 s recycle delay, and 304 scans. 19F single pulse spectra. 19F chemical shifts δCS are reported relative to CFCl3 using PTFE (δCS = -123 ppm) as a secondary standard.

[0161] The spectrum of film 3 obtained after treatment with trifluoroacetic anhydride shows a contribution at -75 ppm, which is clearly observable and not present in the NMR spectrum of film 3. The peak at -75 ppm is attributed to the presence of -CF3 groups, which originates from the conversion of -OH groups in the sample into -CF3 groups by trifluoroacetylation.

[0162] The through-plane conductivity of membranes in alkaline electrolytes was measured using the H-Cell system.

[0163] The determination of membrane conductivity is based on the measurement of the slope of the cell polarization curve in a graph of voltage (V) versus current (I), the measurement being performed with a voltage sweep; the slope represents the resistance of the cell. The area surface resistance (ASR) of each membrane is obtained by subtracting the resistance of the cell without the membrane from the resistance with the membrane and multiplying this value by the free area of ​​the sample.

[0164] The cell consists of two glass chambers separated by a membrane (or a single chamber if no membrane is installed). In each chamber there is a working electrode consisting of a platinum spiral and an Ag / AgCl reference electrode. The reference electrode is inserted into glass tubes (Luggin capillaries) whose ends are placed near the membrane; the voltage on the reference electrode is related to the electrolyte voltage near the tip of the glass tube. The measured resistance of the cell is therefore a function of the distance between the two capillaries.

[0165] The ASR data are reported in Table 3. All films 1 to 3 had a thickness of 310 microns.

[0166] Table 3

[0167]

[0168] The data show that the membranes of the present invention have good ionic conductivity values.

Claims

1. A porous membrane comprising at least one poly(aryletherketone) polymer, said membrane having a contact angle of at least 155° as measured according to the Captured Bubble Contact Angle Test and / or a static contact angle as measured according to ASTM D 5725-99 that decreases over time, preferably a static contact angle that is at least 15° lower than the initial value when measured after 60 seconds, and wherein said membrane comprises at least one surface comprising at least one functionalized poly(aryletherketone) polymer comprising hydroxyl groups bonded to aromatic rings of the poly(aryletherketone) polymer backbone.

2. The film according to claim 1, wherein The poly(aryletherketone) polymer comprises at least 50 mol% of repeating units (R) selected from the group consisting of formulae (JA) to (JO) below. PAEK ): in: Each R' is the same as or different from each other and is selected from the group consisting of: halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali metal or alkaline earth metal sulfonate, alkyl sulfonate, alkali metal or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium; and -j' is zero or an integer from 1 to 4.

3. The film according to claim 2, wherein Repeating unit (R PAEK ) is selected from the group consisting of units having the following formulae (J'-A) to (J'-D) and (J"-B):

4. The film according to any one of claims 1 to 3, wherein The functionalized poly(aryletherketone) polymer comprises repeating units (R PAEK-OH ), these repeating units are selected from the group consisting of units having the following formulae (KA) to (KD): wherein each Q' is -OH and, independently at each occurrence, i is zero or an integer from 1 to 4, provided that in that repeat unit, the sum of all i's is different from zero.

5. The film according to claim 4, wherein The functionalized poly(aryletherketone) polymer further comprises repeating units (R PAEK ), the repeating units being selected from the group consisting of units of formulae (J'-A) to (J'-D) and (J"-B) as defined in claim 3.

6. The film according to any one of claims 1 to 5, wherein The functionalized poly(aryletherketone) polymer comprises a combined amount of at least 50 mol% of repeating units (R PAEK-OH ) and repeating units (R PAEK ).

7. The film according to any one of claims 1 to 6, wherein The functionalized poly(aryletherketone) polymer comprises 0.001 mol% or more of a repeating unit (R PAEK-OH ).

8. The film according to any one of claims 1 to 7, wherein The functionalized poly(aryletherketone) polymer comprises at least 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%, 99 mol%, 100 mol% of repeating units which are a combination of repeating units of formula (KA) and (J'-A) as defined in claims 3 and 4, with the proviso that the amount of repeating unit (KA) is different from zero.

9. The film according to any one of claims 1 to 7, wherein The functionalized poly(aryl) polymer comprises at least 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%, 99 mol%, 100 mol% of repeating units which are a combination of repeating units of formula (KA) and / or (J'-A) and repeating units of formula (KD) and / or (J'-D) as defined in claims 3 and 4, with the proviso that the amount of repeating units (KA)+(KD) is different from zero.

10. A method for producing a film as claimed in any one of claims 1 to 9, the method comprising: - providing a precursor film, the precursor film being a film comprising a poly(aryletherketone) polymer, having a contact angle of less than 155° as measured by the Captured Bubble Contact Angle Test and / or a static contact angle that does not decrease over time; and - chemically treating the precursor film to provide the film having at least one surface comprising hydroxyl groups bonded to aromatic rings in the poly(aryletherketone) polymer backbone and obtaining a contact angle of at least 155° as measured according to the Captured Bubble Contact Angle Test and / or a static contact angle that decreases over time.

11. The method of claim 10, wherein: The precursor film includes at least one surface comprising a poly(aryletherketone) polymer.

12. The method according to claim 10 or 11, wherein: The step of chemically treating the precursor film comprises contacting the precursor film with a peroxide in the presence of an oxidation catalyst comprising iron (II) or iron (III) ions to obtain hydroxyl groups bound to aromatic rings of the poly (aryletherketone) polymer backbone in the precursor film.

13. The method according to any one of claims 10 to 12, wherein: The step of providing the precursor film comprises the following steps: (I) providing a composition comprising at least one poly(aryl ether ketone) polymer, at least one poly(aryl ether sulfone) polymer, and at least one compound comprising a sulfonate or carboxylate of a metal selected from the group consisting of alkali metals, alkaline earth metals, aluminum, iron, zinc, nickel, copper, palladium, and silver; (II) processing the composition to provide pellets; (III) melt-extruding the pellets obtained in step (II) to provide a precursor layer; (IV) contacting the precursor layer with at least one organic solvent or with water and subsequently with at least one organic solvent, thereby providing an intermediate porous layer; (V) contacting the intermediate porous layer obtained in step (IV) with water to provide a porous membrane.

14. An alkaline water electrolysis device, comprising: -anode; -cathode; as well as - The membrane as claimed in any one of claims 1 to 9, which is placed between the anode and the cathode.

15. A method for producing hydrogen, comprising the step of electrolyzing alkaline water by applying a voltage to the alkaline water electrolysis device according to claim 14, the step preferably being performed using a power source derived from renewable energy.

16. A method for filtering at least one fluid, the method comprising contacting the fluid with at least one membrane according to any one of claims 1 to 9, wherein: The at least one fluid is a gas or a liquid and is preferably selected from the group consisting of: biological solutions, buffer solutions, oil / water emulsions, water, hydrocarbons.

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