Separator for alkaline water electrolysis

Abstract

A separator (1) for alkaline water electrolysis with a catalyst layer, comprising a porous support (100), and on at least one side of the support, in order: - an optional porous polymer layer (200), - a non-porous, alkali-stable polymer layer (300), and - a catalyst layer (400).

Description

[Technical Field]

[0001] This invention relates to a separator for alkaline water electrolysis. [Background technology]

[0002] Today, hydrogen is used in a variety of industrial processes, for example, as a raw material in the chemical industry and as a reducing agent in the metallurgical industry. Hydrogen is a fundamental building block for the production of ammonia, and by extension, fertilizers, and methanol (used in the production of many polymers). Petroleum refining, where hydrogen is used to process intermediate oil products, is another area of ​​use. On the other hand, the production of hydrogen from fossil fuels results in large amounts of CO2 emissions.

[0003] Hydrogen is also considered an important future energy carrier, meaning that it can store and deliver energy in a usable form. Energy is released through an exothermic combustion reaction with oxygen, thereby forming water. No carbon-containing greenhouse gases are emitted during such combustion reactions.

[0004] Towards the realization of a low-carbon society, the importance of renewable energy, such as solar and wind power, is increasing even further.

[0005] The production of electricity from wind and solar power systems is highly dependent on weather conditions and therefore prone to fluctuations, leading to an imbalance between electricity supply and demand. In recent years, there has been significant interest in so-called power-to-gas technology, which uses electricity to produce gaseous fuels such as hydrogen in order to store surplus electricity. As the production of electricity from renewable energy sources increases, so does the demand for storing and transporting that energy.

[0006] Water electrolysis is an important manufacturing process in which renewable electricity can be converted into hydrogen. Hydrogen produced in this manner is often referred to as green hydrogen, emphasizing that no greenhouse gases are formed during its production. Ammonia and steel prepared from or using green hydrogen are also referred to as green ammonia and green steel.

[0007] In alkaline water electrolysis (AWE) cells, porous separators are used to prevent short circuits between electrodes of different polarities and to avoid gas crossover, thereby preventing the recombination of hydrogen (formed at the cathode) and oxygen (formed at the anode). Furthermore, the separator should exhibit high ionic conductivity to facilitate the transport of hydroxyl ions from the cathode to the anode. AWE separators (for example, those disclosed in Patent Document 1 (VITO), Patent Document 2, and Patent Document 3 (AGFA-GEVAERT NV and VITO)) typically include a porous polymer layer applied to a porous support. By adding inorganic particles (such as zirconium oxide) to the polymer layer to make it hydrophilic, sufficient electrolyte permeability and minimization of bubble adhesion to the surface of the polymer layer are ensured.

[0008] In a typical AWE cell, a separator is placed between the two electrodes (anode and cathode). Hydrogen is formed at the cathode as a result of the hydrogen evolution reaction (HER), while oxygen is formed at the anode as a result of the oxygen evolution reaction (OER). Catalysts are used to minimize overpotentials to both OER and HER. These catalysts are typically deposited on the electrodes.

[0009] On the other hand, the catalyst may also be attached to the separator surface to further reduce the overpotential. A separator with a catalyst attached to one of its surfaces is typically referred to as a catalyst-layered separator or catalyst-layered electrolyte membrane.

[0010] The method of attaching a catalyst to a non-porous membrane (such as a proton exchange membrane (PEM)) is disclosed in Non-Patent Document 1.

[0011] On the other hand, in AWE, porous separators (such as those mentioned above) are typically used. Patent document 4 (FRAUNHOFER GES) discloses a method for depositing a catalytically active layer onto the surface of a porous membrane ZIRFON PERL supplied by AGFA-GEVAERT NV by plasma spraying. Patent document 5 (UNIV TSINGHUA) discloses an apparatus for manufacturing a catalyst-layered separator in which a catalyst is sprayed onto both sides of a porous separator. Patent document 6 (SIEMENS AG) discloses a catalyst-layered separator for PEM, AEM, and AWE. The catalyst is deposited, for example, onto a ZIRFON PERL separator by vapor deposition.

[0012] Patent Document 7 (KOREA RES INST CHEMICAL TECH) provides a porous separator along with a crosslinked PVA layer containing a metal catalyst. The metal catalyst further reduces HTO by converting hydrogen passing through the porous membrane into water via a catalytic reaction with oxygen, but this comes at the expense of electrochemical efficiency. The PVA layer has also been applied by an ultrasonic spray coating process.

[0013] When a catalyst is attached to the surface of a porous membrane, some of the catalyst may adhere within the membrane's pores. If the catalyst is present within such pores, hydrogen and / or oxygen may form within the membrane. This can lead to an increase in area resistance (a decrease in ionic conductivity) and / or an increase in gas crossover.

[0014] Therefore, a catalyst-layered separator for AWE is required, in which the catalyst is not attached to the pores of the separator. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] European Patent Application Publication No. 1776490 [Patent Document 2] International Publication No. 2009 / 147084 [Patent Document 3] International Publication No. 2009 / 147086 [Patent Document 4] German Patent Application Publication No. 102020208003 [Patent Document 5] Chinese Utility Model Patent No. 219315104 [Patent Document 6] European Patent Application Publication No. 4105359 [Patent Document 7] Korean Patent Publication No. 2022 - 0073190 [Non - Patent Document]

[0016] [Non - Patent Document 1] Bladergroen et al., “Overview of Membrane Electrode Assembly Preparation Methods for Solid Polymer Electrolyte Electrolyzer”, 2012, DOI: 10.5772 / 52947 [Summary of the Invention]

[0017] The object of the present invention is to provide a separator with a catalyst layer in which the adhesion of the catalyst into the pores of the separator is minimized and the gas permeability is improved.

[0018] This object is achieved by using the separator according to claim 1.

[0019] A further object of the present invention will become apparent from the following description of this specification. [Brief Description of the Drawings] <e

[0020] [Figure 1] Several embodiments of the catalyst layer separator according to the present invention are schematically illustrated. [Figure 2] One embodiment of the electrolytic cell according to the present invention is schematically illustrated. [Figure 3] The SEM cross-sections of a comparative catalyst-layer separator S-1 (a) and an embodiment of the catalyst-layer separator according to S-2 of the present invention (b) are shown, both of which were prepared in Example 1. [Figure 4] The images show (a) a top view of the surface of the latest separator ZIRFON and (b) a top view of the surface of separator S-3 containing the non-porous layer prepared in Example 2. [Modes for carrying out the invention]

[0021] Separator with catalyst layer A separator may also be referred to as a diaphragm or membrane, as used herein.

[0022] The alkaline water electrolysis separator with a catalyst layer according to the present invention comprises a porous support (100) and, in order, on at least one side of the support, -Optional porous polymer (200) containing polymer A, - A non-porous layer (300) containing polymer B, and -Catalyst layer (400) Includes.

[0023] It has been observed that the presence of a non-porous layer (300) between the porous support (100) or the porous layer (200) containing polymer A and the catalyst layer (400) prevents the catalyst from adhering to the pores of the porous support or the porous layer containing polymer A (see Examples).

[0024] An optional porous layer containing polymer A, a non-porous layer containing polymer B, and a catalyst layer may be applied independently of each other on one or both sides of the porous support. When these layers are applied on both sides of the porous support, the optional porous layer (200 and 200'), the non-porous layer (300 and 300'), and the catalyst layer (400 and 400') may be identical or different from each other. Figure 1 (Figures 1a to 1f) schematically shows different embodiments of the catalyst-layered separator according to the present invention.

[0025] When only one catalyst layer is provided (for example, in the embodiments shown in Figures 1.a, 1.c, and 1.e), it has been observed that the increase in electrolytic efficiency is maximized when the catalyst layer faces the cathode in the electrolytic cell.

[0026] The catalyst-layer-equipped separator according to the present invention preferably comprises one or two porous layers containing polymer A applied to one or both sides of a porous support, and more preferably comprises two porous layers containing polymer A applied to either side of the porous support.

[0027] The total thickness of the separator with a catalyst layer is preferably 50 to 750 μm, more preferably 75 to 500 μm, and most preferably 100 to 250 μm. The area resistance of a separator typically increases with increasing thickness. On the other hand, a minimum thickness is often required to ensure sufficient mechanical / physical properties of the separator and to facilitate its manufacture and handling.

[0028] The gas permeability of the separator with a catalyst layer is preferably 3 L / min.cm 2 Less than, and more preferably 1.5 L / min.cm² 2 It is less than 0.5 L / min.cm², most preferably 0.5 L / min.cm². 2 It is less than 0.1 L / min.cm², and particularly preferably 0.1 L / min.cm². 2It is less than [value missing]. Gas permeability is preferably measured at 5 bar using a Porolux™ 1000 instrument. If gas permeability is too high, it may lead to an increase in HTO (vol% of hydrogen present in the oxygen stream formed at the anode).

[0029] To maximize ionic conductivity, it is necessary to maximize the penetration of the electrolyte into the separator. The porosity of the separator with the catalyst layer is preferably 40-90%, more preferably 50-80%, and most preferably 60-70%.

[0030] The presence of a non-porous layer does not cause a substantial increase in the area resistance of the separator. The area resistance of the separator with a catalyst layer is preferably 0.35 ohm.cm in a 30 wt% KOH aqueous solution at 25°C. 2 Less than, and more preferably 0.25 ohms / cm² 2 It is less than 0.10 ohms / cm², most preferably 0.10 ohms / cm². 2 It is less than [value]. The area resistance is preferably determined using an Inolab® Multi9310IDS instrument available from VWR (a subsidiary of Avantor) equipped with TetraCon925 conductive cells available from Xylem.

[0031] The bubble point of the separator with a catalyst layer, as measured according to ASTM F316, is preferably at least 5 bar, more preferably at least 6 bar, most preferably at least 7 bar, and particularly preferably at least 8 bar.

[0032] catalyst layer The catalyst-layer-equipped separator according to the present invention includes a catalyst layer (400). The catalyst layer is coated onto a non-porous layer (300), resulting in direct contact between the two layers. This means that under normal operating conditions, the catalyst layer cannot be separated from this layer. When the catalyst layer is applied directly to the non-porous layer, the resulting catalyst surface can be more uniform and smoother compared to when the catalyst is applied onto an electrode. Thus, any voids between the separator and the catalyst layer can be eliminated by obtaining a “true” zero-gap configuration (see below). Such a smooth catalyst layer surface can be advantageous in preventing localized temperature and / or current hotspots in the separator when in contact with the electrode, thereby ensuring increased electron transfer efficiency and preventing localized film degradation.

[0033] In the electrolytic cell, the catalyst layer facing the anode contains one or more catalysts for the oxygen evolution reaction (OER), while the catalyst layer facing the cathode contains one or more catalysts for the hydrogen evolution reaction (HER).

[0034] The thickness of the catalyst layer is preferably 0.5 to 200 μm, more preferably 1 to 100 μm, most preferably 5 to 75 μm, and particularly preferably 10 to 50 μm.

[0035] The catalyst is preferably selected from the group consisting of Ni, Ni / NiO, Ni-Fe, Ni-Co, Ni-Mn, Ni-Mo, Fe-Co, Ni-Zn, Ni-Al, Ni-Mo-Al, Ni-Co-Al, Ni-MnAl, Ni-Si, Ni-B, or Ni-Si-B. A single catalyst or a combination of catalysts may be used. Preferred catalysts for the cathode side of the separator are selected from the group consisting of Ni, Raney Ni, Ni-Fe, Ni-Co, and Ni-Mo. Preferred catalysts for the anode side of the separator are selected from NiO / OH and NiO.

[0036] A catalyst-layered separator may have the catalyst layer on one or both of its surfaces. When the catalyst layer is present on only one surface, the catalyst-layered separator is preferably oriented in the electrolytic cell so that the catalyst layer faces the cathode. Such orientation has been shown to increase the electrolytic efficiency compared to orientation in which the catalyst layer faces the anode.

[0037] Nonporous layer containing polymer B The catalyst layer separator according to the present invention includes a non-porous layer containing polymer B between a porous support or a porous layer containing polymer A and the catalyst layer.

[0038] The presence of a non-porous layer offers the following advantages: - The catalyst must not adhere to the pores of the porous support or porous layer(s). - The gas permeability of the separator with a catalyst layer decreases, and - The smoothness of the non-porous layer improves contact with the catalyst layer (or electrode).

[0039] The nonporous layer containing polymer B, as described below, is nonporous in the traditional sense, meaning it does not have fixed pores (i.e., permanent and clearly defined pores or channels like those found in porous materials). Instead, ion transport through the nonporous layer occurs via transient and dynamic voids or free volume regions between individual polymer chains. These voids are formed due to the thermal motion and packing arrangement of the polymer chains. However, these voids are not static (or "fixed") in structure and size. The size of these dynamic voids is typically less than 5 nm, on the order of angstroms, and between 0.1 and 5 nm (i.e., 1 to 50 Å). According to well-known solution diffusion models, the size and chemistry of the voids allow for the selective transport of ions while excluding larger species. Thus, the nonporous layer containing polymer B lacks fixed pores, and the small, dynamic spaces between polymer chains enable ion transport.

[0040] The layer containing polymer B must not have fixed pores (with clearly defined pore sizes) and therefore must be non-porous. If a porous layer is used, it is not possible to prevent the penetration of the catalyst into the separator, regardless of the pore size. Even if the average pore size of this porous layer is small, it is not possible to completely avoid catalyst penetration. In fact, when the presence of a distribution in the pore size of the separator is combined with a distribution in the particle size of the catalyst, and when a catalyst coating method (which may involve the application of pressure) is added, it is unavoidable that some catalyst will adhere to the pores of the porous layer. On the other hand, since the non-porous layer containing polymer B does not have pores, it is possible to completely eliminate catalyst penetration into the separator.

[0041] The nonporous layer containing polymer B needs to withstand typical AWE conditions (e.g., 80°C, 30 wt% KOH) for extended periods. Therefore, the nonporous layer preferably contains polymer B, which is alkali-stable, making the nonporous layer, and consequently the separator according to the present invention, suitable for alkaline water electrolysis. As used herein, an alkali-stable polymer means a polymer that exhibits minimal degradation of polymer chain length and changes in polymer chemistry even after four weeks of exposure to 120°C, 6 M KOH.

[0042] Furthermore, the non-porous layer cannot adversely affect the area resistance / conductivity of the separator. Therefore, the hydroxyl permeability of the non-porous layer under AWE conditions is sufficient. It must be that way.

[0043] Furthermore, the non-porous layer preferably contains a hydrophilic polymer B, which enhances the solubility of KOH (and water) in the non-porous layer and thus reduces gas permeability without adversely affecting conductivity / area resistance. The contact angle of water on the surface of the non-porous layer, as measured as described below, is preferably less than 90 degrees, more preferably less than 75 degrees, and most preferably less than 60 degrees. Particularly preferably, the contact angle of water on the surface of the non-porous layer is 40 to 60 degrees. It has been observed that area resistance decreases when the adhesion of air bubbles to the hydrophilic non-porous layer is reduced.

[0044] Furthermore, the non-porous layer preferably has a smooth surface to improve contact with the catalyst layer (or electrode). Area resistance. The smooth surface also improves contact between the separator surface and the electrode in the electrolytic cell. The surface of the non-porous layer has been found to be significantly smoother (less rough) than the surface of state-of-the-art separators that do not have such a non-porous layer (see Examples).

[0045] The hydroxyl permeability of the non-porous layer can be adjusted, in particular, by the layer thickness, the properties of polymer B, the degree of crosslinking, the type of crosslinking agent, and the blending of different polymers B into the non-porous layer. This allows for the use of a wide range of polymers with different swelling characteristics in aqueous alkaline media.

[0046] Polymer B is preferably crosslinked to further improve its long-term stability in the highly alkaline electrolyte of the electrolytic cell in which the separator is used.

[0047] The nonporous layer may further contain other components to optimize its properties or other components to optimize the coating process. On the other hand, the nonporous layer of the present invention preferably contains at least 50 parts by weight, more preferably at least 75 parts by weight, and most preferably at least 90 parts by weight of polymer B to ensure sufficient hydroxyl permeability and smoothness of the nonporous layer and to maintain sufficient mechanical properties. Other components include, for example, surfactants (see below), inorganic particles (see below), viscosity modifiers (see below), and recombination catalysts.

[0048] Preferred recombination catalysts are selected from the group consisting of NiO, Pt, Ir, IrO2, and stainless steel.

[0049] The thickness of the non-porous layer is preferably 0.01 to 50 μm, more preferably 0.1 to 30 μm, and most preferably 1 to 20 μm. Even more preferably, the thickness of the porous separator is 7 to 15 μm. If the thickness of the non-porous layer exceeds 50 μm, the overall resistance of the film may become too high. On the other hand, if the thickness of the non-porous layer is less than 0.01 μm, the non-porous layer may not cover the entire separator surface and may not be smooth enough to improve contact with the catalyst layer.

[0050] Polymer B Polymer B can be selected, for example, from optionally modified polybenzimidazole, polysulfone, poly(ethersulfone), poly(etherketone), poly(phenylene ether), poly(ether), poly(acetal), styrene-based polymers and copolymers, as well as poly(olefin)-based polymers and copolymers. Preferred polymers all have a carbon polymer backbone.

[0051] Polymer B is preferably functionalized with nonionic hydrophilic groups, and the modification is preferably The hydrophilic fragments are selected from the group consisting of hydroxylation and ethoxylation. Preferred hydrophilic fragments are selected from the group consisting of polyhydroxyl fragments and poly(ethylene oxide) fragments. The fragments may be part of the polymer backbone or grafted onto the polymer backbone. The hydrophilic fragments may be arranged in different configurations, such as block copolymers or graft copolymers. Poly(ethylene glycol)-based polymers or copolymers, including block copolymers (such as poly(olefin-block co-ethylene glycol)) or graft copolymers (such as poly(ethylene glycol) grafted onto poly(sulfone) or poly(ethersulfone)), are particularly preferred. Polyhydroxyl-containing polymers are most preferred. Typical examples of polyhydroxyl-containing polymers include polysaccharides and vinyl alcohol-based (co) polymers. Preferred polysaccharides include dextran and pullulan and their derivatives, as well as starch derivatives. Preferred vinyl alcohol-based (co) polymers include poly(vinyl alcohol), poly(ethylene-co-vinyl alcohol), and poly(ethylene-co-vinylamine).

[0052] Polymer B is preferably selected from the group consisting of poly(ethylene glycol) or its copolymer, poly(saccharide), poly(ethylene-co-vinyl alcohol), poly(ethylene-co-vinylamine), and poly(vinyl alcohol). Particularly preferred is polymer B to be poly(vinyl alcohol)(PVA) or poly(ethylene-co-vinyl alcohol).

[0053] PVA is typically prepared by hydrolysis of poly(vinyl acetate). The properties of PVA are determined by the degree of hydrolysis. A preferred degree of hydrolysis is 50-100%, more preferably 70-99%, and most preferably 85-98%. Nonporous layers containing PVA with a high degree of hydrolysis, i.e., over 85%, have been shown to be more hydrophilic and less soluble in water.

[0054] The molecular weight of polymer B is preferably 10 to 250 kDa, more preferably 15 to 150 kDa, and most preferably 50 to 125 kDa. Nonporous layers containing polymer B having a high molecular weight, i.e., having an Mw of at least 15 kDa, have been shown to have improved uniformity. Furthermore, if the Mw is less than 15 kDa, the lack of sufficient chain entanglement between polymer chains can result in poor film formation properties and a decrease in the overall durability of the separator. While higher molecular weight polymers result in nonporous layers with improved mechanical properties, if the molecular weight is too high, i.e., if the MW is higher than 150 kDa, it may become difficult to process.

[0055] surfactants The nonporous layer may contain surfactants to optimize the coating process, to obtain a uniform nonporous layer, and / or to optimize the surface properties of the nonporous layer. Surfactants may be added to reduce static and / or dynamic surface tension, to improve wetting on the separator surface, to improve the smoothness of the coated layer, and to avoid coating defects (such as orange peel, craters / fish eyes, mottling, Bénard cells, and Marangoni convection).

[0056] Suitable surfactants include, for example, modified silicone surfactants (such as silicone-polyether graft copolymers and block copolymers or trisiloxanes). Preferred silicone polyether surfactants include Tego wet 240, Tego wet KL 248, Dynol 960, Dynol 980, and Tego Foamex 822 supplied by Evonik; Byk 348 and Byk 3450 supplied by Byk Chemie; Coatosil 7607 and Silwet L 77 supplied by Momentive; and Hydropala supplied by BASF. t WE3220. Byk is a silicone surfactant with high hydrolysis stability. These are Byk3420 supplied by Chemie, and Silwet HS312 and Silwet HS313 supplied by Momentive.

[0057] Another class of surfactants that may be used is fluorotensides (e.g., Tivida FL2500 or Tivida FL2700). However, the use of fluorotensides is not very desirable due to health and safety concerns.

[0058] Other preferred surfactants are alkoxylated surfactants (such as alkyl ethoxylates or alkoxylated block copolymers). Examples include Lutensol AP6, Lutensol A8, Pluronic PE10500, and Kauropal K933 supplied by BASF; Emulgen 109P and Akypo RLM100 supplied by Kao; and Ecosurf EH6 supplied by Dow Chemical.

[0059] In addition, mixtures of silicone additives and alkoxylated surfactants (e.g., Kauropal K933 and Tego foamex822) may also be used.

[0060] Acetylene derivatives (such as Dynol 604, Surfynol 104, Surfynol 420, and Surfynol 465) may be used to reduce the surface tension of the coating solution. Dynol 604 is an ethoxylated surfactant based on 2,5,8,11-tetramethyldodeca-6-in-5,8-diol. The Surfynol grade is based on 2,4,7,9-tetramethyl-5-decine-4,7-diol. Hydrogenated Surfynol derivatives (such as Surfynol AD01) may also be used.

[0061] To optimize compatibility with poly(vinyl alcohol), hydroxyl-functional surfactants (such as alkyl polyglucoside surfactants (e.g., Glucopon 420 or Glucopon 100DK supplied by BASF; Simulsol SL826 supplied by Seppic SA); and polyglycidol or polyglycerol-based surfactants (PGLAL ML04 and PGLAL ML08 supplied by Daicel Europe GmbH; and AEG102 / 61 supplied by Lamberti, etc.)) may be used. Bio-based nonionic surfactants such as HoneySurf LF supplied by Holiferm may also be used.

[0062] To improve coating quality, ionic surfactants may be used in addition to nonionic surfactants; that is, anionic, cationic, or amphoteric surfactants may be used. Precursors of ionic surfactants that become ionic at low or high pH may also be used, for example, carboxylated surfactants that become anionic at basic pH (Akypo RLM45 and Akypo RLM100) or surfactants having a tertiary amine group that become ionic at low pH. Suitable amphoteric surfactants include amine oxide surfactants such as Euroglyc AMS supplied by EOC Surfactants, Arkopon T Paste8015 supplied by Clariant, and Makamine LO supplied by Verdant Specialty Solutions. Suitable anionic surfactants include Aerosol OT100 and Aerosol supplied by Solvay. These are OT75E, Exodiss SE75 supplied by EOC Surfactants, or Marlon A365 supplied by Sasol.

[0063] Some surfactants (e.g., silicone-based products or alkylethoxylates) (T) can be designed as an antifoaming agent. Such surfactants typically have a lower HLB (hydrophilic-lipophilic balance) value. Examples of antifoaming agents include Tego Foamex 3062 or Tego Foamex 884 supplied by Evonik; Airase 5355 or Supread 2059 supplied by Elementis; and AF8014 supplied by Dow Chemical.

[0064] Viscosity modifier The viscosity of polymer B solution can be optimized by adding a so-called thickener or rheological modifier.

[0065] Standard rheological modifiers (such as ASE (alkali-swelling emulsion), HASE (hydrophobically modified alkali-soluble emulsion), or HEUR (hydrophobically ethoxylated urethane polymer)-based thickeners) may be used. Examples of commercially available standard rheological modifiers include Tego Visco Plus3000, Tegovisco Plus3010, Tafigel PUR80, ADDITOL VXW6388E, BYK-LP R21675, Rheovis AS1130, Rheolate278, and Rheolate255.

[0066] Other rheological modifiers are selected from gelatin, dextran, starch, collagen derivatives, alginates, chitosan, collodions, and other polysaccharides (xanthan gum, gum arabic, guar gum, casein, carrageenan, pectin, albumin, and cellulose-based thickeners such as methylcellulose, CMC (carboxymethylcellulose), HPMC (hydroxypropylmethylcellulose), and HEC (hydroxyethylcellulose)). Other preferred thickeners are polyethylene glycol, polyglycerol, polyglycidol or EO-PO copolymer, and poly(vinylpyrrolidone). Examples of specific thickening agent product names include Kelzan S, Kelzan T, Kelzan RD, Natrosol 250HR, Tylose CR 1500, Satialgine S 170, Tylose H 4000P, Ambergum 3031, Walocel CRT 10000, Dextran 60000, Biozan S, Polygel, Kelcogel, and Rheozan.

[0067] Highly preferred rheological modifiers are high molecular weight poly(vinyl alcohol), vinyl alcohol copolymers, or branched poly(vinyl alcohol) (such as KURARAY POVAL105 88 KX SB or KURARAY POVAL200 88 KX SB branched PVA structure (corresponding to CAS registry number 1643793-45-6)). The addition of polyvinyl alcohol or vinyl alcohol copolymer as a thickener provides good compatibility and does not significantly alter the properties of the layer.

[0068] Other thickeners that can be used include inorganic components (such as clay, silica, or other metal oxide particles). Examples include Laponite JS, Laponite RD, Levasil300, Cab-o-sil M5, Aerosil300, Aerosil200, Bindzil CC151 HS, Bindzil CC301, and Luvotix. These are HT, Luvogel4, and Luvogel LD.

[0069] porous support The catalyst-layer-equipped separator according to the present invention includes a porous support. Such a porous support provides mechanical strength to the separator, facilitating its production, handling, and integration into an electrolytic cell.

[0070] The thickness of the porous support is preferably 350 μm or less, and more preferably 200 The thickness is less than or equal to μm, most preferably less than or equal to 100 μm, and particularly preferably less than or equal to 75 μm. It has been observed that the ionic conductivity of the catalyst-layer-equipped separator increases as the thickness of the porous support decreases. However, in order to ensure sufficient mechanical properties of the catalyst-layer-equipped separator, the thickness of the porous support is preferably 20 μm or more, and more preferably 40 μm or more.

[0071] The porous support is preferably a nonwoven fabric, woven fabric, mesh, or felt, and more preferably a nonwoven fabric or woven fabric.

[0072] Woven fabrics typically exhibit better dimensional stability and uniformity in terms of open areas and thickness. However, the manufacture of woven fabrics with a thickness of 100 μm or less is more complex, resulting in more expensive fabrics. The manufacture of nonwoven fabrics, even those with a thickness of 100 μm or less, is not significantly more complex. Furthermore, nonwoven fabrics can have larger open areas.

[0073] The open area of ​​the porous support is preferably 30-80%, more preferably 40-70%, in order to ensure good penetration of the electrolyte into the support.

[0074] The fabric preferably has a fiber diameter of 10 μm to 200 μm, more preferably 20 μm to 150 μm, and most preferably 30 μm to 100 μm. Fabrics with thinner thicknesses preferably have smaller fiber diameters. For example, a fabric with a thickness of 150 μm or less preferably contains fibers with a fiber diameter of 75 μm or less, more preferably 50 μm or less, and most preferably 35 μm or less.

[0075] To further reduce the thickness of the fabric, the ratio of the gauze thickness to the fiber diameter is preferably less than 2.0, more preferably 1.7 or less, and most preferably 1.4 or less. Thinner fabrics allow for the preparation of thinner separators.

[0076] The porous support preferably contains a polymer, such as polypropylene, polyethylene, polysulfone, polyphenylene sulfide, polyamide / nylon, polyethersulfone, polyphenylsulfone, polyethylene terephthalate, polyetheretherketone, sulfonated polyetheretherketone, monochlorotrifluoroethylene, copolymer of ethylene and tetrafluoroethylene or chlorotrifluoroethylene, polyimide, polyetherimide, and m-aramid.

[0077] Preferred porous supports include polyphenylene sulfide (PPS) or polyether ether ketone (PEEK).

[0078] PPS or PEEK-based porous supports exhibit high resistance to high-temperature, high-concentration alkaline solutions and high chemical stability against reactive oxygen species generated from the anode during water electrolysis processes. Furthermore, PPS and PEEK can be easily processed into various forms (such as woven or nonwoven fabrics).

[0079] The density of the porous support is preferably 0.1 to 0.7 g / cm³. 3 That is the case.

[0080] The porous support is preferably a continuous web that enables the manufacturing process disclosed in EP-A1776490 and WO2009 / 147084.

[0081] The width of the web is preferably 30 to 300 cm, and more preferably 40 to 200 cm.

[0082] Porous polymer layer containing polymer A The porous polymer layer comprises polymer A capable of forming a three-dimensional porous network during the phase transition step described below. Such polymers are described below.

[0083] The porous polymer layer may further contain inorganic particles. Such inorganic particles typically improve electrolyte permeability by increasing the hydrophilicity of the porous polymer layer. Furthermore, inorganic particles have been shown to improve the alkali resistance of the polymer. Such inorganic particles are described below.

[0084] Porous polymer layers described for state-of-the-art porous separators (e.g., those disclosed in EP-A3933069 or WO2023 / 280600, both supplied by AGFA-GEVAERT NV) may be used in separators according to the present invention. On the other hand, the porous layer in such state-of-the-art separators is characterized by striking a balance between minimum gas permeability and maximum ionic conductivity. Since a non-porous layer is present in the separator according to the present invention, it is no longer necessary for the gas permeability of the porous polymer layer to be minimum, and the layer can be optimized to maximize ionic conductivity.

[0085] The surface pore diameter of the porous layer may not be so large as to prevent non-uniformity of the non-porous layer, nor so small as to prevent delamination of the non-porous layer from the porous support and / or porous polymer layer. The average surface pore diameter is preferably 0.001 to 10 μm, more preferably 0.01 to 5 μm, and most preferably 0.1 to 1 μm. The surface pore diameter is preferably measured using scanning electron microscopy.

[0086] The pores in the porous polymer layer of the separator according to the present invention may be larger than those in the state-of-the-art separator described above, and this is also due to the presence of a non-porous layer. The porous polymer layer may even contain large-finger-like pores.

[0087] A porous layer containing polymer A may be applied to one or both sides of a porous support. If two porous polymer layers are applied, they may be identical or different from each other.

[0088] The porous layers containing polymer A, applied to both sides of the separator, may be the same as or different from each other. Such porous layers may differ in the following ways: - Composition (e.g., different polymer A or different inorganic particles); - Thickness (for example, as disclosed in WO2023 / 208776 (AGFA-GEVEART NV)); - Pore size or porosity (which can be varied by applying different phase transition conditions to both layers, e.g., as disclosed in EP-A3652362 (AGFA-GEVAERT NV)).

[0089] Polymer A The porous layer comprises polymer A, which is capable of forming a three-dimensional porous network as a result of the phase transition step in the preparation of the separator described below. An aqueous or organic medium may be used for the phase transition that results in the porous structure.

[0090] When an aqueous medium is used for phase conversion, polymer A is preferably an alkali-stable polymer that does not swell in an alkaline aqueous medium. Polymer A is preferably selected from the group consisting of high-performance engineering plastics and polymers having an all-carbon backbone.

[0091] High-performance engineering plastics typically consist of an aromatic hydrocarbon-containing skeleton. Preferably, high-performance engineering plastics are selected from the group consisting of poly(sulfone), poly(ethersulfone), poly(imide), poly(etherimide), poly(amideimide), poly(phenylene sulfide), poly(phenylene oxide), and poly(etherketone).

[0092] Polymers containing an all-carbon backbone are also called poly(hydrocarbons) and are preferably selected from the group consisting of poly(olefin)-based polymers and poly(styrene)-based polymers. Poly(olefins) may be fluorinated or chlorinated. Typical examples of fluorinated and chlorinated poly(hydrocarbons) are poly(vinylidene fluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), poly(vinyl chloride) (PVC), and poly(vinylidene chloride) (PVDC). Poly(hydrocarbons) may be pure hydrocarbons based on unfunctionalized poly(olefins) (such as poly(propylene) (PP) or low-density poly(ethylene)). Poly(styrene)-based polymers may be pure poly(styrene) or styrene-based copolymers (such as SEBS (also known as Kraton®)). Functionalized poly(olefins) (such as hydrophobically modified poly(vinyl alcohol) derivatives) may also be used. In the porous layer according to the present invention, typical derivatives (such as hydrophobic poly(acetal) (e.g., poly(vinylbutyral))) can be used as polymers. Poly(ethylene-co-vinyl alcohol), particularly grades having a high ethylene content, can also be used. In certain cases, non-swelling poly(ester) (such as poly(ethylene terephthalate) and poly(butylene terephthalate)) can be used.

[0093] When an organic medium is used as a phase conversion medium, the layer can be made stable in an alkaline medium by using an alkali-stable hydrophilic polymer for the phase conversion and then crosslinking the hydrophilic polymer. Poly(vinyl alcohol) is a particularly preferred polymer. To make the layer alkali-resistant, crosslinking using a bifunctional or polyfunctional aldehyde is particularly preferred.

[0094] Polymer A is preferably selected from the group consisting of poly(sulfone), poly(ethersulfone), poly(phenylene sulfide), poly(etheretherketone), and poly(phenylsulfone), with poly(sulfone) being the most preferred.

[0095] The porous layer may contain two, three, or more different polymers A described above.

[0096] The molecular weight (Mw) of polymer A is preferably 1,000 to 250,000, and more preferably 25,000 to 250,000. If Mw is too low, the physical strength and durability of the porous layer may be insufficient. If Mw is too high, the viscosity of the doping solution may become too high.

[0097] Examples of poly(sulfones), poly(ethersulfones), and combinations thereof are disclosed in paragraphs

[0021] to

[0032] of EP-A3085815.

[0098] The total amount of polymer A is preferably 5 to 40 wt%, more preferably 10 to 30 wt%, and most preferably 15 to 25 wt%, all relative to the total dry weight of the porous polymer layer.

[0099] inorganic particles The porous polymer layer, for example, has hydrophilic and / or alkaline stability. To improve this, inorganic particles may be further included. Such inorganic particles may also be incorporated into the nonporous layer to further optimize the properties of the nonporous layer.

[0100] Preferred inorganic particles are selected from metal oxides and metal hydroxides.

[0101] Preferred metal oxides are selected from the group consisting of titanium oxide, bismuth oxide, cerium oxide, and magnesium oxide.

[0102] Preferred metal hydroxides are selected from the group consisting of zirconium hydroxide, titanium hydroxide, bismuth hydroxide, cerium hydroxide, and magnesium hydroxide. Particularly preferred magnesium hydroxide is disclosed in paragraphs

[0040] to

[0063] of EP-A3660188.

[0103] Other preferred inorganic particles are calcium, barium, lead, or strontium sulfates, with barium sulfate particles being more preferred. Such barium sulfate particles are disclosed in EP-A3994295.

[0104] Further other inorganic particles that can be used are nitrides and carbides of Group IV elements of the periodic table.

[0105] A combination of one or more different inorganic particles may be used.

[0106] Inorganic particles can be natural or synthetic substances.

[0107] The surface of the inorganic particles may be untreated, or it may be treated with, for example, a silane coupling agent, stearic acid, oleic acid, or a phosphate ester.

[0108] The shape of inorganic particles is not particularly limited as long as they take the form of particles, and can be irregular, spherical (such as perfectly spherical) and ellipsoidal, plate-like (such as flake-like and hexagonal plate-like), or fibrous.

[0109] The inorganic particles preferably have a d50 particle size of 0.05 to 2.0 μm, more preferably 0.1 to 1.5 μm, most preferably 0.15 to 1.00 μm, and most preferably 0.2 to 0.75 μm. The d50 particle size is preferably 0.7 μm or less, more preferably 0.55 μm or less, and most preferably 0.40 μm or less.

[0110] The total amount of inorganic particles is preferably 30-95 wt%, more preferably 50-92 wt%, and most preferably 60-90 wt%, all relative to the total dry weight of the porous layer containing polymer A. The amount of inorganic particles is preferably at least 65 wt%, more preferably at least 75 wt%, all relative to the total dry weight of the porous layer containing polymer A.

[0111] The weight ratio of inorganic particles to polymer in the porous layer containing polymer A is preferably 60 / 40 or more, more preferably 70 / 30 or more, and most preferably 75 / 25 or more.

[0112] Preparation of a separator with a catalyst layer A preferred method for preparing a separator with a catalyst layer according to the present invention is: - A step of providing a porous support (100), -Optionally, the following steps are taken: applying the doping solution described below onto a porous support, performing a phase change with respect to the applied doping solution, thereby forming a porous polymer layer (200) on the porous support; - The steps of applying a polymer B solution onto a porous support or an optional porous layer containing polymer A, thereby forming a non-porous layer (300) containing polymer B, - The step of applying a catalyst composition onto a non-porous layer to form a catalyst layer (or more) (400), Includes.

[0113] After application of the non-porous layer, preferably a drying step is carried out to at least partially remove the solvent of the coating solution. The drying is preferably carried out at a temperature of 60 - 90 °C for 5 - 20 minutes.

[0114] The optional porous layer containing polymer A, the non-porous layer containing polymer B, and the catalyst layer can be applied independently of each other on one or both sides of the porous support. When these layers are applied on both sides of the porous support, the optional porous layers (200 and 200’), non-porous layers (300 and 300’), and catalyst layers (400 and 400’) can be the same as or different from each other.

[0115] The separator with a catalyst layer according to the present invention can also be prepared by starting from a porous separator (both supplied by AGFA-GEVAERT NV) prepared as described in WO2023 / 280600 or WO2023 / 208776. Then, a polymer B solution is applied on one or both sides of such a porous separator, thereby forming one or two non-porous layers containing polymer B, and then a catalyst composition is applied on the non-porous layer(s), thereby forming one or two catalyst layer(s).

[0116] Application of a non-porous layer containing polymer B The non-porous layer containing polymer B is preferably prepared by coating on the porous support (100) or on the optional porous layer, and the polymer B solution has a viscosity of at least 400 mPa·s, preferably at least 500 mPa·s, more preferably at least 800 mPa·s, and most preferably at least 1000 mPa·s when measured at a shear rate of 20 °C, 100 s -1 The non-porous layer containing polymer B is preferably prepared by coating on the porous support (100) or on the optional porous layer, and the polymer B solution has a viscosity of at least 400 mPa·s, preferably at least 500 mPa·s, more preferably at least 800 mPa·s, and most preferably at least 1000 mPa·s when measured at a shear rate of 20 °C, 100 s.

[0117] Any coating method can be used to apply polymer B solution. Preferred coating methods are selected from the group consisting of slot die coating, curtain coating, blade coating, bar coating, air knife coating, cascade coating, extrusion coating, reverse roll coating, kiss coating, and dip coating. Highly preferred coating methods are air knife coating, cascade coating, curtain coating, reverse roll coating, slot die coating, and kiss coating.

[0118] To make the separator production process efficient and cost-effective, the non-porous layer is preferably applied in a single coating step.

[0119] The solvent in the polymer B solution depends on the type of polymer B. If polymer B is a hydrophilic polymer (such as PVA), the polymer B solution is preferably an aqueous solution. On the other hand, the aqueous solution may contain an organic water-soluble solvent (e.g., ethanol, isopropanol, DMSO, or a mixture thereof). However, the solvent is most preferably water.

[0120] Polymer B is preferably crosslinked. Crosslinking has been shown to improve the lifespan of the non-porous layer in the electrolytic cell. When polymer B is poly(vinyl alcohol) or ethylene vinyl alcohol copolymer, crosslinking is preferably carried out using a bifunctional or polyfunctional aldehyde (such as glutaraldehyde and benzene-1,4-dialdehyde). The aldehyde functional group reacts with the hydroxyl group of the poly(vinyl alcohol) or ethylene vinyl alcohol copolymer to form an acetal bond. For example, crosslinked polyvinyl alcohol may be obtained via gas-phase crosslinking of polyvinyl alcohol and glutaraldehyde, as described by KIM et al. (Journal of Power Sources 524(2022)231059). Alternatively, the crosslinked compound is preferably added to the polymer B solution together with a crosslinking catalyst (in the case of PVA and glutaraldehyde, an acid catalyst such as H2SO4 or HCl). The mixture is then stirred while crosslinking occurs. Once the desired viscosity is reached, the mixture is coated onto a porous support or a porous polymer layer. To avoid excessive viscosity increases in the mixture before coating, a crosslinking agent or acid catalyst may be added to the PVA solution immediately before coating. Alternatively, a separator coated with crosslinked polyvinyl alcohol may be obtained by the synthesis procedure described below. The crosslinked mixture is prepared by adding polymer B, a crosslinking agent, and a catalyst to a suitable solvent at pre-selected concentrations. The crosslinked mixture is homogenized by stirring. The desired viscosity of the crosslinked mixture is obtained by adding a viscosity modifier or by selecting a sufficiently high initial polymer concentration. The crosslinked mixture is then rapidly coated onto the substrate without waiting for crosslinking to occur. The coated substrate is then given a specific time to allow crosslinking to occur and then dried in an oven.

[0121] Other crosslinking compounds (such as epoxides and sulfonamides) may also be used. Combinations of crosslinking compounds may also be used.

[0122] After the application of the non-porous layer, a drying step is preferably performed to remove at least partially the solvent from the coating solution. Drying is preferably carried out at a temperature of 60-90°C for 5-20 minutes.

[0123] In cost-effective large-scale manufacturing processes, the non-porous layer containing polymer B is preferably applied on at least one side of the porous support and / or the porous layer containing polymer A in a continuous roll-to-roll process.

[0124] Application of catalyst layer The catalyst may be applied by any application method, for example, as disclosed in Bladergroen et al., “Overview of Membrane Electrode Assembly Preparation Methods for Solid Polymer Electrolyte Electrolyzer”, 2012, DOI:10.5772 / 52947. A well-known application method is the so-called decal method. In this method, a catalyst layer is first deposited onto a temporary substrate (e.g., glass fiber reinforced Teflon). If two catalyst layers are applied, a separator is then sandwiched between two catalyst-coated decals so that the catalyst layers face each other. After the catalyst layers are transferred from the decals to the separator using a hot press, the decals are removed. The catalyst may also be applied directly onto the surface of the separator, for example, by the following: - Electrically assisted catalyst deposition (electrodeposition, electrospray, and electrophoretic deposition methods, etc.) - Application of catalysts as vapors (magnetron sputtering and chemical vapor deposition, etc.) - Plasma spraying, - Dry spray, -Phase conversion, - Coating (slot die coating, curtain coating, blade coating, bar coating, air knife coating, cascade coating, extrusion coating, reverse roll coating, kiss coating, and dip coating, etc.). Preferred coating methods are air knife coating, cascade coating, curtain coating, reverse roll coating, slot die coating, and kiss coating. - Printing (screen printing, gravure printing, inkjet printing, flexographic printing, and 3D printing, etc.).

[0125] A preferred adhesion method is one that does not damage the non-porous polymer layer.

[0126] The catalyst layer(s) are preferably applied inline in the manufacturing equipment to enable an efficient and cost-effective production process.

[0127] When a coating or printing method is used to attach the catalytic material, the catalytic composition is coated or printed onto the surface of the separator, respectively. Such a catalytic composition comprises one or more catalysts and may further comprise a binder, a solvent, and further components (such as a surfactant).

[0128] Application of a porous layer containing polymer A An optional porous layer containing polymer A is imparted to a porous support by applying the doping solution described below onto at least one side of the porous support and performing a phase conversion with respect to the applied doping solution(s), thereby forming at least one porous layer containing polymer A on the porous support.

[0129] The doping solution is preferably completely impregnated into the porous support, after which a phase change is carried out.

[0130] For applying a porous layer onto a porous support, the methods disclosed in EP-A1776490 and WO2009 / 147084 may be used. Other suitable manufacturing methods that may be used are disclosed in EP-A3272908, EP-A3660188, and EP-A3312306.

[0131] dope solution The doped solution preferably comprises the polymer A and a solvent. The doped solution may further contain the inorganic particles.

[0132] The solvent in the doping solution is preferably an organic solvent capable of dissolving the polymer resin. Furthermore, the organic solvent is preferably miscible with water.

[0133] The solvent is preferably selected from N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N-butylpyrrolidone (NBP), N,N-dimethylformamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), acetonitrile, and mixtures thereof. A very preferred solvent is N-butylpyrrolidone (NBP) for health and safety reasons.

[0134] The doping solution may further contain other components to optimize the properties of the resulting polymer layer (e.g., its porosity and maximum pore diameter on its outer surface).

[0135] The doping solution preferably contains additives to optimize the pore size on the surface and within the porous layer. Such additives may be organic compounds, inorganic compounds, or combinations thereof.

[0136] Organic compounds that may affect pore formation in porous layers include polyethylene glycol, polyethylene oxide, polypropylene glycol, ethylene glycol, tripropylene glycol, glycerol, polyhydric alcohols, dibutyl phthalate (DBP), diethyl phthalate (DEP), diundecyl phthalate (DUP), isononanoic acid or neodecanoic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyethyleneimine, polyacrylic acid, methylcellulose, and dextran.

[0137] Preferred organic compounds that can influence pore formation in the porous layer are selected from polyethylene glycol, polyethylene oxide, and polyvinylpyrrolidone. Preferred polyethylene glycol has a molecular weight of 10,000 to 50,000, preferred polyethylene oxide has a molecular weight of 50,000 to 300,000, and preferred polyvinylpyrrolidone has a molecular weight of 30,000 to 1,000,000. Glycerol is a particularly preferred organic compound that can influence pore formation in the porous layer. The amount of compound that can influence pore formation is preferably 0.1 to 15 wt%, more preferably 0.5 to 5 wt%, relative to the total weight of the doped solution. Inorganic compounds that can influence pore formation include calcium chloride, magnesium chloride, lithium chloride, and barium sulfate. A combination of two or more additives that influence pore formation may be used.

[0138] The doping solution applied to either side of the porous support may be the same or different.

[0139] Application of doping solution The doping solution can be applied to the surface of a porous support by any coating or casting method.

[0140] A preferred coating method is extrusion coating. In a very preferred embodiment, the doping solution is applied by a slot-die coating method in which two slot-coating dies are located on either side of the porous support. The slot-coating dies can hold the doping solution at a predetermined temperature, uniformly distribute the doping solution on the support, and adjust the coating thickness of the applied doping solution.

[0141] 100s -1 The shear rate and viscosity of the doping solution, measured at a temperature of 20°C, are preferably at least 7.5 Pa.s, more preferably at least 15 Pa.s, and most preferably at least 30 Pa.s. The doping solution is preferably shear thinning. 100s -1 For viscosity at shear rate, 1s -1 The viscosity ratio at shear rate is preferably at least 2, more preferably at least 2.5, and most preferably at least 5.

[0142] Immediately after the application of the doping solution, the porous support is subjected to impregnation with the doping solution. Preferably, the porous support is subjected to complete impregnation with the applied doping solution.

[0143] Phase transition step After applying the doping solution to the porous support, the applied doping solution is subjected to a phase transition. In the phase transition step, the applied doping solution is transformed into a porous layer.

[0144] In a preferred embodiment, both doping solutions applied to the porous support are subjected to phase transition.

[0145] A porous hydrophilic layer can be prepared from the applied doped solution using any phase transition mechanism.

[0146] The phase transition step preferably includes a so-called liquid-induced phase separation (LIPS) step, a vapor-induced phase separation (VIPS) step, or a combination of the VIPS step and the LIPS step. The phase transition step preferably includes both the VIPS step and the LIPS step.

[0147] Both LIPS and VIPS are non-solvent-induced phase inversion processes.

[0148] In the LIPS step, the doped solution(s) are brought into contact with a non-solvent that is miscible with the solvent of the doped solution.

[0149] Typically, this is done by immersing a porous support coated with a dope solution(s) in a non-solvent bath (also called a coagulation bath).

[0150] The non-solvent is preferably water; a mixture of water and an aprotic solvent selected from the group consisting of N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N-butylpyrrolidone (NBP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMAC); an aqueous solution of a water-soluble polymer (such as PVP or PVA); or a mixture of water and an alcohol (such as ethanol, propanol, or isopropanol). The non-solvent is most preferably water. On the other hand, when using a water-soluble hydrophilic polymer A, the non-solvent is preferably an organic solvent.

[0151] The temperature of the coagulation bath is preferably 20 to 90°C, and more preferably 40 to 70°C.

[0152] The migration of the solvent from the coated polymer A layer to the non-solvent bath, and the migration of the non-solvent into polymer A layer, result in phase transition and the formation of a three-dimensional porous polymer network. As a result of impregnation of the applied doping solution into the porous support, the resulting hydrophilic layer adheres well to the porous support.

[0153] In the VIPS step, the porous support coated with the doping solution is exposed to a non-solvent vapor, preferably high-humidity air.

[0154] Preferably, the solidification step includes both a VIPS step and a LIPS step. Preferably, the VIPS step is performed before the LIPS step. In a particular preferred embodiment, the porous support coated with the doping solution is first exposed to high-humidity air (VIPS step) and then subjected to immersion in a water bath (LIPS step).

[0155] After the phase transition step (preferably a LIPS step in a coagulation bath), a washing step may be performed.

[0156] A drying step may be performed after the phase conversion step or an optional washing step.

[0157] A preferred method for preparing a porous polymer A layer on a porous support is described in paragraphs 117-129 of EP-A3933069 (AGFA-GEVAERT NV) and Figure 2. This is disclosed in section 3.

[0158] Electrolytic cell The catalyst layer-equipped alkaline water electrolysis separator according to the present invention can be used in an alkaline water electrolysis cell.

[0159] Such an electrolytic cell typically comprises at least one electrolytic cell containing two electrodes (anode (A) and cathode (C)) separated by a separator. An electrolyte is present between the two electrodes. The catalyst is typically applied to the electrodes, but in the electrolytic cell according to the present invention, the catalyst is applied to at least one side of the separator. Figure 2 schematically represents one embodiment of the electrolytic cell according to the present invention.

[0160] If the catalyst is applied to only one side of the separator, the catalyst may also be applied to the electrode facing the other side of the separator.

[0161] The electrodes are preferably made of a conductive material selected from the group consisting of nickel, iron, soft steel, stainless steel, vanadium, molybdenum, copper, silver, manganese, platinum group elements, graphite, and chromium. The electrodes may be made of a conductive alloy of two or more metals or a mixture of two or more conductive materials. Preferred materials are nickel or nickel-based alloys. Nickel has good stability in strong alkaline solutions, good conductivity, and is relatively inexpensive.

[0162] The catalyst layer applied to the electrode preferably contains nickel, cobalt, iron, and platinum group elements. The catalyst layer may contain these elements as elemental metals, compounds (e.g., oxides), composite oxides or alloys made of multiple metallic elements, or mixtures thereof. Preferred catalyst layers include plated nickel, nickel and cobalt plated alloys or nickel and iron plated alloys, composite oxides containing nickel and cobalt (such as LaNiO3, LaCoO3, and NiCo2O4), platinum group element compounds (such as iridium oxide), or carbon materials (such as graphene).

[0163] A particularly preferred catalyst layer contains Raney nickel. The Raney nickel structure is formed by selectively leaching out and removing aluminum or zinc from a Ni-Al alloy or Ni-Zn alloy. As a result of the formation of lattice vacancies during the leaching and removal process, the surface area increases, and the lattice defects, which are the active sites where the electron-catalytic reaction occurs, become denser.

[0164] Figure 2 schematically shows one embodiment of the electrolytic cell according to the present invention. A catalyst-layered separator (see Figure 1.f), which includes a catalyst layer, a non-porous layer, and a porous polymer layer applied to both sides of a porous support, is placed between the anode (A) and the cathode (C). Since the catalyst-layered separator includes catalyst layers on both sides, there is no catalyst on the electrodes.

[0165] When an electric current is supplied to the electrolytic cell, hydroxyl ions in the electrolyte are oxidized to oxygen at the anode, and water is reduced to hydrogen at the cathode. The hydroxyl ions formed at the cathode are transferred to the anode via a separator. The separator prevents the mixing of hydrogen and oxygen gases formed during electrolysis.

[0166] The electrolyte solution is typically an alkaline solution. A preferred electrolyte solution is an aqueous solution of an electrolyte selected from sodium hydroxide or potassium hydroxide. Potassium hydroxide electrolyte is often preferred because of its higher specific conductivity. The concentration of the electrolyte in the electrolyte solution is preferably 20-40 wt% of the total weight of the electrolyte solution.

[0167] The electrolyte temperature is preferably 50°C to 120°C, more preferably 75°C to 100°C, and most preferably 80°C to 90°C. On the other hand, higher temperatures, for example, at least 100°C, more preferably 125°C to 165°C, may result in more efficient electrolysis.

[0168] In so-called zero-gap electrolytic cells, the electrodes are arranged to be in direct contact with the separator, thereby reducing the space between the two electrodes. Mesh electrodes or porous electrodes are used to allow the separator to be filled with the electrolyte and to efficiently remove the formed oxygen and hydrogen gases. Preferred porous electrodes and methods for preparing them are disclosed, for example, in paragraphs 23-84 of EP-A3575442. The pore size of the porous electrode can affect the electrolysis efficiency. For example, EP-A3575442 discloses that the preferred pore size of the porous electrode is 10 nm to a maximum of 200 nm.

[0169] Such zero-gap electrolytic cells have been shown to operate at higher current densities.

[0170] On the other hand, in such zero-gap electrolytic cells, it has been acknowledged in WO2023 / 118088 (AGFA-GEVAERT NV) that bubbles formed inside the separator can accumulate on the top of the separator. Such bubble accumulation on the top of the separator can result in increased ion resistance in that part of the cell. If the temperature rises as a result of reduced efficient cooling by the electrolyte in that region of the electrolytic cell, the separator may even burn. By introducing a short distance between one side of the separator and at least one electrode, the accumulation of bubbles inside the separator can be reduced. The distance between one side of the separator and the anode (d1) and the distance between the other side of the separator and the cathode (d2) may be the same or different. The distance between the surface of the separator and at least one electrode is preferably 50 to a maximum of 500 μm, and more preferably 100 to a maximum of 250 μm.

[0171] Barros et al. (International Journal of Hydrogen Energy, Vol. 49, Part C, Pages 886-896) observed that a short distance between the separator surface and the electrode containing the catalyst layer can reduce the supersaturation of gases dissolved in the electrolyte at the separator surface. High supersaturation at the separator surface can lead to increased gas diffusion through the separator. For example, high supersaturation of hydrogen in the electrolyte at the separator surface facing the cathode can lead to an increase in HTO. A short distance d2 between the cathode and the separator surface facing the cathode reduces the supersaturation of hydrogen at the separator surface, thus reducing HTO. The optimal distance d2 was found to be around 100 μm.

[0172] To achieve the required distance between the separator and the electrode, so-called spacers may be used. Such spacers are preferably hydrophilic to avoid adhesion of bubbles to the spacer (the static water contact angle is 90°C or less, preferably 45°C or less). Such spacers preferably have an open structure to ensure ionic conductivity and efficient bubble discharge.

[0173] When using the separator according to the present invention in an electrolytic cell, the distance d2 between the porous surface of the separator (the surface of the porous support and / or the surface of the porous layer containing polymer A) and the electrode can be established by the non-porous layer.

[0174] The non-porous layer of the separator with a catalyst layer can also affect gas permeability. Therefore When the separator with a catalyst layer includes one catalyst layer attached to a non-porous layer, it is preferable that the catalyst layer faces the cathode. This orientation can further reduce HTO.

[0175] A typical alkaline water electrolytic cell contains several electrolytic cells (also called an electrolytic cell stack). Regarding the cell configuration, typically two types of electrolytic cells are used. A unipolar (or "tank-type") electrolytic cell consists of alternating positive and negative electrodes separated by a separator. All positive electrodes are connected together in parallel, as are the negative electrodes, and the entire assembly is immersed in a single electrolyte bath ("tank") to form a unit cell. Therefore, plant-scale electrolytic cells are assembled by electrically connecting these units in parallel. The total voltage applied to the entire electrolytic cell is the same as that applied to the individual unit cells. On the other hand, in a dual-electrode electrolytic cell, adjacent cells are electrically connected in series by a metal sheet (or "dual electrode"). The electrolytic catalyst for the negative electrode is coated on one side of the dual electrode, and the electrolytic catalyst for the positive electrode of the adjacent cell is coated on the back side. In this case, the total cell voltage is the sum of the individual unit cell voltages. Therefore, a series-connected stack of such cells forms a module that operates at higher voltages and lower currents than a tank-type (unipolar) design. To meet the requirements of large electrolytic plants, these modules are connected in parallel to increase the current. [Examples]

[0176] material ZIRFON is Zirfon Perl UTP500 supplied by AGFA-GEVAERT NV.

[0177] PVA is a high molecular weight polyvinyl alcohol supplied by ALDRICH, with a molecular weight of 85-124 kDa and a degree of hydrolysis of over 99%.

[0178] Glutardehyde is available from ALDRICH as a 25 wt% aqueous solution.

[0179] NiO is nickel oxide (99% purity) available from BCR GMBH&CO.

[0180] PVP is polyvinylpyrrolidone with a MW of 8000, available from BCR GmbH & Co.

[0181] The NiO dispersion was prepared by mixing 60% by weight NiO, 7.5% by weight PVP, and 32.5% by weight demineralized water. This mixture was then ground in a stirring bead mill until the Z-average particle size was less than 200 nm.

[0182] measurement Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (SEM-EDX) SEM cross-sections were prepared by cutting the sample and embedding it in epoxy resin. The sample was then mechanically polished and coated with a thin Pt-Pd layer. Surface samples were cut, attached to aluminum stubs using double-sided tape, and coated with a thin Pt-Pd layer.

[0183] Bubble point, minimum pore size, average pore size, gas permeability The pore diameter of the separator was measured using the so-called bubble point test method.

[0184] The bubble point test method involves wetting the pores of the membrane with a wetting liquid, and then completely wetting the membrane with the wetting liquid. This involves measuring the minimum pressure required to overcome the surface tension between the pore wall and the wetted pore. This pressure is called the bubble point pressure.

[0185] In the theory of capillary action, the height of the water column in a capillary is indirectly proportional to the capillary diameter. By using the Young-Laplace equation, the pore diameter of a membrane can be related to the applied pressure required to force the wet liquid out of the pores.

[0186] The procedure for the bubble point test method is described in American Society for Testing and Materials (ASMT) Method F316.

[0187] The top surface of the filter is in contact with the liquid, and the bottom surface is in contact with the air. The filter holder is connected to a source of control pressure. The air pressure is gradually increased until the formation of bubbles is observed on the liquid side. Below the bubble point, the gas passes across the filter by diffusion only. However, as the pressure increases to the point where it displaces the liquid through the pores, a large flow begins, and bubbles become visible. The initial bubble test pressure determines the size (and location) of the largest hole, while the open bubble point pressure determines the average hole diameter of the element.

[0188] The bubble point, average pore diameter, maximum pore diameter, and gas permeability of the separator were measured using the commercially available POROLUX1000 from POROMETER.

[0189] Example 1 Preparation of catalyst-layer-equipped separators S-1 and S-2 The catalyst-layer-equipped separator S-1 was prepared by coating one side of a ZIRFON separator with a NiO dispersion.

[0190] The catalyst-layered separator S-2 was prepared by first coating one side of a ZIRFON separator with a PVA solution to a wet coating thickness of 200 μm, and then drying it in an oven at 80°C to form a PVA layer. Next, a NiO dispersion was coated onto the dried PVA layer.

[0191] The SEM cross-sections of S-1 and S-2 are shown in Figures 3.a and 3.b, respectively.

[0192] From these SEM cross-sections, it can be determined that the thickness of the NiO catalyst layers in S-1 and S-2, and the thickness of the PVA layer in S-2, are 3-4 μm and 7-8 μm, respectively.

[0193] We used SEM-EDX to investigate whether or not NiO had penetrated into the pores of the ZIRFON separator. SEM-EDX analysis of cross-sections of separators S-1 and S-2 revealed that Ni was detectable 20-30 μm directly below the ZIRFON surface in S-1, while it was impossible to detect Ni on or below the ZIRFON surface in S-2. This clearly indicates that the presence of a non-porous, alkali-stable polymer layer between the catalyst layer and the surface of the porous separator prevents the penetration of the catalyst into the pores of the porous separator.

[0194] Example 2 Preparation of separator S-3 Separator S-3 was prepared by coating one side of a ZIRFON separator with a PVA solution (19 wt% in water) to a wet coating thickness of 60 μm, and then drying it in a standard oven at 80°C for 15 minutes.

[0195] Figure 4 shows the effect of coating ZIRFON with a PVA solution on the separator surface roughness. The SEM top view of the surface of ZIRFON without the PVA layer (Figure 4.a) and the SEM top view of the surface of S-3 with the PVA layer (Figure 4.b) clearly show that S-3 has a smoother separator surface.

[0196] The gas permeability and bubble point of S-3, as measured as described above, are 0.01 L / min / cm², respectively. 2 The bar values ​​for both materials are >8 bar, and for ZIRFON, they are 3.8 and 1.9 bar, respectively. This clearly indicates that the presence of a non-porous PVA layer substantially reduces gas permeability and raises the bubble point.

Claims

1. Porous support (100) and On at least one side of the support, in order, -Optional porous layer (200) containing polymer A, - A non-porous layer (300) containing polymer B, and -Catalyst layer (400) A separator for alkaline water electrolysis with a catalyst layer, including the following:

2. The alkaline water electrolysis separator with a catalyst layer according to claim 1, wherein polymer B is selected from the group consisting of poly(ethylene glycol) or its copolymer, poly(saccharide), poly(ethylene-co-vinyl alcohol), poly(ethylene-co-vinylamine), and poly(vinyl alcohol).

3. The alkaline water electrolysis separator with a catalyst layer according to claim 1 or 2, wherein polymer B is poly(vinyl alcohol) or poly(ethylene-co-vinyl alcohol).

4. The alkaline water electrolysis separator with a catalyst layer according to claim 3, wherein the polyvinyl alcohol has a molecular weight of 75 to 150 kDa.

5. A separator for alkaline water electrolysis with a catalyst layer according to any of the prior claims, wherein the non-porous layer is crosslinked.

6. A separator for alkaline water electrolysis with a catalyst layer according to any of the prior claims, wherein the thickness of the non-porous layer containing the polymer B is 0.1 to 25 μm.

7. A separator for alkaline water electrolysis with a catalyst layer according to any of the prior claims, wherein the thickness of the catalyst layer is 0.5 to 200 μm.

8. The catalyst layer-equipped alkaline water electrolysis separator according to any of the prior claims, wherein the catalyst is selected from the group consisting of Ni, NiO, Raney Ni, Ni-Fe, Ni-Co, Ni-Mo, and NiO / NiOH.

9. A separator for alkaline water electrolysis with a catalyst layer according to any of the prior claims, wherein the total thickness of the separator is 50 to 750 μm.

10. A separator for alkaline water electrolysis with a catalyst layer according to any of the prior claims, wherein polymer A is selected from the group consisting of poly(sulfone), poly(ethersulfone), poly(phenylene sulfide), poly(etheretherketone), and poly(phenylsulfone).

11. A method for preparing a separator with a catalyst layer according to any of the prior claims, - The step of providing a porous support (100), -Optionally, a doping solution containing polymer A is applied to a porous support, and a phase conversion step is performed on the applied doping solution, thereby forming a porous layer (200) containing polymer A on the porous support. - The step of applying polymer B solution to the porous support or the optionally selected porous layer, thereby forming a non-porous polymer layer (300), - The step of applying the catalyst composition onto a non-porous layer to form a catalyst layer (400), The method, including the method described above.

12. The viscosity of the polymer B solution is 20°C and 100 s. －１ The method according to claim 11, wherein the shear rate measured is at least 400 mPa·s.

13. The method according to claim 11 or 12, wherein the polymer B solution is applied by a single coating step.

14. An electrolytic cell for alkaline water electrolysis comprising a separator with a catalyst layer according to any one of claims 1 to 10.

15. Use of an alkaline water electrolysis separator with a catalyst layer according to any one of claims 1 to 10 in the production process of green hydrogen, green ammonia, and green steel.

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