Selective separator for water electrolysis applications and method for manufacturing the same

Abstract

A selective separator is described, comprising a porous polymer separator and a selective material on at least one external surface. The selective material, comprising a composite material of an ion exchange polymer and zirconium oxide particles (ZrO2) distributed throughout the ion exchange polymer, can be applied as a liquid by a spray coating method. Selective separators prepared by the method described herein are suitable for use in alkaline water electrolysis applications.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 451,655, filed March 13, 2023, the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Alkaline water electrolysis (AWE) plays a major role in the hydrogen economy due to its well-understood chemical properties. Improving the efficiency of alkaline water electrolyzers is crucial to meeting the low-cost goal for green hydrogen production. High current density operation is a primary strategy for reducing operating costs. High current density is typically achieved by reducing ohmic resistance through the use of thinner separators, larger pore diameters, and / or shorter distances between the separator and electrodes. However, these approaches may have undesirable consequences in terms of mechanical strength, gas crossover, and gas blinding.

[0003] In addition to mechanical strength loss, separators with thinner or larger pore diameters can result in significant gas crossover, reducing Coulomb efficiency and safety. Reducing the gap between the electrode and separator to lower resistance has been shown to cause substantial voltage loss. Hydrogen and oxygen gases generated on the electrode are trapped between the electrode and separator interface, reducing the active film area for ion conduction. A reduction in the active area increases ohmic resistance. Several approaches exist to mitigate the gas clogging effect in electrolytic cells. These approaches include increasing flow through new electrode architectures, materials, and hydrophobic diffusion layers. Furthermore, in laboratory experiments, various operating conditions such as pressure swing, ultrasound, and magnetic fields have been investigated to reduce gas stagnation on the separator surface.

[0004] The design of the electrodes, separator, and electrolytic cell determines the overall efficiency of the electrolytic cell. In water electrolytic cells, high-pressure operation is desirable to improve efficiency. Porous separators limit high-pressure operation.

[0005] Conventional non-porous ion exchange membranes with relatively small and narrow ion channels have been shown to perform worse than porous separators in AWE applications due to their high resistance. For example, Nafion™ membranes, which have significantly smaller channel sizes than porous separators, can result in high ionic resistance. Furthermore, while porous separators allow for the transport of both cations and anions, cation exchange membranes that allow only cation transport limit the mobility of hydroxide ions (OH-). [Overview of the project] [Means for solving the problem]

[0006] The selective separators for alkaline water electrolysis (AWE) described herein include a porous separator layer or structure to which a selective material is applied as a coating to form the outermost surface of the selective separator. The selective material coating includes ion exchange polymers and inorganic particles that provide good ion conductivity, low gas permeability, and improved gas release suitable for use in AWE processes.

[0007] AWE porous selective separators may comprise a porous polyolefin separator layer and a selective material coating comprising an ion exchange polymer and inorganic particles, wherein the coating is on one or both opposing surfaces of the porous polyolefin separator. In one embodiment, a multilayer selective separator comprises a layer of porous polyethylene (PE) and a selective material coating comprising a perfluorosulfonic acid ion exchange polymer and zirconium oxide particles forming the outermost layer of the multilayer selective separator, wherein the particles are attached to one or both opposing surfaces of the porous polyethylene. A method for producing a selective separator involves spray coating a liquid blend of the selective material to form a thin selective layer on one or both surfaces of a porous PE support. The ratio of the ion exchange polymer to the inorganic particles in the selective material, and the amount of dry solid filling of the selective material on the porous polymer separator, are optimized for properties such as gas adhesion and / or gas permeability.

[0008] The novel porous selective separators described herein significantly reduce gas permeability and gas release characteristics without significantly increasing ion resistance. The significant reduction in the gas release angle correlates with enhanced gas release during use. While not theoretically bound, the application of selective materials to porous separators is considered advantageous in that it can provide higher operating pressures for gases and, among other things, reduce operating costs in AWE applications. A challenge in AWEs compared to PEM water electrolyzers is the limited pressure range due to high gas crossover through the large pores of conventional separators. Therefore, pore size optimized by the application of novel selective materials and coating techniques advantageously results in a reduction of gas crossover through the separator. While conventional approaches to reducing gas crossover resulted in an increase in ohmic resistance, the novel porous selective separators described herein have minimal impact on the overall ohmic resistance of the separator. Pore size can be selectively modified by changing the particle size, the ratio of ion exchange polymer to inorganic particles, and the coating technique. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of one embodiment of a highly selective multilayer separator. [Figure 2] This is a top view of an image obtained by scanning electron microscopy (SEM) of one embodiment of a selective layer on a porous separator. [Figure 3] This is an SEM image of a cross-sectional view of one embodiment of a porous selective separator. [Figure 4] This is an SEM image of a cross-sectional view of one embodiment of a porous selective separator. [Figure 5] This is a schematic diagram of one embodiment of an alkaline water electrolysis cell. [Modes for carrying out the invention]

[0010] A novel porous selective separator and a method for manufacturing the same are described. The selective separator is suitable for use in AWE applications, providing improved gas release and gas permeability without significantly altering ion resistance. As shown in Figure 1, the selective separator (100) comprises a porous polymer separator (101) having an outer surface (105a and / or 105b) coated with a selective material (102a and / or 102b) that forms the outermost layer (104a and 104b) of the selective separator, thereby increasing the efficiency of the porous separator in the water electrolysis process by providing hydrophilicity, surface roughness, controlled pore size, pore diameter, and / or percentage porosity passing through the selective separator.

[0011] In one embodiment, the selective separator membrane is described as essentially comprising: 1) a porous polyolefin separator as an unsupported film (101); and 2) a coating of a selective material (102a, 102b) comprising an ion exchange polymer (106) and inorganic particles (103), applied to at least one surface (105a, 105b) of the porous polyolefin separator, wherein the selective material forms the outermost layer of the selective separator. The selective material may be applied to both the first and second opposing surfaces (105a, 105b) of the porous polymer separator. In one embodiment, the polyolefin is polyethylene (PE), and the selective material comprises an ion exchange polymer and zirconium oxide.

[0012] Porous polymer separator Porous separators suitable for use herein may include polymers that do not have chemically reactive functional groups on their polymer structure. Porous polymer separators may include, but are not limited to, polyethylene (PE), including ultra-high molecular weight polyethylene (UHMWPE), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), or polyolefins such as polypropylene (PP). In other embodiments, the porous polymer separator may include fluoropolymers such as polytetrafluoroethylene (PTFE), stretched polytetrafluoroethylene (ePTFE), or polyvinylidene fluoride (PVDF) suitable for use in water electrolysis applications, polystyrene, polysulfone, polyethersulfone, or polyarylethersulfone, polyphenylene sulfide (PPS), or combinations thereof, and may also include materials traded under the name Zirfon® Separator Membrane (trademark of AgfaGevaert NV), as well as materials traded under the names Celgard® 5550, Celgard® 3419S, and Celgard® 3420 (trademarks of Celgard, LLC).

[0013] Porous separators may be hydrophobic or hydrophilic, as measured, for example, by the contact angle method described herein. The hydrophilicity of a porous separator polymer can be increased by adding additives such as ionic surfactants or inorganic materials, or metal oxide fine particles such as silica powder, to the polymer to form a polymer composite. Suitable metal oxides for use in optimizing hydrophobicity or hydrophilicity include zirconium oxide, titanium oxide, bismuth oxide, cerium oxide, and magnesium oxide, as well as combinations thereof. Other hydrophilic particles that may be used include nitrides and carbides of Group IV elements of the periodic table. Inorganic particles may have an average particle size in the range of about 0.5 μm to 5 μm, or 0.5 μm to 2 μm, or 0.15 μm to 1 μm, or 0.15 μm to 0.75 μm, as determined by laser diffraction particle size analysis. Hydrophilic porous polyethylene separators can be formed using composite materials of a hydrophobic polymer such as polyethylene and metal oxide particles such as titanium dioxide or zirconium oxide incorporated into and / or dispersed throughout the polymer matrix.

[0014] The average pore size of the porous separator before application of the selected material may be greater than about 0.1 μm, less than about 4 μm, or in the range of 0.1 μm to 4 μm, 0.1 μm to 2 μm, 0.1 μm to 1 μm, 0.5 μm to 4 μm, 0.5 μm to 3 μm, 0.5 μm to 2 μm, and 0.5 μm to 1 μm, as measured by a capillary flow porometer. In some embodiments, the porous separator includes a microporous layer having an average pore size in the range of, for example, about 0.1 μm to 5 μm, or about 0.3 μm to 2 μm, or about 0.1 μm, or about 0.5 μm, or about 1 μm, before application of the selected material coating. The microporous layer may include a microporous polymer such as a fluoropolymer such as microporous ePTFE.

[0015] The percentage porosity of the porous polymer separator material before coating with the selected material may be about 40% to 80%, or about 50% to 80%, or 60% to 80%, or 50% to 70% by volume. The pore size may be symmetrical or asymmetrical across the thickness of the porous polymer separator in the selected separator construct. Furthermore, the percentage porosity may be uniform or non-uniform across the thickness of the porous polymer separator. In some embodiments, where the selected separator includes a multilayer porous polymer separator, the pore size and percentage porosity may be independently the same or different in each polymer material layer. The pore size distribution of each layer of the multilayer porous polymer separator may be independently symmetrical or asymmetrical across the entire thickness of each layer, and the percentage porosity of each layer may be independently uniform or non-uniform across the entire layer.

[0016] For example, but not limited to, porous polymer separators may be manufactured by casting, extrusion, or phase inversion, or may include, but not limited to, woven or nonwoven fabrics, spun woven mats, meshes, webs, or cast or extruded layers or films. Porous polymer separators may include one or more layers, or other structures or forms.

[0017] The porous separator may be reinforced or self-supporting. One or more reinforcing components may be integrated into or embedded in the separator polymer to increase, for example, the mechanical strength, chemical durability and / or dimensional stability of the final selective separator. The reinforcing components of the multilayer porous selective separator may include a porous continuous reinforcing layer, or optionally a separate structure composed of polymers such as PTFE, ePTFE, or PPS, polypropylene, polyphenylene sulfide, or polyether ether ketone (PEEK). Alternatively, the discontinuous reinforcing component may be in the form of reinforcing fibers or yarns. A cloth including a woven or nonwoven support can be embedded in the polymer structure. The reinforcing components may include the same polymer composition as the porous polymer separator or a different polymer composition.

[0018] In some embodiments, the porous polymer separator comprises a microporous ePTFE membrane bonded to a nonwoven fabric, and a surface hydrophilic treatment may be applied to the opposing unbonded surfaces of one or both of the ePTFE membrane and the nonwoven fabric. The nonwoven fabric may include, but is not limited to, melt-spun PP or PE. In some embodiments, the ePTFE layer of the porous separator may have a thickness in the range of about 0.5 μm to about 2 μm, for example, about 1 μm.

[0019] In one embodiment, prior to the application of the selected material, the porous polymer separator is non-functional and does not contain functional polymers such as sulfonic acid functional groups or carboxylic acid functional groups, or ion exchange polymers having groups convertible to sulfonic acid or carboxylic acid functional groups. In one embodiment where the porous separator includes a reinforcing material, the reinforcing material does not contain ion exchange polymers having sulfonic acid functional groups or carboxylic acid functional groups. In further embodiments, neither the porous polymer separator material nor the reinforcing material contains ion exchange polymers having sulfonic acid functional groups or carboxylic acid functional groups before coating with the selected material. In other embodiments, surface treatments can be applied to impart surface functionality, such as hydrophilicity, to the underlying polymer structure. In some embodiments, ionic surface treatments exist, but neither the porous polymer separator nor the reinforcing material, if present, contains ion exchange functional groups. Suitable surface hydrophilic treatments for use herein include surface coating, plasma treatment, chemical grafting with sulfonate or phosphate functional groups, UV irradiation, and alkali treatment.

[0020] The thickness of the porous polymer separator may be less than 300 μm, less than 250 μm, less than 200 μm, less than 150 μm, or less than 100 μm, or the porous polymer separator layer may have a thickness of 50 μm to 250 μm, 50 μm to 225 μm, 50 μm to 200 μm, 75 μm to 225 μm, 75 μm to 200 μm, or 75 μm to 150 μm. The thickness can be measured by SEM cross-sectional analysis by obtaining the average of at least three thickness measurements through the cross-section.

[0021] Selective materials The selected material mixture is applied to one or more outer surfaces (105a, 105b) of a porous polymer separator. The selected material (102a, 102b) comprises an ion exchange polymer (106) and inorganic particles (103), such as inorganic particles, which impart good ion conductivity, low gas permeability, and improved gas release characteristics in the final selected separator compared to the same porous polymer separator material without the selected material coating.

[0022] The ion exchange polymer may be a cation exchange polymer or an anion exchange polymer. Suitable cation exchange polymers for use herein include one or more fluorinated polymers, such as perfluorinated or partially fluorinated alkyl compounds, which include fluorinated hydrocarbons or aromatic polymers having ionic functional sites. The polymer composition may include, for example, perfluorosulfonic acid (PFSA), sold under the trade name NAFION, which is a material commonly known for use as a solid polymer electrolyte membrane (PEM) in electrochemical devices. The selective polymer material may further include a polyvalent PFSA composition. The selective polymer may be crosslinked, for example, by treatment or exposure to a physical or chemical crosslinking method, including but not limited to irradiation and / or free radicals. Alternatively, the selective polymer may be uncrosslinked, so as the uncrosslinked polymer has not been exposed to the crosslinking method.

[0023] The ion-exchange polymer backbone, which is the main chain of the polymer, may contain units represented by the following formula.

[0024] [Chemical formula] In the formula, m is 1 to 6, and M is an alkali metal.

[0025] [Chemical formula] In the formula, m is 1 to 6, and M is an alkali metal.

[0026] [Chemical formula] In the formula, Q 1 is a perfluoroalkylene group which may have an etheric oxygen atom, Q 2 is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, R 1 is a perfluoroalkyl group which may have an etheric oxygen atom, X 1 is an oxygen atom, a nitrogen atom or a carbon atom, X 1 when X is an oxygen atom, a is 0, X 1 when X is a nitrogen atom, a is 1, X 1 when X is a carbon atom, a is 2, Y is a fluorine atom or a monovalent perfluoro organic group, r is 0 or 1, M is an alkali metal, or

[0027] [Chemical formula] In the formula, R 2 is a single bond or a linear perfluoroalkylene group having 1~6 carbon atoms which may have an etheric oxygen atom, R 3 is a perfluoroalkylene group having 1~6The linear perfluoroalkylene group is such that m is 0 or 1. n is 1 and M is an alkali metal. In some embodiments, the ion-exchange polymer backbone, which is the main chain of the polymer, may contain units represented by the following formula.

[0028] [ka] In the formula, m is 0.1 or 2, n is 0, 1 or 2, and R f1 C 1~6 It is a linear perfluoroalkylene, R f2 C 1~6 It is a linear perfluoroalkylene group, where M is a cation that can be a proton, an alkali metal, or a quaternary ammonium, or

[0029] [ka] In the formula, m is 0.1 or 2, n is 0, 1 or 2, and R f1 C 1~6 It is a linear perfluoroalkylene group, R f2 C 1~6 It is a linear perfluoroalkylene group, where M is a cation that may be a proton, an alkali metal, or a quaternary ammonium. Suitable alkali metals and quaternary ammonium for use in this specification include, for example, K + kaNa + and Li + Examples include, but are not limited to, tetramethylammonium.

[0030] In other embodiments, the ion exchange polymer backbone comprises polyphenylene oxide, polysulfone, polyethylene, or poly(aryl ether sulfone). Functional groups of the cation exchange polymer include, but are not limited to, sulfonate, carboxylate, or phosphate functional groups. In one embodiment, ion exchange polymers suitable for use herein include copolymers derived from the polymerization of tetrafluoroethylene (TFE), derivatives of perfluoro(alkyl vinyl ether), and sulfonylic acid fluorides, such as polymers of the Nafion® brand.

[0031] The anion exchange polymers used herein may have ionic moieties selected from ammonium, quaternary ammonium, piperidinium, imidazolium, guanidinium, benzimidazolium, pyrrolidinium, spiro rings or phosphonium, functional groups and their derivatives, in order to improve ionic conductivity, chemical stability and mechanical properties. In one embodiment, the AEM separator comprises a selected material containing poly(arylpiperidinium) (Versogen, Inc., Newark, DE). In one embodiment, the anion exchange capacity of the cationic or anionic exchange polymer or polyelectrolyte suitable for use in the selected material compositions herein is a dry polymer with an anion exchange capacity of about 0.8 meq / g to 2.5 meq / g.

[0032] The selected material comprises a liquid mixture of inorganic particles dispersed within a polymer and applied as a coating. Suitable inorganic particles for use in the selected material include zirconium oxide, titanium oxide, bismuth oxide, cerium oxide, and magnesium oxide, as well as combinations thereof. Other hydrophilic particles that can be used include nitrides and carbides of Group IV elements of the periodic table. The inorganic particles may have an average particle size in the range of about 0.5 μm to 8 μm, 0.5 μm to 5 μm, or 0.5 μm to 2 μm, or 0.15 μm to 1 μm, or in the range of 0.15 μm to 0.75 μm, as determined by laser diffraction particle size analysis. In one embodiment, the metal oxide particles may have a bimodal particle size distribution, such as 0.5 μm and 5 μm.

[0033] For example, a liquid mixture containing zirconium oxide particles and an ion exchange polymer may be diluted to a viscosity optimized for the selected application technology. The diluent may include volatile materials such as ethanol, n-propanol, or isopropanol. Methods for applying the selected material to the porous polymer separator layer include, but are not limited to, spray coating techniques, doctor blade application, Meyer rod application, and gravure coating. The coating rate of the selected material on the outer surface of the porous polymer separator is approximately 0.1 mg / cm³ of the total combination of ionomer and inorganic solid. 2 ~2 mg / cm³ 2 The dry solid fill amount of the porous polymer separator is provided, or the fill amount is 0.5 mg / cm³. 2 ~1.5 mg / cm³ 2 It may be, and in one particular embodiment, the coating rate is about 0.9 mg / cm² 2 That is the case.

[0034] In some embodiments, the selected material coating is approximately 0.9 mg / cm³ per side of the porous polymer support (i.e., the ePTFE surface and the nonwoven fabric surface), based on the total dry solid weight of the ionomer and inorganic particles. 2 The load can be applied to one or both opposing outer surfaces of a porous polymer separator. In one embodiment, the dry solid weight ratio of the ionomer to inorganic particles may be in the range of 0.1 to 0.8, or 0.1 to 0.6, or 0.3 to 0.4. In other embodiments, the weight ratio of the dry ion exchange polymer solid to the ZrO2 solid of the selected material is in the range of about 0.1 to 0.8, for example, about 0.1 to 0.5.

[0035] In one embodiment, the selective material covers up to about 80%, 90%, or 100% of the outer surface area of ​​the porous separator, and the coated outer surface of the porous selective separator maintains sufficient porosity or permeability to achieve optimized ohmic resistance and gas crossover levels. Conventional liquid ion exchange polymers can form a continuous non-porous coating that occludes the porosity of the porous polymer separator, but in some embodiments disclosed herein, the addition of dispersed metal oxide particles such as zirconia can prevent or disrupt the formation of a compact, continuous polymer matrix on the outer surface of the porous separator, and as a result the porous separator described herein retains at least some continuous open porosity that extends between opposing outer surfaces of the selective separator. Thus, a selective material comprising ion exchange polymers and inorganic particles can be applied to form a porous thin film on the surface of the porous polymer separator. In some embodiments, the porous polymer selective separator has a surface roughness in the range of about 0.1 μm to 4 μm when measured on the coated surface.

[0036] In some embodiments, the selection separator described herein is 0.008 ft when measured according to the method provided herein. 3 / min * ft 2 It has an air permeability of less than 0.007 ft. In other embodiments, when tested according to the method described herein, the selective separator has an air permeability of 0.007 ft. 3 / min * ft 2 Less than 0.005 ft 3 / min * ft 2 Less than 0.004 ft 3 / min * ft 2 Less than, or 0.001 ft 3 / min * ft 2 ~0.008ft 3 / min * ft 2 , or 0.001 ft 3 / min * ft2 ~0.007ft 3 / min * ft 2 , or 0.002 ft 3 / min * ft 2 ~0.004ft 3 / min * ft 2 It has an air permeability of 0.008 ft. In other embodiments, it has an air permeability of 0.008 ft. 3 / min * ft 2 Less than, or 0.001 ft 3 / min * ft 2 ~0.008ft 3 / min * ft 2 A selective separator having an air permeability of 200 mΩ·cm 2 or 150 mΩ·cm 2 Less than 100 mΩ·cm 2 It has an ionic resistance of less than 1.

[0037] A porous selective material layer having a thickness of approximately 1 μm to 10 μm, or 4 μm to 10 μm, or less than 20 μm may be formed on at least one outer surface of the porous polymer separator, and the inorganic particles of the selective material are 0.1 μm or larger. The resulting selective separator has an acceptable ohm resistance that, when tested without the selective material layer, is, for example, within +20% or within +10% of the ohm resistance of the porous polymer separator material constituting the selective separator. In other embodiments, the selective separator is formed to have an ohm resistance that is about 50% or less higher than the ohm resistance of the porous polymer separator material used to form the selective separator.

[0038] In some embodiments, when tested according to the test conditions described herein, the application of the selective material to a porous selective separator yielded a result of 200 mΩ·cm compared to substantially the same porous separator material without the selective material coating. 2This results in an increase in ohm resistance of less than 200 mΩ·cm when measured according to the method described herein. 2 Less than 180 mΩ·cm 2 Less than 150 mΩ·cm 2 It has an ion resistance of less than 20 degrees and a gas release angle of less than 10 degrees. In further embodiments, when tested according to the method described herein, the selective separator has a gas release angle of less than 20 degrees and 0.008 ft. 3 / min * ft 2 Air permeability of less than 200 mΩ·cm 2 It has an ionic resistance of less than 1.

[0039] In one embodiment, the selective separator membrane includes a multilayer porous polymer separator having a uniform distribution of inorganic particles over the entire thickness of a selective material layer applied to at least one surface of the porous polymer separator. In a further embodiment, the pores of the first layer of the multilayer porous polymer separator are substantially free of the selective material, for example, only a very small amount of inorganic particles pass through the porous structure, so that they are visualized, for example, by SEM, and at least a second layer of the multilayer porous polymer separator is substantially permeable by the selective material coating. In a particular embodiment including a multilayer ePTFE microporous film / PP layer separator, inorganic particles such as zirconia particles form a uniform layer on the outer surface of the ePTFE film layer without substantial passage of zirconia particles into the ePTFE microstructure, and a selective coating mixture applied to the opposing surface substantially passes through the pores of the nonwoven PP layer and coats the fibers, and optionally, zirconia particles pass through the pores of the nonwoven PP layer to which they are applied and coat the portion of the ePTFE surface bonded to the PP layer opposite the outer ePTFE surface.

[0040] Regarding the orientation of the porous selective separator within the electrolytic cell, the selective material can be applied to the outer surface facing the anode, the outer surface facing the cathode, or both the outer surfaces facing the anode and cathode of the porous polymer separator. The interaction of the separator surfaces varies depending on the type of gas, and therefore, the selective material composition applied to the anode-facing surface may differ from the selective material composition applied to the opposing cathode-facing surface of the porous polymer separator. In one embodiment, the selective material does not significantly affect the ionic resistance of the final porous separator.

[0041] Electrochemical cells are also provided for use in AWE applications, comprising an anode compartment, an anode located within the anode compartment, a cathode compartment, a cathode located within the cathode compartment, and a porous selective separator located between the anode and the cathode, separating the anode and the cathode, wherein the electrochemical cell is configured to hold a liquid electrolyte solution, and the porous selective separator provides ionic contact between the electrodes. In one embodiment, the porous selective separator comprises 1) a hydrophilic porous polymer separator, and 2) a selective material provided as a coating on at least one outer surface of the hydrophilic porous polymer separator. In one embodiment, the polymer material on which the porous polymer separator structure is formed is essentially a non-functional polymer material. However, in some embodiments, the treatment material may be applied to the porous polymer separator, and the treatment material may include functional or non-functional compositions that improve or provide wettability to porous polymer structures made from non-functional polymers. In some embodiments, the selective material layer forms the outermost surface of the selective separator surface and includes a composite matrix of a discontinuous ion exchange polymer and inorganic particles, such as metal oxide particles, distributed throughout the ion exchange polymer. The average particle size of the inorganic particles of the selective material may be in the range of about 0.1 μm to 4 μm, or 0.1 μm to 5 μm, or 0.1 μm to 6 μm, or 0.1 μm to 8 μm.

[0042] Figure 5 provides an embodiment of an alkaline water electrolytic cell (500) for hydrogen production, comprising a porous selective separator (501) that separates an anode and a cathode, operating in an alkaline electrolyte (502) such as a 25% to 40% by weight KOH aqueous solution. A first selective material coating (503) is provided on the outer surface (505) of a porous polymer separator (504) adjacent to the anode, and a second selective material coating (503) is applied to the opposing outer surface of a porous polymer separator adjacent to the cathode, thereby preventing gas stagnation on and / or within the pores of the selective separator, reducing the crossover of oxygen and hydrogen gases, and forming a porous selective separator through which potassium and hydroxide ions are transported between the cathode and anode.

[0043] The selective material composition and solid filler content of the selective material coating can be modified to adjust surface energy and / or gas adhesion while maintaining low ionic resistance and low gas crossover. The selective material composition may be homogeneous or may form a gradient of selection across the entire thickness of the selective layer.

[0044] A method for producing a selective separator is provided, comprising the steps of: obtaining a porous polymer separator; obtaining a selective material comprising a liquid composition of an ion exchange polymer and inorganic particles having an average particle size of 0.1 μm to 4 μm; and applying the liquid composition to one or both outer surfaces of the porous polymer separator to form a selective layer, wherein the inorganic particles are uniformly distributed throughout the entire thickness of the selective layer without substantially passing through the thickness of the porous polymer separator layer.

[0045] Test method Ionic resistance in KOH: The resistance of spray-coated AWE separators in a 30% KOH solution was determined by measuring their ionic resistance.

[0046] The spray-coated separators were dried in an oven at approximately 90°C. Measurements were performed on the prepared separators. The prepared separators were heated in 60°C water for 6 hours. They were stored overnight in 30% KOH before testing.

[0047] Ionic resistance was characterized by four-probe impedance spectroscopy in a caustic electrolyte. The separator sample was placed between two chambers filled with 30% KOH. Impedance resistance was measured under ambient conditions (approximately 22°C) using an impedance analyzer on a BioLogic Potentiostat SP-240 (Lambda System). The impedance scan was a frequency sweep from 50 kHz to 1 MHz. Resistance values ​​were manually determined from the impedance at the high-frequency intercept in the Nyquist plot.

[0048] Maximum tilt angle for bubble release: The maximum tilt angle for bubble release was used to measure gas release on the surface of the coated select separator. The maximum angle at which bubbles remained on the surface of the AWE separator due to the tilt was measured as follows:

[0049] The separator was heated in 60°C water for 6 hours and then stored in water. The separator was fixed in a captive bubble cell, and the cell was filled with water. Bubbles were introduced at a 0-degree inclination angle (flat). The average bubble size was 2 mm in diameter. The stage (cell holder) was manually tilted until the bubbles moved away from the surface of the separator. The maximum angle reached when the bubbles moved was measured three times and the average was recorded.

[0050] Air permeability measurement using a Gurley densometer The porosity of the separator was measured using a Gurley densometer. The separator was dried in an oven at approximately 90°C for 1 hour, and then immersed in water at 60°C for 6 hours before testing. The separator was equilibrated overnight under 50% RH conditions. The test was performed by measuring the time required for a certain volume of air to pass through the sample. The separator was tested three times, and the average value was taken in ft⁻¹. 3 / min* ft 2 This was reported. The standard deviation of all samples was less than +0.0002. [Examples]

[0051] Coating preparation A selective material mixture for coating on a porous polymer was prepared as follows. In preparing the selective material mixture, the components were added in the following order: zirconium oxide, ion exchange polymer dispersion, and reagent-grade ethanol. The weight ratio of the ion exchange polymer to the ZrO2 solid was approximately 0.1 to 0.6 by dry weight. The Nafion® dispersion contained approximately 10% by weight of perfluorosulfonic acid polymer (1000EW) solids and approximately 90% by weight of water (dispersion Nafion® D1021 from The Chemours Company FC, LLC). Ethanol was added in an amount that provided a material suitable for the selected spray application.

[0052] The components of the selected material mixture were added to a 20 mL glass scintillation vial for mixing. The vial (not shaken before sonication) was sonicated for 5 minutes, then shaken well, and sonicated again for another 5 minutes. Before loading into the application device, the vial containing the selected material mixture was briefly shaken using a vortex mixer.

[0053] Spray coating application technology Before spray coating, the porous polymer separator of the sample was placed on a frame template and secured with clips around the outer periphery of the porous substrate.

[0054] The selected material mixture was applied using an airbrush set, Paasche® Model VL. The selected material mixture was gravity-fed into the airbrush via a cutoff syringe used to contain and supply the mixture within the airbrush gun. An air pressure of 15 psi was maintained during coating. For each substrate sample, an area of ​​approximately 12 cm x 12 cm was spray-coated.

[0055] The migration rate of the selected material mixture, determined by gravimetric method by spraying onto Kapton™ film, is approximately 30% to 50% by weight, or approximately 0.9 mg / cm³. 2 The nominal load was provided.

[0056] Example 1 The AWE selective separator membrane was prepared by spray-coating a selective material mixture onto only one outer surface of a porous PE substrate.

[0057] The PE substrate had a composite material structure of silica powder and polyethylene with an average thickness of approximately 160 microns (obtained from Entek). A selective coating mixture containing ZrO2, Nafion® perfluorosulfonic acid polymer (1000 EW dispersion) (ZrO2 / dry ionomer) in a ratio of approximately 0.1, and ethanol as a solvent was prepared as described above. The average particle size of ZrO2 was approximately 0.8 μm, as determined by laser diffraction particle size analysis (MEL Chemical, MS2 grade). The coating mixture was applied by the spray coating method described herein. Hydrophilic particles of the selective material adhered to the PE porous separator by ion exchange polymer. The average thickness of the final selective separator was approximately 167 μm.

[0058] The load of the selected coating solid on the PE substrate was measured by gravimetric analysis and was approximately 0.9 mg / cm³. 2 The porous selective separators were tested for gas release angle, gas permeability, and ion resistance on the coated surface using the method provided herein, and compared with conventional materials. The results are provided in Table 1. SEM images of the AWE selective separator film (200) are shown in Figure 2, showing a top view of the selective separator illustrating the uniform application of a selective coating mixture (202) having small and large zirconia particles (201a, 201b).

[0059] Example 2 A selective separator was prepared in substantially the same manner as in Example 1. However, the selective material mixture was applied by spray coating to both the anode-facing and cathode-facing outer surfaces of the porous PE. The nominal load of the coating solid on each surface was approximately 0.9 mg / cm³. 2 That was the case.

[0060] Porous selective separators were tested for gas release angle, gas permeability, and ionic resistance using the method provided herein and compared with conventional materials. The results are given in Table 1. Figure 3 shows an SEM image of the AWE selective separator film (300), illustrating a cross-sectional view of the selective separator showing a uniform distribution of zirconia particles (304) uniformly distributed throughout the entire thickness of the selective coating mixture (303) and appearing as white particles forming the outermost surfaces (301a, 301b) of the selective separator film. Minimal passage of the selective coating mixture into and through the porous PE separator structure (302) is observed, and the porous PE separator structure is substantially free of zirconia particles throughout the entire porous PE structure (302).

[0061] Example 3 The selective separator was prepared substantially in the same manner as in Example 2, except that the porous separator was a multilayer having an ePTFE film laminated on a nonwoven polypropylene film, and the ePTFE / polypropylene substrate was obtained from Membrane Solutions, LLC (FPL100A12 hydrophilic PTFE film with a pore size of 1.0 μm, a bubble point of 0.12-0.15 (MPa) at 23°C, a PP support layer, and reporting a bubble point test using purified water as the wetting fluid). The selective material layer was applied to the porous separator substrate by spray coating both the anode-facing and cathode-facing outer surfaces of the ePTFE / polypropylene substrate to form the selective separator. The nominal load of the coating solid on each surface was approximately 0.9 mg / cm³. 2 That was the case.

[0062] Figure 4 shows an SEM image of the selective separator film (400), a cross-sectional view showing a uniform coating of the selective coating mixture (401), where zirconia particles are observed on the outer surface of the ePTFE film (402a) of the porous separator layer (403), indicating that the zirconia passes through the ePTFE microstructure minimally, the selective coating mixture (401) is applied to the opposing surface, substantially passing through the porosity of the nonwoven PP layer (404) and the coating fibers (405), and that the zirconia particles reach the ePTFE surface (402b) opposite the outer ePTFE surface (402a).

[0063] The weight ratio of the ion exchange polymer to the ZrO2 solid was approximately 0.4 by dry weight. The porous selective separator was tested for gas release angle, gas permeability, and ion resistance by the method provided herein and compared with conventional materials. The results are given in Table 1. The final thickness measurements of the porous selective separator were approximately 170 μm to 220 μm when measured at 10 points.

[0064] Comparative Example 4 The porous polyethylene substrates used in Examples 1 and 2 were tested without surface modification or the addition of any selected material. The substrates were tested for gas release angle, gas permeability, and ion resistance using the methods provided herein and compared with conventional materials. The results are provided in Table 1. As reported in Table 1, the coated separators of Examples 1 and 2 showed a significant improvement in gas release angle compared to uncoated plain PE, achieving 71 and 78 mΩcm, respectively, similar to the plain PE separator (PE) of Comparative Example 4. 2 It did not have a significant effect on the ion resistance value.

[0065] Comparative Example 5 The comparative selection separator was prepared substantially in the same manner as in Example 2, except that the inorganic particles in the selection material mixture were ZrO2 nanoparticles with an average particle size of 100 nm. The nominal packing amount of the coating solid on each surface of the porous PE substrate was approximately 0.9 mg / cm³. 2and the weight ratio of the ion exchange polymer to the ZrO2 solid was approximately 0.11 in dry weight and was substantially the same as in Example 2. The coated substrate of Comparative Example 5 was tested for gas release angle, gas permeability, and ionic resistance by the method provided herein and compared with conventional materials. The results provided in Table 1 showed a significantly higher gas release angle (greater than 45 degrees) (compared with Example 2 (less than 2 degrees)), and there was no significant change in ionic resistance (Comparative Example 5 was about 81 mΩ·cm 2 , Example 2 was 78 mΩ·cm 2 ).

[0066] Comparative Examples 6 and 7 The ePTFE / PP porous separator substrate according to Example 3 was prepared by applying the selected material without any surface modification or using no selected material (Comparative Example 6), and by applying the ionomer (Nafion™ ionomer) of the selected material without using inorganic particles to the ePTFE side of the porous separator. The materials were tested for gas release angle, gas permeability, and ionic resistance by the method provided herein and compared with conventional materials. The results are provided in Table 1, showing that the gas release angle was significantly higher compared to Example 3, and thus the gas release from the surface was lower. Compared with Example 3 (about 136 mΩ·cm 2 ), Comparative Example 7 further showed a higher ionic resistance (217 mΩ·cm 2 ), and Comparative Example 6 showed a high air permeability equal to a higher gas crossover.

[0067] Comparative Example 8 Perfluorosulfonic acid-based Nafion® films were also tested for comparison with Examples 1 and 2. Nafion® NR220 films, having a 10 μm thick Nafion® dispersion cast on a 160 μm thick PE separator, were tested for gas release angle, gas permeability, and ionic resistance using the method provided herein and compared with conventional materials. The results are provided in Table 1, showing significantly higher ionic resistance than any of the selected separators prepared according to Examples 1-3. Visual observation indicated that the surface of the Nafion® polymer was not completely wetted in 30% KOH. While we do not wish to be bound by theory, the high resistance may be attributable to the low water content in the Nafion® polymer layer in 30% KOH.

[0068] Comparative Example 9 Zirfon® membrane bleu (UTP500; Agfa-Gevaert NV, Belgium), porous separator, and benchmark membrane (in AWE technology) were obtained. The resistance values ​​reported in Table 1 were obtained from the literature (AGFA Technical Data Sheet Zirfon® Perl UTP 500).

[0069] Comparative Example 10 A 25 μm thick separator film was obtained by Nafion® 211 dispersion casting (The Chemours Company FC, LLC, Wilmington, DE) and tested as reported in Table 1. The dispersion-cast film exhibited significantly higher ionic resistance than any of the selective separators prepared according to Examples 1-3.

[0070] [Table 1] * Based on literature data (AGFA Technical Data Sheet Zirfon® Perl UTP 500)

[0071] The porous selective separator of Example 1 having a first outer surface coated with a selected material, and the porous selective separator of Example 2 having both outer surfaces coated with a selected material, had no selected material layer applied and resulted in significantly lower gas emission angles of about 3.9 degrees and about 1.4 degrees, respectively, than the sample of Comparative Example 4 having the same porous selective separator material having a gas emission angle of about 33 degrees. The material of Comparative Example 7, which is a separator containing an ion exchange polymer having a sulfonic acid functional group, had a gas emission angle exceeding 40 degrees. The lower gas emission angles of Examples 1 to 3 described herein are advantageous for reducing gas blinding at the membrane / electrode interface.

[0072] <00OO381>The porous sample of Comparative Example 5, both outer surfaces of which were coated with zirconium oxide nanoparticles (particle size less than 100 nm), showed a higher gas emission angle (equivalent to lower gas emission) and a higher air permeability (equivalent to higher gas crossover) when compared to Examples 1 and 2, both of which had a selective material layer composed of ZrO2 particles having a larger particle size (about 106 μm), but Examples 1 and 2 maintained similar ion resistance values. Bubbles were still attached to the surface of the sample material of Comparative Example 5 at the maximum angle on the test equipment.

[0073] The porous selective separator of Example 3, i.e., ePTFE laminated on non-woven polypropylene with both outer surfaces coated with a selected material, resulted in a low gas emission angle of about 8.1 degrees at its outermost ePTFE surface. The flat porous polymer separator of Comparative Example 6 lacking a selective layer did not emit gas at the maximum angle limit (45 degrees) of the equipment during testing. Due to the absence of a selected material on the ePTFE / PP structure, the air permeability decreased substantially from about 2.48 ft 3 / min * ft <OO00095>(Comparative Example 6) to about 0.0029 ft 3 / min * ft <Oo00098>(Comparative Example 3).

Claims

1. A selective separator for water electrolysis applications, A porous polymer separator layer having first and second opposing outer surfaces, A selective material layer comprising a composite material of an ion exchange polymer and inorganic particles distributed throughout the ion exchange polymer having an average particle size in the range of 0.1 μm to 8 μm, wherein the selective material layer is located on at least one surface of the porous polymer separator layer. Includes, The selective material layer forms the outermost surface of the selective separator, and the gas release angle is less than 20 degrees.

2. A selective separator for water electrolysis applications, A porous polymer separator layer containing a polymer microporous film laminated on a nonwoven porous material, A selective material layer on at least one surface of the porous polymer separator layer, wherein the selective material is a perfluorinated sulfonic acid polymer and ZrO, uniformly distributed throughout the entire selective material layer. ２ A selected material layer comprising a composite material of an ion exchange polymer containing particles, Includes, The aforementioned Zr ２ A selective separator wherein the average particle size is in the range of 0.1 μm to 4 μm, and the selective material is the outermost surface of the selective separator surface to which it is provided.

3. A selective separator for water electrolysis applications, A porous polymer separator layer having a composite material comprising a polymer and an amount of inorganic particles sufficient to increase the hydrophilicity of the porous polymer separator polymer, A selective material layer on at least one outer surface of the porous polymer separator layer, Essentially, The selected material comprises a composite material comprising an ion exchange polymer containing a perfluorosulfonic acid functional group and zirconium oxide particles having an average particle size in the range of 0.1 μm to 5 μm distributed within the selected material. The selective separator is the outermost surface of the selective separator surface to which the selective material layer is applied.

4. The selective separator according to any one of claims 1 to 3, wherein the porous polymer separator layer comprises polyethylene, polypropylene, fluoropolymer, PTFE, stretched PTFE, PVDF, polysulfone, polyphenylene sulfide, or a combination thereof.

5. The selective separator according to claim 1, wherein the porous polymer separator layer comprises a polymer composite material containing metal oxide fine particles selected from zirconium oxide, titanium oxide, bismuth oxide, cerium oxide, magnesium oxide, and combinations thereof, the metal oxide fine particles increase the hydrophilicity of the polymer.

6. The selective separator according to any one of claims 1 to 3, wherein the average pore size of the porous polymer separator layer is 0.1 μm to 5 μm.

7. The selective separator according to any one of claims 1 to 3, wherein the porous polymer separator layer is self-supporting.

8. The aforementioned selective separator has a gas release angle of less than 20 degrees and a resistance of 200 mΩ·cm. ２ Ionic resistance less than 0.008 ft ３ / min ＊ ft ２ A selective separator according to any one of claims 1 to 3, having an air permeability of less than [amount missing].

9. The selective separator according to any one of claims 1 to 3, wherein the selective material layer is applied to both outer surfaces of the porous polymer separator.

10. The selected material layer is 0.1 mg / cm². ２ ~2 mg / cm³ ２ The selective separator according to claim 1, having a dry solid filler amount containing an ion exchange polymer and inorganic particles.

11. The selected material layer is 0.1 mg / cm ２ to 2 mg / cm ２ and has a dry solid filling amount containing an ion exchange polymer and ZrO ２ particles. The selective separator according to claim 1 or claim 2.

12. The selective separator according to claim 1, wherein the solid weight ratio of the ion exchange polymer to the inorganic particles in the selective material layer is in the range of 0.1 to 0.

6.

13. ZrO ２ A selective separator according to claim 2 or 3, wherein the solid weight ratio of the ion exchange polymer to the solid is 0.1 to 0.

8.

14. The selective separator according to claim 1, wherein the inorganic particles of the selective material layer include at least one material selected from the group consisting of oxides, nitrides, carbides, or mixtures thereof of Group 4 or Group 14 elements.

15. The selective separator according to claim 1, wherein less than 20% by weight of the inorganic particles passes through the pores of the porous polymer separator.

16. The selective separator according to any one of claims 1 to 3, wherein the thickness of the selective material layer on one of the porous polymer separator surfaces is less than 20 μm.

17. The selective separator according to any one of claims 1 to 3, wherein the average thickness of the selective material layer is in the range of 1 μm to 10 μm.

18. The selective separator according to claim 1, wherein the ion exchange polymer is a cation exchange polymer.

19. The selective separator according to claim 1, wherein the ion exchange polymer is an anion exchange polymer.

20. The selective separator according to claim 1, wherein the ion exchange polymer functional group includes, but is not limited to, a sulfonate, carboxylate, or phosphate functional group.

21. The selective separator according to claim 1, wherein the ion exchange polymer is a perfluorinated sulfonic acid polymer.

22. The selective separator according to any one of claims 1 to 3, wherein the ion exchange polymer has an ion exchange capacity of 0.8 meq / g to 2.5 meq / g of dry polymer.

23. The selective separator according to any one of claims 1 to 3, further comprising zirconium oxide particles attached to the selective separator by the ionomer exchange polymer.

24. The selective separator according to any one of claims 1 to 3, wherein the surface roughness of the selective separator is 0.1 μm to 4 μm.

25. The selective separator according to any one of claims 1 to 3, wherein the thickness of the selective material layer on one or both of the outermost surfaces is 300 μm or less.

26. The selective separator according to any one of claims 1 to 3, wherein the thickness of the selective material layer is less than 250 μm.

27. The selective separator according to claim 2 or claim 3, wherein the gas emission angle measured at the outermost surface of the selective separator is less than 20 degrees.

28. The selective separator according to any one of claims 1 to 3, wherein the gas emission angle of the outermost surface of the selective separator is less than 10 degrees.

29. A selective separator according to claim 1, having a first selective material layer on an anode-facing surface and a second selective material layer on a cathode-facing surface, wherein the amount of inorganic particles passing through the first selective material layer is different from the amount of inorganic particles passing through the second selective material layer.

30. The selective separator according to any one of claims 1 to 3, wherein the porous polymer separator comprises at least two layers.

31. The selective separator according to claim 30, wherein the first porous polymer separator layer has an average pore diameter smaller than the average pore diameter of the second porous polymer separator layer.

32. The selected separator according to claim 31, wherein the porous polymer separator layer comprises a microporous film and a nonwoven fabric.

33. The selective separator according to any one of claims 30 to 32, wherein the porous polymer separator layer comprises an ePTFE layer and a nonwoven fabric layer.

34. The selective separator according to any one of claims 30 to 33, wherein the porous polymer separator layer includes a nonwoven fabric between two outer layers of ePTFE.

35. The nonwoven fabric comprises polypropylene or polyethylene, as described in any one of claims 32 to 34.

36. The selective separator according to claim 1, wherein the ohm resistance is less than 100 mΩ·cm² when measured at ambient temperature.

37. Use of a selective separator according to any one of claims 1 to 36 in a water electrolysis cell.

38. An electrochemical cell for use in alkaline water electrolysis (AWE) applications, wherein the electrochemical cell is an arboreal compartment, and an arboreal located within the arboreal compartment, A cathode compartment, a cathode located within the cathode compartment, and an electrochemical cell configured to hold a liquid electrolyte, A selection separator between the anode and the cathode, Hydrophilic porous polymer separator, A selective material layer on at least one outer surface of the porous polymer separator, comprising a composite material of an ion exchange polymer and inorganic particles distributed throughout the ion exchange polymer, Includes a selection separator, Includes, The average inorganic particle size is in the range of 0.1 μm to 4 μm. The selected material layer forms the outermost surface of the selected separator surface to which it is applied in an electrochemical cell.

39. The electrochemical cell according to claim 38, wherein the selective separator is in contact with at least one of the anode and the cathode.

40. The electrochemical cell according to claim 38, wherein the selection separator is configured not to come into contact with the anode or the cathode.

41. A method for manufacturing a selective separator, wherein the method is A process for obtaining a porous polymer separator, A step to obtain a selective material comprising a liquid composition of an ion exchange polymer and inorganic particles having an average particle size of 0.1 μm to 4 μm, A step of applying the liquid composition to one or both outer surfaces of the porous polymer separator to form a selective layer without substantially passing through at least a portion of the thickness of the porous polymer separator layer, A method comprising the inorganic particles being uniformly distributed over the entire thickness of the selected layer.

42. A method for manufacturing the selective separator according to claim 41, wherein the selective separator has a gas discharge angle of less than 20 degrees.

43. The method according to claim 41, wherein the porous polymer separator comprises polyethylene, and the selected material comprises an ion exchange polymer and zirconium oxide particles.

44. The method according to claim 41, further comprising the step of forming a selective material layer having a thickness of less than 10 μm on the outer surface of the porous polymer separator.

45. The method according to claim 41, comprising the step of forming a selective material layer having a thickness of 4 μm to 10 μm on at least one outer surface of the porous polymer separator.

46. The method according to claim 41, wherein the porous polymer separator is formed from a polymer mixture containing polyethylene and silica, and the ion exchange polymer contains perfluorosulfonic acid.

47. The method according to claim 41, wherein the porous polymer separator is formed by coating the selected material containing a perfluorosulfonic acid polymer onto a multilayer porous polymer separator, and the multilayer porous polymer separator includes a microporous ePTFE film laminated on nonwoven polypropylene.

48. The selected material is applied to the outer surface of the porous polymer separator at a concentration of approximately 0.1 mg / cm². ２ ~2 mg / cm³ ２ The method according to claim 41, comprising forming a coating having a dry solid filler amount to form the outermost layer of the selective separator.

49. The method according to claim 47, wherein the selected material containing the inorganic particles forms a layer on the microporous ePTFE film without the inorganic particles substantially passing through the microporous ePTFE, and the selected material passes through the thickness of the nonwoven layer together with the inorganic particles coating the fibers of the nonwoven layer.

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