Improved multilayer proton exchange membrane for water electrolysis

Abstract

There is provided a multi-layer proton exchange membrane for water electrolysis, comprising: at least two reconstitution catalyst layers, each of which comprises a reconstitution catalyst and a first ion exchange material, and at least two reinforcement layers, each of which comprises a reconstitution catalyst and a second ion exchange material, wherein the at least two reconstitution catalyst layers are separated by regions free of or substantially free of reconstitution catalyst, each of the at least two reinforcement layers comprising a microporous polymer structure and a second ion exchange material at least partially absorbed within the microporous polymer structure.

Description

Technical Field

[0001] The present disclosure relates to a multilayer proton exchange membrane for water electrolysis. The present disclosure also relates to a multilayer proton exchange membrane electrode assembly, an electrolysis cell comprising the multilayer proton exchange membrane, use of the multilayer proton exchange membrane in water electrolysis, and a method for manufacturing the multilayer proton exchange membrane. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis is an important and very promising technology for producing hydrogen. During PEM water electrolysis, electrical energy is used to decompose water into oxygen and hydrogen. The hydrogen produced is an energy carrier and can be compressed, stored, and used in, for example, hydrogen fuel cells to generate electricity. The oxygen produced can also be released into the atmosphere or stored and used in industry or as a medical gas.

[0003] An electrolyzer is an electrochemical device in which PEM water electrolysis occurs. An electrolyzer comprises at least a PEM, an anode, and a cathode. The PEM contains an ion exchange material that conducts protons. The anode is typically a layer containing iridium, while the cathode is typically a layer containing platinum. During electrolysis, the half-reaction at the anode is: 2H2O -> O2 + 4H + +4e - , the half reaction at the cathode is: 4H + +4e - ->2H2. H + Cations migrate from the anode to the cathode through the PEM, generating H 2 at the cathode.

[0004] In terms of sustainability and environmental impact, PEM water electrolysis is a promising technology for efficient hydrogen production because it only emits oxygen as a byproduct without any direct carbon emissions. Therefore, to achieve global decarbonization goals, it is desirable to reduce the production costs associated with PEM water electrolysis so that PEM water electrolysis can be more widely used.

[0005] Technologies to reduce production costs associated with PEM water electrolysis include: (i) improving the efficiency of PEM water electrolysis, (ii) increasing hydrogen pressure, thereby reducing downstream compression costs, and (iii) extending the range of electrolyzer operation to very low loads, thereby maximizing the use of renewable energy, (iv) extending the operating life of electrolyzers, and (v) reducing the capital and maintenance costs of hydrogen purification units by increasing the purity level of hydrogen produced directly in the electrolyzers and reducing the need for additional purification processes.

[0006] Improved PEM water electrolysis efficiency can be achieved by reducing PEM thickness and increasing operating temperature. Increasing operating temperature may require increased chemical durability of the PEM to achieve long life. Similarly, increasing hydrogen pressure to reduce downstream compression requires increased mechanical strength of the PEM to withstand operating pressures.

[0007] However, many strategies to reduce production costs—by improving PEM water electrolysis efficiency (by reducing the thickness of the PEM and using higher operating temperatures) and increasing hydrogen pressure, as well as operating in a low load range to reduce overall production costs—lead to increased "hydrogen crossover." Hydrogen crossover refers to the enrichment of hydrogen in the oxygen stream due to the migration of the PEM from the cathode to the anode. Hydrogen crossover causes PEM degradation and leads to safety issues if the hydrogen concentration in the hydrogen-oxygen mixture at the anode exceeds the explosion limit of 4 mol%. Therefore, during electrolysis, it is important to minimize hydrogen permeation through the PEM or minimize the hydrogen concentration in the hydrogen-oxygen mixture so that the hydrogen concentration in the hydrogen-oxygen mixture does not exceed 4 mol%. Safety standards generally stipulate that the hydrogen concentration should not exceed 2 mol%.

[0008] A known strategy for reducing the hydrogen concentration in a hydrogen-oxygen mixture is to employ a single recombination catalyst layer in or on the PEM. Furthermore, a recombination catalyst layer located in or on the PEM can reduce the oxygen concentration in the hydrogen-oxygen mixture, improving the purity of the resulting hydrogen. The recombination catalyst is a catalyst that, in a controlled manner, recombines any permeating hydrogen that passes through the cathode with oxygen to form water, thereby reducing the amount of hydrogen entering the oxygen stream. Typically, the recombination catalyst layer is coated on a surface of the PEM closest to the anode of the electrolytic cell.

[0009] However, as the thickness of the PEM decreases and operating conditions become more aggressive (e.g., higher temperatures and pressures), the coating layer containing the recombination catalyst may not be thick enough to further increase the concentration of the recombination catalyst in the coating layer to mitigate the increased hydrogen flux. In addition, the increased concentration of the recombination catalyst near the anode side of the PEM can lead to unfavorable processes that chemically attack the PEM and electrodes, shortening the life of the electrolytic cell, especially at higher operating temperatures. For example, a high concentration of the recombination catalyst near the anode can lead to the production of peroxides, which in turn generate free radicals that degrade the ion exchange material in the PEM. In addition, as the thickness of the PEM decreases, the coating layer containing the recombination catalyst may not be optimally positioned to simultaneously reduce cross-over oxygen to ensure the purity of the generated hydrogen.

[0010] The problem of excessive hydrogen crossover can be exacerbated by damage or puncture of the PEM due to aggressive operating conditions or cell configurations, particularly when the membrane is relatively thin. One strategy for improving damage or puncture resistance is to include a single reinforcement layer in the PEM. This reinforcement layer can be a microporous polymer structure that incorporates an ion exchange material, which is therefore ionically conductive. However, even a PEM reinforced in this manner can suffer damage or puncture during cell operation and manufacturing.

[0011] Therefore, there is a need for improved multilayer proton exchange membranes for water electrolysis that have reduced production costs. That is, there is a need for improved multilayer proton exchange membranes that can withstand aggressive operating conditions (such as high temperature and pressure), are relatively thin, and limit adverse chemical processes near the anode side of the membrane while mitigating increased hydrogen and oxygen fluxes such that the hydrogen concentration in the oxygen stream is acceptably low and the produced hydrogen has a desired purity level.

[0012] The present disclosure solves the above-mentioned problems. Summary of the Invention

[0013] In a first aspect, a multilayer proton exchange membrane (herein "PEM") for water electrolysis is provided, comprising: (i) at least two recombinant catalyst layers, each of the at least two recombinant catalyst layers comprising a recombinant catalyst and a first ion exchange material, wherein the at least two recombinant catalyst layers are separated by a region that is free or substantially free of recombinant catalyst, and (ii) at least two reinforcement layers, each of the at least two reinforcement layers comprising a microporous polymer structure and a second ion exchange material, the second ion exchange material being at least partially absorbed within the microporous polymer structure.

[0014] A PEM comprising at least two recombination catalyst layers effectively reduces the hydrogen concentration in an oxygen stream to an acceptably low concentration while simultaneously limiting unfavorable chemical processes by optimizing recombination catalyst concentration and layer location, particularly for low-proton, low-hydrogen, and / or low-oxygen barrier multi-layer reinforced PEMs used in electrolytic cells. In particular, in situations where a high concentration of recombinant catalyst is desired, the at least two recombinant catalyst layers in a low-proton, low-hydrogen, and / or low-oxygen barrier multi-layer reinforced PEM can alleviate processing and performance limitations compared to a single recombinant catalyst layer.

[0015] Specifically, having at least two recombination catalyst layers can allow the PEM to accommodate a higher total amount of recombination catalyst than would be possible with a single recombination catalyst layer, as it is not always practical to increase the recombination catalyst concentration sufficiently in a single layer in order to reduce the hydrogen concentration in the oxygen stream and / or the oxygen concentration in the hydrogen stream to acceptably low concentrations.

[0016] In addition, at least two recombination catalyst layers are separated by a region that does not contain or is substantially free of recombination catalyst, allowing the recombination catalyst in the PEM to be located at different positions in the PEM, rather than at a single position in the PEM. Typically, the recombination catalyst is located on one surface of the PEM, which is typically next to the anode in the electrolytic cell. Depending on the design and assembly of the stack, electrodes, and PEM, as well as operating pressure and temperature, the optimal position of the recombination catalyst for maximizing effective recombination may not be close to the anode surface. The optimal position in the PEM may also change over time, for example, due to the effect of hydrogen supersaturation as the pool assembly deteriorates. Having a recombination catalyst at the anode side of the PEM can lead to adverse processes that chemically attack the PEM and electrodes, thereby reducing the life of the electrolytic cell, especially at higher operating temperatures. Therefore, by having the recombination catalyst located at different positions in the PEM, rather than at a single position in the PEM, the recombination catalyst can be located in a wider region in the PEM thickness. This makes it possible to achieve higher recombination efficiency under a wider range of stack design and assembly techniques and different operating pressures and temperatures. Importantly, as the system degrades over time, the recombination catalyst is more widely distributed throughout the thickness of the PEM so that efficient recombination can be maintained over time as the system degrades (e.g., if the supersaturation changes). Some recombination catalysts can be positioned further away from the anode of the electrolytic cell, thereby limiting adverse processes that can occur near the anode side of the PEM. This can thereby improve the life of the PEM and the electrolytic cell. For example, some recombination catalysts can be positioned closer to the cathode.

[0017] The PEM comprising at least two reinforcement layers provides mechanical strength to the PEM, thereby allowing the thickness of the PEM to be reduced, thereby increasing electrolysis efficiency. The at least two reinforcement layers also allow the use of more aggressive operating conditions, such as higher temperatures and pressures, thereby increasing electrolysis efficiency and saving costs.

[0018] Furthermore, the PEM comprising at least two reinforcement layers helps avoid damage and punctures in the PEM that can result from using aggressive operating conditions or electrolytic cell configurations (particularly when the membrane is relatively thin). This helps further extend the life of the PEM and reduces hydrogen and oxygen crossover, which can occur to a greater extent if the PEM is damaged or punctured.

[0019] Thus, the PEMs of the present disclosure allow for reduced production costs during electrolysis. That is, the PEMs of the present disclosure can withstand aggressive operating conditions (such as relatively high temperatures and pressures), can be relatively thin, and can limit adverse chemical processes near the anode side of the membrane while mitigating increased hydrogen flux such that the hydrogen concentration in the oxygen stream is acceptably low; and / or mitigating increased oxygen flux such that the oxygen concentration in the hydrogen stream is acceptably low.

[0020] In one embodiment, the thickness d of the region separating the at least two recombination catalyst layers may be at least about 1 μm at 50% RH (relative humidity). The thickness d of the region separating the recombination catalyst layers at 50% RH may be at least about 2 μm, or at least about 3 μm, or at least about 4 μm, or at least about 5 μm, or at least 10 μm, or at least 20 μm, or at least 30 μm, or at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm, or at least 80 μm.

[0021] In one embodiment, the at least two recombinant catalyst layers may be separated by a region having a thickness d, wherein the thickness d is from about 1 μm to about 80 μm at 50% RH. The thickness d of the region at 50% RH may be from about 1 μm to about 70 μm, or from about 1 μm to about 60 μm, or from about 1 μm to about 50 μm, or from about 1 μm to about 40 μm, or from about 1 μm to about 30 μm, or from about 1 μm to about 20 μm, or from about 1 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 2 μm to about 80 μm, or from about 2 μm to about 60 μm, or from about 2 μm to about 50 μm, or from about 2 μm to about 40 μm, or from about 2 μm to about 30 μm, or from about 2 μm to about 20 μm, or from about 2 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 5 μm to about 80 μm, or from about 5 μm to about 60 μm, or from about 5 μm to about 50 μm, or from about 5 μm to about 40 μm, or from about 5 μm to about 30 μm, or from about 5 μm to about 20 μm, or from about 5 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 10 μm to about 80 μm, or from about 10 μm to about 60 μm, or from about 10 μm to about 50 μm, or from about 10 μm to about 40 μm, or from about 10 μm to about 30 μm, or from about 10 μm to about 20 μm.

[0022] In one embodiment, the region separating the at least two recombinant catalyst layers may comprise at least one layer free of or substantially free of recombinant catalyst. The at least one layer free of or substantially free of recombinant catalyst may comprise at least one reinforcement layer, or at least one layer of ion exchange material, or a combination thereof. The region may comprise more than one layer, such as two or three layers.

[0023] In one embodiment, the recombinant catalyst may comprise one or more selected from the group consisting of platinum, palladium, iridium, rhodium, ruthenium, osmium, nickel, cobalt, titanium, tin, tantalum, niobium, antimony, lead, manganese, and oxides thereof. The recombinant catalyst may comprise at least one platinum group metal selected from the group consisting of platinum, palladium, iridium, rhodium, ruthenium, and osmium. The recombinant catalyst may comprise an alloy of at least one platinum group metal, or a mixed oxide of at least one platinum group metal and other metals such as cerium and titanium. The recombinant catalyst may be present on a support material, which may be a carbon particulate material such as carbon black. In one embodiment, the recombinant catalyst is platinum supported on carbon particulate material.

[0024] The recombinant catalysts in each of the at least two recombinant catalyst layers may be the same or different. In one embodiment, the recombinant catalysts in each of the at least two recombinant catalyst layers may be the same. In another embodiment, the recombinant catalysts in each of the at least two recombinant catalyst layers are different.

[0025] The recombinant catalyst in each of the at least two recombinant catalyst layers may comprise one or more recombinant catalyst species.

[0026] In one embodiment, each of the at least two recombination catalyst layers may have a minimum thickness of about 1 μm at 50% RH, or a thickness in the range of about 1 μm to about 35 μm, or in the range of about 1 μm to about 20 μm, or in the range of about 5 μm to about 35 μm, or in the range of about 5 μm to about 20 μm, or in the range of about 3 μm to about 15 μm, or a thickness in the range of about 4 μm to about 12 μm, or a thickness in the range of about 3 μm to about 8 μm.

[0027] In one embodiment, the recombinant catalyst may be present in each of the at least two recombinant catalyst layers at a loading of up to about 0.10 mg / cm 2 , or the loading is about 0.001 mg / cm 2 to about 0.10 mg / cm 2 range, or the loading range is about 0.001 mg / cm 2 to about 0.09 mg / cm 2 , or a loading of about 0.008 mg / cm 2 to about 0.025 mg / cm 2 within the range.

[0028] In one embodiment, at least one recombinant catalyst layer may include one or more additives selected from antioxidants and free radical scavengers.

[0029] In one embodiment, the PEM may comprise a total of two recombinant catalyst layers. In another embodiment, the PEM may comprise a total of three recombinant catalyst layers. In another embodiment, the PEM may comprise a total of four recombinant catalyst layers.

[0030] In one embodiment, the recombinant catalyst of each of the at least two recombinant catalyst layers can be dispersed in the first ion exchange material. The recombinant catalyst can be substantially uniformly dispersed in the first ion exchange material. In some examples, there can be two recombinant catalysts, each of which can be dispersed in the first ion exchange material, and each of the two recombinant catalysts can be the same or different recombinant catalysts, and each of the two first ion exchange materials can be the same or different first ion exchange materials.

[0031] In one embodiment, the PEM may comprise an ion exchange material layer comprising a third ion exchange material, wherein the ion exchange material layer is free of or substantially free of a microporous polymer structure and a recombinant catalyst. The region separating the at least two recombinant catalyst layers may comprise the ion exchange material layer.

[0032] In one embodiment, the first ion exchange material, the second ion exchange material, and the third ion exchange material may be the same or different. In one embodiment, the first ion exchange material and the second ion exchange material may be the same. The first ion exchange material, the second ion exchange material, and the third ion exchange material may be the same. In one embodiment, the first ion exchange material and the second ion exchange material may be different. The first ion exchange material and the second ion exchange material may be the same, and the at least two recombination catalyst layers and the at least two reinforcement layers may be formed from ion exchange materials from the same ion exchange material dispersion.

[0033] In one embodiment, the first ion exchange material, the second ion exchange material, and the third ion exchange material may each comprise at least one ion cross-linked polymer. The at least one ion cross-linked polymer may comprise a proton conducting polymer. The proton conducting polymer may be selected from the group consisting of hydrocarbon ion cross-linked polymers, perfluorinated ion cross-linked polymers, and perfluorinated sulfonic acid ion cross-linked polymers.

[0034] In one embodiment, the region separating the at least two recombination catalyst layers may include at least one reinforcement layer.

[0035] In one embodiment, the second ion exchange material (which is at least partially absorbed within the microporous polymer structure) can cause occlusion of the microporous polymer structure.

[0036] In one embodiment, the microporous polymer structure may be completely or substantially completely imbibed with the second ion exchange material.

[0037] In one embodiment, the total content of microporous polymer structure in the PEM may be at least about 1 g / m 2 , based on the total area of ​​the PEM.

[0038] In one embodiment, each of the at least two reinforcement layers may have a microporous polymer structure content of at least about 1 g / m 2 , based on the total area of ​​the PEM.

[0039] In one embodiment, the microporous polymer structure of each of the at least two reinforcement layers may comprise at least one fluoropolymer. The fluoropolymer may be selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), and mixtures thereof. The fluoropolymer may be expanded polytetrafluoroethylene (ePTFE).

[0040] In one embodiment, the microporous polymer structure of each of the at least two reinforcement layers may comprise a hydrocarbon polymer. The hydrocarbon polymer may be selected from the group consisting of polyethylene, polypropylene, polycarbonate, polystyrene, polysulfone, polyethersulfone, polyethylene naphthalate, and mixtures thereof.

[0041] In one embodiment, each of the at least two reinforcement layers may be free or substantially free of a recombination catalyst.

[0042] In one embodiment, the total thickness of the PEM at 50% RH (relative humidity) may be from about 20 μm to about 250 μm, or from about 20 μm to about 200 μm, or from about 20 μm to about 150 μm, or from about 20 μm to about 120 μm, or from about 20 μm to about 100 μm, or from about 20 μm to about 90 μm, or from about 20 μm to about 80 μm, or from about 20 μm to about 70 μm, or from about 20 μm to about 60 μm, or from about 20 μm to 50 μm, or from about 20 μm to 45 μm.

[0043] In one embodiment, the PEM may comprise at least the following layers in the following order:

[0044] (i) a recombinant catalyst layer;

[0045] (ii) reinforcement layer;

[0046] (iii) a recombinant catalyst layer;

[0047] (iv) reinforcement layer,

[0048] wherein the reinforcement layer contains no or substantially no recombinant catalyst, and the recombinant catalyst layer contains no or substantially no microporous polymer structure. The PEM may further comprise: (v) an ion exchange material layer in contact with the reinforcement layer (iv), wherein the ion exchange material layer contains no or substantially no microporous polymer structure and recombinant catalyst. In one embodiment, the recombinant catalyst layer (i) is intended to be located at or closest to the anode of the electrolytic cell PEM electrode assembly during use. In another embodiment, the ion exchange material layer may be positioned adjacent to the recombinant catalyst layer (i) such that the ion exchange material layer forms an outer surface layer of the PEM.

[0049] In another embodiment, the PEM may comprise at least the following layers in the following order:

[0050] (i) an ion exchange material layer;

[0051] (ii) a recombinant catalyst layer;

[0052] (iii) reinforcement layer;

[0053] (iv) an ion exchange material layer;

[0054] (v) reinforcement layer;

[0055] (vi) a recombinant catalyst layer;

[0056] (vii) an ion exchange material layer;

[0057] Layers of ion exchange material are provided at both surfaces of the PEM, adjacent to the recombination catalyst layer.

[0058] In another embodiment, the PEM may comprise at least the following layers in the following order:

[0059] (i) reinforcement layer;

[0060] (ii) a recombinant catalyst layer;

[0061] (iii) an ion exchange material layer;

[0062] (iv) a recombinant catalyst layer;

[0063] (v) a reinforcement layer,

[0064] wherein the reinforcing layer contains no or substantially no recombinant catalyst, the recombinant catalyst layer contains no or substantially no microporous polymer structure, and the ion exchange material layer contains no or substantially no microporous polymer structure and recombinant catalyst. In one embodiment, the reinforcing layer (i) or (v) is intended to be located at or closest to the anode of the electrolytic cell PEM electrode assembly during use. The PEM may further comprise additional recombinant catalyst layers, reinforcing layers, and ion exchange material layers. For example, the PEM may comprise additional ion exchange material layers at the outer surface, such that the PEM may comprise at least the following layers in the following order:

[0065] (i) an ion exchange material layer;

[0066] (ii) reinforcement layer;

[0067] (iii) a recombinant catalyst layer;

[0068] (iv) an ion exchange material layer;

[0069] (v) a recombinant catalyst layer;

[0070] (vi) reinforcement layer;

[0071] (vii) Ion exchange material layer.

[0072] The PEM may further comprise an additional reinforcement layer, for example adjacent to the recombination catalyst layer, such that the PEM may comprise at least the following layers in the following order:

[0073] (i) an ion exchange material layer;

[0074] (ii) reinforcement layer;

[0075] (iii) a recombinant catalyst layer;

[0076] (iv) reinforcement layer;

[0077] (iv) an ion exchange material layer;

[0078] (v) reinforcement layer;

[0079] (vi) a recombinant catalyst layer;

[0080] (viii) reinforcement layer;

[0081] (viii) Ion exchange material layer.

[0082] In one embodiment, the recombinant catalyst layer may be disposed in contact with the anode of the PEM electrode assembly. The recombinant catalyst layer may be disposed in contact with the cathode of the PEM electrode assembly.

[0083] In another aspect, a multilayer proton exchange membrane electrode assembly is provided, comprising: at least one electrode; and a PEM of the present disclosure in contact with the at least one electrode.

[0084] In one embodiment, the PEM may be attached to the at least one electrode. The electrode may comprise a porous layer. The electrode may comprise carbon fibers, and optionally the carbon fibers may have a diameter of about 5 to about 30 μm.

[0085] In one embodiment, the PEM electrode assembly may further comprise a fluid diffusion layer selected from the group consisting of felt, paper, woven material, carbon / carbon based diffusion layer, metal mesh or metallic mesh, titanium porous sintered powder mesh, stainless steel mesh, and mixtures thereof.

[0086] In one embodiment, the PEM electrode assembly may comprise a first electrode and a second electrode, optionally wherein the first electrode is an anode and the second electrode is a cathode. The anode may be in contact with a recombinant catalyst layer. The cathode may be in contact with a recombinant catalyst layer. In another embodiment, the cathode may be in contact with another recombinant catalyst layer.

[0087] In another aspect, an electrolytic cell is provided that includes a PEM of the present disclosure or a PEM electrode assembly of the present disclosure.

[0088] In another aspect, there is provided use of a PEM of the present disclosure in water electrolysis.

[0089] In another aspect, there is provided a method of manufacturing the multilayer proton exchange membrane of the present disclosure, the method comprising the steps of:

[0090] At least two reinforcement layers, at least two recombinant catalyst layers, and optionally one or more additional layers are formed, in any order, provided that the resulting PEM comprises at least two recombinant catalyst layers separated by a region free or substantially free of recombinant catalyst.

[0091] The manufacturing method may include forming the PEM in a sequential process, wherein, in a deposition step, the layers of the PEM are deposited sequentially in a desired order. In some embodiments, the PEM may be formed onto a backing layer or another layer. The deposition step may include at least one of coating, positioning, or shaping. The method may include forming two or more layers in a single deposition step. The method may include a drying step between deposition steps and / or between multiple deposition steps. The drying step may include heating or any other drying method.

[0092] The method of the present invention may include forming an ion exchange material layer by depositing an ion exchange material dispersion onto a backing layer or another layer of the PEM (e.g., a microporous polymer structure). In some examples, no backing layer is provided. The ion exchange material may be the first, second, or third ion exchange material.

[0093] The method of the present invention may comprise forming a recombinant catalyst layer by depositing a dispersion comprising an ion exchange material and a recombinant catalyst material onto a backing layer, and / or an additional layer (eg, a microporous polymer structure) of a PEM.

[0094] The manufacturing method of the present invention may include forming a recombinant catalyst layer by depositing a dispersion comprising an ion exchange material and a recombinant catalyst onto a reinforcement layer comprising a microporous polymer structure. The recombinant catalyst particles or aggregates of recombinant catalyst particles in the dispersion may be larger than the pore size of the microporous polymer structure and may not be absorbed into the microporous polymer structure. This method step may allow for the formation of at least a region that is free or substantially free of the recombinant catalyst.

[0095] The manufacturing method of the present invention may include filtering the recombinant catalyst from a dispersion of the ion exchange material and the recombinant catalyst using a microporous structure, thereby forming a recombinant catalyst layer on the surface of the reinforcement layer. The microporous polymer structure may be configured to prevent the recombinant catalyst particles or aggregates from penetrating into the pores of the microporous polymer structure.

[0096] The method of the present invention may include: the recombination catalyst is not absorbed into the reinforcement layer, thereby forming a recombination catalyst layer on the surface of the reinforcement layer.

[0097] The method of the present invention may comprise forming at least one of the at least two recombinant catalyst layers by depositing a microporous polymer structure onto a dispersion comprising an ion exchange material and recombinant catalyst particles or aggregates, and wherein the microporous polymer structure is configured to prevent the recombinant catalyst particles or aggregates from impregnating into the pores of the microporous polymer structure.

[0098] The method of the present invention may include forming a reinforcement layer by causing the microporous polymer structure to absorb the ion exchange material from a dispersion of the ion exchange material and the recombinant catalyst, wherein the microporous polymer structure is configured such that the recombinant catalyst cannot be impregnated into the pores of the microporous polymer structure. The method of the present invention may include forming the recombinant catalyst layer and the reinforcement layer in a single step from the same dispersion containing the ion exchange material and the recombinant catalyst. The ion exchange material may be the first, second, or third ion exchange material described herein. The reinforcement layer thus formed may be free of, or substantially free of, the recombinant catalyst.

[0099] The method of the present invention may comprise forming the reinforcement layer by depositing a dispersion comprising the ion exchange material onto the microporous polymer structure.

[0100] The method of the present invention may comprise forming an ion exchange material layer and an adjacent reinforcement layer in one step, wherein the ion exchange material layer is formed by a layer of dispersion of ion exchange material that is not absorbed into the microporous polymer structure forming the reinforcement layer.

[0101] The method of making a PEM may also include, for example, coating the surface of a tensioned microporous polymer structure and allowing the dispersion to be at least partially absorbed. The method of the present invention may include sequential coating, either by depositing additional microporous polymer structure and subsequently coating the top surface of the microporous polymer structure, or by depositing additional liquid dispersion. The manufacturing method of the present invention may include dip coating the microporous polymer structure in a bath of the dispersion and, for example, either drying or laying down a backing layer, followed by drying or applying a subsequent coating.

[0102] The foregoing aspects and embodiments should not be construed as limiting or otherwise restricting the scope of any of the inventive concepts otherwise provided herein. Although multiple embodiments are disclosed, other embodiments will become apparent to those skilled in the art from the following description and accompanying drawings. Accordingly, the description and accompanying drawings are to be regarded as illustrative rather than restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] Figure 1A -G shows a schematic diagram of a PEM according to the present disclosure.

[0104] Figure 2 Examples 1 and Figure 1C Cross-sectional SEM (scanning electron microscope image) of the PEM in FIG.

[0105] Figure 3 Examples 1 and Figure 1C Cross-sectional backscattered image of the PEM in .

[0106] Figure 4A -4E shows a schematic diagram of a PEM according to some embodiments of the present disclosure.

[0107] Figure 5A Examples 3 and Figure 4A Cross-sectional SEM of the PEM.

[0108] Figure 5B Examples 3 and Figure 4A Cross-sectional backscattered image of the PEM in .

[0109] 6A-6B show schematic diagrams of a PEM as a comparative example of the present disclosure.

[0110] FIG6C shows a cross-sectional SEM of the PEM in FIG6B (Comparative Example 2).

[0111] FIG6D shows a cross-sectional backscattered image of the PEM in FIG6B (Comparative Example 2).

[0112] Figure 7 A schematic diagram of a method of producing a PEM according to the present disclosure is shown.

[0113] Figure 8 A schematic diagram of a PEM electrode assembly according to the present disclosure is shown.

[0114] Figure 9A Shown is a graph of hydrogen crossover versus current density for PEMs according to the present disclosure and comparative examples when used in an electrolytic cell.

[0115] Figure 9B A bar graph showing hydrogen crossover versus current density for PEMs according to the present disclosure and comparative examples when used in an electrolytic cell.

[0116] Figure 9C The oxygen cross-histogram of the PEM of Example 3 and Comparative Example 2 is shown. 2 Measured at a current density of .

[0117] It should be noted that the drawings referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the present disclosure, and in this regard, these drawings should not be considered limiting. DETAILED DESCRIPTION

[0118] The present disclosure provides a multilayer proton exchange membrane (referred to herein as "PEM") for water electrolysis, comprising: at least two recombinant catalyst layers and at least two reinforcement layers, each of the at least two recombinant catalyst layers comprising a recombinant catalyst and a first ion exchange material, wherein the at least two recombinant catalyst layers are separated by a region containing no or substantially no recombinant catalyst; each of the at least two reinforcement layers comprising a microporous polymer structure and a second ion exchange material, the second ion exchange material being at least partially absorbed within the microporous polymer structure.

[0119] The inventors of the present application have unexpectedly discovered that a PEM comprising at least two recombination catalyst layers effectively reduces the hydrogen concentration in an oxygen stream to an acceptably low concentration while simultaneously limiting unfavorable chemical processes by optimizing the recombination catalyst concentration and layer placement, particularly for low-proton and low-hydrogen-blocking, multi-layer reinforced PEMs used in electrolytic cells. Furthermore, the PEM comprising at least two recombination catalyst layers also effectively reduces the oxygen concentration in a hydrogen stream to an acceptably low concentration by optimizing the recombination catalyst concentration and layer placement.

[0120] Specifically, where a high concentration of recombinant catalyst is required, the presence of at least two recombinant catalyst layers in a low proton and low hydrogen barrier multi-layer reinforced PEM can alleviate processing limitations compared to one recombinant catalyst layer.

[0121] Having at least two recombination catalyst layers can allow the PEM to accommodate a higher total amount of recombination catalyst than would be possible with a single recombination catalyst layer, as it is not always practical to increase the recombination catalyst concentration in a single layer sufficiently to reduce the hydrogen concentration in the oxygen stream to an acceptably low concentration and / or to reduce the oxygen concentration in the hydrogen stream to an acceptably low concentration.

[0122] In addition, at least two recombination catalyst layers are separated by regions that contain no or substantially no recombination catalyst, allowing the recombination catalyst in the PEM to be located in different locations or layers in the PEM, rather than in a single location or layer in the PEM. Typically, in membranes of the prior art, the recombination catalyst is located on one surface of the PEM, which is typically located next to the anode in the electrolytic cell. However, having a large amount of recombination catalyst on the anode side of the PEM can lead to adverse processes that can chemically attack the PEM and electrodes, thereby reducing the life of the electrolytic cell, especially at higher operating temperatures. Therefore, by locating the recombination catalyst in different locations or layers in the PEM, rather than in a single location or layer in the PEM, some of the recombination catalyst can be positioned further away from the anode of the electrolytic cell, thereby limiting adverse processes that can occur near the anode side of the PEM without significantly affecting the amount of hydrogen crossover. This improves the life of the PEM and the electrolytic cell.

[0123] The PEM comprising at least two reinforcement layers provides mechanical strength to the PEM, thereby allowing the thickness of the PEM to be reduced, thereby increasing electrolysis efficiency. The at least two reinforcement layers also allow the use of more aggressive operating conditions, such as higher temperatures and pressures, thereby increasing electrolysis efficiency and saving costs.

[0124] Furthermore, the PEM comprising at least two reinforcement layers helps to avoid damage and punctures in the PEM that may result from the use of aggressive operating conditions or electrolytic cell configurations (particularly when the membrane is relatively thin). This helps to further extend the life of the PEM and reduces hydrogen and oxygen crossover, which can occur to a greater extent if the PEM is damaged or punctured. In particular, for a given total amount of microporous polymer structure and PEM thickness at 50% RH, distributing the total content of the microporous polymer structure between two or more reinforcement layers increases the resistance to puncture of the PEM by electrolytic cell components during electrolytic cell manufacture, compared to a PEM having the same reinforcement material content in a single reinforcement layer.

[0125] As mentioned above, depending on the design and assembly of stack, electrode and PEM, and operating pressure and temperature, the optimal position of the recombination catalyst for maximizing effective recombination may not be near the anode surface. The optimal position in the PEM may also change over time, such as due to the effect of hydrogen supersaturation as the pool assembly deteriorates. Therefore, by making the recombination catalyst be located at different positions in the PEM, rather than being located at a single position in the PEM, the recombination catalyst may be located in the wider region in the PEM thickness. This makes it possible to achieve higher recombination efficiency under a wider stack design and assembly technology and different operating pressures and temperatures. Importantly, when the system deteriorates over time, the recombination catalyst is more widely distributed in the entire PEM thickness so that effective recombination can be maintained over time when the system deteriorates (such as if the degree of supersaturation changes). Some recombination catalysts can be located further away from the anode of the electrolyzer, thereby limiting the adverse processes that can occur near the anode side in the PEM. Thereby, this can improve the life of PEM and electrolyzer.

[0126] Thus, the PEM of the present disclosure allows for reduced production costs for water electrolysis. That is, the PEM of the present disclosure can withstand aggressive operating conditions (such as relatively high temperatures and pressures), can be relatively thin, and can limit the adverse chemical processes promoted by the anode side of the membrane, while simultaneously mitigating increased hydrogen flux so that the hydrogen concentration in the oxygen stream is acceptably low, and mitigating increased oxygen flux so that the oxygen concentration in the hydrogen stream is acceptably low.

[0127] [Recombination catalyst layer]

[0128] The PEM of the present invention comprises at least two recombinant catalyst layers, each of which comprises a recombinant catalyst and a first ion exchange material.

[0129] The recombination catalyst is a catalyst that can catalyze the reaction between molecular hydrogen (H2) and molecular oxygen (O2) to produce (H2O), and / or react O2 in the presence of H2 and a catalyst to form H2O. Therefore, the recombination catalyst is a catalyst that can recombine hydrogen that crosses from the cathode of the electrolytic cell PEM electrode assembly with oxygen in a controlled manner to form water, thereby reducing the amount of hydrogen entering the oxygen stream. In addition, the recombination catalyst is a catalyst that can recombine oxygen that crosses from the anode of the electrolytic cell PEM electrode assembly with hydrogen in a controlled manner to form water, thereby reducing the amount of oxygen entering the hydrogen stream. This can improve the purity of the hydrogen stream and eliminate or reduce the need for additional hydrogen processing steps. Therefore, the recombination catalyst layer reduces the amount of hydrogen that crosses into the oxygen stream and the amount of oxygen that crosses into the hydrogen stream.

[0130] In another embodiment, the recombination catalyst is a catalyst that can controllably recombine any permeated oxygen (O2) that crosses the anode of the electrolyzer membrane assembly with hydrogen to form water, thereby reducing the amount of oxygen entering the hydrogen stream and achieving a higher purity H2 product gas stream. The higher purity H2 product gas stream can reduce the need for additional processing steps downstream.

[0131] Thus, the recombination catalyst layer reduces the amount of hydrogen that crosses into the oxygen stream. In other embodiments, the recombination catalyst layer can reduce the amount of hydrogen that crosses into the oxygen stream and reduce the amount of oxygen that crosses into the hydrogen stream.

[0132] The compositions of the at least two recombinant catalyst layers may be the same or different. The at least two recombinant catalyst layers may comprise one or more recombinant catalysts. Each recombinant catalyst layer may comprise a different recombinant catalyst, or may each comprise the same recombinant catalyst.

[0133] The recombinant catalyst may comprise a single recombinant catalyst species or a mixture of recombinant catalyst species. The recombinant catalyst is not particularly limited and any species known in the art may be used. The recombinant catalyst comprises one or more catalytic species selected from the following catalytic species: platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), osmium (Os), nickel (Ni), cobalt (Co), titanium (Ti), tin (Sn), tantalum (Ta), niobium (Nb), antimony (Sb), lead (Pb), manganese (Mn), their oxides, and mixtures thereof. The recombinant catalyst may comprise at least one platinum group metal selected from platinum, palladium, iridium, rhodium, ruthenium, and osmium; alloys of platinum group metals; mixed oxides of platinum group metals and other metals (such as cerium and titanium); and mixtures thereof. Preferably, the recombinant catalyst comprises platinum or palladium.

[0134] The recombinant catalyst of the present invention may have a catalyst particle size of about 0.1 nm to about 20 nm, about 0.1 nm to about 15.0 nm, or about 1.0 nm to about 20.0 nm, or about 1.0 nm to about 10.0 nm, or about 2.0 nm to about 5.0 nm.

[0135] The recombinant catalyst may be present on a support material. The support material is not particularly limited and any material known in the art may be used. The support material may include silica, zeolites, carbon, and oxides and carbides of Group IVB, Group VB, Group VIB, Group VIIB, and Group VIII transition metals, and combinations thereof. Carbon (such as particulate carbon or carbon black) is a preferred support material. Other forms of carbon, such as graphene and graphite, may also be used as the support material.

[0136] Preferably, the support material has a high surface area and should have a small average particle size, for example up to and including 150 nm, up to and including about 75 nm, or up to and including about 50 nm, or up to and including about 25 nm, or up to and including about 5 nm. The average particle size can be in the range of about 5 nm to about 150 nm, or in the range of about 10 nm to 75 nm, or in the range of about 10 nm to about 50 nm, or in the range of about 5 nm to about 25 nm, or any intermediate value or range of values. The use of a high surface area support material is particularly advantageous because it allows the recombinant catalyst to be well dispersed, resulting in higher catalytic activity per unit weight compared to an unsupported, lower surface area catalyst of the same composition.

[0137] The support material particles can be agglomerated together in larger groups of two, three, or more particles. The agglomerated groups can be divided into clusters of several particles.

[0138] In a preferred embodiment, the recombination catalyst may be platinum supported on carbon particles.

[0139] For given recombinant catalyst (with or without supporting material) particle size, or given agglomerated particle size, the microporous polymer structure of reinforcing layer can be selected to (for example, be selected to by filtering) and prevent recombinant catalyst particles or aggregate from being impregnated in the hole of described microporous polymer structure.For example, the bubble point of described microporous polymer structure can be used for showing the characteristic of the microporous polymer structure that can influence this filtration process.For example, described recombinant catalyst particle size or aggregate particle size can be greater than the maximum or average pore size of the microporous polymer structure in at least one of described at least two reinforcing layers.Because recombinant catalyst (with or without described supporting material) can't be impregnated in the hole of described microporous polymer structure, therefore can form the zone that does not contain or does not contain substantially recombinant catalyst. In one embodiment, the agglomerated particle size of the recombinant catalyst may be between 1 μm and 20 μm, or between 0.5 μm and 5 μm, while the bubble point of the microporous polymer structure may be at least 100 kPa, such as between about 100 kPa and about 3000 kPa, or between about 100 kPa and about 1000 kPa, or between about 100 kPa and about 800 kPa, or between about 100 kPa and about 700 kPa, or between about 200 kPa and about 2000 kPa, or between about 200 kPa and about 1000 kPa. kPa, or between about 200 kPa and about 800 kPa, or between about 200 kPa and about 700 kPa, or between about 300 kPa and about 1000 kPa, or between about 300 kPa and about 800 kPa, or between about 300 kPa and about 700 kPa, or between about 400 kPa and about 800 kPa, or between about 400 kPa and about 700 kPa (wherein the bubble point of the microporous polymer structure is measured according to the Bubble Point Method described in the Test Methods section). The average pore size of the microporous polymer structure may be smaller than the recombinant catalyst (with or without support material) particle size, or the agglomerated particle size.

[0140] The recombinant catalyst may be present in each of the at least two recombinant catalyst layers in an amount effective for a particular requirement. The recombinant catalyst may be present in each of the at least two recombinant catalyst layers in an amount of up to about 0.10 mg / cm 2 , or the loading can be about 0.001 mg / cm 2 to about 0.10 mg / cm 2 range; or the loading can be 0.001 mg / cm 2 to about 0.09 mg / cm 2 range, or the loading may be about 0.005 mg / cm 2 to about 0.09 mg / cm 2 range, or the loading may be about 0.001 mg / cm2 to about 0.08 mg / cm 2 range, or the loading may be about 0.0025 mg / cm 2 to about 0.08 mg / cm 2 range, or the loading may be about 0.005 mg / cm 2 to about 0.07 mg / cm 2 range, or the loading may be about 0.0075 mg / cm 2 to about 0.06 mg / cm 2 range, or the loading may be about 0.007 mg / cm 2 to about 0.05 mg / cm 2 range, or the loading may be about 0.008 mg / cm 2 to about 0.04 mg / cm 2 range, or the loading may be about 0.009 mg / cm 2 to about 0.03 mg / cm 2 range, or the loading may be about 0.0095 mg / cm 2 to about 0.02 mg / cm 2 The loading can be calculated based on the concentration of the recombinant catalyst and the coating thickness of the recombinant catalyst layer.

[0141] Water electrolysis cells can experience an undesirable side reaction between hydrogen and oxygen, forming hydrogen peroxide (H2O2). Hydrogen peroxide can decompose into peroxide radicals, which can attack the PEM and electrolysis cell components. To help alleviate this problem, at least one recombinant catalyst layer, or any other layer in the PEM, can include one or more additives for decomposing hydrogen peroxide and / or eliminating peroxide radicals. The additives can be selected from: peroxide decomposition catalysts, free radical scavengers, free radical decomposition catalysts, antioxidants, such as self-regenerating antioxidants, hydrogen donor primary antioxidants, or free radical scavenger secondary antioxidants, oxygen absorbers, and the like.

[0142] The first ion exchange material is a material capable of performing cation exchange, such as proton exchange. The first ion exchange material is not particularly limited, and any species known in the art can be used. A mixture of ion exchange materials can be used as the first ion exchange material. The first ion exchange materials in each recombinant catalyst layer can be the same or different. The term "first ion exchange material" is used to distinguish the ion exchange material of the recombinant catalyst layer of the PEM from the ion exchange materials of the other layers. In some instances, the ion exchange material in the other layers can be the same as the first ion exchange material. In some instances, the first ion exchange material and the ion exchange materials in the other layers can be absorbed by the same imbibing suspension.

[0143] The first ion exchange material may comprise at least one ion cross-linked polymer. The at least one ion cross-linked polymer may comprise a proton conducting polymer. The proton conducting polymer may be selected from: hydrocarbon ion cross-linked polymers, perfluoro ion cross-linked polymers, and perfluorosulfonic acid ion cross-linked polymers. Suitable proton conducting polymers include: perfluorosulfonic acid polymers, perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrenic ion exchange polymers, fluorostyrenic ion exchange polymers, polyaryletherketone ion exchange polymers, polysulfone ion exchange polymers, bis(fluoroalkylsulfonyl)imide, (fluoroalkylsulfonyl)(fluorosulfonyl)imide, polyvinyl alcohol, polyethylene oxide, divinylbenzene, metal salts with or without polymers, and mixtures thereof. Preferably, the first ion exchange material comprises a perfluorosulfonic acid (PFSA) polymer, which is obtained by copolymerization of tetrafluoroethylene and perfluorosulfonyl vinyl ester converted into proton form. Examples of commercially available ion exchange materials include: Nafion TM (DuPont de Nemours, Inc., Wilmington, Delaware, USA), Flemion TM (Asahi Glass Co. Ltd., Tokyo, Japan), Aciplex TM (Asahi Glass, Tokyo, Japan), and Aquivion TM (SolvaySolexis SPA, Italy), which is a perfluorosulfonic acid copolymer.

[0144] The total equivalent weight (EW) of the first ion exchange material may be from about 370 g / mole equivalent to about 2000 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 470 g / mole equivalent to about 1275 g / mole equivalent SO3 -The total equivalent weight (EW) of the ion exchange material may be from about 500 g / mole equivalent to about 1000 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 500 g / mole equivalent to about 900 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 650 g / mole equivalent to about 800 g / mole equivalent SO3 - The equivalent weight of the ion exchange material may be about 725 g / mol equivalent SO3 - The equivalent weight of the ion exchange material may be about 800 g / mol equivalent SO3 - .

[0145] As used herein, the "equivalent weight" of an ionomer or ion exchange material refers to the weight of the polymer (based on molecular weight) per sulfonic acid group in the ionomer. Thus, a lower equivalent weight indicates a higher acid content. The equivalent weight (EW) of an ionomer refers to the EW of the ionomer in its protonated form at 0% RH with negligible impurities. The term "ion exchange capacity" refers to the reciprocal of the equivalent weight (1 / EW).

[0146] The total average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 1200 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 720 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 350 cc / mole equivalent to about 475 cc / mole equivalent. The total average equivalent volume of the ion exchange material may include the total volume of the ion exchange material distributed between all ion exchange material layers of the composite membrane. The ion exchange material may have a density of not less than about 1.9 g / cc at 0% relative humidity.

[0147] As used herein, the "equivalent volume" of an ionomer or ion exchange material refers to the volume of the ionomer per sulfonic acid group. The equivalent volume (EV) of an ionomer refers to the EV of the ionomer at 0% RH, pure and in its protonated form, with negligible impurities.

[0148] The first ion exchange material may include an additive for decomposing hydrogen peroxide and / or eliminating peroxide radicals. Water electrolysis cells may undergo undesirable side reactions between hydrogen and oxygen to form hydrogen peroxide (H2O2), which may decompose into peroxide radicals that can damage membranes and electrolysis cell components. The additive may be a peroxide decomposition catalyst, a free radical scavenger, a free radical decomposition catalyst, a self-regenerating antioxidant, a hydrogen donor primary antioxidant, a free radical scavenger secondary antioxidant, an oxygen absorber, or the like. The additive may include Ce, Mn, or an oxide thereof. For example, the additive may be cerium oxide (ceria).

[0149] The recombination catalyst of each of the at least two recombination catalyst layers may be dispersed in the first ion exchange material. The recombination catalyst may be uniformly dispersed in the first ion exchange material.

[0150] Each of the at least two recombination catalyst layers may have a thickness at 50% relative humidity (RH) of at least about 1 μm, or about 1 μm to about 35 μm, or about 5 μm to about 35 μm, or about 2 μm to about 35 μm, or about 1 μm to about 20 μm, or about 2 μm to about 20 μm, or about 2 μm to about 19 μm, or about 2 μm to about 18 μm, or about 2 μm to about 17 μm, or about 2 μm to about 16 μm, or about 2 μm to about 15 μm, or about 2 μm to about 14 μm, or about 2 μm to about 13 μm, or about 2 μm to about 12 μm, or about 2 μm to about 11 μm, or about 2 μm to about 10 μm, or about 3 μm to about 10 μm, or about 3 μm to about 9 μm, or about 3 μm to about 8 μm, or about 3 μm to about 7 μm, or a thickness in the range of about 4 μm to about 7 μm. The thickness of the recombination catalyst layer can be measured by SEM (scanning electron microscope image) of the PEM.

[0151] The PEM may comprise a total of two recombinant catalyst layers, or a total of three recombinant catalyst layers, or a total of four recombinant catalyst layers, or a total of five recombinant catalyst layers.

[0152] At least two recombinant catalyst layers are separated by a region that is free of or substantially free of recombinant catalyst. In the context of the present disclosure, a region (or layer) that is "substantially free of" a recombinant catalyst (or any other claimed material) may mean that the region is completely free of recombinant catalyst, such that the region does not contain any detectable amount of recombinant catalyst. It may also mean that the region is largely free of recombinant catalyst, but may contain a small amount or trace amount of recombinant catalyst, such as a small amount or trace amount of recombinant catalyst at the interface between the region and the recombinant catalyst layer. The small amount or trace amount of recombinant catalyst may be the result of the manufacturing method used to manufacture the PEM, or may be the result of a small amount or trace amount of recombinant catalyst that migrates from the recombinant catalyst layer to the adjacent separated region. When a region is substantially free of recombinant catalyst, the region is not intentionally made to contain recombinant catalyst, but may be the result of the method for manufacturing the PEM. For example, when preparing a PEM comprising a recombinant catalyst layer and a reinforcement layer (in this order), the situation may be that at the interface between the recombinant catalyst layer and the reinforcement layer, a small amount or trace amount of recombinant catalyst from the recombinant catalyst layer enters or seeps into the microporous polymer structure of the reinforcement layer. However, the reinforcement layer still substantially does not contain a recombinant catalyst.

[0153] The region separating the at least two recombination catalyst layers that is free or substantially free of recombination catalyst may have a thickness d at 50% RH of at least about 1 μm, or at least about 2 μm, or at least about 3 μm, or at least about 4 μm, or at least about 5 μm, or at least 10 μm, or at least 20 μm, or at least 30 μm, or at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm, or at least 80 μm.

[0154] The at least two recombinant catalyst layers may be separated by a region having a thickness d, wherein the thickness d is from about 1 μm to about 80 μm at 50% RH. The thickness d of the region at 50% RH may be from about 1 μm to about 70 μm, or from about 1 μm to about 60 μm, or from about 1 μm to about 50 μm, or from about 1 μm to about 40 μm, or from about 1 μm to about 30 μm, or from about 1 μm to about 20 μm, or from about 1 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 2 μm to about 80 μm, or from about 2 μm to about 60 μm, or from about 2 μm to about 50 μm, or from about 2 μm to about 40 μm, or from about 2 μm to about 30 μm, or from about 2 μm to about 20 μm, or from about 2 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 5 μm to about 80 μm, or from about 5 μm to about 60 μm, or from about 5 μm to about 50 μm, or from about 5 μm to about 40 μm, or from about 5 μm to about 30 μm, or from about 5 μm to about 20 μm, or from about 5 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 10 μm to about 80 μm, or from about 10 μm to about 60 μm, or from about 10 μm to about 50 μm, or from about 10 μm to about 40 μm, or from about 10 μm to about 30 μm, or from about 10 μm to about 20 μm.

[0155] The region separating at least two recombination catalyst layers may contain at least one layer that is free of or substantially free of recombination catalyst. The region may contain more than one layer, such as two layers, three layers, four layers, five layers, or more than five layers.

[0156] The region or at least one layer that is free of or substantially free of recombinant catalyst separating the at least two recombinant catalyst layers is not particularly limited and can be a reinforcement region or layer, or an ion exchange material region or layer, or a combination of the two. The reinforcement layer and ion exchange material layer of the present invention are described below. The at least one layer that separates the at least two recombinant catalyst layers can comprise one layer, or two layers, or three layers, or four layers, or five layers, or more than five layers. Having a region or layer that is free of or substantially free of recombinant catalyst separating the at least two recombinant catalyst layers (e.g., the region or layer that is free of or substantially free of recombinant catalyst is sandwiched between the two recombinant catalyst layers) ensures that not all recombinant catalyst is in one layer, thereby helping to limit adverse reactions occurring near the anode side of the PEM.

[0157] [Enhancement Layer]

[0158] The PEM of the present invention comprises at least two reinforcement layers, each of which comprises a microporous polymer structure and a second ion exchange material at least partially absorbed within the microporous polymer structure. The reinforcement layers provide mechanical support for the PEM and conduct cations because they contain the ion exchange material. The appropriate microporous polymer structure depends largely on the application in which the PEM is used. The microporous polymer structure should be chemically and thermally stable in the environment in which the PEM of the present invention is used and should be tolerant to any additives used in the PEM.

[0159] The PEM of the present invention may comprise two reinforcement layers, or three reinforcement layers, or four reinforcement layers, or five reinforcement layers. In some embodiments, if two or more reinforcement layers are present, the reinforcement layers may be in direct contact with each other, i.e., adjacent layers. Alternatively, the reinforcement layers may not be in direct contact with each other, i.e., they may be non-adjacent layers separated by a layer that is not a reinforcement layer.

[0160] As used herein, the term "reinforcement layer comprising a microporous polymer structure" is intended to refer to a layer that uses a microporous polymer structure having an initial thickness before coating of at least about 3 μm, optionally about 4 μm to about 230 μm, or about 5 μm to about 80 μm, or about 5 μm to about 50 μm, or about 5 μm to about 35 μm. The initial average micropore size of the microporous polymer structure before coating may be about 0.01 μm to about 5 μm, for example, 0.01 μm to 1 μm, or 0.05 μm to 0.5 μm. According to various optional embodiments, the average pore size of the pores of the microporous polymer structure may be 0.01 μm to 5.0 μm, for example, 0.01 to 1 μm, or 0.05 to 0.5 μm.

[0161] The thickness of each reinforcement layer at 50% RH (relative humidity) can be at least about 1 μm, or about 1 μm to about 20 μm, or about 2 μm to about 15 μm, or about 3 μm to about 15 μm, or about 3 μm to about 13 μm, or about 3 μm to about 12 μm, or about 3 μm to about 11 μm, or about 3 μm to about 10 μm, or about 3 μm to about 9 μm, or about 4 μm to about 9 μm, or about 4 μm to about 8 μm. The thickness of the reinforcement layer can be measured by SEM (scanning electron microscope image) of the PEM.

[0162] Each of the at least two reinforcement layers comprises a microporous polymer structure that provides support for the PEM.

[0163] As used herein, the term "microporous polymer structure" refers to a polymer matrix that supports the ion exchange material, adding structural integrity and durability to the resulting composite membrane. In some exemplary embodiments, the microporous polymer structure may comprise expanded polytetrafluoroethylene (ePTFE). In some instances, the ePTFE may have a knot and fibril structure. In other exemplary embodiments, the microporous polymer structure may comprise a track-etched polycarbonate membrane having a smooth, flat surface, a high apparent density, and a well-defined pore size.

[0164] The compositions of the at least two reinforcement layers may be the same or different. The PEM of the present invention may comprise one or more microporous polymer structures. Each reinforcement layer may comprise a different microporous polymer structure, or may each comprise the same microporous polymer structure.

[0165] The microporous polymer structure of the present invention may comprise at least one fluoropolymer. In one embodiment, the fluoropolymer may be selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), and mixtures thereof. Preferably, the fluoropolymer may be expanded polytetrafluoroethylene (ePTFE).

[0166] In another embodiment, the microporous polymer structure may comprise a hydrocarbon polymer. The hydrocarbon polymer may be selected from the group consisting of polyethylene, polypropylene, polycarbonate, polystyrene, polysulfone, polyethersulfone, polyethylene naphthalate, and mixtures thereof.

[0167] The microporous polymer structures of the present invention may have a bubble point of at least 100 kPa. The bubble point of the microporous polymer structure may be between about 100 kPa and about 3000 kPa, or between about 100 kPa and about 1000 kPa, or between about 100 kPa and about 800 kPa, or between about 100 kPa and about 700 kPa, or between about 200 kPa and about 2000 kPa, or between about 200 kPa and about 1000 kPa, or between about 200 kPa and about 800 kPa, or between about 200 kPa and about 700 kPa, or between about 300 kPa and about 1000 kPa, or between about 300 kPa and about 800 kPa, or between about 300 kPa and about 700 kPa, or between about 400 kPa and about 800 kPa, or between about 400 kPa and about 700 kPa (wherein the bubble point of the microporous polymer structure is measured according to the Bubble Point Method described in the Test Methods section).

[0168] In the context of this disclosure, the total content of microporous polymer structure in the PEM can be expressed as the total volume of microporous polymer structure in the PEM / total volume of the PEM. If the layer is non-microporous, the unit (cc / m 2 ) can also be considered as the equivalent thickness of the reinforcement polymer structure (μm). The volume fraction of the microporous polymer structure in the PEM based on the total volume of the PEM can then be estimated simply by dividing the equivalent thickness of the reinforcement polymer structure by the total thickness of the PEM.

[0169] The total mass of the microporous polymer structure in the PEM is considered to be the sum of the mass of the microporous polymer structure in each reinforcement layer. The total mass / microporous polymer structure area in the PEM can be at least about 2 g / m 2 , or at least about 3g / m 2 , or at least about 4 g / m 2 , or at least about 5g / m 2 , or about 2g / m 2 to about 50g / m 2 , or about 3g / m 2 to about 40g / m 2 , or about 4g / m 2 About 30g / m 2 , based on the total area of ​​the PEM.

[0170] In embodiments where the microporous polymer structure comprises ePTFE, the total mass of the microporous polymer structure within the PEM (expressed as mass / area) may be about 8 g / m 2 About 80g / m 2 , or about 8g / m 2 to about 70g / m 2 , or about 8g / m 2 About 60g / m 2 , or about 8g / m 2 About 60g / m 2 , or about 8g / m 2 to about 50g / m 2 , or about 8g / m 2 to about 40g / m 2 , or about 8g / m 2 About 35g / m 2 , or about 8g / m 2 About 30g / m 2 , or about 8g / m 2 to about 20g / m 2 , or about 8g / m 2 About 15g / m 2 , based on the total area of ​​the composite membrane. The total mass / microporous polymer structure area can be about 8 g / m 2About 30g / m 2 , based on the total area of ​​the composite membrane. The total mass / microporous polymer structure area can be about 10 g / m 2 About 15g / m 2 , based on the total area of ​​the composite membrane. The total content of microporous polymer structure in the PEM (expressed as mass / area) can be about 20 g / m 2 About 80g / m 2 , or about 30g / m 2 to about 70g / m 2 , or about 20g / m 2 to about 50g / m 2 , or about 30g / m 2 About 60g / m 2 , based on the total area of ​​the composite film.

[0171] The total volume fraction of the microporous polymer structure in the PEM may be less than 50%. The total volume fraction of the microporous polymer structure in the PEM of the present invention may be between about 0.4% and about 50%, or between about 0.4% and about 40%, or between about 0.4% and about 30%. The total volume fraction of the microporous polymer structure in the PEM of the present invention may be between about 1% and about 50%, or between about 1% and about 40%, or between about 1% and about 30%. The total volume fraction of the microporous polymer structure in the PEM of the present invention may be between about 5% and about 50%, or between about 5% and about 40%, or between about 5% and about 30%.

[0172] The microporous polymer structure mass / area of ​​each of the at least two reinforcement layers may be at least about 1 g / m 2 , or at least about 1.5 g / m 2 , or at least about 2 g / m 2 , or about 1g / m 2 to about 25g / m 2 , or about 1.5g / m 2 to about 20g / m 2 , or about 2g / m 2 About 15g / m 2 , or about 2.5g / m 2 to about 10g / m 2, based on the total area of ​​the PEM. The second ion exchange material is a material capable of performing cation exchange, such as proton exchange. The second ion exchange material is not particularly limited, and any type known in the art can be used. A mixture of ion exchange materials can be used as the second ion exchange material. The second ion exchange material can be the same as the first ion exchange material, or different from the first ion exchange material. In one embodiment, the first ion exchange material and the second ion exchange material are the same. The second ion exchange materials of each reinforcement layer can be the same or different. The term "second ion exchange material" is used to distinguish the ion exchange material of the reinforcement layer of the PEM from the ion exchange materials of other layers. The first and second ion exchange materials can be absorbed by the same absorbent dispersion.

[0173] The second ion exchange material may comprise at least one ion cross-linked polymer. The at least one ion cross-linked polymer may comprise a proton conducting polymer. The proton conducting polymer may be selected from: hydrocarbon ion cross-linked polymers, perfluoro ion cross-linked polymers, and perfluorosulfonic acid ion cross-linked polymers. Suitable proton conducting polymers include: perfluorosulfonic acid polymers, perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrenic ion exchange polymers, fluorostyrenic ion exchange polymers, polyaryletherketone ion exchange polymers, polysulfone ion exchange polymers, bis(fluoroalkylsulfonyl)imide, (fluoroalkylsulfonyl)(fluorosulfonyl)imide, polyvinyl alcohol, polyethylene oxide, divinylbenzene, metal salts with or without polymers, and mixtures thereof. Preferably, the second ion exchange material comprises a perfluorosulfonic acid (PFSA) polymer, which is obtained by copolymerization of tetrafluoroethylene and perfluorosulfonyl vinyl ester converted into proton form. Examples of commercially available ion exchange materials include: Nafion TM (DuPont de Nemours, Inc., Wilmington, Delaware, USA), Flemion TM (Asahi Glass Co. Ltd., Tokyo, Japan), Aciplex TM (Asahi Glass, Tokyo, Japan), and Aquivion TM (SolvaySolexis SPA, Italy), which is a perfluorosulfonic acid copolymer.

[0174] The total equivalent weight (EW) of the second ion exchange material may be from about 370 g / mole equivalent to about 2000 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 470 g / mole equivalent to about 1275 g / mole equivalent SO3 -The total equivalent weight (EW) of the ion exchange material may be from about 500 g / mole equivalent to about 1000 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 500 g / mole equivalent to about 900 g / mole equivalent SO3 - The total equivalent weight (EW) of the ion exchange material may be from about 650 g / mole equivalent to about 800 g / mole equivalent SO3 - The equivalent weight of the ion exchange material may be about 725 g / mol equivalent SO3 - The equivalent weight of the ion exchange material may be about 800 g / mol equivalent SO3 - .

[0175] As used herein, the "equivalent weight" of an ionomer or ion exchange material refers to the weight of the polymer (based on molecular weight) per sulfonic acid group in the ionomer. Thus, a lower equivalent weight indicates a higher acid content. The equivalent weight (EW) of an ionomer refers to the EW of the ionomer in its protonated form at 0% RH with negligible impurities. The term "ion exchange capacity" refers to the reciprocal of the equivalent weight (1 / EW).

[0176] The total average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 1200 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 720 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 350 cc / mole equivalent to about 475 cc / mole equivalent. The total average equivalent volume of the ion exchange material may include the total volume of the ion exchange material distributed between all ion exchange material layers of the composite membrane. The ion exchange material may have a density of not less than about 1.9 g / cc at 0% relative humidity.

[0177] As used herein, the "equivalent volume" of an ionomer or ion exchange material refers to the volume of the ionomer per sulfonic acid group. The equivalent volume (EV) of an ionomer refers to the EV of the ionomer at 0% RH, pure and in its protonated form, with negligible impurities.

[0178] The second ion exchange material may include an additive for decomposing hydrogen peroxide and / or eliminating peroxide radicals. Water electrolysis cells may undergo undesirable side reactions between hydrogen and oxygen to form hydrogen peroxide (H2O2), which may decompose into peroxide radicals that can attack membranes and electrolysis cell components. The additive may be a peroxide decomposition catalyst, a free radical scavenger, a free radical decomposition catalyst, a self-regenerating antioxidant, a hydrogen donor primary antioxidant, a free radical scavenger secondary antioxidant, an oxygen absorber, or the like. The additive may include Ce, Mn, or an oxide thereof. For example, the additive may be cerium oxide (ceria).

[0179] The second ion exchange material is at least partially absorbed (or impregnated) within the microporous polymer structure. The second ion exchange material at least partially absorbed within the microporous polymer structure can render the microporous polymer structure occlusive (i.e., the microporous polymer structure is characterized by a low void volume or is substantially impermeable to gases). The microporous polymer structure can be completely absorbed by the second ion exchange material.

[0180] Each of the at least two reinforcement layers may be free or substantially free of a recombination catalyst. "Substantially free" has a meaning similar to that described above with respect to the regions separating the recombination catalyst.

[0181] The at least two recombination catalyst layers may be separated by at least one reinforcement layer, or at least two reinforcement layers, or at least three reinforcement layers.

[0182] [Ion exchange membrane layer]

[0183] The PEM of the present invention may further comprise an ion exchange material layer comprising a third ion exchange material, wherein the ion exchange material layer contains no or substantially no microporous polymer structure and a recombination catalyst. The meaning of "substantially no" is similar to that described above with respect to the region separating the recombination catalyst.

[0184] The PEM of the present invention may comprise one ion exchange material layer, or two ion exchange material layers, or three ion exchange material layers, or four ion exchange material layers, or five ion exchange material layers. If two or more ion exchange material layers are present, the ion exchange material layers may be in direct contact with each other, i.e., be adjacent layers. Alternatively, the ion exchange material layers may not be in direct contact with each other, i.e., be non-adjacent layers separated by a layer that is not an ion exchange material layer.

[0185] The third ion exchange material is a material capable of performing cation exchange, such as proton exchange. The third ion exchange material is not particularly limited, and any material known in the art may be used. A mixture of ion exchange materials may be used as the third ion exchange material. The third ion exchange material may be the same as the first ion exchange material and / or the second ion exchange material, or may be different from the first ion exchange material and / or the second ion exchange material. Preferably, the first ion exchange material, the second ion exchange material, and the third ion exchange material are the same. The third ion exchange material of each ion exchange material layer may be the same or different. The term "third ion exchange material" is used to distinguish the ion exchange material of the ion exchange material layer in the PEM of the present invention from the ion exchange materials of other layers. The third ion exchange material may be the same as the first and / or second ion exchange material. In instances where the first, second, and third ion exchange materials are the same, the ion exchange material may be formed into the ion exchange layer from the same ion exchange material dispersion as that used to form the recombination catalyst and reinforcement layer.

[0186] The third ion exchange material may comprise at least one ion cross-linked polymer. The at least one ion cross-linked polymer may comprise a proton conducting polymer. The proton conducting polymer may be selected from: hydrocarbon ion cross-linked polymers, perfluoro ion cross-linked polymers, and perfluorosulfonic acid ion cross-linked polymers. Suitable proton conducting polymers include: perfluorosulfonic acid polymers, perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrenic ion exchange polymers, fluorostyrenic ion exchange polymers, polyaryletherketone ion exchange polymers, polysulfone ion exchange polymers, bis(fluoroalkylsulfonyl)imide, (fluoroalkylsulfonyl)(fluorosulfonyl)imide, polyvinyl alcohol, polyethylene oxide, divinylbenzene, metal salts with or without polymers, and mixtures thereof. Preferably, the second ion exchange material comprises a perfluorosulfonic acid (PFSA) polymer, which is obtained by copolymerization of tetrafluoroethylene and perfluorosulfonyl vinyl ester converted into proton form. Examples of commercially available ion exchange materials include: Nafion TM (DuPont de Nemours, Inc., Wilmington, Delaware, USA), Flemion TM (Asahi Glass Co. Ltd., Tokyo, Japan), Aciplex TM (Asahi Glass, Tokyo, Japan), and Aquivion TM (SolvaySolexis SPA, Italy), which is a perfluorosulfonic acid copolymer.

[0187] Each ion exchange material layer may have a thickness at 50% RH (relative humidity) of about 1 μm to about 20 μm, or about 2 μm to about 15 μm, or about 2 μm to about 14 μm, or about 2 μm to about 13 μm, or about 2 μm to about 12 μm, or about 3 μm to about 12 μm, or about 3 μm to about 11 μm, or about 3 μm to about 10 μm, or about 3 μm to about 9 μm. The thickness of the ion exchange material layer can be measured by SEM of a PEM.

[0188] The total equivalent weight (EW) of the third ion exchange material may be from about 370 g / mole equivalent to about 2000 g / mole equivalent SO3 - The total equivalent weight (EW) of the third ion exchange material may be from about 470 g / mole equivalent to about 1275 g / mole equivalent SO3 - The total equivalent weight (EW) of the third ion exchange material may be from about 500 g / mole equivalent to about 1000 g / mole equivalent SO3 - The total equivalent weight (EW) of the third ion exchange material may be from about 500 g / mole equivalent to about 900 g / mole equivalent SO3 - The total equivalent weight (EW) of the third ion exchange material may be from about 650 g / mole equivalent to about 800 g / mole equivalent SO3 - The equivalent weight of the third ion exchange material may be about 725 g / mol equivalent SO3 - The equivalent weight of the third ion exchange material may be about 800 g / mol equivalent SO3 - .

[0189] As used herein, the "equivalent weight" of an ionomer or ion exchange material refers to the weight of the polymer (based on molecular weight) per sulfonic acid group in the ionomer. Thus, a lower equivalent weight indicates a higher acid content. The equivalent weight (EW) of an ionomer refers to the EW of the ionomer in its protonated form at 0% RH with negligible impurities. The term "ion exchange capacity" refers to the reciprocal of the equivalent weight (1 / EW).

[0190] The total average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 1200 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 240 cc / mole equivalent to about 720 cc / mole equivalent. The average equivalent volume of the ion exchange material may be from about 350 cc / mole equivalent to about 475 cc / mole equivalent. The total average equivalent volume of the ion exchange material may include the total volume of the ion exchange material distributed between all ion exchange material layers of the composite membrane. The ion exchange material may have a density of not less than about 1.9 g / cc at 0% relative humidity.

[0191] As used herein, the "equivalent volume" of an ionomer or ion exchange material refers to the volume of the ionomer per sulfonic acid group. The equivalent volume (EV) of an ionomer refers to the EV of the ionomer at 0% RH, pure and in its protonated form, with negligible impurities.

[0192] The third ion exchange material may include an additive for decomposing hydrogen peroxide and / or eliminating peroxide radicals. Water electrolysis cells may experience undesirable side reactions between hydrogen and oxygen, forming hydrogen peroxide (H2O2), which may decompose into peroxide radicals that can damage membranes and electrolysis cell components. The additive may be a peroxide decomposition catalyst, a free radical scavenger, a free radical decomposition catalyst, a self-regenerating antioxidant, a hydrogen donor primary antioxidant, a free radical scavenger secondary antioxidant, an oxygen absorber, or the like. The additive may include Ce, Mn, or an oxide thereof. For example, the additive may be cerium oxide (ceria).

[0193] [Multilayer proton exchange membrane of the present invention]

[0194] The total thickness of the PEM of the present invention at 50% RH (relative humidity) may be from about 20 μm to about 250 μm, or from about 20 μm to about 200 μm, or from about 20 μm to about 150 μm, or from about 20 μm to about 120 μm, or from about 20 μm to about 100 μm, or from about 20 μm to about 90 μm, or from about 20 μm to about 80 μm, or from about 20 μm to about 70 μm, or from about 20 μm to about 60 μm, or from about 20 μm to 50 μm, or from about 20 μm to 45 μm.

[0195] The thickness of the PEM of the present invention was measured using a thickness gauge (obtained from Heidenhain Corporation, USA), as described below. The thickness of each layer in the PEM was measured by SEM of the PEM. Generally speaking, the thinner the membrane, the better the water electrolysis efficiency. However, since the use of thin films exacerbates hydrogen crossover, membranes with a thickness exceeding 100 μm and sometimes exceeding 200 μm are typically used, which negatively affects the water electrolysis efficiency. The PEM of the present disclosure allows the safe use of a thickness of less than 100 μm, and thus increases efficiency.

[0196] In the context of the present disclosure, a film or layer having a thickness of "x μm" refers to the common meaning of film (or layer) thickness in the art, that is, the length of the film (or layer) in the thickness direction is x μm. For the avoidance of doubt, each film (or layer) has a first direction and a second direction, the second direction is orthogonal to the first direction, and the first and second directions are each orthogonal to the thickness direction. The lengths of the first and second directions are greater than the length in the thickness direction. The film (or layer) has two opposing major surfaces, and the first and second directions are in the same plane as the major surfaces, and the thickness direction is perpendicular to the plane of the major surfaces.

[0197] The at least two recombinant catalyst layers are separated by a region that contains no or substantially no recombinant catalyst. The region separating the at least two recombinant catalyst layers may contain at least one layer that contains no or substantially no recombinant catalyst. The region may contain more than one layer, such as two layers, three layers, four layers, or five layers. The at least two recombinant catalyst layers may be separated by a region having a thickness d, wherein the thickness d is about 1 μm to about 20 μm, or about 2 μm to about 15 μm, or about 2 μm to about 12 μm, or about 3 μm to about 11 μm, or about 3 μm to about 10 μm, or about 3 μm to about 9 μm, or about 3 μm to about 8 μm at 50% relative humidity. The thickness d of the region at 50% RH may be about 1 μm to about 70 μm, or about 1 μm to about 60 μm, or about 1 μm to about 50 μm, or about 1 μm to about 40 μm, or about 1 μm to about 30 μm, or about 1 μm to about 20 μm, or about 1 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 2 μm to about 80 μm, or from about 2 μm to about 60 μm, or from about 2 μm to about 50 μm, or from about 2 μm to about 40 μm, or from about 2 μm to about 30 μm, or from about 2 μm to about 20 μm, or from about 2 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 5 μm to about 80 μm, or from about 5 μm to about 60 μm, or from about 5 μm to about 50 μm, or from about 5 μm to about 40 μm, or from about 5 μm to about 30 μm, or from about 5 μm to about 20 μm, or from about 5 μm to about 12 μm. The thickness d of the region at 50% RH may be from about 10 μm to about 80 μm, or from about 10 μm to about 60 μm, or from about 10 μm to about 50 μm, or from about 10 μm to about 40 μm, or from about 10 μm to about 30 μm, or from about 10 μm to about 20 μm. The thickness may be measured by SEM.

[0198] When used in an electrolytic cell, one major surface of the PEM of the present invention can be in contact with the anode. One recombinant catalyst layer can form one major surface of the PEM of the present invention that is in contact with the anode (or configured to be in contact with the anode), while the distance between the other recombinant catalyst layer and the anode recombinant catalyst layer can be at least about 5 μm, or at least about 6 μm, or at least about 7 μm, or at least about 8 μm, or at least about 9 μm, or at least about 10 μm, or at least about 20 μm, or at least about 30 μm, or at least about 40 μm, or at least about 50 μm, or at least about 60 μm, or at least about 70 μm, or at least about 80 μm, or about 1 μm to about 80 μm, or 2 μm to about 80 μm, 5 μm to about 80 μm, or 5 μm to about 25 μm, or about 6 μm to about 20 μm, or about 7 μm to about 15 μm, or about 8 μm to about 14 μm. This distance corresponds to the thickness of the region separating the at least two recombinant catalyst layers.

[0199] The recombinant catalyst layer can be configured to contact the anode of the multilayer proton exchange membrane electrode assembly in which the recombinant catalyst layer is used. That is, the recombinant catalyst layer forms a major surface of the PEM of the present invention. Generally speaking, with respect to preventing hydrogen crossover, it is preferred that the recombinant catalyst layer be configured to be closer to the anode than the cathode. In some instances, an additional recombinant catalyst layer can be configured to be positioned closer to the cathode in order to mitigate oxygen crossover. The position of one or more recombinant catalyst layers can be selected depending on the system design and the intended operating conditions. For example, the recombinant catalyst is placed at different positions in the PEM, rather than in a single position, so that the recombinant catalyst can be located in a wider area of ​​the PEM thickness. This makes it possible to achieve higher recombinant efficiency in a wider range of stack designs and assembly techniques and at different operating pressures and temperatures. This can also enable the PEM to maintain efficiency over time (e.g., as the system deteriorates).

[0200] In one embodiment, the PEM may comprise at least the following layers in the following order:

[0201] (i) a recombinant catalyst layer;

[0202] (ii) reinforcement layer;

[0203] (iii) a recombinant catalyst layer;

[0204] (iv) reinforcement layer,

[0205] Wherein the reinforcing layer does not contain or is substantially free of a recombinant catalyst, and the recombinant catalyst layer does not contain or is substantially free of a microporous polymer structure. No additional layer is present between any of layers (i) to (iv). That is, layer (i) is in contact with layer (ii), layer (ii) is in contact with layer (iii), and layer (iii) is in contact with layer (iv). Alternatively, an additional layer such as an ion exchange material layer may be present between any of layers (i) to (iv). The PEM may further comprise: (v) an ion exchange material layer, which is in contact with the reinforcing layer (iv), wherein the ion exchange material layer does not contain or is substantially free of a microporous polymer structure and a recombinant catalyst. The PEM of the present invention may further comprise an ion exchange material and / or a reinforcing layer after layer (v). In one embodiment, the recombinant catalyst layer (i) is intended to be located at or closest to the anode of the electrolytic cell PEM electrode assembly during use.

[0206] In another embodiment, the PEM of the present invention may comprise the following layers in the following order:

[0207] (i) a recombinant catalyst layer;

[0208] (ii) reinforcement layer;

[0209] (iii) a recombinant catalyst layer;

[0210] (iv) reinforcement layer;

[0211] (v) an ion exchange material layer;

[0212] (vi) reinforcement layer;

[0213] (vii) an ion exchange material layer;

[0214] (viii) reinforcement layers; and

[0215] (ix) Ion exchange material layer.

[0216] In another embodiment, the PEM of the present invention may comprise the following layers in the following order:

[0217] (i) a recombinant catalyst layer;

[0218] (ii) reinforcement layer;

[0219] (iii) a recombinant catalyst layer;

[0220] (iv) reinforcement layer;

[0221] (v) an ion exchange material layer;

[0222] (vi) reinforcement layer;

[0223] (vii) Ion exchange material layer.

[0224] In another embodiment, the PEM may comprise at least the following layers in the following order:

[0225] (i) reinforcement layer;

[0226] (ii) a recombinant catalyst layer;

[0227] (iii) anion exchange material layer;

[0228] (iv) a recombinant catalyst layer;

[0229] (v) a reinforcement layer,

[0230] Wherein the reinforcing layer does not contain or is substantially free of recombinant catalyst, the recombinant catalyst layer does not contain or is substantially free of microporous polymer structure, and the ion exchange material layer does not contain or is substantially free of microporous polymer structure and recombinant catalyst. There is no additional layer between any of layers (i) to (v). That is, layer (i) contacts layer (ii), layer (ii) contacts layer (iii), layer (iii) contacts layer (iv), and layer (iv) contacts layer (v). Alternatively, an additional layer such as an ion exchange material layer may be present between any of layers (i) to (v). Alternatively, an ion exchange material layer may be present on the outer surface of reinforcing layers (i) and (v). In one embodiment, the recombinant catalyst layer (ii) is intended to be closest to the anode of the electrolytic cell PEM electrode assembly.

[0231] Figures 1A to 1G and Figures 4A to 4E Various PEMs according to the present disclosure are shown. Reference numeral 101 refers to a recombination catalyst layer. Reference numeral 102 refers to a reinforcement layer. Reference numeral 103 refers to an ion exchange material layer. Figures 1A to 1G and Figures 4A to 4E The preferred orientation of the PEM relative to the cathode and anode of the electrolytic cell is also described. Figure 1A and 1G ,as well as Figures 4A to 4E The layer sequence of the PEM described in the foregoing is merely exemplary and does not limit the scope of the present disclosure. Figures 6A and 6B show PEMs according to Comparative Examples 1 and 2, respectively.

[0232] Figure 1A The following PEM 100 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (v) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0233] (i) ion exchange material layer 103;

[0234] (ii) a first reinforcement layer 102;

[0235] (iii) a first recombination catalyst layer 101;

[0236] (iv) a second reinforcement layer 102;

[0237] (v) Second recombination catalyst layer 101 .

[0238] This exemplary arrangement is advantageous because the positioning of the recombination catalyst layers (iii) and (v) enables high recombination catalyst loadings near the crossover reaction front, especially in thinner membranes, thereby maximizing hydrogen crossover reduction. This is particularly true compared to providing the recombination catalyst layer at the top surface of the PEM (i.e., at or immediately adjacent to the anode) and the limitations on increasing the recombination catalyst loading.

[0239] Figure 1B A PEM 100 according to Example 2 is shown comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0240] (i) a first ion exchange material layer 103;

[0241] (ii) a first reinforcement layer 102;

[0242] (iii) a second ion exchange material layer 103;

[0243] (iv) a second reinforcement layer 102;

[0244] (v) a first recombination catalyst layer 101;

[0245] (vi) a third reinforcement layer 102;

[0246] (vii) Second recombination catalyst layer 101 .

[0247] This exemplary setup provides the same Figure 1A The same advantages as described above apply, with the addition of reinforcement layers resulting in increased mechanical strength of the PEM and reduced cross-gas flux.

[0248] Figure 1C A PEM 100 according to Example 1 is shown comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (ix) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0249] (i) a first ion exchange material layer 103;

[0250] (ii) a first reinforcement layer 102;

[0251] (iii) second ion exchange material layer 103; 101;

[0252] (iv) a second reinforcement layer 102;

[0253] (v) a third ion exchange material layer 103;

[0254] (vi) a third reinforcement layer 102;

[0255] (vii) a first recombination catalyst layer 101;

[0256] (viii) a fourth reinforcement layer 102;

[0257] (ix) Second recombination catalyst layer.

[0258] This exemplary setup provides the same Figure 1A The same advantages as described above apply, with the addition of reinforcement layers resulting in increased mechanical strength of the PEM and reduced cross-gas flux.

[0259] Figure 1D The following PEM 100 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (ix) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0260] i) a first ion exchange material layer 103;

[0261] ii) a first reinforcement layer 102;

[0262] iii) a first recombination catalyst layer 101;

[0263] iv) a second reinforcement layer 102;

[0264] v) a second ion exchange material layer 103;

[0265] vi) a third reinforcement layer 102;

[0266] vii) a second recombination catalyst layer 101;

[0267] viii) a fourth enhancement layer 102;

[0268] ix)a third ion exchange material layer 103.

[0269] This exemplary setup provides the same Figure 1D The same advantages are achieved, but in addition, this arrangement allows for better optimization of the position of the composite catalyst layer to most effectively reduce hydrogen and oxygen crossover depending on the electrolysis operating pressure and conditions. Furthermore, this arrangement can reduce degradation effects in the membrane by moving the composite catalyst layer away from the electrode facing side. Figure 1EThe following PEM 100 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (ix) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0270] i) a first ion exchange material layer 103;

[0271] ii) a first reinforcement layer 102;

[0272] iii) a first recombination catalyst layer 101;

[0273] iv) a second reinforcement layer 102;

[0274] v) a second recombination catalyst layer 101;

[0275] vi) a third reinforcement layer 102;

[0276] vii) a third recombination catalyst layer 101;

[0277] viii) a fourth enhancement layer 102;

[0278] ix) Second ion exchange material layer 103.

[0279] This exemplary arrangement provides the Figure 1D The same advantages are achieved, but in addition, this configuration provides additional recombination catalyst loading capacity, if needed, by having three recombination catalyst layers, depending on the electrolysis operating pressure and conditions. This can be beneficial in effectively reducing hydrogen and oxygen crossover, and simplifies processing by distributing the required recombination catalyst concentration across the three layers. This configuration can also reduce degradation effects in the membrane by positioning the recombination catalyst layer away from the front face of the electrode. For example, when used in an electrolytic cell, as the system degrades over time, a wider distribution of the recombination catalyst throughout the PEM thickness can maintain efficient recombination over time as the system degrades (e.g., if supersaturation changes).

[0280] Figure 1F The following PEM 100 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (ix) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0281] i) a first ion exchange material layer 103;

[0282] ii) a first reinforcement layer 102;

[0283] iii) a second ion exchange material layer 103;

[0284] iv) a second reinforcement layer 102;

[0285] v) a first recombination catalyst layer 101;

[0286] vi) a third reinforcement layer 102;

[0287] vii) a third ion exchange material layer 103.

[0288] viii) a fourth enhancement layer 102;

[0289] ix) Second recombination catalyst layer 101 .

[0290] This exemplary setup provides the same Figure 1D The same advantages are achieved, but in addition, this arrangement allows for better optimization of the location of the composite catalyst layer to most effectively reduce hydrogen and oxygen crossover depending on the electrolysis operating pressure and conditions. For example, when used in an electrolyzer, as the system degrades over time, a broader distribution of the recombination catalyst throughout the thickness of the PEM allows for efficient recombination to be maintained over time as the system degrades (e.g., if supersaturation changes).

[0291] Figure 1G The following PEM 100 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 100, wherein the top layer (v) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0292] (i) reinforcement layer 102;

[0293] (ii) a recombination catalyst layer 101;

[0294] (iii) ion exchange material layer 103;

[0295] (iv) a recombination catalyst layer 101;

[0296] (v) Reinforcement layer 102 .

[0297] This exemplary arrangement provides the Figure 1A The same advantages apply, but in addition, this exemplary arrangement can reduce degradation effects in the membrane by moving the recombination catalyst layer away from the electrode front face.

[0298] Figure 4A A PEM 300 according to Example 3 is shown comprising the following layers, starting with the bottom layer (i) of the PEM 300, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0299] i) a first recombination catalyst layer 301;

[0300] ii) a first reinforcement layer 302;

[0301] iii) a first ion exchange material layer 303;

[0302] iv) a second reinforcement layer 302;

[0303] v) a second ion exchange material layer 303;

[0304] vi) a third enhancement layer 302;

[0305] vii) Second recombination catalyst layer 301 .

[0306] This exemplary arrangement provides the Figure 1B This exemplary setup provides the same advantages described in , with the added benefit of reducing oxygen crossover to improve hydrogen purity by placing a recombination catalyst layer near the cathode front side.

[0307] Figure 4B The following PEM 300 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 300, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0308] i) a first ion exchange material layer 303;

[0309] ii) a first reinforcement layer 302;

[0310] iii) a first recombination catalyst layer 301;

[0311] iv) a second reinforcement layer 302;

[0312] v) a second recombination catalyst layer 301;

[0313] vi) a third enhancement layer 302;

[0314] vii) A second ion exchange material layer 303 .

[0315] This exemplary arrangement provides the Figure 4A The same advantages are achieved, with the addition that this exemplary arrangement can reduce degradation effects in the membrane by moving the recombination catalyst layer away from the front face of the electrode. For example, when used in an electrolytic cell, as the system degrades over time, the recombination catalyst is more widely distributed throughout the thickness of the PEM (e.g., Figure 4B ) can achieve efficient recombination over time as the system degrades (e.g., if supersaturation changes).

[0316] Figure 4C The following PEM 300 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 300, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0317] i) a first recombination catalyst layer 301;

[0318] ii) a first reinforcement layer 302;

[0319] iii) Second recombination catalyst layer 301

[0320] iv) a second reinforcement layer 302;

[0321] v) a third recombination catalyst layer 301;

[0322] vi) a third reinforcement layer 302;

[0323] vii) First ion exchange material layer 303.

[0324] This exemplary arrangement provides the Figure 4A The same advantages are achieved, but in addition, this arrangement provides additional recombination catalyst loading capacity, if desired, by having three recombination catalyst layers, based on the electrolysis operating pressure and conditions, which can be beneficial in effectively reducing hydrogen and oxygen crossover, and simplifying processing by distributing the desired recombination catalyst concentration across the three layers. For example, when used in an electrolysis cell, as the system degrades over time, the recombination catalyst is more widely distributed throughout the thickness of the PEM (e.g., Figure 4C ) can achieve efficient recombination over time as the system degrades (e.g., if supersaturation changes).

[0325] Figure 4D The following PEM 300 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 300, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0326] i) a first recombination catalyst layer 301;

[0327] ii) a first reinforcement layer 302;

[0328] iii) a second recombination catalyst layer 301;

[0329] iv) a second reinforcement layer 302;

[0330] v) a third recombination catalyst layer 301;

[0331] vi) a third enhancement layer 302;

[0332] vii) The fourth recombination catalyst layer 301 .

[0333] This exemplary arrangement provides the Figure 4AThe same advantages are achieved, but in addition, this arrangement provides additional recombination catalyst loading capacity, if desired, by having four recombination catalyst layers, based on the electrolysis operating pressure and conditions, which can be beneficial in effectively reducing hydrogen and oxygen crossover, and simplifying processing by distributing the desired recombination catalyst concentration across the four layers. For example, when used in an electrolysis cell, as the system degrades over time, the recombination catalyst is more widely distributed throughout the thickness of the PEM (e.g., Figure 4D ) can achieve efficient recombination over time as the system degrades (e.g., if supersaturation changes).

[0334] Figure 4E The following PEM 300 is shown, comprising the following layers, starting with the bottom layer (i) of the PEM 300, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0335] i) a first ion exchange material layer 303;

[0336] ii) a first reinforcement layer 302;

[0337] iii) a first recombination catalyst layer 301;

[0338] iv) a second ion exchange material layer 303;

[0339] v) a second recombination catalyst layer 301;

[0340] vi) a second reinforcement layer 302;

[0341] vii) A third ion exchange material layer 303 .

[0342] This exemplary arrangement provides the Figure 4A The same advantages apply, but in addition, this exemplary arrangement can reduce degradation effects in the membrane by moving the recombination catalyst layer away from the electrode front face.

[0343] FIG6A (Comparative Example 1) shows a PEM 400 comprising the following layers, starting with the bottom layer (i) of the PEM 400, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0344] (i) a first ion exchange material layer 403;

[0345] (ii) a first reinforcement layer 402;

[0346] (iii) a second ion exchange material layer 403;

[0347] (iv) a second reinforcement layer 402;

[0348] (v) a third ion exchange material layer 403;

[0349] (vi) a third enhancement layer 402;

[0350] (vii) Fourth ion exchange material layer 403.

[0351] FIG6B (Comparative Example 2) shows a PEM 400 comprising the following layers, starting with the bottom layer (i) of the PEM 400, wherein the top layer (vii) is intended to be located at or closest to the anode side of the electrolytic cell PEM electrode assembly when in use:

[0352] (i) a first ion exchange material layer 403;

[0353] (ii) a first reinforcement layer 402;

[0354] (iii) a second ion exchange material layer 403;

[0355] (iv) a second reinforcement layer 402;

[0356] (v) a third ion exchange material layer 403;

[0357] (vi) a third enhancement layer 402;

[0358] (vii) First recombination catalyst layer 401 .

[0359] [Method for producing the multilayer proton exchange membrane of the present invention]

[0360] Methods of making the PEM of the present invention may comprise the general steps of forming at least two reinforcement layers, at least two recombinant catalyst layers, and optionally one or more additional layers, in any order, provided that the resulting PEM comprises at least two recombinant catalyst layers separated by a region containing no or substantially no recombinant catalyst.

[0361] The PEM of the present invention can be prepared by a sequential coating method, wherein a composite structure is formed by depositing a coating on the surface of a previous layer, wherein the previous layer comprises a backing layer, a microporous polymer structure, or an intermediate composite layered structure. In one embodiment, the layers of the PEM are sequentially coated onto the backing layer / onto each other in the desired order. The method of the present invention generally begins by coating a layer (e.g., a recombinant catalyst layer or an ion exchange material layer) onto the backing layer. In the case of an ion exchange material layer, a dispersion comprising the third ion exchange material is deposited onto the backing layer. In some embodiments, no backing layer is provided.

[0362] In the case of a recombinant catalyst layer, a dispersion comprising the first ion exchange material and the recombinant catalyst is deposited onto the lining layer. In the case of a reinforcement layer, in one embodiment, a microporous polymer structure is deposited onto the layer comprising the second ion exchange material, and the microporous polymer structure is made to at least partially absorb the ion exchange material. In another embodiment, a dispersion comprising (the first or second) ion exchange material and the recombinant catalyst is deposited onto the lining layer, and the microporous polymer structure is deposited onto the dispersion layer. The microporous polymer structure of the present invention is made to at least partially absorb a portion of the ion exchange material, while at the same time the microporous polymer structure acts as a filter for the recombinant catalyst, wherein the recombinant catalyst is retained in the dispersion that is not absorbed into the microporous polymer structure. The coating step forms two PEM layers in one step: a recombinant catalyst layer and a reinforcement layer. After each coating step, the multilayer structure (or stack) of the present invention can be optionally dried. In particular, a drying step may be included after the coating step of the recombinant catalyst to maintain the recombinant catalyst in the corresponding recombinant catalyst layer and prevent the recombinant catalyst from migrating into other layers of the PEM if the microporous polymer structure is not deposited on the dispersion layer. This process is continued until the final membrane is formed. The ion exchange material layer and the adjacent reinforcement layer can be formed in a similar manner in a single step, wherein the ion exchange material layer is formed from a dispersion layer of ion exchange material that is not absorbed into the microporous polymer structure forming the reinforcement layer.

[0363] The skilled person knows how to vary the thickness of the layers, the concentration of catalysts and additives, etc. in order to prepare a PEM according to the present disclosure.

[0364] Figure 7 A schematic diagram of a method for producing a PEM according to the present disclosure is shown. For example, to produce a PEM according to Figure 1A The exemplary PEM described herein can be used as follows [according to Figure 1A The exemplary PEM comprises the following layers in the following order (starting from the bottom layer, where the bottom layer is intended to be located at or closest to the cathode when used): a first ion exchange material layer (103), a first reinforcement layer (102a), a first recombination catalyst layer (101a), a second reinforcement layer (102b), a second recombination catalyst layer (101b)]:

[0365] In the first step, if Figure 7 As shown in FIG. 5 , a first dispersion 506 comprising a second ion exchange material is deposited onto a backing layer 505 ( Figure 1A (not visible in the middle).

[0366] In a second step, the first microporous polymer structure 507a is deposited onto the second ion exchange material dispersion 506 so that the first microporous polymer structure 507a becomes at least partially imbibed with the second ion exchange material dispersion 506 .

[0367] In an optional third step, the absorbed microporous polymer structure 507a and the second ion exchange material dispersion 506 are dried to form the first ion exchange material layer 103 and the first reinforcement layer 102a.

[0368] In a fourth step, a second dispersion 508a comprising the first ion exchange material and the recombination catalyst is deposited onto the first reinforcement layer 102a (or onto the at least partially absorbed first microporous polymer structure 507a, if it has not already dried to form the reinforcement layer 102a), and in a fifth step, a second microporous polymer structure 507b is deposited onto the second dispersion 508a comprising the first ion exchange material and the recombination catalyst. The second microporous polymer structure 507b is caused to at least partially absorb a portion of the ion exchange material of the dispersion 508a to form the second reinforcement layer 102b. The recombination catalyst in the first dispersion 508a cannot be absorbed into the second microporous polymer structure 507b and the at least partially absorbed first microporous polymer structure 507a because the particle size of the catalyst or agglomerates of catalyst particles (or particles or agglomerates of catalyst and support material) is larger than the pore size of the second microporous polymer structure 507b. Thus, the recombination catalyst is filtered out of the microporous polymer structure 507b and remains in the portion of the dispersion 508a that was not absorbed into the second microporous polymer structure 507b, forming the first recombination catalyst layer 101a. In an optional sixth step, the intermediate composite of step 5 is then dried to form the second reinforcement layer 102b and the first recombination catalyst layer 101a on top of the intermediate composite described in step 3. The first recombination catalyst layer 101a is disposed between the first reinforcement layer 102a and the second reinforcement layer 102b.

[0369] In the seventh step, a third dispersion 508b comprising an ion exchange material and a recombination catalyst is deposited onto the second reinforcement layer 102b (or onto the at least partially absorbed second microporous polymer structure 507b, if it has not yet dried to form the reinforcement layer 102b). Again, the recombination catalyst is not absorbed into the second reinforcement layer 102b, and a second recombination catalyst layer 101b is formed on the surface of the second reinforcement layer 102b, as shown in Figure 6. The third dispersion 508b comprising an ion exchange material and a recombination catalyst can be the same as or different from the second dispersion 508a, for example, comprising a different ion exchange material and / or a different recombination catalyst, and / or a different concentration of the recombination catalyst, and / or the same or different solvent or solvent system, and / or the same or different total solids / solvent concentration.

[0370] In the eighth step, the multilayer structure is dried to form the PEM 100. The second recombination catalyst 101b forms the outer surface of the PEM 100.

[0371] During the manufacturing process, small or trace amounts of recombinant catalyst may migrate or penetrate into the microporous polymer structure of the reinforcement layer. However, this amount is minimal and unintentional. Therefore, the reinforcement layer comprising the microporous polymer structure is said to be substantially free of the recombinant catalyst layer, as described above. To help prevent this recombinant catalyst migration, an optional technique is to dry each layer before applying the next layer, so that no liquid can penetrate the microporous polymer structure.

[0372] [Multilayer proton exchange membrane electrode assembly]

[0373] The PEM electrode assembly may include: at least one electrode; and a PEM of the present disclosure in contact with the at least one electrode. Figure 8 A schematic diagram of a PEM electrode assembly 650 is shown, comprising an anode 610, a cathode 612, and a PEM assembly 600 according to the present disclosure positioned therebetween.

[0374] The PEM of the present invention may be attached to or in contact with the at least one electrode. The electrode assembly of the present invention may comprise: a first electrode and a second electrode, wherein the first electrode is an anode and the second electrode is a cathode. The anode may be in contact with the recombination catalyst layer of the PEM. The cathode may be in contact with the recombination catalyst layer of the PEM. For example, in accordance with Figure 1A In the exemplary PEM described, the second recombination catalyst layer 101 may be in contact with the anode, and the first ion exchange material layer 103 may be in contact with the cathode. Figure 1AThe exemplary PEM is composed of the following layers in order (starting from the bottom layer, where the bottom layer is intended to be located at or closest to the cathode when in use): a first ion exchange material layer 103; a first reinforcement layer 102; a first recombination catalyst layer 101; a second reinforcement layer 102; and a second recombination catalyst layer 101. Figure 4A In the exemplary PEM described, the second recombination catalyst layer 301 may be in contact with the anode, and the first recombination catalyst layer 301 may be in contact with the cathode. Figure 4A The exemplary PEM depicted is composed of the following layers in order (starting from the bottom layer, which is intended to be located at, or closest to, the cathode when in use): a first recombination catalyst layer 301, a first reinforcement layer 302, a first ion exchange material layer 303; a second reinforcement layer 302; a second ion exchange material layer 303; a third reinforcement layer 302, and a second recombination catalyst layer 301.

[0375] Any suitable anode and cathode materials known in the art may be used. The electrodes may be porous. Commonly used anode materials for PEM water electrolysis include iridium. Commonly used cathode materials for PEM water electrolysis include platinum.

[0376] The PEM electrode assembly of the present invention may further comprise a fluid diffusion layer. The fluid diffusion layer may be any suitable fluid diffusion layer known in the art. For example, the fluid diffusion layer may be selected from the group consisting of: felt, paper, woven material, carbon / carbon-based diffusion layer, titanium porous sintered powder mesh, stainless steel mesh, and mixtures thereof.

[0377] The electrode assembly can be prepared by depositing an anode on one surface of a PEM and a cathode on the opposite surface of the PEM. The electrodes can be deposited by any suitable technique known in the art. For example, a solid electrode layer can be pressed against the PEM by any suitable technique. Alternatively, a liquid electrode ink can be applied to the PEM, and upon drying, the solvent of the electrode ink can dry out to form a solid electrode layer. For the avoidance of doubt, the backing layer must be removed from the PEM before applying the electrodes intended to be placed on the surface of the PEM.

[0378] [Electrolytic Cell]

[0379] An electrolytic cell is provided, comprising the PEM of the present disclosure or the PEM electrode assembly of the present disclosure. An electrolytic cell is an electrochemical device in which PEM water electrolysis can occur. The electrolytic cell comprises at least a PEM, an anode, and a cathode. Figure 8 The PEM electrode assembly 650 shown in FIG. 6 can be used in an electrolytic cell.

[0380] [Use of the multilayer proton exchange membrane of the present invention in water electrolysis]

[0381] The PEM of the present invention can be used for water electrolysis to produce hydrogen. Water electrolysis occurs in an electrolysis cell containing the PEM of the present invention. During electrolysis, the half-reaction occurring at the anode is: 2H2O->O2+4H + +4e - , the half reaction at the cathode is: 4H + +4e - ->2H2. H + Cations migrate from the anode to the cathode through the PEM, generating H 2 at the cathode.

[0382] [Test methods and test plans]

[0383] The following test methods and measurement schemes apply to the above description and examples.

[0384] Bubble Point: Bubble point is measured according to the procedure of ASTM F316-86. Isopropyl alcohol is used as the wetting fluid to fill the pores of the specimen. The bubble point is the air pressure required to generate the first continuous stream of bubbles, which can be detected by rising through the isopropyl alcohol layer covering the microporous polymer matrix. The measurement provides a prediction of pore characteristics including maximum pore size, pore tortuosity, and surface energy.

[0385] Mass per unit area: Each microporous polymer structure was fully strained to eliminate wrinkles, and then a 10 cm 2 The test piece. 2 The specimens were weighed on a conventional laboratory scale. The mass per unit area (M / A) was then calculated as the ratio of the measured mass to the known area. This process was repeated twice, and the average value of M / A was calculated. Alternatively, a specimen of known area could be cut using a die, and the mass per unit area calculated based on this known area as described above.

[0386] Thickness of PEM: The PEM is equilibrated in a room where the thickness is measured at least 1 hour before the measurement. The PEM is attached to a backing layer on which the PEM is coated. For each sample, the PEM on its backing layer is placed on a smooth, flat, horizontal marble slab. A thickness gauge (available from Heidenhain Corporation) is brought into contact with the PEM and the height readings of the thickness gauge are recorded at six different points arranged in a grid pattern on the membrane. Subsequently, the sample is removed from the backing layer, the gauge is brought into contact with the backing layer, and the height readings are recorded again at the same six points. The thickness of the PEM at a given relative humidity (RH) in the room is calculated as follows: the difference between the gauge height readings in the presence and absence of the PEM. The local RH is measured using an RH probe (obtained from Fluke Corporation). The thickness at 0% RH is calculated using the following general formula:

[0387]

[0388] where the parameter λ corresponds to the water absorption of the ion exchange material at a given RH, expressed as moles of water per mole of acid groups. For the PFSA ionomer used in the examples (G701-IWI 100-700, from Asashi Glass Co., Japan), the value of λ in the gas phase at any RH (in the range of 0 to 100%) was calculated according to the following formula:

[0389] λ=80.239×RH 6 -38.717×RH 5 -164.451×RH 4 +208.509×RH 3 -91.052×RH 2 +21.740×RH 1 +0.084

[0390] Hydrogen and oxygen crossover test: The hydrogen and oxygen crossover in the examples were calculated by the following procedure: The catalyst coated membrane (CCM) was prepared using the PEM from the examples by the following method: a carbon supported platinum product (50% / NE-F) supplied by NECHEMCAT was used at 0.4 mg / cm 2 The cathode catalyst layer was applied using iridium oxide supplied by Thermoscientific at 0.6 mg / cm 2 The anode catalyst layer was applied. The CCM was preconditioned in liquid deionized water (DI) at 80°C for 24 hours before being assembled in the test cell. AvCarb MGL 280 supplied by AvCarb Material Solutions was used as the gas diffusion layer on the cathode side; Bekaert Ti felt (2GDL10-025) coated with Pt supplied by Bekaert was used as the porous transport layer on the anode side. A 25 cm 2 A single cell was used for the measurements. DI water was fed to the anode side of the cell. During the test, the cell and water temperature were maintained at 80°C. The exhaust gas streams from the anode and cathode were dried and then analyzed by a micro gas chromatograph (GC) model Agilent 990 provided by Teckso. Nitrogen (N2) and helium (He) were used as carriers for H2 and O2 concentration analysis, respectively. The sampling frequency was 100 Hz and the run time was 48 s. The N2 carrier gas injection temperature was set at 50 degrees Celsius, the injection time was 70 ms, and the backflush was 7 seconds. For the He carrier gas, the injection time was 140 ms, and everything else was the same as for N2. The H2 concentration in O2 was calculated as the ratio of the H2 concentration in the anode stream to the O2 concentration. Using GC, the O2 concentration level in H2 was obtained directly from the cathode stream.

[0391] [Example]

[0392] The present invention will be described in more detail with reference to Examples.The present invention is not limited to the following Examples.

[0393] Example 1 ( Figure 1C )

[0394] In Example 1, a PEM of the present disclosure was prepared as follows.

[0395] The first liquid dispersion was prepared as a blend of PFSA ionomers (G701 = IW100-700 and G701NPC = IW101-700) from Asahi Glass (Japan) at 11.2 wt% solids in a solvent blend of 35 wt% water and 65 wt% ethanol. The PFSA ionomer IW101-700 contained a cerium additive. The two ionomers were blended to achieve a Ce wt% of 0.0335% in the dispersion. The second liquid dispersion was prepared as a blend of PFSA ionomers (G701 = IW100-700) from Asahi Glass (Japan) at 11.2 wt% solids in a solvent blend of 35 wt% water and 65 wt% ethanol. This second liquid dispersion formed a mixture containing platinum (Pt) on carbon from NEChemcat Corporation (SA50BK) at a total concentration of 0.164 wt% Pt in the mixture.

[0396] The PET backing layer was coated with the first liquid dispersion to a wet thickness of about 150 μm, and then a PET backing layer having a mass per unit area of ​​about 4 g / m 2 A layer of ePTFE (serving as a microporous polymer structure) is placed on top of the first liquid dispersion and allowed to absorb it. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a first ion exchange material layer and a first reinforcement layer. The intermediate composite is then coated with the same first liquid dispersion to a wet thickness of about 150 μm and then with a mass per unit area of ​​about 4 g / m 2 A second layer of the same ePTFE (serving as the microporous polymer structure) was placed on top of the first liquid dispersion and allowed to absorb it. The composite was then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a second ion exchange material layer and a second reinforcement layer. The composite was then coated with the same first liquid dispersion to a wet thickness of about 150 μm and then with a mass per unit area of ​​about 4 g / m 2A third layer of the same ePTFE (serving as the microporous polymer structure) was placed on top of the dispersion and allowed to absorb it. The composite was then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a third layer of ion exchange material and a third reinforcement layer.

[0397] The composite was then coated with a second liquid dispersion containing recombinant catalyst particles to a wet thickness of approximately 150 μm and then coated with a second liquid dispersion having a mass per unit area of ​​approximately 4 g / m 2 A fourth layer of the same ePTFE (serving as a microporous polymer structure) is placed on top of the second liquid dispersion and is allowed to absorb (the recombinant catalyst particles are not absorbed into the microporous polymer structure and therefore remain in the layer of ion exchange material forming the recombinant catalyst layer, as shown in FIG. Figure 3 , as described below). The composite is then dried first at approximately 105°C for approximately 2.5 minutes and then at approximately 150°C for approximately 2.5 minutes to form a first recombinant catalyst layer and a fourth reinforcement layer. The composite is then coated with a second liquid dispersion containing recombinant catalyst particles to a wet thickness of approximately 90 μm. The composite is then dried first at approximately 105°C for approximately 2.5 minutes and then at approximately 150°C for approximately 2.5 minutes to form a second recombinant catalyst layer. The completed multilayer composite is then further heat-treated at approximately 150°C for approximately 5 minutes to provide the PEM of the present invention.

[0398] Starting from the top of the PEM, the PEM has the following structure (and approximate layer thicknesses), where the top layer is intended to be closest to the anode side of the electrolyzer PEM electrode assembly and the bottom layer is intended to be located on or closest to the cathode side of the electrolyzer PEM electrode assembly when in use: a second recombination catalyst layer (5.46 μm thick), forming the outer surface of the PEM; a fully absorbed fourth reinforcement layer (6.45 μm thick); a first recombination catalyst layer (5.06 μm thick); a fully absorbed third reinforcement layer (5.46 μm thick); a third ion exchange material layer (5.46 μm thick); a second reinforcement layer (7.04 μm thick); a second ion exchange material layer (5.85 μm thick); a first reinforcement layer (7.24 μm thick); and a first ion exchange material layer (3.97 μm thick. The total thickness of the PEM was measured to be approximately 48 μm at about 50% RH.

[0399] The recombination catalyst loadings of the first and second recombination catalyst layers are as follows:

[0400] The catalyst loading of the first recombination catalyst layer between the third and fourth reinforcement layers was approximately 19 μg / cm2 Pt.

[0401] The catalyst coating amount of the second recombination catalyst layer was about 11 μg / cm 2 Pt.

[0402] Figure 1C A schematic diagram of a PEM according to Example 1 is shown. Figure 2 A cross-sectional SEM (scanning electron microscope image) of the PEM of Example 1 is shown, wherein Figure 2 The image relative to Figure 1C Inverted (i.e. Figure 2 In the image, the first recombination catalyst layer 101 is located at the bottom). The PEM is a multilayer membrane containing 9 layers, each with a thickness of Figure 2 . Reference numeral 101 denotes a recombinant catalyst layer. Reference numeral 102 denotes a reinforcement layer. Reference numeral 103 denotes an ion exchange material layer. Reference numeral 200 denotes a lining layer.

[0403] Figure 3 Another cross-sectional image of the PEM of Example 1 is shown, wherein Figure 3 The image relative to Figure 1C Inverted (i.e. Figure 3 In the image, the first recombination catalyst layer 101 is located at the bottom layer). Figure 3 This is a backscattered electron image used to emphasize the presence of recombination catalyst particles (indicated by white markers 210) in the second recombination catalyst layer 101 and the first recombination catalyst layer 101. In all other layers, there are no or negligible amounts of recombination catalyst particles. Thus, it can be seen that the recombination catalyst layer 101 is separated by the reinforcement layer 102, which forms a region without recombination catalyst (white markers 210 are not visible in the reinforcement layer 102). Reference numeral 101 refers to the recombination catalyst layer. Reference numeral 102 refers to the reinforcement layer. Reference numeral 103 refers to the ion exchange material layer.

[0404] Example 2 ( Figure 1B )

[0405] The first liquid dispersion was prepared as a blend of PFSA ionomers (G701 = IW100-700 and G701NPC = IW101-700) from Asahi Glass (Japan) at 13 wt% solids in a solvent blend of 34.9 wt% water and 65.1 wt% ethanol (first ion exchange material). The PFSA ionomer IW101-700 contained a cerium additive. The two ionomers were blended to achieve a Ce weight percent in the dispersion of 0.0452%.

[0406] A second liquid dispersion was prepared containing 13 wt% solids of a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) in a solvent blend of 37.8 wt% water and 62.2 wt% ethanol. From this second liquid dispersion, a mixture was formed containing platinum (Pt) supported on carbon from NEChemcat Corporation (SA50BK) at a total concentration of 0.194 wt% Pt.

[0407] The PET backing layer was coated with the first liquid dispersion to a wet thickness of about 120 μm, and then a PET backing layer having a mass per unit area of ​​about 4 g / m 2 A first layer of ePTFE (serving as a microporous polymer structure) of about 100 μm was placed on top of the first liquid dispersion and allowed to absorb it. The composite was then dried at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a first ion exchange material layer and a first reinforcement layer. The composite was then coated with the first liquid dispersion having a wet thickness of about 120 μm and then a weight per unit area of ​​about 4 g / m 2 A second layer of the same ePTFE (serving as the microporous polymer structure) was placed on top of the dispersion and allowed to absorb it. The composite was then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a second layer of ion exchange material and a second reinforcement layer.

[0408] The composite is then coated with a mixture of the second liquid dispersion and the recombinant catalyst particles to a wet thickness of about 120 μm, and then coated with a mass per unit area of ​​about 4 g / m 2 A third layer of ePTFE (serving as a microporous polymer structure) is placed on top of the mixture and is absorbed (the recombinant catalyst particles are not absorbed into the microporous polymer structure and therefore remain in the layer of ion exchange material forming the recombinant catalyst layer). The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a first recombinant catalyst layer and a third reinforcement layer. The composite is then coated with a mixture of a second liquid dispersion and recombinant catalyst particles to a wet thickness of about 70 μm. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a second recombinant catalyst layer. The complete multilayer composite is then further heat treated at a temperature of about 150°C for about 5 minutes to obtain the PEM of the present invention.

[0409] The PEM of the present invention has the following structure (and approximate layer thicknesses), starting with the last applied layer at the top and going down to the first applied layer on the backing layer: second recombination catalyst layer; third fully absorbed reinforcement layer; first recombination catalyst layer; second fully absorbed reinforcement layer; second ion exchange material layer; first fully absorbed reinforcement layer; and first ion exchange material layer. The total thickness of the PEM was measured to be approximately 38 μm at approximately 50% RH.

[0410] The recombination catalyst loadings of the first and second recombination catalyst layers are as follows:

[0411] The catalyst loading of the first recombination catalyst layer between the second and third reinforcement layers was approximately 19 μg / cm 2 Pt.

[0412] The catalyst loading of the second recombination catalyst layer was approximately 11 μg / cm 2 Pt.

[0413] Comparative Example 1 (Figure 6A):

[0414] The first liquid dispersion was prepared as a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) at 13 wt% solids in a solvent blend of 35.1 wt% water and 64.9 wt% ethanol (first ion exchange material). The second liquid dispersion was prepared as a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) at 13.7 wt% solids in a solvent blend of 33.2 wt% water and 66.8 wt% ethanol.

[0415] The PET backing layer (not visible) was coated with the first liquid dispersion to a wet thickness of approximately 120 μm, and then a PET substrate having a mass per unit area of ​​approximately 4 g / m 2 A first layer of ePTFE (serving as a microporous polymer structure) is placed on top of the first liquid dispersion and allowed to absorb it. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a first ion exchange material layer 403 and a first reinforcement layer 402. The composite is then coated with the first liquid dispersion having a wet thickness of about 120 μm and then with a mass per unit area of ​​about 4 g / m 2A second layer of the same ePTFE (serving as the microporous polymer structure) is placed on top of the dispersion and allowed to absorb it. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a second ion exchange material layer 403 and a second reinforcement layer 402. The composite is then coated with a second liquid dispersion having a wet thickness of about 120 μm and a mass per unit area of ​​about 4 g / m 2 A third layer of the same ePTFE (serving as the microporous polymer structure) is placed on top of the dispersion and allowed to absorb it. The composite is then dried first at approximately 105°C for approximately 2.5 minutes and then at approximately 150°C for approximately 2.5 minutes to form a third ion exchange material layer 403 and a third reinforcement layer 402. The composite is then coated with a second liquid dispersion to a wet thickness of approximately 70 μm. The composite is then dried first at approximately 105°C for approximately 2.5 minutes and then at approximately 150°C for approximately 2.5 minutes to form a fourth ion exchange material layer 403. The completed multilayer composite is then further heat treated at approximately 150°C for approximately 5 minutes to form a PEM. The thickness of the multilayer composite is approximately 38 μm.

[0416] Comparative Example 2 (Figure 6B):

[0417] The first liquid dispersion was prepared as a PFSA ionomer blend (G701 = IW100-700 and G701NPC = IW101-700) from Asahi Glass (Japan) at 13 wt% solids in a solvent blend of 35.1 wt% water and 64.9 wt% ethanol (first ion exchange material). The second liquid dispersion was prepared as a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) at 13.7 wt% solids in a solvent blend of 33.2 wt% water and 66.8 wt% ethanol.

[0418] A third liquid dispersion was prepared containing 12.2 wt% solids of a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) in a solvent blend of 38.7 wt% water and 61.3 wt% ethanol. From this second liquid dispersion, a mixture was formed containing platinum (Pt) supported on carbon from NEChemcat Corporation (SA50BK) at a total concentration of 0.318 wt% Pt.

[0419] The PET backing layer was coated with the first liquid dispersion to a wet thickness of about 120 μm, and then a PET backing layer having a mass per unit area of ​​about 4 g / m 2A first layer of ePTFE (serving as a microporous polymer structure) is placed on top of the first liquid dispersion and allowed to absorb it. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a first ion exchange material layer 403 and a first reinforcement layer 402. The composite is then coated with the first liquid dispersion having a wet thickness of about 120 μm and then with a mass per unit area of ​​about 4 g / m 2 A second layer of the same ePTFE (serving as the microporous polymer structure) is placed on top of the dispersion and allowed to absorb it. The composite is then dried first at a temperature of about 105°C for about 2.5 minutes and then at a temperature of about 150°C for about 2.5 minutes to form a second ion exchange material layer 403 and a second reinforcement layer 402. The composite is then coated with a second liquid dispersion having a wet thickness of about 120 μm and a mass per unit area of ​​about 4 g / m 2 A third layer of the same ePTFE (serving as the microporous polymer structure) is placed on top of the dispersion and allowed to absorb it. The composite is then dried first at a temperature of approximately 110° C. for approximately 2.5 minutes and then at a temperature of approximately 150° C. for approximately 2.5 minutes to form a third ion exchange material layer 403 and a third reinforcement layer 402.

[0420] The composite was then coated with a mixture of a third liquid dispersion and recombinant catalyst particles to a wet thickness of approximately 70 μm. The composite was then dried at approximately 110° C. for approximately 2.5 minutes and then at approximately 150° C. for approximately 2.5 minutes to form a first recombinant catalyst layer 401. The completed multilayer composite was then further heat-treated at approximately 150° C. for approximately 5 minutes to obtain a PEM 400. The catalyst loading of the first recombinant catalyst layer 401 was approximately 18 μg / cm 2 Pt.

[0421] FIG6C shows a cross-sectional SEM of a PEM 400 of Comparative Example 2. Starting from the top of the last coated layer and down to the first coated layer on the backing layer (not shown), PEM 400 comprises: a first recombination catalyst layer 401 (3.97 μm thick); a third reinforcement layer 402 (6.60 μm thick); a third ion exchange material layer 403 (5.51 μm thick); a second reinforcement layer (7.24 μm thick); a second ion exchange material layer 403 (5.95 μm thick); a first reinforcement layer 402 (6.25 μm thick); and a first ion exchange material layer 403 (5.06 μm thick), where the thicknesses are measured at approximately 50% RH. FIG6D shows a backscattered image of a cross-sectional PEM 400 of Comparative Example 2, where recombination catalyst particles are indicated by reference numeral 410 and are present only in the first recombination catalyst layer 401.

[0422] Example 3 ( Figure 4A )

[0423] Figure 4A Another example of a PEM 300 is shown in FIG. The method of constructing the PEM 300 is the same as that described in Examples 1 and 2 above.

[0424] The first liquid dispersion was prepared as a blend of PFSA ionomers (G701 = IW100-700 and G701NPC = IW101-700) from Asahi Glass (Japan) at 15 wt% solids in a solvent blend of 40.0 wt% water and 60.0 wt% ethanol (first ion exchange material). The PFSA ionomer G701NPC contained a cerium additive. The two ionomers were blended to achieve a Ce weight percent of 0.039% in the dispersion.

[0425] A second liquid dispersion was prepared containing 15 wt% solids of a PFSA ionomer (G701 = IW100-700) from Asahi Glass (Japan) in a solvent blend of 40.0 wt% water and 60.0 wt% ethanol. From this second liquid dispersion, a mixture was formed containing platinum (Pt) supported on carbon from NEChemcat Corporation (SA50BK) at a total concentration of 0.371 wt% Pt.

[0426] The PET backing layer was coated with the second liquid dispersion and the recombinant catalyst particles to a wet thickness of about 110 μm, and then the weight per unit area was about 4 g / m 2A first layer of ePTFE (serving as a microporous polymer structure) is placed on top of the second liquid dispersion and absorbed (the recombinant catalyst particles are not absorbed into the microporous polymer structure and therefore remain in the layer of ion exchange material forming the recombinant catalyst layer). The composite is then dried first at a temperature of approximately 140°C for approximately 1 minute and then at a temperature of approximately 170°C for approximately 2 minutes to form a first recombinant catalyst layer, a first ion exchange material layer, and a first reinforcement layer.

[0427] Subsequently, the composite was coated with the same first liquid dispersion at a wet thickness of approximately 110 μm, followed by a coating having a mass per unit area of ​​approximately 4 g / m 2 A second layer of the same ePTFE (serving as the microporous polymer structure) was placed on top of the dispersion and allowed to absorb it. The composite was then dried first at a temperature of about 140°C for about 1 minute and then at a temperature of about 170°C for about 2 minutes to form a second layer of ion exchange material and a second reinforcement layer.

[0428] The composite was then coated with a mixture of the first liquid dispersion to a wet thickness of approximately 110 μm, and then coated with a mixture of the first liquid dispersion to a wet thickness of approximately 4 g / m 2 A third layer of ePTFE (serving as a microporous polymer structure) is placed on top of the mixture and allowed to absorb. The composite is then dried first at a temperature of about 140°C for about 1 minute and then at a temperature of about 170°C for about 2 minutes to form a third reinforcement layer.

[0429] The composite was then coated with a mixture of a second liquid dispersion and recombinant catalyst particles to a wet thickness of approximately 65 μm. The composite was then dried first at approximately 140° C. for approximately 1 minute and then at approximately 170° C. for approximately 2 minutes to form a second recombinant catalyst layer. The completed multilayer composite was then further heat-treated at approximately 160° C. for approximately 6 minutes to obtain the PEM of the present invention.

[0430] The PEM has the following structure (and approximate layer thicknesses, which are determined by Figure 5A), starting with the last coated layer at the top and going down to the first coated layer on the backing layer: second recombination catalyst layer 301 (thickness 4.76 μm); third fully absorbed reinforcement layer 302 (thickness 6.20 μm); second ion exchange material layer 303 (thickness 4.02 μm); second fully absorbed reinforcement layer 302 (thickness 5.85 μm); first ion exchange material layer 303 (thickness 4.32 μm); first fully absorbed reinforcement layer 402 (thickness 6.70 μm); and first recombination catalyst layer 301 (thickness 4.91 μm). The total PEM thickness was measured to be approximately 38 μm at approximately 50% RH.

[0431] The recombination catalyst loadings of the first and second recombination catalyst layers are as follows:

[0432] The catalyst loading of the first recombination catalyst layer was approximately 18 μg / cm 2 Pt.

[0433] The catalyst loading on the surface layer of the second recombination catalyst layer was approximately 11 μg / cm 2 Pt.

[0434] The distance from the first recombination catalyst layer (i) to the anode is 0 μm, and the distance from the second recombination catalyst layer (vii) to the cathode is 0 μm.

[0435] Both recombinant catalyst layers contained antioxidant additives, such as cerium additives (153 mg / m 2 ), and ion exchange materials.

[0436] The recombination catalyst layer near the anode side is intended to reduce H2 in explosive mixtures with O2. The recombination catalyst layer near the cathode side is intended to reduce O2 in H2 to improve H2 purity. The distance from each side can be selected to effectively control the given anode and cathode pressures, and therefore the partial pressures of O2 and H2 within the thickness of the PEM.

[0437] Figure 5B Another cross-sectional image of the PEM of Example 3 is shown. Figure 5B 3 is a backscattered electron image used to emphasize the presence of recombination catalyst particles (shown by white markers 310) in the second recombination catalyst layer 301 and the first recombination catalyst layer 301. In all other layers, no or negligible amounts of recombination catalyst particles are present. Thus, it can be seen that the recombination catalyst layer 301 is separated by the reinforcement layer 302 and the ion exchange material layer 303, forming a region free of recombination catalyst (white markers 310 are not visible in the reinforcement layer 302 and the ion exchange material layer 303).

[0438] Results and Analysis

[0439] Figure 9A Shown are graphs of hydrogen crossover versus current density for the PEMs of Examples 2, 3 and Comparative Examples 1 and 2 when used in electrolytic cells. Figure 9B A histogram of hydrogen crossover versus current density is shown for the PEMs of Examples 2, 3, and Comparative Examples 1 and 2 when used in an electrolyzer. In Comparative Example 1, the concentration of H2 in O2 indicates that hydrogen flux through the following PEM is not reduced in this electrolyzer system, and the PEM is constructed with three reinforcement layers and four ion exchange layers having those thicknesses and specific materials of construction as described above. The data for Comparative Example 2 shows that the concentration of H2 in O2 is reduced by adding a single recombination catalyst layer 401 positioned near the anode. In Example 2, by introducing the first and second recombination catalyst layers, the hydrogen crossover is reduced at high current density (3 A / cm 2 ) and low current density (0.5A / cm 2 ) region, where the first recombination catalyst layer is positioned closer to the middle of the PEM thickness than the second recombination layer (see Figure 1B ). For a specific electrolytic cell and system design and operating conditions at ambient pressure, the first recombination layer can be closer to the optimal efficient position than the second recombination layer closer to the anode. This achieves the observed difference in the 0.5 A / cm2 reaction rate compared to Comparative Example 1. 2 The H2 in O2 was reduced by an extreme 96%, and at 3A / cm 2 Due to the two recombinant catalyst layers in Example 3, which are located towards the cathode and anode, Example 3 is less effective in reducing the H2 concentration in O2, despite having similar total Pt recombinant catalyst loadings in Example 3 and Example 2. For reducing H2 in O2, Example 3 benefits less from the two recombinant catalyst layers relative to Example 2, compared to the effectiveness of the single recombinant catalyst layer in Comparative Example 2.

[0440] Figure 9C It shows that when the PEM of Example 3 and Comparative Example 2 is used in an electrolytic cell, the 2 Histogram of oxygen crossover at current densities of 100 nm and 100 nm. Figure 9C The significant value of the second recombination catalyst layer located near the cathode in reducing the concentration of O2 in H2 was confirmed. Interestingly, when comparing the recombination efficiency of Example 3 with that of Comparative Example 2, the O2 in H2 2 The decrease is about 90%, while the H2 in O2 discussed above is at 3A / cm 2 The decrease is about 7% at 0.5A / cm 2This further demonstrates that the recombination catalyst layer position can be optimized for either H2 reduction in O2 as shown in Example 2, or O2 reduction in H2 as shown in Example 3, and that these strategies can be used to reduce both through further embodiments.

[0441] It can be seen that by incorporating multiple recombination catalyst layers at optimal locations and loadings for a given PEM design and electrolyzer design and operating conditions, the H2 in O2 and O2 in H2 can be significantly reduced. As previously discussed, this can contribute to a number of technologies that reduce production costs associated with PEM water electrolysis, including: (i) improving the efficiency of PEM water electrolysis by achieving lower resistance PEM designs, and (ii) increasing hydrogen pressure, thereby reducing downstream compression costs, (iii) extending the range of electrolyzer operation to very low loads, thereby maximizing the use of renewable energy, and (iv) extending the operating life of the electrolyzer, and (v) reducing the capital and maintenance costs of hydrogen purification units by increasing the purity level of hydrogen produced directly in the electrolyzer, reducing the need for additional purification processes, and making the recombination more efficient and durable.

[0442] As shown herein, the invention discussed herein can uniquely achieve more efficient recombination catalyst efficiencies. It can also be hypothesized that the design of Example 2 is not only more efficient at initially reducing H2 from O2 in the system used in this testing compared to Comparative Example 1, but is also more likely to be more efficient at reducing H2 from O2 under other system designs and operating conditions. It can also maintain efficiency as H2 permeation increases over time (caused by supersaturation due to cracking of the system).

[0443] All ranges described herein are exemplary in nature and include any and all values ​​therebetween. The terms "substantially," "approximately," and "about" as used herein are interchangeable and refer to measurements including the nominal measurement and any measurement that is reasonably close to the nominal measurement. As understood and readily determined by one of ordinary skill in the relevant art, a measurement that is reasonably close to the stated measurement will have a relatively small deviation from the stated measurement. Such deviations may be due to measurement errors, differences in calibration of measurement and / or manufacturing equipment, human error in reading and / or setting measurements, fine-tuning to optimize performance and / or structural parameters due to measurement differences associated with other components, specific implementation scenarios, imprecise adjustment and / or manipulation of objects by humans or machines, and the like. If it is determined that a person with ordinary skill in the relevant art cannot readily determine the value of such a reasonably small difference, the terms "about" and "approximately" may be understood to mean plus or minus 10% of the stated value.

[0444] Throughout the specification and claims, unless the context clearly dictates otherwise, terms shall have the meanings explicitly defined herein.

[0445] Although the phrases "in one embodiment," "in an embodiment," and "in some embodiments" as used herein may refer to the same embodiment, they do not necessarily refer to the same embodiment. Furthermore, the expressions "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to different embodiments, although they may. All embodiments of the present disclosure are intended to be combinable.

[0446] The terms "comprises" and "comprising" mean including but not limited to, such that other features may be present. The term may also mean "consisting of."

[0447] All references and test methods cited herein are incorporated by reference in their entirety.

Claims

1. A multilayer proton exchange membrane for water electrolysis, comprising: (i) at least two recombinant catalyst layers, each of the at least two recombinant catalyst layers comprising a recombinant catalyst and a first ion exchange material, wherein the at least two recombinant catalyst layers are separated by a region that is free or substantially free of recombinant catalyst, and (ii) at least two reinforcement layers, each of the at least two reinforcement layers comprising a microporous polymer structure and a second ion exchange material at least partially absorbed within the microporous polymer structure.

2. The multilayer proton exchange membrane according to claim 1, wherein the thickness of the region separating the at least two recombination catalyst layers is at least about 1 μm at 50% relative humidity (RH).

3. The multilayer proton exchange membrane according to claim 1 or claim 2, wherein the region separating at least two recombination catalyst layers comprises at least one layer containing no or substantially no recombination catalyst.

4. A multilayer proton exchange membrane according to any preceding claim, wherein the recombination catalyst comprises one or more selected from the group consisting of platinum, palladium, iridium, rhodium, ruthenium, osmium, nickel, cobalt, titanium, tin, tantalum, niobium, antimony, lead, manganese, and oxides thereof.

5. The multilayer proton exchange membrane according to claim 4, wherein the recombination catalyst comprises at least one platinum group metal selected from the group consisting of platinum, palladium, iridium, rhodium, ruthenium and osmium.

6. The multilayer proton exchange membrane according to claim 5, wherein the recombination catalyst comprises an alloy of at least one platinum group metal and other metals, such as cerium and titanium, or a mixed oxide of at least one platinum group metal and other metals.

7. A multilayer proton exchange membrane according to any preceding claim, wherein the recombination catalyst is present on a support material.

8. The multilayer proton exchange membrane according to claim 7, wherein the support material is carbon particles, such as carbon black.

9. The multilayer proton exchange membrane according to claim 1, wherein the recombination catalyst is platinum supported on carbon particles.

10. The multilayer proton exchange membrane according to any preceding claim, wherein the recombination catalyst in each of the at least two recombination catalyst layers is the same or different.

11. The multilayer proton exchange membrane of any preceding claim, wherein each of the at least two recombination catalyst layers has a minimum thickness at 50% RH of about 1 μm, or a thickness in the range of about 1 μm to about 35 μm, or a thickness in the range of about 1 μm to about 20 μm, or a thickness in the range of about 3 μm to about 8 μm.

12. The multilayer proton exchange membrane according to any preceding claim, wherein the loading of the recombinant catalyst present in each of the at least two recombinant catalyst layers is at most about 0.10 mg / cm 2 , or the loading is about 0.001 mg / cm 2 to about 0.09 mg / cm 2 range, or a loading of about 0.008 mg / cm 2 to about 0.04 mg / cm 2 within the range.

13. A multilayer proton exchange membrane according to any preceding claim, wherein at least one recombinant catalyst layer comprises one or more additives selected from the group consisting of antioxidants and free radical scavengers.

14. A multilayer proton exchange membrane according to any preceding claim, comprising a total of two recombinant catalyst layers.

15. A multilayer proton exchange membrane according to any preceding claim, comprising a total of three recombinant catalyst layers.

16. A multilayer proton exchange membrane according to any preceding claim, comprising a total of four recombinant catalyst layers.

17. The multilayer proton exchange membrane according to any preceding claim, further comprising an ion exchange material layer comprising a third ion exchange material, wherein the ion exchange material layer is free or substantially free of microporous polymer structures and recombination catalysts.

18. A multilayer proton exchange membrane according to any preceding claim, wherein the first ion exchange material, the second ion exchange material, and the third ion exchange material are the same or different.

19. A multilayer proton exchange membrane according to any preceding claim, wherein the first and second ion exchange materials are the same and are made from a dispersion of ion exchange materials.

20. The multilayer proton exchange membrane according to any preceding claim, wherein the recombination catalyst of each of the at least two recombination catalyst layers is dispersed in the first ion exchange material.

21. The multilayer proton exchange membrane according to claim 19, wherein the recombinant catalyst of each of said at least two recombinant catalyst layers is dispersed in said one ion exchange material dispersion.

22. The multilayer proton exchange membrane according to any preceding claim, wherein the first ion exchange material and the second ion exchange material each comprise a proton conducting polymer selected from the group consisting of hydrocarbon ionomers, perfluoro ionomers, and perfluorosulfonic acid ionomers.

23. The multilayer proton exchange membrane according to claim 17, wherein the region separating at least two recombination catalyst layers comprises the ion exchange material layer.

24. A multilayer proton exchange membrane according to any preceding claim, wherein the region separating at least two recombination catalyst layers comprises at least one reinforcement layer.

25. A multilayer proton exchange membrane according to any preceding claim, wherein the second ion exchange material is at least partially absorbed within the microporous polymer structure, rendering the microporous polymer structure occluded.

26. A multilayer proton exchange membrane according to any preceding claim, wherein the microporous polymer structure fully occludes the second ion exchange material.

27. The multilayer proton exchange membrane according to any preceding claim, wherein the total content of microporous polymer structure in the multilayer proton exchange membrane is at least about 1 g / m 2 , based on the total area of ​​the multilayer proton exchange membrane.

28. The multilayer proton exchange membrane according to any preceding claim, wherein each of the at least two reinforcement layers has a microporous polymer structure content of at least about 1 g / m 2 , based on the total area of ​​the multilayer proton exchange membrane.

29. A multilayer proton exchange membrane according to any preceding claim, wherein the microporous polymer structure of each of the at least two reinforcement layers comprises at least one fluorinated polymer.

30. The multilayer proton exchange membrane according to claim 27, wherein the fluorinated polymer is selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), and mixtures thereof.

31. The multilayer proton exchange membrane according to claim 28, wherein the fluoropolymer is expanded polytetrafluoroethylene (ePTFE).

32. A multilayer proton exchange membrane according to any preceding claim, wherein the microporous polymer structure of each of the at least two reinforcement layers comprises a hydrocarbon polymer.

33. The multilayer proton exchange membrane according to claim 30, wherein the hydrocarbon polymer is selected from the group consisting of polyethylene, polypropylene, polycarbonate, polystyrene, polysulfone, polyethersulfone, polyethylene naphthalate, and mixtures thereof.

34. The multilayer proton exchange membrane according to any preceding claim, wherein each of the at least two reinforcement layers is free or substantially free of a recombination catalyst.

35. The multilayer proton exchange membrane according to any preceding claim, wherein the multilayer proton exchange membrane has a total thickness at 50% relative humidity of about 20 μm to about 250 μm, or about 20 μm to about 120 μm, or about 20 μm to about 60 μm, or about 20 μm to about 50 μm, or about 20 μm to 45 μm.

36. A multilayer proton exchange membrane according to any preceding claim, comprising at least the following layers in the following order: (i) a recombinant catalyst layer; (ii) reinforcement layer; (iii) a recombinant catalyst layer; (iv) reinforcement layer, The reinforcement layer contains no or substantially no recombinant catalyst, and the recombinant catalyst layer contains no or substantially no microporous polymer structure.

37. The multilayer proton exchange membrane according to claim 34, further comprising (v) an ion exchange material layer in contact with the reinforcement layer (iv), wherein the ion exchange material layer is free of or substantially free of microporous polymer structures and recombination catalysts.

38. The multilayer proton exchange membrane according to any of claims 1 to 33, comprising at least the following layers in the following order: (i) reinforcement layer; (ii) a recombinant catalyst layer; (iii) an ion exchange material layer; (iv) a recombinant catalyst layer; (v) reinforcement layer, The reinforcement layer contains no or substantially no recombinant catalyst, the recombinant catalyst layer contains no or substantially no microporous polymer structure, and the ion exchange material layer contains no or substantially no microporous polymer structure and recombinant catalyst.

39. The multilayer proton exchange membrane according to any preceding claim, wherein the at least two recombinant catalyst layers are separated by a distance d, wherein the distance d is from about 1 μm to about 80 μm, or from about 1 to 20 μm, or from about 2 μm to about 12 μm at 50% relative humidity.

40. A multilayer proton exchange membrane according to any preceding claim, wherein the recombinant catalyst layer is arranged in contact with the anode of the multilayer proton exchange membrane electrode assembly.

41. A multilayer proton exchange membrane electrode assembly comprising: (i) at least one electrode; and (ii) A multilayer proton exchange membrane as defined in any of claims 1 to 40, in contact with the at least one electrode.

42. An electrolytic cell comprising a multilayer proton exchange membrane as defined in any of claims 1 to 40, or a multilayer proton exchange membrane electrode assembly as defined in claim 41.

43. Use of a multilayer proton exchange membrane as defined in any of claims 1 to 40 in the electrolysis of water.

44. A method of manufacturing a multilayer proton exchange membrane (PEM) as defined in any of claims 1 to 40, said method comprising the steps of: At least two reinforcement layers, at least two recombinant catalyst layers, and optionally one or more additional layers are formed, in any order, provided that the resulting multilayer proton exchange membrane comprises at least two recombinant catalyst layers separated by a region free or substantially free of recombinant catalyst.

45. The method of claim 44, comprising forming the multilayer PEM in a sequential process wherein, in a depositing step, each layer, or layers of the PEM, are deposited sequentially in a desired order.

46. ​​The method of claim 44 or 45, comprising: forming at least one of the at least two recombinant catalyst layers by depositing a dispersion comprising ion exchange material and recombinant catalyst particles or aggregates onto at least one of the at least two reinforcement layers, the at least two reinforcement layers comprising a microporous polymer structure, and wherein the microporous polymer structure is configured to prevent recombinant catalyst particles or aggregates from impregnating into the pores of the microporous polymer structure.

47. A method according to claim 44 or 45, comprising forming at least one of the at least two recombinant catalyst layers by depositing a microporous polymer structure onto a dispersion comprising ion exchange material and recombinant catalyst particles or aggregates, and wherein the microporous polymer structure is configured to prevent the recombinant catalyst particles or aggregates from impregnating into the pores of the microporous polymer structure.

48. The method according to claim 46 or 47, wherein the microporous polymer structure is at least partially imbibed with the ion exchange material, thereby forming the at least one reinforcement layer; and the recombinant catalyst layer is formed from a dispersion of the recombinant catalyst that is not imbibed into the microporous polymer structure, and The at least one reinforcement layer at least partially forms the region free of or substantially free of recombination catalyst.

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