Bipolar Membrane System and Method

Abstract

Systems and methods for a catalyzed asymmetric bipolar membrane are described. The catalyzed asymmetric bipolar membrane can maintain a desired current density over a long period of time at a low operating voltage. The catalyzed asymmetric bipolar membrane can be implemented in an electrodialysis cell for various applications such as carbon capture.

Description

Technical Field

[0001] This invention was made with government support under Contract No. DE - AR0001407 awarded by the Department of Energy. The government has certain rights in this invention.

[0002] This invention generally relates to systems and methods of asymmetric bipolar membranes, and more particularly to systems and methods of asymmetric bipolar membranes with catalysts.

Background Art

[0003] Ion exchange membranes include polymers containing ionizable functional groups that allow for the selective transport of cations in cation exchange membranes (CEMs) and anions in anion exchange membranes (AEMs). Bipolar membranes (BPMs) include a cation exchange layer (CEL) laminated to an anion exchange layer (AEL), and a water dissociation (WD) catalyst can be dispersed at the CEL - AEL junction. At the CEL - AEL junction, mobile protons and hydroxide ions from the CEL and AEL react to form water, neutralizing the mobile ions to form a space charge depletion region, creating an electric field in the depletion region. When used in an electrochemical system having an anode and a cathode, the BPM can be controlled by applying a bias. By controlling the applied bias at the cathode and anode, protons (H + ) and hydroxide ions (OH - ) can be moved in different directions. When the BPM is placed in an electrochemical cell under reverse bias, the presence of a large electric field causes WD promotion at the junction between the CEL and AEL. H + ions selectively pass through the CEL while OH - ions selectively pass through the AEL, forming separate acidic and basic streams on both sides of the BPM. BPMs enable separated acidic / alkaline regions in electrochemical devices and facilitate a catalyst environment optimized for water electrolysis, CO2 reduction, and electrodialysis.

[0004] Direct ocean capture (DOC) is a carbon capture strategy that can utilize the fact that atmospheric carbon is concentrated in the ocean due to the solvation equilibrium between gaseous CO2 and dissolved CO2. The DOC technology needs to overcome the requirement that a proton transfer reaction occurs in seawater to convert bicarbonate ions (HCO3 - ) into carbonate ions (CO3 2- ) so that they can be precipitated or converted into dissolved CO2 and removed as a gas.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Many embodiments are directed to systems of asymmetric bipolar membranes for electrodialysis cells and related methods.

Means for Solving the Problems

[0006] Embodiments of the present invention include a bipolar membrane comprising an anion exchange layer including an anion exchange membrane, a cation exchange layer including a cation exchange membrane, a cation exchange layer having a thickness different from that of the anion exchange layer so that the water transport rate at the anion exchange layer-cation exchange layer interface is increased, and a catalyst disposed between the anion exchange layer and the cation exchange layer, which catalyzes the water dissociation reaction and includes a plurality of ionized sites having the characteristics of proton donation, proton extraction, or a combination thereof, whereby the plurality of ionized sites enhance the electric field at the anion exchange layer-cation exchange layer interface.

[0007] In another embodiment, the catalyst includes a material selected from the group consisting of two-dimensional materials, graphene oxide, metal oxides, titanium-based polyvalent catalysts, nanomaterials, polymers, and any combination thereof.

[0008] In an additional embodiment, the catalyst layer further includes an ionomer.

[0009] In a further embodiment, the plurality of ionized sites have different pK aIt contains a functional group of value.

[0010] In yet another embodiment, the anion exchange membrane is selected from the group consisting of SELEMION (registered trademark), NEOSEPTA (registered trademark), fumapem (registered trademark) FAA, fumasep (registered trademark) FAP, Sustainion (registered trademark), X37, Versogen (registered trademark), PiperION (registered trademark), Ionomr Aemion (registered trademark), and any combination thereof, and the cation exchange membrane contains Nafion (registered trademark).

[0011] In another additional embodiment, the thickness of the bipolar membrane is 70 microns or more.

[0012] In yet another embodiment, the anion exchange layer has a thickness of less than 100 microns and is thinner than the cation exchange layer.

[0013] In yet another embodiment, the cation exchange layer has a thickness of less than 100 microns and is thinner than the anion exchange layer.

[0014] In yet another embodiment, the membrane is configured to be part of an electrodialysis cell.

[0015] In yet another embodiment, the electrodialysis cell has a configuration selected from the group consisting of an H cell, a cell stack, a flow cell, and a flow stack.

[0016] In yet another additional embodiment, the electrodialysis cell includes cathodes and anodes containing materials selected from the group consisting of metals, alloys, nickel, nickel-based alloys, copper, copper-based alloys, titanium, titanium-based alloys, iron, iron-based alloys, stainless steel, platinum, gold, silver, carbon, carbon cloth, vitreous carbon, graphite, and any combination thereof.

[0017] In yet another embodiment, the electrodialysis cell is part of a carbon recovery system, an electrochemical conversion system, an energy storage system, a water splitting system, or a carbon dioxide reduction system.

[0018] In yet another embodiment, the carbon recovery system is a direct ocean recovery system.

[0019] In another additional embodiment, the electrodialysis cell operates for 60 hours or more at a current density of 100 mA / cm 2 or higher and a voltage of 1.5 V or lower.

[0020] An additional embodiment is an electrodialysis cell comprising an anion exchange layer including an anion exchange membrane, a cation exchange layer including a cation exchange membrane, a cation exchange layer having a thickness different from that of the anion exchange layer such that the water transport rate at the anion exchange layer-cation exchange layer interface is increased, and a catalyst disposed between the anion exchange layer and the cation exchange layer, the catalyst catalyzing a water dissociation reaction and including a plurality of ionized sites having the characteristics of proton donation, proton extraction, or a combination thereof, so that the plurality of ionized sites enhance an electric field at the anion exchange layer-cation exchange layer interface, and an electrodialysis cell comprising a self-supporting bipolar membrane and an anode and a cathode with the self-supporting bipolar membrane disposed therebetween.

[0021] In yet another embodiment, the catalyst comprises a material selected from the group consisting of two-dimensional materials, graphene oxide, metal oxides, titanium-based polyvalent catalysts, nanomaterials, polymers, and any combination thereof.

[0022] In still yet another embodiment, the catalyst layer further comprises an ionomer.

[0023] In yet another embodiment, the plurality of ionized sites comprise functional groups with different pK a values.

[0024] ]> In yet another embodiment, the anion exchange membrane is selected from the group consisting of SELEMION (registered trademark), NEOSEPTA (registered trademark), fumapem (registered trademark) FAA, fumasep (registered trademark) FAP, Sustainion (registered trademark), X37, Versogen (registered trademark), PiperION (registered trademark), Ionomr Aemion (registered trademark), and any combination thereof, and the cation exchange membrane includes Nafion (registered trademark).

[0025] In yet another embodiment, the thickness of the bipolar membrane is 70 microns or more.

[0026] In yet another embodiment, the anion exchange layer has a thickness of less than 100 microns and is thinner than the cation exchange layer.

[0027] In yet another embodiment, the cation exchange layer has a thickness of less than 100 microns and is thinner than the anion exchange layer.

[0028] In yet another embodiment, the electrodialysis cell has a configuration selected from the group consisting of an H cell, a cell stack, a flow cell, and a flow stack.

[0029] In still yet another embodiment, the cathode and anode include materials selected from the group consisting of metals, alloys, nickel, nickel-based alloys, copper, copper-based alloys, titanium, titanium-based alloys, iron, iron-based alloys, stainless steel, platinum, gold, silver, carbon, carbon cloth, glassy carbon, graphite, and any combination thereof.

[0030] In another additional embodiment, the electrodialysis cell is configured to be part of a carbon recovery system, an electrochemical conversion system, an energy storage system, a water splitting system, or a carbon dioxide reduction system.

[0031] In still yet another embodiment, the carbon recovery system is a direct ocean recovery system.

[0032] In yet another embodiment, the electrodialysis cell operates for 60 hours or more at a current density of 100 mA / cm 2 or higher and a voltage of 1.5 V or lower.

[0033] A further embodiment is a method of direct ocean recovery, comprising: contacting a water source containing dissolved carbon with a bipolar membrane, the bipolar membrane comprising an anion exchange layer containing an anion exchange membrane and a cation exchange layer containing a cation exchange membrane, the cation exchange layer having a different thickness than the anion exchange layer so as to increase the water transport rate at the anion exchange layer-cation exchange layer interface, and a catalyst disposed between the anion exchange layer and the cation exchange layer, the catalyst catalyzing a water dissociation reaction and comprising a plurality of ionization sites having the properties of proton donation, proton extraction, or a combination thereof, such that the plurality of ionization sites enhance an electric field at the anion exchange layer-cation exchange layer interface; recovering a carbon dioxide gas stream, the bipolar membrane enhancing the production efficiency of the carbon dioxide gas stream; recovering an output water stream having a lower dissolved carbon concentration than the water source; and a method comprising the steps.

[0034] In yet another embodiment, the catalyst comprises a material selected from the group consisting of two-dimensional materials, graphene oxide, metal oxides, titanium-based polyvalent catalysts, nanomaterials, polymers, and any combination thereof.

[0035] In yet another embodiment, the catalyst layer further comprises an ionomer.

[0036] In yet another embodiment, the plurality of ionization sites comprise functional groups with different pK a values.

[0037] In yet another embodiment, the anion exchange membrane is selected from the group consisting of SELEMION (registered trademark), NEOSEPTA (registered trademark), fumapem (registered trademark) FAA, fumasep (registered trademark) FAP, Sustainion (registered trademark), X37, Versogen (registered trademark), PiperION (registered trademark), Ionomr Aemion (registered trademark), and any combination thereof, and the cation exchange membrane includes Nafion (registered trademark).

[0038] In yet another embodiment, the thickness of the bipolar membrane is 70 microns or more.

[0039] In yet another embodiment, the anion exchange layer has a thickness of less than 100 microns and is thinner than the cation exchange layer.

[0040] In still yet another embodiment, the cation exchange layer has a thickness of less than 100 microns and is thinner than the anion exchange layer.

[0041] In yet another embodiment, the bipolar membrane is part of an electrodialysis cell.

[0042] In a further additional embodiment, the electrodialysis cell has a configuration selected from the group consisting of an H cell, a cell stack, a flow cell, and a flow stack.

[0043] In still yet another embodiment, the electrodialysis cell includes cathodes and anodes comprising a material selected from the group consisting of metals, alloys, nickel, nickel-based alloys, copper, copper-based alloys, titanium, titanium-based alloys, iron, iron-based alloys, stainless steel, platinum, gold, silver, carbon, carbon cloth, vitreous carbon, graphite, and any combination thereof.

[0044] In still yet another embodiment, the water source is selected from the group consisting of natural seawater, river water, pretreated seawater, or any combination thereof.

[0045] Further embodiments and features are, in part, described below, in part will be apparent to those skilled in the art upon examination of this specification, or may be learned by practice of the present disclosure. A further understanding of the nature and advantages of the present disclosure can be realized by reference to the remaining portions of this specification and the drawings, which form a part of this disclosure.

[0046] The description will be more fully understood with reference to the following drawings, which are presented as exemplary embodiments of the invention and should not be construed as a complete description or interpretation of the scope of the invention.

Brief Description of the Drawings

[0047]

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[56] ] Shows the average GrOx surface charge in the BPM CL according to one embodiment.

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[0048] In the description of the drawings, all the catalyst site portions of [FIG. 47A] and [FIG. 47B] are JPEG2025524332000080.jpg971, [FIG. 59A] and [FIG. 59B] show a speed improvement of JPEG2025524332000081.jpg1539.

Mode for Carrying Out the Invention

[0049] Next, referring to the drawings, asymmetric bipolar membranes (BPMs) according to various embodiments are illustrated. In some embodiments, the asymmetric bipolar membrane can be catalyzed. Many embodiments implement a catalyzed asymmetric bipolar membrane in an electrodialysis cell for carbon recovery. A catalyzed asymmetric bipolar membrane according to certain embodiments can be self-supporting, mechanically stable, and structurally intact during the electrodialysis process. In some embodiments, the catalyzed asymmetric bipolar membrane is used for the recovery of carbon dioxide by direct ocean recovery and / or direct air recovery. Carbon recovery processes according to many embodiments can recover dissolved inorganic carbon in water sources including (but not limited to) oceans, rivers, lakes, reservoirs, desalinated water, synthetic seawater, and seawater substitutes. The water source can be pretreated with acidic and / or alkaline solutions or used without pretreatment. Examples of dissolved inorganic carbon include (but are not limited to) dissolved carbon dioxide, bicarbonate, carbonate, carbonic acid, minerals, and precipitates.

[0050] The ocean contains more carbon in the form of dissolved inorganic carbon than atmospheric carbon dioxide (CO2) on a per volume molar basis. The ocean is the largest carbon reservoir in the exchange with atmospheric CO2, and as a result, the ocean exerts a controlling force on atmospheric CO2 levels. Dissolved inorganic carbon in the ocean occurs mainly in three inorganic forms: free dissolved carbon dioxide (CO2(aq)), bicarbonate ions (HCO3 - ), and carbonate ions (CO3 2- ). Most of the dissolved inorganic carbon in the ocean is in the form of HCO3 - . FIG. 1 shows a schematic diagram of dissolved inorganic carbon in the ocean. When CO2 gas dissolves in the ocean, it interacts with water according to Equation 1 to form multiple different compounds.

[0051]

Equation

[0052] One method of direct ocean recovery by electrodialysis is to shift the CO2 - bicarbonate equilibrium or balance towards the dissolved CO2 side by acidifying seawater. The acidified stream can pass through a liquid - gas membrane contactor that recovers CO2 gas from the dissolved CO2 in the water stream. The catalyzed BPM according to many embodiments promotes water electrolysis in the BPM. The increase in proton concentration as a result of water electrolysis enables the equilibrium to shift towards the dissolved CO2 side, thereby enhancing the carbon recovery efficiency. The BPM electrodialysis cell can be used for efficient water separation, CO2 reduction, and direct ocean recovery (DOC) of CO2.

[0053] Conventional BPMs become unstable in the electrodialysis cell when the current density exceeds about 100 mA / cm 2 . Such BPMs are limited to low current densities (less than about 100 mA / cm 2 ), due to the water transport limit of the membrane, which leads to damage in the membrane junction region. To economically enable CO2 recovery from ocean water using a BPM electrodialysis system, a BPM that can withstand a current density of 100 mA / cm 2 or higher is required.

[0054] Many embodiments are 100 mA / cm 2 or higher, or 200 mA / cm 2 or higher, or 300 mA / cm 2 or higher, or 400 mA / cm 2 or higher, or 500 mA / cm 2 or higher, or 600 mA / cm 2 or higher, or 700 mA / cm 2 or higher, or 800 mA / cm 2 or higher, or 900 mA / cm 2 or higher, or 1 A / cm 2Implement a catalytic asymmetric BPM that is stable at the above current density. The catalytic BPM according to some embodiments can be operated at a voltage of about 1.5 V or less or about 1.0 V or less. The catalytic BPM according to many embodiments exhibits voltage stability for a long period of time (but not limited to) 60 hours or more, or 80 hours or more, or 100 hours or more, or 110 hours or more, or 120 hours or more, or 130 hours or more, or 140 hours or more, or 150 hours or more, or 500 hours or more, or 1000 hours or more, or more than 1000 hours. In certain embodiments, the catalytic asymmetric BPM has a current density of about 80 mA cm -2 and maintains a stable voltage for 1100 hours or more, or a current density of about 500 mA cm -2 and maintains a stable voltage for about 100 hours, and / or a current density of about 1 A cm -2 and maintains a stable voltage for about 60 hours.

[0055] In many embodiments, the asymmetric BPM includes a CEL and an AEL, with one layer being thinner than the other. In some embodiments, the CEL can be made thinner than the AEL. In certain embodiments, the AEL can be made thinner than the CEL. The thinner layer of the asymmetric BPM can enable fast water transport at the CEL-AEL junction. The thinner layer can have a thickness of less than about 100 microns, or about 15 microns to about 100 microns, or about 15 microns to about 20 microns, or about 20 microns to about 25 microns, or about 25 microns to about 30 microns, or about 30 microns to about 35 microns, or about 35 microns to about 40 microns, or about 40 microns to about 45 microns, or about 45 microns to about 50 microns, or about 50 microns to about 100 microns. The total thickness of the asymmetric BPM can be about 50 microns to about 1 cm, or about 50 microns to about 100 mm, or about 50 microns to about 10 mm, or about 50 microns to about 1 mm. The thicker the BPM, the stronger the mechanical support and the more stable the film can be formed.

[0056] In some embodiments, the asymmetric BPM can be self - standing without external support such as (but not limited to) gaskets and / or clamps. The self - standing BPM can have a thickness of about 50 microns or more, or about 70 microns or more, or about 90 microns or more, or about 100 microns or more, or about 150 microns or more, or about 200 microns or more, or about 300 microns or more.

[0057] Various types of CEM and AEM can be used for CEL and AEL respectively. Any combination of CEM and AEM can be used in an asymmetric BPM. Some embodiments use commercially available off-the-shelf CEM and / or AEM. Some embodiments form AEM and / or CEM using polymer powder and / or ionomer. In some embodiments, the powder and / or ionomer can be cast (but not limited to) by spin coating to form a layer of AEM and / or CEM. The thickness of the AEM and / or CEM can be determined by scratching the spin-coated deposition layer on the substrate and scanning it with a profiler. The BPM can be assembled by pressing the CEM and AEM together using tools such as hands and / or (but not limited to) clamps, clips, or screws. In some embodiments, the BPM can be manufactured by (but not limited to) spin coating, hot pressing, casting, sandwiching, and any combination thereof. Some embodiments modify the CEM and / or AEM by coating with ionomer (but not limited to) before assembling to form the BPM. The ionomer-modified CEM and / or AEM can be formed by a process including (but not limited to) drop casting, spin coating, spray coating, and any combination thereof. Some embodiments form AEM and / or CEM using ionomer by a process including (but not limited to) drop casting, spin coating, spray coating, and any combination thereof. In many embodiments, the catalyst can be spin-coated on the CEM and / or AEM and heated at a high temperature (about 100 °C or higher) for a generally constant period (1 minute or more, 2 minutes or more, 5 minutes or more, etc.) to dry the catalyst ink. The spin coating and heating of the catalyst can be repeated until the desired catalyst loading is reached. In many embodiments, when depositing the catalyst ink or the bonding layer on the dried membrane surface, water should be removed or dried rapidly, otherwise the dried membrane may become distorted and wrinkled. In some embodiments, when selecting the membrane of the BPM, the thermal stability of the AEM and / or CEM at a temperature exceeding about 40 °C is preferred.Thermal stability can prevent the peeling of the membrane during the long-term operating cycle of the BPM. In many embodiments, the AEM and / or CEM can consist of (but are not limited to) polymers, acids (H. + ) forms of perfluorosulfonic acid (PFSA) / polytetrafluoroethylene (PTFE) copolymers, functionalized poly(arylpiperidinium) polymers, hydrocarbon resins, and poly(arylpiperidinium) resins. The asymmetric BPM according to a particular embodiment selects an AEM that is stable in an alkaline solution. Examples of AEMs include (but are not limited to) SELEMION®, NEOSEPTA®, fumapem FAA, fumasep FAP, Sustainion® X37, Versogen® PiperION, Ionomr Aemion®, Fumasep membrane, Sustainion® membrane, Sustainion® ionomer, PiperION ionomer, and PiperION membrane. Examples of CEMs include (but are not limited to) Nafion®, Nafion® ionomer, Nafion® membrane, and / or any of a wide variety of Nafion® membranes. Examples of ionomers include (but are not limited to) Nafion® D520 ionomer and Versogen® PiperION-A5 ionomer. As can be readily understood, any of a wide variety of AEMs and / or CEMs and / or ionomers can be appropriately utilized according to the specific application requirements of various embodiments of the present invention. In many embodiments, in order to form a structurally stable self-supporting BPM having a desired current density, the materials of the CEM and / or AEM, the ionic conductivity of the CEM and / or AEM, the thickness of the CEM and / or AEM, the thickness of the BPM, the modification of the CEM and / or AEM, and / or the method of forming the BPM can be selected.

[0058] In various embodiments, the asymmetric BPM comprises a catalyst for CEL and AEL junctions. The catalyst can promote water dissociation. The catalyst according to many embodiments has multiple ionization sites. The ionization sites can be different charged groups (positive and / or negative charges) and / or can be modified with these. The charged groups are such that the ionization sites have different pK a and / or pK b values so that they can have different pK a and / or pK b values. In some embodiments, the ionization sites can be (but are not limited to) proton-donating sites and / or proton-withdrawing sites. The ionization sites can be functional groups of polymers, nanomaterials, nanoparticles, mixtures of various nanomaterials and nanoparticles, 2D materials, and any combination thereof. The modification of the ionization sites should be compatible with other properties of the catalyst such as (but not limited to) the dielectric constant, the rigidity of the backbone material, etc. In many embodiments, a catalyst having multiple pK a or pK b values can generate a larger electric field at the AEM and CEM junctions compared to a catalyst having a single pK a or pK b value. By being able to generate a large electric field and catalyze the water dissociation reaction, an asymmetric BPM with a catalyst having desired properties can be used in an electrodialysis cell. Such properties include (but are not limited to) being structurally stable and intact even when used at a high current density (100 mA / cm 2 or higher) for 60 hours or more. Examples of catalysts for the asymmetric BPM include (but are not limited to) two-dimensional catalyst materials, graphene oxide, metal oxides, titanium-based polyvalent catalysts, nanomaterials, polymers, and any combination thereof. Graphene oxide has a low overvoltage for water dissociation and pK aSince it has an ionization site with a clear value, some embodiments use graphene oxide as a catalyst for BPM. The catalyst can be dissolved in water. Some embodiments dissolve the catalyst in a solution containing an ionomer to improve adhesion to the CEL and / or AEL. The dissolution solvent can be deposited on the CEL-AEL junction by a variety of processes including (but not limited to) drop casting, spin coating, spray coating, and any combination thereof. A uniform and flat catalyst morphology can improve AEL and / or CEL adhesion. In some embodiments, the electrostatic force due to the charged groups on the catalyst can also improve the adhesion of the asymmetric BPM and prevent delamination. Various loads such as (but not limited to) concentration, weight, and / or number of layers can be selected to achieve an optimal catalyst loading for the asymmetric BPM. Some embodiments vary the amount of catalyst supported by changing the number of layers of the catalyst solution (or ink) spin-coated on the CEM or AEM during BPM manufacture. The catalyst layer can have various thicknesses from about 10 nm to about 2000 nm, or from about 10 nm to about 100 nm, or from about 10 nm to about 1000 nm, or from about 100 nm to about 1000 nm, or from about 200 nm to about 1000 nm, or from about 300 nm to about 500 nm. To form a uniform and stable catalyst layer and obtain a stable BPM with a desired current density, the catalyst material (or combination of materials), catalyst concentration, catalyst solution, ionomer in the catalyst solution, catalyst thickness, and / or catalyst deposition method can be selected.

[0059] A current can be applied to the BPM using electrodes such as an anode and a cathode. In reverse bias, the cathode can be connected to the CEL and the anode can be connected to the AEL. The anode and cathode can each have a supporting electrolyte solution such as anolyte and catholyte. The cathode and anode can be made of various materials. Examples of electrode materials include, but are not limited to, metals, alloys, nickel, nickel-based alloys, copper, copper-based alloys, titanium, titanium-based alloys, iron, iron-based alloys, stainless steel, platinum, gold, silver, carbon, carbon cloth, vitreous carbon, graphite, and any combination thereof. The electrodes can be of various configurations such as, but not limited to, foils, films, layers, coatings, plates, and any combination thereof. The electrodes can be of various sizes with at least one dimension ranging from 1 mm to about 100 cm. Examples of supporting electrolyte solutions include, but are not limited to, NaCl-HCl solutions, K4Fe(CN)6, K3Fe(CN)6, FeCl2, FeCl3, KOH, K2CO3, KHCO3, NaCl, and any combination thereof.

[0060] In many embodiments, the catalyzed asymmetric BPM can be incorporated into various electrodialysis cells including, but not limited to, H cells, flow cells, cell stacks, and any combination thereof. The BPM is mechanically and structurally stable so as to be self-standing in the electrodialysis cell. The electrodialysis stack can be formed by a configuration of a plurality of ion exchange membranes between the anode and the cathode. The zero cell stack according to some embodiments can include a BPM having two electrolyte outer chambers. In some embodiments, a one-cell stack, a two-cell stack, a three-cell stack, etc. have a group of membranes (in the order of AEM, CEM, and BPM) repeated once, twice, three times, etc. within the zero cell stack. In many embodiments, a single cell stack can consist of BPM, AEM, CEM, and BPM from the anode towards the cathode. In many embodiments, a single cell stack consists of an anode, an anolyte chamber, a CEM, a dilution chamber, an AEM, an acid chamber, a BPM, a base chamber, a CEM, a catholyte, and a cathode.

[0061] In various embodiments, the asymmetric BPM can be self - supporting (but not limited to) without external support such as a gasket. The BPM is mechanically stable through the operation of the electrodialysis cell. The CEM and / or AEM can expand when hydrated during water dissociation. Many embodiments select a CEM and / or AEM having a similar swelling ratio upon hydration to maintain the structural stability of the BPM during operation. The BPM can achieve mechanical stability based on the total thickness of the membrane. In some embodiments, the thick layer of the asymmetric BPM contributes to the mechanical stability of the asymmetric BPM and enables self - supporting operation. Many embodiments select the thickness of the AEM and / or CEM based on the total thickness required to maintain mechanical stability.

[0062] Many embodiments implement a planar BPM. The BPM can be about 1 cm 2 ~ about 1 m 2 or about 1 cm 2 ~ about 10 cm 2 or about 10 cm 2 ~ about 50 cm 2 or about 50 cm 2 ~ about 1 m 2 or about 1 m 2 and can be of various sizes having a planar active surface area greater than.

[0063] Figures 2A and 2B conceptually show a catalyzed asymmetric BPM according to one embodiment. Figure 2A shows a catalyzed asymmetric BPM having a thin AEL102 and a thick CEL104. The AEL102 can have a thickness of about 15 microns to about 100 microns. The CEL104 can have a greater thickness than the AEL102. A catalyst layer (CL) 103 can be formed at the bipolar junction 106 between the AEL102 and the CEL104. At the bipolar junction 106, water can dissociate into protons and hydroxide ions JPEG2025524332000083.jpg1351. The thin AEL102 improves the water transport rate at the junction so that the asymmetric BPM has a higher current density compared to a symmetric configuration. The CL103 contains a catalyst that can facilitate the water dissociation reaction at the bipolar junction 106.

[0064] Figure 2B shows a catalyzed asymmetric BPM having a thick AEL102 and a thin CEL104. CEL104 can have a thickness of from about 15 microns to about 100 microns. The AEL can have a greater thickness than CEL104. The catalyst layer 103 can be formed at the bipolar junction 106 between the AEL102 and the CEL104. At the bipolar junction 106, water can dissociate into protons and hydroxide ions. JPEG2025524332000084.jpg1351. The thin CEL104 improves the water transport rate at the junction so that the asymmetric BPM has a higher current density compared to a symmetric configuration. CL103 contains a catalyst that can promote the water dissociation reaction at the bipolar junction 106.

[0065] Under reverse bias, the anode 101 can be formed adjacent to the AEL102 and the cathode 105 can be formed adjacent to the CEL104. When a current is applied to the BPM, the H + and OH - ions generated by the water dissociation at the junction 106 can carry an ionic current. Since the ions cannot be transported across the BPM, the generated H + can be transported through the CEL104 and the OH - can be transported through the AEL102.

[0066] As can be readily appreciated, the asymmetric BPM can have various configurations that vary in membrane material, membrane layer thickness, membrane deposition process, catalyst filling process, catalyst material, use of ionomer in the junction and / or catalyst solution, and / or catalyst deposition method. The BPM can be manufactured by pressing together an AEM and a CEM, or casting from an ionomer, or spin coating from an ionomer, or a combination of these processes.

[0067] Asymmetric catalytic BPMs can be incorporated into electrodialysis cells for various applications. Examples of such applications can include, but are not limited to, long-term energy storage, electrochemical conversion reactions, water separation reactions, carbon dioxide reduction reactions, electrochemical applications at high current densities, carbon capture, direct ocean capture, and / or direct air capture.

[0068] Many embodiments incorporate a catalytic asymmetric BPM for direct ocean capture. The BPMs according to some embodiments are stable under electrodialysis cell operating conditions and can achieve a current density of about 100 mA / cm 2 or more at an applied voltage of less than about 1.5 V. FIGS. 3A and 3B conceptually show a catalytic asymmetric BPM for DOC configured in a three-compartment electrodialysis cell according to one embodiment of the present invention. FIG. 3A shows a catalytic asymmetric BPM having a thin AEL202 and a thick CEL204. FIG. 3B shows a catalytic asymmetric BPM having a thick AEL202 and a thin Cl204. A catalyst layer (CL) 203 can be formed at the bipolar junction 206 between the ALE202 and the CEL204. At the bipolar junction 206, water can dissociate into protons and hydroxide ions JPEG2025524332000085.jpg1351. The thin AEL202 (or CEL204) improves the water transport rate at the junction so that the asymmetric BPM has a higher current density compared to a symmetric configuration. The CL203 includes a catalyst that can promote the water dissociation reaction at the bipolar junction 106.

[0069] Under reverse bias, the H + and OH - ions generated by water dissociation at the junction 206 can carry an ionic current. Since the ions cannot be transported across the BPM, the generated H + can be transported through the CEL204 and the OH - can be transported through the AEL202. At the CEL-AEL junction, the mobile protons and hydroxide ions from the CEL and the AEL react to form water, neutralize the mobile ions, and form a space charge depletion region of several nanometers, resulting in about 10 8 Vm -1~10 9 Vm -1 An electric field can be generated. Under reverse bias, the electric field at the junction 206 accelerates the hydrolysis dissociation by the second Wien effect to H + and OH - generation can be promoted, whereby an ionic current can be supplied to the CEL204 and AEL202 to form a pH gradient in the BPM. The catalyst of CL203 can increase the electric field by accelerating the hydrolysis dissociation.

[0070] Seawater has a natural pH of about 8.1. Natural seawater can be pretreated using a seawater pretreatment system. The pretreated (or natural) seawater can be acidified by adding an acid to lower the pH to about 4 or less. The water source 212 (such as natural seawater or acidified seawater) can be added to the water channel 215 on the CEL204 side of the asymmetric BPM. Bicarbonate ions (HCO3 - ) in natural seawater can react with H + to form CO2. The AEM216 is arranged between the CEL204 side of the asymmetric BPM and the water channel 215 to prevent H + ions from exiting the acidified stream 214. After recovering and / or neutralizing the acidified stream 214, the partially decarbonated water can be returned to the ocean. The generated CO2 gas can be recovered later for industrial and / or other uses. The water source 212 can be added to the water channel 215 on the AEL202 side of the asymmetric BPM. The CM217 is arranged between the AEL202 of the asymmetric BPM and the water channel 215 to prevent OH - ions from exiting the basified stream 213. CO2 reacts with OH - to form CHO3 -can be formed. The basified stream 213 can be recovered for industrial and / or other uses. In many embodiments, the water source 212 can enter the system either simultaneously or independently. In some embodiments, the acidified stream 214 can be recovered as acidified seawater for further decarbonization treatment. In many embodiments, the acidified stream 214 can be circulated to the same electrodialysis cell or a different electrodialysis cell of the stack as the water source 212. In some embodiments, acidified and / or natural seawater can be introduced into the water channel 215. In many embodiments, acidified seawater can be added to one water channel while natural seawater is added to a different water channel, or acidified seawater can be added to all water channels, or natural seawater can be added to all water channels.

[0071] The described apparatus, system, and method should not be construed as being limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with each other. The methods, systems, and apparatus of the present disclosure are not limited to any particular aspect, feature, or combination thereof, and there need not be one or more specific advantages or problems solved by the methods, systems, and apparatus of the present disclosure.

[0072] For the sake of presentation, some operations of the methods of the present disclosure are described in a particular order, but this presentation method includes permutation as well, unless a particular order is required by the specific language described below. For example, the operations described sequentially can, in some cases, be permuted or performed simultaneously. Further, for simplicity, the accompanying drawings may not show the various ways in which the methods, systems, and apparatus of the present disclosure can be used with other systems, methods, and apparatus.

[0073] The systems and methods of the catalyzed asymmetric BPM system according to various embodiments of the present invention are further described below.

[0074] Catalyzed Asymmetric Bipolar Membrane The BPM can be used in electrochemical technologies such as water electrolysis, CO2 conversion, and carbon removal. The BPM can be incorporated into a brine-fed electrodialysis cell used for pH swing-based direct air capture (DAC), or for the extraction of dissolved inorganic carbon from seawater for direct ocean capture (DOC) and ocean deacidification. In many embodiments, the catalyzed asymmetric BPM can maintain stability in an electrodialysis cell while withstanding high current density operation under reverse bias. Such a BPM can be intact and operational in the separated acidic and alkaline environments within the electrodialysis cell. By being able to maintain a large pH difference, the desired cathode and anode local reaction environments are obtained to achieve high activity, selectivity, and stability of the electrode catalyst based on elements abundant on Earth. In some embodiments, the BPM can operate at a current density of about 500 mA cm -2 or greater, or about 1 A cm -2 or greater and a voltage of about 1.5 V or less.

[0075] Many embodiments implement a BPM comprising a CEL including (but not limited to) Nafion® 212, an AEL including (but not limited to) PiperION® A15R, and a water dissociation (WD) catalyst including (but not limited to) graphene oxide (GrOx). FIG. 4A shows a catalyzed asymmetric BPM according to an embodiment of the present invention. FIG. 4B shows a cross-sectional scanning electron microscope image of a BPM layer according to an embodiment. The catalyzed asymmetric BPM includes a Nafion® 212 CEL 403 with a thickness of about 50 μm, a PiperION® A15R AEL 401 with a thickness of about 20 μm, and a GrOx WD catalyst layer 402 with a thickness of about 200 nm to about 1000 nm. The chemical structure of each layer of the GrOx-catalyzed asymmetric BPM is shown along with the associated catalytic WD improvement reaction. By thinning the AEL and incorporating the GrOx catalyst, the BPM can overcome the water transport limitation and operate at a high current density of about 500 mA cm -2 or greater. GrOx has a distinct pK aIt has three ionized sites with values. The BPM can operate beyond the thermodynamic potential required for WD, with an overpotential of about 1 A cm -2 or more and less than about 250 mV. The BPM can operate at a current density of about 80 mA cm -2 for about 1100 hours, and / or at a current density of about 500 mA cm -2 for about 100 hours, and / or at a current density of about 1 A cm -2 for about 60 hours. The performance shows efficient water transport and stability of the CEL / AEL junction through the BPM.

[0076] Figure 5 shows the measured film thickness according to one embodiment. The film thickness can vary from about 200 nm to about 4 microns depending on the film material and the number of deposited layers.

[0077] Figures 6A - 6D conceptually show a non - limiting method for manufacturing the BPM. Figure 6A conceptually shows the formation of the BPM by spin - coating the AEM onto the CEM. Figure 6B conceptually shows the formation of the BPM by hot - pressing the combined AEM and CEM. Figure 6C conceptually shows the casting of the CEM onto the substrate and subsequent casting of the AEM onto the CEM. Figure 6D conceptually shows the sandwiching of the pre - heated AEM onto the pre - heated CEM.

[0078] Figure 7 shows the process of manufacturing a BPM according to one embodiment. This process includes placing the preheated CEM 702 on a clean slide glass 701, gently pressing it with a Kimwipe (registered trademark) and drying it, flattening the membrane so that there are no air pockets between the slide glass and the membrane, and taping the four sides 703, dropping a catalyst 704 onto the CEM after the start of spinning to prevent the membrane from getting wet and wrinkled, putting the CEM with the catalyst layer into an oven at about 100 °C for about 2 minutes to completely dry the catalyst ink, repeating the spin coating and baking of the catalyst until the desired loading amount is reached, cutting the CEM just inside the tape to wet the membrane again, gently placing the wet AEM on top of the CEM with the catalyst layer, and flattening and stretching it to remove air bubbles. In some embodiments, the process of manufacturing a BPM further includes using a Nafion (registered trademark) ionomer as a binder between the CEM and the AEL, and subjecting the fully laminated BPM to a heat treatment. In some embodiments, the GrOx catalyst ink is made with Nafion (registered trademark) and PiperION (registered trademark) ionomers as binders. In some embodiments, the AEM and / or CEM are made of Nafion (registered trademark) and PiperION (registered trademark) membranes. In some embodiments, the catalyst ink containing the Nafion (registered trademark) ionomer disperses and suspends well, while the catalyst ink containing the PiperION (registered trademark) ionomer forms aggregates in the ink.

[0079] Figure 8 shows the voltages at different current densities of various spin-coated BPMs. The Sustainion (registered trademark) AEM spin-coated on the Nafion (registered trademark) 212 CEM reaches a high voltage (about 10 V) at a low current density (less than about 100 mA / cm 2 ). The Nafion (registered trademark) CEM spin-coated on the Fumasep (registered trademark) AEM has a current density of about 400 mA / cm 2 ~ about 500 mA / cm 2When [conditions], it operates within the same voltage range as the PiperION® AEM spin-coated on Nafion® CEM. The PiperION® AEM spin-coated on Nafion® CEM can operate at a low voltage when the current density is about 100 mA / cm 2 ~ about 400 mA / cm 2 When [conditions].

[0080] Figure 9 shows the voltages at different current densities of the BPMs of Nafion® CEM and the thinner PiperION® AEM manufactured by casting, hot pressing, and sandwiching. The BPM performance of the electrodialysis cell can be affected by the BPM manufacturing method. The hot-pressed combination of Nafion® 212 and PiperION® 15R has the same voltage range as the one where 50 μm of Nafion® 212 is cast on 10 μm of PiperION® 15R when the current density is about 0 mA / cm 2 ~ about 400 mA / cm 2 When [conditions]. The sandwiched combination of Nafion® 212 and PiperION® 15R can operate in a low voltage range (less than about 5 V) when the current density is about 100 mA / cm 2 ~ about 500 mA / cm 2 When [conditions]. By changing the manufacturing method, the operating voltage of the BPM at high current density can be lowered.

[0081] Figure 10 shows the voltages at different current densities of the BPMs with various catalyst materials. By adding a catalyst, the operating voltage of the BPM at high current density can be lowered. Compare the BPMs of Nafion® AEM and PiperION® CEM containing various catalyst materials. The BPMs of Nafion® AEM and PiperION® CEM sandwiched with NiO2 catalyst reach a high voltage (about 6 V) when the current density is about 200 mA / cm 2 When [conditions]. The BPMs of Nafion® AEM and PiperION® CEM sandwiched with IrOx catalyst reach a high voltage (about 6 V) when the current density is about 100 mA / cm 2reaches a high voltage (about 10V) when it is less than. The BPM of Nafion® AEM and PiperION® CEM sandwiched with the GO catalyst operates at a low voltage (less than about 4V) when the current density is about 0 mA / cm 2 ~ about 500 mA / cm 2 and can operate at a low voltage (less than about 1V) when the current density is about 0 mA / cm. The BPM of Nafion® AEM and PiperION® CEM sandwiched with the GrOx catalyst 2 ~ about 500 mA / cm 2 and can operate at a low voltage (less than about 1V) when the current density is about 0 mA / cm. The catalyst material can lower the operating voltage range of the BPM of the electrodialysis cell.

[0082] The Nafion® ionomer can be used as a binder between the CEL and the AEL. Heat treatment can be applied to the fully laminated BPM to improve the adhesion. Figure 11 shows the voltages of different BPMs at different current densities with the addition of the Nafion® ionomer adhesive. During manufacturing, the catalyst layer is deposited on the CEM or AEM. The catalyst-supported membrane is heated at a high temperature. Subsequently, an alternative AEM or CEM is formed on the heat-treated membrane and the catalyst. The alternative AEM and CEM can be manufactured using the Nafion® ionomer adhesive to assist in lamination. After adding an additional membrane, the manufactured BPM can be heated at a high temperature. The BPM heat-treated after lamination reaches a high voltage (about 4V) when the current density reaches about 200 A / cm 2 The BPM heat-treated after lamination with the addition of the Nafion® ionomer adhesive has a voltage range (less than about 3V) similar to that of the BPM heat-treated after lamination without the addition of the Nafion® ionomer adhesive. The commercially available Fumasep® BPM has a current density of about 800 mA / cm 2When it reaches, it reaches a high voltage (about 6V). BPMs without heat treatment after lamination operate in a low voltage range (less than about 3V) in the high current density region. BPMs with a GO catalyst have a voltage range (less than about 3.5V) similar to that of BPMs manufactured with a wet Nafion® ionomer adhesive and a heat-treated GrOx catalyst. BPMs manufactured with a Nafion® ionomer adhesive and a heat-treated GrOx catalyst have a current density of about 0 mA / cm 2 ~ about 800 mA / cm 2 and operate at a low voltage (less than about 3V). BPMs manufactured with a Nafion® ionomer adhesive and a heat-treated GrOx catalyst have a voltage range similar to that of BPMs manufactured without a Nafion® ionomer adhesive and a heat-treated GrOx catalyst in the low current density region.

[0083] The ionomer can be added to the catalyst material. The ionomer can act as a binder. The addition of the ionomer to the catalyst material can be useful for lamination. The addition of the ionomer to the catalyst ink can operate at a high current density and a high voltage. In some embodiments, the GrOx catalyst ink is made of Nafion® ionomer. In some embodiments, the catalyst ink is made of PiperION® ionomer. The BPM is manufactured with Nafion® CEM and PiperION® AEM as the base film on which the catalyst is spin-coated. Figure 12 shows the voltages at different current densities of BPMs manufactured with various combinations of membranes and ionomers. The BPM of Nafion® 212 CEM and PiperION® 15R AEM with a GO catalyst containing PiperION® ionomer reaches a high voltage (about 4V) when the current density is less than about 100 mA / cm 2 The BPM of Nafion® HP CEM and PiperION® 65 AEM with a GO catalyst containing Nafion® ionomer has a current density of about 1000 mA / cm 2It can operate at a high voltage (about 5V or less) under the following conditions. The BPMs of Nafion® HP CEM and PiperION® 65 AEM with GO catalysts containing PiperION® ionomers have a current density of about 1000 A / cm 2 It can operate at a low voltage (about 3V or less) under the following conditions. The BPMs of Nafion® 212 CEM and PiperION® 15R AEM with GO catalysts containing Nafion® ionomers have a current density of about 1000 A / cm 2 It can operate at a low voltage (about 1.5V or less) under the following conditions. The BPMs of Nafion® HP CEM and PiperION® 65 AEM with GO catalysts containing PiperION® ionomers have a current density of about 400 mA / cm 2 Under the following conditions, it has a voltage range similar to that of the BPMs of Nafion® 212 CEM and PiperION® 15R AEM with GO catalysts containing Nafion® ionomers.

[0084] To accurately understand the performance of a BPM for electrodialysis, some embodiments implement a custom electrodialysis cell to measure BPM performance. It is important that the voltage of the BPM can be directly measured without interference from electrolyte resistance or redox reactions. A Luggin capillary with a reference electrode can be implemented in an H-cell to measure the BPM voltage as close as possible to the surface of the membrane. However, in an H-cell configuration, the acid and base concentrations continue to increase (especially at the surface of the BPM) during the application of bias, so equilibrium cannot be reached at each applied current density. To overcome these challenges in the electrochemical testing of the BPM, a custom electrodialysis cell with a Luggin capillary embedded therein according to some embodiments can flow electrolyte into each chamber. FIG. 13A shows a schematic cross-sectional view of an electrodialysis cell designed for direct testing of a BPM according to one embodiment. FIG. 13B shows a schematic view of a flow cell according to one embodiment. The custom 5-chamber electrodialysis flow cell includes a Luggin capillary 1307, a reference electrode 1304, an anode 1309, a cathode 1301, and flow paths (not shown). The Luggin capillary 1307 with an Ag / AgCl reference electrode 1304 is implemented to enable direct measurement of the BPM voltage without interference from electrolyte resistance. The tip of this capillary is positioned approximately 0.1 mm from the surface of the BPM 1312. The active area of the BPM 1312 of the custom cell is about 1 cm 2 2. The AEM 131, CEM 1310, anode 1309, and cathode 1301 have an active area of about 4 cm 2 2. To ensure equilibrium during the experiment, fresh solution can be continuously flowed through each chamber of the electrodialysis cell, and a plate can be placed under the cell to stir the acid / base chamber using a small magnetic stir bar.

[0085] As the current density increases, the concentrations of acid and base increase, so the solution conductivity also increases. Therefore, the solution iR drop cannot be directly calculated from the initial salt conductivity. By flowing and stopping the acid and base chamber solutions, equilibrium can be achieved within the custom electrodialysis cell, so Equation S9 can be implemented to calculate the resistance contribution from the acid and base solutions. In Equation S9, J is the current density, and κ solutionis the conductivity of NaCl, HCl, or NaOH based on current density and flow rate, and d is the distance of the Luggin capillary tip from the BPM surface (about 0.01 cm). Further, using the calculated equilibrium acid and base concentrations along with Equation S10, the Nernst thermodynamic potential required for WD at a specific current density and flow rate is calculated. The final iR contribution from the AEL and CEL is subsequently calculated using Equation S11 with the membrane conductivity values measured using a four-probe system.

[0086]

Number

[0087] Using an accurate pump for the specific flow rate setting and Equations S1 - S8, the theoretical concentrations of H + and OH - in the acid and base chambers of the electrodialysis cell can be calculated.

[0088] Figure 14 shows the current density versus voltage curve of a reverse-biased asymmetric BPM according to one embodiment. In Region 1, the influence of co-ion crossover on the current is significant. In Region 2, the influence of the movement of hydrolysis products on the current is significant. In Region 3, the influence of the water transport limit on the current is significant. These regions are divided by the limiting currents J lim,1 and J lim,2

[0089] Figure 15 shows the current versus voltage curve of a BPM with a thin AEL having 75 μg cm -2 of GrOx ink operating at a maximum of 2 A cm -2 for a BPM junction. The BPM structure with a thin AEL is shown in Figure 4A.

[0090] ​FIG. 16 shows the current density versus voltage of a GrOx-catalyzed asymmetric BPM compared to the same BPM configuration without a GrOx catalyst at the junction, according to one embodiment. It is demonstrated that the voltage of the catalyzed BPM is lower, indicating that the WD is improved by the electric field in the AEL / CEL junction, and that the speed of WD can be further improved by implementing a catalyst in the inner layer of the BPM. The catalyst layer enables a low operating overvoltage.

[0091] FIG. 17 shows the iR-drop effect of an asymmetric BPM in various solutions, according to one embodiment. FIG. 17 shows the measured voltage of a GrOx-catalyzed asymmetric BPM (diamonds), the voltage with the iR subtracted based on the salt conductivity (squares), and the voltage with the iR subtracted based on the acid / base conductivity (circles). This indicates that the calculation of the voltage contribution of the solution resistance is affected by the conductivity based on the acidification and basification of the solution.

[0092] FIG. 18 shows a plot of current density versus voltage of a GrOx BPM compared to a BPM without a catalyst and a Fumasep BPM at low currents, according to one embodiment. The BPM with GrOx shows a greater co-ion leakage than the one without GrOx.

[0093] FIGS. 19A and 19B show the performance of a GrOx-catalyzed asymmetric BPM, according to one embodiment. FIG. 19A shows the polarization curves of a BPM (about 225 μg cm -2 GrOx supported) and a commercially available Fumasep BPM tested in a custom electrodialysis cell compared to the thermodynamic potential of WD. It is desirable to be able to operate the BPM at a high current density and a low voltage since more acid and base can be generated with low capital and operating costs. The GrOx-catalyzed asymmetric BPM operates at 1 V over a current density range of about 80 mA cm -2 to about 1000 mA cm -2 . In contrast, the performance of the Fumasep® BPM can be limited by water transport or WD kinetics at current densities above about 300 mA cm -2 .

[0094] Figure 19B shows the sum of the voltage contributions due to the WD potential, CEL ohmic loss 1904, AEL ohmic loss 1903, and electrolyte ohmic loss 1902, compared to the measured performance 1901 of the BPM. Figure 19B shows that most of the voltage for the BPM can be attributed to the thermodynamic potential required for WD, indicating that the BPM is optimized for WD near maximum efficiency. The catalyzed asymmetric BPM has a calculated kinetic overvoltage of approximately 126 mV at a current density of about 100 mA cm -2 and a calculated kinetic overvoltage of approximately 144 mV at a current density of about 500 mA cm -2 and a calculated kinetic overvoltage of approximately 242 mV at a current density of about 1 A cm -2 and a calculated kinetic overvoltage of less than approximately 250 mV at a current density of about 1 A cm -2 . The total overvoltage for high current density operation can be further reduced by thinning the CEL layer or increasing the ion exchange capacity of the components of both the CEL and AEL.

[0095] BPMs with Nafion® CEL and PiperION® AEL according to various embodiments exhibit strong mechanical adhesion, likely due to strong electrostatic interactions. No obvious delamination of the AEL and CEL is observed. The catalyzed asymmetric BPM can be mechanically and chemically stable in reverse bias operation as well as in acidic and basic environments. The uniform WD catalyst in the BPM junction minimally interferes with the adhesion between the AEL and CEL. The asymmetric BPM can stand on its own during operation without the need for additional mechanical support. One possible reason for strong adhesion when there is a GrOx CL in the asymmetric BPM is that the conductivity of GrOx is high and it can maintain the adhesion with minimal interference due to the electrostatic force between the AEL and CEM. Due to the strong interlayer adhesion of the BPM obtained from the optimized combination of the AEL, CEL, and CL, the BPM can overcome the stability limit due to membrane delamination. Figure 37 shows the T-peel test of the BPM adhesion. The BPM sample 3701 shows the strongest adhesion with an average peel force of 0.071 N·mm -1 and the graphene oxide sample 3702 has an average peel force of about 0.00721 N·mm -1Although it shows an adhesion force one digit lower, according to the experimental results, it is sufficient for self-standing operation in this shape despite the low adhesion force. Since the BPM manufactured with the TIO2 catalyst layer does not adhere when dried, the adhesion force is so weak that it can be said that there is no adhesion force and the peel test is impossible. This shows the self-standing ability of the BPM with the GrOx catalyst compared to the hydrolysis dissociation catalyst of ordinary metal oxides. An oxidized graphene film with strong interfacial adhesion force has been previously reported. The strong adhesion force may be due to, presumably, interfacial van der Waals forces, hydrogen bond interactions, and other physico-chemical properties. The amphiphilicity of oxidized graphene can similarly enhance the adhesion force with the amphiphilic ionomer membrane because beneficial hydrophobic and hydrophilic interactions are likely to increase the adhesion energy. Alternatively, the strong adhesion force may be the result of only minimally interfering with the adhesion force because GrOx has sufficient conductivity to shield the electrostatic adhesion interaction between the AEL and the CEL.

[0096] Figures 20A to 20C show the voltage stability of the catalyzed asymmetric BPM over time at various current densities according to one embodiment. Figure 20A shows an asymmetric BPM having a stability of about 1100 hours at a current density of about 80 mA cm -2 Figure 20B shows an asymmetric BPM having a stability of about 100 hours at a current density of about 500 mA cm -2 Figure 20C shows an asymmetric BPM having a stability of about 60 hours at a current density of about 1000 mA cm -2 The noise seen in the stability data may be due to the formation and final release of dissolved gas bubbles on the surface of the BPM. Furthermore, the presence of such bubbles on the BPM surface that occurs after applying a continuous current for about 1 hour leads to additional resistance and high voltage.

[0097] In some embodiments, testing the asymmetric BPM over several days can lead to a temperature rise (above about 40 °C) of the BPM due to the concentration of the current passing through the custom electrodialysis cell. The temperature rise over time can cause warping and peeling of the membrane at the joints. Figure 21 shows 500 mA cm according to one embodiment -2Exhibits BPM stability over approximately 400 hours. The asymmetric BPM with Nafion® 211 has better stability, and the voltage does not increase over time as much as that of the Nafion® 212 membrane. The inserted photo shows the irreversible depressions and warping that occur in the Nafion® 212 membrane due to the high temperature reached inside the cell during testing at high current density. The same depressions in Nafion® 212 can be observed when the membrane is heated in an oven at approximately 150 °C for about 10 minutes. During the chronopotentiometry experiment, the temperature measured in the bulk 0.5 M NaCl electrolyte on both sides of the BPM was approximately 35 °C at about 500 mA cm -2 and approximately 50 °C at about 1 A cm -2 , indicating that the BPM temperature itself is likely to be high.

[0098] To further understand the possible temperature effects on the membrane, 3D modeling of a custom electrodialysis cell can be performed using COMSOL®. These models show that the BPM temperature reaches an estimated 42 °C at about 500 mA cm -2 and an estimated approximately 80 °C at about 1 A cm -2 . From these temperature measurements and modeling results, heating of the membrane by high current density can be the cause of the slow delamination and voltage increase in the stability test, leading to membrane deformation. During heating tests with various membranes, Nafion® 211 does not show deformation compared to Nafion® 115 and Nafion® 117.

[0099] Some embodiments implement a catalyzed asymmetric BPM in electrodialysis cells of various types and sizes. In certain embodiments, the electrodialysis cell can be an H-cell and / or a cell stack. The electrodialysis cell can have an active area of about 1 cm 2 to about 6 cm 2 (the full size of the BPM is about 35 cm 2 ). Figures 22A and 22B show a catalyzed asymmetric BPM tested in a single-cell electrodialysis stack according to one embodiment. Figure 22A shows an active area of 6 cm 2The schematic diagram of a one-cell electrodialysis stack is shown. The cell stack is referred to as a one-cell electrodialysis stack and is similar to an electrodialysis cell for acid and base generation. The zero-cell stack has a BPM containing two electrolyte outer chambers, and one-cell stacks, two-cell stacks, three-cell stacks, etc. have groups of membranes (in the order of AEM, CEM, and BPM) that are repeated once, twice, three times, etc. within the zero-cell stack.

[0100] The scaled thin-film AEL BPM was tested in zero-cell and one-cell stacks. Figure 22B shows the experimental one-cell polarization curve (dashed line) of a multi-cell stack with a GrOx-catalyzed asymmetric BPM, and the calculated voltage for each part of the one-cell stack (the higher stacked bar) at a current density of 10 mA cm -2 ~500 mA cm -2 and the calculated voltage for each part of the predicted optimized one-cell stack (the lower stacked bar). The higher stacked bar in Figure 22B shows the calculated voltage values for each of these contributions. The gray error bars show the standard deviation of the voltage contributions of the AEM and EM, and the black error bars show the total standard deviation of the voltages of the AEM and CEM. There is no significant error in all other voltage contributions. The sum of the calculated voltage contributions agrees with the experimental one-cell voltage for the BPM with an active area of 6 cm over all current densities, indicating that low operating overvoltage and similar performance are maintained at high current densities for the scaled BPM. 2 The electrodialysis cell stack system according to some embodiments can be formed of thick membranes, gaskets, and / or solution chamber layers to prevent leakage between cell compartments. Certain embodiments use an AEM with a thickness of about 129 μm and a CEM with a thickness of about 125 μm. When thin AEM and CEM layers are used in this stack design, the entire stack may not be compressed sufficiently, and there is a possibility of solution leakage between chambers from the separated gasket layer. By optimizing the electrodialysis cell design, the compression can be increased to enable the implementation of thin AEM and CEM layers. The shorter bars in Figure 22B show the voltage contributions of each layer of the one-cell stack based on the conductivities of the thin AEM, CEM, and gasket. In the case of thin membranes, at 500 mA cm

[0101] -2 ​The total cell voltage therein can drop from about 14 V to less than about 4 V.

[0102] In addition to exhibiting scalability, low overvoltage, and excellent stability at high current density, the catalyzed asymmetric BPM exhibits high Faradaic efficiency (defined as the efficiency of the electron current applied to generate protons and hydroxide ions by FE, WD). FIGS. 23A and 23B show the H + and OH - versus Faradaic efficiency versus current density and voltage for the catalyzed asymmetric BPM according to one embodiment. The BPM has a GrOx loading of about 225 μg cm -2 . As shown in FIG. 23A, the catalyzed asymmetric BPM has a high Faradaic efficiency for acid and base generation at current densities above about 200 mA cm -2 . Due to co-ion leakage through the thin AEL, the FE for H + and OH - is below about 80% at operating current densities below about 200 mA cm -2 (or voltages below about 0.8 V, FIG. 23B). However, at current densities above about 200 mA cm -2 (or voltages above about 0.8 V), the FE for H + and OH - generation is about 95%. This indicates that most of the current flowing through the cell is devoted to the generation of acids and bases as desired for the use of BPMs for DAC and DOC.

[0103] Some embodiments use various catalyst loadings in the catalyzed asymmetric BPM. Catalyst GrOx ink from about 75 μg cm -2 to about 325 μg cm -2 can be filled into the BPM. The catalyst loading can be varied by changing the number of catalyst ink layers spin-coated onto the Nafion® CEL during BPM manufacture. FIGS. 24A - 24G show the effect of catalyst loading on WD improvement in the catalyzed asymmetric BPM according to one embodiment. FIG. 24A shows loadings of about 75 μg cm -2 , about 150 μg cm -2 , about 225 μg cm-2 ,- about 300 μg cm -2 , and about 375 μg cm -2 The polarization curves of BPMs with GrOx inks of are shown. About 10 mA cm -2 , 500 mA cm -2 , and 1000 mA cm -2 Voltage at current densities of (Figure 24B), R WD (Figure 24C), and C WD (Figure 24D) versus GrOx loading are shown. Optical images and auxiliary diagrams of 1 layer of GrOx on Nafion® 212 showing partial coverage (contour representation) of active sites (Figure 24E), 3 layers of GrOx on Nafion® 212 showing complete coverage (Figure 24F), and 5 layers of GrOx on Nafion® 212 showing complete coverage and aggregation (contour representation) (Figure 24G) are also available. The optimal loading of about 225 μg cm -2 is observed in the polarization characteristics of the GrOx-catalyzed asymmetric BPM, and further increases or decreases in the loading may degrade the BPM performance. Figure 24C shows the relationship between the WD resistance R WD and the GrOx catalyst loading. R WD is the lowest in the BPM with a catalyst loading of about 225 μg cm -2 and shows the same trend as demonstrated by the polarization characteristics in Figures 24A and 24B.

[0104] A similar trend is observed in the BPM junction capacitance as a function of the GrOx catalyst loading in Figure 24D, and the junction capacitance is about 225 μg cm -2It is maximized with the catalyst loading. Since the capacitance can correlate with the number of (de)protonatable sites in the BPM junction, these data suggest that the maximum number of catalytic sites is shown by the three-layer GrOx. The increase in capacitance and activity with 1 to 3 layers of GrOx indicates an increase in the catalyst coating in the BPM junction, which is also supported by the optical images and explanatory diagrams shown in FIGS. 24E to 24G. The optical images and supplementary diagrams also show that when 4 and 5 layers are introduced, the GrOx condenses and can cover a certain proportion of the active sites obtained with 3 layers of GrOx. FIGS. 36A to 36C show schematic diagrams of the GrOx coating levels based on the number of spin-coated layers according to one embodiment. In one layer, the Nafion substrate is partially covered with GrOx. In three layers, complete coverage is observed, increasing the number of active sites available for the catalyst and electric field enhancement of the WD. In five layers, aggregation of GrOx begins, indicating that some of the previously obtained active sites are buried within the aggregates.

[0105] To explain the mechanism of WD within the BPM and the sensitivity of BPM performance to CL characteristics, a continuous level model of the BPM can be developed. This model uses a continuum representation of mass conservation in which the fluxes of species are defined by the Poisson-Nernst-Planck equations and the homogeneous phase bulk reaction (i.e., WD) in the BPM domain is described by the mass action chemical kinetics with electric field enhancement. FIG. 25A shows a simulation of the electric field-promoted WD in the CL and ion transport in the polymer and electrolyte layers according to one embodiment. FIG. 25A shows the experimental polarization curve of the GrOx-catalyzed asymmetric BPM with high accuracy. This model can accurately simulate the measured salt crossover and the FE for acid and base generation. FIGS. 52A to 52D show the models used to define the local pH and electrostatic potential profiles within the BPM and CL domains, demonstrating how the pH gradient within the BPM occurs with an increase in voltage. It is observed that most of the pH and applied potential gradients occur at the AEL-CL interface, suggesting that WD mainly occurs at this interface.

[0106] As shown in FIGS. 57A and 57B, it is clear that from the local electric field within BPM CL, the maximum value of the electric field at the AEL-CL interface coincides with the maximum value of the WD velocity due to the second Wien effect shown in FIGS. 58A and 59B. The maximum of the electric field can be explained by examining the concentration profiles of the GrOx functional groups within CL presented in FIGS. 25C and 52A - 55D. The local generation of OH - anions causes most of the acidic GrOx functional groups (i.e., carboxy groups) to be rapidly deprotonated, resulting in a large accumulation of negative charge at that interface, which further enhances the local electric field and accelerates the WD reaction by the second Wien effect. The role of the catalyst is to generate surface charges that enhance the electric field and promote WD. When examining the alternative WD pathways shown in Eqs. S37 - S42 and FIG. 4A along with the experimentally determined concentrations of the ionic groups in the GrOx catalyst, it is found that WD occurs mainly through the reaction of H2O with the least acidic GrOx functional groups (i.e., phenol groups), as shown in FIGS. 25D and 61A - 61D. The fact that WD occurs at a significant rate via the catalytic pathway indicates that the catalyst promotes WD and the formation of the electric field. These simulations show that the stronger acidic GrOx sites enhance the electric field more, and the least acidic GrOx sites provide additional WD pathways. FIG. 25C shows the presence of phenol sites at a concentration exceeding 2M at 100 mA cm -2 . Thus, the different pK a of the acidic groups on GrOx and their concentrations within CL could be the reason for the dual functionality of GrOx.

[0107] To determine the extent to which the pK a of the different acidic groups within CL affects the WD velocity, simulations of BPM are performed, and all sites within CL are set to a single pK a value equal to one of the pK a values related to the phenol and carboxy groups in GrOx (i.e., pK a = 4.3, 6.6, or 9.8). As shown in FIGS. 62 - 64D, these single-site simulations show the pK aAs it decreases, the acidic groups on the catalyst dissociate more readily, enhancing the electric field and accelerating the rate-determining step of WD, which is consistent with the improvement of WD performance. Figure 63 shows that for low pK a (4.3 or 6.6) functional groups, WD is mainly caused by the electric field enhancement process, indicating that there are no neutral sites at the AEL-CL interface and thus no significant WD occurs due to the catalyst. For high pK a (9.8) functional groups, since pK a is large enough to prevent complete deprotonation, WD by the catalyst becomes the central reaction pathway. However, in this case, since there are substantially few negative charges at the AEL-CL interface, the electric field, and thus the WD rate, is significantly slow. Figures 64A - 64D show that for a single pK a = 4.3 site, the theoretical current density is much higher due to the increased concentration of dissociation sites than for multiple acidic sites of GrOx, meaning that the role of electric field enhancement is more important in determining WD performance. The coexistence of multiple sites on GrOx enables the progress of WD through the catalytic reaction mechanism, and the multi-site GrOx CL is significantly more performant than single-site catalysts by simulation with pK a > 5.

[0108] Continuous level modeling also helps to explain the experimental trends observed as the loading of the GrOx catalyst increases. According to the simulations shown in Figure 65, since it is assumed that WD occurs at the AEL-CL interface but not within the bulk of the CL, the change in CL thickness alone cannot explain the observed trends in WD rate. Further modeling shown in Figures 66A and 66B demonstrates that it can explain the experimentally observed performance improvement when the volume concentration of catalyst sites increases with thickness from 1 layer to 3 layers. Such an increase in the volume concentration of GrOx sites is due to the increase in the exposed GrOx surface with the increase in CL thickness, which is consistent with the schematic diagram of the GrOx structure derived from the EIS analysis shown in Figures 24A - 24G.

[0109] The GrOx-catalyzed asymmetric BPM can overcome water transport limitations, operate in reverse bias at high current densities and low overpotentials, and is highly efficient in acid and base generation. Under conditions related to electrodialysis, the BPM according to embodiments can maintain a stable voltage for more than 1100 hours at about 80 mA cm -2 for about 100 hours at about 500 mA cm -2 for about 60 hours at about 1 A cm -2 and above. Further, at an applied current density of 1 A cm -2 , the overpotential exhibited by the BPM is about 242 mV, and the Faradaic efficiency (FE) for acid and base generation is close to 1. Further, the combination of the anion exchange membrane (AEL), cation exchange membrane (CEL), and catalyst (PiperION®, Nafion®, and GrOx) enables good adhesion at the BPM junction, which contributes to long-term stability. Even in the initial tests of the BPM according to some embodiments in an electrodialysis cell stack having a scaled active area of 6 cm 2 , high current density operation at low voltage is demonstrated.

[0110] The performance of the BPM according to specific embodiments can be varied by changing the catalyst loading. By changing the catalyst loading, it is clear that while there is an optimal loading, too little loading results in non-uniform coating of the membrane interface by the catalyst, reducing the catalyst site concentration, and too much catalyst loading results in catalyst aggregation and similar site losses. Continuous level modeling of the BPM can match the experimentally measured polarization curves and FE. These simulations reveal that the high concentration of both low and high pK a deprotonated sites in the GrOx CL enhances the electric field at the AEL-CL interface, providing an alternative path for WD. The self-supporting BPM according to embodiments can be used in a wide range of electrochemical technologies where operation at high current density and low voltage is desirable.

[0111] Exemplary embodiments Specific embodiments of the system and apparatus are described below, but it should be understood that these embodiments are provided by way of example and not with the intention of limitation.

Example

[0112] Materials and Equipment Obtain the following membranes in dry form, pretreat them according to the manufacturer's instructions before use, and store them in DI water (CEM) or 1M NaOH (AEM): Nafion® 212 (50 μm), Nafion® 211 (25 μm), Nafion® 115 (127 μm), PiperION® A15R (15 μm), PiperION® 20 (20 μm), PiperION® 60 (60 μm), Fumasep FAB-PK-130 (110 μm - 140 μm), Fumasep FKB-PK-130 (110 μm - 140 μm), Nafion® D520 (5 wt% ionomer). Use the following chemicals as received: graphene oxide paste (30 g / L), sodium chloride (NaCl), sodium hydroxide (NaOH, pellets), hydrochloric acid (HCl, 1.0 M and 0.1 M), potassium hydroxide (KOH, pellets).

[0113] First, prepare the catalyst ink by diluting the graphene oxide paste from 30 g / L to 10 g / L. Subsequently, mix the diluted graphene oxide dispersion with Nafion® D520 in a 1:1 volume ratio. Ultrasonicate the final ink solution for more than 10 minutes before use.

[0114] First, place one purchased Nafion® membrane (NR212, NR211, NR115) pre-cut to 1.5 cm × 1.5 cm and immersed in DI water for 1 hour or more on a slide glass, gently press it with Kimwipe® and dry. Subsequently, tape all four sides of the membrane to the slide glass with Kapton® tape. Subsequently, spin coat the GrOx catalyst ink onto the Nafion® membrane at about 3000 rpm for about 30 seconds. Next, place the Nafion® membrane with GrOx in an oven at about 100 °C for about 2 minutes. If more layers, i.e., a higher loading amount, are desired, repeat this spin coating and heating process. Finally, re-wet the Nafion® membrane with GrOx with a few drops of DI water, sandwich it with a PiperION® membrane of the desired thickness, and clamp it with gloved fingertips while being careful to squeeze out air pockets. Test immediately after assembling all the membranes. Use the same method for the fabrication of both BPMs with active areas of 1 cm 2 and 6 cm 2 in both cases.

[0115] Measure the conductivity of the AEM and CEM using a four-probe probe. Perform the measurement at about -10 V to about 10 V with a fully hydrated membrane. The measured value indicates the in-plane conductivity, and since the membrane is isotropic, this is equivalent to the conductivity in the membrane thickness direction.

[0116] To determine the loading amount of GrOx ink spin-coated on Nafion®, weigh the Nafion® membrane taped to the slide glass before and after spin coating using an electronic microbalance of the Sartorius CP series. Dry the Nafion® taped to the slide glass at about 100 °C for about 10 minutes before weighing so that the changes in hydration after the addition of GrOx ink and heat treatment do not affect the measured value. After spin coating and heating GrOx onto Nafion®, remove the excess GrOx ink from the tape and glass using Kimwipe®. Calculate the final loading amount based on the exposed Nafion area within the tape boundary.

[0117] Figure 13A shows a schematic diagram of an electrodialysis cell used for BPM testing. The cell consists of an anode 1301, an anolyte chamber 1302, a CEM 1310, a dilution chamber 1303, an AEM 1313, an acid chamber 1305, a BPM 1312 (1 cm 2 active area), a base chamber 1211, a CEM 1210, a catholyte 1208, and a cathode 1309. Both the anode 1301 and the cathode 1309 are made of Ni foil with copper tape as the lead wire. A 1M aqueous NaOH solution is used as both the anolyte 1302 and the catholyte 1508 and recirculated through both chambers at about 10 mL / min. A 3M aqueous NaCl solution is recirculated through the dilution chamber at about 5 mL / min, and a 0.5M aqueous NaCl solution is recirculated through the acid chamber 1305 and the base chamber 1311 at about 0.2 mL / min. Both CEMs used in the cell stack are Nafion® N324 (280 μm), and the AEM 1313 is Fumasep FAB-PK-130 (130 μm). Luggin tubes 1307 holding Ag / AgCl reference electrodes 1304 are placed in the acid chamber 1305 and the base chamber 1311 to enable the most direct measurement of the voltage across the BPM.

[0118] After assembling the above-described electrodialysis cell, the lead wires of the potentiostat are attached in a four-point measurement configuration so that a current can be applied to the full cell and the resulting voltage can be directly measured across the BPM 1312. Chronopotentiometry measurements are used to obtain all reported data for the full polarization curve. At each point, a selected current is applied between the anode and the cathode and held for about 5 minutes to 20 minutes or until the voltage measured across the BPM 1312 reaches a steady state. Subsequently, the current is increased to the next value and the process is continued until all desired current measurements are performed. Examples of current density vs. time plots showing voltage values as the average value of the voltages collected over the steady state region for each chronopotentiometry step can be seen in FIGS. 38A - 38F.

[0119] EIS measurements were performed using the same electrodialysis cell as described above. At each BPM, the measurement was carried out at about 500 mA cm -2Start with and gradually decrease it to each desired current density. At each step, hold the current for about 1 minute, then scan from about 600 kHz to about 20 Hz at an amplitude of about 5% - 10% of the current and record every about 0.5 seconds. Subsequently, fit the Nyquist plot using software as shown in Figure 32. Fit the EIS data using circuit 3201. R Ω is the resistance between the tips of the Luggin tubes, which includes the solution and the membrane, and R WD is the resistance due to the water dissociation reaction, and C WD is the capacitance due to the double layer formed in the inner layer of the BPM.

[0120] Use a 5 - chamber electrodialysis cell similar to the above for the recovery of acid and base samples to measure the Faraday efficiency at various current densities. Flow a 0.5 M NaCl aqueous solution into the acid and base chambers at about 5 mL / min and apply the desired current to the cell until the voltage stabilizes (usually about 10 - 20 minutes). Subsequently, collect the samples from the acid and base chambers into 20 mL vials. Then, increase the current to the next desired value and repeat the process. After collecting the samples, evaluate the H + and OH - activity by pH probe measurement or pH titration. Titration is used for more pH values such as pH values greater than 12 and less than 2.

[0121] Obtain SEM images. Use a spot size of about 5.0 and a voltage of about 10.00 kV for most images. For cross - sectional images of the BPM, embed the membrane in resin and cut it using a microtome. For cross - sections of only Nafion® with GrOx CL, slice the membrane using a razor blade. Use ImageJ to evaluate the membrane and CL thickness from these SEM cross - sections.

[0122] Obtain all optical microscope images. Take images of the GrOx dispersion during the BPM manufacturing process while Nafion® and Nafion® with GrOx are taped to a slide glass and before re - wetting and sandwiching with the AEM again.

[0123] Figure 22A shows a schematic diagram of the fluid flow inside an electrodialysis cell used for testing scaled BPM. A commercially available cell with an iridium oxide mixed metal oxide electrode and an active area of 6 cm 2 is modified by making two holes in the cathode compartment to form inlet 2215 and outlet 2203 ports for the dilution compartment. In the case of a single cell stack, from the anode to the cathode, the membrane stack consists of BPM2204, AEM2206, CEM2208, and BPM2204. All the membranes are cut to a size of approximately 5 cm × 7 cm with a blade. Holes of approximately 2 mm and 4 mm are made in appropriate places so that solutions can flow through the membranes into the acid and base compartments and the dilution compartment respectively. Between the membranes, a modified commercially available polypropylene mesh silicone gasket 2207 (with a thickness of approximately 450 μm for the inner compartments (2205 and 2209) and a thickness of approximately 450 μm for the outer compartments (2202 and 2211)) is used to allow the continuous flow of separated solutions in the inner and outer compartments of the cell. A 1M KOH solution is recirculated at a rate of approximately 1.5 L / min into two separate 5L polypropylene reservoirs for the anode and cathode compartments. A 0.5M NaCl solution flows through the cell from separate source reservoirs for the acid, base, and dilution compartments and exits into a common waste container at rates of approximately 35 mL / min and approximately 45 mL / min in the acid flow paths (2212 and 2214) and the base flow paths (2210 and 2215).

[0124] After assembling the above-described electrodialysis cell, power supply (360W) leads are attached to the cell in a two-point configuration to apply current and measure voltage. A custom LabVIEW VI controls the applied current and uses chronopotentiometry measurements to acquire all reported current density and voltage data. At each point, the selected current is applied between the anode and the cathode and held steady for more than 1 minute or until the measured voltage reaches a steady state. Voltage data is collected at time steps of approximately 5 seconds. Subsequently, the current is increased to the next value and the process is continued until all desired current density measurements are obtained.

[0125] At each selected current, in the steady state, the solution samples are collected from the acid chamber, the base chamber, and the diluent chamber into 50 mL polypropylene conical tubes. Once the samples are collected, the conductivity is measured using a 4-ring conductivity probe and a conductivity meter. The voltage contributions of the inner chamber and the ion exchange membranes (AEM and CEM) are calculated using the following equation.

[0126]

Equation

[0127] where j is the current density (mA cm -2 ), L is the chamber width (i.e., the thickness of the mesh gasket) or the membrane thickness (cm), and K is the conductivity of the solution or the membrane (mS cm -1 ). The membrane thickness is determined using a micrometer. The error in the membrane voltage contribution is determined by calculating the minimum and maximum voltage contributions using the standard errors of the conductivity and thickness measurements. The average value is used for the error bars in Figure 22A. The BPM voltage contribution is determined using the custom BPM test cell described above.

[0128] Simulations are performed using COMSOL Multiphysics® software. The concentrations of H3O + , OH - , Na + , Cl - , and all GrOx surface species, along with the electrostatic potential profile, are solved using the Poisson-Nernst-Planck equations with conservation equations that describe mass and charge transport. Importantly, homogeneous reactions that generate net charge are corrected by the second Wien effect such that ion dissociation, i.e., the forward rate, is substantially enhanced by the electric field.

[0129] Figure 41 shows a control volume analysis of the CL of an asymmetric BPM according to one embodiment. The changes in the proton flux and the hydroxide ion flux of the CL are equivalent due to the stoichiometric nature of the WD. Na + and Cl -Since it is neither generated nor consumed by the buffering action, there is no net change in their fluxes in the CL.

[0130] FIG. 42 shows the calculated flux changes of protons and hydroxide ions in the CL of the asymmetric BPM, along with the integration of the proton and hydroxide ion source terms. The integrated source term is equivalent to the change in flux.

[0131] FIG. 43 shows the flux changes in the CL of an asymmetric BPM according to one embodiment, plotted with the measured fluxes of protons and hydroxide ions measured at the reference electrode to demonstrate flux matching. The generation of protons and hydroxide ions by the WD occurs within the CL.

[0132] FIGS. 44A and 44B show Cl - and Na + fluxes measured in different regions of a model of an asymmetric BPM according to one embodiment. The Cl - and Na + fluxes remain constant throughout because there is no generation or consumption of these species by homogeneous reactions.

[0133] FIG. 45 shows the integration of the water dissociation pathways by the catalyst in the WD catalyst layer. The fluxes of protons and hydroxide ions by each pathway are stoichiometrically linked. The rates of the first and second steps in each of the WD pathways by the catalyst must be equal.

Example

[0134] Characterization and analysis of the GrOx loading

Table 1

Example

[0135] Cell and membrane temperature model The 3D temperature simulation of the custom electrodialysis cell uses a multiphysics finite element model that features current distribution, resistive heating, and hydrodynamics. The current distribution is simulated assuming a primary current model that simulates the current density model with the conductivity assigned to the electrolyte and ion exchange membrane domains instead of explicitly solving for the ion concentration and flux. Three average current density values (80 mA cm -2 , 500 mA cm -2 , 1000 mA cm -2 ) are applied as boundary conditions. The current density within the cell is plotted in FIGS. 39A - 39C using a slice heat map showing the magnitude of the local current density and arrows showing both the direction and magnitude of the current density vector.

[0136] Outside the BPM domain, the local heating power per unit volume is calculated based on the local current density and conductivity in the differential form of the Joule heating equation.

[0137]

Eq.

[0138] where σ is the conductivity and J is the current density. In the BPM domain, part of the potential is consumed as energy to facilitate the water dissociation reaction.

[0139]

Eq.

[0140] Therefore, the differential form of the Joule heating power within the BPM is calculated by the following equation.

[0141]

Eq.

[0142] Plot the temperature after about 1 hour of operation predicted by simulation in FIGS. 39D to 39F. As is clear from the temperature results from this model, when operating at about 80 mA / cm 2 it is possible to maintain a low temperature of about 21.6° C. or less throughout the cell, but when the cell is operating at about 500 mA / cm 2 and 1000 mA / cm 2 the temperature reaches about 42.3° C. and about 80.7° C. respectively at the vicinity of the cylindrical region where the BPM is located.

Example

[0143] Ion transport Related species (OH - , H + , Cl - , and Na + ) Call the conservation of species within the modeled domain to solve for the total concentration and flux of.

[0144]

Number

[0145] where N i is the flux of species i, and R B,i is the source term defined as the generation of species i from homogeneous buffer reactions and water recombination / dissociation. Under dilute solution theory, the molar flux of species is defined by the Nernst - Planck equation.

[0146]

Number

[0147] where D i , c i , μ i are the diffusion coefficient, concentration, and chemical potential of species i respectively. The chemical potential of a given species is defined as follows.

[0148]

Number

[0149] In the above chemical potential formula, the first term is the reference chemical potential of species i, the second term represents the change in the activity of i, the third term represents the electrostatic potential, and it is applied only to charged ionic species (i.e., all species except CO2). Φ is the electrostatic potential in the electrolyte and the membrane phase. R, T, and F are the ideal gas constant, temperature, and Faraday constant, respectively. The activity of a given species is defined by the following formula.

[0150]

Number

[0151] In the formula, c ref is the reference concentration (1 M), and the ratio

[0152]

Number

[0153] represents the change in volume reference between the electrolyte and the liquid filling flow path of the BPM. f i is the activity coefficient, and for all Na + and Cl - it is 1 (f i = 1) (i.e., salt species are treated ideally), and for hydronium ions and hydroxide ions it is a function of the electric field

[0154]

Number

[0155] shall be. This term represents the shift of the hydrolysis dissociation equilibrium in the electric field due to the second Wien effect and is applied only to protons and hydroxide ions. The choice of the square root in this term means that the second Wien effect is applied equally to each dissociated ion. For water, the activity (αH20) shall be 1.

[0156] In the electrolyte phase, the diffusion coefficient is set to its value in water, but in BPM, it is corrected by the following relationship.

[0157]

Number

[0158] In this framework, q is a fitting parameter, and x w is the ratio of the number of moles of water in the membrane to the sum of the number of moles of water and fixed charge groups.

[0159]

Number

[0160] is given by the formula, where λ is the water content of BPM defined as the ratio of the water molecules absorbed in BPM to the fixed charge groups. φ L,M is the volume fraction of water in the ionomer.

[0161]

Number

[0162] JPEG2025524332000101.jpg13153

[0163]

Number

[0164] In the formula, V w and V M are the molar volumes of water and the ionomer.

[0165]

Number

[0166] is the conversion molar mass.

[0167] The water transport limit of BPM does not occur up to a current density exceeding 1 A cm when using a thin ion exchange layer, which exceeds the current density range in this study. The water activity is assumed to be 1, and the membrane channels are completely filled with liquid. In this scenario, the water content λ is only a function of the local ionic environment. -2 and is beyond the current density range in this study. The water activity is assumed to be 1, and the membrane channels are completely filled with liquid. In this scenario, the water content λ is only a function of the local ionic environment.

[0168]

Number

[0169] JPEG2025524332000105.jpg9153

[0170]

Number

[0171] is the water content of the CEL or AEL that has been completely exchanged with protons / hydroxide ions or counterions, and is determined from experimental literature for Nafion® and PiperION® membranes in the form of protons or hydroxide ions and in the form of sodium ions or chloride ions. The water concentration within the domain is defined by the following hyperbolic tangent (called to smooth the boundary gradient at the interface between the membrane and the electrolyte to promote simulation convergence).

[0172]

Number

[0173] In the above formula, x1 is the leftmost position of the CEL, x2 is the rightmost position of the CEL, x3 is the leftmost position of the AEL, and x4 is the rightmost position of the AEL. The characteristic length used in this study is L char = 0.58 nm, which is related to the binding separation distance of water. φ L,CL represents the volume fraction of water in the catalyst layer defined as follows.

[0174]

Number

[0175] φ L,CL and φ Naf,CL Both are fitting parameters. φ Naf,CL is the volume fraction of Nafion® in the catalyst layer and is generally related to the composition of the ionomer ink used for casting the CL. The following terms represent the volume fraction of water in the hydrophilic domain of the Nafion® ionomer in the CL.

[0176]

Number

[0177] φ 0,CL is the volume fraction of water in the as-prepared catalyst layer and can be described as the porosity or void fraction of the entire catalyst layer.

[0178] The fixed charge concentration C in the BPM M (x) is defined by the following hyperbolic tangent.

[0179]

Number

[0180] In the formula, ρ M,wet and IEC are the wet film density and ion exchange capacity, respectively. This distribution is equal to zero in the electrolyte domain and represents negative and positive fixed charges in the CEL and AEL domains, respectively.

Example

[0181] Charge transport Solve the Poisson equation to obtain the electrostatic potential.

[0182]

Number

[0183] ε(x) is the position-dependent permittivity of the medium. This permittivity is defined differently in each domain in the simulation. First, this is defined as the permittivity of water in the electrolyte domain

[0184]

Number

[0185] where ε0 is the permittivity of vacuum and the ratio

[0186]

Number

[0187] is the relative permittivity of water. Σ i z i c i represents the sum of the products of all charged species and their charges, including the charged GrOx surface in the catalyst layer.

[0188] The permittivity of the polymer ion exchange membrane can be approximated as a linear superposition of the permittivity of the aqueous phase in the ionomer and the permittivity of the polymer domain, weighted by the volume fraction of each phase. The relative permittivity of the polymer phase is

[0189]

Number

[0190] obtained as, and the relative permittivity of water in the polymer channel is

[0191]

Number

[0192] obtained as (slightly decreased from the value of bulk water, 78, due to the confinement effect). Due to the lack of high-frequency permittivity studies on PiperION® AEM, the permittivity of Nafion® in the PiperION® phase is also used.

[0193] [Number]

[0194] In the formula, ε M is the dielectric constant of the dry Nafion (registered trademark) polymer.

[0195] Finally, in the catalyst layer, the relative dielectric constant when immersed in water is

[0196] [Number]

[0197] The presence of graphene oxide, which is

[0198] [Number]

[0199] φ M,CL is the volume fraction of the dry Nafion in the CL, and φ L,M,CL is the volume fraction of the liquid water inside the pores of the catalyst layer membrane.

[0200] [Number]

[0201] Finally, φ GrOx,CL is the volume fraction of the solid graphene oxide in the catalyst layer. φ GrOx, = 1 - φ L,CL - φ Naf,C L (S34)

[0202] The position-dependent dielectric constant is also defined by the hyperbolic tangent as follows to promote convergence.

[0203] [Number]

Example

[0204] Homogeneous reaction rate theory and electric field promoted hydrolysis dissociation The homogeneous hydrolysis reaction consumes OH - and H3O + throughout the electrolyte domain.

[0205]

Number

[0206] Furthermore, as shown in Fig. 28, graphene oxide has six different available sites, carboxylic acid groups (group 1) 2801 adjacent to alcohols with a low pK of 4.3 due to electron-withdrawing properties, carboxylic acids without adjacent alcohols (group 2) 2802 with a pK of 6.6, and alcohols (group 3) 2803 with a pK of 9.8. Each of these three groups can exist in protonated (neutral) or deprotonated (-charge) forms. Proton and hydroxide ion transfer reactions are related to the consumption and generation of these surface species. a and carboxylic acids without adjacent alcohols (group 2) 2802 with a pK of 6.6, and alcohols (group 3) 2803 with a pK of 9.8. Each of these three groups can exist in protonated (neutral) or deprotonated (-charge) forms. Proton and hydroxide ion transfer reactions are related to the consumption and generation of these surface species. a and carboxylic acids without adjacent alcohols (group 2) 2802 with a pK of 6.6, and alcohols (group 3) 2803 with a pK of 9.8. Each of these three groups can exist in protonated (neutral) or deprotonated (-charge) forms. Proton and hydroxide ion transfer reactions are related to the consumption and generation of these surface species. a and alcohols (group 3) 2803 with a pK of 9.8. Each of these three groups can exist in protonated (neutral) or deprotonated (-charge) forms. Proton and hydroxide ion transfer reactions are related to the consumption and generation of these surface species.

[0207]

Number

[0208] The overall ratio of these species occurs in the following ratio with respect to the initial coverage of [Gr-COOH]1 0: [Gr-COOH]2 0 : [Gr-OH]3 0 species.

[0209]

Number

[0210] The total concentration of sites on pure graphene oxide is determined by titration to be c0 [Gr] = 27.56. This total concentration is, for the purpose of promoting convergence, as a distribution on the hyperbolic tangent, the fixed site concentration of pure GrOx within the CL multiplied by the volume fraction of GrOx (φ GrOx = 1 - φ L,CL - φ Naf,CL ), and outside it is also defined as 0.

[0211]

Number

[0212] The rates of consumption and generation by the bulk homogeneous reaction are defined using the law of mass action. k n and k -n are rate constants, and K n is the equilibrium constant of the homogeneous reaction n. The consumption rate of species i in the bulk reaction is given as follows.

[0213]

Number

[0214] To solve the mass continuity of the catalyst species, it is assumed that the flux of graphene oxide surface species is not in the membrane thickness direction (i.e., it is fixed on the surface and not transported). Therefore, the mass balance for all graphene oxide species can be written as follows.

[0215]

Number

[0216] Next, since only 3 out of the 6 mass conservation equations are linearly independent, site balance is required.

[0217]

Number

[0218] When solving linearly independent continuity equations and site balances using symbolic matrix inversion in MATLAB®, the following equation is obtained for the activity of graphene oxide surface species.

[0219]

Number

[0220] The rate constants of the above reactions are shown in Table 2. The equilibria (K w , K1, K2, K3) of the reactions that generate net charge are affected by the second Wien effect.

[0221]

Number

[0222] In the equation, b is a dimensionless electric field parameter defined as follows.

[0223]

Number

[0224] α WD is a parameter that conforms to the value of the dimensionless electric field of 0.172 and determines the sensitivity of the WD kinetics to the electric field. l b is the Bjerrum length, and

[0225]

Number

[0226] is obtained. τ is a concentration parameter.

[0227]

Number

[0228] In the equation, σ is a dimensionless number defined by the ratio of the binding dissociation length to the Bjerrum length.

[0229]

Number

[0230] To compare various models of electric field-assisted dissociation in CL, a model with an exponential dependence is also executed.

[0231]

Number

[0232] In the formula, b is a different fit α WD,exp = 1.18 is the defined dimensionless electric field parameter of the concentration.

[0233]

Number

[0234] The choice of the kinetics does not affect the quality of the fitting shown in Figure 53.

Example

[0235] Boundary conditions At the end of the catholyte boundary layer (the leftmost boundary), the Dirichlet boundary condition sets the concentration of all modeled ion species to their bulk electrolyte concentration.

[0236]

Number

[0237] In the formula, the origin is defined at the center of the WD CL, and L CL is the catalyst layer thickness, and L CEL is the CEL thickness, and L cBL is the catholyte boundary layer thickness.

[0238] The electrostatic potential is set to 0 V with another Dirichlet boundary condition.

[0239] [Number]

[0240] At the end of the anolyte boundary layer (the rightmost boundary), the species concentration is set to its bulk value using the Dirichlet boundary condition again.

[0241] [Number]

[0242] L AEL is the AEL thickness, and L aBL is the anolyte boundary layer thickness. Finally, the electrostatic potential is set to the measured membrane potential at the anolyte boundary.

[0243] [Number] [Example]

[0244] Numerical method The governing equations representing the model are solved with a relative tolerance of about 0.001 using two coupled general partial differential equation (g) modules of COMSOL Multiphysics (registered trademark). The modeling domain is discretized with a non-uniform mesh refined near all interfaces (membrane-membrane, membrane-electrolyte, and membrane-CL). The resulting mesh consists of about 11,000 elements depending on the applied current density. A mesh independence study is performed, and as a result, it is found that for meshes with more than 5,000 elements required to achieve convergence, the results are independent of the meshing. Importantly, to achieve initial convergence, the Donnan equilibrium is solved analytically to obtain the respective species concentrations in the membrane layers with the applied membrane potential being zero, and these are supplied to the simulation as initial conditions using hyperbolic tangent analytical functions. The simulation is solved using MUMPS (Multifrontal Massively Parallel sparse direct Solver). [Example]

[0245] Table of parameters used in the model

Table 2

[0246] List of buffer reaction constants. Note: The rate constants are determined assuming a diffusion-limited reaction with H3O + or OH - and are obtained using a bimolecular proton transfer reaction mechanism that is thermodynamically favorable under standard conditions and has encounter-limited / diffusion-limited second-order rate constants.

Table 3

[0247]

Table 4

[0248]

Table 5

[0249]

Table 6

Example

[0250] Titration details To calculate the total number of GrOx sites available for proton transfer from the titration data collected in Figure 50, assume equilibrium GrOx.

[0251]

Number

[0252] JPEG2025524332000146.jpg14153

[0253]

Number

[0254] Na + and Cl - To determine the equilibrium concentrations of Na and Cl, the initial concentrations are changed taking dilution into account.

[0255]

Number

[0256] There must be a site balance in which all GrOx surface species are summed up.

[0257]

Number

[0258] Furthermore, by the integration performed in previous studies, the proportion of each type of site among all sites is determined, and site balance must hold for each type of site on GO.

[0259]

Number

[0260] Electrical neutrality is conserved in the system.

[0261]

Number

[0262] The total GrOx site concentration can be obtained by solving the system of equations.

[0263]

Number

[0264] The concentration basis is then converted back to a molar basis by multiplying it by the total volume of the solution.

[0265]

number

[0266] 0.1 g of GrOx is added to the solution (10 mL of 10 g / L GrOx paste). Therefore, the ion exchange capacity of pure GrOx can be calculated as follows:

[0267]

number

[0268] Finally, the anchoring site concentration in pure GrOx can be determined by multiplying the IEC by the density of GO as follows:

[0269]

number

[0270] Calculation of salt-ion crossover current density To determine the salt crossover current, the contribution to the total current density from the WD measured due to the pH change is subtracted from the total current density. + and OH - Since the current densities are stoichiometrically equivalent, their average is used and subtracted to obtain the salt crossover current density.

[0271]

number

[0272] Doctrine of Equivalents As can be inferred from the above description, the above concepts can be implemented in various configurations according to the embodiments of the present invention. Therefore, although the present invention is described in specific aspects, many modifications and variations will be apparent to those skilled in the art. Therefore, it should be understood that the present invention can be implemented in ways other than those specifically described. Thus, the embodiments of the present invention should be considered exemplary in all respects and not restrictive.

[0273] As used herein, the singular forms "a", "an", and "the" may include plural objects unless the context clearly dictates otherwise. References to an object in the singular are not intended to mean "only" unless explicitly stated, but rather "one or more".

[0274] As used herein, "substantially" and "about" are used to describe and account for minor variations. When used with an event or situation, these terms can refer to both when the event or situation occurs exactly and when it occurs approximately. When used with a numerical value, these terms can refer to a variation range of ±10% or less of that numerical value, such as ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1% or less, or ±0.05% or less.

[0275] Furthermore, quantities, ratios, and other numerical values may be presented in range format in this specification. Such range format is used for convenience and brevity, and should be understood flexibly to include not only the numerical values specified as the limits of the range but also the individual numerical values or sub-ranges subsumed within that range as if each numerical value and sub-range were explicitly recited. For example, a ratio in the range of about 1 to about 200 should be understood to include not only the explicitly recited limits of about 1 and about 200, but also individual ratios such as about 2, about 3, and about 4, and sub-ranges such as about 10 to about 50, about 20 to about 100, etc.

Claims

1. A bipolar membrane, An anion exchange layer containing an anion exchange membrane, A cation exchange layer containing a cation exchange membrane, wherein the cation exchange layer has a different thickness from the anion exchange layer so as to increase the water transport rate at the anion exchange layer-cation exchange layer interface, A catalyst disposed between the anion exchange layer and the cation exchange layer, which catalyzes a water dissociation reaction and includes a plurality of ionization sites having the properties of proton donation, proton abstraction, or a combination thereof, wherein the plurality of ionization sites enhance the electric field at the anion exchange layer-cation exchange layer interface. A bipolar membrane equipped with [a specific feature / feature].

2. The bipolar film according to claim 1, wherein the catalyst is a material selected from the group consisting of a two-dimensional material, graphene oxide, metal oxide, titanium-based polyvalent catalyst, nanomaterial, polymer, and any combination thereof.

3. A bipolar film according to claim 1 or 2, wherein the catalyst layer further comprises a bipolar film containing an ionomer.

4. In the bipolar film according to claim 1 or 2, the plurality of ionization sites have different pK ａ A bipolar film containing the functional group of value.

5. The bipolar membrane according to claim 1 or 2, wherein the anion exchange membrane is selected from the group consisting of SELEMINION®, NEOSEPTA®, fumapem® FAA, fumapep® FAP, Sustainion®, X37, Versogen®, PiperION®, Ionomr Aemion®, and any combination thereof, and the cation exchange membrane is a bipolar membrane containing Nafion®.

6. A bipolar film according to claim 1 or 2, wherein the thickness of the bipolar film is 70 microns or more, or the anion exchange film has a thickness of less than 100 microns and is thinner than the cation exchange layer, or the cation exchange film has a thickness of less than 100 microns and is thinner than the anion exchange layer.

7. A bipolar membrane according to claim 1 or 2, wherein the bipolar membrane is configured to be part of an electrodialysis cell, or the electrodialysis cell is configured to be selected from the group consisting of an H cell, a cell stack, a flow cell, and a flow stack.

8. A bipolar membrane according to claim 7, wherein the electrodialysis cell comprises a cathode and an anode, wherein the material is selected from the group consisting of metal, alloy, nickel, nickel alloy, copper, copper alloy, titanium, titanium alloy, iron, iron alloy, stainless steel, platinum, gold, silver, carbon, carbon cloth, glassy carbon, graphite, and any combination thereof.

9. A bipolar membrane according to claim 7, wherein the electrodialysis cell is part of a carbon recovery system, an electrochemical conversion system, an energy storage system, a water splitting system, or a carbon dioxide reduction system, or the carbon recovery system is directly an ocean recovery system.

10. In the bipolar membrane according to claim 7, the electrodialysis cell is 100 mA / cm². ２ A bipolar film that operates for 60 hours or more at the above current density and voltage of 1.5V or less.

11. It is an electrodialysis cell, It is a self-supporting bipolar membrane, Anion exchange layer containing an anion exchange membrane, A cation exchange layer containing a cation exchange membrane, wherein the cation exchange layer has a different thickness from the anion exchange layer so as to increase the water transport rate at the anion exchange layer-cation exchange layer interface, and A catalyst disposed between the anion exchange layer and the cation exchange layer, which catalyzes a water dissociation reaction and includes a plurality of ionization sites having the properties of proton donation, proton abstraction, or a combination thereof, wherein the plurality of ionization sites enhance the electric field at the anion exchange layer-cation exchange layer interface. A self-supporting bipolar membrane including, The self-supporting bipolar film is positioned between the anode and cathode. An electrodialysis cell equipped with [a specific feature].

12. A cell according to claim 11, wherein the self-supporting bipolar membrane is the bipolar membrane according to claim 1 or 2.

13. A direct ocean recovery method, The step involves bringing a water source containing dissolved carbon into contact with a bipolar membrane, wherein the bipolar membrane is Anion exchange layer containing an anion exchange membrane, A cation exchange layer containing a cation exchange membrane, wherein the cation exchange layer has a different thickness from the anion exchange layer so as to increase the water transport rate at the anion exchange layer-cation exchange layer interface, and A catalyst disposed between the anion exchange layer and the cation exchange layer, which catalyzes a water dissociation reaction and includes a plurality of ionization sites having the properties of proton donation, proton abstraction, or a combination thereof, wherein the plurality of ionization sites enhance the electric field at the anion exchange layer-cation exchange layer interface. Steps including, The step involves recovering the carbon dioxide gas flow, and the bipolar membrane is used to enhance the efficiency of generating the carbon dioxide gas flow. The steps include recovering an output water flow with a lower dissolved carbon concentration than the aforementioned water source, and A method that includes this.

14. A method according to claim 13, wherein the bipolar film is the bipolar film described in claim 1 or 2.

15. The method according to claim 13, wherein the water source is selected from the group consisting of natural seawater, river water, pre-treated seawater, or any combination thereof.

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