Patent Application
20240376254
Renewable energy sources, such as wind and solar power, have transient characteristics, which require energy storage. Renewable energy storage systems such as redox flow batteries (RFBs) have attracted significant attention for electricity grid, electric vehicles, and other large-scale stationary applications. RFB is an electrochemical energy storage system that reversibly converts chemical energy directly to electricity. The conversion of electricity via water electrolysis into hydrogen as an energy carrier without generation of carbon monoxide or dioxide as byproducts enables a coupling of the electricity, chemical, mobility, and heating sectors.
The electrochemical conversion of CO2 via CO2 electrolysis using renewably generated electricity is an appealing approach for the production of sustainable hydrocarbons, alcohols, and carbonyl products widely used in numerous industrial sectors.
Hydrogen as an energy vector for grid balancing or power-to-gas and power-to-liquid processes plays an important role in the path toward a low-carbon energy structure that is environmentally friendly. Water electrolysis produces high quality hydrogen by electrochemically splitting water into hydrogen and oxygen; the reaction is given by Eq. 1 below. The water electrolysis process is an endothermic process, and electricity is the energy source. Water electrolysis has zero carbon footprint when the process is powered by renewable energy sources, such as wind, solar, or geothermal energy. The main water electrolysis technologies include alkaline electrolysis, proton exchange membrane (PEM) water electrolysis as shown in
As shown in
Water electrolysis reaction: 2H2O→2H2+O2 (1)
Oxidation reaction at anode for PEMWE: 2H2O→O2+4H++4e− (2)
Reduction reaction at cathode for PEMWE: 2H++2e−→H2 (3)
AEMWE is a developing technology. As shown in
Reduction reaction at cathode for AEMWE: 4H2O+4e−→2H2+4OH− (4)
Oxidation reaction at anode for AEMWE: 4OH−→2H2O+O2+4e− (5)
AEMWE has an advantage over PEMWE because it permits the use of less expensive platinum metal-free catalysts, such as Ni and Ni alloy catalysts. In addition, much cheaper stainless steel bipolar plates can be used in the gas diffusion layers (GDL) for AEMWE, instead of the expensive Pt-coated Ti bipolar plates currently used in PEMWE. However, the largest impediments to the development of AEM systems are membrane hydroxyl ion conductivity and stability, as well as lack of understanding of how to integrate catalysts into AEM systems. Research on AEMWE in the literature has been focused on developing electrocatalysts, AEMs, and understanding the operational mechanisms with the general objective of obtaining a high efficiency, low cost and stable AEMWE technology.
Fuel cells, as a next generation clean energy resource, convert the energy of chemical reactions such as an oxidation/reduction redox reaction of hydrogen and oxygen into electric energy. The three main types of fuel cells are alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells, and solid oxide fuel cells. Polymer electrolyte membrane fuel cells may include proton exchange membrane fuel cells (PEMFC), anion exchange membrane fuel cells (AEMFC), and direct methanol fuel cells. PEMFC uses a PEM to conduct protons from the anode to the cathode, and it also separates the H2 and O2 gases to prevent gas crossover. AEMFC uses an AEM to conduct OH− from the cathode to the anode, and it also separates the H2 and O2 gases to prevent gas crossover.
Redox flow batteries (RFBs) comprise two external storage tanks filled with active materials comprising metal ions that may be in different valance states, two circulation pumps, and a flow cell with a separation membrane and two electrodes. The separation membrane is located between the anode and the cathode and is used to separate the anolyte and the catholyte, as well as to utilize the current circuit by allowing the transfer of balancing ions. The anolyte, catholyte, anode, and cathode may also be referred to as plating electrolyte or negative electrolyte, redox electrolyte or positive electrolyte, plating electrode or negative electrode, and redox electrode or positive electrode respectively. Among all the redox flow batteries developed to date, all vanadium redox flow batteries (VRFB) have been the most extensively studied. VRFB uses the same vanadium element in both half cells which prevents crossover contamination of electrolytes from one half cell to the other half cell. VRFB, however, is inherently expensive due to the use of high-cost vanadium and an expensive membrane. All-iron redox flow batteries (IFB) are particularly attractive for grid scale storage applications due to the use of low cost and abundantly available iron, salt, and water as the electrolyte and the non-toxic nature of the system.
The membrane is one of the key materials that make up a battery, an electrolysis cell, or a fuel cell, and it is an important driver for safety and performance. Some important properties for membranes for flow batteries, fuel cells, and membrane electrolysis include high conductivity, high ionic permeability, high ionic exchange capacity (for ion-exchange membrane), high ionic/H2 and O2 selectivity (low H2 and O2 permeability/crossover) or high ionic/electrolyte selectivity (low permeability/crossover to electrolytes), low price, low area resistance to minimize efficiency loss resulting from ohmic polarization, high resistance to oxidizing and reducing conditions, being chemically inert at a wide pH range, high thermal stability together with high proton conductivity (greater than or equal to 120° C. for fuel cell), high proton conductivity at high temperature without H2O, high proton conductivity at high temperature with maintained high relative humidity, and high mechanical strength (thickness, low swelling).
Significant advances are needed in cost-effective, high performance, stable ion exchange polymers, membranes, catalyst-coated membranes (CCMs), and other cell stack components for electrolysis, fuel cells, and energy storage with a wide range of applications in renewable energy systems.
Deuterium, a stable hydrogen isotope, has been playing an important role in polymer science. Deuterated polymers have been studied for about 60 years. The substitution of protium with deuterium in polymers has significantly affected their structures and properties and has provided new functional polymers. For example, Deuterated polymers have been used in organic light emitting diodes (OLEDs) for television monitors and the displays for smartphones, tablets, and other devices. By replacing the labile C—H bonds in the host with C-D bonds for the OLED device, an increase in the device lifetime by a factor of five without a loss of efficiency was achieved.
AEMs prepared from ion exchange polymers comprising positively charged anion exchange functional groups are polymeric electrolytes (also called ionomers) that can conduct anions such as OH− or CO32- in an electrochemical reaction system. Different types of quaternary ammonium anion exchange functional groups have been investigated for AEM electrolysis and fuel cell applications. However, most of the commercially available AEMs showed unstable performance towards hydroxide due to different mechanisms of decomposition such as an SN2 reaction mechanism or an E2 mechanism (Hofmann elimination). In an SN2 reaction, the hydroxide anion attacks an electron deficient methylene carbon connected directly to the positively charged anion exchange nitrogen atom. In a Hofmann elimination reaction, the hydroxide abstracts an accessible, relatively acidic proton β to the nitrogen atom. In an AEM electrolysis cell or AEM fuel cell, the hydroxide anions transported through the AEM from the cathode to the anode will attack the positively charged anion exchange functional groups via the reactions mentioned above, which results in the degradation of the anion exchange functional groups and therefore reduces the cell performance. The stability of the AEMs determines the lifetime of the AEM-based electrochemical cell.
The present invention relates to a new type of deuterated anion exchange polymers and anion exchange membranes (AEMs) comprising the deuterated anion exchange polymers. The present invention also relates to new catalyst-coated membranes (CCMs) comprising the deuterated anion exchange polymers, respectively, for electrochemical reactions such as water electrolysis for green H2 production, CO2 electrolysis for the production of sustainable hydrocarbons, alcohols, and carbonyl products, or fuel cell applications.
Deuteration resulted in stronger chemical bonds C-D bonds and stronger van der Waals interactions in the present deuterated anion exchange polymers. Therefore, the stability of the deuterated polymers in the present invention against thermal, oxidative, reductive, and corrosive conditions can be significantly higher than that of its protiated counterpart because the primary polymer degradation process in the AEM-based electrochemical processes involves breaking C—H bonds such as Hofmann elimination.
Novel deuterated anion exchange polymers comprising a plurality of repeating units of formula (I)
The deuterated anion exchange polymers were designed to: enhance chemical and thermal stability by incorporating deuterated X1 or both deuterated X1 and deuterated Ar2 into the anion exchange polymers comprising a plurality of repeating units of formula (I) and a polymer backbone free of ether bonds, enhance OH− conductivity by incorporating a quaternized carbazole derivative, or a quaternized phenothiazine derivative, or both into the polymer side chain comprising piperidinium or a piperidinium salt; and increase polymer backbone rigidity and molecular weight to enhance the mechanical strength of the polymer. The polymers have deuterated hydrophilic polymer side chains, stable hydrophilic quaternary ammonium cationic groups, such as quaternized carbazole derivative, piperidinium ion-conducting functional groups, or quaternized phenothiazine derivative. The deuterated anion exchange polymers enable efficient and stable operation in water or CO2 electrolysis, redox flow battery, and fuel cell applications.
One aspect of the invention is a deuterated anion exchange polymer. In one embodiment, the polymer comprises a plurality of repeating units of formula (I)
In some embodiments, Ar1 is selected from the group consisting of
In some embodiments, Ar1 is selected from the group consisting of
In some embodiments, Ar1 is selected from the group consisting of
In some embodiments, Ar2 is selected from the group consisting of
In some embodiments, X1 is
In some embodiments, X1 is
In some embodiments, X1 is a mixture of
In some embodiments, X1 is a mixture of
In some embodiments, X1 is a mixture of
The deuterated anion exchange polymer comprising a plurality of repeating units of formula (I) may be synthesized by two steps: 1) a superacid or deuterated superacid catalyzed polyhydroxyalkylation reaction of monomers Ar1′ and Ar2′ with deuterated monomer X1′ to form a neutral precursor polymer; and 2) a Menshutkin reaction to convert the neutral precursor polymer with functional groups, such as piperidine-based groups, to the anion exchange polymer comprising a plurality of repeating units of formula (I) with anion-conducting functional groups, such as piperidinium-based cation groups; wherein Ar1′ is selected from the group consisting of:
In some embodiments, the deuterated anion exchange polymer comprising a plurality of repeating units of formula (I) has no Ar2 and may be synthesized by two steps: 1) a superacid or deuterated superacid catalyzed polyhydroxyalkylation reaction of monomers Ar1′ such as a mixture of p-terphenyl and phenanthrene with deuterated monomer X1′ such as N-methyl-4-piperidone-d4 to form a neutral precursor polymer; and 2) a Menshutkin reaction to convert the neutral precursor polymer with functional groups, such as piperidine-based groups, to the anion exchange polymer comprising a plurality of repeating units of formula (I) with anion-conducting functional groups, such as piperidinium-based cation groups.
Optionally, the deuterated anion exchange polymer comprising a plurality of repeating units of formula (I) with anion-conducting functional groups, such as piperidinium-based cation groups, quaternized carbazole derivative cation groups, and negatively charged halide, bicarbonate, or acetate ions is converted to a deuterated anion exchange polymer comprising a plurality of repeating units of formula (I) with anion-conducting functional groups, such as piperidinium-based cation groups, quaternized carbazole derivative cation groups, and negatively charged OH− ions by soaking in a base solution before the polymer is made into a membrane.
The polyhydroxyalkylation reaction of monomer Ar1′ and deuterated monomer Ar2′ with deuterated monomer X1′ provides a deuterated anion exchange polymer with a polymer backbone free of ether bonds, which results in high chemical stability of the polymer. The incorporation of deuterated X1′ monomer or deuterated X1′ and Ar2′ monomers resulted in stronger C-D bonds and stronger van der Waals interactions in the present deuterated anion exchange polymers which helps achieve stable high OH− conductivity. In some cases, the monomer X1′ is a mixture of a deuterated piperidone-based monomer and a non-piperidone-based monomer to enable the formation of a high molecular weight deuterated anion exchange polymer. The combination of the hydrophobic polymer backbone, the hydrophilic polymer side chains, and deuterated monomer provides the novel deuterated anion exchange polymer with high OH− conductivity, high chemical and thermal stability, high mechanical strength, and long-term performance stability. The molar ratio of Ar1′ monomer to Ar2′ monomer can be in a range of 1:0 to 1:50, or in a range of 1:0 to 1:10, or in a range of 20:1 to 1:5. The molar ratio of X1′ monomer to the total of Ar1′ and Ar2′ monomers can be in a range of 1.2:1 to 1:1.2, or in a range of 1.1:1 to 1:1.1, or in a range of 1.05:1 to 1:1.05.
The superacid catalyzed polyhydroxyalkylation reaction can be carried out at −10° C. to 50° C., or at −5° C. to 30° C., or at −5° C. to 25° C. for 2 h to 72 h, or 10 h to 48 h, or 12 to 24 h. Suitable superacid catalysts include, but are not limited to, trifluoromethanesulfonic acid (CF3SO3H (TFSA)), deuterated trifluoromethanesulfonic acid (CF3SO3D (TFSA-d1)), methanesulfonic acid (MSA), deuterated methanesulfonic acid (MSA-d1), fluorosulfuric acid (FSO3H), deuterated fluorosulfuric acid (FSO3D), or mixtures thereof. Solvents for the polyhydroxyalkylation reaction are those that can dissolve one or more of the monomers. Suitable solvents include, but are not limited to, methylene chloride, deuterated methylene chloride, chloroform, deuterated chloroform, trifluoroacetic acid (TFA), deuterated trifluoroacetic acid (TFA-d1), or mixtures thereof.
The Menshutkin reaction is used to react the neutral precursor polymer with an alkyl halide, or with a trialkyl amine first followed by an alkyl halide to convert the neutral precursor polymer to the deuterated anion exchange polymer comprising a plurality of repeating units of formula (I). Suitable alkyl halides include, but are not limited to, alkyl iodides, deuterated alkyl iodides, alkyl bromides, or deuterated alkyl bromides. Suitable alkyl amines include, but are not limited to, trimethyl amine or triethyl amine. The Menshutkin reaction can be carried out at 10° C. to 80° C., or at 20° C. to 30° C. for 2 h to 72 h, or 10 h to 48 h, or 12 to 24 h. Solvents for the Menshutkin reaction are those that can dissolve the neutral precursor polymer. Suitable solvents include, but are not limited to, N-methylpyrrolidone (NMP), N,N-dimethyl acetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,3-dioxolane, deuterated solvents thereof, or mixtures thereof.
The deuterated anion exchange polymer comprising a plurality of repeating units of formula (I) has a weight average molecular weight in a range of 10,000 to 1,000,000 Daltons, or in a range of 50,000 to 500,000 Daltons.
Another aspect of the invention is a deuterated anion exchange membrane comprising the polymer described above. The deuterated anion exchange membrane may be used in a wide variety of applications including, but not limited to, fuel cells, electrolyzers, flow batteries, electrodialyzers, waste metal recovery systems, electrocatalytic hydrogen production systems, desalinators, water purifiers, waste water treatment systems, ion exchangers, or CO2 separators.
In some embodiments, the deuterated anion exchange membrane comprises a nonporous symmetric dense film membrane, an integrally-skinned asymmetric membrane, a reinforced composite membrane, or a thin film composite membrane. By “dense” we mean that the membrane does not have pores larger than 1 nm.
In some embodiments, the reinforced composite membrane or the thin film composite membrane comprises a porous substrate membrane impregnated or coated with the ion exchange polymer. The porous substrate membrane is prepared from a polymer different from the ion exchange polymer.
In some embodiments, the nonporous symmetric dense film membrane, the integrally-skinned asymmetric membrane, the reinforced composite membrane, or the thin film composite membrane may be a flat sheet membrane.
In some embodiments, the nonporous symmetric dense film deuterated anion exchange membrane is prepared using a method comprising: 1) dissolving the deuterated anion exchange polymer in a solvent to form a polymer casting solution; 2) casting the polymer casting solution on a nonporous substrate to form a uniform layer of the polymer casting solution; 3) drying the polymer casting solution layer to form a dried membrane on the nonporous substrate at 50° C. to 180° C., or at 50° C. to 120° C., or at 80° C. to 120° C.; and optionally 4) ion exchanging the halide anions of the deuterated anion exchange polymer in the membrane with hydroxide, bicarbonate, acetate, carbonate ions, or a combination thereof to form the nonporous symmetric dense film deuterated anion exchange polymer membrane. The nonporous substrate is removed from the membrane when the membrane is used in a desired application. The solvent used to dissolve the anion exchange polymer can be selected from, but is not limited to, NMP, DMAc, DMF, DMSO, 1,3-dioxolane, or mixtures thereof. The nonporous substrate used for the fabrication of the nonporous symmetric dense film membrane can be selected from, but is not limited to, glass plate, polyolefin film, polyester film, or fluorocarbon-based polymer film such as poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) film.
In some embodiments, the integrally-skinned asymmetric deuterated anion exchange membrane is prepared using a method comprising: 1) making a deuterated anion exchange polymer membrane casting solution comprising the deuterated anion exchange polymer with formula (I), solvents which are miscible with water and can dissolve the deuterated anion exchange polymer, and non-solvents which cannot dissolve the deuterated anion exchange polymer; 2) casting a layer of the deuterated anion exchange polymer membrane casting solution onto a supporting substrate; 3) evaporating the solvent and non-solvent from the surface of the coated layer and then coagulating the coated polymer layer in a coagulating bath to form the integrally-skinned asymmetric membrane structure; 5) drying the membrane at 50° C. to 150° C., or at 50° C. to 120° C., or at 80° C. to 120° C.; and optionally 6) ion exchanging the halide anions of the deuterated anion exchange polymer in the membrane with hydroxide, bicarbonate, acetate, carbonate ions, or a combination thereof to form the integrally-skinned asymmetric deuterated anion exchange polymer membrane. In some embodiments, the supporting substrate is removed from the membrane when the membrane is used in a desired application. In some embodiments, the supporting substrate is part of the final integrally-skinned asymmetric deuterated anion exchange polymer membrane. The supporting substrate may comprise polyolefin such as polypropylene and polyethylene, polyester, polyamide such as Nylon 6 and Nylon 6,6, cellulose, or fluorocarbon-based polymer such as PTFE and PVDF. The solvents for the preparation of the integrally-skinned asymmetric membrane include, but are not limited to, NMP, DMAc, DMF, DMSO, dioxanes, 1,3-dioxolane, and mixtures thereof. The non-solvents for the preparation of the integrally-skinned asymmetric membrane include, but are not limited to, acetone, methanol, ethanol, tetrahydrofuran (THF), toluene, n-octane, n-decane, lactic acid, citric acid, isopropanol, and mixtures thereof. The integrally-skinned asymmetric membrane may have a thin nonporous dense layer less than 500 nm on a microporous support layer.
In some embodiments, the reinforced composite deuterated anion exchange membrane is prepared using a method comprising: 1) dissolving the deuterated anion exchange polymer in a solvent to form a polymer solution; 2) impregnating a porous matrix support membrane with the deuterated anion exchange polymer solution to fill the pores with the deuterated anion exchange polymer via dip-coating, soaking, spraying, painting, or other known conventional solution impregnating method; 3) drying the impregnated membrane at 50° C. to 150° C., or at 50° C. to 120° C., or at 80° C. to 120° C.; and optionally 4) ion exchanging the halide anions of the deuterated anion exchange polymer in the pores of the reinforced membrane with hydroxide, bicarbonate, acetate, carbonate ions, or a combination thereof to form the reinforced composite deuterated anion exchange membrane with interconnected anion exchange polymer domains in a porous matrix. The solvents for the preparation of the thin film composite deuterated anion exchange membrane include, but are not limited to, NMP, DMAc, DMF, DMSO, dioxanes, 1,3-dioxolane, and mixtures thereof. The porous matrix should have good thermal stability (stable up to at least 120° C.), high stability under high pH condition (e.g., pH greater than 8), high resistance to oxidizing and reducing conditions (insoluble and no performance drop under oxidizing and reducing conditions), high mechanical strength (no dimensional change under the system operation conditions), as well as other factors dictated by the operating conditions for electrochemical reactions. The porous matrix must be compatible with the electrochemical cell chemistry and meet the mechanical demands of cell stacking or winding assembly operations.
The polymers suitable for the preparation of the porous matrix can be selected from, but not limited to, polyolefins such as polyethylene and polypropylene, polyamide such as Nylon 6 and Nylon 6,6, polyester, cellulose acetate, polybenzimidazole, fluorocarbon-based polymer such as PTFE and PVDF, polycarbonate, cellulose, or combinations thereof. These polymers provide a range of properties such as low cost, high stability in alkaline water, good mechanical stability, and ease of processability for porous matrix fabrication.
The porous matrix can either a non-woven matrix or a woven matrix and have either a symmetric porous structure or an asymmetric porous structure. The porous matrix can be formed by an electrospinning process, a phase inversion membrane fabrication approach followed by direct air drying, or by phase inversion followed by solvent exchange methods. The porous matrix also can be fabricated via a dry processing of thermoplastic polyolefins or a wet processing of thermoplastic olefins. The dry processing of thermoplastic polyolefins utilizes extrusion to bring the polymer above its melting point and form it into the desired shape. Subsequent annealing and stretching processes may also be done to increase the crystallinity and orientation and dimension of the pores. The wet processing of polyolefin porous matrix is done with the aid of a hydrocarbon liquid or low molecular weight oil mixed with the polymer resin or a mixture of the polymer resin and inorganic nanoparticles in the melt phase. The melt mixture is extruded through a die similar to the dry processed separators. The thickness of the porous matrix can be in a range of 10-400 micrometers, or a range of 10-200 micrometers, or a range of 10-100 micrometers, or a range of 20-100 micrometers. The pore size of the porous matrix can be in a range of 1 micrometer to 500 micrometers, or a range of 10 micrometer to 200 micrometers, or a range of 50 micrometers to 100 micrometer.
In some embodiments, the thin film composite deuterated anion exchange membrane is prepared using a method comprising: 1) dissolving the deuterated anion exchange polymer in a solvent to form a polymer coating solution; 2) coating a layer of the deuterated anion exchange polymer coating solution on one surface of a microporous support membrane via dip-coating, meniscus coating, spin coating, casting, soaking, spraying, painting, or other known conventional solution coating technologies; 3) drying the coated membrane at 50° C. to 150° C., or at 50° C. to 120° C., or at 80° C. to 120° C.; and optionally 4) ion exchanging the halide anions of the deuterated anion exchange polymer in the coating layer with hydroxide, bicarbonate, acetate, carbonate ions, or a combination thereof to form the thin film composite deuterated anion exchange membrane. The solvents for the preparation of the thin film composite deuterated anion exchange membrane include, but are not limited to, NMP, DMAc, DMF, DMSO, dioxanes, 1,3-dioxolane, and mixtures thereof. The microporous support membrane should have good thermal stability (stable up to at least 120° C.), high stability under high pH condition (e.g., pH greater than 8), high resistance to oxidizing and reducing conditions (insoluble and no performance drop under oxidizing and reducing conditions), high mechanical strength (no dimensional change under the system operation conditions), as well as other factors dictated by the operating conditions for electrochemical reactions. The microporous support membrane must be compatible with the electrochemical cell chemistry and meet the mechanical demands of cell stacking or winding assembly operations.
The polymers suitable for the preparation of the microporous support membrane can be selected from, but not limited to, polyolefins such as polyethylene and polypropylene, polyamide such as Nylon 6 and Nylon 6,6, polyester, cellulose acetate, polybenzimidazole, fluorocarbon-based polymer such as PTFE and PVDF, polycarbonate, cellulose, or combinations thereof. These polymers provide a range of properties such as low cost, high stability in alkaline water, good mechanical stability, and ease of processability for membrane fabrication.
The microporous support membrane can have either a symmetric porous structure or an asymmetric porous structure. The asymmetric microporous support membrane can be formed by a phase inversion membrane fabrication approach followed by direct air drying, or by phase inversion followed by solvent exchange methods. The microporous support membrane also can be fabricated via a dry processing of thermoplastic polyolefins or a wet processing of thermoplastic olefins. The dry processing of thermoplastic polyolefins utilizes extrusion to bring the polymer above its melting point and form it into the desired shape. Subsequent annealing and stretching processes may also be done to increase the crystallinity and orientation and dimension of the micropores. The wet processing of polyolefin separators is done with the aid of a hydrocarbon liquid or low molecular weight oil mixed with the polymer resin or a mixture of the polymer resin and inorganic nanoparticles in the melt phase. The melt mixture is extruded through a die similar to the dry processed separators. The thickness of the microporous support membrane can be in a range of 10-400 micrometers, or a range of 10-200 micrometers, or a range of 10-100 micrometers, or a range of 20-100 micrometers. The pore size of the microporous membrane can be in a range of 10 nanometers to 50 micrometers, or a range of 50 nanometers to 10 micrometers, or a range of 0.2 micrometers to 1 micrometer.
Another aspect of the invention is a membrane electrode assembly. In one embodiment, the membrane electrode assembly comprises: a deuterated anion exchange membrane comprising the deuterated anion exchange polymer described above; an anode comprising an anode catalyst on a first surface of the deuterated ion exchange membrane; and a cathode comprising a cathode catalyst on a second surface of the deuterated anion exchange membrane; and
In some embodiments, the membrane electrode assembly further comprises: an anode porous transport layer adjacent to the anode; and a cathode porous transport layer adjacent to the cathode. In some embodiments, the anode and the cathode catalysts are platinum group metal (PGM)-free electrocatalysts. The anode and the cathode catalysts are for oxygen evolution reaction and hydrogen evolution reaction, respectively. The anode and the cathode catalysts should have low cost, good electrical conductivity, and good electrocatalytic activity and stability. Suitable cathode catalysts can be selected from, but are not limited to, Ni-based alloys such as Ni—Mo, Ni—Al, Ni—Cr, Ni—Sn, Ni—Co, Ni—W, and Ni—Al—Mo, metal carbides such as Mo2C, metal phosphides such as CoP, metal dichalcogenides such as MoSe2, and mixtures thereof. Suitable anode catalysts can be selected from, but are not limited to, Ni—Fe alloy, Ni—Mo alloy, spinel CuxCo3xO3, Ni—Fe layered double hydroxide nanoplates on carbon nanotubes, immobilized metal catalyst on conductive supports, and mixtures thereof.
In some embodiments, the anode comprising an anode catalyst on a first surface of the deuterated anion exchange membrane is formed by coating an anode catalyst ink on the first surface of the deuterated anion exchange membrane via meniscus coating, knife coating, spray coating, painting, or other known conventional ink coating technologies, followed by drying the coated deuterated anion exchange membrane.
In some embodiments, the cathode comprising a cathode catalyst on a second surface of the deuterated anion exchange membrane is formed by coating a cathode catalyst ink on the second surface of the deuterated anion exchange membrane via meniscus coating, knife coating, spray coating, painting, or other known conventional ink coating technologies, followed by drying the deuterated coated anion exchange membrane.
In some embodiments, the anode catalyst ink comprises the anode catalyst, an OH− exchange ionomer selected from the deuterated anion exchange polymer in the present invention as a binder, and a solvent. In some embodiments, the cathode catalyst ink comprises the cathode catalyst, an OH− exchange ionomer selected from the deuterated anion exchange polymer in the present invention as a binder, and a solvent. The OH− exchange ionomer selected from the deuterated anion exchange polymer in the present invention binder creates OH− transport pathways between the membrane and the reaction sites within the electrodes and thus drastically improves the utilization of the electrocatalyst particles while reducing the internal resistance. The OH− exchange ionomer binder can have a chemical structure similar to the deuterated anion exchange polymer described above, so that the binder will allow low interfacial resistance and similar expansion in contact with water to avoid catalyst delamination, but OH− conductivity and high oxygen and hydrogen permeance. The solvent can be selected from, but is not limited to, water, alcohol, or a mixture thereof.
The anode porous transport layer and the cathode porous transport layer simultaneously transport electrons, heat, and products with minimum voltage, current, thermal, interfacial, and fluidic losses. The cathode porous transport layer can be made from, but is not limited to, stainless steel, titanium meshes, titanium felts, titanium foams, or carbon-based materials such as non-woven carbon paper, non-woven carbon cloth, or woven carbon cloth. The anode porous transport layer can be made from, but is not limited to, stainless steel, titanium meshes, titanium felts, or titanium foams.
While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.
A first embodiment of the invention is a deuterated anion exchange polymer for electrochemical reactions. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the electrochemical reactions comprise water electrolysis, CO2 electrolysis, fuel cell, and flow battery. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the deuterated anion exchange polymer comprises a plurality of repeating units of formula (I)
A second embodiment of the invention is a method of making a deuterated anion exchange polymer comprising reacting a deuterated monomer X1′ with monomer Ar1′ and deuterated monomer Ar2′ via a polyhydroxyalkylation reaction in the presence of a super acid or deuterated super acid catalyst to synthesize a neutral precursor polymer; and a Menshutkin reaction to convert the neutral precursor polymer to the deuterated anion exchange polymer comprising a plurality of repeating units of formula (I), wherein Ar1′ is selected from the group consisting of
A third embodiment of the invention is an anion exchange membrane comprising a deuterated anion exchange polymer. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the deuterated anion exchange polymer comprises the deuterated polymer of any one of the first embodiments. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph, wherein the deuterated anion exchange membrane is used in a fuel cell, an electrolyzer, a flow battery, an electrodialyzer, a waste metal recovery system, an electrocatalytic hydrogen production system, a desalinator, a water purifier, a waste water treatment system, an ion exchanger, or a CO2 separator. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the deuterated anion exchange membrane comprises a nonporous symmetric dense film membrane, an integrally-skinned asymmetric membrane, a reinforced composite membrane, or a thin film composite membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the integrally-skinned asymmetric membrane, the reinforced composite membrane, or the thin film composite membrane comprises a porous substrate material impregnated or coated with the deuterated anion exchange polymer.
A fourth embodiment of the invention is a membrane electrode assembly, comprising a deuterated anion exchange membrane comprising a deuterated anion exchange polymer; a cathode comprising a cathode catalyst on a first surface of the deuterated anion exchange membrane; and optionally an anode comprising an anode catalyst on a second surface of the deuterated anion exchange membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the fourth embodiment in this paragraph wherein the deuterated anion exchange polymer comprises the deuterated anion exchange polymer of any one of the first embodiments. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the fourth embodiment in this paragraph further comprising a cathode porous transport layer adjacent to the cathode; and an anode porous transport layer adjacent to the anode or an anode catalyst-coated anode porous transport layer adjacent to the deuterated anion exchange membrane.
Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.
In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.
This application claims priority to U.S. Provisional Patent Application Ser. No. 63/501,915, filed on May 12, 2023, the entirety of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63501915 | May 2023 | US |
