Boron-containing porous membranes and methods of use thereof

Abstract

A proton exchange membrane includes a porous structural framework and a boron-based acid group bonded to the porous structural framework. The porous structural framework may be formed from an amorphous or crystalline inorganic material and / or a synthetic or natural polymer. The boron-based acid group may be a boronic acid derivative, such as a cyclic boronic acid derivative, a boron spiroalkanoic acid, or a boron spiroalkanoic acid derivative. The boron-based acid group may be a reaction product of boric acid or a boric acid derivative with a polyhydroxy compound.

Description

[0001] This application is a divisional application of the invention application with international application number PCT / US2021 / 029705 filed on April 28, 2021, Chinese national application number 202180081973.0, and invention name “Boron-containing porous membrane and method of use thereof”.

[0002] Related applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 63 / 109,943, filed on November 5, 2020, the entire contents of which are incorporated herein by reference. Background Art

[0004] Proton exchange membranes (PEMs) are semipermeable membranes designed to transport protons (H + ), while being impermeable to gases such as hydrogen (H2) and oxygen (O2). PEM can be used in hydrogen fuel cells and water electrolysis systems under acidic conditions. PEM can be composed of a porous framework with mechanical and chemical resistance having highly acidic functional groups. For example, Nafion-based proton exchange membranes contain a polytetrafluoroethylene (PTFE) porous structure framework with sulfonic acid groups. The easily dissociated sulfonic acid groups act as proton transport agents in the membrane. Summary of the Invention

[0005] The following description presents a simplified overview of one or more aspects of the methods and systems described herein in order to provide a basic understanding of these aspects. This summary is not an extensive overview of all contemplated aspects and is neither intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects of the methods and systems described herein in a simplified form as a prelude to the more detailed description presented below.

[0006] In some exemplary embodiments, the proton exchange membrane includes a porous structural framework and boron-based acid groups bound to the porous structural framework.

[0007] In some exemplary embodiments, the boron-based acid group comprises a cyclic boronic acid derivative.

[0008] In some exemplary embodiments, the boron-based acid group comprises borospiranic acid.

[0009] In some exemplary embodiments, the boron-based acid group comprises a catechol derivative.

[0010] In some exemplary embodiments, the porous structural framework comprises solid support particles connected via the boron-based acid groups.

[0011] In some exemplary embodiments, the porous structural framework comprises a porous polymer network, and the boron-based acid groups are bound to pore surfaces of the polymer network.

[0012] In some exemplary embodiments, the porous structural framework comprises an inorganic material.

[0013] In some exemplary embodiments, a method of preparing a proton exchange membrane includes bonding boron-based acid groups to the surfaces of pores contained in a porous structural framework.

[0014] In some exemplary embodiments, the binding comprises reacting boronic acid or a boronic acid derivative with hydroxyl groups present on the surface of the pore.

[0015] In some exemplary embodiments, the binding comprises reacting a polyol with a boronic acid derivative bound to the pore surface.

[0016] In some exemplary embodiments, the method further comprises coupling the nanoparticles to the pore surface via a boron-based acid group.

[0017] In some exemplary embodiments, a membrane electrode assembly includes a cathode, an anode, and a proton exchange membrane located between the cathode and the anode, the proton exchange membrane including a porous structural framework and boron acid groups bonded to pore surfaces in the porous structural framework.

[0018] In some exemplary embodiments, at least one of the anode or cathode includes a catalyst and an ionomer for binding the catalyst, and the ionomer includes a boron-based acid group. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings show various embodiments and are a part of the specification. The embodiments described are examples only and do not limit the scope of the present invention. In all drawings, the same or similar reference numerals represent the same or similar elements.

[0020] Figure 1 An exemplary proton exchange membrane comprising a porous structural framework and boron-based acid groups bound to the pore surfaces of the porous structural framework is shown.

[0021] Figure 2A Shows Figure 1 Exemplary configurations of the porous structural framework and boronate acid groups within the PEM.

[0022] Figure 2B Shows Figure 1 Another exemplary configuration of a porous structural framework and boronate acid groups within a PEM.

[0023] Figure 3AAn exemplary reaction scheme for the synthesis of cyclic boronic acid derivatives is shown.

[0024] Figure 3B An exemplary reaction scheme for the synthesis of boranoic acids is shown.

[0025] Figure 4A An exemplary reaction scheme for the synthesis of solid support-bound monocyclic cyclic boronic acid derivatives is shown.

[0026] Figure 4B An exemplary reaction scheme for the synthesis of solid support-bound boranoic acids having pendant moieties is shown.

[0027] Figure 5A An exemplary reaction scheme for the synthesis of solid support-bound cyclic boronic acid derivatives with catechol derivatives is shown.

[0028] Figure 5B An exemplary reaction scheme for the synthesis of solid support-bound boranoic acids having a catechol derivative and a pendant moiety is shown.

[0029] Figure 6 An exemplary reaction scheme 600 for synthesizing a cross-linked copolymer containing boronate acid groups is shown.

[0030] Figure 7 An exemplary reaction scheme for functionalizing the pore surface of a porous structural framework with boronic acid derivatives is shown.

[0031] Figure 8A Another exemplary reaction scheme for functionalizing the pore surface of a porous structural framework with a boronic acid derivative is shown.

[0032] Figure 8B Another exemplary reaction scheme for functionalizing the pore surface of a porous structural framework with a boronic acid derivative (boronospiroic acid) is shown.

[0033] Figure 9A An exemplary reaction scheme for coupling particles (eg, nanoparticles) to the pore surface of a porous structural framework using a boronic acid derivative (eg, boranoic acid) is shown.

[0034] Figure 9B An exemplary reaction scheme is shown for cross-linking a plurality of particles comprising a plurality of sheets into a polymer structure using a boronic acid derivative.

[0035] Figure 10 An exemplary proton exchange membrane water electrolysis system with a boron-containing porous membrane is shown.

[0036] Figure 11 An exemplary proton exchange membrane fuel cell having a boron-containing porous membrane is shown. DETAILED DESCRIPTION

[0037] Boron-containing porous membranes and methods for preparing and using boron-containing porous membranes are described herein. In some instances, the boron-containing porous membrane comprises a porous structural framework and boron-containing acid groups covalently bonded to the porous structural framework. The porous structural framework can be formed from an amorphous or crystalline inorganic material and / or a synthetic or natural polymer. The boron-containing acid group can be a boronic acid derivative, such as a cyclic boronic acid derivative, boranoic acid, or a boranoic acid derivative. In some instances, the boron-containing acid group is the reaction product of boric acid or a boronic acid derivative and a polyhydroxy compound.

[0038] Boron-containing porous membranes as described herein can be used as PEMs for water electrolysis and / or fuel cell applications operated under acidic conditions. In boron-containing PEMs as described herein, cation (e.g., proton) exchange is provided by ionically connecting to protons on negatively charged tetravalent boron atoms. The presence of oxygen-boron bonds increases the hydrophilicity of the porous structure framework and stabilizes negatively charged boron atoms. Boron-containing PEMs as described herein also have high mechanical strength, high proton conductivity, low electronic conductivity, chemical stability under large pH gradients, durability and low production cost. Boron-containing porous membranes can be prepared by boric acid and its precursor (such as borax), which are naturally abundant and inexpensive. In some instances, boron-containing porous membranes as described herein do not contain toxic substances either.

[0039] The boron-containing porous membranes described herein can also be used to filter and / or neutralize pathogens such as bacteria, viruses, and fungal spores. For example, the boron-containing porous membranes can be implemented in face masks, surgical masks, air filters, and air purification systems for enclosed spaces (e.g., homes, offices, hospitals, factories, vehicles, airplanes, etc.).

[0040] The devices, compositions, and methods described herein can provide one or more of the above benefits and / or various additional and / or further benefits that will become apparent herein. Various embodiments will now be described in more detail with reference to the accompanying drawings. It should be understood that the following embodiments are merely illustrative and not restrictive, as various modifications may be made within the scope of the present disclosure.

[0041] Figure 1 An exemplary proton exchange membrane 100 (PEM 100 ) is shown. The PEM 100 includes a porous structural framework 102 and boronic acid groups 104 distributed throughout the porous structural framework 102 and bonded to the pore surfaces of the porous structural framework 102 .

[0042] The porous structural framework 102 can be formed from any suitable material or combination of materials, including inorganic and / or organic materials. Suitable inorganic materials can include amorphous inorganic materials (e.g., glass, fused silica, or ceramics) and / or crystalline inorganic materials (e.g., quartz, single crystal silicon, or alumina). Suitable organic materials can include, for example, synthetic and / or natural polymers (e.g., cellulose).

[0043] The PEM 100 can have a thickness d ranging from a few microns to several hundred microns. Using the configuration described herein, the PEM 100 can withstand pressure differentials up to 30 atmospheres and acidic pH gradients across the membrane. The PEM 100 is also permeable to water and protons, which can be conducted through the PEM 100 as shown by arrows 106, but the PEM 100 is generally impermeable to gases including hydrogen and oxygen.

[0044] The boronic acid groups 104 can be attached to the pore surfaces within the PEM 100 in at least two different configurations, such as Figure 2A and 2B shown. Figure 2A and 2B An exemplary configuration of the porous structural framework 102 and the boron acid groups 104 within the PEM 100 is shown. It should be appreciated that Figure 2A and 2B Each shows only a portion of the PEM 100 and represents features of the entire PEM 100 .

[0045] exist Figure 2A In the first exemplary configuration 200A shown, the pore surface 202 adjacent to the pore 204 is functionalized with the boronic acid groups 104 such that the boronic acid groups 104 are bound to the pore surface 202. Figure 2A Only one boronic acid group 104 is shown bound to the pore surface 202 , but the porous structural framework 102 can have any number and concentration of boronic acid groups 104 bound to the pore surface 202 .

[0046] In the second exemplary configuration 200B shown in FIG2 , the porous structural framework 102 comprises solid support particles 206 (e.g., solid support particles 206-1 to 206-4) connected together by boron-based acid groups 104. The connected solid support particles 206 form pores 208 in the spaces between the solid support particles 206. The boron-based acid groups 104 are bound to the pore surfaces 210 (e.g., the pore surfaces 210-1 to 210-4 of the solid support particles 206-1 to 206-4). Although Figure 2BFour solid support particles 206 are shown as being linked via the boronic acid groups 104, but any other number of solid support particles 206 may be linked via the boronic acid groups 104. Additionally, each solid support particle 206 may be linked to one or more additional solid support particles via one or more additional boronic acid groups, thereby creating a porous structural framework 102, wherein the boronic acid groups 104 are bound to pore surfaces 210 within the porous structural framework 102.

[0047] The solid support particles 206 can be formed of any suitable material, such as any of the materials described above for the porous structural framework 102, such as inorganic molecules (e.g., fused silica particles, ceramic particles, etc.) or organic molecules (e.g., polymers). The solid support particles 206 can have any suitable shape and size, ranging from tens of nanometers (nm) to 100 microns. The porosity of the PEM 100 can be controlled and defined by the size of the solid support particles 206. The solid support particles 206 can also be selected based on their mechanical strength, durability in high pH gradient environments, and / or their affinity for water (e.g., they can be hydrophilic or hydrophobic based on the desired hydrophilicity balance of the PEM 100).

[0048] In some examples, the boronate group 104 comprises a boronic acid derivative (e.g., a compound or group derived from boronic acid). Boric acid has the molecular formula B(OH)3 and the following structure given by formula (I):

[0049]

[0050] A boronic acid derivative can be any compound or group in which one, two, or all three hydroxyl (OH) groups of the boronic acid have reacted and combined with one or more other compounds. Exemplary boronic acid derivatives are described in more detail below.

[0051] Boric acid derivatives can be formed in any suitable manner. In some instances, boric acid derivatives are formed by reacting one or two hydroxyls of boric acid or another boric acid derivative with one or more other compounds. For example, boric acid or a boric acid derivative can react with a polyol having at least two cis-vicinal hydroxyls. Boric acid derivatives can include any suitable boric acid derivatives, including but not limited to cyclic boronic acid derivatives, boron spiroalkanoic acid, boron spiroalkanoic acid derivatives and any other boric acid derivatives described herein. Polyol can be any suitable polyol, such as a derivative of a polyol, sugar, sugar alcohol (for example, glycerol, mannitol or sorbitol), catechol or any of the above substances. In some instances, polyol has a structure represented by the following formula (IIa) or (IIb):

[0052]

[0053] Wherein W, X, Y and Z are pendant moieties and can be each independently selected from the group consisting of: hydrogen (H), hydroxyl (OH), fluoro (F), chloro (Cl), dialkylamino (NR2), cyano (CN), carboxylic acid (COOH), carboxamide, carboxylate, alkyl, alkoxy and aryl. In some examples, any one or more of the groups W, X, Y and Z can represent C1 to C 30 Alkyl chain, the C1 to C 30 The alkyl chain may optionally contain one or more substituents such as oxygen (O), hydroxyl (OH), fluoro (F), chloro (Cl), dialkylamino (NR2), cyano (CN), carboxylic acid (COOH), carboxamide, carboxylate, alkyl, alkoxy, and aryl groups.

[0054] Now refer to Figure 3A and 3B Exemplary reaction schemes for preparing boronic acid derivatives by reacting boronic acid or boronic acid derivatives with polyhydroxy compounds are shown and described. It should be understood that the following reaction schemes are merely exemplary and not limiting.

[0055] Figure 3A An exemplary reaction scheme 300A for synthesizing cyclic boronic acid derivatives is shown. As shown, boronic acid 302 is combined with glycerol 304 to produce a cyclic boronic acid derivative 306. Glycerol 304 is represented by formula (IIa), wherein X, Y, and Z are each hydrogen (H), and W is hydroxymethyl (CH2OH). Figure 3A Boric acid is shown reacting with glycerol 304, but boric acid 302 can be reacted with any other suitable sugar (e.g., glucose, fructose, etc.), sugar alcohol (e.g., mannitol, sorbitol, etc.), or polyol. Additionally or alternatively, a boronic acid derivative can be used in place of boric acid 302.

[0056] Figure 3B An exemplary reaction scheme 300B for synthesizing borospiranoic acid, which is also a boronic acid derivative, is shown. Figure 3A The cyclic boronic acid derivative 306 prepared in the reaction scheme 300A shown combines with another glycerol molecule 304 to form borospiraic acid 308. Although boric acid 302 is a weak acid, it forms strongly acidic borospiraic acid 308 in the presence of a polyol such as a sugar alcohol (e.g., glycerol 304). Figure 3B Cyclic boronic acid derivative 306 is shown reacting with glycerol 304, but cyclic boronic acid derivative 306 can be reacted with any other suitable sugar, sugar alcohol (e.g., mannitol, sorbitol, etc.), or polyol. Additionally or alternatively, cyclic boronic acid derivative 306 can be replaced with any other suitable cyclic boronic acid derivative.

[0057] Figure 3A and3B The reaction schemes 300A and 300B shown in FIG can be used to generate the boronate acid groups 104 bound to the pore surface 202 (see Figure 2A ) and / or generate boronate acid groups 104 bound to the pore surface 210 (see Figure 2B ). In some examples, the surface of the solid support material (eg, the pore surface 202 or the particle surface 210) can be functionalized with a boronic acid derivative or a polyol. Figures 4A to 9B Exemplary reaction schemes are shown and described for forming boronate acid groups 104 bonded to the pore surfaces of the porous structural framework 102. It should be appreciated that these reaction schemes are exemplary only and not limiting.

[0058] Figure 4A An exemplary reaction scheme 400A for synthesizing a solid support-bound monocyclic cyclic boronic acid derivative is shown. As shown, a solid support 402 is functionalized with a cis-1,2-dihydroxyl group 404 having a cis-vicinal dihydroxyl group. The solid support 402 can be formed from any inorganic or organic solid support material described herein for use in the porous structural framework 102 (e.g., glass, ceramic, synthetic polymer, natural polymer) and can be selected based on its mechanical strength, durability in a high pH gradient environment, and / or its affinity for water (e.g., it can be hydrophilic or hydrophobic based on the hydrophilic balance desired for the PEM 100). The solid support 402 can be similar to the reference Figure 2B Alternatively, the solid carrier 402 may be a particle of the solid carrier particles 206. Figure 2A A portion of the porous structural frame 102.

[0059] like Figure 4A As shown, cis-1,2-dihydroxy 404 has a structure represented by formula (IIa) and includes a side group portion Y' and a connecting chain 406 (represented by a side group W or X in formula (IIa)) bound to a solid support 402. The connecting chain 406 is C1 to C 30 alkyl chain, and optionally having one or more pendant moieties X', which can be the same or different for each atom in the linking chain 406. X' and Y' can each independently be selected from the group consisting of hydrogen (H), hydroxyl (OH), fluoro (F), chloro (Cl), dialkylamino (NR2), cyano (CN), carboxylic acid (COOH), carboxamide, carboxylate, alkyl, alkoxy, and aryl.

[0060] Cis-1,2-dihydroxy 404 reacts with boronic acid 408 to obtain a monocyclic cyclic boronic acid derivative 410 bound to the solid support 402. Through this configuration, the solid support-bound cyclic boronic acid derivative 410 can be bound to the boron acid group 104 on the pore surface of the porous structural framework 102 in the PEM 100. Alternatively, the solid support-bound cyclic boronic acid derivative 410 can be further reacted with a polyhydroxy compound to generate another boronic acid derivative (e.g., boranoic acid), which will now be referred to. Figure 4B Provide a description.

[0061] Figure 4B An exemplary reaction scheme 400B for synthesizing a solid support-bound boranoic acid having a pendant moiety is shown. As shown, a solid support-bound cyclic boronic acid derivative 410 (via Figure 4A The polyol 412 is prepared by reaction scheme 400A as shown in FIG. 4 and is combined with a polyol 412 having pendant moieties A', B', C', and D'. The polyol 412 has a structure as shown in formula (IIa). Thus, the pendant moieties A', B', C', and D' may correspond to the pendant moieties W, X, Y, and Z described with reference to formula (IIa).

[0062] The solid support-bound cyclic boronic acid derivative 410 reacts with the polyol 412 to produce a solid support-bound borosilicate acid 414 having pendant moieties A', B', C', and D'. Through this configuration, the solid support-bound borosilicate acid 414 can achieve boron-based acid groups 104 bound to the pore surfaces of the porous structural framework 102 in the PEM 100. The solid support-bound borosilicate acid 414 can exhibit strong proton exchange properties, depending on the electronic properties of the A', B', C', D', X', and Y' substituents.

[0063] In embodiments where the solid support 402 comprises a polymer network, the solid support-bound cyclic boronic acid derivative 410 and the solid support-bound boranoic acid 414, having controlled loadings of boronic acid and boranoic acid, respectively, can also be used to form ionomers for bonding catalysts in catalyst layers of membrane electrode assemblies, as will be described below. Figure 10 and 11 Provide a description.

[0064] Figure 5A An exemplary reaction scheme 500A for synthesizing a solid support-bound cyclic boronic acid derivative with a catechol derivative is shown. Reaction scheme 500A is similar to reaction scheme 400A, except that in reaction scheme 500A the polyol comprises a catechol derivative.

[0065] In reaction scheme 500A, solid support 502 is functionalized with catechol derivative 504. Solid support 502 can be the same as or similar to solid support 402. Catechol derivative 504 has a structure represented by formula (IIb) and includes pendant moieties W", Y", and Z", and a linker 506 (represented by the pendant group X in formula (IIb)) bound to solid support 502. Linker 506 is C1 to C 30 alkyl chain, and optionally having one or more pendant moieties X", which can be the same or different for each atom in the connecting chain 506. The pendant moieties W", X", Y", and Z" can each be independently selected from the group consisting of hydrogen (H), hydroxyl (OH), fluoro (F), chloro (Cl), dialkylamino (NR2), cyano (CN), carboxylic acid (COOH), carboxamide, carboxylate, alkyl, alkoxy, and aryl.

[0066] The catechol derivative 504 reacts with the boronic acid 508 to form a solid support-bound cyclic boronic acid derivative 510 having the catechol derivative. When the solid support 502 is a polymer, the catechol structure can be introduced during the polymerization process (e.g., to form a catechol-formaldehyde resin), as described below with reference to Figure 6 Alternatively, the catechol structure can be introduced after polymerization (e.g., by functionalization of a Merrifield-type resin).

[0067] By this configuration, the solid support-bound cyclic boronic acid derivative 510 with the catechol derivative can be bound to the boron acid groups 104 on the pore surface of the porous structural framework 102 in the PEM 100. Alternatively, the solid support-bound cyclic boronic acid derivative 510 with the catechol derivative can be further reacted with a polyhydroxy compound to generate another boronic acid derivative (e.g., a boranoic acid derivative), as will now be described with reference to Figure 5B Descriptive.

[0068] Figure 5B An exemplary reaction scheme 500B for synthesizing a solid support-bound borane spiroalkanoic acid derivative having a catechol derivative and a pendant moiety is shown. In reaction scheme 500B, a solid support-bound cyclic boronic acid derivative 510 having a catechol derivative is bound to a polyol 512 having pendant moieties A", B", C", and D". The polyol 512 has a structure represented by Formula (IIa). Thus, the pendant moieties A", B", C", and D" may correspond to the pendant moieties W, X, Y, and Z described with reference to Formula (IIa).

[0069] The solid support-bound cyclic boronic acid derivative 510 having a catechol derivative is combined with a polyol 512 to produce a solid support-bound borospiracid 514 having a catechol derivative and including pendant moieties A", B", C", and D". Through this configuration, the solid support-bound borospiracid 514 having a catechol derivative and including pendant moieties can achieve boron-based acid groups 104 bound to the pore surfaces of the porous structural framework 102 in the PEM 100.

[0070] Figure 6 An exemplary reaction scheme 600 for synthesizing a cross-linked copolymer containing boron acid groups is shown. In reaction scheme 600, catechol 602, formaldehyde 604, and boric acid 606 are combined and polymerized to produce a catechol-formaldehyde-boric acid cross-linked copolymer 608 ("copolymer 608"). Copolymer 608 includes catechol structures 610 connected by boron spiroalkanoic acid groups 612. The individual polymers of copolymer 608 are cross-linked by cross-links 614 between the catechol structures 610. Copolymer 608 may also include other phenolic monomers, such as phenol, resorcinol, and trihydroxyphenol.

[0071] Copolymer 608 is suitable for PEM and ionomer applications. For example, Figure 2B The configuration of the PEM 100 shown can be achieved by a copolymer 608 in which boranoic acid groups 612 (corresponding to the boron-based acid groups 104) are bonded to and connected to catechol structures 610 (corresponding to the solid support particles 206), thereby forming a porous structural framework 102. The mole % content of the boranoic acid groups 612 can be controlled to obtain optimal functional performance as an ionomer of the PEM 100 or as a catalyst for catalyst bonding in a catalyst layer in an MEA, which will be referred to below. Figure 10 and 11 Provide a description.

[0072] As previously mentioned, in some examples, the pore surfaces (e.g., pore surfaces 202) within the porous structural framework 102 are functionalized with boronate acid groups 104 (see Figure 2A ). Figures 7 to 9A Exemplary reaction schemes for functionalizing the pore surfaces of a porous structural framework with boronate acid groups are shown. These reaction schemes are compatible with solid support materials that have one or more hydroxyl groups present on the pore surfaces. Examples of such materials include, but are not limited to, silica, glass, alumina, clay, synthetic polymers, and cellulose.

[0073] Figure 7 An exemplary reaction scheme 700 for functionalizing a pore surface with a boron-based acid group is shown. Figure 7As shown, the solid support 702 includes a surface 704 and hydroxyl groups 706 at the surface 704. The surface 704 of the solid support 702 can be a pore surface of the porous structural framework 102 (e.g., Figure 2A surface 202 as shown) or the surface of a solid support particle (e.g., Figure 2B The surface 210 of the solid support particle 206 is shown). Although Figure 7 Surface 704 is shown as having only one hydroxyl group 706, but surface 704 can have any other number and concentration of hydroxyl groups 706. In reaction scheme 700, surface 704 of solid support 702 is exposed to boric acid 708, which reacts with hydroxyl groups 706 to form boronic acid derivative 710 bound to surface 704. Solid support-bound boronic acid derivative 710 can achieve boron-based acid groups 104 bound to the pore surfaces of porous structural framework 102 in PEM 100. Alternatively, solid support-bound boronic acid derivative 710 can be further reacted with boric acid, another boronic acid derivative, or a polyol to produce another boron derivative.

[0074] Figure 8A Another exemplary reaction scheme 800A for functionalizing the pore surface of a porous structural framework with boronic acid groups is shown. Reaction scheme 800A is similar to reaction scheme 700, except that boronic acid 708 reacts with two hydroxyl groups 706 on surface 704 to produce a cyclic boronic acid derivative 802. In some examples, surface 704 can be pre-activated to increase the surface density of hydroxyl groups 706. Any suitable pre-activation process can be used. Cyclic boronic acid derivative 802 can achieve the boron acid groups 104 incorporated into the pore surface of the porous structural framework 102 in the PEM. Alternatively, cyclic boronic acid derivative 802 can be further reacted to produce another boronic acid derivative, as will now be described with reference to Figure 8B described.

[0075] Figure 8B Another exemplary reaction scheme 800B for functionalizing the pore surface of a porous structural framework with a boronic acid derivative (e.g., a boranoic acid group) is shown. In reaction scheme 800B, Figure 8AThe cyclic boronic acid derivative 802 produced in the reaction scheme 800A shown is combined with a polyol 804 having pendant moieties A'", B'", C'", and D'". The polyol 804 has a structure shown in formula (IIa). Therefore, the pendant moieties A'", B'", C'", and D'" can correspond to the pendant moieties W, X, Y, and Z of the above-mentioned reference formula (IIa). The cyclic boronic acid derivative 802 and the polyol 804 react to produce a borane acid having a pendant moiety 806, which is bound to the pore surface 704. The solid support-bound borane acid having the pendant moiety 806 can achieve the boron-based acid group 104 bound to the pore surface of the porous structural framework 102 in the PEM 100.

[0076] Figure 9A An exemplary reaction scheme 900A is shown for coupling particles (e.g., nanoparticles or microparticles) to the pore surfaces of a porous structural framework via a boronic acid derivative (e.g., boranoic acid). The porosity of the PEM 100 can be controlled and defined by the size of the particles 902. The particles 902 can also be selected based on their mechanical strength, durability in high pH gradient environments, and / or their affinity for water (e.g., they can be hydrophilic or hydrophobic depending on the desired hydrophilicity balance of the PEM 100).

[0077] Scheme 900A is similar to scheme 800A, except that particles 902 having hydroxyl groups 904 present are bound to boric acid 708. Thus, hydroxyl groups 706 on the pore surface 704 are cross-linked with hydroxyl groups 904 on the surface of particles 902 using boric acid 708. This cross-coupling reaction results in particles 902 being attached to the pore surface 704 via borohexanic acid 906. Particles 902 can be formed of any suitable material (e.g., silica, glass, alumina, ceramic, clay, synthetic polymer, cellulose) and can be the same or different than the material of solid support 702.

[0078] Reaction scheme 900A can be controlled to proceed in any order. In some examples, the first step of reaction scheme 900A includes performing reaction scheme 800A to produce solid support-bound cyclic boronic acid derivative 802. In the second step, particle 902 can be exposed to solid support-bound cyclic boronic acid derivative 802 to produce solid support-bound boronic acid 906. Alternatively, particle 902 can be combined with boronic acid 708 in the first step to produce an intermediate boronic acid derivative. In the second step, hydroxyl groups 706 on surface 704 of solid support 702 are exposed to the intermediate boronic acid derivative, which reacts to produce solid support-bound boronic acid 906 and attaches particle 902 to solid support 702. In other examples, reaction scheme 900A can be performed by combining all reactants in a single step.

[0079] Figure 9BAn exemplary reaction scheme 900B for cross-linking a plurality of particles comprising a plurality of sheets within a polymer structure using a boronic acid derivative is shown. Reaction scheme 900B is similar to reaction scheme 900A, except that in reaction scheme 900B, particles 902 (first particles 902) are cross-linked with second particles 908 having two hydroxyl groups 910 (instead of cross-linking with hydroxyl groups 706 on pore surfaces 704). The first particles 902 and the second particles 908 can each be microparticles or nanoparticles and can have any size suitable for a particular implementation (e.g., the size can range from a few nanometers to hundreds of microns). Reaction scheme 900B produces connected particles 912 having borane groups 914. The first particles 902 and the second particles 908 can be made of the same material or using different materials, which can be selected from any solid support material described herein (e.g., silica, glass, alumina, ceramics, clay, synthetic polymers, cellulose, etc.).

[0080] Reaction scheme 900B can be used to produce PEM 100, effectively using Figure 2B The second configuration 200B is shown. The porosity of the PEM 100 can be defined by the size of the first particles 902 and the second particles 908 .

[0081] The boron-containing porous membranes described herein can be used in water electrolysis and / or fuel cell applications. Figure 10 and 11 To describe an exemplary application.

[0082] Figure 10 An exemplary proton exchange membrane water electrolysis system 1000 (PEM water electrolysis system 1000) having a boron-containing porous membrane is shown. The PEM water electrolysis system 1000 uses electricity to split water into oxygen (O2) and hydrogen (H2) through an electrochemical reaction. The configuration of the PEM water electrolysis system 1000 is merely exemplary and not limiting, as other suitable configurations and other suitable water electrolysis systems may incorporate a boron-containing porous membrane.

[0083] like Figure 10 As shown, the PEM water electrolysis system 1000 includes a membrane electrode assembly 1002 (MEA 1002), porous transport layers 1004-1 and 1004-2, bipolar plates 1006-1 and 1006-2, and a power supply 1008. The PEM water electrolysis system 1000 may also include Figure 10 Additional or further elements not shown may be used in certain implementations.

[0084] MEA 1002 includes a PEM 1010 located between a first catalyst layer 1012-1 and a second catalyst layer 1012-2. PEM 1010 electrically isolates the first catalyst layer 1012-1 from the second catalyst layer 1012-2 while providing cations (such as protons (H + )) and is simultaneously impermeable to gases such as hydrogen and oxygen. PEM 1010 can be implemented by any suitable PEM. For example, PEM 1010 can be implemented by a boron-containing porous membrane (e.g., PEM 100) comprising a porous structural framework having boron-containing acid groups bound to the pore surfaces within the porous structural framework.

[0085] The first catalyst layer 1012-1 and the second catalyst layer 1012-2 are conductive electrodes with embedded electrochemical catalysts (not shown), such as platinum, ruthenium and / or cerium (IV) oxide. In some examples, the first catalyst layer 1012-1 and the second catalyst layer 1012-2 are formed using ionomers to bind the catalyst nanoparticles. As previously described, the ionomers used to form the first catalyst layer 1012-1 and the second catalyst layer 1012-2 may include boron acid groups as described herein, such as copolymer 608 (see Figure 6 ).

[0086] MEA 1002 is positioned between porous transport layers 1004 - 1 and 1004 - 2 , which are in turn positioned between bipolar plates 1006 - 1 and 1006 - 2 , with flow channels 1014 - 1 and 1014 - 2 located between bipolar plates 1006 and porous transport layer 1004 .

[0087] In MEA 1002, the first catalyst layer 1012-1 serves as an anode and the second catalyst layer 1012-2 serves as a cathode. When the PEM water electrolysis system 1000 is powered by power supply 1008, an oxygen evolution reaction (OER) occurs at anode 1012-1, represented by the following electrochemical half-reactions:

[0088] 2H2O→O2+4H + +4e -

[0089] Protons are conducted from the anode 1012-1 to the cathode 1012-2 through the PEM 1010, and electrons are conducted from the anode 1012-1 to the cathode 1012-2 through the conduction path around the PEM 1010. The PEM 1010 allows protons (H + ) and water are transported from the anode 1012-1 to the cathode 1012-2, but oxygen and hydrogen are impermeable. At the cathode 1012-2, protons combine with electrons in the hydrogen evolution reaction (HER), represented by the following electrochemical half-reaction:

[0090] 4H + +4e - →2H2

[0091] OER and HER are two complementary electrochemical reactions for splitting water by electrolysis, represented by the following overall water electrolysis reaction:

[0092] 2H2O→2H2+O2

[0093] Figure 11 An exemplary proton exchange membrane fuel cell 1100 (PEM fuel cell 1100) having a boron-containing porous membrane is shown. PEM fuel cell 1100 generates electricity due to an electrochemical reaction. In this example, the electrochemical reaction involves reacting hydrogen (H2) and oxygen (O2) to produce water and electricity. The configuration of PEM fuel cell 1100 is exemplary only and not limiting, as other suitable configurations and other suitable proton exchange membrane fuel cells may incorporate a boron-containing porous membrane.

[0094] like Figure 11 As shown, the PEM fuel cell 1100 includes a membrane electrode assembly 1102 (MEA 1102), porous transport layers 1104-1 and 1104-2, and bipolar plates 1106-1 and 1106-2. An electrical load 1108 can be electrically connected to the MEA 1102 and driven by the PEM fuel cell 1100. The PEM fuel cell 1100 may also include Figure 11 Additional or further elements not shown may be used in certain implementations.

[0095] MEA 1102 includes a PEM 1110 located between a first catalyst layer 1112-1 and a second catalyst layer 1112-2. The PEM 1110 electrically isolates the first catalyst layer 1112-1 from the second catalyst layer 1112-2 and provides cations such as protons (H + ) and is simultaneously impermeable to gases such as hydrogen and oxygen. PEM 1110 can be implemented by any suitable PEM. For example, PEM 1110 can be implemented by a boron-containing porous membrane (e.g., PEM 100) comprising a porous structural framework having boron-containing acid groups bound to the pore surfaces within the porous structural framework.

[0096] The first catalyst layer 1112-1 and the second catalyst layer 1112-2 are conductive electrodes with embedded electrochemical catalysts (not shown). In some examples, the first catalyst layer 1112-1 and the second catalyst layer 1112-2 are formed using ionomers to bind catalyst nanoparticles. In some examples, the ionomers used to form the first catalyst layer 1112-1 and the second catalyst layer 1104-2 include boronic acid derivatives described herein, such as copolymer 608 (see Figure 6 ).

[0097] MEA 1102 is placed between porous transport layers 1104-1 and 1104-2, which are in turn placed between bipolar plates 1106-1 and 1106-2, with flow channels 1114 located therebetween. In MEA 1102, a first catalyst layer 1112-1 serves as a cathode, and a second catalyst layer 1112-2 serves as an anode. Cathode 1112-1 and anode 1112-2 are electrically connected to a load 1108, and the electricity generated by PEM fuel cell 1100 drives load 1108.

[0098] During operation of the PEM fuel cell 1100, hydrogen (H2) flows into the anode side of the PEM fuel cell 1100, and oxygen (O2) flows into the cathode side of the PEM fuel cell 1100. At the anode 1112-2, hydrogen molecules are catalytically decomposed into protons (H2) according to the following hydrogen oxidation reaction (HOR): + ) and electrons (e - ):

[0099] 2H2→4H + +4e -

[0100] Protons are conducted from anode 1112-2 to cathode 1112-1 through PEM 1100, while electrons are conducted from anode 1112-2 to cathode 1112-1 around PEM 1110 through conduction paths and load 1108. At cathode 1112-1, the protons and electrons combine with oxygen according to the following oxygen reduction reaction (ORR):

[0101] O2+4H + +4e - →2H2O

[0102] Therefore, the overall electrochemical reaction of the PEM fuel cell 1100 is:

[0103] 2H2+O2→2H2O

[0104] During the entire reaction, the PEM fuel cell 1100 produces water at the cathode 1112-1. The water can flow from the cathode 1112-1 to the anode 1112-2 through the PEM 1110 and can be removed through the cathode side and / or anode side outlets of the PEM fuel cell 1100. The entire reaction produces electrons at the anode, which drive the load 1108.

[0105] Boron-containing porous membranes as described herein (e.g., PEM 100) can also be used as porous membranes for neutralizing pathogens. For example, the porous structure framework 102 can have sufficiently small holes to prevent pathogens such as bacteria, fungal spores and viruses from passing through. The boron acid groups 104 can also have antipathogenic activity against bacteria, fungi and viruses (including SARS-CoV-2). For example, the basic protein sites of pathogens (including SARS-CoV-2) can be ionically bonded to the acidic boron sites of proton exchange membranes, thereby preventing pathogens from passing through proton exchange membranes. Therefore, proton exchange membranes can be implemented in face masks, surgical masks and air filters and air purification systems for enclosed spaces (e.g., homes, offices, hospitals, factories, vehicles, airplanes, etc.).

[0106] In the foregoing description, various exemplary embodiments have been described with reference to the accompanying drawings. However, it will be apparent that various modifications and variations may be made thereto, and that other implementations may be realized, without departing from the scope of the appended claims. For example, certain features of one embodiment described herein may be combined with or substituted for features of another embodiment described herein. Accordingly, the description and drawings are to be regarded as illustrative rather than restrictive.

[0107] In the foregoing description, various exemplary embodiments have been described with reference to the accompanying drawings. However, it will be apparent that various modifications and variations may be made thereto, and additional embodiments may be implemented, without departing from the scope of the present invention as set forth in the appended claims. For example, certain features of one embodiment described herein may be combined with or substituted for features of another embodiment described herein. Accordingly, the description and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A proton exchange solid support comprising a first solid support, said first solid support comprising a polymer; a second solid support; and The first solid support is connected to the tetravalent boron acid group of the second solid support.

2. The proton exchange solid support according to claim 1, wherein The first solid support comprises a porous structural framework.

3. The proton exchange solid support according to claim 1, wherein The second solid support comprises a polymer.

4. The proton exchange solid support according to claim 3, wherein One or both of the first solid support and the second solid support include a polymer sheet.

5. The proton exchange solid support according to claim 1, wherein The second solid support comprises an inorganic material.

6. The proton exchange solid support according to claim 1, wherein The second solid support comprises a ceramic material. The proton exchange solid support according to claim 1 , wherein the tetravalent boron acid group comprises borospiranoic acid.

8. The proton exchange solid support according to claim 1, wherein The tetravalent boron acid group includes a boric acid derivative.

9. A catalyst layer for an electrochemical cell, comprising: catalyst; a first solid support; and An ionomer, comprising: a second solid support, the second solid support comprising a porous structural framework; and A tetravalent boron acid group.

10. A method for preparing a proton exchange solid support, comprising: The first solid support comprising a polymer is linked to a second solid support via a tetravalent boron acid group.

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