A kind of ionomer, its preparation method and the catalytic layer slurry and membrane electrode for hydrogen production by electrolysis of water

Abstract

The application provides a kind of ionomer, its preparation method and the catalytic layer slurry and membrane electrode for hydrogen production by electrolysis of water, the ionomer includes the repeating unit of structure shown in formula 1, Ar is the group shown in formula a or formula b, Q is the group shown in formula c or formula d, R is substituted or unsubstituted porphyrin or phthalocyanine group.Substituted or unsubstituted porphyrin or phthalocyanine group R and quaternary ammonium ionized group Q + All are side groups on aromatic macromolecule Ar;Formula 1 ionomer and transition metal atom on transition metal catalyst exist specific electrostatic interaction and coordination effect, can realize the uniform distribution of ionomer around catalyst, and inhibit the formation of catalyst aggregate, improve the stability and rheology of catalyst slurry, and then obtain the membrane electrode catalytic layer with good performance.The group on the ionomer that interacts with the catalyst as a protective layer can be used to enhance the bond energy of Fe-O bond and other bonds, slow down the dissolution of Fe and other elements, and improve the thermodynamic stability of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and in particular to an ionomer, its preparation method, and a catalyst slurry and membrane electrode for water electrolysis for hydrogen production. Background Technology

[0002] Renewable energy-driven water electrolysis technology is considered the most promising technology for large-scale, sustainable production of "green hydrogen." Precious metals (such as platinum (Pt) and iridium (Ir) are the most advanced catalysts in electrolysis technology, but their high cost and scarcity severely limit the large-scale commercialization of this technology. The emerging alkaline membrane electrolysis for hydrogen production combines the low cost of alkaline water electrolysis with the high efficiency of proton exchange membrane electrolysis, offering advantages such as allowing the use of non-precious metal catalysts and rapid reaction kinetics in alkaline media, making it considered the preferred green hydrogen production technology for the future. Transition metal (oxygen) hydroxides (NiFe), represented by nickel-iron, are commonly used and commercially promising non-precious metal catalysts in alkaline membrane electrolysis for hydrogen production due to their high electrochemical activity, high abundance, and cost advantages.

[0003] Although transition metal catalysts (such as NiFe) exhibit significant catalytic activity on rotating disk electrodes, their performance deteriorates significantly when fabricated as membrane electrodes. This is primarily due to poor uniformity of catalyst ink dispersion and the poor thermodynamic stability of transition metals, resulting in poor uniformity and stability of the catalyst layer. Electrolytic water electrolysis for hydrogen production membrane electrodes mainly consists of a proton exchange membrane and a catalyst layer. The catalyst layer typically comprises a catalyst and ionomers. Ionomers are ionized polymer materials that act as catalyst binders and ion conductors within the catalyst layer. The catalyst layer is the site of electrochemical reactions, where processes such as ion conduction, electron transfer, and gas transport intertwine, competing for limited space and significantly impacting catalyst activity and utilization. This is particularly pronounced in high-efficiency water electrolyzers, where the uneven distribution of ionomers at high current densities leads to reduced ion accessibility, and localized transport resistance encountered by gas passing through the ionomer film or aggregates exacerbates the poor ion conduction and gas transport within the catalyst layer. Therefore, some problems within the catalyst layer are closely related to the performance of the ionomers. Furthermore, taking NiFe catalyst as an example, its own thermodynamic instability causes iron to dissolve and be lost during operation, thereby reducing the catalyst's activity and stability. This is another key factor restricting the performance and service life of the electrolyzer.

[0004] The construction of a uniform and stable catalyst layer is determined by the interaction between the ionomer and the catalyst, and is mainly affected by the dispersion and deposition process of the catalyst slurry. NiFe catalyst inks, due to their high density, exhibit rapid precipitation. The resulting large agglomerates are the starting point for defect crack structures. During spraying and drying, the imbalance of capillary forces between particles easily leads to crack formation. Specifically, low-quality catalyst inks contain large and uneven agglomerates, causing particle migration and aggregation due to shear during deposition. Subsequently, according to the Marangoni effect, during drying, the difference in surface tension gradient caused by the different agglomerate sizes accelerates the formation of pore defects and mechanical damage in the catalyst layer. Therefore, the quality, especially the stability, of the NiFe-based catalyst ink is a crucial factor affecting the performance of the membrane electrode assembly (MEA), representing a significant technical obstacle to large-scale MEA production.

[0005] Adding suitable ionomers can alleviate the formation of large catalyst agglomerates to some extent. Ionomers adsorb around the catalyst via van der Waals forces between the polymer backbone and the catalyst, forming a catalyst coating. The electrostatic repulsion between the charged ionomers and the steric hindrance of the polymer inhibit further agglomeration of the catalyst coating, thus forming a stable and dispersed catalyst slurry. The network formed by the interconnection of ionomers between catalyst particles imparts high yield stress to the catalyst slurry, making it less prone to sedimentation. However, these van der Waals forces are very weak, making it difficult to prepare catalyst slurries with uniform dispersion and higher stability.

[0006] Furthermore, most NiFe catalysts suffer from severe lattice distortion of NiO6 at high oxidation potentials, causing Fe to transition from a low valence state to a high valence state. Metals in this high valence state are extremely unstable and readily break metal-oxygen bonds, leading to Fe dissolution. The dissolved Fe will then randomly redeposit on the surface or dope in the bulk lattice under oxygen evolution conditions. This dynamic dissolution and redeposition process results in undesirable iron segregation, leading to gradual catalyst deactivation and decreased device performance and stability (Nat. Catal. 2020, 3, 743-753). Existing ionomer skins cannot act as a protective layer to prevent this process. Therefore, developing ionomers that can interact with the catalyst is of great significance for improving electrolysis performance and lifespan. Summary of the Invention

[0007] In view of this, the present invention aims to provide an ionomer that can interact with a catalyst, a method for its preparation, and a catalyst slurry and membrane electrode for hydrogen production by water electrolysis. The ionomer of the present invention can specifically act on transition metal catalysts, thereby improving the stability of the catalyst and its slurry and suppressing problems such as crack formation during catalyst slurry spraying and drying. However, the technology of introducing groups that interact with the catalyst into the preparation of the ionomer to improve the stability of the catalyst ink, the uniformity of the catalyst layer, and the overall catalyst stability has not been reported.

[0008] This invention provides an ionomer comprising repeating units of the structure shown in Formula 1:

[0009]

[0010] In Formula 1, Ar is the group shown in Formula a or Formula b, Q is the group shown in Formula c or Formula d, and R is a substituted or unsubstituted porphyrin or phthalocyanine group.

[0011]

[0012] Wherein, 0≤x≤10, 0≤y≤10; R0~R5 are independently selected from C1~C10 chain alkyl groups; t is selected from integers between 0 and 3.

[0013] In embodiments of the present invention, R is a group represented by formula e or formula f, wherein R' is selected from one or more of hydrogen, amino, and phenylamino.

[0014]

[0015] This invention provides a method for preparing the ionomer described above, comprising the following steps:

[0016] The polymer having repeating units of Formula 2 is reacted with a quaternized monomer to obtain the ionomer shown in Formula 1.

[0017]

[0018] Wherein, X is a halogen or alkyl halogen; the quaternized monomer is a chain-like alkyl-substituted aliphatic amine.

[0019] In a preferred embodiment of the present invention, the polymer having the repeating unit of Formula 2 is prepared as follows:

[0020] The initial polymer is obtained by polycondensation of a conjugated aromatic monomer containing reactive sites, an optional comonomer, and a ketone monomer.

[0021] The initial polymer was reacted with a functional monomer to obtain a polymer having repeating units as shown in Formula 2.

[0022] The conjugated aromatic monomer containing the reactive site is 9,9-bis(6-bromohexyl)-9H-fluorene; the comonomer is selected from one of biphenyl, p-terphenyl, m-terphenyl, fluorene, and dibromoalkylfluorene; the ketone monomer is selected from one of 1,1,1-trifluoroacetone, 2,2,2-trifluoroacetophenone, 2,2,2,4'-tetrafluoroacetophenone, and perfluoroacetophenone.

[0023] The functional monomer is selected from one of 5-(4-aminophenyl)-10,15,20-tris(phenyl)porphyrin, 5,15-(aminophenyl)-10,20-phenylporphyrin, and monoaminophthalocyanine.

[0024] Preferably, the polycondensation reaction is carried out in a first solvent under the action of a first catalyst, wherein the first catalyst is trifluoroacetic acid and / or trifluoromethanesulfonic acid; the temperature of the polycondensation reaction is 0-20°C and the time is 1-48 h.

[0025] Preferably, the Mensoukin reaction is carried out in a second solvent under the action of a second catalyst, the second catalyst being potassium carbonate and / or cesium carbonate; the molar ratio of the initial polymer to the functional monomer is 1:0.1 to 0.5, and the temperature of the Mensoukin reaction is 80 to 100°C.

[0026] Preferably, the molar ratio of the polymer having the repeating unit of Formula 2 to the quaternized monomer is 0.5 to 1:1, the reaction temperature is 30 to 80°C, and the reaction time is 12 to 48 hours.

[0027] Compared with the prior art, the ionomer provided by the present invention includes a repeating unit structure as shown in Formula 1, wherein R is a substituted or unsubstituted porphyrin or phthalocyanine group, and Q is a quaternary ammonium ionized group. + All are side groups on the aromatic macromolecule Ar. In this invention, the ionomer with repeating units as shown in Formula 1 has specific electrostatic interactions and coordination effects with the transition metal atoms on the transition metal catalyst. This enables the ionomer to be uniformly distributed around the catalyst and inhibits the formation of catalyst aggregates, thereby improving the stability and rheological properties of the catalyst slurry and ultimately obtaining a membrane electrode catalytic layer with better performance. Simultaneously, the groups on the ionomer that interact specifically with the catalyst serve as a protective layer, which can enhance the bond energy of Fe-O bonds, slow down the dissolution of transition metals such as Fe, improve the thermodynamic stability of the catalyst, and facilitate its application.

[0028] The present invention provides a catalytic layer slurry for hydrogen production by water electrolysis, comprising a binder, a transition metal catalyst and an organic solvent, wherein the binder is the ionomer described above.

[0029] In embodiments of the present invention, the transition metal catalyst contains transition metal atoms that interact with the ionomer, such as Fe, Ni, Co, Zn, Mn, etc.; the organic solvent is selected from any one or a combination of at least two of isopropanol, methanol, ethanol, n-propanol and water.

[0030] In embodiments of the present invention, the catalyst layer slurry is obtained by ultrasonic dispersion, stirring or ball milling of the ionomer, catalyst and solvent.

[0031] The present invention provides a membrane electrode including a catalyst layer, wherein the catalyst layer is prepared by ultrasonic spraying and / or slit coating of the catalyst layer slurry.

[0032] Furthermore, the present invention provides the application of the membrane electrode in alkaline membrane electrolysis of water to produce hydrogen.

[0033] Based on the ionomer material described above, the membrane electrolysis assembly was installed in an alkaline membrane water electrolysis hydrogen production device and operated under certain conditions. Experiments showed that at 1.8V, the maximum current density for water electrolysis hydrogen production reached 4.06 A / cm, and the electrolysis system achieved a current density ≥1.0 A / cm. 2 It operated stably for 1400 hours under high current density, which improved electrolysis performance and service life. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The ionomer prepared in Example 1 of this invention 1 H NMR spectrum;

[0036] Figure 2 The ionomer prepared for Comparative Example 1 of this invention 1 H NMR spectrum;

[0037] Figure 3 The ionomer prepared in Example 2 of this invention 1 H NMR spectrum;

[0038] Figure 4 The mechanical properties of the ionomer films prepared in Example 1 and Comparative Example 1 of this invention after film formation;

[0039] Figure 5 The thermal stability of the ionomer films prepared in Example 1 and Comparative Example 1 of this invention after film formation;

[0040] Figure 6 Microscopic morphology of the catalyst ink prepared from the ionomer in Example 1 of this invention;

[0041] Figure 7 This is a diagram showing the agglomerate size of the catalyst ink prepared in Example 3 of the present invention;

[0042] Figure 8 The sedimentation stability of the catalyst ink prepared in Example 3 of this invention;

[0043] Figure 9 The rheological properties of the catalyst ink prepared in Example 3 of this invention;

[0044] Figure 10 The large-area catalyst layer prepared in Example 4 of this invention;

[0045] Figure 11 This is a microscopic morphology diagram of the large-area catalyst layer prepared in Example 4 of the present invention;

[0046] Figure 12 The attached figure shows the gas adsorption and desorption of the large-area catalyst layer prepared in Example 4 of this invention;

[0047] Figure 13 This refers to the electrochemically active area of ​​the large-area catalyst layer prepared in Example 4 of the present invention;

[0048] Figure 14 This is a stability test diagram of the large-area catalyst layer prepared in Example 4 of the present invention;

[0049] Figure 15 This is an elemental content detection graph after stability testing of the large-area catalyst layer prepared in Example 4 of the present invention;

[0050] Figure 16 The diagram shows the water electrolysis hydrogen production performance of the large-area catalyst layer prepared in Example 4 of this invention.

[0051] Figure 17 This is a diagram showing the durability of the large-area catalyst layer prepared in Example 4 of the present invention for hydrogen production via water electrolysis. Detailed Implementation

[0052] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, the technical solution of the present invention will now be described in detail with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0053] This invention provides an ionomer comprising repeating units of the structure shown in Formula 1:

[0054]

[0055] In Formula 1, Ar is the group represented by Formula a or Formula b; in Formula a, 0 ≤ x ≤ 10, 0 ≤ y ≤ 10;

[0056]

[0057] Q is a group represented by formula c or formula d, wherein R1 to R5 are each independently selected from C1 to C10 chain alkyl groups; t is selected from integers between 0 and 3;

[0058]

[0059] R is a substituted or unsubstituted porphyrin or phthalocyanine group; R0 is selected from C1 to C10 chain alkyl groups.

[0060] The ionomer comprising the repeating unit shown in Formula 1 can be a homopolymer or a copolymer, and can include other repeating units, such as a copolymer structure comprising biphenyl, p-terphenyl, m-terphenyl, fluorene and dibromoalkylfluorene.

[0061] In some embodiments of the present invention, Ar has a structure of formula a, and the connecting single bonds at both ends of the main chain can be located at one or more of the ortho, meta, and para positions of the benzene ring, preferably in the same position. In formula a, x and y can both be 0, preferably 1≤x≤9, 1≤y≤9, more preferably 2≤x≤7, 2≤y≤7; both are preferably the same, either 5 or 6, as shown in the following formula:

[0062]

[0063] In other embodiments of the present invention, Ar has a structure of formula b, wherein the connecting single bonds at both ends of the main chain can be located at one or more of the ortho, meta, and para positions on the benzene ring, preferably in the same position. Specifically, formula b includes the following structure:

[0064]

[0065] In some embodiments of the present invention, Q is the structure shown in formula c, the cation is located at the nitrogen atom, and it is a chain alkyl quaternary ammonium cation structure, which can be represented as follows, where t is 0, 1, 2 or 3; R1, R2 and R3 are each independently selected from chain alkyl groups of C1 to C10, and can all be alkyl groups with 1 carbon atom, i.e. methyl (CH3);

[0066]

[0067] In some embodiments of the present invention, Q is the structure shown in formula d, the cation is located at the nitrogen atom, and it is an alicyclic quaternary ammonium cation structure, which can be represented as follows, t is 0, 1, 2 or 3, preferably 1; R4 and R5 are each independently selected from C1 to C10 chain alkyl groups, and can both be methyl or both be ethyl;

[0068]

[0069] In formulas a to d described above, the zigzag lines represent the positions where the groups are connected to each other. In the present invention, Ar is connected to C-CF3(RO), and in addition to the trifluoromethyl (CF3) bonded to C, the bonded RO is a C1 to C10 chain alkyl group, preferably methyl or ethyl.

[0070] In this invention, R is a substituted or unsubstituted porphyrin or phthalocyanine group, which can interact with metal atoms such as Fe, Ni, Co, Zn, and Mn in transition metal catalysts. The R can be selected independently depending on the type of catalyst, and is preferably a group shown in formula e or formula f.

[0071]

[0072] R' is selected from one or more of hydrogen (H), amino (NH2), and phenylamino.

[0073] This invention also provides a method for preparing the ionomer, comprising the following steps:

[0074] A) Under the action of a first catalyst, a conjugated aromatic monomer containing reactive sites, an optional comonomer, and a ketone monomer are subjected to a polycondensation reaction in a first solvent to obtain an initial polymer;

[0075] B) Under the action of a second catalyst, the initial polymer and the functional monomer that interacts with the catalyst are subjected to a Mensoukin reaction in a second solvent to obtain a polymer that interacts with the catalyst, i.e., it has a repeating unit of Formula 2, wherein X is a halogen or an alkyl halogen, and the halogen is preferably bromine (Br).

[0076] C) React the polymer shown in Formula 2 and the quaternized monomer in a third solvent to obtain a product with...

[0077] Ionic polymers of repeating structural units of Formula 1;

[0078]

[0079] In an embodiment of the present invention, the conjugated aromatic monomer containing the reactive site is 9,9-bis(6-bromohexyl)-9H-fluorene, with the following structure; the conjugated aromatic monomer containing the reactive site can be obtained by reacting fluorene with 1,6-dibromohexane;

[0080]

[0081] Alternatively, the comonomer is selected from one of biphenyl, p-terphenyl, m-terphenyl, fluorene, and dibromoalkylfluorene. Furthermore, the ketone monomer is selected from one of 1,1,1-trifluoroacetone, 2,2,2-trifluoroacetophenone, 2,2,2,4'-tetrafluoroacetophenone, and perfluoroacetophenone.

[0082] In step A), the first catalyst is preferably selected from trifluoroacetic acid and trifluoromethanesulfonic acid; the molar ratio of the conjugated aromatic monomer containing reactive sites to the comonomer is 1:(0-1); the molar ratio of the conjugated aromatic monomer or comonomer containing reactive sites to the ketone monomer is preferably 1:(1.05-1.2). The volume ratio of the first solvent to the first catalyst can be (0-1):1; the temperature of the polycondensation reaction is preferably 0-20°C, and the time is 1h-2d.

[0083] In step B), the monomer interacting with the catalyst is called the functional monomer, preferably selected from 5-(4-aminophenyl)-10,15,20-tris(phenyl)porphyrin, 5,15-(aminophenyl)-10,20-phenylporphyrin, and monoaminophthalocyanine. The second catalyst is preferably selected from potassium carbonate and cesium carbonate; the molar ratio of the initial polymer to the functional monomer is preferably 1:(0.1-0.5); the second solvent is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, and dimethyl sulfoxide; the temperature of the Mensøe reaction is preferably 80-100°C, and the time is 48-60 h. To facilitate differentiation between the catalyst and solvent in the two steps, they are labeled as "first" and "second," and subsequent steps follow the same pattern. The Mensøe reaction refers to the reaction of a primary amine with a haloalkane to form a quaternary ammonium salt.

[0084] In step C), the quaternizing monomer is a chain-alkyl-substituted aliphatic amine, which can be a chain-alkyl-substituted straight-chain aliphatic amine or an alicyclic amine, such as trimethylamine; the molar ratio of the polymer of the repeating unit shown in Formula 2 to the quaternizing monomer is preferably (0.5-1):1. The third solvent is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, and dimethyl sulfoxide; the reaction temperature is preferably 30-80°C, more preferably 35-70°C, and the reaction time is 12-48 h.

[0085] The ionomers provided in the embodiments of the present invention, or the ionomers obtained by the preparation methods described above, can be used as binder materials in water electrolysis for hydrogen production. The ionomers can form ionomer films with excellent properties.

[0086] This invention provides a catalyst slurry for hydrogen production via water electrolysis, particularly for alkaline membrane water electrolysis. The catalyst slurry comprises a binder, a transition metal catalyst, and an organic solvent. The binder is the ionomer described above. The slurry concentration is between 0.01 and 0.03 wt%, and the mass ratio of catalyst to ionomer is between 5:1 and 3:1. The transition metal catalyst contains transition metal atoms, such as Fe, Ni, Co, Zn, and Mn, that interact with the ionomer. The organic solvent is selected from any one or a combination of at least two of isopropanol, methanol, ethanol, n-propanol, and water.

[0087] The catalyst layer slurry, also known as the catalyst slurry, can be prepared from the ionomer, catalyst, and organic solvent, preferably from the ionomer, catalyst, and organic solvent by ultrasonic dispersion, stirring, or ball milling.

[0088] This invention provides a membrane electrode catalytic layer, which is prepared by ultrasonic spraying and / or slit coating of a catalyst slurry. Correspondingly, this invention provides a membrane electrode including a catalytic layer, which is prepared by ultrasonic spraying and / or slit coating of a catalyst slurry under heating conditions; the catalyst ink spraying flow rate can be 0.05-2.0 mL / min, the heating temperature is between 40-80℃, and the loading is 0.5-4.0 mg / cm³. 2 Area ranges from 1 to 625 cm² 2 .

[0089] This invention provides the application of the membrane electrode in alkaline membrane electrolysis of water for hydrogen production. Specifically, this invention also provides a method for alkaline membrane electrolysis of water for hydrogen production. The water electrolysis fixture consists of anode and cathode end plates, anode and cathode electrode plates, anode and cathode flow channel plates, anode and cathode catalyst layers, and an alkaline membrane. The electrolysis of water for hydrogen production mainly utilizes the membrane electrode catalyst layer. The electrolyte can specifically be 1M KOH, initially at 60℃ and 0.2 A / cm². 2 The electrolyte was activated for 2 hours, and then voltage-current curves were collected at 80°C. Experiments showed that the electrolytic system of this embodiment exhibits good performance, which is beneficial for extending its service life.

[0090] To further understand the present invention, the following detailed description, in conjunction with embodiments, illustrates the ionomer materials provided by the present invention, their preparation methods, and applications. The scope of protection of the present invention is not limited to the following embodiments. In the embodiments, all original reagents and materials are commercially available, and experimental methods not specifying specific experimental conditions are conventional methods and conditions well-known in the art.

[0091]

[0092] 8.31 g (50 mmol) of fluorene and 36.6 g (150 mmol) of 1,6-dibromohexane were weighed into a 500 mL round-bottom flask, and 250 mL of 50% sodium hydroxide aqueous solution was added. The mixture was heated to 90 °C and reacted under a nitrogen atmosphere for 12 h. The product was extracted with dichloromethane and water and purified by column chromatography to obtain 9,9-bis(6-bromohexyl)-9H-fluorene.

[0093] Example 1

[0094] Weigh 4.92 g (10 mmol) of 9,9-bis(6-bromohexyl)-9H-fluorene and 1,1,1-trifluoroacetone (1.35 g (12 mmol)) and add them to a round-bottom flask. Add 15 mL of dichloromethane and 20 mL of trifluoromethanesulfonic acid at 0 °C. React for half an hour. The product precipitates in ethanol. Collect the solid and dry it to obtain the crude product. The crude product is dissolved in chloroform and then precipitated again in methanol to obtain the initial polymer.

[0095] The initial polymer is first used to obtain a polymer of repeating units as shown in Formula 2, and then an ionomer is obtained.

[0096] Specifically, the initial polymer (5.86 g, 10 mmol), 5-(4-aminophenyl)-10,15,20-tris(phenyl)porphyrin (0.694 g, 1.1 mmol), and potassium carbonate (0.453 g, 3.3 mmol) were weighed and dissolved in 100 mL of N,N-dimethylformamide. The mixture was heated to 80 °C and reacted under a nitrogen atmosphere for 48 h. The reaction solution was then cooled to room temperature. 5 mL of trimethylamine was added for quaternization, and the reaction was continued for 24 h. The product precipitated in diethyl ether, and the solid was collected and dried to obtain the ionomer. Figure 1 The image shows the 1H NMR spectrum of the prepared ionomer.

[0097]

[0098] Comparative Example 1

[0099] To better highlight the advantages of introducing catalyst-interacting groups, this comparative example prepared ionomers with the same content of ion-exchange groups but without catalyst-interacting groups. This is the difference between the ionomer of this comparative example and that of Example 1.

[0100] Synthesis of contrast ionomers

[0101] Weigh 2.2 g (4.5 mmol) of 9,9-bis(6-bromohexyl)-9H-fluorene, 0.92 g (5.5 mmol) of fluorene, and 1,1,1-trifluoroacetone (1.35 g, 12 mmol) into a round-bottom flask. Add 8 mL of dichloromethane and 10 mL of trifluoromethanesulfonic acid at 0 °C. React for half an hour. The product precipitates in ethanol. Collect the solid and dry it to obtain the crude product. Dissolve the crude product in chloroform and then precipitate it again in methanol to obtain the comparative polymer. Weigh 4.07 g (10 mmol) of the comparative polymer and dissolve it in 80 mL of N,N-dimethylformamide. Add 4 mL of trimethylamine for quaternization and react at 30 °C for 24 h. After the reaction is complete, precipitate the reaction solution in diethyl ether. Collect the solid and dry it to obtain the comparative ionomer. The specific reaction process is shown below. Figure 2 To prepare the comparative ionomers described above 1 H NMR spectrum;

[0102]

[0103] Example 2

[0104] 1) Synthesis of the initial polymer

[0105]

[0106] Weigh 2.2 g (4.5 mmol) of 9,9-bis(6-bromohexyl)-9H-fluorene, 0.92 g (5.5 mmol) of fluorene, and 1.35 g (12 mmol) of 1,1,1-trifluoroacetone into a round-bottom flask. Add 8 mL of dichloromethane and 10 mL of trifluoromethanesulfonic acid at 0 °C. React for half an hour. The product precipitates in ethanol. Collect the solid and dry it to obtain the crude product. Dissolve the crude product in chloroform and then precipitate it again in methanol to obtain the initial polymer. The specific reaction formula for the above reaction process is shown above.

[0107] 2) Synthesis of repeating unit polymers and ionomers of Formula 2 interacting with a catalyst

[0108]

[0109] Weigh out the initial polymer (5.53 g, 10 mmol), 5-(4-aminophenyl)-10,15,20-tris(phenyl)porphyrin (0.694 g, 1.1 mmol), and potassium carbonate (0.453 g, 3.3 mmol), dissolve them in 100 mL of N,N-dimethylformamide, heat to 80 °C, and react under a nitrogen atmosphere for 48 h. Then, cool the reaction solution to room temperature. Add 5 mL of trimethylamine for quaternization, and continue the reaction for 24 h. The product precipitates in diethyl ether, and the solid is collected and dried to obtain the ionomer. The specific reaction formula for the above reaction process is shown above. Figure 3The ionomers prepared above that interact with the catalyst 1 H NMR spectrum.

[0110] Example 3

[0111] 1) Preparation of ionomer membranes

[0112] Weigh 2g of the polyelectrolyte membrane material from Example 1 and Comparative Example 1 respectively, add 60mL of N-methylpyrrolidone, dissolve it completely into a uniform and transparent solution, coat it onto a glass plate, and dry it on a hot plate at 60°C to form a film, thus obtaining ionomer membranes.

[0113] 2) Testing of ionomer membranes

[0114] The tensile strength of the ionomer film at room temperature was tested using a dynamic mechanical analyzer (model: Q800, manufacturer: TA Instruments, USA). Specifically... Figure 4 As shown, the stress-strain test results show that the tensile strength of Example 1 and Comparative Example 1 is >12MPa and the elongation at break is >10%, indicating that these two ionomers can meet the requirements for use.

[0115] The thermal decomposition stability of the ionomers was tested using a thermogravimetric analyzer (model: Q500IR, manufacturer: TA Instruments, USA) at a rate of 10 °C / min, increasing from room temperature to 800 °C. Specifically... Figure 5 As shown, the thermogravimetric test results indicate that the degradation peaks of Example 1 (QAFLN) and Comparative Example 1 (PyFLN) at around 240°C are attributed to the degradation of quaternary ammonium groups, while the degradation after 450°C is due to the degradation of the polymer backbone. The highest test temperature of the ionomer material in water electrolysis for hydrogen production is 80°C. Therefore, both materials meet the application requirements.

[0116] 3) Preparation of catalyst slurry

[0117] Weigh 1g of the ionomers prepared in Example 1 and Comparative Example 1 respectively, dissolve them in 19mL of dimethyl sulfoxide (DMSO) to prepare an ionomer solution with a mass concentration of 5%. Weigh 5g of the ionomer solution with a mass concentration of 5w%, 1g of NiFe catalyst (obtained by reducing 2.595g NiCl2 and 3.244g FeCl3 dissolved in 10mL of deionized water in 2M NaBH4), and 50g of organic solvent (isopropanol:deionized water = 4:1 volume ratio). Disperse the above mixture for 20 minutes using an ultrasonic probe dispersion method to obtain a catalyst slurry (which can be called catalyst ink).

[0118] 4) Characterization of catalyst slurry

[0119] The microstructure of the catalyst slurry was characterized using a transmission electron microscope (model: JEM-2011, manufacturer: Nippon Electron Ltd.). Specifically, as follows... Figure 6 As shown in the transmission electron microscope test results, the catalyst ink of Example 1 exhibits a uniform dispersion morphology. The presence of porphyrin groups on the ionomer interacts with the catalyst and tends to be uniformly distributed around the catalyst. In contrast, the catalyst ink of Comparative Example 1 has an uneven morphology with large bright areas, which is caused by excessive aggregation of the catalyst. The test results intuitively demonstrate the beneficial effects of the ionomer of the present invention.

[0120] The distribution of catalyst aggregates was determined using dynamic light scattering, specifically as follows: Figure 7 As shown in the test results of dynamic light scattering, the average aggregate size of the catalyst ink in Example 1 (QAFLN) is 687 nm, while the average aggregate size of Comparative Example 1 (PyFLN) is 824 nm. This indicates that the ionomers used in Example 1 are uniformly distributed around the catalyst, and the steric hindrance effect of the ionomers inhibits the aggregation behavior of the catalyst particles. These test results are corroborated by the results of transmission electron microscopy, further demonstrating the beneficial effects of the ionomers of this invention.

[0121] The sedimentation stability of ink is characterized by recording the change in ink sedimentation height over time, specifically as follows: Figure 8 As shown. Figure 8 Part a shows the results of Comparative Example 1 after 12 hours, and Part b shows the results of Example 1 after 108 hours. The test results of the ink sedimentation stability show that the catalyst ink of Comparative Example 1 showed significant sedimentation after 12 hours, while the catalyst ink of Example 1 showed no significant sedimentation after 108 hours. This indicates that due to the excessive agglomeration of the catalyst in Comparative Example 1, the large agglomerates settled rapidly due to greater gravitational influence. In contrast, the uniformly distributed catalyst and ionomers in Example 1, influenced by steric hindrance, van der Waals forces, and double-layer repulsion, were less prone to agglomeration into large agglomerates, resulting in a slower sedimentation rate and superior catalyst ink stability.

[0122] The rheological properties of the catalyst slurry were characterized using a rheometer (model: TADiscovery HR-2, manufacturer: TA Inc., USA). Specifically, as follows... Figure 9 As shown (the horizontal axis represents the shear rate s) -1The vertical axis represents shear viscosity (Pa·s). From the rheological properties of the catalyst ink, it can be seen that under the same shear rate, the shear viscosity of Comparative Example 1 is higher than that of Example 1, indicating that Comparative Example 1 has formed more catalyst agglomerates, and the agglomerates are destroyed when subjected to slight shear force, and the viscosity drops rapidly. Example 1 can reach equilibrium at a smaller shear rate when subjected to shear force, indicating that its dispersion stability is better.

[0123] Example 4

[0124] 1) Preparation of the catalyst layer

[0125] The catalyst slurry was sprayed onto the polyelectrolyte membrane using ultrasonic spraying to obtain the membrane electrode. The spraying temperature was 60°C, and the travel speed was as follows: Figure 10 As shown. Because the ionomers in Example 1 are more uniformly dispersed around the catalyst, the electrostatic repulsion between the charged ionomers and the steric hindrance of the polymer inhibit further agglomeration of the catalyst coating, thereby forming a stable and dispersed catalyst slurry, and thus obtaining a catalyst layer that can be prepared over a large area.

[0126] 2) Characterization of the catalyst layer

[0127] The microstructure of the catalyst layer was characterized using an atomic force microscope (Model: MultiMode V, manufacturer: Veeco, USA). Specifically, as follows... Figure 11 As shown, the microstructure of the catalyst layers prepared by Example 1 and Comparative Example 1 was characterized by atomic force microscopy. It was found that the catalyst layer prepared by Example 1 exhibited a uniform morphology, with ionomers uniformly dispersed around the catalyst to form a skin layer of several nanometers; while in Comparative Example 1, large-area catalyst agglomeration and ionomer agglomeration were observed.

[0128] The specific surface area of ​​the catalyst layer was measured using a specific surface area and pore volume / pore size analyzer, specifically as follows: Figure 12 As shown. The carbon dioxide adsorption test of the catalyst layer shows that, due to the more uniform morphology of the catalyst layer in Example 1, it exhibits a higher gas adsorption capacity, indicating that the catalyst layer constructed in Example 1 has abundant microporous characteristics. In contrast, in Comparative Example 1, due to the presence of large ionomers and catalyst aggregates, the pores of the catalyst layer are blocked, resulting in a lower gas adsorption capacity and fewer micropores.

[0129] 3) Testing of the catalyst layer

[0130] Electrochemical measurements of the samples were recorded using a standard three-electrode configuration workstation (CHI 760E). The catalyst was supported on carbon fiber paper as the working electrode, and the Hg / HgO electrode and platinum plate electrode served as the reference and counter electrodes, respectively. All electrochemical measurements were performed in 1.0 mV H₂O electrolyte. An activation process was performed with time-ampere measurements prior to OER performance testing. Specifically, linear sweep voltammetry (LSV) measurements were first performed on the pristine electrocatalyst to determine the appropriate potential parameters for time-ampere measurements of the activation process. Subsequently, measurements were performed at scan rates of 20–100 mV·s. -1 Cyclic voltammetry (CV) curves were acquired over non-Radatian intervals. The SCE potential was calibrated to RHE:E using the Nernst equation. RHE =E Hg / HgO +0.098 +0.059 × pH; The formula for calculating the electrochemically active surface area (ECSA) is: ECSA = C dl / C s Where Cs is 1.0 M KOH (0.04 mF·cm⁻¹) -2 ) specific capacitance.

[0131] like Figure 13 As shown, the electrochemical performance of the catalyst layers prepared by Example 1 and Comparative Example 1 under a three-electrode system was tested. The results show that Example 1 exhibits a higher electrochemical active area than Comparative Example 1. This indicates that due to the more uniform catalyst layer structure of Example 1, more active sites of the catalyst are exposed, and the utilization rate of the catalyst is increased.

[0132] In addition, time-potential measurements were recorded to evaluate the electrocatalyst at a given constant current density of 10 mA·cm⁻¹. -2 Long-term stability, such as Figure 14 As shown. The metal content of the electrolyte after testing was also tested, as shown... Figure 15 As shown.

[0133] The stability of the catalyst layers prepared in Example 1 and Comparative Example 1 was tested under a three-electrode system. The results showed that the voltage of Example 1 remained almost unchanged during the 100-hour test period, while the voltage of Comparative Example 1 continued to increase. This indicates that Example 1 is more stable. The elemental content of the electrolyte after the test was determined by inductively coupled plasma. The results showed that a higher concentration of iron was detected in Comparative Example 1. This indicates that Example 1 improved the stability of the catalyst layer by inhibiting the loss of iron.

[0134] Example 5

[0135] Hydrogen production test via water electrolysis:

[0136] Cut the anode diffusion electrode (nickel foam) and cathode diffusion electrode (carbon paper) to a size of 2.25cm × 2.25cm. Place them on both sides of the membrane electrode prepared above, and then assemble them in the water electrolysis fixture. Operate the alkaline membrane water electrolysis hydrogen production device under the following conditions: operating temperature set to 80℃, anode feed of 1MKOH, and no cathode feed.

[0137] The polarization curves of the above-mentioned water electrolysis hydrogen production system were tested using a Biologic battery testing system, such as... Figure 16 As shown, the operating current was then set to 1.5 A / cm. 2 The voltage variation over time was measured. The detection results are as follows: Figure 17 As shown. At 1.8V, the maximum current density reaches 4.06A / cm, and the electrolytic system is ≥1.0A / cm. 2 It operated stably for 1400 hours under high current density. The performance and stability test results of water electrolysis for hydrogen production show that Example 1 exhibits higher electrolysis performance and longer-term stability due to its more uniform catalyst morphology and the ability to suppress Fe loss from the NiFe catalyst.

[0138] The above examples are only used to illustrate the technical features and implementation process of the present invention, and are not intended to limit the technical solutions of the present invention. It should be noted that those skilled in the art can still make modifications or equivalent substitutions to the present invention without departing from the principle of the present invention, and all such modifications or substitutions are covered by the protection of the present invention.

Claims

1. A catalytic layer slurry for hydrogen production by water electrolysis, comprising a binder and a transition metal catalyst, characterized in that, The adhesive is an ionomer, and the ionomer comprises repeating units of the structure shown in Formula 1: Formula 1; In Formula 1, Ar is the group represented by Formula a, Q is the group represented by Formula c or Formula d, and R is the group represented by Formula e; Formula a; Equation c, Formula d; Formula e; Wherein, 0≤x≤10, 0≤y≤10; R0~R5 are each independently selected from C1~C10 chain alkyl groups; t is selected from integers between 0 and 3; R' is selected from one or more of hydrogen, amino and phenylamino.

2. The catalyst layer slurry according to claim 1, characterized in that, The method for preparing the ionomer includes the following steps: A polymer having repeating units of Formula 2 is reacted with a quaternized monomer to obtain an ionomer comprising repeating units as shown in Formula 1. Formula 2; Wherein, X is a halogen or alkyl halogen; the quaternized monomer is a chain-like alkyl-substituted aliphatic amine.

3. The catalyst layer slurry according to claim 2, characterized in that, In the preparation method of the ionomer, the polymer having the repeating unit of Formula 2 is prepared as follows: The initial polymer is obtained by polycondensation of conjugated aromatic monomers and ketone monomers containing reactive sites. The initial polymer was reacted with a functional monomer to obtain a polymer having repeating units as shown in Formula 2. The conjugated aromatic monomer containing the reactive site is 9,9-bis(6-bromohexyl)-9H-fluorene; the ketone monomer is selected from 1,1,1-trifluoroacetone or 2,2,2-trifluoroacetophenone. The functional monomer is selected from 5-(4-aminophenyl)-10,15,20-tris(phenyl)porphyrin and 5,15-(aminophenyl)-10,20-phenylporphyrin.

4. The catalyst layer slurry according to claim 3, characterized in that, In the method for preparing the ionomer, the polycondensation reaction is carried out in a first solvent under the action of a first catalyst, wherein the first catalyst is trifluoroacetic acid and / or trifluoromethanesulfonic acid; the temperature of the polycondensation reaction is 0~20℃ and the time is 1~48h.

5. The catalyst layer slurry according to claim 3, characterized in that, In the preparation method of the ionomer, the Mensoukin reaction is carried out in a second solvent under the action of a second catalyst, the second catalyst being potassium carbonate and / or cesium carbonate; the molar ratio of the initial polymer to the functional monomer is 1:0.1~0.5, and the temperature of the Mensoukin reaction is 80~100℃.

6. The catalyst layer slurry according to any one of claims 2-5, characterized in that, In the preparation method of the ionomer, the molar ratio of the polymer having the repeating unit of Formula 2 and the quaternized monomer is 0.5~1:1, the reaction temperature is 30~80℃, and the time is 12~48h.

7. A membrane electrode comprising a catalytic layer, characterized in that, The catalyst layer is prepared by ultrasonic spraying and / or slot coating of the catalyst layer slurry as described in claim 1.

8. The application of the membrane electrode as described in claim 7 in alkaline membrane electrolysis of water to produce hydrogen.

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