Cobalt manganese oxide catalyst-nonporous anion exchange membrane composite system stable in high-temperature alkaline environment

Abstract

The invention relates to the related field of alkaline water electrolysis hydrogen production, in particular to a cobalt manganese oxide catalyst-nonporous anion exchange membrane composite system stable in high-temperature alkaline environment, which comprises a cobalt manganese oxide nanosheet and a quaternized polyarylene ether nitrile nonporous membrane, the metal molar ratio of Co to Mn of the cobalt manganese oxide is 1: 1-3: 1, and the metal molar ratio of the cobalt manganese oxide nanosheet to the quaternized polyarylene ether nitrile nonporous membrane is 1: 1-3: 1. After acid etching, the oxygen vacancy concentration is 0.2-0.5 mmol / g, and the specific surface area is 120-180m < 2 > / g; the quaternization degree of the non-porous membrane is 70-90%, the conductivity at 80 DEG C is greater than or equal to 100mS / cm, and the swelling rate in 10MKOH is 1t; 5%. According to oxygen vacancies (0.2-0.5 mmol / g) and high specific surface area (120-180 m < 2 > / g) formed after cobalt manganese oxide in the composite system is subjected to acid etching, the number of catalytic active sites is remarkably increased, an electronic structure (for example, the ratio of Co < 3 + > is increased) is optimized, the OER overpotential is as low as 210-230 mV under 10 mA / cm < 2 >, the Tafel slope is smaller than or equal to 38 mV / dec, and the charge transfer resistance is smaller than or equal to 20 omega, which are far superior to those of an unetched catalyst and a traditional system; and the water electrolysis oxygen evolution reaction rate is accelerated.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by alkaline water electrolysis, specifically to a composite system of a cobalt manganese oxide catalyst and a non-porous anion exchange membrane (AEM) having excellent stability and catalytic activity in a high-temperature, strong-alkaline environment, and a preparation method thereof. Background Art

[0002] Alkaline water electrolysis is a key green hydrogen production technology for achieving the "dual carbon" goal. Its core bottleneck lies in the high-temperature alkaline stability of the catalyst and anion exchange membrane. Cobalt manganese oxide (CoMnOx) has been widely studied due to its high OER activity and low cost.

[0003] However, in high temperature and strong alkaline environment (such as 80℃, 5MKOH), lattice oxygen loss and metal dissolution (Co 2+ The dissolution rate is 0.15 μg / (cm 2 ·h)); and insufficient intrinsic conductivity (conductivity <0.5S / cm) leads to high charge transfer resistance. Traditional anion exchange membranes (such as quaternized polysulfone membranes) have a swelling rate exceeding 15% at 80°C, and the membrane resistance increases to 20Ω·cm 2 , and the interfacial bonding force with the catalyst is weak (<2MPa), resulting in poor stability of the composite system. In the prior art, the composite of catalyst and membrane mostly adopts physical coating method, such as directly coating CoMnOx particles on the membrane surface. Although the short-term activity is improved, the interface falls off seriously during long-term operation (100-hour shedding rate>30%). Chinese patent CN112375489A discloses a composite membrane of CoMn-LDH and AEM, but its overpotential increase reaches 120mV after running for 500 hours at 60°C and 3MKOH, which cannot meet the long-term operation requirements of industrialization. Therefore, it is of great significance to develop a composite system with strong interface coupling, high conductivity and anti-swelling properties. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a cobalt manganese oxide catalyst-non-porous anion exchange membrane composite system that is stable in a high-temperature alkaline environment.

[0005] A cobalt manganese oxide catalyst-nonporous anion exchange membrane composite system comprises cobalt manganese oxide nanosheets and a quaternized poly (arylene ether nitrile) nonporous membrane, wherein the metal molar ratio Co:Mn of the cobalt manganese oxide is 1:1-3:1, the oxygen vacancy concentration after acid etching is 0.2-0.5 mmol / g, and the specific surface area is 120-180 m 2 / g; the quaternization degree of the non-porous membrane is 70%-90%, the conductivity at 80°C is ≥100mS / cm, and the swelling rate in 10MKOH is <5%.

[0006] Furthermore, the cobalt manganese oxide and the non-porous membrane form a covalent bonding interface through in-situ polymerization, the interface bonding strength is greater than 5MPa, and the bonding mode is a -COC- covalent bond formed by the hydroxyl groups on the catalyst surface and the epoxy groups of the membrane segments.

[0007] Furthermore, in 1MKOH electrolyte, the oxygen evolution reaction (OER) is 10mA / cm 2 The overpotential at the current density is ≤230mV, the Tafel slope is ≤38mV / dec, and the charge transfer resistance is ≤20Ω.

[0008] Furthermore, the preparation of the cobalt manganese oxide includes sol-gel synthesis and acid etching steps. The acid etching uses a 0.1-0.5M trifluoromethanesulfonic acid solution, an etching temperature of 50-70° C., and a time of 1-3 hours.

[0009] Furthermore, the raw materials of the non-porous membrane include poly(arylene ether nitrile) and trifluoroacetophenone, with a molar ratio of 9:1-7:3. The membrane is prepared by quaternization reaction and non-solvent induced phase separation method, and has a membrane thickness of 20-50 μm.

[0010] Furthermore, when continuously operated for ≥1000 hours under 80°C and 5MKOH environment, the oxygen evolution reaction overpotential increase is ≤50mV, the cobalt ion dissolution rate is <5%, and the membrane thickness change rate is <6%.

[0011] Furthermore, the surface hydroxyl density of the cobalt manganese oxide is ≥1.0 mmol / g, and the quaternary ammonium groups (-N + (CH3)3) forms a double anchoring structure of electrostatic adsorption and cooperative covalent bonding.

[0012] Furthermore, the pore size distribution of the non-porous membrane is concentrated in the range of 0.8-1.5 nm, and the hydroxide ion conductivity is ≥130 mS / cm (80° C.) as measured by the BET nitrogen adsorption method.

[0013] A method for preparing the composite system as claimed in claim 1, comprising:

[0014] (1) Preparation of cobalt manganese oxide precursors by sol-gel method;

[0015] (2) Acid etching to control oxygen vacancies;

[0016] (3) Preparation of quaternized poly (arylene ether nitrile) non-porous membrane;

[0017] (4) In situ polymerization achieves covalent bonding between the catalyst and the membrane.

[0018] Furthermore, in step (4), the initiator of the in-situ polymerization is benzoyl peroxide, the reaction temperature is 60-80° C., the time is 2-4 hours, and the solid-liquid ratio of the catalyst to the membrane precursor solution is 1 g:50-200 mL.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The oxygen vacancies (0.2-0.5mmol / g) and high specific surface area (120-180m2) formed by acid etching of cobalt manganese oxide in the composite system 2 / g), significantly increased the number of catalytic active sites, and optimized the electronic structure (such as Co 3+ The ratio is increased), making the OER overpotential at 10mA / cm 2 The voltage drop is as low as 210-230mV, the Tafel slope is ≤38mV / dec, and the charge transfer resistance is ≤20Ω, which is much better than the unetched catalyst and the traditional system, and accelerates the rate of oxygen evolution reaction in water electrolysis.

[0021] 2. The catalyst and the non-porous membrane form a covalent bonding interface (-COC- bond) through in-situ polymerization, with a bonding strength of >5MPa. Combined with the double anchoring structure of electrostatic adsorption, it effectively inhibits the shedding of the catalyst and the dissolution of metal ions in a high-temperature and strong alkaline environment (cobalt ion dissolution rate <5%). The quaternization degree of the non-porous membrane (70%-90%) and the special preparation process make its swelling rate less than 5% at 80°C and 10MKOH, and the overpotential increase is ≤50mV after continuous operation for ≥1000 hours, which solves the problems of severe swelling and poor stability of traditional membranes and meets the needs of long-term industrial operation.

[0022] 3. The pore size distribution of the non-porous membrane is concentrated in the range of 0.8-1.5 nm, and the hydroxide ion conductivity is ≥130 mS / cm at 80°C (up to 150 mS / cm in some embodiments), forming an efficient ion transport channel, reducing membrane resistance, and further improving the electrochemical performance of the composite system.

[0023] 4. Cobalt manganese oxide raw materials are cheap and abundant, and the preparation process adopts simple processes such as sol-gel method and acid etching; the non-porous membrane is prepared by quaternization reaction and non-solvent induced phase separation method. The steps are controllable and suitable for large-scale production. Compared with precious metal catalysts and complex membrane material systems, it significantly reduces the cost of hydrogen production by electrolysis of water.

[0024] 5. The oxygen vacancies in the catalyst enhance the catalytic activity, the covalently bonded interface improves the stability, and the anti-swelling and high ion conductivity of the non-porous membrane form a synergistic effect, which enables the composite system to maintain high efficiency in continuous operation for ≥1000 hours in a high-temperature alkaline environment (80°C, 5MKOH), providing key material support for the industrial application of alkaline water electrolysis hydrogen production technology. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Example 1: CoMnOx-OV / PAEN composite system (Co:Mn=2:1)

[0026] Composite system composition, cobalt manganese oxide (CoMnOx):

[0027] Using a Co:Mn=2:1 molar ratio, the nanosheets with an oxygen vacancy concentration of 0.35 mmol / g and a specific surface area of ​​160 m were formed by etching with 0.3 M trifluoromethanesulfonic acid for 2 hours. 2 / g, surface hydroxyl density 1.2mmol / g.

[0028] Non-porous anion exchange membrane (PAEN):

[0029] Polyarylene ether nitrile (PAEN) is copolymerized with 10% trifluoroacetophenone, with a quaternization degree of 80%, a film thickness of 30 μm, a conductivity of 134 mS / cm at 80°C, and a swelling ratio of 4.2% in 10 M KOH.

[0030] Interface structure:

[0031] Quaternized PAEN segments were grafted onto the surface of CoMnOx by in situ polymerization to form -COC- covalent bonds with an interfacial bonding strength of 5.5 MPa.

[0032] The preparation method is as follows

[0033] Step 1: Synthesize CoMnOx precursor by sol-gel method: dissolve 0.2 mol Co(NO3)2·6H2O and 0.1 mol Mn(NO3)2·4H2O in 200 mL ethylene glycol, add 0.45 mol citric acid, stir at 80 °C until a transparent gel is formed (about 4 hours), transfer to a muffle furnace and calcine at 500 °C for 3 hours (heating rate 5 °C / min), and grind to obtain CoMnOx nanopowder.

[0034] Step 2: Oxygen vacancy control (acid etching), 5g CoMnOx was dispersed in 100mL 0.3M trifluoromethanesulfonic acid solution, magnetically stirred at 60℃ for 2 hours, centrifuged (8000rpm, 10min), washed with deionized water to neutrality, and vacuum dried at 60℃ for 12 hours to obtain oxygen vacancy-enriched CoMnOx-OV.

[0035] Step 3: Preparation of Nonporous PAEN Membrane: 90g of PAEN and 10g of trifluoroacetophenone were dissolved in 1000mL of N,N-dimethylacetamide (DMAc). 50mL of iodomethane was added and the mixture was refluxed at 80°C for 2 hours to obtain a quaternized PAEN solution. Using the nonsolvent-induced phase separation (NIPS) method, the solution was doctor-coated onto a glass plate (film thickness: 30μm) and immersed in an ice-water bath for 10 minutes to form a film. The film was then removed and soaked in deionized water for 24 hours to remove the solvent and dried at 60°C for later use.

[0036] Step 4: Composite System Assembly: 1g of CoMnOx-OV was ultrasonically dispersed in 100mL of a PAEN precursor solution (5wt% solids). 0.5g of benzoyl peroxide (initiator) was added and in-situ polymerization was carried out at 70°C for 3 hours to graft the PAEN segments onto the CoMnOx surface via a hydroxyl condensation reaction. The composite solution was then knife-coated onto the PAEN base film surface, and the NIPS process was repeated to obtain a 50μm thick composite film.

[0037] Preparation details

[0038] (1) CoMnOx synthesis:

[0039] Metal salt concentration: Co 2+ =0.2M, Mn 2+ =0.1M; citric acid dosage: 1.5 times the total molar number of metal ions; roasting heating rate: 5°C / min, holding time: 3 hours.

[0040] (2) Acid etching:

[0041] Etchant: 0.3 M trifluoromethanesulfonic acid; liquid-to-solid ratio: 20 mL / g; reaction temperature: 60° C., reaction time: 2 hours.

[0042] (3) PAEN membrane preparation:

[0043] Quaternizing agent: methyl iodide (monomer molar ratio 1.2:1); membrane-forming solvent: DMAc; gel bath: ice-water mixture.

[0044] Composite process: grafting reaction temperature 70°C, time 3 hours; number of composite film layers: double-sided coating, total thickness 50 μm.

[0045] The performance test is as follows

[0046] Among them, electrochemical test:

[0047] Three-electrode system (Hg / HgO reference electrode, Pt sheet counter electrode), 1M KOH electrolyte, scan rate 5mV / s. OER overpotential 220mV (10mA / cm 2), Tafel slope 35mV / dec, charge transfer resistance 18Ω (EIS test, 100kHz-0.1Hz).

[0048] Among them, the stability test:

[0049] Constant current test (500mA / cm 2 , 80℃, 5MKOH), after 1000 hours, the overpotential increased to 270mV, and the Co dissolution rate was 4.2% (ICP-MS detected Co in the electrolyte 2+ concentration 0.04ppm).

[0050] The membrane properties are as follows:

[0051] Conductivity: 134 mS / cm (80°C, AC impedance method); swelling rate: 4.5% (80°C, thickness change after immersion in 10M KOH for 24 hours); interface bonding strength: 5.2 MPa (90° peel test).

[0052] Example 2: CoMnOx-OV / PAEN composite system (Co:Mn=3:1)

[0053] Composite system composition

[0054] Cobalt manganese oxide (CoMnOx-OV): Using a metal molar ratio of Co:Mn = 3:1, it was etched with 0.5M trifluoromethanesulfonic acid solution at 70°C for 3 hours to form nanosheets with an oxygen vacancy concentration of 0.5mmol / g and a specific surface area of ​​180m 2 / g, surface hydroxyl density 1.5mmol / g.

[0055] Non-porous anion exchange membrane (PAEN): Poly(arylene ether nitrile) and trifluoroacetophenone are copolymerized in a molar ratio of 7:3, with a quaternization degree of 90%, a membrane thickness of 20 μm, a conductivity of 150 mS / cm at 80°C, and a swelling ratio of 3.8% in 10 M KOH.

[0056] Interface structure: -COC- covalent bond connection is formed by in-situ polymerization, and the interface bonding strength is 6.2MPa.

[0057] The preparation method is as follows:

[0058] Preparation of CoMnOx precursor: 0.3 mol Co(NO3)2·6H2O and 0.1 mol Mn(NO3)2·4H2O were dissolved in 200 mL of ethylene glycol, 0.6 mol citric acid (1.5 times the total molar number of metal ions) was added, and stirred at 80°C until a transparent gel was formed (about 5 hours), transferred to a muffle furnace and calcined at 500°C for 3 hours (heating rate 5°C / min), and CoMnOx nanopowder was obtained after grinding.

[0059] Acid etching to regulate oxygen vacancies: 5 g CoMnOx was dispersed in 125 mL 0.5 M trifluoromethanesulfonic acid solution (liquid-to-solid ratio 25 mL / g), magnetically stirred at 70 °C for 3 h, centrifuged (8000 rpm, 10 min), washed with deionized water to neutrality, and vacuum dried at 60 °C for 12 h to obtain CoMnOx-OV.

[0060] Nonporous PAEN membrane preparation: 70 g of poly(arylene ether nitrile) and 30 g of trifluoroacetophenone were dissolved in 1000 mL of N,N-dimethylacetamide (DMAc). 60 mL of iodomethane (monomer molar ratio 1.2:1) was added and refluxed at 80°C for 2 hours to obtain a quaternized PAEN solution. Using a non-solvent-induced phase separation method, the solution was doctor-coated onto a glass plate (film thickness 20 μm) and immersed in an ice-water bath for 10 minutes to form a film. The film was then soaked in deionized water for 24 hours to remove the solvent and dried at 60°C for later use.

[0061] 1 g of CoMnOx-OV was ultrasonically dispersed in 200 mL of PAEN precursor solution (solid content 5 wt%), 0.6 g of initiator benzoyl peroxide was added, and in-situ polymerization was carried out at 80 ° C for 4 hours. The composite solution was scraped onto the surface of the PAEN base film, and the NIPS process was repeated to obtain a composite film with a thickness of 40 μm (double-sided coating).

[0062] Performance Testing

[0063] Among them, the electrochemical performance: in 1MKOH electrolyte, the oxygen evolution reaction (OER) is 10mA / cm 2 The overpotential at this current density is 210 mV, the Tafel slope is 35 mV / dec, and the charge transfer resistance is 15 Ω.

[0064] The stability test showed that after 1200 hours of continuous operation at 80°C and 5MKOH, the overpotential of the oxygen evolution reaction increased by 45mV and the cobalt ion dissolution rate was 3.8%.

[0065] Membrane performance: hydroxide ion conductivity at 80°C is 150 mS / cm, swelling ratio in 10 M KOH is 3.8%, and interfacial bonding strength is 6.2 MPa.

[0066] Example 3: CoMnOx-OV / PAEN composite system (Co:Mn=1:1)

[0067] Composite system composition

[0068] Cobalt manganese oxide (CoMnOx-OV): Co:Mn=1:1, etched with 0.1M trifluoromethanesulfonic acid solution at 50°C for 1 hour, oxygen vacancy concentration 0.2mmol / g, specific surface area 120m 2 / g, surface hydroxyl density 1.0mmol / g.

[0069] Non-porous anion exchange membrane (PAEN): Poly(arylene ether nitrile) and trifluoroacetophenone copolymerized in a molar ratio of 9:1, with a quaternization degree of 70%, a membrane thickness of 50 μm, a conductivity of 100 mS / cm at 80°C, and a swelling ratio of 4.8% in 10 M KOH.

[0070] Interface structure: -COC- covalent bond connection is formed by in-situ polymerization, and the interface bonding strength is 5.0MPa.

[0071] Comparative Example 1: Unetched CoMnOx / Physically Coated PAEN Film

[0072] Preparation differences

[0073] Omit step 2 acid etching and directly use the original CoMnOx (oxygen vacancy concentration 0.1mmol / g, specific surface area 85m 2 / g).

[0074] The composite process adopts physical coating: CoMnOx powder (5wt%) is simply mixed with PAEN solution and then coated by blade without in-situ polymerization.

[0075] Performance data

[0076] Among them, electrochemical test:

[0077] OER overpotential 280mV (10mA / cm 2 ), Tafel slope 50mV / dec, charge transfer resistance 120Ω.

[0078] Among them, the stability test:

[0079] After 100 hours, the overpotential increased to 350mV and the Co dissolution rate was 22% (Co 2+ concentration 0.23ppm).

[0080] Membrane properties:

[0081] The electrical conductivity is 102mS / cm (80℃), the swelling rate is 8.3%, and the interface bonding strength is 2.1MPa.

[0082] Comparative Example 2: Commercially available NiFe-LDH / AEM composite membrane (prepared by CN112375489A method)

[0083] Preparation parameters

[0084] Catalyst: NiFe-LDH (Ni:Fe=3:1), without interface modification.

[0085] Membrane material: quaternized polysulfone (QPSF), quaternization degree 70%, non-porous structure.

[0086] Performance Comparison

[0087] Among them, electrochemical test:

[0088] OER overpotential 250mV (10mA / cm 2 ), Tafel slope 40mV / dec.

[0089] Among them, the stability test:

[0090] After 500 hours, the overpotential increased to 320 mV and the Fe dissolution rate was 15%.

[0091] Membrane properties:

[0092] The conductivity is 110mS / cm (80℃), the swelling rate is 12%, and the interface bonding strength is 3.0MPa. The examples and comparative examples are as follows:

[0093]

[0094] In addition, the embodiment analysis shows that:

[0095] (1) Comparison of catalytic activity

[0096] The oxygen vacancy concentration of the CoMnOx catalyst without acid etching is 0 mmol / g, and the specific surface area is only 80 m 2 / g, the surface hydroxyl density is low (0.5mmol / g), resulting in an OER overpotential as high as 320mV (10mA / cm 2 ), Tafel slope 45mV / dec, charge transfer resistance 30Ω.

[0097] In contrast, in Example 2 of the present invention, 0.5 mmol / g oxygen vacancies were formed by etching with 0.5 M trifluoromethanesulfonic acid, and the specific surface area was increased to 180 m 2 / g, surface hydroxyl density 1.5mmol / g, OER overpotential reduced to 210mV, Tafel slope 35mV / dec, charge transfer resistance 15Ω, and catalytic activity significantly improved.

[0098] The performance disadvantages of precious metal IrO2 catalyst are as follows: the overpotential of IrO2 under acidic conditions is 225mV (10mA / cm 2 ), and the cost is high (Ir dosage is 0.2852mg / cm 2 , hydrogen production cost is $0.96 / kg).

[0099] In contrast, the cobalt manganese oxide of Example 2 of the present invention has a cost of less than 0.1% of IrO 2 , and has a lower overpotential (210 mV) and better stability (overpotential increase of 45 mV after 1200 hours) in an alkaline environment.

[0100] (2) Comparison of interface stability

[0101] The interface bonding strength of the composite system without forming a covalent bond interface is only 2.0 MPa, the catalyst dissolution rate is as high as 8%, and the overpotential increases by more than 80 mV after running at 80°C and 5MKOH for 1000 hours.

[0102] In contrast, Example 2 of the present invention forms a -COC- covalent bond through in-situ polymerization, with an interface bonding strength of 6.2 MPa, a cobalt ion dissolution rate of only 3.8%, an overpotential increase of only 45 mV after 1200 hours of continuous operation, and a stability improvement of more than 50%.

[0103] (3) Comparison of membrane performance

[0104] Traditional anion exchange membranes (such as FAA-3) have a swelling rate of over 15% in 10MKOH, a hydroxide ion conductivity of only 80mS / cm at 80°C, and low interfacial bonding strength (25-40MPa), making them prone to swelling and rupture during long-term operation.

[0105] In contrast, the PAEN membrane of Example 2 of the present invention has a quaternization degree of 90%, a swelling rate of only 3.8%, a conductivity of 150 mS / cm, an interfacial bonding strength of 6.2 MPa, and no significant performance degradation after operating in 10 M KOH for 1200 hours.

[0106] (4) Comparison of synergistic mechanisms

[0107] In traditional systems, there is no chemical bond between the catalyst and the membrane, the ion transport path is tortuous, and the membrane resistance is high (for example, the FAA-3 membrane resistance is 0.6-1.5Ω·cm 2 ), the overall electrolysis efficiency is low (current density <500mA / cm 2 ); On the other hand, the composite system of Example 2 of the present invention forms an efficient ion channel (resistance 0.16Ω·cm) by covalent bond interface and non-porous membrane design. 2 ), the current density reaches 1440mA / cm at 80℃ and 2.0V. 2 , electrolysis efficiency increased by more than 200%.

[0108] (5) Comparison of cost and preparation process

[0109] Precious metal catalysts (such as IrO2) require complex synthesis processes, are expensive (hydrogen production costs $0.96 / kg), and have poor stability (performance decays after 200 hours). In contrast, in the present invention, the cobalt manganese oxide of Example 2 uses a sol-gel method and acid etching process, and the cost is only 0.1% of the precious metal. The PAEN film is prepared by quaternization reaction and non-solvent-induced phase separation method, which has simple steps and is suitable for large-scale production.

[0110] In the oxygen vacancy control mechanism, the acid etching process of Example 2 selectively etches lattice oxygen through trifluoromethanesulfonic acid to form high-density oxygen vacancies (0.5 mmol / g), which significantly improves the Co 3+ Ratio (XPS shows Co 3+ / Co 2+ =1.8), optimize the electronic structure, while Co in the unetched CoMnOx 3+ The ratio is only 0.7.

[0111] In terms of interface bonding strength test, the interface bonding strength of Example 2 was measured to be 6.2 MPa by 90° peeling test, while that of the physical mixing system was only 2.0 MPa, indicating that the covalent bond significantly enhanced the interface stability.

[0112] Comparing the membrane swelling rates, the PAEN membrane of Example 2 swells 3.8% in 10MKOH, while the FAA-3 membrane swells over 15% under the same conditions, resulting in membrane structural damage and decreased ion conduction.

[0113] Moreover, after continuous operation for 1200 hours at 80°C in 5M KOH, the cobalt ion dissolution rate of Example 2 was 3.8%, while the dissolution rate of the physical mixing system reached 8%. The Ir dissolution rate of the precious metal system (such as IrO2) exceeded 5% after 200 hours under acidic conditions. The hydroxyl ion transference number of the PAEN membrane of Example 2 reached 0.98, while that of the FAA-3 membrane was only 0.85, resulting in a 40% reduction in the overall electrolytic cell ohmic resistance (from 0.6Ω·cm 2 Down to 0.36Ω·cm 2 ).

[0114] The catalyst principle is as follows

[0115] (1) Mechanism of oxygen vacancies enhancing catalytic activity

[0116] Active site exposure: Acid etching increases the oxygen vacancy concentration on the CoMnOx surface from 0.1mmol / g to 0.35mmol / g, forming more unsaturated Co 3+ and Mn 4+ Site (XPS showed Co 3+ from 60% to 75%).

[0117] Electronic structure optimization: oxygen vacancies lead to a 0.7 eV decrease in the Co2p3 / 2 binding energy, an upward shift in the d-band center, and enhanced OH - The adsorption capacity of OH was improved (DFT calculation of *OH adsorption energy was optimized from -0.8 eV to -1.2 eV), accelerating the OER rate-determining step (*OOH formation).

[0118] (2) Covalent interface stabilization mechanism

[0119] Chemical anchoring: The epoxy groups of the PAEN chain react with the hydroxyl groups on the surface of CoMnOx to form a -CO-Co- covalent bond (FTIR detection 1050 cm -1 The COC bond peak intensity at the membrane increased by 40%), firmly anchoring the catalyst on the membrane surface to avoid mechanical stripping under alkaline conditions.

[0120] Ion conduction channel: Quaternized PAEN-N + (CH3)3 groups form a continuous ion transport path, the hydroxide migration number reaches 0.85, which is 20% higher than that of traditional membranes, and the membrane resistance is reduced (0.8Ω·cm 2 vs. 1.5Ω·cm for traditional membranes 2 ).

[0121] (3) Anti-swelling mechanism of non-porous membrane

[0122] Molecular structure regulation: The -CF3 group introduced by trifluoroacetophenone enhances the hydrophobicity of the membrane (the contact angle increases from 75° to 92°). At the same time, the rigid aromatic ring structure inhibits chain segment movement, reducing the swelling rate from 12% of traditional membranes to 4.5% (80°C, 10MKOH).

[0123] Dense cross-linked network: The three-dimensional cross-linked structure (cross-linking degree 65%) formed by in situ polymerization further limits the penetration of solvent molecules. The pore size distribution is concentrated in the range of 0.8-1.2 nm, allowing only OH- ions to pass through, blocking the volume expansion effect of the KOH solution.

[0124] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cobalt manganese oxide catalyst-nonporous anion exchange membrane composite system, characterized by: The invention comprises cobalt manganese oxide nanosheets and quaternized poly (arylene ether nitrile) non-porous membrane, wherein the metal molar ratio Co:Mn of the cobalt manganese oxide is 1:1-3:1, the oxygen vacancy concentration after acid etching is 0.2-0.5 mmol / g, and the specific surface area is 120-180 m 2 / g; the quaternization degree of the non-porous membrane is 70%-90%, the conductivity at 80°C is ≥100mS / cm, and the swelling rate in 10MKOH is <5%.

2. The composite system according to claim 1, characterized in that: The cobalt manganese oxide and the non-porous membrane form a covalent bonding interface through in-situ polymerization, the interface bonding strength is greater than 5MPa, and the bonding mode is a -COC- covalent bond formed by the hydroxyl groups on the catalyst surface and the epoxy groups of the membrane chain segments.

3. The composite system according to claim 1, characterized in that: In 1M KOH electrolyte, oxygen evolution reaction (OER) is at 10 mA / cm 2 The overpotential at the current density is ≤230mV, the Tafel slope is ≤38mV / dec, and the charge transfer resistance is ≤20Ω.

4. The composite system according to claim 1, characterized in that: The preparation of the cobalt manganese oxide includes sol-gel synthesis and acid etching steps. The acid etching uses a 0.1-0.5M trifluoromethanesulfonic acid solution, an etching temperature of 50-70°C, and a time of 1-3 hours.

5. The composite system according to claim 1, characterized in that: The non-porous membrane comprises raw materials of poly(arylene ether nitrile) and trifluoroacetophenone in a molar ratio of 9:1-7:

3. The membrane is prepared by quaternization reaction and non-solvent induced phase separation method, and has a thickness of 20-50 μm.

6. The composite system according to claim 1, characterized in that: When continuously operated for ≥1000 hours at 80°C and 5MKOH, the oxygen evolution reaction overpotential increase is ≤50mV, the cobalt ion dissolution rate is <5%, and the membrane thickness change rate is <6%.

7. The composite system according to claim 1, characterized in that: The surface hydroxyl density of the cobalt manganese oxide is ≥1.0 mmol / g, and the quaternary ammonium groups (-N + (CH3)3) forms a double anchoring structure of electrostatic adsorption and cooperative covalent bonding.

8. The composite system according to claim 1, characterized in that: The pore size distribution of the non-porous membrane is concentrated in the range of 0.8-1.5 nm. The hydroxide ion conductivity is measured by the BET nitrogen adsorption method and is ≥130 mS / cm (80° C.).

9. A method for preparing the composite system according to any one of claims 1 to 8, characterized in that include: (1) Preparation of cobalt manganese oxide precursors by sol-gel method; (2) Acid etching to control oxygen vacancies; (3) Preparation of quaternized poly (arylene ether nitrile) non-porous membrane; (4) In situ polymerization achieves covalent bonding between the catalyst and the membrane.

10. The preparation method according to claim 9, characterized in that: In step (4), the initiator of the in-situ polymerization is benzoyl peroxide, the reaction temperature is 60-80° C., the time is 2-4 hours, and the solid-liquid ratio of the catalyst to the membrane precursor solution is 1 g:50-200 mL.

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