CN115093559A

CN115093559A - Self-polymerization microporous ionomer and preparation method and application thereof

Info

Publication number: CN115093559A
Application number: CN202210840616.4A
Authority: CN
Inventors: 申迎华; 王薪; 刘世斌; 李南文
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2022-07-18
Filing date: 2022-07-18
Publication date: 2022-09-23
Anticipated expiration: 2042-07-18
Also published as: CN115093559B

Abstract

The invention discloses a self-polymerization microporous ionomer which has the structure shown in the structural formula (I), has a weight average molecular weight of 7000-70000 and an intrinsic viscosity eta of 1.0-1.5 dL/g, has excellent gas permeability, higher conductivity and proper size swelling rate, shows excellent battery performance, can be used as an electrode adhesive of a membrane electrode and is applied to a cathodeIn the preparation of the membrane electrode cathode catalyst layer in the ion exchange membrane water electrolyzer.

Wherein n represents a positive integer of 10-100 degrees of polymerization.

Description

Self-polymerization microporous ionomer and preparation method and application thereof

Technical Field

The invention belongs to the technical field of membrane electrode assemblies for water electrolysis of anion exchange membranes, and particularly relates to a self-polymerization microporous ionomer capable of being used as an electrode adhesive. The self-polymerization microporous ionomer can improve the gas permeability of the membrane electrode catalyst layer and control the water absorption swelling rate at the same time, thereby obtaining excellent initial performance and service life of electrolyzed water.

Background

China strives to achieve carbon dioxide emission reaching a peak value before 2030 years and carbon neutralization before 2060 years. How to achieve the goal of high quality becomes a necessary requirement for the development and transformation of energy structures in a future period of China.

In order to achieve the aim, the production and consumption links of energy are going to green low-carbon roads. As a secondary energy source, hydrogen energy plays an important role in the global new energy pattern due to the characteristics of greenness, flexibility, wide sources and the like.

The hydrogen source is very wide, the main supply modes comprise reforming hydrogen production by fossil energy such as coal, natural gas and the like, industrial byproduct hydrogen production and electrolytic water hydrogen production, and other modes with large-scale supply potential in the future also comprise biomass hydrogen production, photo-thermal hydrogen production, photo-electric hydrogen production, nuclear energy hydrogen production and the like. However, at present, over 95% of hydrogen comes from hydrogen production by reforming fossil energy and industrial by-product hydrogen, but energy and environmental problems have been the biggest obstacles to the development of hydrogen. Therefore, the real high-efficiency utilization of 'green hydrogen' is realized, and the hydrogen production by electrolyzing water by using renewable energy is a key core technology.

The hydrogen production by water electrolysis is that under the action of direct current, water molecules are dissociated into hydrogen and oxygen through an electrochemical process, and the hydrogen and oxygen are separated out at the cathode and the anode respectively. According to the difference of electrolyte systems, the hydrogen production by water electrolysis can be divided into traditional alkaline electrolyzed water, proton exchange membrane electrolyzed water (PEMBE) and anion exchange membrane electrolyzed water (AEMWE). The three basic principles are consistent, namely, in the oxidation-reduction reaction process, the free exchange of electrons is prevented, and the charge transfer process is decomposed into the electron transfer of an external circuit and the ion transfer of an internal circuit, so that the generation and the utilization of hydrogen are realized.

In conventional alkaline cells, the electrodes are made of porous materialThe diaphragm is separated, the liquid alkaline electrolyte is 30-40 wt% KOH, the operation is carried out at the temperature of 60-90 ℃, and the current density of the battery is only 300-400 mA cm when the voltage of the battery is 1.7-2.4V ^-2 . Probably due to the high concentration of KOH electrolyte which readily forms K ₂ CO ₃ Precipitation, which prevents ion transfer in the pores of the gas diffusion layer, reduces the anode reaction and ionic conductivity. Therefore, when a high-concentration KOH solution is used as an electrolyte, the overall performance of electrolysis may be reduced. At the same time, the relatively low hydrogen yield and sensitivity to pressure differentials have been a significant limitation in the use of alkaline electrolyzers.

Currently, PEMWE are the most advanced membrane technology in water electrolysis. Because the high-conductivity perfluorosulfonic acid (Nafion) membrane is used for conducting protons, the operating current density is 1000-3000 mA cm at 2.0V ^-2 . However, the electrolysis cell requires expensive titanium flow fields and noble metal (PGM) catalysts, which account for over 70% of the total cost of the stack, thus hindering further development and application.

In contrast, the AEMWE combines the advantages of the conventional alkaline cell and the PEMWE: 1) pure water or low-concentration alkaline solution is used for replacing concentrated alkaline electrolyte; 2) reduction of ohmic losses using highly conductive and thin Anion Exchange Membranes (AEMs); 3) transition metal catalysts (Fe, Co, Ni); 4) the use of hydrocarbon membranes can greatly reduce costs.

This technology is still in the laboratory research phase, and still faces many problems in terms of cell efficiency, membrane electrode assembly durability and catalyst loading, production cost, etc., to achieve higher cell performance and better hydrogen economy.

The electrochemical reaction occurs at the three-phase boundary (TPB) of the catalyst, electrode binder (binder), and AEMs, and thus the Membrane Electrode Assembly (MEA) is the core component of the AEMWE, largely determining cell performance.

Over the past few years, many researchers have been working on developing AEMs with excellent performance, whose main function is to transfer hydroxide ions generated at the cathode to the anode to participate in electrochemical reactions; meanwhile, the hydrogen-oxygen composite anode is used as a separator between two electrodes, so that hydrogen and oxygen generated in the electrolysis process are prevented from mutually permeating, and the purity of the product hydrogen is reduced.

However, because of the poor combination of AEMs and binders in alkaline and high temperature environments, the initial performance and operating life of most AEMWE is much worse than the most advanced PEMWE performance, and although AEMs have been extensively studied and the performance has been significantly improved, there is still little interest in binder research and underestimates the impact of binders on AEMWC performance and durability.

Recent studies have shown that binders are more vulnerable to attack by hydroxide ions than AEMs, because in operating AEMWEs the binder is in direct contact with the catalyst that is subjected to the greatest electrochemical stress and therefore plays a critical role in the impact of the AEMWE performance. Its two main roles include: 1) securing discrete catalyst particles to the gas diffusion layer; 2) promotes the transport of hydroxide ions, electrons and reactants/products, forming good TPB between the catalyst layer and the AEMs.

Therefore, in addition to good ionic conductivity and alkaline stability, a high-performance electrode binder is required to have excellent gas permeability. Therefore, how to design the structure of the adhesive is a critical scientific problem which needs to be solved urgently at present.

Previous binders have typically been selected from Polytetrafluoroethylene (PTFE), but PTFE has limited its use in alkaline cells because it is not electrically conductive.

Professor Jan Schauer (Artificial catalyst bonded on trimethyamine-quaternarized poly (2,6-dimethyl-1,4-phenylene oxide)) prepared a binder of quaternized poly (2,6-dimethyl-1,4-phenylene oxide) that produced higher current densities than non-conductive PTFE. However, the binder is susceptible to degradation by a backbone hydrolysis mechanism.

Professor Vijay Ramani (Stability of Poly (2,6-dimethyl-1,4-phenylene), Oxide-Based Exchange Membrane Separator and dissolved Electrode Binder in solution-State Alkaline Water electrozers, J. Electrochem. Soc., 161 (2014)), F1015-F1020.) testing of BrPPO-ABCO by experiments ⁺ And BrPPO-TMA ⁺ At 100mA cm ^-2 After 5h of operation, the cell voltage increased by 0.4V and 0.2V, respectively, and degradation due to the presence of charged cationic groups initiating the hydrolysis of the backbone was confirmed using 1D and 2D NMR spectroscopy. Therefore, it is important to develop more stable anionic conductive polymer type binders.

Professor Yu Seung Kim (Phenyl Oxidation impedances the dual availability of alkali Membrane Water Electrolyzer, ACS appl. mater. Interfaces 2019, 11, 9696-9701.) to determine the cause of rapid loss of cell performance, IrO was used ₂ Anode catalyst, PtRu/C cathode catalyst, quaternized biphenyl ionomer (BPN) and quaternized polyphenylene AEM MEA was manufactured. By running the test at 2.1V for 100h, it was concluded that a new binder with less phenyl moieties or a catalyst with less phenyl adsorption properties should be developed.

Meanwhile, professor Yu Seung Kim (high quality quantized polystyrene ionometers for high performance and exchange membrane water electrolytes, Nature Energy, 2020, 5, 378-385.) has found that AEMWE requires a high content of quaternary ammonium groups to promote the hydrogen and oxygen evolution reactions during electrolysis, thus producing an ammonium-rich polymer electrolyte for use as a binder. Tested using a NiFe catalyst in pure water at 85 ℃ showed 2700mA cm at 1.8V ^-2 The excellent properties of (2).

In addition to the effect of binder structure on the AEMWE performance, researchers have also found that binder content is also an important factor. Therefore, the professor Modestino (Defining Nafion Ionomer coils for Enhancing alkali Oxygen Evolution electrochemical analysis, ACS Catal., 2018, 8, 11688-.

Professor Faid (Effect of exchange ex situ content on electrode performance in AEM water electrolysis, International journal of hydrogen energy, 2020, 45, 28272) found that the cathode overpotential of Ni/C was not negligible and was more affected by the binder content than the anode Ni/O by the rotating disk electrode method (RDE) and in situ half cell measurement analysis using a reference electrode.

Subsequently, The content of The binder in The anode and cathode catalyst layers was analyzed electrochemically and microscopically by teaching Vierrath (The effect of inorganic content in catalyst layers in The formation-exchange membrane catalysts prepared with respect to The regenerated membranes), J. mater. chem. A, 2021, 9, 15744-15754), and The results showed that The cell performance at 2V was The best at 7 wt.% of Aemion + binder, 1000mA cm ^-2 。

However, there has been little or no research on binders to improve gas transport to improve AEMWE performance. Professor Hyoung-Juhn Kim (Application of spirobiindane-based microporus poly (ether sulfone) s as polymeric binder on solid alkali exchange membrane cells, J. Membr. Sci, 2018,568, 67-75.) synthesized a novel poly (arylene ether sulfone) adhesive having spirobiindane structural units. The test results show that the MEA with the spirobiindane-modified PES (QOH-SBIs) shows a higher power density than the MEA without spirobiindane-modified PES (QOH-BPs), since the modified PES (QOH-SBIs) have a higher gas permeability.

Next, the classic theory of the gas separation membrane of reference, taught by Yu Seng Kim (How a small structural change of anode ion meter make a big difference in alkaline membrane fuel cell performance, J. Mater. chem. A, 2019, 7, 25040. 25046.), introduces symmetric dimethyl groups in the polymer backbone to increase the free volume fraction of the polymer, thereby effectively increasing the hydrogen permeability, and membrane electrode assemblies employing modified poly (biphenylalkylene) ionomers at the anode exhibit > 1500mW cm at 80 deg.C ^-2 Peak power density of at 600A cm ^-2 Has stable short-term durability (> 100h) at constant current density. This study provides important insight into the design of anode binders for high performance anion exchange membrane fuel cell AEMFCs.

It is well known that intrinsically microporous Polymers (PIMs) are widely used due to their high specific surface area and microporous structureUsed for developing high-selectivity and permeation separation membranes. The xu-gang control ion-exchange membranes from micro-porous polymers, Angew. chem., int. Ed. 2016, 55, 11499-11502) reported a new anion exchange membrane containing Tr Tiger Base (TB) based on PIM for the first time, when the Ion Exchange Capacity (IEC) is only 0.82mmol g ^-1 When the ionic conductivity is high, the ionic conductivity can reach 164.4mS cm ^-1 。

Professor Fukushima (An anion-conductive microporous polymer composition of a vertical ladder polymer with a proton induced back bone J. mater. chem. A2016, 4, 17655-17659.) synthesized a microporous PIM-1-based polymer for anion conduction having a hydroxide conductivity of 65mS cm at 80 ℃ and 100% relative humidity ^-1 . In addition, modified PIM-1 is also considered a potential AEMs that can be applied to AEMFC.

The QPIM-1 AEMs with excellent mechanical properties and high ionic conductivity are obtained by simple ammonification and quaternization reaction of the PIM-1 membrane by the teaching of Guiiver (mechanical robust chemistry exchange interaction for fuel cells, chem. Eng. J., 2021, 418, 129311). The conductivity of hydroxide at 20 ℃ is up to 57mS cm ^-1 The conductivity of the QPPO AEMs is 2.6-5.3 times that of the compact QPPO AEMs (similar to IEC).

With this in mind, it is contemplated to select a new self-polymerized microporous polymer for use as a binder in the cathode catalyst layer and study its effect on the AEMWC performance and durability by varying the binder to catalyst ratio and the sample preparation process.

Disclosure of Invention

It is an object of the present invention to provide a self-polymerized microporous ionomer having excellent gas permeability, higher electrical conductivity and a moderate dimensional swelling ratio.

The invention also aims to provide a preparation method of the self-polymerization microporous ionomer, which has mild preparation conditions and is easy to synthesize.

It is another object of the present invention to provide the use of the self-polymeric microporous ionomer as an electrode binder for a membrane electrode assembly.

The invention firstly provides a self-polymerization microporous ionomer, which has a structure shown in the following structural formula (I), wherein the weight average molecular weight is 7000-70000, and the intrinsic viscosity eta is 1.0-1.5 dL/g.

Wherein n represents a positive integer of 10-100 of polymerization degree.

The self-polymerization microporous ionomer provided by the invention has excellent performance, and has stable performance under severe conditions of alkali, heat and the like by testing basic performance after film forming, the water absorption swelling rate is less than 40wt%, the hydroxide conductivity at 60 ℃ is higher than 40mS/cm, the hydrogen flux reaches more than 30Barrer, and the excellent battery performance is shown.

Secondly, the invention also provides a method for simply preparing the self-polymerization microporous ionomer by adopting mild polycondensation and quaternization.

Specifically, firstly, through Mannich reaction, the

monomer

3,3,3',3' -tetramethyl-1, 1' -spirobisindane-5, 5',6,6' -tetraol and 4-methylpiperidine are used as raw materials to prepare the polymer monomer shown in the following structural formula (III).

And then carrying out mild polycondensation reaction on the polymer monomer shown in the structural formula (III) and the

monomer

2,3,5, 6-tetrafluoroterephthalonitrile to prepare the copolymer shown in the structural formula (II).

Similarly, n represents a positive integer of 10 to 100 degrees of polymerization.

And finally, carrying out quaternization reaction on the copolymer shown in the structural formula (II) and excessive methyl iodide to prepare the self-polymerization microporous ionomer with the structure shown in the structural formula (I).

Further, the invention also provides a more detailed preparation method of the self-polymerization microporous ionomer.

S1: adding a

monomer

3,3,3',3' -tetramethyl-1, 1' -spirobisindane-5, 5',6,6' -tetraol into a 4-methylpiperidine ethanol solution containing paraformaldehyde under an inert atmosphere, and heating and refluxing for reaction to prepare a polymer monomer white solid.

S2: under the anhydrous condition, anhydrous potassium carbonate is added into an anhydrous dimethylformamide solution of a polymer monomer and tetrafluoroterephthalonitrile, and polycondensation reaction is carried out at 60-80 ℃ to prepare yellow copolymer powder.

S3: and dissolving the copolymer in dimethyl sulfoxide, adding excessive methyl iodide, and performing quaternization at 40-50 ℃ to obtain a self-polymerization microporous ionomer brown solid.

In a preferred embodiment, in step S1, paraformaldehyde is added to an ethanol solution of 4-methylpiperidine under an inert atmosphere, and after a reflux reaction at 60 to 80 ℃ for 0.5 to 1 hour, the

monomer

3,3,3',3' -tetramethyl-1, 1' -spirobiindane-5, 5',6,6' -tetraol is added, and the reflux reaction is continued.

Further, the time of the reflux reaction in the step S1 is preferably 24 to 60 hours.

Furthermore, the polymer monomer prepared in the step S1 is washed with n-hexane for multiple times and then dried in vacuum at 50-70 ℃.

In a further preferred embodiment, in the step S2, the amount of anhydrous potassium carbonate is 2.5 to 3.0 times the total molar number of the polymer monomer and the tetrafluoroterephthalonitrile.

Further, the polycondensation reaction time in the step S2 is preferably 24-60 h.

Further, the present invention dissolves the polymer prepared in the step S2 in chloroform, and precipitates it with methanol, and repeats it several times to obtain a purified polymer.

Further, in a preferred embodiment, the reaction time in the step S3 is 2 to 4 days.

Further, the reaction product of the step S3 is precipitated by normal hexane, washed by water for a plurality of times and dried to obtain brown solid.

The self-polymerization microporous ionomer has excellent gas permeability, higher conductivity and proper size swelling property, can be used as an adhesive and can be applied to preparation of membrane electrodes in an anion-exchange membrane water electrolysis cell.

In particular, the self-polymerized microporous ionomer is applied as an electrode binder of a membrane electrode.

The self-polymerized microporous ionomer is used as an electrode binder for fixing discrete catalyst particles (Pt/C) on a gas diffusion layer (carbon paper), simultaneously promotes the transmission of hydroxide ions, electrons and reactants/products, forms a good three-phase interface between the catalyst layer and AEMs, is used in an anion exchange membrane water electrolyzer, and can improve the initial performance and durability of AEMWC.

Specifically, the self-polymerization microporous ionomer is dissolved in a polar solvent to obtain a solution with the concentration of 2-5 wt%, and the solution is used as an electrode binder.

The polar solvent may include, but is not limited to, dimethyl sulfoxide (DMSO), N-Dimethylformamide (DMF), or N, N-Dimethylacetamide (DMAC).

More specifically, the solution prepared by the self-polymerization microporous ionomer is mixed with a catalyst and then coated on carbon paper to prepare a cathode catalyst layer, and the cathode catalyst layer, the anode catalyst layer and an anion exchange membrane are combined to obtain the membrane electrode.

The self-polymerized microporous ionomer is used as an electrode adhesive to prepare a cathode catalyst layer for an anion exchange membrane water electrolyzer, and the current density of the cathode catalyst layer at the voltage of 2.10V is up to 2000mA/cm ² Moreover, the service life of the battery can reach 360h, the technical index requirements of the ionomer applied to the anion exchange membrane for water electrolysis are met, and excellent battery performance is shown.

Drawings

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of polymer monomer (a), copolymer (b) and self-polymerized microporous ionomer (c).

FIG. 2 is a graph of water absorption of QAPM-Pi films as a function of temperature.

FIG. 3 is a graph of the conductivity of a QAPM-Pi membrane as a function of temperature.

FIG. 4 is H of QAPM-Pi membranes at different temperatures ₂ And (4) flux graph.

FIG. 5 is a graph of the infrared spectra of a self-polymerizing microporous ionomer before and after treatment with lye.

Fig. 6 is a thermogravimetric plot of a self-polymerized microporous ionomer.

FIG. 7 is a graph of the polarization of electrolyzed water at 60 ℃ for membrane electrodes of different ionomer contents.

FIG. 8 is a graph of the polarization of electrolyzed water at different temperatures for a membrane electrode having an ionomer content of 10%.

FIG. 9 is a graph showing the time-dependent changes in voltage (a) and resistance (b) in the case of electrolyzing water in the alkaline water electrolyzers of example 3 and comparative examples 1 to 2.

Fig. 10 is an SEM comparison image of 30000 × magnification before and after membrane electrode stability test of example 3 and comparative example 1.

Fig. 11 is an SEM comparison image of 150 × magnification before and after the membrane electrode stability test of example 3 and comparative example 1.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are only for more clearly illustrating the technical solutions of the present invention so as to enable those skilled in the art to better understand and utilize the present invention, and do not limit the scope of the present invention.

The names and the abbreviations of the experimental methods, the production processes, the instruments and the equipment related to the embodiments and the application examples of the present invention are all conventional names in the art, and are clear and definite in the related application fields, and a person skilled in the art can understand the conventional process steps and apply the corresponding equipment according to the names to implement the method according to the conventional conditions or the conditions suggested by the manufacturer.

The raw materials and reagents used in the examples and application examples of the present invention are not particularly limited in terms of their sources, and are all conventional products that can be commercially obtained. They may also be prepared according to conventional methods well known to those skilled in the art.

An electrolytic cell for anion exchange membrane electrolyzed water (AEMWE) (hereinafter referred to as alkaline water electrolytic cell) in the embodiment of the present invention is mainly composed of a bipolar plate, a Gas Diffusion Layer (GDL), and a Membrane Electrode (MEA).

The bipolar plates are nickel plates and are used as current collectors and flow field plates, respectively. The gas diffusion layer comprises an anode and a cathode, namely a nickel mesh and carbon paper.

The membrane electrode is a key component of the AEMWE and is composed of an anode catalyst layer and a cathode catalyst layer which sandwich an anion exchange membrane AEMs.

The ionomer PAP-TP-85 was used as the anion exchange membrane in the present example. The anion exchange membranes can be prepared in particular according to the literature: poly (aryl piperidine) membranes and oligomers for hydroxide exchange membrane cells,Nat. Energy4(2019), 392-.

The anode catalyst layer is IrO ₂ The catalyst, distilled water and isopropanol are uniformly mixed to obtain catalyst ink, the catalyst ink is uniformly sprayed on two sides of a nickel screen anode, and the catalyst ink is prepared by calcining in a tubular furnace at 450 ℃.

The cathode catalyst layer is prepared by uniformly mixing a Pt/C catalyst, distilled water, isopropanol and an adhesive, spraying the mixture to one side of the carbon paper cathode and drying the mixture.

In the following embodiments of the invention, the influence of changing the structure and content of the ionomer binder in the cathode catalyst layer on the performance and the service life of the electrolytic water of the alkaline water electrolyzer is examined by taking the self-polymerized microporous ionomer prepared by the invention as the binder.

Example 1.

Under the nitrogen atmosphere, 9g of paraformaldehyde and 37ml of 4-methylpiperidine are dissolved in 250ml of ethanol, the temperature is increased to 70 ℃, the mixture is stirred and reacted for 30min, 10.21g of

monomer

3,3,3',3' -tetramethyl-1, 1' -spirobisindane-5, 5',6,6' -tetraol (TTSBI) is slowly added, the reflux reaction is continued for 48h, and white solid is separated out.

And filtering out a reaction product, washing the reaction product for multiple times by using normal hexane, and drying the reaction product at the temperature of 50-70 ℃ in vacuum to obtain white powder of the polymer monomer with the structure shown in the structural formula (III).

FIG. 1(a) shows the NMR spectrum of the polymer monomer. ¹ H NMR (400MHz, CDCl ₃ ) δ (ppm) 6.63 (s, 2H), 3.09 (d, 4H), 2.75-2.89 (br m, 8H), 2.16-2.23 (t, 8H), 1.60-1.78 (br m, 4H), 1.26-1.33 (br m, 12H), 1.14 (s, 2H), 0.89 (d, 6H), proving that the structure of the polymer monomer is as shown in structural formula (III).

20ml of anhydrous Dimethylformamide (DMF) was added to a three-necked flask, nitrogen purging was carried out for 40min to remove dissolved water and air, the flask was heated to 65 ℃ under nitrogen atmosphere, 1.68g of polymer monomer and 0.6g of tetrafluoroterephthalonitrile (TFTPN) were added thereto to dissolve them uniformly, and 1.04g of anhydrous K was further added ₂ CO ₃ And reacting for 48 hours.

And cooling the reactant, slowly pouring the reactant into methanol to separate out bright yellow filaments, filtering and drying to obtain a crude product. And dissolving the crude product in chloroform, pouring the solution into methanol to separate out a precipitate, filtering, washing for 3 times by using methanol, and drying at the temperature of 60 ℃ in vacuum to prepare the copolymer with the structure shown in the structural formula (II).

FIG. 1(b) is a nuclear magnetic resonance hydrogen spectrum of the copolymer. ¹ H NMR (400MHz, CDCl ₃ ) Delta (ppm) 6.77 (s, 2H), 3.10 (d, 4H), 2.90 (br m, 8H), 2.22-2.37 (t, 8H), 1.93 (m, 4H), 1.26-1.37 (br m, 12H), 1.08 (s, 2H), 0.88 (d, 6H), and the success of preparing the copolymer with the structure shown in the structural formula (II) is proved by nuclear magnetic characterization.

2g of the copolymer was weighed, dissolved in 40ml of dimethyl sulfoxide (DMSO), and 1.8ml of methyl iodide was added to the solution, followed by stirring at 45 ℃ for 3 days.

And cooling the reaction liquid, slowly pouring the reaction liquid into n-hexane to separate out a precipitate, filtering, washing with water for 3 times, and drying at 100 ℃ under vacuum to prepare the self-polymerization microporous ionomer brown solid with the structure shown in the structural formula (I), which is called QAPM-Pi for short.

FIG. 1(c) shows the NMR spectrum of the self-polymerized microporous ionomer. ¹ H NMR (400MHz, CDCl ₃ ) Delta (ppm): 7.44 (s, 2H), 3.83 (d, 12H), 2.69 (s, 3H), 2.17 (t, 8H), 1.93 (m, 4H), 1.23 (br m, 12H), 1.02 (s, 2H), 0.89 (d, 6H), nuclear magnetic results indicate that the prepared self-polymerized microporous ionomer has the structure shown in formula (I).

Application example 1: basic performance testing from microporous ionomers.

The self-microporous ionomer cast film prepared in example 1 was cast using a casting method to test the basic properties of the self-microporous ionomer membrane.

0.8g of the self-polymerized microporous ionomer prepared in example 1 was dissolved in 10ml of DMSO to obtain an 8wt% ionomer solution, and then the solution was cast on a glass plate and dried at 60 ℃ for 24 hours to prepare a QAPM-Pi anion exchange membrane having a membrane thickness of 25 μm.

Firstly testing the water absorption rate of the membrane, specifically soaking a QAPM-Pi anion exchange membrane with the specification of 1cm multiplied by 4cm in deionized water at a certain temperature for 24 hours, taking out the membrane after the membrane is completely swelled, quickly wiping the surface moisture of the membrane by using filter paper, and recording the weight of the membraneW _wet (ii) a The film was then dried at 60 ℃ and the weight of the film in the dry state was recordedW _dry (ii) a And finally according to the formula: WU = [ (W _wet －W _dry )/W _dry ]X 100%, the water absorption of the film at this temperature was calculated.

As can be seen from the relationship graph of the QAPM-Pi film temperature-rising water absorption rate of FIG. 2, the water absorption swelling rate of the film is increased along with the increase of the temperature, but the water absorption rate is only 38wt% at 60 ℃, the dimensional stability of the surface film is excellent, and the surface film is suitable for being applied to the anion exchange membrane electrolytic water.

Next, an anion exchange membrane of 1cm × 4cm specification was placed in a Teflon mold, and after connecting to two electrodes on an electrochemical workstation (Bio-logic VSR-300, FR), the mold was placed in deionized water at a certain temperature, and the ionic conductivity σ (mS/cm) of the membrane in a fully hydrated state was tested three times, and the average value was taken.

Setting the scanning frequency range of the electrochemical workstation to be 100 mHz-100 kHz and the distance between two electrodesLAt 0.7cm, the film resistance was read from the Nyquist curve according to the formula σ =L/(R×A) The ionic conductivity was calculated, wherein,Rthe resistance of the film (k Ω),Ais the cross-sectional area (cm) of the membrane ² Film width × film thickness).

Fig. 3 shows the ion conductivity of the QAPIM-Pi membrane as a function of temperature. The ionic conductivity of the membrane gradually increased with increasing temperature, reaching 40mS/cm at 60 ℃. The higher ionic conductivity allows the ionomer QAPIM-Pi to have excellent cell performance.

Finally, the QAPM-Pi membranes were tested for gas permeation flux P (Barrar) using a constant volume pressure swing at 35 deg.C, 60 deg.C and 80 deg.C, respectively, under upstream pressure conditions of 100 psi.

H of QAPM-Pi membranes at different temperatures from FIG. 4 ₂ As can be seen in the flux plots, H of the QAPM-Pi membrane ₂ The flux increased gradually with increasing temperature, reaching 32.4Barrer at 35 ℃ and 38Barrer at 60 ℃.

While PAP-TP-85 membrane was tested for H under the same conditions ₂ Flux, results show its H at 35 deg.C ₂ The flux is only 4.07 Barrer. H of QAPM-Pi membranes of the invention ₂ The flux is 7.96 times higher than the flux.

Higher H ₂ Flux, so that when the ionomer QAPM-Pi is used as a binder, the gas permeability is good, and the battery performance is excellent.

Application example 2: alkaline and thermal stability testing from microporous ionomers.

Soaking the self-polymerized microporous ionomer in a 1M NaOH solution at 80 ℃ for a certain time, washing away residual substances on the surface of the ionomer by using deionized water, testing the structural change of the ionomer by using a PE-1710 Fourier transform infrared spectrometer, and inspecting the alkali resistance stability of the ionomer.

As can be seen from the infrared spectrum of FIG. 5, the functional groups of the ionomer were hardly changed after soaking in 1M NaOH solution at 80 ℃ for 720 hours, demonstrating that the ionomer was excellent in alkali stability.

The operating temperature range based on AEMWE is between 60 and 80 ℃, thus requiring that the initial degradation temperature of the ionomer must be above 60 ℃.

At N ₂ The thermal stability of the ionomers was tested by heating the self-polymerized microporous ionomer from 50 ℃ to 750 ℃ at a ramp rate of 10 ℃/min under an atmosphere. As can be seen from the thermogravimetric graph of FIG. 6, the ionomer QAPM-Pi is decomposed after 250 ℃, shows good thermal stability and meets the working condition of 60-80 ℃ of anion exchange membrane electrolyzed water.

Example 2.

0.5g of the self-polymerized microporous ionomer QAPM-Pi prepared in example 1 was weighed out and dissolved in 10ml of DMSO to obtain an ionomer binder solution having a solid content of 5 wt%.

Weighing 18.75mg of Pt/C catalyst (wherein the Pt content is 40wt%), adding 93.75mg of distilled water for wetting, then adding 375mg of isopropanol, finally adding 23.44mg of the ionomer adhesive solution, magnetically stirring for 3h to uniformly mix the catalyst, and after carrying out ultrasonic treatment for 30min in ice-water bath, uniformly spraying the mixture on a substrate with an effective area of 5cm by adopting a spraying method ² Drying one side of the carbon paper to obtain Pt supported quantity of 1.5mg cm ^-2 And a cathode catalytic layer with 5% of ionomer content.

Weighing 12mg of IrO ₂ Adding 96mg of distilled water for wetting, then adding 384mg of isopropanol, magnetically stirring for 3 hours to uniformly mix the catalyst, performing ultrasonic treatment for 30min in ice-water bath to obtain catalyst ink, and uniformly spraying the catalyst ink on a substrate with an effective area of 5cm by adopting a spraying method ² The two sides of the nickel net are placed in a tubular furnace to be calcined at the temperature of 450 ℃ to prepare IrO ₂ The loading was about 2mg cm ^-2 The anode catalyst layer of (1).

The prepared cathode catalyst layer and anode catalyst layer are used to sandwich AEMs (PAP-TP-85) to prepare MEA by adopting a Catalyst Coating Substrate (CCS) method, and nickel plates are respectively used as a current collector and a flow field plate to assemble the alkaline water electrolysis cell.

Example 3.

Weighing 18.75mg Pt/C catalyst (wherein the Pt content is 40wt%), adding 93.75mg distilled water for wetting, then adding 375mg isopropanol, finally adding 46.87mg ionomer adhesive solution prepared in the above example 2, magnetically stirring for 3h to mix the catalyst uniformly, ultrasonically spraying the mixture on a substrate with an effective area of 5cm by a spraying method after 30min in ice-water bath ² Drying one side of the carbon paper to obtain Pt supported quantity of 1.5mg cm ^-2 Cathode catalytic layer with ionomer content 10%.

Using the cathode catalyst layer prepared above, an alkaline water electrolytic cell was assembled in accordance with the method in example 2.

Example 4.

Weighing 18.75mg Pt/C catalyst (wherein the Pt content is 40wt%), adding 93.75mg distilled water for wetting, then adding 375mg isopropanol, finally adding 93.75mg ionomer adhesive solution prepared in the above example 2, magnetically stirring for 4h to mix the catalyst uniformly, ultrasonically spraying the mixture on a substrate with an effective area of 5cm by a spraying method after 40min in ice-water bath ² Drying one side of the carbon paper to obtain Pt supported quantity of 1.5mg cm ^-2 And a cathode catalytic layer with 20% of ionomer content.

Comparative example 1.

Weighing 18.75mg of Pt/C catalyst (wherein the Pt content is 40wt%), adding 93.75mg of distilled water for wetting, then adding 375mg of isopropanol, magnetically stirring for 3 hours to uniformly mix the catalyst, carrying out ultrasonic treatment in ice-water bath for 30 minutes, and then uniformly spraying the mixture on a substrate with an effective area of 5cm by adopting a spraying method ² Drying one side of the carbon paper to prepare Pt with the loading capacity of 1.5mg cm ^-2 A cathode catalyst layer free of ionomer binder.

An alkaline water electrolytic cell was assembled by the method of example 2 using the binder-free cathode catalyst layer prepared as described above.

Comparative example 2.

0.5g of the ionomer PAP-TP-85 was weighed out and dissolved in 10ml of DMSO to obtain a PAP-TP-85 binder solution with a solid content of 10 wt%.

Weighing 18.75mg Pt/C catalyst (Pt content is 40wt%), adding 93.75mg distilled water for wetting, then adding 375mg isopropanol, finally adding 46.87mg PAP-TP-85 binder solution, magnetically stirring for 3h to uniformly mix the catalyst, ultrasonically spraying the mixture in ice-water bath for 30min, and uniformly spraying the mixture on a substrate with an effective area of 5cm ² Drying one side of the carbon paper to obtain Pt supported quantity of 1.5mg cm ^-2 The PAP-TP-85 binder content 10% of the cathode catalyst layer.

Application example 3: and testing the electrolytic water performance.

The performance of electrolytic water performance was tested by using the alkaline water electrolyzers assembled in examples 2 to 4 and comparative examples 1 to 2, respectively.

Before testing, the MEA is soaked in a 1M NaOH solution for 12-24 h.

Then, 1M NaOH solution was circulated through the two bipolar plates at 37.5mL/min to allow the alkaline water electrolyzer to operate at 60 ℃ and 20mA/cm ² And (5) performing stable operation for 60min, and recording a polarization curve after the voltage is stable.

FIG. 7 shows the water polarization curves of the membrane electrodes prepared in examples 2-4 using different amounts of ionomers as binders at 60 ℃. The test results show that the voltage is lowest and the cell performance is best when the ionomer content is 10% under the same current density. For example, at a current density of 2000mA/cm ² The voltage was 2.26V, which was 2.50V lower than the voltage with 5% ionomer content and 2.40V lower than the voltage with 20% ionomer content.

Further, the polarization curves at different temperatures were further tested for 10% ionomer binders with superior performance.

The 1M NaOH solution was circulated through both bipolar plates at a rate of 37.5mL/min to provide an alkaline water electrolyzer at 20mA/cm ² After the lower stable adjustment is carried out for 60min, three polarization curves corresponding to different temperature records are set.

As can be seen from fig. 8, as the temperature increases, the current density at the same voltage gradually increases. The current density reaches 2000mA/cm at 80 DEG C ² When the voltage is reduced from 2.26V at 60 ℃ to 2.10V, the battery performance is improved when the voltage is reduced.

The alkaline water electrolysis cell assembled in accordance with comparative example 1 was operated at 80 ℃ under the same current density of 2000mA/cm ² At this time, the voltage was as high as 2.42V, showing poor initial performance of electrolyzing water.

Similarly, the alkaline water electrolytic cell assembled in accordance with comparative example 2 was also constructed so that the current density reached 2000mA/cm at 80 deg.C ² The voltage at time 2.27V exhibited an initial performance of electrolyzed water superior to that of comparative example 1, but was still inferior to that of the alkaline water electrolysis cell assembled in example 3.

Application example 4: and (5) testing the stability of the electrolyzed water.

The stability tests of the electrolyzed water were carried out by using the alkaline water electrolyzers assembled in examples 2 to 4 and comparative examples 1 to 2, respectively.

Before testing, the MEA is soaked in a 1M NaOH solution for 12-24 h.

A1M NaOH solution was circulated through both bipolar plates at 37.5mL/min, set at 80 ℃ and a current density of 250mA/cm ² And recording the changes of voltage and resistance in the running process so as to evaluate the stability of different alkaline water electrolyzers.

As can be seen from the time-dependent changes of the voltage (a) and the resistance (b) in the case of electrolyzing water in the alkaline water electrolyzer of example 3 in FIG. 9, the voltage of the membrane electrode prepared by the adhesive with the ionomer content of 10% is stable with the increase of time, and the voltage is still kept at 1.75V and the resistance is only from 0.17 Ω cm to 360h in the continuous test ² Increased to 0.22. omega. cm ² But increased by 0.05 omega cm ² And exhibits excellent battery life.

Meanwhile, the voltage of the membrane electrode prepared by using the adhesive with 10 percent of content of the ionomer PAP-TP-85 in the comparison example 2 is stable, and the membrane electrode can be tested for 200 h. During the test, the voltage was maintained at 1.85V while the resistance was changed from 0.35 Ω cm ² Increased to 0.45 omega cm ² Increased by 0.1 omega cm ² And the battery has excellent service life. Based on the resistance change of more than 0.1 omega cm at 200h ² The change was significant and therefore the test was not continued.

However, for the membrane electrode of comparative example 1, which did not use an ionomer binder, the voltage rise was significant, and the voltage at 100h had increased by 0.4V while the resistance was from 0.56. omega. cm ² Increased to 0.8. omega. cm ² Increased by 0.24 omega cm ² The change is obvious, and the stability of the battery is poor. It is further demonstrated that the addition of an appropriate amount of ionomer as a binder can improve the stability of the battery.

Similarly, for the alkaline water electrolyzer assembled in example 2, the current density at 80 ℃ was 250mA/cm ² The voltage after 250h of the test increased from the initial 1.90V to 1.96V, which was relatively stable.

Similarly, the alkaline water electrolyzer assembled in example 4 has a current density of 250mA/cm at 80 deg.C ² Then, the voltage after 280h of the test increased from the initial 1.88V to 1.92V, showing superior battery stability to example 2.

Application example 5: microscopic characterization of the cathode catalyst layer before and after the electrolyzed water stability test.

SEM images of the cathode catalyst layers before and after the cell stability test under different magnifications were further tested for the electrolyzed water stability data of the membrane electrodes prepared in example 3 and comparative example 1, and the distribution of the catalyst in the cathode catalyst layers before and after the test was observed.

Fig. 10 is a SEM comparison image before and after an electrolyte stability test of a membrane electrode prepared using a binder having an ionomer content of 10% and without using the binder at a magnification of 30000 ×. From a1 and a2, the catalyst of the cathode catalytic layer prepared by adding the adhesive with the ionomer content of 10% is uniformly distributed before and after the test, and the catalyst still keeps complete after the continuous test for 360h, and the a2 has no obvious difference from the a 1. In comparison, the cathode catalytic layer of b1 without added ionomer also did not see a significant difference before the test, but only after 100h of the test of b2, the catalyst loss was very severe, resulting in poor cell stability. This further demonstrates that the addition of an ionomer as a binder can improve the stability of the cell.

And reducing the magnification to show the overall appearance of the membrane electrode after the test. Fig. 11 shows SEM images of the membrane electrode prepared with adhesive (a) having an ionomer content of 10% and without adhesive (b) after electrolytic water stability test at magnification of 150 x. Fig. 11a shows that the catalyst of the cathode catalyst layer remains intact after 360h of continuous testing, while fig. 11b shows that the catalyst on the cathode catalyst layer is almost completely peeled off and the gas diffusion layer (carbon paper) is exposed when only 100h of continuous testing is carried out, and the large-area loss of the catalyst causes the stability of the battery to be poor.

The above embodiments of the present invention are not intended to be exhaustive or to limit the invention to the precise form disclosed. Various changes, modifications, substitutions and alterations to these embodiments will be apparent to those skilled in the art without departing from the principles and spirit of this invention.

Claims

1. A self-polymerized microporous ionomer has a structure shown in the following structural formula (I), the weight average molecular weight is 7000-70000, and the intrinsic viscosity eta is 1.0-1.5 dL/g;

wherein n represents a positive integer of 10-100 of polymerization degree.

2. The method of claim 1 wherein the self-polymerizing cellular polymer is prepared by first preparing a polymer monomer represented by the following structural formula (III) from the monomers 3,3,3',3' -tetramethyl-1, 1' -spirobiindan-5, 5',6,6' -tetraol and 4-methylpiperidine by a Mannich reaction:

then carrying out mild polycondensation reaction on the polymer monomer shown in the structural formula (III) and the monomer 2,3,5, 6-tetrafluoroterephthalonitrile to prepare the copolymer shown in the following structural formula (II):

similarly, n represents a positive integer with the polymerization degree of 10-100;

3. The method of claim 2 wherein the microporous polymer is prepared by:

s1: adding a monomer 3,3,3',3' -tetramethyl-1, 1' -spirobiindane-5, 5',6,6' -tetraol into a 4-methylpiperidine ethanol solution containing paraformaldehyde under an inert atmosphere, and heating and refluxing to react to prepare a polymer monomer white solid;

s2: under the anhydrous condition, adding anhydrous potassium carbonate into an anhydrous dimethylformamide solution of a polymer monomer and tetrafluoroterephthalonitrile, and carrying out polycondensation reaction at 60-80 ℃ to prepare yellow copolymer powder;

s3: dissolving the copolymer in dimethyl sulfoxide, adding excessive methyl iodide, and performing quaternization at 40-50 ℃ to obtain a self-polymerization microporous ionomer brown solid.

4. The method of claim 3, wherein in step S1, paraformaldehyde is added to an ethanol solution of 4-methylpiperidine under an inert atmosphere, the mixture is refluxed at 60-80 ℃ for 0.5-1 h, and then the monomer 3,3,3',3' -tetramethyl-1, 1' -spirobiindane-5, 5',6,6' -tetraol is added, and the reflux reaction is continued.

5. The method of claim 3 or 4, wherein the reaction time of the step S1 is 24-60 h.

6. The method of claim 3, wherein the amount of anhydrous potassium carbonate used in step S2 is 2.5-3.0 times the total molar amount of the polymer monomer and the tetrafluoroterephthalonitrile.

7. The method of claim 3, wherein the polycondensation reaction time in step S2 is 24-60 h.

8. The method of claim 3, wherein the reaction time of step S3 is 2-4 days.

9. Use of the self-polymerizing microporous polymer of claim 1 as a binder in the preparation of membrane electrodes for anion exchange membrane water electrolysers.

10. Use according to claim 9, wherein the self-polymeric microporous ionomer is applied as an electrode binder.