阅读说明：本技术 一种多刺氧化铝纳米纤维复合质子交换膜及其制备方法 (Multi-spine aluminum oxide nanofiber composite proton exchange membrane and preparation method thereof ) 是由 李磊 刘晓莲 康卫民 于 2021-09-08 设计创作，主要内容包括：本发明涉及一种多刺氧化铝纳米纤维复合质子交换膜及其制备方法,属于质子交换膜燃料电池质子交换膜的技术领域。该复合质子交换膜的具体制备方法包括如下步骤：1)将以金属铝粉、氯化铝等为原料,水为溶剂制备的铝溶胶与PTFE乳液按一定的比例混合,持续搅拌至均匀制备纺丝溶液；2)利用EBS技术结合热处理工艺,通过调节热处理工艺参数成功制备多刺氧化铝纳米纤维；3)将所得的多刺氧化铝纳米纤维、N,N-二甲基甲酰胺(DMF)和磺化聚砜(SPSF)按一定比例混合均匀,采用溶液浇铸法制备复合质子交换膜；运用该方法制备的复合质子交换膜在开发作为高性能质子交换膜中展现出独特的优势和潜能。(The invention relates to a multi-spine alumina nano fiber composite proton exchange membrane and a preparation method thereof, belonging to the technical field of proton exchange membranes of proton exchange membrane fuel cells. The specific preparation method of the composite proton exchange membrane comprises the following steps: 1) mixing aluminum sol prepared by taking metal aluminum powder, aluminum chloride and the like as raw materials and water as a solvent with PTFE emulsion according to a certain proportion, and continuously stirring until the uniform spinning solution is prepared; 2) combining the EBS technology with a heat treatment process, and successfully preparing the multi-spine alumina nano-fiber by adjusting the parameters of the heat treatment process; 3) uniformly mixing the obtained multi-spine alumina nano-fiber, N-Dimethylformamide (DMF) and Sulfonated Polysulfone (SPSF) according to a certain proportion, and preparing the composite proton exchange membrane by adopting a solution casting method; the composite proton exchange membrane prepared by the method shows unique advantages and potentials when being developed as a high-performance proton exchange membrane.)

1. A preparation method of a multi-spine alumina nano-fiber composite proton exchange membrane is characterized by comprising the following steps:

(1) preparing an alumina precursor spinning solution: mixing aluminum sol prepared by taking metal aluminum powder, aluminum chloride and the like as raw materials and water as a solvent with PTFE emulsion according to a certain proportion, and continuously stirring until the uniform spinning solution is prepared;

(2) preparing the multi-spine alumina nano fiber: combining the EBS technology with a heat treatment process, and successfully preparing the multi-spine alumina nano-fiber by adjusting the parameters of the heat treatment process;

(3) preparing a composite proton exchange membrane: and uniformly mixing the obtained multi-spine alumina nano-fiber, N-Dimethylformamide (DMF) and Sulfonated Polysulfone (SPSF) according to a certain proportion, and preparing the composite proton exchange membrane by adopting a solution casting method.

2. The multi-spine alumina nanofiber composite proton exchange membrane according to claim 1, wherein: the concentration of the added PTFE solution was 36 wt.%.

3. The heat treatment process of claim 1, heating from room temperature to 1100 ℃ at 5 ℃/min.

4. The multi-spine alumina nanofiber composite proton exchange membrane according to claim 1 or 2, wherein: the concentration ratio of the multi-spine alumina nano fiber to the Sulfonated Polysulfone (SPSF) is 1: 14.

Technical Field

The invention relates to a multi-spine alumina nano fiber composite proton exchange membrane and a preparation method thereof, belonging to the technical field of proton exchange membranes of proton exchange membrane fuel cells.

Background

Proton Exchange Membrane Fuel Cells (PEMFC), especially Direct Methanol Fuel Cells (DMFC), as the latest generation fuel cells, have the advantages of rapid start at room temperature, wide working conditions, high specific power and energy, high resource utilization rate, small volume, light weight, environmental protection and the like, have good development prospects in the aspects of automobile industry, military field, electronic technology field, household standby power supply and the like, especially obtain excellent application in the new energy automobile industry, and are expected to become the most ideal novel energy technology for future development. The proton exchange membrane is a core component of the proton exchange membrane fuel cell, and the performance of the proton exchange membrane directly determines the energy density and the energy conversion efficiency of the cell. In the interior of the cell, the proton exchange membrane on one hand is used for isolating anode methanol, hydrogen fuel and cathode oxygen, and avoiding direct contact of the anode methanol, the hydrogen fuel and the cathode oxygen to generate short circuit. On the other hand, the proton exchange membrane has selective permeability, provides a proton transfer channel for proton conduction, ensures the continuous generation of the total reaction of the battery, and simultaneously realizes the continuous energy supply of electrons through an external circuit. To ensure stable and efficient operation of the fuel cell, the proton exchange membrane should have high proton conductivity, low fuel permeability, and sufficient thermal and mechanical stability. Currently, Nafion is the most advanced perfluorosulfonic acid membrane, which has been widely studied and used for Proton Exchange Membrane Fuel Cells (PEMFCs). The unique bicontinuous structure in the fully hydrated state provides excellent proton conductivity and mechanical strength. Typically, the conductivity can reach about 0.1S/cm at 80 ℃ and 100% relative humidity, which makes the fuel cell performance satisfactory. However, the disadvantages of high methanol permeability, membrane proton selectivity at low humidity and high temperature, reduced mechanical stability, higher cost and the like of the Nafion membrane restrict the large-scale use of the Nafion membrane in fuel cells. Therefore, the development of new proton exchange membrane materials with enhanced performance is urgently needed.

To date, various strategies such as templating, microphase separation and mixing have been used to construct proton-conducting channels to achieve high performance proton exchange membranes. The nano-fiber has high specific surface area, excellent mechanical property and various composition characteristicsThe preparation of Proton Exchange Membranes (PEM) has found widespread use and is considered to be an excellent filler for composite proton exchange membranes. The strategy of fabricating long-range ordered proton transport paths through well-designed nanofiber structures to improve the performance of proton exchange membranes has become a hot point of research. Wang et al (L.Y.Zhang et al, structural Amino-functional flow-like Metal-Organic Framework Nanofibers in Sulfonated Poly (ether sulfone) Proton Exchange Membrane for Simultaneous engineering Interface Compatibility and Proton reduction. ACS applied materials&interfaces 2019, 11(43), 39979-₂Nanofibers (MNF) with high performance MNFs @ SPES hybrid membranes were obtained by adding functional and continuous MNF fillers in a Sulfonated Polyethersulfone (SPES) matrix. Specifically, when the MNFs content was increased to 5 wt%, the proton conductivity was increased to 0.201S/cm, thereby achieving simultaneous improvement in proton conductivity and membrane stability. However, these nanofiber composite membranes face severe transfer anisotropy due to the preferential horizontal alignment of the nanofibers, and the conductivity in the vertical direction is usually much lower than the conductivity in the horizontal direction. In practical applications, the vertical proton conductivity is the factor that determines the performance of the fuel cell.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to prepare a high-performance composite proton exchange membrane which can reduce the transfer anisotropy of protons and increase the conductivity of vertical protons so as to enhance the performance of a fuel cell. The composite proton exchange membrane which takes the multi-spine alumina nano-fiber as the filler and the sulfonated polysulfone as the matrix is prepared by a solution casting method. The composite membrane greatly enhances the proton conductivity and the mechanical stability, reduces the proton transfer anisotropy and the methanol permeability, and effectively improves the performance of the fuel cell.

In order to achieve the purpose, the invention provides a multi-spine alumina nano-fiber composite proton exchange membrane which is characterized by comprising the following steps:

(1) preparing an alumina precursor spinning solution: mixing aluminum sol prepared by taking metal aluminum powder, aluminum chloride and the like as raw materials and water as a solvent with PTFE emulsion according to a certain proportion, and continuously stirring until the uniform spinning solution is prepared;

(2) preparing the multi-spine alumina nano fiber: combining the EBS technology with a heat treatment process, and successfully preparing the multi-spine alumina nano-fiber by adjusting the parameters of the heat treatment process;

(3) preparing a composite proton exchange membrane: uniformly mixing the obtained multi-spine alumina nano-fiber, N-Dimethylformamide (DMF) and Sulfonated Polysulfone (SPSF) according to a certain proportion, and preparing the composite proton exchange membrane by adopting a solution casting method;

the concentration of the added PTFE solution was 36 wt.%.

The heat treatment process is to heat the mixture from room temperature to 1100 ℃ at the speed of 5 ℃/min.

The concentration ratio of the spined alumina nano-fiber Sulfonated Polysulfone (SPSF) is 1: 14.

Due to the adoption of the technical scheme, the multi-spine alumina nano-fiber composite proton exchange membrane has the following characteristics:

1) the spined alumina fiber trunk can provide long-range continuous proton transfer channel to promote proton horizontal transfer, and spines can provide vertical proton transfer channel. The structure reduces the anisotropy of proton transfer and also improves the overall proton conductivity of the composite membrane.

2) The good thermal stability inherent to the alumina nanofibers can better inhibit the decomposition of the polymer chains of the SPSF matrix, thereby further improving the thermal stability of the composite membrane.

3) The multi-spine alumina nano-fiber forms a complex barrier network structure in the membrane, and the diffusion path of methanol is limited; meanwhile, the compatibility between the alumina nano-fiber and the SPSF matrix is also beneficial to improving the methanol permeability resistance of the composite proton exchange membrane.

The three characteristics enable the prepared composite proton exchange membrane to have more excellent performance and practicability in direct methanol fuel cells.

The invention provides a multi-spine alumina nano-fiber composite proton exchange membrane and a preparation method thereof.

Drawings

FIG. 1 is a flow chart of the preparation of a multi-spine alumina nanofiber and a composite proton exchange membrane;

FIG. 2 is an SEM image of a multi-spine alumina nanofiber;

FIG. 3 is an SEM image of a multi-spine alumina nanofiber composite proton exchange membrane;

FIG. 4 is a proton conductivity plot for a composite proton exchange membrane;

FIG. 5 is a graph of methanol permeability for a composite proton exchange membrane;

figure 6 is a graph of the thermal stability of a composite proton exchange membrane.

Detailed Description

The invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) In the invention, firstly, an electrostatic solution-blowing spinning solution is required to be prepared, and the specific steps of the method are that 4g of aluminum chloride hexahydrate and 2g of aluminum powder are dissolved in distilled water, stirred vigorously and condensed and refluxed for 6 hours at 80 ℃ to obtain clear sol. Thereafter, 0.5g of ethyl orthosilicate was added to the above mixed solution, and then 0.1g of PVA was added as a spinning additive to obtain a solution a. Then, 12g of an aqueous polyvinylpyrrolidone solution (PVP, Mw. 1300000g mol) was slowly dropped into the 36 wt% PTFE emulsion^-116.7 wt.%), solution B was obtained with continuous stirring at room temperature. Finally, the solution a is mixed with the solution B by stirring to form a stable solution, obtaining a spinning solution.

(2) Preparing alumina nascent fiber by adopting an electrostatic solution blowing technology: opening a high-pressure air valve, adjusting the pressure to 0.1MPa, applying 40kV high-voltage direct current, drawing by static electricity and high-pressure airflow after the alumina sol flows out of a spinning nozzle, simultaneously quickly evaporating the solvent, solidifying the polymer to form alumina nascent fiber, and depositing the alumina nascent fiber on a non-woven receiving net.

(3) The heat treatment process obtains the multi-spine alumina nano fiber: drying the prepared alumina nascent fiber at 70 ℃ for 2 hours, and then raising the temperature from room temperature to 1100 ℃ at the calcining rate of 5 ℃/min for high-temperature calcining to obtain the multi-spine alumina nanofiber.

(4) And (3) doping the multi-spine alumina nano fiber (2 wt%) in the step (3) into an N, N-dimethylformamide solution containing 28 wt% of SPSF, stirring uniformly, and preparing the composite proton exchange membrane from the stirred solution by adopting a solution casting method.

Example 2

(1) In the invention, firstly, an electrostatic solution-blowing spinning solution is required to be prepared, and the specific steps of the method are that 4g of aluminum chloride hexahydrate and 2g of aluminum powder are dissolved in distilled water, stirred vigorously and condensed and refluxed for 6 hours at 80 ℃ to obtain clear sol. Thereafter, 0.5g of ethyl orthosilicate was added to the above mixed solution, and then 0.1g of PVA was added as a spinning additive to obtain a solution a. Then, 12g of an aqueous polyvinylpyrrolidone solution (PVP, Mw. 1300000g mol) was slowly dropped into the PTFE emulsion of 32 wt%^-116.7 wt.%), solution B was obtained with continuous stirring at room temperature. Finally, the solution a is mixed with the solution B by stirring to form a stable solution, obtaining a spinning solution.

(2) Preparing alumina nascent fiber by adopting an electrostatic solution blowing technology: opening a high-pressure air valve, adjusting the pressure to 0.1MPa, applying 40kV high-voltage direct current, drawing by static electricity and high-pressure airflow after the alumina sol flows out of a spinning nozzle, simultaneously quickly evaporating the solvent, solidifying the polymer to form alumina nascent fiber, and depositing the alumina nascent fiber on a non-woven receiving net.

(3) The heat treatment process obtains the multi-spine alumina nano fiber: drying the prepared alumina nascent fiber at 70 ℃ for 2 hours, and then raising the temperature from room temperature to 1100 ℃ at the calcining rate of 5 ℃/min for high-temperature calcining to obtain the multi-spine alumina nanofiber.

(4) And (3) doping the multi-spine alumina nano fiber (2 wt%) in the step (3) into an N, N-dimethylformamide solution containing 28 wt% of SPSF, stirring uniformly, and preparing the composite proton exchange membrane from the stirred solution by adopting a solution casting method.

Example 3

(1) In the invention, firstly, an electrostatic solution-blowing spinning solution is required to be prepared, and the specific steps are that 4g of hexahydrateAluminum chloride and 2g of aluminum powder were dissolved in distilled water, vigorously stirred and condensed at 80 ℃ under reflux for 6 hours to obtain a clear sol. Thereafter, 0.5g of ethyl orthosilicate was added to the above mixed solution, and then 0.1g of PVA was added as a spinning additive to obtain a solution a. Then, 12g of an aqueous polyvinylpyrrolidone solution (PVP, Mw. 1300000g mol) was slowly dropped into the 30 wt% PTFE emulsion^-116.7 wt.%), solution B was obtained with continuous stirring at room temperature. Finally, the solution a is mixed with the solution B by stirring to form a stable solution, obtaining a spinning solution.

(2) Preparing alumina nascent fiber by adopting an electrostatic solution blowing technology: opening a high-pressure air valve, adjusting the pressure to 0.1MPa, applying 40kV high-voltage direct current, drawing by static electricity and high-pressure airflow after the alumina sol flows out of a spinning nozzle, simultaneously quickly evaporating the solvent, solidifying the polymer to form alumina nascent fiber, and depositing the alumina nascent fiber on a non-woven receiving net.

(3) The heat treatment process obtains the multi-spine alumina nano fiber: drying the prepared alumina nascent fiber at 70 ℃ for 2 hours, and then raising the temperature from room temperature to 1100 ℃ at the calcining rate of 5 ℃/min for high-temperature calcining to obtain the multi-spine alumina nanofiber.

(4) And (3) doping the multi-spine alumina nano fiber (2 wt%) in the step (3) into an N, N-dimethylformamide solution containing 28 wt% of SPSF, stirring uniformly, and preparing the composite proton exchange membrane from the stirred solution by adopting a solution casting method.

And (3) performance testing:

the composite proton exchange membrane disclosed by the application is characterized by being prepared by taking the multi-spine alumina nano fiber as a filler and taking SPSF as a matrix, and has good proton conductivity, low methanol permeability, high mechanical strength and high thermal stability.

FIG. 1 is a preparation process of a multi-spine alumina nano fiber and a composite membrane thereof. The composite proton exchange membrane is prepared by an electrostatic solution blowing technology and a solution casting method.

Fig. 2 is an SEM image of multi-spine alumina nanofibers, from which we can see uniform spines, which can construct long-range ordered proton transport channels in the membrane, and provide additional proton transport sites, thereby improving proton conductivity.

Fig. 3 is an SEM image of the surface of the composite proton exchange membrane, and we see that the surface of the composite membrane is relatively smooth, which indicates that the thorny alumina nano fiber and the SPSF matrix have good compatibility, and a compact composite membrane is formed.

The proton conductivity of three proton exchange membranes was tested to illustrate the effect of the addition of the multi-spine alumina nanofibers on the performance of the composite proton exchange membrane.

Proton conductivity is one of the important indicators of composite membrane performance. The test is carried out by using AC impedance value and formula sigma-LA^{- 1}R^-1And (4) calculating.

The specific test method of the impedance value of the film is as follows: testing the impedance of the proton exchange membrane at different temperatures by AC impedance method using CHI660D electrochemical workstation, and setting the frequency to 0.1-10⁵Hz, the working amplitude is 0.01V; specifically, a 1X 3 cm composite proton exchange membrane was sandwiched between test molds, and then the molds were placed in an environment of 100% humidity and different temperatures (20 ℃, 40 ℃, 60 ℃, 80 ℃) to perform an alternating current impedance test. The R value of the membrane resistance corresponds to the semi-circle diameter corresponding to the high-frequency area in the obtained alternating current impedance spectrum.

The proton conductivity was evaluated by studying the impedance values of pure SPSF proton exchange membranes, smooth alumina nanofiber composite proton exchange membranes and multi-spine alumina nanofiber composite membranes. FIG. 4 shows the proton conductivity of three proton exchange membranes at 20 deg.C, 40 deg.C, 60 deg.C and 80 deg.C. The result shows that the proton conductivity of the multi-spine alumina nanofiber composite proton exchange membrane is the highest and is obviously higher than that of a pure SPSF membrane and a smooth alumina composite proton exchange membrane. The multi-spine alumina nano-fiber composite proton exchange membrane has high proton conductivity of 0.256S/cm at 80 ℃. The reason can be summarized as the following points: (1) the main chain of the multi-spine alumina fiber can provide a long-range continuous proton transfer channel to promote the horizontal transfer of protons, and the spine can provide a vertical proton transfer channel to horizontally and vertically transfer protons, so that the overall proton conductivity of the composite membrane is improved; (2) the hydrophilic metal nano-fiber enables the composite membrane to have enough water molecules to carry out proton transfer through a membrane mechanism.

Methanol permeability is another important indicator of composite membrane performance, and therefore, the methanol permeability of the composite proton exchange membrane is further tested. The specific test method of the methanol permeability comprises the following steps: the test process is started by diffusion equipment which is separated by a composite proton exchange membrane. A quantitative volume of 10M methanol solution was added to one side and the same volume of deionized water was added to the other side. Further, the foregoing solution was stirred by magnetic force to ensure the uniformity of the solution. Then taking a certain amount of liquid from the deionized water diffusion pool as samples at 30min, 50min and 70min respectively, and then calibrating the methanol content of the obtained samples by a gas chromatograph (Agilent 782 instrument manufactured by Agilent technologies, Inc. of America). The diffusion coefficient of methanol is finally determined according to formula C_B(t)＝AV_B ^-1DK^-1C_A(t-t₀) And (4) calculating.

FIG. 5 is a methanol permeability graph for pure SPSF proton exchange membranes, smooth alumina nanofiber composite membranes, and multi-spine alumina nanofiber composite membranes. It can be seen from the test results of fig. 5 that the multi-spine alumina nanofiber composite membrane of the present application has the lowest methanol permeability. The results show that the multi-spine alumina nano-fiber of the present application forms a complex network structure in the membrane, which limits the diffusion path of methanol, and at the same time, the multi-spine alumina nano-fiber can improve the compatibility with the SPSF matrix, which is helpful for improving the methanol permeation resistance of the composite proton exchange membrane.

The thermal stability is also one of the factors for evaluating the performance of the proton exchange membrane, so the thermal stability of the composite membrane is further tested. Thermal decomposition of the composite proton exchange membrane was measured by thermogravimetric analysis (TGA) with test conditions of N₂Heating at 50-800 deg.C for 10 min^-1。

Fig. 6 shows three kinds of proton exchange membrane thermal decomposition processes. From the figure, SPSF andcomposite membranes all undergo three main degradation stages: (1) below 150 c, the bound water and solvent evaporate in the membrane. At this stage, the mass loss of the composite membrane is greater than that of the SPSF membrane (TGA profile); (2) at 250-350 deg.C is-SO in film₃During the thermal desulfurization process, the-SO in the SPSF₃Conversion of H groups to SO₂And SO₃(ii) a (3) The last weight loss phase starts at a temperature of about 450 ℃ and may be related to the thermal decomposition of the main polymer chains. At this stage, the decomposition temperature of the composite membrane is higher than that of the SPSF membrane. The improved thermal stability can be attributed to the ability of the spined alumina nanofiber fibers with good inherent thermal stability to better inhibit the decomposition of the polymer chains of the SPSF matrix, thereby further improving the thermal stability of the composite membrane.

Example 1 is the best example of the present application, and examples 2-3 also show the same performance characteristics through the above performance tests. Therefore, in summary, the composite proton exchange membrane of the present application uses the multi-spine alumina nano-fiber as the filler to provide the composite membrane with high proton conductivity, low methanol permeability and excellent thermal stability, thereby facilitating the transfer of protons in the membrane. Provides a thought for the development of the proton exchange membrane.