阅读说明：本技术 基于真空辅助絮凝技术制备层状结构低温质子交换膜方法 (Method for preparing low-temperature proton exchange membrane with layered structure based on vacuum-assisted flocculation technology ) 是由 车全通 赵静 段向清 潘斌 申思 金瑾 贾婷婷 于 2019-09-16 设计创作，主要内容包括：本发明属于燃料电池技术领域,具体涉及一种基于真空辅助絮凝技术制备具有层状结构低温质子交换膜的方法。首先配制凯夫拉纳米纤维(Kevlar)溶液,聚乙烯醇(PVA)溶液以及氧化碳纳米管(OCNTs)溶液,并依次进行抽滤,再重复1～3次抽滤操作,制备具有2～4层结构的(PVA/Kevlar/OCNTs)<Sub>2-4</Sub>复合膜。将其浸泡在质量分数为50～100％的磷酸(PA)水溶液中,制备(PVA/Kevlar/OCNTs)<Sub>2-4</Sub>/(50～100％)PA复合膜。本发明利用真空辅助絮凝技术制备的具有层状结构的复合膜,具有良好的非水质子电导率以及机械性能。其中,(PVA/Kevlar/OCNTs)<Sub>2-4</Sub>/85％PA复合膜在-30℃时电导率达到0.038S/cm,室温下断裂拉伸强度为5.33MPa,以期待作为非水质子交换膜电解质应用于低温质子交换膜燃料电池。(The invention belongs to the technical field of fuel cells, and particularly relates to a method for preparing a low-temperature proton exchange membrane with a layered structure based on a vacuum-assisted flocculation technology, which comprises the steps of preparing Kevlar nanofiber (Kevlar) solution, polyvinyl alcohol (PVA) solution and Oxidized Carbon Nanotube (OCNTs) solution, carrying out suction filtration in sequence, repeating 1-3 times of suction filtration operation, and preparing a (PVA/Kevlar/OCNTs) 2-4 composite membrane with a 2-4-layer structure, soaking the composite membrane in Phosphoric Acid (PA) aqueous solution with a mass fraction of 50-100% to prepare a (PVA/Kevlar/OCNTs) 2-4 /(50-100%) PA composite membrane.)

1. A method for preparing a layered structure low-temperature proton exchange membrane based on a vacuum assisted flocculation technology is characterized by comprising the following steps:

(1) Adding 2.5-5.0 g Kevlar fiber (Kevlar), 1.5-3.0 g potassium hydroxide and 500mL dimethyl sulfoxide (DMSO) into a 1000mL reagent bottle, and stirring at room temperature to prepare 5-10 g/L Kevlar/DMSO solution;

(2) 1g of multi-walled carbon nanotube, 50mL of sulfuric acid with the mass fraction of 98% and 6g of potassium permanganate are added into a 500mL flask, and ice is addedStirring in water bath for 4 hr, heating to 35 deg.C, stirring for 3 hr, adding 40mL of 5% sulfuric acid, stirring for 30 min, and adding 10mL of 30% H₂O₂Stirring the aqueous solution for 30 minutes, standing for 16 hours, washing the solution to be neutral by using deionized water, and drying the solution for 10 hours at 80 ℃ to obtain carbon oxide nanotubes (OCNTs); adding 0.05g of carbon oxide nanotube and 100mL of dimethyl sulfoxide into a 100mL reagent bottle to prepare 0.5g/L of OCNTs/DMSO;

(3) Adding 0.25-0.50 g of polyvinyl alcohol (PVA) solid with the hydrolysis degree of 99% and 50mL of dimethyl sulfoxide into a 100mL reagent bottle, and stirring at 90 ℃ for 2 hours to prepare 2-10 g/L of PVA/DMSO solution;

(4) Adding 2-10 g/L PVA/DMSO solution into a suction filtration device with a filter membrane with the diameter of 50mm and the pore diameter of 0.22 mu m, carrying out suction filtration for 3 hours, adding 5-10 g/L Kevlar/DMSO solution, carrying out suction filtration for 2 hours, and finally adding 0.5g/L OCNTs/DMSO solution, and carrying out suction filtration for 1 hour;

(5) repeating the step (4) for 1-3 times, adding 2-10 g/L PVA/DMSO solution, performing suction filtration for 4-6 hours, removing the film, and drying at 80 ℃ for 1 hour to prepare (PVA/Kevlar/OCNTs)_2-4Compounding film;

(6) Will (PVA/Kevlar/OCNTs)_2-4soaking the composite membrane in a sealed container filled with a Phosphoric Acid (PA) aqueous solution with the mass fraction of 50-100% for 4-12 hours to prepare (PVA/Kevlar/OCNTs)_2-4/(50 to 100%) of a PA composite film.

2. The method for preparing the low-temperature proton exchange membrane with the layered structure based on the vacuum-assisted flocculation technology as claimed in claim 1, wherein in the step (5), (PVA/Kevlar/OCNTs)_2-4The composite membranes are formed by sequentially overlapping 2-4 groups of PVA/Kevlar/OCNTs composite membranes, and each group of PVA/Kevlar/OCNTs composite membranes are formed by sequentially overlapping a PVA membrane, a Kevlar membrane and an OCNTs membrane; in each group of PVA/Kevlar/OCNTs composite membranes, the thickness of the PVA membrane is 4-8 mu m, the thickness of the Kevlar membrane is 8-15 mu m, and the thickness of the OCNTs membrane is 1-2 mu m; (PVA/Kevlar/OCNTs)_2-4The PVA film is additionally arranged on the topmost layer of the composite film, and the thickness of the PVA film is 5-13 mu m.

3. The method of claim 1the method for preparing the layered structure low-temperature proton exchange membrane based on the vacuum assisted flocculation technology is characterized in that in the step (6), according to the weight percentage, (PVA/Kevlar/OCNTs)_2-4(50-100%) composition of the PA composite membrane: 25-63% of PVA/Kevlar/OCNTs and 37-75% of PA.

4. The method for preparing the low-temperature proton exchange membrane with the layered structure based on the vacuum-assisted flocculation technology as claimed in claim 1, wherein in the step (6), (PVA/Kevlar/OCNTs)_2-4/(50 to 100%) the thickness of the PA composite film is 45 to 185 μm.

Technical Field

The invention belongs to the technical field of fuel cells, and particularly relates to a method for preparing a low-temperature proton exchange membrane with a layered structure based on a vacuum-assisted flocculation technology.

Background

A fuel cell is a device that directly converts chemical energy into electrical energy. As an important branch of fuel cells, Proton Exchange Membrane Fuel Cells (PEMFCs) have been widely used in mobile and standby power devices such as vehicles and mobile phones due to their advantages of high efficiency, zero emission, low noise, and low operating temperature. Proton Exchange Membranes (PEMs) serve as core members of PEMFCs and porous electrode assembly membrane-forming electrodes, and serve to provide sites for electrochemical reactions and to conduct protons. Therefore, the development of PEM plays an important role in promoting the commercialization of PEMFC, and its performance can determine the performance and future application prospects of PEMFC.

Manufactured by Dupont, USAThe series of membranes have good stability, conductivity and mechanical properties, but the proton conduction process of the membranes depends on the participation of water molecules. When the temperature exceeds 80 ℃, the water content in the membrane is sharply reduced due to the change of liquid water into water vapor, and the proton conductivity of the membrane is reduced. Therefore, the temperature of the molten metal is controlled,The working temperature of the membrane is controlled in the range of room temperature to 80 ℃. However, when the temperature is too low, for example, in northern areas of China, the temperature is lowered to minus 30 ℃ for a long time in winter, and liquid water turns into ice, so that the liquid water cannot conduct protons, and the application of the liquid water as a proton exchange membrane in the fields of automobiles and the like is limited. To realize the new method for mounting fuel cell as powerThe further application of the energy automobile, the development of the non-aqueous low-temperature proton exchange membrane, which is expected to realize the application of the proton exchange membrane fuel cell in the low-temperature environment, has important practical significance.

Kevlar (Kevlar) is a novel aramid fiber composite material developed by DuPont company in the last 60 th century, and has a diameter of about 0.01-0.02 mm and a density of 1.43g/cm³And has good stability and mechanical performance. Polyvinyl Alcohol (PVA) is widely used in the field of fuel cells because of its good chemical stability, mechanical strength and film-forming properties. The Zakaaria and the like prepare a polyvinyl alcohol/graphene oxide composite membrane, and the conductivity of the composite membrane is 9.5 multiplied by 10 at the temperature of 30 DEG C^-3S/cm, and the conductivity reaches 3.24 multiplied by 10 at 60 DEG C^-2S/cm. Carbon nanotubes are often added as a reinforcing phase to different matrices to improve the electrochemical properties of the matrix and to improve its mechanical properties. Naebe et al prepared a polyvinyl alcohol/single-walled carbon nanotube composite nanomaterial by an electrostatic spinning method and studied the mechanical properties thereof. Compared with pure PVA nano fiber, the tensile strength of the PVA/single-walled carbon nanotube composite nano material is 3.83MPa, the tensile strength of the PVA/single-walled carbon nanotube composite nano material is improved to 5.97MPa, and the improvement range reaches 56 percent.

Vacuum-assisted flocculation (VAF) is a method of filtering a solution using negative pressure caused by air extraction. The specific method comprises the following steps: adding the solution into a suction filtration device, when negative pressure is formed in a filter flask, allowing the solvent to flow into the filter flask under the action of pressure difference and the solute to remain on the filter membrane, removing the filter flask and drying to obtain the film. The vacuum assisted flocculation technology has the advantages of simple operation, high film forming speed and the like. Compared with the traditional solution pouring method, the film prepared by utilizing the vacuum assisted flocculation technology has an ordered layered structure; compared with the layer-by-layer self-assembly technology, the method has the advantages of rapid film formation, controllable film thickness, easy realization of large-scale production and the like. It is reported that Zhu et al prepared a composite film consisting of Kevlar and multi-walled carbon nanotubes by vacuum assisted flocculation technique with a tensile strength of 383MPa and Young's modulus up to 35 GPa.

Disclosure of Invention

The invention provides a method for preparing a low-temperature proton exchange membrane with a layered structure by utilizing a vacuum-assisted flocculation technology, aiming at preparing a non-aqueous proton exchange membrane with high proton conductivity, good mechanical property and stability, which can be used in a low-temperature environment of-30 ℃ to 30 ℃.

In order to realize the purpose of the invention, the following technical scheme is adopted:

A method for preparing a layered structure low-temperature proton exchange membrane based on a vacuum assisted flocculation technology comprises the following steps:

(1) Adding 2.5-5.0 g Kevlar fiber (Kevlar), 1.5-3.0 g potassium hydroxide and 500mL dimethyl sulfoxide (DMSO) into a 1000mL reagent bottle, and stirring at room temperature to prepare 5-10 g/L Kevlar/DMSO solution;

(2) Adding 1g of multi-walled carbon nanotube, 50mL of sulfuric acid with the mass fraction of 98% and 6g of potassium permanganate into a 500mL flask, stirring in an ice-water bath for 4 hours, heating to 35 ℃, stirring for 3 hours, adding 40mL of sulfuric acid with the mass fraction of 5%, stirring for 30 minutes, and adding 10mL of H with the mass fraction of 30%₂O₂Stirring the aqueous solution for 30 minutes, standing for 16 hours, washing the solution to be neutral by using deionized water, and drying the solution for 10 hours at 80 ℃ to obtain carbon oxide nanotubes (OCNTs); adding 0.05g of carbon oxide nanotube and 100mL of dimethyl sulfoxide into a 100mL reagent bottle to prepare 0.5g/L of OCNTs/DMSO;

(3) Adding 0.25-0.50 g of polyvinyl alcohol (PVA) solid with the hydrolysis degree of 99% and 50mL of dimethyl sulfoxide into a 100mL reagent bottle, and stirring at 90 ℃ for 2 hours to prepare 2-10 g/L of PVA/DMSO solution;

(4) Adding 2-10 g/L PVA/DMSO solution into a suction filtration device with a filter membrane with the diameter of 50mm and the pore diameter of 0.22 mu m, carrying out suction filtration for 3 hours, adding 5-10 g/L Kevlar/DMSO solution, carrying out suction filtration for 2 hours, and finally adding 0.5g/L OCNTs/DMSO solution, and carrying out suction filtration for 1 hour;

(5) Repeating the step (4) for 1-3 times, adding 2-10 g/L PVA/DMSO solution, performing suction filtration for 4-6 hours, removing the film, and drying at 80 ℃ for 1 hour to prepare (PVA/Kevlar/OCNTs)_2-4Compounding film;

(6) Will (PVA/Kevlar/OCNTs)_2-4The composite membrane is soaked in a solution containing the following components in percentage by masspreparing (PVA/Kevlar/OCNTs) in a sealed container of 50-100% Phosphoric Acid (PA) aqueous solution for 4-12 hours_2-4/(50 to 100%) of a PA composite film.

The method for preparing the layered structure low-temperature proton exchange membrane based on the vacuum assisted flocculation technology comprises the step (5), (PVA/Kevlar/OCNTs)_2-4The composite membranes are formed by sequentially overlapping 2-4 groups of PVA/Kevlar/OCNTs composite membranes, and each group of PVA/Kevlar/OCNTs composite membranes are formed by sequentially overlapping a PVA membrane, a Kevlar membrane and an OCNTs membrane; in each group of PVA/Kevlar/OCNTs composite membranes, the thickness of the PVA membrane is 4-8 mu m, the thickness of the Kevlar membrane is 8-15 mu m, and the thickness of the OCNTs membrane is 1-2 mu m; (PVA/Kevlar/OCNTs)_2-4The PVA film is additionally arranged on the topmost layer of the composite film, and the thickness of the PVA film is 5-13 mu m.

the method for preparing the layered structure low-temperature proton exchange membrane based on the vacuum assisted flocculation technology comprises the step (6), wherein (PVA/Kevlar/OCNTs) are calculated according to weight percentage_2-4(50-100%) composition of the PA composite membrane: 25-63% of PVA/Kevlar/OCNTs and 37-75% of PA.

The method for preparing the layered structure low-temperature proton exchange membrane based on the vacuum assisted flocculation technology comprises the step (6), (PVA/Kevlar/OCNTs)_2-4/(50 to 100%) the thickness of the PA composite film is 45 to 185 μm.

The design idea of the invention is as follows:

The invention comprehensively considers the materials and the film forming method in the prior art, takes polyvinyl alcohol, Kevlar and carbon oxide nano tubes as raw materials, utilizes the vacuum auxiliary flocculation technology to realize the ordered assembly of the three components, prepares the non-aqueous proton exchange membrane with a layered structure and realizes the purpose of rapidly transmitting protons at low temperature.

Compared with the prior art, the invention has the characteristics and beneficial effects that:

1. The low-temperature proton exchange membrane with the layered structure is prepared based on the vacuum assisted flocculation technology, so that the fine regulation and control of the membrane composition and the structure are facilitated, and compared with the traditional solution pouring method, the prepared proton exchange membrane has an ordered structure; compared with the layer-by-layer self-assembly technology, the method has the advantages of rapid film formation, controllable film thickness, easy large-scale production and the like.

2. prepared by the invention (PVA/Kevlar/OCNTs)_2-4the/PA composite film has good stability, and can be known from the surface and cross section electron scanning electron microscope pictures of the composite film: (PVA/Kevlar/OCNTs)_2-4The composite membrane has a compact and layered structure, and is beneficial to improving the mechanical property and proton conductivity of the composite membrane. Prepared in the invention (PVA/Kevlar/OCNTs)₃The composite membrane is soaked in a Phosphoric Acid (PA) water solution with the mass fraction of 85% for 6 hours, and the conductivity of the prepared phosphoric acid doped composite membrane is 0.16S/cm at 30 ℃, 0.087S/cm at 0 ℃ and 0.038S/cm at-30 ℃.

Drawings

FIG. 1 is a photograph showing a polymer composite film and a phosphoric acid-doped polymer composite film prepared in example 8 of the present invention; wherein: a is (PVA/Kevlar/OCNTs)₃(ii) a B is (PVA/Kevlar/OCNTs)₃/85％PA；

FIG. 2 shows the electrical conductivity of the phosphoric acid-doped composite membrane prepared by immersing the phosphoric acid-doped polymer composite membrane prepared in examples 6 to 8 in a Phosphoric Acid (PA) solution having a concentration of 60 to 85%; in the figure, the abscissa Temperature represents Temperature (. degree. C.) and the ordinate Conductivity represents Conductivity (S/cm).

FIG. 3 is a scanning electron microscope photograph of the polymer composite films prepared in examples 5 and 4; wherein: a and B are respectively the one prepared in example 5 (PVA/Kevlar/OCNTs)₃Electron microscope pictures of the cross section and the surface of the composite film; c and D are respectively the one prepared in example 4 (PVA/Kevlar/OCNTs)₄Electron microscope pictures of the cross section and the surface of the composite film;

table 1 shows the results of mechanical property tests of the phosphoric acid-doped polymer composite films prepared in examples 8 to 11.

Detailed Description

In the specific implementation process, firstly, Kevlar nanofiber (Kevlar) solution, polyvinyl alcohol (PVA) solution and carbon nanotube Oxide (OCNTs) solution are prepared, suction filtration is sequentially carried out, and suction filtration operation is repeated for 1-3 times to prepare (PVA/Kevlar/OCNTs) with 2-4-layer structure_2-4A composite membrane. Soaking the cells in a Phosphoric Acid (PA) aqueous solution with the mass fraction of 50-100% to prepare (PVA/Kevlar-OCNTs)_2-4/(50 to 100%) of a PA composite film.

The process of the present invention is further illustrated by the following examples.