阅读说明：本技术 功能化石墨烯/Nafion复合质子交换膜及其制备方法和应用 (Functionalized graphene/Nafion composite proton exchange membrane and preparation method and application thereof ) 是由 谢东 李发勇 陈骏佳 王珂 张会平 高旭华 于 2020-06-01 设计创作，主要内容包括：本发明公开了一种功能化石墨烯/Nafion复合质子交换膜及其制备方法和应用,采用重氮盐加成反应和原子转移自由基聚合方法在石墨烯表面接枝含有酸性基团的聚合物,制备功能化石墨烯,最后采用溶液浇铸法制备功能化石墨烯/Nafion复合质子交换膜。本发明制备的功能化石墨烯可提高石墨烯在Nafion基体中的分散性,表面的酸性基团与Nafion基体中的酸性基团在Nafion-石墨烯界面处形成的高效连续子传递通道,实现高温低湿度条件下质子传导的强化。同时石墨烯二维层状结构可有效调控通道尺寸,阻挡甲醇分子的扩散,实现Nafion膜的阻醇性能强化,解决Nafion质子交换膜的共性关键问题。(The invention discloses a functionalized graphene/Nafion composite proton exchange membrane and a preparation method and application thereof. The functionalized graphene prepared by the method can improve the dispersibility of the graphene in a Nafion matrix, and the acid groups on the surface and the acid groups in the Nafion matrix form a high-efficiency continuous proton transfer channel at a Nafion-graphene interface, so that the proton conduction is enhanced under the conditions of high temperature and low humidity. Meanwhile, the graphene two-dimensional layered structure can effectively regulate and control the channel size, block the diffusion of methanol molecules, realize the enhancement of the alcohol-blocking performance of the Nafion membrane and solve the common key problem of the Nafion proton exchange membrane.)

1. The preparation method of the functionalized graphene/Nafion composite proton exchange membrane is characterized by comprising the following steps:

(1) reducing graphene oxide to obtain graphene, grafting an ATRP initiator to the surface of the graphene through diazonium salt addition reaction to obtain ATRP initiator graft modified graphene;

(2) carrying out graft polymerization on a monomer containing an acidic group on the surface of the ATRP initiator graft modified graphene obtained in the step (1) through ATRP reaction to obtain polymer graft graphene containing the acidic group, namely functionalized graphene;

(3) and preparing the functionalized graphene/Nafion composite proton exchange membrane by adopting a solution casting method.

2. The preparation method of the functionalized graphene and Nafion composite proton exchange membrane according to claim 1, wherein the preparation method of the ATRP initiator graft-modified graphene in the step (1) comprises the following steps: firstly, preparing graphene oxide by a Hummers method, ultrasonically dispersing the graphene oxide into deionized water, adding ascorbic acid to reduce the graphene oxide to obtain graphene, dispersing the graphene into the deionized water containing a surfactant, adding 4-aminophenylethanol and isoamyl nitrite, reacting at 80 ℃ overnight, filtering, washing, and vacuum drying to obtain hydroxyl modified graphene, ultrasonically dispersing the hydroxyl modified graphene into tetrahydrofuran, adding triethylamine, cooling to 0 ℃, slowly dropwise adding alpha-bromoisobutyryl bromide in a nitrogen atmosphere, continuously reacting at room temperature for 24 hours after dropwise adding is completed, filtering, washing, and vacuum drying to obtain the ATRP initiator grafted modified graphene.

3. The preparation method of the functionalized graphene/Nafion composite proton exchange membrane according to claim 1, wherein the step (2) of graft polymerizing the monomer containing the acidic group to the ATRP initiator graft-modified graphene through ATRP reaction comprises the following steps: ultrasonically dispersing the ATRP initiator grafted modified graphene obtained in the step (1) into a mixed solvent of deionized water and methanol, adding a monomer containing an acidic group, performing freezing-thawing degassing circulation for three times, adding a catalyst in a nitrogen atmosphere, reacting for 48 hours at room temperature, filtering, washing, and performing vacuum drying to obtain polymer grafted graphene containing the acidic group, namely functionalized graphene.

4. The preparation method of the functionalized graphene/Nafion composite proton exchange membrane according to claim 1 or 3, wherein the acidic group-containing monomer in the step (2) is 3-sulfopropyl methacrylate potassium salt or 4-styrenesulfonic acid sodium salt.

5. The preparation method of the functionalized graphene/Nafion composite proton exchange membrane according to claim 3, wherein the catalyst in the step (2) is 2,2' -bipyridine/cuprous bromide.

6. The functionalized graphene/Nafion composite proton exchange membrane according to claim 1 or 3, wherein in the step (2), the prepared functionalized graphene has the following structure:

7. the preparation method of the functionalized graphene/Nafion composite proton exchange membrane according to claim 1, wherein the preparation method of the functionalized graphene/Nafion composite proton exchange membrane in the step (3) comprises the following steps: firstly, dispersing the functionalized graphene prepared in the step (2) into N, N-dimethylformamide, mixing with Nafion N, N-dimethylformamide solution, obtaining uniform membrane casting solution under the alternate action of ultrasound and stirring, casting to form a membrane, drying in vacuum, and finally treating with hydrogen peroxide, deionized water and sulfuric acid solution in sequence to obtain the functionalized graphene/Nafion composite proton exchange membrane.

8. The preparation method of the functionalized graphene/Nafion composite proton exchange membrane according to claim 7, wherein in the step (3), the mass ratio of Nafion to functionalized graphene is 100: 0.5-2.

9. The functionalized graphene/Nafion composite proton exchange membrane is characterized by being prepared by the preparation method of any one of claims 1 to 8.

10. The use of the functionalized graphene/Nafion composite proton exchange membrane according to claim 9, wherein the membrane is used for preparing a methanol fuel cell.

Technical Field

The invention relates to a fuel cell proton exchange membrane and a preparation method thereof, in particular to a functionalized graphene/Nafion composite proton exchange membrane and a preparation method and application thereof.

Background

Proton Exchange Membrane Fuel Cells (PEMFC) are a clean and efficient green and environment-friendly power supply, have the characteristics of high efficiency, zero pollution and the like, and are widely concerned all over the world. The Proton Exchange Membrane (PEM) is the core component of the PEMFC, and its proton conductivity directly determines the cell performance. Nafion is used as the most advanced proton exchange membrane, is a perfluorosulfonic acid polymer proton exchange membrane, has the advantages of high conductivity, good electrochemical and chemical stability, low gas permeability and the like, and is widely used for proton exchange membrane fuel cells. However, the proton conductivity of the Nafion membrane is very dependent on water and temperature, and proton transmission channels can be collapsed and collapsed under anhydrous or low-humidity conditions and high temperature, so that the proton conductivity is obviously reduced. In addition, when the Nafion membrane is used in a Direct Methanol Fuel Cell (DMFC), fuel methanol permeates seriously, and methanol molecules easily pass through an ion cluster network along with water molecules and penetrate to a cathode, so that not only is fuel wasted, but also normal reaction of the cathode is interfered, and the efficiency of the DMFC is obviously reduced. Therefore, the development of a high proton conductivity, low fuel permeability PEM is critical for large-scale applications of PEMFCs. Studies have shown that the incorporation of inorganic fillers into the Nafion membrane matrix can help in proton conduction by adjusting the microphase separation structure in the membrane matrix.

Graphene is a two-dimensional material composed of sp2 hybridized and connected carbon atom layers, and the special structure of the single atom layer makes the graphene have many unique physicochemical properties, such as high modulus, high strength, high-speed electron mobility at room temperature, high specific surface area, high thermal conductivity and the like. The excellent performances enable the graphene to have bright application prospects in the fields of nano electronic devices, sensors, energy storage, composite materials and the like. Graphene is hydrophobic and is difficult to disperse in water and common organic solvents. Therefore, in order to fully exert the excellent properties of graphene and improve the dispersibility of graphene in a Nafion matrix, it is necessary to functionally modify graphene. J.Phys.chem.C,120(2016),15855-15866, Sulfonated Graphene-Nafion Composite Membranes for polymer electrolyte Membranes Operating under reduced proton exchange membrane, which is prepared by sulfonating and modifying Graphene, introducing sulfonic acid groups on the surface of the Graphene and compounding the sulfonic acid groups with Nafion to prepare a Sulfonated Graphene/Nafion Composite proton exchange membrane, wherein the proton conductivity of the Nafion membrane under a low-Humidity condition is obviously improved, but the quantity of the sulfonic acid groups introduced on the surface of the Graphene is limited.

So far, no research is made on the preparation of a composite proton exchange membrane by introducing an acid group to the surface of graphene through diazonium salt addition reaction and atom transfer radical polymerization reaction and compounding with Nafion.

Disclosure of Invention

The invention provides a functionalized graphene/Nafion composite proton exchange membrane and a preparation method and application thereof to solve the defects.

The purpose of the invention is realized by the following technical scheme: a functionalized graphene/Nafion composite proton exchange membrane is prepared by the following preparation method, wherein the preparation method comprises the following steps:

(1) reducing graphene oxide to obtain graphene, grafting an Atom Transfer Radical Polymerization (ATRP) initiator to the surface of the graphene through a diazonium salt addition reaction to obtain ATRP initiator graft modified graphene;

(2) carrying out graft polymerization on a monomer containing an acidic group to the ATRP initiator graft-modified graphene obtained in the step (1) through ATRP reaction to obtain polymer graft graphene containing the acidic group, namely functionalized graphene;

(3) and preparing the functionalized graphene/Nafion composite proton exchange membrane by adopting a solution casting method.

The method comprises the following specific steps:

the preparation method of the ATRP initiator graft modified graphene in the step (1) comprises the following steps: firstly, Graphene Oxide (GO) prepared by a Hummers method is ultrasonically dispersed into deionized water, ascorbic acid is added to reduce the GO to obtain Graphene, then the Graphene is dispersed into the deionized water containing a surfactant, 4-aminophenylethanol and isoamyl nitrite are added, the reaction is carried out overnight at 80 ℃, the filtration, the washing and the vacuum drying are carried out to obtain hydroxyl modified Graphene (Graphene-OH), the Graphene-OH is ultrasonically dispersed into tetrahydrofuran, triethylamine is added, the alpha-bromoisobutyryl bromide is slowly dripped in the nitrogen atmosphere after the cooling to 0 ℃, the reaction is continuously carried out for 24 hours at room temperature after the dripping is finished, and finally, the filtration, the washing and the vacuum drying are carried out to obtain the ATRP initiator grafted modified Graphene (Graphene-Br).

The method for graft polymerization of the monomer containing the acidic group on the surface of the graphene by the ATRP reaction in the step (2) comprises the following steps: ultrasonically dispersing Graphene-Br obtained in the step (1) into a mixed solvent of deionized water and methanol, adding a monomer containing an acidic group, performing freeze-thaw degassing cycle for three times, adding a catalyst in a nitrogen atmosphere, reacting for 48 hours at room temperature, filtering, washing, and performing vacuum drying to obtain functionalized Graphene, namely the polymer grafted Graphene containing the acidic group.

The acid group-containing monomer used in the step (2) is 3-sulfopropyl methacrylate potassium Salt (SPMA) or 4-styrene sulfonic acid sodium salt (NASS); the catalyst is 2,2' -bipyridine/cuprous bromide; the prepared functionalized graphene, namely the polymer grafted graphene containing the acidic group, has the following structure:

the method for preparing the functionalized graphene/Nafion composite proton exchange membrane in the step (3) comprises the following steps: firstly, dispersing the functionalized graphene prepared in the step (2) into N, N-Dimethylformamide (DMF), mixing the N, N-dimethylformamide with a DMF solution of Nafion, obtaining a uniform membrane casting solution under the alternate action of ultrasound and stirring, casting to form a membrane, drying in vacuum, and finally treating with hydrogen peroxide, deionized water and a sulfuric acid solution in sequence to obtain the functionalized graphene/Nafion composite proton exchange membrane.

In the step (3), the mass ratio of the Nafion to the functionalized graphene is 100: 0.5-2.

The functionalized graphene/Nafion composite proton exchange membrane can be used for a methanol fuel cell.

The invention has the following beneficial effects:

1. according to the invention, a polymer containing an acid group is grafted on the surface of graphene through diazonium salt addition and Atom Transfer Radical Polymerization (ATRP), and is compounded with Nafion to prepare the functionalized graphene/Nafion composite proton exchange membrane, the acid group on the surface of the functionalized graphene and the acid group in a Nafion matrix can form a high-efficiency continuous proton transfer channel at an organic-inorganic interface, meanwhile, the water retention performance of the Nafion membrane can be improved, the water environment of the membrane proton transfer channel is optimized, and thus the proton conduction reinforcement under the conditions of high temperature and low humidity is realized.

2. The polymer grafted graphene containing the acid groups prepared by the method can improve the dispersibility of the graphene in a Nafion matrix, and the two-dimensional layered structure of the graphene can effectively regulate and control the channel size, prevent the diffusion of methanol molecules and realize the reinforcement of the alcohol resistance of a Nafion membrane.

3. The functionalized graphene/Nafion composite proton exchange membrane prepared by the invention can solve the common key scientific problems of rapid attenuation of proton conductivity and high methanol fuel permeability of the Nafion proton exchange membrane under high-temperature and low-humidity conditions, and can enable the Nafion membrane to have wider prospects in the aspect of commercial application and popularization of proton exchange membrane fuel cells.

Drawings

FIG. 1 is an FTIR spectrum of Graphene oxide (a), Graphene (b), hydroxyl-modified Graphene (Graphene-OH) (c), ATRP initiator graft-modified Graphene (Graphene-Br) (d) and polymer graft Graphene (e) containing acidic groups prepared according to the present invention;

FIG. 2a is an SEM image of a pure Nafion membrane;

fig. 2b is an SEM image of the functionalized graphene/Nafion composite proton exchange membrane prepared by the present invention.

Detailed Description

The present invention will be further described with reference to the following examples, but the present invention is not limited thereto.