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.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited thereto.
Example 1
Dispersing 0.5g of Graphene Oxide (GO) prepared by a Hummers method into 250mL of deionized water by ultrasonic for 30 minutes, adding 10g of ascorbic acid, heating to 60 ℃, stirring for 4 hours, cooling to room temperature, filtering, washing with deionized water for three times, adding 0.5g of obtained product and sodium dodecyl sulfate into 250mL of deionized water, performing ultrasonic for 30 minutes, adding 2g of 4-aminophenylethanol and 1.5mL of isoamyl nitrite, reacting at 80 ℃ overnight, cooling to room temperature, filtering, washing with deionized water, absolute ethanol and acetone in sequence, and performing vacuum drying to obtain hydroxyl modified Graphene (Graphene-OH). Adding 0.2g of Graphene-OH into 40mL of tetrahydrofuran, adding 2mL of triethylamine, introducing nitrogen for 10 minutes, cooling to 0 ℃, slowly dropwise adding a solution of 1.2mL of alpha-bromoisobutyryl bromide/10 mL of tetrahydrofuran, continuing to react for 24 hours at room temperature after dropwise adding is finished, finally filtering, washing by sequentially adopting deionized water, absolute ethyl alcohol and acetone, drying in vacuum, and drying in vacuum to obtain the ATRP initiator graft modified Graphene (Graphene-Br).
Dispersing 0.1g of Graphene-Br into 20mL of methanol/deionized water mixed solvent (the mass ratio is 3:2) by ultrasonic dispersion, adding 3.2g of 3-sulfopropyl methacrylate potassium Salt (SPMA), performing freeze-thaw degassing cycle for three times, adding 0.0625g of 2,2' -bipyridine and 0.0287g of cuprous bromide under the nitrogen atmosphere, reacting at room temperature for 48 hours, filtering, washing with deionized water for three times, immersing the product into 1M sulfuric acid solution, standing overnight, washing with deionized water to be neutral, and performing freeze drying to obtain the acid group-containing polymer grafted Graphene.
Dispersing 2.5mg of acid group-containing polymer grafted graphene into 2mL of N, N-Dimethylformamide (DMF) by ultrasonic treatment for 4h, dissolving 0.5g of Nafion into 8mL of DMF, mixing the two solutions, performing ultrasonic treatment for 30 min and stirring for 30 min, circulating for four times to obtain a uniform membrane casting solution, casting to form a membrane, performing vacuum drying at 80 ℃ for 12 h, heating to 120 ℃ and drying for 12 h, and finally sequentially performing treatment with hydrogen peroxide (3%), deionized water and sulfuric acid solution (1M) at 80 ℃ to obtain the 0.5 wt% functionalized graphene/Nafion composite proton exchange membrane.
Example 2
Dispersing Graphene Oxide (GO) prepared by a Hummers method for 0.5 ultrasonic 30 minutes into 250mL of deionized water, adding 10g of ascorbic acid, heating to 60 ℃, stirring for 4 hours, cooling to room temperature, filtering, washing with deionized water for three times, adding the obtained product and 0.5g of sodium dodecyl sulfate into 250mL of deionized water, performing ultrasonic 30 minutes, adding 2g of 4-aminophenylethanol and 1.5mL of isoamyl nitrite, reacting overnight at 80 ℃, cooling to room temperature, filtering, washing with deionized water, absolute ethanol and acetone in sequence, and performing vacuum drying to obtain hydroxyl modified Graphene (Graphene-OH). Adding 0.2g of Graphene-OH into 40mL of tetrahydrofuran, adding 2mL of triethylamine, introducing nitrogen for 10 minutes, cooling to 0 ℃, slowly dropwise adding a solution of 1.2mL of alpha-bromoisobutyryl bromide/10 mL of tetrahydrofuran, continuing to react for 24 hours at room temperature after dropwise adding is finished, finally filtering, washing by sequentially adopting deionized water, absolute ethyl alcohol and acetone, drying in vacuum, and drying in vacuum to obtain the ATRP initiator graft modified Graphene (Graphene-Br).
Dispersing 0.1g of Graphene-Br into 20mL of methanol/deionized water mixed solvent (the mass ratio is 3:2) by ultrasonic dispersion, adding 3.2g of 3-sulfopropyl methacrylate potassium Salt (SPMA), performing freeze-thaw degassing cycle for three times, adding 0.0625g of 2,2' -bipyridine and 0.0287g of cuprous bromide under the nitrogen atmosphere, reacting at room temperature for 48 hours, filtering, washing with deionized water for three times, immersing the product into 1M sulfuric acid solution, standing overnight, washing with deionized water to be neutral, and performing freeze drying to obtain the acid group-containing polymer grafted Graphene.
Dispersing 5mg of acid group-containing polymer grafted graphene into 2mL of N, N-Dimethylformamide (DMF) by ultrasonic treatment for 4h, dissolving 0.5g of Nafion into 8mL of DMF, mixing the two solutions, performing ultrasonic treatment for 30 min and stirring for 30 min, circulating for four times to obtain a uniform membrane casting solution, casting to form a membrane, performing vacuum drying at 80 ℃ for 12 h, heating to 120 ℃ and drying for 12 h, and finally sequentially performing treatment with hydrogen peroxide (3%), deionized water and sulfuric acid solution (1M) at 80 ℃ to obtain the 1 wt% functionalized graphene/Nafion composite proton exchange membrane.
Example 3
Dispersing Graphene Oxide (GO) prepared by a Hummers method for 0.5 ultrasonic 30 minutes into 250mL of deionized water, adding 10g of ascorbic acid, heating to 60 ℃, stirring for 4 hours, cooling to room temperature, filtering, washing with deionized water for three times, adding the obtained product and 0.5g of sodium dodecyl sulfate into 250mL of deionized water, performing ultrasonic 30 minutes, adding 2g of 4-aminophenylethanol and 1.5mL of isoamyl nitrite, reacting overnight at 80 ℃, cooling to room temperature, filtering, washing with deionized water, absolute ethanol and acetone in sequence, and performing vacuum drying to obtain hydroxyl modified Graphene (Graphene-OH). Adding 0.2g of Graphene-OH into 40mL of tetrahydrofuran, adding 2mL of triethylamine, introducing nitrogen for 10 minutes, cooling to 0 ℃, slowly dropwise adding a solution of 1.2mL of alpha-bromoisobutyryl bromide/10 mL of tetrahydrofuran, continuing to react for 24 hours at room temperature after dropwise adding is finished, finally filtering, washing by sequentially adopting deionized water, absolute ethyl alcohol and acetone, drying in vacuum, and drying in vacuum to obtain the ATRP initiator graft modified Graphene (Graphene-Br).
Dispersing 0.1g of Graphene-Br into 20mL of methanol/deionized water mixed solvent (the mass ratio is 3:2) by ultrasonic dispersion, adding 3.2g of 3-sulfopropyl methacrylate potassium Salt (SPMA), performing freeze-thaw degassing cycle for three times, adding 0.0625g of 2,2' -bipyridine and 0.0287g of cuprous bromide under the nitrogen atmosphere, reacting at room temperature for 48 hours, filtering, washing with deionized water for three times, immersing the product into 1M sulfuric acid solution, standing overnight, washing with deionized water to be neutral, and performing freeze drying to obtain the acid group-containing polymer grafted Graphene.
Dispersing 7.5mg of acid group-containing polymer grafted graphene into 2mL of N, N-Dimethylformamide (DMF) by ultrasonic treatment for 4h, dissolving 0.5g of Nafion into 8mL of DMF, mixing the two solutions, performing ultrasonic treatment for 30 min and stirring for 30 min, circulating for four times to obtain a uniform membrane casting solution, casting to form a membrane, performing vacuum drying at 80 ℃ for 12 h, heating to 120 ℃ and drying for 12 h, and finally sequentially performing treatment with hydrogen peroxide (3%), deionized water and sulfuric acid solution (1M) at 80 ℃ to obtain the 1.5 wt% functionalized graphene/Nafion composite proton exchange membrane.
Example 4
Dispersing Graphene Oxide (GO) prepared by a Hummers method for 0.5 ultrasonic 30 minutes into 250mL of deionized water, adding 10g of ascorbic acid, heating to 60 ℃, stirring for 4 hours, cooling to room temperature, filtering, washing with deionized water for three times, adding the obtained product and 0.5g of sodium dodecyl sulfate into 250mL of deionized water, performing ultrasonic 30 minutes, adding 2g of 4-aminophenylethanol and 1.5mL of isoamyl nitrite, reacting overnight at 80 ℃, cooling to room temperature, filtering, washing with deionized water, absolute ethanol and acetone in sequence, and performing vacuum drying to obtain hydroxyl modified Graphene (Graphene-OH). Adding 0.2g of Graphene-OH into 40mL of tetrahydrofuran, adding 2mL of triethylamine, introducing nitrogen for 10 minutes, cooling to 0 ℃, slowly dropwise adding a solution of 1.2mL of alpha-bromoisobutyryl bromide/10 mL of tetrahydrofuran, continuing to react for 24 hours at room temperature after dropwise adding is finished, finally filtering, washing by sequentially adopting deionized water, absolute ethyl alcohol and acetone, drying in vacuum, and drying in vacuum to obtain the ATRP initiator graft modified Graphene (Graphene-Br).
Dispersing 0.1g of Graphene-Br into 20mL of methanol/deionized water mixed solvent (the mass ratio is 3:2) by ultrasonic dispersion, adding 3.2g of 3-sulfopropyl methacrylate potassium Salt (SPMA), performing freeze-thaw degassing cycle for three times, adding 0.0625g of 2,2' -bipyridine and 0.0287g of cuprous bromide under the nitrogen atmosphere, reacting at room temperature for 48 hours, filtering, washing with deionized water for three times, immersing the product into 1M sulfuric acid solution, standing overnight, washing with deionized water to be neutral, and performing freeze drying to obtain the acid group-containing polymer grafted Graphene.
Dispersing 10mg of acid group-containing polymer grafted graphene into 2mL of N, N-Dimethylformamide (DMF) by ultrasonic for 4h, dissolving 0.5g of Nafion into 8mL of DMF, mixing the two solutions, performing ultrasonic treatment for 30 min and stirring for 30 min, circulating for four times to obtain a uniform membrane casting solution, casting to form a membrane, performing vacuum drying at 80 ℃ for 12 h, heating to 120 ℃ and drying for 12 h, and finally sequentially performing treatment with hydrogen peroxide (3%), deionized water and sulfuric acid solution (1M) at 80 ℃ to obtain the 2 wt% functionalized graphene/Nafion composite proton exchange membrane.
As shown in fig. 1, FTIR spectra 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 obtained in the preparation process of the present invention.
Fig. 2a is an SEM image of a pure Nafion membrane, and fig. 2b is an SEM image of a functionalized graphene/Nafion composite proton exchange membrane prepared by the present invention. The performance of the functionalized graphene/Nafion composite proton exchange membrane prepared by the invention is compared with that of a pure Nafion membrane, and the result is shown in Table 1:
TABLE 1 comparison of the Performance of the functionalized graphene/Nafion composite proton exchange membranes with that of the pure Nafion membranes
As can be seen from table 1, the functionalized graphene/Nafion composite proton exchange membrane provided by the invention is obviously superior to a pure Nafion membrane in each performance index.