A two-dimensional material composite proton exchange membrane for hydrogen isotope separation and preparation method thereof

Abstract

The present invention discloses a method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation, comprising the following steps: (1) preparing a PFSA type polymer solution; (2) preparing a nanosheet dispersion; (3) preparing a composite proton exchange membrane: adding the nanosheet dispersion to the PFSA type polymer solution, mixing evenly, pouring the nanosheet dispersion into a mold under heating conditions and standing to form a membrane, finally cooling to room temperature, and taking out the formed membrane, which is the two-dimensional material composite proton exchange membrane for hydrogen isotope separation. The two-dimensional material composite proton exchange membrane prepared by the present invention has good mechanical properties and hydrogen isotope screening ability, and can be applied to a proton exchange membrane (PEM) electrolyzer to significantly reduce the energy consumption of electrolytic separation of protium and tritium, and improve the protium and tritium separation coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membranes, and in particular to a two-dimensional material composite proton exchange membrane for hydrogen isotope separation and a preparation method thereof. Background Art

[0002] The separation and purification of hydrogen isotopes has very important application value in the fields of environment, energy and life sciences, and has attracted extensive attention from scholars at home and abroad. For example, the membrane electrode of the solid polymer electrolyzer (SPE) is mainly composed of an anode catalyst, a proton exchange membrane, and a cathode catalyst. Due to the rapid development of the fuel cell field, the anode catalyst and cathode catalyst processes have become increasingly mature, and the proton exchange membrane has become the main factor affecting the separation coefficient of hydrogen isotopes in SPE electrolysis.

[0003] Traditional hydrogen isotope separation methods include cryogenic distillation, cryogenic molecular sieve chromatography, palladium chromatography, etc., and their protium-tritium separation coefficient is only ~3. At present, there are literature reports that two-dimensional material proton exchange membranes can be used for the separation of hydrogen isotopes "protium-tritium", and the theoretical separation coefficient is high, which can reach ~30, which is about 10 times the traditional separation efficiency. However, there have been no experimental reports on the successful production of such exchange membranes.

[0004] S. Hu (article: Nature, 2014, 516(7530):227-230) proved through conductivity measurement that ionized hydrogen atoms (i.e., protons) can penetrate the lattice network of single-layer hBN, double-layer hBN, and single-layer graphene under the action of an external electric field, which provides ideas for the development of new and efficient hydrogen isotope separation membranes. + , D + , T + ) penetrating the graphene / hBN lattice is a thermally activated process. Under the action of an external electric field, hydrogen isotope ions are activated, and H + First pass through the lattice network of two-dimensional materials, followed by D + and T + The difference in zero-point energy enables graphene and hBN to have excellent hydrogen isotope screening capabilities. Theoretical calculations show that the use of graphene to screen protium and tritium can achieve a protium-tritium separation factor of up to 30, which is much higher than the separation process currently used in industrial applications. Summary of the invention

[0005] The main purpose of the present invention is to provide a two-dimensional material composite proton exchange membrane for hydrogen isotope separation and a preparation method thereof.

[0006] To achieve the above object, the present invention provides a method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation, comprising the following steps:

[0007] (1) Preparation of PFSA polymer solution

[0008] Taking a perfluorosulfonic acid polymer dispersion, evaporating the solvent to obtain a dry resin, then adding an aprotic polar solvent, and heating at a constant temperature to completely dissolve the dry resin and partially volatilize the aprotic polar solvent to obtain a PFSA polymer solution;

[0009] (2) Preparation of nanosheet dispersion

[0010] Take the nanosheets, add a non-protonic polar solvent, disperse by ultrasonication, and then stand at room temperature to obtain a nanosheet dispersion;

[0011] (3) Preparation of composite proton exchange membrane

[0012] The nanosheet dispersion is added to the PFSA polymer solution, mixed evenly, poured into a mold under heating conditions and allowed to stand to form a film, and finally cooled to room temperature. The formed membrane is taken out to be the two-dimensional material composite proton exchange membrane for hydrogen isotope separation.

[0013] Furthermore, in steps (1) and (2), the aprotic polar solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0014] Furthermore, in step (1), the ratio of the non-protonic polar solvent to the perfluorosulfonic acid type polymer dispersion is 2 ml / g to 10 ml / g.

[0015] Furthermore, in step (1), the temperature condition of constant temperature heating is 80-100°C.

[0016] Furthermore, in step (1), the volatility of the aprotic polar solvent is such that the mass of the PFSA polymer solution is 0.5 to 2 times the mass of the perfluorosulfonic acid polymer dispersion.

[0017] Furthermore, in step (2), the nanosheets are graphene nanosheets or hexagonal boron nitride nanosheets.

[0018] Furthermore, in step (2), the ratio of the aprotic polar solvent to the nanosheets is 1 ml / mg to 3 ml / mg.

[0019] Furthermore, in step (3), the volume mass ratio of the nanosheet dispersion to the PFSA type polymer solution is 1 to 7:2 mL / g.

[0020] Furthermore, in step (3), the heating condition of the mold is 100° C., and the static film-forming time is 3 hours.

[0021] The present invention also provides a two-dimensional material composite proton exchange membrane for hydrogen isotope separation, which is prepared according to the above preparation method.

[0022] The beneficial effects of the present invention are embodied in:

[0023] The present invention introduces two-dimensional material nanosheets, which may be graphene nanosheets or hexagonal boron nitride nanosheets, into a proton exchange membrane, and provides a method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation. The nanosheets are ultrasonically dispersed to obtain a dispersion liquid, which is doped into a polymer film-forming skeleton material, thereby improving the hydrogen isotope separation coefficient of the SPE electrolyzer and also enabling the composite proton membrane to have better proton conductivity and mechanical properties.

[0024] The two-dimensional material composite proton exchange membrane prepared by the present invention has good mechanical properties and hydrogen isotope screening ability. When applied to a proton exchange membrane (PEM) electrolyzer, it can significantly reduce the energy consumption of electrolytic separation of protium and tritium and improve the separation coefficient of protium and tritium. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the SEM image of graphene dispersion;

[0026] Figure 2 This is a physical picture of graphene composite proton exchange membrane;

[0027] Figure 3 This is the SEM image of boron nitride dispersion;

[0028] Figure 4 This is a physical picture of the boron nitride composite proton exchange membrane. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with embodiments:

[0030] The various raw materials and equipment used in the following examples, unless otherwise specified, are commercially available products known in the art. Among them, Nafion perfluorosulfonic acid (PFSA) polymer 5% dispersion (D2020) was purchased from DuPont, USA; graphene nanosheets (sheet diameter: 1-3 μm; thickness: 1-5 nm) were purchased from Nanjing Xianfeng Nanomaterial Technology Co., Ltd.; hexagonal boron nitride nanosheets (sheet diameter: 0.1-0.4 μm; purity: 98 wt%) were purchased from Nanjing Xianfeng Nanomaterial Technology Co., Ltd.; N,N-dimethylformamide (anhydrous grade) and N,N-dimethylacetamide (anhydrous grade) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0031] Example 1

[0032] Preparation of graphene composite proton exchange membrane

[0033] Weigh 3.0 g of Nafion perfluorosulfonic acid (PFSA) polymer 5% dispersion (D520) into a beaker, place in a 70°C drying oven to dry, evaporate the solvent to form a dry resin, add 10 ml of N,N-dimethylformamide (DMF) to the beaker, place on a 120°C constant temperature heating table to completely dissolve the polymer resin and evaporate the solvent until 2.0 g of PFSA polymer solution remains in the beaker;

[0034] Weigh 20 mg of graphene nanosheets into a reagent bottle, add 20 mL of N,N-dimethylformamide (DMF), tighten the bottle cap, and perform ultrasonic dispersion for 1 h. Let the obtained graphene dispersion stand for 4 h. Use a pipette to measure 4 mL of the above-prepared graphene dispersion and add it to the prepared PFSA type polymer solution. Ultrasonic dispersion for 30 min to mix the solution evenly, and then pour it into a glass mold placed on a 100 ° C flat heater and let it stand to form a film. The film forming area is 3.0 × 3.0 cm 2 After constant temperature heating for 2 hours, the flat heater was turned off, the mold was removed and cooled to room temperature, and then the formed graphene composite proton exchange membrane was taken out.

[0035] Figure 1 This is the SEM image of graphene nanosheets after ultrasonic dispersion in DMF for 1 hour. Figure 2 This is a physical picture of the graphene composite proton exchange membrane.

[0036] It can be seen that the graphene nanosheets after ultrasonic dispersion have good dispersion effect, and the sheet diameter is less than 3 μm, indicating that the graphene nanosheets are evenly dispersed in the proton exchange membrane. According to the method of the embodiment, the performance parameters of the graphene composite proton exchange membrane obtained are shown in Table 1.

[0037] Table 1 Performance parameters of graphene composite proton exchange membrane

[0038]

[0039] The results show that the present invention successfully prepared a proton exchange membrane with uniformly dispersed graphene nanosheets and good physical properties. When it was loaded into an SPE electrolyzer, a protium-tritium separation factor of 12.56 was obtained, which is more than three times the traditional separation factor. The graphene composite proton exchange membrane prepared by the present invention has important practical value for the efficient separation of hydrogen isotopes by SPE electrolysis.

[0040] Example 2

[0041] Preparation of Boron Nitride Composite Proton Exchange Membrane

[0042] Weigh 4.0 g of Nafion perfluorosulfonic acid (PFSA) polymer 5% dispersion (D520) into a beaker, place in an 80°C drying oven to dry, evaporate the solvent to form a dry resin, add 10 ml of N,N-dimethylacetamide (DMAc) to the beaker, place on a 120°C constant temperature heating table to completely dissolve the polymer resin and evaporate the solvent until 2.0 g of PFSA polymer solution remains in the beaker;

[0043] Weigh 10 mg of hexagonal boron nitride nanosheets into a reagent bottle, add 20 mL of N,N-dimethylacetamide (DMAc), tighten the bottle cap, and disperse it in an ice-water bath for 1 hour. After the ultrasound, let the obtained boron nitride dispersion stand for 4 hours, take the upper layer of the boron nitride stable dispersion in the reagent bottle, and record the volume as 18 mL. The remaining boron nitride nanosheets that have not been dispersed and settled at the bottom are dried and weighed to obtain a mass of 4.0 mg. The concentration of the stable boron nitride dispersion is calculated to be (10 mg-4.0 mg) / 18 mL = 0.33 mg / mL.

[0044] 3.0 mL of the prepared boron nitride stable dispersion was added to the prepared PFSA polymer solution, and the solution was uniformly mixed by ultrasonic dispersion for 30 min. Then, the solution was poured into a homemade glass mold placed on a 100°C flat heater and allowed to stand to form a film. The film-forming area was 3.5×3.5 cm 2 After constant temperature heating for about 3 hours, the flat heater was turned off, the mold was removed and cooled to room temperature, and then the formed boron nitride composite proton exchange membrane was taken out. The boron nitride content of the obtained proton membrane was 0.5 wt%.

[0045] Figure 3 This is the SEM image of hexagonal boron nitride nanosheets after ultrasonic dispersion in DMAc for 1 hour. Figure 4 This is a physical picture of the boron nitride composite proton exchange membrane.

[0046] It can be seen that the boron nitride nanosheets after ultrasonic dispersion are dispersed more evenly, and the particle size is between 0.1μm and 0.4μm. Figure 4 It is not difficult to find that the boron nitride nanosheets are dispersed relatively evenly in the proton exchange membrane. According to the method of this embodiment, the performance parameters of the boron nitride composite proton exchange membrane prepared are shown in Table 2.

[0047] Table 2 Performance parameters of boron nitride composite proton exchange membrane

[0048]

[0049]

[0050] The results show that the present invention successfully prepared a proton exchange membrane with uniformly dispersed boron nitride nanosheets and good proton transmission performance. When it was loaded into the SPE electrolyzer, a protium-tritium separation factor of up to 11.97 was obtained, which is more than 3 times the traditional separation factor. The boron nitride composite proton exchange membrane prepared by the present invention has important practical value for the efficient separation of hydrogen isotopes by SPE electrolysis.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation, characterized in that: The following steps are involved: (1) Preparation of PFSA polymer solution Taking a perfluorosulfonic acid polymer dispersion, evaporating the solvent to obtain a dry resin, then adding a non-protonic polar solvent, and heating at a constant temperature to completely dissolve the dry resin and partially volatilize the non-protonic polar solvent to obtain a PFSA polymer solution; the degree of volatility of the non-protonic polar solvent is such that the mass of the PFSA polymer solution is 0.5 to 2 times the amount of the perfluorosulfonic acid polymer dispersion; (2) Preparation of nanosheet dispersion Taking nanosheets, adding a non-protonic polar solvent, ultrasonically dispersing, and standing at room temperature to obtain a nanosheet dispersion; the nanosheets are graphene nanosheets or hexagonal boron nitride nanosheets; (3) Preparation of composite proton exchange membrane The nanosheet dispersion is added to the PFSA polymer solution, mixed evenly, poured into a mold under heating conditions and allowed to stand to form a film, and finally cooled to room temperature. The formed membrane is taken out to be the two-dimensional material composite proton exchange membrane for hydrogen isotope separation.

2. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1, characterized in that: In steps (1) and (2), the aprotic polar solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

3. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1 or 2, characterized in that: In step (1), the ratio of the non-protonic polar solvent to the perfluorosulfonic acid type polymer dispersion is 2 ml / g to 10 ml / g.

4. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1 or 2, characterized in that: In step (1), the temperature condition of constant temperature heating is 80-100°C.

5. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1, characterized in that: In step (2), the ratio of the aprotic polar solvent to the nanosheets is 1 ml / mg to 3 ml / mg.

6. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1 or 2, characterized in that: In step (3), the volume mass ratio of the nanosheet dispersion to the PFSA type polymer solution is 1 to 7:2 mL / g.

7. The method for preparing a two-dimensional material composite proton exchange membrane for hydrogen isotope separation according to claim 1 or 2, characterized in that: In step (3), the heating condition of the mold is 100° C., and the static film-forming time is 3 hours.

8. A two-dimensional material composite proton exchange membrane for hydrogen isotope separation prepared by the preparation method according to any one of claims 1 to 7.

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