Preparation method and application of nafion / graphene / pes liquid-nafion semi-hydrated composite membrane

Abstract

The application belongs to the technical field of graphene composite membrane preparation, and specifically discloses a preparation method and application of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane, wherein the preparation method comprises the following steps: attaching copper foil with graphene to a solid Nafion membrane, with the side of the copper foil with better graphene growth quality being in contact with the solid Nafion membrane; performing heat pressing treatment on the device; etching off the graphene on the other side of the copper foil that is not in contact with the Nafion membrane by using a dry etching method; removing the copper foil by using a wet etching method; drying the Nafion / graphene composite membrane at room temperature; immersing a PES porous membrane in liquid Nafion to obtain a PES-liquid Nafion sample; placing the sample in a water vapor environment to perform a semi-hydrated reaction and obtain a PES-liquid Nafion semi-hydrated membrane; and after drying at room temperature, attaching the Nafion / graphene composite membrane to the PES-liquid Nafion semi-hydrated membrane to obtain a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane. The semi-hydrated composite membrane prepared by the application can be stably electrolyzed in liquid water for a long time, can enrich heavy water, and can better protect the graphene.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of graphene composite membrane preparation, and particularly relates to a preparation method and application of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane. BACKGROUND

[0002] At present, the conventional preparation method of the Nafion / graphene composite membrane is a hot pressing method, that is, solid Nafion membrane and a copper foil or other substrate with graphene are combined at a solid-solid interface under the application of a certain pressure at about 140 DEG C, and then the copper is etched to leave a clean Nafion / graphene composite membrane. In order to protect the graphene, a layer of solid Nafion membrane is usually hot pressed on the graphene side. This method needs to apply a suitable pressure and has a high requirement for the flatness of the substrate. The composite membrane is mainly used for hydrogen isotope separation from the difference in electrical conductivity and the separation of gases. The surface of the solid Nafion membrane is flat, can be softened at high temperature, and has enhanced adhesion, so that the graphene can be successfully transferred by applying a certain pressure.

[0003] The existing Nafion / graphene composite membrane preparation technology is the combination of solid Nafion membrane and Nafion / graphene composite membrane at a solid-solid interface. Since a certain pressure is applied in the process, the uneven areas of the graphene are extruded and broken when combined with the Nafion membrane, thereby damaging the integrity of the graphene film. In addition, the Nafion membrane is firmly attached to the Nafion / graphene under the hot press, and is prone to bulging during long-term electrolysis in a liquid environment, which causes the breaking of the graphene. Moreover, the above-mentioned composite membrane is only used for hydrogen isotope separation from the difference in electrical conductivity and the separation of gases, and cannot be industrialized. It cannot achieve real hydrogen isotope separation in liquid water for a long time. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art, and provide a preparation method and application of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane. Liquid Nafion is semi-hydrated on PES to form a gas-permeable proton exchange membrane at a certain temperature by a semi-hydrated method, and then the membrane is attached to Nafion-graphene to form a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane with stable structure. The membrane can be used for hydrogen isotope separation in liquid water to achieve the purpose of enriching heavy water.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows: a preparation method of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane, comprising the following steps:

[0006] (1) Attach the copper foil with graphene grown thereon to a solid Nafion film, wherein the side of the copper foil with better graphene growth quality is in contact with the solid Nafion film;

[0007] (2) Perform heat pressing treatment on the solid device obtained in step (1);

[0008] (3) Etch off the graphene on the other side of the copper foil not in contact with the Nafion film by dry etching method for the device subjected to heat pressing treatment in step (2);

[0009] (4) Perform wet etching on the device subjected to dry etching treatment in step (3) to remove the copper foil therefrom;

[0010] (5) Dry the device with the copper foil removed in step (4) at room temperature to obtain a Nafion / graphene composite film;

[0011] (6) Soak a polyether sulfone (PES) porous film in liquid Nafion, so that the liquid Nafion is filled in the pores of the PES porous film to obtain a PES-liquid Nafion sample;

[0012] (7) Perform semi-hydrating reaction on the PES-liquid Nafion sample obtained in step (6) in a water vapor environment to obtain a PES-liquid Nafion semi-hydrated film;

[0013] (8) Dry the PES-liquid Nafion semi-hydrated film obtained in step (7) at room temperature and attach it to the Nafion / graphene composite film obtained in step (5) to obtain a Nafion / graphene / PES-liquid Nafion semi-hydrated composite film.

[0014] In a preferred embodiment of the present application, the heat pressing temperature in step (2) is 130-150°C, the heat pressing pressure is 250-350 kg, and the heat pressing time is 3-7 min.

[0015] In a preferred embodiment of the present application, the dry etching method in step (3) is oxygen plasma etching.

[0016] In a preferred embodiment of the present application, the dry etching conditions in step (3) are 70-90 sccm O2, 15-25 sccm Ar, 40-60 W power radio frequency 80-120 s.

[0017] In a preferred embodiment of the present application, the wet etching conditions in step (4) are 0.4-0.6 mol / L ammonium persulfate solution, etching for 2-4 h; after etching is completed, the device is placed in deionized water for cleaning and soaking to remove the ammonium persulfate on the surface of the device.

[0018] In a preferred embodiment of the present application, the semi-hydration reaction temperature in step (7) is 80-100 DEG C, and the semi-hydration reaction time is 5-15 min.

[0019] A preparation method of the Nafion / graphene / PES-liquid Nafion semi-hydration composite membrane.

[0020] In a preferred embodiment of the present application, the PES-liquid Nafion semi-hydration membrane, graphene and solid Nafion are sequentially arranged from top to bottom.

[0021] Application of the Nafion / graphene / PES-liquid Nafion semi-hydration composite membrane in hydrogen isotope separation in liquid water.

[0022] The preparation method of the composite membrane formed by fusing the polymer solution such as Nafion with the porous substrate and then adhering the two-dimensional material; the two-dimensional material refers to the two-dimensional layered materials such as graphene and its derivatives, transition metal sulfide, transition metal boride, black phosphorus, topological insulator, etc.; the porous substrate refers to all porous media with a porosity of 0-1; the polymer solution refers to all high molecular polymer solutions such as carbon chain polymer, hetero-chain polymer, element organic polymer, etc.; the stable porous substrate proton exchange membrane / two-dimensional material / solid Nafion composite membrane structure formed by fusing the porous substrate and the solution and then combining with the two-dimensional material; the liquid Nafion is semi-hydrated to form a flat composite membrane with the porous membrane, which has the dual effects of proton exchange membrane and porous membrane; the two-dimensional material composite membrane can actually separate hydrogen isotopes by electrolysis in liquid water for a long time.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application adopts the method of semi-hydrating the liquid Nafion on PES to form a gas-permeable proton exchange membrane, which is adhered to the Nafion / graphene composite membrane, thereby protecting the graphene and allowing the gas bubbles generated by electrolysis in liquid water to be permeable, ensuring the effective permeation of gas and proton conduction during the electrolysis process of the graphene side, and without damaging the graphene, and the prepared Nafion / graphene / PES-liquid Nafion semi-hydration composite membrane structure is stable;

[0025] 2. The present application solves the problem of swelling and damage of graphene caused by the bulging of the composite membrane formed by hot pressing the Nafion / graphene membrane and the solid Nafion in the process of long-time electrolysis of hydrogen isotopes in liquid water;

[0026] 3. The Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane prepared by the method can be electrolyzed in liquid water for a long time and remains stable, and can be used for heavy water enrichment. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a structural schematic diagram of the Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane of the present application;

[0028] Figure 2 FIG. 2 is a surface SEM photograph of the Nafion / graphene composite membrane of the present application;

[0029] Figure 3 FIG. 3 is a Raman spectrum test result of the Nafion / graphene composite membrane of the present application;

[0030] Figure 4 FIG. 4 is a comparison of the gas permeability of solid Nafion, liquid Nafion, PES semi-hydrated and PES;

[0031] Figure 5 FIG. 5 is a comparison of the proton conductivity of solid Nafion, liquid Nafion, PES semi-hydrated and PES;

[0032] Figure 6 FIG. 6 is the stability of the composite membrane in long-time electrolysis;

[0033] Figure 7 FIG. 7 is a surface SEM photograph of the graphene membrane device after electrolysis. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application is described in more detail below in combination with the drawings and specific embodiments, but the protection scope of the present application is not limited to these embodiments.

[0035] A preparation method of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane, comprising the following steps:

[0036] (1) attaching a copper foil with graphene grown on the upper and lower surfaces to a solid Nafion membrane, wherein the side with better graphene growth quality on the copper foil is in contact with the solid Nafion membrane;

[0037] (2) performing heat pressing treatment on the device obtained in step (1);

[0038] (3) etching off the graphene on the other side of the copper foil not in contact with the Nafion membrane by using a dry etching method on the device subjected to heat pressing treatment in step (2);

[0039] (4) wet etching the device after the dry etching treatment in step (3) to remove the copper foil therein;

[0040] (5) drying the device after the removal of the copper foil in step (4) at room temperature to obtain a Nafion / graphene composite film;

[0041] (6) immersing a polyether sulfone (PES) porous film in liquid Nafion so that the liquid Nafion fills the pores of the PES porous film to obtain a PES-liquid Nafion sample;

[0042] (7) placing the PES-liquid Nafion sample obtained in step (6) in a water vapor environment to perform a hemihydrate reaction to obtain a PES-liquid Nafion hemihydrate film;

[0043] (8) drying the PES-liquid Nafion hemihydrate film obtained in step (7) at room temperature and then laminating the Nafion / graphene composite film obtained in step (5) to obtain a Nafion / graphene / PES-liquid Nafion hemihydrate composite film.

[0044] In step (2), the hot-pressing temperature is 130-150℃, the hot-pressing pressure is 250-350kg, and the hot-pressing time is 3-7min.

[0045] In step (3), the dry etching method is oxygen plasma etching.

[0046] In step (3), the dry etching conditions are 70-90sccm O2, 15-25sccm Ar atmosphere, 40-60W power radio frequency 80-120s.

[0047] In step (4), the wet etching conditions are 0.4-0.6mol / L ammonium persulfate solution, etching for 2-4h; after etching, the device is placed in deionized water for cleaning and soaking to remove the ammonium persulfate on the surface of the device.

[0048] In step (7), the hemihydrate reaction temperature is 80-100℃, and the hemihydrate reaction time is 5-15min.

[0049] A Nafion / graphene / PES-liquid Nafion hemihydrate composite film prepared by the above method.

[0050] The Nafion / graphene / PES-liquid Nafion hemihydrate composite film comprises, from top to bottom, a PES-liquid Nafion hemihydrate film, graphene, and solid Nafion.

[0051] Use of a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane in hydrogen isotope separation in liquid water.

[0052] Example 1

[0053] A Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane, a schematic diagram of the structure thereof is as Figure 1 , and is prepared by the following preparation method:

[0054] (1) placing a solid Nafion membrane on a PET back plate, and gently pasting a copper foil with graphene grown on the upper and lower surfaces on the solid Nafion membrane, with the side of the graphene grown on the copper foil having a better mass contacting the solid Nafion membrane;

[0055] (2) placing the device obtained in step (1) on a hot press, heating to 140 DEG C, and hot pressing under a pressure of 300 kg for 5 min;

[0056] (3) etching off the graphene on the other side of the copper foil not contacting the Nafion membrane from the device subjected to the hot pressing treatment in step (2) by using an oxygen plasma etching method; the etching conditions are 80 sccm O2, 20 sccm Ar atmosphere, 50 W power radio frequency for 100 s;

[0057] (4) wet etching the device subjected to the dry etching treatment in step (3) by inversely placing it in an ammonium persulfate solution with a concentration of 0.5 mol / L, and after 3 h, the copper foil is completely etched, and it is placed in deionized water for washing twice and soaking for 30 min to remove the ammonium persulfate on the surface of the device;

[0058] (5) drying the device after removing the copper foil in step (4) at room temperature to obtain a Nafion / graphene composite membrane;

[0059] (6) immersing a polyether sulfone (PES) porous membrane in liquid Nafion, so that the liquid Nafion is filled in the pores of the PES porous membrane, to obtain a PES-liquid Nafion sample;

[0060] (7) placing the PES-liquid Nafion sample obtained in step (6) in a water vapor environment at 90 DEG C, and reacting for 10 min to perform a semi-hydrated reaction to obtain a PES-liquid Nafion semi-hydrated membrane;

[0061] (8) after drying the PES-liquid Nafion semi-hydrated membrane obtained in step (7) at room temperature, pasting it with the Nafion / graphene composite membrane obtained in step (5), to finally obtain a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane.

[0062] The Nafion / graphene composite film obtained in step (5) was observed using a scanning electron microscope (SEM), and the results are as follows: Figure 2 As shown, from Figure 2 It can be seen that the transferred graphene is intact with no obvious defects, and the graphene coverage is over 99%. Raman spectroscopy was performed on the Nafion / graphene composite film, and the Raman spectral results are as follows: Figure 3 As shown in the figure, at 2690cm -1 The presence of a distinct 2D peak in graphene indicates that graphene was successfully transferred onto the Nafion film. Figure 4 As shown, the air permeability of solid Nafion membranes, semi-hydrated membranes filled with liquid Nafion in PES, and single PES membranes measured under a helium leak detector shows that the air permeability of the semi-hydrated membrane filled with liquid Nafion in PES is six orders of magnitude greater than that of the solid Nafion membrane. Figure 5 As shown, proton conductivity was tested on solid Nafion membranes, semi-hydrated membranes filled with liquid Nafion in PES, and single PES membranes. The results show that the semi-hydrated membrane filled with liquid Nafion in PES has similar proton conductivity to the solid Nafion membrane. Figure 6 As shown, the Nafion / graphene / PES-liquid Nafion hemihydrate composite membrane was electrolyzed in a PEM electrolyzer, and the composite membrane was able to operate stably for a long time. Figure 7 As shown, the surface of graphene after electrolysis in a PEM electrolytic cell was characterized by SEM of the Nafion / graphene / PES-liquid Nafion semi-hydrated composite film. The graphene remained on the Nafion film after such a long period of electrolysis, indicating that the semi-hydrated film filled with liquid Nafion in PES has a protective effect on graphene.

[0063] Liquid Nafion is infiltrated into a porous PES membrane and semi-hydrated to form a semi-crosslinked solid Nafion, which fills the porous PES membrane, resulting in a flat PES-liquid Nafion semi-hydrated composite membrane. This composite membrane, when bonded to Nafion / graphene, can protect the atomic-level graphene. The PES porous membrane serves as the filling substrate for the Nafion solution, and the semi-hydrated PES-liquid Nafion semi-hydrated composite membrane exhibits proton conductivity similar to that of a solid Nafion membrane. Furthermore, the air permeability of the PES porous membrane as the filling substrate for the Nafion solution is comparable to that of the porous membrane itself. The prepared composite membrane can be combined with a PEM electrolyzer to achieve true electrolysis in liquid water for over 600 hours, and remains highly stable.

[0064] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane, characterized in that, It comprises the following steps: (1) Attach the copper foil with graphene grown thereon to a solid Nafion film, with the side of the copper foil on which the graphene is grown better in quality being in contact with the solid Nafion film; (2) Perform heat pressing treatment on the device obtained in step (1); (3) Etch away the graphene on the other side of the copper foil not in contact with the Nafion film by dry etching; (4) Perform wet etching on the device obtained after dry etching in step (3) to remove the copper foil therefrom; (5) Dry the device obtained after removal of the copper foil in step (4) at room temperature to obtain a Nafion / graphene composite film; (6) Soak a PES porous film in liquid Nafion so that the liquid Nafion fills the pores of the PES porous film to obtain a PES-liquid Nafion sample; (7) Perform a hemihydrate reaction on the PES-liquid Nafion sample obtained in step (6) in a water vapor environment to obtain a PES-liquid Nafion hemihydrate film; (8) Dry the PES-liquid Nafion hemihydrate film obtained in step (7) at room temperature and attach it to the Nafion / graphene composite film obtained in step (5) to obtain a Nafion / graphene / PES-liquid Nafion hemihydrate composite film.

2. The method for preparing Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane according to claim 1, characterized in that, The heat pressing temperature in step (2) is 130-150℃, the heat pressing pressure is 250-350kg, and the heat pressing time is 3-7min.

3. The method for preparing the Nafion / graphene / PES-liquid Nafion hemihydrate composite membrane as described in claim 1, characterized in that, The dry etching method in step (3) is oxygen plasma etching.

4. The method for preparing the Nafion / graphene / PES-liquid Nafion hemihydrate composite membrane as described in claim 1, characterized in that, The dry etching conditions in step (3) are 70-90sccm O2, 15-25sccm Ar, 40-60W power radio frequency, and 80-120s.

5. The method of claim 1, wherein the Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane is prepared by the steps of: The wet etching conditions in step (4) are 0.4-0.6mol / L ammonium persulfate solution, etching for 2-4h; After etching, the device is cleaned and soaked in deionized water to remove ammonium persulfate on the surface of the device.

6. The method of claim 1, wherein the Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane is prepared by the steps of: The hemihydrate reaction temperature in step (7) is 80-100℃, and the hemihydrate reaction time is 5-15min.

7. A Nafion / graphene / PES-liquid Nafion hemihydrate composite film prepared by the method of any one of claims 1-6.

8. A Nafion / graphene / PES-liquid Nafion semi-hydrated composite membrane as claimed in claim 7, characterized in that, From top to bottom, it comprises a PES-liquid Nafion hemihydrate film, graphene, and a solid Nafion.

9. Use of the Nafion / graphene / PES-liquid Nafion hemihydrate composite film of claim 7 for hydrogen isotope separation in liquid water.

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