A graphene oxide composite material, its preparation method and application

Abstract

The present invention discloses a graphene oxide composite material, a preparation method thereof and an application. The preparation method includes the following steps: using graphite as the anode and a platinum sheet as the cathode, preparing intercalated graphite by an electrochemical intercalation method; using the intercalated graphite as the anode and a platinum sheet as the cathode, and using Eaton's reagent as the electrolyte, preparing a graphene oxide dispersion by an electrochemical oxidation and exfoliation method; mixing the graphene oxide dispersion and a polymer monomer uniformly, and carrying out in-situ polymerization on the obtained reaction solution to prepare the graphene oxide composite material. The method of the present invention can fully exert the excellent properties of GO in the composite material, and significantly improve the mechanical properties and electrochemical properties of the composite material. This process omits a large number of cumbersome processes such as washing and drying of graphene oxide, enables graphene oxide to always maintain a few-layer or even single-layer morphology so as to achieve the best modification effect, and avoids the problem of agglomeration of graphene oxide caused by physical blending, which reduces the performance of the composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene oxide composite materials, and in particular to a graphene oxide composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Graphene oxide (GO) is a derivative of graphene, with rich oxygen-containing functional groups and a two-dimensional layered structure. Due to its remarkable chemical stability, mechanical strength, large surface area, and intrinsic electron insulation properties, it has become a material for functional modification and mechanical property enhancement of various polymer materials. GO is formed by oxidizing and exfoliating natural graphite, and the large-scale preparation methods mainly include chemical oxidation method and electrochemical oxidation method. The former requires a large amount of strong oxidants such as concentrated H2SO4, HNO3, and KMnO4. The whole process has a fast oxidation rate, violent reaction, and will produce a large amount of gas and water pollution. The latter is a green, efficient, and controllable method for preparing GO, which has received wide attention in recent years. There have been reports on successfully electrolyzing GO in various acid solutions and salt solutions. However, most of the reported electrochemical oxidation methods for preparing GO are completed in an aqueous solution system, while polymers are mostly synthesized in a non-aqueous environment, which limits its wider application.

[0003] Currently, the preparation methods of GO / polymer composites are mainly blending processing and chemical grafting. However, directly adding GO powder into the polymer system for physical blending cannot uniformly disperse GO nanosheets at the nanoscale, and the van der Waals force between molecules makes GO in an aggregated state. Moreover, the preparation of conventional GO-based composites directly uses GO powder, making it difficult to achieve a good dispersion effect of GO. For example, Chinese Patent CN115133088A discloses a preparation method of a GO / polymer composite material. This patent uses polymer sulfonated polybenzothiazole as the matrix and prepares a composite proton exchange membrane with functionalized inorganic fillers by introducing sulfonated graphene oxide. Chinese Patent CN114914505A discloses a preparation method of applying graphene oxide to a composite proton exchange membrane. This patent mixes graphene oxide, imidazole-based ionic liquid, and organic solvent to obtain a dispersion liquid, directly mixes the dispersion liquid with perfluorosulfonic acid resin to prepare a mixture, and heat-treats the mixture to form a membrane to obtain a composite proton exchange membrane. Chinese Patent CN111261914A discloses a graphene oxide polymer composite proton exchange membrane, a preparation method thereof, and an application. This patent adds graphene oxide modified by adenosine triphosphate into the polymer resin and prepares a composite proton exchange membrane through physical blending. In the above preparation methods, the obtained composite proton exchange membranes directly mix and physically disperse graphene oxide and other materials and then add them to the polymer material during the preparation process. Existing research shows that graphene oxide in the composite material prepared by this method is extremely easy to agglomerate in the composite material, thus unable to fully exhibit its excellent physical and chemical properties.

[0004] Therefore, if a GO dispersion can be directly prepared in a polymer organic synthesis solvent and the dispersion can be directly used for in-situ synthesis of polymers, the steps such as purification and drying in the GO preparation process can be omitted, the re-agglomeration of GO during the purification and drying process can be avoided, the possibility of GO agglomeration in polymers can be greatly reduced, and it is expected to become a new method for preparing GO / polymer composites. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies, and propose a graphene oxide composite material, its preparation method and application, so as to solve the technical problem that graphene oxide is prone to agglomeration when directly physically mixing graphene oxide with polymers in the prior art.

[0006] The first aspect of the present invention provides a preparation method of a graphene oxide composite material, including the following steps:

[0007] Using graphite as the anode and a platinum sheet as the cathode, intercalated graphite is prepared by an electrochemical intercalation method;

[0008] Using the intercalated graphite as the anode and a platinum sheet as the cathode, and using Eaton's reagent as the electrolyte, a graphene oxide dispersion is prepared by an electrochemical oxidation and exfoliation method;

[0009] The graphene oxide dispersion and the polymer monomer are mixed evenly, and the obtained reaction solution is in-situ polymerized to prepare a graphene oxide composite material.

[0010] The second aspect of the present invention provides a graphene oxide composite material, which is obtained by the preparation method of the graphene oxide composite material provided in the first aspect of the present invention.

[0011] The third aspect of the present invention provides an application of a graphene oxide composite material, and the graphene oxide composite material is used as a proton exchange membrane of a fuel cell.

[0012] Compared with the prior art, the beneficial effects of the present invention include:

[0013] The present invention for the first time uses an electrochemical exfoliation method to prepare a GO dispersion by oxidation in Eaton's reagent, and then directly in-situ polymerizes with polymer monomers to prepare a graphene oxide composite material, so that the excellent properties of GO are fully exerted in the composite material, significantly improving the mechanical properties and electrochemical properties of the composite material. This process omits a large number of cumbersome processes such as washing and drying of graphene oxide, enables graphene oxide to always maintain a few-layer or even single-layer morphology to achieve the best modification effect, avoids the problem of graphene oxide agglomeration caused by physical blending, and reduces the performance of the composite material, providing more ideas for the preparation of graphene oxide and graphene oxide-based composite materials, and providing a new method for dispersing few-layer GO in polymer materials. Brief Description of the Drawings

[0014] Figure 1 These are cross-sectional SEM images of the composite membranes of ABPBI-0.5EGO (Example 1), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) prepared by the present invention;

[0015] Figure 2 These are XRD patterns of the composite membranes of ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) prepared by the present invention;

[0016] Figure 3 These are tensile curves of the composite membranes of ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) prepared by the present invention;

[0017] Figure 4 These are the PA doping levels and area swelling rates of the composite membranes of ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) prepared by the present invention;

[0018] Figure 5 These are the proton conductivities of the composite membranes of ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) prepared by the present invention. Detailed implementation manners

[0019] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The first aspect of the present invention provides a method for preparing a graphene oxide composite material, comprising the following steps:

[0021] S1. Using graphite (GP) as the anode and a platinum sheet as the cathode, intercalated graphite (GICP) is prepared by an electrochemical intercalation method;

[0022] S2. Using intercalated graphite (GICP) as the anode, a platinum sheet as the cathode, and Eaton's reagent as the electrolyte, an electrochemical method is used to oxidatively exfoliate and prepare a graphene oxide (GO) dispersion;

[0023] S3. The graphene oxide dispersion and polymer monomers are mixed evenly, and the obtained reaction solution is subjected to in-situ polymerization to prepare a graphene oxide composite material.

[0024] Eaton's reagent is usually a mixed solution composed of phosphorus pentoxide (P2O5) and methanesulfonic acid (MSA). This reagent is a good solvent for a variety of organic synthesis substances and is commonly used to catalyze the ring-closing reaction in acylation. It is widely used in the preparation of polybenzimidazole and its derivatives in polymer materials. The present invention creatively proposes to prepare an Eaton's reagent dispersion of GO by anodic electrochemical oxidation and exfoliation of graphite in Eaton's reagent, and then directly add polymer monomers (such as 3,4-diaminobenzoic acid (DABA), etc.) to the dispersion for in-situ polymerization, successfully preparing a highly dispersed polymer-grafted graphene oxide composite material (such as poly(2,5-benzimidazole)-grafted graphene oxide (ABPBI-EGO) composite material), avoiding the problem of graphene oxide aggregation caused by physical blending and reducing the performance of the composite material. The present invention greatly exerts the performance of the material itself, has a simple preparation process, simple operation, and the prepared composite material has excellent mechanical properties and electrochemical properties.

[0025] In this embodiment, in step S1, the anode is graphite paper.

[0026] In this embodiment, in step S1, the electrolyte is concentrated sulfuric acid, the voltage is 3 - 7V, further 5V, the treatment time is 3 - 15min, further 10min.

[0027] In this embodiment, in step S2, the voltage is 7 - 15V, further 10V, the treatment time is 10 - 50min, further 30min.

[0028] In this embodiment, in step S3, the polymer monomer is 3,4-diaminobenzoic acid (DABA).

[0029] In this embodiment, in step S3, the concentration of the polymer monomer in the reaction solution is 0.1 - 0.2g / ml, further 0.15g / ml; the mass ratio of graphene oxide to the polymer monomer is (0.001 - 0.01):1, further (0.001 - 0.005):1, and even further 0.005:1.

[0030] In this embodiment, in step S3, during the process of uniformly mixing the graphene oxide dispersion and the polymer monomer, an Eaton's reagent can be further added. Here, it should be noted that the present invention does not limit whether the Eaton's reagent needs to be further added during this process, and those skilled in the art can make a choice according to the actual situation.

[0031] In this embodiment, the graphene oxide dispersion and the polymer monomer are uniformly mixed by ultrasonic means. Further, the ultrasonic time is 2 - 4 h.

[0032] In this embodiment, the in-situ polymerization reaction is carried out under a nitrogen atmosphere, the polymerization temperature is 120 - 180 °C, further 150 °C, and the polymerization time is 1 - 5 h, further 2.5 h.

[0033] In this embodiment, after the in-situ polymerization reaction is completed, the polymer needs to be washed and dried.

[0034] In some more specific embodiments of the present invention, after the polymerization reaction is completed, the polymer is poured into deionized water to obtain a fibrous polymer, which is then boiled in a NaOH solution with a mass fraction of 5% - 15% for 2 - 5 h, and then washed with deionized water until the pH is neutral and dried.

[0035] In some more specific embodiments of the present invention, the preparation process of the above graphene oxide composite material further includes: forming a composite proton exchange membrane from the above dried polymer by a casting method. During this process, the solvent can be methanesulfonic acid, etc.

[0036] The second aspect of the present invention provides a graphene oxide composite material, which is obtained by the preparation method of the graphene oxide composite material provided in the first aspect of the present invention.

[0037] The third aspect of the present invention provides an application of the graphene oxide composite material, and the graphene oxide composite material is used as a proton exchange membrane for a fuel cell.

[0038] Example 1

[0039] Preparation of ABPBI-0.5EGO composite proton exchange membrane by in-situ method:

[0040] (1) Cut a clean and dry graphite paper (GP, 0.05 mm) into a size of 6×3 cm 2 and immerse it in an electrolytic cell containing 20 ml of concentrated H2SO4 solution. Using GP as the anode and a platinum sheet as the cathode, connect them to the positive and negative electrodes of a DC power supply respectively. Pretreat it for 10 min at 5 V to obtain intercalated graphite (GICP).

[0041] (2) 20 mL of methanesulfonic acid (MSA) was taken and 6 g of phosphorus pentoxide (P2O5) was added to prepare Eaton's reagent, which was then added to the electrolytic cell. The pretreated GICP was inserted into Eaton's reagent. Using GICP as the anode and Pt as the cathode, they were respectively connected to the positive and negative electrodes of a DC power supply. The voltage was controlled at 10 V and electrolysis was carried out for 30 min to obtain a suspension of GO in Eaton's reagent, and the solid content was measured to be 1.5 mg / ml. -1 。

[0042] (3) 10 mL of the Eaton's reagent dispersion of GO was taken in a 100 mL three-necked flask, 3 g of DABA and 10 mL of pure Eaton's reagent were added. After ultrasonic treatment for 2 h, the suspension was reacted at 150 °C for 2.5 h under a nitrogen protection atmosphere. The resulting viscous polymer was slowly poured into 400 mL of deionized water to obtain a fibrous polymer, which was boiled in 10% NaOH solution at 100 °C for 4 h to remove residual MSA, and then washed with deionized water until the pH was neutral. After drying, 0.4 g of the polymer was weighed, added to 20 mL of MSA solution, and then the ABPBI-0.5EGO composite proton exchange membrane was prepared by the casting method.

[0043] Example 2

[0044] Compared with Example 1, the difference is only that in step (3), 2 mL of the Eaton's reagent dispersion of GO was taken in a 100 mL three-necked flask, and 3 g of DABA and 18 mL of pure Eaton's reagent were added. After the polymer was washed and dried, it was dissolved in MSA and then the ABPBI-0.1EGO composite proton exchange membrane was prepared by the casting method.

[0045] Example 3

[0046] Compared with Example 1, the difference is only that in step (3), 20 mL of the Eaton's reagent dispersion of GO was taken in a 100 mL three-necked flask, and 3 g of DABA was added. After the polymer was washed and dried, it was dissolved in MSA and then the ABPBI-1.0EGO composite proton exchange membrane was prepared by the casting method.

[0047] Control Example 1

[0048] 15 mg of GO powder was taken in a 100 mL three-necked flask, 3 g of DABA and 20 mL of pure Eaton's reagent were added. After ultrasonic treatment for 2 h, the suspension was reacted at 150 °C for 2.5 h under a nitrogen protection atmosphere. The resulting viscous polymer was slowly poured into 400 mL of deionized water to obtain a fibrous polymer, which was boiled in 10% NaOH solution at 100 °C for 4 h to remove residual MSA, and then washed with deionized water until the pH was neutral. After drying, 0.4 g of the polymer was weighed, dissolved in 20 mL of MSA, and then the ABPBI-0.5GO composite proton exchange membrane was prepared by the casting method.

[0049] Control Example 2

[0050] 3 g of DABA and 20 ml of pure Eaton's reagent were added to a 100 ml three-necked flask. After ultrasonic treatment for 2 h, the suspension was reacted at a temperature of 150 °C for 2.5 h under a nitrogen protection atmosphere. The resulting viscous polymer was slowly poured into 400 ml of deionized water to obtain a fibrous polymer, which was boiled in a 10% NaOH solution at 100 °C for 4 h to remove the residual MSA, and then washed with deionized water until the pH was neutral. After drying, 0.4 g of the polymer was weighed, dissolved in 20 ml of MSA, and an ABPBI proton exchange membrane was prepared by the casting method.

[0051] Test Group

[0052] Tensile property test:

[0053] The dumbbell-shaped film material was subjected to a tensile test at room temperature using a CMT4204 type thin film tensile testing machine. The dimensions of the specimen were 10 × 2.5 mm, and the tensile rate was 5 mm / min, and the tensile data were measured.

[0054] Phosphoric acid doping level and area swelling rate test:

[0055] The PA doping levels (PA DLs) of the ABPBI, ABPBI-EGO, and ABPBI-GO composite membranes were estimated based on the weight changes before and after PA doping. After all the membranes were dried in a vacuum oven at 110 °C for 12 hours, their respective weights W undoped and their areas S were calculated from their dimensions in the x and y directions undoped (S = xy). Then the membranes were immersed in a 60% concentration PA solution for 3 days, and the PA solution was oscillated irregularly to allow PA to fully penetrate into the membranes. After the weight of the membranes doped with PA reached a constant value, the membranes doped with PA were rinsed with deionized water to remove the free PA on the membrane surface, and their dimensions were measured again to calculate the area S doped . Then they were dried in a vacuum drying oven at 110 °C for 24 h, and their respective weights were recorded as W doped .

[0056]

[0057]

[0058] Proton conductivity test:

[0059] The AC impedance spectra from 4 MHz to 1 Hz were measured by the two-electrode method. Specifically, the measurements were carried out in an electrochemical workstation and a thermostatic and humidity-controlled chamber, with the temperature range controlled at 120 - 180 °C and the humidity at 0%. The proton conductivity calculation formula is as follows:

[0060]

[0061] Among them, σ, d, R, and A represent proton conductivity (S / cm), the distance between the two electrodes, i.e., the membrane thickness (cm), the resistance of the membrane (Ω), and the contact area between the membrane and the two electrodes (cm 2 ).

[0062] Please refer to Figure 1 , Figure 1 which is the cross-sectional SEM image of the ABPBI-0.5EGO (Example 1), ABPBI-0.5GO (Control Example 1), and ABPBI (Control Example 2) composite membranes prepared by the present invention. It can be seen from Figure 1 that in the cross-section of the ABPBI-0.5EGO membrane prepared by the in-situ synthesis method, GO still maintains a three-dimensional wrinkled morphology, indicating that GO still remains in a few-layer or even single-layer state and is uniformly distributed. In the ABPBI-GO composite membrane prepared by the traditional method of directly adding GO powder, severe agglomeration of GO occurs, and the original wrinkled morphology is no longer retained. There is no wrinkled GO in the cross-sectional morphology of the pure ABPBI proton exchange membrane.

[0063] Please refer to Figure 2 , Figure 2 which is the XRD pattern of the ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Control Example 1), and ABPBI (Control Example 2) composite membranes prepared by the present invention. The XRD results show the influence of the addition of Eaton's reagent GO and powder GO on the crystal structure of the composite membrane. On the XRD pattern of the composite membrane, the relatively broad diffraction peak at 26.55° is caused by the different stacking forms of ABPBI molecular chains, indicating that ABPBI has a quasi-crystalline structure. With the addition of the Eaton's reagent GO dispersion and GO powder, the diffraction peak of ABPBI at 26.55° gradually shifts to the left, and the peak intensity decreases. The left shift of the peak position means an increase in the distance between two parallel benzimidazole chains, which helps to fix more phosphoric acid molecules and thus improve the electrochemical performance. However, while the diffraction peak of the ABPBI-GO composite membrane shifts to the left, the peak intensity decreases significantly, indicating that the regular arrangement structure of ABPBI has been destroyed by the agglomerated GO, and the further increase in the molecular chain spacing also means that PA is easily lost, which is not conducive to the fixation of phosphoric acid molecules.

[0064] Please refer to Figure 3 , Figure 3Tensile curves of the ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) composite membranes prepared by the present invention. Good mechanical properties are the prerequisite and guarantee for the normal use of proton exchange membranes. Through Figure 3 It can be seen that with the addition of Eaton reagent GO, the ABPBI-0.5EGO has the highest tensile strength, reaching 143.2 MPa. This is because the large specific surface area of few-layer GO acts as an adhesive in the ABPBI matrix, enhancing its mechanical properties. When GO powder is added, the GO in ABPBI-GO easily agglomerates, resulting in discontinuous polymer phases and reducing the mechanical properties of the polymer.

[0065] Please refer to Figure 4 , Figure 4 PA doping levels and area swelling rates of the ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) composite membranes prepared by the present invention. Through Figure 4 It can be seen that due to the uniform dispersion of few-layer GO prepared by the in-situ strategy in the ABPBI matrix, GO retains the characteristics of a large specific surface area and high mechanical strength in the ABPBI matrix, making the ABPBI-0.5EGO composite membrane have the highest phosphoric acid doping level and the lowest swelling rate, showing the best phosphoric acid retention ability and dimensional stability of ABPBI-0.5EGO.

[0066] Please refer to Figure 5 , Figure 5 Proton conductivities of the ABPBI-0.5EGO (Example 1), ABPBI-0.1EGO (Example 2), ABPBI-1.0EGO (Example 3), ABPBI-0.5GO (Comparative Example 1), and ABPBI (Comparative Example 2) composite membranes prepared by the present invention. The electrochemical performance of proton exchange membranes is closely related to the PA retention ability. Through Figure 5 It can be seen that the proton conductivities of the ABPBI-EGO composite membranes are greatly improved compared with those of the ABPBI and ABPBI-0.5GO composite membranes. Among them, the highest conductivity of ABPBI-0.5EGO under anhydrous conditions at 180 °C is 47.02 mS cm -1 . On the one hand, it is because the uniformly dispersed GO absorbs more PA in the composite membrane, providing more proton transport carriers; on the other hand, few-layer GO can conduct protons faster, creating a new proton conduction channel.

[0067] The specific embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A preparation method of a graphene oxide composite material, characterized in that, Including the following steps: Using graphite as the anode and a platinum sheet as the cathode, intercalated graphite is prepared by an electrochemical intercalation method; Using the intercalated graphite as the anode and a platinum sheet as the cathode, and using Eaton's reagent as the electrolyte, graphene oxide dispersion is prepared by an electrochemical oxidation exfoliation method; The graphene oxide dispersion and the polymer monomer are mixed evenly, and the obtained reaction solution is subjected to in-situ polymerization to prepare a graphene oxide composite material; wherein, The polymer monomer is 3,4-diaminobenzoic acid; The mass ratio of the graphene oxide to the polymer monomer is (0.001~0.01):

1.

2. The preparation method of the graphene oxide composite material according to claim 1, characterized in that, During the process of preparing the intercalated graphite by the electrochemical intercalation method, the electrolyte is concentrated sulfuric acid, the voltage is 3 - 7 V, and the treatment time is 3 - 15 min; during the process of preparing the graphene oxide dispersion by the electrochemical oxidation exfoliation method, the voltage is 7 - 15 V, and the treatment time is 10 - 50 min.

3. The preparation method of the graphene oxide composite material according to claim 1, characterized in that, The concentration of the polymer monomer in the reaction solution is 0.1~0.2 g / ml.

4. The preparation method of the graphene oxide composite material according to claim 1, wherein The mass ratio of the graphene oxide to the polymer monomer is (0.001~0.005):

1.

5. The preparation method of the graphene oxide composite material according to claim 1, characterized in that, The in-situ polymerization reaction is carried out under a nitrogen atmosphere, the polymerization temperature is 120~180 °C, and the polymerization time is 1~5 h.

6. The preparation method of the graphene oxide composite material according to claim 1, characterized in that, After the polymerization reaction is completed, the polymer is poured into deionized water to obtain a fibrous polymer, which is then boiled in a NaOH solution with a mass fraction of 5%~15% for 2~5 h, and then washed with deionized water until the pH is neutral and dried.

7. The preparation method of the graphene oxide composite material according to claim 6, wherein, The preparation process of the graphene oxide composite material further includes: forming a composite proton exchange membrane from the above-mentioned dried polymer by a casting method.

8. A graphene oxide composite material, characterized in that, The graphene oxide composite material is obtained by the preparation method of the graphene oxide composite material according to any one of claims 1~7.

9. An application of the graphene oxide composite material as described in claim 8, characterized in that, The graphene oxide composite material is used as a proton exchange membrane for a fuel cell.

Images