An amphiphilic three-dimensional graphene film material and a preparation method thereof

Abstract

The present invention relates to the technical field of photothermal conversion materials, and particularly relates to an amphiphilic three-dimensional graphene thin film material and a preparation method thereof. The preparation method comprises the following steps: mixing graphene oxide with solvent A to prepare a graphene oxide dispersion; adding the graphene oxide dispersion on the surface of solvent B to carry out an interfacial solvothermal reaction to obtain a gel-like graphene thin film; carrying out water replacement treatment on the gel-like graphene thin film and then freeze-drying to obtain the amphiphilic three-dimensional graphene thin film material. The preparation method provided by the present invention is convenient and reliable. Using graphene oxide as a raw material, an amphiphilic three-dimensional graphene thin film material with both hydrophilic and hydrophobic properties can be obtained through an interfacial solvothermal method. Compared with traditional three-dimensional graphene materials, the three-dimensional graphene thin film material obtained in the present invention has both hydrophilicity and hydrophobicity, that is, it has amphiphilic characteristics, and can also achieve a solar-steam conversion efficiency of >90%.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal conversion materials, and particularly to an amphiphilic three-dimensional graphene thin film material and a preparation method thereof. Background Art

[0002] Solar-driven interfacial water evaporation is a promising method to solve the shortage of drinking water resources. Developing efficient solar photothermal conversion materials and devices is the key to realizing practical interfacial water evaporation. The sunlight-steam conversion efficiency is an important index for evaluating the performance of solar photothermal conversion materials. A material structure with amphiphilicity (i.e., both hydrophilic and lipophilic) can greatly improve the sunlight-vapor conversion efficiency. Generally, the bottom of the amphiphilic structure is a hydrophilic water absorption layer, mainly used for water absorption and desalination, and the top is a hydrophobic light absorption layer mainly used for converting light into heat energy and facilitating the escape of water vapor. Graphene-based photothermal conversion materials have excellent sunlight absorption performance, a large specific surface area, and a light weight, etc., so they have broad application prospects in solar-driven water evaporation, sewage purification, seawater desalination, etc. At present, the graphene-based materials applied to solar interfacial water evaporation mainly include vacuum filtration graphene thin films, three-dimensional graphene aerogels grown by chemical vapor deposition, three-dimensional graphene foam blocks prepared by solvothermal methods, etc.

[0003] Currently developed graphene-based photothermal conversion materials generally do not have amphiphilicity and need to be compounded with other functional materials to achieve an amphiphilic structure, and the preparation process is complex. At the same time, the structure of the graphene / other functional material composite increases the water transmission path and is not conducive to the improvement of the sunlight-steam conversion efficiency.

[0004] Therefore, there is an urgent need to provide a graphene-based photothermal conversion material with both hydrophilicity and hydrophobicity at present. Summary of the Invention

[0005] The first object of the present invention is to provide an amphiphilic three-dimensional graphene thin film material, which has excellent photothermal conversion efficiency and salt tolerance performance.

[0006] The second object of the present invention is to provide a preparation method of an amphiphilic three-dimensional graphene thin film material, which is simple to operate and has a wide application range.

[0007] The preparation method of an amphiphilic three-dimensional graphene thin film material provided by the present invention includes the following steps:

[0008] (1) Mix graphene oxide with solvent A to prepare a graphene oxide dispersion.

[0009] (2) Solvent B is added into the high-pressure reactor, and then the graphene oxide dispersion prepared in step (1) is added. The density of the graphene oxide dispersion is less than that of solvent B, so that the graphene oxide dispersion floats above solvent B. Then, an interfacial solvothermal reaction is carried out to obtain a gel-like graphene film adsorbed with the solvent.

[0010] In this step, solvent B acts as a soft template with a reducing solvent, and an interfacial solvothermal reaction occurs at the interface adjacent to the graphene oxide dispersion.

[0011] (3) After the gel-like graphene film prepared in step (2) is subjected to water replacement treatment, it is freeze-dried to obtain an amphiphilic three-dimensional graphene film material.

[0012] Preferably, the concentration of the graphene oxide dispersion in step (1) is 0.5 - 10 mg / mL.

[0013] Preferably, solvent A in step (1) includes one or more of acetone, ethanol, methanol, isopropanol, tetrahydrofuran, water, ethylene glycol, propylene glycol, N-methylpyrrolidone, N,N-dimethylformamide, ethyl acetate, benzene, acetophenone, ether, methyl ethyl ketone, cyclohexane, acetonitrile, ethylene glycol dimethyl ether, propionitrile, 1,4-dioxane.

[0014] Preferably, solvent B in step (2) includes one or more of glycerol, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, ethylene glycol, butanediol, furfuryl alcohol, N-methylpyrrolidone, triethylene glycol, diethylene glycol, benzyl alcohol, dimethyl phthalate, ethyl benzoate, 1,1,3-trimethylcyclohexenone, dodecylamine, p-cresol, cresol, acetamide, quinoline, succinonitrile, ethylene glycol carbonate, silicone oil, polyether-modified silicone oil, liquid paraffin.

[0015] When selecting solvents, the density of solvent A is less than that of solvent B to ensure that the graphene oxide dispersion can float above solvent B and enable the interfacial solvothermal reaction to proceed stably.

[0016] Preferably, the volume ratio between the graphene oxide dispersion and solvent B in step (2) is 1:(1 - 10).

[0017] Preferably, the volume ratio between the graphene oxide dispersion and solvent B in step (2) is 1:6.

[0018] Preferably, the reaction temperature of the interfacial solvothermal reaction in step (2) is 150 - 220 °C, and the reaction time is 6 - 24 hours.

[0019] Preferably, the specific steps of step (3) are as follows: Place the gel-like graphene film prepared in step (2) in pure water to replace the solvent adsorbed on its surface with water, and then place it in a freeze dryer and dry it for 6 - 72 h to obtain an amphiphilic three-dimensional graphene film material.

[0020] The present invention also provides an amphiphilic three-dimensional graphene film material prepared by the above preparation method.

[0021] Beneficial effects:

[0022] The preparation method provided by the present invention is convenient and reliable. Using graphene oxide as a raw material, an amphiphilic three-dimensional graphene film material with both hydrophilic and hydrophobic properties can be obtained through an interfacial solvothermal method. Compared with traditional three-dimensional graphene materials, the three-dimensional graphene film material obtained in the present invention has both hydrophilicity and hydrophobicity, that is, it has amphiphilic characteristics.

[0023] The structures and morphologies of both sides of the three-dimensional graphene film material obtained in the present invention are different. One side is in the form of dense and flat stacking of graphene, which can effectively absorb water through capillary action. At the same time, because this surface is relatively smooth, it can effectively achieve self-cleaning of surface salt crystallization, thus achieving a good anti-salt effect; the other side is a three-dimensional porous structure, which can effectively absorb sunlight and is conducive to the escape of water vapor from the film surface. The interior of the film material is a three-dimensional porous structure, which is conducive to the transmission of water inside it, and the film thickness can be regulated, with obvious advantages, and a solar-steam conversion efficiency of > 90% can also be achieved. Description of the drawings

[0024] Figure 1 SEM image of the lower surface of the amphiphilic three-dimensional graphene film material prepared in Example 1;

[0025] Figure 2 SEM image of the upper surface of the amphiphilic three-dimensional graphene film material prepared in Example 1;

[0026] Figure 3 SEM image of the cross-section of the amphiphilic three-dimensional graphene film material prepared in Example 1;

[0027] Figure 4 Schematic diagram of the water contact angle of the upper surface of the amphiphilic three-dimensional graphene film material prepared in Example 1;

[0028] Figure 5 Schematic diagram of the water contact angle of the lower surface of the amphiphilic three-dimensional graphene film material prepared in Example 1. Detailed implementation manners

[0029] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms also include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1

[0033] A method for preparing an amphiphilic three-dimensional graphene thin film material, comprising the following steps:

[0034] (1) Mix graphene oxide with the solvent ethanol, stir, and ultrasonically disperse it to make it uniformly dispersed, and prepare a graphene oxide dispersion with a concentration of 2 mg / mL;

[0035] (2) Add 12 mL of the solvent glycerol to the inner lining of the high-pressure reactor, and then add 2 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent glycerol, and the graphene oxide dispersion cannot be mixed with the solvent glycerol, so that the graphene oxide dispersion floats above the solvent glycerol; then place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 180 °C and a reaction time of 16 hours to obtain a gel-like graphene thin film adsorbed with the solvent;

[0036] (3) Transfer the gel-like graphene thin film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the organic solvent adsorbed by it with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene thin film material. After measurement, the film thickness is 536 μm.

[0037] Test Example 1

[0038] Take the amphiphilic three-dimensional graphene thin film material prepared in this example and observe its morphology using a scanning electron microscope. The side of the thin film material in contact with solvent B is the lower surface, and the other side is the upper surface.

[0039] The SEM image of the lower surface of the amphiphilic three-dimensional graphene thin film material is shown in Figure 1 As shown, it can be seen that the surface has a three-dimensional porous morphology, which can effectively absorb sunlight and is conducive to the escape of water vapor from the film surface. The SEM image of the upper surface is shown in Figure 2 As shown, it can be seen that the surface has a smooth morphology, effectively absorbs water through capillary action, and can also effectively achieve self-cleaning of surface salt crystallization. The SEM image of the cross-section is shown in Figure 3 As shown, it is a porous structure, which is conducive to the transmission of water inside it.

[0040] Example 2

[0041] A preparation method of an amphiphilic three-dimensional graphene thin film material includes the following steps:

[0042] (1) Mix graphene oxide with solvent ethanol, stir, and ultrasonically disperse it to make it evenly dispersed, and prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0043] (2) Add 10 mL of solvent glycerol to the inner lining of the high-pressure reactor, and then add 2 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent glycerol, and the graphene oxide dispersion and the solvent glycerol cannot be mixed, so that the graphene oxide dispersion floats above the solvent glycerol; then place the high-temperature reactor in an oven for interfacial solvothermal reaction, the reaction temperature is 180 °C, and the reaction time is 16 hours to obtain a gel-like graphene thin film adsorbed with the solvent;

[0044] (3) Transfer the gel-like graphene thin film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the organic solvent adsorbed by it with water, after the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene thin film material, and the measured film thickness is 386 μm.

[0045] Example 3

[0046] A preparation method of an amphiphilic three-dimensional graphene thin film material includes the following steps:

[0047] (1) Mix graphene oxide with solvent water, stir, and ultrasonically disperse it to make it evenly dispersed, and prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0048] (2) Add 10 mL of the solvent glycerol into the inner lining of the high-pressure reactor, and then add 1 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent B, and the graphene oxide dispersion cannot be mixed with the solvent glycerol, so that the graphene oxide dispersion floats above the solvent glycerol. Then, place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 180 °C for 16 hours to obtain a gel-like graphene film adsorbed with the solvent;

[0049] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. The measured film thickness is 261 μm.

[0050] Example 4

[0051] A preparation method of an amphiphilic three-dimensional graphene film material, comprising the following steps:

[0052] (1) Mix graphene oxide with the solvent ethylene glycol, stir, and ultrasonically disperse it to make it uniformly dispersed to prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0053] (2) Add 8 mL of the solvent glycerol into the inner lining of the high-pressure reactor, and then add 2 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent glycerol, and the graphene oxide dispersion cannot be mixed with the solvent glycerol, so that the graphene oxide dispersion floats above the solvent glycerol. Then, place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 180 °C for 16 hours to obtain a gel-like graphene film adsorbed with the solvent;

[0054] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. The measured film thickness is 393 μm.

[0055] Example 5

[0056] A preparation method of an amphiphilic three-dimensional graphene film material, comprising the following steps:

[0057] (1) Mix graphene oxide with the solvent ethanol, stir, and ultrasonically disperse it to make it uniformly dispersed to prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0058] (2) Add 10 mL of the solvent glycerol into the inner lining of the high-pressure reactor, and then add 4 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent glycerol, and the graphene oxide dispersion and the solvent glycerol cannot be mixed, so that the graphene oxide dispersion floats above the solvent glycerol. Then, place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 180 °C for 16 hours to obtain a gel-like graphene film adsorbed with the solvent;

[0059] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. After measurement, the film thickness is 522 μm.

[0060] Example 6

[0061] A preparation method of an amphiphilic three-dimensional graphene film material, comprising the following steps:

[0062] (1) Mix graphene oxide with the solvent ethanol, stir, and ultrasonically disperse it to make it uniformly dispersed to prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0063] (2) Add 10 mL of the solvent ethylene glycol into the inner lining of the high-pressure reactor, and then add 3 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of the solvent ethylene glycol, and the graphene oxide dispersion and the solvent ethylene glycol cannot be mixed, so that the graphene oxide dispersion floats above the solvent ethylene glycol. Then, place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 180 °C for 16 hours to obtain a gel-like graphene film adsorbed with the solvent;

[0064] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. After measurement, the film thickness is 481 μm.

[0065] Example 7

[0066] A preparation method of an amphiphilic three-dimensional graphene film material, comprising the following steps:

[0067] (1) Mix graphene oxide with the solvent ethanol, stir, and ultrasonically disperse it to make it uniformly dispersed to prepare a graphene oxide dispersion with a concentration of 1 mg / mL;

[0068] (2) Add 10 mL of Solvent B to the inner lining of the high-pressure reactor. Solvent B is a glycerol / ethylene glycol mixture with a volume ratio of 2:1. Then add 2 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of Solvent B, and the graphene oxide dispersion and Solvent B should not be mixed, so that the graphene oxide dispersion floats on top of Solvent B. Then place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 160 °C for 20 hours to obtain a gel-like graphene film adsorbed with the solvent.

[0069] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. The measured film thickness is 456 μm.

[0070] Example 8

[0071] A method for preparing an amphiphilic three-dimensional graphene film material, comprising the following steps:

[0072] (1) Mix graphene oxide with solvent ethanol, stir, and ultrasonically disperse it to make it evenly dispersed to prepare a graphene oxide dispersion with a concentration of 1 mg / mL.

[0073] (2) Add 8 mL of Solvent Glycerol to the inner lining of the high-pressure reactor. Then add 2 mL of the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of Solvent Glycerol, and the graphene oxide dispersion and Solvent Glycerol should not be mixed, so that the graphene oxide dispersion floats on top of Solvent Glycerol. Then place the high-temperature reactor in an oven for an interfacial solvothermal reaction at a reaction temperature of 120 °C for 24 hours to obtain a gel-like graphene film adsorbed with the solvent.

[0074] (3) Transfer the gel-like graphene film prepared in step (2) out of the high-pressure reactor, place it in pure water to replace the adsorbed organic solvent with water. After the water replacement treatment, place it in a freeze dryer and dry it for 15 h to obtain an amphiphilic three-dimensional graphene film material. The measured film thickness is 415 μm.

[0075] Test Example 2: Amphiphilicity Detection

[0076] Use a contact angle / surface tension measuring instrument to measure the water contact angle of the three-dimensional graphene film. Among them, the lower surface of the graphene film is the surface that directly contacts Solvent B, and the upper surface of the graphene film does not directly contact Solvent B. The results are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] Figure 4 Schematic diagram of the water contact angle on the upper surface of the product in Example 1 Figure 5 Schematic diagram of the water contact angle on the lower surface of the product in Example 1. From Figure 4 、 Figure 5 Combined with Table 1, it can be seen that for the amphiphilic three-dimensional graphene thin film materials prepared in Examples 1-8, the water contact angles on their upper surfaces are all < 90°, showing hydrophilicity, while the water contact angles on their lower surfaces are all > 90°, showing hydrophobicity. This thin film exhibits amphiphilic characteristics. Among them, the product in Example 1 has a smaller water contact angle on the upper surface and a larger water contact angle on the lower surface, with stronger amphiphilicity.

[0081] Test Example 3

[0082] Place the amphiphilic three-dimensional graphene thin film materials prepared in each example on polystyrene foam, and use absorbent cotton as the medium for upward drainage. Use an adjustable power xenon lamp placed directly above the photothermal evaporator as the light source simulating sunlight. The light intensity of the light source is measured using a photometer and controlled within the range of 1.014 kW m -2 to 0.985 kW m -2 , that is, within the range of 1 sun. The evaporation rate of water is recorded in real time through an electronic balance connected to a computer, and the surface temperature of the sample is measured using an infrared thermal imager to evaluate the solar - steam conversion efficiency of the material. The test results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] As can be seen from Table 2, the evaporation rates of the amphiphilic three-dimensional graphene thin film materials prepared in Examples 1-8 are all higher than 1.317 kg m -2 h -1 , and the photothermal conversion efficiencies are all higher than 90%, showing high solar - steam conversion efficiency. Among them, in Example 1, the volume ratio of the graphene oxide dispersion to glycerol is 1:6, and the prepared graphene-based solar water evaporation material has the best photothermal performance.

[0087] In summary, the three-dimensional graphene film prepared by the method of the present invention has amphiphilicity. The two surface structures and morphologies of the film are different. The preparation process is simple and has obvious advantages. The amphiphilic three-dimensional graphene film prepared by the present invention has excellent solar interfacial water evaporation characteristics. Among the two surfaces of the film, the surface with a dense and flat stacking structure is hydrophilic and is conducive to water absorption. In addition, since the surface is relatively smooth, self-cleaning of surface salt crystallization can be effectively achieved, thus achieving a good anti-salt effect. The three-dimensional porous structure inside the film is conducive to water transmission. The other surface of the film is a porous structure, showing hydrophobicity, which can effectively absorb sunlight and is conducive to the escape of water vapor from the film surface. This film can achieve a solar-vapor conversion efficiency of >90%, and has high application value.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; 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 invention.

Claims

1. A preparation method of an amphiphilic three-dimensional graphene thin film material, characterized in that, It includes the following steps: (1) Mix graphene oxide with solvent A to prepare a graphene oxide dispersion; Solvent A includes one or more of ethanol, water, and ethylene glycol; (2) Add solvent B into a high-pressure reactor, and then add the graphene oxide dispersion prepared in step (1). The density of the graphene oxide dispersion is less than that of solvent B, so that the graphene oxide dispersion floats above solvent B; Then carry out an interfacial solvothermal reaction to obtain a gel-like graphene film adsorbed with solvent; Solvent B includes one or more of glycerol and ethylene glycol; (3) Place the gel-like graphene film prepared in step (2) in pure water to replace the solvent adsorbed on its surface with water, and then place it in a freeze dryer for drying for 6 - 72 h to obtain an amphiphilic three-dimensional graphene film material; One side of the amphiphilic three-dimensional graphene film material is a dense graphene flat-packed structure, and the other side is a three-dimensional porous structure; The sunlight-steam conversion efficiency of the amphiphilic three-dimensional graphene film material is greater than 90%; 2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the graphene oxide dispersion is 0.5 - 10 mg / mL.

3. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio between the graphene oxide dispersion and solvent B is 1:(1 - 10).

4. The preparation method according to claim 3, characterized in that, In step (2), the volume ratio between the graphene oxide dispersion and solvent B is 1:

6.

5. The preparation method according to claim 1, characterized in that, In step (2), the reaction temperature of the interfacial solvothermal reaction is 150 - 220 °C, and the reaction time is 6 - 24 hours.

6. An amphiphilic three-dimensional graphene film material prepared by the preparation method according to any one of claims 1 - 5.

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