TWI558662B - Method for manufacturing graphene composite film - Google Patents

Description

Method for preparing graphene composite film

The invention relates to a preparation method of a composite membrane, in particular to a preparation method of a graphene composite membrane.

Graphene has excellent mechanical properties, high thermal conductivity, high electron mobility and high specific surface area. However, graphene prepared by redox method is easily squeezed by temperature, pH value or processing procedure during preparation. The phenomenon of agglomeration causes the specific surface area to decrease and affects the electrical properties of graphene. Therefore, the direct application of such graphene is not high, but the graphene dispersed in the solution is easily mixed with various materials to form a composite system. In addition to the preparation of functional composite materials, it is also possible to add graphitic materials to graphene to enhance the properties of graphene. The composite materials prepared in the literature can exhibit excellent mechanical and electrical properties and have excellent processing properties. , providing a wider application area for composite materials.

Zeolites have regular pores and good heat resistance and pressure resistance. Therefore, if graphene and zeolite are used together to form a composite material, for example, a graphene composite film can be produced, the graphene composite film can be made more than graphene. Good stability, and the three-dimensional structure of the zeolite can improve the convenience of electron in and out, which is beneficial to the redox reaction, and can be applied to supercapacitors, sensors and the like.

The method for preparing a conventional graphene composite film is a graphene prepared by a redox method, comprising providing a suspension of graphene oxide and a suspension of zeolite, and reducing the suspension of graphene oxide to obtain a graphene suspension. And mixing the graphene suspension with the zeolite suspension After the combination, the graphene composite film is formed on the surface of a substrate by a spin coating method in combination with high-temperature baking for several hours.

However, since the conventional graphene composite film is a graphene prepared by a redox method, the number of layers is usually ten or more layers, the thickness is thick, and it is easy to have defects, and then it is produced by a spin coating method. The graphene composite film has poor electrical properties and has disadvantages such as uneven thickness, rough surface and poor adhesion, and the applicability of the graphene composite film is lowered.

The present invention solves the above problems, and provides a method for preparing a graphene composite film, wherein the graphene composite film obtained has good electrical properties, uniform thickness, and smooth surface.

The invention provides a method for preparing a graphene composite film, comprising: providing a zeolite suspension comprising zeolite nanocrystals having a concentration of 50-100 ppm and a particle diameter of 50-80 nm; providing a graphene suspension having a concentration of 50 ~200ppm of graphene oxide; reducing the graphene suspension, the color of the graphene suspension is changed from bright yellow to dark brown, so that the graphene oxide is reduced to form partially reduced graphene; Mixing the reduced graphene suspension and the zeolite suspension with a volume ratio of 9:1, and adding a surfactant to form a composite solution; reducing the composite solution to completely reduce the partially reduced graphene to form graphene; Atomizing the reduced composite solution to form a plurality of atomized droplets; treating the plurality of atomized droplets with a plasma to charge the plurality of atomized droplets; and depositing the plurality of charged charges The atomized droplets are on a substrate having a temperature of 150 to 350 °C. Thereby, a graphene composite film can be obtained.

The method for preparing a graphene composite film according to the present invention, wherein an alkali agent is added to the graphene suspension, and the graphene suspension containing the alkali agent is ultrasonically oscillated at a temperature of 50 to 90 ° C to make the The graphene oxide is reduced to form the partially reduced graphene. Thereby, it is possible to achieve the effect of "avoiding the defect of the partially reduced graphene".

The method for preparing a graphene composite film according to the present invention, wherein the composite solution is ultrasonically oscillated at a temperature of 50 to 90 ° C to completely reduce the partially reduced graphene to form the stone. Motenol. Thereby, it is possible to achieve the effect of "avoiding the defect of the partially reduced graphene".

A method for producing a graphene composite film according to the present invention, wherein the alkali agent is lithium hydroxide, sodium hydroxide, potassium hydroxide or calcium hydroxide. In this way, it is possible to achieve the effect of "avoiding the alkaline agent from harming the environment".

A method for producing a graphene composite film according to the present invention, wherein the surfactant is methyl-1-pyrrolidone, isopropanol, propylene glycol methyl ether, ethyl acetate or methyl ethyl ketone. Thereby, the effect of "reducing the number of layers of the graphene" can be achieved.

The method for preparing a graphene composite film according to the present invention, wherein the zeolite suspension further comprises a metal salt. Thereby, the effect of "increasing the specific capacitance value of the graphene composite film" can be achieved.

A method for producing a graphene composite film according to the present invention, wherein the metal salt is a salt of gold, platinum, silver, copper or nickel. Thereby, the effect of "increasing the specific capacitance value of the graphene composite film" can be achieved.

The method for preparing a graphene composite film according to the present invention, further comprising: mixing the graphene suspension and the zeolite suspension, performing ultrasonic vibration for 2 to 5 hours, and then adding the surfactant. Thereby, the effect of "reducing the number of layers of the graphene" can be achieved.

The method for preparing a graphene composite film according to the present invention, wherein the plurality of atomized droplets are carried by the gas through the plasma to charge the plurality of atomized droplets. Thereby, the effect of "increasing the binding force of the graphene composite film to the substrate" can be achieved.

The method for preparing a graphene composite film according to the present invention, wherein the gas system is argon gas, helium gas or a mixed gas containing one of argon gas and hydrogen gas. Thereby, the "avoid oxidation of the graphene" effect can be achieved.

The method for preparing the graphene composite film of the present invention can reduce the generated graphene by adding the zeolite nanocrystal when the graphene oxide is reduced to form the partially reduced graphene, and then completely reducing the partially reduced graphene. The number of layers is achieved to achieve the effect of "improving the electrical properties of the graphene."

Furthermore, in the method for preparing a graphene composite film of the present invention, the composite solution is formed into the graphene composite film by a plasma aerosol deposition method, and the graphene can be coated with the zeolite nanocrystal to form a surface smoothing. The graphene composite film having a uniform thickness achieves the effect of "increasing the applicability of the graphene composite film".

Further, in the method for producing a graphene composite film of the present invention, by adding the metal salt to the zeolite suspension, metal ions of the metal salt can be introduced into the zeolite nanocrystal, and the graphene composite film can be produced. Moreover, the effect of "increasing the specific capacitance value of the graphene composite film" can be further achieved.

Figure 1a: A thousand-fold SEM image of the Group B1 graphene composite film.

Figure 1b: A 100,000-fold SEM image of the Group B1 graphene composite film.

Figure 1c: A cross-sectional SEM image of the Group B1 graphene composite film.

Figure 2a: A thousand-fold SEM image of the Group B2 graphene composite film.

Figure 2b: 50,000 times SEM image of the Group B2 graphene composite film.

Figure 2c: A cross-sectional SEM image of the Group B2 graphene composite film.

Figure 3a: FT-IR spectrum of graphene oxide.

Figure 3b: FT-IR spectrum of graphene.

Figure 3c: FT-IR spectrum of zeolite.

Fig. 3d is a FT-IR spectrum of the graphene composite film of the present invention.

Figure 4: Electrical analysis of cyclic voltammetry in groups D1 and D5.

The above and other objects, features and advantages of the present invention will become more <RTIgt; Membrane preparation method comprising providing a boiling a stone suspension and a graphene suspension, the graphene suspension comprising graphene oxide; reducing the graphene suspension, reducing the graphene oxide to form a partially reduced graphene, continuing to add the zeolite suspension and an interface After the active agent forms a composite solution, and then reduces the composite solution to completely reduce the partially reduced graphene to form graphene, the composite solution is formed into a graphene composite film on a substrate by plasma aerosol deposition. .

In particular, the zeolite suspension comprises zeolite nanocrystals having a particle size of 50 to 80 nm and may have a concentration of 50 to 100 ppm. The zeolite suspension can be obtained by any conventional method. Further, the zeolite suspension may have a pH of 11 to 13 in a general process. For example, the zeolite nanocrystal may be a yttrium aluminum zeolite, for example, a chemical formula having M _{x / n} [(AlO ₂ ) _x (SiO ₂ ) _y ] ‧ mH ₂ O, and x ≦ y. The above n is the oxidation number of the cation M, and the cation M may be an alkali metal, an alkaline earth metal, a rare earth metal, an ammonium or a hydrogen ion, and the like, and the present invention is not limited thereto.

In this example, 16.04 g of tetramethylammonium hydroxide (TMAOH) was mixed with 25.35 g of pure water, and 3.835 g of aluminum isopropoxide and 6.09 g of cerium oxide were added and stirred. hour. Next, it is placed in a closed container and reacted at 92 ° C for 48 hours, and then the lower layer large particles are removed by low speed centrifugation (for example, 3000 rpm, 30 minutes), and the supernatant liquid is removed after high speed centrifugation (for example, 12000 rpm, 30 minutes). Granules were obtained to obtain about 20 ml of the zeolite suspension, and the zeolite suspension had a pH of about 11.

In addition, in order to make the graphene composite film have a better specific capacitance value, it is also possible to introduce a highly conductive metal ion such as gold, platinum, silver or copper into the zeolite nanocrystal by the ion exchange property of the zeolite. Nickel plasma is understood by those of ordinary skill in the art to which the invention pertains. For example, the zeolite suspension may further comprise a metal salt such that metal ions of the metal salt enter the zeolite nanocrystal. In this embodiment, a 0.3% by weight aqueous solution of silver nitrate (1 M) is added to the above zeolite suspension, placed in a closed plastic bottle, protected from light and shaken in a water bath at 80 ° C for 8 hours, and finally added. Ammonia adjustment to The pH is 11.

The graphene suspension contains the graphene oxide and has a concentration of 50 to 200 ppm, and can be prepared by a conventional method, for example, by mixing a carbon material such as graphite with an oxidizing agent, followed by filtration and washing. In the present example, 0.2 g of flake graphite was mixed with 12 ml of concentrated sulfuric acid under ice bath for 1 hour, and 2 g of potassium permanganate was continuously added and stirred for 1 hour. Then, after stirring at 40 ° C for 1 hour, 25 ml of pure water was added, followed by stirring at 95 to 98 ° C for 15 minutes. Continue to add hydrogen peroxide to the solution to no longer generate bubbles, and then centrifuge at high speed (12000 rpm, 15 minutes) without cooling, then wash to pH 4, and oscillate in pure water to no obvious particles to obtain the graphene suspension. .

Thereafter, the graphene oxide is reduced to form the partially reduced graphene. That is, all of the graphene is partially reduced, for example, the layer is first reduced, and the edge is maintained in an oxidized state. The partially reduced graphene refers to a state between the graphene oxide and the fully reduced graphene. In particular, a reducing gas may be introduced into the graphene suspension, or a reducing agent may be added, and any conventional reducing agent for reducing graphene oxide may be selected. The reducing agent may be basic to match the pH of the zeolite suspension, for example, using a common hydrazine or the like. Alternatively, an alkali agent can be added and ultrasonic vibration can be performed at a temperature of 50 to 90 °C. The base agent can be lithium hydroxide, sodium hydroxide, potassium hydroxide or calcium hydroxide to provide a reducing environment. Such alkaline agents are less harmful to the environment, can provide a slower rate of reduction, do not cause defects in the partially reduced graphene, and are easier to control the rate of reduction. In the present example, 20 ml of a 4 M aqueous sodium hydroxide solution was added per 200 ml of graphene suspension, and ultrasonically oscillated at 50 ° C until the color changed from brownish yellow to dark brown.

Next, when the graphene oxide is reduced to form a partially reduced graphene, the zeolite suspension is continuously added. Since graphene is brownish yellow in the oxidized state and black in the reduced state, when the color of the graphene suspension changes from bright yellow to dark brown, the partially reduced graphene is formed. Those of ordinary skill in the art will understand. More detailed In other words, if the PANTONE color card is taken as an example, the color number 124 is changed to the color number 1405. Furthermore, since the partially reduced graphene still has good suspension properties, the reduced graphene suspension should be centrifuged at 10,000 rpm for 15 minutes without sedimentation.

At this time, the reduced graphene suspension and the zeolite suspension are mixed in a volume ratio of 1:1 to 9:1, and the surfactant is continuously added to form the composite solution. In the case where the alkali agent is already present in the graphene suspension, in order to avoid the reduction rate of the partially reduced graphene being too fast, the reduced graphene suspension may be first transferred to a water bath of 15 ° C, and then The zeolite suspension and the surfactant are added. For example, when the color of the graphene suspension turns brown, the graphene suspension is immediately placed in a water bath at 15 ° C to temporarily stop the reduction reaction. In addition, after the zeolite suspension is added, the ultrasonic wave is shaken for 2 to 5 hours, and the surfactant is added. The surfactant can be selected from any of the conventional methods for preparing graphene by redox method, such as 1-methyl-2-pyrrolidone (NMP), isopropanol, propylene glycol methyl ether, ethyl acetate or methyl ethyl ketone. Wait.

Then, the composite solution is continuously reduced to reduce the partially reduced graphene to form the graphene, for example, the reducing gas can be reintroduced, and the reducing agent or the alkali agent can be further added. Alternatively, the reduction reaction may be continued by the addition of a reducing agent and an alkali agent, for example, ultrasonic vibration for 8 to 24 hours. Here, since the composite solution contains the zeolite nanocrystal, and the particle size of the zeolite nanocrystal is close to the size of the graphene, it is possible to avoid excessive aggregation of the partially reduced graphene during reduction. Further, with the aid of the surfactant, the number of graphene layers formed can be five or less, and the electrical properties can be improved. In this embodiment, the zeolite suspension is added to the above graphene suspension containing sodium hydroxide, and after ultrasonic vibration for 3 hours, 20 ml of methylpyrrolidone is added, and then ultrasonic wave is shaken at 80 ° C for 24 hours. This partially reduced graphene is completely reduced.

After the partially reduced graphene is completely reduced and the graphene is formed, the reduced composite solution is deposited on the substrate by plasma aerosol deposition to form the graphene complex. Film. In particular, first atomizing the reduced composite solution to form a plurality of atomized droplets, such as by using a conventional ultrasonic atomizer, is understood by those of ordinary skill in the art to which the present invention pertains. While forming the plurality of atomized droplets, the graphene contained in the composite solution is coated on the surface of the zeolite nanocrystal to form a structure similar to a graphene sphere.

Next, the plurality of atomized droplets are treated with a plasma and deposited on the substrate. For example, an inert gas (for example, argon gas, helium gas) or a mixed gas (for example, an argon/hydrogen gas mixture) carries the atomized droplets through the plasma, and is continuously deposited on the substrate at a temperature of 150 to 350 ° C. on. The plasma nanocrystal can be activated by plasma treatment, and the crosslinking between the graphene and the zeolite nanocrystal is strengthened to enhance the bonding force between the graphene composite film and the substrate. In this embodiment, the temperature of the substrate is 230 ° C, and the plasma is generated by applying a voltage of 60 to 90 V using an atmospheric plasma system. In addition, a pulsed AC voltage can also be selected. Furthermore, in the present embodiment, the atomized droplets are carried by argon gas, and the supply amount of the argon gas is 6 to 10 l/m. At the same time, the flow rate of the atomized droplets ranges from 60 to 100 ml/min. The above numerical values can be adjusted according to requirements such as the required film thickness, and the present invention is not limited thereto.

Thereby, in the method for preparing the graphene composite film of the present invention, the graphene can be coated with the zeolite nanocrystal, and a graphene composite film having a smooth surface can be formed on the surface of the substrate. At the same time, the graphene has a small number of layers, so that it can have better electrical properties. Therefore, the graphene composite film has the advantages of strong adhesion, smooth surface, and good electrical properties.

In order to confirm that the method for preparing the graphene composite film of the present invention can form the graphene composite film, the graphene composite film simultaneously contains the characteristics of the graphene and the zeolite nanocrystal, and the surface of the graphene composite film is flat and simultaneously With good electrical properties, the following experiment was carried out.

(A) Comparison of graphene quality

In order to confirm that the graphene composite film prepared by the present invention has a small number of layers and defects, the zeolite suspension and the graphene suspension are prepared by the method as described above. Floating liquid. Wherein, in the group A1, when the graphene oxide is reduced to form the partially reduced graphene, the zeolite suspension and the surfactant are added, and the partially reduced graphene is continuously reduced to form the graphene. In the group A2, the graphene oxide is completely reduced, and the zeolite suspension and the surfactant are continuously added. The transmittances of Groups A1 and A2 were measured separately and recorded as shown in Table 1 below.

Since the transmittance of graphene is related to the number of layers and the degree of defects, the higher transmittance means that the number of layers and defects of graphene are less. It can be seen from the first table that the A1 group is added to the zeolite suspension when the graphene oxide is reduced to form the partially reduced graphene, and then the reduction reaction is continued, thereby forming a high transmittance, a number of layers, and defects. Less graphene. On the contrary, the A2 group is added to the zeolite suspension after the complete reduction of the graphene oxide, so that the obtained graphene has low transmittance, a large number of layers and a serious defect.

(B) Comparison of graphene composite membrane types

The zeolite suspension and the graphene suspension were prepared as described above, and the zeolite suspension and the graphene suspension were mixed at a volume ratio of 7:3, and after being ultrasonically shaken for 3 hours, methylpyrrolidone was added. The composite solution is prepared by completely reducing the partially reduced graphene to form the graphene. The graphene composite film is produced by the plasma aerosol deposition method, and is a group B1, which represents a preparation method of the graphene composite film of the invention. The composite solution was further subjected to spin coating to be Group B2 for comparison.

Please refer to Figures 1a and 1b for the SEM image of the graphene composite film of Group B1 at a magnification of one thousand times and 100,000 times, and the first c-figure is a cross-sectional view. In addition, the 2a and 2b graphs are the graphene composite film of the B2 group at a magnification of one thousand times and 50,000 times. The SEM image, and the 2c chart is its cross-sectional view. As shown in the figure, the graphene composite film produced by the present invention has a smooth surface and can see uniform particles upon amplification, indicating that the graphene is combined with the zeolite nanocrystal. On the other hand, if the graphene composite film is prepared by the spin coating method, the aggregation is noticeable and the surface is uneven.

(C) Chemical properties and composition analysis of graphene composite membrane

The graphene suspension was separately taken as the group C1, and the graphene suspension was completely reduced to be the group C2, and the zeolite suspension was taken as the group C3, and the composite solution of the group B1 was used as the group C4, respectively. Films were prepared by plasma aerosol deposition and subjected to FT-IR analysis. The results are shown in Figures 3a to 3d. Referring to Figures 3a and 3b (Groups C1 and C2), it is shown that the peak of the graphene oxide at 1414 cm ^-1 completely disappears upon complete reduction. Continuing with Figure 3d (Group C4), it can be seen from Figures 3a to 3c that the graphene composite film of the present invention does have the characteristics of graphene (at 1620 to 1680 cm ^-1 ) and the characteristics of zeolite (500 to 700 cm). ^-1 ), and the graphene contained has been completely reduced.

Continuing to analyze the characteristics of the graphene composite film (Group C4) by EDS, the ratio of carbon to bismuth is about 2.2, which is substantially consistent with the mixing volume ratio of the graphene suspension and the zeolite suspension, and is formed in the formation of the graphene suspension. When atomizing the droplets, the graphene and the zeolite nanocrystals are surely interlaced according to the mixing ratio, and the uniform distribution of the graphene composite film is continued.

(D) Electrical analysis of graphene composite membrane

The purely graphene (completely the same as the above Group C2) was used as the Group D1, and the zeolite suspension (same as the above Group C3) was used as the Group D2, and the zeolite of the silver ion was introduced as described above. The suspension was used as the D3 group. Further, the above composite solution containing the graphene and the zeolite nanocrystal (same as the above group C4) is taken as the group D4, and a composite solution containing the graphene and the zeolite nanocrystal into which silver ions are introduced is used as Group D5. The D1~D5 groups were deposited as thin films by plasma aerosol deposition method, and the specific capacitance values of the electrolytes and electrolytes (1M potassium hydroxide aqueous solution) were continuously measured, as shown in Table 2 below. Shown.

From the above results, it is understood that the graphene composite film (Group D4) prepared by the present invention has a specific capacitance value equivalent to that of the completely reduced pure graphene (Group D1). The zeolite nanocrystals (Group D3) introduced by silver ions have a larger specific capacitance value than the pure zeolite nanocrystals (Group D3). Further, by introducing silver ions into the zeolite nanocrystal, the graphene composite film (Group D5) is produced, and the specific capacitance value can be further increased with respect to the graphene composite film (Group D4) which is not introduced with silver ions. .

The films deposited in Groups D1 and D5 were also analyzed by cyclic voltammetry, as shown in Figure 4. Among them, in the range of -0.6 to -0.2 V, the current change of the graphene composite film of the present invention (Group D5) is more stable than that of pure graphene (Group D1).

According to the above, the method for preparing the graphene composite film of the present invention can reduce the generated by adding the zeolite nanocrystal when the graphene oxide is reduced to form the partially reduced graphene, and then completely reducing the partially reduced graphene. The number of layers of graphene achieves the effect of "improving the electrical properties of the graphene".

Furthermore, in the method for preparing a graphene composite film of the present invention, the composite solution is formed into the graphene composite film by a plasma aerosol deposition method, and the graphene can be coated with the zeolite nanocrystal to form a surface smoothing. And the uniform thickness of the graphene composite film achieves "uplifting the stone" The applicability of the olefinic composite film.

Further, in the method for producing a graphene composite film of the present invention, by adding the metal salt to the zeolite suspension, metal ions of the metal salt can be introduced into the zeolite nanocrystal, and the graphene composite film can be produced. Moreover, the effect of "increasing the specific capacitance value of the graphene composite film" can be further achieved.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

Claims (9)

A method for preparing a graphene composite film, comprising: providing a zeolite suspension comprising zeolite nanocrystals having a concentration of 50-100 ppm and a particle diameter of 50-80 nm; providing a graphene suspension comprising a concentration of 50-200 ppm Graphene oxide; adding an alkali agent to the graphene suspension, ultrasonically oscillating at a temperature of 50-90 ° C to oscillate the graphene suspension containing the alkali agent, and changing the color of the graphene suspension from bright yellow Dark brown to reduce the graphene oxide to form partially reduced graphene; to mix the reduced graphene suspension and the zeolite suspension in a volume ratio of 1:1 to 9:1, and to add a surfactant Forming a composite solution; reducing the composite solution to completely reduce the partially reduced graphene to form graphene; atomizing the reduced composite solution to form a plurality of atomized droplets; treating the plurality of mists with a plasma The droplets are charged to charge the plurality of atomized droplets; and the plurality of charged atomized droplets are deposited on a substrate having a temperature of 150 to 350 ° C. The method for preparing a graphene composite film according to claim 1, wherein the composite solution is ultrasonically oscillated at a temperature of 50 to 90 ° C to completely reduce the partially reduced graphene to form the graphene. The method for producing a graphene composite film according to claim 1 or 2, wherein the alkali agent is lithium hydroxide, sodium hydroxide, potassium hydroxide or calcium hydroxide. The method for preparing a graphene composite film according to claim 1, wherein the surfactant is methyl-1-pyrrolidone, isopropanol, propylene glycol methyl ether or ethyl acetate. Or butanone. The method for producing a graphene composite film according to claim 1 or 4, wherein the zeolite suspension further comprises a metal salt. The method for producing a graphene composite film according to claim 5, wherein the metal salt is a salt of gold, platinum, silver, copper or nickel. The method for preparing a graphene composite film according to claim 1 or 4, further comprising: after mixing the graphene suspension and the zeolite suspension, performing ultrasonic vibration for 2 to 5 hours, and then adding the Surfactant. The method for preparing a graphene composite film according to claim 1 or 4, wherein the plurality of atomized droplets are carried by the gas through the plasma to cause the plurality of atomized droplets to carry Charge. The method for producing a graphene composite film according to claim 8, wherein the gas system is argon gas, helium gas or a mixed gas containing argon gas and hydrogen gas.