Graphene positive triboelectric sensing material based on carbon network regulation and preparation method thereof

Abstract

The application provides a graphene positive triboelectric sensing material based on carbon network regulation and a preparation method thereof. Through multi-temperature zone thermal reduction treatment on a graphene oxide film, the proportion of carbon and oxygen defects on the carbon network is accurately regulated, the work function is optimized, the mechanical performance is enhanced, and the triboelectric output performance is significantly improved. The preparation process comprises: vacuum treatment and uniform film forming of the graphene oxide solution, and defect distribution regulation at different thermal reduction temperatures. The method optimizes carbon defects, eliminates oxygen defects, and constructs a stable carbon conductive network, so that the graphene film has high positive electric properties and toughness. The friction nanogenerator based on the material has super-high output performance and excellent long-term stability. The preparation method is simple in process and suitable for large-scale production, and provides a new material solution for the fields of flexible electronics, intelligent sensing and nanogeneration, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to the fields of energy and new materials, and in particular to a graphene positive triboelectric sensing material based on carbon network regulation and a preparation method thereof. BACKGROUND

[0002] As sp 2 The most basic form of hybrid carbon allotrope, due to its atomic level thickness Large specific surface area (2630 m 2 / g), high mechanical strength (1TPa), ultra-high carrier mobility (>10 6 cm / V / s) and band gap controllable adjustment, a series of outstanding performances show a wide application prospect in the fields of photoelectric and sensor devices, advanced semiconductors, integrated circuits and nanogenerators. In the TENG research, graphene can not only be used as an electrode, but also as a positive triboelectric material. However, the graphene material prepared by the method of reducing graphene oxide currently has the following problems:

[0003] (1) Low electronegativity: the low work function of the material limits its positive triboelectric performance due to the insufficient optimization of the preparation process.

[0004] (2) Insufficient mechanical properties: the carbon defects in the reduction process can weaken the structural strength of the graphene network, resulting in easy brittle fracture of the film.

[0005] (3) Output performance attenuation: in long-term work, the interface charge capture caused by oxygen defects can cause the output performance to gradually decrease.

[0006] Therefore, the design of triboelectric material with customized work function is the key to improving the output performance of the triboelectric nanogenerator (TENG). SUMMARY

[0007] The application aims to provide a graphene positive triboelectric sensing material based on carbon network regulation and a preparation method thereof, so as to realize the precise regulation of the work function of the triboelectric material and the enhancement of the mechanical properties.

[0008] The technical scheme adopted by the application is as follows: a preparation method of a graphene positive triboelectric sensing material based on carbon network regulation, comprising the following steps:

[0009] Step one: the graphene oxide solution is subjected to negative pressure treatment in a vacuum drying box to remove dissolved air, and a preliminary film preparation solution is obtained;

[0010] Step two: the preliminary film preparation solution is poured into a polytetrafluoroethylene mold and dried in a vacuum oven to prepare a precursor graphene oxide film;

[0011] Step three: heat reduction treatment of the graphene oxide film precursor in a high-temperature graphitization atmosphere furnace to control carbon network defect adjustment, with the conditions being: constant heating to 1500-3000 DEG C reduction, argon protection environment, and finally reduced to room temperature to obtain a carbon network regulated graphene positive triboelectric sensing material.

[0012] Further, in step one, the concentration of the graphene oxide solution is 4-10 mg / ml, the graphene oxide contained therein has a flake diameter of no less than 30 pm, the vacuum drying box is in a negative pressure environment of 1 Pa, and the treatment time is 2 h.

[0013] Further, in step two, the polytetrafluoroethylene mold is a circular mold with a diameter of 10-15 cm, and the vacuum oven drying condition is 40-60 DEG C, and the drying time is 12 h.

[0014] Further, in step three, when heat reduction is performed in the high-temperature graphitization atmosphere furnace, first, heating is performed at a heating rate of 5 DEG C / min to 1000 DEG C, and then heating is performed at a heating rate of 10 DEG C / min to constant temperature at 1500 DEG C, 2000 DEG C, 2500 DEG C or 3000 DEG C; after constant temperature for 1 h, slowly reduced to room temperature, and the argon flow rate is 200-500 sccm.

[0015] Further, in step three, the graphene oxide film needs to be processed in a sandwich structure with two graphite plate interlayers during heat reduction to ensure uniform reduction.

[0016] Another object of the present application is to provide a carbon network regulated graphene positive triboelectric sensing material prepared by the method as described above.

[0017] Another object of the present application is to provide a carbon network regulated graphene positive triboelectric sensing material prepared by the method as described above, which is prepared by heating to constant temperature at 2500 DEG C-3000 DEG C during heat reduction in a high-temperature graphitization atmosphere furnace.

[0018] Another object of the present application is to provide a triboelectric nanogenerator comprising the carbon network regulated graphene positive triboelectric sensing material as described above as a positive triboelectric sensing material and polytetrafluoroethylene as a negative triboelectric material.

[0019] Further, the contact separation frequency of the triboelectric nanogenerator is 2 Hz, and the movement distance is 1 cm.

[0020] The application has the advantages and beneficial effects that the preparation method is simple, suitable for large-scale production, provides a new material solution for the fields of flexible electronics, intelligent sensing and nanogenerator, and has a wide application prospect. Meanwhile, the prepared super-tough high-performance graphene positive triboelectric sensing material has excellent mechanical properties and high triboelectric output performance, the carbon network defects are accurately controlled by thermal reduction to control the proportion of carbon and oxygen defects on the surface and edge of the material, thereby realizing dynamic optimization of the work function and conductive performance of the material, and improving the wide application potential of the graphene material in the fields of nanogenerator, flexible electronics and sensing. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of carbon network regulation and performance optimization strategy of graphene positive triboelectric sensing material; (a)-(b) are energy band diagrams and defect distribution of graphene oxide; (c), (d), (e) are respectively the surface defect distribution of graphene reduced at 1000 DEG C, 2000 DEG C and 3000 DEG C; (f), (g), (h) are respectively the energy band diagrams of graphene reduced at 1000 DEG C, 2000 DEG C and 3000 DEG C; (i) is a schematic diagram of a friction nanogenerator structure.

[0022] Figure 2 It is an electrical and mechanical property diagram of graphene positive triboelectric sensing material; (a) is the electrical conductivity of graphene positive triboelectric sensing material at different reduction temperatures; (b) is a mechanical property display of graphene film reduced at 2500 DEG C.

[0023] Figure 3 It is a simulation result diagram of the regulation mechanism of carbon and oxygen defects on the work function.

[0024] Figure 4 It is a performance test diagram of a friction nanogenerator based on graphene positive triboelectric sensing material; (a) is a schematic diagram of a friction nanogenerator test system containing graphene positive triboelectric sensing material and commercial polytetrafluoroethylene; (b) is the output power density of a friction nanogenerator based on graphene positive triboelectric sensing material at different reduction temperatures. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application will be further described in detail below in combination with examples, and it should be understood that the specific examples described here are only used to explain the application, and are not used to limit the application.

[0026] Example 1

[0027] In combination with Figure 1 The preparation method of the super-tough high-performance graphene positive triboelectric sensing material is as follows in combination with the flow of (b-c-i).

[0028] 1) Large size graphene oxide (about 50 pm in diameter) precursor was prepared by modified Hummers method. 50 ml graphene oxide precursor solution (8 mg / ml) was taken and diluted with 50 ml deionized water. After well mixed, 100 ml solution was poured into a customized polytetrafluoroethylene mold (15 cm in diameter), it is important to use a circular mold for the film forming process, which can eliminate the local stress in the film forming process and ensure the uniformity of the graphene oxide film. Then the mold containing the graphene oxide precursor solution was placed in a vacuum drying oven under a negative pressure environment of 1 Pa for 2 h to fully remove the dissolved air in the solution. After taking out, the mold was vibrated to ensure the flatness of the liquid surface, and then placed in an oven at 60 °C for 12 h to dry, obtaining a graphene oxide film. The film was cut into a 4 cm x 4 cm square for later use.

[0029] 2) The cut graphene oxide film was sandwiched into a sandwich structure using a graphite plate and placed in a high-temperature tube furnace. Argon was introduced as a protective atmosphere, first at a flow rate of 3000 seem for 5 min to fully remove the air in the tube, and then at a flow rate of 200 seem during the thermal reduction process. The high-temperature tube furnace was heated to 1000 °C at a rate of 10 °C / min and kept for 1 h, and then slowly cooled to room temperature to obtain a 1000 °C reduced graphene positive triboelectric sensing material.

[0030] 3) The reduced graphene film was cut into a size of 2 cm x 2 cm and combined with a commercial tribo-negative material polytetrafluoroethylene film (2 cm x 2 cm, thickness 200 pm) to form a triboelectric nanogenerator to test its positive triboelectric sensing performance.

[0031] Example 2:

[0032] In combination Figure 1 (b-e-i) flow, a method for preparing a super-tough high-performance graphene positive triboelectric sensing material is as follows:

[0033] 1) Large size graphene oxide (about 50 pm in diameter) precursor was prepared by modified Hummers method. 100 ml graphene oxide precursor solution (8 mg / ml) was taken and placed in a vacuum drying oven under a negative pressure environment of 1 Pa for 2 h to fully remove the dissolved air in the solution. The well-deaerated solution was added to a customized polytetrafluoroethylene mold (15 cm in diameter) and vibrated to ensure the flatness of the liquid surface. It is important to use a circular mold for the film forming process, which can eliminate the local stress in the film forming process and ensure the uniformity of the graphene oxide film. Then it was placed in an oven at 60 °C for 12 h to dry, obtaining a graphene oxide film. The film was cut into a 4 cm x 4 cm square for later use.

[0034] 2) Using graphite plate to sandwich the cut graphene oxide film into a sandwich structure, and put it into a high-temperature graphitization atmosphere furnace. Argon is introduced as a protective atmosphere. First, 1000 seem of argon is introduced for 30 min to fully remove the air in the furnace, and then the argon flow is maintained at 500 seem during the thermal reduction process, and water cooling measures are taken. The high-temperature graphitization atmosphere furnace is heated to 1000°C at a rate of 5°C / min, and then kept for 30 min, and then heated to 3000°C at a rate of 10°C / min and kept for 1 h. Finally, slowly reduce to room temperature to obtain 3000°C reduced graphene positive triboelectric sensing material.

[0035] 3) The reduced graphene film is cut into a size of 2 cm x 2 cm and combined with a commercial friction negative material polytetrafluoroethylene film (2 cm x 2 cm, thickness 200 pm) to form a triboelectric nanogenerator to test its positive triboelectric sensing performance.

[0036] Example 3:

[0037] In combination Figure 2 and Figure 3 The relationship between the atomic structure and performance of graphene positive triboelectric materials treated at different reduction temperatures is as follows:

[0038] According to the theoretical calculation and experimental characterization:

[0039] During the thermal treatment of graphene oxide, 0°C-1000°C mainly occurs oxygen removal and carbon vacancy generation. In this stage, oxygen defects gradually decrease and carbon defects gradually increase. At 1000°C-3000°C, carbon vacancy repair and carbon conductive network reconstruction occur, accompanied by complete removal of a small amount of residual oxygen. Therefore, the conductivity of graphene positive triboelectric material increases exponentially with the increase of treatment temperature, especially in the carbon conductive network reconstruction process after 1000°C. In addition, the mechanical properties are the worst at 1000°C (the film is brittle), and the main reason is that a large number of carbon vacancies exposed after oxygen removal weaken the strength of the graphene network. As shown in (b), the graphene network is repaired after 2000°C, and the film has excellent toughness. Figure 2

[0040] Figure 3 The influence of carbon and oxygen defects on the work function of graphene material is obtained by first-principles calculation. Carbon defects increase the work function, and oxygen defects significantly reduce the work function. During 0°C-3000°C, oxygen defects continuously decrease, and carbon defects first increase and then decrease. At around 2500°C, the minimum work function is achieved, and at this time, the graphene positive triboelectric material has the highest triboelectric nanogenerator output.

[0041] Example 4:

[0042] In combination Figure 4 ​A preparation method and performance verification of a friction nanogenerator composed of super-tough high-performance graphene positive triboelectric sensing material, as follows:

[0043] 1), as shown in Figure 4 (a), a customized acrylic substrate is used as a shell and a loading device, a spring is used as a support layer and provides a rebound force. The 3000 DEG C reduced graphene film is pasted on one side of the acrylic substrate as an electrode layer using polyurethane double-sided tape, and a red wire is used for lead-out. Then, the 2500 DEG C reduced graphene positive triboelectric sensing material is pasted as a positive triboelectric layer using polyurethane double-sided tape. The 3000 DEG C reduced graphene film is pasted on the other side of the acrylic substrate as an electrode layer using polyurethane double-sided tape, and a black wire is used for lead-out. Then, a commercial polytetrafluoroethylene film is pasted as a negative triboelectric layer using polyurethane double-sided tape. The size of the double-sided tape and each layer of film is 2 cm x 2 cm.

[0044] 2), the above friction nanogenerator device is pushed to perform contact separation movement using a linmot1100 motor. The frequency is 2 Hz, and the movement distance is 1 cm. The friction power generation voltage and current data are measured using a jisiheli electrometer 6514. The output power is calculated, and the Figure 4 (b) power density is obtained.

[0045] As can be seen from the above examples, the present application provides a graphene positive triboelectric sensing material based on carbon network regulation. The entire preparation process is simple in process equipment and high in production efficiency, and is suitable for large-scale production and popularization and application.

Claims

1. A method for preparing graphene positive triboelectric sensing materials based on carbon network modulation, characterized in that, Includes the following steps: Step 1: The graphene oxide solution is subjected to negative pressure treatment in a vacuum drying oven to remove dissolved air and obtain a preliminary film-forming solution; Step 2: The preliminary film-forming solution is poured into a polytetrafluoroethylene mold and dried in a vacuum oven to prepare a precursor graphene oxide film; Step 3: The precursor graphene oxide film is subjected to thermal reduction treatment in a high-temperature graphitization atmosphere furnace to control carbon network defects. The conditions are: constant temperature heating from 1500 ℃ to 3000 ℃ for reduction, argon protective environment, and finally cooling to room temperature to obtain a graphene positive triboelectric sensing material based on carbon network regulation. During the thermal reduction in the high-temperature graphitization atmosphere furnace, the temperature is first raised to 1000 ℃ at a heating rate of 5 ℃ / min, and then raised to 1500 ℃, 2000 ℃, 2500 ℃ or 3000 ℃ at a heating rate of 10 ℃ / min. After holding at the temperature for 1 h, the temperature is slowly lowered to room temperature, and the argon flow rate is 200~500 sccm.

2. The preparation method according to claim 1, characterized in that, In step one, the concentration of the graphene oxide solution is 4~10 mg / ml, the graphene oxide sheet diameter is not less than 30 μm, the negative pressure environment of the vacuum drying oven is 1 Pa, and the processing time is 2 h.

3. The preparation method according to claim 2, characterized in that, In step two, the polytetrafluoroethylene mold is a circular mold with a diameter of 10-15 cm, and the drying conditions of the vacuum oven are 40-60 ℃ and the drying time is 12 h.

4. The preparation method according to claim 3, characterized in that, In step three, the graphene oxide film must be processed in a sandwich structure with two graphite plates sandwiched between them during the thermal reduction process to ensure uniform reduction.

5. A graphene positive triboelectric sensing material based on carbon network regulation prepared according to any one of claims 1-4.

6. A triboelectric nanogenerator, characterized in that, This includes the graphene positive triboelectric sensing material based on carbon network regulation as described in claim 5 as the positive triboelectric sensing material and polytetrafluoroethylene as the negative triboelectric material.

7. The triboelectric nanogenerator according to claim 6, characterized in that, The generator's contact separation frequency is 2 Hz and the movement distance is 1 cm.

Images