Graphene positive triboelectric sensing material regulated and controlled based on carbon network and preparation method of graphene positive triboelectric sensing material

Abstract

The invention provides a graphene positive triboelectric sensing material based on carbon network regulation and a preparation method thereof. The graphene oxide film is subjected to multi-temperature-zone thermal reduction treatment, the ratio of carbon to oxygen defects on a carbon network is accurately regulated and controlled, and work function optimization, mechanical performance enhancement and remarkable improvement of frictional electricity output performance are achieved. The preparation process comprises the following steps: vacuum treatment and uniform film formation of a graphene oxide solution, and regulation and control of defect distribution at different thermal reduction temperatures. According to the method, a stable carbon conductive network is constructed by optimizing carbon defects and eliminating oxygen defects, so that the graphene film has high electropositivity and toughness at the same time. The friction nano-generator constructed based on the material has ultrahigh output performance and excellent long-term stability. The preparation method disclosed by the invention is simple in process and suitable for large-scale production, provides a brand new material solution for the fields of flexible electronics, intelligent sensing and nano power generation, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of energy and new materials, and in particular to a graphene positive triboelectric sensing material regulated based on a carbon network and a preparation method thereof. Background Art

[0002] Graphene material as sp 2 The most basic form of hybrid carbon allotrope, due to its atomic-thickness Large specific surface area (2630m 2 / g), high mechanical strength (1TPa), ultra-high carrier mobility (>10 6 cm / V / s) and a series of excellent properties such as controllable band gap have shown broad application prospects in fields including optoelectronics and sensor devices, advanced semiconductors, integrated circuits and nano-power generation. In TENG research, graphene can be used not only as an electrode, but also as a positive friction material. However, the graphene materials currently prepared by reducing graphene oxide often have the following problems:

[0003] (1) Low electropositivity: The insufficiently optimized preparation process results in a low work function of the material, which limits its positive friction performance.

[0004] (2) Insufficient mechanical properties: Carbon defects during the reduction process will weaken the structural strength of the graphene network, causing the film to be brittle and cracked.

[0005] (3) Output performance decay: During long-term operation, oxygen defects can easily cause interface charge capture, resulting in a gradual decrease in output performance.

[0006] Therefore, the design of triboelectric materials with tailored work functions is the key to improving the output performance of triboelectric nanogenerators (TENGs). Summary of the invention

[0007] The present invention aims to provide a method for preparing a graphene positive triboelectric sensing material based on carbon network regulation, so as to achieve precise regulation of the work function of the triboelectric material and enhancement of the mechanical properties.

[0008] The technical solution adopted by the present invention is as follows: A method for preparing a graphene positive triboelectric sensing material based on carbon network regulation, comprising the following steps:

[0009] Step 1: subjecting the graphene oxide solution to negative pressure treatment in a vacuum drying oven to remove dissolved air to obtain a preliminary film-forming solution;

[0010] Step 2: pouring the preliminary film-making solution into a polytetrafluoroethylene mold, placing it in a vacuum oven for drying, and preparing a precursor graphene oxide film;

[0011] Step three: thermally reduce the precursor graphene oxide film in a high-temperature graphitization atmosphere furnace to control the carbon network defect regulation. The conditions are: constant temperature heating to 1500°C to 3000°C for reduction, argon gas to protect the environment, and finally cooling to room temperature to obtain a graphene positive triboelectric sensing material based on carbon network regulation.

[0012] Furthermore, in step 1, the concentration of the graphene oxide solution is 4-10 mg / ml, the diameter of the graphene oxide flakes contained therein 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.

[0013] Furthermore, in step 2, the polytetrafluoroethylene mold is a circular mold with a diameter of 10 to 15 cm, and the drying condition of the vacuum oven is 40 to 60° C., and the drying time is 12 hours.

[0014] Furthermore, in step three, when thermal reduction is carried out in a high-temperature graphitizing atmosphere furnace, the temperature is first heated to 1000°C at a heating rate of 5°C / min, and then heated to a constant temperature of 1500°C, 2000°C, 2500°C or 3000°C at a heating rate of 10°C / min; after maintaining the temperature for 1 hour, the temperature is slowly lowered to room temperature, and the argon gas flow rate is 200-500sccm.

[0015] Furthermore, in step three, the graphene oxide film needs to be treated with two graphite sheets as a sandwich structure during the thermal reduction process to ensure uniform reduction.

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

[0017] Another object of the present invention is to provide a carbon network-regulated graphene positive triboelectric sensing material prepared by the method described above, wherein the material is obtained by heating to a constant temperature of 2500°C-3000°C during thermal reduction in a high-temperature graphitizing atmosphere furnace.

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

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

[0020] Advantages and beneficial effects of the present invention: The preparation method of the present invention is simple in process and suitable for large-scale production. It provides a new material solution for the fields of flexible electronics, intelligent sensing and nano-power generation, and has broad application prospects. At the same time, the ultra-tough high-performance graphene positive triboelectric sensing material prepared by the present invention has excellent mechanical properties and high triboelectric output performance. The present invention controls the carbon network defects by thermal reduction to accurately regulate the carbon and oxygen defect ratios on its surface and edge, thereby achieving dynamic optimization of the material work function and conductive properties, and improving the potential for wide application of graphene materials in the fields of nano-power generation, flexible electronics and sensing. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 2 The electrical and mechanical properties of graphene positive triboelectric sensing materials; (a) electrical conductivity of graphene positive triboelectric sensing materials at different reduction temperatures; (b) mechanical properties of graphene films reduced at 2500℃.

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

[0024] Figure 4 Performance test diagram of the friction nanogenerator based on graphene positive triboelectric sensing material; (a) Schematic diagram of the friction nanogenerator test system including graphene positive triboelectric sensing material and commercial polytetrafluoroethylene; (b) Output power density of the friction nanogenerator based on graphene positive triboelectric sensing material at different reduction temperatures. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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.

[0026] Embodiment 1:

[0027] Combination Figure 1 The process of (bci), a method for preparing an ultra-tough and high-performance graphene positive triboelectric sensing material, is as follows:

[0028] 1) Large-diameter graphene oxide (about 50 μm in diameter) precursor was prepared by the improved Hummers method. Take 50 ml of graphene oxide precursor solution (8 mg / ml) and add 50 ml of deionized water to adjust the concentration. After fully stirring, add 100 ml of the solution into a customized polytetrafluoroethylene mold (circular with a diameter of 15 cm). Note that the use of a circular mold is crucial for the film-forming process. It can eliminate local stress during the film-forming process and ensure the uniformity of the graphene oxide film. Then put the mold containing the graphene oxide precursor solution into a vacuum drying oven with a negative pressure environment of 1 Pa for 2 hours to fully remove the dissolved air in the solution. After taking it out, vibrate the mold to ensure that the liquid surface is flat, and then put it into an oven and dry it at 60°C for 12 hours to obtain a graphene oxide film. Cut the film into 4 cm×4 cm squares for use.

[0029] 2) Use graphite plates to sandwich the cut graphene oxide films into a sandwich structure and place them in a high-temperature tube furnace. Introduce argon as a protective atmosphere, first pass argon at a flow rate of 3000sccm for 5 minutes to fully exclude the air in the tube, and then keep the argon flowing at a flow rate of 200sccm during the thermal reduction process. The high-temperature tube furnace is heated to 1000℃ at a heating rate of 10℃ / min, and kept warm for 1h, and finally slowly cooled to room temperature to obtain 1000℃ reduced graphene positive triboelectric sensing material.

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

[0031] Embodiment 2:

[0032] Combination Figure 1 (bei) process, a method for preparing an ultra-tough high-performance graphene positive triboelectric sensing material, is as follows:

[0033] 1) Large-diameter graphene oxide (about 50 μm in diameter) precursor was prepared by the improved Hummers method. 100 ml of graphene oxide precursor solution (8 mg / ml) was placed in a vacuum drying oven with a negative pressure of 1 Pa for 2 hours to fully remove the dissolved air in the solution. The fully degassed solution was added to a customized polytetrafluoroethylene mold (circular with a diameter of 15 cm) and vibrated to ensure that the liquid surface was flat. Note that the use of a circular mold is crucial for the film-forming process, as it can eliminate local stress during the film-forming process and ensure the uniformity of the graphene oxide film. It was then placed in an oven and dried at 60°C for 12 hours to obtain a graphene oxide film. The film was cut into 4 cm × 4 cm squares for later use.

[0034] 2) Use graphite plates to sandwich the cut graphene oxide films into a sandwich structure and put them into a high-temperature graphitization atmosphere furnace. Introduce argon as a protective atmosphere. First, pass argon at a flow rate of 1000sccm for 30 minutes to fully exclude the air in the furnace. Then, keep the argon flowing at a flow rate of 500sccm during the thermal reduction process, and take water cooling measures. The high-temperature graphitization atmosphere furnace is heated to 1000℃ at a heating rate of 5℃ / min and kept warm for 30min, then heated to 3000℃ at a heating rate of 10℃ / min and kept warm for 1h. Finally, slowly cool to room temperature to obtain a 3000℃ reduced graphene positive triboelectric sensing material.

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

[0036] Embodiment 3:

[0037] 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 explained as follows:

[0038] According to theoretical calculation and experimental characterization, we get:

[0039] During the heat treatment of graphene oxide, oxygen is released and carbon vacancies are generated at 0℃~1000℃. In this stage, oxygen defects gradually decrease, while carbon defects gradually increase. At 1000℃~3000℃, carbon vacancies are repaired and the carbon conductive network is reconstructed, accompanied by the complete release of the remaining small amount of oxygen. Therefore, the electrical conductivity of graphene positive triboelectric materials increases exponentially with the increase of treatment temperature, especially in the reconstruction process of the carbon conductive network after 1000℃. In addition, the mechanical properties are the worst at 1000℃ (the film is brittle), mainly because a large number of carbon vacancies are exposed after the oxygen is released, which weakens the strength of the graphene network. Figure 2 As shown in (b), after 2000°C, the graphene network is repaired and the film has excellent toughness.

[0040] Figure 3 The effect of carbon and oxygen defects on the work function of graphene materials calculated by first principles. The work function decreases with the increase of carbon defects, and the work function decreases significantly with the decrease of oxygen defects. In the process of 0℃~3000℃, there is a trend that oxygen defects continue to decrease, while carbon defects first increase and then decrease. The minimum work function is achieved near 2500℃, at which time the graphene positive triboelectric material has the highest triboelectric nanopower generation output.

[0041] Embodiment 4:

[0042] Combination Figure 4, a preparation method and performance verification of a friction nanogenerator composed of ultra-tough and high-performance graphene positive triboelectric sensing material are as follows:

[0043] 1) If Figure 4 As shown in (a), a customized acrylic substrate is used as the housing and loading device, and the spring is used as the support layer and provides the rebound force. On one side of the acrylic substrate, a graphene film reduced at 3000℃ is attached with polyurethane double-sided tape as the electrode layer, and a red wire is used to lead out. Subsequently, a graphene positive triboelectric sensing material reduced at 2500℃ is attached with polyurethane double-sided tape as the positive friction layer. On the other side of the acrylic substrate, a graphene film reduced at 3000℃ is attached with polyurethane double-sided tape as the electrode layer, and a black wire is used to lead out. Subsequently, a commercial polytetrafluoroethylene film is attached with polyurethane double-sided tape as the negative friction layer. The size of the double-sided tape and each layer of film is 2cm×2cm.

[0044] 2) Use the linmot1100 motor to drive the above-mentioned friction nanogenerator device to perform contact and separation movement. The frequency is 2Hz and the movement distance is 1cm. Use Keithley electrometer 6514 to measure the friction power generation voltage and current data. Calculate the output power and get Figure 4 (b) Power density.

[0045] From the above examples, it can be seen that the present invention provides a graphene positive triboelectric sensing material based on carbon network regulation. The whole preparation process has simple process equipment and high production efficiency, which is suitable for large-scale production and promotion and application.

Claims

1. A method for preparing a graphene positive triboelectric sensing material based on carbon network regulation, characterized in that: The following steps are involved: Step 1: subjecting the graphene oxide solution to negative pressure treatment in a vacuum drying oven to remove dissolved air to obtain a preliminary film-forming solution; Step 2: pouring the preliminary film-making solution into a polytetrafluoroethylene mold, placing it in a vacuum oven for drying, and preparing a precursor graphene oxide film; Step three: thermally reduce the precursor graphene oxide film in a high-temperature graphitization atmosphere furnace to control the carbon network defect regulation. The conditions are: constant temperature heating at 1500°C to 3000°C for reduction, argon gas to protect the environment, and finally cooling to room temperature to obtain a graphene positive triboelectric sensing material based on carbon network regulation.

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

3. The preparation method according to claim 2, characterized in that: In step 2, the polytetrafluoroethylene mold is a circular mold with a diameter of 10 to 15 cm, and the drying condition of the vacuum oven is 40 to 60° C., and the drying time is 12 hours.

4. The preparation method according to claim 3, characterized in that: In step three, when thermal reduction is carried out in a high-temperature graphitizing atmosphere furnace, first heat to 1000°C at a heating rate of 5°C / min, and then heat to 1500°C, 2000°C, 2500°C or 3000°C at a heating rate of 10°C / min; after keeping the temperature constant for 1 hour, slowly cool to room temperature, and the argon gas flow rate is 200-500sccm.

5. The preparation method according to claim 4, characterized in that: In step three, the graphene oxide film needs to be treated with two graphite sheets as a sandwich structure during the thermal reduction process to ensure uniform reduction.

6. A carbon network-regulated graphene positive triboelectric sensing material prepared according to any one of claims 1 to 5.

7. A carbon network-regulated graphene positive triboelectric sensing material prepared according to any one of claims 1 to 5, wherein the material is prepared by heating to a constant temperature of 2500°C-3000°C during thermal reduction in a high-temperature graphitizing atmosphere furnace.

8. A friction nanogenerator, characterized in that: It includes the carbon network-regulated graphene positive friction electric sensing material as described in claim 7 as the positive friction electric sensing material and polytetrafluoroethylene as the negative friction material.

9. The triboelectric nanogenerator according to claim 8, characterized in that: The contact and separation frequency of the generator is 2 Hz and the movement distance is 1 cm.

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