Joule heat activated graphene film and preparation method thereof

Abstract

The invention discloses a Joule thermal activated graphene film and a preparation method thereof, and the method comprises the following steps: A, preparing a conductive composite film, and enabling an activator crystal to be attached to the interior of the conductive composite film; b, the two ends of the conductive composite film are electrified in the processing environment of inert gas, and the temperature generated by electrification is 300-800 DEG C; and C, cleaning and drying to obtain the Joule heat activated graphene film. Joule heating used in the scheme can achieve rapid and uniform heating, the heating process is highly uniform, heat waste is little, and compared with a traditional combustion heating system, the Joule heating system has the remarkable time advantage. According to the scheme, a relatively high activation reaction temperature can be achieved within several seconds by utilizing a Joule heating mode, and the temperature distribution is uniform and cannot change along with the change of the thickness of the graphene film, so that the problem that the deep hole structure of the porous graphene is difficult to adjust can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene film processing, and particularly relates to a Joule heat-activated graphene film and a preparation method thereof. Background Art

[0002] Graphene is a two-dimensional material composed of a single layer of carbon atoms with sp 2 hybrid orbitals, having many unique physical and chemical properties, and especially with high electrical conductivity, high specific surface area, and high chemical stability, making it show great application potential in the fields of electronics, energy, etc. The activation technology can reconstruct two-dimensional sheet-like graphene into three-dimensional porous materials, and the pore size distribution is mainly composed of nano-scale pores of micropores and mesopores. The graphene treated by activation has a high specific surface area and good electrical conductivity.

[0003] Traditional graphene activation methods generally involve mixing graphene powder with an activator and placing it in a high-temperature furnace for high-temperature heat treatment, or heating graphene powder in a protective atmosphere and then introducing an activation gas such as carbon dioxide for activation. The above methods all use traditional combustion heating systems, and the heating conditions are difficult to control, making it difficult to achieve rapid, uniform, and effective heating, easily leading to heat waste, inconsistent activation effects, and reduced production efficiency, increasing the preparation difficulty and cost of graphene films.

[0004] Laser-induced graphene (LIG) technology is low-cost, maskless, binder-free, pattern-customizable, and does not require any film-forming treatment, and can be prepared on a large scale. It is an efficient, controllable, and environmentally friendly processing method. Using KOH to activate laser-induced graphene can increase the microporous structure of graphene, improve its specific surface area, and increase surface active sites, but it is limited by the fact that the laser generally can only act on the surface of the carbon-based film, which is a huge challenge for regulating the deep porous structure of graphene. Summary of the Invention

[0005] The purpose of the present invention is to provide a Joule heat-activated graphene film and a preparation method thereof, which can effectively solve the technical problem in the prior art that the porous structure inside the graphene film is difficult to accurately regulate, thus restricting the further improvement of the specific surface area of the graphene film, so as to overcome the deficiencies in the prior art.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a Joule heat-activated graphene film, comprising the following steps:

[0008] A. Prepare a conductive composite film, and an activator crystal is attached inside the conductive composite film;

[0009] B. Under the processing environment of inert gas, apply electricity to both ends of the conductive composite film, and the temperature generated by the electricity application is 300 - 800 °C;

[0010] C. After cleaning and drying, obtain the Joule heat-activated graphene film.

[0011] Preferably, in step B, the applied voltage for the electricity application is 10 - 80 V, and the electricity application time is 15 - 60 min.

[0012] Preferably, in step A, the activator crystal is any one of potassium hydroxide, zinc chloride, sodium hydroxide, potassium carbonate, and calcium acetate;

[0013] In step B, connect the current collector to both ends of the conductive composite film respectively, and the electrodes of the discharge power supply are connected to both ends of the conductive composite film through the current collector to apply electricity;

[0014] The distance between the current collectors at both ends of the conductive composite film is 10 - 30 mm.

[0015] Preferably, step A specifically includes:

[0016] A11. Clean and dry the flexible insulating carbon-based film, and make the activator crystal adhere to the inside of the flexible insulating carbon-based film;

[0017] A12. Use laser to act on the surface of the flexible insulating carbon-based film, and obtain the conductive composite film after carbonization and graphitization;

[0018] Among them, in step A11, the thickness of the flexible insulating carbon-based film is 80 - 100 μm, and the mass ratio of the flexible insulating carbon-based film to the activator crystal is 4:(1 - 4);

[0019] In step A12, the wavelength of the laser is 200 - 360 nm, the scanning method is parallel equidistant and row-by-row overlapping scanning, the scanning speed is 40 - 100 mm / s, the overlapping times of the light spot are 6 - 8 times, the laser power is 8.5 - 9.5 W, and the laser scanning spacing is 20 - 30 μm.

[0020] Preferably, the surface of the flexible insulating carbon-based film is hydrophobic;

[0021] Step A11 specifically includes:

[0022] Clean and dry the flexible insulating carbon-based film;

[0023] Modify the surface of the flexible insulating carbon-based film to obtain a hydrophilic surface;

[0024] Prepare the activator into an activator coating, scrape and coat it on the hydrophilic surface, and crystallize it after drying, so that the activator crystals adhere to the inside of the flexible insulating carbon-based film, and the drying temperature for drying is 60-90°C, and the drying time is 5-20 min;

[0025] Among them, the modification treatment is to use a laser to act on the surface of the flexible insulating carbon-based film to process a microstructure array with a spacing of 15-60 μm and a depth of 10-15 μm to form a hydrophilic surface;

[0026] Or use plasma to treat the surface of the flexible insulating carbon-based film to form a hydrophilic surface.

[0027] Preferably, the surface of the flexible insulating carbon-based film is hydrophilic;

[0028] Step A11 specifically includes:

[0029] Clean and dry the flexible insulating carbon-based film;

[0030] Prepare the activator into an activator solution, soak the flexible insulating carbon-based film in the activator solution for 15-30 min, and then place it in a drying oven for drying and crystallization, so that the activator crystals adhere to the inside of the flexible insulating carbon-based film, and the drying temperature of the drying oven is 60-80°C, the relative vacuum degree is -92 to -88 kPa, and the drying time is 15-30 min.

[0031] Preferably, step A specifically includes:

[0032] A21. Clean and dry the flexible conductive carbon-based film;

[0033] A22. Prepare the activator into an activator solution, soak the flexible conductive carbon-based film in the activator solution for 15-30 min, dry it and crystallize it, so that the activator crystals adhere to the inside of the flexible conductive carbon-based film to obtain a conductive composite film;

[0034] Among them, in step A21, the thickness of the flexible conductive carbon-based film is 50-125 μm;

[0035] The mass ratio of the flexible conductive carbon-based film to the activator crystals is 4:(1-4).

[0036] Preferably, step A specifically includes:

[0037] A31. Prepare graphene powder into a graphene solution, and prepare the activator into an activator solution. Mix the graphene solution and the activator solution and perform ultrasonic oscillation to obtain a graphene mixed dispersion;

[0038] A32. Spin-coat the graphene mixed dispersion into a film, and obtain a conductive composite film after drying;

[0039] Among them, in step A31, the mass ratio of the graphene powder to the activator is 4:(1-4);

[0040] The thickness of the conductive composite film is 50-125 μm.

[0041] Preferably, in step B, the inert gas is any one of nitrogen and argon.

[0042] In step C, the cleaning specifically includes:

[0043] Immerse the energized conductive composite film in a neutralizing solution and deionized water in sequence, and the immersion time of the conductive composite film in the neutralizing solution and in the deionized water is both 5-20 min;

[0044] Rinse the immersed conductive composite film with deionized water until the pH value of the rinsed deionized water is neutral.

[0045] A Joule-heated activated graphene film is prepared by the above-mentioned preparation method of the Joule-heated activated graphene film.

[0046] The technical solution provided by the present invention may include the following beneficial effects:

[0047] 1. The Joule heating used in this solution can achieve rapid and uniform heating, making the heating process highly uniform with less heat waste. Compared with the traditional combustion heating system, it has a significant time advantage. By using the Joule heating method, this solution can reach a relatively high activation reaction temperature within a few seconds, and the temperature distribution is uniform, without changing with the thickness of the graphene film, thus effectively solving the problem that it is difficult to adjust the pore structure deep in the porous graphene.

[0048] 2. The preparation method of this solution can effectively realize the continuous and rapid preparation of the activated graphene film, reduce the economic and time costs of the activated graphene film, and the Joule heating activation temperature is relatively low, the activation reaction is mild, which will not damage the flexibility of the graphene film, nor cause large-area damage and collapse of the nanopores. At the same time, it also improves the utilization rate of the specific surface area of graphene and the integrity of the nanoporous structure.

[0049] 3. This solution also uses different technical means to deeply mix the carbide with the activator according to different carbon-based films, so that the activator can enter deeper into the film and promote the deep development of the porous structure. Description of the Drawings

[0050] Figure 1It is a schematic diagram of the device in step B of a method for preparing a Joule heat-activated graphene film according to the present invention.

[0051] Figure 2 It is a schematic diagram of the distance between the current collectors at both ends of the conductive composite film in a method for preparing a Joule heat-activated graphene film according to the present invention.

[0052] Figure 3 It is an infrared thermal imaging picture during the Joule heat activation process in Example 1 of the present invention.

[0053] Figure 4 It is a nitrogen adsorption-desorption isotherm curve of the Joule heat-activated graphene film prepared in Example 1 of the present invention.

[0054] Figure 5 It is a pore size distribution diagram of the Joule heat-activated graphene film prepared in Example 1 of the present invention.

[0055] Figure 6 It is an SEM image (magnification parameter is 10k) of the Joule heat-activated graphene film prepared in Example 1 of the present invention.

[0056] Figure 7 It is an SEM image (magnification parameter is 40k) of the Joule heat-activated graphene film prepared in Example 1 of the present invention.

[0057] Figure 8 It is a nitrogen adsorption-desorption isotherm curve of the Joule heat-activated graphene film prepared in Example 2 of the present invention.

[0058] Figure 9 It is a pore size distribution diagram of the Joule heat-activated graphene film prepared in Example 2 of the present invention.

[0059] Figure 10 It is an SEM image (magnification parameter is 10k) of the Joule heat-activated graphene film prepared in Example 2 of the present invention.

[0060] Figure 11 It is an SEM image (magnification parameter is 40k) of the Joule heat-activated graphene film prepared in Example 2 of the present invention.

[0061] Among them, a vacuum chamber 1, an infrared thermal imager 2, and a conductive composite film 3. Detailed implementation manners

[0062] A method for preparing a Joule heat-activated graphene film, comprising the following steps:

[0063] A. Prepare a conductive composite film, and an activator crystal is attached inside the conductive composite film;

[0064] B. Under the processing environment of inert gas, apply electricity to both ends of the conductive composite film, and the temperature generated by the electricity application is 300 - 800 °C;

[0065] C. After cleaning and drying, a Joule-heated activated graphene film is obtained.

[0066] To solve the technical problem in the prior art that the porous structure inside the graphene film is difficult to precisely control, thus restricting the further improvement of the specific surface area of the graphene film, this technical solution proposes a preparation method for a Joule-heated activated graphene film, mainly including the following two stages:

[0067] The first stage is to prepare a conductive composite film with activator crystals attached inside, so that the activator can penetrate deep into the film to promote the deep development of the porous structure.

[0068] The second stage is to use the Joule heat generated by applying electricity to the conductive composite film to cause the activator that has penetrated deep into the film to undergo an in-situ activation reaction under high temperature, remove the amorphous carbon in the film, and release the gas generated therefrom, leaving many nano-scale pore structures, realizing the etching of the pore structure on the surface of graphene and improving the specific surface area of the graphene film.

[0069] During the Joule heating process, when the Joule heating temperature is too low, the conditions for the activator to participate in the reaction are not met, so the Joule activation effect cannot be achieved; when the Joule heating temperature is too high, the mechanical stress of the graphene film material will change, causing the flexibility of the material itself to be damaged and become brittle. Therefore, in this scheme, the Joule heating temperature is also controlled at 300 - 800 °C.

[0070] It should be noted that Joule heating can achieve rapid and uniform heating, making the heating process highly uniform with less heat waste. Compared with traditional combustion heating systems, it has a significant time advantage. This scheme can reach a relatively high activation reaction temperature within a few seconds by using the Joule heating method, and the temperature distribution is uniform, without changing with the thickness of the graphene film, thus effectively solving the problem that it is difficult to adjust the pore structure deep in the porous graphene.

[0071] In addition, this method can effectively realize the continuous and rapid preparation of the activated graphene film, reduce the economic and time costs of the activated graphene film, and the Joule heat activation temperature is relatively low, the activation reaction is mild, which will not damage the flexibility of the graphene film, and also avoids the large-area damage and collapse of the nano-pores. At the same time, it also improves the utilization rate of the specific surface area of graphene and the integrity of the nano-porous structure.

[0072] Furthermore, compared with the activator solution, the activation reaction after the crystallization of the activator will be more stable, without being affected by the flow of the liquid during processing, nor will it cause uneven regional loading due to the liquid flow, resulting in excessive ablation during the Joule heating process due to excessive local resistance.

[0073] Furthermore, this solution needs to be carried out in an inert gas processing environment to avoid the disturbance of air or oxygen in the air from affecting Joule activation, which may cause excessive local Joule heat energy and ablation by affecting the surface sheet resistance of the graphene film. At the same time, there are almost no water molecules in the inert gas processing environment, and due to the temperature provided by Joule heat, there is no need to take measures to control the temperature and humidity of the processing environment to prevent the activator crystallization from deliquescing.

[0074] Preferably, in step B, the temperature of the external environment of the inert gas (i.e., the environment outside the processing environment) is 55 - 75°C, and the relative humidity < 10%. During the in-situ activation reaction in step B, some of the activator crystals may absorb water molecules from the external environment and deliquesce. Therefore, to prevent the impact of deliquescence on subsequent processing, this solution can also regulate the temperature and humidity of the environment outside the processing environment.

[0075] In a specific embodiment, step B in the method for preparing a graphene film by Joule heat activation according to this solution can be carried out in a device as Figure 1 shown. Specifically, the above device includes a vacuum chamber 1, an infrared thermal imager 2, and a conductive composite film 3. The infrared thermal imager 2 is installed on the inner top of the vacuum chamber 1, and the conductive composite film 3 is installed on the inner bottom of the vacuum chamber 1, and the detection end of the infrared thermal imager 2 faces the surface of the conductive composite film 3. Connect the positive and negative poles of an external power supply to both ends of the conductive composite film 3, then evacuate the air inside the vacuum chamber 1 and introduce an inert gas, and monitor and record the surface temperature of the conductive composite film 3 through the infrared thermal imager 2.

[0076] Furthermore, it should be noted that in step B, the applied voltage is 10 - 80V, and the energization time is 15 - 60 min.

[0077] To ensure the formation of a graphene film with a high specific surface area and a nano-porous structure, this solution also optimizes the voltage and time during the energization process. By applying a voltage to the conductive composite film, Joule heat is generated to rapidly heat up the conductive composite film. Then, heat preservation is carried out under the protection of an inert gas to achieve in-situ assisted activation, enabling the activator crystals to further react inside the carbide, promoting the growth of a deeper porous structure in the film and generating a richer nano-porous structure. Moreover, since the Coulomb force generated by the discharge voltage in this embodiment is small, it can effectively avoid having an adverse effect on the surface structure of the graphene film, thereby affecting the pore structure of the film.

[0078] Furthermore, in step A, the activator crystal is any one of potassium hydroxide, zinc chloride, sodium hydroxide, potassium carbonate, and calcium acetate;

[0079] In step B, the current collector is respectively connected to both ends of the conductive composite film, and the electrodes of the discharge power supply are connected to both ends of the conductive composite film through the current collector to conduct electricity;

[0080] The distance between the current collectors at both ends of the conductive composite film is 10 - 30 mm.

[0081] This solution also optimizes the specific type of the activator crystal. The above-mentioned activator crystals can all achieve a good activation effect when reacting with the carbide.

[0082] In addition, during the Joule activation process, by changing the distance between the current collectors at both ends of the conductive composite film, the resistance value of the part of the conductive composite film connected to the circuit is adjusted. The greater the distance between the current collectors, the greater the resistance value of the conductive composite film, and the greater the Joule heat generated. Coupled with the magnitude of the applied voltage, a larger temperature range can be regulated. For this reason, this solution preferably sets the distance between the two current collectors to 10 - 30 mm, as Figure 2 shown. If the distance is too short, the load resistance between the current collectors is too small, and then the Joule heat may be difficult to reach the temperature suitable for the activator reaction, resulting in poor activation effect; if the distance is longer, the conductive composite film between the current collectors may cause uneven distribution of Joule heat due to resistance differences.

[0083] It should be noted that the current collector in this solution can be any one of copper foil, aluminum foil, nickel foil, and conductive resin, and is connected to the end of the conductive composite film through conductive silver paste, conductive copper paste, or conductive rubber.

[0084] According to different types of carbon-based films, this solution uses different technical means to achieve the deep mixing of activator crystals inside the film to precisely control the porous structure inside the graphene film, specifically including the following:

[0085] In the first embodiment of this solution, step A specifically includes:

[0086] A11. Clean and dry the flexible insulating carbon-based film, and make the activator crystals adhere to the inside of the flexible insulating carbon-based film;

[0087] A12. Apply laser to the surface of the flexible insulating carbon-based film, and obtain a conductive composite film after carbonization and graphitization;

[0088] Among them, in step A11, the thickness of the flexible insulating carbon-based film is 80-100 μm, and the mass ratio of the flexible insulating carbon-based film to the activator crystals is 4:(1-4);

[0089] In step A12, the wavelength of the laser is 200-360 nm, the scanning method is parallel equidistant and progressive overlapping scanning, the scanning speed is 40-100 mm / s, the overlapping times of the light spot are 6-8 times, the laser power is 8.5-9.5 W, and the laser scanning pitch is 20-30 μm.

[0090] For the flexible insulating carbon-based film, in this solution, while using laser to induce carbonization of the flexible insulating carbon-based film loaded with activator crystals, the unreacted activator crystals are brought into the deeper layer of the carbide, realizing uniform mixing of the activator and the carbide, and obtaining a conductive composite film. It should be noted that the flexible insulating carbon-based film used in this solution can be any one of commercially available polyimide films, lignin biomass films, and polyimide papers.

[0091] Specifically, the embodiment mainly uses ultraviolet laser with a wavelength of 200-360 nm. Its short wavelength and small pulse width can provide rich photon energy and high instantaneous energy density, and can be absorbed by the flexible insulating carbon-based film to achieve carbonization and graphitization in a very short time. In this process, part of the activator will absorb the energy of the laser to achieve partial activation, generating larger-sized nano-pores, and part of the unreacted activator can enter the deeper layer under the overlapping scanning of the laser, realizing deep attachment of the activator crystals inside the film.

[0092] More specifically, since the energy distribution of the ultrafast ultraviolet laser is Gaussian distribution, when the laser energy is too concentrated, it may cause the exfoliation of graphene. Therefore, in order to prevent the generated graphene from being blown off by too high laser energy, this solution can also use defocusing treatment to reduce the energy density, and the defocusing distance of the laser is preferably 5-9 mm.

[0093] In addition, flexible insulating carbon-based films with different thicknesses have a certain impact on the processing results of the pore structure. When the film thickness is too small, under the condition of achieving uniform mixing of carbide and activator crystallization by laser, since the thickness of the carbide layer is greater than the film thickness, it is easy to cause the natural shedding of the carbide film; when the film thickness is relatively large, under the condition of achieving uniform mixing of carbide and activator crystallization by laser, due to the possible obstruction in the vertical direction during the heat conduction of the heat provided by the laser in the film, the energy received deep in the film is insufficient to reach the carbonization threshold, resulting in a smaller thickness of the carbide layer, and it is prone to shedding and ablation during subsequent processing.

[0094] Furthermore, the surface of the flexible insulating carbon-based film is hydrophobic;

[0095] Step A11 specifically includes:

[0096] Clean and dry the flexible insulating carbon-based film;

[0097] Modify the surface of the flexible insulating carbon-based film to obtain a hydrophilic surface;

[0098] Prepare the activator into an activator coating, scrape and coat it on the hydrophilic surface, and crystallize it after drying, so that the activator crystals adhere to the inside of the flexible insulating carbon-based film, and the drying temperature for drying is 60 - 90 °C, and the drying time is 5 - 20 min;

[0099] Among them, the modification treatment is to use laser to act on the surface of the flexible insulating carbon-based film to process a microstructure array with a spacing of 15 - 60 μm and a depth of 10 - 15 μm to form a hydrophilic surface;

[0100] Or use plasma to treat the surface of the flexible insulating carbon-based film to form a hydrophilic surface.

[0101] Furthermore, the surface of the flexible insulating carbon-based film is hydrophilic;

[0102] Step A11 specifically includes:

[0103] Clean and dry the flexible insulating carbon-based film;

[0104] Prepare the activator into an activator solution, soak the flexible insulating carbon-based film in the activator solution for 15 - 30 min, and then place it in a drying oven for drying and crystallization, so that the activator crystals adhere to the inside of the flexible insulating carbon-based film, and the drying temperature of the drying oven is 60 - 80 °C, the relative vacuum degree is -92 - -88 kPa, and the drying time is 15 - 30 min.

[0105] As a supplement to the above embodiments, when the surface of the flexible insulating carbon-based film is hydrophobic, in this embodiment, the surface of the film can be first subjected to a hydrophilic modification treatment. Forming a hydrophilic surface can reduce the surface tension, making it easier for the activator coating to spread on the surface and improving the wettability of the film surface.

[0106] In the second embodiment of this solution, step A specifically includes:

[0107] A21. Clean and dry the flexible conductive carbon-based film;

[0108] A22. Configure the activator into an activator solution, soak the flexible conductive carbon-based film in the activator solution for 15 - 30 minutes, then dry and crystallize it, so that the activator crystals adhere to the inside of the flexible conductive carbon-based film to obtain a conductive composite film;

[0109] Among them, in step A21, the thickness of the flexible conductive carbon-based film is 50 - 125 μm;

[0110] The mass ratio of the flexible conductive carbon-based film to the activator crystals is 4:(1 - 4).

[0111] For the flexible conductive carbon-based film, in this solution, the film can be conveniently and simply immersed in the activator solution and then dried and crystallized. It should be noted that the flexible conductive carbon-based film used in this solution can be any one of commercially available carbon paper and carbon nanotube films.

[0112] Preferably, the cleaning steps of the flexible insulating carbon-based film and the flexible conductive carbon-based film both include: using deionized water as the cleaning medium to ultrasonically clean the film, and the ultrasonic frequency of the ultrasonic cleaning is 40 kHz, the cleaning temperature is 30 °C, and the cleaning time is 5 minutes.

[0113] In the third embodiment of this solution, step A specifically includes:

[0114] A31. Configure graphene powder into a graphene solution, and configure the activator into an activator solution. Mix the graphene solution and the activator solution and then perform ultrasonic oscillation to obtain a graphene mixed dispersion;

[0115] A32. Spin-coat the graphene mixed dispersion into a film and dry it to obtain a conductive composite film;

[0116] Among them, in step A31, the mass ratio of the graphene powder to the activator is 4:(1 - 4);

[0117] The thickness of the conductive composite film is 50 - 125 μm.

[0118] For the graphene film, in this solution, graphene powder and an activator can be first configured into a graphene mixed dispersion liquid, and then a film can be formed by spin coating to achieve deep mixing of the activator inside the graphene film.

[0119] It should be noted that in the above embodiments, the concentration of the activator solution used is preferably 100-200 g / L. If the concentration of the activator is too low, the activation effect may be reduced, and the time required in the drying and crystallization process will be longer, affecting the processing efficiency; in some activator solutions, such as potassium hydroxide which is a strong base, if a high-concentration activator solution is used for experiments, there is a relatively high safety risk during the experiment. Therefore, the upper limit of its concentration is also limited in this solution. In addition, water or ethanol can be used as a solvent to configure the activator in this solution, which is not limited here.

[0120] In the above three specific embodiments, the dosage of the activator is preferably selected in this solution to avoid the excessive dosage of the activator affecting the processing of graphene on the premise of ensuring the activation effect of the activator crystallization.

[0121] Furthermore, it is further explained that in step B, the inert gas is any one of nitrogen and argon.

[0122] In step C, the cleaning specifically includes:

[0123] The energized conductive composite film is successively immersed in a neutralizing solution and deionized water, and the immersion time of the conductive composite film in the neutralizing solution and in the deionized water is both 5-20 min;

[0124] The immersed conductive composite film is rinsed with deionized water until the pH value of the rinsed deionized water is neutral.

[0125] Preferably, when nitrogen is used as the inert gas in this solution, a gas flowmeter can be used to control the nitrogen flow rate, and the introduced flow rate is preferably 80-120 mL / min. This is because when the nitrogen flow rate is too fast, it is easy to destroy the stable gas environment on the surface of the graphene film, disrupt the Joule heat field distribution, and at the same time reduce the utilization rate, resulting in waste; while when the nitrogen flow rate is too slow, it is easy to cause the problem of poor sample consistency after Joule activation and also reduce the production efficiency.

[0126] In addition, the cleaning step in step C is further refined in this solution. The neutralizing solution can remove the excess activator crystals remaining on the graphene film, and deionized water has a good cleaning effect and can penetrate into the nano-hole structure for deep cleaning. It should be noted that when the aqueous solution of the activator crystal is acidic, a dilute alkaline solution should be used as the neutralizing solution, and when the aqueous solution of the activator crystal is alkaline, a dilute acidic solution should be used as the neutralizing solution.

[0127] A kind of graphene film activated by Joule heat, which is prepared by the preparation method of the above-mentioned graphene film activated by Joule heat.

[0128] The technical solution of the present invention will be further described below through specific embodiments.

[0129] Example 1

[0130] A. Prepare a conductive composite film, and an activator crystal is attached inside the conductive composite film;

[0131] Among them:

[0132] A11. Clean and dry the polyimide film;

[0133] Modify the surface of the polyimide film to obtain a hydrophilic surface;

[0134] Prepare potassium hydroxide into a potassium hydroxide coating with a concentration of 100 g / L, and scrape it on the hydrophilic surface. After drying and crystallization, the potassium hydroxide crystal is attached to the inside of the polyimide film, and the drying temperature of the drying is 60 °C, and the drying time is 5 min;

[0135] A12. Use laser to act on the surface of the polyimide film, and obtain a conductive composite film after carbonization and graphitization;

[0136] Among them, in step A11, the thickness of the polyimide film is 100 μm, and the mass ratio of the polyimide film to potassium hydroxide is 2:1; the modification treatment is to use a laser with a scanning speed of 800 mm / s and a laser power of 12 W to act on the surface of the polyimide film, and process a microstructure array with a spacing of 50 μm and a depth of 15 μm to form a hydrophilic surface;

[0137] In step A12, the laser is an ultraviolet ultrafast laser, the scanning method is parallel equidistant and row-by-row overlapping scanning, the scanning speed is 60 mm / s, the number of overlapping times of the light spot is 8 times, the laser power is 8.5 W, the laser scanning spacing is 30 μm, and the processing environment temperature of the laser is 50 °C. The thickness of the carbonized layer in the obtained conductive composite film is 60 μm.

[0138] B. Connect both ends of the conductive composite film 3 to the copper foil with conductive silver paste, and make the distance between the two copper foils 20 mm. Then place it in the vacuum box 1. After exhausting the air in the vacuum box 1, introduce nitrogen, and control the nitrogen flow rate to be 100 L / min;

[0139] Pass an electric current between the conductive composite films 3 by using a discharge power supply, the energizing voltage is 60 V, and the infrared thermal imager 2 records that the temperature of the film surface heated by Joule heat is 400 ± 10 °C, as Figure 3 shown, and the energizing time is 30 min.

[0140] C. Immerse the energized conductive composite film in 0.1 M dilute hydrochloric acid for 3 min, and then immerse it in deionized water for 20 min; rinse the soaked conductive composite film with deionized water until the pH value of the rinsed deionized water is neutral to obtain a Joule heat-activated graphene film.

[0141] The Joule heat-activated graphene film prepared in Example 1 has a rich micro-nano porous structure. Perform nitrogen adsorption-desorption tests and scanning electron microscopy (SEM) analysis on it, and the results are as follows Figures 4 - 7 shown. According to Figure 4 the nitrogen adsorption-desorption isotherm curve of Figure 5 and the pore size distribution diagram of Figure 6 it can be obtained that the pore size distribution of the Joule heat-activated graphene film processed in Example 1 is mainly composed of micropores less than 2 nm, and it has a very high specific surface area; according to Figure 6 the SEM images with a magnification parameter of 10k and Figure 7 the SEM images with a magnification parameter of 10k, it can be obtained that the processed Joule-activated graphene film has a regularly arranged "honeycomb"-shaped microporous structure. The formation of this structure is attributed to the activation effect of Joule heat. During the laser carbonization process in step A12, during the mixing of the activator with the carbide, some transition metal ions are embedded inside the graphene, and further reactions occur using Joule heat during the activation process in step B, broadening the size of the porous structure and facilitating the generation of nano-scale pores, forming a Joule heat-activated graphene film with a rich porous structure.

[0142] Example 2

[0143] A. Prepare a conductive composite film, and an activator crystal is attached inside the conductive composite film;

[0144] Among them:

[0145] A21. Clean and dry the carbon paper;

[0146] A22. Prepare a potassium hydroxide solution with a concentration of 100 g / L. Immerse the carbon paper in the potassium hydroxide solution for 30 min, and then dry it at 80 °C for 20 min to crystallize, so that the potassium hydroxide crystals are attached to the inside of the carbon paper to obtain a conductive composite film;

[0147] Among them, in step A21, the thickness of the carbon paper is 60 μm; the mass ratio of the carbon paper to the activator crystal is 2:1.

[0148] B. Connect both ends of the conductive composite film 3 to the copper foil using conductive silver paste, and make the distance between the two copper foils 20 mm. Then place it in the vacuum chamber 1. After exhausting the air in the vacuum chamber 1, introduce nitrogen, and control the nitrogen flow rate to be 100 L / min;

[0149] A discharge power source is used to pass current between the conductive composite film 3, the voltage of which is 80 V, and the infrared thermal imager 2 records that the Joule-heated temperature of the film surface is 600±10° C. The power-on time is 60 min.

[0150] C. Immerse the conductive composite film after power-on in 0.1M dilute hydrochloric acid for 3 minutes, and then immerse it in deionized water for 20 minutes; rinse the immersed conductive composite film with deionized water until the pH value of the deionized water after rinsing is neutral, thereby obtaining a Joule heat-activated graphene film.

[0151] The Joule heat activated graphene film prepared in Example 2 has a rich micro-nano porous structure. It was subjected to nitrogen adsorption and desorption test and scanning electron microscopy (SEM) analysis. The results are as follows: Figures 8 - 11 As shown. Figure 8 The nitrogen adsorption and desorption isotherms and Figure 9 The pore size distribution diagram shows that the Joule heat activated graphene film obtained by Example 2 has an extremely high specific surface area; Figure 10 The magnification parameters are 10k and Figure 11 From the SEM image with a magnification parameter of 10k, it can be seen that the processed Joule-activated graphene film also has a regularly arranged "honeycomb"-like microporous structure. The formation of this structure is attributed to the activation effect of Joule heat. In the activation process of step B, Joule heat is further used to react and expand the size of the porous structure, which is conducive to the generation of nanoscale pores, forming a Joule-activated graphene film with a rich porous structure.

[0152] In addition, the higher activation temperature in Example 2 makes the Joule heat activation reaction more intense and further prolongs the Joule heating time, thereby prolonging the reaction time between the activator and the graphene material, which is beneficial to the activation reaction. The activator fully mixed with the carbon material is further etched in the graphene pore wall and between the graphene layers under the action of Joule heat, thereby generating a richer porous structure.

[0153] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Joule heat activated graphene film, characterized in that: The following steps are involved: A. preparing a conductive composite film, wherein activator crystals are attached to the interior of the conductive composite film; B. In an inert gas processing environment, electrifying both ends of the conductive composite film, wherein the temperature generated by electrification is 300 to 800° C.; C. After cleaning and drying, a Joule heat activated graphene film is obtained.

2. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, In step B, the power-on voltage is 10 to 80 V, and the power-on time is 15 to 60 minutes.

3. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, In step A, the activator crystal is any one of potassium hydroxide, zinc chloride, sodium hydroxide, potassium carbonate and calcium acetate; In step B, current collectors are connected to both ends of the conductive composite film, and electrodes of a discharge power source are connected to both ends of the conductive composite film through the current collectors to conduct electricity; The distance between the current collectors at both ends of the conductive composite film is 10 to 30 mm.

4. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, Step A specifically includes: A11, cleaning and drying the flexible insulating carbon-based film, allowing the activator to crystallize and adhere to the inside of the flexible insulating carbon-based film; A12, using laser to act on the surface of the flexible insulating carbon-based film to obtain a conductive composite film after carbonization and graphitization; Wherein, in step A11, the thickness of the flexible insulating carbon-based film is 80-100 μm, and the mass ratio of the flexible insulating carbon-based film to the activator crystal is 4:(1-4); In step A12, the wavelength of the laser is 200-360nm, the scanning mode is parallel equidistant and line-by-line overlapping scanning, the scanning speed is 40-100mm / s, the number of overlapping times of the light spot is 6-8 times, the laser power is 8.5-9.5W, and the laser scanning spacing is 20-30μm.

5. A method for preparing a Joule heat activated graphene film according to claim 4, characterized in that, The surface of the flexible insulating carbon-based film is hydrophobic; Step A11 specifically includes: washing and drying the flexible insulating carbon-based film; Modifying the surface of the flexible insulating carbon-based film to obtain a hydrophilic surface; The activator is configured into an activator coating, and is applied to the hydrophilic surface by scraping, and then dried and crystallized, so that the activator crystals are attached to the inside of the flexible insulating carbon-based film, and the drying temperature of the drying is 60 to 90° C., and the drying time is 5 to 20 minutes; The modification treatment is to use laser to act on the surface of the flexible insulating carbon-based film to process a microstructure array with a spacing of 15 to 60 μm and a depth of 10 to 15 μm to form a hydrophilic surface; Alternatively, the surface of the flexible insulating carbon-based film is treated with plasma to form a hydrophilic surface.

6. A method for preparing a Joule heat activated graphene film according to claim 4, characterized in that, The surface of the flexible insulating carbon-based film is hydrophilic; Step A11 specifically includes: washing and drying the flexible insulating carbon-based film; The activator is configured into an activator solution, and the flexible insulating carbon-based film is immersed in the activator solution for 15 to 30 minutes, and then placed in a drying oven for drying and crystallization, so that the activator crystals adhere to the inside of the flexible insulating carbon-based film. The drying temperature of the drying oven is 60 to 80°C, the relative vacuum degree is -92 to -88 kPa, and the drying time is 15 to 30 minutes.

7. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, Step A specifically includes: A21, cleaning and drying the flexible conductive carbon-based film; A22, preparing an activator into an activator solution, soaking the flexible conductive carbon-based film in the activator solution for 15 to 30 minutes, drying and then crystallizing, so that the activator crystals adhere to the inside of the flexible conductive carbon-based film, to obtain a conductive composite film; Wherein, in step A21, the thickness of the flexible conductive carbon-based film is 50 to 125 μm; The mass ratio of the flexible conductive carbon-based film to the activator crystals is 4:(1-4).

8. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, Step A specifically includes: A31, configuring graphene powder into a graphene solution, configuring an activator into an activator solution, mixing the graphene solution and the activator solution, and then performing ultrasonic oscillation to obtain a graphene mixed dispersion; A32, spin coating the graphene mixed dispersion into a film, and obtaining a conductive composite film after drying; Wherein, in step A31, the mass ratio of the graphene powder to the activator is 4:(1-4); The thickness of the conductive composite film is 50-125 μm.

9. A method for preparing a Joule heat activated graphene film according to claim 1, characterized in that, In step B, the inert gas is any one of nitrogen and argon; In step C, the cleaning specifically includes: The conductive composite film after being energized is sequentially immersed in a neutralization solution and deionized water, and the immersion time of the conductive composite film in the neutralization solution and in the deionized water are both 5 to 20 minutes; The immersed conductive composite film is rinsed with deionized water until the pH value of the deionized water after rinsing is neutral.

10. A Joule heat activated graphene film, characterized in that: The graphene film is prepared by the method for preparing a Joule heat activated graphene film according to any one of claims 1 to 9.

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