A low-temperature plasma-assisted graphene oxide preparation process

Abstract

The application discloses a kind of based on low temperature plasma auxiliary graphene oxide preparation process, belong to graphene oxide preparation technical field, for solving the technical problem that the defect concentration of existing graphene oxide needs to be further reduced while specific surface area needs to be further improved;The application adopts the synergic system of limited oxygen supply gel, directional catalytic oxygen silicon powder and low temperature plasma to carry out graphite oxidation, and the gel realizes the slow release and limited control of active oxygen, avoids instantaneous strong oxidation;Silicon powder provides enzyme-like catalysis and directional recognition effect, promotes interlayer uniform peeling;Plasma assisted activation improves oxidation efficiency, the three cooperate, make the oxidation process mild and orderly, the integrity of sheet structure is maintained, the defect concentration is moderate, carbon oxygen ratio and specific surface area are in the optimization interval, finally obtain graphene oxide with high specific surface area and good stability.

Description

Technical Field

[0001] This invention relates to the field of graphene oxide preparation technology, and specifically to a low-temperature plasma-assisted graphene oxide preparation process. Background Technology

[0002] As an important derivative of graphite, graphene oxide's performance is closely related to its structural integrity. Early preparation methods often used strong oxidants and acidic environments, which introduced a large number of defects while achieving interlayer exfoliation of graphite, resulting in a generally high defect concentration. With the advancement of research, improved methods such as mild oxidation, catalytic-assisted oxidation, and green oxidation have emerged. By adjusting the reaction conditions and controlling the release rate of oxidants, defect formation has been suppressed to a certain extent, thus improving the structural integrity of graphene oxide.

[0003] On the other hand, the size of the specific surface area directly affects the performance of graphene oxide in applications such as energy storage, electrocatalysis, and composite materials. Early preparation processes often resulted in low specific surface area due to severe layer stacking or insufficient exfoliation. With the improvement of exfoliation methods and the introduction of functional group distribution control, the interlayer unfolding of graphene oxide has gradually increased, and the specific surface area has increased accordingly. It can be seen that the control of defect concentration and specific surface area constitutes an important direction for the evolution of graphene oxide preparation technology.

[0004] While existing graphene oxide preparation processes can yield products with certain properties, they still have limitations in terms of defect concentration and specific surface area. On the one hand, strong oxidizing environments often introduce a large number of structural defects, which can easily damage the carbon skeleton and lead to a decrease in material stability. On the other hand, excessively mild conditions may result in insufficient oxidation and inadequate exfoliation of the sheets, thereby limiting the utilization of specific surface area.

[0005] In addition, the release and action pathways of active species in the existing process are relatively disordered, which can easily lead to uneven oxidation, local over-damage and stacking of sheets, making it difficult to balance low defects and high specific surface area. These problems have, to some extent, restricted the further improvement of graphene oxide performance and affected its application potential in energy storage, catalysis and composite materials.

[0006] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a low-temperature plasma-assisted graphene oxide preparation process to solve the technical problems in the prior art where the defect concentration of graphene oxide needs to be further reduced while the specific surface area needs to be further increased.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A process for preparing graphene oxide based on low-temperature plasma assistance includes the following steps:

[0010] S1. After grinding and mixing graphite powder and confined oxygen supply gel, deionized water is added and allowed to stand for 20-30 minutes. Then, directional oxygen-catalyzing silica powder and disodium ethylenediaminetetraacetate are added and stirred to obtain a reaction slurry.

[0011] S2. The reaction slurry is loaded into a liquid plasma reactor, and an argon / oxygen mixture (volume ratio 9:1, total flow rate 0.8L / min) is introduced. The radio frequency power is set to 40-60W, the reaction temperature is 30-40℃, and the reaction is carried out for 80-120min. After the reaction is completed, the mixture is allowed to cool naturally to obtain the precursor liquid.

[0012] S3. Mix the precursor solution and glacial acetic acid-sodium bicarbonate buffer solution at pH 6.0 and stir for 30 min. Then sonicate for 30 min. Filter and centrifuge to recover the directional oxygen-catalyzing silica powder and crude liquid. Dialyze the crude liquid and then perform post-processing to obtain graphene oxide.

[0013] The reaction principle for preparing graphene oxide is as follows:

[0014] By relying on the slow-release oxygen supply of confined oxygen supply gel and the catalytic effect of directional oxygen-promoting silicon powder, the controllable oxidation and exfoliation of graphite layers can be achieved under low-temperature plasma activation conditions, thereby efficiently obtaining graphene oxide.

[0015] First, the confined oxygen supply gel can stably store and slowly release reactive oxygen species (such as peroxycarbonate and hydrogen peroxide-derived free radicals) in a microenvironment, thereby avoiding the violent reactions caused by traditional strong oxidants and allowing the graphite oxidation process to proceed under mild conditions. At the same time, the imidazole and phenylboronic acid groups modified on the surface of the directional oxygen-catalyzing silica powder provide enzyme-like catalytic activity and molecular recognition function, which can promote the decomposition of peroxides and the directional action of reactive oxygen on the graphite interlayer. The two work together to achieve the spatial confinement effect and selective catalytic effect of the oxidation reaction.

[0016] Based on this, low-temperature plasma provides the system with high-energy active species (such as •OH, •O and...). Through the effects of electric field excitation, these species can disrupt the π-π interactions between graphite layers at lower temperatures, and selectively introduce oxygen-containing functional groups such as carboxyl, hydroxyl, and epoxy groups with the assistance of an oxygen supply system. As a result, graphite is gradually peeled off into graphene oxide sheets with uniformly distributed oxygen-containing functional groups.

[0017] Furthermore, in step S1, the ratio of graphite powder, confined oxygen supply gel, deionized water, directional oxygen-catalyzing silica powder and disodium ethylenediaminetetraacetate is 1g:5-6g:12mL:0.3-0.4g:0.02g.

[0018] Further, in step S3, the ratio of the precursor solution to the pH 6.0 glacial acetic acid-sodium bicarbonate buffer is 1 mL: 3-4 mL, the ultrasonic frequency is 40 kHz, and the power is 150 W. The pH 6.0 glacial acetic acid-sodium bicarbonate buffer is prepared by adding sodium bicarbonate to a 1 M glacial acetic acid aqueous solution until the pH is 6.0. The post-processing includes: after dialysis, the reaction solution is poured into a glass tray and placed in a vacuum oven. It is dried at 40-60℃ and 100-150 mbar for 12-16 h under constant temperature and pressure. Then, it is milled through a 100-mesh sieve to obtain graphene oxide.

[0019] Further, the filtration and centrifugation operation is as follows: the sonicated slurry is filtered through a stack of 10μm filter paper and 0.45μm filter membrane, the filtrate and the precipitate on the 0.45μm filter membrane are collected, the precipitate and deionized water are added to a centrifuge tube at a ratio of 1g:5mL, the centrifuge is centrifuged at 3500rpm for 10min, the precipitate and supernatant are collected, the precipitate is vacuum dried at 80℃ to constant weight to obtain directional oxygen-catalyzing silica powder, and the supernatant and filtrate are mixed to obtain crude liquid;

[0020] Further, the dialysis procedure is as follows: the crude solution is loaded into a dialysis bag with a molecular cutoff of 12-14 kDa, and deionized water is used as the external phase. The volume ratio of the external and internal phases is 1:30. The mixture is stirred at 3-5℃. The water is changed every 1 hour for the first 6 hours, and then every 6-8 hours thereafter. The dialysis is stopped when the conductivity of the external phase is no higher than that of the deionized water by 0.1 mS / cm.

[0021] Furthermore, in step S1, the method for preparing the confined oxygen supply gel includes the following steps:

[0022] A1. Disperse the polyimide salt polymer in deionized water, add saturated potassium bicarbonate solution, stir at room temperature for 3 hours and then dialyze. Cool the reaction system to 0-5℃, add 35wt% hydrogen peroxide aqueous solution and disodium ethylenediaminetetraacetate, let stand for 30 minutes to obtain carbonate polymer solution.

[0023] A2. Polyethylene glycol diacrylate and photoinitiator 2959 were added to the carbonate polymer solution. After degassing, a glass plate was laid flat on a horizontal platform. A silicone pad was placed in the center of the glass plate. The reaction solution was transferred to the mineral tank using a pipette. After the liquid surface was leveled, the upper glass plate was placed on it and cured by irradiation with 365nm ultraviolet light for 5-10 minutes. The post-treatment yielded a confined oxygen supply gel.

[0024] The reaction principle for preparing confined oxygen-supplying gels is as follows:

[0025] First, oxygen-releasing functional groups are introduced into the polymer through the interaction of imidazole salt cations with bicarbonate anions and hydrogen peroxide. Then, they are fixed in the three-dimensional polymer network through photo-initiated free radical crosslinking and curing, thereby constructing a gel material with confined oxygen supply capability.

[0026] First, as a polyelectrolyte containing imidazole salt cationic groups, the side chains of polyimidazolium salt polymer can undergo ion coordination with bicarbonate anions, thereby introducing stably bound carbonate ions into the polymer dispersion. This process endows the polymer system with controllable inorganic anion storage function. Furthermore, hydrogen peroxide can form active oxygen carriers such as peroxycarbonate in the bicarbonate environment, while disodium ethylenediaminetetraacetate avoids the non-selective decomposition of peroxides by complexing impurity metal ions, thereby stabilizing the oxygen source. The resulting carbonate polymer solution is essentially a functionalized precursor system that can "confinedly" store and slowly release oxygen.

[0027] Subsequently, a crosslinking agent containing double bonds and a photoinitiator were introduced into the system. Under the action of ultraviolet light, the crosslinking agent was crosslinked through a free radical photopolymerization reaction, thereby forming a three-dimensional network structure between the polyimide salt polymer segments. This crosslinking network, on the one hand, fixes carbonate and peroxide in the gel microenvironment to prevent rapid loss, and on the other hand, endows the material with stable mechanical properties and spatial confinement effect.

[0028] Furthermore, in step A1, the ratio of the amount of the polyimidazolium salt polymer, deionized water, saturated potassium bicarbonate aqueous solution, 35wt% hydrogen peroxide aqueous solution, and disodium ethylenediaminetetraacetate is 8-10g:100mL:200mL:12-15mL:0.03-0.05g.

[0029] In step A2, the ratio of carbonate polymer solution, polyethylene glycol diacrylate, and photoinitiator 2959 is 300mL:2-3g:0.03-0.05g. The silicone gasket has an inner diameter of 4cm × 4cm, a thickness of 1.0mm, and a light intensity of 5-6mW / cm². 2 Post-processing includes: after demolding, the material is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain confined oxygen-supplying gel;

[0030] Further, in step A1, the dialysis operation is as follows: the reaction solution is loaded into a dialysis bag with a molecular cutoff of 6-8 kDa, the external phase is deionized water, and the volume ratio of the internal and external phases is 1:240. The mixture is stirred at 3-5℃, and the water is changed every 1 hour for the first 4 hours, and then every 3-4 hours thereafter. The dialysis is stopped when the conductivity of the external phase is not higher than that of the deionized water by more than 40 μS / cm.

[0031] Furthermore, the preparation method of the polyimidazolium salt polymer includes the following steps:

[0032] B1. Mix 1-vinylimidazole with anhydrous ethanol, add ethyl chloroacetate dropwise under ice bath, heat to reflux for 5-6 hours, and then process to obtain carboxylate imidazole salt.

[0033] B2. Dissolve carboxylated imidazole salt and azobisisobutyronitrile in a mixed solution and react at 60°C for 12 h. Post-treatment yields polyimidazole salt polymer.

[0034] The reaction principle for preparing polyimidazolium salt polymers is as follows:

[0035] Functionalized imidazole salt monomers are obtained through quaternization reaction, and then free radical polymerization is used to polymerize the double bonds of the monomers into long chain structures, thereby obtaining polymers with imidazole salt groups.

[0036] First, the imidazole ring on the 1-vinylimidazolium molecule has strong nucleophilicity, and its nitrogen atom can undergo nucleophilic substitution reaction with haloesters. When ethyl chloroacetate comes into contact with 1-vinylimidazolium, the chlorine atom, as a good leaving group, is replaced by the nitrogen atom on the imidazole ring, thereby generating an imidazole salt-type ionic monomer with a carboxylic acid ester substituent. In essence, the nitrogen atom of the imidazole ring undergoes a quaternization reaction, which transforms vinylimidazolium into a functionalized monomer with quaternary ammonium structure and ionic properties.

[0037] Subsequently, under the action of a free radical initiator, the vinyl double bond on the monomer molecule is initiated to open the ring and generate free radicals, which then undergo addition polymerization through the free radical chain growth process to form a polymer backbone with carbon-carbon single bonds connecting the main chain. During the polymerization process, the imidazole salt cationic groups introduced on the monomer are completely retained and distributed along the polymerization chain, thereby giving the polymer continuous ionic side groups. Such polymers combine the ionic conductivity of polyelectrolytes with the structural stability of polymer materials.

[0038] Further, in step B1, the ratio of 1-vinylimidazole, anhydrous ethanol, and ethyl chloroacetate is 5-6 g: 20 mL: 6 g. The post-treatment includes: after the reaction is completed, the reaction solution is cooled to room temperature, evaporated under reduced pressure to obtain a crude product, the crude product is added to anhydrous ethanol to obtain a dispersion with a concentration of 200 mg / mL, 8 times the volume of anhydrous diethyl ether is added to the dispersion, and after precipitation is complete, the filter cake is collected by vacuum filtration. The filter cake is placed in a vacuum drying oven at 50°C and vacuum dried to constant weight. The operation is repeated twice to obtain carboxylate imidazole salt.

[0039] Further, in step B2, the ratio of the carboxylate imidazole salt, azobisisobutyronitrile, and the mixed solution is 8-10g:0.1g:40mL. The mixed solution is obtained by mixing anhydrous ethanol and deionized water at a ratio of 4mL:1mL. The post-treatment includes: after the reaction is completed, when the temperature of the reaction solution drops to room temperature, the reaction solution is poured into 2 times the volume of acetone to precipitate. After the precipitation is complete, the filter cake is collected by vacuum filtration and placed in a vacuum drying oven at 50°C to vacuum dry to constant weight to obtain the polyimidazolium salt polymer.

[0040] Furthermore, in step S1, the method for preparing directional oxidizing silica powder includes the following steps:

[0041] C1. Hollow mesoporous silica is dispersed in anhydrous toluene, nitrogen gas is introduced and then γ-aminopropyltriethoxysilane is added. The mixture is refluxed at 110°C for 6-8 hours and then post-treated to obtain amino mesoporous silica powder.

[0042] C2. Disperse amino-mesoporous silica powder, imidazole-1-acetic acid and 4-carboxyphenylboronic acid in MES buffer at pH 5.5, then add activation solution, stir at room temperature for 10-12 h, and then perform post-treatment to obtain directional oxygen-catalyzing silica powder.

[0043] The reaction principle for preparing directional oxygen-catalyzing silica powder is as follows:

[0044] First, silanization is used to modify the surface of mesoporous silicon with amino groups. Then, imidazole and phenylboronic acid functional groups are introduced by carboxyl activation-amide bond coupling, thereby constructing a functionalized mesoporous silicon material with both oxygen-catalyzing activity and directional effect.

[0045] First, the surface of mesoporous silica is rich in silanol groups. Through the condensation reaction with γ-aminopropyltriethoxysilane, stable amino functional groups are introduced on its surface, thereby obtaining aminated mesoporous silica powder that can be further reacted. This step is essentially a silanization reaction, which firmly fixes the organic functional groups on the surface of the inorganic carrier by forming Si-O-Si bonds.

[0046] Subsequently, the aminated mesoporous silica powder undergoes an amide bond coupling reaction with imidazole-1-acetic acid and 4-carboxyphenylboronic acid in a mild buffer system. In this system, carbodiimide / hydroxysuccinimide is used as the activation system to activate the carboxyl group into an intermediate ester, which then reacts efficiently with the amino group to generate a stable amide bond. Through this coupling method, the imidazole structure and phenylboronic acid group are directionally modified on the surface of the mesoporous silica.

[0047] In this process, the imidazole group can act as an enzyme-like active site to promote the decomposition of peroxides and oxygen release, while the phenylboronic acid group has reversible interactions with specific substrates or molecular environments, thereby endowing the material with the ability to directionally regulate the oxygen supply process. The high specific surface area and porous structure of mesoporous silica itself provide a good carrier platform, making the functional groups uniformly and stably distributed.

[0048] Further, in step C1, the ratio of hollow mesoporous silica, anhydrous toluene, and γ-aminopropyltriethoxysilane is 1g:10mL:0.3-0.4mL. The post-processing includes: after the reaction is completed, the reaction solution is cooled to room temperature, the reaction solution is filtered to collect the filter cake, and the filter cake is washed 3-5 times each with anhydrous ethanol and deionized water, and then placed in a drying oven at 60℃ and vacuum dried to constant weight to obtain amino mesoporous silica powder.

[0049] Further, in step C2, the ratio of the amino mesoporous silica powder, imidazole-1-acetic acid, 4-carboxyphenylboronic acid, MES buffer solution with pH=5.5, and activation solution is 2g:0.8-1.0g:0.8-1.0g:100mL:3g. The activation solution is obtained by mixing 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 3g:2g. The post-treatment includes: after the reaction is completed, the reaction solution is filtered and the filter cake is collected. The cake is then washed 3-5 times each with deionized water and anhydrous ethanol, and then placed in a drying oven at 50°C and vacuum dried to constant weight to obtain directional oxygen-catalyzing silica powder.

[0050] The present invention has the following beneficial effects:

[0051] 1. The confined oxygen-supplying gel prepared by this invention achieves the slow release and spatial confinement effect of oxygen source through a three-dimensional network structure, avoiding excessive damage to the carbon skeleton under traditional strong oxidant conditions. The imidazole and phenylboronic acid groups introduced on the surface of the directional oxygen-catalyzing silica powder endow it with catalytic and directional regulation functions, so that active oxygen species preferentially act on the graphite interlayer rather than disorderly attacking the carbon six-membered ring. Under the synergy of the two, the oxidation process is uniform and mild. It can introduce appropriate amounts of carboxyl, hydroxyl and epoxy groups on the surface and edge of graphite sheets to achieve good dispersibility and reactivity, while effectively maintaining the integrity of the graphene skeleton and reducing the generation of defects. The resulting material exhibits a high carbon-to-oxygen ratio and has the advantages of both structural stability and surface functionalization.

[0052] 2. The confined oxygen-supplying gel prepared by this invention achieves the slow release of active oxygen species through a network structure, avoiding the violent impact of instantaneous high-concentration oxidants on the graphite lattice, thereby reducing the probability of disordered destruction of the six-membered carbon rings; the directional oxygen-catalyzing silica powder, with the enzyme-like catalytic effect of the surface imidazole groups and the directional recognition effect of the phenylboronic acid groups, enables the oxidation process to proceed in a controlled manner between graphite layers, preferentially introducing regular oxygen-containing functional groups rather than forming disordered voids; at the same time, low-temperature plasma provides a uniform and controllable excitation environment, assisting in interlayer stripping rather than excessive etching. The synergistic effect of the three ensures that the oxidation reaction proceeds under mild and directional conditions, effectively suppressing the excessive generation of defects, thereby endowing the material with a lower defect concentration and a more complete carbon skeleton structure.

[0053] 3. The confined oxygen-supplying gel prepared by this invention provides a mild and uniform oxygen source during the oxidation process, enabling the graphite sheets to peel off slowly and avoiding sheet breakage and agglomeration caused by violent reactions. The directional oxygen-catalyzing silica powder promotes uniform oxidation between graphite layers through the catalytic and directional effects of surface functional groups, improving the integrity and controllability of interlayer peeling. At the same time, the high-energy active species and electric field effect generated by low-temperature plasma help to weaken the interlayer π-π interaction, further promoting the graphite layers to unfold into single-layer or few-layer sheets. Under the synergistic effect of the three, the graphite sheets can be fully dispersed and maintain a large area, avoiding severe curling or breakage, thereby forming graphene oxide materials with a higher specific surface area. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 SEM image of the graphene oxide prepared in Example 9;

[0056] Figure 2 The image shows a SEM image of the graphene oxide prepared in Comparative Example 1. Detailed Implementation

[0057] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In this application, the polyethylene glycol diacrylate used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number P816111 and an average molecular weight of 700; the photoinitiator 2959 used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number H823463; the hollow mesoporous silica used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number H698118 and a diameter of 800 nm; and the graphite powder used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number G810740 and a mesh size of 325 mesh.

[0059] Example 1

[0060] This embodiment provides a method for preparing confined oxygen-supplying gels for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0061] Step ①: Preparation of carboxylate imidazole salt

[0062] Weigh 50.0 g of 1-vinylimidazole and 200.0 mL of anhydrous ethanol and add them to a reaction vessel. Add 60.0 g of ethyl chloroacetate dropwise under ice bath conditions, and heat the reaction vessel to reflux for 5 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, evaporate to dryness under reduced pressure to obtain crude product. Add the crude product to anhydrous ethanol to obtain a dispersion with a concentration of 200 mg / mL. Add 8 times the volume of anhydrous diethyl ether to the dispersion. After precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50 °C and vacuum dry to constant weight. Repeat the operation twice to obtain carboxymethyl imidazole salt.

[0063] Step 2: Preparation of polyimidazolium salt polymer

[0064] Weigh out 320.0 mL of anhydrous ethanol and 80.0 mL of deionized water and mix them to obtain a mixture;

[0065] Weigh out 80.0g of carboxylated imidazole salt, 1.0g of azobisisobutyronitrile and 400.0mL of mixed solution and add them to the reaction vessel. Raise the temperature of the reaction vessel to 60℃ and keep it at that temperature for 12h. After the reaction is complete, wait for the temperature of the reaction solution to drop to room temperature, pour the reaction solution into 2 times the volume of acetone to precipitate. After the precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50℃ and vacuum dry it to constant weight to obtain polyimidazolium salt polymer.

[0066] Step ③: Preparation of carbonate polymer solution

[0067] Weigh 80.0 g of polyimidazolium salt polymer and 1000.0 mL of deionized water and add them to the reaction vessel. Then, add 2000.0 mL of saturated potassium bicarbonate solution and stir at room temperature for 3 h. Then, transfer the reaction solution into a dialysis bag with a molecular weight cutoff of 6 kDa. Use deionized water as the external phase, with an internal-external phase volume ratio of 1:240. Stir at 3 °C, changing the water every 1 h for the first 4 h, and then every 3 h thereafter. Stop when the external phase conductivity is no higher than 40 μS / cm compared to deionized water. Then, transfer the reaction solution to the reaction vessel and cool it to 5 °C. Add 120.0 mL of 35 wt% hydrogen peroxide aqueous solution and 0.3 g of disodium ethylenediaminetetraacetate. Let it stand for 30 min to obtain the carbonate polymer solution.

[0068] Step 4: Preparation of confined oxygen supply gel

[0069] Weigh out 3000.0 mL of carbonate polymer solution, 20.0 g of polyethylene glycol diacrylate, and 0.3 g of photoinitiator 2959 and add them to the reactor. After degassing, lay a glass plate flat on a horizontal platform. Place a 4 cm × 4 cm, 1.0 mm thick silicone pad in the center of the glass plate. Use a pipette to transfer the reaction solution to the mineral tank. After leveling the liquid surface, place the upper glass plate on top and cure it under 365 nm ultraviolet light for 5 min (light intensity 5 mW / cm²). 2 After demolding, the material is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain a confined oxygen-supplying gel.

[0070] Example 2

[0071] This embodiment provides a method for preparing confined oxygen-supplying gels for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0072] Step ①: Preparation of carboxylate imidazole salt

[0073] Weigh 60.0 g of 1-vinylimidazole and 200.0 mL of anhydrous ethanol and add them to the reaction vessel. Add 60.0 g of ethyl chloroacetate dropwise under ice bath conditions, and heat the reaction vessel to reflux for 6 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, evaporate to dryness under reduced pressure to obtain crude product. Add the crude product to anhydrous ethanol to obtain a dispersion with a concentration of 200 mg / mL. Add 8 times the volume of anhydrous diethyl ether to the dispersion. After precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50 °C and vacuum dry to constant weight. Repeat the operation twice to obtain carboxymethyl imidazole salt.

[0074] Step 2: Preparation of polyimidazolium salt polymer

[0075] Weigh out 400.0 mL of anhydrous ethanol and 100.0 mL of deionized water and mix them to obtain a mixture;

[0076] Weigh out 100.0g of carboxylated imidazole salt, 1.g of azobisisobutyronitrile and 400.0mL of the mixture and add them to the reaction vessel. Raise the temperature of the reaction vessel to 60℃ and keep it at that temperature for 12h. After the reaction is complete, wait for the temperature of the reaction solution to drop to room temperature, pour the reaction solution into 2 times the volume of acetone to precipitate. After the precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50℃ and vacuum dry it to constant weight to obtain polyimidazolium salt polymer.

[0077] Step ③: Preparation of carbonate polymer solution

[0078] Weigh 100.0 g of polyimidazolium salt polymer and 1000.0 mL of deionized water and add them to the reaction vessel. Then, add 2000.0 mL of saturated potassium bicarbonate solution and stir at room temperature for 3 hours. Transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 8 kDa. Use deionized water as the external phase, with a volume ratio of 1:240 between the external and internal phases. Stir at 3°C, changing the water every 1 hour for the first 4 hours and then every 4 hours thereafter. Stop when the conductivity of the external phase is no higher than 40 μS / cm compared to that of the deionized water. Transfer the reaction solution to the reaction vessel and cool it to 0°C. Add 150.0 mL of 35 wt% hydrogen peroxide aqueous solution and 0.5 g of disodium ethylenediaminetetraacetate. Let it stand for 30 minutes to obtain the carbonate polymer solution.

[0079] Step 4: Preparation of confined oxygen supply gel

[0080] Weigh out 3000.0 mL of carbonate polymer solution, 30.0 g of polyethylene glycol diacrylate, and 0.5 g of photoinitiator 2959 and add them to the reactor. After degassing, lay a glass plate flat on a horizontal platform. Place a 4 cm × 4 cm inner diameter and 1.0 mm thick silicone pad in the center of the glass plate. Use a pipette to transfer the reaction solution to the mineral tank. After leveling the liquid surface, place the upper glass plate on top and cure it under 365 nm ultraviolet light for 10 min at a light intensity of 6 mW / cm². 2 After demolding, the material is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain a confined oxygen-supplying gel.

[0081] Example 3

[0082] This embodiment provides a method for preparing confined oxygen-supplying gels for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0083] Step ①: Preparation of carboxylate imidazole salt

[0084] Weigh 54.0 g of 1-vinylimidazole and 200.0 mL of anhydrous ethanol and add them to the reaction vessel. Add 60.0 g of ethyl chloroacetate dropwise under ice bath conditions, and heat the reaction vessel to reflux for 6 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, evaporate to dryness under reduced pressure to obtain the crude product. Add the crude product to anhydrous ethanol to obtain a dispersion with a concentration of 200 mg / mL. Add 8 times the volume of anhydrous diethyl ether to the dispersion. After precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50 °C and vacuum dry to constant weight. Repeat the operation twice to obtain the carboxymethyl imidazole salt.

[0085] Step 2: Preparation of polyimidazolium salt polymer

[0086] Weigh out 400.0 mL of anhydrous ethanol and 100.0 mL of deionized water and mix them to obtain a mixture;

[0087] Weigh out 96.0 g of carboxylated imidazole salt, 1.0 g of azobisisobutyronitrile and 400.0 mL of the mixture and add them to the reaction vessel. Raise the temperature of the reaction vessel to 60 °C and keep it at that temperature for 12 h. After the reaction is complete, wait for the temperature of the reaction solution to drop to room temperature, pour the reaction solution into 2 times the volume of acetone to precipitate. After the precipitation is complete, filter and collect the filter cake. Place the filter cake in a vacuum drying oven at 50 °C and vacuum dry it to constant weight to obtain polyimidazolium salt polymer.

[0088] Step ③: Preparation of carbonate polymer solution

[0089] Weigh 90.0 g of polyimidazolium salt polymer and 1000.0 mL of deionized water and add them to the reaction vessel. Then, add 2000.0 mL of saturated potassium bicarbonate solution and stir at room temperature for 3 h. Then, transfer the reaction solution into a dialysis bag with a molecular weight cutoff of 7 kDa. Use deionized water as the external phase, with an internal-external phase volume ratio of 1:240. Stir at 4 °C, changing the water every 1 h for the first 4 h, and then every 3 h thereafter. Stop when the external phase conductivity is no higher than 40 μS / cm compared to deionized water. Then, transfer the reaction solution to the reaction vessel, cool the reaction vessel to 3 °C, add 136.0 mL of 35 wt% hydrogen peroxide aqueous solution and 0.4 g of disodium ethylenediaminetetraacetate, and let stand for 30 min to obtain the carbonate polymer solution.

[0090] Step 4: Preparation of confined oxygen supply gel

[0091] Weigh out 3000.0 mL of carbonate polymer solution, 25.0 g of polyethylene glycol diacrylate, and 0.4 g of photoinitiator 2959 and add them to the reactor. After degassing, lay a glass plate flat on a horizontal platform. Place a 4 cm × 4 cm, 1.0 mm thick silicone pad in the center of the glass plate. Use a pipette to transfer the reaction solution to the mineral tank. After leveling the liquid surface, place the upper glass plate on top and cure it under 365 nm ultraviolet light for 8 minutes (light intensity 6 mW / cm²). 2 After demolding, the material is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain a confined oxygen-supplying gel.

[0092] Example 4

[0093] This embodiment provides a method for preparing directional catalytic oxidation silicon powder for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0094] Step I: Preparation of amino-mesoporous silica powder

[0095] Weigh 10.0 g of hollow mesoporous silica and 100.0 mL of anhydrous toluene and add them to the reaction vessel. After purging with nitrogen, add 3.0 mL of γ-aminopropyltriethoxysilane and reflux at 110 °C for 6 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, filter the reaction solution and collect the filter cake. Wash the filter cake three times each with anhydrous ethanol and deionized water, and then place it in a drying oven at 60 °C and vacuum dry to constant weight to obtain amino mesoporous silica powder.

[0096] Step II: Preparation of Directional Oxidizing Silica Powder

[0097] Weigh out 9g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 6g of N-hydroxysuccinimide and mix them to obtain an activation solution;

[0098] Weigh out 6.0 g of amino mesoporous silica powder, 2.4 g of imidazole-1-acetic acid, 2.4 g of 4-carboxyphenylboronic acid, and 300.0 mL of MES buffer solution at pH 5.5 and add them to the reaction vessel. Then add 9.0 g of activation solution and stir at room temperature for 10 h. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the cake three times each with deionized water and anhydrous ethanol, and then place it in a drying oven at 50 °C and vacuum dry it to constant weight to obtain directional oxygen-catalyzing silica powder.

[0099] Example 5

[0100] This embodiment provides a method for preparing directional catalytic oxidation silicon powder for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0101] Step I: Preparation of amino-mesoporous silica powder

[0102] Weigh 10.0 g of hollow mesoporous silica and 100.0 mL of anhydrous toluene and add them to the reaction vessel. After purging with nitrogen, add 4.0 mL of γ-aminopropyltriethoxysilane and reflux at 110 °C for 8 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, filter the reaction solution to collect the filter cake, and wash the filter cake 5 times each with anhydrous ethanol and deionized water. Then, place it in a drying oven at 60 °C and vacuum dry it to constant weight to obtain amino mesoporous silica powder.

[0103] Step II: Preparation of Directional Oxidizing Silica Powder

[0104] Weigh out 9.0 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 6.0 g of N-hydroxysuccinimide and mix them to obtain an activation solution;

[0105] Weigh out 6.0 g of amino mesoporous silica powder, 3.0 g of imidazole-1-acetic acid, 3.0 g of 4-carboxyphenylboronic acid, and 300.0 mL of MES buffer solution at pH 5.5 and add them to the reaction vessel. Then add 9.0 g of activation solution and stir at room temperature for 12 h. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the cake five times each with deionized water and anhydrous ethanol, and then place it in a drying oven at 50 °C and vacuum dry it to constant weight to obtain directional oxygen-catalyzing silica powder.

[0106] Example 6

[0107] This embodiment provides a method for preparing directional catalytic oxidation silicon powder for a low-temperature plasma-assisted graphene oxide preparation process, comprising the following steps:

[0108] Step I: Preparation of amino-mesoporous silica powder

[0109] Weigh 10.0 g of hollow mesoporous silica and 100.0 mL of anhydrous toluene and add them to the reaction vessel. After purging with nitrogen, add 3.6 mL of γ-aminopropyltriethoxysilane and reflux at 110 °C for 7 h. After the reaction is complete, wait for the reaction solution to cool to room temperature, filter the reaction solution and collect the filter cake. Wash the filter cake 4 times each with anhydrous ethanol and deionized water, and then place it in a drying oven at 60 °C and vacuum dry to constant weight to obtain amino mesoporous silica powder.

[0110] Step II: Preparation of Directional Oxidizing Silica Powder

[0111] Weigh out 9.0 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 6.0 g of N-hydroxysuccinimide and mix them to obtain an activation solution;

[0112] Weigh out 6.0 g of amino mesoporous silica powder, 2.7 g of imidazole-1-acetic acid, 2.7 g of 4-carboxyphenylboronic acid, and 300.0 mL of MES buffer solution at pH 5.5 and add them to the reaction vessel. Then add 9.0 g of activation solution and stir at room temperature for 11 h. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the cake four times each with deionized water and anhydrous ethanol, and then place it in a drying oven at 50 °C and vacuum dry it to constant weight to obtain directional oxygen-catalyzing silica powder.

[0113] Example 7

[0114] This embodiment provides a low-temperature plasma-assisted graphene oxide preparation process, including the following steps:

[0115] Step 1: Preparation of reaction slurry

[0116] Weigh out 10.0g of graphite powder and 50.0g of confined oxygen-supplying gel prepared in Example 1, grind and mix them, add 120.0mL of deionized water and let stand for 20min, then add 3.0g of directional oxygen-catalyzing silica powder prepared in Example 4 and 0.2g of disodium ethylenediaminetetraacetate, stir and obtain a reaction slurry.

[0117] Step 2: Preparation of precursor solution

[0118] Weigh 110.0 mL of the reaction slurry and place it into a liquid plasma reactor. Introduce an argon / oxygen mixture (volume ratio 9:1, total flow rate 0.8 L / min), set the radio frequency power to 40 W, the reaction temperature to 30 °C, and react for 80 min. After the reaction is complete, allow it to cool naturally to obtain the precursor liquid.

[0119] Step 3: Preparation of graphene oxide

[0120] Weigh out 5000.0 mL of 1 M glacial acetic acid aqueous solution, then add sodium bicarbonate to the solution until pH = 6.0 to obtain glacial acetic acid-sodium bicarbonate buffer solution.

[0121] Weigh out 100.0 mL of precursor solution and 300 mL of pH 6.0 glacial acetic acid-sodium bicarbonate buffer solution, mix and stir for 30 min, then sonicate at 40 kHz and 150 W for 30 min. Filter the sonicated slurry through a stack of 10 μm filter paper and 0.45 μm filter membrane, collect the filtrate and the precipitate on the 0.45 μm filter membrane, add the precipitate and deionized water at a ratio of 1 g: 5 mL into a centrifuge tube, centrifuge at 3500 rpm for 10 min, collect the precipitate and supernatant, and vacuum dry the precipitate at 80 °C to constant weight to obtain directional oxygen-catalyzing silica powder. Mix the supernatant and filtrate to obtain the crude solution.

[0122] The crude solution was placed into a dialysis bag with a molecular cutoff of 12 kDa. The external phase was deionized water, with a volume ratio of 1:30 between the internal and external phases. The mixture was stirred at 3°C, with the water changed every hour for the first 6 hours and then every 6 hours thereafter. The dialysis was stopped when the conductivity of the external phase was no higher than that of the deionized water by 0.1 mS / cm. After dialysis, the reaction solution was poured into a glass tray and placed in a vacuum oven. It was dried at 40°C and 100 mbar for 12 hours under constant temperature and pressure. The solution was then ground through a 100-mesh sieve to obtain graphene oxide.

[0123] Example 8

[0124] This embodiment provides a low-temperature plasma-assisted graphene oxide preparation process, including the following steps:

[0125] Step 1: Preparation of reaction slurry

[0126] Weigh out 10.0g of graphite powder and 60.0g of confined oxygen-supplying gel prepared in Example 2, grind and mix them, add 120.0mL of deionized water and let stand for 30min, then add 4.0g of directional oxygen-catalyzing silica powder prepared in Example 5 and 0.2g of disodium ethylenediaminetetraacetate, stir and obtain a reaction slurry.

[0127] Step 2: Preparation of precursor solution

[0128] Weigh 110.0 mL of the reaction slurry and place it into a liquid plasma reactor. Introduce an argon / oxygen mixture (volume ratio 9:1, total flow rate 0.8 L / min), set the radio frequency power to 60 W, the reaction temperature to 40 °C, and react for 120 min. After the reaction is complete, allow it to cool naturally to obtain the precursor liquid.

[0129] Step 3: Preparation of graphene oxide

[0130] Weigh out 500.0 mL of 1 M glacial acetic acid aqueous solution, then add sodium bicarbonate to the solution until pH = 6.0 to obtain glacial acetic acid-sodium bicarbonate buffer solution.

[0131] Weigh out 100.0 mL of precursor solution and 400.0 mL of pH 6.0 glacial acetic acid-sodium bicarbonate buffer solution, mix and stir for 30 min, then sonicate at 40 kHz and 150 W for 30 min. Filter the sonicated slurry through a stack of 10 μm filter paper and 0.45 μm filter membrane, collect the filtrate and the precipitate on the 0.45 μm filter membrane, add the precipitate and deionized water at a ratio of 1 g: 5 mL into a centrifuge tube, centrifuge at 3500 rpm for 10 min, collect the precipitate and supernatant, and vacuum dry the precipitate at 80 °C to constant weight to obtain directional oxygen-catalyzing silica powder. Mix the supernatant and filtrate to obtain the crude solution.

[0132] The crude solution was placed in a dialysis bag with a molecular cutoff of 14 kDa. The external phase was deionized water, with a volume ratio of 1:30 between the internal and external phases. The mixture was stirred at 5°C, with the water changed every hour for the first 6 hours and every 8 hours thereafter. The dialysis was stopped when the conductivity of the external phase was no higher than that of the deionized water by 0.1 mS / cm. After dialysis, the reaction solution was poured into a glass tray and placed in a vacuum oven. It was dried at 60°C and 150 mbar for 16 hours under constant temperature and pressure. The solution was then ground through a 100-mesh sieve to obtain graphene oxide.

[0133] Example 9

[0134] This embodiment provides a low-temperature plasma-assisted graphene oxide preparation process, including the following steps:

[0135] Step 1: Preparation of reaction slurry

[0136] Weigh out 10.0g of graphite powder and 54.0g of confined oxygen-supplying gel prepared in Example 3, grind and mix them, add 120.0mL of deionized water and let stand for 25min, then add 4.0g of directional oxygen-catalyzing silica powder prepared in Example 6 and 0.2g of disodium ethylenediaminetetraacetate, stir and obtain a reaction slurry.

[0137] Step 2: Preparation of precursor solution

[0138] Weigh 110.0 mL of the reaction slurry and place it into a liquid plasma reactor. Introduce an argon / oxygen mixture (volume ratio 9:1, total flow rate 0.8 L / min), set the radio frequency power to 50 W, the reaction temperature to 35 °C, and react for 100 min. After the reaction is complete, allow it to cool naturally to obtain the precursor liquid.

[0139] Step 3: Preparation of graphene oxide

[0140] Weigh out 5000.0 mL of 1 M glacial acetic acid aqueous solution, then add sodium bicarbonate to the solution until pH = 6.0 to obtain glacial acetic acid-sodium bicarbonate buffer solution.

[0141] Weigh out 100.0 mL of precursor solution and 350.0 mL of pH 6.0 glacial acetic acid-sodium bicarbonate buffer solution, mix and stir for 30 min, then sonicate at 40 kHz and 150 W for 30 min. Filter the sonicated slurry through a stack of 10 μm filter paper and 0.45 μm filter membrane, collect the filtrate and the precipitate on the 0.45 μm filter membrane, add the precipitate and deionized water at a ratio of 1 g: 5 mL into a centrifuge tube, centrifuge at 3500 rpm for 10 min, collect the precipitate and supernatant, and vacuum dry the precipitate at 80 °C to constant weight to obtain directional oxygen-catalyzing silica powder. Mix the supernatant and filtrate to obtain the crude solution.

[0142] The crude solution was placed into a dialysis bag with a molecular cutoff of 13 kDa. The external phase was deionized water, with a volume ratio of 1:30 between the internal and external phases. The mixture was stirred at 4°C, with the water changed every hour for the first 6 hours and every 7 hours thereafter. The dialysis was stopped when the conductivity of the external phase was no higher than that of the deionized water by 0.1 mS / cm. After dialysis, the reaction solution was poured into a glass tray and placed in a vacuum oven. It was dried at 50°C and 120 mbar for 14 hours under constant temperature and pressure. The solution was then milled through a 100-mesh sieve to obtain graphene oxide.

[0143] Comparative Example 1

[0144] Graphene oxide was prepared using the Hummers method: 1 part graphite powder was weighed, 0.5 parts sodium nitrate solid was added, and 15 parts concentrated sulfuric acid were added. The mixture was placed in an ice-water bath and stirred thoroughly. Then, 8 parts potassium permanganate were slowly added in multiple batches, and the reaction temperature was controlled below 20°C. After stirring for 24 hours, 40 parts deionized water and 10 parts hydrogen peroxide were added. The mixture was allowed to stand for 1 hour, and the precipitate was collected by filtration. After washing and drying, graphene oxide was obtained.

[0145] Comparative Example 2

[0146] The difference between this comparative example and Example 9 is that in step one, carbonate polymer liquid is used to replace the confined oxygen supply gel by mass.

[0147] Comparative Example 3

[0148] The difference between this comparative example and Example 9 is that the directional oxygen-catalyzing silica powder is omitted in step one.

[0149] Performance testing:

[0150] The carbon-oxygen ratio of the graphene oxide prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to the standard GB / T 43598-2023 "Determination of oxygen content and carbon-oxygen ratio of nanotechnology graphene powder by X-ray photoelectron spectroscopy".

[0151] The defect concentration of the graphene oxide prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to the standard GB / T 43341-2023 "Defect Concentration Measurement of Nanotechnology Graphene by Raman Spectroscopy".

[0152] The specific surface area of ​​the graphene oxide prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to the standard GB / T 42310-2023 "Determination of Specific Surface Area of ​​Nanotechnology Graphene Powder - Argon Adsorption Static Capacitance Method". The specific data are shown in Table 1.

[0153] Table 1 - Performance test data of each sample

[0154]

[0155] Data Analysis:

[0156] Comparative analysis of the data in Table 1 reveals that the carbon-to-oxygen ratio of the graphene oxide prepared by this method is 3.3, and the defect concentration is 5.0 × 10⁻⁶. 10 cm -2 At the same time, the specific surface area is 728m² 2 ·g -1 All data points are better than the comparative data, indicating that:

[0157] The Hummers method used in Comparative Example 1 uses a strong oxidant as its core, relying on the synergistic effect of high-concentration potassium permanganate and concentrated sulfuric acid to cause interlayer intercalation and destruction of graphite in a violent oxidizing environment. Due to the lack of slow-release oxygen supply and directional catalysis, the active species in this method attack the carbon six-membered ring in a disordered manner, resulting in excessive destruction of the carbon skeleton and the generation of a large number of uncontrollable defects and voids. At the same time, the oxidation reaction rate is much higher than the diffusion and exfoliation rate, and the graphite sheets are often accompanied by fracture and curling, making it difficult to maintain a large area of ​​unfolding, ultimately resulting in a low specific surface area. On the other hand, excessive oxidation makes the introduction of oxygen-containing functional groups lack selectivity, and some areas form supersaturated oxide layers, which weakens the conductivity and structural stability of the sheets. Overall, the mild and controllable oxidation environment is lost, resulting in graphene oxide prepared by this method having problems such as high defect concentration, poor carbon skeleton integrity and limited specific surface area.

[0158] In Comparative Example 2, without the confined oxygen supply gel, the system lost the slow release of oxygen and the spatial confinement effect. The oxidant was released instantaneously during the reaction, resulting in an overly concentrated and intense local oxidation environment. This caused the graphite sheets to be subjected to a high concentration of active oxygen species in a short period of time. Due to the lack of a slow and uniform oxygen supply process, the carbon six-membered rings of the graphite lattice were more susceptible to disordered destruction, forming too many defect points and fracture regions. At the same time, when active oxygen species were present in excessive amounts locally, they would cause non-selective etching of the carbon skeleton, resulting in severe fracture and curling of the sheet edges, thereby reducing the specific surface area and sheet integrity. More seriously, the violent oxidation process could not effectively control the introduction of functional groups, resulting in uneven distribution of surface functional groups, with some areas being over-oxidized and others not being fully oxidized. Overall, due to the loss of the mild environment and controllable reaction path provided by the confined oxygen supply, the sample ultimately suffered from increased defect concentration, decreased carbon-oxygen ratio, and significantly weakened structural stability.

[0159] In Comparative Example 3, without the directional oxygen-catalyzing silica powder, the reaction system lost its catalytic and directional regulation function for the oxidation process. Lacking the enzyme-like activity of imidazole groups, the decomposition rate of peroxides was difficult to maintain at a moderate and controllable level. Reactive oxygen species accumulated and acted on the graphite lattice in a disordered manner. Simultaneously, without the molecular recognition function of phenylboronic acid groups, reactive oxygen no longer preferentially entered the graphite interlayer but randomly attacked the sheet surface and edges, resulting in a disordered distribution of functional groups. Due to the lack of selectivity in the oxidation reaction, the sheet surface was unevenly etched, forming numerous defects and pores, weakening the continuity of the carbon skeleton. Furthermore, the lack of directional catalysis during sheet peeling reduced the interlayer separation efficiency, making it difficult for some graphite sheets to unfold, leading to agglomeration and stacking, ultimately resulting in insufficient specific surface area. Overall, without the synergistic regulation of the directional oxygen-catalyzing silica powder, the reaction process tended towards disorder and crudeness, increasing the defect concentration of graphene oxide, reducing sheet integrity, and weakening its structural and performance advantages.

[0160] Figure 1 The graphene oxide prepared for this example exhibits a large-area, intact, and smooth two-dimensional structure with relatively regular edges, indicating that under confined oxygen supply and directional catalytic oxidation conditions, the graphite layers underwent mild and controllable exfoliation and oxidation, maintaining high sheet integrity and specific surface area; in contrast, Figure 2 The sample prepared for Comparative Example 1 shows that the sheets are severely wrinkled and broken, with obvious edge curling, and in some areas even sheet stacking and collapse. This indicates that the traditional strong oxidation system leads to an overly violent oxidation process, causing disordered destruction of the carbon skeleton and generating a large number of defects and fractures. The comparison between the two fully demonstrates that the method of the present invention can achieve uniform oxidation while maintaining the stability of the sheet structure, which is significantly better than the traditional preparation method.

[0161] This scheme achieves effective control over the degree of oxidation, defect distribution, and sheet structure during the preparation of graphene oxide by constructing a multi-component synergistic system. The confined oxygen-supplying gel stores and slowly releases reactive oxygen species within the polymer network, avoiding excessive oxidation caused by instantaneous release and ensuring a gentle and balanced oxidation process. The directional oxygen-catalyzing silica powder, relying on imidazole and phenylboronic acid groups, provides enzyme-like catalysis and directionality, allowing reactive oxygen species to preferentially act on the graphite interlayer, promoting ordered exfoliation and the introduction of uniform functional groups. Low-temperature plasma further provides energy and reactive species, synergistically enhancing interlayer dissociation and oxidation efficiency. These three components complement each other, overcoming the problems of severe damage and excessive defects in traditional methods, while avoiding the drawbacks of insufficient oxidation and sheet agglomeration. The resulting graphene oxide possesses a high carbon-to-oxygen ratio, moderate defect concentration, and large specific surface area, maintaining good structural integrity and functionalization. The coordinated action of the overall system ensures the stability and controllability of material properties, providing strong support for the preparation of high-quality graphene oxide.

[0162] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0163] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0164] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for preparing graphene oxide based on low-temperature plasma assistance, characterized in that, Includes the following steps: S1. After grinding and mixing graphite powder and confined oxygen supply gel, deionized water is added and allowed to stand for 20-30 minutes. Then, directional oxygen-catalyzing silica powder and disodium ethylenediaminetetraacetate are added and stirred to obtain a reaction slurry. S2. The reaction slurry is loaded into a liquid plasma reactor, and an argon / oxygen mixture (volume ratio 9:1, total flow rate 0.8L / min) is introduced. The radio frequency power is set to 40-60W, the reaction temperature is 30-40℃, and the reaction is carried out for 80-120min. After the reaction is completed, the mixture is allowed to cool naturally to obtain the precursor liquid. S3. Mix the precursor solution and glacial acetic acid-sodium bicarbonate buffer solution at pH 6.0 and stir for 30 min. Then sonicate for 30 min. Filter and centrifuge to recover the directional oxygen-catalyzing silica powder and crude liquid. Dialyze the crude liquid and then process it to obtain graphene oxide. The preparation method of the confined oxygen supply gel includes the following steps: A1. Disperse the polyimide salt polymer in deionized water, add saturated potassium bicarbonate solution, stir at room temperature for 3 hours and then dialyze. Cool the reaction system to 0-5℃, add 35wt% hydrogen peroxide aqueous solution and disodium ethylenediaminetetraacetate, let stand for 30 minutes to obtain carbonate polymer solution. A2. Polyethylene glycol diacrylate and photoinitiator 2959 were added to the carbonate polymer solution. After degassing, a glass plate was laid flat on a horizontal platform. A silicone pad was placed in the center of the glass plate. The reaction solution was transferred to the mineral tank using a pipette. After the liquid surface was leveled, the upper glass plate was placed on it and cured by irradiation with 365nm ultraviolet light for 5-10 minutes. The confined oxygen supply gel was obtained by vacuum drying. The preparation method of the polyimidazolium salt polymer includes the following steps: B1. Mix 1-vinylimidazole with anhydrous ethanol, add ethyl chloroacetate dropwise under ice bath, heat to reflux for 5-6 hours, and then process to obtain carboxylate imidazole salt. B2. Dissolve carboxylated imidazole salt and azobisisobutyronitrile in a mixed solution, react at 60°C for 12 h, and then treat to obtain polyimidazolium salt polymer. The method for preparing the directional oxygen-catalyzing silica powder includes the following steps: C1. Hollow mesoporous silica is dispersed in anhydrous toluene, nitrogen gas is introduced and then γ-aminopropyltriethoxysilane is added. The mixture is refluxed at 110°C for 6-8 hours and then post-treated to obtain amino mesoporous silica powder. C2. Disperse amino-mesoporous silica powder, imidazole-1-acetic acid and 4-carboxyphenylboronic acid in MES buffer at pH 5.5, then add activation solution, stir at room temperature for 10-12 h, and then perform post-treatment to obtain directional oxygen-catalyzing silica powder.

2. The low-temperature plasma-assisted graphene oxide preparation process according to claim 1, characterized in that, In step S1, the ratio of graphite powder, confined oxygen supply gel, deionized water, directional oxygen-catalyzing silica powder, and disodium ethylenediaminetetraacetate is 1g:5-6g:12mL:0.3-0.4g:0.02g. In step S3, the ratio of the precursor solution and pH 6.0 glacial acetic acid-sodium bicarbonate buffer solution is 1mL:3-4mL, the ultrasonic frequency is 40kHz, and the power is 150W. The pH 6.0 glacial acetic acid-sodium bicarbonate buffer solution is prepared by adding sodium bicarbonate to a 1M glacial acetic acid aqueous solution until the pH reaches 6.

0.

3. The low-temperature plasma-assisted graphene oxide preparation process according to claim 1, characterized in that, In step A1, the ratio of the polyimidazolium salt polymer, deionized water, saturated potassium bicarbonate aqueous solution, 35wt% hydrogen peroxide aqueous solution, and disodium ethylenediaminetetraacetate is 8-10g:100mL:200mL:12-15mL:0.03-0.05g; in step A2, the ratio of the carbonate polymer solution, polyethylene glycol diacrylate, and photoinitiator 2959 is 300mL:2-3g:0.03-0.05g, wherein the silicone pad has an inner diameter of 4cm×4cm, a thickness of 1.0mm, and a light intensity of 5-6mW / cm2.

4. The low-temperature plasma-assisted graphene oxide preparation process according to claim 1, characterized in that, In step B1, the ratio of 1-vinylimidazole, anhydrous ethanol, and ethyl chloroacetate is 5-6 g: 20 mL: 6 g; in step B2, the ratio of carboxylate imidazole salt, azobisisobutyronitrile, and the mixture is 8-10 g: 0.1 g: 40 mL, wherein the mixture is obtained by mixing anhydrous ethanol and deionized water in a ratio of 4 mL: 1 mL.

5. The process for preparing graphene oxide based on low-temperature plasma assistance according to claim 1, characterized in that, In step C1, the ratio of hollow mesoporous silica, anhydrous toluene, and γ-aminopropyltriethoxysilane is 1g:10mL:0.3-0.4mL; in step C2, the ratio of amino mesoporous silica powder, imidazole-1-acetic acid, 4-carboxyphenylboronic acid, MES buffer solution with pH=5.5, and activation solution is 2g:0.8-1.0g:0.8-1.0g:100mL:3g, wherein the activation solution is obtained by mixing 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 3g:2g.

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