Preparation method of graphene oxide material taking high-crystallinity nanocellulose thin layer with highly curled and folded structure as precursor

Abstract

The invention belongs to the technical field of carbon materials, and particularly relates to a preparation method of a graphene oxide material taking a highly-crystallized nano cellulose thin layer with a highly-curled and folded structure as a precursor. The preparation method comprises the following steps: treating a macromolecular cellulose raw material by utilizing an acid hydrolysis method to obtain cellulose nanofibers with relatively uniform molecular weight; dissolving cellulose nanofibers to obtain a cellulose solution; the cellulose solution is dialyzed in a poor cellulose solvent, cellulose is gradually separated out, and a high-crystallinity cellulose nanometer material is obtained; the high-crystallinity cellulose nanomaterial can also be subjected to freeze drying, natural drying and stoving treatment to remove the solvent to obtain high-crystallinity nanocellulose powder; and carrying out pyrolysis carbonization treatment on the high-crystallinity nano-crystalline cellulose at 300 DEG C or above to obtain the graphene oxide material with a highly curled and folded structure. According to the method, the high-crystallinity nanocellulose is directly converted into the graphene oxide in one step through low-temperature carbonization, and the method has the characteristics of high efficiency and low energy consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon materials, and in particular relates to a method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor. Background Art

[0002] Graphene (G) is a single layer of sp 2 The two-dimensional honeycomb material composed of hybrid carbon atoms has been widely used in many fields such as military industry and electronic appliances due to its high strength, high thermal conductivity and high electrical conductivity. Its preparation process is usually to first oxidize the stacked graphite layers to make them hydrophilic, and then peel off the single sheets under the action of an ultrasonic field to obtain an aqueous solution of graphene oxide (GO). At present, the common GO production methods are the Brodie method, the Standenmaier method and the Hummers method. Among them, the Brodie method and the Standenmaier method will use potassium hypochlorite and nitric acid in the preparation process, which is not only accompanied by the risk of explosion, but also produces chlorine, NO x , ClO2 and other toxic and harmful substances. Currently, the improved Hummers method is commonly used in the production of GO. However, this method requires a large amount of highly corrosive substances such as concentrated sulfuric acid and perchlorate, and its reaction temperature is high (about 100°C) and the reaction time is long (about 80 hours). In addition, the GO products obtained using the improved Hummers method still have many defects. Therefore, in order to improve this situation, it is necessary to explore a more efficient and rapid method for preparing graphene oxide.

[0003] Biomass, with its widespread availability and renewable nature, aligns with national and societal goals for sustainable development. Furthermore, as an important carbon source, it has garnered widespread international attention. For example, biomass-based activated carbons prepared from biomass feedstocks such as bamboo, cotton, peanut shells, rapeseed meal, and soybean straw are used to adsorb harmful gases and heavy metal ions from aqueous solutions. Despite these recent achievements, current research using biomass as a feedstock has largely focused on the preparation of amorphous carbon. However, relatively little research has focused on the direct conversion of biomass into graphitized carbon materials, particularly the further preparation of graphene oxide. This is primarily because the carbonized product of biomass is non-graphitizable carbon, making it difficult to directly form a graphitized structure even at extremely high temperatures. The carbonization process of conventional feedstocks such as asphalt and petroleum coke also faces this challenge. Researchers have therefore attempted to utilize catalytic graphitization to promote the pyrolysis and carbonization of biomass feedstocks, hoping to achieve the efficient conversion of some non-graphitizable carbons. However, this method is not only complex in preparation but also requires the addition of metal catalysts, which is not environmentally friendly. In addition, for materials that cannot exist stably at high temperatures, such as transition metal sulfides, it is even more difficult to synthesize the required graphitized carbon-based composite materials in one step, not to mention further preparing graphene oxide on this basis. Theoretically, although cellulose carbonization can be used to synthesize graphene oxide through complex chemical reactions and physical processes, this path is neither direct nor simple. First, the amorphous carbon obtained by carbonization needs to be converted into an ordered graphite structure. This process is both energy-intensive and technically difficult. Secondly, even if graphite is successfully obtained, it needs to be further converted into graphene oxide through chemical exfoliation, which undoubtedly increases the cost and reduces the efficiency. Therefore, exploring an efficient, low-cost and environmentally friendly preparation path from biomass directly to graphene oxide is still a major challenge in the current scientific research field. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor. The method comprises dissolving a cellulose raw material in a solvent, slowly precipitating the cellulose in a poor solvent by dialysis for self-assembly, and freeze-drying to obtain a novel highly crystalline nanocellulose. The graphene oxide material is then pyrolyzed and carbonized to obtain the graphene oxide material. The obtained highly crystalline nanocellulose is directly converted into graphene oxide in one step by low-temperature carbonization, which has the characteristics of high efficiency and low energy consumption.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor comprises the following steps:

[0007] Step 1: treating the macromolecular cellulose raw material by acid hydrolysis to obtain cellulose nanofibers with relatively uniform molecular weight;

[0008] Step 2: Swelling the cellulose nanofibers described in step 1 in a solvent at low temperature and dissolving them by sufficient magnetic stirring to obtain a uniform and transparent cellulose solution;

[0009] Step 3: dialyzing the cellulose solution described in step 2 in a poor solvent for cellulose, so that the cellulose is gradually precipitated to obtain a highly crystalline nanocellulose thin layer material having a highly curled and wrinkled structure;

[0010] Step 4: freeze-drying, naturally drying, and drying the high-crystalline nanocellulose thin layer material described in step 3 to remove the solvent, thereby obtaining a high-crystalline nanocellulose powder having a highly curled and wrinkled structure;

[0011] Step 5: The high-crystalline nanocellulose described in step 4 is subjected to pyrolysis and carbonization treatment to obtain an ultra-low-temperature graphene oxide material with the high-crystalline nanocellulose having a highly curled and wrinkled structure as a precursor.

[0012] In the method for preparing graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 1, the macromolecular cellulose raw material includes refined cellulose or cellulose slurry extracted from plant, animal or bacterial sources.

[0013] In the method for preparing the graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 1, the acid used for cellulose hydrolysis includes one or more of sulfuric acid, hydrochloric acid, phosphoric acid and an organic acid.

[0014] In the method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 2, the solvent for the cellulose nanofibers includes sodium hydroxide / urea / water, lithium hydroxide / urea / water, sodium hydroxide / thiourea / water, lithium hydroxide / thiourea / water, dimethyl sulfoxide, or N,N-dimethylacetamide / LiCl.

[0015] In the method for preparing the graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 2, the low temperature of the solvent for the cellulose nanofibers is -30 to 5°C.

[0016] In the method for preparing the graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 3, the cellulose poor solvent includes one or more of water, alcohol, and ketone.

[0017] The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, in step 3, performs dialysis treatment in a poor solvent for 3 to 7 days, replaces the solvent every 6 hours, and removes the solvent of the cellulose nanofibers. The dialysis bag has a molecular weight cutoff of 8000 to 14000 Da.

[0018] The method for preparing a graphene oxide material with a highly crystalline nanocellulose thin layer having a highly curled and wrinkled structure as a precursor, in step 5, the pyrolysis carbonization is low-temperature carbonization, the low-temperature carbonization is carried out under an argon atmosphere, the low-temperature carbonization temperature is 300°C to 900°C, the carbonization time is 0.5 to 5 hours, and the heating rate is 1 to 10°C / min.

[0019] The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor has a uniform graphene oxide material structure, with 2 to 20 atomic layers and a wrinkled and curled structure.

[0020] The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor has a microscopic thickness of 0.5 nanometers to 10 nanometers, an average sheet size distribution of 0.5 micrometers to 10 micrometers, and an oxygen content of 7 vol% to 40 vol%.

[0021] The inventive concept of the present invention is:

[0022] In existing methods, cellulose is usually carbonized at high temperature to convert it into a graphite structure, and then converted into graphene oxide through a chemical exfoliation method. This process not only consumes a lot of energy, but also has high technical difficulty, making it difficult to obtain a uniform graphene oxide material with a small number of atomic layers. Therefore, the present invention, based on the hydrolysis of cellulose nanocrystals, first dissolves the cellulose by destroying the hydrogen bonds between the cellulose molecular chains, and then uses a poor solvent for dialysis to slowly and orderly rearrange the cellulose molecular chains, obtaining a highly crystalline nanocellulose layer. On this basis, a graphene oxide material with a highly crystalline nanocellulose layer having a highly curled and wrinkled structure as a precursor is prepared through low-temperature pyrolysis and carbonization.

[0023] The advantages and beneficial effects of the present invention are:

[0024] The high-crystalline nanocellulose prepared by the present invention is a material preparation method from the bottom up. The method first dissolves the cellulose molecules by destroying the hydrogen bonds between the cellulose molecular chains, and then uses dialysis to force the molecular chains to rearrange in order, thereby obtaining a high-crystalline nanocellulose thin layer with a highly curled and wrinkled structure. The high-crystalline nanocellulose material is then subjected to pyrolysis and carbonization. Since the high-crystalline nanocellulose structure is composed of highly ordered cellulose molecular chain bundles, the ordered segments are connected by the disordered arrangement of the chain bundles, and the structural characteristics of graphene oxide can be directly obtained after pyrolysis and carbonization. This method not only has important guiding significance for industrial production and product development, but also provides a class of green, environmentally friendly and low-cost graphene oxide materials for many fields such as catalysis, electrochemistry, energy and military industry, and wave absorption. More importantly, it provides the possibility of providing a preparation method for preparing graphene oxide-based composite materials at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1-Figure 4 This is a TEM photo of a graphene oxide material prepared in Example 1 of the present invention using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor. Figure 1 This is a TEM photo at low magnification. Figure 2 This is a TEM photo at high magnification. Figure 3 For high-resolution TEM, Figure 4 are selected area electron diffraction rings.

[0026] Figure 5 This is the Raman spectrum of the graphene oxide material prepared in Example 1 of the present invention using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor. In the figure, the horizontal axis Raman shift is the Raman shift (cm -1 ), the vertical axis Intensity is the relative intensity (au).

[0027] Figure 6 This graph shows the specific capacitance of a graphene oxide material prepared in Example 1 using a highly crystalline nanocellulose sheet with a highly curled and wrinkled structure as a precursor. In the graph, the horizontal axis represents the current density (A / g), and the vertical axis represents the specific capacity (F / g). DETAILED DESCRIPTION

[0028] In a specific implementation process, the present invention proposes a method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, the method comprising the following steps:

[0029] (1) The macromolecular cellulose raw material is treated by acid hydrolysis to obtain cellulose nanofibers with relatively uniform molecular weight;

[0030] (2) dissolving the cellulose nanofibers to obtain a cellulose solution;

[0031] (3) dialyzing the cellulose solution in a poor solvent for cellulose, gradually precipitating the cellulose to obtain highly crystalline cellulose nanomaterials;

[0032] (4) The highly crystalline cellulose nanomaterial can also be freeze-dried, naturally dried, and oven-dried to remove the solvent, thereby obtaining a highly crystalline nanocellulose powder sample;

[0033] (5) The highly crystalline nanocellulose is subjected to pyrolysis and carbonization treatment at a temperature of 300° C. or above to obtain a graphene oxide material having a highly curled and wrinkled structure.

[0034] The highly crystalline nanocellulose layer is a cellulose II nanomaterial with a crystallinity of ≥80%. Its crystal structure is a cellulose II structure (monoclinic system), with unit cell parameters of a = 0.81nm, b = 0.903nm, c = 1.031nm, α = β = 90°, and γ = 117.1°. The nanocellulose layer is characterized by a thin film structure, which shrinks into a three-dimensional mass due to curling and wrinkling, and locally forms a hollow polyhedron structure. The film surface is parallel to the cellulose II (020) crystal plane, and the thickness ranges from 1 nanometer to 100 nanometers. The microscopic thickness of the graphene oxide is 0.5 nanometers to 10 nanometers, and the average size of its flakes is distributed between 0.5 micrometers and 10 micrometers. The oxygen content of the graphene oxide material is approximately 7 vol% to 40 vol%.

[0035] The present invention will be further illustrated below by way of examples and accompanying drawings:

[0036] Example 1

[0037] Prepare concentrated sulfuric acid with a mass fraction of 64%, stir in a constant temperature water bath at 45°C, add microcrystalline cellulose after the solution temperature stabilizes, wherein each gram of microcrystalline cellulose corresponds to 8.75 ml of sulfuric acid, react at a stirring speed of 280 rpm for 30 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water three times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 5°C·min -1 The temperature was raised to 500 °C at a rate of 1000 °C and carbonized for 3 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with highly crystalline nanocellulose as a precursor.

[0038] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 2 nanometers, the average size of its flakes is 5 micrometers, and the oxygen content of the graphene oxide material is about 20%.

[0039] Example 2

[0040] Prepare concentrated sulfuric acid with a mass fraction of 64%, stir in a constant temperature water bath at 45°C, add microcrystalline cellulose after the solution temperature stabilizes, wherein each gram of microcrystalline cellulose corresponds to 8.75 ml of sulfuric acid, react at a stirring speed of 280 rpm for 30 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water 4 times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 5°C·min -1 The temperature was raised to 500 °C at a rate of 1000 °C and carbonized for 2 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with high crystalline nanocellulose as a precursor.

[0041] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 5 nanometers, the average size of its flakes is 6 micrometers, and the oxygen content of the graphene oxide material is about 30%.

[0042] Example 3

[0043] Prepare concentrated sulfuric acid with a mass fraction of 64%, stir in a constant temperature water bath at 45°C, add microcrystalline cellulose after the solution temperature stabilizes, wherein each gram of microcrystalline cellulose corresponds to 8.75 ml of sulfuric acid, react at a stirring speed of 280 rpm for 30 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water 5 times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 5°C·min -1 The temperature was raised to 400 °C at a rate of 100 °C and carbonized for 3 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with highly crystalline nanocellulose as a precursor.

[0044] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 8 nanometers, the average size of its flakes is 3 micrometers, and the oxygen content of the graphene oxide material is about 8%.

[0045] Example 4

[0046] Prepare hydrochloric acid with a mass fraction of 30%, stir in a constant temperature water bath at 60°C, add chopped cotton after the solution temperature stabilizes, wherein 15 ml of hydrochloric acid corresponds to each gram of cotton, react at a stirring speed of 280 rpm for 60 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water three times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 5°C·min -1 The temperature was raised to 600 °C at a rate of 1000 °C and carbonized for 3 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with highly crystalline nanocellulose as a precursor.

[0047] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 4 nanometers, the average size of its flakes is 2 micrometers, and the oxygen content of the graphene oxide material is about 12%.

[0048] Example 5

[0049] Prepare hydrochloric acid with a mass fraction of 30%, stir in a constant temperature water bath at 60°C, add chopped cotton after the solution temperature stabilizes, wherein 15 ml of hydrochloric acid corresponds to each gram of cotton, react at a stirring speed of 280 rpm for 60 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water four times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 5°C·min -1 The temperature was raised to 600 °C at a rate of 1000 °C and carbonized for 4 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with high crystalline nanocellulose as a precursor.

[0050] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 7 nanometers, the average size of its flakes is 4 micrometers, and the oxygen content of the graphene oxide material is about 22%.

[0051] Example 6

[0052] Prepare hydrochloric acid with a mass fraction of 30%, stir in a constant temperature water bath at 60°C, add chopped cotton after the solution temperature stabilizes, wherein 15 ml of hydrochloric acid corresponds to each gram of cotton, react at a stirring speed of 280 rpm for 60 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water 5 times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 2°C·min -1 The temperature was raised to 400 °C at a rate of 1 hour and carbonized, and finally naturally cooled to room temperature in the furnace to obtain graphene oxide material with high crystalline nanocellulose as a precursor.

[0053] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 7 nanometers, the average size of its flakes is 7 micrometers, and the oxygen content of the graphene oxide material is about 23%.

[0054] Example 7

[0055] Prepare hydrochloric acid with a mass fraction of 30%, stir in a constant temperature water bath at 60°C, add chopped cotton after the solution temperature stabilizes, wherein 15 ml of hydrochloric acid corresponds to each gram of cotton, react at a stirring speed of 280 rpm for 60 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water three times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 2°C·min -1 The temperature was raised to 400 °C at a rate of 100 °C and carbonized for 3 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with highly crystalline nanocellulose as a precursor.

[0056] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 0.5 nanometers, the average size of its flakes is 5 micrometers, and the oxygen content of the graphene oxide material is about 33%.

[0057] Example 8

[0058] Prepare hydrochloric acid with a mass fraction of 30%, stir in a constant temperature water bath at 60°C, add chopped cotton after the solution temperature stabilizes, wherein 15 ml of hydrochloric acid corresponds to each gram of cotton, react at a stirring speed of 280 rpm for 60 minutes, pour it into 5 times the amount of 0°C ice water after the reaction is completed to obtain a mixed solution; let the mixed solution stand for 12 hours, pour out the upper clear liquid to obtain a lower milky white turbid liquid, centrifuge the lower milky white turbid liquid at 8500 rpm for 20 minutes to obtain a milky white suspension, centrifuge and wash with deionized water 5 times to obtain a milky white sample; put the milky white sample into -20°C for freezing treatment for 1 day, take it out and place it in a freeze dryer, and dry it for 2 days to obtain cellulose nanofibers. Take 2g of cellulose nanofibers and add them to 98g of a mixed aqueous solution of 10wt% sodium hydroxide / 8wt% urea at -20°C. Stir magnetically until it is completely dissolved to obtain a uniform transparent solution. The solution is dialyzed against water for 5 days, with water replaced every 6 hours. The molecular weight cutoff of the dialysis bag is 8000-14000Da. Collect the liquid in the dialysis bag, freeze it at -20°C for 1 day, take it out and place it in a freeze dryer. After drying for 2 days, take it out to obtain highly crystalline nanocellulose. Then, dry it in an argon atmosphere at 2°C·min -1 The temperature was raised to 300 °C at a rate of 100 °C and carbonized for 2 h. Finally, the furnace was naturally cooled to room temperature to obtain graphene oxide material with high crystalline nanocellulose as a precursor.

[0059] In this embodiment, the technical indicators of the graphene oxide material are as follows: the microscopic thickness is measured to be 1 nanometer, the average size of its flakes is 0.8 micrometers, and the oxygen content of the graphene oxide material is about 24%.

[0060] from Figure 1-Figure 4 It can be seen that this type of graphene oxide material still maintains a relatively high crystalline structure and has a good highly curled and wrinkled structure.

[0061] The ratio of peak D to peak G (I D / I G ) has been widely used to study the microstructure of carbon materials. It is a method to quantify the carbon order of carbon materials. Figure 5 It can be seen that the graphitization (G) intensity and disorder (D) intensity change, and this result shows that the high crystalline nanocellulose sample is indeed converted into graphene oxide material under low temperature carbonization.

[0062] from Figure 6 It can be seen that this type of graphene oxide material exhibits a high specific capacitance value and has good capacitance performance.

[0063] Implementation results demonstrate that the present invention significantly reduces energy consumption by directly converting highly crystalline nanocellulose into graphene oxide in a one-step process through low-temperature pyrolysis. Furthermore, the resulting graphene oxide exhibits a uniform structure, with between 2 and 20 atomic layers. Its highly wrinkled and curled structure makes it a promising supercapacitor, demonstrating significant potential in fields such as materials science, energy, the environment, and scientific research, offering new insights into addressing resource utilization and environmental protection.

[0064] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor, characterized in that: The following steps are involved: Step 1: treating the macromolecular cellulose raw material by acid hydrolysis to obtain cellulose nanofibers with relatively uniform molecular weight; Step 2: Swelling the cellulose nanofibers described in step 1 in a solvent at low temperature and dissolving them by sufficient magnetic stirring to obtain a uniform and transparent cellulose solution; Step 3: dialyzing the cellulose solution described in step 2 in a poor solvent for cellulose, so that the cellulose is gradually precipitated to obtain a highly crystalline nanocellulose thin layer material having a highly curled and wrinkled structure; Step 4: freeze-drying, naturally drying, and drying the high-crystalline nanocellulose thin layer material described in step 3 to remove the solvent, thereby obtaining a high-crystalline nanocellulose powder having a highly curled and wrinkled structure; Step 5: The high-crystalline nanocellulose described in step 4 is subjected to pyrolysis and carbonization treatment to obtain an ultra-low-temperature graphene oxide material with the high-crystalline nanocellulose having a highly curled and wrinkled structure as a precursor.

2. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 1, the macromolecular cellulose raw material includes refined cellulose or cellulose pulp extracted from plants, animals or bacteria.

3. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer having a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 1, the acid used for cellulose hydrolysis includes one or more of sulfuric acid, hydrochloric acid, phosphoric acid and organic acid.

4. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 2, the solvent for the cellulose nanofibers includes sodium hydroxide / urea / water, lithium hydroxide / urea / water, sodium hydroxide / thiourea / water, lithium hydroxide / thiourea / water, dimethyl sulfoxide, or N,N-dimethylacetamide / LiCl.

5. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In the step 2, the low temperature of the solvent for the cellulose nanofibers is -30 to 5°C.

6. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 3, the poor solvent for cellulose includes one or more of water, alcohol, and ketone.

7. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 3, dialysis treatment is performed in a poor solvent for 3 to 7 days, and the solvent is replaced every 6 hours to remove the solvent of the cellulose nanofibers. The molecular weight cut-off of the dialysis bag is 8000 to 14000 Da.

8. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: In step 5, the pyrolysis carbonization is low-temperature carbonization, which is carried out in an argon atmosphere, with a low-temperature carbonization temperature of 300° C. to 900° C., a carbonization time of 0.5 to 5 hours, and a heating rate of 1 to 10° C. / min.

9. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: The graphene oxide material has a uniform structure, with atomic layers ranging from 2 to 20 layers and a wrinkled and curled structure.

10. The method for preparing a graphene oxide material using a highly crystalline nanocellulose thin layer with a highly curled and wrinkled structure as a precursor according to claim 1, characterized in that: The microscopic thickness of graphene oxide is 0.5 nanometers to 10 nanometers, the average size of its flakes is distributed between 0.5 micrometers and 10 micrometers, and the oxygen content of the graphene oxide material is 7 vol% to 40 vol%.

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