Method for preparing carbon nano onion from biomass waste, carbon nano onion and application of carbon nano onion

Abstract

The invention provides a method for preparing carbon nano onions from biomass wastes, which comprises the following steps: carbonizing the biomass wastes, and grinding to obtain biomass carbon powder; transferring the biomass carbon powder into absolute ethyl alcohol, stirring, then adding a potassium carbonate solution, centrifuging after stirring, and collecting supernate; mixing the supernate with a dilute nitric acid solution, and stirring to obtain a mixed solution; and carrying out hydrothermal treatment by taking the mixed solution as a raw material to obtain the carbon nano onion. The method is simple to operate, mild in reaction condition, wide in raw material source, few in by-product, low in required cost, small in environmental influence, small in required equipment investment and low in energy consumption, can be used for preparing the carbon nano onion with excellent performance, and has a wide application prospect in the fields of electrochemical energy storage, catalyst carriers, conductive fillers, adsorbents and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon materials, and particularly relates to a method for preparing carbon nano-onions from biomass waste. Background Art

[0002] Scientifically planning the use and management of carbon is of great importance. First, reducing the combustion of fossil fuels and turning to cleaner and lower-carbon energy can not only reduce greenhouse gas emissions but also air pollution. Second, increasing the research and development of renewable energy technologies, improving their efficiency and economy, and achieving industrialization and large-scale production to replace non-renewable fossil fuels. At the same time, establishing a resource recycling system to achieve closed-loop management of carbon resources, and through carbon capture, utilization and storage, etc., turning carbon dioxide into valuable products.

[0003] Biomass is an abundant and renewable resource on the earth. Through its conversion, it not only provides a production route for carbon materials but also offers a new opportunity for the development of renewable energy. Due to its wide source and fast renewal rate, biomass provides a sustainable solution for humans and can long-term support innovation and development in the field of nanomaterials. Therefore, preparing nanocarbon materials from biomass waste conforms to the concepts of green chemistry, circular economy, and sustainable development.

[0004] Biomass waste, such as crop residues, wood waste, and organic garbage, is usually regarded as useless waste. However, by converting these wastes into high-value-added nanocarbon materials, the reuse of resources can be realized, and the overexploitation of natural resources can be reduced. This not only reduces the environmental burden of waste treatment but also creates economic value. The conversion of biomass waste into carbon nanomaterials involves the integration of knowledge in multiple disciplines such as chemistry, materials science, and environmental science. This helps to promote cooperation and communication in multiple fields, accelerate technological innovation and progress, and provide more possibilities for future new material development and environmental protection.

[0005] Carbon nano-onions are a kind of carbon nanomaterial composed of multiple concentric shell layers, which are usually composed of fullerenes wrapped layer by layer. Carbon nano-onions have physical and chemical properties such as high surface area, high conductivity, excellent thermal stability, and mechanical strength. Due to their high conductivity and large specific surface area, they can significantly improve the energy density and power density and are used as electrode materials for supercapacitors. In addition, they show excellent performance as anode materials in lithium-ion batteries, which can improve the charge-discharge efficiency and cycle life of the batteries. Due to their unique electronic structure and surface properties, they are also often applied to electrocatalytic and photocatalytic reactions, such as in oxygen reduction reactions and methane reforming reactions, showing significant catalytic activity. Thanks to their good biocompatibility and functionalized surface, they can also be used for drug delivery and bioimaging.

[0006] In the process of preparing carbon nanomaterials, traditional methods usually consume a large amount of fossil fuels and chemical reagents, producing harmful by-products. The preparation technology using biomass waste as raw materials usually adopts relatively environmentally friendly methods such as pyrolysis and carbonization, reducing environmental pollution; this method can not only effectively reduce energy consumption, but also reduce greenhouse gas emissions, contributing to addressing climate change. Summary of the Invention

[0007] In view of the above technical problems, the object of the present invention is to provide a method for preparing carbon nano-onions from biomass waste with high efficiency, low cost and environmental protection.

[0008] To achieve the above object, the present invention proposes the following solutions: In the first aspect, a method for preparing carbon nano-onions from biomass waste is provided, including: Carrying out carbonization treatment on biomass waste to obtain biomass carbon, and grinding the biomass carbon to obtain biomass carbon powder; Transferring the biomass carbon powder to absolute ethanol and stirring, then adding a potassium carbonate solution, stirring and reacting, and centrifuging to collect the supernatant; Mixing the supernatant with a dilute nitric acid solution and stirring to obtain a mixed solution; Using the mixed solution as a raw material, carrying out hydrothermal treatment to obtain carbon nano-onions.

[0009] Furthermore, the biomass waste is one or a mixture of at least two of tea leaves, peanut shells, ginkgo leaves, sawdust, straw, nut shells, and coconut shells.

[0010] Furthermore, adding the potassium carbonate solution to adjust the pH value of the reaction system to 8.0 - 12.0.

[0011] Furthermore, adding the dilute nitric acid solution to adjust the pH value of the reaction system to 3.0 - 4.0.

[0012] Furthermore, stirring for 5 - 20 min after adding the potassium carbonate solution.

[0013] Furthermore, the carbonization temperature is 600 - 900 °C; the carbonization time is 10 - 120 min; the atmosphere of carbonization is nitrogen.

[0014] Furthermore, ball milling is used to grind the biomass carbon; the rotation speed of the ball milling is 300 - 500 rpm; the time of the ball milling is 10 - 120 min.

[0015] Furthermore, the temperature of the hydrothermal treatment is 170 - 220 °C; the time of the hydrothermal treatment is 1 - 12 h.

[0016] In the second aspect, carbon nano-onions are provided, which are prepared by the aforementioned preparation method.

[0017] In a third aspect, applications of carbon nano-onions in electrochemical energy storage, catalyst carriers, conductive fillers, and adsorbents are provided.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The provided method is simple to operate, has mild reaction conditions, few by-products, low required cost, little environmental impact, low required equipment investment, low energy consumption, and can prepare carbon nano-onions with excellent performance, having broad application prospects in the fields of electrochemical energy storage, catalyst carriers, conductive fillers, adsorbents, etc.

[0019] The provided preparation method uses biomass waste as a raw material to prepare carbon nano-onions, which can not only reduce the quantity of waste and relieve the environmental burden, but also convert the waste into high-value-added products, conforming to the concepts of sustainable development and circular economy; the types of raw material biomass waste required by this preparation method are diverse, the raw material sources are wide, it is easy to obtain, and the price is low or even negligible. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 TEM image of the carbon nano-onions prepared in Example 1.

[0022] Figure 2 TEM image of the carbon nano-onions prepared in Example 2.

[0023] Figure 3 TEM image of the carbon nano-onions prepared in Example 3.

[0024] Figure 4 TEM image of the carbon nano-onions prepared in Example 4.

[0025] Figure 5 Raman spectra of the carbon nano-onions prepared in Examples 1 to 4. Detailed Embodiments

[0026] In view of the technical problems existing in the existing preparation methods of carbon nano-onions, such as high cost of carbon sources, difficulty in obtaining a large amount of raw materials, complex preparation methods or processes, complex equipment, or high energy consumption, etc., the applicant has found through research that carbon powder obtained by carbonizing and grinding biomass waste is used as a raw material, transferred to absolute ethanol and stirred, potassium carbonate solution is added, stirred and reacted, then centrifuged, and the mixed solution of the supernatant and dilute nitric acid solution is used as a precursor solution, and hydrothermal treatment is carried out to obtain carbon nano-onions. Based on this, the present invention is completed.

[0027] Specifically, the present invention provides a method for preparing carbon nano-onions from biomass waste, including: Carrying out carbonization treatment on biomass waste to obtain biomass carbon, and grinding the biomass carbon to obtain biomass carbon powder; Transfer the biomass carbon powder to absolute ethanol and stir, then add potassium carbonate solution, stir and then centrifuge to collect the supernatant; Mix the supernatant and dilute nitric acid solution, stir to obtain a mixed solution; Using the mixed solution as a raw material, carry out hydrothermal treatment to obtain carbon nano-onions.

[0028] In some preferred embodiments, the biomass waste is one or a mixture of at least two of tea leaves, peanut shells, ginkgo leaves, sawdust, straw, nut shells, coconut shells.

[0029] In some preferred embodiments, adding the potassium carbonate solution to adjust the pH value of the reaction system to 8.0 - 12.0, such as 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, etc. It has been found through research that when the pH value is too low, it is not conducive to preparing carbon nano-onions with less impurities, thereby reducing the performance of carbon nano-onions. It should be noted that the potassium carbonate solution can be a potassium carbonate solution with a conventional concentration, and there is no special requirement for the concentration.

[0030] The stirring time after transferring the biomass carbon powder to absolute ethanol is not limited, as long as the biomass carbon powder can be uniformly dispersed in absolute ethanol.

[0031] In some preferred embodiments, the stirring time after adding the potassium carbonate solution is 5 - 20 min, such as 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, etc.

[0032] The rotation speed and time of centrifugation can be the conventional rotation speed and time in the art, for example, centrifuging at 6000 - 10000 rpm for 5 - 10 min.

[0033] In some preferred embodiments, a dilute nitric acid solution is added to adjust the pH value of the reaction system to 3.0 - 4.0, such as 3, 3.5, 4, etc. If the pH value is too low, the graphitization degree of the carbon material will decrease, and carbon nano-onions cannot be prepared. If the pH value is too high, the impurity content of the carbon nano-onions will increase, thereby reducing the performance of the carbon nano-onions. It should be noted that the dilute nitric acid can be dilute nitric acid with a conventional concentration in the art, that is, nitric acid with a mass concentration lower than 31.68%.

[0034] In some preferred embodiments, the carbonization temperature is 600 - 900 °C, such as 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, etc.; the carbonization time is 10 - 120 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.; the atmosphere for carbonization is nitrogen.

[0035] The duration of grinding after carbonization can be determined conventionally according to the grinding method and the requirements for the grinding effect. The grinding method can be conventional ball milling, etc. in the art, and the ball milling speed can be determined conventionally according to the actual situation. In some preferred embodiments, biomass carbon is ground by ball milling; the rotation speed of the ball milling is 300 - 500 rpm; the time of the ball milling is 10 - 120 min.

[0036] In some preferred embodiments, the temperature of the hydrothermal treatment is 170 - 220 °C, such as 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, etc.; the time of the hydrothermal treatment is 1 - 12 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, etc.

[0037] In some preferred embodiments, it further includes the steps of cleaning the biomass waste to remove surface dust and drying. The cleaning can adopt conventional cleaning methods in the art, such as ultrasonic cleaning. The power of ultrasonic cleaning can be 50 - 300 W, and the ultrasonic cleaning time and number of times can be adjusted according to the cleaning effect requirements; the drying can also adopt conventional drying processes, such as drying in an oven, etc.

[0038] In some embodiments, after obtaining carbon nano-onions by hydrothermal reaction, the solution system after the hydrothermal reaction can also be subjected to solid-liquid separation and drying. Specifically, solid-liquid separation can be achieved by high-speed centrifugation, and drying can adopt conventional drying methods in the art.

[0039] The present invention provides carbon nano-onions, which are prepared by the aforementioned preparation method.

[0040] In some preferred embodiments, in the Raman spectrum of the carbon nano-onions, the peak intensity ratio of the D peak at 1350 cm -1 to the G peak at 1580 cm -1 is less than 1, preferably not greater than 0.8, such as 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, etc.

[0041] In some preferred embodiments, the particles of the carbon nano-onions are spherical or quasi-spherical; the particle size of the carbon nano-onions is 20-30 nm, such as 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, etc.

[0042] In some preferred embodiments, the carbon layer thickness of the carbon nano-onions is 5-15 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc.

[0043] The present invention provides the application of the foregoing carbon nano-onions in supercapacitors, lithium-ion batteries, electrocatalysis, and photocatalysis.

[0044] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0046] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0047] Example 1 (1) Take 20 g of dry tea waste and put it into an ultrasonic cleaner, clean it for 10 min at a power of 210 W, continuously clean it 5 times, dry it at 150 °C for 60 min, and carbonize it at 700 °C for 90 min in a nitrogen environment.

[0048] (2) Use a ball mill to grind the carbonized tea at a rotation speed of 500 rpm for 30 min, then transfer it to anhydrous ethanol, use a magnetic stirrer to stir it at 500 rpm, and at the same time add a potassium carbonate solution to make the pH of the mixed solution about 9.5, and the stirring time is 15 min.

[0049] (3) Centrifuge the mixed solution at 10000 rpm for 10 min, collect the supernatant after centrifugation, and stir it with a magnetic stirrer at 750 rpm. At the same time, add a dilute nitric acid solution (mass concentration of 26.4%) to adjust the pH of the mixed solution to about 3.5, and stir for 20 min.

[0050] (4) Transfer the mixed solution to a stainless steel reactor and react at 190 °C for 12 h to obtain carbon nano-onions. Drop the solution after the hydrothermal reaction on a copper grid for detection. The TEM image of the obtained carbon nano-onions is as Figure 1 shown.

[0051] Example 2 (1) Take 25 g of dry peanut shell waste and put it into an ultrasonic cleaner. Clean it at a power of 210 W for 5 min, clean it continuously for 3 times, dry it at 120 °C for 30 min, and carbonize it at 600 °C for 60 min in a nitrogen environment.

[0052] (2) Use a ball mill to grind the carbonized peanut shells at a rotation speed of 500 rpm for 30 min, then transfer them to anhydrous ethanol, stir them with a magnetic stirrer at 500 rpm, and at the same time add a potassium carbonate solution to adjust the pH of the mixed solution to about 9.5, and stir for 15 min.

[0053] (3) Centrifuge the mixed solution at 8000 rpm for 5 min, collect the supernatant after centrifugation, and stir it with a magnetic stirrer at 500 rpm. At the same time, add a dilute nitric acid solution (mass concentration of 26.4%) to adjust the pH of the mixed solution to about 3.5, and stir for 15 min.

[0054] (4) Transfer the mixed solution to a stainless steel reactor and react at 200 °C for 10 h to prepare carbon nano-onions. The TEM image of the obtained carbon nano-onions is as Figure 2 shown.

[0055] Example 3 (1) Take 17 g of dry ginkgo leaf waste and put it into an ultrasonic cleaner. Clean it at a power of 210 W for 5 min, clean it continuously for 3 times, dry it at 120 °C for 30 min, and carbonize it at 750 °C for 30 min in a nitrogen environment.

[0056] (2) Use a ball mill to grind the carbonized ginkgo leaves at a rotation speed of 500 rpm for 20 min, then transfer them to anhydrous ethanol, stir them with a magnetic stirrer at 500 rpm, and at the same time add a potassium carbonate solution to adjust the pH of the mixed solution to about 9.5, and stir for 15 min.

[0057] (3) Centrifuge the mixed solution at 7500 rpm for 5 min, collect the supernatant after centrifugation, and stir it with a magnetic stirrer at 500 rpm. At the same time, add a dilute nitric acid solution (mass concentration of 26.4%) to make the pH of the mixed solution about 3.5, and stir for 15 min.

[0058] (4) Transfer the mixed solution to a stainless steel reactor to prepare carbon nano-onions by reacting at 180 °C for 12 h. The TEM image of the obtained carbon nano-onions is as Figure 3 shown.

[0059] Example 4 (1) Take 30 g of dry sawdust waste and put it into an ultrasonic cleaner. Clean it at a power of 210 W for 10 min, continuously clean it 5 times, dry it at 120 °C for 60 min, and carbonize it at 850 °C for 30 min in a nitrogen environment.

[0060] (2) Use a ball mill to grind the carbonized sawdust at a rotation speed of 500 rpm for 90 min, then transfer it to absolute ethanol, stir it with a magnetic stirrer at 500 rpm, and at the same time add a potassium carbonate solution to make the pH of the mixed solution about 9.5, and stir for 15 min.

[0061] (3) Centrifuge the mixed solution at 10000 rpm for 5 min, collect the supernatant after centrifugation, and stir it with a magnetic stirrer at 500 rpm. At the same time, add a dilute nitric acid solution (mass concentration of 26.4%) to make the pH of the mixed solution about 3.5, and stir for 15 min.

[0062] (4) Transfer the mixed solution to a stainless steel reactor to prepare carbon nano-onions by reacting at 180 °C for 12 h. The TEM image of the obtained carbon nano-onions is as Figure 4 shown.

[0063] It can be seen from Figures 1 - 4 that the carbon layer thickness range of the obtained carbon nano-onions is 5.98 - 11.74 nm; the particles of the carbon nano-onions are spherical or quasi-spherical; the particle size of the carbon nano-onions is 22.74 - 29.21 nm. Among them, Figure 1 the carbon nano-onion particles are spherical or quasi-spherical in structure, arranged in the form of multiple concentric shell layers inside, and the layer spacing is uniform, indicating that the structural integrity of the carbon nano-onions is relatively good. Figure 2 is the SEM image of the carbon nano-onions prepared in Example 2. Its morphology is similar to the former, also showing a multi-layer concentric shell structure, and the particle dispersion is good. Figure 3 shows the SEM image of the carbon nano-onions prepared in Example 3. It can be seen from the figure that the surface morphology is relatively smooth, the sphericity of the particles is relatively high, and there is a clear hierarchical structure inside. Figure 4SEM image of the carbon nano-onions prepared in Example 4, with clear particle lamination, uniform distribution, and relatively compact structure; comparison Figures 1 - 4 It can be seen that the differences in the morphologies of the carbon nano-onions prepared from the four types of biomass, namely tea leaves, peanut shells, ginkgo leaves, and sawdust, are relatively small. Thus, it is speculated that other biomass wastes may also be used as raw materials to replace the above-mentioned biomass, such as straw, nut shells, peanut shells, coconut shells, and other types of leaves.

[0064] The Raman spectra of the carbon nano-onions prepared in Examples 1-4 are as Figure 5 shown. The two peaks appearing in the figure are the characteristic peaks of carbon, namely: the D peak and the G peak. Among them, the D peak is at 1350 cm -1 and belongs to the boundary vibration mode of the hexagonal Brillouin zone induced by disorder, which is used to characterize defects. The higher its intensity, the higher the degree of disorder of the sample. The G peak is at 1580 cm -1 and belongs to the stretching vibration mode of the in-plane bonds of carbon atoms, which is related to the degree of graphitization. Its peak width and intensity are also related to defects. The smaller its full width at half maximum and the lower its intensity, the fewer the defects. Among them, the ratio of ID / IG in the graphite of the carbon nano-onions prepared in Examples 1-4 ranges from 0.6 to 0.8, all less than 1, indicating that the structural defects are less and the graphitization effect of the prepared carbon nano-onions is better.

[0065] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing carbon nano-onions from biomass waste, characterized in that, Comprising: The biomass waste is carbonized to obtain biomass carbon, and the biomass carbon is ground to obtain biomass carbon powder; The biomass carbon powder is transferred to absolute ethanol, stirred, then a potassium carbonate solution is added, stirred and centrifuged, and the supernatant is collected; The supernatant is mixed with a dilute nitric acid solution and stirred to obtain a mixed solution; Using the mixed solution as a raw material, hydrothermal treatment is carried out to obtain carbon nano-onions.

2. The method for preparing carbon nano-onions from biomass waste according to claim 1, characterized in that, The biomass waste is one or a mixture of at least two of tea leaves, peanut shells, ginkgo leaves, sawdust, straw, nut shells, coconut shells.

3. The method for preparing carbon nano-onions from biomass waste according to claim 1, wherein, The potassium carbonate solution is added to adjust the pH value of the reaction system to 8.0 - 12.0; The dilute nitric acid solution is added to adjust the pH value of the reaction system to 3.0 - 4.

0.

4. The method for preparing carbon nano-onions from biomass waste according to claim 1, characterized in that, After adding the potassium carbonate solution, stir for 5 - 20 min.

5. The method for preparing carbon nano-onions from biomass waste according to claim 1, characterized in that, The carbonization temperature is 600 - 900 °C; the carbonization time is 10 - 120 min; the atmosphere of carbonization is nitrogen.

6. The method for preparing carbon nano-onions from biomass waste according to claim 1, characterized in that, The biomass carbon is ground by ball milling; the rotation speed of the ball milling is 300 - 500 rpm; the time of the ball milling is 10 - 120 min.

7. The method for preparing carbon nano-onions from biomass waste according to claim 1, characterized in that, The temperature of the hydrothermal treatment is 170 - 220 °C; the time of the hydrothermal treatment is 1 - 12 h.

8. Carbon nano-onions, characterized in that, Prepared by the preparation method according to any one of claims 1 - 7.

9. The carbon nano-onion according to claim 8, characterized in that, In the Raman spectrum of the carbon nano-onions, the peak intensity ratio of the D peak at 1350 cm -1 to the G peak at 1580 cm -1 is less than 1; The carbon layer thickness of the carbon nano-onions is 5 - 15 nm; The particles of the carbon nano-onions are spherical or quasi-spherical; The particle size of the carbon nano-onions is 20 - 30 nm.

10. Use of the carbon nano-onions according to claim 8 or 9 in electrochemical energy storage, catalyst carriers, conductive fillers, adsorbents.

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