CN117727565A - Carbonized wood/reduced graphene oxide conductive composite material and preparation method and application thereof - Google Patents
Carbonized wood/reduced graphene oxide conductive composite material and preparation method and application thereof Download PDFInfo
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
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Abstract
The invention discloses a carbonized wood/reduced graphene oxide conductive composite material, and a preparation method and application thereof. According to the invention, the carbonized wood/reduced graphene oxide conductive composite material with more excellent electrochemical performance is prepared by filling oxidized graphene in a carbonized wood pore channel after sulfuric acid dispersion, and then performing pre-oxidation, high-temperature carbonization, freeze drying, vacuum impregnation, hydrothermal reduction and other processes. The adsorption effect between sulfuric acid molecules and graphene oxide functional groups is skillfully utilized, the problem that reduced graphene oxide is easy to agglomerate in a carbonized wood pore canal, so that the performance is poor is effectively solved, and the electrochemical performance of wood derived carbon is greatly improved. The invention can effectively fill and utilize the pore canal of the wood derived carbon to improve the performance of the super capacitor, and has very wide application prospect in the energy storage field.
Description
Technical Field
The invention relates to the technical field of supercapacitor electrode materials, in particular to a carbonized wood/reduced graphene oxide conductive composite material, and a preparation method and application thereof.
Background
Energy is an indispensable substance for human society development, and occupies a very important position in national economy. However, with the increasing exhaustion of fossil energy sources such as coal, oil, and gas, and the continuous deterioration of ecological environment, development of efficient, green, and renewable electrochemical storage devices has become urgent. Electrochemical energy storage devices (e.g., supercapacitors, lithium ion batteries, etc.) are considered to be a highly efficient energy storage system, with supercapacitors being considered to be a new type of green energy storage device. In recent years, super capacitors are increasingly favored because of their high power density, rapid charge and discharge, and long cycle life. However, their low energy density limits their application in many fields of automotive and consumer electronics. Thus, researchers have developed a variety of electrode materials, such as carbon materials, transition metal compounds, and conductive polymers, to improve their performance. However, these electrode materials are typically in powder form and require the addition of binders and conductive additives to form a slurry that is then coated onto the nickel foam to form the electrode. Not only does this add additional weight, but the electrode structure is extremely fragile. In addition, the addition of binders can also block the active material channels, thereby limiting the conduction of electrons and ions.
In contrast, wood is the most abundant renewable resource in nature, has the characteristics of being continuous, renewable, biodegradable and the like, and is widely applied to fields of furniture, bridges, buildings, sea water desalination, oil-water separation, papermaking, energy storage and the like in recent years. The method has the greatest advantages in the energy storage application field that the method has a vertical channel with low bending degree and a hierarchical porous structure, and can be directly used as an independent self-supporting electrode after carbonization without a conductive agent and a binder. In addition, the hierarchical porous structure of wood can be used for conveying water, ions and nutrients, the aligned vertical channels are beneficial to shortening the transmission path, and electrons and ions are more convenient to transmit after carbonization, so that the characteristics create great possibility for the application of the wood in the energy storage field. However, the preparation of the carbon electrode material by directly taking carbonized wood as the conductive carbon skeleton has poor performance, which is insufficient to meet the energy storage requirement and limits the development of the carbon electrode material in the energy storage field.
Graphene serving as an electrode material of the supercapacitor generally has the advantages of high specific surface area, excellent conductivity, rapid charge and discharge speed, long service life, stability, light weight, thin design and the like, so that the graphene becomes a very promising carbon material gradually, and the development of the supercapacitor technology can be promoted. However, the easy stacking and agglomeration seriously hampers the transportation of ions and the infiltration of electrolyte, and compared with the traditional super capacitor, the graphene capacitor has relatively low energy density and limited cycle life, and the capacitance performance of the graphene capacitor can be gradually attenuated with the increase of charge and discharge times.
Therefore, how to solve the problem that graphene materials are easy to stack and agglomerate, and how to solve the defect that carbonized wood is used as a conductive carbon skeleton by utilizing the advantages of graphene is a technical problem which needs to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the invention provides a carbonized wood/reduced graphene oxide conductive composite material, and a preparation method and application thereof. In particular to a method for dispersing graphene oxide by sulfuric acid and regulating and controlling a carbonized wood pore canal and application thereof. According to the method, a three-dimensional network structure of reduced graphene oxide is constructed in the pore canal of carbonized wood through the processes of pre-oxidation, high-temperature carbonization, freeze drying, vacuum impregnation, hydrothermal reduction and the like, the specific surface area of the pore canal of carbonized wood is improved while the pore canal of carbonized wood is effectively regulated and controlled by the structure, and the permeation and transmission of ions and electrons are facilitated, so that the electrochemical performance of carbonized wood is improved, and the problems that graphene filled in the pore canal of carbonized wood is easy to stack and serious in agglomeration are solved.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the preparation method of the carbonized wood/reduced graphene oxide conductive composite material comprises the following steps:
1) Preparing carbonized wood;
2) Adding graphene oxide powder into deionized water, uniformly stirring by ultrasonic to obtain a graphene oxide solution, dropwise adding a sulfuric acid solution into the graphene oxide solution, and continuously stirring to obtain a graphene oxide precursor solution;
3) Cutting carbonized wood into carbonized wood chips, placing the carbonized wood chips in graphene oxide precursor solution for multiple vacuum suction filtration, washing the surface with deionized water, and then placing the carbonized wood chips in a refrigerator for freezing;
4) Putting the frozen sample obtained in the step 3) into a vacuum dryer for cold drying to obtain carbonized wood/graphene oxide conductive composite material;
5) And (3) placing the carbonized wood/graphene oxide conductive composite material obtained in the step (4) into a high-pressure reaction kettle for hydrothermal reduction reaction, and freeze-drying after the reaction is finished and cooling to obtain the final carbonized wood/reduced graphene oxide conductive composite material.
Preferably, in the step 1), the wood is cut into blocks, the blocks are placed in a mixed solution of alcohol and deionized water for ultrasonic cleaning, and after freeze drying, pre-oxidation and high-temperature carbonization are carried out, so that carbonized wood is obtained.
Preferably, the wood is aspen, the wood is pre-oxidized, the temperature is raised to 200-300 ℃ at a speed of 5 ℃/min under the air atmosphere, and the temperature is kept for 1-6h; carbonizing, heating to 600-1000 ℃ at 5 ℃/min under nitrogen atmosphere, and preserving heat for 1-6h.
Preferably, in the step 2), the concentration of the graphene oxide solution is 2-8 mg.mL-1, the concentration of the sulfuric acid solution is 0.1M-0.3M, and the volume ratio of the graphene oxide solution to the sulfuric acid solution is 1:2.
preferably, the vacuum filtration in step 3) takes place for a period of 10% per time30min, and maintaining the pressure at normal pressure for 10-30 min each time; repeating for 3-5 times, soaking the materials in a vacuum state for 12-24 hours, flushing the materials after the soaking is finished, and freezing the materials in a refrigerator at the temperature of minus 15-25 ℃ for 8-16 hours; the carbonized wood was polished with 2000 mesh sandpaper and then cut into 1X 1.2X 0.08cm pieces 3 Is a carbonized wood chip.
Preferably, the specific parameters of the cold drying in the step 4) are as follows: the vacuum degree is 10-30 Pa, the condensing temperature is minus 50 ℃ and the time is 24 hours.
Preferably, the specific parameters of the hydrothermal reduction reaction in step 5) are as follows: the temperature is 120-180 ℃, and the hydrothermal time is 4-24 hours. More preferably, the hydrothermal reaction temperature is 180 ℃ and the hydrothermal time is 12 hours.
The preferable scheme has the beneficial effects that sulfuric acid is used as a dispersing agent or an intercalation agent for dispersing graphene oxide for the first time, agglomeration and stacking of the graphene oxide are restrained, so that the graphene oxide has larger specific surface area and more active sites, and the dispersed graphene oxide can be better compounded with carbonized wood, so that a three-dimensional conductive network can be well constructed in a pore channel of the carbonized wood, effective utilization of the pore channel of the carbonized wood is realized, and the electrochemical performance of the carbonized wood is further improved to a great extent.
On the other hand, the invention also provides application of the carbonized wood/reduced graphene oxide conductive composite material in the electrode material of the supercapacitor.
The technical effect achieved by the preferable scheme is that the carbonized wood/reduced graphene oxide conductive composite material prepared by the method is applied to the electrode of the super capacitor, so that the capacitance performance of the capacitor can be remarkably improved.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention fully utilizes the characteristic that the original carbon skeleton can be maintained after the wood is carbonized. The carbonized wood/reduced graphene oxide conductive composite material with larger specific surface area and better conductive performance is prepared by using wood as a carbon source precursor, sulfuric acid as a dispersing agent and graphene oxide as a filler, filling the graphene oxide dispersed by sulfuric acid into pore channels of carbonized wood by using a vacuum impregnation technology, and then performing processes such as freeze drying, hydrothermal reduction and the like, and excellent supercapacitor performance is shown.
(2) The method provided by the invention has the characteristics of simple process, low cost, green pollution-free property and the like, and has the greatest advantages of solving the problem that graphene oxide is easy to stack and agglomerate in a carbonized wood pore canal, so that the finally obtained carbonized wood/reduced graphene oxide conductive composite material shows more excellent electrochemical performance.
(3) The carbonized wood/reduced graphene oxide conductive composite material prepared by the invention is used as an electrode material of a self-supporting supercapacitor, and has higher specific capacity and excellent multiplying power characteristics.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a SEM image of carbonized wood material produced in comparative example 1 of the present invention;
FIG. 2 is a SEM image of the carbonized wood/reduced graphene oxide conductive composite prepared in comparative example 2 of the present invention;
FIG. 3 is a SEM (scanning electron microscope) image of different multiples of the carbonized wood/reduced graphene oxide conductive composite prepared in example 1 of the present invention;
FIG. 4 is a drawing showing that the carbonized wood/reduced graphene oxide conductive composite material prepared in example 1 of the present invention is in the range of 5 to 100mV s -1 Cyclic voltammogram at scan rate;
FIG. 5 is a drawing showing that the carbonized wood/reduced graphene oxide conductive composite material prepared in example 1 of the present invention is 10-100 mA cm -2 Constant current charge-discharge curve graph under current density；
FIG. 6 is a graph showing the area specific capacity as a function of current density for carbonized wood/reduced graphene oxide conductive composites prepared in examples 1-3 of the present invention and comparative examples 1-2.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The medicament required by the embodiment of the invention is a conventional experimental medicament and is purchased from a commercial channel; the experimental methods not mentioned in the examples are conventional experimental methods, and are not described in detail herein.
Comparative example 1
The preparation of the carbonized wood/reduced graphene oxide conductive composite material specifically comprises the following steps:
(1) Cutting poplar wood into pieces of 2×2×0.2cm 3 Then placing the wood block in a mixed solution of absolute ethyl alcohol and deionized water (volume ratio is 1:1) for ultrasonic cleaning;
(2) The wood block in the step (1) is put into a refrigerator to be frozen for 12 hours, then the sample is taken out and put into a vacuum freeze dryer, and freeze drying is carried out for 24 hours at the temperature of minus 55 ℃;
(3) And (3) placing the sample obtained in the step (2) into a tubular furnace for calcination treatment, heating to 260 ℃ at a speed of 5 ℃/min under the atmosphere of air, pre-oxidizing and preserving heat for 6 hours, heating to 1000 ℃ at a speed of 5 ℃/min under the atmosphere of nitrogen, preserving heat for 6 hours, and taking out the sample after natural cooling to obtain the carbonized wood material.
(4) The carbonized wood obtained was polished with 2000 mesh sand paper and then cut into 1X 1.2X 0.08cm pieces 3 Is a carbonized wood chip;
comparative example 2
Steps (1) - (4) are the same as comparative example 1
(5) Weighing a certain massGraphene oxide powder is dispersed in a proper amount of deionized water and stirred by ultrasonic, and the concentration of the graphene oxide powder is 6 mg.mL -1 Is a graphene oxide solution;
(6) Immersing the carbonized wood chip obtained in the step (4) in the step (5) in the graphene oxide mixed solution, carrying out vacuum filtration for 30min each time, maintaining the normal pressure for 10min each time, and repeating for a plurality of times until the carbonized wood chip is not immersed in the graphene oxide mixed solution and keeping the impregnated carbonized wood chip in a vacuum state for 24h;
(7) Washing the sample obtained in the step (6), freezing in a refrigerator at-20 ℃ for 12 hours, taking out, putting in a vacuum freeze dryer, and freeze drying at-55 ℃ for 24 hours;
(8) And (3) placing the sample obtained in the step (7) into a high-pressure reaction kettle to react for 12 hours at the temperature of 180 ℃, cooling the sample, simply washing the sample, then placing the sample into a refrigerator to freeze the sample, and finally obtaining the final carbonized wood/reduced graphene oxide conductive composite material through freeze drying the sample.
Example 1
Compared with comparative example 2, after the graphene oxide mixed solution is obtained in step (5), a sulfuric acid solution with the concentration of 0.1M (the volume ratio of the graphene oxide solution to the sulfuric acid solution is 1:2) is dropwise added, and after uniform stirring, a graphene oxide precursor solution is obtained, and the other steps are the same as those of comparative example 2.
Example 2
Compared with comparative example 2, after the graphene oxide mixed solution is obtained in step (5), a sulfuric acid solution with the concentration of 0.2M (the volume ratio of the graphene oxide solution to the sulfuric acid solution is 1:2) is dropwise added, and after uniform stirring, a graphene oxide precursor solution is obtained, and the other steps are the same as those of comparative example 2.
Example 3
Compared with comparative example 2, after the graphene oxide mixed solution is obtained in step (5), a sulfuric acid solution with the concentration of 0.3M (the volume ratio of the graphene oxide solution to the sulfuric acid solution is 1:2) is then added dropwise, and a graphene oxide precursor solution is obtained after uniform stirring, and the other steps are the same as those of comparative example 2.
The carbonized wood material obtained in comparative example 1 was placed under a scanning electron microscope to be scanned, and an SEM image was obtained, see fig. 1;
placing the carbonized wood/reduced graphene oxide conductive composite material obtained in the comparative example 2 under a scanning electron microscope for scanning to obtain an SEM (scanning electron microscope) graph, see FIG. 2;
placing the carbonized wood/reduced graphene oxide conductive composite material obtained in the example 1 under a scanning electron microscope for scanning to obtain an SEM (scanning electron microscope) graph, see FIG. 3 (A) and FIG. 3 (B); compared with comparative examples 1 and 2, it can be seen that reduced graphene oxide having a single layer is successfully filled into the pores of carbonized wood after sulfuric acid is added as a dispersant, and no stacking agglomeration is performed, which facilitates the transport of electrolyte ions, thereby helping to further enhance the electrochemical performance thereof.
Electrochemical performance test was performed on the material prepared in example 1, under a three-electrode system, using the prepared material as a working electrode, a platinum sheet as a counter electrode, and mercury/oxidized mercury as a reference electrode, 6 mol.L -1 The potassium hydroxide is used as electrolyte, and the test is carried out in a voltage range of-1 to 0V, and the cyclic voltammetry curve graphs under different scanning speeds and the constant current charge-discharge curves under different current densities are shown in figures 4 and 5.
FIG. 4 shows a typical cyclic voltammogram at a scan rate of 2-50 mV.s-1 at a potential window of-1 to 0V, which can be seen to have a rectangular-like shape, meaning that we produce electrode materials with ideal capacitive behavior and fast ion transport kinetics.
Fig. 5 is a constant current charge-discharge curve at different current densities, and it can be seen that it shows almost symmetrical triangles at different current densities, indicating that it has good electric double layer behavior.
Electrochemical performance tests were performed on examples 1-3 and comparative examples 1-2, and calculated to obtain specific capacity comparison graphs at different current densities, see fig. 6.
As can be seen from FIG. 6, the current density was 5mA cm -2 The specific area capacities of examples 1 to 3 and comparative examples 1 to 2 were 4638, 4331, 4110, 3740 and 2508 mF.cm, respectively -2 When the current density was increased to 200 mA.cm -2 Specific area capacities of examples 1 to 3 and comparative examples 1 to 2 were 3771, 2780, 2759, 2704, respectively、1047mF·cm -2 The initial capacity retention rates are 81%, 64%, 67%, 72% and 42%, respectively, which shows that the carbonized wood/reduced graphene oxide conductive composite material prepared by adding a proper amount of sulfuric acid solution into the graphene oxide mixed solution has better multiplying power characteristics. The carbonized wood/reduced graphene oxide conductive composite material obtained when a sulfuric acid solution with a concentration of 0.1M is added to the graphene oxide mixed solution has the most excellent rate characteristics.
The results show that: compared with comparative examples 1 and 2, the method adopts the oxidized graphene dispersed by sulfuric acid to fill and utilize the pore canal of carbonized wood, and can effectively solve the problem that the reduced oxidized graphene is easy to agglomerate and stack in the pore canal of carbonized wood. Based on these characteristics, examples 1 to 3 exhibited more excellent electrochemical properties than comparative examples.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. The preparation method of the carbonized wood/reduced graphene oxide conductive composite material is characterized by comprising the following steps of:
1) Preparing carbonized wood;
2) Adding graphene oxide powder into deionized water, uniformly stirring by ultrasonic to obtain a graphene oxide solution, dropwise adding a sulfuric acid solution into the graphene oxide solution, and continuously stirring to obtain a graphene oxide precursor solution;
3) Cutting carbonized wood into carbonized wood chips, placing the carbonized wood chips in graphene oxide precursor solution for multiple vacuum suction filtration, washing the surface with deionized water, and then placing the carbonized wood chips in a refrigerator for freezing;
4) Putting the frozen sample obtained in the step 3) into a vacuum dryer for cold drying to obtain carbonized wood/graphene oxide conductive composite material;
5) And (3) placing the carbonized wood/graphene oxide conductive composite material obtained in the step (4) into a high-pressure reaction kettle for hydrothermal reduction reaction, and freeze-drying after the reaction is finished and cooling to obtain the final carbonized wood/reduced graphene oxide conductive composite material.
2. The method for preparing the carbonized wood/reduced graphene oxide conductive composite material according to claim 1, wherein in the step 1), wood blocks obtained by cutting wood into certain specifications are placed in a mixed solution of alcohol and deionized water for ultrasonic cleaning, and then freeze drying, pre-oxidation and high-temperature carbonization are performed to obtain the carbonized wood.
3. The method for preparing the carbonized wood/reduced graphene oxide conductive composite material according to claim 2, wherein the wood is populus alba, is pre-oxidized to be heated to 200-300 ℃ at a speed of 5 ℃/min under the air atmosphere, and is preserved for 1-6h; carbonizing, heating to 600-1000 ℃ at 5 ℃/min under nitrogen atmosphere, and preserving heat for 1-6h.
4. The method for preparing carbonized wood/reduced graphene oxide conductive composite material according to claim 1, wherein the graphene oxide solution concentration in step 2) is 2-8 mg/mL -1 The concentration of the sulfuric acid solution is 0.1M-0.3M, and the volume ratio of the graphene oxide solution to the sulfuric acid solution is 1:2.
5. the method for preparing carbonized wood/reduced graphene oxide conductive composite material according to claim 1, wherein the step 3) is vacuum filtrationThe time of (2) is 10-30 min each time, and the time is maintained for 10-30 min each time under normal pressure; repeating for 3-5 times, soaking the materials in a vacuum state for 12-24 hours, flushing the materials after the soaking is finished, and freezing the materials in a refrigerator at the temperature of minus 15-25 ℃ for 8-16 hours; the carbonized wood was polished with 2000 mesh sandpaper and then cut into 1X 1.2X 0.08cm pieces 3 Is a carbonized wood chip.
6. The method for preparing carbonized wood/reduced graphene oxide conductive composite material according to claim 1, wherein the specific parameters of the cold drying in step 4) are: the vacuum degree is 10-30 Pa, the condensing temperature is minus 50 ℃ and the time is 12-48 h.
7. The method for preparing carbonized wood/reduced graphene oxide conductive composite material according to claim 1, wherein the specific parameters of the hydrothermal reduction reaction in step 5) are as follows: the temperature is 120-180 ℃, and the hydrothermal time is 4-24 hours.
8. Carbonized wood/reduced graphene oxide conductive composite material prepared by the preparation method according to any one of claims 1-7.
9. Use of the carbonized wood/reduced graphene oxide conductive composite material according to claim 8 in supercapacitor electrode materials.
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