CN109437162B - Method for producing reduced graphene oxide - Google Patents
Method for producing reduced graphene oxide Download PDFInfo
- Publication number
- CN109437162B CN109437162B CN201811493682.9A CN201811493682A CN109437162B CN 109437162 B CN109437162 B CN 109437162B CN 201811493682 A CN201811493682 A CN 201811493682A CN 109437162 B CN109437162 B CN 109437162B
- Authority
- CN
- China
- Prior art keywords
- graphene oxide
- layer number
- layers
- microwave
- producing reduced
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2204/00—Structure or properties of graphene
- C01B2204/04—Specific amount of layers or specific thickness
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2204/00—Structure or properties of graphene
- C01B2204/20—Graphene characterized by its properties
- C01B2204/32—Size or surface area
Abstract
The invention provides a method for producing reduced graphene oxide. The method comprises the following steps: mixing graphene oxide with a first layer number, a complexing agent and an acidic solution, wherein impurity ions are combined on the functional groups, so as to obtain a mixed solution; ultrasonic oscillation is carried out, so that impurity ions are removed and combined with a complexing agent; filtering to obtain purified graphene oxide; dispersing the purified graphene oxide in water to form a hydrogel; placing the hydrogel at a first temperature and a first pressure to obtain graphene oxide with a second layer number, wherein the second layer number is smaller than the first layer number; placing the obtained graphene oxide in an inert atmosphere; and (3) rapidly heating the graphene oxide to more than 500 ℃ through microwave and light wave irradiation to obtain the reduced graphene oxide. The beneficial effects of the invention include: the purification thoroughness of the graphene oxide can be effectively improved; the graphene oxide sheets subjected to freeze drying have large layer-to-layer spacing and few layers; the heating speed in the optical microwave reduction process is high, the heating is uniform, and the reduction efficiency is high.
Description
Technical Field
The invention relates to the field of preparation of reduced graphene oxide, and particularly relates to a method for producing reduced graphene oxide.
Background
The scientific community appeared the graphite nanoplatelets as a material in the beginning of the 21 st century. In 2006, two scientists of The University of Manchester in The uk skillfully prepared single-layer graphite by a mechanical stripping method, thereby formally disclosing a veil of graphene which is a material, and two people also obtained 2010A nobel prize in physics. The ideal graphene material is composed of a single layer of graphite with sp passing between carbon atoms2The hybrid orbitals are linked to form a stable six-membered ring structure. Researches find that the graphene material has good various physicochemical properties. For example: better electron conductivity than metal gold, better mechanical strength than steel, super-large specific surface area, good optical performance, superconductivity and the like. In view of these special properties, graphene materials have great application potential in military, transportation, mobile devices and the like.
In industrial production, the graphene oxide powder can be prepared on a large scale by applying an oxidation intercalation method. The graphene oxide slurry produced by the oxidation intercalation method contains a large amount of impurity ions, and the existing graphene oxide has the problems of low efficiency, poor washing effect and the like in the purification process; the number of the middle layers of the produced graphene oxide is also large, namely the quality of the produced graphene oxide is not high.
In addition, due to the characteristics of graphene oxide, chemical reduction (such as chemical reducing agents like sodium borohydride, hydrogen iodide, and ascorbic acid), high temperature thermal reduction, and plasma methods are mostly adopted in the market at present. The existing graphene oxide reduction method has the following problems in the production process: firstly, a large amount of chemical reagents are needed for reduction by adopting the chemical reagents, so that the number of by-products is increased, the difficulty of subsequent cleaning is increased, the environmental protection risk is increased, and the cost is increased; secondly, high-temperature thermal reduction is adopted, the reduction temperature of the graphene oxide is high, the quality uniformity of products obtained at different reduction temperatures cannot be guaranteed, and meanwhile, the problems of increase of ash content of the products, serious corrosion of equipment and the like are caused; thirdly, other reduction methods (such as plasma) are adopted, the production technology difficulty and the cost are multiplied, and the industrial large-scale application cannot be obtained.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, an object of the present invention is to provide a method for producing reduced graphene oxide, which produces reduced graphene oxide having a small impurity content and a small number of layers.
In order to achieve the above objects, an aspect of the present invention provides a method of producing reduced graphene oxide. The method may comprise the steps of: mixing oxidized graphene with a first layer number, a complexing agent and an acidic solution, wherein impurity ions are combined on the functional groups, so as to form a mixed solution, wherein the first layer number is tens of layers to tens of layers; performing ultrasonic oscillation on the mixed solution to remove impurity ions combined with the graphene oxide and stably combine the impurity ions with a complexing agent; filtering to obtain purified graphene oxide; dispersing the purified graphene oxide in water to form graphene oxide hydrogel; placing the graphene oxide hydrogel at a first temperature and a first pressure to condense water molecules in the graphene oxide hydrogel into ice molecules and desublimate the ice molecules, so as to obtain graphene oxide with a second layer number, wherein the second layer number is smaller than the first layer number, the first temperature is not higher than-50 ℃ and the temperature change is not more than +/-4 ℃, and the first pressure is lower than 1 atmosphere and the pressure change is not more than +/-100 Pa; placing the graphene oxide with the second layer number in an inert atmosphere; and rapidly heating the graphene oxide with the second layer number to more than 500 ℃ by microwave and light wave irradiation to decompose functional groups carried by the graphene oxide and reduce the layer number of the graphene oxide, so as to obtain the reduced graphene oxide, wherein the microwave can penetrate through the graphene oxide with the second layer number in a traveling wave manner.
According to an exemplary embodiment of the present invention, the impurity ions to which the graphene oxide is bonded may include metal impurity ions, for example, Mn may be included2+、K+And Fe3+At least one of (1).
According to an exemplary embodiment of the present invention, the content of the impurity ions in the graphene oxide having the functional group to which the impurity ions are bonded is 0.01 to 1% by weight, for example, 0.1%.
According to an exemplary embodiment of the present invention, the weight percentage of the impurity ions in the purified graphene oxide is not higher than 0.01%.
According to an exemplary embodiment of the present invention, the complexing agent is added in an amount of 1.0 to 1.2 times a theoretical amount capable of complexing with impurity ions.
According to an exemplary embodiment of the present invention, the acidic solution includes a hydrochloric acid solution having a concentration of 0.005 to 0.02mol/L or a sulfuric acid solution having a concentration of 0.01 to 0.04 mol/L.
According to an exemplary embodiment of the present invention, the pH of the acidic solution is 0.1 to 6.
According to an exemplary embodiment of the present invention, the filtering step includes filtering by a filtering membrane, and a suction filtration mechanism may be provided below the filtering membrane to perform reduced pressure suction filtration.
According to an exemplary embodiment of the present invention, the pressure range of the suction filtration decompression may be 10 to 100 Pa.
According to an exemplary embodiment of the invention, when the ultrasonic oscillation is performed, the frequency of the ultrasonic wave is 50 to 750 Hz.
According to an exemplary embodiment of the present invention, the first number of layers may be 20 to 30 layers, and the second number of layers may be 5 to 7 layers.
According to an exemplary embodiment of the invention, the first temperature may be selected in the range of-55 to-65 ℃ and the temperature may not vary by more than ± 2 ℃.
According to an exemplary embodiment of the present invention, the first pressure may be selected within a range of 10 to 100Pa and a variation of the pressure is not more than + -10 Pa.
According to an exemplary embodiment of the present invention, the graphene oxide hydrogel may have a solid content of 0.1 to 50 wt%.
According to an exemplary embodiment of the present invention, the step of placing the graphene oxide having the second number of layers in an inert atmosphere may include: feeding the graphene oxide with the second layer number into a tubular container filled with nitrogen or inert gas through gas; wherein both ends of the tubular container have openings, the gas is capable of flowing in from one opening of the tubular container, and the gas comprises nitrogen or inert gas.
According to an exemplary embodiment of the present invention, the method may further comprise the steps of: after obtaining the reduced graphene oxide, taking the reduced graphene oxide out of the other opening of the tubular container by means of suction filtration.
According to an exemplary embodiment of the invention, the flow rate of the gas in the tubular container may be at 10cm3Less than s, e.g. 1 to 8cm3S; the amount of the gas capable of being fed into the graphene oxide can be 1g/cm3Below, for example, 0.5. + -. 0.3g/cm3。
According to an exemplary embodiment of the present invention, the irradiation time of the light waves and microwaves may be below 10min, for example, 5 ± 3 min.
According to an exemplary embodiment of the present invention, the direction of the microwave and light wave irradiation and the direction of the gas flow within the tubular container may be perpendicular to each other.
According to an exemplary embodiment of the present invention, a degree of vacuum inside the tubular container may be below 100 Pa.
According to an exemplary embodiment of the present invention, the tubular container may include a quartz tube, and the microwave and light waves may irradiate the graphene oxide through a wall of the quartz tube.
According to an exemplary embodiment of the present invention, the light wave may include infrared rays or far infrared rays.
According to an exemplary embodiment of the present invention, the method may further comprise the steps of: and cooling and drying the obtained reduced graphene oxide.
Compared with the prior art, the invention has the beneficial effects that: the graphene oxide can be effectively separated from impurity ions, and the purification thoroughness of the graphene oxide can be improved; the graphene oxide has high purification efficiency and low cost. The structure of the purified graphite oxide sheet layer can not be damaged in the freeze drying process, functional groups can be well preserved, and the graphite oxide subjected to freeze drying is not easy to agglomerate. The layer-to-layer spacing of the graphene oxide sheets after freeze drying is larger than that of the graphene oxide product dried by other drying methods, and the graphene oxide product has more excellent dispersing performance, fewer layers and larger specific surface area; the heating speed in the optical microwave reduction process is high, the heating is uniform, the thermal inertia is avoided, the energy is saved, the efficiency is high, the reduction efficiency is high, and the selective oxidation of the graphene oxide can be realized.
Drawings
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
fig. 1 shows a schematic flow diagram of a method for producing reduced graphene oxide in an exemplary embodiment of the invention.
FIG. 2 is a schematic diagram illustrating the positional relationship of a microwave and lightwave radiation system with a tubular container in an exemplary embodiment of the invention.
The main illustration is as follows:
1-a quartz tube; 2-a light wave tube; 3-microwave cavity.
Detailed Description
Hereinafter, the method for producing reduced graphene oxide according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
Graphene oxide can be used as a raw material for preparing graphene, and impurity ions are often combined in the graphene oxide, so that the purity of the graphene oxide is not high, and the produced graphene often has high impurity content; and the number of layers of the graphene oxide is large, and the interlayer spacing is small, so that the quality of the produced graphene oxide is not excellent. The conventional heating mode is adopted in the existing heating link in the reduction of graphene oxide, and the conventional heating mode is that heat is firstly transferred to the surface of an object through heat conduction, convection, heat radiation and the like, and then the central temperature of the object is gradually raised through heat conduction.
Therefore, the invention provides a method for producing reduced graphene oxide. Fig. 1 shows a schematic flow diagram of a method for producing reduced graphene oxide in an exemplary embodiment of the invention. FIG. 2 is a schematic diagram illustrating the positional relationship of a microwave and lightwave radiation system with a tubular container in an exemplary embodiment of the invention.
In one exemplary embodiment of the present invention, the method of producing reduced graphene oxide may include the steps of:
and mixing the complexing agent, the acidic solution and the graphene oxide to form a mixed solution, as shown in step S01 in fig. 1. Wherein the functional group of the graphene oxide is bonded with impurity ions and has a first layer number. The first layer number is tens to tens, for example, 20 to 30 layers. The impurity ions bound to the functional groups of the graphene oxide may include Mn2+、K+And Fe3+At least one of (1).
And (3) performing ultrasonic oscillation on the mixed solution to remove impurity ions combined with the graphene oxide and stably combine the impurity ions with the complexing agent, as shown in step S02 in fig. 1. Under the action of ultrasonic waves, impurity ions combined with graphene oxide can be separated from the graphene oxide and combined with a complexing agent with better binding property, and simultaneously, due to the action of ultrasonic waves, the graphene oxide can be better dispersed and combined with H+Binding does not compete for metal ions from the complexing agent.
And filtering to obtain the purified graphene oxide, as shown in step S03 in fig. 1.
Dispersing the purified graphene oxide in water, and forming a graphene oxide hydrogel, as in step S04 in fig. 1. In the dispersing process, the dispersing effect is preferably further enhanced by ultrasonic dispersion, so that water molecules fully enter a lamellar structure or folds of the graphene oxide, or are combined with functional groups on the surface of the graphene oxide to form hydrated ions, thereby forming the graphene oxide hydrogel. The graphene oxide hydrogel has a structure in which water molecules are bonded in its own sheet or wrinkle of graphene oxide. The solid content of the graphene oxide hydrogel can be 0.1-50 wt%. The water used for dispersing the graphene oxide is preferably secondary deionized water.
And (3) performing low-temperature vacuum freeze drying on the graphene oxide hydrogel to obtain graphene oxide with a second layer number, as shown in step S05 in fig. 1. The graphene oxide hydrogel can be placed at a first temperature and a first pressure to condense water molecules in the graphene oxide hydrogel into ice molecules and desublimate the ice molecules, so that graphene oxide with a second layer number is obtained. And the first temperature is controlled to be not higher than-50 ℃ and the temperature variation of the first temperature is always not more than + -4 ℃, the first pressure is controlled to be lower than 1 atmosphere and the variation of the first pressure is always not more than + -100 Pa. Further, the first temperature may be selected within the range of-55 to-65 ℃ and the temperature variation does not exceed ± 2 ℃. The first pressure intensity can be selected within the range of 10-100 Pa, and the pressure intensity variation does not exceed +/-10 Pa. The second layer number is smaller than the first layer number. The second layer number is smaller than the first layer number. The second number of layers may have a significant reduction compared to the first number of layers. Here, the second number of layers may be 1/3-1/6 of the first number of layers. For example, the second number of layers may be 5 to 7.
The graphene oxide having the second layer number is placed in an inert atmosphere, as in step S06 in fig. 1. For example, the graphene oxide having the second number of layers may be fed into a container filled with nitrogen or an inert gas. Wherein the container may comprise a tubular container having openings at both ends. Further, a tubular container which is horizontally and transversely arranged and has openings at the left end and the right end can be included.
The graphene oxide with the second layer number is rapidly heated to more than 500 ℃ by microwave and light wave irradiation to decompose the functional groups carried by the graphene oxide and reduce the layer number of the graphene oxide, so as to obtain reduced graphene oxide (i.e. a product obtained after the graphene oxide is reduced), as shown in step S07 in fig. 1. The microwave can penetrate through the graphene oxide in a traveling wave mode, and a constantly transmitted traveling wave waveform is formed through the unidirectional transmission of the microwave, so that the local high temperature phenomenon caused by the standing wave effect can be avoided, and the processing consistency of the graphene oxide can be improved. The frequency of the microwave can be 300MHz to 300GHz, and further can be 800MHz to 250 GHz. The frequency of the optical wave may be 3 × 1011～3.8×1014Hz, further, may be 2X 1012～2.5×1014Hz. Through the simultaneous action of microwave and light wave, the graphene oxide can be rapidly heated to more than 500 ℃, the functional group of the graphene oxide can be rapidly decomposed, and a large amount of gas such as water vapor and oxygen can be instantly generated during the decomposition due to the oxygen-containing functional group,Carbon dioxide and the like are generated, and gas expands among graphene oxide sheet layers, so that the number of layers of the prepared material is smaller, and the specific surface area is larger. Further, the microwave and the light wave can enable the temperature of the graphene oxide to rise to 500-1000 ℃, such as 800 +/-150 ℃. The main heating source in the heating process can be microwaves, the light waves can play an auxiliary role, and the combination of the microwaves and the light waves can quickly raise the temperature of the heated graphene oxide, so that the deoxidation treatment is facilitated.
In this embodiment, the number of layers of graphene oxide as a raw material may be several tens of layers or more, for example, 30 to 50. The number of layers of the graphene oxide after low-temperature cold drying can be less than 10, for example, 6 to 8.
Due to the low number of layers of the reduction object by the optical microwave, the number of layers of the reduced graphene oxide obtained by the reaction can be lower, for example, below 4 layers, even below 3 layers.
And purifying to remove impurity ions on the graphene oxide fully, wherein the removal rate can be more than 99%. After reduction by optical microwave, functional groups on the graphene oxide can be sufficiently removed, and the removal rate can reach more than 85%, for example 95%.
In this embodiment, the graphene oxide with the functional group bonded with the impurity ion may be obtained by an oxidation intercalation method, and the content of the impurity ion on the graphene oxide functional group may be 0.01 to 1% by weight, for example, 0.1%.
In this embodiment, the raw material used may also be a slurry, such as graphene oxide slurry prepared by an oxidative intercalation method, in which the graphene oxide functional groups also have impurity ions bonded thereto and have the first layer number.
The content of graphene oxide in the slurry can be 0.01-100 g/L, and the mass percentage of impurity ions on the graphene oxide can be 0.01-1%. The addition amount of the complexing agent is 1.0-1.2 times of the theoretical amount of the complexing agent capable of reacting with the impurity ions.
In this embodiment, the graphene oxide containing the impurity and the functional group may also be prepared by:
weighing graphite, potassium nitrate and potassium permanganate in a weight ratio of 0.8-1.2: 0.4-0.6: 2-4, uniformly mixing, and adding concentrated sulfuric acid to obtain a first mixture. Further, the mass ratio of the graphite to the potassium nitrate to the potassium permanganate may be 0.85-1.1: 0.4-0.6: 2-3, and for example, the mass ratio of the graphite to the potassium nitrate to the potassium permanganate may be 1:0.5: 3. The addition amount of the concentrated sulfuric acid can be an empirical value, for example, 115 mL-3450 mL of 98% concentrated sulfuric acid is added corresponding to 5 g-150 g of graphite. The graphite may be one of expanded graphite or flake graphite.
And oxidizing the first mixture at three temperature ranges of 0-4 ℃, 35-45 ℃ and 80-100 ℃ respectively to obtain a second mixture. The first mixture is subjected to three isothermal oxidation periods of low temperature, medium temperature and high temperature. The reaction time at 0-4 ℃ can be 3-40 h, the reaction time at 35-45 ℃ can be 2-6 h, and the reaction time at 80-100 ℃ can be 5-15 min. The oxidant may be hydrogen peroxide. Of course, the reaction time in the above temperature ranges is not limited thereto, and can be adjusted according to the actual reaction conditions.
And adding an oxidant into the second mixture for oxidation, acid washing and water washing to obtain the impurity-containing graphene oxide containing functional groups. The oxidant can be hydrogen peroxide.
In this embodiment, the complexing agent may include citric acid, sodium citrate, sodium thiosulfate, sodium sulfite, sodium ethylenediaminetetraacetate, polyacrylic acid, sodium gluconate, or sodium alginate.
The addition amount of the complexing agent is 1.0-1.2 times of the theoretical amount of the complexing agent capable of reacting with the impurity ions.
In this example, the acidic solution is capable of providing the liquid reaction environment required for the reaction. The acidic solution may include a hydrochloric acid solution having a concentration of 0.005 to 0.02mol/L or a dilute sulfuric acid solution having a concentration of 0.01 to 0.04mol/L, and further, the dilute hydrochloric acid solution may have a concentration of 0.01mol/L and the dilute sulfuric acid solution may have a concentration of 0.02 mol/L.
Further, the acidic solution may include a dilute hydrochloric acid solution, because the bulk of the graphene oxide prepared by the intercalation oxidation method contains a certain amount of sulfuric acid, and the graphene oxide can be cleaned more rapidly by using the dilute hydrochloric acid.
In this embodiment, when ultrasonic oscillation is performed, the frequency of the ultrasonic wave may be 50 to 750Hz, and the ultrasonic frequency in this range enables impurity ions on the graphene oxide functional group to be removed better.
The time of the ultrasonic oscillation is short, for example, within 2min, so that the impurity ions can be removed, and the structure (for example, size and the like) of the graphene oxide cannot be affected.
In this embodiment, after purification, the removal rate of the impurities on the graphene oxide can reach 99% or more, for example, the weight percentage of the impurity ions of the purified graphene oxide can be not higher than 0.01%.
In this embodiment, the graphene oxide may be filtered through a filter membrane to separate the purified graphene oxide from the solution containing impurities. Wherein, the graphene oxide is left on the filter layer, and the solution containing impurities can permeate the filter membrane. The filtration membrane may comprise a polycarbonate membrane (i.e., a PC membrane).
A decompression suction filtration device can be arranged below the filter layer, so that the solution containing impurities can better penetrate through the filter layer. Wherein, the vacuum pump is arranged under the filter membrane to realize the decompression and suction filtration. The pressure range of suction filtration and decompression can be 10-100 Pa.
In this embodiment, when the filtration is performed using a filtration membrane, the method may further include the steps of: a buffer protective layer is arranged on the filtering membrane to absorb and buffer the influence of the ultrasonic wave on the filtering membrane during ultrasonic oscillation. The buffer protective layer can absorb the energy remaining from the sonication to reduce damage to the filtration layer from ultrasonic energy, for example, when the filtration component is a polycarbonate membrane (i.e., a PC membrane), excess ultrasonic energy can cause damage thereto. The buffer protection layer can include the sponge, and the thickness of sponge can be 1 ~ 100 cm.
In this embodiment, the method may further include the steps of: and detecting the ion concentration of the purified graphene oxide to determine whether the graphene oxide needs to be purified continuously. Among them, detection can be performed by an ICP (Inductively Coupled Plasma) ion concentration detector.
In this embodiment, a container (e.g., a crucible) containing the graphene oxide hydrogel may be conveyed to a low-temperature low-pressure cooling device by a conveying mechanism (e.g., a crawler) to implement condensation and desublimation of water molecules in the graphene oxide hydrogel, so as to complete low-temperature low-pressure cooling and drying of the graphene oxide hydrogel, and obtain graphene oxide with a desired low number of layers.
In this embodiment, in the cold drying step, by controlling the first temperature to be not higher than-50 ℃ and the first pressure to be not higher than 1 standard atmospheric pressure, water molecules can be changed into ice molecules, and the lamellar structure of graphite can be further widened by volume expansion; and the ice can be desublimated and volatilized at low temperature and low pressure, the temperature is low, the entropy value is low, the strutted structure of the graphene oxide can be maintained, and the prepared graphene oxide material has good dispersibility and large specific surface area. Moreover, the relatively constant low temperature (for example, not higher than-50 ℃ and the temperature variation in the cavity of the whole cold dry cavity is controlled not to exceed +/-4 ℃) and the relatively constant vacuum degree (for example, lower than 1 atmosphere and the pressure variation in the whole cavity is controlled not to exceed +/-100 Pa) are beneficial to relatively stabilizing the condensation speed and degree of water molecules, so that the 'opening' effect on the graphene oxide layer is stable; but also the ice molecule desublimation speed and degree are relatively stable, thus being beneficial to avoiding local defects caused by the local stress of the graphene oxide layer to a certain degree. Furthermore, the temperature control unit and the pressure control unit are used for controlling the atmosphere of the cold-dry cavity to be within the range of-55 to-65 ℃, the temperature change in the whole cavity is controlled not to exceed +/-2 ℃, the pressure is controlled to be 10 to 100Pa, the pressure change in the whole cavity is controlled not to exceed +/-10 Pa, the condensation speed and the degree of water molecules are further stabilized, and the 'opening' effect on the graphene oxide layer is stabilized; but also the ice molecule desublimation speed and degree are further stabilized, thereby further avoiding local defects caused by the local stress of the graphene oxide layer.
In this embodiment, the graphene oxide having the second layer number may be fed into the tubular container by the gas flow. The resulting reduced graphene oxide may also be conveyed out of the tubular vessel by a gas stream. In other words, the gas flow loaded with graphene oxide can be introduced into one opening of the tubular container; the gas stream can carry (or push) the material through the cavity of the tubular container; during the flowing process, the graphene oxide can be reduced into reduced graphene oxide; the resulting gas stream carries (or pushes) the reduced graphene oxide out of the other opening of the tubular vessel. The gas in the gas stream may comprise nitrogen or an inert gas.
Wherein the flow rate of gas in the pipe container can be 10cm3And the graphene oxide can smoothly enter the tubular container to be fully reduced by the microwave below s. Further, the gas flow velocity can be 0.01-8 cm3And/s, and further, 2 to 5cm3/s。
The amount of graphene oxide loaded (or carried) on the gas stream may be 10g/cm3Below, for example, 0.1 to 10g/cm3Further, it may be 2 to 10g/cm3。
For the graphene oxide, the power of the light wave may be 200-500W, and the power of the microwave may be 500-5500W, for example, 2000W. The treatment time of the light wave and the microwave is the same, and can be controlled below 10mim, such as 30s, 2min or 7 min.
In this embodiment, the selective oxidation of graphene oxide can be realized through the power of optical microwaves and the processing time, that is, reduced graphene oxide with different oxygen contents can be obtained according to the requirement.
In this embodiment, the directions of the microwave and light wave irradiation may be perpendicular to the direction of the gas flow. Can make light wave and microwave can be better pierce through graphite oxide like this, abundant irradiation avoids leading to the microwave reflection because of the material volume grow, and then influences the irradiation of deep granule.
In this embodiment, the tubular container may comprise a quartz tube disposed laterally. The quartz tube is transparent, cannot isolate the penetrating effect of light and microwaves, and has the non-blocking characteristic to light waves and microwaves, namely, the microwaves and the light waves can penetrate through the wall of the quartz tube to irradiate the graphene oxide. The quartz tube is high temperature resistant, has extremely low thermal expansion coefficient, excellent chemical stability, excellent electrical insulation and extremely high microwave permeability. The quartz tube can resist high temperature and can bear rapid cooling and rapid heating; can bear the impact of positive and negative pressure more than 1 Mpa.
In this embodiment, the method may further include the steps of: after obtaining the reduced graphene oxide, taking the reduced graphene oxide out of the other opening of the tubular container by means of suction filtration. After suction filtration, the method further comprises the steps of: and the reduced graphene oxide can be separated from the gas, and the separated gas can be recycled.
In this embodiment, the present invention can emit microwaves through a microwave system, and the microwave system can include a microwave source, a microwave cavity, and a microwave leakage prevention mechanism. The microwave source is an electronic device for generating microwave energy and can be composed of a magnetron, a high-voltage transformer, a high-voltage rectification loop, a heat dissipation fan, an over-current protection device, an abnormal temperature protection device, a waveguide and the like. The microwave cavity is the primary storage vessel for microwave energy and is also the primary region of the microwave puffing reaction. The leakage prevention mechanism can prevent leakage of microwaves.
The invention can emit light waves through a plurality of light wave tubes. The light wave mainly plays a role in heating and warming. The light wave may include infrared rays or far infrared rays.
As shown in fig. 2, the microwave cavity 3 of the microwave system may surround the quartz tube 2, so that the microwave may sufficiently and uniformly irradiate the graphene oxide through the tube wall of the quartz tube in a traveling wave manner; the two light wave tubes 2 can be distributed on two sides of the quartz tube, so that light waves can penetrate through the wall of the quartz tube to irradiate the graphene oxide fully and uniformly. Under the synergistic effect of light waves and microwaves, the graphene oxide can be rapidly heated.
In this embodiment, the reduction of the graphene oxide can be performed in a vacuum environment, which can avoid the influence of air, because the air easily conducts heat away. The vacuum degree in the container may be 100Pa or less. The invention can also be provided with a vacuum meter to conveniently control the vacuum degree.
In this embodiment, the method may further include the steps of: and cooling and drying the obtained graphene oxide. Wherein the step of cooling may comprise water cooling, air cooling, or the like.
In summary, compared with the prior art, the advantages of the present invention can include:
(1) according to the invention, the impurity ions on the graphene oxide can be removed more effectively, and the separated impurity ions can not be combined with the graphene oxide under the action of the complexing agent, so that the purification thoroughness is improved, the repeated combination of the impurity ions is avoided, and the removal rate of the impurities on the graphene oxide can reach more than 99%.
(2) According to the invention, the purified graphene oxide lamella can be further expanded in the drying process, and meanwhile, the lower entropy value of the graphene oxide material is kept at a low temperature, which is beneficial to keeping the microstructure of the expanded graphene oxide lamella, so that the graphene oxide product with higher quality can be obtained. For example, the graphene prepared by the method has a complete microstructure, and the number of layers of the graphene oxide can be reduced to 1/3-1/6 in the prior art, for example, the number of layers can be reduced from 20-30 to 5-7; the specific surface area of the graphene oxide is increased to 1.5 to 2.5 times of the original specific surface area, for example, the specific surface area is from 100 to 200m2The/g is increased to 200-400 m2/g。
(3) The heating speed of the optical microwave reduction is high, and the heating is uniform. If an external heating mode is used for heating, in order to increase the heating speed, the external temperature needs to be increased, and the temperature difference gradient is increased. However, this is accompanied by the generation of exogenous or endogenous phenomena. And no matter how the shape is, the microwave can uniformly permeate to generate heat, so that the uniformity is greatly improved.
(4) Different materials have different absorptivity to microwave, and substances containing moisture can easily absorb microwave energy. Glass, ceramic, polypropylene, polyethylene, fluoroplastic, etc. rarely absorb microwaves, metals reflect waves, and none of these materials can be heated by microwaves. In microwave heating, the heated material is generally placed in a heating chamber, the heating chamber is a closed cavity for electromagnetic waves, the electromagnetic waves cannot be leaked out and only can be absorbed by a heated object, and air in the heating chamber and a corresponding container cannot be heated, so that the heat efficiency is high. Meanwhile, the environmental temperature of a working place cannot be increased, the production environment is obviously improved, and the energy conservation and the high efficiency are realized.
(5) The equipment in the optical microwave reduction process can adopt a corrosion-resistant optical microwave pipeline, does not react with corrosive gas thermally decomposed from graphene oxide, is uniformly heated in the reaction pipeline, does not form hot atmosphere gas mass, and does not have thermal inertia.
(6) When the optical microwave reduction is carried out, a large amount of dust is not generated, and the operation environment is good.
(7) According to the invention, the removal rate of the surface functional groups of the graphene oxide can be determined according to the power of optical microwave and the processing time, so that selective thermal reduction is realized, and reduced graphene oxide materials containing different oxygen contents are prepared
(8) The microwave energy is transmitted in a closed heating chamber and a wave channel pipe, so that the microwave leakage can be strictly controlled within the national safety standard index and is greatly lower than the safety standard established by the country. And the microwave does not belong to radioactive rays and has no harmful gas emission, thereby being a very safe heating technology.
Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method of producing reduced graphene oxide, the method comprising the steps of:
mixing oxidized graphene with a first layer number, a complexing agent and an acidic solution, wherein impurity ions are combined on the functional groups, so as to form a mixed solution, wherein the first layer number is tens of layers to tens of layers;
performing ultrasonic oscillation on the mixed solution to remove impurity ions combined with the graphene oxide and stably combine the impurity ions with a complexing agent;
filtering to obtain purified graphene oxide;
dispersing the purified graphene oxide in water to form graphene oxide hydrogel;
placing the graphene oxide hydrogel at a first temperature and a first pressure to condense water molecules in the graphene oxide hydrogel into ice molecules and desublimate the ice molecules, so that graphene oxide with a second layer number is obtained, wherein the second layer number is smaller than the first layer number, the second layer number is 1/3-1/6 of the first layer number, the first temperature is not higher than-55 ℃, the temperature change is not more than +/-4 ℃, and the first pressure is lower than 1 atmosphere and the pressure change is not more than +/-100 Pa;
placing the graphene oxide with the second layer number in an inert atmosphere;
and rapidly heating the graphene oxide with the second layer number to more than 500 ℃ by microwave and light wave irradiation to decompose functional groups carried by the graphene oxide and reduce the layer number of the graphene oxide, so as to obtain the reduced graphene oxide, wherein the microwave can penetrate through the graphene oxide with the second layer number in a traveling wave manner.
2. The method of producing reduced graphene oxide according to claim 1, wherein the complexing agent comprises citric acid, sodium citrate, sodium thiosulfate, sodium sulfite, sodium ethylenediaminetetraacetate, polyacrylic acid, sodium gluconate, or sodium alginate.
3. The method for producing reduced graphene oxide according to claim 1, wherein the filtering step includes filtering by a filtering membrane, and a suction filtration mechanism is provided below the filtering membrane to perform reduced pressure suction filtration.
4. The method for producing reduced graphene oxide according to claim 1, wherein the first number of layers is 20 to 30 layers, and the second number of layers is 5 to 7 layers.
5. The method for producing reduced graphene oxide according to claim 1, wherein the first temperature is selected in a range of-55 to-65 ℃ and the temperature variation is not more than ± 2 ℃.
6. The method for producing reduced graphene oxide according to claim 1, wherein the first pressure is selected within a range of 10 to 100Pa and a variation in pressure is not more than ± 10 Pa.
7. The method for producing reduced graphene oxide according to claim 1, wherein the graphene oxide hydrogel has a solid content of 0.1 to 50 wt%.
8. The method of producing reduced graphene oxide according to claim 1, wherein the step of placing the graphene oxide having the second number of layers in an inert atmosphere includes: and feeding the graphene oxide having the second layer number into a tubular container filled with nitrogen or an inert gas by a gas, wherein the tubular container has openings at both ends, and the gas can flow in from one opening of the tubular container, and the gas comprises the nitrogen or the inert gas.
9. The method for producing reduced graphene oxide according to claim 8, wherein the direction of the microwave and light wave irradiation and the direction of the gas flow in the tubular container are perpendicular to each other.
10. The method for producing reduced graphene oxide according to claim 8, wherein a degree of vacuum inside the tubular container is 100Pa or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811493682.9A CN109437162B (en) | 2018-12-07 | 2018-12-07 | Method for producing reduced graphene oxide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811493682.9A CN109437162B (en) | 2018-12-07 | 2018-12-07 | Method for producing reduced graphene oxide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109437162A CN109437162A (en) | 2019-03-08 |
| CN109437162B true CN109437162B (en) | 2021-03-09 |
Family
ID=65557385
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811493682.9A Active CN109437162B (en) | 2018-12-07 | 2018-12-07 | Method for producing reduced graphene oxide |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109437162B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111943178A (en) * | 2020-08-21 | 2020-11-17 | 伊诺福科光学技术有限公司 | Method for preparing graphene material through self-sufficient reduction, graphene material, graphene film, electrode and capacitor |
| CN113096973A (en) * | 2021-04-12 | 2021-07-09 | 王晓京 | Method for preparing porous graphene membrane, porous graphene membrane and electrode |
| CN114520333B (en) * | 2022-02-11 | 2023-11-03 | 山东威固新能源科技有限公司 | Aluminum nitride doped reduced graphene oxide-lithium composite material and preparation method and application thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102730678A (en) * | 2012-07-23 | 2012-10-17 | 贵州新碳高科有限责任公司 | Device and method for preparing graphene powder |
| CN103058179A (en) * | 2013-01-21 | 2013-04-24 | 张家港市东大工业技术研究院 | Method for preparing spongy graphene oxide by using freeze-drying method |
| CN103395780A (en) * | 2013-08-19 | 2013-11-20 | 济宁利特纳米技术有限责任公司 | Method for reducing manganese content in graphene oxide |
| CN106517174A (en) * | 2016-11-25 | 2017-03-22 | 西安交通大学 | Quick heating method for graphene and deep processing method based on same |
-
2018
- 2018-12-07 CN CN201811493682.9A patent/CN109437162B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102730678A (en) * | 2012-07-23 | 2012-10-17 | 贵州新碳高科有限责任公司 | Device and method for preparing graphene powder |
| CN103058179A (en) * | 2013-01-21 | 2013-04-24 | 张家港市东大工业技术研究院 | Method for preparing spongy graphene oxide by using freeze-drying method |
| CN103395780A (en) * | 2013-08-19 | 2013-11-20 | 济宁利特纳米技术有限责任公司 | Method for reducing manganese content in graphene oxide |
| CN106517174A (en) * | 2016-11-25 | 2017-03-22 | 西安交通大学 | Quick heating method for graphene and deep processing method based on same |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109437162A (en) | 2019-03-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109437162B (en) | Method for producing reduced graphene oxide | |
| CN109292761B (en) | Method for reducing graphene oxide by optical microwave | |
| CN108251076B (en) | Carbon nanotube-graphene composite heat dissipation film, and preparation method and application thereof | |
| CN106517174B (en) | A kind of quick heating means of graphene and the deep working method based on it | |
| KR101653766B1 (en) | Method and apparatus for modifying graphene | |
| CN102602925B (en) | The method of Graphene is prepared in a kind of high pressure reduction | |
| US8163264B2 (en) | Expanded graphite and process for producing the expanded graphite | |
| EP2714590B1 (en) | Installation and method for the functionalization of particulate and powdered products | |
| CN108123112B (en) | Nitrogen-doped porous graphene aggregate and preparation method and application thereof | |
| WO2012109968A1 (en) | Method for preparing modified graphene material by microwave irradiation in controlled atmosphere | |
| WO2012109969A1 (en) | Method for producing graphene material by microwave irradiation in a vacuum or inert-gas environment | |
| CN104386676A (en) | Preparation method of graphene | |
| CN208964552U (en) | A kind of normal pressure microwave plasma reduction removing graphene oxide device | |
| CN107934945A (en) | A kind of method for preparing magnetic graphene using molysite gas phase intercalation and microwave technology | |
| CN111250135A (en) | Graphite-phase carbon nitride nanosheet material and preparation method and application thereof | |
| Fan et al. | Reducing defects on multi-walled carbon nanotube surfaces induced by low-power ultrasonic-assisted hydrochloric acid treatment | |
| CN104555981A (en) | Method for selectively oxidizing and purifying carbon nano tube by utilizing microwave | |
| KR101419340B1 (en) | Preparation method of Graphite oxide and graphene nanosheet | |
| CN109292765B (en) | Method for preparing reduced graphene oxide with low layer number | |
| EP2778128B1 (en) | Method of thermal reduction of graphene oxide | |
| CN109319769B (en) | Method for preparing graphene through purification and optical microwave reduction | |
| CN106809827A (en) | The magnanimity preparation method of high connductivity iron chloride doped graphene nanometer sheet powder body material | |
| CN109264710B (en) | Method for improving quality of graphene oxide | |
| CN109368630B (en) | System for be used for graphite alkene to form | |
| CN102583505A (en) | Preparation method for ZnO two-dimensional porous material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |