CN109305671B - Method for preparing graphene by using low-layer graphene oxide - Google Patents
Method for preparing graphene by using low-layer graphene oxide Download PDFInfo
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Abstract
The invention provides a method for preparing graphene by using low-layer graphene oxide, which comprises the following steps: purifying the purified object to obtain purified graphene oxide; carrying out freeze drying treatment on the purified graphene oxide to obtain a low-layer graphene oxide; and carrying out reduction treatment on the low-layer graphene oxide to obtain graphene. The method can improve the purification thoroughness of the graphene oxide, can effectively separate the graphene oxide from impurities, and can remove the impurities; the graphene oxide with low layer number is obtained by a freeze drying method, the structure of a graphite oxide sheet layer is not damaged, functional groups are well preserved, and the graphite oxide after freeze drying is not easy to agglomerate; the graphene oxide with the low layer number is reacted at different temperatures and pressure regions by utilizing high temperature and low pressure, the characteristic of high melting point of the graphene is fully utilized, and metal and non-metal impurities in the graphene can be well removed.
Description
Technical Field
The invention relates to the technical field of new material preparation, in particular to a method for preparing graphene by using low-layer graphene oxide.
Background
In the current 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. Moreover, because of poor thermal stability of graphite oxide, pyrolysis often occurs in the drying process, and the heated and dried graphite oxide is easily agglomerated into hard blocks, which is not conducive to subsequent dispersion.
At present, the mainstream graphene preparation method comprises a mechanical stripping method, a redox method, an epitaxial growth method, a chemical vapor deposition method and the like, wherein the redox method is the most commonly used method for industrial production due to the advantages of low cost, simple production equipment, maximum single-time yield, concentrated product layer number, uniform transverse dimension and the like. In the method for preparing graphene, on one hand, the graphene prepared by the redox method is easy to damage the crystal structure of the graphene in the oxidation intercalation process, so that the internal defects of the graphene are increased, and the performance of the graphene is greatly influenced; on the other hand, a large amount of metal and nonmetal impurities still exist in the graphene produced by the oxidation-reduction method, which further influences the large-scale development and application of the graphene.
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 preparing graphene, which can reduce the impurity content of graphene, improve the purity of graphene, and reduce the number of graphene layers.
The invention provides a method for preparing graphene by using low-layer graphene oxide, which comprises the following steps: purifying the purified object to obtain purified graphene oxide; carrying out freeze drying treatment on the purified graphene oxide to obtain a low-layer graphene oxide; reducing the low-layer graphene oxide to obtain graphene, wherein,
the purification object is graphene oxide having a first number of layers in which impurity ions are bonded to functional groups or a slurry containing graphene oxide having a first number of layers in which impurity ions are bonded to functional groups, the first number of layers being ten to several tens of layers;
the step of performing a purification process on the purification object may include: mixing a purified object, a complexing agent and an acidic solution to form a mixed solution; 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;
the step of freeze-drying the purified graphene oxide may include: 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 step of performing reduction treatment on the graphene oxide with the low number of layers may include: sequentially subjecting the low-layer graphene oxide to an ith reaction zone and an nth reaction zone to obtain the low-layer graphene, and respectively controlling the temperature and the pressure of the nth reaction zone to be TnAnd PnControlling the temperature and pressure of the ith reaction zone to be T respectivelyiAnd PiWherein, Ti＝w1·i/n·Tn，Pi＝(P0-Pn) (1-i/n) wherein w1Is selected from 0.80 to 1.20, P0Is 1 standard atmosphere, TnAnd PnRespectively at 1250 deg.C or above and 30 Pa-500 Pa, n is a natural number greater than or equal to 2, and i is selected from all natural numbers less than n.
In an exemplary embodiment of the method for preparing graphene using a low-layer number of graphene oxide according to the present invention, the complexing agent may include citric acid, sodium citrate, sodium thiosulfate, sodium sulfite, sodium ethylenediaminetetraacetate, polyacrylic acid, sodium gluconate, or sodium alginate.
In an exemplary embodiment of the method for preparing graphene by using a low-layer graphene oxide according to the present invention, the pH of the acidic solution may be 0.1 to 6.
In an exemplary embodiment of the method for preparing graphene using a low-layer graphene oxide according to the present invention, the filtering step includes filtering through a filtering membrane, and a suction filtration mechanism is disposed below the filtering membrane to perform reduced pressure suction filtration.
In an exemplary embodiment of the method for preparing graphene using a low-layer graphene oxide according to the present invention, the first layer number may be 20 to 30 layers, and the second layer number may be 5 to 7 layers.
In one exemplary embodiment of the method for preparing graphene using a low-layer number of graphene oxides of the present invention, the first temperature may be selected within a range of-55 to-65 ℃ and a temperature variation of not more than ± 2 ℃.
In an exemplary embodiment of the method for preparing graphene by using a low-layer graphene oxide according to 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.
In an exemplary embodiment of the method for preparing graphene by using a low-layer graphene oxide, the solid content of the graphene oxide hydrogel may be 0.1 to 50 wt%.
In an exemplary embodiment of the method for preparing graphene using a low-layer graphene oxide according to the present invention, the step of performing a reduction treatment on the low-layer graphene oxide may include: sequentially subjecting a bin containing a first batch of low-layer graphene oxide to an ith reaction zone and an nth reaction zone of a first reaction unit, and collecting graphene in the bin; a second batch of low-layer graphene oxide is placed in the bin, and sequentially passes through a jth reaction zone and an mth reaction zone of a second reaction unit, and the graphene in the bin is collected; a third batch of low-layer graphene oxide is placed in the bin, sequentially passes through the ith reaction zone and the nth reaction zone of the first reaction unit, and is collected, wherein the temperature and the pressure of the nth reaction zone are respectively controlled to be TnAnd PnThe temperature and the pressure of the ith reaction zone are respectively controlled to be TiAnd PiWherein, Ti＝w1·i/n·Tn，Pi＝(P0-Pn) (1-i/n) wherein w1Is selected from 0.80 to 1.20, P0Is 1 standard atmosphere, TnAnd PnRespectively at 1250 ℃ or above and 30 Pa-500 Pa, n is a natural number not less than 2, and i takes all natural numbers less than n; the temperature and the pressure of the mth reaction zone are respectively controlled to be tmAnd PmThe temperature and the pressure of the jth reaction zone are respectively controlled to be tjAnd PjWherein, tj＝k1·j/m·tm，Pj＝(P0-Pm) (1-j/m) wherein k1Is selected from 0.80 to 1.20, P0Is 1 standard atmosphere pressure, tmAnd PmRespectively at 1250 deg.C or above and 30-500 Pa, m is a natural number greater than or equal to 2, and j is a natural number smaller than m. Further, the bin can be a graphite bin or a bin with a graphite coating arranged inside.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method can improve the thoroughness of graphene oxide purification, can effectively separate the graphene oxide from impurities, removes the impurities, and has high purification efficiency and low cost;
(2) the graphene oxide with low layer number is obtained by a freeze drying method, the structure of a graphite oxide sheet layer is not damaged, functional groups are well preserved, and the graphite oxide after freeze drying is not easy to agglomerate;
(3) the interlayer spacing of the low-layer graphene oxide obtained by 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;
(4) according to the method, graphene is prepared by reacting low-layer graphene oxide at high temperature and low pressure in different temperature and pressure areas, and the characteristic of high melting point of graphene is fully utilized; in a low-pressure environment, metal and nonmetal impurities in graphene can be removed at high temperature, a large number of oxygen-containing functional groups carried by graphene oxide are removed at the same time, and SP (SP) caused by graphene oxide in the preparation process is repaired3Hybrid defectSinking;
(5) according to the invention, the graphene oxide can be pretreated in a lower temperature region to reduce energy consumption, waste heat can be effectively and reasonably utilized, the reduction efficiency can be obviously improved, and the continuous production of the graphene can be realized;
(6) the low-layer graphene prepared by the method disclosed by the invention is low in impurity content, few in structural defects, low in layer number and excellent in comprehensive performance.
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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 diagram of the arrangement of reaction zones in the reduction step of the low-layer graphene oxide according to an exemplary embodiment of the present invention.
Detailed Description
Hereinafter, a method for preparing graphene using a low-layer number of graphene oxide according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
Fig. 1 shows a schematic diagram of the arrangement of reaction zones in the reduction step of the low-layer graphene oxide according to an exemplary embodiment of the present invention.
In an exemplary embodiment of the method for preparing graphene using a low-layer graphene oxide according to the present invention, the method may include:
and S100, purifying the purified object to obtain the purified graphene oxide. The purification target may be graphene oxide containing a functional group and impurities, the graphene oxide having a first number of layers. The number of the first layers may be tens of layers to tens of layers, for example, 20 to 30 layers, and further, 22 to 28 layers. The graphene oxide contains an oxygen-containing functional group. For example, the graphene oxide having the first layer number may be prepared by intercalating graphite with protonic acid.
The impurities may include metallic impurities and/or non-metallic impurities. For example, the impurities may include one or a combination of iron, manganese, potassium, sodium, sulfur, silicon, and the like. The functional group may include one or more of a carboxyl group, a hydroxyl group, a carbonyl group, an ether bond, and an epoxy group. Of course, the functional group of the present invention is not limited thereto, and for example, the functional group may be an ester group or the like.
And step S200, carrying out freeze drying treatment on the purified graphene oxide to obtain the graphene oxide with a low layer number.
And step S300, reducing the low-layer graphene oxide to obtain graphene.
In this embodiment, for step S100, the step of obtaining purified graphene oxide may include:
s110, mixing the purified object, the complexing agent and the acidic solution to form a mixed solution.
The complexing agent can comprise one or more of citric acid, sodium citrate, sodium thiosulfate, sodium sulfite, sodium ethylene diamine tetracetate, polyacrylic acid, sodium gluconate and sodium alginate.
The acidic solution is capable of providing a 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.
And S120, carrying out ultrasonic oscillation on the mixed solution.
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.
During ultrasonic treatment, the frequency of the ultrasonic wave can be 50-750 Hz, and the ultrasonic frequency in the range can enable impurity ions on the graphene oxide functional groups to be removed better.
The weight percentage of impurity ions on the purified graphene oxide can be not higher than 0.01%; the removal rate of impurities can reach more than 99%.
And S130, filtering to obtain the purified graphene oxide.
The filtration may be performed by a filtration membrane to separate the purified graphene oxide from the solution including 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). Furthermore, a decompression suction filtration device can be arranged below the filter layer, so that the solution containing impurities can better permeate the filter layer. Wherein, the vacuum pump is arranged under the filter membrane to realize the decompression and suction filtration.
When filtration is performed using a filtration membrane, the method may further comprise 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 may comprise a sponge.
Above, the purification method may further comprise the steps of: and detecting the ion concentration of the obtained 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, for step S200, the step of obtaining the low-layer graphene oxide may include:
and step S210, forming the graphene oxide hydrogel.
Dispersing the purified graphene oxide in water, and forming a graphene oxide hydrogel. 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 step S220, carrying out low-temperature vacuum freeze drying on the graphene oxide hydrogel.
And 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 the 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.
Wherein the second number of layers is less than the first number of layers. 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.
In an exemplary embodiment of the present invention, 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 drying 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 of 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, for step S300, the step of reducing the low-layer graphene oxide to obtain graphene with higher purity may include:
and sequentially subjecting the low-layer graphene oxide to an ith reaction zone and an nth reaction zone which are different in temperature and pressure to react to obtain the graphene, wherein n is a natural number and is not less than 2, and i is taken as all natural numbers less than n.
The temperature of the nth reaction zone is measured by TnIndicating pressure by PnAnd (4) showing. Temperature T herenMay be 1250 ℃ or higher, further, the temperature TnMay be 1700 ℃ to 2800 ℃, further still, the temperature TnMay be 2200 deg.c. Since 2200 ℃ is the graphitization temperature of the carbon material, the method is also beneficial to repairing the self defects of the graphene oxide. The pressure PnMay be 30Pa to 500Pa, and further, the pressure PnMay be 60Pa to 100Pa, and further, the pressure PnMay be 85Pa to 95 Pa.
The temperature of the i-th reaction zone is measured by TiIndicating pressure by PiAnd (4) showing. Said temperature TiMay be Ti＝w1·i/n·TnWherein w is1The selection is between 0.80 and 1.20. The pressure PiMay be Pi＝(P0-Pn) (1-i/n) wherein P0Is 1 atm. Different reaction zones are set with different temperatures and pressures, so that the low-layer graphene oxide can be preferably pretreated, and the pretreatment can be performedCan be more favorable to the low number of layers graphene oxide to go miscellaneous and the functional group process of going, can improve the production efficiency of graphite alkene. Further, w1Can be selected from 0.85 to 1.14, for example, w1May be taken to be 0.98. For example, graphene oxide is subjected to 3 reaction zones of 1 st, 2 nd and 3 rd, respectively. The temperature and pressure in the 3 rd reaction zone were set to 1500 ℃ and 100Pa, respectively. Taking w according to the temperature and pressure formula10.9, the temperature of the 1 st reaction zone was T10.9 × 1/3 × 1500 ═ 450 deg.C, pressure P1＝(1.01×105-100)·(1-1/3)＝0.67×105Pa, the temperature of the 2 nd reaction zone is T20.9 × 2/3 × 1500 ═ 900 deg.C, pressure P1＝(1.01×105-100)×(1-2/3)＝0.34×105Pa。
The reaction time of the graphene oxide with the low number of layers in each reaction zone can be determined according to empirical values or actual field operation. For example, assume that the reaction time in the nth reaction zone is tnThe reaction time of the i-th reaction zone may be ti＝r1·i/n·tnSaid r1Can be selected from 0.9 to 1.1.
In this embodiment, for step S300, the step of reducing the low-layer graphene oxide to obtain graphene with higher purity may include:
step S310, as shown in fig. 1, sequentially subjecting a bin containing a first batch of low-layer graphene oxide to an i-th reaction zone and an n-th reaction zone of a first reaction unit, and collecting graphene in the bin. Wherein the temperature and pressure of the nth reaction zone can be controlled to TnAnd PnThe temperature and pressure of the ith reaction zone can be controlled to be T respectivelyiAnd PiWherein, Ti＝w1·i/n·Tn，Pi＝(P0-Pn) (1-i/n) wherein w1Is selected from 0.80 to 1.20, P0Is 1 standard atmospheric pressure, n is a natural number and is more than or equal to 2, and i is taken as all natural numbers less than n.
Said temperature TnMay be 1250 ℃ or higher, further, the temperature is mentionedTnMay be 1700 ℃ to 2800 ℃. Further, the temperature TnMay be 1700 ℃ to 2500 ℃. For example, the temperature may be 2200 ℃, since 2200 ℃ is a carbon material graphitization temperature, and is also beneficial for repairing the defects of graphene oxide itself. The pressure PnMay be 30Pa to 500 Pa. Further, the pressure PnMay be 60Pa to 100 Pa.
The storage bins containing the first batch of low-layer graphene oxide are heated and reacted through areas with different temperatures and pressures, and then the low-layer graphene oxide obtained through reaction is taken out from the final reaction area. The silo has a certain residual heat, so that the silo does not need to be taken out of the last reaction zone and directly enters the 1 st reaction zone of the second reaction unit, as shown in figure 1. Therefore, the waste heat of the storage bin can be effectively utilized, the reaction efficiency is improved, and the energy is saved.
Further, w1Can be selected from 0.85 to 1.14, for example, w1May be taken to be 0.95.
Step S320, after the prepared graphene with a low number of layers is taken out from the nth reaction area of the first reaction unit, adding a second batch of graphene oxide with a low number of layers into the storage bin. The bin is already at a certain temperature in the nth reaction zone, the bin containing the second batch of low-layer graphene oxide directly enters the first reaction zone of the second reaction unit, the second batch of low-layer graphene oxide can be preheated by using waste heat of the bin and sequentially passes through the jth reaction zone and the mth reaction zone of the second reaction unit, and the low-layer graphene prepared in the bin is collected in the mth reaction zone to obtain the second batch of low-layer graphene. Wherein the temperature and pressure of the mth reaction zone are respectively controlled to tmAnd PmThe temperature and the pressure of the jth reaction zone are respectively controlled to be tjAnd Pj. Wherein, tj＝k1·j/m·tm，Pj＝(P0-Pm) (1-j/m) wherein k1Is selected from 0.80 to 1.20, P0Is 1 standard atmospheric pressure, m is a natural number and is more than or equal to 2, and j is all natural numbers less than m. Said temperature TmCan be 1Above 250 ℃, further, the temperature TmMay be 1700 ℃ to 2200 ℃. The pressure PmMay be 30Pa to 500Pa, and further, the pressure PmMay be 85Pa to 95 Pa. Further, k1Can be selected from 0.83 to 1.16, for example, w1May take 0.92.
And the discharge hole of the nth reaction zone of the first reaction unit is adjacent to the feed hole of the 1 st reaction zone of the second reaction unit. After the first batch of low-layer graphene oxide is reacted and the product low-layer graphene oxide is taken out, adding a second batch of low-layer graphene oxide, enabling a bin containing the second batch of low-layer graphene oxide to enter a 1 st reaction zone of a second reaction unit, and reacting in the reaction zone of the second reaction unit. The bin just exiting the nth reaction area of the first reaction unit has a certain amount of waste heat, when entering the second reaction unit, the waste heat of the bin can be utilized to heat the second batch of graphene oxide with a low number of layers, so that the waste heat of the high-temperature material can be effectively utilized, and the energy consumption is saved.
Step S330, after the second batch of graphene oxide with the low layer number is reacted in the second reaction unit, taking out the second batch of graphene oxide with the low layer number from the mth reaction zone of the second reaction unit, simultaneously adding a third batch of graphene oxide with the low layer number, sequentially passing through the ith reaction zone and the nth reaction zone of the first reaction unit, collecting the graphene in the bin, and circulating the processes to realize continuous production of the graphene.
More than, the discharge gate of the mth reaction zone of the second reaction unit and the feed inlet of the 1 st reaction zone of the first reaction unit are adjacently arranged, and the discharge gate of the nth reaction zone of the first reaction unit and the feed inlet of the 1 st reaction zone of the second reaction unit are adjacently arranged, so that a continuous circulating reaction area can be formed, and the continuous production of the low-layer graphene can be realized. Similarly, after the second batch of low-layer graphene oxide is reacted and the product graphene is taken out, the third batch of low-layer graphene oxide is added. And the bin containing the third batch of low-layer graphene oxide enters the 1 st reaction zone of the first reaction unit for reaction. And taking out the graphene after the reaction in the nth reaction zone of the first reaction unit is finished, and adding a fourth batch of graphene oxide with a low layer number.
Also, the reaction time in each reaction zone of the low-layer graphene oxide may be the same as the time in each reaction zone of the graphene oxide in the foregoing exemplary embodiment.
As described above, the purification target may contain at least one impurity selected from manganese, iron, potassium, sodium, sulfur, and silicon. The impurities are generally present in the graphene oxide in the form of ions. The complexing agent used in the purification process may combine with metal impurities in the impurities to remove the metal impurities, e.g., manganese, iron, potassium, sodium, etc. At the moment, 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 impurities. Of course, the metal impurities that can be removed by complexation are not limited thereto, and for example, heavy metal impurities or other impurities that can bind to the complexing agent may be used. After purification to remove a part of impurities, in the reduction step, metallic and non-metallic impurities, such as manganese, iron, potassium, sodium, sulfur, silicon, etc., can be removed under a high temperature and low pressure environment. At high temperature, the melting point and the boiling point of metal impurities and nonmetal impurities contained in the graphene oxide can be reached, and the graphene oxide can be separated from the graphene oxide in a gaseous state. Under certain low-pressure auxiliary conditions, the melting points and boiling points of metal impurities and non-metal impurities can be further reduced, and the metal impurities and the non-metal impurities contained in the graphene oxide can be easily removed through the set temperature and vacuum degree. Impurities contained in the raw materials are removed through the cooperation of the purification process and the high-temperature vacuum reaction process, oxygen-containing functional groups can be well removed under the high-temperature vacuum degree, and graphene with low impurity content can be obtained. In the existing method for preparing graphene, the content of the prepared graphene is generally more than 2000PPm, the content of iron and manganese in the low-impurity-content graphene prepared by the method can reach less than 20PPm, further less than 15PPm, and impurities such as nitrate ions and chloride ions can be well removed, so that the graphene can be well used as a lithium ion battery conductive additive.
For step S300, the temperature T is setnOr TmThe benefit of being above 1250 c is that if the temperature is below 1250 c, it is not conducive to volatilization of the impurities, and the melting and boiling points of some of the impurities may not be reached. For example, the set temperature may be 1250 ℃ to 2500 ℃. If the set temperature is higher than 2800 ℃, the loss of the furnace may be serious, the energy consumption is high, the cost is high, and the high temperature causes the specific surface area of the prepared low-layer graphene to be reduced. Further, the temperature TnOr TmMay be 2200 deg.c. Since 2200 ℃ is the graphitization temperature of the carbon material, the method is also beneficial to repairing the self defects of the graphene oxide. Setting the pressure PnThe advantage of 30 Pa-500 Pa is that under the pressure and vacuum degree, the melting point and the boiling point of impurities contained in the graphene oxide are lower, and the impurities are easier to volatilize and remove.
For any embodiment of step S300, the reaction time in the nth reaction zone and in the mth reaction zone may be 60min to 600 min. The nth reaction zone and the mth reaction zone are both reaction zones with the highest temperature and the lowest pressure of each reaction unit, and are main reaction zones of graphene oxide. If the heating time is less than 60min, the heating time of the graphene oxide is possibly insufficient, and impurities cannot be sufficiently removed; the heating time is longer than 600min, and the energy consumption is too large. Further, the heating time is 120 min-300 min.
In any embodiment of step S300, the oxygen-containing functional group of the purification object can be decomposed into carbon dioxide and water under the high temperature and pressure conditions set by the present invention, so that the oxygen-containing functional group in the graphene oxide can be effectively removed. Theoretically, the functional group can be removed at a temperature of 1000 ℃ and under the vacuum environment of the present invention, but the temperature set by the present invention should be higher than 1250 ℃ because the temperature for removing impurities is high. Of course, the oxygen-containing functional group of the present invention is not limited thereto, and can be decomposed into carbon dioxide and water at the temperature and pressure of the present invention.
In order to avoid the influence of the storage bin on the purity of the prepared graphene, in the treatment process, other element impurities are prevented from being introduced into the graphene due to the material of the storage bin. The melting point of graphite is as high as 3652 ℃, which is far higher than the melting points of common metal impurities and non-metal impurities. Thus, a graphite silo or a silo coated with a graphite layer on its surface, for example, a graphite bowl, can be used. However, the invention is not limited to this, and other materials with higher melting point, such as tungsten foil, tantalum carbide bin or hafnium carbide bin, can be used as the material of the bin. In order to make the heated area of graphene oxide bigger, do benefit to fully getting rid of impurity, simultaneously under the certain amount of circumstances of graphene oxide, generate the bigger graphene of area, preferably, will graphene oxide pave in the feed bin.
According to the method, the melting boiling point difference between the graphene and the impurities contained in the graphene is utilized, different temperature regions and pressure regions are set, and the regional reaction is carried out, so that the impurities can be effectively removed, and the SP in the graphene oxide can be repaired3Structural defects and oxygen-containing functional groups are removed, and high-quality graphene with high purity is further prepared. The appropriate temperature interval can make SP in graphene oxide3The structural defects are repaired, and a large amount of oxidation functional groups carried by the graphene oxide can be removed under the low-pressure condition, and metal and/or nonmetal impurities can be removed from the graphene oxide in a gaseous state. Different temperature and pressure zones are set, so that the graphene oxide can be pretreated, the waste heat generated in the pretreatment process can be reasonably utilized, the energy-saving effect can be realized, and the continuous production of the graphene can be realized. The graphene oxide is reacted under the low pressure condition, the melting point and the boiling point of impurities in the graphene oxide can be reduced, the requirement of the preparation process on the temperature is further reduced, and the effects of energy conservation and compression cost can be achieved.
In conclusion, the method can improve the thoroughness of graphene oxide purification, can effectively separate the graphene oxide from impurities, and has high purification efficiency and low cost; the graphene oxide with low layer number is obtained by a freeze drying method, the structure of a graphite oxide sheet layer is not damaged, functional groups are well preserved, and the graphite oxide after freeze drying is not easy to agglomerate; the raw materials used and a large amount of impurities in the preparation process of the graphene can be removed through the purification step and the reduction step, so that the purity of the graphene can be improved; the prepared graphene with low layer number has low impurity content, few structural defects, low layer number and excellent comprehensive performance.
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 (9)
1. A method for preparing graphene by using graphene oxide with a low layer number is characterized by comprising the following steps:
purifying the purified object to obtain purified graphene oxide;
carrying out freeze drying treatment on the purified graphene oxide to obtain a low-layer graphene oxide;
reducing the low-layer graphene oxide to obtain graphene, wherein,
the purification object is graphene oxide with a functional group combined with impurity ions and a first layer number, wherein the first layer number is tens to tens of layers;
the step of performing purification treatment on the purification object includes:
mixing a purified object, a complexing agent and an acidic solution to form a mixed solution; 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;
the step of freeze-drying the purified graphene oxide comprises:
dispersing the purified graphene oxide in water to form a graphene oxide hydrogel, wherein the solid content of the graphene oxide hydrogel is 0.1-50 wt%, and the graphene oxide hydrogel has a structure that water molecules are combined in sheets or folds of the graphene oxide; 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;
the step of reducing the low-layer graphene oxide includes:
spreading the low-layer graphene oxide in a bin to sequentially pass through an i-th reaction zone and an n-th reaction zone to obtain graphene, and respectively controlling the temperature and the pressure of the n-th reaction zone to be TnAnd PnControlling the temperature and pressure of the ith reaction zone to be T respectivelyiAnd Pi，
Wherein, Ti＝w1·i/n·Tn，Pi＝(P0-Pn) (1-i/n) wherein w1Is selected from 0.80 to 1.20, P0Is 1 standard atmosphere, TnAnd PnRespectively at 1250 deg.C or above and 30 Pa-500 Pa, n is a natural number greater than or equal to 2, and i is selected from all natural numbers less than n.
2. The method for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein the complexing agent comprises citric acid, sodium citrate, sodium thiosulfate, sodium sulfite, sodium ethylene diamine tetracetate, polyacrylic acid, sodium gluconate or sodium alginate.
3. The method for preparing graphene by using the graphene oxide with the low layer number according to claim 1, wherein the pH of the acidic solution is 0.1-6.
4. The method for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein the filtering step comprises filtering through a filtering membrane, and a suction filtration mechanism is arranged below the filtering membrane to perform reduced pressure suction filtration.
5. The method for preparing graphene by using graphene oxide with a low number of layers according to claim 1, wherein the first number of layers is 20-30 layers, and the second number of layers is 5-7 layers.
6. The method for preparing graphene by using the low-layer number of graphene oxide according to claim 1, wherein the first temperature is selected from the range of-55 ℃ to-65 ℃ and the temperature variation is not more than +/-2 ℃.
7. The method for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein the first pressure is selected within a range of 10-100 Pa and the variation of the pressure is not more than +/-10 Pa.
8. The method for preparing graphene by using the graphene oxide with the low number of layers according to claim 1, wherein the step of performing reduction treatment on the graphene oxide with the low number of layers comprises:
sequentially subjecting a bin containing a first batch of low-layer graphene oxide to an ith reaction zone and an nth reaction zone of a first reaction unit, and collecting graphene in the bin;
a second batch of low-layer graphene oxide is placed in the bin, and sequentially passes through a jth reaction zone and an mth reaction zone of a second reaction unit, and the graphene in the bin is collected;
a third batch of graphene oxide with a low layer number is placed in the bin, and sequentially passes through the ith reaction zone and the nth reaction zone of the first reaction unit, and the graphene in the bin is collected, wherein,
the temperature and the pressure of the nth reaction zone are respectively controlled to be TnAnd PnThe temperature and the pressure of the ith reaction zone are respectively controlled to be TiAnd PiWherein, Ti＝w1·i/n·Tn，Pi＝(P0-Pn) (1-i/n) wherein w1Selecting between 0.80-1.20，P0Is 1 standard atmosphere, TnAnd PnRespectively at 1250 ℃ or above and 30 Pa-500 Pa, n is a natural number not less than 2, and i takes all natural numbers less than n;
the temperature and the pressure of the mth reaction zone are respectively controlled to be tmAnd PmThe temperature and the pressure of the jth reaction zone are respectively controlled to be tjAnd PjWherein, tj＝k1·j/m·tm，Pj＝(P0-Pm) (1-j/m) wherein k1Is selected from 0.80 to 1.20, P0Is 1 standard atmosphere pressure, tmAnd PmRespectively at 1250 deg.C or above and 30-500 Pa, m is a natural number greater than or equal to 2, and j is a natural number smaller than m.
9. The method for preparing graphene by using the low-layer graphene oxide according to claim 8, wherein the bin is a graphite bin or a bin with a graphite coating arranged inside.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN106809821A (en) * | 2017-01-19 | 2017-06-09 | 广东烛光新能源科技有限公司 | The preparation method of Graphene |
| CN107815170A (en) * | 2017-11-07 | 2018-03-20 | 成都新柯力化工科技有限公司 | A kind of graphene coating masterbatch and preparation method |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN106809821A (en) * | 2017-01-19 | 2017-06-09 | 广东烛光新能源科技有限公司 | The preparation method of Graphene |
| CN107815170A (en) * | 2017-11-07 | 2018-03-20 | 成都新柯力化工科技有限公司 | A kind of graphene coating masterbatch and preparation method |
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