CN105347340A - The preparation method of graphene oxide - Google Patents

Abstract

The present invention relates to a kind of preparation method of graphene oxide, is to add graphite raw material, pro-oxidant into alkali solution and put in airtight container, wherein, add 1～50g graphite raw material and 1～30g pro-oxidant in every 100ml of alkali solution, use Oxygen replaces the gas in the container and fills it with oxygen until the pressure is 1~20Mpa. The reaction is carried out at a temperature of 101°C~650°C. After the reaction, the reaction product is taken out for solid-liquid separation, and the obtained solid phase is washed and dried to obtain a graphene oxide solid product. , The liquid phase is recovered and recycled after treatment. This reaction can avoid the use of a large amount of strong acid and strong oxidant, reduce the waste acid and waste liquid, and the degree of reaction can be controlled by the reaction temperature and oxygenation pressure, which effectively avoids the structure damage and loss of graphene oxide prepared under strong acidic conditions, and simplifies The tedious separation and washing process of graphite oxide prepared from acid is eliminated. Alkaline solution is recycled to effectively reduce production cost, the process is simple, the process is short, and the cost is low.

Description

The preparation method of graphene oxide

technical field

The invention relates to a method for preparing graphene oxide.

Background technique

Graphene oxide (GO) is an important intermediate for preparing graphene by redox method. In 2004, Andre Geim and Konstantin Novoselov, physicists at the University of Manchester in the United Kingdom, successfully separated single-layer graphene from graphite, confirmed that it can exist alone and discovered the integer quantum Hall effect. And the quantum Hall effect under normal temperature conditions, the two detonated the research on graphene after they jointly won the 2010 Nobel Prize in Physics. The breaking strength of graphene is 200 times that of steel, and it has good elasticity, and the stretching range can reach 20% of its own size. Graphene has great potential to become a substitute for silicon, manufacture ultra-miniature transistors, and be used to produce future supercomputers. The speed of computer processors will increase hundreds of times. Graphene's extremely high light transmittance and dense structure make it very suitable as a raw material for transparent electronic products, such as transparent touch displays, light-emitting panels and solar panels. And its unique surface structure has a good antibacterial effect and has great prospects in the application of medical and aerospace materials. As the thinnest, hardest, and strongest new type of nanomaterials found so far, graphene plays a very important role in the application of cutting-edge technology materials due to its unique physical and chemical properties.

At present, the common methods for preparing graphene are mechanical exfoliation method, redox method, SiC epitaxial growth method and chemical vapor deposition (CVD). However, there are obvious disadvantages in the four methods. The mechanical stripping method has low production capacity, and the redox method uses strong acid and strong oxidant for oxidation, which causes large pollution but high yield. The common problem of SiC epitaxial growth method and chemical vapor deposition method is the requirement for equipment. High, high cost and low productivity.

At this stage, the redox method is the best method for large-scale production of industrial-grade graphene with the lowest operational difficulty and low cost. The specific method of redox method is to use natural flake graphite or expanded graphite as raw material, and then oxidize it with strong acid and strong oxidant (strong acid and strong oxidant are concentrated sulfuric acid, concentrated hydrochloric acid, perchloric acid, potassium permanganate, etc.). This stage of graphene is called the oxidation stage, and then it is reduced by a reducing agent (the reducing agent is hydrazine hydrate, sodium borohydride, etc.) to prepare graphene. However, the traditional oxidation stage will produce a large amount of waste acid, and in the separation stage, dilution and exothermic further oxidation is required, making it difficult to recover concentrated acid, and there are a large number of heavy metal ions in the waste liquid, which is very difficult to separate and treat; oxidation under concentrated acid conditions , the degree of graphite oxidation is difficult to control, and it is easy to destroy the graphite structure, resulting in low quality of prepared graphene.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing graphene oxide with controllable oxidation degree, little damage to graphite structure, and avoiding the use of strong acid in the preparation process.

In order to solve the above technical problems, a kind of preparation method of graphene oxide provided by the present invention is to add graphite raw material and auxiliary oxidant into alkali solution and be placed in a closed container, wherein, add 1～50g of graphite raw material and 1~30g of auxiliary oxidant, replace the gas in the container with oxygen and fill it with oxygen until the pressure is 1~20Mpa, and react at a temperature of 101°C~650°C. After the reaction, take out the reaction product for solid-liquid separation, and the obtained solid phase is washed and dried. The graphene oxide solid product is obtained, and the liquid phase is recovered and treated for recycling.

The idea of the present invention is to prepare graphene oxide by heating and oxidizing graphite raw materials under the action of alkaline solution, oxygen at a certain pressure, and a pro-oxidant, so as to overcome the defects in the oxidation stage of graphene prepared by redox method, and the oxidation degree of this method is controllable , has little damage to the graphite structure, and is an environmentally friendly synthesis route. The lye produced can be recycled after treatment. The cost is low and the method is simple, which effectively avoids the problems of waste acid and separation difficulties in the strong acid oxidation process.

Under the above reaction conditions, the autogenous reaction pressure in the container is between 10Mpa and 60Mpa. The solid-liquid separation method includes suction filtration and centrifugation; the solid product is washed with 5%-10% dilute hydrochloric acid; the solid product drying method includes drying, natural drying, and freeze drying. The liquid phase can be recovered, and the treatment method is: adjust the concentration of the solution according to the concentration of the alkali before the sealed tank, and then use it as an alkali solution for recycling.

As a preferred technical solution, the reaction time is 10 to 72 hours. On this basis, the preferred solution is to dissolve the obtained graphene oxide solid product in water and disperse it ultrasonically to obtain a graphite oxide dispersion solution.

As another preferred technical solution, the solute of the alkaline solution is potassium hydroxide or sodium hydroxide. On this basis, the solvent of the alkaline solution is one of water, methanol, ethanol, ethylene glycol, propanol, glycerol and butanol. Preferably, the alkali solution prepared with the above-mentioned solute and solvent has a substance concentration of 5-20 mol/L.

As another preferred technical solution, the pro-oxidant is one of potassium nitrate, potassium nitrite, sodium nitrate or sodium nitrite.

As another preferred technical solution, the graphite raw material is natural flake graphite or expanded graphite. The particle size of the preferred graphite raw material is 30-500 mesh.

As another preferred technical solution, the reaction is carried out at a temperature of 350°C to 500°C.

The beneficial effects of the method for preparing graphene oxide by alkali oxidation proposed by the present invention are: (1) The reaction can avoid the use of a large amount of strong acid and strong oxidant, reduce a large amount of waste acid and waste liquid, and reduce costs and be environmentally friendly. (2) Graphene oxide is prepared by oxidation of alkaline solution with oxygen and co-oxidant. The degree of reaction can be controlled by controlling the reaction temperature and oxygenation pressure, which effectively avoids the structure damage and loss of graphene oxide prepared under strong acidic conditions. question. (3) With simple operation and easy separation, the cumbersome separation and washing process for preparing graphite oxide from acid is simplified. (4) Alkali solution is recycled to effectively reduce production cost, the process is simple, the process is short, and the cost is low.

Description of drawings

Fig. 1 is the scanning electron micrograph of the sample prepared by the present invention.

detailed description

Example 1

This embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

Take 3g of 325 mesh natural flake graphite, 12g of KOH, and 3g of KNO ₃ , put them into a reaction kettle, add 25ml of deionized water, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then filled with oxygen to 5Mpa, the reactor was heated to 450°C, and the reaction was stirred for 36 hours. After the reaction was completed, cool to room temperature, and the reactant was separated from solid and liquid. The solid product was first washed with 5% dilute hydrochloric acid, then washed with deionized water until neutral, and dried at 100°C to obtain 2.752 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 2

This embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

With 13mL of lye recovered in Example 1, add 6.25gKOH and 17mL deionized water to adjust to the same concentration according to the concentration of KOH measured before the reaction kettle was sealed in Example 1, take 3g325 mesh natural flake graphite, _3gKNO3 , put in In the reaction kettle, add 25ml circulating lye and stir for 10min. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then the reactor was heated to 600° C. with 3 Mpa of oxygen, and the reaction was stirred for 36 hours. After the reaction was completed, it was cooled to room temperature, the reactant was separated from solid and liquid, and the solid product was washed with 5% dilute hydrochloric acid, then washed with deionized water until neutral, and dried at 100°C to obtain 2.804 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 3

The present embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is NaOH, and the prooxidant is NaNO ₃ reaction process and result.

Take 5g of 325 mesh natural flake graphite, 12g of NaOH, and 3g of NaNO ₃ , put them into a reaction kettle, add 25ml of deionized water, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then the reactor was heated to 450° C. with 5 Mpa of oxygen, and the reaction time was stirred for 36 hours. After the reaction was completed, cool to room temperature, the reactants were separated into solid and liquid, and the solid was washed with 10% dilute hydrochloric acid, then washed with deionized water until neutral, and dried at 100°C to obtain 4.763 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the NaOH solution before the reaction, it is recycled as an alkali solution.

Example 4

This embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

Take 3g of 325 mesh natural flake graphite, 25g of KOH, and 5g of KNO ₃ , put them into a reaction kettle, add 25ml of deionized water, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then filled with 5Mpa of oxygen, the reactor was heated to 450°C, and the reaction was stirred for 72 hours. After the reaction, cool to room temperature, separate solid and liquid, wash the solid with 10% dilute hydrochloric acid, then wash with deionized water until neutral, and dry at 100°C to obtain 2.733 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 5

This embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₂ reaction process and result.

Take 3g of 325 mesh natural flake graphite, 12g of KOH, and 3g of KNO ₂ , put them into a reaction kettle, add them into 25ml of ethanol, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then the reactor was heated to 450° C. with 5 Mpa of oxygen, and the reaction was stirred for 36 hours. After the reaction was completed, it was cooled to room temperature, the solid and liquid were separated, the solid was washed with 10% dilute hydrochloric acid, and dried at 100°C to obtain 2.767 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 6

This embodiment illustrates that the graphite is 200 meshes of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

Take 3g of 200 mesh natural flake graphite, 20g of KOH, and 6g of KNO ₃ , put them into a reaction kettle, add 25ml of deionized water, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then filled with 6Mpa of oxygen, the reactor was heated to 450°C, and the reaction was stirred for 50 hours. After the reaction, cool to room temperature, separate solid and liquid, wash the solid with 10% dilute hydrochloric acid, then wash with deionized water until neutral, and dry at 100°C to obtain 2.624 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 7

This embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

Take 3g of 325 mesh natural flake graphite, 12g of KOH, and 3g of KNO ₃ , put them into a reaction kettle, add 25ml of deionized water, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then 7Mpa of oxygen was charged to heat the reactor to 450°C, and the reaction was stirred for 36 hours. After the reaction, cool to room temperature, separate solid from liquid, wash the solid with 10% hydrochloric acid, then wash with deionized water until neutral, and dry at 100°C to obtain 2.749 g of graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution. 0.3 g of the obtained graphene oxide solid was dissolved in 50 ml of distilled water, and ultrasonically treated at 100 W for 20 min to obtain a graphite oxide dispersion solution.

Example 8

This embodiment illustrates that the graphite is expanded graphite 30 mesh, the alkali is KOH, and the prooxidant is KNO ₂ reaction process and result.

Take 0.25g of 30-mesh expanded graphite, 12g of KOH, and 0.25g of KNO ₂ , put them into a reaction kettle, add them into 25ml of glycerol, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then filled with oxygen to 1Mpa, the reactor was heated to 650°C, and the reaction was stirred for 10 hours. After the reaction is completed, cool to room temperature, the reactant is separated from solid and liquid, and the solid product is first washed with 5% dilute hydrochloric acid, then washed with deionized water until neutral, and dried at 100°C to obtain a graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 9

This embodiment illustrates that the graphite is 500 orders of natural flake graphite, the alkali is KOH, and the prooxidant is KNO ₃ reaction process and result.

Take 12.5g of 500 mesh natural flake graphite, 20g of KOH, and 7.5g of KNO ₃ , put them into a reaction kettle, add 25ml of ethylene glycol, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then 20 MPa of oxygen was charged, and the temperature of the reactor was raised to 101° C., and the reaction was stirred for 72 hours. After the reaction, cool to room temperature, separate solid and liquid, wash the solid with 10% dilute hydrochloric acid, then wash with deionized water until neutral, and dry at 100°C to obtain graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 10

This embodiment illustrates that the graphite is expanded graphite 325 mesh, the alkali is KOH, and the prooxidant is KNO ₂ reaction process and result.

Take 3g of 325 mesh expanded graphite, 7g of KOH, and 3g of KNO ₂ , put them into a reaction kettle, add them into 25ml of propanol, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then the reactor was heated to 350° C. with 3 Mpa of oxygen, and the reaction was stirred for 48 hours. After the reaction, cool to room temperature, separate the solid from the liquid, wash the solid with 10% dilute hydrochloric acid, and dry it at 100°C to obtain a graphene oxide solid. The liquid phase is recovered, and after the concentration of the solution alkali is adjusted according to the concentration of the KOH solution before the reaction, it is recycled as an alkali solution.

Example 11

The present embodiment illustrates that the graphite is 325 orders of natural flake graphite, the alkali is NaOH, and the prooxidant is NaNO ₃ reaction process and result.

Take 3g of 325 mesh natural flake graphite, 20g of NaOH, and 3g of NaNO ₃ , put them into a reaction kettle, add them into 25ml of methanol, and stir for 10 minutes. After the reactor was sealed, the gas in the reactor was replaced with oxygen three times, and then the reactor was heated to 500°C with 10Mpa of oxygen, and the reaction was stirred for 48 hours. After the reaction is completed, cool to room temperature, separate the solid from the liquid, wash the solid with 10% hydrochloric acid, then wash it with deionized water until neutral, and dry it at 100°C to obtain a graphene oxide solid. 0.3 g of the obtained graphene oxide solid was dissolved in 50 ml of distilled water, and ultrasonically treated at 100 W for 20 min to obtain a graphite oxide dispersion solution.

Claims (10)

1. a preparation method of graphene oxide is characterized in that: graphite raw material, pro-oxidant are added alkali solution and are placed in airtight container, wherein, add 1～50g graphite raw material and 1～30g pro-oxidant in every 100ml alkaline solution, Replace the gas in the container with oxygen and fill it with oxygen until the pressure is 1~20Mpa, and react at a temperature of 101°C~650°C. After the reaction, the reaction product is taken out for solid-liquid separation, and the obtained solid phase is washed and dried to obtain graphene oxide solid. The product is recovered from the liquid phase and recycled after treatment. 2. The method according to claim 1, characterized in that: the time for reacting is 10 to 72 hours. 3. The method according to claim 2, characterized in that: the obtained graphene oxide solid product is dissolved in water and ultrasonically dispersed to obtain a graphite oxide dispersion solution. 4. The method according to claim 1, 2 or 3, characterized in that: the solute of the alkaline solution is potassium hydroxide or sodium hydroxide. 5. The method according to claim 4, characterized in that: the solvent of the alkaline solution is one of water, methanol, ethanol, ethylene glycol, propanol, glycerol and butanol. 6. The method according to claim 5, characterized in that: the concentration of the substance in the alkaline solution is 5-20 mol/L. 7. The method according to claim 1, 2, 3, 5 or 6, characterized in that: the pro-oxidant is one of potassium nitrate, potassium nitrite, sodium nitrate or sodium nitrite. 8. The method according to claim 7, characterized in that: the graphite raw material is natural flake graphite or expanded graphite. 9. The method according to claim 8, characterized in that: the particle size of the graphite raw material is 30-500 mesh. 10. The method according to claim 1, characterized in that: wherein the liquid phase recovery treatment method is to adjust the concentration of the solution alkali according to the concentration of the alkali before the sealed tank, and then use it as an alkali solution for recycling.