Graphene slurry solid content detection method based on transition metal oxide coordination adsorption

Abstract

The invention relates to the field of graphene slurry solid content determination, in particular to a graphene slurry solid content detection method based on transition metal oxide coordination adsorption, and provides a method for selectively adsorbing and enriching graphene by utilizing a coordination bonding effect of transition metal oxide and a graphene oxygen-containing functional group to form a uniform composite precipitate; and after rapid solid-liquid separation and drying, accurately determining the carbon content in the composite precipitate by using a high-temperature element analyzer, and finally calculating the solid content in the graphene slurry according to a formula x = (m1 * C1%) / (m0 * C2%) * 100%. The method effectively solves the technical problems of large weighing error, long time consumption, poor anti-interference performance and the like of a traditional oven drying method in low-concentration graphene slurry detection, is particularly suitable for high-precision detection of ultralow-solid-content slurry, and meets the rapid and accurate detection requirements of the low-solid-content graphene slurry.

Description

Technical Field

[0001] The present invention relates to the field of graphene slurry solid content determination, and in particular to a graphene slurry solid content detection method based on transition metal oxide coordination adsorption. Background Art

[0002] Graphene, a two-dimensional nanomaterial composed of a single layer of carbon atoms, has become a revolutionary material in energy storage, electronic devices, composite materials, and other fields due to its excellent electrical conductivity, ultra-high thermal conductivity, and extremely high mechanical strength. However, the practical application of graphene usually requires it to be dispersed in a solvent (such as water, DMF, NMP, or ethanol) to form a slurry for coating, injection molding, or composite with other materials. Therefore, the solid content (mass percentage) of graphene in the slurry is a key process parameter that directly affects the overall performance of the final product. Its accurate measurement has become a core link in process optimization and quality control.

[0003] Currently, the industry primarily uses the oven drying method to test the solid content of graphene slurries. This method calculates the solid content by weighing the difference in mass between the slurry before and after drying. Due to its ease of operation and low equipment cost, it has become a common practice in corporate quality inspections and R&D laboratories. However, due to the large specific surface area of graphene, the solid content of graphene in its slurry is often low, and the limitations of the traditional oven drying method are particularly evident in the detection of graphene with low solid content. For example, for a slurry with a solid content of 0.1 wt.%, if a 10g sample is dried, the mass of the graphene is only 0.01g. During the actual drying process and during the collection and transfer of the graphene solids after drying, nano-graphene powders are prone to mass loss due to electrostatic adsorption and scattering. Furthermore, the minimum readability of conventional analytical balances is 0.1mg, and errors are also present in the weighing process, ultimately leading to large deviations in the solid content test results. Increasing the sample size to 100 g to reduce errors can reduce errors in the sample drying, transfer, and weighing processes. However, the evaporation time of high-boiling-point solvents (such as NMP and DMF) will be as long as tens of hours, which is extremely time-consuming and energy-intensive.

[0004] In view of the problems of large test error, long time and low efficiency in the solid content test process of low solid content graphene slurry using the traditional oven method, there is an urgent need to develop a simple, fast, accurate and efficient graphene solid content test method suitable for low solid content graphene slurry system. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting the solid content of graphene slurry based on the coordination adsorption of transition metal oxides to address the above-mentioned problems. This method realizes selective adsorption and enrichment of graphene through the coordination bonding effect of transition metal oxides and graphene oxygen-containing functional groups. Combined with the high-precision measurement advantages of high-temperature element analyzers, it effectively solves the technical difficulties of traditional oven drying method in the detection of low-concentration graphene slurry, such as large weighing error, long time consumption, and poor anti-interference ability. It is particularly suitable for high-precision detection of ultra-low solid content slurry, and meets the needs of fast and accurate detection of low-solid content graphene slurry.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a method for detecting the solid content of graphene slurry based on transition metal oxide coordination adsorption, comprising the following steps:

[0007] (1) Graphene slurry pretreatment: The graphene slurry is fully stirred and ultrasonically treated to uniformly disperse the graphene in the graphene slurry in the solvent to obtain a uniformly dispersed graphene slurry;

[0008] (2) Adsorption treatment: Weigh a uniformly dispersed graphene slurry with a mass of m0, add an excess of transition metal oxide, stir evenly and then heat. Through the coordination bonding between the transition metal oxide and the oxygen-containing functional groups of the graphene, the graphene is completely adsorbed on the surface of the transition metal oxide. After the reaction is completed, the upper layer is a clear liquid and the lower layer forms a composite precipitate;

[0009] (3) solid-liquid separation and drying: remove the supernatant, dry the composite precipitate, weigh the total mass after drying, record it as m1, and take a small amount of the uniformly dispersed graphene slurry obtained in step (1) and dry it to obtain pure graphene solid;

[0010] (4) Carbon analysis: Randomly sample a portion of the composite precipitate after drying in step (3) and measure the carbon content in the sample, which is recorded as C1%. In addition, measure the carbon content in the pure graphene solid in step (3), which is recorded as C2%. If the carbon content of the graphene powder is known, the step of measuring the carbon content C2% in the pure graphene solid can be omitted.

[0011] (5) Calculation of solid content: Calculate the solid content in the graphene slurry according to the following formula:

[0012]

[0013] The method for detecting the solid content of graphene slurry of the present invention can be applied to determine the solid content of graphene slurries of different specifications.

[0014] Preferably, the graphene contains oxygen-containing functional groups, and the oxygen content thereof is 0.1-50 wt.%.

[0015] Preferably, the solvent in the graphene slurry is water, ethanol, N,N-dimethylformamide (DMF) or N-methylpyrrolidone (NMP).

[0016] Preferably, the minimum amount of transition metal oxide added in step (2) is to ensure that all graphene can be coordinated, adsorbed and precipitated with the transition metal oxide, that is, the supernatant is in a clear state.

[0017] Preferably, the transition metal oxide in step (2) is one or more of Fe, Co, Ni, Cu, Mn, and Ti metal oxides, and the carbon content of the transition metal oxide is zero, and the particle size thereof is 0.01-50 μm.

[0018] Preferably, the heating temperature in step (2) is 50-100° C., and the heating time is 5 minutes to 30 minutes.

[0019] Preferably, the specific operation of drying in step (3) is: the composite precipitate after solid-liquid separation is dried under inert atmosphere protection or vacuum environment, and the drying temperature is close to the boiling point of the solvent, but lower than the boiling point of the solvent. The closer the temperature is to the boiling point of the solvent, the faster the drying speed. This method can shorten the drying time to 5-30 minutes.

[0020] Preferably, the amount of graphene slurry taken in step (3) satisfies that the weight of pure graphene solid obtained after drying is greater than 10 mg; and the mass of the composite precipitate sample taken in step (4) is greater than 30 mg.

[0021] Preferably, in step (4), a high-temperature element analyzer is used to determine the carbon content, and the high-temperature element analyzer is a high-temperature combustion type element analyzer to ensure the accuracy of the carbon element determination in the sample.

[0022] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0023] (1) The method for detecting the solid content of graphene slurry provided by the present invention solves the problem of loss during drying and transfer of nanographene powder: in traditional methods, nanographene loses mass after drying due to physical effects such as electrostatic adsorption and scattering. The present invention uses the coordination bonding between transition metal oxides and graphene oxygen-containing functional groups (carboxyl, hydroxyl, etc.) to firmly adsorb graphene on the surface of metal oxides to form a composite precipitate, thereby achieving efficient enrichment and fixation of graphene. After enrichment, the quality of the composite of graphene and metal oxide is significantly improved, and the error amplification effect caused by trace loss during the graphene transfer process is completely avoided, thereby significantly improving the detection reliability of low-solid-content graphene slurry.

[0024] (2) The method for detecting the solid content of graphene slurry provided by the present invention greatly reduces the error of micro-weighing and realizes high-precision detection: the traditional method directly weighs the trace amount of graphene (such as 0.01g) after drying. Due to the precision limit of conventional analytical balance (±0.1mg), the calculated result of solid content has a large deviation. The present invention uses the composite precipitate formed after the adsorption of transition metal oxides to amplify the mass of the sample to be tested to the high confidence interval of the conventional balance, so that the weighing error rate is significantly reduced. In addition, the high-temperature element analyzer can realize the high-precision determination of the carbon content in the composite precipitate. This method transforms the defect of "directly weighing trace graphene" in the traditional process into a technical combination of "weighing large mass composite + precise carbon analysis", which significantly reduces the comprehensive error and is particularly suitable for high-precision detection of ultra-low solid content slurry.

[0025] (3) The method for detecting the solid content of graphene slurry provided by the present invention significantly shortens the processing time of high-boiling-point solvents: For slurries with high-boiling-point solvents such as NMP and DMF, the traditional oven drying method requires dozens of hours to obtain sufficient dry graphene powder for weighing. The present invention reduces the volume of the solvent to be dried by more than 95% through the rapid coordination precipitation of transition metal oxides and the rapid solid-liquid separation by pouring the supernatant. Combined with high-temperature rapid drying in an inert atmosphere or vacuum environment, the drying time is shortened to 5-30 minutes, which is significantly more efficient than traditional methods and also significantly reduces energy consumption.

[0026] (4) The present invention achieves efficient enrichment and uniform adsorption of graphene through coordinated adsorption. This not only avoids the mass loss caused by physical effects such as electrostatic adsorption and scattering of nanopowders during drying and sample transfer in traditional methods, but also significantly shortens the evaporation time of high-boiling-point solvents in traditional methods. It also amplifies trace amounts of graphene to a measurable range. This method is applicable to various solvent systems such as water, ethanol, DMF, and NMP, providing a simple, rapid, accurate, and efficient detection solution for solid content testing of low-concentration graphene slurries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a graphene / NMP slurry with a solid content of 0.1 wt.% in the embodiment.

[0028] Figure 2 This is an SEM image of nickel oxide transition metal oxide coordinated and adsorbed on graphene in the example. DETAILED DESCRIPTION

[0029] The present invention provides a method for detecting the solid content of a graphene slurry based on coordination adsorption of a transition metal oxide, comprising the following steps:

[0030] (1) Pre-treating the graphene slurry: uniformly dispersing the graphene in the slurry in the solvent by mechanical stirring and ultrasonic treatment (ultrasonic power 100-500 W, frequency 20-40 kHz, treatment time 5-20 minutes), ensuring sufficient contact in the subsequent adsorption process, and obtaining a uniformly dispersed graphene slurry; wherein the solvent of the graphene slurry is water, ethanol, DMF or NMP;

[0031] (2) Adsorption treatment: Weigh a uniformly dispersed graphene slurry with a mass of m0, add an excess of transition metal oxide, wherein the transition metal oxide is one or more of Fe, Co, Ni, Cu, Mn, and Ti metal oxides, and the carbon content of the transition metal oxide is zero, and the particle size is 0.01-50 μm, and stir the reaction at 50-90° C. for 5 to 30 minutes; in this step, the metal active sites on the surface of the transition metal oxide and the oxygen-containing functional groups (carboxyl, hydroxyl, epoxy) in the graphene form a composite precipitate through coordination bonding; the minimum amount of transition metal oxide added is to ensure that all graphene can be coordinated, adsorbed, and precipitated with the transition metal oxide, and the final supernatant is clear as the judgment standard;

[0032] (3) Solid-liquid separation and drying: remove the supernatant by decanting, centrifuging or filtering to achieve solid-liquid separation; then dry the separated composite precipitate in an inert atmosphere or vacuum environment, and set the drying temperature to be close to the boiling point of the solvent but lower than the boiling point of the solvent (such as 70°C for ethanol slurry). This method can shorten the drying time to 5-30 minutes; weigh the total mass of the composite precipitate after drying, recorded as m1; and take a small amount of uniformly dispersed graphene slurry separately, and obtain pure graphene solid after drying. The amount of graphene slurry taken should be based on the weight of the pure graphene solid obtained after drying being greater than 10 mg.

[0033] (4) Carbon element analysis: Randomly take samples with a mass greater than 30 mg from the dried composite precipitate and measure the carbon content in the samples using a high-temperature combustion elemental analyzer, which is recorded as C1%. In addition, measure the carbon content in the pure graphene solid obtained in step (3), which is recorded as C2%.

[0034] (5) Calculation of solid content: The solid content of graphene in the graphene slurry is calculated by the formula x = (m1×C1%) / (m0×C2%)×100%. The graphene slurry solid content detection method described in the present invention can be applied to determine the solid content of graphene slurries of different specifications.

[0035] In order to express the present invention more clearly, the present invention is further described below through specific examples.

[0036] Example 1:

[0037] This example verifies the solid content of a graphene slurry with a nominal solid content of 0.1 wt.%, and the specific method is as follows:

[0038] (1) Graphene slurry pretreatment: 100 g of graphene slurry with a nominal solid content of 0.1 wt.%, wherein the solvent used in the graphene slurry is NMP (referred to as graphene / NMP slurry), is placed in a beaker and ultrasonically treated for 30 minutes (power 300 W, frequency 40 kHz) to ensure that the graphene in the slurry is uniformly dispersed in the solvent, and a uniformly dispersed graphene / NMP slurry is obtained, as shown in FIG. Figure 1 As shown;

[0039] (2) Adsorption treatment: Weigh 10 g of uniformly dispersed graphene / NMP slurry (denoted as m0 = 10 g), add 2 g of nickel oxide (NiO, particle size 20 μm, carbon content 0%), transfer the mixture to a constant temperature magnetic stirrer, and stir at 90 ° C and 500 rpm for 30 minutes. After the reaction is completed, the nickel oxide and the oxygen-containing functional groups of the graphene form a uniform coating through coordination bonding (the corresponding SEM image is shown in FIG). Figure 2 As shown), the supernatant is clear, indicating that all graphene can coordinate and adsorb with nickel oxide;

[0040] (3) Solid-liquid separation and drying: The supernatant was removed by pouring, and the precipitate was transferred to a vacuum drying oven and dried at 190°C for 30 minutes under nitrogen protection. The mass of the dried composite was m1 = 2.012 g. At the same time, 5 g of the uniformly dispersed graphene / NMP slurry was vacuum dried at 190°C for 30 minutes to obtain pure graphene solid for determination of C2%.

[0041] (4) Carbon analysis: A 0.2 g sample was randomly taken from the dried composite precipitate, and the carbon content (C1%) in the sample was determined to be 0.341% using a CS-3000G dual-combustion furnace infrared carbon-sulfur analyzer manufactured by Gangyan NAK Testing Technology Co., Ltd. The carbon content (C2%) in the dried pure graphene solid sample was determined to be 68.251%.

[0042] (5) Calculation of solid content: The solid content of the graphene / NMP slurry was calculated according to the formula: x = (2.012 g × 0.341%) / (10 g × 68.251%) × 100% = 0.101%.

[0043] Example 2:

[0044] This example verifies the solid content of a graphene slurry with a nominal solid content of 3 wt.%, and the specific method is as follows:

[0045] (1) Graphene slurry pretreatment: 70 g of graphene slurry with a nominal solid content of 3 wt.%, wherein the solvent used in the graphene slurry is DMF (referred to as graphene / DMF slurry), is placed in a beaker and ultrasonically treated for 30 min (power 600 W, frequency 40 kHz) to uniformly disperse the graphene in the slurry in the solvent, thereby obtaining a uniformly dispersed graphene / DMF slurry;

[0046] (2) Adsorption treatment: Weigh 30 g of uniformly dispersed graphene / DMF slurry (denoted as m0 = 30 g), add 40 g of manganese oxide (MnO2, particle size 20 μm, carbon content 0%), transfer the mixed solution to a constant temperature magnetic stirrer, and stir at 800 rpm at 100°C for 5 minutes. After the reaction, MnO2 and the oxygen-containing functional groups of graphene form a composite precipitate through coordination bonding, and the supernatant is clear, indicating that all graphene can be coordinated and adsorbed with MnO2.

[0047] (3) Solid-liquid separation and drying: The supernatant liquid was removed by pouring, and the composite precipitate was transferred to a vacuum drying oven and dried at 140°C for 10 minutes under a vacuum environment. The mass of the dried composite was m1 = 30.615 g. At the same time, 5 g of the uniformly dispersed graphene / DMF slurry was taken and dried separately at 70°C for 5 minutes in a vacuum to obtain pure graphene solid for the determination of C2%.

[0048] (4) Carbon analysis: A 0.2 g sample was randomly taken from the dried composite precipitate and the carbon content of the sample was measured using a CS-3000G dual combustion furnace infrared carbon-sulfur analyzer manufactured by Gangyan NAK Testing Technology Co., Ltd. The carbon content C1% in the sample was 2.031%. In addition, the carbon content C2% in the pure graphene solid sample after drying alone was measured to be 68.34%.

[0049] (5) Calculation of solid content: The solid content of the graphene / DMF slurry was calculated according to the formula: =(30.615g×2.031%) / (30g×68.34%)×100%=3.033%.

[0050] Example 3:

[0051] This example verifies the solid content of a graphene slurry with a nominal solid content of 0.5 wt.%, and the specific method is as follows:

[0052] (1) Graphene slurry pretreatment: 50 g of graphene slurry with a nominal solid content of 0.5 wt.%, in which the solvent used for the graphene slurry is water (referred to as graphene / water slurry), is placed in a beaker and ultrasonically treated for 20 min (power 250 W, frequency 40 kHz) to ensure that the graphene in the slurry is uniformly dispersed in the solvent, thereby obtaining a uniformly dispersed graphene / water slurry;

[0053] (2) Adsorption treatment: Weigh 20 g of uniformly dispersed graphene / water slurry (denoted as m0 = 20 g), add 5 g of cobalt trioxide (Co3O4, particle size 50 μm, carbon content 0%), transfer the mixed solution to a constant temperature water bath stirrer, and stir at 400 rpm at 70°C for 20 minutes. After the reaction is completed, Co3O4 and the oxygen-containing functional groups of graphene form a composite precipitate through coordination bonding, and the supernatant is clear, indicating that all graphene can be coordinated and adsorbed with Co3O4.

[0054] (3) Solid-Liquid Separation and Drying: The supernatant was removed by decanting, and the precipitate was transferred to a vacuum drying oven and dried at 90°C for 20 minutes under nitrogen. The mass of the dried composite, m1, was 5.095 g. Simultaneously, 5 g of the uniformly dispersed graphene / water slurry was vacuum dried at 90°C for 20 minutes to obtain pure graphene solid for C2% determination.

[0055] (4) Carbon analysis: A 0.2 g sample was randomly taken from the dried composite precipitate and the carbon content of the sample was measured using a CS-3000G dual-combustion furnace infrared carbon-sulfur analyzer manufactured by Gangyan NAK Testing Technology Co., Ltd. The carbon content C1% was 1.501%. In addition, the carbon content of the pure graphene solid sample after drying was measured to be C2% = 75.342%.

[0056] (5) Calculation of solid content: The solid content of the graphene / water slurry was calculated according to the formula: x = (5.095 g × 1.501%) / (20 g × 75.342%) × 100% = 0.508%.

[0057] Example 4:

[0058] This example verifies the solid content of a graphene slurry having a nominal solid content of 1.5 wt.%, and the specific method is as follows:

[0059] (1) Graphene slurry pretreatment: 80 g of graphene slurry with a nominal solid content of 1.5 wt.%, wherein the solvent used in the graphene slurry is ethanol (referred to as graphene / ethanol slurry), is placed in a beaker and ultrasonically treated for 25 min (power 350 W, frequency 40 kHz) to uniformly disperse the graphene in the slurry in the solvent, thereby obtaining a uniformly dispersed graphene / ethanol slurry;

[0060] (2) Adsorption treatment: 30 g of uniformly dispersed graphene / ethanol slurry (denoted as m0 = 30 g) was weighed, 10 g of copper oxide (CuO, particle size 30 μm, carbon content 0%) was added, and the mixture was transferred to a constant temperature magnetic stirrer and stirred at 600 rpm at 50 ° C for 30 minutes. After the reaction, CuO and the oxygen-containing functional groups of graphene formed a composite precipitate through coordination bonding, and the supernatant was clear, indicating that all graphene could be coordinated and adsorbed with copper oxide.

[0061] (3) Solid-liquid separation and drying: The supernatant liquid was removed by pouring, and the composite precipitate was transferred to a vacuum drying oven and dried at 70°C for 5 minutes under vacuum. The mass of the dried composite was m1 = 10.458 g. At the same time, 8 g of the uniformly dispersed graphene / ethanol slurry was taken and dried separately at 70°C for 5 minutes under vacuum to obtain pure graphene solid for the determination of C2%.

[0062] (4) Carbon analysis: A 0.25 g sample was randomly taken from the dried composite precipitate and the carbon content of the sample was measured using a CS-3000G dual-combustion furnace infrared carbon-sulfur analyzer manufactured by Gangyan NAK Testing Technology Co., Ltd. The carbon content C1% in the sample was 3.02%. In addition, the carbon content C2% in the pure graphene solid sample after drying alone was measured to be 69.82%.

[0063] (5) Calculation of solid content: The solid content of the graphene / ethanol slurry was calculated according to the formula: =(10.458g×3.02%) / (30g×69.82%)×100%=1.508%.

[0064] Example 5:

[0065] This example verifies the solid content of a graphene slurry having a nominal solid content of 1.5 wt.%, and the specific method is as follows:

[0066] (1) Graphene slurry pretreatment: 70 g of graphene slurry with a nominal solid content of 1.5 wt.%, wherein the solvent used in the graphene slurry is ethanol (referred to as graphene / ethanol slurry), is placed in a beaker and ultrasonically treated for 25 min (power 350 W, frequency 40 kHz) to uniformly disperse the graphene in the slurry in the solvent, thereby obtaining a uniformly dispersed graphene / ethanol slurry;

[0067] (2) Adsorption treatment: Weigh 40 g of uniformly dispersed graphene / ethanol slurry (denoted as m0 = 40 g), add 20 g of iron oxide (Fe3O4, particle size 30 μm, carbon content 0%), transfer the mixed solution to a constant temperature magnetic stirrer, and stir at 800 rpm at 70°C for 5 minutes. After the reaction, Fe3O4 and the oxygen-containing functional groups of graphene form a composite precipitate through coordination bonding, and the supernatant is clear, indicating that all graphene can be coordinated and adsorbed with iron oxide.

[0068] (3) Solid-liquid separation and drying: The supernatant liquid was removed by pouring, and the composite precipitate was transferred to a vacuum drying oven and dried at 70°C for 5 minutes under a vacuum environment. The mass of the dried composite was m1 = 20.615 g. At the same time, 8 g of the uniformly dispersed graphene / ethanol slurry was taken and dried separately at 70°C for 5 minutes in a vacuum environment to obtain pure graphene solid for the determination of C2%.

[0069] (4) Carbon analysis: A 0.2 g sample was randomly taken from the dried composite precipitate and the carbon content of the sample was measured using a CS-3000G dual combustion furnace infrared carbon-sulfur analyzer manufactured by Gangyan NAK Testing Technology Co., Ltd. The carbon content C1% in the sample was 2.52%. In addition, the carbon content C2% in the pure graphene solid sample after drying alone was measured to be 88.12%.

[0070] (5) Calculation of solid content: The solid content of the graphene / ethanol slurry was calculated according to the formula: =(20.615g×2.52%) / (40g×88.12%)×100%=1.474%.

[0071] It can be seen from the above embodiment that the relative error of the solid content in the graphene slurry measured in this embodiment is less than 2% compared with its calibration value, indicating that the graphene slurry solid content detection method provided by the present invention greatly reduces the weighing error and achieves high-precision detection.

[0072] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for detecting solid content of graphene slurry based on transition metal oxide coordination adsorption, characterized in that: The following steps are involved: (1) Graphene slurry pretreatment: The graphene slurry is fully stirred and ultrasonically treated to obtain a uniformly dispersed graphene slurry; (2) Adsorption treatment: Weigh a uniformly dispersed graphene slurry with a mass of m0, add an excess of transition metal oxide, stir evenly and heat to react. After the reaction is completed, the upper layer is a clear liquid and the lower layer forms a composite precipitate; (3) solid-liquid separation and drying: removing the supernatant liquid, drying the composite precipitate, weighing the total mass after drying as m1, and taking a small amount of the graphene slurry uniformly dispersed in step (1) and drying it to obtain pure graphene solid; (4) Carbon analysis: Randomly sample a portion of the composite precipitate after drying in step (3) and measure the carbon content in the sample, which is recorded as C1%. In addition, measure the carbon content in the pure graphene solid obtained in step (3), which is recorded as C2%. (5) Calculation of solid content: The solid content in the graphene slurry is calculated according to the following formula:

2. The method according to claim 1, characterized in that The graphene in the graphene slurry contains oxygen-containing functional groups, and the oxygen content thereof is 0.1-50 wt.%.

3. The method according to claim 1, characterized in that The solvent in the graphene slurry is water, ethanol, DMF or NMP.

4. The method according to claim 1, wherein The minimum amount of transition metal oxide added in step (2) is to ensure that all graphene can be coordinated, adsorbed and precipitated with the transition metal oxide, that is, the supernatant is in a clear state.

5. The method according to claim 1, wherein The transition metal oxide in step (2) is one or more of Fe, Co, Ni, Cu, Mn, and Ti metal oxides, and the carbon content of the transition metal oxide is zero, and the particle size is 0.01-50 μm.

6. The method according to claim 1, characterized in that In step (2), the heating temperature is 50-100° C., and the heating time is 5 minutes to 30 minutes.

7. The method according to claim 1, characterized in that The specific operation of drying in step (3) is: the composite precipitate after solid-liquid separation is dried under the protection of an inert atmosphere.

8. The method according to claim 1, characterized in that The amount of graphene slurry taken in step (3) satisfies that the weight of pure graphene solid obtained after drying is greater than 10 mg; the mass of the composite precipitate sample taken in step (4) is greater than 30 mg.

9. The method according to claim 1, characterized in that In step (4), a high-temperature element analyzer is used to determine the carbon content, and the high-temperature element analyzer is a high-temperature combustion type element analyzer.

Images