Preparation method of {Mo132} / rGA electrode material

Abstract

The invention relates to a preparation method of {Mo132} polyacid cluster and reduced graphene oxide composite aerogel ({Mo132} / rGA), and belongs to the technical field of electrode materials. The {Mo132} / rGA-6 has a high specific capacitance of 279.8 F / g under a current density of 1A / g. And 92% of initial capacitance is reserved after 5000 times of cyclic charging and discharging under the current density of 5A / g, so that the material has excellent cycle performance. The method comprises the following steps: mixing graphene oxide with deionized water to prepare a graphene suspension, adding {Mo132} polyacid clusters into the graphene suspension, and carrying out hydrothermal reaction and freeze drying to obtain {Mo132} / rGA. The preparation process is simple and convenient, and the obtained product has the advantages of high specific surface area, high specific capacitance, excellent cycle performance and the like, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to a preparation method of a {Mo 132} / rGA electrode material, belonging to the technical field of electrode materials. Background Art

[0002] With the rapid development of technology, the demand for efficient energy storage devices is increasing day by day. As a new type of energy storage device, supercapacitors have attracted much attention due to their high power density, fast charge and discharge, long cycle life and other advantages.

[0003] In the research of supercapacitors, electrode materials play a crucial role. Although traditional electrode materials such as carbon materials and metal oxides meet some requirements to a certain extent, there are still some limitations. For example, the specific capacitance of carbon materials is relatively low, and the cycle stability of metal oxides needs to be improved.

[0004] Polyoxometalates (POMs) have rich redox properties, so they are ideal candidates for realizing enhanced pseudocapacitive behavior in supercapacitors (SCs), and show great potential in fields such as catalysis and energy storage. We fabricated a Keplerate-type high-nuclear molybdenum cluster {Mo 132} ({Mo 132} polyoxoanion cluster is (NH 4 ) 42 [Mo VI 72 Mo V 60 O 372 (CH 3 COO) 30 (H 2 O) 72 ). The {Mo 132} polyoxoanion cluster has a hollow core-shell structure, which is composed of 12 pentagonal [Mo VI 6 units and 30 [Mo V 2 linkers to form a sphere, and is further stabilized by acetate ligands. And the {Mo 132} polyoxoanion cluster has 20 nanoscale windows, which not only means that redox reactions can occur at the interface of the electrolyte and the electrode material, but also makes the reaction more in-depth because electrolyte ions can easily enter through the channels of the structure. At the same time, {Mo 132} has a high electronegativity, which can generate a strong electrostatic effect with the cations in the electrolyte, significantly improving the ion transport efficiency of the electrode material, and greatly accelerating the charge transfer rate, making the supercapacitor have more excellent charge and discharge performance.

[0005] Graphene-based aerogel (GA) is loose and porous, and itself has unique properties such as high specific surface area, high porosity, and excellent chemical stability. When used as an electrode material for supercapacitors, it exhibits a unique structure and remarkable characteristics. Structurally, it constructs a three-dimensional continuous porous network from graphene sheets, and the sheets are interconnected to form abundant and connected pores, with most pore diameters in the nanometer range. This structure endows it with a high specific surface area, providing a large number of active sites for charge storage and greatly enhancing the capacitance performance. The high porosity is conducive to the rapid transmission and diffusion of electrolyte ions, shortening the ion migration path and accelerating the charge and discharge process. Its good electrical conductivity ensures efficient electron transmission, reduces resistance, and improves the rate performance of the electrode material. Moreover, graphene-based aerogel has excellent chemical stability and mechanical flexibility, and can maintain structural stability during multiple charge and discharge cycles, extending the service life of supercapacitors. This graphene-based composite aerogel has excellent electrochemical properties and has significant advantages in adsorption and separation materials, long-life fast-charging batteries, and flexible sensing materials.

[0006] Combining {Mo 132} polyoxometalate clusters with graphene-based aerogel and applying them to supercapacitors is expected to give full play to the advantages of both and overcome the deficiencies of traditional electrode materials. {Mo 132} polyoxometalate clusters can provide abundant redox active sites and increase the specific capacitance of the electrode material. Graphene-based aerogel can provide a fast channel for the transmission of electrons and ions, while enhancing the mechanical stability of the electrode. However, at present, there is little research on the application of {Mo 132} polyoxometalate clusters and reduced graphene oxide-based composite aerogel in supercapacitors, and there are problems such as complex preparation processes, low performance, and insufficient stability, which need to be further studied and explored in depth to achieve their wide application in the field of supercapacitors. Summary of the Invention

[0007] The present invention aims to develop a {Mo 132} / rGA applied to electrode materials. By optimizing the material properties, it has a high electrical conductivity to promote rapid electron transmission, while reducing resistance and energy loss. Explore whether it is possible to maintain high cycle stability while significantly increasing the specific capacitance of the electrode material, and provide an innovative preparation method for {Mo 132} polyoxometalate clusters and reduced graphene oxide-based composite aerogel materials that better meet the requirements of high-performance supercapacitors and other electrochemical energy storage devices.

[0008] The present invention uses reduced graphene oxide as the matrix and {Mo 132} as the active component, and prepares {Mo 132} / rGA by a hydrothermal method. This method includes the following steps:

[0009] Step 1: Preparation of {Mo 132} polyoxometalate clusters

[0010] Add hydrazine sulfate to an aqueous solution of ammonium molybdate tetrahydrate and ammonium acetate, stir magnetically, then add acetic acid. The reaction solution turns green and is stored in an open conical flask. After standing at room temperature for 4 days, wash the reddish-brown crystals with 90% ethanol until the solution is colorless, and finally dry in air to obtain {Mo 132} polyoxometalate clusters.

[0011] Step 2: Preparation of {Mo 132} / rGA

[0012] Add graphene oxide to deionized water and sonicate using a cell disruptor for 5 minutes each time. After the suspension cools, sonicate again, for a total of three times, to obtain a graphene oxide suspension. Add {Mo 132} polyoxometalate clusters to the obtained graphene oxide suspension; sonicate for 15 minutes, pour the mixed solution into a reaction kettle, and react at 180 °C for 12 hours. Freeze-dry the obtained hydrogel at -48 °C for 24 hours to obtain {Mo 132} / rGA;

[0013] Step 3: Preparation of electrode material:

[0014] Mix the obtained {Mo 132} / rGA with conductive carbon black and polyvinylidene fluoride by grinding evenly. Subsequently, add N-methylpyrrolidone dropwise to the mixed powder. Then weigh a piece of nickel foam, evenly coat the obtained black mixture on a clean and dry nickel foam sheet, place the nickel foam with the electrode material in an oven at 60 °C and dry for 24 hours, and then press under a pressure of 10 MPa.

[0015] Preferably, the acetic acid concentration in Step 1 is 50%.

[0016] Preferably, the graphene oxide in Step 2 is prepared by the improved Hummers method.

[0017] Preferably, the concentration of the graphene oxide suspension in Step 2 is 2 mg / mL.

[0018] More preferably, the mass ratio of {Mo 132} polyoxometalate clusters to graphene oxide in Step 2 is 1:4 - 1:8.

[0019] Preferably, the mass ratio of {Mo 132} / rGA to conductive carbon black and polyvinylidene fluoride in Step 3 is 8:1:1.

[0020] Preferably, the addition amount of N-methylpyrrolidone in Step 3 is 60 μL.

[0021] Advantages of the present invention:

[0022] I. The prepared {Mo 132} / rGA-6 of the present invention increases the redox active sites and can perform multi-electron transfer reactions, which enables it to store a large amount of charge, thus providing a high specific capacitance for supercapacitors.

[0023] II. The prepared {Mo 132} / rGA-6 of the present invention has the characteristics of hierarchical porosity and a large specific surface area, which is beneficial to the transport of electrolyte ions in the electrolyte and improves the electrochemical performance. After testing, it has a high specific capacitance of 279.8 F / g at 1 A / g.

[0024] III. The prepared {Mo 132} / rGA-6 of the present invention has good cycle stability. It can be charged and discharged 5000 times at a current density of 5 A / g and retains 92% of the initial capacitance. This structural stability enables the electrode material to withstand multiple charge and discharge cycles without obvious structural damage, thus ensuring the cycle stability of the supercapacitor. Description of the drawings

[0025] Figure 1 Structural diagram of the {Mo 132} polyoxometalate cluster;

[0026] Figure 2 SEM images of {Mo 132} / rGA-6, (a) SEM image of {Mo132} / rGA-4, (b) SEM image of {Mo132} / rGA-6, (c) SEM image of {Mo132} / rGA-8;

[0027] Figure 3 X-ray diffraction pattern of {Mo 132} / rGA;

[0028] Figure 4 Discharge curve of the composite electrode material at a current density of 1 A / g

[0029] Figure 5 Electrochemical performance diagram of {Mo 132} / rGA-6; Detailed implementation manners

[0030] Example 1

[0031] Step 1: Preparation of the {Mo 132} polyoxometalate cluster

[0032] Add 0.8 g of hydrazine sulfate to an aqueous solution (250 mL) of 5.6 g of ammonium molybdate tetrahydrate and 12.5 g of ammonium acetate. Then stir for 10 minutes, and subsequently add 83 mL of acetic acid with a concentration of 50%. The reaction solution is green and stored in an open 500 mL conical flask at a temperature of 20 °C. After 4 days, wash the reddish-brown crystals with 90% ethanol and finally dry them in air to obtain {Mo 132} polyoxometalate clusters.

[0033] Step 2: Preparation of {Mo 132} / rGA

[0034] Mix 30 mg of graphene oxide with 15 mL of deionized water, and perform ultrasonic treatment using a cell disruptor for 5 minutes each time. After the suspension cools, perform ultrasonic treatment again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. Add 7.5 mg of {Mo 132} polyoxometalate clusters to the obtained graphene oxide suspension; perform ultrasonic treatment for 15 minutes, pour the mixed solution into a reaction kettle, react at 180 °C for 12 h, and freeze-dry the obtained hydrogel at -48 °C for 48 h to obtain {Mo 132} / rGA-4;

[0035] Step 3: Preparation of electrode material:

[0036] Mix the obtained {Mo 132} / rGA-4 with conductive carbon black and polyvinylidene fluoride by grinding evenly. Subsequently, add N-methylpyrrolidone dropwise to the mixed powder. Then weigh a piece of nickel foam, evenly coat the obtained black mixture on a clean and dry nickel foam sheet, place the nickel foam with the electrode material in an oven at 60 °C and dry for 24 h, and then press at a pressure of 10 MPa.

[0037] Example 2

[0038] Step 1: Preparation of {Mo 132} polyoxometalate clusters

[0039] Add 0.8 g of hydrazine sulfate to an aqueous solution (250 mL) of 5.6 g of ammonium molybdate tetrahydrate and 12.5 g of ammonium acetate. Then stir for 10 minutes, and subsequently add 83 mL of acetic acid with a concentration of 50%. The reaction solution is green and stored in an open 500 mL conical flask at a temperature of 20 °C. After 4 days, wash the reddish-brown crystals with 90% ethanol and finally dry them in air to obtain {Mo 132} polyoxometalate clusters.

[0040] Step 2: Preparation of {Mo 132} / rGA

[0041] Mix 30 mg of graphene oxide with 15 mL of deionized water, and use a cell crusher for ultrasonic treatment for 5 minutes each time. After the suspension cools down, perform ultrasonic treatment again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. Add 6 mg of {Mo 132} polyoxometalate clusters to the obtained graphene oxide suspension; perform ultrasonic treatment for 15 minutes, pour the mixed solution into a reaction kettle, and react at 180 °C for 12 hours. The obtained hydrogel is freeze-dried at -48 °C for 48 hours to obtain {Mo 132} / rGA-5;

[0042] Step 3: Preparation of electrode material:

[0043] Mix the obtained {Mo 132} / rGA-5 with conductive carbon black and polyvinylidene fluoride by grinding evenly. Subsequently, add N-methylpyrrolidone to the mixed powder. Then weigh a piece of nickel foam, evenly coat the obtained black mixture on a clean and dry nickel foam sheet, place the nickel foam with the electrode material in an oven at 60 °C and dry for 24 hours, and then press it under a pressure of 10 MPa.

[0044] Example 3

[0045] Step 1: Preparation of {Mo 132} polyoxometalate clusters

[0046] Add 0.8 g of hydrazine sulfate to an aqueous solution (250 mL) of 5.6 g of ammonium molybdate tetrahydrate and 12.5 g of ammonium acetate. Then stir for 10 minutes, and then add 83 mL of acetic acid with a concentration of 50%. The reaction solution is green and stored in an open 500 mL conical flask at a temperature of 20 °C. After 4 days, wash the reddish-brown crystals with 90% ethanol and finally dry them in the air to obtain {Mo 132} polyoxometalate clusters.

[0047] Step 2: Preparation of {Mo 132} / rGA

[0048] Mix 30 mg of graphene oxide with 15 mL of deionized water, and use a cell crusher for ultrasonic treatment for 5 minutes each time. After the suspension cools down, perform ultrasonic treatment again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. Add 5 mg of {Mo 132} polyoxometalate clusters to the obtained graphene oxide suspension; perform ultrasonic treatment for 15 minutes, pour the mixed solution into a reaction kettle, and react at 180 °C for 12 hours. The obtained hydrogel is freeze-dried at -48 °C for 48 hours to obtain {Mo 132} / rGA-6;

[0049] Step 3: Preparation of electrode material:

[0050] The obtained {Mo 132} / rGA-6 was respectively mixed and ground evenly with conductive carbon black and polyvinylidene fluoride. Subsequently, N-methylpyrrolidone was added dropwise to the mixed powder. Then, a piece of nickel foam was weighed, and the obtained black mixture was evenly coated on a clean and dry nickel foam sheet. The nickel foam with the electrode material was placed in an oven at 60 °C and dried for 24 h, and then pressed under a pressure of 10 MPa.

[0051] Example 4

[0052] Step 1: Preparation of {Mo 132} polyoxometalate clusters

[0053] 0.8 g of hydrazine sulfate was added to an aqueous solution (250 mL) of 5.6 g of ammonium molybdate tetrahydrate and 12.5 g of ammonium acetate. Then, it was stirred for 10 minutes, and subsequently 83 mL of acetic acid with a concentration of 50% was added. The reaction solution was green and stored in an open 500 mL conical flask at a temperature of 20 °C. After 4 days, the reddish-brown crystals were washed with 90% ethanol and finally dried in air to obtain {Mo 132} polyoxometalate clusters.

[0054] Step 2: Preparation of {Mo 132} / rGA

[0055] 30 mg of graphene oxide was mixed with 15 mL of deionized water and sonicated using a cell disruptor for 5 minutes each time. After the suspension cooled, it was sonicated again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. 4.28 mg of {Mo 132} polyoxometalate clusters was added to the obtained graphene oxide suspension; it was sonicated for 15 minutes, and the mixed solution was poured into a reaction kettle and reacted at 180 °C for 12 h. The obtained hydrogel was freeze-dried at -48 °C for 48 h to obtain {Mo 132} / rGA-7;

[0056] Step 3: Preparation of electrode material:

[0057] The obtained {Mo 132} / rGA-7 was respectively mixed and ground evenly with conductive carbon black and polyvinylidene fluoride. Subsequently, N-methylpyrrolidone was added dropwise to the mixed powder. Then, a piece of nickel foam was weighed, and the obtained black mixture was evenly coated on a clean and dry nickel foam sheet. The nickel foam with the electrode material was placed in an oven at 60 °C and dried for 24 h, and then pressed under a pressure of 10 MPa.

[0058] Example 5

[0059] Step 1: Preparation of {Mo 132} polyoxometalate clusters

[0060] 0.8 g of hydrazine sulfate was added to an aqueous solution (250 mL) of 5.6 g of ammonium molybdate tetrahydrate and 12.5 g of ammonium acetate. Then, it was stirred for 10 minutes, and subsequently, 83 mL of 50% acetic acid was added. The reaction solution was green and stored in an open 500 mL conical flask at a temperature of 20 °C. After 4 days, the reddish-brown crystals were washed with 90% ethanol and finally dried in air to obtain {Mo 132} polyoxometalate clusters.

[0061] Step 2: Preparation of {Mo 132} / rGA

[0062] 30 mg of graphene oxide was mixed with 15 mL of deionized water and sonicated using a cell disruptor for 5 min each time. After the suspension cooled, it was sonicated again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. 3.75 mg of {Mo 132} polyoxometalate clusters were added to the obtained graphene oxide suspension; it was sonicated for 15 min, and the mixed solution was poured into a reaction kettle and reacted at 180 °C for 12 h. The obtained hydrogel was freeze-dried at -48 °C for 48 h to obtain {Mo 132} / rGA-8;

[0063] Step 3: Preparation of electrode material:

[0064] The obtained {Mo 132} / rGA-8 was mixed and ground evenly with conductive carbon black and polyvinylidene fluoride. Subsequently, N-methylpyrrolidone was added dropwise to the mixed powder. Then, a piece of nickel foam was weighed, and the obtained black mixture was evenly coated on a clean and dry nickel foam sheet. The nickel foam with the electrode material was placed in an oven at 60 °C and dried for 24 h, and then pressed under a pressure of 10 MPa.

[0065] Example 6

[0066] Step 1: Preparation of rGA

[0067] 30 mg of graphene oxide was mixed with 15 mL of deionized water and sonicated using a cell disruptor for 5 min each time. After the suspension cooled, it was sonicated again, for a total of three times, to obtain a 2 mg / mL graphene oxide suspension. The mixed solution was poured into a reaction kettle and reacted at 180 °C for 12 h. The obtained hydrogel was freeze-dried at -48 °C for 48 h to obtain rGA;

[0068] Step 2: Preparation of electrode material:

[0069] The obtained rGA was mixed and ground evenly with conductive carbon black and polyvinylidene fluoride respectively. Subsequently, N-methylpyrrolidone was added dropwise to the mixed powder. Then a piece of nickel foam was weighed, and the obtained black mixture was evenly coated on a clean and dry nickel foam sheet. The nickel foam with the electrode material was placed in an oven at 60 °C for 24 h and then pressed under a pressure of 10 MPa.

[0070] Accompanying drawings:

[0071] As Figure 1 shown, {Mo 132} is (NH 4 ) 42 [Mo VI 72 Mo V 60 O 372 (CH 3 COO) 30 (H 2 O) 72 , with a diameter of allowing electrolyte ions to pass through. The {Mo 132} polyoxometalate cluster has a hollow core-shell structure and is composed of 12 pentagonal [Mo VI 6 units and 30 [Mo V 2 connectors to form a sphere and is further stabilized by acetate ligands. And the {Mo 132} polyoxometalate cluster has 20 nanoscale windows, which not only means that redox reactions can occur at the interface between the electrolyte and the electrode material, but also makes the reaction more in-depth because electrolyte ions can easily enter through the channels of the structure.

[0072] As Figure 2 shown, in order to explore the effect of the {Mo 132} polyoxometalate cluster on the morphology of {Mo 132} / rGA, when the mass ratio of the {Mo 132} polyoxometalate cluster to GO is 1:4, 1:6, and 1:8, the aerogels formed are respectively called {Mo 132} / rGA-4, {Mo 132} / rGA-6, and {Mo 132} / rGA-8. Scanning electron microscopy was used to observe the three groups of samples. From Figure 2 (a)-(c), it can be seen that the internal structure of the aerogel has gradually increasing pores with the increase in the content of the {Mo 132} polyoxometalate cluster, and the surface becomes wrinkled, increasing the specific surface area of the aerogel and providing abundant active sites for ion adsorption. And the {Mo 132When too many polyoxometalate clusters are added, the pores gradually decrease. This may be due to {Mo 132} The addition of excessive polyoxometalate clusters causes the graphene sheets to stack and the pores to become blocked. In summary, {Mo 132} Polyoxometalate clusters have a certain pore-expanding effect on the aerogel skeleton and can, to a certain extent, achieve controllable adjustment of the structure of the composite electrode material.

[0073] As shown by Figure 3 , the sample has two diffraction peaks assigned to the (002) and (100) crystal planes at 2θ of 24° and 43.2°, respectively, which are characteristic of amorphous carbon obtained by heteroatom doping. Obviously, the relative intensities of these two peaks decrease with the increase in the amount of dopant, indicating that the graphitization decreases with the increase in the content of {Mo 132} polyoxometalate clusters.

[0074] As shown by Figure 4 , the specific capacitances of {Mo 132} / rGA-4 to GA can be calculated from the discharge curves as 215.7, 267.5, 279.8, 243.3, 202.7, and 185.4 F / g, respectively. With the increase in the mass ratio of {Mo 132} to GO, the specific capacitance value of the sample first increases and then decreases. When the mass ratio is 1:6, the specific capacitance of {Mo 132} / rGA-6 is the largest (279.8 F / g). By comparing the specific capacitance values of {Mo 132} / rGA-7, {Mo 132} / rGA-8 with GA, it can be seen that the incorporation of {Mo 132} polyoxometalate clusters can effectively increase the specific capacitance of the material. However, when the ratio increases from 1:6 to 1:4, the specific capacitance value of the material gradually decreases.

[0075] As shown by Figure 5 , Figure 5 (a) shows the cyclic voltammetry curves at different scanning rates. Figure 5 The CV curves in (a) are all quasi-rectangular in shape, indicating that its charge storage mechanism is a standard electric double-layer capacitance, and the response current increases by approximately the same multiple with the increase in the scan rate, which further reflects its electric double-layer charge storage mechanism. Figure 5 (b) shows the galvanostatic charge-discharge curves of Example 3 at different current densities. Figure 5 The charge-discharge curves in (b) are all relatively standard triangular in shape, and the symmetry of the charge and discharge curves at the same current density is very good, which also fully demonstrates the electric double-layer energy storage mechanism of this microelectrode. After calculation, the specific capacitance is 279.8 F / g at a current density of 1 A / g. Figure 5(c) is the electrochemical impedance spectroscopy (EIS spectrum) of the electrode material in this embodiment at a frequency range of 0.01 - 1000000 Hz. Through the curve near the high-frequency region in the figure, its charge transfer resistance can be estimated to be 1.916 Ω. And in the low-frequency region, the slope value of its curve is relatively large, indicating that under the condition of small internal resistance of the electrode, electrolyte ions can quickly diffuse among the pores of the electrode material, showing the unique advantages of the carbon-based material. Figure 5 (d) is the cycling curve of the micro-supercapacitor in this embodiment at a current density of 5 A / g. It can be calculated that after 5000 cycles, the capacitance retention rate of this device is 92.15%, indicating its stable cycling performance.

[0076] The above-described embodiments only represent the implementation manners of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method of using {Mo 132 Polyoxometalate clusters and reduced graphene oxide composite aerogel ({Mo 132 } / rGA) preparation method, characterized in that Reduced graphene oxide is used as a composite material matrix, and a material with good electrochemical properties is obtained by taking advantage of its high specific surface area, excellent electrochemical conductivity and good electrochemical stability.

2. Use {Mo 132 } polyacid clusters as active components, on the one hand {Mo 132 } Polyacid clusters can provide abundant redox active sites and improve the specific capacitance of electrode materials; on the other hand, {Mo 132 The unique molecular structure of polyacid clusters enables them to have good ion transport channels. During the charge and discharge process, these channels can promote the rapid migration and diffusion of ions, greatly improving the kinetic performance of the electrode reaction.

3. The present invention is characterized in that the solution method is used to prepare {Mo 132 The preparation of the composite material by hydrothermal method is carried out at relatively low temperature and autogenous pressure, avoiding the possibility of high temperature calcination and other factors that may lead to {Mo 132 The factors that cause the destruction of the structure or performance degradation of polyacid clusters and reduced graphene oxide contribute to the maintenance of {Mo 132 The inherent characteristics of polyacid clusters and reduced graphene oxide, and graphene oxide will be reduced to graphene at a certain temperature. After freeze-drying, the composite material, conductive carbon black and polyvinylidene fluoride are mixed, N-methylpyrrolidone is used as a dispersant, and evenly applied on the nickel foam. After drying, it is pressed under a pressure of 10Mpa to obtain the electrode material.

4. Prepare as claimed in claim 3 {Mo 132 } / rGA, graphene oxide was prepared using a modified Hummers method.

5. Prepare as claimed in claim 3 {Mo 132 } / rGA, characterized in that when preparing the graphene oxide suspension, a cell crusher is used for ultrasound, each ultrasound is performed for 5 minutes, and the suspension is cooled and then ultrasound is performed again, for a total of three times. The purpose of ultrasound is to fully disperse the graphene oxide in the aqueous solution, and the graphene oxide sheets do not agglomerate. The purpose of controlling the ultrasound time is to prevent the temperature from affecting the structure of the graphene oxide.

6. Prepare as claimed in claim 5 {Mo 132 } / rGA, the concentration of graphene oxide suspension was 2 mg / mL.

7. Prepare as claimed in claim 3 {Mo 132 When preparing the composite material of} / rGA, the holding temperature is 180℃ and the holding time is 12h.

8. Prepare as claimed in claim 3 {Mo 132 } / rGA, {Mo 132 The mass ratio of polyacid clusters to graphene oxide is 1:4-1:

8.

9. Prepare as claimed in claim 3 {Mo 132 } / rGA, the composites were freeze-dried at -48 °C for 24 h.

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