A phosphonate graphene electrode material and synthesis method thereof

Abstract

The present invention discloses a phosphonate graphene electrode material and a synthesis method thereof, belonging to the field of inorganic materials and electrode synthesis. (1) chlorinated graphene, phosphite and a solvent are ultrasonically mixed; (2) a catalyst is added and reacted at a temperature of 65-166°C; (3) filtering, washing and drying the filter cake to obtain phosphonate graphene. This method introduces phosphonate esters into graphene sheets, thereby avoiding excessive accumulation of sheets and overcoming defects such as a small specific surface area of ​​graphene. The synthesized phosphonate graphene has good quality and a specific surface area of ​​700 square meters per gram or more. Since the phosphonate groups are introduced into graphene, the types of graphene are broadened. Phosphonate graphene has good electrochemical properties when used as an electrode material for supercapacitors and can be used in flame retardancy, sewage treatment, energy, materials and biomedicine. It can also be used as a drug carrier, etc., and has good application prospects.

Description

Technical Field

[0001] The present application relates to the field of supercapacitor electrode materials, and in particular to a phosphonate graphene electrode material and a synthesis method thereof. Background Art

[0002] With the rapid development of society, people's demand for energy is increasing. Problems such as water pollution, the greenhouse effect, and resource shortages caused by the overconsumption of traditional fossil fuels are becoming increasingly serious. New energy sources such as solar energy, wind energy, biomass energy, hydrogen energy, geothermal energy, and ocean energy can effectively solve energy shortages and pollution problems, but the storage of these new energy sources remains a challenge. The development of sustainable and high-performance energy storage devices is urgent. Supercapacitors, as a new type of energy storage device, have attracted widespread attention. Supercapacitors are a new type of energy storage device that lies between traditional capacitors and rechargeable batteries. They combine the energy storage characteristics of batteries with the rapid charge and discharge capabilities of capacitors.

[0003] Compared to traditional energy devices, supercapacitors offer advantages such as fast charge and discharge speeds, high energy density, and good cycling stability. Electrode materials determine the electrochemical performance of supercapacitors. Based on their energy storage mechanism, electrode materials can be divided into double-layer materials and pseudocapacitor materials. Double-layer materials offer the advantages of fast charge and discharge and good cycling stability, while pseudocapacitors offer the advantages of high specific capacitance and high energy density, but suffer from poor cycling stability.

[0004] Double-layer supercapacitors primarily store energy through the adsorption of pure electrostatic charges on the electrode surface. The electrode materials for these supercapacitors are primarily carbon materials, such as activated carbon, ordered mesoporous carbon, carbon fibers, carbon nanotubes, graphene, and graphyne. Given the broad prospects for supercapacitors in power storage, reducing the production cost of their raw materials is of great research significance. Further research is needed on electrode materials and electrodes to continuously improve their performance.

[0005] Double-layer capacitors (EDLCs) utilize ion migration, where electrons or ions form a double layer on the surface of active electrode materials. The resulting charge creates capacitance. Therefore, materials with high surface areas and porous structures are advantageous for storing more charge and accelerating electron transport. Graphene, due to its high surface area, adjustable pore structure, rich surface functional groups and defects, and environmental friendliness, has garnered widespread attention in energy storage.

[0006] Patent document CN116247166A discloses a negative electrode sheet and a method for manufacturing the same. The method used in this patent application is mainly to dope ordinary graphene with phosphorus-containing substances, which is a physical doping method. The subsequent reaction is carried out under high-energy conditions such as lasers. The preparation method is complicated. In addition, the patent document describes the reaction under water conditions, and a large amount of ferric chloride and aluminum bromide are hydrolyzed to form impurities such as ferric hydroxide and aluminum hydroxide.

[0007] A review of various literature and related patents reveals that the synthesis of graphene-based electrode materials still has some drawbacks, such as low yield, demanding synthesis conditions, difficulty in synthesis, and low processing capacity. There are currently no reports of reacting chlorinated graphene with phosphites to introduce phosphonate groups into the graphene to increase capacitor capacity and stability. Summary of the Invention

[0008] The problem to be solved by the present invention is to improve the capacity performance of graphene, thereby improving the ability of supercapacitors to store charge. Phosphorus and other groups are introduced into graphene to improve the ability of graphene to bind charge and increase stability.

[0009] The present invention provides a method for synthesizing a phosphonate graphene electrode material, comprising the following steps:

[0010] (1) Graphene chloride, phosphite and solvent are mixed and ultrasonically mixed; the preparation method of graphene chloride is as follows: first, graphene is added to a sodium hypochlorite solution and adjusted to neutral or acidic with hydrochloric acid; second, it is sealed and subjected to light reaction at a constant temperature of 20-60°C for 36-72 hours; third, graphene chloride is obtained by membrane filtration, washing and drying.

[0011] (2) Add a catalyst and react at a certain temperature;

[0012] (3) filtering, washing, and drying the filter cake to obtain a phosphonate graphene electrode material; the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and tetrahydrofuran; the catalyst is one or more of copper bromide, aluminum bromide, aluminum chloride, and ferric chloride; and the phosphite substance is one or more of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, triisopropyl phosphite, and tributyl phosphite.

[0013] Furthermore, the mass ratio of the phosphite-containing substance to the chlorinated graphene is 0.1-3:1; and the mass ratio of the catalyst to the phosphite-containing substance is 0.01-1:1.

[0014] Furthermore, in step (2), the reaction temperature is 65-166° C. and the reaction time is 5-48 hours.

[0015] The present invention provides a phosphonate graphene electrode material, which is prepared by adopting the above method.

[0016] The present invention also provides a supercapacitor made of the above electrode material. Beneficial effects

[0017] This method avoids excessive stacking of phosphonate graphene sheets during the synthesis process, overcoming drawbacks such as the low specific surface area of ​​graphene. The resulting phosphonate graphene is high-quality, with a specific surface area exceeding 700 m2 / g, and a high yield exceeding 90%. The introduction of phosphonate groups broadens the range of graphene materials, offering excellent electrical properties as an electrode material and promising applications in flame retardancy, wastewater treatment, energy, materials, and biomedicine. It can also serve as a carrier for other compounds (such as drugs), demonstrating its promising application prospects. In this application, the carbon and phosphorus in the graphene sheets directly form covalent bonds. Chlorinated graphene reacts with phosphite to produce a chemical reaction. The principle is clear, the product is distinct, and the process is simple, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the scanning electron micrograph of products T1, T2, T3, and T4;

[0019] Figure 2 is the XRD pattern of graphene T0 and each product (T1, T2, T3, T4);

[0020] Figure 3 It is the cyclic voltammogram of the symmetrical supercapacitor electrode composed of graphene T0 and each product (T1, T2, T3 and T4);

[0021] Figure 4 It is a constant current charge and discharge curve of a symmetrical supercapacitor composed of graphene T0 and each product (T1, T2, T3 and T4). DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below with reference to specific embodiments:

[0023] The self-made chlorinated graphene used in the following examples was prepared by the following method: (1) adding graphene to a sodium hypochlorite solution and adjusting the solution to neutral or acidic with hydrochloric acid; (2) sealing and irradiating the solution with light at a constant temperature of 20-60°C for 36-72 hours; and (3) filtering the solution with a membrane, washing the solution, and drying the solution to obtain the chlorinated graphene. Example 1

[0024] In a reaction kettle, homemade chlorinated graphene (40 g), trimethyl phosphite (4 g), and N,N-dimethylacetamide (200 mL) were added and ultrasonically mixed. Anhydrous copper bromide (0.04 g) was added and heated at 166°C for 48 hours. After cooling, the mixture was poured into 300 mL of water, filtered, washed, and dried at 80°C for 10 hours. This yielded 37 g of phosphonate graphene (T1). The specific surface area of ​​the phosphonate graphene was measured to be 710 m2 / g, and the phosphorus content in the phosphonate graphene was 10.3%. Example 2

[0025] In a reactor, homemade graphene chloride (80 g), triethyl phosphite (40 g), tripropyl phosphite (40 g), and tetrahydrofuran (200 mL) were added. Anhydrous aluminum bromide (40 g) and anhydrous aluminum chloride (40 g) were then added and heated at 65°C for 10 hours. After cooling, the mixture was poured into 300 mL of water. The mixture was filtered, washed, and dried at 80°C for 12 hours. This yielded 76 g of phosphonate graphene (T2). The specific surface area of ​​the phosphonate graphene was measured to be 740 m2 / g, and the phosphorus content in the phosphonate graphene was 14.1%. Example 3

[0026] In a reaction kettle, homemade chlorinated graphene (90 g), triisopropyl phosphite (80 g), and acetonitrile (20 mL) were added. Anhydrous aluminum chloride (5 g) was added and the mixture was heated at 80°C for 24 hours. After cooling, the mixture was poured into 30 mL of water. The mixture was filtered, washed, and dried at 80°C for 12 hours. This yielded 85 g of phosphonate graphene (T3). The specific surface area of ​​the phosphonate graphene was measured to be 760 m2 / g, and the phosphorus content in the phosphonate graphene was 13.6%. Example 4

[0027] In a reactor, homemade chlorinated graphene (100 g), tributyl phosphite (300 g), and N,N-dimethylformamide (200 mL) were added. Anhydrous ferric chloride (194 g) was added and heated at 150°C for 5 hours. After cooling, the mixture was poured into 400 mL of water. The mixture was filtered, washed, and dried at 80°C for 10 hours. This yielded 95 g of phosphonate graphene (T4). The specific surface area of ​​the phosphonate graphene was measured to be 700 m2 / g, and the phosphorus content in the phosphonate graphene was 13.2%.

[0028] from Figure 1 Scanning electron microscopy images show that products T1, T2, T3, and T4 have distinct layers with numerous wrinkles and twists, characteristic of single-layer and few-layer graphene. These layers are more easily accessible to electrolytes, increasing capacitor capacity.

[0029] XPS analysis of the phosphorus content of each product revealed that products T1, T2, T3, and T4 had phosphorus atomic contents of 10.3%, 14.1%, 13.6%, and 13.2%, respectively, indicating that the chlorinated graphene reacted with the phosphite. The introduction of groups into the graphene sheets prevents excessive stacking, which would otherwise hinder contact between the graphene and the electrolyte and affect the supercapacitor's capacity.

[0030] from Figure 2As can be seen in the graphene T0 diffraction peak at 27.6 degrees, corresponding to an interlayer spacing of 0.37 nanometers, which is the interlayer spacing of normal graphene. The diffraction peaks of the phosphonate graphene products T1, T2, T3, and T4 are around 25 degrees, with an interlayer spacing of approximately 0.4 nanometers. This increased interlayer spacing facilitates the entry of electrolytes between the layers, allowing for better contact between the electrolyte and graphene, thereby increasing the capacity of the supercapacitor.

[0031] Appropriate amounts of commercially available graphene (numbered T0) and the products from Examples 1-4 (numbered T1, T2, T3, and T4, respectively) were ground and ultrasonically dispersed in a small amount of alcohol. The mixture was then mixed with conductive graphite and 5% polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) was added dropwise and stirred until a uniform paste formed. The paste was evenly spread on a nickel foam sheet (1 cm × 1 cm) and dried at 100°C for 12 hours. Electrode sheets were then pressed using a tablet press at 10 MPa. The phosphonate graphene mass was controlled between 0.002 and 0.003 g. A symmetrical supercapacitor was assembled using a 0.1 mol / L Na₂SO₄ electrolyte solution and a separator.

[0032] from Figure 3 It can be seen that under the condition of 100mv / s, the cyclic voltammetry curves of the symmetrical supercapacitor electrode composed of products T1, T2, T3 and T4 and the comparison graphene T0 show that the phosphonate graphene has a high response voltage, indicating that the phosphonate graphene is more conductive and has better electrode performance.

[0033] from Figure 4 It can be seen that the symmetrical supercapacitor composed of products T1, T2, T3 and T4 and the comparison graphene T0, the constant current charge and discharge cycle shows that under the current density of 1A / g, the charge and discharge cycle of the symmetrical supercapacitor composed of products T1, T2, T3 and T4 and the comparison graphene T0 shows that phosphonate graphene has a higher specific capacitance.

Claims

1. A method for synthesizing a phosphonate graphene electrode material, characterized in that: The following steps are involved: (1) mixing graphene chloride, phosphite substance and solvent, and ultrasonically mixing; (2) Add a catalyst and react at a certain temperature; (3) filtering, washing, and drying the filter cake to obtain a phosphonate graphene electrode material; the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and tetrahydrofuran; the catalyst is one or more of copper bromide, aluminum bromide, aluminum chloride, and ferric chloride; and the phosphite substance is one or more of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, triisopropyl phosphite, and tributyl phosphite.

2. The method for synthesizing the phosphonate graphene electrode material according to claim 1, wherein The mass ratio of the phosphite-containing substance to the chlorinated graphene is 0.1-3:1; the mass ratio of the catalyst to the phosphite-containing substance is 0.01-1:

1.

3. The method for synthesizing the phosphonate graphene electrode material according to claim 2, wherein: In the step (2), the reaction temperature is 65-166° C., and the reaction time is 5-48 hours.

4. A phosphonate graphene electrode material prepared by the method according to any one of claims 1 to 3.

5. A supercapacitor made of the electrode material according to claim 4.

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