A defect-controllable oligolayer graphite nanosheet, its preparation method and application

Abstract

This invention discloses a defect-controllable oligolayer graphite nanosheet, its preparation method, and its applications. The preparation method includes: preparing oligolayer graphite nanosheets prepared by a physical method into a water-based slurry; adding a small amount of a green oxidant such as ozone or hydrogen peroxide; continuously passing the slurry through a tubular microwave reactor for oxidation under mild conditions; and finally spray drying to obtain the product. By controlling the type of oxidant and reaction conditions, defects can be controllably introduced onto the surface of the graphite sheets while maintaining the intact structure and low oxygen content. This process is suitable for large-scale green production, and the resulting oligolayer graphite nanosheets possess both high conductivity and abundant catalytically active sites. When used as an electrocatalyst for the two-electron oxygen reduction reaction to synthesize hydrogen peroxide, they exhibit high activity, high selectivity, and high stability.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a method for preparing a defect-controllable oligolayer graphite nanosheet and its application in the electrocatalytic synthesis of hydrogen peroxide. Background Technology

[0002] Due to their unique two-dimensional structure, excellent electrical and thermal conductivity, and rich surface chemical properties, oligolayer graphite nanosheets have shown great application potential in energy storage and conversion, catalysis, composite materials and other fields.

[0003] Currently, the mainstream methods for preparing oligolayer graphite nanosheets include chemical and physical methods. Chemical methods, such as the Hummers process and its improvements, utilize excess strong oxidants and strong acids to oxidize, intercalate, and exfoliate graphite. While these methods can achieve large-scale production, they severely damage the sp² conjugated structure of the graphene sheets, introducing numerous oxygen-containing functional groups and structural defects. This leads to a significant decrease in the product's electrical and thermal conductivity, and a deterioration in chemical stability; even reduction treatment cannot restore the intrinsic properties of the graphene sheets. Physical methods, such as liquid-phase ultrasonication and ball milling exfoliation, can better preserve the intrinsic structure of the graphene sheets, but they suffer from extremely high energy consumption, low yield, and uneven sheet thickness. Purely physical exfoliation products have few catalytically active sites on their surface, making subsequent functionalization modification difficult, thus limiting their application in catalysis and other fields.

[0004] Hydrogen peroxide (H2O2) is a widely used green oxidant. Its industrial production relies on the anthraquinone cycle, using organic solvents, hydrogen, oxygen, and noble metal catalysts, resulting in a complex process with high safety risks. Electrocatalytic two-electron oxygen reduction (O2) synthesis of H2O2 uses only water and oxygen as raw materials, with mild reaction conditions, a simple process, high safety, and low product impurity content, offering advantages for distributed production and ultrapure product preparation. Graphene and its derivatives, such as oligolayer graphite nanosheets, have attracted attention in the development of electrocatalysts for H2O2 synthesis due to their high O2 reduction activity. However, oligolayer graphite nanosheets prepared by traditional chemical methods contain residual manganese and other impurity metal ions, exhibiting significant four-electron O2 reduction activity, reducing the selectivity of H2O2 synthesis. Furthermore, these graphene-derived materials have high defect density, are easily oxidized and destroyed by H2O2 during long-term operation, and have poor conductivity, failing to leverage the inherent advantages of graphene. On the other hand, oligolayer graphite nanosheets prepared by purely physical methods have few surface active sites, resulting in low H2O2 synthesis efficiency, limiting their practical application potential.

[0005] Therefore, how to develop a method for preparing oligolayer graphene nanosheets that can controllably introduce active sites, is green and mild, and is suitable for large-scale production, while ensuring the integrity of the graphene sheet structure, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention overcomes the shortcomings of existing technologies by proposing a method for preparing controllable defect-rich oligolayer graphite nanosheets and their applications. The invention utilizes low-concentration, non-salt green oxidants such as ozone and hydrogen peroxide under relatively mild hydrothermal conditions to controllably introduce a small number of defects onto the surface of oligolayer graphite nanosheets through an oxidation reaction. The reaction mixture is then directly spray-dried without separation, thereby efficiently preparing oligolayer graphite nanosheets with intact structure, low oxygen content, controllable defect numbers, good conductivity, and high catalytic activity.

[0007] To achieve the above objectives, the following technical solution is adopted: A method for preparing defect-controllable oligolayer graphite nanosheets includes the following steps: Step 1: Mix the oligolayer graphite nanosheets prepared by physical method with water to prepare a fluid slurry, which facilitates subsequent mixing and feeding; Step 2: Add a non-salt oxidant to the slurry obtained in Step 1, mix well, and obtain a slurry with a solid content of 1-5 wt%. Step 3: Pump the slurry obtained in Step 2 into a tubular microwave reactor, control the residence time of the slurry in the microwave reactor to be 2-5 min, and under microwave heating, raise the temperature of the slurry at the outlet of the microwave reactor to a plateau temperature of 80-150 ℃ and the gauge pressure to 0-0.4 MPa, so that a controllable oxidation reaction occurs on the surface of the oligolayer graphite nanosheets. Step 4: The slurry obtained in Step 3 is pumped into another conventionally heated tubular reactor for heat and pressure maintenance for 10-60 minutes to ensure the oxidation reaction is complete. Step 5: Spray dry the slurry obtained in Step 4 to obtain oligolayer graphite nanosheet powder with controllable defects.

[0008] Further, in step 1, the thinner-layer graphite nanosheets prepared by the physical method have a thickness of 0.3-6 nm, a sheet diameter of 1-10 μm, an oxygen content not exceeding 1.2 wt%, and a fixed carbon content not less than 98 wt%. The properties related to carbon materials in their Raman spectra are: D peak intensity I... D G peak intensity I G and 2D peak intensity I 2D Satisfy: I D <0.2 I G , and I 2D >0.5 I G .

[0009] Furthermore, the peak intensity I of D D Raman shift 1350±10 cm -1 G peak intensity I G Raman shift 1584±10cm -12D peak intensity I 2D Raman displacement 2700±20cm -1 .

[0010] Furthermore, in step 3, the time for the slurry to be heated from room temperature to the platform temperature in the microwave reactor is 2-5 minutes, and the material platform temperature and pressure are monitored by thermocouples and pressure gauges at the reactor outlet.

[0011] Furthermore, the non-salt oxidant mentioned in step 2 is at least one of ozone aqueous solution or hydrogen peroxide aqueous solution, and the pH value of the slurry obtained after step 2 is 5-9.

[0012] Furthermore, in step 2, when ozone is used alone as an oxidant, its concentration in the slurry is not less than 6 × 10⁻⁶. -5 The molar concentration of the oxidant in the slurry is less than 1 / 1000 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry (all molar concentrations are based on the total volume of the slurry).

[0013] Furthermore, in step 2, when hydrogen peroxide is used alone as the oxidant, its concentration in the slurry is not less than 3 × 10⁻⁶. -3 The molar concentration of the oxidant in the slurry is less than 1 / 10 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry (all molar concentrations are based on the total volume of the slurry).

[0014] Furthermore, in step 2, when ozone and hydrogen peroxide are used together as oxidants, the total concentration of both in the slurry shall not be less than 5 × 10⁻⁶. -4 The concentration of oxidant in the slurry is less than 1 / 100 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry (all molar concentrations are based on the total volume of the slurry).

[0015] The present invention provides a defect-controllable oligolayer graphite nanosheet with an oxygen content of 0.9-1.5 wt%.

[0016] The present invention also discloses the application of the aforementioned defect-controllable oligolayer graphite nanosheets in the electrocatalytic synthesis of hydrogen peroxide.

[0017] Compared with the prior art, the beneficial effects of the present invention include: (1) The defect-controllable oligolayer graphite nanosheet preparation process of the present invention uses green oxidants such as ozone and hydrogen peroxide, with lower dosages than traditional chemical oxidation methods and without the use of strong acids. This introduces controllable defect sites into the graphite sheets without deeply oxidizing the graphite sheet matrix. The resulting product has low oxygen content and high sp... 2 The conjugate structure is well preserved.

[0018] (2) By controlling the type, concentration, and reaction time of the oxidant, this invention can regulate the type and density of defects on the surface of graphite nanosheets, thereby generating highly efficient catalytic active centers while maintaining the integrity and high conductivity of the main body of the sheets. The resulting product is used in the two-electron oxygen reduction reaction to synthesize hydrogen peroxide, exhibiting high activity, high selectivity, and good stability.

[0019] (3) The process for preparing defect-controllable oligolayer graphite nanosheets described in this invention is carried out entirely in an aqueous dispersion system. The post-processing is simple, environmentally friendly, and suitable for large-scale production. Attached Figure Description

[0020] Figure 1 These are transmission electron microscope images of the product from Example 1; Figure 2 This is the X-ray photoelectron spectrum (C 1s region) of the product of Example 1. Figure 3 The X-ray photoelectron spectrum (C 1s region) of the product of Comparative Example 1 is shown. Figure 4 These are the oxygen reduction linear sweep voltammetric curves of the products from Examples 1-3 and Comparative Examples 1-3; Figure 5 The values ​​represent the Faraday efficiency of the electrocatalytic synthesis of hydrogen peroxide from the products of Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments: The oligolayer graphite nanosheets prepared by the physical method used in this embodiment of the invention are produced by Hangzhou Xichuang Technology Co., Ltd., with an average thickness of 2 nm, an average sheet diameter of 5 μm, an oxygen content of 0.9 wt%, and a fixed carbon content of 98.5%. D / I G =0.17, I 2D / I G =0.52. D peak intensity I D Raman shift 1350 cm -1 G peak intensity I G Raman shift 1584cm -1 2D peak intensity I 2D Raman displacement 2700cm -1 .

[0022] Example 1: Preparation of a defect-controllable oligolayer graphite nanosheet Step 1: Weigh 100 g of the oligolayer graphite nanosheets prepared by the physical method and disperse them in 2.5 kg of water under stirring at 1000 rpm to make a viscous slurry.

[0023] Step 2: Use an ozone solution with a concentration of 10 ppm as the oxidant solution.

[0024] Step 3: The slurry from Step 1 and the oxidant solution from Step 2 are separately pumped into a dynamic pipeline mixer at a flow rate of 0.5 L / h using metering pumps. After thorough mixing, the slurry has a pH of 7, a solids content of 2 wt%, and an ozone molar concentration of approximately 1 × 10⁻⁶. -4 The concentration of carbon in the slurry is 1.6 mol / L, which is much lower than the concentration of fixed carbon in the oligolayer graphite nanosheets.

[0025] Step 4: The mixed slurry obtained in Step 3 is pumped into a tubular microwave reactor made of borosilicate glass. The tubular microwave reactor is placed in the radiation environment of the microwave device, the microwave power is adjusted to 200W, the residence time of the slurry in the microwave reactor is 3 min, the temperature of the slurry at the outlet of the microwave reactor rises to a plateau temperature of 120 ℃, and the gauge pressure is 0.1 MPa. At this time, ozone reacts with oligolayer graphite nanosheets, introducing surface defects.

[0026] Step 5: The slurry obtained in Step 4 is introduced into a tubular reactor made of 316L stainless steel. The reactor temperature is controlled by an electric heating jacket and maintained at 120 ℃. The pressure is maintained at 0.1 MPa. The hot slurry stays in the reactor for 30 min, at which time the ozone reacts completely with the oligolayer graphite nanosheets.

[0027] Step 6: Subsequently, the reacted slurry is introduced into a spray dryer and dried at an inlet air temperature of 220 ℃ and an outlet air temperature of 100 ℃ to obtain defective oligolayer graphite nanosheet powder.

[0028] Elemental analysis showed that the oxygen content of the product in Example 1 was 1.0 wt%, which is close to that of the oligolayer graphite nanosheet raw material. TEM characterization ( Figure 1 The lattice fringes are found throughout the graphene layered structure, indicating that its structural integrity is preserved; local disturbances are visible in many places along the lattice fringes, proving the presence of point defects. XPS characterization ( Figure 2 The chemical environment of the surface carbon of the product is characterized by unfunctionalized sp. 2 The predominantly hybridized state is consistent with its graphene-dominant layered structure. Furthermore, 4.7% of the carbon is in unfunctionalized sp... 3 The hybrid environment, with 9.5% being functionalized by hydroxyl / ether groups and 3.6% by carbonyl groups, proves that some graphene structures are oxidized and ring-opened, resulting in defects.

[0029] Example 2: Preparation of a defect-controllable oligolayer graphite nanosheet Step 1: Weigh 100 g of the oligolayer graphite nanosheets prepared by the physical method, and disperse them in 4 kg of water at 1000 rpm to make a slurry.

[0030] Step 2: Use a 30 wt% hydrogen peroxide solution as the oxidant solution.

[0031] Step 3: The slurry from Step 1 is pumped at a flow rate of 1 L / h using a metering pump, and the oxidant solution obtained in Step 2 is pumped at a flow rate of 5 mL / h using a metering pump. Both are pumped into a dynamic pipeline mixer. After thorough mixing, the pH of the slurry is 6, the solids content is approximately 2.5 wt%, and the molar concentration of hydrogen peroxide in the slurry is approximately 5 × 10⁻⁶. -2 The concentration of carbon in the slurry is 2 mol / L, which is much lower than the concentration of fixed carbon in the oligolayer graphite nanosheets.

[0032] Step 4: The mixed slurry obtained in Step 3 is pumped into a tubular microwave reactor made of polytetrafluoroethylene. The tubular microwave reactor is placed in the radiation environment of a microwave device, the microwave power is adjusted to 270W, the residence time of the slurry in the microwave reactor is 3 min, the slurry temperature at the microwave reactor outlet rises to a plateau temperature of 150 ℃ and the gauge pressure is 0.4 MPa, which promotes the reaction of hydrogen peroxide with oligolayer graphite nanosheets and introduces surface defects.

[0033] Step 5: The slurry obtained in Step 4 is introduced into a tubular reactor made of 316L stainless steel. The reactor temperature is controlled by an electric heating jacket and maintained at 150 ℃. The pressure is maintained at 0.4 MPa. The hot slurry stays in the reactor for 60 min. At this time, the hydrogen peroxide reacts completely with the oligolayer graphite nanosheets, and the remaining hydrogen peroxide decomposes.

[0034] Step 6: Subsequently, the reacted slurry is introduced into a spray dryer and dried at an inlet air temperature of 220 ℃ and an outlet air temperature of 100 ℃ to obtain defective oligolayer graphite nanosheet powder.

[0035] Elemental analysis showed that the oxygen content of the product in Example 2 was 1.0 wt%, which is close to that of the oligolayer graphite nanosheet raw material.

[0036] Example 3: Preparation of a defect-controllable oligolayer graphite nanosheet Step 1: Weigh 100 g of the oligolayer graphite nanosheets prepared by the physical method, and disperse them in 2.5 kg of water at 1000 rpm to make a viscous slurry.

[0037] Step 2: The slurry from Step 1, a 10 ppm ozone solution, and a 3 wt% hydrogen peroxide solution are pumped together into a stirred tubular mixer at flow rates of 0.5 L / h, 0.5 L / h, and 1 mL / h, respectively. After thorough mixing, the slurry has a pH of 7, a solids content of 2 wt%, and an ozone molar concentration of approximately 1 × 10⁻⁶. -4 The molar concentration of hydrogen peroxide is approximately 9 × 10⁻⁶ mol / L. -4 The total molar concentration of the two oxidants was much lower than the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry, which was 1.6 mol / L.

[0038] Step 3: The mixed slurry obtained in Step 2 is pumped into a tubular microwave reactor made of borosilicate glass. The tubular microwave reactor is placed in the radiation environment of a microwave device, the microwave power is adjusted to 200W, the residence time of the slurry in the microwave reactor is 3 min, the slurry temperature at the outlet of the microwave reactor rises to a plateau temperature of 120 ℃, and the gauge pressure is 0.1 MPa.

[0039] Step 4: The hot slurry from Step 3 is introduced into a tubular reactor made of 316L stainless steel. The reactor temperature is controlled by an electric heating jacket and maintained at 120 ℃. The pressure is maintained at 0.1 MPa. The residence time of the hot slurry in the reactor is 30 min.

[0040] Step 5: Subsequently, the reacted slurry is introduced into a spray dryer and dried at an inlet air temperature of 220 ℃ and an outlet air temperature of 100 ℃ to obtain defective oligolayer graphite nanosheet powder.

[0041] Elemental analysis showed that the oxygen content of the product in Example 3 was 1.1 wt%, which is close to that of the oligolayer graphite nanosheet raw material.

[0042] Compare with Example 1, Preparation of Graphite Nanosheets 1 g of oligolayer graphite nanosheets prepared by physical method was weighed and dispersed in 50 mL of ozone aqueous solution with an ozone content of 5 ppm at 1000 rpm to prepare a slurry. The slurry was allowed to stand at room temperature for 30 min, and then centrifuged at 6000 G. The precipitate was freeze-dried to obtain the product powder.

[0043] Elemental analysis showed that the oxygen content of the product in control example 1 was 0.9 wt%. XPS characterization ( Figure 3 This reveals the chemical environment of surface carbon as unfunctionalized sp. 2 Hybridized state predominates, unfunctionalized sp24-peptide was not detected. 3The hybrid carbon exhibits characteristics consistent with its predominantly layered graphene structure and has a low number of defects. Furthermore, 8.8% of the carbon is functionalized with hydroxyl / ether groups, and 4.0% with carbonyl groups.

[0044] A comparison of the characterization results of the products of Example 1 and Example 1 shows that the controllable oxidation process described in this invention selectively opens the six-membered carbon ring and introduces hydroxyl / ether groups into the graphene structure without significantly increasing the oxygen content.

[0045] Compare with Example 2, Preparation of Graphite Nanosheets The preparation process of graphite nanosheets in Example 2 was repeated in Example 1, except that "the oligolayer graphite nanosheets prepared by the physical method were replaced with the same mass of reduced oxide oligolayer graphite nanosheets prepared by the Hummers method", and all other conditions remained the same.

[0046] The reduced oxide oligolayer graphite nanosheets prepared by the Hummers method in Comparative Example 2 were prepared according to the following steps: 1 L of concentrated sulfuric acid (95 wt%) was placed in a beaker and cooled to 5 °C. 20 g of flake graphite powder (500-800 mesh, fixed carbon content >99%) was added and stirred for 1.5 hours. 3 g of potassium permanganate was added under ice-water bath cooling and stirred for 1.5 hours, followed by the slow addition of 60 g of potassium permanganate and stirring for another 1.5 hours, maintaining the material temperature below 10 °C. Subsequently, the resulting solution was heated to 40 °C in a water bath and stirred for 1 hour. Heating was removed, and 1 L of deionized water was slowly added dropwise, maintaining the solution temperature at 40-50 °C. After the addition was complete, the solution was heated to 95 °C in a water bath, and 600 mL of 10 wt% hydrogen peroxide solution was slowly added dropwise under stirring until it turned light yellow. After the feed solution was cooled to room temperature, it was filtered to obtain a graphite oxide filter cake. The filter cake was washed five times with 10 wt% hydrochloric acid solution, 1 L each time, and then washed with deionized water until the pH of the filtrate was higher than 5. The obtained filter cake was freeze-dried and then calcined at 900 °C for 5 hours under nitrogen protection. After naturally cooling to room temperature, reduced oligolayer graphite oxide nanosheets were obtained.

[0047] Compare with Example 3, Preparation of Graphite Nanosheets The preparation process of Comparative Example 3 was similar to that of Example 1, except that a tubular microwave reactor was not used. After the mixture of oligolayer graphite nanosheets and ozone solution left the stirred tubular mixer, it was directly pumped into a tubular reactor made of 316L stainless steel tube. It was first kept at a temperature of 120 °C and a gauge pressure of 0.1 MPa for 3 min, and then kept at a temperature of 120 °C and a gauge pressure of 0.1 MPa for 30 min, and finally spray dried.

[0048] Application Example 1: Catalyst Performance Testing 3 mg of the graphite nanosheet product from Example 1 was mixed with 30 μL of 5 wt% Nafion solution and 1 mL of isopropanol, and ultrasonically dispersed for 30 min to prepare a catalyst slurry. 5 μL of the slurry was uniformly coated onto a glassy carbon disk (5 mm in diameter) of a rotating ring electrode and dried with an infrared lamp to serve as the working electrode. Graphite nanosheet products from Examples 2-3 and Comparative Examples 1-3 were treated in the same manner as controls.

[0049] The performance of the electrocatalytic oxygen reduction to H₂O₂ synthesis was evaluated by linear sweep voltammetry (LSV) and Faraday efficiency tests in an oxygen-saturated 0.1 M KOH solution. A rotating ring-disk electrode coated with graphite nanosheets served as the working electrode (cathode), a platinum sheet as the counter electrode (anode), and an Hg / HgO electrode as the reference electrode. Results are as follows: Figure 4 As shown, within a wide potential range of 0-0.6 V, the oxygen reduction current density of the products in Examples 1-3 was increased by >50% compared to the control product 1 obtained by ozone treatment at room temperature, while the activity of the control product 3 obtained without microwave treatment was less improved. Figure 5 The results show that the Faradaic efficiency of H2O2 synthesis by the products of Examples 1-3 and Control Example 3 within the same potential range is no more than 8% different from that of Control Example 1. Although the product of Control Example 2, obtained from chemically prepared reduced-oxide oligolayer graphite nanosheets, exhibits high oxygen reduction activity, its Faradaic efficiency for H2O2 synthesis is reduced by more than 20%, indicating that the four-electron oxygen reduction activity is more significant. These results demonstrate that the products of Examples 1-3 improve activity while maintaining the selectivity of the H2O2 synthesis reaction, and therefore have higher application value in the electrocatalytic synthesis of H2O2.

Claims

1. A method for preparing defect-controllable oligolayer graphite nanosheets, characterized in that, Includes the following steps: Step 1: Mix the oligolayer graphite nanosheets prepared by physical method with water to prepare a fluid slurry; Step 2: Add a non-salt oxidant to the slurry obtained in Step 1, mix well, and obtain a slurry with a solid content of 1-5 wt%. Step 3: Pump the slurry obtained in Step 2 into a tubular microwave reactor, control the residence time of the slurry in the microwave reactor to be 2-5 min, and under microwave heating, raise the temperature of the slurry at the outlet of the microwave reactor to a plateau temperature of 80-150 ℃ and the gauge pressure to 0-0.4 MPa, so that a controllable oxidation reaction occurs on the surface of the oligolayer graphite nanosheets. Step 4: The slurry obtained in Step 3 is pumped into another conventionally heated tubular reactor for heat and pressure maintenance for 10-60 minutes to ensure the oxidation reaction is complete. Step 5: Spray dry the slurry obtained in Step 4 to obtain oligolayer graphite nanosheet powder with controllable defects.

2. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 1, characterized in that, In step 1, the thinner-layer graphite nanosheets prepared by the physical method have a thickness of 0.3-6 nm, a sheet diameter of 1-10 μm, an oxygen content not exceeding 1.2 wt%, and a fixed carbon content not less than 98 wt%. The properties related to carbon materials in their Raman spectra are: D peak intensity I... D G peak intensity I G and 2D peak intensity I 2D Satisfy: I D < 0.2 I G , and I 2D > 0.5 I G .

3. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 2, characterized in that, D Peak Intensity I D Raman shift 1350±10 cm -1 G peak intensity I G Raman shift 1584±10cm -1 2D peak intensity I 2D Raman displacement 2700±20cm -1 .

4. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 1, characterized in that, The non-salt oxidant mentioned in step 2 is at least one of ozone aqueous solution or hydrogen peroxide aqueous solution, and the pH value of the slurry obtained after step 2 is 5-9.

5. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 4, characterized in that, Step 2: When ozone is used alone as an oxidant, its concentration in the slurry shall not be less than 6 × 10⁻⁶. -5 The molar concentration of the oxidant in the slurry is less than 1 / 1000 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry.

6. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 4, characterized in that, Step 2: When hydrogen peroxide is used alone as an oxidant, its concentration in the slurry shall not be less than 3 × 10⁻⁶. -3 The molar concentration of the oxidant in the slurry is less than 1 / 10 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry.

7. The method for preparing defect-controllable oligolayer graphite nanosheets according to claim 4, characterized in that, Step 2: When ozone and hydrogen peroxide are used together as oxidants, their total concentration in the slurry should not be less than 5 × 10⁻⁶. -4 The total molar concentration of oxidant in the slurry is less than 1 / 100 of the molar concentration of fixed carbon in the oligolayer graphite nanosheets in the slurry. The ozone and hydrogen peroxide molar ratio is 1:2-10.

8. A defect-controllable few-layer graphite nanosheet, characterized in that, It is prepared by the method described in any one of claims 1-7, and has an oxygen content of 0.9-1.5 wt%.

9. The application of the defect-controllable oligolayer graphite nanosheets as described in claim 8 in the electrocatalytic synthesis of hydrogen peroxide.

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