Preparation method of ultrasonic-assisted carbon quantum dot modified graphite carbon nitride material and application thereof

Abstract

The application relates to a preparation method of an ultrasonic-assisted carbon quantum dot modified graphite carbon nitride material and application thereof, and belongs to the technical field of hydrogen peroxide electrocatalyst synthesis. The preparation method of the ultrasonic-assisted carbon quantum dot modified graphite carbon nitride material comprises the following steps: placing urea in an aluminum crucible with a cover, heating to 500-600 DEG C at a heating rate of 5-10 DEG C / min, calcining for 2-3 h, grinding and collecting a yellow product, marking the product as g-C3N4; dispersing the obtained g-C3N4 in a KOH solution, performing ultrasonic peeling for 8-16 h to obtain supernatant, centrifuging and collecting the supernatant to obtain a sample, and washing and drying the sample with deionized water for multiple times to obtain a carbon quantum dot (CQDs) modified graphite carbon nitride material. The carbon quantum dot modified graphite carbon nitride catalyst is obtained by introducing the carbon quantum dots, and can be applied to a hydrogen peroxide electrocatalytic reaction as a catalyst.

Description

Technical Field

[0001] This invention relates to a method for preparing ultrasonically assisted carbon quantum dot modified graphite carbon nitride materials and their applications, belonging to the technical field of synthesizing hydrogen peroxide electrocatalysts. Background Technology

[0002] Hydrogen peroxide (H₂O₂) is a versatile and environmentally friendly oxidant widely used in bleaching, disinfection, wastewater treatment, chemical synthesis, semiconductor cleaning, and exhaust gas treatment. However, H₂O₂ production still primarily relies on the traditional anthraquinone process, which is costly, polluting, and detrimental to environmental and ecological safety. Compared to the anthraquinone process, electrocatalytic methods for H₂O₂ preparation are promising. However, designing and preparing H₂O₂ with excellent 2e⁻... – Catalysts with high ORR activity and H2O2 selectivity are crucial. Many catalysts have been studied, such as those made of noble metals and their alloys, but their scarcity and cost limit their future commercial-scale application. Currently, metal-free carbon catalysts are favored due to their good conductivity, high specific surface area, ease of modification, high abundance, and low price.

[0003] g-C3N4 nanosheets, with their large specific surface area, short charge transfer distance, high solubility, and tunable electronic structure, are widely used in electrocatalysis. However, the yield of H2O2 catalyzed by pristine g-C3N4 remains far from satisfactory. To improve the efficiency and selectivity of H2O2 production from g-C3N4 and increase the surface active sites, liquid-phase ultrasonic exfoliation has been used as an effective method. The energy of ultrasound can overcome the van der Waals forces between layers, effectively exfoliating g-C3N4 in a suitable solvent to obtain ultrathin g-C3N4 nanosheets.

[0004] Meanwhile, carbon quantum dots (CQDs) are a novel type of carbon nanomaterial with sizes ranging from 2 to 10 nanometers. In recent years, due to their unique properties, such as ultra-small size, low toxicity, water solubility, high photochemical stability, and good conductivity, CQDs have been widely used in the field of electrocatalysis. Furthermore, CQDs possess tunable band gaps and unique charge transfer and storage capabilities, making them widely used to improve catalytic performance. Many methods for synthesizing CQDs have been proposed, such as chemical oxidation, supported synthesis, hydrothermal / solvothermal treatment, microwave, and ultrasonic methods. Among these, ultrasonic methods have emerged as a simple and convenient candidate for CQD preparation. Ultrasonic-assisted preparation of carbon quantum dot-modified graphitic carbon nitride provides a higher specific surface area and a unique porous structure for electrocatalysis, offering more exposed active edges, catalytic sites, and channels for the electrocatalytic oxygen reduction reaction, thereby enhancing catalytic activity.

[0005] Patent application number 2020114308494 discloses a nitrogen-doped carbon quantum dot-modified nitrogen-rich graphitic carbon nitride photocatalyst. This application involves adding prepared C3N4 to anhydrous ethanol solution and stirring until homogeneous. Then, NCDs are added to the solution, the suspension is sonicated, stirred for a period of time, and finally the sample is dried to obtain the product. The catalyst prepared by this patent application is used for hydrogen production processes, but no graphitic carbon nitride catalyst for efficient hydrogen peroxide production is found. Summary of the Invention

[0006] To address the problems and shortcomings of the existing technology, this invention provides a method for preparing ultrasound-assisted carbon quantum dot-modified graphitic carbon nitride materials and their applications. This invention introduces carbon quantum dots to obtain a carbon quantum dot-modified graphitic carbon nitride catalyst, which can be used as a catalyst in the electrocatalytic reaction of hydrogen peroxide. This invention is achieved through the following technical solutions.

[0007] A method for preparing ultrasound-assisted carbon quantum dot-modified graphitic carbon nitride materials includes the following specific steps:

[0008] Step 1: Place urea in a covered aluminum crucible and heat it to 500-600℃ at a heating rate of 5-10℃ / min. Calcine for 2-3 hours to obtain a yellow product. Grind and collect the product and label it as g-C3N4.

[0009] Step 2: Disperse the g-C3N4 obtained in Step 1 in KOH solution, and obtain the supernatant by ultrasonic exfoliation for 8-16 hours. Collect the supernatant by centrifugation to obtain the sample. After washing and drying the sample with deionized water multiple times, CQDs modified graphitic carbon nitride material is obtained.

[0010] In step 2, the solid-liquid ratio of g-C3N4 dispersed in the KOH solution is 1:1 g / L, resulting in a solution concentration of 1 mg / mL. −1 .

[0011] In step 2, the ultrasound parameters are set to 40 kHz and 50-150 W.

[0012] The carbon quantum dot-modified graphitic carbon nitride material prepared in this manner can be used as a catalyst in the electrocatalytic reaction process for preparing hydrogen peroxide.

[0013] The carbon quantum dot-modified graphitic carbon nitride material prepared above is applied by adding a carbon quantum dot-modified graphitic carbon nitride catalyst to the electrode. The specific process is as follows:

[0014] 10 mg of carbon quantum dot (CQD) modified graphitic carbon nitride catalyst was added to 300 μL of 0.5% Nafion ethanol solution and 200 μL of deionized water, and then dispersed uniformly by ultrasonic treatment in a water bath to form a suspension; then 50 μL of the suspension was dropped onto a surface with an area of ​​1 cm².2 The catalyst was applied to a carbon paper electrode; the electrode was allowed to dry naturally at room temperature before measurement; the catalyst content was 1 mg / cm³. 2 .

[0015] The beneficial effects of this invention are:

[0016] (1) The present invention prepares carbon quantum dots by ultrasound, which is a simple and convenient method.

[0017] (2) The carbon quantum dot-modified graphite carbon nitride catalyst obtained in this invention has high electrocatalytic activity and stability under alkaline conditions. Attached Figure Description

[0018] Figure 1 These are images of the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst, and g-C3N4 / CQDs-16 catalyst prepared in this invention, where a is an XRD pattern, b is a magnified XRD pattern, and c is an FTIR pattern.

[0019] Figure 2 These are SEM images of different ultrasonic treatment durations according to the present invention;

[0020] Figure 3 These are AFM images comparing the ultrasonic treatment before and after the present invention, where a is the AFM image of the g-C3N4 catalyst, b is the TEM image of the g-C3N4 catalyst, c is the AFM image of the g-C3N4 / CQDs-12 catalyst, and d is the TEM image of the g-C3N4 / CQDs-12 catalyst.

[0021] Figure 4 This is a TEM characterization of the carbon quantum dots on the surface of the g-C3N4 catalyst prepared in this invention, where ab represents the quantum dots distributed on g-C3N4, c shows the diameter of the CQDs, and d shows the interplanar spacing of the CQDs.

[0022] Figure 5 These are XPS images of the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst and g-C3N4 / CQDs-16 catalyst prepared by this invention, where a is the C1s spectrum, b is the N1s spectrum and c is the O1s spectrum.

[0023] Figure 6 The images show the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst and g-C3N4 / CQDs-16 catalyst prepared by this invention, where a is the N2 adsorption-desorption isotherm diagram and b is the corresponding BJH pore size distribution curve and pore size distribution desorption isotherm diagram.

[0024] Figure 7 The images show the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst and g-C3N4 / CQDs-16 catalyst prepared in this invention, where a is the UV-Vis absorption spectrum, b is the EPR spectrum and c is the electrochemical solution resistance.

[0025] Figure 8 In Figure a, cyclic voltammetry (CV) curves (N2 (dashed line) and O2 (solid line)) of 0.1 M KOH saturated solution are shown; b, polarization curves (solid line) and simultaneous hydrogen peroxide detection current (dashed line) of g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst and g-C3N4 / CQDs-16 catalyst in 0.1 M KOH at 1600 rpm are shown; c, hydrogen peroxide selectivity (relative to reversible hydrogen electrode (RHE)) of g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst and g-C3N4 / CQDs-16 catalyst from 0.1 to 0.6 V are shown; d, the number of transferred electrons (n) of the four materials calculated based on the RRDE electrode at 0.4 V RHE are shown.

[0026] Figure 9 In Figure a, the stability was measured over 12 hours in 0.1 M KOH solution at -0.4 V (relative to RHE); in Figure b, the cumulative hydrogen peroxide yield was measured in 0.1 M KOH solution at -0.4 V (relative to RHE); and in Figure c, the C1 values ​​of the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst, and g-C3N4 / CQDs-16 catalyst were measured. dl Figure d shows the relationship between output and C. dl The relationship between output and S; e represents the relationship between output and S. BET The relationship; f is the S of the three catalysts BET Relationship with H2O2 selectivity;

[0027] Figure 10 TEM images of the g-C3N4 / CQDs-12 catalyst after a 12-hour stability test; where a is magnified 100 nm; b is magnified 50 nm; c is magnified 50 nm; and d is magnified 5 nm.

[0028] Figure 11The images show the spectra of the g-C3N4 catalyst, g-C3N4 / CQDs-8 catalyst, g-C3N4 / CQDs-12 catalyst, and g-C3N4 / CQDs-16 catalyst after 12 hours of stability testing. In the image, a is the C1s spectrum, b is the N1s spectrum, and c is the O1s spectrum. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0030] The method for preparing ultrasound-assisted carbon quantum dot-modified graphitic carbon nitride materials includes the following specific steps:

[0031] Step 1: Place 10g of urea in a covered aluminum crucible and heat it to 500℃ in a muffle furnace at a heating rate of 5℃ / min. Calcine for 2h to obtain a yellow product, then grind and collect it and label it as g-C3N4.

[0032] Step 2: Disperse 20 mg of g-C3N4 obtained in Step 1 in 20 mL of 0.1 M KOH solution, controlling the liquid-to-solid ratio at 1:1 g / L. Exfoliate using ultrasound (ultrasound parameters set to 40 kHz, 120 W) for 8 hours to obtain the supernatant. Collect the supernatant by centrifugation to obtain the sample. Change the water every half hour during the ultrasound process, with a temperature range of 20-40℃. After multiple washes with deionized water and drying, the sample yields CQDs-modified graphitic carbon nitride material, labeled as g-C3N4 / CQDs-8 catalyst. Example 2

[0033] The method for preparing ultrasonically assisted carbon quantum dot modified graphitic carbon nitride material is the same as that in Example 1, except that the supernatant is obtained by ultrasonic exfoliation for 12 hours in step 2. The supernatant is collected by centrifugation to obtain the sample. After the sample is washed and dried with deionized water multiple times, carbon quantum dot (CQDs) modified graphitic carbon nitride material is obtained and labeled as g-C3N4 / CQDs-12 catalyst. Example 3

[0034] The method for preparing ultrasonically assisted carbon quantum dot modified graphitic carbon nitride material is the same as that in Example 1, except that the supernatant is obtained by ultrasonic exfoliation for 16 hours in step 2. The supernatant is collected by centrifugation to obtain the sample. After the sample is washed and dried with deionized water multiple times, carbon quantum dot (CQDs) modified graphitic carbon nitride material is obtained and labeled as g-C3N4 / CQDs-16 catalyst.

[0035] Comparative Example 1

[0036] The method for preparing ultrasonically assisted carbon quantum dot modified graphite carbon nitride material is the same as that in Example 1, except that the supernatant is obtained by ultrasonic exfoliation for 0h in step 2. The supernatant is collected by centrifugation to obtain the sample. After the sample is washed and dried multiple times with deionized water, carbon quantum dot (CQDs) modified graphite carbon nitride material is obtained, which is still labeled as g-C3N4 catalyst.

[0037] The catalysts prepared in Examples 1 to 3 and Comparative Example 1 were tested, specifically as follows:

[0038] First, the crystal structure and chemical properties of nanosheets with different exfoliation times (0, 8, 12, and 16 hours) were investigated by powder X-ray diffraction (XRD) and FT-IR spectroscopy. X-ray diffraction showed... Figure 1 a) Two distinct diffraction peaks were observed in samples treated with ultrasound for 8 hours, 12 hours, and without ultrasound treatment. A strong X-ray diffraction peak at approximately 27° corresponds to the (002) crystal plane, and this peak relates to interlayer stacking at 0.326 nm in the common-channel aromatic system. A peak at approximately 13° is associated with the (100) crystal plane, and this weak peak relates to in-plane stacking of repeating three-layer homogeneous triazine units at a wavelength of 0.675 nm. Notably, the intensity of the (002) peak significantly decreased after the addition of ultrasound, clearly indicating that the delaminated g-C3N4 was successfully exfoliated as expected. We found that when the ultrasound treatment time reached 16 hours, the peak near the (100) crystal plane at 13° disappeared, and the peak from... Figure 1 The magnified image of b shows that the pattern structure of this crystal plane may have been destroyed after prolonged ultrasonic treatment. In addition, the peak intensities of (100) and (002) in g-C3N4 / CQDs-8 and g-C3N4 / CQDs-12 are significantly weaker than those in g-C3N4, indicating that ultrasonic exfoliation treatment leads to the loss of the ordered structure in the g-C3N4 framework.

[0039] FT-IR spectroscopy analysis is used to gain more insights and understanding of the functional groups of the prepared catalyst, such as... Figure 1 As shown in c. At 807cm -1 The sharp peaks are due to the breathing pattern of the tris-s-heptane or tris-s-triazine units, and their intensity disappears with increasing sonication time, causing some damage to the basic unit. FTIR analysis of g-C3N4 showed peaks at 1641, 1570, 1462, and 1412 cm⁻¹. -1 The peak is caused by the tensile vibration of the repeating units of heptazine. It is located at 1200-1650 cm⁻¹. -1The strong band in this region corresponds to the CN / CN tensile vibration mode. The intensity of the peak in this region also decreases with increasing ultrasound duration, indicating that ultrasound damage to the CN bonds. (3000 and 3500 cm⁻¹) -1 The broad peaks between these values ​​correspond to the tensile vibrations of NH, and their intensity gradually decreases with increasing ultrasonic time, even slowly shifting to higher energy levels. FT-IR analysis indicates that ultrasound has some influence on the structure of g-C3N4.

[0040] Scanning electron microscopy images of g-C3N4 at different peeling times (0, 8, 12, 16 h) are shown below. Figure 2 As shown, the exfoliated g-C3N4 nanosheets have irregular morphologies. Porous structures caused by the release of carbon dioxide, ammonia, and water during calcination were observed in all samples. All samples exhibited a two-dimensional structure. After liquid-phase ultrasonic treatment, the size and thickness of the g-C3N4 decreased. With prolonged ultrasonic treatment, the material exhibited an increasing number of pores, larger stacked voids, and increasingly fragmented edges.

[0041] The morphology of graphitic carbon nitride before and after ultrasonic exfoliation was then characterized using transmission electron microscopy (TEM) and atomic force microscopy (AFM), such as... Figure 3 . Figure 3 a and 3b are samples that were not subjected to ultrasonic treatment. Figure 3 c and 3d are samples after 12 hours of ultrasonic treatment. Statistical measurements show that the thickness of the graphitic carbon nitride flakes is in the range of 1-5 nanometers, indicating that they are monolayer and / or multilayer. The graphitic carbon nitride thickness decreased from the original 0.862 nm (approximately three layers) to 0.629 nm (approximately two layers) after 12 hours of exfoliation.

[0042] Transmission electron microscopy (TEM) images such as Figure 4 Clearly, many small quantum dots are distributed on g-C3N4 ( Figure 4 ab), resulting in a micro-regional heterostructure between carbon quantum dots and g-C3N4, showing that the diameter of CQDs is approximately 2~5 nm ( Figure 4 c) High-resolution TEM (HRTEM) analysis showed that CQDs possessed a basic morphology and good crystallinity, with a planar spacing of approximately 0.217 nm. Figure 4 d), which can be attributed to the (101) spacing of graphite carbon.

[0043] XPS spectra of g-C3N4 samples are as follows Figure 5 As shown. The measured g-C3N4 sample mainly contains C and N elements. High-resolution XPS spectrum of C1s ( Figure 5a) Three peaks are observed at 284.8, 286.0, and 288.4 eV. The peak at 284.8 eV corresponds to graphitic carbon coordination (C−C) of surface amorphous carbon. The weak peak at approximately 286.0 eV belongs to C−O bonds of CO2 adsorbed on the sample surface. The main peak at 288.4 eV is named N=C−N2. The high-resolution XPS spectrum of N1s ( Figure 5 b) can be deconvolved into four peaks, namely C=N−C (398.7 eV), tertiary nitrogen N−(C)3 (399.6 eV), N−H (401.2 eV) and Π excitation (404.6 eV). Figure 5 c shows that there is only one O1s peak near 532.4 eV, which is related to the adsorption of carbon dioxide or water on the sample surface.

[0044] The N adsorption-desorption isotherms and BJH pore size distribution curves of the four samples are as follows: Figure 6 As shown, all samples exhibited distinct Type III behavior, which is attributed to the weak interaction between the adsorbent and adsorbate. The sample sonicated for 12 hours showed the largest Bruner-Emmett-Tylene (BET) surface area (approximately 68 m²). 2 g −1 More than 16 hours (approximately 59m) 2 g −1 ) and 8 hours (approximately 57m) 2 g −1 ), and untreated samples (50m) 2 g −1 Furthermore, the porosity after 12 hours was 0.3095 cm⁻¹. 3 g −1 The specific surface area of ​​g-C3N4 was higher than the other three. This shows that the ultrasonic-assisted method not only increases the specific surface area of ​​the sample and provides more reaction sites, but also improves the porosity of g-C3N4, which is beneficial to the mass transfer of reaction intermediates.

[0045] The samples were analyzed using UV-Vis spectroscopy to demonstrate the generation of CQDs. For example... Figure 7 As shown in Figure a, compared to the unultrasonicated g-C3N4, the ultrasonicated sample exhibits significantly enhanced light absorption in the UV-Vis region. This is attributed to the inherent light absorption characteristics of CQDs, indicating that ultrasonication of exfoliated C3N4 leads to the generation of CQDs. Electron paramagnetic resonance (EPR) spectra of the four materials show... Figure 7b. With prolonged sonication time, the EPR signal gradually increased. Compared with g-C3N4, the EPR spin intensity of the ultrasonically treated sample was significantly enhanced, indicating a higher concentration of unpaired electrons, which is highly beneficial for the photogeneration of active radical pairs in the catalytic reaction. Furthermore, the significant increase in EPR intensity indicates an increase in the density state of the conduction band after electron donation by CQD species. To explore the charge transfer capability of introducing CQDs into the ORR process of the g-C3N4 catalyst, electrochemical impedance spectroscopy (EIS) in O2-saturated solution was further investigated. The solution resistance (RS) of the four materials is shown below. Figure 7 As shown in Figure c, it is well known that the lower the resistivity, the higher the conductivity. With the increase of ultrasonic time, the RS value gradually decreases, while the conductivity gradually increases.

[0046] Figure 8 This section presents cyclic voltammetry (CV) curves of four samples saturated with O2 and N2 in 0.1 M KOH. The results show a strong oxygen reduction peak in the oxygen-saturated electrolyte, but no strong oxygen reduction peak in the nitrogen-saturated electrolyte. Linear sweep voltammetry (LSV) curves show that g-C3N4 / CQDs-12 exhibits a strong oxygen reduction peak for 2e2O2 at an initial potential of 0.7 V. - ORR exhibits excellent electrocatalytic performance. Figure 8 b). For example Figure 8 c shows g-C3N4 / CQDs-12 versus 2e - ORR exhibits excellent ORR selectivity. The number of electrons transferred for g-C3N4, g-C3N4 / CQDs-8, g-C3N4 / CQDs-12, and g-C3N4 / CQDs-16 are 2.34, 2.28, 2.22, and 2.38, respectively, with g-C3N4 / CQDs-12 being very close to the ideal two-electron reaction. Figure 8 d).

[0047] Figure 9 As shown in figure a, all four materials exhibit good stability. Figure 9 b shows the long-term hydrogen peroxide production of these four catalysts. After 12 hours, in the g-C3N4 / CQDs-12 catalyst, the concentration of hydrogen peroxide increased linearly in 50 mL of electrolyte, eventually reaching 0.73 M. Figure 9 c shows that the Cdl of g-C3N4 / CQDs-12 is 0.192 mF cm⁻¹. -2 It is almost g-C3N4 (0.0963 mF cm⁻¹) -2 This is twice the size of the target material, indicating that successful exfoliation of the material facilitates the provision of a larger electrochemically active surface area and more reaction sites. For example... Figure 9 As shown in d, g-C3N4 / CQDs-12 in C dlIt is 0.192 mF cm -2 It also has the highest output at that time. Figure 9 e indicates that the porosity and yield of g-C3N4 / CQDs-12 reach their maximum values ​​when the ultrasonic time is 12 hours. Figure 9 f indicates that the electrocatalytic activity increases with increasing porosity.

[0048] Figure 10 Image a shows a TEM image of the g-C3N4 / CQDs-12 sample after a 12-hour stability test; its morphology is consistent with that before the reaction. Figure 10 (bd) shows a large number of CQDs composited on the surface of the material.

[0049] Figure 11 XRS analysis was performed on the reacted samples. The XPS spectrum of the g-C3N4 sample after stability testing is shown below. Figure 11 As shown. The g-C3N4 sample mainly contains C, N, and O elements. High-resolution XPS spectra of C1s (… Figure 11 a) Three peaks are observed at 284.35, 287.68, and 291.13 eV. The peak at 284.35 eV represents a C-C bond, the strong peak at 287.68 eV belongs to C=O, and the peak at 291.13 eV represents an O-C=O group. (High-resolution XPS spectrum of N1s) Figure 11 b) can be deconvolved into four peaks, namely C=N−C (398.28eV), =N− (399.02eV), N1s (400.66eV) and N corresponding to oxidation (403.97eV). Figure 11 c shows that O1s has two peaks: O–C=O bond (531.93 eV) and adsorbed O2 at 534.49 eV. XPS analysis indicates that oxidation has occurred on the sample surface.

[0050] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing ultrasound-assisted carbon quantum dot-modified graphitic carbon nitride materials, characterized in that... The specific steps include the following: Step 1: Place urea in a covered aluminum crucible and heat it to 500-600℃ at a heating rate of 5-10℃ / min. Calcine for 2-3 hours to obtain a yellow product. Grind and collect the product and label it as g-C3N4. Step 2: Disperse the g-C3N4 obtained in Step 1 in KOH solution, and obtain the supernatant by ultrasonic exfoliation for 8-16 hours. Collect the supernatant by centrifugation to obtain the sample. After washing and drying the sample with deionized water multiple times, carbon quantum dot modified graphite carbon nitride material is obtained. In step 2, the ultrasonic parameters are set to 40kHz and 50-150W. The carbon quantum dots are distributed on the graphitic carbon nitride material, and there is a micro-regional heterogeneous structure between the carbon quantum dots and the graphitic carbon nitride material.

2. The method for preparing ultrasound-assisted carbon quantum dot-modified graphitic carbon nitride material according to claim 1, characterized in that: In step 2, the solid-liquid ratio of g-C3N4 dispersed in the KOH solution is 1:1 g / L.

3. A carbon quantum dot-modified graphite carbon nitride material prepared by the ultrasonic-assisted carbon quantum dot-modified carbon nitride material preparation method according to claim 1 or 2 can be used as a catalyst in the preparation of hydrogen peroxide electrocatalytic reaction process.

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