Co-n-s co-doped porous carbon nitride nanosheets and their application in photocatalytic production of h2o2

Abstract

The application belongs to the technical field of photocatalytic H2O2 production, and particularly relates to a kind of cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheet and its application in photocatalytic production of hydrogen peroxide. Cobalt sulfonated phthalocyanine and melamine are mixed uniformly in water, and then subjected to hydrothermal reaction. After the reaction is completed, the mixture is cooled, centrifuged and dried to obtain a light blue powder. The light blue powder is calcined in a tube furnace under a nitrogen atmosphere to obtain a dark green powder Co-N-S / CN. The method has low energy consumption, strong controllability, simple process, and simultaneously realizes element doping and defect modification. The prepared cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheet with nitrogen vacancies has high photogenerated carrier separation efficiency and two-step single-electron oxygen reduction selectivity, and exhibits good photocatalytic H2O2 production capacity under simulated sunlight. The H2O2 production rate of the cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheet with the optimal doping amount is increased by 9 times in the presence of a proton donor, 5-hydroxymethylfurfural.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic H2O2 production technology, specifically relating to a cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheet and its application in photocatalytic hydrogen peroxide production. Background Technology

[0002] Hydrogen peroxide (H2O2) is a widely used chemical substance with unique properties. It has broad applications in chemical synthesis, medical disinfection, and environmental treatment. With technological advancements, H2O2 has become a potential alternative to fossil fuels, serving as a clean liquid fuel that helps reduce environmental pollution. However, the traditional anthraquinone (AQ) process for producing H2O2 is complex, costly, and energy-intensive, and its production process can easily cause secondary pollution. Photocatalytic synthesis of H2O2 utilizes sunlight as a light source and water and oxygen molecules as reducing and oxidizing media. This method is considered green, energy-efficient, and mild, providing a more environmentally friendly and sustainable alternative to traditional H2O2 production.

[0003] Currently, various catalysts are suitable for photocatalytic production of H₂O₂, such as metal-inorganic catalysts TiO₂, Bi-based catalysts, CdS and MoS₂, metal-free organopolymer covalent organic frameworks, and graphitic carbon nitride (g-C₃N₄). g-C₃N₄ is a metal-free polymer semiconductor with unique properties and good chemical stability, a band gap of approximately 2.7 eV, and the ability to effectively absorb visible light. However, g-C₃N₄ has some drawbacks, such as high recombination rates of photogenerated electrons and holes, low visible light utilization, and few oxygen reduction active sites.

[0004] To overcome these shortcomings of g-C3N4, it can be modified, such as through heterostructure construction, morphology control, defect modification, and elemental doping, to improve its photocatalytic performance. However, the construction of heterojunctions requires precise control of interfaces and contacts, which may lead to interface mismatch or poor contact. Morphology control may require complex templates or external structural guidance, making the preparation process relatively cumbersome. Defect modification requires precise control of defect type and concentration; improper control may lead to performance degradation. The selection of doping elements and the control of doping levels are also critical; improper doping may result in structural distortion or performance degradation.

[0005] Furthermore, the yield of H2O2 produced by photocatalysis in water is extremely low, making it difficult to meet the requirements of practical applications. Summary of the Invention

[0006] Existing modifications of g-C3N4 primarily involve one or two methods from the background technologies, which are complex. This invention utilizes a two-step hydrothermal method to bond melamine and sulfonated cobalt phthalocyanine via π-bonds. The sulfonated cobalt phthalocyanine serves as a cobalt, nitrogen, and sulfur source. After calcination, all three elements are simultaneously incorporated into g-C3N4, achieving simultaneous doping of all three elements. Furthermore, the morphology of carbon nitride is controlled and defects are modified simultaneously. The preparation process uses only melamine and sulfonated cobalt phthalocyanine, making the raw materials simple, readily available, and low-cost.

[0007] This invention also provides the application of photocatalytic hydrogen peroxide (H2O2) production based on cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets in conjunction with a proton donor. The Co-NS co-doped porous carbon nitride proposed in this invention exhibits significantly improved photocatalytic H2O2 production activity in a system containing a proton donor compared to a system without a proton donor.

[0008] The method for preparing Co-NS co-doped porous carbon nitride nanosheets provided by this invention is specifically carried out according to the following steps:

[0009] (1) A certain proportion of sulfonated cobalt phthalocyanine and melamine powder were placed in an agate mortar and ground thoroughly. Deionized water was added and the mixture was ultrasonically mixed evenly. The mixed solution was transferred to a reaction vessel and heated in an oven to carry out a hydrothermal reaction. After the reaction was completed, the reaction precipitate was centrifuged, washed and dried to obtain a light blue powder.

[0010] (2) Place the light blue powder obtained in step (1) into a covered quartz boat, then put it into a tube furnace and calcine it in an inert gas atmosphere. After cooling to room temperature, the dark green powder obtained is Co-NS / CN.

[0011] Preferably, in step (1), the molar ratio of sulfonated cobalt phthalocyanine to melamine is 0.005 to 0.025:1.

[0012] The hydrothermal reaction conditions are: reaction at 100℃~180℃ for 6~24h.

[0013] The specific steps for obtaining the Co-NS co-doped porous carbon nitride nanosheet precursor by washing and drying the hydrothermal reaction precipitate are as follows: the blue precipitate is washed with ultrapure water until the filtrate is colorless and transparent, and then washed with ethanol to obtain the light blue powder of the Co-NS co-doped porous carbon nitride nanosheet precursor.

[0014] In step (2), the calcination temperature is 450℃~600℃, the calcination time is 2~4h, and the heating rate is 2~10℃ / min.

[0015] The Co-NS co-doped porous carbon nitride nanosheets prepared by the above method have a porous layered nanosheet structure with a pore size of 10-50 nm.

[0016] The application of the above-mentioned Co-NS co-doped porous carbon nitride nanosheets in photocatalytic H2O2 production includes the following steps: Co-NS co-doped porous carbon nitride nanosheets are placed in a quartz reaction vessel, and H2O2 is obtained under simulated sunlight irradiation in a solution system containing / without proton donor 5-hydroxymethylfurfural (HMF).

[0017] Preferably, the mass-to-volume ratio of Co-NS co-doped porous carbon nitride nanosheets to HMF aqueous solution is 0.0001–0.002:1 g / mL, and the volume fraction of HMF aqueous solution is 0.01%–0.3%.

[0018] Preferably, the wavelength of the simulated sunlight is (320nm ≤ λ ≤ 780nm), and the optical power density is 3sun (0.3W / cm²). 2 ).

[0019] Preferably, the irradiation time for the application in photocatalytic H2O2 production is 60–180 min.

[0020] The technical effects of this invention are:

[0021] (1) The Co-NS co-doped porous carbon nitride nanosheets prepared by the present invention simultaneously achieve defect modification and element doping of graphitic carbon nitride, and have high photogenerated carrier separation efficiency and two-step single-electron oxygen reduction selection efficiency. They also exhibit good photocatalytic H2O2 production ability under simulated sunlight.

[0022] (2) The Co-NS co-doped porous carbon nitride nanosheets proposed in this invention have good photocatalytic H2O2 production activity. In particular, the Co-NS co-doped porous carbon nitride nanosheets prepared with a molar ratio of sulfonated cobalt phthalocyanine to melamine of 0.01:1 have a photocatalytic H2O2 production activity that is 5 times higher than that of unmodified carbon nitride.

[0023] (3) The H2O2 yield of the Co-NS co-doped porous carbon nitride nanosheets proposed in this invention is 9 times that of the HMF system containing the optimal concentration of proton donors. Attached image description:

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the Co-NS co-doped porous carbon nitride nanosheets prepared in Example 1 of this invention.

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the Co-NS co-doped porous carbon nitride nanosheets prepared in Example 1 of this invention.

[0026] Figure 3The image shows the X-ray diffraction (XRD) pattern of the Co-NS co-doped porous carbon nitride nanosheets prepared in Example 1 of this invention. Detailed Implementation

[0027] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0028] The present invention will now be described in detail with reference to specific embodiments.

[0029] Example 1

[0030] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets:

[0031] 0.23 g (0.404 mmol) of sulfonated cobalt phthalocyanine (CoPcS) was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of CoPcS to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 120 °C for 12 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. After grinding with a mortar, green Co-NS co-doped porous carbon nitride nanosheets were obtained.

[0032] The scanning electron microscope (SEM) image of the Co-NS co-doped porous carbon nitride nanosheets prepared in this embodiment is shown below. Figure 1 .

[0033] The transmission electron microscope (TEM) image of the Co-NS co-doped porous carbon nitride nanosheets prepared in this embodiment is shown below. Figure 2 .

[0034] The X-ray diffraction (XRD) pattern of the Co-NS co-doped porous carbon nitride nanosheets prepared in this embodiment is shown in the figure. Figure 3 .

[0035] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0036] 10 mg of Co-NS co-doped porous carbon nitride nanosheet catalyst was dispersed in 50 mL of 0.1 v / v % HMF (5-hydroxymethylfurfural) solution and mixed by ultrasonic treatment for 2 minutes. The mixture was then tested in air at a power density of 0.3 W / cm². 2A 300W xenon lamp was used to produce H2O2 under simulated sunlight (320nm≤λ≤780nm). 2mL samples were taken every 15 minutes of illumination to determine the H2O2 concentration. The H2O2 concentration was determined by iodometric titration: 100μL of sample was added to 900μL of water, followed by the addition of 1mL of 0.1M potassium hydrogen phthalate solution and 1mL of 0.4M potassium iodide solution. After standing in darkness for 30 minutes, the absorbance was measured at 350nm using a UV-Vis spectrophotometer to obtain the corresponding H2O2 concentration. Under these conditions, the H2O2 yield was 1835 μmol g. -1 h -1 The yield of undoped carbon nitride (CN) was 420 μmol g. -1 h -1 4.4 times that.

[0037] Comparative Example 1

[0038] (1) Preparation of undoped modified carbon nitride

[0039] 5 g (40 mmol) of melamine was weighed into 80 mL of ultrapure water, sonicated for 10 min using a cell disruptor, and then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 120 °C for 12 h. After the reaction, the mixture was washed with pure water until the filtrate was clear, and then washed with anhydrous ethanol. The filtrate was dried at 80 °C to obtain a white powder. The white powder was placed in a covered boat and calcined at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. The calcined powder was then ground in a mortar to obtain yellow porous carbon nitride nanosheets, denoted as CN.

[0040] (2) Application of undoped and unmodified carbon nitride in H2O2 production:

[0041] Same as in Example 1, the yield of H2O2 was 420 μmol g. -1 h -1 .

[0042] Comparative Example 2

[0043] (1) Preparation of Co-doped porous carbon nitride nanosheets:

[0044] 0.4 mmol of cobalt nitrate hexahydrate was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of cobalt nitrate to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 120 °C for 12 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. After grinding with a mortar and pestle, Co-doped porous carbon nitride nanosheets were obtained.

[0045] (2) Application of H2O2 production from Co-doped porous carbon nitride nanosheets:

[0046] Same as in Example 1, the yield of H2O2 was 865 μmol g. -1 h -1 .

[0047] Comparative Example 3

[0048] (1) Preparation of Co-S co-doped porous carbon nitride nanosheets:

[0049] Weigh 0.4 mmol of cobalt nitrate hexahydrate and 0.4 mmol of sublimed sulfur into 80 mL of ultrapure water and dissolve by sonication for 5 min. Separately weigh 5 g (40 mmol) of melamine into the above solution (molar ratio of cobalt nitrate, sublimed sulfur, and melamine is 0.01:0.01:1). Sonicate for 10 min using a cell disruptor, then stir magnetically for 4 h. Transfer to a reaction vessel and react at 120 °C for 12 h. After the reaction, wash several times with pure water until the filtrate is transparent, then wash with anhydrous ethanol. Dry at 80 °C to obtain a light blue powder. Place the light blue powder in a covered boat and calcine at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. Grind in a mortar to obtain green Co-S co-doped porous carbon nitride nanosheets.

[0050] (2) Application of H2O2 production from Co-S co-doped porous carbon nitride nanosheets:

[0051] Same as in Example 1, the yield of H2O2 was 1196 μmol g. -1 h -1 .

[0052] Example 2

[0053] The difference lies in the molar ratio of CoPcS to melamine being 0.005:1; the other preparation processes are the same as in Example 1, and the yield of H2O2 is 1452 μmol g. -1 h -1 .

[0054] Example 3

[0055] The difference lies in the molar ratio of CoPcS to melamine being 0.025:1; the other preparation processes are the same as in Example 1, and the yield of H2O2 is 986 μmol g. -1 h -1 .

[0056] Example 4

[0057] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets:

[0058] 0.23 g (0.404 mmol) of CoPcS was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of CoPcS to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 100 °C for 24 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. After grinding with a mortar, green Co-NS co-doped porous carbon nitride nanosheets were obtained.

[0059] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0060] Similar to Example 1, the yield of H2O2 was 926 μmol g. -1 h -1 .

[0061] Example 5

[0062] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets:

[0063] 0.23 g (0.404 mmol) of CoPcS was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of CoPcS to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 180 °C for 6 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 550 °C for 4 h under a nitrogen atmosphere at a heating rate of 2.5 °C / min. After grinding with a mortar, dark green Co-NS co-doped porous carbon nitride nanosheets were obtained.

[0064] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0065] Similar to Example 1, the yield of H2O2 was 1569 μmol g. -1 h -1 .

[0066] Example 6

[0067] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets:

[0068] 0.23 g (0.404 mmol) of CoPcS was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of CoPcS to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 120 °C for 12 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 450 °C for 4 h under a nitrogen atmosphere at a heating rate of 2 °C / min. After grinding with a mortar, green Co-NS co-doped porous carbon nitride nanosheets were obtained.

[0069] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0070] Similar to Example 1, the yield of H2O2 was 522 μmol g. -1 h -1 .

[0071] Example 7

[0072] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets:

[0073] 0.23 g (0.404 mmol) of CoPcS was weighed into 80 mL of ultrapure water and dissolved by sonication for 5 min. Separately, 5 g (40 mmol) of melamine was weighed into the above solution (the molar ratio of CoPcS to melamine was 0.01:1). The mixture was sonicated for 10 min using a cell disruptor, then magnetically stirred for 4 h. The mixture was then transferred to a reaction vessel and reacted at 120 °C for 12 h. After the reaction, the mixture was washed several times with pure water until the filtrate was transparent, and then washed with anhydrous ethanol. The solution was dried at 80 °C to obtain a light blue powder. The light blue powder was placed in a covered boat and calcined at 600 °C for 2 h under a nitrogen atmosphere at a heating rate of 10 °C / min. After grinding with a mortar, gray-green Co-NS co-doped porous carbon nitride nanosheets were obtained.

[0074] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0075] Similar to Example 1, the yield of H2O2 was 713 μmol g. -1 h -1 .

[0076] Example 8

[0077] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets: Same as in Example 1.

[0078] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0079] 100 mg of Co-NS co-doped porous carbon nitride nanosheet catalyst was dispersed in 100 mL of pure water and mixed by ultrasonic treatment for 2 minutes. The mixture was then tested in air at a power density of 0.3 W / cm². 2 A 300W xenon lamp was used to produce H2O2 under simulated sunlight (320nm≤λ≤780nm). 2mL samples were taken every 15 minutes of illumination to determine the H2O2 concentration. The H2O2 concentration was determined by iodometric titration: 100μL of sample was added to 900μL of water, followed by the addition of 1mL of 0.1M potassium hydrogen phthalate solution and 1mL of 0.4M potassium iodide solution. After standing in darkness for 30 minutes, the absorbance was measured at 350nm using a UV-Vis spectrophotometer, yielding a H2O2 yield of 439 μmol g. -1 h -1 .

[0080] Example 9

[0081] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets: Same as in Example 1.

[0082] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0083] 100 mg of Co-NS co-doped porous carbon nitride nanosheet catalyst was dispersed in 50 mL of 0.05 v / v % HMF solution and mixed by sonication for 2 minutes. The catalyst was then tested in air at a power density of 0.3 W / cm². 2A 300W xenon lamp was used to produce H2O2 under simulated sunlight (320nm≤λ≤780nm). 2mL samples were taken every 15 minutes of illumination to determine the H2O2 concentration. The H2O2 concentration was determined by iodometric titration: 100μL of sample was added to 900μL of water, followed by the addition of 1mL of 0.1M potassium hydrogen phthalate solution and 1mL of 0.4M potassium iodide solution. After standing in darkness for 30 minutes, the absorbance was measured at 350nm using a UV-Vis spectrophotometer, yielding a H2O2 yield of 1064 μmol g. -1 h -1 .

[0084] Example 10

[0085] (1) Preparation of Co-NS co-doped porous carbon nitride nanosheets: Same as in Example 1.

[0086] (2) Application of Co-NS co-doped porous carbon nitride nanosheets:

[0087] 10 mg of Co-NS co-doped porous carbon nitride nanosheet catalyst was dispersed in 100 mL of 0.2 v / v % HMF solution and mixed by sonication for 2 minutes. The catalyst was then tested in air at a power density of 0.3 W / cm². 2 A 300W xenon lamp was used to produce H2O2 under simulated sunlight (320nm≤λ≤780nm). 2mL samples were taken every 15 minutes of illumination to determine the H2O2 concentration. The H2O2 concentration was determined by iodometric titration: 100μL of sample was added to 900μL of water, followed by the addition of 1mL of 0.1M potassium hydrogen phthalate solution and 1mL of 0.4M potassium iodide solution. After standing in darkness for 30 minutes, the absorbance was measured at 350nm using a UV-Vis spectrophotometer, yielding a H2O2 yield of 855μmol g. -1 h -1 .

Claims

1. A cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheet, characterized in that, The nanosheets are porous layered nanosheet structures with pore sizes of 10~50 nm. The preparation method of porous carbon nitride nanosheets based on cobalt-nitrogen-sulfur co-doped nanosheets includes the following steps: (1) Sulfonated cobalt phthalocyanine and melamine powder were ground thoroughly in an agate mortar and then deionized water was added. The mixture was ultrasonically mixed and then transferred to a reaction vessel. The mixture was heated in an oven to carry out a hydrothermal reaction. After the reaction was completed, the reaction precipitate was centrifuged, washed and dried to obtain Co-NS co-doped porous carbon nitride nanosheet precursor, which was a light blue powder. The molar ratio of sulfonated cobalt phthalocyanine to melamine is 0.01:1; (2) Place the light blue powder obtained in step (1) into a covered quartz boat, then put it into a tube furnace and calcine it in an inert gas atmosphere. After cooling to room temperature, the dark green powder obtained is the cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets Co-NS / CN.

2. The cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets according to claim 1, characterized in that, In step (1), the hydrothermal reaction conditions are: reacting at 100 ℃~180 ℃ for 6~24 h.

3. The method for preparing porous carbon nitride nanosheets based on cobalt-nitrogen-sulfur co-doped nanosheets according to claim 1, characterized in that, In step (1), the specific steps for obtaining the Co-NS co-doped porous carbon nitride nanosheet precursor by washing and drying the hydrothermal reaction precipitate are as follows: the blue precipitate is washed with ultrapure water until the filtrate is colorless and transparent, and then washed with ethanol to obtain the light blue powder of the Co-NS co-doped porous carbon nitride nanosheet precursor.

4. The method for preparing porous carbon nitride nanosheets based on cobalt-nitrogen-sulfur co-doping according to claim 1, characterized in that, In step (2), the calcination temperature is 450 ℃~600 ℃, the calcination time is 2~4 h, and the heating rate is 2~10 ℃ / min.

5. An application of the cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets according to claim 1, characterized in that, The cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets are used for photocatalytic H2O2 production.

6. The application of cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets according to claim 5, characterized in that, The application method is as follows: placing cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets in a quartz reaction vessel, and obtaining H2O2 in a system containing / without proton donor HMF under simulated sunlight.

7. The application of cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets according to claim 6, characterized in that, When the proton donor HMF is present, the mass-to-volume ratio of Co-NS co-doped porous carbon nitride nanosheets to the proton donor HMF aqueous solution is 0.0001~0.002:1 g / mL, and the volume fraction of the HMF aqueous solution is 0.01%~0.3%.

8. The application of cobalt-nitrogen-sulfur co-doped porous carbon nitride nanosheets according to claim 6, characterized in that, The simulated sunlight has a wavelength of 320 nm ≤ λ ≤ 780 nm and a power density of 0.3 W / cm². 2 The illumination time is 60~180 min.

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