Modified carbon nitride-based composite photocatalyst as well as preparation method and application thereof
By using ammonia pretreatment and potassium bromide-modified graphitic carbon nitride photocatalyst, the problem of insufficient catalytic activity was solved, and efficient photocatalytic synthesis of hydrogen peroxide was achieved, meeting the needs of industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QUZHOU UNIV
- Filing Date
- 2026-01-21
- Publication Date
- 2026-04-17
AI Technical Summary
Existing graphitic carbon nitride photocatalysts suffer from problems such as insufficient catalytic activity, severe recombination of photogenerated carriers, and narrow visible light absorption range, resulting in low efficiency in the photocatalytic synthesis of hydrogen peroxide and making it difficult to meet the needs of industrial applications.
By employing ammonia pretreatment and potassium bromide synergistic modification, a unique electronic structure regulation system is constructed by introducing cyano functionalization and potassium ion doping into carbon nitride materials, thereby optimizing the material's photogenerated charge separation and transport capabilities.
It significantly improves the light absorption capacity and photogenerated charge separation efficiency of the photocatalyst, increases the hydrogen peroxide generation rate, and realizes efficient hydrogen peroxide synthesis under visible light driven conditions, with good cycle stability and environmental friendliness.
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Figure CN121869417A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of graphite phase carbon nitride photocatalyst technology, specifically to a graphite phase carbon nitride-based composite photocatalyst pretreated with ammonia and synergistically modified with potassium bromide, its preparation method, and its application in the photocatalytic preparation of hydrogen peroxide (H2O2) under visible light. Background Technology
[0002] Hydrogen peroxide (H2O2) is an important chemical raw material widely used in medical disinfection, chemical synthesis, and environmental remediation. Currently, the main industrial method for producing hydrogen peroxide is the anthraquinone process. However, this method suffers from significant drawbacks such as high energy consumption, complex processes, and severe environmental pollution, making it difficult to meet the demands of green chemical development.
[0003] In contrast, photocatalytic synthesis of hydrogen peroxide has significant advantages: it is directly driven by solar energy, requiring no additional energy input, thus exhibiting remarkable energy efficiency and economy; simultaneously, it directly reduces oxygen (O2) to hydrogen peroxide through photogenerated electrons, with a simple and environmentally friendly reaction pathway, making it a green synthesis technology with great development potential. However, the large-scale application of current photocatalytic hydrogen peroxide synthesis technology is still limited by a core bottleneck—insufficient catalyst activity leading to a low hydrogen peroxide generation rate.
[0004] Graphitic carbon nitride (g-C3N4), as a non-metallic semiconductor photocatalyst, has shown broad application prospects in the field of photocatalysis due to its excellent visible light response characteristics, tunable band structure, unique two-dimensional conjugated system, good biocompatibility, and low synthesis cost. However, bulk g-C3N4 materials have intrinsic defects, including limited specific surface area, narrow visible light absorption range, and severe recombination of photogenerated carriers. These structural bottlenecks make it difficult for its photocatalytic efficiency to meet the needs of practical applications.
[0005] To overcome these limitations, researchers have developed heteroatom doping strategies to modulate the electronic structure of g-C3N4, thereby optimizing its photoelectric conversion performance. Although existing heteroatom doping techniques have improved the photocatalytic activity of materials to some extent, they still face key scientific challenges such as insufficient doping efficiency and limited synergistic effects, which restrict their further application in highly efficient photocatalytic systems.
[0006] Therefore, developing an efficient and controllable modification strategy to overcome the intrinsic defects of carbon nitride materials, significantly improve their photocatalytic performance, and expand their application scope and depth in the energy and environment fields has become a key scientific problem that urgently needs to be solved in the current photocatalysis research field. Summary of the Invention
[0007] The purpose of this invention is to overcome the problems of insufficient activity and poor synergistic effect of existing graphitic carbon nitride photocatalysts, and to provide a carbon nitride-based composite photocatalytic material modified by ammonia pretreatment and potassium bromide synergistic modification. At the same time, it provides a simple, mild and low-cost preparation method for this material, as well as an application method for the efficient and highly selective preparation of hydrogen peroxide under visible light driving. This provides a new idea for the development of high-performance non-metallic photocatalytic materials and promotes the industrial application of photocatalytic synthesis of hydrogen peroxide technology.
[0008] To solve the above-mentioned technical problems, the present invention provides a method for preparing a modified carbon nitride-based composite photocatalyst, comprising the following steps: (1) Calcine graphite phase carbon nitride under an ammonia atmosphere to obtain ammonia pretreated carbon nitride; (2) Ammonia pretreated carbon nitride and potassium bromide were mixed in proportion and calcined again under nitrogen atmosphere to obtain modified carbon nitride-based composite photocatalyst.
[0009] As a further description of the above technical solution, in step (2), the mass ratio of ammonia pretreatment carbon nitride to potassium bromide is 0.4:(1-5).
[0010] As a further description of the above technical solution, the mixing method of ammonia pretreatment carbon nitride and potassium bromide in step (2) includes grinding and mixing.
[0011] As a further description of the above technical solution, the heating rate of calcination in step (1) is 8-12℃ / min, the calcination temperature is 480-520℃, and the calcination time is 1-2h.
[0012] As a further description of the above technical solution, the heating rate of the second calcination in step (2) is 8-12℃ / min, the calcination temperature is 480-520℃, and the calcination time is 2-4h.
[0013] This invention also provides a modified carbon nitride-based composite photocatalyst, prepared by the above-described method. The modified carbon nitride-based composite photocatalyst uses graphitic carbon nitride (g-C3N4) as a matrix and is constructed through a synergistic modification strategy combining ammonia pretreatment and potassium bromide posttreatment to form a mixture of cyano (-C≡N) functionalized and potassium ion (-C≡N) functionalized components. The unique electronic structure regulation system of "doping synergy" can effectively promote the efficient separation and rapid transport of photogenerated charges, significantly enhance the adsorption and activation ability of materials for oxygen (O2), and thus achieve efficient catalysis of hydrogen peroxide synthesis reaction under visible light drive.
[0014] This invention also provides the application of modified carbon nitride-based composite photocatalysts in the photocatalytic preparation of hydrogen peroxide. The present invention also provides a method for photocatalytic preparation of hydrogen peroxide, specifically: after mixing a modified carbon nitride-based composite photocatalyst with an aqueous solution containing a sacrificial agent, the photocatalytic reaction is carried out under continuous oxygen irradiation by a xenon lamp to obtain hydrogen peroxide.
[0015] As a further description of the above technical solution, the sacrificial agent is at least one of ethanol, isopropanol, methanol or formic acid; the volume fraction of the sacrificial agent in the aqueous solution is 10% to 20%.
[0016] As a further description of the above technical solution, the amount of the modified carbon nitride-based composite photocatalyst added is 1–3 g / L; the light intensity of the xenon lamp is 60–450 mW / cm². 2 The wavelength is >420 nm; the temperature of the photocatalytic reaction is 15-35℃ and the time is 1-6h.
[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention creatively develops a carbon nitride-based composite photocatalyst synergistically modified with ammonia and potassium bromide. Using graphitic carbon nitride (g-C3N4) as the matrix, a strategy of "ammonia pretreatment combined with potassium bromide post-treatment" was employed to successfully construct a "cyano (C≡N) functionalized synergistic potassium ion (… This invention presents a novel electronic structure modulation system based on "K+ doping." Ammonia pretreatment optimizes the material structure and introduces nitrogen-rich reaction sites. Subsequent potassium bromide thermal treatment not only achieves effective K+ doping but, more importantly, induces the formation of strongly electron-withdrawing cyano functional groups. This unique structural synergy significantly enhances the catalyst's light absorption, promotes efficient separation and rapid transport of photogenerated charges, and significantly enhances the material's adsorption and activation capacity for oxygen (O2). Using this invention's K+-based composite photocatalyst, water and oxygen can be selectively converted into hydrogen peroxide under visible light, exhibiting good cycle stability, reusability, and a simple, mild, and low-cost preparation method, meeting the needs of continuous industrial production.
[0018] Experimental results show that the modified carbon nitride-based composite photocatalyst provided in this invention achieves a photocatalytic hydrogen peroxide production rate of up to 3.824 under visible light. It is 48 times that of unmodified graphitic carbon nitride (g-C3N4), and far exceeds that of carbon nitride doped only with potassium bromide (1.846). Furthermore, the photocatalytic reaction is driven by solar energy, with water and oxygen as raw materials, making it environmentally friendly and in line with the development trend of clean energy synthesis and green chemistry. It has important industrial application value in related fields such as medical disinfection, chemical synthesis, and environmental governance. Attached Figure Description
[0019] Figure 1These are the X-ray diffraction (XRD) patterns of the original g-C3N4, g-C3N4-NH3, and g-C3N4-NH3-KBr in Example 1.
[0020] Figure 2 These are Fourier transform infrared (FT-IR) spectra of the three carbon nitride samples from Example 1.
[0021] Figure 3 These are the C1s high-resolution XPS spectra of the three carbon nitride samples from Example 1.
[0022] Figure 4 These are the N1s high-resolution XPS spectra of the three carbon nitride samples from Example 1.
[0023] Figure 5 This is the K2p high-resolution XPS spectrum of g-C3N4-NH3-KBr in Example 1.
[0024] Figure 6 This is a comparison graph showing the rate of hydrogen peroxide production by photocatalysis of the three carbon nitride samples in Example 1 and the comparative example g-C3N4-KBr. Detailed Implementation
[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0026] Example 1 A method for preparing a modified carbon nitride-based composite photocatalyst includes the following steps: (1) Place melamine (5g) in a 30 mL covered crucible and heat it to 550°C in static air at a heating rate of 10°C / min. Keep it at the temperature for 4 hours to obtain a yellow solid. Grind it into a fine powder, which is graphitic carbon nitride (g-C3N4).
[0027] (2) Take 1 g of graphite phase carbon nitride (g-C3N4) and place it in a corundum crucible. Put it into a tube furnace and heat it to 500°C at a heating rate of 10°C / min under an ammonia atmosphere. Hold it at the temperature for 1 hour to obtain ammonia pretreated carbon nitride (g-C3N4-NH3). (3) Take 0.4g of ammonia-pretreated carbon nitride (g-C3N4-NH3) and 1g of potassium bromide and grind them in an agate mortar for 10 minutes until they are mixed evenly. Then place them in a corundum crucible and put them in a tube furnace. Heat them to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere and keep them warm for 2 hours to obtain a yellow solid. Wash it three times with ultrapure water by centrifugation (8000 r / min, 5 min each time) and dry it in a vacuum drying oven at 60°C to obtain ammonia and potassium bromide synergistic modified carbon nitride (g-C3N4-NH3-KBr), which is a modified carbon nitride-based composite photocatalyst product.
[0028] X-ray diffraction (XRD) analysis was performed on the prepared original graphitic carbon nitride (g-C3N4), ammonia-pretreated carbon nitride (g-C3N4-NH3), and synergistically modified carbon nitride (g-C3N4-NH3-KBr). The results are as follows: Figure 1 As shown, all three carbon nitride samples exhibited characteristic diffraction peaks of graphitic carbon nitride at 27.5°, corresponding to the aromatic ring interlayer stacking structure of its (002) crystal plane, indicating that the modification process did not destroy the basic crystal structure of carbon nitride. Comparing the peak intensities of the three curves, the diffraction peak intensity of the synergistically modified g-C3N4-NH3-KBr was significantly higher than that of the original g-C3N4 and g-C3N4-NH3 pretreated only with ammonia, indicating that the synergistic modification effect of ammonia pretreatment and potassium bromide effectively promoted the growth of carbon nitride crystals, improved the crystallinity of the material, and the more regular crystal structure helped to reduce the recombination probability of photogenerated carriers, thereby improving its photocatalytic performance.
[0029] Infrared spectroscopy analysis was performed on the prepared original graphitic carbon nitride (g-C3N4), ammonia-pretreated carbon nitride (g-C3N4-NH3), and synergistically modified carbon nitride (g-C3N4-NH3-KBr). Figure 2 As shown, all three samples exhibited characteristic absorption peaks of graphitic carbon nitride, indicating that the modification process did not disrupt the basic framework structure of g-C3N4. Among them, the peak at 808 cm⁻¹... -1 The absorption peak at 2177 cm⁻¹ corresponds to the characteristic out-of-plane bending vibration of the triazine ring and is one of the hallmark peaks of g-C₃N₄; the synergistically modified g-C₃N₄-NH₃-KBr sample shows an absorption peak at 2177 cm⁻¹. -1A new absorption peak appeared, which can be attributed to the stretching vibration of the C≡N bond, indicating that the synergistic modification of ammonia pretreatment and KBr introduced nitrogen-containing functional groups on the surface of carbon nitride. Compared with the original graphitic carbon nitride (g-C3N4) and ammonia pretreated carbon nitride (g-C3N4-NH3), the characteristic peaks of the synergistically modified carbon nitride (g-C3N4-NH3-KBr) are sharper, more regular in shape, and significantly stronger, reflecting the regulation of functional groups on the material surface and the improvement of structural regularity. This change helps to optimize the electronic structure and photogenerated carrier behavior of carbon nitride, thereby enhancing its photocatalytic activity.
[0030] X-ray photoelectron spectroscopy analysis was performed on the prepared original graphitic carbon nitride (g-C3N4), ammonia-pretreated carbon nitride (g-C3N4-NH3), and synergistically modified carbon nitride (g-C3N4-NH3-KBr). Figures 3-5 As shown, in the C 1s high-resolution spectrum ( Figure 3 In the study, all samples exhibited characteristic peaks at 288.3 eV, 286.0 eV, and 284.8 eV, corresponding to sp in the g-C3N4 framework, respectively. 2 The hybrid C=N and CN bonds, as well as the adsorbed carbon species on the surface, indicate that the modification process did not destroy the basic carbon-nitrogen framework of carbon nitride. Comparative analysis revealed changes in the relative intensities of the characteristic peaks in the synergistically modified g-C3N4-NH3-KBr sample, reflecting a modulation of the surface carbon-nitrogen bonding environment towards a direction more favorable for photogenerated carrier separation. (In the N 1s high-resolution spectrum...) Figure 4 In the figure, the peaks at 398.2 eV, 400.0 eV, and 401.1 eV correspond to the sp in the triazine ring, respectively. 2 Hybridized N, bridged N, and surface amino N, after ammonia pretreatment and synergistic modification with KBr, exhibited slight peak shifts and changes in relative intensity, indicating an optimization of the chemical environment of N in the material. This is beneficial for controlling the separation and migration of photogenerated carriers. (See K 2p high-resolution spectrum). Figure 5 In the study, the synergistically modified g-C3N4-NH3-KBr sample exhibited K 2p at 295.7 eV and 292.9 eV. 1 / 2 and K 2p 3 / 2 The characteristic peaks confirm that KBr was successfully introduced and used as a preservative. The presence of these forms on the material surface further corroborates the effectiveness of synergistic modification. These changes in chemical structure and electronic state provide an electronic basis for improving the photocatalytic performance of the material.
[0031] Example 2 A method for preparing a modified carbon nitride-based composite photocatalyst includes the following steps: (1) Take 5 g of graphite phase carbon nitride (g-C3N4) and place it in a corundum crucible. Put it into a tube furnace and heat it to 520°C at a heating rate of 12°C / min under an ammonia atmosphere. Hold it at the temperature for 2 hours to obtain ammonia pretreated carbon nitride (g-C3N4-NH3). (2) Take 0.8g of ammonia-pretreated carbon nitride (g-C3N4-NH3) and 6g of potassium bromide and grind them in an agate mortar for 15 minutes until they are evenly mixed. Then place them in a corundum crucible and put them in a tube furnace. Heat them to 500°C at a heating rate of 12°C / min under a nitrogen atmosphere and keep them warm for 3 hours to obtain a yellow solid. After washing it three times with ultrapure water by centrifugation, dry it in a vacuum drying oven at 60°C to obtain the modified carbon nitride-based composite photocatalyst product (g-C3N4-NH3-KBr).
[0032] Example 3 A method for preparing a modified carbon nitride-based composite photocatalyst includes the following steps: (1) Take 1 g of graphite phase carbon nitride (g-C3N4) and place it in a corundum crucible. Put it into a tube furnace and heat it to 480°C at a heating rate of 10°C / min under an ammonia atmosphere. Hold it at the temperature for 2 hours to obtain ammonia pretreated carbon nitride (g-C3N4-NH3). (2) Take 0.4g of ammonia-pretreated carbon nitride (g-C3N4-NH3) and 5g of potassium bromide and grind them in an agate mortar for 10 minutes until they are evenly mixed. Then place them in a corundum crucible and put them in a tube furnace. Heat them to 480°C at a heating rate of 8°C / min under a nitrogen atmosphere and keep them warm for 4 hours to obtain a yellow solid. After washing it three times with ultrapure water by centrifugation, dry it in a vacuum drying oven at 60°C to obtain the modified carbon nitride-based composite photocatalyst product (g-C3N4-NH3-KBr).
[0033] Comparative Example Take 0.4g of graphitic carbon nitride (g-C3N4) prepared in Example 1 and 1g of potassium bromide and grind them in an agate mortar for 10 minutes until they are mixed evenly. Then place them in a corundum crucible and put them in a tube furnace. Heat them to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere and keep them at that temperature for 2 hours to obtain a yellow KBr-doped carbon nitride product (g-C3N4-KBr).
[0034] It should be noted that graphitic carbon nitride (g-C3N4) can also be prepared directly using commercially available products or existing methods.
[0035] Catalytic performance testing of modified carbon nitride-based composite photocatalyst (g-C3N4-NH3-KBr) and KBr-doped carbon nitride product (g-C3N4-KBr) for photocatalytic hydrogen peroxide production: 27 mL of deionized water was poured into a 50 mL reaction tube, and 3 mL of ethanol was added as a hole sacrificial agent (isopropanol, methanol, or formic acid can also be used as sacrificial agents). Then, 30 mg of the modified carbon nitride-based composite photocatalyst prepared in Example 1 was added. The mixture was magnetically stirred, and then simulated solar irradiation was performed. The light source system used a 300W xenon lamp (wavelength > 420 nm) equipped with an ultraviolet cutoff filter. The reaction tube was placed in a double-walled glass beaker with external circulating water to maintain the reaction temperature at 25°C, and oxygen was continuously supplied. After 1 hour of reaction, a sample was taken, filtered through a 0.22 μm PTFE filter to remove the catalyst, and 1 mL of 0.462 M titanium sulfate solution was added to 3 mL of the filtrate. After sufficient reaction, the ultraviolet absorption intensity at 408 nm was measured using a UV-Vis spectrophotometer to indirectly determine the concentration of hydrogen peroxide. The KBr-doped carbon nitride product (g-C3N4-KBr) of Comparative Example 1 was tested according to the test method of Example 1, and the results are as follows: Figure 6 As shown. From Figure 6 The photocatalytic hydrogen peroxide production performance test results clearly show that the catalytic activity of carbon nitride samples with different modifications differs significantly under simulated sunlight: the yield of the original g-C3N4 is only 0.079%. The yield of g-C3N4-NH3 increased to 0.135% after ammonia pretreatment. The yield of KBr-doped g-C3N4-KBr was increased to 1.846%. The yield of g-C3N4-NH3-KBr modified by the synergistic effect of ammonia and KBr reached 3.824%. The efficiency is 48 times that of the original g-C3N4 and 2.1 times that of the KBr-doped g-C3N4-KBr in the comparative example. This result indicates that the synergistic effect of ammonia pretreatment and KBr doping can significantly improve the photocatalytic hydrogen peroxide production performance of carbon nitride. Combined with the aforementioned XRD, infrared, and XPS characterization results, this performance improvement stems from the increased crystallinity, surface functional group regulation, and electronic structure optimization of the material after synergistic modification, which effectively promotes the separation and migration of photogenerated carriers, thereby enhancing the generation and utilization efficiency of active species during the catalytic reaction.
[0036] The g-C3N4-NH3-KBr catalyst was repeatedly used in the photocatalytic production of H2O2. After each reaction, the catalyst was centrifuged, washed and dried. After 5 cycles, the yield still remained above 92% of the initial value, demonstrating excellent cycle stability and structural stability.
[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.
Claims
1. A method for preparing a modified carbon nitride-based composite photocatalyst, characterized in that, Includes the following steps: (1) Calcine graphite phase carbon nitride under an ammonia atmosphere to obtain ammonia pretreated carbon nitride; (2) Ammonia pretreated carbon nitride and potassium bromide were mixed in proportion and calcined again under nitrogen atmosphere to obtain modified carbon nitride-based composite photocatalyst.
2. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of ammonia pretreatment carbon nitride to potassium bromide is 0.4:(1-5).
3. The preparation method according to claim 1, characterized in that: In step (2), the mixing method of ammonia pretreatment carbon nitride and potassium bromide includes grinding and mixing.
4. The preparation method according to claim 2, characterized in that: The heating rate of the calcination in step (1) is 8-12℃ / min, the calcination temperature is 480-520℃, and the calcination time is 1-2 h.
5. The preparation method according to claim 2, characterized in that: The heating rate of the second calcination in step (2) is 8-12℃ / min, the calcination temperature is 480-520℃, and the calcination time is 2-4 h.
6. A modified carbon nitride-based composite photocatalyst, characterized in that: The modified carbon nitride-based composite photocatalyst is prepared by the preparation method according to any one of claims 1-5, and has an electronic structure regulation system with cyano functionalization and potassium ion doping.
7. The application of the modified carbon nitride-based composite photocatalyst according to claim 6 in the photocatalytic preparation of hydrogen peroxide.
8. A method for photocatalytic preparation of hydrogen peroxide, characterized in that, The specific process is as follows: the modified carbon nitride-based composite photocatalyst described in claim 6 is mixed with an aqueous solution containing a sacrificial agent, and then subjected to photocatalytic reaction by xenon lamp irradiation under continuous oxygen supply to obtain hydrogen peroxide.
9. The method for photocatalytic preparation of hydrogen peroxide according to claim 8, characterized in that: The sacrificial agent is at least one of ethanol, isopropanol, methanol or formic acid.
10. The method for photocatalytic preparation of hydrogen peroxide according to claim 8, characterized in that: The amount of the modified carbon nitride-based composite photocatalyst added is 1–3 g / L; the light intensity of the xenon lamp is 60–450 mW / cm². 2 The wavelength is >420 nm; the temperature of the photocatalytic reaction is 15-35℃ and the time is 1-6 h.