Resin cross-linked hybrid graphitic carbon nitride and preparation method and application thereof

Abstract

The present application relates to a resin crosslinking hybrid graphite phase carbon nitride and its preparation method and application. In the present application, carbon nitride is first amine functionalized to increase the number of surface reaction sites and provide more defect sites for electron transfer. Then crosslink with MF resin, introduce additional hydroxyl groups through condensation reaction between formaldehyde units and amino groups, and connect the organic framework of MF resin with amine functionalized carbon nitride. Compared with the prior art, the present application improves the adsorption of O2, enhances the electron transfer and surface chemical properties by amine functionalization of carbon nitride and crosslinking with MF resin, greatly increases the production of photocatalytic production of H2O2 under visible light. At the same time, the present application also has the advantages of simple preparation, low cost, no need for sacrificial agent, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and in particular relates to a resin-crosslinked hybrid graphite phase carbon nitride and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is an important inorganic chemical product with widespread applications in printing and dyeing, pharmaceuticals, and biology. Currently, H2O2 is primarily produced using the anthraquinone process, which is energy-intensive and has a low safety factor. Photocatalysis uses water and oxygen to produce H2O2 through a series of sunlight-driven photochemical reactions, offering low cost and minimal pollution. Photocatalytic production of H2O2 is an emerging research area in artificial photosynthesis, and the development of efficient, stable, and inexpensive photocatalysts is a key research priority for scientists.

[0003] Graphitic carbon nitride (g-C3N4) has become a research hotspot in the field of photocatalysis due to its suitable band gap (2.7 eV), good chemical stability, and environmental compatibility. In recent years, numerous studies have demonstrated that carbon nitride photocatalysts possess a unique oxygen reduction reaction (ORR) that selectively generates H2O2, attracting widespread attention.

[0004] However, the carbon nitride prepared by traditional methods has a narrow spectral response range, easy recombination of photogenerated electrons and holes, and low selectivity of oxygen reduction reaction. These problems seriously restrict the activity of carbon nitride in the photocatalytic synthesis of H2O2. In addition, carbon nitride often requires alcohols as sacrificial agents to provide electron donors for the synthesis of hydrogen peroxide, which not only increases the synthesis cost of hydrogen peroxide, but also increases the cost of subsequent separation of hydrogen peroxide. Patent CN 114797931 A discloses a CuO / g-C3N4 photocatalyst and its application in the photocatalytic production of H2O2. However, the preparation method of this photocatalyst introduces metal elements, and isopropyl alcohol still needs to be used as a sacrificial agent during use. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a resin-crosslinked hybrid graphite phase carbon nitride and its preparation method and application.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for preparing resin-crosslinked hybrid graphite phase carbon nitride comprises the following steps:

[0008] (1) calcining melamine and grinding to obtain carbon nitride powder;

[0009] (2) dispersing carbon nitride powder in water to obtain a suspension, adding ethylenediamine to the suspension, stirring, and drying to obtain amine-functionalized carbon nitride powder;

[0010] (3) Amine-functionalized carbon nitride powder is dispersed in water to obtain a suspension, and MF resin (melamine resin) is added to the suspension. After stirring and baking, resin-crosslinked hybrid graphite phase carbon nitride is obtained.

[0011] Furthermore, in step (1), the calcination temperature is 530-600°C, preferably 550°C.

[0012] Furthermore, in step (1), the heating rate of the calcination is 2-4°C / min, preferably 2.5-3.5°C / min, and more preferably 2.5°C / min.

[0013] Furthermore, in step (1), the calcination time is 2-4 hours, preferably 2-3 hours, and more preferably 2.5 hours.

[0014] Furthermore, in step (2), the concentration of carbon nitride in the suspension is 15-25 g / L, preferably 20-25 g / L, and more preferably 25 g / L.

[0015] Furthermore, in step (2), the stirring speed is 300-550 rpm, preferably 350-500 rpm, and more preferably 500 rpm.

[0016] Furthermore, in step (2), the stirring time is 6-10 h, preferably 7-9 h, and more preferably 8 h.

[0017] Furthermore, in step (2), the stirring is preceded by ultrasound at room temperature in the dark for 1 hour.

[0018] Furthermore, in step (2), the mass ratio of carbon nitride to ethylenediamine is 1:(3-5), preferably 1:(3-4.5), and more preferably 1:3.6.

[0019] Furthermore, in step (3), the concentration of the amine-functionalized carbon nitride in the suspension is 15-25 g / L, preferably 20-25 g / L, and more preferably 25 g / L.

[0020] Furthermore, in step (3), the mass ratio of the amine-functionalized carbon nitride to the MF resin is (8-30):1, preferably (15-25):1, and more preferably 20:1.

[0021] Furthermore, in step (3), the ultrasonication time is 0.5-2 h, preferably 1-2 h, and more preferably 1 h.

[0022] Furthermore, in step (3), the stirring speed is 300-550 rpm, preferably 350-500 rpm, and more preferably 500 rpm.

[0023] Furthermore, in step (3), the stirring time is 0.5-2 h, preferably 1-2 h, and more preferably 1 h.

[0024] Furthermore, in step (3), the baking temperature is 150-180°C, preferably 160°C.

[0025] Furthermore, in step (3), the baking is carried out by drying at 70-90°C before the baking, and then the temperature is increased for baking.

[0026] The present invention also provides a resin-crosslinked hybrid graphite phase carbon nitride prepared according to the above preparation method.

[0027] The present invention also provides an application of resin-crosslinked hybrid graphite phase carbon nitride in photocatalytic preparation of H2O2.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention uses electrostatic adsorption to functionalize graphite-phase carbon nitride with ethylenediamine, thereby increasing the number of surface reaction sites and providing more electron transfer defect sites. The amine-functionalized carbon nitride is then cross-linked with the MF resin. The formaldehyde unit in the MF resin undergoes a condensation reaction with the amino group, introducing additional hydroxyl groups and connecting the organic framework of the MF resin with the functionalized carbon nitride. This synergistic effect improves the adsorption of O2, enhances electron transfer and surface chemical properties, and can effectively regulate the charge separation process on the carbon nitride and the selectivity of the oxygen reduction reaction, thereby promoting the photocatalytic and efficient preparation of hydrogen peroxide in pure water.

[0030] (2) The preparation method of the present invention has mild synthesis conditions, which significantly reduces energy consumption and improves the efficiency and cost-effectiveness of the preparation process. Furthermore, the preparation method of the present invention does not require the introduction of difficult-to-remove metal elements and does not require the addition of sacrificial agents during use. It not only has good operability but also can continuously catalyze water to produce H2O2 under visible light and without sacrificial agents, demonstrating good potential for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The infrared spectra (FTIR) of Example 2 and Comparative Examples 1-3 are shown.

[0032] Figure 2 The photoluminescence spectra (PL) of Example 2 and Comparative Examples 1-3 are shown.

[0033] Figure 3 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Example 2 (b, d) and Comparative Example 1 (a, c) are shown.

[0034] Figure 4 Graph showing the photocatalytic H2O2 production of different samples prepared in Examples 1-3 and Comparative Examples 1-3.

[0035] Figure 5 This is a test diagram of the cyclic stability of photocatalytic H2O2 production in Example 2. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] Unless otherwise specified, the reagents, methods, instruments, and equipment used in the present invention are conventional reagents, methods, instruments, and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available and analytically pure. The reagents and raw materials used in the following examples and tests are specifically described as follows: melamine, potassium iodide (analytical grade, Shanghai Titan Technology); ethylenediamine, potassium hydrogen phthalate (analytical grade, Shanghai Titan Technology); MF resin (Jinan Huakai Resin Co., Ltd.).

[0038] Example 1:

[0039] (1) Preparation of carbon nitride (CN): 5 g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 h. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0040] (2) Preparation of amine-functionalized carbon nitride (EDA-CN): 0.5 g of carbon nitride powder was placed in 20 mL of ultrapure water, sonicated for 30 min, and stirred at 500 rpm at room temperature to obtain a carbon nitride suspension. 2 mL of ethylenediamine (1.8 g) was slowly added dropwise to the suspension, sonicated for 1 h at room temperature in the dark, and stirred for 8 h. The mixture was then filtered and washed with water until the filtrate had a pH of 7.0. The sample was freeze-dried and ground into a fine powder for further use.

[0041] (3) Preparation of resin-crosslinked hybrid graphite carbon nitride (ME-CN): Weigh 0.5 g of amine-functionalized carbon nitride and place it in 20 mL of ultrapure water. Ultrasonicate for 30 min and stir the carbon nitride suspension at 500 rpm at room temperature. Add 0.0125 g of MF resin to the suspension, ultrasonicate for 1 h at room temperature in the dark, and stir for 1 h. After preliminary drying at 85 °C, continue baking at 160 °C for 5 min, wash with water, and then freeze-dry in vacuum to obtain resin-crosslinked hybrid graphite carbon nitride.

[0042] Example 2:

[0043] (1) Preparation of carbon nitride (CN): 5 g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 h. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0044] (2) Preparation of amine-functionalized carbon nitride (EDA-CN): 0.5 g of carbon nitride powder was placed in 20 mL of ultrapure water, sonicated for 30 min, and stirred at 500 rpm at room temperature to obtain a carbon nitride suspension. 2 mL of ethylenediamine (1.8 g) was slowly added dropwise to the suspension, sonicated for 1 h at room temperature in the dark, and stirred for 8 h. The mixture was then filtered and washed with water until the filtrate had a pH of 7.0. The sample was freeze-dried and ground into a fine powder for further use.

[0045] (3) Preparation of resin-crosslinked hybrid graphite carbon nitride (ME-CN): Weigh 0.5 g of amine-functionalized carbon nitride and place it in 20 mL of ultrapure water. Ultrasonicate for 30 min and stir the carbon nitride suspension at 500 rpm at room temperature. Add 0.025 g of MF resin to the suspension, ultrasonicate for 1 h at room temperature in the dark, and stir for 1 h. After preliminary drying at 85 °C, continue baking at 160 °C for 5 min, wash with water, and then freeze-dry in vacuum to obtain resin-crosslinked hybrid graphite carbon nitride.

[0046] Example 3:

[0047] (1) Preparation of carbon nitride (CN): 5 g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 h. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0048] (2) Preparation of amine-functionalized carbon nitride (EDA-CN): 0.5 g of carbon nitride powder was placed in 20 mL of ultrapure water, sonicated for 30 min, and stirred at 500 rpm at room temperature to obtain a carbon nitride suspension. 2 mL of ethylenediamine (1.8 g) was slowly added dropwise to the suspension, sonicated for 1 h at room temperature in the dark, and stirred for 8 h. The mixture was then filtered and washed with water until the filtrate had a pH of 7.0. The sample was freeze-dried and ground into a fine powder for further use.

[0049] (3) Preparation of resin-crosslinked hybrid graphite carbon nitride (ME-CN): Weigh 0.5 g of amine-functionalized carbon nitride and place it in 20 mL of ultrapure water. Ultrasonicate for 30 min and stir the carbon nitride suspension at 500 rpm at room temperature. Add 0.05 g of MF resin to the suspension, ultrasonicate for 1 h at room temperature in the dark, and stir for 1 h. After preliminary drying at 85 °C, continue baking at 160 °C for 5 min, wash with water, and then freeze-dry in vacuum to obtain resin-crosslinked hybrid graphite carbon nitride.

[0050] The present invention also provides the following comparative examples to demonstrate the beneficial effects of the present invention.

[0051] Comparative Example 1:

[0052] Comparative Example 1 provides pure carbon nitride (CN) and its preparation method. 5g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 hours. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0053] Comparative Example 2:

[0054] Comparative Example 2 provides an amine-functionalized carbon nitride (EDA-CN) and its preparation method. The preparation method is as follows:

[0055] (1) Preparation of carbon nitride (CN): 5 g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 h. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0056] (2) Preparation of amine-functionalized carbon nitride (EDA-CN): 0.5 g of carbon nitride powder was placed in 20 mL of ultrapure water, sonicated for 30 min, and stirred at 500 rpm at room temperature to obtain a carbon nitride suspension. 2 mL of ethylenediamine (1.8 g) was slowly added dropwise to the suspension, sonicated for 1 h at room temperature in the dark, and stirred for 8 h. The mixture was then filtered and washed with water until the filtrate had a pH of 7.0. The sample was freeze-dried and ground into a fine powder for further use.

[0057] Comparative Example 3:

[0058] Comparative Example 3 provides a resin-crosslinked hybrid graphite phase carbon nitride (MF-CN) that has not been amine-functionalized and a preparation method thereof. The preparation method is as follows:

[0059] (1) Preparation of carbon nitride (CN): 5 g of melamine was weighed and placed in a crucible. The temperature in a muffle furnace was raised from room temperature at a rate of 2.5°C / min to a calcination temperature of 550°C, followed by calcination for 2.5 h. After the muffle furnace cooled to room temperature, the sample was removed and ground into a uniform carbon nitride powder using an agate mortar.

[0060] (2) Preparation of resin-crosslinked hybrid graphite carbon nitride (MF-CN) without amine functionalization: Weigh 0.5 g of carbon nitride and place it in 20 mL of ultrapure water. Ultrasonicate for 30 min and stir the carbon nitride suspension at 500 rpm at room temperature. Add 0.025 g of MF resin to the suspension, ultrasonicate for 1 h at room temperature in the dark, and stir for 1 h. After preliminary drying at 85 ° C, continue baking at 160 ° C for 5 min, wash with water, and then freeze-dry in vacuum to finally obtain resin-crosslinked hybrid graphite carbon nitride without amine functionalization.

[0061] The present invention performs the following tests on Examples 1-3 and Comparative Examples 1-3 to demonstrate the beneficial effects of the present invention:

[0062] (1) The samples of Example 2 and Comparative Examples 1-3 were characterized by infrared spectroscopy using an infrared spectrometer (PerkinElmer Spectrum Two).

[0063] (2) The samples of Example 2 and Comparative Examples 1-3 were characterized by photoluminescence spectrometer (FLS1000, Edinburgh, UK).

[0064] (3) The surface morphology of the samples of Example 2 and Comparative Example 1 was characterized using a scanning electron microscope (S-4800) and a transmission electron microscope (JEM-2100).

[0065] (4) Photocatalytic H2O2 Production Performance Test: Without adding a sacrificial agent, 30 mg of each catalyst sample of Examples 1-3 and Comparative Examples 1-3 was dispersed in 30 ml of ultrapure water and illuminated with a 300 W xenon lamp to simulate visible light. The photocatalytic H2O2 production performance of each sample was tested. During this process, 1 mL of the reaction solution was sampled every 1 h, and then 1 mL of a 0.1 M potassium hydrogen phthalate solution and 1 mL of a 0.4 M potassium iodide solution were immediately added to the reaction solution (the H2O2 yield was determined by iodine titration). The absorbance at 350 nm was then measured to quantitatively determine the H2O2 yield.

[0066] like Figure 1 As shown, the infrared spectra of Example 2 and Comparative Examples 1-3 are generally similar, indicating that the four samples have similar molecular structures. However, upon closer inspection, the infrared spectra of Comparative Example 2 at 3200-3500 cm -1The absorption peak in the region is stronger than that in comparative example 1, which is due to the NH bond vibration of the modified ethylenediamine, and also proves the successful combination of ethylenediamine and graphite phase carbon nitride material. -1 The peaks nearby became weaker, indicating that the -NH2 group reacted with the MF resin to form a new chemical bond, and the vibration peak of -NH2 also weakened.

[0067] like Figure 2 As shown in the figure, the PL emission intensities of Comparative Example 2, Comparative Example 3, and Example 2 are significantly lower than that of Comparative Example 1, among which the PL emission intensity of Example 2 is the weakest. This indicates that the further crosslinking of the amine-functionalized carbon nitride and the MF resin helps to enhance the separation of electron-hole pairs in Example 2.

[0068] like Figure 3 As shown, the morphology of Comparative Example 1 and Example 2 was observed using SEM and TEM. These samples showed similar morphology, both of which were irregular flake structures. TEM observation ( Figure 3 cd) confirmed the similarity of the morphologies of the two groups of samples. However, after the crosslinking reaction, the carbon nitride layer stacking structure of Example 2 deteriorated. This is because during the crosslinking process, the formaldehyde groups in the MF resin reacted with the amino groups on the carbon nitride surface. This reaction resulted in the formation of -NH-CH2-OH between the materials, thereby achieving crosslinking of the MF resin and attaching the MF resin molecules to the carbon nitride surface. Therefore, the introduced resin molecules and the resulting crosslinks will affect the layer stacking structure of the carbon nitride.

[0069] like Figure 4 The amount of H2O2 produced by photocatalysis in Examples 1-3 and Comparative Examples 1-3 changes over time. Compared with the unmodified carbon nitride (i.e., Comparative Example 1), the photocatalytic activity of the other samples has been improved, which shows that the introduction of the amino group of EDA and the MF resin has played a certain positive role in the catalytic production of H2O2. The amount of H2O2 produced by the amine-functionalized and modified carbon nitride in Examples 1-3 is higher than that of the carbon nitride modified with ethylenediamine and MF resin alone. Among them, Example 1 has the best performance in producing H2O2, and can produce 451.6μmol / L of H2O2, which is 10 times that of Comparative Example 1 (45.1μmol / L). The amine-functionalized CN cross-linked with MF significantly improves the photocatalytic H2O2 yield, exceeding the effect of introducing a single functional molecule, indicating that the introduced bimolecular system has a good synergistic effect in achieving excellent photocatalytic H2O2 yield.

[0070] like Figure 5 As shown, Example 2 was subjected to a cyclic stability experiment for photocatalytic production of H2O2. After four cycles of repeated testing, Example 2 still retained 86% of its catalytic activity, indicating that the resin-crosslinked hybrid graphite phase carbon nitride prepared by the present invention has good cyclic stability.

[0071] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing resin-crosslinked hybrid graphite phase carbon nitride, characterized in that: The following steps are involved: (1) calcining melamine and grinding it to obtain carbon nitride powder; (2) dispersing carbon nitride powder in water to obtain a suspension, adding ethylenediamine to the suspension, stirring, and drying to obtain amine-functionalized carbon nitride powder; (3) dispersing the amine-functionalized carbon nitride powder in water to obtain a suspension, adding MF resin to the suspension, stirring, and baking to obtain resin-crosslinked hybrid graphite phase carbon nitride; In step (2), the mass ratio of carbon nitride to ethylenediamine is 1:(3-5); In step (3), the mass ratio of the amine-functionalized carbon nitride to the MF resin is (8-30):

1.

2. The method for preparing a resin-crosslinked hybrid graphite phase carbon nitride according to claim 1, characterized in that: In step (1), the calcination temperature is 530-600°C, the calcination heating rate is 2-3°C / min, and the calcination time is 2-4h.

3. The method for preparing a resin-crosslinked hybrid graphite phase carbon nitride according to claim 1, characterized in that: In step (2), the concentration of carbon nitride in the suspension is 15-25 g / L.

4. The method for preparing a resin-crosslinked hybrid graphite phase carbon nitride according to claim 1, characterized in that: In step (2), the stirring speed is 300-550 rpm, and the stirring time is 6-10 h.

5. The method for preparing a resin-crosslinked hybrid graphite phase carbon nitride according to claim 1, characterized in that: In step (3), the concentration of amine-functionalized carbon nitride in the suspension is 15-25 g / L.

6. The method for preparing a resin-crosslinked hybrid graphite phase carbon nitride according to claim 1, characterized in that: In step (3), the stirring speed is 300-550 rpm, the stirring time is 0.5-2 h, and the baking temperature is 150-180°C.

7. A resin-crosslinked hybrid graphite phase carbon nitride prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the resin-crosslinked hybrid graphite-phase carbon nitride according to claim 7 in the photocatalytic preparation of H2O2.

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