A photocatalyst for supporting Co nanoparticles in S-doped g-C3N4 hollow square tubes and its preparation method

Abstract

This invention discloses a photocatalyst for supporting Co nanoparticles on S-doped g-C3N4 hollow square tubes and its preparation method. The method includes the following steps: 1. First, thiourea, dicyandiamide, cobalt acetate, hexadecyltrimethylammonium bromide, and ammonium fluoride are mixed to obtain mixed powder A; then, deionized water and methanol are added to mixed powder A and stirred. During stirring, concentrated ammonia is added dropwise until the mixture is homogeneous. The mixture is then transferred to the lining of a reaction vessel and sealed; 2. First, a drying oven is preheated to 60-150°C, and then the sealed reaction vessel is placed in the drying oven. After holding the solution at room temperature for 2–10 hours, remove the solution from the reactor and centrifuge, wash, and vacuum dry it to obtain solid product B. 3. Place solid product B in a magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the solution from room temperature to 450–650°C at a heating rate of 2–10°C / min, hold it at this temperature for 2–6 hours, and then cool it to room temperature with the furnace. Collect the product and grind it to obtain Co / S–g–C3N4 photocatalyst, which has good visible light absorption capacity and improves the efficiency of photocatalytic hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, specifically a photocatalyst for supporting Co nanoparticles on S-doped g-C3N4 hollow square tubes and its preparation method. Background Technology

[0002] Photocatalysis technology has been widely used in hydrogen production, organic degradation, and synthesis. Finding photocatalysts with high catalytic activity, low cost, and abundant raw materials is fundamental to the large-scale application of photocatalysis. Graphitic carbon nitride (g-C3N4), as a polymer semiconductor with a typical two-dimensional layered structure and narrow band gap, exhibits excellent visible light absorption, stable physicochemical properties, and excellent photocatalytic activity. However, the g-C3N4 structure produced by the thermally induced polymerization of traditional nitrogen-containing precursors is incomplete, with numerous defects in its bulk and surface. This leads to low conductivity, restricted separation of photoexcitation charges, and a high electron-hole recombination rate, significantly reducing its catalytic activity. Therefore, improving the crystallinity of g-C3N4 is essential.

[0003] Currently, developing novel composite photocatalytic materials using g-C3N4 nanosheets as the matrix is ​​an important approach to improving the performance of photocatalytic hydrogen production. g-C3N4 nanosheets play a crucial role in the composite material; therefore, in-depth comparative analysis of nanosheets obtained by different preparation methods to determine their advantages and disadvantages is of great significance for further development of novel composite photocatalytic materials. Currently, sulfur-doped nitrogen-defective graphitic carbon nitride (g-C3N4) is mostly synthesized using a combination of dicyandiamide and thiourea as mixed precursors via thermal polymerization and a rapid high-temperature method. In the research of g-C3N4 semiconductor photocatalytic hydrogen production, co-catalysts are needed to further enhance the catalytic activity of g-C3N4. Typically, these co-catalysts are rare and expensive metals, leading to high production costs. Therefore, exploring abundant and inexpensive co-catalysts to improve the photocatalytic activity of g-C3N4 is of great importance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a photocatalyst for supporting Co nanoparticles on S-doped g-C3N4 hollow square tubes and its preparation method. This method not only has low production costs but also produces a photocatalyst with good visible light absorption capabilities, thereby improving the efficiency of photocatalytic hydrogen production.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for preparing a photocatalyst with S-doped g-C3N4 hollow square tubes supporting Co nanoparticles includes the following steps:

[0007] Step 1: First, mix thiourea, dicyandiamide, cobalt acetate, hexadecyltrimethylammonium bromide, and ammonium fluoride in a molar ratio of 3:10:1:5:2 to obtain mixed powder A; then, add deionized water and methanol to mixed powder A and stir, adding concentrated ammonia dropwise during stirring. After mixing evenly, quickly transfer the mixture to the liner of the reaction vessel and seal it.

[0008] Step 2: First, preheat the drying oven to 60-150℃, then place the sealed reaction vessel into the drying oven and keep it at that temperature for 2-10 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, and centrifuge, wash and vacuum dry it in sequence to obtain solid product B.

[0009] Step 3: Place solid product B into a magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 450-650℃ at a heating rate of 2-10℃ / min, hold for 2-6 hours, cool the product to room temperature with the furnace, collect the product and grind it to obtain Co / Sg-C3N4 photocatalyst.

[0010] Furthermore, the concentration of concentrated ammonia in step 1 is 0.1 mol / L.

[0011] Furthermore, the stirring in step 1 is performed using a magnetic stirrer for 120–720 minutes.

[0012] Furthermore, the washing in step 2 involves washing with deionized water and anhydrous ethanol at least three times each.

[0013] Furthermore, the drying in step 2 is carried out using a vacuum drying oven at 60°C for 6–24 hours.

[0014] Furthermore, the grinding time in step 3 is 30 to 90 minutes.

[0015] A photocatalyst for supporting Co nanoparticles in an S-doped g-C3N4 hollow square tube is described. The tube is hollow and Co nanosheets are attached to the inner and outer walls of the hollow tube.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] In the preparation of the Co / Sg-C3N4 composite photocatalyst material, this invention first uses a simple hydrothermal method to obtain the precursor, and then through simple solid-state sintering, finally obtains a rare hollow tubular Sg-C3N4, which increases the specific surface area and the active sites for photocatalytic hydrogen production. Furthermore, Co nanosheets are uniformly attached to the inner and outer walls of the Sg-C3N4 hollow tube, enhancing the bonding between the Co nanosheets and Sg-C3N4. The excellent metallic properties of Co endow the composite photocatalyst with excellent visible light absorption, effectively promoting the separation and transport of photogenerated charges in Sg-C3N4 and improving hydrogen production efficiency. Simultaneously, most of the Co nanosheets are mainly attached to the inner wall of the hollow tube, effectively preventing the collapse of the tubular structure and making the photocatalytic performance of Co / Sg-C3N4 more stable. In short, this invention employs a simple method to modify g-C3N4 using abundant sulfur and metallic Co. This method not only has low production costs but also produces Co / Sg-C3N4 composite materials with good morphology and excellent photocatalytic performance, making it easy for industrial production. Attached Figure Description

[0018] Figure 1 This is an X-ray diffraction pattern of Co / Sg-C3N4 prepared in Example 1 of this invention;

[0019] Figure 2 This is a SEM scan of Co / Sg-C3N4 prepared in Example 1 of the present invention;

[0020] Figure 3 The graph shows the catalytic hydrogen production performance of Co / Sg-C3N4 prepared in Example 1 of this invention and that of existing g-C3N4. Detailed Implementation

[0021] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0022] Example 1

[0023] Step 1: Weigh 3 mmol thiourea, 10 mmol dicyandiamide, 1 mmol cobalt acetate, 5 mmol cetyltrimethylammonium bromide and 2 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 24 mL deionized water and 26 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 120 min. During the stirring process, add 3 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer it to the liner of the reaction vessel and seal it.

[0024] Step 2: First, preheat the drying oven to 80°C, then place the sealed reaction vessel into the drying oven and keep it warm for 4 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60°C for 14 hours to obtain solid product B.

[0025] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 550°C at a heating rate of 5°C / min, hold for 4 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 40 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

[0026] See Figure 1 At 13° and 27°, the peaks correspond to the (100) and (002) crystal planes of g-C3N4, respectively. Co / Sg-C3N4 accurately corresponds to g-C3N4PDF#87-1526 and Co PDF#15-0806. The slight shift in the diffraction peaks is due to sulfur doping of carbon nitride, indicating that Co / Sg-C3N4 photocatalyst was successfully prepared.

[0027] See Figure 2 Sg-C3N4 exhibits a good hollow tubular structure, and elemental Co is attached to the inner and outer walls of the hollow tube in a plate-like structure, mainly to the inner wall of the Sg-C3N4 hollow tube. This structure can effectively prevent the collapse of the hollow tubular structure.

[0028] 50 mg of the Co / Sg-C3N4 photocatalyst prepared in Example 1 was placed in a glass reaction vessel containing 90 mL of deionized water. Then, 10 mL of triethanolamine was added to the glass reaction vessel, and the mixture was irradiated for 4 hours. The photocatalytic effect of Co / Sg-C3N4 was tested using a LabSolar 6A instrument. The results are as follows: Figure 3 As shown, the total hydrogen production in 4 hours reached 3571.7 μmol, while under the same conditions, the total hydrogen production of g-C3N4 was only 102 μmol. It can be seen that the Co / Sg-C3N4 photocatalyst prepared in Example 1 has good catalytic hydrogen evolution performance.

[0029] Example 2

[0030] Step 1: Weigh 7.5 mmol thiourea, 25 mmol dicyandiamide, 2.5 mmol cobalt acetate, 12.5 mmol cetyltrimethylammonium bromide, and 5 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 30 mL deionized water and 30 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 150 min. During the stirring process, add 6 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer the mixture to the liner of the reaction vessel and seal it.

[0031] Step 2: First, preheat the drying oven to 100℃, then put the sealed reaction vessel into the drying oven and keep it warm for 6 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60℃ for 10 hours to obtain solid product B.

[0032] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 600°C at a heating rate of 10°C / min, hold for 2 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 60 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

[0033] Example 3

[0034] Step 1: Weigh 9 mmol thiourea, 30 mmol dicyandiamide, 3 mmol cobalt acetate, 15 mmol cetyltrimethylammonium bromide and 6 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 40 mL deionized water and 20 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 200 min. During the stirring process, add 5 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer it to the liner of the reaction vessel and seal it.

[0035] Step 2: First, preheat the drying oven to 90°C, then place the sealed reaction vessel into the drying oven and keep it warm for 3 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60°C for 16 hours to obtain solid product B.

[0036] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 500°C at a heating rate of 4°C / min, hold for 3 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 45 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

[0037] Example 4

[0038] Step 1: Weigh 1.5 mmol thiourea, 5 mmol dicyandiamide, 0.5 mmol cobalt acetate, 2.5 mmol cetyltrimethylammonium bromide and 1 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 20 mL deionized water and 10 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 400 min. During the stirring process, add 2 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer it to the liner of the reaction vessel and seal it.

[0039] Step 2: First, preheat the drying oven to 60°C, then place the sealed reaction vessel into the drying oven and keep it warm for 10 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60°C for 6 hours to obtain solid product B.

[0040] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 600°C at a heating rate of 2°C / min, hold for 5 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 30 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

[0041] Example 5

[0042] Step 1: Weigh 15 mmol thiourea, 50 mmol dicyandiamide, 5 mmol cobalt acetate, 25 mmol cetyltrimethylammonium bromide and 10 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 50 mL deionized water and 40 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 720 min. During the stirring process, add 10 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer it to the liner of the reaction vessel and seal it.

[0043] Step 2: First, preheat the drying oven to 120℃, then put the sealed reaction vessel into the drying oven and keep it warm for 8 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60℃ for 20 hours to obtain solid product B.

[0044] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 450°C at a heating rate of 6°C / min, hold for 6 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 80 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

[0045] Example 6

[0046] Step 1: Weigh 12 mmol thiourea, 40 mmol dicyandiamide, 4 mmol cobalt acetate, 20 mmol cetyltrimethylammonium bromide and 8 mmol ammonium fluoride respectively and mix them to obtain mixed powder A; then weigh 35 mL deionized water and 25 mL methanol and add them to mixed powder A. Stir with a magnetic stirrer for 600 min. During the stirring process, add 8 mL of 0.1 mol / L ammonia water dropwise. After mixing evenly, quickly transfer it to the liner of the reaction vessel and seal it.

[0047] Step 2: First, preheat the drying oven to 150℃, then put the sealed reaction vessel into the drying oven and keep it warm for 2 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, centrifuge and collect the precipitate. Then wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then put it into a vacuum drying oven and dry it at 60℃ for 24 hours to obtain solid product B.

[0048] Step 3: Place solid product B into a white magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 650°C at a heating rate of 5°C / min, hold for 2 hours, and then cool it to room temperature with the furnace. Collect the product and grind it in a mortar for 90 minutes to obtain a pale yellow Co / Sg-C3N4 photocatalyst.

Claims

1. A method for preparing a photocatalyst with S-doped g-C3N4 hollow square tube supporting Co nanoparticles, characterized in that, Includes the following steps: Step 1: First, mix thiourea, dicyandiamide, cobalt acetate, hexadecyltrimethylammonium bromide, and ammonium fluoride in a molar ratio of 3:10:1:5:2 to obtain mixed powder A; then, add deionized water and methanol to mixed powder A and stir, adding concentrated ammonia dropwise during stirring. After mixing evenly, quickly transfer the mixture to the liner of the reaction vessel and seal it. Step 2: First, preheat the drying oven to 60-150℃, then place the sealed reaction vessel into the drying oven and keep it at that temperature for 2-10 hours. When the internal temperature of the drying oven drops to room temperature, take out the solution inside the reaction vessel, and centrifuge, wash and vacuum dry it in sequence to obtain solid product B. Step 3: Place solid product B into a magnetic boat and place it in a tube furnace. Under an argon atmosphere, heat the product from room temperature to 450-650°C at a heating rate of 2-10°C / min, hold for 2-6 hours, cool the product to room temperature with the furnace, collect the product and grind it to obtain Co / Sg-C3N4 photocatalyst.

2. The method for preparing the photocatalyst with S-doped g-C3N4 hollow square tube supported on Co nanoparticles according to claim 1, characterized in that, The concentration of concentrated ammonia in step 1 is 0.1 mol / L.

3. The method for preparing the photocatalyst with S-doped g-C3N4 hollow square tube supported on Co nanoparticles according to claim 1, characterized in that, The stirring in step 1 is performed using a magnetic stirrer for 120–720 minutes.

4. The method for preparing the photocatalyst with S-doped g-C3N4 hollow square tube supported on Co nanoparticles according to claim 1, characterized in that, The washing in step 2 involves washing with deionized water and anhydrous ethanol at least three times each.

5. The method for preparing the photocatalyst with S-doped g-C3N4 hollow square tube supported on Co nanoparticles according to claim 1, characterized in that, The drying in step 2 is carried out using a vacuum drying oven at 60°C for 6–24 hours.

6. The method for preparing the photocatalyst with S-doped g-C3N4 hollow square tube supported on Co nanoparticles according to claim 1, characterized in that, The grinding time in step 3 is 30 to 90 minutes.

7. A photocatalyst for S-doped g-C3N4 hollow square tube-supported Co nanoparticles prepared by the method according to any one of claims 1 to 6, characterized in that, It is a hollow tube, with Co nanosheets attached to the inner and outer walls of the hollow tube.

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