A NiS / WS2 / g-C3N4 photocatalyst and its preparation method

Abstract

This invention discloses a NiS / WS2 / g-C3N4 photocatalyst and its preparation method. The method includes the following steps: 1. Mixing nickel sulfate hexahydrate, sodium tungstate dihydrate, sodium dodecylbenzenesulfonate, melamine, urea, ammonium fluoride, and thioacetamide to obtain mixed powder A; adding deionized water to mixed powder A and sonicating; adding 2-pyrrolidone, mixing well, transferring to the liner of a reaction vessel, and sealing; 2. Preheating a vacuum drying oven to 100-160℃, placing the mixture in the sealed reaction vessel and maintaining the temperature for 8-12 hours; after cooling, sequentially separating the reaction solution... 1. After washing and vacuum drying, product B is obtained; 2. Product B is placed in a ceramic boat and placed in a tube furnace. Under argon protection, the temperature is increased from room temperature to 500-600℃ at a heating rate of 5-10℃ / min, held for 2-5 hours, cooled to room temperature with the furnace, and then increased to 200-400℃ at a heating rate of 2-8℃ / min, held for 1-3 hours, cooled with the furnace, the product is collected and ground to obtain NiS / WS2 / 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 NiS / WS2 / g-C3N4 photocatalyst and its preparation method. Background Technology

[0002] Photocatalytic water splitting for hydrogen production (PHR) is one of the most promising technologies for addressing environmental pollution and the ever-increasing energy demand. However, effectively converting solar energy into storable hydrogen energy presents significant challenges. Graphitic carbon nitride (g-C3N4), as a metal-free organic polymer semiconductor photocatalyst, has attracted widespread attention due to its ease of synthesis, partial absorption of visible light, excellent chemical / thermal stability, and easily tunable band structure. However, the photocatalytic activity of bulk carbon nitride prepared by thermal polymerization in existing technologies is severely limited by its small specific surface area, weak visible light absorption intensity, and high recombination rate of photoexcited electron-hole pairs. Therefore, improving the visible light photocatalytic activity of graphitic carbon nitride (CN) has become a key focus for researchers.

[0003] [Wang Haifei. Preparation of graphite-phase carbon nitride-based photocatalysts and their photocatalytic hydrogen production performance study [D]. University of Science and Technology of China, 2021] Research has found that using a co-catalyst combined with g-C3N4 is an effective way to improve the hydrogen production performance of carbon nitride. Although the noble metal co-catalyst Pt has excellent catalytic performance, its high price and scarce reserves limit its large-scale application. Therefore, seeking non-noble metal co-catalyst materials that can replace Pt and combining them with g-C3N4 is of great significance to promoting the research progress of photocatalytic water splitting for hydrogen production. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a NiS / WS2 / g-C3N4 photocatalyst and its preparation method, which not only has low production cost but also produces a photocatalyst with good visible light absorption capacity, 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 NiS / WS2 / g-C3N4 photocatalyst includes the following steps:

[0007] Step 1: Mix nickel sulfate hexahydrate, sodium tungstate dihydrate, sodium dodecylbenzenesulfonate, melamine, urea, ammonium fluoride, and thioacetamide in a molar ratio of 2:1:0.25:8:1:0.6:3 to obtain mixed powder A; add deionized water to mixed powder A and ultrasonically disperse it according to the ratio of nickel sulfate hexahydrate, deionized water, and 2-pyrrolidone (0.5-1.2 mmol): (30-70 mL): (0.001-0.015 g), then add 2-pyrrolidone and stir to mix it evenly. Quickly transfer the mixture to the liner of the reaction vessel and seal it.

[0008] Step 2: First, preheat the vacuum drying oven to 100-160℃, then place the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 8-12 hours. Once the internal temperature of the vacuum drying oven has dropped to room temperature, remove the reaction solution and centrifuge, wash, and vacuum dry it in sequence to obtain product B.

[0009] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 500-600°C at a heating rate of 5-10°C / min, hold it at that temperature for 2-5 hours, and then cool it to room temperature with the furnace. Next, heat the product to 200-400°C at a heating rate of 2-8°C / min, hold it at that temperature for 1-3 hours, and then cool it to room temperature with the furnace. Collect the product and grind it to obtain the NiS / WS2 / g-C3N4 photocatalyst.

[0010] Furthermore, the ultrasonic dispersion time in step 1 is 30–120 min.

[0011] Furthermore, the stirring in step 1 is performed using a magnetic stirrer for 90–150 minutes.

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

[0013] Furthermore, the vacuum drying in step 2 is carried out using a vacuum drying oven at 60°C for 10–24 hours.

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

[0015] Furthermore, NiS / WS2 exhibits a micron-sized flower-like cluster surrounding the g-C3N4 nanosheets.

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

[0017] This invention combines hydrothermal and solid-state sintering methods. First, NiS / WS2 is synthesized using a hydrothermal method, introducing carbon and nitrogen sources during this process. Then, g-C3N4 is generated through solid-state sintering, ultimately yielding a NiS / WS2 / g-C3N4 composite photocatalyst. NiS / WS2 exhibits a micron-flower-like structure composed of porous nanosheets, which coat the outside of the g-C3N4 nanosheets. Since g-C3N4 itself has a porous nanosheet structure, combined with the micron-flower-like structure of NiS / WS2, the specific surface area and the number of active sites of the NiS / WS2 / g-C3N4 composite photocatalyst are enhanced, resulting in excellent visible light absorption capacity. This effectively promotes the separation and transport of photogenerated charges, improving the catalytic hydrogen production efficiency. Furthermore, the preparation conditions of this invention are simple and easy to control, do not introduce impurities, and do not involve precious metals, resulting in low production costs and ease of industrial-scale production. Attached Figure Description

[0018] Figure 1 The X-ray diffraction pattern of NiS / WS2 / g-C3N4 prepared in Example 1 of this invention is shown below.

[0019] Figure 2 The image shows the X-ray diffraction pattern of NiS / WS2 prepared in Comparative Example 1 of this invention.

[0020] Figure 3 This is a SEM scan of NiS / WS2 prepared in Comparative Example 1 of this invention at 1 μm.

[0021] Figure 4 This is a SEM scan of NiS / WS2 / g-C3N4 prepared in Example 1 of the present invention;

[0022] Figure 5 The graph shows the catalytic hydrogen production performance of NiS / WS2 / g-C3N4 prepared in Example 1 of this invention and that of existing g-C3N4. Detailed Implementation

[0023] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0024] Example 1

[0025] Step 1: Mix 0.75 mmol nickel sulfate hexahydrate, 0.375 mmol sodium tungstate dihydrate, 0.094 mmol sodium dodecylbenzenesulfonate, 3 mmol melamine, 0.375 mmol urea, 0.225 mmol ammonium fluoride, and 1.124 mmol thioacetamide to obtain mixed powder A; first, add 60 mL of deionized water to mixed powder A and ultrasonically disperse for 60 min, then add 0.005 g 2-pyrrolidone, and stir with a magnetic stirrer for 50 min to make it uniformly mixed. Quickly transfer it to the liner of the reaction vessel and seal it.

[0026] Step 2: First, preheat the vacuum drying oven to 140℃, then put the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 10 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60℃ for 15 hours to obtain product B.

[0027] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 550°C at a heating rate of 5°C / min and hold for 4 hours. Then, cool the product to room temperature with the furnace. Next, heat the product to 300°C at a heating rate of 3°C / min and hold for 2 hours. Then, cool the product to room temperature with the furnace. Collect the product and put it into a mortar. Grind the product for 60 minutes to obtain a yellow powdered NiS / WS2 / g-C3N4 photocatalyst.

[0028] See Figure 1 The peak positions at 13° and 27° correspond to the (100) and (002) crystal planes of g-C3N4, respectively. The peak positions of the diffraction peaks accurately correspond to the standard card PDF#02-1280 of NiS, the standard card PDF#08-0237 of WS2, and the standard card PDF#87-1526 of g-C3N4, indicating that the NiS / WS2 / g-C3N4 photocatalyst was successfully prepared in Example 1.

[0029] Example 2

[0030] Step 1: Mix 1 mmol nickel sulfate hexahydrate, 0.5 mmol sodium tungstate dihydrate, 0.125 mmol sodium dodecylbenzenesulfonate, 4 mmol melamine, 0.5 mmol urea, 0.3 mmol ammonium fluoride and 1.5 mmol thioacetamide to obtain mixed powder A; first, add 50 mL of deionized water to mixed powder A and ultrasonically disperse for 80 min, then add 0.015 g 2-pyrrolidone, stir with a magnetic stirrer for 100 min to make it uniform, quickly transfer to the liner of the reaction vessel and seal it;

[0031] Step 2: First, preheat the vacuum drying oven to 160℃, then put the sealed reaction vessel into the vacuum drying oven and keep it warm for 8 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60℃ for 10 hours to obtain product B.

[0032] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 600°C at a heating rate of 10°C / min and hold for 3 hours. Then, cool the product to room temperature with the furnace. Next, heat the product to 400°C at a heating rate of 8°C / min and hold for 3 hours. Then, cool the product to room temperature with the furnace. Collect the product and put it into a mortar. Grind the product for 90 minutes to obtain a yellow powdered NiS / WS2 / g-C3N4 photocatalyst.

[0033] Example 3

[0034] Step 1: Mix 0.5 mmol nickel sulfate hexahydrate, 0.25 mmol sodium tungstate dihydrate, 0.0625 mmol sodium dodecylbenzenesulfonate, 2 mmol melamine, 0.25 mmol urea, 0.15 mmol ammonium fluoride, and 0.75 mmol thioacetamide to obtain mixed powder A; first, add 70 mL of deionized water to mixed powder A and ultrasonically disperse for 30 min, then add 0.012 g 2-pyrrolidone, and stir with a magnetic stirrer for 80 min to make it uniformly mixed. Quickly transfer it to the liner of the reaction vessel and seal it.

[0035] Step 2: First, preheat the vacuum drying oven to 120°C, then place the sealed reaction vessel into the vacuum drying oven and keep it warm for 12 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60°C for 20 hours to obtain product B.

[0036] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 500°C at a heating rate of 8°C / min and hold for 5 hours. Then, cool the product to room temperature with the furnace. Next, heat the product to 200°C at a heating rate of 2°C / min and hold for 3 hours. Then, cool the product to room temperature with the furnace. Collect the product and put it into a mortar. Grind the product for 80 minutes to obtain a yellow powdered NiS / WS2 / g-C3N4 photocatalyst.

[0037] Example 4

[0038] Step 1: Mix 1.05 mmol nickel sulfate hexahydrate, 0.525 mmol sodium tungstate dihydrate, 0.131 mmol sodium dodecylbenzenesulfonate, 4.2 mmol melamine, 0.525 mmol urea, 0.315 mmol ammonium fluoride and 1.575 mmol thioacetamide to obtain mixed powder A; first, add 30 mL of deionized water to mixed powder A and ultrasonically disperse for 100 min, then add 0.008 g 2-pyrrolidone, stir with a magnetic stirrer for 120 min to make it uniform, quickly transfer to the liner of the reaction vessel and seal it;

[0039] Step 2: First, preheat the vacuum drying oven to 100℃, then put the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 11 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60℃ for 24 hours to obtain product B.

[0040] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 600°C at a heating rate of 6°C / min and hold for 2 hours. Then, cool the product to room temperature with the furnace. Next, heat the product to 400°C at a heating rate of 4°C / min and hold for 1 hour. Then, cool the product to room temperature with the furnace. Collect the product and put it into a mortar. Grind the product for 30 minutes to obtain a yellow powdered NiS / WS2 / g-C3N4 photocatalyst.

[0041] Example 5

[0042] Step 1: Mix 1.2 mmol nickel sulfate hexahydrate, 0.6 mmol sodium tungstate dihydrate, 0.15 mmol sodium dodecylbenzenesulfonate, 4.8 mmol melamine, 0.6 mmol urea, 0.36 mmol ammonium fluoride, and 1.8 mmol thioacetamide to obtain mixed powder A; first, add 40 mL of deionized water to mixed powder A and ultrasonically disperse for 120 min, then add 0.001 g 2-pyrrolidone and stir with a magnetic stirrer for 150 min to make it uniformly mixed, then quickly transfer it to the liner of the reaction vessel and seal it;

[0043] Step 2: First, preheat the vacuum drying oven to 150°C, then place the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 9 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge it and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60°C for 12 hours to obtain product B.

[0044] Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 500°C at a heating rate of 10°C / min and hold for 5 hours. Then, cool the product to room temperature with the furnace. Next, heat the product to 300°C at a heating rate of 6°C / min and hold for 1 hour. Then, cool the product to room temperature with the furnace. Collect the product and put it into a mortar. Grind the product for 50 minutes to obtain a yellow powdery NiS / WS2 / g-C3N4 photocatalyst.

[0045] Comparative Example 1

[0046] Step 1: Mix 0.75 mmol nickel sulfate hexahydrate, 0.375 mmol sodium tungstate dihydrate, 0.094 mmol sodium dodecylbenzenesulfonate, 0.375 mmol urea, 0.225 mmol ammonium fluoride and 1.125 mmol thioacetamide to obtain mixed powder A; first, add 60 mL of deionized water to mixed powder A and ultrasonically disperse for 60 min, then add 0.005 g 2-pyrrolidone, stir with a magnetic stirrer for 50 min to make it uniform, quickly transfer to the liner of the reaction vessel and seal it;

[0047] Step 2: First, preheat the vacuum drying oven to 140℃, then put the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 10 hours. After the internal temperature of the vacuum drying oven drops to room temperature, take out the reaction solution, centrifuge and collect the precipitate. Wash the precipitate three times with deionized water and anhydrous ethanol respectively, and then dry it in the vacuum drying oven at 60℃ for 15 hours to obtain product B.

[0048] Step 3: Place product B in a mortar and grind for 60 minutes to obtain yellow powdered NiS / WS2.

[0049] See Figure 2 The positions of the diffraction peaks accurately correspond to the standard card PDF#02-1280 for NiS and the standard card PDF#08-0237 for WS2, indicating that Comparative Example 1 successfully prepared pure phase NiS / WS2.

[0050] See Figure 3 In the 1 μm SEM scan of the NiS / WS2 prepared in Comparative Example 1, a micron-flower-like structure composed of porous nanosheets self-assembled was observed.

[0051] See Figure 4 SEM scans of NiS / WS2 / g-C3N4 prepared in Example 1, compared with... Figure 3 It can be seen that g-C3N4 does not destroy the micron flower cluster structure of NiS / WS2. NiS / WS2 is distributed on the outside of g-C3N4 nanosheets, giving it a larger specific surface area and a greater number of active sites.

[0052] See Figure 530 mg of the NiS / WS2 / g-C3N4 photocatalyst prepared in Example 1 was placed in a glass reaction vessel containing 90 mL of ultrapure water. 10 mL of triethanolamine was then added to the glass reaction vessel, and the mixture was irradiated for 4 hours. The photocatalytic effect of NiS / WS2 / g-C3N4 was tested using a LabSolar 6A instrument. The total hydrogen production after 4 hours reached 2818.4 μmol. Under the same conditions, the total hydrogen production of g-C3N4 was only 136.2 μmol. Therefore, the NiS / WS2 / g-C3N4 photocatalyst prepared in Example 1 improved the efficiency of catalytic hydrogen production.

Claims

1. A method for preparing a NiS / WS2 / g-C3N4 photocatalyst, characterized in that, Includes the following steps: Step 1: Mix nickel sulfate hexahydrate, sodium tungstate dihydrate, sodium dodecylbenzenesulfonate, melamine, urea, ammonium fluoride, and thioacetamide in a molar ratio of 2:1:0.25:8:1:0.6:3 to obtain mixed powder A; add deionized water to mixed powder A and ultrasonically disperse it according to the ratio of nickel sulfate hexahydrate, deionized water, and 2-pyrrolidone (0.5-1.2 mmol): (30-70 mL): (0.001-0.015 g), then add 2-pyrrolidone and stir to mix it evenly. Quickly transfer the mixture to the liner of the reaction vessel and seal it. Step 2: First, preheat the vacuum drying oven to 100-160℃, then place the sealed reaction vessel into the vacuum drying oven and keep it at that temperature for 8-12 hours. Once the internal temperature of the vacuum drying oven has dropped to room temperature, remove the reaction solution and centrifuge, wash, and vacuum dry it in sequence to obtain product B. Step 3: First, place product B into a ceramic boat and put it in a tube furnace. Under argon protection, heat the product from room temperature to 500-600°C at a heating rate of 5-10°C / min, hold it at that temperature for 2-5 hours, and then cool it to room temperature with the furnace. Next, heat the product to 200-400°C at a heating rate of 2-8°C / min, hold it at that temperature for 1-3 hours, and then cool it to room temperature with the furnace. Collect the product and grind it to obtain the NiS / WS2 / g-C3N4 photocatalyst.

2. The preparation method of the NiS / WS2 / g-C3N4 photocatalyst according to claim 1, characterized in that, The ultrasonic dispersion time in step 1 is 30 to 120 minutes.

3. The preparation method of the NiS / WS2 / g-C3N4 photocatalyst according to claim 1, characterized in that, The stirring in step 1 is performed using a magnetic stirrer for 50–150 minutes.

4. The preparation method of the NiS / WS2 / g-C3N4 photocatalyst 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 NiS / WS2 / g-C3N4 photocatalyst according to claim 1, characterized in that, The vacuum drying in step 2 is carried out using a vacuum drying oven at 60°C for 10–24 hours.

6. The method for preparing the NiS / WS2 / g-C3N4 photocatalyst according to claim 1, characterized in that, The grinding time in step 3 is 30 to 90 minutes.

7. A NiS / WS2 / g-C3N4 photocatalyst prepared by the method according to any one of claims 1 to 6, characterized in that, NiS / WS2 appears as micron-sized flower clusters encapsulating the outside of g-C3N4 nanosheets.

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