A zinc-doped nickel selenide / graphitic carbon nitride composite photocatalyst and a preparation method thereof

Abstract

This invention provides a zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst and its preparation method. The method involves adding zinc acetate, nickel chloride hexahydrate, melamine, urea, pyrrole, and polyaniline to deionized water in a mass ratio of (0.5-1.5):(4-6):(4-10):(6-8):(0.125-0.2):(0.25-1) to obtain a mixed solution. The pH of the mixed solution is adjusted to 9-10, and the solution is then mixed thoroughly to obtain a precursor solution. The precipitate obtained after centrifuging the precursor solution is dried to obtain a precursor. The precursor and selenium source are then subjected to a two-stage calcination treatment under an inert atmosphere in a mass ratio of (1-10):(0.2-5). The first stage temperature is 450-600℃, and the second stage temperature is 300-400℃, to obtain the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst. This invention can effectively increase the number of reactive sites in photocatalysts and expand the migration path of photogenerated carriers, thereby effectively reducing the recombination of photogenerated carriers in photocatalytic materials and fundamentally improving their photocatalytic hydrogen evolution efficiency.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst and its preparation method. Background Technology

[0002] Solar-driven photocatalytic water splitting for hydrogen production has become one of the most attractive renewable energy technologies for addressing the energy crisis and environmental problems. However, finding or exploring an ideal photocatalyst that is highly active, low-cost, and stable under visible light over a long period remains a significant challenge. To date, researchers have made considerable efforts to develop suitable semiconductor photocatalysts for highly active water splitting. However, many of the major limitations to achieving high photocatalytic efficiency using solar energy are the constraints imposed by light absorption and the rapid recombination of electron-hole pairs. Therefore, improvements in charge separation and light absorption have proven to be key to enhancing photocatalytic performance.

[0003] In recent years, graphitic carbon nitride (g-C3N4), as a metal-free conjugated polymer semiconductor, has been considered one of the most promising photocatalytic materials. Its advantages, including a suitable band gap (2.7 eV), non-toxicity, excellent chemical stability, low cost, and convenient preparation methods, have attracted considerable attention in the field of photocatalysis. However, its low light absorption in the visible light region, small surface area, and rapid photogenerated electron-hole recombination rate severely limit its photocatalytic activity.

[0004] To date, graphitic carbon nitride can be combined with many materials to form composite photocatalysts, such as titanium carbide, metal porphyrin, tin disulfide and hexagonal boron nitride. Although these composites improve the intrinsic photocatalytic activity of g-C3N4, they still do not have the advantages of superior performance and low cost. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst and its preparation method, wherein the photocatalyst is a composite material composed of Ni-NiSe and g-C3N4.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst includes the following steps:

[0008] S1, zinc acetate, nickel chloride hexahydrate, melamine, urea, pyrrole and polyaniline are added to deionized water in a mass ratio of (0.5-1.5):(4-6):(4-10):(6-8):(0.125-0.2):(0.25-1) to obtain a mixture;

[0009] S2, adjust the pH of the mixture to 9-10, mix thoroughly to obtain the precursor solution, and dry the precipitate obtained after centrifuging the precursor solution to obtain the precursor.

[0010] S3, with a mass ratio of (1-10):(0.2-5), the precursor and selenium source are subjected to a two-stage calcination treatment under an inert atmosphere. The temperature of the first stage is 450-600℃, and the temperature of the second stage is 300-400℃, to obtain a zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst.

[0011] Preferably, the ratio of zinc acetate to deionized water in S1 is (0.5-1.5)g:(80-120)mL.

[0012] Preferably, in S2, a 0.5–1 mol / L sodium hydroxide solution is used to adjust the pH of the mixture.

[0013] Preferably, in step S2, the adjusted mixture is stirred for 360-720 minutes to obtain a precursor solution. The precipitate obtained after centrifuging the precursor solution is dried in a vacuum drying oven for 10-20 hours to obtain the precursor.

[0014] Preferably, the selenium source mentioned in S3 is sodium selenite.

[0015] Preferably, the calcination process in S3 is carried out in a tube furnace, with the precursor and selenium source placed in a ceramic boat. The selenium source is located at the inlet end of the tube furnace, and the precursor is located at the outlet end of the tube furnace.

[0016] Preferably, in S3, the first stage of heat preservation is 1-3 hours, and the second stage of heat preservation is 0.5-2 hours.

[0017] Preferably, in S3, the heating rate of the first stage is 2-5℃ / min, starting from room temperature. After the first stage is completed, the temperature is naturally cooled to room temperature, and then the second stage of calcination is carried out starting from room temperature, with a heating rate of 5-10℃ / min.

[0018] Preferably, after the second stage in S3 is completed, the obtained solid is ground for 30-90 minutes to obtain a zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst.

[0019] A zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst obtained by the preparation method of the zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst described in any one of the above claims.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] This invention discloses a method for preparing a zinc-doped nickel selenide (Zn-NiSe) / graphitic carbon nitride composite photocatalyst. The method employs only solid-state sintering, avoiding the introduction of impurities. Furthermore, the entire preparation process is simple, the conditions are easily controlled, the production cost is low, and it is easy to industrialize. This invention uses a two-stage heat-preserving calcination method, where sodium selenite decomposes into sodium oxide and selenium dioxide at temperatures above 300°C. The selenium dioxide reacts with the precursor to form nickel selenide, resulting in a material with an ultrathin nanostructure and a large specific surface area. This effectively increases the number of reactive sites in the photocatalyst and expands the migration path of photogenerated carriers, thereby effectively reducing the recombination of photogenerated carriers in the photocatalytic material and fundamentally improving its photocatalytic hydrogen evolution efficiency. This invention can effectively enhance the recombination of Zn-NiSe and g-C3N4, promoting the formation of an effective heterogeneous interface, thus greatly suppressing the recombination of photogenerated electrons in the composite catalyst, giving the Zn-NiSe / g-C3N4 composite material excellent photocatalytic hydrogen evolution performance. Furthermore, the combination of the two can be enhanced, giving the Zn-NiSe / g-C3N4 composite catalyst good stability. Attached Figure Description

[0022] Figure 1 The image shows the X-ray diffraction pattern of Zn-NiSe / g-C3N4 prepared in Example 1 of this invention.

[0023] Figure 2 The image shows the scanning pattern of Zn-NiSe / g-C3N4 prepared in Example 1 of this invention at 3 μm.

[0024] Figure 3 The image shows the performance of Zn-NiSe / g-C3N4 prepared in Example 1 of this invention under visible light irradiation. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0026] This invention discloses a method for preparing a Zn-NiSe / g-C3N4 composite photocatalyst, comprising the following steps:

[0027] Step 1: First, weigh out a certain amount of zinc acetate and nickel chloride hexahydrate, and place them in a beaker containing water. Then, add melamine, urea, pyrrole, and polyaniline in sequence. The mass ratio of zinc acetate: nickel chloride hexahydrate: melamine: urea: pyrrole: polyaniline is (0.5-1.5):(4-6):(4-10):(6-8):(0.125-0.2):(0.25-1). The ratio of zinc acetate to deionized water is (0.5-1.5)g:(80-120)mL. Add a certain volume of 0.5-1mol / L sodium hydroxide solution to make the pH of the mixture 9-10.

[0028] Step 2: Place it on a magnetic stirrer and stir for 360-720 min. Then pour out the mixture and centrifuge. Place the precipitate in a vacuum drying oven and dry for 10-20 h to obtain precursor A, which contains metal hydroxides (Zn(OH)2 and Ni(OH)2) and water-insoluble nitrogen and carbon sources.

[0029] Step 3: Weigh precursor A and sodium selenite (selenium source) in a mass ratio of (1-10):(0.2-5) and place them upstream and downstream of a ceramic boat (selenium source is placed upstream, i.e., at the gas inlet of the tube furnace). The mass of precursor A is 0.5-1.2g. Place the ceramic boat in the tube furnace and, under the protection of an inert atmosphere (Ar), set the first stage calcination temperature to 450-600℃, hold for 1-3 hours, and raise the temperature at a rate of 2-5℃ / min, starting from room temperature. The second stage calcination temperature is 300-400℃, hold for 0.5-2 hours, and raise the temperature at a rate of 5-10℃ / min. After the first stage is completed, allow the material to cool naturally to room temperature and then raise the temperature again from room temperature. Sodium selenite decomposes into sodium oxide and selenium dioxide above 300℃. Selenium dioxide reacts with the precursor to form nickel selenide.

[0030] Step 4: After calcination, the sample is naturally cooled in the furnace and ground in a mortar for 30-90 minutes to obtain gray powder B, namely Zn-NiSe (zinc-doped nickel selenide) / g-C3N4 photocatalyst.

[0031] Step 5: The photocatalytic effect of Zn-NiSe / g-C3N4 was tested using a LabSolar 6A all-glass automated online trace gas analysis system.

[0032] The specific test procedure is as follows: Weigh 50mg of photocatalyst and 10mL of triethanolamine, and place them in a glass reaction vessel containing 90mL of ultrapure water, and irradiate with light for 4 hours.

[0033] Example 1:

[0034] This invention discloses a method for preparing a Zn-NiSe / g-C3N4 composite photocatalyst, comprising the following steps:

[0035] Step 1: First, weigh out a certain amount of zinc acetate and nickel chloride hexahydrate, and place them in a beaker containing 80 mL of water. Then, add melamine, urea, pyrrole, and polyaniline in sequence. The mass ratio of zinc acetate: nickel chloride hexahydrate: melamine: urea: pyrrole: polyaniline is 1:3:5:7:0.15:0.3, with specific masses of 1 g, 3 g, 5 g, 7 g, 0.15 g, and 0.3 g, respectively. Add a certain volume of 0.5 mol / L sodium hydroxide solution to make the pH of the mixture 9.5.

[0036] Step 2: Place it on a magnetic stirrer and stir for 420 min. Then pour out the mixture and centrifuge. Place the precipitate in a vacuum drying oven and dry for 12 h to obtain precursor A.

[0037] Step 3: Weigh precursor A and sodium selenite in a mass ratio of 3:2 and place them upstream and downstream of the ceramic boat (the selenium source is placed upstream, i.e., at the gas inlet of the tube furnace). The mass of precursor A is 0.6g. Place the ceramic boat in the tube furnace and, under the protection of an inert atmosphere (Ar), set the first stage calcination temperature to 550℃, hold for 2 hours, and raise the temperature at a rate of 2℃ / min, starting from room temperature. The second stage calcination temperature is 350℃, hold for 1 hour, and raise the temperature at a rate of 10℃ / min. After the first stage is completed, allow the material to cool naturally to room temperature, and then raise the temperature again from room temperature.

[0038] Step 4: After calcination, the sample is naturally cooled in the furnace and ground in a mortar for 60 minutes to obtain gray powder B, namely Zn-NiSe / g-C3N4 photocatalyst.

[0039] Step 5: The photocatalytic effect of Zn-NiSe / g-C3N4 was tested using a LabSolar 6A all-glass automated online trace gas analysis system.

[0040] The specific test procedure is as follows: Weigh 50mg of photocatalyst and 10mL of triethanolamine, and place them in a glass reaction vessel containing 90mL of ultrapure water, and irradiate with light for 4 hours.

[0041] Figure 1 The horizontal axis represents the 2θ angle, and the vertical axis represents the diffraction peak intensity. The peaks at 13° and 27° correspond to the (100) and (002) crystal planes of g-C3N4 (PDF#87-1526), ​​respectively, and Zn-NiSe / g-C3N4 can also accurately correspond to NiSe (PDF#02-0892), indicating that Zn-NiSe / g-C3N4 photocatalysis was successfully prepared.

[0042] from Figure 2It can be clearly observed that both Zn-NiS and g-C3N4 exhibit nanosheet structures. Among them, g-C3N4 exhibits large serrated lettuce-like nanosheet structures, while Zn-NiSe nanosheets are smaller and thinner and grow on g-C3N4 nanosheets.

[0043] from Figure 3 It can be clearly seen that the Zn-NiSe / g-C3N4 photocatalyst sample has excellent hydrogen evolution performance, with a hydrogen evolution rate exceeding 800 μmol / g / h under visible light.

[0044] Example 2:

[0045] This invention discloses a method for preparing a Zn-NiSe / g-C3N4 composite photocatalyst, comprising the following steps:

[0046] Step 1: First, weigh out a certain amount of zinc acetate and nickel chloride hexahydrate, and place them in a beaker containing 100mL of water. Then, add melamine, urea, pyrrole, and polyaniline in sequence. The mass ratio of zinc acetate: nickel chloride hexahydrate: melamine: urea: pyrrole: polyaniline is 1.2:5:6:6:0.2:0.5, with specific masses of 1.2g, 5g, 6g, 6g, 0.2g, and 0.5g, respectively. Add a certain volume of 1mol / L sodium hydroxide solution to make the pH of the mixture = 10.

[0047] Step 2: Place it on a magnetic stirrer and stir for 600 min. Then pour out the mixture and centrifuge. Place the precipitate in a vacuum drying oven and dry for 10 h to obtain precursor A.

[0048] Step 3: Weigh precursor A and sodium selenite in a mass ratio of 3:2 and place them upstream and downstream of the ceramic boat (the selenium source is placed upstream, i.e., at the gas inlet of the tube furnace). The mass of precursor A is 0.9g. Place the ceramic boat in the tube furnace and, under the protection of an inert atmosphere (Ar), set the first stage calcination temperature to 600℃, hold for 1h, and raise the temperature at a rate of 5℃ / min, starting from room temperature. The second stage calcination temperature is 300℃, hold for 1.5h, and raise the temperature at a rate of 6℃ / min. That is, after the first stage is completed, allow it to cool naturally to room temperature, and then raise the temperature again starting from room temperature.

[0049] Step 4: After calcination, the sample is naturally cooled in the furnace and ground in a mortar for 90 minutes to obtain gray powder B, namely Zn-NiSe / g-C3N4 photocatalyst.

[0050] Example 3:

[0051] This invention discloses a method for preparing a Zn-NiSe / g-C3N4 composite photocatalyst, comprising the following steps:

[0052] Step 1: First, weigh out a certain amount of zinc acetate and nickel chloride hexahydrate, and place them in a beaker containing 120 mL of water. Then, add melamine, urea, pyrrole, and polyaniline in sequence. The mass ratio of zinc acetate: nickel chloride hexahydrate: melamine: urea: pyrrole: polyaniline is 1.5:3:4:8:0.18:0.6, with specific masses of 1.5 g, 3 g, 4 g, 8 g, 0.18 g, and 0.6 g, respectively. Add a certain volume of 0.8 mol / L sodium hydroxide solution to make the pH of the mixture = 9.

[0053] Step 2: Place it on a magnetic stirrer and stir for 540 min. Then pour out the mixture and centrifuge. Place the precipitate in a vacuum drying oven and dry for 14 h to obtain precursor A.

[0054] Step 3: Weigh precursor A and sodium selenite in a mass ratio of 1:2 and place them upstream and downstream of the ceramic boat (the selenium source is placed upstream, i.e., at the gas inlet of the tube furnace). The mass of precursor A is 0.8g. Place the ceramic boat in the tube furnace and, under the protection of an inert atmosphere (Ar), set the first stage calcination temperature to 500℃, hold for 3 hours, and raise the temperature at a rate of 5℃ / min, starting from room temperature. The second stage calcination temperature is 400℃, hold for 2 hours, and raise the temperature at a rate of 8℃ / min. After the first stage is completed, allow the material to cool naturally to room temperature, and then raise the temperature again from room temperature.

[0055] Step 4: After calcination, the sample is naturally cooled in the furnace and ground in a mortar for 60 minutes to obtain gray powder B, namely Zn-NiSe / g-C3N4 photocatalyst.

Claims

1. A method for preparing a zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst, characterized in that, Includes the following steps: S1, zinc acetate, nickel chloride hexahydrate, melamine, urea, pyrrole and polyaniline are added to deionized water in a mass ratio of (0.5-1.5):(4-6):(4-10):(6-8):(0.125-0.2):(0.25-1) to obtain a mixture; S2, adjust the pH of the mixture to 9-10, mix thoroughly to obtain the precursor solution, and dry the precipitate obtained after centrifuging the precursor solution to obtain the precursor. S3, with a mass ratio of (1-10):(0.2-5), the precursor and selenium source are subjected to a two-stage calcination process under an inert atmosphere. The temperature of the first stage is 450-600 °C, and the temperature of the second stage is 300-400 °C. After the first stage is completed, the mixture is allowed to cool naturally to room temperature, and then the temperature is raised from room temperature to carry out the second stage of calcination to obtain a zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst.

2. The preparation method of the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, The ratio of zinc acetate to deionized water in S1 is (0.5-1.5)g:(80-120)mL.

3. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, In S2, the pH of the mixture is adjusted using a 0.5~1 mol / L sodium hydroxide solution.

4. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, S2 Stir the adjusted mixture for 360-720 min to obtain the precursor solution. After centrifuging the precursor solution, the resulting precipitate is dried in a vacuum drying oven for 10-20 h to obtain the precursor.

5. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, The selenium source mentioned in S3 is sodium selenite.

6. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, The calcination process in S3 is carried out in a tube furnace. The precursor and selenium source are placed in a ceramic boat. The selenium source is located at the gas inlet end of the tube furnace, and the precursor is located at the gas outlet end of the tube furnace.

7. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, In S3, the first stage of heat preservation is 1-3 hours, and the second stage of heat preservation is 0.5-2 hours.

8. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, In S3, the heating rate in the first stage is 2-5 °C / min, starting from room temperature, and the heating rate in the second stage is 5-10 °C / min.

9. The method for preparing the zinc-doped nickel selenide / graphite-phase carbon nitride composite photocatalyst according to claim 1, characterized in that, After the second stage in S3 is completed, the resulting solid is ground for 30-90 min to obtain a zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst.

10. A zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst obtained by the preparation method of the zinc-doped nickel selenide / graphite phase carbon nitride composite photocatalyst according to any one of claims 1-9.

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