A method for preparing and applying a heterojunction photocatalyst of g-C3N4 and aluminum-doped SrWO4

Abstract

This invention relates to a method for preparing and applying a heterojunction photocatalyst of g-C3N4 and aluminum-doped SrWO4, belonging to the field of photocatalytic materials technology. The invention employs a high-temperature molten salt method to prepare Al-SrWO4 nanoparticles, followed by in-situ growth of g-C3N4 on the surface of the Al-SrWO4 nanoparticles via calcination, ultimately obtaining the target product, a g-C3N4 / Al-SrWO4 heterojunction photocatalyst, which can be applied in the field of photocatalytic hydrogen evolution. Compared to current photocatalysts, the g-C3N4 / Al-SrWO4 heterojunction photocatalyst of this invention exhibits better tunability, effectively suppressing the recombination process of photogenerated electrons and holes, and significantly improving carrier separation efficiency. The preparation process of this invention is simple and easy to implement, uses economical raw materials, and is environmentally friendly and pollution-free throughout the entire production process.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing and applying a heterojunction photocatalyst of aluminum-doped SrWO4 prepared by g-C3N4 and high-temperature molten salt method. Background Technology

[0002] The background technology of photocatalytic hydrogen evolution is based on the photocatalytic effect of semiconductor materials. This technology utilizes ultraviolet light or sunlight to irradiate specific catalytic materials. The catalytic materials absorb photon energy, excite electrons, and promote the photolysis reaction of water molecules to produce hydrogen and oxygen. Photocatalytic hydrogen evolution technology has the advantages of high efficiency, environmental friendliness, and renewability. It is an important way to realize the effective utilization of solar energy and the clean production of hydrogen, providing a new direction for solving energy crises and environmental pollution problems.

[0003] Al-SrWO4 nanoparticles and g-C3N4 are common photocatalysts, and due to their excellent stability, they are used in environmental and energy fields. However, g-C3N4 / Al-SrWO4 has not been reported as a hydrogen evolution heterojunction photocatalyst. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a method for preparing and applying a heterojunction photocatalyst of aluminum-doped SrWO4 prepared by g-C3N4 and high-temperature molten salt method.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a g-C3N4 / Al-SrWO4 heterojunction photocatalyst includes the following steps:

[0007] 1) After thoroughly grinding the mixture of ammonium tungstate, strontium chloride and Al2O3, it was transferred to a muffle furnace for high-temperature calcination. After natural cooling, Al-SrWO4 nanoparticles were obtained.

[0008] 2) After thoroughly grinding the mixture of Al-SrWO4 nanoparticles and urea, the mixture was transferred to a muffle furnace for calcination. After natural cooling, the mixture was washed, dried, and ground to obtain the target product g-C3N4 / Al-SrWO4 heterojunction photocatalyst.

[0009] Furthermore, in the above preparation method, in step 1), the strontium chloride is strontium chloride hexahydrate, the ammonium tungstate is ammonium metatungstate hydrate, and the Al2O3 is commercially available Al2O3, with a molar ratio of 10:1:0.01.

[0010] Furthermore, in the above preparation method, in step 1), the high-temperature calcination temperature is 1100℃ and the time is 10h.

[0011] Furthermore, in the above preparation method, in step 2), the mass ratio of urea to Al-SrWO4 nanoparticles is 20:1.

[0012] Furthermore, in the above preparation method, step 2), the calcination temperature is 500℃, the calcination time is 2h, and the heating rate is 5℃ / min.

[0013] Furthermore, in the above preparation method, step 2), the washing method is centrifugation, with a centrifugation rate of 10000 r / min and a centrifugation time of 10 min.

[0014] Furthermore, in the above preparation method, step 2), the drying temperature is 60°C and the drying time is 12 hours.

[0015] Application of a g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared by any of the above methods in photocatalytic hydrogen evolution.

[0016] Further, the above application is carried out as follows: g-C3N4 / Al-SrWO4 heterojunction photocatalyst is uniformly dispersed in a mixed solution of simulated seawater, triethanolamine and chloroplatinic acid. Argon gas is continuously introduced into the reaction vessel at 30 mL / min for 20 min to obtain a relative vacuum environment, and photocatalytic hydrogen evolution is carried out under simulated sunlight irradiation conditions.

[0017] Furthermore, in the above application, the simulated seawater is a 0.5 mol / L sodium chloride aqueous solution, with a volume of 27 mL; the volume of triethanolamine is 3 mL; and the concentration of chloroplatinic acid is 1 wt%, with a volume of 30 μL.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. This invention utilizes a high-temperature molten salt method to prepare a g-C3N4 / Al-SrWO4 heterojunction photocatalyst, achieving efficient separation of photogenerated carriers.

[0020] 2. The g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared by this invention can suppress the recombination efficiency of photogenerated electrons and holes, and has good photocatalytic hydrogen evolution performance. Moreover, this scheme is simple to operate, does not pollute the environment, has low raw material costs, strong feasibility, and good market prospects. Attached Figure Description

[0021] Figure 1 X-ray diffraction patterns of the Al-SrWO4 photocatalyst prepared in Example 1, the g-C3N4 photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 3.

[0022] Figure 2The fluorescence and photoluminescence spectra of the Al-SrWO4 photocatalyst prepared in Example 1, the g-C3N4 photocatalyst prepared in Example 2, the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 3, and the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 4 are compared.

[0023] Figure 3 Photocatalytic hydrogen evolution activity diagrams of the Al-SrWO4 photocatalyst prepared in Example 1, the g-C3N4 photocatalyst prepared in Example 2, the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 3, and the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 4. Detailed Implementation

[0024] Example 1

[0025] The preparation method of Al-SrWO4 photocatalyst is as follows:

[0026] After thoroughly grinding a mixture of strontium chloride hexahydrate, ammonium metatungstate hydrate, and commercially available Al2O3 in a molar ratio of 10:1:0.01, the mixture was transferred to a muffle furnace for calcination at 1100°C for 10 hours. After natural cooling, Al-SrWO4 nanoparticles were obtained after several washings and drying.

[0027] Example 2

[0028] The preparation method of g-C3N4 photocatalyst is as follows:

[0029] After spreading a certain amount of urea in a crucible, it is transferred to a muffle furnace and calcined at 500℃ (heating rate of 5℃ / min) for 2 hours. After natural cooling, it is ground to obtain g-C3N4.

[0030] Example 3

[0031] The preparation method of g-C3N4 / Al-SrWO4 heterojunction photocatalyst is as follows:

[0032] The mixture of 0.2g of Al-SrWO4 nanoparticles and 4g of urea prepared in Example 1 was thoroughly ground and then transferred to a muffle furnace for calcination at 500℃ (heating rate of 5℃ / min) for 2h. After natural cooling, it was centrifuged and washed (centrifugation rate of 10000r / min for 10min), dried at 60℃ for 12h, and then ground to obtain g-C3N4 / Al-SrWO4 heterojunction photocatalyst, abbreviated as CNSW-2.

[0033] Example 4

[0034] The preparation method of the g-C3N4 / Al-SrWO4 heterojunction photocatalyst comparison sample is as follows:

[0035] Following the preparation method of Example 3, keeping the amount of 4g urea constant, the mass of Al-SrWO4 nanoparticles was changed to 0.133g and 0.4g respectively. After thorough mixing and grinding, the mixture was transferred to a muffle furnace for calcination at 500℃ (heating rate of 5℃ / min) for 2h. After natural cooling, the mixture was centrifuged and washed (centrifugation rate of 10000r / min, centrifugation time of 10min), dried at 60℃ for 12h, and ground to obtain g-C3N4 / Al-SrWO4 heterojunction photocatalyst comparative samples, abbreviated as CNSW-1 and CNSW-3 respectively.

[0036] Figure 1 X-ray diffraction patterns of the Al-SrWO4 photocatalyst prepared in Example 1, the g-C3N4 photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 3. Figure 1 In the fluorescence photoluminescence spectrum, the characteristic diffraction peak at 2θ = 27.4° corresponds to the g-C3N4(002) crystal plane, indicating that the material has a layered structure. Characteristic peaks appear on the Al-SrWO4 nanoparticles at 2θ = 18.1°, 27.7°, 30°, 33.1°, and 38°. Characteristic peaks of Al-SrWO4 nanoparticles and g-C3N4 nanosheets can be observed in the CNSW-2 heterojunction photocatalyst, indicating that the g-C3N4 / Al-SrWO4 heterojunction photocatalyst was successfully prepared. Figure 2 It can be clearly seen that the fluorescence spectrum of the composite sample is reduced, indicating that the recombination of electrons and holes is effectively suppressed after recombination.

[0037] Example 5

[0038] Application of g-C3N4 / Al-SrWO4 heterojunction photocatalyst in catalytic water splitting and hydrogen evolution under light irradiation:

[0039] Under normal temperature and pressure conditions, 30 mg of the g-C3N4 / Al-SrWO4 heterojunction photocatalyst sample prepared in Example 3 was placed in a reactor containing a mixed solution of 27 mL simulated seawater (simulated seawater was a 0.5 mol / L sodium chloride aqueous solution), 3 mL triethanolamine, and 30 μL chloroplatinic acid (concentration of 1 wt%). Argon gas was introduced into the reactor at a rate of 30 mL / min for 20 min to purge air. Under simulated sunlight irradiation, 1000 μL of gas was extracted from the reactor at 30 min and 60 min, respectively, and the collected catalytic products were quantitatively analyzed using gas chromatography.

[0040] Following the steps described above, the g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared in Example 3 was replaced with the Al-SrWO4 photocatalyst prepared in Example 1, the g-C3N4 photocatalyst prepared in Example 2, and CNSW-1 and CNSW-3 prepared in Example 4, respectively. All other conditions remained unchanged, and the gas was taken to determine the hydrogen evolution efficiency.

[0041] Figure 3 The graph shows the relationship between hydrogen content and irradiation time. The peak area of ​​the extracted gas was measured using a gas chromatograph, and then calculated to convert it into its amount of substance, such as... Figure 3 As shown, after 1 h, the H2 yield of the Al-SrWO4 photocatalyst was 0.114 mmol / g, and the H2 yield of the g-C3N4 photocatalyst was 2.2 mmol / g, both showing low activity. The H2 yield of CNSW-2 was 6.98 mmol / g, and the H2 yields of CNSW-1 and CNSW-3 were 5.24 mmol / g and 5.53 mmol / g, respectively, which were several times higher than those of the g-C3N4 and Al-SrWO4 photocatalysts, indicating that the construction of heterostructures has strong activity.

Claims

1. A method for preparing a g-C3N4 / Al-SrWO4 heterojunction photocatalyst, characterized in that, Includes the following steps: 1) A mixture of strontium chloride hexahydrate, ammonium metatungstate hydrate and commercially available Al2O3 in a molar ratio of 10:1:0.01 was thoroughly ground and then transferred to a muffle furnace for high-temperature calcination at 1100℃ for 10 h. After natural cooling, Al-SrWO4 nanoparticles were obtained. 2) The obtained Al-SrWO4 nanoparticles and urea were thoroughly ground into a mixture at a mass ratio of 1:20, and then transferred to a muffle furnace for calcination at a temperature of 500 ℃ for 2 h at a heating rate of 5 ℃ / min. After natural cooling, the mixture was washed, dried and ground to obtain the target product g-C3N4 / Al-SrWO4 heterojunction photocatalyst.

2. The preparation method according to claim 1, characterized in that, In step 2), the washing method is centrifugation, with a centrifugation rate of 10000 r / min and a centrifugation time of 10 min.

3. The preparation method according to claim 1, characterized in that, In step 2), the drying temperature is 60°C and the drying time is 12 hours.

4. The application of a g-C3N4 / Al-SrWO4 heterojunction photocatalyst prepared by the preparation method according to any one of claims 1-3 in photocatalytic hydrogen evolution.

5. The application according to claim 4, characterized in that, The method is as follows: The g-C3N4 / Al-SrWO4 heterojunction photocatalyst is uniformly dispersed in a mixed solution of simulated seawater, triethanolamine and chloroplatinic acid. Argon gas is continuously introduced into the reaction vessel at 30 mL / min for 20 min to obtain a relative vacuum environment. Photocatalytic hydrogen evolution is carried out under simulated sunlight irradiation conditions.

6. The application according to claim 5, characterized in that, The simulated seawater was a 0.5 mol / L sodium chloride aqueous solution, with a volume of 27 mL; triethanolamine was used in a volume of 3 mL; and chloroplatinic acid had a concentration of 1 wt% and a volume of 30 μL.

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