Application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic water decomposition and hydrogen evolution

Abstract

The present invention belongs to the field of photocatalytic hydrogen evolution technology, and in particular to an application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic decomposition of water for hydrogen evolution. The present invention is to uniformly disperse the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared by a high-temperature molten salt method and a high-temperature calcination method in a mixed solution of simulated seawater, triethanolamine and chloroplatinic acid, and continuously introduce argon into the reactor to obtain a relatively vacuum environment, and perform photocatalytic decomposition of water for hydrogen evolution under simulated sunlight. The g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst of the present invention has better stability and light absorption characteristics, can effectively reduce the recombination of photogenerated electrons and holes, and improve photocatalytic activity. The raw material cost of the present invention is affordable, and the reaction conditions are mild, environmentally friendly and pollution-free, and in line with the green environmental protection concept currently advocated.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic hydrogen evolution, and specifically relates to the application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic water decomposition and hydrogen evolution. Background Art

[0002] Photocatalytic hydrogen evolution is primarily based on the photocatalytic effect of semiconductor materials. When a semiconductor absorbs light with photon energy greater than its band gap energy, electrons in the valence band are excited to transition to the conduction band, forming photogenerated electron-hole pairs. This promotes the photolysis of water molecules, producing hydrogen and oxygen. Photocatalytic hydrogen evolution technology uses solar energy as an energy source, converting it into chemical energy and storing it in hydrogen. Using photocatalytic technology to produce hydrogen from water avoids dependence on traditional resources such as limited fossil fuels. The reaction conditions are mild, and it offers advantages such as high efficiency, environmental friendliness, and renewability. This helps ensure a long-term energy supply and provides a new approach to addressing environmental pollution and other issues.

[0003] The photocatalytic efficiency of SrMoO4 ​​nanoparticle photocatalysts is usually limited, which is mainly due to their relatively wide band gap width and the lack of an effective electric field or suitable energy level structure inside them to promote the separation of photogenerated carriers, reducing the number of effective carriers in the photocatalytic reaction and thus reducing the photocatalytic efficiency. The g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst introduced in the present invention can effectively reduce the recombination of photogenerated electrons and holes, thereby improving the photocatalytic activity. In addition, there have been no reports on the use of g-C3N4 / Al-SrMoO4 ​​as a photocatalyst for hydrogen evolution. Summary of the Invention

[0004] In order to solve the problems of the prior art, the present invention provides an application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic water decomposition and hydrogen evolution.

[0005] The technical solution adopted in the present invention is:

[0006] A g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst is used in photocatalytic water decomposition and hydrogen evolution. The method comprises the following steps: uniformly dispersing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in a mixed solution of simulated seawater, triethanolamine, and chloroplatinic acid, continuously introducing argon gas at 30 mL / min into a reactor containing the mixed solution to obtain a relative vacuum environment, and performing photocatalytic water decomposition and hydrogen evolution under simulated sunlight.

[0007] Furthermore, in the above application, the simulated seawater is a 0.5 mol / L sodium chloride aqueous solution, the amount used is 27 mL, the amount used is 3 mL, the concentration of chloroplatinic acid is 1 wt%, and the amount used is 30 μL.

[0008] Furthermore, in any of the above applications, the method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comprises the following steps:

[0009] 1) ammonium molybdate, strontium chloride and aluminum oxide are fully ground and then transferred to a muffle furnace for high-temperature calcination. After natural cooling, Al-SrMoO4 ​​nanoparticles are precipitated by a molten salt method;

[0010] 2) The Al-SrMoO4 ​​nanoparticles obtained in step 1) are fully ground with urea, transferred to a closed porcelain boat for calcination, and after natural cooling, washed, dried, and ground to obtain the target product g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst.

[0011] Furthermore, in the above-mentioned method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 1), the molar ratio of strontium chloride, ammonium molybdate and aluminum oxide is 10:1:0.01.

[0012] Furthermore, in the preparation method of the above-mentioned g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 1), the ammonium molybdate is ammonium molybdate tetrahydrate, the amount of which is 0.96 g, the strontium chloride is strontium chloride hexahydrate, the amount of which is 14.5 g, and the aluminum oxide is commercially available aluminum oxide, the amount of which is 0.0055 g.

[0013] Furthermore, in the preparation method of the above-mentioned g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 1), the high-temperature calcination temperature is 1100°C and the time is 10 hours.

[0014] Furthermore, in the above-mentioned method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 2), the mass ratio of the urea and the Al-SrMoO4 ​​nanoparticles is 20:1.

[0015] Furthermore, in the above-mentioned method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 2), the calcination temperature is 500°C, the heating rate is 5°C / min, and the calcination time is 2h.

[0016] Furthermore, in the above-mentioned method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 2), the washing method is centrifugation, the centrifugal speed is 10000 r / min, and the centrifugal time is 10 min.

[0017] Furthermore, in the above-mentioned method for preparing the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 2), the drying temperature is 60°C and the drying time is 10 hours.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention adopts a high-temperature molten salt method to prepare a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, which realizes the efficient separation of photogenerated carriers.

[0020] 2. The g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared by the present invention broadens the light absorption range by adjusting its energy band structure, thereby improving the photocatalytic reaction efficiency and further improving its solar energy utilization rate.

[0021] 3. The g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared by the present invention has good photocatalytic hydrogen evolution performance, and the scheme is highly feasible, environmentally friendly and pollution-free, has low raw material cost, can be mass-produced, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are the X-ray diffraction patterns of the g-C3N4 photocatalyst prepared in Example 1, the Al-SrMoO4 ​​photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3.

[0023] Figure 2 These are fluorescence photoluminescence spectra of the g-C3N4 photocatalyst prepared in Example 1, the Al-SrMoO4 ​​photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3.

[0024] Figure 3 The photocatalytic hydrogen evolution activity diagram of the g-C3N4 photocatalyst prepared in Example 1, the Al-SrMoO4 ​​photocatalyst prepared in Example 2, the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3, and the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comparison sample prepared in Example 4. DETAILED DESCRIPTION

[0025] Example 1

[0026] The preparation method of g-C3N4 photocatalyst is as follows:

[0027] A certain amount of urea was spread on a closed porcelain boat and then transferred to a muffle furnace for calcination at a temperature of 500°C, a heating rate of 5°C / min, and calcination for 2 hours. After natural cooling, g-C3N4 was obtained by grinding.

[0028] Example 2

[0029] The preparation method of Al-SrMoO4 ​​photocatalyst is as follows:

[0030] 0.96 g of ammonium molybdate tetrahydrate, 14.5 g of strontium chloride hexahydrate and 0.0055 g of commercially available alumina were fully ground and transferred to a muffle furnace for calcination at a high-temperature molten salt temperature of 1100°C for 10 hours. After natural cooling, Al-SrMoO4 ​​nanoparticles were precipitated by the molten salt method.

[0031] Example 3

[0032] The preparation method of g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst is as follows:

[0033] 0.2 g of Al-SrMoO4 ​​nanoparticles prepared in Example 2 and 4 g of urea were fully ground and transferred to a closed porcelain boat and calcined in a muffle furnace at a temperature of 500°C for 2 h at a heating rate of 5°C / min. After natural cooling, they were centrifuged and washed (centrifugal speed of 10,000 r / min for 10 min), dried at 60°C for 10 h, and ground to obtain a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, which was labeled CN-SM-2.

[0034] Example 4

[0035] The preparation method of the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comparison sample is as follows:

[0036] According to the preparation method of Example 3, the amount of urea remained unchanged at 4 g, and the amount of Al-SrMoO4 ​​nanoparticles was changed to 0.4 g and 0.133 g respectively. After thorough mixing and grinding, the mixture was transferred to a closed porcelain boat and calcined in a muffle furnace at a temperature of 500°C for 2 h at a heating rate of 5°C / min. After natural cooling, the mixture was centrifuged and washed (at a centrifugal rate of 10,000 r / min and a centrifugal time of 10 min), dried at 60°C for 10 h, and ground to obtain g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comparison samples, which were labeled CN-SM-1 and CN-SM-3 respectively.

[0037] Figure 1 These are the X-ray diffraction patterns of the g-C3N4 photocatalyst prepared in Example 1, the Al-SrMoO4 ​​photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3. Figure 1The characteristic diffraction peak at 2θ = 27.7° corresponds to the characteristic crystal plane of g-C3N4 (002), and characteristic peaks appear on Al-SrMoO4 ​​nanoparticles at 2θ = 27.7°, 29.8°, 33.4°, 45.3°, and 47.9°. Characteristic peaks of Al-SrMoO4 ​​nanoparticles and g-C3N4 can be observed in the CN-SM-2 heterojunction photocatalyst, indicating that the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst was successfully prepared.

[0038] Figure 2 The fluorescence photoluminescence spectra of the g-C3N4 photocatalyst prepared in Example 1, the Al-SrMoO4 ​​photocatalyst prepared in Example 2, and the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3 are shown. By comparison, it can be observed that the fluorescence photoluminescence spectrum of the CN-SM-2 heterojunction photocatalyst is significantly reduced, indicating that the g-C3N4 / Al-SrMoO4 ​​heterostructure effectively suppresses the recombination of photogenerated electron-hole pairs.

[0039] Example 5

[0040] Application of g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in catalytic water decomposition and hydrogen evolution under light:

[0041] Under normal temperature and pressure conditions, 30 mg of the g-C3N4 / Al-SrMoO4 ​​heterojunction catalyst prepared in Example 3 was placed in a reactor containing a mixed solution of 27 mL of simulated seawater (simulated seawater is a 0.5 mol / L sodium chloride aqueous solution), 3 mL of triethanolamine and 30 μL of chloroplatinic acid (concentration is 1 wt%); argon was introduced into the reactor at a rate of 30 mL / min for 20 minutes to expel the air; under simulated sunlight, 1000 μL of gas in the reactor was extracted at 30 minutes and 60 minutes respectively, and the collected catalytic products were quantitatively analyzed by gas chromatograph.

[0042] The above steps were followed, with all other conditions remaining unchanged, except that the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst prepared in Example 3 was replaced by the samples prepared in Examples 1, 2, and 4, respectively, to measure the hydrogen evolution efficiency.

[0043] Figure 3 The graph is the relationship between hydrogen content and illumination time. The peak area of ​​the extracted gas is measured by gas chromatograph and then converted into the amount of its substance by calculation, such as Figure 3As shown in the figure, after 1 hour, the H2 production rate of Al-SrMoO4 ​​photocatalyst was 0.08mmol / g, and the H2 production rate of g-C3N4 photocatalyst was 2.13mmol / g, and their activities were both relatively low; the H2 production rate of CN-SM-2 was 4.27mmol / g, and the H2 production rates of CN-SM-1 and CN-SM-3 were 3.02mmol / g and 4.09mmol / g, respectively, which were improved compared with g-C3N4 photocatalyst and Al-SrMoO4 ​​photocatalyst, indicating that the constructed heterostructure has stronger activity.

Claims

1. Application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic water decomposition and hydrogen evolution, characterized in that: The application method is as follows: a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst is uniformly dispersed in a mixed solution of simulated seawater, triethanolamine, and chloroplatinic acid. Argon gas is continuously introduced into the reactor containing the mixed solution at a rate of 30 mL / min to expel air. The mixture is then photocatalytically decomposed into water to produce hydrogen under simulated sunlight. The preparation method of the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comprises the following steps: 1) After fully grinding ammonium molybdate, strontium chloride and alumina, transfer them to a muffle furnace for high-temperature calcination. After natural cooling, Al-SrMoO4 ​​nanoparticles are precipitated; 2) The Al-SrMoO4 ​​nanoparticles obtained in step 1) are fully ground with urea, transferred to a closed porcelain boat for calcination, and after natural cooling, washed, dried, and ground to obtain the target product g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst.

2. The use according to claim 1, characterized in that The simulated seawater is a 0.5 mol / L sodium chloride aqueous solution, the amount used is 27 mL, the amount used is 3 mL, the concentration of chloroplatinic acid is 1 wt%, and the amount used is 30 μL.

3. The use according to claim 1, characterized in that In step 1), the molar ratio of strontium chloride, ammonium molybdate and aluminum oxide is 10:1:0.

01.

4. The use according to claim 1, characterized in that In step 1), the ammonium molybdate is ammonium molybdate tetrahydrate, the amount of which is 0.96 g, the strontium chloride is strontium chloride hexahydrate, the amount of which is 14.5 g, and the aluminum oxide is commercially available aluminum oxide, the amount of which is 0.0055 g.

5. The use according to claim 1, characterized in that In step 1), the high-temperature calcination temperature is 1100° C. and the time is 10 h.

6. The use according to claim 1, characterized in that In step 2), the mass ratio of urea to Al-SrMoO4 ​​nanoparticles is 20:

1.

7. The use according to claim 1, characterized in that In step 2), the calcination temperature is 500°C, the heating rate is 5°C / min, and the calcination time is 2 h.

8. The use according to claim 1, characterized in that In step 2), the washing method is centrifugation, the centrifugal speed is 10000 r / min, the centrifugal time is 10 min, the drying temperature is 60 ° C, and the drying time is 10 h.

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