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

Abstract

The invention belongs to the technical field of photocatalytic hydrogen evolution, and particularly relates to application of a g-C3N4 / Al-SrMoO4 heterojunction photocatalyst in hydrogen evolution through photocatalytic decomposition of water. The preparation method comprises the following steps: uniformly dispersing a g-C3N4 / Al-SrMoO4 heterojunction photocatalyst prepared by using a high-temperature molten salt method and a high-temperature calcination method in a mixed solution of simulated seawater, triethanolamine and chloroplatinic acid, continuously introducing argon into a reactor to obtain a relatively vacuum environment, and carrying out photocatalytic decomposition of water to produce hydrogen under the irradiation of simulated sunlight. The g-C3N4 / Al-SrMoO4 heterojunction photocatalyst disclosed by the invention has better stability and light absorption characteristic, can effectively reduce the recombination of photo-induced electrons and holes and improve the photocatalytic activity, is low in raw material cost, mild in reaction condition and environment-friendly and pollution-free, and conforms to the currently advocated green and environment-friendly concept.

Description

Technical Field

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

[0002] Photocatalytic hydrogen evolution is mainly based on the photocatalytic effect of semiconductor materials. When the semiconductor absorbs light with photon energy greater than its band gap energy, the electrons in the valence band will be excited to jump to the conduction band, forming photogenerated electron-hole pairs. This promotes the photolysis reaction of water molecules to produce hydrogen and oxygen. Photocatalytic hydrogen evolution technology uses solar energy as energy, converts solar energy into chemical energy and stores it in hydrogen. It uses water to produce hydrogen through photocatalytic technology, avoiding dependence on traditional resources such as limited fossil fuels. The reaction conditions are mild and it has the advantages of high efficiency, environmental protection, and renewability. It is conducive to ensuring the long-term supply of energy and provides a new way to solve problems such as environmental pollution.

[0003] The photocatalytic efficiency of SrMoO4 ​​nanoparticle photocatalysts is usually limited, which is mainly due to the relatively wide band gap width and the lack of an effective electric field or a suitable energy level structure inside to promote the separation of photogenerated carriers, which reduces the number of effective carriers in the photocatalytic reaction, thereby 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, and g-C3N4 / Al-SrMoO4 ​​as a photocatalyst for hydrogen evolution has not been reported. Summary of the invention

[0004] In order to solve the problems in 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 by the present invention is:

[0006] The invention discloses an application of a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in photocatalytic decomposition of water for hydrogen evolution. The method is as follows: the 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 a reactor containing the mixed solution at a rate of 30 mL / min to obtain a relatively vacuum environment, and photocatalytic decomposition of water for hydrogen evolution is carried out under irradiation of 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 of triethanolamine is 3 mL, the concentration of chloroplatinic acid is 1 wt%, and the amount used is 30 μL.

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

[0009] 1) After fully grinding ammonium molybdate, strontium chloride and alumina, transfer them to a muffle furnace for high-temperature calcination, and after natural cooling, precipitate Al-SrMoO4 ​​nanoparticles by a molten salt method;

[0010] 2) After fully grinding the Al-SrMoO4 ​​nanoparticles obtained in step 1) with urea, transfer them to a closed porcelain boat for calcination, and after natural cooling, wash, dry and grind to obtain the target product g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst.

[0011] Furthermore, in the preparation method of the above-mentioned 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 preparation method of the above-mentioned 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 preparation method of the above-mentioned g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, in step 2), the washing method adopts centrifugation, the centrifugal speed is 10000r / min, and the centrifugal time is 10min.

[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 costs, can be mass-produced, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 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 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 diagrams 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 are shown. DETAILED DESCRIPTION

[0025] Example 1

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

[0027] A certain amount of urea is spread on a closed porcelain boat and then transferred to a muffle furnace for calcination at a temperature of 500°C and a heating rate of 5°C / min for 2 hours. After natural cooling, g-C3N4 can be 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 the 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 rate of 10000 r / min for 10 min), dried at 60°C for 10 h, and ground to obtain a g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst, labeled as 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 4g, and the amount of Al-SrMoO4 ​​nanoparticles was changed to 0.4g and 0.133g respectively. After sufficient 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 2h. The heating rate was 5°C / min. After natural cooling, the mixture was centrifuged and washed (the centrifugal rate was 10000r / min, and the centrifugal time was 10min), dried at 60°C for 10h, and ground to obtain g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comparison samples, which were marked as CN-SM-1 and CN-SM-3 respectively.

[0037] Figure 1 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 1In the figure, the 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°, 47.9°, etc. The 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. 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 inhibits the recombination of photogenerated electron-hole pairs.

[0039] Example 5

[0040] Application of g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst in catalytic decomposition of water 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 0.5 mol / L sodium chloride aqueous solution), 3 mL of triethanolamine and 30 μL of chloroplatinic acid (concentration is 1 wt%); argon gas was introduced into the reactor at a rate of 30 mL / min for 20 min to exhaust the air; under simulated sunlight, 1000 μL of the gas in the reactor was extracted at 30 min and 60 min 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, after 1 h, the H2 yield of Al-SrMoO4 ​​photocatalyst was 0.08 mmol / g, and the H2 yield of g-C3N4 photocatalyst was 2.13 mmol / g, and their activities were both relatively low; the H2 yield of CN-SM-2 was 4.27 mmol / g, and the H2 yields of CN-SM-1 and CN-SM-3 were 3.02 mmol / g and 4.09 mmol / 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.

2. The use according to claim 1, characterized in that: The method is as follows: the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst is uniformly dispersed in a mixed solution of simulated seawater, triethanolamine and chloroplatinic acid, and argon gas is continuously introduced into the reactor containing the mixed solution at 30 mL / min to obtain a relatively vacuum environment, and photocatalytic water decomposition and hydrogen evolution are carried out under simulated sunlight.

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

4. The use according to any one of claims 1 to 3, characterized in that: The preparation method of the g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst comprises the following steps: 1) Grinding ammonium molybdate, strontium chloride and aluminum oxide fully, transferring them to a muffle furnace for high-temperature calcination, and precipitating Al-SrMoO4 ​​nanoparticles after natural cooling; 2) After fully grinding the Al-SrMoO4 ​​nanoparticles obtained in step 1) with urea, transfer them to a closed porcelain boat for calcination, and after natural cooling, wash, dry and grind to obtain the target product g-C3N4 / Al-SrMoO4 ​​heterojunction photocatalyst.

5. The use according to claim 4, characterized in that: In step 1), the molar ratio of strontium chloride, ammonium molybdate and aluminum oxide is 10:1:0.

01.

6. The use according to claim 5, 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.

7. The use according to claim 4, characterized in that: In step 1), the high temperature calcination temperature is 1100° C. and the time is 10 h.

8. The use according to claim 4, characterized in that: In step 2), the mass ratio of urea to Al-SrMoO4 ​​nanoparticles is 20:

1.

9. The use according to claim 4, 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.

10. The use according to claim 4, characterized in that: In step 2), the washing method is centrifugation, the centrifugal speed is 10000r / min, the centrifugal time is 10min, the drying temperature is 60°C, and the drying time is 10h.

Images