Preparation method and application of strontium titanate and carbon nitride composite photocatalyst rich in titanium dioxide
The combination of SrTiO3@TiO2 with g-C3N4 forms a composite photocatalyst that addresses the limitations of g-C3N4 and SrTiO3 by enhancing charge separation and light response, achieving improved hydrogen production efficiency and stability.
Patent Information
- Application Number
- CN202510471074.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-07-15
AI Technical Summary
The existing graphite phase carbon nitride (g-C3N4) photocatalysts have narrow visible light absorption range, high carrier recombination rate and small specific surface area, resulting in low efficiency in photocatalytic hydrogen production applications, while strontium titanate (SrTiO3) has problems such as easy recombination of photogenerated electron-hole pairs and wide band gap.
By preparing a composite material with titanium dioxide-rich strontium titanate (SrTiO3@TiO2) and carbon nitride (g-C3N4) with titanium dioxide, a built-in electric field and heterojunction are formed, which promotes the separation of photogenerated electron-hole pairs, expands the light response range and improves photocatalytic activity.
The photoresponse range of the photocatalyst is expanded, the solar energy utilization rate is improved, the photogenerated electrons and holes are suppressed, and the efficiency of photocatalytic cracking of aquatic hydrogen is improved.
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Figure CN120306007A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor photocatalysts, and particularly relates to a preparation method and application of a titanium strontium oxide and carbon nitride composite photocatalyst rich in titanium dioxide. Background Art
[0002] Due to the limitations of fossil fuels and the increasing carbon dioxide emissions, there is an urgent need to find clean and renewable alternative energy sources to meet the growing energy demand. Photocatalytic water splitting for hydrogen production is considered a promising method because it is environmentally friendly and does not produce destructive by-products. Therefore, photocatalytic technology is considered a potential method to address recent energy and environmental challenges. Graphite phase carbon nitride (g-C3N4), as a two-dimensional non-metallic organic semiconductor material, has been widely studied in photocatalytic hydrogen production and other aspects due to its suitable band gap (~2.7 eV), high stability, environmental friendliness, and easy modification. However, carbon nitride is still far from practical application due to its narrow visible light absorption range, high carrier recombination rate, and small specific surface area. Perovskite oxides have attracted great attention in the field of photocatalysis due to their stable crystal structure, excellent electronic configuration, and good photocatalytic performance. Among them, strontium titanate (SrTiO3), as the earliest studied oxide photocatalytic material, is often used in the research of photocatalytic hydrogen production. However, SrTiO3 has the disadvantages of easy recombination of photo-generated electron-hole pairs and wide band gap. Studies have shown that the band gap value of titanium-rich strontium titanate (SrTiO3@TiO2) is smaller than that of strontium titanate and titanium dioxide, and the energy required for photo-excited electrons is lower than the latter two, so the advantages of titanium-rich strontium titanate are more obvious.
[0003] Composite semiconductors are one of the main methods to improve photocatalytic activity at present. In a binary semiconductor composite system, the energy level difference between the two semiconductors can cause photo-generated electrons and holes to migrate in opposite directions, so that they migrate to different semiconductors, effectively separating the photo-generated electron-hole pairs, inhibiting the recombination of photo-generated carriers, and also expanding the photocatalytic response range of the catalyst. In the present invention, g-C3N4 is combined with SrTiO3@TiO2 to form a composite material. Compared with single g-C3N4, SrTiO3@TiO2, and the composite material of pure SrTiO3 and g-C3N4, its photocatalytic response range is expanded, and the utilization rate of solar energy is improved; and due to the formation of a heterojunction after combination, the separation of photo-generated electron-hole pairs is promoted, so the hydrogen production performance can be improved. Summary of the Invention
[0004] The object of the present invention is to provide a preparation method of a composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride, and to investigate its photocatalytic performance for water splitting to produce hydrogen under visible light. Using urea, titanium dioxide, strontium nitrate, sodium chloride, and potassium chloride as raw materials, strontium titanate rich in titanium dioxide was prepared by a new method, and it was compounded with carbon nitride to obtain a composite material. The band gap value of titanium-rich strontium titanate (SrTiO3@TiO2) is smaller than that of strontium titanate and titanium dioxide, and the energy required for photoexcited electrons is lower than the latter two. After compounding with carbon nitride, a built-in electric field and a heterojunction will be formed, which will accelerate the transport and diffusion of charges, and greatly inhibit the recombination of photogenerated electrons and holes. The composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride has excellent optoelectronic properties and photocatalytic water splitting hydrogen production activity.
[0005] In order to achieve the above object of the invention, the present invention provides the following technical solutions:
[0006] A preparation method of a composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride, characterized by comprising the following steps:
[0007] (1) Put solid urea particles into a crucible with a lid, heat it in a muffle furnace at a certain rate to a specified temperature, keep it warm for a period of time, and then cool it naturally to obtain a carbon nitride composed of heptazine units containing terminal oxygen, denoted as CN.
[0008] (2) Mix titanium dioxide, strontium nitrate, sodium chloride, and potassium chloride, grind them evenly, put them into a crucible with a lid, then heat them in a muffle furnace at a certain rate to a specified temperature, keep it warm for a period of time, and then cool it naturally; wash it with deionized water multiple times to remove the excess salt, and after drying, obtain strontium titanate rich in titanium dioxide, denoted as STO@T.
[0009] (3) Mix the CN and STO@T obtained in step (1) and step (2) in a certain proportion, add a certain volume of pure water, ultrasonicate and then stir, then wash and dry with deionized water. The dried material is put into a crucible with a lid, and then heated in a muffle furnace at a certain rate to a specified temperature, keep it warm for a period of time, and then cool it naturally to obtain a composite material, denoted as STO@T / CN.
[0010] Further, in step (1), the crucible with a lid is kept in a semi-closed state, and the calcination atmosphere is air.
[0011] Further, in step (1), the heating rate is 2-10 °C / min, the holding reaction temperature is 500-600 °C, and the time is 1.5-4 h.
[0012] Further, in step (2), the mass ratio of titanium dioxide to strontium nitrate is 1:(2.6 - 3.2), the mass ratio of titanium dioxide to sodium chloride is 1:(10 - 15), and the mass ratio of titanium dioxide to potassium chloride is 1:(15 - 20).
[0013] Further, the grinding time in step (2) is 20 - 60 min.
[0014] Further, in step (2), the crucible with a lid is kept in a semi-closed state, and the calcination atmosphere is air.
[0015] Further, in step (2), the heating rate is 2 - 10 °C / min, the holding reaction temperature is 700 - 800 °C, and the time is 6 - 8 h.
[0016] Further, the drying temperature in step (2) is 50 - 80 °C, and the time is 4 - 12 h.
[0017] Further, in step (3), the mass ratio of CN to STO@T is (8 - 9.5):1, the ultrasonic time is 1 - 2 h, and the stirring time is 12 - 24 h.
[0018] Further, the drying temperature in step (3) is 50 - 80 °C, and the time is 4 - 12 h.
[0019] Further, in step (3), the crucible with a lid is kept in a semi-closed state, and the calcination atmosphere is air.
[0020] Further, in step (3), the heating rate is 2 - 10 °C / min, the holding reaction temperature is 400 - 500 °C, and the time is 2 - 4 h.
[0021] The present invention also provides an application of the above-mentioned strontium titanate and carbon nitride composite photocatalyst rich in titanium dioxide in photocatalytic water splitting for hydrogen production.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] 1. The present invention provides a novel method for preparing strontium titanate rich in titanium dioxide, as well as a method for preparing a composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride. Using only titanium dioxide and strontium nitrate, strontium titanate rich in titanium dioxide can be prepared through a simple one-step calcination, and a composite material can be obtained through a simple mixed calcination with carbon nitride. The composite material formed by the combination of strontium titanate rich in titanium dioxide and carbon nitride has an expanded light response range compared to single g-C3N4, SrTiO3@TiO2, and the composite materials of pure SrTiO3 and g-C3N4, improving the utilization rate of solar energy. Moreover, due to the formation of a built-in electric field and heterojunction after the combination, the charge transfer and diffusion are accelerated, and the recombination of photogenerated electrons and holes is greatly inhibited.
[0024] 2. The composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride prepared by the present invention has excellent optoelectronic properties and photocatalytic water splitting hydrogen production activity.
[0025] 3. The raw materials provided by the present invention are easily available, low in price, the preparation method of the catalyst is simple, the photocatalytic water splitting hydrogen production efficiency is relatively high, and the stability is good, which is expected to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 SEM image of the 10% STO@T / CN photocatalyst prepared in Example 2;
[0027] Figure 2 Photoluminescence spectra of the 5% STO@T / CN, 10% STO@T / CN, 20% STO@T / CN, and CN photocatalysts prepared in Examples 1, 2, and 3;
[0028] Figure 3 Band gap diagrams of the 10% STO@T / CN, CN, and STO@T photocatalysts prepared in Example 2;
[0029] Figure 4 Transient optoelectronic response curves of the 5% STO@T / CN, 10% STO@T / CN, 20% STO@T / CN, and CN photocatalysts prepared in Examples 1, 2, and 3; DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. However, it should not be construed as a limitation of the present invention. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive.
[0031] Example 1:
[0032] Preparation method of titanium strontium oxide and carbon nitride composite photocatalyst rich in titanium dioxide:
[0033] (1) Weigh 10 g of urea solid particles and place them in a crucible with a lid. Keep the crucible in a semi-closed state and place it in a muffle furnace. Heat it at a heating rate of 5 °C / min to 550 °C and calcine for 2 h. After the calcination, cool it naturally to room temperature to obtain carbon nitride composed of heptazine units containing terminal oxygen, denoted as CN.
[0034] (2) Grind 239.6 mg of titanium dioxide, 761.9 mg of strontium nitrate, 2922.0 mg of sodium chloride, and 3727.6 mg of potassium chloride in a mortar for 30 min to mix them evenly. Put them into a crucible with a lid, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it at a heating rate of 5 °C / min to 700 °C and calcine for 6 h. After the calcination, cool it naturally to room temperature to obtain a solid white product. Disperse it in deionized water, then filter it, and repeat this process 3 times to remove the excess salt. Finally, dry it in a blast drying oven at 60 °C for 12 h to obtain titanium strontium oxide rich in titanium dioxide, denoted as STO@T.
[0035] (3) Put 500 mg of CN and 26.32 mg of STO@T into a beaker, add 200 ml of ultrapure water, sonicate for 1 h, and then stir at 400 r / min for 24 h. After the stirring is completed, filter it 2 - 3 times, dry it in a blast drying oven at 60 °C for 12 h. The obtained solid material is simply ground and then stirred and ground in a mortar for 30 min to mix it evenly. Put it into a crucible with a lid, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it at a heating rate of 5 °C / min to 500 °C and calcine for 2 h. After the calcination, cool it naturally to room temperature to obtain a composite material, denoted as 5% STO@T / CN.
[0036] Example 2:
[0037] Preparation method of titanium strontium oxide and carbon nitride composite photocatalyst rich in titanium dioxide:
[0038] (1) Weigh 10 g of urea solid particles and place them in a crucible with a lid. Keep the crucible in a semi-closed state and place it in a muffle furnace. Heat it at a heating rate of 5 °C / min to 550 °C and calcine for 2 h. After the calcination, cool it naturally to room temperature to obtain carbon nitride composed of heptazine units containing terminal oxygen, denoted as CN.
[0039] (2) Grind 239.6 mg of titanium dioxide, 761.9 mg of strontium nitrate, 2922.0 mg of sodium chloride, and 3727.6 mg of potassium chloride in a mortar for 30 min to mix them evenly. Put them into a crucible with a lid, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it to 700 °C at a heating rate of 5 °C / min and calcine for 6 h. After the calcination, let it cool naturally to room temperature to obtain a solid white product. Disperse it in deionized water, then filter, and repeat 3 times to remove the excess salt. Finally, dry it in a forced-air drying oven at 60 °C for 12 h to obtain strontium titanate rich in titanium dioxide, denoted as STO@T.
[0040] (3) Put 500 mg of CN and 55.56 mg of STO@T into a beaker, add 200 ml of ultrapure water, sonicate for 1 h, and then stir at 400 r / min for 24 h. After stirring, filter 2 - 3 times, dry it in a forced-air drying oven at 60 °C for 12 h. The obtained solid material is simply ground and then stirred and ground in a mortar for 30 min to mix evenly. Put it into a crucible with a lid, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it to 500 °C at a heating rate of 5 °C / min and calcine for 2 h. After the calcination, let it cool naturally to room temperature to obtain a composite material, denoted as 10% STO@T / CN.
[0041] Example 3:
[0042] A preparation method of a composite photocatalyst of strontium titanate rich in titanium dioxide and carbon nitride:
[0043] (1) Weigh 10 g of solid urea particles and put them into a crucible with a lid. Keep the crucible in a semi-closed state and place it in a muffle furnace. Heat it to 550 °C at a heating rate of 5 °C / min and calcine for 2 h. After the calcination, let it cool naturally to room temperature to obtain carbon nitride composed of heptazine units containing terminal oxygen, denoted as CN.
[0044] (2) Grind 239.6 mg of titanium dioxide, 761.9 mg of strontium nitrate, 2922.0 mg of sodium chloride, and 3727.6 mg of potassium chloride in a mortar for 30 min to mix them evenly. Put them into a crucible with a lid, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it to 700 °C at a heating rate of 5 °C / min and calcine for 6 h. After the calcination, let it cool naturally to room temperature to obtain a solid white product. Disperse it in deionized water, then filter, and repeat 3 times to remove the excess salt. Finally, dry it in a forced-air drying oven at 60 °C for 12 h to obtain strontium titanate rich in titanium dioxide, denoted as STO@T.
[0045] (3) Put 500 mg of CN and 125 mg of STO@T into a beaker, add 200 ml of ultrapure water, sonicate for 1 h, then stir at 400 r / min for 24 h. After stirring, filter 2 - 3 times, dry in a forced-air drying oven at 60 °C for 12 h. The obtained solid material is simply ground and then stirred and ground in a mortar for 30 min to mix evenly. Put it into a covered crucible, keep the crucible in a semi-closed state, and place it in a muffle furnace. Heat it to 500 °C at a heating rate of 5 °C / min, calcine for 2 h. After the calcination is completed, cool it naturally to room temperature to obtain the composite material, denoted as 20% STO@T / CN.
[0046] Photocatalytic water splitting for hydrogen production experiment:
[0047] Weigh 25 mg of the photocatalyst and add it to a deionized aqueous solution (25 mL) containing triethanolamine (10 vol.%) and Pt (3 wt.%). Sonicate for 30 min. Before illumination, evacuate the reaction system to a vacuum state using a vacuum pump, and keep the temperature of the reactor at 5 °C using a cooling circulating water. Configure a 300 W xenon lamp with a 420 nm cut-off filter as the light source, and use a thermal conductivity detector and Molecular sieve column on-line gas chromatography to analyze the released hydrogen. The hydrogen production results are shown in Table 1.
[0048] Table 1 shows the average hydrogen production rate of the materials
[0049] Material Name Average Hydrogen Production Rate (μmol / g·h) STO@T 17.42 CN 757.63 5% STO@T / CN 1460.82 10% STO@T / CN 1547.71 20% STO@T / CN 1381.62
[0050] Figure 1 It is the scanning electron microscope image of the 10% STO@T / CN photocatalyst obtained in Example 2. It can be observed from the figure that CN covers STO@T.
[0051] Figure 2 It is the photoluminescence spectra of the 5% STO@T / CN, 10% STO@T / CN, 20% STO@T / CN and CN photocatalysts prepared in Examples 1, 2 and 3. Among all the samples, the photoluminescence emission peak intensity of CN is the largest, indicating the highest recombination rate of photo-generated electron-hole pairs. While the photoluminescence peak intensity of 10% STO@T / CN is significantly reduced, indicating that the recombination of photo-generated electrons and holes is significantly inhibited.
[0052] Figure 3 It is the band gap diagram of the 10% STO@T / CN, CN and STO@T photocatalysts prepared in Example 2. It can be seen from the figure that the band gap of the composite material is reduced compared with STO@T, which is beneficial to the absorption of visible light. And according to the calculation, the positions of the conduction band and valence band of CN and STO@T can be obtained, as well as the conditions for forming a heterojunction by recombination.
[0053] Figure 4Transient photocurrent response curves of 5% STO@T / CN, 10% STO@T / CN, 20% STO@T / CN and CN photocatalysts prepared in Examples 1, 2 and 3. It can be seen that 10% STO@T / CN has the strongest photocurrent response ability, demonstrating that the optoelectronic properties of the composite material have been significantly improved.
Claims
1. A preparation method of a titanium strontium titanate and carbon nitride composite photocatalyst rich in titanium dioxide, characterized in that, It includes the following steps: (1) Put the urea solid particles into a crucible with a lid, heat it to a specified temperature at a certain rate in a muffle furnace, keep it warm for a period of time, and then cool it naturally to obtain carbon nitride composed of heptazine units containing terminal oxygen, denoted as CN. (2) Mix titanium dioxide, strontium nitrate, sodium chloride, and potassium chloride, grind them evenly, put them into a crucible with a lid, then heat it to a specified temperature at a certain rate in a muffle furnace, keep it warm for a period of time, and then cool it naturally; wash it with deionized water several times to remove the excess salt, and after drying, obtain strontium titanate rich in titanium dioxide, denoted as STO@T. (3) Mix CN and STO@T obtained in step (1) and step (2) in a certain proportion, add a certain volume of pure water, ultrasonic it and then stir, then wash it with deionized water and dry it. Put the dried material into a crucible with a lid, then heat it to a specified temperature at a certain rate in a muffle furnace, keep it warm for a period of time, and then cool it naturally to obtain a composite material, denoted as STO@T / CN.
2. The preparation method of STO@T according to claim 1, characterized in that, In step (2), the mass ratio of titanium dioxide to strontium nitrate is 1:(2.6 - 3.2), the mass ratio of titanium dioxide to sodium chloride is 1:(10 - 15), and the mass ratio of titanium dioxide to potassium chloride is 1:(15 - 20).
3. The preparation method of STO@T according to claim 1, characterized in that, The grinding time described in step (2) is 20 - 60 min.
4. The preparation method of STO@T according to claim 1, characterized in that, The crucible with a lid described in step (2) remains in a semi-closed state, and the calcination atmosphere is air.
5. The preparation method of STO@T according to claim 1, wherein The heating rate described in step (2) is 2 - 10 °C / min, the holding reaction temperature is 700 - 800 °C, and the time is 6 - 8 h.
6. The preparation method of STO@T according to claim 1, wherein The drying temperature described in step (2) is 50 - 80 °C, and the time is 4 - 12 h.
7. The preparation method of STO@T / CN according to claim 1, characterized in that, In step (3), the mass ratio of CN to STO@T is (8 - 9.5):1, the ultrasonic time is 1 - 2 h, and the stirring time is 12 - 24 h.
8. The preparation method of STO@T / CN according to claim 1, characterized in that, The drying temperature described in step (3) is 50 - 80 °C, and the time is 4 - 12 h.
9. The preparation method of STO@T / CN according to claim 1, characterized in that, The crucible with a lid described in step (3) remains in a semi-closed state, and the calcination atmosphere is air.
10. The preparation method of STO@T / CN according to claim 1, characterized in that, The heating rate described in step (3) is 2 - 10 °C / min, the holding reaction temperature is 400 - 500 °C, and the time is 2 - 4 h.
11. A titanium strontium titanate and carbon nitride composite photocatalyst rich in titanium dioxide prepared by the method as described in claim 1, characterized in that, An internal electric field and a heterojunction will be formed, reducing the recombination rate of photo-generated electrons and holes.
12. Application of the strontium titanate rich in titanium dioxide and carbon nitride composite photocatalyst as described in claim 9 in photocatalytic water splitting for hydrogen production.