K-doped SrTiO3 photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a K-doped SrTiO3 photocatalyst as well as a preparation method and application thereof. According to the method, SrTiO3 is prepared by adopting a molten salt medium and a high-temperature solid-phase method, gradient doping of K atoms is realized through low-temperature calcination, a promoter is loaded through an in-situ step-by-step photodeposition method, and the method can be applied to the field of photocatalytic full water splitting. Compared with an existing photocatalyst, the low-temperature calcined K-doped SrTiO3 photocatalyst is high in stability, the concentration gradient from the surface to the bulk phase is formed, an energy band is bent, a gradient band gap structure is formed, a built-in electric field is formed, photo-induced electrons are driven to migrate to the surface, holes are driven to diffuse to the bulk phase, and the charge separation efficiency is remarkably improved. In the low-temperature doping process, lattice stress accumulation is slowed down, lattice collapse or defect aggregation caused by K doping is avoided, and the stability of gradient distribution is ensured. The catalyst material is low in preparation cost, non-toxic in reagent and high in yield, conforms to the green and environment-friendly concept advocated at present, and has a wide application market.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of a K-doped SrTiO 3 photocatalyst. Background Art

[0002] Nowadays, due to the extensive combustion of fossil fuels, the exacerbation of global warming and energy shortage, the demand for environmentally friendly and economically viable renewable energy has increased. Photocatalysis is one of the key technologies for converting solar energy into high-density and storable chemical energy. Among these technologies, photocatalytic water splitting for hydrogen production has become a promising method for sustainable energy production. Perovskite oxide materials have attracted great attention in photocatalysis due to their unique crystal structures and are widely used as photocatalysts.

[0003] SrTiO 3 Due to its excellent electrical conductivity, stability, relatively wide band gap and small resistivity, etc., it is widely used in the field of photocatalytic water splitting. However, the photocatalytic efficiency of SrTiO 3 is often limited by factors such as limited surface reactivity and rapid recombination of photo-generated electron-hole pairs. Therefore, doping SrTiO 3 is an effective method to improve solar energy utilization and reduce the recombination of electron-hole pairs. The K-doped SrTiO 3 photocatalyst of the present invention, K + ions gradually replace Sr 2+ to form a concentration gradient from the surface to the bulk phase, resulting in band bending and a gradient band gap structure, expanding the visible light absorption range. By using low-temperature calcination gradient doping, the volatilization loss of K elements at high temperatures can be reduced, ensuring the stability of the gradient distribution. The low-temperature process slows down the accumulation of lattice stress, avoiding lattice collapse or defect aggregation caused by K doping. The gradient doping forms an internal electric field, improving the separation efficiency of photo-generated electrons and holes. K doping can effectively adjust the band gap structure of SrTiO 3 to improve photocatalytic activity, synergistically optimize light absorption and charge transport, and there is no relevant report on the overall water splitting of the K-doped SrTiO 3 photocatalyst yet. Summary of the Invention

[0004] To solve the above problems, the present invention provides a K-doped SrTiO 3 photocatalyst and its preparation method and application.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A K-doped SrTiO 3 photocatalyst, in terms of molar percentage, the doping amount of K is SrTiO 30.1 - 2% of

[0007] A preparation method of K - doped SrTiO 3 photocatalyst, comprising the following steps:

[0008] 1) Put SrTiO 3 and SrCl 2 ·6H 2 O into a mortar and mix and grind them, then transfer to an Al 2 O 3 crucible, calcine in a muffle furnace, filter by suction and dry to obtain SrTiO 3 nanoparticles;

[0009] 2) Ultrasonically disperse the SrTiO 3 nanoparticles in water, and drop the KCl solution into the above - mentioned liquid during stirring, dry, put the dried powder in a porcelain boat, anneal in a muffle furnace, after the annealed powder cools down, put it in a beaker, add 30 mL of water, stir, filter by suction and dry to obtain the K - doped SrTiO 3 photocatalyst.

[0010] Furthermore, in the above - mentioned preparation method, in step 1), the dosage of SrTiO 3 is 1.0 g, and the dosage of SrCl 2 ·6H 2 O is 14.5 g.

[0011] Furthermore, in the above - mentioned preparation method, in step 1), the calcination temperature is 1100 °C and the calcination time is 10 h.

[0012] Furthermore, in the above - mentioned preparation method, in step 2), the concentration of the KCl solution is 0.3727 g / 200 mL, and by molar percentage, the doping amount of K is 0.1%, 0.5% or 2% of SrTiO 3 .

[0013] Furthermore, in the above - mentioned preparation method, in steps 1) and 2), the drying temperature is 60 °C and the drying time is 12 h.

[0014] Furthermore, in the above - mentioned preparation method, in step 2), the ultrasonic dispersion time is 3 min and the stirring process lasts for 20 min.

[0015] Furthermore, in the above - mentioned preparation method, in step 2), the annealing temperature is 400 °C, the heating rate is 5 °C / min, and the annealing time is 2 h.

[0016] The above - mentioned K - doped SrTiO 3 photocatalyst is used in the photocatalytic overall water splitting under visible light irradiation.

[0017] Further, for the above application, the method is as follows: K is doped into SrTiO 3 The photocatalyst is uniformly dispersed in a reaction tank filled with deionized water, and a co-catalyst is in-situ photo-deposited. Then, 126 μL of an aqueous solution of Na 3 RhCl 6 ·12H 2 O with a concentration of 0.59 mg / mL is added. The mass of Rh is 0.1% of that of SrTiO 3 . It is irradiated with a 300 W xenon lamp for 10 min. Then, 10 μL of an aqueous solution of Cr(NO 3 )·9H 2 O with a concentration of 7.7 mg / mL is added. The mass of Cr is 0.05% of that of SrTiO 3 . It is irradiated with a 300 W xenon lamp for 5 min. Next, 21 μL of an aqueous solution of CoCl 2 ·6H 2 O with a concentration of 10 mg / mL is added. The mass of Co is 0.05% of that of SrTiO 3 . It is irradiated with a 300 W xenon lamp for 5 min. Finally, it is irradiated for another 5 min. Argon is continuously introduced into the container containing the mixed solution at a rate of 40 mL / min to create a relatively vacuum environment, and hydrogen is evolved by water decomposition under visible light irradiation.

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

[0019] 1. The present invention uses a molten salt medium and a high-temperature solid-phase method to prepare the SrTiO 3 catalyst, and a low-temperature calcination method to prepare the K-doped SrTiO 3 catalyst, which can adjust the energy band structure, has a stronger ability to absorb visible light, and enhances the photocatalytic activity.

[0020] 2. The K-gradient doped SrTiO 3 catalyst prepared by the present invention forms a built-in electric field. The gradient structure provides a directional carrier transport channel, driving photo-generated electrons to migrate to the surface and holes to diffuse into the bulk phase, significantly improving the charge separation efficiency and accelerating the separation efficiency of photo-generated carriers, which is an effective way to improve the visible light photocatalytic activity.

[0021] 3. The Rh precursor solution, Cr precursor solution, and Co precursor solution of the present invention are used as co-catalysts and loaded on the K-doped SrTiO 3 , which can increase additional reaction sites on different crystal planes of the catalyst and improve the separation efficiency of photo-generated carriers.

[0022] 4. The K-doped SrTiO 3The photocatalyst has good photocatalytic overall water splitting performance. Gradient doping reduces surface defects, inhibits the oxidative corrosion of the photocatalyst by photogenerated holes, improves the cycling stability, and this method is simple, convenient, low-cost, mild in conditions, and conducive to large-scale production. Description of the Drawings

[0023] Figure 1 SrTiO prepared in Example 1 3 Catalyst, 0.1% K-SrTiO prepared in Example 2 3 Catalyst, 0.5% K-SrTiO prepared in Example 3 3 Photocatalyst and 2% K-SrTiO prepared in Example 4 3 Catalyst X-ray diffraction patterns.

[0024] Figure 2 0.5% K-SrTiO prepared in Example 3 3 Hydrogen and oxygen rate diagrams of the photocatalyst.

[0025] Figure 3 SrTiO prepared in Example 1 3 Catalyst, 0.1% K-SrTiO prepared in Example 2 3 Catalyst, 0.5% K-SrTiO prepared in Example 3 3 Photocatalyst and 2% K-SrTiO prepared in Example 4 3 Hydrogen evolution activity comparison diagrams of the catalyst. Detailed Description of the Invention

[0026] Example 1

[0027] SrTiO 3 The preparation method of the catalyst is as follows:

[0028] Weigh 14.5 g of SrCl 2 ·6H 2 O and 1 g of commercially available SrTiO 3 Put them in a mortar, grind for 10 min to make them evenly mixed, and then place them in an Al 2 O 3 crucible, calcine in a muffle furnace at 1100 °C for 10 h, carry out suction filtration, and then dry in an oven at 60 °C for 12 h to obtain SrTiO 3 nanoparticles.

[0029] Example 2

[0030] 0.1% K-SrTiO 3 The preparation method of the catalyst is as follows:

[0031] Take 0.183 g of SrTiO prepared in Example 13 The nanoparticles were ultrasonically dispersed in 30 mL of water for 3 min. During stirring, 40 μL of a KCl solution with a concentration of 0.3727 g / 200 mL was added dropwise to the above liquid, and the mixture was stirred for 20 min, dried at 60 °C, and the dried powder was placed in a porcelain boat and annealed in a muffle furnace at 400 °C (heating rate: 5 °C / min) for 2 h. After the annealed powder was cooled, it was placed in a beaker, 30 mL of water was added, stirred, filtered by suction, and dried at 60 °C for 12 h to obtain 0.1% K-doped SrTiO 3 photocatalyst.

[0032] Example 3

[0033] 0.5% K-SrTiO 3 The preparation method of the catalyst is as follows:

[0034] 0.183 g of SrTiO prepared in Example 1 3 The nanoparticles were ultrasonically dispersed in 30 mL of water for 3 min. During stirring, 200 μL of a KCl solution with a concentration of 0.3727 g / 200 mL was added dropwise to the above liquid, and the mixture was stirred for 20 min, dried at 60 °C, and the dried powder was placed in a porcelain boat and annealed in a muffle furnace at 400 °C (heating rate: 5 °C / min) for 2 h. After the annealed powder was cooled, it was placed in a beaker, 30 mL of water was added, stirred, filtered by suction, and dried at 60 °C for 12 h to obtain 0.5% K-doped SrTiO 3 photocatalyst.

[0035] Example 4

[0036] 2% K-SrTiO 3 The preparation method of the catalyst is as follows:

[0037] 0.183 g of SrTiO prepared in Example 1 3 The nanoparticles were ultrasonically dispersed in 30 mL of water for 3 min. During stirring, 800 μL of a KCl solution with a concentration of 0.3727 g / 200 mL was added dropwise to the above liquid, and the mixture was stirred for 20 min, dried at 60 °C, and the dried powder was placed in a porcelain boat and annealed in a muffle furnace at 400 °C (heating rate: 5 °C / min) for 2 h. After the annealed powder was cooled, it was placed in a beaker, 30 mL of water was added, stirred, filtered by suction, and dried at 60 °C for 12 h to obtain 2% K-doped SrTiO 3 photocatalyst.

[0038] Example 5

[0039] K-SrTiO 3 Application of the photocatalyst in photocatalytic overall water splitting under light irradiation:

[0040] 1) Under normal temperature and pressure conditions, 20 mg of SrTiO prepared in Example 1 3 The photocatalyst was evenly dispersed in a reaction tank filled with deionized water, and the cocatalyst was in-situ photodeposited. An aqueous solution of Na 3 RhCl 6 ·12H 2 O with a concentration of 0.59 mg / mL and 126 μL was added. The mass of Rh was 0.1% of the mass of SrTiO 3 . It was irradiated with a 300 W xenon lamp for 10 min. An aqueous solution of Cr(NO 3 )·9H 2 O with a concentration of 7.7 mg / mL and 10 μL was added. The mass of Cr was 0.05% of the mass of SrTiO 3 . It was irradiated with a 300 W xenon lamp for 5 min. An aqueous solution of CoCl 2 ·6H 2 O with a concentration of 10 mg / mL and 21 μL was added. The mass of Co was 0.05% of the mass of SrTiO 3 . It was irradiated with a 300 W xenon lamp for 5 min, and then irradiated for another 5 min. Argon was continuously introduced into the container containing the mixed solution at a rate of 40 mL / min to create a relatively vacuum environment. Under visible light irradiation conditions, 1000 μL of gas in the container was taken every 30 min using a microsyringe, and a gas chromatograph was used to quantitatively analyze the catalytic products collected.

[0041] 2) Operate according to step 1), except that the SrTiO 3 photocatalyst prepared in Example 1 was replaced with the 0.1% K-SrTiO 3 catalyst prepared in Example 2, the 0.5% K-SrTiO 3 catalyst prepared in Example 3, and the 2% K-SrTiO 3 prepared in Example 4 respectively. Other conditions remained unchanged, and the gases were taken respectively to measure the hydrogen production and oxygen production efficiency.

[0042] Figure 1 is the X-ray diffraction pattern of the K-doped SrTiO 3 photocatalyst prepared for the above examples. The characteristic signal peaks in the figure correspond to the (100), (110), (111), (200), (210), (211), (220), (300), and (310) crystal planes, which are consistent with the SrTiO 3 PDF standard card (PDF#84-0443). It can be seen from Figure 1 that when doped, the characteristic signal peaks of SrTiO 3 shifted, indicating successful K doping.

[0043] Figure 2For the 0.5% K-SrTiO prepared in Example 3 3 Hydrogen and oxygen evolution rate diagrams of the photocatalyst. The results show that within 3 h, the highest hydrogen evolution rate of 0.5% K-SrTiO 3 is 45.32 mmol / g, the highest oxygen evolution rate is 22.76 mmol / g, and the rate ratio of hydrogen to oxygen is approximately 2:1, which is 2.92 times that of SrTiO 3 (15.47 mmol / g) in terms of hydrogen evolution rate. It shows that K-gradient doping of SrTiO 3 improves the separation efficiency of photo-generated carriers in the semiconductor, which is beneficial to improving the photocatalytic overall water splitting activity.

[0044] Figure 3 SrTiO prepared for Example 1, Example 2, Example 3 and Example 4 3 , 0.1% K-SrTiO 3、 0.5% K-SrTiO 3 and 2% K-SrTiO 3 Photocatalyst water splitting hydrogen evolution activity comparison diagram. From Figure 3 it can be seen that after 1 h of light reaction, the H 3 production of SrTiO 2 is 5.48 mmol / g / h, the H 3 production of 0.1% K-SrTiO 2 is 12.04 mmol / g / h, the H 3 production of 0.5% K-SrTiO 2 is 15.87 mmol / g / h, the H 3 production of 2% K-SrTiO 2 is 14.15 mmol / g / h. The hydrogen production performance of K-doped SrTiO 3 photocatalyst is greatly improved compared with that of pure SrTiO 3 . It shows that after K doping, the photo-generated electron transport and transfer ability is strong, and the electron-hole has strong redox ability.

Claims

1. A K-doped SrTiO3 photocatalyst, characterized in that: The K-doped SrTiO3 photocatalyst has a K doping amount of 0.1-2% of SrTiO3 in terms of molar percentage.

2. The method for preparing a K-doped SrTiO3 photocatalyst according to claim 1, characterized in that: The following steps are involved: 1) SrTiO3 and SrCl2·6H2O were mixed and ground in a mortar, and then transferred to an Al2O3 crucible, calcined in a muffle furnace, filtered and dried to obtain SrTiO3 nanoparticles; 2) Ultrasonic dispersion of SrTiO3 nanoparticles in water, dropwise addition of KCl solution into the liquid during stirring, drying, placing the dried powder in a porcelain boat, annealing in a muffle furnace, cooling the annealed powder, placing it in a beaker, adding 30 mL of water, stirring, filtering and drying to obtain a K-doped SrTiO3 photocatalyst.

3. The preparation method according to claim 2, characterized in that: In step 1), the amount of SrTiO3 used is 1.0 g, and the amount of SrCl2·6H2O used is 14.5 g.

4. The preparation method according to claim 2, characterized in that: In step 1), the calcination temperature is 1100° C. and the calcination time is 10 h.

5. The preparation method according to claim 2, characterized in that: In step 2), the concentration of the KCl solution is 0.3727 g / 200 mL, and the doping amount of K is 0.1%, 0.5% or 2% of SrTiO3 by mole percentage.

6. The preparation method according to claim 2, characterized in that: In steps 1) and 2), the drying temperature is 60° C. and the drying time is 12 h.

7. The preparation method according to claim 2, characterized in that: In step 2), the ultrasonic dispersion time is 3 minutes and the stirring process lasts for 20 minutes.

8. The preparation method according to claim 2, characterized in that: In step 2), the annealing temperature is 400° C., the heating rate is 5° C. / min, and the annealing time is 2 h.

9. Use of the K-doped SrTiO3 photocatalyst according to claim 1 in catalytic complete water splitting under visible light irradiation.

10. The use according to claim 9, characterized in that: The method is as follows: K-doped SrTiO3 photocatalyst is uniformly dispersed in a reaction tank filled with deionized water, a co-catalyst is in situ photodeposited, 126 μL of a 0.59 mg / mL Na3RhCl6·12H2O aqueous solution is added, the mass of Rh is 0.1% of SrTiO3, and 300 W xenon lamp is used for irradiation for 10 min, 10 μL of a 7.7 mg / mL Cr(NO3)·9H2O aqueous solution is added, the mass of Cr is 0.05% of SrTiO3, and 300 W xenon lamp is used for irradiation for 5 min, 21 μL of a 10 mg / mL CoCl2·6H2O aqueous solution is added, the mass of Co is 0.05% of SrTiO3, and 300 W xenon lamp is used for irradiation for 5 min, and finally irradiation is carried out for another 5 min, argon gas is continuously introduced into the container containing the mixed solution at 40 mL / min to obtain a relatively vacuum environment, and water is decomposed to release hydrogen under visible light irradiation conditions.

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