Co-catalyst-loaded Al-doped SrTiO3 / TiO2 heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to an Al-doped SrTiO3 / TiO2 heterojunction full-water-splitting photocatalyst loaded with a promoter as well as a preparation method and application of the Al-doped SrTiO3 / TiO2 heterojunction full-water-splitting photocatalyst. The preparation method comprises the following steps: adding titanium dioxide into an Al-SrTiO3 aqueous solution, heating in a water bath, changing the molar ratio of TiO2 to obtain Al-SrTiO3-x% TiO2 with different molar ratios, then adding an Rh precursor solution, a Cr precursor solution and a Co precursor solution, and irradiating under a 300W xenon lamp to obtain the co-catalyst-loaded Al-doped SrTiO3 / TiO2 heterojunction full-water-splitting photocatalyst. The method can be applied to the field of photocatalytic full water splitting. Compared with an existing photocatalyst, the co-catalyst-loaded Al-doped SrTiO3 / TiO2 heterojunction full-water-splitting photocatalyst has the advantages that the controllability is good, the separation efficiency of current carriers is further improved, the composite material is used for photocatalytic full-water-splitting, the hydrogen production amount is high, the stability is good, and the application prospect is wide. The method is simple and convenient to operate, low in cost, mild in condition and beneficial to large-scale production.

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 an Al-doped SrTiO 3 / TiO 2 heterojunction photocatalyst for overall water splitting. Background Art

[0002] In recent years, the problems of energy shortage and environmental damage have severely restricted the sustainable development of society. Developing efficient and green hydrogen resources has become the focus of attention of most researchers. Hydrogen, as an environmentally friendly, sustainable and renewable energy, is becoming increasingly popular because it has the potential to alleviate the energy shortage caused by the abuse of fossil fuels. So far, many methods for producing hydrogen energy have been established, including high-temperature decomposition of water and electrocatalytic water splitting. As global warming has become one of the most urgent problems of this century, there is an urgent need for efficient alternative energy sources to produce clean energy. Hydrogen, due to its abundance and high energy density, is a promising major energy carrier. Photocatalytic water splitting for hydrogen production using a large amount of solar energy has attracted extensive attention.

[0003] SrTiO 3 has received extensive attention and application due to its significant advantages of simple synthesis, environmental friendliness, good stability and suitable band structure. However, the photocatalytic efficiency of pure SrTiO 3 photocatalyst is usually limited, mainly because its development efficiency for sunlight is significantly lower, and there is a large amount of recombination of photo-generated charges. Al-doped SrTiO 3 can narrow the band gap of SrTiO 3 so as to increase the visible light absorption range and the utilization rate of visible light. Forming a heterojunction with other semiconductors after doping is a means to improve the photocatalytic efficiency of SrTiO 3 for overall water splitting. Therefore, an Al-SrTiO 3 / TiO 2 heterojunction is designed as a photocatalyst for overall water splitting, and there is no relevant report on this method yet. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides a preparation method and application of an Al-doped SrTiO 3 / TiO 2 heterojunction photocatalyst for overall water splitting.

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

[0006] An Al-doped SrTiO 3 / TiO 2Heterojunction photocatalyst, by molar percentage, the doping amount of TiO 2 is 5-15% of Al-SrTiO 3 .

[0007] The above-mentioned Al-doped SrTiO 3 / TiO 2 photocatalyst preparation method, including the following steps:

[0008] 1) Add SrTiO 3 , Al 2 O 3 and SrCl 2 ·6H 2 O into a mortar, grind to form a uniform precursor powder, then transfer it to a high-temperature muffle furnace for calcination reaction. After the reaction ends, cool it to room temperature to obtain Al-SrTiO 3 photocatalyst;

[0009] 2) Mix tetrabutyl titanate, absolute ethanol, and acetylacetone evenly under magnetic stirring, and record it as solution A; mix absolute ethanol and deionized water, then add dilute hydrochloric acid to adjust the pH value, and mix evenly, and record it as solution B; slowly drip solution B into solution A under magnetic stirring and continue stirring until the solution shows a sol state, then continue stirring under water bath heating to turn the sol into a gel. After drying the prepared gel in an oven, take out the sample and grind it thoroughly. Put the ground powder into a porcelain boat and transfer it to a muffle furnace for calcination reaction. After the reaction ends, cool it to room temperature to obtain TiO 2 photocatalyst;

[0010] 3) Suspend the Al-SrTiO 3 photocatalyst and the TiO 2 photocatalyst in ethanol solution respectively, and ultrasonically treat the two suspensions before mixing; stir the mixed suspension containing the two photocatalysts under water bath heating; then, obtain the Al-SrTiO 3 / TiO 2 photocatalyst by evaporating ethanol;

[0011] 4) Ultrasonically soak the Al-SrTiO 3 / TiO 2 photocatalyst in deionized water for 20 min, then add the Rh precursor solution and the Cr precursor solution. After irradiating for 1 h under a 300 W xenon lamp, add the Co precursor solution and continue irradiating for 0.5 h under a 300 W xenon lamp. Each time a precursor solution is added, argon is introduced at a constant flow rate to prevent the liquid from contacting the air and exclude the interference of air on the solution. After the reaction ends, cool it to room temperature, filter by suction, and dry it in vacuum to obtain the Al-SrTiO 3 / TiO2 Catalyst

[0012] Furthermore, in the above preparation method, in step 1), in terms of molar ratio, SrTiO 3 :Al 2 O 3 :SrCl 2 ·6H 2 O = 1:0.01:10

[0013] Furthermore, in the above preparation method, in step 1), the calcination is carried out at 1100 °C for 10 h

[0014] Furthermore, in the above preparation method, in step 2), in solution A, tetrabutyl titanate: absolute ethanol: acetylacetone = 10 mL: 30 mL: 1 mL; in solution B, absolute ethanol: deionized water = 10 mL: 6 mL, and the pH value ≤ 3

[0015] Furthermore, in the above preparation method, in step 2), the drying is carried out at 100 °C for 10 h

[0016] Furthermore, in the above preparation method, in step 2), the calcination is carried out at 550 °C for 3 h

[0017] Furthermore, in the above preparation method, in step 3), the water bath heating is carried out at 50 °C for 24 h

[0018] Furthermore, in the above preparation method, in step 4), the Rh precursor solution is: Dissolve Na 3 RhCl 6 ·12H 2 O in deionized water, with a mass percentage concentration of 0.1%

[0019] Furthermore, in the above preparation method, in step 4), the Cr precursor solution is: Dissolve Cr(NO 3 )·9H 2 O in deionized water, with a mass percentage concentration of 0.05%

[0020] Furthermore, in the above preparation method, in step 4), the Co precursor solution is: Dissolve CoCl 2 ·6H 2 O in deionized water, with a mass percentage concentration of 0.05%

[0021] Furthermore, in the above preparation method, in step 4), in terms of the solid-liquid ratio, Al-SrTiO 3 / TiO 2Deionized water: Rh precursor solution: Cr precursor solution: Co precursor solution = 20 mg: 20 mL: 126 μL: 10 μL: 21 μL.

[0022] The above-mentioned Al-doped SrTiO supported with a cocatalyst 3 / TiO 2 Application of the heterojunction photocatalyst in photocatalytic overall water splitting under visible light irradiation.

[0023] Furthermore, for the above-mentioned application, the method is as follows: uniformly disperse the Al-doped SrTiO 3 / TiO 2 heterojunction photocatalyst supported with a cocatalyst in a reaction cell filled with deionized water. Before the reaction, evacuate the system to remove the air in the system, and irradiate it under a 300 W xenon lamp.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention prepares an Al-SrTiO 3 / TiO 2 heterojunction photocatalyst by using a water bath heating method. After Al doping and modification by forming a heterojunction with TiO 2 the transient photocurrent response increases, the charge transfer rate is faster, the transfer resistance is lower, and at the same time, the charge recombination caused by defects is inhibited, enhancing the photocatalytic activity.

[0026] 2. The Al-SrTiO 3 / TiO 2 heterojunction photocatalyst prepared by the present invention has a larger specific surface area, provides more active sites, has a stronger visible light absorption ability, and is an effective way to improve the visible light photocatalytic activity.

[0027] 3. The Al-SrTiO 3 / TiO 2 heterojunction photocatalyst prepared by the present invention has good photocatalytic overall water splitting performance, and this method is simple, convenient, low-cost, mild in conditions, and is conducive to large-scale production. Description of the Drawings

[0028] Figure 1 X-ray diffraction patterns of the Al-SrTiO 3 , TiO 2 , 5-TIO / ASO, 10-TIO / ASO, and 15-TIO / ASO photocatalysts prepared in Example 1.

[0029] Figure 2 Hydrogen and oxygen evolution rate diagrams of the 10-TIO / ASO photocatalyst prepared in Example 1.

[0030] Figure 3 Al-SrTiO prepared for Example 1 3 、TiO 2 Comparison chart of hydrogen evolution activities of 5-TIO / ASO, 10-TIO / ASO, and 15-TIO / ASO photocatalysts for water splitting Specific implementation manners

[0031] Al-doped SrTiO loaded with cocatalyst in Example 1 3 / TiO 2 Heterojunction photocatalyst (1) Preparation of Al-SrTiO 3

[0032] Put 1 mmol SrTiO 3 , 0.01 mmol Al 2 O 3 and 10 mmol SrCl 2 ·6H 2 O into a mortar, mix evenly to form a precursor powder, then put it into a porcelain boat and react in a high-temperature muffle furnace at a heating rate of 5 °C / min for 10 h at 1100 °C, and cool naturally to room temperature to obtain Al-SrTiO 3 .

[0033] (2) Preparation of TiO 2

[0034] Add 10 mL of tetrabutyl titanate to 30 mL of absolute ethanol, stir for 30 min, then add 1 mL of acetylacetone, and mix evenly under magnetic stirring, denoted as solution A; mix 10 mL of absolute ethanol and 6 mL of deionized water, add appropriate amount of dilute hydrochloric acid to adjust the pH ≤ 3, and mix evenly, denoted as solution B. Slowly drip solution B into solution A under magnetic stirring and continue stirring for 2 h until the solution shows a sol state, then continue stirring for 2 h under a water bath at 50 °C to turn the sol into a gel. Put the prepared gel into an oven and dry it at 100 °C for 10 h, then take out the sample and grind it thoroughly. Put the ground powder into a porcelain boat and transfer it to a muffle furnace for calcination at 550 °C for 3 h. After the reaction is completed, cool to room temperature to obtain TiO 2 photocatalyst.

[0035] (3) Preparation of Al-SrTiO 3 / 5% TiO 2 photocatalyst

[0036] 1) Put 1 mmol Al-SrTiO 3 and 0.05 mmol TiO 2 ​​Suspended separately in ethanol solution, the two suspensions were ultrasonically treated for 10 min before mixing. The mixed suspension containing the two photocatalysts was stirred for 24 h under heating in a water bath at 50 °C. Then, by evaporating ethanol, Al-SrTiO with a loading of 5% was obtained 3 / TiO 2 photocatalyst, labeled as Al-SrTiO 3 / 5% TiO 2 .

[0037] 2) Dissolve Na 3 RhCl 6 ·12H 2 O in deionized water to prepare a Rh precursor solution with a mass percentage concentration of 0.1%. Dissolve Cr(NO 3 )·9H 2 O in deionized water to prepare a Cr precursor solution with a mass percentage concentration of 0.05%. Dissolve CoCl 2 ·6H 2 O in deionized water to prepare a Co precursor solution with a mass percentage concentration of 0.05%.

[0038] 3) Ultrasonically soak 20 mg of Al-SrTiO 3 / 5% TiO 2 in 20 mL of deionized water for 20 min, then add 126 μL of the Rh precursor solution and 10 μL of the Cr precursor solution. After irradiating for 1 h under a 300 W xenon lamp, add 21 μL of the Co precursor solution and continue irradiating for 0.5 h under a 300 W xenon lamp. Argon gas was introduced at a constant flow rate after each addition of the precursor solution to prevent the liquid from contacting air and exclude the interference of air on the solution. After the reaction, it was cooled to room temperature, filtered by suction, and dried in vacuum to obtain Al-SrTiO loaded with a cocatalyst 3 / 5% TiO 2 , labeled as 5-TIO / ASO.

[0039] (IV) Preparation of Al-SrTiO 3 / 10% TiO 2 photocatalyst

[0040] 1) Suspend 1 mmol of Al-SrTiO 3 and 0.1 mmol of TiO 2 separately in ethanol solution. The two suspensions were ultrasonically treated for 10 min before mixing. The mixed suspension containing the two photocatalysts was stirred for 24 h under heating in a water bath at 50 °C. Then, by evaporating ethanol, Al-SrTiO with a loading of 10% was obtained 3 / TiO 2Photocatalyst, labeled as Al-SrTiO 3 / 10% TiO 2 .

[0041] 2) Dissolve Na 3 RhCl 6 ·12H 2 O in deionized water to prepare a Rh precursor solution with a mass percentage concentration of 0.1%. Dissolve Cr(NO 3 )·9H 2 O in deionized water to prepare a Cr precursor solution with a mass percentage concentration of 0.05%. Dissolve CoCl 2 ·6H 2 O in deionized water to prepare a Co precursor solution with a mass percentage concentration of 0.05%.

[0042] 3) Ultrasonically soak 20 mg of Al-SrTiO 3 / 10% TiO 2 in 20 mL of deionized water for 20 min, then add 126 μL of the Rh precursor solution and 10 μL of the Cr precursor solution. After irradiating for 1 h under a 300 W xenon lamp, add 21 μL of the Co precursor solution and continue irradiating for 0.5 h under a 300 W xenon lamp. Each time a precursor solution is added, argon is introduced at a constant flow rate to prevent the liquid from contacting the air and exclude the interference of air on the solution. After the reaction, cool to room temperature, filter by suction, and dry in vacuum to obtain Al-SrTiO 3 / 10% TiO 2 loaded with a cocatalyst, labeled as 10-TIO / ASO.

[0043] (V) Preparation of Al-SrTiO 3 / 15% TiO 2 Photocatalyst

[0044] 1) Suspend 1 mmol of Al-SrTiO 3 and 0.15 mmol of TiO 2 separately in ethanol solutions. The two suspensions are ultrasonically treated for 10 min before mixing. Stir the mixed suspension containing the two photocatalysts in a 50 °C water bath for 24 h. Then, obtain an Al-SrTiO 3 / TiO 2 photocatalyst with a loading of 15%, labeled as Al-SrTiO 3 / 15% TiO 2 .

[0045] 2) Dissolve Na 3 RhCl 6 ·12H 2O is dissolved in deionized water to prepare a Rh precursor solution with a mass percentage concentration of 0.1%. Cr(NO 3 )·9H 2 O is dissolved in deionized water to prepare a Cr precursor solution with a mass percentage concentration of 0.05%. CoCl 2 ·6H 2 O is dissolved in deionized water to prepare a Co precursor solution with a mass percentage concentration of 0.05%.

[0046] 3) 20 mg of Al-SrTiO 3 / 15% TiO 2 is ultrasonically soaked in 20 mL of deionized water for 20 min, then 126 μL of the Rh precursor solution and 10 μL of the Cr precursor solution are added. After irradiation under a 300 W xenon lamp for 1 h, 21 μL of the Co precursor solution is added, and irradiation continues under a 300 W xenon lamp for 0.5 h. Argon is introduced at a constant flow rate after each addition of the precursor solution to prevent the liquid from contacting air and exclude the interference of air on the solution. After the reaction, it is cooled to room temperature, filtered by suction, and dried in vacuum to obtain Al-SrTiO 3 / 15% TiO 2 loaded with a cocatalyst, labeled as 15-TIO / ASO.

[0047] (VI) Detection

[0048] Figure 1 are the X-ray diffraction patterns of the Al-SrTiO 3 , TiO 2 and the photocatalysts 5-TIO / ASO, 10-TIO / ASO, 15-TIO / ASO prepared in Example 1. Figure 1 Among them, seven significant characteristic diffraction peaks at 2θ = 22.7°, 32.4°, 39.9°, 46.5°, 52.3°, 57.9° and 67.9° respectively correspond to the (100), (110), (111), (200), (210), (211) and (220) crystal planes of Al-SrTiO 3 (standard card PDF#35-0734). No characteristic peaks of other impurities are observed in Figure 1 , which indicates that SrTiO 2 still retains its original structure after TiO 3 is loaded on Al-SrTiO 3 . No characteristic peaks of TiO 2 are observed, probably due to the low loading amount of TiO 2 .

[0049] Al-doped SrTiO 3 / TiO loaded with a cocatalyst in Example 22 Application of Heterojunction Photocatalyst in the Photocatalytic Overall Water Splitting under Light Irradiation

[0050] The method is as follows: At normal temperature and pressure, deionized water is added to the reaction cell, and then 20 mg of Al-SrTiO prepared in Example 1 3 , TiO 2 and 5-TIO / ASO, 10-TIO / ASO, 15-TIO / ASO photocatalysts are added, and then ultrasonic treatment is carried out for 10 min to obtain a dispersion solution. The container is sealed, and before the reaction, the system is evacuated to remove the air in the system, and the container is kept in a vacuum state all the time. Under the irradiation of visible light (300 W xenon lamp), gaseous products are extracted through an on-line sampling loop system every 30 min, and the components of the sample gas are detected by gas chromatography separation technology, and the hydrogen evolution and oxygen evolution concentrations are measured..

[0051] Figure 2 It is the hydrogen and oxygen evolution rate diagram of the 10-TIO / ASO photocatalyst prepared in Example 1. The results show that the highest hydrogen evolution rate of 10-TIO / ASO within 1 h is 24 mmol·g -1 ·h -1 , and the highest oxygen evolution rate is 12 mmol·g -1 ·h -1 , and the rate ratio of hydrogen to oxygen is 2:1, which is twice that of pure Al-SrTiO 3 (12 mmol·g -1 ·h -1 ), and 428 times that of pure TiO 2 (56 μmol·g -1 ·h -1 ). It shows that the loading of TiO 2 improves the separation efficiency of photogenerated carriers in the semiconductor and is beneficial to improving the photocatalytic overall water splitting activity.

[0052] Figure 3 It is the comparison diagram of the hydrogen evolution activity of Al-SrTiO 3 , TiO 2 and 5-TIO / ASO, 10-TIO / ASO, 15-TIO / ASO photocatalysts prepared in Example 1. As Figure 3 can be seen, after 60 min of light irradiation reaction, the hydrogen production amount of Al-SrTiO 3 is 12 mmol·g -1 ·h -1 , the hydrogen production amount of TiO 2 is 56 μmol·g -1 ·h -1 , and the Al-SrTiO 3 / 5% TiO 2 loaded with co-catalyst produces H2 The amount is 14.8 mmol·g -1 ·h -1 , Al-SrTiO loaded with cocatalyst 3 / 10% TiO 2 The hydrogen production 2 The amount is 23.4 mmol·g -1 ·h -1 , Al-SrTiO loaded with cocatalyst 3 / 15% TiO 2 The hydrogen production 2 The amount is 15.7 mmol·g -1 ·h -1 . The Al-SrTiO loaded with cocatalyst 3 / TiO 2 The hydrogen production performance of the photocatalyst is greatly improved compared with that of pure Al-SrTiO 3 . It shows that after TiO 2 is loaded on Al-SrTiO 3 , the ability of photogenerated electron transfer is strong, and the electron-hole has strong redox ability.

Claims

1. An Al-doped SrTiO3 / TiO2 heterojunction photocatalyst loaded with a promoter, characterized in that: In terms of molar percentage, the doping amount of TiO2 is 5-15% of Al-SrTiO3.

2. The method for preparing a co-catalyst-loaded Al-doped SrTiO3 / TiO2 photocatalyst according to claim 1, characterized in that: The steps include: 1) SrTiO3, Al2O3 and SrCl2·6H2O are added into a mortar, ground into a uniform precursor powder, and then transferred into a high-temperature muffle furnace for calcination reaction. After the reaction is completed, the powder is cooled to room temperature to obtain an Al-SrTiO3 photocatalyst; 2) Tetrabutyl titanate, anhydrous ethanol and acetylacetone are mixed uniformly under magnetic stirring, which is recorded as solution A; after mixing anhydrous ethanol and deionized water, dilute hydrochloric acid is added to adjust the pH value, and the mixture is uniformly mixed, which is recorded as solution B; under magnetic stirring, solution B is slowly added dropwise to solution A, and stirring is continued until the solution is in a sol state, and then stirring is continued under water bath heating to turn the sol into gel, the prepared gel is placed in an oven to dry, the sample is taken out and fully ground, the ground powder is placed in a porcelain boat and transferred to a muffle furnace for calcination reaction, and after the reaction is completed, it is cooled to room temperature to obtain a TiO2 photocatalyst; 3) suspending the Al-SrTiO3 photocatalyst and the TiO2 photocatalyst in an ethanol solution respectively, and subjecting the two suspensions to ultrasonic treatment before mixing; stirring the mixed suspension containing the two photocatalysts under heating in a water bath; and then, obtaining the Al-SrTiO3 / TiO2 photocatalyst by evaporating the ethanol; 4) The Al-SrTiO3 / TiO2 photocatalyst was ultrasonically soaked in deionized water for 20 minutes, and then Rh precursor solution and Cr precursor solution were added. After irradiation under a 300W xenon lamp for 1 hour, Co precursor solution was added and irradiation under a 300W xenon lamp was continued for 0.5 hours. After each addition of the precursor solution, argon gas was introduced at a constant flow rate to prevent the liquid from contacting with the air and to eliminate the interference of air on the solution. After the reaction was completed, it was cooled to room temperature, filtered, and vacuum dried to obtain the Al-SrTiO3 / TiO2 catalyst loaded with the co-catalyst.

3. The preparation method according to claim 2, characterized in that: In step 1), the molar ratio is SrTiO3:Al2O3:SrCl2·6H2O=1:0.01:

10.

4. The preparation method according to claim 2, characterized in that: In step 1), the calcination is carried out at 1100° C. for 10 hours.

5. The preparation method according to claim 2, characterized in that: In step 2), in solution A, tetrabutyl titanate: anhydrous ethanol: acetylacetone = 10 mL: 30 mL: 1 mL; in solution B, anhydrous ethanol: deionized water = 10 mL: 6 mL, and the pH value is ≤3.

6. The preparation method according to claim 2, characterized in that: In step 2), the drying is carried out at 100° C. for 10 hours; and the calcination is carried out at 550° C. for 3 hours.

7. The preparation method according to claim 2, characterized in that: In step 3), the water bath heating is heating at 50° C. for 24 h.

8. The preparation method according to claim 2, characterized in that: In step 4), the Rh precursor solution is: Na3RhCl6·12H2O dissolved in deionized water, with a mass percentage concentration of 0.1%; the Cr precursor solution is: Cr(NO3)·9H2O dissolved in deionized water, with a mass percentage concentration of 0.05%; the Co precursor solution is: CoCl2·6H2O dissolved in deionized water, with a mass percentage concentration of 0.05%.

9. The preparation method according to claim 2, characterized in that: In step 4), according to the solid-liquid ratio, Al-SrTiO3 / TiO2: deionized water: Rh precursor solution: Cr precursor solution: Co precursor solution = 20 mg: 20 mL: 126 μL: 10 μL: 21 μL.

10. Use of the Al-doped SrTiO3 / TiO2 heterojunction photocatalyst loaded with a co-catalyst as claimed in claim 1 in catalytic overall water splitting under visible light irradiation.

Images