Multi-morphology strontium titanate photocatalyst with near-infrared light response as well as preparation method and hydrogen production application thereof

Abstract

The invention discloses a multi-morphology strontium titanate photocatalyst with near-infrared light response as well as a preparation method and hydrogen production application thereof, strontium titanate precursors with different morphologies are synthesized through a hydrothermal method, the strontium titanate precursors are subjected to heat treatment under a protective atmosphere, surface carbonization is realized, and the strontium titanate photocatalyst with near-infrared light response is obtained. The multi-morphology strontium titanate photocatalyst with near-infrared light response is obtained. By selecting different titanium sources and reaction conditions, strontium titanate with various morphologies such as mesoporous microspheres, cubic phases and dendrites can be directionally synthesized, and the requirements of different application scenes on catalyst structures are met. Defects and new energy levels are introduced on the surface of SrTiO3 through surface carbonization treatment, so that the light response range of the SrTiO3 is successfully expanded to a near-infrared region, near-infrared light can be efficiently utilized for water photolysis hydrogen production, and wide application prospects are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalytic materials, in particular to a multi-morphology strontium titanate photocatalyst capable of efficiently utilizing near-infrared light to perform water photolysis for hydrogen production, a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy, as a clean energy, its green preparation technology is a hot research today. Photocatalytic decomposition of water for hydrogen production can directly convert solar energy into chemical energy, and has broad prospects. Strontium titanate (SrTiO3) as a typical perovskite metal oxide, has stable chemical properties, suitable energy band position and high photo-generated carrier mobility, is one of the ideal photocatalytic materials.

[0003] However, the traditional strontium titanate can only respond to ultraviolet light accounting for 43% of solar energy due to its wide band gap characteristics (~3.2 eV), and cannot utilize visible light and near-infrared light accounting for 52% of solar energy, which seriously limits its photocatalytic efficiency. At present, although the methods such as element doping and construction of heterojunction can broaden the spectral response range to a certain extent, the preparation process is complex, and the utilization efficiency of near-infrared light is still very low.

[0004] At the same time, the morphology of the catalyst (such as specific surface area and pore structure) directly affects the number of active sites and mass transfer efficiency. The existing technology cannot accurately control the micro-morphology of the material while broadening the spectral response range, so it cannot simultaneously improve the three key processes of light absorption, charge separation and surface reaction. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a multi-morphology strontium titanate photocatalyst with near-infrared light response and the obtained strontium titanate photocatalyst. The catalyst preparation method is simple and the morphology is controllable. The obtained catalyst can efficiently utilize near-infrared light for water photolysis for hydrogen production, and has broad application prospects.

[0006] The present application can controllably prepare strontium titanate precursors with different morphologies by hydrothermal method, and then realize morphology optimization and spectral broadening through subsequent surface carbonization treatment, finally obtain a multi-morphology strontium titanate photocatalyst with near-infrared light response. The catalyst has the effect of catalyzing hydrogen production under the drive of near-infrared light. The specific technical scheme of the present application is as follows: A preparation method of a multi-morphology strontium titanate photocatalyst with near-infrared light response, the method comprising the following steps: (1) Synthesizing strontium titanate precursor by hydrothermal method; (2) Heat treating the strontium titanate precursor obtained in step (1) under a protective atmosphere to realize surface carbonization, and obtaining a multi-morphology strontium titanate photocatalyst with near-infrared light response.

[0007] Further, in step (1), the morphology of the strontium titanate precursor is mesoporous microspheres, cubic phase or dendritic.

[0008] Further, when the morphology of the strontium titanate precursor is mesoporous microspheres, the preparation process comprises: using tetrabutyl titanate as a titanium source, hydrolyzing in ammonia water, and using polyvinyl alcohol as a morphology control agent to perform hydrothermal reaction.

[0009] Preferably, when the morphology of the strontium titanate precursor is mesoporous microspheres, tetrabutyl titanate is used as a titanium source to generate titanium hydroxide precipitate by hydrolyzing in ammonia water, the precipitate is washed and mixed with strontium nitrate, KOH and a template agent polyvinyl alcohol, and hydrothermal reaction is performed at 200℃ for 12 hours to obtain the mesoporous microspherical strontium titanate precursor.

[0010] Further, when the morphology of the strontium titanate precursor is cubic phase or dendritic, the preparation process comprises: using titanium sulfate as a titanium source, controlling the final morphology by adjusting the concentration of KOH in the hydrothermal reaction system, and the morphology is cubic phase when the concentration of KOH in the hydrothermal system is 1M and is dendritic when the concentration of KOH is 0.1M.

[0011] Preferably, when the morphology of the strontium titanate precursor is cubic phase or dendritic, titanium sulfate is used as a titanium source, titanium hydroxide precipitate is generated after being dissolved in dilute nitric acid and then KOH is added, the precipitate is washed and mixed with equimolar strontium nitrate and KOH of different concentrations, and hydrothermal reaction is performed at 200℃ for 6 hours to obtain the strontium titanate precursor. The morphology is cubic phase when the concentration of KOH in the hydrothermal system is 1M and is dendritic when the concentration of KOH is 0.1M.

[0012] Further, in step (2), the precursor is subjected to heat treatment to form a layer of non-stoichiometric carbide on the surface thereof to complete the surface carbonization modification. The temperature of the heat treatment is 400-600℃, and the time is 1-4 hours.

[0013] Further, in step (2), the protective atmosphere is argon or nitrogen.

[0014] The polymorphous strontium titanate photocatalyst prepared according to the above method is also within the protection scope of the present application.

[0015] The present application also provides the application of the polymorphous strontium titanate photocatalyst in photocatalytic decomposition of water to produce hydrogen. The hydrogen production reaction is performed under full light, visible light and near-infrared light irradiation, the wavelength of the near-infrared light is 800-810 nm, and the hydrogen production reaction is performed at 35-45℃.

[0016] The present application has the following beneficial effects: 1. Controllable morphology and excellent structure: By selecting different titanium sources and reaction conditions, mesoporous microspheres, cubic phase, dendritic and other morphologies of strontium titanate can be synthesized in a targeted manner, meeting the needs of different application scenarios for catalyst structure.

[0017] 2. Broaden the spectrum and use near-infrared light: Surface carbonization treatment introduces defects and new energy levels on the surface of SrTiO3, successfully expanding its light response range to the near-infrared region.

[0018] 3. Hydrogen production performance is greatly improved: Experiments have shown that under full light and visible light beam irradiation, the peak area of surface carbonized SrTiO3 is much larger than that of SrTiO3 calcined in air, indicating that the hydrogen production performance of surface carbonized SrTiO3 under full light and visible light irradiation is significantly better than that of SrTiO3 calcined in air. Under 808 nm near-infrared laser irradiation, the carbonized SrTiO3 catalyst achieves efficient utilization of low-energy photons, while the SrTiO3 calcined in air has almost no hydrogen production performance at this wavelength; indicating that the hydrogen production performance of carbonized SrTiO3 at 808 nm is a breakthrough compared to traditional air calcined SrTiO3.

[0019] 4. Simple process and strong universality: The preparation and modification method has a simple process, good repeatability, and universal enhancement effect on different morphologies of SrTiO3 precursors. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Scanning electron microscope (SEM) images of three different morphologies of SrTiO3 precursors prepared in Examples 1-3, a. Example 1, b. Example 2, c. Example 3.

[0021] Figure 2 The figure is a comparison of the photocatalytic hydrogen production performance of Example 4 (surface carbonized SrTiO3) and Comparative Example 1 (air calcined SrTiO3) under 808 nm near-infrared laser, 40°C conditions. DETAILED DESCRIPTION

[0022] The application will be further described below in conjunction with examples.

[0023] Example 1: Preparation of mesoporous strontium titanate microsphere precursor (1) Dissolve 0.1 mol of tetrabutyl titanate in 100 ml of anhydrous ethanol and stir for 10 minutes.

[0024] (2) Add 0.93 ml of 0.15 M ammonia water and stir for 15 minutes to obtain a titanium hydroxide precipitate.

[0025] (3) Filter and wash the precipitate with deionized water for 6 times.

[0026] (4) The precipitate was re-dispersed in 160 ml of secondary water, and 0.3 mol of strontium nitrate (10.157 g), 0.5 mol of KOH (4.49 g) and 0.64 g of PVA were added successively under strong stirring; (5) The mixed solution was transferred into a 100 ml Teflon-lined autoclave, and reacted in a 200°C muffle furnace for 12 hours.

[0027] (6) After natural cooling, the product was collected by centrifugation, washed with 1% dilute nitric acid and secondary water, and dried at 80°C for 12 hours to obtain mesoporous strontium titanate microspheres.

[0028] Example 2: Preparation of cubic strontium titanate precursor (1) 0.01 mol of titanium sulfate was dissolved in 20 mL of dilute nitric acid, and stirred until completely dissolved to form a clear titanium ion solution.

[0029] (2) Under vigorous stirring, 1 M KOH solution was slowly added dropwise to the above solution until the pH value of the solution reached about 13. After continuing to stir for 30 minutes, the precipitate was separated by centrifugation, and the precipitate was washed with secondary distilled water for 6 times.

[0030] (3) An equimolar amount of strontium nitrate was added to the precipitate, and 60 ml of 1 M KOH solution was added.

[0031] (4) The mixed solution was subjected to hydrothermal reaction (200°C, 6 hours). After the reaction was completed, the product was centrifuged, and washed with dilute hydrochloric acid, secondary water and anhydrous ethanol for 3 times each, and dried at 70°C for 4 hours to obtain cubic strontium titanate.

[0032] Example 3: Preparation of dendritic strontium titanate precursor The preparation process is the same as that of Example 2, the only difference is that in step (3), the concentration of KOH solution added is 0.1 M, and finally dendritic strontium titanate is obtained.

[0033] Example 4: Preparation of surface carbonized strontium titanate photocatalyst (1) 1 g of strontium titanate precursor prepared in Example 1, 2 or 3 was placed in a tube furnace, respectively.

[0034] (2) Under an argon atmosphere, the temperature was raised to 500°C at a rate of 5°C / min, and kept for 2 hours.

[0035] (3) After natural cooling to room temperature, surface carbonized modified photocatalyst products with different morphologies were obtained.

[0036] Comparative Example 1: Preparation of air calcined strontium titanate (1) 1 g of strontium titanate precursor prepared in Example 1 was placed in a muffle furnace.

[0037] (2) In air, the temperature was increased to 500°C at a rate of 5°C / min, and maintained for 2 hours.

[0038] (3) Naturally cooled to room temperature to obtain a comparative sample.

[0039] Performance test (1) 50 mg of mesoporous microspherical photocatalyst prepared in Example 4 and 50 mg of catalyst prepared in Comparative Example 1 were respectively dispersed in 100 ml of deionized water.

[0040] (2) The reaction system was maintained at 40°C, and full light, visible light and 808 nm near-infrared laser were used as light sources to irradiate the aqueous solutions with different catalysts respectively.

[0041] (3) The amount of hydrogen produced in the reaction process was monitored online by gas chromatography, and the "peak area" was used as the response signal for hydrogen detection by gas chromatography. The larger the peak area, the more hydrogen was produced.

[0042] The experimental results are shown in Figure 2 From the figure, it can be seen that under the irradiation of full light, visible light and 808 nm near-infrared light, the hydrogen production peak area of the surface carbonized SrTiO3 is significantly better than that of the SrTiO3 calcined in air: Under full light irradiation, the peak area of the surface carbonized SrTiO3 far exceeds that of the sample calcined in air, and the hydrogen production performance advantage is extremely obvious; Under visible light irradiation, the surface carbonized SrTiO3 still shows a high hydrogen production peak area, while the hydrogen production peak area of the sample calcined in air is extremely low; Under 808 nm near-infrared light irradiation, the surface carbonized SrTiO3 has a clear hydrogen production peak area, and the SrTiO3 calcined in air has almost no response.

Claims

1. A method for preparing a multi-morphology strontium titanate photocatalyst, characterized by, The method comprises the following steps: (1) synthesizing strontium titanate precursor by hydrothermal method; (2) heat treating the strontium titanate precursor obtained in step (1) under a protective atmosphere to realize surface carbonization and obtain a multi-morphology strontium titanate photocatalyst with near-infrared light response.

2. The method of claim 1, wherein, In step (1), the morphology of the strontium titanate precursor is mesoporous microspheres, cubic phase or dendritic.

3. The method of claim 2, wherein, When the morphology of the strontium titanate precursor is mesoporous microspheres, the preparation process comprises: using tetrabutyl titanate as a titanium source, hydrolyzing in ammonia water, and using polyvinyl alcohol as a morphology control agent to perform hydrothermal reaction.

4. The method of claim 2, wherein, When the morphology of the strontium titanate precursor is cubic phase or dendritic, the preparation process comprises: using titanium sulfate as a titanium source, controlling the final morphology by adjusting the concentration of KOH in the hydrothermal reaction system, and the morphology is cubic phase when the concentration of KOH in the hydrothermal system is 1M, and the morphology is dendritic when the concentration of KOH in the hydrothermal system is 0.1M.

5. The method of claim 1, wherein, In step (2), the temperature of the heat treatment is 400-600℃, and the time is 1-4 hours; the protective atmosphere is argon or nitrogen.

6. A multi-morphology strontium titanate photocatalyst prepared by the method of any one of claims 1-5.

7. Application of the multi-morphology strontium titanate photocatalyst of claim 6 in photocatalytic decomposition of water to produce hydrogen.

8. Use according to claim 7, characterized in that, The hydrogen production reaction is performed under near-infrared light irradiation.

9. Use according to claim 8, characterized in that, The wavelength of the near-infrared light is 800-810 nm.

10. Use according to claim 7, characterized in that, The hydrogen production reaction is performed at 35-45℃.

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