A method for preparing porous hollow single crystal strontium titanate

Abstract

The invention relates to the preparation field of porous hollow single crystal strontium titanate, and specifically to a method for preparing porous hollow single crystal strontium titanate by using carbon spheres as templates and hydrothermal reaction. The method utilizes the rich functional groups on the surface of the carbon sphere template to adsorb a large number of precursor ions, hydrothermally grows single crystal strontium titanate with specific crystal planes exposed on the surface of the carbon sphere template, and obtains a porous hollow single crystal strontium titanate material after removing the template by heat treatment. The single crystal characteristics of the material are utilized to promote the transport of photogenerated charges, the porous structure increases the reaction active sites, and the cavity structure realizes the spatial deposition of dual promoters to promote the separation of photogenerated charges, thereby solving the problem of low photocatalytic efficiency caused by the easy recombination of photogenerated charges in photocatalytic reactions. Currently, it has been reported that most porous hollow samples are spherical structures composed of polycrystalline particles. In contrast, the porous hollow single crystal strontium titanate sample prepared by the hydrothermal method of the present invention has specific crystal planes exposed and has single crystal and porous characteristics at the same time, which is conducive to the photocatalytic reaction and improves the efficiency of photocatalytic water splitting.

Description

Technical Field

[0001] The invention relates to the field of preparation of porous hollow single crystal strontium titanate, in particular to a method for preparing porous hollow single crystal strontium titanate by hydrothermal growth using a template method. Background Art

[0002] Strontium titanate (SrTiO3) is a typical perovskite-type composite oxide. Since it was first reported to have photocatalytic hydrogen production activity in water splitting, it has attracted widespread attention due to its high stability, non-toxicity and suitable band structure. For the porous hollow single crystal structure, its pores can provide more active sites and material exchange channels, the single crystal can reduce the transfer resistance of photogenerated charges, and the hollowness helps the rapid separation of photogenerated charges. Therefore, in theory, this structure can effectively promote the photocatalytic reaction. At present, the research on hollow materials is mostly focused on binary systems, and its shell wall is mostly a polycrystalline structure composed of particles, which is not conducive to the transmission of photogenerated charges and the efficient photocatalytic water splitting reaction. Therefore, the preparation of porous hollow single crystal strontium titanate materials is of great guiding significance for obtaining an efficient photocatalytic water splitting system. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing porous hollow single-crystalline strontium titanate, combining a carbon sphere template with the preparation process of strontium titanate, ingeniously utilizing the rich functional groups on the surface of the carbon sphere, preferentially adsorbing a titanium source on its surface, and then obtaining a sample of strontium titanate coated on the surface of the carbon sphere through a hydrothermal reaction, and finally removing the template through heat treatment to obtain a porous hollow single-crystalline strontium titanate material, and further exploring its photocatalytic complete water decomposition activity.

[0004] The technical solution of the present invention is:

[0005] A method for preparing porous hollow single crystal strontium titanate, utilizing the strong adsorption capacity of abundant functional groups on the surface of carbon spheres and the method of hydrothermal growth of strontium titanate, the carbon spheres and strontium titanate growth solution are evenly mixed and put into the inner tank of a reaction kettle, after the reaction is completed, the reaction sample is taken out, centrifugally washed with deionized water and dried in an oven, and finally the carbon sphere template is removed by high-temperature calcination in a muffle furnace, thereby obtaining a porous hollow strontium titanate sample.

[0006] The titanium source precursor is a solution of commercial TiCl4, TiF4 or TiOSO4.

[0007] The material of the reaction kettle is one of stainless steel, aluminum alloy, copper and tantalum, and the inner liner of the reaction kettle is one of polytetrafluoroethylene and high-density polyethylene.

[0008] The strontium source is selected from commercial Sr(OH)2 or SrCl2·6H2O, and the molar concentration thereof is 0.02-0.04 mol / L.

[0009] The molar concentration of the lithium hydroxide solution is 2-5 mol / L; the mass of methanol and 1,2-propylene glycol is 1-5 g.

[0010] When the product is placed in an oven for heating treatment, the heating temperature is 150-250° C. and the heating time is 10 h to 48 h.

[0011] When the deionized water is used for washing and then drying, the drying temperature is 60-100°C.

[0012] The hydrothermal reaction time for preparing the carbon sphere template is 5-10 hours, the concentration of glucose is 0.4-0.6 mol / L, and the size is 200-500 nm.

[0013] When removing the carbon ball template, a muffle furnace high-temperature calcination method is adopted, a corundum crucible is used for calcination, the sample amount calcined is 50-150 mg, the temperature is 500-1000° C., and the heating rate is 5-10° C. / min.

[0014] The method for preparing porous hollow single crystal strontium titanate is to prepare strontium titanate with different morphologies coated with carbon spheres by adding a morphology control agent, and then remove the carbon sphere template by high-temperature calcination to obtain a porous hollow single crystal strontium titanate photocatalytic material.

[0015] The advantages and beneficial effects of the present invention are:

[0016] The present invention provides a method for preparing porous hollow single crystal strontium titanate. In the preparation process, the template method is combined with hydrothermal growth, and the prepared carbon ball template is introduced into the preparation process of single crystal strontium titanate, so as to obtain a sample of strontium titanate coated on the surface of the carbon ball, and finally the template is removed by heat treatment to obtain a porous hollow single crystal strontium titanate material, thereby achieving photocatalytic water splitting performance. In addition, by controlling the amount of carbon balls added, the hydrothermal time and different morphology regulators, the shell wall thickness and morphology of the porous hollow single crystal strontium titanate can be effectively controlled, thereby regulating its photocatalytic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : XRD spectrum of porous hollow single crystal strontium titanate in Example 1 of the present invention, wherein: the X-axis is the diffraction angle 2θ (degrees), and the Y-axis is the intensity (au).

[0018] Figure 2 :Scanning electron microscope image of porous hollow single crystal strontium titanate in Example 1 of the present invention.

[0019] Figure 3 :Scanning electron microscope image of porous hollow single crystal strontium titanate in Example 2 of the present invention.

[0020] Figure 4: Scanning electron microscope image of porous hollow single crystal strontium titanate in Example 3 of the present invention.

[0021] Figure 5 : Transmission electron microscope image of porous hollow single crystal strontium titanate in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] In the specific implementation process, the preparation method of porous hollow single crystal strontium titanate first uses a hydrothermal method to prepare a carbon ball template, and introduces the carbon ball template during the growth process of single crystal strontium titanate. Since the rich functional groups on the surface of the carbon ball can adsorb the titanium source on its surface, the hydrothermal method is then used to obtain a sample of strontium titanate coated on the surface of the carbon ball. Finally, high temperature treatment is used to obtain porous hollow single crystal strontium titanate. Since the porous structure can increase the reactive active sites, the cavity structure can realize the spatial deposition of dual co-catalysts and thus promote the separation of photogenerated charges. Therefore, the present invention solves the problem of low photocatalytic efficiency caused by the easy recombination of photogenerated charges in photocatalytic reactions, and has important value in the future field of photocatalysis.

[0023] The present invention will be described in more detail below in conjunction with the embodiments and drawings.

[0024] Example 1

[0025] In this embodiment, the porous hollow single crystal strontium titanate is prepared by using methanol as a morphology control agent.

[0026] Preparation process of carbon sphere template: first prepare a glucose solution with a concentration of 0.5 mol / L, take 44 ml and put it into a 50 ml polytetrafluoroethylene reactor, the hydrothermal time is 6 hours, and the temperature is 180°C.

[0027] Preparation of porous hollow single crystal strontium titanate: Add 0.26 ml of TiCl4 dropwise into 25 ml of deionized water containing 2 g of methanol, add 90 mg of carbon spheres after mixing evenly, mix them evenly by ultrasonic mixing, then add 30 ml of deionized water containing 4 g of LiOH·H2O, stir for 30 min, add 10 ml of a solution containing 0.7 g of SrCl2·6H2O, finally stir for 30 min, transfer the solution to a 100 ml polytetrafluoroethylene reactor, the hydrothermal reaction temperature is 180 ° C, the reaction time is 24 h, the sample is collected by centrifugation with deionized water, and a hexahedral solid strontium titanate sample coated with carbon spheres is obtained. Take 100 mg of the above collected sample, heat it from room temperature to 600 ° C in a muffle furnace at a heating rate of 10oC / min, and maintain it for 2 h. The XRD, scanning and transmission of the prepared sample are as follows: Figure 1-3 shown.

[0028] Example 2

[0029] On the basis of Example 1, porous hollow single crystal strontium titanate with different morphologies was obtained by adjusting the amount of carbon sphere template.

[0030] Preparation process of carbon sphere template: first prepare a glucose solution with a concentration of 0.5 mol / L, take 44 ml and put it into a 50 ml polytetrafluoroethylene reactor, the hydrothermal time is 6 hours, and the temperature is 180°C.

[0031] Preparation of porous hollow single crystal strontium titanate: Add 0.26 ml of TiCl4 dropwise into 25 ml of deionized water containing 2 g of methanol. After mixing evenly, add 200 mg of carbon spheres, mix them ultrasonically, add 30 ml of deionized water containing 4 g of LiOH·H2O, stir for 30 minutes, add 10 ml of a solution containing 0.7 g of SrCl2·6H2O, and finally stir for 30 minutes before transferring the solution to a 100 ml polytetrafluoroethylene reactor. The hydrothermal reaction temperature is 180°C, the reaction time is 24 hours, and the sample is collected by centrifugation with deionized water to obtain a hexahedral solid strontium titanate sample coated with the surface of the carbon spheres. Then take 100 mg of the above collected sample, heat it from room temperature to 600°C in a muffle furnace at a heating rate of 10°C / min, and maintain it for 2 hours. Its morphology is as follows Figure 4 shown.

[0032] Example 3

[0033] In this embodiment, porous hollow strontium titanate is prepared by taking 1,2-propylene glycol as an example. The preparation process is similar to that of Examples 1 and 2.

[0034] Preparation process of carbon sphere template: first prepare a glucose solution with a concentration of 0.5 mol / L, take 44 ml and put it into a 50 ml polytetrafluoroethylene reactor, the hydrothermal time is 6 hours, and the temperature is 180°C.

[0035] Preparation of porous hollow samples: Add 0.26ml TiCl4 dropwise into 25ml deionized water containing 1g 1,2-propylene glycol. After mixing evenly, add 200mg of carbon spheres, mix them ultrasonically, add 30ml deionized water containing 4g LiOH·H2O, stir for 30min, add 10ml solution containing 0.7g SrCl2·6H2O, and finally stir for 30min before transferring the solution to a 100ml polytetrafluoroethylene reactor. The hydrothermal reaction temperature is 180°C, the reaction time is 12h, and the sample is collected by centrifugation with deionized water to obtain octahedral solid strontium titanate coated on the surface of carbon spheres. Then take 100mg of the collected sample, heat it from room temperature to 600°C in a muffle furnace at a heating rate of 10°C / min, and maintain it for 2h. A strontium titanate sample with a porous hollow structure can be obtained ( Figure 5 ).

[0036] The results of the examples show that the present invention prepares strontium titanate containing a carbon ball template by introducing a template in a hydrothermal process, removes the template by high-temperature calcination, and finally obtains a porous hollow single crystal strontium titanate. The preparation of the porous hollow structure can promote the transport of photogenerated charges, and the porous structure can increase the reaction active sites and the cavity structure to achieve the spatial deposition of dual promoters, solving the problems of easy recombination of electron-hole pairs, low reaction active sites and low photocatalytic efficiency in photocatalysis. The material preparation method obtained by the present invention is simple, easy to operate, and pollution-free, and the material having the structure has broad application prospects in the field of photocatalysis.

Claims

1. A method for preparing porous hollow single crystal strontium titanate, characterized in that: Titanium tetrachloride and strontium chloride are selected as precursors, carbon spheres are used as templates, and methanol or 1,2-propylene glycol is used as morphology control agents. The rich functional groups on the surface of the carbon sphere template can adsorb a large number of precursor ions. The single crystal perovskite oxide with specific crystal plane exposure is coated on the surface of the carbon sphere template through hydrothermal growth. Finally, the template is removed by heat treatment to obtain porous hollow single crystal strontium titanate. The specific process is as follows: (1) using a 0.4-0.6 mol / L glucose solution, using a solvothermal method, and hydrothermally reacting for 5-10 h to obtain a uniformly dispersed carbon sphere template with a size of 200-500 nm; (2) uniformly dispersing a titanium tetrachloride precursor solution and different amounts of carbon sphere templates by ultrasonic dispersion, adding a certain amount of lithium hydroxide solution to regulate the pH value of the solution and the reaction process, adding a certain amount of methanol or 1,2-propylene glycol as a morphology regulator, and adding strontium chloride, finally stirring the above solution and placing it in a reactor, performing high-temperature hydrothermal treatment, taking out the sample after the reaction is completed, washing it with deionized water and drying it, and removing the carbon sphere template by high-temperature calcination in a muffle furnace, thereby obtaining a porous hollow single crystal strontium titanate; Wherein, the volume of titanium tetrachloride is 0.1-1 ml, the molar concentration of strontium chloride is 0.1-0.5 mol / L; the mass of the methanol or 1,2-propylene glycol is 1-5 g; the molar concentration of the lithium hydroxide solution is 2-5 mol / L; The amount of carbon sphere template added is 10mg-500mg.

2. The method for preparing the porous hollow single crystal strontium titanate according to claim 1, characterized in that: The material of the reaction kettle is stainless steel, and the inner liner of the reaction kettle is polytetrafluoroethylene or high-density polyethylene.

3. The method for preparing the porous hollow single crystal strontium titanate according to claim 1, characterized in that: After the centrifugal washing with deionized water, the required temperature for drying is 60-100°C.

4. The method for preparing the porous hollow single crystal strontium titanate according to claim 1, characterized in that When removing the template, a muffle furnace is used for high-temperature calcination, the calcination temperature is 500-1000° C., and a corundum crucible is used for calcination.

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