RHODIUM-DOPED STRONTIUM TITANATE INVERSE OPAL MATERIAL, PREPARATION METHOD THEREOF, AND APPLICATION THEREOF IN PIEZOELECTRIC SYNERGISTIC PHOTOCATALYTIC REMOVAL OF ORGANIC POLLUTANTS

Abstract

Monodisperse polystyrene microspheres are self-assembled on a conductive surface of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template; the three-dimensional ordered photonic crystal opal template is immersed in a solution containing rhodium source, titanium source and strontium source, and is then calcined to prepare a rhodium doped strontium titanate inverse opal material; and the rhodium doped strontium titanate inverse opal material is added to water containing pollutants, and is then subjected to illumination and/or ultrasonic treatment to complete the removal of the pollutants in the water. The three-dimensional ordered macroporous rhodium doped strontium titanate inverse opal material may be applied in the field of photocatalysis. Under the action of external force, a built-in electric field formed by the spontaneous polarization of the material may effectively separate the photo-induced carriers, which may thus enhance the photocatalytic performance and improve the photocatalytic efficiency.

Claims

1. A strontium titanate inverse opal material, characterized in that the preparation method of the strontium titanate inverse opal material comprising the following steps: 1) self-assembling monodisperse polystyrene microspheres on the conductive side of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template; 2) immersing the three-dimensional ordered photonic crystal opal template in the solution containing titanium source and strontium source, and then preparing the strontium titanate inverse opal material by calcination.

2. The strontium titanate inverse opal material according to claim 1, wherein in step 1), the particle size of monodisperse polystyrene microspheres is 250-300 nm; in step 2), the calcination temperature is 400-650° C. and drying before calcination.

3. The strontium titanate inverse opal material according to claim 1, wherein said strontium source is strontium nitrate or strontium acetate; said titanium source is tetra-n-butyl titanate or tetraisopropyl titanate.

4. The strontium titanate inverse opal material according to claim 1, wherein in the solution containing titanium source and strontium source, the solvent is water; the solution containing titanium source and strontium source also contains acetic acid and citric acid.

5. A rhodium doped strontium titanate inverse opal material, characterized in that the preparation method of the rhodium doped strontium titanate inverse opal material comprising the following steps: 1) self-assembling monodisperse polystyrene microspheres on the conductive side of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template; 2) immersing the three-dimensional ordered photonic crystal opal template in the solution containing rhodium source, titanium source and strontium source, and then preparing the rhodium doped strontium titanate inverse opal material by calcination.

6. The rhodium doped strontium titanate inverse opal material according to claim 5, wherein in step 1), the particle size of monodisperse polystyrene microspheres is 250-300 nm; in step 2), the calcination temperature is 400-650° C. and drying before calcination.

7. The rhodium doped strontium titanate inverse opal material according to claim 5, wherein the rhodium source is rhodium chloride or rhodium nitrate; the strontium source is strontium nitrate or strontium acetate; the titanium source is tetra-n-butyl titanate or tetraisopropyl titanate; in the rhodium doped strontium titanate inverse opal, the doping amount of rhodium is 0-F 1% of the molar amount of strontium.

8. The rhodium doped strontium titanate inverse opal material according to claim 5, wherein in the solution containing rhodium source, titanium source and strontium source, the solvent is water; the solution containing rhodium source, titanium source and strontium source also contains acetic acid and citric acid.

9. A method for removing organic pollutants, comprising: providing the strontium titanate inverse opal material according to claim 1; and applying the strontium titanate inverse opal material to remove the organic pollutants.

10. A preparation method of inverse opal material, which is characterized in that comprising the following steps: 1) self-assembling monodisperse polystyrene microspheres on the conductive side of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template; 2) immersing the three-dimensional ordered photonic crystal opal template in the solution containing titanium source and strontium source, and then preparing the inverse opal material by calcination; or immersing the three-dimensional ordered photonic crystal opal template in the solution containing rhodium source, titanium source and strontium source, and then preparing the inverse opal material by calcination.

11. A method for removing organic pollutants, comprising: providing the rhodium doped strontium titanate inverse opal material according to claim 5; and applying the rhodium doped strontium titanate inverse opal material to remove the organic pollutants.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a scanning electron microscope diagram of strontium titanate inverse opal (SrTiO.sub.3 IO) in embodiment 3.

[0026] FIG. 2 is a scanning electron microscope diagram of rhodium doped strontium titanate inverse opal (Rh—SrTiO.sub.3 IO) in embodiment 4.

[0027] FIG. 3 is a transmission electron microscope diagram of rhodium doped strontium titanate inverse opal (Rh-—SrTiO.sub.3 IO) in embodiment 4.

[0028] FIG. 4 is a UV-vis absorption spectrum of rhodium doped strontium titanate inverse opal (Rh—SrTiO.sub.3 IO) in embodiment 4.

[0029] FIG. 5 is an effect diagram of degradation of bisphenol A by strontium titanate inverse opal (SrTiO.sub.3 IO) and rhodium doped strontium titanate inverse opal (Rh—SrTiO.sub.3 IO) in embodiment 6.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The invention modifies strontium titanate nano materials by doping transition metal elements and micro morphology regulation, rhodium doped strontium titanate inverse opal (Rh SrTiO.sub.3 IO) is prepared by template calcination to adjust the band gap of strontium titanate and make it respond to visible light; at the same time, it can use the unique structural characteristics of three-dimensional ordered macropores of inverse opal to improve light absorption, expose more active sites and enhance photocatalytic performance. In addition, the three-dimensional ordered macropore rhodium doped strontium titanate inverse opal material of the invention is a good piezoelectric material. In the photocatalytic process, the invention applies external mechanical force to it to generate a built-in polarization electric field to further separate photogenerated electron holes, so as to further improve the photocatalytic performance and realize the efficient removal of organic pollutants in water body.

[0031] In the present invention, the preparation method of the strontium titanate inverse opal material is as follows:

[0032] 1) self-assembling monodisperse polystyrene microspheres on the conductive side of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template;

[0033] 2) immersing the three-dimensional ordered photonic crystal opal template in the solution containing titanium source and strontium source, and then preparing the strontium titanate inverse opal material by calcination.

[0034] The preparation method of the rhodium doped strontium titanate inverse opal material is as follows:

[0035] 1) self-assembling monodisperse polystyrene microspheres on the conductive side of FTO glass by vertical deposition method to prepare three-dimensional ordered photonic crystal opal template;

[0036] 2) immersing the three-dimensional ordered photonic crystal opal template in the solution containing rhodium source, titanium source and strontium source, and then preparing the rhodium doped strontium titanate inverse opal material by calcination.

[0037] Preferably, the solution containing rhodium source, titanium source and strontium source is composed of acetic acid, citric acid, water, rhodium source, titanium source and strontium source. The solution containing titanium source and strontium source is composed of acetic acid, citric acid, water, titanium source and strontium source.

[0038] The invention is further described below in combination with embodiments.

Embodiment 1

[0039] Preparation of photonic crystal opal template: prepared by vertical deposition method. Firstly, FTO glass is sonicated with acetone, ethanol and deionized water successively for 20 min; dispersing the freeze-dried 280 nm polystyrene microsphere powder into deionized water to obtain 0.125 wt % monodisperse polystyrene microsphere emulsion. Then, 1 ml monodisperse polystyrene microspheres with a concentration of 0.125 wt % is collected in a weighing bottle, and the ultrasonic clean FTO glass is vertically placed into the weighing bottle with the conductive side upside, and leaning the weighing bottle properly so that the liquid surface just comes into contact with the edge of the FTO glass substrate (the monodisperse polystyrene microsphere emulsion is laid on the conductive side of the FTO glass), and then is put into the electrothermal incubator at 45° C. for two days (48 hours) to produce a three-dimensional ordered photonic crystal template, for usage in embodiment 2 to embodiment 5.

Embodiment 2

[0040] Preparation of strontium titanate inverse opal: firstly, 0.01 mol tetrabutyl titanate is mixed with 10 ml acetic acid, and then 10 ml deionized water is added to the solution under continuous stirring. Then, 10 ml of 1M Sr(NO.sub.3).sub.2 is added dropwise to the above solution. Finally, add 10 ml of 2M citric acid solution. The obtained solution is stirred at room temperature for another 30 minutes to obtain a clear solution, which is recorded as solution A. The prepared polystyrene opal template is soaked in solution A, then dried in an oven at 60° C., and then the dried precursor template is calcined in air in a tubular furnace for 2 hours at 650° C., The temperature rise rate is 2° C./min (room temperature rises to 650° C.), and the strontium titanate inverse opal thin film photocatalyst (SrTiO.sub.3 IO) is obtained by natural cooling. It can be seen from FIG. 1 that the strontium titanate inverse opal has a three-dimensional ordered macropore structure, uniform pore size and regular arrangement.

Embodiment 3

[0041] Preparation of 0.3 mol % rhodium doped strontium titanate inverse opal: firstly, tetrabutyl titanate is mixed with 10 ml acetic acid, and then 10 ml deionized water is added to the solution under continuous stirring. After that, drop 10 ml of a mixed solution of 1M strontium nitrate and rhodium trichloride trihydrate to the above solution, (the sum of the moles of tetrabutyl titanate and rhodium trichloride trihydrate is the moles of strontium nitrate), and the moles of rhodium trichloride trihydrate is 0.3% of the moles of strontium nitrate. Finally, add 10 ml of 2 M citric acid solution. Stir the resulting solution at room temperature for another 30 minutes to obtain a clear solution, which is recorded as solution A. Immerse the prepared polystyrene opal template in solution A, Then it is dried in an oven at 60° C., and the dried precursor template is calcined in the air in a tubular furnace for 2 hours. The calcination temperature is 650° C., and the heating rate is 2° C./min (room temperature rose to 650° C.). Rhodium doped strontium titanate inverse opal thin film photocatalyst (0.3 mol % Rh—Sr TiO.sub.3 IO) is obtained by natural cooling.

Embodiment 4

[0042] Preparation of 0.5 mol % rhodium doped strontium titanate inverse opal: firstly, tetrabutyl titanate is mixed with 10 ml acetic acid, and then 10 ml deionized water is added to the solution under continuous stirring. After that, drop 10 ml of a mixed solution of 1 M strontium nitrate and rhodium trichloride trihydrate to the above solution, (the sum of the moles of tetrabutyl titanate and rhodium trichloride trihydrate is the moles of strontium nitrate), and the moles of rhodium trichloride trihydrate is 0.5% of the moles of strontium nitrate. Finally, add 10 ml of 2 m citric acid solution. Stir the resulting solution at room temperature for another 30 minutes to obtain a clear solution, which is recorded as solution A. Immerse the prepared polystyrene opal template in solution A, then it is dried in an oven at 60° C., and the dried precursor template is calcined in the air in a tubular furnace for 2 hours at 650° C., the temperature rise rate is 2° C./min (room temperature rises to 650° C.), and the rhodium doped strontium titanate inverse opal thin film photocatalyst (0.5 mol % rh-srtio3 IO) is obtained by natural cooling. It can be seen from FIG. 2 that the 0.5 mol % Rhodium doped strontium titanate inverse opal still maintains a stable skeleton, uniform pores and regular structure.

Embodiment 5

[0043] Preparation of 1.0 mol % rhodium doped strontium titanate inverse opal: firstly, tetrabutyl titanate is mixed with 10 ml acetic acid, and then 10 ml deionized water is added to the solution under continuous stirring. After that, drop 10 ml of a mixed solution of 1 M strontium nitrate and rhodium trichloride trihydrate to the above solution, (the sum of the moles of tetrabutyl titanate and rhodium trichloride trihydrate is the moles of strontium nitrate), and the moles of rhodium trichloride trihydrate is 1.0% of the moles of strontium nitrate. Finally, add 10 ml of 2 M citric acid solution. Stir the resulting solution at room temperature for another 30 minutes to obtain a clear solution, which is recorded as solution A. Immersing the prepared polystyrene opal template in solution A, then it is dried in an oven at 60° C., and the dried precursor template is calcined in air in a tubular furnace for 2 h. The calcination temperature is 650° C., and the heating rate is 2° C./min (room temperature rose to 650° C.), and the rhodium doped strontium titanate inverse opal thin film photocatalyst (1.0 mol % Rh-—SrTiO.sub.3 IO) is obtained by natural cooling.

[0044] Comparison example:

[0045] Preparation of rhodium doped strontium titanate nanoparticles: synthesized by hydrothermal method, tetrabutyl titanate is dissolved in 20 ml ethylene glycol to form a clear solution, then 20 ml of mixed aqueous solution of 0.5 M strontium nitrate and rhodium trichloride trihydrate and 10 ml of 5 M sodium hydroxide solution are added dropwise under magnetic stirring (the molar ratio of strontium nitrate, tetrabutyl titanate and rhodium trichloride trihydrate is 1:0.995:0.005). After stirring for 30 minutes, the mixture is added to a 100 ml high-pressure reactor and reacted at 200° C. for 24 hours. After the reaction, the product is washed with deionized water and absolute ethanol for several times until the pH reached 7. Then, the product is dried at 70° C. overnight to obtain rhodium doped strontium titanate nanoparticles particles (Rh—SrTiO.sub.3 NPs).

Embodiment 6

[0046] Piezoelectric photocatalytic degradation of bisphenol A by 0.5 mol % Rh—S rTiO.sub.3 IO : weigh 6 mg of the photocatalyst 0.5 mol % Rh—SrTiO.sub.3 IO obtained in embodiment 4 and place it in 10 ml bisphenol A aqueous solution with a concentration of 10 mg/L. Stir in dark for one hour to reach adsorption desorption equilibrium. After balance, place the test tube containing bisphenol A aqueous solution obliquely in the ultrasonic cleaner, irradiate the catalyst with a 300 W xenon lamp, turn on the ultrasonic cleaner, adjust the power to 150 W, sample 1 mL every 15 minutes, and record the retention time by HPLC. Record the peak area of the liquid phase corresponding to the retention time to obtain the concentration of bisphenol A in the corresponding water sample. FIG. 5 is a graph of the relationship between the residue rate of bisphenol A and time. As can be seen from the figure, after adding 0.5 mol % Rh—Sr TiO.sub.3 IO photocatalyst and applying light and ultrasound at the same time, after 30 min of light, Bisphenol A in the aqueous solution is completely removed (residual 0%). The catalyst materials of other embodiments are tested by the same method. After 30 min of illumination, the residual rates of bisphenol A in the aqueous solution are 15% in embodiment 2, 7% in embodiment 3, 9% in embodiment 5 and 43% in the control ratio.

[0047] Replacing the rhodium doping in embodiment 4 with ruthenium doping in the same molar amount. The 0.5 mol % Ru—SrTiO.sub.3 IO obtained by the same preparation method is subjected to the same piezoelectric synergistic photocatalytic degradation experiment of bisphenol A. after 30 min of illumination, 13% of bisphenol A remained in the aqueous solution.

[0048] Changing the particle size of the polystyrene microspheres in embodiment 1 to 420 nm. The other methods are the same to obtain 0.5 mo l% Rh—SrTiO.sub.3 IO. After the same piezoelectric synergistic photocatalytic degradation experiment of bisphenol A, 6% of bisphenol A remained in the aqueous solution after 30 min of illumination. It shows that the pore size of the template has a certain influence on the slow photon effect (light absorption and utilization) of inverse opal, and then affects the photocatalytic performance of the material.

[0049] Replacing the ultrasound in embodiment 6 by magnetic stirring (200 rpm), and the other methods are the same. 0.5 mol % Rh—SrTiO.sub.3 IO is subjected to the same photocatalytic degradation experiment of bisphenol A. After 30 min of illumination, 52% of bisphenol A remained in the aqueous solution, indicating that the mechanical stress caused by ultrasonic vibration plays a great role in the photocatalytic degradation experiment of bisphenol A.

[0050] The invention discloses a preparation method of rhodium doped strontium titanate inverse opal material and its piezoelectric synergistic photocatalytic removal of organic pollutants in water (bisphenol A) application. First, polystyrene is prepared by soap-free emulsion polymerization, and polystyrene opal is obtained by vertical deposition method. A new inorganic nano material of rhodium doped strontium titanate inverse opal is obtained by one-step calcination. In the rhodium doped strontium titanate inverse opal prepared by this method, the transition metal Rh.sup.3+ containing d orbital electrons can be doped into the lattice of strontium titanate. It can effectively reduce the band gap of strontium titanate, make it have visible light response, and solve the problem that strontium titanate only responds to ultraviolet light, which limits its application. At the same time, the strontium titanate inverse opal prepared by the invention is a three-dimensional periodic pore structure and has a slow photon effect, so that it shows better photocatalytic performance compared with ordinary porous materials. In addition, strontium titanate is also a good piezoelectric material. In the process of photocatalysis, external mechanical pressure can be applied to it to generate a built-in polarization electric field, so that the photogenerated electron holes can be further separated. Therefore, the low band gap when doped and its own piezoelectric properties enable strontium titanate to make full use of the slow photon effect and vibration energy to catalyze the degradation of organic pollutants without coupling it with other materials or using external bias, so as to reduce the use cost.