Inverse opal material for visible-light driven photocatalytic degradation of organic pollutants, and preparation method thereof

Abstract

A preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants includes 1) using titanium dioxide precursor as raw material, preparing nitrogen-doped titanium dioxide inverse opal by one-step process in the presence of nitrogen source, and 2) in the presence of reducing agent, using the nitrogen-doped titanium dioxide inverse opal, selenium precursor, and cadmium precursor as raw materials to prepare the cadmium selenide sensitized nitrogen-doped titanium dioxide inverse opal.

Claims

1. A preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants, comprising the following steps: 1) using a titanium dioxide precursor as raw material, preparing a nitrogen-doped titanium dioxide inverse opal by a one-step process in the presence of a nitrogen source; and 2) in the presence of a reducing agent, using the nitrogen-doped titanium dioxide inverse opal, a selenium precursor, and a cadmium precursor as raw materials to prepare a cadmium selenide sensitized nitrogen-doped titanium dioxide inverse opal, wherein the step 1) comprises mixing the titanium dioxide precursor and nitrogen source in ethanol to form a mixed solution of the titanium dioxide precursor and nitrogen source, soaking polymer microsphere templates in the mixed solution of the titanium dioxide precursor and nitrogen source, and then drying and calcining to obtain the nitrogen-doped titanium dioxide inverse opal; and the step 2) comprises mixing the reducing agent, the nitrogen-doped titanium dioxide inverse opal, the selenium precursor, the cadmium precursor and a solvent, heating, cooling, washing and drying to obtain the cadmium selenide sensitized nitrogen-doped titanium dioxide inverse opal.

2. The preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants according to claim 1, wherein said nitrogen source is urea, said titanium dioxide precursor is titanium tetrachloride, tetra-n-butyl titanate, or titanium isopropoxide, said reducing agent is sodium borohydride, sodium bisulfite, or sodium sulfite, said selenium precursor is selenium, and said cadmium precursor is cadmium chloride.

3. The preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants according to claim 1, wherein the quantity of nitrogen source is 0.2-0.6 times of that of titanium dioxide precursor, and the quantity of selenium precursor, cadmium precursor and reducing agent are 0.1-0.3, 0.20.7 and 0.2-0.5 times of that of nitrogen-doped titanium dioxide inverse opal, respectively.

4. The preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants according to claim 1, wherein said polymer microsphere templates are polystyrene spheres with a particle size of 200-600 nm, said solvent in step 2) is water, ethylene glycol or ethanol.

5. The preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants according to claim 1, wherein in step 1), the drying temperature is 50-70 C., and the calcining temperature is 400-500 C., in step 2), the temperature of heating is 180-200 C., the time of heating is 8-10 hours, the drying temperature is 60-80 C.

6. The preparation method of inverse opal material for visible-light-driven photocatalytic degradation of organic pollutants according to claim 1, wherein said polymer microsphere templates are prepared by a vertical deposition method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. SEM images of NTiO.sub.2 IO in Embodiment 2.

(2) FIG. 2. SEM images of CdSe/NTiO.sub.2 IO in Embodiment 3.

(3) FIG. 3. N.sub.2 adsorption-desorption isotherms of CdSe/NTiO.sub.2 IO in Embodiment 3.

DETAILED DESCRIPTION OF THE INVENTION

(4) The invention is further explained according to the figures and the specific embodiments.

Embodiment 1: Synthesis of Nitrogen-Doped TiO.SUB.2 .Inverse Opal (NTiO.SUB.2 .IO)

(5) 0.25 g diethanolamine was dissolved in 15 g anhydrous ethanol, followed by continuous stirring for 20 min. Then, 0.5 g tetrabutyl titanate was added to the mixture, and the mixture was indexed as A solution. Subsequently, 0.29 g urea was added to 30 mL anhydrous ethanol, and the solution was denoted as B solution. Then, 1 mL A solution and 1 mL B solution were mixed homogeneously. The PS opals were immersed into the mixed solution and dried at 60 C. Finally, the PS templates were removed via calcination in air at 500 C. at a heating rate of 1 C. min.sup.1 for 2 h, and NTiO.sub.2 IO was obtained.

Embodiment 2: Synthesis of Nitrogen-Doped TiO.SUB.2 .Inverse Opal (NTiO.SUB.2 .IO)

(6) 0.125 g acetylacetone was dissolved in 17.5 g anhydrous ethanol, followed by continuous stirring for 10 min. Then, 0.5 g tetrabutyl titanate was added to the mixture, and the mixture was indexed as A solution. Subsequently, 0.29 g urea was added to 30 mL anhydrous ethanol, and the solution was denoted as B solution. Then, 1 mL A solution and 1 mL B solution were mixed homogeneously. The PS opals were immersed into the mixed solution and dried at 60 C. Finally, the PS templates were removed via calcination in air at 500 C. at a heating rate of 1 C. min.sup.1 for 2 h, and NTiO.sub.2 IO was obtained. As can be seen in FIG. 1, NTiO.sub.2 IO presents a face centered cubic arrangement with uniform pores.

Embodiment 3: Synthesis of Nitrogen-Doped and CdSe-Sensitized TiO.SUB.2 .Inverse Opal (CdSe/NTiO.SUB.2 .IO)

(7) 0.1830 g CdCl.sub.2, 0.0796 g Se and 0.2520 g Na.sub.2SO.sub.3 were added to 35 mL deionized water. After vigorously stirring at 3000 rpm, the suspension was transferred into a 50 mL Teflon-lined stainless-steel autoclave along with 20 mg NTiO.sub.2 IO. The autoclave was heated to 180 C. for 8 h. After naturally cooling to room temperature, the FTO glass coated with N-doped and CdSe-sensitized TiO.sub.2 inverse opals (CdSe/NTiO.sub.2 IO) was collected and washed with deionized water. As can be seen in FIG. 2, well-ordered inverse opals were retained after the hydrothermal process and a homogeneous coverage of CdSe can be observed without pore clogging. As can be seen in FIG. 3, the isotherms are identified as type III isotherms. The adsorption quantity is low in low specific pressure region, and the higher the relative pressure, the more adsorption quantity.

Embodiment 4: Synthesis of Nitrogen-Doped and CdSe-Sensitized TiO.SUB.2 .Inverse Opal (CdSe/NTiO.SUB.2 .IO)

(8) 0.1830 g CdCl.sub.2, 0.0796 g Se and 0.208 g NaHSO.sub.3 were added to 35 mL deionized water. After vigorously stirring, the suspension was transferred into a 50 mL Teflon-lined stainless-steel autoclave along with 20 mg NTiO.sub.2 IO. The autoclave was heated to 180 C. for 8 h. After naturally cooling to room temperature, the FTO glass coated with N-doped and CdSe-sensitized TiO.sub.2 inverse opals (CdSe/NTiO.sub.2 IO) was collected and washed with deionized water.

Embodiment 5: Photocatalytic Degradation of Rhodamine B by NTiO.SUB.2 .IO

(9) 50 mg NTiO.sub.2 IO obtained in Embodiment 2 was added into 50 mL of Rhodamine B aqueous solution at a concentration of 5 mg/L. The samples were treated in the dark for 30 min at room temperature to achieve adsorption-desorption equilibrium, and the removal efficiency was about 50%. Then the system was illuminated under a 300 W xenon lamp. At each 10 min interval, 3 mL of solution was extracted and analyzed by recording the variations in the absorption band maximum (554 nm) of RhB using a UV-Vis spectrometer. The concentration of Rhodamine B decreased by about 80% after 50 min of illumination, which was lower than the initial value obviously. After 80 min, the removal rate of Rhodamine B in aqueous solution was about 82%.

Embodiment 6: Photocatalytic Degradation of Rhodamine B by CdSe/NTiO.SUB.2 .IO

(10) 50 mg CdSe/NTiO.sub.2 IO obtained in Embodiment 3 was added into 50 mL of Rhodamine B aqueous solution at a concentration of 5 mg/L. The samples were treated in the dark for 30 min at room temperature to achieve adsorption-desorption equilibrium, and the removal efficiency was about 40%. Then the system was illuminated under a 300 W xenon lamp. At each 10 min interval, 3 mL of solution was extracted and analyzed by recording the variations in the absorption band maximum (554 nm) of RhB using a UV-Vis spectrometer. The concentration of Rhodamine B decreased by about 60% after 10 min of illumination, and decreased significantly after 60 min. After 80 min, the removal rate of Rhodamine B in aqueous solution was about 98%. In this experiment, the degradation efficiency of Rhodamine B in water was greatly improved by the synergistic effect of nitrogen doping and sensitization with cadmium selenide.

Embodiment 7: Photocatalytic Degradation of Rhodamine B by CdSe/NTiO.SUB.2 .IO

(11) 50 mg CdSe/NTiO.sub.2 IO obtained in Embodiment 3 was added into 50 mL of Rhodamine B aqueous solution at a concentration of 10 mg/L. The samples were treated in the dark for 30 min at room temperature to achieve adsorption-desorption equilibrium, and the removal efficiency was about 35%. Then the system was illuminated under a 300 W xenon lamp. At each 10 min interval, 3 mL of solution was extracted and analyzed by recording the variations in the absorption band maximum (554 nm) of RhB using a UV-Vis spectrometer. The concentration of Rhodamine B decreased by about 55% after 30 min of illumination, and decreased obviously after 120 min of illumination. When the light time was 150 min, the removal rate of Rhodamine B was 98.5%.

Embodiment 8: Cycling Photocatalytic Degradation of Rhodamine B by CdSe/NTiO.SUB.2 .IO

(12) The composite in Embodiment 6 was washed with water and 95% ethanol, dried and placed in 50 mL of Rhodamine B aqueous solution at a concentration of 5 mg/L. A 300 W Xenon lamp was used to simulate solar radiation for 80 min. At each 10 min interval, 3 mL of solution was extracted and analyzed by recording the variations in the absorption band maximum (554 nm) of RhB using a UV-Vis spectrometer. The degradation efficiency reaches 97%, 97% and 95% after the first, second and third cycle. This indicates that CdSe/NTiO.sub.2 IO shows good stability after each cycle.

(13) This invention adopted the doping of non-metallic element and sensitization of narrow band gap semiconductor to modify TiO.sub.2 nanoparticles. CdSe/NTiO.sub.2 IO was obtained by one-step synthesis of nitrogen-doped and CdSe-sensitized TiO.sub.2 inverse opal. The synergistic effects of nitrogen doping and CdSe sensitization can significantly improve the photocatalytic activity of TiO.sub.2 IO. The modified catalyst had the advantages of high catalytic activity and recyclability.