A silicon-doped modified ZnSn(OH)6 photocatalyst, a preparation method and application thereof

Abstract

The application discloses a silicon-doped modified ZnSn(OH)6 photocatalyst and a preparation method and application thereof, and belongs to the technical field of photocatalytic materials. The preparation method comprises the following steps: (1) mixing Zn(Ac)2.2H2O solution, SnCl4.5H2O solution, NaOH solution, Na2SiO3.9H2O, methyl cellulose solution and distilled water to obtain a mixed solution; and (2) heating the mixed solution to synthesize the silicon-doped modified ZnSn(OH)6 photocatalyst. The product is prepared by using a hydrothermal synthesis method, the method can easily obtain a material with high crystallinity, the morphology and size of the material can be better controlled, the method is easy to operate, and the prepared silicon-doped modified photocatalyst has the characteristics of stable activity, fast carrier migration rate and high separation efficiency, and has excellent catalytic performance on methylbenzene volatile organic pollutants, and has a wide application prospect in the field of environmental pollution control.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic materials, and relates to a silicon-doped modified ZnSn(OH)6 photocatalyst, a preparation method and application thereof, in particular to a silicon-doped modified ZnSn(OH)6 photocatalyst with double anion and cation defect sites, a preparation method and application thereof. BACKGROUND

[0002] ZnSn(OH)6 is a metal hydroxide material with a perovskite crystal structure, has a wide band gap (~4eV), the metal atoms and oxygen atoms present an octahedral coordination structure, forming Sn(OH)6 and Zn(OH)6 two kinds of polyhedron, through sharing "O" angle to form a complete framework. The surface has a large number of hydroxyl groups as active sites, and under low humidity conditions, plays a crucial role in the generation of surface hydroxyl radicals. ZnSn(OH)6 itself has a certain number of oxygen vacancies, and a good electronic environment is more conducive to activating reactants. The photocatalytic performance of ZnSn(OH)6 can catalyze chemical reactions by absorbing visible light. This means that it can promote the degradation of some organic matter, water decomposition and other reactions under visible light irradiation. With the emphasis on environmental protection and renewable energy utilization, ZnSn(OH)6 as a photocatalyst, in the future, can be widely used in water treatment, air purification, photoelectrocatalysis and other fields, to provide effective solutions to environmental problems and energy crisis.

[0003] However, the current modification strategies for morphology control, element doping and heterojunction construction are widely used, but there are many problems, such as expensive modification reagents, no economic benefits; tin oxide is inevitably introduced into ZnSn(OH)6 to form a heterojunction, and general traditional type II and type Z heterojunctions are difficult to effectively separate high redox potential electron-hole pairs. The synthesis scheme of the modification is complex, the preparation process is long, and it is difficult to mass production. The photogenerated carrier separation efficiency and migration rate of the original ZnSn(OH)6 are far from satisfactory, and the existing modification strategies and preparation methods are difficult to realize the fast photogenerated carrier migration rate and stable activity of ZnSn(OH)6 photocatalyst in a short time. In addition, after modification, the degradation efficiency of volatile organic compounds such as toluene is not ideal, and toxic by-products are easy to produce and the preparation process is complex, thus hindering large-scale application in practice.

[0004] Therefore, how to develop a silicon-doped modified ZnSn(OH)6 photocatalyst with double anion and cation defect sites and its preparation method and application is a problem to be solved by those skilled in the art. SUMMARY

[0005] Therefore, the application provides a silicon-doped modified ZnSn(OH)6 photocatalyst, a preparation method and application thereof.

[0006] To achieve the above object, the application adopts the following technical scheme.

[0007] A preparation method of a silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0008] (1) Zn(Ac)2·2H2O solution, SnCl4·5H2O solution, NaOH solution, Na2SiO3·9H2O, methyl cellulose solution and distilled water are mixed to obtain a mixed solution;

[0009] (2) The mixed solution is heated to synthesize the above-mentioned silicon-doped modified ZnSn(OH)6 photocatalyst.

[0010] The reaction mechanism of the application is as follows: according to the "crystallization-dissolution-crystallization" mechanism, the reaction occurs under the hydrothermal synthesis mode: Zn 2+ +Sn 4+ +6OH - +Si 4+ → ZnSn(OH)6 (containing Si atoms). The hydrothermal synthesis strategy can make the reactants fully react, and can effectively incorporate silicon atoms into the ZnSn(OH)6 crystal lattice. The silicon-doped modified ZnSn(OH)6 photocatalyst prepared by this method only contains one phase, has double anion and cation defect sites and the ability to generate high-activity free radicals, has high photo-carrier separation efficiency, and has high photocatalytic degradation activity and stability for toluene. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst has a flocculent material covered cubic structure, and the size is 0.3-0.6 μm. In the hydrothermal reaction of the reaction kettle, water as a medium helps to promote the rapid dissolution of SnCl4·5H2O, Zn(Ac)2·2H2O, NaOH and Na2SiO3·9H2O in water, forming a mixed solution containing a large amount of Sn 4+ 、Zn 2+ 、OH - 、Si 4+ ions, and then subsequent Zn 2+ +Sn 4+ +6OH - +Si 4+Synthesizing ZnSn(OH)6(containing silicon element) ZnSn(OH)6(containing silicon element). The surfactant methyl cellulose can make the ions in the mixture collide effectively by wetting, dispersing and solubilizing, accelerate the reaction and help to provide the basic conditions for the efficient preparation of the silicon-doped modified ZnSn(OH)6 photocatalyst, so that the silicon-doped modified ZnSn(OH)6 catalyst with double anion and cation defect sites can be smoothly prepared in high yield and high activity. The addition of Na2SiO3·9H2O can cause slight deformation of the crystal lattice of the silicon-doped modified ZnSn(OH)6 catalyst, and the morphology of the catalyst changes from the original cube to a cube with a layer of flocculent substance on the surface.

[0011] The beneficial effects of the present application are: the present application adopts a hydrothermal synthesis method to prepare a silicon-doped modified ZnSn(OH)6 photocatalyst with a flocculent substance covered cube, which is easy to obtain a material with high crystallinity, can better control the morphology and size of the material, and is easy to operate. The silicon-doped modified ZnSn(OH)6 photocatalyst with double anion and cation defect sites prepared by this method has the characteristics of stable activity, fast carrier migration rate and high separation efficiency, and has excellent catalytic performance for toluene volatile organic pollutants, and has a wide application prospect in the field of environmental pollution control.

[0012] Further, the concentration of the above-mentioned Zn(Ac)2·2H2O solution is 0.5 mol / L, the concentration of the SnCl4·5H2O solution is 0.5 mol / L, the concentration of the NaOH solution is 3 mol / L, the concentration of the methyl cellulose solution is 2.8 g / L, and the volume ratio of the Zn(Ac)2·2H2O solution, the SnCl4·5H2O solution, the NaOH solution, the methyl cellulose solution and the distilled water is 4:4:4.6:10:100. 0.025-1 g of Na2SiO3·9H2O is added to every 10 mL of the methyl cellulose solution.

[0013] The beneficial effects of the above-mentioned further technical solution are: selecting a suitable parameter for the mass of the added Na2SiO3·9H2O can avoid the waste of drugs, and effectively ensure that the finally prepared silicon-doped modified ZnSn(OH)6 catalyst has high catalytic activity for toluene. If the mass of the added Na2SiO3·9H2O is too small, the silicon element cannot be doped; if the mass of the added Na2SiO3·9H2O is too large, the crystallinity of ZnSn(OH)6 will be reduced, the crystal structure will be damaged, and the activity for toluene will be reduced.

[0014] Further, 0 g, 0.025 g, 0.05 g, 0.75 g, 0.1 g, 0.125 g, 0.25 g, 0.5 g or 1 g of Na2SiO3·9H2O is added to every 10 mL of the methyl cellulose solution.

[0015] Further, the solvents of the Zn(Ac)2·2H2O solution, the SnCl4·5H2O solution and the NaOH solution are water, and the solvents of the methyl cellulose solution are water and ethanol, and the mass ratio of water to ethanol is 5:2.

[0016] Further, in the step (2), the temperature for sealing and heating the mixed solution is 160℃, and the holding time is 390 min.

[0017] The beneficial effects of the further technical solution are as follows: the silicon atoms can be effectively doped into the ZnSn(OH)6 crystal lattice at 160℃. Selecting a suitable synthesis temperature can save synthesis time and effectively ensure that the finally prepared silicon-doped modified ZnSn(OH)6 catalyst has high catalytic activity for toluene. If the synthesis temperature is too low, the silicon element cannot be doped into the ZnSn(OH)6, and the silicon atoms cannot effectively replace the tin atoms, which can easily lead to a decrease in the activity of the generated silicon-doped modified ZnSn(OH)6 catalyst. If the synthesis temperature is too high, not only the energy consumption is increased, but also when the temperature exceeds 170℃, Zn2SnO4 is generated, and the following reaction occurs:

[0018] Zn 2+ + 4OH - → Zn(OH)4 2- and ZnSn(OH)6 + Zn(OH)4 2- → Zn2SnO4 + 4H2O + 2OH - .

[0019] The holding time of 390 min at 160℃ ensures the full reaction of various elements in the reaction kettle and the yield of the silicon-doped modified ZnSn(OH)6 catalyst, which in turn helps to ensure that the silicon element can be successfully doped into the crystal grains of the ZnSn(OH)6 catalyst and successfully introduced Sn 3+ -OVs double anion defect sites. If the holding time is too short, the thermal polymerization reaction of the reactants will not be sufficient, the particle size will be uneven, and the silicon element cannot be doped. If the holding time is too long, Zn2SnO4 will be generated.

[0020] Further, in the step (2), the mixed solution is sealed and heated to synthesize, and the temperature is increased from room temperature to 160℃, and the holding time at 160℃ is 390 min. After the synthesis is completed, the heating temperature is reduced to room temperature.

[0021] Further, the step (2) further comprises: washing the silicon-doped modified ZnSn(OH)6 photocatalyst with distilled water and anhydrous ethanol twice, drying, grinding, and obtaining a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0022] The beneficial effects of the further technical solutions are as follows: the silicon-doped modified ZnSn(OH)6 photocatalyst is fully ground into powder to increase the specific surface area, thereby improving the activity of the catalyst in degrading toluene, and facilitating detection and use.

[0023] Further, the drying temperature is 60℃, and the drying time is 6h.

[0024] Further, the grinding is to a particle size of 0.3-0.6μm.

[0025] Further, the preparation method specifically comprises the following steps:

[0026] 1) Divide the distilled water into two parts, and the volume ratio of the first part of distilled water to the second part of distilled water is 60:40; mix and stir Zn(Ac)2·2H2O solution, SnCl4·5H2O solution, NaOH solution, Na2SiO3·9H2O, and the first part of distilled water to obtain a white solution;

[0027] 2) After adding the methyl cellulose solution to the white solution and continuing to stir, add the second part of distilled water to obtain a mixed solution;

[0028] 3) Seal and heat the mixed solution to synthesize the silicon-doped modified ZnSn(OH)6 photocatalyst.

[0029] The beneficial effects of the further technical solutions are as follows: in the hydrothermal reaction of the reaction kettle, by using water as a medium and utilizing the stirring action of the rotor, the rapid dissolution of SnCl4·5H2O, Zn(Ac)2·2H2O, NaOH, and Na2SiO3·9H2O in water is promoted, a mixed solution containing a large amount of Sn 4+ , Zn 2+ , OH - , Si 4+ ions is formed, and then Zn 2+ +Sn 4+ +6OH - +Si 4+ →ZnSn(OH)6(silicon-containing) is synthesized to obtain ZnSn(OH)6(silicon-containing).

[0030] Further, in step 1), the stirring time is 10min, and the stirring speed is 550r / min; in step 2), the stirring time is 5min, and the stirring speed is 550r / min.

[0031] The beneficial effects of the further technical solutions are as follows: by utilizing the stirring action of the rotor, the rapid dissolution of SnCl4·5H2O, Zn(Ac)2·2H2O, NaOH, and Na2SiO3·9H2O in water is promoted.

[0032] The application also provides the silicon-doped modified ZnSn(OH)6 photocatalyst prepared by the method.

[0033] The application also provides application of the silicon-doped modified ZnSn(OH)6 photocatalyst in removal of toluene pollutants.

[0034] Compared with conventional unmodified ZnSn(OH)6, the silicon-doped modified ZnSn(OH)6 catalyst prepared by the application has a higher photocatalytic (ultraviolet light) toluene activity than the unmodified ZnSn(OH)6. Therefore, the silicon-doped modified ZnSn(OH)6 photocatalyst with double anion and cation defect sites can be applied in removal of toluene pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a test point line graph of photocatalytic removal of toluene activity of the product obtained in Comparative Example 1 under irradiation of ultraviolet light at different humidities of air;

[0036] Figure 2 Figure 2 is a comparison graph of photocatalytic removal of toluene activity of the products obtained in Example 8, Comparative Example 2 and Comparative Example 3 under irradiation of ultraviolet light;

[0037] Figure 3 Figure 3 is a test point line graph of photocatalytic removal of toluene activity of the product obtained in Comparative Example 1 under irradiation of ultraviolet light at different humidities of air;

[0038] Figure 4 Figure 4 is a test point line graph of photocatalytic removal of toluene activity of the product obtained in Example 8 under irradiation of ultraviolet light at different humidities of air;

[0039] Figure 5 Figure 5 is a test point line graph of stability of photocatalytic removal of toluene pollutants of Example 8 within 335 min;

[0040] Figure 6 Figure 6 is an X-ray diffraction spectrum of the cubic silicon-doped modified ZnSn(OH)6 prepared in Comparative Example 1 and Examples 1-8;

[0041] Figure 7 Figure 7 is a scanning electron microscope (SEM) image of the product obtained in Example 8;

[0042] Figure 8 Figure 8 is an XPS full spectrum of Comparative Example 1 and Example 8;

[0043] Figure 9 Figure 9 is an XPS high-resolution O1s spectrum of Comparative Example 1 and Example 8;

[0044] Figure 10 The photocurrent graph of the product obtained in Comparative Example 1 and Example 8;

[0045] Figure 11 The electrochemical impedance graph of the product obtained in Comparative Example 1 and Example 8;

[0046] Figure 12 The electron paramagnetic resonance graph of the product obtained in Comparative Example 1 and Example 8. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0048] The solvent of the methyl cellulose solution in the embodiments and comparative examples of the present application is water and ethanol, and the mass ratio of water to ethanol is 5:2.

[0049] Example 1

[0050] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0051] (1) 4 mL of Zn(Ac)2·2H2O aqueous solution with a concentration of 0.5 mol / L, 4 mL of SnCl4·5H2O aqueous solution with a concentration of 0.5 mol / L, 4.6 mL of NaOH aqueous solution with a concentration of 3 mol / L and 0.025 g of Na2SiO3·9H2O are added into 60 mL of distilled water, mixed and stirred for 10 min at a stirring speed of 550 r / min, to obtain a white solution;

[0052] (2) 10 mL of methyl cellulose solution with a concentration of 2.8 g / L is added into the white solution, continuously stirred for 5 min at a stirring speed of 550 r / min, mixed with 40 mL of distilled water, to obtain a mixed solution;

[0053] (3) the mixed solution is transferred into a stainless steel autoclave with a Teflon liner, the reaction kettle is sealed, and then is placed in an oven for heating synthesis, the temperature is increased from room temperature to 160℃, and the temperature is kept at 160℃ for 390 min, after the synthesis is completed, the heating temperature is reduced to room temperature, the obtained precipitate is washed with distilled water and anhydrous ethanol twice, and is dried at 60℃ for 6 h, to obtain the silicon-doped modified ZnSn(OH)6 photocatalyst, the obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm, to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0054] Example 2

[0055] A method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst, comprising the following steps:

[0056] (1) 4 mL of a 0.5 mol / L Zn(Ac)2·2H2O aqueous solution, 4 mL of a 0.5 mol / L SnCl4·5H2O aqueous solution, 4.6 mL of a 3 mol / L NaOH aqueous solution, and 0.05 g of Na2SiO3·9H2O are added to 60 mL of distilled water, mixed and stirred for 10 min at a stirring speed of 550 r / min, to obtain a white solution;

[0057] (2) 10 mL of a 2.8 g / L methyl cellulose solution is added to the white solution, continuously stirred for 5 min at a stirring speed of 550 r / min, and then mixed with 40 mL of distilled water to obtain a mixed solution;

[0058] (3) The mixed solution is transferred into a stainless steel autoclave lined with Teflon, the reaction kettle is sealed, and then placed in an oven for heating synthesis, the temperature is increased from room temperature to 160°C, and kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is reduced to room temperature. The obtained precipitate is washed twice with distilled water and anhydrous ethanol respectively, and dried at 60°C for 6 h to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0059] Example 3

[0060] A method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst, comprising the following steps:

[0061] (1) 4 mL of a 0.5 mol / L Zn(Ac)2·2H2O aqueous solution, 4 mL of a 0.5 mol / L SnCl4·5H2O aqueous solution, 4.6 mL of a 3 mol / L NaOH aqueous solution, and 0.075 g of Na2SiO3·9H2O are added to 60 mL of distilled water, mixed and stirred for 10 min at a stirring speed of 550 r / min, to obtain a white solution;

[0062] (2) 10 mL of a 2.8 g / L methyl cellulose solution is added to the white solution, continuously stirred for 5 min at a stirring speed of 550 r / min, and then mixed with 40 mL of distilled water to obtain a mixed solution;

[0063] (3) the mixed solution is transferred into a stainless steel autoclave with a Teflon liner, the autoclave is sealed, and then is placed in an oven for heating and synthesis, the temperature is increased from room temperature to 160°C, and is kept at 160°C for 390 min, after the synthesis is completed, the heating temperature is decreased to room temperature, the obtained precipitate is washed with distilled water and anhydrous ethanol twice, and is dried at 60°C for 6 h, to obtain the silicon-doped modified ZnSn(OH)6 photocatalyst, the obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm, to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0064] Example 4

[0065] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0066] (1) 4 mL of a Zn(Ac)2·2H2O aqueous solution with a concentration of 0.5 mol / L, 4 mL of a SnCl4·5H2O aqueous solution with a concentration of 0.5 mol / L, 4.6 mL of a NaOH aqueous solution with a concentration of 3 mol / L, and 0.1 g of Na2SiO3·9H2O are added into 60 mL of distilled water, and are mixed and stirred for 10 min, at a stirring speed of 550 r / min, to obtain a white solution;

[0067] (2) 10 mL of a methyl cellulose solution with a concentration of 2.8 g / L is added into the white solution, and is continuously stirred for 5 min, at a stirring speed of 550 r / min, 40 mL of distilled water is added for mixing, to obtain a mixed solution;

[0068] (3) the mixed solution is transferred into a stainless steel autoclave with a Teflon liner, the autoclave is sealed, and then is placed in an oven for heating and synthesis, the temperature is increased from room temperature to 160°C, and is kept at 160°C for 390 min, after the synthesis is completed, the heating temperature is decreased to room temperature, the obtained precipitate is washed with distilled water and anhydrous ethanol twice, and is dried at 60°C for 6 h, to obtain the silicon-doped modified ZnSn(OH)6 photocatalyst, the obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm, to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0069] Example 5

[0070] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0071] (1) 4mL of Zn(Ac)2·2H2O aqueous solution with a concentration of 0.5 mol / L, 4mL of SnCl4·5H2O aqueous solution with a concentration of 0.5 mol / L, 4.6mL of NaOH aqueous solution with a concentration of 3 mol / L, and 0.125g of Na2SiO3·9H2O were added into 60mL of distilled water and stirred for 10min at a stirring speed of 550r / min to obtain a white solution;

[0072] (2) 10mL of methyl cellulose solution with a concentration of 2.8g / L was added into the white solution and stirred for 5min at a stirring speed of 550r / min, and then 40mL of distilled water was added to obtain a mixed solution;

[0073] (3) The mixed solution was transferred into a stainless steel autoclave with a Teflon liner, the reactor was sealed and then placed in an oven for heating synthesis, the temperature was increased from room temperature to 160℃, and the temperature was kept at 160℃ for 390min. After the synthesis was completed, the heating temperature was decreased to room temperature. The obtained precipitate was washed twice with distilled water and anhydrous ethanol respectively, and dried at 60℃ for 6h to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst was ground to a particle size of 0.3-0.6μm to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0074] Example 6

[0075] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0076] (1) 4mL of Zn(Ac)2·2H2O aqueous solution with a concentration of 0.5 mol / L, 4mL of SnCl4·5H2O aqueous solution with a concentration of 0.5 mol / L, 4.6mL of NaOH aqueous solution with a concentration of 3 mol / L, and 0.5g of Na2SiO3·9H2O were added into 60mL of distilled water and stirred for 10min at a stirring speed of 550r / min to obtain a white solution;

[0077] (2) 10mL of methyl cellulose solution with a concentration of 2.8g / L was added into the white solution and stirred for 5min at a stirring speed of 550r / min, and then 40mL of distilled water was added to obtain a mixed solution;

[0078] (3) the mixed solution is transferred into a stainless steel autoclave with a Teflon liner, the reactor is sealed, and then is placed in an oven for heating and synthesis. The temperature is increased from room temperature to 160°C, and is kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is decreased to room temperature. The obtained precipitate is washed with distilled water and anhydrous ethanol twice, and is dried at 60°C for 6 h to obtain the silicon-doped modified ZnSn(OH)6 photocatalyst. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0079] Example 7

[0080] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0081] (1) 4 mL of a Zn(Ac)2·2H2O aqueous solution with a concentration of 0.5 mol / L, 4 mL of a SnCl4·5H2O aqueous solution with a concentration of 0.5 mol / L, 4.6 mL of a NaOH aqueous solution with a concentration of 3 mol / L, and 1 g of Na2SiO3·9H2O are added into 60 mL of distilled water for mixing and stirring for 10 min at a stirring speed of 550 r / min to obtain a white solution;

[0082] (2) the white solution is added into 10 mL of a methyl cellulose solution with a concentration of 2.8 g / L for further stirring for 5 min at a stirring speed of 550 r / min, and then is mixed with 40 mL of distilled water to obtain a mixed solution;

[0083] (3) the mixed solution is transferred into a stainless steel autoclave with a Teflon liner, the reactor is sealed, and then is placed in an oven for heating and synthesis. The temperature is increased from room temperature to 160°C, and is kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is decreased to room temperature. The obtained precipitate is washed with distilled water and anhydrous ethanol twice, and is dried at 60°C for 6 h to obtain the silicon-doped modified ZnSn(OH)6 photocatalyst. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0084] Example 8

[0085] The preparation method of the silicon-doped modified ZnSn(OH)6 photocatalyst comprises the following steps:

[0086] (1) 4mL of 0.5mol / L Zn(Ac)2·2H2O aqueous solution, 4mL of 0.5mol / L SnCl4·5H2O aqueous solution, 4.6mL of 3mol / L NaOH aqueous solution and 0.25g of Na2SiO3·9H2O were added into 60mL of distilled water and stirred for 10min at a stirring speed of 550r / min to obtain a white solution;

[0087] (2) 10mL of 2.8g / L methyl cellulose solution was added into the white solution and stirred for 5min at a stirring speed of 550r / min, and then 40mL of distilled water was added to obtain a mixed solution;

[0088] (3) The mixed solution was transferred into a Teflon-lined stainless steel autoclave, the reactor was sealed and then placed in an oven for heating synthesis, the temperature was increased from room temperature to 160℃, and the temperature was kept at 160℃ for 390min. After the synthesis was completed, the heating temperature was decreased to room temperature. The obtained precipitate was washed with distilled water and anhydrous ethanol twice, and dried at 60℃ for 6h to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst. The obtained silicon-doped modified ZnSn(OH)6 photocatalyst was ground to a particle size of 0.3-0.6μm to obtain a silicon-doped modified ZnSn(OH)6 photocatalyst powder.

[0089] Comparative Example 1

[0090] The preparation method of the ZnSn(OH)6 photocatalyst comprises the following steps:

[0091] (1) 4mL of 0.5mol / L Zn(Ac)2·2H2O aqueous solution, 4mL of 0.5mol / L SnCl4·5H2O aqueous solution and 4.6mL of 3mol / L NaOH aqueous solution were added into 60mL of distilled water and stirred for 10min at a stirring speed of 550r / min to obtain a white solution;

[0092] (2) 10mL of 2.8g / L methyl cellulose solution was added into the white solution and stirred for 5min at a stirring speed of 550r / min, and then 40mL of distilled water was added to obtain a mixed solution;

[0093] (3) The mixed solution is transferred into a stainless steel autoclave lined with Teflon, the reactor is sealed, and then placed in an oven for heating synthesis. The temperature is raised from room temperature to 160°C, and kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is reduced to room temperature. The obtained precipitate is washed with distilled water and anhydrous ethanol twice, dried at 60°C for 6 h, to obtain ZnSn(OH)6 photocatalyst. The obtained ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm, to obtain ZnSn(OH)6 photocatalyst powder.

[0094] Comparative Example 2

[0095] The preparation method of the silicon-doped modified CaCO3 photocatalyst comprises the following steps:

[0096] (1) 5 g of CaCO3 (5 g is the amount of ZnSn(OH)6 sample for synthesis) and 0.25 g of Na2SiO3·9H2O are added into 60 mL of distilled water, mixed and stirred for 10 min, and the stirring speed is 550 r / min, to obtain a white solution;

[0097] (2) 10 mL of methyl cellulose solution with a concentration of 2.8 g / L is added into the white solution, continuously stirred for 5 min, and then 40 mL of distilled water is added and mixed, to obtain a mixed solution;

[0098] (3) The mixed solution is transferred into a stainless steel autoclave lined with Teflon, the reactor is sealed, and then placed in an oven for heating synthesis. The temperature is raised from room temperature to 160°C, and kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is reduced to room temperature. The obtained precipitate is washed with distilled water and anhydrous ethanol twice, dried at 60°C for 6 h, to obtain ZnSn(OH)6 photocatalyst. The obtained ZnSn(OH)6 photocatalyst is ground to a particle size of 0.3-0.6 μm, to obtain ZnSn(OH)6 photocatalyst powder.

[0099] Comparative Example 3

[0100] The preparation method of the silicon-doped modified TiO2 photocatalyst comprises the following steps:

[0101] (1) 5 g of TiO2 (5 g is the amount of ZnSn(OH)6 sample for synthesis) and 0.25 g of Na2SiO3·9H2O are added into 60 mL of distilled water, mixed and stirred for 10 min, and the stirring speed is 550 r / min, to obtain a white solution;

[0102] (2) 10 mL of methyl cellulose solution with a concentration of 2.8 g / L is added into the white solution, continuously stirred for 5 min, and then 40 mL of distilled water is added and mixed, to obtain a mixed solution;

[0103] (3) The mixed solution is transferred into a stainless steel autoclave lined with Teflon, and after the reactor is sealed, it is placed in an oven for heating synthesis. The temperature is raised from room temperature to 160°C, and the temperature is kept at 160°C for 390 min. After the synthesis is completed, the heating temperature is reduced to room temperature. The obtained precipitate is washed twice with distilled water and anhydrous ethanol, and dried at 60°C for 6 h to obtain a silicon-doped modified TiO2 photocatalyst. The obtained silicon-doped modified TiO2 photocatalyst is ground to a particle size of 0.3-0.6 μm to obtain a silicon-doped modified TiO2 photocatalyst powder.

[0104] Performance characterization experiments of different photocatalysts

[0105] A plurality of characterization experiments are performed on the photocatalysts of Examples 1-8 and Comparative Examples 1-3. Among them, the photocatalysts of Examples 1-8 can be written as ZHS-5, ZHS-10, ZHS-15, ZHS-20, ZHS-25, ZHS-100, ZHS-200, and ZHS-50 in the experimental results, respectively. The photocatalysts of Comparative Examples 1, 2, and 3 are written as ZHS, Si-Ca, and Si-Ti in the experimental results, respectively.

[0106] 1. Photocatalytic activity characterization experiment

[0107] Experimental method:

[0108] The performance of the catalyst is evaluated by real-time monitoring of the instantaneous concentration of ppm-level VOCs in the reaction chamber using a photoacoustic spectrometer at room temperature. The specific operation is as follows: 4 samples of 0.1 g are weighed on a 40 mm x 100 mm rectangular cornered ground glass sheet, evenly dispersed with a small amount of alcohol, and placed in a constant temperature drying oven at 60°C for drying. After cooling to room temperature, the glass sheet loaded with the catalyst is placed in a rectangular continuous flow reaction chamber with a volume of 0.34 L (i.e., 200 mm x 100 mm x 17 mm), and a layer of quartz glass is placed on the reaction chamber. The reaction chamber is sealed (screwed to prevent gas leakage). At the same time, a 300W commercial mercury lamp is used as the ultraviolet light source for photocatalytic reaction above the reaction chamber; the initial concentration of the pollutant is changed by adjusting the flow meter in the gas path, and the flow rate of the wet air is set to 0.5 L·min -1 , the sum of the flow rate of dry air (0.4 L·min -1 ) and the flow rate of the pollutant (0.1 L·min -1 ) is 0.5 L·min -1 . The diluted VOCs pollutant gas is introduced into the reaction chamber. In the dark, after the catalyst reaches adsorption-desorption equilibrium, the light is turned on for pollutant degradation reaction, and the toluene concentration in the reaction chamber is recorded using a photoacoustic spectrometer.

[0109] Figures 1-5The photocatalytic activity of toluene in the experimental process is shown in Table 1, wherein the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively. Figure 2 As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively. Figure 1 As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively.

[0110] As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively. Figure 3 As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively. Figure 4 As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively.

[0111] In addition, the stability of Example 8 is tested (as shown in Table 2), and it is found that the photocatalytic activity of toluene does not decrease within 335 min, and the degradation rate is maintained at 100%, which indicates that the photocatalytic performance of the ZnSn(OH)6 catalyst doped with silicon elements by the hydrothermal method is excellent, stable and efficient. Figure 5 2. XRD characterization experiment

[0112] In order to verify the type of the products obtained in Comparative Example 1 and Examples 1-8, the present application uses a German Bruker D8 Advance X-ray diffractometer (Cu Kα, λ=0.154 nm, working voltage and working current are 40 kV and 40 mA, respectively) to test the XRD of each product.

[0113] As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively.

[0114] As shown in Table 1, the photocatalytic oxidation activity of toluene (50 ppm) of the photocatalyst prepared in Example 8 and Comparative Examples 2 and 3 is 100%, inactivation, activity reduction and re-inactivation, respectively. Figure 6As shown, the XRD results show that the diffraction peaks of the products of Example Comparative Example 1, Examples 1-5, Example 8, Examples 6-7 at 19.69°, 22.78°, 32.44°, 40.04°, 46.64°, 52.42° and 57.72° correspond to the (111), (200), (220), (222), (400), (420) and (422) planes of ZnSn(OH)6(JCPDS 74-1825), respectively, and no other impurity peaks are found. However, as the amount of doping increases, the intensity of the ZHS-x peaks gradually decreases. This indicates that the addition of excess sodium silicate reduces the crystallinity of the material. In addition, all the diffraction peaks are slightly shifted to high diffraction angles. This is probably because the introduction of sodium silicate changes the coordination environment of the crystal, causing the lattice to deform.

[0115] 3. Electron microscopy characterization experiment

[0116] The morphology of the sample of Example 8 was characterized using a Japanese JEOL Model JSM-6490 scanning electron microscope. As shown in Figure 7 , it can be found that the size of the silicon-doped modified ZnSn(OH)6with flocculent covering cubic morphology is between 0.3-0.6 μm.

[0117] 4. XPS characterization experiment

[0118] As shown in Figure 8 , the XPS full spectrum comparison chart of Example 8 and Comparative Example 1 shows that in Example 8, 101.9 eV is assigned to Si 2p, confirming that the silicon element has been doped into ZnSn(OH)6. As shown in Figure 9 , the peak at 531.5 eV in Example 8 is assigned to defect oxygen with a proportion of 70.57%, which is significantly higher than the proportion of defect oxygen peak in Comparative Example 1, indicating that silicon doping introduces more oxygen vacancies, which is beneficial to the activation of small molecules.

[0119] 5. Electrochemical characterization experiment

[0120] As shown in Figure 10 , the photocurrent comparison of Example 8 and Comparative Example 1 shows that the photocurrent of Example 8 is higher than that of Comparative Example 1 within 1400 s, proving that Example 8 is more conducive to the generation of electrons and improves the separation efficiency of electron-hole pairs. As shown in Figure 11 , the electrical impedance of Example 8 is smaller than that of Comparative Example 1, proving that Example 8 accelerates the migration rate of carriers.

[0121] 6. Electron paramagnetic resonance

[0122] Oxygen vacancies and Sn 3+ sites in the crystal structure can usually act as defects that capture electrons and holes, making them paramagnetic centers. AsFigure 12 As shown, by observing electron paramagnetic resonance, it was found that Example 8 had a symmetric peak at 1.96, which was due to trapped photo-generated electrons (i.e. Sn 3+ ). In theory, oxygen vacancies and Sn 3+ sites should coexist on Example 8, but no signal belonging to oxygen vacancies was detected, which can be because the oxygen vacancies present on the surface were not stable, and the defect sites were mainly Sn 3+ . As for Comparative Example 1, no signal of trapped electrons was observed, which indicates that the introduction of silicon elements can induce the generation of Sn 3+ defects.

[0123] The foregoing description of the disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst, characterized in that, The method comprises the following steps: (1) mixing Zn(Ac)2·2H2O solution, SnCl4·5H2O solution, NaOH solution, Na2SiO3·9H2O, methyl cellulose solution and distilled water to obtain a mixed solution; (2) heating the mixed solution to synthesize the silicon-doped modified ZnSn(OH)6 photocatalyst.

2. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 1, characterized in that, The concentration of the Zn(Ac)2·2H2O solution is 0.5 mol / L, the concentration of the SnCl4·5H2O solution is 0.5 mol / L, the concentration of the NaOH solution is 3 mol / L, the concentration of the methyl cellulose solution is 2.8 g / L, and the volume ratio of the Zn(Ac)2·2H2O solution, the SnCl4·5H2O solution, the NaOH solution, the methyl cellulose solution and the distilled water is 4:4:4.6:10:100, and 0.025-1 g of Na2SiO3·9H2O is added to every 10 mL of the methyl cellulose solution.

3. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 1, characterized in that, In step (2), the heating temperature of the mixed solution is 160℃, and the holding time is 390 min.

4. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 1, characterized in that, In step (2), the mixed solution is heated from room temperature to 160℃, and is kept at 160℃ for 390 min, and then the heating temperature is reduced to room temperature after the synthesis is completed.

5. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 1, characterized in that, In step (2), the silicon-doped modified ZnSn(OH)6 photocatalyst is washed with distilled water and anhydrous ethanol twice, dried, ground, and then silicon-doped modified ZnSn(OH)6 photocatalyst powder is obtained.

6. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 5, characterized in that, The drying temperature is 60℃, and the drying time is 6 h.

7. The method according to claim 5, wherein the method is characterized by, The grinding particle size is 0.3-0.6 μm.

8. The method for preparing a silicon-doped modified ZnSn(OH)6 photocatalyst according to claim 1, characterized in that, The method comprises the following steps: 1) Dividing the distilled water into two parts, and the volume ratio of the first part of distilled water to the second part of distilled water is 60:40, mixing and stirring Zn(Ac)2·2H2O solution, SnCl4·5H2O solution, NaOH solution, Na2SiO3·9H2O and the first part of distilled water to obtain a white solution; 2) Adding methyl cellulose solution to the white solution and continuing to stir, then adding the second part of distilled water to obtain a mixed solution; 3) Sealing and heating the mixed solution to synthesize the silicon-doped modified ZnSn(OH)6 photocatalyst.

9. A silicon-doped modified ZnSn(OH)6 photocatalyst prepared by the method of any one of claims 1-8.

10. Application of the silicon-doped modified ZnSn(OH)6 photocatalyst of claim 9 in removing toluene pollutants.

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