Piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite and preparation method and application thereof

Abstract

The invention discloses a piezoelectric enhanced photocatalytic coating based on a BaTiO3 / BiOCl nanocomposite and a preparation method and application thereof.BaTiO3 and BiOCl are compounded to form a p-n junction, the compounding probability of electron-hole pairs can be reduced, and the photocatalytic degradation capacity can be effectively improved by introducing external field mechanical energy; the BaTiO3 / BiOCl nano composite material is prepared into paint to be coated on the surface of the cement-based material to form a coating with self-cleaning performance, so that the durability of the cement-based material can be improved on the premise of not changing the internal structure of the cement-based material, and the service life of the cement-based material is prolonged; meanwhile, under the driving of mechanical energy such as wind energy, tidal energy and ultrasonic waves in the environment where the cement-based material is located, the BaTiO3 / BiOCl nano composite material can release electrons and holes and convert the mechanical energy into electric energy, so that the photocatalytic degradation capacity of the coating is further improved, degradation of pollutants in surrounding water is accelerated, and the photocatalytic degradation efficiency of the coating is improved. And the self-cleaning effect on the self surface is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material, and a preparation method and application thereof. Background Art

[0002] Applying photocatalysts to cement-based materials can give them the effects of pollutant degradation and surface self-cleaning, reduce the corrosion rate of buildings with cement-based materials as the main material, extend service life and improve durability. Since the first report that TiO2 can degrade pollutants under ultraviolet light, there have been numerous studies on photocatalytic cement-based materials. At present, the commonly used preparation methods for photocatalytic cement-based materials are direct internal mixing method, aggregate loading method and surface coating method. The amount of photocatalyst used in the direct internal mixing method is large, and the opacity of the cement matrix leads to waste of photocatalyst and low photocatalytic efficiency. The aggregate loading method is complicated and not easy to mass produce, and the compatibility of the photocatalyst with the cement matrix needs to be considered. The surface coating method can not only reduce the amount of photocatalyst and improve the photocatalytic efficiency, but more importantly, its preparation process is simple and easy. In addition, the surface coating method often uses resins as the dispersion medium, which can effectively improve the surface hydrophobicity and further enhance its self-cleaning performance. Therefore, the surface coating method can give the cement-based material a surface cleaning and purification effect and enhance its corrosion resistance, becoming a research hotspot in the current field of building materials. Efficient conversion of solar energy through photocatalytic technology has great potential for alleviating the current energy crisis and increasingly serious environmental pollution. However, unsatisfactory conversion efficiency still hinders its practical application. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art and provide a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material. BaTiO3 / BiOCl nanocomposite materials can utilize mechanical energy introduced through external fields such as wind energy, tidal energy, and ultrasound in nature to enhance their ability to photocatalytically degrade organic pollutants, showing excellent photocatalytic degradation performance and cycle stability, and showing excellent application prospects in purifying water bodies, improving water quality, etc. The present invention also provides a method for preparing the above-mentioned piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite materials, and the application of coating the same on the surface of cement-based materials.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material, specifically comprising the following steps:

[0006] Step 1: Preparation of BaTiO3 nanomaterials by hydrothermal method:

[0007] Step 1.1: First, TiO2 particles are added to an excess of 8-12 mol / L NaOH aqueous solution and stirred evenly, then placed in a reactor and kept warm at 160-200°C for 10-14 hours, and after cooling, they are washed alternately by centrifugation with deionized water and anhydrous ethanol for 2-6 times each, and the obtained precipitate is dried to obtain Na2Ti3O7 nanowires;

[0008] Step 1.2: Soaking the obtained Na2Ti3O7 nanowires in an excess of 0.1-0.3 mol / L HCl solution and stirring for 2-6 hours, then centrifuging to obtain a precipitate, and drying the obtained precipitate to obtain H2Ti3O7 nanowires;

[0009] Step 1.3: Add the obtained H2Ti3O7 nanowires to an excess of 0.02-0.08 mol / L Ba(OH)2·8H2O aqueous solution, ultrasonically treat for 20-40 min, then stir evenly, put into a reactor and react at 180-240°C for 2-4 h, and after cooling, use 0.1-0.3 mol / L hydrochloric acid solution, deionized water, and anhydrous ethanol to alternately centrifuge and wash until the supernatant is neutral, dry and grind the obtained precipitate to obtain BaTiO3 nanomaterials.

[0010] Step 2: Preparation of BaTiO3 / BiOCl nanocomposite material: Add the obtained BaTiO3 nanomaterial into excess deionized water and ultrasonically disperse it for 20 to 40 minutes, then add BiCl3 at a molar ratio of BaTiO3 to BiCl3 of 1:(2-6) and ultrasonically disperse it again for 20 to 40 minutes, stir for 1 to 3 hours, and then centrifuge to obtain a precipitate. After drying the obtained precipitate, the BaTiO3 / BiOCl nanocomposite material can be obtained.

[0011] Step 3: Add the obtained BaTiO3 / BiOCl nanocomposite material to anhydrous ethanol, ultrasonically disperse it for 20 to 40 minutes, then add polydimethylsiloxane thereto, and ultrasonically disperse it for another 20 to 40 minutes, then stir until the anhydrous ethanol is completely evaporated, then add the curing agent and continue stirring until the rotor stops rotating automatically due to the increase in viscosity of the stirring system, and the coating can be obtained, and then the obtained coating is applied to the surface of the substrate material to form a piezoelectric enhanced photocatalytic coating.

[0012] Preferably, in step 1 and step 2, the drying conditions are both 60-100° C. for 8-16 hours.

[0013] Preferably, in steps 1 to 3, magnetic stirring is used for stirring.

[0014] Preferably, the stirring speed in step 1.2 is 200-400 rpm.

[0015] Preferably, the stirring speed in step 1.3 is 500-700 rpm.

[0016] Preferably, the stirring speed in step 2 is 500-700 rpm.

[0017] Preferably, in step 3, the dosage of BaTiO3 / BiOCl nanocomposite material is 1-5% of the mass of polydimethylsiloxane, and the coating amount of the obtained coating on the surface of the substrate material is 0.5-0.8 kg / m 2 .

[0018] A piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material prepared by the method.

[0019] The invention discloses an application of a piezoelectric enhanced photocatalytic coating based on a BaTiO3 / BiOCl nanocomposite material, wherein the obtained coating is applied on the surface of a cement-based material to form a piezoelectric enhanced photocatalytic coating.

[0020] Beneficial effects of the present invention: The present invention forms a composite of BaTiO3 and BiOCl - n junction, which can not only reduce the recombination probability of electron-hole pairs, but also effectively improve the photocatalytic degradation ability by introducing external mechanical energy. BaTiO3 / BiOCl nanocomposite materials are prepared into coatings and applied to the surface of cement-based materials to form a coating with self-cleaning properties, which can improve its corrosion resistance and durability without changing the internal structure of cement-based materials, thereby increasing its service life; at the same time, driven by natural energy such as wind energy, tidal energy, and ultrasound in the environment where cement-based materials are located, BaTiO3 / BiOCl nanocomposites can release electrons and holes, converting natural energy into electrical energy, thereby further improving the photocatalytic degradation ability of the coating, accelerating the degradation of pollutants in the surrounding water, and improving the self-cleaning effect of its own surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : X-ray powder diffraction patterns of the BaTiO3 / BiOCl nanocomposite material and BaTiO3 and BiOCl monomer nanomaterials prepared by the present invention.

[0022] Figure 2A : Ultraviolet diffuse reflectance images of the BaTiO3 / BiOCl nanocomposite material and BaTiO3 and BiOCl monomer nanomaterials prepared by the present invention.

[0023] Figure 2B: Energy band structure diagram of BaTiO3 / BiOCl nanocomposite material prepared by the present invention.

[0024] Figure 3A : The photocatalytic degradation effect diagram of the BaTiO3 / BiOCl nanocomposite material prepared by the present invention and the BaTiO3 and BiOCl monomer nanomaterials on MB solution.

[0025] Figure 3B : The piezoelectric photocatalytic degradation effect diagram of the BaTiO3 / BiOCl nanocomposite material prepared by the present invention and the BaTiO3 and BiOCl monomer nanomaterials on MB solution.

[0026] Figure 4A : (a) to (e) are the ultra-depth-of-field surface images of the piezoelectrically enhanced photocatalytic coating based on BaTiO3 monomer nanomaterials, the coating based on BiOCl monomer nanomaterials, and the nanocomposite materials based on the molar ratios of BaTiO3 and BiCl3 of 1:2, 1:4, and 1:6, respectively.

[0027] Figure 4B : (f) to (j) are 3D renderings of piezoelectrically enhanced photocatalytic coatings based on BaTiO3 monomer nanomaterials, BiOCl monomer nanomaterials, and nanocomposite materials with molar ratios of BaTiO3 to BiCl3 of 1:2, 1:4, and 1:6, respectively.

[0028] Figure 5A : The photocatalytic degradation effect diagram of the piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material prepared by the present invention, the coating based on BaTiO3 monomer nanomaterial, and the coating based on BiOCl monomer nanomaterial on MB solution.

[0029] Figure 5B : The piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite prepared by the present invention, the coating based on BaTiO3 monomer nanomaterial, and the coating based on BiOCl monomer nanomaterial on the piezoelectric photocatalytic degradation effect of MB solution.

[0030] Figure 5C : The piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite prepared by the present invention, the coating based on BaTiO3 monomer nanomaterial, and the coating based on BiOCl monomer nanomaterial on the cyclic piezoelectric photocatalytic degradation effect of MB solution.

[0031] Fig. 6A: (a) to (e) are the surface wetting properties of the piezoelectrically enhanced photocatalytic coating before degrading MB solution, respectively, based on BaTiO3 monomer nanomaterials, based on BiOCl monomer nanomaterials, and based on nanocomposites with molar ratios of BaTiO3 to BiCl3 of 1:2, 1:4, and 1:6.

[0032] Figure 6B : (f) to (j) are the surface wetting properties of the piezoelectrically enhanced photocatalytic coating after degradation of MB solution, which are based on BaTiO3 monomer nanomaterials, BiOCl monomer nanomaterials, and nanocomposite materials with molar ratios of BaTiO3 to BiCl3 of 1:2, 1:4, and 1:6, respectively. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The cement paste test blocks used in the examples and comparative examples of the present invention were prepared by the following process:

[0035] 100 g of standard cement and 36 g of water were first mixed and stirred at a rotation speed of 60 rpm for 100 s, and then mixed and stirred at a rotation speed of 150 rpm for 100 s to obtain cement slurry; the prepared cement slurry was then poured into a mold and vibrated to form, and a cement slurry test block was obtained after curing for 7 days.

[0036] Example 1

[0037] Preparation of BaTiO3 / BiOCl Nanocomposites :

[0038] Step 1: First, add 1.5 g of TiO2 particles into 60 mL of 10 mol / L sodium hydroxide aqueous solution, place a magnetic stirrer and stir for 2 hours to fully disperse the suspension; transfer the suspension to a high-pressure reactor and keep it at 180°C for 12 hours; after cooling, use deionized water and anhydrous ethanol to wash alternately by centrifugation for 4 times each, and dry the obtained precipitate at 80°C for 12 hours to obtain Na2Ti3O7 nanowires in the form of white powder;

[0039] The obtained Na2Ti3O7 nanowires were immersed in an excess of 0.2 mol / L -1 The mixture was slowly stirred at 300 rpm for 4 h in a hydrochloric acid solution for acidification, and then centrifuged to obtain a precipitate. The precipitate was dried at 80 °C for 12 h to obtain H2Ti3O7 nanowires in the form of white powder.

[0040] Subsequently, 0.2575 g of H2Ti3O7 nanowires were ultrasonically dispersed in 60 mL of 0.05 mol / L Ba(OH)2·8H2O aqueous solution, and ultrasonically treated for 30 min. Then, the suspension was vigorously stirred at 500 rpm for 1 h to obtain a suspension. The suspension was transferred to an autoclave reactor and kept at 210 °C for 3 h. After cooling, 0.2 mol / L -1 The product was washed by alternating centrifugation with hydrochloric acid solution, deionized water and anhydrous ethanol until the supernatant was neutral. The obtained precipitate was dried at 80°C for 12h and then ground to obtain BaTiO3 nanomaterials.

[0041] Step 2: Add the prepared BaTiO3 nanomaterial into 30 mL of deionized water and ultrasonically disperse it for 30 minutes. Then quickly add BiCl3 at a molar ratio of BaTiO3 to BiCl3 of 1:2 and ultrasonically disperse it again for 30 minutes. Then vigorously stir it at a speed of 500 rpm for 1 hour, and then centrifuge to obtain a precipitate. After drying the obtained precipitate at 80°C for 12 hours, a BaTiO3 / BiOCl nanocomposite material with a composite ratio of 1:2 can be obtained.

[0042] Preparation of cement-based coating based on BaTiO3 / BiOCl nanocomposite :

[0043] 0.17 g of the prepared BaTiO3 / BiOCl nanocomposite was added to 20 mL of anhydrous ethanol and ultrasonically dispersed for 30 min. Then, 7.5 g of PDMS was added to the suspension and ultrasonically dispersed for another 30 min. Then, the suspension was stirred until the anhydrous ethanol was completely evaporated. Finally, 0.75 g of curing agent was added and stirring was continued until the rotor stopped rotating due to the increased viscosity of the stirring system. The prepared slurry was immediately heated to 0.65 kg / m 2 The amount of the mixture was applied to the surface of the cement paste specimen and allowed to stand at room temperature for 24 hours to form a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material on the surface of the cement paste specimen after it was fully dried.

[0044] Example 2

[0045] Preparation of BaTiO3 / BiOCl Nanocomposites :

[0046] Step 1: First, add 1.5 g of TiO2 particles into 60 mL of 10 mol / L sodium hydroxide aqueous solution, place a magnetic stirrer and stir for 2 hours to fully disperse the suspension; transfer the suspension to a high-pressure reactor and keep it at 180°C for 12 hours; after cooling, use deionized water and anhydrous ethanol to wash alternately by centrifugation for 4 times each, and dry the obtained precipitate at 80°C for 12 hours to obtain Na2Ti3O7 nanowires in the form of white powder;

[0047] The obtained Na2Ti3O7 nanowires were immersed in an excess of 0.2 mol / L -1 The mixture was slowly stirred at 300 rpm for 4 h in a hydrochloric acid solution for acidification, and then centrifuged to obtain a precipitate. The precipitate was dried at 80 °C for 12 h to obtain H2Ti3O7 nanowires in the form of white powder.

[0048] Subsequently, 0.2575 g of H2Ti3O7 nanowires were ultrasonically dispersed in 60 mL of 0.05 mol / L Ba(OH)2·8H2O aqueous solution, and ultrasonically treated for 30 min. Then, the suspension was vigorously stirred at 500 rpm for 1 h to obtain a suspension. The suspension was transferred to an autoclave reactor and kept at 210 °C for 3 h. After cooling, 0.2 mol / L -1 The product was washed by alternating centrifugation with hydrochloric acid solution, deionized water and anhydrous ethanol until the supernatant was neutral. The obtained precipitate was dried at 80°C for 12h and then ground to obtain BaTiO3 nanomaterials.

[0049] Step 2: Add the prepared BaTiO3 nanomaterial into 30 mL of deionized water and ultrasonically disperse it for 30 min. Then quickly add BiCl3 at a molar ratio of BaTiO3 to BiCl3 of 1:4 and ultrasonically disperse it again for 30 min. Then, vigorously stir at a speed of 500 rpm for 1 h, and then centrifuge to obtain a precipitate. After drying the obtained precipitate at 80°C for 12 h, a BaTiO3 / BiOCl nanocomposite material with a composite ratio of 1:4 can be obtained.

[0050] Preparation of cement-based coating based on BaTiO3 / BiOCl nanocomposite :

[0051] 0.17 g of the prepared BaTiO3 / BiOCl nanocomposite was added to 20 mL of anhydrous ethanol and ultrasonically dispersed for 30 min. Then, 7.5 g of PDMS was added to the suspension and ultrasonically dispersed for another 30 min. Then, the suspension was stirred until the anhydrous ethanol was completely evaporated. Finally, 0.75 g of curing agent was added and stirring was continued until the rotor stopped rotating due to the increased viscosity of the stirring system. The prepared slurry was immediately heated to 0.65 kg / m 2 The amount of the mixture was applied to the surface of the cement paste specimen and allowed to stand at room temperature for 24 hours to form a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material on the surface of the cement paste specimen after it was fully dried.

[0052] Example 3

[0053] Preparation of BaTiO3 / BiOCl Nanocomposites :

[0054] Step 1: First, add 1.5 g of TiO2 particles into 60 mL of 10 mol / L sodium hydroxide aqueous solution, place a magnetic stirrer and stir for 2 hours to fully disperse the suspension; transfer the suspension to a high-pressure reactor and keep it at 180°C for 12 hours; after cooling, use deionized water and anhydrous ethanol to wash alternately by centrifugation for 4 times each, and dry the obtained precipitate at 80°C for 12 hours to obtain Na2Ti3O7 nanowires in the form of white powder;

[0055] The obtained Na2Ti3O7 nanowires were immersed in an excess of 0.2 mol / L -1 The mixture was slowly stirred at 300 rpm for 4 h in a hydrochloric acid solution for acidification, and then centrifuged to obtain a precipitate. The precipitate was dried at 80 °C for 12 h to obtain H2Ti3O7 nanowires in the form of white powder.

[0056] Subsequently, 0.2575 g of H2Ti3O7 nanowires were ultrasonically dispersed in 60 mL of 0.05 mol / L Ba(OH)2·8H2O aqueous solution, and ultrasonically treated for 30 min. Then, the suspension was vigorously stirred at 500 rpm for 1 h to obtain a suspension. The suspension was transferred to an autoclave reactor and kept at 210 °C for 3 h. After cooling, 0.2 mol / L -1 The product was washed by alternating centrifugation with hydrochloric acid solution, deionized water and anhydrous ethanol until the supernatant was neutral. The obtained precipitate was dried at 80°C for 12h and then ground to obtain BaTiO3 nanomaterials.

[0057] Step 2: Add the prepared BaTiO3 nanomaterial into 30 mL of deionized water and ultrasonically disperse it for 30 minutes. Then quickly add BiCl3 at a molar ratio of BaTiO3 to BiCl3 of 1:6 and ultrasonically disperse it again for 30 minutes. Then, vigorously stir at a speed of 500 rpm for 1 hour, and then centrifuge to obtain a precipitate. After drying the obtained precipitate at 80°C for 12 hours, a BaTiO3 / BiOCl nanocomposite material with a composite ratio of 1:6 can be obtained.

[0058] Preparation of cement-based coating based on BaTiO3 / BiOCl nanocomposite :

[0059] 0.17 g of the prepared BaTiO3 / BiOCl nanocomposite was added to 20 mL of anhydrous ethanol and ultrasonically dispersed for 30 min. Then, 7.5 g of PDMS was added to the suspension and ultrasonically dispersed for another 30 min. Then, the suspension was stirred until the anhydrous ethanol was completely evaporated. Finally, 0.75 g of curing agent was added and stirring was continued until the rotor stopped rotating due to the increased viscosity of the stirring system. The prepared slurry was immediately heated to 0.65 kg / m 2The amount of the mixture was applied to the surface of the cement paste specimen and allowed to stand at room temperature for 24 hours to form a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material on the surface of the cement paste specimen after it was fully dried.

[0060] Comparative Example 1

[0061] Preparation of BaTiO3 Monomer Nanomaterials :

[0062] First, 1.5 g of TiO2 particles were added to 60 mL of 10 mol / L sodium hydroxide aqueous solution, and stirred for 2 h in a magnetic stirrer to obtain a fully dispersed suspension; the suspension was transferred to a high-pressure reactor and kept at 180°C for 12 h; after cooling, deionized water and anhydrous ethanol were used for alternating centrifugal washing 4 times each, and the obtained precipitate was dried at 80°C for 12 h to obtain white powdery Na2Ti3O7 nanowires;

[0063] The obtained Na2Ti3O7 nanowires were immersed in an excess of 0.2 mol / L -1 The mixture was slowly stirred at 300 rpm for 4 h in a hydrochloric acid solution for acidification, and then centrifuged to obtain a precipitate. The precipitate was dried at 80 °C for 12 h to obtain H2Ti3O7 nanowires in the form of white powder.

[0064] Subsequently, 0.2575 g of H2Ti3O7 nanowires were ultrasonically dispersed in 60 mL of 0.05 mol / L Ba(OH)2·8H2O aqueous solution, and ultrasonically treated for 30 min. Then, the suspension was vigorously stirred at 500 rpm for 1 h to obtain a suspension. The suspension was transferred to an autoclave reactor and kept at 210 °C for 3 h. After cooling, 0.2 mol / L -1 The product was washed by alternating centrifugation with hydrochloric acid solution, deionized water and anhydrous ethanol until the supernatant was neutral. The obtained precipitate was dried at 80°C for 12h and then ground to obtain BaTiO3 monomer nanomaterial.

[0065] Preparation of cement-based coating based on BaTiO3 monomer nanomaterials :

[0066] 0.17 g of the prepared BaTiO3 monomer nanomaterial was added to 20 mL of anhydrous ethanol, and after ultrasonic dispersion for 30 min, 7.5 g of PDMS was added to the suspension, and ultrasonic dispersion was continued for another 30 min, and then stirred until the anhydrous ethanol was completely evaporated; finally, 0.75 g of curing agent was added and stirring was continued until the rotor stopped rotating due to the increase in viscosity of the stirring system, and the prepared slurry was immediately heated at 0.65 kg / m 2 Apply the amount of the coating to the surface of the cement paste specimen, let it stand at room temperature for 24 hours to form a coating based on BaTiO3 monomer nanomaterial on the surface of the cement paste specimen after it is fully dried.

[0067] Comparative Example 2

[0068] Preparation of BiOCl Monomer Nanomaterials :

[0069] 3.40 g of BiCl3 was added to 30 mL of deionized water, and the mixture was vigorously stirred at 500 rpm for 1 h. The mixture was then centrifugally washed twice with deionized water and anhydrous ethanol. The resulting precipitate was dried at 80° C. for 12 h to obtain BiOCl monomer nanomaterials.

[0070] Preparation of cement-based coating based on BiOCl monomer nanomaterials :

[0071] 0.17 g of the prepared BiOCl monomer nanomaterial was added to 20 mL of anhydrous ethanol and ultrasonically dispersed for 30 min. Then, 7.5 g of PDMS was added to the suspension and ultrasonically dispersed for another 30 min. Then, the suspension was stirred until the anhydrous ethanol was completely evaporated. Finally, 0.75 g of curing agent was added and stirring was continued until the rotor stopped rotating due to the increased viscosity of the stirring system. The prepared slurry was immediately heated to 0.65 kg / m 2 The amount of the coating was applied to the surface of the cement paste specimen, and allowed to stand at room temperature for 24 hours to form a coating based on BiOCl monomer nanomaterials on the surface of the cement paste specimen after it was fully dried.

[0072] The nanomaterials and coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were characterized for their relevant properties. The relevant characterization methods, instruments, etc. are as follows:

[0073] The crystal structure and micromorphology of the samples were characterized by X-ray diffractometer (copper target, scanning range 3-70°, scanning step length 0.02, Rigaku Corporation, model D / MAX-Ultima IV) and scanning electron microscope (voltage 2kV, Japan HITACHI Company, model Hitachi S4800). The band structure of the samples was tested by LAMBDA750 UV-visible-near infrared spectrophotometer produced by PerkinElmer Co., Ltd. (scanning range 200-800nm). An ultrasonic cleaner (Shanghai Shangpu Instrument Co., Ltd., model SN-QX-32, power 220W) was used to provide mechanical action for the samples to verify their piezoelectric degradation ability. A xenon lamp cold light source (Anhui Langxi Bobei Lighting Appliance Co., Ltd., model BBZM-I, power 300W) was used to simulate sunlight for photocatalytic degradation experiments. The absorbance of the sample photocatalytic degradation experimental solution was tested by UV-visible photometer (Shanghai Yidian Analytical Instrument Co., Ltd., model 721G). The surface morphology of the coating was analyzed by Leica DM6M ultra-depth microscope and the flatness of the coating was analyzed by ultra-depth electron microscope (Keyence, Japan, model VHX-600K). The wetting properties of the coating were evaluated by contact angle meter (Shanghai Zhongchen Digital Technology Equipment Co., Ltd., JC2000DM).

[0074] 2. Catalytic performance test:

[0075] A xenon lamp was used as the simulated light source, an ultrasonic cleaner provided mechanical vibration, and methylene blue MB (10 mg / L) was selected as the target pollutant for degradation.

[0076] For nanomaterial powder samples: weigh 0.05 g of powder sample and put it into 50 mL of 10 mg / L methylene blue solution. Take out 10 mL of the sample every 20 minutes, centrifuge and take the supernatant, and measure the absorbance at a wavelength of 664 nm.

[0077] For coating samples: the coated cement paste specimens were placed in 100 mL of 10 mg / L methylene blue solution; during the photocatalytic degradation process, 10 mL of sample was taken out every hour for absorbance measurement, and during the piezoelectric photocatalysis with mechanical vibration provided by an ultrasonic cleaner, 10 mL of sample was taken out every 20 minutes for absorbance measurement.

[0078] The degradation efficiency η is calculated using the following formula:

[0079] η=[(c0-c t ) / c0]×100%

[0080] Where C0 represents the initial absorbance, C t Represents the absorbance at a certain time.

[0081] Analyze the performance characterization results in combination with the attached figures:

[0082] Figure 1 The X-ray powder diffraction patterns of BaTiO3 / BiOCl nanocomposite materials and BaTiO3 and BiOCl monomer nanomaterials are shown in Figure 1. The diffraction peaks of BaTiO3 and BiOCl are both sharp, and no other impurity peaks appear, which correspond to BaTiO3 (PDF#05-0626) and BiOCl (PDF#06-0249), respectively, indicating that the method of the present invention can be used to prepare BaTiO3 and BiOCl with good crystallinity. All peaks of the BaTiO3 / BiOCl nanocomposite materials are sharp, with narrow half-peak widths, and no other impurity peaks appear, indicating that the samples have high purity and good crystallinity. Obvious diffraction peaks appear at 12.0°, 24.1°, 25.9°, 32.5°, etc., corresponding to the characteristic diffraction peaks of BiOCl (PDF#06-0249); obvious diffraction peaks appear at 20.2°, 31.5°, 38.9°, 56.2°, etc., corresponding to the characteristic diffraction peaks of BaTiO3 (PDF#05-0626), confirming that the samples contain BaTiO3 and BiOCl with good crystallinity.

[0083] Figure 2A and Figure 2B The UV diffuse reflectance and band structure diagrams of BaTiO3 / BiOCl nanocomposites and BaTiO3 and BiOCl monomer nanomaterials are shown respectively. The maximum absorption wavelengths of BaTiO3 / BiOCl nanocomposites with composite ratios of 1:2, 1:4, and 1:6 are 407nm, 401nm, and 395nm, respectively, which are better than the maximum absorption wavelength of pure BiOCl (379nm), but smaller than the maximum absorption wavelength of pure BaTiO3 (414nm). The band gap calculated using the Tauc plot method shows that the band gaps of pure BaTiO3 and BiOCl are 2.86eV and 3.23eV, and the band gaps of BaTiO3 / BiOCl nanocomposites with composite ratios of 1:2, 1:4, and 1:6 are 2.90eV, 2.93eV, and 2.97eV, respectively. Compared with pure BiOCl, the band gap of BaTiO3 / BiOCl nanocomposites is significantly narrowed. This is because BiOCl and BaTiO3 have matching band positions, which in turn promotes the separation of electrons and holes.

[0084] Figure 3A and Figure 3BThe photocatalytic degradation effect diagram and piezoelectric photocatalytic degradation effect diagram of BaTiO3 / BiOCl nanocomposites and BaTiO3 and BiOCl monomer nanomaterials on MB solution are shown respectively. Due to the narrow band gap of BaTiO3, its photocatalytic degradation efficiency (35.2%) is higher than that of BiOCl (25.9%). The photocatalytic degradation efficiency of methylene blue of BaTiO3 / BiOCl nanocomposites with different composite ratios is 60.2%, 57.1% and 51.2%, respectively, which is significantly improved compared with monomers BaTiO3 and BiOCl; among them, when the BaTiO3 / BiOCl composite ratio is 1:2, the sample has the best photocatalytic degradation effect on MB, followed by 1:4, and 1:6 has the worst effect. When light and ultrasonic vibration are applied simultaneously, the piezoelectric photocatalytic degradation efficiencies of pure BaTiO3 and BiOCl are 86.7% and 65.0%, respectively, which are 2.46 times and 2.51 times higher than the degradation efficiencies under light alone, fully demonstrating that the piezoelectrically enhanced photocatalytic degradation effect of BaTiO3 is more significant; the piezoelectrically enhanced photocatalytic degradation efficiencies of BaTiO3 / BiOCl-1:2, BaTiO3 / BiOCl-1:4, and BaTiO3 / BiOCl-1:6 are 94.0%, 81.9%, and 68.1%, respectively, which are 1.45, 1.26, and 1.05 times higher than those of BiOCl monomer materials, respectively, indicating that the composite of the two can effectively improve their piezoelectrically enhanced photocatalytic degradation performance. In addition, compared with the degradation efficiency under light irradiation alone, the piezoelectrically enhanced photocatalytic degradation efficiency of BaTiO3 / BiOCl-1:2, BaTiO3 / BiOCl-1:4, and BaTiO3 / BiOCl-1:6 were also improved by 1.56, 1.43, and 1.33 times, indicating the effectiveness of the piezoelectrically enhanced photocatalytic performance caused by ultrasonic vibration.

[0085] Figure 4A and 4BThey are the ultra-depth-of-field surface images and 3D renderings of the piezoelectrically enhanced photocatalytic coating based on BaTiO3 monomer nanomaterials, the coating based on BiOCl monomer nanomaterials, and the nanocomposite materials based on BaTiO3 and BiCl3 with molar ratios of 1:2, 1:4, and 1:6, respectively. The particles in the coating made by dispersing BaTiO3 in PDMS are of different sizes, and the particles agglomerate together. At the same time, the height of the large particles in the 3D image is relatively high; BiOCl is relatively uniformly dispersed in the matrix, and the particle size is slightly smaller than that of BaTiO3, and the distribution of nanomaterials is denser than that of BaTiO3, but there are no bubbles and agglomerations, and the height difference is relatively small; in the cement-based material coating based on BaTiO3 / BiOCl-1:6, the particles of nanomaterials are getting smaller and smaller, and there is no agglomeration phenomenon. It is observed that the number of large particles decreases, indicating that the reduction of barium titanate makes the composite material particles smaller, indicating that the surface of the coating is smoother; BaTiO3 / BiOCl-1:2 and BaTiO3 / BiOCl-1:4, there is no agglomeration of particles, and the distribution density of nanomaterials is smaller than that of BiOCl, and the particle size of BaTiO3 / BiOCl-1:2 is the largest in the composite material. It can be seen that with the increase of BiOCl dosage, the dispersion between materials can be changed, and its flatness will also be improved.

[0086] Figure 5A , 5BFigures 5 and 5C are the piezoelectric enhanced photocatalytic coatings based on BaTiO3 / BiOCl nanocomposites, coatings based on BaTiO3 monomer nanomaterials, and coatings based on BiOCl monomer nanomaterials for the piezoelectric photocatalytic degradation of MB solution. Due to the narrow band gap of BaTiO3, its photocatalytic degradation efficiency (34.9%) is higher than that of BiOCl (30.3%); the photocatalytic degradation efficiency of methylene blue of BaTiO3 / BiOCl with different composite ratios is 50.1%, 38.8%, and 35.1%, respectively, which is significantly improved compared with monomer BaTiO3 and BiOCl; among them, when the composite ratio is 1:2, the sample has the best photocatalytic degradation effect on MB, followed by 1:4, and the worst effect is 1:6, which is consistent with the effect of the powder. When light and ultrasonic vibration were applied simultaneously, the piezoelectric photocatalytic degradation efficiencies of pure BaTiO3 and BiOCl were 73.3% and 56.8%, respectively, which were 2.10 times and 1.87 times higher than those under light alone, fully demonstrating that the piezoelectric enhanced photocatalytic degradation effect of BaTiO3 was more significant; the degradation efficiencies of BaTiO3 / BiOCl-1:2, BaTiO3 / BiOCl-1:4, and BaTiO3 / BiOCl-1:6 were 98.4%, 84.9%, and 44.9%, respectively, which were 1.73 and 1.87 times higher than those of BiOCl monomer materials. 49 and 0.79 times, the effect of BaTiO3 / BiOCl-1:6 became worse, indicating that with the decrease of BaTiO3 dosage, the degradation efficiency will slow down, but the appropriate dosage of the two can effectively improve their piezoelectric enhanced photocatalytic degradation performance; in addition, compared with the degradation efficiency of light alone, the piezoelectric enhanced photocatalytic degradation efficiency of BaTiO3 / BiOCl-1:2, BaTiO3 / BiOCl-1:4, and BaTiO3 / BiOCl-1:6 was also improved by 1.96, 2.19, and 1.28 times, indicating the effectiveness of the piezoelectric enhanced photocatalytic performance caused by ultrasonic vibration. Figure 5C This is the cyclic stability test result of the cement-based material coating based on BaTiO3 / BiOCl-1:2. As can be seen from the figure, after the coating has been degraded for 5 cycles, its stability still reaches 90%, which fully proves that the coating has good stability.

[0087] Fig. 6A and 6BThe surface wetting performance diagrams of the piezoelectric enhanced photocatalytic coating before and after the degradation of MB solution are respectively based on BaTiO3 monomer nanomaterial coating, BiOCl monomer nanomaterial coating and nanocomposite materials with a molar ratio of BaTiO3 to BiCl3 of 1:2, 1:4 and 1:6. The PDMS coating without nanomaterials shows a certain hydrophobicity, and its contact angle is 101°. When the nanomaterials are dispersed in PDMS, the contact angle of the coating is improved. This is because the addition of nanomaterials forms a certain micro-nano structure on the surface of the coating, resulting in a relative increase in its roughness, thereby improving its hydrophobicity. In order to explore whether its contact angle can stably maintain hydrophobicity, the contact angle of the coating is improved after a piezoelectric photocatalytic degradation experiment. This is mainly because under ultrasonic drive, the nanomaterials inside the coating are gradually squeezed and closer to its surface, which increases the contact area between the internal nanomaterials and the outside world, makes its micro-nano structure more prominent, and further increases the surface roughness, thereby improving its hydrophobicity.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material, characterized in that: The following steps are involved: Step 1: Preparation of BaTiO3 nanomaterials by hydrothermal method: Step 1.1: First, TiO2 particles are added to an excess of 8-12 mol / L NaOH aqueous solution and stirred evenly, then placed in a reactor and kept warm at 160-200°C for 10-14 hours, and after cooling, they are washed alternately by centrifugation with deionized water and anhydrous ethanol for 2-6 times each, and the obtained precipitate is dried to obtain Na2Ti3O7 nanowires; Step 1.2: Soaking the obtained Na2Ti3O7 nanowires in an excess of 0.1-0.3 mol / L HCl solution and stirring for 2-6 hours, then centrifuging to obtain a precipitate, and drying the obtained precipitate to obtain H2Ti3O7 nanowires; Step 1.3: Add the obtained H2Ti3O7 nanowires to an excess of 0.02-0.08 mol / L Ba(OH)2·8H2O aqueous solution, ultrasonically treat for 20-40 min, then stir evenly, put into a reactor and react at 180-240° C. for 2-4 h, and after cooling, use 0.1-0.3 mol / L hydrochloric acid solution, deionized water, and anhydrous ethanol to alternately centrifuge and wash until the supernatant is neutral, dry and grind the obtained precipitate to obtain BaTiO3 nanomaterials; Step 2: preparing BaTiO3 / BiOCl nanocomposite materials: adding the obtained BaTiO3 nanomaterials to excess deionized water and ultrasonically dispersing them for 20 to 40 minutes, then adding BiCl3 at a molar ratio of BaTiO3 to BiCl3 of 1:(2-6) and ultrasonically dispersing them again for 20 to 40 minutes, stirring for 1 to 3 hours, and then centrifuging to obtain a precipitate, and drying the obtained precipitate to obtain the BaTiO3 / BiOCl nanocomposite materials; Step 3: Add the obtained BaTiO3 / BiOCl nanocomposite material to anhydrous ethanol, ultrasonically disperse it for 20 to 40 minutes, then add polydimethylsiloxane thereto, and ultrasonically disperse it for another 20 to 40 minutes, then stir until the anhydrous ethanol is completely evaporated, then add the curing agent and continue stirring until the rotor stops rotating automatically due to the increase in viscosity of the stirring system, and the coating can be obtained, and then the obtained coating is applied to the surface of the substrate material to form a piezoelectric enhanced photocatalytic coating.

2. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: In step 1 and step 2, the drying conditions are both drying at 60-100° C. for 8-16 hours.

3. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: In step 1 to step 3, magnetic stirring is used for stirring.

4. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: The stirring speed in step 1.2 is 200-400 rpm.

5. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: The stirring speed in step 1.3 is 500-700 rpm.

6. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: The stirring speed in step 2 is 500-700 rpm.

7. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: In step 3, the dosage of the BaTiO3 / BiOCl nanocomposite material is 1-5% of the mass of the polydimethylsiloxane.

8. The method for preparing a piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 1, characterized in that: In step 3, the coating amount of the obtained coating on the surface of the substrate material is 0.5-0.8 kg / m 2 .

9. A piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material prepared by the method according to any one of claims 1 to 8.

10. An application of the piezoelectric enhanced photocatalytic coating based on BaTiO3 / BiOCl nanocomposite material according to claim 9, characterized in that: The obtained coating is applied on the surface of cement-based materials to form a piezoelectric enhanced photocatalytic coating.

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