A piezoelectric photocatalytic composite material and its preparation method and application

Abstract

The invention discloses a piezoelectric photocatalytic composite material and a preparation method and application thereof, belonging to the field of photocatalysts. Preparation method: SnCl4·5H2O is added to deionized water and stirred, and the pH value of the solution is adjusted to 10.0-12.0; Zn(CH3COO)2·2H2O is added to the above solution, centrifuged after stirring, washed, and dried; the dried solid is ground into powder, placed in a furnace for calcination to obtain ZnSnO3 nanocubes; ZnSnO3 nanocubes, SnCl4·5H2O and InCl3·4H2O are dispersed in ethanol, and then thioacetamide is added, and a homogeneous solution is formed after continuous stirring; subsequently, the homogeneous solution is subjected to a hydrothermal reaction, and the reactant is filtered after cooling, washed, dried, and ground to obtain a piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8. The ZnSnO3 / SnIn4S8 piezoelectric photocatalytic system realizes effective pollutant degradation, and has the characteristics of good stability and reusability.

Description

Technical Field

[0001] The invention belongs to the field of photocatalysts, and in particular relates to a piezoelectric photocatalytic composite material and a preparation method and application thereof. Background Art

[0002] The development of new catalytic technologies is urgent. Piezoelectric catalysis is an emerging catalytic technology based on the piezoelectric potential and piezoelectric properties of catalysts. Its application in energy conversion, organic synthesis and environmental remediation has aroused unprecedented research enthusiasm. It mainly uses the piezoelectric properties of materials to collect mechanical energy such as vibration, friction, natural wind and tides, and then directly combines it with the catalytic reaction process to produce the conversion of mechanical energy and chemical energy.

[0003] In previous reports, piezoelectric materials such as ZnSnO3, ZnO and BaTiO3 have shown obvious piezoelectric-driven catalytic activity for pollutant decomposition. However, how to improve piezoelectric catalytic activity is an urgent task. Therefore, it is possible to try to combine piezoelectric catalysis with other technologies to stimulate their synergistic effects. In the development of photocatalytic technology, people have successfully proposed and implemented a variety of methods such as piezoelectric-photocatalytic coupling, noble metal doping, and synthetic hybrid materials to slow down the carrier recombination velocity and improve catalytic activity.

[0004] In catalytic reactions, the long-range ordered driving force generated by coupling piezoelectric potential and optical properties can regulate the separation and transport of photogenerated carriers (electron-hole pairs) on the surface and in the bulk phase, thereby enhancing its performance. On the other hand, piezoelectric potential can lead to the accumulation / depletion of charges inside the semiconductor and the adsorption of external polar molecules or ions at both ends of the potential, resulting in band rearrangement. The main contribution of piezoelectric potential to photocatalysis is to inhibit the combination of electron-hole pairs and extend the carrier lifetime. External mechanical stress for piezoelectric catalysis is mainly achieved through ultrasonic treatment, ball milling stirring, mechanical stirring or exposure to natural motion (such as wind, tides and water flow).

[0005] ZnSnO3 is a member of the perovskite family, composed of zinc (Zn), tin (Sn) and oxygen (O) ions. The perovskite structure of ZnSnO3 has unique properties, including high stability, tunable band gap and excellent photocatalytic activity, and its band gap is about 3.8-4.1eV. Due to its superior stability compared with zinc oxide and tin oxide, excellent optical properties, high electron mobility, high conductivity, etc., it has attracted much attention among n-type semiconductor materials. However, piezoelectric catalysts often face disadvantages such as weak stress sensitivity, low carrier concentration, fast charge recombination rate, and lack of active sites, which greatly inhibit the catalytic activity of piezoelectric catalysts.

[0006] SnIn4S8 is an n-type semiconductor sulfide with a cubic spinel structure. In recent years, SnIn4S8 has attracted widespread attention due to its suitable band gap, high stability and strong visible light absorption ability. As a typical ternary sulfide semiconductor, it is considered to be an ideal photocatalyst due to its large specific surface area, high stability, low cost and strong absorption ability of visible light, and has therefore attracted widespread attention from researchers. In addition, the narrow band gap (about 2.2eV) and negative conduction band potential of SnIn4S8 make it widely used in the construction of heterojunctions. Therefore, based on the principles of piezoelectric electronics and piezoelectric optoelectronics, the construction of composite piezoelectric photocatalysts can adjust the effective Schottky barrier near the contact position by forming polarized charges on the surface of the material through piezoelectric potential. For composite piezoelectric photocatalysts that are both piezoelectric and photoactive, due to the charge screening effect, a large number of electron-hole pairs will be generated once excited by light, thereby greatly improving the catalytic activity.

[0007] Therefore, developing a heterojunction catalytic material with piezoelectric effect, higher interface charge separation efficiency, simple preparation method, better stability, reusability, and piezoelectric photocatalytic degradation of organic pollutants will be the key research goal of this field of technology. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a piezoelectric photocatalytic composite material to prepare a heterojunction catalytic material with piezoelectric effect, higher interface charge separation efficiency, simple preparation method, better stability, reusability, and piezoelectric photocatalytic degradation of organic pollutants.

[0009] Another object of the present invention is to provide a piezoelectric photocatalytic composite material.

[0010] The third object of the present invention is to provide an application of a piezoelectric photocatalytic composite material.

[0011] The technical solution of the present invention is: (one)

[0013] A method for preparing a piezoelectric photocatalytic composite material comprises the following steps:

[0014] A. Preparation of ZnSnO3 nanocubes by precipitation method: First, SnCl4·5H2O is added to deionized water and stirred, and an appropriate amount of acid or alkali is added to adjust the pH value of the solution to 10.0-12.0; then, an appropriate amount of Zn(CH3COO)2·2H2O is added to the above solution, magnetically stirred and centrifuged, washed with deionized water, and dried; finally, the dried solid is ground into powder and placed in a furnace for calcination to obtain ZnSnO3 nanocubes;

[0015] B. ZnSnO3 nanocubes, SnCl4·5H2O and InCl3·4H2O were dispersed in ethanol by magnetic stirring, and then an appropriate amount of thioacetamide (TAA) was added and stirred continuously to form a homogeneous solution. Subsequently, the homogeneous solution was transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction. After the reactants were cooled, they were filtered, washed with deionized water and ethanol, dried and ground to obtain the piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8.

[0016] As a further improvement of the present invention, in step A, the mass ratio of SnCl4·5H2O to Zn(CH3COO)2·2H2O is 1-2:1.

[0017] As a further improvement of the present invention, in step A, the drying temperature is 60-80° C., and the drying time is 12-24 hours.

[0018] As a further improvement of the present invention, in step A, calcination is carried out in a box furnace, the temperature is increased to 500-600° C. at a heating rate of 5-10° C. / min, and the calcination is maintained for 2-4 hours.

[0019] As a further improvement of the present invention, in step B, the mass ratio of ZnSnO3 nanocubes, SnCl4·5H2O and InCl3·4H2O is 0.5-1:0.3:1.

[0020] As a further improvement of the present invention, in step B, the mass ratio of thioacetamide (TAA) to InCl3·4H2O is 0.6-0.7:1.

[0021] As a further improvement of the present invention, in step B, the temperature of the hydrothermal reaction is 150-170° C., and the time of the hydrothermal reaction is 10-14 h.

[0022] As a further improvement of the present invention, in step B, the drying temperature is 60-80° C., and the drying time is 12-24 hours. (two)

[0024] A piezoelectric photocatalytic composite material is prepared by the preparation method of the piezoelectric photocatalytic composite material.

[0025] Among them, ZnSnO3 has an asymmetric crystal structure, which can induce the catalyst to produce piezoelectric properties. Its close contact with SnIn4S8 can construct a type-Ⅱ heterojunction, further promoting the effective separation of photogenerated carriers. (three)

[0027] The invention discloses an application of a piezoelectric photocatalytic composite material in piezoelectric photocatalytic degradation of organic pollutants in wastewater.

[0028] Organic pollutants in wastewater include but are not limited to atrazine, bisphenol A, carbamazepine, tetracycline, and rhodamine b. Preferably, the composite material ZnSnO3 / SnIn4S8 of the present invention has an exceptionally excellent degradation effect on atrazine under piezoelectric photocatalytic conditions. On the one hand, due to the insufficient visible light absorption of ZnSnO3, it cannot be excited by visible light. Therefore, in the composite material ZnSnO3 / SnIn4S8, only SnIn4S8 can generate photogenerated electrons and photogenerated holes. The matching energy level position enables the photogenerated electrons of the SnIn4S8 conduction band to be transferred across the heterojunction interface to the ZnSnO3 valence band. This type-II charge transfer mechanism greatly promotes carrier separation and avoids the in-situ recombination of photogenerated electron-hole pairs on the surface of the SnIn4S8 material. On the other hand, under the mechanical stress of ultrasonic vibration, the piezoelectric catalytic material ZnSnO3 generates a unidirectional polarized electric field, resulting in the formation of a polarized charge layer at the contact interface between the piezoelectric catalytic material ZnSnO3 and the photocatalytic material SnIn4S8, and inducing the bending of the surface energy band of the piezoelectric catalytic material ZnSnO3, thereby further inducing the migration of electrons from SnIn4S8 to ZnSnO3. The electron cross-interface transfer will effectively inhibit the recombination of electron-hole pairs, thereby significantly improving the charge separation efficiency. In short, the piezoelectric material ZnSnO3, as an electron acceptor, has an energy band bending under the action of mechanical stress, making it easier to accept photogenerated electrons from SnIn4S8. Compared with the traditional type-Ⅱ heterojunction, the energy band bending caused by the Fermi level is small, and the built-in electric field is weak. The ZnSnO3 / SnIn4S8 heterojunction of the present invention significantly improves the carrier migration rate across the heterojunction interface, and ultimately causes the pollutants to be oxidized by surface active oxygen or hydroxyl groups and holes, and finally generates water and carbon dioxide.

[0029] The beneficial effects of the present invention are:

[0030] The present invention discloses a piezoelectric photocatalytic composite material and a preparation method thereof. ZnSnO3 and SnIn4S8 are composited by constructing a heterojunction to construct a piezoelectric photocatalytic nanocomposite material, namely ZnSnO3 / SnIn4S8, which has a piezoelectric effect, a stronger interface carrier separation capability, a wider visible light absorption range, and a higher catalytic activity. The non-centrosymmetric structure of the perovskite oxide ZnSnO3 gives it unique piezoelectric properties, but this property is often ignored by researchers, resulting in its potential as a piezoelectric body not being fully utilized, and a single piezoelectric material has weak stress sensitivity, low carrier concentration, and a fast charge recombination rate. SnIn4S8 is a semiconductor catalytic material with an optical absorption cutoff edge of about 580nm and a narrow band gap, but the charge separation efficiency of a single material is low. The present invention composites ZnSnO3 and SnIn4S8, and successfully realizes the separation of photogenerated electron-hole pairs of ZnSnO3 / SnIn4S8 composite piezoelectric photocatalytic nanomaterials at the heterojunction interface, avoiding the electron-hole recombination problem in the band gap of a single SnIn4S8 catalytic nanomaterial. Under the action of external mechanical stress, the piezoelectric material ZnSnO3 is polarized and a piezoelectric potential difference is generated, so that the electrons in the photoexcited state of SnIn4S8 are transferred to the ZnSnO3 conduction band across the heterojunction interface. When the piezoelectric effect is combined with photocatalysis, the polarized charges in the piezoelectric material induce the generation of a polarized electric field, which can promote the migration and separation of photogenerated charges. The heterojunction interface charge separation and electron transfer are more effectively enhanced by the construction of the heterojunction, greatly improving the photocatalytic activity. Finally, the ZnSnO3 / SnIn4S8 piezoelectric photocatalytic system achieves effective pollutant degradation, and has the characteristics of good stability and reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of ZnSnO3 / SnIn4S8 prepared in Example 1 of the present invention;

[0032] Figure 2 The ultraviolet diffuse reflectance spectra of ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 and Comparative Examples 1 and 2 of the present invention;

[0033] Figure 3 Fourier diffuse reflectance infrared spectra of ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 and Comparative Examples 1 and 2 of the present invention;

[0034] Figure 4 The butterfly amplitude loop and phase hysteresis loop of ZnSnO3 / SnIn4S8 prepared in Example 1 of the present invention;

[0035] Figure 5This is a performance comparison chart of the piezoelectric photocatalytic degradation of atrazine by ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 of the present invention and Comparative Examples 1 and 2;

[0036] Figure 6 This is a degradation diagram of the reusability experiment of atrazine degradation by piezoelectric photocatalysis of ZnSnO3 / SnIn4S8 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific implementation modes.

[0038] Embodiment 1,

[0039] A method for preparing a piezoelectric photocatalytic composite material, characterized by comprising the following steps:

[0040] A. Preparation of ZnSnO3 nanocubes by precipitation method: First, 0.94 g SnCl4·5H2O was added to 60 mL deionized water and stirred for 15 minutes, and an appropriate amount of hydrochloric acid (concentration of 0.1 M) or sodium hydroxide (concentration of 0.1 M) was added to adjust the pH value of the solution to 12; then, 0.5932 g Zn(CH3COO)2·2H2O was added to the above solution, magnetically stirred at 600 r / min for 15 minutes, centrifuged, washed with deionized water, and dried in an oven at 60°C for 24 h; finally, the dried solid was ground into powder, placed in a box furnace and heated to 580°C at a heating rate of 5°C / min, kept calcined for 2 hours, and cooled to room temperature to obtain ZnSnO3 nanocubes;

[0041] B. 0.8 g ZnSnO3 nanocubes, 0.2629 g SnCl4·5H2O and 0.8805 g InCl3·4H2O were dispersed in ethanol by magnetic stirring (600 r / min, 30 min), and then 0.5625 g thioacetamide (TAA) was added and stirred for 30 min to form a homogeneous solution; then, the homogeneous solution was transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction at 160 °C for 12 h; after the reactants were cooled, they were filtered, washed with deionized water and ethanol, dried in an oven at 60 °C for 24 h, and ground to obtain the piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8.

[0042] Figure 1 This is a scanning electron microscope image of ZnSnO3 / SnIn4S8 prepared in this example. Figure 1 As shown, the ZnSnO3 / SnIn4S8 composite photocatalytic nanomaterial is a stacked nanosheet structure, and some nanosheets interact with each other to form nanoflowers, which is conducive to the formation of heterojunction and the enhancement of charge separation and photocatalytic activity.

[0043] Comparative Example 1

[0044] Preparation of ZnSnO3 catalyst only:

[0045] First, 0.94 g SnCl4·5H2O was added to 60 mL deionized water and stirred for 15 minutes, and an appropriate amount of hydrochloric acid (concentration of 0.1 M) or sodium hydroxide (concentration of 0.1 M) was added to adjust the pH value of the solution to 12; then, 0.5932 g Zn(CH3COO)2·2H2O was added to the above solution, magnetically stirred at 600 r / min for 15 minutes and then centrifuged, washed with deionized water, and dried in an oven at 60°C for 24 hours; finally, the dried solid was ground into powder, placed in a box furnace and heated to 580°C at a heating rate of 5°C / min, maintained for calcination for 2 hours, and cooled to room temperature to obtain ZnSnO3 nanocubes.

[0046] Comparative Example 2

[0047] Preparation of SnIn4S8 catalyst only:

[0048] 0.2629 g SnCl4·5H2O and 0.8805 g InCl3·4H2O were dispersed in ethanol by magnetic stirring (600 r / min, 30 min), and then 0.5625 g thioacetamide (TAA) was added and stirred for 30 min to form a homogeneous solution; then, the homogeneous solution was transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction at 160 °C for 12 h; after the reactant was cooled, it was filtered, washed with deionized water and ethanol, dried in an oven at 60 °C for 24 h, and ground to obtain the product SnIn4S8.

[0049] Embodiment 2,

[0050] A method for preparing a piezoelectric photocatalytic composite material, characterized by comprising the following steps:

[0051] A. Preparation of ZnSnO3 nanocubes by precipitation method: First, 0.6 g SnCl4·5H2O was added to 60 mL deionized water and stirred for 15 minutes, and an appropriate amount of hydrochloric acid (concentration of 0.1 M) or sodium hydroxide (concentration of 0.1 M) was added to adjust the pH value of the solution to 11; then, 0.6 g Zn(CH3COO)2·2H2O was added to the above solution, magnetically stirred at 600 r / min for 15 minutes, centrifuged, washed with deionized water, and dried in an oven at 60°C for 24 h; finally, the dried solid was ground into powder, placed in a box furnace and heated to 600°C at a heating rate of 8°C / min, kept calcined for 4 hours, and cooled to room temperature to obtain ZnSnO3 nanocubes;

[0052] B. 0.5 g ZnSnO3 nanocubes, 0.2629 g SnCl4·5H2O and 0.8805 g InCl3·4H2O were dispersed in ethanol by magnetic stirring (600 r / min, 30 min), and then 0.5283 g thioacetamide (TAA) was added and stirred for 30 min to form a homogeneous solution; then, the homogeneous solution was transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction at 150 °C for 14 h; after the reactants were cooled, they were filtered, washed with deionized water and ethanol, dried in an oven at 60 °C for 24 h, and ground to obtain the piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8.

[0053] Embodiment 3,

[0054] A method for preparing a piezoelectric photocatalytic composite material, characterized by comprising the following steps:

[0055] A. Preparation of ZnSnO3 nanocubes by precipitation method: First, 1.2 g SnCl4·5H2O was added to 60 mL deionized water and stirred for 15 minutes, and an appropriate amount of hydrochloric acid (concentration of 0.1 M) or sodium hydroxide (concentration of 0.1 M) was added to adjust the pH value of the solution to 10; then, 0.6 g Zn(CH3COO)2·2H2O was added to the above solution, magnetically stirred at 600 r / min for 15 minutes, centrifuged, washed with deionized water, and dried in an oven at 80°C for 12 h; finally, the dried solid was ground into powder, placed in a box furnace and heated to 500°C at a heating rate of 10°C / min, kept calcined for 3 hours, and cooled to room temperature to obtain ZnSnO3 nanocubes;

[0056] B. 0.4403 g ZnSnO3 nanocubes, 0.2629 g SnCl4·5H2O and 0.8805 g InCl3·4H2O were dispersed in ethanol by magnetic stirring (600 r / min, 30 min), and then 0.6163 g thioacetamide (TAA) was added and stirred for 30 min to form a homogeneous solution; then, the homogeneous solution was transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction at 170 °C for 10 h; after the reactants were cooled and filtered, washed with deionized water and ethanol, dried in an oven at 80 °C for 12 h, and ground to obtain the piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8.

[0057] 1. Evaluation of piezoelectric-photocatalytic degradation performance

[0058] The piezoelectric-photocatalytic degradation performance of the catalysts prepared in Example 1 and Comparative Examples 1 and 2 was evaluated as follows:

[0059] Mechanical vibration was provided by an ultrasonic cleaner (40 kHz, 100 W, Jielimei, Kunshan, China), and sunlight irradiation was simulated by a 300 W xenon lamp (λ>420 nm, Beijing Zhongjiao Jinyuan Technology Co., Ltd.). Before irradiation, a solution (100 mL) containing the catalyst (0.1 g / L) and atrazine (ATZ) (5 mg / L) was placed in a beaker and mechanically stirred for 30 min in the dark to reach adsorption-desorption equilibrium. The beaker was then placed in an ultrasonic cleaner, and ultrasonic vibration (US) and simulated sunlight (SL) were turned on. Ice bags were placed in the ultrasonic cleaner to keep the temperature at around 25 ± 5 °C. At given time intervals, 1 mL of the solution was taken and immediately filtered with a 0.22 μm syringe filter for detection. The concentration of atrazine (ATZ) was measured by HPLC (Shimadzu, LC-16) with an Agilent SB-C18 column (2.1 mm × 100 mm, 1.8 μm) and a UV detector at 225 nm. The mobile phase was methanol and ultrapure water in a volume ratio of 50:50. The relative concentration (C / C0) was used to calculate the degradation efficiency.

[0060] Figure 2 The UV diffuse reflectance spectra of ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 and Comparative Examples 1 and 2 are shown in FIG. Figure 2 As shown in the figure, the light absorption cutoff edge of ZnSnO3 is about 390nm, indicating that it only absorbs in the ultraviolet region and cannot effectively utilize more visible light. The light absorption cutoff edge of SnIn4S8 is about 580nm, and has a weak absorption tail peak, indicating that it has full visible spectrum absorption. For ZnSnO3 / SnIn4S8, the two form a complementary light absorption, which is conducive to improving the overall visible light capture efficiency.

[0061] Figure 3 The Fourier diffuse reflectance infrared spectra of ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 and Comparative Examples 1 and 2 are shown in Figure 1. For ZnSnO3, due to the symmetrical stretching vibration of the zinc oxide group and the tin oxide group, the nanoparticles have a wavelength of 581 cm −1 A broad absorption peak appears near 1103cm, which can be attributed to the Sn-O-Zn bond of ZnSnO3 material. −1 and 1721cm −1 can be assigned to CH and C=O bonds respectively. −1 The broad peak at 1386 cm-1 is attributed to the OH stretching vibration caused by water adsorption on the surface. −1 The peak at 3482 cm −1and 1589cm −1 The broad peak at belongs to the OH stretching vibration caused by water absorption on the surface. In addition, the main typical absorption peaks of the original ZnSnO3 and SnIn4S8 are present in the ZnSnO3 / SnIn4S8 sample, which further indicates the successful synthesis of the ZnSnO3 / SnIn4S8 piezoelectric photocatalyst.

[0062] Figure 4 The butterfly amplitude loop and phase hysteresis loop of ZnSnO3 / SnIn4S8 prepared in Example 1 of the present invention. For ZnSnO3 / SnIn4S8, the piezoelectric coefficient calculated from the amplitude-voltage curve is 0.56 nm / V, indicating that the material has certain piezoelectric properties. This shows that the ZnSnO3 / SnIn4S8 composite material can drive piezoelectric catalytic reactions.

[0063] Figure 5 The performance comparison diagram of the piezoelectric photocatalytic degradation of atrazine by ZnSnO3 / SnIn4S8, ZnSnO3, and SnIn4S8 prepared in Example 1 of the present invention and Comparative Examples 1 and 2. The experimental results show that when the catalyst dosage is 0.1 g / L, the initial concentration of atrazine is 5 mg / L, and the initial temperature is room temperature, when only relying on ultrasonic vibration to provide external mechanical stress to simulate piezoelectric catalysis (without light), the degradation rate of atrazine by single ZnSnO3 is only 16.83%, which indicates that the internal polarization electric field formed by the asymmetric center induced by external mechanical stress causes electrons to be quickly transferred to the surface of the pollutant, which indicates that ZnSnO3 has certain piezoelectric properties. In contrast, the degradation rate of atrazine by single SnIn4S8 under ultrasonic vibration simulated piezoelectric catalysis is only 5.67%, which means that the single SnIn4S8 material does not have piezoelectric properties. Under the action of piezoelectric and visible light, the degradation rates of atrazine by single ZnSnO3 and SnIn4S8 were 19.57% and 64.81%, respectively, which indicates that single ZnSnO3 cannot effectively utilize visible light, and its catalytic degradation activity is similar to that under piezoelectric catalysis. Single SnIn4S8 can further induce the generation of photogenerated electron-hole pairs under photocatalysis, thereby accelerating the degradation efficiency of pollutants, but the removal effect is poor due to the rapid in-situ recombination of carriers. Under the action of piezoelectric-visible light catalysis, the degradation efficiency of ZnSnO3 / SnIn4S8 composite materials for pollutants reached 96.7% within 30 minutes, which indicates that photogenerated electrons migrate rapidly across heterogeneous interfaces under the action of polarized electric fields, further accelerating the degradation efficiency of pollutants. At the same time, in the absence of light, the degradation efficiency of ZnSnO3 / SnIn4S8 composite materials for pollutants is only 27.44%, which means that the composite material cannot achieve good degradation of atrazine by piezoelectric catalysis alone.

[0064] 2. Continuous degradation experiment

[0065] After the first degradation reaction of ZnSnO3 / SnIn4S8 prepared in Example 1 is completed, the post-reaction solution is centrifuged and washed, and the recovered catalyst is dried in a freeze dryer for 48 hours, and then put into the reactor again for the next degradation experiment. Except for the materials, the other degradation reaction conditions are consistent with the first photocatalytic degradation performance evaluation experiment setting procedure; after the second reaction is completed, the above steps are repeated to carry out three degradation experiments.

[0066] Figure 6 The degradation diagram of the reusability experiment of atrazine degradation by piezoelectric photocatalysis of ZnSnO3 / SnIn4S8 prepared in Example 1 of the present invention. After the first degradation reaction is completed, the catalyst is washed with water, centrifuged and freeze-dried for 48 hours, and then put into the reactor again for the next atrazine removal reaction. Except for the material, the other reaction conditions are consistent with the first time; after the second reaction is completed, the above steps are repeated to carry out the third degradation experiment. A total of three degradation experiments were carried out. In three consecutive degradation experiments, the atrazine degradation efficiency was above 90%, which indicates that the photocatalytic activity of the ZnSnO3 / SnIn4S8 piezoelectric photocatalytic nanomaterial remains good after three cycles.

Claims

1. A method for preparing a piezoelectric photocatalytic composite material, characterized in that The following steps are involved: A. Preparation of ZnSnO3 nanocubes by precipitation method: First, SnCl4·5H2O is added to deionized water and stirred, and the pH value of the solution is adjusted to 10.0-12.0; then, Zn(CH3COO)2·2H2O is added to the above solution, stirred, centrifuged, washed, and dried; finally, the dried solid is ground into powder, and placed in a furnace for calcination to obtain ZnSnO3 nanocubes; B. Disperse ZnSnO3 nanocubes, SnCl4·5H2O and InCl3·4H2O in ethanol, then add thioacetamide and continue stirring to form a homogeneous solution; then, subject the homogeneous solution to a hydrothermal reaction, and after the reactants are cooled, filter, wash, dry and grind to obtain a piezoelectric photocatalytic composite material ZnSnO3 / SnIn4S8.

2. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step A, the mass ratio of SnCl4·5H2O to Zn(CH3COO)2·2H2O is 1-2:

1.

3. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step A, the drying temperature is 60-80° C. and the drying time is 12-24 hours.

4. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step A, calcination is carried out in a box furnace, the temperature is increased to 500-600° C. at a heating rate of 5-10° C. / min, and the calcination is maintained for 2-4 hours.

5. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step B, the mass ratio of ZnSnO3 nanocubes, SnCl4·5H2O and InCl3·4H2O is 0.5-1:0.3:

1.

6. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step B, the mass ratio of thioacetamide to InCl3·4H2O is 0.6-0.7:

1.

7. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step B, the temperature of the hydrothermal reaction is 150-170° C., and the time of the hydrothermal reaction is 10-14 h.

8. The method for preparing a piezoelectric photocatalytic composite material according to claim 1, characterized in that: In step B, the drying temperature is 60-80°C and the drying time is 12-24 hours.

9. A piezoelectric photocatalytic composite material, characterized in that: The piezoelectric photocatalytic composite material is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the piezoelectric photocatalytic composite material according to claim 9 in piezoelectric photocatalytic degradation of organic pollutants in wastewater.

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