Dual-piezoelectric heterojunction composite material and preparation method and application thereof

Abstract

The invention discloses a dual-piezoelectric heterojunction composite material and a preparation method thereof, and the composite material is prepared by the following steps: dissolving melamine and sodium polyphosphate in deionized water, carrying out hydrothermal reaction to generate a precursor, and then calcining in a nitrogen atmosphere to obtain a P-TCN carrier with high specific surface area and rich active sites; the preparation method comprises the following steps: carrying out ultrasonic dispersion on an ammonium heptamolybdate solution and P-TCN, anchoring Mo7O246 <-> on the surface of a carrier through electrostatic adsorption, adding thiourea, and carrying out a hydrothermal reaction to realize in-situ growth of MoS2 nanosheets on the surface of the P-TCN so as to finally obtain the dual-piezoelectric heterojunction composite material with strong interface interaction. The process is simple and convenient, the cost is low, and the prepared material has high catalytic activity, excellent stability and environmental adaptability and has wide application prospects in the field of antibiotic degradation.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation and environmental catalysis, and particularly relates to a preparation method and application of a dual piezoelectric heterojunction composite material with strong interface interaction. Background Art

[0002] Semiconductor photocatalytic technology is widely used for the treatment of antibiotics in water due to its green, simple, low-cost, and non-toxic properties. However, the efficiency of photocatalytic degradation depends primarily on the separation efficiency of photogenerated charge carriers. Effectively reducing the recombination efficiency of photogenerated charge carriers is a key challenge in improving photocatalytic performance.

[0003] In recent years, piezoelectric catalysis has attracted considerable attention as an emerging catalytic method. It is a promising green environmental remediation technology, where piezoelectric materials absorb widespread mechanical energy (such as ultrasonic vibration or stirring) in the environment to generate a polarized electric field, driving the migration of free electrons and holes to the material surface to degrade pollutants. However, most current piezoelectric composite systems only have a single component with piezoelectric properties, and this component accounts for a very low proportion. The non-piezoelectric portion of the composite material shields the piezoelectric body, preventing the composite from fully utilizing vibration energy and, to a certain extent, limiting the piezoelectric effect.

[0004] MoS2 is an asymmetric transition metal disulfide. Its two-dimensional S-Mo-S layered structure generates a large piezoelectric potential and a large amount of polarized charge under tensile stress, effectively degrading organic molecules and potentially useful for wastewater treatment. However, current research on MoS2 / P-TCN has largely focused on the effects of heterojunction formation on the photocatalytic performance of the composite, while neglecting the influence of piezoelectric properties on carrier mobility. Furthermore, the interaction forces in most MoS2 / P-TCN heterojunctions are primarily weak van der Waals forces, and poor interfacial contact severely hinders carrier mobility between the two phases. Furthermore, the two-dimensional planar structure of MoS2, due to its densely packed thick layers, suffers from poor electron transport and a limited number of surface active sites. Therefore, overcoming these shortcomings in the prior art and constructing composite heterojunction photocatalysts with dual piezoelectric properties and a tightly connected interface to maximize the built-in electric field strength, leverage the heterojunction and piezoelectric properties to promote carrier separation, and obtain catalysts with high catalytic activity and good stability are of great significance for the efficient degradation of antibiotics in water. Summary of the Invention

[0005] The present invention provides a dual piezoelectric heterojunction composite material prepared based on piezoelectric induction, which has a high specific surface area, multiple reaction active sites, a fast reaction rate, and good stability. Correspondingly, a preparation method of the dual piezoelectric heterojunction composite material with strong interfacial interaction, which has the advantages of simple process, convenient operation, low cost, high preparation efficiency, and high yield, is provided. Furthermore, a use of the dual piezoelectric heterojunction composite material in treating antibiotic wastewater is provided.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: 1. Melamine, sodium polyphosphate and deionized water are mixed, and the mixed solution is transferred to a polytetrafluoroethylene autoclave. After heating at 160°C to 180°C for 12 to 24 hours, the solid and liquid are separated, the solid is washed with deionized water and then dried. The dried product is calcined at 450°C to 550°C in a nitrogen atmosphere for 1 to 5 hours to obtain a hollow tubular phosphorus-containing carbonized nitrogen (P-TCN); The mass ratio of melamine to sodium polyphosphate is 1:0.06-0.1; water or anhydrous ethanol is used for washing, and the number of washing times is 3-5 times; 2. Mix the hollow tubular P-TCN ammonium heptamolybdate and deionized water, and then ultrasonicate the Mo7O 24 6- Pre-anchored on the P-TCN surface; then thiourea was added, and after ultrasonic stirring and mixing, the mixture was reacted at 160℃~180℃ for 12h~24h, solid-liquid separation was performed, the solid was washed with deionized water, and dried at 60℃ to obtain a dual piezoelectric heterojunction composite material with strong interfacial interaction.

[0007] The mass ratio of the hollow tubular P-TCN:ammonium heptamolybdate is 1:6-7, and the mass ratio of the hollow tubular P-TCN:thiourea is 1:13-14; 3. The dual piezoelectric heterojunction composite material with strong interfacial interaction prepared by the above method is applied to the degradation of organic pollutants in water by piezoelectric vibration excitation and visible light irradiation. Specifically, the composite material is mixed with organic pollutant wastewater, stirred, and a catalytic degradation reaction is carried out under piezoelectric vibration excitation and visible light irradiation to complete the degradation of organic pollutants in the water; the organic pollutants in the organic pollutant wastewater are antibiotics; the antibiotic is ciprofloxacin.

[0008] Compared with the prior art, the present invention has the following advantages: (1) The present invention addresses the problems of low piezoelectric performance utilization and low carrier migration efficiency in existing photocatalytic materials, and provides a method for preparing a dual piezoelectric heterojunction composite material with strong interfacial interaction. The method combines hydrothermal reaction and calcination to prepare MoS2 / P-TCN composite photocatalytic materials with excellent performance. Specifically, sodium polyphosphate-assisted hydrothermal-thermal polymerization is used to synthesize hollow tubular phosphorus-doped g-C3N4 (P-TCN). Further, an ultrasound-assisted-hydrothermal method is used to in-situ self-assemble and vertically anchor S-defect-rich MoS2 nanosheets on the hollow tubular g-C3N4 to construct a composite photocatalytic material MoS2 / P-TCN with dual piezoelectric properties. The dual piezoelectric system and abundant S vacancies achieve long-lasting and efficient carrier separation and transmission efficiency as well as high reaction activity. Compared with the existing conventional preparation method, in the method of the present invention, MoS2 nanosheets are vertically anchored on the surface of P-doped g-C3N4 tube (PTCN) by piezoelectric induction to form an S-type heterojunction. This structure not only enhances the piezoelectric performance, but also promotes the migration of electrons from PTCN to MoS2 through the built-in electric field, further improving the carrier separation efficiency. The carrier migration efficiency at the heterojunction interface is enhanced by the synergistic effect of the polarization electric field induced by piezoelectricity and the electrostatic interaction. By introducing P doping and S defects, the electron cloud density distribution of the material is optimized, and the electrostatic interaction is further enhanced. The dual piezoelectric heterojunction composite material with strong interfacial interaction obtained by the method of the present invention has the advantages of high specific surface area, many reaction active sites, good catalytic performance, high metal atom utilization rate, etc. It can be widely used in the degradation of organic pollutants (such as antibiotics), and can achieve good degradation effects, and has good application value and application prospects; at the same time, the preparation method of the present invention also has the advantages of simple process, convenient operation, easy availability of raw materials, low cost, easy to realize industrial production, and has great application prospects, especially in the field of environmental catalysis; (2) The bi-piezoelectric heterojunction composite material with strong interfacial interaction prepared by the present invention includes a tubular P-TCN, wherein MoS2 is embedded in the tube wall and the internal pore structure of the tubular P-TCN, and the material is rich in S defects. By simultaneously embedding MoS2 in the tube wall and filling the internal reticular structure of the tubular P-TCN, the large specific surface area of the tubular P-TCN is conducive to suppressing the agglomeration of MoS2; (3) The catalytic material prepared by the present invention degrades ciprofloxacin under visible light irradiation and ultrasonic vibration conditions. By mixing the catalytic material with ciprofloxacin wastewater, stirring, adding visible light and ultrasonic vibration, ciprofloxacin can be effectively degraded. This method has the advantages of simple process, convenient operation, low cost, high treatment efficiency, and good degradation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1Figure 3 is the SEM image of different catalysts, where Figure a is layered carbonized nitrogen, Figure b is hollow tubular P-TCN, Figure c is N-MoS2 catalyst, Figure d is the composite material MoS2 / P-TCN, and Figure e is the MoS2 / CN catalyst; Figure 2 XRD patterns of different catalysts; Figure 3 The full XPS spectra of different catalysts; Figure 4 Schematic diagram of the efficiency of different catalysts in degrading ciprofloxacin under different conditions, where Figure a is under light irradiation, Figure b is under ultrasonic vibration, and Figure c is light irradiation + ultrasonic vibration; Figure 5 The degradation rate constant fitting diagram of ciprofloxacin degradation under light irradiation and ultrasonic vibration conditions is shown in Figure 2. Figure 6 This is a graph showing the number of cycles-degradation efficiency of the composite material MoS2 / P-TCN in Example 1 for degradation of ciprofloxacin. DETAILED DESCRIPTION

[0010] The present invention will be further described below with reference to the examples. However, the scope of the present invention is not limited to the following examples. Those skilled in the art will appreciate that various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. The instruments, reagents, and materials involved in the following examples, unless otherwise specified, are conventional instruments, reagents, and materials already available in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, are conventional experimental methods and detection methods already available in the prior art.

[0011] Example 1: Preparation of a bi-piezoelectric heterojunction composite material with strong interfacial interaction 1. Dissolve 6.00 g of melamine and 0.50 g of sodium polyphosphate in 70 mL of deionized water, and stir at a constant speed at 25 ° C for 3 h to obtain a uniform mixed solution; transfer the mixed solution to a 100 mL polytetrafluoroethylene autoclave, keep it at 180 ° C for 12 h, and after natural cooling, filter it. After the solid is rinsed with water 5 times, it is dried at 60 ° C for 4 h to obtain a supramolecular precursor; put the supramolecular precursor into a crucible, wrap the crucible with tin foil, and place it in a tube furnace under nitrogen protection. Heat it to 550 ° C at a heating rate of 2.5 ° C / min, and keep it at 550 ° C for 4 h. After natural cooling, take it out to obtain a light yellow powder sample, that is, P-TCN; SEM image of P-TCN is shown in Figure 1 b, it can be seen from the figure that P-TCN is a hollow tubular structure; its XRD pattern is shown in Figure 2Compared with CN, the diffraction peak of the (002) plane of P-TCN has a shift of 27.5 to 27.4°. This is due to the fact that the radius of the P atom (110 pm) is larger than that of the replaced C atom (77 pm), which proves that the hollow tubular P-TCN is successfully prepared. Pure CN (C3N4) catalyst was prepared by adding 6.0 g of melamine to a covered alumina crucible, which was then transferred to a muffle furnace and calcined at 550°C for 4 hours at a heating rate of 2.5°C / min. After cooling, the product was collected and ground to obtain yellow powder CN. 2. Dissolve 0.10 g of P-TCN and 0.618 g of ammonium heptamolybdate in 70 mL of deionized water, ultrasonicate for 30 minutes to adsorb molybdate ions on the surface of P-TCN, add 1.340 g of thiourea, continue ultrasonication for 30 minutes, stir at a constant speed at 25 ° C for 6 hours, and hydrothermally react the mixture at 180 ° C for 16 hours. After natural cooling, filter, rinse the solid with deionized water 5 times, and vacuum dry at 60 ° C for 12 hours to obtain a dual piezoelectric heterojunction composite material (MoS2 / P-TCN) with strong interfacial interaction; SEM image of MoS2 / P-TCN is shown in Figure 1 d, it can be seen from the figure that MoS2 is distributed on the inner and outer walls of the hollow tubular P-TCN, and its XRD pattern is shown in Figure 2 It can be seen from the figure that the characteristic peak of carbonized nitrogen in the graphite phase is obviously retained. Figure 3 The full scan XPS images of P-TCN and MoS2 / P-TCN show the presence of C, N, Mo, S, P, and O, indicating the successful doping of P. The successful combination of P-TCN and MoS2 indicates the successful preparation of a dual piezoelectric heterojunction composite material with strong interfacial interaction. Comparative Example 1: Preparation of N-MoS2 catalyst 1.340 g of thiourea, 0.618 g of ammonium heptamolybdate, and 70 mL of deionized water were mixed and stirred at a constant speed at 25 ° C for 6 h. The mixed solution was ultrasonicated and placed in a polytetrafluoroethylene-lined high-pressure reactor. The mixture was sealed and placed in an oven for hydrothermal reaction at 180 ° C for 12 h. After natural cooling, the mixture was filtered, the solid was rinsed with water 5 times, and vacuum dried at 60 ° C for 12 h to obtain N-MoS2 catalyst ( Figure 1 c); its XRD pattern is shown in Figure 2 ,It can be seen from the figure that its peak corresponds one to one with MoS2 (commercially available, PDF#37-1492), proving that N-MoS2 was successfully prepared.

[0012] Comparative Example 2: The P-TCN prepared in step 1 of Example 1 was used as the catalyst of Comparative Example 1; Comparative Example 3: Preparation of MoS2 / CN Catalyst 2 g of melamine was dissolved in 70 mL of deionized water and stirred at a constant speed at 25 ° C for 3 h to obtain a uniform mixed solution; the mixed solution was transferred to a 100 mL autoclave and kept at 180 ° C for 12 h. After natural cooling, it was filtered, the solid was rinsed with water 5 times, and dried at 60 ° C for 4 h to obtain a supramolecular precursor. The supramolecular precursor solid was placed in a crucible, and the crucible was wrapped with tin foil. It was placed in a tube furnace under nitrogen protection and heated to 550 ° C at a heating rate of 2.5 ° C / min and kept at 550 ° C for 4 h. After natural cooling, it was taken out to obtain a yellow powder sample, which is layered carbon nitride ( Figure 1 a), 0.1 g of layered carbon nitrogen, 1.340 g of thiourea, 0.618 g of ammonium heptamolybdate and 80 mL of deionized water were mixed and stirred at 25 °C for 6 h. The mixture was hydrothermally reacted at 180 °C for 12 h. After natural cooling, the mixture was filtered. The solid was rinsed with water 5 times and then vacuum dried at 60 °C for 12 h to obtain MoS2 / CN catalyst ( Figure 1 e), XRD pattern see Figure 2 , proving that MoS2 / CN was successfully prepared.

[0013] Example 2: Treatment of antibiotic wastewater with catalysts from Example 1, Comparative Examples 1-3, pure CN catalyst, and commercially available MoS2 6 mg of each of the dual piezoelectric heterojunction composite material of Example 1, the N-MoS2 catalyst of Comparative Example 1, the hollow tubular P-TCN of Comparative Example 2, and the MoS2 / CN catalyst of Comparative Example 3 were weighed and placed in 30 mL of a 50 mg / L ciprofloxacin (CIP) solution. A ciprofloxacin solution without any catalyst was also prepared as a blank control. The above reaction system was placed under light irradiation (500W xenon lamp CEL-LB70), ultrasound (ultrasound frequency 40kHz), and light irradiation + ultrasound conditions respectively; See the results Figure 4 The results showed that the removal rates of ciprofloxacin in the blank control were only 3.1% (light irradiation), 5.2% (ultrasound irradiation) and 7.7% (light irradiation + ultrasound irradiation) in 60 min, indicating that CIP has high stability in the environment.

[0014] Compared with other catalysts, the composite material MoS2 / P-TCN of the present invention exhibited high catalytic performance in both photocatalytic and piezoelectric catalytic systems, with CIP degradation rates of 72.1% and 81.6% within 60 minutes, respectively. Under the conditions of light irradiation and ultrasound, MoS2 / P-TCN showed the highest piezoelectric photocatalytic performance within 60 minutes, with a CIP degradation rate of 96.6% ( Figure 4c), which are higher than CN (16.1%), MoS2 (77.4%), PTCN (43.3%), N-MoS2 (58.8%), and MoS2 / CN (88.6%).

[0015] The degradation rate constant fitting diagram of ciprofloxacin degradation by the above catalyst is shown in Figure 5 From the figure, it can be seen that the rate of degradation of ciprofloxacin by the dual piezoelectric heterojunction composite material with strong interfacial interaction is several times or even dozens of times that of other catalysts, which more intuitively illustrates the excellent performance of the composite material.

[0016] Example 3: Stability Experiment of Bi-piezoelectric Heterojunction Composite Material with Strong Interfacial Interaction 1. 30 mg of the piezoelectric material with strong electrostatic interaction prepared in Example 1 was placed in 30 mL of a 50 mg / L ciprofloxacin solution and subjected to a catalytic degradation reaction for 60 min under the action of light and ultrasonic vibration to complete the degradation of organic pollutants in the water, completing one cycle; 2. The reaction system in step 1 was filtered, and the composite material was washed five times with deionized water, dried at 60° C. for 4 h, and repeatedly used for the degradation of ciprofloxacin for a total of five cycles; See the results Figure 6 The figure shows that the composite material of the present invention can still degrade 92.0% of ciprofloxacin after five cycles, demonstrating the excellent stability of the catalyst. This indicates that a bi-piezoelectric heterojunction composite material with strong interfacial interactions is highly stable and has strong activation performance.

Claims

1. A method for preparing a bi-piezoelectric heterojunction composite material, characterized in that: Melamine, sodium polyphosphate and deionized water are mixed and stirred to obtain a mixed solution. The mixed solution is heated at 160°C to 180°C for 12 hours to 24 hours, and then the solid and liquid are separated. The solid is washed with deionized water and then dried. The dried product is calcined at 450°C to 550°C in a nitrogen atmosphere to obtain a hollow tubular phosphorus-containing carbonized nitrogen. The hollow tubular phosphorus-containing carbonized nitrogen, ammonium heptamolybdate and deionized water are mixed and subjected to ultrasonic treatment to remove Mo7O 24 6- Pre-anchored on the P-TCN surface; then adding thiourea, ultrasonically stirring and mixing, the mixture is reacted at 160℃~180℃ for 12h~24h, solid-liquid separation, the solid is washed with deionized water, and dried to obtain a dual piezoelectric heterojunction composite material with strong interfacial interaction.

2. The method for preparing a bi-piezoelectric heterojunction composite material according to claim 1, wherein: The mass ratio of melamine to sodium polyphosphate is 1:0.06-0.1, the mass ratio of hollow tubular phosphorus-containing carbonized nitrogen to ammonium heptamolybdate is 1:6-7, and the mass ratio of hollow tubular phosphorus-containing carbonized nitrogen to thiourea is 1:13-14.

3. A bi-piezoelectric heterojunction composite material obtained by the preparation method of the bi-piezoelectric heterojunction composite material according to any one of claims 1 to 2.

4. Use of the dual piezoelectric heterojunction composite material according to claim 3 in treating antibiotic wastewater.

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