In2O3 / BiVO4 heterojunction piezoelectric material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of piezoelectric materials, and particularly relates to an In2O3 / BiVO4 heterojunction piezoelectric material as well as a preparation method and application thereof. The In2O3 / BiVO4 heterojunction piezoelectric material is prepared by taking soluble In salt and BiVO4 as raw materials, glucose as a dispersing agent and urea as a structure-directing agent through hydrothermal reaction. In the In2O3 / BiVO4 heterojunction piezoelectric material obtained by the method, In2O3 and BiVO4 form a heterojunction, the BiVO4 improves the photo-induced electron transition capability of the main substance In2O3 and generates more. OH,. O2 <-> and < 1 > O2, the oxidation reduction capability of degradation of refractory organic pollutants is improved through generated free radicals, and the technical defects of the In2O3 / BiVO4 heterojunction piezoelectric material without the heterojunction in the prior art are overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric materials, and in particular relates to an In2O3 / BiVO4 heterojunction piezoelectric material and a preparation method and application thereof. Background Art

[0002] Currently, the emerging refractory pollutants include perfluorooctane sulfonic acid and its salts (PFOS), phenols, antibiotics, microplastics, and polychlorinated biphenyl compounds. Most of these pollutants are persistent, bioaccumulative, and multi-toxic, affecting multiple organs of the human body, destroying the ecological balance, and increasing human health risks, such as allergies, carcinogenicity, and drug-resistant bacteria. The main reason why refractory pollutants are difficult to degrade is their chemical structure, which is complex, has stable chemical bonds, and is highly fat-soluble. For example, phenol compounds are difficult to degrade because of the stable structure and strong fat solubility caused by chlorine atoms. These emerging refractory pollutants pose a continuous and severe challenge to the environment and human health, and more effective governance measures are urgently needed.

[0003] Traditional methods of degrading emerging difficult-to-degrade pollutants, such as biodegradation, are easily restricted by environmental factors and have limited ability to degrade complex pollutants; advanced oxidation technologies (Fenton method, ozone oxidation method) have problems of secondary pollution, high cost, and low ozone utilization rate; activated carbon adsorption method is only the transfer of pollutants, with the risk of secondary pollution and high regeneration cost; photocatalytic oxidation method has high recombination rate of photogenerated carriers and limited light response range; the electrodes of electrochemical oxidation method are prone to passivation corrosion, and the maintenance and replacement costs are high. To supplement the above-mentioned deficiencies in existing technologies, piezoelectric photocatalytic technology came into being. As an important semiconductor material, In2O3 has become a research hotspot due to its excellent performance in the field of piezoelectric photocatalysis.

[0004] In recent years, many researchers have found that bismuth vanadate with a band gap energy of 2.4 eV has a high light response ability in the visible light region and can photodegrade organic pollutants under visible light conditions. It is a photocatalyst with great potential uses. Based on this, the existing technology uses In2O3 and BiVO4 to prepare In2O3 / BiVO4 composite materials.

[0005] In terms of preparation methods, the existing technologies either often require the use of more complicated preparation processes, such as high-temperature calcination and doping modification, in order to obtain an indium oxide heterojunction with good performance; or fail to obtain an indium oxide heterojunction.

[0006] Starting from the In2O3 / BiVO4 composite material without a heterojunction, there are the following defects: when a heterojunction is not formed, in order to achieve the high catalytic performance of the In2O3 / BiVO4 composite material, the existing technology needs to add a large amount of In2O3, and the preparation cost of In2O3 is high, which makes the cost of the obtained In2O3 / BiVO4 composite material high, affecting the large-scale application of the In2O3 / BiVO4 composite material; when a heterojunction is not formed, the charge transfer efficiency between the two is low, which limits the effective transfer of photogenerated carriers between the surface of the In2O3 / BiVO4 composite material and the reactants; when a heterojunction is not formed, indium oxide and bismuth vanadate themselves have the defect that photogenerated electrons and holes are easy to recombine, resulting in a decrease in the number of effective carriers that can participate in the redox reaction, thereby reducing the photocatalytic efficiency; when a heterojunction is not formed, the light absorption of indium oxide is mainly concentrated in the ultraviolet light region, and although the light absorption range of bismuth vanadate is relatively wide, the absorption and utilization efficiency of visible light still needs to be improved. Summary of the invention

[0007] In view of the shortcomings of the above-mentioned prior art, the present invention provides an In2O3 / BiVO4 heterojunction piezoelectric material and a preparation method and application thereof. The present invention uses soluble In salt and BiVO4 as raw materials, glucose as a dispersant, and urea as a structure directing agent to prepare the In2O3 / BiVO4 heterojunction piezoelectric material by hydrothermal reaction. In the In2O3 / BiVO4 heterojunction piezoelectric material obtained by the method of the present invention, In2O3 and BiVO4 form a heterojunction, and BiVO4 improves the photogenerated electron transition ability of the main substance In2O3, generating more ·OH, ·O2 - , 1 O2, through the generated free radicals to improve the redox ability of degradation of difficult-to-degrade organic pollutants, overcome the technical defects of the existing In2O3 / BiVO4 composite materials without heterojunction.

[0008] In order to solve the above-mentioned prior art problems, the present invention adopts the following technical solutions:

[0009] The preparation method of In2O3 / BiVO4 heterojunction piezoelectric material comprises the following steps:

[0010] Soluble In salt, glucose and urea are mixed in water, and then BiVO4 is added thereto to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction. During the hydrothermal process, In2O3 / BiVO4 piezoelectric material is obtained. Glucose acts as a reducing agent and has reducing properties, which can reduce In 3+Reduced to low-valent indium ions, thereby promoting the formation of In2O3, while glucose is used as a dispersant to enhance the dispersibility of In2O3 and prevent particle agglomeration; urea plays the role of a structure-directing agent. The addition of urea plays a good role in promoting the control of reaction temperature. The gas produced by the decomposition of urea can form bubbles in the reaction system. These bubbles act as soft templates. The size and shape of the bubbles limit the spatial range of heterojunction growth. The interface between the bubbles and the solution is an important area for heterojunction growth, and In2O3 / BiVO4 heterojunction piezoelectric materials are obtained; it plays a structural guiding role in the growth of At the same time, the preparation process of In2O3 / BiVO4 heterojunction piezoelectric materials generates heat to avoid excessive heating that causes solution instability and generates phase change products, which affects the piezoelectric properties of In2O3 / BiVO4 heterojunction piezoelectric materials.

[0011] Preferably, the molar ratio of soluble In salt, glucose and urea is 0.5-1.5:1:1.

[0012] Preferably, in the mixed solution, the molar ratio of BiVO4 to soluble In salt is 1:7.5-22.5.

[0013] Preferably, the conditions for the hydrothermal reaction are: heating at 100-180° C. for 8-14 h.

[0014] Preferably, BiVO4 is prepared according to the following steps:

[0015] Bi(NO3)3·5H2O and HNO3 solution are mixed to obtain a first mixed solution, NH4VO3 and NaOH solution are mixed to obtain a second mixed solution, after the first mixed solution and the second mixed solution are mixed, the pH is adjusted to 3-12, and then hydrothermally reacted at 140-200°C for 8-24h, and after cooling, washed alternately with ethanol and deionized water for 3 times, dried at 60°C for 12h, and stored away from light to obtain BiVO4.

[0016] The role of HNO3 is to prevent the hydrolysis of Bi(NO3)3·5H2O, adjust the acidity of the solution, improve the solubility of Bi(NO3)3·5H2O, and serve as an oxidant and catalyst for the reaction; the role of NaOH is to promote the dissolution and dispersion of vanadium, remove the interference of ammonium ions, and adjust the pH value.

[0017] The present invention also protects the In2O3 / BiVO4 heterojunction piezoelectric material prepared by the above preparation method.

[0018] Preferably, in the In2O3 / BiVO4 heterojunction piezoelectric material, In2O3 and BiVO4 form a heterojunction.

[0019] The present invention also protects the application of In2O3 / BiVO4 heterojunction piezoelectric materials in the preparation of materials for degradation of refractory organic pollutants.

[0020] Preferably, the refractory organic pollutants are selected from 2,4-dichlorophenol (2,4-DCP), polychlorinated biphenyls (PCBs), dioxins (PCDD), benzyl hexachloride (BHC), DDT (DDT), and perfluorooctanoic acid (PFOA).

[0021] Preferably, the application method is: mixing the refractory organic pollutants with the In2O3 / BiVO4 heterojunction piezoelectric material, and then performing photocatalytic degradation under light conditions.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the present invention, under hydrothermal conditions, a soluble In salt, a precursor of In2O3, and BiVO4 are chemically reacted in an aqueous solution. At this time, the soluble In salt first undergoes a hydrolysis reaction under the hydrothermal conditions, and In 3+ The ions react with water to form indium hydroxide In(OH)3 and H + Ions, the generated indium hydroxide is unstable, and further dehydration condensation reaction will occur. Multiple indium hydroxide molecules combine with each other by removing water molecules, gradually forming larger aggregates or crystal nuclei. As the hydrolysis and dehydration condensation reactions proceed, the concentration of indium oxide in the reaction system gradually increases. When it reaches an oversaturated state, it will precipitate from the solution in the form of crystal nuclei. At the same time, during the hydrothermal reaction, the gas produced by the decomposition of urea can form bubbles in the reaction system. These bubbles can serve as soft templates. The size and shape of the bubbles limit the spatial range of heterojunction growth. The interface between the bubbles and the solution is an important area for heterojunction growth, forming the corresponding In2O3 / BiVO4 precipitation, and realizing the compounding of the two during the precipitation process, and forming the In2O3 / BiVO4 heterojunction at the same time.

[0024] 2. The present invention promotes the formation of Schottky barriers by regulating the hydrothermal reaction conditions and raw material dosage ratio in the preparation process of In2O3 / BiVO4 heterojunction piezoelectric materials, realizes the directional transition of heterojunction energy levels, and inhibits the recombination of electron-hole pairs, thereby enhancing the degradation ability of In2O3 / BiVO4 heterojunction for organic pollutants.

[0025] 3. The energy band structures of In2O3 and BiVO4 of the present invention are different. When they contact to form a heterojunction, energy band bending occurs at the interface, thereby generating a built-in electric field. This provides a driving force for the separation and transfer of photogenerated carriers, effectively reducing the recombination of photogenerated carriers. In2O3 and BiVO4 have different band gaps. Their composite heterojunction can broaden the light absorption range, enabling it to absorb light of a wider wavelength, generate more photogenerated carriers, and provide a stronger redox ability for the degradation of organic matter.

[0026] 4. In2O3 and BiVO4 have some specific active sites on their surfaces, which can adsorb and activate oxygen molecules, making them more easily converted into highly oxidizing active oxygen species, such as superoxide radicals (·O2 - ) and hydroxyl radicals (·OH) and singlet oxygen ( 1 O2). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 In the figure, (a) is the SEM image of In2O3, (b) is the SEM image of BiVO4, and (c) is the SEM image of 40mg-INBV of Example 2.

[0028] Figure 2 In the figure, (a) is a free radical scavenging rate diagram of 40mg-INBV of Example 2, (b) is an EPR spectrum diagram of ·OH, and (c) is 1 EPR spectrum of O2, (d) is O2 - EPR spectrum of .

[0029] Figure 3 Diagram of the charge transfer mechanism at the interface of In2O3 / BiVO4 heterojunction piezoelectric materials in photocatalysis and piezoelectric photocatalysis systems.

[0030] Figure 4 In the figure, (a) is a photocatalytic degradation diagram of 2,4-dichlorophenol by In2O3 of comparative example 1, 20 mg-INBV of example 1, 40 mg-INBV of example 2 and 60 mg-INBV of example 3; (b) is a cyclic degradation diagram of 2,4-dichlorophenol by In2O3 of comparative example 1, 20 mg-INBV of example 1, 40 mg-INBV of example 2 and 60 mg-INBV of example 3.

[0031] Figure 5 This is a graph showing the overall degradation efficiency of In2O3, BiVO4 and 40mg-INBV from Example 2 on 2,4-dichlorophenol. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0033] The present invention uses soluble In salt and BiVO4 as raw materials, glucose as a dispersant, and urea as a structure directing agent to prepare In2O3 / BiVO4 heterojunction piezoelectric materials by hydrothermal reaction. The present invention overcomes the technical problems existing in the preparation of indium oxide heterojunctions in the prior art, and also overcomes the technical defects of the In2O3 / BiVO4 composite materials that do not contain heterojunctions in the prior art by forming heterojunctions, as shown below:

[0034] In In2O3 / BiVO4 composite materials without heterojunctions, In2O3 and BiVO4 are simply combined together, and the charge transfer efficiency of a single indium oxide or bismuth vanadate material is low, which limits the effective transfer of photogenerated carriers between the surface of the In2O3 / BiVO4 composite material and the reactants. The construction of a heterojunction can improve the path and rate of charge transfer, accelerate the migration of photogenerated carriers to the surface of the In2O3 / BiVO4 heterojunction piezoelectric material, and improve the charge transfer efficiency, thereby accelerating the kinetics of the photocatalytic reaction and enhancing the photocatalytic degradation of pollutants.

[0035] The preparation cost of indium oxide is relatively high. The present invention prepares In2O3 / BiVO4 heterojunction piezoelectric material, which improves efficiency while reducing the amount of indium oxide used, thereby saving costs.

[0036] In order to obtain an indium oxide heterojunction with good performance, the prior art often needs to adopt a relatively complex preparation process, such as high-temperature calcination and doping modification. The method of the present invention is only a hydrothermal method, which is relatively simple and has low requirements on equipment.

[0037] Indium oxide and bismuth vanadate have defects that photogenerated electrons and holes are easy to recombine, resulting in a reduction in the number of effective carriers that can participate in the redox reaction, thereby reducing the photocatalytic efficiency. The present invention constructs an In2O3 / BiVO4 heterojunction to form a built-in electric field, promotes the separation of photogenerated carriers, reduces the recombination probability of electrons and holes, and improves the efficiency of the photocatalytic reaction.

[0038] The light absorption of indium oxide is mainly concentrated in the ultraviolet region, while the light absorption range of bismuth vanadate is relatively wide, but the absorption and utilization efficiency of visible light still needs to be improved. After In2O3 and BiVO4 form a heterojunction, the light absorption range is broadened and the utilization rate of visible light is improved.

[0039] The technical solution of the present invention is studied using embodiments and comparative examples below, and the specific research methods and results are as follows:

[0040] Example 1

[0041] The preparation method of In2O3 / BiVO4 heterojunction piezoelectric material comprises the following steps:

[0042] S1. Synthesis of BiVO4:

[0043] 4.8507 g of Bi(NO3)3·5H2O was added to 30 mL of 4 mol / L HNO3 solution and magnetically stirred for 24 h. 1.1796 g of NH4VO3 was added to 30 mL of 4 mol / L NaOH solution and magnetically stirred for 24 h. The two solutions were then mixed and stirred for 5 h. The pH of the mixed solution was adjusted to 9.0, and magnetic stirring was continued for 3 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 180°C for 12 h, washed alternately with ethanol and deionized water for 3 times after cooling, dried at 60°C for 12 h, and stored in the dark to obtain BiVO4.

[0044] S2. Synthesis of In2O3 / BiVO4 heterojunction piezoelectric materials:

[0045] 0.6 g of InCl3, 2.42 g of glucose and 0.85 g of urea were added to 40 mL of deionized water, ultrasonicated for 1 h and then stirred for 3 h to obtain a mixed solution, 20 mg of BiVO4 was added to the mixed solution, and then transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 150°C for 12 h, cooled and washed alternately with ethanol and deionized water for 3 times, and dried at 70°C for 12 h to obtain In2O3 / BiVO4 heterojunction piezoelectric material. At this time, the molar ratio of In2O3 to BiVO4 was 22.5 mmol:1 mmol, recorded as 20 mg-INBV.

[0046] Example 2

[0047] The preparation method of the In2O3 / BiVO4 heterojunction piezoelectric material is the same as the preparation steps of Example 1, except that in step S3, the mass of BiVO4 is replaced from 20 mg to 40 mg, and includes the following steps:

[0048] S1. Synthesis of BiVO4:

[0049] 4.8507 g of Bi(NO3)3·5H2O was added to 30 mL of 4 mol / L HNO3 solution and magnetically stirred for 24 h. 1.1796 g of NH4VO3 was added to 30 mL of 4 mol / L NaOH solution and magnetically stirred for 24 h. The two solutions were then mixed and stirred for 5 h. The pH of the mixed solution was adjusted to 9.0, and magnetic stirring was continued for 3 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 180°C for 12 h, washed alternately with ethanol and deionized water for 3 times after cooling, dried at 60°C for 12 h, and stored in the dark to obtain BiVO4.

[0050] S2. Synthesis of In2O3 / BiVO4 heterojunction piezoelectric materials:

[0051] 0.6 g of InCl3, 2.42 g of glucose and 0.85 g of urea were added to 40 mL of deionized water, ultrasonicated for 1 h and then stirred for 3 h to obtain a mixed solution, 40 mg of BiVO4 was added to the mixed solution, and then transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 150°C for 12 h, cooled and washed alternately with ethanol and deionized water for 3 times, and dried at 70°C for 12 h to obtain In2O3 / BiVO4 heterojunction piezoelectric material. At this time, the molar ratio of In2O3 to BiVO4 was 11 mmol:1 mmol, recorded as 40 mg-INBV.

[0052] Example 3

[0053] The preparation method of the In2O3 / BiVO4 heterojunction piezoelectric material is the same as the preparation steps of Example 1, except that in step S3, the mass of BiVO4 is replaced from 20 mg to 60 mg, and includes the following steps:

[0054] S1. Synthesis of BiVO4:

[0055] 4.8507 g of Bi(NO3)3·5H2O was added to 30 mL of 4 mol / L HNO3 solution and magnetically stirred for 24 h. 1.1796 g of NH4VO3 was added to 30 mL of 4 mol / L NaOH solution and magnetically stirred for 24 h. The two solutions were then mixed and stirred for 5 h. The pH of the mixed solution was adjusted to 9.0, and magnetic stirring was continued for 3 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 180°C for 12 h, washed alternately with ethanol and deionized water for 3 times after cooling, dried at 60°C for 12 h, and stored in the dark to obtain BiVO4.

[0056] S2. Synthesis of In2O3 / BiVO4 heterojunction piezoelectric materials:

[0057] 0.6 g of InCl3, 2.42 g of glucose and 0.85 g of urea were added to 40 mL of deionized water, ultrasonicated for 1 h and then stirred for 3 h to obtain a mixed solution, 60 mg of BiVO4 was added to the mixed solution, and then transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 150°C for 12 h, cooled and washed alternately with ethanol and deionized water for 3 times, and dried at 70°C for 12 h to obtain In2O3 / BiVO4 heterojunction piezoelectric material. At this time, the molar ratio of In2O3 to BiVO4 was 7.5 mmol:1 mmol, recorded as 60 mg-INBV.

[0058] Example 4

[0059] The preparation method of In2O3 / BiVO4 heterojunction piezoelectric material comprises the following steps:

[0060] S1. Synthesis of BiVO4:

[0061] 4.8507 g of Bi(NO3)3·5H2O was added to 30 mL of 4 mol / L HNO3 solution and magnetically stirred for 24 h. 1.1796 g of NH4VO3 was added to 30 mL of 4 mol / L NaOH solution and magnetically stirred for 24 h. The two solutions were then mixed and stirred for 5 h. The pH of the mixed solution was adjusted to 3.0, and magnetic stirring was continued for 3 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 200°C for 8 h, and washed alternately with ethanol and deionized water for 3 times after cooling. The solution was dried at 60°C for 12 h and stored in the dark to obtain BiVO4.

[0062] S2. Synthesis of In2O3 / BiVO4 heterojunction piezoelectric materials:

[0063] 3.1 g of InCl3, 2.42 g of glucose and 0.85 g of urea were added to 40 mL of deionized water, ultrasonicated for 1 h and then stirred for 3 h to obtain a mixed solution, 200 mg of BiVO4 was added to the mixed solution, and then transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 110°C for 14 h, cooled and washed alternately with ethanol and deionized water for 3 times, and dried at 70°C for 12 h to obtain In2O3 / BiVO4 heterojunction piezoelectric material.

[0064] Example 5

[0065] The preparation method of In2O3 / BiVO4 heterojunction piezoelectric material comprises the following steps:

[0066] S1. Synthesis of BiVO4:

[0067] 4.8507 g of Bi(NO3)3·5H2O was added to 30 mL of 4 mol / L HNO3 solution and magnetically stirred for 24 h. 1.1796 g of NH4VO3 was added to 30 mL of 4 mol / L NaOH solution and magnetically stirred for 24 h. The two solutions were then mixed and stirred for 5 h. The pH of the mixed solution was adjusted to 12.0, and magnetic stirring was continued for 3 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 140°C for 14 h, washed alternately with ethanol and deionized water for 3 times after cooling, dried at 60°C for 12 h, and stored in the dark to obtain BiVO4.

[0068] S2. Synthesis of In2O3 / BiVO4 heterojunction piezoelectric materials:

[0069] 4.65 g of InCl3, 2.42 g of glucose and 0.85 g of urea were added to 40 mL of deionized water, ultrasonicated for 1 h and then stirred for 3 h to obtain a mixed solution, 200 mg of BiVO4 was added to the mixed solution, and then transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heated at 180°C for 8 h, cooled and washed alternately with ethanol and deionized water for 3 times, and dried at 70°C for 12 h to obtain In2O3 / BiVO4 heterojunction piezoelectric material.

[0070] Comparative Example 1

[0071] The preparation method of In2O3 piezoelectric material comprises the following steps:

[0072] Add 0.6 g of InCl3, 2.42 g of glucose and 0.85 g of urea into 40 mL of deionized water, first ultrasonicate for 30 min and then stir for 1 h to obtain a mixed solution, transfer the mixed solution to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, heat at 150°C for 12 h, cool and wash alternately with ethanol and deionized water for 3 times, dry at 70°C for 12 h, and store in a dark place to obtain In2O3.

[0073] In Examples 1 to 5 of the present invention, In2O3 / BiVO4 heterojunction piezoelectric materials with excellent photocatalytic degradation performance for difficult-to-degrade organic pollutants are prepared. The In2O3 / BiVO4 heterojunction piezoelectric materials of Examples 1 to 3 are used as examples for research, and compared with In2O3 and BiVO4. The specific research methods and results are as follows:

[0074] from Figure 1 (a) shows that In2O3 is a cluster nanorod structure with a rod diameter of about 1 to 1.5 μm. Figure 1(b) shows that BiVO4 has a relatively regular block structure with a length of about 3μm and a width of 150-400nm. Figure 1 (c) It can be seen that a heterojunction can be observed between In2O3 and BiVO4, and the rod-shaped In2O3 is uniformly aggregated on the BiVO4 nanoblocks, indicating that In2O3 and BiVO4 are successfully combined to form a heterogeneous structure.

[0075] The formation of the S-type heterojunction was identified by free radical capture experiments and EPR (electron paramagnetic resonance) tests. EPR was used to study the generated free radicals. In the experiment, sodium oxalate (Na-OA) was used as the hole (h + ) quencher, p-benzoquinone (PBQ) as a superoxide radical (·O2 - ) quencher, L-histidine (L-Hist) as a singlet oxygen ( 1 O2) as a quencher, and isopropyl alcohol (IPA) as a quencher for hydroxyl radicals (·OH). Figure 2 As shown in (a), after adding the quencher to the system, the degradation performance of 2,4-dichlorophenol (2,4-DCP) was inhibited in all cases. It is worth noting that the system with PBQ added had the lowest degradation rate of 2,4-DCP, which was 48.53%, significantly lower than the 91.18% of the original system, indicating that the degradation rate of ·O2 - The effect is greater. In order: OH, 1 O2 and H + , the removal rates were 52.02%, 52.53% and 63.58% respectively. Figure 2 As shown in (b) to (d), except for the dark condition, obvious EPR signal peaks were observed in the three systems, with typical signal ratios of 1:2:2:1 corresponding to ·OH and 1:1:1:1 corresponding to ·O2 - , O2 - The OH may come from the conduction band of BiVO4 on the 40mg-INBV heterojunction, and the OH may come from the valence band of In2O3 on the 40mg-INBV heterojunction. Due to the rapid depletion of photogenerated holes, the separation efficiency of charge carriers is significantly improved. These results indicate that 40mg-INBV has enhanced redox ability and the electron transfer pathway follows an S-type mechanism.

[0076] Figure 3 Ⅰ shows that since the Fermi level of BiVO4 is higher than that of In2O3, when the two materials come into contact, electrons are reallocated until the Fermi levels of the two materials reach equilibrium, such as Figure 3As shown in Ⅱ, electrons transfer from BiVO4 to In2O3, resulting in the accumulation of electrons in In2O3 causing the energy band to bend downward, while holes migrate from In2O3 to BiVO4, resulting in the accumulation of holes in BiVO4 causing the energy band to bend upward. At the same time, due to the accumulation of electrons and holes, a built-in electric field pointing from BiVO4 to In2O3 is generated. Figure 3 The Ⅲ indicates that in an independent photocatalytic system, when stimulated by light, through the interaction of the built-in electric field, the Coulomb attraction between carriers and the energy band bending, both BiVO4 and In2O3 are excited to generate photogenerated electrons and holes. The electrons generated in the conduction band of In2O3 combine with the holes in the valence band of BiVO4, and the electrons migrate from the conduction band of BiVO4 to the conduction band of In2O3, and the holes migrate from the valence band of In2O3 to the valence band of BiVO4. This is the Type-Ⅱ heterojunction transfer in the traditional mode. However, the conduction band potential of In2O3 (0.1eV) is lower than that of O2 / ·O2 - The redox potential (-0.33 eV) of BiVO4 is still positive, so it is not conducive to the generation of superoxide radicals. Similarly, the valence band of BiVO4 (1.42 eV) is smaller than the redox potential of -OH / ·OH (1.90 eV), so it is not conducive to the generation of ·OH. Therefore, this heterojunction does not conform to the Type-Ⅱ heterojunction charge transfer path, causing them to transfer through the S-scheme heterojunction pathway, such as Figure 3 shown in IV.

[0077] Switching from type II to type S heterojunction provides a higher energy platform for the transition electrons of the main material, thereby achieving the generation of oxygen free radicals and improving the piezoelectric photocatalytic activity of In2O3 / BiVO4 heterojunction piezoelectric materials; Figure 3 As shown in Ⅳ, in the S-type heterojunction formed by the present invention, the valence band of In2O3 (2.42eV) is greater than the redox potential of -OH / ·OH (1.90eV), so the holes accumulated in the valence band are conducive to the generation of ·OH. The conduction band of BiVO4 (-0.71eV) is greater than that of O2 / ·O2 - The redox potential (-0.33 eV) is still negative, so the electrons accumulated in the conduction band of BiVO4 are conducive to the generation of ·O2 - Therefore, the S-scheme charge transfer mechanism in 40mg-INBV explains the - , 1 O2 is the source of these active species in the ultrasound-mediated photocatalytic system. The concentration of active oxygen is enhanced under piezoelectric light conditions, which is confirmed by EPR studies. - , 1 In the piezoelectric photocatalytic degradation system of O2 and holes, the removal rate of 2,4-DCP was significantly improved.

[0078] 0.5 g / L In2O3, 20 mg-INBV, 40 mg-INBV and 60 mg-INBV were used for photocatalytic degradation of 2,4-DCP respectively. The degradation reaction method was as follows: 10 mg / L 2,4-DCP was photocatalytically degraded under simulated sunlight (300 W xenon lamp) and ultrasonic (100 W, 45 kHz) conditions. Figure 4 (a) The results show that under the same piezoelectric photocatalytic conditions, the degradation efficiency of 40mg-INBV for 2,4-DCP is much higher than that of single material In2O3, 20mg-INBV and 60mg-INBV, and the degradation rate is 0.02678min -1 The degradation efficiency can reach 91.08%, which is 1.65 times that of the In2O3 material alone.

[0079] The present invention also conducts a cycle experiment, wherein the In2O3, 20mg-INBV, 40mg-INBV and 60mg-INBV after degradation are first filtered, then washed alternately with deionized water and ethanol for 3 times, and then placed in a drying oven at 70°C for drying for 12 hours. After grinding, 0.5g / L of In2O3, 20mg-INBV, 40mg-INBV or 60mg-INBV are respectively placed in 10mg / L of 2,4-DCP, and 4 cycle tests are carried out. Figure 4 (b) The results show that 20mg-INBV, 40mg-INBV and 60mg-INBV all have excellent cyclic stability.

[0080] Figure 5 This is the overall degradation efficiency diagram. The results show that in a single piezoelectric catalytic system, the degradation efficiency of pure In2O3 is 32.48%, and the degradation efficiency of pure BiVO4 is 24.59%; in a single photocatalytic system, the degradation efficiency of pure In2O3 is 32.48%, and the degradation efficiency of pure BiVO4 is 24.59%; in the piezoelectric photocatalytic system, In2O3 / BiVO4 exhibits the highest catalytic activity, degrading about 91.08% of 2,4-DCP within 60 minutes, which is 1.6 and 2.17 times that of pure In2O3 and pure BiVO4, respectively.

[0081] The present invention uses 50 mg of 40 mg-INBV of Example 2, which can achieve a high degradation rate for 10 mg / L 2,4-dichlorophenol in 60 min, saving the amount of In2O3 and improving the degradation rate; compared with other prior art heterojunction photocatalysts, the 40 mg-INBV of the present invention has the highest degradation efficiency for the target pollutant 2,4-DCP, and the results are shown in Table 1.

[0082] Table 1 Piezoelectric photodegradation performance of different heterojunction photocatalysts

[0083]

[0084] [1]M.Wang,M.Zhang,Z.Wen,C.Li,S.Zhao,J.Ma,Y.Liao,X.Li,Optimizedpreparation ofnitrogen-modified ceria for stable and efficient degradationof2,4-DCP,Journal ofEnvironmental Chemical Engineering,12(2024).

[0085] [2]Y.Chen,R.Su,F.Wang,W.Zhou,B.Gao,Q.Yue,Q.Li,In-situ synthesis ofCuS@carbon nanocomposites and application in enhanced photo-fentondegradation of2,4-DCP,Chemosphere,270(2021)129295.

[0086] [3]H.Zhang,Y.Tang,J.Han,L.Tian,Y.Cao,Z.Zhang,Z.Wei,Z.Wu,Y.Zhu,Q.Guo,Efficient degradation of 2,4-DCP by activated molecular oxygen with theintroduction ofoxygen vacancies in bismuth molybdate catalysts,MolecularCatalysis,564(2024).

[0087] [4]L.Tu,Y.Hou,G.Yuan,Z.Yu,S.Qin,Y.Yan,H.Zhu,H.Lin,Y.Chen,S.Wang,Bio-photoelectrochemcial system constructed with BiVO4 / RGO photocathode for 2,4-dichlorophenol degradation:BiVO4 / RGO optimization,degradation performance andmechanism,J Hazard Mater,389(2020)121917.

[0088] [5]W.Feng,J.Fang,L.Zhang,S.Lu,S.Wu,C.Cheng,Y.Chen,Y.Ling,Z.Fang,Plasmonic metallic Bi deposited Bi 12 SiO 20 crystals with rich oxygen vacanciesfor enhanced photocatalytic degradation of RhB and 2,4-DCP,Materials ResearchBulletin,94(2017)45-53.

[0089] [6]X.Gu,J.Mei,J.Lai,S.Lv,J.Yang,S.Cui,S.Chen,Synthesis ofZ-Schemeheterojunction ZnNb2O6 / g-C3N4 nanocomposite as a high efficient photo-catalystfor the degradation of 2,4-DCP under simulated sunlight,Materials ResearchBulletin,130(2020).

[0090] [7] Q.Jing, Z.Liu,

[0091] [8] X. Sun, T. Xu, T.

[0092] In addition, most of the technical problems solved by the composite materials based on In2O3 in the prior art are photocatalytic degradation, photocatalytic hydrogen production, and CO2 fixation applications. The present invention applies the new semiconductor material based on In2O3 to the piezoelectric photocatalytic degradation of emerging difficult-to-degrade pollutants in water bodies, which is not only an innovation in the prior art, but also can achieve a breakthrough in low cost and high efficiency in practical applications. The composite materials based on In2O3 in the prior art are shown in Table 2.

[0093] Table 2: Composite materials based on In2O3 in the prior art

[0094]

[0095] [9]H.Zhang, Z.Fan, H.Ye, Y.Xie,

[0096]

[10] N.Sun,M.Zhou,X.Ma,Z.Cheng,J.Wu,Y.Qi,Y.Sun,F.Zhou,Y.Shen,S.Lu,Self-assembled spherical In2O3 / BiOI heterojunctions for enhancedphotocatalytic CO2 reduction activity,Journal ofCO2 Utilization,65(2022).

[0097]

[11] Y.Ji,M.Cui,J.Wei,Y.Shi,L.Bao,Z.Tian,X.Hu,X.Zhang,C.Li,Interfacialoxygen vacancy engineering and built-in electric field mediated Z-schemeIn2O3 / Ag3PO4 heterojunction for boosted photocatalytic doxycyclinedegradation,Chemical Engineering Journal,489(2024).

[0098]

[12] Y.Qi,G.Zhou,Y.Wu,H.Wang,Z.Yan,Y.Wu,In-situ construction of In2O3 / In2S3-CdIn2S4 Z-scheme heterojunction nanotubes for enhanced photocatalytichydrogen production,Journal ofColloid and Interface Science,664(2024)107-116.

[0099]

[13] S.Li,K.Long,X.Sun,H.Yuan,W.Li,Activities in photocatalytichydrogen evolution of In2O3 / In2S3 heterostructure and In2O3 / In2S3@PANnanofibers,Ceramics International,49(2023)24093-24099.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations. The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and their protection scope is not limited thereto. Equivalent substitutions or changes made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention, and the protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing In2O3 / BiVO4 heterojunction piezoelectric material, characterized in that: The steps include: Soluble In salt, glucose and urea are mixed together in water, and then BiVO4 is added thereto to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction, and glucose is used as a dispersant to enhance the dispersibility of In2O3 and prevent particle agglomeration. Urea is used as a structure-directing agent to play a structure-directing role in the growth of the heterojunction, thereby obtaining an In2O3 / BiVO4 heterojunction piezoelectric material.

2. The method for preparing the In2O3 / BiVO4 heterojunction piezoelectric material according to claim 1, characterized in that: The molar ratio of soluble In salt, glucose and urea is 0.2-1.5:1:

1.

3. The method for preparing the In2O3 / BiVO4 heterojunction piezoelectric material according to claim 1, characterized in that: In the mixed solution, the molar ratio of BiVO4 to soluble In salt is 1:7.5-22.

5.

4. The method for preparing the In2O3 / BiVO4 heterojunction piezoelectric material according to claim 1, characterized in that: The conditions of the hydrothermal reaction are: heating at 100-180°C for 8-14h.

5. The method for preparing the In2O3 / BiVO4 heterojunction piezoelectric material according to claim 1, characterized in that Bi VO4 is prepared according to the following steps: Bi(NO3)3·5H2O and HNO3 solution are mixed to obtain a first mixed solution, NH4VO3 and NaOH solution are mixed to obtain a second mixed solution, the first mixed solution and the second mixed solution are mixed, the pH is adjusted to 3-12, and then a hydrothermal reaction is carried out at 140-200°C for 8-24h, and BiVO4 is obtained after washing, drying and storing in the dark.

6. An In2O3 / BiVO4 heterojunction piezoelectric material prepared by the preparation method according to any one of claims 1 to 5.

7. The In2O3 / BiVO4 heterojunction piezoelectric material according to claim 6, characterized in that: In the In2O3 / BiVO4 heterojunction piezoelectric material, In2O3 and BiVO4 form a heterojunction.

8. Use of the In2O3 / BiVO4 heterojunction piezoelectric material according to claim 6 in the preparation of materials for degrading refractory organic pollutants.

9. The use according to claim 6, characterized in that: The refractory organic pollutants are selected from 2,4-dichlorophenol, polychlorinated biphenyls, dioxins, hexachloride, DDT or perfluorooctanoic acid.

10. The use according to claim 6, characterized in that: The application method is: after mixing the difficult-to-degrade organic pollutants with the In2O3 / BiVO4 heterojunction piezoelectric material, photocatalytic degradation is carried out under light conditions.

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