A WO2-W2N heterojunction catalyst, preparation method and application thereof

Abstract

The application discloses a WO2-W2N heterojunction catalyst, a preparation method and application thereof, and belongs to the technical field of piezoelectric catalysis. The preparation of the WO2-W2N heterojunction catalyst comprises the following steps: dissolving a tungsten source and a carbon-nitrogen source in water to form a uniform solution; subjecting the uniform solution to microwave reaction to form a porous precursor; and subjecting the porous precursor to joule heat treatment to obtain the WO2-W2N heterojunction catalyst. In the application, the WO2-W2N heterojunction catalyst is prepared by microwave-joule heat cooperation, efficient charge transport channels are constructed through valence state cooperation, energy level alignment and electron orbital coupling, and the separation, transfer and transmission processes of charges are significantly optimized, so that the catalyst has good piezoelectric catalytic performance, can be applied to piezoelectric degradation of pollutants, especially degradation of organic matters in sewage, and good degradation effect is achieved.

Description

Technical Field

[0001] The present application belongs to the field of piezoelectric catalysis technology, and specifically relates to a method for preparing a WO2-W2N heterojunction catalyst and the prepared WO2-W2N heterojunction catalyst, and also relates to the application of the WO2-W2N heterojunction catalyst in piezoelectric catalytic degradation of pollutants. Background Art

[0002] To address the increasingly serious problem of antibiotic water pollution, methods such as advanced oxidation, adsorption, biooxidation, and photodegradation are currently being used to remove or degrade antibiotics in water. Among these, piezocatalysis, a novel catalytic technology, utilizes the piezoelectric effect of materials to convert mechanical energy into electrical energy, thereby driving chemical reactions and achieving efficient degradation of pollutants. Because piezocatalysis requires no external energy input and can utilize natural mechanical energy for in-situ degradation, and because the reaction conditions are mild and do not produce secondary pollution, it holds great promise for degrading pollutants in water.

[0003] Currently, there are many types of piezoelectric materials. Furthermore, some materials are not typically piezoelectric, but can exhibit certain piezoelectric properties under certain conditions. Studies have shown that carbon-nitrogen materials are widely available and can be prepared from naturally abundant carbon and nitrogen sources. They are pale yellow powders at room temperature and pressure, slightly soluble in water, non-toxic, environmentally friendly, and pollution-free. Their optical band gap is approximately 2.76 eV, making them promising catalytic semiconductor materials. Materials such as graphene and g-C3N4 exhibit piezoelectricity and are considered novel piezoelectric catalysts. Tungsten-based materials also possess certain catalytic properties and potential applications. For example, research has developed piezoelectric catalytic materials based on tungsten-based materials, such as tungsten disulfide, WO3, and bismuth tungstate. However, the piezoelectric properties of these piezoelectric catalysts are limited. A heterojunction is an interface formed by two different semiconductor materials. Its unique band structure and carrier characteristics significantly enhance the performance of these materials. Currently, heterojunction catalysts such as tungsten oxide@bismuth tungstate, bismuth tungstate-bismuth oxybromide, tungsten disulfide / bismuth tungstate, and WO2 / MoS2 have been developed for tungsten-based materials. However, the preparation process of these catalysts is relatively complex and has poor controllability.

[0004] Therefore, the present application is dedicated to clarifying a heterostructure constructed based on a carbon-nitrogen source (CN) and a tungsten-based material and its preparation method, combining the excellent properties of CN with the properties of tungsten-based, thereby achieving a piezoelectric catalyst with better piezoelectric catalytic performance. Summary of the Invention

[0005] In view of this, the primary purpose of this application is to provide a method for preparing a WO2-W2N heterojunction catalyst, which utilizes a microwave-Joule heat synergistic process. The preparation process is simple, easy to operate, and has good controllability. The prepared catalyst has excellent piezoelectric catalytic performance and can effectively achieve the adsorption and catalytic degradation of organic pollutants in sewage.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] One aspect of the present application discloses a method for preparing a WO2-W2N heterojunction catalyst, comprising the following steps:

[0008] Dissolve the tungsten source and the carbon and nitrogen source in water to form a uniform solution;

[0009] subjecting the homogeneous solution to a microwave reaction to form a porous precursor;

[0010] The porous precursor is subjected to Joule heat treatment to prepare a WO2-W2N heterojunction catalyst.

[0011] Another aspect of the present application discloses a WO2-W2N heterojunction catalyst, which is prepared using the preparation method described above.

[0012] Another aspect of the present application discloses the use of the WO2-W2N heterojunction catalyst as described above in piezoelectric catalytic degradation.

[0013] Another aspect of the present application discloses a method for removing organic pollutants from sewage, comprising:

[0014] The WO2-W2N heterojunction catalyst described above is added to the sewage to fully adsorb and catalyze the degradation of organic pollutants.

[0015] Beneficial effects of this application:

[0016] The preparation method in this application constructs a WO2-W2N heterojunction catalyst, which constructs an efficient charge transfer channel through valence state coordination, energy level alignment, and electron orbital coupling, significantly optimizing the charge separation, transfer, and transmission processes to achieve excellent piezoelectric catalytic performance.

[0017] The preparation method provided herein utilizes a microwave-Joule heating synergistic technique to significantly enhance catalyst performance. A microwave reaction is employed to induce localized high temperatures in polar molecules within the microwave field, effectively manipulating the electronic spin states of the transition metal in the catalyst (e.g., increasing the electron density of specific spin states). This process also simultaneously optimizes the surface electronic state density, d-band center position, and spin exchange energy, thereby improving its adsorption capacity and reactivity. Furthermore, the Joule heating effect modulates the surface electronic structure of the WO2-W2N heterojunction catalyst through transient high temperatures (rapidly achieved under the action of an electric current), inducing lattice distortion. This distortion generates a localized strong electric field, forcing carriers to form localized small polarons. The synergistic effect of microwaves and Joule heating ultimately significantly enhances the catalyst's ability to adsorb and degrade pollutants, resulting in excellent catalytic performance and stability in treating complex water bodies (e.g., containing organic pollutants such as antibiotics). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scanning electron microscope image of the heterojunction catalyst WO2-W2N-1 prepared in Example 1 of the present invention.

[0019] Figure 2 This is the EDS distribution diagram of the heterojunction catalyst WO2-W2N-1 prepared in Example 1 of the present invention.

[0020] Figure 3 This is the X-ray diffraction pattern of the heterojunction catalyst WO2-W2N-1 prepared in Example 1 of the present invention.

[0021] Figure 4 This is the EPR diagram of the heterojunction catalyst WO2-W2N-1 prepared in Example 1 of the present invention, wherein: Figure 4 A is superoxide radical (O2· - ) spectrum, Figure 4 Where B is singlet oxygen ( 1 O2) spectrum, Figure 4 C in the middle is the spectrum of hydroxyl radical (·OH).

[0022] Figure 5 The diagram shows the adsorption and degradation effects of tetracycline on the catalysts prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the embodiments of the present application. The technical solutions in the embodiments described below are exemplary and are only possible technical implementations of the present application, not all possible implementations. Those skilled in the art can fully combine the embodiments of the present application to obtain other embodiments without creative work, and these embodiments are also within the scope of protection of the present application.

[0024] The first aspect of the present application discloses a method for preparing a WO2-W2N heterojunction catalyst, which is achieved by microwave-Joule heating synergistic technology, and the main steps are as follows:

[0025] S1. Dissolve the tungsten source and the carbon and nitrogen source in water to form a uniform solution.

[0026] In this step, the tungsten source refers to a water-soluble tungsten compound, which may be a metatungstate (such as ammonium metatungstate), a tungstate (such as ammonium tungstate, sodium tungstate, potassium tungstate, calcium tungstate, etc.), or tungstic acid, but is not limited thereto. It is understood that the tungsten source in this application may be used alone or in combination of any two or more.

[0027] The carbon and nitrogen source refers to a nitrogen-rich organic compound, and specific examples thereof include melamine, urea, dicyandiamide, etc., but are not limited thereto. It is understood that the carbon and nitrogen source in this application can be used alone or in combination of any two or more.

[0028] In this application, the homogeneous solution is formed by dissolving a certain amount of tungsten source and carbon and nitrogen source in water and fully dissolving them through mechanical means. As an example, it is formed by ultrasonic dispersion for a certain period of time. The specific ultrasonic process is preferably carried out in a protective atmosphere at 20-40°C to allow dissolution in an air-tight environment. The protective atmosphere here is an inert gas commonly used in the art, which can be nitrogen or a rare gas (such as helium, argon, etc.).

[0029] Furthermore, in this step, the ratio of the tungsten source to the carbon-nitrogen source can be determined based on performance requirements or through experimental methods. Specifically, by adjusting the ratio of the tungsten source to the carbon-nitrogen source, the catalytic performance can be adjusted, thereby obtaining a more excellent piezoelectric catalytic effect. In some specific examples of the present application, the molar ratio of tungsten in the tungsten source to carbon in the carbon-nitrogen source is (2-16):1, for example, it can be any ratio of 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, or a range between any two ratios. As a preferred example, the molar ratio of tungsten in the tungsten source to carbon in the carbon-nitrogen source is (4-12):1, and more preferably, the molar ratio of tungsten in the tungsten source to carbon in the carbon-nitrogen source is 4:1, thereby obtaining a better piezoelectric catalytic effect.

[0030] S2. Subjecting the homogeneous solution to a microwave reaction to form a porous precursor.

[0031] In this step, the uniform solution obtained in step S1 is placed in a microwave reactor and subjected to microwave reaction to form a porous precursor.

[0032] It is understood that there are no particular requirements for the microwave reactor, and any existing or independently developed microwave equipment in the art can be used. Specific microwave reaction parameters can be determined experimentally without particular limitation. In some specific examples, the microwave reaction parameters are: 2.45 GHz, power 900-1200 W, and irradiation time 4-8 min. By controlling the microwave reaction parameters, the synthesis and structural control of the precursor material can be achieved.

[0033] It is understood that after the microwave reaction, the reaction product is centrifuged, washed, and freeze-dried. These steps are conventional in the art and therefore require no special requirements. For example, washing is performed three times alternating between deionized water and ethanol, but the specific number of washing cycles is not limited. Generally, washing is performed until the filtrate is neutral.

[0034] S3. The porous precursor is subjected to Joule heat treatment to obtain a WO2-W2N heterojunction catalyst.

[0035] In this step, the porous precursor prepared in step S2 is subjected to Joule heat treatment to prepare a WO2-W2N heterojunction catalyst.

[0036] Joule heating is a technique for rapid heat treatment that utilizes the Joule heating effect. Its core principle is to rapidly heat a material by utilizing the heat generated when an electric current passes through a conductor or material. This technique enables materials to reach extremely high temperatures (typically 1000-3000°C) in a very short period of time (milliseconds to seconds), and exhibits the characteristics of rapid temperature rise and fall. In this application, existing Joule heating equipment in the art is employed. When a high current passes through a conductive material, instantaneous high temperatures are generated, inducing lattice distortion. This distortion disrupts the material's original charge balance, leading to the separation of local positive and negative charge centers, the formation of a directional superposition of electric dipole moments, and the generation of a concentrated and high-intensity electric field.

[0037] It is understandable that there are no special restrictions or requirements on the parameters of the specific Joule heat treatment, which can be adjusted as needed or determined through experimental methods. In some specific examples of the present application, the parameters of the Joule heat treatment are: 30~50A current, heating to 1400~1600℃ within 1~3s, keeping warm for 10~20s, cooling after the reaction is completed, and cooling to 70~80℃ to turn off the Joule heat.

[0038] The second aspect of the present application discloses a WO2-W2N heterojunction catalyst, which is prepared using the preparation method described in the first aspect of the present application.

[0039] In this application, microwave-Joule heating is used to synergistically control the electronic structure of the catalyst surface to prepare a WO2-W2N heterojunction catalyst with excellent piezoelectric catalytic performance. By optimizing the small polaron effect induced by deformation potential and the electron spin polarization state, the charge separation efficiency, electron transfer rate, adsorption capacity and degradation activity of the catalyst are significantly improved. Specifically:

[0040] (1) Microwave control of electron spin state to optimize catalytic performance

[0041] This application uses microwaves to control the electron spin state of the transition metal (W) in the catalyst, thereby affecting the electronic state density, d-band center position and spin exchange energy on the material surface, and ultimately improving its adsorption energy and reaction activity. The specific mechanism is: ① Induced spin polarization: The number of spin-up and spin-down electrons on the material surface is asymmetric, changing the distribution of electronic state density. ② Control of d-band center: Spin polarization changes the d-band electron distribution and affects the position of the d-band center. The closer the d-band center is to the Fermi level, the stronger its adsorption energy for the adsorbate and the higher the reaction activity. ③ Introducing exchange energy: Spin polarization causes the energy levels of spin-up and spin-down electrons to split (i.e., introduces exchange energy). In summary, increasing the state density of electrons in a specific spin direction (up or down) through the action of microwaves can enhance the interaction between the adsorbate and the atoms on the catalyst surface and increase the adsorption energy. At the same time, the spin-polarized state helps to optimize charge separation and conduction, and enhance the efficiency of interfacial electron transfer.

[0042] (2) Joule heat-induced lattice distortion regulates electronic structure

[0043] During the catalyst synthesis process, Joule heating is used to introduce a rapid temperature ramp, resulting in lattice mismatch at the WO2-W2N interface and the formation of a highly localized lattice distortion region. The deformation potential generated by this lattice distortion (up to 5-8 eV / Å) significantly alters the local electron distribution, manifesting itself in the following ways: ① Reducing the band gap: This enhances carrier excitation efficiency. ② Inducing band bending: This creates a local potential gradient. ③ Promoting carrier localization: The strong localized distortion field induced by the instantaneous temperature increase under the action of current forces the carriers to localize into small polarons, significantly enhancing the interfacial electron transfer efficiency. Taken together, these effects significantly enhance the catalyst's ability to adsorb and degrade pollutants.

[0044] (3) In addition, the synergistic effect of W element valence and spin polarization

[0045] Tungsten (W), a transition metal with multiple valence states (+4, +5, and +6), is supported on a carbon-nitrogen carrier. Under microwave irradiation, its electrons undergo spin polarization, increasing the density of states for electrons with specific spin orientations and thereby enhancing adsorption of the adsorbate. Furthermore, microwave-induced spin polarization optimizes the d-band center position (moving it closer to the Fermi level), further enhancing adsorption energy. This enhanced charge separation, conduction, and interfacial electron transfer efficiency contribute to improved catalytic efficiency.

[0046] In general, this application uses Joule heat to instantaneously induce lattice distortion to generate a strong local electric field (promoting the formation of small polarons and electron transfer), and combines it with microwaves to precisely control the spin state of the transition metal (W) (optimizing the electronic state density, d-band center and charge separation / transfer). The synergistic effect of the two significantly enhances the piezoelectric catalytic performance of the catalyst.

[0047] The third aspect of the present application discloses the application of the WO2-W2N heterojunction catalyst described in the second aspect of the present application in piezoelectric catalytic degradation.

[0048] The fourth aspect of the present application discloses a method for removing organic pollutants in sewage, comprising:

[0049] The WO2-W2N heterojunction catalyst described above is added to the sewage to fully adsorb and catalyze the degradation of organic pollutants.

[0050] The specific processing steps can refer to the piezoelectric catalytic degradation method well known in the art. As an example, the main steps of the method are as follows:

[0051] The WO2-W2N heterojunction catalyst is added to the sewage and fully dispersed; then stirring is continued to allow the WO2-W2N heterojunction catalyst to fully adsorb the organic pollutants in the dispersion; finally, ultrasonic catalytic degradation is performed to remove the organic pollutants in the sewage.

[0052] There are no special restrictions or requirements on the types of organic pollutants in sewage. As an example, the organic pollutants are antibiotics. Specific examples of antibiotics include but are not limited to at least one of tetracycline, oxytetracycline hydrochloride, chlortetracycline hydrochloride, doxycycline and their derivatives.

[0053] As an example, the concentration of organic pollutants in the sewage is 20-100 mg / L.

[0054] It is understandable that the specific amount of WO2-W2N heterojunction catalyst used can be determined according to the concentration of organic pollutants in the sewage, using a range well known in the art or by experimental methods. In some specific examples, the amount of the WO2-W2N heterojunction catalyst added is 50~500 mg / L.

[0055] Furthermore, the adsorption process of the catalyst in the sewage is preferably carried out in a stirring manner. The specific stirring parameters can be set as needed. As an example, the stirring speed is 300-600 rpm and the time is 30-60 min.

[0056] As an example, the catalytic degradation is performed by ultrasound, the power of the ultrasound is 75W, and the reaction time is 30 to 90 minutes.

[0057] In this application, the excellent piezoelectric catalytic performance of the WO2-W2N heterojunction catalyst enables the effective removal of organic pollutants from wastewater. The WO2-W2N heterojunction catalyst removes pollutants in two stages: adsorption and degradation. The adsorption stage uses attractive forces (such as van der Waals forces) generated by electrons on the catalyst surface to enrich organic pollutant molecules in the water and reduce their concentration. The degradation stage uses the piezoelectric catalytic effect to generate free radicals (such as ·OH) or non-radical active species, which react with the adsorbed organic pollutants, breaking them down into small molecules or further mineralizing them into harmless H2O and CO2.

[0058] The technical solution of the present application is further illustrated below with reference to specific embodiments. It should be noted that the following specific embodiments are only for illustrative purposes and do not limit the scope of the present application in any way.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0060] In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used are all commercially available.

[0061] Example 1:

[0062] This embodiment discloses a method for preparing a WO2-W2N heterojunction catalyst, and the specific preparation method is as follows:

[0063] S1, 1.0 mmol of ammonium metatungstate ((NH4)6H2W 12 O 40 ), 1.0 mmol melamine was dissolved in 50 mL water and ultrasonicated for 30 min to form a homogeneous solution;

[0064] S2. placing the homogeneous solution from step S1 in a microwave reactor and irradiating the reaction product at 2.45 GHz and 900 W for 5 minutes, centrifuging, washing, and freeze-drying the reaction product to form a porous precursor; wherein the washing step is performed with water and ethanol three times each;

[0065] S3. Place the porous precursor in step S2 in a Joule heating device, pass a current of 30A, heat it to 1400°C within 3 seconds, keep it warm for 20 seconds, cool it down after the reaction is completed, and turn off the Joule heating when the temperature drops to 80°C. Allow the reaction system to cool naturally to room temperature to obtain catalyst powder, which is recorded as WO2-W2N-1.

[0066] Example 2:

[0067] This embodiment discloses another method for preparing a WO2-W2N heterojunction catalyst, which adopts the same implementation as that of Example 1, except that: (NH4)6H2W 12 O 40 The addition amount of WO2 / W2N-0.5 was 0.5 mmol. The other process steps and parameter conditions were the same as those in Example 1, and the prepared catalyst was recorded as WO2 / W2N-0.5.

[0068] Example 3:

[0069] This embodiment discloses another method for preparing a WO2-W2N heterojunction catalyst, which adopts the same implementation as that of Example 1, except that: (NH4)6H2W 12 O 40 The addition amount of WO2 was 2 mmol. The other process steps and parameter conditions were the same as those in Example 1, and the prepared catalyst was recorded as WO2 / W2N-2.

[0070] Example 4:

[0071] This embodiment discloses another method for preparing a WO2-W2N heterojunction catalyst, which adopts the same implementation as that of Example 1, except that: (NH4)6H2W 12 O 40 The addition amount of WO2 was 3 mmol. The other process steps and parameter conditions were the same as those in Example 1, and the prepared catalyst was recorded as WO2 / W2N-3.

[0072] Example 5:

[0073] This embodiment discloses another method for preparing a WO2-W2N heterojunction catalyst, which adopts the same implementation as that of Example 1, except that: (NH4)6H2W 12 O 40The other process steps and parameters were the same as those in Example 1, and the prepared catalyst was designated as WO2 / W2N-4.

[0074] Comparative Example 1:

[0075] This comparative example discloses another method for preparing a WO2-W2N heterojunction catalyst, which uses the same method as Example 1, except that microwave irradiation is not used. The specific steps are as follows:

[0076] S1, 1.0 mmol of ammonium metatungstate ((NH4)6H2W 12 O 40 ), 1.0 mmol melamine was dissolved in 50 mL water, ultrasonicated for 30 min to obtain a homogeneous solution, filtered and freeze-dried for 72 h to obtain the precursor;

[0077] S2. Place the precursor in a Joule heating device, pass a 30A current, raise the temperature to 1400°C within 3 seconds, keep it warm for 20 seconds, cool it down after the reaction ends, and turn off the Joule heating when the temperature drops to 80°C. Allow the reaction system to cool naturally to room temperature to obtain catalyst powder, recorded as WO2-W2N-5.

[0078] Comparative Example 2:

[0079] This comparative example discloses another method for preparing a WO2-W2N heterojunction catalyst, which uses the same method as Example 1, except that Joule heating is not used. The specific steps are as follows:

[0080] S1, 1.0 mmol of ammonium metatungstate ((NH4)6H2W 12 O 40 ), 1.0 mmol melamine was dissolved in 50 mL water and ultrasonicated for 30 min to form a homogeneous solution;

[0081] S2. placing the homogeneous solution from step S1 in a microwave reactor and irradiating the reaction product at 2.45 GHz and 900 W for 5 minutes, centrifuging, washing, and freeze-drying the reaction product to form a porous precursor; wherein the washing step is performed with water and ethanol three times each;

[0082] S3. Place the porous precursor in step S2 in a tube furnace, introduce Ar gas, raise the temperature to 600°C at 5°C / min, keep the temperature for 2 h, and cool naturally to room temperature to obtain catalyst powder, which is recorded as WO2-W2N-6.

[0083] Test Example 1:

[0084] The WO2-W2N heterojunction catalysts prepared in the above Examples 1-5 or Comparative Examples 1-2 were subjected to relevant performance tests, and the test method was as follows:

[0085] The morphology of the catalysts was characterized using a FEI-Quanta 200 scanning electron microscope (SEM).

[0086] A PANalytical X-ray diffractometer was used to characterize the crystal form and structural characteristics of the material.

[0087] An Agilent 1220 high performance liquid chromatograph was used to measure the concentrations of antibiotics in the treated water samples.

[0088] The EPR signal of the catalyst was detected using an electron spin resonance spectrometer (X-band).

[0089] The specific test objects and test results are as follows:

[0090] (1) Figure 1 and Figure 2 The scanning electron microscope image and EDS distribution diagram of the catalyst WO2-W2N-1 prepared in Example 1 of the present application. Figure 1 It can be seen from the scanning electron microscope image that the material structure curls up to form a nearly "coral-like" morphology; combined with Figure 2 EDS analysis shows that the W element is evenly distributed, indicating that W has been successfully loaded on CN.

[0091] (2) Figure 3 This is the X-ray diffraction pattern of WO2-W2N-1 prepared in Example 1. Comparing the XRD pattern with PDF standard cards reveals that the diffraction peaks of WO2-W2N-1 are consistent with those of the WO2 XRD pattern standard card (PDF#32-1393) and the W2N XRD pattern standard card (PDF#25-1257), indicating that the W element has been successfully loaded onto CN and altered its crystal structure. This demonstrates that Example 1 successfully prepared a WO2-W2N heterojunction catalyst.

[0092] (3) The polaron migration barriers of the WO2-W2N heterojunction catalysts prepared in Examples 1-5 and Comparative Examples 1-2 were calculated using atomic force microscopy (AFM) combined with piezoresponse force microscopy (PFM). The results are shown in Table 1.

[0093] Table 1 Polaron migration barrier results of WO2-W2N heterojunction catalysts

[0094]

[0095] As can be seen from Table 1, the WO2-W2N heterojunction catalysts prepared in the examples of this application have a low polaron migration barrier. In contrast, the polaron migration barriers of the WO2-W2N heterojunction catalysts in Comparative Examples 1 and 2 are higher. This demonstrates that the microwave and Joule heating synergistic treatment technology of this application can significantly reduce the polaron migration barrier of the catalyst.

[0096] (4) Figure 4 The EPR diagram (electron paramagnetic resonance spectrum) of the WO2-W2N heterojunction catalyst prepared in Example 1 is shown in FIG. The horizontal axis is the magnetic field intensity and the vertical axis is the signal intensity. It is detected by an electron spin resonance spectrometer (X-band), using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a free radical scavenger and 2,2,6,6-tetramethylpiperidine (TEMP) as a 1 O2 scavenger, EPR characterization. It can be seen that the superoxide free radical detection results show that DMPO-O2· - The signal is relatively weak ( Figure 4 A); The singlet oxygen detection results show that when TEMP exists alone, TEMP- 1 The weak characteristic signal of O2 ( Figure 4 In the B); DMPO-•OH signal was observed in the hydroxyl radical detection results. The generation of •OH is due to the separation of electrons and holes on the surface of the WO2 / W2N heterojunction catalyst, and then the holes react with water to produce •OH ( Figure 4 Therefore, the combined quenching and EPR results indicate that •OH is the dominant reacting species.

[0097] Test Example 2:

[0098] Taking tetracycline as a pollutant, the adsorption and degradation effects of the WO2-W2N heterojunction catalysts prepared in Examples 1-5 and Comparative Examples 1-2 on tetracycline were tested.

[0099] The specific operations are as follows:

[0100] Prepare a tetracycline aqueous solution with a tetracycline concentration of 20 mg / L, denoted as C0; then divide it into six equal portions, each of 50 mL, as test water samples;

[0101] 5 mg of WO2-W2N-1, WO2-W2N-0.5, WO2-W2N-2, WO2-W2N-3, WO2-W2N-4, WO2-W2N-5, and WO2-W2N-6 heterojunction catalysts were weighed and added to a test water sample respectively, and the catalysts were fully dispersed by ultrasound to obtain each treatment sample;

[0102] Each treated sample was placed on a stirring platform and stirred at 450 rpm for 30 minutes to allow tetracycline to adsorb onto the catalyst surface. Following adsorption, the sample was immediately placed in a 75W ultrasonic machine for 60 minutes of catalytic degradation. At this point, the pH of the mixture was approximately 6.4, requiring no further adjustment. Water samples were collected at -30, -20, -10, 0, 2, 5, 10, 20, and 30 minutes during the degradation reaction. The tetracycline concentration in the water samples was determined using an Agilent 1220 high-performance liquid chromatograph (HPLC), denoted as C.

[0103] The above adsorption and degradation experimental results are as follows: Figure 5 As shown in the figure, the vertical axis C / C0 represents the removal rate of tetracycline. Specifically, -30-0 min is the adsorption stage, and 0-30 min is the catalytic degradation stage. The smaller the value of C / C0, the greater the removal rate of tetracycline; conversely, the larger the value of C / C0, the smaller the removal rate of tetracycline.

[0104] from Figure 5 It can be seen that in the adsorption stage from -30 to 0 min, WO2-W2N-2 has the best adsorption effect. The adsorption effects of the catalysts prepared in the examples are better than those of WO2-W2N-5 in Comparative Example 1 and WO2-W2N-6 in Comparative Example 2, indicating that the catalysts prepared by the preparation method in this application can significantly improve the piezoelectric catalytic performance and enhance the degradation effect of organic pollutants in sewage. In the catalytic degradation stage from 0 to 30 min, the degradation effects of the five catalysts WO2-W2N-1, WO2-W2N-0.5, WO2-W2N-2, WO2-W2N-3, and WO2-W2N-4 are compared, indicating that the degradation effect can be regulated by adjusting the molar ratio of the carbon and nitrogen source to the tungsten source.

[0105] In addition, from Figure 5 It can be seen that the removal rate of tetracycline (i.e., the total effect of adsorption and catalytic degradation) of the WO2-W2N heterojunction catalyst prepared in this application reaches 41-92%.

[0106] Example 6:

[0107] This embodiment discloses another method for preparing a WO2-W2N heterojunction catalyst. The specific preparation method is as follows:

[0108] S1. Dissolve 1.0 mmol of ammonium tungstate and 1.0 mmol of dicyandiamide in 50 mL of water and sonicate for 30 min to form a homogeneous solution.

[0109] S2, the uniform solution in step S1 is placed in a microwave reactor, irradiated at 2.45 GHz, 1000W power for 8 minutes, and the reaction product is centrifuged, washed, and freeze-dried to form a porous precursor; wherein the washing is performed with water and ethanol for 3 times each;

[0110] S3, the porous precursor in step S2 is placed in a joule heat device, a current of 40A is passed, and the temperature is raised to 1600℃ within 2 seconds, and the temperature is kept for 10 seconds, and the reaction is ended by cooling down, when the temperature is reduced to 80℃, the joule heat is turned off, and the reaction system is naturally cooled to room temperature to obtain a catalyst powder, which is recorded as WO2-W2N-7.

[0111] The WO2-W2N heterojunction catalyst prepared in this embodiment is subjected to the test of removing organic pollutants in wastewater as follows:

[0112] An aqueous oxytetracycline hydrochloride solution of 100 mL is configured, wherein the concentration of oxytetracycline hydrochloride is 100 mg / L, 5 mg of the WO2-W2N heterojunction catalyst prepared in this embodiment is added, and ultrasonic is used to make it fully dispersed; then it is placed on a stirring table and stirred at a speed of 300 rpm for 30 min to make the surface of the catalyst adsorb oxytetracycline hydrochloride. After adsorption, the catalytic degradation reaction is carried out at room temperature under ultrasonic power of 75W for 90 min.

[0113] It is detected that the removal rate of the WO2-W2N heterojunction catalyst prepared in this embodiment to oxytetracycline hydrochloride reaches 90%.

[0114] Example 7:

[0115] Another method for preparing a WO2-W2N heterojunction catalyst is disclosed in this embodiment, and the specific preparation method is as follows:

[0116] S1, 2.0 mmol of tungstic acid and 1.0 mmol of urea are dissolved in 50 mL of water, and ultrasonic is used for 30 min to form a uniform solution;

[0117] S2, the uniform solution in step S1 is placed in a microwave reactor, irradiated at 2.45 GHz, 1200W power for 6 minutes, and the reaction product is centrifuged, washed, and freeze-dried to form a porous precursor; wherein the washing is performed with water and ethanol for 3 times each;

[0118] S3, the precursor is placed in a joule heat device, a current of 50A is passed, and the temperature is raised to 1500℃ within 1 second, and the temperature is kept for 10 seconds, and the reaction is ended by cooling down, when the temperature is reduced to 80℃, the joule heat is turned off, and the reaction system is naturally cooled to room temperature to obtain a catalyst powder, which is recorded as WO2-W2N-8.

[0119] The WO2-W2N heterojunction catalyst prepared in this example was tested for removing organic pollutants from sewage as follows:

[0120] Prepare 100 mL of chlortetracycline hydrochloride aqueous solution at a concentration of 50 mg / L. Add 5 mg of the WO2-W2N heterojunction catalyst prepared in this example and thoroughly disperse it under ultrasound. Place the mixture on a stirring platform and stir at 600 rpm / min for 30 minutes to allow the surface of the catalyst to adsorb chlortetracycline hydrochloride. After adsorption, perform a catalytic degradation reaction under ultrasound at 75 W for 30 minutes at room temperature.

[0121] It was tested that the removal rate of chlortetracycline hydrochloride by the WO2-W2N heterojunction catalyst prepared in this embodiment reached 70%.

[0122] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a WO2-W2N heterojunction catalyst, characterized in that: The following steps are involved: Dissolve the tungsten source and the carbon and nitrogen source in water to form a uniform solution; subjecting the homogeneous solution to a microwave reaction to form a porous precursor; The porous precursor is subjected to Joule heat treatment to prepare a WO2-W2N heterojunction catalyst; The microwave reaction parameters are: 2.45 GHz, power 900-1200 W, irradiation 4-8 min; The parameters of the Joule heat treatment are: 30-50A current, heating to 1400-1600°C within 1-3s, keeping warm for 10-20s, cooling after the reaction is completed, and cooling to 70-80°C to turn off the Joule heat.

2. The preparation method according to claim 1, wherein The tungsten source is at least one of ammonium metatungstate, ammonium tungstate, and sodium tungstate; And / or, the carbon and nitrogen source is at least one of melamine, urea, and dicyandiamide.

3. The preparation method according to claim 1, characterized in that the molar ratio of tungsten in the tungsten source to carbon in the carbon-nitrogen source is (2-16):

1.

4. A WO2-W2N heterojunction catalyst, characterized in that: The method is prepared according to any one of claims 1 to 3.

5. Use of the WO2-W2N heterojunction catalyst according to claim 4 in piezoelectric catalytic degradation.

6. A method for removing organic pollutants from sewage, characterized in that: include: The step of adding the WO2-W2N heterojunction catalyst described in claim 4 into sewage to fully adsorb and catalyze the degradation of organic pollutants.

7. The method according to claim 6, wherein The organic pollutants are antibiotics.

8. The method according to claim 6, wherein The concentration of organic pollutants in the sewage is 20-100 mg / L; And / or, based on the volume of sewage, the amount of the WO2-W2N heterojunction catalyst added is 50-500 mg / L; And / or, the adsorption is performed by stirring, the stirring speed is 300-600 rpm, and the time is 30-60 min; And / or, the catalytic degradation is carried out by ultrasound, the ultrasound power is 75W, and the reaction time is 30-90 minutes.

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