Rare earth Eu doped In2O3 / In2S3 heterojunction photocatalytic material as well as preparation method and application thereof

Abstract

The invention provides a rare earth Eu doped In2O3 / In2S3 heterojunction photocatalytic material, and a preparation method and application thereof, the method comprises the following steps: synthesizing an MIL-68 (In) precursor through a hydrothermal method to obtain an In2O3 hollow micron tube photocatalyst; the preparation method comprises the following steps: growing an In2S3 nanosheet on an In2O3 hollow micron tube by using an oil bath method to obtain an In2O3 / In2S3 heterojunction photocatalyst; a rare earth element Eu is doped in a matrix lattice of an In2O3 / In2S3 heterojunction photocatalyst to obtain a heterojunction photocatalytic material; the rare earth Eu doped In2O3 / In2S3 hollow tubular heterojunction (Eu-IOIS) composite photocatalytic material constructed by the invention has a large specific surface area, and is beneficial to exposure of more reaction active sites; the strong built-in electric field of the S-type heterojunction of In2O3 / In2S3 and the action of the electron transport bridge of the rare earth Eu monatomic jointly improve the separation and transfer of photogenerated charges. Therefore, Eu-IOIS shows enhanced performance of synthesizing urea by photocatalytic N2 reduction coupling CH3OH oxidation.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic materials, and in particular relates to a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, a preparation method and an application thereof. Background Art

[0002] Urea is a chemical product with a wide range of applications. Currently, industrial production primarily relies on the reaction of ammonia (NH3) and carbon dioxide (CO2) under high temperature (150-200°C) and high pressure (150-250 bar). The industrial synthesis of ammonia (NH3) also relies on the Haber-Bosch process, which operates at high temperatures (350-550°C) and high pressure (150-250 bar). This results in significant energy consumption and environmental pollution associated with industrial urea synthesis. Therefore, the development of environmentally friendly urea production technologies under mild conditions is needed to achieve sustainable development.

[0003] The sustainability and environmental friendliness of photocatalysis offer a promising avenue for urea synthesis. Currently, photocatalytic urea synthesis primarily relies on the co-reduction of N≡ and CO₂. However, this approach faces numerous challenges. First, both N≡ and CO₂ are extremely chemically inert, requiring very high energies to break the N≡N bond (940.95 kJ / mol) and the C=O bond (750 kJ / mol). Second, N≡ and CO₂ compete for the co-reduction reaction, resulting in reduced efficiency in utilizing photogenerated charge carriers and synthesizing coupled products. Summary of the Invention

[0004] In view of the above situation, the main purpose of the present invention is to propose a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, preparation method and application to solve the above technical problems.

[0005] The present invention proposes a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, wherein the matrix of the In2O3 / In2S3 heterojunction photocatalytic material is In2O3 / In2S3; The MIL-68(In) precursor was synthesized by a hydrothermal method to obtain In2O3 hollow microtube photocatalyst; In2O3 / In2S3 heterojunction photocatalysts were obtained by growing In2S3 nanosheets on In2O3 hollow microtubes using an oil bath method. The matrix lattice of In2O3 / In2S3 heterojunction photocatalyst is doped with rare earth element Eu to obtain heterojunction photocatalytic material; The rare earth element Eu is dispersed in the form of single atoms, and the mass fraction of the rare earth element Eu is 0.22%.

[0006] The present invention proposes a method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, which is used to prepare the above-mentioned In2O3 / In2S3 heterojunction photocatalytic material. The method comprises the following steps: Step 1: Add terephthalic acid to dimethylformamide and stir vigorously to obtain a transparent solution; Indium nitrate hydrate is added to a transparent solution and dispersed and dissolved by ultrasonication to obtain a clear transparent solution; The clear and transparent solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated. After the reaction was completed, the reaction was naturally cooled to room temperature to obtain a white precipitate. The white precipitate was washed alternately with dimethylformamide and anhydrous ethanol. After the alternating washings, the product was collected by centrifugation and transferred to an oven for drying overnight to obtain a MIL-68(In) precursor. The MIL-68(In) precursor was placed on a ceramic boat and transferred to a muffle furnace for a temperature-elevated reaction to obtain an In2O3 hollow microtube photocatalyst. Step 2: adding indium trichloride tetrahydrate, thioacetamide, and citric acid monohydrate into a round-bottom flask, and adding deionized water into the round-bottom flask to obtain a mixture, and uniformly dispersing the mixture using ultrasound to obtain a uniformly dispersed solution; An In2O3 hollow microtube photocatalyst is added to a uniformly dispersed solution and stirred to obtain a stirred solution; the stirred solution is subjected to an oil bath reaction, and after completion of the reaction, the solution is naturally cooled to room temperature, and a product is collected by centrifugation. The collected product is alternately washed with deionized water and anhydrous ethanol, and after the washing is completed, the product is transferred to an oven for drying to obtain an In2O3 / In2S3 heterojunction photocatalyst; Step 3, dispersing the In2O3 / In2S3 heterojunction photocatalyst in a mixed solution of deionized water and ethylene glycol, and stirring to obtain an ethylene glycol dispersion; Europium nitrate hexahydrate is dispersed in deionized water to obtain a europium nitrate hexahydrate solution, the europium nitrate hexahydrate solution is added to an ethylene glycol dispersion and stirred, and then deposited under xenon light after stirring. After deposition, the product is collected by centrifugation and washed alternately with deionized water and anhydrous ethanol. After alternate washing, the product is transferred to a drying oven and dried overnight to obtain an In2O3 / In2S3 heterojunction photocatalytic material.

[0007] The present invention also proposes an application of a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material. The rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material prepared by the above-mentioned preparation method of a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material is applied to the synthesis of urea by visible light photocatalytic nitrogen reduction coupled with methanol oxidation at room temperature and normal pressure.

[0008] Beneficial effects: The present invention constructs a rare earth (Eu)-doped In2O3 / In2S3 hollow tubular heterojunction (Eu-IOIS) composite photocatalytic material with a large specific surface area, which facilitates the exposure of more reactive sites. The strong built-in electric field of the In2O3 / In2S3 S-type heterojunction and the electron transport bridge of the rare earth (Eu) single atoms together enhance the separation and transfer of photogenerated charges. Consequently, the Eu-IOIS exhibits enhanced photocatalytic performance for N2 reduction coupled with CH3OH oxidation to synthesize urea.

[0009] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is the XRD pattern of different samples; Figure 2 SEM, TEM and AC-STEM images of the samples; Figure 3 The urea yield diagram of different samples under light source irradiation; Figure 4 The urea yield of the samples under different conditions is shown in the figure; Figure 5 is the UV diffuse reflectance graph of different samples; Figure 6 is the photocurrent response diagram of the sample; Figure 7 is the impedance diagram of the sample; Figure 8 Photoluminescence spectra of different samples. DETAILED DESCRIPTION

[0011] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0012] These and other aspects of the embodiments of the present invention will become clear with reference to the following description and accompanying drawings. In these descriptions and accompanying drawings, some specific implementations of the embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0013] Example 1 A rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, wherein the matrix of the In2O3 / In2S3 heterojunction photocatalytic material is In2O3 / In2S3; The MIL-68(In) precursor was synthesized by a hydrothermal method to obtain In2O3 hollow microtube photocatalyst; In2O3 / In2S3 heterojunction photocatalysts were obtained by growing In2S3 nanosheets on In2O3 hollow microtubes using an oil bath method. The rare earth element Eu is doped into the matrix lattice of the In2O3 / In2S3 heterojunction photocatalyst to obtain the In2O3 / In2S3 heterojunction photocatalytic material; The rare earth element Eu is dispersed in the form of single atoms, and the mass fraction of the rare earth element Eu is 0.22%.

[0014] Example 2 This embodiment provides a method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, which is used to prepare the above-mentioned rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material. The method includes the following steps: Step 1: 0.170 g of terephthalic acid was added to 57 mL of dimethylformamide and stirred vigorously to obtain a transparent solution; 0.457 g of indium nitrate hydrate was added to the transparent solution and dispersed and dissolved by ultrasonication to obtain a clear transparent solution; The clear, transparent solution was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 95°C for 3.6 h. After the reaction, the mixture was naturally cooled to room temperature to obtain a white precipitate. The white precipitate was washed alternately with dimethylformamide and anhydrous ethanol three times. After alternating washings, the product was collected by centrifugation and transferred to an oven and dried at 76°C overnight to obtain the MIL-68(In) precursor, designated as A1. The MIL-68(In) precursor in A1 was placed on a ceramic boat and transferred to a muffle furnace, where the temperature was raised to 445°C at a heating rate of 4.5°C / min for 3.6 h to obtain a light yellow In2O3 hollow microtube photocatalyst, which was designated as B1. Step 2: 0.278 g of indium trichloride tetrahydrate, 0.333 g of thioacetamide, and 0.931 g of citric acid monohydrate were added to a round-bottom flask, and 66.5 mL of deionized water was added to the round-bottom flask to obtain a mixture, and the mixture was uniformly dispersed using ultrasound to obtain a uniformly dispersed solution; To the uniformly dispersed solution, 47.5 mg of the light yellow In2O3 hollow microtube photocatalyst in B1 was added and stirred to obtain a stirred solution. The stirred solution was subjected to an oil bath reaction at 76°C for 1.8 h. After the reaction, it was naturally cooled to room temperature and the product was collected by centrifugation. The collected product was washed alternately with deionized water and anhydrous ethanol three times. After washing, it was transferred to a 76°C oven and dried for 10.8 h to obtain a yellow In2O3 / In2S3 heterojunction photocatalyst, which was recorded as C1. Step 3: Disperse 0.095 g of the In2O3 / In2S3 heterojunction photocatalyst in C1 in 23.75 mL of a mixed solution of deionized water and ethylene glycol, and stir to obtain an ethylene glycol dispersion. 0.0475 g of europium nitrate hexahydrate was dispersed in 2.375 mL of deionized water to obtain a europium nitrate hexahydrate solution. The europium nitrate hexahydrate solution was added to the ethylene glycol dispersion and stirred in the dark for 18 minutes. After stirring, the mixture was deposited under 300 W xenon lamp light with a wavelength ≥ 420 nm for 54 minutes. After deposition, the product was collected by centrifugation and washed alternately with deionized water and anhydrous ethanol for 3 times. After alternating washing, the product was transferred to a drying oven at 57°C and dried overnight to obtain a yellow In2O3 / In2S3 heterojunction photocatalytic material, which was recorded as D1.

[0015] Example 3 The embodiment provides a method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, which is used to prepare the above-mentioned rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, and the method includes the following steps: Step 1: 0.179 g of terephthalic acid was added to 60 mL of dimethylformamide and stirred vigorously to obtain a transparent solution; 0.481 g of indium nitrate hydrate was added to the transparent solution and dispersed and dissolved by ultrasonication to obtain a clear transparent solution; The clear transparent solution was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 100°C for 4 h. After the reaction, it was naturally cooled to room temperature to obtain a white precipitate. The white precipitate was washed alternately with dimethylformamide and anhydrous ethanol three times. After alternating washings, the product was collected by centrifugation and transferred to an oven and dried at 80°C overnight to obtain a MIL-68(In) precursor, which was recorded as A2. The MIL-68(In) precursor in A2 was placed on a ceramic boat and transferred to a muffle furnace, where the temperature was raised to 450°C at a heating rate of 5°C / min for 4 h to obtain a light yellow In2O3 hollow microtube photocatalyst, which was designated as B2. Step 2: 0.293 g of indium trichloride tetrahydrate, 0.35 g of thioacetamide, and 0.979 g of citric acid monohydrate were added to a round-bottom flask, and 70 mL of deionized water was added to the round-bottom flask to obtain a mixture, and the mixture was uniformly dispersed using ultrasound to obtain a uniformly dispersed solution; 50 mg of the light yellow In2O3 hollow microtube photocatalyst in B2 was added to the uniformly dispersed solution and stirred to obtain a stirred solution. The stirred solution was subjected to an oil bath reaction at 80°C for 2 h. After the reaction, it was naturally cooled to room temperature and the product was collected by centrifugation. The collected product was washed alternately with deionized water and anhydrous ethanol three times. After washing, it was transferred to an 80°C oven and dried for 12 h to obtain a yellow In2O3 / In2S3 heterojunction photocatalyst, which was recorded as C2. Step 3: Disperse 0.1 g of the In2O3 / In2S3 heterojunction photocatalyst in C2 in 25 mL of a mixed solution of deionized water and ethylene glycol, and stir to obtain an ethylene glycol dispersion; 0.05 g of europium nitrate hexahydrate was dispersed in 2.5 mL of deionized water to obtain a europium nitrate hexahydrate solution. The europium nitrate hexahydrate solution was added to the ethylene glycol dispersion and stirred in the dark for 20 minutes. After stirring, the mixture was deposited under 300 W xenon lamp light with a wavelength ≥ 420 nm for 60 minutes. After deposition, the product was collected by centrifugation and washed alternately with deionized water and anhydrous ethanol for 3 times. After alternating washing, the product was transferred to a drying oven at 60°C and dried overnight to obtain a yellow In2O3 / In2S3 heterojunction photocatalytic material, which was recorded as D2.

[0016] Example 4 The embodiment provides a method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, which is used to prepare the above-mentioned rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, and the method includes the following steps: Step 1: 0.188 g of terephthalic acid was added to 63 mL of dimethylformamide and stirred vigorously to obtain a transparent solution; 0.505 g of indium nitrate hydrate was added to the transparent solution and dispersed and dissolved by ultrasonication to obtain a clear transparent solution; The clear, transparent solution was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 105°C for 4.4 h. After the reaction, the mixture was naturally cooled to room temperature to obtain a white precipitate. The white precipitate was washed alternately with dimethylformamide and anhydrous ethanol three times. After alternating washings, the product was collected by centrifugation and transferred to an oven and dried at 84°C overnight to obtain a MIL-68(In) precursor, designated as A3. The MIL-68(In) precursor in A3 was placed on a ceramic boat and transferred to a muffle furnace, where the temperature was raised to 455°C at a heating rate of 5.5°C / min for 4.4 h to obtain a light yellow In2O3 hollow microtube photocatalyst, which was designated as B3. Step 2: 0.308 g of indium trichloride tetrahydrate, 0.367 g of thioacetamide, and 1.0227 g of citric acid monohydrate were added to a round-bottom flask, and 73.5 mL of deionized water was added to the round-bottom flask to obtain a mixture, and the mixture was uniformly dispersed using ultrasound to obtain a uniformly dispersed solution; 52.5 mg of the light yellow In2O3 hollow microtube photocatalyst in B3 was added to the uniformly dispersed solution and stirred to obtain a stirred solution. The stirred solution was subjected to an oil bath reaction at 84°C for 2.2 h. After the reaction, it was naturally cooled to room temperature and the product was collected by centrifugation. The collected product was washed alternately with deionized water and anhydrous ethanol three times. After washing, it was transferred to an 84°C oven and dried for 13.2 h to obtain a yellow In2O3 / In2S3 heterojunction photocatalyst, which was recorded as C3. Step 3: Disperse 0.105 g of the In2O3 / In2S3 heterojunction photocatalyst in C3 in 26.25 mL of a mixed solution of deionized water and ethylene glycol, and stir to obtain an ethylene glycol dispersion; 0.0525 g of europium nitrate hexahydrate was dispersed in 2.625 mL of deionized water to obtain a europium nitrate hexahydrate solution. The europium nitrate hexahydrate solution was added to the ethylene glycol dispersion and stirred in the dark for 22 minutes. After stirring, the mixture was deposited under 300 W xenon lamp light with a wavelength ≥ 420 nm for 66 minutes. After deposition, the product was collected by centrifugation and washed alternately with deionized water and anhydrous ethanol for 3 times. After alternating washing, the product was transferred to a drying oven at 63°C and dried overnight to obtain a yellow In2O3 / In2S3 heterojunction photocatalytic material, which was recorded as D3.

[0017] Application Example 1 An application of a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, wherein the rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material prepared by the above-mentioned method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material is applied to the synthesis of urea by coupled methanol oxidation under visible light photocatalysis at room temperature and pressure; The synthetic urea is measured by diacetyl monoxime method to determine the amount of urea produced; The diacetyl monoxime method specifically comprises the following steps: Step 1: Mix 50 mL of concentrated phosphoric acid with 150 mL of concentrated sulfuric acid and distilled water to obtain a mixed solution. Dissolve 50 mg of ferric chloride in the mixed solution and dilute to 500 mL to obtain an acidic iron solution, which is designated as E1. Step 2: Dissolve 2.5 g of diacetyl monoxime and 50 mg of thiosemicarbazide in distilled water and dilute to 500 mL to obtain a diacetyl monoxime thiosemicarbazide ammonia solution, designated as F1. Step 3, take 2mL of acidic iron solution in E1 and 1mL of diacetyl monoxime thiosemicarbazide ammonia solution in F1 and ultrasonically mix them for 2min, add 1mL of urea solution sample after ultrasonic mixing and vigorously mix them for 2min using ultrasound to obtain a urea mixed solution, transfer the urea mixed solution to a boiling water bath and keep it for 20min. After the reaction is completed, naturally cool to room temperature, and then use a UV-visible photometer to obtain absorbance at 525nm, and obtain the measurement result according to the absorbance.

[0018] The urea solution sample adopts the standard urea solution to obtain the calibration curve to calibrate the yield.

[0019] In order to verify the effectiveness of the present invention, Figure 1 It can be seen that the XRD patterns of In2O3 and In2S3 can well correspond to the standard In2O3 (JCPDS PDF#06-0416) and In2S3 (JCPDS PDF#05-0731). Among them, the characteristic diffraction peaks of In2O3 at 2θ=30.58°, 35.47°, 51.04° and 60.68° are attributed to its (222), (400), (440) and (622) crystal planes, respectively; while the characteristic diffraction peaks of In2S3 at 2θ=28.80°, 33.45° and 48.00° are attributed to its (111), (200) and (220) crystal planes, respectively. In addition, the characteristic diffraction peaks corresponding to In2O3 and In2S3 can be found in the XRD pattern of the heterojunction material IOIS, indicating that In2S3 was successfully grown on In2O3. After further doping with rare earth element Eu, the XRD pattern of Eu-IOIS did not change significantly, and no diffraction peaks that may correspond to Eu metal clusters or Eu oxides appeared, which means that the doped Eu is highly dispersed.

[0020] from Figure 2 It can be seen that the In2O3 obtained by calcining MIL-68(In) maintains a hollow tubular structure ( Figure 2 a in the figure), In2S3 forms micron-scale flower balls in the form of irregular nanosheets ( Figure 2 In addition, from the SEM of Eu-IOIS ( Figure 2 It can be clearly seen in (c) that the originally smooth surface of the hollow tubular In2O3 becomes rough, indicating that the In2S3 nanosheets are successfully grown. Figure 2d) in the figure also proves that the hollow tubular structure is conducive to the contact, adsorption and activation of the catalyst and the reactants. And it can be seen from the HR-TEM image ( Figure 2 e) in the figure, it was found that the lattice fringe spacings of 0.253 nm and 0.268 nm in Eu-IOIS correspond to the (400) crystal plane of In2O3 and the (200) crystal plane of In2S3, respectively.

[0021] In addition, in the selected area electron diffraction (SAED) pattern of Eu-IOIS ( Figure 2 In figure f), diffraction rings corresponding to the (004) and (225) planes of In2O3 and the (002) and (023) planes of In2S3 can also be observed. The distribution of Eu-doped atoms was further observed by AC HAADF-STEM. Figure 2 As shown in g, the bright spots marked are identified as the presence of atomically dispersed Eu. Figure 2 h in the figure is the intensity distribution of the selected area. It can be found that the intensity of the Eu single atom is significantly higher than that of the surrounding atoms. Figure 2 The corresponding element mapping diagram in i shows that Eu, In, O and S elements are evenly distributed in Eu-IOIS.

[0022] like Figure 3 and Figure 4 As shown, after 4 h of photocatalytic reaction ( Figure 3 In (a), the urea yield of In2O3 and In2S3 is very low. Constructing a heterojunction (IOIS) can significantly improve their activity, and the yield of urea synthesized by photocatalytic coupling of N2 and CH3OH is further improved after Eu doping. Figure 3 The average yield of urea, In2O3, In2S3, IOIS and Eu-IOIS are shown to be 1.14, 1.81, 15.17 and 37.04 μmol / g / h, respectively ( Figure 3 b). In addition, the effects of reaction conditions on the photocatalytic coupling reaction were investigated. Figure 4 It can be seen that in the absence of N2 or CH3OH, no urea is produced, indicating that the product comes from the coupling of photocatalytic N2 and CH3OH. In addition, no urea is produced in the absence of catalyst or in the dark.

[0023] Figure 5The UV-vis-DRS spectra of the samples show that all synthesized photocatalysts exhibit a certain degree of light absorption in the UV-visible region. Among them, In2S3 has the best light absorption characteristics, with a light absorption range of up to 600nm and a relative light absorption intensity of 1.6. In2O3 has the worst light absorption characteristics, with a light absorption range of only up to 400nm and a relative light absorption intensity of 1.2. The light absorption characteristics of IOIS and Eu-IOIS are between In2O3 and In2S3, with only a small difference, indicating that Eu doping does not affect the light absorption properties of the samples.

[0024] Figure 6 and Figure 7 The photocurrent response diagram and impedance diagram of the prepared catalyst are shown in Figure 2. The photocurrent density-time curve indicates the generation of photogenerated charges in the semiconductor photocatalyst, while a smaller photocurrent density indicates that the photogenerated electrons and holes have a greater probability of recombination. Figure 6 As shown, Eu-IOIS has a significant high photocurrent response intensity (photocurrent density is 50-120μA·cm -1 range), the photocurrent densities of other samples were all less than 50 μA·cm -1 , which means that Eu-IOIS has the fastest carrier transfer speed and the highest carrier separation efficiency. Electrochemical impedance spectroscopy further studied the charge transfer efficiency of the prepared samples. The curvature radius of the curve in the electrochemical impedance spectroscopy can directly reflect the resistance to charge transfer. Figure 7 As shown in the figure, the curvature radius of Eu-IOIS is the smallest, indicating that the resistance of its photogenerated charges in the transfer process is the smallest and the charge separation efficiency is the highest, which is consistent with the photocurrent test results.

[0025] Figure 8 is the photoluminescence spectrum of the sample. The recombination of photogenerated electrons and holes will dissipate energy in the form of light and heat, generating fluorescence. Therefore, for photocatalysis, a good catalytic effect corresponds to a high separation efficiency of photogenerated charges, that is, a low photoluminescence intensity. As can be seen from the figure, all samples are excited with light of 550 nm wavelength and show an emission light signal near 830 nm. It can be observed that the photoluminescence intensity of IOIS is lower than that of In2O3 and In2S3, which means that the construction of the heterojunction reduces the recombination of photogenerated electrons and holes. In addition, the peak intensity of Eu-IOIS is the lowest, indicating that the recombination rate of photogenerated carriers in Eu-IOIS is the lowest.

[0026] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0027] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, characterized in that: The matrix of the In2O3 / In2S3 heterojunction photocatalytic material is In2O3 / In2S3; The MIL-68(In) precursor was synthesized by a hydrothermal method to obtain In2O3 hollow microtube photocatalyst; In2O3 / In2S3 heterojunction photocatalysts were obtained by growing In2S3 nanosheets on In2O3 hollow microtubes using an oil bath method. The rare earth element Eu is doped into the matrix lattice of the In2O3 / In2S3 heterojunction photocatalyst to obtain the In2O3 / In2S3 heterojunction photocatalytic material; The rare earth element Eu is dispersed in the form of single atoms, and the mass fraction of the rare earth element Eu is 0.22%.

2. A method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: Add terephthalic acid to dimethylformamide and stir vigorously to obtain a transparent solution; Indium nitrate hydrate is added to a transparent solution and dispersed and dissolved by ultrasonication to obtain a clear transparent solution; The clear and transparent solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated. After the reaction was completed, the reaction was naturally cooled to room temperature to obtain a white precipitate. The white precipitate was washed alternately with dimethylformamide and anhydrous ethanol. After the alternating washings, the product was collected by centrifugation and transferred to an oven for drying overnight to obtain a MIL-68(In) precursor. The MIL-68(In) precursor was placed on a ceramic boat and transferred to a muffle furnace for a temperature-elevated reaction to obtain an In2O3 hollow microtube photocatalyst. Step 2: adding indium trichloride tetrahydrate, thioacetamide, and citric acid monohydrate into a round-bottom flask, and adding deionized water into the round-bottom flask to obtain a mixture, and uniformly dispersing the mixture using ultrasound to obtain a uniformly dispersed solution; An In2O3 hollow microtube photocatalyst is added to a uniformly dispersed solution and stirred to obtain a stirred solution; the stirred solution is subjected to an oil bath reaction, and after completion of the reaction, the solution is naturally cooled to room temperature, and a product is collected by centrifugation. The collected product is alternately washed with deionized water and anhydrous ethanol, and after the washing is completed, the product is transferred to an oven for drying to obtain an In2O3 / In2S3 heterojunction photocatalyst; Step 3, dispersing the In2O3 / In2S3 heterojunction photocatalyst in a mixed solution of deionized water and ethylene glycol, and stirring to obtain an ethylene glycol dispersion; Europium nitrate hexahydrate is dispersed in deionized water to obtain a europium nitrate hexahydrate solution, the europium nitrate hexahydrate solution is added to an ethylene glycol dispersion and stirred, and then deposited under xenon light after stirring. After deposition, the product is collected by centrifugation and washed alternately with deionized water and anhydrous ethanol. After alternate washing, the product is transferred to a drying oven and dried overnight to obtain an In2O3 / In2S3 heterojunction photocatalytic material.

3. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: In the step 1, in the process of obtaining the In2O3 hollow microtube photocatalyst, the mass of terephthalic acid is 0.170-0.188 g, the volume of dimethylformamide is 57-63 mL, the mass of indium nitrate hydrate is 0.457-0.505 g, the volume of the polytetrafluoroethylene liner is 100 mL, the heating temperature of the stainless steel autoclave is 95-105°C, the heating time is 3.6-4.4 h, the dimethylformamide and anhydrous ethanol are alternately washed 3 times, and after collection, the mixture is transferred to an oven and dried overnight at a temperature of 76-84°C, the muffle furnace heating rate is 4.5-5.5°C / min, the muffle furnace reaction temperature is 445-455°C, and the reaction treatment time is 3.6-4.4 h.

4. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: The obtained In2O3 hollow microtube photocatalyst is light yellow.

5. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: In the step 2, in the process of obtaining the In2O3 / In2S3 heterojunction photocatalyst, the mass of indium trichloride tetrahydrate is 0.278-0.308 g, the mass of thioacetamide is 0.333-0.367 g, the mass of citric acid monohydrate is 0.931-1.027 g, the volume of deionized water added is 66.5-73.5 mL, the mass of the In2O3 hollow microtube photocatalyst added is 47.5-52.5 mg, the oil bath reaction temperature is 76-84°C, the oil bath reaction time is 1.8-2.2 h, the number of alternating washings with deionized water and anhydrous ethanol is 3 times, the temperature for drying in the oven is 76-84°C, and the time for drying in the oven is 10.8-13.2 h.

6. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: The obtained In2O3 / In2S3 heterojunction photocatalyst is yellow.

7. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: In the step 3, in the process of obtaining the In2O3 / In2S3 heterojunction photocatalytic material, the mass of the In2O3 / In2S3 heterojunction photocatalyst is 0.095-0.105 g, the volume of the mixed solution of deionized water and ethylene glycol is 23.75-26.25 mL, the mass of europium nitrate hexahydrate is 0.0475-0.0525 g, the volume of europium nitrate hexahydrate dispersed in deionized water is 2.375-2.625 mL, the europium nitrate hexahydrate solution is added to the ethylene glycol dispersion and stirred in the dark, the stirring time is 18-22 min, the xenon lamp power is 300 W, the xenon lamp wavelength is ≥420 nm, the light deposition time is 54-66 min, the number of alternating washings with deionized water and anhydrous ethanol is 3 times, and the temperature of the transfer to the drying oven for drying overnight is 57-63 ° C.

8. The method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to claim 2, characterized in that: The obtained In2O3 / In2S3 heterojunction photocatalytic material is yellow.

9. An application of a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material, the In2O3 / In2S3 heterojunction photocatalytic material prepared by the method for preparing a rare earth Eu-doped In2O3 / In2S3 heterojunction photocatalytic material according to any one of claims 2 to 8, characterized in that: The In2O3 / In2S3 heterojunction photocatalytic material is used to measure the amount of urea produced.

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