A bismuth vanadate-based composite nanomaterial, a preparation method and application thereof

Abstract

A kind of bismuth vanadate-based composite nanomaterial and preparation method and application.The present application belongs to the field of photocatalyst.The purpose of the present application is to solve the technical problems of low conduction band position of bismuth vanadate, insufficient oxygen activation ability, low visible light absorption, difficult migration of electron-hole pairs, lack of electron transfer rate and high charge recombination.The method of the present application is as follows: first, Fe-MOF is prepared by hydrothermal reaction of ferric chloride hexahydrate and 1,4-dicarboxybenzene;then, in an acidic solution, bismuth nitrate and ammonium metavanadate are used to prepare a bismuth vanadate precursor solution;finally, Fe-MOF is added to the bismuth vanadate precursor solution, followed by hydrothermal reaction.The present application uses one-step hydrothermal synthesis of bismuth vanadate precursor and Fe-MOF to form a heterojunction, and prepares a composite material with a decahedral structure, which promotes charge transfer, prolongs electron lifetime and improves photocatalytic activity.The present application is applied to the field of photocatalytic degradation of ametryn.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysts, specifically relating to a bismuth vanadate-based composite nanomaterial, its preparation method, and its application. Background Technology

[0002] Bismuth vanadate (BiVO4) has been reported as an excellent visible-light-dependent photocatalyst, operating in the visible light spectrum (45%), making it an efficient, stable, and inexpensive photocatalyst. While BiVO4 is excellent among many other semiconductor photocatalysts, its absorption of only 10% of the solar spectrum, low conduction band position, and insufficient oxygen activation ability, along with its low absorption, poor electron-hole pair (ehps) migration, lack of electron transfer rate, and high charge recombination, limit its application. These technical problems severely restrict the application of bismuth vanadate in photocatalysts and other fields. Therefore, it is essential to provide a simple, green, and efficient method for improving bismuth vanadate. Summary of the Invention

[0003] The purpose of this invention is to solve the technical problems of bismuth vanadate having a low conduction band position, insufficient oxygen activation ability, low visible light absorption, difficulty in electron-hole pair (ehps) migration, lack of electron transfer rate and high charge recombination. This invention provides a bismuth vanadate-based composite nanomaterial, its preparation method and application.

[0004] The technical solution of the present invention is as follows:

[0005] One objective of this invention is to provide a method for preparing bismuth vanadate-based composite nanomaterials, wherein the method includes:

[0006] S1: Ferric chloride hexahydrate and 1,4-dicarboxybenzene were subjected to a hydrothermal reaction in a solvent, and Fe-MOF was obtained after washing.

[0007] S2: In an acidic solution, bismuth nitrate and ammonium metavanadate are mixed to obtain a bismuth vanadate precursor solution;

[0008] S3: Fe-MOF was added to the bismuth vanadate precursor solution, followed by hydrothermal reaction. After washing and drying, bismuth vanadate-based composite nanomaterials were obtained.

[0009] Further specifying, the molar ratio of ferric chloride hexahydrate and 1,4-dicarboxybenzene in S1 is 1:1.

[0010] Further specify that the temperature of the hydrothermal reaction in S1 is 100-120℃ and the time is 12-24h.

[0011] Further specifying, the acidic solution in S2 is nitric acid with pH=1.

[0012] Further specifying, the molar ratio of bismuth nitrate to ammonium metavanadate in S2 is 1:1.

[0013] Further specifying, the hydrothermal reaction temperature in S2 is 110-130℃, and the time is 12-18h.

[0014] Further specified, S2 is mixed by magnetic stirring at 400-600 rpm for 1-2 hours.

[0015] Further specified, the mixer speed in S3 is 500-700 rpm, and the mixing time is 3-8 minutes.

[0016] The second objective of this invention is to provide a bismuth vanadate-based composite nanomaterial prepared by the above method, which has a decahedral structure.

[0017] The third objective of this invention is to provide an application of the bismuth vanadate-based composite nanomaterial prepared by the above method in the photocatalytic degradation of atrazine.

[0018] The advantages of this invention compared to the prior art are:

[0019] The method of this invention utilizes bismuth vanadate to form a heterojunction with Fe-MOF. After forming the heterojunction system, the oxygen activation ability is enhanced, and singlet oxygen becomes the main active group of the composite material. It also exhibits good photogenerated charge separation efficiency, demonstrating excellent photocatalytic degradation activity. Furthermore, the improvement of the preparation method of this invention compared to other methods lies in the in-situ growth method, which improves the material's inhomogeneity, difficulty in loading, and the high adsorption capacity of MOF materials. Fe-MOF is modified under acidic conditions to ensure uniform distribution of iron ions in the bismuth vanadate particles. The dispersion and loading of Fe are driven by the MOF material, and a green, low-cost decahedral composite material is synthesized in one hydrothermal step. Attached Figure Description

[0020] Figure 1 SEM images of the 0.15Fe-MOF / BiVO4 composite nanomaterial prepared in Example 1 of this invention from different angles;

[0021] Figure 2 The X-ray diffraction patterns of Fe-MOF, BiVO4, and 0.15Fe-MOF / BiVO4 in Example 1 of this invention are shown below.

[0022] Figure 3 The solid-state fluorescence (PL) spectra of BiVO4 and 0.15Fe-MOF / BiVO4 in Example 1 of this invention are shown.

[0023] Figure 4 This is a free radical capture experiment diagram of BiVO4 and 0.15Fe-MOF / BiVO4 in Example 1 of the present invention;

[0024] Figure 5aThe ultraviolet-visible diffuse reflectance (DRS) spectra and estimated band gap energies of Fe-MOF, BiVO4, and 0.15Fe-MOF / BiVO4 in Example 1 of this invention are shown.

[0025] Figure 5b The Mott-Schottky curve of 0.15Fe-MOF / BiVO4 prepared in Example 1 of this invention;

[0026] Figure 6a The graph shows the photocatalytic degradation performance of BiVO4 and 0.15Fe-MOF / BiVO4 in Example 1 of this invention.

[0027] Figure 6b for Figure 6a The corresponding quasi-first-level power curve;

[0028] Figure 7 This is a stability test diagram of the photocatalytic degradation of atrazine by 0.15Fe-MOF / BiVO4 in Example 1 of the present invention. Detailed Implementation

[0029] This invention provides a method for preparing bismuth vanadate-based composite nanomaterials, the specific steps of which are as follows:

[0030] (1) Dissolve ferric chloride hexahydrate and 1,4-dicarboxybenzene in N,N-dimethylformamide in a molar ratio of 1:1, stir and mix evenly at room temperature, then hydrothermally react at 100-120℃ for 12-24h, and finally wash with deionized water and ethanol alternately to obtain Fe-MOF;

[0031] (2) Dissolve bismuth nitrate completely in nitric acid at pH=1, then add ammonium metavanadate at a molar ratio of 1:1 to ammonium metavanadate, and stir magnetically at 400-600 rpm for 1-2 hours at room temperature to obtain a pale yellow bismuth vanadate precursor solution.

[0032] (3) Fe-MOF was added to the bismuth vanadate precursor solution at a mass ratio of 1:(0.1-0.2) and then hydrothermally reacted at 110-130℃ for 12-18h. Finally, the mixture was washed alternately with deionized water and ethanol and dried at 60-80℃ for 3-5h to obtain bismuth vanadate-based composite nanomaterials.

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0035] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0036] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0037] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0038] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0039] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] Example 1:

[0041] The preparation method of the bismuth vanadate-based composite nanomaterial in this embodiment is carried out according to the following steps:

[0042] (1) Dissolve 0.01 mol ferric chloride hexahydrate and 0.01 mol 1,4-dicarboxybenzene in 100 mL of N,N-dimethylformamide, stir and mix evenly at room temperature, and then hydrothermally react at 110 °C for 24 h. Finally, wash with deionized water and ethanol alternately, three times each, to obtain Fe-MOF.

[0043] (2) Dissolve 0.01 mol of bismuth nitrate completely in 40 mL of nitric acid with pH = 1, then add 0.01 mol of ammonium metavanadate, and stir magnetically at room temperature and 500 rpm for 2 h to obtain a pale yellow bismuth vanadate precursor solution, denoted as BiVO4;

[0044] (3) Add Fe-MOF to the bismuth vanadate precursor solution, and then perform hydrothermal reaction at 120℃ for 15h. Finally, wash with deionized water and ethanol alternately, three times each, and then dry at 70℃ for 4h to obtain Fe-MOF driven dispersion BiVO4 composite nanomaterial, i.e. 15% Fe-MOF driven dispersion bismuth vanadate-based composite nanomaterial, denoted as 0.15Fe-MOF / BiVO4.

[0045] (I) Scanning electron microscopy was performed on the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1. The test results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the 0.15Fe-MOF / BiVO4 composite material prepared in Example 1 is a three-dimensional nanostructure, forming a relatively regular decahedron.

[0046] (II) XRD tests were performed on the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1. The test results are as follows: Figure 2 As shown. By Figure 2 The diffraction peaks of the sample are consistent with the card number in the standard spectral library (JCPDS No. 14-0668), proving that the prepared nanoparticle sample is a pure phase Fe-MOF / BiVO4. Furthermore, the high peak intensity indicates that the sample has good crystallinity.

[0047] (III) Solid-state fluorescence (PL) spectroscopy was performed on the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1 to study the dynamic changes in charge separation during photocatalysis. Figure 3 This indicates that the recombination of Fe-MOF enables the effective transfer of photogenerated carriers in BiVO4, resulting in a certain degree of fluorescence quenching.

[0048] (iv) Free radical capture experiments were conducted on the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1. These experiments were used to identify the main active species involved in the degradation of atrazine by the catalyst. During the experiments, EDTA-2Na, NaN3, BQ, and IPA were used as h... + , 1 O2、·O2 - ·OH is a ·OH- scavenging reagent. The specific steps are as follows:

[0049] 0.2 g of photocatalyst was placed in a beaker containing 50 mL of atrazine (10 mg / L) aqueous solution. After stirring in the dark until adsorption-desorption equilibrium was reached, 0.8 mL of IPA and 0.8 mL of 0.001 M BQ, EDTA-2Na, and NaN3 were added to the above solution, respectively. Irradiation (300 mW / cm²) was applied. 2 After 30 min, the catalyst was removed by filtration through a 0.22 μm filter membrane. The concentration of the target atrazine in the filtrate was determined by HPLC. The active groups in the photocatalytic degradation process were preliminarily identified by comparing the concentration of residual atrazine after 30 min of illumination with that of the sample without the trapping reagent. Results are as follows: Figure 4 As shown, by Figure 4 It can be determined that the active species for the degradation of atrazine by pure BiVO4 is ·O2. - The active species of the Fe-MOF / BiVO4 composite material is O2. - and 1 O2 is derived from the enhanced conduction band position of the MOF composite material, which improves oxygen activation capacity and even the energy conversion between Fe atoms and BiVO4 at the MOF center. The increased abundance and number of active species significantly enhance the catalytic degradation activity of atrazine.

[0050] (V) The Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1 were subjected to UV-Vis diffuse reflectance spectroscopy (DRS) and Mott-Schottky analysis. The results are shown in Figure 5. The DRS spectra can be used to estimate the band gap energy (E) of Fe-MOF, BiVO4, and 0.15Fe-MOF / BiVO4. g The potentials were 2.77, 2.38, and 2.49 eV, respectively. Meanwhile, Mott-Schottky analysis revealed the flat-band potential (E) of 0.15Fe-MOF / BiVO4. fb = -0.82eV), and its slope is positive, indicating that it is an n-type semiconductor. The conduction band potential (E) of an n-type semiconductor is... CB The value of ) is greater than E fb The negative value is approximately 0.2 eV; therefore, the E of 0.15Fe-MOF / BiVO4 is... CBIt is -1.02 eV. Then, according to E... VB =E CB +E g The valence band position E of 0.15Fe-MOF / BiVO4 can be calculated. VB The band gap is 1.47 eV. As shown in Figure 5, the band gap of 0.15Fe-MOF / BiVO4 increases, improving the absorption and utilization of visible light. Simultaneously, the conduction band position of 0.15Fe-MOF / BiVO4 (E...)... CB =-1.02eV) compared to BiVO4(E CB The value of 0.49eV is much higher, which makes up for the deficiency of the low conduction band position of BiVO4.

[0051] (vi) The degradation activity of the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1 was analyzed. The photocatalytic activity of the catalyst was evaluated by photocatalytic degradation of atrazine. The specific steps are as follows:

[0052] A 300W spherical xenon lamp was used as the light source, and the filter (420nm < λ < 780nm) was placed 10cm above the liquid surface. The light intensity at the center of the reactant was 300mW / cm². 2 Next, 0.2 g of photocatalyst was mixed with 50 mL of atrazine (10 mg / L) aqueous solution and stirred at room temperature in the dark for 30 min until adsorption-desorption equilibrium was reached. The mixture was then stirred and exposed to light. Every 30 minutes, 1 mL of the mixture was taken from the reactor and the catalyst was removed using a 0.22 μm filter membrane. High-performance liquid chromatography (LC-15C, SHIMADZU) was used with a C18 column (4.6 × 250 mm, 5.0 μm), a mobile phase of methanol:water = 70:30, and a flow rate of 1.0 mL / min. -1 The remaining concentration of atrazine was detected at a wavelength of 225 nm. The results are shown in Figure 6. As can be seen from Figure 6, by comparing the first-order kinetic rate constant in the first-order kinetic curve, 0.15Fe-MOF / BiVO4 exhibits a photocatalytic degradation rate constant (k = 0.0132 min⁻¹). -1 ), approximately BiVO4 (k = 0.0019 min -1 The efficiency was 6.9 times that of 0.15Fe-MOF / BiVO4, indicating that the photocatalytic activity of 0.15Fe-MOF / BiVO4 was good and the performance was effectively achieved.

[0053] (vii) The degradation and atrazine stability of the Fe-MOF-driven dispersed BiVO4 composite nanomaterials prepared in Example 1 were analyzed. The stability of the catalyst was confirmed by the photostability test of a continuous reaction of 0.15Fe-MOF / BiVO4. The results are as follows: Figure 7 As shown, by Figure 7It can be seen that the activity of 0.15Fe-MOF / BiVO4 decreased by less than 10% after four cycles, indicating that 0.15Fe-MOF / BiVO4 has good photocatalytic stability.

[0054] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The application of a bismuth vanadate-based composite nanomaterial in the photocatalytic degradation of atrazine, characterized in that, The preparation method of the bismuth vanadate-based composite nanomaterial is as follows: S1: Ferric chloride hexahydrate and 1,4-dicarboxybenzene were subjected to a hydrothermal reaction in a solvent, and Fe-MOF was obtained after washing. S2: In an acidic solution, bismuth nitrate and ammonium metavanadate are mixed to obtain a bismuth vanadate precursor solution; The acidic solution is nitric acid with a pH of 1; S3: Fe-MOF was added to the bismuth vanadate precursor solution, followed by hydrothermal reaction. After washing and drying, bismuth vanadate-based composite nanomaterials were obtained.

2. The application according to claim 1, characterized in that, The molar ratio of ferric chloride hexahydrate to 1,4-dicarboxybenzene in S1 is 1:

1.

3. The application according to claim 1, characterized in that, The hydrothermal reaction in S1 takes place at a temperature of 100-120℃ for 12-24 hours.

4. The application according to claim 1, characterized in that, The molar ratio of bismuth nitrate to ammonium metavanadate in S2 is 1:

1.

5. The application according to claim 1, characterized in that, The hydrothermal reaction in S2 takes place at a temperature of 110-130℃ for 12-18 hours.

6. The application according to claim 1, characterized in that, In S2, the mixture is stirred magnetically at 400-600 rpm for 1-2 hours.

7. The application according to claim 1, characterized in that, The mixer speed in S3 is 500-700 rpm, and the mixing time is 3-8 minutes.

Images