MnIn2S4atVS4 heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a MnIn2S4-coated VS4 heterojunction photocatalyst and a preparation method and application thereof, and relates to the technical field of photocatalytic materials.The preparation method comprises the following steps that vanadium powder, a sulfur source and ethyl alcohol serve as raw materials to be mixed to obtain mixed slurry, the mixed slurry reacts in a ball mill, then filtering, centrifuging and drying are conducted, and VS4 nanosheets are obtained; and epitaxially growing the MnIn2S4 nanosheet on the surface of the VS4 nanosheet at a low temperature to obtain the MnIn2S4-coated VS4 heterojunction photocatalyst with a double-flower-shaped interlaced structure. The VS4 flower-shaped nanosheet is prepared at normal temperature by adopting a ball milling method, the specific surface area is nearly two times that of a hydrothermal method, the problem of insufficient exposure of active sites caused by irregular high-temperature morphology and low specific surface area of a traditional hydrothermal method is solved, non-epitaxial growth caused by high-temperature rapid nucleation is avoided, lattice repair of VS4 is realized, high-temperature or high-pressure equipment is not needed in the whole process, and the preparation method is suitable for industrial production. Compared with a traditional step-by-step hydrothermal method, the working time is shortened by 80%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalytic materials, and particularly relates to a MnIn2S4@VS4 heterojunction photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] With the acceleration of global industrialization, water pollution caused by antibiotic abuse is intensifying, threatening ecological safety and human health. At the same time, the surge in demand for clean energy development is driven by the energy crisis, and photocatalytic technology has become a research hotspot because it can utilize solar energy to degrade pollutants and produce hydrogen. However, existing photocatalysts have weak visible light response and low carrier separation efficiency, making it difficult to balance high degradation and hydrogen production performance. Developing new high-performance photocatalytic materials is of great significance to solving energy and environmental problems.

[0003] Vanadium tetrasulfide (VS4) is a kind of narrow-band-gap semiconductor (Eg≈1.3 eV), which is considered as a potential material in the field of photocatalysts due to its excellent visible light absorption capacity and high carrier mobility. However, these theoretical advantages are difficult to realize in practical applications, mainly due to the lack of control over the material structure in existing synthesis techniques.

[0004] The current mainstream method is high-temperature hydrothermal method. For example, patent document CN118943305A discloses a preparation method and application of a vanadium tetrasulfide-based lithium-sulfur battery positive electrode. In the patent, VS4 is prepared at a temperature of 150-200℃ for 20-30h. Although the VS4 prepared by this method has good electrical properties, the morphology of VS4 is uneven and easy to agglomerate under such high-temperature conditions, and the specific surface area is usually less than 20 m2 / g, resulting in insufficient exposure of active sites, and the degradation efficiency of photocatalysts is positively correlated with specific surface area. Similarly, patent document CN116216777B discloses a honeycomb-like vanadium tetrasulfide material and its preparation method and application. The preparation conditions of VS4 are also under high-temperature conditions of 160-200℃. Although it has good photoelectric properties, it also has the problems of small specific surface area and high carrier recombination rate caused by high-temperature preparation conditions.

[0005] In recent years, some studies have tried to improve it (such as the VS4-based composite material reported in the literature "Hydrothermal Synthesis and Characterization of Sulfur-doped g-C3N4 / VS4 nanocomposite for efficient photocatalytic applications"), but the morphology problem has not been fundamentally solved, and additional costs are introduced.

[0006] To improve the photocatalytic efficiency of a single semiconductor, constructing a heterojunction has become a mainstream strategy, but the core difficulty lies in the interface lattice matching degree. The patent document with publication number CN108889312B discloses a preparation method of a full-waveband photocatalytic nano array, which utilizes the visible-near infrared light response of VS4 and the ultraviolet light catalytic ability of TiO2 to attempt to achieve full spectrum utilization. However, the difference in lattice constants between the two (VS4 (110) crystal plane spacing 0.56 nm vs TiO2 (101) crystal plane spacing 0.35 nm) leads to interface stress accumulation when high-temperature compounding, forming lattice distortion and becoming an electron-hole pair recombination center, which seriously limits the further improvement of its photocatalytic performance. In addition, the patent document with publication number CN115608388A discloses a shell-core type Cs3PMo 12 O 40 / MnIn2S4 composite photocatalyst and its preparation method and application, which realizes the assembly of petal-shaped MnIn2S4 on the surface of Cs3PMo 12 O 40 balls, but due to the difference in crystal structure between MnIn2S4 and Cs3PMo 12 O 40 (the former is hexagonal phase and the latter is cubic phase), the non-epitaxial growth of the heterojunction interface causes lattice distortion, limiting the efficiency of charge directional transmission.

[0007] MnIn2S4 is a photocatalytic material with excellent photoelectric performance, and its (311) crystal plane and VS4 (022) crystal plane spacing match, which is expected to form a heterostructure. However, the preparation process of high-performance MnIn2S4 material is complex and the cost is high. The patent document with publication number CN118594567A discloses an amorphous structure photocatalyst formed by etching MnIn2S4 ultra-thin nanosheets based on H2O2 and its method, which innovatively increases the number of active sites by surface disordering, making the CO2 reduction efficiency increase by 3.8 times. However, this method still relies on the synthesis of precursors by solvothermal method, and the precise control of the etching step (20-40 seconds) greatly increases the process complexity, making it difficult to scale up production.

[0008] In summary, the existing technology has not solved the following core problems: (1) how to realize the controllable morphology, high specific area and low cost mass production of VS4 under mild conditions; (2) how to avoid lattice mismatch caused by high temperature to realize the epitaxial growth of MnIn2S4 on the surface and establish an efficient charge transfer channel, i.e. the lattice matching type heterojunction design of MnIn2S4 and narrow band gap semiconductor; (3) the full-process green, energy-saving and simple synthesis process meets the needs of industrialization. These defects jointly restrict the practical application process of high-efficiency photocatalysts. SUMMARY

[0009] Based on the problems of irregular morphology, low specific surface area and insufficient exposure of active sites of the photocatalyst prepared by the hydrothermal method at present, the purpose of the present application is to provide a MnIn2S4@VS4 heterojunction photocatalyst and a preparation method and application thereof, VS4 flower-like nanosheets are prepared by ball milling at room temperature, the specific surface area is nearly 2 times that of the hydrothermal method, the problems of irregular morphology and low specific surface area of the traditional hydrothermal method leading to insufficient exposure of active sites are solved, and non-epitaxial growth caused by high temperature rapid nucleation is avoided, the lattice repair of VS4 is realized, and the whole process does not need high temperature or high pressure equipment, and the working hours are shortened by 80% compared with the traditional step-by-step hydrothermal method.

[0010] The present application is realized by the following technical solutions: In a first aspect, the present application provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst, comprising the following steps: Vanadium powder, sulfur source and ethanol are mixed as raw materials to obtain mixed slurry, the mixed slurry is reacted in a ball mill, and then filtered, centrifuged and dried to obtain VS4 nanosheets; The MnIn2S4 nanosheets are epitaxially grown on the surface of the VS4 nanosheets to obtain a MnIn2S4@VS4 heterojunction photocatalyst with a double flower-like interlaced structure.

[0011] The purity of the vanadium powder is 99.5%, and the particle size is 325 mesh.

[0012] The ball-milled and sieved products are separated, and washed and dried by alternately centrifuging with water and ethanol, the drying process is at 60-100 DEG C, and the drying time is 8-12 hours.

[0013] The material of the grinding ball is zirconia, and the size is a mixture of 3mm and 5mm, the volume ratio of the ethanol and the solid formed by the grinding ball and the precursor raw material used for ball milling is 1: (0.2-1), and the ratio of the material to the ball is (5-40):1.

[0014] In the currently disclosed technology, the preparation method of VS4 material usually adopts high-temperature solvothermal method, which has high temperature (above 160 DEG C) and long time (more than 12 hours), and the prepared VS4 material has the problems of poor morphology, uneven size and small specific surface area. In addition, there is a lack of corresponding research on the lattice regulation of MnIn2S4 and VS4 by heterojunction engineering and its application in the field of photocatalysis. The present application realizes the low-energy consumption synthesis of VS4 by ball milling, which only needs to react at room temperature, and the amount of VS4 (kilogram level) obtained by single preparation is much larger than that (gram level) obtained by the hydrothermal method.

[0015] The application selects MnIn2S4 and VS4 to form a heterojunction, the (311) crystal surface of MnIn2S4 and the (022) crystal surface of VS4 match in spacing, and when the low-temperature epitaxial growth of MnIn2S4 is performed on the surface of VS4, the MnIn2S4 can gradually nucleate on the surface of VS4 and epitaxially grow along a specific crystal surface, and the lattice distortion is repaired by releasing the interface stress, so that the overall crystallinity of the composite sample is improved. If the high-temperature growth of MnIn2S4 is adopted in the compounding process, the excessively high temperature can cause the random nucleation of MnIn2S4, and the non-epitaxial growth mode can cause the serious mismatch of the lattice, and the excessive growth can also cover the active sites of VS4. The low-temperature oil bath method for epitaxial growth of MnIn2S4 can slowly repair the VS4 lattice and release the stress, and the non-arbitrary sulfide can be compared. Therefore, the application realizes the application purpose by the low-temperature epitaxial growth of MnIn2S4.

[0016] The application proposes a ball milling method for preparing VS4 materials at room temperature, and a low-temperature oil bath method for epitaxially growing MnIn2S4 nanosheets to form a heterojunction composite material under mild conditions. Experimental data show that, compared with the VS4 material prepared by the high-temperature hydrothermal method, the specific surface area of the VS4 material prepared by the ball milling method is increased by nearly 2 times, and the low-temperature epitaxial growth of MnIn2S4 nanosheets (compared with the high-temperature compounding) can significantly repair the lattice of the VS4 material, and the degradation efficiency of ofloxacin is 7.9 times, 6.2 times and 1.3 times that of the VS4 photocatalyst prepared by the hydrothermal method, the VS4 photocatalyst prepared by the ball milling method and the commercial P25 (TiO2) photocatalyst, respectively.

[0017] Further, when the VS4 nanosheet is prepared, the molar ratio of the vanadium powder to the sulfur source is 1: (4-6).

[0018] Further, the sulfur source is a mixture of thioacetamide and thiourea, and the molar ratio of the thioacetamide to the thiourea is 1: (1-2).

[0019] The reason for using thioacetamide and thiourea as the sulfur source (instead of sodium sulfide or sulfur powder) is that the thioacetamide and the thiourea are both easily soluble in water, and the unreacted sulfur source after the ball milling reaction can be removed by water washing, which is a simple operation. If sodium sulfide is used, it will quickly deliquesce and volatilize to generate H2S gas in the air, which not only causes the loss of the sulfur source, but also easily pollutes the environment. If the sulfur powder is used (not soluble in water, slightly soluble in ethanol, and easily soluble in carbon disulfide), it cannot be removed by water and ethanol, and the use of volatile and toxic carbon disulfide will increase the safety hidden danger in the experimental process. On the other hand, the boiling point of the sulfur powder is 444.6℃, and the use of high-temperature calcination to evaporate the sulfur will increase the energy consumption. Therefore, the application uses thioacetamide and thiourea as the sulfur source to avoid the pollution to the environment, and at the same time, the safety in the preparation process is improved.

[0020] Further, the concentration of the solid substance in the mixed slurry is 0.5 mol / L-4 mol / L, and the solid substance is vanadium powder and a sulfur source.

[0021] Further, in the preparation of the VS4 nanosheet, the ball milling is performed in a forward-reverse rotation cycle mode, and the rotation speed of the ball milling is 200-500 revolutions / minute.

[0022] Specifically, the ball milling mode can be set as forward rotation for 10 minutes, followed by pause for 1 minute, then reverse rotation for 10 minutes, and the cycle is repeated until the predetermined ball milling time is reached.

[0023] Further, the method for low-temperature epitaxial growth of the MnIn2S4 nanosheet on the surface of the VS4 nanoflower is as follows: The VS4 nanosheet is added to a deionized water solution, then manganese chloride, indium chloride tetrahydrate and thioacetamide are added, and a solid-liquid mixture is obtained after ultrasonic stirring. The solid-liquid mixture is reacted in an oil bath at a temperature of 60-100°C, then cooled, centrifuged, washed and dried to obtain a MnIn2S4@VS4 heterojunction photocatalyst with a double-flower-like interwoven structure.

[0024] The centrifugation is performed in a centrifuge at a rotation speed of 4000-8000 revolutions / minute for 5-100 minutes, the washing is performed by alternating deionized water and anhydrous ethanol for 3 times or more, the drying temperature is 60-100°C, and the drying time is 8-12 hours.

[0025] Further, the molar ratio of the VS4 nanosheet to manganese chloride is 1:(1-4); and the molar ratio of the manganese chloride, indium chloride tetrahydrate and thioacetamide is 1:2:(4-8).

[0026] Further, the size of the MnIn2S4 nanosheet is 100-1000 nm, and the thickness is 10-100 nm. Further, the size of the VS4 nanosheet is 10-500 nm, the thickness is 10-200 nm, and the size of the micron flower formed is 300-3000 nm. Further, the size of the nanosheet on the MnIn2S4@VS4 heterojunction photocatalyst is 100-1000 nm, the thickness is 10-100 nm, and the size of the micron flower formed is 400-4000 nm. Preferably, the size of the nanosheet on the MnIn2S4@VS4 heterojunction photocatalyst is 500 nm, the thickness is 50 nm, and the size of the micron flower formed is 2500 nm.

[0027] In a second aspect, the application provides a MnIn2S4@VS4 heterojunction photocatalyst prepared by the above preparation method.

[0028] In a third aspect, the application provides an application of the MnIn2S4@VS4 heterojunction photocatalyst, including for photocatalytic decomposition of water to produce hydrogen, overall decomposition of water, or degradation of organic pollutants.

[0029] In the application, the organic pollutants include any one of ofloxacin, tetracycline hydrochloride, phenol, methylene blue, and rhodamine B.

[0030] Compared with the prior art, the application has the following advantages and beneficial effects: (1) In the application, the (311) crystal plane of MnIn2S4 and the (022) crystal plane of VS4 match in spacing, the epitaxial growth of MnIn2S4 nanosheets on the VS4 flower-shaped substrate is realized by a low-temperature oil bath method, a heterojunction interface with atomic-level close contact is formed, the lattice distortion of VS4 is effectively repaired, the heterojunction promotes the directional movement of electrons, the photocurrent density is increased by 40%, the photocatalytic degradation efficiency of ofloxacin is 30% higher than that of a commercial P25 catalyst, and the problem of lattice distortion caused by traditional high-temperature hydrothermal compounding (> 160°C) is completely avoided, thereby providing a new paradigm for efficient type II heterostructures.

[0031] (2) In the application, the VS4 flower-shaped nanosheets are prepared by a ball milling method at room temperature, and the specific surface area is nearly 2 times that of the hydrothermal method, thereby solving the problem of insufficient exposure of active sites caused by irregular morphology and low specific surface area at high temperature in the traditional hydrothermal method. The batch yield reaches the kilogram level, and the whole process has low energy consumption, thereby having good commercialization prospects; a low-temperature oil bath compounding process is simultaneously developed, non-epitaxial growth caused by high-temperature rapid nucleation is avoided, the lattice of VS4 is repaired, the whole process does not need high-temperature or high-pressure equipment, the working hours are shortened by 80% compared with the traditional step-by-step hydrothermal method, and the road for commercial continuous production is smoothed.

[0032] (3) The MnIn2S4@VS4 heterojunction photocatalyst prepared in the application has excellent photocatalytic degradation of organic pollutants and overall decomposition of water. The double-flower-shaped hierarchical structure (VS4 as “petals” and MnIn2S4 as “petals”) promotes the multiple reflection of light to enhance light absorption, and the heterojunction cooperatively promotes the directional movement of photo-generated carriers. In the degradation of ofloxacin, the degradation efficiency of the MnIn2S4@ball-milling VS4 grown by low-temperature oil bath is 2.4 times and 1.3 times that of the MnIn2S4@ball-milling VS4 grown by high-temperature hydrothermal method and the commercial mature P25 photocatalyst, respectively, and after 5 cycles and 10 hours, the initial degradation efficiency still reaches 95%, and under the condition of no noble metal loading and no sacrificial agent, the hydrogen production rate reaches 8.86 mmol·h -1 ·g -1 ·g -1 ·g -1The photocatalytic material has a high oxygen production rate, and shows good multifunctional photocatalytic performance, and breaks through the practical application bottleneck of existing VS4-based materials caused by interface lattice distortion and carrier recombination. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 X-ray diffraction (XRD) patterns of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-6 of the present application, wherein (a) is the XRD pattern of the photocatalytic materials prepared in Comparative Examples 3-6, and (b) is the XRD pattern of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-2; Figure 2 Scanning electron microscope (SEM) morphology diagrams of the photocatalytic materials prepared in Example 1 and Comparative Examples 3-4 of the present application, wherein (a), (b) and (c) are SEM diagrams of the photocatalytic materials prepared in Comparative Example 4, Comparative Example 3 and Example 1, respectively; Figure 3 High-resolution transmission electron microscope (HRTEM) morphology diagrams of the photocatalytic materials prepared in Example 1, Comparative Example 1 and Comparative Example 3 of the present application, wherein (a), (b) and (c) are HRTEM diagrams of the photocatalytic materials prepared in Comparative Example 3, Example 1 and Comparative Example 1, respectively; Figure 4 Photocatalytic performance diagrams of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 of the present application, wherein (a) is a rate curve diagram of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 for degrading ofloxacin, and (b) is a stability comparison columnar diagram of the photocatalytic materials prepared in Example 1 and Comparative Example 7 for degrading ofloxacin, wherein each cycle is subjected to a continuous 2-hour ofloxacin degradation experiment; Figure 5 Photocatalytic performance diagrams of the photocatalytic material prepared in Example 1, wherein (a) and (b) are respectively a rate curve diagram and an average rate columnar diagram of the photocatalytic material prepared in Example 1 for simultaneously producing hydrogen and oxygen in double decomposition of water; Figure 6 Current density curve diagrams of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 of the present application, wherein (a) is a current density curve diagram of the photocatalytic materials prepared in Comparative Examples 3-6, and (b) is a current density curve diagram of the photocatalytic materials prepared in Example 1, Comparative Examples 1-2 and Comparative Example 7; Figure 7A differential charge density map for the photocatalytic material prepared in Example 1. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. The illustrative embodiments of the present application and their description are only used to explain the present application and not as a limitation of the present application.

[0036] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without these specific details. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present application.

[0037] In the description of the present application, the mention of "one embodiment", "an embodiment", "one example" or "an example" means that the particular feature, structure, or characteristic following the phrase is included in at least one embodiment of the present application. Therefore, the appearance of the phrase "in one embodiment", "in an embodiment", "in one example" or "in an example" in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments or examples. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In addition, those skilled in the art will be able to make and use the present application with the different embodiments or examples described in the specification and the features of the different embodiments or examples can be combined and arranged in any suitable manner without departing from the scope of the present application.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Example 1 This embodiment provides a method for preparing a MnIn2S4@VS4 heterojunction photocatalyst using a ball milling combined with a low-temperature oil bath method. The specific preparation steps are as follows: S1. Mix 10 mmol vanadium powder, 20 mmol thioacetamide and 30 mmol thiourea evenly, add 30 mL ethanol and ultrasonically disperse for 10 minutes to form a uniform slurry. S2. The mixed slurry and zirconia grinding balls with a size of 3mm and 5mm are loaded into a grinding jar. The ethanol to solid (formed by the precursor raw material and grinding balls) volume ratio is 1:0.5 and the ball mass ratio is 20:1. The rotation speed is controlled at 300 rpm. The cyclic mode of 10 minutes forward rotation - 1 minute pause - 10 minutes reverse rotation is adopted and the ball milling is continued for 12 hours. S3. After ball milling, rinse the mixture alternately with water and ethanol, and filter through a 400-mesh sieve to separate the grinding balls, unreacted vanadium powder, and other powders. Centrifuge at 5000 rpm for 5 minutes, then wash alternately with water and ethanol 5 times or more, and dry in a drying oven at 80°C. o Drying at C for 12 hours yields VS4 nanosheets obtained by ball milling. S4, 1 mmol of VS4 nanosheets (the size of the VS4 nanosheets is 200 nm, the thickness is 100 nm, and the size of the microflowers formed is 1500 nm) are added to 60 mL of deionized water and ultrasonically stirred and dispersed for 10 minutes, and then 2 mmol of manganese chloride, 4 mmol of indium chloride tetrahydrate, and 12 mmol of thioacetamide are added, and after ultrasonic stirring and dispersion for 10 minutes, a solid-liquid mixture is obtained; wherein the size of the MnIn2S4 nanosheets grown on the VS4 nanosheets is 500 nm, and the thickness is 50 nm; S5, the solid-liquid mixture is transferred to a 150 mL two-necked flask, and then the flask is placed in an oil bath, and the reaction is carried out at 80°C and continuously stirred for 1.5 h, and after the reaction is completed, it is naturally cooled; S6, the cooled sample is centrifuged in a centrifuge at a speed of 5000 revolutions per minute for 5 minutes, washed with water and ethanol alternately for 5 times, and dried in a vacuum oven at 80°C for 12 h to obtain a MnIn2S4@VS4 heterojunction photocatalyst prepared by ball milling combined with a low-temperature oil bath method (the size of the nanosheets on the MnIn2S4@VS4 heterojunction photocatalyst is 500 nm, the thickness is 50 nm, and the size of the microflowers formed is 2500 nm).

[0040] Example 2 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst prepared by ball milling combined with a low-temperature oil bath method, and the difference between the embodiment and example 1 is that the molar ratio of vanadium powder to sulfur source in the embodiment is 1:4, and the molar ratio of thioacetamide to thiourea is 1:1. That is, step S1 is: 10 mmol of vanadium powder and 20 mmol of thioacetamide and 20 mmol of thiourea are uniformly mixed, 30 mL of ethanol is added and ultrasonically dispersed for 10 minutes to form a uniform slurry. The other steps are the same as those in example 1.

[0041] Example 3 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst prepared by ball milling combined with a low-temperature oil bath method, and the difference between the embodiment and example 1 is that the molar ratio of vanadium powder to sulfur source in the embodiment is 1:6, and the molar ratio of thioacetamide to thiourea is 1:2. That is, step S1 is: 10 mmol of vanadium powder and 20 mmol of thioacetamide and 40 mmol of thiourea are uniformly mixed, 30 mL of ethanol is added and ultrasonically dispersed for 10 minutes to form a uniform slurry. The other steps are the same as those in example 1.

[0042] Example 4 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a ball milling combined low-temperature oil bath method, different from the embodiment 1, the oil bath reaction temperature in the embodiment is 60 DEG C, namely, the step S5 is that the solid-liquid mixture is transferred to a 150 mL two-necked flask, then the flask is placed in an oil bath pot, and reaction is carried out at 60 DEG C and continuous stirring is carried out for 1.5 h, and the reaction is naturally cooled after being completed. The other steps are the same as those in the embodiment 1.

[0043] Embodiment 5 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a ball milling combined low-temperature oil bath method, different from the embodiment 1, the oil bath reaction temperature in the embodiment is 100 DEG C, namely, the step S5 is that the solid-liquid mixture is transferred to a 150 mL two-necked flask, then the flask is placed in an oil bath pot, and reaction is carried out at 100 DEG C and continuous stirring is carried out for 1.5 h, and the reaction is naturally cooled after being completed. The other steps are the same as those in the embodiment 1.

[0044] Embodiment 6 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a ball milling combined low-temperature oil bath method, different from the embodiment 1, the molar ratio of the VS4 nanosheet to manganese chloride in the embodiment is 1:1; the molar ratio of manganese chloride, indium chloride tetrahydrate and thioacetamide is 1:2:4. Namely, the step S4 is that 1 mmol of the VS4 nanosheet (the size of the VS4 nanosheet is 200 nm, the thickness is 100 nm, and the size of the micron flower formed is 1500 nm) is added into 60 mL of deionized water and ultrasonic stirring and dispersion are carried out for 10 minutes, then 1 mmol of manganese chloride, 2 mmol of indium chloride tetrahydrate and 4 mmol of thioacetamide are added, and the solid-liquid mixture is obtained after ultrasonic stirring and dispersion for 10 minutes. The other steps are the same as those in the embodiment 1.

[0045] Embodiment 7 The embodiment provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a ball milling combined low-temperature oil bath method, different from the embodiment 1, the molar ratio of the VS4 nanosheet to manganese chloride in the embodiment is 1:4; the molar ratio of manganese chloride, indium chloride tetrahydrate and thioacetamide is 1:2:8. Namely, the step S4 is that 1 mmol of the VS4 nanosheet (the size of the VS4 nanosheet is 200 nm, the thickness is 100 nm, and the size of the micron flower formed is 1500 nm) is added into 60 mL of deionized water and ultrasonic stirring and dispersion are carried out for 10 minutes, then 4 mmol of manganese chloride, 8 mmol of indium chloride tetrahydrate and 32 mmol of thioacetamide are added, and the solid-liquid mixture is obtained after ultrasonic stirring and dispersion for 10 minutes. The other steps are the same as those in the embodiment 1.

[0046] Comparative example 1 The comparative example provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a ball milling combined high-temperature hydrothermal method, which is different from the example 1 in that steps S1-S4 and S6 are retained, and step S5 is replaced by: S5. The solid-liquid mixture is transferred to a 100 mL stainless steel high-temperature reaction kettle with a polytetrafluoroethylene liner, and then the reaction kettle is placed in a high-temperature oven for reaction at 180°C for 8 h. After the reaction is completed, natural cooling is performed.

[0047] Comparative example 2 The comparative example provides a preparation method of a MnIn2S4@VS4 heterojunction photocatalyst by a high-temperature hydrothermal method combined with a low-temperature oil bath method, which is different from the example 1 in that steps S4-S6 are retained, and S1-S3 are replaced by: S1. 10 mmol of sodium orthovanadate and 6 mmol of thioacetamide are uniformly mixed, 60 mL of water is added and ultrasonic dispersion is performed for 10 minutes to form a uniform solution; S2. The above solution is transferred to a 100 mL stainless steel high-temperature reaction kettle with a polytetrafluoroethylene liner, and then the reaction kettle is placed in a high-temperature oven for reaction at 160°C for 24 h. After the reaction is completed, natural cooling is performed; S3. After cooling is completed, centrifugation is performed in a centrifuge at a speed of 5000 revolutions / minute for 5 minutes, and then the above is washed with water and ethanol alternately for 5 times, and is dried in a drying box at 80 o C for 12 h to obtain a VS4 powder by a hydrothermal method.

[0048] Comparative example 3 The comparative example provides a preparation method of a VS4 photocatalyst by a ball milling method, which is different from the example 1 in that steps S4-S6 are omitted, and only steps S1-S3 are retained.

[0049] Comparative example 4 The comparative example provides a preparation method of a VS4 photocatalyst by a hydrothermal method, which is different from the comparative example 2 in that steps S4-S6 are omitted, and only steps S1-S3 are retained.

[0050] Comparative example 5 The comparative example provides a preparation method of a MnIn2S4 photocatalyst by a low-temperature oil bath method, which is different from the example 1 in that steps S1-S3 are omitted, and only steps S4-S6 are retained, wherein no VS4 material is added in step S4, and the remaining steps and parameters are unchanged.

[0051] Comparative example 6 The comparative example provides a preparation method of a MnIn2S4 photocatalyst by a high-temperature hydrothermal method, which is different from the comparative example 1 in that steps S1-S3 are omitted, and only steps S4-S6 are retained, wherein no VS4 material is added in step S4, and the remaining steps and parameters are unchanged.

[0052] Comparative Example 7 This comparative example provides a preparation method of a commercial P25 (TiO2) photocatalyst, which is purchased from the market.

[0053] The photocatalysts prepared in Examples 1-7 and Comparative Examples 1-7 above are respectively denoted as low-temperature MIS@ball-milling VS (Example 1), MIS@ball-milling VS (Example 2), MIS@ball-milling VS (Example 3), MIS@ball-milling VS (Example 4), MIS@ball-milling VS (Example 5), MIS@ball-milling VS (Example 6), MIS@ball-milling VS (Example 7), high-temperature MIS@ball-milling VS (Comparative Example 1), low-temperature MIS@hydrothermal VS (Comparative Example 2), ball-milling VS (Comparative Example 3), hydrothermal VS (Comparative Example 4), low-temperature MIS (Comparative Example 5), high-temperature MIS (Comparative Example 6), and P25 (Comparative Example 7).

[0054] In the above, “low-temperature” refers to a MIS material prepared by a low-temperature oil bath method; “high-temperature” refers to a MIS material prepared by a high-temperature hydrothermal method; “ball-milling” refers to a VS material prepared by a ball-milling method; and “hydrothermal” refers to a VS material prepared by a hydrothermal method.

[0055] Table 1 shows the structural information of the specific surface area and pore volume of the samples in Examples 1-7 and Comparative Examples 1-7 of the present patent. It can be seen from the specific surface area test (BET) characterization that the specific surface area and pore volume of the ball-milling VS (Comparative Example 3) sample are significantly higher than those of the hydrothermal VS (Comparative Example 4) sample, which means that the low-temperature preparation method can significantly increase the active sites of the VS material and is more conducive to participating in the photocatalytic reaction. On the other hand, after the low-temperature epitaxial growth of MnIn2S4nanosheets on the surface of the VS material by the ball-milling method, the specific surface area of the low-temperature MIS@ball-milling VS (Examples 1-7) sample is as high as 104.9 m 2 / g, which is 1.4 times that of the high-temperature MIS@ball-milling VS (Comparative Example 1), and the pore volume increases by nearly 1 times, which indicates that the low-temperature oil bath epitaxial growth is more conducive to the formation of a heterojunction composite material with a high specific surface area. Moreover, the specific surface area of the VS material prepared by the hydrothermal method and also subjected to the low-temperature epitaxial growth of MnIn2S4nanosheets is smaller than that of the VS-based composite material based on the ball-milling method, which is because the high-temperature hydrothermal method destroys the basic structure of the VS material, making it difficult to form a composite material with a high specific surface area in the subsequent composite growth process. It is worth noting that P25 (Comparative Example 7) is a mature photocatalyst product on the market, and its specific surface area is larger than that of either single VS or MIS material, but it is almost half of the composite material of the VS material after the low-temperature epitaxial growth of MnIn2S4nanosheets, which indicates that its photocatalytic performance is not as good as that of the samples prepared in Examples 1-7 of the present invention.

[0056] Table 1. Specific surface area and pore volume of VS, MIS and their composite samples prepared by different preparation processes

[0057] Figure 1 X-ray diffraction (XRD) patterns of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-6 of the present application, wherein (a) is the XRD pattern of the photocatalytic materials prepared in Comparative Examples 3-6, and (b) is the XRD pattern of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-2. From Figure 1 As can be seen from (a), the characteristic peaks of the prepared VS material at 15.8° and 17.0° correspond to the (110) and (020) crystal planes, respectively, which are consistent with the standard XRD card, indicating that the VS is successfully prepared. For the characteristic peak at 15.8°, the half-height width of the ball-milled VS material is 0.4°, while that of the hydrothermal VS material is not only 0.1° larger, but also has a smaller peak intensity, indicating that the VS material prepared by ball milling has better crystallinity. From Figure 1 As can be seen from (b), the composite sample has both the characteristic peaks of VS and MIS, indicating that the MIS does not affect the structure of the VS material when it is epitaxially grown on the surface of the VS material, and the two are successfully combined. It is worth noting that the characteristic peak at 15.8° belongs to VS, and the peak of the low-temperature MIS@ball-milled VS sample is the strongest and has the smallest half-height width (0.2°), which is not only smaller than that of the ball-milled VS before compounding (0.4°), but also smaller than that of the high-temperature MIS@ball-milled VS sample in which MIS nanosheets are grown on the surface of the VS material by high-temperature hydrothermal method (0.5°), indicating that the samples prepared in Examples 1-7 can repair the lattice of the VS material by releasing stress when MIS nanosheets are grown on the surface of the VS material by low-temperature epitaxy, eliminating the structural damage caused by lattice distortion. On the other hand, when MIS is grown on the surface of the VS material at high temperature, the nucleation and growth rate of MIS is faster due to the higher reaction temperature, and this non-epitaxial growth method cannot repair the lattice. In addition, the half-height width of the characteristic peak of the low-temperature MIS@hydrothermal VS sample is 0.1° smaller than that of the hydrothermal VS, which further indicates that the low-temperature epitaxial growth method can effectively repair the lattice of the VS material.

[0058] Figure 2 Scanning electron microscope (SEM) morphology of the photocatalytic materials prepared in Example 1 and Comparative Examples 3-4 of the present application, wherein (a), (b) and (c) are the SEM images of the photocatalytic materials prepared in Comparative Example 4, Comparative Example 3 and Example 1, respectively. From Figure 2It can be seen from (a-b) that the VS materials prepared by the hydrothermal method have different morphologies and the size is about 10 μm, while the VS prepared by the ball milling method shows a flower-like structure formed by self-assembly of nanosheets, and the special structure formed by the mutual intersection of the nanosheets makes it have a larger specific surface area, and the overall size is uniform, which provides a necessary condition for realizing high-efficiency photocatalytic performance. Figure 2 (c) shows the double flower-like hierarchical structure of the low-temperature MIS@ball-milling VS sample (VS4 is the "floral column", and MnIn2S4 is the "petal"), and this special structure can promote multiple reflection of light to enhance light absorption, and the heterojunction can promote directional movement of photo-generated carriers.

[0059] Figure 3 The high-resolution transmission electron microscopy (HRTEM) morphology diagrams of the photocatalytic materials prepared in Example 1, Comparative Example 1 and Comparative Example 3 of the present application, wherein (a), (b) and (c) are the HRTEM diagrams of the photocatalytic materials prepared in Comparative Example 3, Example 1 and Comparative Example 1, respectively. Figure 3 It can be seen from (a-b) that after the MIS nanosheets are grown on the surface of the VS material at low temperature, the two are grown together at the atomic level, which indicates that a heterojunction is formed at the interface. Figure 3 (b) The right area belongs to the ball-milling VS material, and the lattice arrangement is obviously more ordered than Figure 3 (a) The ball-milling VS material shown is more ordered, which further proves from the atomic level that the low-temperature epitaxial growth of the MIS nanosheet can effectively repair the lattice distortion of the VS material (Examples 1-7). And Figure 3 (c) The lattice fringes of the right part of the high-temperature MIS@ball-milling VS material are obviously more ordered than Figure 3 (b) The low-temperature MIS@ball-milling VS material shown is more disordered, and the lattice distortion therein is even more serious than Figure 3 (a) The ball-milling VS material shown is more serious, which indicates that the growth of the MIS nanosheet at high temperature is not helpful for the optimization of the VS lattice.

[0060] Figure 4 The photocatalytic performance diagrams of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 of the present application, wherein (a) is the rate curve diagram of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 for degrading ofloxacin, and (b) is the comparison column chart of the 5-time cycle degradation stability of the photocatalytic materials prepared in Example 1 and Comparative Example 7 for ofloxacin, and each cycle is subjected to a continuous 2-hour ofloxacin degradation experiment. Figure 4(a) It can be seen that the degradation performance of the ball-milling VS material is better than that of the hydrothermal VS material, which is consistent with the previous experimental results. For the composite samples, even if the MIS nanosheets are grown at low temperature by epitaxy, the degradation performance of the low-temperature MIS@hydrothermal VS sample is worse than that of the high-temperature MIS@ball-milling VS sample, which shows that the preparation method of the substrate material VS plays a major role in the photocatalytic process, and when the VS material is prepared by ball milling, compared with the high-temperature MIS nanosheet preparation method on the VS surface, the low-temperature MIS nanosheet grown by epitaxy can effectively improve the photocatalytic degradation performance, and the degradation efficiency of ofloxacin after 2 hours is 96.1%, which is 2.4 times and 1.3 times that of the high-temperature MnIn2S4@ball-milling VS4 and the commercial and mature P25 photocatalyst, respectively, and the cumulative degradation efficiency reaches 95% of the initial degradation efficiency after 10 hours of circulation for 5 times Figure 4 (b), which shows that the heterojunction and morphology regulation can effectively promote the charge transfer, and the low-temperature MIS@ball-milling VS prepared in Examples 1-7 has great commercial prospects.

[0061] Figure 5 The photocatalytic performance of the photocatalytic material prepared in Example 1 of the present application is shown in the figure, wherein (a) and (b) are respectively the rate curve and the average rate columnar graph of the photocatalytic material prepared in Example 1. It can be seen that under the synergistic effect of morphology regulation, crystal quality and heterojunction, the low-temperature MIS@ball-milling VS heterojunction composite material prepared in Examples 1-7 exhibits a hydrogen production rate of 8.86 mmol·h -1 ·g -1 and an oxygen production rate of 4.25 mmol·h -1 ·g -1 , showing good multifunctional photocatalytic performance and breaking through the practical application bottleneck of the existing VS4-based materials caused by interface lattice distortion and carrier recombination.

[0062] Figure 6 The current density curve of the photocatalytic material prepared in Example 1 and Comparative Examples 1-7 of the present application is shown in the figure, wherein (a) is the current density curve of the photocatalytic material prepared in Comparative Examples 3-6; (b) is the current density curve of the photocatalytic material prepared in Example 1, Comparative Examples 1-2 and Comparative Example 7. Figure 6 (a) It can be seen that the photocurrent density of the ball-milling VS material is greater than that of the hydrothermal VS material, which shows that the VS material prepared by ball milling has better charge transfer efficiency. Figure 6 (b) shows the photocurrent density law and Figure 4The degradation performance of (a) is consistent, and the low-temperature epitaxial growth of MIS nanosheets on the surface of VS material (Examples 1-7) can effectively improve the carrier transfer efficiency of the heterojunction composite material.

[0063] Figure 7 The differential charge density map of the photocatalytic material prepared in Example 1 of the present application is shown in the figure. The atomic model on the top of the figure belongs to VS, and the one on the bottom belongs to MIS. First-principle calculation shows that a heterojunction is formed at the interface of VS and MIS, which is specifically manifested as the loss of electrons on the side belonging to VS at the interface, while the side belonging to MIS shows electron aggregation. This theoretically proves that a heterojunction is formed at the interface of MIS and VS, and electrons flow from the side of VS to the side of MIS. This directional movement of electrons indicates that the composite material has excellent carrier separation efficiency and fast carrier dynamics, which provides a theoretical basis for its high-efficiency photocatalytic pollutant degradation and overall water splitting performance.

[0064] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A method for preparing a MnIn2S4@VS4 heterojunction photocatalyst, characterized in that, Includes the following steps: Vanadium powder, sulfur source and ethanol were mixed to obtain a mixed slurry. The mixed slurry was reacted in a ball mill and then filtered, centrifuged and dried to obtain VS4 nanosheets. MnIn2S4 nanosheets were epitaxially grown on the surface of VS4 nanosheets at low temperature to obtain a MnIn2S4@VS4 heterojunction photocatalyst with a double flower-like interwoven structure.

2. The preparation method of a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, When preparing VS4 nanosheets, the molar ratio of vanadium powder to sulfur source is 1:(4~6).

3. The method for preparing a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, The sulfur source is a mixture of thioacetamide and thiourea, wherein the molar ratio of thioacetamide to thiourea is 1:(1~2).

4. The preparation method of a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, The concentration of solids in the mixed slurry is 0.5 mol / L to 4 mol / L, and the solids are vanadium powder and sulfur source.

5. The method for preparing a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, When preparing VS4 nanosheets, ball milling was performed using a forward and reverse rotation cycle at a speed of 200-500 rpm.

6. The method for preparing a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, The method for low-temperature epitaxial growth of MnIn2S4 nanosheets on the surface of VS4 nanoflowers is as follows: VS4 nanosheets were added to a deionized aqueous solution, followed by the addition of manganese chloride, indium chloride tetrahydrate, and thioacetamide. After ultrasonic stirring, a solid-liquid mixture was obtained. The solid-liquid mixture was reacted in an oil bath at a temperature of 60℃~100℃, then cooled, centrifuged, washed, and dried to obtain a MnIn2S4@VS4 heterojunction photocatalyst with a double-flower-like interwoven structure.

7. The method for preparing a MnIn2S4@VS4 heterojunction photocatalyst according to claim 6, characterized in that, The molar ratio of VS4 nanosheets to manganese chloride is 1:(1~4); the molar ratio of manganese chloride, indium chloride tetrahydrate, and thioacetamide is 1:2:(4~8).

8. The method for preparing a MnIn2S4@VS4 heterojunction photocatalyst according to claim 1, characterized in that, The MnIn2S4 nanosheets have a size of 100nm~1000nm and a thickness of 10nm~100nm; And / or, the VS4 nanosheets have a size of 10nm~500nm and a thickness of 10nm~200nm, and the resulting micron flowers have a size of 300nm~3000nm; And / or, the size of the nanosheets on the MnIn2S4@VS4 heterojunction photocatalyst is 100nm~1000nm, the thickness is 10nm~100nm, and the size of the micron flowers formed is 400nm~4000nm.

9. A MnIn2S4@VS4 heterojunction photocatalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the MnIn2S4@VS4 heterojunction photocatalyst according to claim 9, characterized in that, These include applications in photocatalytic water splitting for hydrogen production, total water splitting, or degradation of organic pollutants.

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