A method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 sheet photocatalyst

Abstract

The purpose of this invention is to provide a method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 sheet photocatalyst, belonging to the field of photocatalytic material preparation technology. The method involves sulfiding a pre-prepared Mo-MOF to MoS2, which retains the rod-shaped structure of the Mo-MOF. B-doped g-C3N4 sheets are then prepared, and the two are mechanically ground to prepare a Mo-MOF-derived MoS2 / B-doped g-C3N4 sheet composite photocatalytic material. This invention features a simple material preparation process, controllable product morphology, and a catalyst exhibiting excellent photocatalytic performance and stability.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation technology, specifically relating to a method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 thin-film photocatalyst. Background Technology

[0002] Solar energy, as a crucial option for addressing current climate issues and the energy crisis, has been applied in numerous fields. Among these, semiconductor-based photocatalytic hydrogen evolution technology is considered an ideal method for efficiently utilizing solar energy. However, most single-component photocatalysts currently exhibit limited utilization of sunlight and low photogenerated charge separation efficiency. Existing research has proposed various effective strategies to address these issues, including metal and non-metal doping, dye sensitization, and heterojunction construction. Among these, heterojunction construction is considered the most effective method to improve photogenerated charge separation efficiency. In recent years, g-C3N4 has been widely used in photocatalysis due to its convenient preparation method, good photocatalytic activity, and suitable band gap. However, its low visible light utilization and rapid photogenerated carrier recombination rate greatly limit its photocatalytic activity. In recent years, traditional molybdenum disulfide (MoS2), as a layered transition metal disulfide, has good conductivity, a wide light absorption range, and suitable band positions, but its redox ability is poor. Combining MoS2 with g-C3N4 helps improve its photocatalytic performance. For example, patent CN201811462030.9 provides a method for preparing MoS2 / C3N4 composite photocatalysts via coulombic action. Patent CN202111331505.2 invented a method for preparing MoS2 / g-C3N4 composite hydrogen evolution materials, discovering that two-dimensional layered materials at high temperatures produce more pronounced stratification and become finer after liquid nitrogen quenching, thus achieving a larger specific surface area. Patent CN201811454371.1 prepared g-C3N4 / MoS2 composite photocatalysts using a one-pot method. CN201611113339.8 describes a method for preparing g-C3N4 / MoS2 nanocomposite materials via sulfidation sintering. However, the performance of the composite photocatalysts prepared by the above methods still does not meet the requirements for reagent applications.

[0003] Nanomaterials derived from metal-organic frameworks (MOFs) have shown unique applications in catalysis due to their large specific surface area. Compared with traditional metal sulfides, MOF-derived metal sulfides have shown potential in photocatalysis. The large specific surface area of ​​MOFs as precursors facilitates the dispersion of metal sulfides, while the exposed catalytic sites promote extensive charge transfer and improve photocatalytic efficiency. Therefore, constructing a heterostructure with matched energy bands using MOF-derived molybdenum disulfide and g-C3N4 nanosheets holds promise as a photocatalyst with excellent performance. Summary of the Invention

[0004] The purpose of this invention is to address the relatively poor photocatalytic performance of g-C3N4 and MoS2, and to provide a method and application for preparing a photocatalyst by inducing the formation of a MoS2 rod-shaped structure with Mo-MOF and combining it with B-doped g-C3N4 nanosheets.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 sheet photocatalyst includes the following steps:

[0007] Step 1, Preparation of Mo-MOF: Imidazole and molybdenum trioxide were dissolved in 150-250 mL of deionized water, stirred evenly, and refluxed at 90-120℃ for 12 h. The collected product was washed three times with deionized water and dried in a vacuum drying oven at 80℃ for 12 h to obtain Mo-MOF.

[0008] The second step is the preparation of Mo-MOF-derived MoS2: Mo-MOF and thiourea are placed in two open alumina crucibles respectively, and the alumina crucibles are placed in a tube furnace with thiourea placed upstream. MoS2 is obtained by heating to 450-600℃ at a rate of 2-5℃ / min under a nitrogen atmosphere and holding for 2 h.

[0009] The third step is the preparation of B-doped g-C3N4 sheets: Melamine and boric acid are ground thoroughly and uniformly as a precursor. The ground precursor is uniformly dispersed in a covered alumina crucible and placed in a muffle furnace. The temperature is raised to 450-600℃ at a rate of 2-8℃ / min and held for 4 h. After cooling to room temperature, the obtained product is ground thoroughly and placed in an open alumina crucible. The temperature is raised to 450-600℃ again in a muffle furnace at a rate of 2-8℃ / min and held for 2 h. After cooling to room temperature, B-doped g-C3N4 nanosheets are obtained.

[0010] The fourth step is the preparation of Mo-MOF-derived MoS2 / B-doped g-C3N4 sheet composite photocatalysts: B-doped g-C3N4 sheets were dispersed in 50 mL of deionized water and sonicated for 1 h to obtain a uniformly dispersed solution. Then, MoS2 was added to the solution and magnetically stirred for 1 h. After drying in an oven at 60 °C for 12 h, the mixture was thoroughly ground to obtain Mo-MOF-derived MoS2 / B-doped g-C3N4 sheet composite materials with different proportions.

[0011] Furthermore, the mass ratio of imidazole to molybdenum trioxide in the first step is 1:2.

[0012] Furthermore, the mass ratio of Mo-MOF to thiourea in the second step is 1:8.

[0013] Furthermore, in the third step, the mass ratio of melamine to boric acid is 1:0.005-0.011.

[0014] Furthermore, in the fourth step, the mass ratio of MoS2 to g-C3N4 is 1:20 to 1:5.

[0015] The synthesized composite photocatalyst has a rod-shaped MoS2 structure coated with B-doped g-C3N4 sheets, exhibiting a large specific surface area and excellent photogenerated charge separation capability.

[0016] The beneficial effects of this invention are as follows:

[0017] Compared with existing technologies, the advantages of this invention are as follows: Firstly, this invention obtains B-doped g-C3N4 nanosheets through a two-step thermal polymerization method. Compared with bulk g-C3N4, B doping can reduce the band gap of g-C3N4 and enhance its light absorption capacity. The further processed nanosheets are loosely dispersed flakes, exposing more active sites. MoS2 derived from Mo-MOF has good dispersion and a larger specific surface area, providing more space for the composite of g-C3N4 nanosheets. This invention first improves and optimizes the two materials separately and controls their morphology, facilitating the preparation of composite materials. Furthermore, a MoS2 / B-doped g-C3N4 nanosheet composite photocatalyst is constructed through a mechanical mixing method. The synergistic effect of the heterostructure and B doping can greatly improve the separation efficiency of photogenerated electron-hole pairs and expand the absorption range of visible light, thus significantly increasing the photocatalytic hydrogen evolution rate of the material. This holds promise for application in the field of photocatalytic hydrogen evolution and provides a novel approach for constructing highly efficient hydrogen evolution photocatalysts. Attached Figure Description

[0018] Figure 1 XRD patterns of B-doped g-C3N4, MoS2, and four different proportions of MoS2 / BCN composite materials, and magnified patterns of MoS2.

[0019] Figure 2 XPS full spectrum of the composite material MoS2 / BCN-0.15;

[0020] Figure 3 XPS high-resolution spectrum of the B 1s level;

[0021] Figure 4 XPS high-resolution spectra of Mo 3d energy levels;

[0022] Figure 5 SEM image of MoS2 / BCN-0.15;

[0023] Figure 6 TEM image of MoS2 / BCN-0.15;

[0024] Figure 7 The UV-Vis absorption spectra of B-doped g-C3N4, MoS2, and MoS2 / BCN-0.15 are shown.

[0025] Figure 8 The hydrogen evolution yield performance of B-doped g-C3N4, MoS2, and four different proportions of MoS2 / BCN composite materials is shown in the figure.

[0026] Figure 9 The hydrogen evolution rate performance of B-doped g-C3N4, MoS2, and four different proportions of MoS2 / BCN composites is shown in the figure.

[0027] Figure 10 Transient photocurrent spectra of B-doped g-C3N4, MoS2, and four different proportions of MoS2 / BCN composite materials. Detailed Implementation

[0028] A method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 sheet photocatalyst includes the following steps:

[0029] Step 1, Preparation of Mo-MOF: Imidazole and molybdenum trioxide were dissolved in 150-250 mL of deionized water, stirred evenly, and refluxed at 90-120℃ for 12 h. The collected product was washed three times with deionized water and dried in a vacuum drying oven at 80℃ for 12 h to obtain Mo-MOF.

[0030] The second step is the preparation of Mo-MOF-derived MoS2: Mo-MOF and thiourea are placed in two open alumina crucibles respectively, and the alumina crucibles are placed in a tube furnace with thiourea placed upstream. MoS2 is obtained by heating to 450-600℃ at a rate of 2-5℃ / min under a nitrogen atmosphere and holding for 2 h.

[0031] The third step is the preparation of B-doped g-C3N4 sheets: Melamine and boric acid are ground thoroughly and uniformly as a precursor. The ground precursor is uniformly dispersed in a covered alumina crucible and placed in a muffle furnace. The temperature is raised to 450-600℃ at a rate of 2-8℃ / min and held for 4 h. After cooling to room temperature, the obtained product is ground thoroughly and placed in an open alumina crucible. The temperature is raised to 450-600℃ again in a muffle furnace at a rate of 2-8℃ / min and held for 2 h. After cooling to room temperature, B-doped g-C3N4 nanosheets are obtained.

[0032] The fourth step is the preparation of Mo-MOF-derived MoS2 / B-doped g-C3N4 sheet composite photocatalysts: B-doped g-C3N4 sheets were dispersed in 50 mL of deionized water and sonicated for 1 h to obtain a uniformly dispersed solution. Then, MoS2 was added to the solution and magnetically stirred for 1 h. After drying in an oven at 60 °C for 12 h, the mixture was thoroughly ground to obtain Mo-MOF-derived MoS2 / B-doped g-C3N4 sheet composite materials with different proportions.

[0033] Example

[0034] Step 1: Preparation of B-doped g-C3N4 thin films: 5 g of melamine (C3H6N6) and 0.04 g of boric acid (H3BO3) were thoroughly ground and placed in a covered alumina crucible. The crucible was then placed in a muffle furnace and heated to 550°C at a rate of 5°C / min and held for 4 h. After cooling to room temperature, the product was collected, thoroughly ground, and placed in an open alumina crucible. The crucible was then heated again in a muffle furnace to 500°C at a rate of 5°C / min and held for 2 h. After cooling to room temperature, B-doped g-C3N4 thin films were obtained.

[0035] Step 2: Preparation of MoS2: Dissolve 1.75 g imidazole (C3H4N2) and 3.5 g molybdenum trioxide (MoO3) in 200 mL of deionized water, stir well, and reflux at 100 °C for 12 h. Wash the collected product three times with deionized water by centrifugation, and dry it in a vacuum drying oven at 80 °C for 12 h to obtain Mo-MOF. Take 500 mg of Mo-MOF and 4 g of thiourea (CH4N2S) and place them in two open alumina crucibles. Place the alumina crucible containing thiourea upstream of the tube furnace and the alumina crucible containing Mo-MOF downstream of the tube furnace. Heat to 500 °C at a rate of 5 °C / min under a nitrogen (N2) atmosphere and hold for 2 h to obtain MoS2.

[0036] Step 3: Preparation of MoS2 / B-doped g-C3N4 nanosheet composite material: 2 g of B-doped g-C3N4 nanosheets were dispersed in 50 mL of deionized water and sonicated for 1 h to obtain a uniformly dispersed solution. Then, 0.1, 0.2, 0.3, and 0.4 g of MoS2 were added to the solution and magnetically stirred for 1 h. The mixture was then dried in an oven at 60 °C for 12 h. After thorough grinding, MoS2 / B-doped g-C3N4 nanosheet composite materials with different proportions were obtained (denoted as MoS2 / BCN-0.05, MoS2 / BCN-0.1, MoS2 / BCN-0.15, and MoS2 / BCN-0.2, respectively).

[0037] XRD patterns of B-doped g-C3N4, MoS2, and four different ratios of MoS2 / BCN composite photocatalysts are shown below. Figure 1 As shown, B-doped g-C3N4 and four different proportions of MoS2 / BCN composite photocatalysts all show the (100) and (002) crystal planes of g-C3N4, while the diffraction peaks of MoS2 itself are weak. The (002), (100) and (110) crystal planes of MoS2 can be clearly observed in the magnified spectra.

[0038] Figure 2 The image shows the XPS full spectrum of the composite photocatalyst MoS2 / BCN-0.15. The spectrum reveals the presence of C, N, B, and Mo elements in the composite photocatalyst.

[0039] Figure 3 The figure shows the XPS high-resolution spectrum of the B 1s energy level of the composite photocatalyst MoS2 / BCN-0.15. As can be seen from the figure, the peak at 191.6 eV proves that B has been successfully doped into g-C3N4.

[0040] Figure 4 The figure shows the XPS high-resolution spectrum of the Mo 3d energy level of the composite photocatalyst MoS2 / BCN-0.15. As can be seen from the figure, the high-resolution spectrum after fitting and peak separation shows that the Mo element exists in the +4 valence form, successfully proving the presence of MoS2 in the composite photocatalyst.

[0041] Figure 5 The SEM image of the composite photocatalyst MoS2 / BCN-0.15 shows that MoS2 successfully maintains the rod-like structure of Mo-MOF, with many BCN nanosheets dispersed on the rod-like structure, confirming the simultaneous presence of MoS2 and BCN in the composite photocatalyst.

[0042] Figure 6 The image shows the TEM spectrum of the composite photocatalyst MoS2 / BCN-0.15.

[0043] Figure 7The figures show the UV-Vis absorption spectra of BCN, MoS2, and MoS2 / BCN-0.15. The figures show a redshift at the absorption edge of the composite photocatalyst, indicating its stronger light absorption performance and narrower bandgap compared to BCN.

[0044] Figure 8 The graph shows the hydrogen evolution yield performance of BCN, MoS2, and four different ratios of MoS2 / BCN composite photocatalysts. The graph shows that all composite photocatalysts exhibit improved hydrogen evolution performance compared to MoS2 and BCN alone, with MoS2 / BCN-0.15 showing the best performance.

[0045] Figure 9 The graph shows the hydrogen evolution rate performance of MoS2, BCN, and four different ratios of MoS2 / BCN composite photocatalysts. Among them, MoS2 / BCN-0.15 exhibited the best hydrogen evolution rate performance.

[0046] Figure 10 The transient photocurrent spectra of BCN, MoS2, and MoS2 / BCN-0.15 composite photocatalysts are shown. The figures reveal that the MoS2 / BCN-0.15 composite photocatalyst exhibits a significant increase in photocurrent compared to MoS2 and BCN alone, demonstrating that the combination of MoS2 and BCN can enhance the lifetime of photogenerated carriers and reduce their recombination rate.

[0047] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for preparing a Mo-MoF-derived MoS2 rod-shaped composite B-doped g-C3N4 thin-film photocatalyst, characterized in that: Comprising the following steps: The first step, preparation of Mo-MOF: imidazole and molybdenum trioxide are dissolved in 150-250 mL of deionized water, stirred uniformly, and condensed and refluxed at 90-120℃ for 12 h. The collected product is washed with deionized water three times and dried in a vacuum drying oven at 80℃ for 12 h to obtain Mo-MOF; The second step, preparation of Mo-MOF derived MoS2: Mo-MOF and thiourea are placed in two open alumina crucibles, respectively, and the alumina crucibles are placed in a tube furnace, with thiourea placed upstream. The temperature is raised to 450-600℃ at a rate of 2-5℃ / min under a nitrogen atmosphere, and then held for 2 h to obtain MoS2; The third step, preparation of B-doped g-C3N4 nanosheets: melamine and boric acid are thoroughly ground and uniformly dispersed in a covered alumina crucible as a precursor. The crucible is placed in a muffle furnace and heated to 450-600℃ at a rate of 2-8℃ / min, held for 4 h, and then cooled to room temperature. The resulting product is thoroughly ground and placed in an open alumina crucible. The crucible is again placed in a muffle furnace and heated to 450-600℃ at a rate of 2-8℃ / min, held for 2 h, and then cooled to room temperature to obtain B-doped g-C3N4 nanosheets; The fourth step, preparation of Mo-MOF derived MoS2 / B-doped g-C3N4 nanosheet composite photocatalyst: B-doped g-C3N4 nanosheets are dispersed in 50 mL of deionized water and ultrasonicated for 1 h to obtain a uniformly dispersed solution. MoS2 is then added to the solution and magnetically stirred for 1 h. The mixture is then dried in an oven at 60℃ for 12 h, and then thoroughly ground to obtain Mo-MOF derived MoS2 / B-doped g-C3N4 nanosheet composites with different proportions.

2. The preparation method of a Mo-MoF derived MoS2 rod-like structure composite B-doped g-C3N4 sheet photocatalyst according to claim 1, characterized in that: The mass ratio of imidazole to molybdenum trioxide in the first step is 1:

2.

3. The preparation method of a Mo-MoF derived MoS2 rod-like structure composite B-doped g-C3N4 sheet photocatalyst according to claim 1, characterized in that: The mass ratio of Mo-MOF to thiourea in the second step is 1:

8.

4. The preparation method of a Mo-MoF derived MoS2 rod-like structure composite B-doped g-C3N4 sheet photocatalyst according to claim 1, characterized in that: The mass ratio of melamine to boric acid in the third step is 1:0.005-0.

011.

5. The preparation method of a Mo-MoF derived MoS2 rod-like structure composite B-doped g-C3N4 sheet photocatalyst according to claim 1, characterized in that: The mass ratio of MoS2 to g-C3N4 in the fourth step is 1:20-1:5.

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