Carbonized microcrystalline cellulose@mo s2 nanosheet composite piezoelectric catalyst, preparation method thereof and piezoelectric catalytic water splitting hydrogen production application

Abstract

The application provides a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, a preparation method thereof and piezoelectric catalytic water decomposition hydrogen production application, and relates to the technical field of composite catalyst preparation. The carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst is prepared by first preparing carbonized microcrystalline cellulose microrods, and then growing a specific amount of MoS2 nanosheets on the surface of the carbonized microcrystalline cellulose microrods. The heterojunction structure can effectively promote the separation of piezoelectric carriers. Meanwhile, the MoS2 nanosheets distributed on the outer surface provide abundant high-activity hydrogen evolution sites for the inert carbonized microcrystalline cellulose. The synergistic effect of the two can significantly improve the stability and catalytic property of the composite catalyst in piezoelectric catalytic hydrogen evolution, and endow the composite piezoelectric catalyst with the use performance of decomposing water to produce hydrogen at normal temperature and pressure.

Description

Technical Field

[0001] This invention relates to the field of composite catalyst preparation technology, and in particular to a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, its preparation method, and its application in piezoelectric catalytic water splitting for hydrogen production. Background Technology

[0002] Piezoelectric catalytic water splitting for hydrogen production utilizes waste mechanical energy to convert water into hydrogen at room temperature and pressure, demonstrating unique application advantages. This technology relies on the polarization of non-centrosymmetric crystals under mechanical stress, forming a built-in electric field that promotes charge separation and drives surface redox reactions. Its performance is primarily determined by the material's piezoelectric response strength, charge carrier behavior, and intrinsic catalytic activity.

[0003] Extensive research on piezoelectric catalytic materials encompasses inorganic systems such as BaTiO3, ZnO, MoS2, and BiFeO3. Notably, biomass-derived cellulose crystals have also been found to possess piezoelectric properties in recent years, showing potential in piezoelectric catalytic degradation of pollutants and water splitting for hydrogen production. These materials offer significant advantages in terms of wide availability and low cost. However, cellulose-based catalysts still face three bottlenecks: first, insufficient mechanical stability, making them prone to structural damage under stress; second, a scarcity of surface catalytic active sites, limiting their catalytic hydrogen production efficiency; and third, low efficiency in piezoelectric charge separation and utilization when used as a single component. On the other hand, while MoS2 performs excellently in the electrocatalytic hydrogen evolution reaction and possesses good piezoelectric properties, its piezoelectric catalytic activity is limited by the number of layers; only odd-layer structures exhibit a piezoelectric effect, making it difficult to achieve breakthroughs in performance when used alone as a piezoelectric catalyst.

[0004] In view of this, it is necessary to design an improved carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, its preparation method, and its application in piezoelectric catalytic water splitting for hydrogen production, in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, its preparation method, and its application in piezoelectric catalytic water splitting for hydrogen production.

[0006] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a method for preparing a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, comprising the following steps:

[0007] Carbonized microcrystalline cellulose is obtained by carbonizing microcrystalline cellulose.

[0008] The carbonized microcrystalline cellulose was mixed evenly with Mo salt and S-containing precursor solution, and MoS2 was grown on the surface of the carbonized microcrystalline cellulose by hydrothermal method to obtain the composite catalyst.

[0009] Preferably, the ratio of the mass of carbonized microcrystalline cellulose, the mass of Mo salt, and the volume of the S-containing precursor solution is (0.05-1.2):(1-1.5):(30-40).

[0010] Preferably, the carbonization treatment is carried out at a temperature of 330-350°C for 1-3 hours.

[0011] Preferably, the temperature for hydrothermal growth of MoS2 is 160-200℃ and the time is 16-30h.

[0012] Preferably, the S-containing precursor solution is a thiourea solution with a concentration of 0.6-1.0 mol / L.

[0013] Secondly, a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst includes:

[0014] Carbonized microcrystalline cellulose, used as a supporting substrate, has a rod-like structure and a specific surface area of ​​2.1 m². 2 / g, is a mixture of particles of different sizes with a length of 30-100μm and a width of 10-20μm;

[0015] MoS2 is loaded on the surface of the carbonized microcrystalline cellulose and has a three-dimensional flower-like hierarchical structure; the three-dimensional flower-like hierarchical structure is assembled from MoS2 nanosheets with a thickness of 25 nm and a specific surface area of ​​22.1 m². 2 / g; the MoS2 loading in the composite piezoelectric catalyst is 35-75 wt.%, and the specific surface area of ​​the composite catalyst is 10-20 m². 2 / g.

[0016] Thirdly, the present invention provides a method for applying a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst in piezoelectric catalytic water splitting for hydrogen production, comprising the following steps:

[0017] The composite piezoelectric catalyst was mixed with an aqueous sacrificial agent, and H2PtCl4 solution was added to the resulting mixture under an inert atmosphere. Pt was deposited by photo-treatment, and under ultrasonic conditions, the composite piezoelectric catalyst induced hydrogen evolution reaction in water.

[0018] Preferably, the sacrificial agent aqueous solution is an aqueous solution formed from a mixture of glucose, lactic acid, methanol, triethanolamine, ascorbic acid, Na2S and Na2SO3, and the mass ratio of the composite piezoelectric catalyst to the volume of the sacrificial agent aqueous solution is (5-20):(15-30).

[0019] Preferably, the power of the ultrasonic process is 160-320W, the time is 1-4h, and the temperature is 25-30℃.

[0020] The beneficial effects of this invention are:

[0021] 1. The method for preparing carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst provided by the present invention involves first preparing carbonized microcrystalline cellulose micron rods, and then growing a specific amount of MoS2 nanosheets on their surface. This allows the heterojunction structure to effectively promote the separation of piezoelectric charge carriers, while the MoS2 nanosheets distributed on the outer surface provide abundant highly active hydrogen evolution sites for the inert carbonized microcrystalline cellulose. The synergistic effect of the two can significantly improve the overall performance of the composite material in piezoelectric catalytic hydrogen evolution.

[0022] 2. The carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst provided by this invention achieves uniform MoS2 loading by using carbonized microcrystalline cellulose as the MoS2 loading substrate. Simultaneously, by loading MoS2 onto the surface of carbonized microcrystalline cellulose, the synergistic effect between the two can be fully utilized to improve the performance of the composite catalyst in piezoelectric catalytic water splitting for hydrogen production. This is because: the cellulose phase can effectively capture mechanical energy and generate piezoelectric charges, while MoS2 acts as a highly efficient charge acceptor and catalytic active center, significantly improving the overall efficiency of water splitting for hydrogen production; secondly, the moderate carbonization of the cellulose surface and the formation of the MoS2 coating layer effectively enhance the mechanical stability of the composite catalyst and inhibit the depolymerization of cellulose crystals during ultrasonic vibration.

[0023] 3. The carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst provided by this invention can decompose water to produce hydrogen under normal temperature and pressure with the help of external mechanical force (such as ultrasonic vibration), and its catalytic performance is significantly improved compared with single-component carbonized microcrystalline cellulose and MoS2. Attached Figure Description

[0024] Figure 1 The images show the SEM and EDS-mapping diagrams of the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst prepared in Example 1 of this invention.

[0025] Figure 2 for Figure 1 A magnified view of a portion of the image using SEM.

[0026] Figure 3 This is a SEM image of the carbonized microcrystalline cellulose obtained in Example 1 of the present invention;

[0027] Figure 4 SEM image of the flower-shaped MoS2 nanosheets prepared in Comparative Example 2 of this invention;

[0028] Figure 5 The nitrogen adsorption-desorption curves and corresponding BET specific surface areas of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention are shown.

[0029] Figure 6 The XRD patterns are of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0030] Figure 7 The results of cycle stability tests of the composite piezoelectric catalyst prepared in Example 1 of this invention for piezoelectric catalytic water splitting to produce hydrogen are shown.

[0031] Figure 8 for Figure 7 SEM images and EDS-mapping images of catalyst samples after cyclic stability testing;

[0032] Figure 9 The hydrogen production rates of the composite piezoelectric catalyst prepared in Example 1 of this invention under glucose solutions of different pH values ​​are shown.

[0033] Figure 10 The results show the hydrogen production rates of the composite piezoelectric catalyst prepared in Example 1 of this invention under different Pt loadings.

[0034] Figure 11 The hydrogen production rates of the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalysts prepared in Examples 1 to 7 of this invention;

[0035] Figure 12 This is a comparison of the hydrogen production performance of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention in pure water and solutions with different sacrificial agents. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0038] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] On one hand, the present invention provides a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, comprising:

[0040] Carbonized microcrystalline cellulose, used as a supporting substrate, has a rod-like structure and a specific surface area of ​​2.1 m². 2 / g, is a mixture of particles of different sizes with a length of 30-100μm and a width of 10-20μm;

[0041] MoS2, loaded on the surface of carbonized microcrystalline cellulose, exhibits a three-dimensional flower-like hierarchical structure assembled from MoS2 nanosheets with a thickness of 25 nm and a specific surface area of ​​22.1 m². 2 / g, the loading of MoS2 in the composite piezoelectric catalyst is 35-75 wt.%, and the specific surface area of ​​the composite catalyst is 10-20 m². 2 / g. Preferably, the MoS2 loading in the composite material is 59.2 wt.%.

[0042] In the above technical solution, uniform loading of MoS2 is achieved by using carbonized microcrystalline cellulose as the supporting substrate for MoS2. By loading MoS2 onto the surface of carbonized microcrystalline cellulose, the synergistic effect between the two can be fully utilized to improve the performance of the composite catalyst in piezoelectric catalytic water splitting for hydrogen production. This is because: the cellulose phase can effectively capture mechanical energy and generate piezoelectric charge, while MoS2 acts as a highly efficient charge acceptor and catalytic active center, significantly improving the overall efficiency of water splitting for hydrogen production; secondly, the moderate carbonization of the cellulose surface and the formation of the MoS2 coating layer effectively enhance the mechanical stability of the composite catalyst and inhibit the depolymerization of cellulose crystals during ultrasonic vibration.

[0043] Furthermore, the present invention provides a method for preparing a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, comprising the following steps:

[0044] Carbonized microcrystalline cellulose is obtained by carbonizing microcrystalline cellulose.

[0045] The composite catalyst is prepared by uniformly mixing carbonized microcrystalline cellulose with Mo salt and S-containing precursor solution, and growing MoS2 on the surface of carbonized microcrystalline cellulose using a hydrothermal method.

[0046] In the above technical solution, by first preparing carbonized microcrystalline cellulose microrods and then growing a specific amount of MoS2 nanosheets on their surface, the heterojunction structure can effectively promote the separation of piezoelectric charge carriers. At the same time, the MoS2 nanosheets distributed on the outer surface provide abundant highly active hydrogen evolution sites for the inert carbonized microcrystalline cellulose. The synergistic effect of the two can significantly improve the overall performance of the composite catalyst in piezoelectric catalytic hydrogen evolution.

[0047] The growth mechanism of MoS2 on the surface of carbonized microcrystalline cellulose is as follows: During hydrothermal synthesis, the nanosheets preferentially grow and self-assemble on the surface of carbonized microcrystalline cellulose in a near-vertical orientation. These nanosheets interweave and overlap, eventually forming a three-dimensional hierarchical structure resembling flower petals. The ratio of Mo source to S source precursor to cellulose (i.e., the mass ratio of Mo salt or S precursor to carbonized microcrystalline cellulose) is a key regulatory factor in the formation of the above-mentioned three-dimensional hierarchical structure. As the ratio increases, the number of nucleation sites for MoS2 increases, and the nanosheets grow more densely. When the ratio is too high, nucleation breaks through the template limitation of carbonized microcrystalline cellulose, and homogeneous nucleation becomes dominant, thus forming independent MoS2 spherical aggregates that no longer adhere to the template surface. The essence of this process is the self-assembly behavior of MoS2 nanostructures in a high-temperature and high-pressure hydrothermal environment in order to reduce their high surface energy and tend towards thermodynamic stability.

[0048] In some embodiments, the carbonization treatment temperature is 330-350°C, the time is 1-3 hours, and the temperature rise rate from 25°C to 350°C during the carbonization process is 5. o C / min.

[0049] In some embodiments, the hydrothermal growth of MoS2 nanosheets is carried out at a temperature of 160-200°C for 16-30 h. Preferably, the temperature is 180°C and the time is 24 h. Specifically, the Mo salt is a soluble Mo salt, preferably ammonium heptamolybdate, and the S-containing precursor solution is preferably a thiourea solution with a concentration of 0.83 mol / L.

[0050] More specifically, the ratio of the mass (g) of carbonized microcrystalline cellulose, the mass (g) of Mo salt, and the volume (mL) of the S-containing precursor solution is (0.05-1.2):(1-1.5):(30-40).

[0051] Furthermore, the present invention also provides a method for applying the above-mentioned carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, comprising the following steps:

[0052] The composite piezoelectric catalyst was mixed with an aqueous sacrificial agent, and a Pt salt solution was added to the mixture under an inert atmosphere. Pt was deposited by photo-treatment, and under ultrasonic conditions, the composite piezoelectric catalyst induced a hydrogen evolution reaction in water.

[0053] The mechanism of the hydrogen evolution reaction is as follows: Under the action of ultrasonic mechanical energy, carbonized microcrystalline cellulose microrods with piezoelectric properties deform and become polarized, causing positive and negative charges to accumulate in different regions of their surface. These induced charges can be rapidly captured by the surface-loaded MoS2, thereby driving the proton reduction reaction (generating hydrogen) and the oxidation reaction of the sacrificial agent in the solution, respectively, thus achieving catalytic hydrogen production. In addition, the Pt on the surface of MoS2 can further enhance the catalytic activity of the catalyst and increase the hydrogen yield.

[0054] Specifically, the sacrificial agent aqueous solution is an aqueous solution formed from a mixture of glucose, lactic acid, methanol, triethanolamine, ascorbic acid, Na2S and Na2SO3, and the light source used for the light treatment is a 365 nm ultraviolet LED lamp.

[0055] In some embodiments, the Pt salt solution is an aqueous solution formed from a soluble Pt salt, such as an H2PtCl6 solution. When an H2PtCl6 solution is used, its concentration is 0.01025 mol / L, and the Pt loading is 1-4 wt.% (i.e., the ratio of the mass of Pt in H2PtCl6 to the sum of the mass of Pt and the mass of the composite piezoelectric catalyst is 1-4 wt.%), preferably 2 wt.% Pt loading.

[0056] In some embodiments, the ratio of the mass (mg) of the composite piezoelectric catalyst to the volume (mL) of the sacrificial aqueous solution is (5-20):(15-30), and the pH of the sacrificial aqueous solution is 2-12, preferably 2. In the above technical solution, by adjusting the amount of composite piezoelectric catalyst added and the volume of the sacrificial aqueous solution during application, the efficient hydrogen evolution reaction can be ensured. If the amount of composite piezoelectric catalyst added is insufficient, the catalyst content in the reaction system will be too low, affecting the hydrogen evolution reaction. Conversely, if the volume of the sacrificial aqueous solution is too large, the penetration ability of ultrasonic mechanical energy will be limited, resulting in a decrease in the efficiency of the hydrogen evolution reaction. If the volume of the sacrificial aqueous solution is too small, the reaction will be too vigorous.

[0057] In some embodiments, the ultrasonic process has a power of 160-320W, a duration of 1-4 hours, and a temperature of 25-30℃.

[0058] In some embodiments, the inert atmosphere is argon or the like.

[0059] The following specific embodiments further illustrate the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst proposed in this invention, its preparation method, and its application in piezoelectric catalytic water splitting for hydrogen production:

[0060] Example 1

[0061] This embodiment provides a method for preparing a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, comprising the following steps:

[0062] 2 g of microcrystalline cellulose was placed in a covered crucible and heated at 350 °C for 2 h to obtain carbonized microcrystalline cellulose; wherein the heating rate from 25 °C to 350 °C was 5. o C / min;

[0063] 1.24 g of ammonium molybdate tetrahydrate and 0.15 g of carbonized microcrystalline cellulose were added to a beaker containing 35 mL of thiourea aqueous solution (0.83 mol / L) and ultrasonicated at 160 W for 10 min to obtain a homogeneous mixture. The solution was then transferred to a high-pressure reactor and subjected to a hydrothermal reaction at 180 °C for 24 h. After cooling, the black precipitate at the bottom was collected by centrifugation, washed three times with water and once with ethanol, and then vacuum dried at 70 °C for 12 h to obtain the composite piezoelectric catalyst.

[0064] The SEM and EDS-mapping images of the composite piezoelectric catalyst prepared in this embodiment are as follows: Figure 1 As shown, the SEM image of carbonized microcrystalline cellulose is as follows. Figure 3 As shown, the results indicate that the surface of the composite piezoelectric catalyst is rougher than that of carbonized microcrystalline cellulose. The composite piezoelectric catalyst consists of rod-shaped carbonized microcrystalline cellulose and MoS2 supported on its surface. Furthermore, Figure 1 The EDS-mapping diagram shows that the Mo and S elements in the composite piezoelectric catalyst are uniformly distributed. A magnified view of a portion of the composite piezoelectric catalyst is shown below. Figure 2 As shown in the figure, MoS2 has a three-dimensional flower-like hierarchical structure, which is assembled from MoS2 nanosheets with a thickness of 25 nm. Figure 4 The morphology of the pure MoS2 shown is the same. The nitrogen adsorption-desorption curves of carbonized microcrystalline cellulose and the composite piezoelectric catalyst are shown below. Figure 5 As shown in the figure, the specific surface area of ​​carbonized microcrystalline cellulose increased from 2.1 m² to [missing value]. 2 / g increased to 16.1 m 2 / g; XRD pattern of the composite piezoelectric catalyst is shown below Figure 6 As shown, the results indicate that MoS2 was successfully loaded onto the surface of carbonized microcrystalline cellulose.

[0065] Furthermore, this embodiment also explored the application performance of carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst in piezoelectric catalytic water splitting for hydrogen production. The specific test steps are as follows: 10 mg of composite catalyst was dispersed in 20 mL of glucose solution with a concentration of 1.4 mol / L (pH 7). 100 μL of H2PtCl6 solution with a concentration of 0.01025 mol / L was added under an argon atmosphere, and the loaded Pt (loading amount of 2 wt.%) was treated with a 365 nm ultraviolet LED lamp for 1 h. After loading, the catalyst was purged with Ar. Then, it was ultrasonicated for 3 h at the center position (i.e., the position of strongest vibration) of an ultrasonic cleaner with a power of 160 W and a frequency of 40 kHz. After each hour, the gaseous product was collected using a sampler and injected into a gas chromatograph (s▪sun GC-9860) to detect the H2 production and calculate the hydrogen production rate (v = total H2 mass ÷ catalyst mass ÷ reaction time). After the test, the catalyst was separated from the substrate, the supernatant was removed, and the same volume of freshly prepared glucose solution was added. After purging with argon, the next catalytic water splitting hydrogen production process was started. A total of 5 cycles were tested, with each cycle lasting 3 hours. The results are as follows: Figure 7 As shown in the figure, the catalytic activity of the composite piezoelectric catalyst remained basically unchanged throughout the five cycles, indicating that the composite piezoelectric catalyst has stable performance. Figure 8 SEM and EDS-mapping images confirmed that the sample maintained its original heterojunction structure after the cyclic stability test.

[0066] Specifically, this embodiment also investigated the hydrogen production rate of the composite piezoelectric catalyst in the piezoelectric catalytic water production process under glucose solutions of different pH values. The results are as follows: Figure 9 As shown in the figure, the results indicate that the hydrogen production rate is affected by the substrate pH, and the hydrogen production rate is highest at pH=2; the hydrogen production rate results for different Pt loadings are as follows. Figure 10 As shown, the results indicate that as the Pt loading increases, the hydrogen production rate first increases and then decreases, and the hydrogen production rate is the highest when the Pt loading is 2%.

[0067] Examples 2 to 7

[0068] The only difference between Examples 2 to 7 and Example 1 is that the mass of carbonized microcrystalline cellulose added during the preparation of the composite piezoelectric catalyst is different from that in Example 1. All other experimental parameters and conditions are the same as in Example 1 and will not be repeated here. The mass of carbonized microcrystalline cellulose added in Examples 1 to 7 and the loading of MoS2 are shown in Table 1. The H2 yield of the composite piezoelectric catalyst prepared under the corresponding conditions when used for piezoelectric catalytic water splitting to produce hydrogen is shown in Table 2. The process parameters for application are the same as in Example 1 and will not be repeated here.

[0069] Table 1. Mass of carbonized microcrystalline cellulose and MoS2 loading added in Examples 1 to 7

[0070]

[0071] Table 2. H2 yield of the composite piezoelectric catalysts prepared in Examples 1 to 7 during piezoelectric catalytic water splitting for hydrogen production.

[0072]

[0073] Comparative Example 1

[0074] The only difference between Comparative Example 1 and Example 1 is that MoS2 is not loaded on the surface of carbonized microcrystalline cellulose, and carbonized microcrystalline cellulose is directly used as a composite piezoelectric catalyst. The preparation process of carbonized microcrystalline cellulose is the same as that of Example 1, and will not be repeated here.

[0075] Comparative Example 2

[0076] Comparative Example 2 provides a method for preparing MoS2, comprising the following steps: 1.24 g of ammonium molybdate tetrahydrate and 2.208 g of thiourea are added to 35 mL of deionized water, and the mixture is ultrasonically treated at 160 W for 10 min to obtain a homogeneous mixture; subsequently, the solution is transferred to a high-pressure reactor and subjected to a hydrothermal reaction at 180 °C for 24 h. After cooling, the black precipitate at the bottom is collected by centrifugation, washed three times with water and once with ethanol, and then vacuum dried at 70 °C for 12 h to obtain MoS2. Its SEM image is shown below. Figure 4 As shown in the figure, MoS2 exhibits a three-dimensional flower-like hierarchical structure, assembled from MoS2 nanosheets with a thickness of 25 nm. The nitrogen adsorption-desorption curves are shown in the figure. Figure 5 As shown, the specific surface area of ​​the MoS2 nanosheets is calculated to be 22.1 m². 2 / g.

[0077] To compare the performance of the materials prepared in Comparative Examples 1-2 in piezoelectric catalytic water splitting for hydrogen production, the test method of Example 1 was used. The process parameters were the same as in Example 1. The specific test results are shown in Table 3. The data in the table show that the H2 yield of Comparative Examples 1-2 was lower than that of Example 1, indicating that the composite piezoelectric catalyst prepared using the method proposed in Example 1 has better piezoelectric catalytic performance. This is because the composite catalyst prepared in Example 1 possesses both strong piezoelectric properties and abundant surface active sites, while a single component only has one of these advantages. The composite of carbonized microcrystalline cellulose and MoS2 can fully utilize the piezoelectric properties of carbonized microcrystalline cellulose and the catalytic hydrogen production performance of MoS2; furthermore, the heterojunction structure promotes the separation of piezoelectric charge carriers.

[0078] The hydrogen production rates of the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalysts prepared in Comparative Examples 1-2 and Examples 1-7 are as follows: Figure 11 As shown, the results indicate that the hydrogen production rate of the composite piezoelectric catalyst prepared in the comparative example is lower than that of Examples 1-7, and the hydrogen production rate of Example 1 is the highest. This is because when the MoS2 loading is too low, the density of MoS2 grown on the surface of carbonized microcrystalline cellulose is small, resulting in insufficient piezoelectric charge separation efficiency and hydrogen production active sites, which inhibits catalytic activity. However, when the MoS2 loading is too high, the excess MoS2 forms independent agglomerates and does not form heterojunctions with the carbonized microcrystalline cellulose microrods. In addition, a large number of thick spherical MoS2 agglomerates are also formed on the surface of microcrystalline cellulose, which leads to a decrease in the piezoelectric charge carrier transfer efficiency from the inside to the outside and a decrease in H2 yield.

[0079] Table 3. H2 yield of the composite piezoelectric catalysts prepared in Example 1 and Comparative Examples 1-2

[0080]

[0081] Furthermore, this invention investigated the catalytic activity of different substrates, including a mixture of Na₂S and Na₂SO₃, ascorbic acid solution, lactic acid solution, triethanolamine solution, and methanol solution, in Examples 1 and Comparative Examples 1-2. 10 mg of catalyst was dispersed in 20 mL of pure water or different substrate solutions for testing. The pH of all substrate solutions was 7. The Na₂S and Na₂SO₃ mixture solution was obtained by mixing 0.70 mol / L Na₂S aqueous solution and 0.50 mol / L Na₂SO₃ aqueous solution at a volume ratio of 1:1. The concentrations of the ascorbic acid solution, lactic acid solution, triethanolamine solution, and methanol solution were all 0.01 mol / L, 20 vol.%, 10 vol.%, and 10 vol.% respectively. Then, 100 μL of a 0.01025 mol / L H₂PtCl₆ solution was added under an argon atmosphere, and the mixture was irradiated with a 365 nm UV LED for 1 h to load 2... wt.% Pt was re-purged with argon gas and then ultrasonicated for 3 hours at the center (i.e., the point of strongest vibration) of an ultrasonic cleaner with a power of 160 W and a frequency of 40 kHz. Gaseous products were collected every hour and injected into a gas chromatograph (S▪Sun GC-9860) to detect H2 production and calculate the hydrogen production rate. Results for hydrogen production rates under different substrates are shown below. Figure 12 As shown, the results indicate that the hydrogen production efficiency varies with different substrates, but the performance of the composite catalyst is higher than that of the individual component catalysts, suggesting a synergistic effect between carbonized microcrystalline cellulose and MoS2.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst, characterized in that, Includes the following steps: Carbonized microcrystalline cellulose is prepared by carbonizing microcrystalline cellulose at a temperature of 330-350℃ for 1-3 hours. The carbonized microcrystalline cellulose was mixed evenly with Mo salt and S-containing precursor solution, and MoS2 was grown on the surface of the carbonized microcrystalline cellulose by hydrothermal method to obtain the composite catalyst.

2. The preparation method according to claim 1, characterized in that, The ratio of the mass of carbonized microcrystalline cellulose, the mass of Mo salt, and the volume of the S-containing precursor solution is (0.05-1.2):(1-1.5):(30-40).

3. The preparation method according to claim 1, characterized in that, The hydrothermal growth of MoS2 is carried out at a temperature of 160-200℃ for 16-30 hours.

4. The preparation method according to claim 1, characterized in that, The S-containing precursor solution is a thiourea solution with a concentration of 0.6-1.0 mol / L.

5. A carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst prepared by any one of claims 1-4.

6. The carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst according to claim 5, characterized in that, include: Carbonized microcrystalline cellulose, used as a supporting substrate, has a rod-like structure and a specific surface area of ​​2.1 m². 2 / g, is a mixture of particles of different sizes with a length of 30-100μm and a width of 10-20μm; MoS2, loaded on the surface of the carbonized microcrystalline cellulose, exhibits a three-dimensional flower-like hierarchical structure; this structure is assembled from MoS2 nanosheets with a thickness of 25 nm and a specific surface area of ​​22.1 m². 2 / g; the MoS2 loading in the composite piezoelectric catalyst is 35-75 wt.%, and the specific surface area of ​​the composite catalyst is 10-20 m². 2 / g.

7. A method for applying the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst prepared by any one of claims 1-4 or the carbonized microcrystalline cellulose@MoS2 nanosheet composite piezoelectric catalyst prepared by claim 6 in piezoelectric catalytic water splitting for hydrogen production, characterized in that, Includes the following steps: The composite piezoelectric catalyst was mixed with an aqueous sacrificial agent, and H2PtCl4 solution was added to the resulting mixture under an inert atmosphere. Pt was deposited by photo-treatment, and under ultrasonic conditions, the composite piezoelectric catalyst induced hydrogen evolution reaction in water.

8. The application method according to claim 7, characterized in that, The sacrificial agent aqueous solution is an aqueous solution formed from a mixture of glucose, lactic acid, methanol, triethanolamine, ascorbic acid, Na2S and Na2SO3, and the mass ratio of the composite piezoelectric catalyst to the volume of the sacrificial agent aqueous solution is (5-20):(15-30).

9. The application method according to claim 8, characterized in that, The power of the ultrasonic process is 160-320W, the time is 1-4h, and the temperature is 25-30℃.

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