A piezoelectric catalyst and its preparation method and application

Abstract

The present invention belongs to the field of catalyst technology, specifically relating to a piezoelectric catalyst, its preparation method, and application. The preparation method comprises the following steps: weighing zinc acetate dihydrate and sodium molybdate dihydrate, adding citric acid and water, stirring, adding thioacetamide, continuing stirring, transferring the mixed solution to a reactor, reacting, cooling, washing, and drying to produce the piezoelectric catalyst. The piezoelectric catalyst produced by the present invention exhibits excellent piezoelectric catalytic performance and can achieve high dye degradation efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a piezoelectric catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, piezoelectric materials have provided new ideas for clean energy production by collecting mechanical energy from the environment (such as wind, water flow, vibration and noise) and combining it with different catalytic reaction processes. Among them, piezoelectric two-dimensional materials have attracted increasing attention in recent years. Two-dimensional (2D) layered materials with non-centrosymmetric structures have shown great potential in nanoelectromechanical systems and electronic devices. Two-dimensional transition metal dichalcogenides (2D-TMDs) have attracted widespread attention due to their good flexibility, high piezoelectric coefficient, large specific surface area and abundant active sites. 2H MoS2 has a high piezoelectric coefficient (3.06×10 -10 C / m), abundant reserves, and band gap controllable by adjusting the number of layers were first used in piezoelectric catalysis. Although the considerable piezoelectric catalytic degradation effect of single-layer or few-layer molybdenum disulfide has been confirmed, the MoS2 material itself also has some defects that affect its catalytic reaction efficiency. The catalytic effect depends on the number of active sites on the MoS2 nanosheets. Active sites exist at the edges of the sheet structure, while there are no dangling bond active sites within the basal plane, resulting in low catalytic activity. In addition, due to the high surface energy and the presence of van der Waals forces, stacking occurs between MoS2 layers. The increase in the number of layers hinders deformation, resulting in poor transport performance. In addition, the coexistence of odd and even layers of MoS2 limits the catalytic performance of MoS2 piezoelectric catalysts. Therefore, the modification and structural design of MoS2 to give MoS2 non-layer-controlled piezoelectric properties and increase the number of edge active sites, thereby further improving MoS2's piezoelectric catalytic activity, has become an important research topic for its application as a catalyst. Summary of the Invention

[0003] The present invention aims to provide a piezoelectric catalyst and its preparation method and application. The piezoelectric catalyst prepared by the present invention has good piezoelectric catalytic performance and can achieve high dye degradation efficiency.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: a method for preparing a piezoelectric catalyst, comprising the following steps:

[0005] Weigh zinc acetate dihydrate and sodium molybdate dihydrate, add citric acid and water, stir, add thioacetamide, continue stirring, transfer the mixed solution to a reactor, react, cool, wash, and dry to obtain the piezoelectric catalyst.

[0006] Preferably, the molar ratio of zinc acetate dihydrate to sodium molybdate dihydrate is 1:(4-5).

[0007] Preferably, the added amount of citric acid is 3 to 5 times the mass of zinc acetate dihydrate.

[0008] Preferably, the molar ratio of Mo to S in the thioacetamide and sodium molybdate dihydrate is 1:(2-2.5).

[0009] Preferably, the mass ratio of water to citric acid is (25-30):1.

[0010] Preferably, the reaction temperature is 170-220° C., and the reaction time is 12 to 48 hours.

[0011] More preferably, the reaction temperature is 180-200° C., and the reaction time is 12-24 h.

[0012] Preferably, the stirring time is 10 to 30 minutes.

[0013] Preferably, the cooling is to reduce the temperature to 25-30°C.

[0014] Preferably, the cleaning is performed using water and ethanol.

[0015] The present invention can assist the growth of ZnS, inhibit its anisotropy, and regulate the sample morphology by adding a specific amount of citric acid component during the preparation process. Citric acid (CA) molecules have three carboxyl groups, which can be easily captured on the surface of MoS2 nanosheets and form outward-oriented chelate bonds with -OH functional groups. These groups provided by CA molecules make the surface of the nanosheets negatively charged and guide the Zn provided by zinc acetate to 2+ The ions attached to the -OH groups, forming a thin Zn(OH)2 layer that initially covered the surface of the MoS2 nanosheets. Then, through substitution reactions, a uniform ZnS layer was formed on the MoS2 surface.

[0016] In the preparation method of the piezoelectric catalyst of the present invention, oxygen atoms are incorporated into the molybdenum disulfide crystals by controlling the reaction temperature at a relatively low level. This oxygen incorporation effectively enhances the catalyst's conductivity and improves its piezoelectric properties. At relatively low temperatures, the reaction process is incomplete, and the Mo-O bonds inherited from the molybdate precursor remain. This allows oxygen to be incorporated into the composite material structure. Oxygen substitution maintains the material's charge balance, making it more stable. Furthermore, oxygen incorporation modulates the electronic structure of the molybdenum disulfide, ultimately improving the conductivity of the piezoelectric catalyst.

[0017] The preparation method of the piezoelectric catalyst of the present invention constructs a MoS2 and ZnS nanoheterojunction. After the composite, the two materials have different energy band structures. During the degradation process, free electrons flow from the conduction band of ZnS to the conduction band of MoS2, and hole carriers flow from the valence band of ZnS to the valence band of MoS2, which promotes the separation of carriers and significantly improves the degradation efficiency.

[0018] The oxygen doping technology and the construction of heterojunction can both effectively reduce the AC impedance of the material, thereby promoting the carrier transport process.

[0019] The present invention also claims a piezoelectric catalyst prepared by the preparation method of the piezoelectric catalyst.

[0020] The present invention also claims a use of the piezoelectric catalyst in degrading dyes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention utilizes a one-step hydrothermal method to directly synthesize an oxygen-doped piezoelectric catalyst. The prepared piezoelectric catalyst has good piezoelectric catalytic performance and can achieve higher dye degradation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 These are the Nernquist plots of the catalysts prepared in Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention.

[0024] Figure 2 The figure is a comparison effect diagram of the rate of catalytic degradation of Rhodamine B (RhB) by the catalysts prepared in the examples of the present invention and the comparative examples. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In the Examples and Comparative Examples, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0027] Example 1

[0028] 0.220 g of zinc acetate dihydrate (Zn(OAC)2·2H2O) and 0.968 g of sodium molybdate dihydrate (Na2MoO4·2H2O) were weighed respectively, 0.768 g of citric acid was added, and then 20 ml of deionized water was added, and stirred with a magnetic stirrer until completely dissolved. 0.6 g of thioacetamide (TAA) was added and stirred with a magnetic stirrer for 20 minutes. The mixed solution was transferred to a reactor and maintained at a reaction temperature of 180°C for 24 hours. After cooling, the mixture was taken out, cleaned and dried to obtain the piezoelectric catalyst.

[0029] Example 2

[0030] 0.220 g of zinc acetate dihydrate (Zn(OAC)2·2H2O) and 0.968 g of sodium molybdate dihydrate (Na2MoO4·2H2O) were weighed respectively, 0.768 g of citric acid was added, and then 20 ml of deionized water was added, and stirred with a magnetic stirrer until completely dissolved. 0.6 g of thioacetamide (TAA) was added and stirred with a magnetic stirrer for 20 minutes. The mixed solution was transferred to a reactor and maintained at a reaction temperature of 220°C for 24 hours. After cooling, it was taken out, cleaned and dried to obtain the piezoelectric catalyst.

[0031] Example 3

[0032] 0.220 g of zinc acetate dihydrate (Zn(OAC)2·2H2O) and 0.968 g of sodium molybdate dihydrate (Na2MoO4·2H2O) were weighed respectively, 0.768 g of citric acid was added, and then 20 ml of deionized water was added, and stirred with a magnetic stirrer until completely dissolved. 0.6 g of thioacetamide (TAA) was added and stirred with a magnetic stirrer for 20 minutes. The mixed solution was transferred to a reactor and maintained at a reaction temperature of 200°C for 24 hours. After cooling, the mixture was taken out, cleaned and dried to obtain the piezoelectric catalyst.

[0033] Example 4

[0034] 0.220 g of zinc acetate dihydrate (Zn(OAC)2·2H2O) and 1.210 g of sodium molybdate dihydrate (Na2MoO4·2H2O) were weighed respectively, 1.1 g of citric acid was added, and then 30 ml of deionized water was added, and stirred with a magnetic stirrer until completely dissolved. 0.93 g of thioacetamide (TAA) was added and stirred with a magnetic stirrer for 20 minutes. The mixed solution was transferred to a reactor and maintained at a reaction temperature of 180°C for 24 hours. After cooling, the mixture was taken out, cleaned and dried to obtain the piezoelectric catalyst.

[0035] Example 5

[0036] Compared with Example 1, the only difference in this example is that the amount of citric acid added is 6 times the mass of zinc acetate dihydrate.

[0037] The preparation method is as in Example 1.

[0038] Comparative Example 1-MoS2 180

[0039] Compared with Example 1, the only difference of this comparative example is that zinc acetate dihydrate is not added and the reaction temperature is 180°C.

[0040] The preparation method is as in Example 1.

[0041] Comparative Example 2-MoS2 220

[0042] Compared with Example 1, the difference of this comparative example is that zinc acetate dihydrate is not added and the reaction temperature is 220°C.

[0043] The preparation method is as in Example 1.

[0044] Comparative Example 3-ZnS

[0045] Compared with Example 1, the difference of this comparative example is only that sodium molybdate dihydrate is not added.

[0046] The preparation method is as in Example 1.

[0047] Comparative Example 4

[0048] Compared with Example 1, the only difference of this comparative example is that the reaction temperature is 140°C.

[0049] The preparation method is as in Example 1.

[0050] Comparative Example 5

[0051] Compared with Example 1, the only difference of this comparative example is that no citric acid is added.

[0052] The preparation method is as in Example 1.

[0053] Performance Testing

[0054] The catalysts prepared in the examples and comparative examples were subjected to dye degradation test and electrochemical impedance spectroscopy (EIS) test. The specific experimental methods are as follows:

[0055] Dye degradation: The piezoelectric catalytic activity of the catalyst was studied by measuring the degradation of Rhodamine B (20 mg / L). A magnetic stirrer (450 rpm) provided external mechanical energy. 0.05 g of the prepared sample was dispersed in 50 mL of Rhodamine B solution. After magnetic stirring, 1.6 mL of the solution was collected and centrifuged, and then 2.4 mL of deionized water was added to 0.8 mL of the supernatant. The concentration of Rhodamine B dye was analyzed by UV-visible spectrometry, and the degradation rate of the catalyst within five minutes was calculated based on the first-order kinetic curve.

[0056] Electrochemical impedance spectroscopy (EIS) measurements were performed in a standard three-electrode electrochemical workstation. A saturated calomel electrode was used as the reference electrode, a platinum sheet (Pt) was used as the counter electrode, and an ITO glass coated with the sample served as the working electrode. The electrolyte was a 0.5 mol / L Na2SO4 solution. The working electrode was prepared as follows: 10 mg of sample was ultrasonically dispersed in a mixture containing 20 μL of 0.25% Nafion, 0.8 mL of isopropyl alcohol, and 0.2 mL of water. The sample was then spin-coated onto the conductive surface of a 2 cm × 1 cm ITO conductive glass using a spin coater. The prepared working electrode was dried in a vacuum oven until ready for use. Nyquist plots were measured using AC impedance-frequency sweep mode.

[0057] The experimental results are shown in Table 1 and Figures 1-2 shown.

[0058] Table 1

[0059] Group <![CDATA[Degradation rate (min -1 )]]> Example 1 - ZnS / MS - 180°C 0.424 Example 2 - ZnS / MS - 220°C 0.286 Example 3 - ZnS / MS - 200°C 0.332 Example 4 0.402 Example 5 0.385 Comparative Example 1-MS-180 0.077 Comparative Example 2-MS-220 0.068 Comparative Example 3-ZnS 0.016 Comparative Example 4-140 0.021 Comparative Example 5 0.160

[0060] From Table 1 and Figures 1-2 It can be seen from the data in that the piezoelectric catalyst prepared in the embodiment of the present invention has good piezoelectric catalytic performance and can achieve a high dye degradation efficiency.

[0061] Compared with Example 1, the catalysts prepared in Comparative Examples 1 and 3 only formed a single MoS2 or a single ZnS, and their catalytic performance was significantly worse than that of the embodiment; compared with Comparative Example 1, the reaction temperature of Comparative Example 2 was 220°C, and its catalytic performance was worse than that of Comparative Example 1; the reaction temperature in the preparation process of Comparative Example 4 was too low, resulting in a decrease in the catalytic activity of the prepared catalyst; citric acid was not added during the preparation process of Comparative Example 5, and the degradation performance of the final catalyst on dyes became poor.

[0062] See also Figure 1 , by testing the radius of the Nyquist curve in electrochemical impedance spectroscopy (EIS), the charge transfer resistance (Rct) at the working electrode interface is evaluated. The smaller the radius, the smaller the resistance. Figure 1 As can be seen from (a) and the partially enlarged graph of the curve (b), the catalysts prepared in Examples 1 to 2 of the present invention have smaller radii of the Nyquist curves than those prepared in Comparative Examples 1 to 3, indicating that they have smaller resistance and higher conductivity.

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. Application of a piezoelectric catalyst in the degradation of dyes, characterized in that: The preparation method of the piezoelectric catalyst, The following steps are involved: Weigh zinc acetate dihydrate and sodium molybdate dihydrate, add citric acid and water, stir, add thioacetamide, continue stirring, transfer the mixed solution to a reactor, react at 170-220° C. for 12-48 hours, cool, wash, and dry to obtain the piezoelectric catalyst; The molar ratio of zinc acetate dihydrate to sodium molybdate dihydrate is 1:(4-5); the amount of citric acid added is 3-5 times the mass of zinc acetate dihydrate; the molar ratio of thioacetamide to Mo:S in sodium molybdate dihydrate is 1:(2-2.5); and the mass ratio of water to citric acid is (25-30):

1.

2. The use according to claim 1, characterized in that The reaction temperature is 180-200° C., and the reaction time is 12-24 hours.

3. The use according to claim 1, characterized in that At least one of the following (1) to (3): (1) The stirring time is 10 to 30 minutes; (2) The cooling is to reduce the temperature to 25-30°C; (3) The cleaning is performed using water and ethanol.

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