A modified MoSe2 piezoelectric catalyst, its preparation method and application

Abstract

This invention discloses a modified MoSe2 piezoelectric catalyst, its preparation method, and its application. The catalyst utilizes Mo from MoSe2 nanosheets... 2+ Partially Fe 2+ The modified MoSe2 piezoelectric catalyst is prepared by randomly layering and stacking MoSe2 nanosheets and FeSe2 nanosheets, forming a nanoflower-like structure. The preparation method includes the following steps: uniformly dispersing MoSe2 powder in water, then adding iron salt and hydrazine hydrate, mixing thoroughly, and performing a hydrothermal reaction to obtain the modified MoSe2 piezoelectric catalyst. By introducing FeSe2 into MoSe2, the catalytic activity of MoSe2 is improved. Furthermore, the nanoflower-like structure not only facilitates the induction of piezoelectric polarization but also exposes more edge active sites, thereby improving the piezoelectric catalytic activation efficiency of persulfate.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric catalysis technology, and in particular to a modified MoSe2 piezoelectric catalyst, its preparation method, and its application. Background Technology

[0002] Currently, there are various mainstream piezoelectric catalysts. Among them, molybdenum diselenide (MoSe2), as a typical transition metal chalcogenide, exhibits piezoelectric properties due to its non-centrosymmetric crystal structure and has been widely used in electrochemistry, adsorption, catalysis, and other fields in recent years. Compared with compounds with similar structures, MoSe2 has a larger piezoelectric response, good mechanical flexibility, and a larger specific surface area, and is sensitive to small stresses, making it an ideal material for catalytic applications. However, the practical application of MoSe2 is often limited by its insufficient piezoelectric polarization, limited number of active sites, low free carrier concentration, and slow carrier separation and migration rates. Summary of the Invention

[0003] Objectives of the Invention: The first objective of this invention is to provide a modified MoSe2 piezoelectric catalyst with abundant active sites, fast electron transport, and high catalytic activity; the second objective of this invention is to provide a method for preparing the modified MoSe2 piezoelectric catalyst; and the third objective of this invention is to provide the application of the modified MoSe2 piezoelectric catalyst in the upgrading and conversion of microplastics to CO.

[0004] Technical solution: The modified MoSe2 piezoelectric catalyst of this invention utilizes Mo from MoSe2 nanosheets... 2+ Partially Fe 2+ The substitution process forms a structure of randomly layered MoSe2 nanosheets and FeSe2 nanosheets, exhibiting a nanoflower-like structure.

[0005] MoSe2 nanosheets and FeSe2 nanosheets are both ultrathin nanosheets. Introducing FeSe2 into MoSe2 nanosheets enhances their catalytic activity, and the nanoflower-like structure facilitates the induction of piezoelectric polarization, while also exposing more edge active sites, thereby improving the piezoelectric catalytic activation efficiency of persulfate.

[0006] Preferably, the molar ratio of MoSe2 nanosheets to FeSe2 nanosheets is 15:1 to 5. As the amount of FeSe2 introduced increases, more heterojunctions are formed between the two materials, improving piezoelectric properties; however, excessive FeSe2 introduction may affect the piezoelectric properties of MoSe2 itself.

[0007] The preparation method of the modified MoSe2 piezoelectric catalyst of the present invention includes the following steps: uniformly dispersing MoSe2 powder in water, then adding iron salt and hydrazine hydrate, mixing thoroughly, and then carrying out a hydrothermal reaction. The Mo in MoSe2... 2+ Partially Fe 2+ The modified MoSe2 piezoelectric catalyst was obtained by substitution.

[0008] In the hydrothermal reaction, MoSe2 acts as the selenium source, iron salts as the iron source, and hydrazine hydrate as the reducing agent. Hydrazine hydrate can remove Fe from the iron salts. 3+ Reduced to Fe 2+ Mo in the MoSe2 molecule 2+ Partially replaced with Fe 2+ This process generates some FeSe2, which grows in situ on MoSe2, exhibiting a nanoflower-like structure.

[0009] Preferably, the hydrothermal reaction temperature is 180–220°C.

[0010] Preferably, the hydrothermal reaction time is 22–26 hours.

[0011] Preferably, the iron salt is ferric chloride hexahydrate.

[0012] Preferably, the mass ratio of ferric chloride hexahydrate to MoSe2 is 3 to 12:40.

[0013] The MoSe2 powder was prepared as follows: 0.608 g of sodium borohydride was dissolved in 150 mL of deionized water, and then 0.632 g of selenium powder and 0.968 g of sodium molybdate were thoroughly mixed with it and stirred for 30 min. The resulting mixture was then transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction. After natural cooling, the mixture was washed three times each with deionized water and anhydrous ethanol, and dried overnight under vacuum to obtain MoSe2 powder.

[0014] Preferably, the hydrothermal temperature is 200–220°C and the hydrothermal time is 18–22 hours.

[0015] Preferably, the drying temperature is 50-65°C and the drying time is 12-18 hours.

[0016] The application of the modified MoSe2 piezoelectric catalyst described in this invention in the upgrading and conversion of microplastics to CO.

[0017] Preferably, the application method is as follows: the prepared catalyst is uniformly dispersed in an aqueous solution containing microplastics, and persulfate is added to initiate a piezoelectric catalytic reaction to produce CO. The piezoelectric catalytic reaction is carried out in a gas-closed system using an ultrasonic cleaner.

[0018] Invention Mechanism: This invention employs a MoSe2 / FeSe2 composite as a piezoelectric catalyst. The introduction of Fe increases the concentration of free charge carriers in the material, accelerating the separation and migration of charge carriers. By controlling the iron content in the MoSe2 / FeSe2 composite material, a MoSe2 / FeSe2 piezoelectric catalyst with the optimal iron content was ultimately determined.

[0019] The nanoflower-like structure formed by MoSe2 and FeSe2 not only facilitates the induction of piezoelectric polarization but also exposes more edge active sites, thereby improving the piezoelectric catalytic activation efficiency of persulfate. This catalyst can convert microplastics into CO under ultrasonic conditions, avoiding the generation of greenhouse gases, and does not require light or heating, reducing the difficulty of practical application.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) By introducing FeSe2 into MoSe2, the concentration of free carriers in the material is increased, the separation and migration speed of carriers is accelerated, the catalytic activity of MoSe2 is improved, and the nano-flower structure is not only conducive to inducing piezoelectric polarization, but also exposes more edge active sites, thereby improving the piezoelectric catalytic activation efficiency of persulfate; (2) The catalyst is prepared by hydrothermal method, the raw materials are simple and readily available, the cost is low, the preparation process is simple, the preparation conditions are mild, energy saving and environmental protection are easy to achieve large-scale production; (3) The catalyst is used to upgrade microplastics to CO, avoid the generation of greenhouse gases, and does not require light, heating and other conditions, which reduces the difficulty of practical application. Attached Figure Description

[0021] Figure 1 These are the XRD patterns of the catalysts in Examples 1-3 and Comparative Example 1;

[0022] Figure 2 These are Raman characterization diagrams of the catalysts in Examples 1-3 and Comparative Example 1;

[0023] Figure 3 This is a transmission electron microscope image of the catalyst in Comparative Example 1;

[0024] Figure 4 This is a transmission electron microscope image of the catalyst in Example 2;

[0025] Figure 5 These are performance graphs of the catalysts in Examples 1-3 and Comparative Example 1 for converting 10 mg of polylactic acid into CO;

[0026] Figure 6 This is a graph showing the CO production of the catalyst under different polylactic acid dosages in Example 2;

[0027] Figure 7This is a stability graph of the catalyst in Example 2 converting 20 mg of polylactic acid into CO. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the embodiments.

[0029] Example 1 (MoSe2 / FeSe2-15)

[0030] The modified MoSe2 piezoelectric catalyst of the present invention has a molar ratio of MoSe2 nanosheets to FeSe2 nanosheets of 14.17:1; the preparation method includes the following steps:

[0031] (1) Preparation of MoSe2 powder

[0032] 0.608 g of sodium borohydride was dissolved in 150 mL of deionized water, and then 0.632 g of selenium powder and 0.968 g of sodium molybdate were thoroughly mixed with it and stirred for 30 min. The resulting mixture was then transferred to a 100 mL PTFE-lined stainless steel autoclave and kept at 210 °C for 20 h. After natural cooling, the mixture was washed three times each with deionized water and anhydrous ethanol, and dried under vacuum overnight to obtain MoSe2 powder.

[0033] (2) Preparation of MoSe2 / FeSe2-15

[0034] 200 mg of MoSe2 powder was uniformly dispersed in 30 mL of deionized water, and then 15 mg of ferric chloride hexahydrate and 4 mL of hydrazine hydrate were thoroughly mixed with it. The resulting mixture was transferred to a 100 mL PTFE-lined stainless steel autoclave and kept at 200 °C for 24 h. After cooling to room temperature, the mixture was centrifuged, washed, dried, and ground to obtain the MoSe2 / FeSe2 piezoelectric catalyst, named MoSe2 / FeSe2-15.

[0035] Example 2 (MoSe2 / FeSe2-40)

[0036] The modified MoSe2 piezoelectric catalyst of the present invention has a molar ratio of MoSe2 nanosheets to FeSe2 nanosheets of 5.31:1; the preparation method includes the following steps:

[0037] (1) The preparation of MoSe2 powder is the same as in Example 1.

[0038] (2) Preparation of MoSe2 / FeSe2-40

[0039] 200 mg of MoSe2 powder was uniformly dispersed in 30 mL of deionized water, and then 40 mg of ferric chloride hexahydrate and 4 mL of hydrazine hydrate were thoroughly mixed with it. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and kept at 200 °C for 24 h. After cooling to room temperature, the mixture was centrifuged, washed, dried, and ground to obtain the MoSe2 / FeSe2 piezoelectric catalyst, named MoSe2 / FeSe2-40.

[0040] Example 3 (MoSe2 / FeSe2-60)

[0041] The modified MoSe2 piezoelectric catalyst of the present invention has a molar ratio of MoSe2 nanosheets to FeSe2 nanosheets of 3.54:1; the preparation method includes the following steps:

[0042] (1) The preparation of MoSe2 powder is the same as in Example 1.

[0043] (2) Preparation of MoSe2 / FeSe2-60

[0044] 200 mg of MoSe2 powder was uniformly dispersed in 30 mL of deionized water, and then 60 mg of ferric chloride hexahydrate and 4 mL of hydrazine hydrate were thoroughly mixed with it. The resulting mixture was transferred to a 100 mL PTFE-lined stainless steel autoclave and kept at 200 °C for 24 h. After cooling to room temperature, the mixture was centrifuged, washed, dried, and ground to obtain the MoSe2 / FeSe2 piezoelectric catalyst, named MoSe2 / FeSe2-60.

[0045] Comparative Example 1 (MoSe2)

[0046] By performing only step (1) of Example 1, the MoSe2 piezoelectric catalyst was obtained.

[0047] Structural characterization

[0048] X-ray diffraction (XRD) was used to characterize the different catalysts prepared in Examples 1-3 and Comparative Example 1, such as... Figure 1 As shown.

[0049] Depend on Figure 1 It can be seen that Examples 1-3 and Comparative Example 1 all have a 1T phase MoSe2. Compared with the 2H phase MoSe2, the 1T phase MoSe2 exhibits better catalytic activity due to its relatively higher electronic conductivity. Among them, the XRD patterns of Examples 1-3 show obvious characteristic peaks related to FeSe2, which are consistent with the orthorhombic iron ore standard card (JCPDS No: 74-0247).

[0050] Raman spectroscopy characterization was performed on the different catalysts prepared in Examples 1-3 and Comparative Example 1, such as... Figure 2 As shown.

[0051] Depend on Figure 2 It can be seen that Examples 1-3 and Comparative Example 1 are at 238.6 cm. -1 A small and weak out-of-plane Mo-Se mode (A) of the 2H phase was observed. 1g Peak. In addition, J1, J2, E 1g E 2g 1 The vibration modes of J3 and J4 are 114.1 cm. -1 149.2cm -1 197.9cm -1 282.4cm -1 And 337.0cm -1 The 1T phase is the main signal that distinguishes between the 1T and 2H phases. Several catalysts exhibited similar characteristic peaks, and the 1T phase signal was significantly stronger than the 2H phase signal, indicating that the 1T phase mainly exists in the sample. Therefore, the above results demonstrate the successful preparation of Examples 1-3 and Comparative Example 1.

[0052] The different catalysts prepared in Example 2 and Comparative Example 1 were characterized by transmission electron microscopy (TEM), and the results are as follows: Figures 3-4 As shown.

[0053] from Figure 3 and Figure 4 It can be seen that the prepared MoSe2 and MoSe2 / FeSe2-40 are both composed of randomly layered ultrathin nanosheets, forming a nanoflower-like structure. This helps to increase the specific surface area of ​​the catalyst, provide more edge active sites, and thus improve the catalytic efficiency.

[0054] Performance testing

[0055] 1. Yield test of polylactic acid (PLA) to CO catalyzed by catalyst

[0056] The application of the MoSe2 / FeSe2 piezoelectric catalyst of the present invention in the microplastic upgrading and conversion is specifically applied to the conversion of polylactic acid (PLA) to CO. The application method includes the following steps:

[0057] (1) Place 30 mg of catalyst into a reactor containing 50 mL of an aqueous solution containing a certain amount (5 mg, 10 mg or 20 mg) of PLA;

[0058] (2) The sealed reactor was flushed three times with an oil pump while being kept under an argon atmosphere to ensure complete removal of air;

[0059] (3) The reactor was pressurized to 1 bar with argon gas, and 90 mg of persulfate was added to the system to initiate a piezoelectric catalytic reaction;

[0060] (4) The piezoelectric catalytic reaction was carried out in the gas-closed system using an ultrasonic cleaner (120W, 40kHz). The reaction system was kept at 25℃ under the control of a low-temperature circulating pump. Gas mixtures were collected at time points of 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4h respectively.

[0061] (5) CO concentration was detected by a flame ionization detector (FID).

[0062] When 10 mg of PLA was added to the reaction system, the CO production in Examples 1-3 and Comparative Example 1 was as follows: Figure 5 As shown.

[0063] Depend on Figure 5 It was found that the CO yield of the catalysts prepared in Examples 1-3 and Comparative Example 1 within 4 hours was 41.07 μmolg. -1 65.49 μmol g -1 48.55 μmol g -1 2.88 μmol g -1 The catalyst prepared in Example 2 exhibited the highest CO yield. Compared to Example 2, the conversion rate of PLA by activated persulfate in Comparative Example 1 was significantly reduced. This may be because the combination of MoSe2 and FeSe2 not only provides multiple pathways for activating persulfate but also promotes Fe... 3+ / Fe 2+ Therefore, MoSe2 / FeSe2-40 can serve as a highly efficient piezoelectric catalyst for the upgrading and transformation of microplastics.

[0064] 2. Yield test of polylactic acid (PLA) to CO conversion catalyzed by different amounts of catalyst.

[0065] Example 2 CO production under different PLA dosages: Figure 6 As shown.

[0066] Depend on Figure 6 It can be seen that as the PLA dosage increases, the conversion rate of PLA by MoSe2 / FeSe2-40 continuously increases, and the CO production is highest at a PLA dosage of 20 mg, which may be due to the provision of more carbon source in the reaction system.

[0067] 3. Catalyst Cyclic Stability Test

[0068] 20 mg PLA was added to the reaction system to test the cyclic stability of the catalyst prepared in Example 2. The test method was as follows: after each CO measurement experiment, the catalyst was collected, thoroughly washed and dried, and then the next catalytic experiment was carried out.

[0069] The results are as follows Figure 7As shown. From Figure 7 It can be seen that after four consecutive runs of the catalyst, the CO production increased from 87.65 μmol g. -1 It decreased slightly to 83.16 μmol g -1 This decrease is mainly due to the intermediates in the PLA reaction process covering the active sites of the catalyst. Overall, the catalyst still exhibits good stability and excellent reusability.

Claims

1. A modified MoSe2 piezoelectric catalyst, characterized in that, By using Mo in MoSe2 nanosheets 2+ Partially Fe 2+ The substitution process forms a structure of randomly layered MoSe2 nanosheets and FeSe2 nanosheets, exhibiting a nanoflower-like appearance. The preparation method is as follows: MoSe2 powder is uniformly dispersed in water, then iron salt and hydrazine hydrate are added, and after thorough mixing, a hydrothermal reaction is carried out. The MoSe2 contains Mo... 2+ Partially Fe 2+ The modified MoSe2 piezoelectric catalyst was obtained by substitution; the molar ratio of MoSe2 nanosheets to FeSe2 nanosheets was 15:1~5.

2. The modified MoSe2 piezoelectric catalyst according to claim 1, characterized in that, The molar ratio of MoSe2 nanosheets to FeSe2 nanosheets is 15:2~3.

3. A method for preparing the modified MoSe2 piezoelectric catalyst according to claim 1 or 2, characterized in that, The process includes the following steps: MoSe2 powder is uniformly dispersed in water, then iron salt and hydrazine hydrate are added, and after thorough mixing, a hydrothermal reaction is carried out. The Mo in MoSe2... 2+ Partially Fe 2+ The modified MoSe2 piezoelectric catalyst was obtained by substitution.

4. The method for preparing the modified MoSe2 piezoelectric catalyst according to claim 3, characterized in that, The hydrothermal reaction temperature is 180~220℃.

5. The method for preparing the modified MoSe2 piezoelectric catalyst according to claim 4, characterized in that, The hydrothermal reaction time is 22-26 h.

6. The method for preparing the modified MoSe2 piezoelectric catalyst according to claim 3, characterized in that, The iron salt is ferric chloride hexahydrate.

7. The method for preparing the modified MoSe2 piezoelectric catalyst according to claim 6, characterized in that, The mass ratio of ferric chloride hexahydrate to MoSe2 is 3~12:

40.

8. The application of the modified MoSe2 piezoelectric catalyst according to claim 1 or 2 in the microplastics upgrading to CO.

9. The application according to claim 8, characterized in that, The application method is as follows: the prepared catalyst is uniformly dispersed in an aqueous solution containing microplastics, and persulfate is added to initiate a piezoelectric catalytic reaction to produce CO. The piezoelectric catalytic reaction is carried out in a gas-closed system using an ultrasonic cleaner.

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