Method for preparing photocatalyst suitable for waste plastic conversion through lattice strain strategy

Abstract

The invention discloses a method for preparing a photocatalyst suitable for waste plastic conversion through a lattice strain strategy. The method is used for photocatalytic degradation of waste plastic and hydrogen production. Comprising the following steps: (1) dissolving Cd (CH3COO) 2.2 H2O and Zn (CH3COO) 2.2 H2O in a mixed solution of deionized water and N, N-dimethylformamide, stirring, then adding thioacetamide, and continuously stirring; (2) transferring the obtained solution into a stainless steel autoclave for hydrothermal treatment; and cooling to room temperature, washing with deionized water, and drying to obtain the LS-Cd0. 5Zn0. 5S photocatalyst. According to the LS-Cd0. 5Zn0. 5S photocatalyst, carrier recombination is reduced, charge transfer is promoted, lattice tensile strain induces surface S vacancy to promote generation of. OH, the oxidation-reduction reaction is further enhanced, high-activity photocatalytic performance is achieved, the hydrogen evolution rate reaches 13.83 mmol.g <-1 >. H <-1 >, meanwhile, waste plastic is converted into a pyruvate chemical value-added product, and the waste plastic can be recycled. The preparation method is simple to operate, low in cost and easy for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of environmental purification and energy recovery, and in particular to a method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy. Background Art

[0002] Due to the large-scale production and use of plastic products worldwide, they enter the biogeochemical cycle of nature. Plastic products in the environment will eventually turn into microplastics (plastic particles with a diameter of less than 5 mm) in nature, becoming the main carrier of environmental pollution. As one of the four major new pollutants that have attracted widespread international attention, microplastics have been detected in the deep sea, on land, and in organisms. In order for us to have a more sustainable and environmentally friendly future, it is imperative to establish a new paradigm for plastic degradation and even recycling to prevent the further spread of microplastic pollution. In recent years, the transformation and upgrading of plastic waste into valuable fuels, chemicals or materials with additional economic benefits has received increasing attention.

[0003] The photocatalytic method has the advantages of mild reaction conditions, simple operation, and less secondary pollution. This method can solve environmental problems and generate clean energy in converting waste plastics into hydrogen energy, and has broad application prospects. However, due to the unsatisfactory activity and stability, it is crucial to construct an efficient and stable photocatalytic system for practical application. 0.5 Zn 0.5 S has a continuously adjustable bandgap structure and excellent visible light absorption ability. 0.5 Zn 0.5 S is excited to generate electron-hole pairs, and the holes and electrons will respectively react with the adsorbed Cd 0.5 Zn 0.5 Organic matter and water on the S surface undergo redox reactions, but due to the high recombination efficiency of electron-hole pairs, they cannot react effectively, thereby reducing the photocatalytic efficiency. Therefore, reducing the recombination of electron-hole pairs generated by light can improve the photocatalytic efficiency of Cd 0.5 Zn 0.5 The photocatalytic activity of S is the focus of the present invention.

[0004] Among the modification strategies that have been studied so far, strain engineering can precisely adjust the band structure and photogenerated carrier recombination rate of semiconductor photocatalysts and the adsorption energy of reaction substrates or intermediates, and has great potential in breaking through the bottleneck of photocatalysis. The present invention slows down the precipitation of S ions in thioacetamide by adding N,N-dimethylamide, and the atomic arrangement changes locally, causing lattice deformation, thereby generating lattice strain. Lattice tensile strain is beneficial to hinder the charge recombination in the crystal, providing more electron holes for redox reactions, and lattice tensile strain promotes the formation of S vacancies, enhancing hydrophilicity and OH -The adsorption and generation of oxidative OH consumes the accumulated holes and improves the hydrogen evolution efficiency. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy, wherein the photocatalyst prepared by the method reduces carrier recombination and promotes charge transfer. More S vacancies and ·OH are generated, redox reactions are promoted, and photocatalytic activity is improved. The preparation method of the catalyst is simple to operate, low in cost, and easy to industrialize.

[0006] To achieve the above object, the present invention provides a method for preparing a photocatalyst suitable for waste plastic conversion by a lattice strain strategy, comprising the following steps:

[0007] (1) Dissolve Cd(CH3COO)2·2H2O and Zn(CH3COO)2·2H2O in a mixed solution of deionized water and N,N-dimethylformamide and stir; add thioacetamide to the above solution and continue stirring.

[0008] (2) The solution in step (1) was transferred to a stainless steel autoclave for hydrothermal treatment. After cooling to room temperature, it was washed with deionized water and dried to obtain LS-Cd 0.5 Zn 0.5 S photocatalyst.

[0009] Preferably, in the above technical solution, the molar ratio of Cd(CH3COO)2·2H2O, Zn(CH3COO)2·2H2O and thioacetamide in step (1) is 1:1:2-4.

[0010] Preferably, in the above technical solution, the volume ratio of deionized water to N,N-dimethylamide in step (1) is 1:0.05-4.

[0011] Preferably, in the above technical solution, the stirring time in step (1) is 20 to 40 minutes.

[0012] Preferably, in the above technical solution, the temperature of the hydrothermal reaction of the mixed solution in step (2) is 150-200° C. and the reaction time is 15-20 hours.

[0013] Preferably, in the above technical solution, the mixed solution in step (2) is dried at 50-100° C. for 8-10 h.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) LS-Cd prepared by the method of the present invention 0.5 Zn 0.5The photocatalyst of S reduces carrier recombination and promotes charge transfer, while facilitating redox reactions, greatly improving the LS-Cd 0.5 Zn 0.5 The photocatalytic activity of S. It can degrade waste plastics and produce hydrogen at a rate of 13.83 mmol·g -1 ·h -1 , which has practical application significance in simultaneously degrading waste plastics and producing hydrogen.

[0016] (2) The present invention adjusts the strain of the photocatalyst by adjusting the ratio of N,N-dimethylamide to water. The method is simple and low in cost. 0.5 Zn 0.5 S photocatalyst degradation of waste plastics has mild reaction conditions, simple and easy operation, low cost, and is easy to industrialize. It has broad application prospects in the field of waste plastics treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is Cd prepared according to the method of the present invention 0.5 Zn 0.5 Field emission scanning electron microscopy image of S photocatalyst.

[0018] Figure 2 LS-Cd prepared according to the method of the present invention 0.5 Zn 0.5 Field emission scanning electron microscopy image of S photocatalyst.

[0019] Figure 3 is Cd prepared according to the method of the present invention 0.5 Zn 0.5 S and LS-Cd 0.5 Zn 0.5 X-ray diffraction pattern of S photocatalyst.

[0020] Figure 4 Graph showing the hydrogen production rate of photocatalysts prepared according to the method of the present invention at different degrees of lattice strain.

[0021] Figure 5 is Cd prepared according to the method of the present invention 0.5 Zn 0.5 S and LS-Cd 0.5 Zn 0.5 Liquid NMR spectrum of S photocatalyst for photocatalytic degradation of waste plastics. DETAILED DESCRIPTION

[0022] Example 1

[0023] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0024] (1) Dissolve 10 mmol of Cd(CH3COO)2·2H2O and 10 mmol of Zn(CH3COO)2·2H2O in 60 mL of deionized water and stir for 30 min. Then add 25 mmol of thioacetamide and stir for another 30 min.

[0025] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 180°C for 18 h. After cooling to room temperature, it was washed with deionized water and dried at 60°C for 9 h. After drying, a yellow powder was obtained, which was labeled as Cd 0.5 Zn 0.5 S. Detection of prepared Cd 0.5 Zn 0.5 Field emission scanning electron microscopy image of S, such as Figure 1 As shown; the detected Cd 0.5 Zn 0.5 The X-ray diffraction pattern of S is as follows Figure 3 shown.

[0026] Example 2

[0027] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0028] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 55 mL deionized water and 5 mL N,N-dimethylformamide and stir for 30 min. Then add 25 mmol thioacetamide and stir for another 30 min.

[0029] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 180°C for 18 h. After cooling to room temperature, it was washed with deionized water and dried at 60°C for 9 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S.

[0030] Example 3

[0031] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0032] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 40 mL deionized water and 20 mL N,N-dimethylformamide and stir for 30 min. Then add 25 mmol thioacetamide and stir for another 30 min.

[0033] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 180°C for 18 h. After cooling to room temperature, it was washed with deionized water and dried at 60°C for 9 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S. Detection of prepared LS-Cd 0.5 Zn 0.5 Field emission scanning electron microscopy image of S, such as Figure 2 As shown; the LS-Cd 0.5 Zn 0.5 The X-ray diffraction pattern of S is as follows Figure 3 shown.

[0034] Example 4

[0035] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0036] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 20 mL deionized water and 40 mL N,N-dimethylformamide and stir for 30 min. Then add 25 mmol thioacetamide and stir for another 30 min.

[0037] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 180°C for 18 h. After cooling to room temperature, it was washed with deionized water and dried at 60°C for 9 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S.

[0038] Example 5

[0039] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0040] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 0 mL deionized water and 60 mL N,N-dimethylformamide and stir for 30 min. Then add 25 mmol thioacetamide and stir for another 30 min.

[0041] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 180°C for 18 h. After cooling to room temperature, it was washed with deionized water and dried at 60°C for 9 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S.

[0042] Example 6

[0043] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0044] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 57 mL deionized water and 3 mL N,N-dimethylformamide and stir for 20 min. Then add 20 mmol thioacetamide and stir for another 20 min.

[0045] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 150°C for 15 h. After cooling to room temperature, it was washed with deionized water and dried at 50°C for 8 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S.

[0046] Example 7

[0047] A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy comprises the following steps:

[0048] (1) Dissolve 10 mmol Cd(CH3COO)2·2H2O and 10 mmol Zn(CH3COO)2·2H2O in a mixed solution of 12 mL deionized water and 48 mL N,N-dimethylformamide and stir for 40 min. Then add 40 mmol thioacetamide and stir for another 40 min.

[0049] (2) The obtained solution was transferred to a stainless steel autoclave and hydrothermally treated at 200°C for 20 h. After cooling to room temperature, it was washed with deionized water and dried at 100°C for 10 h. After drying, a yellow powder was obtained, which was labeled as LS-Cd 0.5 Zn 0.5 S.

[0050] Discarded PET plastic fragments were dissolved in 10 M aqueous solution (aq.) of NaOH to form 25 mg mL -1of solution and stirred at 500rpm and 40℃ for 24h. After cooling to room temperature, the mixture was centrifuged at 6500rpm for 3min. The supernatant was used for the next stage of the photocatalytic process. Photocatalytic degradation of waste plastics and hydrogen evolution were carried out in a closed quartz reactor. The light source was a 300W xenon lamp equipped with a 400nm cutoff filter. 1.5mg of the photocatalyst powder prepared in the above embodiment was dispersed in 40mL of the pretreated supernatant. Before starting the hydrogen evolution experiment, the reactor was purged with nitrogen (N2) for 30min to remove any air present. During the reaction, the solution was constantly stirred to maintain uniformity, and the reactor was maintained at room temperature by circulating cooling water. 1mL of gas was periodically extracted from the sealed quartz reactor every 1h and measured by thermal conductivity detector (TCD) gas chromatography (GC7920-T). Chromatographic analysis was performed using N2 as the carrier gas. Each photocatalyst was tested three times under the same conditions. As Figure 4 The LS-Cd with different lattice strains in Examples 1-5 is shown. 0.5 Zn 0.5 The hydrogen production rate diagram of S. Figure 5 Shown are the liquid nuclear magnetic resonance spectra of the solution after pretreatment of waste plastic before irradiation and the liquid nuclear magnetic resonance spectra of the waste plastic solution after 24 hours of irradiation reaction in Example 1 and Example 3.

[0051] The foregoing descriptions of specific exemplary embodiments of the present invention are intended to be illustrative and exemplary. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is apparent that many changes and variations may be made in light of the foregoing teachings. The exemplary implementations are selected and described for the purpose of explaining the specific principles and practical applications of the present invention, thereby enabling those skilled in the art to implement and utilize the various exemplary embodiments of the present invention and the various selections and variations. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a photocatalyst suitable for waste plastic conversion using a lattice strain strategy, characterized in that: The following steps are involved: (1) dissolving Cd(CH3COO)2·2H2O and Zn(CH3COO)2·2H2O in a mixed solution of deionized water and N,N-dimethylamide and stirring the solution; adding thioacetamide to the solution and stirring the solution; (2) The solution in step (1) was transferred to a stainless steel autoclave for hydrothermal treatment. After the hydrothermal treatment was completed and cooled to room temperature, it was washed with deionized water and dried to obtain LS-Cd 0.5 Zn 0.5 S photocatalyst.

2. The method for preparing a photocatalyst suitable for waste plastic conversion by using a lattice strain strategy according to claim 1, characterized in that: The molar ratio of Cd(CH3COO)2·2H2O, Zn(CH3COO)2·2H2O and thioacetamide in step (1) is 1:1:2-4.

3. The method for preparing a photocatalyst suitable for waste plastic conversion by using a lattice strain strategy according to claim 1, characterized in that: The volume ratio of deionized water to N,N-dimethylamide in step (1) is 1:0.05-4.

4. The method for preparing a photocatalyst suitable for waste plastic conversion by using a lattice strain strategy according to claim 1, characterized in that: The stirring time in step (1) is 20 to 40 minutes.

5. The method for preparing a photocatalyst suitable for waste plastic conversion by using a lattice strain strategy according to claim 1, characterized in that: The temperature of the solution hydrothermal reaction in step (2) is 150-200° C., and the reaction time is 15-20 h.

6. The method for preparing a photocatalyst suitable for waste plastic conversion by using a lattice strain strategy according to claim 1, characterized in that: In step (2), the mixed solution is dried at 50-100° C. for 8-10 hours.

Images