A polyethyleneimine-grafted indium sulfide composite containing abundant sulfur vacancies, its preparation method and application

Abstract

The present invention relates to a polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies, a preparation method thereof, and applications thereof, belonging to the technical field of indium sulfide catalyst materials. The composite material of the present invention includes indium sulfide containing abundant sulfur vacancies, and polyethyleneimine grafted onto the indium sulfide containing abundant sulfur vacancies; the Zeta potential on the surface of the indium sulfide containing abundant sulfur vacancies is negative, and the Zeta potential on the surface of polyethyleneimine is positive, and the composite material is formed by an electrostatic self-assembly method. Preparation method: Dispersing an indium source in a sulfur-containing organic substance, and heating to obtain indium sulfide containing abundant sulfur vacancies; adding the obtained indium sulfide containing abundant sulfur vacancies to a polyethyleneimine solution, and heating to obtain the polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies. The obtained PEI / In2S3-S V composite material has the advantages of high hydrogen peroxide yield, simple and controllable preparation process, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of indium sulfide catalyst materials, and in particular to a polyethyleneimine-grafted indium sulfide composite material containing rich sulfur vacancies, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen peroxide (H 2 O 2 ), as one of the most important green chemicals, has been widely used in fields such as chemical synthesis, bleaching, food processing, biomedical treatment, and environmental remediation, and is closely related to human life and industrial production. At present, the continuous production of H 2 O 2 depends on the complex anthraquinone (AQ) process, which involves energy-consuming multi-step hydrogenation and oxidation reactions, running counter to the concept of modern green chemistry. Photocatalytic H 2 O 2 production (PHP) is a sustainable method that uses sunlight as an energy source, mimics photosynthesis, and generates H 2 O 2 from pure water and oxygen. The coupling of H 2 O and O 2 to generate H 2 O 2 is a sunlight-driven reaction (1 / 2O 2 + H 2 O = H 2 O 2 , ΔG = 117 kJ mol -1 ). At present, the concentration of commercial H 2 O 2 is about 30 - 70 wt%, while low-concentration H 2 O 2 is usually used in practical applications. PHP operates completely relying on solar energy and can produce low-concentration H 2 O 2 solution on-site using water and oxygen (air) as raw materials, thus avoiding the transportation, storage costs, and safety hazards brought by high-concentration H 2 O 2 solution.

[0003] There are two possible pathways for photocatalytic generation of H 2 O 2 : (1) The two-electron oxygen reduction reaction (ORR) occurring on the conduction band (CB) of the photocatalyst (O 2 + 2e − + 2H + = H 2 O 2), which is the main pathway; (2) the two-electron water oxidation reaction (2e − WOR) occurring on the valence band (VB) (2H 2 O + 2h + = H 2 O 2 + 2H + ). Among them, ORR can be further divided into a one-step two-electron reaction (O 2 + 2e − + 2H + =H 2 O 2 ) and a two-step one-electron reaction (O 2 + e − = •O 2 − , •O 2 − + e − + 2H + → H 2 O 2 ). It should be noted that in the process of photocatalytic synthesis of H 2 O 2 , most semiconductor materials, such as g-C 3 N 4 , TiO 2 , and CdS, etc., will form intermediate active species •O 2 − . Although indium sulfide containing sulfur vacancies can generate a large number of active species •O 2 − , its hydrogen peroxide production ability is relatively poor. One of the factors limiting the production of H 2 O 2 is that the half-reaction (WOR) with a slower kinetic rate is difficult to provide sufficient protons for the half-reaction (ORR) with a faster kinetic rate. Most previous reports have focused on improving the half-reaction of O 2 reduction, such as by using sacrificial agents such as isopropanol, benzyl alcohol, and 2-propanol, etc., to consume photo-generated holes while generating the protons required for the ORR reaction. However, adding synthetic agents not only increases the overall production cost but also brings challenges in separating by-products, limiting its subsequent applications.

[0004] Based on the above background, if a method can be developed to further protonate and hydrogenate the superoxide radicals generated by indium sulfide containing sulfur vacancies, excellent hydrogen peroxide yields can be obtained, and the cost of hydrogen peroxide production can also be significantly reduced, having great commercial prospects. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies, a preparation method thereof, and an application thereof.

[0006] The first object of the present invention is to provide a polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies, including indium sulfide (In 2 S 3 -S V ) containing abundant sulfur vacancies, and polyethyleneimine (PEI) grafted on the indium sulfide containing abundant sulfur vacancies; the Zeta potential on the surface of the indium sulfide containing abundant sulfur vacancies is negative, and the Zeta potential on the surface of polyethyleneimine is positive, and a composite material (PEI / In 2 S 3 -S V composite material) is formed by an electrostatic self-assembly method.

[0007] In some embodiments of the present invention, the grafting amount of the polyethyleneimine is 1 wt.%-5 wt.%.

[0008] In some embodiments of the present invention, the surface Zeta potential of the polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies is 40-45 mV.

[0009] The second object of the present invention is to provide a preparation method of the polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies, including the following steps:

[0010] S1. Dispersing an indium source in a sulfur-containing organic matter and heating to obtain indium sulfide containing abundant sulfur vacancies;

[0011] S2. Adding the obtained indium sulfide containing abundant sulfur vacancies to a polyethyleneimine solution and heating to obtain the polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies.

[0012] In some embodiments of the present invention, in S1, the indium source is selected from indium chloride and / or indium nitrate;

[0013] The concentration of the indium source is 5-20 g / L;

[0014] The molar ratio of the indium source to the sulfur-containing organic matter is (0.5-1.8):1.

[0015] In some embodiments of the present invention, in S1, the sulfur-containing organic matter is selected from thioacetamide and / or thiourea / L-cysteine;

[0016] The heating temperature is 90-120 °C, and the heating time is 12-36 h.

[0017] In some embodiments of the present invention, in S2, the heating temperature is 50 - 70 °C, and the heating time is 6 - 48 h.

[0018] In some embodiments of the present invention, in S2, the molecular weight of polyethyleneimine in the polyethyleneimine solution is 1800 - 10000;

[0019] The mass concentration of the polyethyleneimine solution is 2.0 - 50%.

[0020] In some embodiments of the present invention, in S2, the mass ratio of indium sulfide rich in sulfur vacancies to polyethyleneimine in the polyethyleneimine solution is (0.5 - 2):1.

[0021] The third object of the present invention is to provide the application of the polyethyleneimine-grafted indium sulfide composite material rich in sulfur vacancies in the reaction for producing hydrogen peroxide.

[0022] In the present invention, PEI has excellent proton adsorption ability and can quickly hydrogenate the superoxide radicals generated by In 2 S 3 -S V to hydrogen peroxide. In addition, the surface of protonated PEI is positively charged, while the superoxide radical is negatively charged. Therefore, the superoxide radical is more easily desorbed from the catalyst surface through electrostatic attraction, and then free hydrogen peroxide is formed to prevent the catalyst from decomposing the in-situ generated hydrogen peroxide.

[0023] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0024] (1) The PEI / In 2 S 3 -S V composite catalyst of the present invention has an excellent hydrogen peroxide generation rate under actual catalytic reaction conditions; this is because the PEI molecules on the surface of the PEI / In 2 S 3 -S V composite material can adsorb hydrogen protons in water, and then quickly adsorb and reduce superoxide radicals, significantly improving the activation efficiency of oxygen molecules.

[0025] (2) The PEI / In 2 S 3 -S VThe composite catalyst has economic benefits and sustainable utilization; this is because no organic sacrificial agent is required in the working conditions of the present invention, and thus there is no need to treat the by-products derived from the organic sacrificial agent; secondly, the present invention can work in the visible light range (λ > 420 nm) without additional energy input, and thus has considerable economic benefits and environmental friendliness.

[0026] (3)The PEI / In described in the present invention 2 S 3 -S V The composite catalyst has excellent long-term catalytic activity (the catalyst can still work after four hours) and recyclability (the catalytic activity remains above 80% after three cycles). Even if the catalyst is deactivated, it can be restored by soaking it in a diluted PEI solution, and the operation is simple. Description of the Drawings

[0027] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention and in combination with the drawings, wherein,

[0028] Figure 1 For the PEI / In in Example 1 of the present invention 2 S 3 -S V X-ray diffraction pattern of the composite material;

[0029] Figure 2 For the PEI / In in Example 1 of the present invention 2 S 3 -S V Surface Zeta potential map of the composite material obtained in Example 1 of the present invention and the material obtained in Comparative Example 1;

[0030] Figure 3 For the PEI / In in Example 1 of the present invention 2 S 3 -S V EPR spectrum of the DMPO-•O 2 − of the composite material;

[0031] Figure 4 Photocatalytic hydrogen peroxide production performance of different catalysts in the present invention;

[0032] Figure 5 For the PEI / In in Example 1 of the present invention 2 S 3 -S V Composite material and the H of the material obtained in Comparative Example 1 2 O 2 Generation and decomposition rates;

[0033] Figure 6 In the PEI / In of Embodiment 1 of the present invention 2 S 3 -S V composite material continuously generates H 2 O 2 performance. Specific implementation manners

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the exemplified embodiments do not limit the present invention.

[0035] Embodiment 1

[0036] This embodiment provides a preparation method and application of a PEI / In 2 S 3 -S V composite material.

[0037] (1). Preparation method of the PEI / In 2 S 3 -S V composite material

[0038] (1) Add 0.2212 g of anhydrous indium chloride and 0.0751 g of thioacetamide to a 100 ml hydrothermal reaction kettle with a PTFE liner containing 35 ml of ultrapure water. After stirring for 30 minutes, place the hydrothermal reaction kettle in an oven and heat it to 90°C at a heating rate of 10°C / min for 12 h. After cooling to room temperature, collect the obtained orange suspension, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60°C to obtain indium sulfide material with rich sulfur vacancies.

[0039] (2) Disperse 0.5 g of the indium sulfide material with rich sulfur vacancies obtained in step (1) in an aqueous solution containing 20 ml of PEI, where the mass fraction of PEI (molecular weight of 10,000) is 2.4 wt%, and then stir at a stirring rate of 500 rmp at 70°C for 12 h. After the reaction, centrifuge to collect the orange solid material, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60°C to obtain the PEI-grafted indium sulfide material with rich sulfur vacancies, that is, the PEI / In 2 S 3 -S V composite material.

[0040] Embodiment 2

[0041] This embodiment provides a PEI / In 2 S 3 -S VPreparation method and application of composite material.

[0042] (I). PEI / In 2 S 3 -S V Preparation method of composite material

[0043] (1) Add 0.2212 g of indium nitrate anhydrous and 0.0751 g of thioacetamide to a 100 ml hydrothermal reaction kettle with a Teflon liner containing 35 ml of ultrapure water. After stirring for 30 minutes, place the hydrothermal reaction kettle in an oven and heat it to 100 °C at a heating rate of 10 °C / min, and react for 15 h. After cooling to room temperature, collect the obtained orange suspension, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain indium sulfide material with rich sulfur vacancies.

[0044] (2) Disperse 0.5 g of the indium sulfide material with rich sulfur vacancies obtained in step (1) in an aqueous solution containing 20 ml of PEI, where the mass fraction of PEI (molecular weight 2500) is 15 wt%, and then stir at a stirring rate of 500 rmp at 60 °C for 20 h. After the reaction, centrifuge to collect the orange solid material, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain a PEI-grafted indium sulfide material with rich sulfur vacancies, namely PEI / In 2 S 3 -S V composite material.

[0045] Example 3

[0046] This example provides a preparation method and application of PEI / In 2 S 3 -S V composite material.

[0047] (I). PEI / In 2 S 3 -S V Preparation method of composite material

[0048] (1) Add 0.2212 g of indium chloride anhydrous and 0.0751 g of thioacetamide to a 100 ml hydrothermal reaction kettle with a Teflon liner containing 35 ml of ultrapure water. After stirring for 30 minutes, place the hydrothermal reaction kettle in an oven and heat it to 90 °C at a heating rate of 10 °C / min, and react for 12 h. After cooling to room temperature, collect the obtained orange suspension, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain indium sulfide material with rich sulfur vacancies.

[0049] (2) Disperse 0.5 g of the indium sulfide material with rich sulfur vacancies obtained in step (1) in an aqueous solution containing 20 ml of PEI, where the mass fraction of PEI (molecular weight 5000) is 10 wt%. Subsequently, stir at a stirring rate of 500 rmp at 70 °C for 12 h. After the reaction, centrifuge to collect the orange solid material, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain a PEI-grafted indium sulfide material with rich sulfur vacancies, namely PEI / In 2 S 3 -S V composite material.

[0050] Example 4

[0051] This example provides a preparation method and application of a PEI / In 2 S 3 -S V composite material.

[0052] (I). Preparation method of PEI / In 2 S 3 -S V composite material

[0053] (1) Add 0.2212 g of anhydrous indium chloride and 0.0751 g of thioacetamide to a 100 ml hydrothermal reaction kettle with a PTFE liner containing 35 ml of ultrapure water. After stirring for 30 minutes, place the hydrothermal reaction kettle in an oven and heat it to 120 °C at a heating rate of 10 °C / min for 12 h. After cooling to room temperature, collect the obtained orange suspension, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain an indium sulfide material with rich sulfur vacancies.

[0054] (2) Disperse 0.5 g of the indium sulfide material with rich sulfur vacancies obtained in step (1) in an aqueous solution containing 20 ml of PEI, where the mass fraction of PEI (molecular weight 3000) is 2.4 wt%. Subsequently, stir at a stirring rate of 500 rmp at 50 °C for 30 h. After the reaction, centrifuge to collect the orange solid material, wash it three times with distilled water and ethanol, and then dry it overnight under vacuum at 60 °C to obtain a PEI-grafted indium sulfide material with rich sulfur vacancies, namely PEI / In 2 S 3 -S V composite material.

[0055] Comparative Example 1

[0056] This comparative example uses In with rich sulfur vacancies without PEI grafting 2 S 3 -SV The catalyst was used as a control.

[0057] (I). In 2 S 3 -S V Preparation method of the catalyst

[0058] 0.2212 g of anhydrous indium chloride and 0.0751 g of thioacetamide were added to a 100 ml hydrothermal reaction kettle with a PTFE liner containing 35 ml of ultrapure water. After stirring for 30 minutes, the hydrothermal reaction kettle was placed in an oven and heated to 90 °C at a heating rate of 10 °C / min for 12 h. After cooling to room temperature, the obtained orange suspension was collected, washed three times with distilled water and ethanol, and then dried overnight under vacuum at 60 °C to obtain indium sulfide material (In 2 S 3 -S V ) with rich sulfur vacancies.

[0059] Structure characterization and performance testing

[0060] (I). The PEI / In 2 S 3 -S V composite material obtained in Example 1 and the In 2 S 3 -S V photocatalytic material obtained in Comparative Example 1 were subjected to structure characterization, and the results are shown in Figure 1 and Figure 2 .

[0061] The X-ray diffraction pattern of the PEI / In 2 S 3 -S V composite material obtained in this example is as shown in Figure 1 . It can be seen from the figure that the composite materials obtained in Example 1 and Comparative Example 1 both have good crystallinity and perfectly match the PDF (#32-0456) of In 2 S 3 . In addition, it also shows that the grafting of PEI does not destroy the crystal structure of In 2 S 3 -S V . The surface Zeta potential characterization result of the PEI / In 2 S 3 -S V composite material is as shown in Figure 2 . The surface Zeta potential of In 2 S 3 -S V is negative. When PEI with a positive surface Zeta potential is grafted, the obtained PEI / In 2S 3 -S V The surface Zeta potential of the composite material is positive, indicating that PEI has been successfully grafted onto In 2 S 3 -S V surface. In Comparative Example 1 2 S 3 -S V The characterization results of the surface Zeta potential of the photocatalytic material are as Figure 2 shown. The surface Zeta potential of In 2 S 3 -S V is -28.28, indicating that In 2 S 3 -S V can be combined with PEI with a positive surface Zeta potential by electrostatic self-assembly method.

[0062] In addition, PEI / In with a positive surface Zeta potential 2 S 3 -S V composite material can also adsorb the superoxide radical •O 2 − photocatalytically generated in situ through electrostatic attraction, making it further converted into H 2 O 2 . The EPR technique with DMPO as the spin trap also reveals the •O 2 S 3 -S V intermediate in the PEI / In 2 − composite material system, and the results are as Figure 3 shown. In the absence of light, no DMPO-•O 2 S 3 -S V characteristic peak was detected in the material system, indicating that •O 2 − is not generated in this system without light irradiation. 2 − . When irradiated for 5 minutes, an obvious DMPO-•O 2 S 3 -S V characteristic peak of the intermediate appeared in the PEI / In 2 − material system, which proves that H 2 O 2 in this system is generated through two-step single electron transfer. The stable concentration of photocatalytic H 2 O 2 is determined by the photocatalytic H 2 O2 Ability and decomposition of H 2 O 2 is determined by the ability, so the photocatalytic H-production 2 S 3 -S V performance of the composite material and the decomposition of H 2 O 2 performance were measured, and the results are as 2 O 2 shown. As can be seen from the figure, the PEI / In Figure 5 obtained in the embodiment of the present invention 2 S 3 -S V composite material has excellent H-production 2 O 2 rate (3.57 μM min -1 ). For Comparative Example 1, In 2 S 3 -S V photocatalytic material has a slower H-production 2 O 2 rate (0.22 μM min -1 ), and a faster H 2 O 2 decomposition rate (0.0187 min -1 ). Therefore, In 2 S 3 -S V photocatalysis has poor hydrogen peroxide production performance. It can be seen that the H 2 O 2 production rate of the material obtained in Example 1 of the present invention is much higher than that of In 2 S 3 -S V in Comparative Example 1 2 O 2 production rate. In addition, the H 2 S 3 -S V composite material has a slower H 2 O 2 decomposition rate (0.0034 min -1 ), which is much lower than that of In 2 S 3 -S V in Comparative Example 1 2 O 2 decomposition rate (0.0187 min -1 ). In summary, the PEI / In 2 S 3 -S V composite material has excellent H-generation2 O 2 performance, due to the excellent H 2 O 2 performance and poor decomposition H 2 O 2 Performance. PEI / In obtained in Example 1 2 S 3 -S V Catalyst stability test diagram of composite materials ( Figure 4 ), the test conditions are the same as those of the hydrogen peroxide reaction experiment. The figure shows that PEI / In 2 S 3 -S V The composite material has good catalytic reaction stability.

[0063] 2. Photocatalytic H production 2 O 2 experiment

[0064] 30 mg of the prepared PEI / In 2 S 3 -S V The composite photocatalyst was dispersed in 30 ml of deionized water (catalyst concentration was 1 g L -1 ) in a 50 ml quartz reactor. Before the reaction, the catalyst was dispersed by ultrasound for 5 min. Subsequently, the reaction system was irradiated with a 300 W xenon lamp (PCX50C, Beijing Perfect Light Source Technology Co., Ltd.) equipped with a 420 nm cutoff filter at room temperature. 2 O 2 The concentration of H generated was analyzed by iodine determination. Typically, 0.5 ml of 0.4 M potassium iodide (KI, purity ≥ 99%, Aladdin) aqueous solution and 0.5 ml of 0.1 M potassium hydrogen phthalate (purity ≥ 99.5%, Aladdin) aqueous solution were added to 1 ml of the aqueous phase product and kept for 30 minutes. The absorbance of the mixed solution at a wavelength of 350 nm was then detected by UV-visible spectroscopy, from which the generated H was estimated. 2 O 2 The mixed solution underwent the following reaction: the generated I 3 − The light absorption peak appears around 350 nm. 2 O 2 + 3I − + 2H + = I 3 − + 2H 2 O

[0065] Figure 4 PEI / In obtained in Example 1 2S 3 -S V Catalyst stability test diagram of the composite material. It can be seen from the figure that PEI / In 2 S 3 -S V has excellent H 2 O 2 production rate (194 μM h -1 ), which is 24.3 times that of the comparative example In 2 S 3 -S V material. The experimental data show that PEI / In 2 S 3 -S V composite material has the feasibility of photocatalytic H 2 O 2 production. Compared with Example 1, the In 2 S 3 -S V photocatalyst material prepared in Comparative Example 1 exhibits lower photocatalytic H 2 O 2 production performance, only 8 μM h -1 .

[0066] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies, characterized in that: The invention comprises indium sulfide rich in sulfur vacancies and polyethyleneimine grafted on the indium sulfide rich in sulfur vacancies; the surface Zeta potential of the indium sulfide rich in sulfur vacancies is negative, the surface Zeta potential of the polyethyleneimine is positive, and a composite material is formed by an electrostatic self-assembly method; the surface Zeta potential of the polyethyleneimine-grafted indium sulfide rich in sulfur vacancies composite material is 40-45 mV.

2. The polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies according to claim 1, characterized in that: The grafting amount of the polyethyleneimine is 1 wt.%-5 wt.%.

3. A method for preparing a polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1. dispersing the indium source in the sulfur-containing organic matter and heating it to obtain indium sulfide containing abundant sulfur vacancies; S2. Adding the obtained indium sulfide rich in sulfur vacancies to a polyethyleneimine solution, and heating to obtain the polyethyleneimine-grafted indium sulfide composite material rich in sulfur vacancies.

4. The preparation method according to claim 3, characterized in that: In S1, the indium source is selected from indium chloride and / or indium nitrate; The concentration of the indium source is 5-20 g / L; The molar ratio of the indium source to the sulfur-containing organic matter is (0.5-1.8):

1.

5. The preparation method according to claim 3, characterized in that: In S1, the sulfur-containing organic matter is selected from thioacetamide and / or thiourea / L-cysteine; The heating temperature is 90-120° C., and the heating time is 12-36 h.

6. The preparation method according to claim 3, characterized in that: In S2, the heating temperature is 50-70°C, and the heating time is 6-48h.

7. The preparation method according to claim 3, characterized in that: In S2, the molecular weight of polyethyleneimine in the polyethyleneimine solution is 1800-10000; The mass concentration of the polyethyleneimine solution is 2.0-50%.

8. The preparation method according to claim 3, characterized in that: The mass ratio of the indium sulfide containing abundant sulfur vacancies to the polyethyleneimine in the polyethyleneimine solution is (0.5-2):

1.

9. Use of the polyethyleneimine-grafted indium sulfide composite material containing abundant sulfur vacancies according to any one of claims 1 to 2 in a hydrogen peroxide production reaction.

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