A preparation method for constructing efficient interface charge transfer heterostructures by in situ reduction

Abstract

This invention belongs to the field of photocatalytic materials technology and discloses a method for preparing a highly efficient interfacial charge transfer heterostructure by in-situ reduction. First, a metal sulfide nanosheet array is synthesized using a hydrothermal method. Then, a non-conjugated polymer (branched polyethyleneimine) is used to in-situ construct metal nanocrystals on the metal sulfide surface. This allows the preparation of a highly efficient interfacial charge transfer metal-sulfide heterostructure at room temperature. Under simulated sunlight (AM 1.5G), this heterostructure exhibits significantly different reducibility and stability than single-component metal sulfides. The entire preparation process is simple and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and in particular relates to a preparation method for constructing a high-efficiency interface charge transfer heterostructure through in-situ reduction. Background Art

[0002] In recent years, photocatalytic technology has been widely used in many fields such as photocatalytic hydrogen production, carbon dioxide reduction and degradation of organic pollutants. Among them, photoelectrochemical water splitting hydrogen production technology is a renewable energy solution that uses solar energy to drive the water splitting reaction. In a typical photoelectrocatalytic system, the photoanode is the core functional unit of energy conversion. Its key parameters such as interfacial charge separation efficiency, carrier transport capacity and surface catalytic activity directly affect the solar-to-hydrogen (STH) conversion efficiency of the entire system. In recent years, photoanode materials represented by metal sulfides have shown significant advantages in the field of wide-spectrum-response photoelectrodes due to their narrow band gap characteristics, high carrier mobility and controllable band structure.

[0003] However, single-phase sulfide photoanodes face three key technical bottlenecks under actual working conditions: (1) high recombination rate of photogenerated carriers and low charge separation efficiency in the bulk phase of the material; (2) insufficient surface catalytic active sites and sluggish reaction kinetics; and (3) poor photocorrosion stability and limited material durability.

[0004] Constructing heterostructures by loading noble metals is an important strategy for improving the performance of sulfide photoanodes. The introduction of noble metals can synergistically improve light absorption, charge separation, and surface reaction kinetics through mechanisms such as interface electron regulation, surface plasmon resonance (SPR) effects, and enhanced catalytic active sites. Surface-ligand-modified noble metals, due to their lower Fermi levels, can rapidly capture photogenerated electrons to promote interfacial charge transfer, thereby extending the lifetime of photogenerated carriers. Simultaneously, photogenerated holes remaining in the valence band after excitation can participate in a series of oxidation reactions, improving the effective utilization of energy. Furthermore, the loading of noble metals can significantly enhance the light absorption capacity of semiconductors, promoting more efficient solar energy conversion. However, the traditional noble metal-loaded sulfide heterostructure construction requires harsh conditions, complex methods, and is not environmentally friendly.

[0005] In summary, how to provide a preparation method for in situ reduction to construct efficient interface charge transfer heterostructures, construct heterostructures with tight interface structure transmission through the loading of precious metals, and improve the photocatalytic performance of sulfides is an urgent problem to be solved. Summary of the Invention

[0006] The present invention aims to address the inadequate catalytic efficiency of single-component semiconductor photocatalysts in the prior art, as well as the complex and poor stability of traditional composite material preparation processes. This method provides a method for constructing efficient interfacial charge transfer heterostructures through in-situ reduction. This method utilizes branched polyethyleneimine to construct a metal-sulfide heterostructure with efficient interfacial charge transfer. This method enables precise control of the interfacial coupling between the sulfide semiconductor and the metal co-catalyst, achieving stable and controllable synthesis of the target product. Compared to traditional preparation processes, the present method is simple to operate, environmentally friendly, and highly efficient and controllable.

[0007] Branched polyethyleneimine molecular chains contain abundant amino groups, which can participate in redox reactions under specific conditions and show mild reducing ability. The reducing properties of branched polyethyleneimine can accurately deposit precious metal nanoparticles on the surface of the material through in-situ reduction technology, thereby successfully constructing a metal-sulfide heterostructure with a tightly bound interface structure. In the present invention, branched polyethyleneimine can be used as a reducing agent to achieve in-situ reduction of metal nanoparticles by utilizing a large number of amino groups in its molecular chain. Traditional synthesis of metal nanocrystals requires the use of protective agents to achieve the stable existence of metal nanocrystals. Non-conjugated polymer polyethyleneimine can replace the protective agents required for the traditional synthesis of metal nanoparticles, avoiding the influence of traditional protective agents on photocharge transport, and achieving uniform and stable growth of metal nanoparticles while constructing a tight interface structure, as well as high charge transfer efficiency.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A preparation method for constructing an efficient interface charge transfer heterostructure by in-situ reduction, comprising the following steps:

[0010] (1) Preparation of In2S3 nanosheet array substrate: FTO conductive glass was cleaned and placed in In2S3 nanosheet precursor solution for hydrothermal reaction. After the reaction was completed, the substrate was cooled, removed, rinsed, and dried to obtain the In2S3 nanosheet array substrate.

[0011] (2) Preparation of In2S3@bPEI material: The In2S3 nanosheet array substrate prepared in step (1) was immersed in a polyethyleneimine solution with a pH of 9-11 and a concentration of 2-8 mg / mL, and reacted at 60-80 °C. After the reaction was completed, the substrate was taken out, rinsed, and dried to obtain the In2S3@bPEI material;

[0012] (3) Preparation of In2S3@bPEI@M heterostructure: The In2S3@bPEI material obtained in step (2) is immersed in a solution containing metal M for reduction reaction. After the reaction is completed, it is taken out, rinsed, and dried to obtain the In2S3@bPEI@M heterostructure; the metal M is any one of Au and Pd.

[0013] Preferably, in step (1), the In2S3 nanosheet precursor solution is prepared by dissolving 240-350 mg of InCl3·4H2O and 200-260 mg of thioacetamide in 20-50 mL of water.

[0014] Preferably, in step (1), the hydrothermal reaction temperature is 150-200 °C, the reaction time is 10-20 h, and the amount of the In2S3 nanosheet precursor solution used is 35-45 times the volume of the FTO conductive glass.

[0015] Preferably, in step (1), the cleaned FTO conductive glass is placed with the conductive surface facing downward in the In2S3 nanosheet precursor solution. More preferably, the cleaned FTO conductive glass is placed with the conductive surface facing downward in the In2S3 nanosheet precursor solution at an angle of 30-60°.

[0016] Preferably, in step (2), the reaction time is 8 to 15 min, the amount of the branched polyethyleneimine solution used is 6 to 20 times the volume of the In2S3 nanosheet array substrate, and the solvent of the branched polyethyleneimine solution is deionized water.

[0017] Preferably, the weight average molecular weight (Mw) of the branched polyethyleneimine is 20,000-30,000, and the structural formula is:

[0018] , n= 40~60.

[0019] Preferably, in step (1), step (2), and step (3), the drying temperature is 50-70°C, and the drying condition is vacuum drying. The drying time in step (1) is not less than 2 hours, and the drying time in step (2) and step (3) is 4-10 minutes.

[0020] Preferably, in step (3), the solution containing metal M is a HAuCl4 solution or a Na2PdCl4 solution, and the In2S3@bPEI@M heterostructure is an In2S3@bPEI@Au heterostructure or an In2S3@bPEI@Pd heterostructure.

[0021] Preferably, in step (3), the concentration of the solution containing metal M is 0.05~2 mg / mL, the solvent is deionized water, the reaction temperature is 60~80 °C, the reaction time is 1~10 min, and the amount of the solution containing metal M is 10~15 times the volume of the In2S3@bPEI material.

[0022] The present invention also provides an in-situ reduction-constructed high-efficiency interface charge transfer heterostructure, which is prepared by the above-mentioned preparation method.

[0023] The specific steps of photoelectrocatalytic water splitting are as follows:

[0024] Photoelectrocatalytic water splitting performance was tested using a standard three-electrode system under simulated sunlight (AM 1.5G). The electrolyte consisted of 100 mL of a mixed solution of 0.5 mol / L Na₂SO₄ and 0.05 mol / L Na₂SO₃ (pH 8.6). An FTO glass slide loaded with an In₂S₃@bPEI@Au nanosheet array served as the working electrode, an Ag / AgCl electrode served as the reference electrode, a Pt electrode served as the counter electrode, and a 300 W xenon lamp served as the light source. The electrode potential was calibrated using a reversible hydrogen electrode (RHE) according to the following formula:

[0025] E REH = E Ag / Cl + 0.059 PH + E° Ag / Cl ( E° Ag / Cl = 0.197 V at 25℃).

[0026] The beneficial effects of the present invention are:

[0027] (1) This invention constructs a metal-sulfide heterostructure with efficient interfacial charge transfer through in situ reduction of branched polyethyleneimine. This allows precise control of the interfacial coupling process between the sulfide semiconductor and the metal co-catalyst, achieving a stable and controllable synthesis of the target product. Compared with traditional preparation processes, the preparation process of this invention is simple to operate, environmentally friendly, has a short cycle time, is easily recyclable, and is highly efficient and controllable.

[0028] (2) The metal-sulfide heterostructure of the present invention is synthesized by a simple in-situ reduction method, using branched polyethyleneimine as a reducing agent to reduce the metal nanoparticles through the amino groups therein. At the same time, the branched polyethyleneimine also serves as a protective agent for the synthesized metal nanoparticles, ensuring that the metal nanoparticles will not further agglomerate and grow, and avoiding the addition of other protective agents that affect the photocharge transfer efficiency. The process is simple to operate and is conducive to large-scale industrial production;

[0029] (3) The metal-sulfide heterostructure prepared by the present invention has excellent photoelectric properties and has reducibility and stability that are significantly different from those of single-component metal sulfides under irradiation with visible light of equal intensity (>420 nm). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope image of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention;

[0031] Figure 2 This is an energy dispersive X-ray spectrum of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention;

[0032] Figure 3 is the UV-visible absorption spectrum of HAuCl4;

[0033] Figure 4 This is a UV-visible absorption spectrum of gold nanoparticles (Au@bPEI NPs) formed in the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention;

[0034] Figure 5 This is a linear sweep voltammetry curve of the In2S3 nanosheet array, In2S3@bPEI material, and In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention under simulated sunlight (AM 1.5G);

[0035] Figure 6 This is a linear sweep voltammetry curve of the In2S3 nanosheet array, In2S3@bPEI material, and In2S3@bPEI@Pd heterostructure prepared in Example 2 of the present invention under simulated sunlight (AM 1.5G). DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels. The methods involved in the embodiments of the present invention are all conventional methods and can be obtained through the corresponding implementation specifications, implementation standards or existing literature in the field.

[0038] Example 1 Preparation of In2S3@bPEI@Au heterostructure

[0039] (1) Preparation of In2S3 nanosheet array substrate:

[0040] FTO conductive glass (50 mm×10 mm×1.6 mm, surface resistance 14 Ω / sq) was ultrasonically cleaned in ethanol and deionized water for 20 min each until the surface was clean. 265.4 mg of InCl3·4H2O and 225.0 mg of thioacetamide (TAA) were dissolved in 30 mL of deionized water and stirred at room temperature for 30 min to form a homogeneous solution (In2S3 nanosheet precursor solution). The homogeneous solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, and the clean FTO conductive glass substrate was placed in the reaction system with the conductive surface facing down. The hydrothermal reaction was carried out at 160°C for 12 h. After cooling naturally to room temperature (25±2℃), the FTO substrate was taken out, and a yellow In2S3 nanosheet array film was formed on its conductive surface. After rinsing with deionized water for 10 s, it was vacuum dried at 50℃ for 2 h. After drying, it was cut into working electrodes with a size of 15 mm×10 mm×1.6 mm (the area of ​​the loaded In2S3 nanosheet array was 10 mm×10 mm, and the other side was a clean conductive surface), obtaining an In2S3 nanosheet array substrate (FTO substrate loaded with In2S3 nanosheet array).

[0041] (2) Preparation of In2S3@bPEI material:

[0042] The FTO substrate loaded with In2S3 nanoarray was immersed in 2 mL of branched polyethyleneimine (bPEI, Mw=25000, pH=10.70, 4 mg / mL) solution and treated at 70°C for 10 min. After treatment, it was taken out and dried at 70°C for 5 min to obtain an FTO substrate loaded with In2S3@bPEI material.

[0043] (3) Preparation of In2S3@bPEI@Au heterostructure:

[0044] The FTO substrate loaded with In2S3@bPEI material was immersed in 2 mL of HAuCl4 solution (pH=3.28, 0.1 mg / mL) and reacted at 70°C for 3 min. After the reaction was completed, it was rinsed with deionized water for 4 seconds and then dried at 70°C for 5 min to obtain the In2S3@bPEI@Au heterostructure.

[0045] Example 2 Preparation of In2S3@bPEI@Pd heterostructure

[0046] The method for preparing the In2S3@bPEI@Pd heterostructure in this example is similar to that in Example 1, except that the HAuCl4 solution in step (3) is replaced with a sodium chloropalladate (Na2PdCl4) solution of equal concentration and volume. The specific steps are as follows:

[0047] (1) Preparation of In2S3 nanosheet array substrate:

[0048] FTO conductive glass (50 mm×10 mm×1.6 mm, surface resistance 14 Ω / sq) was ultrasonically cleaned in ethanol and deionized water for 20 min each until the surface was clean. 265.4 mg of InCl3·4H2O and 225.0 mg of thioacetamide (TAA) were dissolved in 30 mL of deionized water and stirred at room temperature for 30 min to form a homogeneous solution (In2S3 nanosheet precursor solution). The homogeneous solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, and the clean FTO conductive glass substrate was placed in the reaction system with the conductive surface facing down. The hydrothermal reaction was carried out at 160°C for 12 h. After cooling naturally to room temperature (25±2℃), the FTO substrate was taken out, and a yellow In2S3 nanosheet array film was formed on its conductive surface. After rinsing with deionized water for 10s, it was vacuum dried at 50℃ for 2h. After drying, it was cut into working electrodes with a size of 15 mm×10 mm×1.6 mm (the area of ​​the loaded In2S3 nanosheet array was 10 mm×10 mm, and the other side was a clean conductive surface), obtaining an In2S3 nanosheet array substrate (FTO substrate loaded with In2S3 nanosheet array).

[0049] (2) Preparation of In2S3@bPEI material:

[0050] The FTO substrate loaded with In2S3 nanoarray was immersed in 2 mL of branched polyethyleneimine (bPEI, Mw=25000, pH=10.70, 4 mg / mL) solution and treated at 70 °C for 10 min. After treatment, it was taken out and dried at 70 °C for 5 min to obtain an FTO substrate loaded with In2S3@bPEI material.

[0051] (3) Preparation of In2S3@bPEI@Pd heterostructure:

[0052] The FTO substrate loaded with In2S3@bPEI material was immersed in 2 mL of sodium chloropalladate (Na2PdCl4) solution (0.1 mg / mL) and reacted at 70°C for 3 min. After the reaction was completed, it was rinsed with deionized water for 4 s and then dried at 70°C for 5 min to obtain the In2S3@bPEI@Au heterostructure.

[0053] 1. Structural Characterization of the Metal-Sulfide Heterostructure Photocatalyst Prepared by the Present Invention

[0054] The scanning electron microscope image of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention is as follows: Figure 1 As shown, it can be seen that the In2S3@bPEI@Au heterostructure is still a nanosheet array, indicating that the morphology of In2S3 is not changed after wrapping branched polyethyleneimine on the surface and depositing gold nanoparticles.

[0055] Energy dispersive X-ray spectra of In2S3@bPEI@Au heterostructures are shown in Figure 2 , indicating the successful synthesis of In2S3@bPEI@Au heterostructure.

[0056] 2. UV-visible absorption spectroscopy characterization

[0057] The UV-visible absorption spectra of HAuCl4 and gold nanoparticles (Au@bPEI NPs) are shown in Figure 3 、 Figure 4 It can be seen that the SPR absorption peak of gold nanoparticles was not detected in the HAuCl4 solution, but after the HAuCl4 solution was added with the bPEI solution and reacted for a period of time, the SPR characteristic peak of gold nanoparticles could be detected, indicating that it is feasible to reduce HAuCl4 to gold nanoparticles through the reduction characteristics of bPEI.

[0058] 3. Characterization of Photocatalytic Performance

[0059] The linear sweep voltammetry curves of In2S3@bPEI@Au and In2S3@bPEI@Pd prepared in Example 1 and Example 2 of the present invention respectively under simulated sunlight (AM 1.5G) are shown in FIG. Figure 5 、 Figure 6 As shown, under simulated sunlight conditions, the photocurrent density of In2S3@bPEI@Au and In2S3@bPEI@Pd is about 2 times higher than that of In2S3, and both heterostructures have good photocatalytic activity.

[0060] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an efficient interface charge transfer heterostructure by in situ reduction, characterized by: The following steps are involved: (1) Preparation of In2S3 nanosheet array substrate: FTO conductive glass was cleaned and placed in In2S3 nanosheet precursor solution for hydrothermal reaction. After the reaction was completed, the substrate was cooled, removed, rinsed, and dried to obtain the In2S3 nanosheet array substrate. (2) Preparation of In2S3@bPEI material: The In2S3 nanosheet array substrate prepared in step (1) was immersed in a branched polyethyleneimine solution with a pH of 9-11 and a concentration of 2-8 mg / mL, and reacted at 60-80°C. After the reaction was completed, the substrate was taken out, rinsed, and dried to obtain the In2S3@bPEI material; (3) Preparation of In2S3@bPEI@M heterostructure: The In2S3@bPEI material obtained in step (2) is immersed in a solution containing metal M for reduction reaction. After the reaction is completed, the material is taken out, rinsed, and dried to obtain the In2S3@bPEI@M heterostructure; the metal M is any one of Au and Pd; In step (2), the structural formula of the branched polyethyleneimine is: ，n=40~60。 2. The preparation method according to claim 1, wherein: In step (1), the In2S3 nanosheet precursor solution is prepared by dissolving 240~350 mg of InCl3·4H2O and 200~260 mg of thioacetamide in 20~50 mL of deionized water.

3. The preparation method according to claim 1, wherein: In step (1), the hydrothermal reaction temperature is 150-200°C, the reaction time is 10-20 h, and the amount of In2S3 nanosheet precursor solution used is 35-45 times the volume of FTO conductive glass.

4. The preparation method according to claim 1, wherein: In step (2), the reaction time is 8 to 15 min, and the amount of branched polyethyleneimine solution used is 6 to 20 times the volume of the In2S3 nanosheet array substrate.

5. The preparation method according to claim 1, wherein: In step (1), step (2) and step (3), the drying temperature is 50-70°C and the drying condition is vacuum drying.

6. The preparation method according to claim 1, wherein: In step (3), the solution containing metal M is a HAuCl4 solution or a Na2PdCl4 solution, and the In2S3@bPEI@M heterostructure is an In2S3@bPEI@Au heterostructure or an In2S3@bPEI@Pd heterostructure.

7. The preparation method according to claim 1, wherein: In step (3), the concentration of the solution containing metal M is 0.05~2 mg / mL, the reaction temperature is 60~80 °C, the reaction time is 1~10 min, and the amount of the solution containing metal M is 10~15 times the volume of the In2S3@bPEI material.

8. An in-situ reduction method for constructing a high-efficiency interfacial charge transfer heterostructure, characterized by: Prepared by the preparation method according to any one of claims 1 to 7.

Images