Preparation method for constructing efficient interface charge transfer heterostructure through in-situ reduction

Abstract

The invention belongs to the technical field of photocatalytic materials, and discloses a preparation method for constructing an efficient interface charge transfer heterostructure through in-situ reduction. The preparation method comprises the following steps: firstly, synthesizing a metal sulfide nanosheet array by utilizing a hydrothermal method, and then constructing metal nanocrystals on the surface of metal sulfide in situ by utilizing a non-conjugated polymer (branched polyethyleneimine), thereby realizing the preparation of a metal-sulfide heterostructure with efficient interface charge transfer at room temperature. The heterostructure has reducibility and stability obviously different from those of a single-component metal sulfide under irradiation of simulated sunlight (AM 1.5 G), and the whole preparation process is simple in process and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method for in-situ reduction to construct a highly efficient interfacial charge transfer heterostructure. Background Art

[0002] In recent years, photocatalytic technology has been widely applied in many fields such as photocatalytic hydrogen production, carbon dioxide reduction, and organic pollutant degradation. Among them, photoelectrochemical water splitting for hydrogen production technology is a renewable energy solution that uses solar energy to drive the water splitting reaction. In a typical photoelectrochemical system, the photoanode, as the core functional unit for energy conversion, key parameters such as its interfacial charge separation efficiency, carrier transport ability, 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 characteristics of a relatively narrow bandgap, high carrier mobility, and adjustable energy band structure.

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

[0004] Constructing a heterostructure by loading noble metals is one of the important strategies to improve 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 interfacial electron regulation, surface plasmon resonance (SPR) effect, and enhancement of catalytic active sites. The noble metal modified with surface ligands can quickly capture photo-generated electrons due to its lower Fermi level to promote interfacial charge transfer, thereby achieving the effect of prolonging the lifetime of photo-generated carriers; at the same time, the photo-generated holes remaining in the valence band after being excited can participate in a series of oxidation reactions, improving the effective utilization rate of energy; and the loading of noble metals can greatly enhance the light absorption ability of semiconductors to promote more efficient solar energy conversion. However, the conditions for constructing sulfide heterostructures by traditional noble metal loading are harsh, the methods are relatively complex, and they are not environmentally friendly enough.

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

[0006] The object of the present invention is to address the problem of insufficient catalytic efficiency in single-component semiconductor photocatalysts in the prior art, as well as the defects of complex preparation processes and poor stability in traditional composite materials. A preparation method for in-situ reduction to construct a highly efficient interfacial charge transfer heterostructure is provided. By in-situ reduction of branched polyethyleneimine to construct a metal-sulfide heterostructure with highly efficient interfacial charge transfer, it can precisely control the interfacial coupling process between the sulfide semiconductor and the metal cocatalyst, achieving the stable and controllable synthesis of the target product. Compared with traditional preparation processes, the preparation process of the present invention is simple to operate, environmentally friendly, and highly efficient and controllable.

[0007] The molecular chain of branched polyethyleneimine contains abundant amino groups. These amino groups can participate in redox reactions under specific conditions and exhibit mild reducing ability. The reduction characteristics of branched polyethyleneimine can precisely deposit noble metal nanoparticles on the material surface through in-situ reduction technology, thus successfully constructing a metal-sulfide heterostructure with a tightly bound interfacial structure. In the present invention, branched polyethyleneimine can be used as a reducing agent, and a large number of amino groups in its molecular chain are used to achieve the in-situ reduction of metal nanoparticles. Traditional synthesis of metal nanocrystals requires the use of protecting agents to achieve the stable existence of metal nanocrystals. Non-conjugated polymer polyethyleneimine can replace the protecting agents required for traditional synthesis of metal nanoparticles, avoiding the influence of traditional protecting agents on photocharge transport, achieving the uniform and stable growth of metal nanoparticles while constructing a tight interfacial structure, and high charge transport efficiency.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A preparation method for in-situ reduction to construct a highly efficient interfacial charge transfer heterostructure, comprising the following steps: (1) Preparation of the In2S3 nanosheet array substrate: After cleaning the FTO conductive glass, place it in the In2S3 nanosheet precursor solution, carry out a hydrothermal reaction, cool after the reaction is completed, take out the substrate, rinse, and dry to obtain the In2S3 nanosheet array substrate; (2) Preparation of the In2S3@bPEI material: Immerse the In2S3 nanosheet array substrate prepared in step (1) in a polyethyleneimine solution with a pH of 9 - 11 and a concentration of 2 - 8 mg / mL, react at 60 - 80 °C, take out after the reaction is completed, rinse, and dry to obtain the In2S3@bPEI material; (3) Preparation of the In2S3@bPEI@M heterostructure: Immerse the In2S3@bPEI material prepared in step (2) in a solution containing metal M for a reduction reaction, take out after the reaction is completed, rinse, and dry to obtain the In2S3@bPEI@M heterostructure; Metal M is any one of Au and Pd.

[0009] 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.

[0010] 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.

[0011] Preferably, in step (1), the cleaned FTO conductive glass needs to be placed with the conductive surface facing down in the In2S3 nanosheet precursor solution. More preferably, the cleaned FTO conductive glass needs to be placed obliquely with the conductive surface facing down in the In2S3 nanosheet precursor solution, and the oblique angle is 30 - 60°.

[0012] Preferably, in step (2), the reaction time is 8 - 15 min, the amount of the branched polyethyleneimine solution used is 6 - 20 times the volume of the In2S3 nanosheet array substrate, and the solvent of the branched polyethyleneimine solution is deionized water.

[0013] Preferably, the weight - average molecular weight (Mw) of the branched polyethyleneimine is 20000 - 30000, and the structural formula is: , n = 40 - 60.

[0014] Preferably, in steps (1), (2), and (3), the drying temperature is 50 - 70 °C, and the drying condition is vacuum drying. The drying time of step (1) is not less than 2 h, and the drying times of steps (2) and (3) are 4 - 10 min.

[0015] Preferably, in step (3), the solution containing metal M is HAuCl4 solution or Na2PdCl4 solution, and the In2S3@bPEI@M heterostructure is In2S3@bPEI@Au heterostructure or In2S3@bPEI@Pd heterostructure.

[0016] 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 used is 10 - 15 times the volume of the In2S3@bPEI material.

[0017] The present invention also provides an in - situ reduction method for constructing an efficient interfacial charge - transfer heterostructure, which is prepared by the above - mentioned preparation method.

[0018] The specific steps of photocatalytic water splitting are as follows: The photoelectrocatalytic water splitting performance was tested under simulated sunlight (AM 1.5G) using a standard three-electrode system. The electrolyte was a mixed solution of 100 mL of 0.5 mol / L Na2SO4 and 0.05 mol / L Na2SO3 (pH value of 8.6). The FTO glass sheet loaded with In2S3@bPEI@Au nanosheet arrays was used as the working electrode, the Ag / AgCl electrode as the reference electrode, the Pt electrode as the counter electrode, and a 300 W xenon lamp as the light source. The potential of the electrode was calibrated using a reversible hydrogen electrode (RHE) according to the following formula: E REH = E Ag / Cl + 0.059 PH + E° Ag / Cl ( E° Ag / Cl = 0.197 V at 25℃).

[0019] The beneficial effects of the present invention are as follows: (1) By in-situ reduction with branched polyethyleneimine to construct a metal-sulfide heterostructure with efficient interfacial charge transfer, the present invention can precisely control the interfacial coupling process between the sulfide semiconductor and the metal cocatalyst, realizing the stable and controllable synthesis of the target product. Compared with the traditional preparation process, the preparation process of the present invention is simple to operate, environmentally friendly, short in cycle, easy to recycle and highly efficient and controllable.

[0020] (2) The metal-sulfide heterostructure of the present invention is synthesized by a simple in-situ reduction method. Using branched polyethyleneimine as the reducing agent, the amino groups therein are used to reduce metal nanoparticles. At the same time, branched polyethyleneimine also serves as a protective agent for the synthesis of metal nanoparticles, ensuring that the metal nanoparticles will not further agglomerate and grow, and avoiding the influence of additional addition of other protective agents on the photo-charge transfer efficiency. This process is simple to operate and is conducive to large-scale industrial production; (3) The metal-sulfide heterostructure prepared by the present invention has excellent optoelectronic properties and has reducibility and stability significantly different from those of single-component metal sulfides under visible light (>420 nm) irradiation with the same light intensity. Description of the Drawings

[0021] Figure 1 It is a scanning electron microscope image of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention; Figure 2 It is an energy-dispersive X-ray spectroscopy image of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention; Figure 3 It is the ultraviolet-visible absorption spectrum of HAuCl4; Figure 4 UV-Vis absorption spectrum of Au nanoparticles (Au@bPEI NPs) formed in the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention; Figure 5 Linear sweep voltammetry curves 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); Figure 6 Linear sweep voltammetry curves 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 implementation manners

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be obtained 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 this field.

[0024] Example 1 Preparation of In2S3@bPEI@Au heterostructure (1) Preparation of In2S3 nanosheet array substrate: The 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 hydrothermal reaction kettle lined with polytetrafluoroethylene, and the clean FTO conductive glass substrate was placed in the reaction system with the conductive surface facing downwards at an inclination, and hydrothermally reacted at 160 °C for 12 h. Naturally cooled to room temperature (25 ± 2 °C), 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 °C for 2 h. After drying, it was cut into a working electrode with a size of 15 mm × 10 mm × 1.6 mm (the area of the In2S3 nanosheet array loaded was 10 mm × 10 mm, and the other side was a clean conductive surface), and an In2S3 nanosheet array substrate (FTO substrate loaded with In2S3 nanosheet array) was obtained.

[0025] (2)Preparation of In2S3@bPEI material: The FTO substrate loaded with In2S3 nanorod arrays was immersed in 2 mL of branched polyethyleneimine (bPEI, Mw = 25000, pH = 10.70, 4 mg / mL) solution, treated at 70 °C for 10 min, taken out after treatment, and dried at 70 °C for 5 min to obtain an FTO substrate loaded with In2S3@bPEI material.

[0026] (3)Preparation of In2S3@bPEI@Au heterostructure: The FTO substrate loaded with In2S3@bPEI material was immersed in 2 mL of HAuCl4 solution (pH = 3.28, 0.1 mg / mL), reacted at 70 °C for 3 min, rinsed with deionized water for 4 s after the reaction, and then dried at 70 °C for 5 min to obtain an In2S3@bPEI@Au heterostructure.

[0027] Example 2 Preparation of In2S3@bPEI@Pd heterostructure The method for preparing the In2S3@bPEI@Pd heterostructure in this example refers to Example 1, and only the HAuCl4 solution in step (3) is replaced with an equal-concentration and equal-volume sodium palladium chloride (Na2PdCl4) solution. The specific steps are as follows: (1)Preparation of In2S3 nanosheet array substrate: The 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 hydrothermal reaction kettle lined with polytetrafluoroethylene, and the clean FTO conductive glass substrate was placed in the reaction system with the conductive side facing downwards at an angle, and hydrothermally reacted at 160 °C for 12 h. After natural cooling to room temperature (25±2 °C), 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 °C for 2 h. After drying, it was cut into a working electrode with a size of 15 mm×10 mm×1.6 mm (the area of the In2S3 nanosheet array loaded was 10 mm×10 mm, and the other side was a clean conductive surface), and an In2S3 nanosheet array substrate (FTO substrate loaded with In2S3 nanosheet array) was obtained.

[0028] (2) Preparation of In2S3@bPEI material: The FTO substrate loaded with In2S3 nanorods was immersed in 2 mL of branched polyethyleneimine (bPEI, Mw = 25000, pH = 10.70, 4 mg / mL) solution, treated at 70 °C for 10 min, taken out after treatment, and dried at 70 °C for 5 min to obtain an FTO substrate loaded with In2S3@bPEI material.

[0029] (3) Preparation of In2S3@bPEI@Pd heterostructure: The FTO substrate loaded with In2S3@bPEI material was immersed in 2 mL of sodium tetrachloropalladate (Na2PdCl4) solution (0.1 mg / mL), reacted at 70 °C for 3 min, rinsed with deionized water for 4 s after the reaction, and then dried at 70 °C for 5 min to obtain an In2S3@bPEI@Au heterostructure.

[0030] I. Structural characterization of the metal-sulfide heterostructure photocatalyst prepared in the present invention The scanning electron microscope image of the In2S3@bPEI@Au heterostructure prepared in Example 1 of the present invention is as Figure 1 shown, and it can be seen that the In2S3@bPEI@Au heterostructure is still a nanosheet array, indicating that the morphology has not changed after wrapping branched polyethyleneimine on the surface of In2S3 and depositing gold nanoparticles.

[0031] The energy-dispersive X-ray spectroscopy diagram of the In2S3@bPEI@Au heterostructure is shown in Figure 2 , indicating the successful synthesis of the In2S3@bPEI@Au heterostructure.

[0032] II. UV-Visible Absorption Spectroscopy Characterization The UV-visible absorption spectroscopy diagrams of HAuCl4 and gold nanoparticles (Au@bPEI NPs) are shown in Figure 3 、 Figure 4 respectively. It can be seen that no SPR absorption peak of gold nanoparticles is detected in the HAuCl4 solution. However, after reacting the HAuCl4 solution with the bPEI solution for a period of time, the SPR characteristic peak of gold nanoparticles can be detected, indicating that it is feasible to reduce HAuCl4 to gold nanoparticles through the reduction property of bPEI.

[0033] III. Photocatalytic Performance Characterization The linear sweep voltammetry curves of In2S3@bPEI@Au and In2S3@bPEI@Pd prepared in Example 1 and Example 2 of the present invention under simulated sunlight (AM 1.5G) are as shown in Figure 5 、 Figure 6 respectively. It can be seen that under simulated sunlight conditions, the photocurrent density of In2S3@bPEI@Au and In2S3@bPEI@Pd is increased by about 2 times compared with that of In2S3, and both heterostructures have good photocatalytic activity.

[0034] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method for in-situ reduction to construct an efficient interfacial charge transfer heterostructure, characterized in that: It includes the following steps: (1) Preparation of In2S3 nanosheet array substrate: After cleaning the FTO conductive glass, place it in the In2S3 nanosheet precursor solution for hydrothermal reaction. After the reaction is completed, cool it, take out the substrate, rinse it, and dry it to obtain the In2S3 nanosheet array substrate; (2) Preparation of In2S3@bPEI material: Immerse the In2S3 nanosheet array substrate prepared in step (1) in a branched polyethyleneimine solution with a pH of 9 - 11 and a concentration of 2 - 8 mg / mL, and react at 60 - 80 °C. After the reaction is completed, take it out, rinse it, and dry it to obtain the In2S3@bPEI material; (3) Preparation of In2S3@bPEI@M heterostructure: Immerse the In2S3@bPEI material prepared in step (2) in a solution containing metal M for reduction reaction. After the reaction is completed, take it out, rinse it, and dry it to obtain the In2S3@bPEI@M heterostructure; Metal M is any one of Au and Pd.

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

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

5. The preparation method according to claim 1, characterized in that: In step (2), the weight-average molecular weight of the branched polyethyleneimine is 20000 - 30000, and the structural formula is: ，n= 40~60。 6. The preparation method according to claim 1, wherein: In steps (1), (2), and (3), the drying temperature is 50 - 70 °C, and the drying condition is vacuum drying.

7. The preparation method according to claim 1, characterized in that: In step (3), the solution containing metal M is HAuCl4 solution or Na2PdCl4 solution, and the In2S3@bPEI@M heterostructure is In2S3@bPEI@Au heterostructure or In2S3@bPEI@Pd heterostructure.

8. 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 dosage of the solution containing metal M is 10 - 15 times the volume of the In2S3@bPEI material.

9. An in-situ reduction method for constructing an efficient interfacial charge transfer heterostructure, characterized in that: Prepared by the preparation method according to any one of claims 1 - 8.

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