A ferroelectric thin film BiFeO 3 @SnS 2 Methods for preparing composite photoelectrodes

Abstract

This invention relates to the field of nanocomposite material synthesis technology, and discloses a ferroelectric thin film BiFeO 3 @SnS 2 The preparation method of the composite photoelectrode includes the following steps: Step 1, preparing BiFeO by sol-gel method. 3 Precursor solution; Step 2: Preparation of BiFeO by spin coating 3 Photoelectrode thin film; Step 3: In-situ growth of SnS using hydrothermal method 2 Materials, preparation of BiFeO 3 @SnS 2 Composite photoelectrode. This invention utilizes a combination of sol-gel and spin-coating methods to prepare the ferroelectric material BiFeO. 3 Based on thin-film photoelectrodes, two-dimensional tin disulfide (SnS) is grown via a hydrothermal method. 2 BiFeO was thus prepared. 3 @SnS 2 Composite photoelectrodes not only ensure efficient light utilization but also promote the separation and transport of photogenerated carriers.

Description

A method for preparing a ferroelectric thin film BiFeO3@SnS2 composite photoelectrode Technical Field

[0001] This invention relates to the field of nanocomposite material synthesis technology, and in particular to a method for preparing a ferroelectric thin film BiFeO3@SnS2 composite photoelectrode. Background Technology

[0002] Photoelectrochemical technology can convert abundant solar energy into clean electrical energy or chemical energy (hydrogen energy), and has potential applications in solving energy shortages and environmental pollution. A complete photoelectrochemical system, consisting of a semiconductor photoelectrode, a counter electrode, and an electrolyte, typically operates as follows: When light irradiates the surface of the photoelectrode material, valence band electrons transition to the conduction band, forming photogenerated charge carriers (electron-hole pairs); the charge carriers separate and migrate; and the carriers migrate to different electrode surfaces where redox reactions occur. Among numerous photoelectrode materials, bismuth ferroferrite (BiFeO3) possesses advantages such as low cost, environmental friendliness, chemical stability, and the ability to absorb and utilize approximately 40% of the visible light energy (optical band gap of 2.2-2.8 eV). However, the application of BiFeO3 as a photoelectrode material still faces two challenges: how to improve the light capture efficiency and the separation efficiency of photogenerated charge carriers. To address these issues, various improvement methods have been adopted to enhance the photoelectrochemical performance of photoelectrode materials. Related studies have shown that when other narrow bandgap materials are combined with the surface of semiconductor photoelectrode materials, not only can the light energy capture efficiency of the photoelectrode be enhanced, but the energy band matching performance between the two can further ensure the improvement of the separation and transport performance of photogenerated carriers.

[0003] Tin disulfide (SnS2), a two-dimensional sulfide material, exhibits a near-infrared light response range, making it an excellent visible light material that has attracted increasing attention from researchers in the field of photoelectric conversion. Research on SnS2 in photoelectrochemistry mainly focuses on two aspects: first, controlling its morphology and size to alter its band structure and specific surface area, thereby improving the photoelectric conversion efficiency of composite photoelectrochemical devices; second, combining it with other semiconductor materials to form heterojunctions, which not only enhances the absorption of visible light by the photoelectrode but also improves carrier separation efficiency through the heterojunction band matching effect, thus enhancing the photoelectric conversion efficiency of composite photoelectrochemical devices. Therefore, loading two-dimensional sulfide SnS2 onto the surface of a BiFeO3 photoelectrode to prepare a ferroelectric thin-film BiFeO3 / SnS2 photoelectrode can further improve the light absorption and utilization efficiency of the BiFeO3 photoelectrode, and the heterojunction band matching effect formed between BiFeO3 and the two-dimensional sulfide BiFeO3 can further promote the separation and transport performance of photogenerated carriers. Summary of the Invention

[0004] Objective: To address the problems existing in the prior art, this invention provides a method for preparing a ferroelectric thin-film BiFeO3@SnS2 composite photoelectrode. Based on a ferroelectric material BiFeO3 thin-film photoelectrode prepared by a combination of sol-gel and spin-coating methods, a two-dimensional sulfide tin disulfide (SnS2) composite photoelectrode is prepared via a hydrothermal method, thereby improving photoelectric conversion efficiency. The photoelectrode prepared by this invention not only ensures efficient light utilization but also promotes the separation and transport of photogenerated carriers.

[0005] Technical solution: This invention provides a method for preparing a ferroelectric thin film BiFeO3@SnS2 composite photoelectrode, comprising the following steps:

[0006] Step 1: Preparation of BiFeO3 precursor solution using sol-gel method

[0007] Bismuth nitrate and ferric nitrate were added to an ethylene glycol methyl ether solution and stirred until dissolved. Citric acid was then added to the solution to obtain a BiFeO3 precursor solution.

[0008] Step 2: Preparation of BiFeO3 photoelectrode thin film by spin coating

[0009] The BiFeO3 precursor liquid was dropped onto a conductive substrate and rapidly spin-coated to obtain a BiFeO3 photoelectrode wet film. The BiFeO3 photoelectrode wet film was then annealed to obtain a BiFeO3 photoelectrode thin film.

[0010] Step 3: In-situ hydrothermal growth of SnS2 material to prepare BiFeO3@SnS2 composite photoelectrode.

[0011] Tin tetrachloride and thioacetamide were added to anhydrous ethanol solution and ultrasonically dispersed to obtain SnS2 precursor solution. Then, the BiFeO3 photoelectrode film was placed in the SnS2 precursor solution, sealed, and placed in an electric heating drying oven for heat preservation. The photoelectrode after heat preservation was washed and dried to obtain BiFeO3@SnS2 composite photoelectrode.

[0012] Furthermore, in step three, the amount of tin tetrachloride weighed ranges from 14 to 280 mg; the amount of thioacetamide weighed ranges from 15 to 300 mg.

[0013] And / or, the molar ratio of the tin tetrachloride to the Sn source and S source materials in the thioacetamide is 1:5;

[0014] Furthermore, the amount of tin tetrachloride is 140 mg, and the amount of thioacetamide is 150 mg.

[0015] Furthermore, in step three, the volume of the anhydrous ethanol solution is 30 mL.

[0016] Furthermore, in step three, the heat preservation treatment specifically involves heat preservation at 120-160℃ for 8-12 hours;

[0017] Furthermore, in step three, the heat preservation treatment specifically involves heat preservation at 140°C for 10 hours.

[0018] Preferably, in step three, the washing involves washing multiple times with deionized water and anhydrous ethanol, respectively.

[0019] Furthermore, in step one, the molar ratio of metal ions in citric acid, bismuth nitrate, and ferric nitrate is 2:1:1; citric acid, as a chelating agent, can promote the colloidal formation of the BiFeO3 precursor solution.

[0020] Furthermore, in step one, the molar concentration of the BiFeO3 precursor solution ranges from 0.1 to 0.3 mol / L;

[0021] Furthermore, in step one, the molar concentration of the BiFeO3 precursor solution is 0.2 mol / L.

[0022] Furthermore, in step two, the spin coating specifically involves first spin coating at a low speed of 800-1200 rpm / min for 5 seconds, and then spin coating at a high speed of 4000-8000 rpm / min for 30 seconds, repeating this spin coating operation 6-12 times.

[0023] Furthermore, in step two, the spin coating specifically involves first spin coating at a low speed of 1000 rpm / min for 5 seconds, and then spin coating at a high speed of 5000 rpm / min for 30 seconds, repeating this spin coating operation 8 times. The purpose of low-speed spin coating is to uniformly disperse the precursor liquid on the substrate surface, and the purpose of high-speed spin coating is to reduce the thickness of the precursor liquid, thereby preparing a film with a nanometer-thickness.

[0024] Furthermore, in step two, the annealing treatment specifically involves high-temperature treatment at 500-650 ℃ in a muffle furnace for 1-4 hours;

[0025] Furthermore, in step two, the annealing treatment specifically involves high-temperature treatment at 600 °C for 2 hours in a muffle furnace; this process can promote the generation and separation of photogenerated carriers in the material.

[0026] Furthermore, in step two, the conductive substrate can be FTO conductive glass, ITO conductive glass, AZO conductive glass, etc.

[0027] Beneficial effects: The ferroelectric thin film BiFeO3@SnS2 composite photoelectrode prepared by this invention is based on the ferroelectric material BiFeO3 thin film photoelectrode prepared by combining the sol-gel method and spin coating method. The two-dimensional sulfide tin disulfide (SnS2) is grown by hydrothermal method to prepare the BiFeO3@SnS2 composite photoelectrode. On the basis of realizing the effective integrated preparation of ferroelectric thin film / two-dimensional sulfide, the method involved in the process is simple and the equipment cost is low, which is conducive to large-scale industrial production application.

[0028] In this invention, BiFeO3 and SnS2 are both visible light absorbing materials. Combining the two not only ensures the efficiency of light utilization and enhances the absorption of visible light, but also the good band matching between the two materials can promote the separation and transport of photogenerated carriers, thereby improving the photoelectric conversion efficiency. Attached Figure Description

[0029] Figure 1 is a layer diagram of the BiFeO3@SnS2 composite photoelectrode prepared in Embodiment 1;

[0030] Figure 2 shows the photoelectrochemical performance of the BiFeO3@SnS2 composite photoelectrodes prepared in Examples 1-3;

[0031] Figure 3 shows the absorption spectra of the BiFeO3@SnS2 composite photoelectrode, conventional BiFeO3 film, and conventional SnS2 film prepared in Embodiment 1.

[0032] Figure 4 shows the fluorescence spectra of the BiFeO3@SnS2 composite photoelectrode prepared according to Embodiment 1 and the conventional BiFeO3 electrode. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings.

[0034] Implementation method 1:

[0035] This embodiment provides a method for preparing a BiFeO3@SnS2 composite photoelectrode, the specific steps of which are as follows:

[0036] The first step is to prepare the precursor solution of BiFeO3 material by sol-gel method. The specific preparation method is as follows: weigh out equal molar ratios of bismuth nitrate and ferric nitrate, transfer them to ethylene glycol methyl ether solution and stir until dissolved. Then weigh out equal molar ratios of citric acid material and pour it into the ethylene glycol methyl ether solution containing bismuth nitrate and ferric nitrate as chelating agent to promote the colloidal formation of BiFeO3 precursor solution.

[0037] The second step involves preparing a ferroelectric thin film BiFeO3 photoelectrode material using a spin coater. The spin-coated BiFeO3 photoelectrode material is then placed in a muffle furnace for annealing to allow crystallization. This annealing and crystallization process promotes the generation and separation of photogenerated carriers. This method for preparing BiFeO3 photoelectrode films can also be applied to substrates such as FTO conductive glass, ITO conductive glass, and AZO conductive glass.

[0038] The third step involves in-situ growth of SnS2 nanomaterials on the surface of the BiFeO3 photoelectrode film using a hydrothermal method to prepare a BiFeO3 / SnS2 composite photoelectrode film. The specific preparation process is as follows: 70 mg of tin tetrachloride and 75 mg of thioacetamide were weighed using an electronic balance as the Sn source and S source, respectively. 30 mL of anhydrous ethanol solution was poured into a reaction vessel, and the Sn and S source materials were transferred into the ethanol solution and ultrasonically dispersed. Then, the BiFeO3 photoelectrode film prepared by spin-coating was placed in the ethanol solution containing the Sn and S source materials. The reaction vessel was sealed and placed in an electrically heated drying oven for a specific temperature (140℃) and time (10 hours), during which SnS2 nanomaterials grew on the surface of the BiFeO3 photoelectrode film.

[0039] The fourth step involves repeatedly rinsing the material obtained in the third step with deionized water and anhydrous ethanol to remove surface organic matter and impurities. The material is then transferred to an oven and dried at 60 degrees Celsius for 12 hours to obtain the BiFeO3@SnS2 composite photoelectrode, denoted as BiFeO3 / SnS2-1.

[0040] The layer diagram of the BiFeO3@SnS2 composite photoelectrode prepared in this embodiment is shown in Figure 1.

[0041] Implementation Method 2:

[0042] This embodiment is largely the same as Embodiment 1, the main difference being that the amounts of tin tetrachloride and thioacetamide are 140 mg and 150 mg respectively, while other conditions remain unchanged.

[0043] The final BiFeO3@SnS2 composite photoelectrode is denoted as BiFeO3 / SnS2-2.

[0044] Apart from the above, this implementation method is exactly the same as implementation method 1, and will not be described again here.

[0045] Implementation Method 3:

[0046] This embodiment is largely the same as Embodiment 1, the main difference being that the amounts of tin tetrachloride and thioacetamide are 210 mg and 225 mg respectively, while other conditions remain unchanged.

[0047] The final BiFeO3@SnS2 composite photoelectrode is denoted as BiFeO3 / SnS2-3.

[0048] Apart from the above, this implementation method is exactly the same as implementation method 1, and will not be described again here.

[0049] The photoelectrochemical performance of the BiFeO3@SnS2 composite photoelectrodes prepared in Examples 1-3 was compared with that of conventional BiFeO3 thin films, and the results are shown in Figure 2.

[0050] Figure 2 shows the photoelectrochemical performance of the BiFeO3@SnS2 composite photoelectrodes prepared in Examples 1-3. As can be seen from the figure, when the hydrothermal synthesis time and temperature are the same, the photoelectrochemical performance of the composite photoelectrode can be altered by changing the amount of Sn and S source, thus changing the SnS2 loading. When the amounts of Sn and S source are 70 mg and 75 mg, the photoelectrochemical performance of the sample is improved; further increasing the amounts of Sn and S source to 140 mg and 150 mg, respectively, yields the optimal photoelectrochemical performance, with a photocurrent density reaching -22.5 μA·cm⁻¹. -2 However, when the amounts of Sn and S source were further increased to 210 mg and 225 mg, respectively, the photoelectrochemical performance of the sample decreased. This indicates that there exists an optimal SnS2 loading in the SnS2-loaded composite sample. Too low a loading cannot guarantee sufficient light absorption performance, while too high a loading may affect the carrier separation and transport performance of the sample. Therefore, a balance needs to be struck between these two factors.

[0051] Figure 3 shows the absorption spectra of the BiFeO3@SnS2 composite photoelectrode prepared in Embodiment 1, a conventional BiFeO3 thin film, and a conventional SnS2 sample. As can be seen from the figure, the leftmost image represents the absorption spectrum of the BiFeO3 thin film. When SnS2 is loaded, the absorption edge of the sample exhibits a red shift, indicating an increase in the visible light absorption performance of the composite sample.

[0052] Figure 4 shows the fluorescence spectra of the BiFeO3@SnS2 composite photoelectrode prepared in Example 1 and the conventional BiFeO3 electrode. It can be seen that the fluorescence emission intensity of the sample decreases after loading with SnS2, indicating an improvement in carrier separation efficiency and transport performance of the composite sample.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a ferroelectric thin film BiFeO3@SnS2 composite photoelectrode, characterized in that, The process includes the following steps: Step 1: Preparation of BiFeO3 precursor solution using the sol-gel method. Bismuth nitrate and ferric nitrate are added to an ethylene glycol methyl ether solution and stirred until dissolved. Citric acid is then added to the solution to obtain the BiFeO3 precursor solution. Step 2: Preparation of BiFeO3 photoelectrode film using spin coating. The BiFeO3 precursor solution is dropped onto a conductive substrate and spin-coated to obtain a BiFeO3 photoelectrode wet film. The BiFeO3 photoelectrode wet film is then annealed to obtain the BiFeO3 photoelectrode film. Step 3: In-situ hydrothermal growth of SnS2 material to prepare BiFeO3@SnS2 composite photoelectrode. Tin tetrachloride and thioacetamide were added to anhydrous ethanol solution and ultrasonically dispersed to obtain a SnS2 precursor solution. The BiFeO3 photoelectrode film was then placed in the SnS2 precursor solution, sealed, and placed in an electrically heated drying oven for heat preservation. The photoelectrode after heat preservation was washed and dried to obtain the BiFeO3@SnS2 composite photoelectrode. The amount of tin tetrachloride was 14-140 mg; the amount of thioacetamide was 15-150 mg; and the volume of the anhydrous ethanol solution was 30 mL.

2. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step three, the heat preservation treatment specifically involves heat preservation at 120-160℃ for 8-12 hours.

3. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step three, the washing process specifically involves washing multiple times with deionized water and anhydrous ethanol.

4. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step one, the molar ratio of metal ions in citric acid, bismuth nitrate, and ferric nitrate is 2:1:

1.

5. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step one, the molar concentration of the BiFeO3 precursor solution ranges from 0.1 to 0.3 mol / L.

6. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step two, the spin coating specifically involves first spin coating at a low speed of 800-1200 rpm / min for 5 seconds, and then spin coating at a high speed of 4000-8000 rpm / min for 30 seconds. This spin coating operation is repeated 6-12 times.

7. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step two, the annealing process specifically involves high-temperature treatment at 500-650 ℃ in a muffle furnace for 1-4 hours.

8. The method for preparing the ferroelectric thin film BiFeO3@SnS2 composite photoelectrode according to claim 1, characterized in that, In step two, the conductive substrate is FTO conductive glass, ITO conductive glass, or AZO conductive glass.

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