Cu3snS4 quantum dot / g-c3n4 nanosheet composite material, and preparation method and application thereof

Abstract

This invention discloses a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material, its preparation method, and its applications, belonging to the field of photothermal catalysis technology. The method includes the following steps: mixing and stirring a g-C3N4 nanosheet dispersion with a Cu3SnS4 quantum dot solution, followed by vacuum drying to obtain the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material. This invention effectively improves the quantum efficiency of photocatalytic reactions, efficiently utilizing solar energy to achieve photocatalytic water splitting for hydrogen production. The composite material prepared using the method provided by this invention exhibits a high hydrogen production rate and excellent stability. Furthermore, the method provided by this invention is energy-saving, low-consumption, green, and non-toxic.

Description

Technical Field

[0001] This invention belongs to the field of photothermal catalysis technology, and particularly relates to a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material, its preparation method and application. Background Technology

[0002] The development and utilization of new energy sources is one of the effective methods to solve energy and environmental problems. Hydrogen energy has advantages such as high efficiency and cleanliness, and is an important new energy source. Compared with traditional hydrogen production methods such as methane reforming and water electrolysis, photocatalytic water splitting for hydrogen production can be carried out under milder conditions, with low raw material costs, a simple reaction system structure, and environmental friendliness, showing good application prospects. The core component of the photocatalytic water splitting hydrogen production system is the photocatalyst, which is usually composed of semiconductor materials. The structure of the semiconductor photocatalytic material determines its light absorption, carrier transport, and separation performance, thus affecting the reaction efficiency. Currently, graphitic carbon nitride (g-C3N4) is widely used in photocatalytic reactions due to its suitable energy level structure, stable properties, and simple synthesis process. However, the bulk g-C3N4 material prepared by the one-step calcination method has poor crystallinity and many defects, and photogenerated carriers are easily recombine, resulting in low photocatalytic efficiency. Since the CN layers in g-C3N4 are bound together by van der Waals forces, resulting in poor interlayer electron transport performance, preparing thin-layer g-C3N4 nanosheets can improve the transport and separation efficiency of photogenerated carriers, while providing more active sites for adsorption and reaction.

[0003] In photocatalytic water splitting for hydrogen production, slow surface reaction kinetics are a significant factor limiting hydrogen evolution activity. Currently, surface reaction kinetics are often improved by loading noble metal co-catalysts (such as Pt) onto the catalyst surface. This method effectively improves hydrogen production performance, but the high price and scarcity of noble metals increase costs. Studies have shown that low-cost and abundant transition metal sulfides possess metallic properties and high electrical conductivity, making them suitable as co-catalysts. Furthermore, some transition metal sulfides exhibit localized surface plasmon resonance effects, which can further enhance photocatalytic hydrogen production efficiency.

[0004] Therefore, how to provide a method for preparing catalysts for photocatalytic water splitting using transition metal sulfides is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material includes the following steps:

[0008] The g-C3N4 nanosheet dispersion was mixed and stirred with the Cu3SnS4 quantum dot solution, and then dried under vacuum to obtain the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material.

[0009] Beneficial Effects: This invention uses g-C3N4 nanosheets as the main catalyst and Cu3SnS4 quantum dots as a co-catalyst to prepare a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material. This invention utilizes the loading of Cu3SnS4 quantum dots to extend the light absorption range of g-C3N4 nanosheets. Through the Fermi level difference between the two phases, a built-in electric field is formed, driving the directional movement of photogenerated electrons, thereby improving the separation efficiency of photogenerated carriers. Simultaneously, due to the metal-like properties of Cu3SnS4 quantum dots, a photoinduced LSPR (localized surface plasmon resonance) effect can be generated under illumination. This effect not only enhances the spectral response range of the material but also rapidly increases the catalyst surface temperature through a photothermal effect (as shown in the absorption spectrum and surface temperature test results of the samples in the experiment), promoting the activation of H-OH bonds during water dissociation, thereby improving the photocatalytic hydrogen production activity.

[0010] Preferably, the mass fraction of Cu3SnS4 quantum dots in the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material is 1-4%.

[0011] More preferably, the concentration of the g-C3N4 nanosheet dispersion is 40 mg / mL.

[0012] The concentration of the Cu3SnS4 quantum dot solution is 8 mg / mL.

[0013] The volume ratio of the g-C3N4 nanosheet dispersion to the Cu3SnS4 quantum dot solution is 5:(0.25-1).

[0014] More preferably, the mixing and stirring reaction time is 2 hours.

[0015] Beneficial Effects: In the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material, the mass fraction of Cu3SnS4 quantum dots is 1-4%. This is because a low amount of Cu3SnS4 quantum dots cannot effectively enhance light absorption and promote the separation of photogenerated carriers. When the content exceeds 3%, the photocatalytic water splitting hydrogen production performance decreases because excessive Cu3SnS4 quantum dots will cover the active sites on the surface of g-C3N4 nanosheets, thus reducing photocatalytic performance. During the preparation of Cu3SnS4 quantum dots, the amount of Cu3SnS4 quantum dots generated can be controlled by adjusting the amount of raw materials added. Too low a concentration of the quantum dot solution makes collection difficult, while too high a concentration hinders dispersion during the preparation process, leading to particle size increase. In preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composites, the amounts of g-C3N4 nanosheets and Cu3SnS4 quantum dot solution added are mainly controlled based on the mass fraction of Cu3SnS4 quantum dots in the composite. Furthermore, too little hexane is detrimental to uniform mixing, while too much results in waste of reagents and energy. The stirring time is also determined by considering conditions that ensure uniform mixing.

[0016] Preferably, the method for preparing the g-C3N4 nanosheets in the g-C3N4 nanosheet dispersion includes the following steps:

[0017] Melamine and urea were mixed in solution and subjected to a hydrothermal reaction. After the reaction was completed, the resulting precipitate was dried and calcined to obtain the g-C3N4 nanosheets.

[0018] Preferably, the mass ratio of melamine to urea is 5:8.

[0019] Preferably, the hydrothermal reaction is carried out at a temperature of 180°C for 20 hours.

[0020] The calcination was carried out by heating to 500°C at a heating rate of 2.5°C / min and calcining for 4 hours.

[0021] Beneficial effects: The hydrothermal preparation method allows for better control of the microstructure, increases the specific surface area of ​​g-C3N4 nanosheets, and exposes more active sites. On one hand, it facilitates bonding with Cu3SnS4 quantum dots during composite material preparation, resulting in tighter bonding and improved transport and separation efficiency of photogenerated carriers. On the other hand, the exposure of active sites enhances the adsorption and activation of water molecules, thereby improving photocatalytic performance.

[0022] Preferably, the method for preparing Cu3SnS4 quantum dots in the Cu3SnS4 quantum dot solution includes the following steps:

[0023] Cuprous chloride and tin tetrachloride were mixed in a solvent and heated under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, washed, and centrifuged. The resulting precipitate was then placed in n-hexane to obtain the Cu3SnS4 quantum dot solution.

[0024] Preferably, the heating reaction includes the following steps: stirring at room temperature for 15 minutes, then heating to 110°C and stirring for 30 minutes, then further heating to 270°C and stirring for 1 hour.

[0025] Preferably, the mass ratio of cuprous chloride to tin tetrachloride is 3:35.

[0026] Preferably, the solvent is a mixture of dodecanethiol and octadecene in a volume ratio of 1:4.

[0027] Beneficial effects: Based on the stoichiometric ratio of Cu3SnS4, the amounts of cuprous chloride, tin tetrachloride, and dodecyl mercaptan added were determined, and Cu3SnS4 quantum dots were obtained by reacting in octadecene solvent. Under the above reaction temperature, time, and octadecene addition conditions, Cu3SnS4 can be effectively regulated into quantum dots, giving it specific light absorption characteristics. Cu3SnS4 particles obtained by other preparation methods have larger particle sizes.

[0028] A Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material prepared by the method described above.

[0029] Beneficial Effects: In the obtained Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material, Cu3SnS4 is modulated into quantum dots, which are black in color. This structure can enhance light absorption and generate a photothermal effect. It is beneficial to the activation of the H-OH bonds of adsorbed water molecules, accelerating the reaction rate of water dissociation to produce protons. In addition, the microstructure of g-C3N4 is nanosheet, which has a large specific surface area and can expose more active sites, which is conducive to the tight binding with Cu3SnS4 quantum dots and can improve the adsorption capacity of water molecules as a reactant.

[0030] Application of a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material in photocatalytic water splitting for hydrogen production.

[0031] Beneficial effects: When Cu3SnS4 quantum dots and g-C3N4 nanosheets come into contact, due to the difference in their Fermi levels, electrons transfer from the Cu3SnS4 quantum dots to the g-C3N4 nanosheets to balance the Fermi levels, forming a built-in electric field near the interface. Since Cu3SnS4 quantum dots exhibit the LSPR effect under illumination, this activates the sample's light absorption in the near-infrared region. When irradiated with visible and near-infrared light, photogenerated electrons induced by interband transitions migrate from the conduction band of the g-C3N4 nanosheets to the Cu3SnS4 quantum dots under the influence of the built-in electric field, while photogenerated holes migrate from the Cu3SnS4 quantum dots to the g-C3N4 nanosheets, recombinating with photogenerated electrons at the interface, thereby suppressing electron-hole recombination in the two-phase semiconductor. Simultaneously, the heat generated by the LSPR effect is dissipated to the surrounding medium through phonon-phonon coupling, promoting the activation of the H-OH bonds in adsorbed water molecules. The protons generated by dissociation are reduced to hydrogen gas by photogenerated electrons, ultimately improving the slow kinetics of water splitting. Therefore, the synergistic effect of Cu3SnS4 quantum dots in enhancing photoresponse, effectively activating H-OH bonds, and promoting the separation of photogenerated carriers has led to an improvement in the photocatalytic hydrogen evolution performance of the photocatalyst in the visible-near-infrared region.

[0032] Compared with the prior art, the present invention has the following advantages and technical effects:

[0033] This invention addresses the shortcomings of existing g-C3N4-based photocatalytic water splitting materials for hydrogen production by providing a method for preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composite materials and their applications. Using Cu3SnS4 quantum dots as a co-catalyst further improves the quantum efficiency of the photocatalytic reaction. This invention efficiently utilizes solar energy to achieve photocatalytic water splitting for hydrogen production. The composite material prepared using the method provided by this invention exhibits a high hydrogen production rate and excellent stability. Furthermore, the method provided by this invention is energy-saving, low-consumption, green, and non-toxic. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 The XRD patterns are of the g-C3N4 nanosheets obtained in step (1) of Example 1 and the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite materials obtained in step (3) of Examples 1-4;

[0036] Figure 2 The image shows a transmission electron microscope (TEM) image of the CN / CTS-3 composite material obtained in Example 3.

[0037] Figure 3The UV-Vis-NIR absorption spectra of the g-C3N4 nanosheets obtained in step (1) of Example 1 and the CN / CTS-3 composite material obtained in Example 3 are shown below.

[0038] Figure 4 The surface temperature monitoring results of the g-C3N4 nanosheets obtained in step (1) of Example 1 and the CN / CTS-3 composite material obtained in Example 3 under xenon lamp (full spectrum range) irradiation;

[0039] Figure 5 The graph shows the photocatalytic water splitting rate for hydrogen production under visible light (λ≥420nm) of the g-C3N4 nanosheets obtained in step (1) of Example 1 and the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material obtained in step (3) of Examples 1-4.

[0040] Figure 6 The graph shows the rate of photocatalytic water splitting for hydrogen production after three repeated reactions of the CN / CTS-3 composite material obtained in Example 3 under visible light (λ≥420nm). Detailed Implementation

[0041] The technical solutions of 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0044] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0045] Example 1

[0046] A method for preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composite materials includes the following steps:

[0047] (1) Preparation of g-C3N4 nanosheets

[0048] 5g of melamine and 8g of urea were weighed into beakers using an analytical balance, and 70mL of deionized water was added. The mixture was stirred continuously on a magnetic stirrer for 3 hours until homogeneous, and then transferred to a hydrothermal synthesis reactor. The mixture was reacted at 180℃ for 20 hours. After the reaction, the resulting precipitate was washed three times with deionized water and then dried in a 60℃ electric drying oven for 12 hours. The precipitate was then placed in a crucible and placed in a muffle furnace, where it was heated to 500℃ at a rate of 2.5℃ / min and held for 4 hours for heat treatment to obtain g-C3N4 nanosheets, abbreviated as CN.

[0049] (2) Preparation of Cu3SnS4 quantum dots

[0050] Weigh 0.03 g of cuprous chloride and 0.035 g of tin tetrachloride separately using an analytical balance and place them in a three-necked flask. Use a pipette to transfer 3 mL of dodecanethiol and a graduated cylinder to measure 12 mL of octadecene, add them to the three-necked flask, and mix thoroughly with the cuprous chloride and tin tetrachloride. Continuously purge the three-necked flask with nitrogen gas and stir at room temperature for 15 min. Then, raise the temperature to 110 °C and maintain stirring for 30 min, further raise the temperature to 270 °C and stir for 1 h. After the reaction is complete, allow it to cool naturally to room temperature, wash with n-hexane, centrifuge at high speed, and store in n-hexane to obtain a Cu3SnS4 quantum dot solution with a concentration of 8 mg / mL.

[0051] (3) Preparation of Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material

[0052] 200 mg of g-C3N4 nanosheets obtained in step (1) were uniformly dispersed in 5 mL of n-hexane. Then, 0.25 mL of Cu3SnS4 quantum dot solution was added and the mixture was stirred vigorously at 500 rpm for 2 h. The mixture was then placed in an electric thermostatic drying oven and vacuum dried for 2 h (60 °C) to obtain a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material. Based on the different mass percentages of Cu3SnS4 quantum dots in the composite material, the composite material was designated as CN / CTS-1. Here, C and CN represent Cu3SnS4 quantum dots and g-C3N4 nanosheets, respectively, and the number 1 represents the mass percentage of Cu3SnS4 quantum dots.

[0053] Example 2

[0054] A method for preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material is disclosed, differing from Example 1 only in that the amount of Cu3SnS4 quantum dot solution added in step (3) is 0.5 mL, and the resulting composite material is designated CN / CTS-2. All other process steps and parameters are the same as in Example 1.

[0055] Example 3

[0056] A method for preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material is disclosed, differing from Example 1 only in that the amount of Cu3SnS4 quantum dot solution added in step (3) is 0.75 mL, and the resulting composite material is designated CN / CTS-3. All other process steps and parameters are the same as in Example 1.

[0057] Example 4

[0058] A method for preparing Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material is disclosed, differing from Example 1 only in that the amount of Cu3SnS4 quantum dot solution added in step (3) is 1 mL, and the resulting composite material is designated CN / CTS-4. All other process steps and parameters are the same as in Example 1.

[0059] The Pt / g-C3N4 nanosheet composite material obtained in this embodiment can efficiently utilize solar energy to achieve photocatalytic water splitting for hydrogen production. Compared with other methods, it is technologically advanced, energy-saving, low-consumption, and green and non-toxic. Within 4 hours of visible light irradiation, the hydrogen production rate of the CN / CTS-3 composite catalyst obtained in Example 3 reached 4.49 mmol·g⁻¹. -1 ·h -1 Furthermore, this composite catalyst also exhibits excellent stability.

[0060] Comparative Example 1

[0061] A method for preparing a Pt / g-C3N4 nanosheet composite material includes the following steps:

[0062] (1) Preparation of g-C3N4 nanosheets

[0063] Weigh 5g of melamine and 8g of urea into beakers using an analytical balance, add 70mL of deionized water, and stir continuously on a magnetic stirrer for 3 hours until homogeneous. Transfer the mixture to a hydrothermal synthesis reactor and react at 180℃ for 20 hours. After the reaction, wash the resulting precipitate three times with deionized water, then dry it in a 60℃ electric drying oven for 12 hours. Next, place the precipitate in a crucible and put it in a muffle furnace, heating it to 500℃ at a rate of 2.5℃ / min and holding for 4 hours for heat treatment to obtain g-C3N4 nanosheets, abbreviated as CN.

[0064] (2) Place 100 mg of CN sample in a quartz glass reactor, add 240 mL of deionized water, and add 135 μL of chloroplatinic acid solution (0.02 mol / L) under magnetic stirring. After stirring evenly, evacuate the reactor to a pressure less than 3 kPa. Turn on the xenon lamp and perform photodeposition under full-spectrum light irradiation for 1 h. After the reaction is complete, centrifuge the mixture, wash the resulting precipitate three times with deionized water and dry it to obtain Pt / g-C3N4 nanosheet composite material, abbreviated as CN / Pt-0.5. The number 0.5 represents the mass percentage of Pt in the composite material.

[0065] Comparative Example 2

[0066] A method for preparing a Pt / g-C3N4 nanosheet composite material differs from Comparative Example 1 only in that the amount of chloroplatinic acid solution (0.02 mol / L) added is 270 μL, and the resulting Pt / g-C3N4 nanosheet composite material is denoted as CN / Pt-1. All other process steps and parameters are the same as in Comparative Example 1.

[0067] Comparative Example 3

[0068] A method for preparing a Pt / g-C3N4 nanosheet composite material differs from Comparative Example 1 only in that the amount of chloroplatinic acid solution (0.02 mol / L) added is 405 μL, and the resulting Pt / g-C3N4 nanosheet composite material is denoted as CN / Pt-1.5. All other process steps and parameters are the same as in Comparative Example 1.

[0069] Comparative Example 4

[0070] A method for preparing a Pt / g-C3N4 nanosheet composite material differs from Comparative Example 1 only in that the amount of chloroplatinic acid solution (0.02 mol / L) added is 473 μL, and the resulting Pt / g-C3N4 nanosheet composite material is denoted as CN / Pt-1.75. All other process steps and parameters are the same as in Comparative Example 1.

[0071] Comparative Example 5

[0072] A method for preparing a SnS2 / g-C3N4 nanosheet composite material, differing from Comparative Example 1 only in that Cu3SnS4 quantum dots are replaced with SnS2 nanosheets, specifically including the following steps:

[0073] (1) Preparation of g-C3N4 nanosheets

[0074] 5g of melamine and 8g of urea were weighed into beakers using an analytical balance, and 70mL of deionized water was added. The mixture was stirred continuously on a magnetic stirrer for 3 hours until homogeneous, and then transferred to a hydrothermal synthesis reactor. The mixture was reacted at 180℃ for 20 hours. After the reaction, the resulting precipitate was washed three times with deionized water and then dried in a 60℃ electric drying oven for 12 hours. The precipitate was then placed in a crucible and placed in a muffle furnace, where it was heated to 500℃ at a rate of 2.5℃ / min and held for 4 hours for heat treatment to obtain g-C3N4 nanosheets, abbreviated as CN.

[0075] (2) Preparation of SnS2 quantum dots

[0076] Weigh 0.035 g of tin tetrachloride using an analytical balance and place it in a three-necked flask. Use a pipette to transfer 3 mL of dodecanethiol and a graduated cylinder to measure 12 mL of octadecene, add them to the three-necked flask, and mix thoroughly with the tin tetrachloride. Continuously purge the three-necked flask with nitrogen gas and stir at room temperature for 15 min. Then, raise the temperature to 110 °C and maintain stirring for 30 min, further raise the temperature to 270 °C, and stir for 1 h. After the reaction is complete, allow it to cool naturally to room temperature, wash with n-hexane, centrifuge at high speed, and store in n-hexane to obtain a SnS2 quantum dot solution with a concentration of 3.6 mg / mL.

[0077] (3) Preparation of SnS2 / g-C3N4 nanosheet composite material

[0078] 200 mg of g-C3N4 nanosheets obtained in step (1) were uniformly dispersed in 5 mL of n-hexane, followed by the addition of 2 mL of SnS2 solution and vigorous stirring for 2 h. The mixture was then placed in an electric thermostatic drying oven and vacuum dried for 2 h (60 °C) to obtain SnS2 / g-C3N4 nanosheet composite material, wherein the mass fraction of SnS2 was 3%.

[0079] Comparative Example 6

[0080] A method for preparing CdS / g-C3N4 dual nanosheets includes the following steps:

[0081] 10 mg of CdCl₂·2.5H₂O was dispersed in 30 mL of DETA and placed in a 100 mL flask. After ultrasonic dispersion, 10 mg of sulfur powder and 200 mg of g-C₃N₄ nanosheets were added and stirred thoroughly. The flask was then placed in an 80 °C oil bath for 10 h. After cooling to room temperature, the mixture was centrifuged, washed, and dried to obtain CdS / g-C₃N₄ binanosheets, wherein the mass fraction of CdS was 3%.

[0082] Technical effects:

[0083] 1. Performance Characterization

[0084] Figure 1The XRD patterns of the g-C3N4 nanosheets obtained in step (1) of Examples 1-4 and the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material obtained in step (3) are shown in the figures. It can be seen from the figures that the structure of g-C3N4 in both the g-C3N4 nanosheets and the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material remains unchanged. Furthermore, when the mass fraction of Cu3SnS4 quantum dots exceeds 3%, characteristic diffraction peaks of Cu3SnS4 can be detected in the composite sample, indicating that both Cu3SnS4 quantum dots and g-C3N4 nanosheets are pure phases.

[0085] Figure 2 The image shown is a transmission electron microscope (TEM) image of the CN / CTS-3 composite material obtained in Example 3. Figure 2 It can be seen that the g-C3N4 nanosheets do not show obvious lattice fringes. In the CN / CTS-3 composite material, the Cu3SnS4 quantum dots are about 10 nm in size and are deposited on the surface of the g-C3N4 nanosheets.

[0086] Figure 3 The UV-Vis-NIR absorption spectra of the g-C3N4 nanosheets obtained in step (1) of Example 1 and the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material obtained in Example 3 are shown below. Figure 3 As can be seen, after loading with Cu3SnS4 quantum dots, the absorption intensity of the CN / CTS-3 composite sample in the ultraviolet to near-infrared range is significantly enhanced compared to g-C3N4 nanosheets. The absorption performance in the near-infrared range indicates that the CN / CTS-3 composite sample can generate a photothermal effect.

[0087] The surface temperature changes of g-C3N4 nanosheets and CN / CTS-3 under visible light (λ≥420nm) irradiation were tested. Figure 4 As shown, the results indicate that the surface temperature of g-C3N4 nanosheets stabilizes at 60℃ after 2 minutes of illumination, while the CN / CTS-3 composite sample, after being loaded with Cu3SnS4 quantum dots, can reach 159℃ under the same illumination conditions. This demonstrates that Cu3SnS4 quantum dots exhibit a photothermal effect.

[0088] 2. Photocatalytic performance

[0089] The photocatalytic efficiency of different samples in producing hydrogen through water splitting under visible light (λ≥420nm) was tested in a closed-loop glass system (OLPCRS-2). One end of this evaluation system was connected to a vacuum pump, and the other end to a gas chromatograph to monitor hydrogen production over a specific time period. The light source was an HXS-F / UV ​​300 xenon lamp from Beijing Newbit Technology Co., Ltd., with a current of 15A and a visible light wavelength range of λ≥420nm.

[0090] The specific experimental procedure is as follows: 0.1g of the g-C3N4 nanosheets obtained in step (1) of Example 1, and the composite materials of Examples 1-4 and Comparative Examples 1-4 were dispersed in 240mL of deionized water, respectively. 20mL of triethanolamine was added as a hole sacrificial agent under magnetic stirring. After stirring evenly, the reactor was installed on the system, and the system was evacuated to a pressure less than 3kPa. The xenon lamp was turned on, and the water splitting reaction was carried out under visible light. Samples were taken every 1 hour, and the products were analyzed by online gas chromatography.

[0091] Figure 5 The graph shows the photocatalytic hydrogen production rate of g-C3N4 nanosheets and Cu3SnS4 quantum dots / g-C3N4 nanosheet composites under visible light (λ≥420nm). The graph shows that the g-C3N4 nanosheet sample without a deposited co-catalyst showed no hydrogen production activity after 4 hours of illumination. The photocatalytic hydrogen production rate of the samples after combining g-C3N4 nanosheets with Cu3SnS4 quantum dots was significantly improved. The CN / CTS-3 sample showed the highest hydrogen production rate, reaching 4.49 mmol·g⁻¹ within 4 hours of illumination. -1 ·h -1 The relationship between the loading of Cu3SnS4 quantum dots and their performance was obtained through photocatalytic water splitting for hydrogen production. When the loading was below 3%, the separation efficiency of photogenerated carriers did not reach its maximum due to the low content. When the loading was above 3%, it would cover the active sites on the surface of g-C3N4 nanosheets, thus reducing the photocatalytic performance. Therefore, the performance of the prepared product can be controlled by adjusting the content of Cu3SnS4 quantum dots according to requirements.

[0092] The CN / CTS-3 sample with the highest hydrogen production rate was compared with the Pt / g-C3N4 nanosheet composite material, as shown in Table 1:

[0093] Table 1

[0094]

[0095]

[0096] As can be seen from the data in Table 1, under visible light (λ≥420nm) irradiation, within 4 hours of reaction, the hydrogen production rate of the CN / CTS-3 sample was similar to that of the CN / Pt-1.75 (4.06mmol·g) sample. -1 ·h -1 The results are similar. This indicates that the synthesized Cu3SnS4 quantum dots can serve as an effective co-catalyst, improving the photocatalytic water splitting performance of g-C3N4 nanosheets for hydrogen production. Furthermore, without the deposition of the co-catalyst Pt, neither the SnS2 / g-C3N4 nanosheet nor the CdS / g-C3N4 nanosheet composite material exhibited photocatalytic water splitting performance for hydrogen production. This demonstrates that the process steps in this invention are irreplaceable.

[0097] 3. Photocatalytic stability

[0098] The photocatalytic stability of the CN / CTS-3 sample obtained in Example 3, which had the highest hydrogen production efficiency, was tested. For example... Figure 6 As shown, after three cycles of hydrogen production tests under visible light irradiation, the hydrogen production efficiency of the sample did not decrease significantly, indicating that the sample has good photocatalytic stability.

[0099] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite, characterized in that, Includes the following steps: The g-C3N4 nanosheet dispersion was mixed and stirred with Cu3SnS4 quantum dot solution, and then dried under vacuum to obtain the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material. The mass fraction of Cu3SnS4 quantum dots in the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material is 1-4%; The preparation method of the g-C3N4 nanosheets in the g-C3N4 nanosheet dispersion includes the following steps: Melamine and urea were mixed in solution and subjected to a hydrothermal reaction. After the reaction was completed, the resulting precipitate was dried and calcined to obtain the g-C3N4 nanosheets. The method for preparing Cu3SnS4 quantum dots in the Cu3SnS4 quantum dot solution includes the following steps: Cuprous chloride and tin tetrachloride were mixed in a solvent and heated under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, washed, and centrifuged. The resulting precipitate was then placed in n-hexane to obtain the Cu3SnS4 quantum dot solution. The heating reaction includes the following steps: stirring at room temperature for 15 minutes, then heating to 110°C and stirring for 30 minutes, then further heating to 270°C and stirring for 1 hour; The solvent is a mixture of dodecanethiol and octadecene.

2. The preparation method of Cu3SnS4 quantum dots / g-C3N4 nanosheet composite according to claim 1, characterized in that, The hydrothermal reaction was carried out at a temperature of 180°C for 20 hours.

3. The method for preparing a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material according to claim 1, characterized in that, The calcination was carried out by heating to 500°C at a heating rate of 2.5°C / min and calcining for 4 hours.

4. The method for preparing a Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material according to claim 1, characterized in that, The solvent is a mixture of dodecanethiol and octadecene in a volume ratio of 1:

4.

5. The Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material prepared by the preparation method according to any one of claims 1-4.

6. The application of the Cu3SnS4 quantum dot / g-C3N4 nanosheet composite material according to claim 5 in photocatalytic water splitting for hydrogen production.

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