Method for photocatalytic hydrogen production using zinc indium sulfide / manganese sulfide heterojunction composite material

Abstract

This invention discloses a method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material. The method uses this composite material as a photocatalyst for hydrogen production, wherein the indium zinc sulfide / manganese sulfide heterojunction composite material comprises manganese sulfide (α-MnS) and indium zinc sulfide (ZnIn2S4). The indium zinc sulfide / manganese sulfide heterojunction composite material used in this invention is a p-n heterojunction composite photocatalyst composed of α-MnS and ZnIn2S4. On the one hand, it enhances photocatalytic activity; on the other hand, it enhances chemical stability. Therefore, using this high-performance indium zinc sulfide / manganese sulfide heterojunction composite material as a photocatalyst for photocatalytic hydrogen production can effectively improve the hydrogen production rate and yield. This is of great significance for promoting the widespread application of indium zinc sulfide-based photocatalysts in photocatalytic water splitting for hydrogen production under visible light.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic water splitting for hydrogen production, and relates to a method for photocatalytic hydrogen production, specifically a method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material. Background Technology

[0002] Photocatalytic water splitting to produce hydrogen is considered an effective way to solve the world's energy crisis. This technology can use sunlight to generate renewable energy. Developing renewable and green hydrogen energy through photocatalysis can reduce dependence on fossil fuels. Therefore, semiconductor-based photocatalytic water separation is considered a promising and cost-effective method to achieve a sustainable hydrogen supply.

[0003] ZnIn₂S₄ is a ternary sulfide belonging to the AB₂X₄ group of ternary compounds. It is a layered semiconductor with a narrow bandgap, which is tunable (2.06 eV–2.85 eV). However, ZnIn₂S₄ tends to aggregate because it exists in a two-dimensional plate-like structure. This reduces the specific surface area of ​​the catalyst and the exposed active sites in the reaction system. Furthermore, its high recombination rate of photogenerated carriers means that the photocatalytic efficiency of a single ZnIn₂S₄ component in water splitting for hydrogen production is not ideal. This significantly limits the application of indium zinc sulfide in the photocatalytic splitting of water for hydrogen production. For the reasons mentioned above, some researchers have proposed strategies to improve photocatalytic performance by constructing heterojunctions. This involves loading semiconductors onto the surface of ZnIn2S4 nanosheets or ZnIn2S4 nanospheres to form heterojunctions. For example, loading CdS nanospheres onto ZnIn2S4 nanosheets forms a CdS / ZnIn2S4 nanocomposite material, and loading ZnS nanoparticles onto the surface of ZnIn2S4 nanospheres forms a ZnS / ZnIn2S4 nanocomposite material. However, these nanocomposite materials still suffer from low hydrogen yield and poor reusability when used for photocatalytic hydrogen production. This may be because both CdS and ZnS in the nanocomposite materials are n-type semiconductors, thus forming an n-type heterojunction with ZnIn2S4. The lack of a built-in electric field in n-type heterojunctions results in low photogenerated carrier mobility, leading to poor photocatalytic performance of the composite material and hindering effective improvement in hydrogen production. Furthermore, the nanocomposite materials used still suffer from limitations such as small specific surface area, few surface active sites, and poor light absorption, further hindering photocatalytic performance and resulting in low hydrogen production rates and yields. In particular, directly loading CdS nanospheres or ZnS nanoparticles onto the surface of ZnIn2S4 nanosheets or nanospheres leads to low bonding strength and poor structural stability, making them prone to detachment. Moreover, photocorrosion during hydrogen production ultimately causes the composite material to disintegrate or fail, making it difficult to reuse. Furthermore, the aforementioned methods for preparing nanocomposites all involve first preparing ZnIn₂S₄, then preparing CdS nanospheres or ZnS nanoparticles via a hydrothermal reaction and loading them onto ZnIn₂S₄. This preparation method is one of the reasons for the poor structural stability of the composite materials and requires further improvement. Therefore, obtaining a ZnIn₂S₄-based composite photocatalyst with a large specific surface area, numerous surface active sites, strong light absorption capacity, high photocatalytic activity, and stable physicochemical properties, along with a matching simple, convenient, low-cost, and highly efficient preparation method, is of great significance for improving the photocatalytic hydrogen production effect of ZnIn₂S₄-based composite photocatalysts and promoting their widespread application in photocatalytic water splitting for hydrogen production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite materials, which is simple in process, convenient in operation, has high hydrogen production efficiency, high hydrogen production capacity, good reusability, and no secondary pollution.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for photocatalytic hydrogen production using a zinc indium sulfide / manganese sulfide heterojunction composite material, wherein the zinc indium sulfide / manganese sulfide heterojunction composite material is used as a photocatalyst for photocatalytic hydrogen production; the zinc indium sulfide / manganese sulfide heterojunction composite material includes manganese sulfide and zinc indium sulfide; the chemical formula of manganese sulfide is α-MnS; and the chemical formula of zinc indium sulfide is ZnIn2S4.

[0007] The above-mentioned method for photocatalytic hydrogen production using zinc sulfide / manganese sulfide heterojunction composite material is further improved in that the manganese sulfide exists in the form of manganese sulfide nanorods, and the zinc sulfide exists in the form of zinc sulfide nanosheets; the zinc sulfide nanosheets are loaded on the manganese sulfide nanorods to form a zinc sulfide / manganese sulfide heterojunction composite material.

[0008] The above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved in that the mass ratio of manganese sulfide nanorods to indium zinc sulfide nanosheets in the indium zinc sulfide / manganese sulfide heterojunction composite material is 1:1 to 4.

[0009] The above-mentioned method for photocatalytic hydrogen production using zinc sulfide / manganese sulfide heterojunction composite material is further improved in that the zinc sulfide / manganese sulfide heterojunction composite material is prepared by hydrothermal reaction using manganese sulfide nanorods, sulfur source, zinc source, and indium source as raw materials; the mass ratio of manganese sulfide nanorods, sulfur source, zinc source, and indium source is 1-10:4-7:1-4:8-12.

[0010] The above-mentioned method for photocatalytic hydrogen production using zinc sulfide / manganese sulfide heterojunction composite material is further improved in that the mass ratio of manganese sulfide nanorods, sulfur source, zinc source, and indium source is 1-6:4-7:1-4:8-12.

[0011] A further improvement to the above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite materials is that the preparation method of the indium zinc sulfide / manganese sulfide heterojunction composite material includes the following steps:

[0012] S1. Manganese sulfide nanorods are mixed with zinc indium sulfide solution to obtain a precursor solution; the zinc indium sulfide solution is a mixed solution made of sulfur source, zinc source and indium source;

[0013] S2. The precursor solution obtained in step S1 is subjected to a hydrothermal reaction to obtain an indium zinc sulfide / manganese sulfide heterojunction composite material.

[0014] A further improvement to the above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite materials is that, in step S1, the preparation method of the manganese sulfide nanorods includes the following steps:

[0015] (1) Manganese acetate, lithium hydroxide, and thiourea are mixed and ground for 8 to 10 minutes to obtain a mixed powder; the mass ratio of manganese acetate, lithium hydroxide, and thiourea is 2.45:4:4; the manganese acetate is Mn(CH3COO)2·4H2O; the lithium hydroxide is LiOH·H2O; the grinding time is 8 to 10 minutes.

[0016] (2) Add the mixed powder to the reaction vessel, heat to 180℃~210℃, maintain for 12±0.5 hours, centrifuge at 3000rpm~6000rpm for 8min~12min, wash the centrifuged product with water and ethanol in sequence, each washing 2 to 5 times, and dry under vacuum to obtain manganese sulfide nanorods; the drying temperature is 50℃~80℃, and the drying time is 10h~12h.

[0017] The above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved in step S2, wherein the hydrothermal reaction temperature is 140℃~180℃; the hydrothermal reaction time is 4h~10h; after the hydrothermal reaction is completed, the following treatment is further included: washing the hydrothermal reaction product sequentially with ethanol and water, each washing 3 times; centrifuging at 4000rpm~5000rpm for 8 minutes~12 minutes; and drying under vacuum conditions at a temperature of 60℃ for 10h~12h.

[0018] The above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved by using the indium zinc sulfide / manganese sulfide heterojunction composite material as a photocatalyst to carry out a photocatalytic reaction on a hydrogen-containing body, including the following steps: mixing the indium zinc sulfide / manganese sulfide heterojunction composite material with the hydrogen-containing body, carrying out a photocatalytic reaction under visible light irradiation, and collecting hydrogen.

[0019] The above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved in that the ratio of the indium zinc sulfide / manganese sulfide heterojunction composite material to the hydrogen-containing medium is 1 mg to 4 mg: 20 mL; the hydrogen-containing medium is water or an aqueous solution.

[0020] The above-mentioned method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved by including a sacrificial agent in the hydrogen-containing body; the volume fraction of the sacrificial agent in the hydrogen-containing body is ≤20%; and the sacrificial agent is triethanolamine.

[0021] The above-described method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material is further improved by including the following steps during the photocatalytic reaction: adding a co-catalyst to the reaction system; the mass ratio of the co-catalyst to the indium zinc sulfide / manganese sulfide heterojunction composite material is 0-1:5-15, and the amount of co-catalyst is not zero; the co-catalyst is platinum; and the photocatalytic reaction time is 2-20 hours.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) In view of the shortcomings of existing zinc sulfide-based photocatalysts, such as small specific surface area, few surface active sites, low photogenerated carrier mobility, poor catalytic activity, poor absorption capacity, and poor physicochemical stability, and the resulting defects such as difficulty in using visible light for efficient photocatalytic hydrogen production, poor reusability, and easy secondary pollution, this invention creatively proposes a method for photocatalytic hydrogen production using zinc sulfide / manganese sulfide heterojunction composite material. The zinc sulfide / manganese sulfide heterojunction composite material used is used as a photocatalyst for photocatalytic hydrogen production. The zinc sulfide / manganese sulfide heterojunction composite material includes manganese sulfide (α-MnS) and zinc sulfide (ZnIn2S4). By combining α-MnS and ZnIn2S4 together, a pn heterojunction can be formed, which is a pn heterojunction composite photocatalyst. In this invention, the formation of the pn heterojunction can, on the one hand, generate an internal electric field, providing electrostatic force for regulating charge transfer, effectively suppressing the recombination of photogenerated charges, indirectly promoting the separation of photogenerated electrons and holes, and further enhancing photocatalytic activity. On the other hand, it can also effectively prevent the self-oxidation of ZnIn2S4, thereby further enhancing the chemical stability of the photocatalyst. Therefore, using this high-performance indium zinc sulfide / manganese sulfide heterojunction composite material as a photocatalyst for photocatalytic hydrogen production can effectively improve the hydrogen production rate and hydrogen production amount. This is of great significance for promoting the widespread application of indium zinc sulfide-based photocatalysts in photocatalytic water splitting for hydrogen production under visible light.

[0024] (2) In this invention, the indium zinc sulfide / manganese sulfide heterojunction composite material uses manganese sulfide nanorods as the substrate material and loads indium zinc sulfide nanosheets on the manganese sulfide nanorods. On the one hand, manganese sulfide nanorods have a wide light absorption range, which can improve the light absorption capacity of indium zinc sulfide and is beneficial to improving the visible light utilization rate of the composite material. On the other hand, the manganese sulfide nanorods and the indium zinc sulfide nanosheets on their surface form a hierarchical structure, which is more conducive to the formation of pn heterojunctions. This can significantly improve the photoelectron mobility and reduce the recombination rate of photogenerated electrons and holes, and significantly improve the photocorrosion effect of indium zinc sulfide. As a result, the indium zinc sulfide / manganese sulfide heterojunction composite material exhibits excellent photocatalytic performance and stability. In addition, loading indium zinc sulfide nanosheets on manganese sulfide nanorods is also beneficial to increasing the specific surface area and the number of surface active sites of the composite material, thereby improving the hydrogen production efficiency and hydrogen yield of the indium zinc sulfide / manganese sulfide heterojunction composite material. The method of this invention utilizes an indium zinc sulfide / manganese sulfide heterojunction composite material, which possesses advantages such as large specific surface area, numerous surface active sites, strong light absorption capacity, high photogenerated carrier mobility, photocatalytic activity, and stable performance. When used as a photocatalyst, it efficiently photocatalyzes hydrogen production under visible light, significantly improving hydrogen production efficiency and hydrogen yield. It features simple process, convenient operation, high hydrogen production efficiency, high hydrogen yield, good reusability, and no secondary pollution. This method is widely applicable and can efficiently photocatalyze water splitting to produce hydrogen under visible light, possessing high application and commercial value.

[0025] (3) In this invention, by optimizing the amount of manganese sulfide nanorods, specifically, the mass ratio of manganese sulfide nanorods to indium zinc sulfide nanosheets in the zinc sulfide / manganese sulfide heterojunction composite material is 1:1 to 4, especially 1:2 to 3, which is more conducive to the formation of pn heterojunctions. At the same time, sufficient heterojunction interface is conducive to the most efficient transfer and maximum utilization of photogenerated charges, further ensuring the best hydrogen production effect of the composite material. However, too little manganese sulfide will result in incomplete recombination with all ZnIn2S4, thus failing to form a sufficient heterojunction interface, while excessive manganese sulfide loading may cover some active sites, destroying the original structure and thus reducing hydrogen production. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1The images show SEM images of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 of this invention, where (a) is MnS, (b) is ZIS, and (c) is ZM-2.

[0028] Figure 2 The images shown are TEM images of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 of this invention, where (a) is a TEM image and (b) is an HRTEM image.

[0029] Figure 3 The XRD diffraction patterns are those of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) prepared in Example 1 of this invention.

[0030] Figure 4 The UV-Vis diffuse reflectance images are of the manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) prepared in Example 1 of this invention.

[0031] Figure 5 This is a comparison chart of the photocatalytic water splitting hydrogen production effects of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) in Example 1 of the present invention.

[0032] Figure 6 This is a comparison chart showing the effect of photocatalytic water splitting for hydrogen production under different treatment conditions in Example 1 of the present invention.

[0033] Figure 7 This is a comparison diagram of the cyclic hydrogen production effect of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) in Example 2 of the present invention.

[0034] Figure 8 This is a comparison of XRD patterns before and after the reaction of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) in Example 2 of the present invention.

[0035] Figure 9 This is a comparison diagram of the photocatalytic water splitting to produce hydrogen in Example 3 of the present invention using the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) under different triethanolamine addition conditions.

[0036] Figure 10 This is a comparison diagram of the photocatalytic water splitting to produce hydrogen in Example 4 of the present invention under different co-catalyst addition amounts. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0038] The materials and instruments used in the following examples are all commercially available.

[0039] Example 1:

[0040] A method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material, specifically involving the photocatalytic reaction of water with the indium zinc sulfide / manganese sulfide heterojunction composite material to decompose water into hydrogen, includes the following steps:

[0041] 10 mg of zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) were weighed and added to 100 mL of a 10% triethanolamine aqueous solution. 0.2 mg (2 wt.%) of platinum was added, and the mixture was ultrasonically dispersed for 10 min. After vacuuming, the reactor was kept at 5 °C under circulating cooling water. A PLS-SXE300 xenon lamp equipped with a 420 nm filter was used as the light source, and the mixture was irradiated under simulated sunlight (visible light with λ≥420 nm) while stirring. The photocatalytic reaction was carried out for 4 h to complete the decomposition of water to produce hydrogen.

[0042] Control group 1: No photocatalyst, all other conditions are the same.

[0043] Control group 2: No light exposure, all other conditions are the same.

[0044] Control group 3: The photocatalyst used was manganese sulfide (MnS), and other conditions were the same.

[0045] Control group 4: The photocatalyst used was pure zinc indium sulfide (ZIS), and other conditions were the same.

[0046] In this embodiment, the method for preparing manganese sulfide (MnS) includes the following steps:

[0047] (1) Grind 2.45g Mn(CH3COO)2·4H2O, 4g LiOH·H2O and 4g thiourea evenly in a mortar, transfer them into a polytetrafluoroethylene reactor and react at 200℃ for 12 hours. After the reaction is completed, cool to room temperature and centrifuge at 4000rpm for 10min to separate the product.

[0048] (2) Wash the product from step (1) three times with water and three times with ethanol, collect the product, and vacuum dry it at 60°C for 12 hours.

[0049] In this embodiment, the preparation method of pure zinc indium sulfide (ZIS) includes the following steps:

[0050] (1) Add 204.5 mg ZnCl2, 879.7 mg InCl3·4H2O and 458.3 mg thioacetamide to 150 ml of deionized water, stir well, and then transfer 20 ml to a polytetrafluoroethylene reactor. Heat in a 160°C oven for 6 h and centrifuge at 4000 rpm for 10 min to separate the product.

[0051] (2) Wash the product from step (1) three times with ethanol and three times with water, collect the product, and dry it under vacuum at 60°C for 12 hours.

[0052] In this embodiment, the zinc indium sulfide / manganese sulfide pn heterojunction composite material (ZM-2) includes manganese sulfide nanorods and zinc indium sulfide nanosheets.

[0053] In this embodiment, the aforementioned zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) includes manganese sulfide (α-MnS) and zinc indium sulfide (ZnIn2S4). Specifically, manganese sulfide exists in the form of manganese sulfide nanorods, and zinc indium sulfide exists in the form of zinc indium sulfide nanosheets, with the zinc indium sulfide nanosheets loaded on the manganese sulfide nanorods to form the zinc indium sulfide / manganese sulfide heterojunction composite material. The mass ratio of manganese sulfide nanorods to zinc indium sulfide nanosheets in this zinc indium sulfide / manganese sulfide heterojunction composite material is 1:2.

[0054] In this embodiment, the preparation method of the above-mentioned zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) includes the following steps:

[0055] (1) Grind 2.45g Mn(CH3COO)2·4H2O, 4g LiOH·H2O and 4g thiourea evenly in a mortar, transfer them into a polytetrafluoroethylene reactor and react at 200℃ for 12 hours. After the reaction is completed, cool to room temperature and centrifuge at 4000rpm for 10min to separate the product.

[0056] (2) The product from step (1) was washed three times with water and three times with ethanol. The product was collected and dried under vacuum at 60°C for 12 hours to obtain manganese sulfide nanorods, denoted as MnS.

[0057] (3) Add 204.5 mg ZnCl2, 879.7 mg InCl3·4H2O and 458.3 mg thioacetamide to 150 mL of deionized water and stir to form a homogeneous solution.

[0058] (4) Take 20 mL of the solution from step (3), add 30 mg of MnS obtained in step (2), stir evenly, put it into a polytetrafluoroethylene reactor, heat it in an oven at 160 degrees for 6 hours, cool it to room temperature, rinse it three times with ethanol and water, put it into a vacuum drying oven, and vacuum dry it at 60 degrees for 12 hours to obtain the zinc indium sulfide / manganese sulfide heterojunction composite material, denoted as ZM-2.

[0059] In this embodiment, zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-4, ZM-3, and ZM-1) were prepared by adding 15 mg, 20 mg, and 60 mg of manganese sulfide, respectively. Other preparation conditions were the same as those for ZM-2. Furthermore, the mass ratio of manganese sulfide nanorods to zinc indium sulfide nanosheets in the zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-4, ZM-3, and ZM-1) was 1:4, 1:3, and 1:1, respectively.

[0060] Figure 1 SEM images of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 of this invention are shown, where (a) is MnS, (b) is ZIS, and (c) is ZM-2. Figure 1 It can be seen that the prepared MnS is in the form of nanorods, while ZIS and ZM-2 are both in the form of stacked sheet-like nanoflowers. The nanoflowers of ZM-2 have fewer layers than those of ZIS, and the gaps between the layers are larger.

[0061] Figure 2 These are TEM images of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 of this invention, where (a) is a TEM image and (b) is an HRTEM image. Figure 2 (a) It can be seen that ZM-2 is in the form of nanosheets, thick in the middle and thin on the outer layer. Figure 2 (b) It can be seen that the surface of ZM-2 exhibits lattice fringes of two monomers. The lattice fringes of manganese sulfide are 0.19 nm and have a (2 20) crystal plane, while the lattice fringes of indium sulfide are 0.32 nm and have a (1 0 2) crystal plane. This indicates that zinc indium sulfide was successfully grown in situ on the manganese sulfide substrate through a hydrothermal reaction. Combined with... Figure 1 The results show that manganese sulfide nanorods are encapsulated within indium zinc sulfide nanosheets, which helps to improve the structural stability of the composite material.

[0062] Figure 3 The images show the XRD diffraction patterns of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composites (ZM-1, ZM-2, ZM-3, ZM-4) prepared in Example 1 of this invention. Figure 3It can be seen that the prepared MnS and ZIS monomers correspond to the diffraction peaks of α-MnS (PDF 88-2223) and hexagonal ZIS (PDF No. 72-0773), respectively. At the same time, the diffraction peaks of the indium zinc sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) samples contain obvious characteristic peaks of α-MnS (PDF 88-2223) and hexagonal ZIS (PDF No. 72-0773), respectively, indicating that indium zinc sulfide was successfully grown in situ on the manganese sulfide substrate after hydrothermal reaction.

[0063] Figure 4 The images show the UV-Vis diffuse reflectance of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composites (ZM-1, ZM-2, ZM-3, ZM-4) prepared in Example 1 of this invention. Figure 4 It can be seen that, compared with pure ZIS, the addition of MnS improves its light absorption capacity in the infrared region. All composite materials show some improvement in the infrared region, with ZM-2 exhibiting the strongest light absorption capacity in this region. Therefore, the light absorption region of ZM-2 after the hydrothermal reaction is slightly broadened, and the light absorption in the 400nm-800nm ​​range is enhanced. This indicates that the introduction of MnS increases the light absorption capacity of the original ZIS.

[0064] The products from the reaction process are automatically injected once every hour and analyzed by gas chromatography to obtain the results of photocatalytic water splitting for hydrogen production using different photocatalysts, such as... Figure 5 As shown.

[0065] Figure 5 This is a comparison chart showing the photocatalytic water splitting and hydrogen production effects of manganese sulfide (MnS), pure zinc indium sulfide (ZIS), and zinc indium sulfide / manganese sulfide heterojunction composite materials (ZM-1, ZM-2, ZM-3, ZM-4) in Example 1 of this invention. Figure 5It can be seen that under visible light irradiation, with a sacrificial agent triethanolamine addition of 10% and a co-catalyst platinum addition of 0.2 mg (2 wt.%), the hydrogen production of ZM-2 reached 5.95 mmol / g / h after 4 h of reaction, which is far superior to other composite materials with different ratios. This is likely due to its suitable manganese sulfide loading. Furthermore, ZM-1 has a higher manganese sulfide loading, and its hydrogen production is similar to that of pure ZIS (1.51 mmol / g / h). In ZM-3, the hydrogen production is lower than that of ZM-2 (5.04 mmol / g / h), possibly due to insufficient manganese sulfide loading. Therefore, thanks to the tight bonding and suitable ratio between the composite materials, ZM-2 possesses the best light absorption capacity and visible light-based water splitting hydrogen production capability. The hydrogen production capacity of ZM-2 is 3.5 times that of pure ZIS (1.68 mmol / g / h). This may be due to the formation of a pn heterojunction between manganese sulfide and zinc indium sulfide, which creates an internal electric field at the interface, promoting charge transfer and separation of the carrier, thus making the hydrogen production performance of ZM-2 superior to that of ZIS.

[0066] Figure 6 This is a comparison chart showing the effect of photocatalytic water splitting for hydrogen production under different treatment conditions in Example 1 of the present invention. Figure 6 It is evident that the hydrogen production from water splitting is very low without a photocatalyst or light. After adding 10 mg of manganese sulfide (MnS) and pure zinc indium sulfide (ZIS) and reacting for 4 h, the hydrogen production rates from water splitting were only 0.01 mmol / g / h and 1.68 mmol / g / h, respectively. Under the same conditions, the hydrogen production rates of the zinc indium sulfide / manganese sulfide heterojunction composites ZM-2, ZM-3, and ZM-4 were 5.95 mmol / g / h, 5.04 mmol / g / h, and 3.30 mmol / g / h, respectively. Therefore, the hydrogen production effect of ZM-2 is far superior to that of its constituent monomers. Furthermore, through comparisons with other components, it can be seen that the sacrificial agent triethanolamine, the co-catalyst platinum, the photocatalyst, and the light source are all indispensable in this photocatalytic reaction system.

[0067] Example 2:

[0068] A method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material, specifically involving the repeated use of the indium zinc sulfide / manganese sulfide heterojunction composite material to perform a photocatalytic reaction on water, decomposing water into hydrogen, includes the following steps:

[0069] 10 mg of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 was weighed and added to 100 mL of a 10% (v / v) triethanolamine aqueous solution. 0.2 mg (2 wt.%) of platinum was added, and the mixture was sonicated for 10 minutes. The mixture was then placed in a reactor and magnetically stirred at 300 rpm. The sealed system was then evacuated to a vacuum, and the reactor was kept at 5°C under circulating cooling water. A PLS-SXE300 xenon lamp with a 420 nm filter was used as the light source for the photocatalytic reaction. A 4-hour cycle was performed. After each cycle, the reactor was removed, and the reaction solution was centrifuged at 4000 rpm for 10 minutes to separate the photocatalyst ZM-2. The ZM-2 was then vacuum-dried overnight at 60°C. The dried ZM-2 was remixed with 100 mL of a 10% triethanolamine aqueous solution, and the reaction solution was refilled into the reactor. The sealed system was evacuated to a vacuum, and the reactor was maintained at 5°C under circulating cooling water. A PLS-SXE300 xenon lamp equipped with a 420nm filter was used as the light source to conduct the photocatalytic reaction again. The above steps were repeated for 4 cycles. During the photocatalytic reaction, samples were automatically injected every hour and analyzed by gas chromatography to obtain the cyclic experimental results of ZM-2's photocatalytic water splitting for hydrogen production.

[0070] Figure 7 This is a comparison chart of the cyclic hydrogen production performance of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) in Example 2 of this invention. Figure 7 It can be seen that after four consecutive cycles of 16 hours of photocatalytic water splitting to produce hydrogen, the activity of ZM-2 hardly decreased, indicating that ZM-2 has excellent photocatalytic stability.

[0071] Figure 8 This is a comparison of XRD patterns before and after the reaction of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) in Example 2 of this invention. Figure 8 It can be seen that the XRD pattern of ZM-2 did not change significantly before and after illumination, and the characteristic peaks of ZM-2 crystals were still well preserved, indicating that illumination does not damage the crystal structure of ZM-2 and that it has good stability.

[0072] Example 3:

[0073] A method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material, specifically involving the photocatalytic reaction of water with the indium zinc sulfide / manganese sulfide heterojunction composite material to decompose water into hydrogen, includes the following steps:

[0074] Four portions (10 mg each) of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 were weighed and added to 100 mL of pure aqueous solutions containing 0%, 5%, 10%, and 15% (volume fraction) triethanolamine, respectively. 0.2 mg (2%) of platinum co-catalyst was added to each solution. After sonication for 10 minutes, the solutions were placed in a reactor and magnetically stirred at 300 rpm. The sealed system was then evacuated to a vacuum, and the reactor was kept at 5°C under circulating cooling water. A PLS-SXE300 xenon lamp equipped with a 420 nm filter was used as the light source for photocatalytic reaction for 4 hours to complete the decomposition of water to produce hydrogen. During the photocatalytic reaction, samples were automatically injected every hour and analyzed by gas chromatography to obtain the photocatalytic water decomposition hydrogen production effect of ZM-2 under different concentrations of triethanolamine.

[0075] Figure 9 This is a comparison diagram showing the photocatalytic water splitting for hydrogen production of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) in Example 3 of the present invention under different triethanolamine addition levels. Figure 9 It can be seen that, under the same conditions, the ZM-2 composite material exhibits the best photocatalytic water splitting hydrogen production performance (5.95 mmol / g / h) when the triethanolamine content in the pure aqueous solution is 10%, which is better than the hydrogen production corresponding to triethanolamine contents of 5% (2.77 mmol / g / h), 15% (3.48 mmol / g / h), and so on. This may be because ZM-2 generates a large number of holes after illumination. Excessive holes will recombine with photogenerated electrons, thereby weakening the photocatalytic activity of the material. A certain amount of sacrificial agent triethanolamine is needed to quench the holes. However, when the content of sacrificial agent triethanolamine is further increased to 15%, the hydrogen production of the material decreases instead of increasing. This may be because excessively high triethanolamine content is not conducive to the dispersion of the photocatalyst and affects the light absorption capacity of the photocatalyst. Based on this result, we selected a 10% triethanolamine aqueous solution as the optimal concentration of sacrificial agent.

[0076] Example 4:

[0077] A method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material, specifically involving the photocatalytic reaction of water with the indium zinc sulfide / manganese sulfide heterojunction composite material to decompose water into hydrogen, includes the following steps:

[0078] Five portions (10 mg each) of the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) prepared in Example 1 were weighed and added to 100 mL of a pure aqueous solution containing 10% triethanolamine. Then, 0 mg, 0.1 mg, 0.2 mg, 0.3 mg, and 0.4 mg of platinum co-catalyst were added, corresponding to platinum mass fractions of 0%, 1%, 2%, 3%, and 4%, respectively. After sonication for 10 minutes, the mixture was placed in a reactor and magnetically stirred at 300 rpm. The sealed system was then evacuated to a vacuum, and the reactor was maintained at 5°C under circulating cooling water. A PLS-SXE300 xenon lamp equipped with a 420 nm filter was used as the light source to perform a photocatalytic reaction for 4 hours, completing the decomposition of water to produce hydrogen. During the photocatalytic reaction, samples were automatically injected every hour and analyzed by gas chromatography to obtain the photocatalytic water decomposition hydrogen production effect of ZM-2 under different mass platinum co-catalyst conditions.

[0079] Figure 10 This is a comparison diagram of the photocatalytic water splitting for hydrogen production in Example 4 of this invention, using the zinc indium sulfide / manganese sulfide heterojunction composite material (ZM-2) under different co-catalyst addition amounts. Figure 10 It can be seen that when the amount of platinum added is 0.1 mg, 0.2 mg, 0.3 mg, and 0.4 mg, the hydrogen production of ZM-2 is 3.67 mmol / g / h, 5.95 mmol / g / h, 7.96 mmol / g / h, and 6.48 mmol / g / h, respectively. This shows that the addition of the platinum co-catalyst provides reactive sites on the ZM-2 surface, and the hydrogen production of ZM-2 increases significantly after the addition of platinum. Figure 10 It can be seen that, under the same conditions, when the amount of Pt added is 3% and 4%, the hydrogen production effect of ZM-2 is not much different. This is because the more Pt added, the more likely the Pt particles will agglomerate, which will affect the light absorption of the material.

[0080] In summary, the indium zinc sulfide / manganese sulfide heterojunction composite material prepared by this invention has advantages such as large specific surface area, numerous surface active sites, strong light absorption capacity, high photogenerated carrier mobility, photocatalytic activity, and stable performance. When used as a photocatalyst, it can efficiently produce hydrogen under visible light. Specifically, the method of using the indium zinc sulfide / manganese sulfide heterojunction composite material for photocatalytic hydrogen production has advantages such as simple process, convenient operation, high hydrogen production efficiency, high hydrogen production volume, and no secondary pollution. It is a widely applicable method that can efficiently produce hydrogen by photocatalytically splitting water under visible light, and has high application and commercial value.

[0081] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material, characterized in that, The method uses an indium zinc sulfide / manganese sulfide heterojunction composite material as a photocatalyst for photocatalytic hydrogen production. The indium zinc sulfide / manganese sulfide heterojunction composite material comprises manganese sulfide and indium zinc sulfide. The chemical formula of manganese sulfide is α-MnS; the chemical formula of indium zinc sulfide is ZnIn2S4. The manganese sulfide exists in the form of manganese sulfide nanorods, and the indium zinc sulfide exists in the form of indium zinc sulfide nanosheets. The indium zinc sulfide nanosheets are loaded onto the manganese sulfide nanorods to form the indium zinc sulfide / manganese sulfide heterojunction composite material. The mass ratio of manganese sulfide nanorods to indium zinc sulfide nanosheets in the indium zinc sulfide / manganese sulfide heterojunction composite material is 1:2 to 3.

2. The method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 1, characterized in that, The zinc sulfide / manganese sulfide heterojunction composite material is prepared by hydrothermal reaction using manganese sulfide nanorods, sulfur source, zinc source and indium source as raw materials; the mass ratio of manganese sulfide nanorods, sulfur source, zinc source and indium source is 1~10∶4~7∶1~4∶8~12.

3. The method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 2, characterized in that, The mass ratio of the manganese sulfide nanorods, sulfur source, zinc source, and indium source is 1–6:4–7:1–4:8–12.

4. The method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 3, characterized in that, The preparation method of the indium zinc sulfide / manganese sulfide heterojunction composite material includes the following steps: S1. Manganese sulfide nanorods are mixed with zinc indium sulfide solution to obtain a precursor solution; the zinc indium sulfide solution is a mixed solution made of sulfur source, zinc source and indium source; S2. The precursor solution obtained in step S1 is subjected to a hydrothermal reaction to obtain an indium zinc sulfide / manganese sulfide heterojunction composite material.

5. The method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 4, characterized in that, In step S1, the preparation method of the manganese sulfide nanorods includes the following steps: (1) Manganese acetate, lithium hydroxide and thiourea are mixed and ground for 8 to 10 minutes to obtain a mixed powder; the mass ratio of manganese acetate, lithium hydroxide and thiourea is 2.45:4:4; the manganese acetate is Mn(CH3COO)2·4H2O; the lithium hydroxide is LiOH·H2O; (2) Add the mixed powder obtained in step (1) into the reaction vessel, heat it to 180℃~210℃, maintain it for 12±0.5 hours, centrifuge it at 3000rpm~6000rpm for 8 min~12 min, wash the centrifuged product with water and ethanol in sequence, each washing 2 to 5 times, and dry it under vacuum to obtain manganese sulfide nanorods; the drying temperature is 50℃~80℃, and the drying time is 10h~12h; In step S2, the hydrothermal reaction temperature is 140℃~180℃; the hydrothermal reaction time is 4h~10h; after the hydrothermal reaction is completed, the following treatment is also included: washing the hydrothermal reaction product with ethanol and water sequentially, each washing 3 times; centrifuging at 4000 rpm~5000 rpm for 8 minutes~12 minutes; drying under vacuum conditions, the drying temperature is 60℃, and the drying time is 10h~12h.

6. The method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material according to any one of claims 1 to 5, characterized in that, The photocatalytic reaction of hydrogen-containing materials using zinc indium sulfide / manganese sulfide heterojunction composite material as a photocatalyst includes the following steps: mixing zinc indium sulfide / manganese sulfide heterojunction composite material with hydrogen-containing materials, carrying out photocatalytic reaction under visible light irradiation, and collecting hydrogen gas.

7. The method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 6, characterized in that, The ratio of the indium sulfide zinc / manganese sulfide heterojunction composite material to the hydrogen-containing medium is 1 mg to 4 mg: 20 mL; the hydrogen-containing medium is water or an aqueous solution.

8. The method for photocatalytic hydrogen production using indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 7, characterized in that, The hydrogen-containing body also includes a sacrificial agent; the volume fraction of the sacrificial agent in the hydrogen-containing body is ≤20%; the sacrificial agent is triethanolamine.

9. The method for photocatalytic hydrogen production using an indium zinc sulfide / manganese sulfide heterojunction composite material according to claim 8, characterized in that, The photocatalytic reaction process further includes: adding a co-catalyst to the reaction system; the mass ratio of the co-catalyst to the zinc indium sulfide / manganese sulfide heterojunction composite material is 0-1:5-15, and the amount of co-catalyst is not 0; the co-catalyst is platinum; and the photocatalytic reaction time is 2h-20h.

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