CdS / CoSe@MoS2 composite photocatalyst, preparation method and application

Abstract

The application discloses a CdS / CoSe@MoS2 composite photocatalyst, which comprises a CdS base, CoSe connected to the surface of the CdS base through a Co-S covalent bond, and MoS2 connected to the surface of the CoSe; the mass ratio of Co, Mo and the CdS base is 1-4:1-4:100. By introducing CoSe as a heterophase between CdS and MoS2, a core-shell structure CoSe@MoS2 cocatalyst is constructed. The structure can drive the photo-generated electrons to migrate from the CoSe core to the MoS2 shell, so that the S site is converted into an electron-rich state S (2+δ)‑ . The increase of the electron density improves the occupation state of the S-H ad anti-bonding orbital, thereby weakening the S-H ad bond energy, significantly accelerating the H ad desorption process, and finally greatly improving the hydrogen evolution efficiency.

Description

Technical Field

[0001] This invention relates to the field of catalyst materials technology, and in particular to CdS / CoSe@MoS2 composite photocatalysts, their preparation methods, and applications. Background Technology

[0002] In related technologies, metal sulfides are often used as highly efficient cocatalysts to replace noble metals due to their unique electronic structure, suitable band gap width, and excellent photoelectrochemical properties. When metal sulfides are used as cocatalysts, the sulfur (S) atoms on their surface are the key active sites for the photocatalytic hydrogen evolution reaction. During the reaction, the hydrogen intermediate (H... ad SH formed with S atoms ad The strength of the bond directly affects the H ad The adsorption and desorption kinetics are in equilibrium. Excessive SH... ad The bond will cause H ad Excessive occupation of active sites hinders the generation and desorption of hydrogen molecules, while excessively weak bonding is detrimental to initial adsorption. Summary of the Invention

[0003] In view of this, the present invention proposes a CdS / CoSe@MoS2 composite photocatalyst, its preparation method, and its application, aiming to solve the problem that the S sites of metal sulfide co-catalysts are usually in an electron-deficient state after being combined with photocatalysts. (2-δ)- , which led to SH ad The excessively strong bond formation hindered the desorption of hydrogen.

[0004] In a first aspect, the CdS / CoSe@MoS2 composite photocatalyst proposed in this invention includes a CdS matrix, CoSe covalently bonded to the surface of the CdS matrix via Co-S bonds, and MoS2 bonded to the surface of the CoSe; the mass ratio of Co, Mo, and CdS matrix is ​​1-4:1-4:100.

[0005] As can be seen from the above technical solutions, the CdS / CoSe@MoS2 composite photocatalyst proposed in the first aspect of this invention, by connecting CoSe to the CdS surface as a heterophase, achieves the directional migration of photogenerated electrons generated by CdS under light source irradiation from CoSe to the MoS2 shell. This structure can drive the directional migration of photogenerated electrons from the CoSe core to the MoS2 shell, causing its S sites to transform into an electron-rich state. (2+δ)- The increase in electron density enhances SH ad The antibonding orbital occupancy state weakens SH. ad The strength of the bond energy significantly accelerates the H... ad The desorption process. Among them, CdS / CoSe@MoS2 accelerates the desorption of hydrogen intermediates (H... adThe desorption process of CdS / CoSe@MoS2 composite photocatalysts increases surface reaction kinetics, thereby improving the hydrogen evolution performance of the CdS / CoSe@MoS2 composite photocatalyst.

[0006] Secondly, the present invention also provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst. The preparation method includes the following steps: dispersing CdS in a mixed solvent of ethanol and water to form a suspension; adding a cobalt source and a selenium source to the suspension and performing photodeposition under light source irradiation to form a mixture with CdS composite particles having CoSe attached to their surface; adding an ammonium tetrathiomolybdate precursor solution to the mixture and reacting under light source irradiation to deposit MoS2 on the CoSe surface to generate a CdS / CoSe@MoS2 composite photocatalyst.

[0007] As can be seen from the above technical solution, the preparation method of the CdS / CoSe@MoS2 composite photocatalyst proposed in the second aspect of the present invention involves two photodeposition reactions combined with a post-processing step. First, CoSe is deposited on the CdS surface, and then MoS2 is deposited on the CoSe surface. Specifically, in the first photodeposition, CoSe is connected to the CdS substrate surface via Co-S covalent bonds; in the second photodeposition, amorphous MoS2 is deposited on the CoSe surface. Photogenerated electrons generated by CdS under light source irradiation can rapidly transfer to CoSe, and then to the outermost amorphous MoS2 and MoS4 layers. 2- As an electron acceptor, it further captures these electrons, is reduced to insoluble MoS2, and deposited in situ on the CoSe surface, thus exposing more active sites on the amorphous structure and enabling the adsorption of more hydrogen intermediates. CoSe can promote the migration of photogenerated electrons from CdS to MoS2 and inhibit photogenerated electron-hole pair recombination. MoS2 can utilize photogenerated electrons to transform S sites into an electron-rich state. (2+δ)- This process accelerates the desorption of hydrogen intermediates and the generation of hydrogen gas, thereby enhancing photocatalytic activity. Since both photodeposition steps are performed under illumination, the reaction conditions are mild and the operation is simple, allowing for the regulation of charge separation and transport properties on the CdS surface. The core-shell structure formed by this process constructs electron transport channels, greatly promoting the separation of photogenerated electron-hole pairs and improving the migration efficiency of photogenerated electrons, thus endowing the material with high photoelectrochemical performance. This preparation method is not only simple, green, and controllable, but also has a concise synthesis route, making it suitable for industrial production.

[0008] Thirdly, the present invention also provides an application of the CdS / CoSe@MoS2 composite photocatalyst, which is used for photocatalytic hydrogen evolution.

[0009] As can be seen from the above technical solutions, the application of the CdS / CoSe@MoS2 composite photocatalyst proposed in the third aspect of this invention exhibits a higher hydrogen evolution rate and better cycle stability. Therefore, by applying the CdS / CoSe@MoS2 composite photocatalyst to the photocatalytic hydrogen evolution system, stable hydrogen production performance can be achieved under mild conditions. Furthermore, the catalyst is recyclable, easy to operate, and cost-effective, making it suitable for large-scale applications of catalytic hydrogen evolution.

[0010] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the embodiments of the present invention. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the synthesis process according to an embodiment of the present invention; Figure 2 These are the X-ray diffraction (XRD) patterns of Embodiment 1 and Comparative Examples 1-3 of the present invention; Figure 3 This is a scanning electron microscope (SEM) image of Embodiment 1 of the present invention; Figure 4 This is a transmission electron microscope (TEM) image of Embodiment 1 of the present invention; Figure 5 This is a high-resolution transmission electron microscope (HRTEM) image of Embodiment 1 of the present invention, wherein... Figure 5 a in Figure 5 b in Figure 5 The magnification of the HRTEM images shown in c is different; Figure 6 These are the ultraviolet-visible diffuse reflectance (UV-vis) spectra of Embodiment 1 and Comparative Examples 1-3 of the present invention; Figure 7 This is a graph showing the relative pressure (P / P0) versus adsorption capacity (cc / g) for Example 1 and Comparative Examples 1-3 of the present invention. Figure 8 These are the photocatalytic hydrogen evolution rate graphs for Example 1 and Comparative Examples 1-3 of the present invention; Figure 9 This is a photocatalytic cycle stability diagram of Example 1 of the present invention; Figure 10 In the figure, 'a' represents the PL spectra of Example 1 and Comparative Examples 1-3. Figure 10 In the figure, b is the electrochemical impedance spectroscopy (EIS) diagram of Example 1 and Comparative Examples 1-3. Figure 10 In the figure, 'c' represents the linear sweep voltammetry (LSV) curves of Example 1 and Comparative Examples 1-3. Figure 10 In the figure, d represents the transient photocurrent response (it) diagrams of Example 1 and Comparative Examples 1-3; Figure 11 This is a schematic diagram illustrating the principle of antibonding orbital occupancy in an embodiment of the present invention; Figure 12 This is a schematic diagram of the preparation method according to an embodiment of the present invention. Detailed Implementation

[0013] 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, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0014] Unless otherwise specified, the following embodiments and features can be combined with each other. Unless otherwise stated, all reagents and raw materials are commercially available.

[0015] Studies have shown that when metal sulfides act as cocatalysts, the sulfur atoms on their surface are key active sites for the photocatalytic hydrogen evolution reaction. During the reaction, the hydrogen intermediate (H... ad SH formed with S atoms ad The strength of the bond directly affects the H ad Adsorption and desorption kinetics equilibrium: excessively strong SH ad The bond will cause H ad Excessive occupation of active sites hinders the generation and desorption of hydrogen molecules; while excessively weak bonding is detrimental to initial adsorption. Therefore, regulating SH... ad Bond strength is the key to improving hydrogen evolution efficiency.

[0016] Therefore, this invention proposes a CdS / CoSe@MoS2 composite photocatalyst, comprising a CdS matrix, CoSe covalently bonded to the surface of the CdS matrix via Co-S bonds, and MoS2 bonded to the surface of the CoSe. By selecting the CdS matrix and the MoS2 bonded to the CoSe surface, photogenerated electrons generated by illumination of CdS can be directionally migrated from the CoSe core to the MoS2 shell, causing the S sites of MoS2 to transform into an electron-rich S state. (2+δ)- The increase in electron density enhances SH ad The antibonding orbital occupancy state weakens SH. ad Bond energy significantly accelerated Had The desorption process ultimately significantly improves hydrogen evolution efficiency.

[0017] The CdS / CoSe@MoS2 composite photocatalyst proposed in this invention involves depositing amorphous MoS2 on the CoSe surface via Co-S covalent bonds, and further attaching MoS2 to the CoSe surface, forming a core-shell CoSe@MoS2 hydrogen evolution structure with CoSe as the core and MoS2 as the shell. CdS can absorb visible light and generate photogenerated electron-hole pairs, providing the reaction motive force for the photocatalytic reaction. The CdS / CoSe@MoS2 composite photocatalyst prepared in this invention can improve the efficiency of photocatalytic hydrogen evolution.

[0018] It should be noted that in this invention, CoSe and MoS2 can attract each other through electrostatic attraction, thereby depositing amorphous MoS2 on the CoSe surface. Secondly, [MoS4] 2- Rich in sulfur atoms, CdS readily forms Co-S-Mo chemical bonds with transition metals such as cobalt. Especially under illumination, photogenerated electrons from CdS can transfer to CoSe, leading to [MoS4] bonds. 2- As an electron acceptor, it captures photogenerated electrons, is reduced to insoluble MoS2, and is deposited in situ on the CoSe surface, thereby forming stable amorphous MoS2 on the CoSe surface.

[0019] In the various components of this invention, CdS serves as the light-absorbing matrix, responsible for light energy capture and conversion. Specifically, CdS can absorb visible light and generate photogenerated electron-hole pairs, providing the reaction motive force for photocatalytic reactions. CoSe, as an intermediate isomer, is responsible for the directional transport of photogenerated electrons. That is, CoSe can be connected to the CdS surface through Co-S covalent bonds, capturing the photogenerated electrons generated by CdS and driving them to migrate directionally to the MoS2 shell, while inhibiting electron-hole recombination and improving charge separation efficiency. MoS2, as a co-catalytic active component, is responsible for providing an active catalytic interface. Its surface is rich in S atoms. For example, when used in the photocatalytic hydrogen evolution reaction, in the early stage of the hydrogen evolution reaction, S atoms can provide abundant active sites for the hydrogen evolution reaction. S atoms and hydrogen intermediates form a certain amount of SH ad As the hydrogen evolution reaction proceeds, more and more S atoms on the MoS2 surface accept photogenerated electrons transferred from CoSe and generated from CdS, and the S sites transition to an electron-rich state. (2+δ)- This weakens SH ad Bond energy accelerates the desorption of hydrogen intermediates and the generation of hydrogen gas.

[0020] As can be seen from the above, the CdS / CoSe@MoS2 composite photocatalyst proposed in this invention constructs a core-shell structured CdS / CoSe@MoS2 composite photocatalyst by introducing CoSe as a heterophase between CdS and MoS2. Under illumination, photogenerated electrons generated by CdS migrate directionally from the CoSe core to the MoS2 shell, causing the S sites of MoS2 to transform into an electron-rich S state. (2+δ)- The increase in electron density enhances SH ad The antibonding orbital occupancy state weakens SH. ad Bond energy significantly accelerated H ad The desorption process. The CdS / CoSe@MoS2 composite photocatalyst prepared in this invention has a larger specific surface area and higher charge separation efficiency, which ultimately improves the hydrogen evolution efficiency.

[0021] In some embodiments, the mass ratio of Co, Mo, and CdS matrix is ​​1~4:1~4:100; and / or, the specific surface area of ​​the CdS / CoSe@MoS2 composite photocatalyst is 74 m². 2 .g -1 ~84 m 2 .g -1 .

[0022] It should be noted that the mass ratio of the Co, Mo, and CdS matrix of the present invention is 1~4:1~4:100. For example, the mass ratio includes values ​​such as 1:4:100, 3:2:100, and 4:1:100, as well as the range of values ​​defined by any two of these specific ratios as endpoints. As long as the values ​​are within the above-mentioned range, they all conform to the mass ratio of the Co, Mo, and CdS matrix of the present invention.

[0023] In some embodiments, by controlling the mass ratio of Co, Mo, and CdS matrix, a core-shell structured CdS / CoSe@MoS2 composite photocatalyst can be generated. Within the aforementioned ratio range, the MoS2 shell can cover the CoSe surface, providing sufficient S active sites, while reducing the recombination of photogenerated electron-hole pairs. By controlling the mass ratio of Co, Mo, and CdS matrix, the CdS matrix is ​​either granular or a spherical structure with multiple particles stacked, and the particle size of the CdS matrix ranges from 10 nm to 20 nm. The CoSe deposited on the CdS surface is granular, with a particle size range of 10 nm to 20 nm, and the MoS2 deposited on the CoSe surface is amorphous.

[0024] In some exemplary embodiments, the specific surface area of ​​the CdS / CoSe@MoS2 composite photocatalyst is 74 m². 2 .g -1 ~84 m 2 .g-1 For example, the specific surface area of ​​the CdS / CoSe@MoS2 composite photocatalyst is 74 m². 2 .g -1 76 m 2 .g -1 78 m 2 .g -1 80 m 2 .g -1 82 m 2 .g -1 and 84 m 2 .g -1 Equivalent values ​​and ranges defined by any two of these specific ratios as endpoints. In a specific embodiment, the specific surface area of ​​the CdS / CoSe@MoS2 composite photocatalyst is 79.432 m². 2 .g -1 The specific surface area of ​​CdS is 50.008 m². 2 .g -1 The specific surface area of ​​CdS / MoS2 is 68.459 m². 2 .g -1 The specific surface area of ​​CdS / CoSe is 67.284 m². 2 .g -1 As can be seen from the above, the CdS / CoSe@MoS2 composite photocatalyst has a large specific surface area, which not only provides more surface active sites for the photocatalytic hydrogen evolution reaction, but also enhances the adsorption capacity of water molecules and hydrogen intermediates on the surface of the CdS / CoSe@MoS2 composite photocatalyst, thereby improving the activation capacity for hydrogen evolution of water molecules, but also helps to improve the migration efficiency of photogenerated electrons from CdS to the cocatalyst.

[0025] Secondly, in some embodiments, the present invention provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst, as described in the reference. Figure 12 This includes the following steps: Step S100: CdS is dispersed in a mixed solvent of ethanol and water to form a suspension. Cobalt source solution and selenium source solution are added to the suspension, and photodeposition is performed under light source irradiation to form a mixed solution with CdS composite particles with CoSe attached to the surface.

[0026] Step S200: An ammonium tetrathiomolybdate precursor solution is added to the mixture, and photodeposition is performed under light source irradiation to attach amorphous MoS2 to the CoSe surface, thereby generating a CdS / CoSe@MoS2 composite photocatalyst. The core-shell structure CoSe@MoS2 located on the outer layer of CdS in the CdS / CoSe@MoS2 composite photocatalyst can act as a co-catalyst.

[0027] In some embodiments, the preparation method of CdS / CoSe@MoS2 composite photocatalyst further includes the following steps: step S300, post-processing the liquid containing CdS / CoSe@MoS2 composite photocatalyst in step S200 after the reaction is completed.

[0028] In an exemplary embodiment, in step S100, the volume fraction percentage of ethanol and water in the mixed solvent is 5%~15%:85%~95%, for example, including values ​​such as 5%:95%, 10%:90%, and 15%:85%, as well as values ​​within the range defined by any two of the aforementioned ratios. By controlling the ratio of ethanol to water, CdS can be well dissolved in the mixed solvent of ethanol and water, forming a uniform and stable suspension. During the photodeposition of CoSe on the CdS surface, the ethanol in the ethanol and water can increase the wettability of the CdS surface and reduce the surface tension of the mixed solvent.

[0029] In the embodiments, the cobalt source is at least one of cobalt chloride or cobalt nitrate; and / or, the selenium source is at least one of sodium selenite or selenourea. When cobalt chloride is used as the cobalt source, it can release cobalt ions during photodeposition, reacting with the selenium source to generate CoSe particles, which are then deposited on the CdS surface, thereby improving the migration efficiency of photogenerated electrons from CdS to the cocatalyst. Cobalt nitrate can also be used as the cobalt source; nitrate ions are easily removed from the reaction system, reducing impurity residues, increasing the number of active sites, and improving the kinetics of photocatalytic hydrogen evolution. When sodium selenite is used as the selenium source, it can controllably release Se under illumination. 2- The reaction with cobalt ions to form CoSe is beneficial for the formation of a CoSe heterophase on the CdS surface during photodeposition. When selenourea is used as a selenium source, it can provide Se during the photodeposition process. 2- Co in ions and cobalt source 2+ Ionic reactions can regulate the size and distribution of CoSe particles, resulting in uniform CoSe dispersion on the CdS surface. By rationally selecting the combination of cobalt and selenium sources, the electron transport efficiency and photocatalytic hydrogen evolution of the entire core-shell structure CdS / CoSe@MoS2 cocatalyst can be improved.

[0030] In this embodiment, the solvent used for the cobalt source solution is water, and the cobalt source is at least one of cobalt chloride or cobalt nitrate. The cobalt source solution is formed by dissolving the cobalt source in water, and its concentration is 0.01 mol / L to 0.5 mol / L. The solvent used for the selenium source solution is water, and the selenium source is at least one of sodium selenite or selenourea. The concentration of the selenium source solution is 0.01 mol / L to 0.5 mol / L, and the mass ratio of cobalt to CdS in the cobalt source is 0.01 to 10:100. By adding the cobalt source solution to the suspension, the adsorption and photoreduction deposition of cobalt ions on the CdS surface can be promoted. By adding the selenium source solution to the suspension, the reaction between the selenium source and the cobalt source can be achieved.

[0031] In some embodiments, the concentration of the cobalt source solution in step S100 includes values ​​such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, as well as ranges between any two of these specific values. When the concentration of the cobalt source solution is below 0.01 mol / L, the number of CoSe particles generated during photodeposition is relatively small, resulting in a negligible improvement in electron migration efficiency. When the concentration of the cobalt source solution is above 0.5 mol / L, it leads to excessive growth or aggregation of CoSe, forming an uneven accumulation layer on the CdS surface, which hinders interfacial electron transport and even reduces the light absorption sites of CdS, thereby decreasing photocatalytic activity. By controlling the concentration of the cobalt source solution, sufficient cobalt ions can be ensured to participate in the photodeposition reaction, while avoiding aggregation caused by excessive cobalt source.

[0032] In some embodiments, the concentration of the selenium source solution includes values ​​such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, as well as ranges between any two of the above specific values. When the concentration of the selenium source solution is below 0.01 mol / L, the selenium source supply is insufficient, the CoSe formation reaction is incomplete, which may lead to cobalt deposition in other forms or the presence of unreacted cobalt ions, weakening electron transport capability. When the concentration of the selenium source solution is above 0.5 mol / L, excess selenium source is prone to generating byproducts under illumination, interfering with MoS2 deposition. By limiting the concentration of the selenium source solution within the aforementioned range, both the formation of CoSe with the cobalt source and the maintenance of the stability of the core-shell structure can be ensured.

[0033] In some embodiments, the mass ratio of cobalt to CdS includes values ​​such as 0.01:100, 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 5:100, 8:100, and 10:100, as well as ranges between any two of these specific values. When the mass ratio of cobalt to CdS is below 0.01:100, the CoSe loading is too low, resulting in limited improvement in charge separation efficiency. When the mass ratio of cobalt to CdS is above 10:100, excessive CoSe not only over-covers the CdS surface, weakening the light absorption capacity of CdS, but also hinders rapid electron transfer. By limiting the mass ratio of cobalt to CdS in the cobalt source to the aforementioned range, it is possible to ensure the generation of sufficient and uniformly distributed CoSe particles on the CdS surface, forming a good Co-S covalent bonding interface, while avoiding CoSe aggregation, thereby improving charge separation and hydrogen evolution kinetics.

[0034] In this embodiment, step S200 is performed after step S100. In S200, the ammonium tetrathiomolybdate precursor solution is added to the mixture and reacted under light source irradiation to deposit amorphous MoS2 on the CoSe surface to generate a CdS / CoSe@MoS2 composite photocatalyst.

[0035] In some embodiments of this application, the concentration of the ammonium tetrathiomolybdate precursor solution is 0.01 mol / L to 0.5 mol / L, the solvent used for the ammonium tetrathiomolybdate precursor solution is water, and the mass ratio of molybdenum to CdS in the ammonium tetrathiomolybdate precursor solution is 0.01 to 10:100.

[0036] In some embodiments, the concentration of the ammonium tetrathiomolybdate precursor solution in step S200 may include values ​​such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, as well as a range between any two of the above specific values. When the concentration of the ammonium tetrathiomolybdate precursor solution is below 0.01 mol / L, the molybdenum source is insufficient, making it difficult to completely coat the amorphous MoS2 shell on the CoSe surface, resulting in an incomplete core-shell structure, insufficient number of active sites, and limited improvement in hydrogen evolution catalytic efficiency. When the concentration of the ammonium tetrathiomolybdate precursor solution is above 0.5 mol / L, it will lead to excessive deposition of MoS2, forming a dense thick layer on the catalyst surface, increasing charge transport resistance, and reducing overall photocatalytic activity. By controlling the concentration of the ammonium tetrathiomolybdate precursor solution, it is possible to ensure the formation of a uniform and continuous amorphous MoS2 layer on the CoSe surface, while avoiding excessive molybdenum source that could lead to structural accumulation or reduced activity.

[0037] In some embodiments, the mass ratio of molybdenum to CdS includes values ​​such as 0.01:100, 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 5:100, 8:100, and 10:100, as well as ranges between any two of the above specific values. When the mass ratio of molybdenum to CdS is less than 0.01:100, the loading of the MoS2 co-catalyst is insufficient, and it cannot obtain enough catalytic active sites through the relatively small surface area of ​​MoS2, thus affecting the SH... ad Bond regulation and hydrogen desorption promotion are relatively weak; when the mass ratio of molybdenum to CdS is higher than 10:100, the excess MoS2 will agglomerate and stack, which will not only weaken photogenerated electron migration but also reduce active sites and decrease the specific surface area of ​​the composite catalyst. By limiting the mass ratio of molybdenum to CdS within the aforementioned range, both the formation of an amorphous MoS2 shell on the CoSe surface and the provision of abundant electron-rich S can be ensured. (2+δ)-Active sites are created to prevent MoS2 agglomeration and stacking, thereby improving the hydrogen evolution efficiency of photocatalysts.

[0038] In some embodiments, the light source is at least one of an LED or a xenon lamp. The LED or xenon lamp, as the light source, emits a wavelength that matches the absorption range of CdS, exciting CdS to generate photogenerated electron-hole pairs.

[0039] In some embodiments, LED light sources possess stable high light intensity and output, enabling them to drive photodeposition and reduction reactions, which is beneficial for forming uniform and fine CoSe particles and a continuous, dense amorphous MoS2 shell. Xenon lamps have a wide spectral range and sufficient light energy, which can excite CdS to generate photo-generated electrons, thereby increasing the photodeposition rate. By selecting LEDs or xenon lamps as the reaction light source, both a stable supply of photo-generated electrons and the stability of the core-shell CoSe@MoS2 structure can be ensured.

[0040] In this embodiment, step S300 is performed after step S200. In step S300, the mixed solution containing the CdS / CoSe@MoS2 composite photocatalyst after the reaction is post-treated to obtain the CdS / CoSe@MoS2 composite photocatalyst.

[0041] In some embodiments of this application, the post-processing of step S300 is selected from at least one of centrifugation, washing, drying, and grinding; the post-processing includes centrifugation, with a centrifugation speed of 6000 r / min to 12000 r / min; the post-processing includes washing, in which water and ethanol are used for cleaning; the post-processing includes drying, in which an oven or vacuum drying oven is used, with a drying temperature of 60°C to 90°C.

[0042] In some exemplary embodiments, the rotation speed may include values ​​such as 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min and 12000 r / min, as well as a range of values ​​including any two of the above specific values, thereby enabling the separation of photocatalyst products and avoiding over-compaction or structural damage to the CdS / CoSe@MoS2 composite photocatalyst due to excessive rotation speed.

[0043] In some exemplary embodiments, the post-processing of step S300 includes washing, in which water and ethanol are used for cleaning. For example, water can be used to wash away the unreacted precursors remaining on the surface of the product, and then ethanol can be used to wash away organic impurities and accelerate subsequent drying, thereby ensuring the purity of the product.

[0044] In some exemplary embodiments, the post-processing of step S300 includes drying, which is performed using an oven or vacuum drying chamber at a temperature of 60°C to 90°C. For example, the temperature may include values ​​such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, as well as a range consisting of any two of these specific values. This ensures that moisture and solvent residues are fully removed while avoiding damage to the core-shell structure due to excessively high temperatures, thus protecting the structural integrity and photocatalytic activity of the CdS / CoSe@MoS2 composite photocatalyst. The grinding in the post-processing of step S300 disperses any potentially agglomerated product after drying into a uniform powder, facilitating characterization and photocatalytic hydrogen evolution applications.

[0045] In some embodiments of this application, the method for preparing CdS includes the following steps: Step S101: Dissolve cadmium acetate and sodium sulfide in water to form cadmium acetate solution and sodium sulfide solution, respectively; Step S102: Add sodium sulfide solution dropwise to cadmium acetate solution, continue stirring the resulting suspension, and then age it at room temperature; Step S103: The suspension is post-treated to obtain CdS powder. The preparation of CdS yields a CdS matrix with good crystallinity and uniform particle size distribution, providing an adhesion interface for subsequent photodeposition of CoSe, thus providing an adhesion interface for MoS2 photodeposition on CoSe; on the other hand, CdS has good responsiveness to visible light, and can absorb visible light and generate photogenerated electron-hole pairs.

[0046] In step S101 of the embodiment, the concentration of cadmium acetate solution is 0.01 mol / L to 0.5 mol / L, and the concentration of sodium sulfide solution is 0.01 mol / L to 0.5 mol / L.

[0047] In some embodiments of this application, the concentration of the cadmium acetate solution includes values ​​such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, as well as ranges between any two of the above specific values. When the concentration of the cadmium acetate solution is below 0.01 mol / L, the cadmium ion concentration is too low, resulting in fewer CdS nuclei and poor crystallization, leading to insufficient light absorption. When the concentration of the cadmium acetate solution is above 0.5 mol / L, the excessively high cadmium ion concentration easily causes CdS to aggregate or form irregular particles, reducing the specific surface area and the number of surface active sites. By controlling the concentration of the cadmium acetate solution, both sufficient CdS nucleation and crystallization can be ensured, while CdS aggregation can be avoided.

[0048] In some embodiments of this application, the concentration of the sodium sulfide solution includes values ​​such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, as well as ranges between any two of the above specific values. When the concentration of the sodium sulfide solution is below 0.01 mol / L, the supply of sulfur ions is insufficient, resulting in incomplete reaction with cadmium ions and a decrease in product purity. When the concentration of the sodium sulfide solution is above 0.5 mol / L, an excess of sulfur ions can easily lead to excessive adsorption of sulfur ions on the CdS surface, thereby reducing the dispersibility and crystallinity of CdS. By limiting the concentration of the sodium sulfide solution within the aforementioned range, it is possible to ensure the reaction with cadmium acetate to generate CdS while obtaining a CdS matrix with uniform surface dispersion.

[0049] In step S102 of the embodiment, the suspension is stirred for 3 h to 12 h; and aged at room temperature for 24 h to 72 h; so that cadmium acetate and sodium sulfide react fully, ensuring uniform nucleation and growth of CdS particles and achieving uniform dispersion of the product.

[0050] In some embodiments of this application, for example, the stirring time of the suspension includes values ​​such as 3 h, 4 h, 6 h, 8 h, 10 h and 12 h, as well as ranges between any two of the above specific values, so that cadmium acetate and sodium sulfide can fully contact and react, ensuring uniform nucleation and stable dispersion of CdS.

[0051] In some embodiments of this application, for example, the aging time at room temperature can be 24 h, 36 h, 48 h, 60 h and 72 h, or a range between any two of the above specific values, to provide sufficient growth time for CdS, obtain a CdS matrix with good crystallinity and uniform surface chemistry, and avoid excessive particle growth or agglomeration caused by excessive aging time.

[0052] In step S103 of the embodiment, the suspension is post-processed to obtain CdS powder.

[0053] In some embodiments of the present invention, the post-processing method can refer to the description of post-processing in step S300 of the foregoing embodiments, and will not be repeated here. It should be noted that when the post-processing includes grinding, the particle size of the ground CdS powder is 10 nm, which can reduce particle agglomeration, ensure a large specific surface area and provide sufficient active sites, while maintaining good crystallinity.

[0054] Thirdly, embodiments of the present invention provide an application of a CdS / CoSe@MoS2 composite photocatalyst, which is used for photocatalytic hydrogen evolution.

[0055] The photocatalyst was uniformly dispersed in lactic acid and aqueous solution. Nitrogen gas was purged into the reaction flask for 10-30 minutes to purge the air, and the flask was then sealed. After irradiation with a light source at room temperature and under stirring, the photocatalytic hydrogen production was tested using a gas chromatograph. In the cyclic test, nitrogen gas was purged for 10-30 minutes after each reaction to purge the hydrogen, and the photocatalytic hydrogen evolution process was repeated.

[0056] The preparation method of the CdS / CoSe@MoS2 composite photocatalyst of the present invention will be described below with reference to specific embodiments.

[0057] Example 1 This embodiment 1 provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst, including the following steps: 200 mg of CdS powder was accurately weighed and uniformly dispersed in a 10 vol% ethanol-water mixture to form an orange suspension. Under stirring, 1.02 mL of a 0.1 mol / L cobalt chloride solution and 1.02 mL of a 0.1 mol / L sodium selenite solution were added sequentially to the suspension, and stirring was continued for 1 min. After thorough mixing, the reaction system was purged with nitrogen for 15 min to remove air and then sealed. The system was then irradiated with a 420 nm LED light source for 1 h to perform a photodeposition reaction. During this process, the color of the suspension gradually changed from orange to dark brown, indicating that CoSe nanoparticles had been successfully deposited on the CdS surface.

[0058] Subsequently, under stirring, 0.84 mL of a 0.05 mol / L ammonium tetrathiomolybdate precursor solution was added to the above reaction system, and stirring was continued for 1 min. The reaction system was then purged with nitrogen for 15 min to remove air, and the system was sealed. Irradiation was continued for 1 h under a 420 nm LED light source. Under the induction of photogenerated electrons, MoS₄… 2- An autoreduction reaction occurs, forming an amorphous MoS2 shell in situ on the CoSe surface, thus constructing a core-shell structured CoSe@MoS2 cocatalyst. After the reaction, the product is centrifuged, washed, and dried to obtain the final product, a CdS / CoSe@MoS2 composite photocatalyst. The mass ratio of cobalt and molybdenum to the CdS matrix in this catalyst is 3:2:100.

[0059] Example 2 This Example 2 provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst. The preparation steps in this example are the same as in Example 1, except that the amount of the active component precursor solution added is different. Specifically, in this example, the amount of cobalt chloride solution (0.1 mol / L) and sodium selenite solution (0.1 mol / L) added is 1.36 mL; the amount of ammonium tetrathiomolybdate precursor solution (0.05 mol / L) added is 0.42 mL. All other experimental conditions, materials, and operating procedures are the same as in Example 1. The mass ratio of cobalt and molybdenum to the CdS matrix in this catalyst is 4:1:100.

[0060] Example 3 Example 3 provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst. This example follows the preparation steps of Example 1, except for the amount of the active component precursor solution added. Specifically, in this example, the amount of cobalt chloride solution (0.1 mol / L) and sodium selenite solution (0.1 mol / L) added is 0.68 mL; the amount of ammonium tetrathiomolybdate precursor solution (0.05 mol / L) added is 1.25 mL. All other experimental conditions, materials, and operating procedures are the same as in Example 1. The mass ratio of cobalt and molybdenum to the CdS matrix in this catalyst is 2:3:100. Example 4 This fourth embodiment of the present invention provides a method for preparing a CdS / CoSe@MoS2 composite photocatalyst. This embodiment follows the preparation steps of Example 1, except for the amount of the active component precursor solution added. Specifically, in this embodiment, the amount of cobalt chloride solution (0.1 mol / L) and sodium selenite solution (0.1 mol / L) added is 0.34 mL; the amount of ammonium tetrathiomolybdate precursor solution (0.05 mol / L) added is 1.67 mL. All other experimental conditions, materials, and operating procedures are the same as in Example 1. The mass ratio of cobalt and molybdenum to the CdS matrix in this catalyst is 1:4:100.

[0061] Comparative Example 1 Comparative Example 1 is a CdS / CoSe composite photocatalyst. Unlike Example 1, it does not have a MoS2 shell. The preparation method of the CdS / CoSe composite photocatalyst includes the following steps: 200 mg of CdS powder was accurately weighed and uniformly dispersed in a 10 vol% ethanol-water mixture to form an orange suspension. Under stirring, 1.7 mL of a 0.1 mol / L cobalt chloride solution and 1.7 mL of a 0.1 mol / L sodium selenite solution were added sequentially to the suspension, and stirring was continued for 1 min. After thorough mixing, nitrogen gas was purged through the reaction system for 15 min to remove air, and the system was sealed. Photodeposition was performed under a 420 nm LED light source for 2 h. During this process, the suspension color gradually changed from orange to dark brown. After the reaction, the product was centrifuged, washed, and dried to obtain the final product, the CdS / CoSe composite photocatalyst. The mass ratio of cobalt to the CdS matrix was 5:100.

[0062] Comparative Example 2 Comparative Example 2 is a CdS / MoS2 composite photocatalyst. Unlike Example 1, it does not have a CoSe heterophase. The preparation method of the CdS / MoS2 composite photocatalyst includes the following steps: 200 mg of CdS powder was accurately weighed and uniformly dispersed in a 10 vol% ethanol-water mixture to form an orange suspension. Under stirring, 2.09 mL of a 0.05 mol / L ammonium tetrathiomolybdate precursor solution was added to the suspension, and stirring was continued for 1 min. After thorough mixing, nitrogen gas was purged through the reaction system for 15 min to remove air, and the system was sealed. Photodeposition was performed under a 420 nm LED light source for 2 h. During this process, the suspension color gradually changed from orange to orange-red. After the reaction, the product was centrifuged, washed, and dried to obtain the final product, the CdS / MoS2 composite photocatalyst. The mass ratio of molybdenum to the CdS matrix was 5:100.

[0063] Comparative Example 3 Comparative Example 3 is a CdS photocatalyst, which differs from Example 1 in that it does not have a CoSe heterophase or a MoS2 shell. The preparation method of the CdS photocatalyst includes the following steps: 2.665 g of cadmium acetate and 2.4 g of sodium sulfide are dissolved in 200 mL of water respectively; the sodium sulfide solution is added dropwise to the cadmium acetate solution under continuous stirring, the resulting suspension is stirred for 3 h and aged at room temperature for 24 h; then the resulting orange precipitate is separated by centrifugation, washed successively with water and ethanol, and finally dried at 60 °C for 24 h, and ground to obtain orange CdS powder.

[0064] This sample serves as a comparative example, used to compare the performance of the modified composite photocatalyst of this invention.

[0065] Comparative Example 4 Comparative Example 4 is a MoS2 catalyst. The preparation method of the MoS2 catalyst includes the following steps: 100 mg of ammonium tetrathiomolybdate is dissolved in 100 mL of water to obtain a dark red clear solution; then, under stirring, 100 mL of a 10 vol% lactic acid solution is added dropwise; the resulting mixture is stirred thoroughly and then allowed to stand overnight at room temperature. After the reaction is complete, the generated black precipitate is centrifuged and washed successively with water and ethanol, and finally dried under vacuum for 12 h to obtain amorphous MoS2 powder.

[0066] This sample will serve as a comparative example, used to compare it with the modified composite photocatalyst of this invention.

[0067] Test case See attached diagram. Figure 1 This is a schematic diagram of the synthesis process according to an embodiment of the present invention. The CdS / CoSe@MoS2 prepared in Example 1, and the CdS / CoSe, CdS / MoS2, and CdS samples prepared in Comparative Examples 1-3 were systematically characterized, including by X-ray diffraction (XRD). Figure 2 ), ultraviolet-visible absorption spectrum (UV-vis, Figure 6 ), relative pressure versus adsorption amount diagram ( Figure 7 ), photocatalytic hydrogen evolution rate, PL spectrum ( Figure 10 a) Electrochemical impedance spectroscopy (EIS) Figure 10 (b) Linear sweep voltammetry plot (LSV) Figure 10 c) and transient photocurrent response diagram (it, Figure 10 d) Analysis in the text.

[0068] Figure 2 The XRD patterns showed that obvious CdS characteristic diffraction peaks were present in CdS / CoSe@MoS2, CdS / CoSe, CdS / MoS2 and CdS samples, indicating that the successful preparation of the composite catalyst did not change the main crystal structure of CdS.

[0069] from Figure 3 SEM images and Figure 4 The nanoparticle morphology of the CdS / CoSe@MoS2 composite photocatalyst can be clearly observed in the TEM images. Furthermore, Figure 5 The HRTEM images show clear lattice fringes, in which, Figure 5 Figure a shows the position and nanostructure of CoSe / MoS2 in the CdS / CoSe@MoS2 composite photocatalyst; Figure 5Figure b shows the position and nanomorphology of CdS in the CdS / CoSe@MoS2 composite photocatalyst. The measured lattice spacing d=0.34 nm belongs to the (111) crystal plane of CdS, d=0.21 nm belongs to the (220) crystal plane of CdS, and d=0.18 nm belongs to the (311) crystal plane of CdS, which further confirms that the crystal structure of CdS in the composite catalyst is well preserved. Figure 5 Figure c shows that amorphous MoS2 was deposited on the surface of the CoSe particles.

[0070] Figure 6 The UV-Vis diffuse reflectance spectrum of the sample is given. Under UV-Vis irradiation, CdS has excellent light absorption ability and can generate a large number of photogenerated electrons and holes after light absorption.

[0071] Figure 7 The figure shows that CdS / CoSe@MoS2 has the largest specific surface area. The significantly increased specific surface area provides a greater number and denser distribution of surface active sites for the photocatalytic reaction, directly enhancing the adsorption and activation capacity of reactants (water molecules and hydrogen intermediates) on the catalyst surface. Secondly, the larger specific surface area is beneficial for enhancing the capture and scattering of incident light, extending the light propagation path within the material, thereby improving the utilization efficiency of photogenerated electrons and ensuring the continuous driving of the photocatalytic reaction. In the figure, CdS / CoSe@MoS2 is the CdS / CoSe@MoS2 composite photocatalyst from Example 1, with a total Co to Mo mass ratio of 3:2. For CdS / CoSe@MoS2 composite photocatalysts with total Co to Mo mass ratios of 4:1, 2:3, and 1:4, respectively, the specific surface area obtained using the same testing method is 74 m². 2 .g -1 ~84 m 2 .g -1 Within the range.

[0072] Figure 8 The graphs show the photocatalytic hydrogen evolution rate of each sample after preparing the CdS / CoSe@MoS2 composite photocatalysts prepared in Examples 1-4 and the catalysts prepared in Comparative Examples 1-3.

[0073] The method for testing the photocatalytic hydrogen evolution performance is as follows: The photocatalytic hydrogen evolution performance was tested in a self-built reaction apparatus. The gaseous product detection equipment used was a Ruihong Instrument SP-6801A gas chromatograph, and the reaction light source consisted of four LED lamps with a center wavelength of 420 nm and a power of 3 W each. The test procedure was as follows: 20 mg each of CdS, CdS / CoSe, CdS / CoSe@MoS2, and CdS / MoS2 were accurately weighed, with the total Co to Mo mass ratios in CdS / CoSe@MoS2 being 4:1, 3:2, 2:3, and 1:4, respectively. These were dispersed in a mixed solution of 72 mL water and 8 mL lactic acid (in a 100 mL three-necked flask). After sonication for 5 min, a uniform dark green suspension was formed. The three-necked flask was sealed, and high-purity nitrogen was continuously purged for 15 min to ensure an anaerobic environment. Subsequently, under continuous stirring, the reaction solution was irradiated with the aforementioned 420 nm LED light source array to drive the photocatalytic hydrogen evolution reaction.

[0074] During the reaction, the gas composition of the headspace of the reaction system was extracted and quantitatively analyzed online using a gas chromatograph every 30 minutes. The entire test lasted 2 hours, and a total of 4 sets of hydrogen production data were collected. The photocatalytic hydrogen evolution activity results (i.e., the hydrogen production rate versus time curve) are shown below. Figure 8 As shown, CdS has the lowest hydrogen production rate, followed by CdS / MoS2 and CdS / CoSe. The highest hydrogen production rate is achieved when the total mass ratio of Co to Mo in CdS / CoSe@MoS2 is 3:2. The hydrogen production rates of the samples prepared by the CdS / CoSe@MoS2 composite photocatalyst are all better than those of the samples prepared by the catalysts in Comparative Examples 1 to 3.

[0075] The following describes the methods and results of the photocatalytic stability test: The test procedure is basically the same as that for the photocatalytic hydrogen evolution activity test: Accurately weigh 20 mg each of CdS, CdS / CoSe, CdS / CoSe@MoS2, and CdS / MoS2, where the total mass ratio of Co to Mo in CdS / CoSe@MoS2 is 4:1, 3:2, 2:3, and 1:4, respectively. Disperse in an 80 mL mixed solution (in a 100 mL three-necked flask) consisting of 72 mL of water and 8 mL of lactic acid, and sonicate for 5 min to form a homogeneous suspension. Seal the three-necked flask and purge with high-purity nitrogen for 15 min to completely remove air.

[0076] Subsequently, under continuous stirring, the reaction system was irradiated with four LED light sources with a center wavelength of 420 nm and a power of 3 W to drive the hydrogen evolution reaction. Each test cycle lasted for 2 hours, during which the hydrogen production was sampled and measured every 30 minutes. After each cycle, nitrogen gas was purged into the system for 15 minutes to remove the accumulated hydrogen gas in the reaction chamber and create an initial hydrogen-free and oxygen-free environment for the next cycle. The above process was repeated 4 times. The photocatalytic cycle stability test graph for the CdS / CoSe@MoS2 composite photocatalyst with a total Co to Mo mass ratio of 3:2 is shown in the figure below. Figure 9 As shown, through cyclic testing (one cycle every two hours), the hydrogen production curves remained linear for four cycles, with no significant decrease in hydrogen production. This indicates that a stable hydrogen production rate can be maintained under prolonged illumination, without photocorrosion. For CdS / CoSe@MoS2 composite photocatalysts with Co to Mo total mass ratios of 4:1, 2:3, and 1:4, the cyclic stability results were compared with... Figure 9 Similarly, I will not elaborate further here.

[0077] The following describes the test method for photoelectrochemical testing; the test results are shown below. Figure 10 .

[0078] Figure 10 Comparison figures of photoluminescence (PL) spectra, transient photocurrent response (it), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) curves for each sample are shown. Each sample was prepared using a CdS / CoSe@MoS2 composite photocatalyst (taking a total Co to Mo mass ratio of 3:2 as an example), a CdS catalyst, a CdS / CoSe composite photocatalyst, and a CdS / MoS2 composite photocatalyst, respectively.

[0079] Figure 10 The photoluminescence (PL) spectra shown in Figure a indicate that each sample exhibits a characteristic emission peak at 475 nm. High PL intensity typically corresponds to a high electron-hole recombination rate, which is detrimental to photocatalytic reactions. The CdS / CoSe@MoS2 composite photocatalyst prepared in this invention exhibits the lowest PL intensity at this point, indicating that its charge separation efficiency is significantly superior to that of other samples.

[0080] Figure 10 In the EIS spectrum shown in b, the arc radius of the composite catalyst is significantly smaller than that of the single CdS. Among them, the CdS / CoSe@MoS2 composite photocatalyst has the smallest arc radius, indicating that it has the lowest charge transport impedance and the fastest interfacial charge separation and migration rate.

[0081] Figure 10The LSV curve shown in c further demonstrates that the CdS / CoSe@MoS2 composite photocatalyst exhibits the lowest overpotential and the highest cathode current density in the hydrogen evolution reaction, proving that it has optimal catalytic activity.

[0082] Figure 10 In the transient photocurrent response results shown by d in the figure, the CdS / CoSe@MoS2 composite photocatalyst exhibited the strongest and most stable photocurrent response in multiple switching photocycles, further verifying its excellent charge separation and transport capabilities and structural stability.

[0083] like Figure 11 As shown, this clearly elucidates the reaction mechanism by which the CdS / CoSe@MoS2 composite photocatalyst exhibits the highest hydrogen evolution activity. The core of this mechanism lies in the fact that the introduced CoSe, as a heterophase, drives the directional migration of photogenerated electrons to the S sites on the MoS2 shell, thereby forming electron-rich S sites. (2+δ)- Active center. This change in electronic structure enhances SH ad The electronic occupancy of the antibonding orbitals significantly weakens the SH. ad The strength of the bond. This crucial role greatly promotes the formation of the hydrogen intermediate (H). ad The desorption process of the hydrogen molecule allows it to quickly combine and generate hydrogen molecules, ultimately significantly improving the overall photocatalytic hydrogen evolution efficiency.

[0084] This invention provides a core-shell CoSe@MoS2 cocatalyst successfully supported on CdS to form a CdS / CoSe@MoS2 composite photocatalyst. This invention successfully constructed and supported a core-shell structured CoSe@MoS2 cocatalyst on the CdS surface using a simple and safe photodeposition method. This composite catalyst not only has a simple synthesis route, but the formation of the core-shell structure can construct electron transport channels, greatly promoting the separation and migration efficiency of photogenerated electron-hole pairs, thus endowing the material with superior photoelectrochemical performance. The core-shell structured cocatalyst designed in this invention, by coupling CoSe as a heterophase, achieves the directional migration of photogenerated electrons generated by CdS under illumination from CoSe to the MoS2 shell. This process enables the S on the MoS2 surface... 2- Transitioning to the electron-rich state S (2+δ)- SH has been added ad Electron occupation of antibonding orbitals weakens SH. ad Bond strength. This crucial electronic structure modulation significantly accelerated the formation of the hydrogen intermediate (H). ad The desorption process of the composite photocatalyst fundamentally improves the surface reaction kinetics, thereby significantly enhancing the hydrogen evolution performance of the composite photocatalyst.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a CdS / CoSe@MoS2 composite photocatalyst, characterized in that, The preparation method includes the following steps: dispersing CdS in a mixed solvent of ethanol and water to form a suspension, adding a cobalt source solution and a selenium source solution to the suspension, and performing photodeposition under light source irradiation to form a mixed solution with CdS composite particles with CoSe attached to the surface; An ammonium tetrathiomolybdate precursor solution was added to the mixture, and photodeposition was performed under the illumination of the light source to attach MoS2 on the CoSe surface to generate the CdS / CoSe@MoS2 composite photocatalyst. The CdS / CoSe@MoS2 composite photocatalyst comprises a CdS matrix, CoSe covalently bonded to the surface of the CdS matrix via Co-S bonds, and MoS2 bonded to the surface of the CoSe; the mass ratio of Co, Mo, and CdS matrix is ​​1–4:1–4:100; the CdS matrix is ​​in granular form or a spherical structure of multiple stacked particles, with a particle size range of 10 nm to 20 nm; the CoSe deposited on the CdS surface is in granular form, with a particle size range of 10 nm to 20 nm; and the MoS2 deposited on the CoSe surface is in an amorphous form. The CdS / CoSe@MoS2 composite photocatalyst forms a core-shell CoSe@MoS2 hydrogen evolution structure with CoSe as the core and MoS2 as the shell.

2. The preparation method according to claim 1, characterized in that, The specific surface area of ​​the CdS / CoSe@MoS2 composite photocatalyst is 74 m². 2 .g -1 ~84 m 2 .g -1 .

3. The preparation method according to claim 1, characterized in that, The cobalt source solution is at least one of cobalt chloride solution or cobalt nitrate solution, and the solvent used for the cobalt source solution is water; The concentration of the cobalt source solution is 0.01 mol / L to 0.5 mol / L; And / or, the selenium source solution is at least one of sodium selenite solution or selenourea solution, and the solvent used for the selenium source solution is water; the concentration of the selenium source solution is 0.01 mol / L to 0.5 mol / L.

4. The preparation method according to claim 1, characterized in that, The concentration of the ammonium tetrathiomolybdate precursor solution is 0.01 mol / L to 0.5 mol / L, and the solvent used for the ammonium tetrathiomolybdate precursor solution is water.

5. The preparation method according to claim 1, characterized in that, The light source is at least one of LED or xenon lamp; and / or, in the mixed solvent of ethanol and water, the volume fraction percentage of ethanol to water is 5%~15%:95%~85%.

6. The preparation method according to claim 1, characterized in that, The method for preparing CdS includes the following steps: Cadmium acetate and sodium sulfide are dissolved in water to form cadmium acetate solution and sodium sulfide solution, respectively. Sodium sulfide solution was added dropwise to cadmium acetate solution, and the resulting suspension was stirred and then aged at room temperature. The suspension was post-processed to obtain CdS.

7. The preparation method according to claim 6, characterized in that, The concentration of the cadmium acetate solution is 0.01 mol / L to 0.5 mol / L, and the concentration of the sodium sulfide solution is 0.01 mol / L to 0.5 mol / L.

8. The preparation method according to claim 6, characterized in that, The suspension is stirred for 3 h to 12 h; aged at room temperature for 24 h to 72 h; and / or, The post-processing includes centrifugation, washing, drying, and grinding; the post-processing includes centrifugation at a speed of 6000 r / min to 12000 r / min; the post-processing includes washing with water and ethanol; the post-processing includes drying in an oven or vacuum drying oven at a temperature of 60 to 90°C; the post-processing includes grinding, resulting in a CdS powder with a particle size of 10 nm.

9. The application of the CdS / CoSe@MoS2 composite photocatalyst prepared by any one of claims 1 to 8, characterized in that, A CdS / CoSe@MoS2 composite photocatalyst was used for photocatalytic hydrogen evolution.

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