A ReS2 / CdS composite hydrogen evolution material and its preparation method

Abstract

This case involves a ReS2 / CdS composite hydrogen evolution material and its preparation method. A precursor solution was prepared by adding water to CN2H4S and Cd(Ac)2·2H2O. H3NO·HCl and NH4ReO4 were dissolved in the precursor solution and subjected to a hydrothermal reaction. After centrifugation, the precipitate was washed, and the solid was collected, vacuum dried, and ground to obtain the ReS2 / CdS composite hydrogen evolution material. This case successfully loaded ReS2 onto CdS using a simple one-step hydrothermal method, improving the photocatalytic hydrogen evolution performance of CdS and mitigating the photocorrosion problem. The strong interaction between CdS and ReS2 promotes photogenerated electron transfer, thereby inhibiting electron-hole recombination and increasing the active sites of CdS. Only a very small amount of Re source is needed to achieve good and stable hydrogen evolution performance, saving the use of rare metal Re and allowing it to be applied as a photocatalyst material in industrial fields.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic material preparation methods, specifically to a ReS2 / CdS composite hydrogen evolution material and its preparation method. Background Technology

[0002] Energy shortage has become a major challenge facing all of humanity. Therefore, the search for renewable, sustainable, and environmentally friendly new energy sources is particularly urgent. Hydrogen energy has a high calorific value and its combustion product is water, making it a clean and renewable energy source with great application potential. Catalytic hydrogen production from water splitting using sunlight is an effective way to solve the energy crisis. Among semiconductor catalytic materials for photocatalytic water splitting to produce hydrogen, cadmium sulfide (CdS) possesses suitable band levels that meet the thermodynamic requirements for H2 evolution, making it a good photocatalyst. As a direct semiconductor material, pure CdS exhibits strong photoexcitation and support recombination capabilities, but also strong photocorrosion capabilities, resulting in less than ideal overall catalyst activity. Therefore, more attention is being paid to modifying CdS with other materials to improve the activity and stability of photocatalysts. Research shows that semiconductor heterostructure design is one of the most effective methods to improve the activity and stability of CdS, as it can effectively control the electron arrangement, excite active sites, and promote improved charge transport efficiency.

[0003] Rhenium sulfide (ReS2) is a novel two-dimensional layered material that holds promise for replacing other two-dimensional layered materials. Considering this, we expect ReS2 to not only be an effective photocatalyst but also a good co-catalyst to replace noble metals in improving the activity of CdS catalysts, potentially offering new opportunities for the evolution of photocatalytic H2 production. Currently, Chinese patent CN108855141B discloses a ReS2 / CdS photocatalyst, its preparation method, and its applications, providing a novel approach to CdS photocatalytic hydrogen production technology. However, the photocatalyst in this patent is prepared by hydrothermal reaction of a mixture of ammonium perrhenate, thioacetamide, hexamethylenetetramine, and cadmium sulfide; cadmium sulfide needs to be prepared in advance, meaning the preparation method requires a two-step hydrothermal reaction, increasing the number of reaction steps; and hexamethylenetetramine is a potentially explosive and hazardous chemical, increasing safety risks during the experiment. Furthermore, the highest hydrogen production of this photocatalyst is 487 μmol / g / h, indicating significant room for improvement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a ReS2 / CdS composite hydrogen evolution material with adjustable proportions. The preparation process does not require multiple hydrothermal cycles, the method is simple and allows for large-scale growth, improves reaction efficiency, reduces the amount of rare metal Re used, and only 1% Re is needed to obtain the optimal ReS2 / CdS composite hydrogen evolution material. The method is simple, easy to implement, energy-saving, and highly efficient.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a ReS2 / CdS composite hydrogen evolution material includes the following steps:

[0007] 1) Prepare a precursor solution by adding water to CN2H4S and Cd(Ac)2·2H2O;

[0008] 2) H3NO·HCl and NH4ReO4 were dissolved in the precursor solution, stirred, and then transferred to a polytetrafluoroethylene liner for hydrothermal reaction. After the reaction was completed, the mixture was centrifuged and the precipitate was washed with deionized water and ethanol. The solid was collected, vacuum dried, and ground to obtain the ReS2 / CdS composite hydrogen evolution material.

[0009] Furthermore, the molar ratio of NH4ReO4 to Cd(Ac)2·2H2O is 0.005 to 0.05:1.

[0010] Furthermore, the amount of H3NO·HCl used is 3 to 4 times the molar mass of NH4ReO4.

[0011] Furthermore, the amount of CN2H4S used is 5 to 6 times the molar mass of Cd(Ac)2·2H2O.

[0012] Furthermore, the hydrothermal temperature is 160℃~200℃, and the reaction time is 20~24h.

[0013] Compared with existing technologies, the advantages of this application are: This application uses simple raw materials and successfully loads ReS2 onto CdS via a single hydrothermal method, saving both money and time. CdS and ReS2 form a heterojunction, and their strong interaction promotes photogenerated electron transfer, thereby inhibiting electron-hole recombination and increasing the active sites of CdS. Results show that, due to the presence of the co-catalyst ReS2, the hydrogen production activity of CdS is significantly improved without the need for a noble metal catalyst, and the photocorrosion problem of CdS is greatly solved. This method is simple, energy-efficient, and requires only a very small amount of Re source to achieve good and stable hydrogen evolution performance. Only 1% Re is needed to achieve a photocatalytic hydrogen production performance of 103 mmol / g / h for the ReS2 / CdS composite material, saving the use of the rare metal Re and allowing it to be applied as a photocatalyst material in industrial fields. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. 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.

[0015] Figure 1 Planar scanning electron microscope images of CdS-200(A), CdS-160(B), and CdS-1Re(C) composite materials.

[0016] Figure 2 This is a transmission electron microscope image of the ReS2 / CdS composite material prepared in Example 2 of the present invention.

[0017] Figure 3 The X-ray diffraction patterns are those of the ReS2 / CdS composite materials prepared in Examples 1 to 5 of this invention.

[0018] Figure 4 The images show the UV-Vis absorption spectra of the ReS2 / CdS composite materials prepared in Examples 1-4 of this invention.

[0019] Figure 5 The Tauc curves are for the ReS2 / CdS composite materials prepared in Examples 1 to 4 of this invention.

[0020] Figure 6 The graphs show the hydrogen evolution yield performance of the ReS2 / CdS composite materials prepared in Examples 1-4 of this invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example: This case provides a ReS2 / CdS composite hydrogen evolution material

[0024] 1) Dissolve CN2H4S and Cd(Ac)2·2H2O in 60ml of deionized water and stir for 5 minutes to form a homogeneous precursor solution;

[0025] 2) H3NO·HCl and NH4ReO4 were dissolved separately in the precursor solution, stirred for 30 min, and then transferred to a polytetrafluoroethylene liner for hydrothermal treatment at 200℃ for 24 hours. The resulting solution was collected, centrifuged, and the precipitate was washed with deionized water and ethanol. The solid was collected and vacuum dried at 80℃ for 24 hours. Finally, it was ground into powder to obtain the ReS2 / CdS composite hydrogen evolution material.

[0026] Example 1: The molar ratio of NH4ReO4 to Cd(Ac)2·2H2O is 0.005:1

[0027] Dissolve 12 mmol CN2H4S and 2 mmol Cd(Ac)2·2H2O in 60 ml of deionized water and stir for 5 minutes to form a homogeneous CdS precursor solution.

[0028] 0.04 mmol H₃NO·HCl and 0.01 mmol NH₄ReO₄ were dissolved separately in the precursor solution. After stirring for 30 min, the ReS₂ / CdS precursor solution was transferred to a polytetrafluoroethylene liner and hydrothermally heated at 200 °C for 24 h. The resulting solution was collected, centrifuged, and the precipitate was washed with deionized water and ethanol. The solid was collected and vacuum dried at 80 °C for 24 h. Finally, it was ground into powder to obtain the ReS₂ / CdS composite hydrogen evolution material (sample labeled CdS-0.5Re).

[0029] Example 2:

[0030] Same as Example 1, except that the molar ratio of NH4ReO4 to Cd(Ac)2·2H2O is 0.01:1, that is, the amounts of H3NO·HCl and NH4ReO4 are 0.08 mmol and 0.02 mmol, respectively. The rest is the same as Example 1, and the ReS2 / CdS composite hydrogen evolution material (sample labeled CdS-1Re) is obtained.

[0031] Example 3:

[0032] Same as Example 1, except that the molar ratio of NH4ReO4 to Cd(Ac)2·2H2O is 0.02:1, that is, the amounts of H3NO·HCl and NH4ReO4 are 0.16 mmol and 0.04 mmol, respectively. The rest is the same as in Example 1, and the ReS2 / CdS composite hydrogen evolution material (sample labeled CdS-2Re) is prepared.

[0033] Example 4:

[0034] Same as Example 1, except that the molar ratio of NH4ReO4 to Cd(Ac)2·2H2O is 0.04:1, that is, the amounts of H3NO·HCl and NH4ReO4 are 0.32 mmol and 0.08 mmol, respectively. The rest is the same as Example 1, and the ReS2 / CdS composite hydrogen evolution material (sample labeled CdS-4Re) is prepared.

[0035] Compare with Example 1:

[0036] 12 mmol CN2H4S and 2 mmol Cd(Ac)2·2H2O were dissolved in 60 ml of deionized water and stirred for 5 minutes to form a homogeneous CdS precursor solution. CdS was obtained by hydrothermal treatment at 200 °C for 24 h. The sample was labeled as CdS-200.

[0037] Compare with Example 2:

[0038] The temperature of 200℃ in Example 1 was changed to 160℃, and the sample was labeled CdS-160.

[0039] <Performance Characterization>

[0040] like Figure 1 The figures show planar scanning electron microscope (SEM) images of the materials prepared in Example 2 and Comparative Examples 1-2. As can be seen, the morphology of samples prepared at different temperatures differs. Figure A is an SEM image of pure CdS prepared at 200℃ in Comparative Example 1, showing irregular spherical shapes. Figure B shows a CdS sample prepared at 160℃ with added Re, exhibiting CdS nanospheres composed of triangular pyramids. When the temperature rises to 200℃, the higher temperature and pressure cause a large number of nanospheres to gradually break down into irregular conical CdS. Due to the gradual breakdown of regular CdS nanospheres under high temperature and pressure, the CdS generated at 200℃ has a higher specific surface area and a smaller size, exhibiting a nano-triangular pyramidal shape.

[0041] Figure 2 The image is a high-magnification transmission electron microscope image. It can be seen from the image that the lattice spacing of the ReS2 / CdS composite hydrogen evolution material prepared in Example 1 is 0.244 nm and 0.61 nm, which correspond to the (102) plane of CdS and the (001) crystal plane of ReS2, respectively.

[0042] Examples 1-4 of this application obtained ReS2 / CdS composite hydrogen evolution materials with different band gaps and hydrogen evolution performance by changing different Re and Cd molar ratios. Figures 3-5 The images show the X-ray diffraction patterns, UV-Vis absorption spectra, and Tauc curves of ReS2 / CdS composite hydrogen evolution materials with different ratios.

[0043] like Figure 3As shown, with the increase of Re content, the diffraction peaks of the ReS2 / CdS composite sample in the range of 67.1° to 78.3° are relatively weaker than those of the pure CdS sample. This may be because the formation of ReS2 inhibits the crystallinity of these diffraction peaks. The diffraction peaks of CdS correspond to those on the standard card PDF#80-0006. The diffraction peaks at 24.5°, 26.7°, 28.3°, 43.9°, and 52.1° correspond to the (100), (002), (101), (103), and (112) crystal planes of the hexagonal phase, respectively. No diffraction peaks of ReS2 were found in the XRD pattern. This may be because the content of ReS2 is relatively low or the crystallinity of ReS2 is relatively weaker than that of CdS.

[0044] like Figure 4 The image shows the light absorption capacity of ReS2 / CdS prepared with different Re and Cd molar ratios. The light absorption capacity of the samples increases with the increase of Re content.

[0045] Figure 5 The figure shows the Tauc curve of the ReS2 / CdS composite material. The coordinates of the intersection point in the figure represent the band gap of the ReS2 / CdS heterojunction. It can be seen from the figure that the band gap of ReS2 / CdS prepared with different molar ratios of Re and Cd are different. Moreover, the band gap gradually decreases with the increase of Re content. This indicates that the introduction of ReS2 can effectively reduce the band gap of CdS, making it easier for the ReS2 / CdS composite material to gain energy and allow electrons to jump from the valence band to the conduction band.

[0046] The hydrogen evolution yield performance of ReS2 / CdS with different Re and Cd ratios prepared in Examples 1-4 of this invention is examined. From... Figure 6 We can see that the hydrogen performance of ReS2 / CdS prepared with different Re and Cd ratios is significantly different. The ReS2 / CdS prepared in Example 2 has a higher yield than other samples.

[0047] Based on the above research results, it can be seen that the ReS2 / CdS composite material prepared by the single-stage hydrothermal method of this invention is simple to operate and greatly saves the amount of rare metal Re used. This application only requires 1% Re to prepare the ReS2 / CdS composite material and improves the hydrogen evolution performance, significantly mitigating the photocorrosion problem of CdS. By changing the ratio of Re to Cd, the band gap can be controlled, making the energy level distribution of electrons and holes more suitable for photocatalytic reactions. The preparation process does not require complex double hydrothermal treatment, and only 1% Re is needed to achieve optimal photocatalytic hydrogen evolution performance of the ReS2 / CdS composite material. The introduction of Re also greatly improves the photocorrosion problem of CdS, significantly reduces energy consumption and cost, is simple and environmentally friendly, and can be easily industrialized as a photocatalyst material.

[0048] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a ReS 2 / CdS composite hydrogen evolution material, characterized in that, Includes the following steps: 1) Prepare a precursor solution by adding water to CN2H4S and Cd(Ac)2•2H2O; 2) H3NO·HCl and NH4ReO4 were dissolved in the precursor solution, stirred, and then transferred to a polytetrafluoroethylene liner for hydrothermal reaction. After the reaction was completed, the mixture was centrifuged and the precipitate was washed with deionized water and ethanol. The solid was collected, vacuum dried, and ground to obtain ReS2 / CdS composite hydrogen evolution material. The molar ratio of NH4ReO4 to Cd(Ac)2•2H2O was 0.005~0.05:

1.

2. The preparation method of the ReS2 / CdS composite hydrogen evolution material as described in claim 1, characterized in that, The amount of H3NO·HCl used is 3 to 4 times the molar mass of NH4ReO4.

3. The preparation method of the ReS2 / CdS composite hydrogen evolution material as described in claim 1, characterized in that, The amount of CN2H4S used is 5 to 6 times the molar mass of Cd(Ac)2•2H2O.

4. The preparation method of the ReS2 / CdS composite hydrogen evolution material as described in claim 1, characterized in that, The hydrothermal temperature is 160℃~200℃, and the reaction time is 20~24 h.

5. The ReS2 / CdS composite hydrogen evolution material prepared by the preparation method according to any one of claims 1-4.

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