Double-vacancy zn cds solid solution photocatalyst and preparation method and application thereof

Abstract

The application discloses a kind of double-vacancy ZnCdS solid solution photocatalyst and its preparation method and application, preparation method includes adding cadmium source, zinc source and sulfur source into anhydrous ethanol and stirring dissolution, the mass ratio of cadmium source, zinc source, sulfur source is 1:9:3, under the condition of 70~90 ℃ water bath reaction, after suction filtration, washing, drying, obtain powdery ZnCdS solid solution, NaOH is added to water and stirred and dissolved, then add powdery ZnCdS solid solution, again ultrasonic treatment, after suction filtration, washing, drying, obtain double-vacancy ZnCdS solid solution photocatalyst.The preparation method of the application has the advantages of high hydrogen production rate, good repeatability, simple preparation, low cost, etc., the obtained double-vacancy ZnCdS solid solution photocatalyst can be applied to the field of photocatalytic hydrogen production, and the hydrogen production efficiency is as high as 12.69mmol·g ‑1 ·h ‑1 , which is 23.94 times that of pure ZnS and 11.64 times that of pure CdS.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst preparation technology, specifically relating to a dual-vacancy ZnCdS solid solution photocatalyst, its preparation method, and its application. Background Technology

[0002] Due to the gradual depletion of fossil fuels, global industrialization, and the rapid consumption of natural resources, environmental problems and energy crises seriously threaten the sustainable development of today's society. Currently, the solution to the energy crisis still relies heavily on conventional fossil fuels, which increasingly exacerbates environmental pollution. Hydrogen energy, as a clean energy source, with non-toxic and harmless combustion products, is considered a key direction for achieving sustainable energy development.

[0003] Since Fujishima et al. discovered that TiO2 can produce hydrogen under ultraviolet light, photocatalysis research has developed rapidly. Among many photocatalysts, metal sulfides have stood out in photocatalytic hydrogen production. In particular, Zn... x Cd 1-x S, as a ternary metal sulfide solid solution, combines the advantages of narrow bandgap CdS (2.4 eV) and wide bandgap ZnS (3.6 eV). However, experiments have shown that photogenerated holes will transfer to Zn before being consumed by electron donors. x Cd 1-x On the surface of S, in this case, sulfide ions will be oxidized to sulfur or sulfate, resulting in Zn x Cd 1-x Severe photocorrosion of S limits its photocatalytic activity.

[0004] Surface defect engineering of photocatalysts can lead to higher absorption of visible light, forming new catalytically active sites to extend electron and hole lifetimes, thereby dynamically improving the photocatalytic performance of the photocatalyst. Current research mainly focuses on constructing surface defects through hydrothermal / solvothermal methods, chemical reduction methods, and high-temperature calcination methods. However, these methods are complex in terms of procedure and condition control. Hydrothermal / solvothermal methods have high equipment costs and safety risks, chemical reduction methods are highly reagent-dependent and the products are easily contaminated, and high-temperature calcination methods consume huge amounts of energy and are prone to inducing structural changes. Furthermore, in some studies, Zn constructed from surface defects... x Cd 1-x S solid solutions require additional co-catalysts to achieve ideal hydrogen production. Therefore, further research is needed to find simpler methods to break through Zn production barriers. x Cd 1-x S hydrogen production limit, improving Zn x Cd 1-x The stability of hydrogen production in S solid solutions is of great significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a dual-vacancy ZnCdS solid solution photocatalyst with high hydrogen production rate, good repeatability and stability, simple preparation and low cost, as well as its preparation method and application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] A method for preparing a dual-vacancy ZnCdS solid solution photocatalyst includes the following steps:

[0008] (1) Cadmium source, zinc source and sulfur source are added to anhydrous ethanol and stirred to dissolve. The mass ratio of cadmium source, zinc source and sulfur source is 1:9:3, and the mass-volume ratio of zinc source to anhydrous ethanol is 0.45g~0.54g:50mL~60mL. The reaction is carried out under water bath conditions of 70℃~90℃. After the reaction, the solution is filtered, washed and dried to obtain powdered ZnCdS solid solution, specifically powdered Zn 0.9 Cd 0.1 S solid solution;

[0009] (2) Add NaOH to water and stir to dissolve. The mass-volume ratio of NaOH to water is 0.8g~0.9g∶60mL~65mL to obtain NaOH solution. Then add the powdered ZnCdS solid solution obtained in step (1) and control the mass ratio of NaOH to powdered ZnCdS solid solution to be 1∶0.1~0.2. Then perform ultrasonic treatment. The ultrasonic frequency is 35kHz~40kHz and the ultrasonic time is 30min~60min. After ultrasonic treatment, filter, wash and dry to obtain double-vacancy ZnCdS solid solution photocatalyst.

[0010] In the above-mentioned method for preparing the double-vacancy ZnCdS solid solution photocatalyst, preferably, in step (1), the cadmium source is cadmium acetate dihydrate, the zinc source is zinc acetate dihydrate, and the sulfur source is thioacetamide.

[0011] In the preferred method for preparing the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst, in step (1), the ratio of the cadmium source, zinc source, sulfur source, and anhydrous ethanol is 0.06g∶0.54g∶0.18g∶60mL.

[0012] In the preferred method for preparing the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst, in step (2), the mass-to-volume ratio of NaOH to water is 0.8 g: 60 mL, the ultrasonic frequency is 40 kHz, and the ultrasonic time is 45 min.

[0013] In the above-mentioned method for preparing the double-vacancy ZnCdS solid solution photocatalyst, preferably, in step (1), the stirring and dissolving time is 10 min to 15 min, and the reaction time is 1 h to 2 h.

[0014] In the above-mentioned method for preparing the double-vacancy ZnCdS solid solution photocatalyst, preferably, in step (2), the stirring and dissolving time is 10 min to 15 min.

[0015] In the preferred method for preparing the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst, in step (1), the filtration and washing are repeated 3 to 6 times, and then the obtained solid is dried at a temperature of 60℃ to 65℃ for 12h to 14h.

[0016] In the preferred method for preparing the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst, in step (2), the filtration and washing are repeated 3 to 6 times, and then the obtained solid is dried at a temperature of 60℃ to 65℃ for 12h to 14h.

[0017] As a general technical concept, the present invention also provides a method for preparing the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst.

[0018] As a general technical concept, the present invention also provides an application of the above-mentioned dual-vacancy ZnCdS solid solution photocatalyst in the field of photocatalytic hydrogen production.

[0019] In this invention, ZnCdS can also be written as Zn x Cd 1-x S.

[0020] The main innovation of this invention is as follows:

[0021] (1) Preparation of ZnCdS solid solution (Zn) by the present invention x Cd 1-x The cadmium source, zinc source, and sulfur source in the solid solution were in a mass ratio of 1:9:3, and the zinc source to anhydrous ethanol was in a mass-to-volume ratio of 0.45g–0.54g:50mL–60mL, yielding powdered Zn. 0.9 Cd 0.1 The S solid solution photocatalyst reaches its maximum photocatalytic hydrogen evolution rate at x=0.9, which is much higher than the photocatalytic hydrogen evolution performance when x is 0.3, 0.5, 0.7, and 1. The double-vacancy ZnCdS solid solution photocatalyst prepared with x=0.9 has a hydrogen evolution performance several times higher than that of the photocatalyst with other x values, reaching the highest hydrogen production efficiency. This shows that through component optimization, the photocatalytic hydrogen evolution performance of this invention has huge potential for improvement.

[0022] (2) In this invention, powdered ZnCdS solid solution was synthesized entirely in a low-temperature water bath environment of 70℃~90℃. The applicant found that under these conditions, the crystal nucleation and growth rate is slower, which is conducive to the uniform incorporation of defects (such as sulfur vacancies) into the crystal lattice rather than their concentrated formation on the surface. This facilitates the control of defect formation and avoids uneven defect distribution or the generation of unnecessary impurity phases due to excessively rapid reaction. Consequently, a considerable and stable vacancy-forming structure was obtained, which is a prerequisite for achieving dual vacancies. In addition, the 70℃~90℃ water bath reaction is milder and more controllable than the high-temperature hydrothermal method (usually >150℃) of the prior art.

[0023] (3) In this invention, after synthesizing powdered ZnCdS solid solution, double vacancies are constructed. NaOH is added to establish a stable reducing environment with relatively low formation energy. The specific alkaline environment can stimulate the overflow of Zn and S atoms. Then, ultrasonic treatment at a specific time and frequency can effectively accelerate and consolidate the formation of double vacancies.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] 1. The preparation method of this invention uses a specific ratio of cadmium, zinc, and sulfur sources to prepare powdered ZnCdS solid solution under low-temperature water bath conditions of 70℃~90℃ throughout the entire process. The reaction time is only 1-2 hours. After synthesizing the ZnCdS solid solution, an alkaline reducing environment is established using NaOH, which enables the successful construction of surface defects in the ZnCdS solid solution. Simultaneously, ultrasound is used to further accelerate and consolidate the formation of surface defects. The dual-vacancy ZnCdS solid solution photocatalyst prepared by this invention is regulated by sulfur and zinc surface defects. The sulfur and zinc surface defects on the dual-vacancy ZnCdS solid solution photocatalyst act as electron and hole trapping sites, respectively, which not only prolongs the lifetime of holes and electrons but also greatly improves the separation efficiency of electrons and holes. The positively charged state is conducive to providing free charge carriers to the conduction band of the sulfide photocatalyst. At the same time, metal vacancies can induce a negatively charged state, which is conducive to the valence band accepting free holes. The captured photogenerated electrons are used for photocatalytic hydrogen production, and the holes are used for sacrificial agent consumption, which helps to reduce electron-hole pair recombination. The combination of the two synergistically promotes photocatalytic hydrogen production.

[0026] The preparation method of the present invention can achieve a high efficiency improvement in hydrogen production performance without loading any other photocatalysts or co-catalysts. The method does not use any complex reducing agents for defect construction, and induces and consolidates the formation of double vacancies by using NaOH and ultrasonic treatment under specific conditions at room temperature.

[0027] In summary, the preparation method of the present invention has a simpler procedure, shorter preparation time, better hydrogen production effect, higher repeatability and stability, and the raw materials are readily available, with low cost and low energy consumption.

[0028] 2. The double-vacancy ZnCdS solid solution photocatalyst prepared in this invention (i.e., defective V-Zn) x Cd 1-x S) can be applied to the field of photocatalytic hydrogen production, achieving a hydrogen production efficiency of up to 12.69 mmol·g in 10 vol% triethanolamine (TEOA) without any co-catalyst. -1 ·h -1 It is 23.94 times that of pure ZnS and 11.64 times that of pure CdS. Attached Figure Description

[0029] Figure 1 The image shows a SEM image of the dual-vacancy ZnCdS solid solution photocatalyst prepared in Example 1. In the image, EHT represents the accelerating voltage, WD represents the working distance, and Mag represents the magnification.

[0030] Figure 2 This is a TEM image of the double-vacancy ZnCdS solid solution photocatalyst prepared in Example 1.

[0031] Figure 3 Hydrogen production rate graphs for the dual-vacancy ZnCdS solid solution photocatalysts prepared in Examples 1-2, the ZnCdS solid solution photocatalysts prepared in Comparative Examples 1-4, the CdS photocatalyst prepared in Comparative Example 5, the ZnS photocatalyst prepared in Comparative Example 6, and the ZnCdS solid solution photocatalyst prepared in Comparative Example 7.

[0032] Figure 4 XRD patterns of the double-vacancy ZnCdS solid solution photocatalyst prepared in Example 1, the ZnCdS solid solution photocatalysts prepared in Comparative Examples 1-4, the CdS photocatalyst prepared in Comparative Example 5, and the ZnS photocatalyst prepared in Comparative Example 6.

[0033] Figure 5 Electron paramagnetic resonance (EPR) spectra of the double-vacancy ZnCdS solid solution photocatalyst prepared in Example 1 and the ZnCdS solid solution photocatalyst prepared in Comparative Example 1.

[0034] Figure 6 The cycling curve of the double-vacancy ZnCdS solid solution photocatalyst prepared in Example 1 is shown. Detailed Implementation

[0035] 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. All materials and instruments used in the following embodiments are commercially available.

[0036] Example 1

[0037] A method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to the present invention includes the following steps:

[0038] (1) Add 0.06 g of cadmium acetate dihydrate, 0.54 g of zinc acetate dihydrate, and 0.18 g of thioacetamide to 60 mL of anhydrous ethanol, stir thoroughly for 10 min to dissolve until a clear solution is obtained, and place in an 80 °C constant temperature water bath for 1 h to continue the reaction. After the reaction is completed, repeat the filtration and washing 6 times, and dry the obtained solid in a 60 °C forced air drying oven for 12 h to obtain powdered ZnCdS solid solution, specifically powdered Zn 0.9 Cd 0.1 S solid solution;

[0039] (2) Add 0.8g NaOH to 60mL of deionized water and stir thoroughly for 10min to dissolve, thus obtaining a NaOH solution and forming an alkaline reducing environment. Then add 0.1g of powdered Zn. 0.9 Cd 0.1 The solid solution was then subjected to ultrasonic treatment at a frequency of 40 kHz for 45 min. After ultrasonic treatment, the process of filtration and washing was repeated 6 times. The resulting solid was then dried in a forced-air drying oven at 60 °C for 12 h to obtain a double-vacancy ZnCdS solid solution photocatalyst, denoted as Zn. 0.9 Cd 0.1 S-45.

[0040] like Figure 1 As shown, the dual-vacancy ZnCdS solid solution photocatalyst Zn prepared in this embodiment... 0.9 Cd 0.1 The S-45 has a rough, uneven surface with relatively large gaps between pits, which facilitates the formation of vacancy. For example... Figure 2 As shown, Zn 0.9 Cd 0.1 Very distinct, blurry lattice fringes were observed in the irregular white areas of S-45, indirectly indicating that Zn 0.9 Cd 0.1 The S-45 has a large number of surface defects.

[0041] The hydrogen production performance of the photocatalyst was tested as follows:

[0042] Weigh out 20 mg of photocatalyst (specifically Zn in this example). 0.9 Cd 0.1S-45 was added to a reactor containing 90 mL of deionized water, followed by 10 mL of triethanolamine. The mixture was sonicated for 5 minutes to ensure uniform dispersion. The Labsolar-6A online photocatalytic analysis system (manufactured by Beijing Pofilai Technology Co., Ltd.) was connected to the reactor. A vacuum was evacuated for half an hour to remove air from the reaction solution. 20 mL of argon gas was injected into the reactor to protect the instrument. The plunger pump was turned on to ensure uniform dispersion of the argon gas within the system. To maximize the dispersion of the photocatalyst particles, a magnetic stirrer was placed at the bottom of the reactor to agitate the reaction solution. After the plunger pump ran for 15 minutes, a 300W xenon lamp was used to irradiate the reactor from the top to initiate the photocatalytic reaction. The H2 produced during the reaction was quantitatively analyzed online using an SP-7890 gas chromatograph. The results are as follows: Figure 3 As shown, the Zn prepared in this embodiment 0.9 Cd 0.1 The S-45 solid solution photocatalyst achieved a peak hydrogen production efficiency of 12.69 mmol·g. -1 ·h -1 .

[0043] Example 2

[0044] A method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to the present invention includes the following steps:

[0045] (1) Add 0.06 g of cadmium acetate dihydrate, 0.54 g of zinc acetate dihydrate, and 0.18 g of thioacetamide to 60 mL of anhydrous ethanol, stir thoroughly for 10 min to dissolve until a clear solution is obtained, and place in an 80 °C constant temperature water bath for 1 h to continue the reaction. After the reaction is completed, repeat the filtration and washing 6 times, and dry the obtained solid in a 60 °C forced air drying oven for 12 h to obtain powdered ZnCdS solid solution, specifically powdered Zn 0.9 Cd 0.1 S solid solution;

[0046] (2) Add 0.8g NaOH to 60mL of deionized water and stir thoroughly for 10min to dissolve, thus obtaining a NaOH solution and forming an alkaline reducing environment. Then add 0.1g of powdered Zn. 0.9 Cd 0.1 The solid solution was then subjected to ultrasonic treatment at a frequency of 40 kHz for 60 min. After ultrasonic treatment, the process of filtration and washing was repeated 6 times. The resulting solid was then dried in a forced-air drying oven at 60 °C for 12 h to obtain a double-vacancy ZnCdS solid solution photocatalyst, denoted as Zn. 0.9 Cd 0.1 S-60.

[0047] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn0.9 Cd 0.1 The S-60 solid solution photocatalyst achieved a peak hydrogen production efficiency of 10.28 mmol·g. -1 ·h -1 .

[0048] Comparative Example 1

[0049] A method for preparing a ZnCdS solid solution photocatalyst includes the following steps:

[0050] 0.06 g of cadmium acetate dihydrate, 0.54 g of zinc acetate dihydrate, and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C water bath and reacted continuously for 1 h. After the reaction was completed, the mixture was filtered and washed 6 times. The resulting solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered Zn. 0.9 Cd 0.1 S solid solution photocatalyst.

[0051] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn 0.9 Cd 0.1 The highest hydrogen production efficiency of the S solid solution photocatalyst reached 7.01 mmol·g. -1 ·h -1 .

[0052] Comparative Example 2

[0053] A method for preparing a ZnCdS solid solution photocatalyst includes the following steps:

[0054] 0.42 g of cadmium acetate dihydrate, 0.18 g of zinc acetate dihydrate, and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C water bath and reacted continuously for 1 h. After the reaction was completed, the mixture was filtered and washed 6 times. The resulting solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered Zn. 0.3 Cd 0.7 S solid solution photocatalyst.

[0055] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn 0.3 Cd 0.7 The highest hydrogen production efficiency of the S solid solution photocatalyst reached 1.19 mmol·g. -1 ·h -1 .

[0056] Comparative Example 3

[0057] A method for preparing a ZnCdS solid solution photocatalyst includes the following steps:

[0058] 0.3 g of cadmium acetate dihydrate, 0.3 g of zinc acetate dihydrate, and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C water bath and reacted continuously for 1 h. After the reaction was completed, the mixture was filtered and washed 6 times. The resulting solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered Zn. 0.5 Cd 0.5 S solid solution photocatalyst.

[0059] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn 0.5 Cd 0.5 The highest hydrogen production efficiency of the S solid solution photocatalyst reached 1.59 mmol·g. -1 ·h -1 .

[0060] Comparative Example 4

[0061] A method for preparing a ZnCdS solid solution photocatalyst includes the following steps:

[0062] 0.18 g of cadmium acetate dihydrate, 0.42 g of zinc acetate dihydrate, and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C water bath and reacted continuously for 1 h. After the reaction was completed, the mixture was filtered and washed 6 times. The resulting solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered Zn. 0.7 Cd 0.3 S solid solution photocatalyst.

[0063] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn 0.7 Cd 0.3 The highest hydrogen production efficiency of the S solid solution photocatalyst reached 2.59 mmol·g. -1 ·h -1 .

[0064] Comparative Example 5

[0065] A method for preparing a CdS photocatalyst includes the following steps:

[0066] 0.6 g of cadmium acetate dihydrate and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C constant temperature water bath and reacted continuously for 1 h. After the reaction was completed, the mixture was filtered and washed 6 times. The resulting solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered CdS photocatalyst.

[0067] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, the highest hydrogen production efficiency of the CdS photocatalyst reached 1.09 mmol·g. -1 ·h -1 .

[0068] Comparative Example 6

[0069] A method for preparing a ZnS photocatalyst includes the following steps:

[0070] 0.6 g of zinc acetate dihydrate and 0.18 g of thioacetamide were added to 60 mL of anhydrous ethanol and stirred thoroughly for 10 min until a clear solution was obtained. The solution was then placed in an 80 °C constant temperature water bath and reacted continuously for 1 h. After the reaction was completed, the solid was filtered and washed 6 times. The obtained solid was dried in a 60 °C forced-air drying oven for 12 h to obtain powdered ZnS photocatalyst.

[0071] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, the highest hydrogen production efficiency of the ZnS photocatalyst reaches 0.53 mmol·g. -1 ·h -1 .

[0072] Comparative Example 7

[0073] A method for preparing a ZnCdS solid solution photocatalyst includes the following steps:

[0074] (1) Add 0.06 g of cadmium acetate dihydrate, 0.54 g of zinc acetate dihydrate, and 0.18 g of thioacetamide to 60 mL of anhydrous ethanol, stir thoroughly for 10 min to dissolve until a clear solution is obtained, place in an 80 °C constant temperature water bath and continue to react for 1 h. After the reaction is completed, repeat the filtration and washing 6 times, and dry the obtained solid in a 60 °C forced air drying oven for 12 h to obtain powdered Zn. 0.9 Cd 0.1 S solid solution;

[0075] (2) Take 0.1g of powdered Zn 0.9 Cd 0.1The S solid solution was added to 60 mL of deionized water and subjected to ultrasonic treatment at a frequency of 40 kHz for 45 min. After ultrasonic treatment, the process of filtration and washing was repeated 6 times. The resulting solid was dried in a 60℃ forced-air drying oven for 12 h to obtain the ZnCdS solid solution photocatalyst, denoted as Zn. 0.9 Cd 0.1 S / N-45.

[0076] The testing process for the hydrogen production performance of the photocatalyst was the same as in Example 1. The test results showed that... Figure 3 As shown, Zn 0.9 Cd 0.1 The highest hydrogen production efficiency of the S / N-45 solid solution photocatalyst reached 7.22 mmol·g. -1 ·h -1 .

[0077] Figure 3 The graph shows the hydrogen production rates of the photocatalysts in Examples 1-3 and Comparative Examples 1-7. As can be seen from the graph, pure ZnS, due to its wide bandgap, exhibits a hydrogen production rate of 0.53 mmol·g⁻¹ under visible light irradiation. -1 ·h -1 Low hydrogen production efficiency: Pure CdS also exhibits a low hydrogen production efficiency of 1.09 mmol·g due to the recombination rate of photogenerated electrons and holes. -1 ·h -1 For ZnCdS solid solution photocatalysts, as Zn 2+ As the proportion increases, the hydrogen production efficiency gradually improves, especially when ZnCdS is Zn 0.9 Cd 0.1 At time S, the hydrogen production efficiency reaches its maximum value of 7.01 mmol·g. -1 ·h -1 Under the same NaOH concentration, the hydrogen production efficiency of ZnCdS solid solution photocatalysts with different ultrasonic times was higher than that of untreated ZnCdS solid solution photocatalysts. Among them, when the ultrasonic time was 45 min, the hydrogen production efficiency of ZnCdS solid solution photocatalysts reached as high as 12.69 mmol·g. -1 ·h -1 It is 23.94 times that of pure ZnS and 11.64 times that of pure CdS. This is because if the sonication time is too short, the vacancies and atoms may not be completely separated. However, if the sonication time is too long, the vacancies will be saturated, and some of the overflowing atoms will return to the vacancies.

[0078] Figure 4 The figures show the XRD patterns of the photocatalysts in Examples 1-3 and Comparative Examples 1-6. As can be seen from the figures, Zn... 0.9 Cd 0.1 The diffraction peaks of S-45 are compared to those of Zn. 0.9 Cd 0.1 S did not show a significant shift, indicating that Zn treated in an alkaline environment...0.9 Cd 0.1 S-45 did not undergo significant lattice changes, but Zn 0.9 Cd 0.1 The diffraction peak intensity of S-45 is slightly lower than that of Zn. 0.9 Cd 0.1 S, and Zn 0.9 Cd 0.1 The broadening of the S-45 peak indirectly indicates the existence of vacancies.

[0079] Figure 5 The electron paramagnetic resonance (EPR) spectra of the dual-vacancy ZnCdS solid solution photocatalyst prepared in Example 1 and the ZnCdS solid solution photocatalyst prepared in Comparative Example 1 are shown. As can be seen from the figures, Zn... 0.9 Cd 0.1 S-45 and Zn 0.9 Cd 0.1 The S samples all showed a signal at g=2.006, which is generated by anion vacancies (i.e., S vacancies). If the photocatalytic material can provide additional free electrons, it will adsorb atmospheric oxygen and thus easily accept electrons and generate vacancy signals. Theoretically, S vacancies can be used as electron traps to accelerate the transfer of photogenerated charge carriers from the bulk to the catalytic surface, extending the charge lifetime. Meanwhile, untreated Zn... 0.9 Cd 0.1 The presence of sulfur vacancies in sulfur (S) may be due to the random molecular motion during synthesis, leading to insufficient binding of S with Zn and Cd elements and the generation of a small number of sulfur vacancies. The Zn prepared in this invention... 0.9 Cd 0.1 The significantly enhanced and broadened signal of S-45 demonstrates an increase in sulfur vacancy (Sv) concentration and successful defect induction. Meanwhile, for Zn... 0.9 Cd 0.1 In sample S-45, at g=2.014 and g=2.002, the results were attributed to S vacancies and adjacent excess cations (such as Zn). 2+ The two substantial paramagnetic signals may be related to Zn vacancies. This invention uses NaOH, which has strong alkaline properties, to establish a stable reducing environment with relatively low formation energy, which is conducive to the formation of Zn vacancies. Ultrasonic energy can produce a certain physical erosion on the material surface, which can help strip surface atoms (especially sulfur atoms) and promote the formation of sulfur vacancies in conjunction with chemical erosion.

[0080] Figure 6 The cycling curves of the dual-vacancy ZnCdS solid solution photocatalyst prepared in Example 1 are shown. The Zn group was evaluated using a cyclic H2 precipitation experiment. 0.9 Cd 0.1 The stability test results of the S-45 are as follows: Figure 6 As shown, it can be clearly observed that Zn0.9 Cd 0.1 S-45 did not show a significant reduction in H2 production during four cycles of photocatalytic reaction, thus verifying the presence of double-vacancy defects in Zn. 0.9 Cd 0.1 The S-45 solid solution photocatalyst exhibits excellent stability in photocatalytic hydrogen production, and this excellent and stable photocatalytic hydrogen evolution ability can be attributed to Zn. 0.9 Cd 0.1 The formation of S-45 double vacancies and the high charge separation efficiency and interfacial charge transfer caused by S-rich defects.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing a dual-vacancy ZnCdS solid solution photocatalyst, characterized in that, Includes the following steps: (1) Cadmium source, zinc source and sulfur source are added to anhydrous ethanol and stirred to dissolve. The mass ratio of cadmium source, zinc source and sulfur source is 1:9:3, and the mass-volume ratio of zinc source to anhydrous ethanol is 0.45g~0.54g:50mL~60mL. The reaction is carried out under water bath conditions of 70℃~90℃. After the reaction, the solution is filtered, washed and dried to obtain powdered ZnCdS solid solution, specifically powdered Zn 0.9 Cd 0.1 S solid solution; (2) Add NaOH to water and stir to dissolve. The mass-volume ratio of NaOH to water is 0.8g~0.9g∶60mL~65mL to obtain NaOH solution. Then add the powdered ZnCdS solid solution obtained in step (1) and control the mass ratio of NaOH to powdered ZnCdS solid solution to be 1∶0.1~0.

2. Then perform ultrasonic treatment. The ultrasonic frequency is 35kHz~40kHz and the ultrasonic time is 30min~60min. After ultrasonic treatment, filter, wash and dry to obtain double-vacancy ZnCdS solid solution photocatalyst.

2. The method for preparing the dual-vacancy ZnCdS solid solution photocatalyst according to claim 1, characterized in that, In step (1), the cadmium source is cadmium acetate dihydrate, the zinc source is zinc acetate dihydrate, and the sulfur source is thioacetamide.

3. The method for preparing the dual-vacancy ZnCdS solid solution photocatalyst according to claim 1, characterized in that, In step (1), the ratio of cadmium source, zinc source, sulfur source and anhydrous ethanol is 0.06g:0.54g:0.18g:60mL.

4. The method for preparing the dual-vacancy ZnCdS solid solution photocatalyst according to claim 1, characterized in that, In step (2), the mass-to-volume ratio of NaOH to water is 0.8g:60mL, the ultrasonic frequency is 40kHz, and the ultrasonic time is 45min.

5. The method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to any one of claims 1 to 4, characterized in that, In step (1), the stirring and dissolving time is 10 min to 15 min, and the reaction time is 1 h to 2 h.

6. The method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to any one of claims 1 to 4, characterized in that, In step (2), the stirring and dissolving time is 10 min to 15 min.

7. The method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to any one of claims 1 to 4, characterized in that, In step (1), the filtration and washing are repeated 3 to 6 times, and then the obtained solid is dried at a temperature of 60℃ to 65℃ for 12 to 14 hours.

8. The method for preparing a dual-vacancy ZnCdS solid solution photocatalyst according to any one of claims 1 to 4, characterized in that, In step (2), the filtration and washing are repeated 3 to 6 times, and then the obtained solid is dried at a temperature of 60℃ to 65℃ for 12 to 14 hours.

9. A dual-vacancy ZnCdS solid solution photocatalyst prepared by any one of claims 1 to 8.

10. The application of the dual-vacancy ZnCdS solid solution photocatalyst as described in claim 9 in the field of photocatalytic hydrogen production.

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