CuGaS2-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a CuGaS2-based catalyst and a preparation method and application thereof.The catalyst comprises CuGaS2 and graphite phase carbon nitride g-C3N4 nanosheets, CuGaS2 and g-C3N4 are compounded to form an S-type p-n heterojunction, and the preparation method of the CuGaS2-based catalyst comprises the steps that CuGaS2 and g-C3N4 are added into a solvent to be evenly mixed, then solids are dried and calcined, and the CuGaS2-based catalyst is obtained. According to the preparation method, CuGaS2 and g-C3N4 are compounded to form an S-type p-n heterojunction, so that the CuGaS2 / g-C3N4 composite material shows strong light response, rapid separation of photon-generated carriers is realized, and the hydrogen production rate is further improved.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a CuGaS2-based catalyst and a preparation method and application thereof. Background Art

[0002] As global energy demand continues to grow and environmental problems continue to intensify, people are beginning to realize the limitations and unsustainability of fossil fuels. In the past 250 years, mankind has experienced three industrial revolutions in total. The common point is the development and effective utilization of fossil energy. It can be said that fossil energy is the main source of energy for human use. However, over-reliance on fossil fuels has become a key global challenge in today's economy because they are rapidly decreasing. In addition to the gradual decrease in reserves, the use of fossil fuels has also brought serious environmental problems such as climate change, air pollution and water shortages. In particular, the combustion of fossil fuels in climate change will release a large amount of greenhouse gases such as carbon dioxide, leading to rising global temperatures, rising sea levels and increasing extreme weather events. In order to cope with these problems, the international community has begun to promote energy transformation and accelerate the transition to clean energy. Hydrogen energy, as a clean, efficient, safe and sustainable secondary energy, can be obtained through a variety of channels such as primary energy, secondary energy and industrial fields. It can also be widely used in industry, construction, transportation and power industries. It is an important carrier for building a diversified energy supply system dominated by clean energy in the future. It is also called the ultimate energy of the 21st century.

[0003] At present, the main methods of hydrogen production include fossil fuel hydrogen production, water electrolysis hydrogen production, industrial by-product hydrogen production, photolysis of water hydrogen production, etc. The traditional hydrogen production methods have the problems of large system energy consumption and greenhouse gas release caused by the operation process of the hydrogen production reaction. Therefore, it is particularly urgent and important to develop clean, sustainable, and low-cost hydrogen production technology to promote the development of hydrogen energy. Using photocatalytic technology to drive water decomposition to produce hydrogen using solar energy is a promising strategy. Photocatalytic water decomposition technology has become an ideal clean energy production technology due to its unique properties such as deep reaction at room temperature and direct use of sunlight as a light source to drive the reaction. However, the efficiency of solar energy conversion and utilization in this pathway is low. At present, the core of breaking through the bottleneck of this technology is to develop efficient, stable, and easy-to-synthesize semiconductor photocatalysts to achieve the ultimate goal of large-scale promotion of hydrogen energy.

[0004] At present, bimetallic sulfides represented by CuGaS2 are widely used in the field of photocatalytic hydrogen production. However, there are some limitations when used as photocatalytic hydrogen production catalysts, such as low visible light absorption efficiency and high photogenerated carrier recombination rate. Therefore, it needs to be modified. At present, researchers have modified CuGaS2-based materials by morphology control and precious metal loading, but its catalytic activity is still low, which hinders commercial application. Summary of the invention

[0005] Objectives of the invention: The first objective of the present invention is to provide a CuGaS2-based catalyst that improves the efficiency of photocatalytic hydrogen evolution; the second objective of the present invention is to provide a method for preparing the CuGaS2-based catalyst; the third objective of the present invention is to provide the application of the CuGaS2-based catalyst in the photocatalytic production of H2.

[0006] Technical solution: The CuGaS2-based catalyst described in the present invention includes CuGaS2 and graphite phase carbon nitride g-C3N4 nanosheets, and CuGaS2 and g-C3N4 are composited to form an S-type pn heterojunction.

[0007] Preferably, the mass ratio of CuGaS2 to g-C3N4 is 10:1-3. As the proportion of g-C3N4 increases, the photocatalytic hydrogen production increases first and then decreases. When the mass ratio of CuGaS2 to g-C3N4 is 10:2, the H2 generation rate of the material is the highest, which is 140.7 μmol g -1 h -1 , which is about 3.5 times that of CuGaS2.

[0008] Further preferably, the mass ratio of CuGaS2 to g-C3N4 is 10:2 to 3.

[0009] The preparation method of the CuGaS2-based catalyst described in the present invention is characterized in that it includes the following steps: adding CuGaS2 and g-C3N4 to a solvent and mixing them evenly, and then drying the solid and calcining it to obtain the CuGaS2-based catalyst.

[0010] Preferably, the calcination temperature is 70-120° C., the calcination time is 0.5-3 hours, the calcination heating rate is 5° C. / min, and the calcination atmosphere is argon.

[0011] Preferably, the method of adding CuGaS2 and g-C3N4 to a solvent and mixing them uniformly is: adding CuGaS2 and g-C3N4 to an ethanol aqueous solution, ultrasonically dispersing for 0.5 to 3 hours, and then magnetically stirring for 0.5 to 3 hours.

[0012] Preferably, the preparation method of CuGaS2 is: gallium sulfide and cuprous sulfide are fully mixed and ground, and then the mixture is sealed in a quartz tube furnace and calcined at 600-1000°C.

[0013] Preferably, the atomic ratio of copper to gallium in the gallium sulfide and cuprous sulfide is 1:1 to 1.4.

[0014] Preferably, the preparation method of g-C3N4 is: heating dicyandiamide to 500-600°C, annealing for 2-4 hours, and then maintaining for 3-5 hours, and finally obtaining a white powder which is g-C3N4.

[0015] The CuGaS2-based catalyst described in the present invention is used in the photocatalytic production of H2.

[0016] Invention mechanism: The present invention uses a nanocomposite material of p-type CuGaS2 and n-type g-C3N4 semiconductor to construct an S-type pn heterojunction catalyst for photocatalytic hydrogen production. Figure 1 As shown: Under light irradiation, the excess photogenerated electrons in the conduction band of p-type CuGaS2 recombine with holes in the valence band of n-type g-C3N4 through the built-in electric field. This process effectively enhances the separation of electron-hole pairs and retains the strongest redox ability of the system, which conforms to the S-type charge transfer mechanism. By optimizing the band structure to enhance the absorption of the spectrum, the photogenerated electrons and holes are effectively separated, the recombination rate is reduced, and more carriers can participate in the hydrogen production reaction, which is conducive to efficient photocatalytic water decomposition to produce hydrogen.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The S-type pn heterojunction is formed by the composite of CuGaS2 and g-C3N4, thereby improving the catalytic activity of the catalyst; (2) When the mass ratio of CuGaS2 to g-C3N4 is 10:2, a hydrogen production effect of up to 140.7 umol / g / h is achieved; (3) This synthesis method is simple to operate, low-cost, can be prepared in large quantities, the material is recyclable, and has high environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the mechanism diagram of the present invention;

[0019] Figure 2 X-ray diffraction (XRD) patterns of the hydrogen evolution catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 2;

[0020] Figure 3 The transmission electron microscope (TEM) image of the hydrogen evolution catalyst prepared in Example 2;

[0021] Figure 4 Elemental mapping (HAADF-STEM elemental mapping) of the hydrogen evolution catalyst prepared in Example 2;

[0022] Figure 5 The photocatalytic hydrogen production rate diagram of the hydrogen evolution catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 2;

[0023] Figure 6The UV-visible diffuse reflectance spectra (DRS) of the hydrogen evolution catalysts prepared in Example 2 and Comparative Examples 1-2 are shown;

[0024] Figure 7 This is a stability test diagram of the hydrogen evolution catalyst prepared in Example 2. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with embodiments.

[0026] Example 1

[0027] The preparation method of the CuGaS2-based hydrogen evolution catalyst of the present invention comprises the following steps:

[0028] (1) Preparation of CuGaS2

[0029] 330 g of gallium sulfide and 159 mg of cuprous sulfide were thoroughly mixed and ground, and then the mixture was sealed in a quartz tube furnace and calcined at 800° C. for about 10 h.

[0030] (2) Preparation of g-C3N4

[0031] 20 g of dicyandiamide was heated to 550 °C, annealed for 3 h, and then kept for 4 h. The final white powder obtained was g-C3N4.

[0032] (3) Preparation of CuGaS2 / g-C3N4

[0033] 50 mg CuGaS2 and 5 mg g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the mixture prepared above was ultrasonically treated for 1 h and magnetically stirred for 1 h; then, the formed precipitate was filtered, washed several times with deionized water, and dried in an air oven at 60 °C, and then calcined at 100 °C for 2 h.

[0034] Example 2

[0035] The preparation method of the CuGaS2-based hydrogen evolution catalyst of the present invention comprises the following steps:

[0036] (1) Preparation of CuGaS2

[0037] 330 mg of gallium sulfide and 159 mg of cuprous sulfide were thoroughly mixed and ground, and then the mixture was sealed in a quartz tube furnace and calcined at 800° C. for about 10 h.

[0038] (2) Preparation of g-C3N4

[0039] 20 g of dicyandiamide was heated to 550 °C, annealed for 3 h, and then kept for 4 h. The final white powder obtained was g-C3N4.

[0040] (3) Preparation of CuGaS2 / g-C3N4

[0041] 50 mg CuGaS2 and 10 mg g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the mixture prepared above was ultrasonically treated for 1 h and magnetically stirred for 1 h; then, the formed precipitate was filtered, washed several times with double distilled water, and dried in an air oven at 60 °C, and then calcined at 100 °C for 2 h.

[0042] Example 3

[0043] The preparation method of the CuGaS2-based hydrogen evolution catalyst of the present invention comprises the following steps:

[0044] (1) Preparation of CuGaS2

[0045] 330 mg of gallium sulfide and 159 mg of cuprous sulfide were thoroughly mixed and ground, and then the mixture was sealed in a quartz tube furnace and calcined at 800° C. for about 10 h.

[0046] (2) Preparation of g-C3N4

[0047] 20 g of dicyandiamide was heated to 550 °C, annealed for 3 h, and then kept for 4 h. The final white powder obtained was g-C3N4.

[0048] (3) Preparation of CuGaS2 / g-C3N4

[0049] 50 mg CuGaS2 and 15 mg g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the mixture prepared above was ultrasonically treated for 1 h and magnetically stirred for 1 h; then, the formed precipitate was filtered, washed several times with deionized water, and dried in an air oven at 60 °C, and then calcined at 100 °C for 2 h.

[0050] Comparative Example 1

[0051] On the basis of Example 3, steps (1) and (3) are omitted to obtain a g-C3N4 hydrogen evolution catalyst.

[0052] Comparative Example 2

[0053] On the basis of Example 3, without performing steps (2) and (3), a CuGaS2 hydrogen evolution catalyst is obtained.

[0054] Structural characterization

[0055] The hydrogen evolution catalysts of Examples 1 to 3 and Comparative Examples 1 to 2 were characterized by X-ray diffraction (XRD). Figure 2 shown.

[0056] pass Figure 2 It can be seen that Examples 1 to 3 all exhibit characteristic peaks of CuGaS2, indicating the successful synthesis of CuGaS2. At the same time, a prominent diffraction peak near 27.5° can be clearly attributed to the presence of the g-C3N4 crystal structure, indicating the successful loading of graphite phase carbon nitride.

[0057] The catalyst prepared in Example 3 was characterized by transmission electron microscopy (TEM), HAADF-STEM and STEM–EDX elemental mapping. Figures 3-4 shown.

[0058] Depend on Figure 3 From the 20CN / CGS (20g-C3N4 / CuGaS2) graph, it can be seen that the catalyst is composed of CuGaS2 in particle form and g-C3N4 in nanosheet form, which means that the morphology of CuGaS2 and g-C3N4 does not change during the 20CN / CGS combination process.

[0059] pass Figure 4 The elemental mapping of C, N, Cu, Ga, and S on the HAADF-STEM images further demonstrated the elemental composition and distribution in 20CN / CGS, which further demonstrated the successful preparation of the composite and confirmed the presence of these elements in the composite.

[0060] Performance Characterization

[0061] The photocatalytic hydrogen production performance of the hydrogen evolution catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the testing method included the following steps:

[0062] (1) Add 10 mg of hydrogen evolution catalyst, 10 mL of triethanolamine, and 70 mL of ultrapure water into a 100 mL beaker and perform ultrasonic treatment for 30 min;

[0063] (2) transferring the ultrasonic reaction solution into a reactor;

[0064] (3) Install the reactor on the photocatalytic device and start the vacuum pump to evacuate for 20 minutes;

[0065] (4) Then purge the entire reaction device with Ar gas three times to remove air from the device and avoid interference;

[0066] (5) Turn on the magnetic stirrer, xenon lamp power, and gas chromatography;

[0067] (6) Photocatalytic reaction for 4 hours.

[0068] The results are as follows Figure 5As shown, it can be seen that in Examples 1 to 3, as the content of g-C3N4 increases, the hydrogen production rates are 58.03umol / g / h, 140.7umol / g / h, and 119.3umol / g / h, respectively, and the hydrogen production effect shows a trend of first increasing and then decreasing. The hydrogen production rates of Comparative Examples 1 and 2 are significantly lower than the hydrogen production effect of the catalyst of Implementation Example 2. This is because Comparative Example 1 only has g-C3N4, and the light absorption range is narrow; Comparative Example 2 only has CuGaS2, and the separation efficiency of photogenerated carriers is low.

[0069] The hydrogen evolution catalysts prepared in Example 2 and Comparative Examples 1 to 2 were characterized by UV-visible diffuse reflectance spectroscopy (DRS). Figure 6 shown.

[0070] Depend on Figure 6 It can be obtained that the light absorption edge of g-C3N4 is 480nm. Compared with g-C3N4, CuGaS2 shows a light absorption range of visible light. Therefore, the light absorption edge of the catalyst after the combination of g-C3N4 and CuGaS2 materials in Example 2 is significantly shifted to 567nm, and shows enhanced light response ability.

[0071] The stability test of the hydrogen evolution catalyst of Example 2 was performed, and the result is shown in FIG7 .

[0072] pass Figure 7 It can be seen that the H2 evolution rate showed no significant change during the six cycles, indicating that the synthesized samples have excellent photocatalytic stability.

Claims

1. A CuGaS2-based catalyst, characterized in that It includes CuGaS2 and graphite phase carbon nitride g-C3N4 nanosheets, and CuGaS2 and g-C3N4 are composited to form an S-type pn heterojunction.

2. The CuGaS2-based catalyst according to claim 1, characterized in that The mass ratio of CuGaS2 to g-C3N4 is 10:1 to 3.

3. The CuGaS2-based catalyst according to claim 2, characterized in that The mass ratio of CuGaS2 to g-C3N4 is 10:2-3.

4. A method for preparing a CuGaS2-based catalyst according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: adding CuGaS2 and g-C3N4 into a solvent and mixing them evenly, and then drying and calcining the solid to obtain the CuGaS2-based catalyst.

5. The method for preparing a CuGaS2-based catalyst according to claim 4, characterized in that: The calcination temperature is 70-120°C.

6. The method for preparing a CuGaS2-based catalyst according to claim 4, characterized in that: The method for adding CuGaS2 and g-C3N4 into a solvent and mixing them uniformly is as follows: adding CuGaS2 and g-C3N4 into an ethanol aqueous solution, ultrasonically dispersing for 0.5 to 3 hours, and then magnetically stirring for 0.5 to 3 hours.

7. The method for preparing a CuGaS2-based catalyst according to claim 4, characterized in that: The preparation method of CuGaS2 is as follows: gallium sulfide and cuprous sulfide are fully mixed and ground, and then the mixture is sealed in a quartz tube furnace and calcined at 600-1000°C to obtain the CuGaS2.

8. The method for preparing a CuGaS2-based catalyst according to claim 7, characterized in that: The atomic ratio of copper to gallium in gallium sulfide and cuprous sulfide is 1:1 to 1.

4.

9. The method for preparing a CuGaS2-based catalyst according to claim 4, characterized in that: The preparation method of g-C3N4 is as follows: dicyandiamide is heated to 500-600° C., annealed for 2-4 hours, and then maintained for 3-5 hours, and the finally obtained white powder is g-C3N4.

10. Use of the CuGaS2-based catalyst according to any one of claims 1 to 3 in photocatalytic production of H2.

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