A CuGaS2-based catalyst and its preparation method and application

Abstract

The present invention discloses a CuGaS2-based catalyst, its preparation method, and application. The catalyst comprises CuGaS2 and graphite-phase carbon nitride (g-C3N4) nanosheets, wherein the CuGaS2 and g-C3N4 are combined to form an S-type p-n heterojunction. The preparation method comprises adding CuGaS2 and g-C3N4 to a solvent, mixing them uniformly, and then drying and calcining the solid to obtain the CuGaS2-based catalyst. By combining CuGaS2 and g-C3N4 to form an S-type p-n heterojunction, the CuGaS2 / g-C3N4 composite material exhibits a strong light response, achieves rapid separation of photogenerated carriers, and thereby increases the hydrogen production rate.

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] With the continuous growth of global energy demand and the intensification of environmental problems, people are gradually realizing the limitations and unsustainability of fossil fuels. In the past 250 years, humanity has experienced three industrial revolutions, all of which have in common the development and effective utilization of fossil energy. Fossil energy is arguably humanity's primary energy source. However, overreliance on fossil fuels has become a key global challenge in today's economy. These fuels are rapidly dwindling. In addition to dwindling reserves, their use has also led to serious environmental problems such as climate change, air pollution, and water shortages. In particular, the combustion of fossil fuels releases large amounts of greenhouse gases such as carbon dioxide, leading to rising global temperatures, rising sea levels, and more extreme weather events. To address these issues, the international community has begun promoting energy transitions and accelerating the shift to clean energy. Hydrogen, as a clean, efficient, safe, and sustainable secondary energy source, can be obtained through a variety of channels, including primary and secondary energy sources, as well as industrial applications. It can also be widely used in industry, construction, transportation, and the power sector. It is a key component of building a diversified energy supply system dominated by clean energy and is often called the ultimate energy source 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, etc. Traditional hydrogen production methods have the problems of large system energy consumption and greenhouse gas release caused by the operation of the hydrogen production reaction. Therefore, it is particularly urgent and important to develop clean, sustainable, and low-cost hydrogen production technologies 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 splitting technology has become an ideal clean energy production technology due to its unique properties such as deep reaction at room temperature and the ability to directly use sunlight as a light source to drive the reaction. However, the efficiency of solar energy conversion and utilization is low. The key to breaking through this technical bottleneck is to develop efficient, stable, and easy-to-synthesize semiconductor photocatalysts to achieve the ultimate goal of large-scale promotion of hydrogen energy.

[0004] Currently, bimetallic sulfides, represented by CuGaS2, are widely used in photocatalytic hydrogen production. However, their use as photocatalytic hydrogen production catalysts has limitations, such as low visible light absorption efficiency and high recombination rates of photogenerated carriers. Therefore, modification is necessary. Researchers have modified CuGaS2-based materials through methods such as morphology manipulation and precious metal loading, but their catalytic activity remains low, hindering 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 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 to 3. As the ratio of g-C3N4 increases, the photocatalytic hydrogen production first increases 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 by comprising 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 them for 0.5 to 3 hours, and then magnetically stirring them 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 nanocomposites of p-type CuGaS2 and n-type g-C3N4 semiconductors to construct an S-type pn heterojunction catalyst for photocatalytic hydrogen production. Figure 1 As shown, under light irradiation, 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 preserves the system's strongest redox capacity, consistent with an S-type charge transfer mechanism. By optimizing the band structure to enhance spectral absorption and effectively separate photogenerated electrons and holes, the recombination rate is reduced, allowing more carriers to participate in the hydrogen production reaction, thereby facilitating efficient photocatalytic water splitting and hydrogen production.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The catalytic activity of the catalyst is improved by forming an S-type pn heterojunction through the composite of CuGaS2 and g-C3N4; (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 This is a 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 Graph showing the photocatalytic hydrogen production rates 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 will be 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 maintained for 4 h. The final white powder obtained was g-C3N4.

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

[0033] 50 mg of CuGaS2 and 5 mg of g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the above-prepared mixture 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.

[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 maintained for 4 h. The final white powder obtained was g-C3N4.

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

[0041] 50 mg of CuGaS2 and 10 mg of g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the above-prepared mixture 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 maintained for 4 h. The final white powder obtained was g-C3N4.

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

[0049] 50 mg of CuGaS2 and 15 mg of g-C3N4 were dissolved in 50 mL of a water-ethanol (volume ratio 20:30) mixture, and the above-prepared mixture 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.

[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 was 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) diagram, it can be seen that the catalyst is composed of granular CuGaS2 and nanosheet-like g-C3N4, 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 composition and distribution in 20CN / CGS were further demonstrated by elemental mapping of C, N, Cu, Ga, and S on HAADF-STEM images, 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. 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 to a 100 mL beaker and sonicate for 30 min.

[0063] (2) transferring the ultrasonicated 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 apparatus with Ar gas three times to remove air from the apparatus and avoid interference;

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

[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 g-C3N4 content increases, the hydrogen production rates are 58.03umol / g / h, 140.7umol / g / h, and 119.3umol / g / h, respectively, showing 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 Example 2. This is because Comparative Example 1 only contains g-C3N4, which has a narrow light absorption range; Comparative Example 2 only contains CuGaS2, which has a low efficiency in separating photogenerated carriers.

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

[0070] Depend on Figure 6 The absorption edge of g-C3N4 is 480 nm. Compared to g-C3N4, CuGaS2 exhibits a visible light absorption range. Therefore, the absorption edge of the catalyst formed by combining g-C3N4 and CuGaS2 in Example 2 shifts significantly to 567 nm, demonstrating enhanced light response.

[0071] The stability test of the hydrogen evolution catalyst of Example 2 was performed, and the results are shown in Figure 7.

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

Claims

1. A CuGaS2-based catalyst, characterized in that The invention comprises CuGaS2 and graphite phase carbon nitride g-C3N4 nanosheets, wherein the CuGaS2 and g-C3N4 are composited to form an S-type pn heterojunction, and the mass ratio of the CuGaS2 to the g-C3N4 is 10:2-3.

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

3. The method for preparing a CuGaS2-based catalyst according to claim 2, wherein: The calcination temperature is 70-120°C.

4. The method for preparing a CuGaS2-based catalyst according to claim 2, wherein: 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.

5. The method for preparing a CuGaS2-based catalyst according to claim 2, wherein: 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.

6. The method for preparing a CuGaS2-based catalyst according to claim 5, wherein: The atomic ratio of copper to gallium in gallium sulfide and cuprous sulfide is 1:1~1.

4.

7. Use of the CuGaS2-based catalyst according to claim 1 in photocatalytic production of H2.

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