Preparation method and application of indium sulfide photocatalytic material with specific vacancy

Abstract

The invention provides a preparation method and application of an indium sulfide photocatalytic material with a specific vacancy. The method comprises the following steps: forming a first solution from ethanol and deionized water; placing InCl3. 4H2O and thioacetamide, or placing InCl3. 4H2O, thioacetamide and hexamethylenetetramine in the first solution for stirring and dissolving, and obtaining a clear solution after stirring is completed; carrying out constant-temperature reaction on the clarified solution, cooling after the reaction is completed, and centrifuging to collect an obtained product; the obtained product is washed, constant-temperature drying is conducted after washing is completed, and the photocatalytic material with the specific vacancy is obtained after drying is completed. According to the invention, vacancies are introduced into In2S3, so that surface active sites are adjusted, the utilization rate of light and the separation and transfer capability of photon-generated carriers are enhanced, and the activity of reducing N2 into NH3 through photocatalysis is improved.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic material preparation, and in particular to a preparation method and application of an indium sulfide photocatalytic material with specific vacancies. Background Art

[0002] Ammonia (NH3) is an irreplaceable chemical substance for the production of agricultural fertilizers and artificial fibers, and is crucial to society's production and industrial processes. Currently, the Haber-Bosch process is still the main method for synthesizing ammonia. The high temperature (>673 K) and high pressure (>200 bar) reaction conditions of this process are extremely unfriendly to the safety and environment of the production process. In this context, the development of sustainable and energy-saving nitrogen fixation methods is crucial to addressing the challenges of energy and environmental sustainability. Using solar energy to drive the conversion of N2 to NH3 under mild conditions is a green and promising alternative to traditional Haber-Bosch chemistry. However, the energy of breaking the N≡N bond is as high as 940.95 kJ·mol -1 , which makes it very difficult to convert N2 molecules into a usable form. In addition, the photocatalyst itself faces challenges such as light absorption rate, separation and transfer efficiency of photogenerated charges, and conversion efficiency. Therefore, it is necessary to rationally design photocatalysts to promote the efficient conversion of N2 into NH3.

[0003] Among visible light-responsive photocatalysts, metal sulfides have been widely reported for use in photocatalytic environments and energy fields due to their unique properties, high abundance, and simple and low-cost synthesis process. Among the many metal sulfides, In2S3 has multiple advantages that make it one of the most promising photocatalysts. First, In2S3 has a relatively favorable band gap (2.0-2.4 eV), which can capture a large part of the solar spectrum, allowing for efficient light absorption and the formation of photogenerated electron-hole pairs. Secondly, In2S3 has a relatively negative conduction band and a relatively positive valence band position as well as good charge transport ability, so that the carriers generated by its photoexcitation can be effectively transferred to the catalyst surface to participate in redox reactions while having a high redox ability.

[0004] Although the narrow band gap of In2S3 gives it a wide light absorption range, this usually also causes the rapid recombination of photogenerated electrons and holes inside the catalyst. Studies have shown that due to the high recombination rate of photogenerated carriers, only about 10% of the photoexcited electrons in In2S3 can be used for photocatalytic reduction reactions. In addition, due to the high recombination rate of S 2- Ions will be oxidized to atomic S (S) under oxidative conditions (such as various free radicals generated by photogenerated holes and photogenerated carriers). 0) leaching, leading to widespread photocorrosion of metal sulfides, which severely impacts photocatalytic efficiency and long-term stability. Furthermore, the current photocatalytic reaction efficiency is generally low, which has become a bottleneck in the practical application of photocatalysts. Therefore, improving the photocatalytic activity, efficiency, and stability of In2S3 is of great significance. Summary of the Invention

[0005] In view of the above situation, the main purpose of the present invention is to propose a preparation method and application of an indium sulfide photocatalytic material with specific vacancies to solve the above technical problems.

[0006] The present invention provides a method for preparing an indium sulfide photocatalytic material with specific vacancies, the method comprising the following steps: forming a first solution by combining ethanol and deionized water; InCl3·4H2O and thioacetamide, or InCl3·4H2O, thioacetamide and hexamethylenetetramine, are placed in the first solution and stirred to dissolve, and after stirring, a clear solution is obtained; The clarified solution was reacted at a constant temperature, and after completion of the reaction, it was cooled and then centrifuged to collect the obtained product; The obtained product is washed, and then dried at a constant temperature. After the drying is completed, a photocatalytic material with specific vacancies is obtained.

[0007] The present invention also proposes an application of an indium sulfide photocatalytic material with specific vacancies, wherein the photocatalytic material is prepared by the above-mentioned method for preparing an indium sulfide photocatalytic material with specific vacancies, and the photocatalytic material is used for photocatalytic reduction of N2 to NH3.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces vacancies into In2S3, thereby adjusting the surface active sites, enhancing its light utilization and the separation and transfer capabilities of photogenerated carriers, so as to fix N2 in the air and convert it into NH3 under light conditions, and improve the activity of photocatalytic N2 reduction to NH3, which is beneficial to the advancement and development of catalytic materials.

[0009] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 XRD patterns of different samples; Figure 2 SEM and TEM images of the samples; Figure 3 The NH3 yield diagram of different samples under light source irradiation; Figure 4 This is the yield diagram of NH3 of samples under different conditions; Figure 5 UV diffuse reflectance images of different samples; Figure 6 is the photocurrent response diagram of the sample; Figure 7 is the impedance diagram of the sample; Figure 8 Photoluminescence spectra of different samples. DETAILED DESCRIPTION

[0011] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0012] These and other aspects of the embodiments of the present invention will become clear with reference to the following description and accompanying drawings. In these descriptions and accompanying drawings, some specific implementations of the embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0013] Example 1 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 15 mL of ethanol and 15 mL of deionized water were added to form a first solution; 0.2346 g of InCl3·4H2O and 1202 g of thioacetamide were placed in the first solution and stirred for 30 min to obtain a clear solution; The clarified solution was reacted at 160°C for 24 hours, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed three times with deionized water and then three times with anhydrous ethanol. After washing, it was dried at 80°C for 12 hours to obtain In2S3 (vacancy-free) photocatalytic material.

[0014] Example 2 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 10 mL of ethanol and 10 mL of deionized water were added to form a first solution; 0.2 g of InCl3·4H2O and 1000 g of thioacetamide were placed in the first solution and stirred for 20 min to obtain a clear solution; The clear solution was reacted at 140°C for 20 hours, then naturally cooled to room temperature, and the obtained product was collected by centrifugation; The obtained product was washed once with deionized water and once with anhydrous ethanol. After washing, it was dried at 60°C for 10 h to obtain an In2S3 (vacancy-free) photocatalytic material.

[0015] Example 3 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 20 mL of ethanol and 20 mL of deionized water are combined to form a first solution; 0.4 g of InCl3·4H2O and 1300 g of thioacetamide were placed in the first solution and stirred for 25 min to obtain a clear solution; The clear solution was reacted at 150 °C for 22 h, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed 5 times with deionized water and then 5 times with anhydrous ethanol. After washing, it was dried at 70°C for 14 hours to obtain In2S3 (vacancy-free) photocatalytic material.

[0016] Example 4 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 15 mL of ethanol and 15 mL of deionized water were added to form a first solution; 0.3000 g of InCl3·4H2O and 0.2346 g of thioacetamide were placed in the first solution and stirred for 30 min to obtain a clear solution; The clarified solution was reacted at 160°C for 24 hours, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed with deionized water for 3 times and then with anhydrous ethanol for 3 times. After washing, it was dried at 80 °C for 12 h to obtain In2S3-V S (Sulfur vacancy) photocatalytic materials.

[0017] Example 5 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 10 mL of ethanol and 10 mL of deionized water were added to form a first solution; 0.2 g of InCl3·4H2O and 0.2 g of thioacetamide were placed in the first solution and stirred for 20 min to obtain a clear solution; The clear solution was reacted at 140 °C for 20 h, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed once with deionized water and once with anhydrous ethanol. After washing, it was dried at 60 °C for 10 h to obtain In2S3-V S (Sulfur vacancy) photocatalytic materials.

[0018] Example 6 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 20 mL of ethanol and 20 mL of deionized water are combined to form a first solution; 0.4 g of InCl3·4H2O and 0.4 g of thioacetamide were placed in the first solution and stirred for 25 min to obtain a clear solution; The clear solution was reacted at 150 °C for 22 h, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed with deionized water for 5 times and then with anhydrous ethanol for 5 times. After washing, it was dried at 70 °C for 14 h to obtain In2S3-V S (Sulfur vacancy) photocatalytic materials.

[0019] Example 7 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 15 mL of ethanol and 15 mL of deionized water were added to form a first solution; 0.2346 g of InCl3·4H2O, 1202 g of thioacetamide, and 0.3005 g of hexamethylenetetramine were placed in the first solution and stirred for 30 min to obtain a clear solution; The clarified solution was reacted at 160°C for 24 hours, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed with deionized water for 3 times and then with anhydrous ethanol for 3 times. After washing, it was dried at 80 °C for 12 h to obtain In2S3-V In (Indium vacancy) photocatalytic materials.

[0020] Example 8 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 10 mL of ethanol and 10 mL of deionized water were added to form a first solution; 0.2 g of InCl3·4H2O, 1000 g of thioacetamide and 0.2 g of hexamethylenetetramine were placed in the first solution and stirred for 20 min to obtain a clear solution; The clear solution was reacted at 140 °C for 20 h, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed once with deionized water and once with anhydrous ethanol. After washing, it was dried at 60 °C for 10 h to obtain In2S3-V In (Indium vacancy) photocatalytic materials.

[0021] Example 9 This embodiment discloses a method for preparing an indium sulfide photocatalytic material having specific vacancies, the method comprising the following steps: 20 mL of ethanol and 20 mL of deionized water are combined to form a first solution; 0.4 g of InCl3·4H2O, 1300 g of thioacetamide, and 0.4 g of hexamethylenetetramine were placed in the first solution and stirred for 25 min to obtain a clear solution; The clear solution was reacted at 150 °C for 22 h, then naturally cooled to room temperature, and the product was collected by centrifugation. The obtained product was washed with deionized water for 5 times and then with anhydrous ethanol for 5 times. After washing, it was dried at 70 °C for 14 h to obtain In2S3-V In (Indium vacancy) photocatalytic materials.

[0022] Example 10 This embodiment discloses an application of an indium sulfide photocatalytic material with specific vacancies. The photocatalytic material is prepared using the above-mentioned method for preparing an indium sulfide photocatalytic material with specific vacancies. The photocatalytic material is used for photocatalytic reduction of N2 to NH3.

[0023] In order to verify the performance of the indium sulfide photocatalytic material with specific vacancies prepared by the present invention for photocatalytic N2 reduction, the results prepared in Example 1, Example 2 and Example 3 were used for verification, wherein the result prepared in Example 1 was recorded as In2S3 and the result prepared in Example 4 was recorded as In2S3-V S The preparation results of Example 7 are recorded as In2S3-V In , as follows: Photocatalytic N2 reduction experiments were conducted at room temperature in a quartz reaction vessel with a top illumination window. Typically, 50 mg of the prepared photocatalyst powder was added to 100 mL of deionized water and dispersed by ultrasonication for 5 minutes. The resulting photocatalyst suspension was stirred in the dark while high-purity N2 was bubbled continuously into the mixture at a flow rate of 60 mL / min for 30 minutes to eliminate air from the suspension and obtain a N2-saturated aqueous suspension. A 300 W xenon lamp was used as the light source to illuminate the reactor, while circulating cooling water was used to maintain the reaction solution temperature at a constant 20°C. The reaction solution was collected every 30 minutes, the catalyst removed by centrifugation, and the supernatant collected for later use.

[0024] The amount of ammonia produced was determined using the indophenol blue method. To 2 mL of the reaction solution, 2 mL of a 1 M NaOH solution containing 5% (mass fraction) salicylic acid and 5% (mass fraction) sodium citrate, 1 mL of 0.05 M NaClO, and 0.2 mL of a 1% (mass fraction) C5FeN6Na2O (sodium nitroprusside) aqueous solution were added. The solution was then incubated in the dark for 2 hours, and the absorption spectrum of the solution was measured using a UV-visible spectrophotometer. Indophenol blue formation was determined by absorbance at 650 nm. A standard sample of ammonium chloride solution with a specific concentration was prepared to calibrate the yield.

[0025] Figure 1 XRD patterns of each sample, In2S3-V S , In2S3-V In The XRD patterns of In2S3-V have obvious characteristic diffraction peaks at 2θ = 27.43°, 33.23° and 47.71°, which correspond to the (311), (400) and (440) crystal planes of In2S3 (JCPDS PDF#84-1385), respectively. No peaks corresponding to other substances appear in the XRD patterns of all samples, which means that the synthesized samples are of high purity. It is worth noting that for In2S3-V S , In2S3-V In , the crystallinity of the sample decreased due to the existence of its structural defects.

[0026] Figure 2 The SEM and TEM images of the samples are shown. In2S3 exists in the form of irregular nanosheets ( Figure 2 a and Figure 2 b). Further HR-TEM ( Figure 2 In (c) of the image, the lattice fringes of In2S3 are clear and complete, proving that there are basically no atomic vacancies in its lattice. The lattice fringes spacing of 0.27 nm and 0.19 nm are attributed to the (400) and (440) crystal planes of In2S3, respectively.S It is composed of nano flower balls formed by the aggregation of nano sheets ( Figure 2 d and Figure 2 In the HR-TEM image ( Figure 2 f), the lattice fringes with a spacing of 0.27 nm are attributed to the (400) crystal plane of In2S3, and obvious lattice distortion is found, which is attributed to In2S3-V S The S-rich vacancies in the sample ( Figure 2 f in the figure). In2S3-VIn is a microsphere composed of nanosheets ( Figure 2 g and Figure 2 h in In2S3-V In HR-TEM ( Figure 2 In the i in the figure, the lattice fringes with a spacing of 0.38 nm are attributed to the (220) crystal plane of In2S3. In addition, when the red box area is magnified, the part marked by the blue circle can clearly see the lattice defect, and the intensity distribution diagram on line 1 also has obvious intensity loss, which corresponds to the In2S3-V In In vacancies in the sample ( Figure 2 i) in the text.

[0027] like Figure 3 and Figure 4 As shown, after 150 min of reaction time, the NH4 + The amount of generated is very low. After the introduction of S vacancies, In2S3-V S NH4 + The yield has been improved to a certain extent, and the In2S3-V In The nitrogen fixation activity of the first two is significantly higher. Figure 3 NH4 is shown in + The average yield of In2S3-V In NH4 in full spectrum + The yield was 67.23 μmol / g / h, significantly higher than that of In2S3 (2.18 μmol / g / h) and In2S3-V S (11.55 μmol / g / h). At the same time, the reaction conditions were controlled by variable experiments. Figure 4 It can be seen that when In2S3-V In When La atoms were photodeposited on the sample, the photocatalytic nitrogen fixation activity decreased significantly, indicating that In vacancies played an important role in the reaction. In addition, under air conditions, NH4 + The yield decreases and there is almost no NH4 under argon conditions + Production Description NH4 generated in the reaction system +From N2. In addition, when the reaction is carried out without adding catalyst and in dark conditions, there is almost no NH4 + generate.

[0028] Figure 5 The UV-vis-DRS spectra of the samples show that all three samples show a certain absorption of visible light, and In2S3-V S and In2S3-V In Compared with the absorption of In2S3, there is a significant red shift, indicating that the introduction of vacancies can enhance the light absorption of the sample and better utilize visible light.

[0029] Figure 6 and Figure 7 The photocurrent response diagram and impedance diagram of the prepared catalyst are shown in Figure 2. The photocurrent density-time curve indicates the generation of photogenerated charges in the semiconductor photocatalyst, while a smaller photocurrent density indicates that the photogenerated electrons and holes have a greater probability of recombination. Figure 6 As shown, In2S3-V In The highest photocurrent response intensity indicates that it has the best ability to separate photogenerated charges, and can more effectively separate and transfer photogenerated electrons and holes. Electrochemical impedance spectroscopy further studied the charge transfer efficiency of the prepared samples. The curvature radius of the curve in the electrochemical impedance spectroscopy can directly reflect the resistance to charge transfer. Figure 7 As shown, In2S3-V In The smallest curvature radius indicates that it has the smallest electrochemical impedance and the lowest photogenerated carrier transfer resistance, and the highest charge separation efficiency, which is consistent with the photocurrent test results.

[0030] Figure 8 The photoluminescence spectrum of the sample is shown in Figure 2. The recombination of photogenerated electrons and holes will emit energy in the form of light and heat, producing fluorescence. Therefore, for photocatalysis, a good catalytic effect corresponds to a high separation efficiency of photogenerated charges, that is, a low photoluminescence intensity. As can be seen from the figure, under the excitation of light at a wavelength of 551 nm, In2S3, In2S3-V S and In2S3-V In Emission light appears at a wavelength of around 830 nm. S and In2S3-V In The luminescence intensity of is lower than that of In2S3, indicating that the introduction of S vacancies and In vacancies can reduce the recombination rate of photogenerated carriers in the sample, thereby promoting the improvement of its photocatalytic activity.

[0031] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0032] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an indium sulfide photocatalytic material with specific vacancies, characterized in that: The method comprises the following steps: forming a first solution by combining ethanol and deionized water; InCl3·4H2O and thioacetamide, or InCl3·4H2O, thioacetamide and hexamethylenetetramine, are placed in the first solution and stirred to dissolve, and after stirring, a clear solution is obtained; The clarified solution was reacted at a constant temperature, and after completion of the reaction, it was cooled and then centrifuged to collect the obtained product; The obtained product is washed, and then dried at a constant temperature. After the drying is completed, an indium sulfide photocatalytic material with specific vacancies is obtained.

2. The method for preparing an indium sulfide photocatalytic material having specific vacancies according to claim 1, characterized in that: During the stirring and dissolution of InCl3·4H2O and thioacetamide in the first solution, the mass of InCl3·4H2O is 0.2-0.4 g and the mass of thioacetamide is 1000-1300 g, or the mass of InCl3·4H2O is 0.2000-0.4 g and the mass of thioacetamide is 0.2-0.4 g.

3. The method for preparing an indium sulfide photocatalytic material having specific vacancies according to claim 2, characterized in that: During the process of placing InCl3·4H2O, thioacetamide and hexamethylenetetramine in the first solution for stirring and dissolving, the mass of InCl3·4H2O is 0.2-0.4 g, the mass of thioacetamide is 1000-1300 g, and the mass of hexamethylenetetramine is 0.2-0.4 g.

4. The method for preparing an indium sulfide photocatalytic material with specific vacancies according to claim 2, wherein: In the process of forming the first solution from ethanol and deionized water, the volume of ethanol is 10-20 mL, and the volume of deionized water is 10-20 mL; during the stirring and dissolving process, the stirring time is 20-30 min.

5. The method for preparing an indium sulfide photocatalytic material with specific vacancies according to claim 2, wherein: The clarified solution was kept in a constant temperature reaction process at 140-160°C for 20-24 hours; during the cooling process, natural cooling was used to cool the solution to room temperature.

6. The method for preparing an indium sulfide photocatalytic material with specific vacancies according to claim 5, characterized in that: The obtained product is washed with deionized water and anhydrous ethanol in sequence, wherein the deionized water and anhydrous ethanol washings are both performed 1 to 5 times.

7. The method for preparing an indium sulfide photocatalytic material with specific vacancies according to claim 6, characterized in that: During the constant temperature drying process, the temperature is 60~80℃ and the drying time is 10~14h.

8. An application of an indium sulfide photocatalytic material with specific vacancies, characterized in that: An indium sulfide photocatalytic material prepared by the method for preparing an indium sulfide photocatalytic material with specific vacancies according to any one of claims 1 to 7, wherein the indium sulfide photocatalytic material is used for photocatalytic reduction of N2 to NH3.

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