A preparation method of a novel indium oxyhydroxide nanosheet

Abstract

A preparation method of hexagonal InOOH nanosheets, comprising the following steps: (1) mixing an aqueous solution of anionic polyacrylamide and an ethylene glycol solution of indium chloride tetrahydrate and fully stirring; (2) transferring the mixture into a reaction kettle, sealing and keeping at 180±12 DEG C for 10±3 h, centrifugally washing the obtained precipitate, and freeze-drying to obtain hexagonal InOOH nanosheets; the hexagonal InOOH nanosheets are used for photothermal catalysis and good effects can be achieved. The preparation ratio of the aqueous solution of anionic polyacrylamide is: 0.3 g of anionic polyacrylamide is dissolved in 20 mL or more deionized water; the preparation ratio of the ethylene glycol solution of indium chloride tetrahydrate is: 0.1 g of indium chloride tetrahydrate is dissolved in 30 mL or more ethylene glycol.

Description

Technical Field

[0001] This invention relates to a method for preparing hexagonal InOOH nanosheets, which can be used in the field of photothermal catalysis, such as photothermal catalysis of CO2 hydrogenation reaction, and belong to the field of new materials technology. Background Technology

[0002] Utilizing H2 to convert CO2 into high-value-added chemical products or fuels such as methanol can help alleviate global warming caused by the increasing CO2 emissions. The CO2 hydrogenation reaction using traditional thermal catalysts (e.g., Cu-ZnO) often requires a reaction temperature of around 300°C, a H2-rich reaction atmosphere, and a very high reaction pressure. Generally, in traditional thermocatalytic CO2 hydrogenation reactions, the feed ratio of H2 to CO2 needs to be greater than 3:1. Since the reaction of CO2 hydrogenation to produce CH3OH (CO2 + 3H2 → CH3OH + H2O) and the reverse water-gas reaction (CO2 + H2 → CO + H2O) are competing reactions, a H2-rich reaction atmosphere is a necessary condition for achieving the former. Furthermore, a reaction pressure of 5 to 10 Ma is also indispensable for the conversion of CO2 to CH3OH in traditional processes. This is because thermocatalysis requires appropriate high pressure to obtain considerable yields and good product selectivity. Therefore, photothermal catalytic CO2 hydrogenation to CH3OH is a potentially effective method for converting solar energy into chemical energy. Unfortunately, under mild reaction conditions, this reaction not only has a limited CO2 conversion rate, but also exhibits poor selectivity for CH3OH in the products. These problems severely limit the application of photothermal catalysts in CO2 hydrogenation reactions.

[0003] Among various photothermal catalysts, indium oxide (IO) catalysts exhibit excellent performance in adsorbing and activating CO2 molecules and cracking carbon-oxygen bonds in CO2, thus showing broad application prospects in the reaction of CO2 hydrogenation to methanol. Various methods have been explored to promote the activation of CO2 and H2 on the IO surface and reduce the impact of the reverse water-gas reaction on the reaction rate and product selectivity. InOOH is a highly efficient photothermal catalyst, with its surface hydroxyl groups and In atoms being important reactive sites. By adjusting the In-OH functional groups on the InOOH surface, the formation rate and selectivity of CH3OH in the CO2 hydrogenation reaction can be further optimized. Therefore, developing a simple, efficient, energy-saving method for preparing InOOH nanosheets with both high activity and high selectivity is essential.

[0004] CN113877556A relates to an indium hydroxy oxide / acid-modified attapulgite (InOOH / H-ATP) photocatalytic composite material, its preparation method, and its application. Acidified attapulgite and indium nitrate are ultrasonically dissolved in a mixed solution of distilled water and N,N-dimethylformamide; then transferred to a microwave reactor and subjected to microwave solvothermal reaction for a certain time; after cooling to room temperature, the reaction product is collected by centrifugation, washed with water and alcohol, vacuum dried, and ground; finally, it is transferred to a tube furnace for calcination to obtain the InOOH / H-ATP photocatalytic composite material. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing hexagonal InOOH nanosheets. This method prepares InOOH nanosheets through a unique and simple operation, using only two raw materials: indium chloride tetrahydrate and polyacrylamide, and a mixed solvent of water and ethylene glycol. InOOH nanosheets can be obtained through a one-step solvothermal method. This method requires only simple precursors and a single solvothermal step, while general indium oxide-based modification strategies often require multiple steps. The key to this method is to prepare the two precursor materials into aqueous and ethylene glycol solutions respectively, then mix them, and finally maintain the mixture at 180°C for 10 hours in a stainless steel autoclave. This simple solvothermal method may be applicable to the synthesis of more types of In-containing catalysts.

[0006] The present invention also aims to provide an application of InOOH nanosheets, namely, the use of InOOH nanosheets for photothermal catalysis. The main exposed surface of this novel hexagonal InOOH nanosheet is the

[001] face, and the indium-hydroxyl functional groups on its surface can promote the dissociation of H2 and the activation of CO2. Under normal pressure conditions with a CO2 to H2 ratio of 1:1, InOOH nanosheets can efficiently convert CO2 into CH3OH, and the selectivity of CH3OH is close to 60%. Therefore, InOOH nanosheets are a good photothermal catalytic material, and their use in the photothermal catalytic CO2 hydrogenation reaction can achieve good results.

[0007] The technical solution of this invention is as follows: (1) Mix an aqueous solution of polyacrylamide (anionic type) and an ethylene glycol solution of indium chloride tetrahydrate and stir thoroughly. (2) Transfer the above mixture to a reaction vessel (such as a stainless steel high-pressure vessel with a Teflon liner), seal it and keep it at 180±12℃ for about 10±3h, then centrifuge and wash the obtained precipitate, and freeze-dry it to obtain hexagonal InOOH nanosheets;

[0008] The preparation ratio of the aqueous solution of the aforementioned anionic polyacrylamide is: 0.3g of anionic polyacrylamide dissolved in more than 20mL of deionized water.

[0009] The ratio for preparing an ethylene glycol solution of indium chloride tetrahydrate is: 0.1 g of indium chloride tetrahydrate dissolved in more than 30 mL of ethylene glycol.

[0010] Place it in a forced-air drying oven and keep it at 180℃ for 10 hours.

[0011] Add polyacrylamide (anionic) powder to deionized water and stir for more than 10 minutes to dissolve it completely; add indium chloride tetrahydrate powder to ethylene glycol and stir for more than 10 minutes to dissolve it completely.

[0012] An aqueous solution of polyacrylamide (anionic) was added dropwise to an ethylene glycol solution of indium chloride tetrahydrate, and the mixture was stirred for at least 20 minutes until homogeneous.

[0013] After mixing the aqueous solution of polyacrylamide (anionic) and the ethylene glycol solution of indium chloride tetrahydrate, continue stirring for at least 20 minutes.

[0014] The above mixed solution was transferred to a 50 mL Teflon liner and sealed in a stainless steel autoclave.

[0015] Place the stainless steel autoclave in a forced-air drying oven and maintain it at 180℃ for 10 hours.

[0016] After the solvothermal reaction is completed, the precipitate is first obtained by centrifugation, then washed at least 3 times with anhydrous ethanol, then washed several times with deionized water, and then freeze-dried for 20-40 hours to obtain hexagonal InOOH nanosheets.

[0017] The precipitate collected after centrifugation was first washed three times with anhydrous ethanol, and then washed several times with deionized water.

[0018] The final product was freeze-dried for 20–40 hours. This yielded hexagonal InOOH nanosheets, which showed good results when applied to the photothermal catalytic CO2 hydrogenation reaction.

[0019] Beneficial effects: By mixing an aqueous solution of anionic polyacrylamide and an ethylene glycol solution of indium chloride tetrahydrate, InOOH nanosheets can be obtained using a single-step solvothermal method, which is simple and convenient. The InOOH nanosheets obtained by this method expose a large area of ​​

[001] surfaces, which have abundant reaction sites composed of In and -OH, which is very beneficial to the reaction of CO2 hydrogenation to produce CH3OH. Attached Figure Description

[0020] Figure 1 This is the X-ray diffraction (XRD) pattern of the InOOH nanosheets in the embodiment of the present invention, wherein the highest intensity diffraction peak belongs to the (003) crystal plane.

[0021] Figure 2Image (a) is a scanning electron microscope (SEM) image of the product according to an embodiment of the present invention. Figure 2 (b) is a transmission electron microscope (TEM) image. Figure 2 Image (c) is a high-resolution transmission electron microscope (HRTEM) image. Figure 2 Image (d) shows the selected area electron diffraction (SAED) pattern. It can be seen that the product is a hexagonal sheet, approximately 20–40 nm thick, with a side length of approximately 400–700 nm. Combined with… Figure 1 Medium XDR, Figure 2 (c) HRTEM and Figure 2 The SAED information in (d) confirms that the upper and lower surfaces of this hexagonal nanosheet belong to the

[001] crystal plane family.

[0022] Figure 3 This is an X-ray photoelectron spectroscopy (XPS) image of element O in the product of this invention. The O1s peak in the image can be decomposed into two parts: 531.5 eV and 532.5 eV. The former represents lattice O bonded to the metal, and the latter represents hydroxyl O.

[0023] Figure 4 In Figure (a), the yield of CH3OH in the photothermal catalytic CO2 hydrogenation reaction of the product (denoted as S0) in the embodiment of the present invention is shown under both light and dark conditions. Figure 4 (b) shows the yield of CO in the photothermal catalytic CO2 hydrogenation reaction of the product in this embodiment of the invention under both light and no light conditions. Figure 4 (c) is the Arrhenius curve of the yields of CH3OH (bottom) and CO (top) in the photothermal catalytic CO2 hydrogenation reaction of the product of this embodiment. Figure 4 In (d), the selectivity of CH3OH under light-free conditions is shown in the photothermal catalytic CO2 hydrogenation reaction of the product in the embodiment of the present invention. Detailed Implementation

[0024] Process Example:

[0025] (1) Dissolve 0.3g of polyacrylamide (anionic) in 40mL (20 or 80mL is also acceptable) of deionized water and stir continuously for 10min or longer using a magnetic stirrer to ensure it is fully dissolved;

[0026] (2) Dissolve 0.1g of indium chloride tetrahydrate in 70mL (50 or 100mL is also acceptable) of ethylene glycol and stir continuously for 10min or longer using a magnetic stirrer to ensure that it is fully dissolved;

[0027] (3) Add the aqueous solution of polyacrylamide (anionic type) dropwise to the ethylene glycol solution of indium chloride tetrahydrate, and stir continuously with a magnetic stirrer for 20 minutes or longer to ensure thorough mixing.

[0028] (4) After stirring, the mixture was first transferred to four 50mL Teflon-lined containers, and then sealed in four stainless steel autoclaves. The autoclaves were then placed in a forced-air oven and kept at 180℃ for about 10 hours. The autoclaves were heated in the oven, and the forced air was used to ensure uniform heating. The mixed reactants were transferred to the Teflon-lined containers, which also had lids of the same material. The lids were then closed, and the containers were sealed in the autoclaves. This prevented outside air from entering. The entire operation was carried out in the air, so a small amount of air remained inside the Teflon-lined containers, above the reactant mixture, and was sealed inside for oxidation. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation, then washed three times with anhydrous ethanol and several times with deionized water. The final product was freeze-dried for 20–40 hours. InOOH nanosheets were thus obtained, which showed good results when used for photothermal catalysis.

[0029] The products were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS).

[0030] Figure 1 The image shows the XRD pattern of the InOOH nanosheets in this embodiment of the invention. The diffraction peak intensity of the (003) crystal plane is the highest, which suggests that the upper and lower surfaces of the hexagonal nanosheets may belong to the

[001] plane.

[0031] Figure 2 (a) is a SEM image of the product according to an embodiment of the present invention. Figure 2 (b) is a TEM image. Figure 2 (c) is an HRTEM image. Figure 2 (d) is the SAED pattern. It can be seen that the product is a hexagonal sheet, approximately 20–40 nm thick, with a side length of approximately 400–700 nm. Combined with... Figure 1 Medium XDR, Figure 2 (c) HRTEM and Figure 2 The SAED results in (d) confirm that the upper and lower surfaces of this hexagonal nanosheet belong to the

[001] crystal plane family.

[0032] Figure 3 This is an XPS image of the O element in the product of this invention embodiment. The O1s peak in the image consists of two parts located at 531.5 eV and 532.5 eV, where the former represents lattice O bonded to the metal and the latter represents hydroxyl O.

[0033] Application Examples

[0034] The novel hexagonal InOOH nanosheet photocatalyst prepared in this example was used for photothermal catalytic CO2 hydrogenation. Specifically, the reaction was carried out in a custom-designed fixed-bed tubular reactor (made of quartz, with an outer diameter of 8 mm and an inner diameter of 6 mm). First, 40 mg of photothermal catalyst and 150 mg of quartz sand were weighed and thoroughly mixed. The mixture was then loaded into a quartz tube, and appropriate amounts of quartz wool were filled at both ends of the mixture. The quartz wool fixed the catalyst and quartz sand mixture in the catalyst bed within the quartz tube. Subsequently, the quartz tube was placed horizontally in a fixed groove within a heating jacket. The heating jacket provided non-contact heating via four ceramic rods surrounding the tubular reactor (quartz tube). The temperature was controlled by a thermocouple placed near the catalyst bed. The light source for the catalytic system was a 300 W xenon lamp. During the reaction, H2 and CO2 were introduced into the reactor in a 1:1 ratio, and after flowing through the catalyst bed, they were introduced into a gas chromatograph at a total flow rate of 4 mL / min and a pressure of one atmosphere. Turn on the heating mantle and xenon lamp. Once the system temperature reaches the set temperature, use a gas chromatograph to analyze the amount of CH3OH and CO produced.

[0035] The relationship between the amount of CH3OH and CO obtained and time, as well as the product selectivity, are as follows: Figure 4 As shown in (a), (b), and (c), the results demonstrate that the novel hexagonal InOOH nanosheet photocatalyst prepared in the examples can convert CO2 and H2 into CH3OH and CO, and the yield increases with increasing temperature. The highest yield of CH3OH (21.77 μmol g) was observed under illumination at 300 °C. 催化剂 -1 h -1 Furthermore, the selectivity rate reached 59.67%.

[0036] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing hexagonal InOOH nanosheets, characterized in that, The process includes the following steps: (1) mixing an aqueous solution of anionic polyacrylamide and an ethylene glycol solution of indium chloride tetrahydrate and stirring thoroughly; (2) transferring the mixture to a reaction vessel, sealing it, and maintaining it at 180 ±12℃ for 10 ±3h, then centrifuging and washing the resulting precipitate, and freeze-drying it to obtain hexagonal InOOH nanosheets; the preparation ratio of the aqueous solution of anionic polyacrylamide is: 0.3 g of anionic polyacrylamide dissolved in more than 20 mL of deionized water; the preparation ratio of the ethylene glycol solution of indium chloride tetrahydrate is: 0.1 g of indium chloride tetrahydrate dissolved in more than 30 mL of ethylene glycol.

2. The method for preparing hexagonal InOOH nanosheets according to claim 1, characterized in that: The reactor is a stainless steel high-pressure reactor with a Teflon liner, which is placed in a forced-air drying oven and kept at 180 ℃ for 10 h.

3. The method for preparing hexagonal InOOH nanosheets according to claim 1, characterized in that: Add anionic polyacrylamide powder to deionized water and stir for at least 10 minutes to dissolve completely; add indium chloride tetrahydrate powder to ethylene glycol and stir for at least 10 minutes to dissolve completely.

4. The method for preparing hexagonal InOOH nanosheets according to claim 3, characterized in that: An aqueous solution of anionic polyacrylamide was added dropwise to an ethylene glycol solution of indium chloride tetrahydrate, and the mixture was stirred for at least 20 minutes until homogeneous.

5. The method for preparing hexagonal InOOH nanosheets according to claim 4, characterized in that: After mixing the aqueous solution of anionic polyacrylamide and the ethylene glycol solution of indium chloride tetrahydrate, continue stirring for at least 20 minutes.

6. The method for preparing hexagonal InOOH nanosheets according to claim 1, characterized in that: After the solvothermal reaction is completed, the precipitate is first obtained by centrifugation, then washed at least 3 times with anhydrous ethanol, then washed several times with deionized water, and then freeze-dried for 20-40 h to obtain hexagonal InOOH nanosheets.

7. The hexagonal InOOH nanosheets obtained by the preparation method according to any one of claims 1-6 are applied to the photothermal catalytic CO2 hydrogenation reaction.

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