A magnesium-indium hydrotalcite nanosheet catalyst, a preparation method and application thereof

Abstract

The application relates to the field of CO2 electrochemical reduction, and discloses a magnesium-indium hydrotalcite nanosheet catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving a soluble indium salt and a soluble magnesium salt in a mixed solvent of ethanol and water, then adding acetylacetone, and continuously stirring until uniform; then adding propylene oxide, continuously stirring at room temperature, and stopping until the solution becomes gelatinous; and washing, centrifuging and drying the obtained gel to obtain the magnesium-indium hydrotalcite nanosheet catalyst. The sol-gel method is used to prepare the magnesium-indium hydrotalcite nanosheet catalyst with ultrathin and ultrasmall sizes, which is helpful to realize high dispersion of In active sites, thereby improving the activity and selectivity of electrocatalytic CO2 reduction to formic acid.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of CO2 electrochemical reduction, in particular to a magnesium-indium hydrotalcite nanosheet catalyst and a preparation method and application thereof. BACKGROUND

[0002] The electrochemical carbon dioxide reduction technology can efficiently convert CO2 into high-value-added chemicals and fuels. The technology can generate various carbon-containing products, such as carbon monoxide (CO), methane (CH4), formic acid / formate (HCOOH / HCOO - ), ethylene (C2H4) and ethanol (C2H5OH) and the like. Among them, carbon monoxide and formic acid / formate produced through a two-electron reduction process are more superior in economy. Compared with carbon monoxide, formic acid / formate significantly reduces the transportation and storage costs due to its easy separation characteristics. In addition, formic acid / formate has good chemical stability and high energy density, and is therefore highly concerned and becomes a product with high economic value. However, the C=O bond energy of CO2 molecule is about 750 kJ·mol −1 , making the activation process more difficult. At the same time, the CO2 reduction reaction has slow kinetics and high overpotential, which seriously restricts the efficient conversion of CO2 to formic acid / formate. In addition, due to the influence of the competing hydrogen evolution reaction (HER), the CO2 reduction also faces problems such as energy loss and low product selectivity.

[0003] In recent years, indium (In)-based electrocatalysts have shown great application potential in the field of electrocatalytic CO2 reduction due to their good catalytic performance, environmental friendliness and cost-effectiveness. For example, a kind of indium-based hydroxide catalyst for electrocatalytic carbon dioxide to prepare formic acid, a preparation method and an application are disclosed in patent CN116103682A. However, the existing indium hydroxide catalyst has the problems of low conversion efficiency and selectivity of CO2 to formate. Therefore, it has become an urgent task in this field to develop indium-based electrocatalysts with high activity and selectivity to improve the reaction rate and achieve efficient synthesis of formate. SUMMARY

[0004] The application is to overcome the above-mentioned problems of the existing indium-based catalysts, and provides a magnesium-indium hydrotalcite nanosheet catalyst and a preparation method and application thereof. The sol-gel method is used to prepare an ultra-thin and ultra-small magnesium-indium hydrotalcite nanosheet catalyst, which helps to realize the high dispersion of In active sites, thereby improving the activity and selectivity of the electrocatalytic CO2 reduction to formic acid.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of magnesium-indium hydrotalcite nanosheet catalyst, comprising the following steps:

[0007] (1) dissolving a soluble indium salt and a soluble magnesium salt in a mixed solvent of ethanol and water to obtain a mixed solution A;

[0008] (2) adding acetylacetone into the mixed solution A and continuing to stir uniformly to obtain a mixed solution B;

[0009] (3) adding propylene oxide into the mixed solution B and continuously stirring at room temperature until the solution becomes gelatinous;

[0010] (4) washing, centrifuging and drying the obtained gelatinous substance to obtain the magnesium-indium hydrotalcite nanosheet catalyst.

[0011] The magnesium-indium hydrotalcite nanosheet catalyst with ultra-thin and ultra-small size is synthesized by the sol-gel method at room temperature, which can realize the high dispersion of active indium species, and the rich hydroxyl groups on the surface of hydrotalcite can help to improve the local pH value at the reaction interface and enhance the adsorption and activation capacity of CO2, thereby improving the efficiency and selectivity of the conversion of CO2 to formate. Meanwhile, the method of the present application is simple in operation, mild in reaction conditions, and has good scalability and batch production potential, which is conducive to industrial application.

[0012] Preferably, the molar ratio of In ions to Mg ions in the soluble indium salt and the soluble magnesium salt added in step (1) is 1:1-4.

[0013] Preferably, the soluble indium salt is one of indium nitrate and indium chloride; and the soluble magnesium salt is one of magnesium nitrate, magnesium chloride and magnesium sulfate.

[0014] Preferably, the molar ratio of ethanol to water in the mixed solvent of step (1) is 0.4-2.5:1, and the molar ratio of water to indium ions in the soluble indium salt is 10-45:1.

[0015] Preferably, the molar ratio of acetylacetone to indium ions in the soluble indium salt added in step (2) is 0.01-1.5:1.

[0016] Preferably, the molar ratio of propylene oxide to indium ions in the soluble indium salt added in step (3) is 14-40:1.

[0017] Preferably, the standing time in step (4) is 12-24 h; the drying temperature is 40-80℃, and the drying time is 12-24 h.

[0018] In a second aspect, the present application provides a magnesium-indium hydrotalcite nanosheet catalyst prepared by the above preparation method.

[0019] In a third aspect, the application provides a use of the Mg-In layered double hydroxide nanosheet catalyst in an electrocatalytic CO2 reduction reaction to form formate.

[0020] As preferred, the Mg-In layered double hydroxide nanosheet catalyst is mixed with carbon black, ethanol and a Nafion solution to obtain a coating liquid, the coating liquid is coated on a hydrophobic carbon fiber paper, and after drying, a Mg-In layered double hydroxide electrode material is obtained; the Mg-In layered double hydroxide electrode material is used as a working electrode, a KOH solution is used as an electrolyte, and the electrocatalytic CO2 reduction reaction to form formate is carried out at a current density of 50-400 mA·cm -2

[0021] Therefore, the application has the following beneficial effects:

[0022] (1) The Mg-In layered double hydroxide is directly used as a catalyst for the electrocatalytic CO2 reduction reaction to form formate, which not only realizes the high dispersion of active indium species, but also utilizes the rich hydroxyl group on the surface of the layered double hydroxide to help improve the local pH value at the reaction interface, enhance the adsorption and activation ability of CO2, and thus improve the efficiency and selectivity of the conversion of CO2 to formate;

[0023] (2) The ultra-thin and ultra-small Mg-In layered double hydroxide nanosheet catalyst is synthesized by a sol-gel method at room temperature. The method is simple in operation, mild in reaction conditions, has good scalability and batch production potential, and is conducive to industrial application;

[0024] (3) The electrocatalytic CO2 reduction strategy driven by renewable energy not only realizes the effective emission reduction of greenhouse gas CO2, but also selectively generates formate products with high economic value under high current density conditions. Moreover, the electrochemical system has mild reaction conditions, accurate controllable operation parameters, and closed-loop recycling of raw materials. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the X-ray powder diffraction pattern of the Mg2In-LDH in Example 1 of the application.

[0026] Figure 2 is the high-resolution transmission electron microscopy image of the Mg2In-LDH in Example 1 of the application.

[0027] Figure 3 is the element distribution map of the Mg2In-LDH in Example 1 of the application.

[0028] Figure 4 is the linear voltammetry scan curve of Example 1 of the application in a flow cell system under a CO2 atmosphere.

[0029] Figure 5 ​is a formate Faraday efficiency comparison chart of Mg2In-LDH of Example 1 and In(OH)3 of Comparative Example 1 under different current densities.

[0030] Figure 6 is a CO and H2 Faraday efficiency comparison chart of Mg2In-LDH of Example 1 and In(OH)3 of Comparative Example 1 under different current densities. DETAILED DESCRIPTION

[0031] The application will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the field unless otherwise specified.

[0033] General example:

[0034] A preparation method of a magnesium-indium hydrotalcite nanosheet catalyst, comprising the following steps:

[0035] (1) Dissolve a soluble indium salt and a soluble magnesium salt in a mixed solvent of ethanol and water to obtain a mixed solution A;

[0036] (2) Add acetylacetone to the mixed solution A and continue to stir uniformly to obtain a mixed solution B;

[0037] (3) Add propylene oxide to the mixed solution B and continue to stir at room temperature until the solution becomes gelatinous;

[0038] (4) Wash, centrifuge and dry the obtained gel after standing to obtain the magnesium-indium hydrotalcite nanosheet catalyst.

[0039] As a specific embodiment, the molar ratio of In ions to Mg ions in the soluble indium salt and the soluble magnesium salt added in step (1) is 1:1-4.

[0040] As a specific embodiment, the soluble indium salt is one of indium nitrate and indium chloride; and the soluble magnesium salt is one of magnesium nitrate, magnesium chloride and magnesium sulfate.

[0041] As a specific embodiment, the molar ratio of ethanol to water in the mixed solvent of step (1) is 0.4-2.5:1, and the molar ratio of water to indium ions in the soluble indium salt is 10-45:1.

[0042] As a specific embodiment, the molar ratio of acetylacetone to indium ions in the soluble indium salt added in step (2) is 0.01-1.5:1.

[0043] As a specific embodiment, the molar ratio of propylene oxide to indium ions in the soluble indium salt added in step (3) is 14-40:1.

[0044] As a specific embodiment, the standing time in step (4) is 12-24 h; the drying temperature is 40-80℃, and the drying time is 12-24 h.

[0045] Application of the above magnesium-indium hydrotalcite nanosheet catalyst in the electrocatalytic CO2 reduction reaction to form formate: the magnesium-indium hydrotalcite nanosheet catalyst is mixed with carbon black, ethanol and a Nafion solution to obtain a coating liquid, the coating liquid is coated on a hydrophobic carbon fiber paper, and after drying, a magnesium-indium hydrotalcite electrode material is obtained; the magnesium-indium hydrotalcite electrode material is used as a working electrode, a KOH solution is used as an electrolyte, and the electrocatalytic CO2 reduction reaction to form formate is carried out at a current density of 50-400 mA·cm -2 .

[0046] As a specific embodiment, in the coating liquid, the mass ratio of the magnesium-indium hydrotalcite nanosheet catalyst to carbon black is 5:1-3; preferably, the mass ratio of the magnesium-indium hydrotalcite nanosheet catalyst to carbon black is 5:2.5.

[0047] As a specific embodiment, in the coating liquid, the mass-volume ratio of the magnesium-indium hydrotalcite nanosheet catalyst to ethanol and Nafion solution is 5 mg:0.5-2 mL:10-30 μL; preferably, the mass-volume ratio of the magnesium-indium hydrotalcite nanosheet catalyst to ethanol and Nafion solution is 5 mg:1 mL:20 μL.

[0048] As a specific embodiment, the mass concentration of the Nafion solution is 5%.

[0049] As a specific embodiment, the loading amount of the magnesium-indium hydrotalcite nanosheet on the hydrophobic carbon paper is 0.5-5 mg / cm 2 .

[0050] Example 1:

[0051] Application of a magnesium-indium hydrotalcite nanosheet catalyst in the electrocatalytic CO2 reduction reaction to form formate, the steps are as follows:

[0052] (1) Preparation of Mg2In-LDH material: 2.5 mmol of magnesium chloride hexahydrate and 1.25 mmol of indium chloride tetrahydrate were dissolved in 2 mL of ethanol, and stirred until dissolved; then 300 μL of deionized water and 1.27 mmol of acetylacetone were added, and stirred for 30 minutes; then 28.6 mmol of propylene oxide was added, and stirring was continued at room temperature until the solution became gel-like, and then left to stand for 12 h; finally, the obtained gel was washed with ethanol and deionized water, centrifuged, and placed in a vacuum oven at 60 ℃ for drying for 12 h, and finally the magnesium indium hydrotalcite nanosheet catalyst was obtained, which was recorded as Mg2In-LDH.

[0053] The obtained magnesium indium hydrotalcite nanosheet catalyst was characterized, and the X-ray powder diffraction pattern is shown in Figure 1 , which can be seen that Mg2In-LDH exhibits characteristic diffraction peaks of (003), (006), (009) and (110) belonging to LDHs. The TEM image is shown in Figure 2 , which can be seen that the Mg2In-LDH catalyst is in the form of nanosheet, and the particle size is 20-30 nm. The energy spectrum is shown in Figure 3 , which can be seen that the elements of Mg, In and O are uniformly distributed in the Mg2In-LDH material.

[0054] (2) Preparation of Mg2In-LDH catalytic electrode: 5 mg of Mg2In-LDH and 2.5 mg of carbon black were dispersed in 1 mL of ethanol, and then 20 μL of Nafion (mass concentration of 5%) solution was added to prepare a coating liquid; then the coating liquid was coated on a hydrophobic carbon paper, and after drying, a Mg2In-LDH catalytic electrode (Mg2In-LDH loading amount 1 mg / cm 2 ) was obtained.

[0055] (3) Performance test of electrocatalytic CO2 reduction: the electrocatalytic experiment was carried out in a flow-type electrolytic cell, with Mg2In-LDH catalytic electrode as the working electrode, titanium mesh loaded with IrO2 as the counter electrode, and Ag / AgCl electrode as the reference electrode, and 1M KOH solution as the electrolyte, and then electrolysis was carried out at a current density of 50-400 mA cm -2 for 30 minutes; the liquid products after reaction were analyzed by high performance liquid chromatograph (Agilent 1260-Infinity II), and the gas products (such as CO and H2) were analyzed by gas chromatograph (Shimadzu GC-2014). The electrochemical performance test results are shown in Figures 4-6 .

[0056] Example 2:

[0057] An application of a magnesium-indium hydrotalcite nanosheet catalyst in an electrocatalytic CO2 reduction reaction to form formate, the steps being as follows:

[0058] (1) Preparation of Mg3In-LDH material: 3.75 mmol of magnesium chloride hexahydrate and 1.25 mmol of indium chloride tetrahydrate were dissolved in 2 mL of ethanol, and stirred until dissolved; then 300 μL of deionized water and 1.27 mmol of acetylacetone were added, and stirred for 30 minutes; then 36.8 mmol of propylene oxide was added, and stirring was continued at room temperature until the solution became gel-like, and then left to stand for 12 h; finally, the obtained gel was washed with ethanol and deionized water, centrifuged, and placed in a vacuum oven at 60 ℃ for drying for 12 h, and finally a magnesium-indium hydrotalcite nanosheet catalyst was obtained, denoted as Mg3In-LDH.

[0059] (2) Preparation of Mg3In-LDH catalytic electrode: 5 mg of Mg3In-LDH and 2.5 mg of carbon black were dispersed in 1 mL of ethanol, and then 20 μL of Nafion (mass concentration 5%) solution was added to prepare a coating liquid; then the coating liquid was coated on a hydrophobic carbon paper, and after drying, a Mg3In-LDH catalytic electrode (Mg3In-LDH loading amount 1 mg / cm 2 ).

[0060] (3) Performance test of electrocatalytic CO2 reduction: the electrocatalytic experiment was carried out in a flow-type electrolytic cell, with the Mg3In-LDH catalytic electrode as the working electrode, a titanium mesh loaded with IrO2 as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and the electrolyte was 1M KOH solution, and then electrolysis was carried out at a current density of 50 ~ 400 mA cm -2 for 30 minutes; the liquid products after reaction were analyzed qualitatively and quantitatively by high performance liquid chromatography (Agilent 1260-Infinity II), and the gas products (such as CO and H2) were analyzed by gas chromatography (Shimadzu GC-2014). The electrochemical performance test results are shown in Figures 4-6 .

[0061] Example 3:

[0062] An application of a magnesium-indium hydrotalcite nanosheet catalyst in an electrocatalytic CO2 reduction reaction to form formate, the steps being as follows:

[0063] (1) MgIn-LDH material preparation: 1.25 mmol of magnesium chloride hexahydrate and 1.25 mmol of indium chloride tetrahydrate were dissolved in 2 mL of ethanol, and stirred until dissolved; then 300 μL of deionized water and 1.27 mmol of acetylacetone were added, and stirred for 30 minutes; then 20.4 mmol of propylene oxide was added, and stirring was continued at room temperature until the solution became gel-like, and then left to stand for 12 h; finally, the obtained gel was washed with ethanol and deionized water, centrifuged, and placed in a vacuum oven at 60 ℃ for drying for 12 h, and finally a magnesium-indium hydrotalcite nanosheet catalyst was obtained, denoted as MgIn-LDH.

[0064] (2) MgIn-LDH catalytic electrode preparation: 5 mg of MgIn-LDH and 2.5 mg of carbon black were dispersed in 1 mL of ethanol, and then 20 μL of a Nafion solution (mass concentration of 5%) was added to prepare a coating liquid; then the coating liquid was coated on a hydrophobic carbon paper, and after drying, a MgIn-LDH catalytic electrode (MgIn-LDH loading amount of 1 mg / cm 2 ).

[0065] (3) Electro-catalytic CO2 reduction performance test: the electro-catalytic experiment was carried out in a flow-type electrolytic cell, with the MgIn-LDH catalytic electrode as the working electrode, a titanium mesh loaded with IrO2 as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and the electrolyte was a 1M KOH solution, and then electrolysis was carried out at a current density of 50 ~ 400 mA cm -2 for 30 minutes; the liquid products after reaction were analyzed by high performance liquid chromatography (Agilent 1260-Infinity II), and the gas products (such as CO and H2) were analyzed by gas chromatography (Shimadzu GC-2014). The electrochemical performance test results are shown in Figures 4-6

[0066] Example 4:

[0067] The application of a magnesium-indium hydrotalcite nanosheet catalyst in the electro-catalytic CO2 reduction reaction to form formate is as follows:

[0068] ​(1) Preparation of Mg4In-LDH material: 5.00 mmol of magnesium chloride hexahydrate and 1.25 mmol of indium chloride tetrahydrate were dissolved in 2 mL of ethanol, and stirred until dissolved; then 300 μL of deionized water and 1.27 mmol of acetylacetone were added, and stirred for 30 minutes; then 44.9 mmol of propylene oxide was added, and stirring was continued at room temperature until the solution became gel-like, and then left to stand for 12 h; finally, the obtained gel was washed with ethanol and deionized water, centrifuged, and placed in a vacuum oven at 60 ℃ for drying for 12 h, and finally a magnesium indium hydrotalcite nanosheet catalyst was obtained, which was recorded as Mg4In-LDH.

[0069] (2) Preparation of Mg4In-LDH catalytic electrode: 5 mg of Mg4In-LDH and 2.5 mg of carbon black were dispersed in 1 mL of ethanol, and then 20 μL of Nafion (mass concentration of 5%) solution was added to prepare a coating liquid; then the coating liquid was coated on a hydrophobic carbon paper, and after drying, a Mg4In-LDH catalytic electrode (Mg4In-LDH loading amount 1 mg / cm 2 ).

[0070] (3) Performance test of electrocatalytic CO2 reduction: the electrocatalytic experiment was carried out in a flow-type electrolytic cell, with Mg4In-LDH catalytic electrode as the working electrode, titanium mesh loaded with IrO2 as the counter electrode, and Ag / AgCl electrode as the reference electrode, and 1M KOH solution as the electrolyte, and then electrolysis was carried out at a current density of 50 ~ 400 mA cm -2 for 30 minutes; the liquid products after reaction were analyzed by high performance liquid chromatograph (Agilent 1260-Infinity II), and the gas products (such as CO and H2) were analyzed by gas chromatograph (Shimadzu GC-2014). The electrochemical performance test results are shown in Figures 4-6 .

[0071] Comparative Example 1:

[0072] Application of an indium-based catalyst in the reaction of electrocatalytic CO2 reduction to form formate, the steps are as follows:

[0073] (1) Preparation of In(OH)3 catalytic electrode: 5 mg of commercial In(OH)3 powder (Anjieji, particle size ~ 50 nm) and 2.5 mg of carbon black were dispersed in 1 mL of ethanol, and then 20 μL of Nafion (mass concentration of 5%) solution was added to prepare a coating liquid; then the coating liquid was coated on a hydrophobic carbon paper, and after drying, an In(OH)3 catalytic electrode (In(OH)3 loading amount 1 mg / cm 2 ).

[0074] (2) The electrocatalytic CO2 reduction performance test: In a flow-type electrolytic cell, In(OH)3catalytic electrode was used as the working electrode, titanium mesh loaded with IrO2was used as the counter electrode, and Ag / AgCl electrode was used as the reference electrode, and 1 MKOH solution was used as the electrolyte, and then electrolysis was carried out at a current density of 50 ~ 400 mA cm -2 for 30 minutes; the liquid product after the reaction was analyzed by high performance liquid chromatography (Agilent 1260-Infinity II), and the gas product (such as CO, H2) was analyzed by gas chromatography (Shimadzu GC-2014). The electrochemical performance test results are shown in Figures 5-6 .

[0075] As can be seen from Figures 4-6 , compared with the commercial In(OH)3material, the magnesium-indium hydrotalcite nanosheet catalyst prepared in the application shows excellent formate (HCOO -2 ) faradic efficiency (> 89.7%) and low H2selectivity (< 5.0%) in a wide current range (50 ~ 400 mA cm - ), and can still maintain a faradic efficiency of 90% at a high current density of 350 mA cm -2 . This is because the ultra-thin nanosheet structure endows the catalyst with high specific surface area and rich active sites, effectively promotes mass transfer and electron transfer, and thus improves the electrocatalytic performance. At the same time, the In active sites in the magnesium-indium hydrotalcite nanosheet catalyst are in a highly dispersed state, and the hydrotalcite surface is rich in hydroxyl groups, which can promote the adsorption and activation of CO2 through hydrogen bonding, thereby improving the activity and selectivity of electrocatalytic CO2 reduction to formic acid.

[0076] The embodiments only express several embodiments of the application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the application, several modifications and improvements can be made, which are within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method for preparing a magnesium indium hydrotalcite nanosheet catalyst, characterized by, The method comprises the following steps: (1) dissolving a soluble indium salt and a soluble magnesium salt in a mixed solvent of ethanol and water to obtain a mixed solution A; (2) adding acetylacetone to the mixed solution A and continuously stirring to obtain a mixed solution B; (3) adding propylene oxide to the mixed solution B and continuously stirring at room temperature until the solution becomes gelatinous; (4) washing, centrifuging and drying the obtained gel to obtain the magnesium-indium hydrotalcite nanosheet catalyst.

2. The preparation method of the magnesium indium hydrotalcite nanosheet catalyst according to claim 1, characterized in that, In step (1), the molar ratio of In ions to Mg ions in the soluble indium salt and the soluble magnesium salt added is 1:1-4.

3. The method for preparing magnesium indium hydrotalcite nanosheet catalyst according to claim 1 or 2, characterized in that, The soluble indium salt is one of indium nitrate and indium chloride; and the soluble magnesium salt is one of magnesium nitrate, magnesium chloride and magnesium sulfate.

4. The preparation method of the magnesium indium hydrotalcite nanosheet catalyst according to claim 1, characterized in that, In the mixed solvent of step (1), the molar ratio of ethanol to water is 0.4-2.5:1, and the molar ratio of water to indium ions in the soluble indium salt is 10-45:

1.

5. The method for preparing the magnesium indium hydrotalcite nanosheet catalyst according to claim 1, characterized in that, In step (2), the molar ratio of acetylacetone to indium ions in the soluble indium salt added is 0.01-1.5:

1.

6. The method for preparing the magnesium indium hydrotalcite nanosheet catalyst according to claim 1, characterized in that, In step (3), the molar ratio of propylene oxide to indium ions in the soluble indium salt added is 14-40:

1.

7. The preparation method of the magnesium indium hydrotalcite nanosheet catalyst according to claim 1, characterized in that, In step (4), the standing time is 12-24 h; the drying temperature is 40-80°C, and the drying time is 12-24 h.

8. A magnesium-indium hydrotalcite nanosheet catalyst characterized by, The magnesium-indium hydrotalcite nanosheet catalyst is prepared by the method according to any one of claims 1-7.

9. Use of the magnesium-indium hydrotalcite nanosheet catalyst according to claim 8 in electrocatalytic CO2 reduction to form formate.

10. Use of the magnesium-indium hydrotalcite nanoplatelets catalyst according to claim 9 in the electrocatalytic CO2 reduction to formate reaction, characterized in that, The magnesium-indium hydrotalcite nanosheet catalyst is mixed with carbon black, ethanol and a Nafion solution to obtain a coating liquid, the coating liquid is coated on a hydrophobic carbon fiber paper, and after drying, a magnesium-indium hydrotalcite electrode material is obtained; the magnesium-indium hydrotalcite electrode material is used as a working electrode, a KOH solution is used as an electrolyte, and an electrocatalytic CO2 reduction reaction to form formate is carried out at a current density of 50-400 mA·cm -2 .

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