Indium oxide nanocrystal material and preparation method, catalyst and preparation method

Abstract

This invention discloses an indium oxide nanocrystal material and its preparation method, as well as a catalyst and its preparation method. The indium oxide nanocrystal material exhibits a sheet-like morphology with a size of 5-20 nm and a thickness of 2-5 nm. The preparation method of the indium oxide nanocrystal material is as follows: Under an air atmosphere, a solution containing an indium source and a reducing agent with a volume ratio of 0.3-0.4:10-20 and a molar ratio of 0.00075:1-0.0869:1 is reacted at a temperature of 140-220ºC for 4-48 hours to obtain the indium oxide nanocrystal material. This invention relates to the development of indium-based catalysts with higher activity, reducing the overpotential of formate formation, broadening the potential window for highly selective formate production, and improving the energy efficiency of ECO2RR.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to an indium oxide nanocrystal material and its preparation method, a catalyst and its preparation method. Background Technology

[0002] CO2 is one of the major greenhouse gases and has a significant impact on climate change. Therefore, reducing CO2 emissions is one of the major challenges facing the world today. Electrocatalytic CO2 reduction reaction (ECO2RR) provides a sustainable pathway that can utilize renewable energy sources such as solar, wind, and tidal energy to convert CO2 into high-value-added carbon-based compounds, thereby reducing the concentration of CO2 in the atmosphere and helping to alleviate global climate change.

[0003] Compared to traditional chemical reduction methods, electrochemical catalytic reduction technology typically operates under relatively mild conditions, eliminating the need for extreme conditions such as high temperatures or strong acids and bases. This means that catalytic reduction reactions can be achieved with lower energy consumption and operating costs. Furthermore, electrochemical catalytic reduction technology allows for controllability of the reaction by adjusting factors such as the catalyst, reaction potential, and the type and concentration of the electrolyte, thereby obtaining specific reaction products.

[0004] Formic acid is currently widely used in pharmaceuticals, leather, chemicals, rubber, pesticides, and other fields, with great development potential and a very promising market prospect. The industrial production of formic acid is usually achieved through the carbonization of methanol and subsequent hydrolysis of methylformate. However, this process involves high reaction energy, slow reaction rate, few byproducts, and high investment costs. Therefore, under mild conditions, the direct electrochemical reduction of CO2 to formic acid with high energy conversion efficiency is very attractive. Indium-based catalysts have been reported to exhibit excellent formic acid selectivity in ECO2RR, effectively lowering the activation energy of CO2 and promoting the reaction. This means that using indium-based catalysts can achieve efficient CO2 reduction at relatively low potentials, thereby improving the selectivity and energy efficiency of formic acid. Indium is abundant, relatively inexpensive, and resource-sustainable, with low toxicity and environmental friendliness, which is conducive to large-scale application. However, most reported indium-based materials require high overpotentials for ECO2RR and have narrow high-selectivity potential ranges for formicates, necessitating further improvements in their catalytic activity to lower the reaction energy barrier, thereby increasing the energy conversion efficiency and current density of the reaction system. Furthermore, the yield of formic acid is typically low due to the competing reaction of water electrolysis and hydrogen evolution during ECO2RR. Therefore, developing more active indium-based catalysts to reduce the overpotential of formate formation, broaden the potential window for highly selective formate production, and improve the energy efficiency of ECO2RR are crucial for achieving large-scale applications. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] Therefore, the purpose of this invention is to provide an indium oxide nanocrystal material and its preparation method, a catalyst and its preparation method, to develop an indium-based catalyst with higher activity, reduce the overpotential of formate formation, broaden the potential window for highly selective formate production, and improve the energy efficiency of ECO2RR.

[0007] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0008] An indium oxide nanocrystal material comprising: having a sheet-like morphology, with a size of 5-20 nm and a thickness of 2-5 nm.

[0009] A method for preparing indium oxide nanocrystal material, comprising the following steps:

[0010] In an air atmosphere, a solution containing an indium source and a reducing agent in a volume ratio of 0.3-0.4:10-20 and a molar ratio of 0.00075:1-0.0869:1 is reacted at a temperature of 140-220°C for 4-48 hours to obtain the indium oxide nanocrystal material.

[0011] In a preferred embodiment of the preparation method of indium oxide nanocrystal material according to the present invention, the indium source is selected from at least one of indium acetylacetone, indium chloride, indium acetate, indium iodide, indium fluoride, indium bromide, indium sulfate, and indium nitrate.

[0012] The reducing agent is selected from at least one of oleylamine, dodecylamine, trioctylamine, and octylamine.

[0013] A catalyst comprising: an indium oxide nanocrystalline material as described in claim 1, conductive carbon black, and a binder, wherein the indium oxide nanocrystalline material is supported on the conductive carbon black.

[0014] In a preferred embodiment of the catalyst described in this invention, the indium oxide nanocrystal material has a mass content of 15-80%.

[0015] A method for preparing a catalyst, comprising the following steps: centrifuging the indium oxide nanocrystal material solution prepared according to any one of claims 2-3 and washing it 1-3 times with ethanol solution, then adding it to a mixed solution of cyclohexane and isopropanol containing conductive carbon black, and ultrasonically dispersing it evenly, wherein the volume ratio of cyclohexane to isopropanol is 1:1.

[0016] A binder was added to the dispersion of the indium oxide nanocrystal material loaded on conductive carbon black, and the mixture was ultrasonically dispersed again to obtain the catalyst.

[0017] In a preferred embodiment of the catalyst preparation method of the present invention, the binder includes at least one of naphthol film and polyvinylidene fluoride, and the mass content of the binder in the catalyst is 0.1-5%.

[0018] As a preferred embodiment of the method for preparing a catalyst according to the present invention, the method for preparing a catalyst is characterized in that the dispersion includes a dispersant, the dispersant including ethanol and isopropanol, and the amount of the dispersant added is 0.1-5%.

[0019] In a preferred embodiment of the catalyst preparation method described in this invention, the total mass ratio of the conductive carbon black, indium oxide nanocrystal material, and binder to the volume ratio of the dispersant is 0.5-10 mg: 1 mL.

[0020] Application of a catalyst in the electrochemical reduction of carbon dioxide to formic acid.

[0021] Compared with existing technologies, the advantages of this invention are as follows: This invention obtains the catalyst by dispersing indium oxide nanocrystals on conductive carbon black. This catalyst achieves high formic acid selectivity under both neutral and alkaline conditions over a wide potential window, indicating its high electrochemical CO2 reduction catalytic activity. Using an H-type electrolytic cell under neutral conditions, the partial current density of formic acid can reach up to 47 mA / cm² at -1.3 V vs. RHE reaction. -2 Formic acid exhibits a Faradaic efficiency exceeding 90% over a wide potential window from -0.6 to -1.3 V vs. RHE, reaching a maximum of 97% at a reaction potential of -0.7 V vs. RHE. Using a gas diffusion full cell under alkaline conditions, high selectivity (>94%) formic acid is achieved within a battery voltage range of -2.0 to -6.0 V, and the partial current density for formic acid reaches as high as 355 mA / cm² at a battery voltage of -5.0 V. -2 Calculations show that the energy efficiency of electrochemical reduction of carbon dioxide to formic acid reaches a maximum of 73.26% at a battery voltage of -2.0V. The high CO2 reduction activity, high formic acid selectivity, and large reaction current density exhibited by this catalyst are due to the fact that the nano-sized indium oxide crystals expose more highly active reaction sites, which is beneficial to improving the intrinsic activity of the catalyst. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 The image shows the XRD pattern of the sample prepared in Example 1.

[0024] Figure 2 (a) is a high-magnification TEM image of the indium oxide nanosheets prepared in Example 1, and (b) is a size distribution map corresponding to the TEM image of the sample prepared in Example 1.

[0025] Figure 3 The image shows the AFM height distribution of the indium oxide nanosheets prepared in Example 1.

[0026] Figure 4 The catalyst prepared in Example 5 and commercial indium oxide were used in an H-type electrolytic cell with 0.5 M KHCO3 solution as the electrolyte to electrochemically reduce carbon dioxide to formic acid at different potentials, achieving the following Faraday efficiency.

[0027] Figure 5 The partial current density of the electrochemical reduction of formic acid at different potentials was measured using the catalyst prepared in Example 5 and commercial indium oxide in an H-type electrolytic cell with 0.5 M KHCO3 solution as the electrolyte.

[0028] Figure 6 (a) The farad efficiency of formic acid reduction of carbon dioxide in a gas diffusion full cell using 1.0 M KOH solution as electrolyte with the catalyst prepared in Example 5 at different cell voltages; (b) Partial current density diagram of formic acid at different cell voltages.

[0029] Figure 7 The diagram shows the energy conversion efficiency of the catalyst prepared in Example 5 for the electrochemical reduction of carbon dioxide to formic acid under different battery voltages. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] This invention provides an indium oxide nanocrystal material and its preparation method, a catalyst and its preparation method, and develops an indium-based catalyst with higher activity, reduces the overpotential of formate formation, broadens the potential window for highly selective formate production, and improves the energy efficiency of ECO2RR.

[0034] An indium oxide nanocrystal material exhibits a sheet-like morphology with a size of 5-20 nm and a thickness of 2-5 nm. Preferably, the upper limit of the size of the indium oxide nanocrystal material is independently selected from 25 nm and 20 nm, and the upper limit of the thickness is independently selected from 6 nm and 5 nm; the lower limit of the size is independently selected from 5 nm and 3 nm, and the lower limit of the thickness is independently selected from 2 nm and 1 nm.

[0035] The preparation method of the above-mentioned indium oxide nanocrystal material includes the following steps:

[0036] In an air atmosphere, a solution containing an indium source and a reducing agent with a volume ratio of 0.3-0.4:10-20 and a molar ratio of 0.00075:1-0.0869:1 is reacted at a temperature of 140-220°C for 4-48 hours to obtain the indium oxide nanocrystal material. Preferably, the reaction conditions are: a temperature of 160-200°C and a time of 12 hours. The upper limit of the molar ratio of the indium source and the solvent is independently selected from 0.0008:1 and 0. The indium source and solvent have a volume ratio of 0.3:1 to 20:1. The lower limit is independently selected from 0.0007:1, 0.086:1, 0.00068:1, and 0.085:1. The indium source and solvent have a volume ratio of 0.3:1 to 20:1. The indium source is selected from at least one of indium acetylacetone, indium chloride, indium acetate, indium iodide, indium fluoride, indium bromide, indium sulfate, and indium nitrate. The reducing agent is selected from at least one of oleylamine, dodecylamine, trioctylamine, and octylamine.

[0037] The present invention also provides a catalyst, an indium oxide nanocrystalline material, conductive carbon black, and a binder, wherein the indium oxide nanocrystalline material is loaded on the conductive carbon black. Optionally, in the catalyst, the mass content of the indium oxide nanocrystalline material is 15-80%, the upper limit of the mass content of the indium oxide nanocrystalline material is independently selected from 90%, 85%, and 80%, and the lower limit is independently selected from 5%, 10%, and 15%. The mass content of the indium oxide nanocrystalline material is 50-65%. The binder includes at least one of naphthol film and polyvinylidene fluoride. In the catalyst, the mass content of the binder is 0.1-5%.

[0038] A method for preparing the above-mentioned catalyst is provided, comprising the following steps: centrifuging the indium oxide nanocrystal material solution prepared above and washing it with ethanol solution 1-3 times, then adding it to a mixed solution of cyclohexane and isopropanol containing conductive carbon black, and ultrasonically dispersing it evenly, wherein the volume ratio of cyclohexane to isopropanol is 1:1.

[0039] A binder is added to the dispersion of indium oxide nanocrystal material loaded on conductive carbon black, and the mixture is ultrasonically dispersed again to obtain the catalyst. The conductive carbon black is LION Ketjenblack (EC300J, EC600JD) or Carbot carbon black (X-72R). The dispersion includes a dispersant selected from alcohol compounds. The amount of dispersant added is 0.1-5%, and the dispersant includes ethanol and isopropanol. The total mass ratio of the conductive carbon black, indium oxide nanocrystal material, and binder to the volume ratio of the dispersant is 0.5-10 mg:1 mL. The binder is a naphthol film solution, and the ratio of the naphthol film solution to the catalyst (the catalyst is the total mass of conductive carbon black and indium oxide nanocrystal material) is 5 μL (naphthol film solution):3 mg (catalyst) - 20 μL:10 mg.

[0040] This invention also provides the application of a catalyst in the electrochemical reduction of carbon dioxide to formic acid. The apparatus used for the electrochemical reduction of CO2 to formic acid is selected from either an H-type electrolytic cell or a gas diffusion electrolytic cell. In the H-type electrolytic cell, the pH of the electrolyte used is 7.3-9.0, and the electrolyte is selected from a solution containing KHCO3. The electrolyte concentration in the H-type electrolytic cell is 0.1-1.0 M. The working electrode of the H-type electrolytic cell includes a catalyst and a glassy carbon electrode; the catalyst is loaded on the glassy carbon electrode; and the catalyst loading is 0.4-0.6 mg / cm³. -2 The working electrode of the H-type electrolytic cell includes a catalyst and a glassy carbon electrode; the catalyst is loaded on the glassy carbon electrode; the catalyst loading is 0.3-0.5 mg / cm³. -2In the gas diffusion electrolysis cell, the pH of the electrolyte used is 7.3-14.0, the electrolyte concentration is 1-5.0 M, and the electrolyte is selected from solutions containing KOH. The cathode electrode of the gas diffusion electrolysis cell includes a catalyst and a gas diffusion layer; the catalyst is loaded on the gas diffusion layer, which is selected from carbon cloth or carbon paper. In the cathode electrode of the gas diffusion electrolysis cell, the catalyst loading is 1-5 mg / cm³. -2 In the cathode electrode of the gas diffusion electrolysis cell, the catalyst loading is 2-4 mg / cm³. -2 .

[0041] In this application, the size of indium oxide nanosheet material refers to the statistical size of a single nanoparticle.

[0042] To verify the actual efficacy of the indium oxide nanocrystal material and catalyst of the present invention, the present invention provides the following Examples 1-12, and conducts scientific analysis and verification on the indium oxide nanocrystal material and catalyst prepared in Examples 1-14.

[0043] Example 1

[0044] 0.309 g of indium acetylacetonate and 20 mL of dodecylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 180 °C for 12 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0045] Example 2

[0046] 0.166 g of indium chloride and 25 mL of oleylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 200 °C for 8 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0047] Example 3

[0048] 0.218 g of indium acetate and 30 mL of trioctylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 220 °C for 4 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0049] Example 4

[0050] 0.344 g of indium iodide and 35 mL of octylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 140 °C for 48 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0051] Example 5

[0052] 0.129 g of indium fluoride and 40 mL of octylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 160 °C for 16 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0053] Example 6

[0054] 0.160 g of indium bromide and 20 mL of octylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 180 °C for 14 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0055] Example 7

[0056] 0.388 g of indium sulfate and 30 mL of octylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 200 °C for 8 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0057] Example 8

[0058] 0.226 g of indium nitrate and 40 mL of octylamine were added to the polytetrafluoroethylene liner of the reactor and reacted at 220 °C for 6 hours. After naturally cooling to room temperature, the mixture was centrifuged and washed 1-3 times with ethanol solution. Then, it was added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black (volume ratio 1:1) and ultrasonically dispersed until uniform. The catalyst powder was obtained after vacuum drying.

[0059] Example 9

[0060] The samples prepared in Examples 1 to 8 were subjected to XRD pattern testing, with the sample in Example 1 being a typical representative. Figure 1 The image shows the XRD pattern of the indium oxide nanocrystals prepared in Example 1. The XRD pattern shows that the powder obtained is composed of indium oxide nanocrystals and conductive carbon black.

[0061] The samples prepared in Examples 1 to 4 were subjected to TEM testing, with the sample in Example 1 being a typical representative. Figure 2 (a) is a TEM image of the sample in Example 1. It can be seen from the image that the indium oxide nanocrystals exhibit a sheet-like morphology. (b) is a size distribution statistical diagram corresponding to the TEM image. It can be seen from the size distribution statistical diagram that the size of the indium oxide nanosheets is between 5-20 nm. Figure 3 The image shows the AFM height map of indium oxide nanosheets. It can be seen that the average height of the indium oxide nanosheets is 2.645 nm. Combining the TEM morphology and the AFM height map, it can be seen that the morphology of the prepared indium oxide nanocrystals is sheet-like.

[0062] Example 10

[0063] 3 mg of indium oxide nanocrystals prepared in Example 1 and loaded on carbon black were dispersed in 1 mL of ethanol, so that the ratio of catalyst to dispersion was 3 mg: 1 mL, and the mass fraction of indium oxide nanocrystals was 61%. Naphthol film solution (with a catalyst ratio of 7 μL: 1 mg) was added and ultrasonically dispersed.

[0064] Example 11

[0065] 2 mg of indium oxide nanocrystals prepared in Example 1 and loaded on carbon black were dispersed in 1 mL of ethanol, so that the ratio of catalyst to dispersion was 2 mg: 1 mL, and the mass fraction of indium oxide nanocrystals was 49%. Naphthol film solution (with a catalyst ratio of 6 μL: 1 mg) was added and ultrasonically dispersed.

[0066] Example 12

[0067] 1 mg of indium oxide nanocrystals prepared in Example 1 and loaded on carbon black were dispersed in 1 mL of ethanol, so that the ratio of catalyst to dispersion was 1 mg: 1 mL, and the mass fraction of indium oxide nanocrystals was 39%. Naphthol film solution (with a catalyst ratio of 3 μL: 1 mg) was added and ultrasonically dispersed.

[0068] The raw materials and catalysts used in the embodiments of this application were all purchased commercially. Unless otherwise specified, the test methods used were conventional in the art, and the instruments were set to standard configurations.

[0069] The analysis method in the embodiments of this application is as follows:

[0070] Scanning electron microscopy (SEM) analysis was performed using a Ultima Max 170 instrument.

[0071] Transmission electron microscopy (TEM) analysis was performed using a JEM instrument from Tokyo, Japan, at a test voltage of 200 kV.

[0072] X-ray powder diffraction (XRD) analysis was performed using an XRD Ultima IV instrument with a copper target.

[0073] Electrochemical tests were performed using a CHI760E electrochemical workstation.

[0074] The concentration of the gaseous products from the electrochemical reduction of carbon dioxide was measured using a gas chromatograph from Shanghai Kechuang Company.

[0075] The concentrations of the liquid-phase products from the electrochemical reduction of carbon dioxide were measured using a Bruker 600MHz NMR spectrometer.

[0076] In this embodiment, the formulas for calculating the Faradic efficiency (FE, current efficiency) of the gas phase and liquid phase products are as follows:

[0077]

[0078]

[0079] Where n is the number of electrons transferred in the electrochemical reduction of carbon dioxide, G is the flow rate of carbon dioxide during the reaction, Cg is the concentration of the gaseous product, and F is the Faraday constant (96485 Cmol). -1 I is the current density during the electrochemical reduction of carbon dioxide, V is the volume of the electrolyte, and C is the current density during the reduction of carbon dioxide. l The concentration of the liquid-phase product, t is the time of the electrochemical reduction of carbon dioxide.

[0080] The catalyst prepared in Example 10 was characterized for its electrochemical carbon dioxide reduction performance using an H-type electrolytic cell. A naphthol membrane separated the cathode and anode of the electrolytic cell. 100 μL of the catalyst slurry prepared in Example 10 was dropped onto a glassy carbon electrode and allowed to dry naturally before being used as the working electrode. An Ag / AgCl electrode was used as the reference electrode, a Pt mesh as the counter electrode, and a 0.5 M KHCO3 solution as the electrolyte. The test results are shown below. Figure 4 ,from Figure 4 As can be seen, the Faraday efficiency (FE) of formic acid can exceed 90% over a wide potential window (-0.6 to -1.3 V vs. RHE). However, under the same conditions, the formic acid produced by commercial indium oxide nanoparticles exhibits significantly lower activity, with a very narrow high-selectivity potential window for formic acid. Figure 3 ),from Figure 5 The partial current density plot of formic acid also shows that the current density of the indium oxide nanosheets prepared in Example 6 can reach 47 mA / cm² at -1.3 V vs. RHE potential. -2 Commercial indium oxide nanoparticles only reach 20 mA / cm². -2These results demonstrate that the indium oxide nanosheet catalyst provided in this application possesses excellent activity and high selectivity in the electrochemical reduction of carbon dioxide to formic acid.

[0081] The electrochemical reduction performance of the catalyst prepared in Example 10 was characterized using a gas diffusion full cell. The catalyst was loaded onto carbon paper / carbon cloth with a gas diffusion layer as the working electrode, and the catalyst loading on the carbon paper / carbon cloth was 2.5-4 mg / cm³. -2 1.0 MkOH was used as the electrolyte, an anion exchange membrane was used to separate the anode and cathode, and an ethylene tantalum titanium mesh was used as the anode. Test results are shown in [Figure number missing]. Figure 6 (a) shows the farad efficiency of formic acid in the electrochemical reduction of carbon dioxide using 1.0 MkOH solution as the electrolyte in a gas diffusion full cell at different full cell voltages; (b) shows the partial current density of formic acid at different cell voltages. Figure 6 It can be seen that the indium oxide nanocatalyst achieves high selectivity (>94%) for formic acid in the gas diffusion full cell in the battery voltage range of -2.0 to -6.0 V, and the partial current density of formic acid is as high as 355 mA / cm at a battery voltage of -5.0 V. -2 . Figure 7 The graph shows the energy conversion efficiency of the electrochemical reduction of carbon dioxide to formic acid in a gas diffusion full cell at different cell voltages. Calculations show that the energy efficiency of the electrochemical reduction of carbon dioxide to formic acid can reach up to 73.26% when the cell voltage is -2.0V.

[0082] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An indium oxide nanocrystal material, characterized in that, include: It exhibits a sheet-like morphology, with a size of 5-20 nm and a thickness of 2-5 nm; The preparation steps of indium oxide nanocrystal materials are as follows: In an air atmosphere, a solution containing an indium source and a reducing agent in a volume ratio of 0.3-0.4:10-20 and a molar ratio of 0.00075:1-0.0869:1 is reacted at a temperature of 140-220ºC for 4-48 hours to obtain the indium oxide nanocrystal material.

2. The indium oxide nanocrystal material according to claim 1, characterized in that, The indium source is selected from at least one of indium acetylacetone, indium chloride, indium acetate, indium iodide, indium fluoride, indium bromide, indium sulfate, and indium nitrate. The reducing agent is selected from at least one of oleylamine, dodecylamine, trioctylamine, and octylamine.

3. A catalyst characterized by, include: The indium oxide nanocrystal material, conductive carbon black, and binder according to claim 1, wherein the indium oxide nanocrystal material is loaded on the conductive carbon black.

4. The catalyst of claim 3, wherein The indium oxide nanocrystal material has a mass content of 15-80%.

5. A process for the preparation of a catalyst as claimed in any one of claims 3-4, characterized in that, The steps are as follows: After centrifuging the indium oxide nanocrystal material solution prepared according to any one of claims 1-2 and washing it with ethanol solution 1-3 times, it is added to a mixed solution of cyclohexane and isopropanol containing conductive carbon black and ultrasonically dispersed evenly to obtain a dispersion of indium oxide nanocrystal material loaded on conductive carbon black, wherein the volume ratio of cyclohexane and isopropanol is 1:

1. A binder was added to a dispersion of indium oxide nanocrystals supported on conductive carbon black, and the mixture was ultrasonically dispersed again to obtain the catalyst.

6. The method for preparing a catalyst according to claim 5, characterized in that, The binder includes at least one of naphthol film and polyvinylidene fluoride, and the mass content of the binder in the catalyst is 0.1-5%.

7. The method of claim 5, wherein the catalyst is prepared by the steps of: The dispersion includes a dispersant, which includes ethanol and isopropanol, and the amount of the dispersant added is 0.1-5%.

8. The method of claim 5, wherein the catalyst is prepared by the steps of: The total mass ratio of the conductive carbon black, indium oxide nanocrystal material, and binder to the volume ratio of the dispersant is 0.5-10 mg:1 mL.

9. The use of a catalyst as described in any one of claims 3-4 in the electrochemical reduction of carbon dioxide to formic acid.

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