Metal oxide doped bismuth catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemical catalysts, in particular to a metal oxide doped bismuth catalyst and a preparation method and application thereof.The preparation method comprises the steps that organic ligand terephthalic acid, bismuth salt and indium salt are subjected to a hydrothermal reaction in a reaction kettle to prepare an InBi-MOF precursor, the InBi-MOF precursor is calcined under the anaerobic condition, and the metal oxide doped bismuth catalyst is obtained. According to the preparation method, the bismuth source forms a defective bismuth elementary substance, the indium source forms an indium oxide substance after being calcined, indium ions and metal bismuth form a coordination structure through oxygen atoms of the indium ions, and a nano spherical structure with In2O3 nanocrystals uniformly embedded in the surface of the Bi elementary substance is formed, so that the metal oxide doped bismuth catalyst is prepared, and the preparation method has the advantages of simple preparation process, low cost and the like. The preparation method has the characteristics of simple process, cheap and easily available raw materials, low production cost and suitability for large-scale production, and the prepared metal oxide doped bismuth catalyst has the advantages of high selectivity, wide potential window and good stability in the application of electrically catalyzing CO2 reduction to prepare formic acid.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalyst technology, specifically to a metal oxide-doped bismuth catalyst, its preparation method, and its application. Background Technology

[0002] With rapid industrial development, fossil fuels are being consumed at an alarming rate, resulting in the release of large amounts of greenhouse gases such as CO2. Electrocatalysis, which converts CO2 into high-value-added formic acid, is an effective solution, reducing greenhouse gas emissions while producing these chemicals. Electrocatalysts are the core component of electrocatalysis technology. Among traditional electrocatalytic CO2 reduction catalysts for formic acid production, bismuth-based catalysts are considered the most promising metallic material for industrial-scale electrocatalytic CO2-to-formic acid production due to their abundant yield, low toxicity, and effective suppression of hydrogen evolution side reactions.

[0003] In existing technologies, bismuth metal and its oxides are the best catalysts for the electrocatalytic reduction of CO2 to formic acid, such as carbon-supported bismuth particles (Bi@C3N4), bismuth oxide (Bi2O3), and bismuth oxycarbonate (Bi2O2CO3), which can effectively lower the reaction energy barrier during the electrocatalytic reduction of CO2. However, these existing catalysts still have drawbacks in the application of electrocatalytic CO2 reduction to formic acid, such as low selectivity, narrow potential window, and poor stability, which limits their widespread application. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a method for preparing a bismuth-doped metal oxide catalyst. This method is simple and easy to implement, uses inexpensive and readily available raw materials, and the resulting bismuth-doped metal oxide catalyst has the advantages of high selectivity, wide potential window, and good stability in the electrocatalytic reduction of CO2 to formic acid.

[0005] To overcome the shortcomings of the prior art, the second objective of this invention is to provide a bismuth-doped metal oxide catalyst, which has the advantages of high selectivity, wide potential window and good stability in the application of electrocatalytic CO2 reduction to formic acid.

[0006] A third objective of this invention is to provide an application of a bismuth-doped metal oxide catalyst.

[0007] To achieve the first objective of the invention, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing a bismuth-doped metal oxide catalyst, comprising the following steps:

[0009] S1. Preparation of precursor solution: Dissolve bismuth salt, indium salt and organic ligand terephthalic acid in an organic solvent to prepare precursor solution;

[0010] S2. Synthesis of InBi-MOF precursor: The precursor solution was placed in a reaction vessel and heated for reaction, then cooled, washed and dried to obtain the InBi-MOF precursor;

[0011] S3. Calcination: The InBi-MOF precursor is calcined under an inert atmosphere to obtain the metal oxide-doped bismuth catalyst.

[0012] The present invention discloses a method for preparing a bismuth-doped metal oxide catalyst. An InBi-MOF precursor is prepared by hydrothermal reaction of an organic ligand, terephthalic acid, with bismuth and indium salts in a reactor. The InBi-MOF precursor is then calcined under oxygen-free conditions to form defective bismuth elemental material from the bismuth source, while the indium source forms indium oxide after calcination. Indium ions form a coordination structure with metallic bismuth through their own oxygen atoms, resulting in a nanosphere structure with In₂O₃ nanocrystals uniformly embedded on the surface of the Bi elemental material, thereby obtaining the bismuth-doped metal oxide catalyst.

[0013] Furthermore, in step S1, the molar ratio of the bismuth salt to the indium salt is (7~9):(3~1); and / or

[0014] The total metal content of the bismuth salt and indium salt and the molar ratio of the organic ligand are 1:(2~4).

[0015] Furthermore, in step S1, the bismuth salt is bismuth nitrate pentahydrate, and the indium salt is indium nitrate tetrahydrate; and / or

[0016] The organic solvent is N,N-dimethylformamide; and / or

[0017] The precursor solution is prepared by stirring at a speed of 300 r / min to 500 r / min for a duration of 10 min to 40 min.

[0018] Furthermore, in step S2, the temperature of the heating reaction is 105℃~145℃, and the heating reaction time is 6h~24h.

[0019] Furthermore, in step S2, the washing process involves alternating between methanol and water 2-3 times; and / or

[0020] The drying process involves placing the product in an oven at 55℃~65℃ for 20h~24h.

[0021] Furthermore, in step S3, the calcination temperature is 500℃~700℃, and the calcination time is 1.0h~3.5h; and / or

[0022] The inert atmosphere is argon.

[0023] To achieve the second objective of the invention, the technical solution adopted by the present invention is as follows:

[0024] This invention provides a bismuth-doped metal oxide catalyst, which is prepared by the method described above for preparing a bismuth-doped metal oxide catalyst.

[0025] Furthermore, the aforementioned bismuth-doped metal oxide catalyst is composed of elemental Bi and In₂O₃ nanocrystals, wherein the In₂O₃ nanocrystals are embedded on the surface of the elemental Bi; and / or

[0026] The bismuth-doped metal oxide catalyst is a nanosphere, and / or the nanosphere has a particle size of 0.2 µm to 0.5 µm.

[0027] To achieve the third objective of the invention, the technical solution adopted by the present invention is as follows:

[0028] This invention provides an application of a bismuth-doped metal oxide catalyst, specifically the application of the bismuth-doped metal oxide catalyst described above or prepared by the method described above in the electrocatalytic reduction of CO2 to formic acid.

[0029] The bismuth-doped metal oxide catalyst is used as the cathode in an electrocatalytic CO2 reduction formic acid production apparatus; and / or

[0030] The cathode uses carbon paper as the substrate material and Nafion as the binder to support and fix the metal oxide-doped bismuth catalyst on the surface of the carbon paper; and / or

[0031] The loading of the metal oxide-doped bismuth catalyst is 0.5 mg cm⁻¹. -2 ~1.5mg cm -2 .

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) A method for preparing a bismuth-doped metal oxide catalyst of the present invention involves preparing an InBi-MOF precursor by hydrothermal reaction of organic ligand terephthalic acid with bismuth salt and indium salt in a reaction vessel. The InBi-MOF precursor is calcined under oxygen-free conditions to form defective bismuth elemental material from the bismuth source, while the indium source forms indium oxide material after calcination. The indium ions form a coordination structure with the metallic bismuth through their own oxygen atoms, and form a nanosphere structure with In2O3 nanocrystals uniformly embedded on the surface of the Bi elemental material, thereby obtaining a bismuth-doped metal oxide catalyst.

[0034] (2) The preparation method of the metal oxide doped bismuth catalyst of the present invention has the characteristics of simple and easy preparation process, cheap and readily available raw materials, low production cost, and suitability for large-scale production. Moreover, the prepared metal oxide doped bismuth catalyst has the advantages of high selectivity, wide potential window and good stability in the application of electrocatalytic CO2 reduction to formic acid.

[0035] (3) The bismuth-doped metal oxide catalyst of the present invention has the advantages of high selectivity, wide potential window and good stability in the application of electrocatalytic CO2 reduction to formic acid.

[0036] (4) An application of a bismuth-doped metal oxide catalyst of the present invention, which is used for electrocatalytic reduction of CO2 to formic acid and for the cathode in an electrocatalytic CO2 reduction to formic acid device. It can efficiently electrocatalyze the conversion of CO2 to formic acid in neutral or alkaline electrolytes and has the advantages of high selectivity, wide potential window and good stability. This application can save costs and achieve environmental protection, and therefore has a good application prospect. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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.

[0038] Figure 1 The images show the XRD patterns of the catalysts prepared in Examples 1, 2 and Comparative Example 1 of this invention.

[0039] Figure 2 The image shows the XRD pattern of the catalyst prepared in Comparative Example 2.

[0040] Figure 3 The X-ray photoelectron spectrum is shown for the metal oxide-doped bismuth catalyst (In2O3-Bi-500℃) prepared in Example 1 of this invention.

[0041] Figure 4 This is a SEM image of the bismuth-doped metal oxide catalyst of Example 1 of the present invention.

[0042] Figure 5 The image shows the SEM image of the Bi catalyst prepared in Comparative Example 2.

[0043] Figure 6 This is an elemental distribution diagram of the bismuth-doped metal oxide catalyst of Example 1 of the present invention.

[0044] Figure 7 The elemental distribution diagram is shown for the Bi catalyst prepared in Comparative Example 2.

[0045] Figure 8 This is a thermogravimetric analysis diagram of the bismuth-doped metal oxide catalyst of Example 1 of the present invention.

[0046] Figure 9 The thermogravimetric analysis diagram is shown for the Bi catalyst prepared in Comparative Example 2.

[0047] Figure 10 The graph shows the electrocatalytic CO2 reduction performance of the catalysts in Example 1 and Comparative Example 2 of this invention. Detailed Implementation

[0048] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0049] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. In this invention, the singular forms “a,” “described,” and “the” as used in the embodiments and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0050] In this embodiment of the invention, a method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0051] S1. Preparation of precursor solution: Dissolve bismuth salt, indium salt and organic ligand terephthalic acid in an organic solvent to prepare precursor solution;

[0052] S2. Synthesis of InBi-MOF precursor: The precursor solution was placed in a reaction vessel and heated for reaction, then cooled, washed and dried to obtain the InBi-MOF precursor;

[0053] S3. Calcination: The InBi-MOF precursor is calcined under an inert atmosphere to obtain the metal oxide-doped bismuth catalyst.

[0054] In some embodiments, in step S1, the molar ratio of the bismuth salt to the indium salt is (7~9):(3~1); and / or

[0055] The total metal content of the bismuth salt and indium salt and the molar ratio of the organic ligand are 1:(2~4).

[0056] In some embodiments, in step S1, the bismuth salt is bismuth nitrate pentahydrate, and the indium salt is indium nitrate tetrahydrate; and / or

[0057] The organic solvent is N,N-dimethylformamide; and / or

[0058] The precursor solution is prepared by stirring at a speed of 300 r / min to 500 r / min for a duration of 10 min to 40 min.

[0059] In some embodiments, in step S2, the temperature of the heating reaction is 105°C to 145°C, and the heating reaction time is 6h to 24h.

[0060] In some embodiments, in step S2, the washing involves alternating between methanol and water 2-3 times; and / or

[0061] The drying process involves placing the product in an oven at 55℃~65℃ for 20h~24h.

[0062] In some embodiments, in step S3, the calcination temperature is 500℃~700℃, and the calcination time is 1.0h~3.5h; and / or

[0063] The inert atmosphere is argon.

[0064] In this embodiment of the invention, a bismuth-doped metal oxide catalyst is prepared by the method described above for preparing a bismuth-doped metal oxide catalyst.

[0065] The aforementioned bismuth-doped metal oxide catalyst comprises elemental Bi and In₂O₃ nanocrystals, wherein the In₂O₃ nanocrystals are embedded on the surface of the elemental Bi; and / or

[0066] The bismuth-doped metal oxide catalyst is a nanosphere, and / or the nanosphere has a particle size of 0.2 µm to 0.5 µm.

[0067] In this embodiment of the invention, an application of a bismuth-doped metal oxide catalyst is described, specifically the application of the bismuth-doped metal oxide catalyst described above or the bismuth-doped metal oxide catalyst prepared by the method described above in the electrocatalytic reduction of CO2 to formic acid.

[0068] The bismuth-doped metal oxide catalyst is used as the cathode in an electrocatalytic CO2 reduction formic acid production apparatus; and / or

[0069] The cathode uses carbon paper as the substrate material and Nafion as the binder to support and fix the metal oxide-doped bismuth catalyst on the surface of the carbon paper; and / or

[0070] The loading of the metal oxide-doped bismuth catalyst is 0.5 mg cm⁻¹. -2 ~1.5mg cm -2 .

[0071] The following description is based on specific embodiments. Example 1

[0072] A method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0073] S1. Preparation of precursor solution: Dissolve 7 mmol bismuth nitrate pentahydrate (Bi(NO3)3•5H2O), 1 mmol indium nitrate tetrahydrate (In(NO3)3•4H2O) and 24 mmol organic ligand terephthalic acid in 60 mL N,N-dimethylformamide and stir at 400 r / min for 20 min to prepare the precursor solution.

[0074] S2. Synthesis of InBi-MOF precursor: The precursor solution was poured into a 100 mL polytetrafluoroethylene liner and then placed in a stainless steel reactor and heated at 120 °C for 24 h. After cooling to room temperature, it was washed three times alternately with methanol and water and then dried in a constant temperature oven at 60 °C for 24 h to obtain the InBi-MOF precursor, which is a white powder.

[0075] S3. Calcination: The InBi-MOF precursor is placed in a ceramic boat and placed in a calcination furnace. Under an argon atmosphere, it is calcined at 500℃ for 2 hours to obtain the metal oxide doped bismuth catalyst (denoted as In2O3-Bi-500℃). Example 2

[0076] A method for preparing a bismuth-doped metal oxide catalyst is disclosed. The difference between this embodiment and Example 1 is that the calcination temperature in this embodiment is 600°C. The remaining preparation methods are the same as in Example 1, yielding a bismuth-doped metal oxide catalyst (denoted as In2O3-Bi-600°C). Example 3

[0077] A method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0078] S1. Preparation of precursor solution: Dissolve 9 mmol bismuth nitrate pentahydrate, 2 mmol indium nitrate tetrahydrate and 44 mmol organic ligand terephthalic acid in 70 mL N,N-dimethylformamide and stir at 500 r / min for 10 min to prepare precursor solution.

[0079] S2. Synthesis of InBi-MOF precursor: The precursor solution was poured into a 100 mL polytetrafluoroethylene liner and then placed in a stainless steel reactor and heated at 105 °C for 20 h. After cooling to room temperature, it was washed twice with methanol and water respectively, and then dried in a constant temperature oven at 55 °C for 23 h to obtain the InBi-MOF precursor, which is a white powder.

[0080] S3. Calcination: The InBi-MOF precursor is placed in a ceramic boat and placed in a calcination furnace at 700°C for 1.0 h under an argon atmosphere to obtain the metal oxide-doped bismuth catalyst. Example 4

[0081] A method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0082] S1. Preparation of precursor solution: Dissolve 8 mmol bismuth nitrate pentahydrate, 3 mmol indium nitrate tetrahydrate and 22 mmol organic ligand terephthalic acid in 60 mL N,N-dimethylformamide and stir at 300 r / min for 15 min to prepare precursor solution.

[0083] S2. Synthesis of InBi-MOF precursor: The precursor solution was poured into a 100 mL polytetrafluoroethylene liner and then placed in a stainless steel reactor and heated at 145 °C for 12 h. After cooling to room temperature, it was washed three times alternately with methanol and water and then dried in a constant temperature oven at 65 °C for 20 h to obtain the InBi-MOF precursor, which is a white powder.

[0084] S3. Calcination: The InBi-MOF precursor is placed in a ceramic boat and then placed in a calcination furnace and calcined at 550°C for 3.5 hours under an argon atmosphere to obtain the metal oxide-doped bismuth catalyst. Example 5

[0085] A method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0086] S1. Preparation of precursor solution: Dissolve 8.5 mmol bismuth nitrate pentahydrate, 1.5 mmol indium nitrate tetrahydrate and 30 mmol organic ligand terephthalic acid in 60 mL N,N-dimethylformamide and stir at 350 r / min for 40 min to prepare the precursor solution.

[0087] S2. Synthesis of InBi-MOF precursor: The precursor solution was poured into a 100 mL polytetrafluoroethylene liner, then placed in a microwave hydrothermal reactor. The power of the microwave hydrothermal synthesizer was set to 400 W, and the reaction was heated at 120 °C for 6 h. After cooling to room temperature, the product was washed three times alternately with methanol and water, and then dried in a constant temperature oven at 58 °C for 22 h to obtain the InBi-MOF precursor, which was a white powder.

[0088] S3. Calcination: The InBi-MOF precursor is placed in a ceramic boat and then placed in a calcination furnace and calcined at 600°C for 2.5 hours under an argon atmosphere to obtain the metal oxide-doped bismuth catalyst. Example 6

[0089] A method for preparing a bismuth-doped metal oxide catalyst includes the following steps:

[0090] S1. Preparation of precursor solution: Dissolve 8 mmol bismuth nitrate pentahydrate, 2 mmol indium nitrate tetrahydrate and 25 mmol organic ligand terephthalic acid in 60 mL N,N-dimethylformamide and stir at 480 r / min for 30 min to prepare precursor solution.

[0091] S2. Synthesis of InBi-MOF precursor: The precursor solution was poured into a 100 mL polytetrafluoroethylene liner and then placed in a stainless steel reactor and heated at 130 °C for 15 h. After cooling to room temperature, it was washed three times alternately with methanol and water and then dried in a constant temperature oven at 62 °C for 21 h to obtain the InBi-MOF precursor, which is a white powder.

[0092] S3. Calcination: The InBi-MOF precursor is placed in a ceramic boat and placed in a calcination furnace at 650°C for 1.5 h under an argon atmosphere to obtain the metal oxide-doped bismuth catalyst. Example 7

[0093] A bismuth-doped metal oxide catalyst is prepared by any one of the preparation methods of bismuth-doped metal oxide catalysts in Examples 1 to 7. The prepared bismuth-doped metal oxide catalysts are all composed of elemental Bi and In₂O₃ nanocrystals, with the In₂O₃ nanocrystals embedded on the surface of the elemental Bi. Furthermore, the prepared bismuth-doped metal oxide catalysts are nanospherical particles with a particle size of 0.2 µm to 0.5 µm. Example 8

[0094] Application of a bismuth-doped metal oxide catalyst: Examples 1 to 7 describe the application of a bismuth-doped metal oxide catalyst prepared by any one of the preparation methods in the electrocatalytic reduction of CO2 to formic acid. Specifically, the bismuth-doped metal oxide catalyst is used as the cathode in an electrocatalytic CO2 reduction to formic acid apparatus. This cathode uses carbon paper as the substrate material, with Nafion as the binder to support and fix the bismuth-doped metal oxide catalyst on the surface of the carbon paper. The loading amount of the bismuth-doped metal oxide catalyst is 0.5 mg / cm³. -2 ~1.5mg cm -2 .

[0095] Comparative Example 1

[0096] A method for preparing a catalyst is described. The difference between this comparative example and Example 1 is that the calcination temperature in this example is 400°C. The remaining preparation methods in this example are the same as in Example 1, and a catalyst (denoted as Bi catalyst - 400°C) is obtained.

[0097] Comparative Example 2

[0098] A method for preparing a Bi catalyst is disclosed. The difference between this comparative example and Example 1 is that in the preparation step of the precursor solution, indium nitrate tetrahydrate (In(NO3)3•4H2O) is omitted; that is, indium nitrate tetrahydrate is not added to the precursor solution. The remaining preparation methods of this comparative example are the same as in Example 1, yielding a Bi catalyst (denoted as Bi).

[0099] Structural morphology characterization

[0100] (a) X-ray diffraction analysis

[0101] The bismuth-doped metal oxide catalyst (In₂O₃-Bi-500℃) prepared in Example 1, the bismuth-doped metal oxide catalyst (In₂O₃-Bi-600℃) prepared in Example 2, the catalyst prepared in Comparative Example 1 (Bi catalyst-400℃), and the Bi catalyst (Bi) prepared in Comparative Example 2 were subjected to X-ray diffraction (XRD) analysis. The XRD patterns of Examples 1, 2, and 1 are shown below. Figure 1 As shown, the XRD pattern of Comparative Example 2 is as follows: Figure 2 As shown.

[0102] Depend on Figure 1As can be seen, the metal oxide-doped bismuth catalysts (In2O3-Bi-500℃ and In2O3-Bi-600℃) prepared in Examples 1 and 2 both contain characteristic peaks of elemental Bi and In2O3 (standard card numbers 85-1331 and 74-1990) in their X-ray diffraction patterns, indicating that the metal oxide-doped bismuth catalysts prepared in this invention are composed of elemental Bi and In2O3 nanocrystals, and are In2O3-Bi catalysts.

[0103] In addition, by Figure 1 As can be seen, the catalyst prepared in Comparative Example 1 (Bi catalyst - 400℃) contains characteristic peaks of elemental Bi in its X-ray diffraction pattern, but does not contain characteristic peaks of In₂O₃, indicating that calcining the InBi-MOF precursor at 400℃ did not form an In₂O₃ nanocrystalline structure. Furthermore, the XRD pattern also shows diffraction peaks of the organic ligands, indicating that the organic ligands were not completely carbonized under the calcination conditions of 400℃.

[0104] Depend on Figure 2 As can be seen, the Bi catalyst prepared in Comparative Example 2 without adding indium nitrate tetrahydrate (In(NO3)3•4H2O) to prepare the precursor solution exhibits characteristic diffraction peaks of elemental Bi in its X-ray diffraction pattern.

[0105] (ii) X-ray photoelectron spectroscopy test

[0106] The metal oxide-doped bismuth catalyst (In₂O₃-Bi-500℃) prepared in Example 1 was used to perform X-ray photoelectron spectroscopy on indium. The test results are as follows: Figure 3 As shown.

[0107] Depend on Figure 3 It is evident that in the bismuth-doped metal oxide catalyst prepared in this invention, indium exists in a trivalent form.

[0108] (III) Morphological characterization by scanning electron microscopy

[0109] The morphology of the bismuth-doped metal oxide catalyst (In₂O₃-Bi-500℃) prepared in Example 1 and the Bi catalyst (Bi) prepared in Comparative Example 2 were characterized by scanning electron microscopy (SEM). The SEM image of Example 1 is shown below. Figure 4 As shown, the SEM image of Comparative Example 2 is as follows: Figure 5 As shown.

[0110] Depend on Figure 4 As can be seen, the metal oxide doped bismuth catalyst (In2O3-Bi-500℃) prepared in Example 1 of the present invention has an overall stacked spherical structure, wherein the average size of the spherical structure is 0.5µm.

[0111] Depend on Figure 5 As can be seen, the Bi catalyst (Bi) prepared in Comparative Example 2 is spherical in shape, and the average size of the spheres is 0.2µm.

[0112] (iv) SEM-EDS analysis

[0113] The bismuth-doped metal oxide catalyst (In₂O₃-Bi-500℃) prepared in Example 1 and the Bi catalyst (Bi) prepared in Comparative Example 2 were analyzed for elemental distribution by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). The elemental distribution diagram of Example 1 is shown below. Figure 6 As shown, the element distribution diagram of Comparative Example 2 is as follows: Figure 7 As shown.

[0114] Depend on Figure 6 As can be seen, the metal oxide-doped bismuth catalyst (In₂O₃-Bi-500℃) of Example 1 contains Bi, O, and In elements, and the elemental distribution is uniform, indicating that the In₂O₃-Bi catalyst was successfully synthesized. Figure 7 It can be seen that the Bi catalyst (Bi) in Comparative Example 2 contains Bi, O and C elements, and the elements are evenly distributed.

[0115] (v) Thermogravimetric analysis

[0116] The bismuth-doped metal oxide catalyst (In₂O₃-Bi-500℃) prepared in Example 1 and the Bi catalyst (Bi) prepared in Comparative Example 2 were subjected to thermogravimetric analysis (TGA) in an argon atmosphere from 30℃ to 800℃. The TGA chromatogram of Example 1 is shown below. Figure 8 As shown, the thermogravimetric analysis diagram of Comparative Example 2 is as follows: Figure 9 As shown.

[0117] Depend on Figure 8 and Figure 9 It is evident that, within the temperature range of 0℃ to 200℃, the evaporation of adsorbed water on the surface and in the pores of the catalyst in Example 1 (In₂O₃-Bi-500℃) accounted for 2.2% of the total loss, while the catalyst in Comparative Example 2 only suffered a loss of 1.2%. Furthermore, in the temperature range of 384℃ to 563℃, the loss of the catalyst in Example 1 was related to the oxidation and combustion of amorphous carbon. Moreover, due to the incorporation of In, the initial weight loss temperature of Example 1 significantly increased from 337℃ to 384℃ compared to the catalyst in Comparative Example 2. This demonstrates that the bismuth-doped metal oxide catalyst prepared in this invention exhibits significantly improved thermal stability due to the incorporation of In and the formation of In₂O₃ nanocrystals embedded on the surface of elemental Bi, thus possessing the advantage of good thermal stability.

[0118] Electrochemical CO2 Reduction Performance Test

[0119] The bismuth-doped metal oxide catalyst (In2O3-Bi-500℃) prepared in Example 1 and the Bi catalyst (Bi) prepared in Comparative Example 2 were respectively applied to the cathode of the electrocatalytic CO2 reduction to formic acid device according to Example 8, and the electrochemical CO2 reduction performance was tested.

[0120] The cathode is prepared as follows: 1 mL of isopropanol, 1 mL of ultrapure water, and 10 µL of Nafion are mixed to form a dispersion. Then, 10 mg of catalyst powder is added to the dispersion, and after sonication for 30 min, it is dropped onto a 1 x 1 cm plate. -2 The cathode is obtained by placing it on carbon paper and then drying it.

[0121] The system for testing the electrochemical reduction performance of CO2 is as follows: an H-type electrolytic cell (electrolyte is KHCO3), a fluid electrolytic cell (electrolyte is KOH) and a three-electrode system are used. The catalysts of Example 1 and Comparative Example 2 are used as working electrodes (cathodes), platinum sheets are used as counter electrodes, and Ag / AgCl electrodes are used as reference electrodes.

[0122] The formic acid Faradaic efficiency performance of the catalyst was obtained using chronocurrents (It) at different potentials, as shown in the figure. Figure 10 As stated above. Figure 10 In the text, In2O3-Bi represents Example 1, and Bi represents Comparative Example 2.

[0123] Depend on Figure 10 As can be seen, the bismuth oxide-doped catalyst (In₂O₃-Bi-500℃) prepared in Example 1 exhibits a maximum formic acid selectivity of 96.5%, while the Bi catalyst (Bi) prepared in Comparative Example 2 shows a maximum formic acid selectivity of 87%. Furthermore, the potential window of the Bi catalyst (Bi) in Comparative Example 2 is 600 mV, while the potential window of the bismuth oxide-doped catalyst (In₂O₃-Bi-500℃) in Example 1 is 800 mV. Therefore, the bismuth oxide-doped catalyst in Example 1 demonstrates significantly superior selectivity and potential window compared to the undoped Bi catalyst (Bi) in Comparative Example 2. This indicates that doping with In₂O₃ oxide can effectively regulate the electron density, active sites, and reaction microenvironment of the Bi catalyst, significantly improving its electrocatalytic CO₂ reduction performance.

[0124] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a bismuth-doped metal oxide catalyst, characterized in that, Includes the following steps: S1. Preparation of precursor solution: Dissolve bismuth salt, indium salt and organic ligand terephthalic acid in an organic solvent to prepare precursor solution; S2. Synthesis of InBi-MOF precursor: The precursor solution was placed in a reaction vessel and heated for reaction, then cooled, washed and dried to obtain the InBi-MOF precursor; S3. Calcination: The InBi-MOF precursor is calcined under an inert atmosphere to obtain the metal oxide-doped bismuth catalyst.

2. The method for preparing a bismuth-doped metal oxide catalyst as described in claim 1, characterized in that, In step S1, the molar ratio of the bismuth salt to the indium salt is (7~9):(3~1); and / or The total metal content of the bismuth salt and indium salt and the molar ratio of the organic ligand are 1:(2~4).

3. The method for preparing a bismuth-doped metal oxide catalyst as described in claim 1, characterized in that, In step S1, the bismuth salt is bismuth nitrate pentahydrate, and the indium salt is indium nitrate tetrahydrate; and / or The organic solvent is N,N-dimethylformamide; and / or The precursor solution is prepared by stirring at a speed of 300 r / min to 500 r / min for a duration of 10 min to 40 min.

4. The method for preparing a bismuth-doped metal oxide catalyst as described in claim 1, characterized in that, In step S2, the temperature of the heating reaction is 105℃~145℃, and the heating reaction time is 6h~24h.

5. The method for preparing a bismuth-doped metal oxide catalyst as described in claim 1, characterized in that, In step S2, the washing process involves alternating between methanol and water 2-3 times; and / or The drying process involves placing the product in an oven at 55℃~65℃ for 20h~24h.

6. The method for preparing a bismuth-doped metal oxide catalyst as described in claim 1, characterized in that, In step S3, the calcination temperature is 500℃~700℃, and the calcination time is 1.0h~3.5h; and / or The inert atmosphere is argon.

7. A bismuth-doped metal oxide catalyst, characterized in that, It is prepared by the method for preparing a metal oxide-doped bismuth catalyst as described in claims 1 to 6.

8. A bismuth-doped metal oxide catalyst as described in claim 7, characterized in that, It is composed of elemental Bi and In2O3 nanocrystals, wherein the In2O3 nanocrystals are embedded on the surface of elemental Bi. and / or The bismuth-doped metal oxide catalyst is a nanosphere, and / or the nanosphere has a particle size of 0.2 µm to 0.5 µm.

9. The application of a bismuth-doped metal oxide catalyst, characterized in that, The application of a bismuth-doped metal oxide catalyst prepared by the method of preparation of a bismuth-doped metal oxide catalyst according to claim 7 or 8 or any one of claims 1 to 6 in the electrocatalytic reduction of CO2 to formic acid.

10. The application of the bismuth-doped metal oxide catalyst as described in claim 9, characterized in that, The bismuth-doped metal oxide catalyst is used as the cathode in an electrocatalytic CO2 reduction formic acid production apparatus; and / or The cathode uses carbon paper as the substrate material and Nafion as the binder to support and fix the metal oxide-doped bismuth catalyst on the surface of the carbon paper; and / or The loading of the metal oxide-doped bismuth catalyst is 0.5 mg cm⁻¹. -2 ~1.5mg cm -2 .

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