A copper-doped bismuth-based material, a preparation method and application thereof

Abstract

The application discloses a copper-doped bismuth-based material and a preparation method and application thereof. The method comprises the following steps: preparing a nanosheet-shaped copper-doped bismuth-based material through an electrochemical reduction method from a copper-doped bismuth-based organic layer. The copper-doped bismuth-based organic layer is prepared through a hydrothermal method. The copper-doped bismuth-based material is used as an electrocatalyst in the reduction of CO2 in an acidic system. The copper-doped bismuth-based material solves the problem of how to increase the electron-rich bismuth active site, and realizes the good efficiency of electrocatalytic CO2 reduction for formic acid in an acidic electrolyte.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a copper-doped bismuth-based material, its preparation method, and its application. Background Technology

[0002] Electrocatalytic CO2 reduction driven by renewable electricity is an effective decarbonization strategy for converting CO2 into high-value chemicals and fuels. CO2 reduction in alkaline or neutral electrolytes provides a strongly alkaline microenvironment at the cathode interface, effectively suppressing the competitive hydrogen evolution reaction. However, CO2 molecules readily react with hydroxides to form carbonates, which can cross the anion exchange membrane to reach the anode, thus consuming CO2 feedstock and reducing carbon utilization efficiency. Furthermore, carbonates can clog the gaseous pathways for CO2 transport, posing a significant threat to the stability of the CO2 reduction system.

[0003] CO2 reduction in acidic electrolytes can address the aforementioned problems to some extent. The high proton concentration and the use of cation exchange membranes in acidic electrolytes can prevent carbonate formation and cross-conversion of liquid-phase products to the anode. Formic acid has proven to be the most technically and economically viable liquid-phase product in CO2 reduction; in acidic electrolytes, CO2 reduction directly produces formic acid instead of formate, making it easy to extract and purify. Bismuth, due to its environmental friendliness, abundant reserves, and high selectivity in reducing CO2 to formic acid, is a typical metal for CO2 reduction. For acidic CO2 reduction using bismuth-based catalysts, Li et al. prepared electron-rich bismuth nanosheets at 100 mA·cm⁻¹. -2 A formic acid Faradaic efficiency greater than 90% was achieved. Chen et al. obtained indium-doped Bi / BiO4 through in-situ electroreduction. x Nanosheets, at 200 mA / cm -2 The maximum formic acid Faradaic efficiency is 96% at current densities exceeding 300 mA / cm². -2 In acidic electrolytes, the competitive hydrogen evolution reaction is kinetically more favorable, significantly limiting CO2 reduction. Therefore, at industrial currents, promoting the reduction of CO2 to formic acid using bismuth-based catalysts in acidic systems is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide a copper-doped bismuth-based material, its preparation method and application. This invention obtains a copper-doped bismuth-based electrocatalyst by in-situ electrochemical reduction of copper-doped bismuth-based organic layers with different proportions.

[0005] In one aspect of the present invention, a method for preparing copper-doped bismuth-based materials is provided. According to an embodiment of the present invention, the method includes the following steps: preparing nanosheet-like copper-doped bismuth-based materials by electrochemical reduction of a copper-doped bismuth-based organic layer.

[0006] In addition, the method for preparing a copper-doped bismuth-based material according to the above embodiments of the present invention may also have the following additional technical features:

[0007] In some embodiments of the present invention, the copper-doped bismuth-based organic layer is prepared by mixing a bismuth source precursor, a copper source precursor, and a small molecule organic compound, and then obtaining the layer by a hydrothermal method.

[0008] In some embodiments of the present invention, the bismuth source precursor is one or two of bismuth nitrate and bismuth chloride, the copper source precursor is one or two of copper nitrate and copper chloride, the small molecule organic compound is imidazole and piperazine, and the molar ratio of the bismuth source precursor to the copper source precursor is (5:1) to (100:1).

[0009] In some embodiments of the present invention, the temperature of the hydrothermal method is 120–180°C and the time is 12–72 h.

[0010] In some embodiments of the present invention, the copper-doped bismuth-based organic layer is composed of a sheet structure.

[0011] In some embodiments of the present invention, the electrochemical reduction method includes the following steps: dispersing a copper-doped bismuth-based organic layer and a perfluorosulfonic acid-polytetrafluoroethylene copolymer solution in ethanol, ultrasonicating to obtain an ethanol dispersion, uniformly spraying the ethanol dispersion onto hydrophobic carbon paper to form a working electrode, and then using Ag / AgCl saturated with KCl as a reference electrode and a platinum electrode as a counter electrode to perform in-situ electrochemical reduction.

[0012] In some embodiments of the present invention, the amount of the copper-doped bismuth-based organic layer and the perfluorosulfonic acid-polytetrafluoroethylene copolymer solution is 0.1-2 mg / μL, the amount of the copper-doped bismuth-based organic layer relative to ethanol is 1-50 mg / mL, the frequency of the ultrasound is 10-50 kHz, and the duration of the ultrasound is 20-60 minutes.

[0013] In some embodiments of the present invention, the electrochemical reduction is performed by cyclic voltammetry to activate the working electrode in a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode, with a scan rate of 10-100 mV / s; and cyclically in an acidic electrolyte for 50-200 times.

[0014] In another aspect of the present invention, a copper-doped bismuth-based material prepared according to the aforementioned method is provided. According to an embodiment of the present invention, the copper-doped bismuth-based material has a nanosheet morphology with a length and width of 1–10 μm and a thickness of 5–30 nm.

[0015] In another aspect of the invention, an application of the copper-doped bismuth-based material is proposed. According to an embodiment of the invention, the copper-doped bismuth-based material serves as an electrocatalyst in the reduction of CO2 in an acidic system.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) The present invention uses a hydrothermal method to synthesize copper-doped bismuth-based organic layer precatalysts. The synthesis method is simple and the reaction conditions are mild. The obtained materials are easy to use and are conducive to their application in industrial production.

[0018] (2) The copper-doped bismuth-based electrocatalyst of the present invention exhibits excellent CO2 reduction performance in acidic electrolytes, at 400 mA / cm². 2 At industrial-grade current densities, formic acid achieves a Faradaic efficiency of 87.1%. At 300 mA / cm², 2 At a CO2 gas flow rate of 3 sccm, the single-pass conversion efficiency reaches a maximum of 62.1%.

[0019] (3) The present invention first prepares a copper-doped bismuth-based organic layer precatalyst, wherein there is electron transfer between bismuth and copper, and bismuth acts as an electron acceptor, thereby increasing the electron-rich bismuth active sites. By in-situ electroreduction of the organic layer, a nanosheet-like copper-doped bismuth-based catalyst is obtained, which further increases the exposure of active sites. Attached Figure Description

[0020] Figure 1 Bi prepared in Example 1 of this invention 20 XRD patterns of Cu-NS catalysts;

[0021] Figure 2 Bi prepared in Example 1 of this invention 20 SEM images of Cu-NS catalyst at low (left) and high (right) rates;

[0022] Figure 3 Bi prepared in Example 1 of this invention 20 TEM images of Cu-NS catalyst at low magnification;

[0023] Figure 4 Bi prepared in Example 1 of this invention 20 TEM images of Cu-NS catalyst at high magnification;

[0024] Figure 5 Bi prepared in Example 1 of this invention 20 HAADF-STEM images of Cu-NS catalysts, and elemental mapping images of Bi, Cu and O;

[0025] Figure 6The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Examples 1-2 are examples of this invention. x Bi 4fXPS spectrum of Cu organic layer;

[0026] Figure 7 The Bi prepared in Examples 1-3 of this invention x Cu 2p XPS pattern of the Cu organic layer;

[0027] Figure 8 The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Examples 1-2 are examples of this invention. x LSV curve of Cu-NS catalyst;

[0028] Figure 9 The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Example 1 are examples of the Bi-NS prepared in this invention. x Formic acid Faraday efficiency plot of Cu-NS catalyst under different applied current densities;

[0029] Figure 10 The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Example 1 are examples of the Bi-NS prepared in this invention. 20 Energy efficiency and voltage of formic acid cathode of Cu-NS catalyst under different applied current densities;

[0030] Figure 11 Bi prepared in Example 1 of this invention 20 Stability test results of Cu-NS catalyst;

[0031] Figure 12 Bi prepared in Example 1 of this invention 20 Cu-NS catalyst at 300 mA / cm 2 Single-pass conversion efficiency at different CO2 flow rates;

[0032] Figure 13 The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Examples 1-2 are examples of this invention. x Electrochemical impedance spectroscopy of Cu-NS electrocatalyst;

[0033] Figure 14 The Bi-NS prepared in the comparative example of this invention and the Bi prepared in Examples 1-2 are examples of this invention. x Double-layer capacitance diagram of Cu-NS electrocatalyst. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Bi copper-doped bismuth-based materials with a bismuth-copper molar ratio of 20:1 20 The preparation method of Cu-NS includes the following steps:

[0037] (1) Add 2 mmol bismuth nitrate pentahydrate, 0.1 mmol copper nitrate trihydrate, 4 mmol 4,5 imidazole dicarboxylic acid and 2 mmol piperazine to 20 mL of deionized water and stir vigorously for 60 minutes.

[0038] (2) The mixed solution was subjected to hydrothermal reaction at 170℃ for 24 hours. The precipitate was collected, washed several times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain Bi. 20 Cu organic layer.

[0039] (3) Prepared Bi 20 A Cu organic layer of 10 mg and 40 μL of Nafion solution (5 wt%) were dispersed in 960 μL of ethanol. After sonication for 60 minutes, the mixture was uniformly sprayed onto hydrophobic carbon paper to serve as the working electrode. The catalyst loading was controlled at 1.0 mg / cm³. 2 Using the above electrodes as working electrodes (1×1cm) 2 An Ag / AgCl electrode (saturated with KCl) is used as the reference electrode, and a platinum mesh electrode (0.7 × 1.5 cm) is used as the counter electrode. 2 The working electrode was activated by cyclic voltammetry within a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode at a scan rate of 50 mV / s. The catalyst was cycled 100 times in an acidic electrolyte (a mixture of 1 M Cs₂SO₄ and dilute H₂SO₄, pH adjusted to 2) to obtain a nanosheet-like copper-doped bismuth-based catalyst (denoted as Bi). 20 Cu-NS).

[0040] The prepared copper-doped bismuth-based material has a nanosheet morphology with a length and width of 1μm-10μm and a thickness of 5nm-30nm.

[0041] Prepared Bi 20 XRD tests were performed on the Cu-NS electrocatalyst, such as... Figure 1As shown, a sharp peak corresponding to metallic Bi is present at 27°, indicating that the Bi₂O₃ species tends to be reduced after electroreduction. Some smaller peaks attributed to Bi₂O₃ may be due to adsorbed oxygen on the material surface.

[0042] like Figure 2 As shown, SEM images at different magnifications reveal Bi 20 The nanosheet structure of Cu-NS, with its micron-scale wrinkles, increases its surface area. Due to its curved geometry, Bi... 20 Significant tensile strain exists in Cu-NS, which can modulate the electronic structure of Bi atoms, thereby improving the adsorption capacity of key reaction intermediates. For example... Figure 3 As shown, the TEM images further reveal Bi 20 The ultrathin stacked nanosheet structure of Cu-NS results in an abundance of active sites. For example... Figure 4 As shown, the high-resolution TEM images reveal lattice spacings of 0.35 and 0.34 nm, corresponding to the (012) crystal plane of Bi and the (111) crystal plane of Bi₂O₃, respectively. Figure 5 As shown, the elemental composition and distribution were investigated using HAADF-STEM-EDS elemental mapping. Bi and Cu elements were uniformly distributed, with no signs of phase separation. The presence of O is attributed to the easy oxidation of Bi upon exposure to air.

[0043] Example 2

[0044] Bi copper-doped bismuth-based materials with a bismuth-copper molar ratio of 50:1 50 The preparation method of Cu-NS includes the following steps:

[0045] (1) Add 2 mmol bismuth nitrate pentahydrate, 0.04 mmol copper nitrate trihydrate, 4 mmol 4,5 imidazole dicarboxylic acid and 2 mmol piperazine to 20 mL of deionized water and stir vigorously for 60 minutes.

[0046] (2) The mixed solution was subjected to hydrothermal reaction at 170℃ for 24 hours. The precipitate was collected, washed several times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain Bi. 50 Cu organic layer.

[0047] (3) Prepared Bi 50 A Cu organic layer of 10 mg and 40 μL of Nafion solution (5 wt%) were dispersed in 960 μL of ethanol. After sonication for 60 minutes, the mixture was uniformly sprayed onto hydrophobic carbon paper to serve as the working electrode. The catalyst loading was controlled at 1.0 mg / cm³. 2 Using the above electrodes as working electrodes (1×1cm) 2An Ag / AgCl electrode (saturated with KCl) is used as the reference electrode, and a platinum mesh electrode (0.7 × 1.5 cm) is used as the counter electrode. 2 The working electrode was activated by cyclic voltammetry within a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode at a scan rate of 50 mV / s. The catalyst was cycled 100 times in an acidic electrolyte (a mixture of 1 M Cs₂SO₄ and dilute H₂SO₄, pH adjusted to 2) to obtain a nanosheet-like copper-doped bismuth-based catalyst (denoted as Bi). 50 Cu-NS).

[0048] Bi and Bi prepared in Examples 1-2 x XPS characterization of the Cu organic layer:

[0049] Bi x XPS analysis was performed on the Cu and Bi organic layers to investigate the chemical states of elements in the precatalyst, with the binding energy of the C1s peak set at 284.8 eV as a reference. Figure 6 As shown, in the Bi 4f spectrum, the peaks at 164.4 and 159.0 eV belong to Bi(III) Bi 4f, respectively. 7 / 2 and Bi 4f 5 / 2 This indicates the presence of the Bi2O3 phase on the material surface.

[0050] Example 3

[0051] Bi copper-doped bismuth-based materials with a bismuth-copper molar ratio of 99:1 99 The preparation method of Cu-NS includes the following steps:

[0052] (1) Add 2 mmol bismuth nitrate pentahydrate, 0.02 mmol copper nitrate trihydrate, 4 mmol 4,5 imidazole dicarboxylic acid and 2 mmol piperazine to 20 mL of deionized water and stir vigorously for 60 minutes.

[0053] (2) The mixed solution was subjected to hydrothermal reaction at 170℃ for 24 hours. The precipitate was collected, washed several times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain Bi. 99 Cu organic layer.

[0054] (3) Prepared Bi 99 A Cu organic layer of 10 mg and 40 μL of Nafion solution (5 wt%) were dispersed in 960 μL of ethanol. After sonication for 60 minutes, the mixture was uniformly sprayed onto hydrophobic carbon paper to serve as the working electrode. The catalyst loading was controlled at 1.0 mg / cm³. 2 Using the above-mentioned electrode as the working electrode (1×1cm) 2 An Ag / AgCl electrode (saturated with KCl) is used as the reference electrode, and a platinum mesh electrode (0.7 × 1.5 cm) is used as the counter electrode.2 The working electrode was activated by cyclic voltammetry within a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode at a scan rate of 50 mV / s. The catalyst was cycled 100 times in an acidic electrolyte (a mixture of 1 M Cs₂SO₄ and dilute H₂SO₄, pH adjusted to 2) to obtain a nanosheet-like copper-doped bismuth-based catalyst (denoted as Bi). 99 Cu-NS).

[0055] like Figure 7 As shown, Bi 50 Cu and Bi 20 The Cu 2p spectrum of the Cu organic layer shows the corresponding Cu 2p... 1 / 2 and Cu 2p 3 / 2 The peak. With Bi 99 Comparison of Cu 2p spectra of Cu organic layers; due to trace Cu doping, Bi 99 The Cu organic layer only shows a Cu 2p affiliation. 3 / 2 Characteristic peaks. Combined with Figure 6 With increasing Cu content, the Bi 4f spectrum shows a negative shift, while the Cu 2p spectrum shows a positive shift. Compared to undoped Bi organic layers, Bi... 50 Cu and Bi 20 The Bi₄f ions in the Cu organic layer shifted to the lower binding energy region by 0.25 and 0.45 eV. (This is in contrast to Bi₄f.) 99 Compared to the organic layer of Cu, Bi 50 Cu and Bi 20 The Cu 2p region of the Cu organic layer shifted to the high binding energy region by 0.09 and 0.19 eV. These results indicate electron transfer between Bi and Cu, with Bi acting as an electron acceptor. Electron interactions are expected to modulate Bi... x The interfacial electronic structure of Cu organic layer-derived catalysts was optimized to produce formic acid from Bi active sites.

[0056] Comparative Example

[0057] A method for preparing copper-free bismuth-based material Bi-NS includes the following steps:

[0058] (1) Add 2 mmol of bismuth nitrate pentahydrate, 4 mmol of 4,5-imidazolium dicarboxylic acid and 2 mmol of piperazine to 20 mL of deionized water and stir vigorously for 60 minutes.

[0059] (2) The mixed solution was hydrothermally reacted at 170°C for 24 hours. The precipitate was collected, washed with deionized water and anhydrous ethanol, centrifuged several times, and dried in a vacuum drying oven at 60°C for 24 hours to obtain the Bi organic layer.

[0060] (3) 10 mg of the prepared Bi organic layer powder and 40 μL of Nafion solution (5 wt%) were dispersed in 960 μL of ethanol. After sonication for 60 minutes, the mixture was uniformly sprayed onto hydrophobic carbon paper as the working electrode. The catalyst loading was controlled at 1.0 mg / cm³. 2 Using the above-mentioned electrode as the working electrode (1×1cm) 2 An Ag / AgCl electrode (saturated with KCl) is used as the reference electrode, and a platinum mesh electrode (0.7 × 1.5 cm) is used as the counter electrode. 2 The working electrode was activated by cyclic voltammetry within a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode at a scan rate of 50 mV / s. The catalyst was then cycled 100 times in an acidic electrolyte (1 M Cs2SO4 mixed with dilute H2SO4, pH adjusted to 2) to obtain a nanosheet-like copper-doped bismuth-based catalyst (denoted as Bi-NS).

[0061] Application examples

[0062] Bi-NS prepared in the comparative example and Bi prepared in Examples 1-3 x Cu-NS electrocatalyst for CO2 reduction in acidic systems:

[0063] CO2 reduction was carried out in a flow electrolyzer connected to an electrochemical workstation (CHI 760e). Bi loading... x Cu-NS electrocatalyst (1.0 mg / cm³) 2 Gas diffusion electrode (1×1cm) 2 Platinum mesh (0.7×1.5cm) 2 Ag / AgCl electrodes saturated with KCl were used as the cathode, anode, and reference electrodes, respectively. The cathode electrolyte and anolyte chambers were separated by a cation exchange membrane (CEM). 117) Separate. During the measurement, CO2 gas (20 sccm) is supplied to the cathode gas diffusion layer. The anolyte and catholyte are 0.05 M H2SO4 and 1 M Cs2SO4 (pH adjusted to 2 with H2SO4). The electrolyte flow rate is controlled at 15 mL / min. -1 .

[0064] Linear sweep voltammetry (LSV) curves are as follows: Figure 8 As shown, with 50mV s -1 The LSV curve was measured at the scan rate. 20 Cu-NS exhibits a higher current density than the comparative example at -2.55V. RHE Up to 400 mAcm -2 .

[0065] Formic acid Faraday efficiency is as follows Figure 9As shown, in the range of 50 to 400 mA / cm 2 Over a wide current density range, Bi 20 The high formic acid Faradaic efficiency obtained by Cu-NS demonstrates its excellent performance. (At 400 mA / cm²) 2 Under high current density, Bi 20 The formic acid faradaic efficiency of Cu-NS is 87.1%. (At 150 mA / cm²) 2 At this point, the maximum Faraday efficiency reaches 91.3%. For the Bi-NS catalyst, at 150 mA / cm², the efficiency is [missing value]. 2 At that time, the maximum formic acid Faraday efficiency reached 92.5%. However, from 200 mA / cm 2 Initially, the CO2 reduction performance of the Bi-NS electrocatalyst in acidic systems decreased significantly, with the formic acid Faradaic efficiency reaching 400 mA / cm². 2 It decayed to 32.6% over time. 20 Cu-NS achieves high formic acid Faradaic efficiency (~90%) across all applied current densities, while the comparative example achieves efficiency between 200 and 400 mA / cm². -2 It cannot maintain high performance in the high current density range.

[0066] Cathode energy efficiency and potential, such as Figure 10 As shown, Bi-NS and Bi 20 The cathode energy efficiency of Cu-NS electrocatalysts ranges from 100 to 300 mA / cm². 2 Within the current density range, Bi 20 The cathode energy efficiency of Cu-NS is higher than that of Bi-NS. At 100 mA / cm² 2 At that time, the cathode energy efficiency was 54.1%. Furthermore, Bi... 20 The potential of Cu-NS is lower than that of Bi-NS at all applied current densities.

[0067] Besides activity and selectivity, stability is also a key parameter for evaluating the application prospects of electrocatalysts. For example... Figure 11 As shown, in 2M Cs at pH 2 + In the electrolyte, at 200 mA / cm 2 constant current density for Bi 20 Long-term CO2 reduction tests were conducted on Cu-NS. The formic acid Faraday efficiency remained at approximately 90% for 40 hours without significant decay, indicating its excellent stability.

[0068] One-way conversion efficiency, such as Figure 12 As shown, at 300mA / cm 2 At a current density of 3 sccm, when the CO2 gas flow rate is 3 sccm, Bi 20The Cu-NS single-pass conversion efficiency reached as high as 62.1%, revealing the superiority of acidic electrolytes in CO2 utilization.

[0069] like Figure 13 As shown, electrochemical impedance spectroscopy was performed by applying a voltage of -0.9V to study charge transfer. 20 Cu-NS exhibits a smaller charge transfer resistance than the control group, reflecting its faster charge transfer kinetics. Figure 14 This reflects the electrochemical double-layer capacitance (C) of the catalyst. dl ), Bi 20 Cu-NS twice the C dl It is 3.69 mF / cm 2 It is higher than that of Bi-NS (2.21 mF / cm). 2 ) and Bi 50 Cu-NS (1.38 mF / cm). Bi 20 The larger electrochemical active surface area of ​​Cu-NS provides more catalytic active sites for CO2 reduction in acidic systems, resulting in excellent activity. The bimetallic synergistic effect is optimal when the molar ratio of bismuth to copper is 20:1. The resulting electron-rich bismuth-based nanosheets exhibit enhanced intrinsic activity and charge transfer behavior, demonstrating the best performance in the acidic CO2 reduction to formic acid.

[0070] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a copper-doped bismuth-based material, characterized in that, Includes the following steps: A copper-doped bismuth-based nanosheet material was prepared by electrochemical reduction of a copper-doped bismuth-based organic layer. The preparation method of the copper-doped bismuth-based organic layer is as follows: a bismuth source precursor, a copper source precursor and a small molecule organic compound are mixed and then prepared by a hydrothermal method. The bismuth source precursor is one or two of bismuth nitrate and bismuth chloride, the copper source precursor is one or two of copper nitrate and copper chloride, the small molecule organic compound is imidazole and piperazine, and the molar ratio of the bismuth source precursor to the copper source precursor is (5:1) to (100:1).

2. The method for preparing a copper-doped bismuth-based material according to claim 1, characterized in that: The hydrothermal method is performed at a temperature of 120~180℃ for a time of 12~72h.

3. The method for preparing a copper-doped bismuth-based material according to claim 1, characterized in that: The copper-doped bismuth-based organic layer is composed of a sheet structure.

4. The method for preparing a copper-doped bismuth-based material according to claim 1, characterized in that: The electrochemical reduction method includes the following steps: dispersing a copper-doped bismuth-based organic layer and a perfluorosulfonic acid-polytetrafluoroethylene copolymer solution in ethanol, ultrasonicating to obtain an ethanol dispersion, uniformly spraying the ethanol dispersion onto hydrophobic carbon paper to form a working electrode, and then using Ag / AgCl saturated with KCl as a reference electrode and a platinum electrode as a counter electrode to perform in-situ electrochemical reduction.

5. The method for preparing a copper-doped bismuth-based material according to claim 4, characterized in that: The amount of copper-doped bismuth-based organic layer and perfluorosulfonic acid-polytetrafluoroethylene copolymer solution used is 0.1~2 mg / μL, the amount of copper-doped bismuth-based organic layer relative to ethanol is 1~50 mg / mL, the frequency of ultrasound is 10~50 kHz, and the ultrasound time is 20~60 minutes.

6. The method for preparing a copper-doped bismuth-based material according to claim 4, characterized in that: The electrochemical reduction is achieved by activating the working electrode within a potential range of -1.0 to -1.8 V relative to the Ag / AgCl electrode using cyclic voltammetry, with a scan rate of 10-100 mV / s; and cycling 50-200 times in an acidic electrolyte.

7. A copper-doped bismuth-based material prepared by the method according to any one of claims 1-6, characterized in that: The copper-doped bismuth-based material has a nanosheet morphology with a length and width of 1~10 μm and a thickness of 5~30 nm.

8. An application of the copper-doped bismuth-based material according to claim 7, characterized in that: The copper-doped bismuth-based material serves as an electrocatalyst in the reduction of CO2 in an acidic system.

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