Preparation method of low coordination number bi catalyst and application thereof in electrocatalytic carbon dioxide reduction

Abstract

The application belongs to the technical field of catalyst synthesis and energy chemical industry, and particularly relates to a preparation method of a low-coordination-number Bi catalyst and application of the low-coordination-number Bi catalyst in electrocatalytic carbon dioxide reduction. The application takes bismuth sulfide as a precursor, performs secondary solvent thermal treatment on the precursor by using a sulfur-containing reagent to induce structural rearrangement of the precursor, and guides in-situ reconstruction of the precursor under subsequent electrochemical conditions, so as to form a bismuth-based active structure with a low-coordination-number characteristic. Compared with the prior art, the application can effectively control the reconstruction rate and structural evolution path of the bismuth-based material, improve the catalytic activity, is suitable for electrocatalytic carbon dioxide reduction, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalyst synthesis and energy chemical technology, specifically relating to a method for preparing a low coordination number Bi catalyst and its application in electrocatalytic carbon dioxide reduction. Background Technology

[0002] With the advancement of the "dual carbon" goal, the resource conversion of CO2 has received widespread attention. Electrochemical carbon dioxide reduction (ECO2RR) can convert CO2 into formic acid under mild conditions, making it an important technological pathway for achieving renewable energy storage and carbon cycling. Among existing catalytic materials, bismuth-based materials have attracted significant attention due to their strong inhibition of hydrogen evolution reaction and high selectivity for formic acid products. The selectivity and activity of the formic acid pathway are largely influenced by the local coordination environment of the catalytic center. Existing research has shown that increasing the degree of local coordination unsaturation of the catalytic center can regulate the adsorption stability and conversion behavior of key intermediates in the CO2 reduction process, thereby making the reaction more inclined towards the formic acid formation pathway and suppressing competing reactions. Therefore, constructing low-coordination structural features is one of the important strategies for improving the performance of bismuth-based catalysts in the formic acid pathway.

[0003] Several effective strategies have been developed for constructing low-coordination structures, including solvothermal methods, liquid-phase exfoliation, high-temperature reducing atmosphere treatment (such as H2 reduction), chemical post-treatment, plasma etching, and ultraviolet irradiation. While these methods can introduce unsaturated structures in the non-operating state, they often share common limitations: high-temperature treatment is prone to morphological evolution (such as sintering or structural collapse); plasma / external field treatment mainly acts on the surface and is difficult to achieve a uniform distribution of low-coordination structures in the bulk phase; and ultraviolet irradiation has limited applicability due to its weak ability to break high-energy chemical bonds. More importantly, these low-coordination features are mostly obtained in the non-electrochemical operating state and may continue to evolve during electrochemical operation, making it difficult to directly correspond to the operating active structure of the actual reaction interface, and thus difficult to accurately match the structure-activity relationship between catalytic performance and the active site structure.

[0004] Therefore, it is necessary to develop new strategies for constructing low coordination number structures to improve the formation efficiency of low coordination number structural features and further enhance the reactivity of formic acid generation. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for inducing a low coordination number bismuth-based catalyst through secondary sulfidation. This method induces structural rearrangement of the bismuth sulfide precursor by subjecting it to a secondary solvothermal treatment involving a sulfur-containing reagent, which accelerates the subsequent electrochemical reduction process and forms an elemental Bi structure with a low Bi-Bi coordination number, thereby significantly improving its performance in CO2RR for the production of formic acid.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a low coordination number bismuth-based catalyst (SS-Bi), the method comprising the following steps: Synthesis of S1 and Bi2S3 precursors: Bismuth source and sulfur source were dissolved in ethylene glycol, and after solvothermal reaction, they were naturally cooled. The resulting product was washed and dried to obtain the S-Bi2S3 precursor with primary sulfidation. S2. Solvent thermal treatment of secondary sulfur-containing reagent (hereinafter referred to as "secondary sulfidation"): The above-mentioned S-Bi2S3 precursor was dispersed in ethanol and a supplementary sulfur source was added. After the resulting suspension was subjected to a solvothermal reaction, the precipitate was collected, and then washed and dried to obtain the secondary sulfidation modified material SS-Bi2S3. S3, Electrochemical Reconstruction: SS-Bi2S3 and a conductive support are dispersed in a mixed solvent containing a binder to form an ink, and the ink is coated on an electrode substrate to form a working electrode; then, electrochemical in-situ reconstruction is carried out in an electrolyte containing CO2 to obtain the target catalyst.

[0007] The proposed strategy of "secondary sulfidation pretreatment + electrochemical in-situ reconstruction" involves two steps: secondary sulfidation pretreatment pre-regulates the local coordination environment of the bismuth sulfide precursor before the reaction, providing a more suitable structural starting point for the subsequent reduction phase transition; electrochemical in-situ reconstruction directly generates a real active phase dominated by metallic Bi under operating conditions, thereby efficiently obtaining the target local coordination characteristics under conditions closer to the operating state. Through the synergy of these two steps, the formation efficiency of low-coordination structural features is improved, further enhancing the reactivity of formic acid formation.

[0008] Preferably, the temperature of the solvothermal reaction in S1 is 160-200 °C and the time is 12-36 hours.

[0009] Preferably, the temperature of the solvothermal reaction in S2 is 100-150 °C and the time is 12-36 hours.

[0010] Preferably, the electrochemical in-situ reconstruction described in S3 is carried out in an H-type electrolytic cell, with the electrolyte being a 0.1-1.0 M bicarbonate (KHCO3) solution, the potential range being -0.8V to -1.2V relative to the reversible hydrogen electrode (-0.8V to -1.2V vs. RHE), and the time being 2-8 hours.

[0011] Preferably, the bismuth source is selected from BiCl3, the sulfur source is selected from thioacetamide, and the supplementary sulfur source is selected from thiourea.

[0012] Preferably, in S1, the molar ratio of the bismuth source to the sulfur source is 1-3:2-4.

[0013] Preferably, in S2, the mass ratio of the S-Bi2S3 precursor to thiourea is 1-2:2-5.

[0014] Preferably, in S3, the mass ratio of SS-Bi2S3 to the conductive carrier is 3-5:1-2.

[0015] Preferably, the binder-containing mixed solvent is selected from isopropanol / water / Nafion solution, the conductive carrier is selected from carbon black, and the electrode substrate is selected from carbon paper.

[0016] The second aspect of the present invention also provides a low-coordinate bismuth-based catalyst (SS-Bi, bismuth elemental catalyst) prepared by the preparation method described in the first aspect. In this catalyst, the secondary sulfidation treatment in step S2 reduces the Bi-S coordination number in SS-Bi2S3; after electrochemical in-situ reconstruction in step S3, the Bi-Bi coordination number in the resulting bismuth-based electrocatalyst SS-Bi is lower than that of the control catalyst S-Bi obtained without the treatment in step S2.

[0017] The third aspect of the present invention also provides the application of the low-coordinate bismuth-based catalyst described in the second aspect in the electrocatalytic carbon dioxide reduction reaction (CO2RR), particularly suitable for the highly selective electroreduction of CO2 to formic acid.

[0018] The fourth aspect of the present invention also provides a method for electrocatalytic carbon dioxide reduction reaction, specifically: using the low-coordinate bismuth-based catalyst described in the second aspect as the working electrode, an electrochemical reduction reaction is carried out in an electrolyte containing CO2, and the main product obtained after the reaction is formic acid.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a method for preparing a low-coordination Bi catalyst. The method uses bismuth sulfide as a precursor, and through secondary sulfidation treatment, adjusts its local bismuth coordination environment and induces precursor structural rearrangement, accelerating the subsequent electrochemical reduction process and forming a bismuth-based active structure with low-coordination characteristics. Compared with existing bismuth-based sulfides, this invention can effectively control the reconstruction rate and structural evolution path of bismuth-based materials, improving catalytic activity and reproducibility. It is suitable for electrocatalytic carbon dioxide reduction reactions and has good application prospects. Specifically, this invention has the following advantages: (1) Methodological innovation: The "secondary sulfurization treatment" strategy is proposed, which transforms the passive reconstruction process into a designable and guideable active structural evolution path. By introducing low-coordination structures in the precursor stage, the subsequent electrochemical reduction process is accelerated, thereby inducing the formation of a final structure rich in low-coordination active sites.

[0020] (2) Excellent performance: The catalyst prepared by inducing low coordination through secondary sulfidation exhibits significantly improved formic acid Faradaic efficiency and higher current density in CO2RR. Compared with S-Bi2S3 without secondary sulfidation treatment, SS-Bi2S3 has more coordinated unsaturated Bi, which can accelerate the electrochemical reconstruction process and induce the formation of low coordination number Bi elemental. Compared with the control sample S-Bi without secondary sulfidation treatment, the catalyst SS-Bi of this invention exhibits better formic acid selectivity and activity in ECO2RR.

[0021] (3) Strong controllability: The coordination environment and reconstruction behavior of the catalyst can be controlled by secondary sulfidation, the process has good repeatability and has the potential for large-scale application.

[0022] (4) High universality: The “pre-regulation-guided reconstruction” design concept provides a reference technical paradigm for the controllable preparation of other chalcogenides (such as selenides and tellurides) or metal oxide precursor systems.

[0023] (5) Simple operation: The present invention regulates the coordination environment of the precursor through secondary sulfidation treatment, thereby inducing the formation of a high-performance active phase. The whole process does not require complex equipment, has low raw material cost, low energy consumption, and has great industrial application prospects. Attached Figure Description

[0024] Figure 1 A process flow diagram for preparing bismuth-based catalysts by inducing low coordination number structures through secondary sulfidation; Figure 2 The X-ray diffraction (XRD) patterns of S-Bi2S3 and SS-Bi2S3 prepared in Examples 1 and 2 are shown. Figure 3 The images are scanning electron microscope (SEM) images of S-Bi2S3 and SS-Bi2S3 prepared in Examples 1 and 2.

[0025] Figure 4 The EXAFS spectra of S-Bi2S3 and SS-Bi2S3 prepared in Example 1 and Example 2 are compared.

[0026] Figure 5 The in-situ Raman spectral evolution diagrams of S-Bi2S3 and SS-Bi2S3 prepared in Examples 1 and 2 under electrochemical reaction conditions are shown.

[0027] Figure 6 A comparison of the XRD patterns of the catalysts S-Bi and SS-Bi obtained in Example 1 and Example 2; Figure 7 The images show SEM images of the catalysts S-Bi and SS-Bi obtained in Examples 1 and 2, respectively.

[0028] Figure 8 The above is a comparison of the EXAFS spectra of the catalysts S-Bi and SS-Bi obtained in Example 1 and Example 2.

[0029] Figure 9 The graphs show a comparison of the Faradaic efficiency of CO2 reduction to formic acid by catalysts S-Bi and SS-Bi obtained in Examples 1 and 2 at -0.5 ~ -1.0V vs. RHE potential, and a comparison of the formic acid partial current density.

[0030] Figure 10 This is a comparison chart of the electrochemical active surface area (ECSA) of catalysts S-Bi and SS-Bi obtained in Examples 1 and 2. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0033] Example 1: like Figure 1 As shown, it includes the following steps: (1) Synthesis of Bi2S3 precursor: 2.0 mmol BiCl3 and 3.0 mmol thioacetamide were dissolved in 75 mL ethylene glycol and stirred for 2 hours. The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and reacted at 180 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting product was washed with anhydrous ethanol and deionized water and then dried at 60 °C to obtain a once-sulfurized S-Bi2S3 powder.

[0034] (2) Secondary sulfidation treatment: Weigh 0.2 g of the above S-Bi2S3 powder, disperse it in 70 mL of anhydrous ethanol, add 0.4 g of thiourea, sonicate for 1 hour, and then transfer the suspension to a high-pressure reactor and react at 120℃ for 24 hours. After the reaction, centrifuge to collect the precipitate, wash with deionized water and dry at 80℃ to obtain the secondary sulfidation modified material, denoted as SS-Bi2S3.

[0035] (3) Electrochemical reconstruction: 4 mg SS-Bi2S3 and 1 mg carbon black (Vulcan XC-72) were dispersed in 1 mL of a mixed solvent (720 µL isopropanol / 240 µL water / 40 µL Nafion solution) to prepare an ink, which was then coated onto carbon paper (loading 1.0 mg / cm). -2 The working electrode was 0.5 M KHCO3 saturated with CO2, the counter electrode was nickel foam, and the reference electrode was Ag / AgCl (saturated KCl). In an H-type electrolytic cell, 0.5 M KHCO3 saturated with CO2 was used as the electrolyte, and electrolysis was carried out at a constant potential of -1.0 V vs. RHE for 4 hours to complete in-situ reconstruction. The resulting catalyst was denoted as SS-Bi.

[0036] Example 2: Compared with Example 1, the secondary sulfidation treatment in step (2) is not performed. That is, S-Bi2S3 powder is prepared directly according to step (1) of Example 1, and then electrode preparation and electrochemical reconstruction are carried out according to step (3) of Example 1. The resulting catalyst is denoted as S-Bi.

[0037] Experimental Example: Structural and Electrochemical Testing 1. Structural testing (1) X-ray diffraction pattern of precursor Figure 2 The XRD patterns of S-Bi2S3 and SS-Bi2S3 in the examples are shown. The diffraction peak positions of both are consistent with those of standard Bi2S3 (PDF#65-2431), proving that the secondary sulfidation treatment did not change the main crystal phase. Among them, the diffraction peaks of SS-Bi2S3 showed significant intensity changes and slight broadening, indicating that there are differences in the crystallographic structure between the two.

[0038] (2) Scanning electron microscopy test of precursor Figure 3 SEM images show that S-Bi2S3 ( Figure 3 a) It exhibits a relatively large rod-like structure, SS-Bi2S3 ( Figure 3 b) It exhibits a morphological characteristic of small overall particle size, consistent with the results of peak broadening in XRD.

[0039] (3) Precursor extended X-ray absorption fine structure test To investigate the differences in the local structure around Bi atoms in S-Bi₂S₃ and SS-Bi₂S₃, extended X-ray absorption fine structure (EXAFS) measurements were performed on both S-Bi₂S₃ and SS-Bi₂S₃. Figure 4Table 1 shows the EXAFS fitting results, which indicate that the S-Bi2S3 sample contains two Bi-S shells (Bi-S1 coordination number CN≈1.5, bond length R≈2.62; Bi-S2 coordination number CN≈1.0, bond length R≈2.5 Å), while the SS-Bi2S3 precursor also contains two Bi-S coordination shells (Bi-S1 coordination number CN≈1.2, bond length R≈2.65; Bi-S2 coordination number CN≈0.6, bond length R≈2.51 Å). Compared with S-Bi2S3, the average Bi-S coordination number in SS-Bi2S3 is further reduced. This result indicates that secondary sulfidation treatment induces the formation of coordinated unsaturated Bi sites in SS-Bi2S3, laying the structural foundation for faster reconstruction kinetics during subsequent electrochemical reconstruction.

[0040] Table 1: EXAFS fitting parameters of S-Bi2S3 and SS-Bi2S3 Note: This indicates that this value is fixed during the EXAFS fitting process.

[0041] (4) In-situ Raman test Figure 5 The electrochemical reconstruction process was monitored in real time using in-situ Raman spectroscopy. Initially, both SS-Bi2S3 and S-Bi2S3 were at approximately 250 cm⁻¹. -1 A characteristic peak appears at approximately 69 cm⁻¹, which can be attributed to Bi–S bond vibrations. Upon application of a reduction potential, this peak gradually weakens over time, while a peak at approximately 69 cm⁻¹ appears again. -1 and approximately 95 cm -1 Sharp and strong Bi–Bi characteristic peaks gradually appear, corresponding to the formation of the metallic Bi phase, indicating the transformation of the precursor from the sulfide phase to the metallic phase. Comparing the transformation times, the Bi–S peak of SS-Bi₂S₃ basically disappears within about 30 s, while the Bi–Bi peak gradually appears and intensifies; whereas S-Bi₂S₃ requires about 60 s to complete the same transformation, indicating that SS-Bi₂S₃ has a faster electrochemical reconstruction rate and is more likely to form the metallic Bi active phase. Combined with… Figure 5 According to the EXAFS results in Table 1, the average Bi–S coordination number in SS-Bi2S3 is lower than that in S-Bi2S3, and the local coordination environment is less complete. This structural feature makes it easier to trigger Bi–S bond breakage at the reduction potential, thereby accelerating the reconstruction kinetics.

[0042] (5) Reconstructed X-ray diffraction pattern Figure 6The XRD patterns of the catalysts (S-Bi and SS-Bi) obtained by electrochemical reconstruction of SS-Bi₂S₃ and S-Bi₂S₃ are shown. Both exhibit characteristic diffraction peaks of metallic bismuth (Bi, PDF#85-1329), indicating that both SS-Bi₂S₃ and S-Bi₂S₃ are transformed into bismuth-based active phases after electrochemical reconstruction. Compared with S-Bi, the diffraction peaks of SS-Bi are broader, indicating that there is a difference in the crystallographic structure between the two.

[0043] (6) Scanning electron microscopy test after reconstruction Figure 7 The SEM images visually demonstrate the significant differences in the microstructure of S-Bi and SS-Bi. S-Bi ( Figure 7 a) exhibits a large-sized lamellar structure. SS-Bi (which undergoes secondary vulcanization treatment) Figure 7 b) shows a significant reduction in overall particle size, which is consistent with the XRD pattern results. This morphological difference may affect the local structural characteristics.

[0044] (7) Reconstructed extended X-ray absorption fine structure test To investigate the differences in the local structure around Bi atoms in S-Bi and SS-Bi, extended X-ray absorption fine structure (EXAFS) measurements were performed on S-Bi and SS-Bi. Figure 8 Table 2 shows the EXAFS fitting results. It can be seen that the S-Bi sample contains both a Bi-S shell (coordination number CN≈0.2, bond length R≈2.60 Å) and two Bi-Bi shells (CN≈2.1 and 0.7, R≈3.06 Å and 3.54 Å), while the SS-Bi sample only shows Bi-Bi coordination (CN≈2.0 and 0.5, R≈3.07 Å and 3.53 Å), with no Bi-S coordination contribution. Compared to S-Bi, the average coordination number of Bi-Bi in SS-Bi is further reduced, indicating that the secondary sulfidation treatment promotes the formation of low-coordination active structures in the reduced bismuth. These results provide direct local structural evidence for understanding the role of secondary sulfidation treatment in enhancing material activity.

[0045] Table 2: Synchrotron Radiation Fitting Parameters for S-Bi and SS-Bi Continued from the previous table: Note: This indicates that this value is fixed during the EXAFS fitting process.

[0046] 2. Electrochemical testing.

[0047] All electrochemical tests were performed in a three-electrode system, with the working electrode being carbon paper coated with catalysts (such as SS-Bi or S-Bi) at a loading of 1.0 mg / cm³. -2 The counter electrode was nickel foam, and the reference electrode was Ag / AgCl (saturated KCl). Tests were conducted in a flow cell using 1 M CO2-saturated KOH as the electrolyte. Prior to testing, the working electrode was pretreated using cyclic voltammetry: within a potential window from -1.4 V to 0 V vs. RHE, the voltammetry was applied at 100 mV·s⁻¹. -1 The scan rate was continuously scanned for 20 cycles to stabilize the electrode response. For example... Figure 9 As shown, within the same reaction potential range, SS-Bi exhibits higher formic acid Faradaic efficiency and partial current density than S-Bi throughout the entire test interval, and remains stable over a wider potential window. These results indicate that structural modulation introduced through secondary sulfidation can effectively improve the selectivity and stability of the formic acid formation pathway in the carbon dioxide electroreduction reaction.

[0048] To further evaluate the effective active area and interfacial charge transfer characteristics of the two catalysts from an electrochemical perspective, this invention employs double-layer capacitance (C0). dl The electrochemically active surface area (ECSA) is characterized by its electrochemically active surface area (ECSA). The ECSA is measured through the double-layer capacitance (C0). dl Estimation: Select a non-Radaric interval of OCP ± 0.05 V near the open circuit potential (OCP), using 20–100 mV·s -1 CV scans were performed at different scan rates, and Cdl was obtained based on the linear fitting of the capacitor current and the scan rate, which was then used to characterize the relative magnitude of ECSA. For example... Figure 10 As shown, the C of SS-Bi dl It is 4.86 mF·cm -2 It is higher than the 4.02 mF·cm of S-Bi. -2 This indicates that SS-Bi has a larger electrochemically accessible surface area, thus providing more interfacial sites that can participate in the electrochemical process.

[0049] To evaluate the performance level and relative advantages of the catalyst of this invention under relevant conditions in a flow cell, in addition to comparing it with the control sample S-Bi, typical catalysts disclosed in the literature were further compared under the same type of index (formic acid Faradaic efficiency FE). 甲酸 With formic acid partial current density j 甲酸 A comparison was made at the following conditions. The SS-Bi of this invention achieved FE in 1 M KOH electrolyte at -1.0 V vs. RHE potential. 甲酸 = 97.5%, corresponding to j 甲酸 = 484.8 mA·cm -2S-Bi achieves FE under the same conditions 甲酸 =84.1%, corresponding to j 甲酸 = 108.3 mA·cm -2 ( Figure 9 The highly dispersed bismuth nanoparticle catalyst in prior art 1 in 1 MKOH FE 甲酸 It is 95.6%, j 甲酸 It is 102.6 mA·cm -2 (Jia, G., Wang, Y., Sun, M., et al. Sizeeffects of highly dispersed bismuth nanoparticles on electrocatalytic reduction of carbon dioxide to formic acid[J]. Journal of the American Chemical Society, 2023, 145(25): 14133-14142.); BiPO4-derived two-dimensional nanosheets in prior art 2 were used in 1 M KOH for FE 甲酸 It is 91.7%, j 甲酸 200 mA·cm -2 (Wang, Y., Li, Y., Liu, J., et al. BiPO4-derived 2D nanosheets for efficient electrocatalytic reduction of CO2 toliquid fuel[J]. Angewandte Chemie International Edition, 2021, 60(14): 7681-7685.); The ultrathin bismuth nanosheets in prior art 3 were used in FE in 1 M KOH. 甲酸 It is 92.2%, j 甲酸 It is 237.1 mA·cm -2(Han, N., Wang, Y., Yang, H., et al. Ultrathin bismuth nanosheets from insitu topotactic transformation for selective electrocatalytic CO2 reduction to form[J]. Nature Communications, 2018, 9: 1320.). Therefore, under the same electrolyte conditions, the SS-Bi of this invention maintains a high FE... 甲酸 At the same time, it can achieve higher j 甲酸 It demonstrates a strong ability to generate formic acid.

[0050] In summary, this invention achieves effective regulation of the local sulfur coordination environment of the bismuth sulfide precursor by introducing a secondary sulfidation treatment during its preparation. This increases the number of unsaturated coordinated Bi sites in the precursor, thereby accelerating the electrochemical reconstruction process and ultimately forming a metallic bismuth active structure with more unsaturated coordinated Bi atoms. This method provides an effective approach for preparing bismuth-based catalysts with low-coordination structure characteristics and shows promising application prospects in fields such as electrocatalytic carbon dioxide reduction.

[0051] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a low coordination number bismuth-based catalyst, characterized in that, Includes the following steps: Synthesis of S1 and Bi2S3 precursors: Bismuth source and sulfur source were dissolved in ethylene glycol, and after solvothermal reaction, they were naturally cooled. The resulting product was washed and dried to obtain the S-Bi2S3 precursor with primary sulfidation. S2. Solvent thermal treatment of secondary sulfur-containing reagent: The above-mentioned S-Bi2S3 precursor was dispersed in ethanol and a supplementary sulfur source was added. After the resulting suspension underwent a solvothermal reaction, the precipitate was collected, and then washed and dried to obtain the secondary sulfurized modified material SS-Bi2S3. S3, Electrochemical Reconstruction: SS-Bi2S3 and a conductive support are dispersed in a mixed solvent containing a binder to form an ink, and the ink is coated on an electrode substrate to form a working electrode; then, electrochemical in-situ reconstruction is carried out in an electrolyte containing CO2 to obtain the target catalyst.

2. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, The solvothermal reaction described in S1 is carried out at 160-200℃ for 12-36 hours.

3. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, The solvothermal reaction described in S2 is carried out at 100-150 °C for 12-36 hours.

4. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, The electrochemical in-situ reconstruction described in S3 is carried out in an H-type electrolytic cell, with the electrolyte being a 0.1-1.0 M bicarbonate solution, the potential range being -0.8 V to -1.2 V relative to the reversible hydrogen electrode, and the time being 2-8 hours.

5. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, The bismuth source is selected from BiCl3, the sulfur source is selected from thioacetamide, and the supplementary sulfur source is selected from thiourea.

6. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, In S1, the molar ratio of the bismuth source to the sulfur source is 1-3:2-4.

7. The method for preparing a low coordination number bismuth-based catalyst according to claim 1, characterized in that, In S2, the mass ratio of the S-Bi2S3 precursor to thiourea is 1-2:2-5.

8. A low coordination number bismuth-based catalyst prepared by the preparation method according to any one of claims 1-7.

9. The application of the low coordination number bismuth-based catalyst according to claim 8 in the electrocatalytic carbon dioxide reduction reaction.

10. A method for electrocatalytic carbon dioxide reduction reaction, characterized in that, Using the low coordination number bismuth-based catalyst of claim 8 as the working electrode, an electrochemical reduction reaction is carried out in an electrolyte containing CO2, and the main product obtained after the reaction is formic acid.

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