Bi-doped SnO catalyst and preparation method and application thereof, gas diffusion electrode and preparation method and application thereof

Abstract

The invention provides a Bi-doped SnO catalyst and a preparation method and application thereof, a gas diffusion electrode and a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The preparation method comprises the following steps: mixing divalent metal tin salt, a regulator and bismuth salt in water to obtain a mixed solution; and mixing the mixed solution with a sodium hydroxide solution, and reacting to obtain the Bi-doped SnO catalyst. The preparation method is simple, rapid, low in cost, green and free of organic solvent or high-temperature treatment, and the prepared catalyst is stable in structure and lasting in performance. The Faraday efficiency of a gas diffusion electrode prepared by adopting the Bi-doped SnO catalyst for synthesizing formic acid through electrocatalytic reduction of CO2 at-850 mA / cm < 2 > is as high as 98%, the gas diffusion electrode can stably run for more than 140 h under N2 purging in a solid electrolytic tank, and the concentration of formic acid continuously produced exceeds 5 mol / L.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a Bi-doped SnO catalyst, a preparation method and application thereof, and a gas diffusion electrode, a preparation method and application thereof. Background Art

[0002] In recent years, the massive consumption of fossil fuels has led to a significant increase in carbon dioxide (CO2) emissions, exacerbating a series of environmental issues such as global warming. The capture and resource conversion of CO2 is a key path to mitigating the greenhouse effect and building a circular economy.

[0003] The electrocatalytic CO2 reduction reaction (ECO2R) has attracted much attention due to its ability to directly convert CO2 into high-value-added chemicals (such as formic acid, CO, methanol, ethanol, acetic acid, and ethylene) under ambient temperature and pressure. Therefore, the development of efficient, stable, and economical electrocatalysts for the selective conversion of CO2 to low-carbon compounds has important research value and application prospects.

[0004] Currently, metals such as Bi, Sn, In and Pd and their oxide catalysts are considered to be representative systems for electrocatalytic CO2 reduction. In particular, Sn-based catalysts, due to their unique electronic structure, suitable intermediate adsorption performance, low cost and toxicity, show excellent formic acid selectivity and broad application prospects. However, existing Sn-based catalysts still face several key bottlenecks. On the one hand, at industrial-level current densities (>200mA / cm -2 ), their catalytic activity and selectivity generally decrease, and their stability is insufficient, seriously restricting their practical application. On the other hand, Sn oxides are prone to irreversible reconstitution into metallic Sn at negative potentials, resulting in the loss of active sites and rapid degradation of catalytic performance.

[0005] To improve the overall performance of Sn-based catalysts, existing technologies have attempted to introduce precious metal doping strategies (such as Pt and Ag). By manipulating the electronic structure to enhance the adsorption and desorption behavior of intermediates, this has achieved a certain degree of improvement in Faradaic efficiency (FE), with some systems maintaining FE exceeding 80% at moderate current densities. However, precious metal resources are scarce and expensive, making it difficult to meet the needs of large-scale industrial applications.

[0006] In addition, the particle size of the catalyst is also a key factor affecting its performance and processability. Currently, the particle size of some catalysts exceeds 50 μm, which not only leads to a decrease in the catalytic active surface area, but also increases the difficulty of the electrode coating process, affecting the density of the electrode and the mass transfer efficiency of the electrolyte interface. Therefore, the development of new catalyst systems with the following characteristics has become a key direction of current research: (1) based on abundant and environmentally friendly metal elements in the earth's crust; (2) with controllable structure to achieve small particle size and high specific surface area; (3) maintain high product selectivity and stability at industrial current density; (4) with a low-cost and easy-to-scale synthesis process path. Summary of the Invention

[0007] The purpose of the present invention is to provide a Bi-doped SnO catalyst and its preparation method and application, a gas diffusion electrode and its preparation method and application, so as to solve the problems of low selectivity and stability of target products in the electrocatalytic CO2 reduction reaction in the prior art.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing a Bi-doped SnO catalyst, comprising the following steps:

[0010] S1: mixing a divalent metal tin salt, a regulator, and a bismuth salt in water to obtain a mixed solution;

[0011] S2: mixing the mixed solution and the sodium hydroxide solution, and reacting them to obtain a Bi-doped SnO catalyst.

[0012] Preferably, in step S1, the divalent metal tin salt includes one or more of stannous nitrate, stannous chloride, stannous sulfate, stannous phosphate and stannous carbonate; the regulator includes one or more of sodium citrate, hexadecyltrimethylammonium bromide, sodium lauryl sulfonate, polyvinyl pyrrolidone and polyvinyl alcohol; and the bismuth salt includes one or more of bismuth chloride, bismuth nitrate, bismuth sulfate and bismuth phosphate.

[0013] Preferably, in the mixed solution, Sn 2+ The concentration of Bi is 0.1~1mol / L, the concentration of the regulator is 0.01~0.6mol / L, 3+ The concentration is 0.1~9mmol / L.

[0014] Preferably, in step S2, the volume ratio of the mixed solution to the sodium hydroxide solution is 20-50:10-30, wherein the concentration of the sodium hydroxide solution is 0.6-5 mol / L; the reaction temperature is 20-60° C., and the reaction time is 1-24 h.

[0015] The present invention also provides a Bi-doped SnO catalyst prepared by the above-mentioned preparation method of the Bi-doped SnO catalyst.

[0016] The present invention also provides an application of the Bi-doped SnO catalyst described above in the preparation of fine chemicals by electrocatalytic multi-enzyme catalytic coupling and in the preparation of amino acids, polyols, bio-based materials, and liquid fuels by electrocatalytic biocoupling.

[0017] The present invention also provides a gas diffusion electrode, comprising a gas diffusion electrode body and a Bi-doped SnO catalyst coated on the gas diffusion electrode body.

[0018] Preferably, the coating amount of the Bi-doped SnO catalyst is 1 to 10 mg / cm 2 .

[0019] The present invention also provides a method for preparing the gas diffusion electrode described above, comprising the following steps: dispersing a Bi-doped SnO catalyst and a binder in a solvent, drop-coating the obtained catalyst ink on the gas diffusion electrode body, and drying to obtain the gas diffusion electrode.

[0020] The present invention also provides a use of the above-mentioned gas diffusion electrode in CO2 electrocatalytic reduction.

[0021] Beneficial effects of the present invention:

[0022] Compared to currently reported Sn-based catalysts, the preparation method of the present invention is simple, rapid, low-cost, and environmentally friendly. It does not require organic solvents or high-temperature treatment, and the prepared catalyst has a stable structure and long-lasting performance. This overcomes the challenges of prior art catalysts, such as rapid activity decay, high cost, and uncontrollable morphology. The present method for preparing Bi-doped SnO catalysts is scalable, with yields exceeding 80% based on Sn, and has promising prospects for industrial application.

[0023] The Bi-doped SnO catalyst prepared by the present invention has a two-dimensional sheet structure with controllable size. The Bi element is doped in the SnO catalyst body in metallic and oxidized forms, which effectively regulates the electronic structure and surface active sites, and significantly improves the CO2 electroreduction performance and stability without relying on precious metals.

[0024] The gas diffusion electrode of the present invention is -850mA / cm 2 The Faradaic efficiency of electrocatalytic reduction of CO2 to formic acid is as high as 98%. It can operate stably for more than 140 hours under N2 purge in a solid-state electrolytic cell, and continuously produce formic acid at a concentration of more than 5 mol / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1XRD patterns of the SnO catalyst of Comparative Example 1 and the Bi-doped SnO catalysts with different doping ratios prepared in Examples 1 to 3;

[0026] Figure 2 The SEM images of the SnO catalyst of Comparative Example 1 and the Bi-doped SnO catalysts with different doping ratios prepared in Examples 1 to 3 are shown;

[0027] Figure 3 A comparison of the Faradaic efficiencies of electrocatalytic reduction of CO2 to formic acid at different current densities using the gas diffusion electrode of Application Example 1 in a flow battery;

[0028] Figure 4 This is a comparison chart of the Faradaic efficiency of formic acid under different voltage conditions using the gas diffusion electrode of Application Example 1 in a solid-state electrolytic cell;

[0029] Figure 5 For 13 C-labeled CO2 is used as raw material, and the formic acid obtained after the reaction in the solid electrolytic cell using the gas diffusion electrode of Application Example 1 is 13 CNMR spectrum;

[0030] Figure 6 This is a stability test chart of the gas diffusion electrode of Application Example 1 continuously operating in a solid-state electrolytic cell for more than 140 hours under nitrogen purge. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a Bi-doped SnO catalyst, comprising the following steps:

[0032] S1: mixing a divalent metal tin salt, a regulator, and a bismuth salt in water to obtain a mixed solution;

[0033] S2: mixing the mixed solution and the sodium hydroxide solution, and reacting them to obtain a Bi-doped SnO catalyst.

[0034] In the present invention, in step S1, the divalent metal tin salt includes one or more of stannous nitrate, stannous chloride, stannous sulfate, stannous phosphate and stannous carbonate; the regulator includes one or more of sodium citrate, hexadecyltrimethylammonium bromide, sodium lauryl sulfonate, polyvinyl pyrrolidone and polyvinyl alcohol; and the bismuth salt includes one or more of bismuth chloride, bismuth nitrate, bismuth sulfate and bismuth phosphate.

[0035] In the present invention, in the mixed solution, Sn 2+The concentration of is 0.1 to 1 mol / L, preferably 0.2 to 0.8 mol / L, more preferably 0.3 to 0.6 mol / L; the concentration of the regulator is 0.01 to 0.6 mol / L, preferably 0.05 to 0.4 mol / L, more preferably 0.1 to 0.3 mol / L; 3+ The concentration is 0.1 to 9 mmol / L, preferably 0.1 to 6 mmol / L, and more preferably 0.5 to 6 mmol / L.

[0036] In the present invention, the volume ratio of the mixed solution and the sodium hydroxide solution in step S2 is 20-50:10-30, preferably 25-55:15-25, and more preferably 30-50:20, wherein the concentration of the sodium hydroxide solution is 0.6-5 mol / L, preferably 1.0-4 mol / L, and more preferably 1.5-2.0 mol / L.

[0037] In the present invention, the reaction temperature in step S2 is 20-60°C, preferably 25-40°C, more preferably 25-30°C; the reaction time is 1-24h, preferably 2-15h, more preferably 3-10h.

[0038] The present invention also provides a Bi-doped SnO catalyst prepared by the above-mentioned preparation method of the Bi-doped SnO catalyst.

[0039] The present invention also provides an application of the Bi-doped SnO catalyst described above in the preparation of fine chemicals by electrocatalytic multi-enzyme catalytic coupling and in the preparation of amino acids, polyols, bio-based materials, and liquid fuels by electrocatalytic biocoupling.

[0040] The present invention also provides a gas diffusion electrode, comprising a gas diffusion electrode body and a Bi-doped SnO catalyst coated on the gas diffusion electrode body.

[0041] In the present invention, the coating amount of the Bi-doped SnO catalyst on the gas diffusion electrode body is 1-10 mg / cm 2 .

[0042] The present invention also provides a method for preparing the gas diffusion electrode described above, comprising the following steps: dispersing a Bi-doped SnO catalyst and a binder in a solvent, drop-coating the obtained catalyst ink on the gas diffusion electrode body, and drying to obtain the gas diffusion electrode.

[0043] In the present invention, the solvent is isopropyl alcohol; and the adhesive is Nafion adhesive or Sustainion XA-9 ionomer solution.

[0044] In the present invention, the mass volume ratio of the Bi-doped SnO catalyst to isopropyl alcohol is 8-12 mg:1-3 mL, preferably 9-11 mg:2 mL, and more preferably 10 mg:2 mL.

[0045] In the present invention, the volume ratio of the binder to the solvent is 80-120 μL:1-3 mL, preferably 90-110 μL:2 mL, and more preferably 100 μL:2 mL.

[0046] In the present invention, the gas diffusion electrode body is preferably carbon paper.

[0047] The present invention also provides a use of the above-mentioned gas diffusion electrode in CO2 electrocatalytic reduction.

[0048] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] 9mmolSnCl2 and 3.37mmolhexadecyltrimethylammonium bromide were added to 30mL of deionized water, ultrasonically dispersed for 20min, and then 0.0225mmolBi(NO3)3 was added and mixed to obtain a mixed solution. 2+ The concentration of is 0.3 mol / L, the concentration of cetyltrimethylammonium bromide is 0.11 mol / L, Bi 3+ The concentration of the mixture was 0.75 mmol / L; the mixed solution was slowly poured into 20 mL of a 1.5 mol / L NaOH aqueous solution, and the mixture was reacted at 25°C with magnetic stirring for 3 h. After the reaction, the mixture was centrifuged at 5000 rpm, and the precipitate was dried in a vacuum drying oven at 60°C for 24 h to obtain a Bi-doped SnO catalyst, which was recorded as Bi1-SnO.

[0051] Example 2

[0052] The difference from Example 1 is that the amount of Bi(NO3)3 added is 0.045mmol, and the amount of Bi in the mixed solution is 0.045mmol. 3+ The concentration of Bi2-SnO was 1.5 mmol / L, and other conditions were the same to prepare Bi-doped SnO catalyst, which was recorded as Bi2-SnO.

[0053] Example 3

[0054] The difference from Example 1 is that the amount of Bi(NO3)3 added is 0.18mmol, and the amount of Bi in the mixed solution is 0.18mmol. 3+The concentration of Bi8-SnO was 6 mmol / L, and other conditions were the same to prepare a Bi-doped SnO catalyst, which was recorded as Bi8-SnO.

[0055] Comparative Example 1

[0056] 9mmolSnCl2 and 3.37mmolhexadecyltrimethylammonium bromide were added to 30mL of deionized water and ultrasonically dispersed for 20min to obtain a mixed solution. 2+ The concentration of 0.3 mol / L and the concentration of cetyltrimethylammonium bromide were 0.11 mol / L; the mixed solution was slowly poured into 20 mL of a 1.5 mol / L NaOH aqueous solution, and the mixture was magnetically stirred at 25°C for 3 h to react. After the reaction, the mixture was centrifuged at 5000 rpm, and the precipitate was dried in a vacuum drying oven at 60°C for 24 h to obtain a SnO catalyst, which was recorded as SnO.

[0057] The structural and morphological analysis results of the SnO catalyst prepared in Comparative Example 1 and the Bi-doped SnO catalysts prepared in Examples 1 to 3 are as follows: Figure 1 It can be seen that with the increase of Bi doping ratio, the catalyst gradually shows the characteristic diffraction peak of Bi metal, which indicates that 2+ Under the weak reduction effect of 3+ It was reduced to a metallic state and successfully doped into the SnO system.

[0058] from Figure 2 It can be seen that the catalyst prepared after doping with Bi has a smaller sheet diameter, and the particle size is reduced from about 70 μm of the original SnO to about 3 μm. The reason is that Bi 3+ The introduction of increases the nucleation sites, while the bismuth salt is adsorbed on the crystal surface to limit its lateral growth.

[0059] Application Example 1

[0060] 10 mg of the Bi-doped SnO catalyst (Bi2-SnO) of Example 2 was dispersed in 2 mL of isopropanol, 100 μL of Nafion adhesive was added, and the mixture was ultrasonically treated for 60 min to form a catalyst ink. The catalyst ink was then drop-coated on carbon paper (YLS-30T) in small amounts and multiple times, and layer-by-layer deposition was performed using a hot plate drying method to prepare a gas diffusion electrode. The coating amount of the Bi-doped SnO catalyst on the carbon paper (YLS-30T) was 4 mg / cm 2 .

[0061] The gas diffusion electrode described above was used to test the CO2 electroreduction reaction in a flow-type electrolytic cell. The system used an anion exchange membrane to separate the cathode and anode, a 1M KOH solution as the electrolyte, an Ag / AgCl solution as the reference electrode, a platinum sheet as the counter electrode, and the gas diffusion electrode prepared above as the working electrode. CO2 was passed into the reaction cell at a constant flow rate, and the potential was measured with Ag / AgCl and converted to the reversible hydrogen electrode (RHE) potential according to formula (1):

[0062] E(vs.RHE)=E(vs.Ag / AgCl)+0.21 V+0.0591×pH (1)

[0063] The gas phase product was detected by gas chromatography (GC), and the liquid phase product was analyzed by 400 MHz nuclear magnetic resonance spectrometer (NMR). The NMR sample consisted of 300 μL sample solution, 300 μL D2O, and 10 μL DMSO (0.014 M) internal standard. The liquid phase product of the electrocatalytic reduction of CO2 was formic acid (HCOOH). A series of NMR samples were prepared using HCOOH standard solution, and a standard curve (covering low and high concentration ranges) was established for product quantitative analysis. The Faradaic efficiency (FE) was calculated according to formula (2):

[0064] FE=Z×n×F / Q (2)

[0065] Where Z is the number of electrons transferred (2 for HCOOH), n is the number of moles of product, F is the Faraday constant, and Q is the total charge.

[0066] The above-mentioned gas diffusion electrode was used to conduct the test in a solid electrolyte electrolysis cell: the solid electrolyte electrolysis system adopts a two-electrode structure and uses H + Electrodes are isolated using a cation exchange resin and an anion-cation exchange membrane. Products are collected by washing with deionized water or purging with nitrogen (N2) followed by condensation for subsequent quantitative analysis.

[0067] from Figure 3 It can be seen that in the flow electrolytic cell, when the current density is as high as 1550mA / cm 2 When the reaction temperature is 0.05 ℃ and the reaction time is 2 ℃, the Bi-doped SnO catalyst of Example 2 can still maintain a Faradaic efficiency of more than 90%, indicating that the Bi-doped SnO catalyst prepared by the present invention has excellent high current stability and selectivity, which is better than most reported Bi and Sn-based catalysts.

[0068] The performance of the Bi-doped SnO catalyst prepared by the present invention is compared with the current mainstream CO2 reduction catalyst. The comparison results are shown in Table 1:

[0069] Table 1 Performance comparison of Bi-doped SnO catalyst prepared by the present invention and current mainstream CO2 reduction catalyst

[0070]

[0071] Figure 4 The figure shows a comparison of the Faraday efficiencies of formic acid under different voltage conditions using the gas diffusion electrode of Application Example 1 in a solid-state electrolytic cell, indicating that the Bi-doped SnO catalyst prepared in Example 2 has good mass transfer adaptability and energy efficiency under actual working conditions and is suitable for medium- and long-term operation.

[0072] Figure 5 For 13 C-labeled CO2 is used as raw material, and the formic acid obtained by the reaction in the solid electrolytic cell using the gas diffusion electrode of Application Example 1 is 13 C NMR spectrum, we can see: 13 The obvious appearance of C formic acid signal clearly confirmed that the formic acid product was directly derived from CO2, verifying the carbon source attribution and reaction specificity of the reaction pathway.

[0073] Figure 6 This is a stability test chart of continuous operation for more than 140 hours in the gas diffusion electrode solid-state electrolysis cell of Application Example 1 under nitrogen purge. It can be seen that the formic acid concentration is always maintained in the range of >5 mol / L during this period, reflecting that the Bi-doped SnO catalyst of Example 2 has excellent structural stability and catalytic durability under long-term electrolysis conditions.

[0074] Application Example 2

[0075] This application example constructs an electrocatalytic multi-enzyme catalytic coupling system, using formic acid, the product of electrocatalytic reduction of CO2, as a substrate for the synthesis of dihydroxyacetone (DHA):

[0076] The formic acid obtained in Application Example 1 was added to a reaction system containing 100 mM phosphate buffer (pH 6.5, volume 20 mL) to a final formic acid concentration of 50 mmol / L. The following components were then added in sequence: 40 mg formate dehydrogenase (FDH, final concentration 2 g / L), 80 mg formaldehyde dehydrogenase (FALDH, final concentration 4 g / L), 0.142 g reduced nicotinamide adenine nucleotide disodium salt (NADH, final concentration 10 mmol / L), 0.21 g thiamine pyrophosphate (TPP, final concentration 0.5 mmol / L), and 0.476 g anhydrous magnesium chloride (MgCl2, final concentration 5 mmol / L). The mixture was subjected to magnetic stirring at room temperature for 72 hours. Samples were taken every 12 hours, and the concentration of the product dihydroxyacetone (DHA) was determined by high-performance liquid chromatography (HPLC). The final cumulative production of DHA reached 10.3 g / L, confirming the feasibility of converting formic acid into fine chemicals through intermediate states under enzyme-catalyzed conditions, providing a new pathway for CO2 synthesis.

[0077] Application Example 3

[0078] This application example constructs an electrocatalytic biocoupling system, using formic acid, the product of electrocatalytic reduction of CO2, as a substrate for the synthesis of itaconic acid:

[0079] The solid-state electrolytic cell of Application Example 1 was used to carry out the CO2 electrocatalytic reduction reaction to obtain an aqueous formic acid solution with a concentration of 5 g / L. The aqueous formic acid solution was then sterilized by filtration with a 0.22 μm sterile membrane, mixed with glucose and added as a mixed carbon source to the M9 fermentation medium that had been sterilized under high pressure. A recombinant Escherichia coli engineered strain with a formic acid metabolism enhancement pathway and an itaconic acid biosynthesis pathway was inoculated with an inoculation volume of 2 mL, and fermented for 72 hours at 30°C and an initial pH of 6.0. During the fermentation process, the pH was maintained stable by a Ca(OH)2 buffer system. Ultimately, the itaconic acid production reached 300 mg / L, verifying the feasibility and application potential of the electro-biocoupled system constructed by the present invention in the high-value conversion of CO2 into amino acids.

[0080] Application Example 4

[0081] This application example constructs an electrocatalytic biocoupling system, using formic acid, the product of electrocatalytic reduction of CO2, as a substrate for the synthesis of poly (β-hydroxybutyrate) (PHB):

[0082] The solid-state electrolytic cell of Application Example 1 was used to carry out the CO2 electrocatalytic reduction reaction to obtain an aqueous formic acid solution with a concentration of 5 g / L. The aqueous formic acid solution was then sterilized by filtration with a 0.22 μm sterile membrane, mixed with glucose as a mixed carbon source and added to the M9 fermentation medium that had been sterilized under high pressure. The recombinant Escherichia coli engineered strain with a formic acid metabolism enhancement pathway and a PHB biosynthesis pathway was inoculated with an inoculum of 1 mL and transferred to 100 mL of fresh LB culture medium. 100 μL of kanamycin sulfate (final concentration of 50 μg / mL) and 100 μL of ampicillin sodium (final concentration of 100 μg / mL) were added and cultured on a shaking table for 8 hours (37°C, 200 rpm). Finally, the PHB yield reached 120 mg / g 干菌 , which verified the feasibility and application potential of the electrocatalytic-microbial catalytic coupling system constructed by the present invention in the high-value conversion of CO2 to synthesize bio-based materials.

[0083] Application Example 5

[0084] This application example constructs an electrocatalytic bio-coupling system, using formic acid, the product of electrocatalytic reduction of CO2, as a substrate for the synthesis of 2,3-butanediol:

[0085] The solid-state electrolytic cell of Application Example 1 was used to perform the CO2 electrocatalytic reduction reaction, obtaining a 5 g / L aqueous formic acid solution. The formic acid solution was then sterilized by filtration through a 0.22 μm sterile membrane and mixed with glucose as a mixed carbon source, which was added to an autoclaved M9 fermentation medium. A 1 mL inoculum of a recombinant Escherichia coli engineered strain with a 2,3-butanediol biosynthesis pathway was inoculated into 80 mL of fresh LB medium. 80 μL of kanamycin sulfate (final concentration of 50 μg / mL) and 80 μL of ampicillin sodium (final concentration of 100 μg / mL) were added, and the culture was shaken for 8 hours (37°C, 200 rpm). The bacterial solution was resuspended in M9 electrolyte and transferred to a microbial reactor. Finally, after electrosynthesis optimization, the 2,3-butanediol yield reached 3.45 g / L, verifying the feasibility and application potential of the electrocatalytic-microbial catalytic coupling system constructed in the present invention in the high-value conversion of CO2 into liquid fuels.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a Bi-doped SnO catalyst, characterized in that: The steps include: S1: mixing a divalent metal tin salt, a regulator, and a bismuth salt in water to obtain a mixed solution; S2: mixing the mixed solution and the sodium hydroxide solution, and reacting them to obtain a Bi-doped SnO catalyst.

2. The method for preparing the Bi-doped SnO catalyst according to claim 1, wherein: In step S1, the divalent metal tin salt includes one or more of stannous nitrate, stannous chloride, stannous sulfate, stannous phosphate and stannous carbonate; the regulator includes one or more of sodium citrate, hexadecyltrimethylammonium bromide, sodium lauryl sulfonate, polyvinyl pyrrolidone and polyvinyl alcohol; and the bismuth salt includes one or more of bismuth chloride, bismuth nitrate, bismuth sulfate and bismuth phosphate.

3. The method for preparing the Bi-doped SnO catalyst according to claim 1 or 2, wherein: In the mixed solution, Sn 2+ The concentration of Bi is 0.1~1mol / L, the concentration of the regulator is 0.01~0.6mol / L, 3+ The concentration is 0.1~9mmol / L.

4. The method for preparing the Bi-doped SnO catalyst according to claim 3, wherein: In step S2, the volume ratio of the mixed solution to the sodium hydroxide solution is 20-50:10-30, wherein the concentration of the sodium hydroxide solution is 0.6-5 mol / L; the reaction temperature is 20-60° C., and the reaction time is 1-24 h.

5. The Bi-doped SnO catalyst prepared by the method for preparing the Bi-doped SnO catalyst according to any one of claims 1 to 4.

6. Use of the Bi-doped SnO catalyst according to claim 5 in the preparation of fine chemicals by electrocatalytic multi-enzyme catalytic coupling and in the preparation of amino acids, polyols, bio-based materials, and liquid fuels by electrocatalytic biocoupling.

7. A gas diffusion electrode, characterized in that The invention comprises a gas diffusion electrode body and the Bi-doped SnO catalyst according to claim 5 coated on the gas diffusion electrode body.

8. The gas diffusion electrode according to claim 7, characterized in that The coating amount of the Bi-doped SnO catalyst is 1-10 mg / cm 2 .

9. The method for preparing a gas diffusion electrode according to claim 7 or 8, characterized in that: The method comprises the following steps: dispersing Bi-doped SnO catalyst and adhesive in a solvent, drop-coating the obtained catalyst ink on a gas diffusion electrode body, and drying to obtain the gas diffusion electrode.

10. Use of the gas diffusion electrode according to claim 7 or 8 in CO2 electrocatalytic reduction.

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