阅读说明：本技术 一种铋基催化剂的制备方法和应用 (Preparation method and application of bismuth-based catalyst ) 是由 杨世和 龙霞 任佳政 王小亭 于 2021-08-31 设计创作，主要内容包括：本发明属于催化剂技术领域,公开了一种铋基催化剂的制备方法和应用。该制备方法,包括以下步骤：将醇与乙酸混合得混合液,然后向混合液中加入铋盐进行溶剂热反应,过滤,将滤渣干燥,再煅烧,制得铋基催化剂。本发明采用乙酸对反应过程进行调控,使制备的铋基催化剂具有金属铋和三氧化二铋组成的异质结构,其表面丰富的氧空位分布使得催化剂能够在较高电流密度和大电压窗口下保持高甲酸选择性,甲酸法拉第效率大于90％。该制备方法主要包括溶剂热反应和煅烧处理两步,其工艺简单,材料易得,能够实现大规模产业化应用。(The invention belongs to the technical field of catalysts, and discloses a preparation method and application of a bismuth-based catalyst. The preparation method comprises the following steps: mixing alcohol and acetic acid to obtain a mixed solution, then adding bismuth salt into the mixed solution to carry out solvothermal reaction, filtering, drying filter residues, and calcining to obtain the bismuth-based catalyst. The invention adopts acetic acid to regulate and control the reaction process, so that the prepared bismuth-based catalyst has a heterostructure consisting of metal bismuth and bismuth trioxide, the rich oxygen vacancy distribution on the surface of the bismuth-based catalyst enables the catalyst to keep high formic acid selectivity under a high current density and large voltage window, and the formic acid Faraday efficiency is more than 90%. The preparation method mainly comprises two steps of solvothermal reaction and calcination treatment, and has the advantages of simple process, easily obtained materials and capability of realizing large-scale industrial application.)

1. The preparation method of the bismuth-based catalyst is characterized by comprising the following steps: mixing alcohol and acetic acid to obtain a mixed solution, then adding bismuth salt into the mixed solution to perform solvothermal reaction, filtering, drying filter residues, and calcining to obtain the bismuth-based catalyst.

2. The method according to claim 1, wherein the volume ratio of the alcohol to the acetic acid is (1-4): 1.

3. The method as claimed in claim 1, wherein the temperature of the solvothermal reaction is 120-180 ℃, and the time of the solvothermal reaction is 200-600 min.

4. The method of claim 1, wherein the calcining comprises: under the mixed gas of nitrogen and hydrogen, the temperature is raised to 150-300 ℃ at the temperature raising speed of 3-10 ℃/min, and then the temperature is maintained for 10-120 min.

5. The preparation method according to claim 4, wherein the nitrogen-hydrogen mixed gas comprises nitrogen gas and hydrogen gas, and the volume of the hydrogen gas is 5-30% of the volume of the nitrogen-hydrogen mixed gas.

6. A bismuth-based catalyst, characterized by being produced by the production method according to any one of claims 1 to 5; the bismuth-based catalyst has a heterostructure consisting of metal bismuth and bismuth trioxide.

7. A working electrode comprising an electrode material and the bismuth-based catalyst according to claim 6, wherein the bismuth-based catalyst is attached to the surface of the electrode material.

8. The working electrode of claim 7 wherein the electrode material is selected from one of carbon cloth, carbon paper, glassy carbon, or foamed nickel.

9. A catalytic reaction system for reducing carbon dioxide, comprising the working electrode, the counter electrode and the reference electrode according to claim 7 or 8.

10. A catalyst in-situ test system of a carbon dioxide reduction catalytic reaction system, comprising the carbon dioxide reduction catalytic reaction system of claim 9, a mass flow controller, a mass flow monitor, a gas chromatograph, and an electrochemical workstation.

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of a bismuth-based catalyst.

Background

With the rapid development of modern industry, the consumption of traditional fossil energy is continuously increased, the reserves of fossil energy are reduced, and the environmental pollution caused by the combustion of the fossil energy is also serious. The development of new green energy sources that can replace traditional fossil fuels is becoming increasingly important. Carbon dioxide is one of the main products of fossil fuel combustion, and as a gas with a strong greenhouse effect, its excessive emission has a significant negative effect on the ecological environment. Therefore, the carbon dioxide is fully utilized and converted into a reusable fuel resource or a chemical raw material with industrial production significance, so that the current energy crisis can be relieved while climate warming is restrained, and great significance is achieved.

The stable chemical property of carbon dioxide makes the conversion conditions relatively harsh, and the existing carbon dioxide conversion technology comprises a chemical reforming method, a biological conversion method, an electrochemical reduction method and the like. The electrochemical reduction method takes electric energy as a direct energy source, and has the potential of synergistic development with other green energy systems (wind energy, solar energy and the like), so that the electrochemical reduction method is the carbon dioxide conversion technology with the most practical application value. The electrochemical reduction process of carbon dioxide has the potential of converting the carbon dioxide into high value-added chemicals, however, the carbon dioxide has higher reaction energy barrier and low selectivity, so that the conversion process of the carbon dioxide needs a high-activity and high-selectivity carbon dioxide reduction catalyst.

Formic acid is one of products of electrochemical reduction of carbon dioxide, is one of the most basic organic chemical raw materials, and is widely applied to the industrial fields of medicines, pesticides, rubber and the like. At present, a great deal of research on the application of metals such as silver, mercury, platinum, palladium and the like as catalytic materials in the process of preparing formic acid by carbon dioxide electrocatalytic reduction is carried out. The potential of the above catalytic materials for use in large-scale industrial production is very limited due to the limitations of material toxicity and economic cost. The bismuth-based catalyst has equivalent activity of catalyzing carbon dioxide to prepare formic acid by electroreduction, and has low cost and no toxicity compared with the materials. In research, various optimization methods, such as the construction of a nano structure, the development of a heterostructure and the like, have good promotion effects on the catalytic activity of the bismuth-based catalytic material, particularly on the formic acid generating Faraday efficiency of the bismuth-based catalytic material in the carbon dioxide electrocatalytic reduction process. However, the improvement of the formic acid Faraday efficiency by the current optimization method is mainly limited in certain smaller voltage windows, and the practical industrial application value is smaller.

Therefore, it is highly desirable to provide a CO₂The catalyst for reducing the formic acid can show excellent catalytic activity and Faraday efficiency under a large voltage window.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides a preparation method of a bismuth-based catalyst, and the prepared bismuth-based composite catalyst can show excellent catalytic activity and Faraday efficiency under a large voltage window of-0.7 to-1.15V.

The first aspect of the invention provides a preparation method of a bismuth-based catalyst.

Specifically, the preparation method of the bismuth-based catalyst comprises the following steps:

mixing alcohol and acetic acid to obtain a mixed solution, then adding bismuth salt into the mixed solution to carry out solvothermal reaction, filtering after the reaction is finished, drying filter residues, and calcining to obtain the bismuth-based catalyst.

Preferably, the alcohol is ethanol.

Preferably, the bismuth salt is bismuth nitrate. Such as bismuth nitrate pentahydrate.

Preferably, the ratio of the mass of the bismuth salt to the volume of the mixed solution is 1 mg: (10-30) mL; further preferably, the ratio of the mass of the bismuth salt to the volume of the mixed solution is 1 mg: (15-25) mL.

Preferably, the volume ratio of the alcohol to the acetic acid is (1-4): 1; further preferably, the volume ratio of the alcohol to the acetic acid is (1-3): 1.

Preferably, the temperature of the solvothermal reaction is 120-180 ℃, and the time of the solvothermal reaction is 200-600 min; further preferably, the temperature of the solvothermal reaction is 150-180 ℃, and the time of the solvothermal reaction is 300-500 min.

Preferably, the calcination process is as follows: heating to 150-300 ℃ at a heating rate of 3-10 ℃/min under the mixed gas of nitrogen and hydrogen, and then keeping the temperature for 10-120 min; further preferably, the calcining process comprises: under the mixed gas of nitrogen and hydrogen, the temperature is raised to 180 ℃ and 250 ℃ at the temperature raising speed of 3-8 ℃/min, and then the temperature is maintained for 20-100 min.

Preferably, the nitrogen-hydrogen mixed gas comprises nitrogen and hydrogen, and the volume of the hydrogen accounts for 5% -30% of the volume of the nitrogen-hydrogen mixed gas; further preferably, the volume of the hydrogen gas accounts for 5-20% of the volume of the nitrogen-hydrogen mixed gas.

Preferably, before the calcination, the nitrogen-hydrogen mixed gas is introduced to replace air so as to ensure that no oxygen exists in the reaction system.

The invention provides a bismuth-based catalyst, which is prepared by the preparation method and has a heterostructure consisting of metal bismuth and bismuth trioxide.

In a third aspect, the invention provides a working electrode.

Specifically, the working electrode comprises an electrode material and the bismuth-based catalyst, and the bismuth-based catalyst is attached to the surface of the electrode material.

Preferably, the electrode material is selected from one of carbon cloth, carbon paper, glassy carbon or foamed nickel.

In a fourth aspect, the invention provides a method of making the working electrode.

Specifically, the preparation method of the working electrode comprises the following steps:

dispersing the bismuth-based catalyst in a solvent, adding a bonding agent, and mixing to obtain a catalyst dispersion liquid; and then dropwise adding or coating the catalyst dispersion liquid on the electrode material, and drying to obtain the working electrode.

The fifth aspect of the invention provides a carbon dioxide reduction catalytic reaction system.

A carbon dioxide reduction catalytic reaction system comprises the working electrode, a counter electrode and a reference electrode.

Preferably, the counter electrode is a platinum sheet counter electrode.

Preferably, the reference electrode is an Ag/AgCl reference electrode.

Preferably, the carbon dioxide reduction catalytic reaction system further comprises an electrolyte, a proton exchange membrane and an electrolytic cell.

Preferably, the electrolytic cell is an H-type electrolytic cell.

The invention provides a catalyst in-situ test system of a carbon dioxide reduction catalytic reaction system.

Specifically, the catalyst in-situ test system comprises the carbon dioxide reduction catalytic reaction system, a mass flow controller, a mass flow monitor, a gas chromatograph and an electrochemical workstation.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, acetic acid is adopted to regulate and control the reaction process, so that the prepared bismuth-based catalyst has a heterostructure consisting of metal bismuth and bismuth trioxide, the rich oxygen vacancy distribution on the surface of the bismuth-based catalyst enables the catalyst to keep high formic acid selectivity under a large voltage window (-0.7 to-1.15V), the formic acid Faraday efficiency is more than 90%, and the bismuth-based catalyst has a good prospect in the fields of carbon dioxide conversion and formic acid industry.

(2) The preparation method provided by the invention mainly comprises two steps of solvothermal reaction and calcination treatment, and has the advantages of simple process, easily obtained materials and capability of realizing large-scale industrial application.

Drawings

FIG. 1 is a scanning electron microscope photograph of the powder prepared in step S3 of example 1;

FIG. 2 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in example 1;

FIG. 3 is a scanning electron microscope photograph of the powder prepared in step S3 of comparative example 1;

FIG. 4 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in comparative example 1;

FIG. 5 is a scanning electron microscope photograph of the powder prepared in step S3 of comparative example 2;

FIG. 6 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in comparative example 2;

FIG. 7 is an X-ray diffraction pattern of the powder prepared in step S3 of example 1;

FIG. 8 is an X-ray diffraction spectrum of the bismuth-based catalyst obtained in example 1;

FIG. 9 is an X-ray diffraction spectrum of the powder prepared in step S3 of comparative example 1 and a bismuth-based catalyst;

FIG. 10 is an X-ray diffraction spectrum of the powder prepared in step S3 of comparative example 2 and a bismuth-based catalyst;

FIG. 11 is a high-resolution transmission electron microscope photograph of the bismuth-based catalyst prepared in example 1;

FIG. 12 is a high-resolution transmission electron microscope photograph of the bismuth-based catalyst prepared in comparative example 1;

FIG. 13 is a high-resolution transmission electron microscope photograph of the bismuth-based catalyst prepared in comparative example 2;

FIG. 14 is an electron spin resonance spectrum of the bismuth-based catalyst obtained in example 1;

FIG. 15 is an electron spin resonance spectrum of the bismuth-based catalyst prepared in comparative example 1;

FIG. 16 is an electron spin resonance spectrum of the bismuth-based catalyst prepared in comparative example 2;

FIG. 17 is an X-ray electron spectrum of the bismuth-based catalyst prepared in example 1;

FIG. 18 is an X-ray electron spectrum of the bismuth-based catalyst prepared in comparative example 1;

FIG. 19 is an X-ray electron spectrum of the bismuth-based catalyst prepared in comparative example 2;

FIG. 20 is a graph showing a comparison of faradaic efficiencies of formic acid production using the carbon dioxide reduction catalytic reaction systems provided in example 2, comparative example 5, and comparative example 6;

FIG. 21 is a diagram showing CO contents of carbon dioxide reduction catalyst reaction systems provided in application example 2, comparative example 5 and comparative example 6₂Reducing the polarity curve.

Detailed Description

In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.

The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified.

Example 1

A preparation method of a bismuth-based catalyst comprises the following steps:

s1, mix 24mL of absolute ethanol with 12mL of acetic acid and stir gently with a glass rod. 2mg of bismuth nitrate pentahydrate powder is added into the mixed solution, and then the mixed solution is magnetically stirred for 5 minutes at the rotating speed of 500 revolutions per minute, and the color of the final solution is light yellow.

S2, placing the obtained solution into a reaction kettle, and carrying out solvothermal reaction for 390 minutes at the temperature of 160 ℃ to obtain a light yellow precipitate.

S3, filtering the obtained light yellow precipitate, taking out, alternately washing the precipitate for several times by using deionized water and absolute ethyl alcohol, finally, centrifugally separating the precipitate, and drying the precipitate for twelve hours in a vacuum drying oven at the temperature of 60 ℃. Finally grinding it into powder.

S4, first using H at a flow rate of 250mL/min at room temperature₂/N₂Mixed gas (H)₂10%) was passed into the tube furnace for 3 hours to ensure that the residual air in the tube furnace was completely replaced. The powder was then spread flat in a corundum ark and placed in a tube furnace with a tube diameter of 50 mm.

S5, continuously introducing the nitrogen-hydrogen mixed gas (H)₂10%) while increasing the furnace temperature from room temperature to 200 c at a rate of 5 c per minute. And (3) continuously heating the furnace body for half an hour at the temperature of 200 ℃, naturally cooling to room temperature, and taking out the bismuth-based powder material in the tubular furnace to obtain the bismuth-based catalyst.

The bismuth-based catalyst is prepared by the method and has a heterostructure consisting of metal bismuth and bismuth trioxide.

Example 2

A preparation method of a bismuth-based catalyst comprises the following steps:

s1, mix 24mL of absolute ethanol with 12mL of acetic acid and stir gently with a glass rod. 2mg of bismuth nitrate pentahydrate powder is added into the mixed solution, and then the mixed solution is magnetically stirred for 5 minutes at the rotating speed of 500 revolutions per minute, and the color of the final solution is light yellow.

S2, placing the obtained solution into a reaction kettle, and carrying out solvothermal reaction for 450 minutes at the temperature of 150 ℃ to obtain a light yellow precipitate.

S3, filtering the obtained light yellow precipitate, taking out, alternately washing the precipitate for several times by using deionized water and absolute ethyl alcohol, finally, centrifugally separating the precipitate, and drying the precipitate for twelve hours in a vacuum drying oven at the temperature of 60 ℃. Finally grinding it into powder.

S4, first using H at a flow rate of 250mL/min at room temperature₂/N₂Mixed gas (H)₂10%) was passed into the tube furnace for 3 hours to ensure that the residual air in the tube furnace was completely replaced. The powder was then spread flat in a corundum ark and placed in a tube furnace with a tube diameter of 50 mm.

S5, continuously introducing the nitrogen-hydrogen mixed gas (H)₂10%) while increasing the furnace temperature from room temperature to 230 c at a rate of 8 c per minute. And (3) continuously heating the furnace body for half an hour at 230 ℃, naturally cooling to room temperature, and taking out the bismuth-based powder material in the tubular furnace to obtain the bismuth-based catalyst.

Example 3

A preparation method of a bismuth-based catalyst comprises the following steps:

s1, mix 24mL of absolute ethanol with 12mL of acetic acid and stir gently with a glass rod. 2mg of bismuth nitrate pentahydrate powder is added into the mixed solution, and then the mixed solution is magnetically stirred for 5 minutes at the rotating speed of 500 revolutions per minute, and the color of the final solution is light yellow.

S2, placing the obtained solution into a reaction kettle, and carrying out solvothermal reaction for 390 minutes at the temperature of 170 ℃ to obtain a light yellow precipitate.

S3, filtering the obtained light yellow precipitate, taking out, alternately washing the precipitate for several times by using deionized water and absolute ethyl alcohol, finally, centrifugally separating the precipitate, and drying the precipitate for twelve hours in a vacuum drying oven at the temperature of 60 ℃. Finally grinding it into powder.

S4, first using H at a flow rate of 250mL/min at room temperature₂/N₂Mixed gas (H)₂10%) was passed into the tube furnace for 3 hours to ensure that the residual air in the tube furnace was completely replaced. The powder was then spread flat in a corundum ark and placed in a tube furnace with a tube diameter of 50 mm.

S5, continuously introducing the nitrogen-hydrogen mixed gas (H)₂10%) while increasing the furnace temperature from room temperature to 180 c at a rate of 4 c per minute. And (3) continuously heating the furnace body for half an hour at 180 ℃, naturally cooling to room temperature, and taking out the bismuth-based powder material in the tubular furnace to obtain the bismuth-based catalyst.

Application example 1

An electrode was prepared using the bismuth-based catalyst prepared in example 1.

The preparation process comprises the following steps:

s1, dispersing 10mg of the bismuth-based catalyst prepared in example 1 in 950mL of absolute ethanol, then dropwise adding 50mL of 5 wt% Nafion adhesive, and performing ultrasonic treatment for 30 minutes to form a catalyst dispersion liquid.

And S2, dropwise adding 200mL of catalyst dispersion liquid to the surface of clean hydrophobic carbon paper (the area is 3 cm x 1 cm), and drying at room temperature to form a compact film, thereby obtaining the working electrode loaded with the bismuth-based catalytic material.

Application example 2

A gas-liquid-solid double-interface carbon dioxide reduction catalytic reaction system is constructed by taking an electrode prepared in application example 1 as a carbon dioxide reduction working electrode, taking a platinum sheet as a counter electrode, taking Ag/AgCl as a reference electrode, taking a 0.5M potassium bicarbonate aqueous solution as an electrolyte and taking a PE (polyethylene) film as an ion exchange membrane.

Comparative example 1

This comparative example differs from example 1 in that the control was carried out without adding acetic acid.

Specifically, the preparation method of the bismuth-based catalyst comprises the following steps:

s1, adding 2mg of bismuth nitrate pentahydrate powder into 36mL of absolute ethyl alcohol, and magnetically stirring the obtained solution for 5 minutes at the rotation speed of 500 revolutions per minute, wherein the color of the final solution is light yellow.

S2, placing the obtained solution into a reaction kettle, and carrying out solvothermal reaction for 390 minutes at the temperature of 160 ℃ to obtain a light yellow precipitate.

S3, filtering the obtained light yellow precipitate, taking out, alternately washing the precipitate for several times by using deionized water and absolute ethyl alcohol, finally, centrifugally separating the precipitate, and drying the precipitate for twelve hours in a vacuum drying oven at the temperature of 60 ℃. Finally grinding it into powder.

S4, first using H at a flow rate of 250mL/min at room temperature₂/N₂Mixed gas (H)₂10%) was passed into the tube furnace for 3 hours to ensure that the residual air in the tube furnace was completely replaced. The powder was then spread flat in a corundum ark and placed in a tube furnace with a tube diameter of 50 mm.

S5, continuously introducing the nitrogen-hydrogen mixed gas (H)₂10%) while increasing the furnace temperature from room temperature to 200 c at a rate of 5 c per minute. And (3) continuously heating the furnace body for half an hour at the temperature of 200 ℃, naturally cooling to room temperature, and taking out the bismuth-based powder material in the tubular furnace to obtain the bismuth-based catalyst.

Comparative example 2

This comparative example differs from example 1 in that ethylene glycol was used for the conditioning.

Specifically, the preparation method of the bismuth-based catalyst comprises the following steps:

s1, mixing 24mL of absolute ethanol with 12mL of ethylene glycol and gently stirring with a glass rod. 2mg of bismuth nitrate pentahydrate powder is added into the mixed solution, and then the mixed solution is magnetically stirred for 5 minutes, wherein the stirring speed is 500 revolutions per minute, and the color of the final solution is light yellow.

S2, placing the obtained solution into a reaction kettle, and carrying out solvothermal reaction for 390 minutes at the temperature of 160 ℃ to obtain a light yellow precipitate.

S3, filtering the obtained light yellow precipitate, taking out, alternately washing the precipitate for several times by using deionized water and absolute ethyl alcohol, finally centrifugally separating the precipitate, and drying the precipitate for twelve hours at the temperature of 60 ℃ in a vacuum drying oven. Finally grinding it into powder.

S4, first using H at a flow rate of 250mL/min at room temperature₂/N₂Mixed gas (H)₂10%) was passed into the tube furnace for 3 hours to ensure that the residual air in the tube furnace was completely replaced. The powder was then spread flat in a corundum ark and placed in a tube furnace with a tube diameter of 50 mm.

S5, continuously introducing the nitrogen-hydrogen mixed gas (H)₂10%) while increasing the furnace temperature from room temperature to 200 c at a rate of 5 c per minute. And (3) continuously heating the furnace body for half an hour at the temperature of 200 ℃, naturally cooling to room temperature, and taking out the bismuth-based powder material in the tubular furnace to obtain the bismuth-based catalyst.

Comparative example 3

An electrode was prepared using the bismuth-based catalyst prepared in comparative example 1.

The preparation process comprises the following steps:

s1, dispersing 10mg of the bismuth-based catalyst prepared in the comparative example 1 in 950mL of absolute ethanol, then dropwise adding 50mL of 5 wt% Nafion adhesive, and carrying out ultrasonic treatment for 30 minutes to form a catalyst dispersion liquid.

And S2, dropwise adding 200mL of catalyst dispersion liquid to the surface of clean hydrophobic carbon paper (the area is 3 cm x 1 cm), and drying at room temperature to form a compact film, thereby obtaining the working electrode loaded with the bismuth-based catalytic material.

Comparative example 4

An electrode prepared using the bismuth-based catalyst prepared in comparative example 2.

The preparation process comprises the following steps:

s1, dispersing 10mg of the bismuth-based catalyst prepared in the comparative example 2 in 950mL of absolute ethanol, then dropwise adding 50mL of 5 wt% Nafion adhesive, and carrying out ultrasonic treatment for 30 minutes to form a catalyst dispersion liquid.

And S2, dropwise adding 200mL of catalyst dispersion liquid to the surface of clean hydrophobic carbon paper (the area is 3 cm x 1 cm), and drying at room temperature to form a compact film, thereby obtaining the working electrode loaded with the bismuth-based catalytic material.

Comparative example 5

A gas-liquid-solid double-interface carbon dioxide reduction catalytic reaction system is constructed by taking an electrode prepared in comparative example 3 as a carbon dioxide reduction working electrode, taking a platinum sheet as a counter electrode, taking Ag/AgCl as a reference electrode, taking a 0.5M potassium bicarbonate aqueous solution as an electrolyte and taking a PE (polyethylene) film as an ion exchange membrane.

Comparative example 6

A gas-liquid-solid double-interface carbon dioxide reduction catalytic reaction system is constructed by taking an electrode prepared in comparative example 4 as a carbon dioxide reduction working electrode, taking a platinum sheet as a counter electrode, taking Ag/AgCl as a reference electrode, taking a 0.5M potassium bicarbonate aqueous solution as an electrolyte and taking a PE (polyethylene) film as an ion exchange membrane.

Product effectiveness testing

1. The bismuth-based catalysts prepared in example 1, comparative example 1 and comparative example 2 were characterized, including testing using the following techniques or combinations: scanning electron microscopes, X-ray diffractometers, high-resolution transmission electron microscopes, electron spin resonance technology and X-ray photoelectron spectrometers.

(1) Using a scanning electron microscope (SEM, ZEISS)) The materials in the preparation of example 1, comparative example 1 and comparative example 2 and the finally prepared bismuth-based catalyst were characterized.

FIG. 1 is a scanning electron microscope photograph of the powder prepared in step S3 of example 1, and FIG. 2 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in example 1, and it can be seen from FIGS. 1 and 2 that the bismuth-based catalyst formed after the addition of acetic acid and the post-calcination treatment has a nano-scale lamellar structure.

Fig. 3 is a scanning electron microscope photograph of the powder prepared in step S3 of comparative example 1, and fig. 4 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in comparative example 1. As can be seen from fig. 3 and 4, the micro-morphology of the prepared material shows an aggregation state and has no obvious nano-aggregate morphology feature no matter whether the material is calcined or not, without adding acetic acid for regulation.

Fig. 5 is a scanning electron microscope photograph of the powder prepared in step S3 of comparative example 2, and fig. 6 is a scanning electron microscope photograph of the bismuth-based catalyst prepared in comparative example 2. As can be seen from fig. 5 and 6, the ethylene glycol is used for controlling, and the micro-morphology of the prepared material shows an aggregation state regardless of whether the material is calcined or not, and no obvious nano-aggregate morphology feature exists.

(2) CuKa radiation at 40kV, 40mA using an X-ray diffractometer (XRD, D8 Advance, Bruker) The materials in the preparation of example 1, comparative example 1 and comparative example 2, and the finally prepared bismuth-based catalyst were respectively tested in a diffraction angle range of 10-80 ° 2 θ.

FIG. 7 is an X-ray diffraction spectrum of the powder prepared in step S3 of example 1, FIG. 8 is an X-ray diffraction spectrum of the bismuth-based catalyst prepared in example 1, and in FIGS. 7 and 8, the ordinate is Intensity (Intensity) and the abscissa is 2 θ (2 theta). In FIG. 7, #71-0466 and #76-2478 are Bi₂O₃The standard card of (1); in FIG. 8, #14-0717 represents the standard card for Bi smuth oxalate, #71-0466 and #76-2478 represent Bi₂O₃Standard card of (2), and #65-4028 represents Bi₂O_2.7The standard card of (1); #85-1329 represents a standard card of Bi. As can be seen from fig. 7 and 8, the bismuth-based catalyst prepared by using acetic acid control is bismuth trioxide before the calcination treatment (powder prepared in step S3), and a bismuth/bismuth trioxide heterostructure is formed after the calcination.

FIG. 9 is an X-ray diffraction spectrum of the powder prepared in step S3 of comparative example 1 and the bismuth-based catalyst, and in FIG. 9, PDF #71-0466 and PDF #78-1793 represent Bi₂O₃PDF #65-4020 represents the standard card of BiO. As can be seen from fig. 9, when no acetic acid was used for the conditioning, bismuth trioxide was formed before the calcination treatment (the powder prepared in step S3), and a bismuth monoxide/bismuth trioxide structure was formed after the calcination annealing treatment, but no foreign structure was observed. FIG. 10 is an X-ray diffraction pattern of the powder prepared in step S3 of comparative example 2 and a bismuth-based catalystSpectrum, in FIG. 10, PDF #71-0466 and PDF #45-1344 represent Bi₂O₃PDF #85-1331 and PDF #89-2387 represent standard cards of Bi. As can be seen from fig. 10, the bismuth trioxide is controlled by using ethylene glycol before the calcination treatment, and a bismuth/bismuth trioxide heterostructure is formed after the calcination treatment. But the bismuth/bismuth trioxide heterostructure formed by the bismuth-based catalyst prepared by regulating and controlling acetic acid is more stable.

(3) The bismuth-based catalysts prepared in example 1, comparative example 1 and comparative example 2 were characterized by a high-resolution transmission electron microscope (HRTEM, JEM-3200FS, JEOL).

FIG. 11 is a high resolution TEM image of the Bi-based catalyst prepared in example 1, and it can be seen from a) in FIG. 11 that the Bi-based catalyst prepared by acetic acid control has a typical nano-flake structure in the micro-morphology; as shown in b) and c) of fig. 11, the lattice spacing measurement results of the bismuth-based catalyst are consistent with those of the metal bismuth and bismuth trioxide.

Fig. 12 is a high-resolution transmission electron microscope image of the bismuth-based catalyst prepared in comparative example 1, and it can be seen from a) in fig. 12 that the bismuth-based catalyst prepared without acetic acid control has a microstructure characteristic mainly in an irregular aggregation state, and b) and c) in fig. 12 that the lattice spacing measurement result matches with that of bismuth monoxide and bismuth trioxide.

Fig. 13 is a high-resolution transmission electron microscope image of the bismuth-based catalyst prepared in the comparative example 2, and it can be known from a) in fig. 13 that the bismuth-based catalyst prepared by ethylene glycol control has irregular aggregation state in the micro-morphology and a part of the morphology is in a flake shape. In fig. 13, b) and c) show that the lattice spacing measurement result matches the metal bismuth and bismuth trioxide.

(4) The bismuth-based catalysts prepared in example 1, comparative example 1 and comparative example 2 were characterized using electron spin resonance techniques (ESR, MS5000, Bruker). Fig. 14 is an electron spin resonance spectrum of the bismuth-based catalyst prepared in example 1, fig. 15 is an electron spin resonance spectrum of the bismuth-based catalyst prepared in comparative example 1, and fig. 16 is an electron spin resonance spectrum of the bismuth-based catalyst prepared in comparative example 2. In fig. 14 to 16, the ordinate is intensity (intensity) and the abscissa is g value (g value), and it can be seen from fig. 14 to 16 that the bismuth-based catalyst prepared by acetic acid regulation forms oxygen vacancies, but cannot form oxygen vacancies without regulation or regulation by ethylene glycol, and the presence of oxygen vacancies is beneficial for the catalyst to maintain high formic acid faraday efficiency under a larger voltage window.

(5) The bismuth-based catalysts prepared in example 1, comparative example 1 and comparative example 2 were characterized by an X-ray photoelectron spectrometer (XPS, ESCALAB 250Xi, Thermo Fisher), and a high-resolution X-ray photoelectron spectrum at the Bi 4f position was measured. FIG. 17 is an X-ray electron spectrum of the bismuth-based catalyst obtained in example 1, FIG. 18 is an X-ray electron spectrum of the bismuth-based catalyst obtained in comparative example 1, and FIG. 19 is an X-ray electron spectrum of the bismuth-based catalyst obtained in comparative example 2. In FIGS. 17 to 19, the ordinate is absolute strength (Raw intensity) and the abscissa is binding energy (B.E.eV), and it can be seen from FIGS. 17 to 19 that bismuth-based catalysts synthesized by controlling acetic acid and ethylene glycol have bismuth elements mainly present on the surface thereof in the form of metallic bismuth (metallic Bi) and trivalent bismuth (Bi)³⁺) While the bismuth-based catalyst (comparative example 1) prepared without control had the surface bismuth element mainly present in the form of divalent bismuth (Bi)²⁺) And trivalent bismuth (Bi)³⁺)。

2. The performance of the carbon dioxide reduction catalytic reaction systems provided in examples 2, 5 and 6 was tested, the carbon dioxide reduction catalytic reaction system was connected to a mass flow controller, a mass flow monitor, a gas chromatograph, and an electrochemical workstation, and the test electrochemical workstation was a CHI electrochemical workstation (shanghai chenhua) (i.e., a catalyst in-situ test system for a carbon dioxide reduction catalytic reaction system).

Fig. 20 is a graph comparing faradaic efficiencies of formic acid production using the carbon dioxide reduction catalytic reaction systems provided in example 2, comparative example 5, and comparative example 6. In fig. 20, the ordinate is the faraday efficiency (FE of HCOOH/%), and the abscissa is the potential (potential v vs RHE) relative to the reversible hydrogen electrode, and it can be seen from fig. 20 that the carbon dioxide reduction catalytic reaction system (containing the bismuth-based catalyst prepared by acetic acid regulation) provided in application example 2 maintains a higher formic acid faraday efficiency level within a larger voltage window (-0.7 to-1.15), and the formic acid faraday efficiency is greater than 90% and can reach 95% at most. While the carbon dioxide reduction catalytic reaction systems provided in comparative examples 5 and 6 have good methanogenic faradaic efficiency at a voltage of-0.7 v, the methanogenic faradaic efficiency at a voltage of-1.15 is very low, less than 70%.

FIG. 21 is a diagram showing CO contents of carbon dioxide reduction catalyst reaction systems provided in application example 2, comparative example 5 and comparative example 6₂Reducing the polarity curve. In fig. 21, the ordinate is the current density (a/cm2), and the abscissa is the potential (potential v vs RHE) relative to the reversible hydrogen electrode, and it can be seen from fig. 21 that the current density of the carbon dioxide reduction catalytic reaction system provided in application example 2 is much higher than that of comparative examples 5 and 6, and the bismuth-based catalyst prepared by using acetic acid control exhibits a higher current density.

From the above experiments, it can be seen that the bismuth-based catalyst prepared by acetic acid control maintains more excellent catalytic activity at a wider voltage window. The bismuth-based catalysts prepared in examples 2, 3 have similar properties to the bismuth-based catalyst prepared in example 1.

Therefore, when the bismuth-based catalyst prepared by the preparation method of the bismuth-based catalyst is used in the electrocatalytic reduction process of carbon dioxide, the aim of maintaining high formic acid Faraday efficiency under a larger voltage window is fulfilled, and the catalyst has excellent performance; and the preparation method is simple, easy to operate and has wide application prospect.