CN113463119A

CN113463119A - Bismuth-based-silver-based composite material and preparation method and application thereof

Info

Publication number: CN113463119A
Application number: CN202110662682.2A
Authority: CN
Inventors: 李宇航; 李春忠; 刘锦泽; 王雅婷; 肖楚倩; 陈容振
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2021-10-01
Anticipated expiration: 2041-06-15
Also published as: CN113463119B

Abstract

The invention discloses a bismuth-silver-based composite material and a preparation method and application thereof. The preparation method of the bismuth-silver-based composite material includes the following steps: S1: silver nanowires, bismuth chloride, hexadecyltrimethylamine bromide and sodium vanadate are hydrothermally reacted to obtain vanadic acid Bismuth-silver nanowire precatalyst; S2: a substrate coated with a bismuth vanadate-silver nanowire precatalyst is used as a working electrode, and a bismuth-silver-based composite is prepared on the substrate through an in-situ electrochemical reaction Material. In the bismuth-silver-based composite material prepared by the preparation method of the present invention, the bismuth nanosheet has an ultra-small size, and in the electrocatalytic reduction of carbon dioxide to prepare formate, it exhibits excellent formate Faradaic efficiency and cathode. Energy efficiency and better stability.

Description

Bismuth-based-silver-based composite material and preparation method and application thereof

Technical Field

The invention relates to a bismuth-based-silver-based composite material, a preparation method and application thereof.

Background

With the progress of times and the development of science and technology, energy has become an important factor influencing human society. At present, traditional energy sources such as coal, petroleum, natural gas and the like still play a very important role in the economic development of the world, but the energy crisis becomes a problem to be solved urgently by people at present due to the limited fossil energy reserves. The carbon dioxide is converted into fuel with high energy density by electrocatalysis and chemical reaction by utilizing renewable energy, and a feasible strategy is provided for reducing excessive carbon emission and saving fossil energy. Among the numerous products of electrocatalytic reduction of carbon dioxide, formate is an important chemical product that can serve as an alternative feedstock for fuel cells and as an ideal hydrogen storage material.

Nowadays, metal-based materials such as bismuth, palladium, tin, indium and lead all show good advantages in the process of preparing formate by reducing carbon dioxide. Recently, in the prior art, there are two-dimensional bismuth nanosheets obtained by in-situ electrochemical reduction of bismuth-based materials, which can improve the faraday efficiency and catalytic activity of formate in the process of preparing formate by electrocatalysis of carbon dioxide, but the improvement degree is still limited. For example, in the prior report adv.Funct.Mater.2020,30,1910408, albeit at-0.97V_RHEAt potential, the catalyst has better formate Faraday efficiency, but the partial current density is only 4mA cm^-2。

In the prior art, elemental silver is also reported to be applied to a catalyst for preparing formate by reducing carbon dioxide, and a silver nanowire and a tin sulfide nanosheet are compounded by a hydrothermal method to obtain a composite material, wherein the composite material has low formate Faraday efficiency although the partial current density is improved.

In addition, the first and second substrates are,the catalyst in the prior art still has some limiting problems, such as low cathode energy efficiency, especially under the industrial grade current density (for example, 100-250 mA cm)^-2). The lower cathode energy efficiency results in wasted energy, hindering the practical application of the catalyst in formate production.

Therefore, a bismuth-based material needs to be designed, and higher formate Faraday efficiency and higher catalytic activity can be realized at the same time, so that the application prospect of the bismuth-based material in the industrial preparation of formate is further improved.

Disclosure of Invention

The invention aims to solve the technical problem that the defect that the process of preparing formate by electro-catalyzing carbon dioxide under the condition of large current by using a bismuth-based material in the prior art cannot combine the Faraday efficiency and the catalytic activity of formate is overcome, and the bismuth-silver-based composite material and the preparation method and the application thereof are provided. In the bismuth-based-silver-based composite material provided by the invention, the bismuth nanosheet can have a circumscribed circle diameter of 6-8 nm, and the excellent formate Faraday efficiency, cathode energy efficiency and better stability are shown in the reaction of preparing formate by electrocatalytic reduction of carbon dioxide.

The invention solves the technical problems through the following technical scheme.

The invention provides a preparation method of a bismuth-based-silver-based composite material, which comprises the following steps:

s1: reacting silver nanowires, bismuth chloride, hexadecyl trimethyl ammonium bromide and sodium vanadate by a hydrothermal method to prepare a bismuth vanadate-silver nanowire precatalyst;

s2: taking the base material coated with the bismuth vanadate-silver nanowire precatalyst on the surface as a working electrode, and preparing the bismuth-based-silver-based composite material on the base material through in-situ electrochemical reaction.

In S1, the diameter of the silver nanowires is preferably 60 to 100nm, and more preferably 60 to 80 nm.

In S1, the silver nanowires can be prepared by a method conventional in the art, and generally by mixing copper chloride dihydrate, polyvinylpyrrolidone and silver nitrate in the presence of a solvent, and preferably by the following steps:

s11, adding copper chloride dihydrate into the polyvinylpyrrolidone solution to obtain a mixed solution;

s12, adding silver nitrate into the mixed solution, and reacting to obtain the silver nanowire.

In S11, the temperature of the polyvinylpyrrolidone solution may be conventional in the art, and is preferably 170 to 180 ℃, for example 175 ℃.

In S11, the solvent in the polyvinylpyrrolidone solution may be an alcohol solvent conventional in the art, such as ethylene glycol.

In S11, the concentration of polyvinylpyrrolidone in the polyvinylpyrrolidone solution may be conventional in the art, and is preferably 1.04-1.08 mg/mL, for example 1.06 mg/mL.

In S11, the cupric chloride dihydrate is preferably added in the form of a solution, and the solvent in the solution may be an alcoholic solvent conventional in the art, such as ethylene glycol.

When the cupric chloride dihydrate is added as a solution, the concentration of cupric chloride dihydrate may be conventional in the art, and is preferably 3-5 mg/mL, such as 4 mg/mL.

In S12, the silver nitrate is preferably added in the form of a solution, and the solvent in the solution can be an alcohol solvent conventional in the art, such as ethylene glycol.

When the silver nitrate is added in the form of a solution, the concentration of silver nitrate in the silver nitrate solution can be conventional in the art, and is preferably 15.67-16.67 mg/mL, such as 16.15 mg/mL.

When the silver nitrate is added in the form of a solution, the addition rate of the silver nitrate solution is preferably 180 mL/h.

In S12, the reaction time is preferably 5-15 min, for example 10 min.

In S12, after the reaction is completed, a post-treatment operation as conventional in the art is further performed. For example, washing with water, washing with absolute ethanol several times, and drying.

The drying operation and conditions can be conventional in the art, and the drying operation and conditions can be generally 50-60 ℃ for 24 hours.

In the preparation process of the silver nanowire, the mass ratio of the silver nitrate, the polyvinylpyrrolidone and the copper chloride dihydrate is preferably (16-20): (18-24): 1, e.g. 17.25: 21.875: 1.

in a preferred embodiment, the silver nanowires can be prepared by the following method:

adding 138mg of polyvinylpyrrolidone into 130mL of ethylene glycol, heating the mixed solution to 175 ℃, and quickly injecting 2mL of ethylene glycol in which 8mg of copper chloride dihydrate is dissolved;

484.5mg of silver nitrate is dissolved in 30mL of ethylene glycol, the solution is added into the reaction system at the speed of 180mL/h, and the reaction is continued for 10 min;

and after the reaction is finished, washing the product for several times by using deionized water and absolute ethyl alcohol, and drying at the temperature of 60 ℃ to prepare the silver nanowire.

In S1, the silver nanowires, the bismuth chloride, the cetyltrimethylammonium bromide and the sodium vanadate are preferably in a mass ratio of 1: (8-15): (4-6): (12-16), for example, 1: 11.05: 5.25: 14;

in S1, the operation and conditions of the hydrothermal reaction may be conventional in the art. In the hydrothermal reaction process, amorphous bismuth vanadate nanoparticles are prepared on the surface of the silver nanowires.

In S1, the temperature of the hydrothermal reaction is preferably 100-140 ℃, for example, 120 ℃.

In S1, the hydrothermal reaction time is preferably 10 to 14 hours, for example 12 hours.

In S1, the bismuth vanadate-silver nanowire precatalyst may be a solid prepared by reacting the silver nanowire, the bismuth chloride, the hexadecyl trimethyl ammonium bromide and the sodium vanadate by a hydrothermal method.

In S1, the bismuth vanadate-silver nanowire precatalyst is preferably prepared by the following steps: and sequentially adding the bismuth chloride, the hexadecyl trimethyl ammonium bromide and the sodium vanadate into the solution containing the silver nanowires, and carrying out reaction by using a hydrothermal method.

Wherein, in the solution containing the silver nanowires, the solvent used can be alcohol solvent which is conventional in the art, such as ethylene glycol.

Wherein the solution containing the silver nanowires can be prepared by methods conventional in the art, such as ultrasonic dispersion.

The concentration of the silver nanowires in the solution containing the silver nanowires can be conventional in the art, and is preferably 0.25-0.42 mg/mL, such as 0.33 mg/mL.

Wherein, the premixing time of each raw material in the hydrothermal reaction is 20-40 min, for example 30 min.

Wherein, after the hydrothermal reaction is finished, the post-treatment operation which is conventional in the field is required. For example, washing with water, washing with absolute ethanol several times, and drying.

In a preferred embodiment, the bismuth vanadate-silver nanowire precatalyst can be prepared by the following method:

adding 20mg of silver nanowires into 60mL of ethylene glycol, uniformly dispersing by ultrasonic, and sequentially adding 221mg of bismuth chloride, 105mg of hexadecyl trimethyl ammonium bromide and 280mg of sodium vanadate under the stirring condition. After stirring for 30min, the solution was transferred to a 100mL hydrothermal kettle and heated at 120 ℃ for 12 h. And (3) washing the product for several times by using deionized water and absolute ethyl alcohol, and taking out the product after vacuum drying for 24 hours at the temperature of 50 ℃ to obtain the bismuth vanadate-silver nanowire precatalyst.

In S2, the substrate may be a substrate conventional in the art, preferably a carbon paper. The carbon paper is used as a conductive carrier, and the loose and porous structure is favorable for full contact of the catalyst, the electrolyte and the reaction raw material carbon dioxide.

In S2, the substrate may be of a size conventional in the art, for example 1cm by 1 cm.

In S2, the working electrode is preferably prepared by: and coating the dispersion liquid containing the bismuth vanadate-silver nanowire precatalyst and the binder on the substrate, and drying to obtain the catalyst.

Among them, the kind of the binder may be conventional in the art, and preferably a naphthol solution.

Wherein the mass-to-volume ratio of the bismuth vanadate-silver nanowire precatalyst to the binder can be conventional in the field, and is preferably (1-3) mg: 8 μ L, e.g. 1 mg: 4 μ L.

In the dispersion liquid containing the bismuth vanadate-silver nanowire precatalyst and the binder, the concentration of the bismuth vanadate-silver nanowire precatalyst is preferably 0.05-0.15 mg/μ L, for example 0.10mg/μ L.

In the dispersion containing the bismuth vanadate-silver nanowire precatalyst and the binder, the solvent used in the dispersion can be any solvent conventional in the art, such as an alcohol solvent, preferably absolute ethyl alcohol.

The bismuth vanadate-silver nanowire precatalyst and the binder can be dispersed in a manner conventional in the field, such as ultrasonic. The sonication time is preferably 30 min.

The manner of coating may be conventional in the art, such as drop coating, among others.

In the preparation process of the working electrode, the drying operation and conditions can be conventional in the field, and generally can be drying at 50-60 ℃ for 1 h.

In S2, the effective content of the bismuth vanadate-silver nanowire precatalyst on the substrate is preferably 0.5-1.5 mg/cm²E.g. 1mg/cm²。

S2, the effective content of the binder on the substrate is preferably 0.2-0.5 μ L, such as 0.4uL/cm²。

In S2, the counter electrode used in the in-situ electrochemical reaction can be conventional in the art, and is preferably an Ag/AgCl electrode.

In S2, the reference electrode used in the in situ electrochemical reaction may be conventional in the art, and is preferably a platinum mesh electrode.

S2, the electrolyte used in the in situ electrochemical reaction is conventional in the art, and is preferably bicarbonate, such as KHCO₃An aqueous solution.

In S2, the concentration of the electrolyte used in the in-situ electrochemical reaction may be conventional in the art, and is preferably 0.4-0.6M, such as 0.5M.

In S2, the potential used in the in-situ electrochemical reaction can be conventional in the art, and is preferably-1.1 to-0.9V_RHEFor example-1.0V_RHE。

In S2, the time used in the in-situ electrochemical reaction is preferably 0.5 to 1.5 hours, for example, 1 hour.

In a preferred embodiment, the bismuth-based-silver-based composite material can be prepared by the following method:

taking 10mg of bismuth vanadate-silver nanowire precatalyst, sequentially adding 1mL of absolute ethyl alcohol and 40 mu L of naphthol solution, dispersing the precatalyst by ultrasonic wave for 30min, uniformly dripping 100 mu L of dispersion liquid on 1cm by 1cm of carbon paper, drying for 1h at 50 ℃, and taking out. Subjecting the material to 0.5M KHCO₃In aqueous solution at-1.0V_RHEAnd carrying out electrochemical reduction for 1h under the potential to obtain the bismuth-based-silver-based composite material.

The invention also provides a bismuth-based-silver-based composite material which is prepared by adopting the preparation method.

In the invention, the diameter of the maximum circumscribed circle of the bismuth nanosheet in the bismuth-based-silver-based composite material can be 6-8 nm.

The invention also provides application of the bismuth-based-silver-based composite material as a catalyst in preparation of formate by electrocatalytic reduction of carbon dioxide.

In the present invention, the reaction for preparing formate by electrocatalytic reduction of carbon dioxide is preferably prepared according to the following steps:

the bismuth-based-silver-based composite material is used as a cathode of a three-electrode system and is connected to an electrochemical workstation through an electrode clamp, after gas chromatography is stable, the electrochemical workstation is opened to start reaction, and sample injection is carried out within a fixed time interval.

Wherein, in the three-electrode system, the adopted reaction electrolyte can be conventional in the field, such as KHCO₃And (3) solution.

Wherein, in the three-electrode system, the concentration of the adopted electrolyte can be conventional in the field, and is preferably 0.5M.

Wherein, in the three-electrode system, the reaction vessel adopted can be conventional in the field, such as an H-type electrolytic cell.

In the three-electrode system, the electrode clip material used can be conventional in the art, such as a gold electrode clip.

In the three-electrode system, the counter electrode used can be conventional in the art, and is preferably an Ag/AgCl electrode.

In the three-electrode system, the reference electrode used can be conventional in the art, and is preferably a platinum mesh electrode.

Wherein the column oven temperature for the gas chromatography may be conventional in the art, e.g. 80 ℃.

Wherein the inlet temperature of the gas chromatograph may be conventional in the art, such as 150 ℃.

Wherein the detector temperature of the gas chromatograph may be conventional in the art, e.g., 150 ℃.

Wherein the detector current of the gas chromatograph may be conventional in the art, e.g. 60 mA.

Wherein the argon carrier gas pressure for the gas chromatograph may be conventional in the art, such as 0.3 MPa.

In a preferred embodiment, the application of the bismuth-based-silver-based composite material as a catalyst in the reaction of preparing formate by electrocatalytic reduction of carbon dioxide can be realized by the following method:

using 0.5M KHCO₃The solution is used as reaction electrolyte, and an H-shaped electrolytic cell of a three-electrode system is used as a reaction container. Clamping an S-Bi/Ag sample on a gold electrode clamp to serve as a cathode of a three-electrode system, sequentially installing an Ag/AgCl electrode (reference solution is 3.5M KCl aqueous solution) serving as a reference electrode and a platinum mesh electrode (counter electrode) with the area of 1cm x 1cm on a reaction tank, fixing the reaction tank by using a metal clamp, and adding electrolyte. Then clamping the electrode clamps of the electrochemical workstation on the electrodes in sequence, starting up and enabling the electrodes to be in a use state. And after the gas chromatography is stable, opening a corresponding program of the electrochemical workstation, and starting the electrocatalytic reduction reaction of the carbon dioxide. Injecting sample after a fixed time interval according to a standard curve and a 1mL standard gas signal peak surface in a gas chromatographyThe product was calculated as the gas production of hydrogen and carbon monoxide. In the test process, the parameters of the gas chromatography system are set as follows: the temperature of the column furnace is 80 ℃, the temperature of the injection port is 150 ℃, the temperature of the detector is 150 ℃, the current of the detector is 60mA, and the pressure of argon carrier gas is 0.3 MPa.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows:

(1) the bismuth-based-silver-based composite material is prepared by adopting a surfactant ligand auxiliary loading method and an electrochemical synthesis method, the preparation method is simple, no complex instrument is needed in the synthesis process, the operation is simple and convenient, the cost is low, the condition is mild, the bismuth-based-silver-based composite material is safe and non-toxic, the purity of a target product is high, and the large-scale production is facilitated;

(2) the diameter of the maximum circumscribed circle of the bismuth nanosheet in the bismuth-based-silver-based composite material can be 6-8 nm, the ultra-small size of the bismuth nanosheet is maintained, and the agglomeration and reconstruction of the bismuth nanosheet are effectively inhibited, so that the electrochemical active area and edge active sites are increased, and the reaction activity and the cathode energy efficiency in the electrocatalytic reduction of carbon dioxide are effectively improved. The bismuth-based-silver-based composite material disclosed by the invention also has potential application performance in the fields of other energy development and environmental protection.

(3) The bismuth-based-silver-based composite material can realize high faradaic efficiency of formate, high cathode energy efficiency and high current density of formate under industrial-grade heavy current in the reaction of preparing formate by electrocatalysis of carbon dioxide.

Drawings

FIG. 1 is a low resolution TEM of a bismuth-based-silver-based composite prepared in example 2.

FIG. 2 is a high resolution TEM of a bismuth-based-silver-based composite prepared in example 2, where the dashed lines depict ultra-small bismuth nanosheet catalysts, having a particle size of about 8 nm.

Fig. 3 is an EDX elemental analysis of the bismuth-based-silver-based composite material prepared in example 2. Wherein, fig. 3a is a high resolution scanning projection electron microscope image of the bismuth-based-silver-based composite material prepared in example 2, fig. 3b is an element scan of Bi, fig. 3c is an element scan of Ag, and fig. 3d is an element scan of Ag and Bi.

Fig. 4 is an XRD pattern of the bismuth-based-silver-based composite material prepared in example 2.

FIG. 5 is a graph of performance of the bismuth-based-silver-based composite material prepared in example 2 in an H-type electrolytic cell as a formate electrocatalyst for electrocatalytic reduction of carbon dioxide. Wherein, FIG. 5a is a graph of formate Faraday efficiency, and FIG. 5b is a graph of formate current density.

FIG. 6 is a graph of Faraday efficiency of the bismuth-based-silver-based composite material prepared in example 2 as a formate electrocatalyst for electrocatalytic reduction of carbon dioxide in a flow cell. Wherein, FIG. 6a is 1M KHCO₃FIG. 6b shows 1M KOH as the electrolyte.

FIG. 7 is a graph showing the stability test of the bismuth-based-silver-based composite material prepared in example 2 as a formate electrocatalyst for electrocatalytic reduction of carbon dioxide.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Example 1

S1: adding 138mg of polyvinylpyrrolidone into 130mL of ethylene glycol, heating the mixed solution to 175 ℃, and quickly injecting 2mL of ethylene glycol in which 8mg of copper chloride dihydrate is dissolved; 484.5mg of silver nitrate is dissolved in 30mL of ethylene glycol, the solution is added into the reaction system at the speed of 180mL/h, and the reaction is continued for 10 min; and after the reaction is finished, washing the product for several times by using deionized water and absolute ethyl alcohol, and drying at the temperature of 60 ℃ to prepare the silver nanowire.

S2: 20mg of silver nanowires are added into 60mL of ethylene glycol, and after uniform ultrasonic dispersion, 110.5mg of bismuth chloride, 52.5mg of hexadecyl trimethyl ammonium bromide and 140mg of sodium vanadate are sequentially added under the stirring condition. Stirring for 30min, dissolvingThe solution was transferred to a 100mL hydrothermal kettle and heated at 120 ℃ for 12 hours. Washing the product with deionized water and absolute ethyl alcohol for several times, vacuum drying at 50 ℃ for 24h, and taking out to obtain bismuth vanadate-silver nanowire precatalyst (marked as BiVO)₄/Ag(1:4))。

S3: 10mg of BiVO₄the/Ag (1:4) powder was poured into a 3mL straight-mouth screw glass bottle, and 1mL of absolute ethanol and 40. mu.L of naphthol solution were sequentially taken. After the pre-catalyst was dispersed with ultrasound for 30min, 100 μ L of the dispersion was uniformly dropped on 1cm by 1cm carbon paper, the material was dried at 50 ℃ for 1h and then taken out. Subjecting the material to 0.5M KHCO₃In aqueous solution at-1.0V_RHEAnd electrochemically reducing for 1h at a potential to obtain the bismuth-based-silver-based composite material (recorded as S-Bi/Ag (1: 4)).

Example 2

S2: adding 20mg of silver nanowires into 60mL of ethylene glycol, uniformly dispersing by ultrasonic, and sequentially adding 221mg of bismuth chloride, 105mg of hexadecyl trimethyl ammonium bromide and 280mg of sodium vanadate under the stirring condition. After stirring for 30min, the solution was transferred to a 100mL hydrothermal kettle and heated at 120 ℃ for 12 h. Washing the product with deionized water and absolute ethyl alcohol for several times, vacuum drying at 50 ℃ for 24h, and taking out to obtain bismuth vanadate-silver nanowire precatalyst (marked as BiVO)₄/Ag(1:2))。

S3: 10mg of BiVO₄the/Ag (1:2) powder was poured into a 3mL straight-mouth screw glass bottle, and 1mL of absolute ethanol and 40. mu.L of naphthol solution were sequentially taken. After the pre-catalyst was dispersed with ultrasound for 30min, 100 μ L of the dispersion was uniformly dropped on 1cm by 1cm carbon paper, the material was dried at 50 ℃ for 1h and then taken out. Subjecting the material to 0.5M KHCO₃In aqueous solution at-1.0V_RHEElectrochemical reduction at potential 1h, obtaining the bismuth-based-silver-based composite material (recorded as S-Bi/Ag).

Example 3

S2: adding 20mg of silver nanowires into 60mL of ethylene glycol, uniformly dispersing by ultrasonic, and sequentially adding 442mg of bismuth chloride, 210mg of hexadecyl trimethyl ammonium bromide and 560mg of sodium vanadate under the stirring condition. After stirring for 30min, the solution was transferred to a 100mL hydrothermal kettle and heated at 120 ℃ for 12 h. Washing the product with deionized water and absolute ethyl alcohol for several times, vacuum drying at 50 ℃ for 24h, and taking out to obtain bismuth vanadate-silver nanowire precatalyst (marked as BiVO)₄/Ag(1:1))。

S3: 10mg of BiVO₄the/Ag (1:1) powder was poured into a 3mL straight-mouth screw glass bottle, and 1mL of absolute ethanol and 40. mu.L of naphthol solution were sequentially taken. After the pre-catalyst was dispersed with ultrasound for 30min, 100 μ L of the dispersion was uniformly dropped on 1cm by 1cm carbon paper, the material was dried at 50 ℃ for 1h and then taken out. Subjecting the material to 0.5M KHCO₃In aqueous solution at-1.0V_RHEAnd electrochemically reducing for 1h at a potential to obtain the bismuth-based-silver-based composite material (recorded as S-Bi/Ag (1: 1)).

Comparative example 1

S1: 60mL of ethylene glycol was weighed into a 100mL beaker, and 221mg of bismuth chloride, 105mg of cetyltrimethylammonium bromide and 280mg of sodium vanadate were added in this order with stirring. After stirring for 30min, the solution was transferred to a 100mL hydrothermal kettle and heated at 120 ℃ for 12 h. Washing the product with deionized water and absolute ethyl alcohol for several times, then vacuum-drying at 50 ℃ for 24h, and taking out to obtain bismuth vanadate (marked as BiVO)₄)。

S2: 10mg of BiVO₄Pouring the powder into a 3mL straight-mouth threaded glass bottle, and sequentially taking 1mL of anhydrous ethyl acetateAlcohol and 40. mu.L naphthol solution. After the pre-catalyst was dispersed with ultrasound for 30min, 100 μ L of the dispersion was uniformly dropped on 1cm by 1cm carbon paper, the material was dried at 50 ℃ for 1h and then taken out. Subjecting the material to 0.5M KHCO₃In aqueous solution at-1.0V_RHEAnd electrochemically reducing for 1h under the potential to obtain the bismuth nanosheet catalyst (recorded as L-Bi).

Effect example 1 morphological characterization of bismuth-based silver-based composite Material

TEM characterization and EDX elemental analysis (Talos) were performed on the S-Bi/Ag sample obtained in example 2. In the figures 1-3, the bismuth-based material is a nanosheet with the circumscribed circle diameter of 6-8 nm, and is uniformly supported on the surface of a silver nanowire with the diameter of 60-80 nm.

Effect example 2 structural characterization of bismuth-based silver-based composite Material

XRD (D/MAX 2550VB/PC) was performed on the S-Bi/Ag sample obtained in example 2. FIG. 4 is an XRD pattern of S-Bi/Ag prepared in example 2. As can be seen from FIG. 4, the diffraction peaks of the bismuth nanosheets of the composite material of the present invention all correspond to the bismuth standard JCPDS card one to one, indicating that the bismuth nanosheets are successfully synthesized. Meanwhile, the diffraction peak of XRD is sharper, which shows that the crystallinity is better.

Effect example 3 detection of the Performance of electrocatalytic reduction of carbon dioxide

Using 0.5M KHCO₃The solution is used as reaction electrolyte, and an H-shaped electrolytic cell of a three-electrode system is used as a reaction container. The S-Bi/Ag sample obtained in example 2 and the L-Bi sample obtained in comparative example 1 were respectively clamped on a gold electrode holder as a cathode of a three-electrode system, and then an Ag/AgCl electrode (reference solution is 3.5M KCl aqueous solution) as a reference electrode and a platinum mesh electrode having an area of 1cm x 1cm as a counter electrode were sequentially mounted on a reaction cell, the reaction cell was fixed using a metal holder, and an electrolyte was added. Then clamping the electrode clamps of the electrochemical workstation on the electrodes in sequence, starting up and enabling the electrodes to be in a use state. And after the gas chromatography is stable, opening a corresponding program of the electrochemical workstation, and starting the electrocatalytic reduction reaction of the carbon dioxide. Injecting sample after a fixed time interval, and calculating the gas of hydrogen and carbon monoxide according to the standard curve and the peak area of a 1mL standard gas signal in a gas chromatogramVolume production. In the test process, the parameters of the gas chromatography system are set as follows: the temperature of the column furnace is 80 ℃, the temperature of the injection port is 150 ℃, the temperature of the detector is 150 ℃, the current of the detector is 60mA, and the pressure of argon carrier gas is 0.3 MPa.

FIG. 5 is a graph showing the performance of the bismuth-based-silver-based composite material prepared in example 2 and the L-Bi sample obtained in comparative example 1 in an H-type electrolytic cell, respectively, as a formate electrocatalyst prepared by electrocatalytic reduction of carbon dioxide. Wherein, FIG. 5a is a graph of formate Faraday efficiency, and FIG. 5b is a graph of formate current density. Specific data are shown in table 1 below.

The S-Bi/Ag sample obtained in example 2 and the L-Bi sample obtained in comparative example 1 were subjected to potentiostatic test in a potential range of-0.7 to-1.2V, respectively. In FIG. 5a, S-Bi/Ag exhibited the most excellent Faraday efficiency of formic acid (94.7% at-1.0V); the faradaic efficiency of the L-Bi formate can reach 85% at all applied potentials. In FIG. 5b, the formic acid partial current density of S-Bi/Ag at-1.2V reached-45.5 mA cm^-2Greater than L-Bi at each potential, indicating CO for S-Bi/Ag₂The reduction activity is higher.

TABLE 1

To satisfy CO₂The practical application of electrochemical conversion into formic acid requires that the current density is more than 100mA cm^-2. The H-shaped electrolytic cell in the performance detection of the electrocatalytic reduction of carbon dioxide is replaced by a flowing electrolytic cell for testing, wherein the S-Bi/Ag composite material obtained in the example 2 is used as a cathode, the porous foamed nickel is used as an anode, and the saturated Ag/AgCl electrode is used as a reference electrode. Use of flow cells to overcome CO in aqueous electrolytes in H-type cells₂Mass transfer limitation, further evaluating the electrocatalytic reduction carbon dioxide performance of S-Bi/Ag. FIG. 6 shows a bismuth base prepared in example 2 in a flow cellFaradaic efficiency diagram of the silver-based composite as an electrocatalytic reduction of carbon dioxide for the preparation of formate electrocatalysts. Wherein, FIG. 6a is 1M KHCO₃FIG. 6b shows 1M KOH as the electrolyte. At-50 to-250 mA^-2The constant current test is carried out in the total current range of (1), and the specific data are shown in the following table 2.

At 200mA cm^-2The Faraday efficiency of the formate of S-Bi/Ag is 1.0M KHCO at high current density₃And the formate faradaic efficiencies of S-Bi/Ag in the 1.0M KOH electrolyte were 95.7% and 92.8%, respectively, calculating the highest cathode energy efficiency of 74.6%. The cathode Energy Efficiency (EE) of formate was calculated using the following formula_ca)：

Wherein E is_formate＝-0.2V_RHEIs the thermodynamic voltage, FE, of the reduction of carbon dioxide to formate_formateIs the Faraday efficiency of formate production, E_appliedIs the application of a voltage.

TABLE 2

FIG. 7 is a graph showing the stability test of the bismuth-based-silver-based composite material prepared in example 2 as a formate electrocatalyst for electrocatalytic reduction of carbon dioxide. The specific data are shown in the following table 3, and the Faraday efficiencies and the partial current densities of the prepared formate are respectively 92.7 percent and 22.8mA cm when the overpotential is 0.69V in the test process^-2. Meanwhile, the yield of formate does not obviously decrease after 12h of reaction, which indicates that the formate has very good stability.

TABLE 3

Claims

1. a preparation method of bismuth-silver-based composite material, is characterized in that, it comprises the following steps:

S1: silver nanowires, bismuth chloride, hexadecyltrimethylamine bromide and sodium vanadate are hydrothermally reacted to obtain a bismuth vanadate-silver nanowire precatalyst;

S2: A substrate coated with a bismuth vanadate-silver nanowire precatalyst is used as a working electrode, and a bismuth-silver-based composite material is prepared on the substrate through an in-situ electrochemical reaction.

2 . The method for preparing a bismuth-silver-based composite material according to claim 1 , wherein the diameter of the silver nanowires is 60-100 nm, preferably 60-80 nm. 3 .

3. the preparation method of bismuth-based-silver-based composite material as claimed in claim 1, is characterized in that, described silver nanowire is obtained by carrying out mixing reaction with cupric chloride dihydrate, polyvinylpyrrolidone and silver nitrate, It is preferably prepared by the following steps:

S11 adding copper chloride dihydrate into the polyvinylpyrrolidone solution to obtain a mixed solution;

S12 Add silver nitrate into the mixed solution, and prepare the silver nanowires through the reaction.

4. The method for preparing a bismuth-silver-based composite material according to claim 3, wherein the reaction temperature of the polyvinylpyrrolidone solution is 170-180°C, preferably 175°C;

And/or, the solvent in the polyvinylpyrrolidone solution is ethylene glycol;

And/or, the concentration of the polyvinylpyrrolidone is 1.04-1.08 mg/mL, preferably 1.06 mg/mL;

And/or, the copper chloride dihydrate is added in the form of a solution, and the solvent in the solution is ethylene glycol;

When the cupric chloride dihydrate is added in the form of a solution, the concentration of cupric chloride dihydrate is preferably 3-5 mg/mL, more preferably 4 mg/mL;

And/or, the silver nitrate is added in the form of a solution, and the solvent in the solution is ethylene glycol;

When the silver nitrate is added in the form of a solution, the concentration of the silver nitrate solution is preferably 15.67-16.67 mg/mL, more preferably 16.15 mg/mL;

When the silver nitrate is added in the form of a solution, the addition rate of the silver nitrate solution is preferably 180 mL/h;

And/or, the mixing reaction time is 5-15 min, preferably 10 min.

5. the preparation method of bismuth-based-silver-based composite material as claimed in claim 3, is characterized in that, the mass ratio of described silver nitrate, described polyvinylpyrrolidone and described copper chloride dihydrate is (16～20 ): (18-24): 1, preferably 17.25: 21.875: 1.

6. The method for preparing a bismuth-silver-based composite material according to claim 1, wherein the silver nanowires, the bismuth chloride, the cetyltrimethylamine bromide and the The mass ratio of the sodium vanadate is 1:(8-15):(4-6):(12-16), preferably 1:11.05:5.25:14;

And/or, the temperature of the hydrothermal reaction is 100-140°C, preferably 120°C;

And/or, the time of the hydrothermal reaction is 10～14h, preferably 12h;

And/or, the bismuth vanadate-silver nanowire pre-catalyst is prepared by the following steps: adding the bismuth chloride, the hexadecyl trimethyl amine bromide and the sodium vanadate in turn containing In the solution of the silver nanowires, the hydrothermal reaction can be carried out;

Preferably, in the solution containing the silver nanowires, the solvent used is an alcohol solvent, such as ethylene glycol;

Preferably, the solution containing the silver nanowires is dispersed by ultrasonic;

Preferably, in the solution containing the silver nanowires, the concentration of the silver nanowires is 0.25-0.42 mg/mL, more preferably 0.33 mg/mL;

Preferably, the pre-mixing time of each raw material for the hydrothermal reaction is 20-40 min, more preferably 30 min.

7. The preparation method of bismuth-silver-based composite material as claimed in claim 1, wherein the base material is carbon paper;

And/or, the working electrode is prepared by the following steps: coating the dispersion liquid containing the bismuth vanadate-silver nanowire precatalyst and the binder on the substrate, and drying;

Preferably, the binder is a naphthol solution;

Preferably, the mass-volume ratio of the bismuth vanadate-silver nanowire pre-catalyst and the binder is (1-3) mg:8 μL, more preferably 1 mg: 4 μL;

Preferably, in the dispersion liquid containing the bismuth vanadate-silver nanowire precatalyst and the binder, the concentration of the bismuth vanadate-silver nanowire precatalyst is 0.05-0.15 mg/μL, more preferably 0.10 mg /μL;

Preferably, in the dispersion liquid containing the bismuth vanadate-silver nanowire precatalyst and the binder, the type of solvent used is an alcohol solvent, such as absolute ethanol;

Preferably, the coating method is drop coating;

Preferably, in the preparation process of the working electrode, the drying operation and conditions are drying at 50-60° C. for 1 hour;

Preferably, on the substrate, the effective content of the bismuth vanadate-silver nanowire precatalyst is 0.5-1.5 mg/cm ² , more preferably 1 mg/cm ² ;

Preferably, on the substrate, the effective content of the binder is 0.2-0.5 μL/cm ² , more preferably 0.4 μL/cm ² ;

Preferably, in the in-situ electrochemical reaction, the counter electrode is an Ag/AgCl electrode;

Preferably, in the in-situ electrochemical reaction, the reference electrode is a platinum mesh electrode;

Preferably, in the in-situ electrochemical reaction, the electrolyte is bicarbonate, such as _KHCO aqueous solution;

Preferably, in the in-situ electrochemical reaction, the electrolyte concentration is 0.4-0.6M, more preferably 0.5M;

Preferably, in the in-situ electrochemical reaction, the potential is -1.1 to -0.9V _RHE , more preferably -1.0V _RHE ;

Preferably, in the in-situ electrochemical reaction, the reaction time is 0.5-1.5 h, more preferably 1 h.

8. A bismuth-silver-based composite material, characterized in that, it is prepared according to the preparation method for a bismuth-based-silver-based composite material according to any one of claims 1 to 7.

9 . The bismuth-silver-based composite material according to claim 8 , wherein the diameter of the maximum circumscribed circle of the bismuth nanosheets in the bismuth-based-silver-based composite material is 6-8 nm. 10 .

10. The application of a bismuth-based silver-based composite material as claimed in claim 8 or 9 as a catalyst in the electrocatalytic reduction of carbon dioxide to prepare a formate reaction.