1. A catalyst for electrocatalytic carbon dioxide reduction reaction comprises a three-dimensional porous carbon skeleton, and nickel metal monoatomic atoms and nitrogen atoms anchored on the three-dimensional porous carbon skeleton; boron element doped into the three-dimensional porous carbon skeleton; the nickel metal monoatomic, nitrogen atom and boron element form Ni-N₄B₂An active site.

2. The catalyst for electrocatalytic carbon dioxide reduction reaction according to claim 1, wherein the mass of the nickel metal monoatomic atom is 1.31 to 2.38% of the mass of the three-dimensional porous carbon skeleton, the mass of the nitrogen atom is 13 to 14% of the mass of the three-dimensional porous carbon skeleton, and the mass of the boron element is 4.5 to 10% of the mass of the three-dimensional porous carbon skeleton.

3. The catalyst for electrocatalytic carbon dioxide reduction reaction according to claim 1 or 2, wherein the BET surface area of the catalyst for electrocatalytic carbon dioxide reduction reaction is 700 to 720m²/g。

4. A method for producing a catalyst for electrocatalytic carbon dioxide reduction reaction according to any one of claims 1 to 3, comprising the steps of:

mixing sodium chloride, glucose, nickel acetate tetrahydrate, boric acid and water, and freeze-drying to obtain a precursor;

sequentially carbonizing and roasting the precursor to obtain the catalyst for the electrocatalytic carbon dioxide reduction reaction;

the carbonizing includes: under the condition of protective atmosphere, after the temperature is increased to a first carbonization temperature at a first temperature increasing rate, under the condition of mixed atmosphere of ammonia gas and argon gas, the temperature is continuously increased to a second carbonization temperature at the first temperature increasing rate, under the condition of protective atmosphere, the temperature is continuously increased to a third carbonization temperature at the first temperature increasing rate, and then first heat preservation is carried out under the conditions of mixed atmosphere of ammonia gas and argon gas and the third carbonization temperature; and then carrying out second heat preservation under the conditions of protective atmosphere and third carbonization temperature.

5. The method according to claim 4, wherein the mass ratio of the sodium chloride to the glucose to the nickel acetate tetrahydrate to the boric acid is 10000: 750: 12: (20-40).

6. The method according to claim 4, wherein the freeze-drying comprises sequentially freezing and drying; the freezing temperature is-50 ℃, and the time is 12-18 h; the drying temperature is-50 ℃, the pressure is 1-10 Pa, and the time is 48-50 h.

7. The method according to claim 4, wherein the first carbonization temperature is 230 to 240 ℃; the second carbonization temperature is 400 ℃; the third carbonization temperature is 700 ℃; the first heat preservation time is 15-30 min; and the second heat preservation time is 1.5-2.5 h.

8. The production method according to claim 4, wherein the atmosphere of the firing is a protective atmosphere; the roasting temperature is 1000 ℃, and the roasting time is 0.5-1 h.

9. Use of the catalyst for electrocatalytic carbon dioxide reduction reaction according to any one of claims 1 to 3 or the catalyst for electrocatalytic carbon dioxide reduction reaction obtained by the production method according to any one of claims 4 to 8 in an electrocatalytic carbon dioxide reduction reaction, comprising the steps of:

taking platinum as a counter electrode, an Ag/AgCl electrode as a reference electrode, a glassy carbon electrode loaded with a catalyst as a working electrode, and a potassium bicarbonate solution as an electrolyte, and carrying out a reduction reaction under the condition of introducing carbon dioxide;

the loading capacity of the catalyst is 0.10-0.30 mg/cm²；

The catalyst is the catalyst for electrocatalytic carbon dioxide reduction reaction according to any one of claims 1 to 3 or the catalyst for electrocatalytic carbon dioxide reduction reaction obtained by the preparation method according to any one of claims 4 to 8.

10. Use according to claim 9, wherein the parameters of the reduction reaction comprise: the temperature is 25 ℃; the pressure is a standard atmospheric pressure; the reduction potential range is-0.6 to-1.2V relative to the reversible hydrogen electrode.

Background

Carbon dioxide is reduced into chemical raw materials through electrocatalysis, and a promising strategy is provided for promoting global carbon balance. However, since the kinetics of the electrocatalytic carbon dioxide reduction reaction are low and the accompanying side reactions are severe, a carbon dioxide reduction reaction catalyst having both high catalytic activity and high selectivity is still the object of the present search.

The traditional electrocatalytic carbon dioxide reduction catalyst comprises Cu, Au, Ag and alloy thereof, and has larger defects in the aspect of catalytic performance. The single-atom catalyst which is recently developed has relative advantages, but has shortcomings in the aspect of catalytic performance, mainly reflected in low selectivity of products under high current density. Therefore, in response to this problem, it is of practical significance and challenging to design a monatomic catalyst that still has high selectivity at high current densities.

Disclosure of Invention

In view of the above, the present invention provides a catalyst for electrocatalytic carbon dioxide reduction reaction, and a preparation method and an application thereof. The catalyst for the electrocatalytic carbon dioxide reduction reaction provided by the invention still has high selectivity under high current density.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a catalyst for electrocatalysis carbon dioxide reduction reaction, which comprises a three-dimensional porous carbon skeleton, and a nickel metal monoatomic atom and a nitrogen atom which are anchored on the three-dimensional porous carbon skeleton; boron element doped into the three-dimensional porous carbon skeleton; the nickel metal monoatomic, nitrogen atom and boron element form Ni-N₄B₂An active site.

Preferably, the mass of the nickel metal monoatomic atom is 1.31-2.38% of the mass of the three-dimensional porous carbon skeleton, the mass of the nitrogen atom is 13-14% of the mass of the three-dimensional porous carbon skeleton, and the mass of the boron element is 4.5-10% of the mass of the three-dimensional porous carbon skeleton.

Preferably, the BET surface area of the catalyst for the electrocatalytic carbon dioxide reduction reaction is 700-720 m²/g。

The invention also provides a preparation method of the catalyst for the electrocatalytic carbon dioxide reduction reaction, which comprises the following steps:

mixing sodium chloride, glucose, nickel acetate tetrahydrate, boric acid and water, and freeze-drying to obtain a precursor;

sequentially carbonizing and roasting the precursor to obtain the catalyst for the electrocatalytic carbon dioxide reduction reaction;

the carbonizing includes: under the condition of protective atmosphere, after the temperature is increased to a first carbonization temperature at a first temperature increasing rate, under the condition of mixed atmosphere of ammonia gas and argon gas, the temperature is continuously increased to a second carbonization temperature at the first temperature increasing rate, under the condition of protective atmosphere, the temperature is continuously increased to a third carbonization temperature at the first temperature increasing rate, and then first heat preservation is carried out under the conditions of mixed atmosphere of ammonia gas and argon gas and the third carbonization temperature; and then carrying out second heat preservation under the conditions of protective atmosphere and third carbonization temperature.

Preferably, the mass ratio of the sodium chloride to the glucose to the nickel acetate tetrahydrate to the boric acid is 10000: 750: 12: (20-40).

Preferably, the freeze-drying comprises sequentially freezing and drying; the freezing temperature is-50 ℃, and the time is 12-18 h; the drying temperature is-50 ℃, the pressure is 1-10 Pa, and the time is 48-50 h.

Preferably, the first carbonization temperature is 230-240 ℃; the second carbonization temperature is 400 ℃; the third carbonization temperature is 700 ℃; the first heat preservation time is 15-30 min; and the second heat preservation time is 1.5-2.5 h.

Preferably, the roasting atmosphere is a protective atmosphere; the roasting temperature is 1000 ℃, and the roasting time is 0.5-1 h.

The invention also provides an application of the catalyst for electrocatalytic carbon dioxide reduction reaction in the technical scheme or the catalyst for electrocatalytic carbon dioxide reduction reaction obtained by the preparation method in the technical scheme in electrocatalytic carbon dioxide reduction reaction, which comprises the following steps:

taking platinum as a counter electrode, an Ag/AgCl electrode as a reference electrode, a glassy carbon electrode loaded with a catalyst as a working electrode, and a potassium bicarbonate solution as an electrolyte, and carrying out a reduction reaction under the condition of introducing carbon dioxide;

the loading capacity of the catalyst is 0.10-0.30 mg/cm²；

The catalyst is the catalyst for the electrocatalytic carbon dioxide reduction reaction in the technical scheme or the catalyst for the electrocatalytic carbon dioxide reduction reaction obtained by the preparation method in the technical scheme.

Preferably, the parameters of the reduction reaction include: the temperature is 25 ℃; the pressure is a standard atmospheric pressure; the reduction potential range is-0.6 to-1.2V relative to the reversible hydrogen electrode.

The invention provides a catalyst for electrocatalysis carbon dioxide reduction reaction, which comprises a three-dimensional porous carbon skeleton, and a nickel metal monoatomic atom and a nitrogen atom which are anchored on the three-dimensional porous carbon skeleton; boron element doped into the three-dimensional porous carbon skeleton; the nickel metal monoatomic, nitrogen atom and boron element form Ni-N₄B₂An active site. In the catalyst, the three-dimensional porous carbon skeleton is doped with boron element, and the boron element, nitrogen atom and nickel metal monoatomic atom form Ni-N₄B₂The coordination environment of the center of the active site is changed by the doping of the active site, namely boron. Relative to the catalytic site NiN₄In other words, the doping of boron allows the catalytic sites NiN₄B₂The adsorption capacity to reactants CO and an intermediate COOH is improved, the desorption capacity to a product carbon monoxide is improved, and the free energy change of a reaction path is represented as follows: BNC-SANi reduces CO in the main reaction velocity-dependent step₂+*+H⁺+e^-Reaction barrier of → COOH, thereby promoting the occurrence of main reaction. In addition, BNC-SANi increased HER side-reactive H⁺+e^-→H^*The potential barrier for the reaction suppresses the progress of the side reaction. Combining the above analysis, BNC-SANi has an accelerating effect on the main reaction and an inhibiting effect on the side reaction, thereby improving the selectivity to the product, namely the Faraday efficiency of carbon monoxide. Meanwhile, the doping of boron can enhance the adsorption of Ni atoms in the center of the site to carbon dioxide serving as a reactant, so that the adsorption of the Ni atoms in the center of the site to carbon dioxide is enhancedThe utilization of reactants is more sufficient, so that the reaction rate is accelerated, and the catalytic activity is improved.

The invention also provides a preparation method of the catalyst for the electrocatalytic carbon dioxide reduction reaction, which comprises the following steps: mixing sodium chloride, glucose, nickel acetate tetrahydrate, boric acid and water, and freeze-drying to obtain a precursor; sequentially carbonizing and roasting the precursor to obtain the catalyst for the electrocatalytic carbon dioxide reduction reaction; the carbonizing includes: under the condition of protective atmosphere, after the temperature is increased to the first carbonization temperature at the first temperature increasing rate, the temperature is continuously increased to the second carbonization temperature at the first temperature increasing rate under the atmosphere of ammonia gas, the temperature is continuously increased to the third carbonization temperature at the first temperature increasing rate under the condition of protective atmosphere, and then first heat preservation is carried out under the atmosphere of ammonia gas and the condition of the third carbonization temperature; and then carrying out second heat preservation under the conditions of protective atmosphere and third carbonization temperature. According to the preparation method, in the carbonization process, boric acid is decomposed into boron element and is doped into a carbon skeleton formed by the carbonization of glucose; simultaneously, boron element is doped into Ni-N₄Near two N sites, Ni-N is formed₄B₂A site. Namely, the doping of the boron element changes the coordination environment of the active site center, thereby improving the Ni-N content of the catalyst in the electrocatalytic carbon dioxide reduction process₄Faradaic efficiency of the product at high current density of the site.

The data of the examples show that: the catalyst obtained in example 1 was supported on a gas diffusion electrode, and the current density of the catalyst reached 213. + -. 30mA cm at a potential of-1.2V^-2The faradaic efficiency of the product carbon monoxide at this potential is as high as 97.37%.

Drawings

FIG. 1 is a scanning electron micrograph of a catalyst obtained in example 1;

FIG. 2 is a transmission electron micrograph of the catalyst obtained in example 1;

FIG. 3 is a Fourier transform spectrum of the Ni K-edge EXAFS spectra of the catalysts obtained in example 1 and comparative example 1;

FIG. 4 is a Fourier transform fit spectrum of the Ni K-edge EXAFS spectrum of the catalyst obtained in example 1;

FIG. 5 shows different catalyst materials in an H-type electrolytic cell, CO₂Saturated 0.5mol/LKHCO₃Linear sweep voltammograms in solution;

FIG. 6 is a graph of carbon monoxide faradaic efficiency for different catalyst materials at different potentials (relative to RHE) in a type H cell;

FIG. 7 is a graph of current density for reduction of carbon dioxide to carbon monoxide at different potentials (relative to RHE) in a gas diffusion electrode;

figure 8 is the faradaic efficiency of the product of the catalyst obtained in example 1at various potentials (relative to RHE) in the gas diffusion electrode.

Detailed Description

The invention provides a catalyst for electrocatalysis carbon dioxide reduction reaction, which comprises a three-dimensional porous carbon skeleton, and a nickel metal monoatomic atom and a nitrogen atom which are anchored on the three-dimensional porous carbon skeleton; boron element doped into the three-dimensional porous carbon skeleton; the nickel metal monoatomic, nitrogen atom and boron element form Ni-N₄B₂An active site.

In the invention, the mass of the nickel metal monoatomic atom is preferably 1.31-2.38%, more preferably 2.2-2.4%, and even more preferably 2.38% of the mass of the three-dimensional porous carbon skeleton. In the present invention, the mass of the nitrogen atom is preferably 13 to 14%, and more preferably 13.5% of the mass of the three-dimensional porous carbon skeleton. In the present invention, the mass of the boron element is preferably 4.5 to 9%, and more preferably 8.62% of the mass of the three-dimensional porous carbon skeleton.

In the invention, the BET surface area of the catalyst for electrocatalytic carbon dioxide reduction reaction is preferably 700-720 m²/g。

The invention also provides a preparation method of the catalyst for the electrocatalytic carbon dioxide reduction reaction, which comprises the following steps:

mixing sodium chloride, glucose, nickel acetate tetrahydrate, boric acid and water, and freeze-drying to obtain a precursor;

and sequentially carbonizing and roasting the precursor to obtain the catalyst for the electrocatalytic carbon dioxide reduction reaction.

In the present invention, the starting materials used in the present invention are preferably commercially available products unless otherwise specified.

The method comprises the steps of mixing sodium chloride, glucose, nickel acetate tetrahydrate, boric acid and water, and carrying out freeze drying to obtain a precursor.

In the present invention, the mass ratio of the sodium chloride, glucose, nickel acetate tetrahydrate and boric acid is preferably 10000: 750: 12: (20-40), and more preferably 10000: 750: 12: 30.

in the present invention, the water is preferably deionized water. In the present invention, the ratio of the water to the glucose is preferably 80 mL: 750 g.

In the present invention, the freeze-drying preferably includes freezing and drying. In the invention, the freezing temperature is preferably-50 ℃, and the time is preferably 12-18 h. In the invention, the drying temperature is preferably-50 ℃, the pressure is preferably 1-10 Pa, and the time is preferably 48-50 h.

After the precursor is obtained, the precursor is sequentially carbonized and roasted to obtain the catalyst for the electrocatalytic carbon dioxide reduction reaction.

In the present invention, the carbonization includes: under the condition of protective atmosphere, after the temperature is increased to a first carbonization temperature at a first temperature increasing rate, under the mixed atmosphere of ammonia gas and argon gas, the temperature is continuously increased to a second carbonization temperature at the first temperature increasing rate, under the condition of protective atmosphere, the temperature is continuously increased to a third carbonization temperature at the first temperature increasing rate, and under the mixed atmosphere of ammonia gas and argon gas and the condition of the third carbonization temperature, first heat preservation is carried out; and then carrying out second heat preservation under the conditions of protective atmosphere and third carbonization temperature.

In the present invention, the first temperature increase rate is preferably 10 ℃/min. In the present invention, the protective atmosphere is preferably nitrogen or argon, and more preferably argon. In the present invention, the volume ratio of ammonia gas to argon gas in the mixed atmosphere of ammonia gas and argon gas is preferably 1: 4. in the present invention, the first carbonization temperature is preferably 230 to 240 ℃, and more preferably 240 ℃. In the present invention, the second carbonization temperature is preferably 400 ℃. In the present invention, the third carbonization temperature is preferably 700 ℃. In the invention, the first heat preservation time is preferably 15-30 min. In the invention, the second heat preservation time is preferably 1.5-2.5 h. In the present invention, the carbonization is preferably performed in a high-temperature tube furnace.

According to the invention, ammonia gas is introduced in the process of raising the temperature from the first carbonization temperature to the second carbonization temperature, so that a nitrogen source can be introduced, nickel atoms can be coordinated with nitrogen atoms and dispersed in the material in a monoatomic form, and the nickel atoms are prevented from agglomerating; introducing ammonia gas at the third carbonization temperature and carrying out first heat preservation can ensure that B, N, Ni is fully coordinated to form Ni-N₄B₂A site. In the invention, in the carbonization process, the glucose is carbonized to form a carbon skeleton; the boric acid and the nickel acetate are decomposed to form Ni-N together with ammonia gas₄B₂An active site.

After the carbonization, the invention preferably directly bakes the obtained carbonized material.

In the present invention, the atmosphere for the calcination is preferably a protective atmosphere, and the protective atmosphere is preferably nitrogen or argon, and more preferably argon. In the invention, the roasting temperature is preferably 1000 ℃, and the roasting time is preferably 0.5-1 h. In the present invention, the second temperature increase rate at which the temperature is increased from the third carbonization temperature to the temperature for calcination is preferably 20 ℃/min. In the present invention, the calcination is preferably carried out in a high-temperature tube furnace.

In the invention, the sodium chloride template can be melted and removed by roasting; meanwhile, the carbon skeleton can be promoted to form more pores; in addition, the oxygen content of the catalyst can be reduced, and the crystallinity of the carbon substrate is improved, so that the conductivity is improved, and the catalytic performance of the catalyst is improved. In the roasting process, the temperature is directly raised to 1000 ℃ by one step, and the NaCl template is melted at about 800 ℃, so that the formed holes are irregular and part of the holes are broken.

The invention also provides the application of the catalyst for the electrocatalytic carbon dioxide reduction reaction or the catalyst for the electrocatalytic carbon dioxide reduction reaction obtained by the preparation method in the technical scheme in the electrocatalytic carbon dioxide reduction reaction.

In the present invention, the application comprises the following steps: platinum is used as a counter electrode, an Ag/AgCl electrode is used as a reference electrode, a glassy carbon electrode loaded with a catalyst is used as a working electrode, a potassium bicarbonate solution is used as an electrolyte, and reduction reaction is carried out under the condition of introducing carbon dioxide.

In the invention, the catalyst is the catalyst for electrocatalytic carbon dioxide reduction reaction described in the above technical scheme or the catalyst for electrocatalytic carbon dioxide reduction reaction obtained by the preparation method described in the above technical scheme. In the invention, the loading amount of the catalyst is preferably 0.10-0.30 mg/cm²，0.28mg/cm²。

In the present invention, the concentration of the potassium bicarbonate solution is preferably 0.1 to 0.5mol/L, and more preferably 0.5 mol/L.

In the present invention, the flow rate of the carbon dioxide is preferably 10 to 20sccm, and more preferably 20 sccm.

In the present invention, the parameters of the reduction reaction include: the temperature is 25 ℃; the pressure is one standard atmosphere, namely 1 atm; the reduction potential range is preferably-0.6 to-1.2V relative to the reversible hydrogen electrode; the voltage range of the Linear Sweep Voltammetry (LSV) is preferably-0.4 to-1.2V, and the sweep rate is preferably 10 mV/s.

The following will explain the catalyst for electrocatalytic carbon dioxide reduction reaction and the preparation method and application thereof in detail with reference to the examples, but they should not be construed as limiting the scope of the present invention.

Example 1

Sodium chloride (10g), glucose (0.75g), boric acid (30mg) and nickel acetate tetrahydrate (12mg) were dissolved in 80mL of deionized water and frozen at-50 ℃ for 12 h; and then drying the obtained material in the frozen state for 48h at the temperature of minus 50 ℃ and under the condition of 1Pa, so as to sublimate ice and obtain a precursor. And then placing the precursor in a high-temperature tube furnace, heating to 240 ℃ at a speed of 10 ℃/min under the atmosphere of argon, and then adding a catalyst in a volume ratio of ammonia gas to argon gas of 1: 4, continuously heating to 400 ℃ at the speed of 10 ℃/min under the mixed atmosphere; then, the temperature is continuously increased to 700 ℃ at the speed of 10 ℃/min under the atmosphere of argon, and then the reaction is carried out in the volume ratio of ammonia gas to argon gas of 1: 4, preserving the heat for 30min in the mixed atmosphere, and preserving the heat for 1.5h in the argon atmosphere; and then raising the temperature to 1000 ℃ at a speed of 20 ℃/min under the atmosphere of argon, and preserving the temperature for 1h to obtain the catalyst, which is named as BNC-SANi.

The mass of a nickel single atom in the obtained catalyst is 2.38% of the mass of a carbon skeleton by XPS (X-ray diffraction) measurement, and the mass of a nitrogen atom is 13.5% of the mass of the carbon skeleton; the mass of the boron element is 8.62 percent of the mass of the carbon skeleton.

FIG. 1 is a scanning electron micrograph of the catalyst obtained in example 1, and it can be seen from FIG. 1 that: the catalyst BNC-SANi has a three-dimensional porous ultrathin carbon skeleton.

FIG. 2 is a transmission electron micrograph of the catalyst obtained in example 1, from which FIG. 2 it can be seen that: the catalyst BNC-SANi did not present macroscopic nickel particles.

Comparative example 1

Sodium chloride (10g), glucose (0.75g) and nickel acetate tetrahydrate (12mg) were dissolved in 80mL of deionized water and frozen at-50 ℃ for 12 h; and then drying the obtained material in the frozen state for 48h at the temperature of minus 50 ℃ and under the condition of 1Pa, so as to sublimate ice and obtain a precursor. And then placing the precursor in a high-temperature tube furnace, heating to 240 ℃ at a speed of 10 ℃/min under the atmosphere of argon, and then adding a catalyst in a volume ratio of ammonia gas to argon gas of 1: 4, continuously heating to 400 ℃ at the speed of 10 ℃/min under the mixed atmosphere; then, the temperature is continuously raised to 700 ℃ at the speed of 10 ℃/min under the atmosphere of argon, and then the reaction is carried out under the condition that the volume ratio of ammonia gas to argon gas is 1: 4, preserving the heat for 30min in the mixed atmosphere, and preserving the heat for 1.5h in the argon atmosphere; and then heating to 1000 ℃ at a speed of 20 ℃/min under the atmosphere of argon, and preserving heat for 1h to obtain the catalyst, which is named as NC-SANi.

Comparative example 2

Sodium chloride (10g), glucose (0.75g) and boric acid (30mg) were dissolved in 80mL of deionized water and frozen at-50 ℃ for 12 h; and then drying the obtained material in the frozen state for 48h at the temperature of minus 50 ℃ and under the condition of 1Pa, so as to sublimate ice and obtain a precursor. And then placing the precursor in a high-temperature tube furnace, heating to 240 ℃ at a speed of 10 ℃/min under the atmosphere of argon, and then adding a catalyst in a volume ratio of ammonia gas to argon gas of 1: 4, continuously heating to 400 ℃ at the speed of 10 ℃/min under the mixed atmosphere; then, the temperature is continuously raised to 700 ℃ at the speed of 10 ℃/min under the atmosphere of argon, and then the reaction is carried out under the condition that the volume ratio of ammonia gas to argon gas is 1: 4, preserving the heat for 30min in the mixed atmosphere, and preserving the heat for 1.5h in the argon atmosphere; and then raising the temperature to 1000 ℃ at a speed of 20 ℃/min under the atmosphere of argon, and preserving the temperature for 1h to obtain the catalyst, which is named as BNC.

Comparative example 3

Sodium chloride (10g) and glucose (0.75g) were dissolved in 80mL deionized water and frozen at-50 ℃ for 12 h; and then drying the obtained material in the frozen state for 48h at the temperature of minus 50 ℃ and under the condition of 1Pa, so as to sublimate ice and obtain a precursor. And then placing the precursor in a high-temperature tube furnace, heating to 240 ℃ at a speed of 10 ℃/min under the atmosphere of argon, and then adding a catalyst in a volume ratio of ammonia gas to argon gas of 1: 4, continuously heating to 400 ℃ at the speed of 10 ℃/min under the mixed atmosphere; then, the temperature is continuously raised to 700 ℃ at the speed of 10 ℃/min under the atmosphere of argon, and then the reaction is carried out under the condition that the volume ratio of ammonia gas to argon gas is 1: 4, preserving the heat for 30min in the mixed atmosphere, and preserving the heat for 1.5h in the argon atmosphere; and then raising the temperature to 1000 ℃ at a speed of 20 ℃/min under the atmosphere of argon, and preserving the temperature for 1h to obtain the catalyst, which is named as NC.

NiO and Ni Foil, commercial products, were purchased.

FIG. 3 is a Fourier transform of the Ni K-edge EXAFS spectra of the catalysts obtained in example 1 and comparative example 1. from FIG. 3, it can be seen that the catalysts BNC-SANi and NC-SANi have only Ni-N bonds and no peaks corresponding to Ni-Ni bonds in Ni Foil and no peaks corresponding to Ni-O bonds in NiO, and these results indicate that Ni in BNC-SANi and NC-SANi exists in a monoatomic form.

FIG. 4 is a Fourier transform fit spectrum of the Ni K-edge EXAFS spectrum of the catalyst obtained in example 1, as can be seen from FIG. 4: the structure of the nickel monoatomic site is NiN₄B₂。

Electrochemical test 1

4mg of the catalyst obtained in example 1 and comparative examples 1 to 3, 0.7mL of deionized water, 0.25mL of ethanol, and 0.05mL of 5 wt% Nafion117 solution to obtain catalyst dispersion liquid; then dropwise adding the catalyst dispersion liquid onto a glassy carbon electrode (diameter of 3mm), and drying in the air to finally obtain the catalyst loading amount of 0.28mg/cm²The working electrode of (1).

The test adopts a three-electrode electrolytic cell structure, the glassy carbon electrode loaded with the catalyst is used as a working electrode, and a platinum foil (1 multiplied by 1 cm)²) As a counter electrode, an Ag/AgCl electrode (E ═ 0.204V) was used as a reference electrode; measurements were performed in a type H cell at room temperature (25 ℃) and ambient pressure using the CHI 760e electrochemical workstation.

Carbon dioxide gas flow was at a constant 20 mL-min throughout the test^-1At a rate of 0.5mol/L KHCO₃Electrolyte (CO)₂Saturation, pH 7.2).

When testing the Linear Sweep Voltametry (LSV) curve, the electrochemical workstation measured at 10 mV. s^-1The scan rate of (a) was used to collect data, and the scan voltage ranged from 0.4V to-1.2V, with the results shown in fig. 5. As can be seen from fig. 5: the current density of the boron element doped BNC-SANi is larger than that of the NC-SANi, which shows that the catalytic activity of the BNC-SANi is higher than that of the NC-SANi without the boron element. While the comparative example without monatomic nickel sites had little catalytic activity.

In testing the faraday efficiency, the working electrode was held at a constant potential for 30 minutes, potential current data was collected using an electrochemical workstation, and the generated gas product was detected with a Shimadzu GC-2030 gas chromatograph (Shimadzu corporation, japan). The range of the applied voltage during the test is-0.6V to-1.2V; only CO and H in gas phase products₂Was detected and no product was detected in the liquid phase, the results are shown in figure 6. As can be seen from fig. 6: comparative examples 2 and 3 hardly reduce carbon dioxide to carbon monoxide, and catalytic selectivity is poor. Example 1 and comparative example 1, which have nickel monatomic active sites, show better carbon monoxide selectivity; nevertheless, boron doping presents certain advantages compared to NC-SANi: under higher potential (-1.0 to-1.2V), the carbon monoxide Faraday efficiency of BNC-SANi is obviously superior to that of NC-SANi, and is always kept above 90 percent.

All potentials are relative to the Reversible Hydrogen Electrode (RHE), and the associated potential calculations are calculated according to the nernst equation (equation 1):

e (vs. rhe) ═ E (vs. ag/AgCl) +0.204V +0.0591 × pH formula 1.

Electrochemical test 2

Respectively mixing 4mg of the catalyst obtained in example 1 with 0.7mL of deionized water, 0.25mL of ethanol and 0.05mL of 5 wt% Nafion 117 solution to obtain a catalyst dispersion solution; dripping the catalyst dispersion liquid on a gas diffusion electrode, and drying in the air to finally obtain the catalyst loading of 0.80mg/cm²The working electrode of (1).

The test adopts a three-electrode electrolytic cell structure, the gas diffusion electrode loaded with the catalyst is used as a working electrode, an iridium wire is used as a counter electrode, and an Ag/AgCl electrode (E is 0.204V) is used as a reference electrode; measurements were performed at room temperature (25 ℃) and ambient pressure in a gas diffusion electrode cell using the CHI 760e electrochemical workstation.

Carbon dioxide gas flow was at a constant 50mL min throughout the test^-1The rate of the KHCO is introduced into an electrolytic cell, and the cathode and the anode of the electrolytic cell respectively circulate 0.5mol/L KHCO₃And (3) an electrolyte.

When testing the Linear Sweep Voltametry (LSV) curve, the electrochemical workstation measured at 10 mV. s^-1The scan rate of (a) was used to collect data, and the scan voltage ranged from 0.4V to-1.2V, with the results shown in fig. 7. As can be seen from fig. 7: with the help of a gas diffusion electrode, the boron-doped BNC-SANi shows great catalytic activity, and the current density reaches 213 +/-30 mA-cm under the potential of-1.2V^-2。

In testing the faraday efficiency, the working electrode was held at a constant potential for 30 minutes, potential current data was collected using an electrochemical workstation, and the generated gas product was detected with a Shimadzu GC-2030 gas chromatograph (Shimadzu corporation, japan). The range of the applied voltage during the test is-0.6V to-1.2V; only CO and H in gas phase products₂Was detected and no product was detected in the liquid phase, the results are shown in figure 8. As can be seen from fig. 8: the current density of the catalyst reaches 213 +/-30 mA cm^-2When (-1.2V), product one is obtainedThe Faraday efficiency of the carbon oxide is still as high as 97.37%, high selectivity under high current density is realized, and the boron-doped nickel monatomic catalyst BNC-SANi shows excellent catalytic activity and selectivity and has wide industrial prospect.

All potentials are relative to the Reversible Hydrogen Electrode (RHE) and the associated potential calculations are calculated according to the nernst equation (equation 1).

Example 2

The differences from example 1 are: the mass of boric acid was 40 mg. The mass of a nickel single atom in the obtained catalyst is 2.40 percent of the mass of the carbon skeleton by XPS measurement, and the mass of a nitrogen atom is 13.49 percent of the mass of the carbon skeleton; the mass of the boron element is 8.61% of the mass of the carbon skeleton.

Example 3

The differences from example 1 are: the mass of nickel acetate tetrahydrate was 6 mg. The mass of a nickel single atom in the obtained catalyst is 1.31% of the mass of the carbon skeleton by adopting ICP and XPS measurement, and the mass of a nitrogen atom is 11.55% of the mass of the carbon skeleton; the mass of the boron element is 5.95 percent of the mass of the carbon skeleton.

Example 4

The differences from example 1 are: the mass of nickel acetate tetrahydrate was 24 mg. The mass of a nickel single atom in the obtained catalyst is 4.37 percent of the mass of the carbon skeleton by ICP and XPS measurement, and the mass of a nitrogen atom is 9.78 percent of the mass of the carbon skeleton; the mass of the boron element is 5.89% of the mass of the carbon skeleton.

The electrochemical performance of the catalysts obtained in examples 1 to 4 was tested by the electrochemical test method, and the results are shown in table 1.

TABLE 1 results of electrochemical measurements on catalysts obtained in examples 1 to 4

In table 1, 1 represents the results of the test using electrochemical test 1, and 2 represents the results of the test using electrochemical test 2.

As can be seen from table 1: the boron-nitrogen co-doped nickel monatomic catalyst (BNC-SANi) in example 1 shows better inhibition of hydrogen evolution side reaction at high potential and shows very high carbon monoxide selectivity; the BNC-SANi current density was even higher up to 213mA/cm when tested in a flow cell²And simultaneously, the Faraday efficiency of the product carbon monoxide is as high as 97%. The method provides a feasible strategy for the industrial application of the high-efficiency electrocatalytic carbon dioxide reduction.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.