CN113430541A - Preparation method and application of core-shell structure gold-nickel alloy nano catalyst - Google Patents

Abstract

A preparation method and application of a core-shell structure gold-nickel alloy nano catalyst relate to the technical field of alloy nano catalyst preparation. The invention aims to solve the problem of electrocatalytic reduction of CO by the existing noble metal gold-based catalyst₂The problems of low catalytic performance, poor stability, high price and difficult practical application of CO are solved. According to the invention, a gold salt and nickel salt compound is used as a precursor, a surfactant is used as a nano micelle, an alcohol compound is used as a reducing agent, a high-boiling-point organic solvent is used as a reaction solvent by a solvothermal synthesis method, so that the gold-nickel alloy nano catalyst with uniform particle size and element distribution is prepared, and a non-noble metal nickel element on the surface of the nano particle is separated out under the action of an electric field by an in-situ electrochemical activation method, so that the gold-nickel alloy nano catalyst with a gold shell and a core-shell structure is formed. The invention can obtain a preparation method of a core-shell structure gold-nickel alloy nano catalyst and the preparation methodApplication is carried out.

Description

Preparation method and application of core-shell structure gold-nickel alloy nano catalyst

Technical Field

The invention relates to the technical field of alloy nano-catalyst preparation, in particular to a preparation method and application of a core-shell structure gold-nickel alloy nano-catalyst.

Background

In recent years, the industrial development of human society has been heavily dependent on the excessive development and utilization of fossil energy such as coal, oil, and natural gas. The use of these non-renewable fossil energy sources is not only non-sustainable, but also results in atmospheric CO₂Rapid concentrationThe temperature rises dramatically, a series of serious energy and environmental problems are generated, such as greenhouse effect, climate abnormality and the like, which threaten the long-term survival of human beings. 2019, global CO₂The concentration is already as high as 410ppm and this value is increasing continuously. Currently, new methods and techniques are sought for reducing CO in various countries₂Is also the first scientific problem facing contemporary mankind. Plants in nature transform and absorb CO through photosynthesis₂Much lower than the human emission of CO₂The speed of (2). Therefore, a method is sought to convert CO₂The carbon-based energy substances such as CO, methane, ethylene and the like are converted for human utilization, the closed carbon circulation system of the earth can be accelerated, and the effect of killing two birds with one stone is achieved. At present all CO₂In the conversion process, the CO is reduced electrocatalytically₂The method has mild reaction conditions, does not need high temperature and high pressure, is more reliable, and has incomparable high energy utilization efficiency compared with other means. Thus, electrocatalytic reduction of CO₂For solving the current CO₂The problem has great research significance.

Studies have shown that CO can be converted using different types of catalysts₂Reducing into various products, such as CO, methane, ethylene, methanol, ethanol and the like. In view of market price and current level of industrialization, CO is the most desirable product. CO is an important component of synthesis gas (a mixture of CO and hydrogen) which can be converted industrially by Fischer-Tropsch synthesis into liquid hydrocarbons or hydrocarbons. Of all the metallic elements currently studied, gold is responsible for CO₂The reduction to CO has the highest catalytic activity, and the Faraday efficiency of more than 90 percent of CO can be realized by regulating the structure of the catalyst. However, gold is scarce and expensive on earth, and limits the progress of its industrial application. In recent years, the rise of nano materials provides guidance for the development of catalysts, and the nano catalysts have high specific surface area and improve the number of effective catalytic sites, so that the catalytic performance is improved. At present, the focus of research on the nano-catalyst is to regulate and control the microscopic size, morphology, components and the like of the material to improve the quality activity and catalytic performance of the noble metal and achieve the purpose of reducing the consumption of the noble metal.

Currently, the regulation and control means of gold-based catalysts mainly realizes the exposure of specific active surfaces by constructing specific morphologies, increases active sites by manufacturing defects, and the like. By the method, the catalytic activity can be effectively improved, but the consumption of gold is not obviously reduced, and the activity is not essentially improved. Meanwhile, the precise regulation and control means is complex to operate, has high requirements on process conditions, and is difficult to realize large-scale industrial production.

Disclosure of Invention

The invention aims to solve the problem of electrocatalytic reduction of CO by the existing noble metal gold-based catalyst₂The preparation method and the application of the core-shell structure gold-nickel alloy nano catalyst are provided for solving the problems of low catalytic performance, poor stability, high price and difficulty in practical application of CO.

A preparation method of a core-shell structure gold-nickel alloy nano catalyst comprises the following steps:

firstly, preparing a precursor mixed solution: adding a gold salt compound, a nickel salt compound and a reducing agent into a high-boiling-point organic solvent, and uniformly stirring under the conditions of inert gas atmosphere and temperature of 20-80 ℃ to obtain a precursor mixed solution; the ratio of the mass of the gold salt compound, the mass of the nickel salt compound and the mass of the reducing agent to the volume of the high-boiling-point organic solvent is (0.001-1) g: (0.0015-1.5) g: (0.07-70) g: (1-1000) mL; the molar ratio of the gold element in the gold salt compound to the nickel element in the nickel salt compound is 3: 1;

secondly, solvothermal reaction: adding a surfactant into the precursor mixed solution, and uniformly mixing to obtain a mixture, wherein the mass ratio of the surfactant to the volume of the precursor mixed solution is (0.005-5) g: (1-1000) mL; under the atmosphere of inert gas, raising the temperature of the mixture to 240-290 ℃, preserving the heat for 0.5-3 h at the temperature of 240-290 ℃, then cooling to room temperature to obtain a product A, adding an organic solvent into the product A, stirring, separating, removing upper-layer liquid, collecting precipitate, and obtaining the precipitated product A;

thirdly, purifying and dispersing the product, and compounding: cleaning the precipitated product A for 3-5 times by adopting a mixed cleaning solution to obtain a purified product A; dispersing the purified product A in an organic solvent to obtain a dispersion liquid; adding the nano carbon material into the dispersion liquid, ultrasonically mixing, centrifugally separating, removing supernatant liquid to obtain a composite solid product, and drying to obtain a gold-nickel alloy nano catalyst;

fourthly, preparing a preactivation working electrode and a core-shell structure gold-nickel alloy nano catalyst: mixing a gold-nickel alloy nano catalyst, a Nafion solution and a solvent by ultrasonic to obtain catalyst ink, wherein the ratio of the mass of the gold-nickel alloy nano catalyst to the volume of the Nafion solution to the volume of the solvent is (0.1-100) mg: (0.4-400) μ L: (0.025-25) mL; uniformly spraying catalyst ink on carbon paper, and drying after spraying to obtain a pre-activated working electrode; placing a preactivation working electrode in a cathode area of an H-shaped electrolytic cell as a cathode, wherein the cathode area and an anode area of the H-shaped electrolytic cell are separated by a Nafion proton exchange membrane, a graphite or platinum electrode is used as an anode in the anode area, and a saturated calomel electrode is placed in the cathode area as a reference electrode; and adding carbonate electrolyte into the cathode region and the anode region, and electrifying and reacting the cathode region for 10-180 min at a voltage of-1.2V-2V under the protection of inert gas to obtain the core-shell structure gold-nickel alloy nano catalyst.

Application of core-shell structure gold-nickel alloy nano catalyst serving as working electrode for electrocatalytic reduction of CO₂Preparing CO; the core-shell structure gold-nickel alloy nano catalyst is used for electrocatalytic reduction of CO₂The specific steps for preparing CO are as follows:

1) assembling a reactor: an H-shaped three-electrode electrolytic cell is adopted, a cathode cell and an anode cell of the H-shaped three-electrode electrolytic cell are separated by a Nafion 117 proton ion exchange membrane, and KHCO with the concentration of 0.5mol/L is adopted₃Pouring the electrolyte into an H-shaped three-electrode electrolytic cell by taking an aqueous solution as the electrolyte until a channel between an anode cell and a cathode cell in the H-shaped three-electrode electrolytic cell is filled with the electrolyte, taking a platinum sheet as a counter electrode, placing the counter electrode in the anode cell, placing a working electrode and a reference electrode in the cathode cell, wherein the reference electrode is a KCl-saturated Ag/AgCl electrodeThe cathode pool is internally provided with a cathode region air inlet, a cathode region air outlet and CO₂The air inlet pipe extends to the position below the liquid level of the electrolyte through the air inlet of the cathode area, the air outlet of the cathode area is communicated with the gas collecting device, 1 magnetic stirring rotor is placed in the cathode pool, the cathode pool is sealed by adopting a sealing piece, and the contact positions of the working electrode and the reference electrode with the sealing piece are sealed to obtain the electro-catalytic reduction CO₂A CO production device;

2) electrocatalytic reduction: passing CO at a gas flow rate of 20mL/min₂Introducing carbon dioxide gas into the electrolyte of the cathode pool through the gas inlet pipe, starting the power supply and the magnetic stirrer after introducing the carbon dioxide gas for 30min, and introducing CO₂The CO is carried out under the conditions that the gas flow is 1-30 mL/min, the magnetic stirring rotating speed is 500-1200 r/min and the electric potential of the working electrode is-1 to-1.8V₂The gas collecting device collects the gas generated by the reaction in the cathode pool through the cathode region gas outlet to finish the electrocatalytic reduction of CO₂And (5) preparing CO.

The invention has the beneficial effects that:

(1) the invention relates to a preparation method of a core-shell structure gold-nickel alloy nano catalyst, which comprises the steps of firstly preparing a gold-nickel alloy nano catalyst with uniform particle size and element distribution by using a solvent thermal synthesis method and using a gold salt and a nickel salt compound as precursors, using a surfactant as a nano micelle, using an alcohol compound as a reducing agent and using a high-boiling-point organic solvent as a reaction solvent, and separating out non-noble metal nickel elements on the surfaces of nanoparticles under the action of an electric field by using an in-situ electrochemical activation method to form the core-shell structure gold-nickel alloy nano catalyst with a gold shell. The gold elements on the surface of the core-shell structure gold-nickel alloy nano catalyst are rearranged, so that the number of active point positions is greatly increased, the using amount of the noble metal catalyst is reduced, the integral conductivity and catalytic performance of the catalyst are improved, and CO is reduced₂The Faraday efficiency of CO is as high as more than 94%. The invention solves the problem of the electrocatalytic reduction of CO by the existing noble metal gold-based catalyst₂The problems of low catalytic performance, poor stability, high price and difficult practical application of CO are solved.

(2) According to the invention, by compounding gold and non-noble metal nickel, the catalytic performance is improved while the noble metal consumption is reduced, and the cost is saved for industrial application; the invention adopts a solvent thermal synthesis method and an electrochemical activation method, has simple operation and can be scaled up according to the proportion.

The invention can obtain a preparation method and application of a core-shell structure gold-nickel alloy nano catalyst.

Drawings

FIG. 1 is a TEM photograph of the core-shell Au-Ni alloy nanocatalyst prepared in example 1;

FIG. 2 is a high resolution TEM photograph of the core-shell Au-Ni alloy nanocatalyst prepared in example 1;

FIG. 3 is a STEM element line scan graph of single particles of core-shell structure Au-Ni alloy nano-catalyst prepared in example 1, wherein A represents Au and B represents Ni;

FIG. 4 is a HAADF-STEM diagram of the gold-nickel alloy nanocatalyst with a core-shell structure prepared in example 1;

FIG. 5 is a Mapping diagram of the gold element of FIG. 4;

FIG. 6 is a Mapping diagram of the nickel element of FIG. 4;

fig. 7 is an X-ray diffraction pattern in which a represents an X-ray diffraction pattern of the core-shell structure gold-nickel alloy nano-catalyst prepared in example 2, b represents an X-ray diffraction pattern of the core-shell structure gold-nickel alloy nano-catalyst prepared in example 1, c represents an X-ray diffraction pattern of the core-shell structure gold-nickel alloy nano-catalyst prepared in example 3, and d represents an X-ray diffraction pattern of a pure gold nano-catalyst;

FIG. 8 is an X-ray photoelectron spectrum of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 1;

FIG. 9 is an X-ray photoelectron spectrum of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 2;

FIG. 10 shows catalytic reduction of CO₂■ shows the CO catalytic reduction of the core-shell structure Au-Ni alloy nano-catalyst of example 1 in the form of a graph of the Faraday efficiency of CO₂In order to obtain a Faraday efficiency curve chart of CO, the tangle-solidup represents the catalysis of the core-shell structure gold-nickel alloy nano-catalyst in the example 3Crude CO₂T represents the Faraday efficiency graph of CO, and t represents the catalytic reduction of CO by the core-shell structure gold-nickel alloy nano-catalyst of example 2₂Graph of faradaic efficiency for CO;

FIG. 11 shows electrocatalytic reduction of CO₂■ shows the CO catalytic reduction of the core-shell structure Au-Ni alloy nano-catalyst of example 1 in the current density diagram of CO₂Is a CO current density diagram, and the tangle-solidup represents the catalytic reduction of CO by the core-shell structure gold-nickel alloy nano catalyst of the embodiment 3₂Is a current density diagram of CO, and t represents the catalytic reduction of CO by the core-shell structure gold-nickel alloy nano-catalyst of example 2₂The current density of CO is plotted.

Detailed Description

The first embodiment is as follows: the preparation method of the core-shell structure gold-nickel alloy nano catalyst comprises the following steps:

firstly, preparing a precursor mixed solution: adding a gold salt compound, a nickel salt compound and a reducing agent into a high-boiling-point organic solvent, and uniformly stirring under the conditions of inert gas atmosphere and temperature of 20-80 ℃ to obtain a precursor mixed solution; the ratio of the mass of the gold salt compound, the mass of the nickel salt compound and the mass of the reducing agent to the volume of the high-boiling-point organic solvent is (0.001-1) g: (0.0015-1.5) g: (0.07-70) g: (1-1000) mL; the molar ratio of the gold element in the gold salt compound to the nickel element in the nickel salt compound is 3: 1;

secondly, solvothermal reaction: adding a surfactant into the precursor mixed solution, and uniformly mixing to obtain a mixture, wherein the mass ratio of the surfactant to the volume of the precursor mixed solution is (0.005-5) g: (1-1000) mL; under the atmosphere of inert gas, raising the temperature of the mixture to 240-290 ℃, preserving the heat for 0.5-3 h at the temperature of 240-290 ℃, then cooling to room temperature to obtain a product A, adding an organic solvent into the product A, stirring, separating, removing upper-layer liquid, collecting precipitate, and obtaining the precipitated product A;

thirdly, purifying and dispersing the product, and compounding: cleaning the precipitated product A for 3-5 times by adopting a mixed cleaning solution to obtain a purified product A; dispersing the purified product A in an organic solvent to obtain a dispersion liquid; adding the nano carbon material into the dispersion liquid, ultrasonically mixing, centrifugally separating, removing supernatant liquid to obtain a composite solid product, and drying to obtain a gold-nickel alloy nano catalyst;

fourthly, preparing a preactivation working electrode and a core-shell structure gold-nickel alloy nano catalyst: mixing a gold-nickel alloy nano catalyst, a Nafion solution and a solvent by ultrasonic to obtain catalyst ink, wherein the ratio of the mass of the gold-nickel alloy nano catalyst to the volume of the Nafion solution to the volume of the solvent is (0.1-100) mg: (0.4-400) μ L: (0.025-25) mL; uniformly spraying catalyst ink on carbon paper, and drying after spraying to obtain a pre-activated working electrode; placing a preactivation working electrode in a cathode area of an H-shaped electrolytic cell as a cathode, wherein the cathode area and an anode area of the H-shaped electrolytic cell are separated by a Nafion proton exchange membrane, a graphite or platinum electrode is used as an anode in the anode area, and a saturated calomel electrode is placed in the cathode area as a reference electrode; and adding carbonate electrolyte into the cathode region and the anode region, and electrifying and reacting the cathode region for 10-180 min at a voltage of-1.2V-2V under the protection of inert gas to obtain the core-shell structure gold-nickel alloy nano catalyst.

The beneficial effects of the embodiment are as follows:

(1) firstly, gold salt and a nickel salt compound are used as precursors, a surfactant is used as a nano micelle, an alcohol compound is used as a reducing agent, a high-boiling-point organic solvent is used as a reaction solvent by a solvent thermal synthesis method, the gold-nickel alloy nano catalyst with uniform particle size and element distribution is prepared, and non-noble metal nickel elements on the surfaces of the nano particles are separated out under the action of an electric field by an in-situ electrochemical activation method to form the gold-nickel alloy nano catalyst with the core-shell structure and the gold shell. The gold elements on the surface of the core-shell structure gold-nickel alloy nano catalyst are rearranged, so that the number of active point positions is greatly increased, the using amount of the noble metal catalyst is reduced, the integral conductivity and catalytic performance of the catalyst are improved, and CO is reduced₂The Faraday efficiency of CO is as high as more than 94%. The present embodiment solves the problemsElectrocatalytic reduction of CO by noble metal gold-based catalyst₂The problems of low catalytic performance, poor stability, high price and difficult practical application of CO are solved.

(2) According to the embodiment, the gold and the non-noble metal nickel are compounded, so that the catalytic performance is improved while the noble metal consumption is reduced, and the cost is saved for industrial application; the solvent thermal synthesis method and the electrochemical activation method are adopted in the embodiment, the operation is simple, and the scale amplification can be realized according to the proportion.

The second embodiment is as follows: the present embodiment differs from the present embodiment in that: the gold salt compound in the first step is gold acetate or chloroauric acid tetrahydrate, the nickel salt compound is nickel acetylacetonate or nickel chloride, the reducing agent is 1, 2-hexadecanediol, ethylene glycol or glycerol, the high-boiling-point organic solvent is octyl ether or octadecene, and the inert gas is nitrogen or argon.

Other steps are the same as those in the first embodiment.

The third concrete implementation mode: the first or second differences from the present embodiment are as follows: adding a gold salt compound, a nickel salt compound and a reducing agent into a high-boiling-point organic solvent, and stirring at a rotating speed of 300-1000 r/min for 10-60 min under the conditions of inert gas atmosphere and temperature of 20-80 ℃ to obtain a precursor mixed solution.

The other steps are the same as those in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is as follows: and the surfactant in the second step is one or more of oleylamine, oleic acid and polyvinyl polypyrrolidone, and the mixing time of the surfactant and the precursor mixed solution is 30-120 min.

The other steps are the same as those in the first to third embodiments.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: in the second step, the temperature of the mixture is increased to 240-290 ℃ at a heating rate of 3-10 ℃/min under the argon atmosphere.

The other steps are the same as those in the first to fourth embodiments.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is as follows: the volume ratio of the product A to the organic solvent in the step two is 1: 5, the organic solvent is ethanol.

The other steps are the same as those in the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the mixed cleaning solution in the third step is ethanol-n-hexane, and the volume ratio of ethanol to n-hexane in the ethanol-n-hexane is 1: 2.

the other steps are the same as those in the first to sixth embodiments.

The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is: adding the nano carbon material into the dispersion liquid, ultrasonically mixing for 20-40 min, then centrifugally separating at a centrifugal speed of 8000-15000 r/min for 1-5 min, removing supernatant to obtain a composite solid product, placing the composite solid product in a vacuum drying oven, and drying at the temperature of 150-200 ℃ for 8-24 h to obtain the gold-nickel alloy nano catalyst; the ratio of the mass of the purified product A to the volume of the organic solvent in the third step is (0.002-10) g: (5-5000) mL, wherein the organic solvent is n-hexane; the ratio of the mass of the nanocarbon material to the volume of the dispersion liquid is (0.8-800) mg: (1-1000) mL, wherein the nano carbon material is carbon black.

The other steps are the same as those in the first to seventh embodiments.

The specific implementation method nine: the difference between this embodiment and the first to eighth embodiments is: the ratio of the mass of the gold-nickel alloy nano catalyst, the volume of the Nafion solution and the volume of the solvent in the fourth step is 40 mg: 160 μ L: 5 mL; the solvent in the fourth step is methanol, ethanol, acetone, propanol or isopropanol; the volume ratio of the catalyst ink to the area of the carbon paper in the fourth step is (0.01-1) mL: 1cm²(ii) a In the fourth step, the drying temperature after the spraying is finished is 20-80 ℃, and the drying time is 5-300 min; the carbonate electrolyte in the fourth step is potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonateThe concentration is 0.1 to 5 mol/L.

The other steps are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: in the application of the core-shell structure gold-nickel alloy nano catalyst, the core-shell structure gold-nickel alloy nano catalyst is used as a working electrode for electrocatalytic reduction of CO₂Preparing CO; the core-shell structure gold-nickel alloy nano catalyst is used for electrocatalytic reduction of CO₂The specific steps for preparing CO are as follows:

1) assembling a reactor: an H-shaped three-electrode electrolytic cell is adopted, a cathode cell and an anode cell of the H-shaped three-electrode electrolytic cell are separated by a Nafion 117 proton ion exchange membrane, and KHCO with the concentration of 0.5mol/L is adopted₃Pouring electrolyte into an H-shaped three-electrode electrolytic cell by taking an aqueous solution as the electrolyte until a channel between an anode cell and a cathode cell in the H-shaped three-electrode electrolytic cell is filled with the electrolyte, taking a platinum sheet as a counter electrode, placing the counter electrode in the anode cell, placing a working electrode and a reference electrode in the cathode cell, wherein the reference electrode is a KCl-saturated Ag/AgCl electrode, and arranging a cathode region air inlet and a cathode region air outlet in the cathode cell, CO and CO respectively₂The air inlet pipe extends to the position below the liquid level of the electrolyte through the air inlet of the cathode area, the air outlet of the cathode area is communicated with the gas collecting device, 1 magnetic stirring rotor is placed in the cathode pool, the cathode pool is sealed by adopting a sealing piece, and the contact positions of the working electrode and the reference electrode with the sealing piece are sealed to obtain the electro-catalytic reduction CO₂A CO production device;

2) electrocatalytic reduction: passing CO at a gas flow rate of 20mL/min₂Introducing carbon dioxide gas into the electrolyte of the cathode pool through the gas inlet pipe, starting the power supply and the magnetic stirrer after introducing the carbon dioxide gas for 30min, and introducing CO₂The CO is carried out under the conditions that the gas flow is 1-30 mL/min, the magnetic stirring rotating speed is 500-1200 r/min and the electric potential of the working electrode is-1 to-1.8V₂The gas collecting device collects the gas generated by the reaction in the cathode pool through the cathode region gas outlet to finish the electrocatalytic reduction of CO₂And (5) preparing CO.

The following examples were used to demonstrate the beneficial effects of the present invention:

example 1: a preparation method of a core-shell structure gold-nickel alloy nano catalyst comprises the following steps:

firstly, preparing a precursor mixed solution: adding 0.14g of gold acetate, 0.032g of nickel acetylacetonate and 0.65g of 1, 2-hexadecanediol into 10mL of octyl ether, and stirring at the rotating speed of 800r/min for 60min under the conditions of argon atmosphere and 50 ℃ to obtain precursor mixed solution; the molar ratio of gold element in the gold acetate to nickel element in the nickel acetylacetonate is 3: 1;

secondly, solvothermal reaction: 0.03344g of oleylamine and 0.03231g of oleic acid are added into the precursor mixed solution, and the mixture is stirred for 30min at the stirring speed of 800r/min to obtain a mixture; under the argon atmosphere, raising the temperature of the mixture to 260 ℃ at a heating rate of 5 ℃/min, preserving the heat at 260 ℃ for 1h, then cooling to room temperature to obtain a product A, adding 20mL of ethanol into the product A, stirring, carrying out centrifugal separation at a speed of 12000r/min for 3min, removing upper-layer liquid, and collecting precipitates to obtain a solid product;

thirdly, purifying and dispersing the product, and compounding: cleaning the solid product for 3 times by adopting ethanol-n-hexane to obtain a purified solid product, wherein the volume ratio of ethanol to n-hexane in the ethanol-n-hexane is 1: 2; dispersing the purified solid product in 50mL of n-hexane to obtain a dispersion liquid; adding 8.5mg of carbon black into 10mL of dispersion liquid, carrying out ultrasonic mixing for 30min, carrying out centrifugal separation for 3min at a centrifugal speed of 12000r/min, removing supernatant liquid to obtain a composite solid product, placing the composite solid product in a vacuum drying oven, and drying for 24h at the temperature of 180 ℃ to obtain the gold-nickel alloy nano catalyst;

fourthly, preparing a preactivation working electrode and a core-shell structure gold-nickel alloy nano catalyst: mixing gold-nickel alloy nano catalyst, Nafion solution and solvent by ultrasound to obtain catalyst ink, wherein the ratio of the mass of the gold-nickel alloy nano catalyst to the volume of the Nafion solution to the volume of the solvent is 40 mg: 160 μ L: 5 mL; uniformly spraying catalyst ink on carbon paper, and drying after spraying to obtain a pre-activated working electrode; placing a preactivation working electrode in a cathode area of an H-shaped electrolytic cell as a cathode, wherein the cathode area and an anode area of the H-shaped electrolytic cell are separated by a Nafion proton exchange membrane, a graphite or platinum electrode is used as an anode in the anode area, and a saturated calomel electrode is placed in the cathode area as a reference electrode; and adding carbonate electrolyte into the cathode region and the anode region, and electrifying and reacting the cathode region for 30min at a voltage of-1.2V to-2V under the protection of inert gas to obtain the core-shell structure gold-nickel alloy nano catalyst.

The core-shell structure gold-nickel alloy nano catalyst prepared in example 1 is observed by using a transmission electron microscope, as shown in fig. 1, fig. 1 is a transmission electron microscope photograph of the core-shell structure gold-nickel alloy nano catalyst prepared in example 1, and it can be seen that core-shell structure gold-nickel alloy nano particles with darker colors are uniformly loaded on a carbon black carrier with lighter colors.

Fig. 2 is a high-resolution transmission electron microscope photograph of the core-shell structure gold-nickel alloy nano catalyst prepared in example 1, and it can be seen that the core-shell structure gold-nickel alloy nano catalyst has a particle size of about 8 nm and a lattice spacing of 0.23nm, is supported on carbon black having a lattice spacing of 0.34nm, and the two are tightly combined to ensure good conductivity of the catalyst. At the same time, it is evident that the nanoparticles have a lighter shell and a darker core, the shell being approximately 1nm thick.

Fig. 3 is a STEM element line scan graph of a single particle of the core-shell structure gold-nickel alloy nano catalyst prepared in example 1, where a is a signal peak of a gold element, and B is a signal peak of a nickel element, and it is known that a signal of the gold element is about 1nm wider than that of the nickel element, that is, the nano particle has a core-shell structure with a gold shell and a gold-nickel alloy as a core. The peak of gold element is higher than that of nickel element, indicating that the gold element is more abundant than that of nickel element in the gold-nickel alloy nanocatalyst of this example 1.

FIG. 4 is a HAADF-STEM diagram of the gold-nickel alloy nanocatalyst prepared in example 1, wherein the bright areas are gold-nickel alloy nanoparticles and the dark areas are carbon black support and background; performing element Mapping surface scanning on the graph 4 to obtain a Mapping graph of the gold element in the graph 5, and a Mapping graph of the nickel element in the graph 6; as can be seen from fig. 4 to 6, the distribution profiles of the gold element and the nickel element are substantially overlapped, and the area of the gold element is slightly larger than that of the nickel element, which indicates that the core-shell structure gold-nickel alloy nano-catalyst prepared in example 1 is an alloy material in which the gold element and the nickel element are uniformly mixed, and has a core-shell structure in which gold is used as a shell.

Example 2: the present embodiment is different from embodiment 1 in that: in the first step, the molar ratio of the gold element of the gold acetate to the nickel element of the nickel acetylacetonate is 3: the rest was the same as in example 1.

Example 3: the present embodiment is different from embodiment 1 in that: in the first step, the molar ratio of the gold element of the gold acetate to the nickel element of the nickel acetylacetonate is 9: 1, the rest is the same as example 1.

Fig. 7 is an X-ray diffraction pattern of the gold-nickel alloy nanocatalyst prepared in examples 1-3, in which a represents the X-ray diffraction pattern of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 2, b represents the X-ray diffraction pattern of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 1, c represents the X-ray diffraction pattern of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 3, and d represents the X-ray diffraction pattern of the pure gold nanocatalyst; as can be seen from fig. 7, peaks at 38.1 °, 44.3 °, 64.5 ° and 77.6 ° of the core-shell structure gold-nickel alloy nanocatalyst prepared in example 1 correspond to (111), (200), (220), (311) and (222) planes of the pure gold nanocatalyst one by one, which indicates that the crystal structure of the prepared core-shell structure gold-nickel alloy nanocatalyst maintains the same face-centered cubic lattice as that of pure gold, and further indicates that the core-shell structure gold-nickel alloy nanocatalyst is successfully prepared.

Fig. 8 is an X-ray photoelectron spectrum of the gold-nickel alloy nano catalyst with the core-shell structure prepared in example 1, fig. 9 is an X-ray photoelectron spectrum of the gold-nickel alloy nano catalyst with the core-shell structure prepared in example 2, and it can be known from fig. 8 and 9 that peaks of gold element, carbon element and nickel element appear, which indicates that the catalyst contains gold element, nickel element and carbon element, which proves that the gold-nickel alloy nano material with the core-shell structure is successfully prepared and successfully loaded on a carbon black carrier, and also shows that the components of the gold-nickel alloy nano catalyst with the core-shell structure can be changed by changing the charge ratio, and the synthesis method is stable and reliable.

Example 4: application of core-shell structure gold-nickel alloy nano catalyst serving as working electrode for electrocatalytic reduction of CO₂Preparing CO, wherein the area of the working electrode is 1cm multiplied by 2 cm;

the core-shell structure gold-nickel alloy nano catalyst is used for electrocatalytic reduction of CO₂The specific steps for preparing CO are as follows:

1) assembling a reactor: an H-shaped three-electrode electrolytic cell is adopted, a cathode cell and an anode cell of the H-shaped three-electrode electrolytic cell are separated by a Nafion 117 proton ion exchange membrane, and KHCO with the concentration of 0.5mol/L is adopted₃Pouring electrolyte into an H-shaped three-electrode electrolytic cell by taking an aqueous solution as the electrolyte until a channel between an anode cell and a cathode cell in the H-shaped three-electrode electrolytic cell is filled with the electrolyte, taking a platinum sheet as a counter electrode, placing the counter electrode in the anode cell, placing a working electrode and a reference electrode in the cathode cell, wherein the reference electrode is a KCl-saturated Ag/AgCl electrode, and arranging a cathode region air inlet and a cathode region air outlet in the cathode cell, CO and CO respectively₂The air inlet pipe extends to the position below the liquid level of the electrolyte through the air inlet of the cathode area, the air outlet of the cathode area is communicated with the gas collecting device, 1 magnetic stirring rotor is placed in the cathode pool, the cathode pool is sealed by adopting a sealing piece, and the contact positions of the working electrode and the reference electrode with the sealing piece are sealed to obtain the electro-catalytic reduction CO₂A CO production device;

2) electrocatalytic reduction: passing CO at a gas flow rate of 20mL/min₂Introducing carbon dioxide gas into the electrolyte of the cathode pool through the gas inlet pipe, starting the power supply and the magnetic stirrer after introducing the carbon dioxide gas for 30min, and introducing CO₂The CO is carried out under the conditions that the gas flow is 1-30 mL/min, the magnetic stirring rotating speed is 800r/min and the electric potential of the working electrode is-1 to-1.8V (relative to a standard hydrogen electrode)₂The gas collecting device collects the gas generated by the reaction in the cathode pool through the cathode region gas outlet to finish the electrocatalytic reduction of CO₂And (5) preparing CO.

Example 5: the present embodiment is different from embodiment 4 in that: the gold-iron nano-alloy catalyst prepared in example 2 was used in place of the gold-iron nano-alloy catalyst prepared in example 1, and the rest was the same as in example 4.

Example 6: the present embodiment is different from embodiment 4 in that: the gold-iron nano-alloy catalyst prepared in example 3 was used in place of the gold-iron nano-alloy catalyst prepared in example 1, and the rest was the same as in example 4.

FIG. 10 shows catalytic reduction of CO₂■ shows the CO catalytic reduction of the core-shell structure Au-Ni alloy nano-catalyst of example 4 in the form of a graph of the Faraday efficiency of CO₂In order to obtain a Faraday efficiency curve chart of CO, the tangle-solidup represents the CO catalytic reduction of the core-shell structure gold-nickel alloy nano-catalyst of the example 6₂T represents the Faraday efficiency graph of CO, and t represents the catalytic reduction of CO by the core-shell structure gold-nickel alloy nano-catalyst of example 5₂As a graph of the Faraday efficiency of CO, it can be known from FIG. 10 that in the selected point position window, the core-shell structure gold-nickel alloy nano-catalyst realizes excellent CO reduction₂The performance of the sample prepared by CO is different without charge ratio, and the best performance can realize more than 90 percent of Faraday efficiency under minus 0.5V.

FIG. 11 shows reduction of CO₂■ shows the CO catalytic reduction of the core-shell structure Au-Ni alloy nano-catalyst of example 4 in terms of CO current density₂In order to obtain a Faraday efficiency curve chart of CO, the tangle-solidup represents the CO catalytic reduction of the core-shell structure gold-nickel alloy nano-catalyst of the example 6₂T represents the Faraday efficiency graph of CO, and t represents the catalytic reduction of CO by the core-shell structure gold-nickel alloy nano-catalyst of example 5₂As a graph of the Faraday efficiency of CO, it can be seen from FIG. 11 that in the working voltage range, the performance of samples with different charge ratios is different, and the CO can be reduced greatly₂The current density of CO shows that the method can prepare the catalyst with excellent CO production capacity.

Claims (10)

1. A preparation method of a core-shell structure gold-nickel alloy nano catalyst is characterized by comprising the following steps:

firstly, preparing a precursor mixed solution: adding a gold salt compound, a nickel salt compound and a reducing agent into a high-boiling-point organic solvent, and uniformly stirring under the conditions of inert gas atmosphere and temperature of 20-80 ℃ to obtain a precursor mixed solution; the ratio of the mass of the gold salt compound, the mass of the nickel salt compound and the mass of the reducing agent to the volume of the high-boiling-point organic solvent is (0.001-1) g: (0.0015-1.5) g: (0.07-70) g: (1-1000) mL; the molar ratio of the gold element in the gold salt compound to the nickel element in the nickel salt compound is 3: 1;

secondly, solvothermal reaction: adding a surfactant into the precursor mixed solution, and uniformly mixing to obtain a mixture, wherein the mass ratio of the surfactant to the volume of the precursor mixed solution is (0.005-5) g: (1-1000) mL; under the atmosphere of inert gas, raising the temperature of the mixture to 240-290 ℃, preserving the heat for 0.5-3 h at the temperature of 240-290 ℃, then cooling to room temperature to obtain a product A, adding an organic solvent into the product A, stirring, separating, removing upper-layer liquid, collecting precipitate, and obtaining the precipitated product A;

thirdly, purifying and dispersing the product, and compounding: cleaning the precipitated product A for 3-5 times by adopting a mixed cleaning solution to obtain a purified product A; dispersing the purified product A in an organic solvent to obtain a dispersion liquid; adding the nano carbon material into the dispersion liquid, ultrasonically mixing, centrifugally separating, removing supernatant liquid to obtain a composite solid product, and drying to obtain a gold-nickel alloy nano catalyst;

fourthly, preparing a preactivation working electrode and a core-shell structure gold-nickel alloy nano catalyst: mixing a gold-nickel alloy nano catalyst, a Nafion solution and a solvent by ultrasonic to obtain catalyst ink, wherein the ratio of the mass of the gold-nickel alloy nano catalyst to the volume of the Nafion solution to the volume of the solvent is (0.1-100) mg: (0.4-400) μ L: (0.025-25) mL; uniformly spraying catalyst ink on carbon paper, and drying after spraying to obtain a pre-activated working electrode; placing a preactivation working electrode in a cathode area of an H-shaped electrolytic cell as a cathode, wherein the cathode area and an anode area of the H-shaped electrolytic cell are separated by a Nafion proton exchange membrane, a graphite or platinum electrode is used as an anode in the anode area, and a saturated calomel electrode is placed in the cathode area as a reference electrode; and adding carbonate electrolyte into the cathode region and the anode region, and electrifying and reacting the cathode region for 10-180 min at a voltage of-1.2V-2V under the protection of inert gas to obtain the core-shell structure gold-nickel alloy nano catalyst.

2. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, characterized in that in the step one, the gold salt compound is gold acetate or chloroauric acid tetrahydrate, the nickel salt compound is nickel acetylacetonate or nickel chloride, the reducing agent is 1, 2-hexadecanediol, ethylene glycol or glycerol, the high boiling point organic solvent is octyl ether or octadecene, and the inert gas is nitrogen or argon.

3. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, characterized in that in the step one, a gold salt compound, a nickel salt compound and a reducing agent are added into a high boiling point organic solvent, and the mixture is stirred at a rotation speed of 300-1000 r/min for 10-60 min under an inert gas atmosphere and at a temperature of 20-80 ℃ to obtain a precursor mixed solution.

4. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, characterized in that the surfactant in the second step is one or more of oleylamine, oleic acid and polyvinylpyrrolidone, and the mixing time of the surfactant and the precursor mixed solution is 30-120 min.

5. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, characterized in that in the second step, the temperature of the mixture is increased to 240-290 ℃ at a heating rate of 3-10 ℃/min under an argon atmosphere.

6. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, wherein the volume ratio of the product A to the organic solvent in the step two is 1: 5, the organic solvent is ethanol.

7. The preparation method of the core-shell structure gold-nickel alloy nano catalyst according to claim 1, characterized in that the mixed cleaning solution in step three is ethanol-n-hexane, and the volume ratio of ethanol to n-hexane in the ethanol-n-hexane is 1: 2.

8. the preparation method of the gold-nickel alloy nanocatalyst with the core-shell structure, according to the claim 1, is characterized in that the nanocarbon material is added into the dispersion liquid in the third step, ultrasonic mixing is carried out for 20-40 min, then centrifugal separation is carried out for 1-5 min at the centrifugal speed of 8000-15000 r/min, supernatant liquid is removed, a composite solid product is obtained, and the composite solid product is placed in a vacuum drying oven and dried for 8-24 h at the temperature of 150-200 ℃ to obtain the gold-nickel alloy nanocatalyst; the ratio of the mass of the purified product A to the volume of the organic solvent in the third step is (0.002-10) g: (5-5000) mL, wherein the organic solvent is n-hexane; the ratio of the mass of the nanocarbon material to the volume of the dispersion liquid is (0.8-800) mg: (1-1000) mL, wherein the nano carbon material is carbon black.

9. The preparation method of core-shell gold-nickel alloy nano-catalyst according to claim 1, characterized in that the ratio of the mass of gold-nickel alloy nano-catalyst, the volume of Nafion solution and the volume of solvent in step four is 40 mg: 160 μ L: 5 mL; the solvent in the fourth step is methanol, ethanol, acetone, propanol or isopropanol; the volume ratio of the catalyst ink to the area of the carbon paper in the fourth step is (0.01-1) mL: 1cm²(ii) a In the fourth step, the drying temperature after the spraying is finished is 20-80 ℃, and the drying time is 5-300 min; the carbonate electrolyte in the fourth step is potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonate, and the concentration is 0.1-5 mol/L.

10. The application of the core-shell structure gold-nickel alloy nano catalyst as claimed in claim 1, characterized in that the core-shell structure gold-nickel alloy nano catalyst is used as a working electrode for electrocatalysisReduction of CO₂Preparing CO; the core-shell structure gold-nickel alloy nano catalyst is used for electrocatalytic reduction of CO₂The specific steps for preparing CO are as follows:

1) assembling a reactor: an H-shaped three-electrode electrolytic cell is adopted, a cathode cell and an anode cell of the H-shaped three-electrode electrolytic cell are separated by a Nafion 117 proton ion exchange membrane, and KHCO with the concentration of 0.5mol/L is adopted₃Pouring electrolyte into an H-shaped three-electrode electrolytic cell by taking an aqueous solution as the electrolyte until a channel between an anode cell and a cathode cell in the H-shaped three-electrode electrolytic cell is filled with the electrolyte, taking a platinum sheet as a counter electrode, placing the counter electrode in the anode cell, placing a working electrode and a reference electrode in the cathode cell, wherein the reference electrode is a KCl-saturated Ag/AgCl electrode, and arranging a cathode region air inlet and a cathode region air outlet in the cathode cell, CO and CO respectively₂The air inlet pipe extends to the position below the liquid level of the electrolyte through the air inlet of the cathode area, the air outlet of the cathode area is communicated with the gas collecting device, 1 magnetic stirring rotor is placed in the cathode pool, the cathode pool is sealed by adopting a sealing piece, and the contact positions of the working electrode and the reference electrode with the sealing piece are sealed to obtain the electro-catalytic reduction CO₂A CO production device;

2) electrocatalytic reduction: passing CO at a gas flow rate of 20mL/min₂Introducing carbon dioxide gas into the electrolyte of the cathode pool through the gas inlet pipe, starting the power supply and the magnetic stirrer after introducing the carbon dioxide gas for 30min, and introducing CO₂The CO is carried out under the conditions that the gas flow is 1-30 mL/min, the magnetic stirring rotating speed is 500-1200 r/min and the electric potential of the working electrode is-1 to-1.8V₂The gas collecting device collects the gas generated by the reaction in the cathode pool through the cathode region gas outlet to finish the electrocatalytic reduction of CO₂And (5) preparing CO.

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