Zinc-nickel monoatomic alloy catalyst, preparation method and application

Abstract

This invention provides a zinc-nickel single-atom alloy catalyst, its preparation method, and its applications. The invention relates to the field of catalyst synthesis technology. This zinc-nickel single-atom alloy catalyst has a carbon-coated structure with a porous surface. Zinc is dispersed in single-atom form on the surface of nickel particles, forming a single-atom alloy structure, and simultaneously possessing both Lewis acidic and Lewis basic sites. Through innovative material design and preparation methods, this invention successfully synthesizes a novel zinc-nickel single-atom alloy catalyst with superior performance. This catalyst cleverly combines efficient photothermal conversion, the electronic regulation characteristics of single-atom alloys, and the structural advantages of a porous carbon support. It achieves highly efficient and selective conversion of CO2 cycloaddition reactions under mild conditions, while exhibiting significant advantages in energy consumption, cost, and stability, showing promising prospects for industrial applications.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst synthesis, in particular to a zinc-nickel single-atom alloy catalyst, a preparation method and application thereof. BACKGROUND

[0002] The cycloaddition reaction of CO2 and epoxide has 100% atom economy, and is considered as an ideal way to convert CO2 into high-value chemicals. The product cyclic carbonate is widely used in important fields such as organic solvents, pharmaceutical intermediates, lithium ion battery electrolytes, etc. However, the current mature thermal catalytic technology faces the challenges of high energy consumption and carbon emission due to its serious dependence on external heat source. In contrast, the photo-thermal catalytic technology uses light energy to induce local high temperature in situ at the nanoscale, which realizes efficient heating of active sites and provides the possibility to improve catalytic efficiency while significantly reducing overall energy consumption.

[0003] In the photo-thermal catalytic system, single-atom alloy (SAA) as a special single-atom catalyst (SAC) structure that anchors isolated metal atoms on the surface of another metal carrier, provides a new idea. SAA not only inherits the high atom utilization rate of SAC, but also introduces the intermetallic electronic regulation effect. This effect can significantly optimize the electronic structure of the active site, enhance its Lewis acidity, and promote the ring-opening of epoxide; on the other hand, it may also induce or synergize the Lewis basic sites on the surface of the carrier, thereby creating conditions for the simultaneous activation of CO2 and epoxide.

[0004] Despite the above research, the application of SAA, especially non-noble metal-based SAA, to photo-thermal catalytic CO2 cycloaddition reaction still faces challenges, and the existing technology mainly has the following deficiencies:

[0005] ① Limited catalyst structure design: The active sites of existing photo-thermal catalysts (such as noble metal nanoparticles or semiconductors) are usually continuous metal surfaces or limited interface sites, which are insufficient in specific adsorption and synergistic activation of CO2 and epoxide, limiting the reaction efficiency.

[0006] ② Insufficient atom utilization and electronic regulation: Although traditional SACs have high atom utilization rate, the electronic properties of their metal centers are mainly regulated by non-metal ligands, which have limited range and intensity, making it difficult to simultaneously optimize the activation ability of two different nature reactants (Lewis acidic epoxide and Lewis basic CO2) on a single active site.

[0007] ③Coupling between photo-thermal performance and catalytic performance is poor: many materials either have good photo-thermal performance but low catalytic activity, or have catalytic activity but weak photo-thermal conversion ability. How to simultaneously realize efficient light energy capture-thermal energy conversion and excellent catalytic activity in one material system is a key difficulty in designing high-performance photo-thermal catalysts.

[0008] ④Preparation and report of non-noble metal-based high-performance SAA are rare: current research on SAA is mostly focused on noble metal systems (such as Pd-Cu, Pt-Cu, etc.), which are high in cost. Research reports on SAA constructed by inexpensive metals such as zinc (Zn) and nickel (Ni), especially for photo-thermal CO2 conversion, are very limited. The universal preparation method of such catalysts, the clear active structure (especially the existence of Zn in the form of a single atom on the surface of Ni), and the structure-activity relationship in photo-thermal catalysis are still unclear.

[0009] In view of this, the present application is proposed. SUMMARY

[0010] To solve the above technical problems, the present application provides a zinc-nickel single-atom alloy catalyst, a preparation method and an application. Specifically, the catalyst can simultaneously have efficient photo-thermal conversion performance and abundant Lewis acid / base bifunctional active sites that can synergistically activate CO2 and epoxide, thereby realizing high activity and high selectivity of photo-thermal catalytic CO2 cycloaddition reaction under mild conditions.

[0011] In order to achieve the purpose of the present application, the following technical solutions are adopted:

[0012] The present application provides a preparation method of a zinc-nickel single-atom alloy catalyst, comprising the following steps:

[0013] S1, dissolving a nickel source and a zinc source in a first solvent to obtain a metal salt solution;

[0014] S2, dissolving a carbon source and / or a complexing agent in a second solvent to form a carbon source solution;

[0015] S3, dispersing a template agent in a third solvent, heating and stirring until completely dissolved to form a template agent solution;

[0016] S4, sequentially adding the metal salt solution and the carbon source solution to the template agent solution, heating and stirring until completely dissolved, heating to a first temperature and continuing to stir, and completely volatilizing the solvent to obtain a solid precursor;

[0017] S5, under the protection of an inert gas, calcining and cooling the solid precursor to obtain a zinc-nickel single-atom alloy catalyst.

[0018] Further, the first solvent is deionized water;

[0019] The second solvent is anhydrous ethanol;

[0020] The third solvent is a mixed solvent of anhydrous ethanol and deionized water;

[0021] The nickel source is nickel nitrate;

[0022] The zinc source is zinc acetate;

[0023] The carbon source and / or complexing agent is citric acid;

[0024] The template agent is barbituric acid.

[0025] Further, anhydrous ethanol and deionized water are mixed in a volume ratio of 1:1.

[0026] Further, in the metal salt solution, the molar ratio of nickel to zinc is (0.5-2):1;

[0027] Further, the molar ratio of nickel to zinc is 1.3:1;

[0028] The molar ratio of the template agent to all metals in the metal salt solution is (5-20):1.

[0029] Further, in the S4, the first temperature is 100-120 DEG C;

[0030] Further, in the S4, the first temperature is 110 DEG C;

[0031] In the S5, the heating rate of calcination is 3-10 DEG C / min, the calcination temperature is 800-1000 DEG C, and the calcination time is 1-4 h.

[0032] Further, in the S5, the heating rate of calcination is 5 DEG C / min, the calcination temperature is 900 DEG C, and the calcination time is 2 h.

[0033] The application also provides a zinc-nickel single-atom alloy catalyst prepared by the above method, which has a carbon-coated structure, a porous surface, zinc dispersed in the form of single atoms on the surface of nickel particles to form a single-atom alloy structure, and Lewis acid sites and Lewis base sites.

[0034] The application also provides an application of the above zinc-nickel single-atom alloy catalyst in a photo-thermal catalytic CO2 and epoxide cycloaddition reaction.

[0035] Further, the specific steps of the zinc-nickel single-atom alloy catalyst catalyzing the CO2 and epoxide cycloaddition reaction include:

[0036] Sa, the zinc-nickel single-atom alloy catalyst, the promoter, the solvent and the epoxide substrate are sequentially added for reaction, CO2 is introduced to remove air in the reaction system, and then CO2 is continuously introduced until the pressure of the reaction system reaches the target initial pressure;

[0037] Sb, the photo-thermal catalytic reaction is carried out under the conditions of starting magnetic stirring and light source irradiation, so that CO2 reacts with the epoxide to generate the cyclic carbonate.

[0038] Further, the epoxide substrate is at least one of propylene oxide, epichlorohydrin, phenyl glycidyl ether, styrene oxide and 1,2-epoxyhexane.

[0039] Further, the promoter is tetrabutylammonium bromide.

[0040] The solvent is N,N-dimethylformamide.

[0041] Further, the mass ratio of the catalyst to the epoxide substrate is (0.5-1.2):1.

[0042] The molar ratio of the promoter to the epoxide substrate is (0.01-0.05):1.

[0043] Further, in the step of introducing CO2 to remove air in the reaction system in the Sa, the introduction rate of CO2 is 10 mL / min-30 mL / min, and the duration is 5 min-15 min.

[0044] The target initial pressure is 0.05 MPa-0.3 MPa.

[0045] In the Sb, the condition of light source irradiation is a xenon lamp with a power of 300 W, and the reaction time of the photo-thermal catalytic reaction is 5 h-15 h.

[0046] Further, the introduction rate of CO2 is 20 mL / min, and the duration is 10 min.

[0047] The target initial pressure is 0.1 MPa.

[0048] The reaction time of the photo-thermal catalytic reaction is 10 h.

[0049] The present application has the following technical effects:

[0050] This invention successfully synthesizes a novel and high-performance zinc-nickel single-atom alloy catalyst through innovative material design and preparation methods. This catalyst ingeniously combines efficient photothermal conversion, the electronic regulation characteristics of single-atom alloys, and the structural advantages of porous carbon supports. It achieves highly efficient and selective conversion of CO2 cycloaddition reactions under mild conditions, while exhibiting significant advantages in energy consumption, cost, and stability, demonstrating promising prospects for industrial applications. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 X-ray diffraction spectrum;

[0053] Figure 2 Transmission electron microscope image;

[0054] Figure 3 Scanning electron microscope image;

[0055] Figure 4 Scanning electron microscope image;

[0056] Figure 5 Aberration-corrected transmission electron microscope image;

[0057] Figure 6 X-ray photoelectron spectroscopy: full spectrum;

[0058] Figure 7 X-ray photoelectron spectrum: C 1s;

[0059] Figure 8 X-ray photoelectron spectrum: O 1s;

[0060] Figure 9 X-ray photoelectron spectrum: Ni 2p;

[0061] Figure 10 X-ray photoelectron spectrum: N 1s;

[0062] Figure 11 X-ray photoelectron spectrum: Zn 2p;

[0063] Figure 12 Specific surface area analysis;

[0064] Figure 13 Results of the cyclic experiment. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0066] In a first aspect, the present invention provides a method for preparing a zinc-nickel single-atom alloy catalyst, comprising the following steps:

[0067] S1. Dissolve the nickel source and zinc source in the first solvent to obtain a metal salt solution;

[0068] S2. Dissolve the carbon source and / or complexing agent in a second solvent to form a carbon source solution;

[0069] S3. Disperse the template agent in the third solvent, heat and stir until completely dissolved to form a template agent solution;

[0070] S4. The metal salt solution and carbon source solution are added sequentially to the template agent solution, heated and stirred until completely dissolved, heated to the first temperature and stirred continuously to allow the solvent to evaporate completely, thus obtaining a solid precursor.

[0071] S5. Under the protection of an inert gas, the solid precursor is calcined and cooled to obtain a zinc-nickel single-atom alloy catalyst.

[0072] In some embodiments, the first solvent is deionized water;

[0073] The second solvent is anhydrous ethanol;

[0074] The third solvent is a mixture of anhydrous ethanol and deionized water;

[0075] The nickel source is nickel nitrate;

[0076] The zinc source is zinc acetate;

[0077] The carbon source and / or complexing agent is citric acid;

[0078] The template agent is barbituric acid.

[0079] In some embodiments, anhydrous ethanol and deionized water are mixed at a volume ratio of 1:1.

[0080] In some embodiments, the molar ratio of nickel to zinc in the metal salt solution is (0.5-2):1;

[0081] In some embodiments, the molar ratio of nickel to zinc is 1.3:1;

[0082] The molar ratio of the template agent to all metals in the metal salt solution is (5-20):1.

[0083] In some embodiments, in step S4, the first temperature is 100°C-120°C;

[0084] In some embodiments, in step S4, the first temperature is 110°C;

[0085] In S5, the heating rate of calcination is 3℃ / min-10℃ / min, the calcination temperature is 800℃-1000℃, and the calcination time is 1-4h.

[0086] In some embodiments, in step S5, the heating rate of calcination is 5°C / min; the calcination temperature is 900°C; and the calcination time is 2 hours.

[0087] Steps S1-S4 essentially utilize a solvent evaporation-induced self-assembly process. Metal salts (nickel and zinc sources) form a complex metal-organic complex network in solution in the presence of citric acid (a complexing agent) and barbituric acid (a template agent). As the solvent evaporates, these components precipitate and assemble together, forming a structurally uniform solid precursor. Citric acid acts as both a carbon source and a complexing agent, effectively chelating metal ions and preventing excessive aggregation during subsequent calcination.

[0088] The high-temperature pyrolysis in step S5 is crucial. Under an inert atmosphere (such as nitrogen), the organic components (citric acid, barbituric acid) in the precursor carbonize to form a conductive carbon coating layer, which stabilizes the metal particles and promotes photothermal conversion. Simultaneously, the high temperature provides the kinetic energy for atomic migration, allowing zinc atoms to diffuse and embed into the nickel lattice surface, rather than forming independent zinc particles or zinc-nickel alloy particles. This achieves single-atom-level dispersion of zinc on the nickel surface, forming a single-atom alloy structure. At high temperatures, some zinc components vaporize and escape, leaving abundant mesopores or macropores in the material, significantly increasing the specific surface area of ​​the catalyst and providing more contact sites and mass transfer channels for the reactants.

[0089] This method enables the controllable preparation of SAA structures through simple solution mixing and programmed temperature pyrolysis, exhibiting good reproducibility and suitability for scale-up. The resulting catalyst possesses strong structural stability and photothermal properties, along with a high specific surface area.

[0090] Secondly, the present invention also provides a zinc-nickel single-atom alloy catalyst prepared by the above-mentioned method for preparing zinc-nickel single-atom alloy catalyst. The catalyst has a carbon-coated structure with a porous surface. Zinc is dispersed on the surface of nickel particles in the form of single atoms to form a single-atom alloy structure, and simultaneously has Lewis acidic sites and Lewis basic sites.

[0091] In the catalyst precursor prepared by this invention, the organic components are carbonized to form a conductive carbon coating layer. The carbon layer has broad-spectrum absorption and efficient non-radiative relaxation characteristics, which can rapidly convert the absorbed light energy into heat energy, causing the catalyst particles to generate local high temperatures under light irradiation. This is the energy source for "photothermal catalysis".

[0092] Zinc is dispersed as single atoms on the surface of nickel particles. When zinc atoms are introduced onto the nickel substrate surface, the difference in electronegativity and atomic radius between the two leads to a redistribution of the electronic structure on the Ni surface (ligand effect and strain effect). This typically results in charge transfer (electrons may transfer from zinc to nickel, causing a shift in the d-band center of nickel) and the creation of unsaturated sites (isolated zinc atoms and their surrounding nickel atoms may become highly active unsaturated coordination sites). This electronic modulation allows the SAA to simultaneously generate optimized Lewis acidic and Lewis basic sites. Lewis acidic sites (possibly originating from electron-deficient Ni or Zn sites) favor the polarization and activation of CO bonds in the epoxide, promoting ring opening; Lewis basic sites (possibly originating from electron-rich Ni sites or oxygen-containing groups on the carbon support surface) favor the adsorption and activation of acidic CO2 molecules. This bifunctional synergy is key to the efficient catalysis of CO2 cycloaddition.

[0093] The SAA structure offers maximized atom utilization and a highly optimized electronic structure, resulting in high intrinsic catalytic activity. Unique Lewis acid / base sites enable simultaneous and efficient activation of both types of reactants, enhancing reaction efficiency. The carbon-coated structure achieves localized and efficient conversion of light energy to heat energy, with energy consumption far lower than traditional thermocatalysis.

[0094] Thirdly, the present invention also provides the application of the above-mentioned zinc-nickel single-atom alloy catalyst in the photothermal catalytic cycloaddition reaction of CO2 with epoxides.

[0095] In some embodiments, the specific steps of the zinc-nickel single-atom alloy catalyst catalyzing the cycloaddition reaction of CO2 with epoxides include:

[0096] Sa, the zinc-nickel single-atom alloy catalyst, co-catalyst, solvent and epoxide substrate are added in sequence to carry out the reaction, CO2 is introduced to remove air from the reaction system, and then CO2 is continued to be introduced until the pressure of the reaction system reaches the target initial pressure;

[0097] Sb, then under the conditions of magnetic stirring and light source irradiation, a photothermal catalytic reaction is carried out, so that CO2 reacts with epoxide to generate cyclic carbonate.

[0098] In some embodiments, the epoxide substrate is at least one selected from propylene oxide, epichlorohydrin, phenyl glycidyl ether, styrene oxide, and 1,2-epoxyhexane.

[0099] In some embodiments, the co-catalyst is tetrabutylammonium bromide;

[0100] The solvent is N,N-dimethylformamide.

[0101] In some embodiments, the mass ratio of the catalyst to the epoxide substrate is (0.5-1.2):1;

[0102] The molar ratio of the co-catalyst to the epoxide substrate is (0.01-0.05):1.

[0103] In some embodiments, in the step of introducing CO2 into Sa to remove air from the reaction system, the CO2 introduction rate is 10 mL / min-30 mL / min, and the duration is 5 min-15 min;

[0104] The target initial pressure is 0.05 MPa-0.3 MPa;

[0105] In the Sb, the irradiation condition of the light source is a xenon lamp with a power of 300W, and the reaction time of the photothermal catalytic reaction is 5h-15h.

[0106] In some embodiments, the CO2 injection rate is 20 mL / min and the duration is 10 min;

[0107] The target initial pressure is 0.1 MPa;

[0108] The reaction time for the photothermal catalytic reaction is 10 hours.

[0109] The use of tetrabutylammonium bromide (TBAB) as a cocatalyst is a standard choice for this type of reaction, as it acts as a nucleophile to accelerate the ring-opening step of epoxides. Dimethyl sulfoxide (DMF), as a polar solvent, facilitates reactant dissolution and mass transfer. Under irradiation by a light source (such as a xenon lamp), the catalyst absorbs light energy and generates heat, creating a high-temperature microenvironment at the catalyst-reaction liquid interface. This high temperature accelerates molecular motion, adsorption / desorption processes, and the reaction rate. Simultaneously, the bifunctional active sites on the catalyst surface efficiently catalyze the reaction under thermal drive, achieving the conversion of CO₂ + epoxides to cyclic carbonates.

[0110] The following is a detailed explanation using specific embodiments:

[0111] Example 1:

[0112] 0.2908 g of nickel nitrate and 0.1098 g of zinc acetate were dissolved in 10 ml of deionized water; 0.2 g of citric acid was dissolved in 10 ml of anhydrous ethanol; 2 g of barbituric acid was dispersed in a mixed solution of 20 ml of anhydrous ethanol and deionized water (V / V = 1:1), and stirred at 80 °C until completely dissolved. While stirring continuously, the above citric acid solution and metal salt solution were added sequentially to the barbituric acid solution. The mixture was then heated to 110 °C and stirred continuously until the solvent completely evaporated, yielding a solid precursor. Subsequently, under a nitrogen atmosphere, the temperature was increased from room temperature to 900 °C at a rate of 5 °C / min, and calcined at 900 °C for 2 hours to obtain a Ni-Zn / C catalyst.

[0113] 0.06 g of catalyst, 0.048 g of tetrabutylammonium bromide (TBAB), 5 mL of N,N-dimethylformamide (DMF), and 0.1 mL of epichlorohydrin were sequentially added to the reactor. The reactor was sealed, and after confirming good airtightness, high-purity CO2 was continuously introduced into the system at a flow rate of 20 mL / min for 10 minutes to purge air from the reaction system. Subsequently, the outlet valve was closed, and CO2 was continued to be introduced until the initial system pressure reached 0.1 MPa. A magnetic stirrer and a 300 W xenon lamp (equipped with an AM 1.5G filter to simulate the solar spectrum) were turned on, and the reaction was carried out at room temperature for 10 h. After the reaction, the reaction solution was collected and extracted. The organic phases were combined, and the products were qualitatively and quantitatively analyzed using GC and GC-MS. The material showed a 91% conversion rate for the substrate and a 99% selectivity for the target product.

[0114] Example 2:

[0115] The specific implementation method is consistent with Example 1, and the substrate for the change reaction is shown in Table 1:

[0116] Table 1: Yields, products, and yields after changing the reaction substrate

[0117]

[0118] Experimental Example 1: Characterization of the prepared catalyst

[0119] Experimental results are as follows Figures 1-5 As shown, where, Figure 1 This can be seen from the text. Figure 1 The sample is an X-ray diffraction spectrum. The specific testing procedure is as follows: grind the material evenly and press it into a pellet, load it into the sample stage and calibrate the instrument and zero point; set the tube voltage to 45kV, the current to 40mA, the scanning angle range to 10-90°, and the speed to 10° / min; start scanning and acquiring the spectrum; after completion, perform background subtraction, peak finding and phase detection.

[0120] Figure 2 The transmission electron microscope (TEM) image shows the specific testing procedure: the sample was ultrasonically dispersed and a copper mesh was added, dried, and then loaded into the sample holder; vacuum was applied and pressurized, and the beam was centered and adjusted; after low-magnification localization, the focus / image was adjusted, and then the test was performed. The image shows that nickel exists in elemental form within the material.

[0121] Figure 3 and 4 The image shows a scanning electron microscope (SEM) image. The specific testing procedure was as follows: the sample was cut and cleaned, conductive adhesive was fixed to the sample stage and gold was sprayed on; the sample was placed in the cavity and a vacuum was drawn; the accelerating voltage, working distance, and beam current were set; the focus was adjusted to correct astigmatism, and secondary / backscatter imaging was selected, followed by testing. The image shows that the material has a loose, porous structure.

[0122] Figure 5 The image is a transmission electron microscope (TEM) image with spherical aberration correction. The specific testing procedure was as follows: the sample was dried by adding a copper mesh, and then mounted in a double-tilting sample holder; vacuum was applied and pressurized, and the electron gun was centered; after finding the region at low magnification, the image was switched to HRTEM / STEM, and Cs correction and astigmatism correction were performed. The presence of Zn single atoms on the surface of Ni particles was observed, thus confirming the formation of a zinc-nickel single-atom alloy.

[0123] Experimental Example 2: Analysis of the Chemical Properties of Catalyst Surfaces using X-ray Photoelectron Spectroscopy

[0124] The X-ray photoelectron spectroscopy (XPS) testing procedure involves cleaning and drying the sample, fixing it in a sample holder, placing it in a chamber, and evacuating it to an ultra-high vacuum. The X-ray source and energy level are selected, and a full-spectrum survey is performed first, followed by narrow-area elemental scanning. Experimental results are as follows: Figures 6-11 As shown in the figure, it can be seen that zinc and nickel have been successfully introduced into the material, which is composed of five elements: C, N, O, Ni and Zn, with nickel mainly existing in the form of elemental nickel.

[0125] Experimental Example 3: Specific Surface Area Analysis

[0126] The test procedure for specific surface area analysis is as follows: weigh the sample into a sample tube and record the mass; heat under vacuum to degas until constant weight; cool to liquid nitrogen temperature, and adsorb / desorb nitrogen gas point by point according to the set relative pressure; collect isotherms. Experimental results are as follows: Figure 12 As shown, the material has a high adsorption capacity and exhibits typical type IV isotherm characteristics, indicating that it has a large specific surface area.

[0127] Experiment Example 4: Cyclic Experiment

[0128] The cyclic experimental procedure was as follows: after the reaction, the material was recovered, washed, and dried; it was then returned to the reactor and reacted again under the same reaction conditions. This process was repeated multiple times to complete the cyclic test. The experimental results are as follows: Figure 13As shown in the figure, the conversion rate and selectivity did not decrease significantly after multiple cycles, proving that the material has good cyclicity.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a zinc-nickel single-atom alloy catalyst, characterized in that, Includes the following steps: S1. Dissolve the nickel source and zinc source in the first solvent to obtain a metal salt solution; S2. Dissolve the carbon source, or the carbon source and the complexing agent, in a second solvent to form a carbon source solution; S3. Disperse the template agent in the third solvent, heat and stir until completely dissolved to form a template agent solution; S4. The metal salt solution and carbon source solution are added sequentially to the template agent solution, heated and stirred until completely dissolved, heated to the first temperature and stirred continuously to allow the solvent to evaporate completely, thus obtaining a solid precursor. S5. Under the protection of an inert gas, the solid precursor is calcined and cooled to obtain a zinc-nickel single-atom alloy catalyst.

2. The method for preparing the zinc-nickel single-atom alloy catalyst according to claim 1, characterized in that, The first solvent is deionized water; The second solvent is anhydrous ethanol; The third solvent is a mixture of anhydrous ethanol and deionized water; The nickel source is nickel nitrate; The zinc source is zinc acetate; The carbon source and / or complexing agent is citric acid; The template agent is barbituric acid.

3. The method for preparing the zinc-nickel single-atom alloy catalyst according to claim 1, characterized in that, In the metal salt solution, the molar ratio of nickel to zinc is (0.5-2):1; The molar ratio of the template agent to all metals in the metal salt solution is (5-20):

1.

4. The method for preparing the zinc-nickel single-atom alloy catalyst according to claim 1, characterized in that, In step S4, the first temperature is 100℃-120℃; In S5, the heating rate during calcination is 3℃ / min-10℃ / min, the calcination temperature is 800℃-1000℃, and the calcination time is 1-4h.

5. A zinc-nickel single-atom alloy catalyst prepared by the method described in any one of claims 1-4, characterized in that, The catalyst has a carbon-coated structure with a porous surface. Zinc is dispersed on the surface of nickel particles in the form of single atoms, forming a single-atom alloy structure, and simultaneously possesses Lewis acidic sites and Lewis basic sites.

6. The application of the zinc-nickel single-atom alloy catalyst according to claim 5 in the photothermal catalytic cycloaddition reaction of CO2 with epoxides.

7. The application according to claim 6, characterized in that, The specific steps of the zinc-nickel single-atom alloy catalyst catalyzing the cycloaddition reaction of CO2 with epoxides include: Sa, the zinc-nickel single-atom alloy catalyst, co-catalyst, solvent and epoxide substrate are added in sequence to carry out the reaction, CO2 is introduced to remove air from the reaction system, and then CO2 is continued to be introduced until the pressure of the reaction system reaches the target initial pressure; Sb, then under the conditions of magnetic stirring and light source irradiation, a photothermal catalytic reaction is carried out, so that CO2 reacts with epoxide to generate cyclic carbonate.

8. The application according to claim 7, characterized in that, The epoxide substrate is at least one selected from propylene oxide, epichlorohydrin, phenyl glycidyl ether, styrene oxide, and 1,2-epoxyhexane.

9. The application according to claim 7, characterized in that, The mass ratio of the catalyst to the epoxide substrate is (0.5-1.2):1; The molar ratio of the co-catalyst to the epoxide substrate is (0.01-0.05):

1.

10. The application according to claim 7, characterized in that, In the step of introducing CO2 into Sa to remove air from the reaction system, the CO2 introduction rate is 10 mL / min-30 mL / min, and the duration is 5 min-15 min. The target initial pressure is 0.05 MPa-0.3 MPa; In the Sb, the irradiation condition of the light source is a xenon lamp with a power of 300W, and the reaction time of the photothermal catalytic reaction is 5h-15h.

Images