Preparation method of metal monatomic catalyst and metal monatomic catalyst

Abstract

The application discloses a preparation method of a metal single-atom catalyst and the metal single-atom catalyst. The method comprises the following steps: preparing metal nanoparticles by a specific method; coating the metal nanoparticles by using a first carrier to obtain a metal compound; coating the metal compound by using a second carrier to obtain a coated metal compound; and treating the coated metal compound under preset conditions to obtain the metal single-atom catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanomaterials and sub-nanomaterials, and particularly relates to a preparation method of a metal single-atom catalyst and the metal single-atom catalyst. BACKGROUND

[0002] Catalytic reactions usually occur on the surface of a catalyst, because the adsorption and desorption of reactants depend on the surface of the catalyst, and the adsorption and desorption behavior of the reactants can be adjusted by manipulating the electronic and atomic structure of the catalyst surface, so as to control the pathway and kinetics of the catalytic reaction.

[0003] In recent years, single-atom catalysts (SACs) with optimal atomic efficiency and excellent catalytic activity have attracted extensive attention and shown great potential to replace nanoparticles in many important reactions in the field of catalytic energy. Specifically, by placing a single atom as an active site on the support interface, the different surface properties contained in the support interface can be utilized to simultaneously activate the adsorbed molecules and increase the frequency of effective collisions, thereby enhancing the transfer of electrons and reactant species.

[0004] The skilled person in the art usually synthesizes single-atom sites on the surface of a single support by using synthesis methods such as impregnation and thermal reduction, and the adsorption of a precursor on the surface of a single support is not region-selective, so that the single atom cannot provide a wide d-band for the adsorption of multiple reactant molecules, resulting in that the single-atom site is usually insufficient to carry out complex catalytic reactions involving multiple electron and reactant species transfers, and the catalytic efficiency of the catalytic reaction is reduced. SUMMARY

[0005] Therefore, in order to be able to enrich the precursor at the interface between different supports and realize the selective and precise arrangement of a single atom on the interface between different supports, the present application provides a preparation method of a metal single-atom catalyst and the metal single-atom catalyst.

[0006] In order to achieve the above-mentioned purpose, in one aspect, the present application provides a preparation method of a metal single-atom catalyst, comprising:

[0007] Preparation of metal nanoparticles by a specific method;

[0008] Coating the metal nanoparticles with a first support to obtain a metal composite;

[0009] Coating the metal composite with a second support to obtain a coated metal composite;

[0010] Treating the coated metal composite under a preset condition to obtain a metal single-atom catalyst.

[0011] According to the embodiment of the present application, the specific method comprises: oleic acid thermal decomposition method or reduction method; the metal nanoparticles comprise: metal oxide nanoparticles and pure metal nanoparticles; and the metal complex is nanosphere with core-shell structure.

[0012] According to the embodiment of the present application, the metal oxide nanoparticles comprise one of: Fe3O4, MnO2, CoO, FeCoO x or FeMnO x ; and the pure metal nanoparticles comprise one of: Fe, Mn, Co, Ni, Pt, Pd or Au.

[0013] According to the embodiment of the present application, the size of the metal oxide nanoparticles is 5-50 nm; and the size of the pure metal nanoparticles is 3-20 nm.

[0014] According to the embodiment of the present application, the first carrier comprises silicon oxide; and the second carrier comprises carbon layer with heteroatom doping or oxide.

[0015] The heteroatom is a non-metal atom, and the non-metal atom comprises one or more of: N, S, B, P, F, I.

[0016] The oxide comprises one of: cerium oxide, titanium oxide, cobalt oxide, manganese oxide, iron oxide or zinc oxide.

[0017] According to the embodiment of the present application, the thickness of the silicon oxide is 10-100 nm; the thickness of the carbon layer with heteroatom doping is 5-50 nm; and the thickness of the oxide is 10-100 nm.

[0018] According to the embodiment of the present application, the coating method is sol-gel method, the solvent of the sol-gel method comprises cyclohexane solution or aqueous solution; and the surfactant of the sol-gel method comprises nonylphenol polyether-5, cetyltrimethylammonium bromide or tetradecyltrimethylammonium bromide.

[0019] According to the embodiment of the present application, under the preset condition, the coated metal complex is treated to obtain a metal single-atom catalyst, comprising:

[0020] The coated metal complex is pyrolyzed under a preset atmosphere and at a preset temperature to obtain a pyrolysis product;

[0021] The pyrolysis product is soaked in a solution with a preset concentration for a preset time to obtain the metal single-atom catalyst.

[0022] According to the embodiment of the present application, the preset atmosphere is inert atmosphere or air; the preset temperature is 900-1100℃; the solution with the preset concentration is 1 mol / L NaOH aqueous solution; and the preset time is 10-28 h.

[0023] In another aspect, the present application also provides a metal monatomic catalyst prepared by the above preparation method.

[0024] According to the embodiments of the present application, by coating the metal nanoparticles as precursors with different carriers and then treating them, the metal monatomic catalyst is obtained. By utilizing the different interaction forces between the metal nanoparticles and the different carriers, the metal nanoparticles can be promoted to migrate and diffuse at the interface between the different carriers, the selective arrangement of the metal nanoparticles at the interface between the different carriers is realized, the adsorption of the metal nanoparticles at the interface between the different carriers has regional selectivity, the contact between the metal atoms and the reactant species is improved, the uniformity and thermal stability of the monatomic sites are ensured, and the catalytic effect of the catalytic reaction is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A flow chart of the preparation method of the metal monatomic catalyst according to the embodiments of the present application;

[0026] Figure 2a A transmission electron micrograph of the Fe3O4 nanoparticles according to Embodiment One of the present application;

[0027] Figure 2b A size distribution graph of the Fe3O4 nanoparticles according to Embodiment One of the present application;

[0028] Figure 2c A high-resolution transmission electron micrograph of the Fe3O4 nanoparticles according to Embodiment One of the present application;

[0029] Figure 2d An X-ray diffraction pattern of the Fe3O4 nanoparticles according to Embodiment One of the present application;

[0030] Figure 3a A transmission electron micrograph of the Fe3O4@SiO2 nanospheres according to Embodiment One of the present application;

[0031] Figure 3b A particle size distribution graph of the Fe3O4@SiO2 nanospheres according to Embodiment One of the present application;

[0032] Figure 3c An N2 adsorption-desorption curve and the corresponding pore size distribution graph of the Fe3O4@SiO2 nanospheres according to Embodiment One of the present application;

[0033] Figure 4a A synthesis schematic diagram of the metal Fe monatomic catalyst according to Embodiment One of the present application;

[0034] Figure 4b A transmission electron micrograph of the synthesized metal Fe monatomic catalyst according to Embodiment One of the present application;

[0035] Figure 5a In-situ TEM image of Fe3O4@SiO2 / CdS@PDA before pyrolysis for Example 1 of the present application;

[0036] Figure 5b In-situ TEM image of Fe3O4@SiO2 / CdS@PDA after pyrolysis for Example 1 of the present application

[0037] Figure 5c STEM image of area 1 for Figure 5b STEM image of area 1 for

[0038] Figure 5d STEM image of area 2 for Figure 5b STEM image of area 2 for

[0039] Figure 5e In-situ TEM image of pyrolysis process of Fe3O4@SiO2 / CdS@PDA for Example 1 of the present application;

[0040] Figure 6a Oxygen reduction reaction curve of Fe single atom catalyst (Fe SAs / S-NC) prepared in Example 1 of the present application;

[0041] Figure 6b Half-wave potential E 1 / 2 and kinetic current J K of Fe single atom catalyst (Fe SAs / S-NC) prepared in Example 1 of the present application;

[0042] Figure 7 Zn-air battery polarization curve of Fe single atom catalyst (Fe SAs / S-NC) prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with specific examples and with reference to the accompanying drawings.

[0044] For complex reactions involving multiple electrons and molecules, the combination of various functional surfaces to form an active interface can promote the reaction. For example, electron transfer can be promoted on an interface composed of single atoms and clusters / NPs, thereby significantly improving oxygen reduction activity. Therefore, integrating heterogeneous surfaces to form a catalytic interface can effectively provide an optimized electron distribution, synergistic effect or tandem catalysis at the interface.

[0045] Traditional synthesis methods usually synthesize single atom sites on the surface of a single support, and the adsorption of precursors on the surface of a single support is not region-selective. Compared with the surface of a single support, selective and precise arrangement of single atoms requires the enrichment of precursors at the interface between different supports, which is still a major challenge at present. If the skilled person in the art can successfully manipulate the selective enrichment, migration and cleavage of precursors, it is possible to achieve the precise arrangement of single atoms at the interface between different supports.

[0046] Based on this, the present application provides a preparation method of a metal single atom catalyst and a metal single atom catalyst to achieve selective arrangement of single atoms at the interface between different supports.

[0047] Figure 1 Flow chart of the preparation method of the metal single atom catalyst according to an embodiment of the present application.

[0048] As shown in Figure 1 , the method can include operations S101-S104.

[0049] In operation S101, metal nanoparticles are prepared by a specific method.

[0050] In operation S102, the metal nanoparticles are coated with a first support to obtain a metal composite.

[0051] In operation S103, the metal composite is coated with a second support to obtain a coated metal composite.

[0052] In operation S104, the coated metal composite is treated under a predetermined condition to obtain a metal single atom catalyst.

[0053] According to an embodiment of the present application, the metal nanoparticles can include metal oxide nanoparticles and pure metal nanoparticles. The metal oxide nanoparticles can include but are not limited to Fe3O4, MnO2, CoO, FeCoO x or FeMnO x , and the pure metal nanoparticles can include but are not limited to Fe, Mn, Co, Ni, Pt, Pd or Au.

[0054] According to an embodiment of the present application, the preparation of metal nanoparticles by a specific method can include the preparation of metal oxide nanoparticles by a pyrolysis method or the preparation of pure metal nanoparticles by a reduction method.

[0055] According to the embodiment of the present application, the preparation of metal oxide nanoparticles by pyrolysis can include: dissolving a metal compound and an oleate in a mixed solvent composed of water, ethanol, and n-hexane, and performing pyrolysis at a preset temperature to obtain a metal-oleate complex solution; washing the upper organic layer of the metal-oleate complex solution with distilled water in a separatory funnel for several times; after washing, distilling the n-hexane in the metal-oleate complex solution to obtain a metal-oleate complex in a solid form; dissolving the synthesized metal-oleate complex and oleic acid in a 1-octadecene solution to obtain a reaction mixture, which is heated to a preset temperature at a preset constant temperature heating rate, and a violent reaction occurs, the reaction mixture changes from an initial transparent solution to a turbid and brown-black solution, and a solution containing nanocrystals is obtained; then, the solution containing nanocrystals is cooled to room temperature, and an ethanol solution is added to precipitate the nanocrystals, and the nanocrystals are separated by centrifugation, washed, and dried to obtain metal oxide nanoparticles.

[0056] According to the embodiment of the present application, the prepared metal oxide nanoparticles have an oleic acid amine covering on the surface, which is beneficial for subsequent coating of the first carrier, and can be uniformly dispersed by ultrasonic treatment in a cyclohexane solution.

[0057] According to the embodiment of the present application, the preparation of pure metal nanoparticles by reduction can include: adding a metal precursor into a solvent to perform a reduction reaction to produce pure metal nanoparticles.

[0058] According to the embodiment of the present application, the size of the metal oxide nanoparticles can be 5-50 nm, and preferably 5-20 nm.

[0059] According to the embodiment of the present application, the size of the metal oxide nanoparticles can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm; and preferably, the size can be 5 nm, 10 nm, 15 nm, or 20 nm.

[0060] According to the embodiment of the present application, the size of the pure metal nanoparticles can be 3-20 nm, and specifically, the size can be 3 nm, 5 nm, 7 nm, 10 nm, 15 nm, or 20 nm.

[0061] According to the embodiment of the present application, the metal nanoparticles are used as precursors, the size of the metal nanoparticles is controlled, the metal nanoparticles as precursors are controllably enriched and cracked, the selective arrangement of metal atoms at the interface between different carriers and the regulation of the density of metal atom sites are realized, the contact between the metal atoms and the reaction species is improved, and thus the regulation of the catalytic activity is realized.

[0062] According to an embodiment of the present application, the first carrier can be silicon dioxide, and the thickness of the silicon dioxide can be 10-100 nm, preferably 20-50 nm.

[0063] According to an embodiment of the present application, the second carrier can include a carbon layer or a carbon layer with heteroatom doping, and can also be an oxide.

[0064] According to an embodiment of the present application, the carbon layer can be obtained by polymerization of small molecules such as aniline, pyrrole, pyridine, 2,6-diaminopyridine, dopamine, thiophene, or metal organic frameworks.

[0065] According to an embodiment of the present application, the heteroatom in the carbon layer with heteroatom doping can be a non-metal atom, including but not limited to one or more of N, S, B, P, F, and I. For example, it can be a carbon layer doped with one non-metal atom, a carbon layer doped with two non-metal atoms, a carbon layer doped with three non-metal atoms, or a carbon layer doped with more than three non-metal atoms. Heteroatom doping can be achieved by adding hexamine, boric acid, phosphoric acid, disodium hydrogen phosphate, trichloro cyanamide, dicyanediamine, etc. during sintering.

[0066] According to an embodiment of the present application, the oxide can include but is not limited to cerium oxide, titanium oxide, cobalt oxide, manganese oxide, iron oxide, or zinc oxide. The thickness of the oxide can be 10-100 nm.

[0067] According to an embodiment of the present application, the method for coating the metal nanoparticles can include a sol-gel method.

[0068] According to an embodiment of the present application, the coating of the metal nanoparticles with the first carrier can include: coating the metal nanoparticles with silicon oxide in a cyclohexane solution using nonylphenol polyether-5 (CO-520) as a surfactant to generate a metal complex; or can include: coating the metal nanoparticles with silicon oxide in an aqueous solution using hexadecyl trimethyl ammonium bromide or tetradecyl trimethyl ammonium bromide as a surfactant to generate a metal complex.

[0069] According to an embodiment of the present application, the metal complex can be a nanosphere with a core-shell structure, specifically, the inside of the nanosphere is the metal nanoparticles, and the outside is the first carrier silicon dioxide.

[0070] According to an embodiment of the present application, the metal complex obtained above is coated again with the second carrier to obtain a coated metal complex. The outermost layer of the coated metal complex is the second carrier, the middle layer is the first carrier, and the innermost layer is the metal nanoparticles.

[0071] According to an embodiment of the present application, the metal complex after coating is treated under preset conditions to obtain a metal single-atom catalyst, which can include:

[0072] The metal complex after coating is pyrolyzed under a preset atmosphere and at a preset temperature to obtain a pyrolysis product; and the pyrolysis product is soaked in a solution with a preset concentration for a preset time to obtain a metal single-atom catalyst.

[0073] According to an embodiment of the present application, the preset atmosphere can be Ar, N2, He, or other inert gases or air; the preset temperature can be 900-1100℃; the solution with a preset concentration is 1 mol / L NaOH aqueous solution, and the preset time is 10-28h.

[0074] According to an embodiment of the present application, the preset temperature can be 900℃, 1000℃, or 1100℃; and the preset time can be 10h, 15h, 20h, 24h, or 28h.

[0075] According to an embodiment of the present application, in the process of pyrolyzing the metal complex after coating at high temperature, the metal nanoparticles have different interaction forces with different supports. For the supports with weak interaction forces, the metal nanoparticles will migrate on the surface of the supports under the driving of high temperature. However, for the supports with strong interaction forces, the metal nanoparticles will release metal atoms which are anchored in situ by the supports under the driving of high temperature. The two different interaction forces can promote the metal nanoparticles to migrate and diffuse on the surface of different supports, realize the selective arrangement of the metal nanoparticles on the interface between different supports, make the adsorption of the metal nanoparticles on the interface between different supports have regional selectivity, improve the contact of the metal atoms with reactant species, ensure the uniformity and thermal stability of the single-atom sites, and improve the catalytic effect of the catalytic reaction.

[0076] According to an embodiment of the present application, the metal nanoparticles are coated by different supports as precursors, and then treated to obtain a metal single-atom catalyst. The metal single-atom catalyst is arranged at the interface between different supports, which can realize the simultaneous activation of multiple adsorbed reaction molecules and improve the probability of effective collision, thereby improving the transfer of electrons and reaction molecules.

[0077] According to an embodiment of the present application, a metal single-atom catalyst is prepared based on the preparation method of the metal single-atom catalyst. The metal single-atom catalyst has a unique electronic and atomic structure, and can be used for efficient catalysis of various chemical reactions.

[0078] The preparation method of the metal single-atom catalyst is described in further detail below with specific examples. It should be noted that although the following examples illustrate the preparation of metal single-atom catalysts using different metal nanoparticles as precursors, it can be understood that the specific examples can implement the metal single-atom catalysts of the present application in various forms, and are not intended to limit the present application.

[0079] Examples 1-6 illustrate the preparation of metal single-atom catalysts using metal oxide nanoparticles as precursors; and Examples 7-10 illustrate the preparation of metal single-atom catalysts using pure metal nanoparticles as precursors.

[0080] Example 1

[0081] 1) 10.8 g of FeCl3·6H2O and 36.5 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water, and 140 ml of n-hexane. The resulting solution was heated to 70°C and maintained at this temperature for four hours. After the reaction was complete, the upper organic layer containing the iron-oleate complex was washed three times with 30 ml of distilled water in a separatory funnel. After washing, the n-hexane was distilled off to obtain the iron-oleate complex in the form of a waxy solid. 36 g of the synthesized iron-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). Then, the reaction mixture was heated to 320°C at a constant heating rate of 3.3°C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320°C, a vigorous reaction occurred, and the initially transparent solution became turbid and brown-black. Subsequently, the solution containing the nanocrystals was cooled to room temperature, and 500 ml of ethanol was added to precipitate the nanocrystals. The resulting Fe3O4 nanoparticles were separated by centrifugation, washed three times with n-hexane, and dried in a vacuum at 60°C.

[0082] 2) 5 g of CO-520 was added to 100 ml of cyclohexane and ultrasonically treated for 10 minutes. Then, 4 ml of a Fe3O4 solution (concentration of 2 mg / ml, dissolved in cyclohexane) was added to the above solution at room temperature, and ultrasonically treated for 30 min. Subsequently, 2 ml of NH4OH (25%-28% concentration) was added to the above solution, and 2 ml of tetraethyl orthosilicate was added dropwise. After stirring at room temperature for 10 h, Fe3O4@SiO2core-shell nanospheres were collected by adding ethanol and centrifugation. After three ethanol washes, the Fe3O4@SiO2core-shell nanospheres were dispersed in ethanol for further use.

[0083] 3) 200 mg of CdS was dispersed in 200 ml of Fe3O4@SiO2 ethanol solution (concentration of 1 mg / ml) and stirred at room temperature for 10 hours. After centrifugal separation at 11000 rpm / min and drying in vacuum at 60°C, 300 mg of Fe3O4@SiO2 / CdS was obtained. Then, the pre-synthesized Fe3O4@SiO2 / CdS (300 mg) was dispersed in 100 ml of freshly prepared sodium diethylthiocarbamate (Tris) buffer solution (10 mM, pH 8.5) by ultrasonic dispersion. Then, dopamine-HCl (600 mg in 10 ml of H2O) was added in the Tris buffer solution and stirred at room temperature for 12 h. After centrifugal separation and drying in vacuum at 60°C for 6 h, the desired polydopamine-coated Fe3O4@SiO2 / CdS, labeled as Fe3O4@SiO2 / CdS@PDA, was obtained.

[0084] 4) The Fe3O4@SiO2 / CdS@PDA powder was annealed at 1000°C for 3 hours under Ar atmosphere at a heating rate of 5°C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80°C for 24 hours to remove SiO2, thereby obtaining Fe single atom arranged on S-doped carbon carrier, labeled as Fe SAs / S-NC, i.e., Fe single atom catalyst.

[0085] The obtained Fe single atom catalyst can efficiently catalyze oxygen reduction reaction and Zn-air battery, and has higher activity than commercial Pt / C.

[0086] The preparation of the metal single atom catalyst of the present application is briefly described below with reference to the accompanying drawings of Example 1.

[0087] Figure 2a The transmission electron micrograph of the Fe3O4 nanoparticles of Example 1 of the present application; Figure 2b The size distribution graph of the Fe3O4 nanoparticles of Example 1 of the present application; Figure 2c The high-resolution transmission electron micrograph of the Fe3O4 nanoparticles of Example 1 of the present application; Figure 2d The X-ray diffraction pattern of the Fe3O4 nanoparticles of Example 1 of the present application.

[0088] According to the embodiment of the present application, Fe3O4 nanoparticles are used as precursors to synthesize Fe3O4@SiO2 / CdS@PDA, and then Fe3O4@SiO2 / CdS@PDA is annealed to obtain Fe SAs / S-NC. Figures 2a-2d It can be seen that the size of the synthesized Fe3O4 nanoparticles is about 8 nm, and the distribution is uniform. The high-resolution transmission electron micrograph and the X-ray diffraction image of the synthesized Fe3O4 nanoparticles correspond to the standard lattice and diffraction intensity of Fe3O4, respectively.

[0089] Figure 3aTransmission electron micrograph of Fe3O4@SiO2 nanospheres of the embodiment one of the present application; Figure 3b Particle size distribution graph of Fe3O4@SiO2 nanospheres of the embodiment one of the present application; Figure 3c N2 adsorption-desorption curve and corresponding pore size distribution graph of Fe3O4@SiO2 nanospheres of the embodiment one of the present application.

[0090] According to the embodiment of the present application, from Figure 3a It can be seen that a single Fe3O4 nanoparticle is coated in the center of SiO2, wherein the thickness of SiO2 is 15.5 nm; the particle size of Fe3O4@SiO2 nanospheres is about 39 nm; from Figure 3c It can be seen that the surface area of Fe3O4@SiO2 nanospheres is 108 m 2 / g, and the pore size distribution proves that there are a large number of micropores and mesopores, which can provide a channel for the escape of Fe3O4 nanoparticles at high temperature.

[0091] Figure 4a Synthetic schematic diagram of metal Fe single-atom catalyst of the embodiment one of the present application; Figure 4b Transmission electron micrograph of the synthetic metal Fe single-atom catalyst of the embodiment one of the present application.

[0092] According to the embodiment of the present application, Figure 4a and Figure 4b The process of coating Fe3O4@SiO2 / CdS with dopamine, high-temperature pyrolysis and etching of SiO2 is included. Figure 4a Schematic diagram and Figure 4b The corresponding transmission electron micrograph shows the change in the microstructure of the nanomaterial after each processing. Specifically, after coating Fe3O4@SiO2 / CdS with dopamine, a layer of polydopamine with a thickness of 20 nm is uniformly coated on the surface of Fe3O4@SiO2. After high-temperature pyrolysis, the internal Fe3O4 nanoparticles and CdS nanorods disappear. Among them, CdS volatilizes at high temperature, Cd volatilizes due to low melting point, and part of S is doped into the carbon layer (marked as S-NC). After etching of SiO2, a hollow carbon skeleton structure is obtained.

[0093] Figure 5a In-situ transmission electron micrograph of Fe3O4@SiO2 / CdS@PDA before pyrolysis of the embodiment one of the present application; Figure 5b In-situ transmission electron micrograph of Fe3O4@SiO2 / CdS@PDA after pyrolysis according to the embodiment one of the present application.

[0094] According to the embodiment of the present application, from Figure 5a and Figure 5bIt can be seen that after in-situ heat treatment at 1273K, Fe3O4 nanoparticles and CdS nanorods disappear in situ.

[0095] Figure 5c In response to Figure 5b Aberration-corrected high-angle annular dark-field scanning transmission electron microscope image of region 1; Figure 5d In response to Figure 5b High-angle annular dark-field scanning transmission electron microscope image with spherical aberration correction performed in region 2.

[0096] According to an embodiment of the present invention, from Figure 5c and Figure 5d It can be seen that after Fe3O4@SiO2 / CdS@PDA is pyrolyzed at 1273K, Fe is distributed on the carbon support in the form of individual atoms.

[0097] Figure 5e This is an in-situ transmission electron micrograph of the pyrolysis process of Fe3O4@SiO2 / CdS@PDA in Embodiment 1 of the present invention.

[0098] According to an embodiment of the present invention, from Figure 5e This allows us to characterize each step of the material's changes during pyrolysis. Specifically, CdS gradually volatilizes one by one at 650–660 °C, reaching complete volatilization at 900 °C. The temperature is then raised to 1000 °C and held. At 1000 °C for 5 seconds, Fe3O4 nanoparticles escape from the interior of the SiO2 spheres to their surface, reaching the interface between SiO2 and the carbon layer. With increasing holding time, the Fe3O4 nanoparticles migrate at the SiO2-carbon layer interface, while their size gradually decreases, eventually disappearing completely at 1000 °C for 70 seconds. Figure 5e This intuitively demonstrates the synthesis of metal single-atom catalysts at the interface between different supports proposed in this invention.

[0099] Figure 6a The oxygen reduction reaction curve of the Fe single-atom catalyst (Fe SAs / S-NC) prepared in Example 1 of the present invention; Figure 6b The half-wave potential E of the Fe single-atom catalyst (Fe SAs / S-NC) prepared in Example 1 of this invention 1 / 2 and dynamic current J K .

[0100] According to an embodiment of the present invention, Figure 6a The curves show the linear sweep spectroscopy (SSW) of the prepared Fe single-atom catalyst (Fe SAs / S-NC) during the oxygen reduction reaction, demonstrating that Fe SAs / S-NC possesses extremely high oxygen reduction activity, superior to commercial platinum-carbon catalysts. The half-wave potential E0 is also shown. 1 / 2and dynamic current J K like Figure 6b As shown, this further illustrates its excellent oxygen reduction reaction activity.

[0101] Figure 7 Zn-air battery polarization curve of the Fe single-atom catalyst (Fe SAs / S-NC) in Example 1 of this invention.

[0102] According to an embodiment of the present invention, by Figure 7 It is known that integrating Fe SAs / S-NC into a Zn-air battery can achieve a maximum power density of 272 mW / cm³. 2 It is superior to commercial platinum-carbon.

[0103] Example 2

[0104] 1) 5.4 g of MnCl2·4H2O and 24 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water, and 140 ml of n-hexane. The resulting solution was heated to 70 °C and maintained at this temperature for four hours. After the reaction was complete, the upper organic layer containing the manganese-oleate complex was washed three times with 30 ml of distilled water in a separatory funnel. After washing, the n-hexane was distilled off to obtain the manganese-oleate complex in a waxy solid form. 36 g of the synthesized manganese-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). The reaction mixture was then heated to 320 °C at a constant heating rate of 3.3 °C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320 °C, a vigorous reaction occurred, and the initially clear solution became turbid and brownish-black. Subsequently, the solution containing nanocrystals was cooled to room temperature, and 500 ml of ethanol was added to precipitate the nanocrystals. The obtained MnO2 nanoparticles were separated by centrifugation, washed three times with n-hexane, and dried in a vacuum at 60°C.

[0105] 2) Add 5g of CO-520 to 100ml of cyclohexane and sonicate for 10 minutes. Then, at room temperature, add 4ml of Fe3O4 solution (2mg / ml, dissolved in cyclohexane) to the above solution and sonicate for 30 minutes. Subsequently, add 2ml of NH4OH (25%-28% concentration) to the above solution and add 2ml of tetraethyl orthosilicate dropwise. After stirring at room temperature for 10 hours, collect the MnO2@SiO2 core-shell nanospheres by adding ethanol and centrifugation. After washing three times with ethanol, disperse the MnO2@SiO2 core-shell nanospheres in ethanol for further use.

[0106] 3) 200 mg of CdS was dispersed in 200 ml of MnO2@SiO2ethanol solution (1 mg / ml concentration) and stirred for 10 hours at room temperature. After centrifugation at 11000 rpm and drying in vacuum at 60 °C, 300 mg of MnO2@SiO2 / CdS was obtained. Then, the pre-synthesized MnO2@SiO2 / CdS (300 mg) was dispersed in 100 ml of freshly prepared sodium diethylthiocarbamate (Tris) buffer solution (10 mM, pH 8.5) using ultrasonication. Then, dopamine-HCl (600 mg in 10 ml H2O) was added in the Tris buffer solution and stirred for 12 h at room temperature. After centrifugation and drying in vacuum at 60 °C for 6 h, the desired polydopamine-coated MnO2@SiO2 / CdS, labeled as MnO2@SiO2 / CdS@PDA, was obtained.

[0107] 4) The MnO2@SiO2 / CdS@PDA powder was annealed at 1000 °C for 3 hours under Ar atmosphere with a heating rate of 5 °C / min. After cooling to room temperature, the SiO2was removed by soaking in 1 M NaOH aqueous solution at 80 °C for 24 hours, to obtain Mn single atom array on S-doped carbon support, labeled as Mn SAs / S-NC, i.e., Mn single atom catalyst.

[0108] Example 3

[0109] 1) 5.4 g of FeCl3-6H2O, 2.88 g of MnCl2-4H2O and 36.5 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water and 140 ml of n-hexane. The resulting solution was heated to 70 °C and maintained at this temperature for four hours. When the reaction was completed, the upper organic layer containing the iron cobalt-oleate complex was washed with 30 ml of distilled water in a separatory funnel three times. After washing, the n-hexane was distilled off to obtain the iron cobalt-oleate complex in the form of a waxy solid. 36 g of the synthesized iron cobalt-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). Then, the reaction mixture was heated to 320 °C at a constant heating rate of 3.3 °C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320 °C, a vigorous reaction occurred and the initially transparent solution became turbid and brownish black. Subsequently, the solution containing the nanocrystals was cooled to room temperature and 500 ml of ethanol was added to precipitate the nanocrystals. The resulting FeCoO x The nanoparticles were centrifuged, washed with n-hexane three times, and dried in vacuum at 60 °C.

[0110] 2) 5 g of CO-520 was added to 100 ml of cyclohexane and sonicated for 10 minutes. Then, 4 ml of FeCoO x solution (2 mg / ml concentration in cyclohexane) was added to the above solution and sonicated for 30 min. Subsequently, 2 ml of NH4OH (25-28% concentration) was added to the above solution and 2 ml of tetraethyl orthosilicate was added dropwise. After stirring for 10 h at room temperature, FeCoO x @SiO2core-shell nanospheres were collected by adding ethanol and centrifugation. After three ethanol washes, FeCoO x @SiO2core-shell nanospheres were dispersed in ethanol for further use.

[0111] 3) 200 mg of CdS was dispersed in 200 ml of FeCoO x @SiO2ethanol solution (1 mg / ml concentration) and stirred for 10 h at room temperature. After centrifugation at 11000 rpm and drying in vacuum at 60 °C, 300 mg of FeCoO x @SiO2 / CdS was obtained. Then, the pre-synthesized FeCoO x @SiO2 / CdS (300 mg) was dispersed in 100 ml of freshly prepared sodium diethylthiocarbamate (Tris) buffer solution (10 mM, pH 8.5) using sonication. Then, dopamine-HCl (600 mg in 10 ml of H2O) was added to the Tris buffer solution and stirred for 12 h at room temperature. After centrifugation and drying in vacuum at 60 °C for 6 h, the desired polydopamine-coated FeCoO x @SiO2 / CdS was obtained, labeled as FeCoO x @SiO2 / CdS@PDA.

[0112] 4) FeCoO x @SiO2 / CdS@PDA powder was annealed at 1000 °C for 3 h under Ar atmosphere with a heating rate of 5 °C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80 °C for 24 h to remove SiO2, obtaining Fe, Co single-atom arrays on S-doped carbon support, labeled as FeCo SAs / S-NC, i.e., Fe single-atom catalyst.

[0113] Example 4

[0114] 1) 10.8 g of FeCl3-6H2O and 36.5 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water, and 140 ml of n-hexane. The resulting solution was heated to 70°C and maintained at this temperature for four hours. When the reaction was complete, the upper organic layer containing the iron-oleate complex was washed three times with 30 ml of distilled water in a separatory funnel. After washing, the n-hexane was distilled off to obtain the iron-oleate complex in the form of a waxy solid. 36 g of the synthesized iron-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). Then, the reaction mixture was heated to 320°C at a constant temperature increase rate of 3.3°C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320°C, a vigorous reaction occurred and the initially transparent solution became turbid and brownish black. Subsequently, the solution containing the nanocrystals was cooled to room temperature and 500 ml of ethanol was added to precipitate the nanocrystals. The resulting Fe3O4 nanoparticles were separated by centrifugation, washed three times with n-hexane, and dried at 60°C under vacuum.

[0115] 2) 5 g of CO-520 was added to 100 ml of cyclohexane and sonicated for 10 minutes. Then, 4 ml of a Fe3O4 solution (2 mg / ml concentration, dissolved in cyclohexane) was added to the above solution at room temperature and sonicated for 30 min. Subsequently, 2 ml of NH4OH (25-28% concentration) was added to the above solution, and 2 ml of tetraethyl orthosilicate was added dropwise. After stirring at room temperature for 10 h, Fe3O4@SiO2 core-shell spheres were collected by adding ethanol and centrifugation. After three ethanol washes, Fe3O4@SiO2 was dried at 60°C under vacuum for further use.

[0116] 3) 200 mg of Fe3O4@SiO2 was dispersed in 100 ml of freshly prepared sodium diethylthiocarbamate (Tris) buffer solution (10 mM, pH 8.5) using ultrasonication. Then, dopamine-HCl (600 mg in 10 ml of H2O) was added to the Tris buffer solution and stirred at room temperature for 12 h. Centrifugation and drying at 60°C under vacuum for 6 h with deionized water and ethanol three times yielded the desired polydopamine-coated Fe3O4@SiO2, labeled as Fe3O4@SiO2@PDA.

[0117] 4) The Fe3O4@SiO2@PDA powder was annealed at 1000°C for 3 hours under an Ar atmosphere at a temperature increase rate of 5°C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80°C for 24 hours to remove the SiO2, thereby obtaining Fe single atoms arranged on a carbon support, labeled as Fe SAs / NC, i.e., a Fe single atom catalyst.

[0118] Example 5

[0119] 1) 10.8 g of FeCl3-6H2O and 36.5 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water, and 140 ml of n-hexane. The resulting solution was heated to 70°C and maintained at this temperature for four hours. When the reaction was complete, the upper organic layer containing the iron-oleate complex was washed with 30 ml of distilled water three times in a separatory funnel. After washing, the n-hexane was distilled off to obtain the iron-oleate complex in the form of a waxy solid. 36 g of the synthesized iron-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). Then, the reaction mixture was heated to 320°C at a constant heating rate of 3.3°C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320°C, a vigorous reaction occurred and the initially transparent solution became turbid and brownish black. Subsequently, the solution containing the nanocrystals was cooled to room temperature and 500 ml of ethanol was added to precipitate the nanocrystals. The resulting Fe3O4 nanoparticles were separated by centrifugation, washed three times with n-hexane, and dried in a vacuum at 60°C.

[0120] 2) 5 g of CO-520 was added to 100 ml of cyclohexane and sonicated for 10 minutes. Then, 4 ml of a Fe3O4 solution (2 mg / ml concentration, dissolved in cyclohexane) was added to the above solution at room temperature and sonicated for 30 min. Subsequently, 2 ml of NH4OH (25-28% concentration) was added to the above solution, and 2 ml of tetraethyl orthosilicate was added dropwise. After stirring at room temperature for 10 h, Fe3O4@SiO2core-shell spheres were collected by adding ethanol and centrifugation. After three ethanol washes, the Fe3O4@SiO2core-shell nanospheres were dispersed in ethanol for further use.

[0121] 3) 200 mg of CdS was dispersed in 200 ml of Fe3O4@SiO2ethanol solution (concentration of 1 mg / ml) and stirred for 10 hours at room temperature. After centrifugation at 11000 rpm and drying in vacuum at 60 °C, 300 mg of Fe3O4@SiO2 / CdS was obtained. Then, the previously synthesized Fe3O4@SiO2 / CdS (300 mg) and 30 mg of sodium dodecyl benzene sulfonate (SDS) were dispersed in 200 ml of deionized water using ultrasonic waves for 30 min at room temperature. Then, 400.0 μl of aniline, 6.0 ml of 1 M hydrochloric acid and 600 mg of ammonium persulfate were added to the above solution in sequence and stirred for 2 h at room temperature. After that, the suspension was collected by centrifugation and washed with deionized water and ethanol three times. After drying in vacuum at 60 °C for 6 h, the desired polyaniline-coated Fe3O4@SiO2 / CdS, labeled as Fe3O4@SiO2 / CdS@PANI, was obtained.

[0122] 4) The Fe3O4@SiO2 / CdS@PANI powder was annealed at 1000 °C for 3 hours under Ar atmosphere with a heating rate of 5 °C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80 °C for 24 hours to remove SiO2, thus obtaining Fe single atom arranged on S-doped carbon support, labeled as Fe SAs / S-NC(PANI), i.e., Fe single atom catalyst.

[0123] Example 6

[0124] 1) 10.8 g of FeCl3-6H2O and 36.5 g of sodium oleate were dissolved in a mixed solvent consisting of 80 ml of ethanol, 60 ml of distilled water and 140 ml of n-hexane. The resulting solution was heated to 70 °C and maintained at this temperature for four hours. When the reaction was completed, the upper organic layer containing the iron-oleate complex was washed with 30 ml of distilled water in a separatory funnel three times. After washing, the n-hexane was distilled off to obtain the iron-oleate complex in the form of a waxy solid. Then, 36 g of the synthesized iron-oleate complex and 5.7 g of oleic acid (20 mmol, 90%) were dissolved in 200 g of 1-octadecene (90%). Then, the reaction mixture was heated to 320 °C at a constant heating rate of 3.3 °C / min and maintained at this temperature for 30 min. When the reaction temperature reached 320 °C, a violent reaction occurred and the initially transparent solution became turbid and brown-black. Subsequently, the solution containing the nanocrystals was cooled to room temperature and 500 ml of ethanol was added to precipitate the nanocrystals. The resulting Fe3O4nanoparticles were separated by centrifugation, washed with n-hexane three times and dried in vacuum at 60 °C.

[0125] 2) 5 g of CO-520 was added to 100 ml of cyclohexane and sonicated for 10 minutes. Then, 4 ml of Fe3C>4 solution (2 mg / ml concentration, dissolved in cyclohexane) was added to the above solution at room temperature and sonicated for 30 min. Subsequently, 2 ml of NH4OH (25-28% concentration) was added to the above solution and 2 ml of tetraethyl orthosilicate was added dropwise. After stirring for 10 h at room temperature, Fe3C>4@SiC>2 core-shell nanospheres were collected by adding ethanol and centrifugation. After three ethanol washes, the Fe3C>4@SiC>2 core-shell nanospheres were dispersed in ethanol for further use.

[0126] 3) 200 mg of CdS was dispersed in 200 ml of Fe3C>4@SiC>2 ethanol solution (1 mg / ml concentration) and stirred for 10 h at room temperature. After centrifugation at 11000 rpm and drying in vacuum at 60 °C, Fe3C>4@SiC>2 / CdS was obtained. Then, pre-synthesized Fe3C>4@SiC>2 / CdS (100 mg) and 150 mg of 3-aminophenol (3-AP) were dispersed in 50 ml of ethanol / water solution (1 :1 by volume) at room temperature using ultrasonic waves with ethylenediamine (100 μΐ, 57 mg / ml) as catalyst. Subsequently, it was stirred for 24 h at room temperature. Finally, poly-3-aminophenol-coated Fe3C>4@SiC>2 / CdS, labeled as Fe3C>4@SiC>2 / CdS@3-AP, was obtained by centrifugation, purification with distilled water, and drying in vacuum at 343 K for 6 h.

[0127] 4) Fe3C>4@SiC>2 / CdS@3-AP powder was annealed at 1000 °C for 3 h under Ar atmosphere with a heating rate of 5 °C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80 °C for 24 h to remove SiC>2, obtaining Fe single atom arranged on S-doped carbon support, labeled as Fe SAs / S-NC(3-AP), i.e., Fe single atom catalyst.

[0128] Example 7

[0129] 1) Take 0.455 g of cetyltrimethylammonium bromide (CTAB) and mix it with 42 ml of deionized water in a round bottom flask. Then, add to the mixture 5 ml of an aqueous solution of potassium tetrachloroplatinate (K2PtCl4) (concentration 10 mM). The flask is closed with a rubber stopper and the mixture is stirred at 300 rpm / min for 10 min. Subsequently, the flask containing the mixture is heated to 50°C in a silicon oil bath until the surfactant dissolves and the solution becomes almost transparent. Then, an ice-cold aqueous solution of sodium borohydride (NaBH4, concentration 500 mM, 3 ml) is added thereto using a syringe. The H2gas generated inside the flask is released through the needle of the syringe for 20 min. The solution is kept at 50°C under stirring at 300 rpm / min for 15 h of continuous stirring, the final solution turns brown. After cooling to room temperature, 20 ml of the brown solution are mixed with 80 ml of deionized water and to the mixture 2 ml of aqueous ammonia are added. A 10% by volume of TEOS diluted in ethanol, 4 ml, is added for the silicon formation. The mixture is left to react for 1 h under stirring at 500 rpm / min to form Pt@SiO2. Then, the resulting solution is centrifuged at 12000 rpm / min for 15 min, washed three times with deionized water and finally dried in air at 80°C.

[0130] 2) 200 mg of Pt@SiO2are dispersed with ultrasound in 100 ml of a freshly prepared sodium diethylthiocarbamate trihydrate (Tris) buffer solution (10 mM, pH 8.5). Then, dopamine-HCl is added to the Tris buffer solution (600 mg in 10 ml of H2O) and left to stir at room temperature for 12 h. The centrifugally isolated and dried in vacuum at 60°C for 6 h, obtaining the desired Pt@SiO2coated with polydopamine, labeled Pt@SiO2@PDA.

[0131] 3) The Pt@SiO2@PDA powder is annealed at 1000°C for 3 hours under Ar atmosphere with a temperature increase rate of 5°C / min. After cooling to room temperature, it is immersed in 1 M aqueous NaOH solution at 80°C for 24 hours to remove the SiO2, obtaining Pt single-atom arranged on a carbon support, labeled Pt SAs / NC,

[0132] i.e. Pt single-atom catalyst.

[0133] Example 8

[0134] 1) 20 ml of 0.12 mmol Pd(N03)2.2H20 (aq) solution was mixed with 20 ml of 0.2 mmol tetradecyltrimethylammonium bromide (TTAB) solution. Subsequently, 7.1 mmol of N2H4.H20 solution was added, which resulted in Pd nanoparticles protected by TTAB surfactant, as indicated by a rapid color change from bright orange to clear black. The Pd nanoparticle suspension was stirred for 10 minutes and further diluted by adding 120 ml of 1.2 mmol TTAB solution. The diluted suspension showed no sign of any agglomeration and was vigorously stirred for 20 min. After stirring, the pH of the diluted Pd nanoparticle suspension was adjusted to 10.7 using NaOH. In this basic suspension, 10.8 mmol of TEOS diluted in 5 ml of ethanol was added in three equal portions, each 10 min apart. The catalyst was stirred for 24 h to complete the coating of Pd nanoparticles by Si02. Then, the catalyst was collected by centrifugation, washed with water three times, washed with ethanol three times, and finally dried in air at 353 K to obtain Pd@Si02.

[0135] 2) 200 mg of Pd@Si02 was dispersed in 100 ml of freshly prepared sodium diethylthiocarbamate trihydrate (Tris) buffer solution (10 mM, pH 8.5) using ultrasonication. Then, dopamine-HCl (600 mg in 10 ml of H20) was added in the Tris buffer solution and stirred at room temperature for 12 h. The centrifugally isolated and dried at 60 °C under vacuum for 6 h with deionized water and ethanol three times to obtain the desired Pd@Si02 coated with polydopamine, labeled as Pd@Si02@PDA.

[0136] 3) The Pt@Si02@PDA powder was annealed at 1000 °C for 3 h under Ar atmosphere with a heating rate of 5 °C / min. After cooling to room temperature, it was immersed in 1 M NaOH aqueous solution at 80 °C for 24 h to remove Si02, thus obtaining Pd single-atom array on carbon support, labeled as Pd SAs / NC, i.e., Pd single-atom catalyst.

[0137] Example 9

[0138] 1) Take 0.455 g of cetyltrimethylammonium bromide (CTAB) and mix with 42 ml of deionized water in a round bottom flask. Then, add to the mixture 5 ml of an aqueous solution of potassium tetrachloroplatinate (K2PtCl4) (concentration 10 mM). The flask is closed with a rubber stopper and the mixture is stirred at 300 rpm / min for 10 min. Subsequently, the flask containing the mixture is heated to 50°C in a silicon oil bath until the surfactant dissolves and the solution becomes almost transparent. Then, an ice-cold aqueous solution of sodium borohydride (NaBH4, concentration 500 mM, 3 ml) is added thereto using a syringe. The H2gas generated inside the flask is released through the needle of the syringe for 20 min. The solution is kept at 50°C under stirring at 300 rpm / min for 15 h of continuous stirring, the final solution turns brown. After cooling to room temperature, 20 ml of the brown solution are mixed with 80 ml of deionized water and to the mixture 2 ml of aqueous ammonia are added. After 10 min of waiting time for the stabilization and dispersion of the Pt nanoparticles, 4 ml of TEOS diluted in ethanol at 10% by volume are added for the silicon formation. The mixture is left to react for 1 h under stirring at 500 rpm / min to form Pt@SiO2. Then, the resulting solution is centrifuged at 12000 rpm / min for 15 min, washed three times with deionized water and finally dried in air at 80°C.

[0139] 2) The Pt@SiO2particles are dispersed in a mixture containing hydroxypropyl cellulose (HPC, 100 mg), ethanol (20 ml) and water (0.1 ml). After 30 min of stirring of the reaction mixture, tetrabutyl titanate (TBOT, 1 ml) is dissolved in ethanol (5 ml) and slowly added to the mixture by using a syringe pump (0.5 ml / min). After the injection, the temperature is raised to 80°C while the reaction mixture is stirred under reflux conditions for 90 min. The Pt@SiO2@TiO2is collected by centrifugation, washed with ethanol and finally dried in air at 60°C.

[0140] 3) The Pt@SiO2@TiO2powder is annealed at 1000°C for 3 hours under Ar atmosphere with a temperature ramp of 5°C / min. After cooling to room temperature, the SiO2is immersed in a 1 M aqueous solution of NaOH at 80°C for 24 hours to obtain the Pt single-atom arrangement on TiO2, labeled as Pt SAs / TiO2.

[0141] Example 10

[0142] 1) Take 0.455 g of cetyltrimethylammonium bromide (CTAB) and mix it with 42 ml of deionized water in a round bottom flask, then add to the mixture 5 ml of an aqueous solution of potassium tetrachloroplatinate (K2PtCl4) (concentration 10 mM). The flask is closed with a rubber stopper and the mixture is stirred at 300 rpm / min for 10 min. Subsequently, the flask containing the mixture is heated to 50°C in a silicon oil bath until the surfactant dissolves and the solution becomes almost transparent. Then, an ice-cold aqueous solution of sodium borohydride (NaBH4, concentration 500 mM, 3 ml) is added thereto using a syringe. The H2gas generated inside the flask is released through the needle of the syringe for 20 min. The solution is kept at 50°C under stirring at 300 rpm / min for 15 h of continuous stirring, the final solution turns brown. After cooling to room temperature, 20 ml of the brown solution are mixed with 80 ml of deionized water and to the mixture 2 ml of aqueous ammonia are added. A 10% by volume of TEOS diluted in ethanol is added after 10 min of waiting time for the stabilization and dispersion of the Pt nanoparticles, for the silicon formation. The mixture is left to react for 1 h under stirring at 500 rpm / min to form Pt@SiO2. Then, the resulting solution is centrifuged at 12000 rpm / min for 15 min, washed three times with deionized water and finally dried in air at 80°C.

[0143] 2) Pt@SiO2and 0.2171 g of Ce(NO3)3-6H2O (0.50 mmol) are dissolved in a mixture of 96 ml of isopropyl alcohol and glycerol (volume ratio 5:1), then the orange-yellow solution thus obtained is sealed in an autoclave and left at 180°C for 24 hours. Subsequently, it is separated by centrifugation, washed three times with ethanol and finally dried in air at 60°C to obtain Pt@SiO2@CeO2.

[0144] 3) The Pt@SiO2@CeO2powder is annealed at 1000°C for 3 hours under an Ar atmosphere with a temperature increase rate of 5°C / min. After cooling to room temperature, the SiO2is immersed in a 1 M aqueous solution of NaOH at 80°C for 24 hours to obtain the Pt monatomic arrangement on CeO2, labeled Pt SAs / CeO2, i.e. the Pt monatomic catalyst.

[0145] In summary, according to various embodiments, by coating metal nanoparticles as precursors with different carriers and then treating the metal nanoparticles, metal single-atom catalysts are obtained. By using different interaction forces between the metal nanoparticles and the different carriers, the metal nanoparticles can be promoted to migrate and diffuse at the interface between the different carriers, the metal nanoparticles can be selectively arranged at the interface between the different carriers, the adsorption of the metal nanoparticles at the interface between the different carriers has regional selectivity, the contact between the metal atoms and the reactant species is improved, the uniformity and thermal stability of the single-atom sites are ensured, and the catalytic effect of the catalytic reaction is improved.

[0146] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are merely examples of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a metal single-atom catalyst, comprising: Metal oxide nanoparticles including one of Fe3O4, MnO2, CoO, FeCoO x or FeMnO x ; or pure metal nanoparticles including one of Fe, Mn, Co, Ni, Pt, Pd or Au are prepared by pyrolysis or by reduction coating the metal oxide nanoparticles or the pure metal nanoparticles with a first carrier to obtain a metal composite, the first carrier comprising silicon oxide; coating the metal composite with a second carrier to obtain a coated metal composite, the second carrier comprising a carbon layer or an oxide, the carbon layer being obtained by polymerization of aniline, pyrrole, pyridine, 2, 6-diaminopyridine, dopamine, thiophene or metal organic framework, and the oxide comprising one of cerium oxide, titanium oxide, cobalt oxide, manganese oxide, iron oxide or zinc oxide; treating the coated metal composite under preset conditions to obtain a metal single-atom catalyst, including: pyrolyzing the coated metal composite under preset atmosphere and preset temperature to obtain a pyrolysis product; and immersing the pyrolysis product in a solution with a preset concentration for a preset time to obtain the metal single-atom catalyst, the preset atmosphere being inert atmosphere or air, the preset temperature being 900-1100℃, the solution being 1 mol / L NaOH aqueous solution, and the preset time being 10-28 h.

2. The method of claim 1, wherein, The metal composite is a nanosphere with a core-shell structure.

3. The method of claim 1, wherein, The size of the metal oxide nanoparticles is 5-50 nm, and the size of the pure metal nanoparticles is 3-20 nm.

4. The method of claim 1, wherein, The thickness of the silicon oxide is 10-100 nm, and the thickness of the oxide is 10-100 nm.

5. The method of claim 1, wherein, The method for coating the metal oxide nanoparticles or the pure metal nanoparticles with the first carrier is a sol-gel method, the solvent of the sol-gel method comprising cyclohexane solution or aqueous solution, and the surfactant of the sol-gel method comprising nonylphenol polyether-5, cetyltrimethylammonium bromide or tetradecyltrimethylammonium bromide. 6.A metal single-atom catalyst prepared by the method according to any one of claims 1-5.

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