A single-atom catalyst and its preparation method and application

Abstract

The present invention provides a single-atom catalyst, a preparation method thereof and an application thereof, which includes mixing an oxide of a single metal atom with a cerium dioxide support rich in oxygen defects, grinding, and performing a thermal dispersion reaction to obtain the single-atom catalyst; in the oxide of the single metal atom, calculated by the mass of the single metal atom, the mass ratio of the single metal atom to the mass of the support rich in oxygen defects is (0.1-4.0):100. The preparation method provided by the present invention effectively solves the problems in the prior art such as the complex process of single-atom synthesis technology, the difficulty in controlling the single-atom loading amount, and the difficulty in large-scale preparation, and improves the universality of the single-atom catalyst synthesis method.

Description

Technical Field

[0001] The present invention relates to the field of catalysis technology, specifically to single-atom catalysts, and particularly to a single-atom catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Single-atom catalysts have attracted great attention due to their maximized atomic utilization rate and unique structure. Theoretically, single-atom catalysts have a metal dispersion close to 100% and a unique metal coordination environment. The single-atom catalysts with the highest atomic utilization efficiency and unique size quantum effect exhibit excellent catalytic activity in important reactions such as hydrogenation reactions, CO oxidation, and methane conversion. In recent years, various synthesis strategies have emerged, such as pyrolysis and atomic layer deposition. However, due to the disadvantages of low yield, complex process, and high cost, they are not conducive to large-scale production. And the single-atom preparation methods usually only apply to one or several elements, and it is very difficult to extrapolate the preparation method of one single-atom catalyst to another single-atom preparation, and the applicability of the preparation method is poor. In addition, at relatively high reaction temperatures, the aggregation and sintering of small particle nanoparticles and single atoms on the carrier are to some extent inevitable, which greatly hinders the practical application of single-atom catalysts.

[0003] CN112973759A discloses a preparation method of a metal single-atom catalyst. In this preparation method, a coupling agent is first grafted onto a hydroxylated template to form a surface-functionalized first template, and then a metal precursor is monodispersed and anchored on the surface of the first template to form a second template with the metal precursor loaded on the surface. Then, after physically coating and isolating the metal precursor on the surface of the second template with a carbon source, the template is removed to obtain the metal single-atom catalyst. This preparation method is based on the strategy of combining chemical confinement (dispersion and anchoring) and physical confinement (coating and isolation) to achieve the purpose of precisely controllable preparation of the metal single-atom catalyst.

[0004] CN110694669A discloses a preparation method of a single-atom catalyst. This invention adopts a thermal diffusion method. Using a foam transition metal as a metal source, under a mixed atmosphere of ammonia gas and an inert gas, high-temperature heat treatment is carried out. The metal atoms on the surface of the foam transition metal volatilize in the form of M(NH3) x and are subsequently captured by the carrier material, thereby obtaining a large amount of single-atom catalysts at one time and realizing the large-scale preparation of single-atom catalysts.

[0005] CN117504882A discloses a Fe single-atom supported catalyst prepared by confining with an amorphous BaTiO3 layer, its preparation and application. It uses BaTiO3 as a precursor, and through high-temperature hydrothermal reduction with sodium borohydride, Ov-BaTiO3 coated with an amorphous layer on the surface is prepared. Then, the method of modifying and calcining with ferrous bipyridine is applied to form Fe single atoms by confining with the amorphous layer, thereby obtaining the single-atom Fe supported catalyst.

[0006] Therefore, it is of great significance to provide a preparation method of single-atom catalysts with high catalytic activity that is easy for large-scale production. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a single-atom catalyst, its preparation method and application. The present invention selects a cerium dioxide carrier rich in oxygen defects and grinds it with the oxide of metal single atoms. Through a thermal dispersion reaction, a single-atom catalyst is prepared. The preparation method provided by the present invention effectively solves the problems of complex processes in existing single-atom synthesis technologies, difficult control of single-atom loading amounts, and difficulties in large-scale amplification preparation, etc., and improves the universality of the single-atom catalyst synthesis method.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method of a single-atom catalyst. The preparation method includes:

[0010] Mix the oxide of metal single atoms with a cerium dioxide carrier rich in oxygen defects, grind, and perform a thermal dispersion reaction to obtain the single-atom catalyst; in the oxide of metal single atoms, calculated by the mass of metal single atoms, the mass ratio of the metal single atoms to the mass of the carrier rich in oxygen defects is (0.1-4):100.

[0011] The present invention selects a carrier rich in oxygen defects and mixes it with the oxide of metal single atoms. Through grinding treatment, the metal interface interaction is enhanced. During the thermal dispersion reaction, the oxygen vacancies in the cerium dioxide carrier rich in oxygen defects promote the breakage of the M-O bond in the metal oxide, forming single atoms M1, and then a single-atom catalyst is prepared.

[0012] In the preparation method provided by the present invention, calculated by the mass of metal single atoms, the mass ratio of metal single atoms to the mass of the carrier rich in oxygen defects affects the conversion efficiency of the oxide to metal single atoms. If the mass ratio of dispersible single atoms is too high, part of the oxide cannot be converted into metal single atoms.

[0013] The mass ratio of the metal single atom to the oxygen defect-rich carrier is (0.1-4.0):100, for example, 0.1:100, 0.2:100, 0.3:100, 0.5:1, 0.6:100, 0.7:100, 0.9:100, 1.0:100, 1.2:100, 1.4:100, 1.6:100, 1.8:100, 2.0:100, 2.2:100, 2.5:100, 2.8:100, 3.0:100, 3.5:100 or 4.0:100, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably (0.3-2.5):100.

[0014] Preferably, the method of mixing the oxide of metal single atoms and the carrier rich in oxygen defects comprises mixing in an inching mixer.

[0015] In the present invention, grinding is beneficial to increase the interaction between the oxide of the metal single atom and the interface of the cerium dioxide support rich in oxygen defects, increase the dispersion limit, and is beneficial for the oxygen vacancies in the cerium dioxide support rich in oxygen defects to promote the breaking of the MO bond in the oxide of the metal single atom to form a single atom, thereby preparing a single atom catalyst.

[0016] Preferably, the grinding includes mechanical grinding, and the time of the mechanical grinding is 10 min-60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In the present invention, the temperature of the thermal dispersion reaction affects the existence state of metal single atoms. If the temperature of the thermal dispersion reaction is too low, the dispersion of metal single atoms cannot be achieved. If the temperature of the thermal dispersion reaction is too high, the metal single atoms are easily formed into metal single substances. Too high or too low temperature is not conducive to the formation of single atom catalysts.

[0018] Preferably, the temperature of the thermal dispersion reaction is 400°C-900°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, including but not limited to the listed values, and other values ​​not listed in the numerical range are equally applicable. The time of the thermal dispersion reaction is 2.0h-6.0h, for example, it can be 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, 5.5h or 6.0h, including but not limited to the listed values, and other values ​​not listed in the numerical range are equally applicable.

[0019] In the present invention, the atmosphere of the thermal dispersion reaction is not particularly limited, and it can be realized in air or an inert atmosphere. The inert atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include nitrogen and argon, helium and nitrogen, or argon and helium.

[0020] Preferably, the metal single atoms include any one or a combination of at least two of Ti, Cr, Mn, Fe, Co, Ge, Mo, Ru, Cd, In, Sn, Sb, Te, La, Pt, Pb, Bi, Pr, Nd. Typical but non-limiting combinations include the combination of Ti and Cr, the combination of Mn and Fe, the combination of Co and Ge, the combination of Mo and Ru, the combination of Cd and Sb, the combination of Bi and In, the combination of Bi, Mn and Sb, the combination of Bi, Nd and Mo, the combination of Fe, Mo and Sb, the combination of Fe, Mo and Nb, or the combination of Fe, Sb and Nb.

[0021] In the present invention, the oxide of the metal single atom is the oxide well-known in the art for the metal single atom. Exemplarily, the oxide of the metal single atom includes any one or a combination of at least two of TiO2, Cr2O3, Mn2O3, Fe2O3, Co2O3, GeO2, MoO3, RuO2, CdO, In2O3, SnO2, Sb2O3, TeO2, La2O3, PtO2, PbO, Bi2O3, Pr2O3, Nd2O3. Typical but non-limiting combinations include the combination of TiO2 and Cr2O3, the combination of Mn2O3 and Fe2O3, the combination of Co2O3 and GeO2, the combination of MoO3 and RuO2, the combination of CdO and In2O3, the combination of SnO2 and Sb2O3, the combination of TeO2 and La2O3, the combination of PtO2 and PbO, the combination of Bi2O3 and Pr2O3, the combination of Bi2O3 and In2O3, the combination of Bi2O3, Mn2O3 and Sb2O3, the combination of Bi2O3, MoO3 and Nd2O3, the combination of Fe2O3, Nd2O3 and Sb2O3, the combination of Fe2O3, MoO3 and Sb2O3, or the combination of Fe2O3, MoO3 and Nd2O3.

[0022] Preferably, the cerium dioxide carrier rich in oxygen vacancies includes any one or a combination of at least two of cerium dioxide nanorods rich in oxygen vacancies, cerium dioxide cubes rich in oxygen vacancies, or cerium dioxide nanoparticles rich in oxygen vacancies. Typical but non-limiting combinations include the combination of cerium dioxide nanorods rich in oxygen vacancies and cerium dioxide cubes, the combination of cerium dioxide nanoparticles rich in oxygen vacancies and cerium dioxide nanorods, or the combination of cerium dioxide cubes rich in oxygen vacancies and cerium dioxide nanoparticles.

[0023] Preferably, the method for preparing the cerium dioxide support rich in oxygen vacancies includes: calcining a cerium dioxide precursor to obtain the cerium dioxide support rich in oxygen vacancies.

[0024] Preferably, the method for preparing the cerium dioxide precursor includes a hydrothermal method or a microreactor rapid thermal synthesis method.

[0025] Preferably, the method for preparing the cerium dioxide precursor using the hydrothermal method includes: mixing a cerium source solution and an alkali source solution in a hydrothermal reaction kettle, and after a hydrothermal reaction, performing solid-liquid separation to obtain the cerium dioxide support rich in oxygen vacancies.

[0026] The temperature of the hydrothermal reaction is 100°C - 180°C, for example, it can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable; the time of the hydrothermal reaction is 8h - 36h, for example, it can be 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h or 36h, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] The method of mixing the cerium source solution and the alkali source solution in the hydrothermal reaction kettle includes adding the alkali source solution dropwise to the cerium source solution under stirring.

[0028] Preferably, the method for preparing the cerium dioxide precursor using the microreactor rapid thermal synthesis method includes: flowing a cerium source solution and an alkali source solution into a reaction vessel in parallel according to a stoichiometric ratio to obtain a mixed solution, and the mixed solution sequentially flows through a thermal synthesis zone and a cooling zone, and then solid-liquid separation is performed to obtain the cerium dioxide precursor.

[0029] Preferably, the flow rate of the cerium source solution and the alkali source solution flowing into the reaction vessel independently is 0.1 mL / min - 10.0 mL / min, for example, it can be 0.1 mL / min, 0.2 mL / min, 0.5 mL / min, 0.7 mL / min, 0.9 mL / min, 1.0 mL / min, 2.0 mL / min, 3.0 mL / min, 4.0 mL / min, 5.0 mL / min, 6.0 mL / min, 7.0 mL / min, 8.0 mL / min, 9.0 mL / min or 10.0 mL / min.

[0030] Preferably, the pressure of the reaction vessel is 0 MPa - 1.0 MPa. For example, it can be 0 MPa, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, or 1.0 MPa, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the temperature of the thermal synthesis zone is 80°C - 180°C. For example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the temperature of the cooling zone is less than or equal to 30°C. For example, it can be -100°C, -50°C, -10°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, or 30°C, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] For the rapid thermal synthesis method of the microreactor provided by the present invention, the structures of the thermal synthesis zone and the cooling zone are not particularly limited as long as they can heat or cool the mixed solution passing through the corresponding zones to a specific temperature. Exemplarily, the thermal synthesis zone can be a hollow pipe spirally arranged in an oil bath at a specific temperature, and the cooling zone can be a hollow pipe spirally arranged in a water bath or an ice - water bath or liquid nitrogen at a specific temperature.

[0034] In the method for preparing the cerium dioxide precursor provided by the present invention, the cerium source, the base source, and the concentrations of the cerium source solution and the base source solution are all prior arts and are not particularly limited. Among them, according to the stoichiometric ratio, the base source is in excess to ensure complete reaction of the cerium source.

[0035] Exemplarily, the cerium source includes any one or a combination of at least two of ammonium cerium nitrate, cerium chloride, or cerium nitrate. Typical but non - limiting combinations include the combination of ammonium cerium nitrate and cerium chloride, the combination of cerium nitrate and ammonium cerium nitrate, or the combination of cerium chloride and cerium nitrate.

[0036] Exemplarily, the base source includes any one or a combination of at least two of ammonium carbonate, sodium hydroxide, potassium hydroxide, urea, or ammonia water. Typical but non - limiting combinations include the combination of ammonium carbonate and sodium hydroxide, the combination of potassium hydroxide and urea, or the combination of ammonia water and sodium hydroxide.

[0037] Exemplarily, the concentrations of the alkali source solution and the cerium source solution are each independently 2 mol / L - 10 mol / L. For example, they can be 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0038] Preferably, before calcining the cerium dioxide precursor, drying the cerium dioxide precursor is also included. The temperature of the drying is 60°C - 120°C. For example, it can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C. The time of the drying is 8 h - 24 h. For example, it can be 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, or 24 h, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the temperature of the calcination is 300°C - 800°C. For example, it can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C. The time of the calcination is 2 h - 8 h. For example, it can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h. The above calcination temperature and time include but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0040] Preferably, the calcination is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere includes air.

[0041] In a second aspect, the present invention provides a single-atom catalyst, which is obtained by the preparation method described in the first aspect.

[0042] In a third aspect, the present invention further provides an application of the single-atom catalyst described in the second aspect, and the single-atom catalyst is applied to the field of catalytic synthesis.

[0043] Exemplarily, the single-atom catalyst provided by the present invention can catalyze the synthesis of cyclic carbonates.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The preparation method provided by the present invention is simple. A carrier rich in oxygen defects is selected and mixed with a metal single-atom oxide. Through simple grinding treatment, the interaction between the metal single-atom oxide and the interface of the cerium dioxide carrier rich in oxygen defects is increased, the dispersion limit is enlarged, which is conducive to the oxygen vacancies in the cerium dioxide carrier rich in oxygen defects promoting the breaking of the M-O bond in the metal single-atom oxide. Through the thermal dispersion reaction, the direct dispersion of nano-scale or even micro-scale oxides and the direct conversion of oxide nanoparticles into single atoms are realized. It is applicable to the loading of various metal single atoms, effectively solving the deficiencies in the prior art such as complex synthesis, difficult control of single-atom loading amount, and difficulty in large-scale preparation, and improving the universality of the single-atom catalyst synthesis method. Description of the Drawings

[0047] Figure 1 It is a transmission electron microscope (TEM) result diagram of the cerium dioxide particle carrier rich in oxygen defects prepared by the present invention.

[0048] Figure 2 It is an electron paramagnetic resonance (EPR) result diagram of the cerium dioxide particle carrier rich in oxygen defects prepared by the present invention.

[0049] Figure 3 It is a transmission electron microscope (TEM) result diagram of the cerium dioxide nanorod carrier rich in oxygen defects prepared by the present invention.

[0050] Figure 4 It is a synchrotron radiation (XAFS) result diagram of the Bi single-atom catalyst prepared in Example 1.

[0051] Figure 5 It is a synchrotron radiation (XAFS) result diagram of the Co single-atom catalyst prepared in Example 2.

[0052] Figure 6 It is a synchrotron radiation (XAFS) result diagram of the Fe single-atom catalyst prepared in Example 3.

[0053] Figure 7 It is an X-ray diffraction (XRD) result diagram of the Nd single-atom catalyst prepared in Example 4.

[0054] Figure 8 It is a spherical aberration corrected transmission electron microscope (AC-STEM) result diagram of the Nd single-atom catalyst prepared in Example 4.

[0055] Figure 9 It is a synchrotron radiation (XAFS) result diagram of the Ru single-atom catalyst prepared in Example 5.

[0056] Figure 10XRD result diagram of the Sb single-atom catalyst prepared in Example 6.

[0057] Figure 11 XRD result diagram of the Ti single-atom catalyst prepared in Example 7.

[0058] Figure 12 XAFS result diagram of the La single-atom catalyst prepared in Example 8.

[0059] Figure 13 XAFS result diagram of the Mo single-atom catalyst prepared in Example 9.

[0060] Figure 14 XRD result diagram of the Te single-atom catalyst prepared in Example 10.

[0061] Figure 15 XAFS result diagram of the Pt single-atom catalyst prepared in Example 11.

[0062] Figure 16 XAFS result diagram of the Mn single-atom catalyst prepared in Example 12.

[0063] Figure 17 XRD result diagram of the Ge single-atom catalyst prepared in Example 13.

[0064] Figure 18 XRD result diagram of the In single-atom catalyst prepared in Example 14.

[0065] Figure 19 XAFS result diagram of the Pb single-atom catalyst prepared in Example 15.

[0066] Figure 20 XRD result diagram of the Sn single-atom catalyst prepared in Example 16.

[0067] Figure 21 XRD result diagram of the Cr single-atom catalyst prepared in Example 17.

[0068] Figure 22 XRD result diagram of the Cd single-atom catalyst prepared in Example 18.

[0069] Figure 23 XRD result diagram of the Pr single-atom catalyst prepared in Example 19.

[0070] Figure 24The figure shows the results of atomic-level elemental imaging (AC-STEM-Atomic-Mapping) of Bi-In dual single atoms prepared in Example 20 by aberration-corrected transmission electron microscopy.

[0071] Figure 25 The figure shows the X-ray diffraction (XRD) results of the single-atom catalysts prepared in Examples 21-25. Detailed implementation manners

[0072] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0073] The preparation method of the cerium dioxide cube support rich in oxygen defects used in the embodiments and comparative examples of the present invention is as follows:

[0074] (1) Preparation of cerium dioxide cube precursor by microreactor rapid thermal synthesis method: A 2 mol / L cerium nitrate solution and an excessive 5 mol / L sodium hydroxide solution are fed into the reactor in parallel to obtain a mixed solution. The mixed solution flows through a hollow pipe spirally arranged in an oil bath at 170 °C and a hollow pipe spirally arranged in a water bath at 10 °C in sequence, and then solid-liquid separation is carried out. The cerium dioxide cube precursor is obtained by drying at 100 °C for 10 h.

[0075] (2) Preparation of cerium dioxide cube support rich in oxygen defects: The cerium dioxide cube precursor prepared in step (1) is calcined in an air atmosphere at a calcination temperature of 700 °C and a calcination time of 4 h to obtain a cerium dioxide cube support rich in oxygen defects.

[0076] The preparation method of the cerium dioxide particle support rich in oxygen defects used in the embodiments and comparative examples of the present invention is as follows:

[0077] (1) Preparation of cerium dioxide particle precursor by hydrothermal method: A 3 mol / L cerium chloride solution and an excessive 6 mol / L potassium hydroxide solution are added to a hydrothermal reaction kettle. After hydrothermal reaction at 130 °C for 20 h, solid-liquid separation is carried out. The cerium dioxide particle precursor is obtained by drying at 120 °C for 16 h.

[0078] (2) Preparation of cerium dioxide particle support rich in oxygen defects: The cerium dioxide particle precursor prepared in step (1) is calcined in an air atmosphere at a calcination temperature of 350 °C and a calcination time of 8 h to obtain a cerium dioxide particle support rich in oxygen defects. The TEM of the cerium dioxide particle support is as Figure 1 shown, and the EPR test results of the cerium dioxide particles are as Figure 2 shown. EPR proves that the prepared cerium dioxide particle support has abundant oxygen vacancies.

[0079] The preparation method of the oxygen-deficient cerium oxide nanorod carrier used in the examples and comparative examples of the present invention is as follows:

[0080] (1) Preparation of cerium dioxide nanorod precursor by microreactor rapid thermal synthesis method: 2 mol / L cerium chloride solution and excess 8 mol / L potassium hydroxide solution are introduced into a reactor in parallel to obtain a mixed solution, and the mixed solution flows through a hollow pipe spirally arranged in a 90°C oil bath and a hollow pipe spirally arranged in a 25°C water bath in turn, and the solid-liquid separation is carried out, and the cerium dioxide nanorod precursor is obtained by drying at 85°C for 21 hours.

[0081] (2) Preparation of oxygen-deficient ceria nanorod carriers: The ceria particle precursor prepared in step (1) was calcined in an air atmosphere at a thermal dispersion reaction temperature of 550° C. for a thermal dispersion reaction time of 2 h to obtain oxygen-deficient ceria nanorod carriers. The TEM images of the ceria nanorod carriers are as follows: Figure 3 shown.

[0082] Example 1

[0083] This embodiment provides a method for preparing a Bi single-atom catalyst, the preparation method comprising:

[0084] The oxygen-deficient ceria cubic carrier was mixed with Bi2O3 in an inching mixer for 10 minutes, and then transferred to an agate mortar and ground for 10 minutes; the uniformly mixed powder was subjected to a thermal dispersion reaction in a high-purity nitrogen atmosphere to obtain the Bi single-atom catalyst.

[0085] The mass ratio of Bi in the Bi2O3 to the mass ratio of the ceria cubic carrier rich in oxygen defects is 2.42:100, the thermal dispersion reaction temperature is 500°C, and the thermal dispersion reaction time is 3h.

[0086] The synchrotron radiation (XAFS) results of the Bi single atom catalyst prepared in this example are as follows: Figure 4 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Bi-O path, while the Bi-Bi and Bi-O-Bi scattering paths present in Bi element and Bi2O3 are not detected, proving that Bi exists in the catalyst in the form of isolated atoms.

[0087] Example 2

[0088] This embodiment provides a method for preparing a Co single-atom catalyst, the preparation method comprising:

[0089] Mix the ceria particles carrier rich in oxygen vacancies with Co2O3 in a point mixer for 8 min, and then transfer it to an agate mortar and grind for 20 min; perform a thermal dispersion reaction on the uniformly mixed powder in a high-purity nitrogen atmosphere to obtain the Co single-atom catalyst.

[0090] The mass ratio of Co in the Co2O3 to the mass of the ceria particles carrier rich in oxygen vacancies is 0.64:100. The thermal dispersion reaction temperature is 500 °C, and the thermal dispersion reaction time is 3 h.

[0091] The synchrotron radiation (XAFS) results of the Co single-atom catalyst prepared in this example are as Figure 5 shown. There is a main peak in the extended X-ray absorption fine structure (EXAFS) spectrum, attributed to the Co-O path, and no Co-Co and Co-O-Co scattering paths present in Co metal and Co2O3 are detected, proving that Co exists in the catalyst in the form of isolated atoms.

[0092] Example 3

[0093] This example provides a preparation method of an Fe single-atom catalyst. The preparation method includes:

[0094] Mix the ceria nanorod carrier rich in oxygen vacancies with Fe2O3 in a point mixer for 10 min, and then transfer it to an agate mortar and grind for 45 min; perform a thermal dispersion reaction on the uniformly mixed powder in a high-purity nitrogen atmosphere to obtain the Fe single-atom catalyst.

[0095] The mass ratio of Fe in the Fe2O3 to the mass of the ceria nanorod carrier rich in oxygen vacancies is 0.63:100. The temperature of the thermal dispersion reaction is 500 °C, and the time of the thermal dispersion reaction is 3 h.

[0096] The synchrotron radiation (XAFS) results of the Fe single-atom catalyst prepared in this example are as Figure 6 shown. There is a main peak in the extended X-ray absorption fine structure (EXAFS) spectrum, attributed to the Fe-O path, and no Fe-Fe and Fe-O-Fe scattering paths present in Fe metal and Fe2O3 are detected, proving that Fe exists in the catalyst in the form of isolated atoms.

[0097] Example 4

[0098] This embodiment provides a method for preparing a Nd single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Nd2O3, the mass ratio of Nd in the Nd2O3 to the oxygen-deficient cerium dioxide nanorod carrier is 1.51:100, and the thermal dispersion reaction is carried out in a high-purity helium atmosphere.

[0099] The X-ray diffraction (XRD) results of the Nd single atom catalyst prepared in this example are as follows: Figure 7 The results of spherical aberration corrected transmission electron microscopy (AC-STEM) are shown in Figure 8 As shown, after Nd2O3 and the cerium dioxide nanorod carrier are physically mixed, an obvious Nd2O3 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the Nd2O3 characteristic peak disappears, indicating that the Nd element is distributed in the cerium dioxide carrier in a highly dispersed form.

[0100] Example 5

[0101] The present embodiment provides a method for preparing a Ru single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by RuO2, the mass ratio of Ru in the RuO2 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.53:100, the thermal dispersion reaction is carried out in a high-purity argon atmosphere, the thermal dispersion reaction temperature is 600°C, and the thermal dispersion time is 3 hours.

[0102] The synchrotron radiation (XAFS) results of the Ru single atom catalyst prepared in this example are as follows: Figure 9 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Ru-O path, while the Ru-Ru and Ru-O-Ru scattering paths present in Ru element and RuO2 are not detected, proving that Ru exists in the catalyst in the form of isolated atoms.

[0103] Example 6

[0104] This embodiment provides a method for preparing a Sb single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Sb2O3, the mass ratio of Sb in the Sb2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.42:100, and the thermal dispersion reaction is carried out in an air atmosphere.

[0105] The X-ray diffraction (XRD) results of the Sb single atom catalyst prepared in this example are as follows: Figure 10As shown, after physically mixing Sb2O3 and the cerium dioxide nanorod support, obvious Sb2O3 characteristic peaks are shown in the X-ray spectrum. After heat dispersion treatment, the Sb2O3 characteristic peaks disappear, indicating that the Sb element is distributed in the cerium dioxide support in a highly dispersed form.

[0106] Example 7

[0107] This example provides a preparation method of a Ti single-atom catalyst. Except that Fe2O3 is replaced by TiO2, the mass ratio of Ti in the TiO2 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 0.3:100, the heat dispersion reaction temperature is 700 °C, and the heat dispersion time is 2 h, the rest are the same as in Example 3.

[0108] The X-ray diffraction (XRD) results of the Ti single-atom catalyst prepared in this example are as Figure 11 shown. After physically mixing TiO2 and the cerium dioxide nanorod support, obvious TiO2 characteristic peaks are shown in the X-ray spectrum. After heat dispersion treatment, the TiO2 characteristic peaks disappear, indicating that the Ti element is distributed in the cerium dioxide support in a highly dispersed form.

[0109] Example 8

[0110] This example provides a preparation method of a La single-atom catalyst. Except that Fe2O3 is replaced by La2O3, and the mass ratio of La in the La2O3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 1.62:100, the rest are the same as in Example 3.

[0111] The synchrotron radiation (XAFS) results of the La single-atom catalyst prepared in this example are as Figure 12 shown. In the extended X-ray absorption fine structure (EXAFS) spectrum, there is a main peak, which is attributed to the La-O path, and the La-O-La scattering path existing in La2O3 is not detected, proving that La exists in the catalyst in the form of isolated atoms.

[0112] Example 9

[0113] This example provides a preparation method of a Mo single-atom catalyst. Except that Fe2O3 is replaced by MoO3, and the mass ratio of Mo in the MoO3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 0.53:100, the rest are the same as in Example 3.

[0114] The synchrotron radiation (XAFS) results of the Mo single-atom catalyst prepared in this example are as Figure 13As shown, in the extended X-ray absorption fine structure (EXAFS) spectrum, there is a main peak, which is attributed to the Mo-O path, while the Mo-Mo and Mo-O-Mo scattering paths present in elemental Mo and MoO3 are not detected, demonstrating that Mo exists in the catalyst in the form of isolated atoms.

[0115] Example 10

[0116] This example provides a preparation method for a Te single-atom catalyst. Except that Fe2O3 is replaced by TeO2, and the mass ratio of Te in TeO2 to the mass of the ceria nanorod support rich in oxygen defects is 0.72:100, the rest are the same as in Example 3.

[0117] The X-ray diffraction (XRD) results of the Te single-atom catalyst prepared in this example are as Figure 14 shown. After physically mixing TeO2 and the ceria nanorod support, obvious TeO2 characteristic peaks are shown in the X-ray spectrum. After the thermal dispersion treatment, the TeO2 characteristic peaks disappear, indicating that the Te element is distributed in the ceria support in a highly dispersed form.

[0118] Example 11

[0119] This example provides a preparation method for a Pt single-atom catalyst. Except that Fe2O3 is replaced by PtO2, the mass ratio of Pt in PtO2 to the mass of the ceria nanorod support rich in oxygen defects is 1.12:100, the thermal dispersion treatment temperature is 400 °C, and the thermal dispersion treatment time is 6 h, the rest are the same as in Example 3.

[0120] The synchrotron radiation (XAFS) results of the Pt single-atom catalyst prepared in this example are as Figure 15 shown. In the extended X-ray absorption fine structure (EXAFS) spectrum, there is a main peak, which is attributed to the Pt-O path, while the Pt-Pt and Pt-O-Pt scattering paths present in elemental Pt and PtO2 are not detected, demonstrating that Pt exists in the catalyst in the form of isolated atoms.

[0121] Example 12

[0122] This example provides a preparation method for a Mn single-atom catalyst. Except that Fe2O3 is replaced by Mn2O3, and the mass ratio of Mn in Mn2O3 to the mass of the ceria nanorod support rich in oxygen defects is 0.63:100, the rest are the same as in Example 3.

[0123] The synchrotron radiation (XAFS) results of the Mn single-atom catalyst prepared in this example are as Figure 16As shown, in the extended X-ray absorption fine structure (EXAFS) spectrum, there is a main peak, attributed to the Mn-O path, while the Mn-Mn and Mn-O-Mn scattering paths present in elemental Mn and Mn2O3 are not detected, demonstrating that Mn exists in the catalyst in the form of isolated atoms.

[0124] Example 13

[0125] This example provides a method for preparing a Ge single-atom catalyst. Except that Fe2O3 is replaced by GeO2, the mass ratio of Ge in GeO2 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 0.42:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0126] The X-ray diffraction (XRD) results of the Ge single-atom catalyst prepared in this example are as Figure 17 shown. After physically mixing GeO2 and the cerium dioxide nanorod support, obvious GeO2 characteristic peaks are shown in the X-ray spectrum. After thermal dispersion treatment, the GeO2 characteristic peaks disappear, indicating that the Ge element is distributed in the cerium dioxide support in a highly dispersed form.

[0127] Example 14

[0128] This example provides a method for preparing an In single-atom catalyst. Except that Fe2O3 is replaced by In2O3, the mass ratio of In in In2O3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 1.32:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0129] The X-ray diffraction (XRD) results of the In single-atom catalyst prepared in this example are as Figure 18 shown. After physically mixing In2O3 and the cerium dioxide nanorod support, obvious In2O3 characteristic peaks are shown in the X-ray spectrum. After thermal dispersion treatment, the In2O3 characteristic peaks disappear, indicating that the In element is distributed in the cerium dioxide support in a highly dispersed form.

[0130] Example 15

[0131] This example provides a method for preparing a Pb single-atom catalyst. Except that Fe2O3 is replaced by PbO, the mass ratio of Pb in PbO to the mass of the cerium dioxide nanorod support rich in oxygen defects is 1.21:100, the rest are the same as in Example 3.

[0132] The synchrotron radiation (XAFS) results of the Pb single-atom catalyst prepared in this example are as Figure 19As shown, in the extended X-ray absorption fine structure (EXAFS) spectrum, there is a main peak, which is attributed to the Pb-O path, while the Pb-Pb and Pb-O-Pb scattering paths present in elemental Pb and PbO are not detected, demonstrating that Pb exists in the catalyst in the form of isolated atoms.

[0133] Example 16

[0134] This example provides a method for preparing a Sn single-atom catalyst. Except that Fe2O3 is replaced with SnO2, the mass ratio of Sn in SnO2 to the mass of the ceria nanorod support rich in oxygen defects is 0.63:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0135] The X-ray diffraction (XRD) result diagram of the Sn single-atom catalyst prepared in this example is as Figure 20 shown. After physically mixing SnO2 and the ceria nanorod support, obvious SnO2 characteristic peaks are shown in the X-ray spectrum. After thermal dispersion treatment, the SnO2 characteristic peaks disappear, indicating that Sn elements are distributed in the ceria support in a highly dispersed form.

[0136] Example 17

[0137] This example provides a method for preparing a Cr single-atom catalyst. Except that Fe2O3 is replaced with Cr2O3, the mass ratio of Cr in Cr2O3 to the mass of the ceria nanorod support rich in oxygen defects is 0.55:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0138] The X-ray diffraction (XRD) result diagram of the Cr single-atom catalyst prepared in this example is as Figure 21 shown. After physically mixing Cr2O3 and the ceria nanorod support, obvious Cr2O3 characteristic peaks are shown in the X-ray spectrum. After thermal dispersion treatment, the Cr2O3 characteristic peaks disappear, indicating that Cr elements are distributed in the ceria support in a highly dispersed form.

[0139] Example 18

[0140] This example provides a method for preparing a Cd single-atom catalyst. Except that Fe2O3 is replaced with CdO, the mass ratio of Cd in CdO to the mass of the ceria nanorod support rich in oxygen defects is 0.61:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0141] The X-ray diffraction (XRD) results of the Cd single-atom catalyst prepared in this example are as follows: Figure 22 As shown, after physically mixing CdO and the ceria nanorod support, obvious CdO characteristic peaks are shown in the X-ray spectrum. After the thermal dispersion treatment, the CdO characteristic peaks disappear, indicating that Cd elements are distributed in the ceria support in a highly dispersed form.

[0142] Example 19

[0143] This example provides a preparation method of a Pr single-atom catalyst. Except that Fe2O3 is replaced by Pr2O3, the mass ratio of Pr in Pr2O3 to the mass of the oxygen-deficient ceria nanorod support is 1.62:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0144] The X-ray diffraction (XRD) results of the Pr single-atom catalyst prepared in this example are as follows: Figure 23 As shown, after mixing Pr2O3 and the ceria nanorod support, the Pr2O3 characteristic peaks disappear, indicating that Pr elements are distributed in the ceria support in a highly dispersed form.

[0145] Example 20

[0146] This example provides a preparation method of a Bi-In dual single-atom catalyst. Except that Fe2O3 is replaced by Bi2O3 and In2O3, the mass ratio of Bi and In in Bi2O3 and In2O3 to the mass of the oxygen-deficient ceria nanorod support is 1.26:0.66:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0147] The aberration-corrected transmission electron microscopy atomic-level element imaging (AC-STEM-Atomic-Mapping) results of the Bi-In dual single-atom catalyst prepared in this example are as follows: Figure 24 As shown, clear atomic-level distributions of Bi and In are shown in the aberration-corrected microscope, indicating that after mixing Bi2O3, In2O3, and CeO2, atomic-level Bi and In can be obtained through heat treatment.

[0148] Example 21

[0149] This example provides a preparation method of a Bi-Mn-Sb multi-single-atom catalyst. Except that Fe2O3 is replaced by Bi2O3, Mn2O3 and Sb2O3, the mass ratio of Bi, Mn and Sb in Bi2O3, Mn2O3 and Sb2O3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 2.42:0.63:0.67:100, the thermal dispersion treatment temperature is 700 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0150] The X-ray diffraction (XRD) results of the Bi-Mn-Sb multi-single-atom catalyst prepared in this example are as Figure 25 shown. After grinding and heat treatment, only the characteristic peaks of cerium dioxide remain in the XRD pattern, proving that Bi, Mn, and Sb have been distributed in cerium dioxide in a highly dispersed form.

[0151] Example 22

[0152] This example provides a preparation method of a Bi-Mo-Nd multi-single-atom catalyst. Except that Fe2O3 is replaced by Bi2O3, MoO3 and Nd2O3, the mass ratio of Bi, Mo and Nd in Bi2O3, MoO3 and Nd2O3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 1.17:0.27:0.72:100, the thermal dispersion treatment temperature is 600 °C, and the thermal dispersion treatment time is 3 h, the rest are the same as in Example 3.

[0153] The X-ray diffraction (XRD) results of the Bi-Mo-Nd multi-single-atom catalyst prepared in this example are as Figure 25 shown. After grinding and heat treatment, only the characteristic peaks of cerium dioxide remain in the XRD pattern, proving that Bi, Mo, and Nd have been distributed in cerium dioxide in a highly dispersed form.

[0154] Example 23

[0155] This example provides a preparation method of an Fe-Nd-Sb multi-single-atom catalyst. Except that Fe2O3 is replaced by Fe2O3, Nd2O3 and Sb2O3, the mass ratio of Fe, Nd and Sb in Fe2O3, Nd2O3 and Sb2O3 to the mass of the cerium dioxide nanorod support rich in oxygen defects is 0.35:0.72:0.67:100, the rest are the same as in Example 3.

[0156] The X-ray diffraction (XRD) results of the Fe-Nd-Sb multi-single-atom catalyst prepared in this example are as Figure 25As shown, after grinding and heat treatment, only the characteristic peaks of cerium dioxide remain in the XRD pattern, proving that Fe, Nd, and Sb have been distributed in cerium dioxide in a highly dispersed form.

[0157] Example 24

[0158] This example provides a method for preparing an Fe-Mo-Sb multi-single-atom catalyst. Except that Fe2O3 is replaced by Fe2O3, MoO3, and Sb2O3, and the mass ratio of Fe, Mo, and Sb in Fe2O3, MoO3, and Sb2O3 to the mass of the oxygen-deficient cerium dioxide nanorod support is 0.35:0.27:0.67:100, the rest are the same as in Example 3.

[0159] The X-ray diffraction (XRD) results of the Fe-Mo-Sb multi-single-atom catalyst prepared in this example are as Figure 25 shown. After grinding and heat treatment, only the characteristic peaks of cerium dioxide remain in the XRD pattern, proving that Fe, Mo, and Sb have been distributed in cerium dioxide in a highly dispersed form.

[0160] Example 25

[0161] This example provides a method for preparing an Fe-Mo-Nd multi-single-atom catalyst. Except that Fe2O3 is replaced by Fe2O3, MoO3, and Nd2O3, and the mass ratio of Fe, Mo, and Nd in Fe2O3, MoO3, and Nd2O3 to the mass of the oxygen-deficient cerium dioxide nanorod support is 0.35:0.27:0.72:100, the rest are the same as in Example 3.

[0162] The X-ray diffraction (XRD) results of the Fe-Mo-Nd multi-single-atom catalyst prepared in this example are as Figure 25 shown. After grinding and heat treatment, only the characteristic peaks of cerium dioxide remain in the XRD pattern, proving that Fe, Mo, and Nd have been distributed in cerium dioxide in a highly dispersed form.

[0163] Example 26

[0164] This example provides a method for preparing a single-atom catalyst. Except that the thermal dispersion treatment temperature is 300 °C, the rest are the same as in Example 1.

[0165] Example 27

[0166] This example provides a method for preparing a single-atom catalyst. Except that the thermal dispersion treatment temperature is 900 °C, the rest are the same as in Example 1.

[0167] Comparative Example 1

[0168] This comparative example provides a preparation method of a single-atom catalyst. Except that commercially available cerium dioxide is used as a carrier to replace the cerium dioxide cube carrier rich in oxygen vacancies, the rest are the same as in Example 1.

[0169] The cerium dioxide used in this comparative example was purchased from Sinopharm Chemical Reagent Co., Ltd., batch number: 20160224.

[0170] Comparative Example 2

[0171] This comparative example provides a preparation method of a single-atom catalyst. Except that TiO2 with an oxygen vacancy concentration equivalent to that is used as a carrier, the rest are the same as in Example 1. The preparation method of TiO2 used in this comparative example includes:

[0172] (1) Titanium butoxide and hydrofluoric acid were mixed in a Teflon autoclave at a volume ratio of 30:2.4 and reacted at 180 °C for 24 hours. After cooling to room temperature, the reaction solution was centrifuged, the precipitate was collected, and the precipitate was washed repeatedly to obtain a white powder sample.

[0173] (2) In a 10% H2 / Ar atmosphere, the white powder sample obtained in step (1) was sintered at 550 °C for 2 h and cooled to room temperature to obtain TiO2 with oxygen defects.

[0174] Comparative Example 3

[0175] This comparative example provides a preparation method of a single-atom catalyst. Except that the cerium dioxide cube carrier rich in oxygen vacancies and Bi2O3 are not ground, the rest are the same as in Example 1.

[0176] Comparative Example 4

[0177] This comparative example provides a preparation method of a single-atom catalyst. Except that the mass ratio of Bi in Bi2O3 to the mass of the cerium dioxide nanorod carrier rich in oxygen vacancies is 0.05:100, the rest are the same as in Example 1.

[0178] Comparative Example 5

[0179] This comparative example provides a preparation method of a single-atom catalyst. Except that the mass ratio of Bi in Bi2O3 to the mass of the cerium dioxide nanorod carrier rich in oxygen vacancies is 5:100, the rest are the same as in Example 1.

[0180] The present invention also provides the application of the single-atom catalysts prepared in the above Example 1, Example 18, Example 26, Example 27, and Comparative Examples 1 to 5 in the catalytic synthesis of cyclic carbonates. The preparation method includes:

[0181] Mix 0.036 g of the single-atom catalyst prepared in the above examples or comparative examples, 10.8 g of dimethyl carbonate, and 3.6 g of 1,2-butanediol in a 50 mL autoclave, and react at 120 °C for 20 min to prepare 1,2-butene carbonate.

[0182] The present invention also tests the conversion rate and selectivity of the single-atom catalyst prepared in the above examples or comparative examples for catalytic synthesis of cyclic carbonates. The test method is as follows:

[0183] After centrifugal separation of the synthesized cyclic carbonate, an appropriate amount of the supernatant is taken and an internal standard (biphenyl) is added, and quantitative analysis is carried out by gas chromatography internal standard method. The test results are shown in Table 1.

[0184] Application Example 1

[0185] This application example provides an application of the single-atom catalyst prepared in Example 1. The application includes using the single-atom catalyst prepared in Example 1 to catalytically synthesize cyclic carbonates. The synthesis method includes:

[0186] Mix 0.036 g of the single-atom catalyst prepared in Example 1, 10.8 g of dimethyl carbonate, and 3.6 g of 1,2-butanediol in a 50 mL autoclave, and react at 120 °C for 20 min to prepare 1,2-butene carbonate.

[0187] Application Example 2

[0188] Compared with Application Example 1, only the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Example 18, and 3.6 g of 1,2-butanediol is replaced with 3.04 g of 1,3-propanediol, and the rest are the same as Application Example 1.

[0189] Application Example 3

[0190] Compared with Application Example 1, only the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Example 26, and the rest are the same as Application Example 1.

[0191] Application Example 4

[0192] Compared with Application Example 1, only the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Example 27, and the rest are the same as Application Example 1.

[0193] Comparative Application Example 1

[0194] Compared with Application Example 1, only the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Comparative Example 1, and the rest are the same as Application Example 1.

[0195] Comparative Application Example 2

[0196] Compared with Application Example 1, except that the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Comparative Example 2, the rest are the same as Application Example 1.

[0197] Comparative Application Example 3

[0198] Compared with Application Example 1, except that the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Comparative Example 3, the rest are the same as Application Example 1.

[0199] Comparative Application Example 4

[0200] Compared with Application Example 1, except that the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Comparative Example 4, the rest are the same as Application Example 1.

[0201] Comparative Application Example 5

[0202] Compared with Application Example 1, except that the single-atom catalyst prepared in Example 1 is replaced with an equal mass of the single-atom catalyst prepared in Comparative Example 5, the rest are the same as Application Example 1.

[0203] Performance test:

[0204] After centrifugal separation of the cyclic carbonates synthesized in all the above application examples and comparative application examples, an appropriate amount of the supernatant was taken and an internal standard (biphenyl) was added, and quantitative analysis was carried out by the internal standard method of gas chromatography. The test results are shown in Table 1.

[0205] Table 1

[0206]

[0207] According to Examples 1 to 25, the present invention uses a simple and easy-to-implement method of grinding to increase the interaction between the metal single-atom oxide and the cerium dioxide support rich in oxygen vacancies, increase the dispersion limit, and is conducive to the promotion of the M-O bond cleavage in the metal single-atom oxide by the oxygen vacancies in the cerium dioxide support rich in oxygen vacancies to form single atoms, and a single-atom catalyst is prepared. The preparation method provided by the present invention effectively solves the problems of complex process of existing single-atom synthesis technology, difficult control of single-atom loading amount, and difficult large-scale preparation, etc., and improves the universality of the single-atom catalyst synthesis method.

[0208] According to the test results of Application Example 1 and Comparative Application Examples 1 to 2, if cerium dioxide not rich in oxygen vacancies is selected as the support, or a non-cerium dioxide support rich in oxygen vacancies is selected, it will affect the conversion of the metal single-atom oxide to the metal single atom, and thus a single-atom catalyst with excellent catalytic performance cannot be prepared.

[0209] According to the test results of Application Example 1 and Comparative Application Example 3, if the cerium dioxide cubic support rich in oxygen defects and Bi2O3 are not ground, the interfacial interaction cannot be increased and the dispersion limit cannot be increased. During the subsequent thermal dispersion treatment process, the oxygen vacancies in the cerium dioxide support rich in oxygen defects cannot effectively promote the breaking of the M-O bond in the metal single-atom oxide, resulting in the inability to realize the transformation of the metal single-atom oxide into metal single atoms, and thus it is impossible to prepare a single-atom catalyst.

[0210] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a single atom catalyst, characterized in that: The preparation method comprises: The single-atom catalyst is prepared by mixing the oxide of the metal single atom and the ceria carrier rich in oxygen defects, grinding, and thermally dispersing the mixture; In the oxide of the metal single atom, the mass ratio of the metal single atom to the oxygen defect-rich carrier is (0.1-4.0):100, calculated based on the mass of the metal single atom. The temperature of the heat dispersion reaction is 400°C-900°C, and the time of the heat dispersion reaction is 2.0h-6.0h; The grinding includes mechanical grinding, and the time of the mechanical grinding is 10min-60min.

2. The preparation method according to claim 1, characterized in that The metal single atom includes any one of Ti, Cr, Mn, Fe, Co, Ge, Mo, Ru, Cd, In, Sn, Sb, Te, La, Pt, Pb, Bi, Pr, and Nd, or a combination of at least two of them.

3. The preparation method according to claim 1, characterized in that: The preparation method of the cerium dioxide carrier rich in oxygen defects comprises: The ceria precursor is calcined to prepare the ceria carrier rich in oxygen defects.

4. The preparation method according to claim 3, characterized in that: The preparation method of the cerium dioxide precursor includes a hydrothermal method or a microreactor rapid thermal synthesis method.

5. The preparation method according to claim 4, characterized in that: The method for preparing a cerium dioxide precursor using a microreactor rapid thermal synthesis method comprises: According to the stoichiometric ratio, the cerium source solution and the alkali source solution are flowed into the reaction container in parallel to obtain a mixed solution, and the mixed solution flows through the thermal synthesis zone and the cooling zone in sequence, and the solid-liquid separation is performed to obtain the cerium dioxide precursor.

6. The preparation method according to claim 5, characterized in that: The cerium source solution and the alkali source solution are introduced into the reaction container in parallel at a speed of 0.1 mL / min-10.0 mL / min, respectively; and / or, the temperature of the thermal synthesis zone is 80°C-180°C; And / or, the temperature of the cooling zone is less than or equal to 30°C.

7. The preparation method according to claim 3, characterized in that: The calcination temperature is 300° C.-800° C., and the calcination time is 2 h-8 h.

8. An application of a single atom catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The single atom catalyst is used for catalytic synthesis of cyclic carbonate.

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