Monatomic catalyst as well as preparation method and application thereof

Abstract

The invention provides a monatomic catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a metal monatomic oxide and a cerium dioxide carrier rich in oxygen vacancy, grinding, and carrying out a heat dispersion reaction to prepare the monatomic catalyst, in the oxide of the metal monatomic, the mass ratio of the metal monatomic to the carrier rich in oxygen vacancy is (0.1-4.0): 100 according to the mass of the metal monatomic. The preparation method provided by the invention effectively solves the problems that the existing monatomic synthesis technology is complicated in process, the monatomic loading capacity is difficult to control, large-scale preparation is difficult and the like, and the universality of the monatomic catalyst synthesis method is improved.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, in particular to a single-atom catalyst, and in particular to a single-atom catalyst and a preparation method and application thereof. Background Art

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

[0003] CN112973759A discloses a method for preparing a metal single-atom catalyst. The method first grafts a coupling agent onto a hydroxylated template to form a surface-functionalized first template, then monodisperse anchors a metal precursor on the surface of the first template to form a second template with a surface loaded with the metal precursor, and then physically coats and isolates the metal precursor on the surface of the second template using a carbon source, and then de-templates to obtain a metal single-atom catalyst. The method is based on a strategy that combines chemical confinement (dispersed anchoring) with physical confinement (coating isolation) to achieve the purpose of precise and controllable preparation of metal single-atom catalysts.

[0004] CN110694669A discloses a method for preparing a single-atom catalyst. The invention adopts a thermal diffusion method, uses a foam transition metal as a metal source, and heat treats it at a high temperature in a mixed atmosphere of ammonia and inert gas. The metal atoms on the surface of the foam transition metal are M(NH3) x and then captured by the carrier material, thereby obtaining a large number of single-atom catalysts at one time, realizing the large-scale preparation of single-atom catalysts.

[0005] CN117504882A discloses a Fe single-atom supported catalyst prepared by confining an amorphous layer of BaTiO3, and its preparation and application. BaTiO3 is used as a precursor, and an Ov-BaTiO3 coated with a surface amorphous layer is prepared by high-temperature hydrothermal reduction with sodium borohydride. Then, a bipyridine iron modified calcination method is applied to form Fe single atoms by confining the amorphous layer, thereby preparing the single-atom Fe supported catalyst.

[0006] Therefore, it is of great significance to provide a method for preparing single-atom catalysts with high catalytic activity that can be easily produced on a large scale. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a single-atom catalyst and its preparation method and application. The present invention selects a cerium dioxide carrier rich in oxygen defects and a metal single-atom oxide for grinding, and prepares a single-atom catalyst through a thermal dispersion reaction. The preparation method provided by the present invention effectively solves the problems of the existing single-atom synthesis technology, such as the complexity of the process, the difficulty in controlling the single-atom loading amount, and the difficulty in large-scale preparation, thereby improving the universality of the single-atom catalyst synthesis method.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a single atom catalyst. The preparation method comprises:

[0010] The single-atom catalyst is prepared by mixing the oxide of a metal single atom and a cerium dioxide carrier rich in oxygen defects, grinding them, and subjecting them to a thermal dispersion reaction; in the oxide of the metal single atom, the mass ratio of the metal single atom to the carrier rich in oxygen defects is (0.1-4):100, calculated based on the mass of the metal single atom.

[0011] The present invention selects a carrier rich in oxygen defects and mixes it with a metal single atom oxide, and enhances the metal interface interaction through grinding treatment. During the thermal dispersion reaction, the oxygen vacancies in the cerium dioxide carrier rich in oxygen defects promote the breaking of the MO bond in the metal oxide to form a single atom M1, thereby preparing a single atom catalyst.

[0012] In the preparation method provided by the present invention, the mass of the metal single atom is calculated, and the mass ratio of the metal single atom to the oxygen-deficient carrier affects the conversion efficiency of the oxide to the metal single atom. If the mass ratio of the dispersible single atom is too high, some oxides 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 can be achieved in air or inert atmosphere. The inert atmosphere includes any one of nitrogen, argon or helium or a combination of at least two of them. Typical but non-limiting combinations include nitrogen and argon, helium and nitrogen, or argon and helium.

[0020] Preferably, 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. Typical but non-limiting combinations include a combination of Ti and Cr, a combination of Mn and Fe, a combination of Co and Ge, a combination of Mo and Ru, a combination of Cd and Sb, a combination of Bi and In, a combination of Bi, Mn and Sb, a combination of Bi, Nd and Mo, a combination of Fe, Mo and Sb, a combination of Fe, Mo and Nb, or a combination of Fe, Sb and Nb.

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

[0022] Preferably, the oxygen-defect-rich cerium dioxide support comprises any one of oxygen-defect-rich cerium dioxide nanorods, oxygen-defect-rich cerium dioxide cubes or oxygen-defect-rich cerium dioxide nanoparticles, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of oxygen-defect-rich cerium dioxide nanorods and cerium dioxide cubes, a combination of oxygen-defect-rich cerium dioxide nanoparticles and cerium dioxide nanorods, or a combination of oxygen-defect-rich cerium dioxide cubes and cerium dioxide nanoparticles.

[0023] Preferably, the method for preparing the oxygen-deficiency-rich ceria carrier comprises: calcining a ceria precursor to prepare the oxygen-deficiency-rich ceria carrier.

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

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

[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 values ​​not listed in 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 values ​​not listed in 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 comprises adding the alkali source solution dropwise into the cerium source solution under stirring.

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

[0029] Preferably, the cerium source solution and the alkali source solution are introduced into the reaction vessel in parallel at a speed independently of each other of 0.1 mL / min-10.0 mL / min, for example, 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, 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, and other values ​​not listed within the numerical range are also 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, and other unlisted values ​​within the numerical range are also 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, and other unlisted values ​​within the numerical range are also applicable.

[0033] In the microreactor rapid thermal synthesis method provided by the present invention, the structures of the thermal synthesis zone and the cooling zone are not particularly limited, as long as the mixed solution passing through the corresponding zone can be heated or cooled 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 a cerium dioxide precursor provided by the present invention, the cerium source, alkali source, and the concentrations of the cerium source solution and the alkali source solution are all prior art and are not specifically limited. According to the stoichiometric ratio, the alkali source is in excess to ensure complete reaction of the cerium source.

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

[0036] Exemplarily, the alkali source includes any one of ammonium carbonate, sodium hydroxide, potassium hydroxide, urea or ammonia water, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonium carbonate and sodium hydroxide, a combination of potassium hydroxide and urea, or a 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, 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, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, before calcining the cerium dioxide precursor, the cerium dioxide precursor is also dried, and the drying temperature 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, and the drying time is 8h-24h, for example, it can be 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the calcination temperature 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, and the calcination time is 2h-8h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h or 8h. The above calcination temperature and time include but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the calcining is performed in an oxygen-containing atmosphere, which 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 as described in the second aspect, wherein the single-atom catalyst is applied in the field of catalytic synthesis.

[0043] Illustratively, 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 technicians 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 inclusions.

[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, and a carrier rich in oxygen defects is selected to be mixed with an oxide of a metal single atom. Through a simple grinding treatment, the interaction between the interface of the oxide of the metal single atom and the cerium dioxide carrier rich in oxygen defects is increased, and the dispersion limit is increased, which is beneficial for the oxygen vacancies in the cerium dioxide carrier rich in oxygen defects to promote the breaking of MO bonds in the oxide of the metal single atom. After a thermal dispersion reaction, direct dispersion of nanometer-level or even micrometer-level oxides and direct conversion of oxide nanoparticles to single atoms are achieved. The method is suitable for the loading of various metal single atoms, effectively solving the shortcomings of the prior art such as complex synthesis, difficulty in controlling the single atom loading amount, and difficulty in large-scale preparation, and improving the universality of the single-atom catalyst synthesis method. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0048] Figure 2 This 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 This is a transmission electron microscope (TEM) result diagram of the cerium dioxide nanorod support rich in oxygen defects prepared in the present invention.

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

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

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

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

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

[0055] Fig. 9 This is the synchrotron radiation (XAFS) result of the Ru single atom catalyst prepared in Example 5.

[0056] Fig.10This is the X-ray diffraction (XRD) result of the Sb single atom catalyst prepared in Example 6.

[0057] Fig.11 This is the X-ray diffraction (XRD) result of the Ti single atom catalyst prepared in Example 7.

[0058] Fig.12 This is the synchrotron radiation (XAFS) result of the La single atom catalyst prepared in Example 8.

[0059] Fig.13 This is the synchrotron radiation (XAFS) result of the Mo single atom catalyst prepared in Example 9.

[0060] Fig.14 This is the X-ray diffraction (XRD) result of the Te single atom catalyst prepared in Example 10.

[0061] Fig.15 This is the synchrotron radiation (XAFS) result of the Pt single atom catalyst prepared in Example 11.

[0062] Fig.16 This is the synchrotron radiation (XAFS) result of the Mn single atom catalyst prepared in Example 12.

[0063] Fig.17 This is the X-ray diffraction (XRD) result of the Ge single atom catalyst prepared in Example 13.

[0064] Fig.18 This is the X-ray diffraction (XRD) result of the In single atom catalyst prepared in Example 14.

[0065] Fig.19 This is the synchrotron radiation (XAFS) result of the Pb single atom catalyst prepared in Example 15.

[0066] Fig. 20 This is the X-ray diffraction (XRD) result of the Sn single atom catalyst prepared in Example 16.

[0067] Fig.21 This is the X-ray diffraction (XRD) result of the Cr single atom catalyst prepared in Example 17.

[0068] Fig. 22 This is the X-ray diffraction (XRD) result of the Cd single atom catalyst prepared in Example 18.

[0069] Fig.23 This is the X-ray diffraction (XRD) result of the Pr single atom catalyst prepared in Example 19.

[0070] Fig.24This is the result of the Bi-In double single-atom spherical aberration corrected transmission electron microscope atomic-level element imaging (AC-STEM-Atomic-Mapping) prepared in Example 20.

[0071] Fig.25 X-ray diffraction (XRD) results of the single atom catalysts prepared in Examples 21-25. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0073] The preparation method of the oxygen-deficient ceria cubic carrier used in the examples and comparative examples of the present invention is as follows:

[0074] (1) Preparation of cubic ceria precursor by microreactor rapid thermal synthesis method: 2 mol / L cerium nitrate solution and excess 5 mol / L sodium 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 an oil bath at 170°C and a hollow pipe spirally arranged in a water bath at 10°C in sequence, and the solid and liquid are separated, and the cubic ceria precursor is obtained by drying at 100°C for 10 h.

[0075] (2) Preparation of oxygen-deficient ceria cubic carrier: The ceria cubic precursor prepared in step (1) was calcined in an air atmosphere at a temperature of 700° C. for 4 h to obtain an oxygen-deficient ceria cubic carrier.

[0076] The preparation method of the oxygen-deficient cerium oxide particle carrier used in the examples and comparative examples of the present invention is as follows:

[0077] (1) Preparation of cerium dioxide particle precursor by hydrothermal method: 3 mol / L cerium chloride solution and excess 6 mol / L potassium hydroxide solution were added to a hydrothermal reactor, and the reaction was carried out at 130° C. for 20 h, followed by solid-liquid separation, and the cerium dioxide particle precursor was obtained by drying at 120° C. for 16 h.

[0078] (2) Preparing a cerium dioxide particle carrier rich in oxygen defects: The cerium dioxide particle precursor prepared in step (1) was calcined in an air atmosphere at a temperature of 350° C. for 8 h to obtain a cerium dioxide particle carrier rich in oxygen defects. The TEM image of the cerium dioxide particle carrier is as follows: Figure 1 As shown, the EPR test results of the cerium dioxide particles are as follows Figure 2 As 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] The oxygen-deficient cerium dioxide particle carrier is mixed with Co2O3 in an inching mixer for 8 minutes, and then transferred to an agate mortar and ground for 20 minutes; the uniformly mixed powder is subjected to a thermal dispersion reaction 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 ratio of the cerium dioxide particle carrier rich in oxygen defects is 0.64:100, the thermal dispersion reaction temperature is 500°C, and the thermal dispersion reaction time is 3 hours.

[0091] The XAFS results of the Co single-atom catalyst prepared in this example are as follows: Figure 5 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Co-O path, while the Co-Co and Co-O-Co scattering paths present in Co element and Co2O3 are not detected, proving that Co exists in the catalyst in the form of isolated atoms.

[0092] Example 3

[0093] This embodiment provides a method for preparing a Fe single-atom catalyst, the preparation method comprising:

[0094] The oxygen-deficient cerium dioxide nanorod carrier is mixed with Fe2O3 in an inching mixer for 10 minutes, and then transferred to an agate mortar and ground for 45 minutes; the uniformly mixed powder is subjected to a thermal dispersion reaction 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 ratio of the cerium dioxide nanorod carrier rich in oxygen defects is 0.63:100, the temperature of the thermal dispersion reaction is 500°C, and the time of the thermal dispersion reaction is 3 hours.

[0096] The synchrotron radiation (XAFS) results of the Fe single atom catalyst prepared in this example are as follows: Figure 6 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Fe-O path, while the Fe-Fe and Fe-O-Fe scattering paths present in Fe element and Fe2O3 are not 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: Fig. 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: Fig.10As shown, after physically mixing Sb2O3 and the cerium dioxide nanorod carrier, an obvious Sb2O3 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the Sb2O3 characteristic peak disappears, indicating that the Sb element is distributed in the cerium dioxide carrier in a highly dispersed form.

[0106] Example 7

[0107] This embodiment provides a method for preparing a Ti single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by TiO2, the mass ratio of Ti in the TiO2 to the oxygen-deficient cerium dioxide nanorod carrier is 0.3:100, the thermal dispersion reaction temperature is 700°C, and the thermal dispersion time is 2 hours.

[0108] The X-ray diffraction (XRD) results of the Ti single atom catalyst prepared in this example are as follows: Fig.11 As shown, after physically mixing TiO2 and the cerium dioxide nanorod carrier, an obvious TiO2 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the TiO2 characteristic peak disappears, indicating that the Ti element is distributed in the cerium dioxide carrier in a highly dispersed form.

[0109] Example 8

[0110] This embodiment provides a method for preparing a La single atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by La2O3, and the mass ratio of La in the La2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.62:100.

[0111] The XAFS results of the La single atom catalyst prepared in this example are as follows: Fig.12 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the La-O path, while the La-O-La scattering path present in La2O3 is not detected, proving that La exists in the catalyst in the form of isolated atoms.

[0112] Example 9

[0113] This embodiment provides a method for preparing a Mo single-atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by MoO3, and the mass ratio of Mo in the MoO3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.53:100.

[0114] The XAFS results of the Mo single atom catalyst prepared in this example are as follows: Fig.13As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Mo-O path, while the Mo-Mo and Mo-O-Mo scattering paths present in Mo element and MoO3 are not detected, proving that Mo exists in the catalyst in the form of isolated atoms.

[0115] Example 10

[0116] This embodiment provides a method for preparing a Te single atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by TeO2, and the mass ratio of Te in the TeO2 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.72:100.

[0117] The X-ray diffraction (XRD) results of the Te single atom catalyst prepared in this example are as follows: Fig.14 As shown, after physically mixing TeO2 and the cerium dioxide nanorod carrier, an obvious TeO2 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the TeO2 characteristic peak disappears, indicating that the Te element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0118] Embodiment 11

[0119] This embodiment provides a method for preparing a Pt single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by PtO2, the mass ratio of Pt in the PtO2 to the oxygen-deficient cerium dioxide nanorod carrier is 1.12:100, the thermal dispersion treatment temperature is 400°C, and the thermal dispersion treatment time is 6 hours.

[0120] The XAFS results of the Pt single atom catalyst prepared in this example are as follows: Fig.15 As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Pt-O path, while the Pt-Pt and Pt-O-Pt scattering paths present in Pt element and PtO2 are not detected, proving that Pt exists in the catalyst in the form of isolated atoms.

[0121] Example 12

[0122] This embodiment provides a method for preparing a Mn single-atom catalyst, which is the same as Example 3 except that Fe2O3 is replaced by Mn2O3, and the mass ratio of Mn in the Mn2O3 to the oxygen-deficient cerium dioxide nanorod carrier is 0.63:100.

[0123] The XAFS results of the Mn single atom catalyst prepared in this example are as follows: Fig.16As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Mn-O path, while the Mn-Mn and Mn-O-Mn scattering paths present in Mn element and Mn2O3 are not detected, proving that Mn exists in the catalyst in the form of isolated atoms.

[0124] Embodiment 13

[0125] The present embodiment provides a method for preparing a Ge single-atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by GeO2, the mass ratio of Ge in the GeO2 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.42:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0126] The X-ray diffraction (XRD) results of the Ge single atom catalyst prepared in this example are as follows: Fig.17 As shown, after GeO2 and the cerium dioxide nanorod carrier are physically mixed, an obvious GeO2 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the GeO2 characteristic peak disappears, indicating that the Ge element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0127] Embodiment 14

[0128] This embodiment provides a method for preparing an In single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by In2O3, the mass ratio of In in the In2O3 to the oxygen-deficient cerium dioxide nanorod carrier is 1.32:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0129] The X-ray diffraction (XRD) results of the In single atom catalyst prepared in this example are as follows: Fig.18 As shown, after In2O3 and the cerium dioxide nanorod carrier are physically mixed, an obvious In2O3 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the In2O3 characteristic peak disappears, indicating that the In element is distributed in the cerium dioxide carrier in a highly dispersed form.

[0130] Embodiment 15

[0131] This embodiment provides a method for preparing a Pb single-atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by PbO, and the mass ratio of Pb in the PbO to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.21:100.

[0132] The XAFS results of the Pb single atom catalyst prepared in this example are as follows: Fig.19As shown, the extended X-ray absorption fine structure (EXAFS) spectrum shows the presence of a main peak attributed to the Pb-O path, while the Pb-Pb and Pb-O-Pb scattering paths present in Pb element and PbO are not detected, proving that Pb exists in the catalyst in the form of isolated atoms.

[0133] Example 16

[0134] The present embodiment provides a method for preparing a Sn single-atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by SnO2, the mass ratio of Sn in the SnO2 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.63:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0135] The X-ray diffraction (XRD) results of the Sn single atom catalyst prepared in this example are shown in the figure below: Fig. 20 As shown, after SnO2 and the cerium dioxide nanorod carrier are physically mixed, an obvious SnO2 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the SnO2 characteristic peak disappears, indicating that the Sn element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0136] Embodiment 17

[0137] The present embodiment provides a method for preparing a Cr single atom catalyst, which is the same as that of Example 3 except that Fe2O3 is replaced by Cr2O3, the mass ratio of Cr in the Cr2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.55:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0138] The X-ray diffraction (XRD) results of the Cr single atom catalyst prepared in this example are shown in the figure below: Fig.21 As shown, after Cr2O3 and the cerium dioxide nanorod carrier are physically mixed, an obvious Cr2O3 characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the Cr2O3 characteristic peak disappears, indicating that the Cr element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0139] Embodiment 18

[0140] The present embodiment provides a method for preparing a Cd single-atom catalyst. The preparation method is the same as that of Example 3 except that Fe2O3 is replaced by CdO, the mass ratio of Cd in the CdO to the oxygen-deficient cerium dioxide nanorod carrier is 0.61:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0141] The X-ray diffraction (XRD) results of the Cd single atom catalyst prepared in this example are as follows: Fig. 22 As shown, after CdO and the cerium dioxide nanorod carrier are physically mixed, an obvious CdO characteristic peak is shown in the X-ray spectrum. After thermal dispersion treatment, the CdO characteristic peak disappears, indicating that the Cd element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0142] Embodiment 19

[0143] This embodiment provides a method for preparing a Pr single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Pr2O3, the mass ratio of Pr in the Pr2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.62:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0144] The X-ray diffraction (XRD) results of the Pr single atom catalyst prepared in this example are as follows: Fig.23 As shown, after Pr2O3 and cerium dioxide nanorod carrier Pr2O3 characteristic peak disappears, indicating that the Pr element is distributed in the carrier cerium dioxide in a highly dispersed form.

[0145] Embodiment 20

[0146] The present embodiment provides a method for preparing a Bi-In double single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Bi2O3 and In2O3, the mass ratio of Bi and In in Bi2O3 and In2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.26:0.66:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0147] The results of AC-STEM-Atomic-Mapping of the Bi-In double single-atom spherical aberration-corrected transmission electron microscope prepared in this example are as follows: Fig.24 As shown, a clear atomic-level distribution of Bi and In is displayed in a spherical aberration-corrected microscope, indicating that atomic-level Bi and In can be obtained after Bi2O3, In2O3 and CeO2 are mixed and heat treated.

[0148] Embodiment 21

[0149] The present embodiment provides a method for preparing a Bi-Mn-Sb multi-single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Bi2O3, Mn2O3 and Sb2O3, the mass ratio of Bi, Mn and Sb in the Bi2O3, Mn2O3 and Sb2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 2.42:0.63:0.67:100, the thermal dispersion treatment temperature is 700°C, and the thermal dispersion treatment time is 3 hours.

[0150] The X-ray diffraction (XRD) results of the Bi-Mn-Sb multi-single atom catalyst prepared in this example are as follows: Fig.25 As shown, after grinding and heat treatment, only the characteristic peaks of ceria remain in the XRD spectrum, proving that Bi, Mn, and Sb are already distributed in ceria in a highly dispersed form.

[0151] Embodiment 22

[0152] The present embodiment provides a method for preparing a Bi-Mo-Nd multi-single-atom catalyst. The preparation method is the same as Example 3 except that Fe2O3 is replaced by Bi2O3, MoO3 and Nd2O3, the mass ratio of Bi, Mo and Nd in the Bi2O3, MoO3 and Nd2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 1.17:0.27:0.72:100, the thermal dispersion treatment temperature is 600°C, and the thermal dispersion treatment time is 3 hours.

[0153] The X-ray diffraction (XRD) results of the Bi-Mo-Nd multi-single-atom catalyst prepared in this example are as follows: Fig.25 As shown, after grinding and heat treatment, only the characteristic peaks of ceria remain in the XRD spectrum, proving that Bi, Mo, and Nd are already distributed in ceria in a highly dispersed form.

[0154] Embodiment 23

[0155] The present embodiment provides a method for preparing a Fe-Nd-Sb multi-single-atom catalyst, which is the same as Example 3, except that Fe2O3 is replaced by Fe2O3, Nd2O3 and Sb2O3, and the mass ratio of Fe, Nd and Sb in the Fe2O3, Nd2O3 and Sb2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.35:0.72:0.67:100.

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

[0157] Embodiment 24

[0158] The present embodiment provides a method for preparing a Fe-Mo-Sb multi-single-atom catalyst, which is the same as Example 3, except that Fe2O3 is replaced by Fe2O3, MoO3 and Sb2O3, and the mass ratio of Fe, Mo and Sb in the Fe2O3, MoO3 and Sb2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.35:0.27:0.67:100.

[0159] The X-ray diffraction (XRD) results of the Fe-Mo-Sb multi-single atom catalyst prepared in this example are as follows: Fig.25 As shown, after grinding and heat treatment, only the characteristic peaks of ceria remain in the XRD spectrum, proving that Fe, Mo, and Sb are distributed in ceria in a highly dispersed form.

[0160] Embodiment 25

[0161] The present embodiment provides a method for preparing a Fe-Mo-Nd multi-single-atom catalyst, which is the same as Example 3, except that Fe2O3 is replaced by Fe2O3, MoO3 and Nd2O3, and the mass ratio of Fe, Mo and Nd in the Fe2O3, MoO3 and Nd2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.35:0.27:0.72:100.

[0162] The X-ray diffraction (XRD) results of the Fe-Mo-Nd multi-single atom catalyst prepared in this example are as follows: Fig.25 As shown, after grinding and heat treatment, only the characteristic peaks of ceria remain in the XRD spectrum, proving that Fe, Mo, and Nd are already distributed in ceria in a highly dispersed form.

[0163] Embodiment 26

[0164] This embodiment provides a method for preparing a single atom catalyst. The preparation method is the same as that of Embodiment 1 except that the heat dispersion treatment temperature is 300°C.

[0165] Embodiment 27

[0166] This embodiment provides a method for preparing a single atom catalyst. The preparation method is the same as that of Embodiment 1 except that the heat dispersion treatment temperature is 900°C.

[0167] Comparative Example 1

[0168] This comparative example provides a method for preparing a single-atom catalyst. The preparation method is the same as Example 1 except that commercially available ceria is used as a carrier to replace the ceria cubic carrier rich in oxygen defects.

[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 method for preparing a single-atom catalyst, which is the same as Example 1 except that TiO2 with a comparable oxygen vacancy concentration is used as a carrier. The method for preparing 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 multiple times to obtain a white powder sample.

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

[0174] Comparative Example 3

[0175] This comparative example provides a method for preparing a single-atom catalyst, which is the same as Example 1 except that the oxygen-deficient ceria cubic carrier and Bi2O3 are not ground.

[0176] Comparative Example 4

[0177] This comparative example provides a method for preparing a single-atom catalyst, which is the same as Example 1 except that the mass ratio of Bi in Bi2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 0.05:100.

[0178] Comparative Example 5

[0179] This comparative example provides a method for preparing a single-atom catalyst, which is the same as Example 1 except that the mass ratio of Bi in Bi2O3 to the mass ratio of the oxygen-deficient cerium dioxide nanorod carrier is 5:100.

[0180] The present invention also provides the use of the single-atom catalyst prepared in the above-mentioned embodiment 1, embodiment 18, embodiment 26, embodiment 27, and comparative examples 1 to 5 in catalytic synthesis of cyclic carbonates, and the preparation method comprises:

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

[0182] The present invention also tests the conversion rate and selectivity of the cyclic carbonate synthesized by the single-atom catalyst prepared in the above embodiment or comparative example, and the test method is as follows:

[0183] After centrifugal separation of the synthesized cyclic carbonate, an appropriate amount of the supernatant was added with an internal standard substance (biphenyl) and quantitative analysis was performed 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, wherein the application includes using the single-atom catalyst prepared in Example 1 to catalyze the synthesis of cyclic carbonates, and the synthesis method includes:

[0186] 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 were mixed in a 50 mL autoclave and reacted at 120° C. for 20 min to prepare 1,2-butenyl carbonate.

[0187] Application Example 2

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

[0195] Comparative Application Example 2

[0196] Compared with Application Example 1, only the single atom catalyst prepared in Example 1 is replaced by the single atom catalyst prepared in Comparative Example 2 of equal mass, and the rest is the same as Application Example 1.

[0197] Comparative Application Example 3

[0198] Compared with Application Example 1, only the single atom catalyst prepared in Example 1 is replaced by the single atom catalyst prepared in Comparative Example 3 of equal mass, and the rest is the same as Application Example 1.

[0199] Comparative Application Example 4

[0200] Compared with Application Example 1, only the single atom catalyst prepared in Example 1 is replaced by the single atom catalyst prepared in Comparative Example 4 of equal mass, and the rest is the same as Application Example 1.

[0201] Comparative Application Example 5

[0202] Compared with Application Example 1, only the single atom catalyst prepared in Example 1 is replaced by the single atom catalyst prepared in Comparative Example 5 of equal mass, and the rest is the same as Application Example 1.

[0203] Performance Testing:

[0204] After centrifugation, an appropriate amount of the supernatant was added with an internal standard substance (biphenyl) to perform quantitative analysis by gas chromatography internal standard method. The test results are shown in Table 1.

[0205] Table 1

[0206]

[0207] According to Examples 1 to 25, the present invention utilizes grinding, a simple and easy-to-implement method, to increase the interaction between the oxide of the metal single atom and the interface of the ceria carrier rich in oxygen defects, increase the dispersion limit, and facilitate the oxygen vacancies in the ceria carrier rich in oxygen defects to promote the breaking of the MO bond in the oxide of the metal single atom, forming a single atom, and preparing a single atom catalyst. The preparation method provided by the present invention effectively solves the problems of the existing single atom synthesis technology, the difficulty in controlling the single atom loading, and the difficulty in large-scale preparation, 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 Comparative Application Examples 2, if cerium dioxide that is not rich in oxygen defects is selected as a carrier, or a non-cerium dioxide carrier that is rich in oxygen defects is selected, it will affect the conversion of metal single atom oxides to metal single atoms, 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 ceria cubic support rich in oxygen defects and Bi2O3 are not ground, the interface interaction cannot be increased and the dispersion limit cannot be increased. In the subsequent thermal dispersion process, the oxygen vacancies in the ceria support rich in oxygen defects cannot effectively promote the breaking of the MO bonds in the metal single atom oxides, resulting in the inability to convert the metal single atom oxides into metal single atoms, and thus the single atom catalyst cannot be prepared.

[0210] The applicant declares that the above is only a specific implementation mode 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 those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and 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, calculated based on the mass 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.

2. The preparation method according to claim 1, characterized in that The grinding includes mechanical grinding, and the time of the mechanical grinding is 10min-60min; And / or, the temperature of the heat dispersion reaction is 400° C.-900° C., and the time of the heat dispersion reaction is 2.0 h-6.0 h.

3. 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.

4. 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.

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

6. The preparation method according to claim 5, 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.

7. The preparation method according to claim 6, 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.

8. The preparation method according to claim 4, characterized in that: The calcination temperature is 300° C.-800° C., and the calcination time is 2 h-8 h.

9. A single atom catalyst, characterized in that The single atom catalyst is obtained by the preparation method described in any one of claims 1-8.

10. Use of the single atom catalyst as claimed in claim 9, characterized in that: The single-atom catalyst is applied in the field of catalytic synthesis.

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