Method for preparing carbon-supported noble metal / transition metal cross-scale catalyst and application thereof

Abstract

Method for preparing carbon-supported noble metal / transition metal cross-scale catalyst and application thereof, belonging to the technical field of lithium-air battery catalysts. By the method of "Joule heating pre-alloying - ammonia-assisted dealloying", α3β can be formed on a carbon matrix 1‑x alloy nanocrystals + β metal single atoms, α3β 1‑x alloy nanocrystals + β metal single atoms + β highly exposed metal clusters or α3β 1‑x alloy nanocrystals + β highly exposed metal cluster cross-scale combination. This method effectively solves the problem of the single function of a single-component noble metal catalyst. The coexistence and division of labor of β single atoms, β highly exposed clusters and α3β 1‑x alloy nanoparticles solve the problem of insufficient bifunctional catalytic activity when noble metal single atoms are used as active sites in the past.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-air battery catalysts, and particularly relates to a method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst and its application. Background Art

[0002] With the growing demand for extended service life and increased driving range in portable electronic devices and electric vehicles, the development of high-energy-density electrochemical energy storage systems has been rapidly advanced. Among various rechargeable batteries, lithium-ion batteries (LIBs), as a major electrochemical energy storage option, have been widely used in small vehicles and portable electronic devices in the past few decades. However, the battery community has realized that there is an upper limit to the achievable energy density in actual lithium-ion batteries, and even fully developed lithium-ion batteries may not be able to meet future demands for high energy density and long endurance because they are limited by intercalation chemistry, resulting in a relatively low theoretical energy density. Therefore, lithium-sulfur batteries (Li-S) and lithium-air batteries (Li-O 2 ) with high theoretical energy density in different battery chemical systems have developed rapidly. Among them, non-aqueous lithium-air batteries have received much attention in the past few years due to their relatively high theoretical specific energy (≈3500 Wh kg -1 ). However, there are serious polarization problems in non-aqueous systems, that is, due to the large gap between the actual charge-discharge potential and the thermodynamic equilibrium potential, there is a large overpotential even at extremely low current densities. At the same time, the insulation and insolubility of the discharge product Li 2 O 2 are also the fundamental reasons for the poor charge-discharge process kinetics.

[0003] Noble metal M catalysts (M = Pt, Ir, Pd, Ru, Rh, etc.) can effectively reduce the polarization during the charge-discharge process of lithium-air batteries due to their high electrical conductivity and stability, and have excellent catalytic activity. Nevertheless, noble metals are expensive, have limited reserves, and have too high preparation costs, which affect their application in lithium-air batteries. The usual strategy is to load a small amount of noble metal M single atoms on a matrix material to form an M-N-C catalyst. This method can ensure less use of noble metals, uniform distribution on the matrix surface, and maximum exposure of active sites. However, the inherent limitations of M-N-C catalysts limit their further development in the field of lithium-air batteries. The reasons are as follows:

[0004] 1) Usually, M single-atom catalysts are limited by the carbon matrix anchoring sites, resulting in limited loading and active site density.

[0005] 2) M single atoms are usually isolated and randomly loaded in the carbon matrix, and the d-orbital electron synergy between metal active sites cannot be efficiently utilized.

[0006] 3) The oxygen reduction (ORR) and oxygen evolution (OER) processes of lithium-air batteries involve complex reversible conversion processes of multiple intermediate products. The two processes have different rate-determining steps, and it is difficult for active sites with a single specified structure to balance the adsorption and desorption processes of oxygen-containing intermediate products at the same site. Therefore, their bifunctional catalytic activity is usually limited by the competition between ORR / OER at the same site. This means that M-N-C catalysts with a simple coordination environment can usually drive one-way reactions efficiently, but it is difficult to effectively catalyze the reverse process simultaneously, and ultimately, the optimal ORR / OER bifunctional catalytic kinetics cannot be provided. Summary of the Invention

[0007] The present invention discloses a method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst and its application. The present invention effectively solves the kinetic problems of the bidirectional charging and discharging processes of lithium-air batteries by developing a catalyst with multiple-scale active centers that can effectively exert a synergistic effect. The first proposed "Joule heating pre-alloying - ammonia-assisted dealloying" method can form α 3 β 1-x alloy nanocrystals + β metal single atoms, α 3 β 1-x alloy nanocrystals + β metal single atoms + β highly exposed metal clusters or α 3 β 1-x alloy nanocrystals + β highly exposed metal clusters cross-scale combinations on a carbon matrix. Among them, α is one of noble metals Pt, Ir, Pd, Ru, Rh, and β is one of transition metals Fe, Co, Ni, Mn, Cu. The α 3 β 1-x alloy nanocrystals serve as ORR active sites, while β single atoms or β highly exposed metal clusters serve as OER active sites. The catalytic centers of the α 3 β 1-x nanocrystals and β-N-C at two scales have a highly adjustable coordination environment and electronic structure. The synergistic mechanism between the two helps to balance the adsorption, reaction, and desorption behaviors of oxygen-containing reactants and intermediate products at surface sites, helps to simultaneously achieve the ORR and OER reaction processes with rapid conversion, and thus improves the ORR / OER bifunctional catalytic kinetics of α 3 β 1-x @β-N-C. This method effectively solves the problem of the single function of noble metal catalysts with a single component. The coexistence of β single atoms, β highly exposed clusters, and α3β1-x alloy nanoparticles solves the problem of insufficient bifunctional catalytic activity when noble metal single atoms are used as active sites in a collaborative manner.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] Method for preparing carbon-supported noble metal / transition metal cross-scale catalyst, comprising the following steps:

[0010] S1: Preparation of TPB-TFB-COF powder A

[0011] 1,3,5-Tris(4-aminophenyl)benzene, i.e., TPB, and terephthalaldehyde, i.e., TFB, are respectively added into a mortar according to a molar ratio of TPB:TFB of 1:1, ground for 10 min, then an anhydrous ethanol solution is added, stirred for 8 h, centrifuged, and transferred to a vacuum drying oven, dried at 80 °C for 16 h to obtain TPB-TFB-COF powder A;

[0012] S2: Preparation of noble metal salt solution B and transition metal salt solution C

[0013] The noble metal α salt and the transition main group metal β salt are respectively added into deionized water according to a molar ratio, ultrasonicated for 1 h to respectively obtain the noble metal salt solution B and the transition metal salt solution C;

[0014] S3: Preparation of precursor

[0015] The powder A, the noble metal salt solution B, and the transition metal salt solution C are simultaneously added into acetonitrile, stirred for 12 h, centrifuged, and vacuum dried at 60 °C - 80 °C for 12 h to obtain a dark-colored precursor powder B of COFs loaded with metal ions;

[0016] S4: Preparation of alloy nanocrystal catalyst

[0017] The precursor powder B is placed in a Joule heating device, and under an atmosphere of flowing argon, heated from room temperature to 2000 - 3000 °C within 2 - 10 s, and then cooled to room temperature within 8 - 20 s. During this process, the noble metal α and the transition metal β form an α 3 β alloy nanocrystal, and at the same time, TPB-TFB-COF is carbonized to form an N-C matrix, and the resulting powder is the target product α 3 β@N-C catalyst;

[0018] S5: Dealloying process

[0019] The dark-colored α 3 β@N-C catalyst powder obtained after drying is placed in a Joule heating device, and a dealloying process is carried out under an atmosphere of flowing argon / ammonia (volume ratio = 9:1), heated from room temperature to 700 - 1500 °C within 1 - 4 s, held for 30 - 50 s, and then cooled to room temperature within 3 - 10 s; by controlling the Joule heating temperature, the realization of α 3 β 1-x alloy nanocrystal + β metal single atom, α 3 β 1-x alloy nanocrystal + β metal single atom + β highly exposed metal cluster or α3 β 1-x Alloy nanocrystals + β highly exposed metal cluster cross-scale combination regulation; α is one of noble metals Pt, Ir, Pd, Ru, Rh, and β is one of transition metals Fe, Co, Ni, Mn, Cu.

[0020] Preferably, in step S2, the noble metal salt is platinum salt or palladium salt or iridium salt or ruthenium salt or rhodium salt, and the transition metal salt is iron salt or cobalt salt or nickel salt or manganese salt or copper salt.

[0021] Preferably, in step S2, the noble metal salt is platinum salt, the transition metal salt is nickel salt, and the molar ratio is Pt:Ni = 3:1.

[0022] Preferably, in step S4, the argon gas flow rate is 50 sccm.

[0023] Preferably, in step S5, the argon gas flow rate is 90 sccm and the ammonia gas flow rate is 10 sccm.

[0024] Preferably, in step S5, when the dealloying heating temperature is 700 - 900 °C, Pt 3 Ni 1-x alloy nanoparticles and Ni single atoms cross-scale combination are formed; when the temperature is 900 - 1300 °C, Pt 3 Ni 1-x alloy nanoparticles and Ni single atoms, highly exposed Ni metal clusters cross-scale combination are formed; when the temperature rises to 1300 - 1500 °C, Pt 3 Ni 1-x alloy nanoparticles and highly exposed Ni metal clusters cross-scale combination are formed.

[0025] Application of the method for preparing carbon-supported noble metal / transition metal cross-scale catalyst, applied to the OER (Li 2 O 2 product decomposition and O 2 precipitation) and ORR (oxygen reduction to form Li during discharge 2 O 2 ) bifunctional catalyst.

[0026] The beneficial effects of the method and application for preparing carbon-supported noble metal / transition metal cross-scale catalyst of the present invention are as follows:

[0027] (1) By the method of rapid Joule heating, the ordered α 3The β alloy is anchored on the surface of a synthetic N-rich TPB-TFB-COF-derived carbon matrix. Rapid thermal shock causes α noble metal atoms and β transition metal atoms to form an ordered alloy. Meanwhile, rapid cooling prevents the sintering of alloy nanoparticles, forming ultrafine ordered alloy nanoparticles with excellent catalytic activity. Moreover, compared with commercial carbon materials, the abundant imino (-NH 2 -) groups on the TPB-TFB-COF matrix act as ligands and can chelate with metal atoms sufficiently, strengthening the interaction between metal atoms and the matrix, thereby enhancing the stability of the catalyst.

[0028] (2) This method uses the NH 3 dealloying method to construct abundant dislocation defects in alloy nanoparticles, thereby causing compressive strain in the crystal and enhancing the activity of the catalyst. Under the action of NH 3 molecules, transition metal atoms β are continuously leached out, forming β atomic vacancies on the surface of alloy nanocrystals, causing the orderly arranged noble metal α atoms to aggregate towards the surface vacancies, resulting in partial stacking of the face-centered cubic (111) crystal plane of α metal, forming Frank partial dislocations. The resulting compressive strain optimizes the catalytic activity of the defective α 3 β 1-x alloy nanoparticles.

[0029] (3) This method conducts the second-step Joule heating of the material in an Ar / NH 3 atmosphere, regulates different temperatures (700 - 1500 °C), and performs NH 3 assisted dealloying treatment on α 3 β alloy nanoparticles to form active site combinations of different scales. Under the action of NH 3 molecules, transition metal atoms β in the α 3 β alloy will leach out from the alloy and be captured by the abundant N atoms on the carbon matrix to form single atoms with β-N-C coordination or β highly exposed clusters. Specifically: when the temperature is 700 - 900 °C, the leached β atoms are limited, and finally an α 3 β 1-x alloy nanocrystal + β metal single atom cross-scale catalyst is formed. As the temperature rises to 900 - 1300 °C, the leaching of β atoms at the edges of alloy nanoparticles increases, and some β atoms agglomerate on the matrix to form highly exposed β clusters. Finally, an α 3 β 1-x alloy nanocrystal + β metal single atom + β highly exposed cluster cross-scale catalyst is formed. As the temperature rises to 1300 - 1500 °C, most of the β atoms at the edges of alloy nanoparticles are leached out due to the compressive strain of the crystal and agglomerate sufficiently on the matrix to form highly exposed β clusters. Finally, an α 3 β 1-xAlloy nanocrystals + β highly exposed clusters cross-scale catalyst. Therefore, this method can realize the regulation of active sites with three different scale combinations of alloy nanocrystals + single metal atoms, alloy nanocrystals + single metal atoms + highly exposed metal clusters, and alloy nanocrystals + highly exposed metal clusters by adjusting the ammonia-assisted dealloying temperature. An α 3 β alloy nanoparticle is used as the active site for ORR, and β single atoms or β highly exposed clusters are used as the active sites for OER. This synergy meets the requirements of a high-performance bifunctional catalyst for OER and ORR in lithium-air batteries, effectively reducing the overpotential during charge and discharge.

[0030] (4) By utilizing the electronegativity difference between two noble metal / transition metal elements, this method induces charge transfer between them, and regulates the D-band center and valence state of noble metal α through transition metal β, significantly enhancing the 3 β 1-x activity and stability of the @β-N-C catalyst.

[0031] (5) At a high current density of 1000 mAg -1 , α 3 β 1-x @β-N-C shows very excellent performance as the catalytic positive electrode of a lithium-air battery. Due to the charge transfer between the two metals (α and β) and the synergy between catalytic sites of different scales (α 3 β 1-x and β-N-C), the overpotentials of the OER and ORR processes are much smaller than those of the carbon composite electrode loaded only with noble metal α catalyst, and the cycle life is much longer than that of the carbon composite electrode loaded only with noble metal α catalyst. Therefore, the α 3 β 1-x @β-N-C catalyst has great application prospects in the field of lithium-air batteries.

[0032] (6) This method is universal. By changing the types of noble metal salts (platinum salts, palladium salts, iridium salts, ruthenium salts, rhodium salts) and transition metal salts (iron salts, cobalt salts, nickel salts, manganese salts, copper salts), a series of α 3 β 1-x @β-N-C (α is a noble metal, β is a transition metal) catalysts can be obtained.

[0033] (7) The raw materials used in this method are all ordinary commercially available products. The synthesis process is simple, easy to control, has high repeatability, and large output, making it suitable for industrial scale-up production.

[0034] Description of the Drawings

[0035] Figure 1 and Pt formed by ammonia dealloying at 800 °C 3 Ni 1-xHigh-angle annular dark-field scanning transmission electron microscopy images of Ni-N-C catalysts:

[0036] Figure 2 Pt formed by ammonia dealloying at 800 °C 3 Ni 1-x Extended X-ray absorption fine structure of the Ni element in Ni-N-C catalysts

[0037] Figure 3 Pt formed by ammonia dealloying at 800 °C 3 Ni 1-x Charge-discharge performance curves in a lithium-air battery assembled with Ni-N-C catalysts

[0038] Figure 4 Pt formed by ammonia dealloying at 800 °C 3 Ni 1-x Cycling performance graph of a lithium-air battery assembled with Ni-N-C catalysts Detailed implementation methods

[0039] The following descriptions are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0040] Example 1

[0041] A method for preparing carbon-supported noble metal / transition metal cross-scale catalysts, as Figures 1-4 shown, includes the following steps:

[0042] S1: Preparation of TPB-TFB-COF powder A

[0043] 1,3,5-Tris(4-aminophenyl)benzene (TPB) and terephthalaldehyde (TFB) were respectively added to a mortar according to a molar ratio of TPB:TFB of 1:1, ground for 10 min, then an anhydrous ethanol solution was added, stirred for 8 h, centrifuged, transferred to a vacuum drying oven, and dried at 80 °C for 16 h to obtain TPB-TFB-COF powder A;

[0044] S2: Preparation of noble metal salt solution B and transition metal salt solution C

[0045] The noble metal α salt and the transition main group metal β salt were respectively added to deionized water according to a molar ratio, sonicated for 1 h, and the obtained noble metal salt solution B and transition metal salt solution C were obtained respectively;

[0046] S3: Preparation of the precursor

[0047] Powder A, precious metal salt solution B, and transition metal salt solution C are simultaneously added to acetonitrile, stirred for 12 h, centrifuged, and vacuum dried at 60 °C for 12 h to obtain a dark-colored precursor powder B of COFs loaded with metal ions;

[0048] S4: Preparation of alloy nanocrystal catalyst

[0049] The precursor powder B is placed in a Joule heating device. Under the atmosphere of flowing argon, it is heated from room temperature to 2000 °C within 2 s, and then cooled to room temperature within 8 s. During this process, precious metal α and transition metal β form α 3 β alloy nanocrystals, and at the same time, TPB-TFB-COF is carbonized to form an N-C matrix. The resulting powder is the target product α 3 β@N-C catalyst;

[0050] S5: Dealloying process

[0051] The dark-colored α 3 β@N-C catalyst powder obtained after drying is placed in a Joule heating device, and a dealloying process is carried out under the atmosphere of flowing argon / ammonia (volume ratio = 9:1). It is heated from room temperature to 700 °C within 1 s, held for 30 s, and then cooled to room temperature within 3 s; by controlling the Joule heating temperature, the cross-scale combination regulation of α 3 β 1-x alloy nanocrystals + β metal single atoms, α 3 β 1-x alloy nanocrystals + β metal single atoms + β highly exposed metal clusters or α 3 β 1-x alloy nanocrystals + β highly exposed metal clusters is achieved; α is one of precious metals Pt, Ir, Pd, Ru, Rh, and β is one of transition metals Fe, Co, Ni, Mn, Cu.

[0052] Example 2

[0053] A method for preparing a carbon-supported precious metal / transition metal cross-scale catalyst, as Figures 1-4 shown, includes the following steps:

[0054] S1: Preparation of TPB-TFB-COF powder A

[0055] 1,3,5-Tris(4-aminophenyl)benzene, i.e., TPB, and terephthalaldehyde, i.e., TFB, are respectively added to a mortar according to a molar ratio of TPB:TFB of 1:1, ground for 10 min, then an anhydrous ethanol solution is added, stirred for 8 h, centrifuged, transferred to a vacuum drying oven, and dried at 80 °C for 16 h to obtain TPB-TFB-COF powder A;

[0056] S2: Preparation of noble metal salt solution B and transition metal salt solution C

[0057] Add the noble metal α salt and the transition main group metal β salt to deionized water according to the molar ratio respectively, and ultrasonicate for 1 h to obtain the noble metal salt solution B and the transition metal salt solution C respectively;

[0058] S3: Preparation of precursor

[0059] Add the powder A, the noble metal salt solution B and the transition metal salt solution C to acetonitrile simultaneously, stir for 12 h, centrifuge, and dry in vacuum at 80 °C for 12 h to obtain the dark precursor powder B of COFs loaded with metal ions;

[0060] S4: Preparation of alloy nanocrystal catalyst

[0061] Place the precursor powder B in a Joule heating device, under the atmosphere of flowing argon, heat from room temperature to 3000 °C within 10 s, and then cool to room temperature within 20 s. During this process, the noble metal α and the transition metal β form an α 3 β alloy nanocrystal, and at the same time, TPB-TFB-COF is carbonized to form an N-C matrix. The resulting powder is the target product α 3 β@N-C catalyst;

[0062] S5: Dealloying process

[0063] Place the dried dark α 3 β@N-C catalyst powder in a Joule heating device, and carry out the dealloying process under the atmosphere of flowing argon / ammonia (volume ratio = 9:1). Heat from room temperature to 1500 °C within 4 s, keep warm for 50 s, and then cool to room temperature within 10 s; Through the control of the Joule heating temperature, realize the cross-scale combined regulation of α 3 β 1-x alloy nanocrystal + β metal single atom, α 3 β 1-x alloy nanocrystal + β metal single atom + β highly exposed metal cluster or α 3 β 1-x alloy nanocrystal + β highly exposed metal cluster; α is one of noble metals Pt, Ir, Pd, Ru, Rh, and β is one of transition metals Fe, Co, Ni, Mn, Cu.

[0064] Example 3

[0065] Based on Example 1 and 2, this example discloses:

[0066] In the step S2, the noble metal salt is platinum salt or iridium salt or ruthenium salt or rhodium salt, and the transition metal salt is iron salt or cobalt salt or nickel salt or manganese salt.

[0067] Preferably in this embodiment, in step S2, the noble metal salt is a platinum salt, the transition metal salt is a nickel salt, and the molar ratio is Pt:Ni = 3:1.

[0068] Example 4

[0069] Based on Example 3, this example discloses:

[0070] In step S4, the argon gas flow rate is 50 sccm.

[0071] In step S5, the argon gas flow rate is 90 sccm and the ammonia gas flow rate is 10 sccm.

[0072] Example 5

[0073] Based on Example 4, this example discloses:

[0074] In step S5, when the dealloying calcination temperature is 700 - 900 °C, a cross-scale combination of Pt 3 Ni 1-x alloy nanoparticles and Ni single atoms is formed; when the temperature is 900 - 1300 °C, a cross-scale combination of Pt 3 Ni 1-x alloy nanoparticles, Ni single atoms, and highly exposed Ni metal clusters is formed; when the temperature rises to 1300 - 1500 °C, a cross-scale combination of Pt 3 Ni 1-x alloy nanoparticles and highly exposed Ni metal clusters is formed.

[0075] Example 6

[0076] Based on Example 5, this example discloses:

[0077] Application of the method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst in the OER (Li 2 O 2 product decomposition and O 2 evolution) and ORR (oxygen reduction to form Li 2 O 2 ) bifunctional catalysts during the charging and discharging processes of a lithium-air battery.

[0078] The working principle of the present invention:

[0079] The synthesis strategy of the present invention is the "joule heating pre-alloying - ammonia-assisted dealloying" method, that is, first synthesize a covalent organic framework (COFs) precursor, then form a noble metal / transition metal alloy on the surface of the covalent organic framework (COFs) matrix through the joule heat effect, and then use the ammonia-assisted dealloying method to detach some transition metal atoms from the alloy surface. After the COFs matrix is carbonized, abundant N atoms are formed to anchor the detached transition metal atoms around the noble metal / transition metal alloy nanoparticles. By regulating the ammonia-assisted dealloying process, a cross-scale combination of alloy nanocrystals + metal single atoms and alloy nanocrystals + highly exposed metal clusters can be achieved. Specifically: first, use the Schiff base reaction between 1,3,5-tris(4-aminophenyl)benzene (TPB) and terephthalaldehyde (TFB) to dehydrate and condense into a two-dimensional structure-rich imino (-NH 2 -) COFs precursor (TPB-TFB-COF). Then, add noble metal salts (α = Pt, Pd, Ir, Ru, Rh) and transition main group metal salts (β = Fe, Co, Ni, Mn, Cu) solutions and COFs matrix powder into an organic solvent, and use the imino groups on the surface of COFs to fully chelate metal ions. After stirring evenly, centrifuge and vacuum dry to obtain a dark precursor powder. Under the atmosphere of Ar protective gas, use the rapid thermal shock of joule heating to quickly heat the material to 2000-3000 °C within 2-10 s, and then cool it to room temperature within 8-20 s to obtain a carbon-based catalyst powder loaded with α 3 β ordered alloy nanoparticles. Finally, transfer the obtained powder to the joule heating device for the second time, and heat it at 700-1500 °C under the Ar / NH 3 atmosphere to carry out the dealloying process to remove the β atoms on the surface of the α 3 β nanoparticles. Subsequently, the β atoms are captured by the N atoms in the surrounding carbon matrix, and the formed β-N single atoms or β highly exposed clusters are distributed around the α 3 β 1-x nanoparticles. By adjusting the calcination temperature of the dealloying process, this method realizes the regulation of different-scale active sites of the carbon-supported catalyst. The composite material uses carbon nanosheets obtained by high-temperature carbonization of TPB-TFB-COF as the matrix, and the bimetallic alloy, metal single atoms, and metal clusters are directly loaded on the matrix. The mass of the metal single atoms, metal clusters, and alloy is 5 wt% of the mass of the composite material. The noble metal α (Pt, Pd, Ir, Ru, Rh) and the transition metal β (Fe, Co, Ni, Mn, Cu) form α 3 β alloy nanoparticles, and at the same time, form single atoms or clusters coordinated with β-Nx and anchor on the TPB-TFB-COF-derived carbon matrix containing abundant N atoms, thereby constructing a bifunctional catalyst with cross-scale active sites for lithium-air batteries (α 3 β1-x @β-N-C).

Claims

1. A method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst, characterized in that it comprises the following steps: S1: Preparation of TPB-TFB-COF powder A 1,3,5-Tris(4-aminophenyl)benzene (TPB) and trimesaldehyde (TFB) were added to a mortar at a molar ratio of TPB:TFB of 1:1, ground for 10 min, then added with anhydrous ethanol solution, stirred for 8 h, centrifuged, transferred to a vacuum drying oven, and dried at 80 °C for 16 h to obtain TPB-TFB-COF powder A; S2: Preparation of noble metal salt solution B and transition metal salt solution C A noble metal α salt and a transition metal β salt are added to deionized water according to a molar ratio, and ultrasonicated for 1 h to obtain a noble metal salt solution B and a transition metal salt solution C respectively; S3: Preparation of Precursors The powder A, the noble metal salt solution B and the transition metal salt solution C are added to acetonitrile at the same time, stirred for 12 h, centrifuged, and vacuum dried at 60° C.-80° C. for 12 h to obtain a COFs dark precursor powder B loaded with metal ions; S4: Preparation of Alloy Nanocrystal Catalysts Precursor powder B is placed in a Joule heating device, heated from room temperature to 2000-3000°C in 2-10 seconds under a flowing argon atmosphere, and then cooled to room temperature in 8-20 seconds. During this process, the noble metal α and the transition metal β form α3β alloy nanocrystals, and TPB-TFB-COF is carbonized to form an NC matrix. The powder obtained is the target product α3β @ NC catalyst. S5: Dealloying process The dark α3β@NC catalyst powder obtained after drying was placed in a Joule heat device and dealloyed in an atmosphere with a flowing argon / ammonia volume ratio of 9:

1. The powder was heated from room temperature to 700-1500 °C within 1-4 s, kept at this temperature for 30-50 s, and then cooled to room temperature within 3-10 s. The α3β@NC catalyst powder was de-alloyed by controlling the Joule heat temperature. 1-x Alloy nanocrystals + β metal single atoms, α3β 1-x Alloy nanocrystals + β metal single atoms + β highly exposed metal clusters or α3β 1-x Alloy nanocrystals + β highly exposed metal clusters cross-scale combination regulation; the α is one of the noble metals Pt, Ir, Pd, Ru, Rh, and the β is one of the transition metals Fe, Co, Ni, Mn, Cu; In the step S2, the noble metal salt is a platinum salt, a palladium salt, an iridium salt, a ruthenium salt, or a rhodium salt, and the transition metal salt is an iron salt, a cobalt salt, a nickel salt, a manganese salt, or a copper salt.

2. The method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst according to claim 1, characterized in that: In the step S4, the argon gas flow rate is 50 sccm.

3. The method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst according to claim 1, characterized in that: In the step S5, the flow rate of argon gas is 90 sccm, and the flow rate of ammonia gas is 10 sccm.

4. The method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst according to claim 1, characterized in that: In the step S2, the noble metal salt is a platinum salt, the transition metal salt is a nickel salt, and the molar ratio is Pt:Ni=3:

1.

5. The method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst according to claim 4, characterized in that: In the step S5, when the dealloying heating temperature is 700-900°C, Pt3Ni 1-x Cross-scale combination of alloy nanoparticles and Ni single atoms; Pt3Ni is formed when the temperature is 900-1300 ℃ 1-x Cross-scale combination of alloy nanoparticles, Ni single atoms, and highly exposed Ni metal clusters; the temperature rises to 1300-1500℃ to form Pt3Ni 1-x Cross-scale combination of alloy nanoparticles and highly exposed Ni metal clusters.

6. The use of the method for preparing a carbon-supported noble metal / transition metal cross-scale catalyst according to any one of claims 1 to 5, characterized in that: A bifunctional catalyst used for the decomposition of Li2O2 products and O2 precipitation during the OER charging process of lithium-air batteries and the reduction of oxygen to form Li2O2 during the ORR discharge process.

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