Method for preparing asymmetric monatomic catalyst by explosion method

Abstract

The invention discloses a method for preparing an asymmetric monatomic catalyst by an explosion method, and belongs to the field of monatomic catalysts. The method comprises the following steps: uniformly dispersing a metal salt and a carrier material in a solvent; stirring at normal temperature until the metal salt is fully adsorbed in the carrier; washing with water and ethanol for multiple times to remove non-adsorbed metal salt, so as to obtain a mixture; adding a solvent solution containing an energetic compound into the mixture, carrying out ultrasonic treatment and stirring, and then putting the mixture into a drying oven until the mixture is completely dried to obtain brown powder; transferring the brown powder into a tabletting mold, detonating the brown powder by adopting a mechanical impact method, and then collecting a powder sample in the mold to obtain the asymmetric monatomic catalyst. The asymmetric monatomic catalyst is prepared through an explosion method by utilizing the characteristic that an explosive releases a large amount of energy instantly during explosion, the problem that an existing method does not provide enough energy to activate inert bonds and doped heteroatoms can be solved, and the asymmetric monatomic catalyst has the advantages of being wide in application range, simple, convenient and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing an asymmetric single-atom catalyst by an explosion method, and belongs to the field of single-atom catalysts. Background Art

[0002] Single-atom catalysts (SACs) have great potential in catalyzing thermal and electrochemical reactions, and their performance depends largely on their local coordination environment. Typically, in order to maintain structural stability, most SACs with isolated metal centers are coordinated with the same atoms (N / O / C) of the support to achieve a relatively complete symmetrical structure. However, the weakly polar active sites of the symmetrical structure may have less attraction to the reactants, resulting in poor intermediate migration and unsatisfactory catalytic performance. By partially replacing the coordinated N / O / C with weakly coordinated atoms (e.g., P, S, etc.) to construct asymmetric SACs, the symmetry of the metal center can be broken and the polarity of the active site can be increased, which shows great potential for improving the overall catalytic performance. For example, asymmetric Cu-S1N3 SACs show a kinetic current density 6.4 times higher than their symmetric Cu-N4 counterparts in the electrocatalytic ORR reaction. Therefore, it is very desirable to construct asymmetric SACs.

[0003] Compared with the existing synthetic methods for symmetric SACs (e.g., wet impregnation, atomic layer deposition, high-temperature pyrolysis, photochemical routes, and electrochemical deposition), there are relatively few synthetic methods for asymmetric SACs. Under mild conditions, such as slow heating and low pressure, symmetric SACs are thermodynamically more likely to form between metal single atoms and supports than asymmetric SACs. Current methods for preparing asymmetric SACs mainly rely on heteroatom doping by calcination (800-1100°C). However, these methods are limited by the narrow range of metal and support selection. The conditions for different metals to be reduced to single atoms and then coordinated with heteroatoms are different, and the conditions for one metal cannot be simply copied to another metal. In addition, most of these methods are applicable to activated carbon-based supports, but not to inert supports widely used in industrial catalytic reactions, such as metal oxides (e.g., TiO2, CeO2, and ZrO2) and other supports (e.g., SiO2 and zeolites), mainly because the existing methods do not provide enough energy to activate inert bonds (e.g., metal-oxygen and Si-O bonds) and dope heteroatoms. Therefore, developing a universal method to synthesize SACs with asymmetric structures remains a significant challenge. Summary of the invention

[0004] In order to solve the problem that the existing methods do not provide enough energy to activate inert bonds (such as metal-oxygen and Si-O bonds) and dope heteroatoms, the purpose of the present invention is to provide a method for preparing asymmetric single-atom catalysts by explosion, which utilizes the characteristic that explosives release a large amount of energy instantly, and prepares asymmetric single-atom catalysts by explosion. The present invention also has the advantages of wide application range, simplicity and convenience, and no need for additional doping of heteroatoms.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention discloses a method for preparing an asymmetric single-atom catalyst by an explosion method, comprising the following steps:

[0007] Step 1: uniformly dispersing the metal salt and the carrier material in a solvent;

[0008] Step 2, stirring at room temperature until the metal salt is fully adsorbed in the carrier; then washing with water and ethanol for multiple times to remove the unadsorbed metal salt to obtain a mixture;

[0009] Step 3: Add the solvent solution containing the energetic compound to the mixture in step 2, ultrasonicate and stir, and then put it in an oven until it is completely dried to obtain a brown powder;

[0010] Step 4: Transfer the brown powder obtained in step 3 to a tablet pressing mold, detonate it by mechanical impact, and then collect the powder sample in the mold to obtain an asymmetric single atom catalyst.

[0011] The metal salt is metal chloride or metal nitrate.

[0012] The carrier material includes: metal oxide, MOFs material, COFs material or molecular sieve material.

[0013] The energetic materials include 5-NAT, RDX, HMX, and CL-20.

[0014] The added amounts of metal salt, carrier material and energetic material are: mass ratio 1-50:1-200:1-50.

[0015] The dispersion time in step 1 is 0.1 to 2 days; the stirring time in step 2 is 0.1 to 2 days.

[0016] In step 3, the temperature of the oven is 40-100° C., and the drying time is 1 to 3 days.

[0017] The microstructure of the asymmetric single-atom catalyst is composed of isolated metal atoms without agglomeration.

[0018] Beneficial effects:

[0019] 1. The synthesis method of asymmetric SACs has poor universality. The existing asymmetric SACs synthesis method mainly adopts the heteroatom doping method, which is limited to carbon-based carriers and cannot be applied to highly stable carriers (such as SiO2, ZrO2, etc.). The present invention discloses a method for preparing asymmetric single-atom catalysts by explosion, wherein brown powder is transferred to a tableting mold, and it is detonated by mechanical impact, and the asymmetric single-atom catalyst is prepared by utilizing the characteristic that explosives release a large amount of energy instantly, thereby improving the universality of the explosion method for preparing asymmetric single-atom catalysts.

[0020] 2. The present invention discloses a method for preparing asymmetric single-atom catalysts by explosion. Since the explosive used in this method releases a large amount of energy and gas instantly during the explosion, the chemical bonds in the inert carrier can be broken from the molecular thermodynamics and kinetics level, and the asymmetric single-atom catalyst can be prepared without the need for additional doping with heteroatoms.

[0021] 3. Existing methods for preparing asymmetric catalysts often have complicated processes and harsh conditions during preparation. The present invention discloses a method for preparing asymmetric single-atom catalysts by explosion, which realizes the preparation conditions of asymmetric single-atom catalysts through the large amount of energy and gas generated during the explosion of explosives. The process for preparing asymmetric single-atom catalysts is simple, convenient and easy to prepare.

[0022] 4. The present invention discloses a method for preparing an asymmetric single-atom catalyst by an explosion method. The explosive used produces green and pollution-free gases such as CO2 and N2 after detonation, and the energy consumption of the preparation process is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the synthesis of asymmetric single-atom catalyst materials.

[0024] Figure 2 This is the SEM image of the asymmetric single-atom catalyst material.

[0025] Figure 3 This is the X-ray diffraction test result of asymmetric single atom catalyst material.

[0026] Figure 4 This is a spherical aberration TEM image of an asymmetric single-atom catalyst material.

[0027] Figure 5 This is the Ir L3-edge Fourier change EXAFS diagram of the asymmetric single-atom catalyst material. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0029] Embodiment 1:

[0030] This embodiment discloses a method for preparing an asymmetric single-atom catalyst by an explosion method, and the specific implementation steps are as follows:

[0031] IrCl3 (31.2 mg, 0.09 mmol) and H-SBA-15 (200 mg) were thoroughly mixed in 5 mL of water and then treated under ultrasound for 30 min to achieve uniform dispersion. Then, the mixture was stirred at room temperature for 12 h to ensure that IrCl3 was fully adsorbed on the carrier. In order to remove the unadsorbed IrCl3, it was washed twice with water and ethanol respectively. Secondly, 2 mL of ethanol solution containing 5-nitroammonium tetrazole (20 mg, 0.17 mmol) was added to the mixture, ultrasonically treated for 10 min, and stirred for a period of time. The mixture was placed in an oven at 60 ° C until it was completely dried to form a brown powdery solid. Finally, the powders were transferred to a tableting mold with a diameter of 10 mm. The 5-nitroammonium tetrazole was detonated by tapping with a small hammer to obtain an asymmetric Ir single atom catalyst (IrSACs@H-SBA-15).

[0032] Figure 1 This is a schematic diagram of the asymmetric single-atom catalyst material prepared in the example. This method is simple and convenient and does not require heteroatom doping.

[0033] Figure 2 This is the SEM image of the asymmetric single-atom catalyst material prepared in the implementation. The results show that the pore structure of the H-SBA-15 carrier has not been destroyed and still maintains good integrity.

[0034] Figure 3 This is the XRD spectrum of the asymmetric single-atom catalyst material prepared in the implementation. The diffraction peak of Ir element is not captured in the figure, and Ir atoms are not agglomerated.

[0035] Figure 4 This is the spherical aberration TEM image of the asymmetric single-atom catalyst material prepared in the implementation. The results show that a large number of Ir single atoms are loaded on the H-SBA-15 material.

[0036] Figure 5 This is the Ir L3-edge Fourier change EXAFS diagram of the asymmetric single-atom catalyst material prepared in the implementation. The results show that The peak at corresponds to the characteristic peak of Ir-O scattering, while A strong Ir-Si scattering peak was observed at No Ir-Ir scattering peaks were detected in the region of . These findings prove that the iridium atoms in the IrSAC / H-SBA-15 catalyst disperse Ir single atoms in a single-atom form.

[0037] Embodiment 2:

[0038] This embodiment discloses a method for preparing an asymmetric single-atom catalyst by an explosion method, and the specific implementation steps are as follows:

[0039] IrCl3 (31.2 mg, 0.09 mmol) and TiO2 (200 mg) were dispersed in 5 mL of aqueous solution and then treated under ultrasound for 30 min to achieve uniform dispersion. Then, the mixture was stirred at room temperature for 12 h to ensure that IrCl3 was fully adsorbed on the carrier. In order to remove the unadsorbed IrCl3, it was washed twice with water and ethanol respectively. After this step, 2 mL of ethanol solution containing 5-nitroammonium tetrazole (20 mg, 0.17 mmol) was added to the mixture, ultrasonically treated for 10 min, and stirred for a period of time. The mixture was placed in an oven at 60 ° C until it was completely dried to form a brown powdery solid. Finally, the powders were transferred to a tableting mold with a diameter of 10 mm. The 5-nitroammonium tetrazole was detonated by tapping with a small hammer to obtain an asymmetric Ir single atom catalyst (IrSACs@TiO2).

[0040] Embodiment 3:

[0041] This embodiment discloses a method for preparing an asymmetric single-atom catalyst by an explosion method, and the specific implementation steps are as follows:

[0042] IrCl3 (31.2 mg, 0.09 mmol) and UiO-66 (200 mg) were dispersed in 5 mL of aqueous solution and then treated under ultrasound for 30 min to achieve uniform dispersion. Then, the mixture was stirred at room temperature for 12 h to ensure that IrCl3 was fully adsorbed on the carrier. In order to remove the unadsorbed IrCl3, it was washed twice with water and ethanol respectively. After this step, 2 mL of ethanol solution containing 5-nitroammonium tetrazole (20 mg, 0.17 mmol) was added to the mixture, ultrasonically treated for 10 min, and stirred for a period of time. The mixture was placed in an oven at 60 ° C until it was completely dried to form a brown powdery solid. Finally, the powders were transferred to a tableting mold with a diameter of 10 mm. The 5-nitroammonium tetrazole was detonated by tapping with a small hammer to obtain an asymmetric Ir single atom catalyst (IrSACs@UiO-66).

[0043] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an asymmetric single-atom catalyst by an explosion method, characterized in that: The following steps are included: Step 1: uniformly dispersing the metal salt and the carrier material in a solvent; Step 2, stirring at room temperature until the metal salt is fully adsorbed in the carrier; then washing with water and ethanol for multiple times to remove the unadsorbed metal salt to obtain a mixture; Step 3: Add the solvent solution containing the energetic compound to the mixture in step 2, ultrasonicate and stir, and then put it in an oven until it is completely dried to obtain a brown powder; Step 4: Transfer the brown powder obtained in step 3 to a tablet pressing mold, detonate it by mechanical impact, and then collect the powder sample in the mold to obtain an asymmetric single atom catalyst.

2. The method for preparing an asymmetric single-atom catalyst by explosion method according to claim 1, characterized in that: The metal salt is metal chloride or metal nitrate.

3. The method for preparing an asymmetric single-atom catalyst by explosion method according to claim 1, characterized in that: The carrier material includes: metal oxide, MOFs material, COFs material or molecular sieve material.

4. The method for preparing an asymmetric single-atom catalyst by explosion method according to claim 1, characterized in that: The energetic materials include 5-NAT, RDX, HMX, and CL-20.

5. The method for preparing an asymmetric single-atom catalyst by explosion method as claimed in claim 1, characterized in that: The added amounts of metal salt, carrier material and energetic material are: mass ratio 1-50:1-200:1-50.

6. The method for preparing an asymmetric single-atom catalyst by explosion method as claimed in claim 1, characterized in that: The dispersion time in step 1 is 0.1 to 2 days; the stirring time in step 2 is 0.1 to 2 days.

7. The method for preparing an asymmetric single-atom catalyst by explosion method as claimed in claim 1, characterized in that: In step 3, the temperature of the oven is 40-100° C., and the drying time is 1 to 3 days.

8. The method for preparing an asymmetric single-atom catalyst by explosion method as claimed in claim 1, characterized in that: The microstructure of the asymmetric single-atom catalyst is composed of isolated metal atoms without agglomeration.

Images