A method for preparing a platinum-based single-atom catalyst

Abstract

The present invention belongs to the field of single-atom catalyst preparation, and specifically relates to a method for preparing a platinum-based single-atom catalyst. The method steps are as follows: (1) metal organic framework material UiO-66 is uniformly dispersed in deionized water, and then a Pt ion precursor solution is added, and the solid obtained is allowed to stand, centrifuged, and washed after ultrasonic mixing; (2) the solid is uniformly ultrasonically dispersed in ethanol, an energetic compound 5-nitroammonium tetrazole is added, and the solid is dried at 30-80°C after ultrasonic 10-30min to obtain an energetic solid mixture; (3) the energetic solid mixture is placed in a closed container, and the outer wall of the container is knocked or hit to detonate the energetic solid mixture, and the product after the explosion is collected to obtain the platinum-based single-atom catalyst; the method process steps are simple and safe, green and pollution-free, and the yield is close to 100%, and the obtained platinum-based single-atom catalyst has high atomic dispersion, is relatively uniform, and exhibits excellent catalytic performance.

Description

Technical Field

[0001] The invention belongs to the field of single-atom catalyst preparation, and specifically relates to a method for preparing a platinum-based single-atom catalyst. Background Art

[0002] Single-atom catalysts are metals uniformly loaded in the form of single atoms on carriers such as metals, metal oxides, two-dimensional materials and molecular sieves. The single atom is used as the catalytic active center for catalytic reactions. The metal active sites of single-atom catalysts show the characteristics of atomic-level dispersion. In recent years, single-atom catalysts have shown excellent catalytic performance in the fields of electrocatalysis (hydrogen evolution, oxygen evolution, oxygen reduction, etc.), photocatalysis (CO2 reduction), energy storage (zinc-air battery, magnesium-air battery), etc., which mainly benefit from the advantages of the structure of single-atom catalysts themselves: on the one hand, single-atom catalysts have very high atomic utilization, which can theoretically reach 100%, which is especially important for reducing the cost of precious metal (Pt) catalysts; on the other hand, the composition and structure of the active sites of single-atom catalysts are more uniform, and catalysts can be rationally customized for systems with competitive reactions; in addition, single-atom catalysts are atomically dispersed, so the combination between the carrier and the metal of the single-atom catalyst is tighter, which is more conducive to the transmission of electrons, thereby improving the activity of the catalyst.

[0003] Since single-atom catalysts were proposed by Academician Zhang Tao of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences in 2011, various preparation methods have emerged, including high-temperature calcination, photochemical deposition, electrochemical deposition, gas diffusion, atomization, etc. The preparation process of these methods is relatively complicated and requires a lot of energy, so simpler preparation methods have been explored.

[0004] At present, it has been found that there are many types of metals that can be used in the field of single-atom catalysts, including iron, copper, nickel, manganese, titanium, chromium, cobalt, indium, gallium, gold, silver, platinum, etc. The representative advantages of these metals can be integrated into single-atom catalysts. Among them, platinum-based single-atom catalysts refer to isolated single platinum metal atoms dispersed on a solid carrier. There is no form of interaction between each individual atom. The active site is generally composed of a single metal atom and other adjacent atoms on the carrier surface or functional species. Platinum-based single-atom catalysts in the prior art are usually prepared by impregnation-high-temperature calcination method, but the preparation process of the method is relatively complicated, the preparation time is long, and the preparation energy consumption is high.

[0005] Energetic compounds are substances that can undergo rapid redox reactions and release a large amount of energy in a short period of time, which makes it possible to reduce metal ions. However, there are no reports in the prior art on the use of energetic compounds to prepare single-atom catalysts. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a method for preparing a platinum-based single-atom catalyst. The method first composites platinum metal ions and an energetic compound 5-nitroammonium tetrazole onto a carrier metal-organic framework material UiO-66 to obtain an energetic solid mixture, and then detonates the energetic solid mixture by knocking or impacting to reduce the platinum metal ions on the carrier metal-organic framework material UiO-66, thereby preparing a platinum-based single-atom catalyst.

[0007] To achieve the purpose of the present invention, the following technical solutions are provided.

[0008] A method for preparing a platinum-based single-atom catalyst, the method comprising the following steps:

[0009] (1) The metal organic framework material UiO-66 is uniformly dispersed in deionized water, and then a Pt ion precursor solution is added, and the mixture is ultrasonically mixed and then allowed to stand for 12 to 24 hours, and the solid is separated by centrifugation and washing with ethanol;

[0010] The ratio of the mass (g) of the metal organic framework material UiO-66 to the volume (mL) of deionized water is (0.1-0.3): (2.5-5);

[0011] The solute of the Pt ion precursor solution is Na2PtCl4 or K2PtCl4, and the solvent is deionized water; in the Pt ion precursor solution, the mass concentration of the solute is 0.02-0.04 g / mL;

[0012] The mass ratio of the metal organic framework material UiO-66 to the Pt ion precursor is 200:(2-21);

[0013] (2) uniformly dispersing the solid obtained in step (1) in ethanol by ultrasonication, adding the energetic compound 5-nitroammonium tetrazole, continuing ultrasonication for 10 to 30 minutes, and then drying at 30 to 80° C. to obtain an energetic solid mixture;

[0014] The mass ratio of the energetic compound 5-nitroammonium tetrazole to the metal organic framework material UiO-66 in step (1) is 1:(5-20);

[0015] (3) placing the energetic solid mixture obtained in step (2) in a sealed container, knocking or hitting the outer wall of the container to detonate the energetic solid mixture, and collecting the explosion product to obtain the platinum-based single-atom catalyst.

[0016] Preferably, in step (1), the solute of the Pt ion precursor solution is Na2PtCl4, and the mass concentration of the solute is 0.026 g / mL.

[0017] Preferably, in step (1), the ratio of the mass (g) of the metal organic framework material UiO-66 to the volume (mL) of deionized water is 0.2:5.

[0018] Preferably, in step (2), the mass ratio of the energetic compound 5-nitroammonium tetrazole to the metal organic framework material UiO-66 in step (1) is 1:10; the energetic compound 5-nitroammonium tetrazole is added, ultrasonication is continued for 10 minutes, and then drying is carried out at 60°C.

[0019] Beneficial effects:

[0020] (1) The present invention provides a method for preparing a platinum-based single-atom catalyst. The method firstly combines platinum metal ions and an energetic compound 5-nitroammonium tetrazole onto a carrier metal organic framework material UiO-66 to obtain an energetic solid mixture, and then detonates the energetic solid mixture by knocking or impacting, so that the energy provided by a rapid redox reaction reduces the Pt ions on the carrier to prepare a single-atom catalyst. The method has simple process steps, short time, and low energy consumption. Ultrasonication in a solvent and a drying temperature lower than the thermal decomposition temperature of the energetic compound are performed, and the method is easy to control, the process is safe, green and pollution-free, and the yield is close to 100%. In addition, the platinum-based single-atom catalyst prepared by the method has high atomic dispersion and is relatively uniform, showing excellent catalytic performance.

[0021] (2) The present invention provides a method for preparing a platinum-based single-atom catalyst. The method selects a metal organic framework material UiO-66 as a carrier. The metal organic framework material UiO-66 has a large specific surface area and a high porosity, and is easy to adsorb and anchor a Pt ion precursor solution and an energetic compound. 5-ammonium nitrate tetrazole is selected as the energetic compound. 5-ammonium nitrate tetrazole has a high energy density and a moderate sensitivity. Explosives with too low a sensitivity are difficult to detonate, and explosives with too high a sensitivity have safety hazards and are not easy to store and transport. 5-ammonium nitrate tetrazole can be detonated by knocking or hammering, and the operation is simple and convenient.

[0022] (3) The present invention provides a method for preparing a platinum-based single-atom catalyst. In the method, the preferred ultrasonic time is 10 minutes and the drying temperature is 60°C. The temperature and time can not only make the solid obtained in step (1) (generated by the reaction of the metal organic framework material UiO-66 and the Pt ion precursor solution) and the energetic compound 5-nitroammonium tetrazole uniformly dispersed in ethanol, and remove the solvent and dry, but also can avoid the explosion of 5-nitroammonium tetrazole during the preparation process, thereby eliminating safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a high angle annular dark field scanning transmission electron microscope (HAADF-STEM) electron microscope photograph of the final product prepared in Example 1;

[0024] Figure 2 The R space curve diagram of the synchrotron radiation expansion edge of the final product, Pt sheet and PtO2 prepared in Example 1;

[0025] Figure 3 This is a transmission electron microscope photo of the final product prepared in Example 2;

[0026] Figure 4 The element distribution and lattice fringes of the final product prepared in Example 2 were made under a transmission electron microscope. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments of the present invention; in the following comparative examples and embodiments, the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0028] In the following examples, the metal organic framework material UiO-66 is prepared by the following method:

[0029] (1) adding 0.63 g of ZrCl4 and 0.63 g of terephthalic acid to 50 mL of N,N-dimethylformamide solution to obtain a mixed solution;

[0030] (2) Acetic acid was added to adjust the pH of the mixed solution in step (1) to 4, and then the mixed solution was transferred to 10 20 mL polytetrafluoroethylene autoclaves respectively, and hydrothermally reacted at 120° C. for 24 h. After the hydrothermal reaction, the solid was centrifuged to obtain a solid, which was then washed three times with DMF and methanol by centrifugation, and finally placed in a 60° C. forced drying oven for 24 h to obtain a powder product.

[0031] The powder product was characterized by X-ray diffraction (XRD), and the characteristic peaks of the final product were consistent with the characteristic peaks of the metal organic framework material UiO-66, indicating that the powder product prepared by the method is the metal organic framework material UiO-66.

[0032] Example 1

[0033] A method for preparing a platinum-based single-atom catalyst, the method comprising the following steps:

[0034] (1) 200 mg of metal organic framework material UiO-66 was uniformly dispersed in 5 mL of deionized water, and then 80 μL of Pt ion precursor solution was added. After ultrasonic mixing for 10 min, the mixture was allowed to stand for 12 h, centrifuged and washed with ethanol to separate the solid three times;

[0035] The ratio of the mass (g) of the metal organic framework material UiO-66 to the volume (mL) of deionized water is 0.2:5;

[0036] The solute of the Pt ion precursor solution is Na2PtCl4, and the solvent is deionized water; in the Pt ion precursor solution, the mass concentration of the solute is 0.026 g / mL;

[0037] The mass ratio of the metal organic framework material UiO-66 to the Pt ion precursor is 200:2.08;

[0038] (2) uniformly dispersing the solid obtained in step (1) by ultrasonication in 2 mL of ethanol, adding 20 mg of the energetic compound 5-nitroammonium tetrazole, continuing ultrasonication for 10 min, and then drying in a forced air drying oven at 60° C. for 24 h to obtain an energetic solid mixture;

[0039] The mass ratio of the energetic compound 5-nitroammonium tetrazole to the metal organic framework material UiO-66 in step (1) is 1:10;

[0040] (3) placing the energetic solid mixture obtained in step (2) in a sealed container, wherein the sealed container is an infrared spectroscopy tablet pressing mold, striking the outer wall of the mold with a hammer to detonate the energetic solid mixture, and collecting the product after the explosion to obtain a final product.

[0041] The final product, Pt sheet and PtO2 prepared in Example 1 were characterized by synchrotron radiation. Figure 2 As shown in the figure, it can be seen that the final product has no peaks at the Pt-O bond and Pt-Pt bond, proving that there are no Pt particles, Pt clusters, or PtO2 particles, and Pt exists in a single atomic form.

[0042] The final product prepared in Example 1 was characterized by high-angle annular dark field scanning transmission electron microscopy, and the results were as follows: Figure 1 As shown, from Figure 1 It can be seen that Pt single atoms are uniformly distributed on the carrier metal organic framework material UiO-66, and the size of Pt is at the single-atom level, which is consistent with the synchrotron radiation characterization results; this shows that the final product is a platinum-based single-atom catalyst, and the method described in this embodiment can prepare a platinum-based single-atom catalyst.

[0043] Example 2

[0044] A method for preparing a platinum-based single-atom catalyst, the method comprising the following steps:

[0045] (1) 200 mg of metal organic framework material UiO-66 was uniformly dispersed in 5 mL of deionized water, and then 800 μL of Pt ion precursor solution was added. After ultrasonic mixing for 10 min, the mixture was allowed to stand for 24 h, centrifuged, and the separated solid was washed with ethanol three times;

[0046] The ratio of the mass (g) of the metal organic framework material UiO-66 to the volume (mL) of deionized water is 0.2:5;

[0047] The solute of the Pt ion precursor solution is Na2PtCl4, and the solvent is deionized water; in the Pt ion precursor solution, the mass concentration of the solute is 0.026 g / mL;

[0048] The mass ratio of the metal organic framework material UiO-66 to the Pt ion precursor is 200:20.8;

[0049] (2) uniformly dispersing the solid obtained in step (1) by ultrasonication in 2 mL of ethanol, adding 20 mg of the energetic compound 5-nitroammonium tetrazole, continuing ultrasonication for 10 min, and then drying in a forced air drying oven at 60° C. for 24 h to obtain an energetic solid mixture;

[0050] The mass ratio of the energetic compound 5-nitroammonium tetrazole to the metal organic framework material UiO-66 in step (1) is 1:10;

[0051] (3) placing the energetic solid mixture obtained in step (2) in a sealed container, wherein the sealed container is an infrared spectroscopy tablet pressing mold, striking the outer wall of the mold with a hammer to detonate the energetic solid mixture, and collecting the product after the explosion to obtain a final product.

[0052] The final product prepared in Example 2 was characterized by synchrotron radiation. The result was similar to that in Example 1. The final product had no peak at the Pt-Pt bond, proving that there were no Pt particles or Pt clusters, and Pt existed in the form of single atoms.

[0053] The final product prepared in Example 2 was subjected to transmission electron microscopy, and the results were as follows: Figure 3 As shown in the figure, single-atom Pt particles are evenly distributed in the carrier metal organic framework material UiO-66, and the size of Pt is at the single-atom level;

[0054] Figure 4 The element distribution and lattice fringes of the Pt particle catalyst prepared in Example 2 under a transmission electron microscope; the element distribution diagram proves that the particles distributed on the carrier metal organic framework material UIO-66 are Pt particles, and the lattice spacing of the lattice fringes further proves that the exposed crystal plane is the (200) crystal plane of Pt.

[0055] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope 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 protection scope of the present invention.

Claims

1. A method for preparing a platinum-based single-atom catalyst, characterized in that: The method steps are as follows: (1) The metal organic framework material UiO-66 is uniformly dispersed in deionized water, and then the Pt ion precursor solution is added. After ultrasonic mixing, it is allowed to stand for 12 to 24 hours, and the solid is separated by centrifugation and washed with ethanol; The ratio of the mass g of the metal organic framework material UiO-66 to the volume mL of deionized water is (0.1-0.3): (2.5-5); The solute of the Pt ion precursor solution is Na2PtCl4 or K2PtCl4, and the solvent is deionized water; in the Pt ion precursor solution, the mass concentration of the solute is 0.02-0.04 g / mL; The mass ratio of the metal organic framework material UiO-66 to the Pt ion precursor is 200: (2-21); (2) uniformly dispersing the solid in ethanol by ultrasonication, adding the energetic compound 5-nitraminotetrazolyl, continuing ultrasonication for 10 to 30 minutes, and then drying at 30 to 80° C. to obtain an energetic solid mixture; The mass ratio of the energetic compound 5-nitraminotetrazolyl and the metal organic framework material UiO-66 is 1:(5-20); (3) placing the energetic solid mixture in a sealed container, knocking or striking the outer wall of the container to detonate the energetic solid mixture, and collecting the explosion product to obtain the platinum-based single atom catalyst.

2. The method for preparing a platinum-based single-atom catalyst according to claim 1, characterized in that: In step (1), the solute of the Pt ion precursor solution is Na2PtCl4, and the mass concentration of the solute is 0.026 g / mL.

3. A method for preparing a platinum-based single-atom catalyst according to claim 1 or 2, characterized in that: In step (1), the ratio of the mass g of the metal organic framework material UiO-66 to the volume mL of deionized water is 0.2:

5.

4. The method for preparing a platinum-based single-atom catalyst according to claim 1, characterized in that: In step (2), the mass ratio of the energetic compound 5-nitraminotetrazolyl to the metal organic framework material UiO-66 in step (1) is 1:10; the energetic compound 5-nitraminotetrazolyl is added, ultrasonication is continued for 10 minutes, and then drying is performed at 60°C.

5. The method for preparing a platinum-based single-atom catalyst according to claim 2, characterized in that: In step (1), the ratio of the mass g of the metal organic framework material UiO-66 to the volume mL of deionized water is 0.2:5; In step (2), the mass ratio of the energetic compound 5-nitraminotetrazolyl to the metal organic framework material UiO-66 in step (1) is 1:10; the energetic compound 5-nitraminotetrazolyl is added, ultrasonication is continued for 10 minutes, and then drying is performed at 60°C.

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