A method for preparing a noble metal nanocluster by directly introducing a reducing agent, borane cluster, into a carbon carrier

Abstract

The application provides a method for preparing nanometer noble metal by directly introducing reducing agent borane cluster into a carbon carrier, and the method is characterized in that: a borane cluster weak reducing agent is loaded on a carbon carrier to reduce and prepare a supported nanometer noble metal in situ, and the weak reducing property of the borane cluster can avoid the agglomeration of metal sites; the reducing agent is introduced into the carbon carrier, and the hard supporting effect of the carbon carrier can also avoid the large-scale agglomeration of the formed metal. The nanometer gold noble metal is dispersed in the carbon carrier, the dispersion of the nanometer noble metal is good, and the size of the nanometer noble metal is less than 10 nanometers. Compared with the prior art, the reducing agent borane cluster is directly introduced into the surface of the carbon carrier in the application, the in-situ reduction of noble metal ions is realized, and the supported nanometer noble metal with high dispersion and small particle size is effectively obtained. The method is simple in operation, reliable in preparation process and good in repeatability, and is beneficial to large-scale preparation.

Description

Technical Field

[0001] This invention relates to a method for preparing novel nano-noble metal materials, belonging to the field of new material preparation, specifically a method for preparing nano-noble metals by directly introducing a reducing agent borane cluster into a carbon support. Background Technology

[0002] Currently, approximately 80% of industrial catalytic activities require catalysts, and the catalytic performance of these catalysts is crucial to the efficiency of production lines. Traditionally, using large-particle metals as catalysts is detrimental to improving atom utilization and mass activity (activity per unit mass). Over the past decade, researchers have continuously developed advanced nanomaterial preparation techniques to minimize the particle size of metal catalysts and increase the participation of surface atoms. Currently, the mainstream methods for preparing nanomaterials include direct wet reduction using sodium borohydride as a reducing agent, high-temperature reduction under hydrogen atmosphere, hydrothermal / solvothermal preparation in a closed space, and high-temperature heat treatment of metal-organic framework materials. These methods have attracted widespread research participation. Even so, most of the metal catalysts or metal catalyst preparation methods developed in academia have not yet been widely adopted for industrial applications. The main reasons include: (1) Using sodium borohydride as a strong reducing agent to directly prepare nano-metals, the strong reducing property easily leads to metal agglomeration, resulting in larger nano-metal particles; (2) Delaying the reduction process to the high-temperature heat treatment stage easily causes the metal sites to aggregate due to thermal motion when they are formed at high temperatures; (3) The preparation of nano-metals by heat-treating metal-organic framework materials is limited by the high price of metal-organic framework materials. Generally, maintaining the metal size on the surface of metal-based catalysts below 10 nanometers can adapt to most industrial catalytic processes, while also maintaining high unit mass activity. Therefore, continuing to develop new technologies for preparing nano-metal materials is crucial for promoting the development of nano-metal catalysts and their industrial applications. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a method for in-situ constructing highly dispersed nano-noble metal materials by modifying a weak reducing agent onto a carbon support. The nano-metals prepared by the method of this invention have high dispersion and a size of less than 10 nanometers.

[0004] The specific technical solution adopted in this invention is as follows:

[0005] A method for preparing nano-noble metals by directly introducing a reducing agent borane cluster into a carbon support includes the following steps:

[0006] A. Introducing the weak reducing agent of borane clusters onto the carbon support: Dissolve the borane clusters, which are cations of organic matter, in an organic solvent solution, then add the carbon support dispersed in the organic solvent, and then continuously stir and add water, a poor solvent, to precipitate the borane clusters from the surface of the carbon support and load them on the carbon support in situ. Collect the solid by filtration and dry it to introduce the weak reducing agent of borane clusters onto the carbon support.

[0007] B. Preparation of nano-metals by reducing metal ions on a carbon support containing borane clusters: The carbon support loaded with borane clusters obtained in step A is dispersed in water again, and an aqueous solution of noble metal salt is added under reflux at 120°C. The noble metal ions are continuously stirred to convert them into nano-metals on the carbon support. The solid is filtered and dried to achieve the preparation of nano-metals by reducing metal ions on a carbon support.

[0008] In step A, the anionic portion of the borane cluster can be a dodecylborane cluster anion, a decadecylborane cluster anion, or a hexahydrohexaborane cluster anion, and the cation of the borane cluster can be a tetrabutylammonium cation, a protonated triethylammonium cation, or a tetraethylammonium cation.

[0009] In step A, the carbon support may be carbon nanotubes, nitrogen-doped carbon nanotubes, nitrogen-doped hollow carbon nanotubes, graphene, graphene oxide, hollow carbon spheres, or nitrogen-doped hollow carbon spheres.

[0010] In step A, the organic solvent may be methanol, ethanol, acetonitrile, ethyl acetate, dichloromethane, or chloroform.

[0011] Step A Specific Implementation: Weigh 313.0 mg (0.5 mmol) of TBA2(B12H12) (TBA is tetrabutylammonium cation, B12H12 is dodecylborane cluster anion) and dissolve it in 50 mL of methanol. Then add the nitrogen-doped hollow carbon nanotube support dissolved in 50 mL of methanol. Subsequently, under stirring, add 500 mL of ultrapure water dropwise to the above mixture. Separate the solid by suction filtration, and wash the filter cake three times with ultrapure water to obtain nitrogen-doped hollow carbon nanotubes with a surface coated with borane cluster reducing agent.

[0012] In step B, the noble metal salt may be hexachloroplatinic acid, ammonium hexachloroplatinate, potassium hexachloroplatinate, ruthenium trichloride, sodium chloropalladium, tetrachloroauric acid, or iridium trichloride.

[0013] In step B, the continuous stirring can last for 0.5-6 hours.

[0014] The specific implementation plan for step B is as follows: Nitrogen-doped hollow carbon nanotubes coated with borane clusters are redispersed in 200 mL of ultrapure water (in a 500 mL round-bottom flask). The round-bottom flask is then transferred to an oil bath at 120°C. Under reflux, 20 mL of potassium hexachloroplatinate solution (0.05 mol) is added to the mixed dispersion. After reacting for 2 hours, the reaction solution is cooled to room temperature, and the filter cake is collected. The filter cake is washed three times each with ultrapure water and methanol, and then dried at 60°C for 12 hours to obtain nitrogen-doped hollow carbon nanotubes loaded with platinum nanoparticles.

[0015] This invention provides a method for preparing nano-noble metals by directly introducing a reducing agent, borane clusters, into a carbon support, as described above. By loading a weak reducing agent, borane clusters, onto a carbon support for in-situ reduction, supported nano-metals are prepared. The weak reducing properties of the borane clusters prevent metal aggregation at specific sites. Furthermore, the strong support provided by the carbon support also prevents large-scale aggregation of the formed metal. The nano-noble metals are dispersed within the carbon support, exhibiting good dispersion and a size less than 10 nanometers. This invention utilizes the direct introduction of borane clusters onto the surface of the carbon support to achieve in-situ reduction of noble metal ions, effectively obtaining highly dispersed, small-particle-size supported nano-noble metals. This method is simple to operate, reliable, and reproducible, facilitating large-scale preparation. Attached Figure Description

[0016] Figure 1 Aberration-corrected transmission electron microscope image of nitrogen-doped carbon nanotubes loaded with Pt;

[0017] Figure 2 Aberration-corrected transmission electron microscope image of a nitrogen-doped carbon nanotube loaded with Ru;

[0018] Figure 3 Aberration-corrected transmission electron microscope image of a nitrogen-doped hollow carbon nanotube loaded with PtRu;

[0019] Figure 4 The image shows the powder X-ray diffraction signal of mesoporous carbon spheres loaded with platinum nanoparticles. Detailed Implementation

[0020] The specific operation of the present invention is presented below with reference to the embodiments.

[0021]

Example 1

[0022] A method for preparing nano-noble metals by directly introducing a reducing agent borane cluster into a carbon support includes the following steps:

[0023] 313.0 mg (0.5 mmol) of TBA2(B12H12) (TBA is tetrabutylammonium cation, B12H12 is dodecylborane cluster anion) was weighed and dissolved in 50 mL of methanol. Then, nitrogen-doped hollow carbon nanotube support dissolved in 50 mL of methanol was added. Subsequently, 500 mL of ultrapure water was added dropwise to the mixture under stirring. The solid was separated by vacuum filtration, and the filter cake was washed three times with ultrapure water to obtain nitrogen-doped hollow carbon nanotubes with a surface coating of borane cluster reducing agent. Nitrogen-doped hollow carbon nanotubes coated with borane clusters were redispersed in 200 mL of ultrapure water (in a 500 mL round-bottom flask). The round-bottom flask was then transferred to an oil bath at 120 °C. Under reflux, 20 mL of potassium hexachloroplatinate solution (0.1 mol) was added to the mixed dispersion. After reacting for 2 hours, the reaction solution was cooled to room temperature, and the filter cake was collected by filtration. The filter cake was washed three times with ultrapure water and methanol, respectively, and then dried at 60 °C for 12 hours to obtain nitrogen-doped hollow carbon nanotubes loaded with platinum nanoparticles.

[0024] Characterization results of the product obtained in Example 1:

[0025] Figure 1 This is a spherical aberration-corrected transmission electron microscope image of the nitrogen-doped hollow carbon nanotubes loaded with Pt obtained in Example 1. The results show that the hollow carbon nanotubes have been uniformly loaded with nano-metal. In the high-angle annular dark-field imaging mode, the high-contrast white bright spots are metal sites, which are nano-Pt in Example 1. These results indicate that in-situ reduction preparation of loaded nano-Pt by loading a borane cluster as a weak reducing agent onto a carbon support can utilize the weak reducing properties of the borane cluster to prevent Pt aggregation; introducing the reducing agent onto the carbon support, with its rigid support, can also prevent the large-scale aggregation of the formed nano-Pt.

[0026]

Example 2

[0027] 313.0 mg (0.5 mmol) of TBA2(B12H12) (TBA is tetrabutylammonium cation, B12H12 is dodecylborane cluster anion) was weighed and dissolved in 50 mL of methanol. Then, nitrogen-doped hollow carbon nanotube support dissolved in 50 mL of methanol was added. Subsequently, 500 mL of ultrapure water was added dropwise to the mixture under stirring. The solid was separated by vacuum filtration, and the filter cake was washed three times with ultrapure water to obtain nitrogen-doped hollow carbon nanotubes with a surface coating of borane cluster reducing agent. Nitrogen-doped hollow carbon nanotubes coated with borane clusters were redispersed in 200 mL of ultrapure water (in a 500 mL round-bottom flask). The round-bottom flask was then transferred to an oil bath at 120 °C. Under reflux, 20 mL of ruthenium trichloride solution (0.1 mol) was added to the mixed dispersion. After reacting for 2 hours, the reaction solution was cooled to room temperature, and the filter cake was collected by filtration. The filter cake was washed three times with ultrapure water and methanol, respectively, and then dried at 60 °C for 12 hours to obtain nitrogen-doped hollow carbon nanotubes loaded with platinum nanoparticles.

[0028] Characterization results of the product obtained in Example 2:

[0029] Figure 2 This is a spherical aberration-corrected transmission electron microscope image of the nitrogen-doped hollow carbon nanotubes loaded with Ru obtained in Example 2. The results show that the hollow carbon nanotubes have been uniformly loaded with nano-metal. In the high-angle annular dark-field imaging mode, the high-contrast white bright spots are metal sites, which are nano-Ru in Example 1. These results indicate that in-situ reduction preparation of supported nano-Ru by loading a borane cluster weak reducing agent onto a carbon support can utilize the weak reducing property of the borane cluster to prevent Ru aggregation; introducing the reducing agent onto the carbon support, the rigid support of the carbon support can also prevent the large-scale aggregation of the formed nano-Ru.

[0030]

Example 3

[0031] 313.0 mg (0.5 mmol) of TBA2(B12H12) (TBA is tetrabutylammonium cation, B12H12 is dodecylborane cluster anion) was weighed and dissolved in 50 mL of methanol. Then, nitrogen-doped hollow carbon nanotube support dissolved in 50 mL of methanol was added. Subsequently, 500 mL of ultrapure water was added dropwise to the mixture under stirring. The solid was separated by suction filtration, and the filter cake was washed three times with ultrapure water to obtain nitrogen-doped hollow carbon nanotubes with a surface coating of borane cluster reducing agent. Nitrogen-doped hollow carbon nanotubes coated with borane clusters were redispersed in 200 mL of ultrapure water (in a 500 mL round-bottom flask). The round-bottom flask was then transferred to an oil bath at 120 °C. Under reflux, 20 mL of potassium hexachloroplatinate solution (0.05 mol) and 20 mL of ruthenium trichloride solution (0.05 mol) were added to the mixed dispersion. After reacting for 2 hours, the reaction solution was cooled to room temperature, and then the filter cake was collected. The filter cake was washed three times with ultrapure water and methanol, respectively, and then dried at 60 °C for 12 hours to obtain nitrogen-doped hollow carbon nanotubes loaded with platinum nanoparticles.

[0032] Characterization results of the product obtained in Example 3:

[0033] Figure 3 This is a spherical aberration-corrected transmission electron microscope image of the nitrogen-doped hollow carbon nanotubes simultaneously loaded with Pt and Ru obtained in Example 3. The results show that the hollow carbon nanotubes have been uniformly loaded with nano-metals. In high-angle annular dark-field imaging mode, the high-contrast white bright spots are metal sites; in Example 3, these metal sites are nano-PtRu alloys. This result indicates that loading borane clusters as weak reducing agents onto carbon supports can also simultaneously prepare multi-metal alloys, and the weak reducing properties of borane clusters can be used to prevent the agglomeration of nano-alloys.

[0034]

Example 4

[0035] 313.0 mg (0.5 mmol) of TBA2(B12H12) (TBA is a tetrabutylammonium cation, B12H12 is a dodecylborane cluster anion) was weighed and dissolved in 50 mL of methanol. Then, solid mesoporous carbon spheres dissolved in 50 mL of methanol were added. Subsequently, 500 mL of ultrapure water was added dropwise to the mixture under stirring. The solid was separated by suction filtration, and the filter cake was washed three times with ultrapure water to obtain solid mesoporous carbon spheres embedded with the borane cluster reducing agent. Solid mesoporous carbon spheres containing borane clusters were redispersed in 200 mL of ultrapure water (in a 500 mL round-bottom flask). The round-bottom flask was then transferred to an oil bath at 120 °C. Under reflux, 20 mL of potassium hexachloroplatinate solution (0.05 mol) and 20 mL of ruthenium trichloride solution (0.05 mol) were added to the mixed dispersion. After reacting for 2 hours, the reaction solution was cooled to room temperature, and then the filter cake was collected. The filter cake was washed three times with ultrapure water and methanol, respectively, and then dried at 60 °C for 12 hours to obtain solid mesoporous carbon spheres loaded with platinum nanoparticles.

[0036] Characterization results of the product obtained in Example 4:

[0037] Figure 4 The powder X-ray diffraction signal of the Pt-loaded mesoporous carbon spheres (MCSs) obtained in Example 4 shows the (111), (200), (220), and (311) crystal planes of Pt, indicating that Pt has been successfully loaded into the mesoporous carbon spheres.

Claims

1. A method for preparing a noble metal nanomaterial by directly introducing a reducing agent, borane cluster, into a carbon carrier, comprising the following steps: A. Introducing a borane cluster weak reducing agent into a carbon carrier: dissolving a borane cluster with a cation of an organic compound in an organic solvent solution, then adding a carbon carrier dispersed in an organic solvent, then continuously stirring and adding a poor solvent, water, to precipitate the borane cluster from the surface of the carbon carrier and load it in situ on the carbon carrier, collecting the solid by filtration, and drying to achieve the introduction of the borane cluster weak reducing agent into the carbon carrier; the cation of the borane cluster is one of a tetrabutylammonium cation, a protonated triethylammonium cation, and a tetraethylammonium cation; the anion of the borane cluster is one of a dodecahydrododecaborate anion, a decahydrodecaborate anion, and a hexahydrohexaborate anion; B. Reducing metal ions on the carbon carrier containing the borane cluster to prepare a noble metal nanomaterial: resuspending the carbon carrier loaded with the borane cluster obtained in step A in water, adding an aqueous solution of a noble metal salt at 120°C under reflux, continuously stirring to convert the noble metal ions into a noble metal nanomaterial on the carbon carrier, separating the solid by filtration, and drying the solid to achieve the reduction of metal ions on the carbon carrier to prepare a noble metal nanomaterial.

2. The method of claim 1, wherein, The organic solvent is one of methanol, ethanol, acetonitrile, ethyl acetate, dichloromethane, and chloroform.

3. The method of claim 1, wherein, The noble metal salt can be one or two of hexachloroplatinic acid, ammonium hexachloroplatinate, potassium hexachloroplatinate, ruthenium trichloride, sodium chloropalladate, tetrachloroauric acid, and iridium trichloride.

4. A hollow carbon tube material loaded with a noble metal platinum nanomaterial, a hollow carbon tube material loaded with a noble metal ruthenium nanomaterial, a hollow carbon tube material loaded with a noble metal platinum ruthenium nanomaterial, and a mesoporous carbon sphere material loaded with a noble metal platinum nanomaterial, constructed according to the method of any one of claims 1-3.

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