Preparation method of cobalt-loaded halloysite nanotube catalyst based on precious metal doping

Abstract

The invention discloses a preparation method of a cobalt-loaded halloysite nanotube catalyst based on precious metal doping. The preparation method comprises the following steps: dispersing halloysite nanotubes in water to form a solution A; dissolving Cs2B12H12 in water to form a solution B; placing the solution A in a three-necked flask, and placing the solution B in a dropping funnel; stirring the three-necked flask, vacuumizing for a period of time, and slowly adding the solution B; vacuumizing, stirring and reacting, filtering and drying to obtain B12H12 / HNT; the method comprises the following steps: dispersing B12H12 / HNT in water, adding cobalt nitrate hexahydrate, carrying out reduced pressure distillation to remove a solvent, drying, and calcining to obtain a Co / B12H12 / HNT sample; the method comprises the following steps: dispersing a Co / B12H12 / HNT sample into water, adding a noble metal salt solution while stirring at normal temperature, and filtering and drying to obtain the noble metal doped cobalt loaded halloysite nanotube catalyst. The catalyst shows extremely high reaction activity and good stability in catalysis of ammonia borane hydrolysis reaction; according to the invention, the preparation process is simplified, the reaction activity and stability of the catalyst are improved, and the energy consumption and waste treatment cost in the production process are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and more specifically, relates to a method for preparing a halloysite nanotube catalyst based on noble metal-doped cobalt loading. Background Art

[0002] Pt (platinum), Pd (palladium) and other precious metal supported catalysts are widely used in technical fields such as catalytic hydrogenation and catalytic hydrogen production due to their extremely high catalytic activity. Due to the scarcity of precious metal resources, the cost of catalysts is high. In actual applications, precious metal catalysts can only be used at lower loadings. Commonly used carriers for supporting precious metals include MOFs, molecular sieves, etc. The preparation process of the carrier usually also uses expensive templates and chemical reagents, and the post-processing process is complicated. After the carrier is prepared, the precious metal nanoparticles are loaded onto the carrier by impregnation, reduction, etc., resulting in a complex catalyst preparation process that is difficult to control and has high cost. In summary, it is of great significance to find low-cost, controllable preparedness supported precious metal catalysts.

[0003] Coal, oil, and natural gas are still the main energy sources. These fossil energy sources are not sustainable and their excessive use has caused serious environmental pollution problems. The development of new clean energy sources has far-reaching significance for sustainable green development. Hydrogen (H2) has attracted much attention due to its high combustion calorific value and clean combustion products, but its storage and controlled release still face huge challenges. Ammonia borane (NH3BH3) is a common solid hydrogen storage material with a small molecular weight (30.87g·mol -1 Ammonia borane hydrolysis has attracted widespread attention due to its high hydrogen content (19.6 wt%) and room-temperature stability. It can release hydrogen through hydrolysis, alcoholysis, and pyrolysis. Ammonia borane hydrolysis, which utilizes widely available water as a reactant, is particularly valuable for hydrogen production. Precious metal catalysts (such as Pt, Pd, and Ru) exhibit high catalytic activity in ammonia borane hydrolysis, but the high cost of conventionally prepared precious metal catalysts limits their large-scale application.

[0004] Therefore, there is an urgent need for a supported noble metal catalyst with low cost and controllable preparation method. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a method for preparing a halloysite nanotube catalyst based on a noble metal-doped cobalt load, wherein the boron clusters are loaded on the halloysite nanotubes as a precursor of the carrier through the interaction between the boron clusters and the halloysite nanotubes under reduced pressure; further, the cobalt nitrate is attached to the surface of the halloysite nanotubes through interaction with cobalt nitrate, and after calcination, halloysite nanotubes loaded with cobalt oxide and boron clusters are obtained; further, noble metal salts are added to obtain halloysite nanotube catalysts loaded with cobalt oxide doped with noble metals. The present invention uses halloysite nanotubes from a wide range of sources as carriers, reducing the need for expensive templates and complex post-processing, thereby significantly reducing the preparation cost of the catalyst. In addition, the supported structure enables a strong interaction between the noble metal and the halloysite nanotubes, optimizes the electronic distribution of the active center, and improves the intrinsic activity of the catalyst. The large specific surface area and porous structure of the halloysite nanotubes are conducive to the adsorption and diffusion of reactants, further enhancing the catalytic effect, making the catalyst more economical and practical while maintaining high performance.

[0006] The present invention utilizes the special properties of halloysite nanotubes to achieve controllable preparation of a catalyst containing halloysite nanotubes doped with precious metals and loaded with cobalt at low loading, which has extremely high reactivity and good reusability in the reaction of catalyzing the hydrolysis of ammonia borane to produce hydrogen.

[0007] In order to achieve the above object, one aspect of the present invention provides a method for preparing a noble metal-doped cobalt-loaded halloysite nanotube catalyst, comprising the following steps:

[0008] S1: Preparation B 12 H 12 / HNT: Halloysite nanotubes are dispersed in water to form solution A; Cs2B 12 H 12 Dissolve in water to form solution B; place solution A in a three-necked flask and solution B in a dropping funnel; stir the three-necked flask and evacuate for a period of time, then slowly add solution B; continue evacuating and stirring to react, and after the reaction is complete, filter and dry to obtain solution B 12 H 12 / HNT;

[0009] S2: Preparation of Co / B 12 H 12 / HNT: B 12 H 12 / HNT was dispersed in water, cobalt nitrate hexahydrate was added, the solvent was removed by vacuum distillation and dried, and then calcined at 500℃ in air to obtain Co / B 12 H 12 / HNT samples;

[0010] S3: Preparation of noble metal catalyst samples: Co / B12 H 12 The HNT sample is dispersed in water, and a noble metal salt solution is added under stirring at room temperature. The stirring is continued, and the noble metal-doped cobalt-loaded halloysite nanotube catalyst is obtained by filtering and drying.

[0011] Furthermore, in step S1, the boron cluster B 12 H 12 The mass ratio of the nanostructured carbon to the halloysite nanotubes is 0.1 to 1:10.

[0012] Furthermore, in step S1, a circulating water multi-purpose vacuum pump is used for vacuuming and stirring, and the vacuum degree is 0.1 MPa; the vacuum is evacuated to 2000-4000 Pa and maintained for 0.5-1 hour; and the vacuuming and stirring reaction time is continued for 3-6 hours.

[0013] Furthermore, in step S2, the cobalt nitrate hexahydrate and the carrier precursor B 12 H 12 The mass ratio of / HNT is: (5~65):100.

[0014] Furthermore, in step S3, the precious metal and Co / B 12 H 12 The mass ratio of / HNT is (0.25~3):100.

[0015] Furthermore, in step S3, the noble metal salt is any one of potassium chloroaurate, potassium chloroplatinate, and potassium chloropalladate.

[0016] A second aspect of the present invention provides an application of a noble metal-doped cobalt-loaded halloysite nanotube catalyst in an experiment of hydrogen production by hydrolysis of ammonia borane, comprising the following steps:

[0017] Add water to the flask, then add the catalyst to the flask, and stir magnetically to fully disperse the catalyst in the water;

[0018] Ammonia borane is dissolved in water and placed in a constant pressure dropping funnel, which is placed on one of the openings of the flask for standby use, and the other opening of the flask is connected to a dropper through a catheter;

[0019] During the test, the flask was placed in a constant temperature water bath maintained at 25°C. The reaction start time and the volume of the water level drop in the burette were recorded to determine the hydrogen production rate.

[0020] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0021] (1) The present invention provides a method for preparing a halloysite nanotube catalyst based on precious metal-doped cobalt loading. By gradually loading boron clusters, cobalt oxide and precious metals, and utilizing the special properties of halloysite nanotubes, the controllable preparation of a low-load precious metal catalyst is achieved. The prepared catalyst has high activity and good reusability in the ammonia borane hydrolysis reaction to produce hydrogen.

[0022] (2) The present invention provides a method for preparing a noble metal-doped cobalt-loaded halloysite nanotube catalyst. By using halloysite nanotubes as a carrier and combining simple steps such as impregnation, stirring, drying and calcination, the catalyst preparation process is significantly simplified. Compared with the complex templates and multi-step reaction processes commonly used in the prior art, this method does not require expensive chemical reagents and tedious post-processing steps, making the entire preparation process more concise and efficient. At the same time, the operating conditions of each step are easy to control. For example, when loading noble metals, by precisely adjusting parameters such as solution concentration, stirring time and temperature, precise control of the noble metal loading amount and dispersion degree can be achieved, thereby ensuring the stability and consistency of the catalyst quality, which is conducive to large-scale production and industrial application.

[0023] (3) The present invention provides a method for preparing a halloysite nanotube catalyst based on precious metal-doped cobalt loading, which has obvious advantages in reducing costs. First, by optimizing the catalyst structure and preparation method, high catalytic activity can be achieved at a lower precious metal loading, thereby significantly reducing the amount of precious metal used and directly reducing the cost of raw materials. Secondly, halloysite nanotubes are used as carriers, which are widely available and inexpensive, and do not need to rely on expensive templates and complex preparation processes like traditional carriers, further reducing the cost of carrier preparation. In addition, the simplified preparation process reduces production links and energy consumption, reduces energy consumption and waste disposal costs in the production process, improves overall economic efficiency, and makes the catalyst more competitive in practical applications.

[0024] (4) The present invention provides a method for preparing a noble metal-doped cobalt-loaded halloysite nanotube catalyst, and the prepared noble metal-doped cobalt-loaded halloysite nanotube catalyst has excellent performance. The loaded structure enables a strong interaction between the noble metal and the halloysite nanotube, optimizes the electron distribution of the active center, and thus improves the intrinsic activity of the catalyst. At the same time, the large specific surface area and porous structure of the halloysite nanotube are conducive to the adsorption and diffusion of reactants, further enhancing the catalytic effect. In terms of stability, the synergistic effect between the carrier and the active component and the good thermal stability and chemical stability of the carrier itself make it difficult for the active component to aggregate, lose, or destroy the carrier structure during long-term use, and the catalyst has better stability and reusability. In addition, the unique structure and composition can also regulate the reaction path and the adsorption / desorption behavior of the intermediate product, improve the selectivity of the target product, reduce the occurrence of side reactions, and comprehensively improve the overall performance of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the preparation process of a noble metal-doped cobalt-loaded halloysite nanotube catalyst according to an embodiment of the present invention;

[0026] Figure 2 XRD patterns of different sample materials in a method for preparing a noble metal-doped cobalt-loaded halloysite nanotube catalyst according to an embodiment of the present invention;

[0027] Figure 3 The graph shows the change of hydrogen production over time in the experiment of hydrogen production by hydrolysis of ammonia borane using different catalysts;

[0028] Figure 4 Schematic diagram of the performance change of the catalyst in the ammonia borane hydrolysis hydrogen production reaction under different cycles. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] Real-time Example 1

[0031] like Figure 1 As shown, one aspect of the present invention provides a method for preparing a halloysite nanotube catalyst based on noble metal doped cobalt loading, comprising the following steps:

[0032] S1: Preparation B 12 H 12 / HNT(B12 H 12 / HNT means: Load has B 12 H 12 Halloysite nanotubes; B 12 H 12 is a boron cluster, HNT is the abbreviation of halloysite nanotubes): halloysite nanotubes are dispersed in water and stirred to obtain solution A; Cs2B 12 H 12 (Cs2B 12 H 12 : represents cesium dodecaborate) is dissolved in water and stirred to disperse to obtain solution B; solution A is poured into a three-necked flask, and solution B is poured into a dropping funnel; the dropping funnel piston is closed, and the dropping funnel is placed on one of the bottle openings of the three-necked flask for standby use; the three-necked flask is stirred and evacuated with a vacuum pump for a period of time, and then solution B is slowly added, and the evacuation and stirring are continued for a period of time. After the reaction is completed, solution B is filtered and dried. 12 H 12 / HNT;

[0033] S2: Preparation of Co / B 12 H 12 / HNT(Co / B 12 H 12 / HNT means: loaded with cobalt oxide (Co) and boron clusters (B 12 H 12 ) of halloysite nanotubes): a certain amount of B 12 H 12 / HNT was dispersed in water, and a certain amount of cobalt nitrate hexahydrate (chemical formula: Co(NO3)2·6H2O) was added. After stirring at room temperature, the solution was distilled under reduced pressure on a rotary evaporator to remove the solvent. After drying, the sample was taken out and calcined at 500℃ in air to obtain Co / B 12 H 12 / HNT samples;

[0034] S3: Preparation of noble metal catalyst samples: Co / B 12 H 12 The HNT sample is dispersed in water, and a noble metal salt solution is added under stirring at room temperature. The stirring is continued, and the noble metal-doped cobalt-loaded halloysite nanotube catalyst is obtained by filtering and drying.

[0035] Furthermore, in step S1, the boron cluster B 12 H 12 The mass ratio of the precipitate to the halloysite nanotubes is 0.1 to 1:10; a circulating water multi-purpose vacuum pump is used for vacuuming and stirring in step S1, and the vacuum degree is 0.1 MPa; the vacuum is evacuated to 2000 to 4000 Pa and maintained for 0.5 to 1 hour; and the vacuuming and stirring reaction time is 3 to 6 hours.

[0036] Furthermore, in step S2, the cobalt nitrate hexahydrate and the carrier precursor B 12 H 12 The mass ratio of the precious metal and Co / B in step S3 is: (5-65):100, preferably 35:100; 12 H 12 The mass ratio of HNT is (0.25-3):100, preferably 0.5:100.

[0037] Furthermore, the noble metal salt in step S3 is any one of potassium chloropalladate (chemical formula K2PdCl6), potassium chloroplatinate (chemical formula K2PtCl6), and potassium chloroaurate (chemical formula HAuCl4·4H2O); when the noble metal salt is potassium chloropalladate, step S3 is PdCo / B 12 H 12 Preparation of Co / B / HNT catalyst samples: 12 H 12 The HNT sample is dispersed in water, and potassium chloropalladate solution is added under stirring at room temperature. The stirring is continued, and the palladium-doped cobalt-loaded halloysite nanotube catalyst is obtained by filtering and drying.

[0038] Real-time Example 2

[0039] The difference from Example 1 is:

[0040] Step S1 B 12 H 12 Synthesis of HNT: 1.0 g of halloysite nanotubes were dispersed in 20 mL of water and stirred to obtain solution A. 0.1 g of Cs2B 12 H 12 Dissolve in 20 mL of water and stir to disperse to obtain solution B; pour solution A into a three-necked flask and solution B into a dropping funnel, close the dropping funnel piston, and place the dropping funnel at one of the mouths of the three-necked flask for later use; stir the three-necked flask and evacuate with a vacuum pump for 30 minutes, continue evacuating and stirring and slowly add solution B, react at room temperature for 4 hours, and then filter and dry to obtain solution B. 12 H 12 / HNT;

[0041] Co / B in step S2 12 H 12 Preparation of HNT: Take 0.20g B 12 H 12 / HNT was dispersed in 20 mL of water, 0.5813 g of cobalt nitrate hexahydrate was added, and the mixture was stirred at room temperature for 1 hour. The solvent was removed by vacuum distillation on a rotary evaporator. After drying, the sample was taken out and calcined at 500 ° C in a muffle furnace for 2 hours to obtain a sample of Co 35％ / B 12 H12 / HNT(Co 35％ / B 12 H 12 / HNT indicates that the mass percentage of cobalt in the catalyst sample is 35%);

[0042] PdCo / B in step S3 12 H 12 Preparation of HNT samples: 0.12 g Co 35％ / B 12 H 12 / HNT was dispersed in 20mL water, and 850μL of 2g / L potassium chloropalladate solution was added under stirring at room temperature. The stirring was continued for 2h, and the palladium-doped cobalt-supported halloysite nanotube catalyst was obtained by filtration and drying. The corresponding sample was Pd 0.5％ Co 35％ / B 12 H 12 / HNT(Pd 0.5％ Co 35％ / B 12 H 12 / HNT indicates that the mass percentage of palladium element in the catalyst is 0.5%, and the mass percentage of cobalt element in the catalyst is 35%).

[0043] The present invention avoids the use of expensive templates and chemical reagents by using halloysite nanotubes as carriers, thereby reducing the preparation cost of precious metal catalysts. In addition, since HNTs are widely available and inexpensive, the overall cost is further reduced. Combined with simple steps such as impregnation, stirring, drying and calcination, the complex preparation process of traditional precious metal-loaded catalysts is significantly simplified. By directly adding precious metal salt solutions to pretreated HNTs, precious metal loading is achieved without the need for multi-step impregnation and reduction processes, making the preparation process simpler and easier to control. At the same time, precise regulation of precious metal loading and dispersion is achieved, ensuring the stability and consistency of catalyst quality. In terms of cost, the amount of precious metals used is reduced by optimizing the structure and preparation method. In addition, the simplified preparation process reduces production links and energy consumption, reduces energy consumption and waste disposal costs in the production process, improves overall economic efficiency, and has less impact on the environment, which is in line with the development trend of green chemistry and makes the catalyst more competitive in practical applications.

[0044] Real-time Example 3

[0045] The difference from Example 2 is:

[0046] By adjusting the amount of cobalt nitrate hexahydrate used in step S2, the cobalt loading in the halloysite nanotube catalyst is precisely controlled, thereby obtaining a series of catalyst samples with different cobalt contents;

[0047] The specific steps are as follows:

[0048] S1: Preparation B 12 H 12 / HNT: According to the method of step S1 in Example 2, 1.0 g of halloysite nanotubes was dispersed in 20 mL of water and stirred to obtain solution A; at the same time, 0.1 g of Cs2B 12 H 12 Dissolve in 20 mL of water and stir to obtain solution B; pour solution A into a three-necked flask, pour solution B into a dropping funnel, close the dropping funnel stopcock, stir and evacuate the three-necked flask for 30 minutes, then slowly add solution B, continue to evacuate and stir at room temperature for 4 hours, and after the reaction is complete, filter and dry to obtain B12H12 / HNT;

[0049] S2: Preparation of Co / B with different cobalt contents 12 H 12 / HNT: Take 0.20g B 12 H 12 Co / BNT were dispersed in 20 mL of water, and different amounts of cobalt nitrate hexahydrate were added (according to the desired cobalt content, the amount was adjusted to achieve a cobalt loading of 5%, 15%, 25%, 45%, and 65%), and stirred at room temperature for 1 hour. Subsequently, the solution was distilled under reduced pressure on a rotary evaporator to remove the solvent. After drying, the sample was taken out and calcined at 500°C in a muffle furnace for 2 hours to obtain Co / BNT with different cobalt contents (5%, 15%, 25%, 45%, and 65%). 12 H 12 / HNT samples;

[0050] S3: Preparation of noble metal doped cobalt supported halloysite nanotube catalyst: For each different cobalt content Co / B 12 H 12 / HNT samples were dispersed in 20 mL of water according to the method of step S3 in Example 2, and 850 μL of 2 g / L potassium chloropalladate solution was added. The mixture was stirred at room temperature for 2 hours, and filtered and dried to obtain palladium-doped cobalt-supported halloysite nanotube catalysts with different cobalt contents, which were marked as Pd 0.5％ Co 5％ / B 12 H 12 / HNT;Pd 0.5％ Co 15％ / B 12 H 12 / HNT;Pd 0.5％ Co 25％ / B 12 H 12 / HNT,Pd 0.5％ Co45％ / B 12 H 12 / HNT;Pd 0.5％ Co 65％ / B 12 H 12 / HNT.

[0051] Example 3 By varying the amount of cobalt nitrate hexahydrate in step S2, catalyst samples with cobalt contents of 5%, 15%, 25%, 45%, and 65% were prepared, respectively. This method allows for systematic study of the effect of cobalt content on catalyst performance, providing an experimental basis for optimizing catalyst composition and improving catalytic efficiency.

[0052] Real-time Example 4

[0053] The difference from Example 2 is that in step S3, by adjusting the amount of potassium chloropalladate, the palladium (Pd) loading in the halloysite nanotube catalyst with a determined cobalt (Co) content is precisely controlled, thereby preparing a series of catalyst samples with different palladium contents; the specific steps are as follows:

[0054] S1: Preparation B 12 H 12 / HNT: According to the method of step S1 in Example 2, 1.0 g of halloysite nanotubes was dispersed in 20 mL of water and stirred to obtain solution A; at the same time, 0.1 g of Cs2B 12 H 12 Dissolve in 20 mL of water and stir to obtain solution B; pour solution A into a three-necked flask, pour solution B into a dropping funnel, close the dropping funnel stopcock, stir and evacuate the three-necked flask for 30 minutes, then slowly add solution B, continue to evacuate and stir at room temperature for 4 hours, and after the reaction is complete, filter and dry to obtain B12H12 / HNT;

[0055] S2: Preparation of Co / B 12 H 12 / HNT: According to the instructions of step S2 in Example 2, 0.20 g of B 12 H 12 / HNT and dispersed it in 20 ml of water. 0.5813 g of cobalt nitrate hexahydrate was added and stirred at room temperature for 1 hour. After that, the solvent was removed by rotary evaporator under reduced pressure and the obtained sample was dried. Finally, the sample was calcined at 500 ° C in a muffle furnace for 2 hours to obtain Co 35％ / B 12 H 12 / HNT samples;

[0056] S3: Preparation of catalyst samples with different palladium contents: For Co 35％ / B12 H 12 / HNT samples, the amount of potassium chloropalladate solution added was changed to achieve three different palladium loadings of 0.25%, 1%, and 3%; the specific operation was: 12 H 12 / HNT samples were dispersed in 20 ml of water, and different volumes of 2 g / L potassium chloropalladate solution were added to achieve the desired palladium content; after stirring for 2 hours at room temperature, catalyst samples with different palladium contents were obtained through filtration and drying, which were marked as Pd 0.25％ Co 35％ / B 12 H 12 / HNT、Pd 1％ Co 35％ / B 12 H 12 / HNT and Pd 3％ Co 35％ / B 12 H 12 / HNT.

[0057] Example 4 By varying the amount of potassium chloropalladate in step S3, catalyst samples with palladium contents of 0.25%, 1%, and 3% were prepared. The method of this example allows for systematic study of the effect of palladium content on catalyst performance, thereby providing important experimental data and theoretical basis for catalyst optimization.

[0058] Comparative Example

[0059] The difference from Example 3 is that: the boron cluster (B 12 H 12 ) in the catalyst, by omitting the step S1 of Example 3 and adding Cs2B 12 H 12 A series of palladium-doped cobalt-supported halloysite nanotube (HNT) catalysts free of boron clusters were prepared by the following steps:

[0060] Step S1: Prepare HNT dispersion, omitting Cs2B 12 H 12 Addition: 1.0 g of halloysite nanotubes were dispersed in 20 mL of water, stirred and dispersed to obtain solution A, and solution A was poured into a three-necked flask; the three-necked flask was stirred and vacuumed with a vacuum pump for 30 minutes, reacted for 4 hours, and then filtered and dried to obtain a uniform HNT dispersion;

[0061] Step S2: Preparation of Co / HNTs with Different Cobalt Contents: 0.20 g of dispersed HNTs were added with different amounts of cobalt nitrate hexahydrate to achieve cobalt loadings of 5%, 15%, 25%, 35%, 45%, and 65%. The mixture was stirred at room temperature for 1 hour. The solvent was removed under reduced pressure using a rotary evaporator, and the resulting sample was dried and calcined in a muffle furnace at 500°C for 2 hours to obtain Co / HNT samples with different cobalt contents (cobalt content of 5%, 15%, 25%, 35%, 45%, and 65%).

[0062] Step S3: Prepare catalyst samples with the same palladium content as in Example 2: Take 0.12 g of Co / HNT samples with different cobalt contents (cobalt content is 5%, 15%, 25%, 35%, 45%, 65%), disperse them in 20 mL of water, and add 850 μL of 2 g / L potassium chloropalladate solution under stirring at room temperature to achieve a palladium loading of 0.5%; continue stirring for 2 h, and obtain catalyst samples with different cobalt contents through filtration and drying, which are marked as: Pd 0.5％ Co 5％ / HNT;Pd 0.5％ Co 15％ / HNT;Pd 0.5％ Co 25％ / HNT,Pd 0.5％ Co 45％ / HNT;Pd 0.5％ Co 65％ / HNT.

[0063] Through the preparation of this comparative example, the influence of boron clusters in the catalyst can be evaluated, providing comparative data and reference basis for further optimizing the catalyst composition and improving the catalytic efficiency.

[0064] Further, Figure 2 The XRD diagram of different sample materials; the horizontal axis is the 2θ angle, and the vertical axis is the intensity (au); the figure contains the diffraction curves of various samples, such as HNT, B 12 H 12 / HNT、Co 35％ / HNT、Co 35％ / B 12 H 12 / HNT、Pd 0.5％ Co 35％ / HNT and Pd 0.5％ Co 35％ / B 12 H 12 / HNT, etc.; the diffraction peak position and intensity on each curve reflect the crystal structure and phase composition of the sample; from the figure, we can observe the diffraction peak characteristics of different samples, for example, the diffraction peak of HNT may correspond to its unique crystal structure, while the diffraction peak of B 12 H 12 / HNT shows a diffraction peak different from that of HNT, indicating that the introduction of boron clusters changes the crystal structure of the material. 35％ / HNT and Co 35％ / B 12 H 12 The diffraction peaks of the / HNTs exhibit characteristic peaks of cobalt oxide, while the Pd-doped samples exhibit new diffraction peaks corresponding to the crystal structure of palladium. By comparing these diffraction patterns, we can analyze the impact of different preparation methods and compositions on the crystal structure of the materials, and further understand the differences in their performance in applications such as catalysis.

[0065] pass Figure 2 This comparison can highlight the role of individual components (such as boron clusters, cobalt oxide, and precious metals) in the catalyst, as well as the synergistic effects between them. This will help further optimize the catalyst preparation process and component ratio to obtain higher-performance catalysts.

[0066] The comparative example of the present invention is obtained by omitting Cs2B 12 H 12 The addition of boron clusters to the catalyst was compared to verify the effect of boron clusters on catalyst performance. The catalyst performance in the comparative example was significantly lower than that in Example 3, indicating that the addition of boron clusters plays an important role in improving catalyst performance.

[0067] Comparing the catalyst performance of the comparative example and Example 3 demonstrates the rationality of the method for preparing the supported precious metal catalyst employed in the present invention, as well as its superiority in improving catalyst performance. This comparison demonstrates that the catalyst of Example 3 performs better, demonstrating that the technical solution of the present invention can effectively improve catalyst activity and reusability.

[0068] In the prior art, the preparation process of catalysts is complex, difficult to control, and costly. To address these problems, the present invention proposes an improved method. By using halloysite nanotubes as a carrier, the catalyst can be prepared through simple steps such as impregnation, stirring, drying, and calcination. There is no need for complex templates and chemical reagents, and there is no need for multi-step reactions and refining processes, thereby greatly simplifying the preparation process. Each step is simple to operate and the conditions are easy to control. For example, when loading precious metals, by adjusting parameters such as solution concentration, stirring time, and temperature, the loading amount and dispersion of the precious metal can be precisely controlled, which is conducive to large-scale production and quality control of the catalyst. By optimizing the catalyst structure and preparation method, high catalytic activity can be achieved at a low precious metal loading, thereby significantly reducing the amount of precious metal used and reducing the cost of the catalyst. Halloysite nanotubes are widely available and inexpensive as a carrier, and unlike traditional carriers, there is no need for expensive templates and complex preparation processes, further reducing the cost of carrier preparation. No complex post-processing, such as multi-step washing, separation, and purification, is required during the preparation process, reducing production links and costs.

[0069] The supported structure fosters strong interactions between the noble metal and the halloysite nanotubes, optimizing the electron distribution at the active centers and enhancing the intrinsic activity of the catalyst. Furthermore, the large surface area and porous structure of the halloysite nanotubes facilitate the adsorption and diffusion of reactants, further enhancing the catalytic effect. The synergistic effect between the support and the active components, along with the support's excellent thermal and chemical stability, prevents aggregation and loss of active components, or structural damage during long-term use, resulting in enhanced stability and reusability.

[0070] The preparation process is relatively simple, produces less waste and pollutants, and has a minimal impact on the environment. Furthermore, the catalyst exhibits high activity and selectivity during use, lowering reaction conditions such as temperature and pressure, reducing energy consumption and greenhouse gas emissions.

[0071] Application Examples

[0072] This application example is intended to evaluate the catalytic performance of the catalysts prepared in Examples 2 to 4 and the comparative example in the hydrolysis and hydrogen production reaction of ammonia borane (NH3BH3); the experiment was carried out under constant temperature conditions. The catalytic hydrolysis and hydrogen production experiment was carried out in a 20 mL double-necked round-bottom flask. The specific steps are as follows:

[0073] Preparation of catalyst: Accurately weigh 53 mg of the prepared catalyst and add it to a 20 ml double-necked round-bottom flask.

[0074] Setting up the reaction system: Add 8 mL of water to the flask and stir magnetically to fully disperse the catalyst in the water;

[0075] Preparation of ammonia borane solution: Dissolve 0.5 mmol of ammonia borane in 2 mL of water. Place the solution into a constant pressure dropping funnel. Attach the constant pressure dropping funnel to one of the necks of the flask so that the ammonia borane solution can be slowly added during the experiment.

[0076] Preparation of gas collection system: The other port of the flask is connected to a burette through a tube to collect hydrogen released during the reaction;

[0077] Experimental Procedure: Place the flask in a water bath maintained at 25°C and start the timer. Slowly add the ammonia borane solution dropwise to the flask under magnetic stirring to initiate the ammonia borane hydrolysis reaction.

[0078] Determination of hydrogen production rate: Record the reaction start time and monitor the volume of the water level drop in the dropper to calculate the hydrogen production rate.

[0079] like Figure 3 As shown in the figure, the curve of hydrogen production over time of different catalysts in the experiment of hydrogen production by hydrolysis of ammonia borane is shown; the horizontal axis is the reaction time (seconds) and the vertical axis is the volume of hydrogen (ml); each curve in the figure represents a catalyst with a specific composition (such as Pd 0.5％ Co 5％ / B 12 H 12 / HNT;Pd 0.5％ Co 15％ / B 12 H 12 / HNT;Pd 0.5％ Co 25％ / B 12 H 12 / HNT,Pd 0.5％ Co 35％ / B 12 H 12 / HNT,Pd 0.5％ Co 45％ / B 12 H 12 / HNT;Pd 0.5％ Co 65％ / B 12 H 12 / HNT, etc.), showing the hydrogen production corresponding to different time points during the reaction process. The slope of the curve reflects the hydrogen production rate. The larger the slope, the higher the hydrogen production rate. As can be seen from the figure, all catalysts can effectively promote the hydrolysis of ammonia borane to produce hydrogen, and the hydrogen production rate is faster in the initial stage of the reaction, and then gradually stabilizes. There are differences in the amount and rate of hydrogen production of different catalysts, which are related to factors such as the loading ratio of cobalt and palladium in the catalyst, the properties of the carrier, and the dispersion of the active components. By comparing different curves, the performance of various catalysts can be evaluated, providing an experimental basis for the optimization and selection of catalysts.

[0080] like Figure 4 As shown, the performance of the catalyst in the ammonia borane hydrolysis hydrogen production reaction under different numbers of cycles is demonstrated. The horizontal axis is the reaction time (seconds) and the vertical axis is the hydrogen volume (ml). Each curve in the figure represents a specific number of cycles (from 1st to 10th), showing the hydrogen production corresponding to different time points during the reaction. The slope of the curve reflects the hydrogen production rate. The larger the slope, the higher the hydrogen production rate. As can be seen from the figure, the catalyst exhibits stable catalytic performance in multiple cycles, and the hydrogen production increases linearly with time, indicating that the catalyst has good stability and reusability. In the early stage of the reaction, the hydrogen production rate is relatively fast and then remains stable. The difference in hydrogen production and rate under different numbers of cycles is small, indicating that the catalyst can still maintain high activity after multiple uses. By comparing the curves of different numbers of cycles, the stability and life of the catalyst can be evaluated, providing a basis for the practical application and further optimization of the catalyst.

[0081] Application examples show that when the cobalt oxide-doped halloysite nanotube catalyst is used as a catalyst for hydrogen production from the hydrolysis of ammonia borane, the strong metallic interaction between the cobalt element and the precious metal element improves the electron distribution of the active center and effectively enhances the catalytic activity. When catalyzing the hydrolysis of ammonia borane to produce hydrogen at room temperature, the conversion frequency (TOF) is as high as 360 mol·H2(molPd). -1 min -1 The catalyst has no significant decrease in activity even after being reused 10 times. The catalyst prepared by the present invention exhibits extremely high reaction activity and good stability in catalyzing the hydrolysis reaction of ammonia borane.

[0082] Through the experimental design of this application example, the activity and efficiency of different catalysts in the ammonia borane hydrolysis hydrogen production reaction can be systematically compared, thereby verifying the performance of the prepared catalyst and providing an experimental basis for further catalyst optimization.

[0083] The present invention simplifies the preparation process, improves the reaction activity and stability of the catalyst, reduces energy consumption and waste disposal costs during the production process, and provides an effective approach for the preparation and application of low-content noble metal nanocatalysts.

[0084] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements 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 a noble metal-doped cobalt-loaded halloysite nanotube catalyst, characterized in that: The steps include: S1: Preparation B 12 H 12 / HNT: Halloysite nanotubes are dispersed in water to form solution A; Cs2B 12 H 12 Dissolve in water to form solution B; place solution A in a three-necked flask and solution B in a dropping funnel; stir the three-necked flask and evacuate for a period of time, then slowly add solution B; continue evacuating and stirring to react, and after the reaction is complete, filter and dry to obtain solution B 12 H 12 / HNT; S2: Preparation of Co / B 12 H 12 / HNT: B 12 H 12 / HNT was dispersed in water, cobalt nitrate hexahydrate was added, the solvent was removed by vacuum distillation and dried, and then calcined at 500℃ in air to obtain Co / B 12 H 12 / HNT samples; S3: Preparation of noble metal catalyst samples: Co / B 12 H 12 The HNT sample is dispersed in water, and a noble metal salt solution is added under stirring at room temperature. The stirring is continued, and the noble metal-doped cobalt-loaded halloysite nanotube catalyst is obtained by filtering and drying.

2. The noble metal-doped cobalt-supported halloysite nanotube catalyst according to claim 1, characterized in that: Boron cluster B in step S1 12 H 12 The mass ratio of the nanostructured carbon to the halloysite nanotubes is 0.1 to 1:

10.

3. The noble metal-doped cobalt-supported halloysite nanotube catalyst according to claim 2, characterized in that: In step S1, a circulating water multi-purpose vacuum pump is used for vacuuming and stirring, and the vacuum degree is 0.1 MPa; the vacuum is evacuated to 2000-4000 Pa and maintained for 0.5-1 hour; and the vacuuming and stirring reaction time is continued for 3-6 hours.

4. The noble metal-doped cobalt-supported halloysite nanotube catalyst according to claim 3, characterized in that: In step S2, cobalt nitrate hexahydrate and carrier precursor B 12 H 12 The mass ratio of / HNT is: (5~65):

100.

5. The noble metal-doped cobalt-supported halloysite nanotube catalyst according to claim 4, characterized in that: In step S3, precious metals and CoB 12 H 12 The mass ratio of / HNT is (0.25~3):

100.

6. A noble metal-doped cobalt-supported halloysite nanotube catalyst according to any one of claims 1 to 5, characterized in that: In step S3, the noble metal salt is any one of potassium chloroaurate, potassium chloroplatinate, and potassium chloropalladate.

7. Use of the noble metal-doped cobalt-supported halloysite nanotube catalyst according to any one of claims 1 to 6 in ammonia borane hydrolysis hydrogen production experiment, characterized in that: The steps include: Add water to the flask, then add the catalyst to the flask, and stir magnetically to fully disperse the catalyst in the water; Ammonia borane is dissolved in water and placed in a constant pressure dropping funnel, which is placed on one of the openings of the flask for standby use, and the other opening of the flask is connected to a dropper through a catheter; During the test, the flask was placed in a constant temperature water bath maintained at 25°C. The reaction start time and the volume of the water level drop in the burette were recorded to determine the hydrogen production rate.

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