A sub-trillion Ru-based high-entropy alloy and a preparation method thereof

Abstract

The application discloses a sub-three-nanometer Ru-based high-entropy alloy and a preparation method thereof, and belongs to the technical field of materials. The preparation method comprises the following steps: mixing a carbon carrier dispersion liquid and metal precursors to perform a solvothermal reaction; the metal precursors comprise a ruthenium source, in addition to at least one of an iron source, a cobalt source and a nickel source, and one of a molybdenum source, a manganese source, a copper source and a tungsten source. The Ru-based high-entropy alloy prepared by the application has a sub-three-nanometer size of super-small particle size, uniform element distribution, significantly improved exposure degree of active sites and utilization rate of noble metals; the multiple metal elements form a uniform solid solution structure under the nanometer scale, effectively improving the catalytic activity and reaction stability; the high-entropy effect and the slow diffusion effect synergistically act, significantly inhibiting sintering and deactivation under high-temperature conditions; the Ru-based high-entropy alloy prepared by the application exhibits excellent catalytic performance and stability in a thermal catalytic ammonia decomposition hydrogen production reaction, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a sub-3 nanometer Ru-based high-entropy alloy and its preparation method. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, plays a vital role in alleviating the energy crisis and reducing carbon emissions. Ammonia, due to its high hydrogen content, safe storage and transportation, and well-developed infrastructure, is considered a highly promising hydrogen energy carrier. The efficient conversion of ammonia into hydrogen through thermocatalytic ammonia decomposition is one of the key technologies for realizing the conversion of ammonia energy into hydrogen energy. This reaction typically requires high temperatures, placing high demands on the activity, stability, and anti-sintering ability of the catalyst.

[0003] Currently, catalysts used for thermocatalytic ammonia decomposition mainly include noble metal and transition metal systems. Among them, ruthenium (Ru)-based catalysts are considered to be among the best performing catalysts due to their low activation energy and excellent intrinsic activity in the ammonia decomposition reaction. However, traditional Ru-based catalysts generally suffer from problems such as low utilization of noble metals and susceptibility to sintering and deactivation under high-temperature reaction conditions, which limit their industrial application.

[0004] To improve the catalytic performance and stability of Ru-based catalysts, researchers have explored alloying Ru with various transition metal elements to modulate its electronic structure and surface reaction behavior. High-entropy alloys (HEAs) are a class of material systems composed of five or more elements, typically forming a single-phase solid solution structure. The synergistic effect among multiple elements in HEAs can regulate the electronic structure and active site distribution of the catalyst over a wide range, potentially enhancing the catalytic activity of ammonia decomposition. Simultaneously, their high-entropy effect and slow diffusion effect help suppress the migration and aggregation of metal atoms, improving the structural stability and anti-sintering properties of the material under high-temperature conditions.

[0005] However, most of the reported Ru-based high-entropy alloy catalysts are bulk materials or large nanoparticles with limited specific surface area and insufficient exposure of active sites, resulting in low utilization of precious metals. Furthermore, traditional preparation methods often struggle to achieve uniform distribution of multiple metal elements at sub-nanometer or ultra-small scales, easily leading to phase separation or compositional inhomogeneity, which in turn affects the stable performance of the catalysts. In addition, some preparation methods are complex and require stringent conditions, hindering large-scale production and practical applications.

[0006] Therefore, developing a sub-3 nanoscale Ru-based high-entropy alloy catalyst with stable structure, highly uniform element distribution, controllable size, and simple preparation method to achieve its high activity and high stability in the thermocatalytic ammonia decomposition to hydrogen production reaction remains an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a sub-3 nanometer Ru-based high-entropy alloy and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a sub-3 nanometer Ru-based high-entropy alloy, comprising the following steps: mixing a carbon support dispersion and a metal precursor and carrying out a solvothermal reaction; The metal precursor includes at least a ruthenium source, and also includes at least one of an iron source, a cobalt source, and a nickel source, as well as one of a molybdenum source, a manganese source, a copper source, and a tungsten source.

[0009] Preferably, the ruthenium source includes RuCl3, the iron source includes FeCl3, the cobalt source includes CoCl2, the nickel source includes NiCl2, the molybdenum source includes NaMoO4, the manganese source includes MnCl2, the copper source includes CuCl2, and the tungsten source includes WCl6; the metal precursor is composed of nearly equimolar metal atoms, with ruthenium atoms accounting for 5-20 at% of the total metal atoms in the metal precursor, and the other metal elements having the same number of moles; the reaction system also includes a regulator, which is glutamic acid, and the ratio of its added amount to the total mass of metal atoms is fixed at 5:3; before the solvothermal reaction, the pH of the reaction system is adjusted to 13-14, preferably using an ethylene glycol solution of potassium hydroxide to adjust the pH of the system.

[0010] Preferably, the solvent of the carbon support dispersion is an organic solvent, including ethylene glycol or glyoxal; the carbon support includes graphene oxide and / or carbon nanotubes; the ratio of carbon support to organic solvent in the carbon support dispersion is 1 mg: (1.5-2) mL; the carbon support dispersion is pre-dispersed; the dispersion method includes ultrasonic treatment for 1-3 h; the total mass of each metal element to the mass of the carbon support is (1-1.3):1.

[0011] Preferably, the carbon support is graphene oxide and carbon nanotubes in a mass ratio of x:y, wherein 0 <x≤1,0<y≤3。

[0012] Preferably, the solvothermal reaction is carried out in a closed environment at a temperature of 150–180 °C for a time of 6–9 h.

[0013] Preferably, the solvothermal reaction further includes post-treatment processes such as cooling, filtration, washing and dispersing the resulting solid, and vacuum freeze-drying.

[0014] In this invention, graphene oxide and / or carbon nanotubes are used as carbon supports. Their surfaces are rich in functional groups such as hydroxyl, carboxyl, and epoxy groups, which facilitates the uniform adsorption and anchoring of multi-metal precursors. Glutamic acid acts as a complexing and structure-regulating component during the reaction, effectively inhibiting excessive migration and aggregation of metal atoms, thereby promoting the formation of a uniform solid solution structure of multiple metals at the sub-3 nanometer scale. The synergistic effect of alkaline conditions and a solvothermal environment enables the simultaneous reduction and stable loading of multi-metal components onto the carbon support surface, ultimately yielding a Ru-based high-entropy alloy with controllable size and uniform composition.

[0015] The present invention also provides a sub-3 nanometer Ru-based high-entropy alloy prepared according to the preparation method described above.

[0016] Preferably, the alloy has a single-phase solid solution structure with a particle size of less than 3 nm.

[0017] This invention also provides an application of the sub-3 nanometer Ru-based high-entropy alloy described above in the thermocatalytic ammonia decomposition for hydrogen production.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The ruthenium-based high-entropy alloy prepared by the present invention has an ultra-small particle size of sub-three nanometer scale and uniform element distribution, which significantly improves the exposure of active sites and the utilization rate of noble metals; (2) Multi-metal elements form a uniform solid solution structure at the nanoscale, which synergistically regulates the electronic structure and effectively improves catalytic activity and reaction stability; (3) The synergistic effect of high entropy effect and slow diffusion effect significantly inhibits sintering and deactivation under high temperature conditions, enabling the alloy catalyst to maintain excellent anti-sintering performance and structural stability under high temperature reaction conditions, and improving the long-term operational stability of the catalyst. (4) The preparation method of the present invention has simple steps, mild conditions, and good repeatability, making it suitable for large-scale preparation; (5) The ruthenium-based high-entropy alloy prepared by the present invention exhibits excellent catalytic performance and stability in the thermocatalytic ammonia decomposition to produce hydrogen, and has good prospects for industrial application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 In the image, a to f are TEM images of the sub-3 nanoscale Ru-based alloys prepared in Examples 1 to 5 and Comparative Example 5, respectively. Figure 2 The image shows an HR-TEM image of the sub-3 nanoscale RuNiCoFeMo high-entropy alloy obtained in Example 1. Figure 3 In the figure, Figure a is a comparison of the AOR performance of the alloy catalysts in Examples 1 to 5, and Figure b is a comparison of the AOR performance of the alloy catalysts in Comparative Examples 1 to 5. Figure 4 The figure shows the stability test results of the sub-3 nanoscale RuNiCoFeMo high-entropy alloy obtained in Example 1 after 150 h. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0022] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] The raw materials used in the following examples are all commercially available and conventional, and are not particularly limited. They will not be described again below.

[0027] One aspect of the present invention provides a method for preparing a sub-3 nanometer Ru-based high-entropy alloy, comprising the following steps: mixing a carbon support solution and a metal precursor for a solvothermal reaction; The metal precursor includes at least a ruthenium source, and further includes at least one of an iron source, a cobalt source, and a nickel source, as well as one of a molybdenum source, a manganese source, a copper source, and a tungsten source.

[0028] In some preferred embodiments, the ruthenium source is RuCl3, the iron source is FeCl3, the cobalt source is CoCl2, the nickel source is NiCl2, the molybdenum source is NaMoO4, the manganese source is MnCl2, the copper source is CuCl2, and the tungsten source is WCl6. The synergistic effect of multiple metal elements at the nanoscale helps to regulate the electronic structure of Ru, thereby improving the catalytic activity and anti-sintering properties in the ammonia decomposition reaction.

[0029] The specific content of each metal component in the catalyst is not particularly limited. In some preferred embodiments, the metal precursor is composed of nearly equimolar metal atoms, with ruthenium atoms accounting for 5-20 at% of the total metal atoms in the metal precursor, and the other metal elements having the same number of moles. The reaction system also includes a regulator, which includes glutamic acid, and the ratio of its addition to the total mass of metal atoms is fixed at 5:3. Before the solvothermal reaction, the pH of the reaction system is adjusted to 13-14, preferably using an ethylene glycol solution of potassium hydroxide to adjust the pH of the system.

[0030] Glutamic acid dissolves in solution and forms a complex system with metal ions.

[0031] In some embodiments, the solvent for the carbon support dispersion is an organic solvent.

[0032] In some preferred embodiments, the organic solvent is ethylene glycol or glyoxal; the carbon support includes graphene oxide and / or carbon nanotubes; in the carbon support dispersion, the ratio of carbon support to organic solvent is 1 mg: (1.5-2) mL; the carbon support dispersion is pre-dispersed; the total mass of each metal element to the mass of the carbon support is (1-1.3):1.

[0033] The dispersion method of the carbon support dispersion is not particularly limited, as long as the basic structure of graphene oxide and carbon nanotubes is not damaged. In some preferred embodiments, the dispersion method is ultrasonic treatment for 1 to 3 hours. Ultrasonic dispersion can form a stable and uniform dispersion system of graphene oxide and carbon nanotubes in the solvent, providing a good foundation for the subsequent in-situ loading of metal components.

[0034] The carrier is a hybrid structure composed of carbon-based materials. During the preparation process, the carrier can serve as an anchoring site for metal precursors, which is beneficial to the uniform dispersion of multiple metal elements during the reaction process and the formation of ultra-small-sized alloy particles.

[0035] The carrier may include graphene oxide and oxidized carbon nanotubes. The surfaces of graphene oxide and oxidized carbon nanotubes are rich in functional groups such as hydroxyl groups, carboxyl groups, and epoxy groups, which are beneficial to the adsorption and anchoring of metal precursors, thereby promoting the uniform dispersion of multiple metal elements on the surface of the carrier. Graphene oxide and oxidized carbon nanotubes can form a stable three-dimensional network structure through van der Waals forces, π-π stacking, and hydrogen bond interactions, providing a spatial confinement effect for the in-situ generation of metal particles, thereby effectively inhibiting the growth and aggregation of metal particles.

[0036] The mass ratio of graphene oxide to oxidized carbon nanotubes is not particularly limited. In some preferred embodiments, the carbon carrier is graphene oxide and oxidized carbon nanotubes with a mass ratio of x:y, where 0 < x ≤ 1 and 0 < y ≤ 3. In some more preferred embodiments, the mass ratio of graphene oxide to oxidized carbon nanotubes is 3:1. The carbon carrier with the above ratio is beneficial to the formation of a stable dispersion system and further improves the structural stability and electron transport ability of the catalyst.

[0037] When graphene oxide and oxidized carbon nanotubes are compounded in an appropriate ratio, the formed carrier solution has good dispersion stability and spatial confinement effect, which is beneficial to inhibiting the excessive growth of metal particles during the solvothermal reaction process, thereby obtaining Ru-based high-entropy alloy nanoparticles with a particle size less than 3 nm. When the ratio is too high, the carrier sheets are prone to stacking, which is not conducive to the uniform dispersion of metal particles; when the ratio is too low, the spatial confinement effect weakens, and metal particles are prone to aggregation, both of which will affect the structural stability and catalytic performance of the catalyst.

[0038] In some preferred embodiments, the solvothermal reaction is carried out in a closed environment, the reaction temperature is 150 - 180 °C, and the time is 6 - 9 h.

[0039] In some preferred embodiments, after the solvothermal reaction, it further includes natural cooling to room temperature to obtain a black wet sample, filtration, post-treatment of washing the obtained solid and then dispersing it, and vacuum freeze-drying.

[0040] In some preferred embodiments, the filtration method is suction filtration, and the sample obtained after suction filtration is washed repeatedly with deionized water and ethanol to remove unreacted impurities and residual solvents. The sample is kept in a wet state during the washing and suction filtration processes. Subsequently, the washed sample is dispersed in water, subjected to freezing treatment, and vacuum freeze-drying is carried out to obtain a sub-three-nanometer-scale Ru-based high-entropy alloy catalyst.

[0041] The present invention also provides a sub-3 nanometer Ru-based high-entropy alloy prepared according to the preparation method described above.

[0042] This catalyst uses carbon-based materials as a support, with multiple metal elements forming a uniform solid solution structure at the nanoscale, exhibiting ultra-small particle size, high specific surface area, and excellent thermal stability. Due to the high dispersion of the active metals, the reactant diffusion path is significantly shortened, improving the utilization efficiency of metal atoms, thereby effectively reducing the amount of precious metals used and the catalyst cost while ensuring high catalytic activity. The Ru-based high-entropy alloy catalyst demonstrates excellent catalytic performance in the thermocatalytic decomposition of ammonia, achieving a 100% conversion rate of ammonia at 500 °C, showing promising application potential.

[0043] Preferably, the alloy has a single-phase solid solution structure with a particle size of less than 3 nm.

[0044] The morphology of the catalyst is not particularly limited, as long as it has an ultra-small nanoparticle structure, such as a spherical or near-spherical structure. The average particle size of the high-entropy alloy particles is less than 3 nm. Catalysts with the above particle size range can maintain a stable structure under high-temperature reaction conditions, while providing a large number of accessible active sites, which is beneficial to improving the ammonia decomposition reaction rate.

[0045] This invention also provides an application of the sub-3 nanometer Ru-based high-entropy alloy described above in the thermocatalytic ammonia decomposition for hydrogen production.

[0046] The present invention will now be described in further detail with reference to specific embodiments.

[0047] Example 1 Preparation of sub-3 nanoscale RuNiCoFeMo high-entropy alloys (atomic ratio 1:1:1:1:1) 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform and stable carrier dispersion.

[0048] 2. After adding 50 mg of glutamic acid to the above dispersion, RuCl3, NiCl2, CoCl2, FeCl3, and Na2MoO4·2H2O were added sequentially to prepare a metal precursor solution, wherein the molar ratio of each metal element was Ru:Ni:Co:Fe:Mo = 1:1:1:1:1, and the total atomic mass of Ru, Ni, Co, Fe, and Mo was 30 mg. The mixture was further ultrasonically dispersed for 1 h to ensure thorough complexation and uniform dispersion of the metal precursor and the complexing agent. Subsequently, an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to the system under stirring to adjust the pH of the solution to 13.

[0049] 3. Transfer the above mixed solution to a 50 mL sealed reaction vessel and react at 160 °C for 7 h. After the reaction is completed, allow it to cool naturally to room temperature to obtain a black wet solid product.

[0050] 4. The obtained sample was filtered and washed three times each with ethanol and ultrapure water. The precipitate was then redispersed in water and freeze-dried under vacuum to obtain a sub-3 nanoscale RuNiCoFeMo high-entropy alloy catalyst supported on a carbon support.

[0051] Example 2 Preparation of sub-3 nanoscale RuNiCoFeMo high-entropy alloys (atomic ratio 2:1:1:1:1) 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform and stable carrier dispersion.

[0052] 2. Add 50 mg of glutamic acid to the above dispersion, followed by the sequential addition of RuCl3, NiCl2, CoCl2, FeCl3, and Na2MoO4·2H2O to prepare a metal precursor solution. The molar ratio of each metal element is Ru:Ni:Co:Fe:Mo = 2:1:1:1:1, and the total atomic mass of Ru, Ni, Co, Fe, and Mo is 30 mg. Continue ultrasonic dispersion for 1 h to ensure thorough complexation and uniform dispersion of the metal precursor and complexing agent. Subsequently, under stirring conditions, add an ethylene glycol solution containing 8 wt.% potassium hydroxide to the system to adjust the pH of the solution to 13.

[0053] 3. Transfer the above mixed solution to a 50 mL sealed reaction vessel and react at 160 °C for 7 h. After the reaction is completed, allow it to cool naturally to room temperature to obtain a black wet solid product.

[0054] 4. The obtained sample was filtered and washed three times each with ethanol and ultrapure water. The precipitate was then redispersed in water and freeze-dried under vacuum to obtain a sub-3 nanoscale RuNiCoFeMo high-entropy alloy catalyst supported on a carbon support.

[0055] Example 3 Preparation of sub-3 nanoscale RuNiCoFeW high-entropy alloys 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform and stable carrier dispersion.

[0056] 2. After adding 50 mg of glutamic acid to the above dispersion, RuCl3, NiCl2, CoCl2, FeCl3, and WCl6 were added sequentially to prepare a metal precursor solution, wherein the molar ratio of each metal element was Ru:Ni:Co:Fe:W = 1:1:1:1:1, and the total mass of metal atoms was 30 mg. The mixture was then ultrasonically dispersed for 1 h. Subsequently, an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to the system under stirring to adjust the pH of the solution to 13.

[0057] 3. Transfer the above mixed solution to a 50 mL sealed reaction vessel and react at 160 °C for 7 h. After the reaction is complete, allow it to cool naturally to room temperature.

[0058] 4. The obtained sample was filtered and washed three times each with ethanol and ultrapure water. The precipitate was then redispersed in water and freeze-dried under vacuum to obtain a sub-3 nanoscale RuNiCoFeW high-entropy alloy catalyst supported on a carbon support.

[0059] Example 4 Preparation of sub-3 nanoscale RuNiCoFeCu high-entropy alloys (atomic ratio 1:1:1:1:1) 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform and stable carrier dispersion.

[0060] 2. After adding 50 mg of glutamic acid to the above dispersion, RuCl3, NiCl2, CoCl2, FeCl3, and CuCl2 were added sequentially to prepare a metal precursor solution, wherein the molar ratio of each metal element was Ru:Ni:Co:Fe:Cu = 1:1:1:1:1, and the total mass of metal atoms was 30 mg. The mixture was further ultrasonically dispersed for 1 h to ensure thorough complexation and uniform dispersion of the metal precursor and complexing agent. Subsequently, an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to the system under stirring to adjust the pH to 13. The above mixed solution was transferred to a 50 mL sealed reactor and reacted at 160 °C for 7 h. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a black wet solid product.

[0061] 3. The obtained sample was filtered and washed three times each with ethanol and ultrapure water. The precipitate was then redispersed in water and freeze-dried under vacuum to obtain a sub-3 nanoscale RuNiCoFeCu high-entropy alloy catalyst supported on a carbon support.

[0062] Example 5 Preparation of sub-3 nanoscale RuNiCoFeMn high-entropy alloys (atomic ratio 1:1:1:1:1) 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform and stable carrier dispersion.

[0063] 2. After adding 50 mg of glutamic acid to the above dispersion, RuCl3, NiCl2, CoCl2, FeCl3, and MnCl2 were added sequentially to prepare a metal precursor solution, wherein the molar ratio of each metal element was Ru:Ni:Co:Fe:Mn = 1:1:1:1:1, and the total mass of metal atoms was 30 mg. The mixture was further ultrasonically dispersed for 1 h to ensure thorough complexation and uniform dispersion of the metal precursor and complexing agent. Subsequently, an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to the system under stirring to adjust the pH to 13. The above mixed solution was transferred to a 50 mL sealed reactor and reacted at 160 °C for 7 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature to obtain a black wet solid product.

[0064] 3. The obtained sample was filtered and washed three times each with ethanol and ultrapure water. The precipitate was then redispersed in water and freeze-dried under vacuum to obtain a sub-3 nanoscale RuNiCoFeMn high-entropy alloy catalyst supported on a carbon support.

[0065] Comparative Example 1 Similar to Example 1, except that only carbon oxide nanotubes were used as the carrier in step 1. Step 1 of this comparative example involved adding 25.6 mg of carbon oxide nanotubes to 30 mL of ethylene glycol and dispersing them ultrasonically for 2 h to form a uniform and stable carrier dispersion. Other steps were the same as in Example 1. The alloy prepared in this comparative example is designated RuNiCoFeMo-CNT.

[0066] Comparative Example 2 Similar to Example 1, except that only graphene oxide was used as the carrier in step 1. Step 1 of this comparative example involved adding 25.6 mg of graphene oxide to 30 mL of ethylene glycol and dispersing it ultrasonically for 2 h to form a uniform carrier dispersion. Other steps were the same as in Example 1. The alloy prepared in this comparative example is designated RuNiCoFeMo-GO.

[0067] Comparative Example 3 Same as Example 1, except that step 1 is as follows: 25.6 mg of the carrier (graphene oxide: carbon nanotubes = 1:1, mass ratio) is added to 30 mL of ethylene glycol and dispersed by ultrasonication for 2 h to form a uniform carrier dispersion. Other steps are the same as in Example 1. The alloy prepared in this comparative example is designated as RuNiCoFeMo-CNT / GO (1:1).

[0068] Comparative Example 4 Similar to Example 1, except that only RuCl3 was added in step 2. Step 2 of this comparative example was as follows: 50 mg of glutamic acid was added to the above dispersion, followed by the addition of RuCl3 to the dispersion to prepare a metal precursor solution, wherein the mass of Ru was 30 mg. Ultrasonic dispersion was continued for 1 h to ensure sufficient complexation and uniform dispersion of the metal precursor and the complexing agent. Subsequently, an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to the system under stirring to adjust the pH of the solution to 13. The alloy prepared in this comparative example is denoted as Ru.

[0069] Comparative Example 5 Preparation of sub-3 nanoscale RuNiCoFe alloy 1. Add 25.6 mg of carrier (graphene oxide: carbon nanotube oxide = 3:1, mass ratio) to 30 mL of ethylene glycol and disperse by ultrasonication for 2 h to form a uniform carrier dispersion.

[0070] 2. After adding 50 mg of glutamic acid to the above dispersion, RuCl3, NiCl2, CoCl2, and FeCl3 were added sequentially to prepare a metal precursor solution, wherein the molar ratio of each metal element was Ru:Ni:Co:Fe = 1:1:1:1, and the total mass of metal atoms was 30 mg. The mixture was further ultrasonically dispersed for 1 h, and then an ethylene glycol solution containing 8 wt.% potassium hydroxide was added to adjust the pH of the system to 13.

[0071] 3. Transfer the mixed solution to a sealed reaction vessel and react at 160 °C for 7 h. After the reaction is complete, cool to room temperature.

[0072] 4. The obtained sample was filtered and washed three times with ethanol and ultrapure water respectively. After freeze-drying, a sub-3 nanoscale RuNiCoFe alloy catalyst supported on a carbon support was obtained.

[0073] Effect verification Figure 1 In the figures, a to f are transmission electron microscopy (TEM) images of the sub-3 nanoscale Ru-based alloys prepared in Examples 1-5 and Comparative Example 5, respectively. Figure 1 It can be seen that the alloy nanoparticles are uniformly distributed on the carrier, and the average particle size is within 3 nanometers.

[0074] Figure 2 This is a high-magnification transmission electron microscope (HR-TEM) image of the sub-3 nanometer-scale RuNiCoFeMo high-entropy alloy obtained in Example 1. Figure 2 It can be seen that the lattice spacing of RuNiCoFeMo is measured to be about 0.198 nm, which is slightly smaller than that of metallic Ru (0.208 nm), proving the compressive strain caused by alloying with smaller transition metal atoms.

[0075] The Ru-based alloys prepared in Examples 1-5 and Comparative Examples 1-5 were used in the thermocatalytic ammonia decomposition for hydrogen production. The specific operation was as follows: the ammonia decomposition reaction was carried out in a fixed-bed quartz tubular reactor under atmospheric pressure. Before activity testing, the fresh catalyst was pretreated in a pure NH3 stream at 650°C for 3 hours, and then cooled to room temperature. Catalytic performance and stability tests were performed using 0.06 g of catalyst in a pure NH3 stream (flow rate 22 mL / min). -1 The experiments were conducted in the temperature range of 400–650 °C, corresponding to a weight hourly space velocity (WHSV) of 22,000 mL·h. -1 ·g cat -1 The results are as follows: Figure 3 Figures a and b are shown in the diagram. Figure a compares the AOR performance of the alloy catalysts in Examples 1-5, while Figure b compares the AOR performance of the alloy catalysts in Comparative Examples 1-5. Figure 3 It can be seen that the optimized RuNiCoFeMo / CG exhibits significantly enhanced activity at low temperatures, at GHSV = 22,000 mL·h -1 ·g cat -1 At 450°C, the NH3 conversion rate is approximately 80%, significantly higher than that of RuNiCoFe (52%) and Ru (25%) under the same conditions. Upon further heating, RuNiCoFeMo reaches 100% conversion at 500°C, while Ru only reaches 100% conversion at 650°C, highlighting the significantly reduced temperature requirements of multi-metal designs.

[0076] The stability of the sub-3 nanoscale RuNiCoFeMo high-entropy alloy prepared in Example 1 was tested. The same method as described above was used to conduct a thermocatalytic ammonia decomposition reaction to produce hydrogen, and its stability was tested over 150 h. The results are as follows: Figure 4 As shown, by Figure 4 It can be seen that the catalyst maintained stable NH3 conversion and no obvious deactivation within 150 hours, demonstrating good operational stability.

[0077] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a sub-3 nanometer Ru-based high-entropy alloy, characterized in that, Includes the following steps: A carbon support dispersion and a metal precursor are mixed and subjected to a solvothermal reaction. The metal precursor includes a ruthenium source, and also includes at least one of an iron source, a cobalt source, and a nickel source, as well as one of a molybdenum source, a manganese source, a copper source, and a tungsten source.

2. The preparation method according to claim 1, characterized in that, The ruthenium source includes RuCl3, the iron source includes FeCl3, the cobalt source includes CoCl2, the nickel source includes NiCl2, the molybdenum source includes NaMoO4, the manganese source includes MnCl2, the copper source includes CuCl2, and the tungsten source includes WCl6; ruthenium atoms account for 5-20 at% of the total metal atoms in the metal precursor; except for ruthenium, the other metal atoms in the metal precursor have the same molar number; the reaction system also includes a regulator, which is glutamic acid, and the ratio of its added amount to the total mass of metal atoms is 5:3; the pH of the reaction system is adjusted to 13-14 before the solvothermal reaction.

3. The preparation method according to claim 1, characterized in that, The solvent for the carbon support dispersion is an organic solvent, including ethylene glycol or glyoxal; the carbon support includes graphene oxide and / or carbon nanotubes.

4. The preparation method according to claim 3, characterized in that, The carbon support is graphene oxide and carbon nanotubes in a mass ratio of x:y, wherein 0 <x≤1,0<y≤3。 5. The preparation method according to claim 1, characterized in that, The solvothermal reaction is carried out in a closed environment at a temperature of 150–180 °C for 6–9 h.

6. The preparation method according to claim 1, characterized in that, The solvothermal reaction also includes post-treatment processes such as cooling, filtration, washing and dispersing the resulting solid, and vacuum freeze-drying.

7. A sub-3 nanometer Ru-based high-entropy alloy prepared by the preparation method according to any one of claims 1 to 6.

8. The application of a sub-trimium Ru-based high-entropy alloy according to claim 7 in thermocatalytic ammonia decomposition for hydrogen production.

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