Method for constructing high-dispersion high-entropy metal oxide nano-particles by using ligand synergistic anchoring and application of high-dispersion high-entropy metal oxide nano-particles

Abstract

The invention discloses a method for constructing high-dispersion high-entropy metal oxide nano-particles by using ligand synergistic anchoring and application of the high-dispersion high-entropy metal oxide nano-particles, hexagonal boron nitride is used as a carrier, stripping is realized through thermal expansion-liquid nitrogen quenching circulation, nitrogen defects are introduced, a synergistic coordination field is formed by using organic polydentate ligands and defect sites, and the high-dispersion high-entropy metal oxide nano-particles are obtained. The preparation method comprises the following steps of: performing synchronous anchoring and uniform dispersion on a plurality of metal ions by virtue of a functional carrier, performing mixing-ball milling activation treatment on a plurality of metal salts and the functional carrier, and combining multi-stage programmed pyrolysis of low-temperature confinement nucleation-high-temperature interface bonding-structure stabilization, so as to form the high-entropy metal oxide nano-particles with the particle size of about 10-100nm under the regulation and control of a dynamic atmosphere. According to the method, metal precursor migration, particle sintering and element segregation can be effectively inhibited, and high-dispersion loading and stable interface construction of the high-entropy metal oxide are achieved. The obtained catalytic material shows relatively high conversion rate and ammonia selectivity in a reaction for preparing ammonia by electro-catalysis nitrate reduction, and is suitable for preparing a high-performance electro-catalyst.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and electrocatalysis technology, specifically relating to a method for preparing highly dispersed high-entropy metal oxide nanoparticles and their application in the electrocatalytic reduction of nitrate to ammonia. Background Technology

[0002] High-entropy metal oxides are a class of multi-element oxide materials formed by the solid solution of five or more metals in near equimolar ratios. They exhibit significant advantages in catalytic reactions due to their tunable active site structure and remarkable multi-element synergistic effects. However, the high-temperature crystallization process commonly relied upon in existing high-entropy metal oxide preparation processes easily leads to sintering and agglomeration of nanoparticles, directly causing a sharp reduction in the material's specific surface area and a significant decrease in mass transfer efficiency. This, in turn, results in a reduction in the number of active sites and a decline in intrinsic catalytic performance, becoming a core bottleneck restricting their industrial application.

[0003] To address the aforementioned particle agglomeration problem, existing research has explored techniques for loading high-entropy metal oxides onto the surface of two-dimensional materials. Hexagonal boron nitride (h-BN) is considered a highly promising support material due to its excellent thermal stability; however, its extremely strong chemical inertness and lack of tunable chemical anchoring sites hinder the uniform nucleation and stable fixation of metal precursors on its surface, severely impacting the preparation efficiency of supported catalysts. Existing patent literature has proposed solutions for optimizing carrier modification and loading technologies, but all have significant technical shortcomings: CN201610454689.4 discloses a technique for preparing defective h-BN nanosheets using liquid nitrogen physical exfoliation. While this method can introduce some defect sites, the defect distribution is highly random, resulting in limited anchoring ability and poor uniformity, failing to meet the requirements for precise loading of multi-metal ions; CN202410472173.7 uses carbon materials as a carrier, but due to the uncontrollability of the high-temperature pyrolysis process, high-entropy metal oxides are still difficult to effectively disperse; CN202310094201.1 discloses a three-dimensional porous carbon structure carrier, but due to the tendency for structural collapse under high-temperature conditions and the weak interaction force between the carrier and metal components, it is still unable to effectively suppress the grain growth phenomenon of high-entropy structures. In summary, the existing technology system lacks an integrated technical solution that can simultaneously achieve uniform chemical anchoring sites and achieve simultaneous confined nucleation and crystallization of multi-metal ions through precise thermal process control.

[0004] Meanwhile, the electrocatalytic nitrate reduction reaction (NO3RR) produces ammonia (NO3). -→NH3, as an emerging technology with dual value in water pollution control and clean energy conversion, has become a research hotspot in the field of catalysis in recent years. The unique multi-metal synergistic effect and flexible tunable metal valence states of high-entropy metal oxides can provide abundant electronic regulation pathways and highly selective adsorption sites for NO3RR, making them ideal catalytic materials for achieving high activity and high selectivity in this reaction. However, NO3RR places higher demands on the dispersion, stability, and metal valence state regulation of active sites, further highlighting the importance of constructing highly dispersed, interfacially stable high-entropy metal oxide systems. Summary of the Invention

[0005] Based on the aforementioned technological status and application needs, the purpose of this application is to develop a novel method for supporting high-entropy metal oxides. By constructing high-density stable chemical anchoring sites on the support surface and combining precise thermal process control, in-situ nucleation of metal components and inhibition of particle migration are achieved. Ultimately, this results in high dispersibility and long-term structural stability of high-entropy metal oxide nanoparticles. This addresses the problems of existing high-entropy metal oxides, such as the difficulty in uniformly anchoring metal precursors, easy migration and aggregation of particles during high-temperature heat treatment, and structural instability caused by easy segregation of metal elements, as well as their insufficient activity and selectivity in electrocatalytic nitrate reduction reactions. The resulting highly dispersed high-entropy metal oxide nanoparticles are particularly suitable as high-performance catalysts for the electrocatalytic reduction of nitrate to ammonia.

[0006] To achieve the above objectives, this invention proposes a method for preparing high-entropy metal oxide nanoparticles based on "organic ligand synergistic anchoring + multi-stage programmed pyrolysis," comprising the following steps: (1) Preparation of functionalized hexagonal boron nitride support: Commercial hexagonal boron nitride is subjected to thermal expansion-liquid nitrogen rapid cooling cycle treatment, and the layered structure is peeled off by thermal expansion and contraction stress to obtain hexagonal boron nitride nanosheets; The obtained nanosheets are surface modified with organic ligands in a solvent through hydrothermal or solvothermal reaction to form a functionalized support with a synergistic coordination field and simultaneously anchoring multiple metal ions, denoted as Dh-BNNs; The synergistic coordination field refers to the multidentate coordination environment formed by the functional groups of nitrogen defects and organic ligands to achieve simultaneous confined nucleation and crystallization of multiple metal ions; (2) Precursor mixing and coordination dispersion: Five metal salts in equimolar ratios were mixed with the functionalized carrier prepared in step (1) in a solvent and then dried; (3) Mechanical activation treatment: The mixture from step (2) is placed in a ball mill jar and ball milled; (4) Programmed pyrolysis and interface shaping: A multi-stage programmed heating and dynamic atmosphere control pyrolysis process is adopted to complete the crystallization and interface stabilization of high-entropy metal oxides.

[0007] Preferably, the thermal expansion-liquid nitrogen rapid cooling cycle treatment in step (1) includes: preheating hexagonal boron nitride at 400-500℃ for 10-30 min, and then transferring it to a liquid nitrogen environment for rapid freezing within 10 s, with a liquid nitrogen immersion time of 1-10 min; this process is repeated 3-10 times.

[0008] Preferably, in step (1), the multidentate organic ligand includes one of citric acid, oxalic acid, ethylenediaminetetraacetic acid or its derivatives; the solvent is deionized water or ethanol.

[0009] Preferably, the hydrothermal or solvothermal reaction in step (1) is carried out at a temperature of 120-180°C for 12-24 hours.

[0010] Preferably, the mass ratio of the organic ligand to the hexagonal boron nitride nanosheets in step (1) is 1:10-1:30.

[0011] Preferably, the mass ratio of the total mass of the organic ligand and hexagonal boron nitride nanosheets to the solvent in step (1) is 1:10-1:50.

[0012] Preferably, the metal salt in step (2) is a nitrate or an acetate.

[0013] Preferably, the metal element in step (2) includes Ru and / or Ga, which are metals with multiple valence states.

[0014] Preferably, the solvent in step (2) is ethanol.

[0015] Preferably, the mass ratio of the total mass of the metal salt to the mass of the functionalized boron nitride support in step (2) is 1:5-1:10.

[0016] Preferably, the mass ratio of the total mass of the metal salt and the functionalized boron nitride support to the solvent in step (2) is 1:10-1:50.

[0017] Preferably, in step (3), the ball milling uses zirconia grinding beads with a diameter of 3-5 mm, the mass ratio of the mixture to the grinding beads is 1:5-1:10, the ball milling speed is 200-400 rpm, and the ball milling time is 2-4 h.

[0018] Preferably, the programmed pyrolysis and interface forming steps in step (4) include: the first stage of low-temperature pre-decomposition and confined nucleation: under N2 atmosphere, the temperature is increased to 400-600℃ at a rate of 1-5℃ / min and held for 0.5-2h, so that the precursor slowly decomposes and initially forms high-entropy oxide crystal nuclei in the confined space on the surface of the carrier; the second stage of high-temperature crystallization and interface bonding: the atmosphere is switched to a weakly reducing atmosphere (H2 / Ar with a volume fraction of 2%-10%), and the temperature is increased to 800-1000℃ at a rate of 1-5℃ / min and held for 0.5-1h to drive grain growth; the third stage of structure stabilization: the temperature is switched back to N2 and held at the target temperature for another 0.5-2h to complete the crystal structure stabilization.

[0019] A highly dispersed high-entropy metal oxide nanoparticle composite material is prepared by any of the methods described above; wherein the high-entropy metal oxide nanoparticles are uniformly loaded on a functionalized hexagonal boron nitride nanosheet carrier, and the particle size of the nanoparticles is 10-100 nm.

[0020] The application of a highly dispersed, high-entropy metal oxide nanoparticle composite material as a catalyst in the electrocatalytic reduction reaction of nitrate to prepare ammonia, wherein the electrocatalytic nitrate reduction reaction is carried out in an H-type electrolytic cell, the electrolyte is a Na2SO4 solution containing nitrate, and the working potential is -0.8 V (vs. RHE).

[0021] The beneficial effects of this invention are: 1. By using the "liquid nitrogen stripping-ligand anchoring" coupling strategy, high-density and uniformly distributed nitrogen defects are directionally constructed on the surface of boron nitride, and organic ligands are used to form a synergistic coordination field. This coordination field can simultaneously coordinate with multiple metal ions, solving the problems of uneven dispersion and weak anchoring of multi-component metal precursors on the support surface. 2. Unlike traditional single pyrolysis, this invention adopts a multi-stage pyrolysis strategy of "low-temperature confined nucleation-high-temperature interface bonding". Combined with dynamic atmosphere control, the pyrolysis process is transformed from passive sintering to active interface construction, which inhibits sintering and phase separation and induces the formation of a stable interface structure during the pyrolysis process, effectively inhibiting the migration and aggregation of nanoparticles. 3. Excellent product structure and catalytic performance: In the sample prepared by this method, the high-entropy metal oxide nanoparticles are uniformly dispersed on the support, mainly concentrated in the range of 10-100 nm. When the catalyst prepared by this invention is used for electrocatalytic nitrate reduction reaction, the high dispersion of the high-entropy oxide nanoparticles, the synergistic effect of multiple metal active sites, and the stable support interface are conducive to improving the nitrate conversion rate and ammonia yield. Attached Figure Description

[0022] Figure 1This is a high-magnification transmission electron microscope image of the sample prepared in Example 1.

[0023] Figure 2 XPS comparison image of the sample prepared in Example 1 and untreated commercial-grade boron nitride.

[0024] Figure 3 This is a high-magnification transmission electron microscope image of the sample prepared in Example 2.

[0025] Figure 4 This is a high-magnification transmission electron microscope image of the sample prepared for Comparative Example 1.

[0026] Figure 5 This is a high-magnification transmission electron microscope image of the sample prepared in Comparative Example 2.

[0027] Figure 6 This is a high-magnification transmission electron microscope image of the sample prepared in Comparative Example 3.

[0028] Figure 7 The graph shows a comparison of the NO3RR performance of the samples prepared in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0029] The present invention will be further illustrated by specific embodiments below, but the scope of protection of the present invention is not limited thereto.

[0030] Example 1: Preparation of FeCoNiCuRu-Ox / Dh-BNNs catalyst (1) Commercial grade hexagonal boron nitride powder was placed in a porcelain crucible and heated in a muffle furnace at 400℃ for 20 min. Then, it was transferred to a liquid nitrogen environment for rapid freezing within 10 s and the liquid nitrogen immersion time was 1 min. The huge internal stress generated by the rapid temperature difference caused the h-BN sheets to peel off. This process was repeated 10 times to obtain hexagonal boron nitride nanosheets. Subsequently, citric acid and the peeled boron nitride nanosheets were mixed in ethanol at a mass ratio of 1:10, wherein the total mass of citric acid and the peeled boron nitride nanosheets was in a mass ratio of 1:10 to that of ethanol. The mixture was subjected to hydrothermal reaction at 160℃ for 12 h. After the reaction was completed, the mixture was washed 3 times each with ethanol and deionized water, centrifuged, and dried at 80℃ for 12 h to obtain functionalized boron nitride carrier Dh-BNNs. (2) Weigh out equimolar amounts of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate and ruthenium nitrate, so that the total mass of the five metal salts is in a mass ratio of 1:5 to the mass of the functionalized boron nitride carrier. Weigh out the total mass of both, add ethanol in a ratio of 1:10, stir for 2 hours, and then dry at 80°C. (3) Use 5mm zirconia grinding balls, wherein the mass ratio of the mixture to the grinding balls is 1:10, and grind at 300 rpm for 4 hours in a grinding jar; (4) Programmed pyrolysis: The ball-milled precursor powder was placed in a tube furnace for staged heat treatment; the first stage: under N2 atmosphere, the temperature was increased to 500℃ at a rate of 3℃ / min and held for 1h; the second stage: the atmosphere was switched to H2 / Ar with a volume fraction of 2%, the temperature was increased to 900℃ at a rate of 1℃ / min and held for 0.5h; the third stage: the atmosphere was switched back to pure N2 and held at 900℃ for 1h. Finally, the furnace was naturally cooled to room temperature to obtain the final FeCoNiCuRu-Ox / Dh-BNNs catalyst.

[0031] The FeCoNiCuRu-Ox / Dh-BNNs catalyst prepared in this embodiment was used as the working electrode, and the test was carried out in an H-type electrolytic cell with a working electrode area of ​​1 cm². 2 Electrocatalytic nitrate reduction was performed using a 0.1 M Na₂SO₄ + 0.1 M KNO₃ electrolyte (pH=7) at a temperature of 25±1°C and a reversible hydrogen electrode (RHE) as the reference electrode. At a potential of -0.8 V (vs. RHE), the nitrate conversion rate reached 98%, and the ammonia selectivity was 95%.

[0032] Figure 1 This is a high-magnification transmission electron microscope image of the catalyst obtained in Example 1. As shown in the figure, the high-entropy metal oxide nanoparticles are highly dispersed on the layered boron nitride support, with a particle size of approximately 10-100 nm, effectively avoiding high-temperature sintering. Figure 2 The XPS spectra (B 1s) of the Dh-BNNs prepared in Example 1 are compared with those of untreated commercial h-BN. XPS analysis revealed that the functionalized hexagonal boron nitride exhibited a distinct boron-high-entropy metal oxide bonding characteristic peak at a binding energy of approximately 192.6 eV, demonstrating that nitrogen defects were successfully introduced using the treatment method of this invention. These defect sites, together with the organic ligands, form a synergistic coordination field that promotes the interaction with the metal precursor and achieves highly dispersed loading.

[0033] Example 2: Preparation of GaCoNiCuRu-Ox / Dh-BNNs catalyst (1) Commercial grade hexagonal boron nitride powder was placed in a porcelain crucible and heated in a muffle furnace at 500°C for 10 min. Then, it was transferred to a liquid nitrogen environment for rapid freezing within 10 s and the liquid nitrogen immersion time was 10 min. The huge internal stress generated by the rapid temperature difference caused the h-BN sheets to peel off. This process was repeated 3 times to obtain hexagonal boron nitride nanosheets. Subsequently, oxalic acid and the obtained boron nitride nanosheets were mixed in deionized water at a mass ratio of 1:30, wherein the total mass of oxalic acid and the peeled boron nitride nanosheets was in a mass ratio of 1:50 to the deionized water. The mixture was placed in a reaction vessel and subjected to hydrothermal reaction at 180°C for 20 h. After the reaction was completed, the mixture was washed 3 times each with ethanol and deionized water, centrifuged, and dried at 80°C for 12 h to obtain the functionalized carrier Dh-BNNs. (2) Weigh out equimolar amounts of gallium acetate, cobalt acetate, nickel acetate, copper acetate and ruthenium nitrate respectively, so that the total mass of the five metal salts is 1:10 with the mass ratio of the functionalized boron nitride carrier. Weigh out the total mass of the two, add ethanol at a ratio of 1:50, stir for 2 hours and dry at 80°C. (3) Use 3mm zirconia grinding balls, wherein the mass ratio of the mixture to the grinding balls is 1:6, and grind in a grinding jar at 350 rpm for 4 hours; (4) Programmed pyrolysis: The ball-milled precursor was subjected to staged heat treatment in a tube furnace; the first stage: under N2 atmosphere, the temperature was increased to 400℃ at 1℃ / min and held for 2h; the second stage: the temperature was switched to 5% H2 / Ar by volume, and the temperature was increased to 800℃ at 2℃ / min and held for 1h; the third stage: the temperature was switched back to N2 and held at 800℃ for 2h. After natural cooling, the final catalyst was obtained, which is the final GaCoNiCuRu-Ox / Dh-BNNs catalyst.

[0034] Figure 3 The image shows a high-magnification transmission image of the sample obtained in Example 2. As shown in the figure, the high-entropy metal oxide nanoparticles are in a dispersed state and do not exhibit agglomeration or sintering.

[0035] Example 3: Preparation of GaCoNiCuRu-Ox / Dh-BNNs catalyst (1) Commercial grade hexagonal boron nitride powder was placed in a porcelain crucible and heated in a muffle furnace at 450°C for 30 min. Then, it was transferred to a liquid nitrogen environment for rapid freezing within 10 s. The liquid nitrogen immersion time was 5 min. The peeling process was repeated 6 times. Subsequently, ethylenediaminetetraacetic acid and the obtained hexagonal boron nitride nanosheets were mixed in ethanol at a mass ratio of 1:15. The mass ratio of the total mass of ethylenediaminetetraacetic acid and the peeled boron nitride nanosheets to the mass of ethanol was 1:25. The mixture was subjected to a solvothermal reaction at 120°C for 24 h. After the reaction was completed, the mixture was washed 3 times each with ethanol and deionized water. After centrifugation, it was dried at 80°C for 12 h to obtain functionalized boron nitride carrier Dh-BNNs. (2) Weigh out equimolar amounts of ruthenium acetate, cobalt nitrate, nickel acetate, copper nitrate and gallium acetate respectively, so that the total mass of the five metal salts is in the mass ratio of the functionalized boron nitride carrier to 1:8. Weigh out the total mass of the two, add ethanol in a ratio of 1:30, stir for 2 hours, and then dry at 80°C. (3) Use 5mm grinding balls to ball mill the mixture. The mass ratio of the mixture to the grinding balls is 1:8. Ball mill at 350 rpm for 2 hours. (4) Programmed pyrolysis: The ball-milled precursor was heat-treated in stages in a tube furnace; the first stage: under N2 atmosphere, the temperature was increased to 600℃ at 5℃ / min and held for 0.5h; the second stage: the temperature was switched to H2 / Ar with a volume fraction of 10% and increased to 1000℃ at 5℃ / min and held for 1h; the third stage: the temperature was switched back to N2 and held at 1000℃ for 0.5h. After natural cooling, the final GaCoNiCuRu-Ox / Dh-BNNs catalyst was obtained.

[0036] Comparative Example 1: Preparation of FeCoNiCuRu-Ox High-Entropy Metal Oxides Without adding any carrier, only five metal salts (ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and ruthenium nitrate) in equal molar amounts from Example 1 were mixed and ball-milled under the same conditions. Then, they were pyrolyzed under the same heating program and atmosphere as in Example 1 to obtain a blocky high-entropy metal oxide FeCoNiCuRu-Ox. The same electrocatalytic tests were performed on this high-entropy metal oxide. Due to its small specific surface area and few active sites, its nitrate conversion rate and ammonia selectivity were lower than those in Example 1.

[0037] Figure 4 The image shows a high-magnification transmission image of the bulk high-entropy metal oxide FeCoNiCuRu-Ox obtained in Comparative Example 1. The sample exhibits a bulk morphology, indicating that it underwent significant sintering at high temperatures.

[0038] Comparative Example 2: FeCoNiCuRu-Ox / h-BN catalyst supported on untreated commercial-grade h-BN The preparation steps are the same as in Example 1, but the hot and cold cycle exfoliation and ligand modification process in step (1) are omitted, and the raw commercial-grade h-BN powder without any treatment is used directly as the carrier in step (2).

[0039] Figure 5 The image shows a high-magnification transmission image of the sample obtained in Comparative Example 2. As can be seen from the image, due to the smooth surface and high chemical inertness of the untreated commercial-grade h-BN, there is a lack of sufficient anchoring points, and the high-entropy metal oxide precursor cannot be effectively loaded, resulting in severe agglomeration of metal oxides in the product and poor dispersibility.

[0040] Comparative Example 3: FeCoNiCuRu-Ox / h-BNNs catalyst with liquid nitrogen-exfoliated h-BN as the direct support The preparation steps are the same as in Example 1, but the organic ligand modification step in step (1) is omitted. Only hexagonal boron nitride nanosheets that have been exfoliated by liquid nitrogen but have not undergone hydrothermal reaction with oxalic acid are used as the carrier. In addition, the direct pyrolysis method is used, and the nanosheets are calcined at 900°C in a N2 atmosphere for 2 hours with a heating rate of 5°C / min.

[0041] Figure 6 The image shows a high-magnification transmission image of the sample obtained in Comparative Example 3. As can be seen from the image, the high-entropy metal oxides are partially dispersed on the surface of the exfoliated h-BN nanosheets, but there are still a large number of obvious aggregates. This indicates that relying solely on the physical defects generated by liquid nitrogen exfoliation is insufficient in terms of anchoring ability and uniformity, and cannot achieve the high dispersion loading effect described in this invention. This demonstrates the necessity and synergistic effect of the ligand anchoring step.

[0042] Figure 7 The figure shows a comparison of the NO3RR performance of the samples prepared in Example 1 and Comparative Examples 1-3. Electrocatalytic tests show that, due to the severe agglomeration of metal oxides and poor accessibility of active sites, the activity of nitrate reduction and ammonia selectivity of the samples are much lower than those of the catalysts prepared by the method of this invention.

Claims

1. A method for constructing highly dispersed and high-entropy metal oxide nanoparticles using ligand-assisted anchoring, characterized in that, The method comprises the following steps: Preparation of a functionalized hexagonal boron nitride carrier: commercially available hexagonal boron nitride is subjected to a thermal expansion-liquid nitrogen quenching cycle treatment, and the layered structure is exfoliated by thermal expansion and cold shrinkage stress to obtain hexagonal boron nitride nanosheets; then the prepared nanosheets are surface-modified with an organic ligand by a hydrothermal or solvothermal reaction in a solvent to form a functionalized carrier with a synergistic coordination field and simultaneously anchoring multiple metal ions, denoted as D-h-BNNs; the synergistic coordination field refers to a multidentate coordination environment formed by nitrogen defects and functional groups of the organic ligand to realize the synchronous confinement nucleation and crystallization of multiple metal ions; Pre-cursor mixing and coordination dispersion: five kinds of metal salts in an equimolar ratio are mixed with the functionalized boron nitride carrier prepared in step (1) in a solvent and dried; Mechanical activation treatment: the mixture in step (2) is placed in a ball mill jar for ball milling; Programmed pyrolysis and interface formation: a multi-stage programmed pyrolysis process with dynamic atmosphere control is adopted to complete the crystallization and interface stabilization of high-entropy metal oxides.

2. The method of claim 1, wherein the method is characterized by, In step (1), the thermal expansion-liquid nitrogen quenching cycle treatment comprises: preheating the hexagonal boron nitride at 400-500°C for 10-30 min, then transferring it to a liquid nitrogen environment within 10 s for rapid freezing, and soaking in liquid nitrogen for 1-10 min; this process is repeated 3-10 times.

3. The method of claim 1, wherein the method is characterized by, In step (1), the multidentate organic ligand is selected from one of citric acid, oxalic acid, ethylenediaminetetraacetic acid or its derivatives; and the solvent is deionized water or ethanol.

4. The method of claim 1, wherein the method is characterized by, In step (1), the temperature of the hydrothermal or solvothermal reaction is 120-180°C, and the reaction time is 12-24 h.

5. The method of constructing highly dispersed and highly entropic metal oxide nanoparticles with synergistic anchoring of ligands according to claim 1, characterized in that, In step (1), the mass ratio of the organic ligand to the hexagonal boron nitride nanosheets is 1:10-1:30; and the mass ratio of the total mass of the nanosheets and the organic ligand to the solvent is 1:10-1:

50.

6. The method of constructing highly dispersed and highly entropic metal oxide nanoparticles with synergistic anchoring of ligands according to claim 1, characterized in that, In step (2), the metal salt is a nitrate or an acetate; the metal elements include metals with multiple valence states of Ru and / or Ga; and the solvent is ethanol.

7. The method of constructing highly dispersed and high entropy metal oxide nanoparticles with synergistic anchoring of ligands according to claim 1, characterized in that, In step (2), the mass ratio of the total mass of the metal salt to the functionalized boron nitride carrier is 1:5-1:10; and the mass ratio of the total mass of the metal salt and the functionalized boron nitride carrier to the solvent is 1:10-1:

50.

8. The method of constructing highly dispersed high entropy metal oxide nanoparticles with synergistic anchoring of ligands according to claim 1, wherein, In step (4), the multi-stage programmed pyrolysis and interface formation comprises the following stages: First stage: under N2 atmosphere, the temperature is raised to 400-600°C at a rate of 1-5°C / min, and the temperature is kept for 0.5-2 h, so that the precursor is slowly decomposed and high-entropy oxide crystal nuclei are initially formed in the confined space on the surface of the carrier; Second stage: the atmosphere is switched to a weak reducing atmosphere, the weak reducing atmosphere is 2%-10% H2 / Ar by volume fraction, the temperature is raised to 800-1000°C at a rate of 1-5°C / min, and the temperature is kept for 0.5-1 h to drive the grain growth; Third stage: switch back to N2 atmosphere, continue to keep the temperature at the target temperature for 0.5-2 h to complete the crystal structure stabilization.

9. A high dispersion high entropy metal oxide nanoparticle composite material characterized by, The high-entropy metal oxide nanoparticles are uniformly loaded on the functionalized hexagonal boron nitride nanosheet carrier, and the particle size of the nanoparticles is 10-100 nm.

10. Use of the high dispersion high entropy metal oxide nanoparticle composite material as catalyst in the preparation of ammonia by electrocatalytic reduction of nitrate salt according to claim 9, characterized in that, The electrocatalytic nitrate reduction reaction is carried out in an H-type electrolytic cell, the electrolyte is a Na2SO4 solution containing nitrate, and the working potential is-0.8 V (vs. RHE).

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