An fct-phase NiPd nanoparticle catalyst, its preparation method and application

Abstract

This invention discloses an fct-phase NiPd nanoparticle catalyst, its preparation method, and its applications. The fct-phase NiPd nanoparticle catalyst has a core-shell structure, comprising fully ordered atomically arranged fct-phase NiPd nanocrystals and a nitrogen-doped carbon layer coating the surface of the fct-phase NiPd nanocrystals. The fct-phase NiPd nanoparticle catalyst provided by this invention significantly reduces the activation energy of the magnesium hydride system by leveraging the electronic structure advantages of the fct-phase NiPd core and the hydrogen pumping effect of the palladium component. Simultaneously, the robust nitrogen-doped carbon shell generated in situ physically confines the metal core to effectively suppress its agglomeration and sintering, and constructs a low-impedance, high-flux hydrogen diffusion channel within the shell, achieving a dual improvement in kinetics and stability.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial production technology, specifically relating to an fct phase NiPd nanoparticle catalyst, its preparation method, and its application. Background Technology

[0002] Driven by global "dual carbon" goals, hydrogen energy has become a core carrier of clean energy, and its large-scale application relies on safe and efficient solid-state hydrogen storage technology. Magnesium-based hydrogen storage materials are considered to have great commercial potential due to their high theoretical hydrogen storage capacity (7.6 wt%), abundant resources, and low cost. However, they face dual challenges in thermodynamics and kinetics: Thermodynamically, the strong Mg-H bond results in a theoretical hydrogen release temperature of over 300 ℃. The huge enthalpy change of the hydrogen absorption and desorption reactions means that the material can only work under high-temperature conditions, which not only significantly increases the energy consumption of the system but also severely limits its practical application scenarios. Kinetically, the low hydrogen atom diffusion coefficient and the dense oxide film on the surface hinder hydrogen dissociation and permeation, resulting in a slow hydrogen absorption and desorption rate.

[0003] The most similar existing technologies currently employ impregnation reduction or wet chemical methods to prepare nickel-palladium (NiPd) bimetallic alloy catalysts, which are then supported on carbon supports or directly combined with magnesium hydride. This approach utilizes the electronic synergistic effect between Ni and Pd and the "hydrogen pump" mechanism of Pd to lower the dissociation barrier of the Mg-H bond and accelerate hydrogen transport, and is currently the mainstream strategy for improving the hydrogen storage performance of magnesium hydride.

[0004] However, existing technology has the following drawbacks:

[0005] (1) Limited catalytic activity and disordered crystal structure (fcc). Most NiPd nanoparticles prepared by existing technologies exist as disordered face-centered cubic (fcc) solid solutions with randomly distributed atoms. Although this represents an improvement over single metals, its electronic structure (d-band center) is not optimal. Theoretical studies indicate that constructing fully ordered face-centered tetragonal (fct) intermetallic compounds with long-range ordered atomic arrangements would significantly reduce the reaction energy barrier through stronger electronic ligand effects. However, existing technologies struggle to overcome thermodynamic limitations, resulting in catalysts remaining in a disordered solid solution state with low activity. This fails to unleash the full catalytic potential of the NiPd system. The ability of such catalysts to weaken Mg-H bond energy has not yet reached its theoretical optimum, leading to a bottleneck in the improvement of reaction kinetics of magnesium hydride composites and making it difficult to meet the demand for rapid hydrogen adsorption and desorption at low temperatures.

[0006] (2) The thermodynamic contradiction between "structural ordering" and "morphological dispersion". The preparation of highly active fct-NiPd structures faces a significant technological paradox. Inducing the transformation from disordered fcc to ordered fct typically requires overcoming a large atomic diffusion energy barrier, which necessitates long-term high-temperature heat treatment above 600 °C. However, without effective physical confinement protection, nanoparticles inevitably undergo severe Ostwald ripening and violent aggregation under this high-temperature driving force, leading to a sharp decrease in specific surface area and a significant loss of active sites. Existing technologies cannot maintain nanoscale dispersion while obtaining an ordered structure.

[0007] (3) The dilemma of balancing "physical barrier" and "hydrogen transport". To solve the problem of high-temperature sintering, existing technologies attempt to introduce carbon coating. However, traditional post-processing coating processes are difficult to precisely control the shell structure at the nanoscale. To suppress sintering, a thick or dense coating layer is often required, but this will form a severe gas diffusion barrier on the catalyst surface, cutting off the mass transfer path of hydrogen molecules to the active center, resulting in a rapid decline in the kinetic performance of the material in practical applications (especially under cycling conditions of 300-450 °C); conversely, if the coating layer is thinned, it cannot resist metal migration at high temperatures. Existing technologies cannot find a balance between "high-temperature structure locking" and "high-throughput hydrogen transport".

[0008] (4) The inherently slow hydrogen absorption and desorption kinetics of magnesium hydride. Although magnesium hydride (MgH2) has an extremely high theoretical hydrogen storage capacity, its hydrogen absorption and desorption kinetics are very slow in the practical application temperature range due to the excessively high thermodynamic stability of the Mg-H bond (desorption enthalpy of approximately 74.7 KJ / mol) and the extremely low diffusion rate of hydrogen atoms within the magnesium lattice. Without the introduction of a highly efficient catalyst for modification, MgH2 is difficult to achieve rapid dehydrogenation under mild conditions, which severely restricts its practical application as a solid-state hydrogen storage medium.

[0009] Therefore, how to provide strong physical confinement to lock metal particles while constructing a low-impedance, high-flux hydrogen diffusion channel to achieve a dual improvement in kinetics and stability is an urgent technical problem to be solved. Summary of the Invention

[0010] The main objective of this invention is to provide an fct phase NiPd nanoparticle catalyst, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0011] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0012] The first aspect of the present invention provides an fct phase NiPd nanoparticle catalyst having a core-shell structure comprising fct phase NiPd nanocrystals with fully ordered atomic arrangement and a nitrogen-doped carbon layer coating the surface of the fct phase NiPd nanoparticles.

[0013] A second aspect of the present invention provides a method for preparing an fct-phase NiPd nanoparticle catalyst, comprising:

[0014] Palladium source, nickel source, and bifunctional ligand are mixed uniformly to form NiPd nanoparticle precursor material through coordination. Then, the precursor is electrostatically adsorbed and loaded onto the surface of a carbon support to obtain a composite precursor. The composite precursor is subjected to a first high-temperature in-situ pyrolysis reaction under a reducing atmosphere to form a nitrogen-doped carbon layer in situ. At the same time, nickel and palladium atoms are induced to change from a disordered solid solution to a fully ordered face-centered tetragonal structure to obtain an fct phase NiPd nanoparticle catalyst.

[0015] Alternatively, palladium, nickel, and carbon sources are uniformly mixed with a second solvent to form a stable metal-organic precursor network through coordination. Then, a nitrogen source is added to uniformly disperse the nitrogen source in the stable organic precursor network, allowing it to self-assemble and obtain a nitrogen-containing solid precursor. The nitrogen-containing solid precursor undergoes a second high-temperature in-situ pyrolysis reaction under a reducing atmosphere, where nickel and palladium atoms form a fully ordered fct-phase NiPd core, the carbon source is carbonized in-situ to form a carbon layer, and the nitrogen source is thermally decomposed to generate nitrogen-containing gas for nitrogen doping, thus obtaining an fct-phase NiPd nanoparticle catalyst.

[0016] A third aspect of the present invention provides a method for preparing a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material, comprising:

[0017] Provide the aforementioned fct phase NiPd nanoparticle catalyst;

[0018] The fct phase NiPd nanoparticle catalyst was mixed with magnesium hydride and ball-milled to obtain a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

[0019] A fourth aspect of the present invention provides a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material prepared by the above preparation method, wherein the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material has a hydrogen storage capacity greater than 4.0 wt% at 200 °C.

[0020] A fifth aspect of the present invention provides a solid hydrogen storage medium comprising the above-described nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) This invention breaks the inherent limitation of crystal structure on catalytic activity, achieving a qualitative leap in intrinsic catalytic efficiency. The fully ordered face-centered tetragonal (fct) intermetallic compound successfully synthesized in this invention exhibits a stronger electronic ligand effect. This highly ordered atomic arrangement optimizes the electronic structure of the metal surface, enabling a more significant reduction in the dehydrogenation energy barrier of MgH2. Experimental results show that, compared with disordered fcc-NiPd with the same loading, the material of this invention can further reduce the initial hydrogen desorption temperature of magnesium hydride and significantly improve the hydrogen absorption and desorption reaction rate at low temperatures.

[0023] (2) This invention solves the problem of high-temperature "sintering deactivation" and achieves excellent cycling stability. The invention utilizes an in-situ generated nitrogen-doped carbon shell to construct a highly effective nano-confined microenvironment, providing robust physical encapsulation and spatial confinement for fct-NiPd nanoparticles. This structure effectively suppresses the thermal migration and phase separation behavior of metal atoms under high-temperature conditions and during long-term cycling. Even after multiple hydrogen adsorption / desorption operations, the catalyst maintains its original particle size distribution and high dispersion, thus endowing the composite material with excellent long-term cycling stability.

[0024] (3) The drawback of the coating layer's "hydrogen barrier" is overcome, and a high-throughput hydrogen transport channel is constructed. The carbon shell prepared by this invention has the triple characteristics of "ultra-thin, porous, and nitrogen-doped". The ultra-thin thickness shortens the transport path, the abundant porous structure provides physical channels, and the introduction of nitrogen atoms improves the chemical affinity of the interface. This design ensures physical protection while minimizing gas diffusion resistance, achieving a perfect unity of "high stability" and "fast kinetics".

[0025] (4) Improved atomic utilization of the noble metal palladium (Pd) resulted in better economic efficiency. In the fully ordered fct structure, Ni and Pd atoms are arranged in strict accordance with a specific stoichiometric ratio. This highly ordered structure maximizes the surface exposure and catalytic contribution of Pd atoms. Under the premise of achieving the same catalytic effect, this invention can effectively reduce the actual amount of noble metal Pd used or exert stronger catalytic performance at the same amount, resulting in higher cost-effectiveness. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1This is a flowchart illustrating the preparation process of nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material in a typical embodiment of the present invention.

[0028] Figure 2 This is an X-ray powder diffraction (XRD) pattern of the fct phase NiPd nanoparticle catalyst prepared in Example 1 of this invention;

[0029] Figure 3 This is a transmission electron microscope (TEM) image of the fct phase NiPd nanoparticle catalyst prepared in Example 1 of this invention;

[0030] Figure 4 This is a hydrogen absorption curve of the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material of Example 1 of the present invention under hydrogen pressure conditions of 300 °C and 30 MPa.

[0031] Figure 5 This is a hydrogen desorption curve of the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material of Example 1 of the present invention at 350 °C. Detailed Implementation

[0032] In view of the problems existing in the prior art, the inventors of this invention, through extensive and in-depth research, provide an fct phase NiPd nanoparticle catalyst, its preparation method, and its application. The following will further explain the technical solution, its implementation process, and its principles.

[0033] The first aspect of the present invention provides an fct phase NiPd nanoparticle catalyst having a core-shell structure comprising fct phase NiPd nanocrystals with fully ordered atomic arrangement and a nitrogen-doped carbon layer coating the surface of the fct phase NiPd nanocrystals.

[0034] In some implementations, the fct phase is a fully ordered face-centered tetragonal structure.

[0035] In some embodiments, the nitrogen-doped carbon layer has a porous structure.

[0036] Preferably, the porosity of the nitrogen-doped carbon layer is 10-30%, and the pore size in the nitrogen-doped carbon layer is 0.5-2.0 nm.

[0037] In some embodiments, the diameter of the fct phase NiPd nanoparticle catalyst is 10~25 nm.

[0038] In some embodiments, the diameter of the fct phase NiPd nanocrystals is 8~20 nm.

[0039] In some embodiments, the thickness of the nitrogen-doped carbon layer is 1 to 3 nm.

[0040] In some embodiments, the fct phase NiPd nanoparticle catalyst comprises 10-25 wt% Ni, 20-45 wt% Pd, 30-60 wt% C and 1-5 wt% N.

[0041] Specifically, the fct phase NiPd nanoparticle catalyst provided by the present invention is a nitrogen-doped carbon-coated fully ordered fct phase nickel-palladium intermetallic compound (fct-NiPd / NC) nanocatalyst. The core is an fct phase NiPd nanoparticle with long-range ordered atomic arrangement, and the outer layer is an in-situ generated nitrogen-doped carbon shell with a core-shell structure morphology.

[0042] A second aspect of the present invention provides a method for preparing an fct-phase NiPd nanoparticle catalyst, comprising:

[0043] Palladium source, nickel source, and bifunctional ligand are mixed uniformly to form NiPd nanoparticle precursor material through coordination. Then, the precursor is electrostatically adsorbed and loaded onto the surface of a carbon support to obtain a composite precursor. The composite precursor is subjected to a first high-temperature in-situ pyrolysis reaction under a reducing atmosphere to form a nitrogen-doped carbon layer in situ. At the same time, nickel and palladium atoms are induced to change from a disordered solid solution to a fully ordered face-centered tetragonal structure to obtain an fct phase NiPd nanoparticle catalyst.

[0044] Alternatively, palladium, nickel, and carbon sources are uniformly mixed with a second solvent to form a stable metal-organic precursor network through coordination. Then, a nitrogen source is added to uniformly disperse the nitrogen source in the stable organic precursor network, allowing it to self-assemble and obtain a nitrogen-containing solid precursor. The nitrogen-containing solid precursor undergoes a second high-temperature in-situ pyrolysis reaction under a reducing atmosphere, where nickel and palladium atoms form a fully ordered fct-phase NiPd core, the carbon source is carbonized in-situ to form a carbon layer, and the nitrogen source is thermally decomposed to generate nitrogen-containing gas for nitrogen doping, thus obtaining an fct-phase NiPd nanoparticle catalyst.

[0045] In some embodiments, the palladium source includes at least one of palladium nitrate, palladium acetylacetone, and palladium acetate.

[0046] In some embodiments, the nickel source includes at least one of nickel acetylacetonate, nickel nitrate, and nickel acetate.

[0047] In some implementations, the ligand is a bifunctional ligand that functions as both a nitrogen source and a carbon source.

[0048] Preferably, the bifunctional ligand comprises an alkylamine compound having a long-chain hydrophobic structure and an amino functional group.

[0049] In some embodiments, the preparation method includes: uniformly mixing the palladium source, nickel source, bifunctional ligand, ascorbic acid, and hexadecyltrimethylammonium chloride.

[0050] In some embodiments, the carbon support includes at least one of Ketjen black, carbon nanotubes, graphene, reduced graphene oxide, mesoporous carbon, and acetylene black. The carbon support used in this invention is a carbon-based material with high specific surface area and good conductivity, capable of supporting metal particles and constructing a conductive network.

[0051] In some embodiments, the molar ratio of the palladium source to the carbon support is 1~5:20~100.

[0052] In some embodiments, the electrostatic adsorption temperature is 0~25 °C and the time is 1~6 h.

[0053] In some implementations, the temperature of the first high-temperature in-situ pyrolysis reaction is 600~800 °C and the time is 60~360 min.

[0054] In some embodiments, the reducing atmosphere comprises a mixture of argon and hydrogen.

[0055] Preferably, the volume ratio of argon to hydrogen is 90~98:2~10.

[0056] In some embodiments, the molar ratio of the nickel source, palladium source, ascorbic acid, hexadecyltrimethylammonium chloride and bifunctional ligand is (1~3):(1~3):(1~3):(1~3):(5~100).

[0057] In some embodiments, the alkylamine compounds include, but are not limited to, at least one of oleylamine, dodecylamine, hexadecylamine, and octadecylamine. For example, oleylamine is a nitrogen-containing organic molecule with a long carbon chain structure and can act as a bifunctional ligand, serving as both a carbon source and a ligand. That is, the alkylamine compounds with long-chain hydrophobic structures and amino functional groups in this invention can coordinate with metal ions and play a structure-directing role.

[0058] In some embodiments, when the alkylamine compound is dodecylamine, hexadecylamine or octadecylamine, a first solvent is also required.

[0059] Preferably, the first solvent includes, but is not limited to, at least one of oleic acid, 1-octadecene, diphenyl ether, benzyl ether, or liquid paraffin.

[0060] Preferably, the molar ratio of the nickel source, palladium source, ascorbic acid, hexadecyltrimethylammonium chloride, alkylamine compound and the first solvent is (1~3):(1~3):(1~3):(1~3):(5~50):(2~200).

[0061] In some more specific embodiments, the preparation method of the fct phase NiPd nanoparticle catalyst specifically includes the following steps:

[0062] S1: Palladium source, nickel source, ascorbic acid, and hexadecyltrimethylammonium chloride were mixed with oleylamine in a warm water bath for 10 min to obtain a homogeneous solution. The solution was then preheated in an 80 ℃ low-temperature oil bath for 10 min, and then transferred to a 200 ℃ high-temperature oil bath for 10 h for reaction. After the reaction, the solution was allowed to cool naturally to room temperature and aged. 6 ml of cyclohexane and 18 ml of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation, and the precipitate was stored in cyclohexane to obtain a NiPd nanoparticle precursor material (a stable metal-organic complex).

[0063] S2: A uniform suspension of Ketjen black was prepared by dispersing it in a solvent. The previously prepared NiPd nanocrystal dispersion was slowly added to the Ketjen black suspension under ice-water bath and ultrasonication for 3 hours. Electrostatic adsorption was used to uniformly load the NiPd nanocrystals onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the composite precursor material. After drying, the composite precursor material was heated to a target temperature of 600–800 °C at a preset temperature of 2–5 °C / min under a reducing atmosphere (95% Ar + 5% H2) and held for 1–6 hours. During this process, oleylamine ligands undergo in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying, ultimately yielding an fct-phase NiPd nanoparticle catalyst.

[0064] In the above preparation steps, nitrogen-containing organic molecules with long carbon chain structures, such as oleylamine, are used as bifunctional ligands and carbon sources. The metal source and organic ligands are coordinated in an organic solvent to form a stable metal-organic complex. Furthermore, the complex is uniformly anchored on the surface of a pretreated conductive carbon support such as Ketjen black with a high specific surface area by electrostatic adsorption to obtain a composite precursor. Subsequently, the dried precursor is placed in a heating device such as a tube furnace and subjected to high-temperature in-situ pyrolysis under the protection of an argon-hydrogen mixture. During this process, the in-situ carbonization of the organic ligands grows a nitrogen-doped carbon shell with controllable thickness and rich pore structure on the surface of the metal particles. At the same time, the nano-confined microenvironment formed by the carbon shell overcomes the thermodynamic energy barrier of metal atom diffusion and rearrangement and induces nickel and palladium atoms to transform from a disordered solid solution to a fully ordered face-centered tetragonal (fct phase) structure, thereby constructing a highly stable intermetallic compound core.

[0065] In another embodiment of the invention, a nitrogen-free long-chain fatty acid is used in combination with an external nitrogen source. During high-temperature pyrolysis, the synergistic effect of the two can also construct a nitrogen-doped carbon coating layer.

[0066] Furthermore, the nitrogen source includes, but is not limited to, at least one of melamine, urea, and dicyandiamide.

[0067] Furthermore, the carbon source includes, but is not limited to, nitrogen-free long-chain fatty acids.

[0068] Preferably, the nitrogen-free long-chain fatty acids include, but are not limited to, oleic acid.

[0069] In some embodiments, the second solvent includes 1-octadecene (ODE), diphenyl ether, and benzyl ether.

[0070] In some embodiments, the molar ratio of the palladium source, nickel source, nitrogen source, carbon source to the second solvent is (1~3):(1~3):(10~100):(5~50):(2~200).

[0071] In some implementations, the temperature of the second high-temperature in-situ pyrolysis reaction is 600~800 °C and the time is 60~360 min.

[0072] In some more specific embodiments, the preparation method of the fct phase NiPd nanoparticle catalyst can also be achieved through the following steps:

[0073] S1 Liquid-phase coordination and assembly (construction of precursor): Nickel and palladium sources are dissolved in a solvent; then oleic acid is added and stirred at 25-80 °C to allow the carboxyl groups of oleic acid to fully coordinate with the metal ions; then nitrogen source is added and stirred and sonicated for 0.5-4 h to allow the nitrogen source to be uniformly dispersed and crosslinked in the oleic acid-metal complex network.

[0074] S2 Solvent evaporation and drying: The solvent is removed by rotary evaporation or heating, which promotes the self-assembly of the system to obtain a uniformly mixed nitrogen-containing solid precursor.

[0075] S3 High-temperature in-situ pyrolysis and reconstruction (phase formation and shell formation): The precursor is placed in a tube furnace and heated to 600~800 ℃ under the protection of an argon-hydrogen mixture and held for 1~6 h according to a specific heating program. During this process, a series of reactions occur: (1) Nickel-palladium metal ions are reduced and undergo atomic rearrangement to form a fully ordered fct phase NiPd core; (2) The long oleic acid chains wrapped on the surface are heated and carbonized to form a carbon shell physical confinement layer; (3) The nitrogen-rich source dispersed inside is heated and decomposed to release nitrogen-containing reactive gas, which is used to deeply dope the carbon shell that is forming in situ.

[0076] S4 Cooling and Collection: Naturally cool to room temperature to obtain the fct phase NiPd nanoparticle catalyst.

[0077] In the above preparation method, the combination of "oleic acid + nitrogen-rich source" essentially utilizes a synergistic chemical mechanism of "carboxyl group coordination and shaping + long-chain confinement guidance + high-temperature gas-phase in-situ doping," achieving the same high dispersion, high activity, and nitrogen-doped carbon coating effects as a single oleylamine molecule. Oleic acid plays a coordination and structure-guiding role, and the oleic acid molecule has a carboxyl group (-COOH) at one end. During the liquid-phase mixing stage, the oxygen atom in the carboxyl group has a lone pair of electrons, which can interact with the nickel source (Ni... 2+ ) and palladium source (Pd 2+ A strong complexation / coordination reaction occurs, forming a stable metal-oleate precursor network. This perfectly replaces the coordination function of the amino group in oleylamine.

[0078] Oleic acid possesses a hydrophobic carbon chain of up to 18 carbon atoms. When its carboxyl terminus coordinates with a metal ion, the long carbon chain extends outward, forming a dense steric hindrance around the metal core. This surfactant-like encapsulation effectively prevents the disordered aggregation of metal nanoparticles during liquid-phase assembly and subsequent initial heat treatment, precisely controlling the particle size and morphology, thus achieving "structure-guided" processing.

[0079] Meanwhile, the nitrogen source plays a dominant role in "in-situ nitrogen doping." In the liquid phase, the nitrogen source is uniformly dispersed in the metal-oleic acid precursor network. In the high-temperature pyrolysis stage, when the temperature rises, the nitrogen source (such as urea) undergoes thermal decomposition, releasing a large amount of highly reactive nitrogen-containing small molecule gases (such as NH3, HNCO, etc.). These reactive gases react directly with the carbon skeleton while the oleic acid carbon chain is carbonized in situ into a shell, seamlessly embedding nitrogen atoms (N) into the generated carbon layer lattice. Thus, during the high-temperature pyrolysis process, the two work synergistically to construct a nitrogen-doped carbon coating layer.

[0080] A third aspect of the present invention provides a method for preparing a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material, comprising:

[0081] Provide the aforementioned fct phase NiPd nanoparticle catalyst;

[0082] The fct phase NiPd nanoparticle catalyst was mixed with magnesium hydride and ball-milled to obtain a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

[0083] In some embodiments, the mass ratio of the fct phase NiPd nanoparticle catalyst to magnesium hydride is 5~15:85~95.

[0084] In some implementations, the ball mill adopts a forward-reverse-intermittent cycle mode, with a rotation speed of 100~700 r / min and a total ball milling time of 5~10 h.

[0085] In some implementations, the ball mill adopts a cyclic pattern of forward rotation for 2~15 min - reverse rotation for 2~15 min - intermittent rotation for 2~15 min.

[0086] In some more specific embodiments, the preparation method of the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material specifically includes the following steps:

[0087] First, the NiPd nanoparticle catalyst and magnesium hydride in the fct phase were ball-milled at a ratio of 5~15:85~95. The rotation speed was 100~700 r / min, with forward rotation for 2~5 min, reverse rotation for 2~5 min, and intermittent interval for 2~5 min. This constituted one ball-milling cycle. The ball-milling was carried out for 5~10 hours to obtain the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

[0088] For example, a flowchart of the preparation of nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material in a typical embodiment of the present invention is shown below. Figure 1 As shown, fct phase NiPd nanoparticle catalysts were prepared by precursor solution preparation, support loading, in-situ pyrolysis and reduction. Then, the catalysts were mixed with magnesium hydride and ball-milled to obtain nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

[0089] A fourth aspect of the present invention provides a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material prepared by the above preparation method, wherein the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material has a hydrogen storage capacity greater than 4.0 wt% at 200 °C.

[0090] A fifth aspect of this invention provides a solid-state hydrogen storage medium, comprising the aforementioned nitrogen-doped carbon-coated fct-phase NiPd / MgH2 composite hydrogen storage material. The catalysts obtained by the two preparation methods of this invention significantly reduce the activation energy of the magnesium hydride system by leveraging the unique electronic structure advantages of the fct-phase NiPd core and the hydrogen pumping effect of the palladium component. Simultaneously, the robust nitrogen-doped carbon shell generated in situ physically confines the metal core during high-temperature hydrogen adsorption / desorption cycling, effectively suppressing its agglomeration and sintering. Furthermore, the excellent hydrogen permeability of the shell constructs a high-flux hydrogen diffusion channel, thereby simultaneously improving the reaction kinetics and long-term cycling stability of the magnesium hydride hydrogen storage material.

[0091] In summary, this invention employs a high-temperature in-situ pyrolysis and structure-guided strategy, utilizing an in-situ generated nitrogen-doped carbon shell to exert a powerful nano-confining effect on the internal metal particles. This aims to simultaneously overcome the atomic diffusion energy barrier and physically lock the metal core, thereby successfully synthesizing a highly crystalline and highly dispersed fully ordered fct phase NiPd intermetallic compound under high-temperature conditions. This completely solves the technical problem of the difficulty in stably preparing highly active ordered structures.

[0092] Moreover, this invention utilizes an in-situ constructed ultrathin nitrogen-doped carbon shell as a bifunctional interface layer. On the one hand, its robust physical barrier effect effectively inhibits the migration, phase separation, and aggregation of NiPd cores during high-temperature preparation and subsequent long-term hydrogen absorption and desorption cycles, achieving excellent long-term cycle stability. On the other hand, the shell's unique rich pore structure and excellent hydrogen permeability are used to construct a low-impedance, high-flux hydrogen diffusion fast channel, thereby obtaining a high-performance hydrogen storage composite material with both high catalytic activity and rapid kinetic response.

[0093] For experiments not specifically described in the examples, the procedures or conditions can be performed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available. Other unmentioned raw materials and instruments are all conventionally chosen and do not involve the core technical means of this invention.

[0094] Example 1

[0095] Preparation of fct phase NiPd nanoparticle precursor: 55 mg palladium nitrate, 52 mg nickel acetylacetonate, 80 mg ascorbic acid, and 85 mg cetyltrimethylammonium chloride were mixed with 6 mL oleylamine and sonicated in a warm water bath for 10 min to obtain a homogeneous solution. The solution was then preheated in an 80 °C oil bath for 10 min and transferred to a 200 °C oil bath for 10 h for reaction. After the reaction, the solution was naturally cooled to room temperature and allowed to age. 6 mL of cyclohexane and 18 mL of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to prepare the NiPd nanoparticle precursor.

[0096] Preparation of fct-phase NiPd nanoparticles: Ketjen black was dispersed in a solvent to prepare a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanoparticle precursor dispersion was slowly added to the aforementioned Ketjen black suspension. Electrostatic adsorption was used to uniformly load the NiPd nanoparticle precursor onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the obtained supported precursor material was heated to the target temperature of 800℃ at a reducing atmosphere (95% Ar + 5% H2) according to a preset heating program of 2.5 ℃ / min and held for 1 h. During this process, oleylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying, ultimately yielding a nitrogen-doped carbon-coated NiPd nanoparticle catalyst material.

[0097] Figure 2 This is the X-ray powder diffraction (XRD) pattern of the fct phase NiPd nanoparticle catalyst in this embodiment; Figure 3 This is a transmission electron microscope (TEM) image of the fct phase NiPd nanoparticle catalyst in this embodiment.

[0098] Preparation of fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material: First, 0.1 g of fct phase NiPd nanoparticle catalyst and 0.9 g of magnesium hydride were ball-milled at a speed of 600 r / min, with 5 min of forward rotation, 5 min of reverse rotation, and 5 min of interval in between, which constituted one ball-milling cycle. The ball milling was carried out for 6 hours to obtain the fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material.

[0099] like Figure 4 and Figure 5 As shown, the kinetic test results indicate that at 200 °C, the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material reaches saturation hydrogen absorption in just 3.35 min, with a maximum hydrogen storage capacity of 4.83 wt%; at 350 °C, the material completes the dehydrogenation process in just 4.57 min, with an effective dehydrogenation amount of 5.62 wt%.

[0100] Example 2

[0101] Preparation of fct phase NiPd nanoparticle precursor: 50 mg palladium nitrate, 45 mg nickel acetylacetonate, 75 mg ascorbic acid, and 80 mg cetyltrimethylammonium chloride were mixed with 5.5 mL oleylamine and sonicated for 10 min in a warm water bath to obtain a homogeneous solution. The solution was then preheated in an 80 °C oil bath for 10 min and transferred to a 200 °C oil bath for 10 h for reaction. After the reaction, the solution was naturally cooled to room temperature and allowed to age. 6 mL of cyclohexane and 18 mL of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to prepare the NiPd nanoparticle precursor.

[0102] Preparation of fct-phase NiPd nanoparticles: Ketjen black was dispersed in a solvent to prepare a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanoparticle precursor dispersion was slowly added to the aforementioned Ketjen black suspension. Electrostatic adsorption was used to uniformly load the NiPd nanoparticle precursor onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the obtained supported precursor material was heated to a target temperature of 600 ℃ at a preset temperature of 2 ℃ / min under a reducing atmosphere (95 % Ar + 5 % H2) and held for 3 h. During this process, oleylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying, ultimately yielding a nitrogen-doped carbon-coated fct-phase NiPd nanoparticle catalyst material.

[0103] Preparation of fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material: First, 0.1 g of fct phase NiPd nanoparticle catalyst and 0.90 g of magnesium hydride were ball-milled at a speed of 400 r / min, with 8 min of forward rotation, 8 min of reverse rotation, and an 8 min interval in between, which constituted one ball-milling cycle. The ball-milling was carried out for 8 hours to obtain the fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material.

[0104] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption in only 4.55 min, with a maximum hydrogen storage capacity of 4.18 wt%; at 350 °C, the material completes the dehydrogenation process in only 5.12 min, with an effective dehydrogenation amount of 5.25 wt%.

[0105] Example 3

[0106] Preparation of fct phase NiPd nanoparticle precursor: 50 mg palladium acetate, 45 mg nickel acetate, 75 mg ascorbic acid, and 80 mg hexadecyltrimethylammonium chloride were added to a mixture containing 2 g dodecylamine and 8 mL 1-octadecene. The mixture was ultrasonicated for 10 min at 40 ℃ to obtain a homogeneous solution. The solution was then preheated in an 80 ℃ low-temperature oil bath for 10 min, and then transferred to a 200 ℃ high-temperature oil bath for 10 h for reaction. After the reaction, the solution was naturally cooled to room temperature and allowed to age. 8 mL of cyclohexane and 24 mL of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to prepare the NiPd nanoparticle precursor material.

[0107] Preparation of nitrogen-doped carbon-coated fct-phase NiPd nanoparticles: Ketjen black was dispersed in a solvent to prepare a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanoparticle precursor dispersion was slowly added to the aforementioned Ketjen black suspension. Electrostatic adsorption was used to uniformly load the NiPd nanoparticle precursor onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the obtained supported precursor material was heated to a target temperature of 700 ℃ at a preset heating rate of 2.0 ℃ / min under a reducing atmosphere (95% nitrogen + 5% H2) and held for 2 h. During this process, dodecylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying, ultimately yielding a nitrogen-doped carbon-coated fct-phase NiPd nanoparticle catalyst material.

[0108] Preparation of nitrogen-doped carbon-coated fct phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: same as in Example 1.

[0109] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption state in only 4.15 min, with a maximum hydrogen storage capacity of 4.48 wt%; at 350 °C, the material completes the dehydrogenation process in only 4.95 min, with an effective dehydrogenation amount of 5.46 wt%.

[0110] Example 4

[0111] Preparation of fct phase NiPd nanoparticle precursor: same as in Example 1.

[0112] Preparation of fct-phase NiPd nanoparticles: Graphene was dispersed in a solvent to obtain a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanocrystal dispersion was slowly added to the graphene suspension. Electrostatic adsorption was used to uniformly disperse and load the NiPd nanoparticle precursor onto the surface of two-dimensional graphene sheets. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the supported precursor material was heated to a target temperature of 800 ℃ at a preset heating rate of 2.5 ℃ / min under a reducing atmosphere (95% Ar + 5% H2) and held for 1 h. During this process, oleylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying, ultimately yielding a catalyst material based on fct-phase NiPd nanoparticles.

[0113] Preparation of fct phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: same as in Example 1.

[0114] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption in only 3.45 min, with a maximum hydrogen storage capacity of 4.72 wt%; at 350 °C, the material completes the dehydrogenation process in only 4.52 min, with an effective dehydrogenation amount of 5.68 wt%.

[0115] Example 5

[0116] The main difference between this embodiment and Example 1 is that the carbon and nitrogen source system and synthesis route have been changed. Oleic acid and melamine are used as independent carbon and nitrogen sources, and the catalyst is prepared by direct in-situ pyrolysis of the precursor.

[0117] Preparation of fct-phase NiPd nanoparticle precursor: 55 mg palladium nitrate and 52 mg nickel acetylacetonate were dissolved in 10 mL of 1-octadecene; then 2 mL of oleic acid was added, and the mixture was stirred at 60 °C for 1 h to allow the carboxyl groups of oleic acid to fully coordinate with the metal ions; next, 300 mg of melamine was added, and the mixture was continuously stirred and sonicated for 2 h to allow the melamine to be uniformly dispersed and crosslinked in the oleic acid-metal complex network. The solvent in the system was removed by rotary evaporation under reduced pressure to obtain a uniformly mixed nitrogen-containing solid precursor.

[0118] Preparation of fct-phase NiPd nanoparticles: The precursor was placed in a tube furnace and heated to 750 °C at a reducing atmosphere (95% Ar + 5% H2) at a rate of 2.0 °C / min and held for 2 h. During this process, a series of reactions occurred: the long-chain oleic acid carbonized to form a shell, and melamine decomposed upon heating to release nitrogen-containing gas for deep nitrogen doping. Simultaneously, this induced the formation of fully ordered fct-phase cores in NiPd. After natural cooling, the fct-phase NiPd nanoparticle catalyst was obtained.

[0119] Preparation of fct phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: same as in Example 1.

[0120] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption in only 3.58 min, with a maximum hydrogen storage capacity of 4.55 wt%; at 350 °C, the material completes the dehydrogenation process in only 4.62 min, with an effective dehydrogenation amount of 5.70 wt%.

[0121] Example 6

[0122] Preparation of fct phase NiPd nanoparticle precursor: same as in Example 1.

[0123] Preparation of fct phase NiPd nanoparticles: Same as in Example 1.

[0124] Preparation of fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material: First, 0.15 g of fct phase NiPd nanoparticle catalyst and 0.85 g of magnesium hydride were ball-milled at a speed of 600 r / min, with 5 min of forward rotation, 5 min of reverse rotation, and 5 min of interval in between, which constituted one ball-milling cycle. The ball milling was carried out for 6 hours to obtain the fct phase NiPd nanoparticle / magnesium hydride composite hydrogen storage material.

[0125] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption state in only 3.20 min, with a maximum hydrogen storage capacity of 4.03 wt%; at 350 °C, the material completes the dehydrogenation process in only 4.52 min, with an effective dehydrogenation amount of 5.20 wt%.

[0126] Example 7

[0127] Preparation of fct phase NiPd nanoparticle precursor: 2 g hexadecylamine and 8 mL diphenyl ether were added to 55 mg palladium acetylacetonate, 52 mg nickel nitrate, 80 mg ascorbic acid and 85 mg hexadecyltrimethylammonium chloride, and the rest was the same as in Example 1.

[0128] Preparation of fct phase NiPd nanoparticles: The carbon support is carbon nanotubes, and the rest is the same as in Example 1.

[0129] Preparation of fct phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: same as in Example 1.

[0130] Kinetic test results show that at 200 °C, the composite hydrogen storage material reaches saturation hydrogen absorption state in only 5 min, with a maximum hydrogen storage capacity of 4.23 wt%; at 350 °C, the material completes the dehydrogenation process in only 4.52 min, with an effective dehydrogenation amount of 5.68 wt%.

[0131] Comparative Example 1

[0132] The main difference between this comparative example and Example 1 is that a nitrogen-free pure carbon-coated fct phase NiPd nanoparticle catalyst was prepared (using oleic acid and 1-octadecene as a nitrogen-free synthesis system).

[0133] Preparation of nitrogen-free coated NiPd nanoparticle precursor: 55 mg palladium nitrate, 52 mg nickel acetylacetonate, and 80 mg ascorbic acid were mixed with 2 mL oleic acid and 8 mL 1-octadecene (as nitrogen-free ligand and solvent). The mixture was ultrasonically stirred for 10 min in a warm water bath to obtain a homogeneous solution. The solution was then preheated in an 80 ℃ low-temperature oil bath for 10 min, and then transferred to a 200 ℃ high-temperature oil bath for 10 h for reaction. After the reaction, the solution was naturally cooled to room temperature and allowed to stand for aging. 6 mL cyclohexane and 18 mL anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to obtain the nitrogen-free coated NiPd nanoparticle precursor material.

[0134] Preparation of nitrogen-free carbon-coated fct phase NiPd nanoparticles: Ketjen black was dispersed in a solvent to prepare a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanoparticle precursor dispersion was slowly added to the aforementioned Ketjen black suspension. Electrostatic adsorption was used to uniformly load the NiPd nanoparticle precursor onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the obtained supported precursor material was heated to the target temperature of 800℃ at a preset heating rate of 2.5 ℃ / min under a reducing atmosphere (95 % Ar + 5 % H2) and held for 1 h. During this process, the long chains of oleic acid carbonized in situ to form a pure carbon layer (without nitrogen doping), simultaneously inducing NiPd alloying, ultimately yielding a nitrogen-free carbon-coated fct phase NiPd nanoparticle catalyst material.

[0135] Preparation of nitrogen-free carbon-coated fct phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: First, 0.1 g of nitrogen-free carbon-coated fct phase NiPd nanoparticle catalyst and 0.9 g of magnesium hydride were ball-milled at a speed of 600 r / min, with 5 min of forward rotation, 5 min of reverse rotation, and a 5 min interval in between, which constituted one ball-milling cycle. The ball-milling was carried out for 6 hours to obtain the nitrogen-free carbon-coated fct phase NiPd nanoparticles / MgH2 composite hydrogen storage material.

[0136] Kinetic test results show that at 200 °C, due to the lack of nitrogen doping anchoring and anti-sintering effect, the composite hydrogen storage material takes 15.50 min to reach saturated hydrogen absorption state, and the maximum hydrogen storage capacity drops to 2.82 wt%. At 350 °C, the dehydrogenation kinetics of the material is significantly slow, taking 12.35 min to complete the dehydrogenation process, and the effective dehydrogenation amount is only 4.15 wt%.

[0137] Comparative Example 2

[0138] The main difference between this comparative example and Example 1 is that the holding temperature of in-situ pyrolysis was lowered to 400 °C, resulting in a nitrogen-doped carbon-coated NiPd nanoparticle catalyst with disordered fcc phase.

[0139] Preparation of fcc phase NiPd nanoparticle precursor: 55 mg palladium nitrate, 52 mg nickel acetylacetonate, 80 mg ascorbic acid, and 85 mg cetyltrimethylammonium chloride were mixed with 6 mL oleylamine and sonicated in a warm water bath for 10 min to obtain a homogeneous solution. The solution was then preheated in an 80 °C oil bath for 10 min and transferred to a 200 °C oil bath for 10 h for reaction. After the reaction, the solution was allowed to cool naturally to room temperature and aged. 6 mL of cyclohexane and 18 mL of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to prepare the NiPd nanoparticle precursor material.

[0140] Preparation of nitrogen-doped carbon-coated fcc-phase NiPd nanoparticles: Ketjen black was dispersed in a solvent to prepare a uniform suspension. Under ice-water bath and sonication conditions for 3 h, the previously prepared NiPd nanoparticle precursor dispersion was slowly added to the aforementioned Ketjen black suspension. Electrostatic adsorption was used to uniformly load NiPd nanocrystals onto the Ketjen black surface. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the obtained supported precursor material was heated to a target temperature of 400 ℃ in a reducing atmosphere (95% Ar + 5% H2) according to a preset heating program of 2.5 ℃ / min and held for 1 h. During this process, oleylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, simultaneously inducing NiPd alloying. However, due to insufficient temperature to drive long-range atomic ordering, a nitrogen-doped carbon-coated NiPd nanoparticle catalyst material based on a disordered fcc phase was ultimately obtained.

[0141] Preparation of nitrogen-doped carbon-coated fcc phase NiPd nanoparticles / magnesium hydride composite hydrogen storage material: First, 0.1 g of fcc phase NiPd nanoparticle catalyst and 0.9 g of magnesium hydride were ball-milled at a speed of 600 r / min, with 5 min of forward rotation, 5 min of reverse rotation, and a 5 min interval in between, which constituted one ball-milling cycle. The ball-milling was carried out for 6 hours to obtain the nitrogen-doped carbon-coated fcc phase NiPd nanoparticles / MgH2 composite hydrogen storage material.

[0142] Kinetic test results show that at 200 °C, due to the lack of a long-range ordered fct structure in the catalyst, its intrinsic catalytic activity is limited. The composite hydrogen storage material requires 8.25 min to reach saturated hydrogen absorption state, with a maximum hydrogen storage capacity of approximately 3.62 wt%. At 350 °C, the material requires 7.15 min to complete the dehydrogenation process, with an effective dehydrogenation amount of approximately 4.85 wt%.

[0143] Comparative Example 3

[0144] The main difference between this comparative example and Example 1 is that a nickel-free single-metal catalyst was prepared, namely nitrogen-doped carbon-coated Pd nanoparticles.

[0145] Preparation of pure Pd nanoparticle precursor: 55 mg palladium nitrate, 80 mg ascorbic acid, and 85 mg cetyltrimethylammonium chloride were mixed with 6 mL oleylamine and sonicated for 10 min in a warm water bath to obtain a homogeneous solution. The solution was then preheated in an 80 °C oil bath for 10 min and transferred to a 200 °C oil bath for 10 h for reaction. After the reaction, the solution was allowed to cool naturally to room temperature and aged. 6 mL of cyclohexane and 18 mL of anhydrous ethanol were added to the resulting solution, and nanoparticles were precipitated using an antisolvent precipitation method. The solvent was removed by centrifugation to obtain the precursor material, which was then stored in cyclohexane to obtain pure Pd nanocrystalline material.

[0146] Preparation of nitrogen-doped carbon-coated Pd nanoparticles: A uniform suspension of Ketjen black was prepared by dispersing it in a solvent. Under ice-water bath and sonication conditions for 3 h, a previously prepared pure Pd nanocrystal dispersion was slowly added to the Ketjen black suspension. Pd nanocrystals were uniformly loaded onto the Ketjen black surface using electrostatic adsorption. The solvent was removed by centrifugation at 9500 r / min to obtain the supported precursor material. After drying, the supported precursor material was heated to a target temperature of 800 ℃ at a preset heating rate of 2.5 ℃ / min under a reducing atmosphere (95 % Ar + 5 % H2) and held for 1 h. During this process, oleylamine ligands underwent in-situ carbonization to form a nitrogen-doped carbon layer, ultimately yielding a nitrogen-doped carbon-coated Pd nanoparticle catalyst material.

[0147] Preparation of nitrogen-doped carbon-coated Pd nanoparticle / magnesium hydride composite hydrogen storage material: First, 0.1 g of nitrogen-doped carbon-coated Pd nanoparticle catalyst and 0.9 g of magnesium hydride were ball-milled at a speed of 600 r / min, with 5 min of forward rotation, 5 min of reverse rotation, and a 5 min interval in between, constituting one ball-milling cycle. The milling process lasted for 6 hours to obtain the nitrogen-doped carbon-coated Pd nanoparticle / MgH2 composite hydrogen storage material, which is used to improve the hydrogen storage performance of magnesium hydride solid-state hydrogen storage materials. The hydrogen storage capacity of the nitrogen-doped carbon-coated Pd nanoparticle / MgH2 composite hydrogen storage material at 200 °C is approximately 3.2 wt%.

[0148] Kinetic test results show that at 200 °C, due to the lack of NiPd bimetallic synergistic effect, the composite hydrogen storage material takes 14.50 min to reach saturated hydrogen absorption state, and the maximum hydrogen storage capacity drops to 3.22 wt%. At 350 °C, the dehydrogenation kinetics of the material is relatively slow, and it takes 10.55 min to complete the dehydrogenation process, with an effective dehydrogenation amount of about 4.52 wt%.

[0149] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0150] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. An fct phase NiPd nanoparticle catalyst, characterized in that: The fct phase NiPd nanoparticle catalyst has a core-shell structure, comprising fct phase NiPd nanocrystals with fully ordered atomic arrangement and a nitrogen-doped carbon layer coating the surface of the fct phase NiPd nanocrystals.

2. The fct phase NiPd nanoparticle catalyst according to claim 1, characterized in that: The fct phase has a fully ordered face-centered tetragonal structure; And / or, the nitrogen-doped carbon layer has a porous structure; Preferably, the porosity of the nitrogen-doped carbon layer is 10-30%, and the pore size in the nitrogen-doped carbon layer is 0.5-2.0 nm; And / or, the diameter of the fct phase NiPd nanoparticle catalyst is 10~25 nm; And / or, the diameter of the fct phase NiPd nanocrystals is 8~20 nm; And / or, the thickness of the nitrogen-doped carbon layer is 1~3 nm; And / or, the fct phase NiPd nanoparticle catalyst comprises 10~25 wt% Ni, 20~45 wt% Pd, 30~60 wt% C and 1~5 wt% N.

3. A method for preparing an fct phase NiPd nanoparticle catalyst, characterized in that, include: Palladium source, nickel source, and bifunctional ligand are mixed uniformly to form NiPd nanoparticle precursor material through coordination. Then, the precursor is electrostatically adsorbed and loaded onto the surface of a carbon support to obtain a composite precursor. The composite precursor is subjected to a first high-temperature in-situ pyrolysis reaction under a reducing atmosphere to form a nitrogen-doped carbon layer in situ. At the same time, nickel and palladium atoms are induced to change from a disordered solid solution to a fully ordered face-centered tetragonal structure to obtain an fct phase NiPd nanoparticle catalyst. Alternatively, palladium, nickel, and carbon sources are uniformly mixed with a second solvent to form a stable metal-organic precursor network through coordination. Then, a nitrogen source is added to uniformly disperse the nitrogen source in the stable organic precursor network, allowing it to self-assemble and obtain a nitrogen-containing solid precursor. The nitrogen-containing solid precursor undergoes a second high-temperature in-situ pyrolysis reaction under a reducing atmosphere, where nickel and palladium atoms form a fully ordered fct-phase NiPd core, the carbon source is carbonized in-situ to form a carbon layer, and the nitrogen source is thermally decomposed to generate nitrogen-containing gas for nitrogen doping, thus obtaining an fct-phase NiPd nanoparticle catalyst.

4. The preparation method according to claim 3, characterized in that: The palladium source includes at least one of palladium nitrate, palladium acetylacetone, and palladium acetate. And / or, the nickel source includes at least one of nickel acetylacetonate, nickel nitrate, and nickel acetate; And / or, the bifunctional ligand has the functions of both a nitrogen source and a carbon source; Preferably, the bifunctional ligand comprises an alkylamine compound having a long-chain hydrophobic structure and an amino functional group; And / or, the preparation method includes: mixing the palladium source, nickel source, bifunctional ligand, ascorbic acid and hexadecyltrimethylammonium chloride evenly; And / or, the carbon support includes at least one of Ketjen black, carbon nanotubes, graphene, reduced graphene oxide, mesoporous carbon, or acetylene black; And / or, the electrostatic adsorption temperature is 0~25 ℃ and the time is 1~6 h; And / or, the molar ratio of the palladium source to the carbon support is 1~5:20~100; And / or, the temperature of the first high-temperature in-situ pyrolysis reaction is 600~800 ℃, and the time is 60~360 min; And / or, the reducing atmosphere includes a mixture of argon and hydrogen; Preferably, the volume ratio of argon to hydrogen is 90~98:2~10.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the nickel source, palladium source, ascorbic acid, hexadecyltrimethylammonium chloride and bifunctional ligand is (1~3):(1~3):(1~3):(1~3):(5~100); And / or, the alkylamine compound includes at least one of oleylamine, dodecylamine, hexadecylamine, or octadecylamine; Preferably, when the alkylamine compound is dodecylamine, hexadecamine or octadecamine, a first solvent is also required; Particularly preferred is that the first solvent includes at least one of oleic acid, 1-octadecene, diphenyl ether, benzyl ether, or liquid paraffin; Particularly preferred is that the molar ratio of the nickel source, palladium source, ascorbic acid, hexadecyltrimethylammonium chloride, alkylamine compound and the first solvent is (1~3):(1~3):(1~3):(1~3):(5~50):(2~200).

6. The preparation method according to claim 3, characterized in that: The nitrogen source includes at least one of melamine, urea, or dicyandiamide; And / or, the carbon source includes nitrogen-free long-chain fatty acids; Preferably, the nitrogen-free long-chain fatty acid includes oleic acid; And / or, the second solvent includes at least one of 1-octadecene, diphenyl ether, and benzyl ether; And / or, the molar ratio of the palladium source, nickel source, nitrogen source, carbon source to the second solvent is (1~3):(1~3):(10~100):(5~50):(2~200); And / or, the temperature of the second high-temperature in-situ pyrolysis reaction is 600~800 ℃, and the time is 60~360 min.

7. A method for preparing a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material, characterized in that, include: Provide the fct phase NiPd nanoparticle catalyst as described in claim 1 or 2; The fct phase NiPd nanoparticle catalyst was mixed with magnesium hydride and ball-milled to obtain a nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material.

8. The preparation method according to claim 7, characterized in that: The mass ratio of the fct phase NiPd nanoparticle catalyst to magnesium hydride is 5~15:85~95; And / or, the ball mill adopts a forward-reverse-intermittent cycle mode, with a rotation speed of 100~700 r / min and a total ball milling time of 5~10 h; And / or, the ball mill adopts a cyclic pattern of forward rotation for 2~15 min - reverse rotation for 2~15 min - intermittent rotation for 2~15 min.

9. A nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material prepared by the preparation method according to claim 7 or 8, characterized in that: The nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material has a hydrogen storage capacity greater than 4.0 wt% at 200 °C.

10. A solid hydrogen storage medium, characterized in that, This includes the nitrogen-doped carbon-coated fct phase NiPd / MgH2 composite hydrogen storage material as described in claim 9.

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