Preparation method of ammonia decomposition catalyst, supported cobalt-nickel catalyst and application thereof

Abstract

This disclosure relates to the field of catalyst technology, specifically a method for preparing an ammonia decomposition catalyst, a supported cobalt-nickel catalyst, and their applications. The preparation method includes: synthesizing a lanthanum cerate (La₂Ce₂O₇) support using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid, and nitric acid as raw materials via self-propagating combustion; and preparing a supported cobalt-nickel catalyst using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials on the defective fluorite-structured lanthanum cerate La₂Ce₂O₇ support via impregnation. This disclosure synthesizes a supported cobalt-nickel catalyst, providing a highly efficient non-precious metal catalyst, which is beneficial for on-site hydrogen production, achieving high-efficiency ammonia decomposition reaction performance and long-term operational stability.

Description

Technical Field

[0001] This disclosure relates to the field of catalyst technology, and more specifically, to a method for preparing an ammonia decomposition catalyst, a supported cobalt-nickel catalyst, and its applications. Background Technology

[0002] The continued growth in energy demand and increasingly stringent environmental protection requirements are jointly driving the exploration and development of new clean energy sources. Hydrogen energy has attracted much attention due to its high energy density and low carbon footprint. However, its large-scale industrial application faces multiple challenges, including low volumetric energy density, high storage costs, and safety hazards during operation and transportation. An effective strategy to address these issues is to use easily transportable hydrogen carriers to achieve efficient hydrogen transportation and storage, while simultaneously developing on-site hydrogen production technologies to decompose hydrogen storage carriers to obtain hydrogen gas. Ammonia has become a highly promising carbon-free hydrogen carrier due to its high hydrogen storage density, ease of liquefaction and storage under mild conditions, and advanced transportation technologies. However, ammonia decomposition is an endothermic reaction, requiring extremely high temperatures (>1100 ℃) to achieve complete thermodynamic conversion, resulting in huge energy consumption and potential safety hazards. Therefore, to expand the large-scale application of ammonia as a hydrogen carrier, it is necessary to develop efficient catalysts to reduce the reaction activation energy and achieve efficient ammonia decomposition under medium and low temperature conditions.

[0003] However, while noble metal catalysts, such as ruthenium, exhibit superior ammonia decomposition activity and stability at lower temperatures, their high cost limits their industrial application. Although non-noble metal catalysts, such as iron, cobalt, or nickel, have significantly reduced costs, their low-temperature activity and durability are generally inferior to those of noble metals. Therefore, there is an urgent need to develop efficient and low-cost ammonia decomposition catalysts.

[0004] It should be noted that the information in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for preparing an ammonia decomposition catalyst, a supported cobalt-nickel catalyst, and its application, which at least to some extent overcomes the aforementioned technical problems, synthesizes a supported cobalt-nickel catalyst, and provides a highly efficient non-precious metal catalyst, which is beneficial for on-site hydrogen production and achieves high-efficiency ammonia decomposition reaction performance and long-term operational stability.

[0006] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0007] According to one aspect of this disclosure, a method for preparing an ammonia decomposition catalyst is provided, comprising: synthesizing a La2Ce2O7 support by self-propagating combustion using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid and nitric acid as raw materials; and preparing a supported cobalt-nickel catalyst by impregnation of the La2Ce2O7 support using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone and ethanol as raw materials.

[0008] In one exemplary embodiment of this disclosure, a La2Ce2O7 support is prepared by self-propagating combustion synthesis using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid, and nitric acid as raw materials. The process includes: dissolving lanthanum nitrate hexahydrate and cerium nitrate hexahydrate in deionized water to obtain a first nitrate solution; adding citric acid and nitric acid to the first nitrate solution and stirring to obtain a mixture; heating the mixture to perform self-propagating high-temperature combustion synthesis to obtain a first precursor; and grinding and calcining the first precursor to obtain the La2Ce2O7 support.

[0009] In one exemplary embodiment of this disclosure, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water to obtain a first nitrate solution, comprising: dissolving lanthanum nitrate hexahydrate and cerium nitrate hexahydrate in deionized water according to a stoichiometric ratio to obtain a first nitrate solution.

[0010] In one exemplary embodiment of this disclosure, citric acid and nitric acid are added to a first nitrate solution and stirred to obtain a mixture, comprising: adding nitric acid and citric acid sequentially to the first nitrate solution and stirring according to a molar ratio of metal ions:citric acid:HNO3 of 1:(1~1.5):(1~1.5) to obtain a mixture.

[0011] In one exemplary embodiment of this disclosure, the mixture is heated to 300-350 °C until it spontaneously combusts to achieve self-propagating high-temperature combustion synthesis; the first precursor after grinding is calcined at a temperature of 750-800 °C for 4.5-6 hours.

[0012] In one exemplary embodiment of this disclosure, a supported cobalt-nickel catalyst is prepared on a La2Ce2O7 support by impregnation using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials. The process includes: dissolving nickel nitrate hexahydrate and cobalt nitrate hexahydrate in deionized water according to a target ratio to obtain a second nitrate solution; adding glycine, polyvinylpyrrolidone, and ethanol to the second nitrate solution while stirring to obtain a homogeneous solution; adding the La2Ce2O7 support to the homogeneous solution and stirring to obtain a mixed solution; heating the mixed solution to complete combustion to obtain a second precursor; and grinding and calcining the second precursor to obtain the supported cobalt-nickel catalyst.

[0013] In one exemplary embodiment of this disclosure, a La2Ce2O7 support is added to a homogeneous solution and stirred to obtain a mixed solution, and the mixed solution is heated to complete combustion to obtain a second precursor. The process includes: adding the La2Ce2O7 support to a homogeneous solution and stirring at room temperature for 20-24 hours to obtain a mixed solution; heating the mixed solution to 300-350 °C until complete combustion to obtain a second precursor; and grinding the second precursor and calcining it at 550-600 °C for 4.5-5.5 hours to obtain a supported cobalt-nickel catalyst.

[0014] In an exemplary embodiment of this disclosure, the main components of the prepared supported cobalt-nickel catalyst include Co, Ni and La2Ce2O7; wherein the mass ratio of cobalt to nickel in the supported cobalt-nickel catalyst is 1:(0.5~2), and the total loading of cobalt and nickel in the supported cobalt-nickel catalyst is 20~40 wt%.

[0015] In one exemplary embodiment of this disclosure, the hydrogen evolution temperature of the prepared supported cobalt-nickel catalyst is 310~575 °C.

[0016] In one exemplary embodiment of this disclosure, the prepared supported cobalt-nickel catalyst has corresponding alkaline sites at 100~200 °C, 200~400 °C, and 600~700 °C, respectively.

[0017] According to one aspect of this disclosure, a supported cobalt-nickel catalyst is provided, which is prepared by the method described in any of the exemplary embodiments above.

[0018] According to one aspect of this disclosure, an application of a supported cobalt-nickel catalyst in ammonia decomposition is provided, the supported cobalt-nickel catalyst being prepared by the method described in any of the exemplary embodiments above.

[0019] The exemplary embodiment of this disclosure discloses a method for preparing an ammonia decomposition catalyst. Using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid, and nitric acid as raw materials, a self-propagating combustion synthesis is employed to obtain a La₂Ce₂O₇ support. A supported cobalt-nickel catalyst is then prepared by impregnation of the La₂Ce₂O₇ support using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials. This preparation method combines a self-propagating high-temperature combustion method to prepare the support, and then uses an impregnation method combined with hydrogen reduction to deposit the active metal onto the support, synthesizing a supported cobalt-nickel (CoxNiy / La₂Ce₂O₇) catalyst. This catalyst uses defective fluorite-structured lanthanum cerate La₂Ce₂O₇ as a multifunctional support and a cobalt-nickel alloy as the active center. Through the strong interaction between the La₂Ce₂O₇ support and cobalt-nickel, the electronic structure and adsorption characteristics of the active sites are adjusted, thereby lowering the energy barrier of the ammonia decomposition reaction. This provides a highly efficient non-precious metal catalyst, which is beneficial for on-site hydrogen production, achieving excellent ammonia decomposition reaction performance and long-term operational stability, thus promoting industrial applications.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0022] Figure 1 The flowchart illustrates a method for preparing an ammonia decomposition catalyst according to an embodiment of the present disclosure.

[0023] Figure 2 The diagram illustrates a process for synthesizing a catalyst according to an embodiment of the present disclosure.

[0024] Figure 3 This diagram schematically illustrates the temperature-dependent activity of a CoxNiy / La2Ce2O7 catalyst according to an embodiment of the present disclosure.

[0025] Figure 4 This diagram illustrates the effect of CoNi loading on catalyst performance according to an embodiment of the present disclosure.

[0026] Figure 5 The schematic diagram illustrates the hydrogen production rate of a Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of the present disclosure at different temperatures.

[0027] Figure 6 The diagram illustrates a comparison of the NH3 decomposition efficiency of corresponding catalysts on different oxide supports according to embodiments of the present disclosure.

[0028] Figure 7 The diagram illustrates a comparison of reaction rates at different temperatures according to an embodiment of the present disclosure.

[0029] Figure 8 An Arrhenius diagram of an activation energy according to an embodiment of the present disclosure is shown schematically.

[0030] Figure 9 The illustration shows a comparison of mass spectrometry signals of the outlet gas of a CoNi alloy catalyst on different supports according to an embodiment of the present disclosure.

[0031] Figure 10 The diagram illustrates a stability test of a catalyst according to an embodiment of the present disclosure.

[0032] Figure 11 This schematic diagram illustrates an embodiment of the present disclosure of characterizing the crystal structure of a catalyst by XRD detection.

[0033] Figure 12 The illustration schematically shows a high-angle dark-field scanning transmission electron microscope (HAADF-STEM) combined with energy dispersive spectroscopy elemental imaging distribution according to an embodiment of the present disclosure.

[0034] Figure 13 The illustration schematically shows a high-resolution transmission electron microscope (HR-TEM) image according to an embodiment of the present disclosure.

[0035] Figure 14 The schematic diagram illustrates a high-resolution transmission electron microscope image of an embodiment of the present disclosure, showing a schematic structural diagram of a Co1Ni2La2Ce2O7 catalyst.

[0036] Figure 15 The schematic diagram illustrates a high-resolution transmission electron microscope image of another embodiment of the present disclosure, showing a schematic structural diagram of the Co1Ni2 / La2Ce2O7 catalyst.

[0037] Figure 16 An H2-TPR curve diagram of an embodiment of the present disclosure is illustrated schematically.

[0038] Figure 17 A schematic diagram illustrating a CO2 temperature-controlled desorption (CO2-TPD) according to an embodiment of the present disclosure is shown.

[0039] Figure 18 The diagram schematically illustrates a hydrogen temperature-programmed desorption (H2-TPD) diagram according to an embodiment of the present disclosure.

[0040] Figure 19 The diagram illustrates a temperature-controlled desorption (NH3-TPD) curve of ammonia from an embodiment of this disclosure (with different supported catalysts).

[0041] Figure 20 The first XPS spectrum of the Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of the present disclosure is shown schematically.

[0042] Figure 21 The XPS spectrum of the second Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of the present disclosure is shown schematically.

[0043] Figure 22 The XPS spectrum of the third Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of this disclosure is shown schematically.

[0044] Figure 23 The XPS spectrum of the fourth Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of this disclosure is shown schematically.

[0045] Figure 24 The diagram illustrates an ammonia decomposition reaction on a Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of the present disclosure.

[0046] Figure 25 The diagram schematically illustrates the in-situ diffuse reflectance Fourier transform infrared (DRIFT) spectrum of a Co1Ni2 / La2Ce2O7 catalyst according to an embodiment of the present disclosure.

[0047] Figure 26 The diagram illustrates the electronic structure and reaction mechanism of a catalyst according to an embodiment of the present disclosure.

[0048] Figure 27 The schematic diagram illustrates the PDOS spectra of Ni and Co 3d orbitals of two catalysts according to embodiments of the present disclosure.

[0049] Figure 28 The diagram illustrates the PDOS distribution of a nitrogen-adsorbed Co1Ni2 / La2Ce2O7 and Co1Ni2 / CeO2 catalyst according to an embodiment of the present disclosure.

[0050] Figure 29 The diagram illustrates a crystal orbital Hamiltonian particle analysis of Co-N and Ni-N bonds according to an embodiment of the present disclosure.

[0051] Figure 30 The diagram illustrates a free energy curve of N2 generation according to an embodiment of the present disclosure. Detailed Implementation

[0052] The following specific embodiments illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification.

[0053] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0054] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the presence of other method steps before or after the combined steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this disclosure does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present disclosure.

[0055] The continued growth in energy demand and increasingly stringent environmental protection requirements are jointly driving the exploration and development of new clean energy sources. Hydrogen energy has attracted much attention due to its high energy density and low carbon footprint. However, its large-scale industrial application faces multiple challenges, including low volumetric energy density, high storage costs, and safety hazards during operation and transportation. An effective strategy to address these issues is to use easily transportable hydrogen carriers to achieve efficient hydrogen transportation and storage, while simultaneously developing on-site hydrogen production technologies to decompose hydrogen storage carriers to obtain hydrogen gas. Ammonia has become a highly promising carbon-free hydrogen carrier due to its high hydrogen storage density, ease of liquefaction and storage under mild conditions, and advanced transportation technologies. However, ammonia decomposition is an endothermic reaction, requiring extremely high temperatures (>1100 ℃) to achieve complete thermodynamic conversion, resulting in huge energy consumption and potential safety hazards. Therefore, to expand the large-scale application of ammonia as a hydrogen carrier, it is necessary to develop efficient catalysts to reduce the reaction activation energy and achieve efficient ammonia decomposition under medium and low temperature conditions.

[0056] However, while noble metal catalysts, such as ruthenium, exhibit superior ammonia decomposition activity and stability at lower temperatures, their high cost limits their industrial application. Non-noble metal catalysts based on iron, cobalt, or nickel have significantly lower costs, but their low-temperature activity and durability are generally inferior to those of noble metals.

[0057] Based on this, this disclosure provides a method for preparing an ammonia decomposition catalyst, resulting in a supported bimetallic catalyst using defective La₂Ce₂O₇ as a multifunctional support and Co and Ni as active centers. The unique mixed conductivity and abundant oxygen vacancies of this defective fluorite-structured lanthanum cerate support enable deep electronic modulation of the active metal, thereby optimizing reaction kinetics and making it an ideal material for efficient and stable ammonia decomposition catalysts.

[0058] It should be noted that the preparation method of the ammonia decomposition catalyst disclosed herein can be applied to catalyst preparation in fields such as energy chemical engineering, syngas production, and hydrogen source systems. For example, in the ammonia-hydrogen green energy cycle, the catalyst prepared by this method is key to realizing the conversion of ammonia to hydrogen energy, especially beneficial for on-site hydrogen production and promoting industrial applications. This disclosure does not impose any special limitations on the application scenarios of the preparation method.

[0059] like Figure 1 As shown, the preparation method of the ammonia decomposition catalyst disclosed herein may include: Step S110: Using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid and nitric acid as raw materials, a self-propagating combustion synthesis was used to obtain the La2Ce2O7 support.

[0060] Step S120: Using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone and ethanol as raw materials, a supported cobalt-nickel catalyst is prepared on the La2Ce2O7 support by impregnation method.

[0061] This disclosure combines the preparation of defect-rich supports by combustion synthesis with the impregnation method assisted by organic additives to achieve highly dispersed loading, which can solve the problems of insufficient low-temperature activity and easy sintering of active metals in ammonia decomposition catalysts, and realize high activity and high stability of catalysts under mild conditions.

[0062] Steps S110 and S120 will be explained in more detail below.

[0063] In an exemplary embodiment, a La₂Ce₂O₇ support is prepared by self-propagating combustion synthesis using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid, and nitric acid as raw materials, comprising: First, lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O) were dissolved in deionized water to obtain a first nitrate solution. Next, citric acid and nitric acid were added to the first nitrate solution and stirred to obtain a mixture. Finally, the mixture was heated to undergo self-propagating high-temperature combustion synthesis to obtain a first precursor. The first precursor was then ground and calcined to obtain a La2Ce2O7 support.

[0064] Self-propagating high-temperature synthesis (SHS) is a method of synthesizing materials by utilizing the self-heating and self-conduction effects of the high chemical reaction heat between reactants. Once the reaction is locally ignited, the released heat spontaneously triggers reactions in adjacent layers, forming a combustion wave that automatically spreads to unreacted areas until the reaction is complete. Citric acid, acting as a fuel (i.e., a reducing agent), undergoes a vigorous redox reaction with nitrate ions (acting as an oxidant), providing the heat required for self-propagating combustion. Nitric acid provides a strongly acidic pH environment, ensuring that metal ions and citric acid can fully complex to form a stable precursor. The introduction of nitrate ions as an oxidant, matching with citric acid as a reducing agent, constitutes the redox system required for self-propagating combustion. The La₂Ce₂O₇ support possesses a unique defective fluorite structure, adjustable oxygen vacancies and proton / electron conductivity, and can serve as a catalyst support to form a strong synergistic effect with active metals. This can be understood as follows: the structural characteristic of La₂Ce₂O₇ is the presence of a large number of oxygen vacancies in its crystal lattice. These oxygen vacancies facilitate the breaking of NH bonds and the bonding and desorption of nitrogen atoms in the ammonia decomposition reaction, thereby improving catalytic efficiency. This will be explained in detail in the subsequent discussion of the catalyst's mechanism of action.

[0065] Optionally, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate can be dissolved in deionized water according to stoichiometric ratio to obtain a first nitrate solution.

[0066] In this process, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate were dissolved in deionized water at a stoichiometric ratio (La:Ce = 1:1) to obtain a product containing La. 3+ and Ce 4+ A homogeneous, transparent aqueous solution of metal ions.

[0067] Then, citric acid and nitric acid can be added to the first nitrate solution and mixed thoroughly by magnetic stirring to obtain a mixture.

[0068] Optionally, nitric acid and citric acid are added sequentially to the first nitrate solution and stirred to obtain a mixture, with the molar ratio of metal ions:citric acid:HNO3 being 1:(1~1.5):(1~1.5). Specifically, the molar ratio of metal ions:citric acid:HNO3 can be 1:1:1 or 1:1.5:1.5. Preferably, the molar ratio of metal ions:citric acid:HNO3 is 1:1.5:1.5.

[0069] Based on this, the pH value can be adjusted to a suitable range by adjusting the molar ratio of the three components to promote the full complexation of citric acid and metal ions. The appropriate molar ratio can be selected according to the actual required pH value.

[0070] In practice, during the self-propagating high-temperature combustion synthesis stage, the mixture can be placed on a heating device and continuously heated to evaporate moisture. As the moisture decreases, the solution becomes viscous, forming a sol or gel. When the temperature reaches the ignition point, the gel undergoes a violent self-propagating combustion reaction, producing a bright flame and a large amount of gas, rapidly expanding to form a fluffy precursor, i.e., the first precursor. During this process, nitrate (oxidant) and citric acid (reducing agent) undergo a violent redox reaction, instantly releasing a large amount of heat, enabling the synthesis reaction to be self-sustaining and completed rapidly.

[0071] Optionally, the mixture may be heated to 300-350 °C until it spontaneously combusts and undergoes self-propagating high-temperature combustion synthesis, for example, to 300 °C, 320 °C, or 350 °C.

[0072] Optionally, the first precursor after grinding is calcined at a temperature of 750~800 ℃ for a time of 4.5~6 hours. For example, after grinding, it is calcined at 750 ℃, 780 ℃ or 800 ℃ for 4.5 hours, 5 hours or 6 hours.

[0073] In practice, the first precursor powder obtained after combustion is ground and then calcined at 800 °C to remove residual carbon components and improve the crystal structure, ultimately obtaining pure La2Ce2O7 carrier powder.

[0074] This embodiment achieves a molecular-level uniform distribution of La and Ce elements by complexing citric acid with metal ions in the liquid phase. The subsequent self-propagating combustion process is completed instantaneously, avoiding the component segregation caused by slow atomic diffusion in traditional solid-state sintering methods. Combined with subsequent calcination, a pure-phase La2Ce2O7 support can be obtained at a relatively low temperature.

[0075] Optionally, a supported cobalt-nickel catalyst is prepared by impregnation of a La₂Ce₂O₇ support using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials, including: First, according to the target ratio, nickel nitrate hexahydrate and cobalt nitrate hexahydrate were dissolved in deionized water to obtain a second nitrate solution. Second, glycine, polyvinylpyrrolidone, and ethanol were added to the second nitrate solution while stirring to obtain a homogeneous solution. Finally, the La₂Ce₂O₇ support was added to the homogeneous solution and stirred to obtain a mixed solution. The mixed solution was then heated to complete combustion to obtain a second precursor. The second precursor was ground and calcined to obtain a supported cobalt-nickel catalyst.

[0076] The target ratio is determined by the mass ratio of cobalt to nickel in the supported cobalt-nickel catalyst to be prepared. Glycine molecules contain amino (-NH2) and carboxyl (-COOH) groups, which can react with Ni in solution.2+ and Co 2+ Ions form stable complexes. This complexation fixes metal ions at the molecular level, preventing migration or segregation due to solubility differences during impregnation and drying, ensuring uniform distribution of the active component on the carrier surface. In the subsequent heating and combustion step, glycine acts as a reducing agent, undergoing a vigorous redox reaction with nitrate ions provided by nitrate (i.e., glycine-nitrate combustion). This reaction releases a large amount of heat instantaneously, helping the active component to disperse in situ on the carrier surface and form nanoscale particles. In the impregnation solution, polyvinylpyrrolidone (PVP) effectively prevents the aggregation of metal ions or colloidal metal particles through steric hindrance, keeping the solution uniform and stable. It can also selectively adsorb onto specific crystal faces, regulating the nucleation and growth process of metal nanoparticles, which helps form uniformly sized and morphologically controllable nanoscale metal particles. During the subsequent calcination process, the carbon skeleton or residues produced by the decomposition of PPV can isolate the metal particles to a certain extent, inhibiting their migration and sintering at high temperatures, and maintaining the high dispersibility of the active component. Adding ethanol to the impregnation solution can significantly reduce the surface tension of the solution and improve the wettability and permeability of the solution inside and outside the pores of the La2Ce2O7 support. This makes it easier for the active component precursor to enter the deep pore structure of the support and achieve uniform loading on the inner surface. Therefore, this disclosure can further improve the rheological properties of the impregnation system and promote uniform impregnation by using ethanol and polyvinylpyrrolidone together.

[0077] Optionally, effective amounts of glycine, polyvinylpyrrolidone, and anhydrous ethanol are added to form a homogeneous solution suitable for impregnation. The amount added can be determined based on the actual formation of a homogeneous solution to ensure the formation of a suitable homogeneous solution for impregnation. For example, the molar ratio of glycine to the total metal ions in the second nitrate solution is (0.5~2):1, the amount of polyvinylpyrrolidone added is 1%~10% of the total mass of the metal salt, and the volume ratio of anhydrous ethanol added to deionized water is (0.5~2):1. This disclosure includes, but is not limited to, these addition ratios.

[0078] Optionally, the La2Ce2O7 support is added to the homogeneous solution and stirred at room temperature for 20 to 24 hours to obtain a mixed solution. For example, stirring for 20 hours, 22 hours, or 24 hours can be selected according to the actual stirring conditions.

[0079] Optionally, the mixed solution is heated to 300-350 °C until complete combustion is achieved to obtain the second precursor. For example, it is heated to 300 °C, 320 °C, or 350 °C.

[0080] Optionally, the second precursor is ground and then calcined at 550-600 °C for 4.5-5.5 hours to obtain a supported cobalt-nickel catalyst. For example, after grinding, it is calcined at 550 °C or 600 °C for, for example, 4.5 hours, 5 hours or 5.5 hours.

[0081] In practical implementation, during the impregnation and loading stage, the La2Ce2O7 support powder prepared according to the aforementioned examples can be weighed and slowly added to the homogeneous solution, with continuous stirring to form a mixed solution. The stirring time can be 20-24 hours to ensure thorough impregnation. The container containing the mixed solution is then transferred to a heating device and heated gradually. As water and ethanol evaporate, the mixed solution gradually concentrates and becomes viscous. When the temperature reaches the ignition point of the glycine-nitrate system, a self-propagating combustion reaction occurs, generating a flame and releasing a large amount of gas, yielding a fluffy second precursor powder. Furthermore, the burned second precursor can be ground uniformly and placed in a muffle furnace for calcination in a reducing atmosphere or an inert atmosphere / air (determined according to the target active phase) to fully reduce the metal precursor to a metallic CoNi alloy, while removing residual organic matter, ultimately obtaining a La2Ce2O7-supported cobalt-nickel bimetallic catalyst. Its cobalt-nickel mass ratio is denoted as CoxNiy, where x and y represent the mass fractions of cobalt and nickel, respectively.

[0082] This disclosure achieves precise control over the dispersion, particle size, alloying degree, and interfacial interactions of CoNi active components on the La2Ce2O7 support through the synergistic effect of glycine's complexing and combustion functions, PVP's dispersing and stabilizing effects, and ethanol's wetting function, combined with self-propagating combustion synthesis. This provides a key guarantee for obtaining high-performance ammonia decomposition catalysts.

[0083] Optionally, the main components of the prepared supported cobalt-nickel catalyst include Co, Ni and La2Ce2O7; wherein the mass ratio of cobalt to nickel in the supported cobalt-nickel catalyst is 1:(0.5~2), and the total loading of cobalt and nickel in the supported cobalt-nickel catalyst is 20~40 wt%.

[0084] For example, the mass ratio of cobalt to nickel in supported cobalt-nickel catalysts is 1:1, 2:1, or 1:2. The total cobalt and nickel loading of the supported cobalt-nickel catalyst is 20-40 wt%, for example, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0085] Optionally, the hydrogen evolution temperature of the prepared supported cobalt-nickel catalyst is 310~575 °C.

[0086] Optionally, the prepared supported cobalt-nickel catalyst has corresponding alkaline sites at 100~200 ℃, 200~400 ℃ and 600~700 ℃ respectively.

[0087] In this context, a basic site refers to a location on the catalyst surface that can donate electron pairs to adsorbed molecules or accept protons. For ammonia decomposition, basic sites facilitate the adsorption and activation of ammonia and promote the binding and desorption of nitrogen atoms. In TPD (Temperature-Programmed Desorption) experiments, the temperature position of the desorption peak directly reflects the intensity of the site. Low-temperature desorption peaks (100–200 °C) correspond to weakly basic sites, medium-temperature desorption peaks (200–400 °C) correspond to moderately strong basic sites, and high-temperature desorption peaks (600–700 °C) correspond to strongly basic sites. Higher desorption temperatures indicate stronger interactions between the site and the adsorbed molecules. The catalyst prepared in this disclosure exhibits a gradient distribution of weak, moderate, and strong basic sites. This balanced basicity distribution ensures the efficient and continuous advancement of the catalytic cycle and is key to achieving high activity. This will be explained in detail in the subsequent mechanism description.

[0088] In one exemplary embodiment, a supported cobalt-nickel catalyst for ammonia decomposition prepared by the preparation method of any of the above embodiments is also provided. The main components of the supported cobalt-nickel catalyst include Co, Ni and La2Ce2O7; wherein the mass ratio of cobalt to nickel in the supported cobalt-nickel catalyst is 1:(1.5~2), and the total cobalt and nickel loading of the supported cobalt-nickel catalyst is 20~40 wt%.

[0089] In one exemplary embodiment, an application of the supported cobalt-nickel catalyst described above in ammonia decomposition is also provided. This catalyst utilizes a defective fluorite-structured La₂Ce₂O₇ as a multifunctional support and bimetallic cobalt-nickel as the active center. Through strong interaction between the La₂Ce₂O₇ support and cobalt-nickel, the electronic structure and adsorption characteristics of the active sites are adjusted, thereby lowering the energy barrier of the ammonia decomposition reaction. This provides a highly efficient non-precious metal catalyst, which is beneficial for on-site hydrogen production, achieving excellent ammonia decomposition reaction performance and long-term operational stability, thus promoting industrial applications.

[0090] The scheme and mechanism of this disclosure will be specifically described below through specific embodiments.

[0091] Example 1

[0092] 1) La2Ce2O7 support was prepared by self-propagating high-temperature combustion method.

[0093] 0.1 mol of La(NO3)3·6H2O and 0.1 mol of Ce(NO3)3·6H2O were dissolved in 200 ml of deionized water to obtain a first nitrate solution. Nitric acid and citric acid were added sequentially with continuous stirring, controlling the molar ratio of metal ions:citric acid:HNO3 to be 1:1.5:1.5. After thorough stirring, the mixture was placed on a heating device (e.g., an electric furnace) and heated continuously to 300–350 °C (preferably 320 °C) until spontaneous combustion, generating an expanded first precursor. The first precursor was ground into a fine powder and calcined at 750–800 °C (preferably 800 °C) for 5 hours, followed by furnace cooling to obtain the La2Ce2O7 support. The fine powder can be placed in a muffle furnace during calcination.

[0094] 2) Prepared supported CoNi catalyst by impregnation method.

[0095] Weigh out (Ni(NO3)2·6H2O) and (Co(NO3)2·6H2O) according to a cobalt to nickel mass ratio of 1:2. Specifically, weigh out a certain mass of Ni(NO3)2·6H2O and Co(NO3)2·6H2O, such that the mass ratio of metallic Ni to metallic Co is 2:1 (i.e., cobalt:nickel = 1:2). Dissolve the weighed nitrate in 20 mL of deionized water and stir until completely dissolved to obtain a second nitrate solution. Under continuous stirring, add an effective amount of glycine, polyvinylpyrrolidone, and anhydrous ethanol to the above second nitrate solution to form a homogeneous solution suitable for impregnation, i.e., a homogeneous and clear impregnation solution.

[0096] Weigh 5 g of the La2Ce2O7 support prepared according to step 1) and slowly add it to the above impregnation solution, stirring continuously for 24 hours to form a mixed solution. Transfer the container containing the mixed solution to a hot plate and heat to 300-350 °C (preferably 320 °C) until complete combustion. As the solvent evaporates, the solution gradually concentrates and becomes viscous, followed by a self-propagating combustion reaction, generating a flame and releasing gas, yielding a fluffy second precursor. Then, grind the second precursor evenly and calcine it to 550-600 °C (preferably 600 °C) for 5 hours. After cooling, the La2Ce2O7-supported cobalt-nickel bimetallic catalyst Co1Ni2 / La2Ce2O7 is obtained, where the mass ratio of Co to Ni is 1:2. During calcination, the ground second precursor can be placed in a tube furnace. For detailed preparation procedures, please refer to [link to relevant documentation]. Figure 2 The diagram shows a process for catalyst synthesis.

[0097] Example 2

[0098] 1) The La₂Ce₂O₇ support was prepared using a self-propagating high-temperature combustion method. 0.1 mol of La(NO₃)₃·6H₂O and 0.1 mol of Ce(NO₃)₃·6H₂O were dissolved in 200 ml of deionized water to obtain a first nitrate solution. Nitric acid and citric acid were added sequentially with continuous stirring, controlling the molar ratio of metal ions:citric acid:HNO₃ to 1:1.5:1.5. After thorough stirring, the mixture was placed on a heating device (e.g., an electric furnace) and continuously heated to 300–350 °C (preferably 320 °C) until spontaneous combustion, generating an expanded first precursor. The first precursor was ground into a fine powder and calcined at 750–800 °C (preferably 800 °C) for 5 hours, followed by furnace cooling to obtain the La₂Ce₂O₇ support. The fine powder could be placed in a muffle furnace during calcination.

[0099] 2) Preparation of supported CoNi catalyst by impregnation method. Ni(NO3)2·6H2O and Co(NO3)2·6H2O were weighed according to a cobalt to nickel mass ratio of 1:1. Specifically, a certain mass of Ni(NO3)2·6H2O and Co(NO3)2·6H2O was weighed so that the mass ratio of metallic Ni to metallic Co was 1:1 (i.e., cobalt:nickel = 1:1). The weighed nitrate was dissolved in 20 mL of deionized water and stirred until completely dissolved to obtain a second nitrate solution. Under continuous stirring, effective amounts of glycine, polyvinylpyrrolidone, and anhydrous ethanol were added to the above second nitrate solution to form a homogeneous solution suitable for impregnation, i.e., a homogeneous and clear impregnation solution.

[0100] Weigh 5 g of the La2Ce2O7 support prepared according to step 1) and slowly add it to the above impregnation solution, stirring continuously for 24 hours to form a homogeneous mixed solution. Transfer the container containing the mixed solution to a hot plate and heat to 300~350 ℃ (preferably 320 ℃) ​​until complete combustion. As the solvent evaporates, the solution gradually concentrates and becomes viscous, followed by a self-propagating combustion reaction, generating a flame and releasing gas to obtain a fluffy second precursor. Then, grind the second precursor evenly and place it in a tube furnace, heating to 550~600 ℃ (preferably 600 ℃) for calcination for 5 hours. After cooling, the La2Ce2O7-supported cobalt-nickel bimetallic catalyst CoNi / La2Ce2O7 is obtained, wherein the mass ratio of Co to Ni is 1:1.

[0101] Example 3

[0102] 1) The La₂Ce₂O₇ support was prepared using a self-propagating high-temperature combustion method. 0.1 mol of La(NO₃)₃·6H₂O and 0.1 mol of Ce(NO₃)₃·6H₂O were dissolved in 200 ml of deionized water to obtain a first nitrate solution. Nitric acid and citric acid were added sequentially with continuous stirring, controlling the molar ratio of metal ions:citric acid:HNO₃ to 1:1.5:1.5. After thorough stirring, the mixture was placed on a heating device (e.g., an electric furnace) and continuously heated to 300–350 °C (preferably 320 °C) until spontaneous combustion, generating an expanded first precursor. The first precursor was ground into a fine powder and calcined at 750–800 °C (preferably 800 °C) for 5 hours, followed by furnace cooling to obtain the La₂Ce₂O₇ support. The fine powder could be placed in a muffle furnace during calcination.

[0103] 2) Preparation of supported CoNi catalyst by impregnation method. Ni(NO3)2·6H2O and Co(NO3)2·6H2O were weighed according to a cobalt to nickel mass ratio of 2:1. Specifically, a certain mass of Ni(NO3)2·6H2O and Co(NO3)2·6H2O was weighed so that the mass ratio of metallic Ni to metallic Co was 1:2 (i.e., cobalt:nickel = 2:1). The weighed nitrate was dissolved in 20 mL of deionized water and stirred until completely dissolved to obtain a second nitrate solution. Under continuous stirring, effective amounts of glycine, polyvinylpyrrolidone, and anhydrous ethanol were added to the above second nitrate solution to form a homogeneous solution suitable for impregnation, i.e., a homogeneous and clear impregnation solution.

[0104] Weigh 5 g of the La2Ce2O7 support prepared according to step 1) and slowly add it to the above impregnation solution, stirring continuously for 24 hours to form a homogeneous mixed solution. Transfer the container containing the mixed solution to a hot plate and heat to 300~350 ℃ (preferably 320 ℃) ​​until complete combustion. As the solvent evaporates, the solution gradually concentrates and becomes viscous, followed by a self-propagating combustion reaction, generating a flame and releasing gas to obtain a fluffy second precursor. Then, grind the second precursor evenly and place it in a tube furnace, heating it to 550~600 ℃ (preferably 600 ℃) for calcination for 5 hours. After cooling, the La2Ce2O7-supported cobalt-nickel bimetallic catalyst Co2Ni1 / La2Ce2O7 is obtained, wherein the mass ratio of Co to Ni is 2:1.

[0105] Comparative Example 1

[0106] 1) The La₂Ce₂O₇ support was prepared using a self-propagating high-temperature combustion method. 0.1 mol of La(NO₃)₃·6H₂O and 0.1 mol of Ce(NO₃)₃·6H₂O were dissolved in 200 ml of deionized water to obtain a first nitrate solution. Nitric acid and citric acid were added sequentially with continuous stirring, controlling the molar ratio of metal ions:citric acid:HNO₃ to 1:1.5:1.5. After thorough stirring, the mixture was placed on a heating device (e.g., an electric furnace) and continuously heated to 300–350 °C (preferably 320 °C) until spontaneous combustion, generating an expanded first precursor. The first precursor was ground into a fine powder and calcined at 750–800 °C (preferably 800 °C) for 5 hours, followed by furnace cooling to obtain the La₂Ce₂O₇ support. The fine powder could be placed in a muffle furnace during calcination.

[0107] 2) Preparation of supported Ni catalyst by impregnation method. A certain mass of (Ni(NO3)2·6H2O) was weighed, such that the amount of metallic Ni was the same as that of metallic Ni+Co in Examples 1 to 3 above. The weighed nitrate was dissolved in 20 mL of deionized water and stirred until completely dissolved to obtain a second nitrate solution. Under continuous stirring, effective amounts of glycine, polyvinylpyrrolidone, and anhydrous ethanol were added to the above second nitrate solution to form a homogeneous solution suitable for impregnation, i.e., a homogeneous and clear impregnation solution.

[0108] Weigh 5 g of the La2Ce2O7 support prepared according to step 1) and slowly add it to the above impregnation solution, stirring continuously for 24 hours to form a homogeneous mixed solution. Transfer the container containing the mixed solution to a hot plate and heat to 300-350 °C (preferably 320 °C) until complete combustion. As the solvent evaporates, the solution gradually concentrates and becomes viscous, followed by a self-propagating combustion reaction, generating a flame and releasing gas to obtain a fluffy second precursor. Then, grind the second precursor evenly and place it in a tube furnace, heating to 550-600 °C (preferably 600 °C) for calcination for 5 hours. After cooling, the Ni / La2Ce2O7 nickel catalyst supported on La2Ce2O7 is obtained.

[0109] Comparative Example 2

[0110] 1) The La₂Ce₂O₇ support was prepared using a self-propagating high-temperature combustion method. 0.1 mol of La(NO₃)₃·6H₂O and 0.1 mol of Ce(NO₃)₃·6H₂O were dissolved in 200 ml of deionized water to obtain a first nitrate solution. Nitric acid and citric acid were added sequentially with continuous stirring, controlling the molar ratio of metal ions:citric acid:HNO₃ to 1:1.5:1.5. After thorough stirring, the mixture was placed on a heating device (e.g., an electric furnace) and continuously heated to 300–350 °C (preferably 320 °C) until spontaneous combustion, generating an expanded first precursor. The first precursor was ground into a fine powder and calcined at 750–800 °C (preferably 800 °C) for 5 hours, followed by furnace cooling to obtain the La₂Ce₂O₇ support. The fine powder could be placed in a muffle furnace during calcination.

[0111] 2) Preparation of supported Co catalyst by impregnation method. A certain mass of Co(NO3)2·6H2O was weighed, such that the amount of metallic Co was the same as that of metallic Ni+Co in Examples 1 to 3 above. The weighed nitrate was dissolved in 20 mL of deionized water and stirred until completely dissolved to obtain a second nitrate solution. Under continuous stirring, effective amounts of glycine, polyvinylpyrrolidone, and anhydrous ethanol were added to the above second nitrate solution to form a homogeneous solution suitable for impregnation, i.e., a homogeneous and clear impregnation solution.

[0112] Weigh 5 g of the La2Ce2O7 support prepared according to step 1) and slowly add it to the above impregnation solution, stirring continuously for 24 hours to form a homogeneous mixed solution. Transfer the container containing the mixed solution to a hot plate and heat to 300-350 °C (preferably 320 °C) until complete combustion. As the solvent evaporates, the solution gradually concentrates and becomes viscous, subsequently undergoing a self-propagating combustion reaction, generating a flame and releasing gas to obtain a fluffy second precursor. Then, grind the second precursor evenly and place it in a tube furnace, heating it to 550-600 °C (preferably 600 °C) for calcination for 5 hours. After cooling, the La2Ce2O7-supported cobalt catalyst Co / La2Ce2O7 is obtained.

[0113] The catalytic activity of ammonia decomposition was evaluated in a fixed-bed reactor. Prior to the reaction, the catalysts prepared in Examples 1 to 3, and Comparative Examples 1 and 2, were activated for 1 hour in a hydrogen stream at 600 °C. Subsequently, the feed gas was switched to pure ammonia, and ammonia conversion was measured in 50 °C increments within the range of 450 to 650 °C. Figure 3 The figure shows the temperature-dependent activity (GHSV, Gas Hourly Space Velocity) of the CoxNiy / La2Ce2O7 catalyst (30,000). A schematic diagram of ( ). (From) Figure 3It is evident that, under the same total active metal loading, the CoNi bimetallic catalyst supported on the La2Ce2O7 support consistently exhibits a higher ammonia conversion rate than single-metal Co or Ni catalysts. This improvement stems from the synergistic effect of the CoNi bimetallic system, which alters the MN bond energy and enhances catalytic activity. Among the tested CoNi bimetallic catalysts, the one with the highest activity has a CoNi mass ratio of 1:2.

[0114] Comparative Examples 3 to 7, with the CoNi mass ratio fixed at 1:2, adjusted the total CoNi loading on the support to 20 wt%, 25 wt%, 30 wt%, 35 wt%, and 40 wt%, respectively. Other experimental procedures were the same as in Example 1. Figure 4 The diagram illustrates the effect of CoNi loading on catalyst performance. As the loading increases, the ammonia conversion exhibits a volcano-shaped curve, peaking at a loading of 30 wt%. At 550 °C, when the catalyst space velocity reaches 30,000... At a lower loading, the conversion rate reached 97.7%. Increasing the metal content at lower loading levels can increase the number of active sites, meaning more metal nanoparticles provide sites for ammonia adsorption and NH bond breaking, thus accelerating the reaction process. However, when the loading exceeds the ideal value, the limited anchoring sites on the support surface lead to intensified migration and aggregation of the metal precursor during calcination reduction, forming larger metal particles. This results in reduced specific surface area and dispersibility, ultimately decreasing the number of accessible active sites. Furthermore, excessive metal layers or overly large particles weaken the metal-support interaction, altering the electronic state of the metal and thus reducing catalytic activity.

[0115] Furthermore, the ammonia decomposition performance of the Co1Ni2 / La2Ce2O7 catalyst with an active metal loading of 30 wt% was investigated by adjusting the reaction temperature and the GHSV of the ammonia feed. Figure 5 The diagram shows the hydrogen production rate of the Co1Ni2 / La2Ce2O7 catalyst at different temperatures, as the GHSV increases from 6000 to 60000. At relatively low temperatures, ammonia conversion rate decreases. At higher GHSV levels, hydrogen production rate exhibits a decreasing growth trend, eventually stabilizing. Conversely, its growth rate is faster at higher temperatures. Notably, at 600 °C, hydrogen production rate increases almost linearly with increasing GHSV, reaching a peak when GHSV reaches 60,000 °C. It reached 66.78 at that time. Under the same conditions, the rate at 550 °C is 61.49. .

[0116] To further illustrate the role of the La2Ce2O7 support in catalytic performance, the following comparative analysis was conducted.

[0117] Comparative Example 8

[0118] Compared to Example 1, La₂O₃ and CeO₂ support powders were prepared using the same process as a control group, except that the calcination conditions were adjusted to 700 °C for 4 hours. The obtained La₂O₃ and CeO₂ supports were then used to prepare supported Co, Ni, and CoNi catalysts using the same impregnation method as in Example 1. This can be understood as because La₂Ce₂O₇ can be structurally characterized as a CeO₂ lattice with a large amount of La... 3+ The defective fluoride solid solution was formed, so Co1Ni2 / CeO2 and Co1Ni2 / La2O3 catalysts with the same CoNi mass ratio and total metal loading were prepared for comparison and illustration.

[0119] like Figure 6 The figure shows a comparison of the NH3 decomposition efficiency of the corresponding catalysts on different oxide supports. Figure 7 A comparison of reaction rates at different temperatures (GHSV=30000) ). Combination Figure 6 and Figure 7 Within the temperature range of 450–550 °C, the Co1Ni2 / La2Ce2O7 catalyst consistently outperformed the CeO2 and La2O3 supported catalysts in terms of ammonia conversion and hydrogen generation rate. Figure 8 The figure shows the Arrhenius plot of the activation energy. The apparent activation energy of the ADR (Ammonia Decomposition Reaction) catalyst was calculated using the Arrhenius plots of the H2 generation rate at different temperatures. The results show that the Co1Ni2 / La2Ce2O7 catalyst has the lowest activation energy in the test system. Figure 9 The figure shows a comparison of the mass spectrometry signals of the outlet gases (NH3, N2, H2) of CoNi alloy catalysts on different supports. As can be seen, the Co1Ni2 / La2Ce2O7 catalyst exhibits the lowest hydrogen evolution onset temperature (310 °C). With increasing temperature, the MS signals of NH3, N2, and H2 gradually stabilize, reaching a plateau at 575 °C, indicating complete ammonia decomposition. The signals of the catalysts supported by the other two supports only stabilized at 600 °C. This indicates that the La2Ce2O7 support promotes NH bond dissociation and H2 desorption throughout the process. Furthermore, the mass spectrometry signal comparison shows that the desorption temperature of N2 is significantly higher than that of H2, indicating that nitrogen species adsorbed on the catalyst surface have higher binding energies and desorption barriers than hydrogen.

[0120] Furthermore, considering that catalyst stability is a key parameter for practical applications, the present disclosure also includes the following stability tests.

[0121] Example 4

[0122] The prepared Co1Ni2 / La2Ce2O7 catalyst and Co1Ni2 / CeO2 catalyst were placed at 550 °C and subjected to 30,000 [units of temperature / temperature]. Stability tests were conducted using the gas space velocity (GHSV). For example... Figure 10 As shown, after 1000 hours of continuous operation, Co1Ni2 / La2Ce2O7 exhibited better durability, with the NH3 conversion rate decreasing by only 1.7%. In contrast, the Co1Ni2 / CeO2 catalyst deactivated much faster, with the NH3 decomposition rate decreasing by 2.5% after only 150 hours of operation. Furthermore, XRD (X-ray Diffraction) analysis confirmed that the Co1Ni2 / La2Ce2O7 catalyst did not form any new crystalline phases before or after the long-term stability test. Under continuous reaction conditions, both the La2Ce2O7 support and the CoNi alloy exhibited excellent thermal and chemical stability, completely preserving their original crystal structures.

[0123] like Figure 11 The diagram shown illustrates the characterization of the crystal structure of the prepared catalyst using XRD. Figure 11 When CoNi bimetallic species were deposited on three different supports (La₂Ce₂O₇, CeO₂, and La₂O₃), all samples exhibited characteristic diffraction peaks at 44.43° and 51.77°, corresponding to the (111) and (200) crystal planes of the CoNi alloy, respectively. These peak positions closely match those of metallic nickel, showing only a slight low-angle shift. This indicates that the CoNi alloy has a lattice structure similar to nickel, and the peak shift is due to the change in lattice parameters caused by the partial substitution of nickel by cobalt. The average grain size of the CoNi alloy nanoparticles (NPs) was calculated using the Scherer equation. The CoNi nanoparticles supported on the CeO₂ support had a size of 31.6 nm, while those supported on the La₂Ce₂O₇ support shrank significantly to approximately 16 nm. These results indicate a significant correlation between the CoNi nanoparticle size and the support material. The significant reduction in nanoparticle size achieved by La2Ce2O7 enhances catalytic activity and durability through multiple pathways: increasing the number of available active sites, optimizing the electronic structure to promote reactant activation and product desorption, and improving resistance to sintering under reaction conditions.

[0124] like Figure 12Analysis of the Co1Ni2 / La2Ce2O7 catalyst using high-angle dark-field scanning transmission electron microscopy (HAADF-STEM) combined with energy-dispersive X-ray spectroscopy (EDS) elemental imaging confirmed the uniform distribution of La, Ce, and O elements, verifying the formation of the La2Ce2O7 solid solution. Simultaneously, the EDS (Energy Dispersive X-ray Spectroscopy) spectra of Co and Ni showed almost identical spatial distributions and relative intensities, further confirming the formation of the CoNi alloy.

[0125] like Figure 13 The image is a high-resolution transmission electron microscope (HR-TEM) image. As can be seen from the image, the Co1Ni2 / La2Ce2O7 catalyst is composed of uniformly dispersed nanoparticles, which are smaller and more uniform in size than the particles of CeO2 or La2O3 supports. Figure 14 and Figure 15 A schematic diagram of the Co1Ni2 / La2Ce2O7 catalyst structure is shown in high-resolution transmission electron microscopy (TEM) images. All catalysts exhibited lattice fringes with spacings of 0.204 nm and 0.176 nm, corresponding to the (111) and (220) crystal planes of the CoNi alloy, respectively, consistent with XRD results. Furthermore, lattice fringes of 0.321 nm and 0.197 nm were attributed to the (111) and (220) crystal planes of La2Ce2O7, confirming that a phase-pure La2Ce2O7 solid solution was synthesized via combustion, rather than a physical mixture of CeO2 and La2O3.

[0126] Furthermore, considering ammonia as a practical fuel for solid oxide fuel cells (SOFCs), its efficient decomposition is a key upstream process for power generation. To verify the feasibility of on-site hydrogen production, an ammonia cracking reactor equipped with a Co1Ni2 / La2Ce2O7 catalyst was integrated into the SOFC system. The use of catalytic cracking significantly improved the battery power density output, reaching 0.33–1.27 W cm⁻¹ at 600–750 °C. -2 This far exceeds the effect of direct pure NH3 supply (0.17~0.78 Wcm). -2 Its performance is close to that of pure hydrogen (0.24~1.32 W cm⁻¹). -2 These results highlight the promising application of the Co1Ni2 / La2Ce2O7 catalyst in indirect ammonia fuel cell systems.

[0127] To further explain why the catalyst prepared by the method disclosed herein has high catalytic activity in ammonia decomposition, the mechanism of the enhanced activity of the catalyst is explained below.

[0128] To evaluate the metal-support interaction and determine the ideal activation conditions, hydrogen temperature-controlled reduction (H2-TPR) experiments were conducted. Figure 16-25 This is a mechanistic diagram illustrating the structure of the active site and the activation enhancement mechanism. Figure 16 It was found that different reduction peaks existed after deconvolution analysis of the H2-TPR curves. The catalysts based on CeO2 and La2Ce2O7 exhibited a low-temperature peak around 250–260 °C, which can be attributed to Co. 3+ Restored to Co 2+ (Co3O4→CoO). The peak value at approximately 320 °C reflects the presence of Co. 2+ To metal Co 0 The conversion (CoO→Co) is shown. Two other peaks appear near 370 °C and 400 °C, respectively, both attributed to the reduction of NiO species: the former corresponds to large NiO particles with weaker bonding to the support, while the latter corresponds to highly dispersed NiO species with strong bonding to the support. Compared to the CeO2 supported catalyst, the reduction peak of the Co1Ni2 / La2Ce2O7 catalyst is broader and shifted towards higher temperatures. This shift can be explained by the simultaneous reduction of the La2Ce2O7 support itself during the process. (The last sentence appears to be incomplete and possibly refers to a different catalyst.) 4+ To Ce 3+ The broad reduction background associated with the transformation overlaps with the metal reduction peaks. Surface Ce 4+ Partially restored to Ce 3+ Oxygen vacancies are generated, thereby activating the catalyst surface. The increased reduction temperature may also stem from the formation of stable MO-Ce / La bonds, or the partial embedding of Co / Ni ions into the support lattice, hindering the reduction of CoNi species. These characteristics indicate a strong metal-support interaction in the Co1Ni2 / La2Ce2O7 system. In contrast, the H2-TPR curves of the Co1Ni2 / La2O3 catalyst show significant differences. Its low-temperature reduction peak corresponds to the reduction reaction of some Co and Ni oxides, while the high-temperature peak may be related to the hydration of La2O3 to form La(OH)3. The formation of La(OH)3 can encapsulate or strongly interact with metal particles, making the reduction of Co and Ni oxides more difficult compared to inert supports (such as Al2O3 and SiO2), thus requiring a higher reduction temperature. Notably, all three supported catalysts achieved complete reduction at 600 °C, indicating that reduction activation treatment under hydrogen at 600 °C yields the optimally active CoNi catalyst, providing a basis for subsequent ammonia decomposition tests.

[0129] like Figure 17The figure shows the CO2 temperature-controlled desorption (CO2-TPD) curve, which was used to test the basicity of the catalysts. All catalysts supported on La2O3, CeO2, and La2Ce2O7 exhibited desorption peaks in the low-temperature (100–200 °C) and high-temperature (600–700 °C) ranges, corresponding to weakly basic and strongly basic sites, respectively. Furthermore, the catalysts supported on La2O3 and La2Ce2O7 also showed desorption peaks in the mid-temperature range (200–400 °C), attributed to moderately basic sites. These moderately to strongly basic sites are believed to effectively promote electron donation from the support to the active metal, enriching the alloy particles with electrons through electronic effects, thereby promoting nitrogen recombination and desorption, and thus improving catalytic performance. Under high-temperature conditions, the CO2-TPD desorption curve of the Co1Ni2 / CeO2 catalyst showed the largest desorption area, indicating the highest concentration of strongly basic sites. However, this catalyst did not perform better in the ammonia decomposition reaction. This indicates that the improvement in catalytic activity is not always related to an increase in the number of strongly basic sites. One possible explanation is that excessively strong basicity may over-attenuate the NH4+ catalytic activity. x The adsorption capacity of intermediates (x=1,2) reduces the adsorption strength of nitrogen atoms. This may lead to premature desorption of reaction intermediates, hindering the completion of the catalytic cycle and ultimately resulting in reduced activity. Meanwhile, the Co1Ni2 / La2O3 catalyst exhibits extremely strong basicity sites (>700 °C), which may be partly responsible for its lower catalytic activity. In contrast, the Co1Ni2 / La2Ce2O7 catalyst has a gradient distribution of weak, medium, and strong basicity sites. This balanced basicity distribution ensures the efficient and continuous advancement of the catalytic cycle, covering the entire process of reactant adsorption, intermediate conversion, and product desorption, which is key to achieving high activity.

[0130] like Figure 18 The figure shows the hydrogen temperature-programmed desorption (H2-TPD) curve, used to characterize the hydrogen adsorption intensity and desorption behavior on the catalyst surface. All three catalysts exhibit desorption peaks at approximately 175 °C, 265 °C, 330 °C, and 520 °C. The high-temperature peak (>500 °C) originates from the desorption of hydrogen overflowing from the support, while the low-temperature peak is attributed to hydrogen chemisorbed on the CoNi metal sites. Hydrogen atoms generated by the breaking of NH bonds constitute the overflow hydrogen source. These atoms migrate from the active metal sites to the support surface, recombine, and desorb as H2 molecules. In addition to the high-temperature peak, the Co1Ni2 / La2Ce2O7 catalyst also exhibits a significant low-temperature desorption peak with a broad peak area. This indicates that hydrogen generated during ammonia decomposition can easily desorb from the active sites in large quantities. By avoiding blockage of the active sites, the residence time of hydrogen on the catalyst surface is shortened, thereby promoting a sustained ammonia decomposition reaction and improving the overall catalytic activity.

[0131] Figure 19The figure shows the temperature-controlled desorption (TPD) curves of NH3 (with different supported catalysts) for ammonia, used to characterize the surface acidity of the catalysts and the ammonia desorption behavior. Three distinct desorption peaks were identified, corresponding to moderately chemisorbed NH3 (100–200 °C), strongly chemisorbed NH3 (400–500 °C), and very strongly chemisorbed NH3 (>600 °C), respectively. The low-temperature desorption peak (<200 °C) is related to ammonia desorption from Brentster acid sites and Lewis acid sites. Peaks in the 200–350 °C range can be attributed to Brentster acid sites and moderately strong Lewis acid sites, while peaks above 350 °C correspond to NH3 desorbed from strong Lewis acid sites. Due to its high concentration of weak acid sites, the Co1Ni2 / La2Ce2O7 catalyst exhibits the largest low-temperature desorption peak area, resulting in strong ammonia adsorption. This allows NH3 to be efficiently enriched on the catalyst surface, providing sufficient reactants for subsequent reaction stages. Furthermore, weak acid sites promote the initial activation of NH3 and accelerate subsequent reaction processes by lowering the diffusion barrier and weakening NH bonds. Strong acid sites significantly lower the reaction barrier and highly polarize NH bonds, acting as active centers for NH bond breaking, thereby improving reaction efficiency. This catalyst exhibits both high adsorption capacity and high intrinsic activity due to the synergistic effect between weak and strong acid sites. The relatively superior catalytic performance of the Co1Ni2 / La2Ce2O7 catalyst can be attributed to its high adsorption site density and its potential association with Lewis acid sites. The CeO2-supported catalyst exhibits a larger high-temperature peak area, and its NH3-TPD curve characteristics are similar, indicating the presence of more strong acid sites. However, strong adsorption does not necessarily imply significant catalytic activity. Excessive adsorption of NH3 may poison active sites, hindering subsequent reaction steps or product desorption, ultimately leading to reduced catalytic activity.

[0132] like Figure 20-23 The XPS spectrum of the Co1Ni2 / La2Ce2O7 catalyst is shown below. Figure 20 In the reduced Co1Ni2 / La2Ce2O7 catalyst, cerium is present as Ce. 4+ / Ce 3+ The Ce 3d spectrum can be decomposed into ten peaks: the peaks with binding energies of 882.2, 888.9, 898.1, 900.5, 907.3, and 916.1 eV correspond to Ce valence states; 4+ The peaks at 879.4, 885.3, 897.1, and 903.2 eV are attributed to Ce. 3+ This unique Ce 4+ / Ce 3+ Redox pairs are related to the formation of surface oxygen vacancies. For example... Figure 21 The O1s spectrum, after fitting, revealed three components: the 528.9 eV peak corresponds to lattice oxygen (O). LThe 532.7 eV peak is attributed to surface hydroxyl groups (O-OH) formed by adsorbed water, while the 531.2 eV peak is attributed to oxygen vacancies (OV) generated at sites with reduced oxygen coordination numbers. The significant presence of oxygen vacancies in this catalyst may play a crucial role in ammonia decomposition. Figure 22 A double peak at 778.3 eV and 793.9 eV was observed in the Co 2p region, which is attributed to the metallic Co. 0 , and like Figure 23 The analysis of Ni and La is due to La 3d 3 / 2 With Ni 2p 3 / 2 Signal overlap and complexity occur within the composite spectral region, except for those attributed to La. 3+ In addition to the four peaks, the fitted peak at 852.6 eV corresponds to Ni. 0 2p 3 / 2 Notably, no oxidation state of Co or Ni was detected in the reduction catalyst, indicating that metallic Co was not present. 0 and Ni 0 It is a reactive species in the ammonia decomposition reaction. Figure 24 The diagram shows the ammonia decomposition reaction on the Co1Ni2 / La2Ce2O7 catalyst, illustrating the structure of the Co1Ni2 / La2Ce2O7 catalyst and the ammonia decomposition reaction process that occurs on its surface.

[0133] like Figure 25 The image shows the in-situ diffuse reflectance Fourier transform infrared (DRIFT) spectra of the Co1Ni2 / La2Ce2O7 catalyst under an ammonia atmosphere at 250–500 °C. The spectra reveal the species changes during ammonia decomposition at different temperatures, with peak values ​​observed in the 4000–3000 cm⁻¹ region. -1 and 2000~800 cm -1 The spectral regions contain peaks corresponding to ammonia and chemical intermediates adsorbed on the catalyst surface, respectively. Weakly adsorbed NH3 peaks are at 964 and 929 cm⁻¹. -1 The peak values ​​at these locations are reflected in the values ​​at 3333 and 1626 cm⁻¹, while the ammonia adsorbed at Lewis acid sites are represented by values ​​at 3333 and 1626 cm⁻¹. -1 The peak values ​​at these points correspond to the asymmetric bending and stretching vibrations of the NH bond, respectively. The bending vibration mode of -NH starts at 1435 cm⁻¹. -1 The peak value is observed at 1513-1595 cm⁻¹, while the rocking vibration of -NH₂ is observed at 1513-1595 cm⁻¹. -1 and 1077~1114 cm -1 Peak values ​​within the wavenumber range. Among them, 1435 cm⁻¹. -1 The peak value corresponds to the bending mode of -NH, while 1513~1595 cm -1 and 1077~1114 cm -1Peaks within this range correspond to the rocking vibration of -NH2. 3500~3900 cm⁻¹ -1 The peaks within the range are attributed to the OH stretching vibration, indicating that partially dissociated H atoms are adsorbed at the O sites on the support. As the reaction temperature increases, the peak intensities associated with NH3 and -NH2 decrease, while the intensity of the -NH peak increases. This suggests that NH3 and -NH2 undergo a dissociation and dehydrogenation reaction to form the -NH intermediate, indicating that the Co1Ni2 / La2Ce2O7 catalyst possesses strong adsorption strength.

[0134] Furthermore, to characterize the effect of the La2Ce2O7 support on the catalytic performance of the catalyst in the ammonia decomposition reaction, and to simulate the chemical environment of the catalyst active site, Co6Ni-supported catalysts were constructed on the surfaces of La2Ce2O7 (111)-p(4×4) and CeO2 (111)-p(4×4), respectively. 12 Catalyst models supported by metal clusters, such as Figure 26 The diagram shows the electronic structure and reaction mechanism of the catalysts. Baader charge analysis characterized the electronic interactions between the CoNi active metal and the support. The catalysts supported on La2Ce2O7 and CeO2 exhibit significant differences in the electronic states of the CoNi nanoparticles. This is because electron transfer in the Co1Ni2 / CeO2 catalyst mainly occurs from the CoNi nanoparticles towards the CeO2 support. Conversely, the Co1Ni2 / La2Ce2O7 catalyst exhibits the opposite electron transfer direction. This phenomenon is primarily attributed to the inherent oxygen vacancies in La2Ce2O7. When CoNi is supported on an oxygen-vacancy-containing surface, electron enrichment occurs at the active metal center, i.e., metal clusters accumulate charge from the vacancy sites. This indicates that oxygen vacancies enhance the electron density of the active metal by promoting electron transfer from the support to the CoNi alloy. The increased electron density weakens the metal-nitrogen interaction, accelerates nitrogen-associated desorption, and thus drives the entire catalytic process.

[0135] like Figure 27The PDOS (Projected Density of States) spectra of Ni and Co 3d orbitals for two catalysts are shown. The significant peak overlap between Ni and Co 3d orbitals indicates strong electronic coupling between Ni and Co. This coupling helps stabilize the nanocluster structure, preventing sintering or phase separation under reaction conditions, thus maintaining the long-term stability of the catalyst. Although peak overlap is observed in both supports, the overlap peak in the β channel (spin-downward channel) of the Co1Ni2 / La2Ce2O7 catalyst is sharper and higher. This indicates that the La2Ce2O7 support not only promotes CoNi hybridization but also selectively enhances the hybridization intensity and density of states in specific spin directions, thereby inducing a spin-selective synergistic d-band effect. Furthermore, the two catalysts differ in their spin-up / spin-down electron distribution. The La2Ce2O7 supported catalyst exhibits a significant increase in spin splitting energy (e.g., Co increases from 1.77 eV to 2.68 eV), and the d-band centers of the α channel (spin-up) and β channel (spin-down) are reversed. This indicates that the support introduces a strong local exchange field, making the β channel a higher-level occupied state and forming an unconventional spin-electronic configuration. Simultaneously, the energy of the highest occupied state, upon which the catalytic feedback process depends, is maximized. With La₂Ce₂O₇ loading, the most occupied d-band vertex appears in the Co-β channel, with an energy of -0.47 eV, approximately 0.8 eV higher than the similar state on the CeO₂ support (Co-α, -1.29 eV). Therefore, this state is close to the Fermi level, providing a more active electron source for NH bond weakening. Furthermore, this support material induces selective modulation of spin and orbital properties, manifesting as asymmetric orbital renormalization. Especially when the energy of the cobalt β channel is significantly increased while the nickel α channel and its associated orbitals are suppressed, a highly spin-polarized and energy-optimized electron supply pathway is formed. During ammonia decomposition, this unique electronic structure provides an efficient electron feedback source for NH bond breaking and N₂ activation.

[0136] like Figure 28 The PDOS distribution of nitrogen-containing adsorbed Co1Ni2 / La2Ce2O7 and Co1Ni2 / CeO2 catalysts is shown. Compared with CeO2, the La2Ce2O7 support significantly enhances N adsorption. The hybridization strength between the 2p orbitals and the d orbitals of the CoNi alloy. Strong MN hybridization accelerates the dehydrogenation process, providing an efficient pathway for electron feedback to the NH bond, thereby promoting bond weakening and breaking. Ideal MN bond strength is crucial for catalytic performance, as excessively strong MN bonds hinder nitrogen desorption. Therefore, in non-noble metal catalysts, correlated nitrogen desorption is the rate-determining step in ammonia decomposition.

[0137] Figure 29The diagram shows a schematic of the crystal orbital Hamiltonian particle analysis of Co-N and Ni-N bonds. Bond strength and interatomic contact were assessed through crystal orbital Hamiltonian filling analysis. Since the antibonding filling degree of both Co-N and Ni-N bonds in the spin-down channel is lower than that in the spin-up channel, it indicates that the MN bond strength in both catalysts is mainly controlled by the spin-down state. In the Co1Ni2 / La2Ce2O7 catalyst, the MN bond strength is significantly weakened due to the enhanced antibonding characteristics of Co-N and Ni-N bonds near the Fermi level. According to the ICOPHP values, the MN bond in Co1Ni2 / CeO2 is more negative than that in Co1Ni2 / La2Ce2O7, indicating that the / La2Ce2O7 support weakens the MN interaction strength and promotes nitrogen-linked desorption.

[0138] Table 1 below shows the decomposition process of ammonia on a Co1Ni2 / La2Ce2O7 catalyst. The decomposition of ammonia on the catalyst involves multiple steps: ammonia adsorption (… NH3), NH bond breakage ( NH X and H), and recombination and desorption of N2 and H2: Table 1. Decomposition process of ammonia on Co1Ni2 / La2Ce2O7 catalyst

[0139] like Figure 30 The figure shows the free energy curves for the dissociation of NH3 and the formation of N2. NH3 molecules are initially adsorbed onto the active metal sites of the catalyst. Subsequently, the adsorbed NH3 is activated and the NH bonds break, forming... NH2 and H. The energy barrier for this step is 0.75 eV on the Co1Ni2 / CeO2 catalyst surface and 0.61 eV on the Co1Ni2 / La2Ce2O7 catalyst surface, indicating that NH3 is more readily activated on the Co1Ni2 / La2Ce2O7 catalyst. In the subsequent NH bond breaking and hydrogen-related desorption steps, the rate-determining step for the Co1Ni2 / CeO2 catalyst is... Activation and breaking of NH bonds in NH2 (ΔG) H =1.71 eV), while the rate-determining step of the Co1Ni2 / La2Ce2O7 catalyst is Activation and breaking of NH bonds in NH (ΔG) H =1.13 eV). Furthermore, in the hydrogen-related desorption step ( NH2 + 2 H → In NH2, the H2 desorption energy of Co1Ni2 / CeO2 is 0.15 eV, while that of Co1Ni2 / La2Ce2O7 is 0.04 eV. Clearly, the reaction on the surface of the Co1Ni2 / La2Ce2O7 catalyst exhibits a lower NH bond cleavage energy barrier and a lower H2 desorption energy. Regarding the associated desorption of nitrogen, the two N atoms at adjacent active sites... Atoms first combine to form an adsorbed state of N2. Subsequently, N2 is desorbed from the catalyst surface by breaking the MN bond. This process requires overcoming a significant activation energy barrier, and N2 is formed on the surface of the Co1Ni2 / CeO2 catalyst. The required N-N bond formation energy barrier is relatively high (ΔG = 1.95 eV). However, the energy barrier difference between the two catalysts is not significant (1.95 eV and 1.87 eV), indicating that although La2Ce2O7 as a support helps to reduce the nitrogen atom correlation desorption energy barrier, its main role is to accelerate the breaking of NH bonds, thereby promoting the rapid progress of the ammonia decomposition reaction.

[0140] Therefore, according to density functional theory calculations, the main role of the La2Ce2O7 support is to precisely regulate the spin-orbit synergistic effect of the active sites in the alloy through strong metal-support interactions, thereby achieving multi-level regulation of catalytic performance. In particular, the La2Ce2O7 support drives the redistribution of orbital-selective electrons in Ni and Co, leading to spin splitting and orbital sequence reversal in the CoNi alloy. This results in a high-energy, highly active Co 3d spin-down occupied state. Ultimately, the catalyst forms a highly spin-polarized Co-N bond with nitrogen, with a spin polarization far exceeding that of the traditional CeO2 support system. At the kinetic level, this special spin-polarized bonding mechanism achieves synergistic regulation of competing chemical steps. The highly active Co-β electronic state accelerates the dehydrogenation reaction and efficiently promotes NH bond breaking. Simultaneously, spin selectivity is enhanced for N... The adsorption configuration of the intermediate forms a more favorable transition state to facilitate subsequent NN coupling and N2 desorption, thereby simultaneously reducing the energy barrier of the rate-determining step.

[0141] The preparation method disclosed herein utilizes La₂Ce₂O₇, which possesses a unique defective fluorite structure, tunable oxygen vacancies, and proton / electron conductivity, to form a strong synergistic effect with the active metal as a catalyst support. Its abundant intrinsic oxygen vacancies, acting as Lewis acid sites, directly promote the activation of NH₃ molecules and the desorption of N₂, constituting a synergistic catalytic system with the active metal sites. Crucially, the strong metal-support interaction between La₂Ce₂O₇ and the active metal enables precise spin-orbit synergistic regulation of the alloy's active sites, thereby achieving multi-level catalytic performance modulation. Overall, La₂Ce₂O₇, as an active support, optimizes the adsorption strength of CoNi for ammonia decomposition reaction intermediates through the synergistic effect of geometric and electronic effects. Therefore, by selecting an active La₂Ce₂O₇ support and rationally modifying the catalyst's geometry and electronic architecture, excellent ammonia decomposition reaction performance and long-term operational stability can be achieved.

[0142] It should be noted that the above embodiments are merely illustrative of the principles and effects of this disclosure and are not intended to limit this disclosure. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this disclosure. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this disclosure should still be covered by the claims of this disclosure.

Claims

1. A method for preparing an ammonia decomposition catalyst, characterized in that, include: The La2Ce2O7 support was prepared by self-propagating combustion using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid and nitric acid as raw materials. A supported cobalt-nickel catalyst was prepared by impregnation of the La2Ce2O7 support using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials.

2. The preparation method according to claim 1, characterized in that, The La2Ce2O7 support, prepared by self-propagating combustion synthesis using lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, citric acid, and nitric acid as raw materials, comprises: Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate were dissolved in deionized water to obtain the first nitrate solution; Citric acid and nitric acid were added to the first nitrate solution and stirred to obtain a mixture; The mixture is heated to undergo self-propagating high-temperature combustion synthesis to obtain a first precursor, which is then ground and calcined to obtain the La2Ce2O7 support.

3. The preparation method according to claim 2, characterized in that, The process of dissolving lanthanum nitrate hexahydrate and cerium nitrate hexahydrate in deionized water to obtain a first nitrate solution includes: The lanthanum nitrate hexahydrate and the cerium nitrate hexahydrate were dissolved in deionized water according to the stoichiometric ratio to obtain the first nitrate solution.

4. The preparation method according to claim 2, characterized in that, The step of adding citric acid and nitric acid to the first nitrate solution and stirring to obtain a mixture includes: According to the molar ratio of metal ions: citric acid: HNO3 of 1:(1~1.5):(1~1.5), nitric acid and citric acid are added sequentially to the first nitrate solution and stirred to obtain the mixture.

5. The preparation method according to claim 2, characterized in that, The mixture is heated to 300-350°C until it spontaneously combusts, undergoing a self-propagating high-temperature combustion synthesis. The first precursor after grinding is calcined at a temperature of 750~800 ℃ for 4.5~6 hours.

6. The preparation method according to claim 1, characterized in that, The preparation of a supported cobalt-nickel catalyst using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, glycine, polyvinylpyrrolidone, and ethanol as raw materials on the La2Ce2O7 support via an impregnation method includes: According to the target ratio, nickel nitrate hexahydrate and cobalt nitrate hexahydrate are dissolved in deionized water to obtain a second nitrate solution; During stirring, glycine, polyvinylpyrrolidone and ethanol were added to the second nitrate solution to obtain a homogeneous solution; The La2Ce2O7 support was added to the homogeneous solution and stirred to obtain a mixed solution. The mixed solution was then heated to complete combustion to obtain a second precursor. The second precursor was then ground and calcined to obtain the supported cobalt-nickel catalyst.

7. The preparation method according to claim 6, characterized in that, The process involves adding the La2Ce2O7 support to the homogeneous solution and stirring to obtain a mixed solution, then heating the mixed solution to complete combustion to obtain a second precursor. The second precursor is then ground and calcined to obtain the supported cobalt-nickel catalyst, comprising: The La2Ce2O7 support was added to the homogeneous solution and stirred at room temperature for 20-24 hours to obtain the mixed solution; The mixed solution is heated to 300-350 °C until complete combustion is achieved to obtain the second precursor; The second precursor was ground and then calcined at 550-600 °C for 4.5-5.5 hours to obtain the supported cobalt-nickel catalyst.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The main components of the prepared supported cobalt-nickel catalyst include Co, Ni and La2Ce2O7; The mass ratio of cobalt to nickel in the supported cobalt-nickel catalyst is 1:(0.5~2), and the total cobalt and nickel loading of the supported cobalt-nickel catalyst is 20~40 wt%.

9. The preparation method according to any one of claims 1 to 7, characterized in that, The hydrogen evolution temperature of the prepared supported cobalt-nickel catalyst is 310~575 ℃.

10. The preparation method according to any one of claims 1 to 7, characterized in that, The prepared supported cobalt-nickel catalyst has corresponding alkaline sites at 100~200 ℃, 200~400 ℃ and 600~700 ℃ respectively.

11. A supported cobalt-nickel catalyst prepared by any one of claims 1 to 10.

12. The application of the supported cobalt-nickel catalyst as described in claim 11 in ammonia decomposition.

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