Preparation method and application of spherical carbon-coated FeCo2O4 nanocatalysts
Spherical carbon-coated FeCo2O4 nanocatalysts were prepared by hydrothermal synthesis and calcination at a specific temperature, which solved the problems of multiple raw material types and complex processes in the existing technology, improved the adsorption and dissociation efficiency of MgH2 hydrogen storage materials, and achieved higher catalytic performance and stability.
Patent Information
- Application Number
- CN202610093693.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-23
- Publication Date
- 2026-05-26
AI Technical Summary
Existing methods for preparing spherical carbon-coated FeCo2O4 nanocatalysts involve a wide variety of raw materials, high costs, and complex processes, resulting in low adsorption and dissociation efficiency of MgH2 hydrogen storage materials.
Spherical carbon-coated FeCo2O4 nanocatalysts were prepared by hydrothermal synthesis and high-temperature calcination at specific temperatures. By controlling the heating rate and calcination temperature, a uniform spherical morphology and a carbon layer with good conductivity were formed, reducing raw material costs and improving catalytic efficiency.
It significantly improved the hydrogen absorption and desorption kinetics of MgH2, reduced raw material costs and energy consumption, and achieved higher specific surface area and active site density, thus improving the catalyst's dispersibility and stability.
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Figure CN122076439A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of hydrogen storage materials and catalysts in the hydrogen energy sector, specifically relating to a method for preparing spherical carbon-coated FeCo2O4 nanocatalysts and their applications, used to improve the performance of MgH2 solid hydrogen storage materials. Background Technology
[0002] Hydrogen, as a secondary clean energy source, possesses significant advantages such as high energy density, zero pollution, and abundant reserves, making it a crucial component of my country's energy structure. A hydrogen energy system comprises hydrogen production, storage, transportation, and utilization technologies, with storage technology being the key element. Hydrogen can be stored in three forms: cryogenic liquid, highly compressed gas, or solid materials. From the perspective of the development needs of a hydrogen economy, storage systems must be safe, efficient, economical, lightweight, and compact. To achieve this goal, solid-state hydrogen storage materials have become a research focus. The core technology of solid-state hydrogen storage is the storage material itself, which can reversibly absorb and release hydrogen while possessing high safety.
[0003] The applicant of this invention has previously studied and disclosed a method for preparing biphase nanorod catalysts. The research focuses on relying on more precious or rare metals, which is costly. The resulting structure is rod-shaped, and the process involves a complex three-stage stepped heating (120℃→160℃→200℃). Furthermore, the subsequent calcination temperature needs to be as high as 550℃, resulting in even higher energy consumption.
[0004] Therefore, improving the absorption and release performance of hydrogen storage materials in MgH2, and researching catalyst materials that accelerate the adsorption and dissociation of hydrogen on MgH2 while reducing raw material costs and process energy consumption have become key areas of focus in the field of catalyst material technology. Summary of the Invention
[0005] This invention provides a method for preparing spherical carbon-coated FeCo2O4 nanocatalysts and their applications. This aims to address the problems of numerous raw material types, high costs, and complex processes in existing technologies, while also ensuring the acceleration of hydrogen adsorption and dissociation on MgH2 and improving the catalytic efficiency of hydrogen storage systems.
[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing spherical carbon-coated FeCo2O4 nanocatalyst, comprising the following steps: Step (1): Ferric chloride hexahydrate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate and terephthalic acid are mixed to obtain a mixture, wherein the molar ratio of metal salts is Fe:Co:Ni = 8:8:8, the molar ratio of terephthalic acid is 1 to 4, and the molar ratio of terephthalic acid is 3; that is, terephthalic acid participates in the chemical reaction with ferric chloride hexahydrate or cobalt acetate tetrahydrate or nickel acetate tetrahydrate in a molar ratio range of 1:1 to 1:4, preferably 1:3. Step (2): Add deionized water to the mixture and stir at 85±5℃ to obtain a homogeneous and stable wine-red solution. The molar solid-liquid mass ratio of the mixture to deionized water is 166-187 mmol / kg. Step (3): The wine-red solution is transferred to a polytetrafluoroethylene-lined high-pressure reactor for solvothermal reaction. The temperature is raised to 180°C and kept at that temperature for 8-12 hours to form precursor crystals. After the reaction is completed, the precursor powder with a uniform spherical morphology is obtained by cooling, separating, washing and drying. This invention employs direct heating to a specific and suitable temperature of 180°C. Research has found that utilizing this temperature provides a milder and more concentrated thermodynamic environment, which is more conducive to forming a uniform and regular spherical morphology, thus avoiding the inconsistency or defects in crystal growth that may be caused by complex heating procedures.
[0007] Step (4): The precursor powder is ground, calcined at 400°C, and cooled to obtain spherical carbon-coated FeCo2O4 nanocatalyst.
[0008] This invention employs direct heating to 180℃ and holding at that temperature for 8-12 hours to form precursor crystals, ensuring sufficient coordination between metal ions and organic ligands to form precursor crystals. This stage promotes the self-assembly of coordination polymers through a high-temperature, high-pressure environment, forming a nanostructure precursor with a spherical morphology. A calcination temperature of 400℃ is used to form an amorphous carbon layer with good conductivity. This temperature ensures effective carbonization of the organic ligands while preventing over-carbonization that could damage the carbon layer structure or cause excessive reduction of metal particles. This invention saves raw materials while also improving the catalytic efficiency in hydrogen storage systems.
[0009] Based on the above technical solution, the present invention can be further improved as follows.
[0010] Furthermore, in the preparation method of the spherical carbon-coated FeCo2O4 nanocatalyst described above, the magnetic stirrer in step (2) is set to a speed of 80-100 rpm and stirred for 45 min.
[0011] Furthermore, in the preparation method of the spherical carbon-coated FeCo2O4 nanocatalyst as described above, the heating program in step (3) is to heat to 180°C at a rate of 5°C / min and hold for 10 hours.
[0012] Furthermore, in the preparation method of the spherical carbon-coated FeCo2O4 nanocatalyst described above, the calcination is carried out in a tube furnace under a 5% H2 / Ar or Ar protective atmosphere, with the temperature increased to 400°C at a rate of 5°C / min and held for 1 hour. This heating rate and holding parameters effectively prevent excessive graphitization of the carbon framework.
[0013] Extensive experiments in this invention demonstrate that, while considering the combined effects of various factors, using a calcination temperature and heating rate of 400℃ offers the following significant advantages: First, it allows for the formation of smaller crystal particles: high temperatures easily lead to excessive grain growth and agglomeration, thereby reducing specific surface area and activity. This low-temperature calcination allows for better control of the grain size of the ternary material. Second, it effectively promotes the formation of a carbon coating layer. Specifically, under a protective atmosphere, the terephthalic acid in the precursor pyrolyzes at 400℃, forming an amorphous carbon layer with good electrical conductivity.
[0014] Furthermore, in the preparation method of the spherical carbon-coated FeCo2O4 nanocatalyst as described above, the separation in step (3) is centrifugation at 10000 rpm for 5 min, and the washing is washing with deionized water and anhydrous ethanol alternately 3 times each to thoroughly remove residual ions.
[0015] Furthermore, to avoid the agglomeration of nanoparticles due to high surface energy, the drying in step (3) is carried out in an oven at 60°C for 12 hours.
[0016] The present invention also provides a composite hydrogen storage material, which is a composite of spherical carbon-coated FeCo2O4 nanocatalyst prepared by the above preparation method and MgH2, wherein the mass ratio of the spherical carbon-coated FeCo2O4 nanocatalyst to MgH2 ranges from 0.01wt% to 10wt%.
[0017] The beneficial effects of this invention are: by using a hydrothermal synthesis and high-temperature calcination process at a specific temperature, a spherical carbon-coated FeCo2O4 nanocatalyst is obtained, which effectively saves raw materials, reduces energy consumption, and also effectively improves the performance of MgH2 solid hydrogen storage materials.
[0018] The present invention obtains a light yellow precursor powder with a spherical morphology. The powder has a uniform spherical morphology, which lays the structural foundation for the subsequent high-temperature calcination preparation of carbon-coated spinel catalyst.
[0019] The catalyst of this invention is a spherical carbon-coated FeCo2O4 nanocatalyst, which has excellent catalytic performance and significantly improves the hydrogen absorption and desorption kinetics of MgH2.
[0020] This invention employs direct heating to 180°C to obtain a uniform and regular spherical morphology, and a calcination temperature of 400°C to control grain size and form an amorphous carbon layer with good conductivity. The two work together to achieve a synergistic effect of 1+1>2.
[0021] This invention aims to obtain a catalyst with superior overall performance by omitting raw materials and adjusting process parameters. Firstly, the catalytic efficiency is improved through the combination of a spherical structure, a carbon coating layer, and a core spinel phase. Secondly, to achieve the expected synergistic effect, the carbon coating layer not only provides protection but also optimizes the electronic structure through its interfacial effect with the metal oxide. This may enable the catalyst of this invention to exhibit superior performance compared to existing biphase nanorod catalysts in lowering the decomposition temperature of MgH2 and improving hydrogen absorption and desorption kinetics.
[0022] The morphology and structure of the product obtained by this invention represent a strategic shift from "rod-shaped" to "spherical." The morphology of the catalyst is closely related to its performance. Compared with the previously applied "biphase nanorod" structure, the "spherical" structure of this invention has several unique advantages: 1. Higher specific surface area and active site density: Spherical nanoparticles can usually provide a more uniform and higher specific surface area. Although nanorods in the prior art also have a high specific surface area, spherical structures may provide a denser and more accessible active site per unit volume.
[0023] 2. Improved dispersibility and stability: Spherical particles are superior to rod-shaped materials in terms of isotropy, making them easier to disperse uniformly in a matrix (such as MgH2) and reducing agglomeration. More importantly, the carbon coating layer can effectively prevent the oxidation and agglomeration of the core nanoparticles, avoiding environmental influences and thus significantly improving the stability of the catalyst. This "confined" effect is one of the key mechanisms by which carbon materials enhance the performance of transition metal catalysts.
[0024] 3. Optimized mass transfer pathways: In catalytic reactions, reactants and products need to diffuse efficiently to and from active sites. Spherical structures may provide shorter, dead-angle-free mass transfer pathways, which is beneficial for improving reaction kinetics compared to nanorods, which may have longer diffusion distances. Attached Figure Description
[0025] Figure 1 This is a diagram of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1.
[0026] Figure 2 This is the XRD pattern of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1.
[0027] Figure 3 This is a SEM image of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1.
[0028] Figure 4 This is an EDS image of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1.
[0029] Figure 5 This is an EDS image of the spherical carbon-coated FeCo2O4 nanocatalyst powder composite with MgH2 prepared in Example 1.
[0030] Figure 6 The graph shows the catalytic performance of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1 for catalyzing MgH2, where (a) represents hydrogen absorption performance and (b) represents hydrogen release performance.
[0031] Figure 7 The effects of different catalytic systems on the dehydrogenation performance of magnesium hydride (MgH2) were investigated.
[0032] Figure 8 SEM image of the FeCo2O4 catalyst powder prepared for comparison. Detailed Implementation
[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0034] Example 1 The preparation method of spherical carbon-coated FeCo2O4 nanocatalysts includes the following steps: Step (1): Dissolve 8 mmol FeCl3·6H2O, 8 mmol Co(CH3COO)2·4H2O, 8 mmol Ni(CH3COO)2·4H2O, and 2.67 mmol terephthalic acid together in 150 mL of deionized water to obtain a mixture; Step (2): Add deionized water to the mixture, place it on a constant temperature magnetic stirrer, stir for 45 minutes at a speed of 80-100 rpm, and stir at 85±5℃ to obtain a homogeneous and stable wine-red solution. The molar solid-liquid mass ratio of the mixture to deionized water is 180 mmol / kg. Step (3): The wine-red solution is transferred to a polytetrafluoroethylene-lined high-pressure reactor, sealed, and then placed in a vacuum drying oven for hydrothermal reaction. The heating program is to raise the temperature to 180°C at a rate of 5°C / min and keep it at that temperature for 10 hours to form precursor crystals. After the reaction is completed, the precursor powder with a uniform spherical morphology is obtained by cooling, separating, washing, and drying. Step (4): The light yellow precursor powder was ground in an agate mortar and placed in a tube furnace. Under a 5% H2 / Ar or Ar protective atmosphere, the temperature was increased to 400℃ at 5℃ / min and held for 1 hour. After calcination, the furnace was cooled to obtain black spherical carbon-coated FeCo2O4 nanocatalyst.
[0035] Figure 1 The macroscopic morphology and physical state of spherical carbon-coated FeCo2O4 nanocatalyst powder were obtained for Example 1. Figure 1 The spherical carbon-coated FeCo2O4 nanocatalyst is shown as a black powder. Figure 3 The powder appears to be composed of spherical nanoparticles.
[0036] XRD patterns are a core tool for analyzing the crystal structure and phase composition of materials. By analyzing the position (2θ angle) and intensity of diffraction peaks, it is possible to accurately determine which crystalline phases are present in a powder. For example... Figure 2 XRD analysis of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1 showed that amorphous carbon-coated spinel-type FeCo2O4 nanocrystals were successfully prepared in Example 1. The diffraction peaks at specific 2θ angles (e.g., ~18.3°, 30.1°, 35.5°, 43.2°, 57.1°, 62.7°) in the spectrum matched well with the standard card (PDF#03-0864) of spinel-structured FeCo2O4, confirming the formation of the main crystalline phase. Simultaneously, the broadened diffraction peak observed at ~26° belongs to the (002) crystal plane of amorphous carbon, indicating that the carbon coating layer was successfully formed. No obvious diffraction peaks of metallic elements or other impurity phases were found in the spectrum, indicating that the product phase is pure and has high crystallinity, with an estimated grain size in the range of 10-20 nm. In summary, the XRD results confirmed the core structural characteristics of the target product.
[0037] Crystallinity can also be determined by peak shape: the sharpness and intensity of the peaks reflect the degree of crystallinity of the material. A sharper peak indicates good crystallinity; a wider peak indicates that the material has nanoscale grain size. Figure 2 The spherical carbon-coated FeCo2O4 nanocatalyst powder shown has sharp peaks, indicating good crystallinity. According to... Figure 2 The spherical carbon-coated FeCo2O4 nanocatalyst powder shown has no diffraction peaks of other impurity phases (such as unreacted precursors), proving that the spherical carbon-coated FeCo2O4 nanocatalyst powder has been successfully synthesized.
[0038] Figure 3 The SEM images clearly show spherical carbon-coated FeCo2O4 nanocatalysts with relatively uniform dispersion and slight agglomeration. Figure 3The SEM images clearly show that the prepared spherical carbon-coated FeCo2O4 nanocatalyst exhibits a good spherical morphology, uniform particle size, and relatively uniform overall dispersion, although slight local agglomeration is present. This spherical structure helps to provide a larger specific surface area and denser active sites. Slight agglomeration is relatively common in the preparation of nanomaterials, mainly due to the high surface energy of nanoparticles, but the presence of the carbon coating layer can inhibit severe particle agglomeration to a certain extent. This uniform spherical morphology and moderate dispersion are conducive to the uniform distribution and close contact of the catalyst in the MgH2 hydrogen storage matrix, thus laying the structural foundation for its excellent catalytic performance.
[0039] like Figure 4 The EDS image of the spherical carbon-coated FeCo2O4 nanocatalyst powder prepared in Example 1 is shown. The image shows uniform cross-sectional scans of elements such as Fe, Co, and Ni, confirming that all of them contain the expected elements.
[0040] Example 2 Preparation of composite hydrogen storage materials The spherical carbon-coated FeCo2O4 nanocatalyst prepared by the method in Example 1 was combined with MgH2, and the mass ratio of the spherical carbon-coated FeCo2O4 nanocatalyst to MgH2 was 5wt%.
[0041] like Figure 5 EDS image of spherical carbon-coated FeCo2O4 nanocatalyst powder composite with MgH2 in Example 1.
[0042] like Figure 6 The graphs shown in Example 1 depict the catalytic performance of spherical carbon-coated FeCo2O4 nanocatalyst powder against MgH2. (a) represents hydrogen absorption performance, and (b) represents hydrogen release performance. Figure 6 Figure (a) shows the kinetic hydrogen absorption diagram of the MgH2 and MgH2 composite spherical carbon-coated FeCo2O4 nanocatalyst at 300℃, and Figure (b) shows the kinetic hydrogen release diagram of the MgH2 and MgH2 composite spherical carbon-coated FeCo2O4 nanocatalyst at 300℃. It can be seen that the hydrogen absorption and release kinetics of MgH2 are significantly improved.
[0043] like Figure 7The figure shows the effect of different catalytic systems on the dehydrogenation performance of magnesium hydride (MgH2). The figure illustrates the changes in hydrogen release (H2 content, wt.%) as a function of temperature during heating for pure MgH2, the MgH2 / FeCoNiMoV-O / C catalyst composite system, and the MgH2 / FeCo2O4@C catalyst composite system. In the figure, the horizontal axis represents temperature (°C), and the vertical axis represents H2 content (wt.%), with negative values indicating hydrogen release. The inset is a magnified view of the low-temperature region to more clearly show the differences in the initial stage of the curves. The results show that the initial dehydrogenation temperature of pure MgH2 is approximately 297°C; after adding the existing FeCoNiMoV-O / C catalyst, the initial dehydrogenation temperature decreases to approximately 229°C; and after adding the FeCo2O4@C catalyst, the initial dehydrogenation temperature further decreases to approximately 190°C. This indicates that both catalysts significantly improve the dehydrogenation performance of MgH2, with FeCo2O4@C showing a more prominent catalytic effect.
[0044] Comparative Example The calcination temperature of 400℃ in Example 1 was adjusted to 450℃. For example... Figure 8 The results showed that the obtained sample exhibited a dense sintered blocky structure with a significantly increased particle size, and the spherical nanostructure observed in Example 1 of this invention was not formed. This demonstrates that the calcination temperature of 400℃ is one of the key process parameters for obtaining the product structure of this invention, further illustrating that changes in the process and parameters during the preparation of nanocatalysts have a significant impact on product performance.
[0045] This invention reduces the amount of raw materials while successfully achieving a perfect combination of an "active core" (FeCo2O4 with suitable crystallinity and abundant defects) and a "functional shell" (a carbon layer that can disperse, protect, and conduct electricity) through specific calcination temperatures. By selecting appropriate raw materials and processes, this invention not only achieves superior catalytic performance but also significantly reduces the cost of precious metal raw materials.
[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing spherical carbon-coated FeCo2O4 nanocatalysts, characterized in that, It is made from ferric chloride hexahydrate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, and terephthalic acid, and includes the following steps: Step (1): Ferric chloride hexahydrate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate and terephthalic acid are mixed to obtain a mixture, wherein the molar ratio of metal salts is Fe:Co:Ni = 8:8:8 and the molar ratio of terephthalic acid is 1-4. Step (2): Add deionized water to the mixture and stir at 85±5℃ to obtain a homogeneous and stable wine-red solution. The molar solid-liquid mass ratio of the mixture to deionized water is 166-187 mmol / kg. Step (3): The wine-red solution is transferred to a polytetrafluoroethylene-lined high-pressure reactor for solvothermal reaction. The high-pressure reactor is heated to 180°C and kept at that temperature for 8-12 hours to form precursor crystals. After the reaction is completed, the precursor powder with a uniform spherical morphology is obtained by cooling, separating, washing and drying. Step (4): The precursor powder is ground, calcined at 400°C, and cooled to obtain spherical carbon-coated FeCo2O4 nanocatalyst.
2. The preparation method of the spherical carbon-coated FeCo2O4 nanocatalyst according to claim 1, characterized in that, Step (2) Stir for 45 minutes at a magnetic stirrer speed of 80-100 rpm.
3. The method for preparing spherical carbon-coated FeCo2O4 nanocatalyst according to claim 1, characterized in that, The heating program raises the temperature to 180°C at a rate of 5°C / min and holds it at that temperature for 10 hours.
4. The method for preparing spherical carbon-coated FeCo2O4 nanocatalyst according to claim 1, characterized in that, The calcination in step (4) is carried out in a tube furnace under a 5% H2 / Ar or Ar protective atmosphere, with the temperature increased to 400℃ at 5℃ / min and held for 1h.
5. The method for preparing the spherical carbon-coated FeCo2O4 nanocatalyst according to any one of claims 1 to 4, characterized in that, The separation in step (3) is centrifugation at 10,000 rpm for 5 minutes, and the washing is washing with deionized water and anhydrous ethanol alternately until residual ions are completely removed.
6. The method for preparing the spherical carbon-coated FeCo2O4 nanocatalyst according to any one of claims 1 to 4, characterized in that, The drying process described in step (3) involves drying in an oven at 60°C for 12 hours.
7. The method for preparing the spherical carbon-coated FeCo2O4 nanocatalyst according to any one of claims 1 to 4, characterized in that, The molar ratio of terephthalic acid is 3.
8. The application of the spherical carbon-coated FeCo2O4 nanocatalyst obtained by the preparation method of any one of claims 1 to 7 in the MgH2 hydrogen storage system.
9. A composite hydrogen storage material, characterized in that, The spherical carbon-coated FeCo2O4 nanocatalyst prepared by the preparation method according to any one of claims 1 to 7 is combined with MgH2, wherein the mass ratio of the spherical carbon-coated FeCo2O4 nanocatalyst to MgH2 is in the range of 0.01 wt% to 10 wt%.