LaCoO3-based high-entropy oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a LaCoO3-based high-entropy oxide catalyst as well as a preparation method and application thereof. The chemical formula of the LaCoO3-based high-entropy oxide catalyst is La (Co < 0.2 > Cu < 0.2 > Fe < 0.2 > Ni < 0.2 > M < 0.2 >) O3, wherein M is Al, Cr, Mn or Zr. The LaCoO3-based high-entropy oxide which does not contain elements such as Sr, Ba and Bi is designed by preferably selecting high-entropy components and controlling a preparation process, so that the high-entropy oxide catalyst which is low in Co content and stable is obtained, and the high-entropy oxide catalyst has high activity and low surface specific resistance which is 0.15-0.80 ohm cm < 2 > when being used for a symmetric battery test.

Description

Technical Field

[0001] The invention belongs to the technical field of energy catalytic materials, and specifically relates to a LaCoO3-based high-entropy oxide catalyst and a preparation method and application thereof. Background Art

[0002] Global sustainable development urgently needs renewable energy, such as wind energy, solar energy, etc., but these energy sources are mostly intermittent energy sources, and the electricity they generate is difficult to connect to the grid. Hydrogen energy has attracted much attention due to its high weight energy density. If the electricity generated by renewable energy can be used to electrolyze water to produce hydrogen, it will have broad application prospects in the fields of fuel cell vehicle transportation, ammonia production, steelmaking, etc. Solid oxide cells can produce hydrogen in electrolysis mode and generate electricity in fuel cell mode. They have the advantages of reversibility, high conversion efficiency, and the ability to utilize industrial waste heat. They are a very promising hydrogen production device. At present, the development of solid oxide cells is still limited by the low catalytic activity of air electrode materials, so there is an urgent need to develop new types of air electrode catalysts.

[0003] In recent years, high entropy oxides have shown broad application prospects in the fields of lithium-ion batteries, dielectric materials, magnetic materials, etc., making them a hot topic in current catalytic material research. High entropy oxides refer to solid solutions containing five or more atoms with equal or similar atomic fractions. As the number of elements increases, the mixing entropy increases, the Gibbs free energy decreases, the solid solution stability increases, and Co substitution will significantly reduce the Co content, which is expected to obtain materials with low thermal expansion coefficients and promote the development of solid oxide air electrodes.

[0004] For example, Chinese patent CN114249593A discloses a high entropy perovskite cathode material, whose chemical formula is La 0.6 Bi 0.2 Sr 0.2 (CoFeMnNiCuCr) 1 / 6 O 3-δ Chinese patent CN116581314A discloses a high entropy oxide catalyst for fuel cells. The chemical formula of the high entropy oxide catalyst is: (La 1-x A x ) n+1 B n O 3n+1-δ , wherein A is at least one of Ca, Sr, and Ba, B is at least five of Ni, Cu, Fe, Co, Mn, Zn, Cr, Ti, Al, and Ga, and the molar ratio of each element in B is 0.6 to 1.7, x is 0.075 to 0.925, and n is 2 or 3. However, these high entropy oxide materials often contain elements such as Sr and Ba, which are very easy to segregate in a high water pressure atmosphere, change morphology, become unstable, and degrade battery performance. Summary of the invention

[0005] In view of this, the present invention provides a LaCoO3-based high entropy oxide catalyst and a preparation method and application thereof, which does not contain elements such as Sr and Ba, and obtains a low Co content and stable high entropy oxide catalyst with high activity and low surface resistivity.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a LaCoO3-based high entropy oxide catalyst, wherein the chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3, wherein M is Al, Cr, Mn or Zr.

[0008] As a preferred technical solution, the chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Cr 0.2 )O3.

[0009] As a preferred technical solution, the chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )O3.

[0010] The present invention provides a method for preparing a LaCoO3-based high entropy oxide catalyst, the preparation method comprising the following steps:

[0011] (1) Sol-gel reaction: Using metal nitrate or carbonate as raw material, according to La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3 in a stoichiometric ratio, weigh and prepare the ingredients, add water to dissolve, add citric acid and ethylenediaminetetraacetic acid, and heat to carry out complex reaction until a gel is formed;

[0012] (2) Thermal decomposition and ball milling reaction: Place the gel in a muffle furnace, heat it to 300-500°C, and keep it warm for 0.5-2h. Cool it down, take it out and ball mill it to obtain the precursor.

[0013] (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5-10°C min-1 The temperature is raised to 800-1000° C. at a heating rate of , and kept at this temperature for 4-10 hours to obtain the LaCoO3-based high entropy oxide catalyst.

[0014] As a preferred technical solution, the conditions for the sol-gel reaction in step (1) are: the temperature is controlled at 50-80°C, the pH value is controlled at 6-8, and the molar ratio of the total Co-site metal ions: citric acid: ethylenediaminetetraacetic acid is 1:4:4-1:1:1.

[0015] As a preferred technical solution, in the step (2), the rotation speed during ball milling is 250 to 450 rpm, and the ball milling time is 4 to 10 hours.

[0016] The present invention also provides the application of the LaCoO3-based high entropy oxide catalyst as an air electrode material for a solid oxide battery.

[0017] The beneficial effects of the present invention are:

[0018] The present invention designs a LaCoO3-based high entropy oxide without Sr, Ba and other elements by optimizing high entropy components and controlling the preparation process, thereby obtaining a low Co content and stable high entropy oxide catalyst, which is used for symmetric battery testing and has high activity and low surface resistivity of 0.15-0.80Ωcm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0020] Figure 1 : The high entropy oxide La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 X-ray diffraction pattern shows that the prepared high entropy oxide is pure phase, which is in good agreement with the LaCoO3 standard card (PDF#86-1663).

[0021] Figure 2 : The high entropy oxide La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 powder, it can be seen that La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2)The grain size of O3 powder is about 100nm.

[0022] Figure 3 : The high entropy oxide La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )Inductively coupled plasma emission test of O3 powder shows that the element ratio of Co, Cu, Fe, Ni and Zr is close to 1.

[0023] Figure 4 : The high entropy oxide La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )O3 powder symmetric cell impedance spectrum, indicating that the La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 ) The surface resistivity of the O3 catalyst at 600°C is 0.48Ωcm 2 , with high activity.

[0024] Figure 5 : The high entropy oxide La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 ) SEM photos of O3 before and after boiling in boiling water. After 100h of water resistance treatment, no precipitation occurred on the SEM surface.

[0025] Figure 6 : High entropy oxide La obtained in Comparative Example 1 0.75 Sr 0.25 (Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 ) SEM photos of O3 before and after boiling in boiling water. The SEM morphology changed significantly after 100h of water resistance treatment.

[0026] Figure 7 : High entropy oxide (LaPrBaScCa) obtained in Comparative Example 2 0.2 CoO3 and high entropy oxide (LaSrBaScCa) obtained in Comparative Example 3 0.2 From the SEM image of CoO3, we can see that (LaPrBaScCa) 0.2CoO3 and (LaSrBaScCa) 0.2 Particles are precipitated on the surface of CoO3. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0028] Example

[0029] A method for preparing a LaCoO3-based high entropy oxide catalyst, the preparation method specifically comprising the following steps:

[0030] (1) Sol-gel reaction: Using metal nitrate with a purity greater than 98% as raw material, La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3 in a stoichiometric ratio, weigh the ingredients, add deionized water to dissolve in a porcelain crucible, adjust the pH value to 6-8, add citric acid and ethylenediaminetetraacetic acid after stabilization, the molar ratio of the total metal ions at the Co position: citric acid: ethylenediaminetetraacetic acid is 1:4:4-1:1:1, heat to carry out complexation reaction, and control the temperature at 50-80°C until a gel is formed;

[0031] (2) Thermal decomposition and ball milling reaction: Place the porcelain crucible containing the gel in a muffle furnace, heat it to 300-500°C, and keep it warm for 0.5-2h; cool it down and take it out, use ethanol as a solvent, place it in a ball mill, and mill it at a speed of 250-450 rpm for 4-10h to obtain a precursor;

[0032] (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5-10°C min -1 The temperature is raised to 800-1000° C. at a heating rate of , and kept at this temperature for 4-10 hours to obtain the LaCoO3-based high entropy oxide catalyst.

[0033] Table 1 Synthesis of La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3 embodiment

[0034]

[0035]

[0036] The La(Co 0.2 Cu0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 powder was analyzed and tested. Figure 1 It can be seen that the high entropy oxide prepared by the present invention has high crystallinity and is pure phase, which is consistent with the standard card (PDF#86-1663). Figure 2 ) can be seen that La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )The grain size of O3 powder is about 100nm.

[0037] The La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )O3 powder was tested by inductively coupled plasma emission and symmetrical battery test. Figure 3 It can be seen that the element ratio of Co, Cu, Fe, Ni, and Zr is close to 1. When it is used as an air electrode catalyst, the surface resistivity at 600°C is 0.48Ωcm 2 ( Figure 4 ), with high activity.

[0038] As can be seen from Table 1, the LaCoO3-based high entropy oxide of the present invention has high activity and low surface resistivity, which is 0.15-0.80 Ωcm 2 , among which La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Cr 0.2 )O3 and La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )O3, has lower surface resistivity.

[0039] Comparative Example 1

[0040] La 0.75 Sr 0.25 (Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 ) A method for preparing an O3 high entropy oxide catalyst, the preparation method specifically comprising the following steps:

[0041] (1) Sol-gel reaction: Using metal nitrate with purity greater than 98% as raw material, according to La 0.75 Sr 0.25 (Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 in a stoichiometric ratio, weigh the ingredients, add deionized water to dissolve in a porcelain crucible, adjust the pH value to 7, add citric acid and ethylenediaminetetraacetic acid after stabilization, the molar ratio of the total metal ions at the Co position: citric acid: ethylenediaminetetraacetic acid is 1:2:1, heat to carry out complexation reaction, and control the temperature at 50°C until a gel is formed;

[0042] (2) Thermal decomposition and ball milling reaction: Place the porcelain crucible containing the gel in a muffle furnace, heat it to 300°C, and keep it warm for 1 hour; cool it down and take it out, use ethanol as a solvent, place it in a ball mill, and mill it at a speed of 450 rpm for 5 hours to obtain a precursor;

[0043] (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5°C min -1 The temperature was raised to 900℃ at a heating rate and kept at this temperature for 5h to obtain La 0.75 Sr 0.25 (Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 high entropy oxide catalyst.

[0044] The La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 powder and comparative example 1 were tested for water resistance stability. Figure 5 It can be seen that the high entropy oxide prepared by the present invention has high stability, and no precipitation occurs on the SEM surface after 100h water resistance treatment. Figure 6 It can be seen that La 0.75 Sr 0.25 (Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Al 0.2 )O3 undergoes significant changes in SEM morphology after 100h of water resistance treatment.

[0045] Comparative Example 2

[0046] (LaPrBaScCa) 0.2A method for preparing a CoO3 high entropy oxide catalyst, the preparation method specifically comprising the following steps:

[0047] (1) Sol-gel reaction: Using metal nitrate with a purity greater than 98% as raw material, according to (LaPrBaScCa) 0.2 The stoichiometric ratio of CoO3 was weighed and dissolved in a porcelain crucible with deionized water, and the pH value was adjusted to 7. After stabilization, citric acid and ethylenediaminetetraacetic acid were added, and the molar ratio of the total metal ions at the Co position: citric acid: ethylenediaminetetraacetic acid was 1:2:1, and the complexation reaction was carried out by heating, and the temperature was controlled at 50°C until a gel was formed;

[0048] (2) Thermal decomposition and ball milling reaction: Place the porcelain crucible containing the gel in a muffle furnace, heat it to 300°C, and keep it warm for 1 hour; cool it down and take it out, use ethanol as a solvent, place it in a ball mill, and mill it at a speed of 450 rpm for 5 hours to obtain a precursor;

[0049] (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5°C min -1 The temperature was raised to 900 °C at a rate of 1.5 °C and kept at this temperature for 5 h to obtain (LaPrBaScCa) 0.2 CoO3 high entropy oxide catalyst.

[0050] from Figure 7 It can be seen that (LaPrBaScCa) 0.2 Particles precipitate on the surface of CoO3.

[0051] Comparative Example 3

[0052] (LaSrBaScCa) 0.2 A method for preparing a CoO3 high entropy oxide catalyst, the preparation method specifically comprising the following steps:

[0053] (1) Sol-gel reaction: Using metal nitrate with a purity greater than 98% as raw material, according to (LaSrBaScCa) 0.2 The stoichiometric ratio of CoO3 was weighed and dissolved in a porcelain crucible with deionized water, and the pH value was adjusted to 7. After stabilization, citric acid and ethylenediaminetetraacetic acid were added, and the molar ratio of the total metal ions at the Co position: citric acid: ethylenediaminetetraacetic acid was 1:2:1, and the complexation reaction was carried out by heating, and the temperature was controlled at 50°C until a gel was formed;

[0054] (2) Thermal decomposition and ball milling reaction: Place the porcelain crucible containing the gel in a muffle furnace, heat it to 300°C, and keep it warm for 1 hour; cool it down and take it out, use ethanol as a solvent, place it in a ball mill, and mill it at a speed of 450 rpm for 5 hours to obtain a precursor;

[0055] (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5°C min -1 The temperature was raised to 900 °C at a rate of 1.5 °C and kept at this temperature for 5 h to obtain (LaSrBaScCa) 0.2 CoO3 high entropy oxide catalyst.

[0056] from Figure 7 It can be seen that (LaSrBaScCa) 0.2 Particles precipitate on the surface of CoO3.

[0057] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A LaCoO3-based high entropy oxide catalyst, characterized in that: The chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3, wherein M is Al, Cr, Mn or Zr.

2. The LaCoO3-based high entropy oxide catalyst according to claim 1, characterized in that: The chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Cr 0.2 )O3.

3. The LaCoO3-based high entropy oxide catalyst according to claim 1, characterized in that: The chemical formula of the LaCoO3-based high entropy oxide catalyst is La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 Zr 0.2 )O3.

4. The method for preparing the LaCoO3-based high entropy oxide catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) Sol-gel reaction: Using metal nitrate or carbonate as raw material, according to La(Co 0.2 Cu 0.2 Fe 0.2 Ni 0.2 M 0.2 )O3 in a stoichiometric ratio, weigh and prepare the ingredients, add water to dissolve, add citric acid and ethylenediaminetetraacetic acid, and heat to carry out complex reaction until a gel is formed; (2) Thermal decomposition and ball milling reaction: Place the gel in a muffle furnace, heat it to 300-500°C, and keep it warm for 0.5-2h. Cool it down, take it out and ball mill it to obtain the precursor. (3) High temperature sintering: Place the precursor in a crucible boat in an air atmosphere at 5-10°C min -1 The temperature is raised to 800-1000° C. at a heating rate of , and kept at this temperature for 4-10 hours to obtain the LaCoO3-based high entropy oxide catalyst.

5. The method for preparing a LaCoO3-based high entropy oxide catalyst according to claim 4, characterized in that: The conditions of the sol-gel reaction in step (1) are: the temperature is controlled at 50-80° C., the pH value is controlled at 6-8, and the molar ratio of the total metal ions at the Co position: citric acid: ethylenediaminetetraacetic acid is 1:4:4-1:1:

1.

6. The method for preparing a LaCoO3-based high entropy oxide catalyst according to claim 4, characterized in that: In the step (2), the rotation speed during ball milling is 250 to 450 rpm, and the ball milling time is 4 to 10 hours.

7. Use of the LaCoO3-based high entropy oxide catalyst according to any one of claims 1 to 3 as an air electrode material for a solid oxide battery.

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