A bionic structural ceramic catalyst, its preparation method and application

Abstract

The present invention provides a bionic structure ceramic catalyst, and the bionic structure ceramic catalyst includes "mesophyll", "vein" and "epidermis" structures; the "mesophyll" is the main structure, which is composed of one of perovskite structure, double perovskite structure or Ruddlesden-Popper structure; the "vein" is a network structure located inside the "mesophyll", the "epidermis" is a coating layer located on the surface of the "mesophyll", and the "vein" and "epidermis" are cubic fluorite structure or perovskite structure. The "epidermis" structure located on the surface of the "mesophyll" has abundant oxygen vacancies, which is beneficial to the processes of oxygen adsorption, dissociation and entering the lattice during the oxygen catalysis process. The network-like "vein" structure located inside the "mesophyll" provides a fast channel for the conduction of oxygen ions, making the catalyst have excellent oxygen ion conduction ability.

Description

Technical Field

[0001] The invention belongs to the technical field of clean energy, and in particular relates to a ceramic catalyst and a preparation method and application thereof. Background Art

[0002] As a functional ceramic material, ceramic catalysts have a series of advantages such as a wide source of raw materials, simple preparation process, low price and strong anti-poisoning ability. Taking ceramic materials as oxygen catalysts as an example, it can be used as the cathode material of solid oxide fuel cells (SOFCs) to achieve efficient catalysis of oxygen reduction reactions under high temperature environments. It can also be used as the anode material of solid oxide electrolyzers (SOECs) to achieve efficient catalysis of oxygen ion oxidation reactions under high temperature hydrogen production conditions. In addition, ceramic catalysts have broad application prospects in fields such as high-temperature oxygen dialysis membranes and high-temperature oxygen sensors. The development and progress of ceramic catalyst technology will lay the foundation for the development of green new energy technologies in my country and help achieve my country's "dual carbon" goals.

[0003] The application of ceramic catalysts in the field of SOFC is further explained. SOFC is a green power technology that can directly generate electricity using clean energy such as hydrogen and carbon-based fuels. It has a wide range of raw material sources, can achieve all-weather distributed power generation, low power generation cost, high battery output power and energy density, high fuel utilization, zero / low carbon emissions, no noise, green environmental protection and other advantages. It is in line with the national "carbon peak" and "carbon neutrality" goals, and has potential application value in communication base station power supply, data center power supply, household cogeneration system, commercial center power supply, office building / school / hospital power supply, electric ship power supply, heavy truck power supply, drone and submarine power supply, traditional pit power station and coal-fired power station alternatives, rural green energy network and other fields. And as a distributed all-weather energy source, SOFC can greatly supplement intermittent energy such as wind power, hydropower and solar energy to ensure the electricity demand of the people. Among them, the ceramic oxygen catalyst is one of the key materials for SOFC to achieve efficient, stable and cheap power generation. However, the SOFC high-temperature ceramic catalyst currently used in the market has not yet achieved the performance of both high oxygen catalytic activity and long-term working stability. This is mainly because this type of ceramic catalyst is essentially a polycrystalline metal oxide material. There is lattice strain caused by ion radius mismatch and electrostatic interaction caused by chemical defects inside the material. At high temperatures, the kinetic energy of metal cations increases. Under the combined action of lattice strain and electrostatic force, some metal cations will diffuse to the surface of the material, gradually enriching and forming an electrochemically inert coating on the surface of the material. As a result, the oxygen catalytic performance of the material decays rapidly, affecting its practical application in SOFC. Therefore, it is necessary to develop a high-temperature ceramic catalyst that can work stably for a long time and has high oxygen catalytic activity. Summary of the invention

[0004] The technical problem to be solved by the present invention is that existing high-temperature ceramic catalysts cannot achieve both high oxygen catalytic activity and high working stability. To overcome the above-mentioned deficiencies and defects in the background technology, a bionic structure ceramic catalyst, its preparation method and application are provided.

[0005] To solve the above technical problem, the technical solution proposed by the present invention is as follows:

[0006] A bionic structure ceramic catalyst, the bionic structure ceramic catalyst includes a "mesophyll", "vein" and "epidermis" structure; the "mesophyll" is the main structure, which is composed of one of a perovskite structure, a double perovskite structure or a Ruddlesden-Popper structure; the "vein" is a network structure located inside the "mesophyll", and the "epidermis" is a layered structure located on the surface layer of the "mesophyll", and the "vein" and "epidermis" are cubic fluorite structures or perovskite structures.

[0007] The leaves of plants are devices that have withstood the test of nature and can carry out stable photosynthesis for a long time. Its core feature is the epidermis growing on the surface of the mesophyll and the veins in the mesophyll. The epidermis provides good protection for other components of the leaf and provides a gas exchange channel. The veins provide a fast material transport channel for the leaf and provide physical support for the leaf. In view of this idea, the present invention proposes a bionic structure ceramic catalyst.

[0008] The "epidermis" structure located on the surface of the "mesophyll" has abundant oxygen vacancies, which is beneficial to the processes of oxygen adsorption, dissociation and entry into the lattice during the oxygen catalytic process. In addition, the "epidermis" of the catalyst has the following characteristics:

[0009] (1) Stabilize the microstructure of the catalyst surface. ① The material of the catalyst "epidermis" is more stable than its "mesophyll" in the working environment and can protect the "mesophyll"; ② Without the "epidermis" of the catalyst, the periodic structure of the surface phase of the "mesophyll" is damaged. Under the working conditions of the catalyst, segregation of components and reconstruction of the microscopic crystal structure will occur on the surface of the "mesophyll", and finally an electrochemically inert coating will be formed. The in-situ grown "epidermis" layer changes the chemical environment of the catalyst surface layer, such as the space charge layer distribution, and effectively inhibits the segregation of catalyst components and the formation of electrochemically inert coatings.

[0010] (2) Excellent oxygen catalytic performance. The "epidermis" grows in-situ on the surface of the catalyst "mesophyll". The "mesophyll" has a higher coefficient of thermal expansion than the "epidermis". During the process of heating the catalyst from room temperature to the target working temperature, the "epidermis" will be subjected to tensile stress from the "mesophyll", causing the lattice of the "epidermis" to expand, which is beneficial to the formation and conduction of oxygen vacancies, and thus very excellent oxygen catalytic activity is obtained.

[0011] The network-like "vein" structure located inside the "mesophyll" provides a fast channel for the conduction of oxygen ions, enabling the catalyst to have excellent oxygen ion conduction ability. In addition, the network-like "vein" structure has the following characteristics:

[0012] (1) The network-like "vein" structure grows in-situ with the "mesophyll" main body, and a certain amount of elemental interdiffusion occurs between the two, which can make the chemical defects of the "mesophyll" main body less, and the elemental interdiffusion can also reduce the stress caused by electrostatic force and improve the stability of the catalyst.

[0013] (2) The network-like "vein" of the catalyst grows in-situ in the "mesophyll". Due to the different thermal expansion coefficients of the "vein" and "mesophyll" materials, a certain amount of microscopic thermal strain will be generated at the "vein" / "mesophyll" interface during the process of the catalyst heating from room temperature to the target working temperature. This characteristic can generate a large number of oxygen vacancies at the interface, thereby improving the oxygen conduction performance of the catalyst.

[0014] Preferably, in the perovskite structure ABO3, double perovskite structure A2B2O 5+δ and Ruddlesden-Popper structure A2BO4, A is one or more of La, Pr, Gd, Nd, Sm, Sr, Ba, and Ca, and B is one or more of Fe, Co, or Ni.

[0015] Preferably, the cubic fluorite structure or perovskite structure includes Gd 1-x Ce x O 2-δ 、Sm 1-x Ce x O 2-δ or La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ one or more of them, where x = 0 - 0.5.

[0016] Preferably, the thickness of the "epidermis" is 2 - 10 nm.

[0017] Preferably, the diameter of the "vein" is 2 - 20 nm.

[0018] Preferably, the "vein" and "epidermis" structures of the biomimetic structure ceramic catalyst grow in-situ in the "mesophyll" structure.

[0019] The ceramic catalyst does not resemble a leaf in morphology, but has a nanoscale coating layer and "veins" similar to the "epidermis" of a leaf at the nanoscale structure, and the "epidermis" and "veins" have an in-situ growth relationship with the "mesophyll" of the catalyst main body.

[0020] Under the same inventive concept, the present invention also provides a method for preparing a bionic structural ceramic catalyst. Preferably, the specific steps of the preparation are as follows:

[0021] (1) Use an aqueous solution of complexing agent A to complex the soluble nitrate corresponding to the "mesophyll" of the catalyst, adjust the pH value to 6 - 7 to obtain solution A; use an aqueous solution of complexing agent B to complex the soluble metal salts corresponding to the "vein" and "epidermis" of the catalyst, and adjust the pH value to 6 - 7 to obtain solution B;

[0022] (2) Place solution A in a closed container, heat and stir to obtain sol A; place sol A in an open container, heat and stir to obtain gel A; heat gel A to self - ignite, and further remove carbon from the self - ignited powder to obtain nano - powder A; place solution B in a closed container, heat and stir to obtain sol B;

[0023] (3) Place nano - powder A in sol B, impregnate in a vacuum environment; then use the suction filtration method to remove part of sol B to obtain filtrate C; freeze - dry filtrate C to obtain precursor D;

[0024] (4) Perform heat treatment on precursor D to obtain the bionic structural ceramic catalyst.

[0025] Preferably, in step (1), the complexing agent A is a combination of glycine and one of citric acid, ethylenediaminetetraacetic acid or urea, and the molar ratio of glycine to the other complexing agent is 3:1 - 1:3; the soluble nitrates corresponding to the "mesophyll" include one or more of lanthanum nitrate, praseodymium nitrate, gadolinium nitrate, neodymium nitrate, samarium nitrate, strontium nitrate, barium nitrate, calcium nitrate, iron nitrate, cobalt nitrate or nickel nitrate; the molar ratio of complexing agent A to the metal cations of the nitrate is 1:1 - 2:1; the metal cation concentration of solution A is 0.1 - 1M; the complexing agent B is one or more of citric acid, ethylenediaminetetraacetic acid or urea, and the soluble metal salts corresponding to the "vein" and "epidermis" of the catalyst specifically refer to one or more of gadolinium nitrate, gadolinium acetate, cerium nitrate, cerium acetate, samarium nitrate, samarium acetate, lanthanum nitrate, lanthanum acetate, strontium nitrate, strontium acetate, gallium nitrate, gallium acetate, magnesium nitrate, magnesium acetate and magnesium acetate; the molar ratio of complexing agent B to the cations in the soluble metal salt is 1:1 - 2:1, and the material for adjusting the pH value is ammonia water; the metal cation concentration of solution B is 0.02 - 0.2M.

[0026] The preferred complexing agents and soluble metal salts in the present application can enable the "vein" and "epidermis" structures of the bionic structural ceramic catalyst to grow in - situ in the "mesophyll" structure.

[0027] Preferably, in step (2), the temperature for heating and stirring solution A in a closed container is 60 - 90°C, and the stirring time is 2 - 5 h; the temperature for heating and stirring solution A in an open container is 80 - 95°C, and the time length is 5 - 10 h; gel A self-ignites in a crucible, and the heating temperature is 150 - 300°C; the self-ignited powder is decarbonized in a muffle furnace at a temperature of 500 - 600°C under an air atmosphere; the temperature for heating and stirring solution B in a closed container is 60 - 90°C, and the stirring time is 5 - 24 h; in step (3), the vacuum degree of the surrounding environment when nanoflour A is impregnated in sol B is 0.01 - 1 Pa, and the impregnation time is 0.5 - 10 h. The pressure of vacuum freeze-drying is 3 - 10 Pa, the temperature is -30°C to -70°C, and the time is 12 - 24 h; in step (4), the heat treatment temperature of precursor D is 900 - 1200°C, the heating and cooling rate is 0.5 - 2°C / min, and the holding time at the highest temperature is 2 - 8 h.

[0028] Under the same inventive concept, the present invention also provides an application of the bionic structure ceramic catalyst, and the bionic structure ceramic catalyst is used for the oxygen electrodes of solid oxide fuel cells and solid oxide electrolyzers.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) High oxygen catalytic activity: ① The "skin" with a cubic fluorite and perovskite structure contains abundant oxygen vacancies, which helps the occurrence of electrochemical processes such as oxygen adsorption, dissociation, reduction, and entry into the lattice; ② The "skin" grows in situ on the surface of the catalyst "mesophyll", and the "mesophyll" has a higher coefficient of thermal expansion than the "skin". During the process of the catalyst heating from room temperature to the target working temperature, the "skin" will be subjected to tensile stress from the "mesophyll", causing the lattice of the "skin" to expand, which is conducive to the formation and conduction of oxygen vacancies, and thus obtaining very excellent oxygen catalytic activity; ③ The "veins" with a cubic fluorite and perovskite structure have a higher oxygen ion conductivity than the "mesophyll". The introduction of the "vein" structure can form a rapid transport channel for oxygen ions, greatly improving the oxygen ion conduction ability of the catalyst, and thus showing higher oxygen catalytic activity; ④ The network-shaped "veins" of the catalyst grow in situ in the "mesophyll". Due to the different coefficients of thermal expansion of the "vein" and "mesophyll" materials, a certain amount of microscopic thermal strain will be generated at the "vein" / "mesophyll" interface during the process of the catalyst heating from room temperature to the target working temperature. This feature can generate a large number of oxygen vacancies at the interface, thereby improving the oxygen conduction performance of the catalyst, and macroscopically showing higher oxygen catalytic activity.

[0031] (2) Good working stability: ① The material of the "epidermis" of the catalyst is more stable than its "mesophyll" in the working environment, and can protect the "mesophyll"; ② Without the "epidermis" of the catalyst, the periodic structure of the surface phase of the "mesophyll" is damaged. Under the working conditions of the catalyst, segregation of components and reconstruction of the microscopic crystal structure will occur on the surface of the "mesophyll", and finally an electrochemically inert coating will be formed. The in-situ grown "epidermis" layer changes the chemical environment of the catalyst surface layer, such as the space charge layer distribution, and effectively inhibits the segregation of catalyst components and the formation of electrochemically inert coatings. ③ The thermal expansion coefficients of the "epidermis" and "veins" are closer to those of the electrolyte and other components, which helps to improve the thermal shock resistance of the catalyst.

[0032] (3) Wide range of applicable fields: It has potential applications in fields such as solid oxide fuel cells (SOFCs), solid oxide electrolyzers (SOECs), high-temperature oxygen dialysis membranes, and high-temperature oxygen sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments or comparative examples of the present invention, the following will briefly introduce the drawings required for the description of the embodiments or comparative examples. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 Macrophotograph of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 for Example 1;

[0035] Figure 2 Macrophotograph of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 Scanning electron microscope image of the bionic catalyst; and (c - e) Transmission electron microscope images of the bulk phase;

[0036] Figure 3 Macrophotograph of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1Ce 0.9 O 1.95 Transmission electron microscopy image of the surface of the biomimetic catalyst;

[0037] Figure 4 For La of Example 1 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 Transmission electron microscopy image of the bulk of the biomimetic catalyst;

[0038] Figure 5 For La of Example 1 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 C-AFM image of;

[0039] Figure 6 For La of Example 1 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 Single cell test performance curve of;

[0040] Figure 7 For La of Example 1 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 Long-time working curve of;

[0041] Figure 8 For PrBaCo2O of Example 2 5+δ #Sm 0.1 Ce 0.9 O 1.95 Curve of electrical conductivity varying with temperature in air;

[0042] Figure 9 For PrBaCo2O of Example 2 5+δ #Sm 0.1 Ce 0.9 O 1.95 Electrochemical impedance spectroscopy image of the symmetric cell with cathode coating;

[0043] Figure 10 Macrophotograph of La2NiO4#La of Example 3 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ ;

[0044] Figure 11 Macrophotograph of La2NiO4#La of Example 3 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ and comparative curve of oxygen exchange rate of La2NiO4;

[0045] Figure 12 Open circuit voltage curve of La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 of Example 4;

[0046] Figure 13 Open circuit voltage curve of La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 and La 0.6 Sr 0.4 CoO 3-δ long - term comparative curve;

[0047] Figure 14 SEM micrograph of the surface microstructure of La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 single cell after long - term operation;

[0048] Figure 15 Flow chart of the production steps of the bionic structure ceramic catalyst;

[0049] Figure 16 For La of Example 5 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ +Gd 0.1 Ce 0.9 O 1.95Transmission electron microscope image;

[0050] Figure 17 For La of Example 5 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ + Gd 0.1 Ce 0.9 O 1.95 Single cell test performance curve of;

[0051] Figure 18 For La of Example 5 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ + Gd 0.1 Ce 0.9 O 1.95 Long - term working curve of. Detailed implementation mode

[0052] For ease of understanding the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0053] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0054] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0055] Example 1:

[0056] The ceramic catalyst with a bionic structure in this example has a chemical composition of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 , and the macroscopic property is a loose black massive material, which can be used as a cathode catalyst for solid oxide fuel cells.

[0057] The bionic structure ceramic catalyst includes "mesophyll", "vein", and "epidermis" structures; the "mesophyll" is the main structure, and its chemical formula is La 0.6 Sr 0.4 Co 0.2 Fe0.8 O 3-δ ; The "leaf vein" is a network structure inside the "mesophyll", the "epidermis" is a layered structure on the surface layer of the "mesophyll", and the chemical formulas of the "leaf vein" and "epidermis" are Gd 0.1 Ce 0.9 O 1.95 . Among them, the thickness of the "epidermis" is 5 - 10 nm, and the diameter of the "leaf vein" is 10 - 15 nm.

[0058] As a bionic structural ceramic catalyst, the production process steps are as Figure 15 shown, and the specific steps of its preparation process are as follows:

[0059] (1) Dissolve glycine and citric acid in pure water at a ratio of 3:1 as complexing agents, so that the concentrations of glycine and citric acid are 1 mol / L;

[0060] (2) Dissolve lanthanum nitrate, strontium nitrate, cobalt nitrate, and iron nitrate corresponding to the "mesophyll" in the above solution, so that the molar ratio of metal cations to glycine and citric acid is 1:1;

[0061] (3) Adjust the pH value of the above solution to 7 with ammonia water, and name this solution Solution A;

[0062] (4) Place Solution A in a closed container and heat and stir at 60 °C for 5 h to obtain Sol A; place Sol A in an open container and heat and stir at 80 °C for 10 h to obtain Gel A;

[0063] (5) Place Gel A in a heat-resistant crucible and heat it at 230 °C to make it self-ignite, and place the self-ignited powder in a muffle furnace for further carbon removal at 500 °C for 6 h to obtain Nano-powder A;

[0064] (6) Use citric acid as a complexing agent and dissolve gadolinium nitrate and cerium nitrate corresponding to the "epidermis" and "leaf vein" in pure water, so that the molar ratio of metal cations to citric acid is 1:1, adjust the pH value of the solution to 7 with ammonia water, and name this solution Solution B;

[0065] (7) Place Solution B in a sealed container and stir at 60 °C for 24 h to convert Solution B into Sol B;

[0066] (8) Place Nano-powder A in Sol B and impregnate it in a vacuum environment of 0.01 Pa for 0.5 h; then use the filtration method to remove part of Sol B to obtain Filter C; freeze-dry Filter C at 4 Pa and -60 °C for 18 h to obtain Precursor D;

[0067] (9) Heat-treat Precursor D at 900 °C, with a heating and cooling rate of 0.5 °C / min and a holding time of 8 h, and the bionic structural ceramic catalyst disclosed in the present invention can be obtained.

[0068] The macroscopic morphology of the material after sintering is a loose black mass, and the scanning image of the mass is as shown in Figure 1 and the microscopic structure is as shown in Figures 2 - 4 In order to verify the integrity of the "epidermis" structure in the bionic structure of the material, we characterized the material by C-AFM, and the results are as shown in Figure 5 indicating that the "epidermis" of the bionic structure is very complete, proving that the material synthesis process is mature. In order to verify the high oxygen ion conductivity, oxygen catalytic activity, and the characteristics of long-term efficient and stable operation of the material under medium and low temperature conditions, we ground La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ #Gd 0.1 Ce 0.9 O 1.95 into micron-scale powders, and mixed them with terpineol and ethyl cellulose to make a slurry according to the weight ratio of powder:terpineol:ethyl cellulose = 1:0.9:0.1. Then, it was evenly coated on the anode-supported single cell and sintered at 1000 °C in a box furnace, and tested by the four-electrode method. The test results are as shown in Figure 6 and we can see that the output power of the material can reach 1.8 W / cm 2 at 800 °C, indicating that the material has excellent oxygen catalytic activity and oxygen ion transport performance. It is a very excellent cathode material for solid oxide fuel cells. In order to verify the long-term working stability of the material, we made it work at a constant voltage of 0.7 V at 750 °C for a long time, and the test results are as shown in Figure 7 and we can see that the material can output stably and its performance is increasing continuously, indicating that the bionic catalyst disclosed in this embodiment has very excellent working stability.

[0069] Example 2:

[0070] The high-temperature ceramic catalyst with a bionic structure in this embodiment has a chemical composition of PrBaCo2O 5+δ #Sm 0.1 Ce 0.9 O 1.95 and has extremely high oxygen catalytic activity and is suitable for solid oxide electrolytic cells.

[0071] The bionic structure ceramic catalyst includes "mesophyll", "vein" and "epidermis" structures; the "mesophyll" is the main structure with the chemical formula PrBaCo2O 5+δ ; the "vein" is a network structure located inside the "mesophyll", the "epidermis" is a coating layer located on the surface layer of the "mesophyll", and the chemical formulas of the "vein" and "epidermis" are Sm 0.1 Ce0.9 O 1.95 Among them, the thickness of the "epidermis" is 10 - 20 nm, and the diameter of the "vein" is 10 - 15 nm.

[0072] As a high-temperature ceramic catalyst, the specific preparation process is as follows:

[0073] (1) Dissolve glycine and ethylenediaminetetraacetic acid in pure water at a ratio of 2:1 as complexing agents, so that the concentrations of glycine and ethylenediaminetetraacetic acid are 0.5 mol / L;

[0074] (2) Dissolve praseodymium nitrate, barium nitrate, and cobalt nitrate corresponding to the "mesophyll" in the above solution, so that the molar ratio of metal cations to glycine and ethylenediaminetetraacetic acid is 1:1.5;

[0075] (3) Adjust the pH value of the above solution to 6.5 with ammonia water, and name this solution Solution A;

[0076] (4) Place Solution A in a closed container and heat and stir at 70 °C for 4 h to obtain Sol A; place Sol A in an open container and heat and stir at 85 °C for 8 h to obtain Gel A;

[0077] (5) Place Gel A in a heat-resistant crucible and heat it at 250 °C to make it self-ignite, and place the self-ignited powder in a muffle furnace for further carbon removal at 550 °C for 4 h to obtain Nano-powder A;

[0078] (6) Use ethylenediaminetetraacetic acid as a complexing agent and dissolve samarium acetate and cerium acetate corresponding to the "epidermis" and "vein" in pure water, so that the molar ratio of metal cations to ethylenediaminetetraacetic acid is 1.5:1, adjust the pH value of the solution to 6.5 with ammonia water, and name this solution Solution B;

[0079] (7) Place Solution B at 70 °C and seal and stir for 18 h to convert Solution B into Sol B;

[0080] (8) Place Nano-powder A in Sol B and impregnate it in a vacuum environment of 0.05 Pa for 3 h; then use the filtration method to remove part of Sol B to obtain Filter C; freeze-dry Filter C in a vacuum at 3 Pa and -30 °C for 24 h to obtain Precursor D;

[0081] (9) Heat-treat Precursor D at 1000 °C, with a heating and cooling rate of 1 °C / min and a holding time of 6 h, then the bionic structure ceramic catalyst disclosed in the present invention can be obtained.

[0082] To verify the high electronic conductivity of the material, we ground the sintered powder, then pressed it into a long strip under a pressure of 200 MPa and sintered it at 1100 °C. Subsequently, the electronic conductivity of the sintered long strip in air at 100 - 850 °C was analyzed using the four-electrode method. The test results are as Figure 8 shown. The electronic conductivity of the material is higher than 200 S / cm within the test temperature range, meeting the requirements of the solid oxide electrolytic cell for the electronic conductivity of the oxygen catalyst. To verify

[0083] PrBaCo2O 5+δ #Sm 0.1 Ce 0.9 O 1.95 ceramics as the oxygen catalytic performance of the solid oxide electrolytic cell, we ball-milled and crushed it to make a slurry, and coated the slurry on both sides of the Gd 0.1 Ce 0.9 O 1.95 electrolyte sheet to form a symmetric cell. We characterized the oxygen catalytic activity of the corresponding symmetric cell in air at 600 - 800 °C using electrochemical impedance spectroscopy technology. The results are as Figure 9 shown. It can be seen from the figure that the impedance at 700 °C is only 0.037 Ω·cm 2 , indicating that the material has very excellent oxygen catalytic activity.

[0084] Example 3:

[0085] The high-temperature ceramic catalyst with a bionic structure in this example has a chemical composition of La2NiO4#La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ , and has extremely high oxygen catalytic activity and oxygen transport performance, and can be applied to high-temperature oxygen dialysis membranes.

[0086] The bionic structure ceramic catalyst includes "mesophyll", "vein" and "epidermis" structures; the "mesophyll" is the main structure with a chemical formula of La2NiO4; the "vein" is a network structure located inside the "mesophyll", and the "epidermis" is a layered structure located on the surface layer of the "mesophyll". The chemical formulas of the "vein" and "epidermis" are La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ . Among them, the thickness of the "epidermis" is 30 - 50 nm, and the diameter of the "vein" is 20 - 30 nm.

[0087] As a high-temperature ceramic catalyst, the specific preparation process steps are as follows:

[0088] (1) Dissolve glycine and urea as complexing agents in pure water at a ratio of 1:1, so that the concentrations of glycine and urea are 0.2 mol / L;

[0089] (2) Dissolve lanthanum nitrate and nickel nitrate corresponding to "mesophyll" in the above solution, so that the molar ratio of metal cations to glycine and urea is 1:2;

[0090] (3) Adjust the pH value of the above solution to 6 with ammonia water, and name this solution Solution A;

[0091] (4) Place Solution A in a closed container and heat and stir it at 80 °C for 3 h to obtain Sol A; place Sol A in an open container and heat and stir it at 90 °C for 6 h to obtain Gel A;

[0092] (5) Place Gel A in a heat-resistant crucible and heat it at 270 °C to make it self-ignite, and place the self-ignited powder in a muffle furnace to further remove carbon at 600 °C for 2 h to obtain Nano-powder A;

[0093] (6) Dissolve urea as a complexing agent and lanthanum nitrate, strontium nitrate, gallium nitrate and magnesium nitrate corresponding to "epidermis" and "vein" in pure water, so that the molar ratio of metal cations to urea is 2:1, and adjust the pH value of the solution to 7 with ammonia water, and name this solution Solution B;

[0094] (7) Place Solution B at 80 °C and seal and stir it for 12 h to transform Solution B into Sol B;

[0095] (8) Place Nano-powder A in Sol B and impregnate it in a vacuum environment of 0.1 Pa for 6 h; then use the suction filtration method to remove part of Sol B to obtain Filter C; freeze-dry Filter C at 5 Pa and -50 °C for 15 h to obtain Precursor D;

[0096] (9) Perform heat treatment on Precursor D at 1100 °C, with a heating and cooling rate of 1.5 °C / min and a holding time of 3 h, and the bionic structure ceramic catalyst disclosed in the present invention can be obtained.

[0097] The macroscopic property of this material is a dense black block, and the macroscopic photo is as follows Figure 10 shown. In order to verify the high oxygen catalysis and oxygen transport performance of this material, we cut the sintered block material into long strips, measured its oxygen exchange rate at 700 °C by the four-electrode method, and then compared it with the oxygen exchange rate of the long strip made of La2NiO4 material by the same process at 700 °C. As Figure 11 shown, we can find that La2NiO4#La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δThe long strip reached equilibrium in only 500 s, while the La2NiO4 long strip took 1200 s, indicating that the prepared high-temperature ceramic catalyst with a bionic structure has extremely high oxygen catalytic and oxygen transport performance, and its structure is very conducive to oxygen transport.

[0098] Example 4:

[0099] The high-temperature ceramic catalyst with a bionic structure in this example has a chemical composition of La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 , has high oxygen ion conductivity and can be applied to high-temperature oxygen sensors.

[0100] The bionic structure ceramic catalyst includes "mesophyll", "vein" and "epidermis" structures; the "mesophyll" is the main structure with a chemical formula of La 0.6 Sr 0.4 CoO 3-δ ; the "vein" is a network structure located inside the "mesophyll", the "epidermis" is a layered structure located on the surface layer of the "mesophyll", and the chemical formula of the "vein" and "epidermis" is Sm 0.1 Ce 0.9 O 1.95 . The thickness of the "epidermis" is 2 - 8 nm, and the diameter of the "vein" is 15 - 20 nm.

[0101] As a high-temperature ceramic catalyst, the specific preparation process is as follows:

[0102] (1) Dissolve glycine and citric acid in pure water at a ratio of 1:3 as complexing agents, so that the concentrations of glycine and citric acid are 0.5 mol / L;

[0103] (2) Dissolve lanthanum nitrate, strontium nitrate and cobalt nitrate corresponding to the "mesophyll" in the above solution, so that the molar ratio of metal cations to ethylenediaminetetraacetic acid and citric acid is 1:1;

[0104] (3) Adjust the pH value of the above solution to 7 with ammonia water, and name this solution Solution A;

[0105] (4) Place Solution A in a closed container and heat and stir it at 90 °C for 2 h to obtain Sol A; place Sol A in an open container and heat and stir it at 95 °C for 5 h to obtain Gel A;

[0106] (5) Place Gel A in a heat-resistant crucible and heat it at 200 °C to make it self-ignite, and place the self-ignited powder in a muffle furnace for further carbon removal at 500 °C for 8 h to obtain Nano-powder A;

[0107] (6) Citric acid was used as a complexing agent, and samarium acetate and cerium acetate corresponding to the "epidermis" and "vein" were dissolved in pure water, so that the molar ratio of metal cations to citric acid was 1:1. The pH value of the solution was adjusted to 7 with ammonia water, and this solution was named solution B;

[0108] (7) Solution B was placed in a sealed container and stirred at 90 °C for 8 h to transform solution B into sol B;

[0109] (8) Nanopowder A was placed in sol B and impregnated for 8 h in a vacuum environment of 0.5 Pa; then part of sol B was removed by suction filtration to obtain filtrate C; filtrate C was vacuum freeze-dried at 6 Pa and -60 °C for 8 h to obtain precursor D;

[0110] (9) Precursor D was heat-treated at 1200 °C with a heating and cooling rate of 2 °C / min and a holding time of 2 h to obtain the bionic structure ceramic catalyst disclosed in the present invention.

[0111] To verify the catalytic performance of this material at high temperatures, we ground La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 and La 0.6 Sr 0.4 CoO 3-δ into micron-sized powders respectively, and mixed them with terpineol and ethyl cellulose according to the weight ratio of powder:terpineol:ethyl cellulose = 1:0.95:0.05 to make a slurry, and then evenly coated it on the anode-supported single cell. After sintering at 950 °C for 4 h in a box furnace, it was tested by the four-electrode method. When working for a long time in an environment of 750 °C and high oxygen concentration, its open circuit voltage is as Figure 12 shown. The working results are as Figure 13 shown. It can be seen that La 0.6 Sr 0.4 CoO 3-δ #Sm 0.1 Ce 0.9 O 1.95 works stably. After the work is completed, the surface of the material is observed by scanning electron microscopy. The typical figure is as Figure 14 shown. It can be seen that there is no obvious precipitation on the surface, which proves that this material can work sensitively for a long time at high temperatures and has the potential to be used as a high-temperature oxygen sensor.

[0112] Comparative Example 1:

[0113] The ceramic catalyst without bionic structure in this example has a chemical composition of La 0.6 Sr 0.4 Co 0.2 Fe0.8 O 3-δ and Gd 0.1 Ce 0.9 O 1.95 Since it does not have the characteristics of a biomimetic structure, it is named separately from the biomimetic catalyst and named La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ +Gd 0.1 Ce 0.9 O 1.95 Its macroscopic property is a dense black massive material, which can be used as a cathode catalyst for solid oxide fuel cells.

[0114] As a high-temperature ceramic catalyst, the specific preparation process steps are as follows:

[0115] (1) Dissolve glycine and citric acid in pure water at a ratio of 3:1 as complexing agents, so that the concentrations of glycine and citric acid are 1 mol / L;

[0116] (2) Dissolve lanthanum nitrate, strontium nitrate, cobalt nitrate, and iron nitrate corresponding to "mesophyll" in the above solution, so that the molar ratio of metal cations to glycine and citric acid is 1:1;

[0117] (3) Adjust the pH value of the above solution to 7 with ammonia water, and name this solution Solution A;

[0118] (4) Place Solution A in an open container and heat and stir at 80 °C for 12 h to obtain Gel A;

[0119] (5) Place Gel A in a heat-resistant crucible and heat it at 230 °C to make it self-ignite, and place the self-ignited powder in a muffle furnace for further carbon removal at 500 °C for 6 h to obtain Nanopowder A;

[0120] (6) Use citric acid as a complexing agent and dissolve gadolinium nitrate and cerium nitrate corresponding to "epidermis" and "vein" in pure water, so that the molar ratio of metal cations to citric acid is 1:1, and adjust the pH value of the solution to 7 with ammonia water, and name this solution Solution B;

[0121] (7) Let Solution B stand at room temperature for 12 h to turn Solution B into Sol B;

[0122] (8) Place Nanopowder A in Sol B and evaporate it to dryness in an open container at 80 °C to obtain Precursor D;

[0123] (9) Perform heat treatment on Precursor D at 900 °C, with a heating and cooling rate of 0.5 °C / min and a holding time of 8 h, and a ceramic catalyst without a biomimetic structure can be obtained.

[0124] The morphology of the material is as Figure 16 shown. It can be found that Gd, which should have been the "epidermis", 0.1 Ce 0.9 O 1.95 did not tightly wrap around the "mesophyll", but instead became small particles adsorbed on the surface of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ and this cannot function as a biomimetic catalyst. To verify the difference in the influence of this structure and the biomimetic structure on the material properties, we ground

[0125] La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ +Gd 0.1 Ce 0.9 O 1.95 into micron-sized powders, and mixed them with terpineol and ethyl cellulose according to the weight ratio of powder:terpineol:ethyl cellulose = 1:0.9:0.1 to make a slurry, then evenly coated it on the anodic-supported single cell and sintered it in a box furnace at 1000 °C. After that, long-term tests were carried out at 750 °C by the four-electrode method. The test results are as Figure 17 shown. The maximum output power at 800 °C does not exceed 1.5 W / cm 2 . To verify the long-term output performance of this material, we made it work at a constant voltage of 0.7 V at 750 °C for a long time. The test results are as Figure 18 shown. We can see that the material starts to decay after growing for a period of time, and the decay is very severe, indicating that the long-term output stability of this material is very poor and there is a large gap from the biomimetic structure catalyst.

Claims

1. A bionic structural ceramic catalyst, characterized in that, The bionic structural ceramic catalyst includes "mesophyll", "vein" and "epidermis" structures; the "mesophyll" is the main structure, which is composed of one of perovskite structure ABO3, double perovskite structure A2B2O 5+δ or Ruddlesden-Popper structure A2BO4; the "vein" is a network structure located inside the "mesophyll", the "epidermis" is a coating layer located on the surface of the "mesophyll", and the "vein" and "epidermis" are cubic fluorite structure or perovskite structure; In the perovskite structure ABO3, double perovskite structure A2B2O 5+δ and Ruddlesden-Popper structure A2BO4, A is one or more of La, Pr, Gd, Nd, Sm, Sr, Ba, and Ca, and B is one or more of Fe, Co, or Ni; The cubic fluorite structure or perovskite structure of the "epidermis" and "vein" includes Gd 1-x Ce x O 2-δ 、Sm 1-x Ce x O 2-δ or La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ and one of them, where x = 0 - 0.5; The "vein" and "epidermis" structures of the bionic structural ceramic catalyst grow in-situ in the "mesophyll" structure; The preparation method steps of the bionic structural ceramic catalyst are as follows: (1) Complex the soluble nitrate corresponding to the "mesophyll" of the catalyst with an aqueous solution of complexing agent A, adjust the pH value to 6-7 to obtain solution A; complex the soluble metal salts corresponding to the "vein" and "epidermis" of the catalyst with an aqueous solution of complexing agent B, and adjust the pH value to 6-7 to obtain solution B; (2) Place solution A in a closed container, heat and stir to obtain sol A; place sol A in an open container, heat and stir to obtain gel A; heat gel A to self-ignite, and further remove carbon from the self-igniting powder to obtain nanopowder A; place solution B in a closed container, heat and stir to obtain sol B; (3) Place nanopowder A in sol B and impregnate it in a vacuum environment; then use the suction filtration method to remove part of sol B to obtain filtrate C; freeze-dry filtrate C to obtain precursor D; (4) Heat-treat precursor D to obtain the bionic structural ceramic catalyst.

2. The bionic structural ceramic catalyst according to claim 1, wherein The thickness of the "epidermis" is 2-10 nm.

3. The bionic structural ceramic catalyst according to claim 1, wherein, The diameter of the "vein" is 2-20 nm.

4. A method for preparing a bionic structural ceramic catalyst according to any one of claims 1-3, characterized in that, The specific preparation steps are as follows: (1) Complex the soluble nitrate corresponding to the "mesophyll" of the catalyst with an aqueous solution of complexing agent A, adjust the pH value to 6-7 to obtain solution A; complex the soluble metal salts corresponding to the "vein" and "epidermis" of the catalyst with an aqueous solution of complexing agent B, and adjust the pH value to 6-7 to obtain solution B; (2) Place solution A in a closed container, heat and stir to obtain sol A; place sol A in an open container, heat and stir to obtain gel A; heat gel A to self-ignite, and further remove carbon from the self-igniting powder to obtain nanopowder A; place solution B in a closed container, heat and stir to obtain sol B; (3) Place nanopowder A in sol B and impregnate it in a vacuum environment; then use the suction filtration method to remove part of sol B to obtain filtrate C; freeze-dry filtrate C to obtain precursor D; (4) Heat-treat precursor D to obtain the bionic structural ceramic catalyst.

5. The preparation method according to claim 4, characterized in that, In step (1), the complexing agent A is a combination of glycine and one of citric acid, ethylenediaminetetraacetic acid or urea, and the molar ratio of glycine to the other complexing agent is 3:1 - 1:3; the soluble nitrate corresponding to "mesophyll" includes one or more of lanthanum nitrate, praseodymium nitrate, gadolinium nitrate, neodymium nitrate, samarium nitrate, strontium nitrate, barium nitrate, calcium nitrate, iron nitrate, cobalt nitrate or nickel nitrate; the molar ratio of complexing agent A to the metal cation of the nitrate is 1:1 - 2:1; the metal cation concentration of solution A is 0.1 - 1 M; the complexing agent B is one or more of citric acid, ethylenediaminetetraacetic acid or urea, and the soluble metal salts corresponding to the catalysts "vein" and "epidermis" specifically refer to one or more of gadolinium nitrate, gadolinium acetate, cerium nitrate, cerium acetate, samarium nitrate, samarium acetate, lanthanum nitrate, lanthanum acetate, strontium nitrate, strontium acetate, gallium nitrate, gallium acetate, magnesium nitrate, magnesium acetate and magnesium acetate; the molar ratio of complexing agent B to the cation in the soluble metal salt is 1:1 - 2:1, and the material for adjusting the pH value is ammonia water; the metal cation concentration of solution B is 0.02 - 0.2 M.

6. The preparation method according to claim 4, characterized in that, In step (2), the temperature for heating and stirring solution A in a closed container is 60 - 90 °C, and the stirring time is 2 - 5 h; the temperature for heating and stirring solution A in an open container is 80 - 95 °C, and the time length is 5 - 10 h; gel A self-ignites in a crucible, and the heating temperature is 150 - 300 °C; the self-ignited powder is decarbonized in a muffle furnace at a temperature of 500 - 600 °C, in an air atmosphere; the temperature for heating and stirring solution B in a closed container is 60 - 90 °C, and the stirring time is 5 - 24 h; in step (3), the vacuum degree of the surrounding environment when nanopowder A is impregnated in sol B is 0.01 - 1 Pa, and the impregnation time is 0.5 - 10 h; the freeze-drying pressure is 3 - 10 Pa, the temperature is -30 °C to -70 °C, and the time is 12 - 24 h; in step (4), the heat treatment temperature of the precursor D is 900 - 1200 °C, the heating and cooling rate is 0.5 - 2 °C / min, and the holding time at the highest temperature is 2 - 8 h.

7. Use of a bionic structural ceramic catalyst as described in any one of claims 1-3, characterized in that, The bionic structure ceramic catalyst can be used for the oxygen electrodes of solid oxide fuel cells and solid oxide electrolyzers.

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