Cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material and preparation method thereof

Abstract

The invention discloses a cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material and a preparation method of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material. The cathode material is of an A2BO4 type Ruddlesden-Popper phase structure, and the structure of the cathode material is as shown in the specification. Wherein the A-site element is composed of La, Pr, Nd and Sr which are mixed according to the molar ratio of 3: 3: 3: 1, and the B-site element is Ni element; the molar ratio of the A-site element to the B-site element is 2: 1; the chemical formula of the material is La0. 6Pr0. 6Nd0. 6Sr0. 2NiO4, and the material has excellent conductivity and peak output power density, and shows excellent carbon dioxide tolerance and remarkable cost advantage. And the service life of the SOFC is prolonged, and industrialization promotion of the SOFC is facilitated.

Description

Technical Field

[0001] The present invention relates to a solid oxide fuel cell material for chemical power sources, and to a cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material and a preparation method thereof. Background Art

[0002] A solid oxide fuel cell (SOFC) is an all-solid-state energy conversion device that directly converts the chemical energy of a fuel into electrical energy through an electrochemical reaction. As an efficient energy conversion device, a fuel cell can directly convert the chemical energy of a fuel into electrical energy, with a higher energy conversion efficiency. In addition, the fuel sources of fuel cells are extensive and the cost is relatively low. For this reason, fuel cells are regarded as the fourth-generation power generation technology after thermal power, hydropower and nuclear power generation.

[0003] Traditional SOFCs usually operate under high-temperature conditions of 800 - 1000 °C. Such high-temperature operations bring many severe challenges, such as high manufacturing costs, slow battery start-stop, rapid performance degradation, poor thermal matching, insufficient mechanical stability, component aging, etc. These disadvantages seriously limit the further development and large-scale commercial application of SOFC technology. In contrast, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have become a more promising research direction due to their advantages of good low operating temperature (600 - 800 °C), high operating stability, fast startup, a wide range of packaging material selections, and relatively low manufacturing costs. Therefore, it is of great significance to promote the development of IT-SOFC technology.

[0004] However, when SOFCs operate in the intermediate-temperature range of 600 - 800 °C, they often face problems such as a significant increase in cathode polarization resistance and material performance degradation. Therefore, more stringent requirements are imposed on cathode materials. Although traditional cobalt-based cathode materials have excellent catalytic activity, their inherent defects restrict their large-scale application: high price, high thermal expansion coefficient, susceptibility to corrosion by water vapor and carbon dioxide, etc. In contrast, nickel-based cathode catalysts have advantages such as good thermal matching, high oxygen reduction activity, and high cost-effectiveness, and show broad application prospects in fields such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). However, nickel-based materials generally have poor stability, resulting in rapid attenuation of their electrochemical performance, which has become a key bottleneck restricting their commercial application. Taking the typical RP-phase layered oxide La2NiO4 as an example, its initial ORR activity is excellent, and a peak power density (PPD) of 0.77 W·cm -2 can be achieved under test conditions at 750 °C. But after continuous operation for 20 hours, the PPD drops sharply to 0.47 W·cm -2(The attenuation rate reaches 39%), how to improve the stability of nickel-based cathode catalytic materials has become an urgent problem to be solved. Therefore, it is extremely urgent to adopt the strategy of high-entropy design to improve the stability, electrocatalytic activity and carbon dioxide tolerance of nickel-based materials.

[0005] Chinese Patent Application CN118572133 A discloses a high-entropy double perovskite cathode material and its preparation. The cathode material of this technology is an ABO3-type high-entropy perovskite material, and its general formula is LnXnO 3-δ , where Xn is composed of two or more elements in an equal atomic ratio, including Co and Fe elements; Ln is composed of five or more elements in an equal atomic ratio, including Pr, Ba and Ca elements. Synthesize a compound with a high-entropy perovskite structure containing low-cost alkaline earth metals Ba 2+ and Ca 2+ and use it as the cathode material of a medium and low temperature solid oxide fuel cell to improve its oxygen reduction catalytic activity and chemical stability. However, its PPD is only 576 mW (750 °C), and there is still a large room for improvement. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the present invention aims to provide a cobalt-free high-entropy Ruddlesden-Popper (R-P) phase solid oxide fuel cell (SOFC) cathode material and its preparation method; this cathode material has excellent conductivity, peak output power density, exhibits excellent carbon dioxide tolerance and significant cost advantages, and is beneficial to extending the service life of SOFC.

[0007] Another object of the present invention is to provide the application of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material in the preparation of solid oxide fuel cells.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material has an A2BO4-type Ruddlesden-Popper phase structure; the A-site elements are composed of four elements, La, Pr, Nd, and Sr, and are mixed in a molar ratio of 3:3:3:1, and the B-site element is Ni; the molar ratio of the A-site element to the B-site element is 2:1.

[0010] To further achieve the object of the present invention, preferably, the material chemical formula is La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4.

[0011] The preparation method of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material comprises the following steps:

[0012] S1: Dissolve the precursors corresponding to the constituent elements La, Pr, Nd, Sr, and Ni of the solid oxide fuel cell cathode material in water according to the stoichiometric ratio to obtain an aqueous metal ion solution;

[0013] S2: Add a complexing agent to the aqueous metal ion solution obtained in step S1 and adjust the pH value to 1-5 to obtain a complexing sol;

[0014] S3: Heat and stir the complexing sol obtained in step S2 to evaporate and form a gel, and then dry it into a dry gel;

[0015] S4: Dry and calcine the dry gel obtained in step S3 to obtain the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material.

[0016] Preferably, in step S1, the precursors of the constituent elements La, Pr, Nd, Sr, and Ni are La, Pr, Nd, Sr, and Ni nitrates respectively.

[0017] Preferably, in step S2, the complexing agent is one or two of citric acid, oxalic acid, ethylenediaminetetraacetic acid, and glycine; the molar ratio of the complexing agent to the total molar amount of metal ions is 1:1 to 2:1; the pH value is adjusted by adding ammonia water.

[0018] Preferably, in step S3, the heating is carried out in a water bath stirring pot, the heating temperature is 60-100 °C, and the heating time is 30-90 min.

[0019] Preferably, in step S4, the drying is carried out in a high-temperature drying oven at a temperature of 80-200 °C for 5-25 h; the calcination is carried out in a muffle furnace and calcined at a temperature in the range of 800-1100 °C for 1-10 h.

[0020] The cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material is used in the preparation of solid oxide fuel cells.

[0021] Preferably, with the said La 0.6 P r0.6 Nd 0.6 Sr 0.2NiO4 is used as the cathode material, gadolinium-doped ceria (GDC) is used as the barrier layer material, yttria-stabilized zirconia (YSZ) is used as the electrolyte material, nickel oxide and zirconia (AFL) are used as the anode functional layer, and nickel oxide and zirconia (NiO-YSZ) are used as the anode support to prepare the anode-supported full cell NiO-YSZ|AFL|YSZ|GDC|La 0.6 P r0.6 Nd 0.6 Sr 0.2 NiO4.

[0022] Preferably, the fuel of the solid oxide battery is hydrogen.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1) The cobalt-free high-entropy Ruddlesden-Popper (R-P) phase La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material is doped with multiple elements (La, Pr, Nd, Sr) through high-entropy design, which significantly improves its electrochemical performance, high-temperature stability, peak output power in the medium-temperature range, and carbon dioxide tolerance. It has excellent comprehensive performance and provides a new solution to solve the problem of power attenuation of traditional cathode materials in a carbon dioxide atmosphere.

[0025] 2) The present invention dopes rare earth elements and alkaline earth metal elements La, Pr, Nd, Sr at the A site. This cathode material is a mixed ionic conductor with good conductivity, and the ionic radii of the above 4 A-site elements are close, and the ionic size difference is small, which is conducive to the formation of a stable single-phase structure.

[0026] 3) After testing, the high-entropy La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 is a Ruddlesden-Popper type mixed ionic conductor cathode material and can maintain stable electrochemical performance in a carbon dioxide atmosphere, showing excellent carbon dioxide tolerance. While improving the stability of the fuel cell in a complex working environment, it also helps to extend the battery life. It can effectively improve the working stability of SOFC.

[0027] 4) The high-entropy nickel-based cathode material La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 significantly improves the oxygen reduction reaction (ORR) catalytic activity of the cathode material, which helps to improve the output power of the fuel cell.

[0028] 5) The high-entropy nickel-based cathode material La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 of the present invention does not utilize the high-cost cobalt element. Compared with traditional cobalt-based materials, the high-entropy nickel-based cathode material of the present invention significantly reduces the cost and has a significant cost advantage.

[0029] 6) The preparation method of the cathode material of the present invention is simple and can be applied to solid oxide fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the XRD pattern of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material synthesized in Example 1.

[0031] Figure 2 is the graph of the relationship between the conductivity of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material synthesized in Example 1 and temperature.

[0032] Figure 3 is the micrograph of the single cell (YSZ-NiO|AFL|YSZ|GDC|La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4) in the application example.

[0033] Figure 4 is the I-V graph of the single cell assembled with the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material in the application example at different temperatures.

[0034] Figure 5 is the Nyquist plot of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 symmetrical cell at different carbon dioxide partial pressures in the application example.

[0035] Figure 6 is the La at 700 °C in the application example 0.6 Pr 0.6 Nd 0.6 Sr 0.2Time-dependent curve of polarization impedance of NiO4 cathode material at different CO2 concentrations.

[0036] Figure 7 is Application Example La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 Microstructure image of NiO4 cathode before CO2 poisoning.

[0037] Figure 8 is Application Example 700 °C, (10% CO2, 90% air) environment La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 Microstructure image of NiO4 cathode material after 10 h of poisoning. Detailed implementation manners

[0038] To better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the implementation manners of the present invention are not limited thereto. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0039] In the field of solid oxide fuel cells (SOFCs), the current mainstream cathode material is the cobalt-based perovskite system La 0.6 Sr 0.6 Co 0.4 Fe 0.6 O 3-δ (LSCF). However, cobalt-based materials are costly, and LSCF has a high thermal expansion coefficient and shows poor stability in water vapor and carbon dioxide environments, which together hinder the process of its large-scale commercial application.

[0040] In the present invention, rare earth elements and alkaline earth metal elements La, Pr, Nd, Sr are doped at the A site. This cathode material is a mixed ionic conductor with good conductivity, and the ionic radii of the above 4 A-site elements are close, and the ionic size difference is small, which is conducive to the formation of a stable single-phase structure; after testing, the high-entropy La 0.6 Pr 0.6 Nd 0.6 Sr 0.2NiO4 is a Ruddlesden-Popper type mixed ionic conductor cathode material, and its electrochemical performance can remain stable in a carbon dioxide atmosphere, showing excellent carbon dioxide tolerance. While improving the stability of the fuel cell in a complex working environment, it also helps to extend the battery life. It can effectively enhance the working stability of SOFC; moreover, the high-entropy nickel-based cathode material La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 of the present invention significantly improves the catalytic activity of the oxygen reduction reaction (ORR) of the cathode material, which helps to increase the output power of the fuel cell; at the same time, the high-entropy nickel-based cathode material La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 of the present invention does not use high-cost cobalt elements. Compared with traditional cobalt-based materials, the high-entropy nickel-based cathode material of the present invention greatly reduces the cost and has a significant cost advantage.

[0041] A cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material of the present invention has an A2BO4 type Ruddlesden-Popper phase structure; the A-site elements are composed of four elements, La, Pr, Nd, and Sr, mixed in a molar ratio of 3:3:3:1, and the B-site element is a transition metal element Ni; the molar ratio of the A-site element to the B-site element is 2:1. This material is a mixed conductor cathode material with large electrocatalytic activity, and the ionic radii of the above 4 A-site elements are close, and the ionic size difference is small, which is conducive to the formation of a stable single-phase structure; the specific chemical formula is: La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4.

[0042] The preparation method of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material described above includes the following steps:

[0043] S1: Dissolve the corresponding precursors of the solid oxide fuel cell cathode material components La, Pr, Nd, Sr, and Ni in water according to the stoichiometric ratio to obtain an aqueous metal ion solution;

[0044] S2: Add a complexing agent to the aqueous metal ion solution obtained in step S1 and adjust the pH value to 1-5 to obtain a complexing sol;

[0045] S3: Heat and stir the complexing sol obtained in step S2 to evaporate and form a gel, and dry it into a dry gel;

[0046] S4: Dry and calcine the xerogel obtained in step S3 to obtain a cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material.

[0047] For the preparation method of the present invention, in step S1, the precursors of the constituent elements La, Pr, Nd, Sr, and Ni are La, Pr, Nd, Sr, and Ni nitrates respectively. In step S2, the complexing agent is preferably one or two of citric acid, oxalic acid, ethylenediaminetetraacetic acid, and glycine; the molar ratio of the complexing agent to the total molar number of metal ions is from 1:1 to 2:1.

[0048] In step S3, the heating is carried out in a water bath stirrer, the heating temperature is 60 - 100 °C, and the heating time is 30 - 90 min.

[0049] In step S4, the drying is preferably carried out in a high-temperature drying oven at a temperature of 80 - 200 °C for 5 - 25 h; the calcination is preferably carried out in a muffle furnace and calcined at a temperature in the range of 800 - 1100 °C for 1 - 10 h. The purpose of drying is to discharge ammonia in the nitrate and moisture in the raw materials to obtain a dry and porous xerogel, thereby reducing the powder synthesis temperature. The purpose of calcination is to remove organic substances and synthesize a Ruddlesden-Popper type perovskite-like cathode with a smaller grain size under high-temperature conditions.

[0050] The present invention also protects the application of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material in the preparation of solid oxide fuel cells. The solid oxide fuel cell uses La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 as the cathode material, gadolinium-doped ceria (GDC) as the barrier layer material, yttria-stabilized zirconia (YSZ) as the electrolyte material, nickel oxide and zirconia (AFL) as the anode functional layer, and nickel oxide and zirconia (NiO-YSZ) as the anode support to prepare an anode-supported full cell NiO-YSZ|AFL|YSZ|GDC|La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4. The fuel of the solid oxide fuel cell is hydrogen.

[0051] Example 1:

[0052] Prepare La using the Pechini method 0.6 Pr 0.6 Nd 0.6 Sr 0.2NiO4 High-Entropy Ruddlesden-Popper Structure Cathode Material.

[0053] S1, According to the chemical formula La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4, Weigh La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sr(NO3)2, and Ni(NO3)2·6H2O respectively according to the stoichiometric ratio and dissolve them in deionized water in turn. After the nitrates are completely dissolved, add complexing agents (citric acid, ethylene glycol) and stir to dissolve. The molar ratio of metal cations to citric acid is 1:1, and the ratio of ethylene glycol to metal cations is 1:1. Add the solution and add ammonia water to adjust the pH value to 1.5 to obtain a complex sol;

[0054] S2, Heat and stir the complex sol obtained in step S1 on a magnetic stirring table at 80 °C for 30 min to form a gel;

[0055] S3, Then transfer the gel obtained in step S2 to an oven and dry it at 100 °C for 20 h to obtain a dry gel;

[0056] S4, Put the dry gel obtained in step S3 into a crucible and transfer it to a high-temperature furnace for drying and calcination. Raise the temperature to 1000 °C at a heating rate of 10 °C / min, hold for 2 h at 1000 °C, and then cool it to room temperature with the furnace to obtain La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material powder.

[0057] Perform XRD analysis on the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode powder obtained in Example 1, and the results are as Figure 1 shown. Figure 1 It shows that the XRD diffraction peak positions of the cathode material powder prepared in step S4 of this Example 1 are highly consistent with the tetragonal Ruddlesden-Popper phase, which proves that the high-entropy Ruddlesden-Popper structure cathode material can be successfully prepared by the Pechini method. From the mass ratio of the four elements La, Pr, Nd, and Sr at the A site, the dosage ratio of the Ni element at the B site in Example 1, and the fact that none of these raw materials have volatile elements and the cathode calcination temperature is relatively low (below 1100 °C), it can be determined that the chemical formula of the obtained cathode material powder is La 0.6 Pr 0.6 Nd 0.6 Sr0.2 NiO4.

[0058] The La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode powder was dry-pressed and sintered to density, and its conductivity at 400 - 800 °C was measured. The conductivity-temperature curve is as Figure 2 shown. At the test temperature, the conductivity of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 material all exceeded the minimum conductivity requirement of 100 S / cm and had a relatively high electronic conductivity.

[0059] Example 2:

[0060] The La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 high-entropy Ruddlesden-Popper structured cathode material was prepared by the Pechini method.

[0061] S1. According to the chemical formula La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4, La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sr(NO3)2, and Ni(NO3)2·6H2O were weighed respectively according to the stoichiometric ratio and dissolved in deionized water in turn. After the nitrates were completely dissolved, a complexing agent (citric acid, ethylene glycol) was added and stirred to dissolve. The molar ratio of metal cations to citric acid was 1:1.5, and the ratio of ethylene glycol to metal cations was 1:1.5. Ammonia water was added to the solution to adjust the pH value to 1.2 to obtain a complexing sol;

[0062] S2. The complexing sol obtained in step S1 was heated and stirred on a magnetic stirring table at 85 °C to evaporate and form a gel;

[0063] S3. Subsequently, the gel obtained in step S2 was transferred to an oven and dried at 120 °C for 15 h to obtain a dry gel;

[0064] S4. The dry gel obtained in step S3 was placed in a crucible and transferred to a high-temperature furnace for drying and calcination. It was heated to 950 °C at a heating rate of 8 °C / min, held at 950 °C for 3 h, and then cooled to room temperature with the furnace to obtain La 0.6 Pr 0.6 Nd 0.6 Sr0.2 NiO4 cathode material powder.

[0065] Example 3:

[0066] Prepare La by Pechini method 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 high-entropy Ruddlesden-Popper structure cathode material.

[0067] S1. According to the chemical formula La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4, weigh La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sr(NO3)2, Ni(NO3)2·6H2O separately according to the stoichiometric ratio and dissolve them in deionized water in turn. After the nitrates are completely dissolved, add complexing agents (citric acid, ethylene glycol) and stir to dissolve. The molar ratio of metal cations to citric acid is 1:2, and the ratio of ethylene glycol to metal cations is 1:2. Add the solution and add ammonia water to adjust the pH value to 2.0 to obtain a complexing sol;

[0068] S2. Heat and stir the complexing sol obtained in step S1 on a magnetic stirring table at 90 °C to evaporate and form a gel;

[0069] S3. Then transfer the gel obtained in step S2 to an oven and dry it at 150 °C for 10 h to obtain a dry gel;

[0070] S4. Put the dry gel obtained in step S3 into a crucible and transfer it to a high-temperature furnace for drying and calcination. Raise the temperature to 1050 °C at a heating rate of 8 °C / min, keep it at 1050 °C for 1 h, and then cool it down to room temperature with the furnace to obtain La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode material powder.

[0071] Application example:

[0072] A. Mix and grind the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode powder and binder (4 wt% ethyl cellulose + 96 wt% terpineol) according to a mass ratio of 6:4 to obtain La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode slurry;

[0073] B. Coating the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 slurry on the anode-supported cell and heat-treating it at 1000 °C for 2 hours;

[0074] C. Coating the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 slurry on both sides of the YSZ electrolyte sheet and heat-treating it at 1000 °C for 2 hours;

[0075] D. Encapsulating the single cell obtained in step B, heating it to the test temperature of 750 °C, and testing the performance of the single cell with the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode.

[0076] E. Encapsulating the symmetrical cell obtained in step C and heating it to 700 °C to test the polarization resistance of the symmetrical cell with the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode.

[0077] Figure 3 is the cross-sectional microstructure of the single cell obtained in step C. Figure 3 It shows the interfacial characteristics and distribution states of each functional layer. The interlayer bonding is dense and the transition is uniform, indicating that the cell structure is reasonable. It can be inferred that in the application example, the NiO-YSZ|AFL|YSZ|GDC|La Figure 3 Pr 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 full cell structure has been successfully prepared.

[0078] In the field of solid oxide fuel cell cathode technology, cobalt-based cathode materials have good electrochemical performance, and it is currently difficult for cathodes with other components to surpass cobalt-based cathode materials. In this test, hydrogen at 50 ml / min is used as fuel and introduced into the anode side, and air is introduced into the cathode side. At 750, 700, 650, and 600 °C, the peak output powers of the single cell with the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode are 962, 772, 540, and 324 mW cm -2 respectively, and its I-V curve and I-P curve are as followsFigure 4 As shown, its peak output power is greater than that of some reported conventional cobalt-based cathode materials such as La 0.6 S r0.4 CoO 3-δ (650 mW cm -2 , 700 °C), La 0.5 Sr 0.5 CoO 3-δ (680 mW cm -2 , 700 °C). Therefore, the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode has good electrochemical performance.

[0079] Electrochemical impedance spectroscopy has the highest sensitivity in characterizing the performance degradation of cathode materials in a CO2 atmosphere. Therefore, 0%, 2%, 5%, 10%, 15%, and 0% volume fractions of CO2 were successively introduced into both sides of the symmetrical cell, and the polarization impedance of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode symmetrical cell was tested at 700 °C and different CO2 concentrations, as Figure 5 shown. As the CO2 concentration increases, the cathode polarization impedance gradually increases; when the CO2 atmosphere is removed, the polarization impedance returns to the initial value, indicating that the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode does not undergo irreversible CO2 poisoning, demonstrating its excellent CO2 tolerance.

[0080] In the above tests, different volume fractions of CO2 were prepared by mixing pure CO2 and air in the required proportions. 0%, 2%, 5%, 10%, 15%, and 0% volume fractions of CO2 were successively introduced into both sides of the symmetrical cell, the test temperature was 700 °C, each CO2 concentration was held for 2 h, and the polarization impedance of the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 cathode symmetrical cell was tested every 40 minutes, as Figure 6 shown. At a constant CO2 concentration, the cathode polarization impedance remains almost constant. After removing the CO2 atmosphere, the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2The polarization resistance of the NiO4 cathode also did not increase significantly. However, for the conventional cathode PrSrNiO4 under the same test conditions, its polarization resistance increased by about 20%, which fully demonstrated its excellent electrochemical stability in a CO2 environment.

[0081] In the above tests, CO2 with different volume fractions was prepared by mixing pure CO2 and air in the required proportions. For the cathode poisoned by CO2, the porous structure on its surface was damaged, thus hindering the ORR reaction process of the cathode. Figure 7 Shows La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 Microstructure image of the LPNSr0.2 cathode before CO2 poisoning; Figure 8 Shows the microstructure image of the LPNSr0.2 cathode material after being poisoned by CO2 for 10 h under the atmosphere of 700 °C, 10% CO2, and 90% air. Tests found that neither the cathode particle size nor the porosity changed significantly, indicating that the LPNSr0.2 cathode could still maintain good structural stability and excellent carbon dioxide tolerance in a high-concentration CO2 environment. 0.6 Pr 0.6 Nd 0.6 Sr 0.2 It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

[0082] ​

Claims

1. A cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material, characterized in that, It is of the A2BO4-type Ruddlesden-Popper phase structure; among which the A-site elements are composed of four elements, namely La, Pr, Nd, and Sr, and are mixed in a molar ratio of 3:3:3:1, and the B-site element is Ni; the molar ratio of the A-site element to the B-site element is 2:

1.

2. The cathode material of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell according to claim 1, characterized in that The chemical formula of the material is La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 3. The preparation method of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material according to claim 1 or 2, characterized in that It includes the following steps: S1: Dissolve the precursors corresponding to the constituent elements La, Pr, Nd, Sr, and Ni of the cathode material of the solid oxide fuel cell in water according to the stoichiometric ratio to obtain an aqueous solution of metal ions; S2: Add a complexing agent to the aqueous solution of metal ions obtained in step S1, and adjust the pH value to 1-5 to obtain a complexing sol; S3: Heat and stir the complexing sol obtained in step S2 to evaporate to form a gel, and dry it into a dry gel; S4: Dry and calcine the dry gel obtained in step S3 to obtain a cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material.

4. The preparation method according to claim 3, characterized in that, In step S1, the precursors of the constituent elements La, Pr, Nd, Sr, and Ni are La, Pr, Nd, Sr, and Ni nitrates respectively.

5. The preparation method according to claim 3, characterized in that, In step S2, the complexing agent is one or two of citric acid, oxalic acid, ethylenediaminetetraacetic acid, and glycine; the molar ratio of the complexing agent to the total molar number of metal ions is 1:1 to 2:1; the pH value is adjusted by adding ammonia water.

6. The preparation method according to claim 3, characterized in that, In step S3, the heating is carried out in a water bath stirring pot, the heating temperature is 60-100 °C, and the heating time is 30-90 min.

7. The preparation method according to claim 3, characterized in that, In step S4, the drying is carried out in a high-temperature drying oven at a temperature of 80-200 °C for 5-25 h; the calcination is carried out in a muffle furnace and calcined at a temperature in the range of 800-1100 °C for 1-10 h.

8. The application of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material according to claim 1 in the preparation of a solid oxide fuel cell.

9. Use of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material according to claim 8 in the preparation of a solid oxide fuel cell, characterized in that: Using the La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4 as the cathode material, gadolinium-doped ceria as the barrier layer material, yttria-stabilized zirconia as the electrolyte material, nickel oxide and zirconia as the anode functional layer, and nickel oxide and zirconia as the anode support, to prepare an anode-supported all-cell NiO-YSZ|AFL|YSZ|GDC|La 0.6 Pr 0.6 Nd 0.6 Sr 0.2 NiO4.

10. Use of the cobalt-free high-entropy Ruddlesden-Popper phase solid oxide fuel cell cathode material according to claim 9 in the preparation of a solid oxide fuel cell, characterized in that: The fuel of the solid oxide cell is hydrogen.

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