SOEC hydrogen electrode, preparation method thereof and solid oxide electrolytic tank

Abstract

The invention provides an SOEC hydrogen electrode, a preparation method thereof and a solid oxide electrolytic cell, and belongs to the field of solid oxide electrolytic cells, a compound (LaXSr1-X) 0.9 Co0. 2Fe0. 7Ni0. 1 is used as a cathode material, the range of X is 0.6-0.8, and the preparation method comprises the following steps: S1, preparing material powder of the compound (LaXSr1-X) 0.9 Co0. 2Fe0. 7Ni0. 1; s2, mixing the material powder with electrolyte to prepare slurry; s3, printing by using the slurry through an additive manufacturing technology to obtain a printed piece; and S4, drying and sintering the printed piece to obtain the SOEC hydrogen electrode. The compound selected as the cathode material shows the lowest resistance in an LSCFN-GDC symmetric battery test, and the material reduces the resistance and reduces the current loss, so that the energy conversion efficiency of the whole system is directly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide electrolytic cells, and in particular to a SOEC hydrogen electrode and a preparation method thereof, and a solid oxide electrolytic cell. Background Art

[0002] High-temperature solid oxide electrolysis (SOEC) is an effective water-splitting technology that produces hydrogen from water using high-temperature electrolysis. In SOEC systems, the performance of the hydrogen electrode active layer plays a key role in overall efficiency and durability. However, existing technologies have shortcomings in the following areas:

[0003] 1) Electrode material stability: Existing hydrogen electrode materials are prone to degradation under high-temperature operating conditions, especially during long-term operation. This degradation may be caused by phase transitions, increased lattice defects, or incompatibility with the electrolyte.

[0004] 2) Insufficient electrode reaction activity: Although many traditional hydrogen electrode materials perform well at low temperatures, their electrochemical activity decreases significantly under the high temperature environment required by SOEC. This limits the electrolysis efficiency and hydrogen yield.

[0005] 3) Mismatch in thermal expansion coefficients: Mismatch in thermal expansion coefficients between hydrogen electrode materials and electrolytes or other electrode materials may lead to mechanical stress during cyclic use, causing cracks or delamination, affecting the structural stability and life of the electrode.

[0006] Therefore, the above-mentioned defects of existing hydrogen electrodes limit their widespread commercial application, greatly increasing the difficulty of implementing high-temperature solid oxide water electrolysis hydrogen production technology. Summary of the Invention

[0007] In view of this, the present invention proposes a SOEC hydrogen electrode and a preparation method thereof and a solid oxide electrolytic cell, which are used to solve the problems of electrode material stability, poor electrode activity in high temperature environment and mismatch of electrode thermal expansion coefficient in existing hydrogen electrodes.

[0008] The technical solution of the present invention is achieved as follows: The present invention provides a SOEC hydrogen electrode, with a compound (La X Sr 1-X ) 0.9 C o0.2 Fe 0.7 Ni 0.1As a cathode material, where X ranges from 0.6 to 0.8. This formula has been optimized to have high electrochemical activity and good thermal stability. The introduction of nickel (Ni) enhances the material's electrical conductivity and chemical stability at high temperatures, while the presence of iron (Fe) and cobalt (Co) promotes the electrode's catalytic efficiency. This formula was chosen for the following reasons:

[0009] 1) See Figure 4 When conducting LSCFN-GDC symmetrical battery tests, it was found that the compound (La X Sr 1-X ) 0.9 C o0.2 Fe 0.7 Ni 0.1 (abbreviated here as LSCFN) as a cathode material, the formula showed very low resistance values. This result shows that the formula has significant advantages in electrochemical activity and ionic conductivity, thereby effectively reducing the overall energy consumption of the battery and improving the efficiency of the electrochemical reaction.

[0010] 2) See Figure 5 In the LSCFN-GDC full cell test, the formulation showed the best performance under the operating conditions of 800 ° C. This shows that the material has excellent stability and durability in high-temperature SOEC applications and can withstand long-term high-temperature operation without degradation.

[0011] When X is selected in the range of 0.6 to 0.8, LSCFN can stably maintain the perovskite structure, avoid phase separation, and ensure structural stability for long-term operation. At the same time, the component ratio ensures the optimization of the mixed conductivity of electrons and oxygen ions, wherein the appropriate Sr content promotes the formation of oxygen vacancies and increases the oxygen ion diffusion rate, while the control of the La content avoids the decrease in conductivity caused by excessively high or low oxygen vacancy concentrations. In addition, when X<0.6, an excessively high Sr content is prone to high-temperature volatilization, resulting in interface deactivation, while when X>0.8, an excessively high La content reduces the ability to form oxygen vacancies and affects the activity of the oxygen reduction reaction (ORR). Therefore, the selection range of the present invention ensures the high-temperature chemical stability of the material and has good chemical compatibility with electrolytes (such as GDC or YSZ), thereby improving the long-term durability and electrochemical performance of the cathode.

[0012] In a second aspect, the present invention also provides a method for preparing a SOEC hydrogen electrode, comprising the following steps: S1, preparing a compound (La X Sr 1-X ) 0.9 C o0.2 Fe 0.7 Ni 0.1Material powder; S2, mixing the material powder obtained in step S1 with the electrolyte to form a slurry; S3, using the slurry to print using additive manufacturing technology to obtain a print; specifically, the hydrogen electrode of this scheme uses a droplet deposition printer to spray-print the hydrogen electrode active layer. This method can accurately control the deposition of materials and ensure the uniformity and thickness consistency of the electrode layer. This high-precision spraying technology not only improves the microstructure quality of the electrode layer, but also reduces material waste in the manufacturing process; S4, drying and sintering the print to obtain the SOEC hydrogen electrode; the sintering temperature can be set to 1100°C. The present invention optimizes the microstructure and phase interface of the electrode material, improves the mechanical and chemical bonding strength between the electrode and the electrolyte, thereby enhancing the durability and operating life of the entire electrode.

[0013] By employing the aforementioned technical approaches, the material formulation and preparation method of the present invention significantly improve the stability and electrochemical performance of the hydrogen electrode compared to existing technologies. Furthermore, through improved spraying technology, the present invention achieves higher production efficiency and cost-effectiveness while reducing operational complexity, making it more suitable for large-scale commercial applications. In this way, the present invention not only solves several technical challenges of the existing technology but also provides a reliable method to improve the overall efficiency and cost-effectiveness of SOEC systems.

[0014] On the basis of the above technical solution, preferably, step S1 includes the following steps: S11, preparing lanthanum oxide (La2O3), strontium oxide (SrO), cobalt oxide (CoO), iron oxide (Fe2O3) and nickel oxide (NiO) as raw materials, all of which are chemically pure. The mass of the required raw materials is converted according to the molar ratio of each component element in the compound and accurately weighed and used; S12, after the raw materials are evenly mixed in a high-temperature crucible, they are first kept at 900°C for 1 to 2 hours to remove organic impurities and moisture, and then raised to 1250°C to 1400°C and kept for 6 to 10 hours, which is to optimize the formation of the crystal phase to obtain high-performance multi-component composite oxides; after sintering, a multi-component composite oxide is obtained, and the sintering is completed and then naturally cooled to room temperature; S13, the multi-component composite oxide is finely ground by a ball mill to obtain material powder. Secondary sintering or heat treatment in a specific atmosphere can also be performed subsequently, the purpose of which is to further optimize the material properties according to demand.

[0015] On the basis of the above technical solution, preferably, step S2 includes the following steps: S21, weighing the material powder obtained in step S1, gadolinium cerium oxide powder (GDC), butyl acetate (Butyl acetate), ethanol (Ethanol), a dispersant, a plasticizer and a binder, wherein the dispersant is usually Dow dispersant (Solplus D540), the plasticizer is tributyl citrate (Citroflex A-4), and the binder is ethyl cellulose (Ethyl cellulose); wherein the ratio of the material powder to the gadolinium cerium oxide powder is 1:1, which is a conventional empirical selection that can effectively print the LSFCN-GDC hydrogen electrode, and the ratio of xylene to n-butanol is 1:1; S22, first uniformly mixing the material powder obtained in step S1 with the gadolinium cerium oxide powder in a large container to obtain a solid mixture; uniformly mixing butyl acetate, ethanol, a dispersant, a plasticizer and a binder in another container to obtain a liquid mixture; slowly adding the liquid mixture to the solid powder and stirring it evenly, stirring it with a mechanical stirrer while adding it to ensure uniform mixing and avoid the formation of lumps; and at the same time, Butyl acetate or ethanol is added to adjust the ratio of butyl acetate to ethanol to adjust the viscosity of the mixture. The initial ratio of butyl acetate to ethanol is designed to be 1:1, which helps to adjust the viscosity at this time. During the adjustment process, the viscosity of the slurry is measured using a viscometer to achieve a viscosity suitable for printing. S23, after the mixing is completed, it is allowed to stand and filter and stored as a printing slurry. Standing for a period of time allows the bubbles in the slurry to naturally discharge. The slurry is filtered through a fine mesh filter to remove any large particles or impurities that are not mixed evenly. When storing, the prepared slurry is sealed and stored in a cool and dry place, avoiding direct sunlight and high temperature to maintain its stability and printing performance. The key to the preparation of this slurry is to ensure that all ingredients are evenly mixed and reach a viscosity suitable for printing. The correct preparation and storage methods will ensure that the slurry can be effectively sprayed when using a droplet deposition printer and that a high-quality hydrogen electrode active layer can be formed during the sintering process.

[0016] On the basis of the above technical solution, preferably, step S3 includes the following steps: S31, preparing a PTFE substrate and setting printing parameters; PTFE is selected as the printing base material due to its excellent heat resistance and chemical stability to ensure that the material does not chemically react or adhere to the base during printing; a nozzle with an inner diameter of 250 μm is usually selected. A nozzle of this size can ensure fine material output and is suitable for printing hydrogen electrode active layers that require high-precision details; the pneumatic injection pressure of the printer is set to 16 psi. This pressure level is sufficient to push the slurry through the smaller nozzle while preventing the material from flowing out too quickly and causing confusion; S32, using the printing slurry for single-layer printing and obtaining a printout, specifically: printing Before printing begins, the printer control system adjusts the valve opening wait time to 0.05 seconds. This ensures a brief buffer between the command and the start of material flow, thereby synchronizing the printing action. The print head moves at a standard printing speed of 100 mm / s, which balances printing efficiency and quality. The valve opening and closing speeds are 15 mm / s and 12 mm / s, respectively. These speed settings help quickly and accurately control the start and stop of material flow, avoiding dripping or smearing. Because the hydrogen electrode is extremely thin, a single layer can be printed. After printing is completed, the print coolant is solidified in step S33. The print is then naturally cooled to room temperature within the printer to avoid damage to material properties due to rapid temperature changes. This printing process ensures print quality and accuracy.

[0017] More preferably, in step S31 , the printing layer thickness is set to 40-80 μm. This layer height range can ensure sufficient material thickness to construct a stable electrode structure, while not being too thick to affect the adhesion between layers.

[0018] On the basis of the above technical solutions, preferably, in order to ensure the high performance and good structure of the hydrogen electrode active layer, the sintering process and the drying process must be precisely controlled. In step S4, a staged heating strategy is adopted to heat the printed part to 1100°C for sintering. After the sintering is completed, it is quickly cooled to 800°C and then naturally cooled. Specifically, the following steps are included: S41, first, the prepared printed part is placed in an oven and dried at 30°C. The drying process does not use vacuum and continues overnight (usually about 12 hours) to ensure that all solvents are completely evaporated to avoid bubbles or cracks during the sintering process; the printed part is dried and then sintered, and the sintering furnace temperature is heated from room temperature to 250°C at a rate of 0.6°C / min and kept warm for 120 minutes. This step is mainly used to remove residual organic matter and promote preliminary bonding; S42, continue to heat the temperature from 250°C at a rate of 0.6°C / min To 400℃ and keep it at 400℃ for 120min. This stage further removes the organic components and begins to form a preliminary oxide network structure; S43, heat again from 400℃ to 800℃ at a rate of 0.6℃ / min and keep it at 800℃ for 30min. This step strengthens the bonding of the materials and the formation of the crystal structure; S44, heat from 800℃ to 1000℃ at a rate of 1.5℃ / min and keep it at 1100℃ for 120min. This is a key step in forming the final stable crystal phase and optimizing the electrode microstructure; S45, cool from 1100℃ to 800℃ at a rate of 1.5℃ / min. By controlling the cooling rate, the material is prevented from cracking or stressing due to rapid cooling; then starting from 800℃, the sintered body is allowed to cool naturally to room temperature by furnace cooling. This process can prevent rapid environmental changes from damaging the material structure. Through a strictly controlled drying and sintering process, the optimal physical and chemical properties of the electrode material can be ensured, aiming to optimize the material's microstructure and improve its efficiency and durability in SOECs.

[0019] In a third aspect, the present invention also provides a solid oxide electrolytic cell, which uses the above-mentioned SOEC hydrogen electrode as a cathode, an anode made of nickel-yttria-stabilized zirconia as a raw material, and a gadolinium oxide-doped cerium oxide as an electrolyte.

[0020] Based on the above technical solution, preferably, the solid oxide electrolytic cell has a symmetrical electrode configuration. A symmetrical electrode configuration is an electrode design that uses the same or similar positive electrode materials and negative electrode materials, and has a symmetrical electrochemical interface and reaction mechanism. This design enables the electrolytic cell to more uniformly carry out ion transport and charge transfer during the charge and discharge process, thereby improving the performance and stability of the electrolytic cell. Figure 5AC impedance measurements show that the cathode material formulation of this solution has significant advantages in electrochemical activity and ionic conductivity, thereby effectively reducing the overall energy consumption of the battery and improving the efficiency of the electrochemical reaction. Therefore, applying the hydrogen electrode active layer material of the present invention to a symmetrical battery can make the battery have stronger performance and stability.

[0021] On the basis of the above technical solution, preferably, the operating temperature of the solid oxide electrolytic cell is 600°C to 800°C. Figure 4 Comparison of electrochemical impedance spectroscopy of the hydrogen electrode of this scheme under symmetrical cell testing at operating conditions of 600°C to 800°C reveals that this cathode material formulation exhibits optimal performance at 800°C. This demonstrates that this material possesses excellent stability and durability in high-temperature SOEC applications, and can withstand long-term high-temperature operation without degradation.

[0022] The SOEC hydrogen electrode, preparation method thereof, and solid oxide electrolytic cell of the present invention have the following advantages over the prior art:

[0023] (1) The compound selected as the cathode material in the present invention shows the lowest resistance in the LSCFN-GDC symmetric battery test. This material reduces resistance and reduces current loss, thereby directly improving the energy conversion efficiency of the entire system. Lower resistance means that the battery can operate at lower energy consumption and achieve higher energy efficiency, which is particularly important for energy-intensive industrial applications.

[0024] (2) The material provided by the present invention has optimal performance at an operating temperature of 800°C, which is a common high-temperature environment in solid oxide water electrolysis technology. The optimized high-temperature performance of the material ensures stability and reliability during long-term operation, reduces maintenance and replacement costs, and significantly improves the overall economic benefits of the equipment.

[0025] (3) The present invention improves the thermal expansion coefficient matching between the material, the electrolyte and other components through carefully designed chemical ratios. This matching reduces the internal stress caused by long-term high-temperature operation, prevents material rupture or interlayer separation, and thus extends the service life of the battery components.

[0026] (4) The present invention uses a solid-phase reaction method to prepare electrode materials. Compared with traditional methods, this method has the advantages of simple process and low cost. The simplified production process not only reduces production costs but also improves production efficiency, making this material more suitable for large-scale commercial production. At the same time, when selecting the manufacturing process and materials, the present invention takes environmental factors into consideration. By reducing the use of harmful chemicals and optimizing the production process, the environmental impact is reduced. This environmentally friendly production method is in line with the trend of global sustainable development and increases the competitiveness and attractiveness of the product in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the process of step S1 in the method for preparing a SOEC hydrogen electrode of the present invention;

[0029] Figure 2 Schematic diagram of the process of step S2 in the method for preparing a SOEC hydrogen electrode of the present invention;

[0030] Figure 3 Schematic diagram of the process of steps S3 and S4 in the method for preparing a SOEC hydrogen electrode of the present invention;

[0031] Figure 4 Comparison of electrochemical impedance spectra of symmetrical battery tests performed in Examples 1 to 3 of the present invention at 600°C to 800°C. The top three images are polarization impedance comparisons, and the bottom three images are ohmic impedance comparisons.

[0032] Figure 5 This is a comparison of the IV curves of Examples 1 to 3 of the present invention when conducting full battery tests at 800°C;

[0033] Figure 6 This is a comparison of electrochemical impedance spectra of Examples 1 to 3 of the present invention when conducting symmetrical battery tests at 800° C.

[0034] Figure 7 This is a comparison chart of the iV curves of Examples 1 to 3 of the present invention and a commercial LSCF material electrode when conducting full battery testing under 750°C operating conditions;

[0035] Figure 8 This is a comparison of the electrochemical impedance spectra of Examples 1 to 3 of the present invention and a commercial LSCF material electrode when conducting full battery testing at 750°C;

[0036] Figure 9 This is a comparison of the iV curves of Example 1 of the present invention and a commercial LSCF material electrode when conducting full battery testing at 750°C operating conditions;

[0037] Figure 10 Comparison of electrochemical impedance spectra of Example 1 of the present invention and a commercial LSCF material electrode during full battery testing at 800°C;

[0038] Figure 11 Calculation curve of oxygen vacancy formation energy for different La / Sr ratios of the present invention;

[0039] Figure 12 This is the rheological curve of the slurry of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] A SOEC hydrogen electrode of the present invention is based on a compound (La 0.6 Sr 0.4 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 As a cathode material, its preparation method includes the following steps:

[0043] S1, preparation of compound (La 0.6 Sr 0.4 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 Material powder;

[0044] S11, according to the molar ratio of each component element in the compound, the mass of the required raw materials is converted, and 47.39g of La2O3, 18.65g of SrO, 7.04g of CoO, 27.75g of Fe2O3 and 3.58g of NiO are prepared as raw materials;

[0045] S12, after mixing the raw materials for 4-6 hours to ensure uniform mixing, the mixture is first heated to 900° C. in a high-temperature crucible and maintained for 1-2 hours, then raised to 1250° C. to 1400° C. and maintained for 6-10 hours to form a uniform multi-component composite oxide structure, and sintered to obtain 100 g of the multi-component composite oxide;

[0046] S13, after sintering, the sample is allowed to cool naturally to room temperature, and then the multi-component composite oxide is finely ground into fine powder by a ball mill to obtain 100 g of material powder for subsequent use.

[0047] S2, mixing material powder with electrolyte to form slurry;

[0048] S21, weigh 26 g of material powder, 26 g of gadolinium cerium oxide powder, 19.5 g of butyl acetate, 19.5 g of ethanol, 1.6 g of dispersant, 5.8 g of plasticizer, and 8.3 g of binder, such that the ratio of material powder to gadolinium cerium oxide powder is 1:1, and the ratio of butyl acetate to ethanol is 1:1; Dow dispersant (Solplus D540) is used as the dispersant, tributyl citrate (Citroflex A-4) is used as the thickener, and ethyl cellulose is used as the binder;

[0049] S22, first uniformly mixing the material powder and the gadolinium cerium oxide powder to form a solid mixture, then uniformly mixing butyl acetate, ethanol, a dispersant, a plasticizer, and a binder to form a liquid mixture, slowly adding the liquid mixture to the solid powder and stirring uniformly, and adjusting the viscosity of the mixture by adding butyl acetate or ethanol to adjust the ratio of butyl acetate to ethanol;

[0050] S23, after the mixing is completed, the mixture is allowed to stand, filtered, and stored as a printing slurry.

[0051] S3, using the slurry to print through additive manufacturing technology to obtain the printed part;

[0052] S31, preparing a PTFE substrate and setting printing parameters; using a droplet deposition printer for printing, the set parameters are: nozzle size 250 μm, printing speed 100 mm / s, and spraying the slurry evenly on the PTFE support layer during printing;

[0053] S32, performing single-layer printing using the printing slurry and obtaining a printed part; the printing layer thickness is 60 μm;

[0054] S33, after printing is completed, the printed part coolant is solidified.

[0055] S4, drying and sintering the printed part to obtain the SOEC hydrogen electrode.

[0056] S41, after drying the printed part, sintering it, heating the sintering furnace temperature from room temperature to 250°C at a rate of 0.6°C / min and keeping it at this temperature for 120 minutes;

[0057] S42, continue heating the temperature from 250°C to 400°C at a rate of 0.6°C / min, and keep at 400°C for 120 min;

[0058] S43, heating again from 400°C to 800°C at a rate of 0.6°C / min and holding at 800°C for 30 min;

[0059] S44, heating from 800°C to 1100°C at a rate of 1.5°C / min and holding at 1100°C for 120 min;

[0060] S45, cooled from 1150°C to 800°C at a rate of 0.8°C / min, and then naturally cooled to room temperature.

[0061] The solid oxide electrolytic cell of the present invention utilizes the aforementioned SOEC hydrogen electrode as a cathode, an anode made of nickel-yttria-stabilized zirconia, and a gadolinium oxide-doped ceria as an electrolyte. The cell exhibits excellent ionic conductivity at high temperatures. Furthermore, the solid oxide electrolytic cell of the present invention is a symmetrical cell.

[0062] Example 2

[0063] A SOEC hydrogen electrode of the present invention is based on a compound (La 0.7 Sr 0.3 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The cathode material was prepared in the same manner as in Example 1: 53.86 g of La2O3, 14.04 g of SrO, 7.04 g of CoO, 27.75 g of Fe2O3, and 3.58 g of NiO were prepared as raw materials. A solid oxide electrolytic cell was also prepared using the SOEC hydrogen electrode of this example as the cathode.

[0064] Example 3

[0065] A SOEC hydrogen electrode of the present invention is based on a compound (La 0.8 Sr 0.2 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The cathode material was prepared in the same manner as in Example 1: 60.33 g of La2O3, 9.43 g of SrO, 7.04 g of CoO, 27.75 g of Fe2O3, and 3.58 g of NiO were prepared as raw materials. A solid oxide electrolytic cell was also prepared using the SOEC hydrogen electrode of this example as the cathode.

[0066] Example 4

[0067] The SOEC hydrogen electrode and the solid oxide electrolytic cell prepared in the present invention are the same as those in Example 3, except that the printing layer thickness during printing is 40 μm.

[0068] Example 5

[0069] The SOEC hydrogen electrode and the solid oxide electrolytic cell prepared in the present invention are the same as those in Example 3, except that the printing layer thickness during printing is 80 μm.

[0070] By observing and comparing the SOEC hydrogen electrode preparation samples of Examples 3 to 5, it can be found that when the printing layer thickness is 40 μm, the hydrogen electrode is extremely thin, resulting in insufficient strength of the hydrogen electrode and easy damage; when the printing layer thickness is 80 μm, the layer thickness of the hydrogen electrode is too thick, which will affect the adhesion effect between the layers when the electrodes are stacked and packaged.

[0071] Example 6

[0072] A SOEC hydrogen electrode of the present invention is based on a compound (La 0.5 Sr 0.5 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The cathode material was prepared in the same manner as in Example 1: 40.92 g of La2O3, 23.26 g of SrO, 7.04 g of CoO, 27.75 g of Fe2O3, and 3.58 g of NiO were prepared as raw materials. A solid oxide electrolytic cell was also prepared using the SOEC hydrogen electrode of this example as the cathode.

[0073] Example 7

[0074] A SOEC hydrogen electrode of the present invention is based on a compound (La 0.9 Sr 0.1 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The cathode material was prepared in the same manner as in Example 1: 66.80 g of La2O3, 4.82 g of SrO, 7.04 g of CoO, 27.75 g of Fe2O3, and 3.58 g of NiO were prepared as raw materials. A solid oxide electrolytic cell was also prepared using the SOEC hydrogen electrode of this example as the cathode.

[0075] The LSCFN-GDC full cell test is an important method for evaluating the performance of solid oxide electrolysis cells (SOFCs) or solid oxide water electrolysis cells. This test is designed to evaluate the performance of materials under actual operating conditions, especially the electrochemical activity and stability in high temperature environments. The test steps for the LSCFN-GDC full cell test are as follows:

[0076] First, the SOEC hydrogen electrode from each of the above examples was used as the cathode, an anode made of nickel-yttria-stabilized zirconia, and a gadolinium-doped ceria as the electrolyte. The prepared cathode, electrolyte, and anode layers were stacked in sequence, and each layer was sealed with a high-temperature, durable sealing material to prevent gas leakage during testing.

[0077] Then, set up the test device. Install the assembled battery on the test bench and connect the necessary electrical connectors to measure the battery output. Set up a data acquisition system to record test data such as voltage, current and temperature in real time. Temperature and atmosphere need to be controlled during the test. The battery needs to be heated to the test temperature (the required operating condition is 800°C) to ensure uniform heating of the entire battery and control the atmosphere in the test environment. Usually, air or oxygen-rich atmosphere is used on the cathode side, and hydrogen or other reducing gases are used on the anode side.

[0078] During the test, electrochemical performance tests were conducted, using electrochemical impedance spectroscopy (EIS) technology to measure the battery's impedance at multiple frequency points and analyze the battery's electrochemical kinetics. Current-voltage (IV) characteristic tests were also performed to determine the battery's power density and efficiency. Finally, the test results were compared and analyzed. By analyzing the collected data, the overall performance of the battery, including power output, stability, and efficiency, was evaluated. Particular attention was paid to performance at 800°C, a critical temperature for evaluating the material's suitability for practical applications.

[0079] After the test is complete, the temperature is gradually lowered and all equipment is shut down. The battery is disassembled and subsequent microstructural analysis is performed to assess the impact of high-temperature operation on the battery material structure.

[0080] To compare the comprehensive performance of different LSCFN formulations in full and symmetric cells, the solid oxide electrolysis cells of Examples 1 to 3 were used as test samples. The test platform was as follows: full-cell tests used an SSZ-supported half-cell structure with a commercial LSM-GDC oxygen electrode; symmetric cell tests used the same formulation on both sides; the test atmosphere was 50% H2 + 50% H2O; and the test temperature was 800°C.

[0081] Record voltage, current and power density curves (iV curves) in full battery test to obtain Figure 5 .according to Figure 5 It can be seen that in the full battery test, (La 0.8 Sr 0.2 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 Shows the highest power density, better than (La 0.6 Sr 0.4 )0.9 Co 0.2 Fe 0.7 Ni 0.1 and(La 0.7 Sr 0.3 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 .

[0082] In the symmetrical battery test, the AC impedance is analyzed by Nyquis diagram, including ohmic impedance and polarization impedance, to obtain Figure 6 .according to Figure 6 It can be seen that in the symmetrical battery test, (La 0.7 Sr 0.3 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 It exhibits the lowest ohmic impedance, indicating that its interfacial conductivity is higher.

[0083] Therefore, it can be found that different formulations show their own advantages under different test conditions. 0.8 Sr 0.2 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 More suitable for high-efficiency water electrolysis; it is inferred that the poor performance of commercial LSCF in symmetric cells may be due to surface cracking. In addition, the study found that circular printing on SSZ half-cells can produce fine crack-free electrodes, while square printing on SSZ supports in symmetric cells can lead to surface cracks, which depends on factors such as ink rheology and powder size.

[0084] In order to study the synergistic optimization effect of chemical formula and temperature on the performance of LSCFN materials, it is necessary to explore the synergistic effect of A-site doping ratio (X value) and operating temperature on the performance of LSCFN materials. The solid oxide electrolytic cells of Examples 1 to 3 were used as test samples, and the solid oxide electrolytic cells prepared by commercial LSCF were used as the control group. The test platform is as follows: the full cell test uses an SSZ-supported half-cell structure, and the oxygen electrode is a commercial LSM-GDC; the symmetric cell test uses the same formula on both sides; the test atmosphere is 50% H2+50% H2O; the test temperature is 750°C.

[0085] Perform full battery test and record voltage, current and power density curves (iV curves) to obtain Figure 7 .according to Figure 7 It can be seen that the A-site doping ratio has a significant impact on performance: (La 0.8 Sr 0.2 )0.9 Co 0.2 Fe 0.7 Ni 0.1 The best performance is achieved at 750°C, with the lowest impedance, which may be due to the improved ionic conductivity caused by the increase in Sr content.

[0086] Symmetrical battery tests were performed and Nyquis plots were recorded using EIS to analyze the changes in ohmic impedance and polarization impedance. Figure 8 .according to Figure 8 It can be learned that (La 0.7 Sr 0.3 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The IV performance is the lowest.

[0087] Therefore, it can be inferred that the comprehensive performance of LSCFN materials in SOEC can be synergistically improved by optimizing the A-site doping ratio and operating temperature.

[0088] In order to compare the performance of the LSCFN material of this scheme with that of the commercial LSCF material, (La 0.6 Sr 0.4 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 electrodes (Example 1) and were simultaneously printed and sintered with commercial LSCF materials.

[0089] Conduct full battery iV curve test, record voltage, current and power density, and obtain Figure 9 Symmetrical battery tests were performed and EIS was used to test the AC impedance of the two materials to analyze the electrochemical properties and obtain Figure 10 . It can be learned that (La 0.6 Sr 0.4 ) 0.9 Co 0.2 Fe 0.7 Ni 0.1 The power density of the electrode is significantly higher than that of commercial LSCF, indicating that it has lower ohmic impedance and polarization impedance; the commercial LSCF electrode shows higher impedance at high temperature, which may be related to interface failure and insufficient thermal stability.

[0090] Therefore, the LSCFN material formulated in this scheme is significantly superior to the commercial LSCF material in terms of electrical conductivity, interface bonding and high-temperature stability, and is suitable for high-performance SOEC application requirements under high-temperature operating conditions.

[0091] In solid oxide electrolysis cells (SOFCs), the mixed electron-ion conductivity (MIEC) and oxygen vacancy concentration of cathode materials directly influence oxygen reduction reaction (ORR) activity and overall cell performance. Therefore, to compare the conductivity and oxygen vacancy concentration of cathode materials with different X values, the oxygen vacancy concentration was measured through conductivity testing and thermogravimetric analysis (TGA), and the effect of different La / Sr ratios on cathode material performance was explored.

[0092] Before the experiment, cathode material samples of Examples 1 to 3, 6 and 7 were prepared respectively. The raw materials were weighed according to the stoichiometric ratio and ground in a ball mill for 4 hours to fully mix the raw materials. Then, they were pre-fired at 1000°C for 5 hours, ground again and pressed into tablets, and then sintered at 1300°C for 10 hours to form a dense structure to obtain samples.

[0093] During the conductivity measurement test, electrodes (made of Pt) were first coated on both sides of the sample using platinum slurry. After sintering at 900°C for 1 hour, the sample was then tested using a high-temperature conductivity tester using the four-probe method (Van der Pauw method) to measure the conductivity at various temperatures, with the stable value at 800°C recorded. The test temperature range was from room temperature to 900°C, and the test atmosphere was air. Table 1 below shows the conductivity of LSCFN samples from different examples measured at 800°C.

[0094] Table 1

[0095] X value Conductivity (S / cm) 0.5 6.2 0.6 12.7 0.7 15.5 0.8 11.1 0.9 9.1

[0096] The above experiments show that Example 2 has the best electronic conductivity, which is due to the optimized La / Sr ratio in its formulation, which improves the electronic transition of Co and Fe. In Example 6, the excessive Sr causes lattice distortion, resulting in Sr volatilization, inducing cathode deactivation, and causing changes in the Co / Fe valence state, thereby reducing electronic conductivity. In Example 7, the excessive La leads to a decrease in oxygen vacancies, reduces oxygen diffusion capacity, affects oxygen ion conductivity, and thus reduces the overall conductivity, affecting the long-term performance of the electrolytic cell.

[0097] Oxygen vacancy concentration measurements were conducted using a TA Instruments Q500 thermogravimetric analyzer (TGA) over a temperature range of 600-900°C. The oxygen vacancy concentration was estimated by calculating the oxygen weight loss (Δm / Delta mΔm). The test atmosphere was high-purity oxygen (99.99% O₂), and the sample weight was 20 mg. Table 2 below shows the oxygen vacancy concentrations of LSCFN with different X values.

[0098] Table 2

[0099] X value Oxygen vacancy concentration (%) 0.5 5.1 0.6 4.3 0.7 3.8 0.8 3.0 0.9 2.4

[0100] Through the above experiments, it can be found that the oxygen vacancy concentration of Example 2 is moderate (3.8%), and its oxygen ion diffusion capacity is optimal, which is conducive to enhancing the oxygen reduction reaction (ORR) activity and long-term stability; the oxygen vacancy concentration of Example 6 is the highest (5.1%), but excessive oxygen vacancies lead to structural instability; the oxygen vacancy concentration of Example 7 is very low (2.4%), which leads to a decrease in its oxygen diffusion coefficient, affecting the performance of the electrolytic cell.

[0101] In summary, according to the above experiments, LSCFN with an X value range of 0.6-0.8 has the best electrochemical performance and is suitable for SOFC cathode materials, achieving high conductivity, stable oxygen vacancy concentration and excellent interface compatibility.

[0102] In order to study the effect of La / Sr ratio on material properties and process adaptability, samples of Examples 1 to 3 and 6 were prepared, and the phase purity, oxygen vacancy concentration and thermal expansion behavior of each sample were tested. The physical and chemical properties test results of the samples of each example are shown in Table 3 below, and the oxygen vacancy formation energy calculation curves of different La / Sr ratios are obtained, as shown in Table 3. Figure 11 shown.

[0103] Table 3

[0104]

[0105]

[0106] According to the data in Table 1, it can be found that the phase purity of Example 2 reaches 98% of the theoretical density when the sintering temperature is 1150°C. The principle can be attributed to the following: La 3+ Higher ionic radius helps promote diffusion; and Sr 2+ The appropriate amount of doping (30%) can optimize the lattice energy. The other embodiments all require higher sintering temperatures. Therefore, it can be seen that when the La / Sr ratio is 7:3, the sample can form the most stable cubic perovskite phase (XRD refinement shows a cubic factor of 0.998), and deviation from this ratio will easily lead to the appearance of impurity phases. The preparation of Example 2 has the following process window advantages compared to other embodiments: 1) Example 2 has better drying adaptability, and its linear shrinkage rate is only 5.2%, while the other groups are all greater than 7%. Therefore, the cracking of the sample can be effectively suppressed during the preparation process of Example 2; 2) Example 2 has a better sintering tolerance, and it can obtain a density of >95% in the range of 1100-1200°C, while the other groups require strict temperature control of ±20°C.

[0107] In addition, the present application also compares the electrochemical performance of the electrode sample of Example 2 with a commercially available electrode sample, wherein the preparation material of the commercially available electrode sample is (La 0.7Sr 0.3 ) 0.9 Co 0.2 Fe 0.7 Nb 0.1 , which is obtained by solid phase sintering at 1300 ° C. The electrochemical performance data of the two are tested to obtain the following Table 4, as well as the rheological curve of the slurry during sintering, as shown in Table 4. Figure 12 shown.

[0108] Table 4

[0109]

[0110] By comparing the data in Table 4, it can be found that compared with the commercially available products, the area specific impedance and polarization impedance of Example 2 are greatly reduced, while the oxygen surface exchange coefficient is greatly improved. Figure 12 It can be seen that the slurry of Example 2 shows a more gentle shear thinning behavior during the sintering process, and is therefore more suitable for high-precision printing. The principle of the above performance improvement is inferred to be: 1) Lattice dynamics analysis of the two shows that the Nb in the commercial product 50 Ionic radius It will cause the lattice to shrink, so high temperature compensation is required; in this embodiment, Ni 2+ with Fe 3+ Forming an ideal match is beneficial to reducing the sintering activation energy; 2) Analysis of the interface stability of the two shows that the commercially available product uses a Nb doping system, which will lead to the presence of SrZrO3 impurities in the sample; while this Example 2 uses a Ni doping system, the sample interface is purer and the interface interdiffusion layer is narrower.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A SOEC hydrogen electrode, characterized in that: Compound (La X Sr 1-X ) 0.9 C o0.2 Fe 0.7 Ni 0.1 As a cathode material, wherein the range of X is 0.6 to 0.

8.

2. The method for preparing the SOEC hydrogen electrode according to claim 1, wherein: The following steps are included: S1, preparation of compound (La X Sr 1-X ) 0.9 C o0.2 Fe 0.7 Ni 0.1 Material powder; S2, mixing the material powder obtained in step S1 with an electrolyte to form a slurry; S3, using the slurry to print through additive manufacturing technology to obtain the printed part; S4, drying and sintering the printed part to obtain the SOEC hydrogen electrode.

3. The method for preparing a SOEC hydrogen electrode according to claim 2, wherein: The step S1 includes the following steps: S11, preparing La2O3, SrO, CoO, Fe2O3 and NiO as raw materials, and calculating the mass of the raw materials required based on the molar ratio of each component element in the compound; S12, mixing the raw materials uniformly and then sintering to obtain a multi-component composite oxide; S13, finely grinding the multi-component composite oxide by a ball mill to obtain material powder.

4. The method for preparing a SOEC hydrogen electrode according to claim 2, wherein: The step S2 includes the following steps: S21, weighing the material powder obtained in step S1, gadolinium cerium oxide powder, butyl acetate, ethanol, a dispersant, a plasticizer, and a binder, wherein the ratio of the material powder to the gadolinium cerium oxide powder is 1:1, and the ratio of xylene to n-butanol is 1:1; S22, first uniformly mixing the material powder obtained in step S1 with the gadolinium cerium oxide powder to obtain a solid mixture; then uniformly mixing butyl acetate, ethanol, a dispersant, a plasticizer, and a binder to obtain a liquid mixture; slowly adding the liquid mixture to the solid powder and stirring uniformly, and adjusting the viscosity of the mixture by adding xylene or n-butanol to adjust the ratio of xylene to n-butanol; S23, after the mixing is completed, the mixture is allowed to stand, filtered, and stored as a printing slurry.

5. The method for preparing a SOEC hydrogen electrode according to claim 2, wherein: The step S3 includes the following steps: S31, prepare Teflon (PTFE) substrate and set printing parameters; S32, performing single-layer printing using the printing slurry and obtaining a printed part; S33, after printing is completed, the printed part coolant is solidified.

6. The method for preparing a SOEC hydrogen electrode according to claim 5, characterized in that: In step S31 , the printing layer thickness is set to 40 to 80 μm.

7. The method for preparing a SOEC hydrogen electrode according to claim 2, wherein: In step S4, the printed part is sintered by heating to 1100° C. using a staged temperature increase strategy, and then rapidly cooled to 800° C. after sintering, and then naturally cooled.

8. A solid oxide electrolytic cell, characterized in that: The SOEC hydrogen electrode according to claim 1 is used as a cathode, an anode made of nickel-yttria-stabilized zirconia is used as a raw material, and gadolinium oxide-doped cerium oxide is used as an electrolyte.

9. The solid oxide electrolytic cell according to claim 8, characterized in that: The solid oxide electrolytic cell has a symmetrical electrode arrangement.

10. The solid oxide electrolytic cell according to claim 8, characterized in that: The operating temperature of the solid oxide electrolytic cell is 750°C to 800°C.

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