A symmetrical composite electrode, its preparation method and application

Abstract

This invention relates to the field of electrode technology, and more particularly to symmetrical composite electrodes, their preparation methods, and applications. This invention utilizes a one-pot method for self-assembly of doped cubic lanthanum ferrite-based perovskite oxide and doped cubic fluorite-type cerium oxide, followed by in-situ precipitation of doped metal nanoparticles. The chemical formula of the doped cubic lanthanum ferrite-based perovskite is (La... 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0‑x M x ]O 3‑δ The chemical formula of doped fluorite-type cerium oxide is Gd. 0.075 Ce 0.925‑y M y O 2‑δ The doped metal nanoparticles are elemental M. When a reducing gas is introduced, the metal nanoparticles M precipitate in situ. This heterogeneous structure of the metal particles is tightly bonded to the composite electrode material, exhibiting good dispersion, and the embedded structure ensures excellent electrode stability. As a symmetrical electrode for SOEC, this invention achieves superior catalytic activity for carbon dioxide reduction and methanol oxidation.

Description

Technical Field

[0001] This invention relates to the field of electrode technology, and in particular to a symmetrical composite electrode, its preparation method, and its application. Background Technology

[0002] Solid oxide electrolyzers (SOECs) have the ability to convert CO2 into CO or other high-value chemicals. However, in traditional SOECs, the anode is directly exposed to the air, which results in an excessively high oxygen partial pressure on the anode side, hindering oxygen ion transfer. Overcoming this obstacle requires a large amount of electricity, making electricity a major cost of the technology. From an economic perspective, reducing electricity demand is crucial for the application of SOECs. Regarding electrolysis performance, SOEC electrode materials typically employ a physical mixture of two materials, one possessing good catalytic activity for the carbon dioxide reduction reaction (CO2RR) and the other good ionic and electronic conductivity, to create a composite cathode. However, this composite cathode suffers from drawbacks such as uneven phase distribution and a scarcity of active sites. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a symmetrical composite electrode, its preparation method, and its application.

[0004] This invention discloses a symmetrical composite electrode. The catalyst for this symmetrical composite electrode is a one-pot self-assembled doped cubic lanthanum ferrite-based perovskite oxide and doped cubic fluorite-type cerium oxide, with in-situ precipitation of doped metal nanoparticles. The chemical formula of the doped cubic lanthanum ferrite-based perovskite is (La... 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ The chemical formula of doped fluorite-type cerium oxide is Gd. 0.075 Ce 0.925-y M y O 2-δ M is any one of the transition metal elements Ru, Rh, Co, Ni, and Cu, with x = 0 to 0.2, y = 0 to 0.05, and δ = 0 to 0.15. The doped metal nanoparticles are elemental M.

[0005] Furthermore, doped cubic lanthanum ferrite-based perovskite (La) was prepared via a one-pot self-assembly process. 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075Ce 0.925-y M y O 2-δ The specific operation of the composite precursor is as follows:

[0006] S11: Dissolve citric acid in water in equal amounts of metal ions and stir until completely dissolved. Then dissolve La source, Sr source, Fe source, Nb source, Gd source, Ce source and M source according to stoichiometric ratio. M can be any one of Ru, Rh, Co, Ni and Cu. After all the above metal salts are dissolved, first add concentrated nitric acid to adjust the pH value to 1, then add EDTA. The molar ratio of EDTA to metal ions is 2:1. Adjust the pH value to 6-7 with ammonia water. Heat and stir until the spontaneous combustion process occurs. Collect the black powder after spontaneous combustion.

[0007] S12: The black powder obtained in step S11 is subjected to heat preservation for carbon removal and high-temperature sintering to obtain doped cubic lanthanum ferrite-based perovskite (La). 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925- y M y O 2-δ Composite precursor powder.

[0008] Furthermore, in step S12, cubic lanthanum ferrite-based perovskite (La) is doped. 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0- x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925-y M y O 2-δ The mass ratio is 6-7:3-4.

[0009] Furthermore, in step S12, after the black powder is kept at 550-650℃ for 2 hours to remove carbon, the resulting powder is sintered at 1000-1200℃ for 5 hours.

[0010] A method for preparing a symmetrical composite electrode as described above includes the following steps:

[0011] S1: Preparation of doped cubic lanthanum ferrite-based perovskite (La) using a one-pot self-assembly method. 0.5 Sr 0.5 )[(Fe0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925-y M y O 2-δ Composite precursor;

[0012] S2: Mix and grind the precursor and additives to prepare a slurry, screen print it onto both sides of the solid electrolyte layer and sinter it to prepare the battery;

[0013] S3: The battery is reduced in situ at the operating temperature and in a reducing atmosphere, and metal nanoparticles are precipitated in the electrode precursor to obtain the symmetrical composite electrode.

[0014] Furthermore, in step S2, the auxiliary agent is terpineol containing 7.5 to 10 wt.% ethyl cellulose.

[0015] Furthermore, the mass ratio of the precursor to the auxiliary is 1:1 to 2.

[0016] Furthermore, in step S3, the working temperature is 700℃~800℃, the reducing atmosphere is pure hydrogen, and the in-situ reduction time is 30~60min.

[0017] An application of the symmetrical composite electrode as described above is used as the cathode and anode of a solid oxide electrolytic cell for the electrolysis of carbon dioxide.

[0018] Furthermore, a methanol atmosphere is maintained at the anode of the solid oxide electrolytic cell, while CO2 is continuously input at the cathode. Simultaneously, CO2 is electrolyzed while methanol is oxidized at the anode.

[0019] This invention utilizes a one-pot method and in-situ exsolution to prepare a unique composite electrode for the first time. This composite electrode comprises lanthanum ferrite-doped perovskite, cerium oxide-doped catalyst, and its surface is coated with nano-metal particles M. Compared to composite electrodes prepared using traditional physical mixing methods, the perovskite-electrolyte interface synthesized via the one-pot method exhibits numerous advantages, such as better two-phase bonding, a lower coefficient of thermal expansion, and more active sites. This results in superior catalytic activity for the oxygen reduction reaction (OER) and carbon dioxide reduction reaction (CO2RR). When the battery is operating at 700-800℃, the nano-metal particles M precipitate in situ upon the introduction of a reducing gas. The heterostructure of these metal particles is tightly bonded to the composite electrode material, exhibiting good dispersion. The embedded structure ensures excellent electrode stability and effectively solves the problems of carbon deposition and agglomeration that easily occur during the deposition process of traditional nano-metal catalysts.

[0020] The composite electrode of this invention is synthesized under simple conditions, is easy to implement, low in cost, and has good reproducibility. Furthermore, this electrode exhibits excellent electrocatalytic activity for both methanol oxidation and carbon dioxide reduction.

[0021] This invention aims to reduce the cost of SOEC and improve its reaction efficiency by proposing a method of reducing energy consumption by introducing CH3OH as an auxiliary gas at the anode. At the anode, CH3OH undergoes an oxidation reaction to produce CO and H2, two valuable gases ideal for the Fischer-Tropsch synthesis reaction. Simultaneously, the anode can transfer electrons to the cathode through the solid electrolyte, participating in the reduction reaction on the cathode side, thereby reducing the reaction overpotential and effectively improving the reaction rate and efficiency. Furthermore, the reduction in oxygen partial pressure at the anode helps overcome the oxygen ion transfer barrier, and the partial oxidation reaction at the anode can compensate for the heat required for co-electrolysis, achieving the effects of reducing power consumption and costs. Experimental results show that methanol assistance at the anode significantly reduces the applied voltage, polarization resistance, and total energy consumption of SOEC electrolysis, providing a new approach and application prospect for CO2 conversion and energy utilization.

[0022] Furthermore, methanol, due to its unique production method and physicochemical properties, possesses advantages such as low price, ease of transportation and storage, resistance to decomposition, and a well-established industrial chain with considerable economies of scale. The high heat demand of SOEC can be met by utilizing waste heat resources, such as industrial waste heat and low-cost electricity during peak shaving and valley filling periods. In summary, this invention provides new ideas and methods for reducing the energy consumption of SOEC and opens up new application avenues for industrial waste heat utilization and carbon dioxide conversion. Attached Figure Description

[0023] Figure 1a Thermodynamic analysis diagram of SOEC in Example 1 using conventional CO2 electrolysis;

[0024] Figure 1b Thermodynamic analysis diagram of CO2 electrolysis using CH3OH-assisted SOEC in Example 1;

[0025] Figure 2a The image shows the XRD pattern of the Ru-LSFN / Ru-GDC composite electrode precursor prepared by the one-pot method in Example 1.

[0026] Figure 2b XRD pattern of Ru@Ru-LSFN / Ru@Ru-GDC prepared by in-situ exsolution method;

[0027] Figure 3a SEM image of the Ru-LSFN / Ru-GDC precursor prepared in Example 1;

[0028] Figure 3bSEM image of Ru@Ru-LSFN / Ru@Ru-GDC prepared in Example 1;

[0029] Figure 4a -d is an XPS comparison image of Ru 3p, Ce 3d, Fe 2p, and O 1s of the Ru-LSFN / Ru-GDC precursor and Ru@Ru-LSFN / Ru@Ru-GDC prepared according to the technical solution of this embodiment;

[0030] Figure 5a Current-voltage diagrams for conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis of SOEC in Example 1;

[0031] Figure 5b Impedance diagrams of SOEC under open-circuit voltage for conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis in this embodiment 1;

[0032] Figure 6 A comparison chart showing the power consumption of conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis of SOEC in Example 1 of this invention;

[0033] Figure 7 A schematic diagram of the process of using CH3OH to assist SOEC in CO2 electrolysis. Detailed Implementation

[0034] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0035] Example 1:

[0036] (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Ru 0.2 ]O 3-δ (hereinafter referred to as Ru-LSFN) and Gd 0.075 Ce 0.875 Ru 0.05 O 2-δ (Hereinafter referred to as Ru-GDC) The composite electrode with a mass ratio of 6:4 is abbreviated as (Ru-LSFN / Ru-GDC). Weigh out the same molar amount of citric acid as the metal ions in the two chemical formulas mentioned above, add it to 100 mL of deionized water, and stir until completely dissolved. Then, weigh out La(NO3)3·6H2O, Sr(NO3)2, Fe(NO3)3·9H2O, and C according to the stoichiometric ratio. 10 H5NbO 20xH2O, RuCl3, Gd(NO3)3·6H2O, and (NH4)2Ce(NO3)6 were dissolved sequentially. Concentrated nitric acid was then added to adjust the pH to 1, followed by the addition of EDTA (EDTA:total cations molar ratio of 2:1). The pH was adjusted to 6-7 with ammonia. The solution was heated and stirred continuously until a gel formed and spontaneous combustion occurred. The resulting powder was transferred to a muffle furnace and held at 600℃ for two hours. After cooling, the powder was thoroughly ground and then heated to 1100℃ and held for 5 hours to obtain the composite electrode precursor.

[0037] The previously prepared composite electrode precursor was mixed with terpineol containing 7.5–10 wt.% ethyl cellulose, maintaining a precursor-to-terpineol mass ratio of 1:1.5. The mixture was then ground for several hours to obtain an electrode slurry. The electrode slurry was uniformly coated onto both sides of a dense LSGM electrolyte with a thickness of 250 μm using screen printing. The electrode was then dried. After drying, it was sintered in air at 1050 °C for 2 hours to complete the fabrication of the single cell.

[0038] The single cell was packaged and tested. The cathode and anode were first purged with N2 at 800℃, then reduced in situ with pure H for 30 minutes, reducing the precursor powder to Ru@(La). 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Ru 0.2 ]O 3-δ / Ru@Gd 0.075 Ce 0.875 Ru 0.05 O 2-δ (Hereinafter referred to as Ru@Ru-LSFN / Ru@Ru-GDC). After purging excess H2 with N2, methanol is introduced at the anode and CO2 is introduced at the cathode for SOEC electrolysis testing.

[0039] Table 1 Comparison of thermodynamic and operating parameters of different electrolyzers

[0040]

[0041] Referring to Appendix Table 1, in various anolyte-assisted electrolysis reactions of carbon dioxide, the anolyte CH3OH(g)-assisted electrolysis of CO2 exhibits significant advantages. Compared with other common reactions involving C and CH4(g) assistance, the total energy required for anolyte CH3OH(g)-assisted electrolysis of CO2 is relatively low. From the energy data, the total energy required for CH3OH(g)-assisted electrolysis of carbon dioxide is only 139.17 kJ / mol. -1 The total energy required for the electrolysis of C is 169.88 kJ / mol. -1The total energy required for the electrolysis of CH4(g) is as high as 293.45 kJ / mol. -1 Furthermore, the electricity required for the auxiliary electrolysis of CO2 with CH3OH(g) is -161.53 kJ / mol. -1 The anode CH3OH(g)-assisted SOEC exhibits the lowest energy demand among several reactions, meaning it is more economical in terms of electricity consumption. Overall, CH3OH(g)-assisted SOEC demonstrates significant advantages in energy requirements, offering higher energy efficiency and lower operating costs. Furthermore, the high heat demand of CH3OH(g)-assisted SOEC can be obtained through waste heat resource utilization. This heat can come from industrial waste heat, concentrated solar panels, or waste heat electricity, etc. Taking ethylene production as an example, the cracking furnace is the core equipment in ethylene production, with an outlet temperature reaching 800℃-900℃, and the cracked gas contains a large amount of waste heat.

[0042] Appendix Figure 1a This is a thermodynamic analysis diagram of traditional CO2 electrolysis, attached. Figure 1b This is a thermodynamic analysis diagram of CO2 electrolysis using SOEC assisted by CH3OH at the anode. At 800℃ and with a CH3OH atmosphere at the anode, the total Gibbs free energy of the reaction increases from 189.21 kJ / mol. -1 It dropped to -161.93 kJ / mol. -1 This indicates that, theoretically, the energy requirement of CH3OH-assisted SOEC is much lower than that of traditional SOEC. The thermal effect of the partial oxidation reaction of CH3OH at the anode can provide the heat required for SOEC operation, and can also reduce the partial pressure of oxygen at the anode and accelerate the kinetics of CO2RR at the cathode.

[0043] See appendix Figure 2a The image shows the XRD pattern of the Ru-LSFN / Ru-GDC composite electrode precursor prepared by the one-pot method according to the technical solution of this embodiment. The results show that the precursor materials Ru-LSFN exhibit a cubic perovskite phase structure, while Ru-GDC exhibits a cubic fluorite phase structure.

[0044] See appendix Figure 2b The image shows the XRD pattern of Ru@Ru-LSFN / Ru@Ru-GDC prepared by in-situ exsolution according to the technical solution of this embodiment. A peak of metallic Ru appears after in-situ reduction. The reduced material includes cubic perovskite-type doped lanthanum ferrite perovskite, cubic fluorite-type doped cerium oxide, and elemental metal M precipitated in-situ on the surfaces of both materials.

[0045] See appendix Figure 3a The image shows a SEM image of the Ru-LSFN / Ru-GDC precursor prepared according to the technical solution of this embodiment. The image reveals particle aggregation with a cloud-like structure, indicating a tight bond between the two different powders, Ru-LSFN and Ru-GDC, demonstrating a good binding effect. See attached image. Figure 3bThe image shows a SEM image of Ru@Ru-LSFN / Ru@Ru-GDC prepared according to the technical solution of this embodiment. The results show that the material surface is uniformly covered with metallic Ru nanoparticles embedded in the substrate.

[0046] See appendix Figure 4a -d represents the XPS comparison images of Ru 3p, Ce 3d, Fe 2p, and O 1s of the Ru-LSFN / Ru-GDC precursor and Ru@Ru-LSFN / Ru@Ru-GDC prepared according to the technical solution of this embodiment; Ru can be observed from the Ru 3p spectrum. 0 The signal indicates that some Ru was reduced to Ru metal precipitation. XPS comparison images of Ce 3d and Fe 2p show that Ru@Ru-LSFN / Ru@Ru-GDC has a lower ionic valence state compared to Ru-LSFN / Ru-GDC. According to the principle of electroneutrality, a decrease in the valence state of metal ions usually corresponds to the generation of oxygen vacancies to maintain electroneutrality. XPS comparison images of O 1s show that the lattice oxygen content of Ru@Ru-LSFN / Ru@Ru-GDC decreases after reduction, while the surface oxygen vacancies increase, which facilitates the formation and diffusion of oxygen vacancies.

[0047] See appendix Figure 5a The figure shows the IV curves for CO2 electrolysis using a conventional CO2 electrolysis process with a SOEC assembled according to Example 1 and a CH3OH-assisted SOEC. The results show that the CH3OH-assisted anode significantly reduces the applied voltage. For example, at 0.8 A cm⁻¹... -2 At the electrolysis current density, SOEC requires a voltage of 1.5V for CO2 electrolysis alone, while with CH3OH as the anode auxiliary, the applied voltage is only 0.33V, a reduction of 1.17V.

[0048] See appendix Figure 5b The figure shows the impedance diagrams at open-circuit voltage for conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis using SOEC according to Example 1. After introducing CH3OH into the anode, the polarization resistance at 800°C decreased significantly.

[0049] See appendix Figure 6 This chart compares the energy consumption of conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis using SOEC according to Example 1. It can be seen that the energy required to produce one cubic meter of CO is significantly reduced with CH3OH-assisted SOEC. For example, at 800°C and with a voltage of 1.5V, the energy consumed to produce one cubic meter of CO is 3.68 kWh / m³. -3 Meanwhile, the voltage applied for the CH3OH-assisted electrolysis of SOEC at the same current density is only 0.33V, and the required power consumption is only 0.40kWh / m³. -3It is only 10.87% of the cost of traditional SOEC. The huge energy-saving effect has significantly reduced the cost, and CH3OH-assisted SOEC shows a wider range of application prospects in the fields of energy conversion and chemical industry.

[0050] Figure 7 A schematic diagram of the process of using CH3OH to assist SOEC in CO2 electrolysis.

[0051] Example 2:

[0052] (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Rh 0.2 ]O 3-δ (hereinafter referred to as Rh-LSFN) and Gd 0.075 Ce 0.875 Rh 0.05 O 2-δ (Hereinafter referred to as Rh-GDC) The composite electrode with a mass ratio of 6:4 is abbreviated as (Rh-LSFN / Rh-GDC). Weigh out the same molar amount of citric acid as the metal ions in the two chemical formulas mentioned above, add it to 100 mL of deionized water, and stir until completely dissolved. Then, weigh out La(NO3)3·6H2O, Sr(NO3)2, Fe(NO3)3·9H2O, and C according to the stoichiometric ratio. 10 H5NbO 20 ·xH2O, Rh(NO3)3·nH2O, Gd(NO3)3·6H2O, and (NH4)2Ce(NO3)6 were dissolved sequentially. Then, concentrated nitric acid was added to adjust the pH to 1. EDTA was then added, with a molar ratio of EDTA to total cations of 2:1. The pH was adjusted to 6–7 with ammonia. The solution was heated and stirred continuously until a gel formed and spontaneous combustion occurred. The self-ignited powder was transferred to a muffle furnace and held at 600°C for two hours. After cooling, the resulting powder was thoroughly ground and then heated to 1100°C and held for 5 hours to obtain the composite electrode precursor.

[0053] The previously prepared composite electrode precursor was mixed with terpineol containing 7.5–10 wt.% ethyl cellulose, maintaining a precursor-to-terpineol mass ratio of 1:1.5. The mixture was then ground for several hours to obtain an electrode slurry. The electrode slurry was uniformly coated onto both sides of a dense LSGM electrolyte with a thickness of 250 μm using screen printing. The electrode was then dried. After drying, it was sintered in air at 1050 °C for 2 hours to complete the fabrication of the single cell.

[0054] The single cell was packaged and tested. The cathode and anode were first purged with N2 at 800℃, then reduced in situ with pure H for 60 minutes, reducing the precursor powder to Rh@(La). 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Rh 0.2 ]O 3-δ / Rh@Gd 0.075 Ce 0.875 Rh 0.05 O 2-δ (Hereinafter referred to as Rh@Rh-LSFN / Ru@Rh-GDC). After purging excess H2 with N2, methanol was introduced at the anode and CO2 at the cathode for SOEC electrolysis testing. The performance results of conventional CO2 electrolysis and CH3OH-assisted CO2 electrolysis according to Example 2 show that at 0.8 A cm⁻¹... -2 At the electrolysis current density, SOEC requires a voltage of 1.5V to electrolyze CO2 alone, while with CH3OH as the anode auxiliary, the applied voltage is only 0.54V, a reduction of 0.96V.

[0055] Example 3:

[0056] (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Co 0.2 ]O 3-δ (hereinafter referred to as Co-LSFN) and Gd 0.075 Ce 0.875 Co 0.05 O 2-δ (Hereinafter referred to as Co-GDC) The composite electrode with a mass ratio of 6:4 is abbreviated as (Co-LSFN / Co-GDC). Weigh out the same molar amount of citric acid as the metal ions in the two chemical formulas mentioned above, add it to 100 mL of deionized water, and stir until completely dissolved. Then, weigh out La(NO3)3·6H2O, Sr(NO3)2, Fe(NO3)3·9H2O, and C according to the stoichiometric ratio. 10 H5NbO 20·xH2O, Co(NO3)3·6H2O, Gd(NO3)3·6H2O, and (NH4)2Ce(NO3)6 were dissolved sequentially. Then, concentrated nitric acid was added to adjust the pH to 1. EDTA was then added, with a molar ratio of EDTA to total cations of 2:1. The pH was adjusted to 6–7 with ammonia. The solution was heated and stirred continuously until a gel formed and spontaneous combustion occurred. The self-ignited powder was transferred to a muffle furnace and held at 600°C for two hours. After cooling, the resulting powder was thoroughly ground and then heated to 1100°C and held for 5 hours to obtain the composite electrode precursor.

[0057] The previously prepared composite electrode precursor was mixed with terpineol containing 7.5–10 wt.% ethyl cellulose, maintaining a precursor-to-terpineol mass ratio of 1:1.5. The mixture was then ground for several hours to obtain an electrode slurry. The electrode slurry was uniformly coated onto both sides of a dense LSGM electrolyte with a thickness of 250 μm using screen printing. The electrode was then dried. After drying, it was sintered in air at 1050 °C for 2 hours to complete the fabrication of the single cell.

[0058] The single cell was packaged and tested. The cathode and anode were first purged with N2 at 800℃, then reduced in situ with pure H2 for 60 minutes, reducing the precursor powder to Co@(La). 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Co 0.2 ]O 3-δ / Co@Gd 0.075 Ce 0.875 Co 0.05 O 2-δ (Hereinafter referred to as Co@Co-LSFN / Ru@Co-GDC). After purging excess H2 with N2, methanol was introduced at the anode and CO2 at the cathode for SOEC electrolysis testing. The test results showed that at 0.8 A cm⁻¹ -2 At the electrolysis current density, SOEC requires a voltage of 1.5V to electrolyze CO2 alone, while with CH3OH as the anode, the applied voltage is only 0.61V, a reduction of 0.89V.

[0059] Example 4:

[0060] (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Ni 0.2 ]O 3-δ (hereinafter referred to as Ni-LSFN) and Gd0.075 Ce 0.875 Ni 0.05 O 2-δ (Hereinafter referred to as Ni-GDC) The composite electrode with a mass ratio of 7:3 is abbreviated as (Ni-LSFN / Ni-GDC). Weigh out the same molar amount of citric acid as the metal ions in the two chemical formulas mentioned above, add it to 100 mL of deionized water, and stir until completely dissolved. Then, weigh out La(NO3)3·6H2O, Sr(NO3)2, Fe(NO3)3·9H2O, and C according to the stoichiometric ratio. 10 H5NbO 20 The following ingredients were dissolved sequentially: xH₂O, Ni(NO₃)₂·6H₂O, Gd(NO₃)₃·6H₂O, and (NH₄)₂Ce(NO₃)₆. Concentrated nitric acid was then added to adjust the pH to 1. EDTA was then added, with a molar ratio of EDTA to total cations of 2:1. Ammonia was used to adjust the pH to 6–7. The solution was heated and stirred continuously until a gel formed and spontaneous combustion occurred. The self-ignited powder was transferred to a muffle furnace and held at 600°C for two hours. After cooling, the powder was thoroughly ground and then heated to 1100°C and held for 5 hours to obtain the composite electrode precursor.

[0061] The previously prepared composite electrode precursor was mixed with terpineol containing 7.5–10 wt.% ethyl cellulose, maintaining a precursor-to-terpineol mass ratio of 1:1.5. The mixture was then ground for several hours to obtain an electrode slurry. The electrode slurry was uniformly coated onto both sides of a dense LSGM electrolyte with a thickness of 250 μm using screen printing. The electrode was then dried. After drying, it was sintered in air at 1050 °C for 2 hours to complete the fabrication of the single cell.

[0062] The single cell was packaged and tested. The cathode and anode were first purged with N2 at 800℃, then reduced in situ with pure H for 60 minutes, reducing the precursor powder to Ni@(La). 0.5 Sr 0.5 )1[(Fe 0.9 Nb 0.1 ) 0.8 Ni 0.2 ]O 3-δ / Ni@Gd 0.075 Ce 0.875 Ni 0.05 O 2-δ (Hereinafter referred to as Ni@Ni-LSFN / Ru@Ni-GDC). After purging excess H2 with N2, methanol was introduced at the anode and CO2 at the cathode for SOEC electrolysis testing. The single-cell performance test results show that at 0.8 Acm -2At the electrolysis current density, SOEC requires a voltage of 1.5V to electrolyze CO2 alone, while with CH3OH as the anode, the applied voltage is only 0.64V, a reduction of 0.86V.

[0063] Example 5:

[0064] (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 0.8 Cu 0.2 ]O 3-δ (hereinafter referred to as Cu-LSFN) and Gd 0.075 Ce 0.875 Ru 0.05 O 2-δ (Hereinafter referred to as Cu-GDC) The composite electrode with a mass ratio of 6:4 is abbreviated as (Cu-LSFN / Cu-GDC). Weigh out the same molar amount of citric acid as the metal ions in the two chemical formulas mentioned above, add it to 100 mL of deionized water, and stir until completely dissolved. Then, weigh out La(NO3)3·6H2O, Sr(NO3)2, Fe(NO3)3·9H2O, and C according to the stoichiometric ratio. 10 H5NbO 20 ·xH2O, Cu(NO3)2·3H2O, Gd(NO3)3·6H2O, and (NH4)2Ce(NO3)6 were dissolved sequentially. Then, concentrated nitric acid was added to adjust the pH to 1. EDTA was then added, with a molar ratio of EDTA to total cations of 2:1. The pH was adjusted to 6–7 with ammonia. The solution was heated and stirred continuously until a gel formed and spontaneous combustion occurred. The self-ignited powder was transferred to a muffle furnace and held at 600°C for two hours. After cooling, the powder was thoroughly ground and then heated to 1100°C and held for 5 hours to obtain the composite electrode precursor.

[0065] The previously prepared composite electrode precursor was mixed with terpineol containing 7.5–10 wt.% ethyl cellulose, maintaining a precursor-to-terpineol mass ratio of 1:1.5. The mixture was then ground for several hours to obtain an electrode slurry. The electrode slurry was uniformly coated onto both sides of a dense LSGM electrolyte with a thickness of 250 μm using screen printing. The electrode was then dried. After drying, it was sintered in air at 1050 °C for 2 hours to complete the fabrication of the single cell.

[0066] The single cell was packaged and tested. The cathode and anode were first purged with N2 at 800℃, then reduced in situ with pure H for 30 minutes, reducing the precursor powder to Cu@(La). 0.5 Sr 0.5 )[(Fe 0.9Nb 0.1 ) 0.8 Cu 0.2 ]O 3-δ / Cu@Gd 0.075 Ce 0.875 Cu 0.05 O 2-δ (Hereinafter referred to as Cu@Cu-LSFN / Ru@Cu-GDC). After purging excess H2 with N2, methanol was introduced at the anode and CO2 at the cathode for SOEC electrolysis testing. The single-cell performance test results showed that at 0.8 Acm -2 At the electrolysis current density, SOEC requires a voltage of 1.5V to electrolyze CO2 alone, while with CH3OH as the anode, the applied voltage is only 0.53V, a reduction of 0.97V.

[0067] For any points not covered above, existing technologies shall apply.

[0068] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a symmetrical composite electrode, characterized in that: Includes the following steps: S1: Preparation of doped cubic lanthanum ferrite-based perovskite (La) using a one-pot self-assembly method. 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0- x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925-y M y O 2-δ Composite precursor; S2: Mix and grind the precursor and additives to prepare a slurry, screen print it onto both sides of the solid electrolyte layer and sinter it to prepare the battery; S3: The battery is reduced in situ at the operating temperature and in a reducing atmosphere, and metal nanoparticles are precipitated in the electrode precursor to obtain the symmetrical composite electrode. M is any one of the transition metal elements Ru, Rh, Co, Ni, and Cu, x is greater than 0 and not greater than 0.2, y = 0~0.05, δ = 0~0.15, and the doped metal nanoparticles are elemental M. Doped cubic lanthanum ferrite-based perovskite (La 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925-y M y O 2-δ The mass ratio is 6-7:3-4.

2. The preparation method according to claim 1, characterized in that: Doped cubic lanthanum ferrite-based perovskite (La) was prepared by a one-pot self-assembly method. 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925- y M y O 2-δ The specific operation of the composite precursor is as follows: S11: Dissolve citric acid in water in equal amounts of metal ions and stir until completely dissolved. Then dissolve La source, Sr source, Fe source, Nb source, Gd source, Ce source and M source according to stoichiometric ratio. M can be any one of Ru, Rh, Co, Ni and Cu. After all the above metal salts are dissolved, first add concentrated nitric acid to adjust the pH value to 1, then add EDTA. The molar ratio of EDTA to metal ions is 2:

1. Adjust the pH value to 6~7 with ammonia water. Heat and stir until the spontaneous combustion process occurs. Collect the black powder after spontaneous combustion. S12: The black powder obtained in step S11 is subjected to heat preservation for carbon removal and high-temperature sintering to obtain doped cubic lanthanum ferrite-based perovskite (La). 0.5 Sr 0.5 )[(Fe 0.9 Nb 0.1 ) 1.0-x M x ]O 3-δ and doped fluorite-type cerium oxide Gd 0.075 Ce 0.925-y M y O 2-δ Composite precursor powder.

3. The preparation method according to claim 2, characterized in that: In step S12, after the black powder is decarburized by holding it at 550~650°C for 2 hours, the resulting powder is sintered at 1000~1200°C for 5 hours.

4. The preparation method according to claim 1, characterized in that: In step S2, the auxiliary agent is terpineol containing 7.5~10 wt.% ethyl cellulose.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the precursor to the auxiliary is 1:1~2.

6. The preparation method according to claim 1, characterized in that: In step S3, the working temperature is 700 °C ~ 800 °C, the reducing atmosphere is pure hydrogen, and the in-situ reduction time is 30 ~ 60 min.

7. A symmetrical composite electrode prepared by the preparation method according to any one of claims 1-6.

8. An application of the symmetrical composite electrode as described in claim 7, characterized in that: Used as the cathode and anode in a solid oxide electrolytic cell for the electrolysis of carbon dioxide.

9. An application as described in claim 8, characterized in that: A methanol atmosphere is maintained at the anode of a solid oxide electrolyzer, while CO2 is continuously input at the cathode. The CO2 is electrolyzed while the methanol is oxidized at the anode.

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